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1.
Autophagy ; : 1-16, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34985382

RESUMO

Barth syndrome (BTHS) is an X-linked genetic disorder caused by mutations in the TAFAZZIN/Taz gene which encodes a transacylase required for cardiolipin remodeling. Cardiolipin is a mitochondrial signature phospholipid that plays a pivotal role in maintaining mitochondrial membrane structure, respiration, mtDNA biogenesis, and mitophagy. Mutations in the TAFAZZIN gene deplete mature cardiolipin, leading to mitochondrial dysfunction, dilated cardiomyopathy, and premature death in BTHS patients. Currently, there is no effective treatment for this debilitating condition. In this study, we showed that TAFAZZIN deficiency caused hyperactivation of MTORC1 signaling and defective mitophagy, leading to accumulation of autophagic vacuoles and dysfunctional mitochondria in the heart of Tafazzin knockdown mice, a rodent model of BTHS. Consequently, treatment of TAFAZZIN knockdown mice with rapamycin, a potent inhibitor of MTORC1, not only restored mitophagy, but also mitigated mitochondrial dysfunction and dilated cardiomyopathy. Taken together, these findings identify MTORC1 as a novel therapeutic target for BTHS, suggesting that pharmacological restoration of mitophagy may provide a novel treatment for BTHS.Abbreviations: BTHS: Barth syndrome; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CL: cardiolipin; EIF4EBP1/4E-BP1: eukaryotic translation initiation factor 4E binding protein 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; KD: knockdown; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; LV: left ventricle; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; OCR: oxygen consumption rate; PE: phosphatidylethanolamine; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PINK1: PTEN induced putative kinase 1; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; qRT-PCR: quantitative real-time polymerase chain reaction; RPS6KB/S6K: ribosomal protein S6 kinase beta; SQSTM1/p62: sequestosome 1; TLCL: tetralinoleoyl cardiolipin; WT: wild-type.

2.
J Clin Invest ; 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34730111

RESUMO

Dysregulation in adipokine biosynthesis and function contributes to obesity-induced metabolic diseases. However, the identities and functions of many of the obesity-induced secretory molecules remain unknown. Here, we report the identification of leucine-rich alpha-2-glycoprotein 1 (LRG1) as an obesity-associated adipokine that exacerbates high fat diet-induced hepatosteatosis and insulin resistance. Serum levels of LRG1 were markedly elevated in obese humans and mice compared to their respective controls. LRG1 deficiency in mice greatly alleviated diet-induced hepatosteatosis, obesity, and insulin resistance. Mechanistically, LRG1 bound with high selectivity to the liver and promoted hepatosteatosis by increasing de novo lipogenesis and suppressing fatty acid ß-oxidation. LRG1 also inhibited hepatic insulin signaling by down-regulating insulin receptor substrates 1 and 2. Our study identified LRG1 as a key molecule that mediates the crosstalk between adipocytes and hepatocytes in diet-induced hepatosteatosis and insulin resistance. Suppressing LRG1 expression and function may be a promising strategy for the treatment of obesity-related metabolic diseases.

3.
Diabetes ; 70(10): 2333-2343, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34244238

RESUMO

Obesity and type 2 diabetes mellitus (T2DM) are the leading causes of cardiovascular morbidity and mortality. Although insulin resistance is believed to underlie these disorders, anecdotal evidence contradicts this common belief. Accordingly, obese patients with cardiovascular disease have better prognoses relative to leaner patients with the same diagnoses, whereas treatment of T2DM patients with thiazolidinedione, one of the popular insulin-sensitizer drugs, significantly increases the risk of heart failure. Using mice with skeletal musclespecific ablation of the insulin receptor gene (MIRKO), we addressed this paradox by demonstrating that insulin signaling in skeletal muscles specifically mediated cross talk with the heart, but not other metabolic tissues, to prevent cardiac dysfunction in response to metabolic stress. Despite severe hyperinsulinemia and aggregating obesity, MIRKO mice were protected from myocardial insulin resistance, mitochondrial dysfunction, and metabolic reprogramming in response to diet-induced obesity. Consequently, the MIRKO mice were also protected from myocardial inflammation, cardiomyopathy, and left ventricle dysfunction. Together, our findings suggest that insulin resistance in skeletal muscle functions as a double-edged sword in metabolic diseases.

