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Bukhari SNA. An insight into the multifunctional role of ghrelin and structure activity relationship studies of ghrelin receptor ligands with clinical trials. Eur J Med Chem 2022; 235:114308. [PMID: 35344905 DOI: 10.1016/j.ejmech.2022.114308] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 02/06/2022] [Accepted: 03/18/2022] [Indexed: 11/30/2022]
Abstract
Ghrelin is a multifunctional gastrointestinal acylated peptide, primarily synthesized in the stomach and regulates the secretion of growth hormone and energy homeostasis. It plays a central role in modulating the diverse biological, physiological and pathological functions in vertebrates. The synthesis of ghrelin receptor ligands after the finding of growth hormone secretagogue developed from Met-enkephalin led to reveal the endogenous ligand ghrelin and the receptors. Subsequently, many peptides, small molecules and peptidomimetics focusing on the ghrelin receptor, GHS-R1a, were derived. In this review, the key features of ghrelin's structure, forms, its bio-physiological functions, pathological roles and therapeutic potential have been highlighted. A few peptidomimetics and pseudo peptide synthetic perspectives have also been discussed to make ghrelin receptor ligands, clinical trials and their success.
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Affiliation(s)
- Syed Nasir Abbas Bukhari
- Department of Pharmaceutical Chemistry, College of Pharmacy, Jouf University, Sakaka, Aljouf, 2014, Saudi Arabia.
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2
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Cordeiro JP, Silva VLD, Campos DH, Cicogna AC, Leopoldo AS, Lima-Leopoldo AP. Isolated obesity resistance condition or associated with aerobic exercise training does not promote cardiac impairment. ACTA ACUST UNITED AC 2021; 54:e10669. [PMID: 34287576 PMCID: PMC8289349 DOI: 10.1590/1414-431x2020e10669] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 05/28/2021] [Indexed: 11/30/2022]
Abstract
Mechanisms involved in cardiac function and calcium (Ca2+) handling in obese-resistant (OR) rats are still poorly determined. We tested the hypothesis that unsaturated high-fat diet (HFD) promotes myocardial dysfunction in OR rats, which it is related to Ca2+ handling. In addition, we questioned whether exercise training (ET) becomes a therapeutic strategy. Male Wistar rats (n=80) were randomized to standard or HFD diets for 20 weeks. The rats were redistributed for the absence or presence of ET and OR: control (C; n=12), control + ET (CET; n=14), obese-resistant (OR; n=9), and obese-resistant + ET (ORET; n=10). Trained rats were subjected to aerobic training protocol with progressive intensity (55-70% of the maximum running speed) and duration (15 to 60 min/day) for 12 weeks. Nutritional, metabolic, and cardiovascular parameters were determined. Cardiac function and Ca2+ handling tests were performed in isolated left ventricle (LV) papillary muscle. OR rats showed cardiac atrophy with reduced collagen levels, but there was myocardial dysfunction. ET was efficient in improving most parameters of body composition. However, the mechanical properties and Ca2+ handling from isolated papillary muscle were similar among groups. Aerobic ET does not promote morphological and cardiac functional adaptation under the condition of OR.
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Affiliation(s)
- J P Cordeiro
- Programa de Pós-Graduação em Educação Física, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - V L da Silva
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - D H Campos
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - A C Cicogna
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - A S Leopoldo
- Programa de Pós-Graduação em Educação Física, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - A P Lima-Leopoldo
- Programa de Pós-Graduação em Educação Física, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
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Moghadam AA, Moran TH, Dailey MJ. Alterations in circadian and meal-induced gut peptide levels in lean and obese rats. Exp Biol Med (Maywood) 2017; 242:1786-1794. [PMID: 29191090 DOI: 10.1177/1535370217732041] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Alterations in gut hormone signaling are a likely contributing factor to the metabolic disturbances associated with overweight/obesity as they coordinate the timing of feeding behavior, absorption, and utilization of nutrients. These hormones are released in response to food intake, or follow a circadian or anticipatory pattern of secretion that is independent of nutrient stimulation. The aim of this study was to identify the degree to which high-fat diet-induced obesity would alter the daily rhythm of gut peptide plasma levels (glucagon-like peptide-1 [GLP-1], peptide YY [PYY], insulin or amylin [AMY]) or meal-induced levels in the middle of the light or dark cycle. Male Sprague-Dawley rats were fed a high-fat diet (OBESE) or chow (LEAN), implanted with jugular catheters, and blood samples were taken every 2 h throughout the light/dark cycle while freely feeding or after an Ensure liquid meal. We found that even when OBESE and LEAN animals ate the same kcals and have a similar pattern of food intake, there is a difference in both the levels and rhythm of plasma gut peptides. GLP-1 and PYY are higher during the light cycle in LEAN animals and AMY is higher in the OBESE group throughout the light/dark cycle. There was also a differential response of plasma gut signals after the Ensure meal, even though the composition and amount of intake of the meal were the same in both groups. These changes occur prior to the high-fat diet induced loss of glycemic control and may be a target for early intervention. Impact statement The aim of this study was to test if obesity would alter the daily rhythm of gut peptides or meal-induced levels in the middle of the light or dark cycle. We found that even when animals are eating the same amount (in kcal) of food that the obese animals have altered daily rhythms and meal-induced gut peptide levels. In particular, we are the first to show that obesity induces increases in peptide YY levels during the light cycle and amylin remains high throughout the light and dark cycle in obese animals. These changes occurred prior to a loss of glycemic control. Thus, the rhythm of gut peptides could be used as an early indicator of later and more serious metabolic disturbances and may be a target for early intervention.
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Affiliation(s)
- Alexander A Moghadam
- 1 Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10591, USA
| | - Timothy H Moran
- 2 Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Megan J Dailey
- 3 Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Kucukkurt I, Akkol EK, Karabag F, Ince S, Süntar I, Eryavuz A, Sözbilir NB. Determination of the regulatory properties of Yucca schidigera extracts on the biochemical parameters and plasma hormone levels associated with obesity. REVISTA BRASILEIRA DE FARMACOGNOSIA-BRAZILIAN JOURNAL OF PHARMACOGNOSY 2016. [DOI: 10.1016/j.bjp.2015.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Zhang SR, Fan XM. Ghrelin-ghrelin O-acyltransferase system in the pathogenesis of nonalcoholic fatty liver disease. World J Gastroenterol 2015; 21:3214-3222. [PMID: 25805927 PMCID: PMC4363750 DOI: 10.3748/wjg.v21.i11.3214] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Revised: 12/29/2014] [Accepted: 01/30/2015] [Indexed: 02/06/2023] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is currently considered as the most common liver disease in Western countries, and is rapidly becoming a serious threat to public health worldwide. However, the underlying mechanisms leading to the development of NAFLD are still not fully understood. The ghrelin-ghrelin O-acyltransferase (GOAT) system has recently been found to play a crucial role in both the development of steatosis and its progression to nonalcoholic steatohepatitis. Ghrelin, the natural ligand of the growth hormone secretagogue receptor, is a 28-amino acid peptide possessing a unique acylation on the serine in position 3 catalyzed by GOAT. The ghrelin-GOAT system is involved in insulin resistance, lipid metabolism dysfunction, and inflammation, all of which play important roles in the pathogenesis of NAFLD. A better understanding of ghrelin-GOAT system biology led to the identification of its potential roles in NAFLD. Molecular targets modulating ghrelin-GOAT levels and the biologic effects are being studied, which provide a new insight into the pathogenesis of NAFLD. This review probes into the possible relationship between the ghrelin-GOAT system and NAFLD, and considers the potential mechanisms by which the ghrelin-GOAT system brings about insulin resistance and other aspects concerning NAFLD.
