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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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2
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Pan S, Worker CJ, Feng Earley Y. The hypothalamus as a key regulator of glucose homeostasis: emerging roles of the brain renin-angiotensin system. Am J Physiol Cell Physiol 2023; 325:C141-C154. [PMID: 37273237 PMCID: PMC10312332 DOI: 10.1152/ajpcell.00533.2022] [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] [Received: 11/29/2022] [Revised: 05/26/2023] [Accepted: 05/26/2023] [Indexed: 06/06/2023]
Abstract
The regulation of plasma glucose levels is a complex and multifactorial process involving a network of receptors and signaling pathways across numerous organs that act in concert to ensure homeostasis. However, much about the mechanisms and pathways by which the brain regulates glycemic homeostasis remains poorly understood. Understanding the precise mechanisms and circuits employed by the central nervous system to control glucose is critical to resolving the diabetes epidemic. The hypothalamus, a key integrative center within the central nervous system, has recently emerged as a critical site in the regulation of glucose homeostasis. Here, we review the current understanding of the role of the hypothalamus in regulating glucose homeostasis, with an emphasis on the paraventricular nucleus, the arcuate nucleus, the ventromedial hypothalamus, and lateral hypothalamus. In particular, we highlight the emerging role of the brain renin-angiotensin system in the hypothalamus in regulating energy expenditure and metabolic rate, as well as its potential importance in the regulation of glucose homeostasis.
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Affiliation(s)
- Shiyue Pan
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Department of Physiology & Cell Biology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Center for Molecular and Cellular Signaling in the Cardiovascular System, University of Nevada, Reno, Reno, Nevada, United States
| | - Caleb J Worker
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Department of Physiology & Cell Biology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Center for Molecular and Cellular Signaling in the Cardiovascular System, University of Nevada, Reno, Reno, Nevada, United States
| | - Yumei Feng Earley
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Department of Physiology & Cell Biology, School of Medicine, University of Nevada, Reno, Reno, Nevada, United States
- Center for Molecular and Cellular Signaling in the Cardiovascular System, University of Nevada, Reno, Reno, Nevada, United States
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3
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Nakaya Y, Kosukegawa S, Kobayashi S, Hirose K, Kitano K, Mayahara K, Takei H, Motoyoshi M, Kobayashi M. Insulin potentiates inhibitory synaptic currents between fast-spiking and pyramidal neurons in the rat insular cortex. Neuropharmacology 2023:109649. [PMID: 37393988 DOI: 10.1016/j.neuropharm.2023.109649] [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: 04/28/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/04/2023]
Abstract
Insulin plays roles in brain functions such as neural development and plasticity and is reported to be involved in dementia and depression. However, little information is available on the insulin-mediated modulation of electrophysiological activities, especially in the cerebral cortex. This study examined how insulin modulates the neural activities of inhibitory neurons and inhibitory postsynaptic currents (IPSCs) in rat insular cortex (IC; either sex) by multiple whole-cell patch-clamp recordings. We demonstrated that insulin increased the repetitive spike firing rate with a decrease in the threshold potential without changing the resting membrane potentials and input resistance of fast-spiking GABAergic neurons (FSNs). Next, we found a dose-dependent enhancement of unitary IPSCs (uIPSCs) by insulin in the connections from FSNs to pyramidal neurons (PNs). The insulin-induced enhancement of uIPSCs accompanied decreases in the paired-pulse ratio, suggesting that insulin increases GABA release from presynaptic terminals. The finding of miniature IPSC recordings of the increased frequency without changing the amplitude supports this hypothesis. Insulin had little effect on uIPSCs under the coapplication of S961, an insulin receptor antagonist, or lavendustin A, an inhibitor of tyrosine kinase. The PI3-K inhibitor wortmannin or the PKB/Akt inhibitors, deguelin and Akt inhibitor VIII, blocked the insulin-induced enhancement of uIPSCs. Intracellular application of Akt inhibitor VIII to presynaptic FSNs also blocked insulin-induced enhancement of uIPSCs. In contrast, uIPSCs were enhanced by insulin in combination with the MAPK inhibitor PD98059. These results suggest that insulin facilitates the inhibition of PNs by increases in FSN firing frequency and IPSCs from FSNs to PNs. (250 words).
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Affiliation(s)
- Yuka Nakaya
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Satoshi Kosukegawa
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Satomi Kobayashi
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Biology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kensuke Hirose
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Pedodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kouhei Kitano
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kotoe Mayahara
- Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Hiroki Takei
- Department of Dentistry, Saitama Prefectural Children's Medical Center, 1-2, Shintoshin, Chuo-ku, Saitama-shi, 3330-8777, Japan
| | - Mitsuru Motoyoshi
- Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Masayuki Kobayashi
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
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4
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Cauli B, Dusart I, Li D. Lactate as a determinant of neuronal excitability, neuroenergetics and beyond. Neurobiol Dis 2023:106207. [PMID: 37331530 DOI: 10.1016/j.nbd.2023.106207] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 06/13/2023] [Accepted: 06/15/2023] [Indexed: 06/20/2023] Open
Abstract
Over the last decades, lactate has emerged as important energy substrate for the brain fueling of neurons. A growing body of evidence now indicates that it is also a signaling molecule modulating neuronal excitability and activity as well as brain functions. In this review, we will briefly summarize how different cell types produce and release lactate. We will further describe different signaling mechanisms allowing lactate to fine-tune neuronal excitability and activity, and will finally discuss how these mechanisms could cooperate to modulate neuroenergetics and higher order brain functions both in physiological and pathological conditions.
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Affiliation(s)
- Bruno Cauli
- Sorbonne Université, CNRS, INSERM, Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS-IBPS), 9 quai Saint Bernard, 75005 Paris, France.
| | - Isabelle Dusart
- Sorbonne Université, CNRS, INSERM, Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS-IBPS), 9 quai Saint Bernard, 75005 Paris, France
| | - Dongdong Li
- Sorbonne Université, CNRS, INSERM, Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS-IBPS), 9 quai Saint Bernard, 75005 Paris, France
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5
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Becerra LA, Gavrieli A, Khan F, Novak P, Lioutas V, Ngo LH, Novak V, Mantzoros CS. Daily intranasal insulin at 40IU does not affect food intake and body composition: A placebo-controlled trial in older adults over a 24-week period with 24-weeks of follow-up. Clin Nutr 2023; 42:825-834. [PMID: 37084469 PMCID: PMC10330069 DOI: 10.1016/j.clnu.2023.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 03/27/2023] [Accepted: 04/07/2023] [Indexed: 04/23/2023]
Abstract
Centrally administered insulin stimulates the reward system to reduce appetite in response to food intake in animal studies. In humans, studies have shown conflicting results, with some studies suggesting that intranasal insulin (INI) in relatively high doses may decrease appetite, body fat, and weight in various populations. These hypotheses have not been tested in a large longitudinal placebo-controlled study. Participants in the Memory Advancement with Intranasal Insulin in Type 2 Diabetes (MemAID) trial were enrolled in this study. This study on energy homeostasis enrolled 89 participants who completed baseline and at least 1 intervention visit (42 women; age 65 ± 9 years; 46 INI, 38 with type 2 diabetes) and 76 completed treatment (16 women, age 64 ± 9; 38 INI, 34 with type 2 diabetes). The primary outcome was the INI effect on food intake. Secondary outcomes included the effect of INI on appetite and anthropometric measures, including body weight and body composition. In exploratory analyses, we tested the interaction of treatment with gender, body mass index (BMI), and diagnosis of type 2 diabetes. There was no INI effect on food intake or any of the secondary outcomes. INI also showed no differential effect on primary and secondary outcomes when considering gender, BMI, and type 2 diabetes. INI did not alter appetite or hunger nor cause weight loss when used at 40 I.U. intranasally daily for 24 weeks in older adults with and without type 2 diabetes.
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Affiliation(s)
- Laura Aponte Becerra
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Anna Gavrieli
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Faizan Khan
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Peter Novak
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Vasileios Lioutas
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Long H Ngo
- Department of Medicine, Beth Israel Deaconess Medical Center and School of Public Health, Harvard Medical School, Boston, MA, USA
| | - Vera Novak
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Christos S Mantzoros
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Medicine, Boston VA Healthcare System, Boston, MA, USA.
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6
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Hernandez CC, Gimenez LE, Dahir NS, Peisley A, Cone RD. The unique structural characteristics of the Kir 7.1 inward rectifier potassium channel: a novel player in energy homeostasis control. Am J Physiol Cell Physiol 2023; 324:C694-C706. [PMID: 36717105 PMCID: PMC10026989 DOI: 10.1152/ajpcell.00335.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 01/12/2023] [Accepted: 01/13/2023] [Indexed: 02/01/2023]
Abstract
The inward rectifier potassium channel Kir7.1, encoded by the KCNJ13 gene, is a tetramer composed of two-transmembrane domain-spanning monomers, closer in homology to Kir channels associated with potassium transport such as Kir1.1, 1.2, and 1.3. Compared with other channels, Kir7.1 exhibits small unitary conductance and low dependence on external potassium. Kir7.1 channels also show a phosphatidylinositol 4,5-bisphosphate (PIP2) dependence for opening. Accordingly, retinopathy-associated Kir7.1 mutations mapped at the binding site for PIP2 resulted in channel gating defects leading to channelopathies such as snowflake vitreoretinal degeneration and Leber congenital amaurosis in blind patients. Lately, this channel's role in energy homeostasis was reported due to the direct interaction with the melanocortin type 4 receptor (MC4R) in the hypothalamus. As this channel seems to play a multipronged role in potassium homeostasis and neuronal excitability, we will discuss what is predicted from a structural viewpoint and its possible implications for hunger control.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Luis E Gimenez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Naima S Dahir
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Alys Peisley
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Roger D Cone
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States
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7
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Yang B, Yao JL, Huo JY, Feng YL, Coetzee WA, Xu GY, Yang HQ. Rab35 GTPase positively regulates endocytic recycling of cardiac K ATP channels. Channels (Austin) 2022; 16:137-147. [PMID: 35754325 DOI: 10.1080/19336950.2022.2090667] [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: 11/03/2022] Open
Abstract
ATP-sensitive K+ (KATP) channel couples membrane excitability to intracellular energy metabolism. Maintaining KATP channel surface expression is key to normal insulin secretion, blood pressure and cardioprotection. However, the molecular mechanisms regulating KATP channel internalization and endocytic recycling, which directly affect the surface expression of KATP channels, are poorly understood. Here we used the cardiac KATP channel subtype, Kir6.2/SUR2A, and characterized Rab35 GTPase as a key regulator of KATP channel endocytic recycling. Electrophysiological recordings and surface biotinylation assays showed decreased KATP channel surface density with co-expression of a dominant negative Rab35 mutant (Rab35-DN), but not other recycling-related Rab GTPases, including Rab4, Rab11a and Rab11b. Immunofluorescence images revealed strong colocalization of Rab35-DN with recycling Kir6.2. Rab35-DN minimized the recycling rate of KATP channels. Rab35 also regulated KATP channel current amplitude in isolated adult cardiomyocytes by affecting its surface expression but not channel properties, which validated its physiologic relevance and the potential of pharmacologic target for treating the diseases with KATP channel trafficking defects.
