Abstract
In order to investigate the pancreatic β-cell function in insulin-treated diabetics and in a patient with insulin-autoimmune disease in whom a direct measurement of IRI is impossible because of the presence of an insulin antibody in their sera, the concentration of CPR (C-peptide immunor-eactivity) was determined during the oral glucose tolerance test in 40 insulin-treated diabetics (D2 & D3) and the patient with insulin-autoimmune disease (I. A.). These results were compared with those of 6 normal subjects (N), 4 obese patients (O) and 10 newly diagnosed diabetics (D1).
According to the reactivity of their β-cell to glucose the patients treated with insulin were divided into two groups: 32 responder (D2) and 8 non-responder (D3). The mean fasting and peak levels of CPR in these groups are as follows:
N: 1.37 ± 0.77 and 5.05 ± 1.09 mμg/ml,
O: 5.04 ± 1.11 and 13.2 ± 4.88 mμg/ml,
D1: 3.75 ± 0.79 and 10.2 ± 3.58 mμg/ml,
D2: 2.92 ± 1.58 and 5.33 ± 2.86 mμg/ml,
D3: 0.77 ± 0.53 mμg/ml and no noticeable peak,
I. A.: 38.0 and 49.6 mμg/ml.
The CPR values obtained from N, O and D1 during OGTT were positively correlated with immunoreactive insulin levels. When the sera of high CPR values containing insulin antibodies were acidified and gel-filtered it was revealed that a main component of CPR was proinsulin. In 10 insulin-treated juvenile diabetics only 4 patients were non-responders. Residual β-cell secretory capacity is thus present in many insulin-treated juvenile diabetics.
The relationship between residual β-cell secretory capacity and the metabolic stability of diabetic patients is discussed.
