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1.
PLoS One ; 15(10): e0236000, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33002003

RESUMO

Non-alcoholic fatty liver disease (NAFLD) affects a significant number of people worldwide and currently there are no pharmacological treatments. NAFLD often presents with obesity, insulin resistance, and in some cases cardiovascular diseases. There is a clear need for treatment options to alleviate this disease since it often progresses to much more the much more severe non-alcoholic steatohepatitis (NASH). The REV-ERB nuclear receptor is a transcriptional repressor that regulates physiological processes involved in the development of NAFLD including lipogenesis and inflammation. We hypothesized that pharmacologically activating REV-ERB would suppress the progression of fatty liver in a mouse model of NASH. Using REV-ERB agonist SR9009 in a mouse NASH model, we demonstrate the beneficial effects of REV-ERB activation that led to an overall improvement of hepatic health by suppressing hepatic fibrosis and inflammatory response.


Assuntos
Hepatopatia Gordurosa não Alcoólica , Membro 1 do Grupo D da Subfamília 1 de Receptores Nucleares/efeitos dos fármacos , Pirrolidinas/farmacologia , Tiofenos/farmacologia , Animais , Modelos Animais de Doenças , Humanos , Inflamação/metabolismo , Lipogênese/fisiologia , Fígado/metabolismo , Fígado/patologia , Cirrose Hepática/patologia , Camundongos , Hepatopatia Gordurosa não Alcoólica/tratamento farmacológico , Hepatopatia Gordurosa não Alcoólica/patologia , Obesidade/metabolismo
2.
Nat Commun ; 11(1): 4056, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32792483

RESUMO

Autophagy has been associated with oncogenesis with one of its emerging key functions being its contribution to the metabolism of tumors. Therefore, deciphering the mechanisms of how autophagy supports tumor cell metabolism is essential. Here, we demonstrate that the inhibition of autophagy induces an accumulation of lipid droplets (LD) due to a decrease in fatty acid ß-oxidation, that leads to a reduction of oxidative phosphorylation (OxPHOS) in acute myeloid leukemia (AML), but not in normal cells. Thus, the autophagic process participates in lipid catabolism that supports OxPHOS in AML cells. Interestingly, the inhibition of OxPHOS leads to LD accumulation with the concomitant inhibition of autophagy. Mechanistically, we show that the disruption of mitochondria-endoplasmic reticulum (ER) contact sites (MERCs) phenocopies OxPHOS inhibition. Altogether, our data establish that mitochondria, through the regulation of MERCs, controls autophagy that, in turn finely tunes lipid degradation to fuel OxPHOS supporting proliferation and growth in leukemia.


Assuntos
Autofagia/fisiologia , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Leucemia Mieloide Aguda/metabolismo , Leucemia/metabolismo , Mitocôndrias/metabolismo , Animais , Autofagia/genética , Linhagem Celular Tumoral , Proliferação de Células/genética , Proliferação de Células/fisiologia , Citometria de Fluxo , Humanos , Leucemia/genética , Leucemia Mieloide Aguda/patologia , Metabolismo dos Lipídeos/genética , Metabolismo dos Lipídeos/fisiologia , Lipogênese/genética , Lipogênese/fisiologia , Camundongos , Mitocôndrias/genética , Oxirredução , Fosforilação Oxidativa
3.
Life Sci ; 258: 118240, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32781072

RESUMO

As a dicarboxylic acid with the structural formula HOOCCH (OH) COOH, tartronic acid is considered as an inhibitor of the transformation of carbohydrates into fat under fat-deficient diet conditions. However, the effect of tartronic acid on lipogenesis under high-fat diet conditions has yet to be established. In this work, we investigated the regulatory role of tartronic acid in lipogenesis in 3T3-L1 adipocytes and C57BL/6J mice. The results confirmed that tartronic acid promoted weight gain (without affecting food intake) and induced adipocyte hypertrophy in epididymal white adipose tissue and lipid accumulation in the livers of high-fat diet-induced obese mice. In vitro, tartronic acid promoted 3T3-L1 adipocyte differentiation by increasing the protein expression of FABP-4, PPARγ and SREBP-1. Moreover, the contents of both acetyl-CoA and malonyl-CoA were significantly upregulated by treatment with tartronic acid, while the protein expression of CPT-1ß were inhibited. In summary, we proved that tartronic acid promotes lipogenesis by serving as substrates for fatty acid synthesis and inhibiting CPT-1ß, providing a new perspective for the study of tartronic acid.


