Comment on “Renail failure suppresses muscle irisin expression, and irisin blunts cortical bone loss in mice” by Kawao et al. ‐ the authors' reply

• Published in: Journal of cachexia, sarcopenia and muscle Vol. 14; no. 1; pp. 661 - 662
• Main Authors: Kawao, Naoyuki, Kawaguchi, Miku, Ohira, Takashi, Ehara, Hiroki, Mizukami, Yuya, Takafuji, Yoshimasa, Kaji, Hiroshi
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.02.2023; John Wiley and Sons Inc; Wiley
• Subjects: Animals; Atrophy; Bone and Bones - metabolism; Bone Diseases, Metabolic; Conflicts of interest; Cortical Bone - metabolism; Fibronectins - metabolism; Mice; Muscles - metabolism; Replies; Reply
• ISSN: 2190-5991; 2190-6009
• DOI: 10.1002/jcsm.13135

[...]irisin treatment blunted cortical bone loss induced by renal failure in mice. [...]5/6 Nx induced renal fibrosis and decreased glomerular filtration rate in C57BL/6J mice. 10,11 We therefore believe that C57BL/6 mice could be used as a model to exhibit muscle atrophy and bone loss with the progression of CKD after 5/6 Nx. Kim et al. recently have shown that Nx-induced muscle atrophy was blunted in female C57BL/6J mice (6%–13% reduction), compared with male (18%–24% reduction), suggesting that there might be sex differences of muscle atrophy in C57BL/6J mice after 5/6 Nx. 6 Nonetheless, we showed that 5/6 Nx elevated serum levels of blood urea nitrogen, creatinine and parathyroid hormone in female C57BL/6J mice. 2 Moreover, 5/6 Nx decreased body weight, muscle mass in the whole body and lower limbs assessed by quantitative computed tomography, tissue weights of skeletal muscles and cortical bone mineral density at the femurs in female C57BL/6J mice. 2 Previous studies showed that 5/6 Nx decreased cortical thickness in female C57BL/6J mice, 8,12 which are consistent with our findings. 2 However, 5/6 Nx did not affect expressions of protein degradation-related genes in muscular tissues of female C57BL/6J mice in our study. 2 Although its reason has still remained unclear in our study, Svensson et al. revealed that estradiol suppresses atrogin-1 mRNA level in the gastrocnemius muscles of male C57BL/6J mice. 13 We therefore speculate that oestrogen might affect muscle protein degradation in female mice.