RESUMEN
BACKGROUND: Glucokinase (GK) plays a key role in glucose metabolism. In the liver, GK is regulated by GK regulatory protein (GKRP) with nuclear sequestration at low plasma glucose level. Some GK activators (GKAs) disrupt GK-GKRP interaction which increases hepatic cytoplasmic GK level. Excess hepatic GK activity may exceed the capacity of glycogen synthesis with excess triglyceride formation. It remains uncertain whether hypertriglyceridemia associated with some GKAs in previous clinical trials was due to direct GK activation or impaired GK-GKRP interaction. METHODS: Using publicly available genome-wide association study summary statistics, we selected independent genetic variants of GCKR and GCK associated with fasting plasma glucose (FPG) as instrumental variables, to mimic the effects of impaired GK-GKRP interaction and direct GK activation, respectively. We applied two-sample Mendelian Randomization (MR) framework to assess their causal associations with lipid-related traits, risks of metabolic dysfunction-associated steatotic liver disease (MASLD) and cardiovascular diseases. We verified these findings in one-sample MR analysis using individual-level statistics from the Hong Kong Diabetes Register (HKDR). RESULTS: Genetically-proxied impaired GK-GKRP interaction increased plasma triglycerides, low-density lipoprotein cholesterol and apolipoprotein B levels with increased odds ratio (OR) of 14.6 (95% CI 4.57-46.4) per 1 mmol/L lower FPG for MASLD and OR of 2.92 (95% CI 1.78-4.81) for coronary artery disease (CAD). Genetically-proxied GK activation was associated with decreased risk of CAD (OR 0.69, 95% CI 0.54-0.88) and not with dyslipidemia. One-sample MR validation in HKDR showed consistent results. CONCLUSIONS: Impaired GK-GKRP interaction, rather than direct GK activation, may worsen lipid profiles and increase risks of MASLD and CAD. Development of future GKAs should avoid interfering with GK-GKRP interaction.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Glucemia , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Glucoquinasa , Análisis de la Aleatorización Mendeliana , Humanos , Proteínas Adaptadoras Transductoras de Señales/genética , Factores de Riesgo , Medición de Riesgo , Glucemia/metabolismo , Glucoquinasa/genética , Glucoquinasa/metabolismo , Biomarcadores/sangre , Lípidos/sangre , Fenotipo , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Polimorfismo de Nucleótido Simple , Factores de Tiempo , Dislipidemias/genética , Dislipidemias/sangre , Dislipidemias/diagnóstico , Dislipidemias/epidemiología , Dislipidemias/enzimología , Hígado Graso/genética , Hígado Graso/enzimología , Hígado Graso/sangreRESUMEN
The enzyme xanthine oxidoreductase (XOR) catalyzes the synthesis of uric acid (UA) from hypoxanthine and xanthine, which are products of purine metabolism starting from ribose-5-phosphate. Several studies suggested a relationship between hyperuricemia and hepatic steatosis; however, few previous studies have directly examined the relationship between XOR activity and hepatic steatosis. A total of 223 subjects with one or more cardiovascular risk factors were enrolled. The liver-to-spleen (L/S) ratio on computed tomography and the hepatic steatosis index (HSI) were used to assess hepatic steatosis. We used a newly developed highly sensitive assay based on [13C2, 15N2] xanthine and liquid chromatography/triple quadrupole mass spectrometry to measure plasma XOR activity. Subjects with the L/S ratio of < 1.1 and the HSI of < 36 had increased XOR activity and serum UA levels. Independent of insulin resistance and serum UA levels, multivariate logistic regression analysis revealed that plasma XOR activity was associated with the risk of hepatic steatosis as assessed by the L/S ratio and HSI. According to the findings of this study, plasma XOR activity is associated with hepatic steatosis independent of insulin resistance and serum UA levels.
Asunto(s)
Hígado Graso , Xantina Deshidrogenasa , Cromatografía Liquida , Hígado Graso/enzimología , Hígado Graso/metabolismo , Humanos , Resistencia a la Insulina , Espectrometría de Masas , Xantina/metabolismo , Xantina Deshidrogenasa/metabolismoRESUMEN
Ambient temperature is an important determinant of both the alternative bile acid synthesis pathway controlled by oxysterol 7-α hydroxylase (CYP7B1) and the progression of metabolic-associated fatty liver disease (MAFLD). Here, we investigated whether CYP7B1 is involved in the etiology of MAFLD under conditions of low and high energy expenditure. For this, Cyp7b1-/- and wild type (WT) mice were fed a choline-deficient high-fat diet and housed either at 30 °C (thermoneutrality) or at 22 °C (mild cold). To study disease phenotype and underlying mechanisms, plasma and organ samples were analyzed to determine metabolic parameters, immune cell infiltration by immunohistology and flow cytometry, lipid species including hydroxycholesterols, bile acids and structural lipids. In WT and Cyp7b1-/- mice, thermoneutral housing promoted MAFLD, an effect that was more pronounced in CYP7B1-deficient mice. In these mice, we found higher plasma alanine aminotransferase activity, hyperlipidemia, hepatic accumulation of potentially harmful lipid species, aggravated liver fibrosis, increased inflammation and immune cell infiltration. Bile acids and hydroxycholesterols did not correlate with aggravated MAFLD in Cyp7b1-/- mice housed at thermoneutrality. Notably, an up-regulation of lipoprotein receptors was detected at 22 °C but not at 30 °C in livers of Cyp7b1-/- mice, suggesting that accelerated metabolism of lipoproteins carrying lipotoxic molecules counteracts MAFLD progression.
