The Kinetics of Plasma Free Fatty Acid and Triglyceride Transport in Patients with Idiopathic Hypertriglyceridaemia and Their Relation to Carbohydrate Metabolism

Abstract. Plasma free fatty acid and triglyceride transport kinetics were assessed in 20 patients with idiopathic hypertriglyceridaemia. None of these patients had abnormal glucose tolerance. They included 10 patients in whom the serum triglyceride elevation was due to an increase in the circulating VLDL (Fredrickson Type IV) and 10 in whom the increase in plasma VLDL was associated with hyperchylomicronaemia (Fredrickson Type V). These were compared with a control group of 27 normal subjects.–Increased plasma triglyceride turnover with normal clearance was observed in the Type IV patients suggesting that the hypertriglyceridaemia in these patients was predominantly due to enhancement of plasma triglyceride production. The plasma triglyceride concentration correlated closely with the changes in triglyceride turnover rate.–Studies performed in the Type V patients showed an increase in the plasma triglyceride turnover rate in only 3 subjects, while in the remaining patients the turnover values were similar to those of the control subjects. The increase in serum triglyceride concentration found in some of the patients was due to an increase in plasma triglyceride production. However, in the majority of patients in this group impairment of plasma triglyceride clearance was the predominant abnormality.–In both hypertriglyceridaemic groups the plasma FFA flux was markedly increased and correlated significantly with the degree of hypertriglyceridaemia. The increase in triglyceride turnover observed in Type IV patients and some of the Type V patients correlated closely with the enhancement of plasma FFA flux suggesting that the increase in triglyceride production in these patients was secondary to enhanced lipolysis.–The plasma insulin response to an oral glucose load was markedly increased in both groups of hypertriglyceridaemic patients and correlated significantly with the elevation in serum triglyceride concentration. The plasma insulin response also correlated with the plasma free fatty acid turnover.–The results suggest that the initial lesion in these patients was related to insulin unresponsiveness in adipose tissue resulting in enhanced lipolysis with secondary changes in insulin secretion and plasma triglyceride transport kinetics.