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1.
EMBO Mol Med ; 11(11): e9127, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31532577

RESUMO

The function of nuclear receptor corepressor 1 (NCoR1) in cardiomyocytes is unclear, and its physiological and pathological implications are unknown. Here, we found that cardiomyocyte-specific NCoR1 knockout (CMNKO) mice manifested cardiac hypertrophy at baseline and had more severe cardiac hypertrophy and dysfunction after pressure overload. Knockdown of NCoR1 exacerbated whereas overexpression mitigated phenylephrine-induced cardiomyocyte hypertrophy. Mechanistic studies revealed that myocyte enhancer factor 2a (MEF2a) and MEF2d mediated the effects of NCoR1 on cardiomyocyte hypertrophy. The receptor interaction domains (RIDs) of NCoR1 interacted with MEF2a to repress its transcriptional activity. Furthermore, NCoR1 formed a complex with MEF2a and class IIa histone deacetylases (HDACs) to suppress hypertrophy-related genes. Finally, overexpression of RIDs of NCoR1 in the heart attenuated cardiac hypertrophy and dysfunction induced by pressure overload. In conclusion, NCoR1 cooperates with MEF2 and HDACs to repress cardiac hypertrophy. Targeting NCoR1 and the MEF2/HDACs complex may be an attractive therapeutic strategy to tackle pathological cardiac hypertrophy.

2.
Circulation ; 140(7): 566-579, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31177839

RESUMO

BACKGROUND: The unfolded protein response plays versatile roles in physiology and pathophysiology. Its connection to cell growth, however, remains elusive. Here, we sought to define the role of unfolded protein response in the regulation of cardiomyocyte growth in the heart. METHODS: We used both gain- and loss-of-function approaches to genetically manipulate XBP1s (spliced X-box binding protein 1), the most conserved signaling branch of the unfolded protein response, in the heart. In addition, primary cardiomyocyte culture was used to address the role of XBP1s in cell growth in a cell-autonomous manner. RESULTS: We found that XBP1s expression is reduced in both human and rodent cardiac tissues under heart failure. Furthermore, deficiency of XBP1s leads to decompensation and exacerbation of heart failure progression under pressure overload. On the other hand, cardiac-restricted overexpression of XBP1s prevents the development of cardiac dysfunction. Mechanistically, we found that XBP1s stimulates adaptive cardiac growth through activation of the mechanistic target of rapamycin signaling, which is mediated via FKBP11 (FK506-binding protein 11), a novel transcriptional target of XBP1s. Moreover, silencing of FKBP11 significantly diminishes XBP1s-induced mechanistic target of rapamycin activation and adaptive cell growth. CONCLUSIONS: Our results reveal a critical role of the XBP1s-FKBP11-mechanistic target of rapamycin axis in coupling of the unfolded protein response and cardiac cell growth regulation.

3.
J Am Heart Assoc ; 8(12): e012673, 2019 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-31185774
4.
Curr Top Med Chem ; 19(21): 1902-1917, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31109279

RESUMO

Cardiovascular disease is the leading cause of death worldwide. Despite overwhelming socioeconomic impact and mounting clinical needs, our understanding of the underlying pathophysiology remains incomplete. Multiple forms of cardiovascular disease involve an acute or chronic disturbance in cardiac myocytes, which may lead to potent activation of the Unfolded Protein Response (UPR), a cellular adaptive reaction to accommodate protein-folding stress. Accumulation of unfolded or misfolded proteins in the Endoplasmic Reticulum (ER) elicits three signaling branches of the UPR, which otherwise remain quiescent. This ER stress response then transiently suppresses global protein translation, augments production of protein-folding chaperones, and enhances ER-associated protein degradation, with an aim to restore cellular homeostasis. Ample evidence has established that the UPR is strongly induced in heart disease. Recently, the mechanisms of action and multiple pharmacological means to favorably modulate the UPR are emerging to curb the initiation and progression of cardiovascular disease. Here, we review the current understanding of the UPR in cardiovascular disease and discuss existing therapeutic explorations and future directions.


