ACE and kidney disorder: Plasma AOPP concentration was lower in participants without nephropathy (60±3 μmol/l, n = 131), intermediate in participants with incipient nephropathy (64±4 μmol/l, n = 83) and higher in participants with established/advanced nephropathy (70±3 μmol/l, n = 167, p = 0.03, mean ± SEM, ANCOVA adjusted for sex, age, HbA1c levels and use of ACE inhibitors).