Glucocorticoid receptor concentrations in muscle biopsies from patients with neuromuscular diseases

Increases in circulating glucocorticoids promote catabolism, particularly in skeletal muscle. The sensitivity of the muscle to glucocorticoids can be altered by a change in the number of glucocorticoid receptors in the muscle, or by a change in the proportions of activated receptors (between binders IB and II). We have investigated the concentration of glucocorticoid receptors, and the proportions of types IB and II, in healthy and diseased muscle. We found significantly reduced concentrations of glucocorticoid receptors in the group of inflammatory myopathies (51% reduction; P < 0.05, Wilcoxon signed rank test). No significant changes in the relative proportions of binders IB and II were found in pathological muscle, although the proportion of binder IB tended towards elevated values (especially in the diabetic neuropathies, with a 17% increase). We conclude that the sensitivity of muscle to glucocorticoids can be reduced in neuromuscular diseases, especially in myositis, by a reduction in the number of glucocorticoid receptors in the tissue, but that no relevant shift in the relation between activated receptor types is present. This could be important in relation to the risk of a secondary steroid myopathy and catabolism of skeletal muscle in the treatment of inflammatory myopathies with glucocorticoids.