Islet-cell dysfunction induced by glucocorticoid treatment: potential role for altered sympathovagal balance?

Aim. Glucocorticoids impair glucose tolerance by inducing insulin resistance. We investigated the dose-dependent effects of glucocorticoid treatment on islet-cell function in healthy males and studied the role of the autonomic nervous system. Design and Methods. A randomized, placebo-controlled, double-blind, dose-response intervention study was conducted in 32 healthy males (age: 21±2 years; BMI: 21.9±1.7 kg/m2). Participants were allocated to prednisolone 7.5 mg once daily (n=12), prednisolone 30 mg once daily (n=12), or placebo (n=8) for two weeks. Beta-cell function was measured by hyperglycemic clamp with arginine stimulation, glucagon levels were measured following a standardized meal test. Results. We found that prednisolone treatment dose-dependently reduced C-peptide secretion following arginine stimulation on top of hyperglycemia (ASI-iAUCCP): -2.8 (-5.2;0.2) and -3.1 (-8.8; -1.0) nmol L-1 min-1 for prednisolone 7.5 mg and prednisolone 30 mg, respectively (P=0.035 vs. placebo). Fasting glucagon levels increased dose-dependently (vs. placebo; P=0.001), whereas postprandial glucagon levels were only increased by prednisolone 30 mg. Changes in parasympathetic activity related with changes in fasting glucose levels (r=-0.407; P=0.03) and showed a trend towards correlation with fasting glucagon concentrations (r=-0.337; P=0.07). The change in sympathovagal balance was inversely related to ASI-iAUCCP (r=-0.365; P=0.05).