Neonatal treatment with monosodium glutamate lastingly facilitates spreading depression in the rat cortex

Pomegranate peel extracts effects to reduce mono sodium glutamate toxic effects on chicken embryos: Morphological studies

Background

Monosodium glutamate (MSG) is a flavoring agent added to various foods. This experimental study investigated MSG effects on chicken embryos morphology and the possible ameliorative effects of pomegranate peel extracts (PPE) at different incubation periods.

Methods

Seven hundred and twenty fertilized chicken eggs were used and divided into six groups: control, PPE, MSG, PPE + MSG, preventive (PPE–MSG) and therapeutic (MSG–PPE) groups. Fertile chicken eggs were injected with MSG (0.1 ml) and/or PPE (0.3 ml) twice before incubation at days 0, 1. Embryos were extracted at days 7, 10, 12, 14 and 16. Effects of MSG and/ or PPE on embryo development during different incubation periods were studied.

Results

MSG injected into embryos led to congenital anomalies that appeared mainly in MSG and MSG + PPE groups. These anomalies included growth retardation, absent eye, abdominal swelling and hernia. Mortality rate was the highest in MSG, then in MSG + PPE and MSG–PPE groups. PPE treatment reduced MSG toxic effects and these results were better in MSG–PPE and PPE–MSG groups than MSG + PPE group.

Conclusions

MSG injection affected chicken embryonic development causing growth retardation and decline in total body length, break length, and total body weight in all the treated groups. These harmful actions can be ameliorated with PPE treatment depending on embryo age.

Glutamate - A multifaceted molecule: Endogenous neurotransmitter, controversial food additive, design compound for anti-cancer drugs. A critical appraisal

One of the most widely used flavour enhancers in the food industry is monosodium glutamate (MSG). MSG consumption has been on an upward trend, worrying in terms of potential toxic effects. This review is focused on the long-term toxicity of MSG and the experimental evidence that supports it. The article's primary purpose was to survey recently published data regarding the consumption of MSG within safe limits. The administered doses in animal models are very varied and have given rise to controversy. Also, the paper comprises pathways to lower MSG toxicity and highlight other underexploited biological effects, as anti-cancer potential. The administration of MSG, combined with various compounds, has been shown benefit against toxic effects. Several recent studies have identified a possible mechanism that recommends MSG and some derivatives as potential anti-cancer agents. New anti-cancer compounds based on the glutamic acid structure must be studied and further exploited. International regulations require harmonization of safe doses of MSG based on current scientific studies. Replacing MSG with other umami flavour enhancers may be a safer alternative for human health in the future. The biological consequences of MSG consumption or therapeutical administration have not been fully deciphered yet.

Neonatal pyridoxine administration long lastingly accelerates cortical spreading depression in male rats, without affecting anxiety-like behavior

Objectives: Pyridoxine plays a key role in the development of the human nervous system. Several reports suggest that administration of high doses of pyridoxine can be helpful in improving disturbances such as anxiety and pyridoxine-dependent epilepsy, although it has also been associated with a proconvulsive action. In this study, we investigated in developing rats the effects of repeated administration of various doses of pyridoxine on anxiety-like behavior and the brain excitability-related phenomenon known as cortical spreading depression (CSD).Methods: From postnatal day (P) 7 to P27, Wistar rat pups received per gavage pyridoxine hydrochloride (1 mg/kg/day, or 5 mg/kg/day, or 10 mg/kg/day). On P60-70, the animals were tested in the elevated plus maze (EPM) to evaluate anxiety-like behavior. On P71-80, we recorded the CSD (4-hour recording session).Results: Compared with naïve (gavage-free) and saline-treated controls, pyridoxine-treated groups displayed a significant (p < 0.001) increase in CSD propagation velocity and amplitude of the CSD negative direct-current (DC)-shift, and a decrease in the CSD DC-shift duration. These effects were long-lasting and dose-dependent. In the EPM, no significant pyridoxine-associated effect was observed.Discussion: Our data demonstrate a novel action of pyridoxine on an electrical activity-related phenomenon (CSD) in the developing brain, confirming the hypothesis that the chronic treatment with pyridoxine early in life modulates CSD. Data on CSD propagation suggest that pyridoxine at a high dose might act as a prooxidant agent in the developing brain, a hypothesis that deserves further testing.