Assuntos
Acetilcoenzima A/biossíntese , Carnitina O-Palmitoiltransferase/antagonistas & inibidores , Lipogênese/efeitos dos fármacos , Malonil Coenzima A/biossíntese , Tartronatos/farmacologia , Regulação para Cima/efeitos dos fármacos , Células 3T3-L1 , Animais , Carnitina O-Palmitoiltransferase/metabolismo , Dieta Hiperlipídica/efeitos adversos , Lipogênese/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Regulação para Cima/fisiologia
4.
Metabolism ; 108: 154261, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32407726

RESUMO

BACKGROUND: Fibronectin type IIIdomain-containing protein 4 (FNDC4) constitutes a secreted factor showing a high homology in the fibronectin type III and transmembrane domains with the exercise-associated myokine irisin (FNDC5). We sought to evaluate whether FNDC4 mimics the anti-obesity effects of FNDC5/irisin in human adipose tissue. METHODS: Plasma and adipose tissue samples of 78 patients with morbid obesity undergoing bariatric surgery and 26 normal-weight individuals were used in the present study. RESULTS: Plasma FNDC4 was decreased in patients with morbid obesity, related to obesity-associated systemic inflammation and remained unchanged six months after bariatric surgery. Visceral adipose tissue from patients with morbid obesity showed higher expression of FNDC4 and its putative receptor GPR116 regardless of the degree of insulin resistance. FNDC4 content was regulated by lipogenic, lipolytic and proinflammatory stimuli in human visceral adipocytes. FNDC4 reduced intracytosolic lipid accumulation and stimulated a brown-like pattern in human adipocytes, as evidenced by an upregulated expression of UCP-1 and the brown/beige adipocyte markers PRDM16, TMEM26 and CD137. Moreover, FNDC4 treatment upregulated mitochondrial DNA content and factors involved in mitochondrial biogenesis (TFAM, NRF1 and NRF2). Human FNDC4-knockdown adipocytes exhibited an increase in lipogenesis and a reduction of brown/beige-specific fat markers as well as factors involved in mitochondrial biogenesis. CONCLUSIONS: Taken together, the novel adipokine FNDC4 reduces lipogenesis and increases fat browning in human visceral adipocytes. The upregulation of FNDC4 in human visceral fat might constitute an attempt to attenuate the adipocyte hypertrophy, inflammation and impaired beige adipogenesis in the obese state.


Assuntos
Adipócitos/metabolismo , Adipocinas/metabolismo , Tecido Adiposo Marrom/metabolismo , Lipogênese/fisiologia , Proteínas/metabolismo , Adipócitos Bege/metabolismo , Células Cultivadas , Estudos Transversais , Feminino , Humanos , Inflamação/metabolismo , Resistência à Insulina/fisiologia , Gordura Intra-Abdominal/metabolismo , Masculino , Pessoa de Meia-Idade , Mitocôndrias/metabolismo , Obesidade/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Proteína Desacopladora 1/metabolismo , Regulação para Cima/fisiologia
5.
Nat Commun ; 11(1): 1891, 2020 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-32312974

RESUMO

Hepatic steatosis is associated with poor cardiometabolic health, with de novo lipogenesis (DNL) contributing to hepatic steatosis and subsequent insulin resistance. Hepatic saturated fatty acids (SFA) may be a marker of DNL and are suggested to be most detrimental in contributing to insulin resistance. Here, we show in a cross-sectional study design (ClinicalTrials.gov ID: NCT03211299) that we are able to distinguish the fractions of hepatic SFA, mono- and polyunsaturated fatty acids in healthy and metabolically compromised volunteers using proton magnetic resonance spectroscopy (1H-MRS). DNL is positively associated with SFA fraction and is elevated in patients with non-alcoholic fatty liver and type 2 diabetes. Intriguingly, SFA fraction shows a strong, negative correlation with hepatic insulin sensitivity. Our results show that the hepatic lipid composition, as determined by our 1H-MRS methodology, is a measure of DNL and suggest that specifically the SFA fraction may hamper hepatic insulin sensitivity.


Assuntos
Ácidos Graxos/metabolismo , Resistência à Insulina/fisiologia , Lipogênese/fisiologia , Fígado/metabolismo , Tecido Adiposo , Adulto , Idoso , Estudos Transversais , Diabetes Mellitus Tipo 2/metabolismo , Feminino , Humanos , Lipídeos , Fígado/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Hepatopatia Gordurosa não Alcoólica/metabolismo , Triglicerídeos/metabolismo
6.
Diabetes ; 69(4): 525-531, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32198196

RESUMO

Hepatosteatosis, which is frequently associated with development of metabolic syndrome and insulin resistance, manifests when triglyceride (TG) input in the liver is greater than TG output, resulting in the excess accumulation of TG. Dysregulation of lipogenesis therefore has the potential to increase lipid accumulation in the liver, leading to insulin resistance and type 2 diabetes. Recently, efforts have been made to examine the epigenetic regulation of metabolism by histone-modifying enzymes that alter chromatin accessibility for activation or repression of transcription. For regulation of lipogenic gene transcription, various known lipogenic transcription factors, such as USF1, ChREBP, and LXR, interact with and recruit specific histone modifiers, directing specificity toward lipogenesis. Alteration or impairment of the functions of these histone modifiers can lead to dysregulation of lipogenesis and thus hepatosteatosis leading to insulin resistance and type 2 diabetes.


