1
|
Watts AG, Kanoski SE, Sanchez-Watts G, Langhans W. The physiological control of eating: signals, neurons, and networks. Physiol Rev 2022; 102:689-813. [PMID: 34486393 PMCID: PMC8759974 DOI: 10.1152/physrev.00028.2020] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.
Collapse
Affiliation(s)
- Alan G Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Scott E Kanoski
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Graciela Sanchez-Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule-Zürich, Schwerzenbach, Switzerland
| |
Collapse
|
2
|
Jeong B, Kim KK, Lee TH, Kim HR, Park BS, Park JW, Jeong JK, Seong JY, Lee BJ. Spexin Regulates Hypothalamic Leptin Action on Feeding Behavior. Biomolecules 2022; 12:biom12020236. [PMID: 35204737 PMCID: PMC8961618 DOI: 10.3390/biom12020236] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 02/01/2023] Open
Abstract
Spexin (SPX) is a recently identified neuropeptide that is believed to play an important role in the regulation of energy homeostasis. Here, we describe a mediating function of SPX in hypothalamic leptin action. Intracerebroventricular (icv) SPX administration induced a decrease in food intake and body weight gain. SPX was found to be expressed in cells expressing leptin receptor ObRb in the mouse hypothalamus. In line with this finding, icv leptin injection increased SPX mRNA in the ObRb-positive cells of the hypothalamus, which was blocked by treatment with a STAT3 inhibitor. Leptin also increased STAT3 binding to the SPX promoter, as measured by chromatin immunoprecipitation assays. In vivo blockade of hypothalamic SPX biosynthesis with an antisense oligodeoxynucleotide (AS ODN) resulted in a diminished leptin effect on food intake and body weight. AS ODN reversed leptin’s effect on the proopiomelanocortin (POMC) mRNA expression and, moreover, decreased leptin-induced STAT3 binding to the POMC promoter sequence. These results suggest that SPX is involved in leptin’s action on POMC gene expression in the hypothalamus and impacts the anorexigenic effects of leptin.
Collapse
Affiliation(s)
- Bora Jeong
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
| | - Kwang-Kon Kim
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
| | - Tae-Hwan Lee
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
| | - Han-Rae Kim
- Department of Pharmacology and Physiology, School of Medicine & Health Sciences, The George Washington University, Washington, DC 22037, USA; (H.-R.K.); (J.-K.J.)
| | - Byong-Seo Park
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
| | - Jeong-Woo Park
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
| | - Jin-Kwon Jeong
- Department of Pharmacology and Physiology, School of Medicine & Health Sciences, The George Washington University, Washington, DC 22037, USA; (H.-R.K.); (J.-K.J.)
| | - Jae-Young Seong
- Graduate School of Medicine, Korea University, Seoul 02841, Korea
- Correspondence: (J.-Y.S.); (B.-J.L.)
| | - Byung-Ju Lee
- Department of Biological Sciences, College of Natural Sciences, University of Ulsan, Ulsan 44610, Korea; (B.J.); (K.-K.K.); (T.-H.L.); (B.-S.P.); (J.-W.P.)
- Correspondence: (J.-Y.S.); (B.-J.L.)