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Familia 7 del Citocromo P450/metabolismo , Hígado Graso/enzimología , Hígado Graso/metabolismo , Esteroide Hidroxilasas/metabolismo , Temperatura , Animales , Biomarcadores/metabolismo , Familia 7 del Citocromo P450/deficiencia , Inflamación/patología , Metabolismo de los Lípidos , Hígado/metabolismo , Hígado/patología , Cirrosis Hepática/metabolismo , Cirrosis Hepática/patología , Ratones , Ratones Noqueados , Fenotipo , Receptores de Lipoproteína/metabolismo , Bazo/inmunología , Esteroide Hidroxilasas/deficiencia , Regulación hacia ArribaRESUMEN
Acetyl-CoA carboxylase (ACC) 1 and ACC2 are essential rate-limiting enzymes that synthesize malonyl-CoA (M-CoA) from acetyl-CoA. ACC1 is predominantly expressed in lipogenic tissues and regulates the de novo lipogenesis flux. It is upregulated in the liver of patients with nonalcoholic fatty liver disease (NAFLD), which ultimately leads to the formation of fatty liver. Therefore, selective ACC1 inhibitors may prevent the pathophysiology of NAFLD and nonalcoholic steatohepatitis (NASH) by reducing hepatic fat, inflammation, and fibrosis. Many studies have suggested ACC1/2 dual inhibitors for treating NAFLD/NASH; however, reports on selective ACC1 inhibitors are lacking. In this study, we investigated the effects of compound-1, a selective ACC1 inhibitor for treating NAFLD/NASH, using preclinical in vitro and in vivo models. Compound-1 reduced M-CoA content and inhibited the incorporation of [14C] acetate into fatty acids in HepG2 cells. Additionally, it reduced hepatic M-CoA content and inhibited de novo lipogenesis in C57BL/6J mice after a single dose. Furthermore, compound-1 treatment of 8 weeks in Western diet-fed melanocortin 4 receptor knockout mice-NAFLD/NASH mouse model-improved liver hypertrophy and reduced hepatic triglyceride content. The reduction of hepatic M-CoA by the selective ACC1 inhibitor was highly correlated with the reduction in hepatic steatosis and fibrosis. These findings support further investigations of the use of this ACC1 inhibitor as a new treatment of NFLD/NASH. SIGNIFICANCE STATEMENT: This is the first study to demonstrate that a novel selective inhibitor of acetyl-CoA carboxylase (ACC) 1 has anti-nonalcoholic fatty liver disease (NAFLD) and anti-nonalcoholic steatohepatitis (NASH) effects in preclinical models. Treatment with this compound significantly improved hepatic steatosis and fibrosis in a mouse model. These findings support the use of this ACC1 inhibitor as a new treatment for NAFLD/NASH.
Asunto(s)
Acetil-CoA Carboxilasa/antagonistas & inhibidores , Inhibidores Enzimáticos/uso terapéutico , Cirrosis Hepática/tratamiento farmacológico , Cirrosis Hepática/enzimología , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Enfermedad del Hígado Graso no Alcohólico/enzimología , Acetil-CoA Carboxilasa/metabolismo , Animales , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Hígado Graso/tratamiento farmacológico , Hígado Graso/enzimología , Hígado Graso/patología , Células Hep G2 , Humanos , Cirrosis Hepática/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Enfermedad del Hígado Graso no Alcohólico/patologíaRESUMEN
BACKGROUND AND AIMS: Oxidative stress plays a key role in the development of metabolic complications associated with obesity, including insulin resistance and the most common chronic liver disease worldwide, nonalcoholic fatty liver disease. We have recently discovered that the microRNA miR-144 regulates protein levels of the master mediator of the antioxidant response, nuclear factor erythroid 2-related factor 2 (NRF2). On miR-144 silencing, the expression of NRF2 target genes was significantly upregulated, suggesting that miR-144 controls NRF2 at the level of both protein expression and activity. Here we explored a mechanism whereby hepatic miR-144 inhibited NRF2 activity upon obesity via the regulation of the tricarboxylic acid (TCA) metabolite, fumarate, a potent activator of NRF2. METHODS: We performed transcriptomic analysis in liver macrophages (LMs) of obese mice and identified the immuno-responsive gene 1 (Irg1) as a target of miR-144. IRG1 catalyzes the production of a TCA derivative, itaconate, an inhibitor of succinate dehydrogenase (SDH). TCA enzyme activities and kinetics were analyzed after miR-144 silencing in obese mice and human liver organoids using single-cell activity assays in situ and molecular dynamic simulations. RESULTS: Increased levels of miR-144 in obesity were associated with reduced expression of Irg1, which was restored on miR-144 silencing in vitro and in vivo. Furthermore, miR-144 overexpression reduces Irg1 expression and the production of itaconate in vitro. In alignment with the reduction in IRG1 levels and itaconate production, we observed an upregulation of SDH activity during obesity. Surprisingly, however, fumarate hydratase (FH) activity was also upregulated in obese livers, leading to the depletion of its substrate fumarate. miR-144 silencing selectively reduced the activities of both SDH and FH resulting in the accumulation of their related substrates succinate and fumarate. Moreover, molecular dynamics analyses revealed the potential role of itaconate as a competitive inhibitor of not only SDH but also FH. Combined, these results demonstrate that silencing of miR-144 inhibits the activity of NRF2 through decreased fumarate production in obesity. CONCLUSIONS: Herein we unravel a novel mechanism whereby miR-144 inhibits NRF2 activity through the consumption of fumarate by activation of FH. Our study demonstrates that hepatic miR-144 triggers a hyperactive FH in the TCA cycle leading to an impaired antioxidant response in obesity.
