ABSTRACT
To determine the influence of residual ß-cell function on retinopathy and microalbuminuria we measured basal C-peptide in 50 type 1 diabetic outpatients aged 24.96 + or - 7.14 years, with a duration of diabetes of 9.1 + or - 6.2 years. Forty-three patients (86 percent) with low C-peptide (<0.74 ng/ml) had longer duration of diabetes than 7 patients (14 percent) with high C-peptide (<0.74 ng/ml) (9 (2-34) vs 3 (1-10) years, P = 0.01) and a tendency to high glycated hemoglobin (HBA1) (8.8 (6-17.9) vs 7.7 (6.9-8.7)percent, P = 0.08). Nine patients (18 percent) had microalbuminuria (two out of three overnight urine samples with an albumin excretion rate (AER)> or - 20 and <200 µg/min) and 13 (26 percent) had background retinopathy. No association was found between low C-peptide, microalbuminuria and retinopathy and no difference in basal C-peptide was observed between microalbuminuric and normoalbuminuric patients (0.4 + or - 0.5 vs 0.19 + or - 0.22 ng/ml, P = 0.61) and between patients with or without retinopathy (0.4 + or - 0.6 vs 0.2 + or - 0.3 ng/ml, P = 0.43). Multiple regression analysis showed that duration of diabetes (r = 0.30, r2 = 0.09, P = 0.031) followed by HBA1 (r = 0.41, r2 = 0.17, P = 0.01) influenced basal C-peptide, and this duration of diabetes was the only variable affecting AER (r = 0.40, r2 = 0.16, P = 0.004). In our sample of type 1 diabetic patients residual ß-cell function was not associated with microalbuminuria or retinopathy