Objective
Pharmacotherapy for diabetes mellitus (DM) with anti-diabetic agents such as insulin carries the risk of acute hypoglycemia (<70 mg/dl). Recent evidence suggests that patients exposed to hypoglycemia have worsened health outcomes than DM patients who do not experience hypoglycemia. The objective of the study is to determine the impact of hypoglycemia on ischemia-reperfusion injury to brain in mice and investigate the role of underlying cerebral vascular and hemodynamic mechanisms.
Methods
We subjected male C57Bl/6 J mice to either single episode (acute hypoglycemia) or five episodes (recurrent hypoglycemia, RH) insulin-induced hypoglycemia or saline injection (RS, control). We employed two-photon microscopy in isoflurane anesthetized animals with cranial windows over somatosensory cortex for imaging cerebral vasculature. We induced cerebral ischemia-reperfusion injury in mice by transient middle cerebral occlusion using filament method.
Results
We found that acute hypoglycemia but not RH promotes increase in cerebral capillary diameter in vivo. However, experimental stroke induced 24 h after the final episode of RH was found to increase infarct volume in mice, suggesting that RH promotes long-lasting vulnerability to ischemic brain injury beyond the duration of hypoglycemia. Diameter of capillaries was found to increase over the reperfusion time course similarly in RH and RS groups. In contrast, animals subjected to RH displayed increased normalized RBC flux over the reperfusion period when compared to RS group.
Conclusions
Acute hypoglycemia induces changes to cerebral vascular diameter; however, RH promotes increased ischemic injury and altered hemodynamics of arterial blood flow without altering the diameter of cerebral penetrating arteries or capillaries.
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