| |
Collapse
|
3
|
Harris RBS. Phosphorylation of STAT3 in hypothalamic nuclei is stimulated by lower doses of leptin than are needed to inhibit food intake. Am J Physiol Endocrinol Metab 2021; 321:E190-E201. [PMID: 34121448 PMCID: PMC8321824 DOI: 10.1152/ajpendo.00143.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/03/2021] [Accepted: 06/07/2021] [Indexed: 01/08/2023]
Abstract
This experiment investigated which hypothalamic nuclei were activated by a dose of leptin that inhibited food intake. Foodnot intake, energy expenditure, respiratory exchange ratio (RER), and intrascapular brown adipose tissue (IBAT) temperature were measured in male and female Sprague Dawley rats for 36 h following an intraperitoneal injection of 0, 50, 200, 500, or 1,000 µg leptin/kg with each rat tested with each dose of leptin in random order. In both males and females, RER and 12-h food intake were inhibited only by 1,000 µg leptin/kg, but there was no effect on energy expenditure or IBAT temperature. At the end of the experiment, phosphorylated signal transducer and activator of transcription 3 (pSTAT3) immunoreactivity was measured 1 h after injection of 0, 50, 500, or 1,000 µg leptin/kg. In male rats, the lowest dose of leptin produced a maximal activation of STAT3 in the Arc and nucleus of the solitary tract (NTS). There was no response in the dorsomedial hypothalamus, but there was a progressive increase in ventromedial nucleus of the hypothalamus (VMH) pSTAT3 with increasing doses of leptin. In female rats, there was no significant change in Arc and pSTAT3 NTS activation was maximal with 500 mg leptin/kg, but only the highest dose of leptin increased VMH pSTAT3. These results suggest that the VMH plays an important role in the energetic response to elevations of circulating leptin but do not exclude the possibility that multiple nuclei provide the appropriate integrated response to hyperleptinemia.NEW & NOTEWORTHY The results of this experiment show that doses of leptin too small to inhibit food intake produce a maximal response to leptin in the arcuate nucleus. By contrast the VMH shows a robust response that correlates with inhibition of food intake. This suggests that the VMH plays an important role in the energetic response to hyperleptinemia.
Collapse
Affiliation(s)
- Ruth B S Harris
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia
| |
Collapse
|
4
|
Harris RBS. Loss of leptin receptor-expressing cells in the hindbrain decreases forebrain leptin sensitivity. Am J Physiol Endocrinol Metab 2020; 318:E806-E816. [PMID: 32228323 PMCID: PMC7272723 DOI: 10.1152/ajpendo.00020.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/18/2020] [Accepted: 03/24/2020] [Indexed: 01/12/2023]
Abstract
Previous studies indicate that inhibition of food intake by leptin is mediated by an integrated response to activation of hypothalamic and hindbrain receptors. This study tested whether loss of hindbrain leptin receptor signaling changed sensitivity to forebrain leptin. Injections of leptin-conjugated saporin (Lep-Sap) into the medial nucleus of the solitary tract (NTS) were used to destroy hindbrain leptin receptor-expressing neurons of male Sprague-Dawley rats. Controls were injected with saporin conjugated with a nonsense peptide (Blk-Sap). Lep-Sap had no effect on daily food intake or body weight, but expression of phosphorylated signal transducer and activator of transcription 3 (pSTAT3) in the NTS following a peripheral injection of leptin was abolished 26 days after Lep-Sap injections. To test forebrain leptin sensitivity, Lep-Sap and Blk-Sap rats received third-ventricle injections of 0, 0.05, 0.1, 0.25, or 0.5 μg leptin. Food intake was inhibited by 0.25 and 0.5 μg leptin in Blk-Sap rats, but there was no significant effect of leptin on food intake of Lep-Sap rats. There was no difference in hypothalamic pSTAT3 in unstimulated conditions, but pSTAT3 was lower in the dorsomedial region of the ventromedial nucleus of the hypothalamus (VMH) of Lep-Sap rats compared with Blk-Sap rats following a third-ventricle injection of 0.25 μg leptin. These results are consistent with previous data showing that loss of VMH leptin receptor-expressing cells prevents weight loss caused by fourth-ventricle leptin infusion and show that the integrated response between the hindbrain and forebrain is heavily dependent on leptin activity in the VMH.
