Monday, May 28, 2018

Speculation on the effect of subcutaneous adipocytes implanted in to the mesentery of mice

Taking a piece of subcutaneous fat from a sacrificed mouse and implanting in to the mesentery of a recipient mouse causes weight loss in the recipient, starting once the surgery has healed. We know that healing takes something just over six weeks:

Is the effect replicable? Yes, fairly well, here it is in a second cohort by the same group:

While this is pretty certain, the explanation is very speculative. Note the effect kicked in slightly sooner in cohort 2, I would assume that healing was a little quicker for this cohort. Maybe the researchers got better at performing the surgery. The 12 week weights are essentially identical between cohorts.

So......... Adding extra adipocytes causes overall fat loss, as in this image from Cohort 1 featured in the last post:

I find this rather interesting, to say the least. The black squares represent mice which have had subcutaneous adipose tissue implanted around their mesentery so that a significant proportion of its venous drainage enters the portal vein and goes directly to the liver.

I've looked through the data from the paper for any suggestion as to an explanation of why the weight loss occurred. There is nothing anywhere to suggest uncoupling while the mice where in the CLAMS apparatus (though calorie restriction is a good way to suppress uncoupling acutely). Calorie malabsorption through surgical damage to the mesentery seems unlikely as similar surgery to implant visceral fat gave normal weight gain compared to control mice.

So I think the mice in the SC-VIS group simply cut their ad-lib calories. Food intake was only measured over the one day in the CLAMS apparatus so we'll never know what the overall food intake was relative to controls, but I can't see any other explanation.

Which leads to the question as to why they might have cut calories, other than the obvious: They we not as hungry as the control mice. This effect occurred with mesenteric implanted subcutaneous adipocytes, but not with implanted visceral adipocytes. So we have to ask what the difference might be between the adipocyte types.

Visceral adipocytes are more insulin sensitive than subcutaneous adipocytes. They will store fat more easily and refuse to release it until insulin drops down to absolutely basal levels. On an ad-lib high carbohydrate diet this will not happen very often. As far as the liver is concerned, the visceral fat in the mesentery and omentum is non existent for most of the time. Adding extra visceral adipocytes at this site will not change this.

Subcutaneous adipocytes are less sensitive to insulin, they will store fat at high insulin levels but release FFAs easily as insulin levels fall. Obviously, they are always smaller than visceral adipocytes and they stay that way when implanted in to the recipient mice. If they are implanted in a location from which their easily released FFAs go directly to the liver they are in a position to have a metabolic effect.

Summary of the speculation so far: Visceral fat adds nothing to the FFA level of portal vein blood unless insulin level is well below that of a mouse on ad lib standard mouse chow. Placing subcutaneous adipocytes where their venous drainage goes directly to the liver supplies supplementary FFAs directly to the liver when insulin levels are merely low rather than rock bottom.

It has been known for a very, very long time that infusing FFAs in to the portal vein suppresses appetite and that this effect requires a functional vagal nerve supply to the liver. This group of rats is receiving an oleic acid infusion (if you are going to secure a long term cannula in to the portal vein then something larger than a mouse might make the surgery slightly more practical and less challenging) in to their portal vein:

Hepatic-portal oleic acid inhibits feeding more potently than hepatic-portal caprylic acid in rats

Oleic acid infused in to the portal vein at 14mcg/min for six hours reduced food intake during the 12 hour dark period from 23g in the controls to 17g in the oleic acid group. At 14mcg/min the infusion supplies 840mcg/h and over six hours this supplies just over 5mg, ie 0.005g in total dose, roughly 0.05kcal, 0.21kJ of oleic acid. This is enough to drop food intake by six grams of food at 12.4kJ/g, ie 74kJ.

This group looked at 14mcg/min because they knew it would work. We don't know how low an infusion rate could go while still having an effect on appetite (from this paper anyway). The two unanswerable questions we are left with are: What was the augmentation of FFA supply to the liver from SC adipocytes in the mesentery of the operated rats in Kahn's study? Was this enough to limit food intake? We don't know the answers but you can imagine what my guess is.

Getting access to the portal vein to either measure or infuse anything is a complete surgical nightmare. Kahn's group looked at all sorts of systemic messengers in terms of cytokines and adipokines and found absolutely nothing to explain their phenomenon.

Perhaps they were looking in the wrong place.


I guess the third question is why the SC adipocyte recipient mice actually ate a little more than the controls in the CLAMS apparatus (as judged by RQ). I'd still bet on differences in total fat mass available over-riding the stress induced refusal to eat, irrespective of degree of hunger in any mouse through the rest of the study... You could throw in cortisol, adrenalin and the lack of neural innervation of transplanted adipoctes but let's leave it simple (and possibly incorrect).

More supplementary speculation: Is the normal profound fall in appetite on induction of ketogenic eating in humans directly related to the sudden access to visceral abdominal fat, secondary to the major reduction in circulating insulin? This would suggest that the satiating effect of ketogenic diets might be more marked in people with significant visceral obesity. It would become less obvious as weight loss progresses until the majority of remaining fat is where it should be, in the non-visceral adipocytes of a normal shaped human being... The effect might even be virtually non existent in young, fit, healthy folks who would simply eat under ketosis to maintain their current rather normal bodyweight.

Sunday, May 20, 2018

Guddling in the dark for a respiratory quotient (2)

OK. I've been bugged by the RQ values which come out of CLAMS equipment. For months. Multiple papers have values that don't make sense, which is an issue making me doubt my sanity and is damaging to my personal extensive set of confirmation biases. They also produce basic contradictions of the physiology of the oxidation of glucose vs the oxidation of fatty acids. But now I think I can go back and explain much of the peculiarity in this image from Kahn's group, the one which triggered this previous post. Two sets of mice, on the same chow, having sustained differences in RQ, in a way I couldn't understand:

Well now I think I can. The insight needed comes from a non related paper on the effect of knocking out the sweet taste receptor in mice.

So, let's have a look at the RQ data from the CLAMS apparatus in this paper:

Disruption of the sugar-sensing receptor T1R2 attenuates metabolic derangements associated with diet-induced obesity

And in particular from this next set of graphs. They are interesting because they cover two complete days in the CLAMS equipment.

Look at the grey and the black lines first, these are control and sweet receptor KO mice, being fed pretty standard low fat crapinabag. We can see that between day one dark period and day two dark period in the CLAMS equipment that a) the peak height of the RQ rises, b) carbohydrate oxidation rises and c) lipid oxidation falls. No one did stats to compare these two days with each other so I don't know what the p value might be, but the trend certainly looks very real to me. No one altered the food macros between day one and day two.

I think mice, like humans, cut their calories when you put them in to a respiratory chamber or in to a CLAMS apparatus. Certainly for the first two or three days of mice in CLAMS.

In this T1R2 KO study you can see evidence for the the improving intake of (carbohydrate based) food between day one and day two which is inseparably linked to the rising RQ. There had been a day of acclimatisation before the two study days which will have minimised this trend but it's very much still visible. The change is less obvious (but still present) for the fat fed mice (red coloured traces) but it's not so clear cut in these mice because they are largely either oxidising fat from their diet or fat from their adipocytes, both of which look pretty much the same from the RQ point of view.

Core insight. You can alter RQ away from the macros of a (high carbohydrate) diet by simply eating less. Adipocyte fat makes up the difference in calories and this automatically drops the RQ. Let's take this idea and look at the RQ figure from Kahn's paper.

In a normal mouse, on normal low fat chow, the RQ during the early feeding period rises to above 1.0 due to de novo lipogenesis combined with fat repletion/storage. Kahn's control mice (SHAM) started with a RQ at around 0.88 and they slept through the light period so dropped their RQ to around 0.75. When they started to feed with the arrival of the dark period (on their high carbohydrate chow) in the CLAMS apparatus the RQ only rises to 0.88. In real mice eating this sort of chow the RQ should rise to 1.2 for a few hours.

