1
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Li K, Hu L, Li X, Yuan Z, He J, Liu D, Yang G, Yuan L. Effect of C-reactive protein deficiency on insulin resistance reversal in rats with polycystic ovary syndrome through augmented leptin action. Diabetol Metab Syndr 2023; 15:180. [PMID: 37660067 PMCID: PMC10474659 DOI: 10.1186/s13098-023-01155-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/27/2023] [Indexed: 09/04/2023] Open
Abstract
BACKGROUND C-reactive protein(CRP), is an inflammatory marker that weaken leptin bioavailability and insulin sensitivity to disturb energy and glucose metabolism. Polycystic ovary syndrome (PCOS) exhibit a metabolic component consisting of higher plasma CRP levels, hyperinsulinemic and hyperleptinemia. The ability of leptin to regulation of hepatic glucose production (HGP) in the absence of CRP in PCOS remain unknown. METHODS Dehydroepiandrosterone (DHEA) was used to induce PCOS in rats. We assessed the effects of CRP gene knockout in PCOS model rats on body weight, energy expenditure glucose metabolism and insulin sensitivity. We conducted experiments involving the administration of leptin to both the peripheral and central systems in PCOS model rats with CRP knockout, and studied the effects on changes in glucose kinetics during hyperinsulinemic-euglycemic clamps. RESULTS In female PCOS rats, the lack of CRP resulted in decreased leptin resistance and weight gain, increased energy expenditure, and improved insulin sensitivity. Additionally, the deletion of the CRP gene strengthened the HGP-lowering effects of leptin when administered peripherally or centrally. This effect was accompanied by a decrease in the expression of hepatic gluconeogenic enzymes and an increase in hepatic insulin signaling. Finally, inhibition of glucose production was also enhanced for central leptin administration during lipid infusion in PCOS rats. CONCLUSIONS Our findings highlight the therapeutic potential of targeting CRP to restore glucose homeostasis and insulin sensitivity for leptin in PCOS.
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Affiliation(s)
- Ke Li
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Lingling Hu
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Xinrun Li
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Zhibin Yuan
- Department of general surgery, People's Hospital, Hubei University of Medicine, Xiangyang No.1, Xiangyang, 441100, China
| | - Jia He
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Dongfang Liu
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Gangyi Yang
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China
| | - Lei Yuan
- Department of Endocrinology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, 400010, China.
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2
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Huang X, He Q, Zhu H, Fang Z, Che L, Lin Y, Xu S, Zhuo Y, Hua L, Wang J, Zou Y, Huang C, Li L, Xu H, Wu D, Feng B. Hepatic Leptin Signaling Improves Hyperglycemia by Stimulating MAPK Phosphatase-3 Protein Degradation via STAT3. Cell Mol Gastroenterol Hepatol 2022; 14:983-1001. [PMID: 35863745 PMCID: PMC9490031 DOI: 10.1016/j.jcmgh.2022.07.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 07/12/2022] [Accepted: 07/12/2022] [Indexed: 01/31/2023]
Abstract
BACKGROUND & AIMS Obesity-related hyperglycemia, with hepatic insulin resistance, has become an epidemic disease. Central neural leptin signaling was reported to improve hyperglycemia. The aim of this study was to investigate the effect of hepatic leptin signaling on controlling hyperglycemia. METHODS First, the effect of leptin signaling on gluconeogenesis was investigated in primary mouse hepatocytes and hepatoma cells. Second, glucose tolerance, insulin tolerance, blood glucose levels, and hepatic gluconeogenic gene expression were analyzed in obese mice overexpressing hepatic OBRb. Third, expression of mitogen-activated protein kinase phosphatase (MKP)-3, phosphorylation level of signal transducer and activator of transcription (STAT) 3, and extracellular regulated protein kinase (ERK) were analyzed in hepatocytes and mouse liver. Fourth, the role of MKP-3 in hepatic leptin signaling regulating gluconeogenesis was analyzed. Lastly, the role of ERK and STAT3 in the regulation of MKP-3 protein by leptin signaling was analyzed. RESULTS Activation of hepatic leptin signaling suppressed gluconeogenesis in both hepatocytes and obese mouse liver, and improved hyperglycemia, insulin tolerance, and glucose tolerance in obese mice. The protein level of MKP-3, which can promote gluconeogenesis, was decreased by leptin signaling in both hepatocytes and mouse liver. Mkp-3 deficiency abolished the effect of hepatic leptin signaling on suppressing gluconeogenesis in hepatocytes. STAT3 decreased the MKP-3 protein level, while inactivation of STAT3 abolished the effect of leptin signaling on reducing the MKP-3 protein level in hepatocytes. Moreover, STAT3 could combine with MKP-3 and phospho-ERK1/2, which induced the degradation of MKP-3, and leptin signaling enhanced the combination. CONCLUSIONS Hepatic leptin signaling could suppress gluconeogenesis at least partially by decreasing the MKP-3 protein level via STAT3-enhanced MKP-3 and ERK1/2 combination.
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Affiliation(s)
- Xiaohua Huang
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China,Key Laboratory of Animal Disease-Resistant Nutrition of Ministry of Education, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Qin He
- Hallett Center for Diabetes and Endocrinology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island,School of international education, Xihua University, Chengdu, Sichuan, China
| | - Heng Zhu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Zhengfeng Fang
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China,Key Laboratory for Food Science and Human Health, College of Food Science, Sichuan Agricultural University, Ya’an, Sichuan, China
| | - Lianqiang Che
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Yan Lin
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Shengyu Xu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Yong Zhuo
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Lun Hua
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Jianping Wang
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Yuanfeng Zou
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Chao Huang
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Lixia Li
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Haiyan Xu
- Hallett Center for Diabetes and Endocrinology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island,Department of Quantitative Biosciences, Merck & Co., Inc., Boston, Massachusetts
| | - De Wu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China,Key Laboratory of Animal Disease-Resistant Nutrition of Ministry of Education, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Bin Feng
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, Sichuan, China,Key Laboratory of Animal Disease-Resistant Nutrition of Ministry of Education, Sichuan Agricultural University, Chengdu, Sichuan, China,Hallett Center for Diabetes and Endocrinology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island,Key Laboratory for Food Science and Human Health, College of Food Science, Sichuan Agricultural University, Ya’an, Sichuan, China,Correspondence Address correspondence to: Bin Feng, PhD, Sichuan Agricultural University, 211 Huimin Road, Wenjiang District, Chengdu 611130, China. fax: (86) 028-82652669.
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3
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SOCS3 Ablation in Leptin Receptor-Expressing Cells Causes Autonomic and Cardiac Dysfunctions in Middle-Aged Mice despite Improving Energy and Glucose Metabolism. Int J Mol Sci 2022; 23:ijms23126484. [PMID: 35742928 PMCID: PMC9223472 DOI: 10.3390/ijms23126484] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/03/2022] [Accepted: 06/06/2022] [Indexed: 02/04/2023] Open
Abstract
Leptin resistance is a hallmark of obesity. Treatments aiming to improve leptin sensitivity are considered a promising therapeutical approach against obesity. However, leptin receptor (LepR) signaling also modulates several neurovegetative aspects, such as the cardiovascular system and hepatic gluconeogenesis. Thus, we investigated the long-term consequences of increased leptin sensitivity, considering the potential beneficial and deleterious effects. To generate a mouse model with increased leptin sensitivity, the suppressor of cytokine signaling 3 (SOCS3) was ablated in LepR-expressing cells (LepR∆SOCS3 mice). LepR∆SOCS3 mice displayed reduced food intake, body adiposity and weight gain, as well as improved glucose tolerance and insulin sensitivity, and were protected against aging-induced leptin resistance. Surprisingly, a very high mortality rate was observed in aging LepR∆SOCS3 mice. LepR∆SOCS3 mice showed cardiomyocyte hypertrophy, increased myocardial fibrosis and reduced cardiovascular capacity. LepR∆SOCS3 mice exhibited impaired post-ischemic cardiac functional recovery and middle-aged LepR∆SOCS3 mice showed substantial arhythmic events during the post-ischemic reperfusion period. Finally, LepR∆SOCS3 mice exhibited fasting-induced hypoglycemia and impaired counterregulatory response to glucopenia associated with reduced gluconeogenesis. In conclusion, although increased sensitivity to leptin improved the energy and glucose homeostasis of aging LepR∆SOCS3 mice, major autonomic/neurovegetative dysfunctions compromised the health and longevity of these animals. Consequently, these potentially negative aspects need to be considered in the therapies that increase leptin sensitivity chronically.
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4
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Kasacka I, Piotrowska Ż, Domian N, Lewandowska A, Acewicz M. Immunohistochemical identification and assessment of the location of leptin, visfatin and chemerin in the liver of men with different body mass index. BMC Gastroenterol 2022; 22:233. [PMID: 35549673 PMCID: PMC9097377 DOI: 10.1186/s12876-022-02299-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 04/21/2022] [Indexed: 11/17/2022] Open
Abstract
Background Adipokines such as leptin, visfatin and chemerin play a pivotal role not only in the pathogenesis of excessive weight gain but also impact on hepatic metabolism. However, alterations in the production of these peptides in the liver of overweight individuals have not been fully elucidated yet. The aim of the study was to evaluate changes in leptin, visfatin and chemerin biosynthesis in the liver of men with different BMI. Methods Fourteen adult men without symptoms from the digestive system were recruited. Research material consisted of liver samples. Study participants were divided into two groups: lean (BMI ≤ 25 kg/m2) and overweight subjects (BMI > 25 kg/m2). Paraffin liver sections were processed by immunohistochemistry for detection of leptin, visfatin and chemerin. Hepatic expression of leptin, visfatin and chemerin genes was determined by qRT-PCR method. Results Increased immunoreactivity for leptin and chemerin, and decreased immunoreaction for visfatin were observed in the liver of overweight men in comparison to lean subjects. Overweight subjects with hepatic steatosis displayed increased immunoreactivity for leptin and weaker immunoreaction against visfatin and chemerin in the liver, compared to individuals with normal organ structure. Expression of leptin and chemerin was enhanced in the liver of overweight individuals, with the highest expression observed in subjects with hepatic steatosis. Conversely, expression of visfatin in the male liver was decreased in overweight subjects and those with and liver steatosis. Conclusions The present study proves that the expression of leptin, visfatin and chemerin in the male liver is altered in overweight individuals. Our report also indicates the potential importance of these peptides in hepatic steatosis associated with overweight.