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Affiliation(s)
- Bo Yang
- Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China
| | - Jia-Lu Yao
- Department of Cardiology, the First Affiliated Hospital of Soochow University, Soochow University, Suzhou, Jiangsu, China.,Department of Cardiology, Dushu Lake Hospital Affiliated to Soochow University, Medical Center of Soochow University, Suzhou Dushu Lake Hospital, Suzhou, Jiangsu, China
| | - Jian-Yi Huo
- Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China
| | - Yu-Long Feng
- Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China
| | - William A Coetzee
- Departments of Pathology, Neuroscience & Physiology, Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Guang-Yin Xu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, Jiangsu, China.,Center for Translational Medicine, The Affiliated Zhangjiagang Hospital of Soochow University, Suzhou, Jiangsu, China
| | - Hua-Qian Yang
- Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China
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Chadwick SR, Güler AD. Local Drd1-neurons input to subgroups of arcuate AgRP/NPY-neurons. iScience 2022; 25:104605. [PMID: 35789850 PMCID: PMC9250019 DOI: 10.1016/j.isci.2022.104605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 05/02/2022] [Accepted: 06/08/2022] [Indexed: 11/21/2022] Open
Abstract
Obesity is a pandemic afflicting more than 300 million people worldwide, driven by consumption of calorically dense and highly rewarding foods. Dopamine (DA) signaling has been implicated in neural responses to highly palatable nutrients, but the exact mechanisms through which DA modulates homeostatic feeding circuits remains unknown. A subpopulation of arcuate (ARC) agouti-related peptide (AgRP)/neuropeptide Y (NPY) (ARCAgRP/NPY+) neurons express the D(1A) dopamine receptor (Drd1) and are stimulated by DA, suggesting one potential avenue for dopaminergic regulation of food intake. Using patch clamp electrophysiology, we evaluated the responses of ARC Drd1-expressing (ARCDrd1+) neurons to overnight fasting and leptin. Collectively, ARCDrd1+ neurons were less responsive to caloric deficit than ARCAgRP/NPY+ neurons; however, ARCDrd1+ neurons were inhibited by the satiety hormone leptin. Using Channelrhodopsin-2-Assisted Circuit Mapping, we identified novel subgroups of ARCDrd1+ neurons that inhibit or excite ARCAgRP/NPY+ neurons. These findings suggest dopamine receptive neurons have multimodal actions in food intake circuits.
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Affiliation(s)
- Sean R. Chadwick
- Program in Fundamental Neuroscience and the Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Ali D. Güler
- Program in Fundamental Neuroscience and the Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
- Department of Neuroscience, School of Medicine, University of Virginia, Charlottesville, VA 22903, USA
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9
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McNeilly AD, Yianakas A, Gallagher JG, Tarlton J, Ashford ML, McCrimmon RJ. Central deficiency of IL-6Ra in mice impairs glucose-stimulated insulin secretion. Mol Metab 2022; 61:101488. [PMID: 35470093 PMCID: PMC9065900 DOI: 10.1016/j.molmet.2022.101488] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 03/16/2022] [Accepted: 03/28/2022] [Indexed: 11/16/2022] Open
Affiliation(s)
- Alison D McNeilly
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK.
| | - Adonis Yianakas
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Jennifer G Gallagher
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Jamie Tarlton
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Michael Lj Ashford
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Rory J McCrimmon
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
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Yu T, Zhang L, Wang Y, Shen X, Lin L, Tang Y. Effect of visfatin on K ATP channel upregulation in colonic smooth muscle cells in diabetic colon dysmotility. Aging (Albany NY) 2022; 14:1292-1306. [PMID: 35113808 PMCID: PMC8876906 DOI: 10.18632/aging.203871] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 01/04/2022] [Indexed: 06/14/2023]
Abstract
The mechanisms of diabetes-related gastrointestinal dysmotility remains unclear. This study aimed to investigate the effect and mechanisms of proinflammatory adipokine visfatin (VF) in the contractile dysfunction of diabetic rat colonic smooth muscle. Twenty Sprague-Dawley rats were randomly divided into control and type 2 diabetes mellitus groups. VF levels in the serum and colonic muscle tissues were tested, the time of the bead ejection and contractility of colonic smooth muscle strips were measured, and the expression of ATP-sensitive potassium (KATP) channels in the colonic muscle tissues was analyzed. In vitro, we tested VF's effects on intracellular reactive oxygen species (ROS) levels, NF-κB's nuclear transcription, KATP channel expression, intracellular Ca2+ concentrations, and myosin light chain (MLC) phosphorylation in colonic smooth muscle cells (CSMCs). The effects of NAC (ROS inhibitor) and BAY 11-7082 (NF-κB inhibitor) on KATP expression were also tested. Diabetic rats showed elevated VF levels in serum and colonic muscle tissues, a delayed distal colon ejection response time, weakened contractility of colonic smooth muscle strips, and increased KATP channel expression in colonic muscle tissues. VF significantly inhibited the contractility of colonic smooth muscle strips from normal rats. In cultured CSMCs, VF caused ROS overload, increased NF-κB nuclear transcription activity and increased expression of Kir6.1, eventually reducing intracellular Ca2+ levels and MLC phosphorylation. NAC and BAY 11-7082 inhibited the VF-induced Kir6.1 upregulation. In conclusion, VF may cause contractile dysfunction of CSMCs by upregulating the expression of the Kir6.1 subunit of KATP channels via the ROS/NF-κB pathway and interfering with Ca2+ signaling.
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Affiliation(s)
- Ting Yu
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
| | - Lin Zhang
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
- Department of Gastroenterology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing 210029, Jiangsu Province, China
| | - Yan Wang
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
| | - Xiaoxue Shen
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
| | - Lin Lin
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
| | - Yurong Tang
- Department of Gastroenterology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029, Jiangsu Province, China
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11
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Bhusal A, Rahman MH, Suk K. Hypothalamic inflammation in metabolic disorders and aging. Cell Mol Life Sci 2021; 79:32. [PMID: 34910246 PMCID: PMC11071926 DOI: 10.1007/s00018-021-04019-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/01/2021] [Accepted: 10/29/2021] [Indexed: 12/15/2022]
Abstract
The hypothalamus is a critical brain region for the regulation of energy homeostasis. Over the years, studies on energy metabolism primarily focused on the neuronal component of the hypothalamus. Studies have recently uncovered the vital role of glial cells as an additional player in energy balance regulation. However, their inflammatory activation under metabolic stress condition contributes to various metabolic diseases. The recruitment of monocytes and macrophages in the hypothalamus helps sustain such inflammation and worsens the disease state. Neurons were found to actively participate in hypothalamic inflammatory response by transmitting signals to the surrounding non-neuronal cells. This activation of different cell types in the hypothalamus leads to chronic, low-grade inflammation, impairing energy balance and contributing to defective feeding habits, thermogenesis, and insulin and leptin signaling, eventually leading to metabolic disorders (i.e., diabetes, obesity, and hypertension). The hypothalamus is also responsible for the causation of systemic aging under metabolic stress. A better understanding of the multiple factors contributing to hypothalamic inflammation, the role of the different hypothalamic cells, and their crosstalks may help identify new therapeutic targets. In this review, we focus on the role of glial cells in establishing a cause-effect relationship between hypothalamic inflammation and the development of metabolic diseases. We also cover the role of other cell types and discuss the possibilities and challenges of targeting hypothalamic inflammation as a valid therapeutic approach.
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Affiliation(s)
- Anup Bhusal
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
| | - Md Habibur Rahman
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea
- Division of Endocrinology, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, 08901, USA
| | - Kyoungho Suk
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea.
- Brain Science and Engineering Institute, Kyungpook National University, Daegu, 41944, Republic of Korea.
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12
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Wang X, Huang H, Zhu Y, Li S, Zhang P, Jiang J, Xi C, Wu L, Gao X, Fu Y, Zhang D, Chen Y, Hu S, Lai J. Metformin acts on the gut-brain axis to ameliorate antipsychotic-induced metabolic dysfunction. Biosci Trends 2021; 15:321-329. [PMID: 34588398 DOI: 10.5582/bst.2021.01317] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Antipsychotic-induced metabolic dysfunction (AIMD) is an intractable clinical challenge worldwide. The situation is becoming more critical as second-generation antipsychotics (SGAs), to a great extent, have replaced the role of first-generation antipsychotics in managing major psychiatric disorders. Although the exact mechanisms for developing AIMD is intricate, emerging evidence has indicated the involvement of the microbiota-gut-brain axis in AIMD. SGAs treatment may change the diversity and compositions of intestinal flora (e.g., decreased abundance of Bacteroidetes and Akkermansia muciniphila, and increased Firmicutes). Short-chain fatty acids and other metabolites derived from gut microbiota, on the one hand, can regulate the activity of intestinal endocrine cells and their secretion of satiety hormones (e.g., glucagon-like peptide 1, peptide YY, cholecystokinin and ghrelin); on the other hand, can activate the vagus nerve or transport into the brain to exert a central modulation of foraging behaviors via binding to neuropeptide receptors. Interestingly, metformin, a classical antidiabetic agent, is capable of alleviating AIMD possibly by regulating the microbiota-gut-brain axis. That is, metformin can not only partially reverse the alterations of gut microbial communities due to SGAs treatment, but also play a positive role in rectifying the disturbances of peripheral and central satiety-related neuropeptides. Current evidence has indicated a promising role for metformin on ameliorating AMID, but further verifications in well-designed clinical trials are still warranted.
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Affiliation(s)
- Xiaorong Wang
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,The Key Laboratory of Mental Disorder's Management in Zhejiang Province, Hangzhou, Zhejiang, China.,Brain Research Institute of Zhejiang University, Hangzhou, Zhejiang, China.,Zhejiang Engineering Center for Mathematical Mental Health, Hangzhou, Zhejiang, China
| | - Huimin Huang
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yiyi Zhu
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Shaoli Li
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Peifen Zhang
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Jiajun Jiang
- The Key Laboratory of Mental Disorder's Management in Zhejiang Province, Hangzhou, Zhejiang, China
| | - Caixi Xi
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Lingling Wu
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xingle Gao
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yaoyang Fu
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Danhua Zhang
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yiqing Chen
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Shaohua Hu
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,The Key Laboratory of Mental Disorder's Management in Zhejiang Province, Hangzhou, Zhejiang, China.,Brain Research Institute of Zhejiang University, Hangzhou, Zhejiang, China.,Zhejiang Engineering Center for Mathematical Mental Health, Hangzhou, Zhejiang, China
| | - Jianbo Lai
- Department of Psychiatry, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,The Key Laboratory of Mental Disorder's Management in Zhejiang Province, Hangzhou, Zhejiang, China.,Brain Research Institute of Zhejiang University, Hangzhou, Zhejiang, China.,Zhejiang Engineering Center for Mathematical Mental Health, Hangzhou, Zhejiang, China
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13
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Perissinotti PP, Martínez-Hernández E, He Y, Koob MD, Piedras-Rentería ES. Genetic Deletion of KLHL1 Leads to Hyperexcitability in Hypothalamic POMC Neurons and Lack of Electrical Responses to Leptin. Front Neurosci 2021; 15:718464. [PMID: 34566565 PMCID: PMC8458657 DOI: 10.3389/fnins.2021.718464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/05/2021] [Indexed: 11/13/2022] Open
Abstract
Kelch-like 1 (KLHL1) is a neuronal actin-binding protein that modulates voltage-gated calcium channels. The KLHL1 knockout (KO) model displays altered calcium channel expression in various brain regions. We analyzed the electrical behavior of hypothalamic POMC (proopiomelanocortin) neurons and their response to leptin. Leptin's effects on POMC neurons include enhanced gene expression, activation of the ERK1/2 pathway and increased electrical excitability. The latter is initiated by activation of the Jak2-PI3K-PLC pathway, which activates TRPC1/5 (Transient Receptor Potential Cation) channels that in turn recruit T-type channel activity resulting in increased excitability. Here we report over-expression of CaV3.1 T-type channels in the hypothalamus of KLHL1 KO mice increased T-type current density and enhanced POMC neuron basal excitability, rendering them electrically unresponsive to leptin. Electrical sensitivity to leptin was restored by partial blockade of T-type channels. The overexpression of hypothalamic T-type channels in POMC neurons may partially contribute to the obese and abnormal feeding phenotypes observed in KLHL1 KO mice.
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Affiliation(s)
- Paula P Perissinotti
- Cell and Molecular Physiology Department and Neuroscience Division of the Cardiovascular Research Institute, Loyola University Chicago, Maywood, IL, United States
| | - Elizabeth Martínez-Hernández
- Cell and Molecular Physiology Department and Neuroscience Division of the Cardiovascular Research Institute, Loyola University Chicago, Maywood, IL, United States
| | - Yungui He
- Institute for Translational Neuroscience and Department of Lab Medicine & Pathology, University of Minnesota, Minneapolis, MN, United States
| | - Michael D Koob
- Institute for Translational Neuroscience and Department of Lab Medicine & Pathology, University of Minnesota, Minneapolis, MN, United States
| | - Erika S Piedras-Rentería
- Cell and Molecular Physiology Department and Neuroscience Division of the Cardiovascular Research Institute, Loyola University Chicago, Maywood, IL, United States
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14
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Wołodko K, Castillo-Fernandez J, Kelsey G, Galvão A. Revisiting the Impact of Local Leptin Signaling in Folliculogenesis and Oocyte Maturation in Obese Mothers. Int J Mol Sci 2021; 22:4270. [PMID: 33924072 PMCID: PMC8074257 DOI: 10.3390/ijms22084270] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 12/28/2022] Open
Abstract
The complex nature of folliculogenesis regulation accounts for its susceptibility to maternal physiological fitness. In obese mothers, progressive expansion of adipose tissue culminates with severe hyperestrogenism and hyperleptinemia with detrimental effects for ovarian performance. Indeed, maternal obesity is associated with the establishment of ovarian leptin resistance. This review summarizes current knowledge on potential effects of impaired leptin signaling throughout folliculogenesis and oocyte developmental competence in mice and women.