The RQ will not rise to 1.0 if the mice fail to eat enough carbohydrate to meet or exceed their energy needs. If they don't eat enough they will continue to utilise body fat and this will lower their RQ below that of a mouse eating to weight stability. These mice did not eat enough carbohydrate to suppress fat oxidation. The RQ says so. The absolute food intakes are below but these are fairly irrelevant compared to the RQ data.

They were put in to the CLAMS apparatus with no suggestion (in the methods) of an acclimatisation period. I think the mice were frightened and dropped their food intake. We can see from the RQ of both groups that at no point does this even approach, let alone exceed, 1.0 (in the acclimatised mice in the T1R2 KO paper figure the RQ reaches 1.1 at the peak of feeding on day 2, ie CLAMS day 3).

Summary: Both of Kahn's groups are oxidising fat to give a low RQ on an high carbohydrate diet and the only way they can be doing this is if the fat is coming from their adipocytes. They are not eating enough of their carbohydrate based diet to maintain fat storage or to raise the RQ.

That just leaves us to ask why the control group are oxidising more fat than the intervention group. Is this a magical preference of the intervention group to oxidise glucose? Is that why they are so slim? I know that sounds strange but that's the conclusion in the paper. Logically, oxidising FAT makes you slim. Storing fat makes you fat. But that's under ad-lib conditions. At the time of the hypocaloric 24 hours for Kahn's mice in the CLAMS apparatus we have these data available from which we can estimate fat stores at a given time, week ten in particular:

The white diamonds are still the controls/sham operated. They carry about 10g of fat at week ten. The black squares are the intervention group, they carry about 5g of body fat at this time. If both groups cut calories acutely during their day of anorexia in the CLAMS apparatus, I would expect the animals with the most adipose tissue to release the most FFAs. And oxidise the most FFAs. That has to be the control group, because they're a lot fatter to start with. The intervention group has less stored fat available, so oxidises less fat. Interestingly the fatter control group ate 3.9g of carbohydrate based food in the CLAMS vs 4.2g for the slimmer intervention group (ns), which just might reflect less hunger in the fatter control mice because they are accessing their bigger fat stores, ie the control mice appear to run on fat (because they are doing so on this one single day). A lack of stored fat in the intervention group is why they ate more (carbohydrate based) food and utilised less adipose derived fat. So this group appears to run on carbs, judging by their RQ. But the RQ over the rest of their lives, in either group, while eating normally, to satiety, outside the CLAMS apparatus, is a mystery.

But yay! The CLAMS equipment is almost certainly working correctly. The RQ graph is very explicable. It probably tells us NOTHING about the substrate oxidation under non-CLAMS conditions, but we can speculate about that in another post.

Trying to make inferences about overall post-intervention metabolism, based on a single day in a very novel (and possibly frightening) environment under acute hypocaloric conditions will set you up for a hiding to nothing as far as comprehension and understanding of your intervention are concerned. But given enough thought the results at least become comprehensible.

Now I'm happy.


Now that I'm happy I might have a think about why the slim, subcutaneous to visceral fat-transplanted mice in Kahn's study might have come to remain slim. Clearly, from the fat mass graph, the transplantation of subcutaneous fat in to the location of visceral fat does do something...

Saturday, May 12, 2018

Nighttime Eaters have an elevated RQ on a given macro ratio diet. They're getting fat

I picked up this paper via Face-ache so cannot recall to whom I should credit for the find. Sorry. The post is also highly speculative.

Higher 24-h Respiratory Quotient and Higher Spontaneous Physical Activity in Nighttime Eaters

It's worth noting that the difference is small but probably biologically significant. Statistically p is less than 0.05. Before we think about it we need some background. That comes from the same group in an earlier paper:

Nighttime eating: commonly observed and related to weight gain in an inpatient food intake study

They looked at accurately measured food intake for Nighttime Eaters (NEs) under in-patient conditions at near identical macros to non-NEs:

and at weight gain over the subsequent 3.4 years, while the subjects were free living. Weight gain is, not surprisingly, higher in the NEs:

To me, NEs wake up in the night and go to the fridge and eat some food because they are hungry. Control subjects do not get up at night and do not go to the fridge and do not eat food, because they are not hungry. Note that hunger is a slippery term and these researchers have a psychiatry based view of obesity*. In Table 2 there is no significant difference in "cognitive hunger" between NEs and non-NEs. However in the methods the term used is "perceived hunger" and this is described thus:

"... perceived hunger (ie, the susceptibility of eating in response to subjective feelings of hunger)"

So NEs may not eat any more than non-NEs when they are "subjectively" hungry. My argument is that they are simply hungry more frequently, including right through the night in fact.

*Aside: But they are learning! Quote of the century from the paper: "These differences in substrate oxidation and SPA indicate that the night eating behavior phenotype may have physiologic underpinnings"

OMG gluttony may just be physiology!!!!!!!!!!!!!! End aside.


Why might NE people be hungry more often than non-NEs? From the adipocentric view of obesity, when dietary fat falls in to their adipocytes and stays there, NE subjects "lose" this fat. In the absence of a decent supply of metabolisable fat there is nothing left to oxidise except carbohydrate, with its high associated RQ (pax protein). Once the bulk of the ingested carbohydrate is metabolised and the fat is in the adipocytes for the duration, there is nothing for it but to get some more carbohydrate to eat and metabolise. The signal for this need to eat is called hunger. The fat loss phenomenon is not huge, the RQ for NEs is 0.85 and for non-NEs is 0.83. But I think that is enough.

Eating another mixed meal or mixed macro snack supplies necessary glucose for oxidation but the fat is again "lost" in to adipocytes. This keeps happening.

So. Are these folks going to get heavier? Of course they are. That is intrinsic to the elevated RQ compared to non-NEs while eating a similar macro ratio diet. It can only occur during fat accumulation. People with high RQs gain weight over the years. The high RQ is a direct result of the loss of dietary fat in to adipocytes. From the respiratory chamber study it would be about ten grams of fat per day "lost" in to adipocytes. In the background paper the NEs weight gain over 3.4 years was actually roughly five grams per day rather than ten grams per day, but people are more active when outside a respiratory chamber! Obviously fat "lost" in to adipocytes is fat gained on the scales.

Are NEs insulin sensitive or insulin resistant?

That's easy. Their RQ is high, they are losing fat in to storage. The fat is staying in storage within the adipocytes. They must be insulin sensitive. Think of the Laron dwarf humans, genetically GH-receptor deficient with subsequent exquisite insulin sensitivity. Short of stature and seriously obese at the same time as maintaining that exquisite insulin sensitivity...

To look for data to confirm my biases we have to move along to

Circadian rhythm profiles in women with night eating syndrome

This is by a different group. They are less psychiatric in outlook but fail to perceive that obesity might be a significantly adipocyte related problem. They mention stomach and liver and circadian rhythms, but not adipocytes. Their data are a little shaky but certain features come through as plausible. They measured a ton of (mostly) hormones but the only two parameters which grab my attention are insulin and glucose.

Now, the x axis is as clear as mud (like much of the rest of the paper). It really is "time of day", sort of. The first sample was taken at 8am, this is the start of each of the graphs, eight is interpolated between six and ten. Twenty four hours later, 8am next day is at 32 on the x axis and we get an extra data point taken at 9am on the second morning, ie 25 hours in to the study, it's at 33 on the x axis. Simple huh? Sorry if I've insulted the clarity of mud.

Three meals were served during daytime and snacks were available and consumed ad-lib, including through the night if so needed. Solid lines are controls, dashed lines are NEs. Macros of intakes were not controlled.

Control group (non-NEs) eat through the day. Glucose and insulin peak at around 5pm, probably around evening meal time, and both trough at around 4am because these folks would like to sleep through the night (they were blood sampled once an hour so...) and don't eat while asleep or wanting to be asleep.