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Delporte C. Structure and physiological actions of ghrelin. SCIENTIFICA 2013; 2013:518909. [PMID: 24381790 PMCID: PMC3863518 DOI: 10.1155/2013/518909] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/10/2013] [Indexed: 05/30/2023]
Abstract
Ghrelin is a gastric peptide hormone, discovered as being the endogenous ligand of growth hormone secretagogue receptor. Ghrelin is a 28 amino acid peptide presenting a unique n-octanoylation modification on its serine in position 3, catalyzed by ghrelin O-acyl transferase. Ghrelin is mainly produced by a subset of stomach cells and also by the hypothalamus, the pituitary, and other tissues. Transcriptional, translational, and posttranslational processes generate ghrelin and ghrelin-related peptides. Homo- and heterodimers of growth hormone secretagogue receptor, and as yet unidentified receptors, are assumed to mediate the biological effects of acyl ghrelin and desacyl ghrelin, respectively. Ghrelin exerts wide physiological actions throughout the body, including growth hormone secretion, appetite and food intake, gastric secretion and gastrointestinal motility, glucose homeostasis, cardiovascular functions, anti-inflammatory functions, reproductive functions, and bone formation. This review focuses on presenting the current understanding of ghrelin and growth hormone secretagogue receptor biology, as well as the main physiological effects of ghrelin.
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Affiliation(s)
- Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Université Libre de Bruxelles, 808 Route de Lennik, Bat G/E-CP611, 1070 Brussels, Belgium
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Abstract
Leptin has a crucial role in regulating food intake and maintaining metabolic homeostasis. Although little is known about the process of leptin secretion, insulin, which has an important role in the metabolism of glucose and lipids, is believed to regulate leptin secretion through a posttranscriptional mechanism in the short term, and via glucose metabolism in the long term. The gastric mucosa secretes leptin, but this mechanism has not been completely elucidated. Understanding the mechanism of insulin-regulated leptin secretion could lead to the development of new treatment methods for obesity and its comorbidities, which are serious public health concerns.
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Affiliation(s)
- Minglun Tsai
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Akihiro Asakawa
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Haruka Amitani
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Akio Inui
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
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Bruijnzeel AW, Qi X, Corrie LW. Anorexic effects of intra-VTA leptin are similar in low-fat and high-fat-fed rats but attenuated in a subgroup of high-fat-fed obese rats. Pharmacol Biochem Behav 2012; 103:573-81. [PMID: 23107643 DOI: 10.1016/j.pbb.2012.10.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 10/12/2012] [Accepted: 10/22/2012] [Indexed: 12/13/2022]
Abstract
Leptin is an adiposity hormone that plays an important role in regulating food intake and energy homeostasis. This study investigated the effects of a high-fat (HF) and a low-fat, high-carbohydrate/sugar (LF) diet on leptin sensitivity in the ventral tegmental area (VTA) in rats. The animals were exposed to a HF or LF diet for 16 weeks. Then the effects of intra-VTA leptin (150 and 500 ng/side, unilateral dose) on food intake and body weights were investigated while the animals were maintained on the HF or LF diet. Long-term exposure to the HF or LF diet led to similar body weight gain in these groups. The HF-fed animals consumed a smaller amount of food by weight than the LF-fed animals but both groups consumed the same amount of calories. The bilateral administration of leptin into the VTA decreased food intake (72 h) and body weights (48 h) to a similar degree in the HF and LF-fed animals. When the HF-fed animals were ranked by body weight gain it was shown that the diet-induced obese rats (HF-fed DIO, upper quartile for weight gain) were less sensitive to the effects of leptin on food intake and body weights than the diet-resistant rats (HF-fed DR, lower quartile for weight gain). A control experiment with fluorescent Cy3-labeled leptin showed that leptin did not spread beyond the borders of the VTA. This study indicates that leptin sensitivity in the VTA is the same in animals that are exposed to a HF or LF diet. However, HF-fed DIO rats are less sensitive to the effects of leptin in the VTA than HF-fed DR rats. Leptin resistance in the VTA might contribute to overeating and weight gain when exposed to a HF diet.
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Affiliation(s)
- Adrie W Bruijnzeel
- Department of Psychiatry, McKnight Brain Institute, University of Florida, 1149 Newell Dr, Gainesville, FL 32611, USA.
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Delporte C. Recent advances in potential clinical application of ghrelin in obesity. J Obes 2012; 2012:535624. [PMID: 22523666 PMCID: PMC3317165 DOI: 10.1155/2012/535624] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 12/04/2011] [Indexed: 02/07/2023] Open
Abstract
Ghrelin is the natural ligand of the growth hormone secretagogue receptor (GHS-R1a). Ghrelin is a 28 amino acid peptide possessing a unique acylation on the serine in position 3 catalyzed by ghrelin O-acyltransferase (GOAT). Ghrelin stimulates growth hormone secretion, but also appetite, food intake, weight gain, and gastric emptying. Ghrelin is involved in weight regulation, obesity, type 2 diabetes, and metabolic syndrome. Furthermore, a better understanding of ghrelin biology led to the identification of molecular targets modulating ghrelin levels and/or its biological effects: GOAT, ghrelin, and GHS-R1a. Furthermore, a recent discovery, showing the involvement of bitter taste receptor T2R in ghrelin secretion and/or synthesis and food intake, suggested that T2R could represent an additional interesting molecular target. Several classes of ghrelin-related pharmacological tools for the treatment of obesity have been or could be developed to modulate the identified molecular targets.
