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Huang KP, Ronveaux CC, de Lartigue G, Geary N, Asarian L, Raybould HE. Deletion of leptin receptors in vagal afferent neurons disrupts estrogen signaling, body weight, food intake and hormonal controls of feeding in female mice. Am J Physiol Endocrinol Metab 2019; 316:E568-E577. [PMID: 30753113 PMCID: PMC6482667 DOI: 10.1152/ajpendo.00296.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Deletion of the leptin receptor from vagal afferent neurons (VAN) using a conditional deletion (Nav1.8/LepRfl/fl) results in an obese phenotype with increased food intake and lack of exogenous cholecystokinin (CCK)-induced satiation in male mice. Female mice are partially protected from weight gain and increased food intake in response to ingestion of high-fat (HF) diets. However, whether the lack of leptin signaling in VAN leads to an obese phenotype or disruption of hypothalamic-pituitary-gonadal axis function in female mice is unclear. Here, we tested the hypothesis that leptin signaling in VAN is essential to maintain estrogen signaling and control of food intake, energy expenditure, and adiposity in female mice. Female Nav1.8/LepRfl/fl mice gained more weight, had increased gonadal fat mass, increased meal number in the dark phase, and increased total food intake compared with wild-type controls. Resting energy expenditure was unaffected. The decrease in food intake produced by intraperitoneal injection of CCK (3 μg/kg body wt) was attenuated in female Nav1.8/LepRfl/fl mice compared with wild-type controls. Intraperitoneal injection of ghrelin (100 μg/kg body wt) increased food intake in Nav1.8/LepRfl/fl mice but not in wild-type controls. Ovarian steroidogenesis was suppressed, resulting in decreased plasma estradiol, which was accompanied by decreased expression of estrogen receptor-1 (Esr1) in VAN but not in the hypothalamic arcuate nucleus. These data suggest that the absence of leptin signaling in VAN is accompanied by disruption of estrogen signaling in female mice, leading to an obese phenotype possibly via altered control of feeding behavior.
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Affiliation(s)
- Kuei-Pin Huang
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis , Davis, California
| | - Charlotte C Ronveaux
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis , Davis, California
| | - Guillaume de Lartigue
- John B. Pierce Laboratory/Cellular and Molecular Physiology Department, Yale University School of Medicine , New Haven, Connecticut
| | - Nori Geary
- Department of Psychiatry, Weill Medical College of Cornell University , New York, New York
| | - Lori Asarian
- Department of Medicine-Immunobiology, Robert Larner College of Medicine, University of Vermont , Burlington, Vermont
| | - Helen E Raybould
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis , Davis, California
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Central and peripheral effects of physical exercise without weight reduction in obese and lean mice. Biosci Rep 2018; 38:BSR20171033. [PMID: 29371411 PMCID: PMC5835714 DOI: 10.1042/bsr20171033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 12/26/2017] [Accepted: 01/15/2018] [Indexed: 11/26/2022] Open
Abstract
To investigate the central (hypothalamic) and peripheral effects of exercise without body weight change in diet-induced obesity (DIO). Twelve-week-old male C57Bl/6 mice received a control (C) or a high-fat diet (H). Half of them had free access to running wheels for 5 days/week for 10 weeks (CE) and HE, respectively). Hypothalamic expression of genes related to energy homeostasis, and leptin (Stat3 and p-Stat3) and insulin (Akt and p-Akt) signaling were evaluated. Glucose and leptin tolerance, peripheral insulin sensitivity, and plasma insulin, leptin and adiponectin were determined. Perigonadal and retroperitoneal fat depots were increased by diet but reduced by exercise despite lack of effect of exercise on body weight. Blood glucose during intraperitoneal glucose tolerance test (ipGTT) was higher and glucose decay during intraperitoneal insulin tolerance test (ipITT) was lower in H and HE compared with C and CE. Exercise increased liver p-Akt expression and reduced fast glycemia. High-fat diet increased plasma insulin and leptin. Exercise had no effect on insulin but decreased leptin and increased adiponectin. Leptin inhibited food intake in all groups. Hypothalamic total and p-Stat3 and Akt were similar amongst the groups despite higher plasma levels of leptin and insulin in H and HE mice. High-fat diet modulated gene expression favoring a positive energy balance. Exercise only marginally changed the gene expression. Exercise induced positive changes (decreased fast glycemia and fat depots; increased liver insulin signaling and adiponectin concentration) without weight loss. Thus, despite reducing body weight could bring additional benefits, the effects of exercise must not be overlooked when weight reduction is not achieved.
