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A compendium of G-protein-coupled receptors and cyclic nucleotide regulation of adipose tissue metabolism and energy expenditure. Clin Sci (Lond) 2020; 134:473-512. [PMID: 32149342 DOI: 10.1042/cs20190579] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 02/17/2020] [Accepted: 02/24/2020] [Indexed: 12/15/2022]
Abstract
With the ever-increasing burden of obesity and Type 2 diabetes, it is generally acknowledged that there remains a need for developing new therapeutics. One potential mechanism to combat obesity is to raise energy expenditure via increasing the amount of uncoupled respiration from the mitochondria-rich brown and beige adipocytes. With the recent appreciation of thermogenic adipocytes in humans, much effort is being made to elucidate the signaling pathways that regulate the browning of adipose tissue. In this review, we focus on the ligand-receptor signaling pathways that influence the cyclic nucleotides, cAMP and cGMP, in adipocytes. We chose to focus on G-protein-coupled receptor (GPCR), guanylyl cyclase and phosphodiesterase regulation of adipocytes because they are the targets of a large proportion of all currently available therapeutics. Furthermore, there is a large overlap in their signaling pathways, as signaling events that raise cAMP or cGMP generally increase adipocyte lipolysis and cause changes that are commonly referred to as browning: increasing mitochondrial biogenesis, uncoupling protein 1 (UCP1) expression and respiration.
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Mountjoy KG. Pro-Opiomelanocortin (POMC) Neurones, POMC-Derived Peptides, Melanocortin Receptors and Obesity: How Understanding of this System has Changed Over the Last Decade. J Neuroendocrinol 2015; 27:406-18. [PMID: 25872650 DOI: 10.1111/jne.12285] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 04/04/2015] [Accepted: 04/07/2015] [Indexed: 12/19/2022]
Abstract
Following the cloning of the melanocortin receptor and agouti protein genes, a model was developed for the central melanocortin system with respect to the regulation of energy and glucose homeostasis. This model comprised leptin regulation of melanocortin peptides and agouti-related peptide (AgRP) produced from central pro-opiomelanocortin (POMC) and AgRP neurones, respectively, as well as AgRP competitive antagonism of melanocortin peptides activating melanocortin 4 receptor (MC4R) to Gαs and the cAMP signalling pathway. In the last decade, there have been paradigm shifts in our understanding of the central melanocortin system as a result of the application of advanced new technologies, including Cre-LoxP transgenic mouse technology, pharmacogenetics and optogenetics. During this period, our understanding of G protein coupled receptor signal transduction has also dramatically changed, such that these receptors are now known to exist in the plasma membrane oscillating between various inactive and active conformational states, and the active states signal through G protein-dependent and G protein-independent pathways. The present review focuses on evidence obtained over the past decade that has changed our understanding of POMC gene expression and regulation in the central nervous system, POMC and AgRP neuronal circuitry, neuroanatomical functions of melanocortin receptors, melanocortin 3 receptor (MC3R) and MC4R, and signal transduction through MC3R and MC4R.
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Affiliation(s)
- K G Mountjoy
- Departments of Physiology and Molecular Medicine and Pathology, School of Medical Sciences, Faculty of Medical and Health Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
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Bradley RL, Mansfield JPR, Maratos-Flier E. Neuropeptides, Including Neuropeptide Y and Melanocortins, Mediate Lipolysis in Murine Adipocytes. ACTA ACUST UNITED AC 2012; 13:653-61. [PMID: 15897473 DOI: 10.1038/oby.2005.73] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To determine whether key appetite-regulating neuropeptides such as melanin-concentrating hormone (MCH), neuropeptide Y (NPY), and alpha-melanocyte-stimulating hormone (alpha-MSH), which are known to mediate energy balance through centrally mediated pathways, also have direct acute effects on the lipolytic activity of murine adipocytes. RESEARCH METHODS AND PROCEDURES Fully differentiated 3T3-L1 adipocytes serum starved overnight in Dulbecco's modified Eagle medium containing 2% bovine serum albumin or freshly isolated mouse adipocytes were incubated for up to 2 hours in the absence and presence of 100 nM each of NPY, MCH, alpha-MSH, the melanocortin receptor agonist MTII, or isoproterenol as a control. Free fatty acids secreted into the incubation medium were measured using a commercially available nonesterified fatty acid C test kit. RESULTS Treatment of 