Dietary Supplementation with Monosodium Glutamate Suppresses Chemotherapy-Induced Downregulation of the T1R3 Taste Receptor Subunit in Head and Neck Cancer Patients.

(Background) We investigated the effect of dietary supplementation with monosodium glutamate (MSG) on chemotherapy-induced downregulation of the T1R3 taste receptor subunit expression in the tongue of patients with advanced head and neck cancer. (Methods) Patients undergoing two rounds of chemoradiotherapy were randomly allocated to a control or intervention group (dietary supplementation with MSG at 2.7 g/day during the second round of chemotherapy). The relative expression of T1R3, a subunit of both umami and sweet taste receptors, in the tongue was assessed by quantitative polymerase chain reaction analysis. Dysgeusia was assessed with a visual analog scale and daily energy intake was evaluated. (Results) T1R3 expression levels in the tongue, taste sensitivity, and daily energy intake were significantly reduced after the first round of chemotherapy compared with before treatment. Furthermore, these parameters significantly decreased after the second round of chemotherapy, but the extent of decrease was significantly attenuated in the MSG group compared with the control group. (Conclusions) MSG supplementation suppresses chemotherapy-induced dysgeusia, possibly due to the inhibition of the T1R3-containing taste receptor downregulation in the tongue, thereby increasing energy intake in patients with advanced head and neck cancer.

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.

Coconut Water Prevents Renal and Hepatic Changes in Offspring of Monosodium Glutamate-Treated Wistar Rat Dams.

Monosodium glutamate (MSG) is a widely-consumed taste enhancer which has been implicated in the aetiology of renal and hepatic dysfunction in adults and their offspring. There is increasing evidence on the therapeutic properties of Coconut Water (CW) in kidney and liver disorders. This study investigated the effects of CW on renal and hepatic functions in offspring of MSG-fed dams. Twelve female Wistar rats (120 - 140 g) were grouped into four as follows; Control (10 ml/Kg distilled water), MSG (0.08 mg/Kg), CW (10 ml/Kg) and MSG+CW. Treatments were given orally daily commencing two weeks prior to mating, throughout mating and gestation until parturition. All dams received standard rodent diet and drinking water ad libitum throughout the study. After weaning on Post-Natal Day (PND) 28, serum was obtained from offspring for assay of liver and renal function. Histological analysis of the livers and kidneys were performed on both dams and offspring. There was no significant difference in liver enzymes, urea, creatinine and albumin levels amongst the offspring on PND 28. However, liver and kidney sections from MSG dams and their offspring showed early degenerative changes which were not evident in renal and hepatic tissues from CW and MSG+CW dams and offspring. These observations suggest that coconut water protects against monosodium glutamate-induced renal and hepatic dysfunction in dams and offspring.

Effect of monosodium L-glutamate (umami substance) on cognitive function in people with dementia.

BACKGROUND/OBJECTIVES: This study assessed the effect of continuous ingestion of monosodium L-glutamate (MSG) on cognitive function and dietary score in dementia patients. SUBJECTS/METHODS: This was a single-blind, placebo-controlled trial involving 159 subjects with dementia residing in a hospital or nursing home. We assigned the subjects to a group that ingested MSG thrice daily (0.9 g/dose) (MSG group; n = 79) or a group that ingested NaCl thrice daily (0.26 g/dose) (Control group; n = 80). This study consisted of a 12-week intake period, followed by a 4-week follow-up period without the ingestion of MSG or NaCl. We performed physical examination, cognitive symptom tests (the Touch Panel-type Dementia Assessment Scale (TDAS) and Gottfries-Bråne-Steen Scale (GBSS)), palatability and behaviour questionnaires, and blood tests before and after the intervention and after the follow-up period. RESULTS: There were no significant differences in the TDAS and GBSS total scores between the groups before and after the intervention. However, regarding the TDAS sub-items, "the accuracy of the order of a process" did not deteriorate in the MSG group compared with that observed in the Control group (p < 0.05). At the follow-up assessment, the TDAS total scores in the MSG group showed significant improvement compared with those reported in the Control group (p < 0.05). Furthermore, there was a correlation of changes from pre-intervention to post-intervention between the TDAS and enjoyment of the meal (r = -0.299, p = 0.049). CONCLUSIONS: Our results suggest that continued ingestion of MSG has an effect on cognitive function. Furthermore, the patients with improved questionnaires about palatability survey showed greater improvement in cognitive function.