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Affiliation(s)
- Christine Delporte
- Laboratory of Biological Chemistry and Nutrition, Faculty of Medicine, Université libre de Bruxelles, 1070 Brussels, Belgium
- *Christine Delporte:
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Wang Y, Asakawa A, Inui A, Kosai KI. Leptin gene therapy in the fight against diabetes. Expert Opin Biol Ther 2011; 10:1405-14. [PMID: 20690892 DOI: 10.1517/14712598.2010.512286] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
IMPORTANCE OF THE FIELD The incidence of diabetes is increasing worldwide, yet current treatments are not always effective for all patient or disease types. AREAS COVERED IN THIS REVIEW Here, we summarize the biologic and clinical roles of leptin in diabetes, and discuss candidate viral vectors that may be employed in the clinical use of central leptin gene therapy for diabetes. WHAT THE READER WILL GAIN We discuss how studies on leptin, a regulator of the insulin-glucose axis, have significantly advanced our understanding of the roles of energy homeostasis and insulin resistance in the pathogeneses of metabolic syndrome and diabetes. Recent studies have demonstrated the long-term therapeutic effects of central leptin gene therapy in obesity and diabetes via decreased insulin resistance and increased glucose metabolism. Many of these studies have employed viral vectors, which afford high in vivo gene transduction efficiencies compared with non-viral vectors. TAKE HOME MESSAGE Adeno-associated viral vectors are particularly well suited for central leptin gene therapy owing to their low toxicity and ability to drive transgene expression for extended periods.
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Affiliation(s)
- Yuqing Wang
- Kagoshima University Graduate School of Medical and Dental Sciences, Department of Gene Therapy and Regenerative Medicine, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
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Kalra SP. Pivotal role of leptin-hypothalamus signaling in the etiology of diabetes uncovered by gene therapy: a new therapeutic intervention? Gene Ther 2011; 18:319-25. [PMID: 21209624 DOI: 10.1038/gt.2010.164] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The incidence of diabetes mellitus has soared to epidemic proportion worldwide. The debilitating chronic hyperglycemia is caused by either lack of insulin as in diabetes type 1 or its ineffectiveness as in diabetes type 2. Frequent replacement of insulin with or without insulin analogs for optimum glycemic control are the conventional cumbersome therapies. Recent application of leptin gene transfer technology has uncovered the participation of adipocytes-derived leptin-dependent hypothalamic neural signaling in glucose homeostasis and demonstrated that a breakdown in this communication due to leptin insufficiency in the hypothalamus underlies the etiology of chronic hyperglycemia. Reinstatement of central leptin sufficiency by hyperleptinemia produced either by intravenous leptin infusion or a single systemic injection of recombinant adenovirus vector encoding leptin gene suppressed hyperglycemia and evoked euglycemia only transiently in rodent models of diabetes type 1. In contrast, stable restoration of leptin sufficiency, solely in the hypothalamus, with biologically active leptin transduced by an intracerebroventicular injection of recombinant adeno-associated virus vector encoding leptin gene (rAAV-lep) abolished hyperglycemia and imposed euglycemia through the extended duration of experiment by stimulating glucose disposal in the periphery in models of diabetes type 1. Further, similar hypothalamic leptin transgene expression abrogated chronic hyperglycemia and hyperinsulinemia, the predisposing risk factors of the age and environmentally acquired diabetes type 2, and instituted euglycemia by independently activating relays that stimulate glucose metabolism and repress hyperinsulinemia and improve insulin sensitivity in the periphery. Consequently, this durable antidiabetic efficacy of one time rAAV-lep neurotherapy offers a potential novel substitute for insulin therapy following preclinical trials in subhuman primates and humans.
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Affiliation(s)
- S P Kalra
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610-0244, USA.
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12
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De Vriese C, Perret J, Delporte C. Focus on the short- and long-term effects of ghrelin on energy homeostasis. Nutrition 2010; 26:579-84. [DOI: 10.1016/j.nut.2009.09.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 09/17/2009] [Indexed: 02/06/2023]
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Avci G, Küçükkurt I, Küpeli Akkol E, Yeşilada E. Effects of escin mixture from the seeds of Aesculus hippocastanum on obesity in mice fed a high fat diet. PHARMACEUTICAL BIOLOGY 2010; 48:247-252. [PMID: 20645808 DOI: 10.3109/13880200903085466] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Escins, a triterpene glycoside mixture obtained from the ethanol extract of Aesculus hippocastanum L. (Hippocastanaceae) seed, was evaluated for its in vivo effects on the plasma levels of some hormones (leptin, insulin, FT(3), FT(4)) and biochemical parameters (glucose, triglyceride, total cholesterol, HDL-C, LDL-C concentrations) in mice fed with a high fat diet for 5 weeks. A high fat diet induced a remarkable increment in the plasma leptin (p <0.01), total cholesterol (p <0.01) and LDL-C (p <0.001) concentrations compared to control group animals. Combined administration of a high-fat diet with escins decreased leptin (31.6%) (p<0.05) and FT(4) (36.0%) (p<0.05) levels, increased HDL-C concentration (17.0%), while remained ineffective on LDL-C concentration in mice. Results have shown that escins may have beneficial effects in the understanding of obesity.
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Affiliation(s)
- Gülcan Avci
- Department of Biochemistry, Faculty of Veterinary Medicine, Afyon Kocatepe University, Afyonkarahisar, Turkey
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14
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Neuroendocrine Control of Energy Homeostasis: Update on New Insights. PROGRESS IN BRAIN RESEARCH 2010; 181:17-33. [DOI: 10.1016/s0079-6123(08)81002-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Kalra SP. Central leptin gene therapy ameliorates diabetes type 1 and 2 through two independent hypothalamic relays; a benefit beyond weight and appetite regulation. Peptides 2009; 30:1957-63. [PMID: 19647774 PMCID: PMC2755606 DOI: 10.1016/j.peptides.2009.07.021] [Citation(s) in RCA: 30] [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] [Received: 06/24/2009] [Revised: 07/22/2009] [Accepted: 07/23/2009] [Indexed: 01/12/2023]
Abstract
Although its role in energy homeostasis is firmly established, the evidence accumulated over a decade linking the adipocyte leptin-hypothalamus axis in the pathogenesis of diabetes mellitus has received little attention in the contemporary thinking. In this context various lines of evidence are collated here to show that (1) under the direction of leptin two independent relays emanating from the hypothalamus restrain insulin secretion from the pancreas and mobilize peripheral organs--liver, skeletal muscle and brown adipose tissue--to upregulate glucose disposal, and (2), leptin insufficiency in the hypothalamus produced by either leptinopenia or restriction of leptin transport across the blood brain barrier due to hyperleptinemia of obesity and aging, initiate antecedent pathophysiological sequalae of diabetes type 1 and 2. Further, we document here the efficacy of leptin replenishment in vivo, especially by supplying it to the hypothalamus with the aid of gene therapy, in preventing the antecedent pathophysiological sequalae--hyperinsulinemia, insulin resistance and hyperglycemia--in various animal models and clinical paradigms of diabetes type 1 and 2 with or without attendant obesity. Overall, the new insights on the long-lasting antidiabetic potential of two independent hypothalamic relays engendered by central leptin gene therapy and the preclinical safety indicators in rodents warrant further validation in subhuman primates and humans.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, PO Box 100244, Gainesville, FL 32610-0244, United States.