3T3-L1 cells with 100 nM NPY decreased basal free fatty acid secretion (basal, 0.006 +/- 0.001 vs. NPY, 0.001 +/- 0.0003 nM at 90 minutes; p < 0.05), whereas both alpha-MSH and MTII stimulated up to a 7-fold increase in free fatty acid release (MTII, 0.238 +/- 0.004 vs. basal, 0.024 +/- 0.002 nM at 2 hours; p < 0.05; and alpha-MSH, 0.22 +/- 0.005 vs. basal, 0.04 +/- 0.003 nM at 2 hours; p < 0.05). Treatment with 100 nM MCH had no effect on basal free fatty acid release or on alpha-MSH-induced lipolysis during concurrent treatment. Conversely, concurrent treatment with 100 nM NPY dramatically inhibited (by approximately 90%) alpha-MSH-induced lipolysis. Similar treatment of freshly isolated mouse adipocytes showed virtually identical results. DISCUSSION In addition to their centrally mediated actions, appetite-regulating neuropeptides modulate adipose tissue mass through direct peripheral effects. Systemic administration of pharmacological agents altering the effects of these neuropeptides may form the basis of future obesity therapies. Thus, some of these agents will likely have direct effects on adipocytes that may serve to alter their therapeutic effectiveness.
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Local Agouti Signaling Protein/Melanocortin Signaling System that Possibly Regulates Lipid Metabolism in Adipose Tissues of Chickens. J Poult Sci 2010. [DOI: 10.2141/jpsa.009110] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Bicknell KA, Harmer SC, Yiangson S, Lockwood W, Bicknell AB. Lys-gamma3-MSH: a global regulator of hormone sensitive lipase activity? Mol Cell Endocrinol 2009; 300:71-6. [PMID: 18977407 DOI: 10.1016/j.mce.2008.09.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 09/23/2008] [Accepted: 09/23/2008] [Indexed: 11/18/2022]
Abstract
Gamma-melanocyte stimulating hormone (gamma-MSH) is a peptide derived from the ACTH precursor, pro-opiomelanocortin (POMC), and belongs to a family of peptides called the melanocortins that also comprises alpha- and beta-MSH. Although conserved in tetrapods, the biological role of gamma-MSH remains largely undefined. It has been demonstrated previously that gamma-MSH is involved in the regulating the activity of hormone sensitive lipase (HSL) activity in the adrenal and more recently, in the adipocyte. It has been shown also to have effects on the cardiovascular and renal systems. This short review will provide a brief overview of the role of gamma-MSH in the adrenal and the more recent report that it can also regulate HSL function in the adipocyte. We also present some preliminary data purporting a direct role for Lys-gamma(3)-MSH in the regulation of HSL phosphorylation in the heart. Taken together these data suggest that gamma-MSH peptides might play a more widespread role in lipid and cholesterol utilization.
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Affiliation(s)
- Katrina A Bicknell
- School of Pharmacy, The University of Reading, Whiteknights, PO Box 228, Reading, Berkshire, RG6 6AJ, UK
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Harmer SC, Pepper DJ, Cooke K, Bennett HPJ, Bicknell AB. Evidence of a possible role for Lys-gamma3-MSH in the regulation of adipocyte function. J Endocrinol 2008; 196:149-58. [PMID: 18180326 PMCID: PMC2216415 DOI: 10.1677/joe-07-0391] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lys-gamma3-MSH is a melanocortin peptide derived from the C-terminal of the 16 kDa fragment of POMC. The physiological role of Lys-gamma3-MSH is unclear, although it has previously been shown that, although not directly steroidogenic, it can act to potentiate the steroidogenic response of adrenal cortical cells to ACTH. This synergistic effect appears to be correlated with an ability to increase the activity of hormone sensitive lipase (HSL) and therefore the rate of cholesterol ester hydrolysis. Ligand binding studies have suggested that high-affinity binding sites for Lys-gamma3-MSH exist in the adrenal gland and a number of other rat tissues that express HSL, including adipose, skeletal muscle and testes. To investigate the hypothesis that Lys-gamma3-MSH may play a wider role in cholesterol and lipid metabolism, we tested the effect of Lys-gamma3-MSH on lipolysis, an HSL-mediated process, in 3T3-L1 adipocytes. In comparison with other melanocortin peptides, Lys-gamma3-MSH was found to be a potent stimulator of lipolysis. It was also able to phosphorylate HSL at key serine residues and stimulate the hyperphosphorylation of perilipin A. The receptor through which the lipolytic actions of Lys-gamma3-MSH are being mediated is not clear. Attempts to characterise this receptor suggest that either the pharmacology of the melanocortin receptor 5 in 3T3-L1 adipocytes is different from that described when expressed in heterologous systems or the possibility that a further, as yet uncharacterised, receptor exists.