Oral administration of antibiotics results in fecal occult bleeding due to metabolic disorders and defective proliferation of the gut epithelial cell in mice.

Antibiotics sometimes exert adverse effects on the pathogenesis of colitis due to the dysbiosis resulting from the disruption of gut homeostasis. However, the precise mechanisms underlying colitogenic effects of antibiotic-induced colitis are largely unknown. Here, we show a novel murine fecal occult bleeding model induced by the combinatorial treatment of ampicillin and vancomycin, which is accompanied by an enlarged cecum, upregulation of pro-inflammatory cytokines IL-6 and IL-12, a reduction in Ki-67-positive epithelial cell number and an increase in the apoptotic cell number in the colon. Moreover, gas chromatography-tandem mass analysis showed that various kinds of metabolites, including glutamic acid and butyric acid, were significantly decreased in the cecal contents. In addition, abundance of butyric acid producer Clostridiales was dramatically reduced in the enlarged cecum. Interestingly, supplementation of monosodium glutamate or its precursor glutamine suppressed colonic IL-6 and IL-12, protected from cell apoptosis and prevented fecal occult blood indicating that the reduced level of glutamic acid is a possible mechanism of antibiotic-induced fecal occult bleeding. Our data showed a novel mechanism of antibiotic-induced fecal occult bleeding providing a new insight into the clinical application of glutamic acid for the treatment of antibiotic-induced colitis.

(p-ClPhSe)2 stabilizes metabolic function in a rat model of neuroendocrine obesity induced by monosodium glutamate.

Obesity is a chronic and complex medical condition characterized by excessive fat accumulation and its complications include metabolic syndrome, diabetes and chronic inflammation. The aim of this study was to expand the knowledge about p-chloro-diphenyl diselenide (p-ClPhSe)2 effects on enzymes and proteins involved in the metabolism of lipids and carbohydrates in a model of neuroendocrine obesity induced by MSG. Male Wistar rats were treated during the first ten postnatal days with MSG (4 g/kg, s.c.) and received (p-ClPhSe)2 (10 mg/kg, i.g.) from 90th to 97th postnatal day. The hypothalamic function, insulin resistance and other biochemical parameters were determined in the rat blood, liver and skeletal muscle. The MSG administration induced hypothalamic neurotoxicity accompanied by metabolic disorders, including obesity, a transient insulin resistance, and metabolic alterations, demonstrated in the blood, liver and skeletal muscle, and lipotoxicity, characterized in the liver and skeletal muscle. The metabolic disorders in the liver and skeletal muscle were accompanied by the decrease in AMPK phosphorylation and activation of Akt. (p-ClPhSe)2 restored most of metabolic parameters altered by MSG administration in rats. The hypothalamic neurotoxicity induced by MSG was accompanied by metabolic disorders in rats, which were regulated by (p-ClPhSe)2.

Taurine supplementation regulates Iκ-Bα protein expression in adipose tissue and serum IL-4 and TNF-α concentrations in MSG obesity.