Asunto(s)
Hígado Graso/enzimología , Fumarato Hidratasa/metabolismo , Resistencia a la Insulina , Hígado/enzimología , Macrófagos/enzimología , MicroARNs/metabolismo , Factor 2 Relacionado con NF-E2/metabolismo , Obesidad/enzimología , Animales , Carboxiliasas/genética , Carboxiliasas/metabolismo , Ciclo del Ácido Cítrico , Modelos Animales de Enfermedad , Hígado Graso/genética , Fumarato Hidratasa/genética , Fumaratos/metabolismo , Humanos , Hidroliasas/genética , Hidroliasas/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , MicroARNs/genética , Factor 2 Relacionado con NF-E2/genética , Obesidad/genética , Estrés Oxidativo , Células RAW 264.7 , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal , Succinatos/metabolismoRESUMEN
The present study aimed to elucidate the mechanism of dietary betaine, as a lipid-lowering substance, on the regulation of lipid metabolism and inflammation in juvenile black seabream (Acanthopagrus schlegelii) fed a high fat diet. An 8-week feeding trial was conducted in black seabream with an initial weight of 8.39 ± 0.01g fed four isonitrogenous diets including Control, medium-fat diet (11%); HFD, high-fat diet (17%); and HFD supplemented with two levels (10 and 20 g/kg) of betaine, HFD+B1 and HFD+B2, respectively. SGR and FE in fish fed HFD+B2 were significantly higher than in fish fed HFD. Liver histology revealed that vacuolar fat droplets were smaller and fewer in bream fed HFD supplemented with betaine compared to fish fed HFD. Betaine promoted the mRNA and protein expression levels of silent information regulator 1 (Sirt1), up-regulated mRNA expression and protein content of lipid peroxisome proliferator-activated receptor alpha (pparα), and down-regulated mRNA expression and protein content of sterol regulatory element-binding protein-1(srebp-1). Furthermore, the mRNA expression levels of anti-inflammatory cytokines in liver and intestine were up-regulated, while nuclear factor kB (nf-kb) and pro-inflammatory cytokines were down-regulated by dietary betaine supplementation. Likewise, in fish that received lipopolysaccharide (LPS) to stimulate inflammatory responses, the expression levels of mRNAs of anti-inflammatory cytokines in liver, intestine and kidney were up-regulated in fish fed HFD supplemented with betaine compared with fish fed HFD, while nf-kb and pro-inflammatory cytokines were down-regulated. This is the first report to suggest that dietary betaine could be an effective feed additive to alleviate hepatic steatosis and attenuate inflammatory responses in black seabream fed a high fat diet by modulating the Sirt1/Srebp-1/PparÉ pathway.
Asunto(s)
Betaína/administración & dosificación , Dieta Alta en Grasa/efectos adversos , Suplementos Dietéticos , Hígado Graso/veterinaria , Enfermedades de los Peces/prevención & control , Proteínas de Peces/metabolismo , Inflamación/veterinaria , Hígado/enzimología , PPAR alfa/metabolismo , Dorada/metabolismo , Sirtuina 1/metabolismo , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Factores de Edad , Alimentación Animal , Animales , Citocinas/genética , Citocinas/metabolismo , Hígado Graso/enzimología , Hígado Graso/inmunología , Hígado Graso/prevención & control , Enfermedades de los Peces/enzimología , Enfermedades de los Peces/inmunología , Proteínas de Peces/genética , Inflamación/inmunología , Inflamación/metabolismo , Inflamación/prevención & control , Hígado/inmunología , PPAR alfa/genética , Dorada/genética , Dorada/inmunología , Sirtuina 1/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/genéticaRESUMEN
OBJECTIVES: The incidence of metabolic associated fatty liver disease (MAFLD) induced by high fructose consumption is dramatically increasing in the world while lacking specifically therapeutic drugs. The present study aimed to investigate the effect of complement C1q/tumor necrosis factor-related protein-3 (CTRP3) on fructose-induced MAFLD and its potential mechanisms. METHOD: The animal models with MAFLD were built with Sprague-Dawley (SD) rats drinking 10 % fructose solution for 12 weeks. Then, specific hepatic CTRP3 overexpression was conducted by a single caudal-vein injection of CTRP3-expressing adenoviruses. Rats were sacrificed two weeks later. RESULTS: Drinking 10 % fructose solution for 12 weeks successfully built the rats models with MAFLD. Fructose feeding markedly decreased hepatic CTRP3 expression in rats. However, CTRP3 overexpression in liver alleviated hyperuricemia, dyslipidemia, liver function injury, intrahepatic triglyceride (TG) accumulation and histological changes of hepatic steatosis in rats fed with fructose. CTRP3 overexpression also inhibited hepatic XO activity in liver and improved subsequent oxidative stress, accompanied with downregulation of gene expression of sterol-regulatory element binding protein 1c (SERBP-1c) and fatty acid synthase (FAS). CONCLUSION: CTRP3 attenuates MAFLD induced by fructose, which maybe partially attribute to rescued oxidative stress related with xanthine oxidase overactivity.
