SYMPATHETIC-NERVE ACTIVITY AND INSULIN IN OBESE NORMOTENSIVE AND HYPERTENSIVE MEN

The relationship between resting levels of muscle sympathetic nerve ac tivity (MSA) and blood pressure is a matter of controversy. Body weigh t has recently been identified as an independent determinant of muscle sympathetic discharge, which may have influenced previous studies foc used on MSA and mechanisms of hypertension. In the present study, we m easured resting MSA and plasma insulin levels in 18 obese (body mass i ndex, 32+/-4 kg/m(2)) (mean+/-SD), middle-aged (52+/-6 years) hyperten sive (155+/-11/97+/-8 mm Hg) subjects and 16 age- and body mass index- matched normotensive control subjects. In the postabsorptive state, re sting MSA was similar in the hypertensive and normotensive groups (43/-4 versus 39+/-3 bursts per minute, 69+/-5 versus 64+/-5 bursts per 1 00 heart beats, P=NS) (mean+/-SEM) and did not correlate with either s ystolic or diastolic blood pressure. Weak but significant positive cor relations were found between resting MSA and both fasting insulin leve ls (P<.05) and body mass index (P=.05) in hypertensive but not normote nsive subjects. There was a strong positive correlation between fastin g insulin and body mass index in both normotensive subjects and the en tire study group (P<.005). Fasting insulin and body mass index correla ted with diastolic blood pressure (P<.05) in the entire study group. I n conclusion, a relationship between fasting insulin, body mass index, and blood pressure was confirmed, whereas only a weak correlation was found between MSA and fasting insulin in hypertensive but not normote nsive subjects. The fact that MSA was similar in the two groups argues strongly against augmented MSA being important for the maintenance of hypertension, at least in middle-aged, obese men.