PURPOSE: Obesity is usually associated with low-grade inflammation, which impairs insulin action. The amino acid, taurine (TAU), regulates glucose homeostasis and lipid metabolism and presents anti-inflammatory actions. Here, we evaluated whether inflammatory markers are altered in the serum and retroperitoneal adipose tissue of monosodium glutamate (MSG) obese rats, supplemented or not with TAU. METHODS: Male Wistar rats received subcutaneous injections of MSG (4 mg/kg body weight/day, MSG group) or hypertonic saline (CTL) during the first 5 days of life. From 21 to 120 days of age, half of each of the MSG and CTL groups received 2.5 % TAU in their drinking water (CTAU and MTAU). RESULTS: At 120 days of age, MSG rats were obese and hyperinsulinemic. TAU supplementation reduced fat deposition without affecting insulinemia in MTAU rats. MSG rats presented increased pIκ-Bα/Iκ-Bα protein expression in the retroperitoneal adipose tissue. TAU supplementation decreased the ratio of pIκ-Bα/Iκ-Bα protein, possibly contributing to the increased Iκ-Bα content in MTAU adipose tissue. Furthermore, MSG obesity or supplementation did not alter TNF-α, IL-1ß or IL-6 content in adipose tissue. In contrast, MSG rats presented lower serum TNF-α, IL-4 and IL-10 concentrations, and these alterations were prevented by TAU treatment. CONCLUSION: MSG obesity in rats was not associated with alterations in pro-inflammatory markers in retroperitoneal fat stores; however, reductions in the serum concentrations of anti-inflammatory cytokines and of TNF-α were observed. TAU treatment decreased adiposity, and this effect was associated with the normalization of circulating TNF-α and IL-4 concentrations in MTAU rats.

Alterations in taste perception as a result of hyperbaric oxygen therapy.

The present study evaluates the effect of hyperbaric oxygen therapy on taste sensitivity, hedonic perception of taste, and food preferences. The studied groups included 197 people in total (79 in the study group; 118 in the control group). All patients from the study group were treated with hyperbaric oxygen therapy due to chronic non-healing wounds. The control group consisted of healthy people, who did not receive hyperbaric oxygen therapy. The taste intensity, recognition thresholds, and hedonic perception were examined using gustatory tests. The aqueous solutions of sucrose for sweet, sodium chloride for salty, citric acid for sour, quinine hydrochloride for bitter, and monosodium glutamate for umami taste were used. The participants fulfilled the questionnaire to examine pleasure derived from eating certain types of dishes. Gustatory tests and analyses of the pleasure derived from eating in the study group were carried out before the first exposure to hyperbaric oxygen and then at the end of therapy, after at least 25 sessions of treatment. In the control group, examination of perception of taste sensations was conducted only once. The results of comparing patients with non-healing wounds with healthy people are characterized by reduced taste sensitivity. After participation in hyperbaric oxygen therapy, the improvement in perception of taste sensations and changes in hedonic evaluation have occurred among patients with non-healing wounds. In terms of food preference, a decreased desire for eating sweet desserts, chocolate, and crisps was observed in those patients who received hyperbaric oxygen therapy.

Monosodium glutamate intake affect the function of the kidney through NMDA receptor.

AIMS: We investigated whether the chronic intake of monosodium glutamate (MSG) with food affects kidney function, and renal response to glycine. We also established if the NMDA receptors are involved in the changes observed. MAIN METHODS: Male Wistar rats (5weeks old) were fed a diet supplemented with MSG (3g/kg b.w./day), five days a week, and spontaneous ingestion of a 1% MSG solution during 16weeks. NaCl rats were fed a diet with NaCl (1g/kg b.w./day) and 0.35% NaCl solution at the same frequency and time. Control group was fed with normal chow and tap water. We utilized clearance techniques to examine glomerular filtration rate (GFR) and cortical renal plasma flow (CRPF) response to glycine and glycine+MK-801 (antagonist NMDA-R), and we determined NMDA-R1 in kidney by immunohistochemistry. KEY FINDINGS: The addition of MSG in the diet of rats increased both GFR and CRPF with an increase of absolute sodium reabsorption. However, hyperfiltration was accompanied with a normal response to glycine infusion. Immunostain of kidney demonstrate that the NMDA receptor is upregulated in rats fed with MSG diet. NMDA-R antagonist MK-801 significantly reduced both the GFR and CRPF; however the percentage of reduction was significantly higher in the group MSG. MK-801 also reduces fractional excretion of water, sodium and potassium in the three groups. SIGNIFICANCE: Renal NMDAR may be conditioned by the addition of MSG in the diet, favoring the hyperfiltration and simultaneously Na retention in the body.

Both dietary supplementation with monosodium L-glutamate and fat modify circulating and tissue amino acid pools in growing pigs, but with little interactive effect.