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Ji L, Wu HT, Qin XY, Lan R. Dissecting carboxypeptidase E: properties, functions and pathophysiological roles in disease. Endocr Connect 2017; 6:R18-R38. [PMID: 28348001 PMCID: PMC5434747 DOI: 10.1530/ec-17-0020] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 03/27/2017] [Indexed: 01/02/2023]
Abstract
Since discovery in 1982, carboxypeptidase E (CPE) has been shown to be involved in the biosynthesis of a wide range of neuropeptides and peptide hormones in endocrine tissues, and in the nervous system. This protein is produced from pro-CPE and exists in soluble and membrane forms. Membrane CPE mediates the targeting of prohormones to the regulated secretory pathway, while soluble CPE acts as an exopeptidase and cleaves C-terminal basic residues from peptide intermediates to generate bioactive peptides. CPE also participates in protein internalization, vesicle transport and regulation of signaling pathways. Therefore, in two types of CPE mutant mice, Cpefat/Cpefat and Cpe knockout, loss of normal CPE leads to a lot of disorders, including diabetes, hyperproinsulinemia, low bone mineral density and deficits in learning and memory. In addition, the potential roles of CPE and ΔN-CPE, an N-terminal truncated form, in tumorigenesis and diagnosis were also addressed. Herein, we focus on dissecting the pathophysiological roles of CPE in the endocrine and nervous systems, and related diseases.
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Affiliation(s)
- Lin Ji
- Department of Cell Biology & Medical GeneticsSchool of Medicine, Shenzhen University, Shenzhen, China
| | - Huan-Tong Wu
- Beijing Engineering Research Center of Food Environment and HealthCollege of Life & Environmental Sciences, Minzu University of China, Beijing, China
| | - Xiao-Yan Qin
- Beijing Engineering Research Center of Food Environment and HealthCollege of Life & Environmental Sciences, Minzu University of China, Beijing, China
| | - Rongfeng Lan
- Department of Cell Biology & Medical GeneticsSchool of Medicine, Shenzhen University, Shenzhen, China
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He L, Li Z, Zhou D, Ding Y, Xu L, Chen Y, Fan J. Galanin receptor 2 mediates antifibrogenic effects of galanin on hepatic stellate cells. Exp Ther Med 2016; 12:3375-3380. [PMID: 27882166 DOI: 10.3892/etm.2016.3764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 09/09/2016] [Indexed: 12/24/2022] Open
Abstract
Galanin is an endogenous factor involved in the negative regulation of the biological effects of leptin in bioenergetic metabolism. Leptin promotes fibrogenic effects in hepatic stellate cells (HSCs), however, little is known about the effects of galanin on HSCs. In the present study, the biological functions of galanin and its receptors (GalRs) in HSCs were investigated using cell culture in vitro. It was found that galanin and GalR3 mRNA are expressed in quiescent and activated HSCs. GalR2 expression was undetectable in quiescent HSCs but was markedly induced in activated HSCs. In the HSC-T6 cell line, which is an activated rat HSC cell line, treatment with 100 nmol/l galanin significantly inhibited cell proliferation. It also inhibited transforming growth factor (TGF)-β1 and α-smooth muscle actin (SMA) expression and upregulated peroxisome proliferator-activated receptor (PPAR)-γ expression. Following the knockdown of GalR2 by specific small interfering RNA, the activation of GalR3 by galanin does not influence these effects of galanin on HSCs. However, activation of GalR2 alone by galanin following the knockdown of GalR3 inhibits HSC proliferation and TGF-β1 and α-SMA expression, in addition to inducing PPAR-γ expression. These data suggest that galanin inhibits HSC activation and suppresses the profibrogenic features of these cells, and these effects might be mediated by GalR2. Thus, galanin is a potential endogenous factor in the inhibition of liver fibrosis.
