The KID Study V: the natural history of type 2 diabetes in younger patients still practising a profession. Heterogeneity of basal and reactive C-peptide levels in relation to BMI, duration of disease, age and HbA1

In a detailed evaluation of the data accumulated for 493 type 2 diabetics who participated in the KID Study, pre- and postprandial C-peptide was correlated with blood glucose level, HbA1, body mass index (BMI), duration of disease and age. As described earlier the KID-Study examined a younger cohort of type 2 diabetics predominately practising a profession. Our investigations demonstrate a significant increase of pre- as well as postprandial C-peptide levels with increasing obesity. However, delta C-peptide, as an indicator at the reaction capacity of pancreatic secretion, decreases significantly and continuously. Pre- as well as postprandial C-peptide levels decrease significantly with up to 15-20 years duration of disease. The preprandial pancreatic secretion is usually even at a high normal level at such a late stage whereas the secretory reserve of normal or mildly overweight as well as of obese type 2 diabetics is more impaired. In contrast to patients with a BMI 30 will also develop impairment of basal insulin secretion over decades. The patient's age did not influence the pre- or postprandial insulin secretion. The quality of metabolic control as measured by the HbA1 has nearly exclusive impact on the secretory reserve capacity. Correlation with increasing HbA1 concentrations, the postprandial but not the preprandial C-peptide levels decreased significantly and continuously. Predictive factors for a deterioration in pancreatic function are in order of importance: the extent of obesity, the quality of metabolic control and only last the duration of diabetes. Fortunately, consistent diabetic care can have an impact on the first two.