口服草酸降解酶/二氧化硅复合纳米胶囊治疗高草酸尿症的研究

Urolithiasis is one of the most common disease in urology. Calcium oxalate is the most common urolith composition type with high recurrence rate but without effective and easy preventive measures. Hyperoxaluria is the major lithogenic risk factor of calcium oxalate stones. Oxalate can’t be metabolic degradated by human body and eventually be excreted through urine with prototype form,exogenous oxalate from diet intake is a main resource of uric oxalate. Many daily consumed vegetable & fruit are oxalate-rich food ,so hyperoxaluria may be reduced by low-oxalate diet, but successful dietary management is difficult to stick up for a long time because of monotonous diet . The specific oxalate-degrading enzymes, oxalate decarboxylase and oxalate oxidase have shown significant potential for the treatment of hyperoxaluria. Nanoparticles drug delivery system can release protein drugs according to various pH value to a specific part of gastrointestinal tract for slower releasing in the delivery process, which can avoid proteometabolism by pepsin and improve drug bioavailability. To degrade the dietary oxalte sustainably and efficiently, this study tries to obtain purified oxalate-degrading enzymes by genetic engineering expression system and encapsulate them into mesoporous silica nanocapsules. Then the bioactivity of the constructed silica nanocapsules in various pH value and drug loading and release rate will be verified in vitro.At last the idiopathic hyperoxaluria rats will be given drugs via intragastric administration to identify the effect of reducing hyperoxaluria.

尿石症是泌尿外科常见疾病之一，草酸钙结石是最常见的尿石类型，缺乏有效持久的预防措施，复发率高，亟待解决。高草酸尿是草酸钙结石的主要成石风险因素。草酸是人体不能代谢的物质，只能以原型形式从尿中排出，饮食中摄入的外源性草酸是尿草酸的重要来源。日常食用的很多蔬果中富含草酸，草酸钙结石患者通过限制高草酸饮食摄入虽可控制高草酸尿，但饮食单调难以长期坚持。自然界中存在特异性的草酸降解酶-草酸脱羧酶和草酸氧化酶在降低尿草酸方面极具潜力。纳米颗粒载药系统可将药物基于不同pH值选择性释放，使药物从胃到肠道的转运过程中在相应位置缓释，可避免酶蛋白受消化道蛋白酶分解，提高了药物生物利用度。为持续有效降解外源性草酸，本项目拟采用基因工程获取高纯度的草酸脱羧酶和草酸氧化酶，并采用二氧化硅纳米胶囊包裹草酸降解酶，探索其酶活、最佳pH选择性、载药量和释放速率，验证草酸降解酶复合纳米胶囊灌胃对特发性高草酸尿症模型鼠的疗效

草酸钙结石是最常见的尿石类型，复发率高，缺乏有效的预防措施，亟待解决。高草酸尿是草酸钙结石的主要成石风险因素。草酸是人体不能代谢的物质，只能以原型形式从尿中排出，饮食中摄入的外源性草酸是尿草酸的重要来源。日常食用的很多蔬果中富含草酸，草酸钙结石患者通过限制高草酸饮食摄入虽可控制高草酸尿，但饮食单调难以长期坚持。自然界中存在特异性的草酸降解酶-草酸脱羧酶和草酸氧化酶在降低尿草酸方面极具潜力。本研究将草酸脱羧酶及草酸氧化酶基因转入乳酸菌中，使其表达草酸降解酶，达到持续有效降解草酸的效果，通过口服途径减少食源性草酸的吸收，从而预防草酸钙结石的形成。 成功构建重组pMG36e-ODC，pMG36e-OxO乳酸菌，两者都可在含100 mmol/L草酸的培养基中生长，20h左右开始进入对数期，40h左右进入稳定期。其中pMG36e-ODC乳酸菌可明显降低培养基内草酸浓度，48h内可降解30%，而培养pMG36e-OxO乳酸菌和正常乳酸菌后培养基中草酸含量无明显变化，48h内草酸含量水平下降了约15%。pMG36e-ODC乳酸菌喂养可显著降低高草酸饮食大鼠尿液中草酸含量。结论 重组ODC乳酸菌可有效降解草酸，并可通过降解食物中草酸缓解模型大鼠高草酸尿症。