Plasma angiotensin II, renin activity and serum angiotensin-converting enzyme activity in non-insulin dependent diabetes mellitus patients with diabetic nephropathy

The renin-angiotensin system (RAS) has been unequivocally implicated as a mediator of diabetic complications. The present study was designed to evaluate the RAS in non-insulin dependent diabetic patients with diabetic nephropathy. Plasma renin activity, plasma angiotensin II and serum angiotensin-converting enzyme (ACE) activity were measured in 45 non-insulin dependent diabetes mellitus (NIDDM) patients and 15 healthy non-diabetic controls. Diabetics were subdivided into 15 normoalbuminuric NIDDM subjects, 15 NIDDM patients with microalbuminuria and 15 diabetics with macroalbuminuria. Mean plasma renin activity for macroalbuminuric diabetics (0.65+/-0.10 ng/ml/hr) was significantly reduced than the controls (1.28+/-0.37 ng/ml/hr) (P < 0.001), the diabetic group with microalbuminuria (1.08+/-0.48 ng/ml/hr) (P < 0.05) and normoalbuminuric patients (1.56 +/- 0.82 ng/ml/hr) (P < 0.001). A significant negative correlation was obtained between serum creatinine and plasma renin activity (r = -0.842, p < 0.001) in macroalbuminuric NIDDM patients. Plasma angiotensin II was significantly decreased in non-complicated diabetics compared to healthy controls (4.36 +/- 1.49 pg/ml vs 14.87 +/- 3.48 pg/ml respectively, p<0.001). Non-insulin dependent diabetic patients with nephropathy had significantly higher plasma angiotensin II levels (28.99 +/- 5.88 pg/ml) than non-complicated diabetics (p < 0.001). Serum ACE activity was increased in 53.3% of NIDDM patients. All diabetic groups showed increased serum ACE activity (normoalbuminuric NIDDM 114.9+/-28.3 nmol/min/ml, microalbuminuric NIDDM 127.9+/-31.2 nmol/min/ml and macroalbuminuric NIDDM 127.0+/-29.3 nmol/min/ml) when compared to the normal control group (76.3 +/- 16.5 nmol/min/ml) (p<0.001). No significant difference in serum ACE activity was obtained between normoalbuminuric and nephropathic diabetics or between diabetics with and without retinopathy. No significant correlation was obtained between serum ACE activity and blood pressure, blood glucose level and duration of diabetes. Thus plasma renin activity is decreased in diabetic nephropathy and negatively correlates with serum creatinine. Plasma angiotensin II is decreased in normoalbuminuric diabetics and elevated in diabetic nephropathy. Serum ACE activity is raised in NIDDM patients with no relation to albumin excretion rate. The role of increased ACE activity in NIDDM remains to be established.