REN and diabetes mellitus: Because they reportedly protect renal function,5 renin–angiotensin system (RAS) inhibitors, such as angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARB), are recommended as first-line antihypertensive therapy for DM.6, 7 However, BP control using monotherapy is often difficult in patients with DM; treatment with multiple drugs with different mechanisms for BP reduction is necessary.8