Oat β-Glucan and Lacticaseibacillus paracasei K56 synergistically ameliorate hypercholesterolemia in mice by modulating gut microbiota and bile acid metabolism

Hypercholesterolemia is one of the major risk factors for cardiovascular diseases. While probiotics and prebiotics show cholesterol-lowering potential, current evidence suggests limited efficacy when used alone. This study investigated the synergistic effects of oat β-glucan (OBG) and Lacticaseibacillus paracasei K56 (L. paracasei K56) against diet-induced hypercholesterolemia in mice. Hypercholesterolemic mice were treated for 12 weeks with atorvastatin (5 mg/kg/day), L. paracasei K56 (5 × 10⁹ CFU/kg), OBG (1 g/kg/day) or their combination. The combination treatment demonstrated superior efficacy, reducing total cholesterol (TC) by 41.19 ± 7.13 % (vs model group) and low-density lipoprotein cholesterol (LDL-C) by 37.47 ± 6.55 % (vs model group), with 24.37 ± 9.18 % (vs OBG group) and 15.10 ± 10.30 % (vs K56 group) greater TC reduction. Liver histopathology showed 3.7-fold reduction in steatosis scores versus model group. Mechanistically, compared with the model group, the combination upregulated hepatic CYP7A1/CYP27A1 expression by 5.75 ± 0.51-fold and 2.34 ± 0.21-fold respectively, increased fecal bile acids and enriched bile acid producing bacteria. In summary, L. paracasei K56 and OBG synergistically regulate gut microbiota and bile acid metabolism, promoting the conversion of cholesterol into bile acids, thereby alleviating hypercholesterolemia in mice.