4.
Mol Ther ; 29(12): 3498-3511, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34111561

RESUMO

Cardiolipin is a mitochondrial signature phospholipid that plays a pivotal role in maintaining cardiac health. A loss of tetralinoleoyl cardiolipin (TLCL), the predominant cardiolipin species in the healthy mammalian heart, is implicated in the pathogenesis of coronary heart disease (CHD) through poorly defined mechanisms. Here, we identified acyl-coenzyme A:lysocardiolipin acyltransferase-1 (ALCAT1) as the missing link between hypoxia and CHD in an animal model of myocardial infarction (MI). ALCAT1 is an acyltransferase that promotes mitochondrial dysfunction in aging-related diseases by catalyzing pathological remodeling of cardiolipin. In support of a causative role of ALCAT1 in CHD, we showed that ALCAT1 expression was potently upregulated by MI, linking myocardial hypoxia to oxidative stress, TLCL depletion, and mitochondrial dysfunction. Accordingly, ablation of the ALCAT1 gene or pharmacological inhibition of the ALCAT1 enzyme by Dafaglitapin (Dafa), a potent and highly specific ALCAT1 inhibitor, not only restored TLCL levels but also mitochondrial respiration by attenuating signal transduction pathways mediated by hypoxia-inducible factor 1α (HIF-1α). Consequently, ablation or pharmacological inhibition of ALCAT1 by Dafa effectively mitigated CHD and its underlying pathogenesis, including dilated cardiomyopathy, left ventricle dysfunction, myocardial inflammation, fibrosis, and apoptosis. Together, the findings have provided the first proof-of-concept studies for targeting ALCAT1 as an effective treatment for CHD.

5.
Mol Metab ; 42: 101055, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32738348

RESUMO

OBJECTIVE: Cholesterol plays a pivotal role in mitochondrial steroidogenesis, membrane structure, and respiration. Mitochondrial membranes are intrinsically low in cholesterol content and therefore must be replenished with cholesterol from other subcellular membranes. However, the molecular mechanisms underlying mitochondrial cholesterol transport remains poorly understood. The Aster-B gene encodes a cholesterol binding protein recently implicated in cholesterol trafficking from the plasma membrane to the endoplasmic reticulum (ER). In this study, we investigated the function and underlying mechanism of Aster-B in mediating mitochondrial cholesterol transport. METHODS: CRISPR/Cas9 gene editing was carried out to generate cell lines deficient in Aster-B expression. The effect of Aster-B deficiency on mitochondrial cholesterol transport was examined by both confocal imaging analysis and biochemical assays. Deletion mutational analysis was also carried out to identify the function of a putative mitochondrial targeting sequence (MTS) at the N-terminus of Aster-B for its role in targeting Aster-B to mitochondria and in mediating mitochondrial cholesterol trafficking. RESULTS: Ablation of Aster-B impaired cholesterol transport from the ER to mitochondria, leading to a significant decrease in mitochondrial cholesterol content. Aster-B is also required for mitochondrial transport of fatty acids derived from hydrolysis of cholesterol esters. A putative MTS at the N-terminus of Aster-B mediates the mitochondrial cholesterol uptake. Deletion of the MTS or ablation of Arf1 GTPase which is required for mitochondrial translocation of ER proteins prevented mitochondrial cholesterol transport, leading to mitochondrial dysfunction. CONCLUSIONS: We identified Aster-B as a key regulator of cholesterol transport from the ER to mitochondria. Aster-B also coordinates mitochondrial cholesterol trafficking with uptake of fatty acids derived from cholesterol esters, implicating the Aster-B protein as a novel regulator of steroidogenesis.


Assuntos
Fator 1 de Ribosilação do ADP/metabolismo , Colesterol/metabolismo , Proteínas de Membrana/metabolismo , Fator 1 de Ribosilação do ADP/fisiologia , Animais , Transporte Biológico , Proteínas de Transporte , Linhagem Celular , Retículo Endoplasmático/metabolismo , Células HeLa , Humanos , Proteínas de Membrana Transportadoras/metabolismo , Camundongos , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Elastase Pancreática
6.
EMBO Rep ; 21(9): e49898, 2020 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-32648345

RESUMO

Nutrient sensing by the mTOR complex 1 (mTORC1) requires its translocation to the lysosomal membrane. Upon amino acids removal, mTORC1 becomes cytosolic and inactive, yet its precise subcellular localization and the mechanism of inhibition remain elusive. Here, we identified Aster-C as a negative regulator of mTORC1 signaling. Aster-C earmarked a special rough ER subdomain where it sequestered mTOR together with the GATOR2 complex to prevent mTORC1 activation during nutrient starvation. Amino acids stimulated rapid disassociation of mTORC1 from Aster-C concurrently with assembly of COP I vesicles which escorted mTORC1 to the lysosomal membrane. Consequently, ablation of Aster-C led to spontaneous activation of mTORC1 and dissociation of TSC2 from lysosomes, whereas inhibition of COP I vesicle biogenesis or actin dynamics prevented mTORC1 activation. Together, these findings identified Aster-C as a missing link between lysosomal trafficking and mTORC1 activation by revealing an unexpected role of COP I vesicles in mTORC1 signaling.


