Thursday, 23 February 2017
Dr Yu's group have produced (in 2015) a re-analysis of their diet data from the HALT-C study; the original paper, which led me to look into liver cholesterol mechanisms a few years back in the NASH series, had an increased risk of transplantation and death in people on the HALT-C trial (a long-term, low-dose trial of alpha-interferon for prevention of cirrhosis and hepatocellular cancer in Hep C, mostly geno 1) for people with higher intakes of dietary cholesterol.
Thanks to Olga Kuchukov for bringing this 2015 paper to my attention.
The new look at the same data is stratified by sex and finds no association at all between dietary cholesterol and harm for men, but a strong association for women, mainly for post-menopausal women.
Each higher quartile of cholesterol intake was associated with an increased risk for liver-related death or transplantation in women (adjusted hazard ratio (AHR) 1·83; 95 % CI 1·12, 2·99; P trend=0·02), but not in men (AHR 0·96; 95 % CI 0·76, 1·22; P trend=0·73). Compared with women whose cholesterol intake was within the recommended guidelines (300 mg/d with a 8368 kJ (2000 kcal) diet), women who consumed more cholesterol had significantly increased risk for liver-related death or transplantation (AHR 4·04; 95 % CI 1·42, 11·5).
This degree of sex difference isn't plausible - in terms of metabolic risk post-menopausal women are more similar to men than are pre-menopausal women, and something that is harmful to women may be less harmful or more harmful to men - sex differences are common - but it's very unlikely to have no effect at all on men if it has a strong effect on women.
Mechanistic data are currently lacking to explain this sex
difference. In fact, most animal studies showing hepatotoxicity
from dietary cholesterol all involved males(6,7,25,26). Female
mice, however, have been demonstrated to absorb cholesterol
more efficiently than male mice, possibly owing to their larger
bile acid pool(27). In the setting of a cholesterol ‘challenge’,
female mice developed significantly more hepatic accumulation
of free cholesterol than did males(27). To our knowledge, there
is no direct evidence of a sex difference in humans in terms of
cholesterol absorption or hepatic cholesterol accumulation in
response to dietary cholesterol.
Cholesterol is protective in animal models of alcoholic liver disease, it takes very large doses no human would eat to produce harm in these animal models.In rats given intragastric ethanol and either corn or fish oil, addition of cholesterol (1%) does not change the degree of fatty infiltration but prevents hepatic necrosis and inflammation and enhances hepatic fibrosis. Cholesterol in this model decreases the enhanced low-density lipoprotein receptor message, eliminates messages for TNF-a and COX-2, and decreases plasma and liver levels of thromboxane B2, and products of lipid peroxidation, whereas it increases transforming growth factor-b message. The anti-inflammatory effects of cholesterol are most likely related to a decreased uptake of arachidonic acid caused by downregulation of the low density lipoprotein receptor and its decreased conversion to eicosanoids via decreased COX-2 activity. Enhanced fibrosis may be mediated by increased transforming growth factor-b.
The variation in cholesterol in the HALT-C trial is not large, and nowhere near the 1% of diet used in animal trials.
In terms of
metabolic parameters, higher cholesterol intake was associated
with higher BMI, fasting glucose, insulin, homoeostatic model
assessment (HOMA-IR) and prevalence of diabetes.
Cholesterol could not possibly cause these things, yet they would contribute to the risk of cirrhosis and liver cancer. They would also over-ride the normal adjustment to dietary cholesterol, because insulin stimulates the liver to make cholesterol.[3,4]
The second limitation of our study is that the relationship
between cholesterol intake and liver-related mortality or
transplantation may be confounded by other factors, despite
our extensive adjustments. The most obvious potential confounders
are other dietary factors. Although we adjusted for
total energy intake, to what extent other nutrients confound the
observed association between categorised cholesterol intake
and liver-related mortality is unknown. One known example is
dietary fructose, which has also been implicated as a cofactor in
Fructose was not measured in HALT-C, and nor was linoleic acid (total PUFA would have been sufficient).
So why was there ZERO correlation between high cholesterol intake and cirrhosis in men, yet a strong one in women?
Here's a suggested explanation; 1) that some post-menopausual women with Hep C are more health-conscious so consume more linoleic acid (omega-6 PUFA than men), 2) that some post-menopausal women with Hep C consume more baked desserts and pastries (combinations of palm oil, butter or hydrogenated vegetable fat and refined carbohydrates, often made with eggs especially at home) that increase insulin resistance. The two are not mutually exclusive; it's common for a health conscious person to try to offset behaviours they know to be unhealthy with others they've been led to believe are protective.