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Affiliation(s)
- Lingnan He
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Zhenghong Li
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Da Zhou
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Yongnian Ding
- Department of Gastroenterology, Second Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830028, P.R. China
| | - Leiming Xu
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Yuanwen Chen
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Jiangao Fan
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
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Ronveaux CC, Tomé D, Raybould HE. Glucagon-like peptide 1 interacts with ghrelin and leptin to regulate glucose metabolism and food intake through vagal afferent neuron signaling. J Nutr 2015; 145:672-80. [PMID: 25833771 PMCID: PMC4381768 DOI: 10.3945/jn.114.206029] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 01/16/2015] [Indexed: 12/25/2022] Open
Abstract
Emerging evidence has suggested a possible physiologic role for peripheral glucagon-like peptide 1 (GLP-1) in regulating glucose metabolism and food intake. The likely site of action of GLP-1 is on vagal afferent neurons (VANs). The vagal afferent pathway is the major neural pathway by which information about ingested nutrients reaches the central nervous system and influences feeding behavior. Peripheral GLP-1 acts on VANs to inhibit food intake. The mechanism of the GLP-1 receptor (GLP-1R) is unlike other gut-derived receptors; GLP-1Rs change their cellular localization according to feeding status rather than their protein concentrations. It is possible that several gut peptides are involved in mediating GLP-1R translocation. The mechanism of peripheral GLP-1R translocation still needs to be elucidated. We review data supporting the role of peripheral GLP-1 acting on VANs in influencing glucose homeostasis and feeding behavior. We highlight evidence demonstrating that GLP-1 interacts with ghrelin and leptin to induce satiation. Our aim was to understand the mechanism of peripheral GLP-1 in the development of noninvasive antiobesity treatments.
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Affiliation(s)
- Charlotte C Ronveaux
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA; and,Department of Nutrition and Physiology and Ingestive Behavior, AgroParisTech, Paris, France
| | - Daniel Tomé
- Department of Nutrition and Physiology and Ingestive Behavior, AgroParisTech, Paris, France
| | - Helen E Raybould
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA; and
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Ronveaux CC, de Lartigue G, Raybould HE. Ability of GLP-1 to decrease food intake is dependent on nutritional status. Physiol Behav 2014; 135:222-9. [PMID: 24955496 DOI: 10.1016/j.physbeh.2014.06.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 06/11/2014] [Accepted: 06/13/2014] [Indexed: 01/05/2023]
Abstract
UNLABELLED Gut-derived glucagon like peptide-1 (GLP-1) acts in the postprandial period to stimulate insulin secretion and inhibit gastrointestinal motor and secretory function; whether endogenous peripheral GLP-1 inhibits food intake is less clear. We hypothesized that GLP-1 inhibits food intake in the fed, but not fasted, state. There is evidence that GLP-1 acts via stimulation of vagal afferent neurons (VAN); we further hypothesized that the satiating effects of endogenous GLP-1 in the postprandial period is determined either by a change in GLP-1 receptor (GLP-1R) expression or localization to different cellular compartments in VAN. METHODS Food intake was recorded following administration of GLP-1 (50μg/kg or 100μg/kg) or saline (IP) in Wistar rats fasted for 18h or fasted then re-fed with 3g chow. GLP-1R protein expression and localization on VAN were determined by immunocytochemistry and immunoblots in animals fasted for 18h or fasted then re-fed for 40min. GLP-1R mRNA level was detected in animals fasted for 18h or fasted and re-fed ad libitum for 2h. RESULTS GLP-1 (100μg/kg) significantly reduced 40min food intake by 38% in re-fed but not fasted rats (p<0.05). GLP-1R mRNA or protein levels in VAN were unchanged in re-fed compared to fasted rats. However, GLP-1R localization to the plasma membrane was significantly increased in VAN by feeding. CONCLUSION Feeding changes the ability of peripheral GLP-1 to inhibit food intake. GLP-1Rs are trafficked to the plasma membrane in response to a meal. GLP-1 may play a role in regulating food intake in the postprandial period.
