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Roberts A, Lynch B, Rietjens IMCM. Risk Assessment Paradigm for Glutamate. ANNALS OF NUTRITION AND METABOLISM 2018; 73 Suppl 5:53-64. [PMID: 30508819 DOI: 10.1159/000494783] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND Re-evaluation of the use of glutamic acid and glutamate salts (referred to as glutamate hereafter) by the European Food Safety Authority (EFSA) proposed a group acceptable daily intake (ADI) of 30 mg/kg body weight (bw)/day. SUMMARY This ADI is below the normal dietary intake, while even intake of free glutamate by breast-fed babies can be above this ADI. In addition, the pre-natal developmental toxicity study selected by EFSA, has never been used by regulatory authorities worldwide for the safety assessment of glutamate despite it being available for nearly 40 years. Also, the EFSA ignored that toxicokinetic data provide support for eliminating the use of an uncertainty factor for interspecies differences in kinetics. Key Messages: A 3-generation reproductive toxicity study in mice that includes extensive brain histopathology, provides a better point of departure showing no effects up to the highest dose tested of 6,000 mg/kg bw/day. Furthermore, kinetic data support use of a compound-specific uncertainty factor of 25 instead of 100. Thus, an ADI of at least 240 mg/kg bw/day would be indicated. In fact, there is no compelling evidence to indicate that the previous ADI of "not specified" warrants any change.
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Affiliation(s)
- Ashley Roberts
- Intertek Scientific and Regulatory Consultancy Health, Environmental and Regulatory Services (HERS), Mississauga, Ontario, Canada
| | - Barry Lynch
- Intertek Scientific and Regulatory Consultancy Health, Environmental and Regulatory Services (HERS), Mississauga, Ontario, Canada
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Schoelch C, Hübschle T, Schmidt I, Nuesslein-Hildesheim B. MSG lesions decrease body mass of suckling-age rats by attenuating circadian decreases of energy expenditure. Am J Physiol Endocrinol Metab 2002; 283:E604-11. [PMID: 12169455 DOI: 10.1152/ajpendo.00439.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Suckling-age rats display endogenous circadian rhythmicity of metabolic rate (MR) with energy-saving, torpor-like decreases, which are sympathetically controlled and suppressed by leptin treatment. We investigated whether neonatal monosodium glutamate (MSG) treatment, known to cause arcuate nucleus damage and adult-age obesity, alters energy balance in the first two postnatal weeks. Continuously recorded MR and core temperatures (T(c)) show that MSG treatment disinhibits the periodic, sympathetically controlled, energy-saving drops of T(c) and MR. Increased energy expenditure thus explains reduced body fat at normal lean body mass found in MSG-treated pups artificially nourished identically to controls. In MSG-treated mother-reared pups, lean body mass is additionally reduced, suggesting that MSG also reduces suckling. Plasma leptin levels are similar in controls and MSG-treated pups but higher per unit of fat mass in the latter. We conclude that the postweaning development of MSG obesity and depressed thermogenesis are preceded by an early phase of increased energy expenditure with decreased fat deposition during suckling age and hypothesize cell damage in the arcuate nucleus to be involved in both.
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Affiliation(s)
- Corinna Schoelch
- Max-Planck-Institut für Physiologische und Klinische Forschung, W. G. Kerckhoff-Institut, D-61231 Bad Nauheim, Germany
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Nemeroff CB, Grant LD, Bissette G, Ervin GN, Harrell LE, Prange AJ. Growth, endocrinological and behavioral deficits after monosodium L-glutamate in the neonatal rat: possible involvement of arcuate dopamine neuron damage. Psychoneuroendocrinology 2001; 2:179-96. [PMID: 601168 DOI: 10.1016/0306-4530(77)90023-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Ebling FJ, Arthurs OJ, Turney BW, Cronin AS. Seasonal neuroendocrine rhythms in the male Siberian hamster persist after monosodium glutamate-induced lesions of the arcuate nucleus in the neonatal period. J Neuroendocrinol 1998; 10:701-12. [PMID: 9744488 DOI: 10.1046/j.1365-2826.1998.00253.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The aim of these experiments was to examine the role of the arcuate nucleus in the control of seasonal cycles of body weight, feed intake, moulting and reproduction in the Siberian hamster. The arcuate nucleus has previously been implicated as a central site where systemic feedback signals (e.g. leptin) might act to regulate feed intake and body weight, so it was predicted that hamsters with lesions of this structure would be unable to display the inhibitory effects of short days on these parameters. In the first series of studies, lesions that destroyed approximately 80% of the cells in the arcuate nucleus were produced by treating hamsters neonatally with monosodium glutamate (MSG; 4 mg/g body weight sc), and vehicle- and MSG-treated males were raised from birth in long days (LD) or short days (SD). In hamsters raised in LD, the initial gain in body weight and testicular growth were significantly reduced by MSG treatment, however, growth rate and testis weight were still significantly greater than in vehicle- or MSG-treated hamsters raised in SD. In the second study, hamsters treated neonatally with vehicle or MSG were raised in LD for 8 weeks and, subsequently, approximately half in each group were transferred to SD for 18 weeks. As expected, vehicle-treated hamsters showed a characteristic decline in body weight when exposed to SD, while those remaining in LD continued to increase body weight. Feed intake decreased in parallel with the decline in body weight in SD, a complete moult to the white winter pelage occurred by 16 weeks in SD, and testicular regression occurred. Responses to SD also occurred in the MSG-treated hamsters: body weight decreased in SD but increased in their lesioned litter mates remaining in LD, and feed intake paralleled body weight changes in these groups. The moult to winter pelage was significantly retarded in MSG-treated hamsters transferred to SD. The testes were completely regressed in sham- and MSG-treated hamsters exposed to SD, whereas testes weights in MSG-treated hamsters maintained in LD were intermediate between those in vehicle-treated hamsters in SD and LD. Thus, despite initial effects on growth, the MSG-treated hamsters bearing substantial lesions of the arcuate nucleus were able to show appropriate responses to photoperiod, although not always of the same magnitude as the unlesioned controls. We conclude that feedback mechanisms operating via the arcuate nucleus are not the major regulators of seasonal cycles of body weight, feed intake, pelage and reproduction.
