The association between omentin and diabetes: a systematic review and meta-analysis of observational studies

Aims: A number of studies have examined the association between the serum levels of omentin and diabetes, but the findings have been inconclusive. Herein, we systematically reviewed available observational studies to elucidate the overall relationship between omentin and diabetes, including type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), and impaired glucose tolerance (IGT) among adolescent and adult population. Methods: PubMed, Cochrane's Library, Science Direct, Scopus, Google Scholar, and ISI Web of Science databases were searched for all available literature until January 2019 for studies assessing the association between omentin and diabetes. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of each study. Results: A total of 28 articles met the inclusion criteria and were included in our systematic review and meta-analysis. There was a significant association between serum omentin and diabetes (WMD-1.68; 95% CI, -2.17 to -1.19; P<0.001). The result of our sub-group analysis based on participants' health status revealed that omentin was significantly lower in T2DM and IGT subjects but not in T1DM ones compared to healthy controls. Conclusion: We found that serum omentin level is significantly lower in T2DM and IGT patients but not in T1DM ones. These data could be used by clinicians for early diagnosis and management of diabetes. Furthermore, we need more clinical trials to investigate new agents which could influence omentin levels.