Update

Lots of posts part written but currently I'm getting camping gear ready for our family holiday with kayaks, hills and tents. At the same time the essential big car is in the garage getting it's rear differential fixed/replaced and I'm not sure we would all fit into the MX5...

Normal service will be resumed when I get some time!

Peter

Nourish Balance Thrive Podcast

I had a chat with Megan Hall of Nourish Balance Thrive. I feel it went quite well and I got most of the core ideas of the Protons/ROS hypothesis over in a relatively concise manner. The microphone continues to work:

Here it is on Apple Podcasts

The True Cause of Insulin Resistance and Obesity (and What To Do Instead)

and on the NBT website

The True Cause of Insulin Resistance and Obesity (and What To Do Instead)

Peter

Jay Bhattacharya in conversation with Lord Sumption

This came to me via Ivor and Facebook. I keep struggling with the worry that the current pandemic might be the beginning of the end of western liberal democracy. The interview is not encouraging and Lord Sumption does encapsulate exactly where this feeling I have might be coming from.

A Conversation with Lord Sumption

If anyone is hopeful that we are getting out of this mess anytime soon then they had better not watch it.

Peter

More time wasted on vaccines

My thanks to Jonathan Engler for the tweet. This is HMS Queen Elizabeth.

She has a complement of 1,600 when fully staffed (dirtied my hands in Wikipedia to check that) so 1,400 on board sounds very plausible.  All are fully vaccinated and work under navy orders specifying social distancing, masks and track-n-trace. Those 1,400 people service a set of warplanes with armaments which you would not want to be on the receiving end of.

There are 100 COVID-19 cases so far, no deaths. I wonder if the case numbers might not have peaked yet.

This is the Diamond Princess.

She had a crew of 1045, looking after a passenger list of 2,666 whose demographic included 14 people sufficiently elderly (and I presume diabetic enough) that they died of COVID-19.

So the crew, who continued to service the passengers at some level throughout the infection period, were exposed to SARS-CoV-2 containing aerosols much of the time. 

In this case 145 contracted COVID-19. None died.

Considering that the HMS Queen Elizabeth's COVID-19 count is likely to be incomplete you have to ask yourself what, exactly, has the vaccine achieved?

Then if you look at the UK, which had a decent COVID-19 wave in spring of 2020, a completion of that wave in autumn 2020 and a marked atypical spike in Jan/Feb 2021 coincident with vaccine roll-out, the two summer nadirs are indistinguishable, you could even argue that summer 2020 had a slightly lower 7 day average death rate than we have currently.

Matt Hancock oversaw massive care-home fatalities in the first wave and failed to set up any way of separating COVID-19 patients from the elderly needing hospital treatment during last winter. So many of the people who might die of COVID-19 today are already dead. Another thing which disgusts me. But if this winter turns out to be a standard influenza year, with real influenza, no doubt the vaccines will get the credit.

Finally, I'd missed Peter Doshi's BMJ letter making some pertinent points about the Pfizer initial trial (or should I call it an advertising campaign?)

Peter Doshi: Pfizer and Moderna’s “95% effective” vaccines—we need more details and the raw data

I guess the real question is: Can you develop and market a massively profitable product to the whole world which doesn't actually work?

The pharmaceutical industry did this in slow motion with the biggest blockbuster drugs of all time.

The statins.

Are the vaccines any better? I hope so. Not looking good at the moment.

Peter

Lockdowns Summit

You can register for free on-line access. Donations are optional.

Lockdowns Summit

Someone has to map out a route out of the current political cesspit. I wonder if the press will turn up or report it? Last anti-lockdown demo in London was probably genuinely over half a million people, nothing on the BBC.

Peter

Mongongo nuts

Just recently Raphi had a very interesting and very thought provoking chat with Herman Pontzer.

They touched upon honey and the Hadza but didn't mention mongongo nuts and the !Kung San people.

So I will. I might get back to honey in another post.

Mongongo nuts are a major problem for the ROS hypothesis of obesity.

The !Kung San people live on the edge of the Kalahari Desert, as do mongongo trees. The nuts are freely available, storable and edible cooked or raw. They sound quite nice. They go by several names, Manketti nut is the one used in this paper:

Characterization of Schinziophyton rautanenii (Manketti) nut oil from Namibia rich in conjugated fatty acids and tocopherol

With a linoleic acid content just over 30%, and frequently providing a large proportion of the !Kung San people's calories, they should cause obesity, by the ROS hypothesis. If you read the abstract and look at the commas very carefully it almost suggests that the LA is actually conjugated linoleic acid but absolutely doesn't confirm this in the fine print of the full text. With the locations specified for double bonds at 9 and 12 this really is your normal, common-or-garden LA.

So the !Kung should be obese and/or hungry. And they're not.

How come? Another 30-ish% of the fatty acids in the nuts are from alpha eleostearic acid, a triple double bond isomer of alpha linolenic acid. This really is a conjugated fatty acid with double bonds at 9, 11 and 13. Conjugated means the double bonds alternate with single bonds. For ordinary PUFA there are two single bonds between each double bond.

Alpha eleostearic acid is something of a wonder drug, curing everything from cancer to whatever you fancy. It also is very easily converted (by rats at least) in to conjugated linoleic acid (CLA), presumably by hydrogenating the 13 double bond to give cis-9, trans-11 CLA:

Alpha-eleostearic acid (9Z11E13E-18:3) is quickly converted to conjugated linoleic acid (9Z11E-18:2) in rats

CLA is, undoubtedly, a weight/fat loss drug. I glossed over it when it was reported in this paper

Comparison of dietary conjugated linoleic acid with safflower oil on body composition in obese postmenopausal women with type 2 diabetes mellitus

but it seems to be real as in

Isomer-specific effects of conjugated linoleic acid (CLA) on adiposity and lipid metabolism

The CLA/safflower paper was using 6.4g of mixed CLA isomers per day, on a high linoleic acid background (by definition, the subjects were type 2 diabetics with BMI >30, ie LA intoxicated), and got steady weight loss over 18 weeks from this small supplement.

Eating a 1000kcal portion of mongongo nuts would give around 30g of alpha eleostearic acid to convert to CLA. Subsisting on primarily mongongo nuts might supply twice that. Sixty grams of eleostearic acid being converted to just under 60g of cis-9, trans-11 CLA might be enough to offset the LA content.

The situation for the !Kung San seems quite unique and I can't quite imagine any other nut providing an almost year round supply of high fat calories. Any examples gratefully received. In temperate climates nuts are very seasonal and largely supply linoleic acid.

Peter

Addendum from Tucker via twitter; it's not completely clear how important mongongo nuts really are to the !Kung:

Mongongo: The ethnography of a major wild food resource

however there will always be a roughly 1:1 ratio of LA to CLA precursor when they are consumed, in whatever quantities.

Obesity and diabetes (3) Acipimox

I first went looking for papers on Acipimox in 2014. I had read that it was an inhibitor of lipolysis and I was interested in how much weight gain it caused. Back in those days I was still fairly attached to the most basic of carbohydrate-insulin-models of obesity. If you consider that insulin causes weight gain by the inhibition of lipolysis, giving a non-insulin inhibitor of lipolysis should do the same... Shouldn't it?

