Abstract
•MSG is a worldwide used food flavoring agent included in food industry and common household. No doubt it is wonderful in taste, but in the current study we found that oral administration of MSG to male albino rats caused evident histological and biochemical changes in the cerebellum and thyroid gland of adult male albino rats.•Basing on the obtained results, MSG has a toxic effect causing degenerative alterations in neurons and astrocytes in cerebellum with degeneration of thyroid gland of albino with rats when consumed in high dose and affected their functions.•Examination by immunohistochemistry (IHC) provided strong evidence for the toxic effect of MSG.•The toxic effect of MSG on cerebellum and thyroid gland may be initiated by oxidative stress. The appearance of cytoplasmic and nuclear abnormalities in the cerebellum and thyroid gland cells might suggest that MSG interact with proteins and enzymes of cerebellum and thyroid gland interfering with the antioxidant defense mechanism leading to generation and accumulation of ROS which in turn may induce inflammatory response and mitochondrial destruction exerting stress in the cells to undergo degeneration.•Vitamin C and Nigella sativa oil have been shown to protect and restore the structural and functional injury via inhibiting oxidative damage. As such, a focus on foods that contain high levels of Vitamin C and juices rich in Vitamin C as well as additional supplementation with Nigella sativa as a spice and food preservative in our food industry as well as a health remedy in traditional medicine may be a straightforward and inexpensive means to protect different tissues against oxidative damage induced by monosodium glutamate usage as a flavor enhancer in most of our managed foods.
Monosodium glutamate (MSG) is a major taste enhancer that is used as a food additive. Vitamin C (Vit C) and Nigella sativa oil (NSO) are known for their potent antioxidant activities.
This study investigates the adverse effect of MSG on the thyroid gland and cerebellum of adult male albino rats and the protection against MSG-mediated toxicity provided by Vit C and NSO.
Fifty rats were divided into five groups that were treated via oral gavage. Group I (control) rats received distilled water, Group II rats were treated with MSG (6 mg/gm body weight/day), Group III rats were treated with MSG and Vit C (100 mg/kg body weight /day), Group IV rats were treated with MSG and NSO (50 mg/kg body weight two times per week), and Group V rats were treated with MSG together with both Vit C and NSO with MSG. After 60 days of treatment, rats were euthanized and histological sections were prepared from the thyroid gland and the cerebellum for routine staining and immunohistochemical detection of glial fibrillar acidic protein (GFAP), Caspase-3 and proliferating cell nuclear antigen (PCNA), respectively. Cerebellar tissue was also evaluated to determine glutathione (GSH) and malondialdehyde (MDA) levels; GSH was also measured in thyroid tissue. Serum levels of fT3, fT4 and TSH (thyroid stimulating hormone) were also evaluated.
Microscopic examination of cerebellar tissues revealed significant cerebellar injury and cellular apoptosis among the rats in Group II. The thyroid glands of Group II rats were notable for degenerating follicles, loss of colloid, sloughed follicular cells and congested blood vessels. The cerebellar and thyroid tissues from rats in treatment Groups III, IV and V revealed significantly less pathology. Cerebellar and thyroid tissues from Group II rats that were treated with MSG alone revealed intense GFAP and caspase-3 (cerebellar) and PCNA (thyroid) immunoreactivity. Furthermore, cerebellar tissues from rats received MSG alone (Group II) were notable for decreased levels of GSH and increased levels of MDA; thyroid tissue from rats in Group II also demonstrated decreased levels of GSH. Likewise, serum fT3 and fT4 levels were significantly decreased, while serum TSH was significantly increased among rats in Group II. Combined administration of Vit C and NSO together with MSG (Group V) revealed some variations in oxidative parameters compared to those in the Group I control rats.
Oral intake of MSG resulted in degenerative changes in neurons and astrocytes in cerebellum and, also degeneration of the thyroid glands of albino rats. Concomitant administration of Vit C and NSO may limit MSG-induced damage to the cerebellum and thyroid glands and thereby provide significant protection against the oxidative damage induced by MSG.