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Zoi Michailidou Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Anthony P Coll Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Christopher J Kenyon Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Nicholas M Morton Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Stephen O’Rahilly Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Jonathan R Seckl Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Karen E Chapman Endocrine Unit, Queen’s Medical Research Institute, Centre for Cardiovascular Sciences, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
Departments of Clinical Biochemistry and Medicine, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge CB2 2XY, UK

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Proopiomelanocortin (POMC) deficiency causes severe obesity through hyperphagia of hypothalamic origin. However, low glucocorticoid levels caused by adrenal insufficiency mitigate against insulin resistance, hyperphagia and fat accretion in Pomc−/−mice. Upon exogenous glucocorticoid replacement, corticosterone-supplemented (CORT) Pomc−/− mice show exaggerated responses, including excessive fat accumulation, hyperleptinaemia and insulin resistance. To investigate the peripheral mechanisms underlying this glucocorticoid hypersensitivity, we examined the expression levels of key determinants and targets of glucocorticoid action in adipose tissue and liver. Despite lower basal expression of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which generates active glucocorticoids within cells, CORT-mediated induction of 11β-HSD1 mRNA levels was more pronounced in adipose tissues of Pomc−/−mice. Similarly, CORT treatment increased lipoprotein lipase mRNA levels in all fat depots in Pomc−/− mice, consistent with exaggerated fat accumulation. Glucocorticoid receptor (GR) mRNA levels were selectively elevated in liver and retroperitoneal fat of Pomc−/− mice but were corrected by CORT in the latter depot. In liver, CORT increased phosphoenolpyruvate carboxykinase mRNA levels specifically in Pomc−/− mice, consistent with their insulin-resistant phenotype. Furthermore, CORT induced hypertension in Pomc−/−mice, independently of adipose or liver renin–angiotensin system activation. These data suggest that CORT-inducible 11β-HSD1 expression in fat contributes to the adverse cardiometabolic effects of CORT in POMC deficiency, whereas higher GR levels may be more important in liver.

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Elisa Villalobos University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom

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Allende Miguelez-Crespo University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Ruth A Morgan University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
Scotland’s Rural College, The Roslin Institute, Easter Bush Campus, United Kingdom

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Lisa Ivatt University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Mhairi Paul University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Joanna P Simpson University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Natalie Z M Homer University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Dominic Kurian The Roslin Institute, Royal (Dick) School of Veterinary Studies, College of Medicine and Veterinary Medicine, University of Edinburgh, Easter Bush Campus, Edinburgh, United Kingdom

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Judit Aguilar The Roslin Institute, Royal (Dick) School of Veterinary Studies, College of Medicine and Veterinary Medicine, University of Edinburgh, Easter Bush Campus, Edinburgh, United Kingdom

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Rachel A Kline The Roslin Institute, Royal (Dick) School of Veterinary Studies, College of Medicine and Veterinary Medicine, University of Edinburgh, Easter Bush Campus, Edinburgh, United Kingdom

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Thomas M Wishart The Roslin Institute, Royal (Dick) School of Veterinary Studies, College of Medicine and Veterinary Medicine, University of Edinburgh, Easter Bush Campus, Edinburgh, United Kingdom

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Nicholas M Morton University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
Centre for Systems Health and Integrated Metabolic Research, Nottingham Trent University, Nottingham, United Kingdom

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Roland H Stimson University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Ruth Andrew University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Brian R Walker University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom

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Mark Nixon University/British Heart Foundation Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom

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Glucocorticoids modulate glucose homeostasis, acting on metabolically active tissues such as liver, skeletal muscle, and adipose tissue. Intracellular regulation of glucocorticoid action in adipose tissue impacts metabolic responses to obesity. ATP-binding cassette family C member 1 (ABCC1) is a transmembrane glucocorticoid transporter known to limit the accumulation of exogenously administered corticosterone in adipose tissue. However, the role of ABCC1 in the regulation of endogenous glucocorticoid action and its impact on fuel metabolism has not been studied. Here, we investigate the impact of Abcc1 deficiency on glucocorticoid action and high-fat-diet (HFD)-induced obesity. In lean male mice, deficiency of Abcc1 increased endogenous corticosterone levels in skeletal muscle and adipose tissue but did not impact insulin sensitivity. In contrast, Abcc1-deficient male mice on HFD displayed impaired glucose and insulin tolerance, and fasting hyperinsulinaemia, without alterations in tissue corticosterone levels. Proteomics and bulk RNA sequencing revealed that Abcc1 deficiency amplified the transcriptional response to an obesogenic diet in adipose tissue but not in skeletal muscle. Moreover, Abcc1 deficiency impairs key signalling pathways related to glucose metabolism in both skeletal muscle and adipose tissue, in particular those related to OXPHOS machinery and Glut4. Together, our results highlight a role for ABCC1 in regulating glucose homeostasis, demonstrating diet-dependent effects that are not associated with altered tissue glucocorticoid concentrations.

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Andrea Lovdel University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Karla J Suchacki University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Fiona Roberts University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Richard J Sulston University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Robert J Wallace Department of Orthopaedics, The University of Edinburgh, Edinburgh, UK

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Benjamin J Thomas University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Rachel M B Bell University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Iris Pruñonosa Cervera University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Gavin J Macpherson Department of Orthopaedic Surgery, Royal Infirmary of Edinburgh, Edinburgh, UK

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Nicholas M Morton University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK
Centre for Systems Health and Integrated Metabolic Research, Department of Biosciences, School of Science and Technology, Nottingham Trent University, Nottingham, UK

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Natalie Z M Homer University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Karen E Chapman University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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William P Cawthorn University/BHF Centre for Cardiovascular Science, The University of Edinburgh, The Queen’s Medical Research Institute, Edinburgh BioQuarter, Edinburgh, UK

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Bone marrow adipose tissue (BMAT) comprises >10% of total adipose mass in healthy humans. It increases in diverse conditions, including ageing, obesity, osteoporosis, glucocorticoid therapy, and notably, during caloric restriction (CR). BMAT potentially influences skeletal, metabolic, and immune functions, but the mechanisms of BMAT expansion remain poorly understood. Our hypothesis is that, during CR, excessive glucocorticoid activity drives BMAT expansion. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies glucocorticoid activity by catalysing intracellular regeneration of active glucocorticoids from inert 11-keto forms. Mice lacking 11β-HSD1 resist metabolic dysregulation and bone loss during exogenous glucocorticoid excess; thus, we hypothesised that 11β-HSD1 knockout mice would also resist excessive glucocorticoid action during CR, thereby restrining BMAT expansion and bone loss. To test this, we first confirmed that 11β-HSD1 is expressed in mouse and human bone marrow. We then investigated the effects of CR in male and female control and 11β-HSD1 knockout mice from 9 to 15 weeks of age. CR increased Hsd11b1 mRNA in adipose tissue and bone marrow. Deletion of Hsd11b1 did not alter bone or BMAT characteristics in mice fed a control diet and had little effect on tibial bone microarchitecture during CR. Notably, Hsd11b1 deletion attenuated the CR-induced increases in BMAT and prevented increases in bone marrow corticosterone in males but not females. This was not associated with suppression of glucocorticoid target genes in bone marrow. Instead, knockout males had increased progesterone in plasma and bone marrow. Together, our findings show that knockout of 11β-HSD1 prevents CR-induced BMAT expansion in a sex-specific manner and highlights progesterone as a potential new regulator of bone marrow adiposity.

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