Unraveling the MSG-Headache Controversy: an Updated Literature Review

PURPOSE OF REVIEW

To review the evidence and role of monosodium glutamate (MSG) as a headache and migraine trigger.

RECENT FINDINGS

MSG is a common food additive, has widely been linked as a trigger of headache, as well as other symptoms. However, the evidence for MSG as a causative agent for headache is debated. Various clinical trials over the past several decades have reported conflicting results, with studies suggesting that MSG does and does not increase the incidence of headache. However, the dosages of MSG exposure are often inconsistent across studies, with many studies administering a dose significantly higher than the average consumption.. Additionally, there are misconceptions about which foods and cuisines have MSG in them. MSG could be a potential trigger for migraine and headaches. It is unclear exactly how MSG plays into the migraine pathophysiology. It's crucial to accurately determine if MSG is present in one's diet to evaluate its potential impact on headaches.

Immunoreactivity of glutamine synthetase in satellite glia around various subpopulations of lumbar dorsal root ganglia neurons in adult rats treated with monosodium glutamate

Satellite glial cells (SGCs), involved inter alia in glutamate (Glu) metabolism, form a glial sheath around sensory neurons of dorsal root ganglia (DRGs). SGCs show a presence of glutamine synthetase (GS) which transform uptaken Glu into glutamine (Gln). In DRGs, this aminoacid is used mainly by small neurons which are able to synthetize substance P (SP) that play a crucial role in nociception. The aim of the study was to define the influence of monosodium glutamate (MSG) on GS immunoreactivity in satellite glia around various subpopulations of neurons including SP immunopositive cells in DRGs of adult rats. The studies were carried out on lumbar DRGs slides in rats which received subcutaneous injection of saline solution (control group) or 4 g/kg b. w. of MSG (MSG group). Immunofluorescence reactions were conducted with use of anti-GS and anti-SP antibodies. Administration of MSG to adult rats increased the GS immunoexpression in SGCs. In rats receiving MSG, a number of small neurons with GS-immunopositive glial sheath was not altered when compared to control individuals, whereas there was a statistically significant increase of GS immunoexpression in SGCs around large and medium neurons. Moreover, in these animals, a statistically significant increase in the number of small SP-positive neurons with GS-positive glial sheath was observed. SP is responsible for transmission of pain, thus the obtained results may be useful for further research concerning the roles of glia in nociceptive pathway regulation.

The Role of monosodium glutamate (MSG) in Epilepsy and other Neurodegenerative Diseases: Phytochemical-based Therapeutic Approaches and Mechanisms

Epilepsy is a common neurological disease affecting 50 million individuals worldwide, and some forms of epilepsy do not respond to available treatments. Overactivation of the glutamate pathway and excessive entrance of calcium ions into neurons are proposed as the biochemical mechanisms behind epileptic seizures. However, the overactivation of neurons has also been associated with other neurodegenerative diseases (NDDs), such as Alzheimer's, Parkinson's, Huntington's, and multiple sclerosis. The most widely used food ingredient, monosodium glutamate (MSG), increases the level of free glutamate in the brain, putting humans at risk for NDDs and epilepsy. Glutamate is a key neurotransmitter that activates nerve cells. MSG acts on glutamate receptors, specifically NMDA and AMPA receptors, leading to an imbalance between excitatory glutamate and inhibitory GABA neurotransmission. This imbalance can cause hyperexcitability of neurons and lead to epileptic seizures. Overuse of MSG causes neuronal cells to become overexcited, which in turn leads to an increase in the flow of Ca2+ and Na+ ions, mutations, and upregulation in the enzymes superoxide dismutase 1 (SOD-1) and TDP43, all of which contribute to the development of NDDs. While TDP43 and SOD-1 protect cells from damage, a mutation in their genes makes the proteins unprotective and cause neurodegeneration. Yet to what extent mutant SOD1 and TDP43 aggregates contribute to neurotoxicity is generally unknown. This study is focused on neuroprotective herbal medications that can pass the blood-brain barrier and cure MSG-induced NDDs and the factors that influence MSG-induced glutaminergic, astrocyte, and GABAergic neuron abnormalities causing neurodegeneration.

Effect of monosodium glutamate on fetal development and progesterone level in pregnant Wistar Albino rats

Monosodium glutamate (MSG) is a widespread flavor enhancer and stabilizer in manufactured or packaged foods that possess myriad adverse effects. This study aimed to evaluate the effect of MSG on placental progesterone receptors and fetal development. Thirty pregnant Wistar Albino rats were divided into three groups (ten/each). The control group (G1) gavaged distilled water only, low-dose treated group (G2) gavaged 3 g/kg MSG, and high-dose treated group (G3) gavaged 6 g/kg MSG from 1st to 18th days of gestation, and all pregnant rats were sacrificed on the 19th day of gestation. The effect of MSG on fetal weights, crown vertebral length (CVL), placental weight, placental ghrelin expression, and fetal skeleton examination were estimated. MSG induced a significant decrease in fetal weights, CVL lengths, placental weight, and ghrelin expression in both treatment groups compared to the control group. Several parts of the fetal skeleton showed incomplete ossification and delayed chondrification in which high-dose maternally treated fetuses were more affected. Many degenerative changes were detected in both maternal and fetal liver and kidney tissues in MSG-treated groups. Moreover, MSG caused a significant increase in serum ALT, ALP, and creatinine levels in pregnant rats' blood. Serum progesterone was only elevated in G3 on the 19th day of gestation. This study showed that the administration of MSG during pregnancy adversely influences fetal growth and skeletal development and caused several biochemical and histological changes in the maternal and fetal liver and kidney tissues which assure the toxic and teratogenic effects of MSG.

Development of an Enzymatic Biosensor Using Glutamate Oxidase on Organic-Inorganic-Structured, Electrospun Nanofiber-Modified Electrodes for Monosodium Glutamate Detection

Herein, dendrimer-modified montmorillonite (Mt)-decorated poly-Ɛ-caprolactone (PCL) and chitosan (CHIT)-based nanofibers were prepared. Mt was modified with a poly(amidoamine) generation 1 (PAMAM_G1) dendrimer, and the obtained PAMAM_G1-Mt was incorporated into the PCL-CHIT nanofiber's structure. The PCL-CHIT/PAMAM_G1-Mt nanofibers were conjugated with glutamate oxidase (GluOx) to design a bio-based detection system for monosodium glutamate (MSG). PAMAM_G1-Mt was added to the PCL-CHIT backbone to provide a multipoint binding side to immobilize GluOx via covalent bonds. After the characterization of PCL-CHIT/PAMAM_G1-Mt/GluOx, it was calibrated for MSG. The linear ranges were determined from 0.025 to 0.25 mM MSG using PCL-CHIT/Mt/GluOx and from 0.0025 to 0.175 mM MSG using PCL-CHIT/PAMAMG₁-Mt/GluOx (with a detection limit of 7.019 µM for PCL-CHIT/Mt/GluOx and 1.045 µM for PCL-CHIT/PAMAMG₁-Mt/GluOx). Finally, PCL-CHIT/PAMAMG₁-Mt/GluOx was applied to analyze MSG content in tomato soup without interfering with the sample matrix, giving a recovery percentage of 103.125%. Hence, the nanofiber modification with dendrimer-intercalated Mt and GluOx conjugation onto the formed nanocomposite structures was performed, and the PCL-CHIT/PAMAM_G1-Mt/GluOx system was successfully developed for MSG detection.

