糖尿病诱导剂链脲佐菌素与原核表达的家蚕素Ⅱ对家蚕血糖含量的影响

Effects of the Diabetogenic Agent Streptozotocin and the Bombyxin ⅡDerived from Prokaryotic Expression on Content of Blood Sugar in the Silkworm,Bombyx mori

为探讨高等动物糖尿病诱导剂对家蚕血糖含量的影响以及鉴定原核表达的家蚕素Ⅱ（BBXⅡ）的降血糖活性,通过给家蚕幼虫注射糖尿病诱导剂链脲佐菌素和BBXⅡ,调查家蚕的生理效应及血糖含量变化。分别以50-500μg/g的剂量给4龄24 h幼虫注射链脲佐菌素后12--48 h,会引起蚕体血液中的海藻糖含量升高,但与对照组的差异不显著;以250μg/g的剂量给5龄24 h幼虫注射链脲佐菌素后6 h,血液中的海藻糖含量显著升高,海藻糖酶活性显著降低。蚕体注射链脲佐菌素后表现出不同程度中毒症状,生长发育、存活率、茧质、眠性及后代的滞育性等均受到不同程度的影响。半定量RT-PCR检测表明,链脲佐菌素会导致家蚕体内BBX-Ⅱ基因的表达量下调,其中对4龄期幼虫的影响大于5龄期幼虫。用原核表达的BBXⅡ注射正常饲养的家蚕幼虫、饥饿后进食的幼虫和经链脲佐菌素处理的幼虫,均可引起血液中海藻糖含量显著降低和海藻糖酶活性升高,显示原核表达的BBXⅡ对家蚕具有降血糖活性。

To explore effects of diabetogenic agent of higher animal on the content of blood sugar of silkworm larvae, and to identify hypoglycemic activity of Bombyxin- Ⅱ （BBX Ⅱ ） derived from prokaryotic expression, we investigated the physiological effects of diabetogenic agent streptozotocin and BBX Ⅱ on silkworm and changes of the content of blood sugar in silkworm larvae that were injected with streptozotocin and BBX Ⅱ. At 12 to 48 h after 24 h old silkworm larvae of the 4th instar were injected with streptozotocin at dosage of 50-500 μg/g, the content of trehalose in blood of silkworm body was increased, but had no significant difference with the control group. At 6 h after injecting streptozotocin to 24 h old silkworm larvae of the 5th instar at dosage of 250μg/g, the content of trehalose was significantly increased, but the activity of trehalase was significantly reduced. Moreo- ver, varying degrees of poisoning symptoms occurred and the growth and development, survival rate, cocoon quality, moultinism, progeny diapause and other aspects suffered different influences when streptozotocin was in- jected into silkworm larvae. Semi-quantitative RT-PCR analysis showed that injection of streptozotocin resulted in reduction of BBX- Ⅱ gene expression level, and the effect of streptozotocin on the 4th instar larvae was more obvious than that on the 5th instar larvae. After injection of BBX-Ⅱ derived from prokaryotic expression into silkworm larvae reared under normal condition and starvation condition and into those treated with streptozotocin, the content of trehalose was significantly decreased and the activity of trehalase was significantly increased in all three groups, suggesting that pro- karyotic expressed BBX- Ⅱ has hypoglycemic activity on silkworm larva.