Sepsis impairs the propagation of cortical spreading depression in rats and this effect is prevented by antioxidant extract

Sepsis is a clinical syndrome with high morbidity and mortality. It is characterized by acute inflammatory response and oxidative stress, which is implicated in cerebral dysfunction. Murici (Byrsonimacrassifolia (L.) Kunth) is a fruit rich in antioxidant compounds, which could be an alternative to prevent damage to tissues induced by sepsis . Here, we evaluated the effects of sepsis on the propagation of cortical spreading depression (CSD) and oxidative stress, and tested the action of murici antioxidant extract in prevention against the effect of sepsis. Male Wistar rats (90-210 days, n = 40) were previously supplemented, orogastrically, with murici extract (150 mg/kg/day or 300 mg/kg/day), or an equivalent volume of the vehicle solution, for fifteen days. Then the animals were subjected to experimental sepsis through cecal ligation and perforation (CLP). Subsequently, CSD recordings were obtained and brain oxidative stress was evaluated. Sepsis decelerated CSD and increased the malondialdehyde (MDA) levels in the brain cortex of the animals. In contrast, septic rats that had been previously supplemented with murici antioxidant extract in doses of 150 and 300 mg/kg/day showed an increase in CSD propagation velocity, low levels of MDA and GSH/GSSG ratio and an increase of superoxide dismutase (SOD) activity, regardless of the dose tested. Our results demonstrate that sepsis affects brain excitability and that this effect can be prevented by murici antioxidant extract. The effects of sepsis and/or murici extract on CSD may be due to the oxidative state of the brain.

Dietary Glutamic Acid, Obesity, and Depressive Symptoms in Patients With Schizophrenia

Introduction: Schizophrenia is a lifelong condition associated with several comorbid conditions such as physical illnesses like obesity, as well as co-occurring psychiatric symptoms such as depression. Research regarding susceptibility to some of these comorbidities has primary focused on genetic risks or neurotransmitters and very little work has been done to understand environmental factors such as diet. In particular, understanding the role of dietary glutamic acid consumption on co-morbidities in patients with schizophrenia is important, as evidence suggests that glutamic acid consumption may directly influence glutamatergic neurotransmission; a key neurotransmitter related to schizophrenia, its associated co-morbidities, and depression. Therefore, the aim of this study was to examine the potential relationship between dietary glutamic acid and depressive symptomatology in patients with schizophrenia, stratified by obesity status, due to its relationship with inflammation, antipsychotic use, and depressive symptoms. Methods: Subjects included in this analysis, were part of a parent cross-sectional study in which included three dietary recalls analyzed using protocols outlined as part of the National Health and Nutrition Examination Surveys (NHANES) standardized criteria. Additionally, body mass index (BMI), and Beck Depression Inventory were obtained at this visit. Subjects with a BMI ≥ 30 kg/m2 were included in the obesity group, and the relationship between glutamic acid consumption and BDI scores was analyzed after controlling for age, race, sex, antidepressant and antipsychotic use, and animal and vegetable protein intake which provide natural forms of dietary glutamic acid. Results: A total of 168 participants were included in this study, of which 42.5% were female and 52.9% were White. The mean BMI for the group as a whole was 33.5 ± 8.7 (kg/m2) and the mean BDI was 14.5 ± 10.2 (range 2-50). No differences were found between obesity groups, other than a greater hyperlipidemia, hypertension, and lower waist to hip ratio. Overall, no relationship was found between dietary glutamic acid and BDI scores, However, for non-obese participants, diets higher levels of glutamic acid were associated with greater depression symptomatology (p = 0.021). Conclusion: These preliminary results indicate a possible correlation between dietary glutamic acid a depressive symptoms in non-obese patients with schizophrenia, although further research is needed to specifically examine this relationship.

Lactation in large litters influences anxiety, memory, and spreading depression in adult male rats that were chronically subjected to a non-convulsive pilocarpine dose

Objectives: Unfavorable lactation influences brain excitability and behavioral reactions in adults. Administration early in life of the cholinergic agonist, pilocarpine, even at non-convulsive doses, alters the brain excitability-related phenomenon known as cortical spreading depression (CSD), and produce anxiogenic-like behavior. However, the influence of unfavorable lactation on the CSD- and memory-effects of pilocarpine administration late in life has not been investigated. Herein, we analyzed the ponderal, electrophysiological (CSD), and behavioral effects of chronic treatment with a non-convulsive dose of pilocarpine, in adult rats suckled under favorable and unfavorable conditions.Methods: Wistar rats were suckled in litters with 9 or 15 pups (groups L₉ and L₁₅, respectively). A very low dose of pilocarpine (45/mg/kg/day) was chronically administered in mature rats from postnatal day (PND) 69-90. Behavioral tests occurred at PND91 [elevated plus maze (EPM)], PND93 [open field (OF)], and PND94-95 [object recognition memory (ORM)]. CSD was recorded between PND96-120.Results: Pilocarpine-treated rats performed worse in the anxiety and memory tests, and displayed lower CSD propagation velocity when compared with saline-treated controls. In addition, L₁₅ rats showed an increase in the distance traveled and a decrease in the immobility time in the EPM, impaired ORM, and accelerated CSD propagation when compared with L₉ rats (p ≤ 0.05).Discussion: These data suggest that sub-convulsive pilocarpine treatment in adult rats can affect behavioral and excitability-related reactions. In addition, unfavorable lactation increases the ambulatory effects of pilocarpine. Further studies should investigate the possible cholinergic molecular mechanisms involved in these effects.

