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Sunday 31 August 2014

Plasma phospholipid linoleic acid is a marker of health.

A nicely controversial new paper from the American Heart Association, in which linoleic acid in plasma phospholipids is the only PUFA with negative correlation with total mortality. The more LA n-6 in the membranes of your red and white blood cells, together with your lipoproteins, the longer you live. So should we switch back from butter to margarine? 
(tl;dr; if you really care eat some nuts, nuts are the only LA source convincingly associated with reduced mortality, although nuts also being associated with exercise, wealth, not smoking and other markers of virtue, it's hard to be sure, but this latest research does help the nut case).
Here's the abstract

Circulating Omega-6 Polyunsaturated Fatty Acids and Total and Cause-Specific Mortality: The Cardiovascular Health Study

Background—While omega-6 polyunsaturated fatty acids(n-6 PUFA) have been recommended to reduce CHD, controversy remains about benefits vs. harms, including concerns over theorized pro-inflammatory effects of n-6 PUFA. We investigated associations of circulating n-6 PUFA including linoleic acid(LA, the major dietary PUFA), γ-linolenic acid(GLA), dihomo-γ-linolenic acid(DGLA), and arachidonic acid(AA),with total and cause-specific mortality in the Cardiovascular Health Study, a community-based US cohort.
Methods and Results—Among 2,792 participants(age≥65y) free of CVD at baseline, plasma phospholipid n-6 PUFAwere measured at baseline using standardized methods. All-cause and cause-specific mortality, and total incident CHD and stroke, were assessed and adjudicated centrally. Associations of PUFA with risk were assessed by Cox regression. During 34,291 person-years of follow-up (1992-2010), 1,994 deaths occurred (678 cardiovascular deaths), with 427 fatal and 418 nonfatal CHD, and 154 fatal and 399 nonfatal strokes. In multivariable models, higher LA was associated with lower total mortality, with extreme-quintile HR=0.87 (P-trend=0.005). Lower death was largely attributable to CVD causes, especially nonarrhythmic CHD mortality (HR=0.51, 95%CI=0.32-0.82, P-trend=0.001). Circulating GLA, DGLA, and AA were not significantly associated with total or cause-specific mortality; e.g., for AA and CHD death, the extreme-quintile HR was 0.97 (95%CI=0.70-1.34, P-trend=0.87). Evaluated semi-parametrically, LA showed graded inverse associations with total mortality (P=0.005). There was little evidence that associations of n-6 PUFA with total mortality varied by age, sex, race, or plasma n-3 PUFA. Evaluating both n-6 and n-3 PUFA, lowest risk was evident with highest levels of both.
Conclusions—High circulating LA, but not other n-6 PUFA, was inversely associated with total and CHD mortality in older adults.

You'll notice the name of Dariush Mozzafarian as senior author (he's from the U.S. but the research was done in Sydney, Australia, so it's unlikely he supervised it in person). Mozaffarian is open-minded about saturated fat and low-carb diets and has played a major role in rehabilitating dairy fat, which ought to lay to rest conspiracy theories about the study (publication bias might be another question). The result makes sense to me.
Remember that these are plasma phospholipids, that is, they exist in the oxidising environment of human blood. We make use of this dual state system of redox balance; antioxidant enzymes and glutathione keep the intracellular balance in favour of reduction, and the non-enzymatic reactions inevitable in the anarchic extracellular environment, and the relative lack of extracellular antioxidant enzymes, reverse that, so that insulin and amylin molecules and immunoglubulins adopt their active, oxidised structures only after exiting cells, and ascorbic acid is oxidised to dehydroascorbic acid before being taken up and regenerated - reduced - inside cells.
Everyone knows what happens if this balance is lost either way; reductive stress limits the cell's ability to perform metabolic functions, oxidative stress degrades cellular structures and closes them down.
Cardiolipin - the 4 radicals are predominantly C18:2, linoleate.
Linoelic acid is a major determinant of cellular health, because it's incorporated into a phospholipid called cardiolipin, which sits in mitochondrial membranes; the linoleate is essential precisely because it's the most easily oxidisable PUFA in living systems. When cardiolipin oxidises faster than glutathione and its enzymes can repair it, it's time to close that mitochondrion and start another - in this way, inefficient mitochondria that spew free radicals aren't kept alive forever. This isn't the only function of cardiolipin, but canary in the metabolic coalmine is a pretty useful job.
Cardiolipin radicals

