The Roles of Autophagy in Indoxyl Sulfate-induced Uremic Sarcopenia Emphasize in Cellular Mechanisms

• Main Authors: Ting-wei Mai, 麥庭威
• Other Authors: Chih- Kang Chiang
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/m75xt6

碩士 === 國立臺灣大學 === 毒理學研究所 === 106 === Uremic sarcopenia is a muscle wasting syndrome that often observed in chronic kidney disease (CKD) patients, which is associated with increased mortality. Therefore, developing therapeutic strategy for treating CKD-associated sarcopenia is important. However, the underlying molecular mechanism of CKD-associated sarcopenia is still poorly understood. Our previous study demonstrated that indoxyl sulfate (IS), one of the protein-bound uremic toxins, dysregulates myogenic differentiation. Other studies also showed that IS strongly accelerates skeletal muscle atrophy through oxidative stress-mediated metabolism alteration, which in turn adversely contribute to sarcopenia. It has been demonstrated that IS also induces mitochondria dysfunction in skeletal muscle cells. Currently, physiologic activation of autophagy has been reported in skeletal muscles. However, whether impaired autophagy involved in uremic sarcopenia remains unclear. In this study, we hypothesized that uremic toxins may exert its anti-myogenesis by impaired autophagy. To verify this hypothesis and elucidate the mechanism, we examined the effects of IS on skeletal muscle differentiation in mouse C2C12 myoblast cells with a focus on alterations in autophagic process. The expression of myogenic differentiation markers, autophagy-related markers, mitochondria -related markers were determined by western blotting and quantitative PCR. Our results indicated that IS treatment induces a complete autophagy as demonstrated by LC3 turnover assay. Based on the preliminary data, we further explore whether the IS-induced autophagy interferes the mitophagy, mitochondrial functions and dynamic. We observed that the expression of p62 levels, which is a mitophagy marker, were increased in the mitochondria extracts from IS-treated C2C12 cells, which accompanied with the decrease of the levels of mitochondrial function markers, PGC-1α, TOM70 and dynamic marker, OPA1. In conclusion, the present study indicated that IS exposure might interfere with myoblast differentiation by dysregulation of autophagy. And the exposure of IS might impair the mitochondrial functions and dynamics, which associated with the induction of mitophagy in C2C12 differentiation. However, further experiments are indicated to clarify the molecular mechanisms, which are responsible for IS-induced autophagy and mitophagy.