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Affiliation(s)
- Charlotte C Ronveaux
- Dept. of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; AgroParisTech, UMR914 Nutrition Physiology and Ingestive Behavior, Paris 75005, France
| | - Guillaume de Lartigue
- Dept. of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA
| | - Helen E Raybould
- Dept. of Anatomy, Physiology and Cell Biology, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA.
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Renquist BJ, Zhang C, Williams SY, Cone RD. Development of an assay for high-throughput energy expenditure monitoring in the zebrafish. Zebrafish 2013; 10:343-52. [PMID: 23705823 DOI: 10.1089/zeb.2012.0841] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Energy homeostasis is maintained by balancing energy intake and expenditure. Many signals regulating energy intake are conserved between the human and teleost. However, before this work, there was no sensitive high-throughput system to monitor energy expenditure in the teleost. We exploit the nonfluorescent and fluorescent properties of resazurin and its reduced form resorufin (alamarBlue(®)) to monitor energy expenditure responses to drug application and genetic manipulation. We show that leptin, insulin, and alpha-melanocyte-stimulating hormone (α-MSH) increase energy expenditure dose dependently in the larval zebrafish. As previously established in the mouse, etomoxir, a carnitine palmitoyl transferase I inhibitor, blocks leptin-induced energy expenditure in the zebrafish. Metformin, the most commonly prescribed insulin sensitizer, increases the insulin-induced metabolic rate. Using genetic knockdown, we observed that α-MSH treatment increases the metabolic rate, as does knockdown of the melanocortin antagonist, agouti-related protein. The agouti-related protein and multiple melanocortin receptors are shown to be involved in these effects. These studies confirm that aspects of hormonal regulation of energy expenditure are conserved in the teleost, and suggest that this assay may provide a unique tool to perform in vivo screens for drugs or genes that affect the metabolic rate, including insulin or leptin sensitizers.
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Sekar R, Chow BKC. Metabolic effects of secretin. Gen Comp Endocrinol 2013; 181:18-24. [PMID: 23246720 DOI: 10.1016/j.ygcen.2012.11.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 11/23/2012] [Accepted: 11/27/2012] [Indexed: 12/25/2022]
Abstract
Secretin (Sct), traditionally a gastrointestinal hormone backed by a century long research, is now beginning to be recognized also as a neuroactive peptide. Substantiation by recent evidence on the functional role of Sct in various regions of the brain, especially on its potential neurosecretion from the posterior pituitary, has revealed Sct's physiological actions in regulating water homeostasis. Recent advances in understanding the functional roles of central and peripheral Sct has been made possible by the development of Sct and Sct receptor (SctR) knockout animal models which have led to novel approaches in research on the physiology of this brain-gut peptide. While research on the role of Sct in appetite regulation and fatty acid metabolism has been initiated recently, its role in glucose homeostasis is unclear. This review focuses mainly on the metabolic role of Sct by discussing data from the last century and recent discoveries, with emphasis on the need for revisiting and elucidating the role of Sct in metabolism and energy homeostasis.
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Affiliation(s)
- Revathi Sekar
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong
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Cohen JI, Maayan L, Convit A. Preliminary evidence for obesity-associated insulin resistance in adolescents without elevations of inflammatory cytokines. Diabetol Metab Syndr 2012; 4:26. [PMID: 22682228 PMCID: PMC3509401 DOI: 10.1186/1758-5996-4-26] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 04/24/2012] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND To ascertain whether the associations between obesity, inflammation, and insulin resistance established in human adult studies are found among adolescents. METHODS We contrasted 36 obese and 24 lean youth on fasting glucose, insulin levels, lipid profile, hemoglobin A1C, markers of hepatic function, white blood cell count, C-reactive protein (CRP) and fibrinogen levels. The cytokines IL-6, TNF-α, IFN-γ, IL-10 and IL-4 and the adipokines leptin, resistin, and adiponectin were also compared between the two groups. The fasting glucose and insulin values were used to estimate the degree of insulin resistance with the homeostatic model assessment of insulin resistance (HOMA-IR). T-tests and correlations were run to examine group differences and associations between groups. In addition, regression analyses were used to ascertain whether the markers of inflammation were predictive of the degree of insulin resistance. RESULTS Although obese adolescents had clear evidence of insulin resistance, only CRP, fibrinogen and leptin were elevated; there were no group differences in pro- or anti-inflammatory cytokines nor adiponectin and resistin. Anthropometric measures of obesity and level of insulin resistance were highly correlated to the acute phase reactants CRP and fibrinogen; however, the degree of insulin resistance was not predicted by the pro- or anti-inflammatory cytokine markers. Obese adolescents had higher white blood cell counts. In addition they had higher circulating alanine aminotransferase concentrations and lower circulating albumin and total protein than lean adolescents, possibly as a result of hepatocyte damage from fatty liver. CONCLUSION Unlike rodent or adult studies, we found that wide-spread systemic inflammation is not necessarily associated with insulin resistance among adolescents. This finding does not support the current paradigm that the associations between obesity and insulin resistance are, to a significant degree, mediated by low grade systemic inflammation. These data support the need for further adolescent studies to explore these associations.