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Lee MJ, Fried SK. Integration of hormonal and nutrient signals that regulate leptin synthesis and secretion. Am J Physiol Endocrinol Metab 2009; 296:E1230-8. [PMID: 19318513 PMCID: PMC2692400 DOI: 10.1152/ajpendo.90927.2008] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This review summarizes recent advances in our understanding of the pre- and posttranscriptional mechanisms that regulate leptin production and secretion in adipocytes. Basal leptin production is proportional to the status of energy stores, i.e., fat cell size, and this is mainly regulated by alterations in leptin mRNA levels. Leptin mRNA levels are regulated by hormones, including glucocorticoids and catecholamines, but little is known about the transcriptional mechanisms involved. Leptin synthesis and secretion is also acutely modulated in response to hormones such as insulin and the availability of metabolic fuels. Acute variations in leptin production over a time course of minutes to hours are mediated at the levels of both translation and secretion. Increases in amino acids and insulin after a meal activate the mammalian target of rapamycin (mTOR) pathway, leading to an increase in specific rates of leptin biosynthesis. Cross-talk among mTOR, PKA, and AMP-activated protein kinase pathways appears to integrate hormonal and nutrient signals that regulate leptin mRNA translation, at least in part through mechanisms involving its 5'- and 3'-untranslated regions. In addition, the rate of leptin secretion from preformed stores in response to hormonal cues is also regulated. Insulin stimulates, and adrenergic agonists inhibit, leptin secretion, and this likely contributes to variations in the magnitude of nutrition-related leptin excursions and oscillations. Overall, the study of leptin production has contributed to a deepening understanding of leptin biology and, more broadly, to our understanding of the cellular and molecular mechanisms by which the adipocyte integrates hormonal and nutrient signals to regulate adipokine production.
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Affiliation(s)
- Mi-Jeong Lee
- Division of Endocrinology, Diabetes, and Nutrition, Department of Medicine, University of Maryland, School of Medicine, Baltimore, MD, USA
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Kojima S, Asakawa A, Amitani H, Sakoguchi T, Ueno N, Inui A, Kalra SP. Central leptin gene therapy, a substitute for insulin therapy to ameliorate hyperglycemia and hyperphagia, and promote survival in insulin-deficient diabetic mice. Peptides 2009; 30:962-6. [PMID: 19428774 DOI: 10.1016/j.peptides.2009.01.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 01/08/2009] [Accepted: 01/09/2009] [Indexed: 12/22/2022]
Abstract
Long-term benefits of central leptin gene therapy in insulin-deficient diabetes are not known despite its therapeutic effects in obesity animal models such as ob/ob and diet-induced obese mice. Adult male mice were injected intraperitoneally with streptozotocin (STZ, 200mg/kg) to induce insulitis. A week later, only diabetic STZ-pretreated mice (blood glucose >350 mg/dl) received intracerebroventricularly (icv) an injection of recombinant adeno-associated virus vector (rAAV) encoding either green fluorescent protein (control), or leptin gene (rAAV-lep). Body weight (BW), food intake, blood glucose, insulin and survival rate responses were monitored post-icv injection at regular intervals for 52 weeks. The STZ pre-injected diabetic mice remained hyperphagic, gradually lost BW and died by week 6 after receiving control vector. In marked contrast, injection of rAAV-lep to raise hypothalamic leptin levels, rescued the STZ-pretreated mice from early mortality, gradually curbed hyperphagia to normalize intake by week 20, and maintained BW at significantly lower than the control range. Blood glucose levels in these mice started to recede dramatically by week 2-3 to normalize by week 8, and euglycemia was sustained during the remaining course of the experiment. rAAV-lep injected mice did not exhibit any discernible untoward gross behavioral changes and diabetic complications and showed a partial return of pancreatic beta-cell function. These results show for the first time that one time central leptin gene therapy is effective and durable in reinstating euglycemia and energy homeostasis for extended periods in the absence of insulin.
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Affiliation(s)
- Shinya Kojima
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
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Kalra SP. Disruption in the leptin-NPY link underlies the pandemic of diabetes and metabolic syndrome: new therapeutic approaches. Nutrition 2009; 24:820-6. [PMID: 18725078 DOI: 10.1016/j.nut.2008.06.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 06/11/2008] [Indexed: 12/11/2022]
Abstract
Multidisciplinary research from my and my colleagues' laboratory has shown that disruption at various levels of leptin signaling to the interactive hypothalamic network of neuropeptide Y (NPY) and cohorts contributes to the antecedent pathophysiologic sequelae of the disease cluster of the metabolic syndrome. Disruptions in NPY signaling due to high or low abundance of NPY and cognate receptors dysregulate the homeostatic milieu to promote hyperinsulinemia, hyperglycemia, fat accrual, and overt diabetes. Hyperleptinemia induced by consumption of energy-rich diets inhibits leptin transport across the blood-brain barrier and thereby produces leptin insufficiency in the hypothalamus. Sustained leptin insufficiency results in loss of hypothalamic restraint on pancreatic insulin secretion and diminished glucose metabolism and energy expenditure. This chain of events culminates in hyperinsulinemia, hyperglycemia, and diabetes. Our recent studies have shown that increasing the supply of leptin centrally by gene therapy reinstates the restraint on hypothalamic NPY signaling and ameliorates diabetes and the attendant disease cluster of the metabolic syndrome. Thus, newer therapies that would enhance leptin transport across the blood-brain barrier in a timely manner or reinstate leptin restraint on NPY signaling through central leptin gene therapy or pharmacologically with leptin mimetics are likely to curtail the pathophysiologic sequelae of diabetes and related ailments of the metabolic syndrome.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, University of Florida, McKnight Brain Institute, Gainesville, Florida, USA.
