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1.
Circulation ; 2021 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-34583519

RESUMO

Background: The integrated stress response (ISR) is an evolutionarily conserved process to cope with intracellular and extracellular disturbances. Myocardial infarction is a leading cause of death worldwide. Coronary artery reperfusion is the most effective means to mitigate cardiac damage of myocardial infarction, which however causes additional reperfusion injury. This study aimed to investigate the role of the ISR in myocardial ischemia/reperfusion (I/R). Methods: Cardiac-specific gain- and loss-of-function approaches for the ISR were employed in vivo. Myocardial I/R was achieved by the ligation of the cardiac left anterior descending artery for 45 minutes, followed by reperfusion for different times. Cardiac function was assessed by echocardiography. Additionally, cultured H9c2 cells, primary rat cardiomyocytes, and mouse embryonic fibroblasts were used to dissect underlying molecular mechanisms. Moreover, tandem mass tag (TMT) labeling and mass spectrometry was conducted to identify protein targets of the ISR. Pharmacological means were tested to manipulate the ISR for therapeutic exploration. Results: We show that the PERK/eIF2α axis of the ISR is strongly induced by I/R in cardiomyocytes in vitro and in vivo. We further reveal a physiological role of PERK/eIF2α signaling by showing that acute activation of PERK in the heart confers robust cardioprotection against reperfusion injury. In contrast, cardiac-specific deletion of PERK aggravates cardiac responses to reperfusion. Mechanistically, the ISR directly targets mitochondrial complexes via translational suppression. We identify NDUFAF2, an assembly factor of mitochondrial complex I, as a selective target of PERK. Overexpression of PERK suppresses the protein expression of NDUFAF2 while PERK inhibition causes an increase of NDUFAF2. Silencing of NDUFAF2 significantly rescues cardiac cell survival from PERK knockdown under I/R. Further, we show that activation of PERK/eIF2α signaling reduces mitochondrial complex-derived reactive oxygen species and improves cardiac cell survival in response to I/R. Moreover, pharmacological stimulation of the ISR protects the heart against reperfusion damage, even after the restoration of occluded coronary artery, highlighting a clinical relevance for myocardial infarction treatment. Conclusions: These studies suggest that the ISR improves cell survival and mitigate reperfusion damage by selectively suppressing mitochondrial protein synthesis and reducing oxidative stress in the heart.

2.
Cell Metab ; 33(10): 2059-2075.e10, 2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34536344

RESUMO

Myocardial ischemia-reperfusion (MIR) injury is a major cause of adverse outcomes of revascularization after myocardial infarction. To identify the fundamental regulator of reperfusion injury, we performed metabolomics profiling in plasma of individuals before and after revascularization and identified a marked accumulation of arachidonate 12-lipoxygenase (ALOX12)-dependent 12-HETE following revascularization. The potent induction of 12-HETE proceeded by reperfusion was conserved in post-MIR in mice, pigs, and monkeys. While genetic inhibition of Alox12 protected mouse hearts from reperfusion injury and remodeling, Alox12 overexpression exacerbated MIR injury. Remarkably, pharmacological inhibition of ALOX12 significantly reduced cardiac injury in mice, pigs, and monkeys. Unexpectedly, ALOX12 promotes cardiomyocyte injury beyond its enzymatic activity and production of 12-HETE but also by its suppression of AMPK activity via a direct interaction with its upstream kinase TAK1. Taken together, our study demonstrates that ALOX12 is a novel AMPK upstream regulator in the post-MIR heart and that it represents a conserved therapeutic target for the treatment of myocardial reperfusion injury.

