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In the article, the name of the co-author was given incorrectly. The correct name of the author is Mohammad Ali Mansournia. In the abstract section the correct abbreviation of “mean difference” is MD., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (© Georg Thieme Verlag KG Stuttgart · New York.)

This systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to clarify the effect of melatonin supplementation on glycemic control. Databases including PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials were searched until July 30th, 2018. Two reviewers independently assessed study eligibility, extracted data, and evaluated the risk of bias for included trials. Heterogeneity among included studies was assessed using Cochran's Q test and I-square (I 2 ) statistic. Data were pooled using random-effect models and standardized mean difference (MD) was considered as the overall effect size. Twelve trials out of 292 selected reports were identified eligible to be included in current meta-analysis. The pooled findings indicated that melatonin supplementation significantly reduced fasting glucose (SMD=-6.34; 95% CI, -12.28, -0.40; p=0.04; I 2 : 65.0) and increased the quantitative insulin sensitivity check index (QUICKI) (SMD=0.01; 95% CI, 0.00, 0.02; p=0.01; I 2 : 0.0). However, melatonin administration did not significantly influence insulin levels (SMD=-1.03; 95% CI, -3.82, 1.77; p=0.47; I 2 : 0.53), homeostasis model assessment of insulin resistance (HOMA-IR) (SMD=-0.34; 95% CI, -1.25, 0.58; p=0.37; I 2 : 0.37) or HbA1c levels (SMD=-0.22; 95% CI, -0.47, 0.03; p=0.08; I 2 : 0.0). In summary, the current meta-analysis showed a promising effect of melatonin supplementation on glycemic control through reducing fasting glucose and increasing QUICKI, yet additional prospective studies are recommended, using higher supplementation doses and longer intervention period, to confirm the impact of melatonin on insulin levels, HOMA-IR and HbA1c., Competing Interests: The authors declare that they have no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

This systematic review and meta-analysis of randomized controlled trials (RCTs) were conducted to summarize the effect of vitamin D supplementation on endothelial function among people with metabolic syndrome and related disorders. Cochrane library, Embase, PubMed, and Web of Science database were searched to identify related RCTs published up 20th May 2018. To check heterogeneity a Q-test and I 2 statistics were used. Data were pooled by using the random-effect model and standardized mean difference (SMD) was considered as summary effect size. Twenty-two trials of 931 potential citations were found to be eligible for current meta-analysis. The pooled findings by using random effects model indicated that vitamin D supplementation to individuals with MetS and related disorders significantly increased flow-mediated dilatation (FMD) (SMD=1.10; 95% CI, 0.38, 1.81, p=0.003). However, it did not affect pulse-wave velocity (PWV) (SMD=0.04; 95% CI, -0.25, 0.33, p=0.80) and augmentation index (AI) (SMD=0.07; 95% CI, -0.25, 0.40; p=0.65). Overall, this meta-analysis demonstrated that vitamin D supplementation to patients with metabolic syndrome and related disorders resulted in an improvement in FMD, but did not influence PWV and AI., Competing Interests: The authors declare that they have no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

The current systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize the effect of vitamin D supplementation on biomarkers of inflammation and oxidative stress among women with polycystic ovary syndrome (PCOS). Cochrane library, Embase, PubMed, and Web of Science database were searched to identify related randomized-controlled articles (RCTs) published up to November 2017. Two researchers assessed study eligibility, extracted data, and evaluated risk of bias of included RCTs, independently. To check heterogeneity Q-test and I 2 statistics were used. Data were pooled by using the random-effect model and standardized mean difference (SMD) was considered as summary effect size. Seven RCTs were included into our meta-analysis. The findings showed that vitamin D supplementation in women with PCOS significantly decreased high-sensitivity C-reactive protein (hs-CRP) (SMD -1.03; 95% CI, -1.58, -0.49; p <0.001) and malondialdehyde (MDA) (SMD -1.64, 95% CI -2.26 to -1.02, p <0.001), and significantly increased total antioxidant capacity (TAC) levels (SMD 0.86, 95% CI 0.08 to 1.64, p=0.03). Vitamin D supplementation had no significant effect on nitric oxide (NO) (SMD 0.11, 95% CI -0.44 to 0.66, p=0.69) and total glutathione (GSH) levels (SMD 0.54, 95% CI -0.20 to 1.28, p=0.15). Overall, the current meta-analysis demonstrated that vitamin D supplementation to women with PCOS resulted in an improvement in hs-CRP, MDA and TAC, but did not affect NO and GSH levels., Competing Interests: The authors declare that they have no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)