The insulin peak is lower for the NEs as (I am assuming) they are insulin sensitive so they easily distend their adipocytes. Insulin sensitive adipocytes need less insulin to squirrel away diet derived fat. The insulin peak is delayed because these people are NEs, nighttime eaters, by definition. Eating later gives a later insulin peak. The NE insulin curve also never shows that drop in the early hours because NEs continue to eat at night. Because they're hungry at night. That's why they are called... You get the gist.

The glucose curve is equally explicable in terms of pathological insulin sensitivity. Just a little insulin lowers the blood glucose and facilitates its oxidation (daytime dip in glucose) and facilitates uptake in to adipocytes to generate glycerol for triglyceride sequestration. Gradually falling insulin due to lower (but not zero) food intake in the early hours of the morning allows some recovery of blood glucose levels, probably assisted by the surge of growth hormone in the early hours of the morning with its mild glucose raising, insulin resistance effect.

Night Eaters are pathologically insulin sensitive. Like the Laron dwarf humans and Laron mice, extreme insulin sensitivity causes obesity, given ad lib food. Unlike the Laron individuals with their genetic oddity of long term preserved insulin sensitivity, NE people will eventually distend their adipocytes to the level of leaking free fatty acids.

But until their adipocytes become dysfunctional NE people are insulin sensitive, hungry, and lose the fat component of their diet in to their adipocytes. Of course, once their adipocytes become distended and start to leak FFAs they will stop getting fatter and start to access the spilled fat. Oxidising this will drop their RQ but they will at this time become IGT/diabetic due to unregulated and inappropriate FFA release.

If I had to suggest an explanation for NE patho-physiology it would be PUFA, mostly linoleic acid... I'd expect NEs to be people who avoid saturated fat and prefer corn oil, over the long haul. More victims of the cardiologists.


Friday, April 13, 2018

AHA approved egg!

One of the full size chickens miss-fired yesterday and produced this minute egg:

I was pretty sure this would be an AHA approved egg. Zero fat. Zero cholesterol. Tiny amount of protein. You don't have to include the eggshell (unless you feel a calcium supplement is a good idea. Could treat your acid reflux at the same time!).

Of course it should be fried in corn oil. Still hungry?

Fill up on sugar!

Ah, the decades of stupidity that have now been mostly overturned. Just the corn oil to get rid of.


Monday, April 09, 2018

Pasta for weight loss

This paper hit T'internet recently and has been cited all over the place:

Effect of pasta in the context of low-glycaemic index dietary patterns on body weight and markers of adiposity: a systematic review and meta-analysis of randomised controlled trials in adults

Obviously the sole claim to fame for the paper is the conflict of interest statement. I've greyed it out so no-one is tempted to read it in full, the flavour is all you need:

"Competing interests: All authors have completed the Unified Competing Interest form (available on request from the corresponding author) and declare: LC has worked as a clinical research coordinator at Glycaemic Index Laboratories, Toronto, Ontario, Canada. CWCK has received research support from the Advanced Food Materials Network, Agriculture and Agri-Foods Canada (AAFC), Almond Board of California, American Pistachio Growers, Barilla, California Strawberry Commission, Calorie Control Council, Canadian Institutes of Health Research (CIHR), Canola Council of Canada, International Nut and Dried Fruit Council, International Tree Nut Council Research and Education Foundation, Loblaw Brands Ltd, Pulse Canada, Saskatchewan Pulse Growers and Unilever. He has received in-kind research support from the Almond Board of California, California Walnut Council, American Peanut Council, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (Pepsico), Pristine Gourmet, Kellogg Canada, WhiteWave Foods. He has received travel support and/or honoraria from the American Peanut Council, American Pistachio Growers, Barilla, Bayer, California Walnut Commission, Canola Council of Canada, General Mills, International Tree Nut Council, Loblaw Brands Ltd, Nutrition Foundation of Italy, Oldways Preservation Trust, Orafti, Paramount Farms, Peanut Institute, Pulse Canada, Sabra Dipping Co., Saskatchewan Pulse Growers, Sun-Maid, Tate & Lyle, Unilever and White Wave Foods. He has served on the scientific advisory board for the International Tree Nut Council, McCormick Science Institute, Oldways Preservation Trust, Paramount Farms and Pulse Canada. He is a member of the International Carbohydrate Quality Consortium (ICQC), Executive Board Member of the Diabetes and Nutrition Study Group (DNSG) of the European Association for the Study of Diabetes (EASD), is on the Clinical Practice Guidelines Expert Committee for Nutrition Therapy of the EASD and is a Director of the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. DJAJ has received research grants from Saskatchewan Pulse Growers, the Agricultural Bioproducts Innovation Program through the Pulse Research Network, the Advanced Foods and Material Network, Loblaw Companies Ltd., Unilever, Barilla, the Almond Board of California, Agriculture and Agri-food Canada, Pulse Canada, Kellogg’s Company, Canada, Quaker Oats, Canada, Procter & Gamble Technical Centre Ltd., Bayer Consumer Care, Springfield, NJ, Pepsi/Quaker, International Nut & Dried Fruit (INC), Soy Foods Association of North America, the Coca-Cola Company (investigator initiated, unrestricted grant), Solae, Haine Celestial, the Sanitarium Company, Orafti, the International Tree Nut Council Nutrition Research and Education Foundation, the Peanut Institute, the Canola and Flax Councils of Canada, the Calorie Control Council (CCC), the CIHR, the Canada Foundation for Innovation and the Ontario Research Fund. He has received in-kind supplies for trial as a research support from the Almond Board of California, Walnut Council of California, American Peanut Council, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (Pepsico), Kellogg Canada, and WhiteWave Foods. He has been on the speaker’s panel, served on the scientific advisory board and/or received travel support and/or honoraria from the Almond Board of California, Canadian Agriculture Policy Institute, Loblaw Companies Ltd, the Griffin Hospital (for the development of the NuVal scoring system, the Coca-Cola Company, EPICURE, Danone, Diet Quality Photo Navigation (DQPN), Better Therapeutics (FareWell), Verywell, True Health Initiative, Institute of Food Technologists (IFT), Saskatchewan Pulse Growers, Sanitarium Company, Orafti, the Almond Board of California, the American Peanut Council, the International Tree Nut Council Nutrition Research and Education Foundation, the Peanut Institute, Herbalife International, Pacific Health Laboratories, Nutritional Fundamental for Health, Barilla, Metagenics, Bayer Consumer Care, Unilever Canada and Netherlands, Solae, Kellogg, Quaker Oats, Procter & Gamble, the Coca-Cola Company, the Griffin Hospital, Abbott Laboratories, the Canola Council of Canada, Dean Foods, the California Strawberry Commission, Haine Celestial, PepsiCo, the Alpro Foundation, Pioneer Hi-Bred International, DuPont Nutrition and Health, Spherix Consulting and WhiteWave Foods, the Advanced Foods and Material Network, the Canola and Flax Councils of Canada, the Nutritional Fundamentals for Health, Agri-Culture and Agri-Food Canada, the Canadian Agri-Food Policy Institute, Pulse Canada, the Saskatchewan Pulse Growers, the Soy Foods Association of North America, the Nutrition Foundation of Italy (NFI), Nutra-Source Diagnostics, the McDougall Program, the Toronto Knowledge Translation Group (St. Michael’s Hospital), the Canadian College of Naturopathic Medicine, The Hospital for Sick Children, the Canadian Nutrition Society (CNS), the American Society of Nutrition (ASN), Arizona State University, Paolo Sorbini Foundation and the Institute of Nutrition, Metabolism and Diabetes. He received an honorarium from the United States Department of Agriculture to present the 2013 W.O. Atwater Memorial Lecture. He received the 2013 Award for Excellence in Research from the International Nut and Dried Fruit Council. He received funding and travel support from the Canadian Society of Endocrinology and Metabolism to produce mini cases for the Canadian Diabetes Association (CDA). He is a member of the International Carbohydrate Quality Consortium (ICQC). His wife, ALJ, is a director and partner of Glycemic Index Laboratories, Inc., and his sister received funding through a grant from the St. Michael’s Hospital Foundation to develop a cookbook for one of his studies. JLS has received research support from the Canadian Institutes of health Research (CIHR), Diabetes Canada, PSI Foundation, Banting and Best Diabetes Centre (BBDC), Canadian Nutrition Society (CNS), American Society for Nutrition (ASN), Calorie Control Council, INC International Nut and Dried Fruit Council Foundation, National Dried Fruit Trade Association, The Tate and Lyle Nutritional Research Fund at the University of Toronto, and The Glycemic Control and Cardiovascular Disease in Type 2 Diabetes Fund at the University of Toronto (a fund established by the Alberta Pulse Growers). He has received in-kind research support from the Almond Board of California, California Walnut Commission, American Peanut Council, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (Pepsico), Kellogg Canada, WhiteWave Foods. He has received travel support, speaker fees and/or honoraria from Diabetes Canada, Canadian Nutrition Society (CNS), Mott’s LLP, Dairy Farmers of Canada, Sprim Brasil, WhiteWave Foods, Rippe Lifestyle, mdBriefcase, Alberta Milk, FoodMinds LLC, Memac Ogilvy & Mather LLC, PepsiCo, The Ginger Network LLC, International Sweeteners Association, Nestlé Nutrition Institute, Pulse Canada, Canadian Society for Endocrinology and Metabolism (CSEM), Barilla Centre for Food and Nutrition (BCFN) Foundation, and GI Foundation. He has ad hoc consulting arrangements with Winston & Strawn LLP, Perkins Coie LLP, and Tate & Lyle. He is a member of the European Fruit Juice Association Scientific Expert Panel. He is on the Clinical Practice Guidelines Expert Committees of Diabetes Canada, European Association for the study of Diabetes (EASD), Canadian Cardiovascular Society (CCS), and Canadian Obesity Network. He serves as an unpaid scientific advisor for the Food, Nutrition, and Safety Program (FNSP) and the Technical Committee on Carbohydrates of the International Life Science Institute (ILSI) North America. He is a member of the International Carbohydrate Quality Consortium (ICQC), Executive Board Member of the Diabetes and Nutrition Study Group (DNSG) of the EASD, and Director of the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. His wife is an employee of Unilever Canada. No competing interests were declared by CRB, SBM and LAL".

