HDAC4 and cardiac hypertrophy: Following ISO administration in the ISO group, the heart weight index and left ventricle weight index increased significantly as an indication of cardiac hypertrophy, which might be caused by increased water and protein content, edematous intramuscular space, necrosis of cardiac muscle fibers, and activation of Calcium/calmodulin-dependent protein kinase II/ histone deacetylase 4 (CamKII/HDAC4) pathway [56,61,62].