代謝症候群、缺血性膀胱與下泌尿道症狀：流行病學證據與病生理機制

Abstract

背景 下泌尿道症狀和代謝症候群都是盛行率很高的公共衛生問題，尤其是在較年長的族群。 而近來許多的流行病學研究皆顯示代謝症候群是造成下泌尿道症狀的可能因子之一。根據第三次美國國家健康與營養調查研究，60歲以上男性若有三個以上代謝症候群之危險因子，會增加得到下泌尿道症狀的風險(勝算比=1.80；95%信賴區間1.10-2.94)；而有代謝症候群的男性攝護腺之生長速率(0.92毫升/年)也較沒有代謝症候群的男性(0.64毫升/年)為高。兩者之間的關連性目前已有一些可能的機制被提出，包括內皮細胞功能異常、自主神經過度活化、Rho-kinase活化增加及骨盆腔血管硬化等。 糖尿病常見的併發症除了腎臟病變、神經病變及視網膜病變外，許多糖尿病患也會合併下泌尿道功能的障礙，導致所謂的下泌尿道症狀。但是臨床上糖尿病下泌尿道症狀之表現相當地多變，有些人以儲尿症狀如膀胱過動症表現；有些人則以排尿症狀如排尿困難為主，部分甚至惡化成末期膀胱病變，導致殘尿量增加，進而增加泌尿道感染與腎臟傷害的機會。雖然糖尿病造成下泌尿道症狀的證據越來越充分，但是目前對於其危險因子仍然不甚了解，基於糖尿病患常常同時合併代謝症候群，我們對於代謝症候群在此族群病患之下泌尿道症狀所扮演的角色相當的有興趣，因此設計了兩部分的研究予以探索。 本論文分為兩部分。第一部分為流行病學研究，我們以第二型糖尿病女性病患為研究對象，探討代謝症候群對糖尿病患下泌尿道之影響；第二部分為基礎研究，目標為探討缺血性膀胱功能失調之分子機轉與可能治療方式。 研究方法 第一部份為一橫斷面的流行病學研究，自2005年10月至2007年6月，我們總共收錄了518位第二型糖尿病女性病患的臨床資料，包括了病史、生化檢查、身體檢查及下泌尿道症狀問卷等。而根據美國國家膽固醇教育計畫成人治療專家組第三次指南對於代謝症候群之定義，我們將病患分為兩組：糖尿病合併代謝症候群組及糖尿病無合併代謝症候群組。病患之下泌尿道功能則分別以美國泌尿科醫學會症狀評分表、IUSS問卷、尿流速等檢查來評估。我們以統計方法來比較兩組病患之各項數據。 第二部分之基礎研究共分三個階段，第一階段我們將大白鼠的兩側膀胱動脈結紮二至四週後，期望能建立局部缺血造成膀胱病變的大白鼠動物模式；第二階段則以第一階段的結果為基礎，進行各項分子生物學的研究，探索可能的致病機轉；第三階段我們將探討可能治療的藥物，包括了蕈鹼類受體拮抗劑、嘌呤 類受體拮抗劑及抗氧化劑蘿蔔硫素，測試其是否能改善缺血所誘導的膀胱病變。 結果 從流行病學研究中，我們發現糖尿病患若同時合併有代謝症候群，會有較嚴重的下泌尿道症狀，尤其是膀胱過動症症狀。而隨著代謝症候群之危險因子數目越多，下泌尿道症狀和膀胱過動症的盛行率和嚴重程度也越高。多變數分析則發現糖尿病女性病患下泌尿道症狀最重要的預測因子並不是代謝症候群，而是周邊神經病變；但是如果我們再針對神經病變做調整分析後，代謝症候群則仍然扮演著很重要的角色。 在動物實驗中，我們成功地建立局部缺血造成膀胱病變的大白鼠動物模式。缺血不但造成膀胱活體自由基的上升，也促進了細胞反應如內質網壓力(GRP78/CHOP)、細胞自噬(Beclin-1/p62/LC3 II)及細胞凋亡(caspase 3)的表現，並干擾了Keap1-Nrf2抗氧化系統；更重要的，缺血傷害也影響了膀胱蕈鹼類與嘌呤類訊息傳導路徑之表現，而其可能是膀胱過動之主因。而投予蕈鹼類或嘌呤類受體拮抗劑無法完全改善因缺血導致的膀胱功能失調，只有抗氧化劑蘿蔔硫素不但有效地緩解了各種細胞反應，並活化了Keap1-Nrf2抗氧化系統；更重要的是，蘿蔔硫素顯著地改善因缺血而導致的膀胱功能失調。 結論 我們推測糖尿病周邊神經病變是影響糖尿病女性病患下泌尿道症狀最重要的危險因子，若病患同時合併了代謝症候群，則有可能透過動脈粥樣硬化而導致了骨盆腔器官如膀胱的缺血，進而加重下泌尿道症狀的風險。而缺血性膀胱的動物模型更進一步地証實我們的假設。局部缺血不但增加了氧化壓力與相關的細胞反應，更影響了膀胱訊息傳導路徑，造成膀胱功能失調。而以抗氧化劑蘿蔔硫素治療可以有效地緩解因缺血而導致的膀胱功能失調。