Quite what is wrong with CRB, SBM and LAL that they have no competing interest to declare is not specified.

So. This a BMJ publication. The critical aspect to me is the publication date.

Was it April the first?

Well. It should have been, except April the first this year was Easter Sunday. Not even at BMJ do they hit the "publish" button on a Sunday morning. Easter Monday appears fair game and someone at BMJ appears to have been at work to hit said publish button on April the 2nd.

Ah, the twists of fate produced by the lunacy of the movement of Easter through the calendar.

I think someone at the BMJ may have a sense of humour. Reading the conflict of interest statement, I wonder if the authors do too and whether there was some collusion in the choice of publication date.

Otherwise it's not funny.


Wednesday, March 21, 2018

Guddling in the dark for a respiratory quotient

Here's a paradox: How can two groups of mice, on exactly the same chow, have different 24h averaged RQs, p less than 0.05?

It's from here if anyone wants to peek at the methods. Two sets of animals on the same chow. It's 9F 5020, 21% of calories from fat (7% of calories from PUFA) and 55% from carbohydrate.

At all time points the SC-VIS mice have an higher RQ, ie are oxidising more glucose, than the SHAM mice. But they are all fed the same chow, which should average out at the same overall RQ.

Clearly you can increase the RQ, even above 1.0, during de novo lipogenesis, especially when hungry mice suddenly eat carbohydrate. But there is either a payback during the sleep phase where RQ falls below the food derived RQ while that carbohydrate-derived fat is oxidised or there can be no fall in that fasting RQ if the DNL generated fat is "lost" in to adipocytes and stays there, ie under weight gain. Of course simply sequestering dietary fat in to adipocytes will generate an RQ more typical of glucose oxidation because less fat is being oxidised, full stop, during weight gain.

During on-going fat loss the extra low RQ from adipose derived fat oxidation does not have to be payed back either. "Food" of very low RQ, has been supplied from adipocytes. It's gone out of the body as CO2 and water.

But the black square mice are weight stable or actually losing adipose weight (ie should have an extra low RQ) at the time these RQs were measured, while the open diamond mice are actively gaining weight (including adipose tissue), so should have that higher RQ.

Food intakes are describes as "no significant difference" between the groups, despite the differential weight shifts.

To me this is inexplicable and should have been discussed in the paper. My feeling is the CLAMS equipment is generating a totally illogical result.

Unless I've totally missed something. I would really like to know whether I have totally missed something.

Just on general principles of substrate oxidation, never mind what they have done to the mice.......


Sunday, March 18, 2018

Eating lots of meat and nothing much else

Wooo has posted a couple of times about Dr Shawn Baker who eats an all meat, very high protein diet, maybe over 400g/d protein intake. His HbA1c is reported as 6.3%. Personally I have absolutely no interest in this style of eating but the underlying mechanism is obviously interesting.

How about this for a hypothetical marked protein ingestion scenario:

A person eats a lot of meat. In response to the insulinogenic amino acids present they secrete insulin. This will be amino acid specific, I’ve not looked in to how amino acids trigger insulin secretion in detail but it will NOT be through pancreatic glucokinase and subsequent glucose metabolism, as is the case for glucose triggered insulin secretion. So they secrete post prandial insulin but not using glucokinase. The insulin will be exactly in balance with the glucagon for that specific protein meal.

The expression of the gene for generating pancreatic glucokinase is controlled by the carbohydrate content of the diet. Glucose means glucokinase is required. All amino acid diet, no glucose, down-regulate glucokinase.

So, as glucose is subsequently and gradually produced from gluconeogenic amino acids and then released from the liver over several hours (in the presence of only basal insulin), there is only a mild glucose derived stimulus to trigger insulin secretion, and this slow release of glucose by the liver also provides only a minimal drive to express the gene for pancreatic glucokinase. Also hepatic glucose output shouldn’t trigger any of the gut derived insulin secretion potentiating hormones (GLP-1 and the like).

So pancreatic glucokinase is mothballed. Modest glucose release from protein metabolism won’t trigger insulin secretion without the glucose sensor. End result is low insulin with moderately elevated glucose, especially during the time protein is being processed. Which I'd guess is pretty well all of the time on greater than 300g/d. How high should glucose go? High enough to allow a slow trickle to be taken up by constitutive transporters and so deal with hepatic glucose output in this way, without insulin facilitated augmentation. Facilitated by exercise if you like that sort of thing.

How toxic is glucose in the absence of hyperinsulinaemia, given that HbA1c over 6%? Dr Baker will let us know over the next 15 years!

Of course exactly the same happens on LCHF eating, just fat does not provoke chronic glucose release from its metabolism outside of a little glycerol derived gluconeogenesis… It probably happens too in some of the weird sucrose based weight loss diets where the mice (it's mostly mice but we all know that you can do "carbosis" in humans too) are hypoinsulinaemic (otherwise they would be fat!) but glucose intolerant. A diet based on a non-insulinogenic sugar (fructose) and its palmitate derivative will mothball pancreatic glucokinase too.


Friday, March 16, 2018

On phosphorylating AKT in GHrKO Laron mice

OK. I started this whole adipocyte thread because I was interested in the longevity effect in the GHrKO mouse, the Laron mouse. These posts get written because I am compelled to, I have no choice in it. I never know where they are going to end up as they start. This one has involved a lot of looking at the various types of adipocytes and how they function in normal physiology and what happened when transplanted to more unusual places. Much of it makes sense, and it does put a very different perspective on the roles of visceral and subcutaneous adipose tissue. What I was looking for was what might be special about Laron dwarf mouse derived adipocytes. You can't quite find all of the answers you want to because not all of the questions have really been asked directly, but I think you can get close. I think this is going to be the last post in the series, a relief to me, and possibly to readers too.

