Ni Ting, Hu Yuanlei, Sun Li, Chen Xi, Zhong Jin, Ma Hong, Lin Zhhongping
National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing, PR China.
Int J Mol Med. 2007 Jul;20(1):45-51.
Oral administration of insulin to control blood glucose has become a hot area of diabetes research. The major issue is to produce enough insulin and prevent insulin degradation in the acidic environment of the stomach. We hypothesize that the natural structure of the cell wall and the endoplasmic reticulum in Ganoderma lucidum should help resist the digestion of insulin produced in these cells, making this fungus a feasible production and a new delivery system for oral insulin. A new mini-proinsulin gene was constructed and was transformed into G. lucidum by the Agrobacterium-mediated method. Driven by a strong promoter of GPD isolated from Lentinus edodes, expression of mini-proinsulin reached < or =10.4% of total soluble protein, equal to 174 microg/g wet weight, which is sufficient for oral route. Oral route of transgenic G. lucidum significantly reduced blood glucose in streptozocin-induced diabetic rats, as compared to rats fed with saline (P<0.0002) or non-transgenic G. lucidum (P<0.0002). Blood glucose was reduced < or =64% in 80% of diabetic rats. Evaluation of pancreatic pathology showed that 54.5% rats in the transgenic group had no pathological changes, as compared to 25% in the saline group and 33.3% in the non-transgenic group. Rats in transgenic group had insulitis score <2, while 30% of rats in the saline group had insulitis score >2. These experimental results indicate that oral route of mini-proinsulin-expressing G. lucidum can be used to control blood glucose in diabetes and to improve pancreatic cell function.
口服胰岛素以控制血糖已成为糖尿病研究的一个热点领域。主要问题是要产生足够的胰岛素，并防止其在胃的酸性环境中降解。我们推测，灵芝细胞壁和内质网的天然结构应有助于抵抗这些细胞中产生的胰岛素的消化，使这种真菌成为口服胰岛素的可行生产和新型递送系统。构建了一个新的微型胰岛素原基因，并通过农杆菌介导的方法将其转化到灵芝中。在从香菇分离的强启动子GPD的驱动下，微型胰岛素原的表达达到总可溶性蛋白的≤10.4%，相当于174微克/克湿重，这对于口服途径来说已经足够。与喂食生理盐水的大鼠（P<0.0002）或非转基因灵芝的大鼠（P<0.0002）相比，转基因灵芝的口服途径显著降低了链脲佐菌素诱导的糖尿病大鼠的血糖。80%的糖尿病大鼠血糖降低了≤64%。胰腺病理学评估显示，转基因组54.5%的大鼠没有病理变化，而生理盐水组为25%，非转基因组为33.3%。转基因组大鼠的胰岛炎评分<2，而生理盐水组30%的大鼠胰岛炎评分>2。这些实验结果表明，表达微型胰岛素原的灵芝的口服途径可用于控制糖尿病患者的血糖并改善胰腺细胞功能。
