Exercise performance is not improved in mice with skeletal muscle deletion of natriuretic peptide clearance receptor

Natriuretic peptides (NP), including atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP), play essential roles in regulating blood pressure, cardiovascular homeostasis, and systemic metabolism. One of the major metabolic effects of NP is manifested by their capacity to stimulate lipolysis and the thermogenesis gene program in adipocytes, however, their metabolic effect on skeletal muscle is much less appreciated. There are three NP receptors (NPR): NPRA, NPRB, and NPRC, and all three NPR genes are expressed in C2C12 myocytes. Treatment with either ANP, BNP, or CNP evokes the cGMP signaling process in C2C12 myocytes. We then generated a genetic model with Nprc gene deletion in skeletal muscle and tested whether enhancing NP signaling by preventing its clearance in skeletal muscle would improve exercise performance in mice. Under sedentary conditions, Nprc skeletal muscle knockout (MKO) mice showed comparable exercise performance to their floxed littermates in terms of maximal running velocity and total endurance running time. Eight weeks of voluntary running-wheel training in a young cohort increased exercise performance, but no significant differences were observed in MKO compared with control mice. Furthermore, 6-weeks of treadmill training in a relatively aged cohort also increased exercise performance compared with their baseline but did not result in an improvement in MKO mice compared with the controls. In summary, our study suggests that NP signaling is potentially important in myocytes but its function in skeletal muscle in vivo needs to be further studied in alternative physiological conditions or with new genetic mouse models.