Structural insight on the liquid silk from the middle silk gland of non-mulberry silkworm Antheraea assamensis

This study highlights the preliminary characterization of liquid silk from the middle silk gland (MSG) along with the in-silico analysis of the sericin protein of a less explored non mulberry silkworm Antheraea assamensis which is endemic to the North Eastern region of India. Various biophysical methods have been applied to elucidate the conformational patterns of the liquid silk present inside the MSG without removing the sericin layer. This will help us to know the actual features of the in vivo transitional status of the silk in the MSG which travel towards the anterior silk gland (ASG) prior to spinning. The SDS PAGE analysis represented the existence of the both fibroin and sericin bands in the sample. The structural pattern of the MSG liquid silk as revealed by various methods denoted the occurrence of β-sheet component along with some random coil and β-turn components which in turn suggests the transitional state of the liquid silk attributed to the existence of both the crystalline and amorphous contents. The thermo gravimetric study and the aggregation behavior analysis results proposed the occurrence of intermolecular hydrogen bonding between the sericin and fibroin in the MSG. This study will sensitize the better understanding of the behavior of the liquid silk in the MSG of non-mulberry silkworm A. assamensis and will open avenues for various application-based studies of this silk.Communicated by Ramaswamy H. Sarma.

Perspective: Might Maternal Dietary Monosodium Glutamate (MSG) Consumption Impact Pre- and Peri-Implantation Embryos and Their Subsequent Development?

MSG alters metabolism, especially in the brain, when administered to experimental animals via gavage or similar means. Such administration is, however, not applicable to humans. More recently, though, MSG was shown to have these effects even when added to the food of mammals. Moreover, the levels of MSG in food needed to cause these metabolic changes are the same as those needed for optimum flavor enhancement. Near physiological concentrations of glutamate also cause mammalian blastocysts to develop with fewer cells, especially in their inner cell masses, when these embryos are cultured with this amino acid. We propose that consumption of MSG in food may overwhelm the otherwise well-regulated glutamate signaling needed for optimal development by pre- and peri-implantation mammalian embryos. In addition to immediate changes in cellular proliferation and differentiation as embryos develop, MSG ingestion during early pregnancy might result in undesirable conditions, including metabolic syndrome, in adults. Since these conditions are often the result of epigenetic changes, they could become transgenerational. In light of these possibilities, we suggest several studies to test the merit of our hypothesis.

The protective effect of L-carnitine on testosterone synthesis pathway, and spermatogenesis in monosodium glutamate-induced rats

Background

Monosodium glutamate (MSG) is a food ingredient that is increasingly used commercially. MSG leads to oxidative stress, consequently suppressing steroid hormone production that causes defects in male reproductive system. This study aimed to evaluate the effect of L-carnitine as an antioxidant on testicular damage in MSG-induced male rats.

Methods

Sixty adult male Spargue-Dawley rats were randomly divided into six groups of ten as follows: control (water), sham (normal saline), L-carnitine (200 mg/kg b.w), MSG (3 g/kg b.w), MSG + L-carnitine 100 (3 g/kg b.w of MSG and 100 mg/kg b.w of L-carnitine), and MSG + L-carnitine 200 (3 g/kg b.w of MSG and 200 mg/kg b.w of L-carnitine). The treatment was administered by oral gavage for six months. Serum levels of Malondialdehyde (MDA), Total Anti-oxidant Capacity (TAC), LH, FSH, testosterone, and mRNA expressions of Star, Cyp11a1, and Hsd17b3 genes, and histological and stereological changes were assessed.

Results

L-carnitine led to a significant decrease in the level of MDA and a significant rise in the serum levels of TAC, LH, FSH, and mRNA expression of Star and Cyp11a1 compared to the MSG group (p < 0.05). Furthermore, stereological results indicated a significant increment in the number of sexual lineage cells, the total volume of the testis, length, diameter, and volume of seminiferous tubules, the height of the germinal epithelium, sperm count, and sperm motility (p < 0.05) in MSG + L-carnitine 200 compare to MSG group.

Conclusion

The study’s findings demonstrated that L-carnitine due to its anti-oxidant properties, ameliorated the reproductive abnormalities in the male rats exposed to MSG.

Reaction Mixtures Rich in [γ-Glu](n≥1)-Arg Derived from Enzymatic Synthesis as Potential Salt and Umami Enhancers

Some arginyl dipeptides and γ-glutamyl peptides have been identified as salt and umami enhancers. These compounds provide an operable approach for reducing sodium uptake without losing the palatability of foods. γ-Glu-Arg was hinted to have a taste-enhancing effect in the past, but few research studies have focused on it. In the present study, a series of γ-glutamyl peptides containing Arg such as γ-Glu-Arg, [γ-Glu]_(n=2)-Arg, [γ-Glu]_(n=3)-Arg, [γ-Glu]_(n=4)-Arg, [γ-Glu]_(n=5)-Arg, [γ-Glu]_(n=6)-Arg, [γ-Glu]_(n=7)-Arg, and [γ-Glu]_(n=8)-Arg were synthesized using glutaminase from Bacillus amyloliquefaciens in the presence of Gln and Arg. A high solid concentration of 30% was found to increase the production of [γ-Glu]_(1≤n≤4)-Arg. Sensory evaluation revealed that individual [γ-Glu]_(n=1,2,3,4)-Arg has a slightly bitter and astringent taste. [γ-Glu]_(n=1,2)-Arg (1.0 mg/mL) significantly increased the umaminess in the mixture of salt and sodium glutamate but showed no significant effect on saltiness in the salt solution, whereas [γ-Glu]_(n=3,4)-Arg and postenzymatic reaction mixtures (1.0 mg/mL) significantly increased both saltiness and umaminess. [γ-Glu]_(n=3,4)-Arg and postenzymatic mixtures in the system with 30% solid concentrations showed a high and similar taste-enhancing effect. Moreover, umaminess and saltiness increased 1.9 and 2.4 times in the simulated broth, respectively, while saltiness increased 1.5 times in the salt solution by the addition of postenzymatic reaction mixtures in the system with 30% solid concentrations at 20.0 mg/mL. These results indicated that [γ-Glu]_(n=1,2,3,4)-Arg and postenzymatic reaction mixtures rich in [γ-Glu]_(n≥1)-Arg were potential salt or umami enhancers.

Dietary supplementation with monosodium glutamate enhances milk production by lactating sows and the growth of suckling piglets

This study was conducted to test the hypothesis that increasing dietary content of glutamate through addition of monosodium glutamate (MSG) enhances milk production by lactating sows and the growth of their offspring. Thirty multiparous sows (Landrace × Large White) were assigned randomly into one of three dietary groups: control (a corn- and soybean meal-based diet), the basal diet + 1% MSG, and the basal diet + 2% MSG. Diets were made isonitrogenous by the addition of appropriate amounts of L-alanine. Lactating sows had free access to drinking water and were fed twice daily their respective diets. The number of live-born piglets was standardized to 9 per sow at day 0 of lactation (the day of farrowing). On days 3, 15, and 29 of lactation, body weight and milk consumption of piglets were measured, and blood samples obtained from sows and piglets at 2 h and 1 h after feeding, respectively. Feed intake of sows did not differ (P > 0.05) among the three groups of sows. Concentrations of aspartate, glutamine, citrulline, arginine, tryptophan, proline, branched-chain amino acids, and glutamate were greater (P < 0.05) in the plasma of MSG-supplemented sows and their piglets than for controls. When compared with the control, dietary supplementation with 1-2% MSG increased (P < 0.05): concentrations of many free amino acids (including glutamate plus glutamine) and all protein-bound amino acids in milk; the milk intake of piglets by 14-25%; and daily weight gains of piglets by 23-44%. These results indicate that dietary supplementation with 1-2% MSG to lactating sows enhances milk production to support the growth of sow-reared piglets.