Dietary cholesterol should reduce expression of HMG-CoA reductase via an efficient feedback loop, but the effect of high linoleate intakes or of hyperinsulinaemia over-ride this mechanism.
12.5% of carbon from linoleate that reaches the liver is converted to cholesterol and other sterols.
This means that just 6mls of soybean oil, if all of it reaches the liver (which isn't the case, but much of it will) supplies as much cholesterol as 100 grams of eggs.
Linoleate will also upregulate the LDL receptor, bringing additional cholesterol out of circulation into the liver.
Add to this the effect of insulin - "β-Hydroxy-β-methylglutaryl coenzyme A reductase activity in rat liver increased 2 to 7-fold after subcutaneous administration of insulin into normal or diabetic animals." and we can produce a context in which dietary cholesterol cannot be compensated for and contributes to excess.
But we can also create a context in which the anti-inflammatory effects of dietary cholesterol (and egg phospholipids rich in omega-3s) predominate, just by restricting carbohydrate, and avoiding excessive linoleate intakes.
With genotype 1 HCV, the virus itself is causing insulin resistance; the treatment plan highlighted in this blog (very low carbohydrate, low linoleate, including some SFA with MUFA in a 1:2 ratio and ample DHA and EPA, some intermittent fasting or time-restricted feeding) reduces viral load and corrects hyperinsulinaemia (saturated fat of C:16, C:18 chain length can add to insulin resistance in a high carbohydrate diet, but will have no harmful effect in a low-carbohydrate diet because serum levels of these fats are controlled by carbohydrate and insulin.)
To quote insulin resistance expert Benjamin Bikeman PhD, it's better for your health to be getting your cholesterol from low carbohydrate food rather than making it because your insulin is too high. (follow him on twitter @BenBikmanPhD ). And, I'd add, because your linoleate intake is also too high. That's the perfect storm.
There's one case-control study of HCV and diet showing that higher intakes of PUFA and carbohydrate (but not SFA or MUFA) are associated with liver damage, consistent with the pathways I've discussed here (and with other mechanisms discussed elsewhere on this blog).
"Intake of carbohydrates, lipids and polyunsaturated fatty acids, and alcohol consumption were independent factors of liver damage at histology (logistic regression analysis)."
There are low-quality sources of cholesterol, such as processed meats, where the phospholipids that accompany cholesterol in natural foods are absent or damaged and the cholesterol is likely to be oxidised. (The role of oxidised cholesterol in disease is another factor which I've left out of this discussion).
I prefer sources of cholesterol and phospholipids that are minimally processed or heated - eggs, cheese, fish roe. And some good hepatoprotective fat sources have no cholesterol - coconut, olive oil.
 Yu L, Morishima C, Ioannou GN. Sex difference in liver-related mortality and transplantation associated with dietary cholesterol in chronic hepatitis C virus infection. British Journal of Nutrition (2016), 115, 193–201.
 Mezey E. Dietary Fat and Alcoholic Liver Disease. Hepatology 1998; 28(4) Link
 Ness GC, Zhao Z, Wiggins L. Insulin and glucagon modulate hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity by affecting immunoreactive protein levels. J Biol Chem. 1994 Nov 18;269(46):29168-72.
 Lakshmanan MR, Nepokroeff CM, Ness GC et al. Stimulation by insulin of rat liver β-hydroxy-β-methylglutaryl coenzyme A reductase and cholesterol-synthesizing activities. Biochemical and Biophysical Research Communications
Volume 50, Issue 3, 5 February 1973, Pages 704-710
 Cunnane SC, Belza K, Anderson MJ, Ryan MA. Substantial carbon recycling from linoleate into products of de novo lipogenesis occurs in rat liver even under conditions of extreme dietary linoleate deficiency. J Lipid Res. 1998 Nov;39(11):2271-6.
 Ratliff JC, Mutungi G, Puglisi MJ, et al. Eggs modulate the inflammatory response to carbohydrate restricted diets in overweight men. Nutrition & Metabolism 2008; 5(6).
 Loguercio C, Federico A, Masarone M et al. The impact of diet on liver fibrosis and on response to interferon therapy in patients with HCV-related chronic hepatitis. Am J Gastroenterol. 2008 Dec;103(12):3159-66.