Amylin is a postprandial metabolic hormone co-secreted with Insulin by pancreatic β cells. It limits continuous nutrient influx by promoting meal termination, delaying gastric emptying, and regulating prandial Glucagon secretion. The Amylin receptor is not a single receptor protein but a receptor complex composed of the Calcitonin receptor (CTR) as the core and different Receptor Activity-Modifying Proteins (RAMPs). The development of Amylin analogs such as Pramlintide and Cagrilintide has expanded this receptor system from postprandial metabolic regulation to an important target for weight-loss drugs.

Keywords: Amylin receptor; Amylin; Calcitonin receptor; RAMP; Cagrilintide; Pramlintide; weight loss

1 Physiological Basis of Amylin and the Amylin Receptor

1.1 Postprandial Secretion of Amylin

Amylin consists of 37 amino acids and is mainly stored in secretory granules of pancreatic β cells. It is co-released with Insulin after stimulation by nutrients such as glucose. Insulin mainly promotes glucose utilization and nutrient storage, whereas Amylin regulates nutrient input by promoting Satiation, delaying gastric emptying, and suppressing inappropriate prandial Glucagon secretion, thereby coordinating the rate at which nutrients enter the circulation with the metabolic processing capacity of the body.

1.2 Receptor Composition of the Amylin Receptor

(1) CTR Forms the Receptor Core

The transmembrane core of the Amylin receptor is the Calcitonin receptor (CTR, CALCR), which belongs to the Class B1 G protein-coupled receptor family. When expressed alone, CTR can form a functional Calcitonin receptor. When CTR forms a complex with a RAMP, the extracellular ligand-recognition environment and overall receptor conformation are altered, markedly enhancing the functional response to Amylin.

(2) RAMPs Form Different Receptor Subtypes

CTR can combine with RAMP1, RAMP2, or RAMP3 to form AMY1R, AMY2R, and AMY3R, respectively. RAMPs are not merely accessory proteins that promote CTR expression; they can influence ligand recognition, receptor conformation, cell-surface trafficking, and signal output. Therefore, the potency of the same ligand can differ markedly among different CTR-RAMP combinations.

(3) CTR and AMYR Need to Be Distinguished

CTR and AMYR share the same CTR transmembrane core but are not equivalent. When CTR exists alone, it mainly exhibits Calcitonin receptor pharmacology, whereas addition of a RAMP forms a receptor complex with an Amylin receptor phenotype. Some Amylin analogs can also activate both AMYR and CTR. Therefore, experimental studies need to define the specific receptor composition rather than treating “Amylin receptor” as a single target.

1.3 Signal Transduction of the Amylin Receptor

After activation, the Amylin receptor mainly promotes Adenylate Cyclase activation through Gs, increases intracellular cAMP, and further regulates downstream effector systems such as PKA. It can also generate Ca²⁺, ERK, and receptor-internalization responses. CTR splice variants, RAMP subtype, cellular background, and ligand structure can all alter signal magnitude and duration. Therefore, EC₅₀ and Emax values in different AMYR systems need to be interpreted according to the specific receptor composition.

2 Major Pharmacological Effects of the Amylin Receptor

2.1 Suppression of Food Intake and Promotion of Meal Termination

The most direct weight-loss-related effect of Amylin receptor activation is enhanced Satiation, allowing a meal to reach the termination threshold earlier and thereby reducing Meal Size and Food Intake. Native Amylin mainly produces short-duration prandial and postprandial signals, whereas long-acting Amylin analogs extend receptor stimulation, allowing total Energy Intake to remain reduced across multiple feeding cycles. Reductions in Body Weight and Fat Mass are long-term consequences of decreased food intake rather than direct pharmacological effects independent of feeding regulation.

