Serum squalene and noncholesterol sterols before and after delivery in normal and cholestatic pregnancy

Mechanisms of hyperlipidemia were studied by measurement of serum lipid concentrations and the ratios of cholesterol precursors (squalene, delta 8-cholestenol, desmosterol, and lathosterol), plant sterols (campesterol and sitosterol), and cholestanol (a 5 alpha-derivative of cholesterol) to cholesterol in nonpregnant women, and normal and cholestatic pregnancies near term, and a few days and 6 weeks after delivery. The ratios of the precursors are known to reflect cholesterol synthesis, those of plant sterols and cholestanol the absorption efficiency and biliary sterol secretion of cholesterol. In normal pregnancy, increased serum cholesterol was associated with up to 2-fold increases in squalene, desmosterol, and lathosterol proportions, and the values remained elevated, especially for desmosterol, during the lactation period. These findings suggest that pregnancy and lactation are associated with increased cholesterol synthesis. The proportions of plant sterols were slightly lower, but that of cholestanol was 2-fold that of the nonpregnant women. In contrast to the latter group, the cholestanol proportions were not related to those of plant sterols or the campesterol/sitosterol ratio. The values, especially of cholestanol, became normal during lactation. In cholestatic pregnancy the changes were basically similar, but the serum values of delta 8-cholestenol increased more, and those of squalene, desmosterol and lathosterol less markedly, and the mean cholestanol proportion was 40% higher and the campesterol/sitosterol ratio 15% lower than in the normal pregnancy. Cholestanol was positively related to serum bilirubin and bile acids in cholestatic pregnancy, yet only one-third of the cholestatic pregnant women exhibited cholestanol values higher than in the healthy pregnant women.