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DiGiacomo K, Simpson S, Leury BJ, Dunshea FR. Dietary Betaine Impacts Metabolic Responses to Moderate Heat Exposure in Sheep. Animals (Basel) 2023; 13:1691. [PMID: 37238121 PMCID: PMC10215872 DOI: 10.3390/ani13101691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 05/16/2023] [Accepted: 05/18/2023] [Indexed: 05/28/2023] Open
Abstract
Dietary betaine supplementation can ameliorate physiological responses to heat exposure (HE) in sheep. This experiment measured metabolic responses to glucose (intravenous glucose tolerance, IVGTT), insulin (insulin tolerance test, ITT), and adrenocorticotropic hormone (ACTH) challenges in Merino ewes (n = 36, 39.7 kg) maintained at thermoneutral (TN, 21 °C) or HE (18-43 °C) and supplemented with either 0, 2, or 4 g/day dietary betaine (n = 6 per group). Sheep had ad libitum access to water and were pair-fed such that the intake of the TN sheep mimicked that of the HE sheep. After 21 days of treatment, sheep were fitted with jugular catheters and subjected to consecutive daily challenges (IVGTT, ITT, and ACTH, d 21-23, respectively), followed by skeletal muscle and subcutaneous adipose tissue biopsy collections for gene expression analysis (d 24). The HE-treated sheep had a greater insulin:glucose ratio (p = 0.033), a greater estimated homeostatic model assessment of insulin resistance (HOMAIR; p = 0.029), and a reduced revised quantitative insulin sensitivity check index (RQUICKI; p = 0.015). Sheep fed betaine (2 + 4 g/day) had a greater basal plasma insulin (p = 0.017) and a reduced basal non-esterified fatty acid (NEFA; p = 0.036) concentration, while the RQUICKI was reduced (p = 0.001) in sheep fed betaine. The results suggested that betaine supplementation alters lipid metabolism by potentially improving insulin signaling, although these responses differ between TN and HE conditions. There was no other impact of temperature or dietary treatments on the tissue gene expressions measured. Our results support the notion that betaine, in part, acts to modify lipid metabolism.
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Affiliation(s)
- Kristy DiGiacomo
- School of Agriculture, Food and Ecosystem Science, Faculty of Science, The University of Melbourne, Parkville, VIC 3010, Australia (B.J.L.); (F.R.D.)
| | - Sarah Simpson
- School of Agriculture, Food and Ecosystem Science, Faculty of Science, The University of Melbourne, Parkville, VIC 3010, Australia (B.J.L.); (F.R.D.)
| | - Brian J. Leury
- School of Agriculture, Food and Ecosystem Science, Faculty of Science, The University of Melbourne, Parkville, VIC 3010, Australia (B.J.L.); (F.R.D.)
| | - Frank R. Dunshea
- School of Agriculture, Food and Ecosystem Science, Faculty of Science, The University of Melbourne, Parkville, VIC 3010, Australia (B.J.L.); (F.R.D.)
- Faculty of Biological Sciences, The University of Leeds, Leeds LS2 9JT, UK
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2
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De Jesus AN, Henry BA. The role of oestrogen in determining sexual dimorphism in energy balance. J Physiol 2023; 601:435-449. [PMID: 36117117 PMCID: PMC10092637 DOI: 10.1113/jp279501] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 07/26/2022] [Indexed: 02/03/2023] Open
Abstract
Energy balance is determined by caloric intake and the rate at which energy is expended, with the latter comprising resting energy expenditure, physical activity and adaptive thermogenesis. The regulation of both energy intake and expenditure exhibits clear sexual dimorphism, with young women being relatively protected against weight gain and the development of cardiometabolic diseases. Preclinical studies have indicated that females are more sensitive to the satiety effects of leptin and insulin compared to males. Furthermore, females have greater thermogenic activity than males, whereas resting energy expenditure is generally higher in males than females. In addition to this, in post-menopausal women, the decline in sex steroid concentration, particularly in oestrogen, is associated with a shift in the distribution of adipose tissue and overall increased propensity to gain weight. Oestrogens are known to regulate energy balance and weight homeostasis via effects on both food intake and energy expenditure. Indeed, 17β-oestradiol treatment increases melanocortin signalling in the hypothalamus to cause satiety. Furthermore, oestrogenic action at the ventromedial hypothalamus has been linked with increased energy expenditure in female mice. We propose that oestrogen action on energy balance is multi-faceted and is fundamental to determining sexual dimorphism in weight control. Furthermore, evidence suggests that the decline in oestrogen levels leads to increased risk of weight gain and development of cardiometabolic disease in women across the menopausal transition.
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Affiliation(s)
- Anne Nicole De Jesus
- Metabolism, Obesity and Diabetes Program, Biomedicine, Discovery Institute, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Belinda A Henry
- Metabolism, Obesity and Diabetes Program, Biomedicine, Discovery Institute, Department of Physiology, Monash University, Clayton, Victoria, Australia
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3
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Ji K, Jiao D, Yang G, Degen AA, Zhou J, Liu H, Wang W, Cong H. Transcriptome analysis revealed potential genes involved in thermogenesis in muscle tissue in cold-exposed lambs. Front Genet 2022; 13:1017458. [PMID: 36338953 PMCID: PMC9634817 DOI: 10.3389/fgene.2022.1017458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 10/05/2022] [Indexed: 11/28/2022] Open
Abstract
Cold tolerance is an important trait for sheep raised at high altitudes. Muscle tissue, comprising 30–40% of the total body mass, produces heat during cold exposure. However, little is known about the genetic mechanisms of this tissue and its role in thermogenesis in lambs. We examined genes in skeletal muscle tissue in a cold-adapted sheep breed, Altay, and a cold-intolerant sheep breed, Hu, when exposed to low air temperature. Three ewe-lambs of each breed were maintained at −5°C and three ewe-lambs of each breed were maintained at 20°C. After cold exposure for 25 days, the longissimus dorsi of each lamb was collected, and transcriptome profiles were sequenced and analyzed. The results of RNA-seq showed that the average reads among the four groups were 11.0 Gbase. The genome mapping rate averaged 88.1% and the gene mapping rate averaged 82.5%. The analysis of differentially expressed genes (DEGs) indicated that the peroxisome proliferator-activated receptors (PPAR), cAMP, and calcium signaling pathways and muscle contraction in muscle tissue were linked to thermogenesis in cold-exposed lambs. Furthermore, PCK1 (phosphoenolpyruvate carboxykinase1) increased glyceroneogenesis in cold-exposed Altay lambs, and APOC3 (apolipoprotein C3), LPL (lipoprotein lipase), and FABP4 (fatty acid binding protein 4, adipocyte) were involved in the intake and transport of free fatty acids. In Hu sheep, cAMP biosynthesis from ATP hydrolysis was regulated by ADCY10 (adenylate cyclase) and ADORA2a (adenosine A2a receptor). Skeletal muscle contraction was regulated by MYL2 (myosin light chain 2). In conclusion, cold exposure altered the expression level of genes involved in heat production in muscle tissue. Some potential mechanisms were revealed, including calcium ion transport in the calcium signaling pathway, fatty acid metabolism in the PPAR signaling pathway, and cAMP biosynthesis in the cAMP signaling pathway. This study implied that skeletal muscle plays an important role in thermoregulation in lambs.
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Affiliation(s)
- Kaixi Ji
- Key Laboratory of Stress Physiology and Ecology of Gansu Province, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Dan Jiao
- Key Laboratory of Stress Physiology and Ecology of Gansu Province, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China
| | - Guo Yang
- Key Laboratory of Stress Physiology and Ecology of Gansu Province, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China
- *Correspondence: Guo Yang,
| | - Abraham Allan Degen
- Desert Animal Adaptations and Husbandry, Wyler Department of Dryland Agriculture, Blaustein Institutes for Desert Research, Ben-Gurion University of Negev, Beer Sheva, Israel
| | - Jianwei Zhou
- State Key Laboratory of Grassland and Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Hu Liu
- College of Ecology, Lanzhou University, Lanzhou, China
| | - Wenqiang Wang
- College of Ecology, Lanzhou University, Lanzhou, China
| | - Haitao Cong
- Dongying Modern Animal Husbandry Development Service Center, Dongying, China
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4
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Bal NC, Gupta SC, Pant M, Sopariwala DH, Gonzalez-Escobedo G, Turner J, Gunn JS, Pierson CR, Harper SQ, Rafael-Fortney JA, Periasamy M. Is Upregulation of Sarcolipin Beneficial or Detrimental to Muscle Function? Front Physiol 2021; 12:633058. [PMID: 33732165 PMCID: PMC7956958 DOI: 10.3389/fphys.2021.633058] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/21/2021] [Indexed: 11/25/2022] Open
Abstract
Sarcolipin (SLN) is a regulator of sarco/endo plasmic reticulum Ca2+-ATPase (SERCA) pump and has been shown to be involved in muscle nonshivering thermogenesis (NST) and energy metabolism. Interestingly, SLN expression is significantly upregulated both during muscle development and in several disease states. However, the significance of altered SLN expression in muscle patho-physiology is not completely understood. We have previously shown that transgenic over-expression of SLN in skeletal muscle is not detrimental, and can promote oxidative metabolism and exercise capacity. In contrast, some studies have suggested that SLN upregulation in disease states is deleterious for muscle function and ablation of SLN can be beneficial. In this perspective article, we critically examine both published and some new data to determine the relevance of SLN expression to disease pathology. The new data presented in this paper show that SLN levels are induced in muscle during systemic bacterial (Salmonella) infection or lipopolysaccharides (LPS) treatment. We also present data showing that SLN expression is significantly upregulated in different types of muscular dystrophies including myotubular myopathy. These data taken together reveal that upregulation of SLN expression in muscle disease is progressive and increases with severity. Therefore, we suggest that increased SLN expression should not be viewed as the cause of the disease; rather, it is a compensatory response to meet the higher energy demand of the muscle. We interpret that higher SLN/SERCA ratio positively modulate cytosolic Ca2+ signaling pathways to promote mitochondrial biogenesis and oxidative metabolism to meet higher energy demand in muscle.
