摘要:全球約有1.8億人口為慢性C型肝炎病毒帶原者。根據世界衛生組織估計,每年有超過六百四十萬以上的人遭受到急性C型肝炎病毒感染。急性C型肝炎病毒感染後有50-80%的患者會轉變為慢性C型肝炎病毒感染,慢性C型肝炎病毒感染者中有五分之一的人最終會變成肝硬化,之後每年有1-5%的患者最後會產生肝細胞癌。因此C型肝炎病毒感染是一個影響全球醫療、公共衛生與社會經濟的重要健康課題。C型肝炎病毒感染除了造成肝臟的發炎外,還會影響身體其他的器官與系統,造成C肝患者各種不同的肝外臨床表現。特別在生活型態改變所引起的肥胖症及糖尿病等代謝性疾病的全球大流行,以及代謝性肝臟疾病盛行率大幅增加後,C肝病毒與代謝間交互作用已成為肝臟醫學研究領域中的顯學。流行病學上除了發現C肝病毒感染會有肝臟脂肪變性、胰島素抗性或是第二型糖尿病的臨床表現外,也發現慢性C肝患者常有較高的胰島素抗性以及較低的血清中脂肪與膽固醇濃度。當C肝患者同時伴有胰島素抗性、肥胖或是第二型糖尿病時,常會有較嚴重程度的肝臟纖維化,並且對於抗病毒藥物治療的反應也會較差。此外部份慢性C肝患者接受抗病毒藥物治療成功後,其血清中的脂肪與膽固醇濃度會飆升至增加心血管疾病危險性的程度。另一方面,基因轉殖動物與細胞實驗的研究發現,C肝病毒蛋白會影響肝臟細胞內脂肪與胰島素的訊息傳遞途徑,並且能藉由影響脂肪代謝途徑來干擾C肝病毒的複製。然而不同C肝病毒基因型與宿主代謝反應的關聯性並不相同。因此不同C肝病毒基因型感染的患者在臨床疾病與代謝的表現上,以及對細胞內訊息傳遞的影響上都有相當大的差異性。由於仍有20-50%的C肝患者對於標準長效型干擾素合併口服雷巴威林的治療方式反應不佳,因此尋找各種可能影響治療反應的相關因子,了解其可能的影響機轉,就成為相當重要的研究課題。利用C肝病毒感染、複製與葡萄糖及脂肪代謝的關聯性,就成為改善現今C肝患者治療效果的可行方式。目前的臨床研究證據指出,C肝患者在接受標準治療前有較低的血清中三酸甘油脂濃度、較低的高密度脂蛋白濃度、較高的低密度脂蛋白濃度,以及曾經接受降膽固醇藥物(statin)治療者,接受治療後會有較佳的SVR。實驗室的研究也發現,C肝病毒在血清當中會與脂蛋白相結合,並且藉由與細胞膜上的低密度脂蛋白受體(LDLR)、高密度脂蛋白受體(SCARB1)、CD81、claudin-1以及occludin的作用下進入肝臟細胞內。C肝病毒複製時需要依賴細胞內脂肪滴(lipid droplet)以及脂肪代謝途徑的協助。因此C肝病毒與宿主脂肪代謝及受體間交互作用關係著病毒的感染、進入細胞內以及病毒本身的複製。由於不同C肝病毒基因型有不同的病毒動力學變化,並且對於肝臟細胞內脂肪代謝途徑的影響作用也不同。因此吾人認為,不同C肝病毒基因型與脂肪代謝及C肝病毒受體相關因子間應有不同的交互作用存在。假如此假設為真,C肝不同病毒基因型以及病毒基因型特異蛋白應該與胰島素、脂肪代謝途徑以及病毒與病毒受體相關因子結合的反應上會有相當大的差異。基於此項假說,吾人將探討不同C肝基因型病毒以及病毒特異蛋白對於胰島素、葡萄糖、脂質代謝途徑以及與C肝病毒受體相關因子(LDLR、SR-B1、CD81、claudin-1、occludin、EGFR與EphA2)的影響。在此,吾人提出三年之研究計畫。第一年將以病例對照的研究設計(case-control study),比較100例慢性C肝基因型第ㄧ型病毒感染患者、100例慢性C肝基因型第二或三型病毒感染患者與100位非慢性C肝感染之對照組的血清C肝病毒量、代謝指標與病毒受體相關因子基因表現的關連性是否有所差異。第二年將比較100例慢性C肝達持續病毒反應者(sustained virologic response, SVR)與100位無持續病毒反應(non-SVR)之對照組,其抗病毒藥物治療反應與病毒受體相關因子基因表現的關連性。第三年將著重於細胞生物學的研究,利用不同C肝病毒基因型的傳染性病毒株(infectious clones) 來感染各種肝癌細胞株,以及使用能夠表現各式C肝病毒特異蛋白的細胞株進行分析研究,藉由比較不同基因型病毒以及病毒蛋白對於細胞受體、細胞內胰島素、葡萄糖以及脂肪代謝訊息傳遞的影響,以了解不同C肝病毒基因型在病生理機轉上差異性。希望最後能以此研究所獲得的知識應用於臨床醫藥衛生科學上,使C肝病毒感染的防治與治療更臻完善。
Abstract: Chronic hepatitis C virus (HCV) infection affects more than 180 million people worldwide, and is an important etiology of chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The clinical manifestations of chronic HCV infection vary widely. In addition to hepatic injury, several extrahepatic disorders have been linked to HCV infection. Among them, recent attention is focused on the interactions between chronic HCV infection and metabolic derangements, including glucose, lipid, insulin resistance, adipokines and cytokines. Ample experimental, clinical and epidemiological data all demonstrate a close linkage between chronic HCV infection and metabolic derangements. Chronic HCV infection has been shown to be an independent predictor of metabolic abnormality such as insulin resistance, steatosis and diabetes mellitus. In addition, metabolic profiles can also affect treatment outcomes in chronic hepatitis C patients.To eradicate HCV infection or to attain a sustained virological response (SVR) in chronic hepatitis C (CHC) patients, peginterferon (PEG-IFN) plus ribavirin (RBV) combination therapy is the current standard of care. However, the regimen has many undesirable side effects, is expensive and not effective in a substantial proportion of patients, especially in Western countries. Therefore, identifying patients who are difficult to achieve SVR before or during the therapy is clinically important. In our clinical practice, several baseline and on-treatment factors have been used to predict the disease progression and therapeutic response in CHC patients. They are viral factors, host factors, metabolic factors, histological factors, type of regimens, and duration of infection. Among them, metabolic factors have driven much attention in recent years. Baseline elevated serum LDL levels or low HDL levels and preemptive statin usage were associated with higher SVR rates in patients receiving chronic hepatitis C therapy. Several lines of evidence have shown the essential roles of “lipid droplet” and lipid metabolism for HCV replication. In addition, HCV is known to be associated with VLDL or LDL in the bloodstream, may bind the basolateral surface of hepatocytes through LDLR, and be engulfed into cells under the help of SR-B1, CD81, claudin-1, occluding, EGFR and EphA2. Because different HCV genotypes have different viral kinetics and host lipid factors may affect HCV infection, viral entry, and virions replication, it is reasonable to hypothesize that different HCV genotypes and viral specific encoded proteins may affect insulin, glucose, lipid metabolism and host factors for viral entry differently.Herein, we propose a 3-year study to examine to examine the differential effects of different HCV genotypes and on the interaction of insulin, glucose, lipid metabolism and host factors for viral entry by using clinical and molecular methods. In the first year study, by using the case-control study design, we will compare the expression profiles of genes associated with viral entry, serum viral loads and lipid profiles among 100 genotype 1 (GT1) CHC patients, 100 GT2 or 3 CHC patients, and 100 non-HCV infected subjects. In the second year study, we will compare the expression profiles of genes associated with viral entry between 100 patients with SVR and 100 patients without SVR. In the third year study, we will explore the mechanisms involved in different HCV genotypes and metabolic derangements by comparing the expression profiles of genes associated with insulin resistance, lipid, glucose metabolism, and viral entry in cell lines transfected with plasmids harboring HCV encoded proteins from different genotypes and infectious clones of different HCV genotypes. The effects of various interventions (e.g.: chemicals or siRNA) on the expression of these genes will also be performed.