Effect of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin on Muscle Mass and the Muscle/Fat Ratio in Patients With Type 2 Diabetes

BACKGROUND: We previously reported the effect of sitagliptin or glimepiride treatment for 24 weeks on body composition in Japanese overweight and obese patients with type 2 diabetes. Although the degree of HbA1c reduction was similar between the two groups, significant reduction of intrahepatic lipid (IHL), determined by proton magnetic resonance spectroscopy ((1)H-MRCP), and fat mass (FM), determined by dual-energy X-ray absorptiometry (DXA), was observed in the sitagliptin group but not in the glimepiride group. As both IHL and FM are known as associating factors of insulin resistance, these reductions may lead to improvement of insulin sensitivity, which in turn may contribute to sitagliptin-induced amelioration of glycemic control. On the other hand, muscle and muscle/fat ratio were also reported to be positively correlated with insulin sensitivity, but we did not evaluate these factors. METHODS: DXA separates the whole body into three major components, bone mass (BM), FM and fat and bone-free mass (FBFM), and measures the weight of each component. FBFM is normally used as a good marker of muscle mass; therefore, in this post-hoc analysis, we investigated whether sitagliptin treatment for 24 weeks influenced the FBFM and FBFM/FM ratio. RESULTS: After 24 weeks, the FBFM and FBFM/FM ratio significantly increased in the sitagliptin group (47.6 ± 10.3 to 48.8 ± 11.0 kg, P < 0.05 and 2.0 ± 0.8 to 2.1 ± 0.8, P < 0.05), but not in the glimepiride group (49.7 ± 10.6 to 49.3 ± 9.9, P = 0.655 and 2.1 ± 0.9 to 2.0 ± 0.7, P = 0.855). The mean change of FBFM and FBFM/FM ratio from baseline to 24 weeks in the sitagliptin and glimepiride groups was 1.24 ± 2.01 (sitagliptin group) vs. -0.34 ± 2.63 kg (glimepiride group) (P = 0.074) and 0.13 ± 0.17 (sitagliptin group) vs. -0.11 ± 0.30 (glimepiride group) (P < 0.05), respectively. CONCLUSIONS: Sitagliptin 24-week treatment demonstrated not only reduction of body fat and liver fat but also an increase of muscle and muscle/fat ratio. These changes may partly explain the mechanism underlining sitagliptin-induced improvement of glycemic control.