Piro S, Spadaro L, Russello M, Spampinato D, Oliveri C E, Vasquez E, Benigno R, Brancato F, Purrello F, Rabuazzo A M
Clinica di Medicina Interna, Dipartimento di Medicina Interna e Medicina Specialistica, Università degli Studi di Catania, Ospedale Garibaldi Nesima, Via Palermo, 636, 95122 Catania, Italy.
Nutr Metab Cardiovasc Dis. 2008 Oct;18(8):545-52. doi: 10.1016/j.numecd.2007.08.002. Epub 2007 Dec 11.
Non-alcoholic-steatohepatitis (NASH) is closely related to insulin resistance, but it is unknown whether insulin resistance may be localized in hepatocytes. This study investigates insulin signalling in liver tissue from NASH, and the molecular mechanisms by which insulin-resistance could lead to liver damage (apoptosis). Moreover, to investigate the mechanisms of lipid overload we studied key enzymes in hepatocytes lipid metabolism.
In liver specimens from 11 patients with NASH and 7 histological normal livers, we measured total and phosphorylated Akt (active form), Bax and Bcl-2 by Western-blot analysis. In addition, we studied AMP-activated protein Kinase and Carnitine-Palmitoyl-Transferase-1 gene expression, key regulators of non-esterified fatty acid synthesis and oxidation, by reverse transcription polymerase chain reaction. In NASH, phosphorylated Akt was impaired (104.3+/-10.6 vs 152.6+/-22.4 AU, p<0.002) and correlated with necroinflammatory score (r=-0.62; p<0.05). Bax/Bcl-2 ratio was increased in NASH. Moreover, we observed a decrease of AMP-activated protein Kinase (10.74+/-6 vs 144.7+/-41.6 AU, p<0.0001) and Carnitine-Palmitoyl-Transferase-1 gene expression (38.7+/-14.6 vs 192.1+/-26.2 AU, p<0.0001), and both were correlated with steatosis score (r=-0.56, p<0.05, r=-0.87, p<0.05 respectively).
Akt, a key molecule of insulin signalling and cell apoptosis is impaired in NASH, suggesting an important role of hepatic insulin resistance in liver failure. Moreover, decreased non-esterified fatty acid oxidation may cause hepatic lipid overload.
非酒精性脂肪性肝炎（NASH）与胰岛素抵抗密切相关，但胰岛素抵抗是否局限于肝细胞尚不清楚。本研究调查了NASH肝组织中的胰岛素信号传导，以及胰岛素抵抗导致肝损伤（凋亡）的分子机制。此外，为了研究脂质过载的机制，我们研究了肝细胞脂质代谢中的关键酶。
在11例NASH患者和7例组织学正常肝脏的肝标本中，我们通过蛋白质免疫印迹分析测量了总Akt和磷酸化Akt（活性形式）、Bax和Bcl-2。此外，我们通过逆转录聚合酶链反应研究了AMP激活蛋白激酶和肉碱-棕榈酰转移酶-1基因表达，它们是非酯化脂肪酸合成和氧化的关键调节因子。在NASH中，磷酸化Akt受损（104.3±10.6对152.6±22.4 AU，p<0.002），并与坏死性炎症评分相关（r=-0.62；p<0.05）。NASH中Bax/Bcl-2比值升高。此外，我们观察到AMP激活蛋白激酶降低（10.74±6对144.7±41.6 AU，p<0.0001）和肉碱-棕榈酰转移酶-1基因表达降低（38.7±14.6对192.1±26.2 AU，p<0.0001），两者均与脂肪变性评分相关（分别为r=-0.56，p<0.05；r=-0.87，p<0.05）。
Akt是胰岛素信号传导和细胞凋亡的关键分子，在NASH中受损，提示肝脏胰岛素抵抗在肝衰竭中起重要作用。此外，非酯化脂肪酸氧化减少可能导致肝脏脂质过载。