Background Lower urinary tract symptoms (LUTS) and metabolic syndrome (MS) are both highly prevalent public health problems, especially in the elderly population. Many recent epidemiological evidences have shown that MS is one of the possible factors for the development of LUTS. In the Third National Health and Nutrition Examination Survey conducted on men > 60 years, the risks of having LUTS increased significantly in men with ≥ 3 MS components when compared with their control counterparts (OR 1.80; 95% CI 1.11–2.94). Men with MS also had a higher growth rate of prostate versus men without MS. Several mechanisms between LUTS and MS have been proposed, including endothelial dysfunction, autonomic hyperactivity, upregulation of Rho-kinase and pelvic atherosclerosis. In addition to common diabetic complications such as nephropathy, neuropathy and retinopathy, diabetic patients are also predisposed to LUT dysfunction, leading to bothersome LUTS, especially the overactive bladder (OAB). However, the clinical manifestations of diabetic LUT dysfunction are mixed, and may progress into end stage bladder disease, resulting in chronic retention, urinary tract infection and kidney damage. Although the association between diabetes and LUT dysfunction is evident, it is still not well known about its risk factors. Based on the fact that MS is common among patients with diabetes, it is of interest to investigate whether MS plays a critical role in the development of LUTS in women with diabetes. This thesis contains 2 studies. The goal of the first part (an epidemiological study) is to evaluate the role of MS in the development of LUTS/OAB in women with diabetes. The goal of the second part (a basic research) is to study the underlying mechanisms of ischemia-induced bladder dysfunction and explore the possible therapeutic agents for this entity. Materials and methods The first part is a cross-sectional epidemiological study. From October 2005 to June 2007, a total of 518 women with type 2 diabetes were enrolled in our study. Their clinical data including medical history, biochemical tests, physical examination and questionnaire results for LUTS were collected. All patients were divided into 2 groups as diabetes with MS group and diabetes without MS group, according to the definition of MS by National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). LUT function were evaluated with the American Urological Association Symptom Index (AUA-SI), Indevus Urgency Severity Scale (IUSS) questionnaire and uroflowmetry, respectively. We analyzed the data of these two groups with statistical methods. The second part is a basic research, which is divided into three phases. In the first phase, we established the animal model of ischemia-induced bladder dysfunction by bilateral partial arterial occlusion (BPAO) in rat. In the second phase, we sought to investigate the molecular mechanism of the ischemia-induced bladder dysfunction. In the third phase, we examined the effectiveness of therapeutic agents, including a muscarinic receptor antagonist, a purinergic receptors antagonist and a Nrf2 activator sulforaphane. Results In our epidemiological study, diabetic women with MS had significantly higher storage and total AUA-SI scores as well as a higher prevalence of LUTS/OAB. Most intriguingly, the number of MS components was strongly associated with the LUTS severity and OAB prevalence. Multivariate analysis revealed that peripheral neuropathy, but not MS, significantly predicted LUTS/OAB in diabetic women after age adjustment. However, MS remained significantly predictive for LUTS after additional adjustment for neuropathy. In the experimental study, the animal model of bladder ischemia was successfully established by BPAO in rats. We found that BPAO significantly induced the presence of oxidative stress and upregulated the expressions of several molecular reactions including endoplasmic reticulum stress (GRP78/CHOP), autophagy (Beclin-1/p62/LC3 II) and apoptosis (caspase 3). BPAO also disturbed the Keap1-Nrf2 pathways. The most importantly, BPAO altered bladder neurotransmission by upregulating muscarinic and purinergic signaling, which might be the main cause of ischemia-induced bladder dysfunction. Treatment with a muscarinic or purinergic receptor antagonist was failed to restore bladder function. On the other hand, sulforaphane effectively attenuated ischemia-associated cellular responses in the bladder, subsequently ameliorated ischemia-induced bladder dysfunction and might emerge as a novel strategy to protect the bladder against ischemia-induced oxidative damage. Conclusions We hypothesize that diabetic peripheral neuropathy is the most important predictor for the development of LUTS in women with type 2 diabetes. However, the presence of MS components may compound the risks of LUTS through atherosclerosis and subsequent bladder ischemia. Our animal model of ischemic bladder further confirms our hypothesis. Ischemia not only increases the expressions of oxidative stress and associated cellular responses, but also affects the bladder neurotransmission pathways, resulting in bladder dysfunction. Treatment with Nrf2 activator sulforaphane is able to attenuate the ischemia-induced bladder dysfunction effectively.