Diurnal profiles of serum insulin, C-peptide and blood intermediary metabolites in insulin treated diabetics, their relationship to the control of diabetes and the role of endogenous insulin secretion.

The 24-hour profiles of blood metabolites, serum free and total insulin, and C-peptide were measured in 16 insulin dependent diabetics, and then analysed in order to compare the effects of the presence or absence of residual endogenous insulin secretion and the presence of good or bad diabetic control as judged by the levels of blood glucose or total ketone bodies. Retention of endogenous insulin secretion, responsive to meals, and changes in the level of blood glucose and serum free insulin, were detected in nine patients, its presence having important effects in maintaining metabolic regulation closer towards normal. Despite the fact that apparently well controlled diabetics were selected for the study, the diurnal changes of the levels of blood metabolites, serum free and total insulin and their interrelationships were all grossly abnormal. The levels of both the blood total ketone bodies and the blood glucose were found to be a poor guide to the presence or absence of other metabolic abnormalities of diabetes. High levels of blood total ketone bodies appeared to have a protein sparing effect.