Sunday, March 05, 2023

How can insulin resistance cause weight gain? (5) MCTs

The problems posed to the Protons hypothesis by the failure of fully hydrogenated coconut oil to suppress obesity in rodent models continues to draw me. In the recent past I've gone to Pubmed and searched on "octanoate + ROS" and "coconut oil + ROS".

This paper is pure confirmation bias for saturates resisting insulin signalling via ROS:

This is from 2006 and the software for identifying and quantifying changes in cell appearance was not available (and looks like colour imaging wasn't either!). Now, these are 3T3-L1 "adipocytes" which are the "sort of" fat cells that many people work with in obesity research. 

The white signifies ROS generation. Upper left is control and upper right is with added 1000μM pure octanoate. So a model, using fasting levels of FFA of a composition never seen in vivo. But it generates lots of ROS which can be normalised by adding N-acetyl cysteine. Not only that but it inhibits lipogenesis too:

Bear in mind that you can show almost anything you like by adjusting the conditions during the development of 3T3-L1 adipocyte-like cells, but at face value octanoate is a potential weight loss drug. They didn't look at insulin signalling per se but reduced adipogenesis combined with high ROS generation implies ROS mediated insulin resistance. To me anyway.

The exact opposite is encapsulated in this paper:

Here they used rat brain neurons in culture and used a mix of fatty acids from coconut oil giving in the region of 100μM of mixed, mostly medium chain length fatty acids. So slightly different. We can ignore all of the data relating to Aβ because it's irrelevant and I think that's the wrong paradigm for Alzheimers disease anyway. What I want are the data relating to ROS generation from medium chain triglycerides. This is what they found:

Okay, 24h of incubation with mixed, mostly MCT fatty acids has no affect on ROS. If there is any trend it is downwards. From the Protons perspective reduced ROS lead to preservation of insulin signalling when it should be limited, ie reduced ROS allow excess caloric ingress. 

So look at this. Amongst the many things they measured they looked at the phosphorylation of AKT and it was increased. More insulin signalling will facilitate more fat storage, under fixed conditions:

So what are the differences between the two studies?

In this study these cells are being grown in Neurobasal™ Medium  which comes with the usual 25mM of glucose, enough to support the growth and replication of cells in the complete absence of fatty acids. Some degree of insulin signalling is on-going because it's routine to add supplement B-27 which specifically contains insulin. How much insulin is a trade secret but it is clearly a reasonable amount to ensure effective utilisation of glucose for growth but is unlikely to provide pharmacological levels of insulin exposure which would generate insulin resistance per se. This gives a certain level of phosphorylation of AKT as an effect of that insulin. That's the control cells. Simply adding 100μM of mostly MCTs increases insulin signalling at the pAKT level.

We are talking physiological insulin levels with high glucose and a little coconut oil, compatible with normal conditions after a carbohydrate based meal.

If we go back to the initial octanoate paper we are now talking about the same 25mM of glucose, ie higher than recently fed levels, plus a "fasting" exposure to 1000μM of octanoate. Oh, and 170mM of insulin (that's that 170 times peak post prandial level from previous discussions). This mix is the equivalent of the inability to suppress FFAs under high glucose/insulin, aka loss of metabolic flexibility, aka metabolic syndrome.

Here these adipocytes are awash in a sea of calories and an absolutely supra maximal level of insulin. I think it is reasonable to suggest their electron transport chains are screaming and their need to resist insulin is marked. Using lots of ROS. Almost certainly generated by high delta psi.

What might this tell us?

Under semi-physiological conditions adding even relatively small amounts of mostly medium chain fatty acids increases the phosphorylation of AKT, at a fixed level of insulin. Obviously, to anyone other than myself, that increase in pAKT would be a Good Thing. Insulin sensitising is good, yes? Recall this one:

Small amounts of dietary medium-chain fatty acids protect against insulin resistance during caloric excess in humans

with the effect of eliminating the correct physiological resistance to insulin signalling under forced overfeeding of humans:

Both solid columns are the control state, left hand hatched brown column is the increased insulin resistance of overfeeding fat and the green hatched column on the right is overfeeding very similar fat but with partial replacement by MCT lipids. You can avoid insulin resistance from overfeeding mostly saturated fat using MCT lipids. "Stopping" this insulin resistance is considered a Good Thing.

Except enhancing insulin signalling enhances fat storage.