BACKGROUND: The Chinese population has undergone rapid transition to a high-fat diet. Furthermore, monosodium L-glutamate (MSG) is widely used as a daily food additive in China. Little information is available on the effects of oral MSG and dietary fat supplementation on the amino acid balance in tissues. The present study aimed to determine the effects of both dietary fat and MSG on amino acid metabolism in growing pigs, and to assess any possible interactions between these two nutrients. METHODS AND RESULTS: Four iso-nitrogenous and iso-caloric diets (basal diet, high fat diet, basal diet with 3% MSG and high fat diet with 3% MSG) were provided to growing pigs. The dietary supplementation with fat and MSG used alone and in combination were found to modify circulating and tissue amino acid pools in growing pigs. Both dietary fat and MSG modified the expression of gene related to amino acid transport in jejunum. CONCLUSIONS: Both dietary fat and MSG clearly influenced amino acid content in tissues but in different ways. Both dietary fat and MSG enhance the absorption of amino acids in jejunum. However, there was little interaction between the effects of dietary fat and MSG.

Application of diet-derived taste active components for clinical nutrition: perspectives from ancient Ayurvedic medical science, space medicine, and modern clinical nutrition.

The principal objective of this paper is to demonstrate the role of taste and flavor in health from the ancient science of Ayurveda to modern medicine; specifically their mechanisms and roles in space medicine and their clinical relevance in modern heath care. It also describes the brief history of the use of the monosodium glutamate or flavor enhancers ("Umami substance") that improve the quality of food intake by stimulating chemosensory perception. In addition, the dietary nucleotides are known to be the components of "Umami substance" and the benefit of their use has been proposed in various types of patients with cancer, radiation therapy, organ transplantation, and for application in space medicine.

Oral administration of MSG increases expression of glutamate receptors and transporters in the gastrointestinal tract of young piglets.

Glutamate receptors and transporters, including T1R1 and T1R3 (taste receptor 1, subtypes 1 and 3), mGluRs (metabotropic glutamate receptors), EAAC-1 (excitatory amino acid carrier-1), GLAST-1 (glutamate-aspartate transporter-1), and GLT-1 (glutamate transporter-1), are expressed in the gastrointestinal tract. This study determined effects of oral administration of monosodium glutamate [MSG; 0, 0.06, 0.5, or 1 g/kg body weight (BW)/day] for 21 days on expression of glutamate receptors and transporters in the stomach and jejunum of sow-reared piglets. Both mRNA and protein levels for gastric T1R1, T1R3, mGluR1, mGluR4, EAAT1, EAAT2, EAAT3, and EAAT4 and mRNA levels for jejunal T1R1, T1R3, EAAT1, EAAT2, EAAT3 and EAAT4 were increased (P < 0.05) by MSG supplementation. Among all groups, mRNA levels for gastric EAAT1, EAAT2, EAAT3, and EAAT4 were highest (P < 0.05) in piglets receiving 1 g MSG/kg BW/day. EAAT1 and EAAT2 mRNA levels in the stomach and jejunum of piglets receiving 0.5 g MSG/kg BW/day, as well as jejunal EAAT3 and EAAT4 mRNA levels in piglets receiving 1 g MSG/kg BW/day, were higher (P < 0.05) than those in the control and in piglets receiving 0.06 g MSG/kg BW/day. Furthermore, protein levels for jejunal T1R1 and EAAT3 were higher (P < 0.05) in piglets receiving 1 g MSG/kg BW/day than those in the control and in piglets receiving 0.06 g MSG/kg BW/day. Collectively, these findings indicate that dietary MSG may beneficially stimulate glutamate signaling and sensing in the stomach and jejunum of young pigs, as well as their gastrointestinal function.

No effects of monosodium glutamate consumption on the body weight or composition of adult rats and mice.