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Affiliation(s)
- I Kasacka
- Department of Histology and Cytophysiology, Medical University of Białystok, Mickiewicza 2C Street, 15-222, Białystok, Poland.
| | - Ż Piotrowska
- Department of Histology and Cytophysiology, Medical University of Białystok, Mickiewicza 2C Street, 15-222, Białystok, Poland
| | - N Domian
- Department of Histology and Cytophysiology, Medical University of Białystok, Mickiewicza 2C Street, 15-222, Białystok, Poland
| | - A Lewandowska
- Department of Histology and Cytophysiology, Medical University of Białystok, Mickiewicza 2C Street, 15-222, Białystok, Poland
| | - M Acewicz
- Department of Histology and Cytophysiology, Medical University of Białystok, Mickiewicza 2C Street, 15-222, Białystok, Poland
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5
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Grasso P. Harnessing the Power of Leptin: The Biochemical Link Connecting Obesity, Diabetes, and Cognitive Decline. Front Aging Neurosci 2022; 14:861350. [PMID: 35527735 PMCID: PMC9072663 DOI: 10.3389/fnagi.2022.861350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/21/2022] [Indexed: 12/02/2022] Open
Abstract
In this review, the current understanding of leptin’s role in energy balance, glycemic regulation, and cognitive function is examined, and its involvement in maintaining the homeostatic “harmony” of these physiologies is explored. The effects of exercise on circulating leptin levels are summarized, and the results of clinical application of leptin to metabolic disease and neurologic dysfunction are reviewed. Finally, pre-clinical evidence is presented which suggests that synthetic peptide leptin mimetics may be useful in resolving not only the leptin resistance associated with common obesity and other elements of metabolic syndrome, but also the peripheral insulin resistance characterizing type 2 diabetes mellitus, and the central insulin resistance associated with certain neurologic deficits in humans.
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Affiliation(s)
- Patricia Grasso
- Department of Medicine, Albany Medical College, Albany, NY, United States
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States
- *Correspondence: Patricia Grasso,
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6
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DiNicolantonio JJ, O'Keefe JH. Low-grade metabolic acidosis as a driver of insulin resistance. Open Heart 2021; 8:openhrt-2021-001788. [PMID: 34497064 PMCID: PMC8438953 DOI: 10.1136/openhrt-2021-001788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/27/2021] [Indexed: 11/03/2022] Open
Affiliation(s)
- James J DiNicolantonio
- Department of Preventive Cardiology, Saint Luke's Mid America Heart Institute, Kansas City, Missouri, USA
| | - James H O'Keefe
- University of Missouri-Kansas City, Saint Lukes Mid America Heart Institute, Kansas City, Missouri, USA
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7
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Fujikawa T. Central regulation of glucose metabolism in an insulin-dependent and -independent manner. J Neuroendocrinol 2021; 33:e12941. [PMID: 33599044 DOI: 10.1111/jne.12941] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 12/17/2022]
Abstract
The central nervous system (CNS) contributes significantly to glucose homeostasis. The available evidence indicates that insulin directly acts on the CNS, in particular the hypothalamus, to regulate hepatic glucose production, thereby controlling whole-body glucose metabolism. Additionally, insulin also acts on the brain to regulate food intake and fat metabolism, which may indirectly regulate glucose metabolism. Studies conducted over the last decade have found that the CNS can regulate glucose metabolism in an insulin-independent manner. Enhancement of central leptin signalling reverses hyperglycaemia in insulin-deficient rodents. Here, I review the mechanisms by which central insulin and leptin actions regulate glucose metabolism. Although clinical studies have shown that insulin treatment is currently indispensable for managing diabetes, unravelling the neuronal mechanisms underlying the central regulation of glucose metabolism will pave the way for the design of novel therapeutic drugs for diabetes.
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Affiliation(s)
- Teppei Fujikawa
- Center for Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
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8
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Pereira S, Cline DL, Glavas MM, Covey SD, Kieffer TJ. Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism. Endocr Rev 2021; 42:1-28. [PMID: 33150398 PMCID: PMC7846142 DOI: 10.1210/endrev/bnaa027] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Indexed: 12/18/2022]
Abstract
The discovery of leptin was intrinsically associated with its ability to regulate body weight. However, the effects of leptin are more far-reaching and include profound glucose-lowering and anti-lipogenic effects, independent of leptin's regulation of body weight. Regulation of glucose metabolism by leptin is mediated both centrally and via peripheral tissues and is influenced by the activation status of insulin signaling pathways. Ectopic fat accumulation is diminished by both central and peripheral leptin, an effect that is beneficial in obesity-associated disorders. The magnitude of leptin action depends upon the tissue, sex, and context being examined. Peripheral tissues that are of particular relevance include the endocrine pancreas, liver, skeletal muscle, adipose tissues, immune cells, and the cardiovascular system. As a result of its potent metabolic activity, leptin is used to control hyperglycemia in patients with lipodystrophy and is being explored as an adjunct to insulin in patients with type 1 diabetes. To fully understand the role of leptin in physiology and to maximize its therapeutic potential, the mechanisms of leptin action in these tissues needs to be further explored.
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Affiliation(s)
- Sandra Pereira
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Daemon L Cline
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Maria M Glavas
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Scott D Covey
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada.,Department of Surgery, University of British Columbia, Vancouver, Canada.,School of Biomedical Engineering, University of British Columbia, Vancouver, Canada
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9
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Landry T, Shookster D, Chaves A, Free K, Nguyen T, Huang H. Energy Status Differentially Modifies Feeding Behavior and POMC ARC Neuron Activity After Acute Treadmill Exercise in Untrained Mice. Front Endocrinol (Lausanne) 2021; 12:705267. [PMID: 34220725 PMCID: PMC8253227 DOI: 10.3389/fendo.2021.705267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
Emerging evidence identifies a potent role for aerobic exercise to modulate activity of neurons involved in regulating appetite; however, these studies produce conflicting results. These discrepancies may be, in part, due to methodological differences, including differences in exercise intensity and pre-exercise energy status. Consequently, the current study utilized a translational, well-controlled, within-subject, treadmill exercise protocol to investigate the differential effects of energy status and exercise intensity on post-exercise feeding behavior and appetite-controlling neurons in the hypothalamus. Mature, untrained male mice were exposed to acute sedentary, low (10m/min), moderate (14m/min), and high (18m/min) intensity treadmill exercise in a randomized crossover design. Fed and 10-hour-fasted mice were used, and food intake was monitored 48h. post-exercise. Immunohistochemical detection of cFOS was performed 1-hour post-exercise to determine changes in hypothalamic NPY/AgRP, POMC, tyrosine hydroxylase, and SIM1-expressing neuron activity concurrent with changes in food intake. Additionally, stains for pSTAT3tyr705 and pERKthr202/tyr204 were performed to detect exercise-mediated changes in intracellular signaling. Results demonstrated that fasted high intensity exercise suppressed food intake compared to sedentary trials, which was concurrent with increased anorexigenic POMC neuron activity. Conversely, fed mice experienced augmented post-exercise food intake, with no effects on POMC neuron activity. Regardless of pre-exercise energy status, tyrosine hydroxylase and SIM1 neuron activity in the paraventricular nucleus was elevated, as well as NPY/AgRP neuron activity in the arcuate nucleus. Notably, these neuronal changes were independent from changes in pSTAT3tyr705 and pERKthr202/tyr204 signaling. Overall, these results suggest fasted high intensity exercise may be beneficial for suppressing food intake, possibly due to hypothalamic POMC neuron excitation. Furthermore, this study identifies a novel role for pre-exercise energy status to differentially modify post-exercise feeding behavior and hypothalamic neuron activity, which may explain the inconsistent results from studies investigating exercise as a weight loss intervention.
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Affiliation(s)
- Taylor Landry
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
| | - Daniel Shookster
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
| | - Alec Chaves
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
| | - Katrina Free
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
| | - Tony Nguyen
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
| | - Hu Huang
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Human Performance Laboratory, College of Human Performance and Health, East Carolina University, Greenville, NC, United States
- Department of Physiology, East Carolina University, Greenville, NC, United States
- *Correspondence: Hu Huang,
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10
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Faber CL, Deem JD, Campos CA, Taborsky GJ, Morton GJ. CNS control of the endocrine pancreas. Diabetologia 2020; 63:2086-2094. [PMID: 32894319 PMCID: PMC7983553 DOI: 10.1007/s00125-020-05204-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/07/2020] [Indexed: 12/30/2022]
Abstract
Increasing evidence suggests that, although pancreatic islets can function autonomously to detect and respond to changes in the circulating glucose level, the brain cooperates with the islet to maintain glycaemic control. Here, we review the role of the central and autonomic nervous systems in the control of the endocrine pancreas, including mechanisms whereby the brain senses circulating blood glucose levels. We also examine whether dysfunction in these systems might contribute to complications of type 1 diabetes and the pathogenesis of type 2 diabetes. Graphical abstract.
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Affiliation(s)
- Chelsea L Faber
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, 750 Republican St, Box 358062, Seattle, WA, 98109, USA
- Department of Medicine, University of Washington, Seattle, WA, USA
| | - Jennifer D Deem
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, 750 Republican St, Box 358062, Seattle, WA, 98109, USA
- Department of Medicine, University of Washington, Seattle, WA, USA
| | - Carlos A Campos
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, 750 Republican St, Box 358062, Seattle, WA, 98109, USA
- Department of Medicine, University of Washington, Seattle, WA, USA
| | - Gerald J Taborsky
- Department of Medicine, University of Washington, Seattle, WA, USA
- Veterans Affairs Puget Sound Health Care System, Department of Veterans Affairs Medical Center, Seattle, WA, USA
| | - Gregory J Morton
- UW Medicine Diabetes Institute, Department of Medicine, University of Washington, 750 Republican St, Box 358062, Seattle, WA, 98109, USA.
- Department of Medicine, University of Washington, Seattle, WA, USA.
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11
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Wondmkun YT. Obesity, Insulin Resistance, and Type 2 Diabetes: Associations and Therapeutic Implications. Diabetes Metab Syndr Obes 2020; 13:3611-3616. [PMID: 33116712 PMCID: PMC7553667 DOI: 10.2147/dmso.s275898] [Citation(s) in RCA: 258] [Impact Index Per Article: 64.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 09/23/2020] [Indexed: 01/12/2023] Open
Abstract
Obesity is a triggering factor for diabetes associated with insulin resistance. In individuals who are obese, higher amounts of non-esterified fatty acids, glycerol, hormones, and pro-inflammatory cytokines that could participate in the development of insulin resistance are released by adipose tissue. Besides, endoplasmic reticulum stress, adipose tissue hypoxia, oxidative stress, lipodystrophy, and genetic background have a role in insulin resistance. However, no effective drug therapy was developed for type 2 diabetes mellitus targeting these physiological factors. This is might be due to a lack of agreement on the comprehensive mechanism of insulin resistance. Therefore, this review assesses the cellular components of each physiologic and pathophysiologic factors that are involved in obesity associated insulin resistance, and may encourage further drug development in this field.
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Affiliation(s)
- Yohannes Tsegyie Wondmkun
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
- Correspondence: Yohannes Tsegyie Wondmkun Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Email
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12
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Bruder-Nascimento T, Kress TC, Belin de Chantemele EJ. Recent advances in understanding lipodystrophy: a focus on lipodystrophy-associated cardiovascular disease and potential effects of leptin therapy on cardiovascular function. F1000Res 2019; 8:F1000 Faculty Rev-1756. [PMID: 31656583 PMCID: PMC6798323 DOI: 10.12688/f1000research.20150.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/08/2019] [Indexed: 01/09/2023] Open
Abstract
Lipodystrophy is a disease characterized by a partial or total absence of adipose tissue leading to severe metabolic derangements including marked insulin resistance, type 2 diabetes, hypertriglyceridemia, and steatohepatitis. Lipodystrophy is also a source of major cardiovascular disorders which, in addition to hepatic failure and infection, contribute to a significant reduction in life expectancy. Metreleptin, the synthetic analog of the adipocyte-derived hormone leptin and current therapy of choice for patients with lipodystrophy, successfully improves metabolic function. However, while leptin has been associated with hypertension, vascular diseases, and inflammation in the context of obesity, it remains unknown whether its daily administration could further impair cardiovascular function in patients with lipodystrophy. The goal of this short review is to describe the cardiovascular phenotype of patients with lipodystrophy, speculate on the etiology of the disorders, and discuss how the use of murine models of lipodystrophy could be beneficial to address the question of the contribution of leptin to lipodystrophy-associated cardiovascular disease.