Assuntos
Fármacos Cardiovasculares/farmacologia , Doenças Cardiovasculares/tratamento farmacológico , Animais , Doenças Cardiovasculares/patologia , Retículo Endoplasmático/efeitos dos fármacos , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Humanos , Resposta a Proteínas não Dobradas/efeitos dos fármacos
5.
Nature ; 568(7752): 351-356, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30971818

RESUMO

Heart failure with preserved ejection fraction (HFpEF) is a common syndrome with high morbidity and mortality for which there are no evidence-based therapies. Here we report that concomitant metabolic and hypertensive stress in mice-elicited by a combination of high-fat diet and inhibition of constitutive nitric oxide synthase using Nω-nitro-L-arginine methyl ester (L-NAME)-recapitulates the numerous systemic and cardiovascular features of HFpEF in humans. Expression of one of the unfolded protein response effectors, the spliced form of X-box-binding protein 1 (XBP1s), was reduced in the myocardium of our rodent model and in humans with HFpEF. Mechanistically, the decrease in XBP1s resulted from increased activity of inducible nitric oxide synthase (iNOS) and S-nitrosylation of the endonuclease inositol-requiring protein 1α (IRE1α), culminating in defective XBP1 splicing. Pharmacological or genetic suppression of iNOS, or cardiomyocyte-restricted overexpression of XBP1s, each ameliorated the HFpEF phenotype. We report that iNOS-driven dysregulation of the IRE1α-XBP1 pathway is a crucial mechanism of cardiomyocyte dysfunction in HFpEF.

6.
Hypertension ; 73(2): 390-398, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30580686

RESUMO

The heart manifests hypertrophic growth in response to elevation of afterload pressure. Cardiac myocyte growth involves new protein synthesis and membrane expansion, of which a number of cellular quality control machineries are stimulated to maintain function and homeostasis. The unfolded protein response is potently induced during cardiac hypertrophy to enhance protein-folding capacity and eliminate terminally misfolded proteins. However, whether the unfolded protein response directly regulates cardiac myocyte growth remains to be fully determined. Here, we show that GRP78 (glucose-regulated protein of 78 kDa)-an endoplasmic reticulum-resident chaperone and a critical unfolded protein response regulator-is induced by cardiac hypertrophy. Importantly, overexpression of GRP78 in cardiomyocytes is sufficient to potentiate hypertrophic stimulus-triggered growth. At the in vivo level, TG (transgenic) hearts overexpressing GRP78 mount elevated hypertrophic growth in response to pressure overload. We went further to show that GRP78 increases GATA4 (GATA-binding protein 4) level, which may stimulate Anf (atrial natriuretic factor) expression and promote cardiac hypertrophic growth. Silencing of GATA4 in cultured neonatal rat ventricular myocytes significantly diminishes GRP78-mediated growth response. Our results, therefore, reveal that protein-folding chaperone GRP78 may directly enhance cardiomyocyte growth by stimulating cardiac-specific transcriptional factor GATA4.

7.
Circ Res ; 122(11): 1545-1554, 2018 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-29669712

RESUMO

RATIONALE: Restoration of coronary artery blood flow is the most effective means of ameliorating myocardial damage triggered by ischemic heart disease. However, coronary reperfusion elicits an increment of additional injury to the myocardium. Accumulating evidence indicates that the unfolded protein response (UPR) in cardiomyocytes is activated by ischemia/reperfusion (I/R) injury. Xbp1s (spliced X-box binding protein 1), the most highly conserved branch of the unfolded protein response, is protective in response to cardiac I/R injury. GRP78 (78 kDa glucose-regulated protein), a master regulator of the UPR and an Xbp1s target, is upregulated after I/R. However, its role in the protective response of Xbp1s during I/R remains largely undefined. OBJECTIVE: To elucidate the role of GRP78 in the cardiomyocyte response to I/R using both in vitro and in vivo approaches. METHODS AND RESULTS: Simulated I/R injury to cultured neonatal rat ventricular myocytes induced apoptotic cell death and strong activation of the UPR and GRP78. Overexpression of GRP78 in neonatal rat ventricular myocytes significantly protected myocytes from I/R-induced cell death. Furthermore, cardiomyocyte-specific overexpression of GRP78 ameliorated I/R damage to the heart in vivo. Exploration of underlying mechanisms revealed that GRP78 mitigates cellular damage by suppressing the accumulation of reactive oxygen species. We go on to show that the GRP78-mediated cytoprotective response involves plasma membrane translocation of GRP78 and interaction with PI3 kinase, culminating in stimulation of Akt. This response is required as inhibition of the Akt pathway significantly blunted the antioxidant activity and cardioprotective effects of GRP78. CONCLUSIONS: I/R induction of GRP78 in cardiomyocytes stimulates Akt signaling and protects against oxidative stress, which together protect cells from I/R damage.

