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Soo Yeon Jang Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea

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Kyung Mook Choi Division of Endocrinology and Metabolism, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea

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Osteosarcopenia, which refers to the concomitant presence of osteoporosis and sarcopenia, is expected to increase in the rapidly progressive aging world, with serious clinical implications. However, the pathophysiology of osteosarcopenia has not been fully elucidated, and no optimal treatment specific to osteosarcopenia is available. The RANKL–RANK pathway is widely used as a therapeutic target for osteoporosis. Growing evidence supports the importance of the RANKL–RANK pathway, not only in bone, but also in muscle, and the therapeutic potential of targeting this pathway in muscle diseases has been noted. The muscles and bones closely communicate with each other through various secretory factors called myokines and osteokines. This review covers the roles of the RANKL–RANK pathway in the bone and muscle and their reciprocal interactions. Moreover, we will suggest future directions to move forward for the treatment of osteosarcopenia to prepare for an upcoming aging society.

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Emre Murat Altinkilic Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
Department of BioMedical Research, University of Bern, Bern, Switzerland

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Philipp Augsburger Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
Department of BioMedical Research, University of Bern, Bern, Switzerland
Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland

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Amit V Pandey Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
Department of BioMedical Research, University of Bern, Bern, Switzerland

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Christa E Flück Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
Department of BioMedical Research, University of Bern, Bern, Switzerland

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Biallelic variants of steroidogenic acute regulatory protein (STAR/STARD1) may cause primary adrenal insufficiency and 46,XY disorder of sex development. STAR plays a pivotal role in transporting cholesterol into mitochondria where cholesterol serves as an essential substrate for initiating steroid biosynthesis by its conversion to pregnenolone. Generally, loss-of-function mutations of STAR cause the classic form of lipoid congenital adrenal hyperplasia (LCAH) where steroidogenesis of the adrenal cortex and the gonads is severely affected. By contrast, partial activity of STAR causes a less severe phenotype, the non-classic LCAH, which is characterized by later onset and initial manifestation with isolated adrenal insufficiency only. Disease-causing STAR variants are very rare. Numerous variants of all types have been described worldwide. Prevailing variants have been reported from Japan and Korea and in some population clusters where STAR is more common. Genotype–phenotype correlation is pretty good for STAR variants. While the exact mechanisms of cholesterol transport into mitochondria for steroidogenesis are still under investigation, the important role of STAR in this process is evident by inactivating STAR variants causing LCAH. The mechanism of disease with STAR deficiency is best described by a two-hit model: the first hit relates to impaired cholesterol import into mitochondria and thus lack of substrate for all steroid hormone biosynthesis; the second hit then relates to massive cytoplasmic lipid overload (evidenced by typically enlarged and fatty adrenal glands) leading to cell death and organ destruction. This review summarizes phenotype and genotype characteristics of human STAR variants found through the ClinVar database.

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Katarzyna Czarzasta Department of Experimental and Clinical Physiology, Laboratory of Center for Preclinical Research, Medical University of Warsaw, Warszawa, Poland

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Luminita H Pojoga Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women’s Hospital/Harvard Medical School, Boston, Massachusetts, USA

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Over the past decades, research has clearly established the important role of the mineralocorticoid receptor (MR) in both renal and extra-renal tissues. Recently, caveolin-1 (Cav-1) has emerged as a mediator of MR signaling in several tissues, with implications on cardiovascular and metabolic dysfunction. The main structural component of caveolae (plasma membrane invaginations with diverse functions), Cav-1 is a modulator of cardiovascular function, cellular glucose, and lipid homeostasis, via its effects on signal transduction pathways that mediate inflammatory responses and oxidative stress. In this review, we present evidence indicating an overlap between the roles of the MR and Cav-1 in cardiometabolic disease and the relevant signaling pathways involved. Furthermore, we discuss the potential use of Cav-1 as a biomarker and/or target for MR-mediated dysfunction.