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Affiliation(s)
- Karolina Wołodko
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, Tuwima 10, 10-748 Olsztyn, Poland;
| | | | - Gavin Kelsey
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; (J.C.-F.); (G.K.)
- Centre for Trophoblast Research, University of Cambridge, Cambridge CB2 3EG, UK
| | - António Galvão
- Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, Tuwima 10, 10-748 Olsztyn, Poland;
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; (J.C.-F.); (G.K.)
- Centre for Trophoblast Research, University of Cambridge, Cambridge CB2 3EG, UK
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15
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Yoshida R, Margolskee RF, Ninomiya Y. Phosphatidylinositol-3 kinase mediates the sweet suppressive effect of leptin in mouse taste cells. J Neurochem 2021; 158:233-245. [PMID: 33319361 DOI: 10.1111/jnc.15268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 12/08/2020] [Accepted: 12/10/2020] [Indexed: 12/20/2022]
Abstract
Leptin is known to selectively suppress neural and taste cell responses to sweet compounds. The sweet suppressive effect of leptin is mediated by the leptin receptor Ob-Rb, and the ATP-gated K+ (KATP ) channel expressed in some sweet-sensitive, taste receptor family 1 member 3 (T1R3)-positive taste cells. However, the intracellular transduction pathway connecting Ob-Rb to KATP channel remains unknown. Here we report that phosphoinositide 3-kinase (PI3K) mediates leptin's suppression of sweet responses in T1R3-positive taste cells. In in situ taste cell recording, systemically administrated leptin suppressed taste cell responses to sucrose in T1R3-positive taste cells. Such leptin's suppression of sucrose responses was impaired by co-administration of PI3K inhibitors (wortmannin or LY294002). In contrast, co-administration of signal transducer and activator of transcription 3 inhibitor (Stattic) or Src homology region 2 domain-containing phosphatase-2 inhibitor (SHP099) had no effect on leptin's suppression of sucrose responses, although signal transducer and activator of transcription 3 and Src homology region 2 domain-containing phosphatase-2 were expressed in T1R3-positive taste cells. In peeled tongue epithelium, phosphatidylinositol (3,4,5)-trisphosphate production and phosphorylation of AKT by leptin were immunohistochemically detected in some T1R3-positive taste cells but not in glutamate decarboxylase 67-positive taste cells. Leptin-induced phosphatidylinositol (3,4,5)-trisphosphate production was suppressed by LY294002. Thus, leptin suppresses sweet responses of T1R3-positive taste cells by activation of Ob-Rb-PI3K-KATP channel pathway.
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Affiliation(s)
- Ryusuke Yoshida
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | | | - Yuzo Ninomiya
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Oral Science Research Center, Tokyo Dental College, Tokyo, Japan.,Division of Sensory Physiology, Research and Development Center for Five-Sense Device, Kyushu University, Fukuoka, Japan
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16
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Evans MC, Hill JW, Anderson GM. Role of insulin in the neuroendocrine control of reproduction. J Neuroendocrinol 2021; 33:e12930. [PMID: 33523515 DOI: 10.1111/jne.12930] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/18/2020] [Accepted: 12/07/2020] [Indexed: 12/13/2022]
Abstract
Infertility associated with insulin resistance is characterised by abnormal hormone secretion by the hypothalamus, pituitary gland and gonads. These endocrine tissues can maintain insulin sensitivity even when tissues such as the muscle and liver become insulin-resistant, resulting in excessive insulin stimulation as hyperinsulinaemia develops. Experiments conducted to determine the role of neuronal insulin signalling in fertility were unable to recapitulate early findings of hypogonadotrophic hypogonadism in mice lacking insulin receptors throughout the brain. Rather, it was eventually shown that astrocytes critically mediate the effects of insulin on puberty timing and adult reproductive function. However, specific roles for neurones and gonadotrophs have been revealed under conditions of hyperinsulinaemia and by ablation of insulin and leptin receptors. The collective picture is one of multiple insulin-responsive inputs to gonadotrophin releasing hormone neurones, with astrocytes being the most important player.
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Affiliation(s)
- Maggie C Evans
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - Jennifer W Hill
- Department of Physiology and Pharmacology, University of Toledo, Toledo, OH, USA
| | - Greg M Anderson
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago, Dunedin, New Zealand
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17
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Wright H, Aylwin CF, Toro CA, Ojeda SR, Lomniczi A. Polycomb represses a gene network controlling puberty via modulation of histone demethylase Kdm6b expression. Sci Rep 2021; 11:1996. [PMID: 33479437 PMCID: PMC7819995 DOI: 10.1038/s41598-021-81689-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
Female puberty is subject to Polycomb Group (PcG)-dependent transcriptional repression. Kiss1, a puberty-activating gene, is a key target of this silencing mechanism. Using a gain-of-function approach and a systems biology strategy we now show that EED, an essential PcG component, acts in the arcuate nucleus of the hypothalamus to alter the functional organization of a gene network involved in the stimulatory control of puberty. A central node of this network is Kdm6b, which encodes an enzyme that erases the PcG-dependent histone modification H3K27me3. Kiss1 is a first neighbor in the network; genes encoding glutamatergic receptors and potassium channels are second neighbors. By repressing Kdm6b expression, EED increases H3K27me3 abundance at these gene promoters, reducing gene expression throughout a gene network controlling puberty activation. These results indicate that Kdm6b repression is a basic mechanism used by PcG to modulate the biological output of puberty-activating gene networks.
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Affiliation(s)
- Hollis Wright
- Division of Neuroscience, Oregon National Primate Research Center/OHSU, Beaverton, OR, USA
| | - Carlos F Aylwin
- Division of Neuroscience, Oregon National Primate Research Center/OHSU, Beaverton, OR, USA
| | - Carlos A Toro
- Division of Neuroscience, Oregon National Primate Research Center/OHSU, Beaverton, OR, USA
| | - Sergio R Ojeda
- Division of Neuroscience, Oregon National Primate Research Center/OHSU, Beaverton, OR, USA
| | - Alejandro Lomniczi
- Division of Neuroscience, Oregon National Primate Research Center/OHSU, Beaverton, OR, USA.
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18
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Belsham DD, Dalvi PS. Insulin signalling in hypothalamic neurones. J Neuroendocrinol 2020; 33:e12919. [PMID: 33227171 DOI: 10.1111/jne.12919] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 12/15/2022]
Abstract
Subsequent to the discovery of insulin by Banting and Best in the Department of Physiology at the University of Toronto 100 years ago, the field of insulin signalling and action has grown at a remarkable pace. Yet, the recognition that insulin action in the brain is critical for whole body homeostasis has only recently been appreciated. The hypothalamus is a key region in the brain that responds to circulating insulin by engaging a complex signalling cascade resulting in the ultimate release of neuropeptides that control hunger and feeding. Disruption of this important feedback system can lead to a phenomenon called cellular insulin resistance, where the neurones cease to sense insulin. The factors contributing to insulin resistance, as well as the resulting detrimental effects, include the induction of neuroinflammation, endoplasmic reticulum stress and alterations in the architecture of the blood-brain barrier that allow transport of insulin into the brain. These manifestations usually change energy balance, causing weight gain, often resulting in obesity and its deadly comorbidities, including type 2 diabetes mellitus, cardiovascular disease and metabolic syndrome. Nonetheless, there is still hope because the signal transduction pathways can be targeted at a number of levels by neurone-specific therapeutics. With the advent of unique cell models for investigating the mechanisms involved in these processes, the discovery of novel targets is increasingly possible. Although we are still looking for a cure for diabetes, Banting and Best would be impressed at how far their discovery has advanced and the contemporary knowledge that has been accumulated based on insulin action.
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Affiliation(s)
- Denise D Belsham
- Departments of Physiology, Obstetrics and Gynaecology and Medicine, University of Toronto, Toronto, ON, Canada
| | - Prasad S Dalvi
- Biology Department, Morosky College of Health Professions and Sciences, Gannon University, Erie, PA, USA
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19
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Sarvestani FS, Zare MA, Saki F, Koohpeyma F, Al-Abdullah IH, Azarpira N. The effect of human wharton's jelly-derived mesenchymal stem cells on MC4R, NPY, and LEPR gene expression levels in rats with streptozotocin-induced diabetes. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2020; 23:214-223. [PMID: 32405365 PMCID: PMC7211357 DOI: 10.22038/ijbms.2019.39582.9387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 08/03/2019] [Indexed: 12/17/2022]
Abstract
OBJECTIVES Type 1 diabetes (T1D) is an autoimmune disease resulting from inflammatory destruction of islets β-cells. Nowadays, progress in cell therapy, especially mesenchymal stem cells (MSCs) proposes numerous potential remedies for T1D. We aimed to investigate the combination therapeutic effect of these cells with insulin and metformin on neuropeptide Y, melanocortin-4 receptor, and leptin receptor genes expression in TID. MATERIALS AND METHODS One hundreds male rats were randomly divided into seven groups: the control, diabetes, insulin (Ins.), insulin+metformin (Ins.Met.), Wharton's Jelly-derived MSCs (WJ-MSCs), insulin+metformin+WJ-MSCs (Ins.Met.MSCs), and insulin+WJ-MSCs (Ins.MSCs). Treatment was performed from the first day after diagnosis as diabetes. Groups of the recipient WJ-MSCs were intraportally injected with 2× 10⁶ MSCs/kg at the 7th and 28th days of study. Fasting blood sugar was monitored and tissues and genes analysis were performed. RESULTS The blood glucose levels were slightly decreased in all treatment groups within 20th and 45th days compared to the diabetic group. The C-peptide level enhanced in these groups compared to the diabetic group, but this increment in Ins.MSCs group on the 45th days was higher than other groups. The expression level of melanocortin-4 receptor and leptin receptor genes meaningfully up-regulated in the treatment groups, while the expression of neuropeptide Y significantly down-regulated in the treatment group on both times of study. CONCLUSION Our data exhibit that infusion of MSCs and its combination therapy with insulin might ameliorate diabetes signs by changing the amount of leptin and subsequent changes in the expression of neuropeptide Y and melanocortin-4 receptor.
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Affiliation(s)
| | - Mohammad Ali Zare
- Transplant Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Forough Saki
- Endocrinology and Metabolism Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Farhad Koohpeyma
- Endocrinology and Metabolism Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Ismail H Al-Abdullah
- Department of Translational Research and Cellular Therapeutics, Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, USA
| | - Negar Azarpira
- Transplant Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
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20
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Morris G, Maes M, Berk M, Carvalho AF, Puri BK. Nutritional ketosis as an intervention to relieve astrogliosis: Possible therapeutic applications in the treatment of neurodegenerative and neuroprogressive disorders. Eur Psychiatry 2020; 63:e8. [PMID: 32093791 PMCID: PMC8057392 DOI: 10.1192/j.eurpsy.2019.13] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Nutritional ketosis, induced via either the classical ketogenic diet or the use of emulsified medium-chain triglycerides, is an established treatment for pharmaceutical resistant epilepsy in children and more recently in adults. In addition, the use of oral ketogenic compounds, fractionated coconut oil, very low carbohydrate intake, or ketone monoester supplementation has been reported to be potentially helpful in mild cognitive impairment, Parkinson’s disease, schizophrenia, bipolar disorder, and autistic spectrum disorder. In these and other neurodegenerative and neuroprogressive disorders, there are detrimental effects of oxidative stress, mitochondrial dysfunction, and neuroinflammation on neuronal function. However, they also adversely impact on neurone–glia interactions, disrupting the role of microglia and astrocytes in central nervous system (CNS) homeostasis. Astrocytes are the main site of CNS fatty acid oxidation; the resulting ketone bodies constitute an important source of oxidative fuel for neurones in an environment of glucose restriction. Importantly, the lactate shuttle between astrocytes and neurones is dependent on glycogenolysis and glycolysis, resulting from the fact that the astrocytic filopodia responsible for lactate release are too narrow to accommodate mitochondria. The entry into the CNS of ketone bodies and fatty acids, as a result of nutritional ketosis, has effects on the astrocytic glutamate–glutamine cycle, glutamate synthase activity, and on the function of vesicular glutamate transporters, EAAT, Na+, K+-ATPase, Kir4.1, aquaporin-4, Cx34 and KATP channels, as well as on astrogliosis. These mechanisms are detailed and it is suggested that they would tend to mitigate the changes seen in many neurodegenerative and neuroprogressive disorders. Hence, it is hypothesized that nutritional ketosis may have therapeutic applications in such disorders.
