Betaine inhibited adipogenesis in 3T3-L1 preadipocytes and alleviated obesity-related disorders in high-fat diet-fed C57BL/6 mice by modulating gut microbiota composition.

The rising prevalence of obesity underscores the urgent need to develop safe and effective alternative therapies. Betaine, a quaternary amine-type alkaloid with established antioxidant and antiinflammatory properties, has shown promise in metabolic regulation. However, the mechanisms by which betaine exerts antiobesity effects, especially the contribution of gut microbiota and intestinal barrier function, remain to be elucidated. In this study, the effects of betaine on inhibiting adipogenesis in 3T3-L1 preadipocytes and alleviating obesity in high-fat diet (HFD)-fed C57BL/6 J mice were evaluated. The results revealed that betaine suppressed adipogenesis by downregulating adipogenic transcription factors and upregulating brown fat-specific markers. In HFD-fed mice, betaine treatment reduced body weight gain and tissue weight, improved glucose metabolism, alleviated inflammation, and mitigated tissue damage. Betaine also reshaped gut microbiota composition, enriching beneficial taxa (Muribaculaceae, Allobaculum, and Parabacteroides) and reducing harmful taxa (Colidextribacter and Desulfovibrionaceae), which correlated strongly with obesity-related indicators. Importantly, these beneficial effects were markedly attenuated in pseudo-germ-free mice, suggesting a relationship between gut microbiota and the antiobesity effects of betaine. It was hypothesized that betaine would alleviate obesity by suppressing adipogenesis and improving metabolic homeostasis through gut microbiota-dependent mechanisms, and the findings of this study supported this hypothesis. Overall, betaine exerts antiobesity effects through a gut microbiota-barrier-metabolism axis, combining inhibition of adipogenesis, promotion of browning, and restoration of intestinal barrier function. These findings provide novel mechanistic insights and suggest the potential of betaine as a dietary supplement or functional food for obesity and related metabolic disorders.