GHK gene-expression figures
The largest numbers in this literature are also the ones most easily detached from what was counted.
The threshold in the analysis
A large gene count can lend an argument the appearance of depth before it has explained a single outcome. I was susceptible to that appeal here. The gene-data review reports that GHK modulates expression of approximately 31.2% of human genes at a threshold of a 50%-or-greater change. The observation concerns gene expression—how active genes were in the analysis. Its scale is striking.
The threshold is essential to understanding the scale. The same review’s reported analysis separates increases from decreases: 59% of affected genes increased in expression and 41% decreased. It also discusses repair, protein-quality-control, DNA-repair and antioxidant gene sets. The mixture matters to me. Even the headline percentage contains changes in opposing directions, so “more gene activity” would be a poor description of the whole pattern. Once those details are restored, the number describes a pattern of activity with a defined cutoff. It acquires a shape instead of merely sounding enormous.
The commonly repeated figure of about 4,000 genes is an extrapolation; the table at the 50%-or-greater threshold reports on the order of 2,100 genes. I care about this distinction because the larger number is so portable. The threshold and the counting rule tend to travel less well than the headline. They are the parts that let the count mean something.
Repair and protection gene sets
The analysis draws on gene-expression and database work, with cell-culture validation. Its reported shift toward repair and cellular protection makes the biological argument interesting. This is the attractive part, to my mind: the pattern suggests questions that can be pursued in experiments with specific tissues and outcomes.
A count of affected genes leaves open the practical consequence of those changes. A cosmetic claim needs a cosmetic observation. A claim about lasting change needs the passage of time to be observed. Molecular scale cannot do that work, however splendid the figure. The breadth of the analysis leaves me keen to see its next experimental test; it does not allow me to picture a particular change in a face.
There is also a naming issue. The reported gene-expression claim concerns GHK, while the review's title discusses GHK-Cu. That is a reason to attend to the material used in a particular experiment. Broad discussions of related forms can be helpful, but an individual result still has to be attached to the form that produced it.
Plasma GHK and age
The skin-regeneration review reports plasma GHK declining from about 200 ng/mL at age 20 to about 80 ng/mL by age 60. That observation gives the anti-aging argument an intuitively attractive beginning. Something present in the body is lower at an older age. The temptation is to supply the rest of the story immediately.
I understand that temptation, and I resist it. The reported age-related difference describes plasma GHK. It leaves the consequences of changing that level to be investigated. Neither a cosmetic improvement nor its duration can be calculated from those concentrations. A topical application also poses the separate delivery questions that the skin research examines.
My opinion has become a little less grand and considerably more curious. The repair-related gene activity described in the review is a reason to ask focused questions about biological effects. The skin observations are a reason to examine specific cosmetic outcomes. Joining them into an everlasting result would require the missing observations, however appealing the story sounds. Give me a durable, clearly measured skin change before a larger gene count.