- 學位論文
洛神葉對糖尿病腎病變的抑制作用之體內外研究
The inhibitory effect of Hibiscus leaf extracts on diabetic nephropathy in vivo and in vitro
摘要
糖尿病腎病變(diabetic nephropathy, DN)為末期糖尿病患之主要死因，在高血糖環境所誘發的氧化壓力(oxidative stress)可能是促進DN的主要機轉。已知富含多酚(polyphenols)的洛神葉萃取物(Hibiscus leaf extracts, HLE)具有降血糖、抗氧化、抗發炎、抗動脈粥狀化及抗癌之潛力，本文擬探討HLE是否具有抑制DN作用及其分子機制之釐清。首先，利用高脂飲食(high-fat diet, HFD)合併腹腔注射鏈脲佐菌素(streptozotocin, STZ)誘發小鼠DN之動物模式，研究證實HLE可顯著改善腎功能、降低高血糖和高血脂之血清指標數值，對於白蛋白尿也有抑制的效果。腎組織病理切片染色結果顯示HLE能改善腎絲球萎縮、腎組織結構異常，以及DN致慢性損傷病徵之纖維化(fibrosis)形成。分子機制亦顯示HLE能抑制HFD/STZ誘發纖維化指標蛋白-轉化生長因子(transforming growth factor-beta, TGF-)和脂質調控因子-固醇調節元件結合蛋白(sterol regulatory element-binding protein 1, SREBP-1)之表現。細胞實驗分析HLE及其主成份-鞣花酸(ellagic acid, EA)保護小鼠腎間質細胞(renal mesangial cells) SV40MES13對抗高糖(high glucose, high Glc)所造成的細胞增生(hyperplasia)的能力。實驗發現處理HLE或EA對於高糖誘發細胞生長週期(cell cycle) S期表現增加、活性氧物質(reactive oxygen species, ROS)含量、糖化終產物(advanced glycation end products, AGE)產生與脂質堆積(lipid accumulation)皆具有抑制作用，HLE或EA也具有調控纖維化分子、脂質代謝關鍵分子及細胞週期蛋白之表現。總結，我們預期HLE可能藉由降低氧化壓力，發揮抗增生、修正脂質代謝異常，以及抗纖維化作用，達到改善DN的功效。
並列摘要
Diabetic nephropathy (DN) is the major cause of end-stage renal disease, and the effective and new therapeutic approaches are needed in DN and chronic kidney diseases. Oxidative stress process is an important factor contributing to DN by increasing production of oxidants. There is increasing evidence suggesting that plant-derived antioxidants may protect kidneys on the progression of DN. Hibiscus leaf extract (HLE), rich in polyphenols, has been shown to possess hypoglycemic, antioxidant, anti-inflammatory, anti-atherosclerotic and anticancer effects. The aim of the study is to examine the in vivo and in vitro nephroprotective effect of HLE on DN. In the combination of high-fat diet (HFD) with streptozotocin (STZ)-induced DN mice, severe hyperglycemia and albuminuria were markedly developed. Treatment with 1% HLE for 6-weeks decreased levels of blood glucose, blood urea nitrogen (BUN), creatinine (Cre) and urine protein amounts in diabetic mice. HFD/STZ-induced the renal morphological alterations and the expression levels of sterol regulatory element-binding protein 1 (SREBP-1) and transforming growth factor-beta (TGF-) were significantly decreased by HLE treatment. Mouse renal glomerular mesangial SV40MES13 cells pre-treated with high glucose (high Glc) were demonstrated to trigger cell hyperplasia and oxidative stress. Non-cytotoxic doses of HLE and its main component ellagic acid (EA) abolished the high Glc-induced can increase in S phase of cell cycle, reactive oxygen species (ROS) generation and lipid accumulation. Molecular data showed that HLE and EA corrected the advanced glycation end products (AGE) production and lipid metabolism, as well as renal fibrosis under high Glc stimulation. In conclusion, these data demonstrated that HLE potentially could be developed as an anti-DN agent.