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Affiliation(s)
- Thiago Bruder-Nascimento
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, USA
- Department of Pediatrics, Division of Endocrinology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Taylor C. Kress
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Eric J. Belin de Chantemele
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA, USA
- Department of Medicine, Section of Cardiology, Medical College of Georgia at Augusta University, Augusta, GA, USA
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13
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Pedroso JAB, Ramos-Lobo AM, Donato J. SOCS3 as a future target to treat metabolic disorders. Hormones (Athens) 2019; 18:127-136. [PMID: 30414080 DOI: 10.1007/s42000-018-0078-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/29/2018] [Indexed: 12/20/2022]
Abstract
The suppressors of cytokine signaling (SOCS) are a group of eight proteins responsible for preventing excessive cytokine signaling. Among this protein family, SOCS3 has received special attention. SOCS3 expression is important to control certain allergy autoimmune diseases. Furthermore, SOCS3 expression is elevated in obesity and it is involved in the inhibition of leptin and insulin signaling, two important hormones involved in the control of energy metabolism. Therefore, increased SOCS3 expression in obese individuals is associated with several metabolic disorders, including reduced energy expenditure, increased food intake and adiposity, and insulin and leptin resistance. In addition, recent studies found that SOCS3 expression regulates energy and glucose homeostasis in several metabolic conditions, such as pregnancy, caloric restriction, and refeeding. Importantly, attenuation of SOCS3 expression in most cases improves leptin and insulin sensitivity, leading to beneficial metabolic effects. This review aims to discuss the role of SOCS3 in the control of blood glucose levels as well as in energy homeostasis. The development of pharmacological compounds to inhibit SOCS3 activity and/or expression may represent a promising therapeutic approach to treat type 2 diabetes mellitus, obesity, and other metabolic imbalances.
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Affiliation(s)
- João A B Pedroso
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes, 1524, São Paulo, 05508-000, Brazil.
| | - Angela M Ramos-Lobo
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes, 1524, São Paulo, 05508-000, Brazil
| | - Jose Donato
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes, 1524, São Paulo, 05508-000, Brazil
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14
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A hindbrain inhibitory microcircuit mediates vagally-coordinated glucose regulation. Sci Rep 2019; 9:2722. [PMID: 30804396 PMCID: PMC6389891 DOI: 10.1038/s41598-019-39490-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 12/14/2018] [Indexed: 02/07/2023] Open
Abstract
Neurons in the brainstem dorsal vagal complex integrate neural and humoral signals to coordinate autonomic output to viscera that regulate a variety of physiological functions, but how this circuitry regulates metabolism is murky. We tested the hypothesis that premotor, GABAergic neurons in the nucleus tractus solitarius (NTS) form a hindbrain micro-circuit with preganglionic parasympathetic motorneurons of the dorsal motor nucleus of the vagus (DMV) that is capable of modulating systemic blood glucose concentration. In vitro, neuronal activation or inhibition using either excitatory or inhibitory designer receptor exclusively activated by designer drugs (DREADDs) constructs expressed in GABAergic NTS neurons increased or decreased, respectively, action potential firing of GABAergic NTS neurons and downstream synaptic inhibition of the DMV. In vivo, DREADD-mediated activation of GABAergic NTS neurons increased systemic blood glucose concentration, whereas DREADD-mediated silencing of these neurons was without effect. The DREADD-induced hyperglycemia was abolished by blocking peripheral muscarinic receptors, consistent with the hypothesis that altered parasympathetic drive mediated the response. This effect was paralleled by elevated serum glucagon and hepatic phosphoenolpyruvate carboxykinase 1 (PEPCK1) expression, without affecting insulin levels or muscle metabolism. Activity in a hindbrain inhibitory microcircuit is sufficient to modulate systemic glucose concentration, independent of insulin secretion or utilization.
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15
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Balland E, Chen W, Dodd GT, Conductier G, Coppari R, Tiganis T, Cowley MA. Leptin Signaling in the Arcuate Nucleus Reduces Insulin’s Capacity to Suppress Hepatic Glucose Production in Obese Mice. Cell Rep 2019; 26:346-355.e3. [DOI: 10.1016/j.celrep.2018.12.061] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 11/29/2018] [Accepted: 12/13/2018] [Indexed: 12/18/2022] Open
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16
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Balland E, Chen W, Tiganis T, Cowley MA. Persistent Leptin Signaling in the Arcuate Nucleus Impairs Hypothalamic Insulin Signaling and Glucose Homeostasis in Obese Mice. Neuroendocrinology 2019; 109:374-390. [PMID: 30995667 DOI: 10.1159/000500201] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/02/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND Obesity is associated with reduced physiological responses to leptin and insulin, leading to the concept of obesity-associated hormonal resistance. OBJECTIVES Here, we demonstrate that contrary to expectations, leptin signaling not only remains functional but also is constantly activated in the arcuate nucleus of the hypothalamus (ARH) neurons of obese mice. This state of persistent response to endogenous leptin underpins the lack of response to exogenous leptin. METHODS AND RESULTS The study of combined leptin and insulin signaling demonstrates that there is a common pool of ARH neurons responding to both hormones. More importantly, we show that the constant activation of leptin receptor neurons in the ARH prevents insulin signaling in these neurons, leading to impaired glucose tolerance. Accordingly, antagonising leptin signaling in diet-induced obese (DIO) mice restores insulin signaling in the ARH and improves glucose homeostasis. Direct inhibition of PTP1B in the CNS restores arcuate insulin signaling similarly to leptin inhibition; this effect is likely to be mediated by AgRP neurons since PTP1B deletion specifically in AgRP neurons restores glucose and insulin tolerance in DIO mice. CONCLUSIONS Finally, our results suggest that the constant activation of arcuate leptin signaling in DIO mice increases PTP1B expression, which exerts an inhibitory effect on insulin signaling leading to impaired glucose homeostasis.
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Affiliation(s)
- Eglantine Balland
- Department of Physiology, Metabolism, Diabetes and Obesity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia,
| | - Weiyi Chen
- Department of Physiology, Metabolism, Diabetes and Obesity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Tony Tiganis
- Department of Biochemistry and Molecular Biology , Metabolism, Diabetes and Obesity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Michael A Cowley
- Department of Physiology, Metabolism, Diabetes and Obesity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
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17
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Rodrigues AA, Andrade RSB, Vasconcelos DFP. Relationship between Experimental Diet in Rats and Nonalcoholic Hepatic Disease: Review of Literature. Int J Hepatol 2018; 2018:9023027. [PMID: 30515333 PMCID: PMC6234452 DOI: 10.1155/2018/9023027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/05/2018] [Accepted: 09/25/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The pathophysiology of nonalcoholic fatty liver disease (NAFLD) is related to unhealthy lifestyles that combine sedentary lifestyle, hypercaloric diets, excessive saturated fats, refined carbohydrates, and high intake of fructose as a food additive to various processed products. Both the broader recognition of the disease and the additional efforts to elucidate the NAFLD pathogenesis have led to an increase in animal models in recent years. Objective. This review was performed to provide better understanding of the association between the NAFLD and animal models. METHODS The search in the literature occurred before May of 2018 in the PUBMED database. RESULTS Most studies investigating the influence of diet on liver fat content have been performed using a high-calorie diet that leads to a significant increase in fat content in the liver. CONCLUSION The findings of this review show that diet is one of the factors that predisposes to the appearance of NAFLD and that the studies presented a wide variety of designs.
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Affiliation(s)
- Ayane A. Rodrigues
- Postgraduate Program in Biomedical Sciences, Federal University of Piaui, Parnaiba, PI, Brazil
| | - Raíssa S. B. Andrade
- Postgraduate Program in Biotechnology, Federal University of Piaui, Parniba, PI, Brazil
| | - Daniel F. P. Vasconcelos
- Postgraduate Program in Biomedical Sciences, Federal University of Piaui, Parnaiba, PI, Brazil
- Postgraduate Program in Biotechnology, Federal University of Piaui, Parniba, PI, Brazil
- Department of Biomedicine, Federal University of Piaui, Parnaiba, PI, Brazil
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18
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Pozo M, Claret M. Hypothalamic Control of Systemic Glucose Homeostasis: The Pancreas Connection. Trends Endocrinol Metab 2018; 29:581-594. [PMID: 29866501 DOI: 10.1016/j.tem.2018.05.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/10/2018] [Accepted: 05/12/2018] [Indexed: 12/22/2022]
Abstract
Maintenance of glucose homeostasis is mandatory for organismal survival. It is accomplished by complex and coordinated interplay between glucose detection mechanisms and multiple effector systems. The brain, in particular homeostatic regions such as the hypothalamus, plays a crucial role in orchestrating such a highly integral response. We review here current understanding of how the hypothalamus senses glucose availability and participates in systemic glucose homeostasis. We provide an update of the relevant signaling pathways and neuronal subsets involved, as well as of the mechanisms modulating metabolic processes in peripheral tissues such as liver, skeletal muscle, fat, and especially the pancreas. We also discuss the relevance of these networks in human biology and prevalent metabolic conditions such as diabetes and obesity.
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Affiliation(s)
- Macarena Pozo
- Neuronal Control of Metabolism (NeuCoMe) Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
| | - Marc Claret
- Neuronal Control of Metabolism (NeuCoMe) Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBER) de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 08036 Barcelona, Spain.
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19
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Della Guardia L, Thomas MA, Cena H. Insulin Sensitivity and Glucose Homeostasis Can Be Influenced by Metabolic Acid Load. Nutrients 2018; 10:E618. [PMID: 29762478 PMCID: PMC5986498 DOI: 10.3390/nu10050618] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 05/08/2018] [Accepted: 05/10/2018] [Indexed: 01/04/2023] Open
Abstract
Recent epidemiological findings suggest that high levels of dietary acid load can affect insulin sensitivity and glucose metabolism. Consumption of high protein diets results in the over-production of metabolic acids which has been associated with the development of chronic metabolic disturbances. Mild metabolic acidosis has been shown to impair peripheral insulin action and several epidemiological findings suggest that metabolic acid load markers are associated with insulin resistance and impaired glycemic control through an interference intracellular insulin signaling pathways and translocation. In addition, higher incidence of diabetes, insulin resistance, or impaired glucose control have been found in subjects with elevated metabolic acid load markers. Hence, lowering dietary acid load may be relevant for improving glucose homeostasis and prevention of type 2 diabetes development on a long-term basis. However, limitations related to patient acid load estimation, nutritional determinants, and metabolic status considerably flaws available findings, and the lack of solid data on the background physiopathology contributes to the questionability of results. Furthermore, evidence from interventional studies is very limited and the trials carried out report no beneficial results following alkali supplementation. Available literature suggests that poor acid load control may contribute to impaired insulin sensitivity and glucose homeostasis, but it is not sufficiently supportive to fully elucidate the issue and additional well-designed studies are clearly needed.
