1
|
Song J. Amygdala activity and amygdala-hippocampus connectivity: Metabolic diseases, dementia, and neuropsychiatric issues. Biomed Pharmacother 2023; 162:114647. [PMID: 37011482 DOI: 10.1016/j.biopha.2023.114647] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 03/30/2023] [Accepted: 03/31/2023] [Indexed: 04/04/2023] Open
Abstract
With rapid aging of the population worldwide, the number of people with dementia is dramatically increasing. Some studies have emphasized that metabolic syndrome, which includes obesity and diabetes, leads to increased risks of dementia and cognitive decline. Factors such as insulin resistance, hyperglycemia, high blood pressure, dyslipidemia, and central obesity in metabolic syndrome are associated with synaptic failure, neuroinflammation, and imbalanced neurotransmitter levels, leading to the progression of dementia. Due to the positive correlation between diabetes and dementia, some studies have called it "type 3 diabetes". Recently, the number of patients with cognitive decline due to metabolic imbalances has considerably increased. In addition, recent studies have reported that neuropsychiatric issues such as anxiety, depressive behavior, and impaired attention are common factors in patients with metabolic disease and those with dementia. In the central nervous system (CNS), the amygdala is a central region that regulates emotional memory, mood disorders, anxiety, attention, and cognitive function. The connectivity of the amygdala with other brain regions, such as the hippocampus, and the activity of the amygdala contribute to diverse neuropathological and neuropsychiatric issues. Thus, this review summarizes the significant consequences of the critical roles of amygdala connectivity in both metabolic syndromes and dementia. Further studies on amygdala function in metabolic imbalance-related dementia are needed to treat neuropsychiatric problems in patients with this type of dementia.
Collapse
Affiliation(s)
- Juhyun Song
- Department of Anatomy, Chonnam National University Medical School, Hwasun 58128, Jeollanam-do, Republic of Korea.
| |
Collapse
|
2
|
Chia CW, Yeager SM, Egan JM. Endocrinology of Taste with Aging. Endocrinol Metab Clin North Am 2023; 52:295-315. [PMID: 36948781 PMCID: PMC10037529 DOI: 10.1016/j.ecl.2022.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Taste is one of our five primary senses, and taste impairment has been shown to increase with aging. The ability to taste allows us to enjoy the food we eat and to avoid foods that are potentially spoiled or poisonous. Recent advances in our understanding of the molecular mechanisms of taste receptor cells located within taste buds help us decipher how taste works. The discoveries of "classic" endocrine hormones in taste receptor cells point toward taste buds being actual endocrine organs. A better understanding of how taste works may help in reversing taste impairment associated with aging.
Collapse
Affiliation(s)
- Chee W Chia
- Intramural Research Program, National Institute on Aging, National Institutes of Health, 3001 S. Hanover Street, 5th Floor, Room NM536, Baltimore, MD 21225, USA
| | - Shayna M Yeager
- Intramural Research Program, National Institute on Aging, National Institutes of Health, 3001 S. Hanover Street, 5th Floor, Room NM547, Baltimore, MD 21225, USA
| | - Josephine M Egan
- Intramural Research Program, National Institute on Aging, National Institutes of Health, 3001 S. Hanover Street, 5th Floor, Room NM527, Baltimore, MD 21225, USA.
| |
Collapse
|
3
|
Sun H, Li J, Yan J, Sun B, Wei X, Song L, Yan J. Decreased taste sensitivity to sucrose in dopamine D3 receptor mutant mice. Chem Senses 2022; 47:6619054. [PMID: 35762652 DOI: 10.1093/chemse/bjac014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dopamine plays a key role in food rewards and sweet-taste stimulation. We examined the basis for behavioral responses to sweet taste in dopamine D3 receptor-deficient (D3-/-) mice by determining whether the absence of D3 receptors affects the sensitivity to dilute sucrose solutions. In experiment 1, we measured the intensity generalization threshold of conditioned taste aversion (CTA) to a 0.2 M sucrose solution. Results showed that the generalization thresholds were 0.025-0.05 M in D3-/- mice and 0.0025-0.005 M in wild-type (WT) mice. In experiment 2, we found that D3-/- and WT mice had similar capabilities to form and extinguish CTAs. Since the intensity generalization threshold is mainly due to a combination of sweet-taste sensitivity and the robust nature of CTA formation, the results showed that taste sensitivity to sucrose in D3-/- mice was lower than that in WT mice. In experiment 3, to test whether the peripheral sensory signaling may also be affected by the disruption of the dopamine D3 receptors, the mRNA expression levels of sweet-taste-related proteins in taste buds of D3-/- mice were determined. The T1R1 and BDNF mRNA expression levels in D3-/- mice were higher than the controls, whereas T1R2, T1R3, α-gustducin, and TRPM5 mRNA were similar. These findings suggest that disruption of dopamine D3 receptor-mediated signaling decreases the sweet-taste sensitivity and alters the mRNA expression levels of some taste-related molecules.