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Affiliation(s)
- Naresh C Bal
- School of Biotechnology, KIIT University, Bhubaneswar, India
| | - Subash C Gupta
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States.,Department of Biochemistry, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Meghna Pant
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States
| | - Danesh H Sopariwala
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States
| | - Geoffrey Gonzalez-Escobedo
- Departments of Microbiology and Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States
| | - Joanne Turner
- Departments of Microbiology and Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States.,Texas Biomedical Research Institute, San Antonio, TX, United States
| | - John S Gunn
- Departments of Microbiology and Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States.,Center for Microbial Pathogenesis, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH, United States
| | - Christopher R Pierson
- Department of Pathology and Laboratory Medicine, Nationwide Children's Hospital, Columbus, OH, United States.,Department of Pathology, The Ohio State University, Columbus, OH, United States.,Department of Biomedical Education and Anatomy, The Ohio State University, Columbus, OH, United States
| | - Scott Q Harper
- Department of Laboratory Medicine, Nationwide Children's Hospital, Columbus, OH, United States
| | - Jill A Rafael-Fortney
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States
| | - Muthu Periasamy
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States.,Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
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5
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Siemienowicz K, Rae MT, Howells F, Anderson C, Nicol LM, Franks S, Duncan WC. Insights into Manipulating Postprandial Energy Expenditure to Manage Weight Gain in Polycystic Ovary Syndrome. iScience 2020; 23:101164. [PMID: 32464593 PMCID: PMC7256642 DOI: 10.1016/j.isci.2020.101164] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/08/2020] [Accepted: 05/11/2020] [Indexed: 11/30/2022] Open
Abstract
Women with polycystic ovary syndrome (PCOS) are more likely to be obese and have difficulty in losing weight. They demonstrate an obesity-independent deficit in adaptive energy expenditure. We used a clinically realistic preclinical model to investigate the molecular basis for the reduced postprandial thermogenesis (PPT) and develop a therapeutic strategy to normalize this deficit. Sheep exposed to increased androgens before birth develop the clinical features of PCOS. In adulthood they develop obesity and demonstrate an obesity-independent reduction in PPT. This is associated with reduced adipose tissue uncoupling protein expression and adipose tissue noradrenaline concentrations. These sheep are insulin resistant with reduced insulin signaling in the brain. Increasing brain insulin concentrations using intranasal insulin administration increased PPT in PCOS sheep without any effects on blood glucose concentrations. Intranasal insulin administration with food is a potential novel strategy to improve adaptive energy expenditure and normalize the responses to weight loss strategies in women with PCOS. Obesity can be prenatally programmed by androgens in an ovine model of PCOS This model has the same deficit in postprandial energy expenditure as women with PCOS Reduced adipose tissue thermogenesis links to lower central insulin signaling Therapeutic intranasal insulin raises postprandial energy expenditure in PCOS sheep
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Affiliation(s)
- Katarzyna Siemienowicz
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh EH16 4TJ, UK; School of Applied Sciences, Edinburgh Napier University, Edinburgh EH11 4BN, UK
| | - Michael T Rae
- School of Applied Sciences, Edinburgh Napier University, Edinburgh EH11 4BN, UK
| | - Fiona Howells
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Chloe Anderson
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Linda M Nicol
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh EH16 4TJ, UK
| | - Stephen Franks
- Institute of Reproductive and Developmental Biology, Imperial College, London W12 0HS, UK
| | - William C Duncan
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, The University of Edinburgh, Edinburgh EH16 4TJ, UK.
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6
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Gregg BA, Parker PA, Waller KM, Schneider LG, Garcia M, Bradford B, Daniel JA, Whitlock BK. Effects of central and peripheral administration of an acute-phase protein, α-1-acid-glycoprotein, on feed intake and rectal temperature in sheep. J Anim Sci 2019; 97:4783-4791. [PMID: 31679022 PMCID: PMC6915238 DOI: 10.1093/jas/skz336] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 10/29/2019] [Indexed: 12/21/2022] Open
Abstract
In rodents, an acute-phase protein, α-1-acid-glycoprotein (AGP), was shown to provide a link between inflammation and suppression of feed intake by acting as a leptin receptor agonist. The objective of this study was to determine the effects of AGP on feed intake and rectal temperature in sheep. Ewes were ovariectomized, implanted with a cannula into a lateral ventricle of the brain, and kept indoors in individual pens. Feed intake and rectal temperature were determined for sheep in all experiments. In the first experiment, ewes (n = 4) received 1 of 4 treatments [0 (control), 0.012 (low), 0.06 (medium), or 0.30 (high) mg/kg BW AGP] into the lateral ventricle (ICV). All sheep received all treatments in a Latin square design balanced for carryover effects with 10 d between treatments. In the second experiment, ewes (n = 10) received 1 of 2 treatments (0 and 3 mg/kg BW of AGP) intravenously (IV) in a completely randomized design. In the third experiment, ewes (n = 19) received peripheral treatments (IV) of an antipyretic [0 (control) or 2.2 mg/kg BW flunixin meglumine (FLU)] 30 min before receiving central AGP [0 (control) or 0.3 mg/kg BW of AGP] in a completely randomized design. All data were analyzed using a mixed model analysis of variance and tested for effects of treatment, time, and the interaction of treatment and time. Cumulative 48-h feed intake after administration of treatments was also determined. In the first experiment, there was no effect of ICV treatment (P = 0.37) on feed intake rate or on cumulative feed intake (P = 0.31). There was an effect of ICV treatment (P = 0.002) on rectal temperatures, which were greater (P < 0.05) after the high dose of centrally administered AGP. In the second experiment, there was no effect of AGP administration IV on feed intake rate (P = 0.98), on cumulative feed intake (P = 0.41) or on rectal temperature (P = 0.71). In the third experiment, there was an effect of central AGP treatment (P < 0.0001) and an interaction of central AGP and time (P < 0.0001) on rectal temperature, whereas FLU had no effect (P = 0.93), demonstrating that AGP increased rectal temperatures regardless of antipyretic treatment. These results indicate that central AGP increases rectal temperature in sheep by pathways that do not involve prostaglandins. Further research is needed to determine whether AGP may be an important integrator of energy balance and inflammation.
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Affiliation(s)
- Brittany A Gregg
- College of Veterinary Medicine, University of Tennessee, Knoxville, TN
- Department of Animal Science, University of Tennessee, Knoxville, TN
| | - Paxton A Parker
- College of Veterinary Medicine, University of Tennessee, Knoxville, TN
| | - Kathryn M Waller
- College of Veterinary Medicine, University of Tennessee, Knoxville, TN
| | | | - Miriam Garcia
- Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS
| | - Barry Bradford
- Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS
| | - Joseph A Daniel
- School of Mathematical and Natural Sciences, Berry College, Mount Berry, GA
| | - Brian K Whitlock
- College of Veterinary Medicine, University of Tennessee, Knoxville, TN
- Department of Animal Science, University of Tennessee, Knoxville, TN
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7
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Jorquera-Chavez M, Fuentes S, Dunshea FR, Jongman EC, Warner RD. Computer vision and remote sensing to assess physiological responses of cattle to pre-slaughter stress, and its impact on beef quality: A review. Meat Sci 2019; 156:11-22. [PMID: 31121361 DOI: 10.1016/j.meatsci.2019.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 05/04/2019] [Accepted: 05/06/2019] [Indexed: 10/26/2022]
Abstract
Pre-slaughter stress is well-known to affect meat quality of beef carcasses and methods have been developed to assess this stress. However, development of more practical and less invasive methods are required in order to assess the response of cattle to pre-slaughter stressors, which will potentially also assist with the prediction of beef quality. This review outlines the importance of pre-slaughter stress as well as existing and emerging technologies for quantification of the pre-slaughter stress. The review includes; i) indicators of meat quality and how they are affected by pre-slaughter stress in cattle, ii) contact techniques that have been commonly used to measure stress indicators in animals, iii) remotely sensed imagery techniques recently used as non-invasive methods to monitor physiological and behavioural parameters and iv) potential implementation of remotely sensed imagery data to perform contactless assessment of physiological measurements, which could be related to the pre-slaughter stress, as well as to the indicators of beef quality. Relevance to industry, conclusions and recommendations for research are included.
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Affiliation(s)
- Maria Jorquera-Chavez
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia.
| | - Sigfredo Fuentes
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Frank R Dunshea
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Ellen C Jongman
- Animal Welfare Science Centre, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Robyn D Warner
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC 3010, Australia
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8
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Fuller-Jackson JP, Henry BA. Adipose and skeletal muscle thermogenesis: studies from large animals. J Endocrinol 2018; 237:R99-R115. [PMID: 29703782 DOI: 10.1530/joe-18-0090] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 04/05/2018] [Indexed: 12/30/2022]
Abstract
The balance between energy intake and energy expenditure establishes and preserves a 'set-point' body weight. The latter is comprised of three major components including metabolic rate, physical activity and thermogenesis. Thermogenesis is defined as the cellular dissipation of energy via heat production. This process has been extensively characterised in brown adipose tissue (BAT), wherein uncoupling protein 1 (UCP1) creates a proton leak across the inner mitochondrial membrane, diverting protons away from ATP synthesis and resulting in heat dissipation. In beige adipocytes and skeletal muscle, thermogenesis can occur independent of UCP1. Beige adipocytes have been shown to produce heat via UCP1 as well as via both futile creatine and calcium cycling pathways. On the other hand, the UCP1 homologue UCP3 is abundant in skeletal muscle and post-prandial thermogenesis has been associated with UCP3 and the futile calcium cycling. This review will focus on the differential contributions of adipose tissue and skeletal muscle in determining total thermogenic output and energy expenditure in large mammals. Sheep and pigs do not have a circumscribed brown fat depot but rather possess white fat depots that contain brown and beige adipocytes interspersed amongst white adipose tissue. This is representative of humans, where brown, beige and white adipocytes have been identified in the neck and supraclavicular regions. This review will describe the mechanisms of thermogenesis in pigs and sheep and the relative roles of skeletal muscle and adipose tissue thermogenesis in controlling body weight in larger mammals.
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Affiliation(s)
| | - Belinda A Henry
- Metabolism, Diabetes and Obesity Program, Monash Biomedicine Discovery Institute, Department of Physiology, Monash University, Clayton, Victoria, Australia
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9
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Smith JT, Roseweir A, Millar M, Clarke IJ, Millar RP. Stimulation of growth hormone by kisspeptin antagonists in ewes. J Endocrinol 2018; 237:165-173. [PMID: 29549187 DOI: 10.1530/joe-18-0074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 03/15/2018] [Indexed: 11/08/2022]
Abstract
Kisspeptin signalling is indispensable for fertility, stimulating gonadotropin-releasing hormone (GnRH) secretion and mediating gonadal steroid feedback on GnRH neurons. Moreover, kisspeptin neurons have been implicated in other non-reproductive neuroendocrine roles. Kisspeptin appears to also regulate growth hormone secretion but much of the data appear contradictory. We sought to clarify a potential role of kisspeptin in growth hormone (GH) regulation by examining the effect of kisspeptin antagonists on GH secretion in ewes under various physiological conditions. Our data show clear and robust increases in GH secretion following lateral ventricle or third ventricle infusion of kisspeptin antagonists p-234 and p-271 in either ovariectomized or anestrous ewes. Central infusion of kisspeptin-10 had no effect on GH secretion. To determine the level at which kisspeptin may influence GH secretion, we examined expression of the cognate kisspeptin receptor, GPR54, in pituitary cells and showed by immunocytochemistry that the majority of somatotropes express GPR54 while expression was largely negative in other pituitary cells. Overall, we have demonstrated that blocking kisspeptin signalling by antagonists stimulates GH secretion in ewes and that this is likely mediated by inhibiting endogenous kisspeptin activation of GPR54 expressed on somatotropes. The findings suggest that endogenous kisspeptin inhibits GH secretion through GPR54 expressed on somatotropes.
