EFFECTS OF TOTAL PARENTERAL-NUTRITION ON LIPID-METABOLISM IN RATS

Background: The pathophysiologic mechanisms behind the development of liver steatosis during total parenteral nutrition (TPN) and the possib le relationship to alterations of lipoprotein lipase activities in dif ferent tissues are not fully known. It is also unknown whether continu ous and discontinuous administration of TPN affect lipid metabolism di fferently. Methods. TPN, including 8.4 g of triglycerides per kilogram per day, was given for 10 days to two groups of male Sprague-Dawley r ats that received the infusions discontinuously and continuously, resp ectively. Freely fed rats were used as controls. Results: TPN led to h yperlipidemia and accumulation of triglycerides in the liver. High-den sity lipoproteins were enriched in triglycerides, whereas high-density lipoprotein cholesterol and phospholipid levels were low. The activit ies of hepatic lipase were markedly deer-eased, and lipoprotein lipase activities in adipose tissue and in cardiac muscle were both up-regul ated. The increased levels of cholesterol acid phospholipids in the se rum of TPN animals were more pronounced after discontinuous administra tion. Conclusions: TPN including lipids interferes with the normal reg ulation of lipid metabolism. Although the mechanisms remain obscure, t he elevation of lipoprotein lipase activities seems functionally impor tant to accommodate the increased input of triglycerides during TPN. P ossibly, the observed alterations in lipase activities may be attribut ed to a state of hypothyroidism.