Therefore it seems to me that the presence of higher levels of LA in plasma phospholipids, in an oxidising environment, is not a mere indication of its dietary ingestion, but rather a marker of the antioxidant status of the blood and of the lipoproteins, which carry carotenoids, coQ10, retinol, tocopherol and other lipid antioxidants to and from cells. This explains why nut consumption is inversely associated with mortality, but overall LA consumption is not (if it was, the authors of this study would have mentioned it - senior author Hu is the nut guy).
It would be pretty hard to have a less than adequate LA intake on a high-fat paleo diet, as I discussed here.

Another process destructive of plasma phospholipid LA is inflammation; the conversion of arachidonic acid to prostaglandins and eicosanoids. Because AA itself is essential and conserved in the cell membrane, there is a flux through AA, with a constant replacement from LA. And guess what? Plasma phospholipid PUFAs, including LA, are preserved on very low carb diets - one of the anti-inflammatory benefits.

In other words, the paper under discussion seems to support the good, old-fashioned, free radical theory of disease and ageing, as well as the inflammatory theory of CHD. It doesn't support the intake of high levels of high LA seed oils, because what is going to happen to that LA? Almost all of it is going to be oxidised in the liver, with 22% of the acetyl-CoA produced going to make cholesterol.
You heard me - linoleic acid has the opposite effect from statins, increasing hepatic cholesterol synthesis. It also increases hepatic LDL receptors and pulls cholesterol in from the blood stream. Sometimes too much cholesterol, because all this free cholesterol oxidises easily, and when it does, cardiolipin also oxidises and mitochondria die (all this is referenced in my NASH series, see the Labels sidebar). Statins, if you overlook the side effects, are probably anti-inflammatory; I don't think there's much chance that seed-oils are.

Tuesday 26 August 2014

Amylin - the "root cause" of diabetes?

When this story broke, I had to look up amylin in my biochemistry (Mathews, Van Holde, Aherne 2000) and physiology (Best and Taylor, 1984) texbooks. Neither has amylin indexed. Nor do I remember any insightful blogs about amylin from the usual suspects recently. Flyin' blind here. Thank God for wikipedia.

This news story linking amylin build up to diabetes, based on new research conducted jointly in Auckland, New Zealand and Manchester England, makes the case reasonably clearly:

What does it mean?

Diabetes is defined as the loss  of beta-cells, so that insulin production ceases - the insulin dependent stage. Interestingly, amylin allegedly plays the same role in type 1 and 2 diabetes, and the aggregates of amylin are amyloid formations similar to those seen in alzheimers. Before you start thinking of type 3 diabetes, though, the amyloids in Alzheimers aren't made of amylin. Amyloid just means "starch-like". What they have in common is beta-sheet protein structures (nothing to do with beta-cells) misfolding in a contagious, prion-like process.

What is amylin?

Amylin, AKA Islet Amyloid Polypeptide (IAPP) is a protein produced by beta-cells in tandem with insulin. Insulin promotes glucose uptake and metabolism in cells, amylin slows glucose - and other food - uptake from the gut, by delaying gastric emptying, and decreases appetite; it also seems to be responsible from the switch from muscle glycogenogenesis to adipose lipogenesis, so probably has a role in obesity. According to wiki the ratio is 100:1 in favour of amylin (unless I've read it wrong and it's the other way round). Is the ratio always constant? Does amylin have any independence from insulin? In any case, amylin plus glucose represents a two-pronged approach to preventing systemic over-exposure to glucose; insulin pulls glucose out of, amylin slows access into, the blood.
Some people think amylin should be included with injectible insulin for type 1 diabetics.