Optimization of γ-Aminobutyric Acid (GABA) Accumulation in Germinating Adzuki Beans (Vigna angularis) by Vacuum Treatment and Monosodium Glutamate, and the Molecular Mechanisms

This study aimed to investigate the optimal hypoxic and monosodium glutamate (MSG) stress conditions for the enrichment of γ-Aminobutyric acid (GABA) in germinating adzuki beans and to reveal the potential underlying molecular mechanisms of GABA accumulation. Using single-factor experiments and response surface model, we investigated the effects of germination time, germination temperature, vacuum time, and MSG concentration on GABA contents, and further explored the activity and gene expression of glutamate decarboxylase (GAD) and polyamine oxidase (PAO) critical rate restriction enzymes during GABA synthesis. The optimal soaking temperature, soaking time, and pH conditions were 35°C, 16 h, and 5, respectively. Furthermore, the optimal germination conditions for optimal GABA enrichment were 48 h, 1.99 mg/ml MSG concentration, germination temperature of 31.49°C, and vacuum time of 15.83 h. Under such conditions, the predicted GABA concentration was 443.57 ± 7.18 mg/100 g, with no significant difference between the predicted and experimental data. The vacuum + MSG (FZM) treatment has a maximum contribution rate of GABA to 38.29%, which significantly increase GABA content, and the increase was associated with increased GAD and PAO activity. In addition, MSG in combination with vacuum treatment could significantly induce VaGAD4 and VaGAD6 genes in 2 days germination of adzuki beans. According to the results of the present study, vacuum + MSG treatment is an effective approach to enhancing GABA accumulation in germinating adzuki beans, which could be employed in enhancing the functional quality of germinating adzuki beans.

Omega-3 Rich Oils Attenuate ADHD-Like Behaviour Induced by Dietary Monosodium Glutamate in Rats

&lt;b&gt;Background and Objective:&lt;/b&gt; Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity and cognitive dysfunction. The present study was designed to examine the possible modulatory effect of Fish, Walnuts or Fenugreek Oils against Attention Deficit Hyperactivity Disorder (ADHD)-like Behavior induced by Monosodium Glutamate (MSG) in Rats. &lt;b&gt;Materials and Methods:&lt;/b&gt; Fifty weaning rats were divided into five groups, (each group contain 10 rats) as follows: Group 1: Normal control rats were fed on a balanced diet. Groups from 2-5 rats were fed on a balanced diet+MSG (0.4 g kg&lt;sup&gt;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; diet), Group 2 served as a positive control group whereas group 3, 4 and 5 treated with Fish, Walnuts and Fenugreek oil, respectively, (200 mg kg&lt;sup&gt;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; b.wt.) by intra-gastric tube. Biochemical and behavioural parameters were tested as well as microscopic examination of brain tissue was done. &lt;b&gt;Results:&lt;/b&gt; MSG ingestion caused marked disruption in locomotors activity, memory function and brain tissue structure along with significant abnormalities in some bio-markers and reduction in the gene expression level of Bcl-2 in brain tissue. However, treatment with the tested oils showed remarkable effect by reversing the condition. &lt;b&gt;Conclusion:&lt;/b&gt; Dietary supplementation with walnut; fenugreek or fish oils at the tested dose could modulate the condition of ADHD in rats.

The Effect of Monosodium Glutamate on Neuronal Signaling Molecules in the Hippocampus and the Neuroprotective Effects of Omega-3 Fatty Acids

Monosodium glutamate (MSG) is a flavoring substance added to many ready-to-eat foods and has known neurotoxic effects. This study was performed in order to examine the potential toxic effect of MSG on neurons in various regions of the hippocampus in prepubertal rats. It also investigated the protective effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on brain-derived neurotropic factor (BDNF), n-methyl-d-aspartate receptor (NMDA-R), and neuropeptide-Y (NPY) expression in the brain, using immunohistochemical and biochemical methods. Six female prepubertal Wistar albino rats were used in each group. Group 1, the control group, received 0.9% saline solution subcutaneously (sc) on days 1, 3, 5, 7, and 9. Group 2 received 4 mg/g MSG sc on days 1, 3, 5, 7, and 9. Group 3 received MSG + EPA (4 mg/g sc on days 1, 3, 5, 7, and 9. Oral 300 mg/kg for 9 d), while Group 4 received MSG + DHA (4 mg/g sc on days 1, 3, 5, 7, and 9 and 300 mg/kg orally for 9 d, respectively). At the end of the ninth day the hippocampal regions of the brain were removed and either fixed for immunohistochemical staining or stored at -80 °C for biochemical parameter investigation. BDNF, NMDA-R, and NPY expression results were evaluated using immunohistochemistry and an enzyme-linked immunosorbent assay. According to our findings, neurons in the control group hippocampal CA1 and DG regions exhibited strong BDNF, NPY, and NMDA-R reactions, while an expression in both regions decreased in the MSG group (p < 0.00). However, in the MSG-EPA and MSG-DHA groups, BDNF, NPY, and NMDA-R immunoreactions in neurons in the same region were similar to those of the control group (p = 0.00). No significant difference was observed in terms of expression in hippocampal neurons between the MSG-EPA and MSG-DHA groups (p > 0.00). In conclusion, since MSG caused a decrease in BDNF, NMDA-R, and NPY neural signaling molecules in the CA1 and DG regions of the hippocampus of prepubertal rats compared to the control group, care is required over the consumption of MSG, since it may affect memory-related neurons in these age groups. In addition, we concluded that the use of omega-3 fatty acids such as EPA and DHA in addition to MSG may protect against the neurotoxic effects of MSG.

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.

Pharmacology of the Umami Taste Receptor

Umami, the fifth taste, has been recognized as a legitimate taste modality only recently relative to the other tastes. Dozens of compounds from vastly different chemical classes elicit a savory (also called umami) taste. The prototypical umami substance glutamic acid or its salt monosodium glutamate (MSG) is present in numerous savory food sources or ingredients such as kombu (edible kelp), beans, soy sauce, tomatoes, cheeses, mushrooms, and certain meats and fish. Derivatives of glutamate (Glu), other amino acids, nucleotides, and small peptides can also elicit or modulate umami taste. In addition, many potent umami tasting compounds structurally unrelated to amino acids, nucleotides, and MSG have been either synthesized or discovered as naturally occurring in plants and other substances. Over the last 20 years several receptors have been suggested to mediate umami taste, including members of the metabotropic and ionotropic Glu receptor families, and more recently, the heterodimeric G protein-coupled receptor, T1R1/T1R3. Careful assessment of representative umami tasting molecules from several different chemical classes shows activation of T1R1/T1R3 with the expected rank order of potency in cell-based assays. Moreover, 5'-ribonucleotides, molecules known to enhance the savory note of Glu, considerably enhance the effect of MSG on T1R1/T1R3 in vitro. Binding sites are found on at least 4 distinct locations on T1R1/T1R3, explaining the propensity of the receptor to being activated or modulated by many structurally distinct compounds and these binding sites allosterically interact to modulate receptor activity. Activation of T1R1/T1R3 by all known umami substances evaluated and the receptor's pharmacological properties are sufficient to explain the basic human sensory experience of savory taste and it is therefore unlikely that other receptors are involved.

