Cerebral Microvascular Bioenergetics and Neurovascular Coupling

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Principal Investigator: Prasad V Katakam
Organization: TULANE UNIVERSITY OF LOUISIANA
Fiscal Year: 2024
Award: $463,813
Funding agency: National Institute of Neurological Disorders and Stroke

Summary
Brain microvessels play an important role in the neurovascular coupling (NVC). Mitochondria are energy sensors
of cells. My work for the first time demonstrated the link between mitochondrial depolarization and activation of
nitric oxide synthases (NOS). Recently, we have made a novel discovery of a neuronal NOS (nNOS) isoform in
endothelial cells that uniquely produce reactive oxygen species (ROS). The nNOS is co-expressed with NO-
producing eNOS in endothelial cells and both isoforms are involved in the bidirectional regulation of
mitochondria. Diabetes mellitus (DM) increases the risk of cerebrovascular dysfunction and dementia.
Importantly, hypoglycemia is a dangerous side effect of DM treatments, particularly insulin-therapy. Patients with
DM often experience mild hypoglycemia, but these episodes are unaccounted for in determining the
cardiovascular morbidity and mortality. We achieved a technological breakthrough utilizing Seahorse XFe24
analyzer and determined the mitochondrial respiration and cellular bioenergetics of brain microvessels. We made
a novel observation that five episodes of recurrent hypoglycemia (RH) impaired the microvascular mitochondrial
function. Notably, single episode of acute mild or severe hypoglycemia as well as Impairments of NOS activity
was found to mediate RH-induced alterations of cellular bioenergetics. Thus, we hypothesize that mild RH
disrupts NVC by promoting microvascular mitochondrial dysfunction leading to impaired cognitive function. We
further hypothesize that increased nNOS-induced oxidative stress coupled with reduced eNOS-derived NO
contribute to the mitochondrial dysfunction following RH. We propose to use streptozotocin treated C57Bl/6 mice
and db/db mice with leptin receptor mutation as models of diabetes with untreated mice as controls. In addition,
we will employ eNOS knockout and inducible endothelial cell specific nNOS knockout mice to investigate the
role of NOS isoforms in RH-induced microvascular dysfunction. Each animal will be subjected to five episodes
(one per day) of mild (blood glucose 70-80 mg/dl) or severe (blood glucose 40-54 mg/dl) insulin-induced
hypoglycemia or saline control. Aim 1 is to demonstrate that mild and severe RH (in vivo) can increase the
production of NOS-derived ROS and display RH-induced functional mitochondrial respiration deficits in cerebral
microvessels (ex vivo). Aim 2 is to establish the impact of RH on NVC in vivo. We will determine the RH-induced
deficits in NVC by measuring the changes in arteriolar and capillary diameter in response to neuronal activation
(whisker stimulation) in awake mice using two-photon laser scanning microscopy. Aim 3 is to determine the
impact of RH on cognitive function using novel texture discrimination task and modified Y-maze test. The results
of this proposal would identify the mechanistic link between mild RH and the cerebral microvascular mitochondria
dysfunction and challenge the existing dogma to demonstrate that mild RH is equally detrimental as severe RH
in contributing to the DM-induced cerebrovascular dysfunction, impaired NV, and cognitive dysfunction.