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Affiliation(s)
- Jessica I Cohen
- Department of Psychiatry, New York University School of Medicine, 145 East 32nd St, New York, NY, 10016, USA
| | - Lawrence Maayan
- Department of Psychiatry, New York University School of Medicine, 145 East 32nd St, New York, NY, 10016, USA
- Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd, Orangeburg, NY, 10962, USA
| | - Antonio Convit
- Department of Psychiatry, New York University School of Medicine, 145 East 32nd St, New York, NY, 10016, USA
- Department of Medicine, New York University School of Medicine, 145 East 32nd St, New York, NY, 10016, USA
- Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd, Orangeburg, NY, 10962, USA
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Saqui-Salces M, Dowdle WE, Reiter JF, Merchant JL. A high-fat diet regulates gastrin and acid secretion through primary cilia. FASEB J 2012; 26:3127-39. [PMID: 22516298 DOI: 10.1096/fj.11-197426] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of primary cilia in the gastrointestinal tract has not been examined. Here we report the presence of primary cilia on gastric endocrine cells producing gastrin, ghrelin, and somatostatin (Sst), hormones regulated by food intake. During eating, cilia in the gastric antrum decreased, whereas gastric acid and circulating gastrin increased. Mice fed high-fat chow showed a delayed decrease in antral cilia, increased plasma gastrin, and gastric acidity. Mice fed high-fat chow for 3 wk showed lower cilia numbers and acid but higher gastrin levels than mice fed a standard diet, suggesting that fat affects gastric physiology. Ex vivo experiments showed that cilia in the corpus responded to acid and distension, whereas cilia in the antrum responded to food. To analyze the role of gastric cilia, we conditionally deleted the intraflagellar transport protein Ift88 (Ift88(-/fl)). In fed Ift88(-/fl) mice, gastrin levels were higher, and gastric acidity was lower. Moreover, gastrin and Sst gene expression did not change in response to food as in controls. At 8 mo, Ift88(-/fl) mice developed foveolar hyperplasia, hypergastrinemia, and hypochlorhydria associated with endocrine dysfunction. Our results show that components of food (fat) are sensed by antral cilia on endocrine cells, which modulates gastrin secretion and gastric acidity.
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Affiliation(s)
- Milena Saqui-Salces
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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Owyang C, Heldsinger A. Vagal control of satiety and hormonal regulation of appetite. J Neurogastroenterol Motil 2011; 17:338-48. [PMID: 22148102 PMCID: PMC3228973 DOI: 10.5056/jnm.2011.17.4.338] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 09/10/2011] [Accepted: 09/15/2011] [Indexed: 12/27/2022] Open
Abstract
The paradigm for the control of feeding behavior has changed significantly. In this review, we present evidence that the separation of function in which cholecystokinin (CCK) controls short-term food intake and leptin regulate long-term eating behavior and body weight become less clear. In addition to the hypothalamus, the vagus nerve is critically involved in the control of feeding by transmitting signals arising from the upper gut to the nucleus of the solitary tract. Among the peripheral mediators, CCK is the key peptide involved in generating the satiety signal via the vagus. Leptin receptors have also been identified in the vagus nerve. Studies in the rodents clearly indicate that leptin and CCK interact synergistically to induce short-term inhibition of food intake and long-term reduction of body weight. The synergistic interaction between vagal CCK-A receptor and leptin is mediated by the phosphorylation of signal transducer and activator of transcription3 (STAT3), which in turn, activates closure of K(+) channels, leading to membrane depolarization and neuronal firing. This involves the interaction between CCK/SRC/phosphoinositide 3-kinase cascades and leptin/Janus kinase-2/phosphoinositide 3-kinase/STAT3 signaling pathways. It is conceivable that malfunctioning of these signaling molecules may result in eating disorders.
