Abstract P3016: High Glucose Induced Diabetic Dementia is Mediated by Mitochondria Dysfunction

Abstract

Diabetes is an important risk factor for dementia. We previously reported that cognitive dysfunction is associated with impaired cerebral vascular function in our diabetic rat model. Hyperglycemia contributes to endothelial dysfunction by increasing the production of reactive oxygen species (ROS). However, the role of changes in mitochondrial dynamics in altering autoregulation of cerebral blood flow and the loss of cognitive function in diabetes is unknown. The present study examined the myogenic response of middle cerebral arteries (MCAs), as well as mitochondrial function and fission in primary vascular smooth muscle cells (VSMCs) maintained in normal glucose (NG) or high glucose (HG). ROS production assessed by DHE staining was significantly increased in freshly isolated MCAs of diabetic rats (55.77 ± 11.27 arbitrary unit (a.u.), n=4) vs. Sprague Dawley (SD, 15.46 ± 1.92 a.u. n=4) rats. In addition, HG-treated primary VSMCs from SD rats exhibited more mitochondrial ROS than controls, as detected by MitoSOX. The myogenic response of MCAs was impaired in 3-month old diabetic rats compared to age-matched controls. Treatment with superoxide dismutase (150 U/mL) restored the myogenic response. Mitochondrial respiration was decreased in HG-treated (91.1 ± 7.6 pmol/min/mg/ml, n=6) vs. NG-treated (153.2 ± 6.3 pmol/min/mg/ml, n=9) VSMCs as measured by a Seahorse XF e 24 analyzer. Treatment with HG also caused mitochondrial depolarization as assessed by staining with JC-1. The length of mitochondria in high glucose-treated VSMCs was significantly less than in control VSMCs (HG: 5.66 ± 0.14 μm vs. Control: 11.70 ± 0.23 μm, n=3, 100) as seen by Tomm20 immunostaining. In addition, levels of OPA1 were significantly lower and MFF levels were higher in HG-treated cells compared to controls, indicating an increase in mitochondrial fission and a decrease in fusion in the HG-treated VSMCs. This was associated with decreased levels of p-AMPK in HG-treated vs. control VSMCs. These results demonstrate that the impaired myogenic response in cerebral arteries in diabetes is associated with impaired mitochondrial dysfunction and elevated production of ROS via the p-AMPK/MFF signaling pathway, which may contribute to the loss of cognitive function in diabetes.