3.
Circulation ; 144(9): 712-727, 2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34102853

RESUMO

BACKGROUND: Metabolic remodeling precedes most alterations during cardiac hypertrophic growth under hemodynamic stress. The elevation of glucose utilization has been recognized as a hallmark of metabolic remodeling. However, its role in cardiac hypertrophic growth and heart failure in response to pressure overload remains to be fully illustrated. Here, we aimed to dissect the role of cardiac PKM1 (pyruvate kinase muscle isozyme 1) in glucose metabolic regulation and cardiac response under pressure overload. METHODS: Cardiac-specific deletion of PKM1 was achieved by crossing the floxed PKM1 mouse model with the cardiomyocyte-specific Cre transgenic mouse. PKM1 transgenic mice were generated under the control of tetracycline response elements, and cardiac-specific overexpression of PKM1 was induced by doxycycline administration in adult mice. Pressure overload was triggered by transverse aortic constriction. Primary neonatal rat ventricular myocytes were used to dissect molecular mechanisms. Moreover, metabolomics and nuclear magnetic resonance spectroscopy analyses were conducted to determine cardiac metabolic flux in response to pressure overload. RESULTS: We found that PKM1 expression is reduced in failing human and mouse hearts. It is important to note that cardiomyocyte-specific deletion of PKM1 exacerbates cardiac dysfunction and fibrosis in response to pressure overload. Inducible overexpression of PKM1 in cardiomyocytes protects the heart against transverse aortic constriction-induced cardiomyopathy and heart failure. At the mechanistic level, PKM1 is required for the augmentation of glycolytic flux, mitochondrial respiration, and ATP production under pressure overload. Furthermore, deficiency of PKM1 causes a defect in cardiomyocyte growth and a decrease in pyruvate dehydrogenase complex activity at both in vitro and in vivo levels. CONCLUSIONS: These findings suggest that PKM1 plays an essential role in maintaining a homeostatic response in the heart under hemodynamic stress.

4.
J Hepatol ; 75(2): 387-399, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33746082

RESUMO

BACKGROUND & AIMS: We have previously reported that the mitochondrial dicarboxylate carrier (mDIC [SLC25A10]) is predominantly expressed in the white adipose tissue (WAT) and subject to regulation by metabolic cues. However, the specific physiological functions of mDIC and the reasons for its abundant presence in adipocytes are poorly understood. METHODS: To systemically investigate the impact of mDIC function in adipocytes in vivo, we generated loss- and gain-of-function mouse models, selectively eliminating or overexpressing mDIC in mature adipocytes, respectively. RESULTS: In in vitro differentiated white adipocytes, mDIC is responsible for succinate transport from the mitochondrial matrix to the cytosol, from where succinate can act on the succinate receptor SUCNR1 and inhibit lipolysis by dampening the cAMP- phosphorylated hormone-sensitive lipase (pHSL) pathway. We eliminated mDIC expression in adipocytes in a doxycycline (dox)-inducible manner (mDICiKO) and demonstrated that such a deletion results in enhanced adipocyte lipolysis and promotes high-fat diet (HFD)-induced adipocyte dysfunction, liver lipotoxicity, and systemic insulin resistance. Conversely, in a mouse model with dox-inducible, adipocyte-specific overexpression of mDIC (mDICiOE), we observed suppression of adipocyte lipolysis both in vivo and ex vivo. mDICiOE mice are potently protected from liver lipotoxicity upon HFD feeding. Furthermore, they show resistance to HFD-induced weight gain and adipose tissue expansion with concomitant improvements in glucose tolerance and insulin sensitivity. Beyond our data in rodents, we found that human WAT SLC25A10 mRNA levels are positively correlated with insulin sensitivity and negatively correlated with intrahepatic triglyceride levels, suggesting a critical role of mDIC in regulating overall metabolic homeostasis in humans as well. CONCLUSIONS: In summary, we highlight that mDIC plays an essential role in governing adipocyte lipolysis and preventing liver lipotoxicity in response to a HFD. LAY SUMMARY: Dysfunctional fat tissue plays an important role in the development of fatty liver disease and liver injury. Our present study identifies a mitochondrial transporter, mDIC, which tightly controls the release of free fatty acids from adipocytes to the liver through the export of succinate from mitochondria. We believe this mDIC-succinate axis could be targeted for the treatment of fatty liver disease.

6.
Cell Rep ; 32(9): 108087, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32877669

RESUMO

The heart manifests hypertrophic growth in response to high blood pressure, which may decompensate and progress to heart failure under persistent stress. Metabolic remodeling is an early event in this process. However, its role remains to be fully characterized. Here, we show that lactate dehydrogenase A (LDHA), a critical glycolytic enzyme, is elevated in the heart in response to hemodynamic stress. Cardiomyocyte-restricted deletion of LDHA leads to defective cardiac hypertrophic growth and heart failure by pressure overload. Silencing of LDHA in cultured cardiomyocytes suppresses cell growth from pro-hypertrophic stimulation in vitro, while overexpression of LDHA is sufficient to drive cardiomyocyte growth. Furthermore, we find that lactate is capable of rescuing the growth defect from LDHA knockdown. Mechanistically, lactate stabilizes NDRG3 (N-myc downregulated gene family 3) and stimulates ERK (extracellular signal-regulated kinase). Our results together suggest that the LDHA/NDRG3 axis may play a critical role in adaptive cardiomyocyte growth in response to hemodynamic stress.


