AZP-3404, a Peptide Analog of IGFBP-2, Induces Weight Loss and Improves Glucose Metabolism in Leptin-Resistant db/db Mice

Insulin-like growth factor binding protein-2 (IGFBP-2) has been demonstrated to be a key mediator of the peripheral metabolic actions of leptin. The metabolic activity of IGFBP-2 is independent of IGF1 binding, and can be localized to a unique heparin-binding domain (HBD-1) within its structure. AZP-3404 is a 9-amino acid analog of the IGFBP-2 HBD-1 that reproduces the activity of IGFBP-2 on adipocyte and osteoblast differentiation. In addition, AZP-3404 has been demonstrated to increase glucose uptake by differentiated mouse myotubes in vitro, and to increase glucose disposal following an intraperitoneal glucose tolerance test (IPGTT) in leptin-deficient ob/ob mice. In the present study, we hypothesized that AZP-3404 should be able to improve metabolic regulation in the db/db mouse, which is leptin-resistant due to a mutation in the leptin receptor, and, as a result, is also IGFBP-2 deficient. Following pre-treatment with vehicle for 1 week to establish a baseline, 9-week old male db/db mice were treated with either vehicle or AZP-3404 at doses of 1, 3 or 6 mg/kg, sc, bid (n=10/group) for 8 weeks. At the initiation of treatment, the mice weighed an average of 39.7 + 0.3 grams, and after 8 weeks, vehicle-treated mice had gained an average 8.2 + 1.6 grams of body weight. Mice treated with AZP-3404 displayed a progressive decrease in body weight gain that began after 2 weeks and that continued through the 8 weeks of treatment, ultimately resulting in less than 50% of the weight gain observed in the vehicle-treated mice, and without an apparent change in food intake. To assess the impact on glucose disposal, after both 4 and 8 weeks of treatment, and following an overnight fast, the mice were administered an IPGTT (blood glucose measured 0, 30, 60, 90, 120 and 240 minutes post-ip injection of 1 g glucose/kg). By 4 weeks of treatment, a significant increase in glucose disposal was observed in mice treated with the 6 mg/kg dose of AZP-3404 (AUC glucose decreased by 28.7%) versus vehicle-treated controls. By 8 weeks of treatment, all three doses produced similar increases in glucose disposal (AUC glucose decreased by 18.8, 21.4 and 23.1% with 1, 3 and 6 mg/kg AZP-3404, respectively) versus vehicle controls. Correspondingly, 4-hour fasted plasma insulin was decreased by 54, 48 and 52%, and the HOMA measure of insulin resistance was decreased by 55, 52 and 67%, in mice treated for 8 weeks with 1, 3 and 6 mg/kg AZP-3404, respectively, as compared with vehicle-treated mice. These results, demonstrating both improved glucose metabolism and decreased body weight gain in the leptin-resistant db/db mouse, further confirm the ability of AZP-3404 to reproduce the metabolic activity of IGFBP-2, and support the development of AZP-3404 as a novel therapy for disease states characterized by insulin resistance and/or obesity.