Amylin overproduction results in incompleted (proamylin, or proIAPP) molecules being retained in cells; these serve to promote crystalization of further amylin beta-sheets in the cell, the amyloid clumps then initiate apoptosis, killing of the beta-cells with eventual loss of insulin - and amylin - production.

This looks like the end-stage of hyperinsulinaemia; this over-production of amylin (and insulin) is being driven by excess glucose intake, the amylin incompletion and insulin resistance may also indicate an overall micronutrient deficiency, and the out-of-phase insulin response to begin with indicates a) salivary amylase polymorphism, b) presence of excess omega 6 -> PGE2, c) absence of factors inhibiting PGE2, e.g. omega 3, CLA (the most likely reason for the diabetes-protective effect of dairy fat, or, if you don't eat dairy, ruminant fats).
Note that PGE2, an omega 6 series prostaglandin, inhibits glucose uptake, and to a somewhat lesser extent fructose, in sheep, but increases it in rats - probably the better model for human response. If this is the case, PGE2 is increasing glucose uptake as it decreases first phase insulin response, which is already diminished in individuals with fewer salivary amylase gene copies. The compensatory rise in second phase insulin response - exacerbated by 12-HETE, an omega 6 series eicosanoid - results in a larger area under the curve for both glucose and insulin; i.e., in hyperglycaemia and hyperinsulinaemia.

It is interesting that this hyperinsulinaemia-related problem with amylin is also causative in type 1 diabetes. It means that lower carb diets can be recommended to those at risk of this disease.
The T1D connection is really interesting. .I have a friend who is T1 diabetic; he said when he was 12 he got a craving to eat dry Milo (Nestles chocolate flavoured drink sweetened with maltose, i.e. glucose), ate a big tin of it in one day, crashed into a coma and woke up in hospital on insulin. That seems to show pronounced hyperinsulinaemia immediately preceding beta-cell burn out. Perhaps a combination of sudden hyperinsulinaemia from an inflammatory, infective, or autoimmune cause together with a low tolerance for amylin production.

Both insulin and amylin contain disulfide bridges (Cys-S-S-Cys) and this is interesting as the bridges are only meant to form outside the cell (the peptide is expressed as a string from the reducing environment of the cell, where the cysteine residues exist as 2x Cys-S-H, into the more oxidising serum enviroment, where the sulfur bonds snap together as the cysteine residues are oxidised to Cys-S-S-Cys plus H2O). If insulin output is very high, this puts a heavy demand on the reducing systems of the cell; glutathione, glutathione reductase, thioredoxin reductase and so on. Hydrogen sulfide - H2S - is also protective in the beta-cell for some reason. These are mostly selenocysteine enzymes, and selenocysteine is also required for a protein folding enzyme. (note though, supplying 200mcg Se as selenomethionine in America, not overall a selenium deficient country, has been associated with double the rate of diabetes in one study that was not directed at glycemic endpoints).  

Selenoprotein S is involved in retrotranslocation of misfolded proteins from the endoplasmic reticulum to the cytosol. This protein may also be involved in inflammatory and immune responses

Here is the Wiki page on amylin. It's interesting, has the background to the latest research, and I wonder why we never hear about this hormone in diet-health discussions? I guess that from now on we will be hearing more of it.

The take home - keep insulin production under control by counting carbs and avoiding vegetable seed oils, and amylin should tag right along, ensuring beta-cell function lasts a lifetime.

Sunday 17 August 2014

The Difficulty of Attributing Ends to Means - Selenium and Heart Disease

One of the arguments used by New Zealand's Public Health experts still opposed to LCHF and Paleo diets - opposed, that is to the idea of the more saturated animal fats being safe, either overall, or in a mainly wholefood, low carb context - is that low-fat dietary guidelines, and the decreased intake of butter, with increased use of margarine and seed oils, ought to be given some of the credit for a decreased rate of heart disease in the past 30 years.
They'll acknowledge that smoking cessation (to be fair, they had a bit to do with this too) accounts for some of the decrease.
But is that accounting for every factor likely to be significant? Most people who had heart attacks In New Zealand prior to 1984 went through the Great Depression, World War 2, and the 1951 Waterfront Strike. They had parents who lived through the 1919 influenza outbreak. Their lives were different in many ways from those of the generation dying early or living longer today.

