Monosodium glutamate-induced oxidative kidney damage and possible mechanisms: a mini-review

Epithelial barrier dysfunction and associated diseases in companion animals: Differences and similarities between humans and animals and research needs

Since the 1960s, more than 350,000 new chemicals have been introduced into the lives of humans and domestic animals. Many of them have become part of modern life and some are affecting nature as pollutants. Yet, our comprehension of their potential health risks for both humans and animals remains partial. The "epithelial barrier theory" suggests that genetic predisposition and exposure to diverse factors damaging the epithelial barriers contribute to the emergence of allergic and autoimmune conditions. Impaired epithelial barriers, microbial dysbiosis, and tissue inflammation have been observed in a high number of mucosal inflammatory, autoimmune and neuropsychiatric diseases, many of which showed increased prevalence in the last decades. Pets, especially cats and dogs, share living spaces with humans and are exposed to household cleaners, personal care products, air pollutants, and microplastics. The utilisation of cosmetic products and food additives for pets is on the rise, unfortunately, accompanied by less rigorous safety regulations than those governing human products. In this review, we explore the implications of disruptions in epithelial barriers on the well-being of companion animals, drawing comparisons with humans, and endeavour to elucidate the spectrum of diseases that afflict them. In addition, future research areas with the interconnectedness of human, animal, and environmental well-being are highlighted in line with the "One Health" concept.

Hematological changes, oxidative stress assessment, and dysregulation of aquaporin-3 channel, prolactin, and oxytocin receptors in kidneys of lactating Wistar rats treated with monosodium glutamate

High consumption of locally produced delicacies could expose nursing mothers to high monosodium glutamate (MSG) levels, frequently used as a necessary condiment in low-income countries. Thus, this study evaluated some novel preliminary changes in renal hormonal receptors, the aquaporin-3 channel, oxidative stress markers, and hematological indices induced by monosodium glutamate in lactating rats. Post-parturition, twenty-four (24) lactating Wistar rats were divided into four (4) groups of six rats each (n = 6). Oral administration of distilled water and MSG started three (3) days postpartum as follows: group 1: distilled water (1 ml/kg BW), group 2: MSG (925 mg/kg BW), group 3: MSG (1850 mg/kg BW), and group 4: MSG (3700 mg/kg BW). At the end of the experiment, which lasted fourteen (14) days, animals were sacrificed and samples of blood and tissues were obtained for biochemical analysis. MSG administration significantly (p < 0.05) increased ROS and MDA, with a significant (p < 0.05) decrease in kidney antioxidants. Serum creatinine, total, conjugated, and unconjugated bilirubin significantly (p < 0.05) increased with MSG administration. The prolactin receptor was significantly reduced (p < 0.05), while the oxytocin receptor and aquaporin-3 channel were significantly (p < 0.05) increased in the MSG-administered groups. There were significant (p < 0.05) changes in the hematological indices of the MSG-administered animals. Thus, the findings of this study suggest that high MSG consumption causes hematological alterations and may alter renal function via increased ROS production and dysregulation of the AQP-3 channel, prolactin, and oxytocin receptors in the kidneys of lactating Wistar rats.

Monosodium glutamate altered renal architecture and modulated expression of NMDA-R, eNOS, and nNOS in normotensive and hypertensive rats

Monosodium glutamate (MSG) administration has been shown to pronounce hypertension and oxidative status with increased renal blood flow (RBF), however, the precise mechanisms of action have never been demonstrated. This study aimed to investigate the MSG action by studying the alteration in renal architecture and specific protein expression in 2-kidney-1-clip hypertensive comparing to sham operative normotensive rats. The administered doses of MSG were 80, 160, or 320 mg/kg BW daily for 8 weeks. Using routine chemical staining, the congestion of glomerular capillaries, a lesser renal corpuscles and glomeruli size, a widen Bowman capsule's space, an increase in mesangial cell proliferation and mesangial matrix, renal interstitial fibrosis, focal cloudy swelling of renal tubular epithelial cells were observed. Immunological study revealed an increase in the expression of N-methyl-D-aspartate receptor (NMDA-R) and endothelial nitric oxide synthase (eNOS) but a decrease in neuronal NOS (nNOS). It is suggested that MSG may upregulate the NMDA-R levels which responsible for the oxidative stress, glomerular injury, and renal interstitial fibrosis. The NMDA-R may also stimulate eNOS overexpression which resulted in renal microvascular dilatation, a raise in RBF and GFR, and natriuresis and diuresis promotion. Long-term exposure of MSG may trigger adaptation of tubuloglomerular feedback through nNOS downregulation.

Protective effect of Danshensu against neurotoxicity induced by monosodium glutamate in adult mice and their offspring

Excessive neuronal excitation by glutamate is a well-established cause of neurotoxicity, leading to severe impairment of brain function. Excitotoxicity is a key factor in numerous neurodegenerative conditions. In this study, we investigated the neuroprotective effects of Danshensu (DSS) against monosodium glutamate (MSG)-induced neurotoxicity in adult mice and their offspring. We randomly divided one hundred 8-week-old Kunming mice (equal number of males and females) into a control group and an experimental group. The experimental group was further subdivided into various treatment groups, including MSG gavage treatment, bwbw DSS treatment group 1 (bwbw DSS treatment group 2, a drug control group, and a normal control group (receiving an equal volume of physiological saline for ten consecutive days). Additionally, another one hundred healthy 8-week-old Kunming mice were similarly divided into groups and treated. These mice were paired randomly (one male and one female) and pregnant females were housed separately to obtain offspring. Subsequently, we conducted histological and behavioral analyses on adult mice and their offspring. MSG treatment induced significant cellular edema and hippocampal damage in both the treated mice and their offspring. However, varying doses of DSS effectively counteracted the neurotoxic effects of MSG, with no adverse impact on brain tissue structure or neural function in either adult mice or their offspring. Behavioral experiments further confirmed that DSS exerted a substantial protective effect against MSG-induced impairment of learning and memory in the treated adult mice and their offspring, in addition to mitigating central nervous system overexcitation and inhibiting exploratory behavior. In conclusion, DSS exerts significant protective effects against MSG-induced neurotoxicity in both adult mice and their offspring.

