Hyperglycemia and type 2 diabetes : impact on neural cardiovascular control
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Alterations in blood pressure regulation are linked with increased risk for cardiovascular disease and mortality. Type 2 diabetes is often characterized by impairment in blood pressure regulation; however, few studies have focused on neural mechanisms involved with blood pressure regulation in this population. High levels of blood glucose and insulin are hallmarks of type 2 diabetes, and gaining a greater understanding of the direct influence of insulin and glucose on neural mechanisms involved with blood pressure regulation is important and clinically relevant. In study #1, the effects of acute increases in blood glucose on blood pressure regulation was examined in healthy subjects, and the findings demonstrated a reduction in neural control of heart rate that was independent of reductions in insulin sensitivity, a main characteristics of type 2 diabetes. Similar results were found when blood insulin was acutely elevated independent of glucose. Further studies were performed in type 2 diabetes patients to examine the influence of chronically elevated blood glucose and insulin on blood pressure regulation. Not unlike study #1, reductions in neural control of heart rate were seen in type 2 diabetes patients, but these finding were largely explained by excessive body weight. No impairment was observed in neural control of sympathetic nerve activity, which is also an important neural mechanism involved in blood pressure regulation. Finally, given the known impairment in blood pressure regulation during stressors such as exercise in type 2 diabetes patients, study #3 focused on blood pressure and sympathetic nerve activity responses to activation of important neural feedback from exercising skeletal muscle involved in blood pressure regulation. The results demonstrated exaggerated increases in blood pressure and sympathetic nerve activity to activation of neural skeletal muscle feedback in type 2 diabetes patients, providing important information regarding the neural mechanisms involved in the impairment in blood pressure regulation during exercise in this population.
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