One of those differences is environmental - the toxicity of industrial, urban, and rural environments has changed, mostly for the better; testing and legislation is mainly a product of 1970's environmental activism. And particulate vehicle emissions, to give the best-researched example, do seem to be causative of atherosclerosis. The last few decades have seen tighter and tighter restrictions on vehicle exhaust emissions on our roads and on the burning of fossil fuels and wood in private fireplaces in our cities.

Another change is genetic - in 1984, Wang was not the most common surname in Auckland. New Zealand has always had a small population, with a tendency for Kiwis to seek their fortunes offshore, and this loss has been offset and the population increased steadily through immigration, with the migrants' countries of origin altering over time.

Another change is in the micronutrient content of the diet. In early days, the poor were at more risk of deficiency diseases than they are today. Vitamins and minerals are added to junk food to give the advertisers something to boast about, and even to improve shelf life; the use of ascorbic acid as an antioxidant (E300-304) is no doubt a safeguard against scurvy in the least-well fed populations.

This change also applies to wholefoods - since the 80's, NZ's importation of foods - esp grains, legumes and fruit has increased, which means a wider spread of micronutrition. There is a wider variety of foods, and of ingredients; market d
eregulation since the 1980's means the New Zealand food environment has altered significantly.

See, for example Medsafe on selenium
The intake of selenium by New Zealanders has increased since the earlier Total Diet Surveys in 1982 and 1987/88. To prevent animal diseases, farm animals are drenched with selenium-enriched products and the meal fed to poultry has selenium added. Generally bread made in the South Island is lower in selenium than bread made in the North. Since deregulation of the grain industry much North Island bread has a significant proportion of imported, largely Australian wheat which is selenium-rich. But South Island bread is made predominantly with wheat grown locally in low-selenium soils. Current practices need to continue for the selenium intake of New Zealanders to remain around recommended levels.Meats, eggs, dairy products and bread are the main sources of selenium in New Zealand diets.6 Kidney, liver and seafood, and for the vegetarian, imported legumes are rich in selenium.

The relevance of this is that Finland - a seriously deficient country like NZ was 30 years ago - mandated selenium in fertilizer in the 1980s to reduce CVD incidence, raising serum Se levels within a short time.
Result? (or, correlation?)

Between 1982 and 1997, coronary heart disease mortality rates [in Finland] declined by 63%, with 373 fewer deaths in 1997 than expected from baseline mortality rates in 1982. Improved treatments explained approximately 23% of the mortality reduction, and risk factors explained some 53–72% of the reduction.

This, of course, has been attributed to lipids and SFA too - selenium has been completely forgotten, it seems - but this was a huge, and brave, public health effort in Finland, comparable to iodised salt being introduced to iodine-deficient societies in the 1920s. And matched by what NZ has done, albeit by chance more than by design. Finland was one of Ancel Key's strongest statistical supports - and the methodologically questionable Finnish Mental Hospital Study is still a mainstay of lipid hypothesis epidemiology. We are not talking selenium supplementation above requirements, which doesn't prevent CVD, but correcting selenium deficiency. (If you ask me, the micronutrient theory of diet-health correlations is sadly neglected at present. What slows the oxidation of lipoproteins? Not so much any antioxidant tested separately at megadose intakes - just the whole antioxidant defense system working smoothly on a little bit of everything it needs. Selenium, zinc, etc., etc., etc.).
2014 is not just 1984 with less saturated fat.

There is more detail about the Finnish selenium program here.

I bought this 45RPM record at a thrift shop the other day. Blue Band, by Bobongo Stars - the full version (it covers both sides) is pretty cool, with a great old-school synthesizer solo. The story of the song, and of Marsavco margarine is told here; it's a palm oil product (so not much need for hydrogenation), and today it's fortified with vitamins including nicotinamide; probably a good thing in the corn-eating regions of Africa. The song is credited to Marsavco-Zaire.