Collapse
Affiliation(s)
- Huiling Sun
- Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, Research Center of Stomatology College, Xi'an Jiaotong University, 98 Xi Wu Road, Xi'an, Shaanxi 710004, P.R. China.,Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Jinrong Li
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Junbao Yan
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Bo Sun
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Xiaojing Wei
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Lin Song
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| | - Jianqun Yan
- Department of Physiology and Pathophysiology, Health Science Center, Xi'an Jiaotong University, 76 West Yan Ta Road, Xi'an, Shaanxi 710061, P.R. China
| |
Collapse
|
4
|
Meta-analysis of cognitive and behavioral tests in leptin- and leptin receptor-deficient mice. Neurosci Res 2020; 170:217-235. [PMID: 33316303 DOI: 10.1016/j.neures.2020.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 10/06/2020] [Accepted: 11/11/2020] [Indexed: 01/19/2023]
Abstract
Leptin is a hormone produced by adipocytes that regulates food intake and metabolism. Leptin-related gene-deficient mice, such as db/db and ob/ob mice, are widely used to study diabetes and its related diseases. However, broad effects of leptin appear to cause variability in behavioral test results. We performed a meta-analysis of major behavioral tests in db/db and ob/ob mice. These mice exhibited significant impairments in the Morris water maze, forced swim, novel object recognition, Y-maze, tail suspension, and light-dark box tests, whereas the elevated plus maze and open field tests did not reveal significant changes. We also performed correlation and regression analyses between the animals' performances and the experimental protocols and conditions. The memory-related tests were characterized by the correlations of their results with animal age, while the performances in the elevated plus-maze and forced swim tests were affected by the width of the devices used. In conclusion, db/db and ob/ob mice mainly exhibit memory deficits and depression-like behavior, although experimenters should be aware of animal age and device size in conducting experiments.
Collapse
|
5
|
McCluskey LP, He L, Dong G, Harris R. Chronic exposure to liquid sucrose and dry sucrose diet have differential effects on peripheral taste responses in female rats. Appetite 2019; 145:104499. [PMID: 31669578 DOI: 10.1016/j.appet.2019.104499] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/18/2019] [Accepted: 10/22/2019] [Indexed: 11/29/2022]
Abstract
Sugar-sweetened beverages are the major source of added calories in the Western diet and their prevalence is associated with obesity and metabolic disruption. Despite the critical role of the taste system in determining food selection and consumption, the effects of chronic sucrose consumption on the peripheral taste system in mammals have received limited attention. We offered female Sprague Dawley rats free access to water and one of three diets for up to 40 days: (1) sucrose-free chow or "NS" diet; (2) a high-sucrose dry diet or "HS"; or (3) 30% sucrose solution and the NS diet, designated "LiqS" diet. Sucrose consumption by LiqS rats gradually increased and by day 14 was equal to that of HS rats. Food intake decreased in LiqS rats, but their energy intake remained higher than for NS or HS rats. There was no significant difference in weight gain of the groups during the study. Recordings from the chorda tympani nerve (CT), which innervates taste buds on the anterior tongue, revealed decreased responses to 1 M sucrose in both LiqS and HS rats and to acesulfame K and salt tastants in LiqS rats after 40 days on diet. Umami, bitter, and acid response magnitudes were unchanged in both groups. These results demonstrate that chronic sucrose exposure inhibits taste responses to higher concentrations of sweet stimuli. More surprisingly, CT responses to NaCl and 0.5M NaAc were significantly reduced in rats on the LiqS diet. Thus, the physical form of the diet influences taste responsiveness to salt and sweet taste function. These data suggest that taste buds are previously unappreciated targets of chronic sucrose consumption.