Factors affecting detection of bimodal sour-savory mixture and inter-individual umami taste perception

While basic taste interactions have been the subject of many research studies, there is one combination where data is limited in the literature: sour and umami. This combination is universal in culinary preparations and of key interest to the food industry. Therefore, the primary goal of the present study is to assess how increasing concentrations of acidity (citric acid) affect, if at all, the intensity of a constant concentration of umami (monosodium glutamate, MSG). The secondary goal is to investigate other possible factors in umami taste perception. Here, a crowdsourced cohort of 734 individuals (age range 8-81) tasted and rated the intensity of 50 mM MSG alone, and in combination with citric acid at varying concentrations (1.25 mM, 6.25 mM, 31.25 mM). Participants were also genotyped for the single nucleotide polymorphism rs34160967 in the T1R1 gene. The results show a significant decrease in the intensity perception of umami as sour concentration increases (low: p = 0.005, medium: p < 0.001, high: p < 0.001). Situational factors such as participant hunger level and time since last eating also have a significant effect on umami intensity perception. Neither the biological factors of sex, age, and ancestry appear to play a role in umami perception, nor does variation in gene TAS1R1 at rs34160967. These new data contribute to the growing field of taste and sensory interaction by giving evidence that sour suppresses umami taste perception in bi-model samples.

Females' ability to discriminate MSG from NaCl influences perceived intensity but not liking of MSG added vegetable broths

This study investigated whether ability to taste monosodium glutamate (MSG) is associated with liking and intensity of sodium-reduced vegetable broths with added MSG. Six vegetable broths, with varying concentrations of added NaCl and MSG, were evaluated for overall intensity, and liking, by n = 115 female participants, mean age 24.1 ± 5.4. Broths evaluated included: control broth (0 g NaCl, 0 g MSG), high NaCl broth (0.8 g/100 mL), medium NaCl (0.4 g/100 mL), low NaCl (0.2 g/100 ml), medium NaCl (0.4 g/100 ml) + 29 mM MSG and, low NaCl (0.2 g/100 mL) + 29 mM MSG. Participant's umami discrimination status was determined using forced-choice triangle tests (29 mM MSG vs 29 mM NaCl), and suprathreshold salt taste intensity (NaCl) was measured. A 7% Na reduction was possible by partially replacing NaCl with MSG without influencing intensity or liking in the low NaCl broth, in comparison to the highest liked NaCl only broth (medium NaCl). There was no significant difference in liking of broths between MSG discriminators (n = 37) and nondiscriminators (n = 78) (P > 0.2). MSG discriminators rated all broths as significantly more intense overall (except for control broth, P > 0.2) than nondiscriminators (P < 0.05). A significant relationship was found between MSG discrimination status, and salt taste intensity tertiles (χ² (2, N = 115) = 8.45; P < 0.02) indicating that the Na ion dominates taste profile. The ability to discriminate MSG from NaCl does not influence liking of salt-reduced broths with added MSG. MSG discrimination status was associated with NaCl taste intensity, indicating that the sodium ion is dominant in influencing intensity (common to both MSG and NaCl). PRACTICAL APPLICATION: The addition of MSG to vegetable broths is an effective way to reduce total sodium in the broths without reducing liking of the broths, this is irrespective of an individual's ability to taste MSG or salt. Salt taste and umami taste (MSG) appear to be associated, indicating the sodium is important in influencing taste intensity for both salty and umami taste.

Neuroprotective Potential of Allium sativum against Monosodium Glutamate-Induced Excitotoxicity: Impact on Short-Term Memory, Gliosis, and Oxidative Stress

This study evaluated the neuroprotective potential of Allium sativum against monosodium glutamate (MSG)-induced neurotoxicity with respect to its impact on short-term memory in rats. Forty male Wistar albino rats were assigned into four groups. The control group received distilled water. The second group was administered Allium sativum powder (200 mg/kg of body weight) orally for 7 successive days, then was left without treatment until the 30th day. The third group was injected intraperitoneally with MSG (4 g/kg of body weight) for 7 successive days, then left without treatment until the 30th day. The fourth group was injected with MSG in the same manner as the third group and was treated with Allium sativum powder in the same manner as the second group, simultaneously. Phytochemical analysis of Allium sativum powder identified the presence of diallyl disulphide, carvone, diallyl trisulfide, and allyl tetrasulfide. MSG-induced excitotoxicity and cognitive deficit were represented by decreased distance moved and taking a long time to start moving from the center in the open field, as well as lack of curiosity in investigating the novel object and novel arm. Moreover, MSG altered hippocampus structure and increased MDA concentration and protein expression of glial fibrillary acidic protein (GFAP), calretinin, and caspase-3, whereas it decreased superoxide dismutase (SOD) activity and protein expression of Ki-67 in brain tissue. However, Allium sativum powder prevented MSG-induced neurotoxicity and improved short-term memory through enhancing antioxidant activity and reducing lipid peroxidation. In addition, it decreased protein expression of GFAP, calretinin, and caspase-3 and increased protein expression of Ki-67 in brain tissues and retained brain tissue architecture. This study indicated that Allium sativum powder ameliorated MSG-induced neurotoxicity through preventing oxidative stress-induced gliosis and apoptosis of brain tissue in rats.

Evaluation of the effects of the green nanoparticles zinc oxide on monosodium glutamate-induced toxicity in the brain of rats

Background

Monosodium glutamate (MSG) is used extensively as a food additive in the diets of many countries around the world.

Aim of the study

Our aim was to determine the effects of green zinc oxide nanoparticles on MSG-induced oxidative damage, neurotransmitter changes, and histopathological alternation in the cerebral cortexes of rats.

Methods

MSG was administered orally at two doses of 6 and 17.5 mg/kg body weight. The higher dose was associated with a significant decline in the activities of superoxide dismutase, catalase, and glutathione peroxidase, as well as the levels of brain-derived neurotrophic factor (BDNF) and glutathione (GSH) in the cerebral cortex of rats.

Results

The administration of zinc oxide nanoparticles/green tea extract (ZnO NPs/GTE) to 17.5 mg/kg MSG-treated rats was associated with significant improvements in all parameters previously shown to be altered by MSG. The higher dose of MSG induced significant histopathological variation in brain tissue. Co-treatment of rats with ZnO NPs/GTE and MSG-HD inhibited the reduction of neurotransmitters and acetylcholinesterase by MSG.

Conclusions

ZnO NPs/GTE have the potential to protect against oxidative stress and neuronal necrosis induced by MSG-HD. ZnO NPs/GTE conferred a greater benefit than the control treatment or ZnO NPs or GTE administered separately.

Differential Effects of Dietary MSG on Hippocampal Dependent Memory Are Mediated by Diet

Introduction

Free glutamate is a common dietary flavor enhancer and is also an important excitatory neurotransmitter in the body. A good number of food additives which contain glutamate are found in the Western Diet, and this diet has also been linked to increased risk of cognitive dysfunction.

Objective

To examine the effects of dietary glutamate on hippocampal and non-hippocampal memory performance, and whether consuming a diet high in fat/sugar could influence any observed associations.

Methods

Sixty-four adult male Sprague-Dawley rats were trained concurrently on two different discrimination problems: (1) Pavlovian serial feature negative (sFN) discrimination, in which a brief tone stimulus was reinforced with sucrose pellets when it was presented alone (T+ trials) and non-reinforced on trials when it was preceded by the presentation of a brief light (LT− trials); and (2) a simple discrimination (SD) problem in which a white noise (WN+) cue was reinforced with sucrose pellets and a clicker (C-) stimulus was not reinforced. Previous research has shown that sFN, but not SD performance, depends on the functional integrity of the hippocampus. After solving both problems, the rats were assigned to one of four ad libitum-fed diet groups, matched on weight and discrimination performance: (1) high fat, high sugar western-style diet (WD), (2) standard laboratory rodent chow diet (chow), (3) WD + monosodium glutamate (MSG), or (4) chow + MSG.