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Affiliation(s)
- Gerwyn Morris
- Deakin University, IMPACT Strategic Research Centre, Barwon Health, School of Medicine, Geelong, Victoria, Australia
| | - Michael Maes
- Deakin University, IMPACT Strategic Research Centre, Barwon Health, School of Medicine, Geelong, Victoria, Australia.,Department of Psychiatry, Chulalongkorn University, Faculty of Medicine, Bangkok, Thailand
| | - Michael Berk
- Deakin University, IMPACT Strategic Research Centre, Barwon Health, School of Medicine, Geelong, Victoria, Australia.,Deakin University, CMMR Strategic Research Centre, School of Medicine, Geelong, Victoria, Australia.,Orygen, The National Centre of Excellence in Youth Mental Health, The Department of Psychiatry and the Florey Institute for Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - André F Carvalho
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada.,Centre for Addiction and Mental Health (CAMH), Toronto, Ontario, Canada
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21
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van Gastel J, Leysen H, Santos-Otte P, Hendrickx JO, Azmi A, Martin B, Maudsley S. The RXFP3 receptor is functionally associated with cellular responses to oxidative stress and DNA damage. Aging (Albany NY) 2019; 11:11268-11313. [PMID: 31794429 PMCID: PMC6932917 DOI: 10.18632/aging.102528] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/18/2019] [Indexed: 12/19/2022]
Abstract
DNA damage response (DDR) processes, often caused by oxidative stress, are important in aging and -related disorders. We recently showed that G protein-coupled receptor (GPCR) kinase interacting protein 2 (GIT2) plays a key role in both DNA damage and oxidative stress. Multiple tissue analyses in GIT2KO mice demonstrated that GIT2 expression affects the GPCR relaxin family peptide 3 receptor (RXFP3), and is thus a therapeutically-targetable system. RXFP3 and GIT2 play similar roles in metabolic aging processes. Gaining a detailed understanding of the RXFP3-GIT2 functional relationship could aid the development of novel anti-aging therapies. We determined the connection between RXFP3 and GIT2 by investigating the role of RXFP3 in oxidative stress and DDR. Analyzing the effects of oxidizing (H2O2) and DNA-damaging (camptothecin) stressors on the interacting partners of RXFP3 using Affinity Purification-Mass Spectrometry, we found multiple proteins linked to DDR and cell cycle control. RXFP3 expression increased in response to DNA damage, overexpression, and Relaxin 3-mediated stimulation of RXFP3 reduced phosphorylation of DNA damage marker H2AX, and repair protein BRCA1, moderating DNA damage. Our data suggests an RXFP3-GIT2 system that could regulate cellular degradation after DNA damage, and could be a novel mechanism for mitigating the rate of age-related damage accumulation.
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Affiliation(s)
- Jaana van Gastel
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.,Translational Neurobiology Group, Centre for Molecular Neuroscience, VIB, Antwerp, Belgium
| | - Hanne Leysen
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.,Translational Neurobiology Group, Centre for Molecular Neuroscience, VIB, Antwerp, Belgium
| | - Paula Santos-Otte
- Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
| | - Jhana O Hendrickx
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.,Translational Neurobiology Group, Centre for Molecular Neuroscience, VIB, Antwerp, Belgium
| | - Abdelkrim Azmi
- Translational Neurobiology Group, Centre for Molecular Neuroscience, VIB, Antwerp, Belgium
| | - Bronwen Martin
- Faculty of Pharmaceutical, Veterinary and Biomedical Science, University of Antwerp, Antwerp, Belgium
| | - Stuart Maudsley
- Receptor Biology Lab, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.,Translational Neurobiology Group, Centre for Molecular Neuroscience, VIB, Antwerp, Belgium
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22
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Ganglioside deficiency in hypothalamic POMC neurons promotes body weight gain. Int J Obes (Lond) 2019; 44:510-524. [PMID: 31168055 DOI: 10.1038/s41366-019-0388-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 03/15/2019] [Accepted: 04/05/2019] [Indexed: 11/09/2022]
Abstract
BACKGROUND Glucosylceramide synthase (GCS; gene: UDP-glucose:ceramide glucosyltransferase (Ugcg))-derived gangliosides comprise a specific class of lipids in the plasma membrane that modulate the activity of transmembrane receptors. GCS deletion in hypothalamic arcuate nucleus (Arc) neurons leads to prominent obesity. However, it has not yet been studied how ganglioside depletion affects individual Arc neuronal subpopulations. The current study investigates the effects of GCS deletion specifically in anorexigenic pro-opiomelanocortin (POMC) neurons. Additionally, we investigate insulin receptor (IR) signaling and phosphatidylinositol-(3,4,5)-trisphosphate (PIP3) binding to ATP-dependent K+ (KATP) channels of GCS-deficient POMC neurons. MATERIALS AND METHODS We generated Ugcgf/f-Pomc-Cre mice with ganglioside deficiency in POMC neurons. Moreover, the CRISPR (clustered regulatory interspaced short palindromic repeats)/Cas9 technology was used to inhibit GCS-dependent ganglioside biosynthesis in cultured mouse POMC neurons, yielding UgcgΔ-mHypoA-POMC cells that were used to study mechanistic aspects in further detail. Proximity ligation assays (PLAs) visualized interactions between gangliosides, IR, and KATP channel subunit sulfonylurea receptor-1 (SUR-1), as well as intracellular IR substrate 2 (IRS-2) phosphorylation and PIP3. RESULTS Chow-fed Ugcgf/f-Pomc-Cre mice showed a moderate but significant increase in body weight gain and they failed to display an increase of anorexigenic neuropeptide expression during the fasting-to-re-feeding transition. IR, IRS-2, p85, and overall insulin-evoked IR and IRS-2 phosphorylation were elevated in ganglioside-depleted UgcgΔ-mHypoA-POMC neurons. A PLA demonstrated that more insulin-evoked complex formation occurred between PIP3 and SUR-1 in ganglioside-deficient POMC neurons in vitro and in vivo. CONCLUSION Our work suggests that GCS deletion in POMC neurons promotes body weight gain. Gangliosides are required for an appropriate adaptation of anorexigenic neuropeptide expression in the Arc during the fasting-to-re-feeding transition. Moreover, gangliosides might modulate KATP channel activity by restraining PIP3 binding to the KATP channel subunit SUR-1. Increased PIP3/SUR-1 interactions in ganglioside-deficient neurons could in turn potentially lead to electrical silencing. This work highlights that gangliosides in POMC neurons of the hypothalamic Arc are important regulators of body weight.
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23
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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24
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Huang Y, He Z, Gao Y, Lieu L, Yao T, Sun J, Liu T, Javadi C, Box M, Afrin S, Guo H, Williams KW. Phosphoinositide 3-Kinase Is Integral for the Acute Activity of Leptin and Insulin in Male Arcuate NPY/AgRP Neurons. J Endocr Soc 2018; 2:518-532. [PMID: 29850651 PMCID: PMC5961025 DOI: 10.1210/js.2018-00061] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 04/23/2018] [Indexed: 11/19/2022] Open
Abstract
Neuropeptide Y (NPY)/Agouti-related protein (AgRP) neurons in the arcuate nucleus of the hypothalamus are part of a neuroendocrine feedback loop that regulates feeding behavior and glucose homeostasis. NPY/AgRP neurons sense peripheral signals (including the hormones leptin, insulin, and ghrelin) and integrate those signals with inputs from other brain regions. These inputs modify both long-term changes in gene transcription and acute changes in the electrical activity of these neurons, leading to a coordinated response to maintain energy and glucose homeostasis. However, the mechanisms by which the hormones insulin and leptin acutely modify the electrical activity of these neurons remain unclear. In this study, we show that loss of the phosphoinositide 3-kinase catalytic subunits p110α and p110β in AgRP neurons abrogates the leptin- and insulin-induced inhibition of AgRP neurons. Moreover, continual disruption of p110α and p110β in AgRP neurons results in increased weight gain. The increased adiposity was concomitant with a hypometabolic phenotype: decreased energy expenditure independent of changes in food intake. Deficiency of p110α and p110β in AgRP neurons also impaired glucose homeostasis and insulin sensitivity. In summary, these data highlight the requirement of both p110α and p110β in AgRP neurons for the proper regulation of energy balance and glucose homeostasis.
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Affiliation(s)
- Yiru Huang
- The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Zhenyan He
- The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Yong Gao
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas.,National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Linh Lieu
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ting Yao
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Jia Sun
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Tiemin Liu
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Chris Javadi
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Maria Box
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Sadia Afrin
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Hongbo Guo
- The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Kevin W Williams
- Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, Texas
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25
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Calisi RM, Austin SH, Lang AS, MacManes MD. Sex-biased transcriptomic response of the reproductive axis to stress. Horm Behav 2018; 100:56-68. [PMID: 29378207 DOI: 10.1016/j.yhbeh.2017.11.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 11/16/2017] [Accepted: 11/17/2017] [Indexed: 02/07/2023]
Abstract
Stress is a well-known cause of reproductive dysfunction in many species, including birds, rodents, and humans, though males and females may respond differently. A powerful way to investigate how stress affects reproduction is by examining its effects on a biological system essential for regulating reproduction, the hypothalamic-pituitary-gonadal (HPG) axis. Often this is done by observing how a stressor affects the amount of glucocorticoids, such as cortisol or corticosterone, circulating in the blood and their relationship with a handful of known HPG-producing reproductive hormones, like testosterone and estradiol. Until now, we have lacked a full understanding of how stress affects all genomic activity of the HPG axis and how this might differ between the sexes. We leveraged a highly replicated and sex-balanced experimental approach to test how male and female rock doves (Columba livia) respond to restraint stress at the level of their transcriptome. Females exhibit increased genomic responsiveness to stress at all levels of their HPG axis as compared to males, and these responsive genes are mostly unique to females. Reasons for this may be due to fluctuations in the female endocrine environment over the reproductive cycle and/or their evolutionary history, including parental investment and the potential for maternal effects. Direct links between genome to phenome cause and effect cannot be ascertained at this stage; however, the data we report provide a vital genomic foundation on which sex-specific reproductive dysfunction and adaptation in the face of stress can be further experimentally studied, as well as novel gene targets for genetic intervention and therapy investigations.
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Affiliation(s)
- Rebecca M Calisi
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, United States.
| | - Suzanne H Austin
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, United States
| | - Andrew S Lang
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, United States
| | - Matthew D MacManes
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, United States
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26
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Krumm EA, Patel VJ, Tillery TS, Yasrebi A, Shen J, Guo GL, Marco SM, Buckley BT, Roepke TA. Organophosphate Flame-Retardants Alter Adult Mouse Homeostasis and Gene Expression in a Sex-Dependent Manner Potentially Through Interactions With ERα. Toxicol Sci 2018; 162:212-224. [PMID: 29112739 PMCID: PMC6735580 DOI: 10.1093/toxsci/kfx238] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Flame retardants (FRs) such as polybrominated diphenyl ethers and organophosphate FR (OPFR) persist in the environment and interact with multiple nuclear receptors involved in homeostasis, including estrogen receptors (ERs). However, little is known about the effects of FR, especially OPFR, on mammalian neuroendocrine functions. Therefore, we investigated if exposure to FR alters hypothalamic gene expression and whole-animal physiology in adult wild-type (WT) and ERα KO mice. Intact WT and KO males and ovariectomized WT and KO females were orally dosed daily with vehicle (oil), 17α-ethynylestradiol (2.5 μg/kg), 2,2', 4,4-tetrabromodiphenyl ether (BDE-47, 1 or 10 mg/kg), or an OPFR mixture {1 or 10 mg/kg of tris(1, 3-dichloro-2-propyl)phosphate, triphenyl phosphate, and tricresyl phosphate each} for 28 days. Body weight, food intake, body composition, glucose and insulin tolerance, plasma hormone levels, and hypothalamic and liver gene expression were measured. Expression of neuropeptides, receptors, and cation channels was differentially altered between WT males and females. OPFR suppressed body weight and energy intake in males. FR increased fasting glucose levels in males, and BDE-47 augmented glucose clearance in females. Liver gene expression indicated FXR activation by BDE-47 and PXR and CAR activation by OPFR. In males, OPFR increased ghrelin but decreased leptin and insulin independent of body weight. The loss of ERα reduced the effects of both FR on hypothalamic and liver gene expression and plasma hormone levels. The physiological implications are that males are more sensitive than ovariectomized females to OPFR exposure and that these effects are mediated, in part, by ERα.