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Affiliation(s)
- J T Smith
- School of Human SciencesThe University of Western Australia, Perth, Western Australia, Australia
| | - A Roseweir
- Academic Unit of SurgerySchool of Medicine, University of Glasgow, Royal Infirmary, Glasgow, UK
- Unit of Experimental TherapeuticsInstitute of Cancer Sciences, University of Glasgow Glasgow, UK
| | - M Millar
- Queen's Medical Research InstituteUniversity of Edinburgh, Edinburgh, UK
| | - I J Clarke
- Department of PhysiologyMonash University, Clayton, Victoria, Australia
| | - R P Millar
- Centre for NeuroendocrinologyDepartment of Immunology and Physiology, University of Pretoria, Pretoria, South Africa
- Institute for Infectious Diseases and Molecular MedicineUniversity of Cape Town, Cape Town, South Africa
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10
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Côté I, Sakarya Y, Green SM, Morgan D, Carter CS, Tümer N, Scarpace PJ. iBAT sympathetic innervation is not required for body weight loss induced by central leptin delivery. Am J Physiol Endocrinol Metab 2018; 314:E224-E231. [PMID: 29089334 PMCID: PMC5899217 DOI: 10.1152/ajpendo.00219.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We evaluated the contribution of brown adipose tissue (BAT) sympathetic innervation on central leptin-mediated weight loss. In a short- and long-term study, F344BN rats were submitted to either a denervation of interscapular BAT (Denervated) or a sham operation (Sham). Animals from each group received the Ob (Leptin) or green fluorescent protein (GFP; Control) gene through a single injection of recombinant adeno-associated virus delivered centrally. Changes in body weight were recorded for 14 or 35 days, after which adipose tissues and skeletal muscles were weighed. In both studies, hypothalamic phosphorylated STAT3 (P-STAT3) was significantly higher in Sham-Leptin and Denervated-Leptin groups compared with their respective Control groups ( P < 0.01), indicating that leptin signaling was enhanced at the end point. We measured uncoupling protein 1 (UCP1), a marker of BAT thermogenic activity, and found a significant induction in Leptin in Sham animals ( P < 0.001) but not in Denervated animals, demonstrating that BAT UCP1 protein was only induced in Sham rats. Both Sham-Leptin and Denervated-Leptin rats lost ~15% of their initial body weight ( P < 0.001) by day 14 and reached a maximum of 18% body weight loss that stabilized over week 3 of treatment, indicating that sympathetic outflow to BAT is not required for leptin-mediated weight loss. In summary, interscapular BAT (iBAT) denervation did not prevent body weight loss following central leptin gene delivery. The present data show that sympathetic innervation of iBAT is not essential for leptin-induced body weight loss.
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Affiliation(s)
- Isabelle Côté
- Department of Pharmacology and Therapeutics, University of Florida , Gainesville, Florida
| | - Yasemin Sakarya
- Department of Pharmacology and Therapeutics, University of Florida , Gainesville, Florida
| | - Sara M Green
- Department of Pharmacology and Therapeutics, University of Florida , Gainesville, Florida
| | - Drake Morgan
- Department of Psychiatry, University of Florida , Gainesville, Florida
| | - Christy S Carter
- Department of Aging and Geriatric Research, University of Florida , Gainesville, Florida
| | - Nihal Tümer
- Department of Pharmacology and Therapeutics, University of Florida , Gainesville, Florida
| | - Philip J Scarpace
- Department of Pharmacology and Therapeutics, University of Florida , Gainesville, Florida
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11
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Clarke IJ, Li Q, Henry BA, Millar RP. Continuous Kisspeptin Restores Luteinizing Hormone Pulsatility Following Cessation by a Neurokinin B Antagonist in Female Sheep. Endocrinology 2018; 159:639-646. [PMID: 29126131 DOI: 10.1210/en.2017-00737] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 10/27/2017] [Indexed: 11/19/2022]
Abstract
Pulsatile secretion of the gonadotropin-releasing hormone (GnRH) drives pulsatile secretion of the luteinizing hormone (LH), with evidence that this depends on kisspeptin (Kiss) input to GnRH neurons. Kiss administration causes acute GnRH/LH secretion, and electrophysiological data suggest that Kiss neurons may act in a phasic manner to drive GnRH secretion, but there is not definitive evidence for this. The product of the Kiss-1 gene is proteolytically cleaved to smaller products, and the 10 amino acid C-terminal product (Kiss-10) displays full bioactivity. We have shown previously that continuous delivery of Kiss-10 to anestrous ewes can cause a surge in GnRH secretion and ovulation and increases LH pulse frequency in humans. Here, we tested the hypothesis that continuous Kiss-10 delivery can support pulsatile GnRH/LH secretion in the sheep. Neurokinin B (NKB) provides positive drive to Kiss neurons, so we therefore infused an NKB antagonist (ANT-08) intracerebroventricularly to induce cessation of pulsatile GnRH/LH secretion, with or without concomitant continuous Kiss-10 infusion. ANT-08 suppressed GnRH/LH pulsatility, which was immediately restored with continuous Kiss-10 infusion. These data support the notion that Kiss-10 action is downstream of NKB signaling and that continuous Kiss-10 stimulation of GnRH neurons is sufficient to support a pulsatile pattern of GnRH/LH secretion. This offers further support to the theory that GnRH pulse generation is intrinsic to GnRH neurons and that pulsatile GnRH release can be affected with continuous stimulation by Kiss-10.
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Affiliation(s)
- Iain J Clarke
- Neuroscience Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Qun Li
- Neuroscience Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Belinda A Henry
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
- Metabolic Disease and Obesity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Robert P Millar
- Division of Medical Biochemistry, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- Department of Physiology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
- Department of Immunology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
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12
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Henry BA, Pope M, Birtwistle M, Loughnan R, Alagal R, Fuller-Jackson JP, Perry V, Budge H, Clarke IJ, Symonds ME. Ontogeny and Thermogenic Role for Sternal Fat in Female Sheep. Endocrinology 2017; 158:2212-2225. [PMID: 28431116 DOI: 10.1210/en.2017-00081] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 04/14/2017] [Indexed: 02/05/2023]
Abstract
Brown adipose tissue acting through a unique uncoupling protein (UCP1) has a critical role in preventing hypothermia in newborn sheep but is then thought to rapidly disappear during postnatal life. The extent to which the anatomical location of fat influences postnatal development and thermogenic function in adulthood, particularly following feeding, is unknown, and we examined both in our study. Changes in gene expression of functionally important pathways (i.e., thermogenesis, development, adipogenesis, and metabolism) were compared between sternal and retroperitoneal fat depots together with a representative skeletal muscle over the first month of postnatal life, coincident with the loss of brown fat and the accumulation of white fat. In adult sheep, implanted temperature probes were used to characterize the thermogenic response of fat and muscle to feeding and the effects of reduced or increased adiposity. UCP1 was more abundant in sternal fat than in retroperitoneal fat and was retained only in the sternal depot of adults. Distinct differences in the abundance of gene pathway markers were apparent between tissues, with sternal fat exhibiting some similarities with muscle that were not apparent in the retroperitoneal depot. In adults, the postprandial rise in temperature was greater and more prolonged in sternal fat than in retroperitoneal fat and muscle, a difference that was maintained with altered adiposity. In conclusion, sternal adipose tissue retains UCP1 into adulthood, when it shows a greater thermogenic response to feeding than do muscle and retroperitoneal fat. Sternal fat may be more amenable to targeted interventions that promote thermogenesis in large mammals.
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Affiliation(s)
- Belinda A Henry
- Metabolic Disease and Obesity Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Mark Pope
- Early Life Research Unit, Division of Child Health, Obstetrics & Gynaecology, School of Medicine, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Mark Birtwistle
- Early Life Research Unit, Division of Child Health, Obstetrics & Gynaecology, School of Medicine, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Rachael Loughnan
- Metabolic Disease and Obesity Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Reham Alagal
- Early Life Research Unit, Division of Child Health, Obstetrics & Gynaecology, School of Medicine, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - John-Paul Fuller-Jackson
- Metabolic Disease and Obesity Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Viv Perry
- School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington LE12 5RD, United Kingdom
| | - Helen Budge
- Early Life Research Unit, Division of Child Health, Obstetrics & Gynaecology, School of Medicine, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Iain J Clarke
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Michael E Symonds
- Early Life Research Unit, Division of Child Health, Obstetrics & Gynaecology, School of Medicine, University of Nottingham, Nottingham NG7 2UH, United Kingdom
- Nottingham Digestive Disease Centre and Biomedical Research Unit, School of Medicine, Queen's Medical Centre, The University of Nottingham, Nottingham NG7 2UH, United Kingdom
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13
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Enriori PJ, Chen W, Garcia-Rudaz MC, Grayson BE, Evans AE, Comstock SM, Gebhardt U, Müller HL, Reinehr T, Henry BA, Brown RD, Bruce CR, Simonds SE, Litwak SA, McGee SL, Luquet S, Martinez S, Jastroch M, Tschöp MH, Watt MJ, Clarke IJ, Roth CL, Grove KL, Cowley MA. α-Melanocyte stimulating hormone promotes muscle glucose uptake via melanocortin 5 receptors. Mol Metab 2016; 5:807-822. [PMID: 27688995 PMCID: PMC5034615 DOI: 10.1016/j.molmet.2016.07.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 07/26/2016] [Accepted: 07/28/2016] [Indexed: 01/21/2023] Open
Abstract
Objective Central melanocortin pathways are well-established regulators of energy balance. However, scant data exist about the role of systemic melanocortin peptides. We set out to determine if peripheral α-melanocyte stimulating hormone (α-MSH) plays a role in glucose homeostasis and tested the hypothesis that the pituitary is able to sense a physiological increase in circulating glucose and responds by secreting α-MSH. Methods We established glucose-stimulated α-MSH secretion using humans, non-human primates, and mouse models. Continuous α-MSH infusions were performed during glucose tolerance tests and hyperinsulinemic-euglycemic clamps to evaluate the systemic effect of α-MSH in glucose regulation. Complementary ex vivo and in vitro techniques were employed to delineate the direct action of α-MSH via the melanocortin 5 receptor (MC5R)–PKA axis in skeletal muscles. Combined treatment of non-selective/selective phosphodiesterase inhibitor and α-MSH was adopted to restore glucose tolerance in obese mice. Results Here we demonstrate that pituitary secretion of α-MSH is increased by glucose. Peripheral α-MSH increases temperature in skeletal muscles, acts directly on soleus and gastrocnemius muscles to significantly increase glucose uptake, and enhances whole-body glucose clearance via the activation of muscle MC5R and protein kinase A. These actions are absent in obese mice, accompanied by a blunting of α-MSH-induced cAMP levels in skeletal muscles of obese mice. Both selective and non-selective phosphodiesterase inhibition restores α-MSH induced skeletal muscle glucose uptake and improves glucose disposal in obese mice. Conclusion These data describe a novel endocrine circuit that modulates glucose homeostasis by pituitary α-MSH, which increases muscle glucose uptake and thermogenesis through the activation of a MC5R-PKA-pathway, which is disrupted in obesity. Glucose stimulates α-MSH release from the pituitary. Systemic α-MSH drives glucose disposal and thermogenesis in skeletal muscles. α-MSH acts on MC5R expressed on skeletal muscles and activate cAMP-PKA pathway. The combined treatment of nonselective or selective PDE 4 inhibitor and α-MSH ameliorates glucose intolerance in obese mice.
