Hypertension and abnormalities of carbohydrate metabolism: possible role of sympathetic nervous system

To investigate the relationships between the sympathetic nervous system (SNS) and parameters of glucose metabolism in arterial hypertension, daily urinary excretion of catecholamines and plasma glucose, insulin, and C-peptide response to an oral glucose load (OGL) have been evaluated in 77 untreated patients with mild-to-moderate essential hypertension and in 31 normotensive controls. Urinary excretion of norepinephrine (UNE) was positively correlated with body mass index and with plasma glucose levels both at fast and after OGL. No correlations were found between urinary excretion of catecholamines and plasma insulin and C-peptide levels both at fast and in response to OGL. Because the frequency distribution of UNE was bimodal, hypertensive subjects were separated into two subgroups using an arbitrary cutoff, and the parameters of glucose metabolism were compared. Subjects with UNE ú 205 mg / day had greater levels of fasting glucose and greater glycemic response to OGL than subjects with UNE õ 205 mg / day, whereas no significant differences between the groups were found in fasting and stimulated plasma insulin and C- peptide. Thus, activation of SNS is related to glucose tolerance but not hyperinsulinemia and insulin hypersecretion in essential hypertension. Plasma glucose levels, independent of insulin, may contribute to the relationship between SNS activity and blood pressure in essential hypertension.