Asunto(s)
Adipoquinas/metabolismo , Hígado Graso/enzimología , Hígado Graso/patología , Estrés Oxidativo , Xantina Oxidasa/metabolismo , Animales , Ácido Graso Sintasas/genética , Ácido Graso Sintasas/metabolismo , Hígado Graso/sangre , Conducta Alimentaria , Fructosa , Lípidos/sangre , Masculino , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas Sprague-Dawley , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Ácido Úrico/sangreRESUMEN
Alcohol-related liver disease is associated with intestinal dysbiosis. Functional changes in the microbiota affect bile acid metabolism and result in elevated serum bile acids in patients with alcohol-related liver disease. The aim of this study was to identify the potential role of the bile acid sequestrant colesevelam in a humanized mouse model of ethanol-induced liver disease. We colonized germ-free (GF) C57BL/6 mice with feces from patients with alcoholic hepatitis and subjected humanized mice to the chronic-binge ethanol feeding model. Ethanol-fed gnotobiotic mice treated with colesevelam showed reduced hepatic levels of triglycerides and cholesterol, but liver injury and inflammation were not decreased as compared with non-treated mice. Colesevelam reduced hepatic cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1) protein expression, although serum bile acids were not lowered. In conclusion, our findings indicate that colesevelam treatment mitigates ethanol-induced liver steatosis in mice.
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Colesterol 7-alfa-Hidroxilasa/biosíntesis , Clorhidrato de Colesevelam/farmacología , Etanol/toxicidad , Hígado Graso , Vida Libre de Gérmenes , Animales , Hígado Graso/inducido químicamente , Hígado Graso/tratamiento farmacológico , Hígado Graso/enzimología , Femenino , RatonesRESUMEN
BACKGROUND: Platelet-activating-factor (PAF) is a lipid inflammatory mediator implicated in liver disease. Its main biosynthetic enzymes are cytidine diphosphate (CDP)-choline: 1-alkyl-2-acetyl-sn-glycerol-cholinephosphotransferase (PAF-CPT) and acetyl-coenzyme A: lyso-PAF-acetyltransferases (Lyso-PAF-AT). At the same time, PAF acetylhydrolase (PAF-AH) and lipoprotein-associated phospholipase A2 (Lp-PLA2 ) degrade PAF. OBJECTIVE: To explore the relation of PAF metabolism with liver diseases and non-alcoholic fatty liver disease, as reflected by the fatty liver index (FLI). METHODS: In 106 healthy volunteers, PAF concentration, the activity of its metabolic enzymes and gamma-glutamyl transferase (GGT) were measured in whole blood, leukocytes and serum, respectively and the FLI was calculated. Partial correlations and linear regression models were used. RESULTS: In males, serum GGT activity was positively correlated with abdominal fat (as assessed by analysis of a manually defined region of interest in dual-energy X-ray absorptiometry), triacylglycerols, bound-PAF and Lp-PLA2 , while the FLI was positively correlated with Lp-PLA2 activity. In females, serum GGT activity was negatively associated with high-density lipoprotein cholesterol (HDL-C) (age adjusted correlations, all p<0.05). Lp-PLA2 was a significant determinant of serum GGT activity in males after controlling for age, low- density lipoprotein cholesterol (LDL-C) and abdominal fat. The addition of bound-PAF in the model significantly increased the explained variance of serum GGT activity (total variance explanation 30%). CONCLUSION: Bound-PAF and Lp-PLA2 activity predicted serum GGT activity while Lp-PLA2 was also related to FLI. Our findings shed light on the metabolic pathways linking Lp-PLA2 to other atherosclerosis and/or oxidative markers, such as HDL-C, LDL-C, GGT and FLI and underline the important role of PAF.
Asunto(s)
Hígado Graso , Factor de Activación Plaquetaria , gamma-Glutamiltransferasa , Hígado Graso/enzimología , Femenino , Voluntarios Sanos , Humanos , Masculino , Factor de Activación Plaquetaria/metabolismo , gamma-Glutamiltransferasa/metabolismoRESUMEN
Deficiency of polyunsaturated fatty acids (PUFAs) is known to induce hepatic steatosis. However, it is not clearly understood which type of PUFA is responsible for the worsening of steatosis. This study observed a marked accumulation of hepatic triacylglycerol and cholesterol in fatty acid desaturase 2 knockout (FADS2-/- ) mice lacking both C18 and ≥ C20 PUFAs that were fed a PUFA-depleted diet. Hepatic triacylglycerol accumulation was associated with enhanced sterol regulatory element-binding protein (SREBP)-1-dependent lipogenesis and decreased triacylglycerol secretion into the plasma via very-low-density lipoprotein (VLDL). Furthermore, upregulation of cholesterol synthesis contributed to increased hepatic cholesterol content in FADS2-/- mice. These results suggest that ≥ C20 PUFAs synthesized by FADS2 are important in regulating hepatic triacylglycerol and cholesterol accumulation during PUFA deficiency.
