- 學位論文
探討芭樂對降低 STZ 糖尿病大鼠血糖及氧化傷害之作用
Antihyperglycemic and antioxidative potential of Psidium guajava in STZ-induced diabetic rats
摘要
芭樂 (psidium guajava, PG) 是重要且廣泛的水果，有豐富的維生素 C 和類黃酮 (flavonoids)，其抗氧化物質含量豐富。研究證實，芭樂葉萃取物在小鼠 streptozotocin (STZ) 誘導第一型糖尿病的試驗中具有降血糖作用，且該作用可能與多酚物質有關。另外，注射芭樂汁 (1 g/kg; i.p.) 可有效降低正常小鼠以及 alloxan 處理之糖尿病小鼠血糖。但目前為止，食用芭樂是否同樣具有降血糖作用，以及作用機制為何，仍不清楚。本研究以 STZ (i.p.) 誘發 Sprague-Dawley (SD) 大鼠產生第一型糖尿病，探討芭樂對糖尿病病症以及抗氧化之作用。首先分析芭樂各部位的總酚含量，發現果肉中含量最高，故本研究以果肉進行試驗。在注射 STZ 一星期後誘發高血糖 (> 300mg/dL)，之後管餵低高劑量芭樂汁 (125 和 250 mg PG/kg BW，2次/週) 持續四週。結果發現，高劑量 PG 在急性降血糖試驗中具有降低血糖的作用，管餵後 1 小時即可降低 48 % (P <0.05)。實驗期間，PG 同樣有效降低血糖，尤其第四週時高劑量組較 STZ 組降低約 45 % (P<0.05)。觀察高劑量 PG 組蘭氏小島外型較 STZ 組完整，其 beta 細胞面積也多 1.9 倍 (P<0.05)，因此血漿 insulin 的濃度也有較高趨勢 (較 STZ 組多 38 %)。因此推測 PG 藉由保護蘭氏小島而改善血糖調控。另外，在心血管疾病的指標，LPG 和 HPG 血液 TG 濃度較 STZ 組降低 66 和 69 % (P<0.05)，而 LDL 也略微降低。抗氧化方面：STZ 會促進氧化壓力並造成單核球、胰、腎和肝組織 DNA 傷害 (增加 12、2.25、14 和 2.3 倍)，以及胰、腎和肝組織脂質過氧化 (增加 5、2 和 20 倍)，同時也使 AST 和 ALT 顯著上升 77 和 75 %；而管餵 PG 可顯著降低 STZ 造成之氧化傷害，HPG 可降低單核球、胰、腎和肝組織 DNA 損傷分別為 47 、38、85 和 38 %，抑制脂質過氧化約 80、65 和 61 %，以及分別降低 AST 和 ALT 27 和 68 %，減少 GSH-Px 生成 (約 51 %)。此抗氧化作用可能與 PG 保護 beta 細胞有關於。體外試驗中，PG (0.75 mg/mL) 可抑制內皮細胞生長 (48 小時抑制 23 %)，且可降低 H2O2 (1mM) 造成之 DNA 損傷 (降低 69 %)。綜合以上結果，本研究證實芭樂具有改善糖尿病病症之作用，其作用機制可能透過降低 STZ 之氧化傷害進而保護 beta 細胞。
並列摘要
Psidium guajava (PG) is an important tropical fruit, widely consumed fresh and also processed (beverages, syrup, and jams), and rich in vitamin C and flavonoids. Several studies suggested that the extract from PG leaves possesses antidiabetic effects in diabetic mice model and these effects are speculated to account its polyphenolic compounds. Oxidative stress play a crucial role in the development of diabetic complications The aims of this study were to investigate whether PG could reduce hyperglycaemic and ameliorate oxidative stress of the streptozotocin (STZ; 55 mg/kg, i.p.) -induced diabetic rats. Male Sprague-Dawley (SD) rats were divided into four equal groups (n=13): control, diabetes, orally with different doses of PG (120 and 250 mg/kg-2d for 4 weeks; LPG and HPG) diabetic rats from one week after STZ administration. Fasting blood glucose levels, serum insulin, lipid peroxidation (malondialdehyde), DNA breakage, reduced glutathione (GSH), GSH peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT) levels were measured, and immunohistochemical studies were performed in all of the groups. The obtained data showed that STZ resulted in oxidative stress and affected the antioxidant status. Treatment with different dose of PG significantly reduced fasting hyperglycemia and oxidative stress, and augmented the antioxidant system. In histological investigations, PG treatment protected the majority of the pancreatic islet cells, with respect to the control group. As a result, PG exhibited significant antihyperglycemic effect and protected beta-cells in STZ-diabetic rats, in a dose-dependent manner, and diminished the hyperglycemia-related oxidative stress.
參考文獻
延伸閱讀
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