Assuntos
Diabetes Mellitus/metabolismo , Epigênese Genética , Fígado Gorduroso/metabolismo , Lipogênese/fisiologia , Fígado/metabolismo , Animais , Humanos , Resistência à Insulina , Síndrome Metabólica/metabolismo
7.
Nat Commun ; 11(1): 796, 2020 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-32034158

RESUMO

Fatty acid and triglyceride synthesis increases greatly in response to feeding and insulin. This lipogenic induction involves coordinate transcriptional activation of various enzymes in lipogenic pathway, including fatty acid synthase and glycerol-3-phosphate acyltransferase. Here, we show that JMJD1C is a specific histone demethylase for lipogenic gene transcription in liver. In response to feeding/insulin, JMJD1C is phosphorylated at T505 by mTOR complex to allow direct interaction with USF-1 for recruitment to lipogenic promoter regions. Thus, by demethylating H3K9me2, JMJD1C alters chromatin accessibility to allow transcription. Consequently, JMJD1C promotes lipogenesis in vivo to increase hepatic and plasma triglyceride levels, showing its role in metabolic adaption for activation of the lipogenic program in response to feeding/insulin, and its contribution to development of hepatosteatosis resulting in insulin resistance.


Assuntos
Histona Desmetilases com o Domínio Jumonji/metabolismo , Lipogênese/fisiologia , Oxirredutases N-Desmetilantes/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Animais , Dieta Hiperlipídica/efeitos adversos , Ingestão de Alimentos/genética , Ingestão de Alimentos/fisiologia , Feminino , Regulação da Expressão Gênica , Estudo de Associação Genômica Ampla , Células Hep G2 , Histonas/metabolismo , Humanos , Insulina/metabolismo , Insulina/farmacologia , Resistência à Insulina , Histona Desmetilases com o Domínio Jumonji/genética , Lipogênese/efeitos dos fármacos , Lipogênese/genética , Lisina/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oxirredutases N-Desmetilantes/genética , Fosforilação , Regiões Promotoras Genéticas , Triglicerídeos/sangue , Triglicerídeos/metabolismo , Fatores Estimuladores Upstream/metabolismo
8.
Int J Mol Sci ; 21(3)2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32033474

RESUMO

Gangliosides are constituents of the mammalian cell membranes and participate in the inflammatory response. However, little is known about the presence and enzymatic activity of ganglioside sialyltransferases at the cell surface of macrophages, one of the most important immune cells involved in the innate inflammatory process. In the present study, using biochemical and fluorescent microscopy approaches, we found that endogenous ST8Sia-I is present at the plasma membrane (ecto-ST8Sia-I) of murine macrophage RAW264.7 cells. Moreover, ecto-ST8Sia-I can synthetize GD3 ganglioside at the cell surface in lipopolysaccharide (LPS)-stimulated macrophages even when LPS-stimulated macrophages reduced the total ST8Sia-I expression levels. Besides, cotreatment of LPS with an inhibitor of nitric oxide (NO) synthase recovered the ecto-ST8Sia-I expression, suggesting that NO production is involved in the reduction of ST8Sia-I expression. The diminution of ST8Sia-I expression in LPS-stimulated macrophages correlated with a reduction of GD3 and GM1 gangliosides and with an increment of GD1a. Taken together, the data supports the presence and activity of sialyltransferases at the plasma membrane of RAW264.7 cells. The variations of ecto-ST8Sia-I and ganglioside levels in stimulated macrophages constitutes a promissory pathway to further explore the physiological role of this and others ganglioside metabolism-related enzymes at the cell surface during the immune response.


Assuntos
Membrana Celular/metabolismo , Gangliosídeo G(M1)/metabolismo , Gangliosídeos/metabolismo , Macrófagos/metabolismo , Sialiltransferases/metabolismo , Animais , Células CHO , Linhagem Celular , Cricetulus/metabolismo , Lipogênese/fisiologia , Lipopolissacarídeos/metabolismo , Camundongos , Óxido Nítrico/metabolismo , Células RAW 264.7
9.
Nat Commun ; 11(1): 575, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31996678

