Quercetin Attenuates Non-Alcoholic Fatty Liver Disease in Association with the Inhibition of Hepatic IL-1β/iNOS and IL-1β/CD45 Axes of Inflammation and Fibrosis Accompanied by Reduced Endogenous Metabolites and Apoptosis.

Abstract

Background: Liver inflammation and fibrosis are directly associated with non-alcoholic fatty liver disease (NAFLD). Dysregulation of the potent pro-inflammatory cytokine interleukin-1 beta (IL-1β), inducible nitric oxide synthase (iNOS), and tissue leukocyte infiltration (CD45 +ve) are connected with multiorgan injury and fibrosis. We investigated whether the induction of NAFLD can cause dysregulation in the hepatic IL-1β/iNOS and IL-1β/CD45 axes of inflammation and fibrosis, as well as in endogenous metabolites (lipids, glucose, and insulin) and apoptosis, in the presence and absence of the flavonoid quercetin.

Methods: The model group of rats was fed with a high-fat and high-carbohydrate diet (HFCD) for 4 weeks. The protective group of rats was given both quercetin (50 mg/kg) and HFCD for 4 weeks. All rats were sacrificed on day 29.

Results: NAFLD was induced in rats as demonstrated by dyslipidemia, hyperglycemia, insulin resistance, liver inflammation, and elevation of liver injury enzymes. NAFLD was also associated with the upregulation of hepatic IL-1β, iNOS, CD45, and apoptosis (p53). Biomarkers of fibrosis (TIMP-1 and α-SMA) were also elevated, and fibrosis was confirmed in the model group by increased collagen deposition and elevated stages of fibrosis score (Stage 1 to 2 of Brunt's NASH classification). All these parameters were significantly (p < 0.01) modulated by quercetin treatment. Additionally, a significant (p < 0.001) correlation between IL-1β and hepatic injury parameters was observed.

Conclusions: These findings suggest a potential association between NAFLD and the IL-1β/iNOS and IL-1β/CD45 axes of liver injury and fibrosis, as well as dyslipidemia, glycemia, and apoptosis, with quercetin exhibiting beneficial hepatic pleiotropic effects.