The Antidiabetic Drug Metformin Attenuated Depressive and Anxiety-like Behaviors and Oxidative Stress in the Brain in a Rodent Model of Inflammation Induced by Lipopolysaccharide in Male Rats

Background: Inflammation is considered to be a link between diabetes and central nervous system (CNS) disorders, including depression and anxiety. Metformin is suggested to have antioxidant, anti-inflammatory, and mood-improving effects. The aim of the current research was to investigate the effects of the antidiabetic drug metformin on depressive- and anxiety- like behaviors and oxidative stress in the brain in a rodent model of inflammation induced by lipopolysaccharide (LPS) in male rats. Materials and Methods: The rats were treated as follows: (1) Vehicle instead of metformin and lipopolysaccharide, (2) Lipopolysaccharide (1 mg/ kg) + vehicle instead of metformin, (3-5) Lipopolysaccharide + 50, 100, or 150 mg/ kg of metformin. After the behavioral tests, including open field (OF), elevated pulse maze (EPM), and force swimming (FS) tests, the brains were removed, and malondialdehyde (MDA), nitric oxide (NO) metabolites, total thiol, catalase (CAT) activity, interleukin-6 (IL-6) and superoxide dismutase (SOD) activity were determined. Results: In the EPM, metformin increased the open arm time and entry and decreased closed arm time and entry. In the FS test, metformin lowered the immobility and increased active time compared to lipopolysaccharide. In the OF test, metformin increased total crossing and total distance, time spent, traveled distance, and crossing number in the central zone. As a result of metformin administration, IL-6, MDA, and NO metabolites were decreased while thiol content, SOD, and CAT activity were increased. Conclusion: The results indicated that the well-known antidiabetic drug metformin attenuated depressive- and anxiety-like behaviors induced by inflammation in rats. These beneficial effects are suggested to be due to their attenuating effects on neuroinflammation, oxidative stress, and NO in the brain.