Nutritional effectors of hepatic steatosis induced by parenteral nutrition in the rat.

The relative importance of three nutritional variables, nonprotein energy level, glucose-lipid calorie distribution and amino acid nitrogen level, in contributing to the steatosis that develops during a short course of parenteral nutrition was studied in intravenously fed rats. Eight infusates were tested that contained various combinations of glucose, lipid emulsion and amino acids. The infusate nonprotein energy level was the predominant effector of liver lipid content. The excessive energy level was associated with significant increments in steatosis, ranging from a 26% increase for high-fat, adequate-nitrogen infusates to a 95% increase for low-fat, adequate-nitrogen infusates. An interaction of amino nitrogen level and glucose-lipid calorie distribution also affected the severity of steatosis. The steatosis observed with inadequate-nitrogen infusates was accentuated in combination with the high-fat calorie distribution and was attenuated with the low-fat calorie distribution. The most striking effect of nitrogen inadequacy was a 3-fold increase in liver lipid content with the excessive calorie, high-fat infusates. The infusate that minimized steatosis provided energy and nitrogen at adequate levels and was low in fat content. This infusate also led to liver lipid composition and plasma lipid levels that most closely resembled those of rats fed stock diet.