RESUMEN
Branched fatty acid (FA) esters of hydroxy FAs (HFAs; FAHFAs) are recently discovered lipids that are conserved from yeast to mammals1,2. A subfamily, palmitic acid esters of hydroxy stearic acids (PAHSAs), are anti-inflammatory and anti-diabetic1,3. Humans and mice with insulin resistance have lower PAHSA levels in subcutaneous adipose tissue and serum1. PAHSA administration improves glucose tolerance and insulin sensitivity and reduces inflammation in obesity, diabetes and immune-mediated diseases1,4-7. The enzyme(s) responsible for FAHFA biosynthesis in vivo remains unknown. Here we identified adipose triglyceride lipase (ATGL, also known as patatin-like phospholipase domain containing 2 (PNPLA2)) as a candidate biosynthetic enzyme for FAHFAs using chemical biology and proteomics. We discovered that recombinant ATGL uses a transacylation reaction that esterifies an HFA with a FA from triglyceride (TG) or diglyceride to produce FAHFAs. Overexpression of wild-type, but not catalytically dead, ATGL increases FAHFA biosynthesis. Chemical inhibition of ATGL or genetic deletion of Atgl inhibits FAHFA biosynthesis and reduces the levels of FAHFA and FAHFA-TG. Levels of endogenous and nascent FAHFAs and FAHFA-TGs are 80-90 per cent lower in adipose tissue of mice in which Atgl is knocked out specifically in the adipose tissue. Increasing TG levels by upregulating diacylglycerol acyltransferase (DGAT) activity promotes FAHFA biosynthesis, and decreasing DGAT activity inhibits it, reinforcing TGs as FAHFA precursors. ATGL biosynthetic transacylase activity is present in human adipose tissue underscoring its potential clinical relevance. In summary, we discovered the first, to our knowledge, biosynthetic enzyme that catalyses the formation of the FAHFA ester bond in mammals. Whereas ATGL lipase activity is well known, our data establish a paradigm shift demonstrating that ATGL transacylase activity is biologically important.
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Aciltransferasas , Ésteres , Ácidos Grasos , Hidroxiácidos , Aciltransferasas/genética , Aciltransferasas/metabolismo , Tejido Adiposo/química , Tejido Adiposo/metabolismo , Animales , Diglicéridos , Esterificación , Ésteres/química , Ésteres/metabolismo , Ácidos Grasos/biosíntesis , Ácidos Grasos/química , Humanos , Hidroxiácidos/química , Hidroxiácidos/metabolismo , Resistencia a la Insulina , Ratones , TriglicéridosRESUMEN
RATIONALE: Since June 2018, globally large numbers of pharmaceuticals have been recalled due to the unexpected presence of nitrosamines. Beginning with the class of pharmaceuticals known as sartans, subsequent lines of inquiry included antidiabetic medicines, antihistamines, and antibiotics. A critical review of the U.S. Food and Drug Administration database reveals that the highest number of products recall due to the presence of unacceptable levels of nitrosamines were losartan potassium drug products and their coformulations with other drug substances. The problem can be mainly attributed to naively adopted approval revisions and the lack of sufficient current analytical technologies to detect those contaminants in time. In this work, we developed a specific, selective, accurate, precise, and robust ultra-performance liquid chromatography-triple quadrupole-mass spectrometry (UPLC-TQ-MS/MS) method for the estimation of eight genotoxic nitrosamine impurities in losartan and hydrochlorothiazide (HCTZ) tablets, which is the only fixed-dosage combination approved by the USFDA to treat hypertension. METHODS: All the nitrosamine impurities along with the drug substances were separated using an Agilent Pursuit XRs Ultra diphenyl column (150 × 2.0 mm, 2.8 µm) with mobile phase A (0.1% formic acid in water) and mobile phase B (0.1% formic acid in methanol) at a flow rate of 0.4 ml/min using the gradient elution program. The proposed method was validated per ICH (International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use) Q2 (R1) guidelines to ensure the method is suitable for its intended purpose. RESULTS: Limit of detection and limit of quantification were obtained in the range of 0.25-0.5 ng/mL, which was very low compared to levels specified by the USFDA, European Medicines Agency (EMA), and other regulatory authorities that ensure the sensitivity of the method in its entire life cycle. CONCLUSIONS: The developed method can be incorporated into an official monograph and applied for routine quality control analysis of losartan and HCTZ fixed-dose combination tablets.
