Protective Effects of Melatonin on Hepatic Injury Due to Chronic Monosodium Glutamate Consumption in Adult Female Rats

In the present study, it was aimed to investigate the effects of Monosodium Glutamate (MSG) consumption on rat liver and the possible antioxidant and anti-inflammatory effects of melatoninin protecting against MSG-induced hepatic damage. Thirty two adult female rats were randomly divided into 4 groups. For 30 days, MSG (2g/kg/day) or melatonin (4mg/kg/day) was given daily in drinking water or both melatonin and MSG were given simultaneously at the same doses, while normal drinking water was given to the control group. Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) levels were investigated in the serum of rats decapitated at the end of the experiment. In liver sections, Hematoxylin-Eosin (H-E), Sirius red, Periodic Acid Schiff (PAS) staining for histopathological damage examination, Nuclear Factor-kappa B (NF-κB), smooth muscle a-actin [alpha-Smooth Muscle Actin (a-SMA)], NADPH Oxidase (NOX-2), Transforming Growth Factor (TGF)-β1, SMAD2, SMAD7 immunohistochemistry were applied. At the end of the experiment, % body weight change in MSG group rats was high, and serum ALT and AST levels were increased compared to control group, while these levels weredecreased with melatonin administration. In addition, vacuolization in hepatocytes, dilatation in sinusoids, increase in Kupffer cells andinflammatory cell foci were detected in the MSG group. When melatonin wasadded to MSG, decreased hepatocyte glycogen content and SMAD7 immunoreactivity with increased a-SMA were observed along with improvements in NF-kB, NOX-2, TGF-β1, SMAD2 immunoreactivity. Our findings suggest that melatonin, with its antioxidant and anti-inflammatory effects, may be a potential agent to prevent liver damage that can be caused by MSG in the diet.