De novo sterologenesis in intact primates

Recent studies have demonstrated that in intact rodents, extrahepatic tissues are much more important sites of de novo sterologenesis than previously appreciated. The present investigation was undertaken to localize the sites of cholesterol and nonsaponifiable lipid synthesis in intact primates. Tritiated water was employed as the radiolabeled tracer for quantifying sterol synthesis. Our results indicate that in the intact primate, tissues other than the liver account for the majority of the newly synthesized cholesterol (74.5% to 84.4%) and nonsaponifiable lipids (77.3% of 86.5%). This extrahepatic sterologenesis is primarily localized to the intestine, skin, and carcass (all tissues not specifically analyzed). Sterologenesis in the other tissues made only a minor contribution to total animal cholesterol and nonsaponifiable lipid synthesis. Moreover, cholesterol feeding that inhibited hepatic and small intestinal sterol synthesis did not greatly affect skin or carcass sterologenesis. This indicates that transport of sterols from either the live or intestine to peripheral tissues does not contribute greatly to the newly synthesized sterols localized in extrahepatic, extraintestinal sites.