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20
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Priego T, Sánchez J, Picó C, Palou A. Sex-associated differences in the leptin and ghrelin systems related with the induction of hyperphagia under high-fat diet exposure in rats. Horm Behav 2009; 55:33-40. [PMID: 18718472 DOI: 10.1016/j.yhbeh.2008.07.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 07/21/2008] [Accepted: 07/21/2008] [Indexed: 10/21/2022]
Abstract
Leptin and ghrelin are known to be main hormones involved in the control of food intake, with opposing effects. Here we have explored whether changes in the leptin and ghrelin system are involved in the long-term effects of high-fat (HF) diet feeding in rats and whether sex-associated differences exist. Male and female Wistar rats were fed until the age of 6 months with a normal-fat (NF) or an HF-diet. Food intake and body weight were followed. Gastric and serum levels of leptin and ghrelin, and mRNA levels of leptin (in stomach and adipose tissue), ghrelin (in stomach), and NPY, POMC, and leptin and ghrelin receptors (OB-Rb and GHS-R) (in the hypothalamus) were measured. In both males and females, total caloric intake and body weight were greater under the HF-diet feeding. In females, circulating ghrelin levels and leptin mRNA expression in the stomach were higher under HF-diet. HF-diet feeding also resulted in higher hypothalamic NPY/POMC mRNA levels, more marked in females, and in lower OB-Rb mRNA levels, more marked in males. In addition, in females, serum ghrelin levels correlated positively with hypothalamic NPY mRNA levels, and these with caloric intake. In males, hypothalamic OB-Rb mRNA levels correlated positively with POMC mRNA levels and these correlated negatively with caloric intake and with body weight. These data reflect differences between sexes in the effects of HF-diet feeding on food intake control systems, suggesting an impairment of the anorexigenic leptin-POMC system in males and an over-stimulation of the orexigenic ghrelin-NPY system in females.
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Affiliation(s)
- Teresa Priego
- Laboratory of Molecular Biology, University of the Balearic Islands and CIBER Fisiopatología de la Obesidad y Nutrición, Palma de Mallorca, Spain
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21
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LI JM, WANG C, HU QH, KONG LD. Fructose Induced Leptin Dysfunction and Improvement by Quercetin and Rutin in Rats. Chin J Nat Med 2008. [DOI: 10.1016/s1875-5364(09)60038-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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Romanovsky D, Walker JC, Dobretsov M. Pressure pain precedes development of type 2 disease in Zucker rat model of diabetes. Neurosci Lett 2008; 445:220-3. [PMID: 18790004 DOI: 10.1016/j.neulet.2008.08.087] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 08/08/2008] [Accepted: 08/29/2008] [Indexed: 12/01/2022]
Abstract
Decreased hind limb pressure pain threshold (PPT) is an early indicator of insulinopenia and neuropathy developing in STZ-rat models of type 1 diabetes and pre-diabetes. To test if pain on pressure is also a hallmark of compensated insulin resistance and type 2 diabetes in this work we measured PPT of Zucker lean (ZL), Zucker fatty (ZF) and Zucker fatty diabetic rats (ZDF; 8 animals per group). Using clinically accepted cut-off values for diagnosis of human diabetes and pre-diabetes, at 6th week of age (the study entry), all animals maintained random blood glucose within a normal range (< 7.9 mM). Over the following 4 weeks, the random glucose remained normal in lean and ZF rats; it however crossed 11 mM cut-off for the diagnosis of diabetes in all ZDF rats. With no detectable relation to blood glucose levels or changes throughout the study, lean, ZF and ZDF rats maintained respectively highest, intermediate and lowest PPT levels (83+/-1, 70+/-1 and 59+/-1 g; mean values for all tests per group). Thus in Zucker rat model, type 2 diabetes-associated impairment of nerve function precedes the development of hyperglycemia. Furthermore, since normoglycemic, but displaying decreased PPT, ZF rats were strongly hyperinsulinemic (plasma insulin concentration 30+/-4 ng/ml vs. 2.4+/-0.3 ng/ml in lean rats) these data suggest that hyperinsulinemia compensating for glucose metabolism might not restore compromised nerve function.
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Affiliation(s)
- Dmitry Romanovsky
- Department of Anesthesiology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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23
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Central leptin insufficiency syndrome: an interactive etiology for obesity, metabolic and neural diseases and for designing new therapeutic interventions. Peptides 2007; 29:127-38. [PMID: 18053615 DOI: 10.1016/j.peptides.2007.10.017] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 10/17/2007] [Accepted: 10/18/2007] [Indexed: 01/10/2023]
Abstract
This review critically reappraises recent scientific evidence concerning central leptin insufficiency versus leptin resistance formulations to explain metabolic and neural disorders resulting from subnormal or defective leptin signaling in various sites in the brain. Research at various fronts to unravel the complexities of the neurobiology of leptin is surveyed to provide a comprehensive account of the neural and metabolic effects of environmentally imposed fluctuations in leptin availability at brain sites and the outcome of newer technology to restore leptin signaling in a site-specific manner. The cumulative new knowledge favors a unified central leptin insufficiency syndrome over the, in vogue, central resistance hypothesis to explain the global adverse impact of deficient leptin signaling in the brain. Furthermore, the leptin insufficiency syndrome delineates a novel role of leptin in the hypothalamus in restraining rhythmic pancreatic insulin secretion while concomitantly enhancing glucose metabolism and non-shivering thermogenic energy expenditure, sequelae that would otherwise promote fat accrual to store excess energy resulting from consumption of energy-enriched diets. A concerted effort should now focus on development of newer technologies for delivery of leptin or leptin mimetics to specifically target neural pathways for remediation of diverse ailments encompassing the central leptin insufficiency syndrome.
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Abstract
PURPOSE OF REVIEW The purpose of this review is to provide updated information on the role of ghrelin in food intake and energy homeostasis, and on its mechanism of action. Moreover, the potential of ghrelin as a target for drugs to treat cachexia and obesity will be discussed. RECENT FINDINGS Whereas the effects of ghrelin in the regulation of appetite, food intake and energy homeostasis have been fairly well documented, the pathways responsible for the effects of ghrelin are now increasingly being understood. As a consequence, clinical applications of ghrelin are now being developed. SUMMARY Ghrelin is an endogenous orexigenic peptide recently discovered in the stomach. Ghrelin is involved in short-term regulation of food intake since its plasma levels increase before meals and decrease strongly postprandially. Ghrelin is also involved in long-term body-weight regulation by inducing adiposity. Ghrelin might be useful for cachexia and obesity treatment.
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Affiliation(s)
- Carine De Vriese
- Laboratory of Biological Chemistry and Nutrition, Université Libre de Bruxelles, Brussels, Belgium
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25
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Berkane AA, Nguyen HTT, Tranchida F, Waheed AA, Deyris V, Tchiakpe L, Fasano C, Nicoletti C, Desseaux V, Ajandouz EH, Comeau D, Comeau L, Hiol A. Proteomic of lipid rafts in the exocrine pancreas from diet-induced obese rats. Biochem Biophys Res Commun 2007; 355:813-9. [PMID: 17320817 DOI: 10.1016/j.bbrc.2007.02.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 02/08/2007] [Indexed: 01/18/2023]
Abstract
In the present work, we induced obesity in rats with high-energy-starch diet and studied exocrine pancreas response. The zymogen granule (ZG) or purified plasma membrane (PM) from the exocrine pancreas was used for the isolation of the detergent-resistant membranes (DRMs). Based on high content of cholesterol, GM1, the bile salt dependent lipase (BSDL), and GP2 enrichment, the low-density fractions were defined as lipid rafts. Additionally, the rafts vesicles were determined by immunogold labeling with anti BSDL. By combining MALDI-TOF/MS and nano-LC ESI Q-TOF MS/MS proteomic identification we have selected 33 proteins from the lipid rafts which were classified into at least four functional families. Our data suggest that the acinar PM from the diet-induced obesity rats may be organized into lipid rafts, and characterization of rafts proteome can contribute to improve our understanding of food digestion under obesity.