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Affiliation(s)
- Chung Owyang
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
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Wang L, Stengel A, Goebel M, Martinez V, Gourcerol G, Rivier J, Taché Y. Peripheral activation of corticotropin-releasing factor receptor 2 inhibits food intake and alters meal structures in mice. Peptides 2011; 32:51-9. [PMID: 20969907 PMCID: PMC3010521 DOI: 10.1016/j.peptides.2010.10.017] [Citation(s) in RCA: 21] [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: 09/04/2010] [Revised: 10/11/2010] [Accepted: 10/12/2010] [Indexed: 10/18/2022]
Abstract
The orexigenic effect of urocortins (Ucns), namely Ucn 1, Ucn 2 and Ucn 3 through activation of corticotropin-releasing factor (CRF) receptors, has been well characterized after injection into the brain but not in the periphery. We examined the role of CRF receptor subtype 2 (CRF(2)) in the regulation of food intake using intraperitoneal (ip) injection of Ucns and the selective CRF(2) antagonist, astressin(2)-B, and CRF(2) knockout (-/-) mice. Meal structures were monitored using an automated episodic solid food intake monitoring system. Ucn 2 (3, 10 or 30 μg/kg, ip) induced a rapid in onset, long lasting and dose-dependent decrease (38%, 66% and 86%, respectively at 4h) of cumulative food intake after an overnight fast in mice. Ucn 3 anorexic effect was 10-times less potent. Astressin(2)-B (30 or 100 μg/kg) injected ip, but not intracerebroventricularly, blocked the inhibitory effect of ip Ucn 1 and Ucn 2 (10 μg/kg). Fasted CRF(2-/-) mice did not respond to ip Ucn 1 (10 μg/kg). Meal microstructure analysis of the 4-h re-feeding response to an overnight fast showed that Ucn 2 (10 μg/kg, ip) decreased meal size and duration, but increased meal frequency. In mice fed ad libitum, Ucn 2 (30 μg/kg) injected ip before the dark phase decreased the 4-h nocturnal meal size and duration without influencing meal frequency while the 10 μg/kg dose had no effect. These data indicate that Ucns, through peripheral CRF(2) receptor-mediated induction of satiation, inhibit the eating response to a fast more potently than the physiological nocturnal feeding in mice.
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Affiliation(s)
- Lixin Wang
- CURE Digestive Diseases Research Center, Center for Neurobiology of Stress, Department of Medicine/Digestive Diseases Division, David Geffen School of Medicine, UCLA and VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
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Nefti W, Chaumontet C, Fromentin G, Tomé D, Darcel N. A high-fat diet attenuates the central response to within-meal satiation signals and modifies the receptor expression of vagal afferents in mice. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1681-6. [DOI: 10.1152/ajpregu.90733.2008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During digestion, macronutrients are sensed within the small intestine. This sensory process is dependent upon the action of gut mediators, such as cholecystokinin (CCK) or serotonin (5-HT), on vagal afferents that, in turn, convey peripheral information to the brain to influence the control of food intake. Recent studies have suggested that dietary conditions alter vagal sensitivity to CCK and 5-HT. This phenomenon may be of importance to the onset of eating disorders. The aim of the present study was thus to investigate the effects of subjecting mice to 15 days of either an HF diet (30% fat, 54% carbohydrate) or an NF diet (10% fat, 74% carbohydrate) on 1) daily and short-term food intake, 2) vagal sensitivity to peripheral anorectic factors and macronutrient loads, and 3) vagal afferent neuron receptor expression. The results indicated that compared with an NF diet, and while increasing food intake and body weight gain, an HF diet altered the short-term response to CCK-8 and intragastric macronutrient loads, while decreasing vagal activation by CCK-8 and modifying the receptor expression of vagal neurons. These findings, therefore, suggest that dietary intervention effect on food intake could be linked to changes in vagal afferent receptor profiles.
