Brain Activation by Umami Substances via Gustatory and Visceral Signaling Pathways, and Physiological Significance

Kondoh, Takashi; Torii, Kunio

doi:10.1248/bpb.31.1827

Cited by 36 publications

(39 citation statements)

References 31 publications

(32 reference statements)

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“…Furthermore, these investigators made use of intragastric infusions of complex carbohydrates and proteins (polycose vs casein, respectively), raising the possibility that digestive processes independent from postabsorptive metabolic processes influenced the behavioral choices. More recently, an interesting series of studies by Kondoh, Torii, and colleagues have demonstrated specific postingestive effects produced by L-glutamate versus glucose in flavor nutrient-conditioning paradigms (Kondoh and Torii, 2008). In addition to sugar versus L-amino acid conditioning having occurred during different sessions, this latest study differs from ours with respect to the glucose concentrations used: Kondoh et al (2008) intentionally used molar glucose concentrations that are insufficient to induce conditioning (ϳ60 mM).…”

Section: Discussionmentioning

confidence: 82%

“…More recently, an interesting series of studies by Kondoh, Torii, and colleagues have demonstrated specific postingestive effects produced by L-glutamate versus glucose in flavor nutrient-conditioning paradigms (Kondoh and Torii, 2008). In addition to sugar versus L-amino acid conditioning having occurred during different sessions, this latest study differs from ours with respect to the glucose concentrations used: Kondoh et al (2008) intentionally used molar glucose concentrations that are insufficient to induce conditioning (ϳ60 mM). Future studies must directly compare the postingestive effects produced by complex carbohydrates and proteins.…”

Section: Discussionmentioning

confidence: 82%

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Nutrient Selection in the Absence of Taste Receptor Signaling

Ren¹,

Ferreira²,

Zhou³

et al. 2010

Journal of Neuroscience

141

161

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When allowed to choose between different macronutrients, most animals display a strong attraction toward carbohydrates compared with proteins. It remains uncertain, however, whether this food selection pattern depends primarily on the sensory properties intrinsic to each nutrient or, alternatively, metabolic signals can act independently of the hedonic value of sweetness to stimulate elevated sugar intake. Here we show that Trpm5 Ϫ/Ϫ mice, which lack the cellular mechanisms required for sweet and several forms of L-amino acid taste transduction, develop a robust preference for D-glucose compared with isocaloric L-serine independently of the perception of sweetness. Moreover, a close relationship was found between glucose oxidation and taste-independent nutrient intake levels, with animals increasing intake as a function of glucose oxidation rates. Furthermore, microdialysis measurements revealed nutrient-specific dopaminergic responses in accumbens and dorsal striatum during intragastric infusions of glucose or serine. Specifically, intragastric infusions of glucose induced significantly higher levels of dopamine release compared with isocaloric serine in both ventral and dorsal striatum. Intragastric stimulation of dopamine release seemed to depend on glucose utilization, because administration of an anti-metabolic glucose analog resulted in lower dopamine levels in striatum, an effect that was reversed by intravenous glucose infusions. Together, our findings suggest that carbohydrate-specific preferences can develop independently of taste quality or caloric load, an effect associated with the ability of a given nutrient to regulate glucose metabolism and stimulate brain dopamine centers.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 82%

Nutrient Selection in the Absence of Taste Receptor Signaling

Ren¹,

Ferreira²,

Zhou³

et al. 2010

Journal of Neuroscience

141

161

View full text Add to dashboard Cite

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“…The remaining glutamate units are used for the biosynthesis of amino acids (aspartate, alanine, proline), glutathione or proteins. Therefore, glutamate levels in the blood and brain remain stable for several hours following food intake (2,26,61).…”

Section: Glutamate Transporters and Absorptionmentioning

confidence: 99%

“…Ingestion of MSG solutions (240-600 mM) is clearly reduced after selective abdominal vagotomy (24,26). The strengths of the va go t om y -i nd u ce d re du c ti o ns are as fo l lo w s: subdiaphragmatic total vagotomy (TVX) = gastric vagotomy > celiac vagotomy > hepatic vagotomy = intact controls.…”

Section: Effects Of Vagotomy On Msg Ingestive Behaviormentioning

confidence: 99%

“…Some of these brain areas might be responsive to luminal glutamate through activation of vagal afferents. Functional magnetic resonance imaging (fMRI) studies in anesthetized rats indicate that intragastric administration of nutritive substances [glucose, MSG and NaCl at 60 mM which correspond to the most preferred concentration of MSG by rats (24)(25)(26)] activates a number of brain areas, including the cortex, basal ganglia, limbic system, and hypothalamus (23,(26)(27)(28)51). All of these regions receive vagal information through the NST (4).…”

Section: Forebrain Activation By Intragastric Nutrient Administrationmentioning

confidence: 99%

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Physiological Significance of Glutamate Signaling in Gut-Brain Communication

Kondoh

Mallick

Torii

2009

Bioscience Microflora

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L-Glutamate is involved in the perception of umami taste, intermediary metabolism, and excitatory neurotransmission. In addition, recent studies have uncovered a variety of physiological roles for dietary glutamate, as evidenced by the fact that intragastric glutamate infusions induce flavor preference learning in rats. Moreover, glutamate increases digestive juice secretion and gastric emptying of protein-rich meals. Glutamate levels in blood and brain remain stable all day long even after the food intake since most of glutamate absorbed is oxidized in the mucosa of the small intestine as a primary energy source. Chronic ad libitum ingestion of glutamate solution contributes to reducing weight gain, fat deposition, and plasma leptin levels in comparison to ingestion of water. Glutamate receptors and their cellular transduction molecules have recently been identified in gut epithelial cells. Stimulation of gut glutamate receptors enhances the apical expression of glutamate transporters and also triggers the release of nitric oxide. Nitric oxide in its turn induces gut serotonin release, which increases vagal afferent inputs to different brain regions. Notably, three brain areas, i.e., the medial preoptic area, the dorsomedial nucleus of the hypothalamus, and the habenular nucleus are activated by intragastric glutamate infusions. Total subdiaphragmatic vagotomy abolishes this response. Consistent with the above, vagotomy specifically reduces the overall intake of glutamate. Taken together, these findings contribute to the growing body of evidence indicating that glutamate signaling via dedicated taste and gut receptors influences multiple physiological functions including gut secretion, motility, digestion, absorption, metabolism and energy homeostasis.

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