Serum C-Peptide and IRI Levels after Administration of Glucagon and Glucose in Non-Insulin-Dependent Diabetics

Abstract

A comparative study was carried out on B cell response to alternative intravenous glucagon (1.0 mg) and intravenous glucose (0.33 g per kg body weight) in healthy non-obese persons (C-NOb), healthy obese persons (C-Ob), non-obese non-insulin-dependent diabetics (NIDD-NOb) and obese non-insulin-dependent diabetics (NIDD-Ob). Each group comprised ten subjects. C-peptide (CP immunoassay using antiserum M 1230) and IRI in the serum were measured for each person fasting and over 30 min throughout each test. After glucose load the B-cell responses were significantly lower in both the diabetic groups than in the normal groups. After glucagon injection there were no significant differences in IRI and CP levels between NIDD-NOb and C-NOb, however, significantly lower levels of serum CP were noted among NIDD-Ob in comparison to C-Ob with a lack of these differences in IRI levels. This phenomenon is well reflected by the molar IRI/CP ratio expressed as a percentage. In the fasting state IRI accounted in C-Ob for 8.8 ± 3.5 per cent of CP, while in NIDD-Ob for up to 25.5 ± 10.4 percent of CP (p = 0.0004). In the latter group of patients, the IRI/CP ratio after glucagon reached the highest values (over 30 per cent) observed in this study. These data suggest the important role in insulin disposal played by the liver in non-insulin-dependent diabetes associated with obesity. Another explanation for these data is that more proinsulin is secreted in this group of patients as compared to other groups.