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Yoshida R, Ninomiya Y. Mechanisms and Functions of Sweet Reception in Oral and Extraoral Organs. Int J Mol Sci 2024; 25:7398. [PMID: 39000505 PMCID: PMC11242429 DOI: 10.3390/ijms25137398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 06/27/2024] [Accepted: 07/03/2024] [Indexed: 07/16/2024] Open
Abstract
The oral detection of sugars relies on two types of receptor systems. The first is the G-protein-coupled receptor TAS1R2/TAS1R3. When activated, this receptor triggers a downstream signaling cascade involving gustducin, phospholipase Cβ2 (PLCβ2), and transient receptor potential channel M5 (TRPM5). The second type of receptor is the glucose transporter. When glucose enters the cell via this transporter, it is metabolized to produce ATP. This ATP inhibits the opening of KATP channels, leading to cell depolarization. Beside these receptor systems, sweet-sensitive taste cells have mechanisms to regulate their sensitivity to sweet substances based on internal and external states of the body. Sweet taste receptors are not limited to the oral cavity; they are also present in extraoral organs such as the gastrointestinal tract, pancreas, and brain. These extraoral sweet receptors are involved in various functions, including glucose absorption, insulin release, sugar preference, and food intake, contributing to the maintenance of energy homeostasis. Additionally, sweet receptors may have unique roles in certain organs like the trachea and bone. This review summarizes past and recent studies on sweet receptor systems, exploring the molecular mechanisms and physiological functions of sweet (sugar) detection in both oral and extraoral organs.
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Affiliation(s)
- Ryusuke Yoshida
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan
- Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan
| | - Yuzo Ninomiya
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan
- Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA
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Langhans W, Watts AG, Spector AC. The elusive cephalic phase insulin response: triggers, mechanisms, and functions. Physiol Rev 2023; 103:1423-1485. [PMID: 36422994 PMCID: PMC9942918 DOI: 10.1152/physrev.00025.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 11/04/2022] [Accepted: 11/20/2022] [Indexed: 11/25/2022] Open
Abstract
The cephalic phase insulin response (CPIR) is classically defined as a head receptor-induced early release of insulin during eating that precedes a postabsorptive rise in blood glucose. Here we discuss, first, the various stimuli that elicit the CPIR and the sensory signaling pathways (sensory limb) involved; second, the efferent pathways that control the various endocrine events associated with eating (motor limb); and third, what is known about the central integrative processes linking the sensory and motor limbs. Fourth, in doing so, we identify open questions and problems with respect to the CPIR in general. Specifically, we consider test conditions that allow, or may not allow, the stimulus to reach the potentially relevant taste receptors and to trigger a CPIR. The possible significance of sweetness and palatability as crucial stimulus features and whether conditioning plays a role in the CPIR are also discussed. Moreover, we ponder the utility of the strict classical CPIR definition based on what is known about the effects of vagal motor neuron activation and thereby acetylcholine on the β-cells, together with the difficulties of the accurate assessment of insulin release. Finally, we weigh the evidence of the physiological and clinical relevance of the cephalic contribution to the release of insulin that occurs during and after a meal. These points are critical for the interpretation of the existing data, and they support a sharper focus on the role of head receptors in the overall insulin response to eating rather than relying solely on the classical CPIR definition.
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Affiliation(s)
- Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, Schwerzenbach, Switzerland
| | - Alan G Watts
- Department of Biological Sciences, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida
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Tsan L, Chometton S, Hayes AM, Klug ME, Zuo Y, Sun S, Bridi L, Lan R, Fodor AA, Noble EE, Yang X, Kanoski SE, Schier LA. Early-life low-calorie sweetener consumption disrupts glucose regulation, sugar-motivated behavior, and memory function in rats. JCI Insight 2022; 7:e157714. [PMID: 36099052 PMCID: PMC9714783 DOI: 10.1172/jci.insight.157714] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 09/12/2022] [Indexed: 01/12/2023] Open
Abstract
Low-calorie sweetener (LCS) consumption in children has increased dramatically due to its widespread presence in the food environment and efforts to mitigate obesity through sugar replacement. However, mechanistic studies on the long-term impact of early-life LCS consumption on cognitive function and physiological processes are lacking. Here, we developed a rodent model to evaluate the effects of daily LCS consumption (acesulfame potassium, saccharin, or stevia) during adolescence on adult metabolic, behavioral, gut microbiome, and brain transcriptomic outcomes. Results reveal that habitual early-life LCS consumption impacts normal postoral glucose handling and impairs hippocampal-dependent memory in the absence of weight gain. Furthermore, adolescent LCS consumption yielded long-term reductions in lingual sweet taste receptor expression and brought about alterations in sugar-motivated appetitive and consummatory responses. While early-life LCS consumption did not produce robust changes in the gut microbiome, brain region-specific RNA-Seq analyses reveal LCS-induced changes in collagen- and synaptic signaling-related gene pathways in the hippocampus and nucleus accumbens, respectively, in a sex-dependent manner. Collectively, these results reveal that habitual early-life LCS consumption has long-lasting implications for glucoregulation, sugar-motivated behavior, and hippocampal-dependent memory in rats, which may be based in part on changes in nutrient transporter, sweet taste receptor, and central gene pathway expression.
