Combination of hydroxycitric acid and capsaicin regulates IRS-1/AMPK-mTOR-SREBP-1c Axis/NLRP3-NF-κB/Nrf-2-ARE signaling pathways to ameliorate the two-hit process in high-fat diet-induced hepatic steatosis

Abstract

Metabolic (Dysfunction) Associated Steatotic Liver Disease (MASLD) is a complex metabolic condition, the progression of which toward steatohepatitis can be explained by the ‘two-hit’ hypothesis: the first hit involves lipid accumulation, and the second hit involves inflammation and oxidative stress. In this study, we aimed to evaluate the protective effects of a combination of hydroxycitric acid and capsaicin (CHC) against high-fat diet (HFD)-induced MASLD in rats, specifically by targeting the mechanisms associated with both hits. To establish the experimental model, rats were fed a HFD for 16 weeks, followed by treatment with CHC for 6 weeks starting on day one of the 16th week of HFD feeding. CHC treatment effectively mitigated the first hit by improving insulin sensitivity via IRS-1 upregulation and activating AMPK signaling, which in turn inhibited mTOR activity and suppressed key lipogenic markers including SREBP-1c, FAS, ACC, and PPAR-γ. Simultaneously, CHC countered the second hit by enhancing antioxidant defense through Nrf-2 and HO-1 upregulation, while attenuating hepatic inflammation via downregulation of NF-κB, TNF-α, IL-6, and NLRP3 at both mRNA and protein levels. In conclusion, CHC can effectively protect against MASLD in HFD-fed rats by defending against the “first and second hit” by mediating the IRS-1/AMPK-mTOR-SREBP-1c axis/NLRP3-NF-κB/Nrf-2-ARE signaling pathways.