Amylin-blocker research tool (mouse/rat Amylin 8-37)

What this is

Amylin (8-37) (mouse, rat) is a truncated fragment of amylin — also called islet amyloid polypeptide (IAPP) — a 37-amino-acid hormone co-secreted with insulin from pancreatic beta cells. This version spans residues 8 through 37 of the rodent (mouse and rat) amylin sequence, missing the seven N-terminal amino acids of the full-length hormone. That deletion is what transforms it from an agonist into an antagonist: it can still bind amylin receptors but cannot activate them, making it a pharmacological tool for blocking amylin signaling rather than mimicking it. The stored sequence (ATQRLANFLVRSSNNLGPVLPPTNVGSNTY) is the bare 30-residue backbone; commercial preparations carry a C-terminal amide that is absent from this representation.

History

Amylin itself was independently characterized in 1986–1987, when researchers studying pancreatic amyloid deposits in patients with type 2 diabetes identified the peptide accumulating in islet tissue. The name "amylin" was proposed after the peptide was shown to have hormone-like biological activity alongside its amyloidogenic properties. Truncated antagonist fragments like the 8-37 form emerged in the early 1990s through structure-activity studies showing that N-terminal deletions across the calcitonin peptide family systematically convert agonists into antagonists. The specific mouse/rat 8-37 fragment became a widely used research reagent because rodent amylin differs from human amylin at several key residues — including a natural in vivo cleavage pattern in rats and mice that occurs between residues 18 and 19 rather than at positions 16–17 as in humans — making species-matched fragments important for interpreting rodent data (Bower and Hay, British Journal of Pharmacology, 2016).

What it does

Amylin (8-37) (mouse, rat) occupies amylin receptors without triggering the downstream signals that full-length amylin produces. In intact animals and isolated tissues, this makes it a blocker of the effects that endogenous amylin would otherwise cause — suppression of food intake, slowing of gastric emptying, inhibition of glucagon release, and inhibition of glycogen synthesis in muscle. When researchers administer this fragment and then observe what changes, the changes (or their absence) reveal what endogenous amylin was doing. Studies in normal and growth-hormone-infused insulin-resistant rats found that blocking amylin with the rat 8-37 fragment enhanced several measures of whole-body and muscle insulin sensitivity and altered plasma lipid profiles, supporting the idea that tonic amylin activity contributes to baseline insulin resistance in those models (Hettiarachchi and colleagues, American Journal of Physiology, 1997). The fragment has also been used to probe cardiac effects: in isolated perfused rat hearts, amylin fragment 8-37 produced a biphasic change in contractile force and increased heart rate at two higher concentrations, though it did not change coronary perfusion pressure (Kaygisiz and colleagues, Acta Physiologica Hungarica, 2003).

Evidence

• Human: No human clinical trials. Amylin (8-37) (mouse, rat) is a research tool peptide used in preclinical and in vitro experiments only.
• Animal: Used in normal and insulin-resistant rat models to probe the metabolic role of tonic amylin signaling; in isolated perfused rat heart preparations to investigate amylin's cardiovascular actions; and in hamster microvascular preparations to map which receptor subtypes mediate amylin's vasodilatory effects.
• In vitro: Binding and functional assays at calcitonin receptor (CTR) and CTR/RAMP heteromers demonstrate that the 8-37 fragment occupies the receptor's extracellular domain but fails to activate intracellular cAMP signaling, consistent with a competitive antagonist profile (Lee, Hay, and Pioszak, Journal of Biological Chemistry, 2016).

