Bifidobacterium bifidum enhances hepatic mitochondrial β-oxidation and ameliorates MAFLD in a high-fat diet rat model

Non-alcoholic fatty liver disease (NAFLD), recently reclassified as metabolic dysfunction-associated fatty liver disease (MAFLD), is closely linked to mitochondrial dysfunction and impaired lipid metabolism. Bifidobacterium bifidum has emerged as a promising probiotic candidate for restoring metabolic balance, yet its mitochondrial-targeted mechanisms remain underexplored. This study investigates the role of B. bifidum in modulating hepatic mitochondrial β-oxidation pathways and key transcriptional regulators involved in fatty acid metabolism. MAFLD was induced in male Sprague-Dawley rats using a high-fat diet and streptozotocin (STZ). Following disease induction, B. bifidum was administered over two treatment durations (6 and 14 weeks). Liver function tests, lipid profiles, and stereological analyses were performed, and hepatic gene expression of UCP2, CPT1A, PGC-1α, PPAR-α, and PPAR-γ was evaluated using quantitative RT-PCR. B. bifidum treatment significantly reduced serum triglycerides, total cholesterol, and LDL-C levels, while showing a non-significant upward trend in HDL-C levels. Gene expression analysis revealed that B. bifidum restored downregulated PGC-1α, CPT1A, and PPAR-α expression and normalized elevated UCP2 and PPAR-γ levels, suggesting enhanced mitochondrial fatty acid oxidation. Histological and stereological assessments confirmed structural improvements in liver tissue, including reduced steatosis and improved hepatocyte morphology. These findings provide new mechanistic evidence that B. bifidum exerts hepatoprotective effects by reprogramming mitochondrial lipid metabolism through the PPAR-α/PGC-1α/CPT1A axis. This probiotic may offer a novel, mitochondria-targeted therapeutic strategy for managing MAFLD and related metabolic disorders. Further studies are warranted to evaluate strain-specific effects and long-term outcomes in clinical settings.