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Affiliation(s)
- Lucio Della Guardia
- Laboratory of Dietetics and Clinical Nutrition Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy.
| | - Michael Alex Thomas
- Department of Biology, Center for Obesity Reversal, Georgia State University, Atlanta, GA 30302, USA.
| | - Hellas Cena
- Laboratory of Dietetics and Clinical Nutrition Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy.
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20
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Abraham MA, Rasti M, Bauer PV, Lam TKT. Leptin enhances hypothalamic lactate dehydrogenase A (LDHA)-dependent glucose sensing to lower glucose production in high-fat-fed rats. J Biol Chem 2018; 293:4159-4166. [PMID: 29374061 DOI: 10.1074/jbc.ra117.000838] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/10/2018] [Indexed: 01/15/2023] Open
Abstract
The responsiveness of glucose sensing per se to regulate whole-body glucose homeostasis is dependent on the ability of a rise in glucose to lower hepatic glucose production and increase peripheral glucose uptake in vivo In both rodents and humans, glucose sensing is lost in diabetes and obesity, but the site(s) of impairment remains elusive. Here, we first report that short-term high-fat feeding disrupts hypothalamic glucose sensing to lower glucose production in rats. Second, leptin administration into the hypothalamus of high-fat-fed rats restored hypothalamic glucose sensing to lower glucose production during a pancreatic (basal insulin)-euglycemic clamp and increased whole-body glucose tolerance during an intravenous glucose tolerance test. Finally, both chemical inhibition of hypothalamic lactate dehydrogenase (LDH) (achieved via hypothalamic LDH inhibitor oxamate infusion) and molecular knockdown of LDHA (achieved via hypothalamic lentiviral LDHA shRNA injection) negated the ability of hypothalamic leptin infusion to enhance glucose sensing to lower glucose production in high fat-fed rats. In summary, our findings illustrate that leptin enhances LDHA-dependent glucose sensing in the hypothalamus to lower glucose production in high-fat-fed rodents in vivo.
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Affiliation(s)
- Mona A Abraham
- From the Toronto General Hospital Research Institute, University Health Network, Toronto M5G 1L7, Canada.,Departments of Physiology and
| | - Mozhgan Rasti
- From the Toronto General Hospital Research Institute, University Health Network, Toronto M5G 1L7, Canada
| | - Paige V Bauer
- From the Toronto General Hospital Research Institute, University Health Network, Toronto M5G 1L7, Canada.,Departments of Physiology and
| | - Tony K T Lam
- From the Toronto General Hospital Research Institute, University Health Network, Toronto M5G 1L7, Canada, .,Departments of Physiology and.,Medicine, University of Toronto, Toronto M5S 1A8, Canada, and.,Banting and Best Diabetes Centre, University of Toronto, Toronto M5G 2C4, Canada
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21
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Hussain Z, Khan JA. Food intake regulation by leptin: Mechanisms mediating gluconeogenesis and energy expenditure. ASIAN PAC J TROP MED 2017; 10:940-944. [PMID: 29111188 DOI: 10.1016/j.apjtm.2017.09.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 08/30/2017] [Accepted: 09/11/2017] [Indexed: 12/22/2022] Open
Abstract
Regulation of blood glucose levels and body fat is critical for survival. Leptin circulates freely in blood and controls body weight and food intake mainly through hypothalamic receptors and regulates glucose metabolism in the liver both directly through leptin receptors and indirectly via the hypothalamic receptors of central nervous system. Leptin affects food intake regulation and eventually glucose metabolism, lipometabolism, endocrine and immune functions, reproductive function, adipose tissue metabolism and energy expenditure. Leptin also exerts peripheral effects directly on glucose metabolism and gluconeogenesis. Most of obese human subjects have elevated plasma levels of leptin associated to the size of their total adipose tissue mass. Hence gluconeogenic function may be an essential factor in the regulation of nutritional intake and weight gain. The aim of this review is therefore to identify and module the possible effects of leptin with special application in gluconeogenesis. In addition, this review includes the study of fat consumption and energy expenditure in the body. Specific modulation of leptin receptors and adipose tissues functioning could have important inference on therapeutic strategies.
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Affiliation(s)
- Zulfia Hussain
- Institute of Pharmacy, Physiology and Pharmacology, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Junaid Ali Khan
- Institute of Pharmacy, Physiology and Pharmacology, University of Agriculture, Faisalabad, 38040, Pakistan.
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22
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Harris RBS. Low-dose leptin infusion in the fourth ventricle of rats enhances the response to third-ventricle leptin injection. Am J Physiol Endocrinol Metab 2017; 313:E134-E147. [PMID: 28442484 PMCID: PMC6109645 DOI: 10.1152/ajpendo.00052.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 03/27/2017] [Accepted: 04/18/2017] [Indexed: 01/11/2023]
Abstract
We previously reported that low-dose leptin infusions into the third or fourth ventricle that do not affect energy balance when given independently cause rapid weight loss when given simultaneously. Therefore, we tested whether hindbrain leptin enhances the response to forebrain leptin or whether forebrain leptin enhances the response to hindbrain leptin. Rats received fourth-ventricle infusions of saline or 0.01, 0.1, 0.3, or 0.6 μg leptin/day for 13 days. On days 9 and 13, 0.1 μg leptin was injected into the third ventricle. The injection inhibited food intake for 36 h in saline-infused rats but for 60 h in those infused with 0.6 μg leptin/day. Leptin injection increased intrascapular brown fat temperature in leptin-infused, but not saline-infused, rats. In a separate experiment, rats received third-ventricle infusions of saline or 0.005, 0.01, 0.05, or 0.1 μg leptin/day and fourth-ventricle injections of 1.0 μg leptin on days 9 and 13 Leptin injection inhibited food intake, respiratory exchange ratio, and 14-h food intake in rats infused with saline or the two lowest doses of leptin. There was no effect with higher-dose leptin infusions because food intake, body fat, and lean mass were already inhibited. These data suggest that activation of leptin receptors in the hindbrain enhances the response to third-ventricle leptin, whereas activation of forebrain leptin receptors does not enhance the response to fourth-ventricle leptin, consistent with our previous finding that weight loss in rats treated with fourth-ventricle leptin is associated with indirect activation of hypothalamic STAT3.
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Affiliation(s)
- Ruth B S Harris
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia
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23
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Shin AC, Filatova N, Lindtner C, Chi T, Degann S, Oberlin D, Buettner C. Insulin Receptor Signaling in POMC, but Not AgRP, Neurons Controls Adipose Tissue Insulin Action. Diabetes 2017; 66:1560-1571. [PMID: 28385803 PMCID: PMC5440019 DOI: 10.2337/db16-1238] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 03/22/2017] [Indexed: 12/31/2022]
Abstract
Insulin is a key regulator of adipose tissue lipolysis, and impaired adipose tissue insulin action results in unrestrained lipolysis and lipotoxicity, which are hallmarks of the metabolic syndrome and diabetes. Insulin regulates adipose tissue metabolism through direct effects on adipocytes and through signaling in the central nervous system by dampening sympathetic outflow to the adipose tissue. Here we examined the role of insulin signaling in agouti-related protein (AgRP) and pro-opiomelanocortin (POMC) neurons in regulating hepatic and adipose tissue insulin action. Mice lacking the insulin receptor in AgRP neurons (AgRP IR KO) exhibited impaired hepatic insulin action because the ability of insulin to suppress hepatic glucose production (hGP) was reduced, but the ability of insulin to suppress lipolysis was unaltered. To the contrary, in POMC IR KO mice, insulin lowered hGP but failed to suppress adipose tissue lipolysis. High-fat diet equally worsened glucose tolerance in AgRP and POMC IR KO mice and their respective controls but increased hepatic triglyceride levels only in POMC IR KO mice, consistent with impaired lipolytic regulation resulting in fatty liver. These data suggest that although insulin signaling in AgRP neurons is important in regulating glucose metabolism, insulin signaling in POMC neurons controls adipose tissue lipolysis and prevents high-fat diet-induced hepatic steatosis.
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Affiliation(s)
- Andrew C Shin
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Nika Filatova
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Claudia Lindtner
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Tiffany Chi
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Seta Degann
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Douglas Oberlin
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Christoph Buettner
- Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY
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24
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D'souza AM, Neumann UH, Glavas MM, Kieffer TJ. The glucoregulatory actions of leptin. Mol Metab 2017; 6:1052-1065. [PMID: 28951828 PMCID: PMC5605734 DOI: 10.1016/j.molmet.2017.04.011] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 04/18/2017] [Accepted: 04/24/2017] [Indexed: 12/28/2022] Open
Abstract
Background The hormone leptin is an important regulator of metabolic homeostasis, able to inhibit food intake and increase energy expenditure. Leptin can also independently lower blood glucose levels, particularly in hyperglycemic models of leptin or insulin deficiency. Despite significant efforts and relevance to diabetes, the mechanisms by which leptin acts to regulate blood glucose levels are not fully understood. Scope of review Here we assess literature relevant to the glucose lowering effects of leptin. Leptin receptors are widely expressed in multiple cell types, and we describe both peripheral and central effects of leptin that may be involved in lowering blood glucose. In addition, we summarize the potential clinical application of leptin in regulating glucose homeostasis. Major conclusions Leptin exerts a plethora of metabolic effects on various tissues including suppressing production of glucagon and corticosterone, increasing glucose uptake, and inhibiting hepatic glucose output. A more in-depth understanding of the mechanisms of the glucose-lowering actions of leptin may reveal new strategies to treat metabolic disorders.
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Affiliation(s)
- Anna M D'souza
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Ursula H Neumann
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Maria M Glavas
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.,Department of Surgery, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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25
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Dorfman MD, Krull JE, Scarlett JM, Guyenet SJ, Sajan MP, Damian V, Nguyen HT, Leitges M, Morton GJ, Farese RV, Schwartz MW, Thaler JP. Deletion of Protein Kinase C λ in POMC Neurons Predisposes to Diet-Induced Obesity. Diabetes 2017; 66:920-934. [PMID: 28073831 PMCID: PMC5360303 DOI: 10.2337/db16-0482] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 01/02/2017] [Indexed: 12/16/2022]
Abstract
Effectors of the phosphoinositide 3-kinase (PI3K) signal transduction pathway contribute to the hypothalamic regulation of energy and glucose homeostasis in divergent ways. Here we show that central nervous system (CNS) action of the PI3K signaling intermediate atypical protein kinase C (aPKC) constrains food intake, weight gain, and glucose intolerance in both rats and mice. Pharmacological inhibition of CNS aPKC activity acutely increases food intake and worsens glucose tolerance in chow-fed rodents and causes excess weight gain during high-fat diet (HFD) feeding. Similarly, selective deletion of the aPKC isoform Pkc-λ in proopiomelanocortin (POMC) neurons disrupts leptin action, reduces melanocortin content in the paraventricular nucleus, and markedly increases susceptibility to obesity, glucose intolerance, and insulin resistance specifically in HFD-fed male mice. These data implicate aPKC as a novel regulator of energy and glucose homeostasis downstream of the leptin-PI3K pathway in POMC neurons.
