Increased serum angiotensin converting enzyme activity in type T insulin—dependent diabetes mellitus: its relation to metabolic control and diabetic complications

Abstract. Serum angiotensin‐converting enzyme (ACE) was measured in 150 insulin‐dependent diabetes mellitus (IDDM) patients and 72 healthy subjects by radioassay, using [3H]‐hippuryl‐glycyl‐glycine as a substrate. Mean (SD) serum ACE activity in diabetic patients was 120 ± 33 nmol ml−1 min−1 (range 46–215) and was significantly increased by 56% compared to control values (77 ± 23 nmol ml−1 min−1, range 46–125, P < 0·001). ACE activity > 125 nmol ml−1 min−1 was observed in 60 of 150 IDDM patients. 96 IDDM patients were normoalbuminuric (< 22 mg 24 h−1) and 49 patients were micro‐ or macroalbuminuric (range 22–6010 mg 24 h−1). Micro‐ and macroalbuminuric IDDM patients were found to have significantly greater ACE activity values than normoalbuminuric patients (128 ± 36 vs. 115 ± 30 nmol ml−1 min−1, P = 0·025). Metabolically well‐controlled IDDM patients (glycosylated haemoglobin ≤ 8%) had lower ACE activity values than the patients with glycosylated haemoglobin greater than 8% (109 ± 20 vs. 127 ± 32 nmol ml−1 min−1, P < 0·02). A significant correlation between degree of metabolic control and ACE activity was found (r = 0.435, P < 0·001) so that an increase in one glycosylated quartile unit is accompanied by an increase in ACE activity of 10·5 nmol ml−1 min−1. Thus ACE activity in the serum of IDDM patients was increased by 56% in 40% of the patients. It was increased in IDDM patients without complications and in patients with retinopathy or nephropathy. In diabetic patients with nephropathy, ACE activity was greater than in diabetic patients without nephropathy. ACE activity was positively correlated with metabolic control. The role of increased ACE activity in the development of diabetic nephropathy remains to be established.