Summary: The closer you get to physiological conditions the more the suggestion is that medium chain triglycerides facilitate insulin mediated fat storage.

Random thought: You have to wonder if they also stimulate overall growth via facilitated insulin signalling. As in milk fatty acids might be designed, along with milk proteins, to turn baby cows in to grown up cows. Ditto breast fed baby humans.

"How" is a much harder question. Right from near the start of Protons I have accepted at Dr Speijer's idea that very long chain fatty acids, especially saturated VLCFAs go to peroxisomes because mitochondrial oxidation would generate toxic levels of ROS. Later it dawned on me that VLCFA PUFAs probably go to peroxisomes too as they would generate too little ROS for healthy signalling. Now it looks like MCTs carry a different message and are processed differently to longer saturates to provide the specific advantage of maximal growth pre-weaning. Generally adult ROS signalling seems to come from 16 and 18 carbon fatty acids, saturates to resist insulin and MUFA to work in cooperation with insulin. And linoleic acid to muck up the whole system once you get above a certain level of consumption.

There are, if you set your model correctly, parallels between MCTs and linoleic acid of the ROS front. Which leaves me thinking about coconut based cultures with excellent insulin sensitivity but no obesity.

Interesting things, MCTs!



  1. Resisting the urge to extrapolate a reductionist conclusion to apply to a complex system, I eagerly await the next installment.

    i.e. I won't give away my coconut oil or goat milk just yet.

  2. It is profoundly interesting but I'm hanging on to my butter also.

    Peroxisomes are pretty busy:

    "Peroxisomal beta-oxidation and peroxisome proliferator-activated receptor alpha: an adaptive metabolic system"

    I have been wondering what happens to the various residues from beta oxidation of pufa, not just HNE. This is an old but interesting paper:

    "Beta-oxidation of polyunsaturated fatty acids having double bonds at even-numbered positions in isolated rat liver mitochondria",degradation%20of%20polyunsaturated%20fatty%20acids.

    "We conclude that 2,4-dienoyl-CoA reductase is an important auxiliary enzyme in the beta-oxidation of polyunsaturated fatty acids. Induction of this enzyme by clofibrate or by certain high-fat diets increases mitochondrial capacity for the degradation of polyunsaturated fatty acids."

  3. Note, in the abstract of that peroxisome paper " and in the process they generate H2O2."

  4. Provocative post. I need to read up on peroxisomes at some point

    Too much ROS = toxic => ship them (VLCSFAs) to peroxisomes
    Too little ROS = fattening => ship them (VLCPUFAs) to peroxisomes

    I'm unclear on why you think MCTs provide 'too little ROS'? Is it because they only have 6-10 saturated bonds?

    And would MCTs be a 'good' way to fatten (infants) because they could grow their adipose tissue to support a certain degree of metabolic autonomy (i.e. energy reserves), but without introducing highly oxidation prone fatty acids?

  5. cave, the more ketogenic a diet (ignoring ketogenic diets based on MCTs for the time being) the less important insulin signalling is. If your fatty acid(s) enhances insulin signalling by, say, 10%, then 10% in response to 50pM insulin matters a lot less than 10% in response to 500pM insulin based on the carbs in the meal...

    Pass, yes, peroxisomes generate hydrogen peroxide, not superoxide. So they are sending a signal over a medium intracellular distance, certainly to the nucleus and probably to the closely associated mitochondria. That signal will be important and tightly controlled. I've mentioned before that peroxisome research is in its infancy.

    Raphi, I don't know why. They are diverted away from the systemic circulation and directly to the liver via the portal vein. In the liver there are no restrictions to their access to mitochondria, ie no control via the carnitine shuttle. So they *should* produce tons of hepatic mitochondrial ROS via massive delta psi. They don't. They are diverted to ketones (ie they don't turn the TCA) or exported after anabolism to palmitate (I think the paper I have showed this for adipocytes rather than hepatocytes but you get the idea). My frustration is that this is all at the "higher" organisational level leading to the structure/functional adaptation of an organism with a liver and a portal vein, ie it's not a basic physiological process the way you can view C16 and C18 mitochondrial metabolism. Invoking high level modifications/processes like this always seem like a cop-out to me but there you go!


  6. I do not read a lot of studies, but those I see using coconut oil frequently use hydrogenated coconut oil, which I do not understand (except maybe from a chemistry viewpoint). Using high heat with solvents saturates the oil but can easily rearrange the plant molecules. It also seems to remove the lauric acid. I never found a reputable health food store that sells the stuff. And I tend to ignore those studies.

