An ethanolic extract of Artemisia dracunculus L. regulates gene expression of ubiquitin-proteasome system enzymes in skeletal muscle: Potential role in the treatment of sarcopenic obesity
Heather Kirk-Ballard Nutrition Available online 14 March 2014
Obesity is linked to insulin resistance, a primary component of metabolic syndrome and type 2 diabetes. The problem of obesity-related insulin resistance is compounded when age-related skeletal muscle loss, called sarcopenia, occurs with obesity. Skeletal muscle loss results from elevated levels of protein degradation and prevention of obesity-related sarcopenic muscle loss will depend on strategies that target pathways involved in protein degradation. An extract from Artemisia dracunculus, termed PMI5011 improves insulin signaling and increases skeletal muscle myofiber size in a rodent model of obesity-related insulin resistance. This study examines the effect of PMI5011 on the ubiquitin-proteasome system, a central regulator of muscle protein degradation.
Materials and Methods
Gastrocnemius and vastus lateralis skeletal muscle was obtained from KK-Ay obese diabetic mice fed a control or 1% (w/w) PMI5011-supplemented diet. Regulation of genes encoding enzymes of the ubiquitin-proteasome system was determined using realtime qRT-PCR.
While MuRF-1 ubiquitin ligase gene expression is consistently down-regulated in skeletal muscle, atrogin-1, Fbxo40 and Traf6 expression is differentially regulated by PMI5011. Genes encoding other enzymes of the ubiquitin-proteasome system ranging from ubiquitin to ubiquitin-specific proteases are also regulated by PMI5011. In addition, expression of the gene encoding the microtubule-associated protein-1 light chain 3 (LC3), a ubiquitin-like protein pivotal to autophagy-mediated protein degradation, is down-regulated by PMI5011 in the vastus lateralis.
PMI5011 alters the gene expression of ubiquitin-proteasome system enzymes that are essential regulators of skeletal muscle mass. This suggests PMI5011 has therapeutic potential in the treatment of obesity-linked sarcopenia by regulating ubiquitin-proteasome-mediated protein degradation.
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