- 學位論文
原發性腎病症候群與血管轉化酶基因多重性之關聯
Angiotensin converting enzyme gene polymorphism in idiopathic nephrotic syndrome
摘要
原發性腎病症候群(idiopathic nephrotic syndrome)為兒童常見的腎臟方面的疾病，主要的表現為蛋白尿(proteinuria)、白蛋白降低(hypoalbuminemia)、高血脂 (hyperlipidemia)以及水腫(edema)。根據International Study of Kidney Disease in Children，罹患腎病症候群的兒童中有76%在病理表現上為微小性變化(minimal change)。大部分在病理變化上呈現微小性變化的腎病症候群的兒童，對於類固醇 (prednisolone)的標準療程具有很好的反應以及預後。有80%的病童可以達到完全緩解的情形(complete remission)，不過有40-50%的比例有frequent relapse的現象。而在治療的期間，隨著對類固醇反應不同，大致可以分為類固醇敏感(steroid sensitive)、依賴(steroid-dependent) 以及抗性(steroid-resistant)。而根據病理切片的結果，若為局部巢狀腎絲球硬化(focal segmental glomerulosclerosis, FSGS)，則對於類固醇的治療反應不佳，並且有可能進行成末期腎病變(end-stage renal failure)。若病童屬於類固醇依賴(steroid-dependent)的情形，可能就需要高劑量的類固醇治療，甚至需要免疫抑制劑(immunosuppressant)的治療，才能改善蛋白尿的情形。腎絲球硬化(glomerulosclerosis)在某種程度上與動脈硬化相似，會造成腎臟功能逐漸喪失，而renin-angiotensin system (RAS)為引起動脈硬化的一個重要因子，其中以血管轉化酶 (angiotensin converting enzyme)的基因多重性佔了重要的一個角色。 Renin-angiotensin aldosterone system(RAAS)在心血管疾病和腎臟的生理病理學上具有關鍵性的角色，血管轉化酶(angiotensin converting enzyme)的基因多重性，對於circulating 和cellular ACE的濃度，有顯著的影響。血管轉化酶(ACE)由ACE gene轉譯而來，而ACE gene具有diallelic polymorphism，此gene位於chromosome 17q23處，在intron16的地方有287 bp DNA的變異。 一般認為，此種insertion/deletion polymorphism決定血液中50% ACE的level 。ACE 基因I/D多重性於孩童腎病症候之研究僅有極少數報告，韓國學者發現局部巢狀腎絲球硬化孩童較多具DD基因型，而認為可能是類固醇治療反應不佳及發展成慢性腎衰竭之危險因素，科威特學者則發現阿拉伯孩童的腎病症候群（包括微小變化者）有較多的DD基因型，因此，此基因型與疾病之嚴重度（如高血壓、血尿及腎衰竭）有相關性。 本實驗的目的在於探討血管轉化酶基因的多重性與腎病症候群和其對類固醇治療反應的關聯性，我們將利用較新、敏感度更高的方法變性高效能液態色層分析（automatic denaturing high performance liquid chromatography system, DHPLC），來取代傳統的電泳，對於血管轉化酶基因多重性去作更進一步的分析。 共有59位臨床上診斷為原發性腎病症候群的病童加入本實驗，我們另外收集80位正常國小學齡兒童(6歲-12歲)，其無腎臟疾病以及其他病史的檢體，作為基因分析中控制組的比較與對照。我們將59位病童根據其臨床表現以及對類固醇的治療反應分成兩組：SS組主要以對類固醇反應有效的病童，包含不常反覆發作(infrequent)或是反覆發作 (frequent)的復發者(relapsers)；而non-SS組則主要包含類固醇抗性以及類固醇依賴的病童。而利用變性高效能液態色層分析去分析血管轉化酶基因的多重性，其中基因型為DD佔31位、ID為6位、II為22位病童。而臨床上的表現方面，除了在non-SS組有三酸甘油酯顯著增高的情形之外，其他包括發病年齡、收縮壓與舒張壓的變化、腎臟功能、白蛋白以及補體C3等等在兩組比較上，並無顯著性的差異。在基因分析中，原發性腎病症候群的兒童在血管轉化酶多重性中DD基因型的表現顯著的較對照組多(DD vs. non-DD; p<0.001)；具D-allele的基因型也較對照組多(D-allele + vs. D-allele -; p<0.001)。其中在次族群分析中，原發性腎病症候群的兒童具DD基因型比上具ID或II基因型也較對照組多(DD vs. ID; DD vs. II; p均<0.001)。在59位為原發性腎病症候群的病童中，DD基因型在non-SS組在比例上有顯著增高(p=0.026)，而具有D-allele的表現在non-SS組亦有顯著增加的情形(p=0.024)。 我們發現在原發性腎病症候群的兒童在血管轉化酶多重性中DD基因型的表現及具D-allele的基因型顯著的較對照組多。而在類固醇抗性以及類固醇依賴的病童中，有較高比例具有DD基因型和D-allele。因此，我們認為在腎病症候群的病童中，具有DD基因型者較有可能為屬於類固醇抗性以及類固醇依賴，也因此血管張力素(angiotensin II)在腎病症候群的病童對類固醇治療反應上，可能扮演一重要角色。
並列摘要
Nephrotic syndrome is a common renal disease in children and it is defined as proteinuria, hypolbuminemia, hyperlipidemia and edema. According to the study from International Study of Kidney Disease in Children, 76.6% showed minimal change disease in nephrotic syndrome in children. Most patients with minimal change proven by renal biopsy have a good response after a standard course of prednisolone treatment. A complete remission is induced in about 80% cases and 40-50% of these relapse frequently. According to the biopsy results, patients with focal segmental glomerulosclerosis (FSGS) respond poorly to steroid therapy and tend to progress end-stage renal failure compared with patients with minimal change nephrotic syndrome (MCNS). In patients with steroid-dependent nephrotic syndrome (SDNS), in addition to high dosage of steroid therapy, some patients may need immunosuppressants to improve proteinuria. Glomerulosclerosis, leading to progressive loss of renal function in various kidney diseases, is analogous