RESUMO

mTORC2 phosphorylates AKT in a hydrophobic motif site that is a biomarker of insulin sensitivity. In brown adipocytes, mTORC2 regulates glucose and lipid metabolism, however the mechanism has been unclear because downstream AKT signaling appears unaffected by mTORC2 loss. Here, by applying immunoblotting, targeted phosphoproteomics and metabolite profiling, we identify ATP-citrate lyase (ACLY) as a distinctly mTORC2-sensitive AKT substrate in brown preadipocytes. mTORC2 appears dispensable for most other AKT actions examined, indicating a previously unappreciated selectivity in mTORC2-AKT signaling. Rescue experiments suggest brown preadipocytes require the mTORC2/AKT/ACLY pathway to induce PPAR-gamma and establish the epigenetic landscape during differentiation. Evidence in mature brown adipocytes also suggests mTORC2 acts through ACLY to increase carbohydrate response element binding protein (ChREBP) activity, histone acetylation, and gluco-lipogenic gene expression. Substrate utilization studies additionally implicate mTORC2 in promoting acetyl-CoA synthesis from acetate through acetyl-CoA synthetase 2 (ACSS2). These data suggest that a principal mTORC2 action is controlling nuclear-cytoplasmic acetyl-CoA synthesis.


Assuntos
ATP Citrato (pro-S)-Liase/metabolismo , Adipócitos Marrons/metabolismo , Lipogênese/fisiologia , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Acetato-CoA Ligase/metabolismo , Animais , Proteínas de Transporte , Epigênese Genética , Ácido Graxo Sintases , Edição de Genes , Expressão Gênica , Transportador de Glucose Tipo 4/genética , Transportador de Glucose Tipo 4/metabolismo , Células HEK293 , Histonas/metabolismo , Humanos , Lipogênese/genética , Camundongos , Camundongos Endogâmicos C57BL , PPAR gama/metabolismo , Fosforilação , Proteômica , Elementos de Resposta
10.
J Exp Med ; 217(3)2020 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-31961917

RESUMO

Cancer cells often proliferate under hypoxia and reprogram their metabolism. However, how to find targets to effectively block the hypoxia-associated metabolic pathways remains unclear. Here, we developed a tool to conveniently calculate electrons dissipated in metabolic transformations. Based on the law of conservation of electrons in chemical reactions, we further built up an electron balance model for central carbon metabolism, and it can accurately outline metabolic plasticity under hypoxia. Our model specifies that glutamine metabolism reprogrammed for biosynthesis of lipid and/or proline actually acts as the alternative electron bin to enable electron transfer in proliferating cells under hypoxia. Inhibition of both proline biosynthesis and lipogenesis can synergistically suppress cancer cell growth under hypoxia and in vivo tumor onset. Therefore, our model helps to reveal combinations of potential targets to inhibit tumor growth by blocking hypoxia-rewired metabolism and provides a useful tool for future studies on cancer metabolism.


Assuntos
Proliferação de Células/fisiologia , Lipogênese/fisiologia , Neoplasias/metabolismo , Prolina/biossíntese , Prolina/metabolismo , Células A549 , Animais , Hipóxia Celular/fisiologia , Linhagem Celular Tumoral , Feminino , Glutamina/metabolismo , Células HeLa , Células Hep G2 , Humanos , Células MCF-7 , Redes e Vias Metabólicas/fisiologia , Camundongos , Camundongos Nus
11.
Artigo em Inglês | MEDLINE | ID: mdl-31816411

RESUMO

The dermal adipocytes, superficial fascia and subcutaneous adipose tissue (SAT) exist in the interspaces between the dermis and muscular fascia. They are adjacent to each other and traditionally recognized as one SAT. Recently, the dermal adipocyte was redefined as a unique population independent from the SAT. Also, we identified a novel type of adipogenic progenitors in rat superficial fascia. This study aimed to examine cytological and functional characteristics of fascial adipocytes in rats. Superficial fascia had no adipocytes in neonatal rats but gradually appeared numbers of adipocytes in growing rats. Adipogenic progenitors were found to reside in fascia and had strong ability in spontaneous and induced adipogenic differentiation in vitro. Differentiated fascial adipocytes versus subcutaneous or visceral adipocytes expressed increased adipose triglyceride lipase but decreased beta-adrenoreceptor, perilipin-1 and hormone-sensitive lipase (HSL), thus having high basal lipolysis but low lipolysis response to catecholamines. Phosphorylation of perilipin-1 and HSL and translocation of HSL to lipid droplets were attenuated in response to catecholamines rather than post-adrenoreceptoral lipolytic stimulators. The results suggested that superficial fascia was an origin of adipocytes with distinct developmental, cytological and functional characteristics. We proposed that fascial adipocytes could be considered as a unique population of adipocytes in the body. The fascia origin of adipocytes as an adipogenic model might logically explain fat neogenesis occurred at anatomical locations where originally exist no adipose tissues and thereby no adipose-derived stromal precursors. Also, the special histoanatomical relations and overlaps between the dermis, superficial fascia, SAT, and their adipocytes were discussed.


