RESUMO
BACKGROUND: Peroxisome proliferator-activated receptor γ (PPARγ) activation suppresses HSC activation and liver fibrosis. Moreover, autophagy is implicated in hepatic lipid metabolism. Here, we determined whether PPARγ activation ameliorates HSC activation by downregulating transcription factor EB (TFEB)-mediated autophagy. METHODS AND RESULTS: Atg7 or Tfeb knockdown in human HSC line LX-2 cells downregulated the expression of fibrogenic markers including α smooth muscle actin, glial fibrillary acidic protein, and collagen type 1. Conversely, Atg7 or Tfeb overexpression upregulated fibrogenic marker expression. Rosiglitazone (RGZ)-mediated PPARγ activation and/or overexpression in LX-2 cells and primary HSCs decreased autophagy, as indicated by LC3B conversion, total and nuclear-TFEB contents, mRFP-LC3 and BODIPY 493/503 colocalization, and GFP-LC3 and LysoTracker colocalization. RGZ treatment decreased liver fat content, liver enzyme levels, and fibrogenic marker expression in high-fat high-cholesterol diet-fed mice. Electron microscopy showed that RGZ treatment restored the high-fat high-cholesterol diet-mediated lipid droplet decrease and autophagic vesicle induction in primary HSCs and liver tissues. However, TFEB overexpression in LX-2 cells offset the aforementioned effects of RGZ on autophagic flux, lipid droplets, and fibrogenic marker expression. CONCLUSIONS: Activation of PPARγ with RGZ ameliorated liver fibrosis and downregulation of TFEB and autophagy in HSCs may be important for the antifibrotic effects of PPARγ activation.
Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Células Estreladas do Fígado , PPAR gama , Animais , Humanos , Camundongos , Autofagia/genética , Células Estreladas do Fígado/metabolismo , Hepatócitos/metabolismo , Cirrose Hepática/patologia , PPAR gama/genética , PPAR gama/metabolismo , Rosiglitazona/farmacologia , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismoRESUMO
BACKGROUND: Fatty liver and/or increased liver enzyme values have been reported to be associated with incident diabetes. We sought to determine whether increased visit-to-visit liver enzyme variability is associated with incident diabetes. METHODS: Study participants were recruited from the Korean Genome and Epidemiologic Study (KoGES). A total of 4,151 people aged 40 to 69 years was recruited and tested every 2 years for up to 12 years. Visit-to-visit aspartate aminotransferase (AST) and alanine aminotransferase (ALT) variability was evaluated in first the 6-year period through the use of various variability measurements: standard deviation (SD), average successive variability, coefficient of variation (CV), and variation independent of mean (VIM). Oral glucose tolerance test was performed at every visit. RESULTS: During the 6-year follow-up appointments, 13.0% (538/4,151) of people developed incident diabetes. Visit-to-visit AST variability was associated with an increased risk of diabetes independent of conventional risk factors for diabetes (hazard ratio per 1-SD increment [95% confidence interval]: 1.06 [1.00 to 1.11], 1.12 [1.04 to 1.21], and 1.13 [1.04 to 1.22] for SD, CV, and VIM, respectively; all P<0.05); however, no such associations were observed in the visit-to-visit ALT variability. According to alcohol consumption status, both AST and ALT variability were independent predictors for incident diabetes in subjects with heavy alcohol consumption; however, neither AST nor ALT variability was associated with diabetes risk in subjects who did not drink alcohol heavily. CONCLUSION: Visit-to-visit liver enzyme variability is an independent predictor of incident diabetes. Such association was more evident in those who consumed significant amounts of alcohol.