Scientific Glossary

Peptides of the innate immune system with antimicrobial activity. Their mechanism of action differs from that of classical antibiotics.

Programmed cell death through the activation of caspases. A fundamental mechanism of tissue homeostasis.

A 191-amino-acid protein secreted in a pulsatile manner by the anterior pituitary. It regulates growth, protein synthesis, lipolysis, and glucose metabolism.

A cellular mechanism for degrading and recycling damaged organelles via lysosomes. Regulated by mTOR and AMPK.

The proportion of an administered substance that reaches the systemic circulation in active form. Bioavailability depends on the route of administration, stability, and first-pass metabolism.

A 43-amino-acid protein that regulates actin polymerization. TB-500 is reported as a synthetic fragment/analogue.

A reduced cellular response to insulin. A central mechanism in type 2 diabetes and metabolic syndrome.

A controlled study in humans. Phase 1: safety. Phase 2: efficacy/dose. Phase 3: large scale. Phase 4: post-approval monitoring.

Signalling proteins that regulate immune responses (e.g. TNF-α, IL-6, IL-10).

The hydrolysis of triglycerides into glycerol and free fatty acids. A target of body-composition management peptides.

The process of generating new mitochondria through transcriptional programming (PGC-1α, ERRα).

The ability of the nervous system to reorganize its synaptic connections.

A family of proteins (BDNF, NGF, NT-3, NT-4) that support the survival, growth, and plasticity of neurons.

An imbalance between the production of free radicals (ROS) and antioxidant defence.

A chain of amino acids (typically 2–50) linked by peptide bonds. Peptides differ from proteins in size — they are generally considered smaller molecules with diverse biological activities.

Research in animal models or cellular systems before testing in humans. The results do not automatically translate into efficacy in humans.

The enzymatic hydrolysis of proteins into smaller peptides or amino acids. A basic mechanism of peptide degradation in vivo.

An inhibitory hormone that suppresses the secretion of GH, insulin, and glucagon.

A ribonucleoprotein enzyme that adds telomeric repeats to the ends of chromosomes, offsetting their shortening during cell division.

Repeated DNA sequences (TTAGGG) at the ends of chromosomes that protect genetic information. They shorten with each cell division.

The gold standard of clinical research. Participants are allocated at random to a treatment or placebo group.

The time required for the plasma concentration of a substance to decrease by 50%. A short half-life means rapid degradation — for example, many natural peptides degrade within minutes.

An energy-status sensor kinase that is activated at low energy levels. It regulates glucose metabolism and mitochondrial biogenesis.

A peptide sequence reported as a fragment of gastric juice. The majority of data comes from animal models.

A pharmacy that prepares individualized formulations. The FDA (Category 2 Guidance 2023–2024) restricted the ability to compound many research peptides.

A permanent identifier link for a digital object. Unlike URLs, DOIs are stable.

An orphan nuclear receptor that regulates mitochondrial biogenesis and oxidative metabolism.

Signalling via γ-aminobutyric acid (GABA), the principal inhibitory neurotransmitter in the CNS.

A 28-amino-acid peptide hormone ('the hunger hormone') that acts through the GHS-R1a receptor. GHRPs are synthetic ghrelin agonists.

A hypothalamic hormone that stimulates the release of GH from the pituitary. Sermorelin and CJC-1295 are GHRH analogues.

An incretin secreted by the K-cells of the intestine. It works synergistically with GLP-1 in glucose regulation. Tirzepatide is a dual GIP/GLP-1 agonist.

An incretin secreted by the L-cells of the intestine following food intake. It stimulates insulin secretion, inhibits glucagon, and slows gastric emptying.

Good Manufacturing Practice standards that ensure the stability, purity, and quality of pharmaceutical products.

A growth factor that mediates many of the actions of GH. It is produced mainly in the liver. Elevated levels have been associated with anabolic effects but also with a risk of neoplasms.

Experiments in a controlled laboratory environment (cell cultures, biochemical assays), outside a living organism.

A family of peptides (α-MSH, β-MSH, γ-MSH, ACTH) that act through melanocortin receptors (MC1R–MC5R). They regulate pigmentation, inflammation, and energy homeostasis.

Peptides encoded by mitochondrial DNA. They function as retrograde mitochondria-to-nucleus communication signals.

A serine/threonine kinase that functions as a central regulator of cell growth, protein synthesis, and autophagy.

A growth factor (TGF-β superfamily) that acts as a negative regulator of muscle growth.

A transcription factor that regulates genes involved in inflammation, immunity, and cell survival. Peptides such as KPV are studied as NF-κB inhibitors.

The attachment of polyethylene glycol (PEG) to a peptide. Increases half-life by reducing renal clearance.

A key transcriptional coactivator for mitochondrial biogenesis. Activated by exercise and energy stress.

A unique identification number for a publication in the PubMed/MEDLINE database.

A rapid decrease in pharmacological response following repeated administration. Reported for certain GH secretagogues.

A tetrapeptide (Thr-Lys-Pro-Arg) of the natural immune system. Selank was designed as a modified tuftsin analogue.