Metformin Treatment Shows Beneficial Effects on RTT-Associated Phenotypical Deficits in Mecp2 T158M Male Mice

Background: Rett Syndrome (RTT) is a progressive neurodevelopmental disorder caused by MECP2 gene mutations. MeCP2 protein binding to methylated DNA is involved in normal brain development and function. T158M is a common RTT-associated mutation, where a threonine is replaced with a methionine, affecting protein function and stability. RTT has recently been identified as a neurometabolic disorder, with metformin emerging as a potential candidate drug. Metformin is a safe and accessible drug, commonly used for Type 2 diabetes. Our team previously studied the regulatory role of metformin on the expression of RTT-related genes/proteins using in vitro and in vivo approaches. However, the phenotypical and behavioral impact of metformin in transgenic mice carrying the common T158M mutation was not explored. Methods: Wild type (WT) and mutant Mecp2^T158M (Mecp2^tm4.1Bird) male mice were subjected to daily intraperitoneal injection of metformin for 20 days. The control mice received a daily intraperitoneal injection of the solvent. The main RTT-like phenotypical criteria were assessed daily. Behavioral tests included the open field test and elevated plus maze. Results: Behavioral tests indicated no significant effect of metformin on the anxiety levels, locomotion, and exploratory behaviors in the hemizygous male Mecp2^T158M mice, despite our observation of increased anxiety levels in the WT counterparts. In hemizygous male Mecp2^T158M mice, metformin treatment showed beneficial effects on RTT-like phenotypes, including breathing irregularities, gait abnormalities, hindlimb clasping, and overall total score. The positive effect of metformin was also observed on the body weight in the hemizygous male Mecp2^T158M mice. Conclusions: Our findings provide evidence for potential therapeutic effects of metformin for MeCP2-associated neurological disorders.