Assuntos
Complexo I de Proteína do Envoltório , Lisossomos , Complexo I de Proteína do Envoltório/metabolismo , Lisossomos/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Transporte Proteico , Transdução de Sinais
7.
Cell Mol Gastroenterol Hepatol ; 7(4): 763-781, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30831319

RESUMO

BACKGROUND & AIMS: Obesity promotes the development of nonalcoholic fatty liver diseases (NAFLDs), yet not all obese patients develop NAFLD. The underlying causes for this discrepancy remain elusive. LPGAT1 is an acyltransferase that catalyzes the remodeling of phosphatidylglycerol (PG), a mitochondrial phospholipid implicated in various metabolic diseases. Here, we investigated the role of LPGAT1 in regulating the onset of diet-induced obesity and its related hepatosteatosis because polymorphisms of the LPGAT1 gene promoter were strongly associated with susceptibility to obesity in Pima Indians. METHODS: Mice with whole-body knockout of LPGAT1 were generated to investigate the role of PG remodeling in NAFLD. RESULTS: LPGAT1 deficiency protected mice from diet-induced obesity, but led to hepatopathy, insulin resistance, and NAFLD as a consequence of oxidative stress, mitochondrial DNA depletion, and mitochondrial dysfunction. CONCLUSIONS: This study identified an unexpected role of PG remodeling in obesity, linking mitochondrial dysfunction to NAFLD.


Assuntos
Fígado Gorduroso/metabolismo , Fígado Gorduroso/patologia , Mitocôndrias/patologia , Fosfatidilgliceróis/metabolismo , Aciltransferases/deficiência , Aciltransferases/metabolismo , Animais , Cardiolipinas/metabolismo , Dieta , Estresse do Retículo Endoplasmático , Feminino , Hepatócitos/metabolismo , Hepatócitos/patologia , Insulina/metabolismo , Resistência à Insulina , Cirrose Hepática/patologia , Masculino , Camundongos Knockout , Mitocôndrias/metabolismo , Hepatopatia Gordurosa não Alcoólica/patologia , Obesidade/metabolismo , Obesidade/patologia , Estresse Oxidativo , Transdução de Sinais
8.
Aging Cell ; 18(3): e12941, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30838774

RESUMO

Cardiolipin (CL) is a mitochondrial signature phospholipid that is required for membrane structure, respiration, dynamics, and mitophagy. Oxidative damage of CL by reactive oxygen species is implicated in the pathogenesis of Parkinson's disease (PD), but the underlying cause remains elusive. This work investigated the role of ALCAT1, an acyltransferase that catalyzes pathological remodeling of CL in various aging-related diseases, in a mouse model of PD induced by 1-methyl-4-phenyl-1,2,4,6-tetrahydropyridine (MPTP). We show that MPTP treatment caused oxidative stress, mtDNA mutations, and mitochondrial dysfunction in the midbrain. In contrast, ablation of the ALCAT1 gene or pharmacological inhibition of ALCAT1 prevented MPTP-induced neurotoxicity, apoptosis, and motor deficits. ALCAT1 deficiency also mitigated mitochondrial dysfunction by modulating DRP1 translocation to the mitochondria. Moreover, pharmacological inhibition of ALCAT1 significantly improved mitophagy by promoting the recruitment of Parkin to dysfunctional mitochondria. Finally, ALCAT1 expression was upregulated by MPTP and by α-synucleinopathy, a key hallmark of PD, whereas ALCAT1 deficiency prevented α-synuclein oligomerization and S-129 phosphorylation, implicating a key role of ALCAT1 in the etiology of mouse models of PD. Together, these findings identify ALCAT1 as a novel drug target for the treatment of PD.


Assuntos
Aciltransferases/metabolismo , Locomoção , Intoxicação por MPTP/metabolismo , Mitocôndrias/metabolismo , Degeneração Neural/metabolismo , alfa-Sinucleína/metabolismo , Aciltransferases/antagonistas & inibidores , Aciltransferases/genética , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Cardiolipinas/química , Cardiolipinas/metabolismo , Linhagem Celular Tumoral , Modelos Animais de Doenças , Humanos , Locomoção/efeitos dos fármacos , Locomoção/genética , Camundongos , Camundongos Transgênicos , Mitocôndrias/genética , Dinâmica Mitocondrial/efeitos dos fármacos , Dinâmica Mitocondrial/genética , Mitofagia/efeitos dos fármacos , Mitofagia/genética , Degeneração Neural/genética , Degeneração Neural/mortalidade , Fosforilação , Espécies Reativas de Oxigênio/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , alfa-Sinucleína/química
9.
Medicine (Baltimore) ; 97(30): e11438, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30045265