Monosodium Glutamate Even at Low Dose May Affect Oxidative Stress, Inflammation and Neurodegeneration in Rats

Monosodium glutamate (MSG) is a widely used flavour enhancer. A daily intake of MSG at high dosage (2000-4000 mg/kg body weight) is reported to be toxic to humans and experimental animals. The present study aims to investigate the toxic effect of oral administration of MSG at low concentrations (30 and 100 mg/kg body weight) by evaluating biochemical parameters of oxidative stress and inflammation in blood; expression of neuroinflammatory gene and histopathological changes in brain on male Wistar rats. The administration of MSG significantly increases serum level of fasting glucose, insulin, triglycerides, total cholesterol, low-density lipoprotein and decrease level of high-density lipoprotein. Significant low level of FRAP, GSH, SOD, CAT and higher level of MDA, PCO, AOPP, PMRS, NO, CRP, IL-6, TNF-α confirms substantial oxidative stress followed by inflammation after 100 mg MSG treatment. RT-PCR figure shows significant expression of neuroinflammatory gene IL-6 and TNF-α and histopathological examination revealed severe neurodegeneration in hippocampus (CA1 and CA3) and cerebral cortex region of brain at 100 mg MSG treatment. Our result provides evidence that MSG administration at 30 mg does not impose toxicity, however at 100 mg/kg body weight, which is considered a low dose, there is significant toxic effects and may be detrimental to health.

Investigating the Chemical Composition of Lepidium sativum Seeds and Their Ability to Safeguard against Monosodium Glutamate-Induced Hepatic Dysfunction

Monosodium glutamate (MSG) is one of the most frequently used food additives that endanger public health. The antioxidant, hyperlipidemic, and cytoprotective properties of Lepidium sativum seeds (LSS) as a natural remedy can minimize the harmful effects of MSG. This study investigated the potential protective effect of LSS against MSG-induced hepatotoxicity in rats. Male albino Sprague Dawley rats (n = 24) were equally divided into four groups for 30 days: the control group (G1) received a basal diet without supplement, group (G2) was fed a basal diet + MSG (30 g/kg b.w.) as a model group, group (G3) was fed a basal diet + MSG (30 g/kg b.w.) + LSS (30 g/kg b.w.), and group (G4) was fed a basal diet + MSG (30 g/kg b.w.) + LSS (60 g/kg b.w.). LSS enhanced serum alkaline phosphatase activity as well as total cholesterol, triglyceride, and glucose levels. It can decrease peroxide content in serum lipids and inhibit glutathione reductase and superoxide dismutase in hepatic cells. The dietary supplementation with LSS provided cytoprotection by enhancing the histoarchitecture of the liver and decreasing the number of apoptotic cells. Due to their antioxidant and anti-apoptotic properties, LSS effectively protect against the hepatotoxicity of MSG. These findings are of the highest significance for drawing attention to incorporating LSS in our food industry and as a health treatment in traditional medicine to combat MSG-induced hepatic abnormalities.

MORPHOLOGICAL PECULIARITIES OF THE PANCREAS OF MALE RATS AFTER PROLONGED ADMINISTRATION OF MONOSODIUM GLUTAMATE DURING THE RECOVERY PERIOD

OBJECTIVE

The aim: To study changes in the exocrine and endocrine parts of the pancreas of rats after abolition of monosodium glutamate (MSG) administered in the diet.

PATIENTS AND METHODS

Materials and methods: White male laboratory rats with a baseline weight of 120 ± 5 g were randomized into 3 groups: 1 - control, 2 - animals with daily feeding of 70 mg/ kg MSG for 8 weeks, 3 - abolition of MSG with transfer of animals to a standard diet and pancreatic examination after 8 weeks. We used histological studies with morphometric analysis and statistical processing of acini and acinar cell areas, Langerhans islets, connective tissue (according to Stolte M.) and adipose tissue. Preparations of pancreas were stained with hematoxylin and eosin and azan.

RESULTS

Results: The animals of groups 2 and 3 showed atrophic, degenerative and inflammatory disturbances in the exocrine and endocrine parts of the pancreas, which worsened after 8 weeks of MSG withdrawal (3 rd group). In the preparations, the Langerhans islets were of different shapes and sizes. Small islets predominated, as well as islets with low density of α- and β-cells, different capillary filling with blood and overgrowth of connective tissue in the capillary areas. The acinar cells and acini were reduced, and degenerative abnormalities were detected in the structures.

CONCLUSION

Conclusions: After daily administration of 70 mg/kg MSG for 8 weeks, atrophic and degenerative changes in the exocrine and endocrine parts of the pancreas were revealed. No recovery of pancreatic structures was observed 8 weeks after MSG withdrawal.

Monosodium glutamate in a type 2 diabetes context: A large scoping review

This scoping review aimed to map and elaborate the heterogenous and inconclusive body of evidence relating monosodium glutamate (MSG) and type 2 diabetes (T2DM). For this reason, multiple health outcomes related to T2DM were included and a systematic search was conducted. Experimental and observational trials between 1995 and January 2021 were collected. The tests were highly heterogenous in their samples, doses, route of exposures, durations, diets and conclusions. There was a pattern of negative effects of MSG at oral doses ≥2,000 mg/kg of body weight, and by gavage or injection at any given dose. Evidence was lacking in many areas and most of the evidence relied on short term tests. Further research should focus on standardizing and justifying methodologies, conducting long term studies and toxicokinetic tests, and avoiding bias. Focusing on the gaps highlighted and investigating mechanisms of action of MSG is crucial. Evidence-based toxicology is encouraged.

Renoprotective and Cardioprotective Potential of Moricandia sinaica (Boiss.) against Carbon Tetrachloride-Induced Toxicity in Rats

The goal of the current study was to assess the nephroprotective and cardioprotective potential of Moricandia sinaica methanol extract (MOR-1), as well as its butanol (MOR-2) and aqueous (MOR-3) fractions against carbon tetrachloride (CCl₄)-induced nephro and cardio-toxicity. Cardiac function was assessed using the biochemical parameters lactate dehydrogenase (LDH) and creatinine kinase (CK). Renal function was examined using the biochemical parameters creatinine and uric acid. The levels of nonprotein sulfhydryls (NPSH) and malondialdehyde (MDA) were used as markers of oxidative strain. A dose of 100 and 200 mg/kg of butanol fraction given prior to CCl₄ treatment significantly (p < 0.05 − 0.001) protected against elevated LDH and CK levels. Similarly, treatment with silymarin (10 mg/kg) and butanol fraction (100 and 200 mg/kg) significantly (p < 0.05 − 0.001) boosted total protein levels compared to CCl₄ treatment alone. The silymarin (10 mg/kg) and butanol fraction (100 and 200 mg/kg) also provided a significant (p < 0.05 − 0.001) protective effect for MDA levels. Methanol extract (MOR-1) and butanol (MOR-2) showed significant results and were recommended for further pharmacological and screening for active constituents.