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Affiliation(s)
- Pablo J Enriori
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Weiyi Chen
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Maria C Garcia-Rudaz
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | | | - Anne E Evans
- Division Neuroscience, Oregon Health and Science University, Oregon, USA
| | - Sarah M Comstock
- Division Neuroscience, Oregon Health and Science University, Oregon, USA
| | - Ursel Gebhardt
- Department of Pediatrics, Vestische Children Hospital Datteln, University of Witten/Herdecke, Germany
| | - Hermann L Müller
- Department of Pediatrics, Vestische Children Hospital Datteln, University of Witten/Herdecke, Germany
| | - Thomas Reinehr
- Department of Pediatrics, Klinikum Oldenburg GmbH, Germany
| | - Belinda A Henry
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Russell D Brown
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Clinton R Bruce
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Stephanie E Simonds
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Sara A Litwak
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Sean L McGee
- Metabolic Research Unit, School of Medicine, Deakin University, Vic, Australia
| | - Serge Luquet
- Univ Paris Diderot, Sorbonne Paris Cité, Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, F-75205 Paris, France
| | - Sarah Martinez
- Univ Paris Diderot, Sorbonne Paris Cité, Unité de Biologie Fonctionnelle et Adaptative, CNRS UMR 8251, F-75205 Paris, France
| | - Martin Jastroch
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg & Division of Metabolic Diseases, Technische Universität, München, Germany
| | - Matthias H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg & Division of Metabolic Diseases, Technische Universität, München, Germany
| | - Matthew J Watt
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Iain J Clarke
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia
| | - Christian L Roth
- Division of Endocrinology, Seattle Children's Hospital Research Institute, WA, USA
| | - Kevin L Grove
- Division Neuroscience, Oregon Health and Science University, Oregon, USA
| | - Michael A Cowley
- Biomedical Discovery Institute/Department of Physiology, Monash University, Vic, Australia.
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14
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Hewagalamulage SD, Lee TK, Clarke IJ, Henry BA. Stress, cortisol, and obesity: a role for cortisol responsiveness in identifying individuals prone to obesity. Domest Anim Endocrinol 2016; 56 Suppl:S112-20. [PMID: 27345309 DOI: 10.1016/j.domaniend.2016.03.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 03/14/2016] [Accepted: 03/18/2016] [Indexed: 11/22/2022]
Abstract
There is a strong inter-relationship between activation of the hypothalamo-pituitary-adrenal axis and energy homeostasis. Patients with abdominal obesity have elevated cortisol levels. Furthermore, stress and glucocorticoids act to control both food intake and energy expenditure. In particular, glucocorticoids are known to increase the consumption of foods enriched in fat and sugar. It is well-known that, in all species, the cortisol response to stress or adrenocorticotropin is highly variable. It has now emerged that cortisol responsiveness is an important determinant in the metabolic sequelae to stress. Sheep that are characterized as high-cortisol responders (HRs) have greater propensity to weight gain and obesity than low-cortisol responders (LRs). This difference in susceptibility to become obese is associated with a distinct metabolic, neuroendocrine, and behavioral phenotype. In women and ewes, HR individuals eat more in response to stress than LR. Furthermore, HR sheep have impaired melanocortin signaling and reduced skeletal muscle thermogenesis. High-cortisol responder sheep exhibit reactive coping strategies, whereas LRs exhibit proactive coping strategies. This complex set of traits leads to increased food intake and reduced energy expenditure in HR and thus, predisposition to obesity. We predict that cortisol responsiveness may be used as a marker to identify individuals who are at risk of weight gain and subsequent obesity.
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Affiliation(s)
| | - T K Lee
- Department of Physiology, Monash University, VIC 3800, Australia
| | - I J Clarke
- Department of Physiology, Monash University, VIC 3800, Australia
| | - B A Henry
- Department of Physiology, Monash University, VIC 3800, Australia.
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15
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Henry BA, Loughnan R, Hickford J, Young IR, St John JC, Clarke I. Differences in mitochondrial DNA inheritance and function align with body conformation in genetically lean and fat sheep. J Anim Sci 2016; 93:2083-93. [PMID: 26020304 DOI: 10.2527/jas.2014-8764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Body weight and adiposity are determined by the balance between energy intake, energy expenditure, and nutrient deposition. We have identified differences in appetite-regulating peptides in sheep selectively bred to be either lean or fat, wherein gene expression for orexin and melanin-concentrating hormone are elevated in the lean group. Despite this, the underlying mechanisms leading to differences in body composition in the lean and fat lines remains unknown. We measured postprandial temperature in adipose tissue and muscle to ascertain whether a difference in thermogenesis is associated with the difference in body composition in genetically lean (n = 8) and fat (n = 12) ewes. Body weight was higher (P < 0.01) but percent fat mass was lower (P < 0.001) in the lean group. The percent lean mass was similar in lean and fat groups. Animals received intracerebroventricular cannulae and temperature probes implanted into the retroperitoneal fat and the hind-limb skeletal muscle (vastus lateralis). Animals were meal fed (1100-1600 h) to entrain postprandial thermogenesis. Food intake was similar between lean and fat animals. Postprandial thermogenesis was greater (P < 0.05) in the retroperitoneal adipose tissue of lean animals but not in skeletal muscle. Intracerebroventricular infusion of leptin reduced (P< 0.05) food intake by an equal extent in both groups. Postprandial expression of UCP1 mRNA was greater (P < 0.05) in retroperitoneal fat of lean animals, with similar UCP3 expression in skeletal muscle. Mitochondrial genome sequencing indicated haplotypic clustering in lean and fat animals within both the encoding and nonencoding regions. This demonstrates that differences in body composition may be underpinned by differences in thermogenesis, specifically within adipose tissue. Furthermore, thermogenic differences may be associated with specific mitochondrial DNA haplotypes, suggesting a strong genetic component inherited through the maternal lineage.
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16
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Fraser GL, Hoveyda HR, Clarke IJ, Ramaswamy S, Plant TM, Rose C, Millar RP. The NK3 Receptor Antagonist ESN364 Interrupts Pulsatile LH Secretion and Moderates Levels of Ovarian Hormones Throughout the Menstrual Cycle. Endocrinology 2015; 156:4214-25. [PMID: 26305889 DOI: 10.1210/en.2015-1409] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Women's health disorders such as uterine fibroids and endometriosis are currently treated by GnRH modulators that effectively suppress the hypothalamic-pituitary-gonadal axis. The neurokinin-3 receptor (NK3R) is an alternative target with an important role in the modulation of this axis. In this report, we demonstrate that systemic administration of an NK3R antagonist (ESN364) prolongs the LH interpulse interval in ovarectomized ewes and significantly lowers plasma LH and FSH concentrations in castrated nonhuman primates (Macaca fascicularis). Moreover, daily oral dosing of ESN364 throughout the menstrual cycle in M fascicularis lowered plasma estradiol levels in a dose-dependent manner, although nadir levels of estradiol were maintained well above menopausal levels. Nevertheless, estradiol levels during the follicular phase were sufficiently inhibited at all doses to preclude the triggering of ovulation as evidenced by the absence of the LH surge and failure of a subsequent luteal phase rise in plasma progesterone concentrations, consistent with the absence of normal cycle changes in the uterus. Apart from the point at surge, FSH levels were not altered over the course of the menstrual cycle. These effects of ESN364 were reversible upon cessation of drug treatment. Together these data support the proposed role of neurokinin B-NK3R signaling in the control of pulsatile GnRH secretion. Furthermore, in contrast to GnRH antagonists, NK3R antagonists induce a partial suppression of estradiol and thereby offer a viable therapeutic approach to the treatment of ovarian sex hormone disorders with a mitigated risk of menopausal-like adverse events in response to long-term drug exposure.
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Affiliation(s)
- Graeme L Fraser
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Hamid R Hoveyda
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Iain J Clarke
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Suresh Ramaswamy
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Tony M Plant
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Claudia Rose
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
| | - Robert P Millar
- Euroscreen SA (G.L.F., H.R.H.), 6041 Gosselies, Belgium; Department of Physiology (I.J.C.), Monash University, Clayton 3800, Victoria, Australia; Department of Obstetrics, Gynecology, and Reproductive Sciences (S.R., T.M.P.), University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; Covance Laboratories GmbH (C.R.), 48163 Münster, Germany; Mammal Research Unit (R.P.M.), University of Pretoria and Medical Research Center Receptor Biology Unit, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, 7701 Cape Town, South Africa
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Beneficial role of bitter melon supplementation in obesity and related complications in metabolic syndrome. J Lipids 2015; 2015:496169. [PMID: 25650336 PMCID: PMC4306384 DOI: 10.1155/2015/496169] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 12/05/2014] [Indexed: 02/06/2023] Open
Abstract
Diabetes, obesity, and metabolic syndrome are becoming epidemic both in developed and developing countries in recent years. Complementary and alternative medicines have been used since ancient era for the treatment of diabetes and cardiovascular diseases. Bitter melon is widely used as vegetables in daily food in Bangladesh and several other countries in Asia. The fruits extract of bitter melon showed strong antioxidant and hypoglycemic activities in experimental condition both in vivo and in vitro. Recent scientific evaluation of this plant extracts also showed potential therapeutic benefit in diabetes and obesity related metabolic dysfunction in experimental animals and clinical studies. These beneficial effects are mediated probably by inducing lipid and fat metabolizing gene expression and increasing the function of AMPK and PPARs, and so forth. This review will thus focus on the recent findings on beneficial effect of Momordica charantia extracts on metabolic syndrome and discuss its potential mechanism of actions.
