Bruschi Francesca V, Tardelli Matteo, Herac Merima, Claudel Thierry, Trauner Michael
Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Internal Medicine III, Medical University of Vienna, Vienna, Austria.
Division of Gastroenterology and Hepatology, Joan and Sanford I. Weill Cornell Department of Medicine, Weill Cornell Medical College, New York, NY, USA.
Liver Int. 2020 May;40(5):1098-1110. doi: 10.1111/liv.14402. Epub 2020 Mar 1.
The genetic PNPLA3 polymorphism I148M has been extensively associated with higher risk for development and progression of NAFLD towards NASH.
PNPLA3 and α-SMA expression were quantified in liver biopsies collected from NASH patients (n = 26) with different fibrosis stages and PNPLA3 genotypes. To study the potential mechanisms driving PNPLA3 expression during NASH progression towards fibrosis, hepatocytes and hepatic stellate cells (HSCs) were cultivated in low and high glucose medium. Moreover, hepatocytes were treated with increasing concentrations of palmitic acid alone or in combination with glucose. Conditioned media were collected from challenged hepatocytes to stimulate HSCs.
Tissue expression of PNPLA3 was significantly enhanced in biopsies of patients carrying the I148M polymorphism compared to wild type (WT). In NASH biopsies, PNPLA3 significantly correlated with fibrosis stage and α-SMA levels independently of PNPLA3 genotype. In line, PNPLA3 expression was higher in α-SMA positive cells. Low glucose increased PNPLA3 in HSCs, whereas high glucose induced PNPLA3 and de-novo lipogenesis-related genes expression in hepatocytes. Palmitic acid induced fat accumulation and cell stress markers in hepatocytes, which could be counteracted by oleic acid. Conditioned media collected from lipotoxic challenged hepatocytes markedly induced PNPLA3 mRNA and protein levels, fibrogenic and autophagic markers and promoted migration in HSCs. Notably, conditioned media collected from hepatocytes cultivated with both glucose and palmitic acid exacerbated HSCs migration, PNPLA3 and fibrogenic gene expression, promoting release of cytokines from HSCs.
Collectively, our observations uncover the diverse metabolic regulation of PNPLA3 among different hepatic cell populations and support its relation to fibrosis progression.
PNPLA3基因多态性I148M与非酒精性脂肪性肝病（NAFLD）发展为非酒精性脂肪性肝炎（NASH）的更高风险密切相关。
对不同纤维化阶段和PNPLA3基因型的NASH患者（n = 26）的肝活检组织中PNPLA3和α - SMA的表达进行定量分析。为研究NASH向纤维化进展过程中驱动PNPLA3表达的潜在机制，将肝细胞和肝星状细胞（HSC）分别置于低糖和高糖培养基中培养。此外，单独用不同浓度的棕榈酸或棕榈酸与葡萄糖联合处理肝细胞。收集受刺激肝细胞的条件培养基以刺激HSC。
与野生型（WT）相比，携带I148M多态性的患者活检组织中PNPLA3的组织表达显著增强。在NASH活检组织中，PNPLA3与纤维化阶段和α - SMA水平显著相关，且与PNPLA3基因型无关。同样，α - SMA阳性细胞中PNPLA3表达更高。低糖增加HSC中PNPLA3的表达，而高糖诱导肝细胞中PNPLA3和从头脂肪生成相关基因的表达。棕榈酸诱导肝细胞中的脂肪堆积和细胞应激标志物，油酸可抵消这种作用。从脂毒性刺激的肝细胞收集的条件培养基显著诱导HSC中PNPLA3的mRNA和蛋白水平、纤维化和自噬标志物，并促进其迁移。值得注意的是，从同时用葡萄糖和棕榈酸培养的肝细胞收集的条件培养基加剧了HSC的迁移、PNPLA3和纤维化基因的表达，促进了HSC中细胞因子的释放。
总体而言，我们的观察结果揭示了不同肝细胞群体中PNPLA3的多种代谢调节方式，并支持其与纤维化进展的关系。
