Kobayashi T, Nakanishi K, Nakase H, Kajio H, Okubo M, Murase T, Kosaka K
Department of Endocrinology and Metabolism, Toranomon Hospital, Okinaka Memorial Institute for Medical Research, Tokyo, Japan.
Diabetes. 1997 Oct;46(10):1567-71. doi: 10.2337/diacare.46.10.1567.
Changes in the pancreas of diabetic patients with the A-to-G mitochondrial DNA (mtDNA) mutation at nucleotide position 3243 base pair (bp) have not previously been described. The clinical phenotypes of diabetes associated with the mtDNA 3243 mutation range from NIDDM to IDDM. We sought the presence of the mutation and studied volume of beta-, alpha-, and delta-cells, mitochondrial enzyme activity, and presence of apoptosis in diabetic pancreases obtained at autopsy. Pancreases were obtained from 16 patients with IDDM, from 18 patients with NIDDM, and from 11 nondiabetic patients. Mitochondrial enzyme activity was determined for cytochrome c oxidase (COX), the subunits of which are partially encoded by mtDNA, and for succinate dehydrogenase (SDH), the subunits of which are solely encoded by nuclear DNA. The volumes of islet beta-, alpha-, and delta-cells were estimated by computerized morphometry. Pancreatic cells were examined for apoptosis by an in situ end-labeling procedure. The mtDNA 3243 mutation was detected in 1 of 16 (6%) pancreases from the IDDM patients; none of the pancreases from 18 NIDDM patients and 11 nondiabetic patients had the mutation. The single patient with the mtDNA 3243 mutation was a 56-year-old woman with IDDM, aged 39 years at diabetes onset, whose mother was diagnosed with NIDDM. The patient had a history of secondary failure of oral hypoglycemic agents and had a marked decrease in the number of beta-cells. The islet beta-cells and non-beta-cells of the patient showed extremely decreased COX enzyme activity. The islet cells in the patient showed a high activity when examined for SDH. Some pancreatic exocrine cells also showed decreased COX activity with high SDH activity. In IDDM, NIDDM, and nondiabetic patients without the mtDNA 3243 mutation, only weak staining for SDH of the islet cells showed. The percentage of heteroplasmy of the mtDNA 3243 mutation in pancreatic micropunched islet specimens was 63 +/- 5% (mean +/- SD) in the islets, 32 +/- 3% in the exocrine pancreas, and 8 +/- 1% in peripheral polymorphonuclear cells. Apoptotic cells were not observed in the IDDM pancreas in the patient with the mtDNA 3243 mutation. The fact that higher levels of mutated mtDNA at 3243 bp were found in affected islets rather than in other tissue suggests that the distribution of the mutant may determine the effect on islet function. A characteristic decrease in the mitochondrial enzyme with COX activity and accelerated SDH activity of the affected islets may provide new insights into the pathogenesis of mitochondrial diabetes.
此前尚未有人描述过患有腺嘌呤（A）到鸟嘌呤（G）线粒体DNA（mtDNA）突变（位于核苷酸位置3243碱基对（bp））的糖尿病患者胰腺的变化情况。与mtDNA 3243突变相关的糖尿病临床表型范围从非胰岛素依赖型糖尿病（NIDDM）到胰岛素依赖型糖尿病（IDDM）。我们探寻该突变的存在情况，并研究了尸检获得的糖尿病胰腺中β细胞、α细胞和δ细胞的体积、线粒体酶活性以及细胞凋亡情况。胰腺取自16例IDDM患者、18例NIDDM患者以及11例非糖尿病患者。测定了细胞色素c氧化酶（COX）的线粒体酶活性，其亚基部分由mtDNA编码，同时还测定了琥珀酸脱氢酶（SDH）的活性，其亚基仅由核DNA编码。通过计算机形态计量学估算胰岛β细胞、α细胞和δ细胞的体积。采用原位末端标记法检查胰腺细胞的凋亡情况。在16例IDDM患者的胰腺中，有1例（6%）检测到mtDNA 3243突变；18例NIDDM患者和11例非糖尿病患者的胰腺中均未发现该突变。携带mtDNA 3243突变的唯一患者是一名56岁的女性，患有IDDM，糖尿病发病年龄为39岁，其母亲被诊断为NIDDM。该患者有口服降糖药继发性失效史，β细胞数量显著减少。该患者的胰岛β细胞和非β细胞显示细胞色素c氧化酶活性极度降低。检测该患者的胰岛细胞时发现琥珀酸脱氢酶活性较高。一些胰腺外分泌细胞也显示细胞色素c氧化酶活性降低而琥珀酸脱氢酶活性较高。在未发生mtDNA 3243突变的IDDM、NIDDM和非糖尿病患者中，胰岛细胞的琥珀酸脱氢酶仅显示弱阳性染色。在胰腺微穿刺胰岛标本中，mtDNA 3243突变的异质性百分比在胰岛中为63±5%（平均值±标准差），在外分泌胰腺中为32±3%，在外周多形核细胞中为8±1%。在携带mtDNA 3243突变的IDDM患者的胰腺中未观察到凋亡细胞。在受影响的胰岛中而非其他组织中发现3243 bp处突变型mtDNA水平较高这一事实表明，突变体的分布可能决定对胰岛功能的影响。受影响胰岛中线粒体酶细胞色素c氧化酶活性的特征性降低以及琥珀酸脱氢酶活性的加速可能为线粒体糖尿病的发病机制提供新的见解。