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Affiliation(s)
- Amine Adda Berkane
- Université Paul Cézanne, FST-Institut Méditerranéen de Recherche en Nutrition IMRN, UMR INRA 1111/PNV UMR 6153 1147, Marseille, France
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26
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Lee MJ, Wang Y, Ricci MR, Sullivan S, Russell CD, Fried SK. Acute and chronic regulation of leptin synthesis, storage, and secretion by insulin and dexamethasone in human adipose tissue. Am J Physiol Endocrinol Metab 2007; 292:E858-64. [PMID: 17122089 DOI: 10.1152/ajpendo.00439.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Serum leptin levels are upregulated in proportion to body fat and also increase over the short term in response to meals or insulin. To understand the mechanisms involved, we assessed leptin synthesis and secretion in samples of adipose tissue from subjects with a wide range of BMI. Tissue leptin content and relative rates of leptin biosynthesis, as determined by metabolic labeling, were highly correlated with each other and with BMI and fat cell size. To understand mechanisms regulating leptin synthesis in obesity, we used biosynthetic labeling to directly assess the effects of insulin and glucocorticoids (dexamethasone) on leptin synthesis and secretion in human adipose tissue. Chronic treatment (1-2 days in organ culture) with insulin increased relative rates of leptin biosynthesis without affecting leptin mRNA levels. In contrast, dexamethasone increased leptin mRNA and biosynthesis in parallel. Acute treatment with insulin or dexamethasone (added during 1-h preincubation and 45-min pulse labeling) did not affect relative rates of leptin biosynthesis, but pulse-chase studies showed that addition of insulin nearly doubled the release of [35S]leptin after a 1-h chase. We conclude that the higher leptin stores in adipose tissue of obese humans are maintained by chronic effects of insulin and glucocorticoids acting at pre- and posttranslational levels and that the ability of insulin to increase the release of preformed leptin may contribute to short-term variations in circulating leptin levels.
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Affiliation(s)
- Mi-Jeong Lee
- Division of Endocrinology, School of Medicine, University of Maryland, 660 West Redwood St., Baltimore, MD 21201, USA
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27
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Leite-Moreira AF, Soares JB. Physiological, pathological and potential therapeutic roles of ghrelin. Drug Discov Today 2007; 12:276-88. [PMID: 17395087 DOI: 10.1016/j.drudis.2007.02.009] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 01/16/2007] [Accepted: 02/14/2007] [Indexed: 12/21/2022]
Abstract
Ghrelin, a hormone that is produced mainly by the stomach, was identified originally as the endogenous ligand of the growth hormone secretagogue (GHS) receptor. Ghrelin might also be synthesized in other organs, where it might have autocrine or paracrine effects. GHS receptors are present in tissues other than the hypothalamus and pituitary, which indicates that ghrelin has other effects in addition to stimulating the release of growth hormone. Recently, it has been suggested that ghrelin might be involved in the pathogenesis of many diseases and be a therapeutic target in these diseases. Here, we provide an overview of the physiological effects of ghrelin and of its pathological and potential therapeutic roles.
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Affiliation(s)
- Adelino F Leite-Moreira
- Department of Physiology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal.
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28
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Kalra SP, Kalra PS. To subjugate NPY is to improve the quality of life and live longer. Peptides 2007; 28:413-8. [PMID: 17215061 PMCID: PMC1839846 DOI: 10.1016/j.peptides.2006.08.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 08/09/2006] [Indexed: 10/23/2022]
Abstract
The interactive network of neuropeptide Y (NPY) and cohorts is necessary for integrating the hypothalamic regulation of appetite and energy expenditure with the endocrine and neuroendocrine systems on a daily basis. Genetic and environmental factors that produce an insufficiency of leptin restraint on NPY and cognate receptors deregulate the homeostasis to engender various life-threatening risk factors. Recent studies from our laboratory show that neurotherapy consisting of a single central administration of recombinant adeno-associated virus vector encoding the leptin gene can repress the hypothalamic NPY system for the lifetime of rodents. A major benefit of this stable tonic restraint is deceleration of pathophysiologic sequalae that shorten life span. These include suppression of weight gain, fat accumulation, circulating adipokines, amelioration of major symptoms of metabolic syndrome, improved reproduction and bone health. Thus, sustained repression of NPY signaling in the hypothalamus by leptin transgene expression can improve the quality of life and extend longevity.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, McKnight Brain Institute, University of Florida, PO Box 100244, Gainesville, FL 32610-0244, USA.
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29
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Boghossian S, Dube MG, Torto R, Kalra PS, Kalra SP. Hypothalamic clamp on insulin release by leptin-transgene expression. Peptides 2006; 27:3245-54. [PMID: 16962683 DOI: 10.1016/j.peptides.2006.07.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 07/24/2006] [Accepted: 07/26/2006] [Indexed: 12/15/2022]
Abstract
The effects of sustained leptin action locally in the hypothalamus on the functional link between fat accrual and insulin secretion after chronic high fat diet (HFD) consumption in leptin-deficient ob/ob mice, and on the post-prandial insulin response in rats consuming regular chow diet (RCD), was examined in this study. A single intracerebroventricular (icv) injection of recombinant adeno-associated virus vector encoding leptin gene (rAAV-lep) enhanced hypothalamic leptin-transgene expression in ob/ob mice consuming RCD and suppressed the time-related weight gain and fat accumulation concomitant with abrogation of hyperinsulinemia and enhanced glucose tolerance. This increased hypothalamic leptin-transgene expression continued to impose insulinopenia and increased glucose tolerance but was ineffective in suppressing weight gain and fat accumulation after these mice were switched to chronic HFD consumption. A similar icv rAAV-lep pretreatment in rats consuming RCD markedly attenuated the post-prandial rise in insulin release concomitant with suppressed weight and fat depots. These results show for the first time that a sustained hypothalamic leptin action can stably clamp pancreatic insulin secretion independent of the status of fat accrual engendered by diets of varying caloric enrichment. Thus, the efficacy of increased leptin afferent signaling in the hypothalamus to persistently restrain pancreatic insulin release and insulin resistance can be explored as an adjunct therapeutic modality to alleviate pathophysiological derrangements that confer type 2 diabetes.
