INCREASED SERUM ANGIOTENSIN-CONVERTING ENZYME-ACTIVITY IN TYPE-T INSULIN-DEPENDENT DIABETES-MELLITUS - ITS RELATION TO METABOLIC CONTROL AND DIABETIC COMPLICATIONS

Serum angiotensin-converting enzyme (ACE) was measured in 150 insulin- dependent diabetes mellitus (IDDM) patients and 72 healthy subjects by radioassay, using [H-3]-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% compar ed 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 15 0 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 ha ve significantly greater ACE activity values than normoalbuminuric pat ients (128+/-36 vs. 115+/-30 nmol ml(-1) min(-1), P=0.025). Metabolica lly well-controlled IDDM patients (glycosylated haemoglobin less than or equal to 8%) had lower ACE activity values than the patients with g lycosylated haemoglobin greater than 8% (109+/-20 vs. 127+/-32 nmol ml (-1) min(-1), P < 0.02), A significant correlation between degree of m etabolic 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 in crease 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 patie nts. It was increased in IDDM patients without complications and in pa tients with retinopathy or nephropathy. In diabetic patients with neph ropathy, ACE activity was greater than in diabetic patients without ne phropathy. ACE activity was positively correlated with metabolic contr ol. The role of increased ACE activity in the development of diabetic nephropathy remains to be established.