PROINSULIN LEVELS IN NEWBORN SIBLINGS OF TYPE-1 (INSULIN-DEPENDENT) DIABETIC CHILDREN AND THEIR MOTHERS

Elevated proinsulin levels have been observed in healthy first degree relatives of Type 1 (insulin-dependent) diabetic patients. This elevat ion could reflect a sequele after a previous attack on the beta-cells not necessarily leading to diabetes, or represent a family trait relat ed to the development of diabetes. When cord plasma levels of proinsul in, insulin and C-peptide from 14 newborn siblings of Type 1 diabetic patients were compared with 21 newborn control siblings unrelated to d iabetic subjects, no differences were observed. Neither were any diffe rences observed between their mothers at delivery when comparing the s ame parameters. In cord plasma the proinsulin levels (median and range ) were higher than those in plasma from 35 adult fasting women unrelat ed to diabetic subjects (10, 5-83 pmol/l vs 4, 2-33 pmol/l; p < 0.001) whereas the C-peptide levels (median and range) were lower (0.20, 0.1 1-0.56 nmol/l vs 0.37, 0.21-0.69 nmol/l; p < 0.001). No differences in insulin levels using a highly specific insulin assay were observed. T he results suggest that newborn children have high proinsulin and low C-peptide levels unrelated to heredity of diabetes and that the previo usly described elevated proinsulin level observed in older first degre e relatives of diabetic subjects occurs later in life.