Collapse
Affiliation(s)
- Ruth B S Harris
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia
| |
Collapse
|
5
|
Seamon M, Ahn W, Li AJ, Ritter S, Harris RBS. Leptin receptor-expressing neurons in ventromedial nucleus of the hypothalamus contribute to weight loss caused by fourth ventricle leptin infusions. Am J Physiol Endocrinol Metab 2019; 317:E586-E596. [PMID: 31361549 PMCID: PMC6842917 DOI: 10.1152/ajpendo.00205.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 07/11/2019] [Accepted: 07/22/2019] [Indexed: 12/24/2022]
Abstract
Leptin administration into the hindbrain, and specifically the nucleus of the solitary tract, increases phosphorylated signal transducer and activator of transcription 3 (pSTAT3), a marker of leptin receptor activation, in hypothalamic nuclei known to express leptin receptors. The ventromedial nucleus of the hypothalamus (VMH) shows the greatest response, with a threefold increase in pSTAT3. This experiment tested the importance of VMH leptin receptor-expressing neurons in mediating weight loss caused by fourth ventricle (4V) leptin infusion. Male Sprague-Dawley rats received bilateral VMH 75-nL injections of 260 ng/μL of leptin-conjugated saporin (Lep-Sap) or blank-saporin (Blk-Sap). After 23 days they were fitted with 4V infusion cannulas and 1 wk later adapted to housing in a calorimeter before they were infused with 0.9 μg leptin/day for 14 days. There was no effect of VMH Lep-Sap on weight gain or glucose clearance before leptin infusion. Leptin inhibited food intake and respiratory exchange ratio in Blk-Sap but not Lep-Sap rats. Leptin had no effect on energy expenditure or brown adipose tissue temperature of either group. Inguinal and epididymal fat were significantly reduced in leptin-treated Blk-Sap rats, but the response was greatly attenuated in Lep-Sap rats. VMH pSTAT3 was increased in leptin-treated Blk-Sap but not Lep-Sap rats. These results support the concept that leptin-induced weight loss results from an integrated response across different brain areas. They also support previous reports that VMH leptin receptors do not play a significant role in maintaining energy balance in basal conditions but limit weight gain during positive energy balance.
Collapse
Affiliation(s)
- Marissa Seamon
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia
| | - WonMo Ahn
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia
| | - Ai-Jun Li
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, Washington
| | - Sue Ritter
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, Washington
| | - Ruth B S Harris
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia
| |
Collapse
|
6
|
Harris RBS. Low-dose infusions of leptin into the nucleus of the solitary tract increase sensitivity to third ventricle leptin. Am J Physiol Endocrinol Metab 2019; 316:E719-E728. [PMID: 30721096 PMCID: PMC6580178 DOI: 10.1152/ajpendo.00562.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Previous studies suggest that weight loss occurs when leptin receptors in both the forebrain and hindbrain are activated. Experiments described here tested whether this integration is mediated through a neural connection or by leptin diffusion through the subarachanoid space. If the hypothalamus and hindbrain communicated through a neural pathway, then a very low dose of leptin infused directly into the nucleus of the solitary tract (NTS) would enhance the response to third ventricle (3V) leptin but would have no effect if infused into the fourth ventricle (4V). A 12-day infusion of 10 ng/24 h into the 4V or the NTS reduced body fat. Leptin at 5 ng/24 h into the 4V or NTS had no effect on food intake or body composition, but infusion of 5 ng of leptin/24 h into the NTS combined with a 3V injection of 0.1 μg of leptin inhibited food intake between 6 and 12 h after injection. Cumulative intake was inhibited for up to 36 h. 3V leptin had no effect on food intake of rats receiving the 4V leptin infusion. Similar results were found using infusions of 5 ng leptin/24 h and a 3V injection of 0.025 μg leptin. These data suggest that activation of leptin receptors in the NTS lowers the threshold for response to leptin in the forebrain through a neural network.
