Circulating LEAP-2 is associated with puberty in girls

CRISPR/Cas9-induced LEAP2 and GHSR1a knockout mutant zebrafish displayed abnormal growth and impaired lipid metabolism

Investigating the principles of fish fat deposition and conducting related research are current focal points in fish nutrition. This study explores the endocrine regulation of LEAP2 and GHSR1a in zebrafish by constructing mutantmodels andexamining the effects of the endocrine factors LEAP2 and its receptor GHSR1a on zebrafish growth, feeding, and liver fat deposition. Compared to the wild type (WT), the mutation of LEAP2 results in increased feeding and decreased swimming in zebrafish. The impact is more pronounced in adult female zebrafish, characterized by increased weight, length, width, and accumulation of lipid droplets in the liver.Incontrast, deficiency in GHSR1a significantly reduces the growth of male zebrafish and markedly decreases liver fat deposition.These research findings indicate the crucial roles of LEAP2 and GHSR1a in zebrafish feeding, growth, and intracellular fat metabolism. This study, for the first time, investigated the endocrine metabolic regulation functions of LEAP2 and GHSR1a in the model organism zebrafish, providing initial insights into their effects and potential mechanisms on zebrafish fat metabolism.

Preliminary study on the diagnostic value of LEAP-2 and CK18 in biopsy-proven MAFLD

Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD) has become the leading cause of chronic liver disease. Liver biopsy, as the diagnostic gold standard, is invasive and has sampling bias, making it particularly important to search for sensitive and specific biomarkers for diagnosis. Cytokeratin 18 (CK18) M30 and M65 are products of liver cell apoptosis and necrosis, respectively, and liver-expressed antimicrobial peptide 2 (LEAP-2) is a related indicator of glucose and lipid metabolism. Correlation studies have found that all three indicators positively correlate with the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Through comparison of diagnostic values, it was found that CK18 M65 can better distinguish between healthy individuals and MAFLD; LEAP-2 can effectively distinguish MAFLD from other liver diseases, especially ALD.

Decoding the influence of central LEAP2 on food intake and its effect on accumbal dopamine release

The gut-brain peptide ghrelin and its receptor are established as a regulator of hunger and reward-processing. However, the recently recognized ghrelin receptor inverse agonist, liver-expressed antimicrobial peptide 2 (LEAP2), is less characterized. The present study aimed to elucidate LEAP2s central effect on reward-related behaviors through feeding and its mechanism. LEAP2 was administrated centrally in mice and effectively reduced feeding and intake of palatable foods. Strikingly, LEAP2s effect on feeding was correlated to the preference of the palatable food. Further, LEAP2 reduced the rewarding memory of high preference foods, and attenuated the accumbal dopamine release associated with palatable food exposure and eating. Interestingly, LEAP2 was widely expressed in the brain, and particularly in reward-related brain areas such as the laterodorsal tegmental area (LDTg). This expression was markedly altered when allowed free access to palatable foods. Accordingly, infusion of LEAP2 into LDTg was sufficient to transiently reduce acute palatable food intake. Taken together, the present results show that central LEAP2 has a profound effect on dopaminergic reward signaling associated with food and affects several aspects of feeding. The present study highlights LEAP2s effect on reward, which may have applications for obesity and other reward-related psychiatric and neurological disorders.

Pre-prandial plasma liver-expressed antimicrobial peptide 2 (LEAP2) concentration in humans is inversely associated with hunger sensation in a ghrelin independent manner

PURPOSE

The liver-expressed antimicrobial peptide 2 (LEAP2) is a newly recognized peptide hormone that acts via the growth hormone secretagogue receptor (GHSR) blunting the effects of ghrelin and displaying ghrelin-independent actions. Since the implications of LEAP2 are beginning to be elucidated, we investigated if plasma LEAP2 concentration varies with feeding status or sex and whether it is associated with glucose metabolism and appetite sensations.

METHODS

We performed a single test meal study, in which plasma concentrations of LEAP2, ghrelin, insulin and glucose as well as visual analogue scales for hunger, desire to eat, prospective food consumption, fullness were assessed before and 60 min after breakfast in 44 participants (n = 21 females) with normal weight (NW) or overweight/obesity (OW/OB).