RESUMO

This study is to characterize the transcription factor expression profiles for the peripheral CD4 T-cell subsets, and analyze its associations with the clinical measures of the hepatitis B virus (HBV) infection.Totally 275 subjects were included. The expression levels of transcription factors (T-bet, GATA-3, Foxp3, RORγt, and Bcl-6) in the peripheral blood mononuclear cells (PBMCs) were determined by the real-time fluorimetry quantitative PCR (FQ-PCR).Lowest expression levels of all these transcription factors were observed for the HBsAb(-) group, which were higher in the HBsAb(+) and RHB groups. The T-bet/GATA-3 ratios in the CHB and RHB groups were significantly lower than the HBsAb(-) group, whereas the RORγt/Foxp3 ratios in the AHB and RHB groups were significantly higher than the CHB and HBsAb(+) groups. Furthermore, the RORγt mRNA expression levels were significantly different among groups with different disease severities or with different alanine aminotransferase (ALT) levels. The asymptomatic carrier (AsC) group and the group with ALT ≤ 40 had the highest express level. The mRNA expression levels of T-bet, GATA-3, Foxp3, and RORγt varied along with the aspartate aminotransferase (AST) levels, with AST ≤ 40 having the highest expression levels. In addition, significant differences were observed in the transcription factor expression levels between the group with the serum HBV DNA load of (1.000-9.999) × 10 copies/mL and other groups.Expression profile of critical transcription factors for peripheral CD4 T-cell subsets may indicate clinical outcomes of HBV infection.


Assuntos
Alanina Transaminase/sangue , Aspartato Aminotransferases/sangue , Linfócitos T CD4-Positivos/patologia , Fatores de Transcrição Forkhead/genética , Hepatite B , Leucócitos Mononucleares , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/genética , Adulto , Feminino , Hepatite B/sangue , Hepatite B/diagnóstico , Hepatite B/genética , Vírus da Hepatite B/imunologia , Humanos , Leucócitos Mononucleares/imunologia , Leucócitos Mononucleares/patologia , Masculino , Pessoa de Meia-Idade , Prognóstico , RNA Mensageiro/genética , Índice de Gravidade de Doença , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/patologia , Fatores de Transcrição/genética
10.
Endocrinology ; 159(8): 3036-3047, 2018 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-29873699

RESUMO

Rho GDP-dissociation inhibitor (GDIα) inhibits glucose-stimulated insulin secretion (GSIS) in part by locking Rho GTPases in an inactive GDP-bound form. The onset of GSIS causes phosphorylation of GDIα at Ser174, a critical inhibitory site for GDIα, leading to the release of Rho GTPases and their subsequent activation. However, the kinase regulator(s) that catalyzes the phosphorylation of GDIα in islet ß cells remains elusive. We propose that SAD-A, a member of AMP-activated protein kinase-related kinases that promotes GSIS as an effector kinase for incretin signaling, interacts with and inhibits GDIα through phosphorylation of Ser174 during the onset GSIS from islet ß cells. Coimmunoprecipitation and phosphorylation analyses were carried out to identify the physical interaction and phosphorylation site of GDIα by SAD-A in the context of GSIS from INS-1 ß cells and primary islets. We identified GDIα directly binds to SAD-A kinase domain and phosphorylated by SAD-A on Ser174, leading to dissociation of Rho GTPases from GDIα complexes. Accordingly, overexpression of SAD-A significantly stimulated GDIα phosphorylation at Ser174 in response to GSIS, which is dramatically potentiated by glucagonlike peptide-1, an incretin hormone. Conversely, SAD-A deficiency, which is mediated by short hairpin RNA transfection in INS-1 cells, significantly attenuated endogenous GDIα phosphorylation at Ser174. Consequently, coexpression of SAD-A completely prevented the inhibitory effect of GDIα on insulin secretion in islets. In summary, glucose and incretin stimulate insulin secretion through the phosphorylation of GDIα at Ser174 by SAD-A, which leads to the activation of Rho GTPases, culminating in insulin exocytosis.