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Affiliation(s)
- Mauricio D Dorfman
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Jordan E Krull
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Jarrad M Scarlett
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Stephan J Guyenet
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Mini P Sajan
- Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL
- Research & Internal Medicine Services, James A. Haley VA Medical Center, Tampa, FL
| | - Vincent Damian
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Hong T Nguyen
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Michael Leitges
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - Gregory J Morton
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Robert V Farese
- Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL
- Research & Internal Medicine Services, James A. Haley VA Medical Center, Tampa, FL
| | - Michael W Schwartz
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
| | - Joshua P Thaler
- UW Diabetes Institute and Department of Medicine, University of Washington, Seattle, WA
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26
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Cady G, Landeryou T, Garratt M, Kopchick JJ, Qi N, Garcia-Galiano D, Elias CF, Myers MG, Miller RA, Sandoval DA, Sadagurski M. Hypothalamic growth hormone receptor (GHR) controls hepatic glucose production in nutrient-sensing leptin receptor (LepRb) expressing neurons. Mol Metab 2017; 6:393-405. [PMID: 28462074 PMCID: PMC5404104 DOI: 10.1016/j.molmet.2017.03.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 02/28/2017] [Accepted: 03/04/2017] [Indexed: 12/22/2022] Open
Abstract
Objective The GH/IGF-1 axis has important roles in growth and metabolism. GH and GH receptor (GHR) are active in the central nervous system (CNS) and are crucial in regulating several aspects of metabolism. In the hypothalamus, there is a high abundance of GH-responsive cells, but the role of GH signaling in hypothalamic neurons is unknown. Previous work has demonstrated that the Ghr gene is highly expressed in LepRb neurons. Given that leptin is a key regulator of energy balance by acting on leptin receptor (LepRb)-expressing neurons, we tested the hypothesis that LepRb neurons represent an important site for GHR signaling to control body homeostasis. Methods To determine the importance of GHR signaling in LepRb neurons, we utilized Cre/loxP technology to ablate GHR expression in LepRb neurons (LeprEYFPΔGHR). The mice were generated by crossing the Leprcre on the cre-inducible ROSA26-EYFP mice to GHRL/L mice. Parameters of body composition and glucose homeostasis were evaluated. Results Our results demonstrate that the sites with GHR and LepRb co-expression include ARH, DMH, and LHA neurons. Leptin action was not altered in LeprEYFPΔGHR mice; however, GH-induced pStat5-IR in LepRb neurons was significantly reduced in these mice. Serum IGF-1 and GH levels were unaltered, and we found no evidence that GHR signaling regulates food intake and body weight in LepRb neurons. In contrast, diminished GHR signaling in LepRb neurons impaired hepatic insulin sensitivity and peripheral lipid metabolism. This was paralleled with a failure to suppress expression of the gluconeogenic genes and impaired hepatic insulin signaling in LeprEYFPΔGHR mice. Conclusion These findings suggest the existence of GHR-leptin neurocircuitry that plays an important role in the GHR-mediated regulation of glucose metabolism irrespective of feeding. GHR and LepRb are co-localized in the ARH, DMH and LHA neurons. GHR signaling does not regulate food intake and body weight in LepRb neurons. Diminished GHR signaling in LepRb neurons impairs hepatic glucose production.
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Key Words
- ARH, arcuate nucleus of the hypothalamus
- CNS, central nervous system
- DMH, dorsomedial hypothalamic nucleus
- GH, growth hormone
- GHR, growth hormone receptor
- Glucose production
- Growth hormone receptor
- Hypothalamus
- LHA, lateral hypothalamus
- Lepr, leptin receptor
- Leptin receptor
- Liver
- POMC, proopiomelanocortin
- PVH, paraventricular hypothalamic nucleus
- Stat3, signal transducer and activator of transcription 3
- Stat5, signal transducer and activator of transcription 5
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Affiliation(s)
- Gillian Cady
- Department of Pathology and Geriatrics Center, University of Michigan Medical School, USA
| | - Taylor Landeryou
- Department of Pathology and Geriatrics Center, University of Michigan Medical School, USA
| | - Michael Garratt
- Department of Pathology and Geriatrics Center, University of Michigan Medical School, USA
| | - John J Kopchick
- Edison Biotechnology Institute, Ohio University, Athens, OH, USA
| | - Nathan Qi
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - David Garcia-Galiano
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Carol F Elias
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Martin G Myers
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Richard A Miller
- Department of Pathology and Geriatrics Center, University of Michigan Medical School, USA
| | - Darleen A Sandoval
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Marianna Sadagurski
- Division of Geriatric and Palliative Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA.
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Hill JW, Faulkner LD. The Role of the Melanocortin System in Metabolic Disease: New Developments and Advances. Neuroendocrinology 2017; 104:330-346. [PMID: 27728914 PMCID: PMC5724371 DOI: 10.1159/000450649] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 05/01/2016] [Indexed: 12/17/2022]
Abstract
Obesity is increasing in prevalence across all sectors of society, and with it a constellation of associated ailments including hypertension, type 2 diabetes, and eating disorders. The melanocortin system is a critical neural system underlying the control of body weight and other functions. Deficits in the melanocortin system may promote or exacerbate the comorbidities of obesity. This system has therefore generated great interest as a potential target for treatment of obesity. However, drugs targeting melanocortin receptors are plagued by problematic side effects, including undesirable increases in sympathetic nervous system activity, heart rate, and blood pressure. Circumnavigating this roadblock will require a clearer picture of the precise neural circuits that mediate the functions of melanocortins. Recent, novel experimental approaches have significantly advanced our understanding of these pathways. We here review the latest advances in our understanding of the role of melanocortins in food intake, reward pathways, blood pressure, glucose control, and energy expenditure. The evidence suggests that downstream melanocortin-responsive circuits responsible for different physiological actions do diverge. Ultimately, a more complete understanding of melanocortin pathways and their myriad roles should allow treatments tailored to the mix of metabolic disorders in the individual patient.
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Affiliation(s)
- Jennifer W Hill
- Department of Physiology and Pharmacology, College of Medicine, The University of Toledo, Toledo, OH, USA
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Bruce KD, Zsombok A, Eckel RH. Lipid Processing in the Brain: A Key Regulator of Systemic Metabolism. Front Endocrinol (Lausanne) 2017; 8:60. [PMID: 28421037 PMCID: PMC5378716 DOI: 10.3389/fendo.2017.00060] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 03/17/2017] [Indexed: 12/25/2022] Open
Abstract
Metabolic disorders, particularly aberrations in lipid homeostasis, such as obesity, type 2 diabetes mellitus, and hypertriglyceridemia often manifest together as the metabolic syndrome (MetS). Despite major advances in our understanding of the pathogenesis of these disorders, the prevalence of the MetS continues to rise. It is becoming increasingly apparent that intermediary metabolism within the central nervous system is a major contributor to the regulation of systemic metabolism. In particular, lipid metabolism within the brain is tightly regulated to maintain neuronal structure and function and may signal nutrient status to modulate metabolism in key peripheral tissues such as the liver. There is now a growing body of evidence to suggest that fatty acid (FA) sensing in hypothalamic neurons via accumulation of FAs or FA metabolites may signal nutritional sufficiency and may decrease hepatic glucose production, lipogenesis, and VLDL-TG secretion. In addition, recent studies have highlighted the existence of liver-related neurons that have the potential to direct such signals through parasympathetic and sympathetic nervous system activity. However, to date whether these liver-related neurons are FA sensitive remain to be determined. The findings discussed in this review underscore the importance of the autonomic nervous system in the regulation of systemic metabolism and highlight the need for further research to determine the key features of FA neurons, which may serve as novel therapeutic targets for the treatment of metabolic disorders.
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Affiliation(s)
- Kimberley D. Bruce
- University of Colorado School of Medicine, Division of Endocrinology, Metabolism and Diabetes, Aurora, CO, USA
- *Correspondence: Kimberley D. Bruce,
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, USA
| | - Robert H. Eckel
- University of Colorado School of Medicine, Division of Endocrinology, Metabolism and Diabetes, Aurora, CO, USA
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Rehman K, Akash MSH. Mechanisms of inflammatory responses and development of insulin resistance: how are they interlinked? J Biomed Sci 2016; 23:87. [PMID: 27912756 PMCID: PMC5135788 DOI: 10.1186/s12929-016-0303-y] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 11/24/2016] [Indexed: 02/06/2023] Open
Abstract
Background Insulin resistance (IR) is one of the major hallmark for pathogenesis and etiology of type 2 diabetes mellitus (T2DM). IR is directly interlinked with various inflammatory responses which play crucial role in the development of IR. Inflammatory responses play a crucial role in the pathogenesis and development of IR which is one of the main causative factor for the etiology of T2DM. Methods A comprehensive online English literature was searched using various electronic search databases. Different search terms for pathogenesis of IR, role of various inflammatory responses were used and an advanced search was conducted by combining all the search fields in abstracts, keywords, and titles. Results We summarized the data from the searched articles and found that inflammatory responses activate the production of various pro-inflammatory mediators notably cytokines, chemokines and adipocytokines through the involvement of various transcriptional mediated molecular pathways, oxidative and metabolic stress. Overnutrition is one of the major causative factor that contributes to induce the state of low-grade inflammation due to which accumulation of elevated levels of glucose and/or lipids in blood stream occur that leads to the activation of various transcriptional mediated molecular and metabolic pathways. This results in the induction of various pro-inflammatory mediators that are decisively involved to provoke the pathogenesis of tissue-specific IR by interfering with insulin signaling pathways. Once IR is developed, it increases oxidative stress in β-cells of pancreatic islets and peripheral tissues which impairs insulin secretion, and insulin sensitivity in β-cells of pancreatic islets and peripheral tissues, respectively. Moreover, we also summarized the data regarding various treatment strategies of inflammatory responses-induced IR. Conclusions In this article, we have briefly described that how pro-inflammatory mediators, oxidative stress, transcriptional mediated molecular and metabolic pathways are involved in the pathogenesis of tissues-specific IR. Moreover, based on recent investigations, we have also described that to counterfeit these inflammatory responses is one of the best treatment strategy to prevent the pathogenesis of IR through ameliorating the incidences of inflammatory responses.
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Affiliation(s)
- Kanwal Rehman
- Institute of Pharmacy, Physiology and Pharmacology, University of Agriculture, Faisalabad, Pakistan
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30
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Emerging role of the brain in the homeostatic regulation of energy and glucose metabolism. Exp Mol Med 2016; 48:e216. [PMID: 26964832 PMCID: PMC4892882 DOI: 10.1038/emm.2016.4] [Citation(s) in RCA: 213] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/07/2015] [Accepted: 12/09/2015] [Indexed: 12/12/2022] Open
Abstract
Accumulated evidence from genetic animal models suggests that the brain, particularly the hypothalamus, has a key role in the homeostatic regulation of energy and glucose metabolism. The brain integrates multiple metabolic inputs from the periphery through nutrients, gut-derived satiety signals and adiposity-related hormones. The brain modulates various aspects of metabolism, such as food intake, energy expenditure, insulin secretion, hepatic glucose production and glucose/fatty acid metabolism in adipose tissue and skeletal muscle. Highly coordinated interactions between the brain and peripheral metabolic organs are critical for the maintenance of energy and glucose homeostasis. Defective crosstalk between the brain and peripheral organs contributes to the development of obesity and type 2 diabetes. Here we comprehensively review the above topics, discussing the main findings related to the role of the brain in the homeostatic regulation of energy and glucose metabolism.
