Effect of metformin on cognitive dysfunction in animal with insulin resistance a non quantitative systematic review of randomized controlled trials
Background: Current reports from observational studies and randomized controlled trials (RCTs) on the effect of metformin on cognitive dysfunction are inconsistent. This systematic review aimed at analyzing the effect of metformin on cognitive and memory function in animal models with insulin resistance (IR) Methods: We conducted a literature search of PubMed, Embase, Sinomed, the Cochrane library, CNKI, Wanfang, VIP and clinical trial registries, for English and Chinese articles on RCTs exploring the association between metformin and cognitive dysfunction induced by IR in animals. Heterogeneity and paucity of original data precluded a meta analysis, and hence, two independent reviewers performed a non quantitative systematic review of RCTs. Results: Eight studies met the inclusion criteria; two were in English and others in Chinese. Two studies were in mice models and the rest in rat models. Coincidently, all of these studies reported that metformin had beneficial effects on cognitive function. Conclusions: Studies in animal models with IR suggest improvements in cognitive dysfunction by metformin. The results imply a possible therapeutic benefit of peripheral insulin sensitizer metformin in AD and mild cognitive impairment (MCI) These findings also provide direct evidences linking IR and AD or MCI. However, further studies are required to confirm the effects of metformin on cognitive dysfunction.