Tumor necrosis factor-beta gene NcoI polymorphism decreases insulin resistance in Japanese men

Given that the Ncol polymorphism of the tumor necrosis factor-beta (TNF-bet a) gene has been shown to be associated with tumor necrosis factor-alpha (T NF alpha) secretory capacity, we know that this TNF-beta gene polymorphism may influence insulin resistance. In Caucasians, 2 polymorphisms of the TNF -alpha promoter region (positions -308 and -238) have been reported to he a ssociated with insulin resistance. Thus, we investigated how genetic variat ion in the TNF-beta and TNF-alpha genes was associated with insulin resista nce in 211 Japanese men. The frequency of the TNF-beta gene polymorphism wa s 0.41, and insulin resistance, estimated by homeostasis model assessment ( HOMA), was significantly lower in variant homozygotes versus wild-type alle le. The frequencies of the -308 and -238 polymorphisms were 0.01 and 0.02, respectively, and these polymorphisms were not associated with insulin resi stance. Our results suggest that the TNF-beta gene polymorphism decreases i nsulin resistance, and that the -308 and -238 polymorphisms of the TNF-alph a promoter region are not a major contributing factor to insulin resistance in Japanese men. Copyright (C) 2000 by W.B. Saunders Company.