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Affiliation(s)
- F J Ebling
- Department of Anatomy, University of Cambridge, Downing Site, UK
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Rietveld WJ, Meijer JH, Ruis J, Buys P. The effect of neonatal administration of monosodium glutamate on the circadian control of food intake in the rat. ACTA ACUST UNITED AC 1986. [DOI: 10.1080/09291018609359924] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Goldman M, Stowe GE. The modifying influence of aging on behavior in mice neonatally injected with monosodium glutamate. Psychopharmacology (Berl) 1985; 86:359-64. [PMID: 3929306 DOI: 10.1007/bf00432229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Newborn mice were injected with monosodium glutamate (MSG), and behavioral testing and physical development in neonatal, juvenile, adult, and aged mice were observed by means of a battery of appropriate tests. Early exposure to MSG resulted in altered behavioral performances postnatally, which were transitory and reflected the neurotoxicity of the chemical. Although behavioral deficits were not observed in mice neonatally treated with MSG at 1 month of age, a definite decline was manifested at 12 months and 34 months of age.
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Dalkin AC, Duncan JA, Regiani S, Marshall JC. Reduction of pituitary GnRH receptors in immature rats treated with monosodium glutamate. THE AMERICAN JOURNAL OF PHYSIOLOGY 1985; 248:E126-31. [PMID: 2981479 DOI: 10.1152/ajpendo.1985.248.1.e126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The number of pituitary gonadotropin-releasing hormone (GnRH) receptors increases during sexual maturation in the rat and probably reflects changes in hypothalamic GnRH secretion. As GnRH is synthesized in various hypothalamic nuclei, including the arcuate nucleas (ARC), we investigated the effects of monosodium glutamate (MSG)-induced lesions of the ARC in the rat. In males and females treated with MSG during the first 10 days of life, GnRH receptor content (GnRH-RC) was unchanged from controls at 10 days but was decreased at 20 and 30 days of age (P less than 0.01). Serum concentrations of luteinizing hormone (LH) were similar in MSG-treated and control males but were significantly lower in 10-day-old females (P less than 0.01). Injections of GnRH (3 micrograms every 8 h on days 18 and 19) restored GnRH-RC to control values in MSG-treated rats. Both MSG and untreated control rats showed similar LH responses to acute injections of GnRH, but responses were attenuated (P less than 0.05) after 2 days pretreatment with GnRH in rats that had received MSG. Ovarian GnRH-RC was similar in both MSG-treated and untreated controls. These data indicate that MSG-induced lesions of the ARC reduce pituitary GnRH-RC in immature rats, and the more marked effects in females suggest a more significant role in the ARC in the control of GnRH secretion during maturation in females. The lack of MSG-induced changes in ovarian GnRH-RC indicates that GnRH from the arcuate nucleus is not responsible for the increase in ovarian GnRH receptors seen during sexual maturation.
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Abstract
This review provides extensive presentation and evaluation of data relative to flavor potentiation, including the historical, chemical, organoleptic, metabolic, physiological, and consumptive properties of the commonly available flavor potentiators, which are primarily monosodium glutamate and 5'-nucleotides. In addition, their food occurrences, mode of action, manufacturing procedures, and methods of analyses will be discussed. Also, attention will be given to miscellaneous compounds that possess flavor potentiating properties.
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Garris DR, Smith C, Davis D, Diani AR, Gerritsen GC. Morphometric evaluation of the hypothalamic-ovarian axis of the ketonuric, diabetic Chinese hamster: relationship to the reproductive cycle. Diabetologia 1982; 23:275-9. [PMID: 6890001 DOI: 10.1007/bf00252855] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The relationship between diabetes and the morphological alterations which occur in hypothalamic and ovarian tissue was examined in the long-term, ketonuric-diabetic Chinese hamster. Matched diabetic and non-diabetic control hamsters were inspected daily for changes in the reproductive cycle by vaginal lavage. On dioestrus, animals were perfused, the hypothalamus and ovaries collected, prepared for microscopy and morphometrically analyzed. The nuclei in the medial basal hypothalamus of diabetic hamsters exhibited a decreased area (p less than 0.01) and neuronal population (p less than 0.05-0.01) compared with controls. The ovaries of the diabetic animals had a reduced follicular population (p less than or equal to 0.05) and an increased atresia rate (p less than or equal to 0.05) compared with controls. In addition, all diabetic hamsters were acyclic. In diabetic animals, the corpora luteal cells contained a reduced lipid content (p less than or equal to 0.001) which was possibly functionally related to a significant decline in serum progesterone levels (p less than or equal to 0.01). Based on these results it is suggested that the hypothalamic-ovarian axis is both morphologically and functionally impaired in the diabetic hamster.