Results

After 14 weeks, rats fed WD had higher adiposity than rats fed chow. Consistent with previous findings, rats fed WD exhibited impaired performance on the sFN problem, but not on the SD, relative to rats fed chow. Adding MSG to WD abolished this impairment, whereas rats fed chow + MSG had impaired sFN performance compared to rats fed chow alone. No differences in performance on the SD task were observed.

Conclusion

This study demonstrates differing effects of dietary glutamate on hippocampal dependent memory function, with MSG impairing hippocampal function in animals receiving chow, while improving hippocampal function in animals receiving a Western-type diet, high in fat and sugar. More research will be needed to explore the cause of these differential effects.

College Students' Experience of a Food Safety Class and Their Responses to the MSG Issue

This study examines whether students' experience in a food safety class affected their responses to the monosodium glutamate (MSG) issue and to message framing. We differentiated students into two groups depending on their involvement in a food safety class. The data were collected through in-class surveys in South Korea. A structural equation model was used where the dependent variable was students' intention to avoid MSG; the mediating variables were knowledge, trust, attitude, and risk perception; and the exogenous variable was class experience. A difference-in-differences scheme was used to analyze the interaction between class experience and message frame. Empirical results show that students who took the class had relatively more knowledge of MSG along with lower risk perceptions or fears of MSG and thus a reduced intention to avoid it. The class experience also affected their trust in overall food safety in the domestic market as well as in food-related institutions and groups. Students showed sensitivity to message framing, although the sensitivity did not statistically differ by students' class experience status. Our results imply that cultivating students' knowledge of food additives through a food safety class enables them to respond more reasonably toward food additives.

A survey of free glutamic acid in foods using a robust LC-MS/MS method

An effective and simultaneous liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used with the aim of quantifying monosodium glutamate (MSG) in foodstuffs, such as chips, taste cubes, sauces and soups. The results were linear (R² = 1), with very low LOD and LOQ values, 1.0 µg/kg, 5.0 µg/kg, respectively. Excellent repeatability and reproducibility were also achieved. This highly sensitive and robust LC-MS/MS technique was applied successfully for the detection and quantification of MSG in a wide variety of foodstuffs. MSG contents ranged from 0.01 g/100 g to 15.39 g/100 g in food samples. Importantly, determination of free glutamic acid in the daily diet could also prevent various side effects associated with consumption of excess free glutamic acid.

Properties of Kimchi Fermented with GABA-Producing Lactic Acid Bacteria as a Starter

Kimchi (a traditional Korean fermented vegetable) was prepared with a starter, Lactobacillus zymae GU240 producing γ-aminobutyric acid (GABA), and one precursor of GABA (glutamic acid, glutamic acid monosodium salt (MSG), or kelp extract). L. zymae GU240, an isolate from kimchi, can grow at 7% NaCl and low temperature. Five different kimchi samples were fermented for 20 weeks at -1°C. Kimchi with starter alone could not produce GABA. The GABA content was highest in kimchi with co-inoculation of the starter and MSG (1% (w/w)). Kimchi co-inoculated with the starter and kelp extract powder (3% (w/w)) had the second highest GABA content. Addition of glutamic acid powder (1% (w/w)) caused a reduction in the pH level of kimchi and growth inhibition of lactic acid bacteria and yeasts. Kimchi samples with MSG or kelp extract showed improvement of sensory evaluation scores. The results demonstrate the possibility to produce kimchi with improved functionality and taste by using L. zymae GU240 as a starter along with a suitable precursor such as MSG or kelp extract.

Could dietary glutamate be contributing to the symptoms of obsessive-compulsive disorder?

A 50-year-old man who had suffered from daily obsessive-compulsive disorder (OCD) symptoms for 39 years, in addition to fibromyalgia and irritable bowel syndrome symptoms, was enrolled in a randomized double-blind placebo-controlled clinical trial to test the effects of a low-glutamate diet on fibromyalgia/irritable bowel syndrome symptoms. After 1 month on the low-glutamate diet all of his symptoms remitted, including his OCD, which had previously been nonresponsive to pharmacological treatment. This case study is limited by self-report of symptoms; however, glutamatergic neurotransmission appears to be dysregulated in OCD, suggesting biological plausibility for this observation. Future research is needed.

Circular transcriptome sequencing of the middle silk gland and posterior silk gland in the Bombyx mori

Circular transcriptome sequencing of the middle silk gland (MSG) and posterior silk gland (PSG) in the Bombyx mori are presented. The middle silk gland and posterior silk gland were collected from the third day of fifth-instar B.mori larvae. The circular RNAs enriched by using RNase R to degrade the linear RNA molecules, and circular RNA sequencing (circRNA-seq) was performed using an Illumina Hiseq. 2500 sequencing platform. Samples are described in the SRA portal (SRP100385) and FASTQ files have been deposited in Sequence Read Archive (accession numbers: SRX2577343 and SRX2577342). The interpretation of these data is presented in the following research article: "Identification of circular RNA in the Bombyx mori silk gland" [1] (Gan et al., 2017).

Can we spice up our Christmas dinner? : Busting the myth of the 'Chinese restaurant syndrome'

Background

Monosodium glutamate (MSG), also referred to as Vetsin or E621, is a flavour enhancer frequently used in Asian cuisine and abundantly present in the famous Chinese dish Peking duck. MSG is notorious for triggering the onset of the so-called ‘Chinese restaurant syndrome’ (CRS), a complex of unpleasant symptoms, which might include flushing, sweating and the onset of atrial fibrillation (AF). This study aims to determine the effects of MSG on the occurrence of AF.

Methods

We conducted a placebo self-controlled single-arm study in the Academic Medical Centre in Amsterdam. We included paroxysmal AF patients who reported a consistent onset of AF upon MSG intake. During three admissions, participants were subsequently administered: placebo, 1.5 g and 3 g MSG. If AF was recorded after the dose of 1.5 g MSG, patients were given another placebo instead of 3 g MSG. The primary outcome was the onset of AF registered by 24-hour Holter monitoring. The secondary outcomes were any other arrhythmia and the onset of CRS defined as two or more symptoms of CRS after MSG intake.

Results

Six men participated in the study. Both 1.5 g and 3 g MSG were unrelated to CRS, arrhythmias or AF occurrence.

Conclusion

Peking duck can be put on the Christmas menu without risking guests to be admitted to the emergency department with new episodes of AF.

Electronic supplementary material

The online version of this article (10.1007/s12471-017-1053-5) contains study inlcusion and exclusion criteria and recipe of Peking duck, which is available to authorized users.

