Studies on effect of monosodium glutamate (MSG) on various fractions of lipids and certain carbohydrate metabolic enzymes in liver and blood of adult male mice

Migraine: A disorder of metabolism?

The treatment and prevention of migraine within the last decade has become largely pharmacological. While there is little doubt that the advent of drugs (e.g. triptans) has helped many migraine sufferers to lead a normal life, there is still little knowledge with respect to the factors responsible for precipitating a migraine attack. Evidence from biochemical and behavioural studies from a number of disciplines is integrated to put forward the proposal that migraine is part of a cascade of events, which together act to protect the organism when confronted by a metabolic challenge.

Biochemical alterations during the obese-aging process in female and male monosodium glutamate (MSG)-treated mice

Obesity, from children to the elderly, has increased in the world at an alarming rate over the past three decades, implying long-term detrimental consequences for individual’s health. Obesity and aging are known to be risk factors for metabolic disorder development, insulin resistance and inflammation, but their relationship is not fully understood. Prevention and appropriate therapies for metabolic disorders and physical disabilities in older adults have become a major public health challenge. Hence, the aim of this study was to evaluate inflammation markers, biochemical parameters and glucose homeostasis during the obese-aging process, to understand the relationship between obesity and health span during the lifetime. In order to do this, the monosodium glutamate (MSG) obesity mice model was used, and data were evaluated at 4, 8, 12, 16 and 20 months in both female and male mice. Our results showed that obesity was a major factor contributing to premature alterations in MSG-treated mice metabolism; however, at older ages, obesity effects were attenuated and MSG-mice became more similar to normal mice. At a younger age (four months old), the Lee index, triglycerides, total cholesterol, TNF-α and transaminases levels increased; while adiponectin decreased and glucose tolerance and insulin sensitivity levels were remarkably altered. However, from 16 months old-on, the Lee index and TNF-α levels diminished significantly, while adiponectin increased, and glucose and insulin homeostasis was recovered. In summary, MSG-treated obese mice showed metabolic changes and differential susceptibility by gender throughout life and during the aging process. Understanding metabolic differences between genders during the lifespan will allow the discovery of specific preventive treatment strategies for chronic diseases and functional decline.

Is there a relationship between dietary MSG and [corrected] obesity in animals or humans?

The sodium salt of glutamate (monosodium glutamate; MSG) imparts a savory/meaty taste to foods, and has been used as a flavoring agent for millennia. Past research on MSG/glutamate has evaluated its physiologic, metabolic and behavioral actions, and its safety. Ingested MSG has been found to be safe, and to produce no remarkable effects, except on taste. However, some recent epidemiologic and animal studies have associated MSG use with obesity and aberrations in fat metabolism. Reported effects are usually attributed to direct actions of ingested MSG in brain. As these observations conflict with past MSG research findings, a symposium was convened at the 13th International Congress on Amino Acids, Peptides and Proteins to discuss them. The principal conclusions were: (1) the proposed link between MSG intake and weight gain is likely explained by co-varying environmental factors (e.g., diet, physical activity) linked to the "nutrition transition" in developing Asian countries. (2) Controlled intervention studies adding MSG to the diet of animals and humans show no effect on body weight. (3) Hypotheses positing dietary MSG effects on body weight involve results from rodent MSG injection studies that link MSG to actions in brain not applicable to MSG ingestion studies. The fundamental reason is that glutamate is metabolically compartmentalized in the body, and generally does not passively cross biologic membranes. Hence, almost no ingested glutamate/MSG passes from gut into blood, and essentially none transits placenta from maternal to fetal circulation, or crosses the blood-brain barrier. Dietary MSG, therefore, does not gain access to brain. Overall, it appears that normal dietary MSG use is unlikely to influence energy intake, body weight or fat metabolism.

Protective effect of Trigonella foenum-graecum Linn. on monosodium glutamate-induced dyslipidemia and oxidative stress in rats

Objectives:

The present study was designed to evaluate the effect of aqueous extract of Trigonella foenum-graecum(AqE-TFG) seeds on monosodium glutamate (MSG)-induced dyslipidemia and oxidative stress in Wistar rats.

