Overload Induced Heat Shock Proteins (HSPs), MAPK and MiRNA (miR-1 and MiR133a) Response in Insulin-resistant Skeletal Muscle

Background: Insulin resistance (IR) may decrease muscle adaptability. Heat shock proteins (HSPs), mitogen-activated protein kinases (MAPKs), and miRNA are thought to play a role in muscle hypertrophy but it is unclear if IR may affect their regulation.

Methods: Soleus muscles of lean Zucker (LZ) and insulin resistant obese Zucker (OZ) rats were overloaded for 7 or 21 days and subjected to immunoblotting and RT-PCR.

Results: IR was associated with decreased muscle hypertrophy. Overload increased HSP27 phosphorylation in both the LZ and OZ rats at day 7 but only in the LZ at day 21. IR was associated with diminished overload induced MAPK phosphorylation and decreased expression of miR-1 and miR133. Overload decreased mir-1 levels in both the LZ and OZ but to a greater extent in the LZ animals.

Conclusion: These results suggest that alterations in the regulation of HSPs, MAPKs and miRNA may be associated with the diminished hypertrophy of IR muscle.