Decreased serum lecithin:cholesterol acyltransferase activity in spontaneous cases of fatty liver in cows.

摘要

The lecithin-cholesterol acyltransferase (LCAT) [phosphatidylcholine-sterol acyltransferase] activity of 16 cows with fatty liver (631?2 U, mean ?s.e.m., decrease in nmol of free cholesterol per h per ml of serum) was significantly lower than thatin 16 healthy cows (979 ?22 U). In addition to the decrease in LCAT activity, the concentrations of phosphatidylcholine (a fatty aryl donor for esterification of free cholesterol) and of cholesteryl esters (products of the LCAT reaction) were reduced in high-density lipoprotein fractions from cows with fatty livers. The serum concentration of apolipoprotein A-I, an activator of LCAT, was also reduced in cows with fatty livers. It is suggested that decreased LCAT activity, which may be caused by impaired hepatic secretion or by reduced plasma concentrations of phosphatidylcholine and apolipoprotein A-I, resulted in lower plasma levels of cholesteryl esters. It is further suggested that because cholesteryl esters are used in steroidogenic tissues for the synthesis of steroid hormones such as progesterone and glucocorticoids, a reduction in their supply may contribute to the reduced fertility and immune competence observed in cows with fatty livers.