VDR and diabetes mellitus: We therefore designed the VALIDATE-D study: an ongoing randomized, double-blinded, placebo-controlled study to assess whether direct VDR activation: Aim 1) lowers circulating RAS activity in human diabetes; Aim 2) lowers renal-vascular tissue-RAS activity in human diabetes; and Aim 3) in combination with ACE inhibition, exerts an additive or synergistic effect on the renal-vascular tissue-RAS and proteinuria.