2.2 Delayed Gastric Emptying

Amylin receptor activation can reduce the rate at which gastric contents are delivered to the small intestine, thereby slowing the rate at which glucose and other nutrients reach absorptive sites and enter the circulation. Delayed gastric emptying not only helps limit rapid postprandial increases in Glucose but also prolongs the mechanical and nutrient feedback generated by gastric contents, acting together with central meal-termination signals to reduce nutrient intake per unit time.

2.3 Suppression of Prandial Glucagon Secretion

Amylin can suppress inappropriate Glucagon secretion during feeding, preventing the liver from maintaining excessive glucose output when large amounts of nutrients are entering the circulation. This effect mainly contributes to postprandial glucose homeostasis and acts together with delayed gastric emptying and Insulin to limit postprandial glucose fluctuations. It is not the primary direct mechanism underlying Amylin-mediated weight loss.

3 Central Regulation of Food Intake by the Amylin Receptor

3.1 Amylin Sensing in the Area Postrema

The Area Postrema (AP) is located in a hindbrain region where the blood-brain barrier is relatively permeable, allowing circulating Amylin and peripherally administered Amylin analogs to access this brain region relatively easily. CTR/Amylin receptor-related neurons are present in the AP and can convert circulating postprandial peptide-hormone signals into changes in neural activity, making the AP an important entry point through which peripheral Amylin signals access central feeding networks.

3.2 AP-NTS-Related Feeding Networks

(1) Integration of Circulating and Visceral Nutrient Signals

The AP and Nucleus Tractus Solitarius (NTS) jointly receive circulating hormonal signals, vagal input, and gastrointestinal visceral information. After Amylin receptor activation, the hindbrain network becomes more responsive to postprandial nutrient input, allowing a smaller amount of food intake to generate a sufficiently strong meal-termination signal and shifting feeding behavior from continued intake toward termination of the current meal.

(2) Transmission of Feeding Signals to Higher Central Regions

Amylin-related neural output generated in the hindbrain can also be transmitted to the Parabrachial Nucleus (PBN) and other feeding-regulatory regions, integrating gastrointestinal load, circulating hormones, and visceral sensation into a more complete food-intake-suppressing signal. The central action of the Amylin receptor is not an isolated receptor event within the AP but a multi-node signaling process initiated by the hindbrain nutrient-sensing network.

3.3 Integration With Long-Term Energy-State Signals

Amylin mainly reflects nutrient input generated by the current meal, whereas signals such as Leptin and Insulin more strongly reflect long-term fat stores and energy status. These two classes of signals can be integrated within central neural networks, allowing feeding behavior to be adjusted according to Meal Size, postprandial nutrient load, and long-term Energy Store. The Amylin receptor therefore serves as an important component linking meal-related Satiation with long-term energy balance.

3.4 Satiety and Aversive Responses

The Area Postrema participates not only in physiological Satiation and meal termination but also in visceral defense signals such as Nausea and Aversion. Excessive or inappropriate hindbrain pharmacological stimulation may therefore recruit different neural networks simultaneously. Ideal Amylin receptor-targeted weight-loss pharmacology should mainly enhance physiological Satiation rather than rely on obvious discomfort to reduce Food Intake. Distinguishing satiety from aversive responses is therefore an important pharmacological dimension when evaluating potent or long-acting Amylin analogs.

4 Amylin Receptor Subtypes and Structural Basis

4.1 Receptor Assembly of CTR and RAMP

CTR provides the Class B1 GPCR transmembrane core, intracellular G-protein coupling interface, and major ligand-binding framework, whereas RAMP forms a stable complex with CTR and alters the structural environment of the extracellular receptor region. Different RAMPs can influence receptor conformation and peptide-ligand binding, allowing the same CTR core to generate different Amylin receptor phenotypes. This is also the structural basis for the differences among AMY1R, AMY2R, and AMY3R.

4.2 AMY1R, AMY2R, and AMY3R

Table 1 Major Forms of the Amylin Receptor

AMY1R, AMY2R, and AMY3R are not three independent GPCRs but share the same CTR core. CTR splice variants, RAMP subtype, and host-cell environment can all alter the final receptor phenotype. Therefore, the specific receptor composition is an important variable for explaining differences in ligand activity among different experimental systems.

