Targeting a metabolic OA in vivo model by a novel dual amylin calcitonin receptor agonist, KBP-056

Abstract

Purpose: Salmon calcitonin (sCT), a hormone acting through CT and amylin receptors, have in multiple preclinical models been demonstrated to improve bone homeostasis and attenuate joint destruction, in part through the anti-resorptive property. In addition, sCT have recently been shown to have a positive effect on obesity and diabetes. These properties may be particularly beneficial for certain OA patients whose disease is driven by obesity and an unhealthy metabolism. Through a larger screening program we identified a novel synthetic peptide mimicking sCT that activates the CT and amylin receptors with higher potency. This novel peptide was named KBP-056, and is part of the Dual Amylin Calcitonin Receptor Agonist (DACRA) family. Here we wish to characterize the effects of KBP-056 on metabolism, bone and cartilage in a metabolic OA in vivo model driven by an unhealthy diet, age and menopause. Methods: Female Sprague Dawley rats (Taconic, Ry, Denmark) were fed a high-fat diet (HFD) or normal diet for 3 months before initiation of the study. At 6 months of age the rats were randomized into 10 groups (n = 12) based on body weight (BW), and subjected to either ovariectomy (OVX) or sham surgery, resulting in the following groups; (1) Lean-Sham, (2) Lean-OVX, (3) HFD-Sham, (4–7) HFD-OVX. Lean-Sham, Lean-OVX, HFD-Sham and one HFD-OVX group received vehicle (saline) by subcutaneous injections (SC) twice daily (bis in die, BID), while the remaining HFD-OVX groups received either 10 μg/Kg KBP-056 SC BID, 30 μg/Kg Alendronate sodium trihydrate (ALE) SC three times weekly, or 30 μg/day 17α-ethynylestradiol (EE2) by slow-release pellets implanted under the skin. The better characterized ALE and EE2 were included as controls. Diets and treatments were continued for 6 months. BW and food intake were recorded continuously. Blood was collected from overnight fasted rats regularly, both before and 3 hrs after the morning dose. Oral glucose tolerance tests (OGTTs) were performed at weeks 8, 16 and 24. At termination, relevant organs were isolated, weighed and prepared for further analyses. The degradation products of C-terminal telopeptides of type II collagen (CTX-II) were measured in plasma by ELISA, as a biomarker of cartilage degradation. Mean values and standard errors of the mean (SEM) were reported. Significance levels between groups at each time point were found using one-way ANOVA assuming normal distribution. These are indicated by asterisks; *P < 0.05, **P < 0.01, ***P < 0.001. Results: HFD-Sham rats had a significantly higher BW than Lean-Sham rats throughout the study (P < 0.001). In both HDF and Lean rats, the OVX caused a significant increase in BW within two weeks after surgery (P < 0.01), that was sustained throughout the study. In HFD-OVX rats, both KBP-056 and EE2 caused an immediate decrease in both food intake and BW within days, and while food intake gradually returned to vehicle level over the first eight weeks, the weight loss remained until termination (P < 0.001). Based on the glucose tolerance, the vehicle groups ranked from highest to lowest tolerance; Lean-Sham, Lean-OVX, HFD-Sham, HFD-OVX. KBP-056 significantly increased glucose tolerance of HFD-OVX rats, whereas EE2 had a slightly increasing effect, though not statistically significant. ALE had no effect on the above mentioned parameters. Plasma levels of CTX-II, a biomarker of cartilage degradation, were increased in both HFD and Lean rats two weeks after OVX. This OVX-induced release of CTX-II was suppressed by both KBP-056 (P < 0.01), EE2 (P < 0.01) and to some extent ALE, after dosing. CTX-II suppression was observed already after the first administered dose of KBP-056 (P < 0.01), whereas EE2 and ALE took a longer dosing period to exert their effect. Conclusions: KBP-056 demonstrates positive effects on both metabolic health and cartilage degradation, and may therefore represent a possible multimodal treatment opportunity for OA patients driven by an unhealthy phenotype. Further analyses of structural changes in both cartilage and bone will show whether OA-like changes have occurred and been prevented. This may be a first step on the way to match the optimal treatment opportunity with the right OA patient for a personalized health care approach for OA.