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18
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Hewagalamulage SD, Clarke IJ, Young IR, Rao A, Henry BA. High cortisol response to adrenocorticotrophic hormone identifies ewes with reduced melanocortin signalling and increased propensity to obesity. J Neuroendocrinol 2015; 27:44-56. [PMID: 25315658 DOI: 10.1111/jne.12233] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 09/16/2014] [Accepted: 10/11/2014] [Indexed: 12/26/2022]
Abstract
We have identified female sheep that have either high (HR) or low (LR) cortisol responses to adrenocorticotrophin. On a high-energy diet, HR have greater propensity to weight gain and obesity, although the underlying mechanisms remain to be determined. Hypothalamic appetite-regulating peptides (ARP) exert reciprocal effects on food intake and energy expenditure. We aimed to quantify the expression and function of ARP in LR and HR ewes (n = 4 per group). Gene expression for neuropeptide Y (NPY), agouti-related peptide (AgRP) pro-opiomelanocortin (POMC), melanin-concentrating hormone (MCH), orexin and the melanocortin receptors (MC3R and MC4R) was measured by in situ hybridisation. Expression of NPY, AgRP and POMC was similar in HR and LR, although expression of orexin, MCH, MC3R and MC4R was higher (P < 0.05) in LR. Intracerebroventricular infusions of a low dose (50 μg/h) of NPY, α-melanocyte-stimulating hormone (αMSH), orexin and MCH were performed between 10.00 h and 16.00 h in meal-fed ewes (n = 6-7 per group). Skeletal muscle and retroperitoneal (RP) fat temperatures were recorded using dataloggers. Post-prandial thermogenesis in muscle was higher (P < 0.05) in LR. There was little effect of ARP infusion on muscle or fat temperature in either group. Infusion of these doses of NPY, MCH or orexin did not stimulate food intake in meal-fed ewes, although αMSH reduced (P < 0.01) food intake in LR only. Using 24-h ARP infusions with ad lib. feeding, NPY increased (P < 0.001) food intake in both groups but αMSH was only effective in LR (P < 0.05). In summary, we show that HR are resistant to the satiety effects of αMSH and this coincides with a reduced expression of both the MC3R and MC4R in the paraventricular nucleus of the hypothalamus. We conclude that an increased propensity to obesity in HR female sheep is associated with reduced melanocortin signalling.
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19
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Lee TK, Lee C, Bischof R, Lambert GW, Clarke IJ, Henry BA. Stress-induced behavioral and metabolic adaptations lead to an obesity-prone phenotype in ewes with elevated cortisol responses. Psychoneuroendocrinology 2014; 47:166-77. [PMID: 25001966 DOI: 10.1016/j.psyneuen.2014.05.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 04/26/2014] [Accepted: 05/21/2014] [Indexed: 11/17/2022]
Abstract
The underlying cause of predisposition to obesity is complex but one marker is cortisol responsiveness. Selection of sheep for high (HR) or low (LR) cortisol responses to adrenocorticotropin shows that HR are more likely to become obese. Increased propensity to obesity is associated with reduced skeletal muscle thermogenesis. We sought to determine whether metabolic or behavioral responses to stress also contribute to altered propensity to obesity in LR and HR. Animals (n=5-10/group) were exposed to 3 stressors and we measured food intake and thermogenesis (recorded with dataloggers implanted into muscle). Stressors were hypoglycaemia (0.125 units/kg insulin, IV), a barking dog and immune challenge (200 ng/kg lipopolysaccharide--LPS, IV). LR animals showed a greater catabolic state in response to both immune and psychosocial stressors. LPS reduced (P<0.01) food intake in both groups but LR showed a greater (P<0.05) reduction in food intake and a more substantial (P<0.05) rise in muscle temperature. Introduction of the barking dog reduced (P<0.05) food intake in LR only. These metabolic differences coincided with differences in cortisol responsiveness, where HR animals had increased (P<0.05) cortisol in response to both immune and psychosocial stressors. We also assessed behavior in the following paradigms: 1, isolation in the open field test; 2, response to a human intruder; and 3, food competition. LR had greater (P<0.05) activity, reduced fearfulness and displayed a proactive coping style of behavior. Thus we demonstrate that high cortisol responsiveness identifies animals with stress-induced metabolic and behavioral traits that may contribute to susceptibility to obesity.
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Affiliation(s)
- T Kevin Lee
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Caroline Lee
- CSIRO Animal, Food and Health Sciences, Armidale, NSW 2350, Australia
| | - Robert Bischof
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Gavin W Lambert
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria 3004, Australia; Central Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Iain J Clarke
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Belinda A Henry
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia.
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20
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Yau SW, Henry BA, Russo VC, McConell GK, Clarke IJ, Werther GA, Sabin MA. Leptin enhances insulin sensitivity by direct and sympathetic nervous system regulation of muscle IGFBP-2 expression: evidence from nonrodent models. Endocrinology 2014; 155:2133-43. [PMID: 24654786 DOI: 10.1210/en.2013-2099] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Leptin is produced from white adipose tissue and acts primarily to regulate energy balance. Obesity is associated with leptin resistance and increased circulating levels of leptin. Leptin has recently been shown to influence levels of IGF binding protein-2 (IGFBP-2), a protein that is reduced in obesity and type 2 diabetes. Overexpression of IGFBP-2 protects against obesity and type 2 diabetes. As such, IGFBP-2 signaling may represent a novel pathway by which leptin regulates insulin sensitivity. We sought to investigate how leptin regulates skeletal muscle IGFBP-2 levels and to assess the impact of this on insulin signaling and glucose uptake. In vitro experiments were undertaken in cultured human skeletal myotubes, whereas in vivo experiments assessed the effect of intracerebroventricular leptin on peripheral skeletal muscle IGFBP-2 expression and insulin sensitivity in sheep. Leptin directly increased IGFBP-2 mRNA and protein in human skeletal muscle through both signal transducer and activator of transcription-3 and phosphatidylinositol 3-kinase signaling, in parallel with enhanced insulin signaling. Silencing IGFBP-2 lowered leptin- and insulin-stimulated protein kinase B phosphorylation and glucose uptake. In in vivo experiments, intracerebroventricular leptin significantly increased hind-limb skeletal muscle IGFBP-2, an effect completely blocked by concurrent peripheral infusion of a β-adrenergic blocking agent. Sheep receiving central leptin showed improvements in glucose tolerance and circulating insulin levels after an iv glucose load. In summary, leptin regulates skeletal muscle IGFBP-2 by both direct peripheral and central (via the sympathetic nervous system) mechanisms, and these likely impact on peripheral insulin sensitivity and glucose metabolism.
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Affiliation(s)
- Steven W Yau
- Centre for Hormone Research (S.W.Y., V.C.R., G.A.W., M.A.S.), Murdoch Childrens Research Institute and Royal Children's Hospital, and Department of Paediatrics (S.W.Y., V.C.R., G.A.W., M.A.S.), University of Melbourne, Melbourne, Victoria 3052, Australia; Department of Physiology (S.W.Y., B.A.H., I.J.C., M.A.S.), Monash University, Melbourne, Victoria 3800, Australia; and Institute of Sport, Exercise and Active Living and the College of Health and Biomedicine (G.K.M.), Victoria University, Melbourne, Victoria 3011, Australia
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Clarke IJ. Interface between metabolic balance and reproduction in ruminants: focus on the hypothalamus and pituitary. Horm Behav 2014; 66:15-40. [PMID: 24568750 DOI: 10.1016/j.yhbeh.2014.02.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 02/13/2014] [Accepted: 02/15/2014] [Indexed: 01/24/2023]
Abstract
This article is part of a Special Issue "Energy Balance". The interface between metabolic regulators and the reproductive system is reviewed with special reference to the sheep. Even though sheep are ruminants with particular metabolic characteristics, there is a broad consensus across species in the way that the reproductive system is influenced by metabolic state. An update on the neuroendocrinology of reproduction indicates the need to account for the way that kisspeptin provides major drive to gonadotropin releasing hormone (GnRH) neurons and also mediates the feedback effects of gonadal steroids. The way that kisspeptin function is influenced by appetite regulating peptides (ARP) is considered. Another newly recognised factor is gonadotropin inhibitory hormone (GnIH), which has a dual function in that it suppresses reproductive function whilst also acting as an orexigen. Our understanding of the regulation of food intake and energy expenditure has expanded exponentially in the last 3 decades and historical perspective is provided. The function of the regulatory factors and the hypothalamic cellular systems involved is reviewed with special reference to the sheep. Less is known of these systems in the cow, especially the dairy cow, in which a major fertility issue has emerged in parallel with selection for increased milk production. Other endocrine systems--the hypothalamo-pituitary-adrenal axis, the growth hormone (GH) axis and the thyroid hormones--are influenced by metabolic state and are relevant to the interface between metabolic function and reproduction. Special consideration is given to issues such as season and lactation, where the relationship between metabolic hormones and reproductive function is altered.
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Affiliation(s)
- Iain J Clarke
- Monash University, Department of Physiology, Wellington Road, Clayton 3168, Australia.
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DiGiacomo K, Leury BJ, Dunshea FR. Potential nutritional strategies for the amelioration or prevention of high rigor temperature in cattle – a review. ANIMAL PRODUCTION SCIENCE 2014. [DOI: 10.1071/an13303] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Environmental conditions influence animal production from an animal performance perspective and at the carcass level post-slaughter. High rigor temperature occurs when the animal is hyperthermic pre-slaughter, and this leads to tougher meat. Hyperthermia can result from increased environmental temperature, exercise, stress or a combination of these factors. Consumer satisfaction with beef meat is influenced by the visual and sensory traits of the product when raw and cooked, with beef consumers commonly selecting tenderness of the product as the most important quality trait. High rigor temperature leads to a reduction in carcass and eating quality. This review examines some possible metabolic causes of hyperthermia, with focus on the importance of adipose tissue metabolism and the roles of insulin and leptin. Potential strategies for the amelioration or prevention of high rigor temperature are offered, including the use of dietary supplements such as betaine and chromium, anti-diabetic agents such as thiazolidinediones, vitamin D, and magnesium (Mg) to provide stress relief.