Changes in the expression level of MAPK pathway components induced by monosodium glutamate-administration produce neuronal death in the hippocampus from neonatal rats

Excessive Glutamate (Glu) release may trigger excitotoxic cellular death by the activation of intracellular signaling pathways that transduce extracellular signals to the cell nucleus, which determines the onset of a death program. One such signaling pathway is the mitogen-activated protein kinases (MAPK), which is involved in both survival and cell death. Experimental evidences from the use of specific inhibitors supports the participation of some MAPK pathway components in the excitotoxicity mechanism, but the complete process of this activation, which terminates in cell damage and death, is not clearly understood. The present work, we investigated the changes in the expression level of some MAPK-pathway components in hippocampal excitotoxic cell death in the neonatal rats using an experimental model of subcutaneous monosodium glutamate (MSG) administration on postnatal days (PD) 1, 3, 5 and 7. Data were collected at different ages through PD 14. Cell viability was evaluated using fluorescein diacetate mixed with propidium iodide (FDA-PI), and the Nissl-staining technique was used to evaluate histological damage. Transcriptional changes were also investigated in 98 components of the MAPK pathway that are associated with cell damage. These results are an evidence of that repetitive use of MSG, in neonatal rats, induces cell damage-associated transcriptional changes of MAPK components, that might reflect a differential stage of both biochemical and molecular brain maturation. This work also suggests that some of the proteins evaluated such as phosphorylated retinoblastoma (pRb) protein, which was up-regulated, could regulate the response to excitotoxic through modulation of the process of re-entry into the cell cycle in the hippocampus of rats treated with MSG.

An Examination of the Role of L-Glutamate and Inosine 5'-Monophosphate in Hedonic Taste-Guided Behavior by Mice Lacking the T1R1 + T1R3 Receptor

The heterodimeric T1R1 + T1R3 receptor is considered critical for normal signaling of L-glutamate and 5'-ribonucleotides in the oral cavity. However, some taste-guided responsiveness remains in mice lacking one subunit of the receptor, suggesting that other receptors are sufficient to support some behaviors. Here, mice lacking both receptor subunits (KO) and wild-type (WT, both n = 13) mice were tested in a battery of behavioral tests. Mice were trained and tested in gustometers with a concentration series of Maltrin-580, a maltodextrin, in a brief-access test (10-s trials) as a positive control. Similar tests followed with monosodium glutamate (MSG) with and without the ribonucleotide inosine 5'-monophosphate (IMP), but always in the presence of the epithelial sodium channel blocker amiloride (A). Brief-access tests were repeated following short-term (30-min) and long-term (48-h) exposures to MSG + A + IMP and were also conducted with sodium gluconate replacing MSG. Finally, progressive ratio tests were conducted with Maltrin-580 or MSG + A + IMP, to assess appetitive behavior while minimizing satiation. Overall, MSG generated little concentration-dependent responding in either food-restricted WT or KO mice, even in combination with IMP. However, KO mice licked less to the amino acid stimuli, a measure of consummatory behavior in the brief-access tests. In contrast, both groups initiated a similar number of trials and had a similar breakpoint in the progressive ratio task, both measures of appetitive (approach) behavior. Collectively, these results suggest that while the T1R1 + T1R3 receptor is necessary for consummatory responding to MSG (+IMP), other receptors are sufficient to maintain appetitive responding to this "umami" stimulus complex in food-restricted mice.

Increasing the yield of middle silk gland expression system through transgenic knock-down of endogenous sericin-1

Various genetically modified bioreactor systems have been developed to meet the increasing demands of recombinant proteins. Silk gland of Bombyx mori holds great potential to be a cost-effective bioreactor for commercial-scale production of recombinant proteins. However, the actual yields of proteins obtained from the current silk gland expression systems are too low for the proteins to be dissolved and purified in a large scale. Here, we proposed a strategy that reducing endogenous sericin proteins would increase the expression yield of foreign proteins. Using transgenic RNA interference, we successfully reduced the expression of BmSer1 to 50%. A total 26 transgenic lines expressing Discosoma sp. red fluorescent protein (DsRed) in the middle silk gland (MSG) under the control of BmSer1 promoter were established to analyze the expression of recombinant. qRT-PCR and western blotting showed that in BmSer1 knock-down lines, the expression of DsRed had significantly increased both at mRNA and protein levels. We did an additional analysis of DsRed/BmSer1 distribution in cocoon and effect of DsRed protein accumulation on the silk fiber formation process. This study describes not only a novel method to enhance recombinant protein expression in MSG bioreactor, but also a strategy to optimize other bioreactor systems.

Glibenclamide treatment blocks metabolic dysfunctions and improves vagal activity in monosodium glutamate-obese male rats

BACKGROUND/AIMS

Autonomic nervous system imbalance is associated with metabolic diseases, including diabetes. Glibenclamide is an antidiabetic drug that acts by stimulating insulin secretion from pancreatic beta cells and is widely used in the treatment of type 2 diabetes. Since there is scarce data concerning autonomic nervous system activity and diabetes, the aim of this work was to test whether glibenclamide can improve autonomic nervous system activity and muscarinic acetylcholine receptor function in pre-diabetic obese male rats.

METHODS

Pre-diabetes was induced by treatment with monosodium L-glutamate in neonatal rats. The monosodium L-glutamate group was treated with glibenclamide (2 mg/kg body weight /day) from weaning to 100 days of age, and the control group was treated with water. Body weight, food intake, Lee index, fasting glucose, insulin levels, homeostasis model assessment of insulin resistance, omeostasis model assessment of β-cell function, and fat tissue accumulation were measured. The vagus and sympathetic nerve electrical activity were recorded. Insulin secretion was measured in isolated islets challenged with glucose, acetylcholine, and the selective muscarinic acetylcholine receptor antagonists by radioimmunoassay technique.

RESULTS

Glibenclamide treatment prevented the onset of obesity and diminished the retroperitoneal (18%) and epididymal (25%) fat pad tissues. In addition, the glibenclamide treatment also reduced the parasympathetic activity by 28% and glycemia by 20% in monosodium L-glutamate-treated rats. The insulinotropic effect and unaltered cholinergic actions in islets from monosodium L-glutamate groups were increased.

CONCLUSION

Early glibenclamide treatment prevents monosodium L-glutamate-induced obesity onset by balancing autonomic nervous system activity.

Evaluation of the automated Becton Dickinson MAX real-time PCR platform for detection of Pneumocystis jirovecii

AIM

We evaluated the performance of the automated quantitative BD MAX (Becton Dickinson) real-time PCR platform for detecting Pneumocystis jirovecii.

MATERIALS & METHODS

A total of 34 retrospective and 137 prospective samples were included.

RESULTS

Retrospectively, all (100%) positive samples were correctly detected by this platform compared with a nested PCR. Among prospective samples, the overall sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were 92.6%, 94.5%, 17.0 and 0.1, respectively. All bronchoalveolar lavage fluid (BALF)/bronchial washing samples were correctly identified by this platform. Samples from patients with colonization had significantly higher median amplification cycle threshold values than patients with P. jirovecii pneumonia.

CONCLUSION

The quantitative BD MAX real-time PCR is a rapid and highly sensitive modality for detecting P. jirovecii, especially in samples from bronchoalveolar lavage fluid/bronchial washing fluid.

Effects of Physical Exercise on the Intestinal Mucosa of Rats Submitted to a Hypothalamic Obesity Condition

The small intestine plays a role in obesity as well as in satiation. However, the effect of physical exercise on the morphology and function of the small intestine during obesity has not been reported to date. This study aimed to evaluate the effects of physical exercise on morphological aspects of the rat small intestine during hypothalamic monosodium glutamate (MSG)-induced obesity. The rats were divided into four groups: Sedentary (S), Monosodium Glutamate (MSG), Exercised (E), and Exercised Monosodium Glutamate (EMSG). The MSG and EMSG groups received a daily injection of monosodium glutamate (4 g/kg) during the 5 first days after birth. The S and E groups were considered as control groups and received injections of saline. At weaning, at 21 days after birth, the EMSG and E groups were submitted to swimming practice 3 times a week until the 90th day, when all groups were sacrificed and the parameters studied recorded. Exercise significantly reduced fat deposits and the Lee Index in MSG-treated animals, and also reduced the thickness of the intestinal wall, the number of goblet cells and intestinal alkaline phosphatase activity. However, physical activity alone increased the thickness and height of villi, and the depth of the crypts. In conclusion, regular physical exercise may alter the morphology or/and functions of the small intestine, reducing the prejudicial effects of hypothalamic obesity. Anat Rec, 299:1389-1396, 2016. © 2016 Wiley Periodicals, Inc.