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Affiliation(s)
- Elizabeth A Krumm
- Department of Animal Sciences, School of Environmental & Biological Sciences
- Graduate Program in Endocrinology and Animal Biosciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
| | - Vipa J Patel
- Department of Animal Sciences, School of Environmental & Biological Sciences
| | - Taylor S Tillery
- Department of Animal Sciences, School of Environmental & Biological Sciences
| | - Ali Yasrebi
- Department of Animal Sciences, School of Environmental & Biological Sciences
- Graduate Program in Endocrinology and Animal Biosciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
| | - Jianliang Shen
- Department of Pharmacology and Toxicology, School of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
| | - Grace L Guo
- Department of Pharmacology and Toxicology, School of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
| | | | - Brian T Buckley
- Environmental and Occupational Health Science Institute, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Troy A Roepke
- Department of Animal Sciences, School of Environmental & Biological Sciences
- Graduate Program in Endocrinology and Animal Biosciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
- Joint Graduate Program in Toxicology
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27
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Shen L, Lo CC, Woollett LA, Liu M. Apolipoprotein A-IV exerts its anorectic action through a PI3K/Akt signaling pathway in the hypothalamus. Biochem Biophys Res Commun 2017; 494:152-157. [PMID: 29037812 DOI: 10.1016/j.bbrc.2017.10.063] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Accepted: 10/12/2017] [Indexed: 12/11/2022]
Abstract
Apolipoprotein A-IV (apoA-IV) is a satiation factor that acts in the hypothalamus, however, the intracellular mechanisms responsible for this action are still largely unknown. Here we report that apoA-IV treatment elicited a rapid activation of the phosphatidylinositol-3-kinase (PI3K) signaling pathway in cultured primary hypothalamic neurons, and this effect was significantly attenuated by pretreatment with LY294002, an inhibitor of the PI3K pathway. To determine if the activation of PI3K is required for apoA-IV's inhibitory effect on food intake, apoA-IV was administered intracerebroventricularly. We found that apoA-IV significantly reduced food intake and activated PI3K signaling in the hypothalamus, and these effects were abolished by icv pre-treatment with LY294002. To identify the distinct brain sites where apoA-IV exerts its anorectic action, apoA-IV was administered into the ventromedial hypothalamus (VMH) through implanted bilateral cannula. At a low dose (0.5 μg), apoA-IV significantly inhibited food intake and activated PI3K signaling pathway in the VMH of lean rats, but not in high-fat diet-induced obese (DIO) rats. These results collectively demonstrate a critical role of the PI3K/Akt pathway in apoA-IV's anorectic action in lean rats and suggest a defective PI3K pathway in the VMH is responsible for the impaired apoA-IV's anorectic action in the DIO animals.
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Affiliation(s)
- Ling Shen
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Chunmin C Lo
- Department of Biomedical Sciences and Diabetes Institute, Ohio University, Athens, OH, USA
| | - Laura A Woollett
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Min Liu
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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28
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McGregor G, Harvey J. Food for thought: Leptin regulation of hippocampal function and its role in Alzheimer's disease. Neuropharmacology 2017; 136:298-306. [PMID: 28987937 DOI: 10.1016/j.neuropharm.2017.09.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 09/27/2017] [Accepted: 09/30/2017] [Indexed: 01/08/2023]
Abstract
Accumulating evidence indicates that diet and body weight are important factors associated with Alzheimer's disease (AD), with a significant increase in AD risk linked to mid-life obesity, and weight loss frequently occurring in the early stages of AD. This has fuelled interest in the hormone leptin, as it is an important hypothalamic regulator of food intake and body weight, but leptin also markedly influences the functioning of the hippocampus; a key brain region that degenerates in AD. Increasing evidence indicates that leptin has cognitive enhancing properties as it facilitates the cellular events that underlie hippocampal-dependent learning and memory. However, significant reductions in leptin's capacity to regulate hippocampal synaptic function occurs with age and dysfunctions in the leptin system are associated with an increased risk of AD. Moreover, leptin is a potential novel target in AD as leptin treatment has beneficial effects in various models of AD. Here we summarise recent advances in leptin neurobiology with particular focus on regulation of hippocampal synaptic function by leptin and the implications of this for neurodegenerative disorders like AD. This article is part of the Special Issue entitled 'Metabolic Impairment as Risk Factors for Neurodegenerative Disorders.'
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Affiliation(s)
- Gemma McGregor
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Jenni Harvey
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom.
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29
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Kamitakahara A, Bouyer K, Wang CH, Simerly R. A critical period for the trophic actions of leptin on AgRP neurons in the arcuate nucleus of the hypothalamus. J Comp Neurol 2017; 526:133-145. [PMID: 28891045 DOI: 10.1002/cne.24327] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/31/2017] [Accepted: 09/01/2017] [Indexed: 12/11/2022]
Abstract
In the developing hypothalamus, the fat-derived hormone leptin stimulates the growth of axons from the arcuate nucleus of the hypothalamus (ARH) to other regions that control energy balance. These projections are significantly reduced in leptin deficient (Lepob/ob ) mice and this phenotype is largely rescued by neonatal leptin treatments. However, treatment of mature Lepob/ob mice is ineffective, suggesting that the trophic action of leptin is limited to a developmental critical period. To temporally delineate closure of this critical period for leptin-stimulated growth, we treated Lepob/ob mice with exogenous leptin during a variety of discrete time periods, and measured the density of Agouti-Related Peptide (AgRP) containing projections from the ARH to the ventral part of the dorsomedial nucleus of the hypothalamus (DMHv), and to the medial parvocellular part of the paraventricular nucleus (PVHmp). The results indicate that leptin loses its neurotrophic potential at or near postnatal day 28. The duration of leptin exposure appears to be important, with 9- or 11-day treatments found to be more effective than shorter (5-day) treatments. Furthermore, leptin treatment for 9 days or more was sufficient to restore AgRP innervation to both the PVHmp and DMHv in Lepob/ob females, but only to the DMHv in Lepob/ob males. Together, these findings reveal that the trophic actions of leptin are contingent upon timing and duration of leptin exposure, display both target and sex specificity, and that modulation of leptin-dependent circuit formation by each of these factors may carry enduring consequences for feeding behavior, metabolism, and obesity risk.
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Affiliation(s)
- Anna Kamitakahara
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California.,Program in Neuroscience, University of Southern California, Los Angeles, California
| | - Karine Bouyer
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California
| | - Chien-Hua Wang
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California.,Program in Neuroscience, University of Southern California, Los Angeles, California
| | - Richard Simerly
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California.,Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
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30
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Evans MC, Anderson GM. Neuroendocrine integration of nutritional signals on reproduction. J Mol Endocrinol 2017; 58:R107-R128. [PMID: 28057770 DOI: 10.1530/jme-16-0212] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 01/05/2017] [Indexed: 12/28/2022]
Abstract
Reproductive function in mammals is energetically costly and therefore tightly regulated by nutritional status. To enable this integration of metabolic and reproductive function, information regarding peripheral nutritional status must be relayed centrally to the gonadotropin-releasing hormone (GNRH) neurons that drive reproductive function. The metabolically relevant hormones leptin, insulin and ghrelin have been identified as key mediators of this 'metabolic control of fertility'. However, the neural circuitry through which they act to exert their control over GNRH drive remains incompletely understood. With the advent of Cre-LoxP technology, it has become possible to perform targeted gene-deletion and gene-rescue experiments and thus test the functional requirement and sufficiency, respectively, of discrete hormone-neuron signaling pathways in the metabolic control of reproductive function. This review discusses the findings from these investigations, and attempts to put them in context with what is known from clinical situations and wild-type animal models. What emerges from this discussion is clear evidence that the integration of nutritional signals on reproduction is complex and highly redundant, and therefore, surprisingly difficult to perturb. Consequently, the deletion of individual hormone-neuron signaling pathways often fails to cause reproductive phenotypes, despite strong evidence that the targeted pathway plays a role under normal physiological conditions. Although transgenic studies rarely reveal a critical role for discrete signaling pathways, they nevertheless prove to be a good strategy for identifying whether a targeted pathway is absolutely required, critically involved, sufficient or dispensable in the metabolic control of fertility.
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Affiliation(s)
- Maggie C Evans
- Centre for Neuroendocrinology and Department of AnatomyUniversity of Otago School of Medical Sciences, Dunedin, New Zealand
| | - Greg M Anderson
- Centre for Neuroendocrinology and Department of AnatomyUniversity of Otago School of Medical Sciences, Dunedin, New Zealand
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31
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Dadak S, Beall C, Vlachaki Walker JM, Soutar MPM, McCrimmon RJ, Ashford MLJ. Oleate induces K ATP channel-dependent hyperpolarization in mouse hypothalamic glucose-excited neurons without altering cellular energy charge. Neuroscience 2017; 346:29-42. [PMID: 28087336 PMCID: PMC5346158 DOI: 10.1016/j.neuroscience.2016.12.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 12/29/2016] [Indexed: 11/29/2022]
Abstract
Oleate and low glucose hyperpolarize and inhibit GT1-7 and mouse GE neurons by activation of KATP. Oleate inhibition of GT1-7 neuron activity is not mediated by AMPK or fatty acid oxidation. Activation of KATP by oleate requires ATP hydrolysis but does not reduce the levels ATP or the ATP:ADP ratio. GT1-7 hyperpolarization by oleate is not dependent on UCP2. Oleate and low glucose depolarize a subpopulation of hypothalamic GI neurons.
The unsaturated fatty acid, oleate exhibits anorexigenic properties reducing food intake and hepatic glucose output. However, its mechanism of action in the hypothalamus has not been fully determined. This study investigated the effects of oleate and glucose on GT1-7 mouse hypothalamic cells (a model of glucose-excited (GE) neurons) and mouse arcuate nucleus (ARC) neurons. Whole-cell and perforated patch-clamp recordings, immunoblotting and cell energy status measures were used to investigate oleate- and glucose-sensing properties of mouse hypothalamic neurons. Oleate or lowered glucose concentration caused hyperpolarization and inhibition of firing of GT1-7 cells by the activation of ATP-sensitive K+ channels (KATP). This effect of oleate was not dependent on fatty acid oxidation or raised AMP-activated protein kinase activity or prevented by the presence of the UCP2 inhibitor genipin. Oleate did not alter intracellular calcium, indicating that CD36/fatty acid translocase may not play a role. However, oleate activation of KATP may require ATP metabolism. The short-chain fatty acid octanoate was unable to replicate the actions of oleate on GT1-7 cells. Although oleate decreased GT1-7 cell mitochondrial membrane potential there was no change in total cellular ATP or ATP/ADP ratios. Perforated patch and whole-cell recordings from mouse hypothalamic slices demonstrated that oleate hyperpolarized a subpopulation of ARC GE neurons by KATP activation. Additionally, in a separate small population of ARC neurons, oleate application or lowered glucose concentration caused membrane depolarization. In conclusion, oleate induces KATP-dependent hyperpolarization and inhibition of firing of a subgroup of GE hypothalamic neurons without altering cellular energy charge.