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Colesterol/biosíntesis , Ácido Graso Desaturasas/genética , Ácidos Grasos Insaturados/deficiencia , Hígado Graso/genética , Triglicéridos/biosíntesis , Animales , Carnitina O-Palmitoiltransferasa/genética , Carnitina O-Palmitoiltransferasa/metabolismo , Dieta/efectos adversos , Modelos Animales de Enfermedad , Ácido Graso Desaturasas/deficiencia , Acido Graso Sintasa Tipo I/genética , Acido Graso Sintasa Tipo I/metabolismo , Hígado Graso/enzimología , Hígado Graso/etiología , Hígado Graso/patología , Expresión Génica , Perfilación de la Expresión Génica , Lipogénesis/genética , Lipoproteínas VLDL/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Estearoil-CoA Desaturasa/genética , Estearoil-CoA Desaturasa/metabolismo , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismoRESUMEN
This study aimed to analyze the association between elevated gamma-glutamyl transpeptidase (GGT) and metabolic syndrome (MetS), hepatic steatosis, and fibrosis in patients with nonalcoholic fatty liver disease (NAFLD). From August 2013 to August 2018, a community-based study was conducted in the northeastern part of Taiwan. Patients who underwent abdominal ultrasonography (US) and had no history of alcoholic liver disease were included. According to a US examination showing fatty liver degree, 1566 patients with NAFLD were divided into four groups: normal GGT, isolated GGT elevation, isolated alanine aminotransferase (ALT) elevation, and both GGT and ALT elevation groups. Further 1147 participants with normal serum ALT, GGT, and the abdominal US were included as the control group. GGT levels were associated with high sensitivity C-reactive protein, lower adiponectin, diabetes mellitus, and chronic kidney disease. A stepwise increase in odds ratio (OR) for MetS was found in the normal GGT group (OR = 1.71), isolated GGT elevation group (OR = 3.06), isolated ALT elevation (OR = 4.00), and both GGT + ALT elevation group (OR = 4.17) than the control group. Linear regression analysis revealed a positive association between GGT/ALT value and hepatic steatosis degree, GGT value, and degree of hepatic fibrosis. Hence, GGT elevation is associated with MetS, hepatic steatosis, and fibrosis in patients with NAFLD.
Asunto(s)
Hígado Graso/enzimología , Cirrosis Hepática/enzimología , Síndrome Metabólico/enzimología , Enfermedad del Hígado Graso no Alcohólico/sangre , gamma-Glutamiltransferasa/sangre , Abdomen/diagnóstico por imagen , Adulto , Alanina Transaminasa/sangre , Aspartato Aminotransferasas/sangre , Proteína C-Reactiva/metabolismo , Estudios Transversales , Hígado Graso/sangre , Femenino , Humanos , Cirrosis Hepática/sangre , Masculino , Síndrome Metabólico/sangre , Persona de Mediana Edad , Taiwán , UltrasonografíaRESUMEN
Tumor progression locus 2 (Tpl2, gene name MAP3K8), a mitogen-activated protein kinase, is widely expressed in immune and non-immune cells to integrate tumor necrosis factor (TNF), toll-like receptors (TLRs), and interleukin-1 (IL1) receptor signaling to regulate inflammatory response. Given its central role in inflammatory response, Tpl2 is an attractive small molecule drug target. However, the role of Tpl2 as an oncogene or tumor suppressor gene remains controversial, and its function outside immune cells is not understood. We therefore utilized a Tpl2 kinase dead (Tpl2-KD) mouse model in an 18-month aging study to further elucidate Tpl2 effects on lifespan and chronic disease. Histopathological studies revealed the incidence and severity of spontaneous tumors and non-neoplastic lesions were comparable between wild type and Tpl2-KD mice. The only finding was that male Tpl2-KD mice had higher bodyweight and an increased incidence of liver steatosis, suggesting a sex-specific role for Tpl2 in hepatic lipid metabolism. In conclusion, loss of Tpl2 kinase activity did not lead to increased tumorigenesis over aging in mice but affected likely alterations in lipid metabolism in male animals.
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Hígado Graso/enzimología , Inflamación/enzimología , Hígado/enzimología , Quinasas Quinasa Quinasa PAM/metabolismo , Neoplasias/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Factores de Edad , Animales , Hígado Graso/genética , Hígado Graso/patología , Femenino , Genotipo , Inflamación/genética , Metabolismo de los Lípidos , Hígado/patología , Quinasas Quinasa Quinasa PAM/deficiencia , Quinasas Quinasa Quinasa PAM/genética , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Neoplasias/genética , Neoplasias/patología , Fenotipo , Proteínas Proto-Oncogénicas/deficiencia , Proteínas Proto-Oncogénicas/genética , Factores SexualesRESUMEN
Modulation of adipocyte lipolysis represents an attractive approach to treat metabolic diseases. Lipolysis mainly depends on two enzymes: adipose triglyceride lipase and hormone-sensitive lipase (HSL). Here, we investigated the short- and long-term impact of adipocyte HSL on energy homeostasis using adipocyte-specific HSL knockout (AHKO) mice. AHKO mice fed high-fat-diet (HFD) progressively developed lipodystrophy accompanied by excessive hepatic lipid accumulation. The increased hepatic triglyceride deposition was due to induced de novo lipogenesis driven by increased fatty acid release from adipose tissue during refeeding related to defective insulin signaling in adipose tissue. Remarkably, the fatty liver of HFD-fed AHKO mice reversed with advanced age. The reversal of fatty liver coincided with a pronounced lipodystrophic phenotype leading to blunted lipolytic activity in adipose tissue. Overall, we demonstrate that impaired adipocyte HSL-mediated lipolysis affects systemic energy homeostasis in AHKO mice, whereby with older age, these mice reverse their fatty liver despite advanced lipodystrophy.
