Abstract
The recently identified adipocytokine omentin was previously found to be expressed mainly in human omental and visceral adipose tissues. As such, reduced plasma concentrations of omentin were revealed to be associated with increased risks of cardiovascular diseases. Omentin has also been previously demonstrated to exert anti-inflammatory effects. By contrast, resistin is a protein that has been associated with obesity and type-2 diabetes mellitus, and the serum concentration of resistin is increased significantly in these populations. Resistin is involved in mediating inflammation development, where they can promote cardiac hypertrophy in humans through toll-like receptor 4 (TLR4)-related signaling. In the present study, the potential effects of omentin on resistin-induced hypertrophy in H9c2 cardiomyoblasts were investigated. In the absence/presence of omentin, H9c2 cardiomyoblasts were treated with resistin. Omentin was found to significantly inhibit resistin-induced increases in the surface area of H9c2 cardiomyoblasts as determined by immunofluorescence. In addition, omentin significantly inhibited resistin-induced increases in the mRNA expression of atrial natriuretic factor, brain natriuretic peptide, β-myosin heavy chain (which is a characteristic feature of cardiac hypertrophy) and TLR4, which was determined using reverse-transcription-quantitative PCR. According to western blotting results, omentin significantly inhibited resistin-induced ERK phosphorylation, which is an important mediator of cardiomyoblast hypertrophy. Furthermore, omentin significantly inhibited resistin-induced protein expression of TLR4, myeloid differentiation factor 88 (MyD88) and NF-κB phosphorylation, both of which are important members of inflammatory signaling. To conclude, data from the present study suggest that omentin can inhibit resistin-induced H9c2 cardiomyoblast hypertrophy through inhibition of the TLR4/MyD88/NF-κB signaling pathway. Therefore, omentin serve as an attractive therapeutic target against resistin-induced cardiac hypertrophy.