KLK4 and diabetic kidney disease: Plasma kallikrein activity decreased with more advanced stages of diabetic nephropathy: normoalbuminuria (median 2.53, [IQR 1.37–4.23]; n = 165), microalbuminuria (2.04 [1.23–3.40]; n = 41), macroalbuminuria (1.31 [0.91–2.81]; n = 37), and ESRD (1.23 [0.66–1.72]; n = 52; p < 0.001) (Fig. 1a).