The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline 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, GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link