In the human, diabetic pregnancy induces marked abnormalities in glucose homeostasis and insulin secretion in the fetus that results in aberrant fetal growth. Studies have suggested that there are long-term consequences for the offspring of diabetic mothers. We have developed a model of gestational diabetes (GDM) in the rat to determine whether an altered metabolic intrauterine milieu is directly linked to the development of diabetes later in life. Uteroplacental insufficiency is induced in the pregnant rat on day 19 of gestation. Offspring are growth retarded at birth, however they catch-up by 5- 7 weeks of age. At 8 weeks of age they are bred to normal males. During pregnancy these animals develop hyperglycemia, hyperinsulinemia, and hyperlipidemia accompanied by impaired glucose tolerance and insulin resistance. Offspring, (F2's) are heavier at birth and remain heavy throughout life. F2's are insulin resistant very early in life and glucose homeostasis is progressively impaired. F2 rats go on to develop diabetes as adults. Although F2 animals display marked insulin resistance, the failure of the Beta-cell to compensate for defects in insulin action is the essential factor coincident with onset of diabetes. This failure of the Beta-cell to compensate may be due to a lack of compensatory increase in insulin secretion, an increased rate of cell death, a reduction in the rate of Beta-cell proliferation, or a combination of these events. The mechanism(s) underlying this lack of Beta-cell compensation and eventual decrease in Beta-cell mass in F2 animals are the focus of this proposal. We hypothesize that mitochondrial DNA damage from hyperglycemia via the production of reactive oxygen species (ROS) results in further escalation of genetic damage in the mitochondria, specifically in mutations. A self- reinforcing cycle of progressive deterioration in mitochondrial function leads to a corresponding decline in Beta-cell function. Finally, a threshold in mitochondrial dysfunction and ROS production is reached and Beta-cell death occurs. The onset of diabetes ensues when a critical level of abnormal Beta-cell insulin secretion combined with Beta-cell loss is reached. We will test the hypothesis that GDM does in fact cause mitochondrial dysfunction, oxidative stress, and deletions in mtDNA in the Beta-cell of the offspring, and whether these effects act synergistically to lead to the development of the Beta-cell failure and type II diabetes. To link the damage to the mitochondria caused by hyperglycemia to the Beta-cell phenotype observed in type II diabetes we will induce Beta-cell failure in vitro by transferring damaged mitochondria from F2 animals into Beta-cells from unaffected. non-F2 animals.