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Improvement in glycemia after glucose or insulin overload in leptin-infused rats is associated with insulin-related activation of hepatic glucose metabolism. Nutr Metab (Lond) 2016; 13:19. [PMID: 26937247 PMCID: PMC4774133 DOI: 10.1186/s12986-016-0079-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 02/25/2016] [Indexed: 11/16/2022] Open
Abstract
Background Insulin regulates glucose homeostasis through direct effects on the liver, among other organs, with leptin modulating insulin’s hepatic actions. Since central leptin may modify insulin signaling in the liver, we hypothesized that leptin infusion activates hepatic glycogen synthesis following peripheral administration of a bolus of glucose or insulin, thus regulating glycemia. Findings Oral glucose and intraperitoneal insulin tolerance tests were performed in control, intracerebroventricular leptin-treated and pair-fed rats during 14 days. An improvement in glycemia and an increase in hepatic free glucose and glycogen concentrations after glucose or insulin overload were observed in leptin-treated rats. In order to analyze whether the liver was involved in these changes, we studied activation of insulin signaling by Western blotting and multiplex bead immunoassay after leptin infusion. Our studies revealed an increase in phosphorylation of insulin receptor substrate-1 and Akt in leptin-treated rats. Examination of parameters related to glucose uptake and metabolism in the liver revealed an augment in glucose transporter 2 and a decrease in phosphoenolpyruvate carboxylase protein levels in this group. Conclusions These results indicate that central leptin increases hepatic insulin signaling, associated with increased glycogen concentrations after glucose or insulin overload, leading to an improvement in glycemia.
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Central administration of vaspin inhibits glucose production and augments hepatic insulin signaling in high-fat-diet-fed rat. Int J Obes (Lond) 2016; 40:947-54. [PMID: 26975443 DOI: 10.1038/ijo.2016.24] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 11/27/2015] [Accepted: 12/22/2015] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To investigate the effects of vaspin signaling conveyed by the brain on liver glucose fluxes in rats. METHODS To determine the effects and underlying mechanisms of central vaspin signaling, normal-chow-diet- and high-fat-diet (HFD)-fed rats with or without hepatic branch vagotomy (HBV) received acute infusion of vaspin to the third cerebral ventricle or MK801, a dorsal vagal complex (DVC) N-methyl-D-aspartate (NMDA) receptor inhibitor, to the DVC during the pancreatic euglycemic clamp. RESULTS Central administration of vaspin in HFD-fed rats significantly increased glucose infusion required to maintain euglycemia owing to an inhibition of glucose production during the clamps. These changes were accompanied by decreased hepatic phosphoenolpyruatecarboxykinase and G6Pase expression levels and increased hepatic insulin receptor, insulin receptor substrate-1, Akt kinase and the forkhead box-containing protein of the O subfamily-1 phosphorylation, suggesting improving hepatic insulin sensitivity in these animals. Conversely, selective HBV or DVC MK-801 infusion in HFD-fed rats blocked the effect of central vaspin on glucose production and hepatic insulin sensitivity. CONCLUSIONS Our findings suggest that brain vaspin inhibited hepatic glucose production and improved insulin sensitivity via DVC to the hepatic branch of the vagus nerve in insulin resistance rats induced by HFD.
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O'Hare JD, Zsombok A. Brain-liver connections: role of the preautonomic PVN neurons. Am J Physiol Endocrinol Metab 2016; 310:E183-9. [PMID: 26646097 PMCID: PMC4838125 DOI: 10.1152/ajpendo.00302.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 12/01/2015] [Indexed: 12/28/2022]
Abstract
Diabetes mellitus and the coexisting conditions and complications, including hypo- and hyperglycemic events, obesity, high cholesterol levels, and many more, are devastating problems. Undoubtedly, there is a huge demand for treatment and prevention of these conditions that justifies the search for new approaches and concepts for better management of whole body metabolism. Emerging evidence demonstrates that the autonomic nervous system is largely involved in the regulation of glucose homeostasis; however, the underlying mechanisms are still under investigation. Within the hypothalamus, the paraventricular nucleus (PVN) is in a unique position to integrate neural and hormonal signals to command both the autonomic and neuroendocrine outflow. This minireview will provide a brief overview on the role of preautonomic PVN neurons and the importance of the PVN-liver pathway in the regulation of glucose homeostasis.
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Affiliation(s)
- James D O'Hare
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
| | - Andrea Zsombok
- Department of Physiology, School of Medicine, Tulane University, New Orleans, Louisiana
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34
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Burgos-Ramos E, Canelles S, Rodríguez A, Gómez-Ambrosi J, Frago LM, Chowen JA, Frühbeck G, Argente J, Barrios V. Chronic central leptin infusion modulates the glycemia response to insulin administration in male rats through regulation of hepatic glucose metabolism. Mol Cell Endocrinol 2015; 415:157-72. [PMID: 26296906 DOI: 10.1016/j.mce.2015.08.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 08/06/2015] [Accepted: 08/09/2015] [Indexed: 10/23/2022]
Abstract
Leptin and insulin use overlapping signaling mechanisms to modify hepatic glucose metabolism, which is critical in maintaining normal glycemia. We examined the effect of an increase in central leptin and insulin on hepatic glucose metabolism and its influence on serum glucose levels. Chronic leptin infusion increased serum leptin and reduced hepatic SH-phosphotyrosine phosphatase 1, the association of suppressor of cytokine signaling 3 to the insulin receptor in liver and the rise in glycemia induced by central insulin. Leptin also decreased hepatic phosphoenolpyruvate carboxykinase levels and increased insulin's ability to phosphorylate insulin receptor substrate-1, Akt and glycogen synthase kinase on Ser9 and to stimulate glucose transporter 2 and glycogen levels. Peripheral leptin treatment reproduced some of these changes, but to a lesser extent. Our data indicate that leptin increases the hepatic response to a rise in insulin, suggesting that pharmacological manipulation of leptin targets may be of interest for controlling glycemia.
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Affiliation(s)
- Emma Burgos-Ramos
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; IMDEA Food, CEI UAM+CSIC, Carretera de Cantoblanco 8, Madrid, E-28049, Spain
| | - Sandra Canelles
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain
| | - Amaia Rodríguez
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain; Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Pamplona, E-31008, Spain
| | - Javier Gómez-Ambrosi
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain; Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Pamplona, E-31008, Spain
| | - Laura M Frago
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain
| | - Julie A Chowen
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain
| | - Gema Frühbeck
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain; Metabolic Research Laboratory, Clínica Universidad de Navarra, IdiSNA, Pamplona, E-31008, Spain
| | - Jesús Argente
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain
| | - Vicente Barrios
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, E-28009, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Madrid, E-28009, Spain.
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Leptin Is Required for Glucose Homeostasis after Roux-en-Y Gastric Bypass in Mice. PLoS One 2015; 10:e0139960. [PMID: 26445459 PMCID: PMC4596552 DOI: 10.1371/journal.pone.0139960] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/18/2015] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND & AIMS Leptin, the protein product of the ob gene, increases energy expenditure and reduces food intake, thereby promoting weight reduction. Leptin also regulates glucose homeostasis and hepatic insulin sensitivity via hypothalamic proopiomelanocortin neurons in mice. Roux-en-Y gastric bypass (RYGB) induces weight loss that is substantial and sustained despite reducing plasma leptin levels. In addition, patients who fail to undergo diabetes remission after RYGB are hypoletinemic compared to those who do and to lean controls. We have previously demonstrated that the beneficial effects of RYGB in mice require the melanocortin-4 receptor, a downstream effector of leptin action. Based on these observations, we hypothesized that leptin is required for sustained weight reduction and improved glucose homeostasis observed after RYGB. METHODS To investigate this hypothesis, we performed RYGB or sham operations on leptin-deficient ob/ob mice maintained on regular chow. To investigate whether leptin is involved in post-RYGB weight maintenance, we challenged post-surgical mice with high fat diet. RESULTS RYGB reduced total body weight, fat and lean mass and caused reduction in calorie intake in ob/ob mice. However, it failed to improve glucose tolerance, glucose-stimulated plasma insulin, insulin tolerance, and fasting plasma insulin. High fat diet eliminated the reduction in calorie intake observed after RYGB in ob/ob mice and promoted weight regain, although not to the same extent as in sham-operated mice. We conclude that leptin is required for the effects of RYGB on glucose homeostasis but not body weight or composition in mice. Our data also suggest that leptin may play a role in post-RYGB weight maintenance.
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Lu RH, Zhou Y, Yuan XC, Liang XF, Fang L, Bai XL, Wang M, Zhao YH. Effects of glucose, insulin and triiodothyroxine on leptin and leptin receptor expression and the effects of leptin on activities of enzymes related to glucose metabolism in grass carp (Ctenopharyngodon idella) hepatocytes. FISH PHYSIOLOGY AND BIOCHEMISTRY 2015; 41:981-989. [PMID: 25952973 DOI: 10.1007/s10695-015-0063-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 04/25/2015] [Indexed: 06/04/2023]
Abstract
Leptin is an important regulator of appetite and energy expenditure in mammals, but its role in fish metabolism control is poorly understood. Our previous studies demonstrated that leptin has an effect on the regulation of food intake and energy expenditure as well as lipid metabolism (stimulation of lipolysis and inhibition of adipogenesis) in the grass carp Ctenopharyngodon idella. To further investigate the role of leptin in fish, the effects of glucose, insulin and triiodothyroxine (T3) on the expression levels of leptin and leptin receptor (Lepr) and the effects of leptin on the activities of critical glucose metabolism enzymes in grass carp hepatocytes were evaluated in the present study. Our data indicated that leptin gene expression was induced by glucose in a dose-dependent manner, while Lepr gene expression exhibited a biphasic change. A high dose of insulin (100 ng/mL) significantly up-regulated the expression of leptin and Lepr. Leptin expression was markedly up-regulated by a low concentration of T3 but inhibited by a high concentration of T3. T3 up-regulated Lepr expression in a dose-dependent manner. Together, these data suggest that leptin had a close relationship with three factors (glucose, insulin and T3) and might participate in the regulation of glucose metabolism in grass carp. In addition, we also found that leptin affected the activities of key enzymes that are involved in glucose metabolism, which might be mediated by insulin receptor substrate-phosphoinositol 3-kinase signaling.
