GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? Defy GHK Cu (glycyl L histidyl L lysine) is a naturally occurring copper binding peptide found in human plasma. As levels decline with age, so may its support of the biological processes involved in collagen production, skin The glycyl l histidyl l lysine Cu2+ tripeptide complex attenuates lung inflammation and fibrosis in silicosis by targeting peroxiredoxin 6 ScienceDirect The potential of GHK as an anti aging peptide Dou Aging Pathobiology and Therapeutics