Effect of Nigella sativa L. Seed on the Kidney of Monosodium Glutamate Challenged Rats

Monosodium glutamate (MSG) consumption is responsible for a wide spectrum of health hazards including nephrotoxicity. The search for phytochemical strategies having broad safety profile to counter MSG toxicity is worthwhile. Nigella sativa L. seed (NSS) is very promising in this regard owing to its antioxidant and cytoprotective nature. Therefore, we attempted to investigate the potential protective effect of NSS on MSG-induced renal toxicity in rats. To accomplish this objective, fifteen adult Wistar albino rats were randomly and equally divided into three groups for 21 days: the control group received no treatment, MSG group supplemented with MSG at a dose of 30 g/kg feed, and MSG + NSS group supplemented with MSG at the same previous dose in conjugation with NSS at a dose of 30 g/kg feed. MSG and its combination with NSS failed to cause any significant difference in the kidney function parameters in comparison with the control. A significant elevation in lipid peroxides (LPO) level, glutathione-S-transferase activity and total antioxidant capacity (TAC) and a significant reduction in superoxide dismutase activity were found in MSG group. LPO level and TAC in MSG intoxicated rats significantly normalized by NSS ingestion. NO level showed absence of significant difference among all experimental groups. MSG elicited histopathological lesions such as decreased glycoprotein content and fibrosis however, NSS succeeded in enhancing all these features. MSG group showed positive glutathione reductase and superoxide dismutase 2 immuno-expression whereas, MSG + NSS group showed weak immunostaining. A significant increase in the number of apoptotic cells was observed in MSG group compared to the control. On the other hand, MSG + NSS group exhibited a significant decrease in the number of apoptotic cells. NSS mitigated MSG-induced renal impairments by ameliorating oxidative stress and exerting anti-apoptotic effect.

MONOSODYUM GLUTAMAT, LEZZET ARTTIRICI MI, ÖLDÜREN LEZZET Mİ?

Monosodium glutamat (MSG) 1800’lü yıllardan beri lezzet artırıcı katkı maddesi olarak, işlenmiş ve paketlenmiş tuzlu veya tatlı gıdalarda kullanılmaktadır. Yapılan birçok çalışma MSG kullanımının çok sayıda yapısal ve fonksiyonel bozukluklara yol açabileceğini ortaya çıkarmıştır. Son yıllarda MSG kullanımının çok artması gıda güvenliği konusunda endişelerinde artmasına neden olmuştur.

Protocatechuic acid abrogates oxidative insults, inflammation, and apoptosis in liver and kidney associated with monosodium glutamate intoxication in rats

Monosodium glutamate (MSG), a commonly used flavor enhancer, has been reported to induce hepatic and renal dysfunctions. In this study, the palliative role of protocatechuic acid (PCA) in MSG-administered rats was elucidated. Adult male rats were assigned to four groups, namely control, MSG (4 g/kg), PCA (100 mg/kg), and the last group was co-administered MSG and PCA at aforementioned doses for 7 days. Results showed that MSG augmented the hepatic and renal functions markers as well as glucose, triglycerides, total cholesterol, and low-density lipoprotein levels. Moreover, marked increases in malondialdehyde levels accompanied by declines in glutathione levels and notable decreases in the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were observed in MSG-treated group. The MSG-mediated oxidative stress was further confirmed by downregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) gene expression levels in both tissues. In addition, MSG enhanced the hepatorenal inflammation as witnessed by increased inflammatory cytokines (interleukin-1b and tumor necrosis factor-α) and elevated nuclear factor-κB (NF-κB) levels. Further, significant increases in Bcl-2-associated X protein (Bax) levels together with decreases in B-cell lymphoma 2 (Bcl-2) levels were observed in MSG administration. Histopathological screening supported the biochemical and molecular findings. In contrast, co-treatment of rats with PCA resulted in remarkable enhancement of the antioxidant cellular capacity, suppression of inflammatory mediators, and apoptosis. These effects are possibly endorsed for activation of Nrf-2 and suppression of NF-kB signaling pathways. Collectively, addition of PCA counteracted MSG-induced hepatorenal injuries through modulation of oxidative, inflammatory and apoptotic alterations.

The protective effect of Nigella sativa seeds against monosodium glutamate-induced hepatic dysfunction in rats

•

MSG-challenged rats were characterized by hepatic dysfunction and redox imbalance along with increased programmed cell death.

•

The negative consequences of MSG consumption have been partially overcome by the nutritional inclusion of NSS.

•

NSS restores the redox potential and ameliorates the histopathological deteriorations and apoptosis in the liver.

•

These outcomes are of major importance in paving the road towards the incorporation of NSS as a candidate strategy against MSG-related abnormalities.

Monosodium glutamate (MSG) is one of the most commonly used feed additives which poses a threat to public health. Nigella sativa is a promising natural approach in this issue due to its antioxidant, hypolipidemic, and cytoprotective characters. Here, we investigated the potential protective effect of Nigella sativa seed (NSS) against MSG-induced hepatotoxicity in rats. To accomplish this objective, fifteen adult Wistar albino rats were randomly and equally divided into three groups for 21 days: the control group received no treatment, MSG group supplemented with MSG at a dose of 30 g/kg feed, and MSG + NSS group supplemented with MSG at the same previous dose together with NSS at a dose of 30 g/kg feed. NSS succeeded in boosting serum alkaline phosphatase activity and total cholesterol, triglycerides, and glucose levels. It reduced lipid peroxides in the serum and down-regulated glutathione reductase and superoxide dismutase 2 immuno-expression in the hepatic cells. NSS intervention provided cytoprotection by improving the histo-architecture of the liver and reducing the number of apoptotic cells. NSS was effective in protecting against the hepatotoxicity of MSG through its antioxidant and anti-apoptotic effects. These findings are of utmost significance in directing the attention towards the incorporation of NSS in our food industry as well as a health remedy in traditional medicine to fight MSG-related hepatic abnormalities.

Monosodium glutamate causes hepato-cardiac derangement in male rats

People in the fast-food era rely on pre-packaged foods and engage in limited physical activity, which leads to a shift in eating patterns. Monosodium glutamate (MSG), a dietary ingredient used in this sort of cuisine, has been found to be hazardous to both experimental animals and humans. The objective of this study was to explore at the unnecessary changes caused by consuming MSG in secret and exceeding the recommended dosage. Hence, we decided to evaluate the impact of MSG by using three different doses (200, 400, and 600 mg/kg body weight orally) for 28 days in rats. We uncovered that all three MSG dosages result in a rise in body weight, dyslipidemia, inflammatory response, and hepato-cardiac marker enzymes, all of which imply hepatic and cardiac toxicity. Furthermore, changes in redox status suggest oxidative stress, which was higher in all three MSG dosages although not as much as in the MSG-600 group when compared to control. Such effects eventually manifested themselves in tissue architecture of the liver and heart, resulting in severe hepato-cardiac derangement, but the degree of tissue damage was greater in the MSG-600 group. As a result, it is possible that MSG has a negative influence on the liver and heart. However, the MSG-600 group showed a substantial effect, indicating that MSG should not be used in food preparation. Therefore, the findings of the study may aid in the formulation of health-care strategies and serve as a warning to the general public regarding the use of MSG in daily diet.

