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Shemery AM, Zendlo M, Kowalski J, Gorrell E, Everett S, Wagner JG, Davis AE, Koch LG, Britton SL, Mul JD, Novak CM. Reduced contextually induced muscle thermogenesis in rats with calorie restriction and lower aerobic fitness but not monogenic obesity. Temperature (Austin) 2023; 10:379-393. [PMID: 37554387 PMCID: PMC10405760 DOI: 10.1080/23328940.2023.2171669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/29/2023] Open
Abstract
We have previously identified predator odor as a potent stimulus activating thermogenesis in skeletal muscle in rats. As this may prove relevant for energy balance and weight loss, the current study investigated whether skeletal muscle thermogenesis was altered with negative energy balance, obesity propensity seen in association with low intrinsic aerobic fitness, and monogenic obesity. First, weight loss subsequent to 3 wk of 50% calorie restriction suppressed the muscle thermogenic response to predator odor. Next, we compared rats bred based on artificial selection for intrinsic aerobic fitness - high- and low-capacity runners (HCR, LCR) - that display robust leanness and obesity propensity, respectively. Aerobically fit HCR showed enhanced predator odor-induced muscle thermogenesis relative to the less-fit LCR. This contrasted with the profound monogenic obesity displayed by rats homozygous for a loss of function mutation in Melanocortin 4 receptor (Mc4rK3a,4X/K314X rats), which showed no discernable deficit in thermogenesis. Taken together, these data imply that body size or obesity per se are not associated with deficient muscle thermogenesis. Rather, the physiological phenotype associated with polygenic obesity propensity may encompass pleiotropic mechanisms in the thermogenic pathway. Adaptive thermogenesis associated with weight loss also likely alters muscle thermogenic mechanisms.
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Affiliation(s)
- Ashley M Shemery
- School of Biomedical Sciences, Kent State University, Kent, OH, USA
| | - Meredith Zendlo
- Department of Biological Sciences, Kent State University, Kent, OH, USA
| | - Jesse Kowalski
- Department of Biological Sciences, Kent State University, Kent, OH, USA
| | - Erin Gorrell
- School of Biomedical Sciences, Kent State University, Kent, OH, USA
| | - Scott Everett
- Department of Biological Sciences, Kent State University, Kent, OH, USA
| | - Jacob G Wagner
- Department of Biological Sciences, Kent State University, Kent, OH, USA
| | - Ashley E Davis
- School of Biomedical Sciences, Kent State University, Kent, OH, USA
| | - Lauren G Koch
- Department of Physiology and Pharmacology, the University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA
| | - Steven L Britton
- Department of Anesthesiology, and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Joram D Mul
- Brain Plasticity Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, the Netherlands
| | - Colleen M Novak
- School of Biomedical Sciences, Kent State University, Kent, OH, USA
- Department of Biological Sciences, Kent State University, Kent, OH, USA
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2
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Administration of recombinant human placental growth factor decreases blood pressure in obese hypertensive pregnant rats. J Hypertens 2021; 38:2295-2304. [PMID: 32618892 DOI: 10.1097/hjh.0000000000002528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVES Although epidemiological studies have shown that obesity is associated with increased incidence of hypertension during pregnancy, the mechanisms linking these two comorbidities are not as well studied. Previous investigations detected lower levels of the anti-hypertensive and pregnancy-related factor, placental growth factor (PlGF), in obese hypertensive pregnancies. Therefore, we examined whether obese hypertensive pregnant rats have reduced PlGF and whether increasing its levels by administering recombinant human (rh)PlGF reduces their blood pressure. METHODS We utilized a genetic model of obesity characterized to be heavier, hypertensive and fertile, namely rats having heterozygous deficiency of the melanocortin-4 receptor (MC4R-def). RESULTS MC4R-def obese rats had lower circulating levels of PlGF than wild-type lean controls at gestational day 19. Also, assessment of the PlGF receptor, Flt-1, in the vasculature showed that its levels were reduced in aorta and kidney glomeruli but increased in small mesenteric arteries. Chronic intraperitoneal administration of rhPlGF from gestational day 13-19 significantly increased circulating PlGF levels in both obese and lean rats, but reduced blood pressure only in the obese pregnant group. The rhPlGF treatment did not alter maternal body and fat masses or circulating levels of the adipokines, leptin and adiponectin. In addition, this treatment did not impact average foetal weights but increased placental weights regardless of obese or lean pregnancy. CONCLUSION PlGF is reduced in MC4R-def obese hypertensive pregnant rats, which is similar to findings in obese hypertensive pregnant women, while increasing its levels with exogenous rhPlGF reduces their blood pressure.