Assuntos
Glucose/metabolismo , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Inibidor alfa de Dissociação do Nucleotídeo Guanina rho/metabolismo , Animais , Linhagem Celular , Exenatida/farmacologia , Peptídeo 1 Semelhante ao Glucagon/farmacologia , Glucose/farmacologia , Incretinas/farmacologia , Secreção de Insulina/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Masculino , Camundongos , Fosforilação/efeitos dos fármacos , Ligação Proteica , Ratos
11.
J Med Virol ; 90(5): 926-935, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29350417

RESUMO

Hepatic fibrosis is a frequent feature of chronic hepatitis C virus (HCV) infection. Some evidence has suggested the potential role of silent information regulator 1 (SIRT1) in organ fibrosis. The aim of this study was to investigate the effect of HCV core protein on expression of SIRT1 of liver sinusoidal endothelial cell (LSEC) and function of LSEC. LSECs were co-cultured with HepG2 cells or HepG2 cells expressing HCV core protein and LSECs cultured alone were used as controls. After co-culture, the activity and expression levels of mRNA and protein of SIRT1 in LSEC were detected by a SIRT1 fluorometric assay kit, real time-PCR (RT-PCR), Western blot, respectively. The levels of adiponectin receptor 2 (AdipoR2), endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) were measured by Western blot. Cluster of differentiation 31 (CD31), CD14, and von Willebrand factor (vWf) of LSECs was performed by flow cytometry. The level of reactive oxygen species (ROS) was assayed. Malondialdehyde (MDA), superoxide dismutase (SOD), adiponectin, nitric oxide (NO), and endothelin-1 (ET-1) levels in the co-culture supernatant were measured. The co-culture supernatant was then used to cultivate LX-2 cells. The levels of α-smooth muscle actin (ASMA) and transforming growth factor-ß1 (TGF-ß1) protein in LX-2 cells were measured by Western blot. Compared with LSEC co-cultured with HepG2 cells group, in LSEC co-cultured with HepG2-core cells group, the activity and expression level of mRNA and protein of SIRT1 reduced; the level of adiponectin reduced and the expression level of AdipoR2 protein decreased; ROS levels increased; the expression level of eNOS, VEGF protein decreased; and the expression level of CD14 decreased; the expression level of vWf and CD31 increased; NO and SOD levels decreased; whereas ET-1 and MDA levels increased; the levels of ASMA and TGF-ß1 protein in LX-2 cells increased. SIRT1 activator improved the above-mentioned changes. HCV core protein may down-regulate the activity and the expression of SIRT1 of LSEC, then decreasing synthesis of adiponectin and the expression of AdipoR2, thus inducing contraction of LSEC and hepatic sinusoidal capillarization and increasing oxidative stress, ultimately cause hepatic stellate cell (HSC) activation. Treatment with SIRT1 activator restored the function of LSEC and inhibited the activation of HSC.


Assuntos
Regulação para Baixo , Células Endoteliais/patologia , Hepatite C Crônica/complicações , Interações Hospedeiro-Patógeno , Cirrose Hepática/patologia , Sirtuína 1/biossíntese , Proteínas do Core Viral/metabolismo , Western Blotting , Células Cultivadas , Meios de Cultivo Condicionados , Citometria de Fluxo , Hepatite C Crônica/patologia , Humanos , Fígado/patologia , Modelos Biológicos , Espécies Reativas de Oxigênio/análise
12.
Nat Commun ; 8: 15986, 2017 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-28656979

RESUMO

Excessive activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome is involved in many chronic inflammatory diseases, including cardiovascular and Alzheimer's disease. Here we show that microtubule-affinity regulating kinase 4 (MARK4) binds to NLRP3 and drives it to the microtubule-organizing centre, enabling the formation of one large inflammasome speck complex within a single cell. MARK4 knockdown or knockout, or disruption of MARK4-NLRP3 interaction, impairs NLRP3 spatial arrangement and limits inflammasome activation. Our results demonstrate how an evolutionarily conserved protein involved in the regulation of microtubule dynamics orchestrates NLRP3 inflammasome activation by controlling its transport to optimal activation sites, and identify a targetable function for MARK4 in the control of innate immunity.


Assuntos
Inflamassomos/metabolismo , Macrófagos/enzimologia , Microtúbulos/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , /metabolismo , Animais , Humanos , Interleucina-1beta/metabolismo , Masculino , Camundongos , Centro Organizador dos Microtúbulos , Cultura Primária de Células
13.
Nat Commun ; 8: 14824, 2017 03 22.
Artigo em Inglês | MEDLINE | ID: mdl-28327662

RESUMO

Hepatic de novo lipogenesis (DNL) converts carbohydrates into triglycerides and is known to influence systemic lipid homoeostasis. Here, we demonstrate that the zinc finger protein Zbtb20 is required for DNL. Mice lacking Zbtb20 in the liver exhibit hypolipidemia and reduced levels of liver triglycerides, along with impaired hepatic lipogenesis. The expression of genes involved in glycolysis and DNL, including that of two ChREBP isoforms, is decreased in livers of knockout mice. Zbtb20 binds to and enhances the activity of the ChREBP-α promoter, suggesting that altered metabolic gene expression is mainly driven by ChREBP. In addition, ChREBP-ß overexpression largely restores hepatic expression of genes involved in glucose and lipid metabolism, and increases plasma and liver triglyceride levels in knockout mice. Finally, we show that Zbtb20 ablation protects from diet-induced liver steatosis and improves hepatic insulin resistance. We suggest ZBTB20 is an essential regulator of hepatic lipogenesis and may be a therapeutic target for the treatment of fatty liver disease.


