Diabetes, Vol 48, Issue 5 1088-1092, Copyright © 1999 by American Diabetes Association
Isolated low HDL cholesterol: an insulin-resistant state only in the presence of fasting hypertriglyceridemia
ES Tai, SC Emmanuel, SK Chew, BY Tan and CE Tan
Department of Endocrinology, Singapore General Hospital, Republic of Singapore. eshyong@pacific.net.sg
Individuals with isolated low HDL cholesterol are at increased risk of
coronary artery disease. It has been reported previously that this is an
insulin-resistant state. We analyzed data from the 1992 Singapore National
Health Survey with the objective of defining the clinical and metabolic
parameters associated with isolated low HDL cholesterol. A total of 3,568
individuals were selected by stratified random sampling. Subjects with low
HDL cholesterol (<0.9 mmol/l) and "ideal" total cholesterol (<5.2
mmol/l) were identified. Data on anthropometry, blood pressure (BP),
insulin resistance, glucose tolerance, sex, smoking habit, and ethnic group
were examined. We found that this group was heterogeneous. Those with
fasting triglyceride (TG) >1.7 mmol/l (low HDL/high TG) displayed
features of the insulin resistance syndrome characterized by obesity,
higher diastolic BP, greater insulin resistance, and a greater tendency to
have diabetes or impaired glucose tolerance (IGT). If fasting TG was
<1.7 mmol/l (isolated low HDL cholesterol), individuals were similar to
the general population in terms of insulin resistance and obesity. Both
groups were more commonly men and Asian Indian. The ethnic difference in
prevalence could not be explained by differences in diet, exercise, alcohol
ingestion, or smoking. Our data support the view that Asian Indians are
genetically predisposed to isolated low HDL cholesterol as well as the
insulin resistance syndrome. The higher prevalence of isolated low HDL
cholesterol, the young age at which individuals exhibit this phenotype
(mean age 32.5 years), along with the greater propensity for Asian Indians
to develop insulin resistance and IGT contribute to the threefold increased
incidence of myocardial infarction in those <65 years of age in this
ethnic group.