The invention provides composition comprising a fragment, derivative or variant of sortilin, or a sortilin mimetic, for use in medicine, wherein the sortilin mimetic is not SorCS1, SorCS2, SorCS3 or SorLA. The composition preferably for use in treating or preventing diabetes mellitus, insulin resistance, obesity, metabolic disorders, polycystic ovary syndrome, non-alcoholic fatty liver disease, retinopathy, neuropathy, nephropathy, Alzheimer's disease and/or cardiovascular disease in a subject in need thereof. Also provided are isolated polypeptides, nucleic acids encoding the polypeptides, vectors, host cells and expression systems containing the nucleic acids and methods for making the polypeptides.