Collapse
Affiliation(s)
- Lynnette Phillips McCluskey
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, United States.
| | - Lianying He
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, United States; Department of Pathology and Laboratory Medicine, Medical University of South Carolina, United States
| | - Guankuo Dong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, United States
| | - Ruth Harris
- Department of Physiology, Medical College of Georgia at Augusta University, United States
| |
Collapse
|
6
|
Recent Advances in Molecular Mechanisms of Taste Signaling and Modifying. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 323:71-106. [PMID: 26944619 DOI: 10.1016/bs.ircmb.2015.12.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The sense of taste conveys crucial information about the quality and nutritional value of foods before it is ingested. Taste signaling begins with taste cells via taste receptors in oral cavity. Activation of these receptors drives the transduction systems in taste receptor cells. Then particular transmitters are released from the taste cells and activate corresponding afferent gustatory nerve fibers. Recent studies have revealed that taste sensitivities are defined by distinct taste receptors and modulated by endogenous humoral factors in a specific group of taste cells. Such peripheral taste generations and modifications would directly influence intake of nutritive substances. This review will highlight current understanding of molecular mechanisms for taste reception, signal transduction in taste bud cells, transmission between taste cells and nerves, regeneration from taste stem cells, and modification by humoral factors at peripheral taste organs.
Collapse
|
7
|
Elson AE, Simerly RB. Developmental specification of metabolic circuitry. Front Neuroendocrinol 2015; 39:38-51. [PMID: 26407637 PMCID: PMC4681622 DOI: 10.1016/j.yfrne.2015.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 09/18/2015] [Accepted: 09/21/2015] [Indexed: 01/16/2023]
Abstract
The hypothalamus contains a core circuitry that communicates with the brainstem and spinal cord to regulate energy balance. Because metabolic phenotype is influenced by environmental variables during perinatal development, it is important to understand how these neural pathways form in order to identify key signaling pathways that are responsible for metabolic programming. Recent progress in defining gene expression events that direct early patterning and cellular specification of the hypothalamus, as well as advances in our understanding of hormonal control of central neuroendocrine pathways, suggest several key regulatory nodes that may represent targets for metabolic programming of brain structure and function. This review focuses on components of central circuitry known to regulate various aspects of energy balance and summarizes what is known about their developmental neurobiology within the context of metabolic programming.
Collapse
Affiliation(s)
- Amanda E Elson
- The Saban Research Institute, Children's Hospital Los Angeles, University of Southern California, Keck School of Medicine, Los Angeles, CA 90027, USA
| | - Richard B Simerly
- The Saban Research Institute, Children's Hospital Los Angeles, University of Southern California, Keck School of Medicine, Los Angeles, CA 90027, USA.
| |
Collapse
|
8
|
Castanon N, Luheshi G, Layé S. Role of neuroinflammation in the emotional and cognitive alterations displayed by animal models of obesity. Front Neurosci 2015; 9:229. [PMID: 26190966 PMCID: PMC4490252 DOI: 10.3389/fnins.2015.00229] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 06/11/2015] [Indexed: 12/15/2022] Open
Abstract
Obesity is associated with a high prevalence of mood disorders and cognitive dysfunctions in addition to being a significant risk factor for important health complications such as cardiovascular diseases and type 2 diabetes. Identifying the pathophysiological mechanisms underlying these health issues is a major public health challenge. Based on recent findings, from studies conducted on animal models of obesity, it has been proposed that inflammatory processes may participate in both the peripheral and brain disorders associated with the obesity condition including the development of emotional and cognitive alterations. This is supported by the fact that obesity is characterized by peripheral low-grade inflammation, originating from increased adipose tissue mass and/or dysbiosis (changes in gut microbiota environment), both of which contribute to increased susceptibility to immune-mediated diseases. In this review, we provide converging evidence showing that obesity is associated with exacerbated neuroinflammation leading to dysfunction in vulnerable brain regions associated with mood regulation, learning, and memory such as the hippocampus. These findings give new insights to the pathophysiological mechanisms contributing to the development of brain disorders in the context of obesity and provide valuable data for introducing new therapeutic strategies for the treatment of neuropsychiatric complications often reported in obese patients.
