INTRODUCTION: Epidemiological studies have demonstrated higher incidence and mortality rate of nonalcoholic steatohepatitis (NASH) in the elderly population than in younger groups. However, the mechanisms underlying this age-related exacerbation remain poorly understood.
OBJECTIVE: This study aimed to elucidate the specific pathways through which aging exacerbates NASH progression, using an integrated in vivo and in vitro model.
METHODS: Aged (18-month-old) and young (6-week-old) mice were fed a high-fat diet (HFD) for 16 weeks to induce NASH. A senescence-associated cellular model of NASH was established by co-treating murine hepatocyte AML-12 with HOand free fatty acid (FFA). Gene expression profiling of liver tissue was performed using RNA sequencing to identify molecular signatures. Interventions were as follows: (1) In vitro, BMAL1 overexpression plasmids were transfected into AML-12 cells, followed by treatment with 2-deoxy-D-glucose (2-DG, a glycolysis inhibitor) and 2-methoxyestradiol (2-ME2, a HIF-1α inhibitor); (2) in vivo, hepatocyte-specific BMAL1 overexpression was achieved in aged HFD-fed mice through adeno-associated virus serotype 8 (AAV8) delivery. Mechanism validation was performed using biochemical assays, Western blot, cell staining, molecular docking, and Co-IP. 2 2
RESULTS: Aged HFD-fed mice exhibited more severe NASH phenotypes than young mice. Transcriptomic analysis identified NLRP3-related signaling and circadian rhythm pathways as central contributors to age-specific NASH pathogenesis. These mice also exhibited elevated NLRP3 inflammasome activity, enhanced glycolysis, and reduced BMAL1 expression. In senescent NASH cells, BMAL1 overexpression along with 2-DG or 2-ME2 treatment significantly downregulated NLRP3 expression and attenuated lipid accumulation, inflammation, oxidative stress, and fibrosis. Mechanistically, BMAL1 directly bound to HIF-1α, thereby suppressing glycolysis. Hepatocyte-specific BMAL1 overexpression in aged HFD-fed mice markedly inhibited glycolysis and NLRP3 activation, resulting in an improvement in NASH-related pathologies.
CONCLUSION: This study revealed a novel mechanism in which BMAL1 downregulation under aging and HFD conditions promotes NASH progression by binding to HIF-1α and modulating the glycolysis-NLRP3 inflammasome axis.
