Bile acids and plasma high density lipoproteins: biliary lipid metabolism in fish eye disease

Cholesterol in plasma high density lipoproteins (HDL) has been proposed to serve as preferential precursor for bile acid biosynthesis in the liver. Furthermore, a negative relationship between plasma levels of HDL cholesterol and biliary saturation with cholesterol has been reported in healthy females. We have performed metabolic studies on a female patient with fish eye disease, a familial condition where plasma HDL levels are reduced by 90% and the concentration of plasma triglycerides is moderately increased. Both the total production of bile acids and the net steroid 'balance' (reflecting total body cholesterol synthesis) were within the range seen in normolipidaemic as well as in hypertriglyceridaemic females. Also the biliary lipid composition and cholesterol saturation of bile were normal. A qualitative abnormality in the bile acid pattern was observed, however, in that the ratio between the synthesis of cholic acid and chenodeoxycholic acid was reduced. It is concluded that a low HDL cholesterol level is not necessarily associated with quantitative abnormalities of biliary lipid metabolism. The abnormal bile acid synthesis ratio may reflect changes in the hepatic precursor pools of cholesterol as the consequence of HDL deficiency, however.