Liver fat content influences cholesterol metabolism
MedWire News: Researchers in Finland have found a strong association between cholesterol synthesis and absorption and liver fat content, independent of body weight, in nondiabetic adults.
Their study, which investigates the influence of non-alcoholic fatty liver disease (NAFLD) on cholesterol metabolism, found that patients with NAFLD showed an increased synthesis and decreased absorption of cholesterol compared with controls.
In the Journal of Hepatology, Piia Simonen (University of Helsinki, Finland) and colleagues say that this implies "the more fat the liver contains, the higher the synthesis and the lower the absorption of cholesterol."
In all, 242 nondiabetic participants (aged 20-65 years) were divided into those with NAFLD (n=114; liver fat greater than 5.56%) and those without the condition (n=128; liver fat less than 5.56%), who served as controls. Their cholesterol metabolism was assayed by measuring serum non-cholesterol sterols, surrogate markers of cholesterol synthesis, and absorption.
Simonen's team shows that liver fat content is positively associated with markers of cholesterol synthesis and inversely associated with markers of cholesterol absorption (9% and 7% correlation, respectively), implying that the more fat the liver contains, the higher the synthesis and lower the absorption of cholesterol.
The cholesterol synthesis markers cholestenol, desmosterol, and lathosterol were significantly higher in patients with NAFLD than in controls (54.4 vs 45.9 µg/dl, 191.2 vs 164.9 µg/dl, and 356.6 vs 291.2 µg/dl, respectively), while the cholesterol absorption markers cholestanol, campersterol, and sitosterol were significantly lower (240.1 vs 256 µg/dl, 351.4 vs 459.8 µg/dl, and 174.5 vs 225 µg/dl, respectively).
These differences remained significant after adjustment for body mass index and gender.
There was an inverse relationship between markers of cholesterol synthesis and absorption, suggesting that the homeostatic regulation of cholesterol metabolism was not altered in the study population.
Low-density lipoprotein (LDL) cholesterol levels were similar in the two groups.
The researchers say: "Although LDL cholesterol concentrations are unchanged, cholesterol metabolism in NAFLD is characterized by increased synthesis and diminished absorption of cholesterol."
They add that an increase in cholesterol synthesis in the liver could contribute to the pathogenesis of NAFLD, and its progression to steathohepatitis, due to the toxic nature of free cholesterol in these cells.
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By Nikki Withers