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Affiliation(s)
- Stephen C Harmer
- School of Biological Sciences, The University of ReadingWhiteknights, PO Box 228, Reading, Berkshire RG6 6AJUK
| | - David J Pepper
- School of Biological Sciences, The University of ReadingWhiteknights, PO Box 228, Reading, Berkshire RG6 6AJUK
| | - Katy Cooke
- School of Biological Sciences, The University of ReadingWhiteknights, PO Box 228, Reading, Berkshire RG6 6AJUK
| | - Hugh P J Bennett
- Endocrine Laboratory, Royal Victoria Hospital687 Pine Avenue West, Montreal, Quebec H3A1A1Canada
| | - Andrew B Bicknell
- School of Biological Sciences, The University of ReadingWhiteknights, PO Box 228, Reading, Berkshire RG6 6AJUK
- (Correspondence should be addressed to A B Bicknell; )
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Della-Fera MA, Baile CA. Roles for melanocortins and leptin in adipose tissue apoptosis and fat deposition. Peptides 2005; 26:1782-7. [PMID: 16002187 DOI: 10.1016/j.peptides.2004.12.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2004] [Accepted: 12/12/2004] [Indexed: 10/25/2022]
Abstract
Leptin has a wide range of effects on physiological functions related to the regulation of body energy balance. Many of leptin's effects are mediated through neuropeptide-containing neurons and neuropeptide receptors in the hypothalamus. The melanocortin system includes both agonist (alpha-melanocyte stimulating hormone, alphaMSH) and antagonist peptides (agouti related peptide, AGRP). Increased melanocortin receptor stimulation following leptin administration plays an important role in leptin-induced hypophagia and increased sympathetic nervous system activity and is partly responsible for leptin-induced weight loss. However, melanocortins do not appear to mediate some of the more striking centrally-mediated effects of leptin on adipose tissue, including adipose tissue apoptosis, that lead to the extensive depletion of fat.
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Affiliation(s)
- Mary Anne Della-Fera
- Department of Animal and Dairy Science, University of Georgia, 444 Animal Science Complex, Athens, GA 30602-2771, USA
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Noon LA, Clark AJL, King PJ. A peroxisome proliferator-response element in the murine mc2-r promoter regulates its transcriptional activation during differentiation of 3T3-L1 adipocytes. J Biol Chem 2004; 279:22803-8. [PMID: 15028712 DOI: 10.1074/jbc.m401861200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adrenocorticotropic hormone can stimulate lipolysis and suppress leptin expression in murine adipocytes. These effects are mediated via the melanocortin 2 receptor (MC2-R), which is expressed when 3T3-L1 cells are induced to undergo adipogenesis. In this study, we have characterized the mc2-r promoter in the murine adipocyte, one of the few extra-adrenal sites of expression and a cell type that lacks steroidogenic factor 1 (SF-1), a transcription factor that is required for mc2-r expression in adrenal cells. Transcriptional regulation of the mc2-r in the absence of SF-1 was investigated by 5' deletion analysis of the murine mc2-r promoter in both undifferentiated and differentiated 3T3-L1 cells. The results revealed the presence of a 59-base pair regulatory region within the promoter containing an adipocyte-specific enhancer. The ability of this region to confer enhanced activity in the adipocyte was mapped to a peroxisome proliferator-response element (PPRE)-like sequence that bound to peroxisome proliferator-activated receptor gamma (PPARgamma) and its heterodimeric partner retinoid X receptor alpha (RXRalpha) in adipocyte nuclear extracts. Co-transfection of PPARgamma2/RXRalpha with the pMC2-R(-112/+105)GL3 reporter resulted in transcriptional activation in preadipocytes, and this response required an intact PPRE. Mutation of the PPRE to prevent PPARgamma/RXRalpha binding resulted in a complete abrogation of the pMC2-R(-112/+105)GL3 reporter activity in day 3 differentiated 3T3-L1 cells, demonstrating a key role played by this site in regulating MC2-R expression in the murine adipocyte. These data highlight a novel mechanism for mc2-r transcription, which may have significance in both adrenal and extra-adrenal sites of expression.
