Metabolism of linoleate and palmitate in patients with hypertriglyceridemia and heart disease

Abstract

The metabolism of linoleate and palmitate was studied in 8 subjects with coronary heart disease with plasma triglyceride concentrations ranging from 66 to 275 mg. per 100 ml. Linoleic acid-1-C14 and palmitic acid-9,10-H 3 were complexed with albumin and injected intravenously. In every experiment the fractional turnover rate of linoleic acid was greater than that of palmitic acid. The fractional turnover rate of linoleic acid, but not of palmitic acid, was found to be significantly and inversely related to the plasma triglyceride concentrations. Both labelled fatty acids were incorporated into the triglycerides of plasma very low density lipoproteins and reached peak specific radioactivity at about 2 hours after injection. The rates of disappearance of the 2 isotopes from triglycerides were then found to be exponential over a period of at least 4 hours. The fractional turnover rate of palmitate did not vary significantly with the triglyceride concentration, but the fractional turnover rate of linoleate was significantly and inversely related to the triglyceride concentration. The per cent palmitate content of triglycerides of low density lipoproteins was determined by gas chromatography and was found not to vary with the concentration of triglyceride. The per cent linoleate content was, however, reduced at higher triglyceride levels. The studies were repeated in 2 subjects whose plasma triglyceride concentrations were halved by an over-all restriction of calories. There was a corresponding increase in the fractional turnover rate of triglyceride linoleate but that of palmitate remained unchanged. It is concluded that the development of some varieties of hypertriglyceridemia is accompanied by a corresponding increase in the turnover of palmitate but not of linoleate, and that this may represent increased synthesis of lipid from carbohydrate.