Assuntos
Lipogênese , Fígado/metabolismo , Fatores de Transcrição/metabolismo , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Carboidratos/química , Núcleo Celular/metabolismo , Carboidratos da Dieta , Fígado Gorduroso/genética , Fígado Gorduroso/patologia , Deleção de Genes , Regulação da Expressão Gênica , Glucose/metabolismo , Glicólise , Homeostase , Humanos , Resistência à Insulina , Lipogênese/genética , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Nucleares/metabolismo , Transporte Proteico , Fatores de Transcrição/deficiência , Transcrição Genética , Triglicerídeos/sangue , Triglicerídeos/metabolismo
14.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1862(1): 114-129, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27502688

RESUMO

Autophagy is an evolutionarily conserved mechanism that maintains nutrient homeostasis by degrading protein aggregates and damaged organelles. Autophagy is reduced in aging, which is implicated in the pathogenesis of aging-related diseases, including cancers, obesity, type 2 diabetes, cardiovascular diseases, and neurodegenerative diseases. Mitochondria-derived phospholipids cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol are critical throughout the autophagic process, from initiation and phagophore formation to elongation and fusion with endolysosomal vesicles. Cardiolipin is also required for mitochondrial fusion and fission, an important step in isolating dysfunctional mitochondria for mitophagy. Furthermore, genetic screen in yeast has identified a surprising role for cardiolipin in regulating lysosomal function. Phosphatidylethanolamine plays a pivotal role in supporting the autophagic process, including autophagosome elongation as part of lipidated Atg8/LC3. An emerging role for phosphatidylglycerol in AMPK and mTORC1 signaling as well as mitochondrial fission may provide the first glimpse into the function of phosphatidylglycerol apart from being a precursor for cardiolipin. This review examines the effects of manipulating phospholipids on autophagy and mitophagy in health and diseases, as well as current limitations in the field. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.


Assuntos
Autofagia/fisiologia , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Fosfolipídeos/metabolismo , Envelhecimento/metabolismo , Envelhecimento/patologia , Animais , Humanos , Dinâmica Mitocondrial/fisiologia , Mitofagia/fisiologia
15.
Nat Commun ; 7: 11121, 2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-27079169

RESUMO

The anterior pituitary harbours five distinct hormone-producing cell types, and their cellular differentiation is a highly regulated and coordinated process. Here we show that ZBTB20 is essential for anterior pituitary development and lactotrope specification in mice. In anterior pituitary, ZBTB20 is highly expressed by all the mature endocrine cell types, and to some less extent by somatolactotropes, the precursors of prolactin (PRL)-producing lactotropes. Disruption of Zbtb20 leads to anterior pituitary hypoplasia, hypopituitary dwarfism and a complete loss of mature lactotropes. In ZBTB20-null mice, although lactotrope lineage commitment is normally initiated, somatolactotropes exhibit profound defects in lineage specification and expansion. Furthermore, endogenous ZBTB20 protein binds to Prl promoter, and its knockdown decreases PRL expression and secretion in a lactotrope cell line MMQ. In addition, ZBTB20 overexpression enhances the transcriptional activity of Prl promoter in vitro. In conclusion, our findings point to ZBTB20 as a critical regulator of anterior pituitary development and lactotrope specification.


Assuntos
Linhagem da Célula/genética , Lactotrofos/metabolismo , Adeno-Hipófise/metabolismo , Fatores de Transcrição/genética , Animais , Western Blotting , Proliferação de Células/genética , Regulação da Expressão Gênica no Desenvolvimento , Hipopituitarismo/genética , Hipopituitarismo/metabolismo , Hipotálamo/embriologia , Hipotálamo/crescimento & desenvolvimento , Hipotálamo/metabolismo , Imuno-Histoquímica , Hibridização In Situ , Lactotrofos/citologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Adeno-Hipófise/embriologia , Adeno-Hipófise/crescimento & desenvolvimento , Prolactina/genética , Prolactina/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/metabolismo
16.
Sci Rep ; 6: 20453, 2016 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-26857140