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Affiliation(s)
- Luke A Noon
- Molecular Endocrinology Center, William Harvey Research Institute, Bart's and the London, Queen Mary University of London, London, EC1A 7BE, United Kingdom
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Kiwaki K, Levine JA. Differential effects of adrenocorticotropic hormone on human and mouse adipose tissue. J Comp Physiol B 2003; 173:675-8. [PMID: 12925881 DOI: 10.1007/s00360-003-0377-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2003] [Indexed: 10/26/2022]
Abstract
Adrenocorticotropic hormone (ACTH) induces lipolysis in a dose-dependent fashion in rodent adipose tissue and adipocytes in vitro. The role of ACTH on lipolysis in human adipose tissue is less clear, however. In this study, we address the hypothesis that ACTH induces lipolysis in human adipose tissue. We used ex vivo organ culture to examine lipolysis in human and mouse adipose tissue. Adipose tissue fragments suspended in culture medium and human ACTH, isoproterenol (positive control), or insulin (negative control) was added in varying concentrations. Lipolysis was measured using glycerol appearance. ACTH receptor mRNA expression was assessed using reverse-transcription polymerase chain reaction (RT-PCR). In mouse adipose tissue, ACTH induced lipolysis in dose-dependent manner; 100 pmol/l ACTH induced 67+/-19% of isoproterenol-stimulated lipolysis and 500 pmol/l ACTH: 86+/-13%. In contrast, human adipose tissue shared no significant response to 100 pmol/l ACTH; ACTH was associated with 9+/-6% and 500 pmol/l of ACTH, 8+/-6% of isoproterenol-stimulated lipolysis. ACTH receptor mRNA was present in mouse adipose tissue, but undetectable in human adipose tissue. These results suggest lipolysis regulation differs between human and mouse adipose tissue in response to ACTH.
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Affiliation(s)
- K Kiwaki
- Endocrine Research Unit, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA
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Brennan MB, Costa JL, Forbes S, Reed P, Bui S, Hochgeschwender U. Alpha-melanocyte-stimulating hormone is a peripheral, integrative regulator of glucose and fat metabolism. Ann N Y Acad Sci 2003; 994:282-7. [PMID: 12851327 DOI: 10.1111/j.1749-6632.2003.tb03191.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Melanocortins are known to affect feeding and probably insulin activity through the central nervous system. It was also recently shown that peripheral alpha-melanocyte-stimulating hormone (alpha-MSH) administration can reduce weight gain in both genetic and diet-induced obese mice. As obesity is often associated with disregulation of glucose and insulin, we investigated the nature of glucose homeostasis in the obese pro-opiomelanocortin (POMC) knockout mouse. Here we report that though they are obese, mice deficient in POMC (and, thereby, deficient in alpha-MSH) are euglycemic throughout their lives. While these mice are euinsulinemic, they are hypersensitive to exogenous insulin. This defect can be reversed through administration of alpha-MSH. We demonstrate that the actions of alpha-MSH in the periphery, known from our work to include lipid metabolism effects, are also involved in glucose homeostasis. These findings substantiate a pivotal role of the POMC gene products in integrating metabolism.
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Affiliation(s)
- Miles B Brennan
- Eleanor Roosevelt Institute for Cancer Research, Denver, Colorado 80206, USA.