Assuntos
Adipócitos Brancos/metabolismo , Lipogênese/fisiologia , Lipólise/fisiologia , Tela Subcutânea/metabolismo , Adipócitos Brancos/citologia , Animais , Catecolaminas/metabolismo , Diferenciação Celular/fisiologia , Gotículas Lipídicas/metabolismo , Masculino , Células-Tronco Mesenquimais/fisiologia , Modelos Biológicos , Perilipina-1/metabolismo , Fosforilação , Ratos , Esterol Esterase/metabolismo
12.
Artigo em Inglês | MEDLINE | ID: mdl-31740387

RESUMO

Adverse effects of aging can be delayed with life-style interventions. We examined how exercise training (ET) alone or combined with omega-3 polyunsaturated fatty acid (PUFA) affects serum and adipose tissue (AT) lipidome in older women. Fifty-five sedentary older women were included in the physical activity program and given either sunflower (Placebo) or wax esters-rich (Calanus) oil capsules for 4 months. Serum and subcutaneous abdominal AT samples were acquired while maximum rates of oxygen consumption (VO2 max), insulin sensitivity (hyperinsulinemic-euglycemic clamps) and comprehensive lipidome profiles were determined before and after the study. ET increased VO2 max in both groups. Lipidomics profiling revealed unusual serum triacylglycerols and phospholipids with ether-bound alkyls in the Calanus group, while ET generally induced shorter-chain triacylglycerols in AT, suggesting increased de novo lipogenesis. The latter was positively associated with whole-body insulin sensitivity. Unexpectedly, insulin-sensitizing lipokines from the family of branched palmitic acid esters of hydroxy stearic acid (PAHSAs) were elevated in both serum and AT after ET, while PAHSAs-containing triacylglycerols were detected in AT. ET stimulated beneficial changes in AT, including PAHSAs synthesis. Although the added value of omega-3 PUFA supplementation was not proven, our discovery can help understand the nature of the metabolic benefits of exercise.


Assuntos
Tecido Adiposo/metabolismo , Exercício Físico/fisiologia , Ácidos Graxos Ômega-3/administração & dosagem , Insulina/metabolismo , Síndrome Metabólica/prevenção & controle , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/fisiologia , Terapia Combinada , Suplementos Nutricionais , Ésteres/metabolismo , Feminino , Humanos , Lipidômica , Lipogênese/fisiologia , Síndrome Metabólica/metabolismo , Síndrome Metabólica/fisiopatologia , Ácido Palmítico/metabolismo , Ácidos Esteáricos/metabolismo , Resultado do Tratamento
13.
Gen Comp Endocrinol ; 288: 113371, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31857076

RESUMO

Mammalian bombesin-related peptide, neuromedin B (NMB) action is mediated by its receptor (NMBR), and NMB/NMBR system plays a major role in regulating hormone secretions, reproduction and cell growth. Here we report the functions of NMB in regulating steroidogenesis (testosterone synthesis), cell viability and apoptosis. The primary rabbit Leydig cells were employed as the paradigm for this research. We initially confirmed that NMBR is distributed in Leydig cells of rabbit testis, and a certain dose of NMB could increase the secretion of testosterone in primary cultured rabbit Leydig cells. Subsequently, the accumulated NMBR, StAR, CYP11A1, 3ß-HSD and PKC protein could be induced by a certain dose of NMB in Leydig cells. Moreover, we found that NMB could decrease the cell viability, and decreased the expression of PCNA protein in Leydig cells; meanwhile, except for 100 nM, other doses of NMB could suppress the cell apoptosis, and regulate Caspase-3 protein expression in Leydig cells, respectively. These results identify that NMB may be a key factor in regulating testosterone synthesis through taking part in NMBR/PKC/steroidogenesis signaling pathway, as well as the cell viability and proliferation in rabbit Leydig cells.


Assuntos
Apoptose/efeitos dos fármacos , Hormônios Esteroides Gonadais/biossíntese , Células Intersticiais do Testículo/efeitos dos fármacos , Células Intersticiais do Testículo/fisiologia , Neurocinina B/análogos & derivados , Animais , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Lipogênese/efeitos dos fármacos , Lipogênese/fisiologia , Masculino , Redes e Vias Metabólicas/efeitos dos fármacos , Neurocinina B/farmacologia , Coelhos , Receptores da Bombesina/metabolismo , Testosterona/biossíntese , Testosterona/metabolismo
14.
J Nutr ; 150(4): 672-684, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31858105