Asunto(s)
Adipocitos/enzimología , Metabolismo Energético , Hígado Graso/enzimología , Lipodistrofia/enzimología , Lipólisis , Hígado/metabolismo , Esterol Esterasa/deficiencia , Adipocitos/patología , Factores de Edad , Animales , Glucemia/metabolismo , Modelos Animales de Enfermedad , Hígado Graso/genética , Hígado Graso/patología , Insulina/metabolismo , Lipodistrofia/genética , Lipodistrofia/patología , Hígado/patología , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , PPAR gamma/metabolismo , Esterol Esterasa/genética , Factores de TiempoRESUMEN
The fatty acid desaturase 1 (FADS1), also known as delta-5 desaturase (D5D), is one of the rate-limiting enzymes involved in the desaturation and elongation cascade of polyunsaturated fatty acids (PUFAs) to generate long-chain PUFAs (LC-PUFAs). Reduced function of D5D and decreased hepatic FADS1 expression, as well as low levels of LC-PUFAs, were associated with nonalcoholic fatty liver disease. However, the causal role of D5D in hepatic lipid homeostasis remains unclear. In this study, we hypothesized that down-regulation of FADS1 increases susceptibility to hepatic lipid accumulation. We used in vitro and in vivo models to test this hypothesis and to delineate the molecular mechanisms mediating the effect of reduced FADS1 function. Our study demonstrated that FADS1 knockdown significantly reduced cellular levels of LC-PUFAs and increased lipid accumulation and lipid droplet formation in HepG2 cells. The lipid accumulation was associated with significant alterations in multiple pathways involved in lipid homeostasis, especially fatty acid oxidation. These effects were demonstrated to be mediated by the reduced function of the peroxisome proliferator-activated receptor alpha (PPARα)-fibroblast growth factor 21 (FGF21) axis, which can be reversed by treatment with docosahexaenoic acid, PPARα agonist, or FGF21. In vivo, FADS1-knockout mice fed with high-fat diet developed increased hepatic steatosis as compared with their wild-type littermates. Molecular analyses of the mouse liver tissue largely corroborated the observations in vitro, especially along with reduced protein expression of PPARα and FGF21. Conclusion: Collectively, these results suggest that dysregulation in FADS1 alters liver lipid homeostasis in the liver by down-regulating the PPARα-FGF21 signaling axis.
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Ácido Graso Desaturasas/metabolismo , Hígado Graso/enzimología , Factores de Crecimiento de Fibroblastos/metabolismo , Hígado/enzimología , PPAR alfa/metabolismo , Animales , Ácidos Docosahexaenoicos/administración & dosificación , Regulación hacia Abajo , Ácidos Grasos Insaturados/metabolismo , Células Hep G2 , Homeostasis , Humanos , Metabolismo de los Lípidos , Ratones , Ratones Noqueados , PPAR alfa/agonistas , Transducción de SeñalRESUMEN
The fatty liver hemorrhage syndrome in laying hens is a disease of lipid metabolism disorders. Importantly, energy sensor AMP-activated protein kinase (AMPK) plays an essential role in homeostasis regulation of liver lipid. The current research aims to investigate the relationship between AMPK signaling pathway and lipid metabolism in laying hen hepatocytes and explore the underlying mechanisms. The steatotic hepatocytes model of laying hen was established and treated with AMPK agonist AICAR and inhibitor compound C. The results showed that the levels of triglyceride, total cholesterol, and low-density lipoprotein cholesterol significantly declined while high-density lipoprotein cholesterol level increased in the AICAR-treated steatosis group compared with the steatosis group. Furthermore, the mRNA levels of liver kinase B1 and AMP-activated protein kinase α1 declined significantly in the steatosis group compared with those in the normal group. However, AMPK activation significantly upregulated the mRNA levels of peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase-1 while downregulated the mRNA levels of acetyl CoA carboxylase, fatty acid synthase, 3-hydroxy-3-methyl glutaryl coenzyme A reductase, Sn-glycerol-3-phosphate acyltransferase, and hepatocyte nuclear factor 4α. These results suggest that activated AMPK signaling pathway increases fatty acid oxidation and reduces lipid synthesis in laying hen hepatocytes, thereby ameliorating liver steatosis.