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Hoogduijn MJ, McGurk S, Smit NPM, Nibbering PH, Ancans J, van der Laarse A, Thody AJ. Ligand-dependent activation of the melanocortin 5 receptor: cAMP production and ryanodine receptor-dependent elevations of [Ca(2+)](I). Biochem Biophys Res Commun 2002; 290:844-50. [PMID: 11785979 DOI: 10.1006/bbrc.2001.6283] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The melanocortins are involved in the regulation of various cognitive and physiological processes such as learning, feeding, immune suppression, pigmentation, and sebum production. Five melanocortin receptors have been identified, of which the melanocortin 5 receptor (MC5R) has the most widespread distribution. This subtype is found in the brain, and at numerous peripheral sites including the skin where it is expressed in the sebaceous glands. The purpose of this study was to identify the peptide that functions as a natural ligand at the MC5R in the skin. alpha-MSH, ACTH1-39, ACTH1-17, ACTH1-10, and ACTH4-10 all increased the production of cAMP in HEK293 cells transfected with the mouse MC5R. alpha-MSH and ACTH1-17 were the most potent in this respect. In addition, all peptides stimulated a rapid and transient increase in [Ca(2+)](i), and, ACTH1-10 was the most potent. The increases in [Ca(2+)](i) were of intracellular origin, but not associated with inositol phosphate production. The elevations in [Ca(2+)](i) were reduced by ruthenium red and procaine and it is therefore possible that they were mediated via ryanodine receptors.
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Affiliation(s)
- M J Hoogduijn
- Department of Biomedical Sciences, University of Bradford, Bradford, United Kingdom
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Forbes S, Bui S, Robinson BR, Hochgeschwender U, Brennan MB. Integrated control of appetite and fat metabolism by the leptin-proopiomelanocortin pathway. Proc Natl Acad Sci U S A 2001; 98:4233-7. [PMID: 11259669 PMCID: PMC31208 DOI: 10.1073/pnas.071054298] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Leptin deficiency results in a complex obesity phenotype comprising both hyperphagia and lowered metabolism. The hyperphagia results, at least in part, from the absence of induction by leptin of melanocyte stimulating hormone (MSH) secretion in the hypothalamus; the MSH normally then binds to melanocortin-4 receptor expressing neurons and inhibits food intake. The basis for the reduced metabolic rate has been unknown. Here we show that leptin administered to leptin-deficient (ob/ob) mice results in a large increase in peripheral MSH levels; further, peripheral administration of an MSH analogue results in a reversal of their abnormally low metabolic rate, in an acceleration of weight loss during a fast, in partial restoration of thermoregulation in a cold challenge, and in inducing serum free fatty acid levels. These results support an important peripheral role for MSH in the integration of metabolism with appetite in response to perceived fat stores indicated by leptin levels.
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Affiliation(s)
- S Forbes
- Eleanor Roosevelt Institute for Cancer Research, 1899 Gaylord Street, Denver, CO 80206, USA
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Abstract
It has been demonstrated that adipocytes express high affinity ACTH and alpha-MSH binding sites, and that ACTH, alpha-MSH, and beta-LPH are potent lipolytic hormones. Considerable species variability exists in the lipolytic response to melanocortins, however. Recently, MC2 and MC5 receptor-mRNA was found in both murine adipocytes and in the 3T3-L1 murine embryonic fibroblast cell line, but only after the 3T3-L1 cells had differentiated into adipocytes. The 3T3-L1 cell line was used to characterize the pharmacological properties of both MC2 and MC5 receptors in situ. Both murine MC2 and MC5 receptors are functional in the adipocyte, although the MC5 receptor required high doses of alpha-MSH to activate cylase. ACTH potently stimulates cyclase with EC50 values that are consistent with the hypothesis that the murine MC2 receptor, not the MC5 receptor, mediates stress-induced lipolysis via release of ACTH from the pituitary.
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Affiliation(s)
- B A Boston
- Department of Pediatrics, Oregon Health Sciences University, Portland 97201, USA.
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Asher C, Moshitzky P, Ramachandran J, Applebaum SW. The effects of synthetic locust adipokinetic hormone on dispersed locust fat body cell preparations: cAMP induction, lipid mobilization, and inhibition of protein synthesis. Gen Comp Endocrinol 1984; 55:167-73. [PMID: 6090263 DOI: 10.1016/0016-6480(84)90098-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A procedure for the preparation of functional cells from adult locust fat bodies by collagenase treatment has been developed. The high variability of replicates encountered when whole fat bodies are incubated in vitro is greatly reduced in incubation of the dispersed cells. Synthetic locust adipokinetic hormone (AKH) (40 nM) stimulated release of lipids from the dispersed fat body cells at a rate comparable to that observed using whole fat bodies in vitro. Synthetic AKH elevated cAMP levels sixfold in dispersed cells. In addition, AKH inhibited protein synthesis to a maximum of 50-70% in a concentration-dependent manner. None of these actions of AKH required the presence of locust hemolymph components. These results demonstrate the utility of the isolated locust fat body cells for investigating hormonal action in vitro.
