Angiotensin-converting enzyme (ACE): relationship to insulin-dependent diabetes and microangiopathy

Angiotensin-converting enzyme (ACE) is secreted by the vascular endothelium and serum activity may reflect endothelial damage. A study of 48 insulin-dependent diabetics, 15 with and 33 without evidence of diabetic retinopathy and 41 non-diabetic controls was performed. ACE activity was significantly elevated in the diabetics compared with controls (mean +/- SD 46 +/- 14 vs 35 +/- 9 U/l, p less than 0.001) (units in micromoles substrate converted/min/l serum). This elevation was more marked in diabetics with such evidence of microangiopathy as retinopathy or raised albumin excretion rate (AER) (51 +/- 14 U/l, p less than 0.0001), and also in those with raised AER alone (47.2 +/- 15 U/l, p less than 0.002). Patients with both raised AER and retinopathy had significantly higher ACE activities than those with no complications (53 +/- 15 vs 41.2 +/- 15 U/l, p less than 0.05). No correlation was found with glycosylated haemoglobin or smoking habits. We conclude that mean serum angiotensin converting enzyme activity is increased in insulin-dependent diabetes, particularly in those with evidence of microangiopathy and this may reflect microvascular damage.