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Losartán , Nitrosaminas , Humanos , Losartán/análisis , Losartán/química , Hidroclorotiazida/química , Cromatografía Líquida de Alta Presión/métodos , Espectrometría de Masas en Tándem/métodos , Cromatografía Liquida , ComprimidosRESUMEN
Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are endogenous lipids with antidiabetic and anti-inflammatory effects. Each FAHFA family consists of esters with different acyl chains and multiple isomers with branch points at different carbons. Some FAHFAs, including palmitic acid hydroxy stearic acids (PAHSAs), improve insulin sensitivity and glucose tolerance in mice by enhancing glucose-stimulated insulin secretion (GSIS), insulin-stimulated glucose transport, and insulin action to suppress hepatic glucose production and reducing adipose tissue inflammation. However, little is known about the biological effects of other FAHFAs. Here, we investigated whether PAHSAs, oleic acid hydroxy stearic acid, palmitoleic acid hydroxy stearic acid, and stearic acid hydroxy stearic acid potentiate GSIS in ß-cells and human islets, insulin-stimulated glucose uptake in adipocytes, and anti-inflammatory effects in immune cells. We also investigated whether they activate G protein-coupled receptor 40, which mediates the effects of PAHSAs on insulin secretion and sensitivity in vivo. We show that many FAHFAs potentiate GSIS, activate G protein-coupled receptor 40, and attenuate LPS-induced chemokine and cytokine expression and secretion and phagocytosis in immune cells. However, fewer FAHFAs augment insulin-stimulated glucose uptake in adipocytes. S-9-PAHSA, but not R-9-PAHSA, potentiated GSIS and glucose uptake, while both stereoisomers had anti-inflammatory effects. FAHFAs containing unsaturated acyl chains with higher branching from the carboxylate head group are more likely to potentiate GSIS, whereas FAHFAs with lower branching are more likely to be anti-inflammatory. This study provides insight into the specificity of the biological actions of different FAHFAs and could lead to the development of FAHFAs to treat metabolic and immune-mediated diseases.
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Ésteres/metabolismo , Ácidos Grasos/metabolismo , Adulto , Ésteres/química , Ácidos Grasos/química , Femenino , Glucosa/metabolismo , Humanos , Secreción de Insulina , Masculino , Persona de Mediana Edad , Estructura Molecular , EstereoisomerismoRESUMEN
Stress hormones bind and activate the glucocorticoid receptor (GR) in many tissues including the brain. We identified arginine and glutamate rich 1 (ARGLU1) in a screen for new modulators of glucocorticoid signaling in the CNS. Biochemical studies show that the glutamate rich C-terminus of ARGLU1 coactivates multiple nuclear receptors including the glucocorticoid receptor (GR) and the arginine rich N-terminus interacts with splicing factors and binds to RNA. RNA-seq of neural cells depleted of ARGLU1 revealed significant changes in the expression and alternative splicing of distinct genes involved in neurogenesis. Loss of ARGLU1 is embryonic lethal in mice, and knockdown in zebrafish causes neurodevelopmental and heart defects. Treatment with dexamethasone, a GR activator, also induces changes in the pattern of alternatively spliced genes, many of which were lost when ARGLU1 was absent. Importantly, the genes found to be alternatively spliced in response to glucocorticoid treatment were distinct from those under transcriptional control by GR, suggesting an additional mechanism of glucocorticoid action is present in neural cells. Our results thus show that ARGLU1 is a novel factor for embryonic development that modulates basal transcription and alternative splicing in neural cells with consequences for glucocorticoid signaling.