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3
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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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Palei AC, Martin HL, Wilson BA, Anderson CD, Granger JP, Spradley FT. Impact of hyperleptinemia during placental ischemia-induced hypertension in pregnant rats. Am J Physiol Heart Circ Physiol 2021; 320:H1949-H1958. [PMID: 33710923 DOI: 10.1152/ajpheart.00724.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The prevalence of preeclampsia and obesity have increased. Although obesity is a major risk factor for preeclampsia, the mechanisms linking these morbidities are poorly understood. Circulating leptin levels increase in proportion to fat mass. Infusion of this adipokine elicits hypertension in nonpregnant rats, but less is known about how hyperleptinemia impacts blood pressure during placental ischemia, an initiating event in the pathophysiology of hypertension in preeclampsia. We tested the hypothesis that hyperleptinemia during reduced uterine perfusion pressure (RUPP) exaggerates placental ischemia-induced hypertension. On gestational day (GD) 14, Sprague-Dawley rats were implanted with osmotic mini-pumps delivering recombinant rat leptin (1 µg/kg/min iv) or vehicle concurrently with the RUPP procedure to induce placental ischemia or Sham. On GD 19, plasma leptin was elevated in Sham + Leptin and RUPP + Leptin. Leptin infusion did not significantly impact mean arterial pressure (MAP) in Sham. MAP was increased in RUPP + Vehicle vs. Sham + Vehicle. In contrast to our hypothesis, placental ischemia-induced hypertension was attenuated by leptin infusion. To examine potential mechanisms for attenuation of RUPP-induced hypertension during hyperleptinemia, endothelial-dependent vasorelaxation to acetylcholine was similar between Sham and RUPP; however, endothelial-independent vasorelaxation to the nitric oxide (NO)-donor, sodium nitroprusside, was increased in Sham and RUPP. These findings suggest that NO/cyclic guanosine monophosphate (cGMP) signaling was increased in the presence of hyperleptinemia. Plasma cGMP was elevated in Sham and RUPP hyperleptinemic groups compared with vehicle groups but plasma and vascular NO metabolites were reduced. These data suggest that hyperleptinemia during placental ischemia attenuates hypertension by compensatory increases in NO/cGMP signaling.NEW & NOTEWORTHY Ours is the first study to examine the impact of hyperleptinemia on the development of placental ischemia-induced hypertension using an experimental animal model.
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Affiliation(s)
- Ana C Palei
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi
| | - Hunter L Martin
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi.,Department of Physiology and Biophysics, The University of Mississippi Medical Center, Jackson, Mississippi
| | - Barbara A Wilson
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi
| | - Christopher D Anderson
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi
| | - Joey P Granger
- Department of Physiology and Biophysics, The University of Mississippi Medical Center, Jackson, Mississippi
| | - Frank T Spradley
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi.,Department of Physiology and Biophysics, The University of Mississippi Medical Center, Jackson, Mississippi
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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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Gava FN, da Silva AA, Dai X, Harmancey R, Ashraf S, Omoto ACM, Salgado MC, Moak SP, Li X, Hall JE, do Carmo JM. Restoration of Cardiac Function After Myocardial Infarction by Long-Term Activation of the CNS Leptin-Melanocortin System. JACC Basic Transl Sci 2021; 6:55-70. [PMID: 33532666 PMCID: PMC7838051 DOI: 10.1016/j.jacbts.2020.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 11/12/2020] [Accepted: 11/12/2020] [Indexed: 12/17/2022]
Abstract
Leptin protects against progression to heart failure after myocardial infarction. This beneficial effect requires activation of the brain melanocortin system. Stimulation of brain MC4R recapitulates the cardiac protective effects of leptin. Leptin-MC4R activation improves cardiac substrate oxidation and mitochondrial function. It also improves Ca2+ coupling and contractile function in viable cardiomyocytes after MI.
Heart failure has a high mortality rate, and current therapies offer limited benefits. The authors demonstrate that activation of the central nervous system leptin-melanocortin pathway confers remarkable protection against progressive heart failure following severe myocardial infarction. The beneficial cardiac-protective actions of leptin require activation of brain melanocortin-4 receptors and elicit improvements in cardiac substrate oxidation, cardiomyocyte contractility, Ca2+ coupling, and mitochondrial efficiency. These findings highlight a potentially novel therapeutic approach for myocardial infarction and heart failure.
