Muscle sympathetic nerve activity in patients with acromegaly.

Abstract

Muscle sympathetic nerve activity was measured in nine acromegalic patients (age, 35 +/- 4 yr; body mass index, 28 +/- 2 kg/m2) and eight healthy subjects (age, 32 +/- 3 yr; body mass index, 25 +/- 2 kg/m2) by combining the forearm arterial-venous difference technique with the tracer method [infusion of tritiated norepinephrine (NE)]. Muscle NE release was quantified both at rest and during physiological hyperinsulinemia while maintaining euglycemia (approximately 90 mg/dL) by means of the euglycemic clamp. Arterial plasma NE was similar in the two groups at rest (197 +/- 28 and 200 +/- 27 pg/mL (-1) and slightly increased during insulin infusion. Forearm NE release was 2.33 +/- 0.55 ng x liter(-1) x min(-1) in healthy subjects and 2.67 +/- 0.61 ng x liter(-1) x min(-1) in acromegalic subjects in the basal state and increased to a similar extent during insulin infusion in both groups (3.13 +/- 0.71 and 3.32 +/- 0.75 ng x L(-1) x min(-1), P < 0.05 vs. basal), indicating a normal stimulatory effect of insulin on muscle sympathetic activity. In contrast, insulin-stimulated forearm glucose uptake was markedly lower in acromegalic patients (2.3 +/- 0.4 mg x L(-1) x min(-1)) than in control subjects (7.9 +/- 1.3 mg x L(-1) x min(-1), P < 0.001), indicating the presence of severe insulin resistance involving glucose metabolism. Our data demonstrate that patients with long-term acromegaly have normal sympathetic activity in the skeletal muscle in the basal, postabsorptive state and normal increments in NE spillover in response to the sympatho-excitatory effect of insulin. Thus, the presence of severe insulin resistance in acromegaly is not accounted for by adrenergic mechanisms.

• Authors: B Capaldo, G Lembo, V Rendina, R Guida, P Marzullo, A Colao, G Lombardi, L Saccà
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 85 Issue 9 Pg. 3203-7 (Sep 2000) ISSN: 0021-972X [Print] United States
• PMID: 10999809 (Publication Type: Clinical Trial, Journal Article)

Chemical References

• Blood Glucose
• Hypoglycemic Agents
• Insulin
• Norepinephrine

Topics

• Acromegaly (physiopathology)
• Adult
• Blood Glucose (metabolism)
• Blood Pressure (drug effects, physiology)
• Body Mass Index
• Female
• Forearm (blood supply)
• Humans
• Hypoglycemic Agents (blood, pharmacology)
• Insulin (blood, pharmacology)
• Male
• Muscle, Skeletal (innervation, physiopathology)
• Norepinephrine (blood, metabolism)
• Regional Blood Flow (physiology)
• Sympathetic Nervous System (physiopathology)