Uraemic toxins impair skeletal muscle regeneration by inhibiting myoblast proliferation, reducing myogenic differentiation, and promoting muscular fibrosis

Abstract

Uraemic toxins increase in serum parallel to a decline in the glomerular filtration rate and the development of sarcopenia in patients with chronic kidney disease (CKD). This study analyses the role of uraemic toxins in sarcopenia at different stages of CKD, evaluating changes in the muscular regeneration process. Cultured C2C12 cells were incubated with a combination of indoxyl sulphate and p-cresol at high doses (100 µg/mL) or low doses (25 µg/mL and 10 µg/mL) resembling late or early CKD stages, respectively. Cell proliferation (analysed by scratch assays and flow cytometry) was inhibited only by high doses of uraemic toxins, which inactivated the cdc2-cyclin B complex, inhibiting mitosis and inducing apoptosis (analysed by annexin V staining). By contrast, low doses of uraemic toxins did not affect proliferation, but reduced myogenic differentiation, primed with 2% horse serum, by inhibiting myogenin expression and promoting fibro-adipogenic differentiation. Finally, to assess the in vivo relevance of these results, studies were performed in gastrocnemii from uraemic rats, which showed higher collagen expression and lower myosin heavy chain expression than those from healthy rats. In conclusion, uraemic toxins impair the skeletal muscular regeneration process, even at low concentrations, suggesting that sarcopenia can progress from the early stages of CKD.

Prevalence of Sarcopenia and Its Impact on Cardiovascular Events and Mortality among Dialysis Patients: A Systematic Review and Meta-Analysis

“…Alcalde-Estévez. et al [ 70 ] showed that PBUTs (combination of indoxyl sulphate and p-cresol) impaired the skeletal muscular regeneration process by inhibiting myoblast proliferation, reducing myogenic differentiation, and promoting muscular fibrosis, even at low concentrations, in a uremic rat model. From all the above factors including limited physical activity, the assessment timing, HD-related factors, and less-preserved RKF, the higher prevalence of muscle wasting and weakness in HD patients compared with PD patients was illustrated in our study ( Table 5 ).…”

Indoxyl sulfate- and P-cresol-induced monocyte adhesion and migration is mediated by integrin-linked kinase-dependent podosome formation

“…pc, pCS and IS all significantly elevate miR-421 levels and decrease ACE2 transcript levels in THP-1 monocytes, which may contribute to the low expression of the enzyme in leukocytes of CKD patients and to the development of atherosclerotic events 50 . Both IS plus pc and IS plus pCS impair skeletal muscle regeneration by reducing myoblast proliferation and preventing chromosome condensation 31 . Moreover, we and others have found similar effects with pooled uremic serum from CKD patients, stimulated endothelial cells and cells exposed to IS plus pc, which induced loss of human endothelial barrier function 51 , decreased cell proliferation, and increased apoptosis and ROS production 24 .…”

“…The uremic toxins pc, IS, and pCS were tested at concentrations in the uremic range as previously described 24 , 31 . Briefly, pc was prepared in methanol at a stock concentration of 100 mg ml −1 , and IS and pCS were prepared in water at a stock concentration of 12.5 mg ml −1 .…”

Muscle fibrosis and maladaptation occur progressively in CKD and are rescued by dialysis

“…Although dialysis does not restore a “youthful” milieu, it clears from the systemic circulation a number of potentially toxic solutes that accumulate due to kidney failure ( 65 ), likely beginning early in CKD ( 66 , 67 ). For example, certain uremic toxins — which accumulate systemically with decreased GFR — impair myogenic progenitor proliferation and differentiation ( 68 ), blunting muscle regenerative capacity. Removal of these and other toxins by dialysis treatment may mediate a restoration of satellite cell activity and result in the rescued satellite cell abundance we observed in subjects with CKD upon initiation of dialysis, supporting restoration of muscle regeneration and a healthier skeletal muscle phenotype.…”