Biochemical and Biophysical Research Communications
Musclin gene expression is strongly related to fast-glycolytic phenotype
Section snippets
Methods
Animals. Experiments were carried out in accordance with the Helsinki Accords for Human Treatment of Animals during Experimentation. Wistar rats were housed with free access to food and water. Animals were studied at rest (control experiment) or after either mechanical unloading or overload. For the unloading protocol, we used the tail-suspension model, a valid model of removal of weight-bearing activity of soleus muscle [13]. Rats were hindlimb suspended for 3 weeks and then sacrificed. The
Whole muscle musclin mRNA in control animals
In soleus muscles, musclin mRNA levels were only detectable as traces. In contrast, musclin mRNA levels were markedly higher in plantaris and at a 2.2-fold higher level in gastrocnemius muscles than in plantaris (P < 0.01) (Fig. 1).
Musclin mRNA levels within single pure fibers
Musclin mRNA levels were only examined in pure fiber types, those expressing only one MHC isoform at the protein level (about 40% of all isolated single fibers). As shown in Fig. 2, musclin mRNA expression was highly fiber-type specific (main effect P < 0.001). Musclin
Discussion
The control of musclin expression as well as the exact function of this new muscle-derived factor remain largely unknown. The present study has investigated the fiber-type specificity of musclin expression and whether its transcription is coordinated with phenotypic changes. Results show that (1) musclin mRNA is almost undetectable in the slow-twitch soleus muscle whereas high levels are found in the fast-twitch plantaris and white gastrocnemius muscles, (2) musclin is produced by muscle cells
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2021, Handbook of Hormones: Comparative Endocrinology for Basic and Clinical ResearchSkeletal muscle as a protagonist in the pregnancy metabolic syndrome
2019, Medical HypothesesCitation Excerpt :High insulin activates AKT, which in turn phosphorylates FoxO1, producing a de-repression of the musclin gene, then linking the excess of insulin, typical of a state of IR, to a higher production of musclin, favoring a vicious circle that further generates more IR [81,128]. As expected if it were a myokine related to IR, it is upregulated by palmitate in myocytes [129] and is expressed predominantly in fast-glycolytic fibers [130], which are predominant in obese and diabetic patients [107] and have a kind of unhealthy phenotype, as shown before. Musclin is increased in murine models fed with a high-fat diet [131,132,133], but is reduced in serum and SKM after exercise [131].
Regulation of myokine expression: Role of exercise and cellular stress
2016, Free Radical Biology and MedicineCitation Excerpt :Over ten years ago, musclin (also termed osteocrin) has first been described as a factor secreted from skeletal muscle whose expression is tightly regulated by nutritional changes [158]. It is produced in myocytes in a highly fiber-type specific manner with almost exclusive expression in fast-glycolytic type IIb fibers [159]. Musclin was reported to be involved in insulin resistance [160] and hypertension [161] and thus seems to exert non-beneficial metabolic effects.
Loss of ovarian function in mice results in abrogated skeletal muscle PPARδ and FoxO1-mediated gene expression
2010, Biochemical and Biophysical Research CommunicationsCitation Excerpt :These changes are consistent with a fiber type shift, as myogenin specifically promotes the development of type I oxidative fibers [8], while myoD promotes the development of type II glycolytic fibers [9]. Finally, the expression of musclin, which is negatively regulated by FoxO1 [10] and made exclusively by type II fibers [11], was increased 1.6-fold (p < 0.05) in muscle from OVX mice. These data, presented in Fig. 1, collectively suggest that OVX in mice results in a fiber type switch toward a less type I oxidative muscle.