Exercise Training Enhances Tumor Necrosis Factor-α–Induced Expressions of Anti-Apoptotic Genes without Alterations in Caspase-3 Activity in Rat Epididymal Adipocytes

Abstract

The effect of exercise training on tumor necrosis factor-α (TNF-α) signaling was investigated in rat epididymal adipocytes. Incubation of isolated adipocytes with TNF-α (20 ng/ml) for 5 h enhanced the expression of the inhibitor apoptosis protein 2 (IAP2) gene without any enhancement of caspase-3 activity in both the sedentary control (C) and exercise-trained (TR) groups. However, the ability of TNF-α to enhance IAP2 gene expression was significantly greater in TR than in C rats. The basal expression of the IκB kinase β (IKK β) gene and that of the BCL-x_L gene were also higher in TR than in C rats. Mn-superoxidedismutase contents in adipocytes were higher in TR than in C rats. Moreover, no apoptotic nucleuses of adipocytes in response to acute exercise were observed in either group at least up to 5 h after exercise. Exercise training also enhanced the inhibitory effect of TNF-α on the gene expression of the fatty acid synthase (FAS), a lipogenic enzyme, suggesting that fatty acid synthesis may be reduced. Thus, exercise training enhanced TNF-α signaling directed toward the expressions of survival signals and the suppression of FAS gene expression.