Molecule guides
Obesity and Appetite Research: Peptide Families, Antisera and Assay Kits
A circuit, not a tissue: peripheral hunger and satiety signals, the hypothalamic neuropeptides they act on, and the adipokines — mapped to the reagents that study them.
What holds this area together is a circuit rather than any one tissue. Hormones released by gut and fat report the body's energy status to the arcuate nucleus of the hypothalamus, where two opposing neuronal populations — NPY/AgRP on one side, POMC/CART on the other — shape feeding behaviour by way of the melanocortin receptors. Our obesity topic page assembles the peptide standards, antisera, tracers and immunoassay kits used along that circuit. Below, we map the families the topic contains, explain what each is bought for, and match reagent formats to research questions.
What the obesity topic covers
A family is filed here when published models show its parent peptide influencing food intake, energy expenditure or the biology of adipose tissue. That reaches across peripheral hunger and satiety signals, neuropeptides of the hypothalamus, components of the melanocortin system, adipokines, and the more recent myokines and browning-associated peptides. Overlap with other topics is deliberate and extensive: leptin and adiponectin are shared with diabetes, while NPY, orexin and galanin also appear under neuropeptides. Everything is supplied for in-vitro use and approved animal research only, and nothing here is a weight-management product.
Signals from the periphery: hunger, satiety, adiposity
- Leptin — the adiposity signal from fat whose discovery created the field, sold as recombinant standards, fragments and antagonists together with the antisera and kits used to quantify it in rodent plasma.
- Ghrelin — the one circulating orexigenic hormone that is firmly established. Receptor activity belongs to the octanoylated form, while des-acyl ghrelin supports a separate literature of its own.
- Obestatin — encoded within the same preproghrelin transcript, with a disputed anorexigenic literature, and a neat illustration of inclusion reflecting active study rather than consensus.
- PYY — the Y2-selective satiety fragment is PYY(3–36); full-length PYY(1–36) has a different receptor profile, so the form must always be stated.
- Amylin and oxyntomodulin — satiety peptides released alongside other hormones and now pivotal to research on combination pharmacology.
- CCK — the original satiety hormone, with sulfated CCK-8 as the standard active form; removing the sulfate destroys potency at the CCK-A receptor.
- GLP-1 — influences appetite as well as glycaemia; see the incretin pathway hub.
Hypothalamic and melanocortin families
- NPY — the most powerful orexigenic peptide yet characterised, with Y1-, Y2- and Y5-selective fragments available for taking the circuit apart.
- AgRP — an endogenous inverse agonist at MC3R and MC4R, expressed alongside NPY; AgRP(83–132) is the usual active fragment.
- POMC, MSH and melanocortin — the appetite-suppressing side. α-MSH at MC4R is the best-validated node in monogenic obesity, and the family page carries receptor-selective analogues.
- CART — expressed together with POMC, with the (55–102) fragment being the commonly used active form.
- MCH — melanin-concentrating hormone, an orexigenic peptide of the lateral hypothalamus.
- Orexin — orexin-A and orexin-B tie arousal to feeding and sit at the interface between sleep and metabolism.
- Galanin and spexin — exert opposing influences on macronutrient preference and energy balance; spexin joined the field relatively recently and its literature is expanding quickly.
- Nesfatin-1, neuromedin U and neuromedin S — appetite-suppressing hypothalamic peptides used for circuit mapping and receptor studies.
- GnIH/RFRP — links energy status to the reproductive axis, and is ordered where a design covers both.
Families from adipose tissue, muscle and browning research
- Adiponectin and resistin — the classical adipokines; bear in mind that adiponectin's activity depends on its multimeric state, something peptide fragments cannot reproduce.
- Adipocyte-derived factors — a broad family page gathering the less-studied peptides secreted by fat.
- Irisin and FNDC5 — the exercise-induced browning candidate and its precursor. Because antibody specificity in this family has been publicly questioned, validated reagents and blocking-peptide controls carry more weight here than usual.
- Meteorin-like (Metrnl) and musclin — myokines investigated in thermogenesis and adaptation to exercise.
- Apelin and adropin — metabolic peptides that connect this topic to cardiovascular research.