  7. Michael, my understanding was that there is very little pufa in coconut oil mostly linoleic acid, and hydrogenating that is enough to change a pasty liquid into a greasy solid at room temperature. Everything else is already saturated. I don't know about the lauric acid? But cooking up lipids, these are like Swiss army knife chemicals so anything can happen, peroxidation of unsaturated bonds and often strange things result such as cyclisation, polymerisation etc etc.

  8. Peter, isn't it the case that by harnessing these refined and highly evolved ROS based intra-cellular regulatory systems to the inter-cellular control signals such as insulin that you have already moved to a "higher" level system?

  9. Michael, I'm interested in understanding. Studies which are inexplicable are the most important. Ditto very high intakes of linoleic acid -> weight loss and normalisation of pathological insulin resistance.

    Pass, absolutely yes. I would put 4-HNE as the layer above superoxide and protein signalling above that. I'm also thinking about sulphydryl groups converting to disulphide bonds within proteins as a marker to become a long distance signal about more localised redox conditions. Clearly insulin carries three -S-S- linkages. If I recall correctly so does the plant version of insulin. I keep wondering if these are functionally similar because the conversion of a pair of -SH to a -S-S- in triplicate "means" that ROS have acted on a protein and then that protein goes off around the body to tell all of the other cells that there's enough food coming (the trigger for ROS generation) to prepare for taking it up and doing some growing. It might make a post if it comes together enough...


  10. " the plant version of insulin" ... aieee more rabbit holes to explore. At a time when I have real pesky rabbits in my garden to dig out. Here bunny, bunny,

    It would be interesting if the people making fluorescent visualisations of plant chemical digals would do some of these specific

  11. .. signals... ... specific pathways. (ie plant insulin ) I suppose salicylate is involved somehow??

  12. Salicylate is clearly a toxin produced because willow tress hate bark boring insects. We use it and its mimetics to feel better during a cold at the cost of delaying our recovery for a few days by suppressing our massively evolutionarily conserved febrile response. Unless we take too much of course. Then we die. Like my imaginary bark boring beetles... It's a feature not a bug (pun intended).


  13. Ooh look, aspirin as the original remdesivir!


  14. Salicylate is also a plant growth hormone irc. Totally unsuitable for consumption by any animal. The plant insulin equivalent seems to be Trehalose 6 phosphate. Used to regulate sucrose metabolism, sucrose being the plant glucose equivalent.

  15. And e.g

  16. Pass, I was thinking more of this insulin like peptide

    "The leginsulin was sequenced by automated Edman degradation and electrospray ionization mass spectrometry. It consisted of 37 amino acid residues with six half-cystines in three disulfide bridges"


    Works in rat adipocytes.


  17. Ooooh, I like the Trehalose 6 phosphate but it seems more plant like than speaking as a pre metazoan signal. But fascinating. Layers upon layers. 2-4 billion years is quite a while! I wonder if it acts on mammalian adipocytes????


    1. The leginsulin is amazin'. All seeds are amazing examples of complex life --- you might almost expect soybeans to sprout legs.

      Tangential but this popped up while searching around the topic area:

      But bear the following in mind before you try rolling your own rhododenron flower extracts

      "Grayanotoxins are produced by Rhododendron species and other plants in the family Ericaceae. Honey made from the nectar and so containing pollen of these plants also contains grayanotoxins and is commonly referred to as mad honey. "

  18. Really Pass, you've not spent enough time in the Erowid vaults. In common with Broom flowers, those of the rhododendron have to be wilted for several days (sealed jam jar is recommended) to detoxify before being smoked as an intoxicant. I thought everyone knew this.


  19. The mad honey is a recreational substance is some countries. Double hit: sugar plus psychotoxins! I had also heard rumours from my Scottish associates that 'the blooming heather', another Ericacea, can be a mind altering drug. That probably explains all the folk songs about it.

  20. The local wattle trees ( acacia spp) flower so prolifically that they cover everything with a dust of yellow pollen. It was a traditional food source if you knew which one to harvest, protein and carbs. Pollen might be a bit animal-like in some ways. Of course some of them are psychotropic, no plant wants stupid animals to eat its flowers. There may have been detoxification techniques to make it safe for humans to eat but nothing stops possums eating it. They occupy the local arboreal monkey niche and seem to be perpetually stoned from their diet.