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Affiliation(s)
- Rong-Hua Lu
- College of Fisheries, Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Huazhong Agricultural University, Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, No. 1 Shizishan Street, Hongshan District, Wuhan, 430070, Hubei Province, China
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37
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Coppari R. Hypothalamic neurones governing glucose homeostasis. J Neuroendocrinol 2015; 27:399-405. [PMID: 25778859 DOI: 10.1111/jne.12276] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 12/24/2022]
Abstract
The notion that the brain directly controls the level of glucose in the blood (glycaemia) independent of its known action on food intake and body weight has been known ever since 1849. That year, the French physiologist Dr Claude Bernard reported that physical puncture of the floor of the fourth cerebral ventricle rapidly leads to an increased level of sugar in the blood (and urine) in rabbits. Despite this important discovery, it took approximately 150 years before significant efforts aimed at understanding the underlying mechanism of brain-mediated control of glucose metabolism were made. Technological developments allowing for genetically-mediated manipulation of selected molecular pathways in a neurone-type-specific fashion unravelled the importance of specific molecules in specific neuronal populations. These neuronal pathways govern glucose metabolism in the presence and even in the absence of insulin. Also, a peculiarity of these pathways is that certain biochemically-defined neurones govern glucose metabolism in a tissue-specific fashion.
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Affiliation(s)
- R Coppari
- Department of Cellular Physiology and Metabolism, University of Geneva, Geneva, Switzerland
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Moon HS, Huh JY, Dincer F, Schneider BE, Hasselgren PO, Mantzoros CS. Identification and saturable nature of signaling pathways induced by metreleptin in humans: comparative evaluation of in vivo, ex vivo, and in vitro administration. Diabetes 2015; 64:828-39. [PMID: 25249580 PMCID: PMC4338590 DOI: 10.2337/db14-0625] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Signaling pathways activated by leptin in metabolically important organs have largely been studied only in animal and/or cell culture studies. In this study, we examined whether leptin has similar effects in human peripheral tissues in vivo, ex vivo, and in vitro and whether the response would be different in lean and obese humans. For in vivo leptin signaling, metreleptin was administered and muscle, adipose tissue, and peripheral blood mononuclear cells were taken for analysis of signal activation. Experiments were also done ex vivo and with primary cultured cells in vitro. The signal activation was compared between male versus female and obese versus lean humans. Acute in vivo, ex vivo, and/or in vitro metreleptin administration similarly activated STAT3, AMPK, ERK1/2, Akt, mTOR, NF-κB, and/or IKKα/β without any differences between male versus female and obese versus lean subjects. All signaling pathways were saturable at ∼30-50 ng/mL, consistent with the clinical evidence showing no additional effect(s) in obese subjects who already have high levels of leptin. Our data provide novel information on downstream effectors of metreleptin action in humans that may have therapeutic implications.
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Affiliation(s)
- Hyun-Seuk Moon
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Joo Young Huh
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Fadime Dincer
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Benjamin E Schneider
- Division of Minimally Invasive Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Per-Olof Hasselgren
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Christos S Mantzoros
- Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA Section of Endocrinology, Boston VA Healthcare System, Harvard Medical School, Boston, MA
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Abstract
The increase in the number of patients with diabetes has become a worldwide healthcare issue, with numbers predicted to reach approximately 600 million by 2035. In Asia-Pacific region, the prevalence of type 2 diabetes has increased dramatically in recent decades, of which the major causes are believed to be modern lifestyle changes, e.g., Western dietary pattern and reduced physical activity, on their genetic basis of lower insulin secretory capacity. Particularly, in East Asian countries, the amount of fat intake has increased nearly three-fold over this half of century; dietary fat appears to be the major culprit of type 2 diabetes pandemic in East Asia. However, convincing evidence has not yet been provided as to whether high-fat diet causes type 2 diabetes in epidemiological cohort studies. Here, we summarize clinical studies regarding fat intake and type 2 diabetes, and animal studies on high-fat diet-induced diabetes including our recent works on the novel mouse lines (selectively bred diet-induced glucose intolerance-prone [SDG-P] and -resistant [SDG-R]) to address the etiology of high-fat diet-induced diabetes. These epidemiological and experimental findings would provide further insight into the etiology of type 2 diabetes under the modern nutritional environment, namely in the context of increased fat intake.
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Affiliation(s)
- Mototsugu Nagao
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo 113-8603 Japan
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40
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Meek TH, Matsen ME, Damian V, Cubelo A, Chua SC, Morton GJ. Role of melanocortin signaling in neuroendocrine and metabolic actions of leptin in male rats with uncontrolled diabetes. Endocrinology 2014; 155:4157-67. [PMID: 25137027 PMCID: PMC4197991 DOI: 10.1210/en.2014-1169] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although the antidiabetic effects of leptin require intact neuronal melanocortin signaling in rodents with uncontrolled diabetes (uDM), increased melanocortin signaling is not sufficient to mimic leptin's glucose-lowering effects. The current studies were undertaken to clarify the role of melanocortin signaling in leptin's ability to correct metabolic and neuroendocrine disturbances associated with uDM. To accomplish this, bilateral cannulae were implanted in the lateral ventricle of rats with streptozotocin-induced diabetes, and leptin was coinfused with varying doses of the melanocortin 3/4 receptor (MC3/4R) antagonist, SHU9119. An additional cohort of streptozotocin-induced diabetes rats received intracerebroventricular administration of either the MC3/4R agonist, melanotan-II, or its vehicle. Consistent with previous findings, leptin's glucose-lowering effects were blocked by intracerebroventricular SHU9119. In contrast, leptin-mediated suppression of hyperglucagonemia involves both melanocortin dependent and independent mechanisms, and the degree of glucagon inhibition was associated with reduced plasma ketone body levels. Increased central nervous system melanocortin signaling alone fails to mimic leptin's ability to correct any of the metabolic or neuroendocrine disturbances associated with uDM. Moreover, the inability of increased melanocortin signaling to lower diabetic hyperglycemia does not appear to be secondary to release of the endogenous MC3/4R inverse agonist, Agouti-related peptide (AgRP), because AgRP knockout mice did not show increased susceptibility to the antidiabetic effects of increased MC3/4R signaling. Overall, these data suggest that 1) AgRP is not a major driver of diabetic hyperglycemia, 2) mechanisms independent of melanocortin signaling contribute to leptin's antidiabetic effects, and 3) melanocortin receptor blockade dissociates leptin's glucose-lowering effect from its action on other features of uDM, including reversal of hyperglucagonemia and ketosis, suggesting that brain control of ketosis, but not blood glucose levels, is glucagon dependent.
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Affiliation(s)
- Thomas H Meek
- Diabetes and Obesity Center of Excellence (T.H.M., M.E.M.,. V.D., A.C., G.J.M.), Department of Medicine, University of Washington, Seattle, Washington 98109; and Division of Endocrinology (S.C.C.), Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
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Weissmann L, Quaresma PGF, Santos AC, de Matos AHB, Pascoal VDB, Zanotto TM, Castro G, Guadagnini D, da Silva JM, Velloso LA, Bittencourt JC, Lopes-Cendes I, Saad MJA, Prada PO. IKKε is key to induction of insulin resistance in the hypothalamus, and its inhibition reverses obesity. Diabetes 2014; 63:3334-45. [PMID: 24812431 DOI: 10.2337/db13-1817] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
IKK epsilon (IKKε) is induced by the activation of nuclear factor-κB (NF-κB). Whole-body IKKε knockout mice on a high-fat diet (HFD) were protected from insulin resistance and showed altered energy balance. We demonstrate that IKKε is expressed in neurons and is upregulated in the hypothalamus of obese mice, contributing to insulin and leptin resistance. Blocking IKKε in the hypothalamus of obese mice with CAYMAN10576 or small interfering RNA decreased NF-κB activation in this tissue, relieving the inflammatory environment. Inhibition of IKKε activity, but not TBK1, reduced IRS-1(Ser307) phosphorylation and insulin and leptin resistance by an improvement of the IR/IRS-1/Akt and JAK2/STAT3 pathways in the hypothalamus. These improvements were independent of body weight and food intake. Increased insulin and leptin action/signaling in the hypothalamus may contribute to a decrease in adiposity and hypophagia and an enhancement of energy expenditure accompanied by lower NPY and increased POMC mRNA levels. Improvement of hypothalamic insulin action decreases fasting glycemia, glycemia after pyruvate injection, and PEPCK protein expression in the liver of HFD-fed and db/db mice, suggesting a reduction in hepatic glucose production. We suggest that IKKε may be a key inflammatory mediator in the hypothalamus of obese mice, and its hypothalamic inhibition improves energy and glucose metabolism.
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Affiliation(s)
- Laís Weissmann
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Paula G F Quaresma
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Andressa C Santos
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Alexandre H B de Matos
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | | | - Tamires M Zanotto
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Gisele Castro
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Dioze Guadagnini
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | | | - Licio A Velloso
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Jackson C Bittencourt
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Iscia Lopes-Cendes
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Mario J A Saad
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Patricia O Prada
- Department of Internal Medicine, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil School of Applied Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
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Abstract
The fat‐derived hormone, leptin, is well known to regulate body weight. However, there is now substantial evidence that leptin also plays a primary role in the regulation of glucose homeostasis, independent of actions on food intake, energy expenditure or body weight. As such, leptin might have clinical utility in treating hyperglycemia, particularly in conditions of leptin deficiency, such as lipodystrophy and diabetes mellitus. The mechanisms through which leptin modulates glucose metabolism have not been fully elucidated. Leptin receptors are widely expressed in peripheral tissues, including the endocrine pancreas, liver, skeletal muscle and adipose, and both direct and indirect leptin action on these tissues contributes to the control of glucose homeostasis. Here we review the role of leptin in glucose homeostasis, along with our present understanding of the mechanisms involved. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2012.00203.x, 2012)
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Affiliation(s)
- Heather C Denroche
- Department of Cellular and Physiological Sciences, The Life Sciences Institute
| | - Frank K Huynh
- Department of Cellular and Physiological Sciences, The Life Sciences Institute
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, The Life Sciences Institute ; Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
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Schiavon FPM, Marques ADCR, Carrara MA, de Souza HM, Schamber CR, Curi R, Bazotte RB. Pivotal role of cAMP in the activation of liver glycogen breakdown in high-fat diet fed mice. Life Sci 2014; 109:111-5. [PMID: 24968301 DOI: 10.1016/j.lfs.2014.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 06/06/2014] [Accepted: 06/09/2014] [Indexed: 01/14/2023]
Abstract
AIMS Liver glycogen catabolism was evaluated in male Swiss mice fed a high-fat diet rich in saturated fatty acids (HFD) or normal fat diet (NFD) during one week. MAIN METHODS Liver glycogenolysis (LG) and liver glucose production (LGP) were measured either under basal or stimulated conditions (infusion of glycogenolytic agents). Thus, isolated perfused livers from HFD and NFD mice were infused with glycogenolytic agents, i.e., glucagon, epinephrine, phenylephrine, isoproterenol, adenosine-3'-5'-cyclic monophosphate (cAMP), N(6),2'-O-dibutyryl-cAMP (DB-cAMP), 8-bromoadenosine-cAMP (8-Br-cAMP) or N(6)-monobutyryl-cAMP (N6-MB-cAMP). Moreover, glycemia and liver glycogen content were measured. KEY FINDINGS Glycemia, liver glycogen content and basal rate of LGP and LG were not influenced by the HFD. However, LGP and LG were lower (p<0.05) in HFD mice during the infusions of glucagon (1 nM), epinephrine (20 μM) or phenylephrine (20 μM). In contrast, the activation of LGP and LG during the infusion of isoproterenol (20 μM) was not different (HFD vs. NFD). Because glucagon showed the most prominent response, the effect of cAMP, its intracellular mediator, on LGP and LG was investigated. cAMP (150 μM) showed lower activation of LGP and LG in the HFD group. However, the activation of LGP and LG was not influenced by HFD whether DB-cAMP (3 μM), 8-Br-cAMP (3 μM) or N6-MB-cAMP (3 μM) were used. SIGNIFICANCE The activation of LGP and LG depends on the intracellular availability of cAMP. It can be concluded that cAMP played a pivotal role on the activation of LG in high-fat diet fed mice.