8.
Cell Death Differ ; 25(12): 2181-2194, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29666470

RESUMO

Secretory and transmembrane proteins rely on proper function of the secretory pathway for folding, posttranslational modification, assembly, and secretion. Accumulation of misfolded proteins in the endoplasmic reticulum (ER) stimulates the unfolded protein response (UPR), which communicates between the ER and other organelles to enhance ER-folding capacity and restore cellular homeostasis. Glucose-regulated protein of 78 kDa (GRP78), an ER-resident protein chaperone, is a master regulator of all UPR signaling branches. Accumulating studies have established a fundamental role of GRP78 in protein folding, ER stress response, and cell survival. However, role of GRP78 in the heart remains incompletely characterized. Here we showed that embryos lacking GRP78 specifically in cardiac myocytes manifest cardiovascular malformations and die in utero at late gestation. We went further to show that inducible knockout of GRP78 in adult cardiac myocytes causes early mortality due to cardiac cell death and severe decline in heart performance. At the cellular level, we found that loss of GRP78 increases apoptotic cell death, which is accompanied by reduction in AKT signaling and augmentation of production for reactive oxygen species. Importantly, enhancing AKT phosphorylation and activity leads to decreases in oxidative stress and increases in cardiac myocyte survival. Collectively, our results demonstrate an essential role of GRP78 in ensuring normal cardiogenesis and maintaining cardiac contractility and function.

10.
Mol Metab ; 11: 212-217, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29650351

RESUMO

OBJECTIVE: Both Type I and Type II diabetes mellitus result from insufficient functional ß-cell mass. Efforts to increase ß-cell proliferation as a means to restore ß-cell mass have been met with limited success. Suppression of Tumorigenicity 5 (ST5) activates Ras/Erk signaling in the presence of Epidermal Growth Factor (EGF). In the pancreatic islet, Ras/Erk signaling is required for augmented ß-cell proliferation during pregnancy, suggesting that ST5 is an appealing candidate to enhance adult ß-cell proliferation. We aimed to test the hypothesis that overexpression of ST5 drives adult ß-cell proliferation. METHODS: We utilized a doxycycline-inducible bitransgenic mouse model to activate ß-cell-specific expression of human ST5 in adult mice at will. Islet morphology, ß-cell proliferation, and ß-cell mass in control and ST5-overexpressing (ST5 OE) animals were analyzed by immunofluorescent staining, under basal and two stimulated metabolic states: pregnancy and streptozotocin (STZ)-induced ß-cell loss. RESULTS: Doxycycline treatment resulted in robust ST5 overexpression in islets from 12-16 week-old ST5 OE animals compared to controls, without affecting the islet morphology and identity of the ß-cells. Under both basal and metabolically stimulated pregnancy states, ß-cell proliferation and mass were comparable in ST5 OE and control animals. Furthermore, there was no detectable difference in ß-cell proliferation between ST5 OE and control animals in response to STZ-induced ß-cell loss. CONCLUSIONS: We successfully derived an inducible bitransgenic mouse model to overexpress ST5 specifically in ß-cells. However, our findings demonstrate that ST5 overexpression by itself has no mitogenic effect on the adult ß-cell under basal and metabolically challenged states.

11.
Mol Metab ; 11: 1-17, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29551634

RESUMO

OBJECTIVE: The spliced transcription factor Xbp1 (Xbp1s), a transducer of the unfolded protein response (UPR), regulates lipolysis. Lipolysis is stimulated by fasting when uridine synthesis is also activated in adipocytes. METHODS: Here we have examined the regulatory role Xbp1s in stimulation of uridine biosynthesis in adipocytes and triglyceride mobilization using inducible mouse models. RESULTS: Xbp1s is a key molecule involved in adipocyte uridine biosynthesis and release by activation of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, dihydroorotase (CAD), the rate-limiting enzyme for UMP biosynthesis. Adipocyte Xbp1s overexpression drives energy mobilization and protects mice from obesity through activation of the pyrimidine biosynthesis pathway. CONCLUSION: These observations reveal that Xbp1s is a potent stimulator of uridine production in adipocytes, enhancing lipolysis and invoking a potential anti-obesity strategy through the induction of a futile biosynthetic cycle.