Collapse
Affiliation(s)
- Nathalie Castanon
- Nutrition and Integrative Neurobiology, INRA, UMR 1286, Université de Bordeaux Bordeaux, France
| | - Giamal Luheshi
- Department of Psychiatry, Douglas Mental Health University Institute, McGill University Montreal, Canada
| | - Sophie Layé
- Nutrition and Integrative Neurobiology, INRA, UMR 1286, Université de Bordeaux Bordeaux, France
| |
Collapse
|
9
|
Abstract
In addition to metabolic and cardiovascular disorders, obesity is associated with adverse cognitive and emotional outcomes. Its growing prevalence during adolescence is particularly alarming since recent evidence indicates that obesity can affect hippocampal function during this developmental period. Adolescence is a decisive period for maturation of the amygdala and the hypothalamic-pituitary-adrenal (HPA) stress axis, both required for lifelong cognitive and emotional processing. However, little data are available on the impact of obesity during adolescence on amygdala function. Herein, we therefore evaluate in rats whether juvenile high-fat diet (HFD)-induced obesity alters amygdala-dependent emotional memory and whether it depends on HPA axis deregulation. Exposure to HFD from weaning to adulthood, i.e., covering adolescence, enhances long-term emotional memories as assessed by odor-malaise and tone-shock associations. Juvenile HFD also enhances emotion-induced neuronal activation of the basolateral complex of the amygdala (BLA), which correlates with protracted plasma corticosterone release. HFD exposure restricted to adulthood does not modify all these parameters, indicating adolescence is a vulnerable period to the effects of HFD-induced obesity. Finally, exaggerated emotional memory and BLA synaptic plasticity after juvenile HFD are alleviated by a glucocorticoid receptor antagonist. Altogether, our results demonstrate that juvenile HFD alters HPA axis reactivity leading to an enhancement of amygdala-dependent synaptic and memory processes. Adolescence represents a period of increased susceptibility to the effects of diet-induced obesity on amygdala function.
Collapse
|
10
|
Modeling combined schizophrenia-related behavioral and metabolic phenotypes in rodents. Behav Brain Res 2014; 276:130-42. [PMID: 24747658 DOI: 10.1016/j.bbr.2014.04.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/08/2014] [Accepted: 04/09/2014] [Indexed: 12/11/2022]
Abstract
Schizophrenia is a chronic, debilitating disorder with a complex behavioral and cognitive phenotype underlined by a similarly complex etiology involving an interaction between susceptibility genes and environmental factors during early development. Limited progress has been made in developing novel pharmacotherapy, partly due to a lack of valid animal models. The recent recognition of the potentially causal role of central and peripheral energy metabolism in the pathophysiology of schizophrenia raises the need of research on animal models that combine both behavioral and metabolic phenotypic domains, similar to what have been identified in humans. In this review we focus on selected genetic (DBA/2J mice, leptin receptor mutants, and PSD-93 knockout mice), early neurodevelopmental (maternal protein deprivation) and pharmacological (acute phencyclidine) animal models that capture the combined behavioral and metabolic abnormalities shown by schizophrenic patients. In reviewing behavioral phenotypes relevant to schizophrenia we apply the principles established by the Research Domain Criteria (RDoC) for better translation. We demonstrate that etiologically diverse manipulations such as specific breeding, deletion of genes that are primarily involved in metabolic regulation and in synaptic plasticity, as well as early metabolic deprivation and adult pharmacological challenge of the glutamate system can lead to schizophrenia-related behavioral and metabolic phenotypes, which suggest that these pathways might be interlinked. We propose that using animal models that combine different domains of schizophrenia can be used as a translationally valid approach to capture the system-level complex interplay between peripheral and central processes in the development of psychopathology.
