The effect of carbohydrate intake on the lipolytic rate in depleted patients

The effect of intravenous carbohydrate intake on glycerol turnover and fat metabolism was estimated in six nutritionally depleted surgical patients requiring total parenteral nutrition. Two diets were given. Nitrogen intake was the same in both diets. The calorie intake, adjusted by varying glucose intake, provided either 72% or 128% of the measured resting energy expenditure. Glycerol turnover was measured during administration of 5% dextrose solutions before starting total parenteral nutrition, and again after 4 days on each diet. Turnover rates of glycerol were closely correlated with plasma concentrations. However, fractional turnover rates were only two-thirds of normal values, indicating decreased clearance possibly due to decreased hepatic blood flow. Glycerol turnover, plasma free fatty acid concentrations, and rate of fat oxidation declined progressively with increased glucose intake. When compared with these results, previous studies of injured and septic patients showed: higher values for glycerol turnover, FFA concentrations, and fat oxidation; poor corrlation between glycerol turnover and concentration; inhibition of lipogenesis at high glucose intake; and high rates of norepinephrine excretion. The data suggest that in severe injury, counter regulatory hormones may almost completely block the effects of insulin on hormone sensitive lipase but have less influence on insulin stimulation of FFA esterification and inhibition of ketone body synthesis.