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Abstract
Synthetic [125I]-Tyr23, Phe2, Nle4-adrenocorticotropin (ACTH)-(1-38) [( 125I]-ACTH analog) with full biological potency and near theoretical specific radioactivity (1800 +/- 75 Ci/mmol) was used to investigate ACTH receptors on isolated rat adipocytes derived from 42-day-old rats. Binding to adipocytes was studied in the presence of 1% bovine serum albumin (BSA) as well as 4% BSA. The interaction of the [125I]-ACTH analog with adipocytes was highly specific, rapid, saturable, and reversible. Scatchard analysis of the binding data obtained in medium containing 1% BSA revealed a single class of binding sites with an apparent KD = 170 +/- 11.9 pM. Competition experiments with unlabeled ACTH also yielded a comparable value for the apparent KD (143 +/- 16.5 pM). The number of receptors per adipocyte was quite low (521-841/cell). The stimulation of lipolysis by ACTH was closely correlated with the binding, the apparent Km being 145-177 pM. At a concentration of 4% BSA in the incubation medium, the binding curve was shifted significantly to the right (apparent KD = 446 +/- 77 pM) and the binding capacity was also significantly enhanced (1663 +/- 208/cell) without any change in the apparent Km for glycerol release (187 +/- 7.1 pM).
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Rudman D, Hollins BM, Kutner MH, Moffitt SD, Lynn MJ. Three types of alpha-melanocyte-stimulating hormone: bioactivities and half-lives. THE AMERICAN JOURNAL OF PHYSIOLOGY 1983; 245:E47-54. [PMID: 6869528 DOI: 10.1152/ajpendo.1983.245.1.e47] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Three types of alpha-melanocyte-stimulating hormone (alpha MSH) that differ in the acetyl status of the N-terminal serine have been found in the neurointermediate lobe of the pituitary gland and in the brain: desacetyl alpha MSH, which lacks an acetyl group; monoacetyl alpha MSH, in which the amino group of the serine is acetylated; and diacetyl alpha MSH, in which both amino and hydroxy groups of the serine are acetylated. We compared the lipolytic and melanotropic actions of these three peptides, and their rates of disappearance from plasma, both in vitro and in vivo. The following differences were found. a) For in vitro lipolytic actions on rabbit adipose tissue slices, the potencies differed according to the order diacetyl = monoacetyl greater than desacetyl. On rabbit isolated adipocytes, however, the three peptides were equipotent. b) For in vivo lipolytic action in the rabbit, not only potency but also kinetics differed. Diacetyl alpha MSH had the slowest onset, longest duration, and greatest potency. The desacetyl variant had the quickest onset, shortest duration, and least potency. c) The half-life for elimination from rabbit plasma both in vitro and in vivo was shortest for the desacetyl form and longest for the diacetyl peptide. d) For in vitro melanotropic effect on frog skin, kinetics of action were the same for all three peptides, but potency differed according to the order diacetyl = monoacetyl greater than desacetyl. Thus acetylation of alpha MSH alters lipolytic and melanotropic potencies in vitro and lipolytic potency and kinetics in vivo. These differences result in part from the fact that acetylation slows the degradation of the tridecapeptide both inside and outside the circulation.
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Abstract
The total synthesis of human beta-lipotropin has been accomplished by the new segment-coupling method in aqueous solution. The peptides Ac-Arg-beta-lipotropin-(61-89) (I) and [GlyS60]-beta-lipotropin-(1-60) (II) were synthesized by the solid-phase method. Reaction of peptide I with citraconic anhydride followed by brief digestion with trypsin to remove the acetylarginyl group, gave Ia. Reaction of peptide II with citraconic anhydride gave the citraconyl peptide IIa. Ia and IIa were coupled together in 50% dimethylformamide by reaction with silver nitrate/N-hydroxysuccinimide. After removal of the citraconyl groups in 25% acetic acid, a 10% yield of synthetic beta-lipotropin could be isolated. The synthetic product was shown to be identical to native human beta-lipotropin by paper electrophoresis, isoelectric focusing, HPLC, lipolytic activity in isolated rabbit fat cells, and radioimmunoassay.
