Effect of metformin on adiponectin in PCOS: A meta-analysis and a systematic review

Background Conflicting results have been reported regarding the effect of metformin on adiponectin levels in women with polycystic ovary syndrome (PCOS). This meta-analysis reviewed all studies comparing adiponectin levels before and after metformin treatment in PCOS women. Additionally, changes in other indicators, including long-term complications associated with PCOS, such as inflammatory, metabolism factors and hormonal profile, were investigated following metformin treatment. We conducted subgroup analysis based on body mass index (BMI) stratification and appropriate pooling. Methods We searched literature in PUBMED, EMBASE, the Cochrane Library, and CNKI databases. The main meta-analysis included 11 studies containing data on 353 subjects. Results Metformin treatment was associated with significantly increased serum adiponectin concentrations [10 studies, random-effects SMD (95% CI) −0.58 [-1.03, −0.13]; I2 = 86%; P = 0.01]. Additionally, the meta-analysis revealed that circulating tumor necrosis factor-α(TNF-α) and C-reactive protein (CRP) concentrations were significantly decreased after metformin treatment, with corresponding SMDs of 1.01 (95% CI: 0.74–1.28, P＜0.00001) and 0.48(95% CI: 0.35–0.60, P＜0.00001). Conclusion Following metformin administration, serum adiponectin concentrations of PCOS women were found to be significantly increased, accompanied by a significant improvement in other indicators. Further investigation with a larger sample size should be conducted to validate optimal dose and duration of metformin.