Probing Preptin Functionality Effects Of preptin and analogues on insulin production and signaling

Abstract

Preptin is a 34-amino-acid peptide that was originally discovered in a mouse-derived β-cell line (βTC6-F7 cell). Preptin was found to be co-secreted with insullin in the presence of glucose, and it promoted insulin secretion from both βTC6-F7 cells and isolated perfused rat pancreas. Preptin exhibits some incretin-like properties, and it can stimulate proliferation and differentiation of osteoblasts, promoting survival of these cells. Preptin was also found to have a short half-life of less than 5 minutes and is quickly cleared from circulation. This current project modified preptin by substituting D-amino acids at position Phenylalanine-21 (one site of preptin cleavage observed in vivo) to increase its resistance to enzymatic cleavage. Both in vitro and in vivo invesigations of the resistance to enzymatic cleavage were performed. Furthermore, the ability of preptin to stimulate insulin secretion from βTC6-cells was compared to the appropriate analogues, and an ex vivo study of preptin and analogues in isolated perfused liver was carried out to investigate preptin uptake. The role of preptin in stimulating pERK and cAMP signaling pathways was also investigated in this study. The modification did not alter the normal biological function of preptins. While human preptin and analogues had no observable effect on insulin secretion from βTC6-F7 cells, rat preptin and analogues showed very similar effects in promoting of insulin secretion from this model in the presence of glucose or exendin-4. However no effects on either pERK or cAMP signaling pathways were observed. The in vitro chymotrypsin experiment on preptin and analogues showed increased enzymatic resistance of the analogues, however, results from the in vivo study were ambiguous. Preptin and analogues did not appear to be taken up by the liver, however, this was a preliminary study, and more experiments need to be carried out. Further investigation into preptin is required to elucidate the bioactivity of this peptide and to explore the possibility of using preptin as a potential treatment for metabolic diseases.