MUSCLE SYMPATHETIC-NERVE ACTIVITY IS HIGHER IN INTENSIVELY VERSUS CONVENTIONALLY TREATED IDDM SUBJECTS

OBJECTIVE - To determine whether poor long-term glycemic control may p lay a role in the lower muscle sympathetic nerve activity (MSNA) level s in insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND M ETHODS - Intraneural electrodes were used to record MSNA from the pero neal nerve al baseline and during euglycemic insulin infusion (120 mU . m(-2) . min(-1)) in 16 IDDM subjects enrolled in the Diabetes Contro l and Complications Trial(DCCT), 8 intensively treated (HbA(1c) 7.1 +/ - 1.2%) and 8 conventionally treated (HbA,, 9.0 +/- 1.5%; P < 0.05). R ESULTS - 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; inte nsive, 5.1 +/- 0.4 mmol/l). Plasma free insulin levels did not differ between groups either before or during insulin infusion. The intensive ly treated group had significantly higher MSNA levels than the convent ionally 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 euglyc emia (27.8 +/- 2.1 vs. 17.5 +/- 5.2 bursts/min). CONCLUSIONS - MSNA le vels in intensively treated IDDM subjects are higher than in conventio nally treated subjects. These results suggest that improved long-term glycemic control is associated with increased sympathetic neural outfl ow to muscle. The mechanism for this effect remains unclear.