The Muscle Metaboreflex in Patients with Diabetic Autonomic Neuropathy

The autonomic nervous system plays a critical role in cardiovascular responses to exercise through activation of the muscle metaboreflex. Subjects with diabetic autonomic neuropathy demonstrate impaired cardiovascular responses to exercise. We hypothesised that such patients would demonstrate impaired metaboreflex function. We assessed metaboreflex activity in six subjects with type 1 diabetes mellitus and autonomic neuropathy and eight subjects with type 1 diabetes mellitus without autonomic neuropathy. We used rhythmic handgrip exercise to fatigue followed by post-exercise muscle ischaemia, an established method of assessing metaboreflex function. Subjects with autonomic neuropathy had an attenuated heart rate response to exercise. Blood pressure remained elevated during post-exercise muscle ischaemia in both groups, suggesting intact metaboreflex function. Heart rate fell rapidly to baseline in both groups, suggesting normal baroreflex buffering of the metaboreflex. We conclude that the metaboreflex is important in the control of blood pressure during exercise in patients with diabetic autonomic neuropathy.