The Reproductive Toxicity of Monosodium Glutamate by Damaging GnRH Neurons Cannot Be Relieved Spontaneously Over Time

Objective

The present study aims to evaluate the effect of monosodium glutamate on testicular spermatogenesis in mice from the perspective of the hypothalamic-pituitary-testicular axis and whether this destructive effect is alleviated with time.

Methods

Neonatal mice were randomly divided into a monosodium glutamate (MSG) group and a control group, just below the interscapular region after birth with 10 µL MSG to deliver 4 mg/g (body mass), or with equivalent volumes of 0.9% saline. Samples which involved blood, brains and testicles of mice were collected and measured at puberty at 60 days and adulthood at 90 days.

Results

The results show that the fluorescence intensity of GnRH nerve fibers, the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) hormones in the reproductive system, the number of spermatocytes and spermatozoa in testicular sections, the body length, body weight, testicular weight, and testicular index in the 60-day-old mice in monosodium glutamate group (MSG60 group) and the MSG90 group were lower than those in the 60-day-old mice in normal control group (NC60 group) (p < 0.05), but the number of apoptotic cells in the testicular section was higher than in the NC60 group (p < 0.05). When the 90-day-old mice in monosodium glutamate group (MSG90 group) was compared with the MSG60 group, except for body weight and testicular weight increase (p < 0.05), there is no significant difference in the other parameters mentioned above (p > 0.05).

Conclusion

Monosodium glutamate can cause reproductive toxicity to male mice by damaging GnRH neurons, and this reproductive toxicity cannot be relieved spontaneously over time. These findings are supported by observed histological changes.

Antioxidant and cytoprotective effects of Nigella sativa L. seeds on the testis of monosodium glutamate challenged rats

Monosodium glutamate (MSG) is one of the most widely spread food additives that might cause male infertility. However, Nigella sativa L. seeds (NSS) could provide a solution. This study was designed to investigate the potential effects of NSS on rats ingesting MSG. To achieve this aim, adult male albino rats were randomly equally assigned into three groups for 21 days: control group received no treatment, MSG group received MSG as 30 g/kg feed, and MSG + NSS group received MSG as 30 g/kg and NSS as 30 g/kg feed. Testis histomorphometry showed marked deterioration by MSG as atrophic seminiferous tubules with degeneration of their lining cells, damaged Leydig cells and decreased germ cells number. Periodic Acid Schiff stain indicated irregular interrupted basement membranes. Glutathione reductase, superoxide dismutase 2 (SOD2), and caspase-3 immuno-expressions increased in testicular cells. Testosterone levels were significantly decreased in MSG challenged rats along with significant increase in luteinizing hormone levels, whereas NSS normalized this hormonal profile. MSG exposure also caused significantly increased lipid peroxides (LPO), glutathione-S-transferase, and total antioxidant capacity (TAC) whereas nitric oxide and SOD2 were significantly decreased. NSS succeeded in rebalance LPO and TAC and ameliorated the histoarchitectural disturbances. NSS mitigated MSG-induced testicular impairment by its antioxidant and cytoprotective activities.

Potential therapeutic effects of Ulva lactuca water fraction on monosodium glutamate-induced testicular and prostatic tissue damage in rats

Male infertility is considered one of the most critical health problems that are expected to expand worldwide. Ulva lactuca is a species of green seaweeds which is known to be a rich source of many important nutrients. Accordingly, this study is designated to investigate the therapeutic role of Ulva lactuca water fraction (UL) against monosodium glutamate (MSG)-induced male reproductive system disorders in male rats. Ulva lactuca methanolic crude extract was prepared firstly, and then water-dissolved compounds of this crude methanolic extract were separated. Ulva lactuca water fraction active phenolic compounds were determined using high-performance liquid chromatography (HPLC). Thirty-two male rats were divided equally into four groups; male infertility was induced in sixteen experimental animals by MSG at dose of 15 mg/Kg for 45 days. Eight infertile animals were treated with 100 mg/Kg of Ulva lactuca water fraction for 30 days. The rest of the animals were divided into two control groups; one control group (eight animals) was used to study the effect of UL on healthy rats at dose of 100 mg/Kg for 30 days and healthy control group (eight animals). Semen quality parameters (concentration and motility ratio), serum testosterone, prostate-specific antigen (PSA), and phosphatases were estimated by using standard protocols. Moreover, prooxidants and endogenous antioxidant enzymes were measured in prostate and testis homogenates. In addition, relative expression of pro-inflammatory genes (inducible nitric oxide synthase (i-NOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α alpha (TNF-α), and tumor protein (P53)) were assessed in testicular and prostatic tissues. Finally, histological alterations were measured by hematoxylin and eosin (H&E) stain. Results revealed that Ulva lactuca water fraction contains active phenolic constituents responsible for its antioxidant bioactivity. Oral administration of MSG significantly induced histological alterations. Oxidative stress was observed with elevated levels of nitric oxide (NO), thiobarbituric acid reactive substances (TBARS), and xanthine oxidase (XO) activity in both testis and prostate tissues. MSG adversely affected prostate function via elevation of PSA, prostatic acid phosphatases (PAPs), and total acid phosphatases (TAPs). In addition, it upregulated pro-inflammatory genes in testis and prostate tissues. Meanwhile, MSG reduced serum testosterone, semen quality, and antioxidant enzyme activities (glutathione peroxidase (GPx), glutathione-s-transferase (GST), and superoxide dismutase (SOD)). Treatment with UL notably ameliorated the state of oxidative stress and downregulated the expression of pro-inflammatory gene markers. This study highlighted the potential efficacy of Ulva lactuca water fraction on MSG-induced male infertility in rats. Therapeutic effect of UL on oxidative stress and inflammation induced by MSG in testicular and prostatic tissues.

The effects of L-carnitine on renal function and gene expression of caspase-9 and Bcl-2 in monosodium glutamate-induced rats

BACKGROUND

Monosodium glutamate (MSG) is frequently consumed as a flavor enhancer or food additive. Possible damages induced by MSG effects on some organs have been stated in experimental animal models. The aim of the present study was to evaluate the protective effects of L-carnitine (L-ca) on the renal tissue in MSG-Induced Rats.

METHODS

In this regard, 60 male rats were randomly divided into six groups (n = 10/each): 1 (Control); 2 (sham); 3 (L-carnitine 200 mg/kg b.w); 4 (MSG 3 g/kg b.w); 5 (MSG + L-carnitine 100 mg/kg); and 6 (MSG + L-carnitine 200 mg/kg). After 6 months, the rats were sacrificed, the blood sample collected and the kidneys harvested for evaluation of biochemical analytes, genes expression, and histopathological changes.

