MALAT1 and diabetes mellitus: Importantly, HCN downregulation was reported also in pacemaker cells [20], in sinoatrial node [20] and whole cardiac conduction system [40] of rats with type 1 diabetes mellitus induced by STZ manifesting in lower intrinsic heart rate, a lengthened sinoatrial conduction time and rate-corrected maximal sinoatrial node recovery time in vivo as well as a longer cycle length in vitro [20].