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Lee TK, Clarke IJ, John JS, Young IR, Leury BL, Rao A, Andrews ZB, Henry BA. High cortisol responses identify propensity for obesity that is linked to thermogenesis in skeletal muscle. FASEB J 2013; 28:35-44. [DOI: 10.1096/fj.13-238345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- T. Kevin Lee
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
| | - Iain J. Clarke
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
| | - Justin St. John
- Monash Institute of Medical ResearchMonash Medical CentreClaytonVictoriaAustralia
| | - I. Ross Young
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
| | - Brian L. Leury
- Melbourne School of Land and EnvironmentUniversity of MelbourneMelbourneVictoriaAustralia
| | - Alexandra Rao
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
| | - Zane B. Andrews
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
| | - Belinda A. Henry
- Department of PhysiologyMonash UniversityClaytonVictoriaAustralia
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Clarke SD, Clarke IJ, Rao A, Evans RG, Henry BA. Differential effects of acute and chronic estrogen treatment on thermogenic and metabolic pathways in ovariectomized sheep. Endocrinology 2013. [PMID: 23183185 DOI: 10.1210/en.2012-1758] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Estrogen is protective against weight gain, but the underlying mechanisms are not fully elucidated. We sought to characterize the effects of estrogen on energy expenditure in skeletal muscle and adipose tissue in ovariectomized sheep. Temperature probes were implanted into sc (gluteal) and visceral (retroperitoneal) fat depots and skeletal muscle of the hind limb (vastus lateralis). Food was available from 1100-1600 h to entrain postprandial thermogenesis. We characterized the effects of single (50 μg estradiol benzoate, im) and repeated (25 μg estradiol-17β, iv) injections as well as chronic (3 × 3 cm estradiol-17β implants for 7 d) treatment on heat production. A single injection of estrogen increased heat production in visceral fat and skeletal muscle, without an effect on food intake. Increased heat production in skeletal muscle was sustained by repeated estradiol-17β injections. On the other hand, continuous treatment reduced food intake but had no effect on thermogenesis. To determine possible mechanisms that underpin estradiol-17β-induced heat production, we measured femoral artery blood flow, the expression of uncoupling protein (UCP) mRNA and the phosphorylation of AMP-activated protein kinase and Akt in fat and muscle. There was little effect of either single or repeated injections of estradiol-17β on the expression of UCP1, -2, or -3 mRNA in visceral fat or skeletal muscle. Acute injection of estradiol-17β increased the phosphorylation of AMP-activated protein kinase and Akt in muscle only. Estradiol-17β treatment did not alter femoral artery blood flow. Thus, the stimulatory effect of estradiol-17β on thermogenesis in female sheep is dependent upon a pulsatile pattern of treatment and not constant continuous exposure.
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Affiliation(s)
- Scott D Clarke
- Research Fellow, Monash University, Physiology, Building 13F, Wellington Road, Clayton, Victoria 3168, Australia
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Traurig MT, Perez JM, Ma L, Bian L, Kobes S, Hanson RL, Knowler WC, Krakoff JA, Bogardus C, Baier LJ. Variants in the LEPR gene are nominally associated with higher BMI and lower 24-h energy expenditure in Pima Indians. Obesity (Silver Spring) 2012; 20:2426-30. [PMID: 22810975 PMCID: PMC3479320 DOI: 10.1038/oby.2012.159] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Genome-wide association studies (GWASs) have been used to search for susceptibility genes for type 2 diabetes and obesity in the Pima Indians, a population with a high prevalence of both diseases. In these studies, a variant (rs2025804) in the LEPR gene was nominally associated with BMI in 1,082 subjects (P = 0.03 adjusted for age, sex, birth year, and family membership). Therefore the LEPR and leptin overlapping transcript (LEPROT) genes were selected for further sequencing and genotyping in larger population-based samples for association analyses with obesity-related phenotypes. Selected variants (n = 80) spanning these genes were genotyped in a sample of full-heritage Pima Indians (n = 2,842) and several common variants including rs2025804 were nominally associated with BMI (P = 0.05-0.003 adjusted for age, sex, birth year, and family membership). Four common tag variants associated with BMI in the full-heritage Pima Indian sample were genotyped in a second sample of mixed-heritage Native Americans (n = 2,969) and three of the variants showed nominal replication (P = 0.03-0.006 adjusted as above and additionally for Indian heritage). Combining both samples provided the strongest evidence for association (adjusted P = 0.0003-0.0001). A subset of these individuals (n = 403) had been metabolically characterized for predictors of obesity and the BMI risk alleles for the variants tagged by rs2025804 were also associated with lower 24-h energy expenditure (24hEE) as assessed in a human respiratory chamber (P = 0.0007 adjusted for age, sex, fat mass, fat-free mass, activity, and family membership). We conclude that common noncoding variation in the LEPR gene is associated with higher BMI and lower energy expenditure in Native Americans.
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Affiliation(s)
- Michael T Traurig
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health Phoenix, Phoenix, Arizona, USA
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Clarke SD, Lee K, Andrews ZB, Bischof R, Fahri F, Evans RG, Clarke IJ, Henry BA. Postprandial heat production in skeletal muscle is associated with altered mitochondrial function and altered futile calcium cycling. Am J Physiol Regul Integr Comp Physiol 2012; 303:R1071-9. [DOI: 10.1152/ajpregu.00036.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study aimed to determine whether postprandial temperature excursions in skeletal muscle are consistent with thermogenesis or altered blood flow. Temperature probes were implanted into the vastus lateralis muscle of ovariectomized ewes, and blood flow was assessed using laser-Doppler flowmetry (tissue flow) and transit-time ultrasound flowmetry (femoral artery flow). The animals were program-fed between 1100 and 1600, and temperature and blood flow were measured during intravenous administration of either isoprenaline or phenylephrine and during feeding and meal anticipation. In addition, muscle biopsies were collected prefeeding and postfeeding to measure uncoupling protein (UCP) expression and mitochondrial function, as well as indices of calcium cycling (ryanodine 1 receptor: RyR1 and sarcoendoplasmic calcium-dependent ATPases SERCA1/ SERCA2a). Isoprenaline increased femoral artery blood flow, whereas phenylephrine reduced blood flow. At high doses only, isoprenaline treatment increased heat production in muscle. Phenylephrine treatment did not alter muscle temperature. Meal anticipation was evoked in fasted animals (previously program-fed) that were housed beside animals that were fed. Increases in muscle temperature were elicited by feeding and meal anticipation, without changes in blood flow during either paradigm. Analyses of respiration in isolated mitochondria indicated that the postprandial increase in heat production was associated with an increase in state 4 respiration, without increased UCP1, UCP2, or UCP3 expression. Feeding increased the expression of RyR1 and SERCA2a. We conclude that excursions in muscle temperature may occur independent of blood flow, suggesting that postprandial heat production is driven by altered mitochondrial function and changes in calcium cycling.
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Affiliation(s)
- Scott D. Clarke
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Kevin Lee
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Zane B. Andrews
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Robert Bischof
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Fahri Fahri
- School of Land and Environment, University of Melbourne, Victoria, Australia
| | - Roger G. Evans
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Iain J. Clarke
- Department of Physiology, Monash University, Victoria, Australia; and
| | - Belinda A. Henry
- Department of Physiology, Monash University, Victoria, Australia; and
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Liu P, Hu Y, Grossmann R, Zhao R. In ovo leptin administration accelerates post-hatch muscle growth and changes myofibre characteristics, gene expression and enzymes activity in broiler chickens. J Anim Physiol Anim Nutr (Berl) 2012; 97:887-95. [PMID: 22853698 DOI: 10.1111/j.1439-0396.2012.01334.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To evaluate the effect of maternal leptin on muscle growth, we injected 0 μg (control, CON), 0.5 μg (low leptin dose, LL) or 5.0 μg (high leptin dose, HL) of recombinant murine leptin dissolved in 100 μl of PBS into the albumen of broiler eggs prior to incubation. The newly hatched chicks were all raised under the same conditions until 21 days of age (D21), when body weight was measured and samples of gastrocnemius muscle were collected and weighed. Myosin ATPase staining was applied to identify myofibre types and measure the cross-sectional area (CSA) of myofibres. Real-time PCR was performed to quantify leptin receptor (LEPR), insulin-like growth factor 1 (IGF-1), IGF-1 receptor (IGF-1R), growth hormone receptor (GHR) and myostatin (MSTN) mRNA expression in the gastrocnemius muscle. The activity of calpains (CAPNs) in the gastrocnemius muscle was measured using a quantitative fluorescence detection kit. Male chickens treated with both high and low doses of leptin had significantly higher (p < 0.05) body weight on D21. The high leptin significantly increased the CSA (p < 0.05) of gastrocnemius muscle in male chickens, which coincided with a 93% increase (p < 0.05) in IGF-1 mRNA expression. Likewise, the LL dose increased the weight of gastrocnemius muscle in male chickens (p < 0.05), which was accompanied by a 41% down-regulation (p < 0.05) of MSTN mRNA expression and a decreased activity of CAPNs. However, all these changes were not observed in female chickens. The proportion of myofibre types did not altered. No significant change was detected for LEPR and GHR mRNA expression. These results indicate that in ovo leptin treatment affects skeletal muscle growth in chickens in a dose-dependent and sex-specific manner. The altered expression of IGF-1, MSTN mRNA and activity of CAPNs in skeletal muscle may be responsible for such effects.
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Affiliation(s)
- P Liu
- Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, Nanjing, China Key Laboratory of Poultry Heredity and Breeding, Institute of Poultry Science of Jiangsu Province, Yangzhou, Jiangsu, China Department of Functional Genomics and Bioregulation, Institute of Animal Genetics, FLI, Mariensee, Neustadt, Germany
| | - Y Hu
- Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, Nanjing, China Key Laboratory of Poultry Heredity and Breeding, Institute of Poultry Science of Jiangsu Province, Yangzhou, Jiangsu, China Department of Functional Genomics and Bioregulation, Institute of Animal Genetics, FLI, Mariensee, Neustadt, Germany
| | - R Grossmann
- Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, Nanjing, China Key Laboratory of Poultry Heredity and Breeding, Institute of Poultry Science of Jiangsu Province, Yangzhou, Jiangsu, China Department of Functional Genomics and Bioregulation, Institute of Animal Genetics, FLI, Mariensee, Neustadt, Germany
| | - R Zhao
- Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, Nanjing, China Key Laboratory of Poultry Heredity and Breeding, Institute of Poultry Science of Jiangsu Province, Yangzhou, Jiangsu, China Department of Functional Genomics and Bioregulation, Institute of Animal Genetics, FLI, Mariensee, Neustadt, Germany
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Cloning and ontogenetic expression of the uncoupling protein 1 gene UCP1 in sheep. J Appl Genet 2012; 53:203-12. [DOI: 10.1007/s13353-012-0086-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 01/26/2012] [Accepted: 01/26/2012] [Indexed: 12/19/2022]
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Clarke IJ, Smith JT, Henry BA, Oldfield BJ, Stefanidis A, Millar RP, Sari IP, Chng K, Fabre-Nys C, Caraty A, Ang BT, Chan L, Fraley GS. Gonadotropin-inhibitory hormone is a hypothalamic peptide that provides a molecular switch between reproduction and feeding. Neuroendocrinology 2012; 95:305-16. [PMID: 22286004 DOI: 10.1159/000332822] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 09/02/2011] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Gonadotropin-inhibitory hormone (GnIH)-3 is a neuropeptide that plays a major role in the regulation of reproduction and feeding in mammals. MATERIALS AND METHODS We measured endocrine and behavioural parameters of reproduction in sheep, and sexual behaviour in sheep, mice and cynomolgus monkeys. In addition, GnIH gene expression (in situ hybridization) was examined in ewes, and effects of GnIH-3 on food intake and energy expenditure were measured in various species. GnIH-3 was infused (i.v.) into ewes after an i.m. injection of estradiol benzoate to determine whether the peptide blocks the surge in luteinizing hormone (LH) secretion. RESULTS GnIH gene expression was reduced in the preovulatory period in ewes. Infusion (i.v.) of GnIH-3 blocked the estrogen-induced LH surge (in ewes). Intracerebroventricular infusion had no effect on female or male sexual behaviour in each of the three species, but increased food intake. There were no effects on energy expenditure in sheep or rats. GnIH increased fos protein (immunohistochemistry) was seen in orexigenic neurons (in sheep and rats), but also in anorexigenic neurons (in sheep). CONCLUSIONS GnIH-3 reduces reproductive hormone levels and increases food intake in mammals without reducing energy expenditure. There is minimal effect on reproductive behaviour. The dual effect on reproduction and feeding suggests that GnIH-3 provides a molecular switch between these two functions. Blockade of the positive feedback effect of estrogen with parenteral infusion indicates that this peptide may have utility as a blocker of reproductive function in mammals.
