Ark shell oligopeptides Bu1 and Bu2 attenuate hepatic steatosis in HFD mice and HepG2 cells

Nonalcoholic fatty liver disease (NAFLD) is a progressive metabolic disorder lacking effective therapeutic options, ranging from simple steatosis to non-alcoholic steatohepatitis (NASH) and cirrhosis. It is characterized by excessive lipid accumulation in hepatocytes. Current treatments are often lifestyle-based, highlighting an urgent need for pharmacological interventions. This study explores novel oligopeptides derived from ark shells as potential bioactive agents to address the underlying lipid dysregulation in NAFLD.

Researchers investigated two novel ark shell-derived oligopeptides, Bu1 (LLRLTDL) and Bu2 (GYALPCDCL), for their hepatoprotective effects. In vitro, they treated oleic acid (OA) induced HepG2 cells with the peptides to assess lipid accumulation, gene expression (qPCR), and protein activation (Western blot). In vivo, Bu1 and Bu2 were administered to high-fat diet (HFD) induced obese mice. Primary endpoints included body weight, relative liver weight, hepatic lipid accumulation, serum lipid profiles (ELISA), liver histology, and systemic inflammatory markers.

Both Bu1 and Bu2 demonstrated significant amelioration of hepatic lipid accumulation in OA-induced HepG2 cells. This was achieved through a multi-targeted mechanism involving the suppression of lipogenesis, attenuation of fatty acid uptake, and promotion of fatty acid oxidation. The peptides downregulated key lipogenic transcription factors, including PPAR-γ, SREBP-1c, C/EBPα, and FAS, while moderately reducing fatty acid uptake via decreased CD36 expression. Notably, peptide treatment activated AMPK signaling, which subsequently increased p-HSL and CPT1A expression, thereby promoting lipolysis and accelerating intracellular lipid clearance. The involvement of AMPK was further supported by partial attenuation of peptide effects with AMPK inhibitor Compound C. In vivo, Bu1 and Bu2 administration attenuated body weight gain, relative liver weight, and hepatic lipid accumulation in HFD mice, independent of food intake.

Hepatic lipid profiles, including TG, FFA, free glycerol release, HDL, and LDL, were significantly improved. Liver histology confirmed the reversal of hepatic steatosis, and molecular analysis via Western blot substantiated these ameliorative effects. Furthermore, Bu1 and Bu2 exerted anti-inflammatory effects by reducing systemic inflammatory markers and reduced hepatocellular injury, indicated by lower serum AST and ALT levels.