Amylin

Amylin — also known as islet amyloid polypeptide (IAPP) — is a 37-amino-acid peptide hormone co-secreted with insulin from pancreatic beta cells in response to food intake. It was identified in 1987 as the major component of amyloid deposits in the pancreatic islets of type 2 diabetics, but its physiological role as a satiety and glucose-regulatory hormone is now well established.

Physiological functions

Amylin has three primary metabolic actions, all of which complement insulin's effects:

Gastric emptying

Amylin slows gastric emptying in a dose-dependent manner. This reduces the rate at which glucose enters the bloodstream after a meal, flattening the postprandial glucose spike. The effect is mediated via vagal afferent signaling and is clinically significant — pramlintide (synthetic amylin analog) reduces postprandial glucose excursions by 40–50% in type 1 diabetes.

Glucagon suppression

Amylin suppresses postprandial glucagon secretion from pancreatic alpha cells. Glucagon drives hepatic glucose output; suppressing it after meals reduces inappropriate liver glucose release that contributes to hyperglycemia. This is particularly relevant in type 1 diabetes, where the loss of beta cells means loss of amylin co-secretion and unregulated postprandial glucagon.

Satiety signaling

Amylin acts on the area postrema — a circumventricular organ in the brainstem that lacks a complete blood-brain barrier — to promote satiety and reduce meal size. This is the basis for the obesity drug development pipeline targeting amylin receptors.

Amylin receptors

Amylin receptors are heterodimers composed of the calcitonin receptor (CTR) combined with receptor activity-modifying proteins (RAMPs). Three amylin receptor subtypes exist:

• AMY1 = CTR + RAMP1
• AMY2 = CTR + RAMP2
• AMY3 = CTR + RAMP3

The RAMP component modifies the calcitonin receptor's ligand specificity, conferring high-affinity amylin binding. This shared receptor architecture with calcitonin explains some of amylin's effects on bone metabolism and calcium regulation.

Clinical analogs

Pramlintide (Symlin)

The first amylin analog approved for clinical use (FDA 2005). It is a synthetic form with three proline substitutions at positions 25, 28, and 29 that prevent the amyloid aggregation that makes native human amylin unsuitable for pharmaceutical use. Approved as an adjunct to insulin in type 1 and type 2 diabetes. Major limitation: requires injection before each meal (3× daily), limiting patient adherence.

Cagrilintide

A long-acting acylated amylin analog developed by Novo Nordisk. The acylation enables weekly dosing (vs. pramlintide's thrice-daily). Currently in Phase 3 trials as:

• Monotherapy for obesity (~10% weight loss)
• CagriSema (cagrilintide + semaglutide 2.4 mg) — the combination targets both amylin and GLP-1 pathways, achieving ~24% weight loss in Phase 3 REDEFINE trials

CagriSema represents the dual-agonist approach to obesity: two independent satiety pathways producing additive weight loss beyond what either achieves alone.

Amylin in disease

Type 2 diabetes

In T2D, amylin production initially increases (paralleling hyperinsulinemia) but the peptide misfolds into amyloid fibrils that deposit in pancreatic islets. These amyloid deposits are toxic to beta cells, contributing to progressive beta-cell loss. This creates a vicious cycle: more amyloid → fewer beta cells → less insulin and amylin → worse glucose control.

Type 1 diabetes

Beta-cell destruction eliminates both insulin and amylin production. The loss of amylin contributes to postprandial glucose volatility through unregulated gastric emptying and glucagon secretion — problems that insulin alone does not fully address. Pramlintide was developed specifically for this unmet need.

Amylin vs. GLP-1

Both amylin and GLP-1 agonists reduce appetite and slow gastric emptying, but through distinct mechanisms:

| Feature | Amylin | GLP-1 |

|---|---|---|

| Receptor | AMY1–3 (CTR + RAMPs) | GLP-1R |

| Primary brain target | Area postrema | Hypothalamus + area postrema |

| Gastric emptying | Strong slowing | Strong slowing |

| Insulin secretion | No direct effect | Glucose-dependent stimulation |

| Glucagon | Suppresses postprandially | Suppresses postprandially |

| Weight loss (monotherapy) | ~10% (cagrilintide) | ~16% (semaglutide 2.4 mg) |

The independence of these pathways is why combination therapy (CagriSema) produces greater weight loss than either agent alone — each pathway has its own ceiling, and combining them raises the total ceiling.