PDE5A and diabetes mellitus: The NO–sGC–cGMP–PKG signalling pathway has been described to get disturbed in DM through several mechanisms, such as increased formation of reactive nitrogen (RNS) and oxygen species (ROS) (nitro-oxidative stress), eNOS uncoupling and decreased NO bioavailability, increased expression of the cGMP-degrading enzyme phosphodiesterase (PDE)-5 [1].