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Affiliation(s)
- Iain J Clarke
- Department of Physiology, Monash University, Clayton, Vic 3800, Australia. iainclarke @ monash.edu
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Clarke SD, Clarke IJ, Rao A, Cowley MA, Henry BA. Sex differences in the metabolic effects of testosterone in sheep. Endocrinology 2012; 153:123-31. [PMID: 22128020 DOI: 10.1210/en.2011-1634] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Adiposity is regulated in a sexually divergent manner. This is partly due to sex steroids, but the differential effects of androgens in males and females are unclear. We investigated effects of testosterone on energy balance in castrated male (n = 6) and female sheep (n = 4), which received 3 × 200 mg testosterone implants for 2 wk or blank implants (controls). Temperature probes were implanted into retroperitoneal fat and skeletal muscle. Blood samples were taken to measure metabolites and insulin. In males, muscle and fat biopsies were collected to measure uncoupling protein (UCP) mRNA and phosphorylation of AMP-activated protein kinase and Akt. Testosterone did not change food intake in either sex. Temperature in muscle was higher in males than females, and testosterone reduced heat production in males only. In fat, however, temperature was higher in the castrate males compared with females, and there was no effect of testosterone treatment in either sex. Preprandial glucose levels were lower, but nonesterified fatty acids were higher in females compared with males, irrespective of testosterone. In males, the onset of feeding increased UCP1 and UCP3 mRNA levels in skeletal muscle, without an effect of testosterone. During feeding, testosterone reduced glucose levels in males only but did not alter the phosphorylation of AMP-activated protein kinase or Akt in muscle. Thus, testosterone maintains lower muscle and fat temperatures in males but not females. The mechanism underlying this sex-specific effect of testosterone is unknown but may be due to sexual differentiation of the brain centers controlling energy expenditure.
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Affiliation(s)
- Scott D Clarke
- Department of Physiology, Monash University, Wellington Road, Clayton, Victoria 3168, Australia
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Symonds ME, Budge H, Perkins AC, Lomax MA. Adipose tissue development – Impact of the early life environment. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 106:300-6. [DOI: 10.1016/j.pbiomolbio.2010.11.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 11/18/2010] [Accepted: 11/26/2010] [Indexed: 12/21/2022]
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Henry BA, Andrews ZB, Rao A, Clarke IJ. Central leptin activates mitochondrial function and increases heat production in skeletal muscle. Endocrinology 2011; 152:2609-18. [PMID: 21558317 DOI: 10.1210/en.2011-0143] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Leptin acts on the brain to increase postprandial heat production in skeletal muscle of sheep. To determine a mechanism for this effect, we examined the role of mitochondrial uncoupling and AMP-activated protein kinase (AMPK). Ovariectomized ewes (n=4/group) received infusion lines into the lateral cerebral ventricle, and leptin (10 μg/h) was infused to increase heat production in skeletal muscle. In animals that were program fed (1100-1600 h), skeletal muscle biopsies were taken after either central infusion of leptin or vehicle to measure the expression of uncoupling protein (UCP) mRNA and the phosphorylation status of AMPK. Respiratory function was also quantified in mitochondria isolated from skeletal muscle. Leptin infusion increased the expression of UCP2 and UCP3 mRNA as well as UCP3 protein but not UCP1 mRNA in muscle. Leptin also increased substrate-driven, coupled (ADP-driven), and uncoupled (oligomycin) respiration but had no effect on the total respiratory capacity. The respiratory control ratio was lower in leptin-treated (vs. vehicle-treated) animals, indicating a predominant effect on uncoupled respiration. There was no effect of central leptin treatment on AMPK phosphorylation. We then infused 5-aminoimidazole-4-carboxamide-1β-riboside (AICAR) (10 mg/h for 6 h) directly into the femoral artery and measured skeletal muscle temperature; muscle was also collected for isolated mitochondria studies. AICAR had no effect on heat production or substrate-driven, uncoupled, or total respiratory states in skeletal muscle mitochondria. However, AICAR increased ADP-driven (coupled) respiration in mitochondria. In conclusion, leptin acts at the brain to increase heat production in muscle through altered mitochondrial function, indicative of adaptive thermogenesis.
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Affiliation(s)
- Belinda A Henry
- Department of Physiology, Monash University, Building 13F, Wellington Road, Clayton, Victoria 3800, Australia.
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van den Berg SAA, van Marken Lichtenbelt W, Willems van Dijk K, Schrauwen P. Skeletal muscle mitochondrial uncoupling, adaptive thermogenesis and energy expenditure. Curr Opin Clin Nutr Metab Care 2011; 14:243-9. [PMID: 21415733 DOI: 10.1097/mco.0b013e3283455d7a] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
PURPOSE OF REVIEW The prevalence of obesity is still increasing, despite obesity treatment strategies that aim at reducing energy intake. In addition to this, exercise programmes designed to increase energy expenditure have only a low efficiency and have generated mixed results. Therefore, strategies based on increasing energy expenditure via nonexercise means are currently under investigation. One novel strategy is the modulation of adaptive thermogenesis. RECENT FINDINGS Among others, adaptive thermogenesis can be modulated by changing dietary composition, treatment with hormone mimetics as well as by cold exposure. In humans, a large part of the adaptive thermogenic response is, in addition to a putative role of brown adipose tissue, determined by the skeletal muscle mass via the process of mitochondrial uncoupling. Here, we describe the molecular processes involved in mitochondrial uncoupling, state-of-the-art techniques to measure mitochondrial uncoupling in vitro and in vivo, as well as the current strategies to mitochondrial uncoupling. SUMMARY Data generated in rodents and humans implicate that increasing adaptive thermogenesis by increasing skeletal muscle mitochondrial uncoupling indeed elevates total energy expenditure and thus may provide a promising target for the treatment of obesity.
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Smith JT, Li Q, Yap KS, Shahab M, Roseweir AK, Millar RP, Clarke IJ. Kisspeptin is essential for the full preovulatory LH surge and stimulates GnRH release from the isolated ovine median eminence. Endocrinology 2011; 152:1001-12. [PMID: 21239443 DOI: 10.1210/en.2010-1225] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Kisspeptins are the product of the Kiss1 gene and potently stimulate GnRH secretion. In sheep, Kiss1 mRNA-expressing cells are found in the arcuate nucleus (ARC) and dorsal-lateral preoptic area and both appear to mediate the positive feedback effect of estradiol to generate the preovulatory GnRH/LH surge. To determine the role of kisspeptin in transmitting estrogen-positive feedback in the hypothalamus, we administered the kisspeptin antagonist p-271 to ewes subjected to an estradiol benzoate-induced LH surge. Kisspeptin antagonist treatment significantly attenuated these LH surges. We further examined the response to kisspeptin treatment prior to the LH surge. Kisspeptin significantly stimulated GnRH secretion into the hypophysial portal system, but the response to kisspeptin was similar in luteal and late-follicular phase ewes. Kiss1r mRNA expression in GnRH neurons was also similar across the estrous cycle. To examine alternative pathways for kisspeptin stimulation of GnRH neurons, we examined the origin of kisspeptin neuronal fibers in the external zone of the median eminence (ME) using neuronal tracing and immunohistochemical techniques. ARC populations of kisspeptin neurons project fibers to the ME. Finally, we showed kisspeptin stimulates GnRH release from ovine ME-cultured explants. This suggests direct kisspeptin to GnRH terminal-to-terminal communication within the ME. Overall, these data indicate an essential role for kisspeptin in receiving stimulatory estrogen signals and generating the full positive feedback GnRH/LH surge. Kisspeptin neurons of the ARC project to the external zone of the ME and kisspeptin acts upon the GnRH fibers at this level.
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Affiliation(s)
- Jeremy T Smith
- Department of Physiology, Building 13F, Monash University, Clayton, Victoria 3880, Australia.
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35
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Laker RC, Henry BA, Wadley GD, Clarke IJ, Canny BJ, McConell GK. Central infusion of leptin does not increase AMPK signaling in skeletal muscle of sheep. Am J Physiol Regul Integr Comp Physiol 2010; 300:R511-8. [PMID: 21148475 DOI: 10.1152/ajpregu.00079.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In sheep, central leptin infusion reduces food intake and increases energy expenditure in adipose tissue and skeletal muscle. The mechanisms for these peripheral effects of central leptin in sheep are not known but, on the basis of rodent studies, may involve AMPK. In mice, central leptin acutely increases both skeletal muscle AMPK activation and glucose uptake. Thus, to investigate whether these effects exist in higher-order mammals, ovariectomized Corriedale ewes (n = 4 per group) received a continuous lateral ventricular infusion (60 μl/h) of either leptin (50 μg/h) or artificial cerebrospinal fluid (aCSF; CON) for 8 days. Tritiated glucose (3-(3)H-glucose) was infused intravenously for calculation of whole body glucose turnover during both acute (6 h) and chronic (7-8 days) leptin/aCSF infusion. Muscle biopsies were also obtained. Leptin infusion reduced (P < 0.05) food intake and body weight, and it also increased plasma epinephrine concentration at 6 h and 7 days, suggesting increased sympathetic nerve activity. Despite this, and in contrast to rodent studies, central leptin infusion did not increase skeletal muscle AMPKα Thr(172) phosphorylation or ACCβ Ser(221) phosphorylation. Surprisingly, the glucose rate of appearance (glucose Ra) and rate of disappearance (glucose Rd) were reduced by both acute and chronic leptin infusion. Direct infusion of the AMPK activator 5-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR) into the femoral artery increased skeletal muscle AMPK phosphorylation. In conclusion, although central leptin infusion in sheep caused the predicted reduction in food intake and increases plasma epinephrine concentration, it had no effect on AMPK activation in skeletal muscle and actually reduced glucose disposal. This suggests that there are species differences in the peripheral responses to central leptin infusion.