4.3 Cross-Ligand Activity of CTR and AMYR

The Calcitonin, Amylin, and CGRP families do not correspond to completely isolated receptor systems. Some Calcitonin-family ligands can activate both CTR and AMYR, while AMY1R also shows a certain degree of responsiveness to CGRP-related ligands. Therefore, studies of ligand selectivity need to consider CTR, RAMP composition, and peptide structure simultaneously and cannot determine the actual receptor spectrum solely from labels such as “Amylin analog” or “Calcitonin analog.”

5 Weight-Loss Mechanisms of Long-Acting Amylin Analogs

5.1 From Meal-Related Signals to Sustained Receptor Stimulation

Native Amylin generates short-duration physiological signals associated with food intake, with its major actions concentrated during and after meals. Long-acting Amylin analogs increase stability and extend systemic exposure, expanding the Satiation signal generated during a single meal into a longer time window so that Meal Size and total Energy Intake remain controlled across multiple feeding cycles.

5.2 Cross-Activation of AMYR and CTR

Some long-acting Amylin analogs are not highly selective for only one AMYR subtype but can simultaneously generate activity at AMYR and CTR. This cross-receptor activity causes the overall effect to depend on tissue CTR expression, RAMP composition, relative ligand potency, and duration of drug exposure. Therefore, the entire functional profile cannot be explained by a single Amylin receptor subtype.

5.3 Sustained Food-Intake Suppression and Long-Term Weight Loss

Long-acting ligands extend the transient meal-termination signal across multiple feeding cycles, gradually transforming control of a single Meal Size into a reduction in total daily Energy Intake. Sustained negative energy balance then leads to decreases in Fat Mass and Body Weight. The core value of half-life extension is therefore to prolong and stabilize Amylin-like feeding regulation rather than alter its fundamental pharmacological direction.

6 Representative Drugs Related to the Amylin Receptor

6.1 Pramlintide

(1) Amylin Analog

Pramlintide is an Amylin analog generated through amino acid substitutions in Human Amylin. Introduction of Proline reduces the aggregation tendency of native Human Amylin while preserving Amylin-like receptor activity. Its actions remain mainly centered on meal-related Amylin functions and, compared with newer long-acting analogs, more closely resemble pharmacological enhancement of physiological postprandial signaling.

(2) Promotion of Satiety and Reduction of Food Intake

Pramlintide enhances Satiation and reduces Meal Size through Amylin receptor-related central neural networks, causing individual meals to terminate earlier. Sustained reductions in meal size can gradually decrease daily Energy Intake and eventually produce changes in body weight and fat mass.

(3) Regulation of Postprandial Nutrient Input

Pramlintide can also delay gastric emptying and suppress prandial Glucagon, jointly limiting postprandial Glucose load by slowing nutrient absorption and reducing hepatic glucose output. These effects reflect its postprandial metabolic-regulatory properties, while the main weight-loss mechanism remains centered on feeding and meal termination.

6.2 Cagrilintide

(1) Long-Acting AMYR/CTR Agonism

Cagrilintide is a long-acting Amylin analog whose receptor activity is not limited to a single AMYR subtype but involves both the Amylin receptor and CTR. Half-life extension converts receptor stimulation from a short postprandial signal into sustained pharmacological input, allowing the Amylin pathway to participate stably in long-term control of food intake.

(2) Sustained Suppression of Energy Intake

Cagrilintide continuously enhances Amylin-like satiety and meal-termination signals, reducing Food Intake over a longer timescale. Reductions in Body Weight and Fat Mass are mainly produced by the cumulative effect of long-term decreases in Energy Intake rather than by a direct action independent of central feeding regulation.

