Alzheimer?s disease is the most common form of dementia, affecting over 45 million people worldwide and costing over $800 billion in medical care. It is characterized by the accumulation of extracellular amyloid-beta (A?) plaques and intracellular neurofibrillary tau tangles, which occur 5 to 15 years before symptom onset. Metabolic perturbation and sleep disturbance are key features of Alzheimer?s disease, where they represent both cause and consequence of disease pathophysiology. A bidirectional relationship exists between the two where impaired sleep and metabolism individually contribute to Alzheimer?s disease development while the presence of pathology leads to decreased cerebral metabolism, peripheral glucose intolerance, and disrupted sleep. Further, individuals with type-2-diabetes (T2D) have a 2-4-fold increased risk of developing Alzheimer?s disease, suggesting an underlying common mechanism. Chronic hyperglycemia, a defining characteristic of T2D, leads to increased neuronal activity and A? levels within the hippocampus, an effect exacerbated by the presence of A? pathology, indicating a relationship between peripheral metabolism, neuronal activity, and A? production that is compromised by plaque pathology. These metrics all have diurnal rhythms maintained by the sleep/wake cycle; therefore, acute changes in peripheral blood glucose levels, or glycemic variability, may be sufficient to drive sleep disruptions and further peripheral metabolic dysfunction by modifying the relationship between cerebral glucose metabolism and neuronal activity. The purpose of the training grant is to determine how acute glycemic variability, common in both the development and treatment of T2D, synergizes with Alzheimer?s disease pathology to affect cerebral metabolism, neuronal activity, and sleep/wake cycles. We will directly evaluate the impact of peripheral glycemic challenges using biosensors implanted into the hippocampus of mice measuring changes in interstitial fluid (ISF) glucose and lactate levels, measures of cerebral metabolism and neuronal activity, respectively. We will determine the impact of glycemic variability on sleep/wake cycles through simultaneous EEG/EMG recordings, evaluating both the total duration in each state as well as sleep fragmentation. Finally, we will characterize baseline peripheral metabolism of the genetic model mice and determine the effect of sleep deprivation and sleep rescue on peripheral glucose tolerance. Together, this proposal will establish glycemic variability as mechanism driving decreased sleep, increased cerebral metabolism and neuronal activity, and further peripheral glucose intolerance, all of which are well established risk-factors in the development of Alzheimer?s disease. Defining these relationships will offer a more efficacious approach to targeting the interactions between T2D and Alzheimer?s disease.
As the population in the United States continues to age, the incidence of Alzheimer?s disease is expected to triple and affect nearly 88 million Americans by 2050. Individuals with type-2-diabetes have a 2-4 fold greater risk of developing Alzheimer?s disease, and, as the prevalence of diabetes continues to rise with the obesity epidemic, understanding this relationship between Alzheimer?s disease and diabetes is crucial. Thus, the goal of this project is to determine how fluctuations in peripheral glucose metabolism affect the relationship between cerebral metabolism, neuronal activity, sleep/wake cycles, and Alzheimer?s disease pathology, thereby potentially offering more efficacious therapeutic targets.
