Scientific Glossary

AMPK is activated when the AMP:ATP ratio increases (low energy state). It promotes fatty acid oxidation, glucose uptake, mitochondrial biogenesis, and autophagy — essentially a "fuel-efficiency" program. MOTS-c, exercise, and caloric restriction all activate AMPK. AMPK opposes mTOR, creating a see-saw relationship between growth (mTOR) and maintenance/recycling (AMPK). Many longevity interventions are thought to work partly through AMPK activation.

Autophagy (Greek: "self-eating") is a lysosomal degradation pathway that removes cellular debris: damaged proteins, dysfunctional mitochondria (mitophagy), and excess organelles. Activated by nutrient deprivation, exercise, and mTOR inhibition. Reduced autophagy with aging is associated with accumulation of cellular damage. Research into peptides that modulate autophagy is active in longevity science. Rapamycin's lifespan-extending effects in mice appear partly mediated through autophagy enhancement.

Amino acids share a common structure: a central carbon (alpha-carbon) bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen, and a variable side chain (R group). The R group determines each amino acid's properties — charged, polar, nonpolar, aromatic. Peptide bonds form between the carboxyl of one amino acid and the amino group of the next, with water released. The sequence and composition of amino acids determines a peptide's three-dimensional shape, receptor affinity, and function.

Collagen is a triple-helix protein made from collagen alpha chains rich in glycine-proline-hydroxyproline repeats. Over 28 types exist (Type I dominant in skin/bone, Type II in cartilage, Type III in blood vessels). GHK-Cu (copper peptide) is among the most studied research compounds for its ability to upregulate collagen and elastin gene expression. Vitamin C is essential for collagen hydroxylation — deficiency causes scurvy. Research into peptides for collagen synthesis is active in wound care, dermatology, and musculoskeletal medicine.

The ECM provides structural support, mediates cell signaling, and controls cell behavior. Key components: fibrous proteins (collagen, elastin), adhesive glycoproteins (fibronectin, laminin), and proteoglycans (hyaluronic acid, aggrecan). Matrix metalloproteinases (MMPs) remodel the ECM during wound healing — BPC-157 and TB-500 both modulate MMP activity. ECM disruption underlies fibrosis, aging-related tissue stiffness, and impaired wound healing. Research peptides for ECM modulation are studied across dermatology, orthopedics, and cardiology.

GPCRs are transmembrane receptors that couple to intracellular G proteins upon ligand binding. The G protein then activates secondary messengers (cAMP, IP3, DAG) to produce cellular responses. The GLP-1 receptor, ghrelin receptor (GHSR), melanocortin receptors (MC1R-MC5R), GnRH receptor, and KISS1R are all GPCRs. Over 30% of approved drugs target GPCRs, highlighting their pharmaceutical importance. GPCR activation and desensitization mechanisms are critical for understanding peptide pharmacology.

Gene expression involves two steps: transcription (DNA → mRNA) and translation (mRNA → protein). Regulatory factors (transcription factors, epigenetic marks, non-coding RNAs) control which genes are expressed, when, and at what level. Research peptides often work by modulating gene expression programs. GHK-Cu is notable for being studied across 4,000+ gene activation/suppression effects. Epithalon is proposed to work through epigenetic gene regulation pathways. Understanding gene expression changes is now routinely studied via RNA sequencing in peptide research.

Proteases are ubiquitous: in digestive secretions (pepsin, trypsin, chymotrypsin), in blood (DPP-4, NEP, ACE), and intracellularly. Most therapeutic peptides are rapidly cleaved by proteases, limiting their half-life and restricting delivery to injectable routes. Semaglutide overcomes this through C-18 fatty acid conjugation (albumin binding) and selective amino acid modifications. Research strategies to resist proteolysis include: D-amino acid substitution, PEGylation, cyclization, and N-terminal acetylation. Understanding proteolytic stability is essential for interpreting peptide pharmacokinetic data.

VEGF (primarily VEGF-A) binds VEGFR-2 on endothelial cells, triggering proliferation, migration, and tube formation. Critical for wound healing (supplying new blood vessels to healing tissue), normal development, and physiological adaptation to exercise. BPC-157 research consistently shows VEGF upregulation as a proposed mechanism for its tissue repair effects. Pathological VEGF overexpression drives tumor angiogenesis (cancer blood supply) and diabetic retinopathy. Anti-VEGF therapies are standard-of-care for these conditions.