Monosodium glutamate (MSG) is pervasively consumed as a flavor enhancer so there are important implications to understanding its physiological actions, particularly its effects on body weight. Previous studies suggest that MSG increases, decreases, or has no effect on the body weight of rodents. However, most of these studies involved administration of MSG to immature rodents and consequently may not be relevant for understanding human obesity. We report here five experiments in which we measured the body weights of a total of 32 groups of 10-12 adult rats or mice given various diets to eat and MSG to eat or drink. We found no evidence that MSG influenced body weight, energy intake, or body composition. To the extent that experiments in rodents illuminate mechanisms involved in human obesity and body weight control, our results suggest that MSG is unlikely to be a useful anti-obesity supplement but neither is it responsible for exacerbating obesity.

Effects of supplementation on food intake, body weight and hepatic metabolites in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double-knockout mouse model of human citrin deficiency.

The C57BL/6:Slc23a13(-/-);Gpd2(-/-) double-knockout (a.k.a., citrin/mitochondrial glycerol 3-phosphate dehydrogenase double knockout or Ctrn/mGPD-KO) mouse displays phenotypic attributes of both neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2), making it a suitable model of human citrin deficiency. In the present study, we show that when mature Ctrn/mGPD-KO mice are switched from a standard chow diet (CE-2) to a purified maintenance diet (AIN-93M), this resulted in a significant loss of body weight as a result of reduced food intake compared to littermate mGPD-KO mice. However, supplementation of the purified maintenance diet with additional protein (from 14% to 22%; and concomitant reduction or corn starch), or with specific supplementation with alanine, sodium glutamate, sodium pyruvate or medium-chain triglycerides (MCT), led to increased food intake and body weight gain near or back to that on chow diet. No such effect was observed when supplementing the diet with other sources of fat that contain long-chain fatty acids. Furthermore, when these supplements were added to a sucrose solution administered enterally to the mice, which has been shown previously to lead to elevated blood ammonia as well as altered hepatic metabolite levels in Ctrn/mGPP-KO mice, this led to metabolic correction. The elevated hepatic glycerol 3-phosphate and citrulline levels after sucrose administration were suppressed by the administration of sodium pyruvate, alanine, sodium glutamate and MCT, although the effect of MCT was relatively small. Low hepatic citrate and increased lysine levels were only found to be corrected by sodium pyruvate, while alanine and sodium glutamate both corrected hepatic glutamate and aspartate levels. Overall, these results suggest that dietary factors including increased protein content, supplementation of specific amino acids like alanine and sodium glutamate, as well as sodium pyruvate and MCT all show beneficial effects on citrin deficiency by increasing the carbohydrate tolerance of Ctrn/mGPD-KO mice, as observed through increased food intake and maintenance of body weight.

Decreased glutamate, glutamine and citrulline concentrations in plasma and muscle in endotoxemia cannot be reversed by glutamate or glutamine supplementation: a primary intestinal defect?

Endotoxemia affects intestinal physiology. A decrease of circulating citrulline concentration is considered as a reflection of the intestinal function. Citrulline can be produced in enterocytes notably from glutamate and glutamine. The aim of this work was to determine if glutamate, glutamine and citrulline concentrations in blood, intestine and muscle are decreased by endotoxemia, and if supplementation with glutamate or glutamine can restore normal concentrations. We induced endotoxemia in rats by an intraperitoneal injection of 0.3 mg kg(-1) lipopolysaccharide (LPS). This led to a rapid anorexia, negative nitrogen balance and a transient increase of the circulating level of IL-6 and TNF-α. When compared with the values measured in pair fed (PF) animals, almost all circulating amino acids (AA) including citrulline decreased, suggesting a decrease of intestinal function. However, at D2 after LPS injection, most circulating AA concentrations were closed to the values recorded in the PF group. At that time, among AA, only glutamate, glutamine and citrulline were decreased in gastrocnemius muscle without change in intestinal mucosa. A supplementation with 4% monosodium glutamate (MSG) or an isomolar amount of glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscle. However, MSG supplementation led to an accumulation of glutamate in the intestinal mucosa. In conclusion, endotoxemia rapidly but transiently decreased the circulating concentrations of almost all AA and more durably of glutamate, glutamine and citrulline in muscle. Supplementation with glutamate or glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscles. The implication of a loss of the intestinal capacity for AA absorption and/or metabolism in endotoxemia (as judged from decreased citrulline plasma concentration) for explaining such results are discussed.