Well, no, it doesn't. Acipimox produces a profound fall in free fatty acids and a marked improvement in glucose tolerance. Very, very occasionally I found snippets in discussion fora that it could increase hunger but this was not by any means routine. These give the flavour:

Effect of the Antilipolytic Nicotinic Acid Analogue Acipimox on Whole-Body and Skeletal Muscle Glucose Metabolism in Patients with Non-insulin-dependent Diabetes Mellitus

Effect of a Sustained Reduction in Plasma Free Fatty Acid Concentration on Intramuscular Long-Chain Fatty Acyl-CoAs and Insulin Action in Type 2 Diabetic Patients

Effects on insulin secretion and insulin action of a 48-h reduction of plasma free fatty acids with acipimox in nondiabetic subjects genetically predisposed to type 2 diabetes

All of which sounds very good (unless you are into the CIM of obesity!) and you have to wonder quite why Acipimox has not become standard of care and have largely reversed the current global diabetes pandemic. In fact, a recent 2020 meta-analysis of niacin (the parent compound from which Acipimox is derived) trials suggests we might be remiss in failing to do so:

Effectiveness of niacin supplementation for patients with type 2 diabetes: A meta-analysis of randomized controlled trials

But then you could go on to ask why giving niacin itself  might actually make people with impaired glucose tolerance flip in to frank type two diabetes (amongst other medical catastrophes) with worrying regularity

Effects of extended-release niacin with laropiprant in high-risk patients

Of course you could blame the laropiprant, given to suppress the niacin flushing. Or you could more usefully think about the metabolic consequences of dropping plasma FFAs by using a potent inhibitor of lipolysis.

If we work on the basis that DMT2 is essentially the down stream consequence of the inability of distended adipocytes to limit basal lipolysis, it comes as no surprise that artificially shutting down release of FFAs might improve markers of metabolic health.

The cost would be larger adipocytes.

But this doesn't happen, at least not much. The explanation is contained in this paper from 1992, largely looking at the reasons for the long term failure of Acipimox to control FFA levels:

Effects of prolonged Acipimox treatment on glucose and lipid metabolism and on in vivo insulin sensitivity in patients with non-insulin dependent diabetes mellitus 

It's simple. Making adipocytes retain their lipids increases their size. There is no suggestion that tolerance develops to this. All that happens is that there is a rebound increase in basal lipolysis as the Acipimox wears off. The drug-induced transient fall in FFAs produces a transient decrease in the oversupply of calories from FFAs, so cells should and must adapt to by reducing insulin resistance. Numbers improve at the cost of bigger adipocytes. As soon as the drug wears off the adipocytes, now bigger, reinstate basal lipolysis at their previous high rate plus some extra due to the extra distending effect of Acipimox. As they off-load their extra size by releasing FFAs, the physiological need of other cells in the body to resist insulin is both restored and augmented.

There is no net benefit and all the drug might do, if it does produce any increase in adipocyte size, is to convert IGT people, with some reserve function remaining in their adipocytes, in to very sightly heavier diabetics who have less ability to suppress adipocyte size-induced increased basal lipolysis.

If you are pre diabetic but not glycosuric and you become glycosuric in the periods between Acipimox/niacin doses you will convert from pre-diabetic to diabetic, assuming you use glycosuria as your marker for diabetes.

Peter

Obesity and diabetes (2) Basal lipolysis and weight gain

This is a paper at the "dislike" end of my bias spectrum:

In Vitro Lipolysis is Associated with Whole Body Lipid Oxidation and Weight Gain in Humans

which can be summed up by the first line of the introduction

"Positive energy balance results in greater triglyceride storage in adipose tissue and resultant accumulation of body fat."

which explicitly states that they have the arrow of causation at 180 degrees to the correct direction. So don't expect too much from the paper. I also hate that they omitted to mention in the title that the association with weight gain is negative.

Beyond that the methods are sketchy and the results are limited to a number of model derived correlations subjected, eventually, to multiple unspecified adjustments. So not a lot of hope for the group or for the largely Pima Indian population under their misguided care. But I digress.

Once again adipocyte size is quite tightly correlated with basal lipolysis, like this

which looks quite linear until we convert the log numbers to normal numbers like this

which shows us that basal lipolysis rises progressively sharply with adipocyte size. There is an upper limit to adipocyte size, and this will be set by rising basal lipolysis equaling the obesogenic effect of linoleic acid facilitating the over action of insulin.

They fed the subjects a fixed macro, calorically calculated diet for three days before a day in a metabolic chamber, where they ate three similarly fixed macro/calorie meals.

People turned out to have differing RQs (they use RQ, respiratory quotient, as their term rather than RER, respiratory exchange ratio. My brain works this way too, it's about the only bit of the paper I like, even though RER is probably the correct term) on a fixed macro diet. So clearly something is happening on a fuel partitioning basis.

People who oxidised the most fat in the metabolic chamber were the least likely to gain weight over the following eight or so years. Those oxidising the most carbohydrate were likely to gain the most weight.

Funny that.

I can't see any explanation in the discussion of why that might be.

From the ROS/Protons perspective it is quite clear that people with smaller adipocytes have not finished gaining weight. They are part way to becoming obese because they are consuming LA in combination with an insulogenic diet so are over-storing fat. When they eat a fixed macro/calorie diet they sequester lipid in to adipocytes, fail to retrieve it and run their metabolism on the more accessible carbohydrate. They're probably the most hungry, in my book.

Those with maximum sized adipocytes eat the same fixed macro diet, sequester the same lipids in to their large adipocytes via LA augmentation of insulin's fat storage signal but then go on to release much of that extra stored fat by the increase in basal lipolysis which is associated with trying to further stretch large adipocytes. This supplies continuously elevated FFAs, with subsequent fat oxidation, despite the presence of glucose and insulin at the same time. They should be the least hungry.

What can a cell do when presented with a ton of FFAs and a ton of glucose, both having their uptake facilitated by insulin?

That's right. Resisting insulin is the correct option. That's what the systemic cells do.

The cost shows as elevated glucose in combination with the elevated fat oxidation (eventually FFAs rise measurably but early on the fat oxidation increase precedes the rise in plasma FFAs).

It is metabolic inflexibility encapsulated.

Of course the obvious question is whether that increased fat oxidation, associated with reduced rate of weight gain, is positively associated with insulin resistance. Alongside the reduced weight gain.

From the same institution, back in 1991 and forgotten about during the last 30 years, we have this paper:

Insulin Resistance Associated with Lower Rates of Weight Gain in Pima Indians

Insulin resistance is, indeed, associated with limited weight gain. As you would expect.

Summary overall:

Fat oxidation a major mechanism of insulin resistance. Increased basal lipolysis is a mechanism of both increased fat oxidation and decreased weight gain. Linoleic acid is the mechanism of increased adipocyte size to drive increased basal lipolysis. Some degree of insulin signalling is essential for linoleic acid to drive adipocyte size increase.

