Safety assessment of monosodium glutamate based on intestinal function and flora in mice

Although monosodium glutamate(MSG)is a widely used food additive,its safety and systemic side effects have not been fully clarified.The intestinal flora is closely associated with human health;however,it remains unclear whether MSG consumption can affect health by acting on the intestinal flora.In this study,serum biomarkers,intestinal structure,intestinal immunity,and intestinal flora were examined to investigate the effects of different doses of sodium glutamate on the body,intestinal function,and intestinal flora of mice.The results showed that 30 mg/kg MSG had no significant effect on serum C-reactive protein,trimethylamine N-oxide,angiotensin II,intestinal interleukin(IL)-1β,IL-6,tumor necrosis factor-α,secretory IgA and fecal albumin in mice,but also promoted intestinal development and regulated the intestinal flora.Moreover,1500 mg/kg MSG increased the risk of cardiovascular disease and damaged the intestinal structure and flora.In this study,MSG was also found to be healthier than salt at the equivalent sodium concentration.Collectively,these findings suggested that low doses of MSG were safe for mice and may have some health benefits as a probiotic by promoting intestinal development and regulating the intestinal flora.

Dietary Monosodium Glutamate Does Not Affect the Electrocardiographic Profiles of Diabetic and Nondiabetic Wistar Rats

Background and Aims: Some studies have recently indicated that dietary monosodium glutamate (MSG) is linked to obesity and the development of diabetes. Both diseases induce cardiovascular changes, such as increases in blood pressure and arrhythmias, including ventricular fibrillation, which may result in sudden death. Here, we aimed to investigate the effects of oral MSG administration on the electrical conduction and histological dysfunctions of the heart in control and diabetic Wistar rats. Methods and Results: Twenty-one-day-old Wistar rats were fed diets containing 0.0%, 1.0%, 2.5% or 5.0% MSG for 70 days. After this period, diabetes was induced with streptozotocin (STZ;50 mg/kg bw) in half the rats and after an additional 21 days period;the electrocardiographic parameters and heart histology were evaluated. Diabetic rats demonstrated a reduction in heart rate as well as an enlargement of the QRS complex and QT and QTc intervals. Nevertheless, those changes are typical of STZ-induced diabetes, mainly because of electrolyte disturbances. The presence of MSG in the diet did not change the parameters evaluated between the group that received MSG and the group that did not receive MSG. Moreover, no histological alterations in the heart were observed due to MSG ingestion. Conclusion: Based on this evidence, diets containing MSG did not interfere with cardiovascular changes due to diabetes;there were no differences in the electrocardiographic and histological characteristics of the hearts of rats treated with MSG.

Toxic effects of wastewater from various phases of monosodium glutamate production on seed germination and root elongation of crops

To make a comprehensive assessment on mono-sodium glutamate(MSG)wastewater pollution,a pollution exposure experiment was carried out on the seed germination and root elongation of wheat,Chinese cabbage and tomato by using the wastewater discharged from different processing phases of MSG production.The results showed that there were significantly positive linear relationships between the inhibitory rates of wheat seed germination and root elonga-tion and the CODcr of the mother liquor scraps.The toxicity of MSG wastewater to the test crops was in the order of tomato>Chinese cabbage>wheat,indicating that tomato was the most sensitive to the wastewater,and could be considered as an ideal toxic bioindicator.The half-effect concentrations(IC50)based on the seed germination and root elongation of the test crops exposed to the wastewater discharged from various processing phases of MSG produc-tion was 22.0-32432 and 17.3-3320 mg/L,respectively.

Investigating the influence of monosodium L-glutamate on brain responses via scalp-electroencephalogram(scalp-EEG)

As the relevance between left and right brain neurons when transmitting electrical signals of umami taste is unknown,the aim of this work was to investigate responsive regions of the brain to the umami tastant monosodium glutamate(MSG)by using scalp-electroencephalogram(EEG)to identify the most responsive brain regions to MSG.Three concentrations of MSG(0.05,0.12,0.26 g/100 mL)were provided to participants for tasting while recoding their responsive reaction times and brain activities.The results indicated that the most responsive frequency to MSG was at 2 Hz,while the most responsive brain regions were T4 CzA2,F8 CzA2,and Fp2 CzA2.Moreover,the sensitivity of the brain to MSG was significantly higher in the right brain region.This study shows the potential of using EEG to investigate the relevance between different brains response to umami taste,which contributes to better understanding the mechanism of umami perception.

Sensory and Nutritional Properties and Stability of Formulated Organic Food Flavour Enhancers