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Proteínas Quinasas Activadas por AMP , Hepatocitos , Metabolismo de los Lípidos , Transducción de Señal , Proteínas Quinasas Activadas por AMP/genética , Proteínas Quinasas Activadas por AMP/metabolismo , Animales , Pollos/metabolismo , Activación Enzimática , Hígado Graso/enzimología , Hígado Graso/fisiopatología , Hígado Graso/veterinaria , Femenino , Hepatocitos/enzimología , Hepatocitos/patología , Metabolismo de los Lípidos/fisiología , Hígado/citología , Hígado/enzimología , Hígado/fisiopatologíaRESUMEN
Neuronal nitric oxide synthase (nNOS) interacts with its adaptor protein NOS1AP through its PZD domain in the neurons. Previously, we had reported that NOS1AP enhanced hepatic insulin sensitivity through its PZD-binding domain, which suggested that nNOS might mediate the effect of NOS1AP. This study aimed to examine the role and underlying mechanisms of nNOS in regulating hepatic insulin sensitivity. nNOS co-localized with NOS1AP in mouse liver. The overexpression of NOS1AP in mouse liver decreased the level of phosphorylated nNOS (p-nNOS (Ser1417)), the active form of nNOS. Conversely, the liver-specific deletion of NOS1AP increased the level of p-nNOS (Ser1417). The overexpression of nNOS in the liver of high-fat diet-induced obese mice exacerbated glucose intolerance, enhanced intrahepatic lipid accumulation, decreased glycogen storage, and blunted insulin-induced phosphorylation of IRbeta and Akt in the liver. Similarly, nNOS overexpression increased triglyceride production, decreased glucose utilization, and downregulated insulin-induced expression of p-IRbeta, p-Akt, and p-GSK3beta in the HepG2 cells. In contrast, treatment with Nω-propyl-L-arginine (L-NPA), a selective nNOS inhibitor, improved glucose tolerance and upregulated insulin-induced phosphorylation of IRbeta and Akt in the liver of ob/ob mice. Furthermore, overexpression of nNOS increased p38MAPK phosphorylation in the HepG2 cells. In contrast, inhibition of p38MAPK with SB203580 significantly reversed the nNOS-induced inhibition of insulin-signaling activity (all P < 0.05). This indicated that hepatic nNOS inhibited the insulin-signaling pathway through the activation of p38MAPK. These findings suggest that nNOS is involved in the development of hepatic insulin resistance and that nNOS might be a potential therapeutic target for diabetes.
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Resistencia a la Insulina , Hígado/enzimología , Óxido Nítrico Sintasa de Tipo I/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Animales , Metabolismo de los Hidratos de Carbono , Hígado Graso/enzimología , Células Hep G2 , Humanos , Sistema de Señalización de MAP Quinasas , Masculino , RatonesRESUMEN
High-fat diet (HFD)-induced inflammation and steatosis of adipose tissue and liver are associated with a variety of serious health risks. Sialic acids are found as the distal terminal sugar on glycoproteins, which are removed by sialidases (neuraminidases). In humans and mice, pulmonary fibrosis is associated with up-regulation of sialidases, and injections of sialidase inhibitors attenuate bleomycin-induced pulmonary fibrosis. Sialidase levels are altered in obese rodents and humans. This report shows that for mice on an HFD, injections of the sialidase inhibitor N-acetyl-2,3-dehydro-2-deoxyneuraminic acid inhibit weight gain, reduce steatosis, and decrease adipose tissue and liver inflammation. Compared with control, mice lacking the sialidase neuraminidase 3 have reduced HFD-induced adipose tissue and liver inflammation. These data suggest that sialidases promote adipose and liver inflammation in response to a high-fat diet.
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Dieta Alta en Grasa/efectos adversos , Hígado Graso/enzimología , Hepatitis/enzimología , Inflamación/enzimología , Neuraminidasa/metabolismo , Paniculitis/enzimología , Tejido Adiposo/patología , Animales , Hígado Graso/etiología , Hepatitis/etiología , Inflamación/etiología , Masculino , Ratones , Ratones Endogámicos C57BL , Paniculitis/etiologíaRESUMEN
Hyperlipidaemia is one of the major risk factors for atherosclerosis, coronary heart disease, stroke and diabetes. In the present study, we synthesized a new anthraquinone compound, 1,8-dihydroxy-3-succinic acid monoethyl ester-6-methylanthraquinone, and named it Kanglexin (KLX). The aim of this study was to evaluate whether KLX has a lipid-lowering effect and to explore the potential molecular mechanism. In this study, Sprague-Dawley rats were fed a high fat diet (HFD) for 5 weeks to establish a hyperlipidaemia model; then, the rats were orally administered KLX (20, 40, and 80 mg kg-1·d-1) or atorvastatin calcium (AT, 10 mg kg-1·d-1) once a day for 2 weeks. KLX had prominent effects on reducing blood lipids, hepatic lipid accumulation, body weight and the ratio of liver weight/body weight. Furthermore, KLXdramatically reduced the total cholesterol (TC) and triglyceride (TG) levels and lipid accumulation in a HepG2 cell model of dyslipidaemia induced by 1 mmol/L oleic acid (OA). KLX may decrease lipid levels by phosphorylating adenosine monophosphate-activated protein kinase (AMPK) and the downstream sterol regulatory element binding protein 2 (SREBP-2)/proprotein convertase subtilisin/kexin type 9 (PCSK9)/low-density lipoprotein receptor (LDLR) signalling pathway in the HFD rats and OA-treated HepG2 cells. The effects of KLX on the AMPK/SREBP-2/PCSK9/LDLR signalling pathway were abolished when AMPK was inhibited by compound C (a specific AMPK inhibitor) in HepG2 cells. In summary, KLX has an efficient lipid-lowering effect mediated by activation of the AMPK/SREBP-2/PCSK9/LDLR signalling pathway. Our findings may provide new insight into and evidence for the discovery of a new lipid-lowering drug for the prevention and treatment of hyperlipidaemia, fatty liver, and cardiovascular disease in the clinic.