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Key Words
- AMPK, adenosine monophosphate–activated protein kinase
- BP, blood pressure
- CNS, central nervous system
- HF, heart failure
- HR, heart rate
- ICV, intracerebroventricular
- LV, left ventricular
- MC4R
- MC4R, melanocortin-4 receptor
- MI, myocardial infarction
- MTII, melanotan II
- appetite
- blood pressure
- cardiac metabolism
- heart failure
- mTOR, mechanistic target of rapamycin
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Affiliation(s)
- Fabio N Gava
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA.,Department of Veterinary Clinics, Londrina State University, Parana, Brazil
| | - Alexandre A da Silva
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Xuemei Dai
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Romain Harmancey
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Sadia Ashraf
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Ana C M Omoto
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA.,Department of Physiology, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil
| | - Mateus C Salgado
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA.,Centro Universitário Barão de Mauá, Ribeirão Preto, São Paulo, Brazil
| | - Sydney P Moak
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Xuan Li
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - John E Hall
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Jussara M do Carmo
- Department of Physiology and Biophysics and Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
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da Silva AA, Pinkerton MA, Spradley FT, Palei AC, Hall JE, do Carmo JM. Chronic CNS-mediated cardiometabolic actions of leptin: potential role of sex differences. Am J Physiol Regul Integr Comp Physiol 2020; 320:R173-R181. [PMID: 33206555 DOI: 10.1152/ajpregu.00027.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Previous studies using male rodents showed the adipocyte-derived hormone leptin acts in the brain to regulate cardiovascular function, energy balance, and glucose homeostasis. The importance of sex differences in cardiometabolic responses to leptin, however, is still unclear. We examined potential sex differences in leptin's chronic central nervous system (CNS)-mediated actions on blood pressure (BP), heart rate (HR), appetite, and glucose homeostasis in normal and type 1 diabetic rats. Female and male Sprague-Dawley (SD) rats were instrumented with intracerebroventricular cannulas for continuous 7-day leptin infusion (15 µg/day), and BP and HR were measured by telemetry 24 h/day. At baseline, females had lower mean arterial pressure (MAP) (96 ± 3 vs. 104 ± 4 mmHg, P < 0.05) but higher HR (375 ± 5 vs. 335 ± 5 beats/min, P < 0.05) compared with males. After leptin treatment, we observed similar increases in BP (∼3 mmHg) and HR (∼25 beats/min) in both sexes. Females had significantly lower body weight (BW, 283 ± 2 vs. 417 ± 7 g, P < 0.05) and caloric intake (162 ± 20 vs. 192 ± 9 kcal/kg of body wt, P < 0.05) compared with males, and leptin infusion reduced BW (-10%) and caloric intake (-62%) similarly in both sexes. In rats with streptozotocin-induced diabetes (n = 5/sex), intracerebroventricular leptin treatment for 7 days completely normalized glucose levels. The same dose of leptin administered intraperitoneally did not alter MAP, HR, glucose levels, or caloric intake in normal or diabetic rats. These results show that leptin's CNS effects on BP, HR, glucose regulation, and energy homeostasis are similar in male and female rats. Therefore, our results provide no evidence for sex differences in leptin's brain-mediated cardiovascular or metabolic actions.
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Affiliation(s)
- Alexandre A da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Mark A Pinkerton
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Frank T Spradley
- Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi
| | - Ana C Palei
- Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi
| | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Jussara M do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
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Abstract
PURPOSE OF REVIEW In this brief review, we highlight studies that have contributed to our current understanding of glucose homeostasis by the central nervous system (CNS) leptin-melanocortin system, particularly proopiomelanocortin neurons and melanocortin-4 receptors (MC4R). RECENT FINDINGS Leptin deficiency is associated with insulin resistance and impaired glucose metabolism whereas leptin administration improves tissue glucose uptake/oxidation and reduces hepatic glucose output. These antidiabetic effects of leptin have been demonstrated in experimental animals and humans, even when circulating insulin levels are barely detectable. Recent evidence suggests that these antidiabetic actions of leptin are mediated, in large part, by stimulation of leptin receptors (LRs) in the CNS and require activation of proopiomelanocortin (POMC) neurons and MC4R. These chronic antidiabetic effects of the CNS leptin-melanocortin system appear to be independent of autonomic nervous system and pituitary-thyroid-adrenal (PTA) axis mechanisms. The powerful antidiabetic actions of the CNS leptin-melanocortin system are capable of normalizing plasma glucose even in the absence of insulin and involve interactions of multiple neuronal populations and intracellular signaling pathways. Although the links between the CNS leptin-melanocortin system and its chronic effects on peripheral tissue glucose metabolism are still uncertain, they are independent of insulin action, activation of the autonomic nervous system, or the PTA axis. Unraveling the pathways that contribute to the powerful antidiabetic effects of the CNS leptin-melanocortin system may provide novel therapeutic approaches for diabetes mellitus.