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Affiliation(s)
- Linda Tsan
- Neuroscience Graduate Program and
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Sandrine Chometton
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Anna M.R. Hayes
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Molly E. Klug
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Yanning Zuo
- Department of Integrative Biology and Physiology, University of California at Los Angeles, Los Angeles, California, USA
| | - Shan Sun
- Department of Bioinformatics and Genomics at the University of North Carolina at Charlotte, Charlotte, North Carolina, USA
| | - Lana Bridi
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Rae Lan
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Anthony A. Fodor
- Department of Bioinformatics and Genomics at the University of North Carolina at Charlotte, Charlotte, North Carolina, USA
| | - Emily E. Noble
- Department of Nutritional Sciences, University of Georgia, Athens, Georgia, USA
| | - Xia Yang
- Department of Integrative Biology and Physiology, University of California at Los Angeles, Los Angeles, California, USA
| | - Scott E. Kanoski
- Neuroscience Graduate Program and
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
| | - Lindsey A. Schier
- Neuroscience Graduate Program and
- Department of Biological Sciences, Human and Evolutionary Biology Section, University of Southern California, Los Angeles, California, USA
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Abstract
Psychological and neural distinctions between the technical concepts of "liking" and "wanting" pose important problems for motivated choice for goods. Why could we "want" something that we do not "like," or "like" something but be unwilling to exert effort to acquire it? Here, we suggest a framework for answering these questions through the medium of reinforcement learning. We consider "liking" to provide immediate, but preliminary and ultimately cancellable, information about the true, long-run worth of a good. Such initial estimates, viewed through the lens of what is known as potential-based shaping, help solve the temporally complex learning problems faced by animals.
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Affiliation(s)
- Peter Dayan
- MPI for Biological Cybernetics, Tübingen, Germany
- University of Tübingen, Tübingen, Germany
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Malone IG, Hunter BK, Rossow HL, Herzog H, Zolotukhin S, Munger SD, Dotson CD. Y1 receptors modulate taste-related behavioral responsiveness in male mice to prototypical gustatory stimuli. Horm Behav 2021; 136:105056. [PMID: 34509673 PMCID: PMC8640844 DOI: 10.1016/j.yhbeh.2021.105056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 10/20/2022]
Abstract
Mammalian taste bud cells express receptors for numerous peptides implicated elsewhere in the body in the regulation of metabolism, nutrient assimilation, and satiety. The perturbation of several peptide signaling pathways in the gustatory periphery results in changes in behavioral and/or physiological responsiveness to subsets of taste stimuli. We previously showed that Peptide YY (PYY) - which is present in both saliva and in subsets of taste cells - can affect behavioral taste responsiveness and reduce food intake and body weight. Here, we investigated the contributions of taste bud-localized receptors for PYY and the related Neuropeptide Y (NPY) on behavioral taste responsiveness. Y1R, but not Y2R, null mice show reduced responsiveness to sweet, bitter, and salty taste stimuli in brief-access taste tests; similar results were seen when wildtype mice were exposed to Y receptor antagonists in the taste stimuli. Finally, mice in which the gene encoding the NPY propeptide was deleted also showed reduced taste responsiveness to sweet and bitter taste stimuli. Collectively, these results suggest that Y1R signaling, likely through its interactions with NPY, can modulate peripheral taste responsiveness in mice.
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Affiliation(s)
- Ian G Malone
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Brianna K Hunter
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Heidi L Rossow
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | | | - Sergei Zolotukhin
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA; Department of Pediatrics, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Steven D Munger
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA; Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL 32610, USA; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Cedrick D Dotson
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA.