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Desarrollo Embrionario , Glucocorticoides/farmacología , Péptidos y Proteínas de Señalización Intracelular/fisiología , Empalme del ARN/genética , Activación Transcripcional/genética , Empalme Alternativo/efectos de los fármacos , Empalme Alternativo/genética , Animales , Animales Modificados Genéticamente , Células Cultivadas , Embrión no Mamífero , Desarrollo Embrionario/efectos de los fármacos , Desarrollo Embrionario/genética , Glucocorticoides/metabolismo , Células HEK293 , Humanos , Ratones , Ratones Endogámicos C57BL , Neurogénesis/efectos de los fármacos , Neurogénesis/genética , Empalme del ARN/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Transactivadores/fisiología , Activación Transcripcional/efectos de los fármacos , Pez CebraRESUMEN
The glucocorticoid receptor (GR) represents the crucial molecular mediator of key endocrine, glucocorticoid hormone-dependent regulatory circuits, including control of glucose, protein, and lipid homeostasis. Consequently, aberrant glucocorticoid signaling is linked to severe metabolic disorders, including insulin resistance, obesity, and hyperglycemia, all of which also appear upon chronic glucocorticoid therapy for the treatment of inflammatory conditions. Of note, long-term glucocorticoid exposure under these therapeutic conditions typically induces glucocorticoid resistance, requiring higher doses and consequently triggering more severe metabolic phenotypes. However, the molecular basis of acquired glucocorticoid resistance remains unknown. In a screen of differential microRNA expression during glucocorticoid-dependent adipogenic differentiation of human multipotent adipose stem cells, we identified microRNA 29a (miR-29a) as one of the most down-regulated transcripts. Overexpression of miR-29a impaired adipogenesis. We found that miR-29a represses GR in human adipogenesis by directly targeting its mRNA, and downstream analyses revealed that GR mediates most of miR-29a's anti-adipogenic effects. Conversely, miR-29a expression depends on GR activation, creating a novel miR-29-driven feedback loop. miR-29a and GR expression were inversely correlated both in murine adipose tissue and in adipose tissue samples obtained from human patients. In the latter, miR-29a levels were additionally strongly negatively correlated with body mass index and adipocyte size. Importantly, inhibition of miR-29 in mice partially rescued the down-regulation of GR during dexamethasone treatment. We discovered that, in addition to modulating GR function under physiologic conditions, pharmacologic glucocorticoid application in inflammatory disease also induced miR-29a expression, correlating with reduced GR levels. This effect was abolished in mice with impaired GR function. In summary, we uncovered a novel GR-miR-29a negative feedback loop conserved between mice and humans, in health and disease. For the first time, we elucidate a microRNA-related mechanism that might contribute to GR dysregulation and resistance in peripheral tissues.-Glantschnig, C., Koenen, M., Gil-Lozano, M., Karbiener, M., Pickrahn, I., Williams-Dautovich, J., Patel, R., Cummins, C. L., Giroud, M., Hartleben, G., Vogl, E., Blüher, M., Tuckermann, J., Uhlenhaut, H., Herzig, S., Scheideler, M. A miR-29a-driven negative feedback loop regulates peripheral glucocorticoid receptor signaling.
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Adipocitos/citología , Regulación de la Expresión Génica , Glucocorticoides/metabolismo , MicroARNs/metabolismo , Adipocitos/metabolismo , Adipogénesis , Animales , Corticosterona/metabolismo , Retroalimentación Fisiológica , Femenino , Células HEK293 , Humanos , Inflamación , Insulina/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Obesidad/cirugía , Sobrepeso/cirugía , Fenotipo , ARN Interferente Pequeño/metabolismo , Receptores de Glucocorticoides/metabolismo , Transducción de Señal , Células Madre/citología , TransfecciónRESUMEN