Known effects

• Amylin receptor antagonism — Binds AMY1 and AMY2 receptors without activating them; classified as a weak antagonist with pKb values reported in the 5.5–6.2 range at AMY receptor subtypes (Lee, Hay, and Pioszak, 2016)
• Enhanced insulin sensitivity (rodent) — Blocking tonic amylin action in rat models increases muscle and whole-body insulin sensitivity and reduces plasma insulin (Hettiarachchi and colleagues, 1997)
• Altered lipid metabolism (rodent) — Reduces plasma non-esterified fatty acids and muscle triglyceride content in normal rats (Hettiarachchi and colleagues, 1997)
• Cardiac effects (isolated preparation) — Biphasic change in contractile force and positive chronotropy in isolated rat hearts at micromolar concentrations; no change in coronary perfusion pressure (Kaygisiz and colleagues, 2003)
• Limited vascular antagonism — Does not significantly inhibit amylin-induced vasodilation in hamster cheek pouch preparations, where vasodilatory effects appear to be mediated via CGRP receptors rather than dedicated amylin receptors (Hall and Brain, British Journal of Pharmacology, 1999)

Mechanism

Amylin receptors are not simple single-protein GPCRs. They are heteromeric complexes formed by the calcitonin receptor (CTR) — a secretin-family class B GPCR — combined with one of three receptor activity-modifying proteins (RAMP1, RAMP2, or RAMP3), producing the AMY1, AMY2, and AMY3 receptor subtypes respectively (Barwell and colleagues, British Journal of Pharmacology, 2012). CTR alone binds calcitonin preferentially; when paired with a RAMP, the complex shifts selectivity toward amylin and gains the pharmacological properties of an amylin receptor (Lee, Hay, and Pioszak, 2016).

Peptide activation of these receptors follows a two-domain mechanism: the C-terminal portion of the ligand binds to the receptor's extracellular N-terminal domain, docking the peptide in the correct orientation; the N-terminal portion then engages the transmembrane bundle and extracellular loops, triggering receptor activation and cAMP production. Amylin (8-37) retains the C-terminal docking domain but lacks the critical N-terminal segment (residues 1-7, including the Cys2-Cys7 disulfide ring that is essential for activation). It binds — particularly when RAMP1 or RAMP2 are present, which enhance affinity — but cannot complete the activation step (Lee, Hay, and Pioszak, 2016). A modified variant, rAmy(8-37) Y37P, has been shown to improve antagonist affinity and selectivity for AMY1 over CTR, demonstrating that the C-terminal tyrosine is a site for engineering (Lee, Hay, and Pioszak, 2016).

Compared with AC187 (another commonly used amylin antagonist), the 8-37 fragment shows generally weaker binding at the isolated CTR extracellular domain and is considered a less potent tool, though the two antagonists have different selectivity profiles: the 8-37 fragment (and the related CGRP fragment 8-37) is a stronger blocker of amylin's vascular/hypotensive actions, while AC187 is more effective at blocking metabolic actions such as glycogen synthesis inhibition in muscle (Beaumont and colleagues, Canadian Journal of Physiology and Pharmacology, 1995).

Regulatory status

• US: No regulatory status. Research reagent only; not approved or in clinical development.
• EU: Research reagent only.
• WADA: Not listed on the prohibited list. No performance context established.

Related peptides

• Amylin (8-37) (human) (/card/pep-10499) — The human-sequence equivalent of this fragment; the two forms share the same 30-residue backbone region but differ at species-variable positions including residue 18 (His in human, Arg in rodent), making the rodent form the appropriate tool for mouse and rat studies.
• Amylin (mouse, rat) (/card/pep-10609) — The full-length 37-aa rodent amylin parent; this fragment lacks its first seven residues and the Cys2-Cys7 disulfide ring, converting the agonist into the antagonist form catalogued here.
• Cagrilintide (/card/pep-10997) — A long-acting amylin analog designed for once-weekly dosing, acting through AMY1 and AMY3 receptor subtypes; used in the CagriSema combination with semaglutide. The amylin 8-37 fragment can serve as a negative-control or receptor-blocking tool in studies probing cagrilintide's mechanism.
• Salmon Calcitonin (/card/pep-04432) — Acts at the same calcitonin receptor (CTR) core that forms the basis of all amylin receptor subtypes; calcitonin is the primary CTR ligand when RAMP is absent, while amylin takes over when RAMP is present (Barwell and colleagues, 2012).