RESULTS

Pre-prandial plasma LEAP2 concentration was ~ 1.6-fold higher whereas ghrelin was ~ 2.0-fold lower in individuals with OW/OB (p < 0.001) independently of sex. After adjusting for body mass index (BMI) and sex, pre-prandial plasma LEAP2 concentration displayed a direct relationship with BMI (β: 0.09; 95%CI: 0.05, 0.13; p < 0.001), fat mass (β: 0.05; 95%CI: 0.01, 0.09; p = 0.010) and glycemia (β: 0.24; 95%CI: 0.05, 0.43; p = 0.021), whereas plasma ghrelin concentration displayed an inverse relationship with BMI and fat mass but not with glycemia. Postprandial plasma LEAP2 concentration increased ~ 58% in females with OW/OB (p = 0.045) but not in females with NW or in males. Pre-prandial plasma LEAP2 concentration displayed an inverse relationship with hunger score (β: - 11.16; 95% CI: - 18.52, - 3.79; p = 0.004), in a BMI-, sex- and ghrelin-independent manner.

CONCLUSIONS

LEAP2 emerges as a key hormone implicated in the regulation of metabolism and appetite in humans.

TRIAL REGISTRATION

The study was retrospectively registered in clinicaltrials.gov (April 2023).

CLINICALTRIALS

gov Identifier: NCT05815641.

The effects of ghrelin and LEAP-2 in energy homeostasis are modulated by thermoneutrality, high-fat diet and aging

PURPOSE

Liver-expressed antimicrobial peptide 2 (LEAP-2) has been recently identified as the endogenous non-competitive allosteric antagonist of the growth hormone secretagogue receptor 1a (GHSR1a). In rodents, LEAP-2 blunts ghrelin-induced feeding and its plasma levels are modulated in response to nutritional status, being decreased upon fasting and increased in high-fat diet (HFD) fed mice. Clinical data support the regulation of circulating LEAP-2 by nutrient availability in humans. In this work, our primary objective was to examine the chronic effects of ghrelin and LEAP-2 administration on food intake, adiposity, and energy expenditure in young mice subjected to standard and HFD at both room temperature and at thermoneutrality. Furthermore, we aimed to assess the impact of these two hormones on aging mice.

RESULTS

Our results indicate that LEAP-2 produces a significant decrease of body weight and adiposity, an increase in energy expenditure, and activation of the thermogenic program in white and brown adipose tissue depots. However, this effect is not maintained under HFD or under thermoneutral conditions and is only partially observed in aging mice.

CONCLUSION

In summary our studies describe the central effects of LEAP-2 within distinct experimental contexts, and contribute to the comprehension of LEAP-2's role in energy metabolism.

Cluster analysis in gambling disorder based on sociodemographic, neuropsychological, and neuroendocrine features regulating energy homeostasis

BACKGROUND

The heterogeneity of gambling disorder (GD) has led to the identification of different subtypes, mostly including phenotypic features, with distinctive implications on the GD severity and treatment outcome. However, clustering analyses based on potential endophenotypic features, such as neuropsychological and neuroendocrine factors, are scarce so far.

AIMS

This study firstly aimed to identify empirical clusters in individuals with GD based on sociodemographic (i.e., age and sex), neuropsychological (i.e., cognitive flexibility, inhibitory control, decision making, working memory, attention, and set-shifting), and neuroendocrine factors regulating energy homeostasis (i.e., leptin, ghrelin, adiponectin, and liver-expressed antimicrobial peptide 2, LEAP-2). The second objective was to compare the profiles between clusters, considering the variables used for the clustering procedure and other different sociodemographic, clinical, and psychological features.

METHODS

297 seeking-treatment adult outpatients with GD (93.6% males, mean age of 39.58 years old) were evaluated through a semi-structured clinical interview, self-reported psychometric assessments, and a protocolized neuropsychological battery. Plasma concentrations of neuroendocrine factors were assessed in peripheral blood after an overnight fast. Agglomerative hierarchical clustering was applied using sociodemographic, neuropsychological, and neuroendocrine variables as indicators for the grouping procedure. Comparisons between the empirical groups were performed using Chi-square tests (χ2) for categorical variables, and analysis of variance (ANOVA) for quantitative measures.

RESULTS

Three-mutually-exclusive groups were obtained, being neuropsychological features those with the greatest weight in differentiating groups. The largest cluster (Cluster 1, 65.3%) was composed by younger males with strategic and online gambling preferences, scoring higher on self-reported impulsivity traits, but with a lower cognitive impairment. Cluster 2 (18.2%) and 3 (16.5%) were characterized by a significantly higher proportion of females and older patients with non-strategic gambling preferences and a worse neuropsychological performance. Particularly, Cluster 3 had the poorest neuropsychological performance, especially in cognitive flexibility, while Cluster 2 reported the poorest inhibitory control. This latter cluster was also distinguished by a poorer self-reported emotion regulation, the highest prevalence of food addiction, as well as a metabolic profile characterized by the highest mean concentrations of leptin, adiponectin, and LEAP-2.

