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The mineralocorticoid system, comprising the renin-angiotensin-aldosterone system (RAAS) and associated receptors, is traditionally viewed as a regulator of sodium and fluid balance and blood pressure (BP), with the main mineralocorticoid hormone aldosterone acting via the mineralocorticoid receptor (MR) in distal renal tubules. Over the past few decades, there has been a wider understanding of the role of the mineralocorticoid system in regulating both classical BP-dependent and non-BP-dependent systemic effects. Mounting evidence indicates the novel role of the mineralocorticoid system in cardiometabolic health with excess mineralocorticoid system activity being associated with adiposity, diabetes, insulin resistance and cardiovascular diseases independent of its effect on BP, and RAAS blockade and MR antagonists offering protection against cardiometabolic dysfunction. The metabolic manifestations of mineralocorticoid system overactivation are mainly mediated by their interactions with adipose tissue which orchestrates energy, lipids and glucose homeostasis via effects on the functions of brown and white adipocytes and immune cells. Adipose tissue can in turn influence mineralocorticoid system activity by harbouring its own RAAS system and by releasing mineralocorticoid-secretory factors/adipokines, with resultant further progression of cardiometabolic dysfunction. This article discusses the interplay between the mineralocorticoid system and adipose tissue in the pathophysiology of cardiometabolic diseases.
The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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The Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
National Clinical Research Center for Cardiovascular Diseases, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
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Hypercholesterolemia is an independent risk factor for cardiovascular disease and lowering circulating levels of low-density lipoprotein cholesterol (LDL-C) can prevent and reduce cardiovascular events. MicroRNA-181d (miR-181d) can reduce the levels of triglycerides and cholesterol esters in cells. However, it is not known whether miR-181d-5p can lower levels of circulating LDL-C. Here, we generated two animal models of hypercholesterolemia to analyze the potential relationship between miR-181d-5p and LDL-C. In hypercholesterolemia model mice, adeno-associated virus (AAV)-mediated liver-directed overexpression of miR-181d-5p decreased the serum levels of cholesterol and LDL-C and the levels of cholesterol and triglyceride in the liver compared with control mice. Target Scan 8.0 indicated Proprotein convertase subtilisin/kexin type 9 (PCSK9) to be a possible target gene of miR-181d-5p, which was confirmed by in vitro experiments. miR-181d-5p could directly interact with both the PCSK9 3′-UTR and promoter to inhibit PCSK9 translation and transcription. Furthermore, Dil-LDL uptake assays in PCSK9 knockdown Huh7 cells demonstrated that miR-181d-5p promotion of LDL-C absorption was dependent on PCSK9. Collectively, our findings show that miR-181d-5p targets the PCSK9 3′-UTR to inhibit PCSK9 expression and to reduce serum LDL-C. miR-181d-5p is therefore a new therapeutic target for the development of anti-hypercholesterolemia drugs.
Department of Internal Medicine IV, Division of Diabetology, Endocrinology and Nephrology, Eberhard-Karls University of Tübingen, Tübingen, Germany
Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard-Karls University of Tübingen, Tübingen, Germany
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Department of Internal Medicine IV, Division of Diabetology, Endocrinology and Nephrology, Eberhard-Karls University of Tübingen, Tübingen, Germany
Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, Eberhard-Karls University of Tübingen, Tübingen, Germany
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The root cause of type 2 diabetes (T2D) is insulin resistance (IR), defined by the failure of cells to respond to circulating insulin to maintain lipid and glucose homeostasis. While the causes of whole-body insulin resistance are multifactorial, a major contributing factor is dysregulation of liver and adipose tissue function. Adipose dysfunction, particularly adipose tissue-IR (adipo-IR), plays a crucial role in the development of hepatic insulin resistance and the progression of metabolic dysfunction-associated steatotic liver disease (MASLD) in the context of T2D. In this review, we will focus on molecular mechanisms of hepatic insulin resistance and its association with adipose tissue function. A deeper understanding of the pathophysiological mechanisms of the transition from a healthy state to insulin resistance, impaired glucose tolerance, and T2D may enable us to prevent and intervene in the progression to T2D.
Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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Scotland’s Rural College, The Roslin Institute, Easter Bush Campus, United Kingdom
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Centre for Systems Health and Integrated Metabolic Research, Nottingham Trent University, Nottingham, United Kingdom
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Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, 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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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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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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Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, USA
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Department of Obstetrics, The Second Hospital of Shandong University, Jinan, Shandong, People’s Republic of China
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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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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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Cardiovascular outcome trials (CVOTs) in people living with T2DM and obesity have confirmed the cardiovascular benefits of glucagon-like peptide 1 receptor agonists (GLP-1RA), including reduced cardiovascular mortality, lower rates of myocardial infarction, and lower rates of stroke. The cardiovascular benefits observed following GLP-1RA treatment could be secondary to improvements in glycemia, blood pressure, postprandial lipidemia, and inflammation. Yet, the GLP-1R is also expressed in the heart and vasculature, suggesting that GLP-1R agonism may impact the cardiovascular system. The emergence of GLP-1RA combined with glucose-dependant insulinotropic polypeptide (GIP) and glucagon (GCG) receptor agonists has shown promising results as new weight loss medications. Dual-agonist and tri-agonist therapies have demonstrated superior outcomes in weight loss, lowered blood sugar and lipid levels, restoration of tissue function, and enhancement of overall substrate metabolism compared to using GLP-1R agonists alone. However, the precise mechanisms underlying their cardiovascular benefits remain to be fully elucidated. This review aims to summarize the findings from CVOTs of GLP-1RAs, explore the latest data on dual and triagonist therapies, and delve into potential mechanisms contributing to their cardioprotective effects. It also addresses current gaps in understanding and areas for further research.
VCA Colonial Animal Hospital, Ithaca, New York, USA
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Weill Cornell College of Medicine, New York, New York, USA
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Fate Therapeutics, San Diego, California, USA
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Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California, 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.