Most food flavours have been shown to contain high quantities of cooking salt, followed by flavour enhancers such as sodium glutamate, disodium inosinate, disodium guanylate and hydrogenated oils. Excess of these substances is associated with cardiovascular diseases and neurodegenerative disorders. In an effort to reduce the harmful effects of these synthetic substances, this study therefore aimed to formulate organic, nutritious food flavours with good storage stability from less harmful locally available food ingredients. A survey was carried out in 130 households and restaurants in the city of Yaoundé Cameroon, in order to evaluate the level of consumption of industrial flavours. Certain ingredients such as prawns, onions, garlic, white peppers, gingers and salt were used in some households as organic flavours. These ingredients and others were used to prepare 5 organic flavours. Their sensory and nutritional analyses and stability to storage within 90 days were evaluated. The survey revealed that 74.6% of respondents consume industrial flavours, with the cube flavour being the most widely consumed (81%). Two of the 5 organic flavours (434 and 634) had highest scores for general acceptability. The nutritional analyses of the formulae retained (434 and 634), showed that they contained: 11.08% and 10.68% fresh weight for moisture, 47.63% and 43.53% protein, 16.52% and 13.62% lipids, 2.20% and 2.44% fibres, 11.69% and 16.39% carbohydrates. Formula 434, the most accepted, had higher contents of Ca (257.97), Mg (115.91), K (1163), Zn (2.98), Cu (1.02) and Fe (12.43 mg/100g DM) while the second (634) had higher contents of sodium (3270.48) and manganese (2.18 mg/100g). Their water activity during storage in polypropylene bags for 90 days ranged from 0.39 - 0.58 at a temperature of 26.6˚C - 37˚C. The oxidative stability (90 days), determined by the acid and peroxide indices, was 9.18 - 14.13 mg KOH/g and 1.98 - 6.46 meq O2/Kg, respectively indicating good stability for 90 days of storage. The high levels of proteins and minerals in our two products justify their umami taste and can be used as highly nutritional food flavour enhancers to prevent cardiovascular diseases, especially in the elderly.

Cognitive deficits and Alzheimer-like neuropathological impairments during adolescence in a rat model of type 2 diabetes mellitus

Numerous studies have shown that many patients who suffer from type 2 diabetes mellitus exhibit cognitive dysfunction and neuronal synaptic impairments. Therefore, growing evidence suggests that type 2 diabetes mellitus has a close relationship with occurrence and progression of neurodegeneration and neural impairment in Alzheimer＇s disease. However, the relationship between metabolic disorders caused by type 2 diabetes mellitus and neurodegeneration and neural impairments in Alzheimer＇s disease is still not fully determined. Thus, in this study, we replicated a type 2 diabetic animal model by subcutaneous injection of newborn Sprague-Dawley rats with monosodium glutamate during the neonatal period. At 3 months old, the Barnes maze assay was performed to evaluate spatial memory function. Microelectrodes were used to measure electrophysiological function in the hippocampal CA1 region. Western blot assay was used to determine expression levels of glutamate ionotropic receptor NMDA type subunit 2 A（GluN2A） and GluN2B in the hippocampus. Enzyme-linked immunosorbent assay was used to determine levels of interleukin-1β, tumor necrosis factor α, and interleukin-6 in the hippocampus and cerebral cortex, as well as hippocampal amyloid beta（Aβ）1-40 and Aβ_（1-42） levels. Our results showed that in the rat model of type 2 diabetes mellitus caused by monosodium glutamate exposure during the neonatal period, latency was prolonged and the number of errors increased in the Barnes maze. Further, latency was increased and time in the escape platform quadrant shortened. Number of times crossing the platform was also reduced in the Morris water maze. After high frequency stimulation of the hippocampus, synaptic transmission was inhibited, expression of GluN2A and GluN2B were decreased in the hippocampus, expression of interleukin 1β, interleukin 6, and tumor necrosis factor α was increased in the hippocampus and cortex, and levels of Aβ_（1-40） and Aβ_（1-42） were increased in the hippocampus. These findings confirm that type 2 diabetes mellitus induced by neonatal monosodium glutamate exposure results in Alzheimer-like neuropathological changes and further causes cognitive deficits and neurodegeneration in young adulthood.

Screening for glutamate-induced and dexamethasone-downregulated epilepsy-related genes in rats by mRNA differential display

Background It is known that excessive release of glutamate can induce excitotoxicity in neurons and lead to seizure. Dexamethasone has anti-seizure function. The aim of this study was to investigate glutamatedexamethasone interaction in the pathogenesis of epilepsy, identify differentially expressed genes in the hippocampus of glutamate-induced epileptic rats by mRNA differential display, and observe the effects of dexamethasone on these genes expression. Methods Seizure models were established by injecting 5μl （250 μg/μl） monosodium glutamate （MSG） into the lateral cerebral ventricle in rats. Dexamethasone （5 mg/kg） was injected intraperitoneally at 30 minutes after MSG inducing convulsion. The rats＇ behavior and electroencephalogram （EEG） were then recorded for 1 hour. The effects of dexamethasone on gene expression were observed in MSG-induced epileptic rats at 1 hour and 6 hours after the onset of seizure by mRNA differential display. The differentially expressed genes were confirmed by Dot blot. Results EEG and behaviors showed that MSG did induce seizure, and dexamethasone could clearly alleviate the symptom, mRNA differential display showed that MSG increased the expression of some genes in epileptic rats and dexamethasone could downregulate their expression. From more than 10 differentially expressed eDNA fragments, we identified a 226 bp eDNA fragment that was expressed higher in the hippocampus of epileptic rats than that in the control group. Its expression was reduced after the administration of dexamethasone. Sequence analysis and protein alignment showed that the predicted amino acid sequence of this cDNA fragment kept 43% identity to agmatinase, a member of the ureohydrolase superfamily. Conclusions The results of the current study suggest that the product of the 226 bp eDNA has a function similar to agmatinase. Dexamethasone might relax alleviate seizure by inhibiting expression of the gene.