Sub-chronic concomitant ingestion of L-arginine and monosodium glutamate improves feed efficiency, lipid metabolism and antioxidant capacity in male Wistar rats.

The use of L-arginine (ARG) is common in supplements, whereas, Monosodium Glutamate (MSG) is widely used as flavor enhancing food additive. Thus, ARG and MSG may be present together in human diets, warranting this study aimed at investigating the effect of concomitant ingestion of ARG and MSG on some biochemical indices in male rats. Twelve male albino rats were grouped into three (n = 4) and concomitantly exposed to 0:0, 20:5 and 60:15 mg kg(-1) of ARG:MSG. Exposure was peroral and every twenty four h for 28 days. ARG plus MSG treatment caused a significant (p < or = 0.05) increase in Feed Efficiency (FE) (Low dose: 5.23 +/- 22%; High dose: 5.60 +/- 11%), whereas, it decreased (p < or = 0.05) the serum Total Cholesterol (T-Chol) (low dose: 80.83 +/- 0.11 mg/100 mL, high dose: 92.55 +/- 0.14 mg/100 mL), triacylglycerol (TAG) (low dose: 179.91 +/- 0.09 mg/100 mL, high dose: 119.77 +/- 0.32 mg/100 mL) and malondialdehyde (MDA) (low dose: 5.00 +/- 0.07 mg/100 mL, high dose: 24.36 +/- 0.10 mg/100 mL) concentrations of the rats in a dose dependent manner. However, (at the high dose) the increase in Body Weight (BW) (0.08 +/- 0.07 kg), Feed Intake (FI) (0.40 +/- 0.03 kg) and Water Intake (WI) (0.65 +/- 0.18 L) induced by ARG plus MSG exposure was not significant (p < or = 0.05), suggesting non treatment related effect on these routine parameters. However, exposure to ARG plus MSG may significantly improve feed efficiency, lipid metabolism and antioxidant capacity in the male rats.

Low fish oil intake improves insulin sensitivity, lipid profile and muscle metabolism on insulin resistant MSG-obese rats.

BACKGROUND: Obesity is commonly associated with diabetes, cardiovascular diseases and cancer. The purpose of this study was to determinate the effect of a lower dose of fish oil supplementation on insulin sensitivity, lipid profile, and muscle metabolism in obese rats. METHODS: Monosodium glutamate (MSG) (4 mg/g body weight) was injected in neonatal Wistar male rats. Three-month-old rats were divided in normal-weight control group (C), coconut fat-treated normal weight group (CO), fish oil-treated normal weight group (FO), obese control group (Ob), coconut fat-treated obese group (ObCO) and fish oil-treated obese group (ObFO). Obese insulin-resistant rats were supplemented with fish oil or coconut fat (1 g/kg/day) for 4 weeks. Insulin sensitivity, fasting blood biochemicals parameters, and skeletal muscle glucose metabolism were analyzed. RESULTS: Obese animals (Ob) presented higher Index Lee and 2.5 fold epididymal and retroperitoneal adipose tissue than C. Insulin sensitivity test (Kitt) showed that fish oil supplementation was able to maintain insulin sensitivity of obese rats (ObFO) similar to C. There were no changes in glucose and HDL-cholesterol levels amongst groups. Yet, ObFO revealed lower levels of total cholesterol (TC; 30%) and triacylglycerol (TG; 33%) compared to Ob. Finally, since exposed to insulin, ObFO skeletal muscle revealed an increase of 10% in lactate production, 38% in glycogen synthesis and 39% in oxidation of glucose compared to Ob. CONCLUSIONS: Low dose of fish oil supplementation (1 g/kg/day) was able to reduce TC and TG levels, in addition to improved systemic and muscle insulin sensitivity. These results lend credence to the benefits of n-3 fatty acids upon the deleterious effects of insulin resistance mechanisms.

Dietary glutamate signal evokes gastric juice excretion in dogs.