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Proteínas Quinasas Activadas por AMP/metabolismo , Antraquinonas/farmacología , Hígado Graso/prevención & control , Hepatocitos/efectos de los fármacos , Hiperlipidemias/tratamiento farmacológico , Hipolipemiantes/farmacología , Lípidos/sangre , Hígado/efectos de los fármacos , Proproteína Convertasa 9/metabolismo , Receptores de LDL/metabolismo , Proteína 2 de Unión a Elementos Reguladores de Esteroles/metabolismo , Animales , Antraquinonas/síntesis química , Biomarcadores/sangre , Dieta Alta en Grasa , Modelos Animales de Enfermedad , Hígado Graso/sangre , Hígado Graso/enzimología , Hígado Graso/patología , Células Hep G2 , Hepatocitos/enzimología , Hepatocitos/patología , Humanos , Hiperlipidemias/sangre , Hiperlipidemias/enzimología , Hipolipemiantes/síntesis química , Hígado/enzimología , Hígado/patología , Masculino , Ratas Sprague-Dawley , Transducción de SeñalRESUMEN
Fluoxetine is a first-line selective serotonin reuptake inhibitor widely applied for the treatment of depression; however, it induces abnormal hepatic lipid metabolism. Considering decreased expression or function of glucose-6-phosphatase (G6Pase), a key enzyme in gluconeogenesis, or the upregulation of fatty acid uptake, causes hepatic lipid accumulation. The aim of this study was to elucidate whether G6Pase regulation and fatty acid uptake alteration contribute to fluoxetine-induced abnormal hepatic lipid metabolism. Our study revealed that 8-week oral administration of fluoxetine dose-dependently increased hepatic triglyceride, causing hepatic steatosis. Concomitantly, the expression of G6Pase in mouse livers and primary mouse hepatocytes (PMHs) was downregulated in a concentration-dependent manner. Furthermore, fluoxetine increased the concentrations of glucose-6-phosphate (G6Pase substrate) and acetyl CoA (the substrate for de novo lipogenesis) in mouse livers. Additionally, fluoxetine also induced lipid accumulation and downregulated G6Pase expression in HepG2 cells. However, the uptake of green fluorescent fatty acid (BODIPY™ FL C16) in PMHs was not changed after fluoxetine treatment, indicating that fluoxetine-induced hepatic steatosis was not associated with fatty acid uptake alteration. In conclusion, fluoxetine downregulated hepatic G6Pase expression, subsequently enhanced the transformation of glucose to lipid, and ultimately resulted in hepatic steatosis, but with no impact on fatty acid uptake.
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Hígado Graso/inducido químicamente , Fluoxetina/toxicidad , Glucosa-6-Fosfatasa/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/toxicidad , Animales , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo , Hígado Graso/enzimología , Hígado Graso/metabolismo , Células Hep G2/efectos de los fármacos , Hepatocitos/efectos de los fármacos , Hepatocitos/enzimología , Hepatocitos/metabolismo , Humanos , Hígado/efectos de los fármacos , Hígado/enzimología , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Triglicéridos/metabolismoRESUMEN
AIMS: It has been widely reported that autophagy and inositol-requiring enzyme-1α (IRE1α)-c-Jun N-terminal kinase (JNK) pathway was involved in cell survival under endoplasmic reticulum (ER) stress, but their specific roles in hepatic steatosis remain unclear. This study aimed to determine the interaction between autophagy and IRE1α-JNK pathway on cell survival in response to ER stress during the initial phase of hepatic steatosis. METHODS: Hepatic steatosis was induced in HepG2 cells by supplementing oleic acid (OA). Lipid accumulation was evaluated by BODIPY493/503 staining. ER stress and IRE1α-JNK signaling were investigated by western blot. Autophagy was monitored by western blot, GFP-LC3 plasmid and immunofluorescence staining, while apoptosis was determined by western blotting, Annexin-V-FITC/PI staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. KEY FINDINGS: Aggravated lipid accumulation was found under increased ER stress during the initial phase of hepatic steatosis. Meanwhile, an increase of autophagy and no alteration of apoptosis were observed under increased ER stress. Interestingly, autophagy was induced by ER stress, while autophagy suppression led to an increase of apoptosis in response to ER stress Moreover, further study showed that IRE1α-JNK pathway was activated after ER stress and consequently induced autophagy, which promoted cell survival in the initial phase of hepatic steatosis. SIGNIFICANCE: We conclude that IRE1α-JNK pathway was activated during ER stress in the initial phase of hepatic steatosis and promoted cell survival by enhancing autophagy. Targeting IRE1α-JNK-autophagy signaling may provide new insight into preventive strategies for hepatic steatosis.