慢性C型肝炎患者胰島素抗性、代謝和脂肪激素狀態： 病例對照研究與致病機轉探討

Insulin resistance, metabolic and adipokine profiles in chronic hepatitis C patients: Case-control study and mechanistic exploration

許景盛(Ching-Sheng Hsu)

指導教授 ： 高嘉宏

共同指導教授 ： 楊偉勛(Wei-Shiung Yang)

國立臺灣大學/醫學院/臨床醫學研究所/博士(2010年)

https://doi.org/10.6342/NTU.2010.02882

摘要

C型肝炎病毒感染一直是全球公共衛生上的重要課題。根據世界衛生組織的估計，全球目前至少有一億八千萬以上的人遭到C肝病毒的感染。就C肝病毒感染的自然史而言，急性C肝病毒感染後有百分之五十五到八十五的人會變成為慢性的C肝病毒感染。這些慢性C肝病毒感染者中有七成在10年後變成慢性C型肝炎的患者，變成慢性C型肝炎的患者中，有近兩成的人在20年後會產生肝硬化。在肝硬化的C肝患者中，每年有百分之一到四的風險產生肝癌，百分之四到五的風險肝臟衰竭。
慢性C肝病毒感染治療的主要目標為永久消滅病毒，也就是持續追蹤檢驗C肝患者時仍檢測不到血清C肝病毒的核醣核酸。臨床上稱這些人為達到持續病毒學反應(sustained virologic response, SVR)，就是病毒學上的C肝治癒(cure)。然而C肝病毒感染治療的終極目標為希望使C肝患者的肝臟組織學及臨床的相關參數能夠進步，一方面能減緩肝臟組織纖維化的進展及肝硬化產生，另一方面則希望能夠防止肝臟衰竭與肝癌的發生。
目前臨床上已有許多C肝病程進展以及干擾素治療的預測因子可以評估患者未來的預後以及接受治療後的反應，這些因素主要分為兩大類，一類是與病毒相關的因子，另一類則是與宿主(host)相關的因子，利用這些預測因子吾人將可以給予病人個人化的C肝追蹤及治療。與病毒相關的預測因子中，除了治療前的C肝病毒量與病毒基因型外，評估C肝患者接受治療時的C肝病毒量變化為目前臨床上預測患者SVR的重要參考指標。值得注意的是，最近許多臨床及實驗室研究皆指出，C肝病毒感染與宿主的葡萄糖代謝、脂質代謝及肝臟脂肪變性有密切的關係存在，宿主的代謝特徵會影響C肝患者的抗病毒治療效果。因此清楚了解C肝病毒感染與宿主葡萄糖代謝及脂質代謝的關係已經成為現今全球肝病研究中的熱門課題。
因此吾人研究的主要目標為釐清C肝病毒感染對葡萄糖代謝與脂肪代謝的影響，並且探討脂肪變性、胰島素抗性、以及脂肪細胞激素與C肝病毒感染的關係。找尋影響C肝病態生理機轉的可能標的，進而改善未來C肝患者臨床預後與治療。
因此在臨床研究部分，吾人首先比較C肝患者及健康成人在血清中代謝特徵的差異性。吾人發現，C肝患者會較健康成年人有較高的血清高密度脂蛋白膽固醇(high-density lipoprotein-cholesterol, HDL)、脂締素(adiponectin)濃度、但是較低的總膽固醇、三酸甘油酯與低密度脂蛋白膽固醇(low-density lipoprotein-cholesterol, LDL)濃度值。進一步比較C肝患者血清中代謝特徵與抗病毒治療效果時亦發現，C肝患者接受干擾素相關治療時的早期病毒量下降程度與身體質量指標(BMI)以及血清中的HDL 濃度有關。此外吾人亦發現血清中的C肝病毒量與血清中胰島素及三酸甘油酯濃度間存有正比例的關係，並且血清中C肝病毒量與宿主脂肪代謝特徵的關係會隨著C肝病毒基因型的不同而不同。進一步的研究更發現，雖然宿主的代謝特徵會影響C肝患者肝臟組織的纖維化，然而這個影響作用也會因不同C肝病毒基因型的感染而產生不一樣的效果。
另一方面，幾個重要的研究團隊最近共同指出，與介白質28B(interleukin 28B, IL28B, 合成interferon-λ3)相關之單核苷酸多形性(single nucleotide polymorphism, SNP)和C肝患者接受干擾素抗病毒藥物的治療效果間存有強烈的關聯性。因此吾人進一步研究C肝患者血清脂肪代謝特徵與IL28B SNP的關係性。初步的研究發現，帶有IL28B SNP rs8099917 的TT 基因型患者除了會較GT基因型患者在接受標準長效型干擾素治療後有較高的SVR外，TT 基因型患者也較GT基因型患者在接受治療前有較低的血清中三酸甘油酯濃度。
實驗室研究方面，吾人利用能表現不同濃度C肝基因型第一型病毒核心蛋白(HCV core protein)的肝癌細胞株(Huh 7-based cell lines)來分析宿主脂肪與膽固醇合成途徑上重要基因的表現。研究發現，表現C肝基因型第一型病毒核心蛋白的細胞較控制組有較低的細胞內三酸甘油酯與膽固醇濃度。此外不同濃度的C肝病毒核心蛋白對於細胞內膽固醇與脂肪酸製造途徑上的基因表現可以產生不同的影響，表現C肝基因型第一型病毒核心蛋白的細胞較控制組細胞，在3-羥基-3-甲基戊二酸單醯輔酶A合成酶 (3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) synthase)、還原酶(HMG-CoA reductase)以及微粒体三酸甘油酯轉移蛋白(microsomal triglyceride transfer protein, MTTP) 的mRNA表現量上都相對降低，但是在法尼基轉移酶1 (farnesyl-diphosphate farnesyltransferase 1， FDFT1)與ATP citrate lyase mRNA的表現量上則相對增加。C肝病毒核心蛋白低表現量細胞中SREBP1c的mRNA表現量為增加，但是其表現量會隨著C肝病毒核心蛋白量增加而逐漸下降。另外，表現C肝病毒核心蛋白的細胞較控制組在SREBP2 mRNA的表現量上相對增加，但是其表現量也會隨著C肝病毒核心蛋白量的增加而下降。