Laron mice (GHrKO) are the longest lifespan mice ever engineered by humans. They are dwarf and obese and the obesity tends to be central. They have exquisitely low blood insulin levels and it is thought that the reduced signalling through the GH/IGF-1/insulin system is responsible for their longevity. Adding GHrKO adipocytes to the abdomen of normal mice improves their glucose tolerance significantly.

The role of transplanted visceral fat from the long-lived growth hormone receptor knockout mice on insulin signaling

N-S mice are normal mice with a sham implantation which adds no extra adipose tissue, N-N are normal mice receiving extra intra-abdominal adipose tissue from normal mice (these should really have had some enhanced glucose tolerance but all of these transplant models differ slightly in technique) and in this case the GTT was done at about eight days post op, ie there may well have been a lot of healing derived IL-6 visiting the liver. The N-GHrKO mice are Bl/6 mice which have received adiopcytes from GHrKO dwarves, shown as black squares:

The GHrKO adipocytes are clearly a bit more effective than the normal eWAT adipocytes from the last post. Personally, I was surprised at how relatively small the enhancement of the glucose tolerance was, but then there is always that IL-6 to overcome, so perhaps they really are Super Adipocytes.

GHrKO mice develop extremely elevated GH levels, probably through a total lack of IGF-1 negative feedback, but this GH does nothing. Without a receptor the GH, functionally, isn't there. The lack of GH induced lipolysis pushes the balance of adipocyte size towards the obese phenotype. It seems to affect pretty well all adipose depots fairly equally. If we then go on to look at adipose specific FaGHrKO mice, these are obese too but lack any of the insulin sensitising effects of the whole body GHrKO mice:

The Role of GH in Adipose Tissue: Lessons from Adipose-Specific GH Receptor Gene-Disrupted Mice

"Surprisingly, FaGHRKOs shared only a few characteristics with global GHR−/− mice. Like the GHR−/− mice, FaGHRKO mice are obese with increased total body fat and increased adipocyte size. However, FaGHRKO mice have increases in all adipose depots with no improvements in measures of glucose homeostasis".

My assumption that lack it is the of growth hormone signalling in adipocytes which promotes obesity may not be the whole explanation. It is also true that these FaGHrKO adipocytes, which are possibly very insulin sensitive, are working in a mouse with normal insulin signalling outside of those KO adipocytes. This means that the mice will have normal levels of systemic insulin sensitivity/resistance. Putting calories anywhere other than their special adipocytes will have the potential to induce insulin resistance and any increase in insulin to deal with this will undoubtedly put more triglyceride in to the insulin hyper-sensitive FaGHrKO adipocytes.

So much for GH.

The second effect in whole body GHrKO mice is that there is essentially no IGF-1 produced either by the liver or as a local tissue hormone in response the "invisible" GH. This is not the case in FaGHrKO mice, their adipocytes may never see GH but they see plenty of IGF-1 which is coming from the perfectly normal GH sensitive liver of the recipient mouse. So is it a lack of IGF-1 signalling which underlies the insulin sensitising effect of GHrKO mice?

"Maybe" is the definitive answer and "probably" the more borderline answer... I guess "dunno" still has to rate pretty well too.

If you disrupt the IGF-1 receptor of cell lines in tissue culture post-developmentally (using siRNAs) or if you study genetically IGF-1 knockout foetal derived fibroblasts, they all show marked increases in insulin signalling, which is inducible by the siRNAs when these are used. I've stuck the studies down at the end of the post. Note that none of the studies used adipocytes, but the effect appears generic to pretty well all cell lines tested.

Now, this is either receptor suppression or a receptor absence being used to generate this effect in all of the studies I've found. It has nothing to do with IGF-1 signalling, ie it's not a metabolic effect, it mostly seems to be that IGF-1 receptors associate with insulin receptors and stop them working as well as they can do. So it doesn't appear a loss of ligand induced signalling effect (though obviously there is no signalling if there is no receptor), it's the physical lack of IGF-1 receptors which causes the effect. Clearly GHrKO mice do have IGF-1 receptors, they just never manufacture any IGF-1 to stimulate them. Do these unused receptors have the effect of suppressing long term insulin signalling? I suppose it is possible that permanent, lifelong, severe elimination of all IGF-1 exposure might actually down-regulate IGF-1 receptor gene expression, so allow insulin receptors to work more effectively. We'd need an IGF-1 receptor count to be done on some true GHrKO Laron mice to find out if this is the case. The study hasn't been done that I can find but, if IGF-1 receptor genes are mothballed in GHrKO mice, this would provide a complete explanation of the Laron insulin sensitivity effect and the rest of this post is irrelevant. Just in-case it's not so, here is the rest of the post. It is very, very speculative. And might be wrong:

There is just one paper which suggests that setting up a near-complete cessation of IGF-1 exposure, with normal IGF-1 receptor genes still present, at around 10 days of age (mice again) has a long term effect to enhance insulin receptor gene expression. To emphasise: these mice have the IGF-1 receptor gene (so they should be making IGF-1 receptors), just minimal IGF-1 exposure, rather like the Laron mice. Inducing this state very early in life appears to be key for sensitising to insulin signalling.

IGF-1 Regulates Vertebral Bone Aging Through Sex-Specific and Time-Dependent Mechanisms

"Within 3 months of a loss of IGF-1, there was a 2.2-fold increase in insulin receptor expression within the vertebral bones of our female mice, suggesting that local signaling may compensate for the loss of circulating IGF-1".

The ad hoc hypothesis in this last paper is that insulin signalling increases to meet metabolic needs, despite there still being IFG-1 receptors present to potentially interfere with insulin receptor function. This is the suggestion that makes me think that total loss of IGF-1 signalling, with genetically preserved IGF-1 receptor genes (but which no longer get expressed), might underlie the Laron GHrKO mouse insulin sensitivity effect. It's not just in adipose tissue, it's whole body. Everything becomes insulin sensitive and the level of insulin needed to maintain normoglycaemia plummets. Low insulin signalling = long life.

You then have to ask why this might happen if we are looking for a metabolic effect in excess of insulin receptor function modification.

IGF-1, in addition to it's anabolic role, also facilitates glucose ingress, much as insulin does. We know that this is the case from a number of studies including those involving humans with defective insulin receptors (Donohue Syndrome or Leprechaunism) or in severe lipodystrophy (such as Berardeinelli-Seip Syndrome) where IGF-1 facilitates glucose uptake clinically. This would allow tonic insulin-independent uptake of glucose to generate NADH for activation of the glycerophosphate shuttle (mtG3Pdh) and set bias for reducing the CoQ couple.

Overlaid above this we have genuine insulin signalling, used to facilitate closely controlled caloric ingress and glycolytic NADH generation for CoQ couple reduction. Only small amounts of insulin would be needed in excess of IGF-1 delivered glucose to allow enough extra ingress to instigate insulin signalling. Under caloric excess smaller than anticipated amounts of insulin would be need to induce insulin resistance promptly because there is the background IGF-1 facilitated glucose ingress.

Without the tonic IGF-1 facilitated glucose supply all glucose would have to come via insulin signalling. Insulin would find each cell calorically "emptier" of glucose than it would be had IGF-1 been signalling. With an enhanced extracellular to intracellular glucose gradient more glucose should enter the cell per GLUT4 translocated. In the post prandial state all glucose entry would be via insulin alone. There would be much less need to activate insulin-induced insulin resistance, or at least it would be significantly delayed, in the process of controlling caloric ingress. Much of the time insulin could be allowed to signal and that signalling would still merely supply cellular needs without needing to induce any insulin resistance for negative feedback.

You could describe the whole body lack of an IGF-1 background glucose supply as making all cells chronically "hungry", so improving both insulin signalling and glucose ingress per unit insulin signalling enacted.

This apparent  chronic hunger due to lack of IGF-1 signalling might be where the longevity effect come from and might be why genuine caloric restriction of GHrKO mice does not add to their already considerable lifespan.

That's how it looks to me.

