Isolated low HDL cholesterol - An insulin-resistant state only in the presence of fasting hypertriglyceridemia

Individuals with isolated low HDL cholesterol are at increased risk of coro nary artery disease. It has been reported previously that this is an insuli n-resistant state. We analyzed data from the 1992 Singapore National Health Survey with the objective of defining the clinical and metabolic parameter s associated with isolated low HDL cholesterol. A total of 3,568 individual s were selected by stratified random sampling. Subjects with low HDL choles terol (<0.9 mmol/l) and "ideal" total cholesterol(<5.2 mmol/l) mere identif ied. Data on anthropometry, blood pressure (BP), insulin resistance, glucos e tolerance, sex, smoking habit, and ethnic group were examined. me found t hat this group was heterogeneous. Those with fasting triglyceride (TG) >1.7 mmol/l (low HDL/high TG) displayed features of the insulin resistance synd rome characterized by obesity, higher diastolic BP, greater insulin resista nce, and a greater tendency to have diabetes or impaired glucose tolerance (IGT). If fasting TG was <1.7 mmol/l (isolated low HDL cholesterol), indivi duals were similar to the general population in terms of insulin resistance and obesity. Both groups were more commonly men and Asian Indian. The ethn ic difference in prevalence could not be explained by differences in diet, exercise, alcohol ingestion, or smoking. Our data support the view that Asi an Indians are genetically predisposed to isolated low HDL cholesterol as w ell as the insulin resistance syndrome. The higher prevalence of isolated l ow HDL cholesterol, the young age at which individuals exhibit this phenoty pe (mean age 32.5 years), along with the greater propensity for Asian India ns to develop insulin resistance and IGT contribute to the threefold increa sed incidence of myocardial infarction in those <65 years of age in this et hnic group.