BACKGROUND & AIMS: Little is known about the effects of the vitamin D receptor (VDR) on hepatic activity of human cholesterol 7α-hydroxylase (CYP7A1) and cholesterol metabolism. We studied these processes in mice in vivo and mouse and human hepatocytes. METHODS: Farnesoid X receptor (Fxr)(-/-), small heterodimer partner (Shp)(-/-), and C57BL/6 (wild-type control) mice were fed normal or Western diets for 3 weeks and were then given intraperitoneal injections of vehicle (corn oil) or 1α,25-dihydroxyvitamin D3 (1,25[OH]2D3; 4 doses, 2.5 µg/kg, every other day). Plasma and tissue samples were collected and levels of Vdr, Shp, Cyp7a1, Cyp24a1, and rodent fibroblast growth factor (Fgf) 15 expression, as well as levels of cholesterol, were measured. We studied the regulation of Shp by Vdr using reporter and mobility shift assays in transfected human embryonic kidney 293 cells, quantitative polymerase chain reaction with mouse tissues and mouse and human hepatocytes, and chromatin immunoprecipitation assays with mouse liver. RESULTS: We first confirmed the presence of Vdr mRNA and protein expression in livers of mice. In mice fed normal diets and given injections of 1,25(OH)2D3, liver and plasma concentrations of 1,25(OH)2D3 increased and decreased in unison. Changes in hepatic Cyp7a1 messenger RNA (mRNA) correlated with those of Cyp24a1 (a Vdr target gene) and inversely with Shp mRNA, but not ileal Fgf15 mRNA. Similarly, incubation with 1,25(OH)2D3 increased levels of Cyp24a1/CYP24A1 and Cyp7a1/CYP7A1 mRNA in mouse and human hepatocytes, and reduced levels of Shp mRNA in mouse hepatocytes. In Fxr(-/-) and wild-type mice with hypercholesterolemia, injection of 1,25(OH)2D3 consistently reduced levels of plasma and liver cholesterol and Shp mRNA, and increased hepatic Cyp7a1 mRNA and protein; these changes were not observed in Shp(-/-) mice given 1,25(OH)2D3 and fed Western diets. Truncation of the human small heterodimer partner (SHP) promoter and deletion analyses revealed VDR-dependent inhibition of SHP, and mobility shift assays showed direct binding of VDR to enhancer regions of SHP. In addition, chromatin immunoprecipitation analysis of livers from mice showed that injection of 1,25(OH)2D3 increased recruitment of Vdr and rodent retinoid X receptor to the Shp promoter. CONCLUSIONS: Activation of the VDR represses hepatic SHP to increase levels of mouse and human CYP7A1 and reduce cholesterol.
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Calcitriol/farmacología , Colesterol 7-alfa-Hidroxilasa/metabolismo , Colesterol/metabolismo , Hepatocitos/efectos de los fármacos , Hígado/efectos de los fármacos , Receptores de Calcitriol/agonistas , Receptores Citoplasmáticos y Nucleares/metabolismo , Animales , Sitios de Unión , Modelos Animales de Enfermedad , Factores de Crecimiento de Fibroblastos/metabolismo , Regulación Enzimológica de la Expresión Génica , Células HEK293 , Hepatocitos/enzimología , Humanos , Hipercolesterolemia/tratamiento farmacológico , Hipercolesterolemia/enzimología , Hipercolesterolemia/genética , Íleon/efectos de los fármacos , Íleon/enzimología , Hígado/enzimología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Regiones Promotoras Genéticas , ARN Mensajero/metabolismo , Receptores de Calcitriol/metabolismo , Receptores Citoplasmáticos y Nucleares/deficiencia , Receptores Citoplasmáticos y Nucleares/genética , Esteroide Hidroxilasas/metabolismo , Factores de Tiempo , Transfección , Vitamina D3 24-HidroxilasaRESUMEN
To introduce products in the US market, pharmaceutical companies must first obtain FDA clearance. Manufacturers might recall a product if it poses a risk of damage or violates FDA regulations. This study investigates the types, causes and consequences of recalls, as well as FDA participation and suitable recall strategies. We relied on the FDA website to gather recall data sets from 2012 to 2023, collecting information on the date of issuance, company and type of violation. The most frequent causes for recalls were sterility issues and inadequate compliance with current good manufacturing practices (cGMP). An examination of sterility recalls revealed two primary causes: a lack of assurance in sterility (accounting for 48% of recalls) and instances of non-sterility (making up 45% of recalls). A thorough examination of cGMP recalls revealed five primary types of violations: process control issues, inadequate storage practices, manufacturing problems, the presence of nitroso-amine impurities and concerns regarding stability. The findings demonstrate that sterility and cGMP compliance are FDA priorities. Pharmaceutical companies must, therefore, enhance quality compliance and create effective quality management systems that oversee the manufacturing process, quality control, personnel training and documentation to avoid these recalls. Companies should establish an internal compliance checklist and be prepared for the rectification process.