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Affiliation(s)
- Selma Dadak
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Marc P M Soutar
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
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32
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Jyotaki M, Sanematsu K, Shigemura N, Yoshida R, Ninomiya Y. Leptin suppresses sweet taste responses of enteroendocrine STC-1 cells. Neuroscience 2016; 332:76-87. [PMID: 27353597 DOI: 10.1016/j.neuroscience.2016.06.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 06/17/2016] [Accepted: 06/22/2016] [Indexed: 12/26/2022]
Abstract
Leptin is an important hormone that regulates food intake and energy homeostasis by acting on central and peripheral targets. In the gustatory system, leptin is known to selectively suppress sweet responses by inhibiting the activation of sweet sensitive taste cells. Sweet taste receptor (T1R2+T1R3) is also expressed in gut enteroendocrine cells and contributes to nutrient sensing, hormone release and glucose absorption. Because of the similarities in expression patterns between enteroendocrine and taste receptor cells, we hypothesized that they may also share similar mechanisms used to modify/regulate the sweet responsiveness of these cells by leptin. Here, we used mouse enteroendocrine cell line STC-1 and examined potential effect of leptin on Ca(2+) responses of STC-1 cells to various taste compounds. Ca(2+) responses to sweet compounds in STC-1 cells were suppressed by a rodent T1R3 inhibitor gurmarin, suggesting the involvement of T1R3-dependent receptors in detection of sweet compounds. Responses to sweet substances were suppressed by ⩾1ng/ml leptin without affecting responses to bitter, umami and salty compounds. This effect was inhibited by a leptin antagonist (mutant L39A/D40A/F41A) and by ATP gated K(+) (KATP) channel closer glibenclamide, suggesting that leptin affects sweet taste responses of enteroendocrine cells via activation of leptin receptor and KATP channel expressed in these cells. Moreover, leptin selectively inhibited sweet-induced but not bitter-induced glucagon-like peptide-1 (GLP-1) secretion from STC-1 cells. These results suggest that leptin modulates sweet taste responses of enteroendocrine cells to regulate nutrient sensing, hormone release and glucose absorption in the gut.
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Affiliation(s)
- Masafumi Jyotaki
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; Monell Chemical Senses Center, Philadelphia, PA, United States
| | - Keisuke Sanematsu
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; OBT Research Center, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Monell Chemical Senses Center, Philadelphia, PA, United States.
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33
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Gavello D, Carbone E, Carabelli V. Leptin-mediated ion channel regulation: PI3K pathways, physiological role, and therapeutic potential. Channels (Austin) 2016; 10:282-96. [PMID: 27018500 DOI: 10.1080/19336950.2016.1164373] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Leptin is produced by adipose tissue and identified as a "satiety signal," informing the brain when the body has consumed enough food. Specific areas of the hypothalamus express leptin receptors (LEPRs) and are the primary site of leptin action for body weight regulation. In response to leptin, appetite is suppressed and energy expenditure allowed. Beside this hypothalamic action, leptin targets other brain areas in addition to neuroendocrine cells. LEPRs are expressed also in the hippocampus, neocortex, cerebellum, substantia nigra, pancreatic β-cells, and chromaffin cells of the adrenal gland. It is intriguing how leptin is able to activate different ionic conductances, thus affecting excitability, synaptic plasticity and neurotransmitter release, depending on the target cell. Most of the intracellular pathways activated by leptin and directed to ion channels involve PI3K, which in turn phosphorylates different downstream substrates, although parallel pathways involve AMPK and MAPK. In this review we will describe the effects of leptin on BK, KATP, KV, CaV, TRPC, NMDAR and AMPAR channels and clarify the landscape of pathways involved. Given the ability of leptin to influence neuronal excitability and synaptic plasticity by modulating ion channels activity, we also provide a short overview of the growing potentiality of leptin as therapeutic agent for treating neurological disorders.
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Affiliation(s)
- Daniela Gavello
- a Department of Drug Science , Lab of Cellular Physiology and Molecular Neuroscience, NIS Center of Excellence, University of Torino , Torino , Italy
| | - Emilio Carbone
- a Department of Drug Science , Lab of Cellular Physiology and Molecular Neuroscience, NIS Center of Excellence, University of Torino , Torino , Italy
| | - Valentina Carabelli
- a Department of Drug Science , Lab of Cellular Physiology and Molecular Neuroscience, NIS Center of Excellence, University of Torino , Torino , Italy
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34
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Röder PV, Wu B, Liu Y, Han W. Pancreatic regulation of glucose homeostasis. Exp Mol Med 2016; 48:e219. [PMID: 26964835 PMCID: PMC4892884 DOI: 10.1038/emm.2016.6] [Citation(s) in RCA: 454] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/03/2015] [Accepted: 12/06/2015] [Indexed: 12/11/2022] Open
Abstract
In order to ensure normal body function, the human body is dependent on a tight control of its blood glucose levels. This is accomplished by a highly sophisticated network of various hormones and neuropeptides released mainly from the brain, pancreas, liver, intestine as well as adipose and muscle tissue. Within this network, the pancreas represents a key player by secreting the blood sugar-lowering hormone insulin and its opponent glucagon. However, disturbances in the interplay of the hormones and peptides involved may lead to metabolic disorders such as type 2 diabetes mellitus (T2DM) whose prevalence, comorbidities and medical costs take on a dramatic scale. Therefore, it is of utmost importance to uncover and understand the mechanisms underlying the various interactions to improve existing anti-diabetic therapies and drugs on the one hand and to develop new therapeutic approaches on the other. This review summarizes the interplay of the pancreas with various other organs and tissues that maintain glucose homeostasis. Furthermore, anti-diabetic drugs and their impact on signaling pathways underlying the network will be discussed.
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Affiliation(s)
- Pia V Röder
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
| | - Bingbing Wu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Yixian Liu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Weiping Han
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
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35
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Jourdain P, Allaman I, Rothenfusser K, Fiumelli H, Marquet P, Magistretti PJ. L-Lactate protects neurons against excitotoxicity: implication of an ATP-mediated signaling cascade. Sci Rep 2016; 6:21250. [PMID: 26893204 PMCID: PMC4759786 DOI: 10.1038/srep21250] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 01/20/2016] [Indexed: 12/20/2022] Open
Abstract
Converging experimental data indicate a neuroprotective action of L-Lactate. Using Digital Holographic Microscopy, we observe that transient application of glutamate (100 μM; 2 min) elicits a NMDA-dependent death in 65% of mouse cortical neurons in culture. In the presence of L-Lactate (or Pyruvate), the percentage of neuronal death decreases to 32%. UK5099, a blocker of the Mitochondrial Pyruvate Carrier, fully prevents L-Lactate-mediated neuroprotection. In addition, L-Lactate-induced neuroprotection is not only inhibited by probenicid and carbenoxolone, two blockers of ATP channel pannexins, but also abolished by apyrase, an enzyme degrading ATP, suggesting that ATP produced by the Lactate/Pyruvate pathway is released to act on purinergic receptors in an autocrine/paracrine manner. Finally, pharmacological approaches support the involvement of the P2Y receptors associated to the PI3-kinase pathway, leading to activation of KATP channels. This set of results indicates that L-Lactate acts as a signalling molecule for neuroprotection against excitotoxicity through coordinated cellular pathways involving ATP production, release and activation of a P2Y/KATP cascade.
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Affiliation(s)
- P Jourdain
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.,Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
| | - I Allaman
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - K Rothenfusser
- Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
| | - H Fiumelli
- King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - P Marquet
- Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
| | - P J Magistretti
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.,King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia.,Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
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36
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Imbalanced insulin action in chronic over nutrition: Clinical harm, molecular mechanisms, and a way forward. Atherosclerosis 2016; 247:225-82. [PMID: 26967715 DOI: 10.1016/j.atherosclerosis.2016.02.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 12/31/2015] [Accepted: 02/02/2016] [Indexed: 02/08/2023]
Abstract
The growing worldwide prevalence of overnutrition and underexertion threatens the gains that we have made against atherosclerotic cardiovascular disease and other maladies. Chronic overnutrition causes the atherometabolic syndrome, which is a cluster of seemingly unrelated health problems characterized by increased abdominal girth and body-mass index, high fasting and postprandial concentrations of cholesterol- and triglyceride-rich apoB-lipoproteins (C-TRLs), low plasma HDL levels, impaired regulation of plasma glucose concentrations, hypertension, and a significant risk of developing overt type 2 diabetes mellitus (T2DM). In addition, individuals with this syndrome exhibit fatty liver, hypercoagulability, sympathetic overactivity, a gradually rising set-point for body adiposity, a substantially increased risk of atherosclerotic cardiovascular morbidity and mortality, and--crucially--hyperinsulinemia. Many lines of evidence indicate that each component of the atherometabolic syndrome arises, or is worsened by, pathway-selective insulin resistance and responsiveness (SEIRR). Individuals with SEIRR require compensatory hyperinsulinemia to control plasma glucose levels. The result is overdrive of those pathways that remain insulin-responsive, particularly ERK activation and hepatic de-novo lipogenesis (DNL), while carbohydrate regulation deteriorates. The effects are easily summarized: if hyperinsulinemia does something bad in a tissue or organ, that effect remains responsive in the atherometabolic syndrome and T2DM; and if hyperinsulinemia might do something good, that effect becomes resistant. It is a deadly imbalance in insulin action. From the standpoint of human health, it is the worst possible combination of effects. In this review, we discuss the origins of the atherometabolic syndrome in our historically unprecedented environment that only recently has become full of poorly satiating calories and incessant enticements to sit. Data are examined that indicate the magnitude of daily caloric imbalance that causes obesity. We also cover key aspects of healthy, balanced insulin action in liver, endothelium, brain, and elsewhere. Recent insights into the molecular basis and pathophysiologic harm from SEIRR in these organs are discussed. Importantly, a newly discovered oxide transport chain functions as the master regulator of the balance amongst different limbs of the insulin signaling cascade. This oxide transport chain--abbreviated 'NSAPP' after its five major proteins--fails to function properly during chronic overnutrition, resulting in this harmful pattern of SEIRR. We also review the origins of widespread, chronic overnutrition. Despite its apparent complexity, one factor stands out. A sophisticated junk food industry, aided by subsidies from willing governments, has devoted years of careful effort to promote overeating through the creation of a new class of food and drink that is low- or no-cost to the consumer, convenient, savory, calorically dense, yet weakly satiating. It is past time for the rest of us to overcome these foes of good health and solve this man-made epidemic.
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Stark R, Reichenbach A, Andrews ZB. Hypothalamic carnitine metabolism integrates nutrient and hormonal feedback to regulate energy homeostasis. Mol Cell Endocrinol 2015; 418 Pt 1:9-16. [PMID: 26261054 DOI: 10.1016/j.mce.2015.08.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Revised: 07/31/2015] [Accepted: 08/03/2015] [Indexed: 01/11/2023]
Abstract
The maintenance of energy homeostasis requires the hypothalamic integration of nutrient feedback cues, such as glucose, fatty acids, amino acids, and metabolic hormones such as insulin, leptin and ghrelin. Although hypothalamic neurons are critical to maintain energy homeostasis research efforts have focused on feedback mechanisms in isolation, such as glucose alone, fatty acids alone or single hormones. However this seems rather too simplistic considering the range of nutrient and endocrine changes associated with different metabolic states, such as starvation (negative energy balance) or diet-induced obesity (positive energy balance). In order to understand how neurons integrate multiple nutrient or hormonal signals, we need to identify and examine potential intracellular convergence points or common molecular targets that have the ability to sense glucose, fatty acids, amino acids and hormones. In this review, we focus on the role of carnitine metabolism in neurons regulating energy homeostasis. Hypothalamic carnitine metabolism represents a novel means for neurons to facilitate and control both nutrient and hormonal feedback. In terms of nutrient regulation, carnitine metabolism regulates hypothalamic fatty acid sensing through the actions of CPT1 and has an underappreciated role in glucose sensing since carnitine metabolism also buffers mitochondrial matrix levels of acetyl-CoA, an allosteric inhibitor of pyruvate dehydrogenase and hence glucose metabolism. Studies also show that hypothalamic CPT1 activity also controls hormonal feedback. We hypothesis that hypothalamic carnitine metabolism represents a key molecular target that can concurrently integrate nutrient and hormonal information, which is critical to maintain energy homeostasis. We also suggest this is relevant to broader neuroendocrine research as it predicts that hormonal signaling in the brain varies depending on current nutrient status. Indeed, the metabolic action of ghrelin, leptin or insulin at POMC or NPY neurons may depend on appropriate nutrient-sensing in these neurons and we hypothesize carnitine metabolism is critical in the integrative processing. Future research is required to examine the neuron-specific effects of carnitine metabolism on concurrent nutrient- and hormonal-sensing in AgRP and POMC neurons.