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Affiliation(s)
- Stéphane Boghossian
- Department of Neuroscience, University of Florida, McKnight Brain Institute, PO Box 100244, Gainesville, FL 32610-0244, USA
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30
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Gil-Campos M, Aguilera CM, Cañete R, Gil A. Ghrelin: a hormone regulating food intake and energy homeostasis. Br J Nutr 2006; 96:201-26. [PMID: 16923214 DOI: 10.1079/bjn20061787] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Regulation of energy homeostasis requires precise coordination between peripheral nutrient-sensing molecules and central regulatory networks. Ghrelin is a twenty-eight-amino acid orexigenic peptide acylated at the serine 3 position mainly with an n-octanoic acid, which is produced mainly in the stomach. It is the endogenous ligand of the growth hormone secretagogue (GHS) receptors. Since plasma ghrelin levels are strictly dependent on recent food intake, this hormone plays an essential role in appetite and meal initiation. In addition, ghrelin is involved in the regulation of energy homeostasis. The ghrelin gene is composed of four exons and three introns and renders a diversity of orexigenic peptides as well as des-acyl ghrelin and obestatin, which exhibit anorexigenic properties. Ghrelin stimulates the synthesis of neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus neurons of the hypothalamus and hindbrain, which in turn enhance food intake. Ghrelin-expressing neurons modulate the action of both orexigenic NPY/AgRP and anorexigenic pro-opiomelanocortin neurons. AMP-activated protein kinase is activated by ghrelin in the hypothalamus, which contributes to lower intracellular long-chain fatty acids, and this appears to be the molecular signal for the expression of NPY and AgRP. Recent data suggest that ghrelin has an important role in the regulation of leptin and insulin secretion and vice versa. The present paper updates the effects of ghrelin on the control of energy homeostasis and reviews the molecular mechanisms of ghrelin synthesis, as well as interaction with GHS receptors and signalling. Relationships with leptin and insulin in the regulation of energy homeostasis are addressed.
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Affiliation(s)
- Mercedes Gil-Campos
- Unit of Paediatric Endocrinology, Reina Sofia University Hospital, Cordoba, Spain
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31
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Hermsdorff HHM, Volp ACP, Santos RGC, Viana ML, Bressan J. [Effect of diet macronutrients profile on leptin concentration]. ARQUIVOS BRASILEIROS DE ENDOCRINOLOGIA E METABOLOGIA 2006; 50:934-43. [PMID: 17160220 DOI: 10.1590/s0004-27302006000500017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 07/14/2006] [Indexed: 05/12/2023]
Abstract
The aim of this study was to investigate the effect of ingesting high-sucrose (HSD) and high-lipid diets (HLD) on the concentrations of plasma glucose and leptin in lean and overweight women. Twenty healthy women were selected: 13 lean (G1) and 7 overweight (G2). The test diets HSD (23% sucrose) and HLD (45% lipid) were calculated for intake under non-restrictive conditions during 14 days. Anthropometry, body composition, plasma glucose and leptin determinations were carried out. The fasting and postprandial plasma leptin values were higher in G2 (p< 0.05), correlating positively with the anthropometry and body composition data (p< 0.05), and special positive correlation with hip circumference. Glucose and leptin concentrations did not differ between diets. Circulating glucose 30 (p< 0.01) and 60 (p< 0.05) minutes after ingestion of HSD were positively correlated with postprandial leptin concentration. The results confirm the positive association between plasma leptin concentration and body fat, specifically the subcutaneous fat tissue, and suggest that more studies are necessary to identify the modulating role of energy intake and macronutrients profile on leptin concentration.
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32
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Levin BE. Central regulation of energy homeostasis intelligent design: how to build the perfect survivor. Obesity (Silver Spring) 2006; 14 Suppl 5:192S-196S. [PMID: 17021365 DOI: 10.1038/oby.2006.307] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The perfect survivor must be able to eat and store as many calories as possible when food is readily available as a buffer against periods of scarcity. He must also reduce energy expenditure when food is scarce and efficiently and accurately restore lost adipose stores when food is again available. These processes are dependent on information relayed to a distributed central network of metabolic sensing neurons through hard-wired neural, metabolic, and hormonal signals from the periphery. These sensing neurons engage neuroendocrine, autonomic, and motor processes involved in arousal, motor activity, and the ingestion, absorption, assimilation, storage, and expenditure of calories. A raised threshold in these metabolic sensors for detecting inhibitory signals from increasing adipose stores allows continued intake of excess calories when they are readily available. Unfortunately, this mechanism for surviving periods of feast and famine predisposes the perfect survivor to become obese when highly palatable, energy dense foods are readily available at low energetic cost. It further assures that raised adipose stores are metabolically defended against attempts to lower them. Thus, effective treatment of obesity will only come with a better understanding of the physiological, metabolic, and neurochemical processes that ensure this defense of an elevated body weight.
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Affiliation(s)
- Barry E Levin
- Neurology Service, VA Medical Center, 385 Tremont Avenue, East Orange, NJ 07018-1095, USA.
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33
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Cummings DE. Ghrelin and the short- and long-term regulation of appetite and body weight. Physiol Behav 2006; 89:71-84. [PMID: 16859720 DOI: 10.1016/j.physbeh.2006.05.022] [Citation(s) in RCA: 410] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Accepted: 05/24/2006] [Indexed: 12/17/2022]
Abstract
Ghrelin, an acylated upper gastrointestinal peptide, is the only known orexigenic hormone. Considerable evidence implicates ghrelin in mealtime hunger and meal initiation. Circulating levels decrease with feeding and increase before meals, achieving concentrations sufficient to stimulate hunger and food intake. Preprandial ghrelin surges occur before every meal on various fixed feeding schedules and also among individuals initiating meals voluntarily without time- or food-related cues. Ghrelin injections stimulate food intake rapidly and transiently, primarily by increasing appetitive feeding behaviors and the number of meals. Preprandial ghrelin surges are probably triggered by sympathetic nervous output. Postprandial suppression is not mediated by nutrients in the stomach or duodenum, where most ghrelin is produced. Rather, it results from post-ingestive increases in lower intestinal osmolarity (information probably relayed to the foregut via enteric nervous signaling), as well as from insulin surges. Consequently, ingested lipids suppress ghrelin poorly compared with other macronutrients. Beyond a probable role in meal initiation, ghrelin also fulfills established criteria for an adiposity-related hormone involved in long-term body-weight regulation. Ghrelin levels circulate in relation to energy stores and manifest compensatory changes in response to body-weight alterations. Ghrelin crosses the blood-brain barrier and stimulates food intake by acting on several classical body-weight regulatory centers, including the hypothalamus, hindbrain, and mesolimbic reward system. Chronic ghrelin administration increases body weight via diverse, concerted actions on food intake, energy expenditure, and fuel utilization. Congenital ablation of the ghrelin or ghrelin-receptor gene causes resistance to diet-induced obesity, and pharmacologic ghrelin blockade reduces food intake and body weight. Ghrelin levels are high in Prader-Willi syndrome and low after gastric bypass surgery, possibly contributing to body-weight alterations in these settings. Extant evidence favors roles for ghrelin in both short-term meal initiation and long-term energy homeostasis, making it an attractive target for drugs to treat obesity and/or wasting disorders.
