Hepatoprotective Effect of L-Carnitine is Achieved via Activating Nrf2 and Targeting TLR4 Signaling Pathways in Thioacetamide – Induced Liver Fibrosis in Rats

Background: Liver fibrosis is a critical health problem that can result in serious illness and death. L-carnitine (LC) is a naturally occurring compound which transports fatty acids through the inner mitochondrial membrane for consequent beta-oxidation. It acts as an antioxidant to lessen cellular oxidative stress. Carnitine is essential for the transfer of long-chain fatty acids across the inner mitochondrial membrane for subsequent β-oxidation. This study was carried out to investigate the hepatoprotective effects of LC via modulation of Nrf2 signaling and TLR4 targeting pathways in rats with liver fibrosis induced by Thioacetamide (TAA). Methods: Twenty-four adult male Wister rats were assigned into four groups as follows: Group 1 served as a normal non- treated control. Rats in group 2 were injected intraperitoneally (IP) with Thioacetamide (TAA) twice a week at a dose of 200 mg/kg B.wt for 6 weeks to produce liver fibrosis. Two weeks following TAA injections, 50 and 100 mg/kg of LC were administered to the rats in groups 3 and 4, respectively concurrently with TAA injections until end of the experiment (6 weeks). Results: Intraperitoneal injection of LC decreased the levels of liver enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in rats with liver fibrosis induced by TAA. Malondialdehyde (MDA), tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and toll-like receptor 4 (TLR4) levels were significantly decreased in LC treated groups. LC injection increased albumin, superoxide dismutase (SOD), heme oxygenase-1 (HO-1), nuclear factor erythroid 2-related factor 2 (Nrf2), and glutathione (GSH) levels. Additionally, expression of Phosphoinositide 3-kinase (PI3K) was increased and expression of TLR4 was decreased in LC treated groups according to PCR data. The biochemical findings were supported by histopathological findings. Regarding immunohistopathological examination, the LC treated groups reduced hepatic expression of caspase-3 an