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Affiliation(s)
- Romana Stark
- Department of Physiology, Monash University, Clayton, Victoria 3183, Australia
| | - Alex Reichenbach
- Department of Physiology, Monash University, Clayton, Victoria 3183, Australia
| | - Zane B Andrews
- Department of Physiology, Monash University, Clayton, Victoria 3183, Australia.
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38
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Wei W, Pham K, Gammons JW, Sutherland D, Liu Y, Smith A, Kaczorowski CC, O'Connell KMS. Diet composition, not calorie intake, rapidly alters intrinsic excitability of hypothalamic AgRP/NPY neurons in mice. Sci Rep 2015; 5:16810. [PMID: 26592769 PMCID: PMC4655371 DOI: 10.1038/srep16810] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 10/20/2015] [Indexed: 02/03/2023] Open
Abstract
Obesity is a chronic condition resulting from a long-term pattern of poor diet and lifestyle. Long-term consumption of high-fat diet (HFD) leads to persistent activation and leptin resistance in AgRP neurons in the arcuate nucleus of the hypothalamus (ARH). Here, for the first time, we demonstrate acute effects of HFD on AgRP neuronal excitability and highlight a critical role for diet composition. In parallel with our earlier finding in obese, long-term HFD mice, we found that even brief HFD feeding results in persistent activation of ARH AgRP neurons. However, unlike long-term HFD-fed mice, AgRP neurons from short-term HFD-fed mice were still leptin-sensitive, indicating that the development of leptin-insensitivity is not a prerequisite for the increased firing rate of AgRP neurons. To distinguish between diet composition, caloric intake, and body weight, we compared acute and long-term effects of HFD and CD in pair-fed mice on AgRP neuronal spiking. HFD consumption in pair-fed mice resulted in a significant increase in AgRP neuronal spiking despite controls for weight gain and caloric intake. Taken together, our results suggest that diet composition may be more important than either calorie intake or body weight for electrically remodeling arcuate AgRP/NPY neurons.
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Affiliation(s)
- Wei Wei
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Kevin Pham
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Jesse W Gammons
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Daniel Sutherland
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Yanyun Liu
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163.,College of Basic Medicine, Hubei University of Chinese Medicine, Wuhan City, Hubei Province, China 430065
| | - Alana Smith
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Catherine C Kaczorowski
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163.,The Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN 38163
| | - Kristen M S O'Connell
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163.,The Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN 38163
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Yoshida R, Noguchi K, Shigemura N, Jyotaki M, Takahashi I, Margolskee RF, Ninomiya Y. Leptin Suppresses Mouse Taste Cell Responses to Sweet Compounds. Diabetes 2015; 64:3751-62. [PMID: 26116698 PMCID: PMC4876703 DOI: 10.2337/db14-1462] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 06/16/2015] [Indexed: 01/19/2023]
Abstract
Leptin is known to selectively suppress neural and behavioral responses to sweet-tasting compounds. However, the molecular basis for the effect of leptin on sweet taste is not known. Here, we report that leptin suppresses sweet taste via leptin receptors (Ob-Rb) and KATP channels expressed selectively in sweet-sensitive taste cells. Ob-Rb was more often expressed in taste cells that expressed T1R3 (a sweet receptor component) than in those that expressed glutamate-aspartate transporter (a marker for Type I taste cells) or GAD67 (a marker for Type III taste cells). Systemically administered leptin suppressed taste cell responses to sweet but not to bitter or sour compounds. This effect was blocked by a leptin antagonist and was absent in leptin receptor-deficient db/db mice and mice with diet-induced obesity. Blocking the KATP channel subunit sulfonylurea receptor 1, which was frequently coexpressed with Ob-Rb in T1R3-expressing taste cells, eliminated the effect of leptin on sweet taste. In contrast, activating the KATP channel with diazoxide mimicked the sweet-suppressing effect of leptin. These results indicate that leptin acts via Ob-Rb and KATP channels that are present in T1R3-expressing taste cells to selectively suppress their responses to sweet compounds.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Kenshi Noguchi
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan Section of Orthodontics and Dentofacial Orthopedics, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Masafumi Jyotaki
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Ichiro Takahashi
- Section of Orthodontics and Dentofacial Orthopedics, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | | | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
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40
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Kentish SJ. Vagal K(ATP) channels are the key to ghrelin's orexigenic action. J Physiol 2015; 593:4515-6. [PMID: 26466756 DOI: 10.1113/jp271396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 08/26/2015] [Indexed: 11/08/2022] Open
Affiliation(s)
- Stephen J Kentish
- Discipline of Medicine, University of Adelaide, Frome Road, Adelaide, SA, 5005, Australia.,South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
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41
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Findlay JA, Hamilton DL, Ashford MLJ. BACE1 activity impairs neuronal glucose oxidation: rescue by beta-hydroxybutyrate and lipoic acid. Front Cell Neurosci 2015; 9:382. [PMID: 26483636 PMCID: PMC4589671 DOI: 10.3389/fncel.2015.00382] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 09/14/2015] [Indexed: 11/13/2022] Open
Abstract
Glucose hypometabolism and impaired mitochondrial function in neurons have been suggested to play early and perhaps causative roles in Alzheimer's disease (AD) pathogenesis. Activity of the aspartic acid protease, beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), responsible for beta amyloid peptide generation, has recently been demonstrated to modify glucose metabolism. We therefore examined, using a human neuroblastoma (SH-SY5Y) cell line, whether increased BACE1 activity is responsible for a reduction in cellular glucose metabolism. Overexpression of active BACE1, but not a protease-dead mutant BACE1, protein in SH-SY5Y cells reduced glucose oxidation and the basal oxygen consumption rate, which was associated with a compensatory increase in glycolysis. Increased BACE1 activity had no effect on the mitochondrial electron transfer process but was found to diminish substrate delivery to the mitochondria by inhibition of key mitochondrial decarboxylation reaction enzymes. This BACE1 activity-dependent deficit in glucose oxidation was alleviated by the presence of beta hydroxybutyrate or α-lipoic acid. Consequently our data indicate that raised cellular BACE1 activity drives reduced glucose oxidation in a human neuronal cell line through impairments in the activity of specific tricarboxylic acid cycle enzymes. Because this bioenergetic deficit is recoverable by neutraceutical compounds we suggest that such agents, perhaps in conjunction with BACE1 inhibitors, may be an effective therapeutic strategy in the early-stage management or treatment of AD.
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Affiliation(s)
- John A Findlay
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
| | - David L Hamilton
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
| | - Michael L J Ashford
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
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42
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Gavello D, Vandael D, Gosso S, Carbone E, Carabelli V. Dual action of leptin on rest-firing and stimulated catecholamine release via phosphoinositide 3-kinase-driven BK channel up-regulation in mouse chromaffin cells. J Physiol 2015; 593:4835-53. [PMID: 26282459 DOI: 10.1113/jp271078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/12/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Leptin is an adipokine produced by the adipose tissue regulating body weight through its appetite-suppressing effect and, as such, exerts a relevant action on the adipo-adrenal axis. Leptin has a dual action on adrenal mouse chromaffin cells both at rest and during stimulation. At rest, the adipokine inhibits the spontaneous firing of most cells by enhancing the probability of BK channel opening through the phosphoinositide 3-kinase signalling cascade. This inhibitory effect is absent in db(-) /db(-) mice deprived of Ob receptors. During sustained stimulation, leptin preserves cell excitability by generating well-adapted action potential (AP) trains of lower frequency and broader width and increases catecholamine secretion by increasing the size of the ready-releasable pool and the rate of vesicle release. In conclusion, leptin dampens AP firing at rest but preserves AP firing and enhances catecholamine release during sustained stimulation, highlighting the importance of the adipo-adrenal axis in the leptin-mediated increase of sympathetic tone and catecholamine release. ABSTRACT Leptin is an adipokine produced by the adipose tissue regulating body weight through its appetite-suppressing effect. Besides being expressed in the hypothalamus and hippocampus, leptin receptors (ObRs) are also present in chromaffin cells of the adrenal medulla. In the present study, we report the effect of leptin on mouse chromaffin cell (MCC) functionality, focusing on cell excitability and catecholamine secretion. Acute application of leptin (1 nm) on spontaneously firing MCCs caused a slowly developing membrane hyperpolarization followed by complete blockade of action potential (AP) firing. This inhibitory effect at rest was abolished by the BK channel blocker paxilline (1 μm), suggesting the involvement of BK potassium channels. Single-channel recordings in 'perforated microvesicles' confirmed that leptin increased BK channel open probability without altering its unitary conductance. BK channel up-regulation was associated with the phosphoinositide 3-kinase (PI3K) signalling cascade because the PI3K specific inhibitor wortmannin (100 nm) fully prevented BK current increase. We also tested the effect of leptin on evoked AP firing and Ca(2+) -driven exocytosis. Although leptin preserves well-adapted AP trains of lower frequency, APs are broader and depolarization-evoked exocytosis is increased as a result of the larger size of the ready-releasable pool and higher frequency of vesicle release. The kinetics and quantal size of single secretory events remained unaltered. Leptin had no effect on firing and secretion in db(-) /db(-) mice lacking the ObR gene, confirming its specificity. In conclusion, leptin exhibits a dual action on MCC activity. It dampens AP firing at rest but preserves AP firing and increases catecholamine secretion during sustained stimulation, highlighting the importance of the adipo-adrenal axis in the leptin-mediated increase of sympathetic tone and catecholamine release.
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Affiliation(s)
- Daniela Gavello
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - David Vandael
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy.,Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg, Austria
| | - Sara Gosso
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - Emilio Carbone
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
| | - Valentina Carabelli
- Department of Drug Science and Technology, University of Torino, Torino, Italy.,NIS Center, CNISM, University of Torino, Torino, Italy
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43
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Lee DK, Jeong JH, Chun SK, Chua S, Jo YH. Interplay between glucose and leptin signalling determines the strength of GABAergic synapses at POMC neurons. Nat Commun 2015; 6:6618. [PMID: 25808323 PMCID: PMC4375782 DOI: 10.1038/ncomms7618] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 02/12/2015] [Indexed: 01/31/2023] Open
Abstract
Regulation of GABAergic inhibitory inputs and alterations in POMC neuron activity by nutrients and adiposity signals regulate energy and glucose homeostasis. Thus, understanding how POMC neurons integrate these two signal molecules at the synaptic level is important. Here we show that leptin’s action on GABA release to POMC neurons is influenced by glucose levels. Leptin stimulates the JAK2-PI3K pathway in both presynaptic GABAergic terminals and postsynaptic POMC neurons. Inhibition of AMPK activity in presynaptic terminals decreases GABA release at 10 mM glucose. However, postsynaptic TRPC channel opening by the PI3K-PLC signaling pathway in POMC neurons enhances spontaneous GABA release via activation of presynaptic MC3/4 and mGlu receptors at 2.5 mM glucose. High-fat feeding blunts AMPK-dependent presynaptic inhibition, whereas PLC-mediated GABAergic feedback inhibition remains responsive to leptin. Our data indicate that the interplay between glucose and leptin signaling in glutamatergic POMC neurons is critical for determining the strength of inhibitory tone towards POMC neurons.
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Affiliation(s)
- Dong Kun Lee
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Jae Hoon Jeong
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Sung-Kun Chun
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Streamson Chua
- Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Young-Hwan Jo
- 1] Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA [2] Department of Molecular Pharmacology, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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44
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Wellhauser L, Gojska NM, Belsham DD. Delineating the regulation of energy homeostasis using hypothalamic cell models. Front Neuroendocrinol 2015; 36:130-49. [PMID: 25223866 DOI: 10.1016/j.yfrne.2014.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 08/28/2014] [Accepted: 09/02/2014] [Indexed: 12/27/2022]
Abstract
Attesting to its intimate peripheral connections, hypothalamic neurons integrate nutritional and hormonal cues to effectively manage energy homeostasis according to the overall status of the system. Extensive progress in the identification of essential transcriptional and post-translational mechanisms regulating the controlled expression and actions of hypothalamic neuropeptides has been identified through the use of animal and cell models. This review will introduce the basic techniques of hypothalamic investigation both in vivo and in vitro and will briefly highlight the key advantages and challenges of their use. Further emphasis will be place on the use of immortalized models of hypothalamic neurons for in vitro study of feeding regulation, with a particular focus on cell lines proving themselves most fruitful in deciphering fundamental basics of NPY/AgRP, Proglucagon, and POMC neuropeptide function.