結語

醫學進步已使現今慢性C型肝炎病毒的感染成為一種可以治療、甚至治癒的疾病。目前臨床上依據不同的預測因子，包括C肝病毒基因型、治療中的病毒動力學變化以及宿主不同的單核苷酸多形性，已經可以給予患者更有效率與更少副作用的個人化治療。然而臨床因子對於C肝患者的自然病史以及抗病毒治療的影響，特別是宿主代謝因子對C肝患者干擾素治療的影響，以及背後的病態生理機轉，仍有待吾人累積更多的研究資料加以闡明。如果未來能夠對於宿主代謝因子與C肝病毒間之作用關係更加了解，吾人相信這些知識將能應用於臨床上，改善未來C肝患者的藥物治療方式，使其變得更有效率、副作用也更加減少。

關鍵字

慢性C型肝炎 ； C型肝炎病毒 ； 持續病毒學反應 ； 胰島素抗性 ； 代謝 ； 脂肪激素 ； 單核苷酸多形性

並列摘要

Hepatitis C virus (HCV) is a major causative agent of chronic hepatitis, liver cirrhosis, end-stage liver disease and hepatocellular carcinoma worldwide. About 55% to 85% HCV infected people will become chronic hepatitis, 5% to 20% of them will turn to liver cirrhosis after duration of 20 to 25 years, 30 % of these cirrhotic patients will become end stage liver disease in 10 years, and once cirrhosis is established, the risk of hepatocellular carcinoma is approximately 1% to 5 % per year. In Taiwan, about 2–4% Taiwanese people are chronic carriers of HCV; hence, effective tackling this virus is an important issue in Taiwan.
The goal of treating chronic hepatitis C (CHC) patients is to eradicate the virus or, in a clinical term, to attain a sustained virological response (SVR, defined as undetectable serum HCV RNA level 24 weeks after treatment cessation). However, currently approved pegylated interferon (Peg-IFN) plus ribavirin (RBV) therapy has many unpleasant side effects and is only effective in a certain proportion of patients with HCV genotype 1 (GT1) infection, especially in Western countries. Therefore, identifying baseline and on-treatment factors predictive of SVR in CHC patients is important in terms of increasing efficacy, avoiding unnecessary side effects and saving medical costs.
Several factors have been linked to the therapeutic response of CHC patients, including viral factors, host factors, metabolic factors, histological factors, the type of regimens, and the duration of infection. Among these factors, early viral kinetics following therapy has become increasingly recognized and widely used in both clinical trials and daily practice. On the other hand, there is increasing interest in the impact of chronic HCV infection on metabolic abnormalities, including glucose, lipid, cytokines, insulin resistance and adipokines. Insulin resistance and type 2 diabetes have inceased incidence in CHC patients than in other disease or chronic hepatitis B patients, and serum lipid profiles as well as hepatic steatosis are associated with HCV infection and may afftect the therapeutic response of CHC patients. Howevr, the interacions between HCV infection and host metabolism as well as the underlying mechanisms remained not fully clarified.
To examine the influence of hepatitis C virus infection on adipokines, glucose and lipid metabolism, we examine the underlying mechanisms by which HCV affects host adipokines, glucose and lipid metabolism, and vice versa, from both clinical and molecular points of views. We found CHC patients had higher alanine aminotransferase (ALT) and high-density lipoprotein-cholesterol levels, but lower total cholesterol (TC), triglyceride (TG), and low-density lipoprotein-cholesterol levels than controls. By using multiple linear regression analyses for subjects with available adiponectin data, presence of HCV infection was independently associated with higher serum adiponectin. In addition, we found body mass index and genotype were related to viral load decline at day 2, and baseline viral load and HDL level were correlated with viral load decline between day 2 and day 28 in multivariate analysis. Genotype 2, lower baseline viral load and more substantial viral load decline at day 28 predicted a higher SVR.
