Back to libraryMetabolic, repair & endocrine pathways.
Step-by-step signalling pathways that connect receptor activation to downstream physiological outcomes.
Incretin → insulin axis
- 1Nutrient ingestion
- 2L-cell GLP-1 + K-cell GIP release
- 3GLP-1R / GIPR on pancreatic β-cells
- 4Gαs → cAMP → PKA / Epac2
- 5KATP closure → Ca²⁺ influx
- 6Glucose-dependent insulin granule exocytosis
Modulated by: semaglutide, liraglutide, tirzepatide, retatrutide.
Hypothalamic appetite control
- 1Vagal & humoral signals reach NTS
- 2Projection to arcuate nucleus
- 3POMC / CART (satiety) vs AgRP / NPY (hunger)
- 4Second-order PVN MC4R neurons
- 5Net signal → cortical reward / brainstem motor output
GLP-1, MC4R agonists, leptin, ghrelin all converge here.
GHRH + GHRP → GH → IGF-1
- 1GHRH (sermorelin / CJC-1295) at GHRHR
- 2+ GHRP (ipamorelin) at GHS-R1a
- 3Synergistic pituitary somatotroph stimulation
- 4Pulsatile GH release into circulation
- 5Hepatic JAK2/STAT5 → IGF-1 production
- 6Systemic anabolic & lipolytic signalling
Pulsatility preserves receptor sensitivity vs continuous rhGH.
Tissue-repair / angiogenic cascade
- 1Injury → local cytokine release
- 2BPC-157 upregulates VEGFR2
- 3eNOS → nitric oxide release
- 4Endothelial migration (FAK / paxillin)
- 5Capillary tubule formation
- 6Collagen organisation & re-epithelialisation
Preclinical models: Achilles tendon, gastric mucosa, ligament.
Mitochondrial bioenergetics
- 1Substrate oxidation → NADH / FADH₂
- 2Electron transport chain (Complex I–IV)
- 3Proton gradient (ΔΨm) across IMM
- 4ATP synthase (Complex V) → ATP
- 5SS-31 stabilises cardiolipin / supercomplexes
- 6MOTS-c → AMPK → ↑ glucose uptake
Targets: SS-31 (elamipretide), MOTS-c, humanin.
Immune T-cell maturation
- 1Thymosin α-1 binds TLR9 on dendritic cells
- 2MyD88-dependent NF-κB activation
- 3IL-12 / IFN-α production
- 4Th1 polarisation of naïve CD4⁺ T-cells
- 5Enhanced CTL response & antibody class-switching
Clinical use: hepatitis B, vaccine adjuvant (35+ countries).
Melanocortin sexual-arousal pathway
- 1PT-141 / bremelanotide at MC4R
- 2Hypothalamic PVN activation
- 3Descending oxytocinergic projections
- 4Spinal MC4R modulation
- 5Pro-erectile / pro-arousal autonomic output
FDA-approved (Vyleesi) for HSDD in premenopausal women.
Neurotrophic / BDNF axis
- 1Semax / Selank at brain barrier
- 2Hippocampal BDNF + NGF transcription
- 3TrkB receptor autophosphorylation
- 4PI3K/Akt + MAPK/ERK activation
- 5Synaptic plasticity & dendritic spine growth
Modulates anxiety, learning and ischaemic neuroprotection.