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Affiliation(s)
- Rhianna C Laker
- Department of Physiology, University of Melbourne, Victoria, Australia
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Hsu YW, Pan YJ, Cho YM, Liou TH, Chou P, Wang PS. Aging effects on exercise-induced alternations in plasma acylated ghrelin and leptin in male rats. Eur J Appl Physiol 2010; 111:809-17. [DOI: 10.1007/s00421-010-1704-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2010] [Indexed: 01/06/2023]
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Henry BA, Blache D, Rao A, Clarke IJ, Maloney SK. Disparate effects of feeding on core body and adipose tissue temperatures in animals selectively bred for Nervous or Calm temperament. Am J Physiol Regul Integr Comp Physiol 2010; 299:R907-17. [DOI: 10.1152/ajpregu.00809.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In addition to homeostatic regulation of body mass, nonhomeostatic factors impact on energy balance. Herein we describe effects of temperament on adipose and core body temperatures in sheep. Animals were genetically selected for Nervous or Calm traits. We characterized the effects of 1) high- and low-energy intake and maintenance feeding, 2) meal anticipation, and 3) adrenocorticotropin challenge on core body and adipose temperatures. Temperature measurements (5 min) were made using a thermistor inserted into the carotid artery (core body) and a probe in the retroperitoneal fat. An imposed feeding window was used to establish postprandial elevations in temperature. Fat tissue was taken from retroperitoneal and subcutaneous regions for real-time PCR analyses. We demonstrate that innate differences in temperament impact on adipose and core body temperatures in response to various dietary and evocative stimuli. In response to homeostatic cues (low-energy intake and maintenance feeding) core body temperature tended to be higher in Calm compared with Nervous animals. In contrast, in response to nonhomeostatic cues, Nervous animals had higher anticipatory thermogenic responses than Calm animals. Expression of uncoupling protein (UCP)-1 and -2 mRNA were higher in retroperitoneal tissue than in subcutaneous tissue, but UCP3 and leptin mRNA levels were similar at both sites; expression of these genes was similar in Nervous and Calm animals. There were no differences in stress responsiveness. We conclude that temperament differentially influences adipose thermogenesis and the regulation of core body temperature in responses to both homeostatic and nonhomeostatic stimuli.
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Affiliation(s)
- Belinda A. Henry
- Department of Physiology, Monash University, Wellington Road, Melbourne, Victoria, Australia
| | | | - Alexandra Rao
- Department of Physiology, Monash University, Wellington Road, Melbourne, Victoria, Australia
| | - Iain J. Clarke
- Department of Physiology, Monash University, Wellington Road, Melbourne, Victoria, Australia
| | - Shane K. Maloney
- Department of Physiology, School of Biomedical, Biomolecular and Chemical Science, The University of Western Australia, Crawley, Western Australia, Australia
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Qi Y, Henry BA, Oldfield BJ, Clarke IJ. The action of leptin on appetite-regulating cells in the ovine hypothalamus: demonstration of direct action in the absence of the arcuate nucleus. Endocrinology 2010; 151:2106-16. [PMID: 20308532 DOI: 10.1210/en.2009-1283] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
It is widely accepted that leptin acts on first-order neurons in the arcuate nucleus (ARC) with information then relayed to other hypothalamic centers. However, the extent to which leptin mediates its central actions solely, or even primarily, via this route is unclear. We used a model of hypothalamo-pituitary disconnection (HPD) to determine whether leptin action on appetite-regulating systems requires the ARC. This surgical preparation eliminates the ARC. We measured effects of iv leptin to activate hypothalamic neurons (Fos labeling). In ARC-intact animals, leptin increased the percentage of Fos-positive melanocortin neurons and reduced percentages of Fos-positive neuropeptide Y neurons compared with saline-treated animals. HPD itself increased Fos labeling in the lateral hypothalamic area (LHA). Leptin influenced Fos labeling in the dorsomedial nucleus (DMH), ventromedial nucleus, and paraventricular nucleus (PVN) in HPD and normal animals, with effects on particular cell types varying. In the LHA and DMH, leptin decreased orexin cell activation in HPD and ARC-intact sheep. HPD abolished leptin-induced expression of Fos in melanin-concentrating hormone cells in the LHA and in CRH cells in the PVN. In contrast, HPD accentuated activation in oxytocin neurons. Our data from sheep with lesions encompassing the ARC do not suggest a primacy of action of leptin in this nucleus. We demonstrate that first order to second order signaling may not represent the predominant means by which leptin acts in the brain to generate integrated responses. We provide evidence that leptin exerts direct action on cells of the DMH, ventromedial nucleus, and PVN.
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Affiliation(s)
- Yue Qi
- Department of Physiology, Monash University, Clayton, Victoria, Australia
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Backholer K, Bowden M, Gamber K, Bjørbæk C, Iqbal J, Clarke IJ. Melanocortins mimic the effects of leptin to restore reproductive function in lean hypogonadotropic ewes. Neuroendocrinology 2010; 91:27-40. [PMID: 19923792 PMCID: PMC2857620 DOI: 10.1159/000260060] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 05/25/2009] [Indexed: 02/02/2023]
Abstract
BACKGROUND/AIMS Leptin restores gonadotropic function in lean hypogonadotropic animals by an unknown mechanism. We aimed to test the hypothesis that restoration of gonadotropic function is a result of an upregulation of central acetylated melanocortin production. METHODS AND RESULTS Lean ovariectomised (OVX) ewes received intracerebroventricular (i.c.v.) infusions of leptin (or vehicle) for 3 days, which upregulated proopiomelanocortin (POMC) mRNA and restored pulsatile luteinizing hormone (LH) secretion. A melanocortin agonist (MTII), but not naloxone treatment, reinstated pulsatile LH secretion in lean OVX ewes. We treated (i.c.v.) lean OVX ewes with leptin (or vehicle) and measured peptide levels and post-translational modification in the arcuate nucleus (ARC). Levels of beta-endorphin (beta-END) were lower in lean animals, with no effect of leptin treatment. Desacetyl-alpha-MSH was the predominant form of alpha-melanocyte-stimulating hormone (alpha-MSH) in the ARC and levels were similar in all groups. In another group of lean and normal-weight OVX ewes, we measured the different forms of alpha-MSH in ARC, hypothalamus (ARC-removed) and the preoptic area (POA). Acetylated alpha-MSH levels were lower in lean animals in the terminal beds of the hypothalamus and POA but not the ARC. CONCLUSIONS Leptin corrects the hypogonadotropic state in the lean condition by upregulation of POMC gene expression, and may increase transport and acetylation of melanocortins to target cells in the brain. Melanocortin treatment restores LH secretion in lean animals.
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Affiliation(s)
- Kathryn Backholer
- Department of Physiology, Monash University, Monash, Vic., Australia
| | - Marissa Bowden
- Prince Henry's Institute of Medical Research, Clayton, Vic., Australia
| | - Kevin Gamber
- Division of Endocrinology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass., USA
| | - Christian Bjørbæk
- Division of Endocrinology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass., USA
| | - Javed Iqbal
- Department of Physiology, Monash University, Monash, Vic., Australia
| | - Iain J. Clarke
- Department of Physiology, Monash University, Monash, Vic., Australia
- *Iain J. Clarke, Department of Physiology, Monash University, PO Box 13F, Clayton, Vic. 3800 (Australia), Tel. +61 3 9905 2554, Fax +61 3 9905 2566, E-Mail
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Backholer K, Smith J, Clarke IJ. Melanocortins may stimulate reproduction by activating orexin neurons in the dorsomedial hypothalamus and kisspeptin neurons in the preoptic area of the ewe. Endocrinology 2009; 150:5488-97. [PMID: 19819961 DOI: 10.1210/en.2009-0604] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To further test the hypothesis that melanocortins stimulate the reproductive axis, we treated ewes with melanocortin agonist (MTII) in the luteal phase of the estrous cycle and during seasonal anestrus. Lateral ventricular infusion of MTII (10 microg/h) during the luteal phase increased LH secretion. Retrograde neuronal tracing in the brain showed few proopiomelanocortin or kisspeptin cells in the arcuate nucleus, but more than 70% of kisspeptin cells in the dorsolateral preoptic area (POA), projecting to the ventromedial POA in which GnRH cells are located. MTII infusion (20 h) was repeated in luteal phase ewes and brains were harvested to measure gene expression of preproorexin and kisspeptin. Expression of orexin in the dorsomedial hypothalamus and kisspeptin in the POA was up-regulated by MTII treatment and Kiss1 in the arcuate nucleus was down-regulated. Seasonally anestrous ewes were progesterone primed and then treated (lateral ventricular) with MTII (10 microg/h) or vehicle for 30 h, and blood samples were collected every 2 h from 4 h before infusion until 6 h afterward to monitor acute response in terms of LH levels. A rise in basal LH levels was seen, but samples collected around the time of the predicted LH surge did not indicate that an ovulatory event occurred. We conclude that melanocortins are positive regulators of the reproductive neuroendocrine system, but treatment with melanocortins does not fully overcome seasonal acyclicity. The stimulatory effect of melanocortin in the luteal phase of the estrous cycle may be via the activation of kisspeptin cells in the POA and/or orexin cells in the dorsomedial hypothalamus.
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Affiliation(s)
- Kathryn Backholer
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
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Abstract
The last few years have seen major advances in common non-syndromic obesity research, much of it the result of genetic studies. This Review outlines the competing hypotheses about the mechanisms underlying the genetic and physiological basis of obesity, and then examines the recent explosion of genetic association studies that have yielded insights into obesity, both at the candidate gene level and the genome-wide level. With obesity genetics now entering the post-genome-wide association scan era, the obvious question is how to improve the results obtained so far using single nucleotide polymorphism markers and how to move successfully into the other areas of genomic variation that may be associated with common obesity.
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Abstract
Over the past decade, adipose tissue has been shown to produce numerous factors that act as hormones. Many of these act on the brain to regulate energy balance via dual effects on food intake and energy expenditure. These include well-characterised hormones such as leptin, oestrogen and glucocorticoids and novel factors such as adiponectin and resistin. This review provides a perspective on the role of these factors as lipostats.
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Affiliation(s)
- B A Henry
- Department of Physiology, Monash University, Melbourne, Vic, Australia
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