Tumor necrosis factor-alpha, transforming growth factor-beta1, and insulin-like growth factor-I mRNA levels in the skeletal muscle of Hispanic elders with type 2 diabetes: Effects of strength training

The purpose of this study was to determine whether differences exist in the levels of tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), and insulin-like growth factor-I (IGF-I) mRNAs in skeletal muscle, and/or circulating levels of TNF-α between Hispanic diabetic and non-diabetic elders. Thirty moderately obese men (n = 15) and women (n = 15) aged 67.0 ± 7.3 years, with type 2 diabetes, and 9 moderately obese non-diabetic men (n = 4) and women (n = 5), aged 60 ± 4 years were studied. An additional purpose was to study the effects of strength training (ST) on the mRNA levels of these factors in muscle. Diabetic subjects were randomized into two groups. The training (EX) group, (8 women, 7 men) participated in 16 weeks of ST, and the control (CON) group (7 women, 8 men) maintained their usual diabetic care only. Non-diabetic subjects served as a baseline comparison group. There were no differences in weight, waist hip ratio or plasma TNF-α levels between diabetic and non-diabetic subjects. Diabetic subjects had higher plasma TNF soluble receptor (sTNFRII) levels (P < 0.001), and higher muscle TNF-α (P < 0.01), TGF-β1 (P < 0.01) and IGF-I (P < 0.05) mRNA levels, than non-diabetics. ST resulted in a reduction in % HbA1c (P < 0.01), a decrease in fasting plasma insulin (P < 0.05), and increases in fat free mass (P < 0.005) and strength (P < 0.001). Also, ST resulted in an increase in TNF-α mRNA expression (P < 0.05) that was significantly correlated (r = 0.86, P < 0.001) with a ST-induced increase in TGF-β1 mRNA (P < 0.05). This increase in TGF-β1 mRNA was correlated (r = 0.74, P < 0.001) with a 2-fold increase (P < 0.001) in IGF-1 mRNA. All changes, except for fasting insulin and TNF-α mRNA, were significant when compared to the CON group (P < 0.05). There were no changes in fasting glucose, plasma TNF-α or sTNFRII in either group. Thus, as an adjunct of diabetic care, ST results in improved glycemic control in Hispanic elders with type 2 diabetes, despite lack of change in circulating TNF-α, and an elevation in muscle TNF-α mRNA levels.