FGF21 ameliorates nonalcoholic fatty liver disease by inducing autophagy

The aim of this study is to evaluate the role of fibroblast growth factor 21 (FGF21) in nonalcoholic fatty liver disease (NAFLD) and seek to determine if its therapeutic effect is through induction of autophagy. In this research, Monosodium L-glutamate (MSG)-induced obese mice or normal lean mice were treated with vehicle, Fenofibrate, and recombinant murine FGF21, respectively. After 5 weeks of treatment, metabolic parameters including body weight, blood glucose and lipid levels, hepatic and fat gene expression levels were monitored and analyzed. Also, fat-loaded HepG2 cells were treated with vehicle or recombinant murine FGF21. The expression levels of proteins associated with autophagy were detected by western blot, real-time PCR, and transmission electron microscopy (TEM). Autophagic flux was monitored by laser confocal microscopy and western blot. Results showed that FGF21 significantly reduced body weight (P < 0.01) and serum triglyceride, improved insulin sensitivity, and reversed hepatic steatosis in the MSG model mice. In addition, FGF21 significantly increased the expression of several proteins related to autophagy both in MSG mice and fat-loaded HepG2 cells, such as microtubule associated protein 1 light chain 3, Bcl-2-interacting myosin-like coiled-coil protein-1 (Beclin-1), and autophagy-related gene 5. Furthermore, the evidence of TEM revealed an increased number of autophagosomes and lysosomes in the model cells treated with FGF21. In vitro experimental results also showed that FGF21 remarkably increased autophagic flux. Taken together, FGF21 corrects multiple metabolic parameters on NAFLD in vitro and in vivo by inducing autophagy.

Acceleration-selective arterial spin labeling for intracranial MR angiography with improved visualization of cortical arteries and suppression of cortical veins

PURPOSE

A new approach for intracranial MR angiography (MRA) is introduced, using acceleration-selective arterial spin labeling (AccASL). The aim of this study was to investigate the arterial visualization and venous suppression using AccASL.

METHODS

Intracranial MRA images obtained by AccASL and time-of-flight (TOF) were compared in seven healthy volunteers and one patient with occlusion of the terminal portion of the left internal carotid artery. The volunteer images were assessed by measuring the contrast-to-noise ratio (CNR) between the middle cerebral artery (MCA) and white matter (WM) and between the confluence of sinuses and WM. Additionally, visualized peripheral arteries were counted and qualitative scoring of the MCA visualization and vein signal contamination was conducted.

RESULTS

The CNR at the M4 branch and the number of visualized arteries was significantly higher using AccASL compared with that in TOF (P < 0.05). In the qualitative comparison, the score for artery visualization was higher using AccASL (P < 0.05), while minimizing signal contamination by cortical veins. Additionally, in patient examination, the collateral flow visualization was better with AccASL.

CONCLUSION

AccASL enables better efficiency for visualizing peripheral arteries compared with TOF, while suppressing cortical vein signal. Magn Reson Med 77:1996-2004, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Reduction of sodium content in spicy soups using monosodium glutamate

Background

Excessive dietary sodium intake causes several diseases, such as hypertension, cardiovascular and renal disease, etc. Hence, reducing sodium intake has been highly recommended. In this study the effect of monosodium glutamate (MSG), as an umami substance, on saltiness and sodium reduction was investigated.

Methods and Results

The trained panellists were presented with basic spicy soups (curry chicken and chili chicken) containing different amounts of sodium chloride (NaCl) (0–1.2%) and MSG (0–1.2%). They tasted the optimum concentrations of NaCl and MSG for the two spicy soups and the overall acceptability were 0.8% and 0.7%, respectively. There was no significant effect of spiciness level on the saltiness and umami taste of both soups. The optimum levels of combined NaCl and MSG for overall acceptance in the chili and curry soups were 0.3% and 0.7%, respectively. The results showed that with the addition of MSG, it is possible to reduce sodium intake without changing the overall acceptability of the spicy soup. A 32.5% reduction in sodium level is made feasible by adding 0.7% MSG to the spicy soups.

Conclusions

This study suggests that low-sodium soups can be developed by the addition of appropriate amounts of MSG, while maintaining the acceptability of the spicy soups. It was also proven that it is feasible to reduce sodium intake by replacing NaCl with MSG.

Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats

BACKGROUND

Monosodium glutamate (MSG) is a flavor-enhancer widely used as a food additive. However, its safe dietary concentration and its toxicity, including its possible implication in the recent metabolic syndrome pandemia, is still a controversial issue. Therefore, a deep knowledge of its effects upon regular dietary use is needed. Our aim was to evaluate the effects of chronic exposure to MSG on feeding behavior, abdominal fat, gastrointestinal motility, and cardiovascular function in rats.

METHODS

Two groups of adult male Wistar rats were used: control and treated with MSG (4 g/L in drinking water) for 6 weeks. Different functional parameters were determined and the histological structure was analyzed in tissues of interest.

KEY RESULTS

Compared to control animals, chronic MSG increased water intake but did not modify food ingestion or body weight gain. Neither the abdominal fat volume nor the fat fraction, measured by magnetic resonance imaging, was modified by MSG. Monosodium glutamate did not alter general gastrointestinal motility, but significantly increased the colonic response to mechanical stimulation. It slightly reduced endothelium-dependent relaxation in aorta, without significantly modifying any other cardiovascular parameters. No significant histological alterations were detected in salivary glands, intestinal wall, aorta, heart, and kidney.

CONCLUSIONS & INFERENCES

Chronic treatment with MSG in the adult rat increased water intake. This supports its potential to improve acceptance of low-fat regimens and to increase hydration in the elderly and sportspeople, often at risk of dehydration. Changes in colonic contractility and cardiovascular function could have some long-term repercussions warranting further research.

A study on sensory properties of sodium reduction and replacement in Asian food using difference-from - control test

This study examined the effects of sodium reduction and flavor enhancers on the sensory profile of two types of hawker foods commonly consumed in Singapore, namely chicken rice and mee soto broth. The ‘difference‐from‐control’ test was the method adopted in this study involving 24–29 trained panelists. Combinations included blind control, two levels of sodium reduction, and two levels of flavor enhancers in sodium‐reduced recipes. In the sodium‐reduced recipes, two levels of NaCl, 0.48% and 0.55%, for chicken rice, and 0.76% and 0.86% for mee soto (equivalent to 31% and 22% reduction in NaCl), were used. Monosodium glutamate (MSG) or Ajiplus^® (a blend of MSG and nucleotides) at 0.20% and 0.40% were added to the recipes comprising a reduction of 40% in NaCl (equivalent to 31% and 22% reduction in sodium, respectively) compared with the control. It was found that the inclusion of MSG or Ajiplus^® in 40% NaCl‐reduced recipe resulted in a significant increase in perception of umami taste (P < 0.05) when compared to the control. By adding flavor enhancers into the 40%‐reduced salt chicken rice recipes, the perception of saltiness was significantly increased when compared to 22% and 31% sodium reduced recipes. Similarly for mee soto broth, there was a significant increase in perception of chicken flavor, umami taste, mouthfeel sensation, and sweet taste (P < 0.05) with a decrease in the perception of sour and bitter taste when compared to control. By adding 0.40% MSG into the 40%‐reduced salt recipes, the perception of saltiness was maintained when compared with control.

