High impact information on OSTN

• The mammalian members are atrial natriuretic peptide, B-type natriuretic peptide, C-type natriuretic peptide, and possibly osteocrin/musclin [1].
• In myocytes, insulin increased, while epinephrine, isoproterenol, and forskolin reduced musclin mRNA, all of which are known to increase the cellular content of cyclic AMP, a counter-regulator to insulin [2].
• Here, we report the identification of a novel secretory factor, musclin, by signal sequence trap of mouse skeletal muscle cDNAs [2].
• Osteocrin, a novel bone-specific secreted protein that modulates the osteoblast phenotype [3].
• Treatment of cultures with 1,25-dihydroxyvitamin D3 resulted in a rapid dose-dependent down-regulation of osteocrin expression, suggesting direct regulation [3].

Biological context of OSTN

• Osteocrin shows no homology with any known gene except for two conserved sequence motifs reminiscent of dibasic cleavage sites found in peptide hormone precursors [3].
• Musclin has been described as a muscle-derived secretory peptide, responsive to insulin in vivo, and inducing insulin resistance in vitro [4].
• Musclin gene expression is strongly related to fast-glycolytic phenotype [4].
• These results demonstrate that Ostn is expressed in human skeletal tissue, particularly in osteoblasts in developing bone and at sites of bone remodeling, suggesting a role in bone formation [5].

Anatomical context of OSTN

• Functionally, recombinant musclin significantly attenuated insulin-stimulated glucose uptake and glycogen synthesis in myocytes [2].
• A single fiber analysis showed that musclin was produced by muscle fibers themselves, almost exclusively type IIb fibers [4].
• In adult bone, Ostn expression was specifically localized to osteoblasts and young osteocytes at bone-forming sites [5].
• Slow to fast transition of soleus phenotype after hindlimb suspension increased musclin mRNA levels, whereas fast to slow transition of plantaris phenotype after functional overload decreased musclin mRNA levels [4].

Associations of OSTN with chemical compounds

• Low-dose estradiol decreased Ostn expression time dependently (p<0.05), whereas Ostn expression in cultures treated with high-dose estradiol was not significantly changed [5].
• The PPARgamma Agonist Troglitazone Induces Musclin mRNA Expression in Human Myotubes [6].

Analytical, diagnostic and therapeutic context of OSTN

• Immunofluorescence and Western blot analysis confirmed the secretory nature of osteocrin [3].

References