Hyperlipid by Petro Dobromylskyj
14 April 2021You need to get calories from somewhere, should it be from carbohydrate or fat?
Edit: The capitalisation of Reward is sarcasm. End edit.Corn oil is very Rewarding™ for rodents. These people are working hard at the mechanism:so let's not assume that Reward is some airy fairy concept, it's fully physiological. How Rewarding corn oil is in rodents is beautifully illustrated by the paper I discussed recently in which mice, when given the choice, voluntarily consumed pure corn oil until it comprised roughly 84% of the total calories in their diet. Of pure fat. Without training of any sort. This is the paper:Voluntary corn oil ingestion increases energy expenditure and interscapular UCP1 expression through the sympathetic nerve in C57BL/6 miceSo of course the mice became obese. Okay, I'm making that bit up. Massive consumption of Rewarding corn oil does not make mice obese. They eat a little extra, admittedly, but that is because the metabolic effect of an 84% corn oil diet is to instigate uncoupling. A quirk of the biochemistry of linoleic acid, uncoupling proteins and rodent brown adipose tissue means that a certain amount of energy is wasted as heat, so the mice have to consume a little more corn oil to make up for this loss. A few extra total calories were consumed without any extra weight gain.Metabolism + extra heat production = an extra amount of food has to be is eaten to maintain normal weight.Simple.Going on to look at mechanisms of Reward, this studyIncreased Levels of Extracellular Dopamine in the Nucleus Accumbens and Amygdala of Rats by Ingesting a Low Concentration of a Long-Chain Fatty Acidfound that the Reward of corn oil is neuronal, it comes from local metabolism of the oil on the tongue using a lingual lipase so that a tiny concentration of FFAs is sensed by receptors in the mouth and nerve signalling from here drives the dopamine release in the brain. You can bypass the lipase on the tongue by adding as little as 1% unesterified linoleic acid to mineral oil which mimics the approximate amount of FFAs provided as a stimulus from the more normal corn oil/lipase process.To make it absolutely clear:Mineral oil carrying 1% of free linoliec acid is as Rewarding as 100% neat corn oil because both provide roughly the same FFA drive to the sensory cells. You can measure the dopamine release in the rodent brain. It's the same because the sensory cells on the tongue see the same concentration of FFAs.I have a thought experiment.What if one group of mice/rats were given chow plus access to neat corn oil and another group of mice were given chow plus access to mineral oil with 1% free linoleic acid added?The oils are equally Rewarding.Would the mice consume the oils in equal amounts because both are equally Rewarding?If the oils were consumed in equal amounts would the mineral oil mice lose weight?Or would they eat extra chow?My bet is that if you ran such a study for eight weeks the mice with access to the mineral oil wouldn't touch it with a barge pole. It might release dopamine in the nucleus accumbens but it's not going to do much to fuel metabolism. That would need chow. Maybe there might be some recreational flavoured mineral oil consumption but I think that would pale quite rapidly.Oooooooh! They might develop Reward Resistance! Like leptin resistance but dumber.Reward is the refuge of researchers who consider obesity is caused by eating in excess of your metabolic needs.A more sensible view of obesity is that it results from a metabolically mediated loss of calories in to adipocytes which then requires more calories to be eaten to meet normal metabolic needs. In the same way as orlistat requires over eating to compensate for fat loss via faeces, so "fake" corn oil (1% linoleic acid in mineral oil) would require extra chow to make up for the lack of calories in that highly Rewarding fake oil. And why feeding D12492 means rodents have to consume extra D12492 because they lose calories in their adipocytes.
Just to summarise: high Reward food makes you fat only if its metabolism result in energy sequestration in to adipocytes.Real corn oil at 84% of calories is not obesogenic because it does't sequester calories in to fat cells. I don't care how Rewarding it is. Nor does metabolism care.Peter
I've been interested in the Surwit diet for years. It's a fascinating diet, high in saturated fat, low in PUFA yet undoubtedly obesogenic.
