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:
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!
Peter
