Abstract: The disclosure shows that inflammation in metabolic syndrome is augmented by a hitherto overlooked lock-and-key activation of the elastin receptor, a protein involved in vascular (blood vessel) inflammation and elastin repair, with the C-peptide, a small protein that is produced in a 1:1 ratio alongside with widely known insulin. The elastin receptor is the lock that is activated by a key motif of amino acids (PG-domain) found in C-peptide and in breakdown products (PG-domain-fragments) thereof. Until now, no one has ever discovered this lock-and-key interaction between the two, now providing novel inroads in diagnosis, prevention and development of novel compounds for treatment of metabolic syndrome, exploiting the finding that not only the normal keys of the elastin receptor (elastin peptides), but also the C-peptide, a peptide we produce together with insulin every time glucose rises in our blood after a meal, interacts in a lock-and-key mode with the elastin receptor.