Mechanism of Action
Ghrelin Receptor Antagonism
LEAP-2 binds GHSR1a (the active ghrelin/" class="wiki-internal-link">ghrelin receptor) with high affinity and blocks ghrelin binding, acting as a competitive antagonist. Beyond simple blockade, LEAP-2 acts as an inverse agonist, suppressing the constitutive (ligand-independent) activity of GHSR1a. GHSR1a has one of the highest constitutive activities of any known GPCR (~50% basal signaling without ligand), which drives baseline hunger signaling. LEAP-2 suppression of this constitutive activity reduces hunger tone independent of circulating ghrelin.
Postprandial Regulation
LEAP-2 is secreted from hepatocytes and enterocytes in response to glucose, insulin, and lipids, signals of adequate nutrition. Its postprandial rise opposes ghrelin's fasting-induced rise, creating a complementary see-saw. As a meal-responsive GHSR antagonist, LEAP-2 contributes to meal termination and postprandial satiety signaling. This function was overlooked before the receptor connection was made; LEAP-2 is now considered a genuine counter-regulatory hormone to ghrelin.
Growth Hormone Regulation
By blocking GHSR1a in the hypothalamus and pituitary, LEAP-2 reduces ghrelin-stimulated growth hormone release. Elevated LEAP-2 in obesity may partly explain the blunted GH pulse amplitude and reduced IGF-1 seen in obese individuals. LEAP-2 also suppresses ghrelin-driven GH secretion during sleep, potentially contributing to the obesity-associated disruption of nocturnal GH peaks.
Research Summary
Appetite and Obesity
PreclinicalLEAP-2 administration reduces food intake and body weight in diet-induced obese mice, even when ghrelin is absent (via inverse agonism at constitutive GHSR activity). LEAP-2 knockout mice show increased GHSR-dependent feeding, hyperphagia, and greater obesity susceptibility. In humans, plasma LEAP-2 rises with BMI, though whether this represents pathological compensatory elevation or causative signaling is being studied.
LEAP-2/Ghrelin Ratio
Clinical BiomarkerThe molar LEAP-2/ghrelin ratio is a more informative biomarker of metabolic state than either hormone alone. During fasting, low LEAP-2 and high ghrelin create a high ratio of GHSR activation. In obesity, elevated LEAP-2 and suppressed ghrelin may impair the normal hunger signaling that regulates meal patterns. This ratio may predict response to ghrelin-system therapies and bariatric surgery outcomes.
Alcohol Use and Neurological
EmergingGHSR plays roles in reward, motivation, and alcohol seeking behavior. LEAP-2 reduces ghrelin-driven alcohol preference in rodent models, suggesting it may modulate addictive behaviors mediated by the ghrelin/GHSR system. Central LEAP-2 effects on dopamine reward circuits via GHSR are an emerging research area with implications for addiction and mood disorders.
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Appetite suppression (rodent) | 10-50 mg/kg SC | Once daily for 1-2 weeks | SC |
| GH suppression study | 1-10 mg/kg IV | Acute; measure GH at 15, 30, 60 min | IV bolus |
| GHSR binding assay | 1-1000 nM | Concentration-response curve | In vitro receptor binding |
Human dosing not yet established. LEAP-2 is in early preclinical-to-clinical translation with most data from rodent models.
Interactions
Safety Profile
LEAP-2 has no established human safety profile. Rodent studies show reduced food intake and body weight as primary effects without gross toxicity. Suppression of constitutive GHSR activity raises theoretical concerns about overly suppressing GH pulsatility, which could impair muscle maintenance and metabolic rate over the long term. The rapid receptor action of LEAP-2 suggests short-term use for appetite control would be different from chronic GH suppression. No hepatotoxicity, cardiovascular, or immunological adverse effects noted in current animal studies.
References
- [1]Ge X, et al. LEAP2 is an endogenous antagonist of the ghrelin receptor. Cell Metab. 2018;27:461-469.
- [2]M'Kadmi C, et al. LEAP2 inhibits ghrelin-stimulated GH secretion and food intake. Mol Cell Endocrinol. 2019.
- [3]Muller TD, et al. Ghrelin. Mol Metab. 2015.