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Industria Farmacéutica , United States Food and Drug Administration , Estados Unidos , Industria Farmacéutica/normas , Recall de Medicamento , Humanos , Estudios RetrospectivosRESUMEN
The membrane-associated drug transporter P-glycoprotein (P-gp) plays an essential role in drug efflux from the brain. Induction of this protein at the blood-brain barrier (BBB) could further affect the ability of a drug to enter the brain. At present, P-gp induction mediated by antiretroviral drugs at the BBB has not been fully investigated. Since P-gp expression is regulated by ligand-activated nuclear receptors, i.e., human pregnane X receptor (hPXR) and human constitutive androstane receptor (hCAR), these receptors could represent potential pathways involved in P-gp induction by antiretroviral drugs. The aims of this study were (i) to determine whether antiretroviral drugs currently used in HIV pharmacotherapy are ligands for hPXR or hCAR and (ii) to examine P-gp function and expression in human brain microvessel endothelial cells treated with antiretroviral drugs identified as ligands of hPXR and/or hCAR. Luciferase reporter gene assays were performed to examine the activation of hPXR and hCAR by antiretroviral drugs. The hCMEC/D3 cell line, which is known to display several morphological and biochemical properties of the BBB in humans, was used to examine P-gp induction following 72 h of exposure to these agents. Amprenavir, atazanavir, darunavir, efavirenz, ritonavir, and lopinavir were found to activate hPXR, whereas abacavir, efavirenz, and nevirapine were found to activate hCAR. P-gp expression and function were significantly induced in hCMEC/D3 cells treated with these drugs at clinical concentrations in plasma. Together, our data suggest that P-gp induction could occur at the BBB during chronic treatment with antiretroviral drugs identified as ligands of hPXR and/or hCAR.
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Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/agonistas , Antivirales/farmacología , Células Endoteliales/efectos de los fármacos , Receptores Citoplasmáticos y Nucleares/agonistas , Receptores de Esteroides/agonistas , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Encéfalo/irrigación sanguínea , Encéfalo/citología , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Línea Celular , Receptor de Androstano Constitutivo , Células Endoteliales/citología , Células Endoteliales/metabolismo , Endotelio Vascular/citología , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Regulación de la Expresión Génica , Genes Reporteros , Humanos , Luciferasas/genética , Luciferasas/metabolismo , Microvasos/citología , Microvasos/efectos de los fármacos , Microvasos/metabolismo , Receptor X de Pregnano , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/metabolismo , Receptores de Esteroides/genética , Receptores de Esteroides/metabolismo , Transducción de SeñalRESUMEN
Synthetic glucocorticoids (GCs), including dexamethasone (DEX), are powerful anti-inflammatory drugs. Long-term use of GCs, however, can result in metabolic side effects such as hyperglycemia, hepatosteatosis, and insulin resistance. The GC receptor (GR) and liver X receptors (LXRα and LXRß) regulate overlapping genes involved in gluconeogenesis and inflammation. We have previously shown that Lxrß-/- mice are resistant to the diabetogenic effects of DEX but still sensitive to its immunosuppressive actions. To determine whether this finding could be exploited for therapeutic intervention, we treated mice with GSK2033, a pan-LXR antagonist, alone or combined with DEX. GSK2033 suppressed GC-induced gluconeogenic gene expression without affecting immune-responsive GR target genes. The suppressive effect of GSK2033 on DEX-induced gluconeogenic genes was specific to LXRß, was liver cell autonomous, and occurred in a target gene-specific manner. Compared with DEX treatment alone, the coadministration of GSK2033 with DEX decreased the recruitment of GR and its accessory factors MED1 and C/EBPß to the phosphoenolpyruvate carboxykinase promoter. However, GSK2033 had no effect on DEX-mediated suppression of inflammatory genes expressed in the liver or in mouse primary macrophages stimulated with lipopolysaccharides. In conclusion, our study provides evidence that the gluconeogenic and immunosuppressive actions of GR activation can be mechanistically dissociated by pharmacological antagonism of LXRß. Treatment with an LXRß antagonist could allow the safer use of existing GC drugs in patients requiring chronic dosing of anti-inflammatory agents for the treatment of diseases such as rheumatoid arthritis and inflammatory bowel disease.