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Affiliation(s)
- Alexandre A da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, and Cardiovascular-Renal Research Center, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216-4505, USA.
| | - Jussara M do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, and Cardiovascular-Renal Research Center, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216-4505, USA
| | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, and Cardiovascular-Renal Research Center, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS, 39216-4505, USA
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Spradley FT, Palei AC, Anderson CD, Granger JP. Melanocortin-4 Receptor Deficiency Attenuates Placental Ischemia-Induced Hypertension in Pregnant Rats. Hypertension 2019; 73:162-170. [PMID: 30571561 DOI: 10.1161/hypertensionaha.118.12028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Preeclampsia is a pregnancy-specific disorder of new-onset hypertension linked to placental ischemia. While obesity is a major risk factor for preeclampsia, not all obese pregnant women develop pregnancy-induced hypertension or preeclampsia. Previously, we reported that placental ischemia-induced hypertension is dependent upon intact signaling of the sympathetic nervous system. Moreover, in various models of obesity, blockade of MC4R (melanocortin-4 receptor) signaling protects against the development of hypertension via suppression of the sympathetic nervous system. Less is known about this pathway during obese pregnancy. Although blockade of MC4R may lead to increased body weight during pregnancy, we tested the hypothesis that placental ischemia-induced hypertension is attenuated in obese MC4R-deficient pregnant rats. On gestational day 14, MC4R wild-type or heterozygous-deficient (MC4R-def) rats were subjected to chronic placental ischemia via the reduced uterine perfusion pressure procedure or Sham surgery then examined on gestational day 19. In Sham MC4R-def versus Sham wild-type pregnant rats, there was increased body weight, fat mass, and circulating leptin levels but they had similar fetus weights. Reduced uterine perfusion pressure reduced fetus weights in both strains. Reduced uterine perfusion pressure increased blood pressure in wild-type rats but this response was significantly attenuated in MC4R-def rats, although blood pressure was elevated in Sham MC4R-def over Sham wild-type. These data indicate that while obese MC4R-def pregnant rats have higher blood pressure during pregnancy, placental ischemia-induced hypertension is attenuated in obese MC4R-def pregnant rats. Thus, obese women with abnormal MC4R signaling may be less susceptible to the development of placental ischemia-induced hypertension.
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Affiliation(s)
- Frank T Spradley
- From the Department of Surgery (F.T.S., A.C.P., C.D.A.), The University of Mississippi Medical Center, Jackson.,Department of Physiology and Biophysics (F.T.S., J.P.G.), The University of Mississippi Medical Center, Jackson
| | - Ana C Palei
- From the Department of Surgery (F.T.S., A.C.P., C.D.A.), The University of Mississippi Medical Center, Jackson
| | - Christopher D Anderson
- From the Department of Surgery (F.T.S., A.C.P., C.D.A.), The University of Mississippi Medical Center, Jackson
| | - Joey P Granger
- Department of Physiology and Biophysics (F.T.S., J.P.G.), The University of Mississippi Medical Center, Jackson
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Singha AK, Yamaguchi J, Gonzalez NS, Ahmed N, Toney GM, Fujikawa T. Glucose-Lowering by Leptin in the Absence of Insulin Does Not Fully Rely on the Central Melanocortin System in Male Mice. Endocrinology 2019; 160:651-663. [PMID: 30698681 PMCID: PMC6388659 DOI: 10.1210/en.2018-00907] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/24/2019] [Indexed: 12/11/2022]
Abstract
Central leptin administration can ameliorate hyperglycemia in insulin-deficient rodent models independently of insulin; however, the underlying neuronal mechanism are unclear. Here, we investigate the contribution of key elements within the central melanocortin system by examining whether central leptin injection can ameliorate hyperglycemia in total insulin-deficient mice that either lacked melanocortin 4 receptors (MC4Rs) in the whole body [knockout (KO); MC4R KO] or selectively, in single-minded homolog 1 (SIM1)-expressing neurons (SIM1ΔMC4R). We further investigated the contribution of leptin receptors (LEPRs) in agouti-related protein (AgRP)-expressing neurons (AgRP∆LEPR). Leptin injections into the cerebral ventricle attenuated mortality and elevated blood glucose in total insulin-deficient MC4R KO mice. Total insulin-deficient SIM1ΔMC4R mice exhibited the same magnitude reduction of blood glucose in response to leptin injections as MC4R KO mice, suggesting SIM1 neurons are key to MC4R-mediated, insulin-independent, glucose-lowering effects of leptin. Central leptin injection also partially rescued glucose levels in total insulin-deficient AgRP∆LEPR mice. In brain slice studies, basal discharge of AgRP neurons from mice with total insulin deficiency was increased and leptin partially reduced their firing rate without membrane potential hyperpolarization. Collectively, our findings indicate that, contrary to glucose-lowering effects of leptin in the presence of insulin or partial insulin deficiency, MC4Rs in SIM1 neurons and LEPRs in AgRP neurons are not solely responsible for glucose-lowering effects of leptin in total insulin deficiency. This indicates that the central melanocortin system operates with other neuronal systems to fully mediate glucose-lowering effects of leptin in an insulin-independent manner.
