Influence of Obesity on the Relationship Between Insulin and Triglyceride Levels in Endogenous Hypertriglyceridemia

Abstract

In order to assess the influence of obesity on the relationship between insulin and triglyceride levels, basal plasma triglyceride (TG) and immunoreactive insulin (IRI) levels prior to and during oral glucose (100 gm.) tolerance tests were compared in nonlipemic control subjects and patients with endogenous hypertriglyceridemia with comparable glucose tolerance. Basal IRI and body weight correlated closely in both lipemic (r = +.75, p < .001) and nonlipemic groups (r = +.72, p < .001), and no significant increase in basal IRI was observed in the lipemic subjects when matched for weight. In both lipemic and control groups basal IRI and TG levels were related to a comparable degree (r = +.44, p < .01); however, for any given basal IRI, TG levels in the lipemic group were dramatically increased. No relationship was demonstrable between TG and stimulated IRI levels expressed either as absolute increments or when the effects of obesity on insulin secretion were excluded by expression of each insulin response to glucose as a percentage of the basal level. In both groups, glucose intolerance and the per cent increment in IRI at both sixty and 180 min. were inversely related, and when matched for glucose tolerance, no quantitative difference in stimulated IRI levels was demonstrable in patients with endogenous hypertriglyceridemia and the control group. When factors such as glucose intolerance have been controlled, variations in IRI are best explained by variations in body weight. These findings indicate that the high IRI levels often observed in patients with endogenous hypertriglyceridemia result from coexisting obesity.