BMAL1 downregulation exacerbates age-related nonalcoholic steatohepatitis by promoting NLRP3 inflammasome activation via HIF-1ɑ-mediated glycolysis.

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 H2O2 and 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.

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.