RESULTS

MSG significantly increased the serum level of MDA, BUN, creatinine, uric acid and renal Caspase-9, NGAL and KIM-1 expression, but it decreased the serum activity also renal expression of SOD, catalase, GPX, and Bcl-2 expression compared to the control group. Treatment with L-ca significantly reduced the serum BUN, creatinine, uric acid and MDA level and increased catalase, GPX and SOD compared to the MSG group. However, only administration of L-ca 200 significantly decreased the caspase-9, NGAL and KIM-1; also, it increased the Bcl-2 expression in the kidney compared to the MSG group.

CONCLUSIONS

Our findings indicated that L-carnitine had a major impact on the cell protection and might be an effective therapy in ameliorating the complications of the kidney induced by MSG via its antioxidant and anti-apoptotic properties.

Worldwide flavor enhancer monosodium glutamate combined with high lipid diet provokes metabolic alterations and systemic anomalies: An overview

•

Flavor enhancing high lipid diet acts as silent killer.

•

Monosodium glutamate mixed with high lipid diet alters redox-status.

•

Monosodium glutamate mixed with high lipid diet induces systemic anomalies.

In this fast-food era, people depend on ready-made foods and engage in minimal physical activities that ultimately change their food habits. Majorities of such foods have harmful effects on human health due to higher percentages of saturated fatty acids, trans-fatty acids, and hydrogenated fats in the form of high lipid diet (HLD). Moreover, food manufacturers add monosodium glutamate (MSG) to enhance the taste and palatability of the HLD. Both MSG and HLD induce the generation of reactive oxygen species (ROS) and thereby alter the redox-homeostasis to cause systemic damage. However, MSG mixed HLD (MH) consumption leads to dyslipidemia, silently develops non-alcoholic fatty liver disease followed by metabolic alterations and systemic anomalies, even malignancies, via modulating different signaling pathways. This comprehensive review formulates health care strategies to create global awareness about the harmful impact of MH on the human body and recommends the daily consumption of more natural foods rich in antioxidants instead of toxic ingredients to counterbalance the MH-induced systemic anomalies.

Vagotomy associated with splenectomy reduces lipid accumulation and causes kidneys histological changes in rats with hypothalamic obesity

Purpose

To evaluate the influence of autonomic vagal and splenic activities on renal histomorphometric aspects in obese rats.

Methods

Thirty male Wistar rats were used, of which, 24 received subcutaneous injections of monosodium glutamate (MSG) during the first 5 days of life (4 g/kg body weight) and six control animals received injections of saline solution (CON). Five experimental groups were organized (n = 6/group): falsely-operated control (CON-FO); falsely-operated obese (MSG-FO); vagotomized obese (MSG-VAG); splenectomized obese (MSG-SPL); vagotomized and splenectomized obese (MSG-VAG-SPL).

Results

The MSG-FO group animals showed a significant reduction in body weight and nasal-anal length when compared to CON-FO group animals (p < 0.05). The MSG-VAG-SPL group showed significant reduced in most biometric parameters associated with obesity. Falsely-operated obese animals showed a significant reduction in renal weight, glomerular diameters, glomerular tuff and capsule areas and Bowman’s space compared to CON-FO group animals (p < 0.05). There was a significant reduction in diameter, glomerular tuft and capsule areas, and Bowman’s space in MSG-VAG, MSG-SPL, MSG-VAG-SPL groups when compared to the MSG-FO group.

Conclusions

Vagotomy associated with splenectomy induces a reduction in the adiposity and causes histological changes in the kidney of obese rats.

L-Glutamic acid monosodium salt reduces the harmful effect of lithium on the development of Xenopus laevis embryos

Many xenobiotics in the environment affect the human body in various ways. Among those xenobiotics, lithium chloride (Li, LiCl) and monosodium glutamate (L-glutamic acid monosodium salt, MSG) compounds affect the crucial processes of stem cell differentiation, cell proliferation, developmental gene expression, and overall development in animals. In this study, we aimed to examine the developmental effects of exposure to flavor enhancer MSG and LiCI medicament on Xenopus embryos using the frog embryo teratogenesis assay of Xenopus test. To this purpose, Xenopus laevis embryos were exposed to four different concentrations of MSG (120, 500, 750, 1000 mg/dL) and Li (0.02 g/L) alone and in combinations for a period of 96 h, and then normal, abnormal, and death ratios were determined in all exposure groups. Besides, length values of all groups and membrane potentials of fertilized and non-fertilized oocyte groups treated with 120- and 500-mg/dL MSG doses and 0.02-g/L LiCI dose were measured. Treatment with ADI (acceptable daily intake) dose of MSG alone did not lead to a substantial effect on the development of Xenopus laevis embryos. But, exposure to daily doses exceeding the ADI level (500, 750, 1000 mg/dL) caused significant harmful effects. Besides, Li-involving treatments caused dramatic deleterious effects on embryo development. MSG attenuated harmful effects of Li in MSG+Li combined treatments. Membrane potentials of non-fertilized oocytes and fertilized eggs were significantly changed in all groups that their membrane potentials were measured. Extrapolating these results into humans require similarly designed studies conducted on human embryos.

The Development of Pathological Dependence after Intermittent Use of Sodium Glutamate, but Not Sucrose or Sodium Chloride Solutions

The possibility of development of dependence was studied during the intermittent consumption of sucrose, sodium chloride, and sodium glutamate solutions. Rats were allowed to choose and consume solutions of sucrose, sodium chloride, and sodium glutamate for 28 days. On days 29-31 of the experiment, the animals were deprived of the preferred solutions. On days 32-33, the solutions of sucrose, sodium chloride, and sodium glutamate, but not water were provided again. The consumption of sucrose and sodium chloride solutions did not increase, but consumption of 0.5 and 1% sodium glutamate solutions increased after 3-days withdrawal. The consumption of 2% solution of sodium glutamate was the same before and after withdrawal. The observed effects of sodium glutamate deprivation probably indicate the development of pathological glutamate dependence.