Assuntos
Cardiomegalia/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Lactato Desidrogenase 5/metabolismo , Células Cultivadas , Hemodinâmica , Humanos , Transdução de Sinais
7.
Nat Commun ; 11(1): 2551, 2020 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-32439985

RESUMO

Forkhead box O (FoxO) proteins and thyroid hormone (TH) have well established roles in cardiovascular morphogenesis and remodeling. However, specific role(s) of individual FoxO family members in stress-induced growth and remodeling of cardiomyocytes remains unknown. Here, we report that FoxO1, but not FoxO3, activity is essential for reciprocal regulation of types II and III iodothyronine deiodinases (Dio2 and Dio3, respectively), key enzymes involved in intracellular TH metabolism. We further show that Dio2 is a direct transcriptional target of FoxO1, and the FoxO1-Dio2 axis governs TH-induced hypertrophic growth of neonatal cardiomyocytes in vitro and in vivo. Utilizing transverse aortic constriction as a model of hemodynamic stress in wild-type and cardiomyocyte-restricted FoxO1 knockout mice, we unveil an essential role for the FoxO1-Dio2 axis in afterload-induced pathological cardiac remodeling and activation of TRα1. These findings demonstrate a previously unrecognized FoxO1-Dio2 signaling axis in stress-induced cardiomyocyte growth and remodeling and intracellular TH homeostasis.


Assuntos
Proteína Forkhead Box O1/metabolismo , Iodeto Peroxidase/metabolismo , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Hormônios Tireóideos/metabolismo , Animais , Animais Recém-Nascidos , Cardiomegalia/metabolismo , Cardiomegalia/patologia , Cardiomegalia/fisiopatologia , Células Cultivadas , Proteína Forkhead Box O1/genética , Regulação da Expressão Gênica , Iodeto Peroxidase/antagonistas & inibidores , Iodeto Peroxidase/genética , Camundongos , Camundongos Knockout , Ratos , Transdução de Sinais , Remodelação Ventricular
8.
Nat Commun ; 11(1): 1771, 2020 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-32286306

RESUMO

The hexosamine biosynthetic pathway (HBP) plays critical roles in nutrient sensing, stress response, and cell growth. However, its contribution to cardiac hypertrophic growth and heart failure remains incompletely understood. Here, we show that the HBP is induced in cardiomyocytes during hypertrophic growth. Overexpression of Gfat1 (glutamine:fructose-6-phosphate amidotransferase 1), the rate-limiting enzyme of HBP, promotes cardiomyocyte growth. On the other hand, Gfat1 inhibition significantly blunts phenylephrine-induced hypertrophic growth in cultured cardiomyocytes. Moreover, cardiac-specific overexpression of Gfat1 exacerbates pressure overload-induced cardiac hypertrophy, fibrosis, and cardiac dysfunction. Conversely, deletion of Gfat1 in cardiomyocytes attenuates pathological cardiac remodeling in response to pressure overload. Mechanistically, persistent upregulation of the HBP triggers decompensated hypertrophy through activation of mTOR while Gfat1 deficiency shows cardioprotection and a concomitant decrease in mTOR activity. Taken together, our results reveal that chronic upregulation of the HBP under hemodynamic stress induces pathological cardiac hypertrophy and heart failure through persistent activation of mTOR.


Assuntos
Hexosaminas/metabolismo , Miócitos Cardíacos/metabolismo , Acetilglucosamina , Animais , Proliferação de Células/genética , Proliferação de Células/fisiologia , Ecocardiografia , Glutamina-Frutose-6-Fosfato Transaminase (Isomerizante)/genética , Glutamina-Frutose-6-Fosfato Transaminase (Isomerizante)/metabolismo , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Miócitos Cardíacos/efeitos dos fármacos , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase em Tempo Real , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Sirolimo/farmacologia , Proteína 1 de Ligação a X-Box/genética , Proteína 1 de Ligação a X-Box/metabolismo
9.
EMBO Mol Med ; 11(11): e9127, 2019 11 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.


Assuntos
Cardiomegalia/fisiopatologia , Regulação da Expressão Gênica , Miócitos Cardíacos/fisiologia , Correpressor 1 de Receptor Nuclear/metabolismo , Animais , Técnicas de Silenciamento de Genes , Técnicas de Inativação de Genes , Redes Reguladoras de Genes , Humanos , Fatores de Transcrição MEF2/metabolismo , Camundongos , Camundongos Knockout , Correpressor 1 de Receptor Nuclear/deficiência , Ligação Proteica , Mapeamento de Interação de Proteínas
11.
Circulation ; 140(7): 566-579, 2019 08 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.


