LEAP2 competes directly with ghrelin for the GHSR1a receptor but shows unusual pharmacology — acting as either a competitive or non-competitive antagonist depending on whether it binds the receptor before or simultaneously with ghrelin.
Dual antagonist behaviorLEAP2 can act as either a competitive or non-competitive ghrelin receptor antagonist depending solely on whether it reaches the receptor before or at the same time as ghrelin — an unusual pharmacological property driven by its slow dissociation rate.
What the researchers found
The study revealed several key insights into LEAP2-GHSR1a binding:
- LEAP2 and ghrelin bind GHSR1a competitively (sharing the same or overlapping binding sites), contrary to prior reports of non-competitive binding
- LEAP2 shows dual antagonistic behavior depending on timing:
- Added before ghrelin: acts as a non-competitive antagonist (reduces maximal ghrelin effect)
- Added simultaneously with ghrelin: acts as a competitive antagonist (shifts the dose-response curve)
- This unusual pharmacological profile is likely caused by LEAP2's slow dissociation rate from the receptor
- The N-terminal fragment of LEAP2 is critical for receptor binding
- These findings resolve conflicting reports in the literature about LEAP2's mechanism
Why it matters
The ghrelin-GHSR1a system is a major regulator of appetite, body weight, and growth hormone release. LEAP2 naturally counterbalances ghrelin's hunger-promoting effects. Understanding exactly how LEAP2 blocks this receptor could enable the design of new drugs for obesity and metabolic disorders that mimic or enhance LEAP2's action — potentially offering a different approach to weight management than current GLP-1 medications.
How the study worked
The researchers used cell-based binding assays (measuring competitive displacement of labeled ghrelin by LEAP2) and receptor activation assays (measuring calcium signaling through GHSR1a) in cultured cells. LEAP2 was added either before or simultaneously with ghrelin to characterize its antagonistic behavior. Truncated LEAP2 fragments were tested to identify which regions are required for receptor binding.
What this study cannot tell us
This is an in vitro study using cell-based assays that may not fully reflect in vivo pharmacology. The slow dissociation rate hypothesis for LEAP2's dual behavior is proposed but not directly measured with kinetic binding studies. The study focuses on receptor binding and activation but does not assess downstream metabolic effects. The concentration ranges used in cell assays may not reflect physiological LEAP2 and ghrelin levels. No animal or human studies were conducted.
How to read the evidence
This is a basic science in vitro study characterizing receptor-ligand pharmacology using cell-based assays. While it provides detailed mechanistic insights into LEAP2-GHSR1a binding, it does not address in vivo effects, clinical applications, or metabolic outcomes. It represents foundational research for future drug development.
When this study was published
Published in 2019, this study is relatively recent and was published shortly after LEAP2's role as a ghrelin antagonist was first discovered (2018), making it an early but important mechanistic contribution to this rapidly evolving field.
The bigger picture
The ghrelin-LEAP2 axis is emerging as a key regulatory system for energy balance. While GLP-1-based obesity drugs work by enhancing satiety signals, LEAP2-based approaches would work by blocking hunger signals — a complementary mechanism. Understanding LEAP2's unusual binding pharmacology (switching between competitive and non-competitive antagonism) is essential for drug designers aiming to create synthetic GHSR1a antagonists that mimic LEAP2's natural function.
Questions still open
- Could synthetic peptides based on LEAP2's N-terminal region be developed as anti-obesity drugs targeting the ghrelin receptor?
- How do circulating LEAP2 and ghrelin levels change in obesity, and could restoring the LEAP2-ghrelin balance promote weight loss?
- Would combining a LEAP2-based ghrelin receptor antagonist with a GLP-1 agonist produce additive weight-loss effects?
Common questions
What is LEAP2 and how does it relate to hunger?
Could LEAP2 be used to make weight-loss drugs?
Read the original research
Identifying the binding mechanism of LEAP2 to receptor GHSR1a.
The FEBS journal, 286(7), 1332-1345
Citation
Wang, Jia-Hui; Li, Hao-Zheng; Shao, Xiao-Xia; Nie, Wei-Han; Liu, Ya-Li; Xu, Zeng-Guang; Guo, Zhan-Yun. (2019). Identifying the binding mechanism of LEAP2 to receptor GHSR1a.. The FEBS journal, 286(7), 1332-1345. https://doi.org/10.1111/febs.14763