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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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Nawal A Yahya Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Steven R King Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA
Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, USA

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Bo Shi Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Aisha Shaaban Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Nicole E Whitfield Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Chunmei Yan Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA
Department of Obstetrics, The Second Hospital of Shandong University, Jinan, Shandong, People’s Republic of China

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Richard J Kordus Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Gail F Whitman-Elia Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Holly A LaVoie Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, USA

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Cells actively engaged in de novo steroidogenesis rely on an expansive intracellular network to efficiently transport cholesterol. The final link in the transport chain is STARD1, which transfers cholesterol to the enzyme complex that initiates steroidogenesis. However, the regulation of ovarian STARD1 is not fully characterized, and even less is known about the upstream cytosolic cholesterol transporters STARD4 and STARD6. Here, we identified both STARD4 and STARD6 mRNAs in the human ovary but only detected STARD4 protein since the primary STARD6 transcript turned out to be a splice variant. Corpora lutea contained the highest levels of STARD4 and STARD1 mRNA and STARD1 protein, while STARD4 protein was uniformly distributed across ovarian tissues. Cyclic AMP analog (8Br-cAMP) and phorbol ester (PMA) individually increased STARD1 and STARD4 mRNA along with STARD1 protein and its phosphoform in cultured primary human luteinized granulosa cells (hGCs). STARD6 transcripts and STARD4 protein were unresponsive to these stimuli. Combining lower doses of PMA and 8Br-cAMP blunted the 8Br-cAMP stimulation of STARD1 protein. Increasing cholesterol levels by blocking its conversion to steroid with aminoglutethimide or by adding LDL reduced the STARD4 mRNA response to stimuli. Sterol depletion reduced the STARD1 mRNA and protein response to PMA. These data support a possible role for STARD4, but not STARD6, in supplying cholesterol for steroidogenesis in the ovary. We demonstrate for the first time how cAMP, PMA and sterol pathways separately and in combination differentially regulate STARD4, STARD6 and STARD1 mRNA levels, as well as STARD1 and STARD4 protein in human primary ovarian cells.

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Ryan A Lafferty Diabetes Research Centre, Schools of Biomedical Sciences and Pharmacy & Pharmaceutical Sciences, Ulster University, Coleraine, Northern Ireland, UK

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Peter R Flatt Diabetes Research Centre, Schools of Biomedical Sciences and Pharmacy & Pharmaceutical Sciences, Ulster University, Coleraine, Northern Ireland, UK

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Victor A Gault Diabetes Research Centre, Schools of Biomedical Sciences and Pharmacy & Pharmaceutical Sciences, Ulster University, Coleraine, Northern Ireland, UK

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Nigel Irwin Diabetes Research Centre, Schools of Biomedical Sciences and Pharmacy & Pharmaceutical Sciences, Ulster University, Coleraine, Northern Ireland, UK

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Recent approval of the dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, tirzepatide, for the management of type 2 diabetes mellitus (T2DM) has reinvigorated interest in exploitation of GIP receptor (GIPR) pathways as a means of metabolic disease management. However, debate has long surrounded the use of the GIPR as a therapeutic target and whether agonism or antagonism is of most benefit in management of obesity/diabetes. This controversy appears to be partly resolved by the success of tirzepatide. However, emerging studies indicate that prolonged GIPR agonism may desensitise the GIPR to essentially induce receptor antagonism, with this phenomenon suggested to be more pronounced in the human than rodent setting. Thus, deliberation continues to rage in relation to benefits of GIPR agonism vs antagonism. That said, as with GIPR agonism, it is clear that the metabolic advantages of sustained GIPR antagonism in obesity and obesity-driven forms of diabetes can be enhanced by concurrent GLP-1 receptor (GLP-1R) activation. This narrative review discusses various approaches of pharmacological GIPR antagonism including small molecule, peptide, monoclonal antibody and peptide-antibody conjugates, indicating stage of development and significance to the field. Taken together, there is little doubt that interesting times lie ahead for GIPR agonism and antagonism, either alone or when combined with GLP-1R agonists, as a therapeutic intervention for the management of obesity and associated metabolic disease.

