Effects of testosterone on insulin receptor substrate-1 and glucose transporter 4 expression in cells sensitive to insulin

Abstract

To investigate the molecular mechanism of the influence of testosterone (T) on insulin sensitivity. Preadipocytes of the line 3T3-L1 and myoblasts of the line C2C12 were cultured to develop into mature adipocytes and skeleton muscle cells. Testosterone of the concentration of 10(-9) mol/l was added into the culture fluids for 0, 4, 8, 12, 24 and 40 hours. And testosterone of the concentrations increased by 10 times from 10(-12) mol/L, 10(-5) mol/L was added for 24 hours. Then the cell protein was extracted and the expression of insulin receptor substrate-1 (IRS-1) and glucose transporter 4 (GLUT4) in were measured by Western blotting. (1) Treated with T of the concentration of 10(-9) mol/L, the IRS-1 expression in the 3T3-L1 adipocytes increased along with the treatment time, peaked 12 hours later with a peak value 1.42 +/- 0.42 times that at the 0 h, and the values 4, 8, and 24 hours later were 1.13 +/- 0.03, 1.19 +/- 0.05, and 1.08 +/- 0.02 times that at the 0 h (all P < 0.05). The expression of IRS-1 in the C2C12 cells increased along with the treatment time of the testosterone of the concentration of 10(-9) mol/L too, peaked 24 hours later, with the values 8, 12, and 24 hours later 1.41 +/- 0.18, 1.53 +/- 0.14, and 1.50 +/- 0.14 times that at the 0 h (all P < 0.05). The GLUT4 expression value in the 3T3-L1 adipocytes increased since 4 hours after the treatment, peaked 24 hours after the treatment (3.22 +/- 0.10 that at the 0 h) (all P < 0.05). The GLUT4 expression value in the C2C12 cells increased since 4 hours after the treatment, peaked 24 hours after the treatment (5.17 +/- 1.06 that at the 0 h) (all P < 0.05). (2) The IRS-1 expression in the 3T3-L1 adipocytes and C2C12 cells increased dose-dependently along with the increase of the T concentration and peaked when the T concentration was 10(-9) mol/l (4.23 +/- 0.27 and 3.16 +/- 0.15 times that of blank controls respectively, both P < 0.05), and then turned to decrease. (3) The GLUT4 expression in the C2C12 cells increased along with the increase of the T concentration, peaked when the T concentration was 10(-7) mol/L (2.99 +/- 0.15 times that of the blank control, P < 0.05), and then remained at the similar level. (4) The GLUT4 expression in the 3T3-L1 adipocytes was highest when treated with 10(-11) mol/L testosterone (2.58 +/- 0.02 times that of the blank control, P < 0.05), and then decreased along with the increase of the T concentration (P < 0.05). Testosterone has bidirectional dose- and time-dependent effects on the cellular expression of IRS-1 and GLUT4, which increase with low dose and short time testosterone treatment and decrease with higher dose and longer time treatment.