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Zorrilla EP, Sanchez-Alavez M, Sugama S, Brennan M, Fernandez R, Bartfai T, Conti B. Interleukin-18 controls energy homeostasis by suppressing appetite and feed efficiency. Proc Natl Acad Sci U S A 2007; 104:11097-102. [PMID: 17578927 PMCID: PMC1904154 DOI: 10.1073/pnas.0611523104] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Circulating levels of the cytokine interleukin 18 (IL-18) are elevated in obesity. Here, we show that administration of IL-18 suppresses appetite, feed efficiency, and weight regain in food-deprived male and female C57BL/6J mice. Intraperitoneal vs. intracerebroventricular routes of IL-18 administration had similar potency and did not promote formation of a conditioned taste aversion (malaise-like behavior). Mice partially (Il18(+/-)) or totally (Il18(-/-)) deficient in IL-18 were hyperphagic by young adulthood, with null mutants then becoming overweight by the fifth month of life. Adult Il18(-/-) mice gained 2- to 3-fold more weight than WT mice per unit energy consumed of low- or high-fat diet. Indirect calorimetry revealed reduced energy expenditure in female Il18(-/-) mice and increased respiratory exchange ratios [volume of carbon dioxide production (VCO(2))/volume of oxygen consumption (VO(2))] in mutants of both sexes. Hyperphagia continued in maturity, with overeating greatest during the mid- to late-dark cycle. Relative white fat-pad mass of Il18(-/-) mice was approximately 2- to 3-fold greater than that of WT, with gonadal, mesenteric, and inguinal depots growing most. The data suggest that endogenous IL-18 signaling modulates food intake, metabolism, and adiposity during adulthood and might be a central or peripheral pharmacological target for controlling energy homeostasis.
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Affiliation(s)
- Eric P. Zorrilla
- *Harold L. Dorris Neurological Research Institute
- Committee on the Neurobiology of Addictive Disorders, and
- To whom correspondence may be addressed. E-mail: or
| | - Manuel Sanchez-Alavez
- *Harold L. Dorris Neurological Research Institute
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
| | - Shuei Sugama
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo 113-8602, Japan
| | - Molly Brennan
- *Harold L. Dorris Neurological Research Institute
- Committee on the Neurobiology of Addictive Disorders, and
| | - Rosette Fernandez
- *Harold L. Dorris Neurological Research Institute
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
| | - Tamas Bartfai
- *Harold L. Dorris Neurological Research Institute
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
| | - Bruno Conti
- *Harold L. Dorris Neurological Research Institute
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
- To whom correspondence may be addressed. E-mail: or
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Abstract
In a previous study, we established that leptin controls food intake and immune responses by acting on intestinal vagal chemosensitive mechanoreceptors via a functional link with interleukin-1 beta (Il-1 beta). Since the control of intestinal motility is one of the main roles of the vagal afferent fibres, we investigated the effects of leptin on intestinal electromyographic (EMG) activity which reflects intestinal motility. For this purpose, the effects of locally injected leptin on small intestine spontaneous EMG activity were studied in 23 anaesthetised cats. The EMG activity was recorded using bipolar electrodes implanted in the proximal small intestine. Leptin and Il-1 beta (0.1, 1 and 10 microg), administered through the artery irrigating the upper part of the intestine 20 min after cholecystokinin (CCK, 10 microg, I.A.), had significant (P < 0.001) excitatory effects on intestinal EMG activity. The effects of both substances were blocked by the endogenous interleukin-1 beta receptor antagonist (Il-1ra, 250 microg, I.A.), by atropine (250 microg, I.A.) and by vagotomy. In the absence of CCK, leptin and Il-1 beta had no effect on intestinal electrical activity. It can therefore be concluded that: (1) leptin is effective only after the previous intervention of CCK, (2) the enhancement of the electrical activity induced by leptin involves Il-1 beta receptors and the cholinergic excitatory pathway, (3) the modes whereby the leptin-induced enhancement of EMG activity occurs strongly suggest that these effects are due to a long-loop reflex involving intestinal vagal afferent fibres and the parasympathetic nervous system.