I'd sort of hoped that would be it for this thread but certain adipocyte transplant studies keep niggling at the back of my mind. I'm trying to ignore them.


Here are those IGF-1 receptor disruption/deletion studies:

Down-regulation of Type I Insulin-like Growth Factor Receptor Increases Sensitivity of Breast Cancer Cells to Insulin

"We used small interfering RNA (siRNA) to specifically target down- regulation of IGF1R and found that IGF1R was efficiently suppressed without affecting IR expression. However, IGF1R down-regulation by siRNA sensitized cells to insulin. Our results suggest that specific targeting of IGF1R alone enhances insulin signaling, which may be an undesirable effect in breast cancer cells".

Disruption of the Insulin-like Growth Factor Type 1 Receptor in Osteoblasts Enhances Insulin Signaling and Action

"A striking observation from our studies was the increase in insulin responsivity in osteoblasts following deletion of the IGF-1R".

Insulin Receptor (IR) Pathway Hyperactivity in IGF-IR Null Cells and Suppression of Downstream Growth Signaling Using the Dual IGF-IR/IR Inhibitor, BMS-754807

"The insulin receptor (IR) pathway in IGF-IR null MEFs was hypersensitive to insulin ligand stimulation resulting in greater AKT phosphorylation than in wt or het MEFs stimulated with the same ligand".

Differential Roles of the Insulin and Insulin-like Growth Factor-I (IGF-I) Receptors in Response to Insulin and IGF-I

"In IGFRKO cells, insulin-induced phosphorylation of IRS-1 was enhanced, suggesting that IGFR may actually inhibit IR signaling to some extent".

Sunday, March 11, 2018

On phosphorylating AKT: the penultimate half post

I'm going to use some of Konrad's data to try and understand Kahn's data and the see if it will extrapolate to growth hormone receptor knockout (GHrKO) adipoctes. That's the plan. Time will tell... I'm going to use the term eWAT for epididymal adipose tissue.

There are three curves here from Konrad.

The open circles are mice with extra eWAT carefully added to a mesenteric (liver draining) site only. The eWAT is inflamed, leaking IL-6 and this goes directly to the liver. This IL-6 is causing hepatic insulin resistance with glucose intolerance, as per the last post. There is no elevation of portal FFAs after a three hour fast (not surprising when you recall that you need seriously low insulin levels to access visceral fat, three hours won't hack it). So we can ignore the open circles.

The black circles are the controls.

The grey circles are mice with eWAT (this is normal eWAT from normal sacrificed Bl/6 mice) added to the peritoneum with all of its venous drainage going to the systemic circulation. This too is leaking IL-6 but by the time it's diluted throughout the whole systemic circulation it causes no insulin resistance. Result: adding eWAT without hitting the liver with IL-6 simply provides extra adipocytes, they accept glucose, glucose tolerance test results improve. This is a generic effect of adding extra adipose tissue, it doesn't seem to matter what the source of adipose tissue is or where you put it, so long as it isn't trickling IL-6 in to the liver, any extra fat improves glucose tolerance. Think thiazolidines, more new fat cells, they're empty, glucose tolerance improves as the cells fill up.

Here is a graph from Kahn; the effect of extra fat, when it isn't dumping IL-6 directly to the liver, is always to improve insulin sensitivity, even adding eWAT to mesentery, here called VIS-VIS:

Clearly only subcuticular fat transplanted to the mesenteric site reaches statistical significant (SC-VIS). But you can see the trend...

This is the exact converse of the diabetes of lipodystrophy cases: in lipodydtrophy there is no adipose anywhere, nowhere to put glucose/fatty acids, all stored triglyceride is ectopic, so your end result is severe glucose intolerance.

Now to look at basal lipolysis from Masternak and Bartke's group. This is an in-vitro measurement, performed on aliquots of adipose tissue in Dulbecco’s modified Eagle medium with or without 10% FBS (foetal bovine serum) where they started looking at lipolysis from GHrKO adipocytes, harvested from congenitally Laron dwarf mice. I'm guessing the 10% FBS made no difference because this is the only figure we get in the supplemental data:

Now, you have to be very careful with this data. Basal lipolysis is not the same as lipolysis under fasting levels of insulin. Basal lipolysis would produce a ketoacidotic fatality because no insulin is obviously the equivalent of severe T1DM and is rapidly fatal without a very expensive trip to A and E (unless you have the NHS). Next we have the problem that this lipolysis measurement is made per gram of tissue, but in the whole animal some tissue depots are bigger than others as a % of bodyweight and all GHrKO mice are obese, so they have much more fat to provide FFAs per unit muscle etc. The approximate total fat mass of a GHrKO dwarf mouse is actually very similar to that of a normal Bl/6 mouse, it's only the fat free mass which is small. So glycerol release per gram of adipose tissue may be lower in the dwarf mice, but total lipolysis might be very similar to Bl/6 mice. Merely adding basal insulin would produce a normal, hungry mouse but we have no idea what the rates of lipolysis would be then and if they might change more in some tissues than others. So a little caution, to say the least, is needed.

With that said I was going to go on to say all sorts of things about lipolysis but at this point the penny dropped, as we say in the UK. I've stopped following the trail and I think I know why GHrKO mice are the longest living mice ever engineered. Perhaps I should put that in to a final post in the series.


Thursday, March 08, 2018

On phosphorylating AKT: Interleukin-6 and a tale of two (or three) studies

I've spent the last few days looking in great detail at this next paper. Mostly I'm interested in the effect of subcutaneous fat transplanted to the omentum/mesentery. It does Good Things, the title says it all. I'll probably post more about it soon:

Beneficial Effects of Subcutaneous Fat Transplantation on Metabolism

Even transplanting supplemetary monstrousvisceralfat to the omentum/mesentery of recipient mice improves their insulin sensitivity (admittedly ns). I like this research group. They are reporting data and don't seem to have a specific point they are trying to prove. The down side is that I think their CLAMS equipment, core to understanding certain aspects, didn't work very well. You can tell they feel the same way by the turns of phrase they use to describe some of their utterly inexplicable peripheral data like RQs. I'll call it the Kahn paper.

This next paper has Konrad as senior author. He has an agenda. Just click on the author to see his other publications. He knows monstrousvisceralfat is evil. He just needs the correct model to show this. This one hit paydirt:

The Portal Theory Supported by Venous Drainage–Selective Fat Transplantation

OK, let's compare.

Kahn's group transplanted epididymal fat in to the mesentery and omentum of recipient mice, this drains to the liver directly. By their surgical technique some of this fat will have also had systemic drainage. They waited for 12 weeks. They then ran an hyperinsulinaemic euglycaemic clamp. There was a modest (ns) improvement in insulin sensitivity. They checked the histology for macrophages, there were a few. They checked these for IL-6 production, it was minimal. Happy fat, happy mice, no hepatic insulin resistance.

Konrad's group also transplanted epididymal fat in to the mesentery of recipient mice. They waited for five weeks then did a clamp and showed marked hepatic insulin resistance. There was no increase in portal FFAs or liver triglycerides. They stained the fat for macrophages. There were loads. They checked for IL-6 production. There was loads. They did it all again but with IL-6 knockout mice. Minimal macrophages in the adipose tissue, obviously no IL-6, no insulin resistance in the liver.

To Konrad it's cut and dried. Visceral adipocytes cause hepatic insulin resistance using IL-6.

Kahn's group check for this and found nothing of the sort. What's going on?

It took me about 12 seconds on google to pull up this abstract. It's not terribly important but does bring home the functions of IL-6, there are many:

Essential involvement of IL-6 in the skin wound-healing process as evidenced by delayed wound healing in IL-6-deficient mice

IL-6 is deeply involved in wound healing. Obviously IL-6 does cause insulin resistance, we know from Konrad's study. And we know that all of Konrad's implants were inflamed and secreting IL-6 at the end of the study, five weeks after the surgery. Was that because visceral adipocytes are just evil and want to kill us with IL-6 or is it because the healing process after transplantation uses IL-6 and is incomplete at five weeks? What if they had waited another whole seven weeks before testing at 12weeks?