12.
Cell Rep ; 22(7): 1760-1773, 2018 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-29444429

RESUMO

The antidiabetic potential of glucagon receptor antagonism presents an opportunity for use in an insulin-centric clinical environment. To investigate the metabolic effects of glucagon receptor antagonism in type 2 diabetes, we treated Leprdb/db and Lepob/ob mice with REMD 2.59, a human monoclonal antibody and competitive antagonist of the glucagon receptor. As expected, REMD 2.59 suppresses hepatic glucose production and improves glycemia. Surprisingly, it also enhances insulin action in both liver and skeletal muscle, coinciding with an increase in AMP-activated protein kinase (AMPK)-mediated lipid oxidation. Furthermore, weekly REMD 2.59 treatment over a period of months protects against diabetic cardiomyopathy. These functional improvements are not derived simply from correcting the systemic milieu; nondiabetic mice with cardiac-specific overexpression of lipoprotein lipase also show improvements in contractile function after REMD 2.59 treatment. These observations suggest that hyperglucagonemia enables lipotoxic conditions, allowing the development of insulin resistance and cardiac dysfunction during disease progression.

13.
J Mol Cell Cardiol ; 117: 19-25, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29470977

RESUMO

Ischemic heart disease is a severe stress condition that causes extensive pathological alterations and triggers cardiac cell death. Accumulating evidence suggests that the unfolded protein response (UPR) is strongly induced by myocardial ischemia. The UPR is an evolutionarily conserved cellular response to cope with protein-folding stress, from yeast to mammals. Endoplasmic reticulum (ER) transmembrane sensors detect the accumulation of unfolded proteins and stimulate a signaling network to accommodate unfolded and misfolded proteins. Distinct mechanisms participate in the activation of three major signal pathways, viz. protein kinase RNA-like ER kinase, inositol-requiring protein 1, and activating transcription factor 6, to transiently suppress protein translation, enhance protein folding capacity of the ER, and augment ER-associated degradation to refold denatured proteins and restore cellular homeostasis. However, if the stress is severe and persistent, the UPR elicits inflammatory and apoptotic pathways to eliminate terminally affected cells. The ER is therefore recognized as a vitally important organelle that determines cell survival or death. Recent studies indicate the UPR plays critical roles in the pathophysiology of ischemic heart disease. The three signaling branches may elicit distinct but overlapping effects in cardiac response to ischemia. Here, we outline the findings and discuss the mechanisms of action and therapeutic potentials of the UPR in the treatment of ischemic heart disease.

14.
Am J Physiol Heart Circ Physiol ; 313(6): H1119-H1129, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-28822967

RESUMO

Hypertension is one of the most important risk factors of heart failure. In response to high blood pressure, the left ventricle manifests hypertrophic growth to ameliorate wall stress, which may progress into decompensation and trigger pathological cardiac remodeling. Despite the clinical importance, the temporal dynamics of pathological cardiac growth remain elusive. Here, we took advantage of the puromycin labeling approach to measure the relative rates of protein synthesis as a way to delineate the temporal regulation of cardiac hypertrophic growth. We first identified the optimal treatment conditions for puromycin in neonatal rat ventricular myocyte culture. We went on to demonstrate that myocyte growth reached its peak rate after 8-10 h of growth stimulation. At the in vivo level, with the use of an acute surgical model of pressure-overload stress, we observed the maximal growth rate to occur at day 7 after surgery. Moreover, RNA sequencing analysis supports that the most profound transcriptomic changes occur during the early phase of hypertrophic growth. Our results therefore suggest that cardiac myocytes mount an immediate growth response in reply to pressure overload followed by a gradual return to basal levels of protein synthesis, highlighting the temporal dynamics of pathological cardiac hypertrophic growth.NEW & NOTEWORTHY We determined the optimal conditions of puromycin incorporation in cardiac myocyte culture. We took advantage of this approach to identify the growth dynamics of cardiac myocytes in vitro. We went further to discover the protein synthesis rate in vivo, which provides novel insights about cardiac temporal growth dynamics in response to pressure overload.


