Effect of metformin intervention on circulating irisin levels in polycystic ovary syndrome: a systematic review and collaborative meta-analysis.

BACKGROUND: Irisin is an adipo-myokine with potential implications in metabolic disorders such as polycystic ovary syndrome (PCOS). Despite of a strong evidence showing increased irisin level in PCOS, there is no conclusive evidence on the effect of metformin intervention on circulatory irisin in PCOS. AIM: The aim of this meta-analysis was to compare the circulatory (serum/plasma) irisin levels before and after metformin intervention in subjects with PCOS. METHODS: Relevant studies were retrieved by online database and manual searching. The standardized mean differences (SMDs) with 95% confidence intervals (CIs) were obtained by a random-effects meta-analysis. A one-study leave-out sensitivity analysis was conducted to validate the overall obtained results. RESULTS: A total of five observations were included in this meta-analysis. The results based on random effects meta-analysis indicated that irisin levels were significantly decreased after metformin intervention as compared to the baseline pretreatment levels in PCOS (SMD: -1.00, 95% CI: -1.60 to -0.41, Z: 3.29, p = .001). The sensitivity analysis leaving-out a particular observation at a time and repeating the meta-analysis validated the robustness of the overall finding suggesting the significant effect of metformin treatment on irisin levels in PCOS. CONCLUSION: Circulating irisin levels were significantly decreased upon metformin intervention in PCOS patients. The higher pretreatment irisin levels in PCOS may recede once the altered metabolic state is restored upon metformin intervention. Well-designed randomized trials with large sample sizes are warranted to further substantiate the reported evidence reported and to establish the possible mechanisms.

Adropin levels and its associations as a fat-burning hormone in patients with polycystic ovary syndrome: a correlational meta-analysis.

AIMS: Adropin is a peptide hormone with potential implications in patients with polycystic ovary syndrome (PCOS). The aim of this meta-analysis was to compare the circulating (serum/plasma) and follicular fluid adropin levels between human PCOS patients and non-PCOS controls. METHODS: Relevant studies were retrieved by online database and manual searching. The standardized mean differences (SMDs) with 95% confidence intervals (CIs) were obtained by a random-effects meta-analysis. Meta-analysis of correlations was performed for the associations of adropin with anthropometric, lipid, insulin resistance and hormonal covariates. The funnel plot analysis with Begg's and Egger's tests was used for publication bias. RESULTS: A total of 9 studies were included in this meta-analysis. The results indicated that the adropin levels were significantly decreased in PCOS patients as compared to non-PCOS controls (SMD = -1.87, 95% CI = -2.55 to -1.18, p < .0001). This decrease was more evident in overweight PCOS patients than their normoweight counterparts (SMD = -0.55, 95% CI = -0.80 to -0.30, p < .0001). A one-study leave-out sensitivity analysis indicated that no single study had a significant influence on the overall outcome, suggesting the robustness of this meta-analysis. There were significant associations of decreased adropin levels with the body mass index, dyslipidemia and insulin resistance in PCOS. CONCLUSION: Adropin levels are significantly reduced in PCOS patients compared to controls, and this decrease was more evident in overweight PCOS patients.