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Muramoto K, Buckley DI, Ramachandran J. Preparation of photoreactive derivatives of alpha-melanotropin by selective modification of the lysine or tryptophan residue. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1982; 20:366-70. [PMID: 6816747 DOI: 10.1111/j.1399-3011.1982.tb00901.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Ng TB, Li CH. Corticotropin inhibiting peptide and a synthetic beta-melanotropin analog inhabit the lipolytic activity of corticotropin and melanotropins. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1982; 19:562-4. [PMID: 6288597 DOI: 10.1111/j.1399-3011.1982.tb02643.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Lipolysis in isolated rabbit fat cells induced by beta-melanotropin, alpha-melanotropin and corticotropin was inhibited by both corticotropin inhibiting peptide and [Gly10]-beta-melanotropin. Corticotropin inhibiting peptide was a more potent antagonist than [Gly10]-beta-melanotropin.
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Rybak SM, Ramachandran J. Comparison of the structural features of corticotropin required for stimulation of steroidogenesis and cAMP production in rat and rabbit adrenocortical cells. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 18:148-53. [PMID: 6273347 DOI: 10.1111/j.1399-3011.1981.tb02052.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The steroidogenic activities of ACTH, alpha-MSH, beta-MSH as well as analogs of the hormones have been compared in rat and rabbit adrenocortical cells. ACTH is equally active in both species and the melanotropins have very low steroidogenic potency in either species. The steroidogenic potencies of the peptide analogs are strikingly similar in the two species, suggesting that the structural requirements for eliciting steroidogenesis are the same in rat and rabbit adrenocortical cells. The analog NPS-ACTH has low, comparable steroidogenic activity in both species. NPS-ACTH is a potent antagonist of ACTH-induced cAMP production in rat adrenocortical cells but acts as a weak partial agonist in rabbit adrenocortical cells. These results suggest that steroidogenesis may be mediated by receptors different from those involved in the cAMP response observed at supraphysiological concentrations of ACTH.
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Buckley DI, Houghten RA, Ramachandran J. Isolation of alpha-melanotropin and N, O-diacetylserine1-alpha-melanotropin from porcine pituitary extracts. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 17:508-13. [PMID: 7309355 DOI: 10.1111/j.1399-3011.1981.tb02021.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In the course of isolation of alpha-melanotropin (alpha-MSH) from porcine pituitary extracts, a peptide with identical amino acid composition but slightly less polar properties compared to alpha-MSH was detected and isolated by partition chromatography. The new peptide was identified as N, O-diacetyl-Ser1-alpha-MSH by high resolution nuclear magnetic resonance spectroscopy. N, O-diacetyl-Ser1-alpha-MSH was readily converted to alpha-MSH by incubation at pH 9.5. The O-acetyl analog of alpha-MSH was found to be as active as alpha-MSH in stimulating lipolysis in isolated rabbit adipocytes.
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Buckley DI, Ramachandran J. Preparation of tritiated alpha-melanotropin with high specific radioactivity. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 17:514-8. [PMID: 7309356 DOI: 10.1111/j.1399-3011.1981.tb02022.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
alpha-Melanotropin (alpha-MSH) was iodinated and 3,5-diiodotyr2-alpha-MSH was isolated by reverse phase high performance liquid chromatography (HPLC). Catalytic dehalogenation of the diiodo derivative in the presence of tritium resulted in the formation of 3,5-ditritiotyr2-alpha-MSH. The tritiated peptide was purified by ion exchange and partition chromatography. The radioactive peptide was found to be homogeneous and identical to alpha-MSH by paper electrophoresis and HPLC. The tritiated alpha-MSH stimulated lipolysis in rabbit adipocytes nearly as well as alpha-MSH. The specific radioactivity of tritiated alpha-MSH was 42 Ci/mmol or 73% of the theoretical value.