Life is logical.

Peter

Extra thoughts: During weight gain, while calories are being lost in to adipocytes, the rest of the body is in caloric deficit. Calories lost to adipocytes must be replaced by extra food. This is the correct arrow of causation. There is insulin sensitivity.

Once adipocyte basal lipolysis equals or occasionally outstrips fat sequestration in to adipocytes, the rest of the body is being provided with supplementary FFAs. It is in caloric surplus. Insulin resistance is then physiologically appropriate.

There is a gradual transition between the two states.

Obesity and diabetes (1)

There is absolutely no doubt in my mind that adipocytes can become insulin resistant. The most convincing paper I've come across is this one

Basal lipolysis, not the degree of insulin resistance, differentiates large from small isolated adipocytes in high-fat fed mice

They took adipose tissue from a group of mice which had been made insulin resistant, and obese, by feeding a high coconut fat/sucrose (ie Surwit-like) diet and extracted a supply of adipocytes. Whether these cells were large or small, provided they had been exposed to Surwit-derived conditions for eight weeks, they were all equally insulin resistant. Big ones and little ones. Size made no difference. Insulin resistance is real but not associated with adipocyte distention.

What they also found was that size of adipocytes was very closely and positively associated with basal lipolysis, that is with the rate of lipolysis in the absence of insulin or sympathomimetic agents.

This is not a new finding. From 1972:

Effect of cell size on lipolysis and antilipolytic action of insulin in human fat cells

I like this paper. I have certain biases, one of the strongest of which is that I like papers in which you are given the concentration of glucose which is used in their cell culture medium. Here they happen to have used 1mmol/l, which might rightly be considered a little low, but at least they tell you. Unlike many papers.

Basal lipolysis correlated well with cell diameter. If basal lipolysis is related to the function of lipid droplet surface proteins this is completely plausible and almost predictable. Here's their graph:

The ability to suppress basal lipolysis using insulin appears to be completely determined by the conditions you use to incubate your cells, higher glucose appears to make insulin more effective on suppressing basal lipolysis, but that's an aside. This current study used a glucose concentration of 1mmol/l and showed absolutely no effect of insulin on basal lipolysis. In fact, as you increase the concentration of insulin from zero through high physiological to gross pharmacological the rate of basal lipolysis actually increases. Like this:

If anyone thinks this might represent insulin induced insulin resistance I might be tempted to agree, though the significance to anything physiological of exposure to 100,000microU/ml of insulin seems somewhat dubious.

They did find that physiological insulin exposure suppressed sympathomimetic induced lipolysis, an effect blunted by a grossly pharmacological overdose of insulin. Again, something confirmatory to my biases:

The take home message is that insulin is not particularly effective at suppressing basal lipolysis and that basal lipolysis increases with adipocyte cell size.

We have certain inter related processes here. Insulin facilitates lipid storage in adipocytes and we know that this function is both normally self limiting via ROS generation and is augmented pathologically by the oxidation of polyunsaturated fatty acids, leading to increased adipocyte size.

As adipocyte size increases the separate process facilitating basal lipolysis progressively increases, which cannot be suppressed by hyperinsulinaemia, certainly not completely.

Above a certain size it becomes almost impossible to suppress free fatty acid release from adipocytes using insulin. Under these circumstances there is a continuous supply of free fatty acids, despite the presence of insulin and a copious supply of post prandial glucose.

At a certain point the processes of augmented lipid storage and increasing basal lipolysis will come in to something approaching equilibrium.

The size of adipocytes at this point will be determined by the level of insulin being generated by the diet, the degree of augmentation of that insulin signalling by linoleic acid and whatever factors influence the rate of rise of basal lipolysis with increasing adipocyte size (currently unclear).

That's assuming a pancreas of steel which can crank out insulin at adequate levels to control glycaemia to non diabetic levels despite an increasingly un-suppressible fatty acid supply.

This will be relatively easy, provided adipocytes remain insulin sensitive. We know from 

Diet fat composition alters membrane phospholipid composition, insulin binding, and glucose metabolism in adipocytes from control and diabetic animals

that it is perfectly possible to have insulin sensitive adipocytes, adipocyte distention and systemic insulin resistance without those adipocytes becoming insulin resistant themselves. Under these circumstances the is ample scope for further weight gain. Provided the pancreas can hypersecrete insulin, glycaemia can stay fairly well controlled as weight increases.

Whatever causes adipocytes to change from insulin sensitive, as in this last paper, to insulin resistant, as in the first paper, will markedly increase the demand for insulin to maintain normoglycaemia. If the pancreas cannot meet this demand or beta cells start to undergo apoptosis secondary to exposure to elevated glucose and free fatty acids in combination, progression to DMT2 occurs where insulin secretion can no longer control glycaemia, let alone FFAs.

With the onset of DMT2 weight gain will stall. It is perfectly possible to facilitate the process of further weight gain (and associated increased basal lipolysis) by continuing to squeeze more insulin out of the pancreas using a sulphonyl urea drug or by the injection of exogenous insulin. Both approaches appear to be favourites with diabetologists once they've started with metformin.

To summarise: Excess insulin sensitivity from linoleic acid, combined with elevated insulin secretion, expands adipocytes. Expanded adipocytes increase basal lipolysis, which is difficult to suppress. With increased basal lipolysis fat oxidation, whole body, increases and induces the normal physiological insulin resistance which occurs via ROS/Protons mechanism. Eventually reduced pancreatic function leads to diabetes primarily via the inability to secrete enough insulin to normalise glucose levels while FFAs are elevated.

There's more to this.

Peter

Metformin (12) You don't need to be SHORT

Metformin is a drug which blunts the action of insulin.

Metformin is the most widely prescribed insulin sensitising agent in the world.

Discuss.

It is quite core to any logical self consistent view of the world that metformin is an agent which blunts insulin signalling, as per the ROS/Protons hypothesis via inhibition of mitochondrial glycerophosphate dehydrogenase.

The first clinical hint that this might be correct was from this study

Metformin paradoxically worsens insulin resistance in SHORT syndrome

discussed in this post.

If you are unlucky enough to be born with with SHORT Syndrome, a genetic defect in the insulin signalling pathway, you need to be hyperinsulinaemic to maintain normoglycaemia, especially during an OGTT. If some joker puts you on to metformin for 4 days then repeats the OGTT the level of insulin needed to maintain normoglycaemia goes from extremely high (690microU/ml, pax the typo on the graph) up to way too high to measure (well over 1000microU/ml for over an hour), like this:

Note, apart from the typo for insulin units, that the colours were switched between the graphs. Oops.

SHORT Syndrome is rare. Finding studies of the effect of acute metformin administration on the results of an OGTT in normal people is quite difficult. The closest I have is looking at the effect of metformin on an OGTT in obese people who still have a normal OGTT result. This is the paper

Effects of short-term metformin treatment on insulin sensitivity of blood glucose and free fatty acids

and here are the results for the obese normal OGTT people. Dashed line is under metformin after a ten day course, solid line before metformin:

The increased level of insulin secreted is not quite enough to effectively control blood glucose. As I might have mentioned, metformin blunts insulin signalling. No surprises there then. 