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Yoshida R, Yasumatsu K, Ninomiya Y. The sweet taste receptor, glucose transporters, and the ATP-sensitive K+ (KATP) channel: sugar sensing for the regulation of energy homeostasis. CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2021.01.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Kendig MD, Martire SI, Boakes RA, Rooney KB. Comparable metabolic effects of isocaloric sucrose and glucose solutions in rats. Physiol Behav 2021; 229:113239. [PMID: 33152355 DOI: 10.1016/j.physbeh.2020.113239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/30/2020] [Accepted: 11/01/2020] [Indexed: 10/23/2022]
Abstract
Much of the global increase in sugar intake is attributable to rising consumption of sugar-sweetened beverages (SSBs). Because people compensate poorly for liquid calories, SSB consumption increases total energy intake, raising the risk of harmful metabolic effects in addition to possible effects of sugars per se. Glucose and fructose, the constituent sugars in sucrose, can exert distinct effects on metabolism and also differ in their satiating properties, suggesting that compensation for the calories in these sugars may also vary. In light of claims that the fructose within sucrose is particularly harmful, the present study compared the effects of giving rats access to either a sucrose or an isoenergetic glucose solution. Adult male rats were fed standard chow and water supplemented with 95 ml of 10% glucose (Glucose group; n = 10), 9% sucrose solution (Sucrose group; n = 10) or water only (Control group; n = 10) daily for 7 weeks. Sugar-fed groups had higher total energy intakes than the Control group, but the extent of this incomplete compensation did not vary between Sucrose and Glucose groups. In a short-term compensation test, sugar groups were less sensitive to the effects of a sweet pre-meal, with no differences between the Glucose and Sucrose groups. Relative to water, both sugars reduced insulin sensitivity after 4 weeks on the diets and elevated fat mass at 7 weeks. Results suggest that sucrose and glucose induce comparable metabolic impairments and alter the homeostatic regulation of food intake even under conditions where daily access is capped.
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Affiliation(s)
- Michael D Kendig
- School of Psychology, University of Sydney, NSW, 2006, Australia.
| | - Sarah I Martire
- School of Psychology, University of Sydney, NSW, 2006, Australia.
| | - Robert A Boakes
- School of Psychology, University of Sydney, NSW, 2006, Australia.
| | - Kieron B Rooney
- Faculty of Medicine and Healthy, University of Sydney, NSW, 2006, Australia.
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Sclafani A, Zukerman S, Ackroff K. Residual Glucose Taste in T1R3 Knockout but not TRPM5 Knockout Mice. Physiol Behav 2020; 222:112945. [PMID: 32417232 DOI: 10.1016/j.physbeh.2020.112945] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/29/2020] [Accepted: 04/29/2020] [Indexed: 12/19/2022]
Abstract
Knockout (KO) mice missing the sweet taste receptor subunit T1R3 or the signaling protein TRPM5 have greatly attenuated sweetener preferences. Yet both types of KO mice develop preferences for glucose but not fructose in 24-h tests, which has been attributed to the postoral reinforcing actions of glucose. Here we probed for residual sugar taste sensitivity in KO mice. Unlike wildtype (WT) mice, food-restricted T1R3 KO and TRPM5 KO mice displayed little attraction for 8% glucose and 8% fructose in 1-min, two-bottle choice tests. However, in 1-h tests about half of the T1R3 KO mice displayed a significant preference for glucose over fructose (78-84%), while WT mice showed either no or weak preferences (41-56%) for glucose. Following one-bottle training sessions, WT mice display greater glucose preferences although still weaker than those observed in T1R3 KO mice. In contrast, TRPM5 KO mice were indifferent to sugars in 1-h tests but developed a strong preference for glucose over fructose in 24-h tests. T1R3 taste cells contain the sodium glucose cotransporter 1 (SGLT1) and the ATP-gated K+ (KATP) metabolic sensor, which may mediate the unlearned glucose preference displayed by T1R3 KO mice. Unlike WT mice, many T1R3 KO mice strongly preferred glucose to a non-metabolizable glucose analog (α-methyl-D-glucopyranoside, MDG) in initial 1-h choice tests. Glucose and MDG are both ligands for SGLT1 which indicates that SGLT1 sensing does not mediate the glucose preference of T1R3 KO mice. Instead, KATP sensing and/or other oral sensors are implicated. The MDG findings also argue against postoral sensing as the primary source of the initial glucose preference displayed by T1R3 KO mice. Why only half of the T1R3 KO mice showed this preference in 1-h tests remains to be determined. All T1R3 KO mice preferred glucose to fructose in 24-h tests, which appears to be due to both oral and postoral glucose sensing.
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Affiliation(s)
- Anthony Sclafani
- Department of Psychology, Brooklyn College of City University of New York, Brooklyn, New York 11210, USA.
| | - Steven Zukerman
- Department of Psychology, Brooklyn College of City University of New York, Brooklyn, New York 11210, USA
| | - Karen Ackroff
- Department of Psychology, Brooklyn College of City University of New York, Brooklyn, New York 11210, USA
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