Abstract 10665: The Glycemic and Insulin Levels Contribute to the Sympathetic Response to Exercise in Individuals With and Without Diabetes Mellitus

Introduction: Exaggerated responses in blood pressure (BP) and muscle sympathetic nerve activity (MSNA) during exercise are suggested to contribute to adverse cardiovascular events. The risk of developing cardiovascular disease is elevated in patients suffering from diabetes mellitus (DM) and pre-DM; however, the relationship between the sympathetic responses to exercise and the glycemic and insulin indices in DM and non-DM remain unclear.Hypothesis: We hypothesized that the magnitude of MSNA response to exercise is related with glycemic and insulin indices in DM and Pre-DM subjects. Method: Eleven clinically diagnosed T2DM patients (54.0 ± 2.7 yrs) and 20 non-DM subjects (58.6 ± 2.3 yrs, 10 pre-DM [5.7% ≤ HbA1c < 6.5%] and 10 healthy subjects) were examined. All non-DM subjects, including pre-DM subjects, had no noted diseases and were not on any medication. Five DM patients were on antihypertensive agents. The BP and glycemic control in the DM patients was relatively well managed with medications (HbA1c, 6.8 ± 0.3 %) and were without other cardiovascular complications. Beat-by-beat BP, heart rate, and MSNA were recorded simultaneously under a resting condition and during static handgrip exercise (HGe) at 30% maximal voluntary contraction until fatigue. Results: Resting MSNA in DM was lower than non-DM subjects (P < 0.05). However, the MSNA response (i.e., the change) to HGe in DM was higher than non-DM (139% vs 75% increase, P < 0.05). The MSNA response to HGe was significantly correlated (R = 0.59, P < 0.05) with fasting blood glucose (FBG) across all subjects. Even in only pre-DM subjects, the MSNA response to HGe was significantly correlated with glucose/insulin indices (vs. FBG, R = 0.91, P < 0.05; vs. blood insulin concentration, R = 0.84, P < 0.05). Conclusion: In the present study, the MSNA response to exercise in T2DM patients was greater than that in non-DM subjects. Importantly, the MSNA response to exercise was correlated with glycemic/insulin indices over a broad range. This relationship was observed even before the development of DM. We speculate that the altered glycemic/insulin levels may contribute to the exaggerated sympathetic response to stress and in turn, contribute to the higher risk of cardiovascular diseases in these individuals.