Insulin and C-peptide response in healthy persons and individuals with impaired glucose metabolism during oral glucose tolerance test

The change in the circulating insulin-like growth factor binding protein 1 isoform pattern during the course of oral glucose tolerance test

There is a tight connection between insulin-like growth factor binding protein 1 (IGFBP-1) and nutrient/energy supply, suggesting modulation of the short-term insulin-like activity and glucose homeostasis by IGFBP-1. Differential phosphorylation of IGFBP-1 alters its affinity for insulin-like growth factors (IGFs) and its capacity to modulate cellular response. The object of this study was to define the time course of changes in the IGFBP-1 isoform pattern during an oral glucose tolerance test. Besides changing in counterdirections, the alterations in glucose/insulin/C-peptide and IGF-I/IGFBP-1 concentrations were phase-shifted. Denaturing electrophoresis revealed that the IGFBP-1 proteolytic activity was not increased after glucose ingestion. In native electrophoresis, the isoform that moved most anodically, with the greatest phosphate content, was markedly reduced during the course of oral glucose tolerance test; and it disappeared after 3 hours. Our data show that both a change in the total amount of IGFBP-1 and an alteration in the relative amount (ratio) of the specific phosphoforms of IGFBP-1 are part of the mechanism involved in modulation of the insulin-like activity.

Insulin-like growth factor I (IGF-I) as a sensitive biomarker of catabolism in patients with gastrointestinal diseases

Gastrointestinal ailments evoke changes in the hypothalamic-pituitary-adrenal (HPA) axis and modulation of hepatic protein synthesis. We examined the catabolic effect of certain primary gastrointestinal diseases and surgery on the concentration of insulin-like growth factor I (IGF-I). Blood samples from patients with gastric cancer (GC), cholecystitis (CC), or inguinal hernia (IH) were taken before and after surgery. The concentrations of IGF-I, IGF binding protein-1 (IGFBP-1), insulin, cortisol, and glucose were determined. In GC patients the concentration of IGF-I was reduced and the concentrations of IGFBP-1 and cortisol were elevated preoperatively; after surgery, IGFBP-1 normalized. In CC patients the concentration of IGF-I was low and the concentration of IGFBP-1 was high before cholecystectomy; after surgery IGFBP-1 returned to normal and the concentration of cortisol increased. In IH patients the concentration of IGF-I was low and the concentrations of IGFBP-1 and cortisol were high before surgery; after laparotomy IGFBP-1 returned to normal. The metabolic changes were present in all analyzed patient groups, regardless of the severity of disease and nutrition. The concentration of IGF-I was reduced before surgery and remained reduced after, recommending IGF-I as a metabolic marker in both pre and postoperative examination of patients.