Materials and Methods:

Neonatal Wistar rats were treated subcutaneously with MSG (4 g/kg b.w.) from day 2 to 14 after birth, on alternate days. After attaining six-weeks of age, MSG-treated rats were administered with AqE-TFG (0.5 and 1 g/kg b.w., orally) or orlistat (10 mg/kg b.w., orally) for 28 days, respectively. Serum chemistry and relevant enzymes in hepato-cardiac tissues were assessed on day 29.

Results:

AqE-TFG produced significant reduction in serum total cholesterol (TC), triglycerides (TGs), lactate dehydrogenase (LDH), aspartate amino transferase (AST), alanine amino transferase (ALT), hepatic and cardiac lipid peroxides (MDA) levels and elevation in serum high density lipoprotein cholesterol (HDL-C), hepatic and cardiac antioxidant enzymes [glutathione (GSH), and superoxide dismutase (SOD) and catalase (CAT)] levels.

Conclusion:

Results were comparable with orlistat, a standard anti-obesity drug, and provide clear evidence that the AqE-TFG treatment offered significant protection against MSG-induced dyslipidemia and oxidative stress, and may play an important role in amelioration of the free radical generated consequences like dyslipidemia and atherosclerosis.

Effect of monosodium glutamate on lipid peroxidation and certain antioxidant enzymes in cardiac tissue of alcoholic adult male mice

BACKGROUND

Monosodium glutamate (MSG), a sodium salt of glutamic acid is commonly used as flavor enhancer in Chinese, Japanese and ready to serve foods all over the World, is the inducer of oxidative stress. In the present era, MSG and alcohol is becoming a part of daily food. Concomitantly, there is a tremendous increase in the incidences of cardiovascular diseases. So, the present study was designed to elucidate the effect of MSG by evaluating the changes in oxidative stress markers in cardiac tissue of normal and alcoholic adult male mice.

MATERIALS AND METHODS

Animals were divided into six groups of six mice each and MSG at dose levels of 0, 4, and 8 mg/g body weight was given orally for seven consecutive days (that is from 31st day to 37(th) day of alcohol ingestion) to chronic alcoholic (30% ethanol/100 g body weight) adult male mice. After the dose period (38(th) day), animals were fasted overnight, sacrificed by decapitation and hearts were removed for the estimation of lipid peroxidation (LPO), xanthine oxidase (XOD), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) and its metabolizing enzymes like glutathione peroxidase (GPx) and glutathione reductase (GR).

RESULTS

A significant (P < 0.001) increase was observed in LPO and XOD levels while a significant decrease (P < 0.001) in the levels of SOD, CAT, GSH, GPx and GR was found in cardiac tissue of normal and alcoholic animals.

CONCLUSION

These observations suggested that oral ingestion of MSG at dose levels of 4 mg/g body weight and above with and without alcohol increased the oxidative stress and thereby, could act as an additional factor for the initiation of atherosclerosis.

Effect of monosodium glutamate on various lipid fractions and certain antioxidant enzymes in arterial tissue of chronic alcoholic adult male mice

Oral ingestion of monosodium glutamate (MSG) to chronic alcoholic adult male mice at dose levels of 4 and 8 mg/g body weight for seven consecutive days caused a significant increase in lipid fractions, lipid peroxidation, xanthine oxidase, whereas the levels of superoxide dismutase, catalase, glutathione, and its metabolizing enzymes like glutathione peroxidase and glutathione reductase were significantly decreased in the arterial tissue. These observations suggested that ingestion of MSG to chronic alcoholic animals had no beneficial effect and thereby, could act as an additional factor for the initiation of atherosclerosis.