However, if you give the metformin to someone who is already insulin resistant or has type 2 diabetes, the opposite happens, same study:

This has a lot of bearing on what we mean by diabetes but might be better left for a few posts while I run though the transition form health through obesity to impaired glucose tolerance to frank DMT2.

Peter

Ossabaw pigs

I notice that Brad Marshall has a great post out on PUFA/insulin sensitivity and especially ALA. Brad is seriously thinking along ROS/Protons lines. He looks at ideas I've toyed with over the years but never found the papers to follow through on, finds the papers and follows through. Enjoy.

Obesity prone pigs go from Normal to Pathological Insulin Sensitivity to Torpor when given enough PUFA

Peter

Random musings on uncoupling (7) DNP and metformin

NAFLD, NASH, ALD and alcoholic steatohepatitis (ASH?) are all associated with the accumulation of lipid within liver cells. The two primary culprits are fructose and alcohol. Both undergo rapid metabolism to acetyl CoA (+/- lactate) with the potential to generate lipid within hepatocytes as a result.

Sadly life is never quite that simple. Certainly some of the liver lipid does indeed come from the metabolism of fructose or ethanol, but back in this post there are the papers which suggest fructose acts systemically to induce acute insulin resistance in adipocytes and so releases fatty acids which transfer to the liver (and visceral fat) stores:

Fructose and lipolysis

and this post points out the same about ethanol:

Alcohol and weight loss

Hepatic lipid delivery should trigger hepatic insulin resistance and the resultant persistence of metabolic substrate in the blood should signal to the hypothalamus that there are plenty of calories available, ie it's not time to eat yet. You have only to look at the hepatic response of FGF21 production, which increases thermogenesis, in response to both alcohol or fructose to see this in action. FGF21, when not produced in response to starvation (which it is), signifies that the liver sees enough calories to stimulate thermogenesis in excess of obligate needs.

So what goes wrong in fatty liver disease?

The action of insulin on hepatocytes is to suppress glucose release, facilitate lipogenesis and facilitate triglyceride formation. You just have to ask yourself, is there any dietary component which facilitates the excessive action of insulin? Which might make a perfectly reasonable process into a lipid-storage overload pathology?

Could that be linoleic acid? Which induces a failure to resist caloric ingress at times when that would be appropriate.

Fatty liver disease, from fructose or ethanol, looks to me very much like the result of excess insulin action on hepatocytes. The same linoleic acid which produces this accumulation of lipid in adipocytes  will also facilitate accumulation in hepatocytes and facilitate the conversion of benign fatty liver into inflamed hepatitis though its lipoxide derivatives.

We've known for years that a high saturated fat diet protects against NASH: 

Long term highly saturated fat diet does not induce NASH in Wistar rats

provided it is very low in PUFA. In fact the low PUFA is probably more important than the high saturated fat content.

If we accept this chain of thought, fatty liver represents an accumulation of lipid in response to linoleic acid facilitated excessive action of insulin. It happens because while the oxidation of linoleic acid generates enough ROS to allow insulin signalling to occur, it does not allow the generation of enough ROS to limit insulin's actions when the hepatocytes are full. Exactly as for adipocytes.

So hepatic lipid accumulation is a consequence of excess insulin signalling, and only once the ability to accumulate any more intrahepatic lipid has been exceeded does the generation of ROS become adequate to resist insulin's caloric ingress/retain signal. After that, hepatic insulin resistance will occur, glucose will no longer be retained and the liver will no longer be a sump for absorbing FFAs.

Systemic levels of FFAs and glucose will rise and the rest of the body will have to go in to anti-oxidant defence mode, AKA whole body insulin resistance. Hunger will plateau and weight will stabilise.

So. The primary problem is the excess storage of (largely adipocyte derived) FFAs as intra hepatocellular triglyceride, beyond the point where this is adaptive.

It cannot happen without the LA facilitated augmentation of insulin signalling. This does not happen if the lipids being oxidised within the liver are predominantly saturated, as in the NASH prevention paper above.

Looking at hepatic lipid accumulation in these terms suggests that blunting insulin signalling might he a simple solution. Hence the efficacy of 2,4-dinitrophenol. You could view DNP as acting as a caloric sump for hepatocytes, burning off the fat and introducing a caloric deficit. Or you could speculate that all that is needed is a small drop in mitochondrial membrane potential, to produce a reduction of insulin signalling to approximately offset the augmentation induced by LA, and the problem would self correct.

I tend to favour the latter option. But then I would.

My personal view is that this is what low dose DNP does. It blunts insulin signalling in hepatocytes. Blunted insulin signalling blunts lipid accumulation and the liver never accumulates enough lipid intermediates to generate insulin resistance. Without the enhanced insulin signalling sequestering calories into lipid stores the liver will allow more glucose and FFAs in the systemic circulation which will reduce hunger. This might not be enough to generate detectable weight loss in a few weeks of a rodent study but it just might over a few years.

The parallel with metformin is that I consider metformin's core action at therapeutic dose rates is the inhibition of the mitochondrial component of the glycerophosphate shuttle, limiting FADH2 input to the CoQ couple and so limiting the ROS generation which is needed to maintain insulin signalling (and to markedly reduce insulin-induced insulin resistance, but that's another story). It does this at micromolar concentrations in the cytoplasm, where it can easily access mtG3Pdh.

Metformin and DNP both reduce the generation of ROS needed to maintain insulin signalling, all be it by different mechanism. Insulin signalling is blunted. Excess lipid (and glucose) storage is inhibited. There might be a trivial loss of weight due to reduced hunger.

ASIDE Obviously as metformin/DNP reduce ROS and insulin signalling they allow increased fat oxidation, largely via AMPK, and some "new" ROS will be generated to replace those suppressed by metformin/DNP. But the "cost" of these "new" ROS is fat loss. Which is a win overall for metformin/DNP/obesity END ASIDE.

Interestingly both metformin and vintage DNP increase lactate formation systemically, presumably because glycolysis is still on going, especially when glucose levels are raised post prandially, and the activation of the pyruvate dehydrogenase complex is blunted in proportion to the blunting of insulin signalling. Hence pyruvate to lactate becomes the preferred route to continue glycolysis.

Also both are longevity drugs, even using old fashioned plain DNP in rodent drinking water

Mild mitochondrial uncoupling in mice affects energy metabolism, redox balance and longevity

Blunting insulin signalling certainly does interesting things.

I have tried to resist insulin for decades. So far, so good...

Peter

Random musings on uncoupling (6) Nouveaux DNP

 I started here with with DNP

2,4 Dinitrophenol as Medicine

Several links came out of the paper. First was this one from Shulman's group

Controlled-release mitochondrial protonophore reverses diabetes and steatohepatitis in rats

The paper contains a great deal of information about the development of the sustained release DNP formulation, which sounds good. All we know about the rats and diets are that they were Sprague Dawley rats or Zucker Diabetic Fatty rats and the diets are minimally described as safflower oil 60% fat for NAFLD or methionine/choline deficient for NASH.

