Tannic acid protection against oxidative and inflammatory effects of monosodium glutamate on testis: Molecular and biochemical approach

In this study, the toxic effects of monosodium glutamate (MSG), a widely used food additive, on rat testicular tissue were evaluated and the potential protective role of tannic acid (TA), a natural polyphenolic compound, against this toxicity was investigated. For this purpose, 24 rats were divided into four groups (n=6). They were administered 2 g/kg monosodium glutamate (MSG) for 21 days. Subsequently, they were treated with 50 mg/kg tannic acid (TA). At the end of this period, testicular tissues were collected for molecular and biochemical analyses. Antioxidant enzyme activities (SOD, CAT, GPx, GST, GR), oxidative stress markers (GSH, MDA), inflammatory markers (TNF-α, iNOS, COX-2) and DNA damage indicator 8-OHdG (8-hydroxy-2′-deoxyguanosine) levels were analyzed in the experimental groups. In addition, expression levels of antioxidant defense (Sod, Cat, Gpx, Gst, Gr), inflammation (Tnf-α, Il-6, Nf-κB, Cox-2, Inos, Foxo1, Foxo3) and reproductive function-related genes (Dazl, Ddx4, Amh) were evaluated by qPCR. In the MSG group, a decrease in GSH level and a significant increase in MDA, TNF-α, iNOS and 8-OHdG levels were found (P<0.01). While a decrease was observed in SOD, CAT, GST and GR enzyme activities (P<0.01), no significant change was found in GPx activity. At the gene level, MSG administration suppressed the expression of genes related to antioxidant and germ cell functions and increased the expression of Tnf-α, lL-6, Cox-2 and Foxo3 (P<0.001). On the other hand, TA, both alone and in combination with MSG, demonstrated ameliorative effects on inflammation and oxidative stress, although not on all parameters. The data suggest that MSG induces oxidative stress, inflammation, DNA damage, and impaired germ cell function in testicular tissue. It was concluded that TA treatment suppresses these harmful effects, supports cellular defenses, and may help preserve testicular function.