Metformin Partially Lessens Autism‐Related Behaviors in Mice Subjected to Maternal Separation Stress by Combating Hippocampal Neuroinflammation and Oxidative Stress Imbalance

Autism spectrum disorder (ASD) is a neurological condition with growing global prevalence. One of the important factors involved in the pathophysiology of ASD is experiencing stress during early life, such as maternal separation (MS). Metformin, a well-founded glucose-lowering agent, possesses neuroprotective properties. This research aims to investigate the effects of metformin on autism-related behaviors in MS mice, with a focus on its probable effects on ameliorating hippocampal oxidative stress imbalance and neuroinflammation. In this study, 40 male mice were randomly assigned to five experimental groups. The control group received an intraperitoneal injection of normal saline (10 ml/kg), while normal saline (10 ml/kg) or metformin at doses of 100, 200, and 300 mg/kg were injected into the MS mice for 2 weeks. Behavioral trials, including the three-chamber sociability test, the shuttle box test, and the marble burying test (MBT) were conducted to evaluate autism-related behaviors. Malondialdehyde (MDA), nitrite, total antioxidant capacity (TAC), and expression of inflammatory cytokines including TLR4, TNF-α, IL-1β, and NLRP3 at the gene level were evaluated in the hippocampus. The results revealed that metformin enhanced the social preference index (SPI) and sociability index (SI) in the three-chamber test, improved passive avoidance memory in the shuttle box test, and reduced repetitive behaviors as assessed by the MBT. Furthermore, metformin decreased hippocampal levels of nitrite, MDA and the gene expression of inflammatory cytokines. In conclusion, metformin appears to alleviate autism-related behaviors in MS mice, possibly through combating oxidative stress imbalance and mRNA expression of inflammatory cytokines within the hippocampus.