Effect of intraperitoneal insulin delivery on growth hormone binding protein, insulin-like growth factor (IGF)-I, and IGF-binding protein-3 in IDDM

Low plasma insulin-like growth factor (IGF)-I despite high circulating growth hormone (GH) in insulin-dependent diabetes mellitus (IDDM) indicate a hepatic GH resistance. This state may be reflected by the reduction of the circulating GH binding protein (GHBP), corresponding to the extracellular domain of the GH receptor, and the reduction of insulin-like growth factor binding protein (IGFBP)-3, major IGF-I binding protein, upregulated by GH. We carried out two studies. In the first, plasma GHBP activity was compared in patients with IDDM on continuous subcutaneous insulin infusion (CSII) or on conventional therapy and in healthy subjects. In the second study, the 18 patients on GSII at baseline were then treated by continuous intraperitoneal insulin infusion with an implantable pump (CPII) and prospectively studied for GH-IGF-I axis. Although HbA(1c) was lower in patients on CSII than in those on conventional therapy, GHBP was similarly reduced in both when compared to control subjects (10.2 ± 0.8 and 11.6 ± 0.9% vs 21.0 ± 1.3, p < 0.01). CPII for 12 months resulted in: a slight and transient improvement in HbA(1c) (Time (T)0: 7.6 ± 0.2%, T3: 7.1 ± 0.2%, T12: 7.5 ± 0.2%, p < 0.02), improvement in GHBP (T0: 10.2 ± 0.8%, T12: 15.5 ± 1.5, p < 0.0001), near-normalization of IGF-I (T0: 89.4 ± 8.8 ng/ml, T12: 146.9 ± 15.6, p < 0.002) and normalization of IGFBP-3 (T0: 1974 ± 121 ng/ml, T12: 3534 ± 305, p < 0.0001). The hepatic GH resistance profile in IDDM does not seem to be related to glycaemic control, but partly to insufficient portal insulinization. Intraperitoneal insulin delivery, allowing primary portal venous absorption, may influence GH sensitivity, and improve hepatic IGF-I and IGFBP-3 generation.