Effects of metformin treatment on blood leptin and ghrelin levels in patients with type 2 diabetes mellitus

Background: The aim of the present study was to conduct a meta-analysis of randomized controlled trials (RCTs) that investigated the effects of metformin on blood leptin and ghrelin levels in patients with type 2 diabetes mellitus (T2DM).

Methods: Literature searches were performed using MEDLINE, Cochrane Controlled Trials Registry, and ClinicalTrials.gov, and RCTs that investigated the effects of metformin on blood leptin and ghrelin levels in patients with T2DM were selected. Standardized mean differences (SMDs) and 95 % confidence intervals (CIs) were calculated.

Results: Twelve RCTs met the eligibility criteria and were included in the meta-analysis. There was no significant difference in blood leptin between the metformin and control groups (SMD 0.03; 95 % CI -0.35 %, 0.42 %; P = 0.86), although there was a significant difference in blood leptin levels between the metformin group and the group on oral antidiabetic drugs (OADs) other than metformin (SMD -0.39; 95 % CI -0.76 %, -0.01 %; P = 0.04). There were no significant differences in blood ghrelin levels.

Conclusions: Metformin treatment was not associated with a decrease in blood leptin levels in patients with T2DM compared with levels in patients in the control group. Moreover, metformin treatment was not associated with increases in blood ghrelin levels compared with the control and other OADs groups. However, blood leptin levels were significantly lower in the metformin compared with the other OADs group.