Objective: Tumor necrosis factor-alpha (TNF-alpha) is one of the proposed mediators of insulin resistance, upregulated in human obesity. Insulin resistance, however, might precede the development of obesity, especially in subjects with a family history of type 2 diabetes. Therefore, the aim of the present study was to assess plasma levels of TNF-alpha and soluble forms of its receptors (soluble TNF-alpha receptors 1 [sTNFR1] and 2 [sTNFR2]) and to evaluate the relationship of the TNF-alpha system with insulin resistance in lean, nondiabetic offspring of type 2 diabetic patients.
Research design and methods: We compared 20 lean offspring (BMI <25 kg/m(2), 8 men and 12 women) of type 2 diabetic patients with 20 lean subjects with no family history of diabetes, matched for age, sex, and BMI (control group). Anthropometry and blood biochemical parameters were measured, and insulin sensitivity was evaluated with the euglycemic-hyperinsulinemic clamp technique.
Results: Both men and women in the offspring group were markedly more insulin-resistant and had higher plasma levels of sTNFR2 (all P < 0.05). TNF-alpha, sTNFR1, and other examined parameters did not differ between the studied groups. Both TNF-alpha receptors were related to waist-to-hip ratio (WHR), fat-free mass (FFM), plasma total cholesterol, HDL cholesterol, LDL cholesterol, and nonesterified fatty acids (NEFAs). sTNFR2, but not sTNFR1, was also associated with insulin sensitivity (r = -0.49, P = 0.001). This relationship remained significant after adjustment for WHR, FFM, plasma insulin, and NEFA.
Conclusions: TNF-alpha system might be involved in modulating insulin action before the onset of obesity in subjects at high risk for type 2 diabetes.