RESUMO

Bif-1 is a membrane-curvature inducing protein that is implicated in the regulation of autophagy and tumorigenesis. Here, we report that Bif-1 plays a critical role in regulating lipid catabolism to control the size of lipid droplets and prevent the development of obesity and insulin resistance upon aging or dietary challenge. Our data show that Bif-1 deficiency promotes the expansion of adipose tissue mass without altering food intake or physical activities. While Bif-1 is dispensable for adipose tissue development, its deficiency reduces the basal rate of adipose tissue lipolysis and results in adipocyte hypertrophy upon aging. The importance of Bif-1 in lipid turnover is not limited to adipose tissue since fasting and refeeding-induced lipid droplet clearance is also attenuated by Bif-1 loss in the liver. Interestingly, obesity induced by a high fat-diet or Bif-1 deficiency downregulates the expression of proteins involved in the autophagy-lysosomal pathway, including Atg9a and Lamp1 in the adipose tissue. These findings thus identify Bif-1 as a novel regulator of lipid homeostasis to prevent the pathogenesis of obesity and its associated metabolic complications.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/deficiência , Tecido Adiposo , Resistência à Insulina/genética , Gotículas Lipídicas , Metabolismo dos Lipídeos/genética , Obesidade , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Animais , Proteínas Relacionadas à Autofagia/genética , Proteínas Relacionadas à Autofagia/metabolismo , Gotículas Lipídicas/metabolismo , Gotículas Lipídicas/patologia , Glicoproteínas de Membrana Associadas ao Lisossomo/genética , Glicoproteínas de Membrana Associadas ao Lisossomo/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo , Obesidade/patologia , Proteínas de Transporte Vesicular/genética , Proteínas de Transporte Vesicular/metabolismo
17.
Sci Rep ; 6: 20438, 2016 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-26830324

RESUMO

The recombination efficiency and cell specificity of Cre driver lines are critical for exploring pancreatic ß cell biology with the Cre/LoxP approach. Some commonly used Cre lines are based on the short Ins2 promoter fragment and show recombination activity in hypothalamic neurons; however, whether this stems from endogenous Ins2 promoter activity remains controversial. In this study, we generated Ins2-Cre knockin mice with a targeted insertion of IRES-Cre at the Ins2 locus and demonstrated with a cell lineage tracing study that the Ins2 gene is not transcriptionally active in the hypothalamus. The Ins2-Cre driver line displayed robust Cre expression and activity in pancreatic ß cells without significant alterations in insulin expression. In the brain, Cre activity was mainly restricted to the choroid plexus, without significant recombination detected in the hippocampus or hypothalamus by the LacZ or fluorescent tdTomato reporters. Furthermore, Ins2-Cre mice exhibited normal glucose tolerance and insulin secretion upon glucose stimulation in vivo. In conclusion, this Ins2-Cre driver line allowed high-fidelity detection of endogenous Ins2 promoter activity in vivo, and the negative activity in the hypothalamus demonstrated that this system is a promising alternative tool for studying ß cell biology.


Assuntos
Técnicas de Introdução de Genes , Loci Gênicos , Hipotálamo/citologia , Hipotálamo/metabolismo , Insulina/genética , Integrases/genética , Integrases/metabolismo , Neurônios/metabolismo , Animais , Ativação Enzimática , Ordem dos Genes , Marcação de Genes , Vetores Genéticos/genética , Glucose/metabolismo , Recombinação Homóloga , Insulina/metabolismo , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Camundongos , Camundongos Transgênicos , Fenótipo
18.
Biol Trace Elem Res ; 171(2): 419-426, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26463750

RESUMO

Selenium (Se) mainly performs its function through Se-containing proteins. Selenoprotein W (SelW), one member of the selenoprotein family, plays important roles in the normal function of the heart. To investigate the possible relationship between Se and SelW for the regulation of oxidative damage in chicken embryo myocardial cells, we treated myocardial cells with Se and H2O2. Then, the levels of lactate dehydrogenase (LDH) and 3,4-methylenedioxyamphetamine in the culture media, levels of SelW, inflammatory genes NF-κB, tumor necrosis factor (TNF)-α, p53, and the cell cycle were analyzed. Furthermore, the correlation between SelW and the levels of these factors was determined. The results indicated that Se treatment increased the expression of SelW (P < 0.05) and caused a downregulation of p53, NF-κB, and TNF-α (P < 0.05). In contrast, H2O2 increased the expression of p53, NF-κB, TNF-α, and LDH (P < 0.05) and induced early cell apoptosis, which was alleviated by treatment with Se. In addition, SelW had a positive correlation with the levels of inflammatory genes investigated. Taken together, our findings suggested that SelW is sensitive to Se levels and oxidative stress, and may play a role in the protective function of Se against oxidative damage and inflammation in chicken myocardial cells.