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Affiliation(s)
- Ashish K Singha
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Junya Yamaguchi
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Nancy S Gonzalez
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Newaz Ahmed
- Department of Internal Medicine, Division of Hypothalamic Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Glenn M Toney
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
- Center for Biomedical Neuroscience, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Teppei Fujikawa
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
- Center for Biomedical Neuroscience, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
- Mouse Genome Engineering and Transgenic Facility, Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas
- Correspondence: Teppei Fujikawa, PhD, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229. E-mail:
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da Silva AA, Freeman JN, Hall JE, do Carmo JM. Control of appetite, blood glucose, and blood pressure during melanocortin-4 receptor activation in normoglycemic and diabetic NPY-deficient mice. Am J Physiol Regul Integr Comp Physiol 2017; 314:R533-R539. [PMID: 29351428 DOI: 10.1152/ajpregu.00293.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although central melanocortin 4 receptor (MC4R) blockade abolishes the central nervous system (CNS)-mediated anorexogenic, antidiabetic, and cardiovascular actions of leptin, chronic MC4R stimulation fails to completely mimic the effects of leptin. Because neuropeptide Y (NPY) and MC4R exert opposite effects on cardiovascular and metabolic functions, we tested the role of NPY in offsetting the long-term actions of MC4R activation. Wild-type (WT) and NPY-deficient (NPY-/-) mice were implanted with telemetry probes for measuring mean arterial pressure (MAP) and heart rate (HR) 24 h/day. After the mice recovered from surgery and stable baseline measurements, the MC3/4R agonist melanotan II (MTII, 120 μg·kg-1·day-1 iv) was infused for 7 days followed by a recovery period. No major differences between groups were observed at baseline except for slightly higher food intake and HR in NPY-/- mice (4.3 ± 0.2 vs. 3.4 ± 0.2 g/day and 567 ± 14 vs. 522 ± 13 beats/min). Chronic MTII infusion reduced food intake in both groups while causing transient increases in MAP and HR only in WT mice (peaks of 11 ± 3 mmHg and 126 ± 13 beats/min). To examine whether NPY deficiency would amplify the antidiabetic effects of MC4R activation, diabetes was induced with streptozotocin (STZ) 1 wk before baseline measurements were taken, and the same experimental protocol was followed. In WT and NPY-/- mice, STZ-induced diabetes led to similar hyperphagia, hyperglycemia, and weight loss, which were not reversed by chronic MTII treatment. Our results demonstrate that chronic MC4R activation, even in NPY-deficient mice, does not mimic chronic antidiabetic, cardiovascular, or metabolic actions of leptin, and that NPY is not essential for hyperphagia or cardiovascular changes associated with diabetes.
