Gene Expression of Muscle-Specific Ubiquitin Ligase, Atrogin-1/MAFbx, Positively Correlates with Skeletal Muscle Proteolysis in Food-Deprived Broiler Chickens

Abstract

A relationship between skeletal muscle proteolysis and mRNA expression of atrogin-/MAFbx, a muscle-specific ubiquitin ligase, was examined in food-deprived broiler chickens. In response to food deprivation for and h, body and muscle weights decreased in a time-dependent manner. Muscle free N -methylhistidine content, an index of myofibrillar proteolysis, was . -fold and . -fold greater than that of fed controls following and h of food deprivation, respectively. Gene expression of atrogin-/MAFbx drastically increased in response to food deprivation in a time-dependent manner. At h of food deprivation, the induction of atrogin-/MAFbx mRNA expression level elevated up to -fold greater than that of fed controls. By contrast, mRNA expression levels of S proteasome C and C subunits tended to decrease with time. No significant di erence was seen in the change of ubiquitin mRNA expression. A highly significant linear negative relationship (r . , . ) was found between atrogin-/MAFbx expression and muscle mass, while a highly significant linear positive relationship (r . , . ) was found between atrogin-/MAFbx expression and muscle free N -methylhistidine content. These results indicate that atrogin-/MAFbx plays a critical role in the development of muscle proteolysis and its gene expression is a reliable index of muscle proteolysis in broiler chickens.: atrogin-/MAFbx, broiler chicken, food deprivation, myofibrillar proteolysis, skeletal muscle mass an increase in the overall rate of muscle protein breakdown leading to a rapid loss of muscle mass and myoSkeletal muscle mass is determined by the di erence fibrillar protein (Jagoe ). Enhancement of between the amount of protein synthesized and the overall proteolysis in atrophying muscles results mainly amount of protein degraded (Waterlow ). If from a general activation of the ubiquitin-proteasome the balance between synthesis and degradation changes pathway (UPP) (Lecker ). Among the UPP into catabolic state, muscle protein content decreases, components, atrogin-/MAFbx, a muscle-specific ubiqresulting in less muscle mass or muscle wasting (Mayer uitin ligase, plays a key role in the initiation and develop-) a cause of decreased productivity in broiler ment of muscle atrophy (Bodine ; Gomes farms. E orts are needed to prevent the loss of accu-). The atrogin-/MAFbx gene is rapidly induced mulated muscle protein as well as to increase the amount early on during the atrophy process, and a rise in its of muscle protein for the broiler production industry.expression precedes the loss of muscle weight (Gomes Muscle protein serves as a primary reserve of amino ). Atrogin-/MAFbx mRNA has been shown to acids that can be mobilized upon fasting and disease to linearly and positively correlate with the overall rate of provide a source of amino acids for hepatic gluconeprotein breakdown, as measured by the release of radioogenesis and energy production (Mitch and Goldberg, labeled tyrosine in glucocorticoid-treated C C myotube ). An important physiological adaptation to fasting is cell...

The IGF-1/Akt/S6 Signaling Pathway is Age-Dependently Downregulated in the Chicken Breast Muscle

“…We previously showed that myostatin expression was significantly suppressed by fasting in chickens, whereas atrogin-1 expression was significantly induced (Saneyasu et al, 2015). Similar results were reported concerning myostatin (Guernec et al, 2004) and atrogin-1 (Ohtsuka et al, 2011) in broiler chickens. It is therefore possible that myostatin is not involved in the upregulation of atrogin-1 expression in the chicken skeletal muscle.…”

Effects of Insulin-Like Growth Factor-I on the Expression of Atrogin-1/MAFbx in Chick Myotube Cultures

“…Atrogin-1/MAFbx plays a critical role in muscle proteolysis, and the level of atrogin-1/MAFbx gene expression is a reliable index of muscle proteolysis in chicken (Ohtsuka et al, 2011). Although it is well known that IGF-I have a regulatory effect on the expression of atrogin-1/MAFbx in mammalian skeletal muscle, its effect in chicken muscle cells is largely unknown.…”

<i>In vivo </i>Administration of β₂-agonist Clenbuterol and Subsequent Increase in Skeletal Muscle Mass in Neonatal Chicks

“…These observations suggested that clenbuterol might affect either proteolysis in skeletal muscle or expression of atrogin-1/MAFbx. In addition, Ohtsuka et al (2011) reported that gene expression of atrogin-1/MAFbx positively correlates with skeletal muscle proteolysis in chickens, hence it is possible that a single administration of clenbuterol to neonatal chicks resulted in the increase in the weight of skeletal muscle by decrease in atrogin-1 mRNA expression. Further studies are needed to gain more information about the molecular mechanisms underlie that hypertrophic effects of clenbuterol on skeletal muscle of neonatal chicks.…”

“…In addition, Navegantes et al (2001) reported that clenbuterol treatment decreases proteolysis in the skeletal muscle of rats. In chicken, gene expression of atrogin-1/MAFbx positively correlates with skeletal muscle proteolysis (Ohtsuka et al, 2011). Therefore, we also examined gene expression of atrogin-1/MAF box as a representative of proteolysis related proteins in skeletal muscle of chicks.…”