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 GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? GHK Cu Copper Peptide Benefits, Uses & Safety Intra V Frontiers Exploring the beneficial effects of GHK Cu on an experimental model of colitis and the underlying mechanisms