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Dexametasona/farmacología , Expresión Génica/efectos de los fármacos , Glucocorticoides/farmacología , Gluconeogénesis/genética , Inflamación/genética , Receptores X del Hígado/antagonistas & inhibidores , Receptores de Glucocorticoides/metabolismo , Animales , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Inflamación/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Receptores X del Hígado/metabolismo , Ratones , Sulfonamidas/farmacologíaRESUMEN
We found previously that short-term curcumin gavage stimulated mouse hepatic fibroblast growth factor 21 (Fgf21) expression. Here we conducted mechanistic exploration and investigated the potential pathophysiological relevance on this regulation. Fgf21 stimulation was observed at messenger RNA and protein levels in mice with daily curcumin gavage for 4 or 8 days and in primary hepatocytes with curcumin treatment. Using peroxisome proliferator-activated receptor α (PPARα) agonist and antagonist, along with luciferase reporter and chromatin immune-precipitation approaches, we determined that curcumin stimulates Fgf21 transcription in a mechanism involving PPARα activation. High-fat diet (HFD) feeding also increased mouse hepatic and serum Fgf21 levels, whereas dietary curcumin intervention attenuated these increases. We found that HFD feeding reduced hepatic expression levels of genes that encode FGFR1 and ßKlotho, PGC1α, and the targets of the PPARα-PGC1α axis, whereas concomitant curcumin intervention restored or partially restored their expression levels. Importantly, hepatocytes from HFD-fed mice showed a loss of response to FGF21 treatment on Erk phosphorylation and the expression of Egr1 and cFos; this response was restored in hepatocytes from HFD-fed mice with curcumin intervention. This investigation expanded our mechanistic understanding of the metabolic beneficial effects of dietary curcumin intervention involving the regulation of Fgf21 production and the attenuation of HFD-induced Fgf21 resistance.
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Curcumina/farmacología , Dieta Alta en Grasa/efectos adversos , Factores de Crecimiento de Fibroblastos/metabolismo , Hígado/efectos de los fármacos , Animales , Curcumina/uso terapéutico , Regulación de la Expresión Génica , Células Hep G2 , Humanos , Hígado/metabolismo , Masculino , Enfermedades Metabólicas/etiología , Enfermedades Metabólicas/prevención & control , Ratones , Obesidad/etiología , Obesidad/prevención & control , PPAR alfa/metabolismoRESUMEN
Glucocorticoids (GCs) have unparalleled anti-inflammatory and immunosuppressive properties, which accounts for their widespread prescription and use. Unfortunately, a limitation to GC therapy is a wide range of negative side effects including Cushing's syndrome, a disease characterized by metabolic abnormalities including muscle wasting and osteoporosis. GC-induced osteoporosis occurs in 30% to 50% of patients on GC therapy and thus, represents an important area of study. Herein, we characterize the molecular and physiologic effects of GC-induced osteoporosis using the Cushing's mouse model, the corticotropin releasing hormone (CRH) transgenic mouse (CRH-Tg). The humeri, femurs, and tibias from wild-type (WT) and CRH-Tg male mice, aged 13 to 14 weeks old were subjected to multiple bone tests including, micro-computed tomography (µCT), static and dynamic histomorphometry, strength testing, and gene expression analyses. The CRH-Tg mice had a 38% decrease in cortical bone area, a 35% decrease in cortical thickness, a 16% decrease in trabecular thickness, a sixfold increase in bone adiposity, a 27% reduction in osteoid width, a 75% increase in bone-resorbing osteoclast number/bone surface, a 34% decrease in bone formation rate, and a 40% decrease in bone strength compared to WT mice. At the gene expression level, CRH-Tg bone showed significantly increased osteoclast markers and decreased osteoblast markers, whereas CRH-Tg muscle had increased muscle atrophy gene markers compared to WT mice. Overall, the CRH-Tg mouse model aged to 14 weeks recapitulated many features of osteoporosis in Cushing's syndrome and thus, represents a useful model to study GC-induced osteoporosis and interventions that target the effects of GCs on the skeleton. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.
