Muscle Sympathetic Nerve Activity Is Higher in Intensively versus Conventionally Treated IDDM Subjects

Abstract

OBJECTIVE To determine whether poor long–term glycemie control may play a role in the lower muscle sympathetic nerve activity (MSNA) levels in insulindependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS Intraneural electrodes were used to record MSNA from the peroneal nerve at baseline and during euglycemic insulin infusion (120 mU · m−2 · min−1) in 16 IDDM subjects enrolled in the Diabetes Control and Complications Trial (DCCT), 8 intensively treated (HbAlc 7.1 ± 1.2%) and 8 conventionally treated (HbA1c 9.0 ± 1.5%; P < 0.05). RESULTS Fasting plasma glucose levels tended to be higher at baseline in the conventionally treated group (11.3 ± 1.7 mmol/l) than in the intensively treated group (7.4 ±1.1 mmol/l, P < 0.1), but did not differ during insulin infusion (conventional, 5.0 ± 0.3 mmol/l; intensive, 5.1 ± 0.4 mmol/l). Plasma free insulin levels did not differ between groups either before or during insulin infusion. The intensively treated group had significantly higher MSNA levels than the conventionally treated group both in the fasting state (16.2 ± 2.7 vs. 10.5 ± 4.4 bursts/min, P < 0.05) and during insulin infusion with euglycemia (27.8 ± 2.1 vs. 17.5 ± 5.2 bursts/min). CONCLUSIONS MSNA levels in intensively treated IDDM subjects are higher than in conventionally treated subjects. These results suggest that improved long-term glycemie control is associated with increased sympathetic neural outflow to muscle. The mechanism for this effect remains unclear.