Oral Monosodium Glutamate Differentially Affects Open-Field Behaviours, Behavioural Despair and Place Preference in Male and Female Mice

Background:

Monosodium glutamate (MSG) is a flavour enhancer which induces behavioural changes in animals. However the influence of sex on the behavioural response to MSG has not been investigated.

Objective:

The sex-differential effects of MSG on open-field behaviours, anxiety-related behaviour, behavioural despair, place-preference, and plasma/brain glutamate levels in adult mice were assessed.

Methods:

Mice were assigned to three groups (1-3), based on the models used to assess behaviours. Animals in group 1 were for the elevated-plus maze and tail-suspension paradigms, group 2 for the open-field and forced-swim paradigms, while mice in group 3 were for observation in the conditioned place preference paradigm. Mice in all groups were further assigned into five subgroups (10 males and 10 females), and administered vehicle (distilled water at 10 ml/kg) or one of four doses of MSG (20, 40, 80 and 160 mg/kg) daily for 6 weeks, following which they were exposed to the behavioural paradigms. At the end of the behavioural tests, the animals were sacrificed, and blood was taken for estimation of glutamate levels. The brains were also homogenised for estimation of glutamate levels.

Results:

MSG was associated with a reduction in locomotion in males and females (except at 160 mg/kg, male), an anxiolytic response in females, an anxiogenic response in males, and decreased behavioural despair in both sexes (females more responsive). Postconditioning MSG-associated place-preference was significantly higher in females. Plasma/ brain glutamate was not significantly different between sexes.

Conclusion:

Repeated MSG administration alters a range of behaviours in a sex-dependent manner in mice.

Endurance training on rodent brain antioxidant capacity: A meta-analysis

The influence of physical exercise on brain antioxidant defense mechanisms has been studied. Nevertheless, the effect of training volume on the brain`s redox balance remains unclear. In this meta-analysis, we compared the effect of training volume on antioxidant enzymatic resource and lipid peroxidation on various brain regions. The activities of the enzymes glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) and the levels of thiobarbituric acid reactive substances (TBARS) were also evaluated. The effects of training periods (weeks) and exercise duration were compared. Meta-analysis revealed that protocols over 8 weeks were associated with an increase in SOD (p =  0.0008) and CAT activities (p =  0.0001). Exercise durations for 30 and 60 min were associated with higher CAT activity (p =  0.04). Joint analysis revealed that moderate physical exercise over 4 and 8 weeks promoted a healthy enzymatic balance. However, high volumes of exercise over 8 weeks were associated with the increased antioxidant enzymatic activity, indicating higher reactive oxygen species (ROS) levels. The data also indicated that there is still limited research and inaccurate information, on the safety conditions of training periods that simulate tests of ultra resistance in humans.

Monosodium glutamate and treadmill exercise: Anxiety-like behavior and spreading depression features in young adult rats

OBJECTIVES

The route of administration is an important factor in determining the action of some drugs. We previously demonstrated that subcutaneous monosodium glutamate (MSG) accelerated cortical spreading depression (CSD) in the rat and that treadmill exercise attenuated this effect. This study evaluated whether other routes of administration exert the same action by testing orogastric (gavage) and topical cortical MSG administration in treadmill-exercised and sedentary rats. Additionally, in the orogastric treatment we tested anxiety-like behavior.

METHODS

Exercised and sedentary rats received per gavage water or MSG (1 or 2 g/kg) daily from postnatal (P) day 7 to 27. Behavioral tests (open field and elevated plus-maze) occurred at P53 ± 3. At P56 ± 3, we analyzed CSD parameters (velocity, amplitude, and duration of the negative potential change). Other three groups of rats received an MSG solution (25, 50 or 75 mg/ml) topically to the intact dura mater during CSD recording.

RESULTS

MSG-gavage increased anxiety-like behavior and the CSD velocities compared with water-treated controls (P < 0.05). Exercise decelerated CSD. In contrast to gavage, which accelerated CSD, topical MSG dose-dependently and reversibly impaired CSD propagation, reduced CSD amplitude and increased CSD duration (P < 0.05).

CONCLUSIONS

The exercise-dependent attenuation of the effects of MSG confirms our previous results in rats treated subcutaneously with MSG. CSD results suggest two distinct mechanisms for gavage and topical MSG administration. Additionally, data suggest that exercise can help protect the developing and adult brain against the deleterious actions of MSG.

