Biomedical subjects

Bastiaan E De Galan

Publications and source records attributed to Bastiaan E De Galan.

3 recordsLinked to original sources

PubMed2006

Preserved sensitivity to beta2-adrenergic receptor agonists in patients with type 1 diabetes mellitus and hypoglycemia unawareness.

BACKGROUND AND OBJECTIVE: Use of beta(2)-adrenergic receptor agonists has been advocated for the treatment of hypoglycemia unawareness in type 1 diabetes. In vitro, however, hypoglycemia unawareness has been associated with reduced beta(2)-adrenergic sensitivity. Therefore, in vivo sensitivity to beta(2)-adrenergic receptor agonist stimulation was compared between type 1 diabetic patients with and without hypoglycemia unawareness and nondiabetic controls. METHODS: Ten type 1 diabetic patients with hypoglycemia unawareness, 12 type 1 diabetic patients with intact hypoglycemic awareness, and 11 healthy controls were enrolled. beta(2)-Adrenergic sensitivity was determined by measuring the forearm vasodilator response to intraarterial infusion of salbutamol. Salbutamol was infused in six increasing doses ranging from 0.003 to 1.0 mug(1).min(-1).dl(-1). Forearm blood flow (FBF) was bilaterally measured by venous occlusion plethysmography. Diabetic patients received low-dose insulin before FBF measurements to ensure that experiments were carried out under normoglycemic conditions. RESULTS: At baseline, FBF was 1.9 +/- 0.3 ml(1).min(-1).dl(-1) in controls, 2.3 +/- 0.4 ml(1).min(-1).dl(-1) in patients with intact awareness, and 1.4 +/- 0.1 ml(1).min(-1).dl(-1) in patients with hypoglycemia unawareness (P = 0.048 vs. aware patients). In response to salbutamol, FBF increased 9.1-fold in controls, 8.0-fold in patients with intact awareness, and 10.7-fold in patients with hypoglycemia unawareness (P = NS). Heart rate increased in all groups due to systemic spillover of salbutamol but appeared blunted, considering a greater fall in mean arterial pressure in patients with hypoglycemia unawareness. CONCLUSIONS: Sensitivity to beta(2)-adrenergic receptor agonist stimulation is preserved in type 1 diabetic patients with hypoglycemia unawareness.

Adrenergic beta-2 Receptor Agonists↗

PubMed2004

Plasma metanephrine levels are decreased in type 1 diabetic patients with a severely impaired epinephrine response to hypoglycemia, indicating reduced adrenomedullary stores of epinephrine.

A defective epinephrine response to hypoglycemia is a common disorder in type 1 diabetes. We assessed the role of the adrenomedullary capacity to secrete epinephrine in this disorder by measuring plasma metanephrine levels in affected type 1 diabetic patients compared with those in matched nondiabetic controls. Metanephrine is formed from epinephrine that leaks from adrenomedullary storage vesicles by catechol-O-methyl transferase (COMT) and is continuously released into the circulation. Thus, plasma metanephrine levels reflect adrenomedullary epinephrine content and, provided there is normal COMT activity, the adrenomedullary capacity to secrete epinephrine. Diabetic patients had approximately 25% lower plasma metanephrine levels than controls (0.18 +/- 0.09 vs. 0.24 +/- 0.02 nmol/liter; P = 0.012), whereas plasma epinephrine, norepinephrine, and normetanephrine levels were comparable between patients and controls. In response to hypoglycemia, the increments in plasma epinephrine and plasma metanephrine levels were both significantly lower in diabetic patients than in controls (P < 0.001), but the increase in plasma metanephrine as a percentage of the increase in plasma epinephrine was identical, indicating similar COMT activity. We conclude that type 1 diabetic patients with an impaired epinephrine response to hypoglycemia have lower plasma metanephrine levels than matched controls, reflecting decreased adrenomedullary stores of epinephrine and indicating reduced adrenomedullary capacity to secrete epinephrine.

Adrenal Medulla↗

PubMed2002

Caffeine can decrease insulin sensitivity in humans.

OBJECTIVE: Caffeine is a central stimulant that increases the release of catecholamines. As a component of popular beverages, caffeine is widely used around the world. Its pharmacological effects are predominantly due to adenosine receptor antagonism and include release of catecholamines. We hypothesized that caffeine reduces insulin sensitivity, either due to catecholamines and/or as a result of blocking adenosine-mediated stimulation of peripheral glucose uptake. RESEARCH DESIGN AND METHODS: Hyperinsulinemic-euglycemic glucose clamps were used to assess insulin sensitivity. Caffeine or placebo was administered intravenously to 12 healthy volunteers in a randomized, double-blind, crossover design. Measurements included plasma levels of insulin, catecholamines, free fatty acids (FFAs), and hemodynamic parameters. Insulin sensitivity was calculated as whole-body glucose uptake corrected for the insulin concentration. In a second study, the adenosine reuptake inhibitor dipyridamole was tested using an identical protocol in 10 healthy subjects. RESULTS: Caffeine decreased insulin sensitivity by 15% (P < 0.05 vs. placebo). After caffeine administration, plasma FFAs increased (P < 0.05) and remained higher than during placebo. Plasma epinephrine increased fivefold (P < 0.0005), and smaller increases were recorded in plasma norepinephrine (P < 0.02) and blood pressure (P < 0.001). Dipyridamole did not alter insulin sensitivity and only increased plasma norepinephrine (P < 0.01). CONCLUSIONS: Caffeine can decrease insulin sensitivity in healthy humans, possibly as a result of elevated plasma epinephrine levels. Because dipyridamole did not affect glucose uptake, peripheral adenosine receptor antagonism does not appear to contribute to this effect.

Adult↗