Effects of dietary pectin on the hepatic activities of hydroxymethyl glutaryl CoA reductase and acyl CoA cholesterol acyltransferase in cholesterol supplemented mice

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Plasma lipoprotein cholesterol and hepatic activities of hydroxymethyl glutaryl CoA reductase (HMGR) and acyl CoA cholesterol acyltransferase (ACAT) in mice fed a semi-synthetic diet supplemented with 5% low methoxyl pectin with or without addition of 0.5% cholesterol for 4 weeks were examined. While plasma concentrations of total cholesterol and triglycerides were significantly reduced, the hepatic levels of total and esterified cholesterol were markedly increased, and triglyceride levels remained unaffected when cellulose in the diet was substituted for by pectin in the cholesterol-enriched diet. The administration of 0.5% cholesterol to control animals resulted in a 50% reduction in the hepatic HMGR activity. This activity was restored to its control level when cellulose was substituted by pectin in the diet. The hepatic ACAT activity, on the other hand, was significantly increased when fed a diet containing 0.5% cholesterol. This effect remained unchanged when pectin was administered. The hypolipidemic action of pectin does not appear to be mediated through inhibition of cholesterol synthesis. It is possible that the decreased plasma level of cholesterol is the reflection of its accumulation in the liver.