| Abstract: | 糖尿病是全球性流行的慢性疾病，根據統計目前全世界之糖尿病盛行率約為5％，患者將近1.94億人。近十幾年來糖尿病患者人數更是急速增加，預計西元2010年之糖尿病患者將增加到2.2億人，而西元2025年則將增加到近3.3億人。糖尿病主要可分為兩類，第一型糖尿病(type 1 diabetes mellitus, T1DM)主要是器官特異性自體免疫疾病，而第二型糖尿病(type 2 diabetes mellitus, T2DM)的主要特徵則為胰島素阻抗性(insulin resistance)。本論文分為二大部分探討糖尿病，第一部分分析T1DM病人自體抗體表現的情形，第二部分探討T2DM與Th2細胞激素基因多型性以及胰島素啟動子因子-1(insulin promoter factor-1, IPF-1)基因點突變之間的關聯性。麩胺酸脫羧(glutamic acid decarboxylase, GAD)、第二型去氧核糖核酸拓撲異構(type II topoisomerase, TopII)以及類酥胺酸磷酸分子(protein tyrosine phosphatase [PTP]-like molecules, IA-2)是引發T1DM胰島β細胞自體免疫反應的主要自體抗原。為了解自體抗體和台灣本土T1DM的關係，本論文分析GAD自體抗體(GADA)、TopII自體抗體(TopIIA)以及IA-2自體抗體(IA-2A)等抗體的盛行率，以及這些抗體和病人臨床表徵的關聯性。實驗結果顯示T1DM患者IA-2A、GADA與TopIIA的盛行率分別是23.6%、47.1%與55.2%。GADA 的盛行率與患者平均發病年齡有顯著相關性(GADA+患者10.82 ± 0.76 歲，GADA－患者8.38 ± 0.77歲， p=0.026)；青春期發病患者的GADA 盛行率較高，而且胰島β細胞分泌胰島素的殘餘功能也較佳。此外，本論文利用聚合連鎖反應與限制片段長度多型性技術分別分析T2DM患者之Th2細胞激素介白質素-6(interleukin-6, IL-6)、介白質素-10(IL-10)之基因多型性與IPF-1基因C18R、Q59L、D76N 與 R197H等四種基因點突變情形，並探討他們與T2DM患者臨床表徵之間的相關性。結果顯示所有參與本研究的T2DM病人以及對照組個體的IL-6 C-174G均為同合子G對偶基因型，而IL-10啟動子基因型的分佈在T2DM病人與對照組之間雖然無統計差異，但是較多T2DM病人帶有高分泌能力之IL-10 -592＊C對偶基因(34.28%, p＝0.027)。另外，實驗結果並未發現台灣T2DM病人之IPF-1基因的C18R、Q59L、D76N 與 R197H有突變發生。整體而言，由於台灣本土T1DM患者TopIIA與GADA盛行率比IA-2A高，而且在病程中持續出現的時間也比較長，因此本論文認為TopIIA與GADA比較適合作為預測台灣本土T1DM之發病、糖尿病的診斷與病情追蹤的標記。雖然白種人之IL-6與IL-10基因多型性與T2DM發病有關，但上述相關性並不適用於台灣本土之糖尿病患者，不過較多之台灣T2DM病人帶有IL-10分泌能力較高的-592＊C對偶基因，此外，實驗結果也證明IPF-1基因突變則並非是引發台灣本土T2DM的重要因子。綜合上述研究結果，本論文最重要之發現為不論是T1DM或T2DM，台灣本土之糖尿病患都有與西方人不同之獨特基因型與免疫反應。本論文希望能提供並建立台灣本土糖尿病免疫反應與基因型等之相關資訊與資料，期以更深入瞭解糖尿病之發病機制以提供研發預防與治療策略之參考資訊。
Diabetes mellitus (DM) is an important global chronic disease, and with increased incidence during the last decade. Currently approximately 5% of worldwide population, which corresponds to 194 million, suffer from diabetes. It is estimated that 220 and 330 million people worldwide, respectively, will have diabetes in year 2010 and 2025. DM is mainly classified into 2 types: Type 1 diabetes mellitus (T1DM) is a chronic disease associated with the selectively destruction of pancreatic β-cells, and type 2 diabetes mellitus (T2DM) is a disease characterized by insulin resistance. This study is devided into 2 sections: The first one focused on the investigation of autoantibody prevalences in T1DM patients, and the second, association between Th2 cytokine gene polymorphisms and insulin promoter factor-1 (IPF-1) point mutations with T2DM. In the first section, the prevalence of autoantibodies against glutamic acid decarboxylase (GADA), type II topoisomerase (TopIIA) and protein tyrosine phosphatase (PTP)-like molecules (IA-2A) in Taiwanese T1DM patients were investigated to explore the association of autoantibodies with T1DM. Our results showed that prevalence of IA-2A, GADA and TopIIA in our patients was 23.6%, 47.1% and 55.2%, respectively. Presence of GADA was correlated with the mean age of onset (10.82 ± 0.76 vs. 8.38 ± 0.77 years for GADA+ and GADA- patients, p=0.026). Patients with adolescent onset have higher GADA prevalence and better residual β-cell functions. In the second section, genetic polymorphisms of Th2 cell-secreted cytokine genes, including interleukin-6 (IL-6, C-174G) and Interleukin-10 (IL-10, A-592C and T-819C), and IPF-1 point mutations (C18R, Q59L, D76N and R197H) were examined to explore putative correlation of the above gene variations with T2DM. All of our T2DM patients and non-diabetic healthy individuals carried homologous G alleles at IL-6 -174 position. Though no significant association was detected between either IL-10 A-592C (p=0.088) or T-819C (p=0.160) polymorphisms and T2DM, significant more T2DM subjects carried -592*C (34.27%, p=0.027) which were associated with high levels of IL-10 production. Nevertheless, no association was found between the above polymorphisms with biochemical markers for T2DM. No IPF-1 C18R, Q59L, D76N and R197H mutations were found among Taiwanese patients with common late-onset T2DM. In summary, our results suggested that TopIIA and GADA might be better markers for prediction of diabetic onset, disease diagnosis and follow-up among Taiwanese T1DM patients because of their higher prevalence and persistence. Besides, the conclusion that IL-6 and IL-10 genetic polymorphisms are correlated with T2DM in Caucasian study might not be applied to Taiwanese T2DM, neither is the conclusion in regard to IPF-1 mutations. Nevertheless, our study demonstrated that significantly more T2DM patients carried the alleles with higher IL-10 secretion ability. This study revealed that Taiwanese DM patients show certain unique characteristics of immune responses and genotypes, compared to Caucasian subjects. Hopefully, this study can provide information and establish data bank regarding immune responses and genotypes of Taiwanese DM patients for further understanding of diabetic pathogenesis and development of strategies for diabetic prevention and treatment. |