Collapse
|
11
|
Diet-induced obesity reduces the responsiveness of the peripheral taste receptor cells. PLoS One 2013; 8:e79403. [PMID: 24236129 PMCID: PMC3827352 DOI: 10.1371/journal.pone.0079403] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 09/30/2013] [Indexed: 11/19/2022] Open
Abstract
Introduction Obesity is a growing epidemic that causes many serious health related complications. While the causes of obesity are complex, there is conclusive evidence that overconsumption coupled with a sedentary lifestyle is the primary cause of this medical condition. Dietary consumption is controlled by appetite which is in turn regulated by multiple neuronal systems, including the taste system. However, the relationship between taste and obesity has not been well defined. Growing evidence suggests that taste perception in the brain is altered in obese animals and humans, however no studies have determined if there are altered taste responses in the peripheral taste receptor cells, which is the initiation site for the detection and perception of taste stimuli. Methodology/Principal Findings In this study, we used C57Bl/6 mice which readily become obese when placed on a high fat diet. After ten weeks on the high fat diet, we used calcium imaging to measure how taste-evoked calcium signals were affected in the obese mice. We found that significantly fewer taste receptor cells were responsive to some appetitive taste stimuli while the numbers of taste cells that were sensitive to aversive taste stimuli did not change. Properties of the taste-evoked calcium signals were also significantly altered in the obese mice. Behavioral analyses found that mice on the high fat diet had reduced ability to detect some taste stimuli compared to their littermate controls. Conclusions/Significance Our findings demonstrate that diet-induced obesity significantly influences peripheral taste receptor cell signals which likely leads to changes in the central taste system and may cause altered taste perception.
Collapse
|
12
|
Patel V, Joharapurkar A, Gandhi T, Patel K, Dhanesha N, Kshirsagar S, Dhote V, Detroja J, Bahekar R, Jain M. Omeprazole improves the anti-obesity and antidiabetic effects of exendin-4 in db/db mice (-4 db/db)*. J Diabetes 2013; 5:163-71. [PMID: 22830490 DOI: 10.1111/j.1753-0407.2012.00227.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND In addition to its glucoregulatory actions, exendin-4, a stable glucagon-like peptide-1 receptor agonist, exhibits protective effects in the pancreas and anti-obesity effects. Suitable combination treatment with other anti-obesity or pancreas protective agents would be an effective approach to optimize these additional effects. In the present study, we investigated the effects of the addition of omeprazole, a proton pump inhibitor, to exendin-4 in db/db mice, an experimental model of obesity and type 2 diabetes. METHODS The effects repeated dose treatment for 14 days with exendin-4 (8 μg/kg, s.c.) and omeprazole (30 mg/kg, s.c.) on glycemic control, food intake, and body weight were determined in obese and hyperglycemic db/db mice. The effects of these treatments on plasma gastrin, ghrelin, and leptin levels were determined, along with effects on nausea-like symptoms. The pancreatic effects of the repeated dose treatment were assessed by measuring %HbA1c in the circulation as well as pancreatic insulin and glucagon content and glucokinase activity. RESULTS Combination treatment resulted in significant decreases in plasma leptin and ghrelin levels after repeated dosing. Omeprazole improved the anorectic and body weight-lowering effects and reversed the inhibitory effect of exendin-4 on gastrin levels after repeated dose treatment. The 14-day combination treatment significantly reduced glucose excursion and improved insulin levels, with a concomitant decrease in %HbA1c levels. It also improved glucokinase activity and pancreatic insulin content, with a significant decrease in glucagon content. CONCLUSIONS Combined treatment with omeprazole with exendin-4 reduces food intake and body weight gain, most likely through changes in plasma ghrelin and leptin levels, and improves pancreatic insulin and glucagon content by improving glucokinase activity.
Collapse
Affiliation(s)
- Vishal Patel
- Department of Pharmacology & Toxicology, Zydus Research Centre, Cadila Healthcare Limited, Moraiya, Ahmedabad Anand Pharmacy College, Anand, Gujarat, India
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Yoshida R, Niki M, Jyotaki M, Sanematsu K, Shigemura N, Ninomiya Y. Modulation of sweet responses of taste receptor cells. Semin Cell Dev Biol 2012; 24:226-31. [PMID: 22947916 DOI: 10.1016/j.semcdb.2012.08.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 08/20/2012] [Indexed: 11/17/2022]
Abstract
Taste receptor cells play a major role in detection of chemical compounds in the oral cavity. Information derived from taste receptor cells, such as sweet, bitter, salty, sour and umami is important for evaluating the quality of food components. Among five basic taste qualities, sweet taste is very attractive for animals and influences food intake. Recent studies have demonstrated that sweet taste sensitivity in taste receptor cells would be affected by leptin and endocannabinoids. Leptin is an anorexigenic mediator that reduces food intake by acting on leptin receptor Ob-Rb in the hypothalamus. Endocannabinoids such as anandamide [N-arachidonoylethanolamine (AEA)] and 2-arachidonoyl glycerol (2-AG) are known as orexigenic mediators that act via cannabinoid receptor 1 (CB1) in the hypothalamus and limbic forebrain to induce appetite and stimulate food intake. At the peripheral gustatory organs, leptin selectively suppresses and endocannabinoids selectively enhance sweet taste sensitivity via Ob-Rb and CB1 expressed in sweet sensitive taste cells. Thus leptin and endocannabinoids not only regulate food intake via central nervous systems but also modulate palatability of foods by altering peripheral sweet taste responses. Such reciprocal modulation of leptin and endocannabinoids on peripheral sweet sensitivity may play an important role in regulating energy homeostasis.