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Lorena González Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Ma Eugenia Díaz Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Johanna G Miquet Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Ana I Sotelo Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Diego Fernández Cátedra de Bioquímica Humana, Facultad de Medicina (UBA), Buenos Aires, Argentina

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Fernando P Dominici Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Andrzej Bartke Geriatrics Research, Departments of Internal Medicine and Physiology, School of Medicine, Southern Illinois University, Springfield, Illinois, USA

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Daniel Turyn Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina

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Michael Merkhassine Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA
VCA Colonial Animal Hospital, Ithaca, New York, USA

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Reilly W Coch Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA
Weill Cornell College of Medicine, New York, New York, USA

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Carol E Frederick Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA

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Lucinda L Bennett Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA

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Seth A Peng Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA
Fate Therapeutics, San Diego, California, USA

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Benjamin Morse Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA

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Bethany P Cummings Center for Alimentary and Metabolic Science, Department of Surgery, School of Medicine, University of California, Davis, Sacramento, California, USA
Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California, USA

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John P Loftus Loftus Laboratory, Department of Clinical Sciences, Cornell University, College of Veterinary Medicine, Ithaca, New York, USA

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Glucagon plays a central role in amino acid (AA) homeostasis. The dog is an established model of glucagon biology, and recently, metabolomic changes in people associated with glucagon infusions have been reported. Glucagon also has effects on the kidney; however, changes in urinary AA concentrations associated with glucagon remain under investigation. Therefore, we aimed to fill these gaps in the canine model by determining the effects of glucagon on the canine plasma metabolome and measuring urine AA concentrations. Employing two constant rate glucagon infusions (CRI) – low-dose (CRI-LO: 3 ng/kg/min) and high-dose (CRI-HI: 50 ng/kg/min) on five research beagles, we monitored interstitial glucose and conducted untargeted liquid chromatography–tandem mass spectrometry (LC-MS/MS) on plasma samples and urine AA concentrations collected pre- and post-infusion. The CRI-HI induced a transient glucose peak (90–120 min), returning near baseline by infusion end, while only the CRI-LO resulted in 372 significantly altered plasma metabolites, primarily reductions (333). Similarly, CRI-HI affected 414 metabolites, with 369 reductions, evidenced by distinct clustering post-infusion via data reduction (PCA and sPLS-DA). CRI-HI notably decreased circulating AA levels, impacting various AA-related and energy-generating metabolic pathways. Urine analysis revealed increased 3-methyl-l-histidine and glutamine, and decreased alanine concentrations post-infusion. These findings demonstrate glucagon’s glucose-independent modulation of the canine plasma metabolome and highlight the dog’s relevance as a translational model for glucagon biology. Understanding these effects contributes to managing dysregulated glucagon conditions and informs treatments impacting glucagon homeostasis.

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Jordan S F Chan Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Amanda A Greenwell Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Christina T Saed Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Magnus J Stenlund Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Indiresh A Mangra-Bala Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Seyed Amirhossein Tabatabaei Dakhili Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Kunyan Yang Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Sally R Ferrari Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Farah Eaton Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Keshav Gopal Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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John R Ussher Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
Cardiovascular Research Institute, University of Alberta, Edmonton, Alberta, Canada

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Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist used for the treatment of T2D, has been shown to alleviate diabetic cardiomyopathy (DbCM) in experimental T2D, which was associated with increased myocardial glucose oxidation. To determine whether this increase in glucose oxidation is necessary for cardioprotection, we hypothesized that liraglutide’s ability to alleviate DbCM would be abolished in mice with cardiomyocyte-specific deletion of pyruvate dehydrogenase (PDH; Pdha1 CM−/− mice), the rate-limiting enzyme of glucose oxidation. Male Pdha1 CM−/− mice and their α-myosin heavy chain Cre expressing littermates (αMHCCre mice) were subjected to experimental T2D via 10 weeks of high-fat diet supplementation, with a single low-dose injection of streptozotocin (75 mg/kg) provided at week 4. All mice were randomized to treatment with either vehicle control or liraglutide (30 µg/kg) twice daily during the final 2.5 weeks, with cardiac function assessed via ultrasound echocardiography. As expected, liraglutide treatment improved glucose homeostasis in both αMHCCre and Pdha1 CM−/− mice with T2D, in the presence of mild weight loss. Parameters of systolic function were unaffected by liraglutide treatment in both αMHCCre and Pdha1 CM−/− mice with T2D. However, liraglutide treatment alleviated diastolic dysfunction in αMHCCre mice, as indicated by an increase and decrease in the e′/a′ and E/e′ ratios, respectively. Conversely, liraglutide failed to rescue these indices of diastolic dysfunction in Pdha1 CM−/− mice. Our findings suggest that increases in glucose oxidation are necessary for GLP-1R agonist mediated alleviation of DbCM. As such, strategies aimed at increasing PDH activity may represent a novel approach for the treatment of DbCM.

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