Bottom line is that a sustained release hepatic targeted DNP preparation is enormously safe and produces marked amelioration of liver disease in all of the models tested.

Using Bl/6 mice they also show that the degree of hepatocyte mitochondrial uncoupling was so minor as to be undetectable in a CLAMS apparatus.

Next is this one, again from Shulman's lab, where the hydrogen of the DNP hydroxyl group was replaced with a methyl moiety, rendering this DNP derivative inactive. This was then converted to active DNP primarily in the liver by cytochrome P450, with no detectable toxicity and no detectable increase in oxygen consumption on a whole body basis:

Reversal of Hypertriglyceridemia, Fatty Liver Disease and Insulin Resistance by a Liver-Targeted Mitochondrial Uncoupler

There is pretty convincing evidence that both of the above modified DNP delivery systems were fairly tightly targeted to the liver. Relatively little appeared to act on other organs and there is no information about the action on adipose tissue, but then these experiments were not looking for weight loss, merely controlling the liver damage/dysfunction of metabolic syndrome.

And the drugs do control metabolic syndrome. Here are the intraperitoneal glucose tolerance test results for the high fat fed Sprague Dawley rats, red being the treatment groups throughout:

and the insulin levels at the same times:

and the results for the Zucker Diabetic Fatty rats are even more impressive:

and insulin levels:

All of this is merely by limiting lipid accumulation within hepatocytes.

And the rats stayed fat.

You have to look at this and wonder: Here we have an intervention which primarily blunts insulin signalling originating from the mitochondria of hepatocytes. A drug which reduces insulin signalling and yet leads to a dramatic improvement of of whole body insulin sensitivity.

The parallels with metformin are striking

Peter

Random musings on uncoupling (5) Vintage 2,4-dinitrophenol

Thinking about uncoupling leads to the idea that it is wasteful if it occurs in excess of that needed for useful thermogenesis. Being energetically wasteful on a fixed calorie input means you do not have adequate calories left for your metabolism (though you might cut a few metabolic corners) so you should be hungry in proportion to the extra calories-out as heat. On a non restricted diet you should just eat more.

When I started thinking about the activation of uncoupling proteins by linoleic acid and its derivatives it seemed logical to have a look at the metabolic effects of other mechanisms of uncoupling, the best known of which is 2,4-dinitrophenol (DNT). It is, at first glance, a much simpler situation than that of LA because there is no feature of its metabolic effects which might promote excess caloric storage.
All it does is uncouple respiration and turn food, mostly fat, in to heat.

A more nuanced reflection would be that such a huge calories-out might be the equivalent to climbing Ben Nevis several times a day. Which ought to make you hungry.

While high dose DNP undoubtedly does make you hungry, the increase in hunger can be relatively easily offset by mild stimulators of lipolysis such as caffeine and/or sympathomimetics.

It would take more than a couple of cups of coffee to get you up and down Ben Nevis four times in a day.

So DNP not only increases calories-out, it must also be increasing access to calories-stored, allowing them to become calories-in so as to convert them to calories-out without excessive hunger.

Reverse electron transport, needed to generate the ROS which are essential to maintain insulin signalling, is highly dependent on the mitochondrial membrane potential. The core function of DNP is to lower that membrane potential and it should lower ROS generation and so blunt insulin signalling.

The effect is non specific, it doesn't matter where the FADH2 and NADH inputs are coming from, if membrane potential is artificially lowered, all of insulin's signalling will be reduced.

Not eliminated, but enough to access adipose tissue's stored fat in proportion to the blunting of insulin's action. Clearly there is no obvious need for the decrease in insulin signalling to exactly offset the increased heat generation. It happens to be close and a bit of caffeine appears to match things up nicely.

This is how I view the high dose rate fat loss facilitating effect of DNP. It still seems to be used as such in cultures where rapid loss of residual fat is required to get the perfect physique for a competitive edge in physical culture circles. Risk of death is of little concern, after all, exogenous insulin is used to bulk up muscle before cutting fat with DNP, if you are dedicated enough.

There are currently attempts to rehabilitate low dose/sustained release DNP as a useful drug. This review was written by a researcher heavily committed to such a drug development project. He's biased, of course, but that doesn't stop him being correct:

2,4 Dinitrophenol as Medicine

In some ways I approve, getting rid of people's fatty liver for them, or even correcting full blown NASH, is a Good Thing. Except I'm uncomfortable with the concept of applying a sticking plaster to metabolic syndrome and then waiting to see what other catastrophes turn up further down the road. After all, you only have metabolic syndrome because you have chronic linoleic acid intoxication.

However this might be quite a good sticking plaster, as sticking plasters go.

Peter

Random musings on uncoupling (4) coconut

Feeding mice on a high sucrose, low linoleic acid diet activates FGF21 production by the liver which stimulates heat generation in brown adipose tissue, leading to a lean phenotype, marked insulin sensitivity and poor glucose tolerance secondary to down regulated glucokinase in the liver. This latter is not surprising as fructokinase has a much higher rate constant for fructose phosphorylation than glucokinase does. Use it or lose it applies, even if only temporarily, so glucokinase down regulates. A bit like eating a low carb diet also down regulates glucokinase.

This is the post and this is the paper:

Chronic high-sucrose diet increases fibroblast growth factor 21 production and energy expenditure in mice

Edit, this one too

Ingestion of a moderate high-sucrose diet results in glucose intolerance with reduced liver glucokinase activity and impaired glucagon-like peptide-1 secretion

End edit

My basic feeling was that fructose generated a caloric overload in the liver. Rather than dealing with this issue using hepatocyte mitochondrial uncoupling the task of dealing with the excess was delegated to brown adipose tissue and FGF21 was the messenger. "Higher  level" signalling. BAT uncouples on behalf of the liver. 

Of course that immediately suggests that other caloric overloads, especially if uncontrolled, might do the same thing. George Henderson tweeted this paper, which I've known about for years but have never gone in to in great detail:

Long term highly saturated fat diet does not induce NASH in Wistar rats

I hadn't realised how much uncoupling these rats were doing. They all weighed pretty much the same but caloric intake was way higher in the butter fed rats and even higher still in the coconut fed rats. That's interesting compared to coconut oil used in the Surwit type diets but these current diets are low in PUFA and sucrose free. Here are the caloric intakes:

The coconut based diet was particularly interesting as the rats were consuming twice the calories of the chow fed rats and weighed exactly the same. You could argue that coconut just tastes better than chow and the rats over ate then uncoupled. Or, more interestingly, you could suggest that medium chain fatty acids enter liver mitochondria in an unregulated manner and generate large amounts of input to the electron transport chain. If hepatocytes are experiencing a caloric overload what else should they do other than generate FGF21 and sub contract a calorie disposal solution to the BAT?

This arrangement would benefit, as with fructose, from the hepatocytes being the primary cells targeted to receive the unregulated caloric supply and is a good reason for keeping MCTs out of chylomicrons and passing them directly to the liver via the portal vein. Which is what happens.

