Evaluation of a fermented citrus bioconversion product: metabolic and hepatic effects in high-fat diet-fed mice

Despite growing interest in fermented citrus-derived functional ingredients, their metabolic effects in diet-induced obesity and the chemical characteristics of the fermented preparations remain insufficiently characterized. This study characterized a fermented citrus bioconversion product (FCBP) and evaluated its metabolic effects in a high-fat diet (HFD)-induced obese mouse model. FCBP was produced by microbial fermentation of a citrus flavonoid-rich substrate using Bacillus subtilis and characterized by HPLC fingerprinting. Mice fed an HFD containing 45% kcal from fat received FCBP (10 or 20 mg/kg/day) orally for 8 weeks, with hesperidin included as a comparative reference compound. FCBP at 20 mg/kg significantly attenuated body-weight gain and reduced plasma triglyceride levels compared with the HFD group. Histological analysis further demonstrated that FCBP significantly reduced HFD-induced hepatic steatosis. FCBP was also associated with alterations in hepatic expression of genes related to glucose and lipid metabolism, including SREBP1c, ACC1, PPARγ, GLUT4 (Slc2a4), PGC-1α, and PPARα. Notably, increased SREBP1c mRNA expression was accompanied by decreased ACC1 expression and reduced hepatic steatosis, indicating that the transcriptional responses did not support a simple model of uniform suppression of hepatic lipogenesis. FCBP treatment also reduced aortic VCAM-1- and ICAM-1-positive areas under HFD conditions. Collectively, these findings demonstrate selected metabolic and tissue-level effects of FCBP in HFD-fed mice. However, because a matched non-fermented citrus preparation was not included, the observed effects cannot be attributed specifically to the fermentation process, and further comprehensive chemical and mechanistic characterization is warranted.