Relationship between pituitary and adipose tissue after hypothalamic denervation in the female rat. A morphometric immunohistochemical study

Neonatal administration of monosodium glutamate (MSG) to rats produces severe lesions in certain hypothalamic nuclei, with repercussions in different neuroendocrine axes, and serves as a model for their study. In addition, adipose tissue, as a target organ, is known to be directly related to several neurondocrine axes. We used 21-day-old female Sprague-Dawley rats that had received a neonatal treatment with MSG (4 mg/g body weight, i.p., from day 2 up to day 10 of age) in addition to control rats (injected with 10% NaCl solution, on a similar schedule). We performed a specific immunohistochemical study on each anterior-pituitary cell population, along with the morphometry of these cells and of the parietal and visceral adipose tissue, and measured the levels of serum leptin and triglycerides. The MSG animals evinced significant changes in volume density (VD), cell density (CD), and cell size (CS) in the corticotropes, thyrotropes, and LH gonadotropes, but not in the somatotropes, lactotropes, and FSH gonadotropes. The modification common to the three cell types was a hyperplasia, but with different results depending on cell size. Furthermore, in the MSG rats significant changes were also observed in the VD, CD, and CS of the adipose tissue, consisting of adipogenesis and decrease of adipocyte size in visceral fat, together with probable lipogenesis as judged by an increase in adipocyte size in the parietal fat. The serum levels of leptin and triglycerides appeared significantly higher in MSG animals. For the first time in this animal model, and at the level of three neuroendocrine axes, our results suggest changes that correlate hypothalamic damage, cellular pituitary alterations, and the response of the adipose tissue as a target organ for MSG insult.

Alteration in some antioxidant enzymes in cardiac tissue upon monosodium glutamate [MSG] administration to adult male mice

4mg and 8mg monosodium glutamate per gram body weight was administered subcutaneously for 6 consecutive days to normal adult male mice and its effect was seen on 31(st) day after the last injection on some antioxidant enzymes in heart. A significant dose dependent increase in lipid peroxidation and xanthine oxidase level was observed, whereas the activity of free radical scavenging enzymes such as superoxide dismutase and catalase was decreased in both monosodium glutamate treated groups (Group-2 and Group-3). So, the present work suggested that monosodium glutamate at dose level of 4mg/g body weight and above induced oxidative stress in the cardiac tissue by changing the activity of free radical initiating enzyme such as xanthine oxidase and scavenging enzymes like superoxide dismutase and catalase.

Studies on the effect of monosodium glutamate (MSG) administration on the activity of xanthine oxidase, superoxide dismutase and catalase in hepatic tissue of adult male mice

Subcutaneous administration of monosodium glutamate (MSG), to normal adult male mice, for six consecutive days at dose levels of 4 and 8 mg/g body weight, significantly increased the level of free radical initiating enzyme, xanthine oxidase, whereas the activity of free radical scavenging enzymes, like catalase and superoxide dismutase was significantly decreased in hepatic tissue. These observations suggested that ingestion of MSG at dose level of 4 mg/g body weight and above, induced oxidative stress in the hepatic tissue of adult male mice.

Studies on the effects of monosodium glutamate on hepatic microsomal lipid peroxidation, calcium, ascorbic acid and glutathione and its dependent enzymes in adult male mice

Daily administration of monosodium glutamate (MSG) to adult male mice subcutaneously, for 6 days, at dose levels of 4 and 8 mg/g body weight, significantly increased lipid peroxidation in the hepatic microsomes, as seen 31 days after the last injection. A highly significant increase was observed in the level of hepatic calcium and ascorbic acid. The glutathione (GSH) content was significantly decreased but the activities of glutathione dependent enzymes like GR, GPX, GSTs were found to be significantly increased. These observations suggested that MSG at dose levels above 4 mg/g body weight induced oxidative stress in hepatic microsomes. Attempts to maintain the redox state of the cell are suggested by increase in the ascorbic acid content and the activities of glutathione dependent enzymes.

Studies on the effects of monosodium glutamate (MSG) on oxidative stress in erythrocytes of adult male mice

Subcutaneous administration of monosodium glutamate (MSG) to normal adult male mice for 6 days at dose levels of 4 and 8 mg/g body weight caused a significant increase in erythrocyte glucose content accompanied by increased lipid peroxidation. The levels of total glutathione and protein-bound glutathione were significantly increased in the erythrocytes, whereas non-protein glutathione was significantly decreased. The administration of 4 and 8 mg/g body weight of MSG significantly increased the activities of glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione peroxidase (GPX). It was observed that MSG, above 4 mg/g body weight, produced oxidative stress which was counteracted by the body by maintaining the level of glutathione, which was done by increasing the activity of its metabolizing enzymes.