Increased Serum Soluble (Pro)renin Receptor Levels in Patients with Sarcopenia

Abstract

Purpose. Sarcopenia is an advancing and widespread skeletal muscle condition characterized by the depletion of skeletal muscle mass. The (pro)renin receptor ((P)RR) is a multifaceted protein with both pathophysiological and physiological functions. (P)RR is cleaved to generate soluble (P)RR, whose blood concentration may reflect the expression level of tissue (P)RR. We have discovered that the expression of (P)RR was elevated in the atrophied skeletal muscles of aged mice and humans. Methods. In this study, we examined the correlation between muscle atrophy and serum soluble (P)RR levels in bedridden patients with sarcopenia. Results. In total, 45 subjects were enrolled. Their ages were 81 (59–89) y.o., and serum soluble (P)RR levels were 30.5 ± 7.3 ng/ml. Lean body mass ratio (lean body mass/body weight), an index of muscle mass, was independently significantly and negatively correlated with serum soluble (P)RR concentrations in all patients. In addition, the lean body mass ratio was independently significantly and negatively correlated with serum soluble (P)RR concentrations in older patients (≥82 y.o.) but not in younger patients (<82 y.o.). Conclusion. These data suggested that patients with sarcopenia, especially in elderly patients, may be associated with increased (P)RR expression. The serum soluble (P)RR level could be a biomarker of sarcopenia although this issue should be investigated by future studies.