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Affiliation(s)
- Stéphanie Gaigé
- Laboratoire de Physiologie Neurovégétative, UMR CNRS 6153, UMR INRA, Faculté des Sciences et Techniques Saint-Jérôme, Université Aix-Marseille 3, Case postale 351-352, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France
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16
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Boyer BB, Ormseth OA, Buck L, Nicolson M, Pelleymounter MA, Barnes BM. Leptin prevents posthibernation weight gain but does not reduce energy expenditure in arctic ground squirrels. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1997; 118:405-12. [PMID: 9467893 DOI: 10.1016/s0742-8413(97)00172-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In mammals, leptin reduces energy intake and may increase energy expenditure as a means to maintain body weight and/or adiposity at an appropriate level. Hibernating mammals seasonally alter body mass, food intake, and body composition and, therefore, represent an attractive model for investigating the physiological regulation of changing body mass and adiposity. Previous experiments in our laboratory demonstrated that administration of mouse recombinant leptin reduces food intake and body weight in arctic ground squirrels during prehibernation fattening. In addition, leptin appeared to reduce metabolic efficiency (weight gain per unit of energy intake). This result suggests that reduced food intake alone may not account for the observed weight loss. Here, we describe the effect of a 3-week constant infusion of leptin given to posthibernation arctic ground squirrels on food consumption and energy expenditure. Mouse recombinant leptin (1 mg/ml) was administered through subcutaneously implanted mini-osmotic pumps (10 microliters/hr flow rate). Resting metabolic rate was monitored before and during the 3-week leptin administration period by indirect calorimetry. Body temperature and locomotory activity were monitored continuously by abdominal radiotransmitters. At the end of the leptin administration period, thermogenic capacity was evaluated by measuring brown fat uncoupling protein-1 mRNA and protein levels. Leptin administration resulted in reduced food intake and prevented posthibernation weight gain, but it did not alter any of the measured parameters of energy expenditure.
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Affiliation(s)
- B B Boyer
- Institute of Arctic Biology, University of Alaska Fairbanks, AK 99775-7000, USA.
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17
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Barrachina MD, Martínez V, Wang L, Wei JY, Taché Y. Synergistic interaction between leptin and cholecystokinin to reduce short-term food intake in lean mice. Proc Natl Acad Sci U S A 1997; 94:10455-60. [PMID: 9294232 PMCID: PMC23384 DOI: 10.1073/pnas.94.19.10455] [Citation(s) in RCA: 345] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Leptin is a circulating protein involved in the long-term regulation of food intake and body weight. Cholecystokinin (CCK) is released postprandially and elicits satiety signals. We investigated the interaction between leptin and CCK-8 in the short-term regulation of food intake induced by 24-hr fasting in lean mice. Leptin, injected intraperitoneally (i.p.) at low doses (4-120 microg/kg), which did not influence feeding behavior for the first 3 hr postinjection, decreased food intake dose dependently by 47-83% during the first hour when coinjected with a subthreshold dose of CCK. Such an interaction was not observed between leptin and bombesin. The food-reducing effect of leptin injected with CCK was not associated with alterations in gastric emptying or locomotor behavior. Leptin-CCK action was blocked by systemic capsaicin at a dose inducing functional ablation of sensory afferent fibers and by devazepide, a CCK-A receptor antagonist but not by the CCK-B receptor antagonist, L-365,260. The decrease in food intake which occurs 5 hr after i.p. injection of leptin alone was also blunted by devazepide. Coinjection of leptin and CCK enhanced the number of Fos-positive cells in the hypothalamic paraventricular nucleus by 60%, whereas leptin or CCK alone did not modify Fos expression. These results indicate the existence of a functional synergistic interaction between leptin and CCK leading to early suppression of food intake which involves CCK-A receptors and capsaicin-sensitive afferent fibers.
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Affiliation(s)
- M D Barrachina
- CURE: Digestive Diseases Research Center, West Los Angeles Veterans Affairs Medical Center, Department of Medicine, and Brain Research Institute, University of California, Los Angeles, CA 90073, USA
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