RESUMEN
Hormones such as fibroblast growth factor 21 (FGF21) and glucocorticoids (GCs) play crucial roles in coordinating the adaptive starvation response. Here we examine the interplay between these hormones. It was previously shown that FGF21 induces corticosterone levels in mice by acting on the brain. We now show that this induces the expression of genes required for GC synthesis in the adrenal gland. FGF21 also increases corticosterone secretion from the adrenal in response to ACTH. We further show that the relationship between FGF21 and GCs is bidirectional. GCs induce Fgf21 expression in the liver by acting on the GC receptor (GR). The GR binds in a ligand-dependent manner to a noncanonical GR response element located approximately 4.4 kb upstream of the Fgf21 transcription start site. The GR cooperates with the nuclear fatty acid receptor, peroxisome proliferator-activated receptor-α, to stimulate Fgf21 transcription. GR and peroxisome proliferator-activated receptor-α ligands have additive effects on Fgf21 expression both in vivo and in primary cultures of mouse hepatocytes. We conclude that FGF21 and GCs regulate each other's production in a feed-forward loop and suggest that this provides a mechanism for bypassing negative feedback on the hypothalamic-pituitary-adrenal axis to allow sustained gluconeogenesis during starvation.
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Factores de Crecimiento de Fibroblastos/metabolismo , Glucocorticoides/farmacología , Corteza Suprarrenal/citología , Corteza Suprarrenal/metabolismo , Hormona Adrenocorticotrópica/farmacología , Animales , Emparejamiento Base , Sitios de Unión , Cromatina/metabolismo , Corticosterona/biosíntesis , Dexametasona/farmacología , Sitios Genéticos , Humanos , Hígado/efectos de los fármacos , Hígado/metabolismo , Ratones Endogámicos C57BL , Ratones Transgénicos , Modelos Biológicos , PPAR alfa/metabolismo , Unión Proteica/efectos de los fármacos , Receptores de Glucocorticoides/metabolismo , Sitio de Iniciación de la Transcripción , Activación Transcripcional/efectos de los fármacosRESUMEN
The glucocorticoid receptor (GR) was one of the first nuclear hormone receptors cloned and represents one of the most effective drug targets available today for the treatment of severe inflammation. The physiologic consequences of endogenous or exogenous glucocorticoid excess are well established and include hyperglycemia, insulin resistance, fatty liver, obesity, and muscle wasting. However, at the molecular and tissue-specific level, there are still many unknown protein mediators of glucocorticoid response and thus, much remains to be uncovered that will help determine whether activation of the GR can be tailored to improve therapeutic efficacy while minimizing unwanted side effects. This review summarizes recent discoveries of tissue-selective modulators of glucocorticoid signaling that are important in mediating the unwanted side effects of therapeutic glucocorticoid use, emphasizing the downstream molecular effects of GR activation in the liver, adipose tissue, muscle, and pancreas.
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Glucocorticoides/farmacología , Receptores de Glucocorticoides/metabolismo , Transducción de Señal/fisiología , Adipogénesis/fisiología , Tejido Adiposo/metabolismo , Animales , Glucocorticoides/efectos adversos , Gluconeogénesis/fisiología , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Humanos , Inflamación/tratamiento farmacológico , Lipogénesis/fisiología , Lipólisis/fisiología , Hígado/metabolismo , Ratones , Músculos/metabolismo , Páncreas/metabolismoRESUMEN
Although widely prescribed for their potent antiinflammatory actions, glucocorticoid drugs (e.g., dexamethasone) cause undesirable side effects that are features of the metabolic syndrome, including hyperglycemia, fatty liver, insulin resistance, and type II diabetes. Liver x receptors (LXRs) are nuclear receptors that respond to cholesterol metabolites and regulate the expression of a subset of glucocorticoid target genes. Here, we show LXRß is required to mediate many of the negative side effects of glucocorticoids. Mice lacking LXRß (but not LXRα) were resistant to dexamethasone-induced hyperglycemia, hyperinsulinemia, and hepatic steatosis, but remained sensitive to dexamethasone-dependent repression of the immune system. In vivo, LXRα/ß knockout mice demonstrated reduced dexamethasone-induced expression of the key hepatic gluconeogenic gene, phosphoenolpyruvate carboxykinase (PEPCK). In perfused liver and primary mouse hepatocytes, LXRß was required for glucocorticoid-induced recruitment of the glucocorticoid receptor to the PEPCK promoter. These findings suggest a new avenue for the design of safer glucocorticoid drugs through a mechanism of selective glucocorticoid receptor transactivation.