MafA基因部分敲除对于胰岛素产生的影响及机制研究

Role of MafA gene in insulin production--Analysis of heterozygous knockout mice

目的通过观察肌腱膜纤维肉瘤肿瘤基因同系物A（MafA）基因杂合子小鼠在胰岛素分泌、相关基因表达、血糖及血清胰岛素水平等方面的变化，探讨MafA基因在青少年起病的成人型糖尿病（MODY）发生中的作用。方法将动物分为MafA杂合子组及野生（C57BL／6J）对照组，采用腹腔葡萄糖耐量实验（IPGTT）观察杂合子小鼠血糖经时分布曲线及血清胰岛素的变化；胰岛素耐量实验了解两组动物对胰岛素的敏感性；半定量PCR法检测杂合子小鼠MafA、胰岛素以及PdXl和Beta2等基因的表达水平；组织免疫荧光法观察胰腺中胰岛的组织形态并进行ot、B细胞计数分析。结果（1）MafA杂合子小鼠在生后2周开始呈现血糖增高及体重减轻、胰岛素分泌明显下降（P〈0．05或P〈0．01），胰岛素敏感性未发生明显改变。（2）MafA杂合子小鼠胰岛体积较对照组明显增大，但胰腺细胞数量、p细胞的分布形态及比值无明显变化。（3）半定量PCR结果显示，与对照组相比，MafA杂合子小鼠MafA基因、胰岛素基因、Beta2基因表达水平均明显降低（均P〈0．05）．而胰高血糖素及Pdxl水平没有变化。结论MafA基因杂合子小鼠在出生早期即表现为血糖升高、体重减轻、胰岛素产生能力下降等。MafA基因的表达对糖尿病的发生起重要作用。该基因可能是一种新的MODY致病基因。

Objective To clarify the role of MafA gene in development of MODY （ maturity onset diabetes of the young） by studying insulin production, gene expression, and serum glucose level in heterozygous MafA gene knockout mice. Methods C57BL/6J mice were used as control animals, MafA gene heterozygous mice were analyzed. The distribution curve of blood sugar levels over time and serum insulin of heterozygous mice were determined by using IPGTI＇. The sensitivity of the mice to insulin was examined by injecting insulin assay. The expression levels of genes of MafA, insulin, pdX1, Beta2, and other genes of heterozygous mice were analyzed by semi-quantitative RT-PCR. Morphological changes in pancreatic tissue and c^- and 13-cell counts were obtained by using immunofluorescence/histological examination. Results （ 1 ） Two weeks after birth, MafA gene heterozygous mice began to show that the blood glucose level was increased, weight was reduced, and the amount of insulin secretion was cleaAy decreased （ P〈0.05 or P〈0.01 ） while the insulin sensitivity did not change significantly. （ 2 ） The islet volume in MafA gene heterozygons mice was increased significantly as compared with the control group. However there were no significant changes in the number of pancreatic cells, distribution patterns, and the ratio of a and 13 cell. （3） Semi-quantitative RT-PCR detection showed that, compared with the control group, MafA gene level, the amount of insulin and Beta2 gene in MafA gene heterozygous mice were significantly reduced（ all P〈0.05 ） , while no changes in the amount of glucagons and level of Pdxl were found. Conclusions The blood glucose level of MafA gene heterozygous mice was raised early after birth. MafA gene is likely to be a new disease ralated gene of MODY.