RESUMO

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. Hepatic de novo lipogenesis (DNL) has been suggested to contribute to the pathogenesis of NAFLD. Recent studies have demonstrated that niacin (NA) modulates hepatic DNL through GPR109A. However, the underlying mechanism remains largely unknown. OBJECTIVES: This study aims to elucidate the potential molecular mechanism by which GPR109A inhibits hepatic DNL. METHODS: C57BL/6 wild-type (WT) and Gpr109a knockout (KO) mice (male, 5 wk old) were fed a high-fat diet (60% energy from fat) firstly for 6 wk to generate a diet-induced obese model. Subsequently, they were randomly divided into 4 groups for the next 8-9 wk: WT mice with oral water [WT + vehile (VE)], WT mice with oral NA (50 mM, dissolved in water) (WT + NA), KO mice with oral water (KO + VE), and KO mice with oral NA (50 mM) (KO + NA). Mechanisms were examined in HepG2 cells. Body composition, liver histology, biomarkers of hepatic function, lipid accumulation, and lipid synthesis signals in HepG2 cells were measured. RESULTS: Upon activation, GPR109A apparently protected against obesity and hepatic steatosis (P < 0.05). The concentrations of hepatic Tnf-α in the WT + NA group were about 50% of those in the WT + VE group (P < 0.05). The activities of serum alanine transaminase and aspartate transaminase were 26.7% and 53.5% lower in the WT + NA group than in the WT + VE group, respectively (P < 0.05). In HepG2 cells, activation of GPR109A resulted in remarkable inhibition of oleic acid-induced lipid accumulation via a protein kinase C-extracellular signal-regulated kinase-1/2-AMP-activated protein kinase signaling pathway. CONCLUSIONS: NA inhibits hepatic lipogenesis in C57BL/6 mice through a GPR109A-mediated signaling pathway, consistent with the mechanistic studies in HepG2 cells, suggesting its potential for treatment of NAFLD and other fatty liver diseases.


Assuntos
Adenilato Quinase/metabolismo , Lipogênese/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Niacina/administração & dosagem , Hepatopatia Gordurosa não Alcoólica/prevenção & controle , Receptores Acoplados a Proteínas-G/fisiologia , Animais , Dieta Hiperlipídica , Técnicas de Silenciamento de Genes , Células Hep G2 , Humanos , Lipogênese/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Hepatopatia Gordurosa não Alcoólica/etiologia , Obesidade/etiologia , Obesidade/prevenção & controle , Receptores Acoplados a Proteínas-G/deficiência , Transdução de Sinais
15.
Mol Pharmacol ; 97(3): 212-225, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31871304

RESUMO

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor family, playing pivotal roles in regulating glucose and lipid metabolism as well as inflammation. While characterizing potential PPARγ ligand activity of natural compounds in macrophages, we investigated their influence on the expression of adipophilin [perilipin 2 (PLIN2)], a well-known PPARγ target. To confirm that a compound regulates PLIN2 expression via PPARγ, we performed experiments using the widely used PPARγ antagonist 2-chloro-5-nitro-N-phenylbenzamide (GW9662). Surprisingly, instead of blocking upregulation of PLIN2 expression in THP-1 macrophages, expression was concentration-dependently induced by GW9662 at concentrations and under conditions commonly used. We found that this unexpected upregulation occurs in many human and murine macrophage cell models and also primary cells. Profiling expression of PPAR target genes showed upregulation of several genes involved in lipid uptake, transport, and storage as well as fatty acid synthesis by GW9662. In line with this and with upregulation of PLIN2 protein, GW9662 elevated lipogenesis and increased triglyceride levels. Finally, we identified PPARδ as a mediator of the substantial unexpected effects of GW9662. Our findings show that: 1) the PPARγ antagonist GW9662 unexpectedly activates PPARδ-mediated signaling in macrophages, 2) GW9662 significantly affects lipid metabolism in macrophages, 3) careful validation of experimental conditions and results is required for experiments involving GW9662, and 4) published studies in a context comparable to this work may have reported erroneous results if PPARγ independence was demonstrated using GW9662 only. In light of our findings, certain existing studies might require reinterpretation regarding the role of PPARγ SIGNIFICANCE STATEMENT: Peroxisome proliferator-activated receptors (PPARs) are targets for the treatment of various diseases, as they are key regulators of inflammation as well as lipid and glucose metabolism. Hence, reliable tools to characterize the molecular effects of PPARs are indispensable. We describe profound and unexpected off-target effects of the PPARγ antagonist 2-chloro-5-nitro-N-phenylbenzamide (GW9662) involving PPARδ and in turn affecting macrophage lipid metabolism. Our results question certain existing studies using GW9662 and make better experimental design of future studies necessary.


Assuntos
Anilidas/farmacologia , Lipogênese/fisiologia , PPAR delta/metabolismo , PPAR gama/metabolismo , Perilipina-2/biossíntese , Triglicerídeos/metabolismo , Animais , Células Cultivadas , Feminino , Expressão Gênica , Humanos , Lipogênese/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , PPAR delta/antagonistas & inibidores , PPAR gama/antagonistas & inibidores , Perilipina-2/genética , Células RAW 264.7 , Células U937
16.
Mol Cell ; 76(5): 811-825.e14, 2019 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-31628041

