Lack of relationship between sympathetic nervous system activity, measured by two circulating markers, and blood pressure in diabetic and nondiabetic subjects

Two putative sympathetic nervous system (SNS) markers, noradrenaline and neuropeptide Y (NPY) were related to 24-h ambulatory blood pressure (BP) in 59 normotensive subjects, 34 non-insulin-dependent diabetics, and 25 controls. Plasma NPY levels were not significantly different between the two groups [non-insulin-dependent (NIDDM) diabetes mellitus 4.33 (3.25-5.78), controls 5.68 (3.39-6.97) p = 0.26] as were those of noradrenaline (1.51 +/- 0.69 versus 1.78 +/- 0.55; p = 0.053). There were correlations, controlled for age and obesity, of plasma NPY with clinic and night time diastolic BP in the control group only (r = 0.49 [p = 0.013] and r = 0.48 [p = 0.023] respectively). No similar correlation was found in the NIDDM group, or between plasma noradrenaline and blood pressure in either group. No correlation was found between plasma insulin and NPY or noradrenaline levels. There is a weak independent relationship between NPY and blood pressure in normotensive nondiabetics but not in NIDDM subjects. We found no evidence for the hypothesis that insulin modulates blood pressure through activity of the SNS. (C) 1998 Elsevier Science Inc.