Abstract
The clinical insulin requirement of diabetic patients changes after they develop renal dysfunction or start hemodialysis (HD). Therefore, an index of endogenous insulin secretion for such patients is needed in the management.
Plasma C-peptide immunoreactivity (CPR) is a likely laboratory index, but it has not been clinically useful for patients with chronic renal failure, because degradation of C-peptide is much impaired and modulated in these patients.
However retention of C-peptide is almost the same in the final stage of renal failure because there is no more urinary excretion of C-peptide: Thus the plasma level of CPR may depend on the degree of insulin secretion in HD patients.
To evaluate the usefulness of plasma CPR measurement in patients with diabetes mellitus (DM) under HD, we selected 46 patients and divided them into three groups for this study. Group A consisted of six patients with insulin-dependent DM, group B 18 patients with non-insulin-dependent DM, and group C 22 non-DM patients. All subjects were undergoing regular HD.
The mean fasting plasma CPR level in group A was significantly lower than that in the other groups (p<0.001). Also, this level in group B was significantly lower than that in group C (p<0.01). When plasma CPR was measured during the 50g oral glucose tolerance test, the mean plasma CPR rose significantly in group C (p<0.01), but not in the other groups. The mean plasma CPR was lower after glucose loading in the patients in group B who were treated with insulin than in those in the same group who were not treated with insulin. There was negative correlation between insulin requirement and the fasting plasma CPR level in the patients treated with insulin (r=-0.63, p<0.05).
The level of fasting plasma CPR was correlated to the endogenous insulin secretion in our subjects with DM who were on HD. These results suggest that the plasma level of CPR is a clinically useful index of insulin secretion in such patients.
