Tight control of serum glucose levels is critically important in reducing long-term complications of diabetes mellitus. Accumulating evidence suggests that these long-term benefits are not risk-free, and that recurrent episodes of hypoglycemia, or severe hypoglycemic coma secondary to incorrect insulin dosing, have significant morbidity. Damage to the hippocampus and cerebral cortex has been noted, as have cognitive defects in humans and in animal models. However, the mechanisms that underlie hypoglycemic damage to the nervous system, particularly during embryogenesis, remain largely unknown. We propose to better define how neurons are damaged by hypoglycemia in the nervous system, whether synaptic connectivity and neuronal development are affected, and whether hypoglycemia triggers expression of particular genes within the brain, providing insight into the type of damage that is sustained and identifying possible avenues of therapeutic intervention. Using two complementary hippocampal primary culture models, we plan to identify the pathways that lead to neuronal injury in response to hypoglycemia (Specific Aim I). Neuronal vulnerability to cell death will be determined; type of cell death, death pathways and active intermediates, and the transmitter phenotypes of the affected hippocampal neurons will be defined. In addition, effects of hypoglycemia to delay or disrupt neuronal polarization, axonal and dendritic outgrowth, selective axonal and dendritic protein transport, and synaptogenesis will be analyzed. Since recurrent bouts of hypoglycemia in utero are associated with postnatal cognitive impairment, we propose to examine whether cell death pathways are activated in the hippocampus through exposure to hypoglycemia in utero (Aim II). In addition, we propose to identify genes that are regulated in the embryonic and early post-natal hippocampus by hypoglycemia, which we hope will offer insight into the mechanism(s) by which the hippocampus is damaged.