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Affiliation(s)
- Alexandre A da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center , Jackson, Mississippi.,Barão de Mauá University Center , Ribeirão Preto, Sao Paulo , Brazil.,Universidade Estadual de Minas Gerais, Passos, Minas Gerais , Brazil
| | - J Nathan Freeman
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center , Jackson, Mississippi
| | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center , Jackson, Mississippi
| | - Jussara M do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center , Jackson, Mississippi
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Faulkner JL, Belin de Chantemèle EJ. Sex Differences in Mechanisms of Hypertension Associated With Obesity. Hypertension 2017; 71:15-21. [PMID: 29133358 DOI: 10.1161/hypertensionaha.117.09980] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jessica L Faulkner
- From the Vascular Biology Center, Medical College of Georgia at Augusta University, GA
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13
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Zhang HH, Liu J, Qin GJ, Li XL, Du PJ, Hao X, Zhao D, Tian T, Wu J, Yun M, Bai YH. Melanocortin 4 Receptor Activation Attenuates Mitochondrial Dysfunction in Skeletal Muscle of Diabetic Rats. J Cell Biochem 2017; 118:4072-4079. [PMID: 28409883 DOI: 10.1002/jcb.26062] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 04/13/2017] [Indexed: 12/25/2022]
Abstract
A previous study has confirmed that the central melanocortin system was able to mediate skeletal muscle AMP-activated protein kinase (AMPK) activation in mice fed a high-fat diet, while activation of the AMPK signaling pathway significantly induced mitochondrial biogenesis. Our hypothesis was that melanocortin 4 receptor (MC4R) was involved in the development of skeletal muscle injury in diabetic rats. In this study, we treated diabetic rats intracerebroventricularly with MC4R agonist R027-3225 or antagonist SHU9119, respectively. Then, we measured the production of reactive oxygen species (ROS), the levels of malondialdehyde (MDA) and glutathione (GSH), the mitochondrial DNA (mtDNA) content and mitochondrial biogenesis, and the protein levels of p-AMPK, AMPK, peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), sirtuin 1 (SIRT1), and manganese superoxide dismutase (MnSOD) in the skeletal muscle of diabetic rats. The results showed that there was significant skeletal muscle injury in the diabetic rats along with serious oxidative stress and decreased mitochondrial biogenesis. Treatment with R027-3225 reduced oxidative stress and induced mitochondrial biogenesis in skeletal muscle, and also activated the AMPK-SIRT1-PGC-1α signaling pathway. However, diabetic rats injected with MC4R antagonist SHU9119 showed an aggravated oxidative stress and mitochondrial dysfunction in skeletal muscle. In conclusion, our results revealed that MC4R activation was able to attenuate oxidative stress and mitochondrial dysfunction in skeletal muscle induced by diabetes partially through activating the AMPK-SIRT1-PGC-1α signaling pathway. J. Cell. Biochem. 118: 4072-4079, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Hao-Hao Zhang
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Jiao Liu
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Gui-Jun Qin
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Xia-Lian Li
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Pei-Jie Du
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Xiao Hao
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Di Zhao
- Division of Endocrinology, Department of Internal Medicine, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Tian Tian
- Department of Neurology, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Jing Wu
- Department of Pediatrics, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Meng Yun
- Department of MRI, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
| | - Yan-Hui Bai
- Department of Ophthalmology, First Affiliated Hospital of Zhengzhou University, 40 Daxue Road, Zhengzhou 450052, China
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14
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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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15
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da Silva AA, Hall JE, Moak SP, Browning J, Houghton HJ, Micheloni GC, do Carmo JM. Role of autonomic nervous system in chronic CNS-mediated antidiabetic action of leptin. Am J Physiol Endocrinol Metab 2017; 312:E420-E428. [PMID: 27923809 PMCID: PMC5451526 DOI: 10.1152/ajpendo.00301.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 12/02/2016] [Accepted: 12/02/2016] [Indexed: 01/13/2023]
Abstract
This study tested whether ganglionic blockade or hepatic vagotomy attenuates the chronic central nervous system (CNS)-mediated antidiabetic and cardiovascular effects of leptin. Male Sprague-Dawley rats were instrumented with telemetry probes and arterial and venous catheters for determination of blood pressure (BP), heart rate (HR), blood sampling, and intravenous (iv) infusions. An intracerebroventricular (ICV) cannula was placed into the brain lateral ventricle for infusion of leptin or vehicle. After control measurements, streptozotocin (STZ) was injected iv (50 mg/kg) to induce diabetes, and 5 days later leptin (n = 6) or saline vehicle (n = 5) was infused ICV for 12 days via osmotic pumps. Beginning on day 6 of leptin treatment, the ganglionic blocker hexamethonium (15 mg·kg-1·day-1 iv) was infused, while leptin infusion was continued, to assess the role of the autonomic nervous system. Induction of diabetes was associated with increases in blood glucose (98 ± 7 to 350 ± 19 mg/dl), food intake (23 ± 3 to 43 ± 3 g/day), decreases in HR (-70 ± 11 beats/min), polyuria, and increased water consumption, which were all completely normalized by ICV leptin infusion. Although hexamethonium attenuated leptin's effect on HR, it failed to impair leptin's ability to restore euglycemia or to prevent the polyuria or increased water intake in STZ-diabetic rats. We also found that after pretreatment with hexamethonium (n = 8), ICV leptin infusion, during continued ganglionic blockade, completely normalized blood glucose in diabetic rats. In addition, selective hepatic vagotomy did not attenuate leptin's ability to restore euglycemia in diabetic rats. These results suggest that leptin's powerful chronic CNS antidiabetic actions are mediated primarily via nonautonomic mechanisms.