It's an interesting paradox to think about. As occasionally happens I found a non related paper which gives some suggestion of the mechanism. Here it is:
Characterizing the effects of saturated fatty acids on insulin signaling and ceramide and diacylglycerol accumulation in 3T3-L1 adipocytes and C2C12 myotubesThe paper uses adipocyte-like 3T3-L1 cells or muscle-like C2C12 myotubes. The 3T3-L1 cells might be worth another post in future, today is about the myotubes.They looked at many things, but most interesting are the data on the ability of insulin to promote the storage of glucose in glycogen granules. I, being me, would look at this as a surrogate for un-measured lipid storage as lipid droplets in muscle cells. One of the cardinal rules of ectopic lipid deposition research is to never, ever suggest that myocyte lipid droplets might be enlarged by insulin signalling. They will be. Just like glycogen granules are enlarged by insulin.So, practicalities. The myotubes were prepared in "low glucose" DMEM which is probably code for 5mmol/l, ie a normal physiological glucose concentration. To this medium was added a fatty acid at 0.75mmol/l, ie moderate fasting levels. Cells were incubated for 16 hours and then treated with supra-maximal insulin.They noted that elevated pure palmitate is utterly harmless to cells in culture with normal glucose levels:"Under these conditions, no signs of cell death were observed"which certainly is not the case using 25mmol/l of glucose!Here are the gels they obtained:
The top row, highlighted in red, is demonstrating the presence of phosphorylated (activated) Akt, a core insulin signalling step. We are comparing P-Akt under insulin and 5mmol/l glucose with that under insulin and 5mmol/l glucose plus 0.75mmol/l palmitate. It's clear that insulin signalling is markedly blunted by palmitate. If we look at the dashed oval we can see that the P-Akt band under oleate is comparable to that of the control.The same applies to the level of phosphorylated glycogen synthase kinase 3 beta, a key enzyme in activating glycogen formation and outlined in blue. P-MAPK is irrelevant today but, again, might be interesting in the future.Convincingly, palmitate causes insulin resistance and oleate doesn't. Bear in mind that this is a highly constrained experiment to make a specific point. These is no mention of ROS generation but it is worth looking at this from the Protons/ROS viewpoint.Palmitate has an FADH2:NADH ratio of 0.484Oleate has an F:N ratio of 0.457In this experiment conditions are carefully controlled to give us an all or nothing response, almost like switch. The switch trips somewhere between an F:N of 0.484 and 0.457. Insulin resistant vs insulin sensitive. No double bonds vs one double bond.It is possible to adjust the F:N ratio by smaller amounts than by adding a double bond simply by altering the length of a saturated fat. If we consider myristic acid the F:N ratio is 0.482 and for lauric acid it is 0.478.The paper went on to look at insulin signalling using these fats and here are the gels they obtained:At the extreme left is the control without insulin, next is control with supra-maximal insulin but no fatty acid, then rest of the bands have the indicated fatty acids added, all at 0.75mmol/l. I've put in the red line to divide insulin sensitive from insulin resistant results. Everything to the left of the line causes no insulin resistance, to the right significant insulin resistance. The switch is between myritic acid and palmitic acid, F:N 0.482 and 0.484.I would expect C10 capric acid to be insulin signal facilitating and probably C8 caprylic acid too, although its strongly ketogenic effect and partial conversion to palmitate might make that less predictable.Coconut oil is primarily medium chain triglycerides with F:N ratios on the insulin sensitising side of the switch. Formulating a high fat diet out of insulin sensitising fats combined with an insulogenic carbohydrate load seems like a good recipe for obesity.It's always worth reiterating that there is no "switch" as such, there is a general integration of information about energy status and demand using ROS which can be pushed towards lipid storage or use depending on particular inputs. The F:N ratio looks like a switch in a very simple model asking a very simple yes-no question. But that's still useful information for understanding the Surwit diet.Peter
Miki Ben-dor has a new post on his blog
The complete and unifying explanation of human evolution
If you've not read his blog before, now would be a good time to start.
TLDR: If resisting insulin is rendered impossible due to very, very high PUFA diets then mitochondria resort to uncoupling.This paper
Synergy of fatty acid and reactive alkenal activation of proton conductance through uncoupling protein 1 in mitochondriareiterated the well known essentiality of FFAs for the activation of UCP-1 and added in the significant role of reactive alkenyl species. In more common parlance that would be lipid peroxides, primarily those derived from linoleic acid. I thought about it in this post.
