Primitive Peptides and the art of reuse

Collagen, taken apart

Collagen gives skin and connective tissue their structure. Tucked inside it is the sequence glycine–histidine–lysine, or GHK. When collagen breaks down, that small piece can be released into the surrounding tissue; bound to copper, it has been studied for its part in repair. The review of GHK and skin regeneration puts destruction and rebuilding surprisingly close together.

The dismantling was the part I hadn't expected to enjoy. A fragment of the material being cleared away can participate in what happens next. Much of the evidence for those cellular effects comes from laboratory work, and the human studies concern topical skin preparations. Even within those limits, the idea has more substance than another general promise of rejuvenation.

Primitive suggests making use of what is already at hand. That is the attraction here: existing sequences, pieces and recycling pathways being put to work. It would be a mistake to turn that attraction into a claim that a natural molecule is automatically safe. The ingenuity appeals to me; a treatment claim still has to earn its place.

GHK and copper

The tiny sequence is only the beginning of the GHK-Cu story. Copper binding changes the form being studied, and skin presents an awkward obstacle to a water-loving peptide. A review of topical GHK delivery describes poor passage through the outer skin layer and the formulation work intended to improve it.

That is where the reuse metaphor earns its place for me. Finding a promising piece of material starts a job. Making it work somewhere else requires its own effort. The GHK-Cu research peptide page follows the copper peptide serum question through the small human studies, the skin barrier and the much larger claims made for systemic use.

Two pieces of alpha-MSH

KPV and PT-141 both lead back to alpha-melanocyte-stimulating hormone, yet their experiments tell different stories. KPV corresponds to the hormone's last three amino acids. In mouse colitis experiments, its anti-inflammatory activity persisted without MC1R, a receptor used by the parent hormone. Removing most of a molecule can change the way its remaining piece operates.

PT-141, or bremelanotide, involves deliberate rebuilding: a cyclic structure and amino-acid substitutions. It reached two Phase 3 trials in premenopausal women with HSDD and an approved formulation with a narrow indication. KPV has no published human clinical trial. The shared parent supplies a starting point; the two records deserve separate consideration.

The KPV essay spends time with the missing receptor. The PT-141 essay looks at the consequences of making a melanocortin compound last longer.

NAD+ salvage

NAD+ joins this collection as a coenzyme rather than a peptide. Cells recycle its components through what biochemistry calls the salvage pathway, alongside other routes for making it. The review of NAD+ metabolism describes an economy of production and consumption: some enzymes use NAD+ up while it also cycles through energy metabolism.

Salvage sounds apt to me because it gives that ordinary cellular work some weight. The difficult question is what happens when extra precursor enters the system. Human trials can raise blood NAD+, and some report functional changes, while the human ageing review judges overall efficacy limited and tissue-level information sparse. NAD+ salvage and replacement follows that distinction. The comparison brings all four compounds together, and the questions page covers the points that tend to get lost between them.