常见胰岛自身抗体阴性1型糖尿病的病因探讨

Etiological dissection in common anti-islet autoantibody-negative patients with type 1 diabetes

目的 从自身免疫和分子遗传学两个角度,探讨常见胰岛自身抗体阴性的1型糖尿病患者的病因。方法 对33例GAD-Ab、IA2-Ab、IAA及TGA、TPO-Ab等自身抗体检测均为阴性的、以自发酮症起病的糖尿病患者进行少见型胰岛自身抗体——羧基肽酶H抗体(CPH-Ab)、SOX13(ICA12)抗体以及MODY3(:HNF-1α)、MODY6(NeuroD1/Beta2)和线粒体基因突变的检测。CPH-Ab及SOX13抗体以放射配体法测定,MODY3、MODY6基因突变的检测采用PCR-SSCP-测序法,线粒体基因突变的检测采用PCR-RFLP法。结果 33例患者中,发现2例为SOX13抗体阳性,而未发现CPH-Ab阳性病例。基因突变检测发现1例为HNF-1αR321H(CGC→CAC)突变,1例为线粒体ND1mt3316 G→A突变。结论 自身免疫和单基因突变(如HNF-1α、线粒体基因突变)是部分常见型胰岛自身抗体阴性1型糖尿病患者的病因;诊断特发性1型糖尿病需进一步排除自身免疫及MODY和线粒体糖尿病。

Objective To explore the immunological and genetic factors of common anti-islet autoantibody-negative patients with type 1 diabetes. Methods Specimens of peripheral blood were collected from 33 common autoantibody (GAD-Ab, IA2-Ab, IAA, TGA and TPO-Ab) negative diabetic patients with new-onset of unprovoked ketosis ( or ketoacidosis) , and genome DNA was extracted. The antibodies to carboxypeptide-H (CPH) and SOX13 (ICA12) were detected by radioligand assay. The gene mutations of MODY3(HNF-1α)and MODY6 (NeuroD1/Beta2) were detected by PCR-SSCP sequencing. Mitochondrial gene mutations were analyzed with PCR-RFLP. Results Two ( 6% ) of the patients were SOX13-Ab positive, while none of them was positive for CPH-Ab. Gene mutation detection found one case of a new mutation, R321H ( CGC→CAC) in the exon 5 of HNF-1α gene and one case with ND1 mt3316 G→A mutation in mitochondrial DNA. In addition to the diabetes-associated mutations described above, seven polymorphisms of HNF-1α gene, including L17L, I27L, LA59L, S487N, IVS5+9C>G, IVS6-42G>T, and IVS7 +7 G > A, and one NeuroD1/Beta2 gene polymorphic variant Ala45Thr, were found. Conclusion Autoimmunity and gene mutations (such as MODY3 and mitochondrial genes mutations) may be etiological in a few cases initially diagnosed as autoantibody-negative type 1 diabetes. Autoimmunity and MODY and mitochondrial diabetes should be excluded if idiopathic type 1 (type 1B) diabetes is diagnosed.