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Affiliation(s)
- Alexandre A da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
- Barão de Mauá University Center, Ribeirão Preto, São Paulo, Brazil
| | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Sydney P Moak
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Jackson Browning
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Haley J Houghton
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
| | | | - Jussara M do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi; and
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16
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17
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Elfers CT, Roth CL. Robust Reductions of Excess Weight and Hyperphagia by Beloranib in Rat Models of Genetic and Hypothalamic Obesity. Endocrinology 2017; 158:41-55. [PMID: 27849360 DOI: 10.1210/en.2016-1665] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 11/15/2016] [Indexed: 02/08/2023]
Abstract
Hypothalamic lesions or deficient melanocortin (MC) signaling via MC4 receptor (MC4r) mutations often lead to hyperphagia and severe treatment-resistant obesity. We tested the methionine aminopeptidase 2-inhibitor beloranib (ZGN-440) in 2 male rat models of obesity, one modeling hypothalamic obesity with a combined medial hypothalamic lesion (CMHL) and the other modeling a monogenic form of obesity with MC4r mutations (MC4r knockout [MC4rKO]). In CMHL rats (age 3 months), postsurgery excess weight gain was significantly inhibited (ZGN-440, 0.2 ± 0.7 g/d; vehicle, 3.8 ± 0.6 g/d; P < 0.001) during 12 days of ZGN-440 treatment (0.1 mg/kg daily subcutaneously) together with a 30% reduction of daily food intake vs vehicle injection. In addition, ZGN-440 treatment improved glucose tolerance and reduced plasma insulin, and circulating levels of α-melanocyte stimulating hormone were increased. Serum lipid levels did not differ significantly in ZGN-440-treated vs vehicle-treated rats. Similar results were found in MC4rKO rats: ZGN-440 treatment (14-21 d) was associated with significant reductions of body weight gain (MC4rKO, -1.7 ± 0.6 vs 2.8 ± 0.4 g/d; lean wild-type controls, -0.7 ± 0.2 vs 1.7 ± 0.7 g/d; ZGN-440 vs vehicle, respectively), reduction of food intake (MC4rKO, -28%; lean controls, -7.5%), and insulin resistance, whereas circulating levels of interleukin-1β did not change. In both obesity models, body temperature and locomotor activity were not affected by ZGN-440 treatment. In conclusion, the robust reduction of body weight in response to ZGN-440 observed in rats with severe obesity is related to a strong reduction of food intake that is likely related to changes in the central regulation of feeding.
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Affiliation(s)
- Clinton T Elfers
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101; and
| | - Christian L Roth
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101; and
- Division of Endocrinology, Department of Pediatrics, University of Washington, Seattle, Washington 98105
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18
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Almundarij TI, Smyers ME, Spriggs A, Heemstra LA, Beltz L, Dyne E, Ridenour C, Novak CM. Physical Activity, Energy Expenditure, and Defense of Body Weight in Melanocortin 4 Receptor-Deficient Male Rats. Sci Rep 2016; 6:37435. [PMID: 27886210 PMCID: PMC5122857 DOI: 10.1038/srep37435] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 10/28/2016] [Indexed: 01/28/2023] Open
Abstract
Melanocortin 4 receptor (MC4R) variants contribute to human obesity, and rats lacking functional MC4R (Mc4rK314X/K314X) are obese. We investigated the hypothesis that low energy expenditure (EE) and physical activity contribute to this obese phenotype in male rats, and determined whether lack of functional MC4R conferred protection from weight loss during 50% calorie restriction. Though Mc4rK314X/K314X rats showed low brown adipose Ucp1 expression and were less physically active than rats heterozygous for the mutation (Mc4r+/K314X) or wild-type (Mc4r+/+) rats, we found no evidence of lowered EE in Mc4rK314X/K314X rats once body weight was taken into account using covariance. Mc4rK314X/K314X rats had a significantly higher respiratory exchange ratio. Compared to Mc4r+/+ rats, Mc4rK314X/K314X and Mc4r+/K314X rats lost less lean mass during calorie restriction, and less body mass when baseline weight was accounted for. Limited regional overexpression of Mc3r was found in the hypothalamus. Although lower physical activity levels in rats with nonfunctional MC4R did not result in lower total EE during free-fed conditions, rats lacking one or two functional copies of Mc4r showed conservation of mass, particularly lean mass, during energy restriction. This suggests that variants affecting MC4R function may contribute to individual differences in the metabolic response to food restriction.
