Combination of luteolin and lycopene effectively protect against the “two-hit” in NAFLD through Sirt1/AMPK signal pathway

Luteolin and lycopene are common natural products, widely existing in nature, and both of which were reported to have various biological functions including anti-inflammatory, anti-obesity and anti-NAFLD. In the present study, we aimed to evaluate the therapeutic efficacy of luteolin and lycopene in combination and its latent molecular mechanisms in vitro and in vivo models of NAFLD.Sodium palmitate (PA)-induced steatotic HepG2 cells and primary hepatocytes, and high-fat diet-induced C57BL/6J obese mice were treated with luteolin, lycopene and their combination. Metabolic parameters were measured.We found that luteolin (20 μM) + lycopene (10 μM) was the best therapeutic combination in PA-induced HepG2 cells, and significantly improve cell viability and lipid accumulation in PA-induced HepG2 cells and primary hepatocytes. In addition, luteolin (20 mg/kg) + lycopene (20 mg/kg) could ameliorate increased body weight and hepatocyte steatosis; regulate serum triglycerides, serum total cholesterol, hepatic triglycerides and hepatic total cholesterol; decrease serum alanine transaminase and aspartate transaminase. Furthermore, in vivo and in vitro, luteolin, lycopene and their combination had no effect on Sirt1 expression, but all of them could upregulate the expression of NAMPT, which could increase the level of NAD+, the co-substrate of Sirt1, indirectly activating Sirt1/AMPK pathway, and then inhibited lipogenesis and increased β-oxidation, defensing the "first hit"; they also inactivated nuclear factor-κB (NF-κB) and decreased the levels of IL-6, IL-1β and TNF-α, defensing the "second hit".Thus, luteolin and lycopene in combination can effectively ameliorate "two-hit" in NAFLD through activation of the Sirt1/AMPK pathway.