Insulin Regulates Hepatic Triglyceride Secretion and Lipid Content via Signaling in the Brain

Hepatic steatosis is common in obesity and insulin resistance and results from a net retention of lipids in the liver. A key mechanism to prevent steatosis is to increase secretion of triglycerides (TG) packaged as VLDLs. Insulin controls nutrient partitioning via signaling through its cognate receptor in peripheral target organs such as liver, muscle, and adipose tissue and via signaling in the central nervous system (CNS) to orchestrate organ cross talk. While hepatic insulin signaling is known to suppress VLDL production from the liver, it is unknown whether brain insulin signaling independently regulates hepatic VLDL secretion. Here, we show that in conscious, unrestrained male Sprague Dawley rats the infusion of insulin into the third ventricle acutely increased hepatic TG secretion. Chronic infusion of insulin into the CNS via osmotic minipumps reduced the hepatic lipid content as assessed by noninvasive (1)H-MRS and lipid profiling independent of changes in hepatic de novo lipogenesis and food intake. In mice that lack the insulin receptor in the brain, hepatic TG secretion was reduced compared with wild-type littermate controls. These studies identify brain insulin as an important permissive factor in hepatic VLDL secretion that protects against hepatic steatosis.

Brain effects of the lectin from Canavalia ensiformis in adult rats previously suckled in favorable and unfavorable conditions: A spreading depression and microglia immunolabeling study

OBJECTIVE

To evaluate in adult rats, previously suckled under favorable and unfavorable conditions, the brain electrophysiological and microglial effects of the treatment early in life with the lectin (ConA) from Canavalia ensiformis.

METHODS

Male Wistar newborn rats (n = 89) were suckled under favorable or unfavorable conditions, represented by litters with 6-7 pups or 12-14 pups (groups N6 and N12, respectively). From postnatal days 5-24, they were treated intraperitoneally with 1 or 10 mg/kg ConA (groups L1 and L10, respectively), or with saline solution (group Sal), or no treatment (group Naïve). At 90-120 days of age, cortical spreading depression (CSD) was recorded at two parietal points for 4 hours, and CSD parameters (velocity of propagation and amplitude and duration of the DC slow potential change) were measured. Fixative-perfused brain sections were reacted with anti-Iba1 antibodies to quantify immunolabeled microglia.

RESULTS

Compared with the control groups, ConA-treated animals dose-dependently presented with reduced CSD propagation velocities and increased amplitude and duration of the CSD slow potential change. Microglia Iba-1 immunoreactivity was lower in both nutritional groups treated with ConA, in comparison with the control groups. The CSD hemisphere presented with higher immunoreactivity compared with the CSD-free hemisphere.

DISCUSSION

Attenuation in CSD propagation and microglia reaction was associated in adulthood with ConA treatment during brain development, indicating that the lectin can affect the electrophysiological and microglial development, and suggesting long-lasting protective action of the lectin on the rat brain, which is not impeded by the unfavorable suckling condition.

Spreading depression features and Iba1 immunoreactivity in the cerebral cortex of developing rats submitted to treadmill exercise after treatment with monosodium glutamate

Physical exercise and excessive consumption of monosodium glutamate (MSG) can affect the morphological and electrophysiological organization of the brain during development. However, the interaction of both factors remains unclear. We analyzed the effect of this interaction on the excitability-related phenomenon known as cortical spreading depression (CSD) and the microglial reaction expressed as Iba1-immunolabeled cells in the rat motor cortex. MSG (2g/kg or 4g/kg) was administered every other day during the first 14 postnatal days. Treadmill exercise started at 21-23 days of life and lasted 3 weeks, 5 days/week, for 30min/day. At 45-60 days, CSD was recorded for 4h at two cortical points and the CSD parameters (velocity, amplitude, and duration of the negative potential change) calculated. Confirming previous observations, exercised rats presented with lower CSD velocities (3.29±0.18mm/min) than the sedentary group (3.80±0.18mm/min; P<0.05). MSG increased CSD velocities in the exercised rats compared to saline-treated and exercised animals in a dose-dependent manner (3.49±0.19, 4.05±0.18, and 3.27±0.26 for 2g/kg MSG, 4g/kg MSG, and saline, respectively; P<0.05). The amplitude (ranging from 14.3±5.9 to 18.7±6.2mV) and duration (46.7±11.1 to 60.5±11.6s) of the negative slow potential shift of the CSD were similar in all groups. Both exercise and MSG treatment increased Iba1 immunolabeling. The results confirm that physical exercise decelerates CSD propagation. However, it does not impede the CSD-accelerating action of MSG. These effects were accompanied by a cortical microglia reaction. Therefore, the data suggest that treadmill exercise early in life can influence the development of cortical electrical activity.