In Kahn's paper the beneficial effect of adipose transplantation showed best for SC fat placed in the mesentery/omentum. The benefits started to show in bodyweight and fat percentage at eight weeks and were more obvious at 12 weeks post op. The hyperinsulinaemic clamp at 12 weeks showed insulin sensitivity was improved, p less than 0.05 in this group. The visceral to mesenteric transplants were similar but not as marked, mostly p stayed above 0.05.

Kahn's paper was 2008. Konrad's was 2011. Who to believe? Who might have read whom and worked out a counter study? Perhaps the matter has now been pretty well settled by the surgeons mentioned in the last post (Oregon excepted)?

I think it is quite likely that over-distended adipocytes do produce IL-6. But you're not going to show this in normal mice eating normal chow.

Clinical aside. If a case with pancreatitis, underlying an acute abdomen, ends up as an ex-lap, you get to see the state of the omentum and mesenteric fat under necrotising pancreatitis conditions. It's not pretty. In view of IL-6 and insulin resistance it should come as no surprise that acute pancreatitis is associated with diabetes, which resolves as the pancreatitis does, assuming a good outcome. Not always, but it's well recognised. I think IL-6 as a cause of hepatic insulin resistance is very real. I also think it is total artefact in Konrad's paper but, if it could be made to happen as a direct result of severe obesity (about which we have no idea from Konrad's paper), I might consider it to be a messenger. Looks like this hadn't happened in the morbidly obese folks going under the knife.

I found a mini-review by that one group of successful omentectomy surgeons in Oregon, listing all of the omentectomy studies which have failed to improve insulin sensitivity (no explanation was offered), in which there is actually one very small study mentioned in which an omentectomy only was performed, removing just under a kilo of omental fat on average. That's a lot of omental fat in my book. Not only that, but the subjects were all obese and diabetic. I mean, visceral fat, hepatically drained, distended adipocytes, insulin resistance. How could an omentectomy fail? Spectacularly is the word and the authors say so point blank. I'd already decided I like these omentectomy-only surgeons before I found that three of them are part of Atkins Center of Excellence in Obesity Medicine. They might just share my biases!


Anyone wanting that last paper, it's here:

Surgical removal of omental fat does not improve insulin sensitivity and cardiovascular risk factors in obese adults

I particularly like the rise in HbA1c, statistically ns but clinically perhaps so...

Sunday, March 04, 2018

On phosphorylation of AKT in real, live humans. They're just like mice!

This first paper is very neat. They enrolled study subjects who were scheduled for an elective laparotomy and persuaded them to consent to an IV bolus of insulin during surgery and to allow biopsies of SC fat and omental fat to be taken at the 6 minute mark and at the 30 minute mark after this bolus. They were given some IV glucose to keep them alive after the insulin. Omental fat is possibly the most visceral of visceral fat depots, probably similar to mesenteric fat. Here's the paper:

Insulin Signaling in Human Visceral and Subcutaneous Adipose Tissue In Vivo

This is what they found. The black squares are the omental fat:

The x axis is non linear. Insulin signaling kicks in much faster in visceral adipocytes and is more effective at activating the whole signaling cascade (phosphorylation of AKT included) than it is in subcutaneous adipocytes. As the authors comment:

"We show that visceral fat is characterized by higher expression levels of specific insulin signaling proteins and more pronounced and earlier activation of the insulin receptor, Akt, glycogen synthase kinase (GSK)-3, and ERK-1/2 in response to insulin".

EDIT: Just look at those basal relative IR phosphorylation levels, visceral adipocytes have four times the insulin signaling as subcutaneous adipocytes after an overnight pre-surgical fast. I love this paper. END EDIT.

I think that it is unarguable that visceral adipocytes are more insulin sensitive than subcutaneous adipocytes.

Just to confirm that bias, this next paper is looking at glucose uptake in volunteers, using all sorts of clever non-invasive techniques. And some of those volunteers were obese. I think it's very clear that visceral fat, under hyperinsulinaemic euglycaemic clamp conditions, is more insulin sensitive than subcutaneous fat. Any visceral fat, any subcutaneous fat, any bodyweight of owner. From this paper

Glucose uptake and perfusion in subcutaneous and visceral adipose tissue during insulin stimulation in nonobese and obese humans

we have this:

First and 4th pairs of columns are SC adipose tissue, 2nd and 3rd are visceral. Even in obese subjects the glucose uptake by visceral fat, under clamp conditions, is higher than in SC adipose tissue. Lots of significant p values.

Now the flip side, rather more speculative here: let's revisit this paper from several years ago, looking at healthy humans under hypoinsulinaemic states:

Prolonged Fasting Identifies Skeletal Muscle Mitochondrial Dysfunction as Consequence Rather Than Cause of Human Insulin Resistance

Ignore the mindset of the researchers, just look at their data:

In a normally fed Dutchman the fasting FFAs are around 0.2mmol/l at some time in the morning. This is the amount of FFAs being released under a plasma insulin of about 13.0microU/ml. At this level of insulin I very much doubt if any of these FFAs are coming from visceral adipocytes because insulin is still too high for this. This a workaday "ready for breakfast" sort of a combination of FFAs and insulin. I think it is very reasonable to consider that these FFAs are coming primarily from the subcutaneous adipose stores.

By 36 hours of fasting insulin has dropped to around 7.0microU/ml and it stays there. At this level of insulin we have FFAs rising through 1.0mmol/l to 2.0mmol/l, that's very high. Insulin is now very low, low enough for visceral fat to release a lot of FFAs and the body is set up to run on fat and ketones. It could do with some hepatic insulin resistance to facilitate hepatic glucose output and the specifically portal vein draining fat depots (omental and mesenteric) are set up to do exactly this. Evolution has punished, by non survival, individuals who failed to follow this pattern.

I think it is a pretty sound case that visceral fat does very little, other than hoover up a few calories, while ever insulin is above 12microU/ml. In the USA insulin probably never falls below this level. If you have to get up at 2am for a few bagels, doughnuts or a bucket of (low fat/high sugar) ice cream your body will forget what an insulin of 12microU/ml ever felt like.

Visceral fat is a surrogate for chronic hyperinsulinaemia. It will be associated with metabolic syndrome because hyperinsulinaemia, not visceral fat, is metabolic syndrome. Given that nice, clear cut, pretty water tight case, what should a bariatric surgeon do about omental fat?

Why not chop it out? I mean its full of fat. All people who have metabolic syndrome have tons of the stuff. Really, it has to be the root of all evil. You know, fat... But:

Hepatic and Peripheral Insulin Sensitivity and Diabetes Remission at 1 Month After Roux-en-Y Gastric Bypass Surgery in Patients Randomized to Omentectomy

"Peripheral insulin sensitivity did not improve 1 month after RYGB, irrespective of omentectomy, diabetes, or diabetes remission. Hepatic insulin sensitivity improved at 1 month after RYGB and was more pronounced in patients with diabetes..." [but not associated with omentectomy, my addition]

Potential Additional Effect of Omentectomy on Metabolic Syndrome, Acute-Phase Reactants, and Inflammatory Mediators in Grade III Obese Patients Undergoing Laparoscopic Roux-en-Y Gastric Bypass

"Omentectomy does not have an ancillary short-term significant impact on the components of metabolic syndrome and does not induce important changes in the inflammatory mediators in patients undergoing LRYGB. Operative time is more prolonged when omentectomy is performed".

A prospective randomized study comparing patients with morbid obesity submitted to sleeve gastrectomy with or without omentectomy

"The theoretical advantages of omentectomy in regard to weight loss and obesity-related abnormalities are not confirmed in this prospective study. Furthermore, omentectomy does not induce important changes in the inflammatory status in patients undergoing SG".

These people got paydirt:

Omentectomy added to Roux-en-Y gastric bypass surgery: A randomized, controlled trial

"Omentectomy added to a LRYGB results in favorable changes in glucose homeostasis, lipid levels, and adipokine profile at 90-days"

but the changes were small and didn't look particularly clinically significant to me. But then, I am very biased. Better hope this last group aren't effective medical politicos!