RESUMO

Physical contact between organelles is vital to the function of eukaryotic cells. Lipid droplets (LDs) are dynamic organelles specialized in lipid storage that interact physically with mitochondria in several cell types. The mechanisms coupling these organelles are, however, poorly understood, and the cell-biological function of their interaction remains largely unknown. Here, we discover in adipocytes that the outer mitochondrial membrane protein MIGA2 links mitochondria to LDs. We identify an amphipathic LD-targeting motif and reveal that MIGA2 binds to the membrane proteins VAP-A or VAP-B in the endoplasmic reticulum (ER). We find that in adipocytes MIGA2 is involved in promoting triglyceride (TAG) synthesis from non-lipid precursors. Our data indicate that MIGA2 links reactions of de novo lipogenesis in mitochondria to TAG production in the ER, thereby facilitating efficient lipid storage in LDs. Based on its presence in many tissues, MIGA2 is likely critical for lipid and energy homeostasis in a wide spectrum of cell types.


Assuntos
Adipócitos/metabolismo , Lipogênese/fisiologia , Proteínas de Membrana/metabolismo , Proteínas Mitocondriais/metabolismo , Células 3T3 , Adipócitos/fisiologia , Animais , Células COS , Diferenciação Celular/fisiologia , Chlorocebus aethiops , Retículo Endoplasmático/metabolismo , Células HEK293 , Humanos , Gotículas Lipídicas/metabolismo , Lipogênese/genética , Proteínas de Membrana/fisiologia , Camundongos , Mitocôndrias/metabolismo , Proteínas Mitocondriais/fisiologia , Triglicerídeos/biossíntese , Proteínas de Transporte Vesicular/metabolismo
17.
Am J Physiol Gastrointest Liver Physiol ; 317(6): G811-G823, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31604029

RESUMO

Nonalcoholic fatty liver disease (NAFLD) is very prevalent worldwide and is associated with insulin resistance and metabolic syndrome. Stress is a physiological and biological response to maintain homeostasis of the body against stressors while severe stress response is an important contributor to various illnesses, including metabolic syndrome and brain disorders. We have evaluated the effects of intermittent restraint stress on NAFLD in a high-fat diet (HFD)-fed mouse model. C57/BL6 mice had free access to a 60% HFD for 8 wk, with or without intermittent restraint stress (3 h) conducted three times a week. HFD administration increased fat accumulation in liver tissues. Unlike the stressed standard diet group, the levels of hepatic total cholesterol and triglycerides were significantly ameliorated in the HFD with stress group compared with the HFD alone group. These beneficial results were in accordance with serum levels of liver enzymes (aspartate transaminase, alanine transaminase) and hepatic levels of TNF-α and oxidative stress parameters (reactive oxygen species, nitric oxide, and malondialdehyde). The intermittent restraint stress significantly attenuated the HFD-derived alterations in serum insulin levels, hepatic protein kinase B activity, and gene expression, especially related to lipogenesis. This intermittent restraint stress also elevated the serum epinephrine concentration and activated the adrenergic receptor ß2 or ß3 in livers or white adipose tissue (WAT). Activation of energy expenditure markers (uncoupling protein 1, peroxisome proliferator-activated receptor-γ coactivator-1α) in brown adipose tissue and the browning of WAT were also observed in the HFD with stress group. Taken together, our findings showed the beneficial effects of sympathetic activation by intermittent restraint stress on HFD-induced hepatic steatosis and partial inflammation.NEW & NOTEWORTHY In modern society, stress is a part of daily life, and a certain level of stress is inevitable to most of the general population. Uncontrolled severe stress is obviously harmful; however, certain kind/level of stress could be beneficial on lipid metabolism via sympathetic activation. Our data suggest that a sympathetic activation by intermittent restraint stress could play a positive role in maintaining the balance of hepatic lipid metabolism, especially under high-fat diet conditions.


Assuntos
Inflamação/metabolismo , Lipogênese/fisiologia , Fígado/metabolismo , Hepatopatia Gordurosa não Alcoólica/metabolismo , Estresse Fisiológico/fisiologia , Sistema Nervoso Simpático/fisiologia , Tecido Adiposo/metabolismo , Animais , Colesterol/metabolismo , Dieta Hiperlipídica/efeitos adversos , Camundongos , Camundongos Endogâmicos C57BL , Receptores Adrenérgicos beta 2/análise , Triglicerídeos/metabolismo
18.
Obesity (Silver Spring) ; 27(10): 1555-1557, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31479202

RESUMO

The discovery that functional brown adipose tissue (BAT) in adult humans is inversely related to body fat mass and may reflect metabolic health has stimulated adipose tissue research to explore activation of BAT as a potential target for antiobesity treatments. In addition to the capacity of BAT to increase energy expenditure and glucose and lipid uptake, BAT secretes factors that may contribute to the regulation of whole-body metabolism. Among signals released from BAT, neuregulin 4 (NRG4) has been recently identified as an endocrine factor that may link the activation of BAT to protection against diet-induced obesity, insulin resistance, and hepatic steatosis. NRG4 was shown to directly reduce lipogenesis in hepatocytes, and it could indirectly activate BAT via sympathetic neurons or via inducing brown adipocyte-like signatures in white adipocytes in a paracrine manner. However, the potential relevance of NRG4 as a diagnostic tool or target for the treatment of obesity-related diseases remains to be explored.


