Tuesday, May 25, 2021

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 :

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:

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.



Frédéric Lacroix said...

Interested to know why you don't buy the Protein leverage hypothesis, which is all the rage right now and seem pretty well demonstrated across multiple species?

Unknown said...

Hi Peter,

If you could design your own rodent study what would it look like and what results would you expect?

And now the same question again, but for a human study.


Passthecream said...

Thanks Peter.

I haven't thought about how it relates to uncoupling but I was reminded of this item from Richard Feinman:
https://feinmantheother.com/2017/04/01/calories-in-calories-out-substrate-cycles-and-diesel-engines/ futile cycling

Peter said...

Frédéric, It's too high level a concept. There is nothing about basic nuts and bolts in it that I have picked up on. I can accept that certain amino acids cause insulin resistance (probably because their catabolism generates FADH2) so they might assist hunger control/deferment, but I don't see a basic mechanism. There is no doubt that amino acid catabolism is thermogenic and that some degree of thermogenesis is a homeothermic metabolic requirement but excess heat generation, in addition to that essential for allowing normothermia, will simply generate hunger. You need a certain metabolic energy supply. If you "waste" it on unnecessary thermogenesis, you should just eat more. This is certainly what happens with self selecting mice eating 80% of calories from corn oil. They are normal weight, uncoupled and eat slightly extra to keep themselves normal weight, ie to offset the extra thermogenesis. If you did the same with protein you would expect the same effect. If your high protein diet supplies bulk non-protein energy from say white rice you would be on a low PUFA diet. If you supplied it from butter you would do the same. Start adding in seed oils and you are back to ROS/Protons.

Unknown. I don't know enough about anything to answer that. Currently I would like to see fixed macro diets with progressively increasing sucrose plus oxygen consumption measurements. Ditto progressively increasing PUFA contents because I want to know where weight gain becomes offset by uncoupling by each intervention. Even that is not simple as you have to ask questions about insulin signalling and uncoupling. Uncoupled mitochondria do not drive ROS. Do they even generate ROS to maintain insulin signalling? Is this last how UCPs facilitate weight loss/lack of weight gain? Next week it will be something else.

Pass, uncoupling has lots of interesting aspects. There is work going on rehabilitating 2,4, dinitrophenol at non-weight loss dose rates in which it appears to completely ameliorate metabolic syndrome. I have fructose, PUFA, UCPs and DNP all pulling at me at the moment re insulin signalling/uncoupling/weight change. I'm waiting for it all to make sense.


baggirl said...

How do excess calories that your body throws off as heat generate hunger? Doesn't the process of throwing off the excess inform the body that it has enough - no need to generate hunger?

Peter said...

You have to look at the process. If your body needs (say) 2000kcal to run for a day and you eat a food which automatically generates 500kcal of excess heat as part of being utilised, you will have lost 500kcal of the normal 2000kcal you eat. You cannot run your metabolism on 1500kcal, you need those 500kcal which have gone out as heat. So you eat an extra 500kcal.

You cannot fool your metabolism. A little tweaking perhaps but not major changes.

This is exactly what those mice on 80% linoleic acid diets did. They ate their "2000kcal equivalent", lost 10% of it as heat, so ate (drank?) an extra 200kcal/d. Scaled to mouse size of course. It is completely different from a paid over eating experiment where you force feed yourself and have to do something with the excess calories. That is "off-loading" calories and clearly wouldn't make you hungry.

Long term obesity/weight loss cannot involve forced over or under feeding. I am, at heart, a CICOtard. But with subtlety and (hopefully) insight...


karl said...

Carbosis uncoupling or some other function of fructose?

I remember from a time long long ago, where I binged on sugar food - and started sweating - and felt sick - sick enough that I didn't want to eat. It was this episode that started my quest for sound diet information and did a GTT trying to figure out what was going on. (My hunch today is that the sweating was from decoupling).

I had been doing the accepted dogma of the horrible low-fat starvation diet (the high calories per gram of fat narrative seemed to make sense). But then I changed to low-carb with success. But everything I read contradicted everything else - I did figure out that the health-care people were clueless - just parroting things - and no one was willing to say they didn't 'know'.

But in this quest, I discovered fructose - the difference between starches and sucrose - the fructose story that showed up in the chemically defined diet work to spike trygly. I suspect that there is more going on than the liver working overtime to get rid of the fructose. Robert Lustig is convinced that the fructose causes T2D, I think it is likely even more complicated.

So fructose can be used by muscles - but most seems to end up in the liver and kidneys --
(Lots of links to follow from this paper)

I think fructose in the brain increases appetite..(why?) and adipose tissue has GLUT5 receptors..

It is tempting to think there is a single cause of the T2D/obesity pandemic, but it could be the combination of 2 or more changes in the western diet.

I think it is better to eat starch than fructose containing sugars. Not sure the levels that appear to cause uncoupling are common in humans?

Peter said...

Yes karl, the current narrative re fructose doesn't seem nuanced enough. If you acutely feed radiolabelled fructose very little of it ends up in hepatic triglycerides, I think I've seen a value as low as 3% cited. Much as for alcohol, the hepatic lipids appear to come from increased adipocyte lipolysis and resterification of those FFAs as triglycerides in the liver.

I can understand this better if I accept that fructose generates FGF21, triggers uncoupling and this suppresses ROS generation from RET, so insulin signalling is suppressed. But this is clearly a higher level signalling system, what basic process is it amplifying?


Justin said...

Talk of ephadra and caffeine instantly transports me back to my days in the Mojave Desert of 29 Palms when we would go on death runs in the dessert mountains of that dreadful place. PT in the mornings and then 8 to 10 hours of basic electronic, radio fundamental and system classes. That was (with the incorporation of aspirin) on of the most awesome over the counter supplements available back then. Thank god they made it...

Justin said...


Brad Marshall said...

I have found the record for lard!! 54% linoleic acid!!


Peter said...

Amazing! Do they melt on a hot day????

All the best


Oh, Justin. Forgot to reply. Aspirin is an uncoupler too. Giving your supplement to the pigs might also melt them!