(3) Receptor Spectrum Influences Overall Pharmacology

Cagrilintide acts on both AMYR and CTR, so its pharmacological intensity depends not only on half-life extension but also on tissue-specific CTR-RAMP composition and relative activity at different receptors. AMYR/CTR cross-agonism is an important basis for understanding the differences between Cagrilintide and traditional Amylin analogs.

6.3 Calcitonin- and CGRP-Class Ligands

The major value of Calcitonin- and CGRP-related peptides in Amylin receptor research is to dissect cross-activity within the CTR-RAMP receptor family. Calcitonin-class ligands can help determine the shared contributions of CTR and AMYR, whereas CGRP-class ligands are suitable for analyzing ligand selectivity in RAMP1-related receptor environments, allowing functional differences among different Amylin receptor subtypes to be further separated.

Table 2 Functional Characteristics of Representative Amylin Receptor-Related Ligands

7 Amylin Receptor and Multi-Pathway Weight Loss

7.1 Synergy With GLP-1R

Both the Amylin receptor and GLP-1R can reduce Food Intake, but the receptor structures and major neural entry points of the two systems are not completely identical. The Amylin receptor prominently involves CTR-RAMP-related hindbrain meal-termination networks, whereas GLP-1R regulates feeding through another set of gastrointestinal-brain and central neural circuits. Combined activation can reduce energy intake through different nodes, providing a mechanistic basis for combining Cagrilintide with GLP-1R agonists such as Semaglutide.

7.2 Relationship With the GIPR Network

The direct satiety signal generated by the Amylin receptor is also regulated by higher-level feeding networks. GIPR and other energy-state signals can alter the sensitivity of the central nervous system to Amylin input. Multi-receptor weight loss should therefore not be understood simply as an additive effect of multiple receptors; whether one receptor changes the network gain of another satiety pathway also needs to be determined.

8 Key Experiments in Amylin Receptor Research

8.1 Receptor Composition and Ligand Activity

Amylin receptor research first needs to determine whether the experimental system expresses CTR alone or a complex of CTR with RAMP1, RAMP2, or RAMP3. cAMP, EC₅₀, and Emax can describe basic receptor activity, but molecules with cross-activity such as Cagrilintide and Calcitonin-class ligands should also be compared separately in CTR, AMY1R, AMY2R, and AMY3R backgrounds to determine their true receptor spectrum.

8.2 Food Intake and Gastrointestinal Function

Food Intake and Meal Size are the most direct behavioral indicators in Amylin weight-loss research, with Meal Size being particularly suitable for reflecting Satiation and meal-termination effects. Gastric emptying can be used to assist in evaluating regulation of gastrointestinal nutrient input. Body Weight and Body Composition mainly reflect long-term energy-balance outcomes, and observing final body-weight changes alone is insufficient to demonstrate a direct Amylin receptor effect.

8.3 Central Neural Responses

The AP/NTS is an important observation region for central Amylin actions, and neural-activity indicators such as c-Fos can be used to determine whether peripheral Amylin or its analogs recruit related hindbrain networks. For potent or long-acting ligands, feeding behavior also needs to be used to distinguish enhanced Satiation from Aversion-related reductions in food intake, avoiding interpretation of nonspecific discomfort-induced Food Intake reduction as an ideal weight-loss effect.

9 Research Products Related to the Amylin Receptor

9.1 Amylin, CTR, and Related Ligands

9.2 AMYR/CTR Signaling and Central Response Research

9.3 Combined Weight-Loss and Metabolic Function Evaluation

The key to Amylin receptor-targeted weight loss lies in the combined action of the CTR-RAMP receptor-complex structure and the hindbrain meal-termination network. Native Amylin mainly mediates postprandial Satiation and regulation of nutrient input, Pramlintide enhances classical Amylin-like actions, and Cagrilintide extends this physiological signal into sustained body-weight management through long-acting AMYR/CTR agonism. Complementarity with pathways such as GLP-1R further increases the research value of the Amylin receptor in multi-pathway weight-loss drugs.

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