Terms: <2-photon><Active Oxygen><Acute><Adult-Onset Diabetes Mellitus><Amentia><Animals><Anti-diabetic Agents><Anti-diabetic Drugs><BNOS><Bioenergetics><Biology><Blood Glucose><Blood Sugar><Blood Vessels><Blood capillaries><Brain><Brain Nervous System><Brain Vascular><Brain Vascular Disorders><Brittle Diabetes Mellitus><C57BL/6 Mouse><Cardiovascular><Cardiovascular Body System><Cardiovascular Organ System><Cardiovascular system><Cell Body><Cells><Cerebrovascular Circulation><Cerebrovascular Disease><Cerebrovascular Disorders><Cerebrum><Clinical><Cognitive><Cognitive Disturbance><Cognitive Impairment><Cognitive decline><Cognitive function abnormal><Complications of Diabetes Mellitus><Coupled><Dangerousness><Data><Dementia><Diabetes Complications><Diabetes Mellitus><Diabetes-Related Complications><Diabetic Complications><Diameter><Disturbance in cognition><EDRF Synthase><EPR spectroscopy><ESR Spectroscopy><Electron Paramagnetic Resonance><Electron Spin Resonance><Electron Spin Resonance Spectroscopy><Encephalon><Endogenous Nitrate Vasodilator><Endothelial Cells><Endothelium><Endothelium-Derived Growth Factor Synthase><Endothelium-Derived Nitric Oxide><Generations><Genus Hippocampus><Guanylyl Cyclase-Activating Factor Synthase><Heart Vascular><Humulin R><Hypoglycemia><IDDM><Impaired cognition><Impairment><Injury><Insulin><Insulin-Dependent Diabetes Mellitus><Intracranial Vascular Diseases><Intracranial Vascular Disorders><Isoforms><Juvenile-Onset Diabetes Mellitus><KO mice><Ketosis-Prone Diabetes Mellitus><Ketosis-Resistant Diabetes Mellitus><Knock-out><Knock-out Mice><Knockout><Knockout Mice><Laser Scanning Microscopy><Leptin receptor mutation><Link><Maturity-Onset Diabetes Mellitus><Measures><Mediating><Meta-Analysis><Methods><Mice><Mice Mammals><Microvascular Dysfunction><Mitochondria><Modeling><Mononitrogen Monoxide><Morbidity><Morbidity - disease rate><Murine><Mus><NC-NOS><NIDDM><NNOS><NO Synthase><NOS 1 protein><NOS type I><NOS1><NOS1 gene><NOS1 protein><Nerve Cells><Nerve Unit><Neural Cell><Neural Constitutive Nitric Oxide Synthase><Neurocyte><Neurons><Nitric Oxide><Nitric Oxide Synthase><Nitric Oxide Synthase Type I><Nitric-Oxide Synthetase><Nitrogen Monoxide><Nitrogen Protoxide><Non-Insulin Dependent Diabetes><Non-Insulin-Dependent Diabetes Mellitus><Noninsulin Dependent Diabetes><Noninsulin Dependent Diabetes Mellitus><Novolin R><Null Mouse><Oxidative Stress Induction><Oxygen Consumption><Oxygen Radicals><Paramagnetic Resonance><Patients><Peripheral><Physiologic><Physiological><Play><Pro-Oxidants><Production><Protein Isoforms><Reactive Oxygen Species><Recurrence><Recurrent><Regular Insulin><Regulation><Research><Respiration><Risk><Role><STZ><Saline><Saline Solution><Seahorse><Slow-Onset Diabetes Mellitus><Somatosensory Cortex><Stable Diabetes Mellitus><Streptozocin><Streptozotocin><Sudden-Onset Diabetes Mellitus><Symptoms><T1 DM><T1 diabetes><T1D><T1DM><T2 DM><T2D><T2DM><Technology><Testing><Texture><Therapeutic><Time><Type 1 Diabetes Mellitus><Type 1 diabetes><Type 2 Diabetes Mellitus><Type 2 diabetes><Type I Diabetes Mellitus><Type II Diabetes Mellitus><Type II diabetes><Variant><Variation><Vibrissae><Whiskers><Work><Zanosar><abnormal brain function><adult onset diabetes><anti-diabetic><awake><blood flow in brain><blood glucose regulation><brain blood circulation><brain blood flow><brain dysfunction><brain endothelial cell><brain impairment><brain microvascular endothelial cell><brain microvasculature><brain microvessels><brain nitric oxide synthase><brain vascular disease><brain vascular dysfunction><brain vascular endothelial cell><capillary><cardiovascular disease risk><cardiovascular disorder risk><cerebral><cerebral blood flow><cerebral circulation><cerebral endothelial cell><cerebral microvascular endothelial cell><cerebral microvasculature><cerebral microvessels><cerebral vascular><cerebral vascular disease><cerebral vascular dysfunction><cerebral vascular endothelial cell><cerebro-vascular><cerebrocirculation><cerebrovascular><cerebrovascular blood flow><cerebrovascular dysfunction><circulatory system><cognitive dysfunction><cognitive function><cognitive loss><db/db mouse><dementia risk><diabetes><diabetic patient><discrimination task><dysfunctional brain><electron paramagnetic resonance spectroscopy><endothelial cell derived relaxing factor><experience><extracellular><glucose control><glucose homeostasis><glucose regulation><hypoglycemia unawareness><hypoglycemic><hypoglycemic episodes><in vivo><injuries><injury to the vasculature><insulin dependent diabetes><insulin dependent type 1><intracranial vascular dysfunction><juvenile diabetes><juvenile diabetes mellitus><ketosis prone diabetes><ketosis resistant diabetes><maturity onset diabetes><microvascular complications><microvascular disease><mitochondrial><mitochondrial dysfunction><mortality><nNOS enzyme><neglect><neuro-vascular coupling><neuronal><neuronal NOS><neuronal form of nitric oxide synthase><neuronal nitric oxide synthase><neurovascular coupling><nitric oxide synthase 1><novel><respiratory mechanism><response><risk factor for dementia><risk for dementia><sensor><side effect><small vessel disease><social role><somesthetic sensory cortex><two-photon><type 2 DM><type I diabetes><type II DM><type one diabetes><type two diabetes><vascular><vascular injury>