OBJECTIVE: Tumor necrosis factor-a (TNF-a) is expressed primarily in adipocytes, and elevated levels of this cytokine have been linked to obesity and insulin resistance. Recently, the A allele of a polymorphism in the 5H -¯anking region of the TNF-a gene (G7308A) has been reported to be more frequent in obese than in lean subjects and has also been associated with increased expression of this cytokine in fat tissue and in¯uences fat mass and insulin resistance. We, therefore, examined the relationship between this variant and obesity in a German Caucasian population.
SUBJECTS AND METHODS:We genotyped 176 index subjects recruited within the framework of the BErG (Berlin Erna Èhrung Geschwister)-Study for the TNF-a-G7308A polymorphism. Subjects were characterized for weight, height, waist and hip circumference, body mass index (BMI), body composition, glucose tolerance, leptin and angiotensinogen levels. RESULTS: The frequency of the 7308A allele (0.18) was similar to that reported previously and genotype distribution was in Hardy ± Weinberg equilibrium (GG, n 118; GA, n 53; AA, n 5). There was a signi®cant difference in allele frequencies of the polymorphism by BMI quartiles (I,`27.3 kgam 2 ; II, 27.3 ± 31.9 kgam 2 ; III, 31.9 ± 36.5 kgam 2 ; IV, b 36.5 kgam 2 , in each quartile n 44) with 7308A allele carriers having a higher BMI than G allele carriers (P 0.013). Despite previous smaller studies that have related insulin resistance to the G7308A polymorphism, we found no relationship between glucose and insulin response during an oral glucose tolerance test (OGTT) and the polymorphism. Furthermore, none of the plasma parameters were related to the polymorphism. CONCLUSION: Our ®ndings support the hypothesis that the G7308A polymophism of the TNF-a gene is associated with BMI. The G7308A polymorphism may, therefore, represent a genetic marker for increased susceptibility for obesity in Caucasians.