Recently, several groups have found that the genetic polymorphism near IL28B gene may predict the therapeutic response of CHC GT 1 infected patients receiving Peg-IFN plus RBV. Thus, it is important and will be informative to evaluate the association of genetic polymorphism near IL28B gene, SVR and metabolic profiles in CHC GT 1 infected patients. We found Taiwanese CHC patients with rs8099917 TT genotype have a better SVR and lower baseline serum TG level than subjects with GT gentype.
In the in vitro studies, we found that cells expressing HCV core proteins had lower cellular triglyceride and total cholesterol levels than controls (P<0.05, ANOVA; P<0.05, Nonparametric test for trend). HCV GT1 core proteins might down-regulate mRNA expressions of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) synthase, HMG-CoA reductase and microsomal triglyceride transfer protein, but up-regulate mRNA expressions of farnesyl-diphosphate farnesyltransferase 1and ATP citrate lyase. Although mRNA expression of SREBP1c was up-regulated under lower levels of HCV core proteins, its expression was down-regulated with increasing HCV core protein levels. The mRNA expression of SREBP2 was up-regulated by HCV core proteins, but down-regulated with the increasing HCV core protein levels.
CONCLUSIONS: HCV is a curable disease, and the evaluation of HCV genotype, viral kinetic parameters as well as host gene SNPs before treatment has let individualized therapies for CHC patients become possible approaches. However, the interactions and underlying mechanisms of host factors and HCV infection, especially glucose and lipid metabolsim as well as their impacts on therapeutic resposes, remain not fully understood. Further experimental and clinical studies based on these lines of evidence are needed to clearly clarify underlying mechanisms and provide clinicians useful information to opitimize the mangement of chronic HCV infection.

並列關鍵字

hepatitis C virus ； chronic hepatitis C ； insuin resistance ； lipid metabolism ； adipokines ； sustained virologic response ； single nucleotide polymorphism

參考文獻

1. Seeff LB. Natural history of chronic hepatitis C. Hepatology. Nov 2002;36(5 Suppl 1):S35-46.

2. Chen DS. Hepatitis C virus in chronic liver disease and hepatocellular carcinoma in Taiwan. Princess Takamatsu Symp. 1995;25:27-32.

3. National Institutes of Health Consensus Development Conference Statement: Management of hepatitis C: 2002--June 10-12, 2002. Hepatology. Nov 2002;36(5 Suppl 1):S3-20.

4. Poynard T, Yuen MF, Ratziu V, Lai CL. Viral hepatitis C. Lancet. Dec 2003;362(9401):2095-2100.

5. Alter MJ, Margolis HS, Krawczynski K, et al. The natural history of community-acquired hepatitis C in the United States. The Sentinel Counties Chronic non-A, non-B Hepatitis Study Team. N Engl J Med. Dec 1992;327(27):1899-1905.