ABSTRACT
OBJECTIVE: Our objective was to perform a systematic review and meta-analysis on randomized controlled trials (RCTs) assessing the effect of flaxseed supplementation on serum adiponectin and leptin concentration. METHODS: Electronic searches were performed in PubMed, Scopus, Web of Science, and Google Scholar up to May 2019 without any restriction. All RCTs that reported the effect of flaxseed supplementation on circulating adiponectin and leptin concentration were included. A random-effects model was used to pool calculated effect sizes. RESULTS: Nine RCTs (11 arms) were eligible to be included. Our analysis showed that flaxseed supplementation did not significantly affect adiponectin (weighted mean difference [WMD]: 0.15 µg/ml; 95% CI [-0.16, 0.47], p = .34) and leptin (WMD: 0.47 ng/ml; 95% CI [-3.10, 4.06], p = .79) concentration in comparison with control. Furthermore, subgroup analysis revealed that effects remained nonsignificant in all subgroups of trial duration, flaxseed type, and health status of participants. The pooled effect size was also robust and remained nonsignificant in the sensitivity analysis. CONCLUSION: Flaxseed supplementation had no significant effect on adiponectin and leptin levels in adults. However, future well-designed trials are still needed to confirm these results.
Subject(s)
Adiponectin/blood , Dietary Supplements/analysis , Flax/chemistry , Leptin/blood , Humans , Randomized Controlled Trials as TopicABSTRACT
A meta-analysis was performed to summarize the evidence from observational studies regarding the association between serum osteocalcin (OC) and C-reactive protein (CRP). A systemic research of the literature databases including PubMed, SCOPUS, and Google Scholar was performed to identify the relevant studies up to March 2018. We used the random-effects model by the method of DerSimonian and Laird to calculate the overall effect size. Q-test and I 2-statistics were used to assess between-study heterogeneity. In addition, we did subgroup analysis to detect possible sources of heterogeneity based on BMI range, gender, type of study population and age. We identified 21studies of association between serum osteocalcin and CRP eligible for the meta-analysis. The overall effect size showed a significant inverse association between OC and CRP (Fisher's z=-0.127; 95% CI: -0.166, -0.088, p<0.0001). However, the significant chi-squared statistic result, indicates a heterogeneity of effect sizes (I 2=61.6, df=20, p<0.0001). The subgroup analysis found BMI range, type of study population, and age were the potential sources of heterogeneity. In addition, the strongest correlation was observed in the subgroup of obese subjects (Fisher's z=-0.264, p=0.002), less than 40 years old (Fisher's z=-0.115, p<0.0001) and healthy subjects (Fisher's z=-0.115, p<0.0001). These findings suggest that there is a significant inverse association between serum OC and CRP levels in the adult population.