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Affiliation(s)
- Fabiana P M Schiavon
- Department of Pharmacology and Therapeutic, State University of Maringá, Maringá, PR 87020-900, Brazil
| | | | | | - Helenir Medri de Souza
- Department of Physiological Sciences, State University of Londrina, Londrina, PR 86051-990, Brazil
| | | | - Rui Curi
- Department of Physiology and Biophysics, University of São Paulo, São Paulo, SP 05508-900, Brazil
| | - Roberto B Bazotte
- Department of Pharmacology and Therapeutic, State University of Maringá, Maringá, PR 87020-900, Brazil.
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Drougard A, Duparc T, Brenachot X, Carneiro L, Gouazé A, Fournel A, Geurts L, Cadoudal T, Prats AC, Pénicaud L, Vieau D, Lesage J, Leloup C, Benani A, Cani PD, Valet P, Knauf C. Hypothalamic apelin/reactive oxygen species signaling controls hepatic glucose metabolism in the onset of diabetes. Antioxid Redox Signal 2014; 20:557-73. [PMID: 23879244 PMCID: PMC3901354 DOI: 10.1089/ars.2013.5182] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
AIMS We have previously demonstrated that central apelin is implicated in the control of peripheral glycemia, and its action depends on nutritional (fast versus fed) and physiological (normal versus diabetic) states. An intracerebroventricular (icv) injection of a high dose of apelin, similar to that observed in obese/diabetic mice, increase fasted glycemia, suggesting (i) that apelin contributes to the establishment of a diabetic state, and (ii) the existence of a hypothalamic to liver axis. Using pharmacological, genetic, and nutritional approaches, we aim at unraveling this system of regulation by identifying the hypothalamic molecular actors that trigger the apelin effect on liver glucose metabolism and glycemia. RESULTS We show that icv apelin injection stimulates liver glycogenolysis and gluconeogenesis via an over-activation of the sympathetic nervous system (SNS), leading to fasted hyperglycemia. The effect of central apelin on liver function is dependent of an increased production of hypothalamic reactive oxygen species (ROS). These data are strengthened by experiments using lentiviral vector-mediated over-expression of apelin in hypothalamus of mice that present over-activation of SNS associated to an increase in hepatic glucose production. Finally, we report that mice fed a high-fat diet present major alterations of hypothalamic apelin/ROS signaling, leading to activation of glycogenolysis. INNOVATION/CONCLUSION: These data bring compelling evidence that hypothalamic apelin is one master switch that participates in the onset of diabetes by directly acting on liver function. Our data support the idea that hypothalamic apelin is a new potential therapeutic target to treat diabetes.
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Affiliation(s)
- Anne Drougard
- 1 Institut National de la Santé et de la Recherche Médicale (INSERM) , Toulouse, France
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Santos GA, Moura RF, Vitorino DC, Roman EAFR, Torsoni AS, Velloso LA, Torsoni MA. Hypothalamic AMPK activation blocks lipopolysaccharide inhibition of glucose production in mice liver. Mol Cell Endocrinol 2013; 381:88-96. [PMID: 23916575 DOI: 10.1016/j.mce.2013.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 06/28/2013] [Accepted: 07/19/2013] [Indexed: 01/17/2023]
Abstract
Endotoxic hypoglycaemia has an important role in the survival rates of septic patients. Previous studies have demonstrated that hypothalamic AMP-activated protein kinase (hyp-AMPK) activity is sufficient to modulate glucose homeostasis. However, the role of hyp-AMPK in hypoglycaemia associated with endotoxemia is unknown. The aims of this study were to examine hyp-AMPK dephosphorylation in lipopolysaccharide (LPS)-treated mice and to determine whether pharmacological hyp-AMPK activation could reduce the effects of endotoxemia on blood glucose levels. LPS-treated mice showed reduced food intake, diminished basal glycemia, increased serum TNF-α and IL-1β levels and increased hypothalamic p-TAK and TLR4/MyD88 association. These effects were accompanied by hyp-AMPK/ACC dephosphorylation. LPS-treated mice also showed diminished liver expression of PEPCK/G6Pase, reduction in p-FOXO1, p-AMPK, p-STAT3 and p-JNK level and glucose production. Pharmacological hyp-AMPK activation blocked the effects of LPS on the hyp-AMPK phosphorylation, liver PEPCK expression and glucose production. Furthermore, the effects of LPS were TLR4-dependent because hyp-AMPK phosphorylation, liver PEPCK expression and fasting glycemia were not affected in TLR4-mutant mice. These results suggest that hyp-AMPK activity may be an important pharmacological target to control glucose homeostasis during endotoxemia.
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Affiliation(s)
- G A Santos
- Departamento de Medicina Interna, Faculdade de Ciências Médicas, Universidade Estadual de Campinas-UNICAMP, Campinas, São Paulo, Brazil
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Carey M, Kehlenbrink S, Hawkins M. Evidence for central regulation of glucose metabolism. J Biol Chem 2013; 288:34981-8. [PMID: 24142701 DOI: 10.1074/jbc.r113.506782] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Evidence for central regulation of glucose homeostasis is accumulating from both animal and human studies. Central nutrient and hormone sensing in the hypothalamus appears to coordinate regulation of whole body metabolism. Central signals activate ATP-sensitive potassium (KATP) channels, thereby down-regulating glucose production, likely through vagal efferent signals. Recent human studies are consistent with this hypothesis. The contributions of direct and central inputs to metabolic regulation are likely of comparable magnitude, with somewhat delayed central effects and more rapid peripheral effects. Understanding central regulation of glucose metabolism could promote the development of novel therapeutic approaches for such metabolic conditions as diabetes mellitus.
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Affiliation(s)
- Michelle Carey
- From the Department of Medicine and Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
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47
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Zsombok A. Vanilloid receptors--do they have a role in whole body metabolism? Evidence from TRPV1. J Diabetes Complications 2013; 27:287-92. [PMID: 23332888 PMCID: PMC3633635 DOI: 10.1016/j.jdiacomp.2012.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 12/16/2022]
Abstract
With increasing lifespan, therapeutic interventions for the treatment of disorders such as type 2 diabetes mellitus are in great demand. Despite billions of dollars invested to reduce the symptoms and complications due to diabetes mellitus, current treatments (e.g., insulin replacements, sensitization) remain inadequate, justifying the search for novel therapeutic approaches or alternative solutions, including dietary supplementation, for the treatment of diabetes mellitus in every age group. The involvement of the vanilloid system in the regulation of metabolism has been identified, and the emerging role of its receptors, the transient receptor potential vanilloid type 1 (TRPV1), in diabetes was recently demonstrated. Indeed, beneficial effects of dietary capsaicin, an agonist of TRPV1 receptors, were identified for improving glucose, insulin and glucagon-like peptide-1 levels. Recent findings regarding TRPV1 receptors in association with whole body metabolism including glucose homeostasis will be reviewed in this article.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, Endocrinology Section, Tulane University, School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112, USA.
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48
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Zsombok A. Autonomic control and bariatric procedures. Auton Neurosci 2013; 177:81-6. [PMID: 23538033 DOI: 10.1016/j.autneu.2013.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 10/10/2012] [Accepted: 03/01/2013] [Indexed: 12/12/2022]
Abstract
The sudden improvement of metabolic profile and the remission of type 2 diabetes after bariatric surgery, well before weight loss, raise important new questions regarding glycemic control. Currently, various types of bariatric procedures target type 2 diabetes in obese and non-obese patients. Nevertheless, the origin of the dramatic metabolic improvements, including glucose homeostasis, is poorly understood, and the role of the gastrointestinal (GI) tract remains relatively speculative, as well as why these procedures are variably effective. One neglected explanation is that such interventions disrupt neural networks mediating GI-brain communication and could alter the autonomic output to the visceral organs, including the liver. Incretins, e.g., glucagon-like peptide 1 (GLP-1), have major influence on the central nervous system. Moreover, the level of GLP-1 is observed to significantly increase after bariatric surgery and could be a key factor in the weight-independent, anti-diabetic effect. Therefore, this review will evaluate the effect of GLP-1 on the central nervous system, with emphasis on the cellular effects of GLP-1, and will provide an overview of the autonomic control of the liver.
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Affiliation(s)
- Andrea Zsombok
- Department of Physiology, Endocrinology Section, Tulane University, School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112, United States; Department of Medicine, Endocrinology Section, Tulane University, School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112, United States.
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Scherer T, Lehnert H, Hallschmid M. Brain insulin and leptin signaling in metabolic control: from animal research to clinical application. Endocrinol Metab Clin North Am 2013; 42:109-25. [PMID: 23391243 DOI: 10.1016/j.ecl.2012.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Besides the well-characterized effects of brain insulin and leptin in regulating food intake, insulin and leptin signaling to the central nervous system modulates a variety of metabolic processes, such as glucose and lipid homeostasis, as well as energy expenditure. This review summarizes the current literature on the contribution of central nervous insulin and leptin action to metabolic control in animals and humans. Potential therapeutic options based on the direct delivery of these peptides to the brain by, for example, intranasal administration, are discussed.
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Affiliation(s)
- Thomas Scherer
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna 1090, Austria.
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50
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Arble DM, Sandoval DA. CNS control of glucose metabolism: response to environmental challenges. Front Neurosci 2013; 7:20. [PMID: 23550218 PMCID: PMC3581798 DOI: 10.3389/fnins.2013.00020] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 02/04/2013] [Indexed: 01/07/2023] Open
Abstract
Over the last 15 years, considerable work has accumulated to support the role of the CNS in regulating postprandial glucose levels. As discussed in the first section of this review, the CNS receives and integrates information from afferent neurons, circulating hormones, and postprandially generated nutrients to subsequently direct changes in glucose output by the liver and glucose uptake by peripheral tissues. The second major component of this review focuses on the effects of external pressures, including high fat diet and changes to the light:dark cycle on CNS-regulating glucose homeostasis. We also discuss the interaction between these different pressures and how they contribute to the multifaceted mechanisms that we hypothesize contribute to the dysregulation of glucose in type 2 diabetes mellitus (T2DM). We argue that while current peripheral therapies serve to delay the progression of T2DM, generating combined obesity and T2DM therapies targeted at the CNS, the primary site of dysfunction for both diseases, would lead to a more profound impact on the progression of both diseases.
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Affiliation(s)
- Deanna M Arble
- Department of Medicine, University of Cincinnati Cincinnati, OH, USA
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