Collapse
Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | | | | | | | | | | |
Collapse
|
14
|
Finger BC, Dinan TG, Cryan JF. Progressive ratio responding in an obese mouse model: Effects of fenfluramine. Neuropharmacology 2010; 59:619-26. [DOI: 10.1016/j.neuropharm.2010.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 07/14/2010] [Accepted: 08/10/2010] [Indexed: 10/19/2022]
|
15
|
Sharma AN, Elased KM, Garrett TL, Lucot JB. Neurobehavioral deficits in db/db diabetic mice. Physiol Behav 2010; 101:381-8. [PMID: 20637218 DOI: 10.1016/j.physbeh.2010.07.002] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 07/07/2010] [Accepted: 07/08/2010] [Indexed: 01/02/2023]
Abstract
Recent clinical studies indicate neurobehavioral disturbances in type-2 diabetics. However, there is paucity of preclinical research to support this concept. The validity of db/db mouse as an animal model to study type-2 diabetes and related complications is known. The present study was designed to investigate comprehensively the db/db mouse behavior as preclinical evidence of type-2 diabetes related major neurobehavioral complications. We tested juvenile (5-6weeks) and adult (10-11weeks) db/db mice for behavioral depression in forced swim test (FST), psychosis-like symptoms using pre-pulse inhibition (PPI) test, anxiety behavior employing elevated plus maze (EPM) test, locomotor behavior and thigmotaxis using open field test and working memory deficits in Y-maze test. Both juvenile and adult group db/db mice displayed behavioral despair with increased immobility time in FST. There was an age-dependent progression of psychosis-like symptoms with disrupted PPI in adult db/db mice. In the EPM test, db/db mice were less anxious as observed by increased percent open arms time and entries. They were also hypo-locomotive as evident by a decrease in their basic and fine movements. There was no impairment of working memory in the Y-maze test in db/db mice. This is the first report of depression, psychosis-like symptoms and anxiolytic behavior of db/db mouse strain. It is tempting to speculate that this mouse strain can serve as useful preclinical model to study type-2 diabetes related neurobehavioral complications.
Collapse
Affiliation(s)
- Ajaykumar N Sharma
- Wright State University, Boonshoft School of Medicine, Department of Pharmacology and Toxicology, Dayton, OH 45435, USA
| | | | | | | |
Collapse
|
16
|
Finger BC, Dinan TG, Cryan JF. Leptin-deficient mice retain normal appetitive spatial learning yet exhibit marked increases in anxiety-related behaviours. Psychopharmacology (Berl) 2010; 210:559-68. [PMID: 20422404 DOI: 10.1007/s00213-010-1858-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 03/31/2010] [Indexed: 10/19/2022]
Abstract
RATIONALE The individual's emotional state influences food intake in both humans and rodents. Moreover, specific cognitive processes regulating the salient aspects of food reward are also critical for ingestive behaviour. However, the molecular mechanisms underlying such influence remain unclear. Genetic mouse models thus are important tools in dissecting the molecular and pathophysiological processes which cause complex human diseases. Leptin, encoded by the ob gene, plays an important part in the energy homeostasis and is critical for the development of obesity. OBJECTIVES In these studies, we assess the impact of leptin on behaviours relevant to anxiety and appetitive learning. METHODS Anxiety-related behaviour was assessed in the light dark box and two tests of hyponeophagia. Spatial learning and behavioural flexibility by re-learning was assessed in an appetitive Y-maze task. RESULTS Leptin-deficient (ob/ob) mice displayed higher levels of anxiety-related behaviour in both anxiety tests. In the appetitive Y-maze task, leptin deficiency caused no deficit in learning or re-learning and acute restrained stress had no influence on the learning process. CONCLUSIONS These results emphasise that whilst leptin has previously been shown to modulate aversively motivated learning we found no difference between leptin-deficient mice and their controls in an appetitive learning task. Moreover, both groups showed behavioural flexibility under stressful conditions. On the other hand, leptin deficiency resulted in marked alterations in behaviours relevant to anxiety.