Assuntos
Proliferação de Células/fisiologia , DNA Recombinante/biossíntese , Miócitos Cardíacos/metabolismo , Serina-Treonina Quinases TOR/biossíntese , Proteína 1 de Ligação a X-Box/biossíntese , Adolescente , Adulto , Animais , Animais Recém-Nascidos , Células Cultivadas , DNA Recombinante/genética , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Pessoa de Meia-Idade , Ratos , Ratos Sprague-Dawley , Serina-Treonina Quinases TOR/genética , Proteína 1 de Ligação a X-Box/genética , Adulto Jovem
12.
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
13.
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.


Assuntos
Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/fisiopatologia , Estresse Nitrosativo , Volume Sistólico , Animais , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Endorribonucleases/metabolismo , Insuficiência Cardíaca/prevenção & controle , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico Sintase Tipo II/antagonistas & inibidores , Óxido Nítrico Sintase Tipo II/deficiência , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Fenótipo , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Proteína 1 de Ligação a X-Box/genética , Proteína 1 de Ligação a X-Box/metabolismo
14.
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.


Assuntos
Fator de Transcrição GATA4/fisiologia , Proteínas de Choque Térmico/fisiologia , Miócitos Cardíacos/patologia , Animais , Hipertrofia , Camundongos , Camundongos Endogâmicos C57BL , Dobramento de Proteína , Serina-Treonina Quinases TOR/fisiologia , Resposta a Proteínas não Dobradas
15.
Mol Metab ; 11: 212-217, 2018 05.
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.


Assuntos
Proliferação de Células , Proteínas de Ligação a DNA/genética , Diabetes Mellitus Experimental/metabolismo , Células Secretoras de Insulina/metabolismo , Proteínas Supressoras de Tumor/genética , Regulação para Cima , Animais , Proteínas de Ligação a DNA/metabolismo , Diabetes Mellitus Experimental/genética , Feminino , Células Secretoras de Insulina/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Transdução de Sinais , Proteínas Supressoras de Tumor/metabolismo
16.
Cell Death Differ ; 25(12): 2181-2194, 2018 12.
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.


Assuntos
Proteínas de Choque Térmico/metabolismo , Miócitos Cardíacos/citologia , Miócitos Cardíacos/metabolismo , Animais , Sobrevivência Celular , Células Cultivadas , Ecocardiografia , Proteínas de Choque Térmico/deficiência , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Ratos , Ratos Sprague-Dawley
18.
Circ Res ; 122(11): 1545-1554, 2018 05 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.


Assuntos
Proteínas de Choque Térmico/metabolismo , Isquemia Miocárdica/prevenção & controle , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Miócitos Cardíacos/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Resposta a Proteínas não Dobradas , Animais , Apoptose , Células Cultivadas , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Isquemia Miocárdica/complicações , Isquemia Miocárdica/metabolismo , Traumatismo por Reperfusão Miocárdica/etiologia , Traumatismo por Reperfusão Miocárdica/metabolismo , Estresse Oxidativo , Fosfatidilinositol 3-Quinases/metabolismo , Ratos , Espécies Reativas de Oxigênio/metabolismo , Regulação para Cima
19.
Mol Metab ; 11: 1-17, 2018 05.
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.


Assuntos
Adipócitos/metabolismo , Obesidade/metabolismo , Uridina/metabolismo , Proteína 1 de Ligação a X-Box/metabolismo , Animais , Células Cultivadas , Lipólise , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proteína 1 de Ligação a X-Box/genética
20.
Cell Rep ; 22(7): 1760-1773, 2018 02 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.


Assuntos
Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/fisiopatologia , Glucose/metabolismo , Coração/fisiopatologia , Receptores de Glucagon/antagonistas & inibidores , Adenilato Quinase/metabolismo , Animais , Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/uso terapêutico , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/enzimologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/enzimologia , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Cardiomiopatias Diabéticas/complicações , Cardiomiopatias Diabéticas/patologia , Cardiomiopatias Diabéticas/prevenção & controle , Modelos Animais de Doenças , Ativação Enzimática/efeitos dos fármacos , Gluconeogênese/efeitos dos fármacos , Teste de Tolerância a Glucose , Hiperglicemia/complicações , Hiperglicemia/metabolismo , Hiperglicemia/patologia , Insulina/farmacologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Lipídeos/toxicidade , Fígado/metabolismo , Camundongos , Receptores de Glucagon/metabolismo
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