Assuntos
Aorta Torácica/fisiopatologia , Pressão Arterial , Cardiomegalia/patologia , Proliferação de Células , Miócitos Cardíacos/patologia , Animais , Animais Recém-Nascidos , Aorta Torácica/cirurgia , Cardiomegalia/etiologia , Cardiomegalia/metabolismo , Cardiomegalia/fisiopatologia , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Constrição , Modelos Animais de Doenças , Regulação da Expressão Gênica , Masculino , Camundongos Endogâmicos C57BL , Proteínas Musculares/biossíntese , Proteínas Musculares/genética , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Biossíntese de Proteínas , Puromicina/metabolismo , Ratos Sprague-Dawley , Fatores de Tempo
15.
J Biol Chem ; 292(33): 13774-13783, 2017 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-28705935

RESUMO

Autophagy has been shown to be important for normal homeostasis and adaptation to stress in the kidney. Yet, the molecular mechanisms regulating renal epithelial autophagy are not fully understood. Here, we explored the role of the stress-responsive transcription factor forkhead box O3 (FoxO3) in mediating injury-induced proximal tubular autophagy in mice with unilateral ureteral obstruction (UUO). We show that following UUO, FoxO3 is activated and displays nuclear expression in the hypoxic proximal tubules exhibiting high levels of autophagy. Activation of FoxO3 by mutating phosphorylation sites to enhance its nuclear expression induces profound autophagy in cultured renal epithelial cells. Conversely, deleting FoxO3 in mice results in fewer numbers of autophagic cells in the proximal tubules and reduced ratio of the autophagy-related protein LC3-II/I in the kidney post-UUO. Interestingly, autophagic cells deficient in FoxO3 contain lower numbers of autophagic vesicles per cell. Analyses of individual cells treated with autophagic inhibitors to sequentially block the autophagic flux suggest that FoxO3 stimulates the formation of autophagosomes to increase autophagic capacity but has no significant effect on autophagosome-lysosome fusion or autolysosomal clearance. Furthermore, in kidneys with persistent UUO for 7 days, FoxO3 activation increases the abundance of mRNA and protein levels of the core autophagy-related (Atg) proteins including Ulk1, Beclin-1, Atg9A, Atg4B, and Bnip3, suggesting that FoxO3 may function to maintain components of the autophagic machinery that would otherwise be consumed during prolonged autophagy. Taken together, our findings indicate that FoxO3 activation can both induce and maintain autophagic activities in renal epithelial cells in response to injury from urinary tract obstruction.


Assuntos
Autofagia , Núcleo Celular/metabolismo , Modelos Animais de Doenças , Proteína Forkhead Box O3/metabolismo , Regulação para Cima , Obstrução Ureteral/metabolismo , Transporte Ativo do Núcleo Celular , Animais , Proteínas Relacionadas à Autofagia/genética , Proteínas Relacionadas à Autofagia/metabolismo , Biomarcadores/metabolismo , Hipóxia Celular , Núcleo Celular/patologia , Células Cultivadas , Feminino , Proteína Forkhead Box O3/genética , Deleção de Genes , Genes Reporter , Túbulos Renais Proximais/citologia , Túbulos Renais Proximais/metabolismo , Túbulos Renais Proximais/patologia , Camundongos Knockout , Camundongos Transgênicos , Proteínas Associadas aos Microtúbulos/metabolismo , Mutação , Fosforilação , Processamento de Proteína Pós-Traducional , Obstrução Ureteral/patologia
16.
Proc Natl Acad Sci U S A ; 114(25): 6611-6616, 2017 06 20.
Artigo em Inglês | MEDLINE | ID: mdl-28584109