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Affiliation(s)
- Leigh Wellhauser
- Department of Physiology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
| | - Nicole M Gojska
- Department of Physiology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
| | - Denise D Belsham
- Departments of Physiology, Medicine and OB/GYN, University of Toronto, Toronto, Ontario M5G 1A8, Canada; Division of Cellular and Molecular Biology, Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario M5S 1A8, Canada.
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45
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Hussain S, Richardson E, Ma Y, Holton C, De Backer I, Buckley N, Dhillo W, Bewick G, Zhang S, Carling D, Bloom S, Gardiner J. Glucokinase activity in the arcuate nucleus regulates glucose intake. J Clin Invest 2014; 125:337-49. [PMID: 25485685 DOI: 10.1172/jci77172] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 11/06/2014] [Indexed: 01/21/2023] Open
Abstract
The brain relies on a constant supply of glucose, its primary fuel, for optimal function. A taste-independent mechanism within the CNS that promotes glucose delivery to the brain has been postulated to maintain glucose homeostasis; however, evidence for such a mechanism is lacking. Here, we determined that glucokinase activity within the hypothalamic arcuate nucleus is involved in regulation of dietary glucose intake. In fasted rats, glucokinase activity was specifically increased in the arcuate nucleus but not other regions of the hypothalamus. Moreover, pharmacologic and genetic activation of glucokinase in the arcuate nucleus of rodent models increased glucose ingestion, while decreased arcuate nucleus glucokinase activity reduced glucose intake. Pharmacologic targeting of potential downstream glucokinase effectors revealed that ATP-sensitive potassium channel and P/Q calcium channel activity are required for glucokinase-mediated glucose intake. Additionally, altered glucokinase activity affected release of the orexigenic neurotransmitter neuropeptide Y in response to glucose. Together, our results suggest that glucokinase activity in the arcuate nucleus specifically regulates glucose intake and that appetite for glucose is an important driver of overall food intake. Arcuate nucleus glucokinase activation may represent a CNS mechanism that underlies the oft-described phenomena of the "sweet tooth" and carbohydrate craving.
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46
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Sumita T, Ono H, Suzuki T, Sakai G, Inukai K, Katagiri H, Asano T, Katayama S, Awata T. Mediobasal hypothalamic PTEN modulates hepatic insulin resistance independently of food intake in rats. Am J Physiol Endocrinol Metab 2014; 307:E47-60. [PMID: 24824654 DOI: 10.1152/ajpendo.00361.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Phosphatase and tensin homolog (PTEN) dephosphorylates phosphatidylinositol (PI) 3,4,5-triphosphate and antagonizes PI 3-kinase. Insulin acts in the mediobasal hypothalamus (MBH) to not only suppress food intake and weight gain but also improve glucose metabolism via PI 3-kinase activation. Thus, the blocking of hypothalamic PTEN is a potential target for treating obesity as well as diabetes. However, genetic modification of PTEN in specific neuronal populations in the MBH yielded complex results, and no postnatal intervention for hypothalamic PTEN has been reported yet. To elucidate how postnatal modification of hypothalamic PTEN influences food intake as well as glucose metabolism, we bidirectionally altered PTEN activity in the MBH of rats by adenoviral gene delivery. Inhibition of MBH PTEN activity reduced food intake and weight gain, whereas constitutive activation of PTEN tended to induce the opposite effects. Interestingly, the effects of MBH PTEN intervention on food intake and body weight were blunted by high-fat feeding. However, MBH PTEN blockade improved hepatic insulin sensitivity even under high-fat-fed conditions. On the other hand, constitutive activation of MBH PTEN induced hepatic insulin resistance. Hepatic Akt phosphorylation and the G6Pase expression level were modulated bidirectionally by MBH PTEN intervention. These results demonstrate that PTEN in the MBH regulates hepatic insulin sensitivity independently of the effects on food intake and weight gain. Therefore, hypothalamic PTEN is a promising target for treating insulin resistance even in states of overnutrition.
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Affiliation(s)
- Takashi Sumita
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
| | - Hiraku Ono
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan;
| | - Tokuko Suzuki
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
| | - Gota Sakai
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
| | - Kouichi Inukai
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
| | - Hideki Katagiri
- Department of Metabolic Diseases, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan; and
| | - Tomoichiro Asano
- Department of Medical Science, Graduate School of Medicine, University of Hiroshima, Hiroshima, Japan
| | - Shigehiro Katayama
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
| | - Takuya Awata
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Moroyama, Saitama, Japan
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Leptin modulates the intrinsic excitability of AgRP/NPY neurons in the arcuate nucleus of the hypothalamus. J Neurosci 2014; 34:5486-96. [PMID: 24741039 DOI: 10.1523/jneurosci.4861-12.2014] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The hypothalamic arcuate nucleus (ARH) is a brain region critical for regulation of food intake and a primary area for the action of leptin in the CNS. In lean mice, the adipokine leptin inhibits neuropeptide Y (NPY) and agouti-related peptide (AgRP) neuronal activity, resulting in decreased food intake. Here we show that diet-induced obesity in mice is associated with persistent activation of NPY neurons and a failure of leptin to reduce the firing rate or hyperpolarize the resting membrane potential. However, the molecular mechanism whereby diet uncouples leptin's effect on neuronal excitability remains to be fully elucidated. In NPY neurons from lean mice, the Kv channel blocker 4-aminopyridine inhibited leptin-induced changes in input resistance and spike rate. Consistent with this, we found that ARH NPY neurons have a large, leptin-sensitive delayed rectifier K(+) current and that leptin sensitivity of this current is blunted in neurons from diet-induced obese mice. This current is primarily carried by Kv2-containing channels, as the Kv2 channel inhibitor stromatoxin-1 significantly increased the spontaneous firing rate in NPY neurons from lean mice. In HEK cells, leptin induced a significant hyperpolarizing shift in the voltage dependence of Kv2.1 but had no effect on the function of the closely related channel Kv2.2 when these channels were coexpressed with the long isoform of the leptin receptor LepRb. Our results suggest that dynamic modulation of somatic Kv2.1 channels regulates the intrinsic excitability of NPY neurons to modulate the spontaneous activity and the integration of synaptic input onto these neurons in the ARH.
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Kocalis HE, Hagan SL, George L, Turney MK, Siuta MA, Laryea GN, Morris LC, Muglia LJ, Printz RL, Stanwood GD, Niswender KD. Rictor/mTORC2 facilitates central regulation of energy and glucose homeostasis. Mol Metab 2014; 3:394-407. [PMID: 24944899 PMCID: PMC4060224 DOI: 10.1016/j.molmet.2014.01.014] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 01/24/2014] [Accepted: 01/29/2014] [Indexed: 01/15/2023] Open
Abstract
Insulin signaling in the central nervous system (CNS) regulates energy balance and peripheral glucose homeostasis. Rictor is a key regulatory/structural subunit of the mTORC2 complex and is required for hydrophobic motif site phosphorylation of Akt at serine 473. To examine the contribution of neuronal Rictor/mTORC2 signaling to CNS regulation of energy and glucose homeostasis, we utilized Cre-LoxP technology to generate mice lacking Rictor in all neurons, or in either POMC or AgRP expressing neurons. Rictor deletion in all neurons led to increased fat mass and adiposity, glucose intolerance and behavioral leptin resistance. Disrupting Rictor in POMC neurons also caused obesity and hyperphagia, fasting hyperglycemia and pronounced glucose intolerance. AgRP neuron specific deletion did not impact energy balance but led to mild glucose intolerance. Collectively, we show that Rictor/mTORC2 signaling, especially in POMC-expressing neurons, is important for central regulation of energy and glucose homeostasis.
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Affiliation(s)
- Heidi E. Kocalis
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Scott L. Hagan
- Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Leena George
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Maxine K. Turney
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Michael A. Siuta
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN, United States
- Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Gloria N. Laryea
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN, United States
| | - Lindsey C. Morris
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Louis J. Muglia
- Center for Prevention of Preterm Birth, Cincinnati Children’s Hospital Medical Center, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Richard L. Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Gregg D. Stanwood
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Kevin D. Niswender
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
- Department of Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN, United States
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
- Corresponding author. 7435G MRB IV, Vanderbilt Medical Center, Nashville, TN 37232, United States. Tel.: +1 615 936 0500.
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49
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Jiang Y, Zsombok A. Regulation of neurons in the dorsal motor nucleus of the vagus by SIRT1. Front Neurosci 2014; 7:270. [PMID: 24454277 PMCID: PMC3887315 DOI: 10.3389/fnins.2013.00270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 12/20/2013] [Indexed: 12/29/2022] Open
Abstract
Neurons in the dorsal motor nucleus of the vagus (DMV) play a critical role in the regulation of autonomic functions. Previous studies indicated that central activation of sirtuin 1 (SIRT1) has beneficial effects on homeostasis, most likely via modulation of the autonomic output. Sirtuins are NAD+-dependent deacetylases and have been associated with longevity. SIRT1 is one of the best-characterized sirtuins expressed in mammals, and may be involved in the regulation of metabolism. Resveratrol, a SIRT1 activator reduced hyperglycemia likely through activation of vagal output; however, the cellular mechanisms of action have not been determined. In this study, whole-cell patch-clamp electrophysiology on acute brainstem slices was used to test the hypothesis that activation of SIRT1 with resveratrol enhances neurotransmission in DMV neurons. Application of resveratrol increased the frequency of spontaneous excitatory postsynaptic currents (sEPSC). This effect was KATP channel-dependent and was prevented with pre-application of SIRT1 inhibitor, EX527. Resveratrol also increased miniature EPSC (mEPSC) frequency without change in amplitude. Furthermore, our data demonstrated that resveratrol regulates excitatory neurotransmission in a PI3 kinase-dependent manner, since wortmannin, a PI3K inhibitor prevented the increase of mEPSC frequency caused by resveratrol. In conclusion, our data demonstrate that resveratrol via SIRT1 increases excitatory neurotransmission to DMV neurons. These observations suggest that activation of SIRT1 may regulate the function of subdiaphragmatic organs through controlling the activity of parasympathetic DMV neurons.
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Affiliation(s)
- Yanyan Jiang
- Neuroscience Program, School of Science and Engineering, Tulane University New Orleans, LA, USA ; Department of Physiology, School of Medicine, Tulane University New Orleans, LA, USA
| | - Andrea Zsombok
- Neuroscience Program, School of Science and Engineering, Tulane University New Orleans, LA, USA ; Department of Physiology, School of Medicine, Tulane University New Orleans, LA, USA
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50
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Nadkarni P, Chepurny OG, Holz GG. Regulation of glucose homeostasis by GLP-1. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014. [PMID: 24373234 DOI: 10.1016/b978-0-12-800101-1.00002-8.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/01/2022]
Abstract
Glucagon-like peptide-1(7-36)amide (GLP-1) is a secreted peptide that acts as a key determinant of blood glucose homeostasis by virtue of its abilities to slow gastric emptying, to enhance pancreatic insulin secretion, and to suppress pancreatic glucagon secretion. GLP-1 is secreted from L cells of the gastrointestinal mucosa in response to a meal, and the blood glucose-lowering action of GLP-1 is terminated due to its enzymatic degradation by dipeptidyl-peptidase-IV (DPP-IV). Released GLP-1 activates enteric and autonomic reflexes while also circulating as an incretin hormone to control endocrine pancreas function. The GLP-1 receptor (GLP-1R) is a G protein-coupled receptor that is activated directly or indirectly by blood glucose-lowering agents currently in use for the treatment of type 2 diabetes mellitus (T2DM). These therapeutic agents include GLP-1R agonists (exenatide, liraglutide, lixisenatide, albiglutide, dulaglutide, and langlenatide) and DPP-IV inhibitors (sitagliptin, vildagliptin, saxagliptin, linagliptin, and alogliptin). Investigational agents for use in the treatment of T2DM include GPR119 and GPR40 receptor agonists that stimulate the release of GLP-1 from L cells. Summarized here is the role of GLP-1 to control blood glucose homeostasis, with special emphasis on the advantages and limitations of GLP-1-based therapeutics.
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Affiliation(s)
- Prashant Nadkarni
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Joslin Diabetes Center, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - Oleg G Chepurny
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA
| | - George G Holz
- Department of Medicine, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA; Department of Pharmacology, State University of New York (SUNY), Upstate Medical University, Syracuse, New York, USA.
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