Fat tissue and insulin resistance in American Americans

Nutrition Research Newsletter, Sept, 2004

Obesity, especially abdominal obesity, is associated with insulin resistance and its complications such as hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol, altered lipoprotein metabolism, elevated serum glucose, and hypertension. Many studies have shown an association between visceral adiposity and insulin resistance and its metabolic consequences. However, other studies have demonstrated that subcutaneous abdominal adipose tissue (SAT) may have an equally strong or even superior relationship to insulin resistance than visceral adipose tissue (VAT). Consideration of race also has to be noted. There are also well-described racial differences in central body fat distribution between VAT and SAT compartments.

The goal of a recent study was to evaluate the relationship in African Americans among VAT, SAT, and insulin resistance. Additionally, researchers wanted to determine the clinical impact of the relationship among insulin resistance and each of these fat depots by examining the correlations of both VAT and SAT with the consequences of insulin resistance, specifically, lower HDL-cholesterol, higher triglycerides (TGs), increased low-density lipoprotein (LDL) particle number, small LDL and HDL particle size, higher systolic and diastolic blood pressure, and increased fasting glucose.

The subjects included 78 African American men and women, and visited the Clinical. Center over a 3-month period. A history and physical exam was performed. Visits 2 to 4 occurred in the morning after the subjects had fasted for 12 hr. At each visit, a fasting lipid profile was obtained. At visit 2, a 2 hr 75 g oral glucose tolerance test was performed. At visit 4, an insulin-modified frequently sampled intravenous glucose tolerance test was performed. Anthropometric measurements and body fat analysis was performed.

In the subjects tested, both VAT and SAT were negatively correlated with the insulin sensitivity index (r for both correlations = -0.57; p<0.01). In women, the correlation coefficient between VAT and the insulin sensitivity index was -0.50 (p<0.01) and between SAT and insulin sensitivity index was -0.67 (p<0.01). In women, the correlation coefficient for the insulin sensitivity factor with SAT was significantly greater than the correlation coefficient with VAT (p = 0.02).

Both SAT and VAT appear to be strongly correlated with insulin resistance in African Americans. For African American women, SAT may have a greater effect than VAT on insulin resistance.

M. Tulloch-Reid, R. Hanson, N. Sebring, et al. Both subcutaneous and visceral adipose tissue correlate highly with insulin resistance in African Americans. Obes Res; 12:1352-1359 (August, 2004). [Correspondence: Anne E. Sumner, Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 10, Room 8S 235D, MSC 1770, Bethesda, MD 20892-1770. E-mail: AnneS@intra.niddk.nih.gov].