Insulin Resistance and Inflammation in Hypogonadotropic Hypogonadism and Their Reduction After Testosterone Replacement in Men With Type 2 Diabetes

Abstract

Objective: One-third of men with type 2 diabetes have hypogonadotropic hypogonadism (HH). We conducted a randomized placebo-controlled trial to evaluate the effect of testosterone replacement on insulin resistance in men with type 2 diabetes and HH.

Research design and methods: A total of 94 men with type 2 diabetes were recruited into the study; 50 men were eugonadal, while 44 men had HH. Insulin sensitivity was calculated from the glucose infusion rate (GIR) during hyperinsulinemic-euglycemic clamp. Lean body mass and fat mass were measured by DEXA and MRI. Subcutaneous fat samples were taken to assess insulin signaling genes. Men with HH were randomized to receive intramuscular testosterone (250 mg) or placebo (1 mL saline) every 2 weeks for 24 weeks.

Results: Men with HH had higher subcutaneous and visceral fat mass than eugonadal men. GIR was 36% lower in men with HH. GIR increased by 32% after 24 weeks of testosterone therapy but did not change after placebo (P = 0.03 for comparison). There was a decrease in subcutaneous fat mass (-3.3 kg) and increase in lean mass (3.4 kg) after testosterone treatment (P < 0.01) compared with placebo. Visceral and hepatic fat did not change. The expression of insulin signaling genes (IR-β, IRS-1, AKT-2, and GLUT4) in adipose tissue was significantly lower in men with HH and was upregulated after testosterone treatment. Testosterone treatment also caused a significant fall in circulating concentrations of free fatty acids, C-reactive protein, interleukin-1β, tumor necrosis factor-α, and leptin (P < 0.05 for all).

Conclusions: Testosterone treatment in men with type 2 diabetes and HH increases insulin sensitivity, increases lean mass, and decreases subcutaneous fat.

Trial registration: ClinicalTrials.gov NCT01127659.

Figure 1

A: Basal mRNA expression of insulin signaling mediators (IR-β, IRS-1, GLUT4, and AKT-2) in adipose tissue from HH and eugonadal men. N = 26 vs. 27 (HH vs. eugonadal). The mRNA expression of IR-β, IRS-1, AKT-2, and GLUT4 was significantly lower by 39%, 37%, 41%, and 33%, respectively, in men with HH (P < 0.01 for all). B: Representative Western blot showing basal protein levels of IR-β subunit and AKT-2 in adipose tissue from 4 HH and 4 eugonadal men with type 2 diabetes. C: Basal protein levels of IR- β subunit and AKT-2 in adipose tissue from HH and eugonadal men. N = 26 vs. 27 (HH vs. eugonadal). The protein levels of IR-β subunit and AKT-2 were lower by 24% and 21%, respectively, in men with HH (P < 0.05). We were unable to detect an evaluable protein signal for IRS-1 and GLUT4, possibly due to quality of antibodies used. Data are represented as mean ± SE. Densitometry is corrected for loading using actin protein levels. *P < 0.05 by t test.

Figure 2

A: Percent change in mRNA expression of insulin signaling mediators (IR-β, IRS-1, GLUT4, and AKT-2) in adipose tissue after 24 weeks of testosterone or placebo treatment. N = 16 vs. 10 (testosterone vs. placebo). IR, IRS-1, AKT-2, and GLUT4 mRNA expression increased significantly by 60 ± 11%, 54 ± 10%, 54 ± 12%, and 59 ± 10%, respectively, after testosterone treatment compared with placebo (P < 0.01 for all). B: Representative Western blot showing basal protein levels of IR-β subunit and AKT-2 in adipose tissue after 24 weeks of testosterone or placebo treatment. C: Percent change in protein levels of IR-β subunit and AKT-2 in adipose tissue after 24 weeks of testosterone or placebo treatment. N = 16 vs. 10 (testosterone vs. placebo). Protein density was measured and corrected for loading with actin. Protein levels of IR-β subunit and AKT-2 increased by 29 ± 10% and 25 ± 11%, respectively (P < 0.05), after testosterone treatment compared with placebo. Data are represented as mean ± SE. Baselines normalized to 100% and changes from baselines calculated; therefore, the first bar in each group is the baseline for both testosterone and placebo treatment. Change in testosterone group was compared by t test with baseline (*P < 0.05) and with placebo (#P < 0.05).