MITOCHONDRIAL-DNA IS REQUIRED FOR REGULATION OF GLUCOSE-STIMULATED INSULIN-SECRETION IN A MOUSE PANCREATIC BETA-CELL LINE, MIN6

To determine whether mtDNA and mitochondrial respiratory function in p ancreatic beta cells are necessary for the phenotypic expression of gl ucose-stimulated in sulin secretion, we used a cultured mouse pancreat ic beta cell line, MIN6, and two derivative lines, mtDNA knockout MIN6 (rho(0) MIN6) and mtDNA repopulated cybrid MIN6. The MIN6 cells retai n the property of glucose-stimulated insulin secretion, but their mtDN A knockout induced the loss of mitochondrial transcription, translatio n, and respiration activity, without inhibition of transcription of th e insulin gene or loss of succinate dehydrogenase activity, indicating that the observed mitochondrial dysfunction in rho(0) MIN6 cells was not due to a cytotoxic side effect derived from the mtDNA knockout. Mo reover, the mtDNA depletion also inhibited both the glucose-stimulated increase in the intracellular free Ca2+ content and the elevation of insulin secretion. The possibility of the involvement of nuclear genom e encoded factors in this process was excluded by the observation that the missing sensitivity to extracellular glucose stimulation in rho(0 ) MIN6 cells was restored reversibly by repopulation with foreign mtDN A and isolating cybrid MIN6 clones. Therefore, these findings provide unambiguous evidence for the involvement of the mitochondrial dysfunct ion induced by mtDNA impairment in developing pathogeneses of some for ms of diabetes mellitus.