Peptides are chains of amino acids, the same building blocks as proteins, but shorter, typically between 2 and 50 amino acids in length. Where proteins are structural or enzymatic, performing their function through their three-dimensional shape over extended periods, peptides are primarily signalling molecules: they communicate between cells, tissues, and organs, directing biological activity with remarkable specificity. The human body naturally produces hundreds of peptides, from insulin and glucagon that regulate blood glucose, to oxytocin and vasopressin that govern social bonding and fluid balance, to the defensins and cathelicidins of the immune system. Peptides are not exotic or artificial; they are among the most fundamental mediators of life.
How Peptides Work
Peptides exert their effects by binding to specific receptors on cell surfaces, triggering intracellular signalling cascades that alter gene expression, enzyme activity, or cellular behaviour. Their small size and specificity makes them among the most potent biological signalling molecules per molecule, and their relatively short half-lives means their effects are tightly regulated. This specificity distinguishes them from many pharmaceutical drugs, which often have broader mechanisms and correspondingly broader side effect profiles.
Categories of Therapeutic Interest
- Growth hormone secretagogues: peptides including CJC-1295, ipamorelin, and sermorelin stimulate the pituitary gland to produce more growth hormone; used in clinical settings for growth hormone deficiency and age-related decline in GH secretion
- Gut-healing peptides: BPC-157, derived from a protein found in gastric juice, has demonstrated remarkable tissue-healing properties in animal models across multiple tissues including gut mucosa, tendon, and nerve
- Immune-modulating peptides: thymosin alpha-1, approved in several countries for hepatitis B and C treatment, modulates T-cell function and has been used in cancer and viral illness contexts
- Antimicrobial peptides: defensins and cathelicidins are naturally produced by the innate immune system; research into synthetic analogues as alternatives to antibiotics is active
- Collagen peptides: hydrolysed collagen consisting of short peptide chains including hydroxyproline-proline-glycine sequences; the most extensively clinically validated category, with multiple randomised trials supporting their effects on skin elasticity, joint cartilage turnover, and bone density
- Food-derived bioactive peptides: peptides released from dietary proteins during digestion that have demonstrable physiological effects, including ACE-inhibitory peptides from milk proteins that reduce blood pressure and opioid peptides from wheat and dairy that affect gut motility
The Regulatory Landscape
The regulatory status of peptides varies considerably. Insulin is the most well-known therapeutic peptide and has been in clinical use for a century. Many growth hormone secretagogues are in a grey regulatory area in the UK: they are not licensed medicines and cannot be prescribed in mainstream NHS practice, but they are not scheduled substances. Collagen peptides are sold as food supplements with an excellent safety record. Those considering peptide therapies beyond food supplement peptides should seek guidance from a specialist practitioner and should be aware that the evidence base for many therapeutic peptides derives primarily from animal studies and small human trials.
Sources
- Fosgerau, K., & Hoffmann, T. (2015). Peptide therapeutics: current status and future directions. Drug Discovery Today, 20(1), 122-128.
- Kastin, A.J. (2013). Handbook of Biologically Active Peptides. Academic Press, 2nd edition.
- Lau, J.L., & Dunn, M.K. (2018). Therapeutic peptides: historical perspectives, current development trends, and future directions. Bioorganic and Medicinal Chemistry, 26(10), 2700-2707.
- Imai, K., & Takaoka, A. (2006). Comparing antibody and small-molecule therapies for cancer. Nature Reviews Cancer, 6(9), 714-727.
- Chhikara, N., et al. (2018). Bioactive peptides of food: a review. International Journal of Peptide Research and Therapeutics, 25(2), 1-18.