So we can look at this study (just ignore everything about stress response and how a few ketones will do horrendous things to you):

Dietary Manipulations That Induce Ketosis Activate the HPA Axis in Male Rats and Mice: A Potential Role for Fibroblast Growth Factor-21

Here is what gavaging a chow fed rat with MCT oil does to FGF21 an hour later

LCT stands for corn oil. The acute effect of a low dose is almost nothing. Corn oil enters the systemic circulation in chylomicrons via the thoracic duct. It will be obesogenic as per ROS/Protons and only very mildly stimulating of FGF21 generation. Long term at high dose rates it will, as we've noted, uncouple enough to offset the metabolic syndrome induced as per ROS/Protons and result in a slim rodent which needs to over eat mildly to compensate for the side effect of uncoupling.

After coconut oil the uncoupling effect via FGF21 is marked so the compensatory eating has also got to be marked because the primary source of calories floods liver mitochondria with medium chain fatty acids.

So......... Localised hepatic caloric overload is a stimulus for FGF21 production leading to BAT thermal caloric disposal. As far as the rest of the body is concerned there is just the BAT caloric loss induced deficit to be perceived. There is a hypercaloric state in hepatocytes and a hypocaloric state in other systems, hypothalmus included. Food intake rises to maintain a normal energy supply to avoid weight loss.

Note the arrow of causality. The rats/mice are not over eating and burning off the excess. They are eating extra using an appropriate appetite to cope with BAT calorie expenditure/loss. They might not want to be hot but they have no choice. They eat to make up for it.

Peter

BTW there is this:

FGF21 treatment ameliorates alcoholic fatty liver through activation of AMPK-SIRT1 pathway

with alcohol being another hepatocyte caloric overload source which also generates FGF21 to "dispose" of the excess hepatic calories via BAT.

Using AMPK.

Which is where things get complicated.

Random musings on uncoupling (3) oxygen consumption

This is an nice little study from Japan looking at the effect of fat composition of diet on oxygen consumption before and after a meal:

Diet-Induced Thermogenesis Is Lower in Rats Fed a Lard Diet Than in Those Fed a High Oleic Acid Safflower Oil Diet, a Safflower Oil Diet or a Linseed Oil Diet

We can accept changes in oxygen consumption as a pretty good surrogate for the degree of uncoupling.

These are the diets used

The sucrose content is around 5% of calories so no confounder there. Fat is consistently 40% of calories and they measured the composition of the fats used. Like this

This lard is Japanese lard, produced in the early years of the 1990s. It's 7% linoleic acid. With lipids at 40 % of the calories in the diet this means that overall the LA provides 2.8% of the calories. So this is not an obesogenic diet*. However we get very little information about that because the rats were grown under a time restricted, calorie restricted protocol. An energy intake value was chosen as about the amount of food that a hungry rat would eat in an hour. This amount was fed twice a day. So there is no browsing allowed which suggests that some modest degree of caloric restriction is in place and the absolute supply of calories will be the same for all groups, despite each group have differing overall metabolic needs.

*[If the old anecdote about pork consumption in Okinawa is true this lipid profile might explain any possible longevity effect.]

The high oleic safflower oil diet provides 6% of calories as LA, the safflower oil diet provides 30% of calories as LA and the linseed oil diet provides 6% LA but this is combined with 21% as ALA. Alpha linolenic acid, from the ROS/Protons perspective, is an extreme version of LA although hard evidence for this is very thin on the ground. There are many studies using ALA which show that it is marvellous stuff at any dose rate but these studies almost always use "pair fed" or fixed calorie, mildly restricted protocols.

The protocol here also describes confirming that none of the diets generated lipid peroxides before being fed to the rats. The group is quite meticulous, so refreshing.

Here are the oxygen consumptions, indicating the degree of uncoupling present in the immediate post-meal period:

We can see that lard at 2.8 % of calories as LA shows very little uncoupling. Diets with LA between 6% and 30% LA uncouple more, although there is no evidence of a graduated response, and that a mix of 6%LA with 21% ALA uncouples the most, although this latter is only statistically ns greater than for the other PUFA groups, with a group size of six rats.

So. Given a fixed, mildly restricted calorie intake, we can take the lard fed rats as being very close to metabolically "normal", and eating closest to what they might want if fed ad-lib. Then we have three groups of rats, fed exactly the same number of calories, whose diet has been modified to induced a significant amount of uncoupling. All animals are at the same room temperature so obligatory thermogenic needs should be equal. So higher PUFA groups of animals will waste some of their consumed energy and not be allowed to replace it. What happens to body weights?
 

The low PUFA lard fed rats are the heaviest and carry about 5% more carcass fat than the PUFA fed rats. I consider them to be at normal body weight. Visceral fat, a surrogate for metabolic damage, is identical across the groups, all are free from clinical metabolic syndrome.

I would argue that the heavier rats are the least hungry, the high oleic acid safflower fed rats are a little more hungry and the two high PUFA diet rats are the most hungry. Quite what would have happened if the study had included an ad-lib fed arm we will never know.

So here's some speculation about "what if" there had been an ad-lib arm to the study:

The lard fed rats (this time) are our normal group and would weigh only a little more due to relief from calorie restriction. It would be nice if the ad-lib fed 6% LA group might have ended up with modest excess energy storage as fat gain and shown extra food consumption to match the extra weight gain. The high ALA fed group should have consumed even more food with less or similar weight gain because uncoupling is having a significant effect. Finally the group with 30% calories as LA should have come out somewhere between. The group having 30% of LA calories seems to be just on the border between where the ROS calorie storage effect transitions to the uncoupling effect in terms of dominance. From other studies 45% of calories as LA might have had the uncoupling effect absolutely dominating, so a slim phenotype would show, but that would be impossible in a diet where only 40% of calories are from fat in total.

How does this fit in to cellular "hunger" concept? At levels of linoleic acid where facilitated diversion of calories to storage predominates, excessive insulin signalling is dominant. The cell is dealing with an hypercaloric state.

Under marked uncoupling conditions the cellular state is the opposite. A separate defence mechanism against caloric excess is being activated, whether there is a caloric excess or not, by dropping the mitochondrial membrane potential because the closer a diet gets to 45% LA diet the more it provides a supra-physiological level of LA for the uncoupling protein function to maximise, combined with copious supplies of oxidative products such as 4-HNE to activate those uncoupling proteins.

At this point ROS generation is suppressed because, whatever the FADH2:NADH ratio, high mitochondrial membrane potential is still essential for reverse electron transport. There will be a transition from failure to limit ROS generation (forcing a cellular energy surfeit) to a reduction in insulin signalling as the result of a process which also involves the direct loss of calories by uncoupling (an hypocaloric state). The fact that suppressed insulin signalling releases fatty acids is over ridden by their loss through overactive uncoupling.

So PUFA are able to produce both cellular repletion and cellular hunger depending on the concentration.

It feels counterintuitive that a metabolite should, by one action, generate an hypercaloric state with excess energy storage and yet, by a separate process, go on to produce the opposite effect via uncoupling at higher levels of exposure.

