This may be due to copper's ability to enhance the expression of metalloproteinases (MMPs).16 MMPs normally regulate the degradation of collagen, and a specific one, MMP-1, may be responsible for the initiation of collagen fragmentation.17 Supporting this, a 2024 study noted that elevated MMP-1 levels appear to contribute to aging skin and that higher MMP-1 levels in mice led to:18 The loss and fragmentation of dermal collagen fibrils Contracted fibroblast morphology Reduced collagen production Increased expression of pro-inflammatory mediators Additionally, a 2016 study found that GHK-Cu significantly increased gene expression of MMP-1 and MMP-2 at the lowest concentration, which the studys authors considered to be one of the reasons the peptide was able to increase collagen and elastin production.19 So, what this could ultimately mean is that using too much GHK-Cu (or other copper peptides) may in theory increase the skins MMP-1 concentration above the levels involved in healthy collagen production, taking it into the collagen fragmentation and breakdown territory seen in older skin with naturally higher MMP-1 levels

Box 2 shows an area with microglial processes that extend and converge on a particular area, which is followed by the formation of a continuous barrier at the glial limitans similar to the jellyfish microglia in Box 2
GSH synthesis is primarily regulated by GCLC activity, cysteine availability, and feedback inhibition by GSH itself
There are many different types of vitamin B12 available, including: cyanocobalamin methylcobalamin adenosylcobalamin hydroxycobalamin While cyanocobalamin is the Vitamin B12 supplements are available in a wide range of doses as well, including high dose supplements with 1,000 mcg to 2,000 mcg per serving