Melanocortin Peptides, NAD+ & Longevity Compounds
A research reference on melanocortin receptor pharmacology, PT-141, Melanotan II, AOD-9604, and longevity compounds including NAD+, MOTS-c, and GHK-Cu — covering mechanisms, receptor subtypes, and research applications.
The Melanocortin Receptor System
Melanocortin peptides act on a family of five G protein-coupled receptors (MC1R through MC5R) distributed across skin, brain, adrenal glands, and peripheral tissues. All five receptors couple to Gs proteins and signal primarily through adenylate cyclase activation and cAMP elevation, but they differ significantly in their tissue distribution, ligand selectivity, and physiological roles. This receptor diversity makes melanocortin peptides particularly valuable research tools for studying multiple physiological systems — pigmentation biology, sexual function, energy homeostasis, and inflammation — often within the same compound class.
The endogenous melanocortin ligands include alpha-melanocyte-stimulating hormone (α-MSH), beta-MSH, gamma-MSH, ACTH, and their derivatives, all derived from the proopiomelanocortin (POMC) precursor protein through tissue-specific post-translational processing. Synthetic melanocortin analogs used in research are typically cyclic peptides engineered for improved receptor selectivity, metabolic stability, and potency compared to the linear endogenous ligands.
PT-141: MC3R/MC4R Agonism & CNS Research
PT-141 (Bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist derived from Melanotan II through removal of the C-terminal amide group. It has preferential activity at MC3R and MC4R, with lower affinity for MC1R and MC5R. This receptor selectivity profile makes PT-141 a widely used research tool for studying central nervous system pathways involved in sexual arousal and appetite regulation, both of which are mediated in part through hypothalamic MC3R and MC4R signaling.
MC4R is expressed at high levels in the paraventricular nucleus (PVN) of the hypothalamus, a region critical for integrating autonomic, endocrine, and behavioral responses. Research using PT-141 has investigated the role of hypothalamic MC4R signaling in sexual behavior, feeding behavior, and the interaction between these two systems — areas of significant interest given the known relationship between energy balance and reproductive function.
Unlike peripherally acting compounds, PT-141 crosses the blood-brain barrier and produces its primary effects through central melanocortin receptor activation, making it a useful tool for studying CNS melanocortin pharmacology in preclinical models. Research has also explored its effects on blood pressure and heart rate through peripheral MC3R and MC4R activation, providing a more complete picture of systemic melanocortin receptor physiology.
Melanotan II & AOD-9604: Metabolic Research Tools
Melanotan II (MT-2) is a cyclic analog of alpha-melanocyte-stimulating hormone (α-MSH) with broad melanocortin receptor activity across MC1R, MC3R, MC4R, and MC5R. Beyond its well-documented role in melanogenesis research (via MC1R activation in melanocytes), Melanotan II has been used in preclinical models investigating energy expenditure, feeding behavior, and erectile function — reflecting the broad physiological reach of the melanocortin system. Its cyclic structure confers greater metabolic stability than linear α-MSH, making it a practical research tool for in vivo studies.
AOD-9604 is a modified fragment of human growth hormone corresponding to amino acids 176–191 of the hGH polypeptide, with a tyrosine residue added at the N-terminus for stability. This C-terminal fragment retains the lipolytic activity of the full hGH molecule — mediated through beta-3 adrenergic receptor stimulation and inhibition of lipogenesis — without the growth-promoting effects of the full molecule, which are mediated through the N-terminal region. This makes AOD-9604 a useful tool for studying fat metabolism pathways in isolation from the anabolic effects of full-length GH.
NAD+: Cellular Energy & Sirtuin Research
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme found in all living cells that plays a central role in cellular energy metabolism, DNA repair, and gene expression regulation. It functions as an electron carrier in the mitochondrial electron transport chain, shuttling electrons from metabolic substrates to oxygen to drive ATP synthesis. NAD+ is also the obligate substrate for sirtuins (SIRT1–SIRT7), a family of NAD+-dependent deacylases that regulate gene expression, DNA repair, mitochondrial biogenesis, and cellular stress responses — pathways directly implicated in cellular aging.
Research interest in NAD+ has intensified with the discovery that cellular NAD+ levels decline with age in multiple tissues, and that this decline correlates with reduced sirtuin activity, impaired mitochondrial function, and increased DNA damage accumulation. Research using NAD+ as a tool compound investigates whether restoring NAD+ levels can reverse age-associated functional decline in cellular models, and which downstream pathways (SIRT1, SIRT3, PARP1, CD38) mediate the observed effects.
MOTS-c & GHK-Cu: Mitochondrial & Tissue Research
MOTS-c is a 16-amino acid peptide encoded within the 12S rRNA gene of mitochondrial DNA — making it one of the few known peptides encoded by the mitochondrial genome rather than the nuclear genome. It is released from mitochondria in response to metabolic stress and acts as a retrograde signal to the nucleus, regulating nuclear gene expression programs involved in metabolic adaptation. Research has demonstrated that MOTS-c activates AMPK signaling, improves insulin sensitivity in skeletal muscle, and enhances metabolic flexibility in response to dietary and exercise challenges.
GHK-Cu (copper peptide) is a naturally occurring tripeptide — Gly-His-Lys — with high affinity for copper(II) ions. It is found in human plasma, saliva, and urine, and its plasma concentration declines significantly with age. Research has studied GHK-Cu for its roles in wound healing, collagen synthesis, and antioxidant gene expression. It appears to activate the SPARC (secreted protein acidic and rich in cysteine) protein and modulate TGF-β signaling, both of which are involved in extracellular matrix remodeling and tissue repair. Research has also explored GHK-Cu's ability to upregulate antioxidant enzymes including superoxide dismutase and catalase through Nrf2 pathway activation.
Research Use Disclaimer
All compounds described are sold by Aldera Bio Labs strictly for in-vitro laboratory research by qualified professionals. Not for human or animal consumption. Not FDA-approved. Must be 21+ to purchase.