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Affiliation(s)
- Tariq I Almundarij
- College of Agriculture and Veterinary Medicine, Al-Qassim University, Buraydah, Al-Qassim Province, Saudi Arabia.,Department of Biological Sciences, Kent State University, Kent, OH, 44242, US
| | - Mark E Smyers
- School of Biomedical Sciences, Kent State University, Kent, OH, 44242, US
| | - Addison Spriggs
- Department of Biological Sciences, Kent State University, Kent, OH, 44242, US
| | - Lydia A Heemstra
- Department of Biological Sciences, Kent State University, Kent, OH, 44242, US
| | - Lisa Beltz
- Department of Natural Sciences, Malone University, Canton, OH, 44709, US
| | - Eric Dyne
- School of Biomedical Sciences, Kent State University, Kent, OH, 44242, US.,Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, US
| | - Caitlyn Ridenour
- Department of Natural Sciences, Malone University, Canton, OH, 44709, US
| | - Colleen M Novak
- Department of Biological Sciences, Kent State University, Kent, OH, 44242, US.,School of Biomedical Sciences, Kent State University, Kent, OH, 44242, US
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19
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Spradley FT, Sasser JM, Musall JB, Sullivan JC, Granger JP. Nitric oxide synthase-mediated blood pressure regulation in obese melanocortin-4 receptor-deficient pregnant rats. Am J Physiol Regul Integr Comp Physiol 2016; 311:R851-R857. [PMID: 27534879 DOI: 10.1152/ajpregu.00285.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 08/14/2016] [Indexed: 11/22/2022]
Abstract
Although obesity increases the risk for hypertension in pregnancy, the mechanisms responsible are unknown. Increased nitric oxide (NO) production results in vasodilation and reduced blood pressure during normal pregnancy in lean rats; however, the role of NO is less clear during obese pregnancies. We examined the impact of obesity on NO synthase (NOS)-mediated regulation of blood pressure during pregnancy by testing the hypothesis that NOS activity, expression, and regulation of vascular tone and blood pressure are reduced in obese pregnant rats. At gestational day 19, melanocortin-4 receptor (MC4R)-deficient obese rats (MC4R) had greater body weight and fat mass with elevated blood pressure and circulating sFlt-1 levels compared with MC4R pregnant rats. MC4R pregnant rats also had less circulating cGMP levels and reduced total NOS enzymatic activity and expression in mesenteric arteries. Despite decreased biochemical measures of NO/NOS in MC4R rats, NOS inhibition enhanced vasoconstriction only in mesenteric arteries from MC4R rats, suggesting greater NOS-mediated tone. To examine the role of NOS on blood pressure regulation in obese pregnant rats, MC4R and MC4R pregnant rats were administered the nonselective NOS inhibitor NG-nitro-l-arginine methyl ester (l-NAME, 100 mg/l) from gestational day 14 to 19 in drinking water. The degree by which l-NAME raised blood pressure was similar between obese and lean pregnant rats. Although MC4R obese pregnant rats had elevated blood pressure associated with reduced total NOS activity and expression, they had enhanced NOS-mediated attenuation of vasoconstriction, with no evidence of alterations in NOS-mediated regulation of blood pressure.
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Affiliation(s)
- Frank T Spradley
- Department of Surgery, The University of Mississippi Medical Center, Jackson, Mississippi; .,Department of Physiology and Biophysics, The University of Mississippi Medical Center, Jackson, Mississippi.,Cardiovascular-Renal Research Center, The University of Mississippi Medical Center, Jackson, Mississippi.,Women's Health Research Center, The University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Jennifer M Sasser
- Department of Pharmacology and Toxicology, The University of Mississippi Medical Center, Jackson, Mississippi.,Cardiovascular-Renal Research Center, The University of Mississippi Medical Center, Jackson, Mississippi.,Women's Health Research Center, The University of Mississippi Medical Center, Jackson, Mississippi; and
| | | | | | - Joey P Granger
- Department of Physiology and Biophysics, The University of Mississippi Medical Center, Jackson, Mississippi.,Cardiovascular-Renal Research Center, The University of Mississippi Medical Center, Jackson, Mississippi.,Women's Health Research Center, The University of Mississippi Medical Center, Jackson, Mississippi; and
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