Endocrine Abstracts

Introduction: Chronic kidney disease (CKD) is characterised by an ongoing reduction in kidney function and is associated with comorbidities such as muscle wasting that greatly increase mortality. Both acidosis and elevated glucocorticoids levels are hallmarks of CKD and implicated as having a synergistic role in driving muscle wasting. We investigated the synergistic effects of acidosis and the glucocorticoid cortisol on muscle metabolism and fibre size using primary human muscle culture.

Methods: Primary human muscle cells from a single osteoarthritic donor were collected after surgery and exposed to a pH of 7.1 or 7.4 in combination with cortisol (100 or 1000 nmol/l) for 48h. 3H-tyrosine assays were utilised to determine protein synthesis and degradation. Histological analyses of primary muscle culture diameter were determined using ImageJ software and genes regulating muscle metabolism were assessed by quantitative RT-PCR.

Results: In primary muscle culture, no changes in protein synthesis or protein degradation were evident when cells were exposed to pH7.1 or cortisol (100-1000nmol/l) alone. In contrast, the combination of pH 7.1 and cortisol at 1000 nmol/l significantly reduced protein synthesis (21.2%, P=0.0321) and increased protein degradation (13.34%, P=0.0066). These changes were matched by a significant decrease in muscle fibre diameter in vitro after exposure to pH7.1 and cortisol at 100 nmol/l (13%, P<0001), but not with individual interventions. RT-PCR analysis indicated a trend towards an increase in the catabolic FOXO-1 and TRIM63 genes in response to acidosis and cortisol.

Conclusion: This data reveal for the first time in primary human muscle cultures, that the combination of glucocorticoids and acidosis possess an increased capacity to induce muscle wasting than either factor independently. This study will inform future strategies aiming to prevent muscle wasting in CKD.