RESUMO

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a class of antidiabetic drug used for the treatment of diabetes. These drugs are thought to lower blood glucose by blocking reabsorption of glucose by SGLT2 in the proximal convoluted tubules of the kidney. To investigate the effect of inhibiting SGLT2 on pancreatic hormones, we treated perfused pancreata from rats with chemically induced diabetes with dapagliflozin and measured the response of glucagon secretion by alpha cells in response to elevated glucose. In these type 1 diabetic rats, glucose stimulated glucagon secretion by alpha cells; this was prevented by dapagliflozin. Two models of type 2 diabetes, severely diabetic Zucker rats and db/db mice fed dapagliflozin, showed significant improvement of blood glucose levels and glucose disposal, with reduced evidence of glucagon signaling in the liver, as exemplified by reduced phosphorylation of hepatic cAMP-responsive element binding protein, reduced expression of phosphoenolpyruvate carboxykinase 2, increased hepatic glycogen, and reduced hepatic glucose production. Plasma glucagon levels did not change significantly. However, dapagliflozin treatment reduced the expression of the liver glucagon receptor. Dapagliflozin in rodents appears to lower blood glucose levels in part by suppressing hepatic glucagon signaling through down-regulation of the hepatic glucagon receptor.


Assuntos
Compostos Benzidrílicos/farmacologia , Diabetes Mellitus Experimental/tratamento farmacológico , Glucagon/metabolismo , Glucosídeos/farmacologia , Hipoglicemiantes/farmacologia , Transdução de Sinais/efeitos dos fármacos , Animais , Glicemia/efeitos dos fármacos , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Regulação para Baixo/efeitos dos fármacos , Células Secretoras de Glucagon/efeitos dos fármacos , Células Secretoras de Glucagon/metabolismo , Glucose/metabolismo , Túbulos Renais Proximais/efeitos dos fármacos , Túbulos Renais Proximais/metabolismo , Masculino , Camundongos , Ratos , Ratos Sprague-Dawley , Ratos Zucker , Roedores/metabolismo , Transportador 2 de Glucose-Sódio/metabolismo
17.
Science ; 355(6330)2017 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-28302796

RESUMO

Uridine, a pyrimidine nucleoside present at high levels in the plasma of rodents and humans, is critical for RNA synthesis, glycogen deposition, and many other essential cellular processes. It also contributes to systemic metabolism, but the underlying mechanisms remain unclear. We found that plasma uridine levels are regulated by fasting and refeeding in mice, rats, and humans. Fasting increases plasma uridine levels, and this increase relies largely on adipocytes. In contrast, refeeding reduces plasma uridine levels through biliary clearance. Elevation of plasma uridine is required for the drop in body temperature that occurs during fasting. Further, feeding-induced clearance of plasma uridine improves glucose metabolism. We also present findings that implicate leptin signaling in uridine homeostasis and consequent metabolic control and thermoregulation. Our results indicate that plasma uridine governs energy homeostasis and thermoregulation in a mechanism involving adipocyte-dependent uridine biosynthesis and leptin signaling.


Assuntos
Adipócitos/metabolismo , Regulação da Temperatura Corporal , Metabolismo Energético , Jejum/metabolismo , Eliminação Hepatobiliar , Uridina/biossíntese , Uridina/sangue , Animais , Glicemia/metabolismo , Humanos , Leptina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Ratos , Ratos Sprague-Dawley , Transdução de Sinais
18.
J Cell Mol Med ; 20(12): 2249-2258, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27489081

RESUMO

The liver X receptor (LXR) is a cholesterol-sensing nuclear receptor that has an established function in lipid metabolism; however, its role in inflammation is elusive. In this study, we showed that the LXR agonist GW3965 exhibited potent anti-inflammatory activity by suppressing the firm adhesion of monocytes to endothelial cells. To further address the mechanisms underlying the inhibition of inflammatory cell infiltration, we evaluated the effects of LXR agonist on interleukin-8 (IL-8) secretion and nuclear factor-kappa B (NF-κB) activation in human umbilical vein endothelial cells (HUVECs). The LXR agonist significantly inhibited lysophosphatidylcholine (LPC)-induced IL-8 production in a dose-dependent manner without appreciable cytotoxicity. Western blotting and the NF-κB transcription activity assay showed that the LXR agonist inhibited p65 binding to the IL-8 promoter in LPC-stimulated HUVECs. Interestingly, knockdown of the indispensable small ubiquitin-like modifier (SUMO) ligases Ubc9 and Histone deacetylase 4 (HDAC4) reversed the increase in IL-8 induced by LPC. Furthermore, the LPC-induced degradation of inhibitory κBα was delayed under the conditions of deficient SUMOylation or the treatment of LXR agonist. After enhancing SUMOylation by knockdown SUMO-specific protease Sentrin-specific protease 1 (SENP1), the inhibition of GW3965 was rescued on LPC-mediated IL-8 expression. These findings indicate that LXR-mediated inflammatory gene repression correlates to the suppression of NF-κB pathway and SUMOylation. Our results suggest that LXR agonist exerts the anti-atherosclerotic role by attenuation of the NF-κB pathway in endothelial cells.


