Synthesis of truncated analogues of preptin-(1–16), and investigation of their ability to stimulate osteoblast proliferation.

Preptin, a 34-amino acid residue peptide hormone is co-secreted with insulin from the β-pancreatic cells and is active in fuel metabolism. We have previously established that a shorter fragment of preptin, namely preptin-(1–16), stimulates bone growth by proliferation and increasing the survival rate of osteoblasts. This was demonstrated in both in vitro and in vivo models. These findings suggest that preptin-(1–16) could play an important role in the anabolic therapy of osteoporosis. However, due to the large size of the peptide it is not an ideal therapeutic agent. The aim of this study was to identify the shortest preptin analogue that retains or even increases the bone anabolic activity as compared to the parent preptin-(1–16) peptide. Truncations were made in a methodical manner from both the N-terminus and the C-terminus of the peptide, and the effect of these deletions on the resulting biological activity was assessed. In order to improve the enzymatic stability of the shortest yet active analogue identified, ruthenium-catalysed ring closing metathesis was used to generate a macrocyclic peptide using allylglycine residues as handles for ring formation. We have successfully identified a short 8-amino acid preptin (1–8) fragment that retains an anabolic effect on the proliferation of primary rat osteoblasts and enhances bone nodule formation. Preptin (1–8) is a useful lead compound for the development of orally active therapeutics for the treatment of osteoporosis.