GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? Frontiers Exploring the beneficial effects of GHK Cu on an experimental model of colitis and the underlying mechanisms By age 30, your skin produces about 25% less collagen. By 40, that number can reach 40%. This decline affects more than just how your skin looks. It changes how it heals, The naturally occurring peptide GHK reverses age related fibrosis by modulating myofibroblast function He Aging Pathobiology and Therapeutics