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Takasaki Y, Sekine S, Matsuzawa Y, Iwata S, Sasaoka M. Effects of parenteral and oral administration of monosodium l-glutamate (MSG) on somatic growth in rats. Toxicol Lett 1979. [DOI: 10.1016/0378-4274(79)90044-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Studies on reproductive endocrine function in rats treated with monosodium l-glutamate early in life. Toxicol Lett 1979. [DOI: 10.1016/0378-4274(79)90046-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Eskay RL, Brownstein MJ, Long RT. alpha-Melanocyte-stimulating hormone: reduction in adult rat brain after monosodium glutamate treatment of neonates. Science 1979; 205:827-9. [PMID: 462194 DOI: 10.1126/science.462194] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Intraperitoneal injection of monosodium glutamate in neonatal rates resulted in a 90 percent loss of alpha-melanocyte-stimulating hormone in hypothalamic and extrahypothalamic areas of the brain, whereas the amount of hormone in the pituitary gland did not change. The dramatic reduction of alpha-melanocyte-stimulating hormone in the brain suggests that is primary source there is the neuronal perikarya of the arcuate nucleus.
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Pizzi WJ, Tabor JM, Barnhart JE. Somatic, behavioral, and reproductive disturbances in mice following neonatal administration of sodium L-aspartate. Pharmacol Biochem Behav 1978; 9:481-5. [PMID: 733835 DOI: 10.1016/0091-3057(78)90046-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Sodium L-aspartate (ASP) was administered to neonatal mice according to an increasing dose schedule from Days 2--11 after birth. Adult ASP-treated animals showed large increases in body weight over controls along with stunted body length. The ASP group also showed decreases in locomotor and exploratory behavior. Reproductive dysfunction occurred in both female and male ASP-treated animals. Among treated animals, females had fewer pregnancies and smaller litters while males showed reduced fertility. Evidence of multiple endocrine dysfunction in ASP-treated animals was reflected by decreased pituitary, thyroid, ovaries and tested weights, along with delayed onset of puberty in females. These results demonstrate that sodium L-aspartate produces a syndrome similar to that seen following the administration of monosodium L-glutamate.
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Shinobu Y, Yoshimasa M. Effect of monosodium glutamate on serum luteinizing hormone and testosterone in adult male rats. Toxicol Lett 1978. [DOI: 10.1016/0378-4274(78)90049-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Cameron DP, Cutbush L, Opat F. Effects of monosodium glutamate-induced obesity in mice on carbohydrate metabolism in insulin secretion. Clin Exp Pharmacol Physiol 1978; 5:41-51. [PMID: 639358 DOI: 10.1111/j.1440-1681.1978.tb00650.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
1. The syndrome of obesity induced by neonatal injection of monosodium glutamate (MSG) has been further studied in mice. In confirmation of previous studies stunting and decreased pituitary and gonadal weights were observed. 2. After weaning food intake was consistently less in MSG-treated than control mice. Body lipid stores were significantly elevated in MSG-treated mice by 2 weeks of age and increased progressively up to 4 months. 3. Plasma glucose was comparable between MSG-treated and control mice in the fed state whereas after an overnight fast MSG-treated mice exhibited relative hypoglycaemia. 4. Obese MSG-treated mice did not exhibit resistance to exogenous insulin and disposed of an intravenous glucose load more rapidly than control mice. 5. Hyperinsulinaemia was present inconsistently in both fed and fasted mice and in response to administered glucose. 6. Neonatal administration of MSG provides a useful additional model for studying the role of the hypothalamus in obesity.
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Pizzi WJ, Barnhart JE, Fanslow DJ. Monosodium glutamate admlinistration to the newborn reduces reproductive ability in female and male mice. Science 1977; 196:452-4. [PMID: 557837 DOI: 10.1126/science.557837] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Monosodium glutamate (MSG) administered during the neonatal period (days 2 to 11) resulted in a sequence of events that were manifested in adulthood. Reproductive dysfunction was seen in both female and male animals. Females treated with MSG had fewer pregnancies and smaller litters, while males treated with MSG showed reduced fertility. The MSG-treated mice showed increased body weight and decreased pituitary, thyroid, ovary, or testis weights.
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Olney JW, Cicero TJ, Meyer ER, de Gubareff T. Acute glutamate-induced elevations in serum testosterone and luteinizing hormone. Brain Res 1976; 112:420-4. [PMID: 782658 DOI: 10.1016/0006-8993(76)90298-5] [Citation(s) in RCA: 85] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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