This is the next step, which I specifically went looking for because this is how I think life should be organised. It is a perfect example of me having a huge bias, knowing what I want, and going looking for it. You have been warned.It is utterly clear that UCPs in general suppress ROS generation and that some members of the family are not being used for thermogenesis at all, more likely for prevention of the generation of supra-physiological levels of ROS.We have an interesting situation where PUFAs, the prime pathology of which is their failure to generate adequate ROS, are also extremely effective at facilitating uncoupling, which needs significant ROS generation to happen. Where does this superoxide come from?This is the core question.Warning: I think step f) is the one I have least evidence for. Life is like that sometimes.Okay. The story so far:Caloric ingress in to a cell is controlled to an appropriate level while calories are freely available by limiting insulin signalling.Insulin signalling is curtailed by driving electrons in reverse through complex I to generate superoxide and hydrogen peroxide which disable/limit said insulin signalling.This reverse electron transport rises in direct proportion of FADH2 supplied compared to the amount of NADH.The presence of double bonds in fatty acids limits FADH2 generation, limited FADH2 generation limits the control of insulin facilitated caloric ingress and continued insulin signalling diverts calories in to storage.I have to accept that not all excess calories will be stored, some will continue to enter the electron transport chain as both NADH and FADH2. If electrons enter the electron transport chain when there is a low (relative) demand for ATP thena) mitochondria membrane potential will rise, a direct consequence of the inability to limit electrons entering the ETC through complex I and multiple FADH2 entrance points. Protons are pumped but not usedb) the cytochrome C pool will become progressively more reduced, limiting it's ability to accept electrons from complex IIIc) electrons will be transported through the cytochrome b centre of complex III back on to the CoQ coupled) these electrons will replace those absent as a result of double bond containing fatty acid oxidation and will restore superoxide productione) superoxide production, under these circumstances, is being facilitated only at the cost of high membrane potential secondary to low ATP synthase activity in parallel to excess calorie storagef) if the double bond content of the lipids providing input to the CoQ couple from beta oxidation is very, very high then the need for negative feedback through complex III will be very, very high as well and will be associated with an excessively high membrane potentialg) the answer to excess membrane potential is uncouplingh) superoxide positively regulates the activity of UCP-1 as do superoxide derivatives of LAi) uncoupling allows the flow of electrons down the electron transport chain and lowers membrane potential, it immediately stops reverse electron transport/superoxide generation and converts the excess calories entering the cell in to heat, water and carbon dioxideSummary:Normally regulated calorie ingress to a cell occurs when linoleic acid is low.Excess ingress from LA is dealt with by diversion to storage, leading to obesity.Marked excess is dealt with by uncoupling which does not "require" obesity.There are no hard boundaries between the above conditions, there simply appears to be an inverse "U" shaped curve in response to the content of linoleic acid in the diet. Such curves are common in nature.A few last thoughts:Simply looking at the experimental data the situation appears to be that including linoleic acid at levels between somewhere just under 10% up to somewhere in the high 20%s will facilitate excess insulin action and excess lipid storage. As we increase the supply of linoleic acid through the 30%s and in to the 40% region of calories then uncoupling becomes the primary molecular solution to a progressively more intractable problem.It is worth pointing out that in a given mitochondrion there are lots of CoQ/CoQH2 molecules, lots of beta oxidation sites and, while the calculation of FADH2:NADH is useful for insight as to how RET works for a single fatty acid molecule, the mitochondria are integrating lots of FADH2 production sources, lots of NADH sources and are continuously monitoring the membrane potential (which is an integration of energy input/need) as well as the redox state of the CoQ couple.What happens on a whole organism basis is also an integration of all of these effects. The mechanism for weight loss in high PUFA diets is both comprehensible and plausible.The studies are real, the data are real.Personally I still wouldn't go there, but understanding them is key.Peter
Here we go with ad-lib corn oil.
Voluntary corn oil ingestion increases energy expenditure and interscapular UCP1 expression through the sympathetic nerve in C57BL/6 mice
Mice were either offered chow from a hopper or chow from a hopper with the option of corn oil from a drinker bottle in addition. They like corn oil.
The mice with access to corn oil ate more calories than those without:but most calories weren't from chow, top line is grams of chow only, bottom line the weight of chow eaten when there is access to ad lib corn oil:We can look at the total amount of corn oil consumed:Assuming 9kcal/g we can now reverse engineer that to 16kcal of corn oil a day as part of a total daily intake of 19kcal. So that's 84% of calories from corn oil. As 55% of this 84% is linoleic acid that gives 46% of calories as LA. Well in to the weight loss range of intake noted for high LA safflower oil, in fact that's verging on a self selected ketogenic diet, which complicates matters a little. With 16% of calories from chow this will also be rather low in protein, though far from zero carb. Just look at the RER if they have access to corn oil, the black circles. Yes, these mice really are oxidising lipid and very little else, but also bear in mind that exactly the same effect could be obtained with safflower oil under far from ketogenic/low protein conditions. Here are the RERs:Anyhoo. What was the end result? These are the body weights at the end of the eight week trial:
More calories, more oxygen consumption, same body weight.This looks like a generic property of linoleic acid in exactly the same way as weight gain is at lower levels. The Jacobs study rats were around 24%, on the border between obesogenic and weight limiting effects, on the obesity side.To get weight loss you need to go higher with the LA.Just before I finish and post some speculation about mechanisms it's clear from the rest of this study that uncoupling is the answer to the paradox. In modern mice this is mediated through UCP-1 within the interscapular brown adipose tissue, as the paper went to considerable lengths to demonstrate.This is the current level of development in the modern evolutionary terms of rodents. It's a sophisticaled high level system which will overlay the insulin system which will overlay the ROS system. It is perfectly possible to make a case for why this high level system is advantageous by thinking about the underlying ROS system.I'll have a discuss about that in the next post.This series is looking at body weight. Using an approach to normalise body weight which involves the incorporation of markedly unsaturated lipids in to the inner mitochondrial membrane does not strike me as a sensible thing to do. Might be a technique for looking good in your coffin.Peter