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Affiliation(s)
- David E Cummings
- Department of Medicine, Division of Metabolism, Endocrinology and Nutrition, University of Washington, VA Puget Sound Health Care System, 1660 South Columbian Way, S-111-Endo, Seattle, WA 98108, USA.
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34
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Kalra SP, Kalra PS. Subjugation of hypothalamic NPY and cohorts with central leptin gene therapy alleviates dyslipidemia, insulin resistance, and obesity for life-time. EXS 2006:157-69. [PMID: 16383005 DOI: 10.1007/3-7643-7417-9_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An interactive network comprised of neuropeptide Y (NPY) and cohorts is obligatory in the hypothalamic integration of appetite and energy expenditure on a minute-to-minute basis. High or low abundance of NPY and cognate receptors dysregulates the homeostatic milieu engendering hyperphagia, decreased energy expenditure, obesity and attendant metabolic syndrome cluster of dyslipidemia, glucose intolerance, insulin resistance and hyperinsulinemia, risk factors for type II diabetes and cardiovascular diseases. Increasing the supply of the endogenous repressor hormone leptin locally in the hypothalamus with the aid of leptin gene therapy, blocked age-related and dietary obesities, and the sequential development of dyslipidemia, hyperglycemia, and insulin resistance. Thus, sustained repression of NPY signaling with increased leptin selectively in the hypothalamus can avert environmental obesity and the risks of metabolic diseases.
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Affiliation(s)
- Satya P Kalra
- University of Florida McKnight Brain Institute, Department of Neuroscience, PO Box 100244, Gainesville, Florida 32610-0244, USA.
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35
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Jenkins JB, Omori T, Guan Z, Vgontzas AN, Bixler EO, Fang J. Sleep is increased in mice with obesity induced by high-fat food. Physiol Behav 2006; 87:255-62. [PMID: 16360185 DOI: 10.1016/j.physbeh.2005.10.010] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Revised: 09/07/2005] [Accepted: 10/19/2005] [Indexed: 11/20/2022]
Abstract
Excessive daytime sleepiness has been associated with obesity in humans. However, experimental studies on sleep in obese animals are scarce and the results are not consistent. To test the hypothesis that obesity is associated with increased sleep, we examined the effects of obesity, induced by high-fat food, on sleep in mice. We first determined baseline sleep in adult C57BL/6 mice (6 months of age). In the following 6 weeks, the experimental mice (n = 12) were switched to high-fat food, in which fat provided 59% of calories, and the control mice (n = 11) were continuously fed with regular lab chows, in which fat provided 16% of calories. The body weights increased steadily in the high-fat group, but maintained constant in the controls. Wakefulness was reduced when assessed after 2, 4, and 6 weeks of high-fat feeding. Concurrently, there were large increases (about 80-100 min/day) in non-rapid eye movement sleep (NREMS). Rapid eye movement sleep (REMS) was not altered. The numbers of NREMS and REMS episodes were increased, whereas the duration of waking episodes was reduced, mainly during the dark period. These alterations in sleep were not observed in the controls. In the high-fat group, the increases of body weight, but not the amounts of energy intake, were negatively correlated with the change in the amounts of wakefulness and positively correlated with the change in the amounts of NREMS. These results indicate that the obese animals have increased sleep pressure and difficulties in maintaining wakefulness during the active phase.
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Affiliation(s)
- Joe B Jenkins
- Department of Psychiatry, Pennsylvania State University College of Medicine, Hershey, Room C5654, 500 University Drive, PA 17033, USA
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36
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Otukonyong EE, Dube MG, Torto R, Kalra PS, Kalra SP. Central leptin differentially modulates ultradian secretory patterns of insulin, leptin and ghrelin independent of effects on food intake and body weight. Peptides 2005; 26:2559-66. [PMID: 15936848 DOI: 10.1016/j.peptides.2005.04.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2005] [Revised: 04/25/2005] [Accepted: 04/25/2005] [Indexed: 10/25/2022]
Abstract
We tested the hypothesis that leptin acts centrally to differentially modulate the ultradian communication of leptin, insulin and ghrelin with the hypothalamus. The ultradian fluctuation of these hormones in plasma after central leptin gene therapy was analyzed. Increased leptin transgene expression in the hypothalamus significantly decreased energy intake and body weight concomitant with severe hypoleptinemia and hypoinsulinemia resulting from drastically suppressed peak heights with unchanged frequency discharge of these hormones. Ghrelin secretion was, however, increased solely due to increased pulse amplitude. In pair-fed control rats leptin and ghrelin secretion was unchanged. In conclusion, independent of restraint on caloric intake and weight, leptin acting centrally modulates only the pulse amplitude of ultradian rhythmicity of the three afferent signals involved in the hypothalamic integration of energy balance. Since rhythmic discharge patterns dictate target response of hormones, these findings reveal a novel hypothalamic action of leptin in the pathophysiology of the obesity-dependent metabolic syndrome.
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Affiliation(s)
- Effiong E Otukonyong
- Department of Neuroscience, McKnight Brain Institute, University of Florida, College of Medicine, P.O. Box 100244, Gainesville, FL 32610-0244, USA
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Kalra SP, Kalra PS. Gene-transfer technology: a preventive neurotherapy to curb obesity, ameliorate metabolic syndrome and extend life expectancy. Trends Pharmacol Sci 2005; 26:488-95. [PMID: 16125798 DOI: 10.1016/j.tips.2005.08.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2005] [Revised: 07/25/2005] [Accepted: 08/12/2005] [Indexed: 11/29/2022]
Abstract
Leptin insufficiency at crucial target sites in the hypothalamic circuitries that integrate energy intake and expenditure underlies abnormal rates of fat accumulation. The payload of this "fat burden" is metabolic syndrome, a cluster of life-threatening metabolic afflictions, and a shorter lifespan. Currently available therapies employed to combat obesity have disadvantages such as poor compliance for lifestyle modification or transient effectiveness and undesirable side-effects of pharmacological interventions. Recent studies suggest that neurotherapy comprising a single central administration of recombinant adeno-associated virus vector encoding the leptin gene severely depletes fat and ameliorates the major symptoms of metabolic syndrome for extended periods in rodents. These persistent benefits avert the deleterious impact of the "fat burden" and extend life expectancy. Thus, the novel approach of central gene-transfer technology has distinct advantages over current therapies and has the potential to correct or slow the progression of inherited or acquired hypothalamic diseases.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, College of Medicine, University of Florida McKnight Brain Institute, Gainesville, FL 32610, USA.
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