Quercetin mitigates monosodium glutamate-induced excitotoxicity of the spinal cord motoneurons in aged rats via p38 MAPK inhibition

Various studies reported the possibility of deterioration of blood-brain barrier (BBB) integrity owing to the aging process. The current work was performed to investigate the ability of Monosodium glutamate (MSG) to cross BBB in aged rats, the damage affecting the anterior horn cells of the spinal cord due to excitotoxicity, and the mechanisms by which quercetin (Que) administration might suppress such damage. Forty male rats aged 18 months were assigned equally to 4 groups: control group, Que group (received Que, 20 mg/kg/d intraperitonealy for 10 days), MSG group (received MSG, 4.0 g/kg/d subcutaneously for 10 days), MSG + Que group (received both Que and MSG as done in the Que and MSG groups respectively). Cervical spinal cord specimens were obtained and prepared for routine histological study, immunohistochemical staining by caspase-3 and glial fibrillary acidic protein (GFAP), assessment of oxidative stress, measurement of cytokines, assessment of caspase-3 activity and GFAP levels as well as for western blotting of phosphorylated activating transcription factor 2 (ATF2^pp) as an indicator for the activity of p38 mitogen-activated protein kinase (MAPK). The MSG group revealed variable degenerative and apoptotic changes in the motoneurons and neuroglia, a marked rise in the cytoplasmic caspase-3 expression in motoneurons and a significant reduction (p < 0.001) in the astrocyte surface area percentage. In addition, the spinal cord tissue exhibited a significant elevation (p < 0.001) in the levels of malondialdehyde (MDA), IL-1, IL-6, TNFα, INFɣ, caspase-3 activity and ATF2 ^pp expression as well as a significant reduction (p < 0.001) in SOD, IL-10 and GFAP levels compared with the control group. On combining Que with MSG, most of the degenerative changes were reversed and all the impaired parameters were nearly normalized except for IL-6 and GFAP levels which were still significantly (p < 0.05) different from those of the control group. Our study suggests that MSG can break through the BBB of the aged rats and induce excitotoxicity dependent changes in spinal cord motoneurons. Most of these changes were reversed by Que probably via targeting the p38 MAPK-ATF2 pathway, antagonizing oxidative stress, anti-inflammatory effect, and promoting GFAP expression.

A combination of monosodium glutamate and high-fat and high-fructose diets increases the risk of kidney injury, gut dysbiosis and host-microbial co-metabolism

Consumption of either monosodium glutamate (MSG) or high-fat and high-fructose (HFF) diets changes the gut microbiome and hence contributes to development of several diseases. In this study, with an emphasis on kidney injury, hamsters were divided into 4 groups as follows: (1) hamsters fed with standard diet (control); (2) hamsters fed with standard diet and MSG in drinking water (MSG); (3) hamsters fed with high-fat and high-fructose diets (HFF), and (4) animals fed MSG+HFF. After 8 months, the animals were used for the study. Despite showing normal kidney function, hamsters fed with MSG+HFF exhibited signs of kidney damage as demonstrated by the highest expression levels of high-mobility group box-1 and kidney injury molecule-1 in kidney tissues, while slight changes of histopathological features in H&E-stained sections and normal levels of creatinine were observed, indicating possible early stages of kidney injury. Sequencing of the microbial 16S rRNA gene revealed that animals fed with the MSG+HFF diet had a higher ratio of gut Firmicutes/Bacteroidetes along with marked changes in abundance and diversity of gut microbiome compared to hamsters fed with MSG or HFF alone. In addition, ¹H Nuclear magnetic resonance spectroscopy showed an elevation of urine p-cresol sulfate levels in the MSG+HFF group. These results indicate that consumption of both MSG and HFF increases the risk of kidney injury, induces gut dysbiosis and an increase in the amount of p-cresol sulfate in hamsters.

Tetrastigma hemsleyanum Vine Flavone Ameliorates Glutamic Acid-Induced Neurotoxicity via MAPK Pathways

Glutamic acid (Glu) is a worldwide flavor enhancer with various positive effects. However, Glu-induced neurotoxicity has been reported less. Tetrastigma hemsleyanum (TH), a rare herbal plant in China, possesses high medicinal value. More studies paid attention to tuber of TH whereas vine part (THV) attracts fewer focus. In this study, we extracted and purified flavones from THV (THVF), and UPLC-TOF/MS showed THVF was consisted of 3-caffeoylquinic acid, 5-caffeoylquinic acid, quercetin-3-O-rutinoside, and kaempferol-3-O-rutinoside. In vitro, Glu caused severe cytotoxicity, genotoxicity, mitochondrial dysfunction, and oxidative damage to rat phaeochromocytoma (PC12) cells. Conversely, THVF attenuated Glu-induced toxicity via MAPK pathways. In vivo, the neurotoxicity triggered by Glu restrained the athletic ability in Caenorhabditis elegans (C. elegans). The treatment of THVF reversed the situation induced by Glu. In a word, Glu could cause neurotoxicity and THVF owns potential neuroprotective effects both in vitro and in vivo via MAPK pathways.

Admissible daily intake for glutamate

PURPOSE OF REVIEW

Total glutamate (Glu) intake is 5-20 g/day in adults and about 40 mg/kg in breast-fed infant. Glu intake is constituted by Glu from protein and free Glu from certain foods and flavor-enhancing additive. The admissible intake of free Glu additive is addressed.

RECENT FINDING

In the gut, Glu is actively metabolized by enterocytes and because of this metabolism, the systemic availability of ingested Glu remains relatively low. Human studies are preferred to assess the transfer in blood of dietary free Glu salts and their possible risks. When human data are not available, experimental animal models provide the basis to assess the risks to humans but toxicity studies in rodents remain for a part controversial. A No Observable Adverse Effect Level (NOAEL) in rodent of 3200 mg/kg/day and an uncertainty factor of 100 lead to an acceptable daily intake (ADI) of 30 mg/kg/day for free Glu salts used as additives, whereas a NOAEL higher than 6000 mg/kg/day and an uncertainty factor of 25 leads to an ADI of 240 mg/kg/day for free Glu salts.

SUMMARY

Current discussions indicate an ADI from 30 to 240 mg/kg/day depending on the chosen NOAEL in animal model and compound-specific uncertainty factor (from 25 to 100).

In vitro genotoxicity assessment of monopotassium glutamate and magnesium diglutamate

Food additives are approved chemicals used for various purposes in foods; to provide nutritional safety, increase flavor, extend shelf life, reduce nutrient losses etc. In this study, the in vitro genotoxic effects of flavor enhancers, Monopotassium glutamate (MPG) and Magnesium diglutamate (MDG) were investigated in human peripheral blood lymphocytes by using chromosome aberrations (CAs), sister chromatid exchanges (SCEs), cytokinesis-block micronucleus cytome (CBMN-Cyt), and comet assays. Four concentrations of MPG (125, 250, 500, and 1000 μg/mL) and MDG (93.75, 187.5, 375, and 750 μg/mL) were used. Both food additives significantly reduced mitotic index and increased the frequency of CAs at high concentrations. MPG and MDG (except 93.75 μg/mL) significantly increased SCEs/Cell in concentration-dependent manner. In the CBMN-Cyt test, both MPG and MDG increased the formation of micronucleus, nuclear buds, and nucleoplasmic bridges compared to control in a concentration-dependent manner. However, these increases were statistically significant at higher concentrations. MPG (at 500 and 1000 μg/mL) and MDG (except 93.75 μg/mL) significantly increased DNA damages observed by comet assay. It is concluded from these results that MPG and MDG have clastogenic, mutagenic, aneugenic, and cytotoxic effects, particularly at high concentrations in human lymphocytes in vitro.