But this appears to be the case.

It becomes much clearer using pharmacological uncoupling, which takes us back to 2,4-dinotrophenol.

Peter

Random musings on uncoupling (2) revised

Okay, here is how I ended the last post:

"It's also worth pointing out that this appears to be an ancient system and that high PUFA exposure might uncouple in anticipation of the cellular caloric influx which PUFA signify. It has become pre emptive and has, certainly in rodents, largely been shifted from "all" cells primarily to the brown adipose tissue. The PUFA signal might also be very central to the browning of white adipose tissue to beige. That's a process you would never want to have to use, being in a situation where generating beige adipose tissue might be helpful is not somewhere you want to go."

which is wooly thinking, to say the least.

Uncoupling is triggered by ROS generation using a locally available PUFA derived lipoxide signal combined with whatever fatty acids are available in the immediate vicinity of the mitochonrial inner membrane uncoupling proteins. A supply of PUFA is absolutely needed for the signalling molecule generation (4-HNE and related) and intact PUFA have been selected to uncouple better than saturated fats do. These features might be related.

PUFA are always present in the inner mitochondrial and have many functions. this function of acting as a safety valve appears to be one of them. It will not need to be specifically linked to bulk PUFA induced cellular caloric excess. I envisage it as a response to any excess caloric ingress, hyperglycaemia or markedly elevated FFAs post prandially (or even elevated levels of systemic fructose) when the law of mass action (ie a large concentration gradient) overwhelms the normal response of insulin resistance when cells are replete.

I view this aspect as the ancient system. It applies to any caloric overload and happens to use a PUFA/ROS signal to limit excessive mitochondrial membrane potential using uncoupling.

The fact that this system is functional at levels of PUFA intake far in excess of those that a particular species (humans) might be adapted to is perhaps unexpected but does seem to be the case, but this is more understandable if it is viewed as a generic safety mechanism.

Whether those slim rodent models consuming 45% of their calories as linoleic acid are dealing with excess caloric ingress by uncoupling or whether they are actually under caloric deficit because the emergency uncoupling system is being activated inappropriately due to oversupply of signalling precursors/uncoupling facilitating fatty acids is not clear.

Peter

Seasonality

I see winter has arrived in Melbourne. 😞

Peter

Random musings on uncoupling (1)

I thought I'd just take a break from trying to find any studies where sucrose-in-chow causes obesity in the absence of greater than 8% of calories as linoleic acid. That's becoming rather frustrating but is turning up some interesting studies on uncoupling and PUFA along the way.

So just for this post I thought I'd get even more speculative than normal about uncoupling.

Thermogenesis. Thermogenesis makes you hungry. That is not a completely intuitive statement.

It's easiest if we start with a food source which generates heat without utilising uncoupling because there are far less variables to think about. So think protein. Deconstructing a protein chain, processing amino acids to their core constituent energetic compounds such as pyruvate, glutamate etc requires energy and this energy shows up as heat.

Let's say 1000kcal of protein generates 300kcal of heat. I've no idea of (or interest in) the exact value, I just know you can warm a hypothermic patient post operatively using an IV amino acid infusion.

So if you are used to eating 2000kcal of fat a day to run your metabolism, you metabolism requires 2000kcal, tightly controlled. Let's also imagine you live in a thermoneutral environment and so are not muddying the water with (usually necessary) thermogenesis to maintain your body temperature.

If you swap your 2000kcal of fat for 1000kcal of fat plus 1000kcal of protein things change. The 1000kcal of protein provides 700kcal of usable energy and 300kcal of waste heat, which you don't need as you are in a thermoneutral environment.

So you get hot and uncomfortable and have a 300kcal deficit. You cannot run your metabolism of 1700kcal, you need 2000kcal. The hypothalamus notices this 300kcal deficit. What would you do? You would feel hungry and eat enough extra food to ensure that you actually get the 2000kcal you need for metabolism, tolerating the excess heat generation as an unwanted side effect. You would stay weight stable, eat a little extra to hunger and be sweaty.

Forced overfeeding is equally straightforward. You eat too much, uncouple, lose heat and hope you don't really live in a theroneutral environment.

Next is what happens under spontaneous eating but including more than 8% of calories as linoleic acid in your diet.

Here my hypothesis is that excess calories are available, the cell fills up and poorly-opposed insulin allows more calories to enter and for those calories to be sequestered out of the way as lipid (and probably glycogen too). From the cellular point of view energy status is fine (not overloaded) so long as the excess calories entering are being sequestered away from metabolism. The hypothalamus might perceive too few calories in the arterial blood in direct proportion to those being lost into storage in the periphery. So you eat more.

The next step in thinking is 2,4-dinotrophenol. This is a classical uncoupler and probably the most effective weight loss drug, particularly for fat loss, ever marketed. Sadly the therapeutic margin is narrow, unpredictable and can change suddenly.

High dose rate, rapid weigh loss DNP administration uncouples respiration to the point of ATP reduction and massive heat generation. AMPK is activated by the consequences of the fall in ATP, ensuring effective fat oxidation. With a marked fall in mitochondrial membrane potential there is going to be a cessation of reverse electron transport and the mitochondrial component of the ROS generation essential to maintain insulin signalling will collapse. At this point calories will be entering the cell through AMPK facilitated GLUT4s (and probably CD36s as well) and will not be diverted to storage but used for a combination of running metabolism plus extra calories equal to those lost as heat.

I understand from reading around a little that DNP does, indeed, make you hungry. The calories pouring though the mitochondria are coming from fat primarily and if the fat supply cannot keep up with the uncoupling-augmented metabolic needs then blood energy content will fall and the hypothalamus will notice. Also interesting is the use of drugs such as caffeine and ephedrine to control that hunger, both of which are reputed to work. They increase basal and sympathomimetic induced lipolysis, supply more fat and so control the hunger. So the loss of fat from adipocytes due to failed insulin signalling cannot quite keep up with the increased metabolic heat production without a little help. Not surprising because the shrinkage of adipocytes is from a failure of insulin signalling to facilitate fatty acid uptake combined with unopposed basal/sympathetic lipolysis. Neither is directly related to the huge loss of calories from unrestrained uncoupling. It surprises me a little that the supply and demand are so closely matched in such a complex system, especially with a major spanner dropped in to the works.

Which just leaves us with PUFA. These appear to facilitate uncoupling in proportion to the amount present in the diet, even on a meal by meal basis. My mental image for this phenomenon is that, intrinsically, PUFA allow too many calories in to a cell if insulin is the facilitating hormone. The more pronounced this effect, the more the need for uncoupling.

Modest excess, say over 8% of the diet by calories, works by the standard ROS/Protons concept of sequestration of excess calories. But you can only sequester so many excess calories and very high percentages of PUFA have the potential to overwhelm the system. We are talking 35% or over for uncoupling to predominate, but I think this might be a linear effect which is over-shaddowed by the ROS effect at lower concentrations but comes to dominate at very high concentrations.

