Study on the pathogenetic roles of mutation of mitochondrial DNA at position 3243 on diabetes mellitus

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In situ characterization of the islet in diabetics with mitochondrial DNA mutation at 3243 base pair (mt DNA 3243 mutation) was carried out.In the present study, the islets in the diabetic patients with mt DNA 3243 mutation were examined in terms of beta cell volume and mitochondrial enzyme activities.Thirty-four pancreata, including 10 pancreata from NIDDM patients, 14 pancreata from IDDM patients, and 10 non-diabetics, were composed of the subjects. Cytochrome c oxidase (COX) and succinate dehydrogenase (SDH) activities of the pancreas were stained histochemically.mtDNA 3243 was detected in only 1 of 34 pancreata. Pancreatic beta cell volume in this case was decrease to 0.22 g. Fifty-two islets were examined in a section stained for mitochondrial enzymes including COX and SDH.All islets of an IDDM case with mtDNA 3243 mutation lacked COX enzyme activity, while other islets from 13 IDDM patients, 10 NIDDM patients and 10 non-diabetics had positive COX activity. All islets in the case with mtDNA 3243 mutation examined for SDH activity showed positive enzyme activity, while there were weak activity in the islet for SDH in IDDM,NIDDM and non-diabetics, who did not have the mutation. Pancreatic amyloid was demonstrated in a case with mtDNA 3243.In conclusion, markedly decreased beta cell volume with diminished activity of mitochondrial DNA encoded-enzyme (COX) was demonstrated in an IDDM patients with mtDNA 3243 mutation.