AIMS: Alpha-adrenergic receptor-mediated vasoconstriction might underlie the insulin resistance seen in conditions associated with increased sympathetic tone, like chronic heart failure (CHF). Alpha-adrenergic receptor blockade by phentolamine could improve forearm blood flow (FBF) and forearm glucose uptake (FGU) in CHF patients. METHODS AND RESULTS: In 8 CHF patients and in 12 healthy volunteers, FBF (plethysmography) and FGU were measured in both forearms during a 150 min hyperinsulinaemic euglycaemic clamp procedure. During the final 30 min of the clamp, phentolamine was infused into one arm (experimental arm) at a dose of 5.0 μg; min(-1) dL(-1) of forearm volume. Insulin infusion (t = 0-120 min) increased FGU in the two groups, without affecting FBF. In the CHF group, α-adrenergic receptor blockade by phentolamine (t = 120-150 min) further increased FGU in the experimental arm from 3.0 ± 0.7 to 5.0 ± 0.9 μmol min(-1) dL(-1) (P = 0.03). Forearm glucose uptake in the contralateral forearm remained unchanged. In the control group, phentolamine infusion did not increase FGU in the experimental forearm. The increase in blood flow in response to phentolamine was similar in both groups (CHF: 2.1 ± 0.3-7.5 ± 1.7 mL min(-1) dL(-1), P < 0.001; controls 1.5 ± 0.2-5.5 ± 0.8 mL min(-1) dL(-1), P < 0.001 for both, CHF vs. control, P = 0.2). Phentolamine did not affect FBF in the control arm in either group. CONCLUSION: Alpha-adrenergic receptor blockade improves FGU in CHF patients. As the increase in FBF is similar in controls and CHF patients, this might be explained by an improved glucose-extraction capacity in CHF patients.
RCT Entities:
AIMS: Alpha-adrenergic receptor-mediated vasoconstriction might underlie the insulin resistance seen in conditions associated with increased sympathetic tone, like chronic heart failure (CHF). Alpha-adrenergic receptor blockade by phentolamine could improve forearm blood flow (FBF) and forearm glucose uptake (FGU) in CHFpatients. METHODS AND RESULTS: In 8 CHFpatients and in 12 healthy volunteers, FBF (plethysmography) and FGU were measured in both forearms during a 150 min hyperinsulinaemic euglycaemic clamp procedure. During the final 30 min of the clamp, phentolamine was infused into one arm (experimental arm) at a dose of 5.0 μg; min(-1) dL(-1) of forearm volume. Insulin infusion (t = 0-120 min) increased FGU in the two groups, without affecting FBF. In the CHF group, α-adrenergic receptor blockade by phentolamine (t = 120-150 min) further increased FGU in the experimental arm from 3.0 ± 0.7 to 5.0 ± 0.9 μmol min(-1) dL(-1) (P = 0.03). Forearm glucose uptake in the contralateral forearm remained unchanged. In the control group, phentolamine infusion did not increase FGU in the experimental forearm. The increase in blood flow in response to phentolamine was similar in both groups (CHF: 2.1 ± 0.3-7.5 ± 1.7 mL min(-1) dL(-1), P < 0.001; controls 1.5 ± 0.2-5.5 ± 0.8 mL min(-1) dL(-1), P < 0.001 for both, CHF vs. control, P = 0.2). Phentolamine did not affect FBF in the control arm in either group. CONCLUSION: Alpha-adrenergic receptor blockade improves FGU in CHFpatients. As the increase in FBF is similar in controls and CHFpatients, this might be explained by an improved glucose-extraction capacity in CHFpatients.
Authors: Michael G Clark; Michelle G Wallis; Eugene J Barrett; Michelle A Vincent; Stephen M Richards; Lucy H Clerk; Stephen Rattigan Journal: Am J Physiol Endocrinol Metab Date: 2003-02 Impact factor: 4.310
Authors: Ida Gustafsson; Bente Brendorp; Marie Seibaek; Hans Burchardt; Per Hildebrandt; Lars Køber; Christian Torp-Pedersen Journal: J Am Coll Cardiol Date: 2004-03-03 Impact factor: 24.094