Permanent uncoupling of male-specific CYP2C11 transcription/translation by perinatal glutamate

Perinatal exposure of rats and mice to the typically reported 4mg/g bd wt dose of monosodium glutamate (MSG) results in a complete block in GH secretion as well as obesity, growth retardation and a profound suppression of several cytochrome P450s, including CYP2C11, the predominant male-specific isoform--all irreversible effects. In contrast, we have found that a lower dose of the food additive, 2mg/g bd wt on alternate days for the first 9days of life results in a transient neonatal depletion of plasma GH, a subsequent permanent overexpression of CYP2C11 as well as subnormal (mini) GH pulse amplitudes in an otherwise normal adult masculine episodic GH profile. The overexpressed CYP2C11 was characterized by a 250% increase in mRNA, but only a 40 to 50% increase in CYP2C11 protein and its catalytic activity. Using freshly isolated hepatocytes as well as primary cultures exposed to the masculine-like episodic GH profile, we observed normal induction, activation, nuclear translocation and binding to the CYP2C11 promoter of the GH-dependent signal transducers required for CYP2C11 transcription. The disproportionately lower expression levels of CYP2C11 protein were associated with dramatically high expression levels of an aberrant, presumably nontranslated CYP2C11 mRNA, a 200% increase in CYP2C11 ubiquitination and a 70-80% decline in miRNAs associated, at normal levels, with a suppression of CYP2C expression. Whereas the GH-responsiveness of CYP2C7 and CYP2C6 as well as albumin was normal in the MSG-derived hepatocytes, the abnormal expression of CYP2C11 was permanent and irreversible.

Effect of NaCl/Monosodium Glutamate (MSG) Mixture on the Sensorial Properties and Quality Characteristics of Model Meat Products

Sodium chloride is an important ingredient added to most of foods which contributes to flavor enhancement and food preservation but excess intake of sodium chloride may also cause various diseases such as heart diseases, osteoporosis and so on. Therefore, this study was carried out to investigate the effect of monosodium glutamate (MSG) as a salty flavor enhancer on the quality and sensorial properties of the NaCl/MSG complex and actual food system. For characterizing the spray-dried NaCl/MSG complex, surface dimension, morphology, rheology, and saltiness intensity were estimated by increasing MSG (0-2.0%) levels at a fixed NaCl concentration (2.0%). MSG levels had no effect of the characteristics of the NaCl/MSG complex, although the addition of MSG increased the surface dimension of the NaCl/MSG complex significantly (p<0.05). Furthermore, the effect of MSG on enhancing the salty flavor was not observed in the solution of the NaCl/MSG complex. In the case of an actual food system, model meat products (pork patties) were prepared by replacing NaCl with MSG. MSG enhanced the salty flavor, thereby increasing overall acceptability of pork patties. Replacement of NaCl with MSG (<1.0%) did not result in negative sensorial properties of pork patties, although quality deterioration such as high cooking loss was found. Nevertheless, MSG had a potential application in meat product formulation as a salty flavor enhancer or a partial NaCl replacer when meat products were supplemented with binding agents.

A high-resolution genetic map of yellow monkeyflower identifies chemical defense QTLs and recombination rate variation

Genotyping-by-sequencing methods have vastly improved the resolution and accuracy of genetic linkage maps by increasing both the number of marker loci as well as the number of individuals genotyped at these loci. Using restriction-associated DNA sequencing, we construct a dense linkage map for a panel of recombinant inbred lines derived from a cross between divergent ecotypes of Mimulus guttatus. We used this map to estimate recombination rate across the genome and to identify quantitative trait loci for the production of several secondary compounds (PPGs) of the phenylpropanoid pathway implicated in defense against herbivores. Levels of different PPGs are correlated across recombinant inbred lines suggesting joint regulation of the phenylpropanoid pathway. However, the three quantitative trait loci identified in this study each act on a distinct PPG. Finally, we map three putative genomic inversions differentiating the two parental populations, including a previously characterized inversion that contributes to life-history differences between the annual/perennial ecotypes.

Indirect use of deuterium in solution NMR studies of protein structure and hydrogen bonding

A description of the utility of deuteration in protein NMR is provided with an emphasis on quantitative evaluation of the effects of deuteration on a number of NMR parameters of proteins: (1) chemical shifts, (2) scalar coupling constants, (3) relaxation properties (R1 and R2 rates) of nuclei directly attached to one or more deuterons as well as protons of methyl groups in a highly deuterated environment, (4) scalar relaxation of 15N and 13C nuclei in 15N-D and 13C-D spin systems as a measure of hydrogen bonding strength, and (5) NOE-based applications of deuteration in NMR studies of protein structure. The discussion is restricted to the 'indirect' use of deuterium in the sense that the description of NMR parameters and properties of the nuclei affected by nearby deuterons (15N, 13C, 1H) is provided rather than those of deuterium itself.

Flavor preferences conditioned by intragastric monosodium glutamate in mice

The consumption of monosodium glutamate (MSG) solutions has been shown to reinforce preferences for MSG and for MSG-paired flavors in mice. These effects appear to have a strong postoral component, such that MSG detected in the gut is associated with concurrently consumed flavors. Two experiments investigated postoral MSG reward by infusing 400mM MSG intragastrically (IG) to C57BL/6 mice as they consumed a conditioned stimulus (CS+) flavor. An alternate CS- flavor was paired with IG water. In Experiment 1, the grape and cherry CS flavors were unsweetened, and intakes and preferences for the CS+ flavor were modest. Experiment 2 attempted to generate stronger preferences by adding 0.05% saccharin to the CS flavors. Sweet taste did enhance intakes during training and testing but did not significantly increase percent CS+ intake or persistence of the preference. However, only conditioning with the sweet CS+ resulted in the mice expressing a preference for oral MSG in an initial choice test with water. These findings extend recent studies demonstrating postoral MSG conditioning in rats.

Protective Effect of Calendula officinalis L. Flowers Against Monosodium Glutamate Induced Oxidative Stress and Excitotoxic Brain Damage in Rats

Monosodium glutamate (MSG) is a popular flavour enhancer used in food industries; however, excess MSG is neurotoxic. Oxidative stress is well documented in MSG induced neurotoxicity. The compounds having antioxidant and anti-inflammatory properties reportedly possess beneficial effects against various neurotoxic insults. Calendula officinalis Linn. flower extract (COE) is known for its potent antioxidant and anti-inflammatory activities. Hence, this present study has been designed to evaluate the neuroprotective effect of COE on MSG-induced neurotoxicity in rats. Adult Wistar rats were administered systemically for 7 days with MSG and after one h of MSG injection, rats were treated with COE (100 and 200 mg/kg) orally. At the end the treatment period, animals were assessed for locomotor activity and were sacrificed; brains were isolated for estimation of LPO, GSH, CAT, TT, GST, Nitrite and histopathological studies. MSG caused a significant alteration in animal behavior, oxidative defense (raised levels of LPO, nitrite concentration, depletion of antioxidant levels) and hippocampal neuronal histology. Treatment with COE significantly attenuated behavioral alterations, oxidative stress, and hippocampal damage in MSG-treated animals. Hence, this study demonstrates that COE protects against MSG-induced neurotoxicity in rats. The antioxidant and anti-inflammatory properties of COE may be responsible for its observed neuroprotective action.