BACKGROUND: Dietary-free L-glutamate (Glu) in the stomach interacts with specific Glu receptors (T1R1/T1R3 and mGluR1-8) expressed on surface epithelial and gastric gland cells. Furthermore, luminal Glu activates the vagal afferents in the stomach through the paracrine cascade including nitric oxide and serotonin (5-HT). AIM: To elucidate the role of dietary Glu in neuroendocrine control of the gastrointestinal phase of gastric secretion. METHODS: In Pavlov or Heidenhain gastric pouch dogs, secretion was measured in the pouch while monosodium glutamate (MSG) was intubated into the main stomach alone or in combination with liquid diets. RESULTS: In both experimental models, supplementation of the amino acid-rich diet with MSG (100 mmol/l) enhanced secretions of acid, pepsinogen and fluid, and elevated plasma gastrin-17. However, MSG did not affect secretion stimulated by the carbohydrate-rich diet and had no effect on basal secretion when applied in aqueous solution. Effects of MSG were abolished by denervation of the stomach and proximal small intestine with intragastrically applied lidocaine and partially suppressed with the 5-HT(3) receptor blocker granisetron. CONCLUSIONS: Supplementation of amino acid-rich liquid diets with MSG enhances gastrointestinal phase secretion through neuroendocrine pathways which are partially mediated by 5-HT. Possible mechanisms are discussed.

New frontiers in gut nutrient sensor research: monosodium L-glutamate added to a high-energy, high-protein liquid diet promotes gastric emptying: a possible therapy for patients with functional dyspepsia.

Functional dyspepsia is a clinical syndrome that features abdominal symptoms centered in the upper abdomen without an organic basis. Three possible mechanisms of gastric dysfunction could be related to functional dyspepsia: 1) delayed gastric emptying, 2) impaired gastric accommodation to food intake, and 3) hypersensitivity to gastric distention. Delayed gastric emptying has been suggested to lead to prolonged antral distension that causes dyspeptic symptoms. Delayed gastric emptying is therefore a focal point of debate about anorexia caused by dyspepsia, and prokinetic agents are often administered in Japan for its treatment. Recently, we found that addition of monosodium L-glutamate (MSG) to a high-energy liquid diet rich in casein promoted gastric emptying in healthy men. Therefore, another potential method to improve delayed gastric emptying could be enhancement of chemosensors that activate the autonomic nervous system innervating the gastrointestinal tract. In conclusion, enrichment with glutamate promoted gastric emptying after intake of a high-protein meal, suggesting that free glutamate is important for protein digestion and that MSG may be helpful for management of delayed gastric emptying in patients with functional dyspepsia.

Optimal preferred MSG concentration in potatoes, spinach and beef and their effect on intake in institutionalized elderly people.

BACKGROUND: Elderly people may benefit from sensory stimulation to increase food intake since anorexia of ageing is prevalent among them. An optimal MSG concentration may increase the palatability of foods but this depends on the food and chemosensory status of the taster. Currently, the results on taste enhancing to increase intake are inconsistent. OBJECTIVE: To find an optimal preferred MSG concentration in mashed potatoes, spinach and ground beef and to determine whether this concentration increases consumption of these foods among institutionalized elderly people. DESIGN: Single blind within subject cross-over study performed at the laboratory and in the residents' own apartments. PARTICIPANTS: 33 elderly and 29 young people in the sensory study and 53 elderly people in the intake study. MEASUREMENTS: Pleasantness of the foods was rated of the foods each with 0, 0.5, 0.8, 1.3 and 2.0 g of MSG/100g. Intake was measured by weighing back leftovers of 2 meals with MSG (0.5% in mashed potatoes, 2% in spinach and ground meat) and without MSG. RESULTS: 0.5% MSG (p < 0.05) was preferred in mashed potatoes but no optimal preferred concentration was found for spinach and ground beef, possibly because of their complex taste. Intake was not different between the foods with and without MSG or the total meal (all p > 0.68). CONCLUSION: MSG (0.5% and 2%) does not guarantee a higher intake among elderly. The chemosensory heterogeneity of the elderly population requires more individual flavor enhancement to improve the dietary intake and sensory experience.