Assuntos
Células Endoteliais da Veia Umbilical Humana/metabolismo , Interleucina-8/metabolismo , Receptores X do Fígado/metabolismo , Lisofosfatidilcolinas/farmacologia , NF-kappa B/metabolismo , Transdução de Sinais/efeitos dos fármacos , Sumoilação/efeitos dos fármacos , Adesão Celular/efeitos dos fármacos , Linhagem Celular , Humanos , Interleucina-8/biossíntese , Receptores X do Fígado/agonistas , Monócitos/citologia , Monócitos/efeitos dos fármacos , Monócitos/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos
19.
Mol Metab ; 5(7): 437-448, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27408770

RESUMO

BACKGROUND: Evidence hints at the ability of ß-cells to emerge from non-ß-cells upon genetic or pharmacological interventions. However, their quantitative contributions to the process of autonomous ß-cell regeneration without genetic or pharmacological manipulations remain to be determined. METHODS & RESULTS: Using PANIC-ATTAC mice, a model of titratable, acute ß-cell apoptosis capable of autonomous, and effective islet mass regeneration, we demonstrate that an extended washout of residual tamoxifen activity is crucial for ß-cell lineage tracing studies using the tamoxifen-inducible Cre/loxP systems. We further establish a doxycycline-inducible system to label different cell types in the mouse pancreas and pursued a highly quantitative assessment to trace adult ß-cells after various metabolic challenges. Beyond proliferation of pre-existing ß-cells, non-ß-cells contribute significantly to the post-challenge regenerated ß-cell pool. α-cell trans-differentiation is the predominant mechanism upon post-apoptosis regeneration and multiparity. No contributions from exocrine acinar cells were observed. During diet-induced obesity, about 25% of α-cells arise de novo from ß-cells. Ectopic expression of Nkx6.1 promotes α-to-ß conversion and insulin production. CONCLUSIONS: We identify the origins and fates of adult ß-cells upon post-challenge upon autonomous regeneration of islet mass and establish the quantitative contributions of the different cell types using a lineage tracing system with high temporal resolution.

20.
Nat Med ; 22(7): 771-9, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27270587

RESUMO

The discovery of genetic mechanisms for resistance to obesity and diabetes may illuminate new therapeutic strategies for the treatment of this global health challenge. We used the polygenic 'lean' mouse model, which has been selected for low adiposity over 60 generations, to identify mitochondrial thiosulfate sulfurtransferase (Tst; also known as rhodanese) as a candidate obesity-resistance gene with selectively increased expression in adipocytes. Elevated adipose Tst expression correlated with indices of metabolic health across diverse mouse strains. Transgenic overexpression of Tst in adipocytes protected mice from diet-induced obesity and insulin-resistant diabetes. Tst-deficient mice showed markedly exacerbated diabetes, whereas pharmacological activation of TST ameliorated diabetes in mice. Mechanistically, TST selectively augmented mitochondrial function combined with degradation of reactive oxygen species and sulfide. In humans, TST mRNA expression in adipose tissue correlated positively with insulin sensitivity in adipose tissue and negatively with fat mass. Thus, the genetic identification of Tst as a beneficial regulator of adipocyte mitochondrial function may have therapeutic significance for individuals with type 2 diabetes.


Assuntos
Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Tipo 2/genética , Resistência à Insulina/genética , Mitocôndrias/metabolismo , Obesidade/genética , Tiossulfato Sulfurtransferase/genética , Animais , Diferenciação Celular , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Dieta Hiperlipídica , Técnicas de Introdução de Genes , Técnica Clamp de Glucose , Teste de Tolerância a Glucose , Humanos , Camundongos , Camundongos Endogâmicos , Camundongos Transgênicos , Modelos Animais , Terapia de Alvo Molecular , Obesidade/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Tiossulfato Sulfurtransferase/metabolismo
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