Collapse
Affiliation(s)
- Ruth B S Harris
- Department of Physiology, Medical College of Georgia at Augusta University , Augusta, Georgia
| |
Collapse
|
7
|
Chu SC, Chen PN, Chen JR, Yu CH, Hsieh YS, Kuo DY. Role of hypothalamic leptin-LepRb signaling in NPY-CART-mediated appetite suppression in amphetamine-treated rats. Horm Behav 2018; 98:173-182. [PMID: 29307696 DOI: 10.1016/j.yhbeh.2017.12.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/22/2017] [Accepted: 12/29/2017] [Indexed: 12/15/2022]
Abstract
Leptin is an adipose tissue hormone which plays an important role in regulating energy homeostasis. Amphetamine (AMPH) is a drug of appetite suppressant, which exerts its effect by decreasing the expression of hypothalamic neuropeptide Y (NPY) and increasing that of cocaine- and amphetamine-regulated transcript (CART). This study investigated whether leptin, the leptin receptor (LepRb) and the signal transducer and activator of transcription-3 (STAT3) were involved in NPY/CART-mediated appetite suppression in AMPH-treated rats. Rats were given AMPH daily for four days, and changes in the levels of blood leptin and hypothalamic NPY, CART, LepRb, Janus kinases 2 (JAK2), and STAT3 were assessed and compared. During the AMPH treatment, blood leptin levels and hypothalamic NPY expression decreased, with the largest reduction observed on Day 2. By contrast, the expression of hypothalamic CART, LepRb, JAK2, and STAT3 increased, with the maximum response on Day 2. Furthermore, the binding activity of pSTAT3/DNA increased and was expressed in similar pattern to that of CART, LepRb, and JAK2. An intracerebroventricular infusion of NPY antisense 60min prior to AMPH treatment increased the levels of leptin, as well as the expression in LepRb, JAK2, and CART, whereas an infusion of STAT3 antisense decreased these levels and the expression of these parameters. The results suggest that blood leptin and hypothalamic LepRb-JAK2-STAT3 signaling involved in NPY-CART-regulated appetite suppression in AMPH-treated rats. The findings may aid understanding the role of leptin-LepRb during the treatment of anorectic drugs.
Collapse
Affiliation(s)
- Shu-Chen Chu
- Department of Food Science, Central Taiwan University of Science and Technology, Taichung City 406, Taiwan
| | - Pei-Ni Chen
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Chung Shan Medical University Hospital, Taichung City 40201, Taiwan
| | - Jeng-Rung Chen
- Department of Veterinary Medicine, National Chung Hsing University, Taichung City 40201, Taiwan
| | - Ching-Han Yu
- Department of Physiology, Chung Shan Medical University, Chung Shan Medical University Hospital, Taichung City 40201, Taiwan
| | - Yih-Shou Hsieh
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Chung Shan Medical University Hospital, Taichung City 40201, Taiwan
| | - Dong-Yih Kuo
- Department of Physiology, Chung Shan Medical University, Chung Shan Medical University Hospital, Taichung City 40201, Taiwan.
| |
Collapse
|
8
|
Harris RBS. Low-dose leptin infusion in the fourth ventricle of rats enhances the response to third-ventricle leptin injection. Am J Physiol Endocrinol Metab 2017; 313:E134-E147. [PMID: 28442484 PMCID: PMC6109645 DOI: 10.1152/ajpendo.00052.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/27/2017] [Accepted: 04/18/2017] [Indexed: 01/11/2023]
Abstract
We previously reported that low-dose leptin infusions into the third or fourth ventricle that do not affect energy balance when given independently cause rapid weight loss when given simultaneously. Therefore, we tested whether hindbrain leptin enhances the response to forebrain leptin or whether forebrain leptin enhances the response to hindbrain leptin. Rats received fourth-ventricle infusions of saline or 0.01, 0.1, 0.3, or 0.6 μg leptin/day for 13 days. On days 9 and 13, 0.1 μg leptin was injected into the third ventricle. The injection inhibited food intake for 36 h in saline-infused rats but for 60 h in those infused with 0.6 μg leptin/day. Leptin injection increased intrascapular brown fat temperature in leptin-infused, but not saline-infused, rats. In a separate experiment, rats received third-ventricle infusions of saline or 0.005, 0.01, 0.05, or 0.1 μg leptin/day and fourth-ventricle injections of 1.0 μg leptin on days 9 and 13 Leptin injection inhibited food intake, respiratory exchange ratio, and 14-h food intake in rats infused with saline or the two lowest doses of leptin. There was no effect with higher-dose leptin infusions because food intake, body fat, and lean mass were already inhibited. These data suggest that activation of leptin receptors in the hindbrain enhances the response to third-ventricle leptin, whereas activation of forebrain leptin receptors does not enhance the response to fourth-ventricle leptin, consistent with our previous finding that weight loss in rats treated with fourth-ventricle leptin is associated with indirect activation of hypothalamic STAT3.
Collapse
Affiliation(s)
- Ruth B S Harris
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia
| |
Collapse
|