The optimal fat/glucose ratio for TPN was determined, using oxidation and distribution of (14)C labeled fat emulsion and glucose. Animals were divided into five groups according to percentage of energy supplied as fat i·e. 0%, 20%, 40%, 60% and 80%, respectively.
(14)C-labeled fat emulsion and glucose were injected during TPN and the rate of oxidation to (14)CO(2) as well as (14)C distribution in various organs were measured. Oxidation of (14)C-glucose was constant in all groups and that of (14)C-labeled fat emulsion was inversely related to the amount of glucose administered simultaneously. (14)C-distribution in adipose tissue was correlated to the amount of glucose infused. As oxidation of glucose was significantly higher than that of fat, the higher the fat content of non-protein calorie, the less oxidation was observed. The groups given 60% and 80% energy composed of fat, showed less nitrogen retention and glycogen content in liver and muscle. These two groups exhibited high blood levels of free fatty acid, cholesterol and phospholipids. These findings suggest that the optimal blending ratio of fat would be around 20-40% of the non-protein calories.