- Visfatin and vaspin — fat-derived peptides featuring in insulin-sensitivity studies.
Formats found in the obesity topic
Synthetic peptide standards predominate: central administration in rodents, receptor pharmacology and assay calibration all begin with them, and receptor-selective fragments are the principal means of separating Y-receptor from melanocortin-receptor contributions. ELISA and EIA kits measure leptin, ghrelin, PYY and adipokines in plasma. Polyclonal antisera serve hypothalamic immunohistochemistry, where co-localising NPY/AgRP with POMC/CART markers is routine. Labelled peptides provide binding tracers and fluorescent ligands for imaging receptor trafficking, and magnetic beads support multiplex metabolic panels.
Choosing within a family
Which fragment you order is the first decision and the one most frequently mishandled: PYY(3–36) is not PYY(1–36), AgRP(83–132) is not full-length AgRP, and CART(55–102) is not CART(62–102). Swapping one for another alters the pharmacology, not merely the potency. Modification state comes second — sulfated CCK-8, acylated ghrelin and amidated C-termini are functional necessities rather than decoration; see C-terminal amidation. Species is third, since rodent and human sequences differ in several of these families and antibody cross-reactivity cannot be taken on trust, so check species reactivity. Lastly, when the question is a concentration in a sample, a validated kit outperforms assembling parts; when it is localisation or mechanism, buy the peptide and the antiserum separately.
Handling notes specific to this topic
Three warnings. Acyl-ghrelin is fragile: without acidification and protease inhibition, what you end up measuring is des-acyl ghrelin. Amylin aggregates, being amyloidogenic by nature, so solutions must be freshly made in suitable solvents and ageing stock can give irreproducible results (see peptide solubility). Peptides intended for central administration need their vehicle compatibility established beforehand, not mid-experiment. Beyond that the usual workflow applies: sealed vials at −20 °C, aliquots for single use and as little freeze–thaw as possible — details are in the storage guide, aliquoting guide and COA guide.
Where to look next
Browse the complete obesity topic, the adipose tissue hub or the melanocortin pathway hub. Related guides cover the diabetes and metabolism section and the neuropeptide section, which shares most of the hypothalamic families.
Questions
Should I order PYY(3–36) or PYY(1–36)?
These are distinct tools. DPP-4 cleavage produces PYY(3–36), which is Y2-selective and the form used in satiety research, whereas full-length PYY(1–36) keeps Y1 activity and behaves differently in feeding assays. State the fragment explicitly; both appear in catalog entries because both appear in the literature.
Why must CCK be supplied sulfated?
High-affinity binding at the CCK-A receptor depends on the sulfated tyrosine seven residues from the C-terminus. Strip that sulfate and CCK-8 loses nearly all its potency there while remaining active at CCK-B. Because sulfation is easily lost under acidic conditions, verify it on the certificate of analysis instead of assuming it.
Can peptide standards be used for central administration work?
They are the usual tools for it within approved animal protocols, but confirm vehicle compatibility, endotoxin status and solubility at the concentration you need before starting. Research-grade peptides are neither sterile nor endotoxin-controlled unless an item specifically says so, which matters for intracerebroventricular studies.
What makes irisin contentious?
Early measurements depended on antibodies subsequently shown to cross-react with unrelated proteins, and the human FNDC5 start codon is unusual. The molecule exists and the field continues, but reagent validation matters more than usual here: use blocking-peptide controls and antibodies validated by mass spectrometry wherever the conclusion rests on absolute quantitation.
Is α-MSH sufficient, or do I need receptor-selective melanocortin analogues?
Since α-MSH activates MC1R, MC3R, MC4R and MC5R alike, it cannot pin a feeding effect to any one receptor. The selective agonists and antagonists on the melanocortin family page exist for exactly that purpose: use α-MSH as the physiological ligand and the selective compounds to identify the receptor involved.
Are these peptides intended for weight loss?
No. Every item in the research catalog is supplied for in-vitro assays and approved animal research. Some molecules in this topic do have approved therapeutic counterparts, but catalog material is not manufactured to pharmaceutical standards.