Assuntos
Miócitos Cardíacos/efeitos dos fármacos , Estresse Oxidativo , Selênio/farmacologia , Selenoproteína W/metabolismo , Animais , Apoptose/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Galinhas , Relação Dose-Resposta a Droga , Peróxido de Hidrogênio/antagonistas & inibidores , Peróxido de Hidrogênio/farmacologia , Miócitos Cardíacos/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Selênio/administração & dosagem , Relação Estrutura-Atividade
19.
Diabetologia ; 59(2): 316-24, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26564177

RESUMO

AIMS/HYPOTHESIS: 'Glucotoxicity' is a term used to convey the negative effect of hyperglycaemia on beta cell function; however, the underlying molecular mechanisms that impair insulin secretion and gene expression are poorly defined. Our objective was to define the role of transcription factor v-ets avian erythroblastosis virus E26 oncogene homologue 1 (Ets-1) in beta cell glucotoxicity. METHODS: Primary islets and Min6 cells were exposed to high glucose and Ets-1 expression was measured. Recombinant adenovirus and transgenic mice were used to upregulate Ets-1 expression in beta cells in vitro and in vivo, and insulin secretion was assessed. The binding activity of H3/H4 histone on the Ets-1 promoter, and that of forkhead box (FOX)A2, FOXO1 and Ets-1 on the Pdx-1 promoter was measured by chromatin immunoprecipitation and quantitative real-time PCR assay. RESULTS: High glucose induced upregulation of Ets-1 expression and hyperacetylation of histone H3 and H4 at the Ets-1 gene promoter in beta cells. Ets-1 overexpression dramatically suppressed insulin secretion and biosynthesis both in vivo and in vitro. Besides, Ets-1 overexpression increased the activity of FOXO1 but decreased that of FOXA2 binding to the pancreatic and duodenal homeobox 1 (PDX-1) homology region 2 (PH2), resulting in inhibition of Pdx-1 promoter activity and downregulation of PDX-1 expression and activity. In addition, high glucose promoted the interaction of Ets-1 and FOXO1, and the activity of Ets-1 binding to the Pdx-1 promoter. Importantly, PDX-1 overexpression reversed the defect in pancreatic beta cells induced by Ets-1 excess, while knockdown of Ets-1 prevented hyperglycaemia-induced dysfunction of pancreatic beta cells. CONCLUSIONS/INTERPRETATION: Our observations suggest that Ets-1 links glucotoxicity to pancreatic beta cell dysfunction through inhibiting PDX-1 expression in type 2 diabetes.


Assuntos
Diabetes Mellitus Experimental/genética , Proteínas de Homeodomínio/genética , Hiperglicemia/genética , Células Secretoras de Insulina/fisiologia , Proteína Proto-Oncogênica c-ets-1/fisiologia , Transativadores/genética , Animais , Glicemia/fisiologia , Células Cultivadas , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Experimental/complicações , Diabetes Mellitus Experimental/fisiopatologia , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Regulação da Expressão Gênica , Proteínas de Homeodomínio/metabolismo , Hiperglicemia/sangue , Hiperglicemia/fisiopatologia , Células Secretoras de Insulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Ratos , Ratos Sprague-Dawley , Transativadores/metabolismo
20.
Autophagy ; 11(4): 643-52, 2015 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-25919711

RESUMO

Tafazzin (TAZ) is a phospholipid transacylase that catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mutations of TAZ cause Barth syndrome, which is characterized by mitochondrial dysfunction and dilated cardiomyopathy, leading to premature death. However, the molecular mechanisms underlying the cause of mitochondrial dysfunction in Barth syndrome remain poorly understood. Here we investigated the role of TAZ in regulating mitochondrial function and mitophagy. Using primary mouse embryonic fibroblasts (MEFs) with doxycycline-inducible knockdown of Taz, we showed that TAZ deficiency in MEFs caused defective mitophagosome biogenesis, but not other autophagic processes. Consistent with a key role of mitophagy in mitochondria quality control, TAZ deficiency in MEFs also led to impaired oxidative phosphorylation and severe oxidative stress. Together, these findings provide key insights on mitochondrial dysfunction in Barth syndrome, suggesting that pharmacological restoration of mitophagy may provide a novel treatment for this lethal condition.


Assuntos
Autofagia/fisiologia , Cardiolipinas/metabolismo , Mitofagia/fisiologia , Fatores de Transcrição/metabolismo , Aciltransferases , Animais , Autofagia/genética , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/metabolismo , Cardiomiopatia Dilatada/patologia , Humanos , Camundongos , Mitocôndrias/genética , Mutação/genética , Fatores de Transcrição/deficiência , Fatores de Transcrição/genética
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