Tumor necrosis factor alpha gene G-308A polymorphism, insulin resistance, and fasting plasma glucose in young, older, and diabetic Japanese men

In obese subjects, the levels of tumor necrosis factor alpha (TNF-α) expression and protein synthesis in adipocytes are increased. A recent study of Caucasians suggested that the TNF-α gene promoter region polymorphism at position -308 influences insulin resistance and percent body fat and increases serum leptin levels, although conflicting data are also reported. The present study was performed to investigate the relationship between this polymorphism and the body mass index (BMI), blood pressure, glucose and lipid profiles, and serum leptin in 122 healthy young men aged 21 to 29, 177 older men aged 45 to 65, and 71 type 2 diabetic male patients aged 42 to 78. The BMI, blood pressure, and fasting plasma glucose (FPG), serum lipids, uric acid, insulin, and leptin concentrations were measured. The TNF-α G-308A polymorphism was assessed by the polymerase chain reaction restriction fragment length polymorphism method. In the young group, 4 subjects (3.3%) were heterozygous for the TNF2 (G-308A-positive) allele, but there were no significant differences between the TNF1 (wild-type) and TNF2 groups in any measured anthropometric or metabolic parameter. In the older group, the frequency of the TNF2 group was 2.8%, and FPG was significantly higher in the TNF2 versus the TNF1 group (108 ± 7 v 99 ± 9 mg/dL, P = .042 by Mann-Whitney U test). Plasma triglycerides and the insulin resistance index tended to be higher and high-density lipoprotein (HDL) cholesterol tended to be lower in the TNF2 group (P = .06, .20, and .07, respectively), although these differences were not statistically significant. In type 2 diabetic subjects, the frequency of the TNF2 group was also 2.8%, and there were no significant differences between the TNF1 and TNF2 groups in any parameter. HDL cholesterol tended to be lower (P = .10) in the TNF2 group, although it was not statistically significant. In conclusion, no major difference was associated with TNF1 and TNF2 polymorphisms in terms of obesity, blood pressure, lipids, or glucose in young, older, or diabetic Japanese men, although FPG was significantly higher in older men, possibly through increased insulin resistance.