In a cross-sectional single-centre study we evaluated the levels of circulating serum soluble Klotho in 33 participants with type 1 diabetes and a history of microalbuminuria (receiving renin–angiotensin system [RAS] inhibitors) and 45 participants with type 1 diabetes without a history of microalbuminuria (not receiving RAS or other antihypertensive drugs). The gene discussed is REN; the disease is type 1 diabetes mellitus.