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Behrens CM, Ramachandran J. The effect of glucocorticoids on adipocyte corticotropin receptors and adipocyte responses. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 672:268-79. [PMID: 6260229 DOI: 10.1016/0304-4165(81)90293-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A specific and sensitive assay for determining the binding of adrenocorticotropin (ACTH) to isolated rat adipocytes has been developed and utilized to study the effect of glucocorticoids on ACTH receptor. Measurement of the binding of tritiated ACTH (spec. act. 90 Ci/mmol) to adipocytes isolated from normal, adrenalectomized, and adrenalectomized dexamethasone-treated rats indicated that there are no differences among these three populations in either the magnitude or the affinity of the binding reaction. The binding interaction was found to be of high affinity (Kd = 5.23 + 1.92 . 10(-9) M and paralleled closely the stimulation of lipolysis (Km = 2.09 +/- 0.35 . 10(-9) M. About 16,300 receptors were calculated to be presented per adipocyte. Hormone-induced cyclic 3',5'-adenosine monophosphate production remained intact after adrenalectomy, thereby confirming that receptors are not lost during steroid deprivation. The lipolytic response did, however, become less sensitive to both ACTH and epinephrine following adrenalectomy. Pre-treatment of adrenalectomized rats with dexamethasone resulted in an increase in basal and hormone-stimulated levels of cyclic AMP and glycerol production to super-normal values. In adipocyte ghost preparations, ACTH and epinephrine sensitive adenylate cyclase activity was not decreased by adrenalectomy and dexamethasone administration did not result in a selective enhancement of ACTH sensitive adenylate cyclase activity. Our results indicate that glucocorticoids do not cause their permissive effects by specific regulation of the ACTH receptor on the adipocyte.
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Blake J, Rao AJ, Li CH. Adrenocorticotropin. 52 Synthesis and biological activity of adrenocorticotropic peptides with cystine bridges. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1979; 13:346-52. [PMID: 218890 DOI: 10.1111/j.1399-3011.1979.tb01891.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Three analogs of the amino terminal nonadecopeptide of adrenocorticotropin which incorporate cystine cystine bridges between positions (5, 10), (3, 10), or (2, 10) have been synthesized. All of the peptide analogs showed reduced biological activity; however, the peptide with the 5, 10 cystine bridge was shown to possess significantly higher lipolytic activity in rat fat cells than the peptides with a 3, 10 or 2, 10 cystine bridge.
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Free fatty acid content in muscles after administration of ACTH and hydrocortisone. Bull Exp Biol Med 1978. [DOI: 10.1007/bf00800111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ramachandran J, Behrens C. Preparation and characterization of specifically tritiated adrenocorticotropin. Biochim Biophys Acta Gen Subj 1977; 496:321-8. [PMID: 189837 DOI: 10.1016/0304-4165(77)90314-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The catalytic dehalogenation of iodinated derivatives of corticotropin in the presence of tritium was investigated. In 0.1 M acetic acid, complete and rapid removal of iodine was achieved in the presence of freshly prepared palladium or palladium oxide as catalyst, but the specific radioactivity of the product was only 10-20% of the theoretically attainable value. Synthetic human corticotropin containing a 3,5-diiodo tyrosine in position 23 in place of tyrosine was successfully dehalogenated in solvent mixture 0.1 M acetic acid: hexamethylphosphoramide: dimethylformamide (1 : 10 : 90, v/v) in the presence of palladium oxide and calcium carbonate. The product was obtained in 30% yield after purification by carboxymethyl cellulose chromatography. The tritiated hormone had a specific radioactivity of 46 Ci/mmol (80% of the theoretical value) and was as potent as synthetic human corticotropin in stimulating steroidogenesis and lipolysis.
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Ramachandran J, Farmer SW, Liles S, Li CH. Comparison of the steroidogenic and melanotropic activities of corticotropin, alpha-melanotropin and analogs with their lipolytic activities in rat and rabbit adipocytes. Biochim Biophys Acta Gen Subj 1976; 428:347-54. [PMID: 179570 DOI: 10.1016/0304-4165(76)90042-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability of alpha-melanotropin and a series of synthetic peptides related to adrenocorticotropin (ACTH) to stimulate steroidogenesis in isolated rat adrenal cells, melanin dispersion in frog melanophores and lipolysis in rat and rabbit fat cells have been studied. It was found that the steroidogenic activity closely paralleled the lipolytic activity of these peptides in rat fat cells, whereas the melanocyte stimulating activity paralleled the lipolytic activity in rabbit fat cells. These results indicate that the structural requirements for stimulating steroidogenesis in isolated rat adrenal cells and lipolysis in isolated rat fat cells are quite similar. The structural features required for eliciting lipolysis in rabbit fat cells appear to be very similar to those necessary for stimulating frog melanophores. The possibility that regulation of lipid metabolism in the rabbit may be a new function acquired by melanotropin is discussed.
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