Comparison of the effects of hydroalcoholic extract of Capparis spinosa fruit, quercetin and vitamin E on monosodium glutamate-induced toxicity in rats

Capparis spinosa L. has many biological effects such as antioxidant properties. In the present study, we compared the effects of the hydro-alcoholic extract of Capparis spinosa fruit, quercetin (Q), and vitamin E (Vit E) on monosodium glutamate (MSG)-induced toxicity. The following groups were designed: Control groups (normal saline and/or corn oil); MSG group (4.00 g kg^-1 MSG); MSG + low dose extract group (4.00 g kg^-1 MSG with 100.00 mg kg^-1 extract); MSG + high dose extract (HDE) group (4.00 g kg^-1 MSG with 300.00 mg kg^-1 extract); MSG + Q group (4.00 g kg^-1 MSG with 10.00 mg kg^-1 Q); MSG + Vit E group (4.00 g kg^-1 MSG with 200.00 mg kg^-1 Vit E). All chemicals were orally administered for 14 consecutive days. Tissue specimens from the heart, kidney, and liver tissues and blood samples were collected for histopathological and biochemical evaluations. The results showed that the MSG-induced tissue edema, congestion, and inflammatory cell infiltration were resolved by HDE, Q, and Vit E treatments. These chemicals also restored tissue malondialdehyde level and superoxide dismutase activity. Besides, alterations induced by MSG in serum levels of aspartate transaminase, alanine aminotransferase, urea, lactate dehydrogenase, and creatine kinase-MB were also resolved. It is concluded that Capparis spinosa fruit extract, Q and Vit E can produce approximately similar protective effects on tissue function through oxidative stress alleviation and antioxidant mechanisms restoration.

Chronic toxicity of low dose monosodium glutamate in albino Wistar rats

OBJECTIVE

The objective of this study was to observe the effects of chronic dosing with monosodium glutamate on mortality, fertility, major organ functions and histology in albino Wistar rats.

RESULTS

6 male and 6 female rats (age 6 weeks) were bred in a cage, feeding on standard growers' mash, with monosodium glutamate added (120 mg/kg/day). 12 corresponding breeding rats (on standard feed without MSG) were controls. Chronic dosing with monosodium glutamate in albino Wistar rats (at a dose consistent with the human ADI) led to increased mortality, fertility impairment, and significant changes in major organ function tests and histology. 23 deaths were recorded in the rats fed with MSG additive, while mortality was zero in the control animals. Fertility was lower in rats on MSG (48 births) than in controls (117 births). The weight gain of the MSG rats was higher than in controls. Biochemical parameters and organ histology remained normal in control animals. In MSG-treated rats however, liver/renal function tests, fasting serum cholesterol and triglyceride, serum uric acid showed a significant rise at trimestrial time-points. Histology showed mild portal inflammation in MSG rats, with periglomerular fibrosis and interstitial nephritis in two rats, at 6-12 months.

Evaluation of the Effect of Nanoparticles Zinc Oxide/Camellia sinensis Complex on the Kidney of Rats Treated with Monosodium Glutamate: Antioxidant and Histological Approaches

Background:

Zinc oxide nanoparticles (ZnO NPs) are robustly used biomedicine. Moreover, no study has been conducted to explore the consequence of green synthesis of ZnO NPs with Camellia sinensis (green tea extract, GTE) on kidneys of rats treated with monosodium glutamate (MSG).

Methods:

Therefore, the objective of the research was designed to explore the possible defensive effect of GTE/ZnO NPs against MSG-induced renal stress investigated at redox and histopathological points.

Results:

The levels of urea and creatinine increased as the effect of a high dose of MSG, in addition, the myeloperoxidase and xanthine oxidase activates were elevated significantly with the high dose of MSG. The levels of non-enzymatic antioxidants (uric acid, glutathione, and thiol) were decreased sharply in MSG-treated rats as compared to the normal group.

Conclusion:

The data displayed that GTE/ZnO NPs reduced the effects of MSG significantly by reduction of the level peroxidation and enhancement intracellular antioxidant. These biochemical findings were supported by histopathology evaluation, which showed minor morphological changes in the kidneys of rats.

Gender-Specific Differences of Oxidative Processes in the Population of Circulating Neutrophils of Rats in a Setting of Prolonged Administration of Monosodium Glutamate

Background and aims: Monosodium salt of glutamic acid (MSG) is one of the most common food additives. The aim of study was to assess, in gender-specific terms, how prolonged administration of MSG effects on reactive oxygen and nitrogen species formation and the apoptotic/necrotic processes in the population of rats circulating neutrophils.

Material and methods: Experimental studies were conducted on 32 mature white rats. MSG was administered intragastrical at a dose of 30 mg/kg body weight for 30 days. The analysis of cell samples to determine neutrophils with overproduction of reactive oxygen species (ROS) and signs of apoptosis\necrosis was evaluated with flow laser cytometry method. The total nitric oxide synthase (NOS) activity was determined by monitoring the rate of conversion of L-arginine into citrulline. The total quantity of NO metabolites was assessed by evaluating of nitrite and nitrate ions.

Results: We found a significant increase in generation of ROS, intensification of nitroxydergic processes, an increase in the percentage of apoptotic neutrophils and no changes in the percentage of necrotic neutrophils.

Conclusions: We observed activation of oxidative and nitroxydergic processes in rats with prolonged administration of MSG, which initiate apoptosis. In gender-specific terms, a more pronounced changes were seen in male rats.

Effects of monosodium glutamate on apoptosis of germ cells in testicular tissue of adult rat: An experimental study

Background

Monosodium glutamate (MSG) is used as a flavoring and food seasoning. Some studies have reported the oxidative effects of using this substance on various tissues.

Objective

This study has investigated the effects of MSG and the protective effect of vitamin C (vit C) on apoptosis of testicular germ cells and biochemical factors.

Materials and Methods

In this experimental study, 24 adult male Wistar rats were randomly divided into four groups: control (received distilled water), vit C group (150 mg/kg), experimental group 1 (MSG 3 gr/kg), experimental group 2 (MSG 3 gr/kg + vit C 150 mg/kg). The rats were gavaged for 30 days, and then were sacrificed, the right testis was isolated for biochemical examinations for the glutathione, malondialdehyde, and left testis used in histological experiments. Tunnel staining was used to determine the number of apoptotic cells.