Assuntos
Tecido Adiposo Marrom/metabolismo , Fígado/metabolismo , Neurregulinas/fisiologia , Adipócitos Marrons/metabolismo , Adulto , Animais , Metabolismo Energético/fisiologia , Fígado Gorduroso/etiologia , Fígado Gorduroso/metabolismo , Glucose/metabolismo , Humanos , Resistência à Insulina/fisiologia , Lipogênese/fisiologia , Camundongos , Obesidade/complicações , Obesidade/metabolismo , Obesidade/patologia , Transdução de Sinais/fisiologia , Termogênese/fisiologia
19.
Nat Commun ; 10(1): 4255, 2019 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-31534141

RESUMO

Caspase-10 belongs to the class of initiator caspases and is a close homolog of caspase-8. However, the lack of caspase-10 in mice and limited substrate repertoire restricts the understanding of its physiological functions. Here, we report that ATP-citrate lyase (ACLY) is a caspase-10 substrate. Caspase-10 cleaves ACLY at the conserved Asp1026 site under conditions of altered metabolic homeostasis. Cleavage of ACLY abrogates its enzymatic activity and suppresses the generation of acetyl-CoA, which is critical for lipogenesis and histone acetylation. Thus, caspase-10-mediated ACLY cleavage results in reduced intracellular lipid levels and represses GCN5-mediated histone H3 and H4 acetylation. Furthermore, decline in GCN5 activity alters the epigenetic profile, resulting in downregulation of proliferative and metastatic genes. Thus caspase-10 suppresses ACLY-promoted malignant phenotype. These findings expand the substrate repertoire of caspase-10 and highlight its pivotal role in inhibiting tumorigenesis through metabolic and epigenetic mechanisms.


Assuntos
ATP Citrato (pro-S)-Liase/antagonistas & inibidores , Carcinogênese/patologia , Caspase 10/metabolismo , Epigênese Genética/genética , Neoplasias/patologia , Células A549 , Acetilcoenzima A/biossíntese , Acetilação , Animais , Carcinogênese/genética , Linhagem Celular Tumoral , Proliferação de Células/genética , Feminino , Células HCT116 , Células HEK293 , Histonas/metabolismo , Humanos , Lipogênese/fisiologia , Camundongos , Camundongos Nus , Transplante de Neoplasias , Transplante Heterólogo , Fatores de Transcrição de p300-CBP/metabolismo
20.
Nat Rev Endocrinol ; 15(12): 689-700, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31554932

RESUMO

Nonalcoholic fatty liver disease (NAFLD) is an increasing global public health burden. NAFLD is strongly associated with type 2 diabetes mellitus, obesity and cardiovascular disease and begins with intrahepatic triacylglycerol accumulation. Under healthy conditions, the liver regulates lipid metabolism to meet systemic energy needs in the fed and fasted states. The processes of fatty acid uptake, fatty acid synthesis and the intracellular partitioning of fatty acids into storage, oxidation and secretion pathways are tightly regulated. When one or more of these processes becomes dysregulated, excess lipid accumulation can occur. Although genetic and environmental factors have been implicated in the development of NAFLD, it remains unclear why an imbalance in these pathways begins. The regulation of fatty acid partitioning occurs at several points, including during triacylglycerol synthesis, lipid droplet formation and lipolysis. These processes are influenced by enzyme function, intake of dietary fats and sugars and whole-body metabolism, and are further affected by the presence of obesity or insulin resistance. Insight into how the liver controls fatty acid metabolism in health and how these processes might be affected in disease would offer the potential for new therapeutic treatments for NAFLD to be developed.


Assuntos
Diabetes Mellitus Tipo 2/epidemiologia , Ácidos Graxos/biossíntese , Ácidos Graxos/metabolismo , Resistência à Insulina , Hepatopatia Gordurosa não Alcoólica/epidemiologia , Estado Nutricional , Doenças Cardiovasculares/prevenção & controle , Diabetes Mellitus Tipo 2/diagnóstico , Diabetes Mellitus Tipo 2/metabolismo , Gorduras na Dieta/metabolismo , Feminino , Humanos , Incidência , Metabolismo dos Lipídeos , Lipogênese/fisiologia , Masculino , Monitorização Fisiológica/métodos , Hepatopatia Gordurosa não Alcoólica/diagnóstico , Hepatopatia Gordurosa não Alcoólica/metabolismo , Prognóstico , Saúde Pública , Medição de Risco , Índice de Gravidade de Doença
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