Bottom line: Visceral fat does not cause metabolic syndrome. Association is not causation. Omentectomy is no panacea (no sniggering at the back there) unless you come from Oregon, with apologies to more sensible folks from Oregon.


Saturday, March 03, 2018

On phosphorylating AKT in visceral adipocytes under starvation

I was hoping to ignore the CR mice in the paper

Differential response to caloric restriction of retroperitoneal, epididymal, and subcutaneous adipose tissue depots in rats

but I don't think I can do it. OK, here we go.

Below are the same images as in the last post showing phosphorylation of AKT as a marker of insulin signalling. The fed CR mice have an insulin level of 1787.84pg/ml, pretty much the same as the fed AL mice (1549.76pg/ml).

Let's look at subcutaneous adipocytes (sWAT) first.

The fed level of plasma insulin is supporting twice the level of insulin signalling in the sWAT from a starving mouse as it is in an ad lib mouse. An adipocyte from a starving mouse  is more insulin sensitive than one from a plump mouse. Not unexpected and clearly the adipocytes are small and desperate to have more fat.

In the fasted state the plasma insulin is much lower in the CR mice (224.56pg/ml) vs fasting AL mice (477.25pg/ml) and this low insulin level supports the same degree of signalling in the fasted CR mice as the higher value in the plump but fasted mice. Again CR adipocytes are more insulin sensitive.

Next is the situation in retroperitoneal visceral fat (rWAT). Any value of plasma insulin between the AL fasted of 477.25pg/ml and somewhere around 1500pg/ml of either AL-fed or CR-fed state gives very similar levels of insulin signalling. Maybe a little higher in the recently fed CR mice:

But when we get down to the CR fasting insulin level of 224.56pg/ml we actually have significantly reduced insulin signalling in the visceral adipocytes of starving mice. A drop in insulin signalling is synonymous with increased lipolysis in adipocytes. Accessing visceral fat really does happen, but only at very low insulin levels.

Does this show in fat depot size? Not really. The fall in subcutaneous fat volume is there but the fall in retroperitoneal fat is minimal. Bear in mind these guys are dissecting out very small tissue depots. If you look at the histology/computer image analysis derived values for adipocyte size you can see that the CR visceral adipocytes do really shrink and this might even achieve statistical significance. It's the two columns at the right we're looking at:

Pretty much the same thing happens  in the subcutaneous adipocytes but we get no asterisks for the changes here. It's possible the visceral adipocytes might shrink more than the subcutaneous adipocytes, if you are hungry enough:

So I think it is reasonable to assume that lipolysis in visceral adipocytes becomes real at plasma insulin levels somewhere between 477.25pg/ml and 224.56pg/ml. To achieve this in a mouse needs a combination of long term caloric restriction plus total fasting for about 24 hours. At this plasma insulin level it is even possible that their rate of lipolysis exceeds that of subcutaneous adipocytes but that might be stretching the data even further than I have done already. Under normal mouse husbandry conditions visceral adipose tissue is there to stay. It won't release FFAs unless the adipocytes get so large that they leak some FFAs in the presence of insulin signalling.....

OK, I'll try to leave those poor starving mice alone now.


Friday, March 02, 2018

On phosphorylating AKT within visceral fat

I've been thinking quite a lot about the difference between subcutaneous adipocytes and visceral adipocytes. The difference appears to be much deeper than location, though that matters. The next paper is one of those terribly clever research projects where enormous amounts of information is accumulated but little integration or understanding seems to take place. Here it is:

Differential response to caloric restriction of retroperitoneal, epididymal, and subcutaneous adipose tissue depots in rats

One problem is that they are trying to do too much, so just ignore any of the bits about caloric restriction (CR) which creep in to the butchered graphs. All I'm really interested in is ad-lib (AL in the graphs) fed mice and their adipocytes. I want to know about normal insulin signalling. Here are the fed and fasted insulin levels from those mice. Fed on the left, fasted on the right, part of Table 1:

The dollar signs denote statistical significance (not paydirt). Next are excerpts from Figure 5. I've cropped out the bar graphs showing the pAKT levels from fed and fasted mice. The group is using pAKT as a good marker of insulin signalling. First here's the SC (sWAT) graph:

We only need to look at the AL group. There is a fed insulin of 1549.76pg/ml supporting the reference level of insulin signalling. Next to it we have the fasted level of insulin signalling, somewhere around half reference value. This is being supported by a plasma insulin level of 477.25pg/ml. Simple. More insulin, more pAKT, more insulin signalling. It seems reasonable to consider that the fed insulin level supports lipid storage in subcutaneous adipocytes and that half this level (fasting) might allow lipolysis. We can ignore the CR group.

Here is the same graph from a sample of retroperitoneal adipocytes:

Here we have, again, the level of insulin signalling supported by a fed state plasma insulin of 1549.76pg/ml as reference and just look at the level of insulin signalling being supported by the fasting insulin level of 477.25pg/ml. It's no different to the fed level of signalling. Hmmmmm.

So, theoretically, most of the fat loss under fasting should come from the subcutaneous adipocytes. We need to go back to Table 1 for that:

There we go, the tissue with the least fasting insulin signalling (sWAT) loses over four times as much lipid as the tissue where insulin signalling is maintained at the lower (fasting, 477.25pg/ml) insulin level (rWAT).

This looks very much like one of the intrinsic differences between subcutaneous adipocytes and visceral adipocytes is that visceral adipocytes maintain insulin signalling at much lower levels of plasma insulin than do subcutaneous adipocytes. You have to store calories which arrive without insulin somewhere. Looks like this is the place!

I'm interested in this because I want to know why VLDLs, released from the liver following lipid overload (from fructose DNL, alcohol DNL or inappropriate FFA release from adipocytes under fructose or alcohol) end up in visceral adipocytes. We know these VLDLs are only released under low insulin levels (that was a long time ago!) and this current paper tells me why the VLDL lipids end up in visceral adipocytes. It's not an address technique, it's just that visceral adipocytes are programmed to store fat under relatively low insulin levels. To get decent lipolysis from visceral fat I suspect that you need really low insulin levels, something a bit like those of ketogenic diets. Well, what do you know...

What is it about the visceral adipocytes that programs this?

Perhaps we should look at IGF-1 for the answer to that one.


EDIT We don't know the absolute level of signaling in either the sWAT or rWAT tissue. Fed is taken as reference and fasted is shown as the percentage change from the fasted state. The reference value may differ between the two depots. Just needs bearing in mind. END EDIT

Thursday, March 01, 2018

Saturated fats vs PUFA in a 5 day human ketosis trial

Just a one-liner (as if!) via mommymd commenting on an old post:

Differential Metabolic Effects of Saturated Versus Polyunsaturated Fats in Ketogenic Diets

I think I worked through this several years ago but didn't have the tools to comment on it at the time. The recall I have is of reading what the high PUFA group ate. Fake bacon, soy nuts, vegetable oil. Lovely. BUT they ended up much more insulin sensitive than the saturated fat group did over 5 days. Higher ketones, lower glucose, lower trigs, higher insulin sensitivity. I had no explanation for this.

Once you appreciate the Protons concept this is exactly what you would expect. There is continued insulin signalling when there should be physiological insulin resistance. While ever adipocyte size is kept low, via the ketogenic nature of the diet, enhanced insulin sensitivity should persist.

The down side is that glucose metabolism will continue. If your approach to life is to stop using glucose as an energy substrate there is absolutely no need to maintain glycolysis in the face of a ketogenic diet. Simply refusing to listen to insulin is my preferred option. Someone running their metabolism of fats should have minimal need for insulin sensitivity and buying insulin sensitivity at the cost of metabolising linoleic acid, with its daughters 4-HNE and 13-HODE, is not something which appeals to me. But be aware of the study and the joy it will give to the saturophobes...