Improved metabolic stability in iNOS knockout mice with Lactobacillus supplementation

Oxidative and nitrosative stress play pivotal roles in normal physiological processes and the pathogenesis of metabolic disorders. Previous studies from our lab demonstrated insulin resistance (IR), and dyslipidemia in iNOS^−/− mice, emphasizing the importance of maintaining optimal redox balance. These mice exhibited altered gut microbiota with decreased Lactobacillus. Therefore, we hypothesized that Lactobacillus supplementation could mitigate metabolic disturbances in iNOS^−/− mice. To test this hypothesis, iNOS^−/− mice and wild-type (WT) mice were divided into four groups: iNOS^−/- with or without Lactobacillus supplementation, WT with or without Lactobacillus supplementation and glucose tolerance, insulin resistance, gluconeogenesis, lipids, gene expression related to glucose and lipid metabolism (qPCR), fecal gut microbiota (16S rRNA sequencing), and serum and caecum metabolomics (LC-MS) were monitored. IR and dyslipidemic iNOS^−/− mice exhibited reduced microbial diversity, diminished presence of Lactobacillus, and altered serum metabolites, indicating metabolic dysregulation. Lactobacillus supplementation in iNOS^−/− mice effectively reversed glucose intolerance, IR, dyslipidemia, and associated metabolic irregularities compared to WT. These improvements correlated with changes in gene expression related to fatty acid synthesis in liver and adipose tissue, lipid oxidation in liver, and lipid efflux in intestinal tissue as compared to untreated iNOS^−/− mice. Despite the positive effects on metabolic markers, Lactobacillus supplementation did not reduce body weight or rectify disrupted energy balance, as evidenced by reduced VCO₂ production, heat generation, and metabolic rates in iNOS^−/− mice. The results suggest that Lactobacillus supplementation ameliorates metabolic disturbances but did not fully restore disrupted energy balance, highlighting complex interactions between the gut microbiome and metabolism.