in some aspects of atherosclerosis including a regulatory role of the renin-angiotensin system (RAS), especially in angiotensin-converting enzyme (ACE) gene polymorphism. The variable steroid response of children with idiopathic nephrotic syndrome has not been explained. Angiotensin II may induce proteinuria, while angiotensin converting enzyme (ACE) inhibitors may reduce proteinuria and even get remission in nephrotic syndrome. Whether angiotensin II related to steroid threshold in difficult steroid dependent and steroid resistant nephrotic syndrome remains undetermined. The genotypes in ACE gene polymorphism can influence plasma and tissue angiotensin II levels. ACE gene insertion/deletion (I/D) polymorphism with DD genotype is a risk factor for cardiovascular disease and renal disease. ACE gene has been identified I/D polymorphism on the ACE locus on chromosome 17q23 of a 287-basepair fragment on intron 16. Lee et al. reported a markedly different distribution of ACE genotypes in FSGS and MCNS in their Korean patients in which the DD genocypte was significantly associated with FSGS. Al-Eisa et al. described that an association of the D-allele of the ACE gene I/D polymorphism with the clinical manifestation in nephrotic syndrome in Kuwaiti children. The purpose of this study was to examine the association between the ACE I/D genotype distribution in children with nephrotic syndrome and the response to steroid therapy. We used the newly developed automatic denaturing high performance liquid chromatography system (DHPLC) instead of gel electrophoresis to analyze PCR amplicons. A total of 59 children diagnosed as nephrotic syndrome at the age of 1 to 10 year-old were recruited in this study. Eighty children without renal diseases were also recruited as control group in genetic analysis. The patients were divided into 2 groups according to their clinical response to steroid: SS group including infrequent and frequent relapsers and non-SS group including steroid resistant (SR) and steroid dependent (SD) patients. Clinical parameters including the age of onset, systolic and diastolic blood pressure, renal function, albumin and C3 level showed no difference between two groups except for significantly elevated triglyceride in the non-SS group. In genetic study for ACE I/D genotype distribution, patients had significantly higher percentage to have DD genotype (DD vs. non-DD; p<0.001) and D-allele (D-allele + vs. D-allele -; p<0.001) than control group. Furthermore, patients also had significantly higher percentage to have DD genotype than ID or II genotype than control group. Among 59 patients with nephritic syndrome, the distribution of DD, ID and II genotype was 52.5% (31/59), 10.2% (6/59) and 37.3% (22/59), respectively. DD genotype showed significantly higher in the non-SS group than SS group (p=0.026). And non-SS group also had significantly higher incidence in D-allele presentation than SS group (p=0.024). Our data shows that patients with nephrotic syndrome had higher rate to have DD genotype and D allele than control group. Among these patients, SD and SR patients had higher percentage of D-allele and DD genotype in ACE gene polymorphism. This finding suggests that DD genotype may indeed be a risk factor for steroid dependence and steroid resistance, and angiotensin II may be involved in the steroid response of idiopathic nephrotic syndrome.
參考文獻
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