Wheat bran insoluble fiber with varying particle distributions orchestrates microbial metabolism to counteract obesity and hyperlipidemia

Lipid metabolic dysfunction, often resulting from high-fat diets, has become an increasingly prevalent issue in contemporary society. Wheat bran has emerged as a promising by-product with potential to regulate metabolic disorders associated with obesity. This study investigated the regulatory mechanisms of ultrafine ground wheat bran insoluble dietary fiber (WBIDF) with varying particle sizes on obesity through dietary interventions in both normal and high-fat diet-fed mice models. The results indicated that WBIDF significantly reduced weight gain in HFD-fed mice, decreased serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, and improved atherosclerosis and hepatic oxidative stress. Additionally, WBIDF modulated the gut microbiota, increasing the relative abundance of beneficial bacteria such as Enterococcus, Akkermansia, and Romboutsia, while decreasing the Firmicutes-to-Bacteroidetes (F/B) ratio. A significant reduction in the levels of acetic acid, propionic acid, and butyric acid was also observed (HFCW1.8). Thus, the WBIDF with smaller particle sizes exhibits superior regulation of lipid homeostasis. Our findings demonstrate that WBIDF mitigates obesity by improving lipid metabolism, modulating gut microbiota, and reducing hepatic oxidative stress, highlighting its potential as a functional dietary supplement for lipid metabolic homeostasis. • Finer WBIDF particles enhance lipid metabolism, prevent atherosclerosis, and improve liver-bile health. • Small-sized WBIDF particles reduce weight gain and visceral fat accumulation in obese mice. • Small WBIDF particles lower F/B ratio, restoring gut microbiota balance disrupted by high-fat diets. • At the genus level, WBIDF increased Enterococcus and Akkermansia abundance.