Collapse
Affiliation(s)
- Beate C Finger
- School of Pharmacy, Cavanagh Pharmacy Building, University College Cork, Cork, Ireland
| | | | | |
Collapse
|
17
|
Leptin signaling in brain: A link between nutrition and cognition? Biochim Biophys Acta Mol Basis Dis 2008; 1792:401-8. [PMID: 19130879 DOI: 10.1016/j.bbadis.2008.12.004] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 12/05/2008] [Accepted: 12/07/2008] [Indexed: 12/22/2022]
Abstract
Leptin is a protein hormone that acts within the hypothalamus to suppress food intake and decrease body adiposity, but it is increasingly clear that the hypothalamus is not the only site of leptin action, nor food intake the only biological effect of leptin. Instead, leptin is a pleiotropic hormone that impinges on many brain areas, and in doing so alters food intake, motivation, learning, memory, cognitive function, neuroprotection, reproduction, growth, metabolism, energy expenditure, and more. This diversity of function also means that a dysregulation of leptin secretion and signaling can have far reaching effects. To date research on leptin signaling has focused primarily on the hypothalamus, and the result is a relative lack of information regarding the impact of leptin signaling and leptin resistance in non-hypothalamic areas, despite a growing literature implicating leptin in the regulation of neuronal structure and function in the hippocampus, cortex and other brain areas associated with cognition.
Collapse
|
18
|
Reizes O, Clegg DJ, Strader AD, Benoit SC. A role for syndecan-3 in the melanocortin regulation of energy balance. Peptides 2006; 27:274-80. [PMID: 16289473 DOI: 10.1016/j.peptides.2005.02.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2004] [Accepted: 02/15/2005] [Indexed: 11/23/2022]
Abstract
Since the discovery that central melanocortin peptides play an important role in the control of body weight, an impressive amount of research has focused on understanding this complex neuroendocrine system. However, this research has also uncovered new complexities. One of these complexities is the recently discovered putative melanocortin "co-receptor," syndecan-3. In this review, we present an overview of the biology and potential functions of syndecan-3 and describe a novel hypothesis for its regulation of energy balance.
Collapse
Affiliation(s)
- Ofer Reizes
- Procter & Gamble Pharmaceuticals Inc. Health Care Research Center, Mason, OH 45040, USA
| | | | | | | |
Collapse
|
19
|
Biessels GJ, Gispen WH. The impact of diabetes on cognition: What can be learned from rodent models? Neurobiol Aging 2005; 26 Suppl 1:36-41. [PMID: 16223548 DOI: 10.1016/j.neurobiolaging.2005.08.015] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2005] [Accepted: 08/29/2005] [Indexed: 11/25/2022]
Abstract
Diabetes mellitus is associated with modest impairments in cognition, particularly in the elderly. In addition, the risk of dementia is increased. We review herein studies in rodent models that may help to identify the mechanisms that underlie these adverse effects of diabetes on the brain. Abnormalities in learning and memory, synaptic plasticity, and glutamatergic neurotransmission have now been identified in a number of these models. In general, observations in models characterized by chronic hyperglycaemia and hypoinsulinaemia (referred to as models of type 1 diabetes) are quite consistent, and these models are being increasingly used to study the pathogenesis and to develop new treatments. However, results from models characterized by insulin resistance, hyperinsulinaemia, and modest hyperglycaemia (referred to as models of type 2 diabetes) are much more variable. Moreover, the possible interaction between diabetes and aging has not been examined in sufficient detail. Because clinically relevant cognitive deficits mainly occur in elderly patients with type 2 diabetes, the challenge for researchers in this field will be to further develop adequate models.
Collapse
Affiliation(s)
- Geert Jan Biessels
- Department of Neurology, G03.228, University Medical Center Utrecht, PO Box 85500, 3508 GA, Utrecht, The Netherlands.
| | | |
Collapse
|