Unraveling the Beneficial Role of Resveratrol in Fructose-Induced Non-Alcoholic Steatohepatitis with a Focus on the AMPK/Nrf2 Signaling Axis

Abstract

Background and Objectives: High fructose intake is associated with non-alcoholic fatty liver disease (NAFLD), a chronic liver disease that is on the rise worldwide. New alternatives for treatment, such as bioactive phytochemicals, are needed. The aim of this study was to investigate the beneficial role of resveratrol in treating non-alcoholic steatohepatitis (NASH). Materials and Methods: Sixty male albino rats were allocated to three groups: group I, the normal control group; group II, the fructose-enriched diet group (FED), which was fed a 70% fructose diet for six weeks to induce NASH; and group III, the resveratrol-FED group (RES + FED), which was given the same FED diet plus an oral dose of 70 mg/kg resveratrol (RES) every day for an additional six weeks. We performed histological evaluations and assessed blood lipids and liver enzymes to study resveratrol's impact on NASH. Quantitative real-time PCR was used to assess the mRNA expression of nuclear factor E2-related factor 2 (Nrf2) in the liver samples. ELISA was used to measure Beclin 1, AMPK, IL-6, and the DNA-binding activity of Nrf2. Oxidative stress indicators, including GSH, SOD, and MDA, were evaluated spectrophotometrically. Results: Resveratrol effectively alleviated the biochemical and histopathological abnormalities associated with NASH, improving autophagy by raising Beclin 1 levels while reducing inflammation by decreasing IL-6 levels. Furthermore, resveratrol restored the liver architecture and the oxidative balance, as evidenced by the decreased MDA levels and improved antioxidant status via elevated GSH and SOD activities, as well as the activation of the AMPK/Nrf2 signaling axis. Conclusions: This study specifically examines resveratrol's therapeutic effects in a high-fructose diet-induced NASH model, focusing on the AMPK/Nrf2 signaling pathway to address oxidative stress and autophagy, providing novel insights into its molecular mechanism of action. Resveratrol reduces NASH by boosting autophagy and activating the AMPK/Nrf2 pathway. These findings underscore the potential of resveratrol as a promising therapeutic agent that can support treatment alongside conventional medications in the management of non-alcoholic steatohepatitis (NASH).

Keywords: albino rats; non-alcoholic steatohepatitis (NASH); oxidative stress; resveratrol.

Figure 1

Light microscopy of liver sections from adult male rats from groups I–III. Panel (A,D) represents group I (control group). Panel (B,E) represents group II (FED group). Panel (C,F) represents group III (RES + FED group). (A) Hepatocytes (H) are arranged in cords radiating from the central vein (CV) and are separated by the blood sinusoids (S), which are lined by flat endothelial cells (E) and von Kupffer cells (K). (B) Hepatic cords are not radially arranged around the central vein (CV). They are separated by blood sinusoids (S). Most hepatocytes have vacuolated cytoplasm (V) with displaced nuclei, and some of their nuclei are small and deeply stained (P). (C) Anastomosing hepatic cords radiating from the central vein (CV). The blood sinusoids (S) are lined by flat endothelial cells (E) and von Kupffer cells (K). Most hepatocytes appear normal (H). Few focal areas of vacuolated hepatocytes (V). (D) Branches of the portal vein (PV) and the bile duct (BD) are shown. The hepatocytes (H) are separated by blood sinusoids (S), which are lined by flat endothelial cells (E) and von Kupffer cells (K). (E) Most hepatocytes around the portal vein (PV) have vacuolated cytoplasm (V) with displaced nuclei. Some nuclei are small and deeply stained (P). The hepatocytes are separated by blood sinusoids (S). Lymphocytic infiltration of the portal tract was observed (In). (F) Anastomosing hepatic cords, portal vein (PV), bile duct (BD), and blood sinusoids (S), which are lined by flat endothelial cells (E) and von Kupffer cells (K). Most hepatocytes appear normal (H). Few focal areas of vacuolated hepatocytes (V). All panels were stained with hematoxylin and eosin and originally viewed at ×400 magnification.

Figure 2

Light microscopy of liver sections of adult male rats from groups I–III. Panel (A) represents group I (control). Panel (B) represents group II (FED group). Panel (C) represents group III (RES + FED group). (A) Normal distribution of collagen fibers around the portal tract (PT). (B) A marked increase in collagen fiber distribution is seen around the elements of the portal tract (PT). (C) A mild increase in the level of collagen fiber distribution is seen around the elements of the portal tract (PT). All panels were stained with Masson’s trichrome and originally viewed at ×400 magnification.

Figure 3

Schematic summary of the proposed protective roles of resveratrol through the induction of AMPK/Nrf2 in non-alcoholic steatohepatitis. The classical understanding is that Nrf2 coordinates the elimination of ROS and electrophiles derived from lipid peroxidation, thus preventing hepatocellular oxidative stress and mitochondrial dysfunction. In addition, there is growing evidence in the literature that Nrf2 regulates fatty acid metabolism by repressing genes that promote lipid accumulation in hepatocytes. AMPK induction by resveratrol also activates autophagy that lowers hepatic lipid load via lipophagy, eliminates dysfunctional mitochondria, and hence reduces the ROS level. Resveratrol → KEAP1: Inhibits KEAP1, activating NRf2. KEAP1 → NRf2: KEAP1 suppresses NRf2; Resveratrol removes this suppression. NRf2 → Antioxidant: Increases antioxidant gene expression. Antioxidant → Oxidative Stress: Antioxidants reduce oxidative stress. Oxidative Stress → NASH: Promotes liver damage leading to NASH. Oxidative Stress → Inflammation: Stimulates inflammatory cytokines like IL-6. Inflammation → NASH: Chronic inflammation worsens NASH. Resveratrol → AMPK: Activates AMPK, regulating energy metabolism. AMPK → Lipid Metabolism: Enhances lipolysis, reduces lipid and cholesterol. AMPK → mTOR: Suppresses mTOR, reducing lipid synthesis. AMPK → Autophagy: Promotes autophagy, reducing lipid accumulation. Autophagy → Lipogenesis: Decreases lipogenesis and triacylglycerol. Lipogenesis → Steatosis: Excess lipids lead to steatosis. Steatosis → NASH: Steatosis progresses to NASH with inflammation.