Carnosine vs Ghrelin

Dipeptide that buffers lactic acid in muscle during high-intensity exercise; chelates metal ions; prevents and reverses protein glycation; scavenges aldehyde oxidative byproducts

Carnosine is a naturally occurring dipeptide (β-alanyl-L-histidine) synthesized in skeletal muscle and other excitable tissues from β-alanine and histidine, where it functions as an intracellular pH buffer, antioxidant, and antiglycation agent that supports cellular homeostasis under metabolic stress. Its principal role in exercise physiology centers on buffering the proton accumulation associated with high-intensity anaerobic work, attenuating acidosis-driven impairment of contractile function and extending time to fatigue during supra-threshold effort. Human randomized controlled trials using β-alanine supplementation — which elevates muscle carnosine content by increasing substrate availability — have demonstrated attenuation of fatigue during repeated high-intensity exercise bouts in trained athletes, providing the primary human evidence base for carnosine's performance effects. Carnosine is available as an oral dietary supplement in many jurisdictions; the evidence base for muscle carnosine loading via oral β-alanine supplementation is established in human RCTs, while direct exogenous carnosine administration by injection remains investigational with no regulatory approval or established clinical evidence base.

Must be acylated at Ser3 (by GOAT enzyme) for GHSR-1a binding. Receptor activation in the pituitary stimulates GH release; hypothalamic action via NPY/AgRP neurons increases appetite and reduces energy expenditure.

Ghrelin is an endogenous 28-amino-acid peptide hormone produced primarily by X/A-like cells of the gastric fundus, characterized by a unique octanoyl modification at Ser3 required for GHS-R1a receptor binding; it is the endogenous ligand for the growth hormone secretagogue receptor and functions as a dual regulator of GH secretion and energy homeostasis. Ghrelin acts centrally via hypothalamic GHS-R1a receptors to potently stimulate GH release from the pituitary and to promote appetite through NPY/AgRP pathway activation, and has peripheral effects on gastric motility and insulin secretion, establishing it as a key integrator of nutritional status, GH axis activity, and energy balance. The pharmacology of GHS-R1a activation in humans is validated through macimorelin (Macrilen), an FDA-approved oral ghrelin receptor agonist; Phase 1 and Phase 2 randomized controlled trials of macimorelin demonstrated robust and reliable GH stimulation in adults, supporting FDA approval in 2017 for the diagnosis of adult GH deficiency and confirming the human physiological relevance of ghrelin receptor activation. Ghrelin itself is not therapeutically administered; it has a very short plasma half-life and the active acylated form is rapidly degraded in circulation; FDA-approved ghrelin receptor agonists require prescription and are indicated for diagnostic rather than therapeutic use, while ghrelin peptide is used exclusively as a research tool compound in neuroendocrine pharmacology studies.