At these very high levels of uncoupling the body is in caloric deficit because it is actually losing the calories as heat. It is metabolically the equivalent of the hunger of a high fat (10-30% PUFA) diet but does not involve the distention of adipocytes to achieve it. The degree of hunger would be in proportion to the deficit between lipolysis and heat loss via uncoupling and would require (not allow) a few extra calories to be eaten.

EDIT: This last section is poor logic. It might be worth a post to clarify or just a an edit to correct. I'm thinking about it.  I'll take it out and put a more considered discussion up as a follow on post. END EDIT.

Peter

Of mice and men (3) Sucrose

There is a lot of variability in the linoleic acid content of lard. Good studies get round this by measuring LA using gas chromatography. From this paper we have Chinese lard containing 10% LA and from this paper we have Brazilian lard containing 17% LA. I've seen values cited as high as 30% but they have never been quite as convincing as the results table in a publication, though I see no reason to doubt them per se.

From the Protons/ROS perspective even 8% of total calories as linoleic acid is usually enough to get to be obesogenic, particularly if a little extra soybean oil is added as an "essential fatty acid source" (no sniggering at the back), which nicely explains most obesity paradoxes.

I have been revisiting various high and low fat diets in the aftermath of the Speakman paper which was so confusing as regards D12451 and its specifically marketed control diet D12451B.

Here are the compositions of both because Research Diets no longer lists D12451B as a standard diet:

So we have D12451B, a slimming diet, used as the control diet in the paper discussed in the last post. That will relate to the LA content which I calculate out at 3.2% of calories. The obesogenic D12451 comes out at 6.7% of calories as LA if we used Chinese lard, 9.5% using Brazilian lard and goodness knows how much using lard from the USA or UK.

The sucrose values are fascinating. D12451B provides 35% of calories as sucrose plus 35% as starch/maltodextrin and is slimming. D12451 provides 17% of calories as sucrose and is obesogenic. So this long established, slightly old fashioned pair of diets speak strongly against sucrose being the driver of obesity, they are more compatible with it being linoleic acid.

However I find the sucrose cannot be ignored. You can design your study to show sucrose as good, bad or mystifying. Let's think about sucrose.

I used to really rather like this group, which I've mentioned before :

Ingestion of a moderate high-sucrose diet results in glucose intolerance with reduced liver glucokinase activity and impaired glucagon-like peptide-1 secretion

In this first paper they either fed mice on CE-2 standard Japanese laboratory rodent chow. It's specified at around 6% LA acid of total calories so is borderline high, has no sucrose and is clearly functional as a lab chow. They had two intervention groups, for one they diluted CE-2 down with starch and for the other they diluted CE-2 down with sucrose. As they say:

"the latter two diets were prepared by the addition of corn starch or sucrose, respectively, to CE‐2 (Table 1)."

Here is how the diets turned out:

This simple action diluted the protein, fat and vitamin/mineral content as was clearly documented. I don't really buy in to the protein leverage hypothesis so I'm not surprised that all groups ended up at exactly the same bodyweight despite reducing protein calories for two of the groups.

What I do tend to take note of is the fat dilution. The fat is all of the same composition, around half of the 12% total fat calories is LA, giving 6% for CE-2. Diluting its 12% of total fat calories to 7.7% reduces LA from 6% of total calories to 3.7% of total calories for either intervention. Neither the high starch nor high sucrose diet produced any excess weight gain, much as you would expect for a either diet with LA at 3.7% of calories.

Now, their second paper is MUCH more interesting. Here it is:

Chronic high-sucrose diet increases fibroblast growth factor 21 production and energy expenditure in mice

and here are the diets:

There is no suggestion of grinding up CE-2 with extra starch or sucrose this time. These are custom diets of unspecified origin/composition (so I'm going off these people now). I'm going to assume NC (normal chow) is still CE-2 and that the 12% fat in each diet is still soybean oil.

The protein is reduced for both intervention diets (just as it was diluted in the previous study), carbohydrate sources and quantities are kept unchanged.

But the fat is NOT reduced/diluted. If we assume that the now maintained 12% of calories is still mostly soybean oil we are now at 6% of calories as LA in the intervention groups, up from 3.7% in the previous experiments. Back to borderline obesogenic. 

This time their very high starch diet is grossly obesogenic, their chow (lower starch, possibly less refined) is not and the high sucrose diet is positively slimming. And these sucrose fed mice are definitely not "skinny-fat", see the rest of the paper re insulin sensitivity. Okay, here's the insulin tolerance test, it's from the first paper, the ITT in the second paper is similar but doesn't drop quite as low because there is a little more fat in the diet. I'm impressed by the drop to 20% so I like this particular image!

You can't use an OGTT or IPGTT as a high sucrose diet down regulates hepatic glucokinase so a glucose tolerance test would (and does) generate systemic hyperglycaemic for a short period. And here are the weights:

All of the mice this time are on 6% LA (assuming I'm correct re composition). The grey circles are mice on a very high starch diet, they get fat. The open circles are on chow. We could describe them as also being on a 6% LA diet with modest carbohydrate restriction cf the high starch fed mice on the same LA percentage. They don't get particularly fat. In the presence of 6% LA even modest carbohydrate reduction appears to be slimming.

Then we have the diet with 38.5% of calories from sucrose as the black circles. These mice are slim, absolutely not insulin resistant and they happen to have hot brown adipose tissue secondary to uncoupled mitochondria through generation of FGF-21 secondary to fructose ingestion.

I do not have the mechanism for this. It will undoubtedly be driven by ROS generation and this will more likely be driven by NOX enzymes than mitochondrial reverse electron transport. I am also suspicious that modest sucrose ingestion might drive obesity as in the Surwit diets and D12451 but that a very high sucrose diet might uncouple respiration and prevent obesity and metabolic syndrome. Why?

Consider the parallels with PUFA diets with between around 8% and 30% of calories from LA. These fail to limit insulin signalling and allow excess calories in to a cell. At these modest levels of LA the inappropriate excess caloric ingress can be stored by the inappropriate transfer in to triglycerides. Both ingress and storage are both allowed and achieved by un-resisted insulin signalling.

At very high levels of LA, moving from over 30% of calories from LA to over 45%, then limitations become apparent to this stratagem of "diversion to storage". A more potent mechanism for ameliorating the pathological ingress of excess calories is is to uncouple respiration. A concept I explored here for PUFA.

What if sucrose does the same? Moderate levels, say 17%, allow fructose to enter cells without insulin mediated control. At this level I would expect fructose to generate enough ROS to limit insulin action by just the correct amount to down regulate glucose ingress to compensate for the energy from metabolised fructose.

If sucrose is very high, say 38.5% of calories, perhaps the unregulated fructose ingress cannot successfully offset enough of insulin's action on glucose ingress to balance the books. It looks like the solution in response to un-manageable caloric ingress might be to uncouple respiration so as to off-load the excess calories as heat.

Parallels between dose response to LA and fructose? Medium doses are dealt with by storage, high doses require uncoupling.

Some Surwit diets and D12451 combine maximally problematic levels of both fructose and linoleic acid.

These are things I'm thinking about at the moment.

Peter