Results

The results showed that apoptotic cells in the MSG group had a significant increase compared to the control group (P = 0.001), but the number of these cells in the MSG co-administered with vit C and vit C groups were significantly lower than the MSG group. Germinal epithelial thickness also decreased in MSG group compared to the control group.

Conclusion

MSG can lead to increase apoptotic changes in the germinal epithelial of the testicle, and vit C as an antioxidant can modify the pathological and biochemical changes induced by MSG.

Monosodium glutamate daily oral supplementation: study of its effects on male reproductive system on rat model

Monosodium glutamate (MSG) is widely used in food preparation industry and has been consumed regularly. Previous studies had reported on effects of MSG when given at extremely high dosages, the results are not applicable to human equivalent intake. Therefore, the present study aimed to evaluate the effect of MSG on sperm quality and changes in reproductive organs of adult male rats when taken at average human daily intake (ADI). Twenty-four adult male rats were randomly assigned into three groups; NC (Normal control), MSG60 and MSG120 where MSG was given orally at 60 mg/kg and 120 mg/kg to each respective group. All treatments were conducted for 28 consecutive days. MSG at estimated ADI of 120 mg/kg body weight resulted in a significant drop in sperm quality (p < 0.05) when compared to both control and MSG60 groups. A significant decrease in the weight of reproductive organs was also apparent (p < 0.05). Moreover, oxidative status evaluation showed that treatment of MSG induces oxidative stress in the testis, more severely at a dose of 120 mg/kg body weight. These findings are supported by alterations in the observed histology of reproductive organs. This study shows that an intake dose of 120 mg/kg body weight MSG could cause significant damage to the reproductive system. Abbreviations: MSG: Monosodium glutamate; ADI: average daily intake; PUFA: polyunsaturated fatty acid; FSH: follicle stimulating hormone; LH: luteinizing hormone; TCA: tricarbocylic acid; PF: prostatic fluid.

Group I metabotropic glutamate receptor activation induces TRPC6-dependent calcium influx and RhoA activation in cultured human kidney podocytes

Researches have shown that mice lacking the metabotropic glutamate receptor 1 (mGluR) showed albuminuria, remodeling of F-actin, with loss of stress fibers. Selective group I mGluRs agonist (S)-3,5-dihydroxyphenylglycine (DHPG) attenuated albuminuria in several rodent models of nephrotic syndrome. However, the molecular mechanism is obscure. Using a human podocyte cell line, we here investigated the molecular mechanisms of group I mGluRs-induced calcium influx and the formation of stress fibers. Our data showed that group I mGluRs activation by DHPG induced a significant calcium influx, and promoted cytoskeletal stress fiber formation and focal adhesions in podocytes. Pre-incubating podocytes with non-selective inhibitor of transient receptor potential channels (TRPC), or the knockdown of TRPC6 attenuated the calcium influx and the stress fiber formation induced by DHPG. Further, DHPG resulted in an increase of active RhoA expression. However, the knockdown of RhoA by siRNA abolished the DHPG-induced increase in stress fibers. Additionally, nonselective inhibitors of TRPC or TRPC6 knockdown clearly inhibited RhoA activation induced by DHPG, as assessed by Glutathione-S-transferase pull-down assay followed by Western blotting. Taken together, our findings suggest TRPC6 regulates actin stress fiber formation and focal adhesions via the RhoA pathway in response to group I mGluRs activation. Our data can potentially explain the mechanism of protective action of group I mGluRs in glomerular podocyte injury.

Effect of dietary inclusions of bitter kola seed on geotactic behavior and oxidative stress markers in Drosophila melanogaster

This study evaluated the effect of dietary inclusions of Garcinia kola (GK) seed on geotactic behavior and some oxidative stress markers in wildߚtype fruit flies (Drosophila melanogaster). Flies were raised on diet supplement with GK seed for 5 days. The negative geotactic behavior of flies which was used to evaluate their locomotor performance was thereafter evaluated. The flies were subsequently homogenized and the reactive oxygen species (ROS) level, acetylcholinesterase (AChE), catalase and glutathioneߚSߚtransferase (GST) activities, as well as nitric oxide (NO) and total thiol contents were assayed. The phytochemical constituents of GK seed were also determined. It was observed that higher dietary inclusions of GK seed reduced the survival rate of D. melanogaster more significantly compared to control flies. Also, higher dietary inclusions of GK seed significantly reduced locomotor performance and AChE activity, while the ROS level was increased compared to the control. Activities of GST and catalase were significantly increased in flies fed diet supplemented with higher GK seed inclusions but their NO content was significantly reduced compared to control. Phytochemical analysis of GK seed revealed abundance of saponin > glycosides > alkaloids > phenols > flavonoids. These results have shown that dietary inclusion of GK seed at higher concentrations reduced survival rate of D. melanogaster and impaired cholinergic system, with elevated activities of some antioxidant enzymes under acute exposure. These observations could be associated with bioactivities of predominant phytochemicals in GK seed such as saponin and glycosides which have been reportedly toxic at high concentration. Therefore, this study suggests that high consumption of GK seed could induce some toxicological effects and moderate consumption is hence recommended.

Elevation in and persistence of multiple urinary biomarkers indicative of oxidative DNA stress and inflammation: Toxicological implications of maleic acid consumption using a rat model

Maleic acid (MA), an intermediate reagent used in many industrial products, instigated public health concerns in Taiwan when it was used to adulterate an array of starch-based delicacies to improve texture and storage time. Established studies reported that exposure to high concentrations of MA induce renal injury; little is known whether oxidative stress is induced at a relative low dose. This study aims to investigate the effect of oral single dose exposure of MA on the status of oxidative stress and inflammation. Single dose of MA at 0, 6 and 60 mg/kg (control, low- and high-dose groups, respectively) were orally administered to adult male and female rats. Urine samples were collected and analyzed to measure 8-hydroxy-2’-deoxyguanosine (8-OHdG), 8-iso-prostaglandin F_2α (8-IsoPGF_2α), 8-nitroguanine (8-NO₂Gua) and N-acetyl-S-(tetrahydro-5-hydroxy-2-pentyl-3-furanyl)-L-cysteine (HNE-MA) using LC-MS/MS. Results revealed that oral consumption of MA induced oxidative DNA damage and lipid peroxidation, as demonstrated by the statistically significant increases in urinary levels of 8-NO₂Gua, 8-OHdG, and 8-isoPGF_2α, in high-dosed male rats within 12 h of oral gavage (p < 0.05). Additionally, increases in concentration of these biomarkers persist for days after consumption; male rats appear to be more sensitive to oxidative burden compared to their counterparts. The aforementioned findings could help elucidate the mechanisms through which nephrotoxicity occur.