CONCLUSIONS

To the best of our knowledge, this is the first study to identify well-differentiated GD clusters using neuropsychological and neuroendocrine features. Our findings reinforce the heterogeneous nature of the disorder and emphasize a role of potential endophenotypic features in GD subtyping. This more comprehensive characterization of GD profiles could contribute to optimize therapeutic interventions based on a medicine of precision.

Liver-expressed antimicrobial peptide 2 elevation contributes to age-associated cognitive decline

Elderly individuals frequently report cognitive decline, while various studies indicate hippocampal functional declines with advancing age. Hippocampal function is influenced by ghrelin through hippocampus-expressed growth hormone secretagogue receptor (GHSR). Liver-expressed antimicrobial peptide 2 (LEAP2) is an endogenous GHSR antagonist that attenuates ghrelin signaling. Here, we measured plasma ghrelin and LEAP2 levels in a cohort of cognitively normal individuals older than 60 and found that LEAP2 increased with age while ghrelin (also referred to in literature as "acyl-ghrelin") marginally declined. In this cohort, plasma LEAP2/ghrelin molar ratios were inversely associated with Mini-Mental State Examination scores. Studies in mice showed an age-dependent inverse relationship between plasma LEAP2/ghrelin molar ratio and hippocampal lesions. In aged mice, restoration of the LEAP2/ghrelin balance to youth-associated levels with lentiviral shRNA Leap2 downregulation improved cognitive performance and mitigated various age-related hippocampal deficiencies such as CA1 region synaptic loss, declines in neurogenesis, and neuroinflammation. Our data collectively suggest that LEAP2/ghrelin molar ratio elevation may adversely affect hippocampal function and, consequently, cognitive performance; thus, it may serve as a biomarker of age-related cognitive decline. Moreover, targeting LEAP2 and ghrelin in a manner that lowers the plasma LEAP2/ghrelin molar ratio could benefit cognitive performance in elderly individuals for rejuvenation of memory.

Are Signals Regulating Energy Homeostasis Related to Neuropsychological and Clinical Features of Gambling Disorder? A Case-Control Study

Gambling disorder (GD) is a modestly prevalent and severe condition for which neurobiology is not yet fully understood. Although alterations in signals involved in energy homeostasis have been studied in substance use disorders, they have yet to be examined in detail in GD. The aims of the present study were to compare different endocrine and neuropsychological factors between individuals with GD and healthy controls (HC) and to explore endocrine interactions with neuropsychological and clinical variables. A case−control design was performed in 297 individuals with GD and 41 individuals without (healthy controls; HCs), assessed through a semi-structured clinical interview and a psychometric battery. For the evaluation of endocrine and anthropometric variables, 38 HCs were added to the 41 HCs initially evaluated. Individuals with GD presented higher fasting plasma ghrelin (p < 0.001) and lower LEAP2 and adiponectin concentrations (p < 0.001) than HCs, after adjusting for body mass index (BMI). The GD group reported higher cognitive impairment regarding cognitive flexibility and decision-making strategies, a worse psychological state, higher impulsivity levels, and a more dysfunctional personality profile. Despite failing to find significant associations between endocrine factors and either neuropsychological or clinical aspects in the GD group, some impaired cognitive dimensions (i.e., WAIS Vocabulary test and WCST Perseverative errors) and lower LEAP2 concentrations statistically predicted GD presence. The findings from the present study suggest that distinctive neuropsychological and endocrine dysfunctions may operate in individuals with GD and predict GD presence. Further exploration of endophenotypic vulnerability pathways in GD appear warranted, especially with respect to etiological and therapeutic potentials.

Beta-Hydroxybutyrate Suppresses Hepatic Production of the Ghrelin Receptor Antagonist LEAP2

INTRODUCTION

Liver-expressed antimicrobial peptide-2 (LEAP2) is an endogenous ghrelin receptor antagonist, which is upregulated in the fed state and downregulated during fasting. We hypothesized that the ketone body beta-hydroxybutyrate (BHB) is involved in the downregulation of LEAP2 during conditions with high circulating levels of BHB.

METHODS

Hepatic and intestinal Leap2 expression were determined in 3 groups of mice with increasing circulating levels of BHB: prolonged fasting, prolonged ketogenic diet, and oral BHB treatment. LEAP2 levels were measured in lean and obese individuals, in human individuals following endurance exercise, and in mice after BHB treatment. Lastly, we investigated Leap2 expression in isolated murine hepatocytes challenged with BHB.

RESULTS

We confirmed increased circulating LEAP2 levels in individuals with obesity compared to lean individuals. The recovery period after endurance exercise was associated with increased plasma levels of BHB levels and decreased LEAP2 levels in humans. Leap2 expression was selectively decreased in the liver after fasting and after exposure to a ketogenic diet for 3 weeks. Importantly, we found that oral administration of BHB increased circulating levels of BHB in mice and decreased Leap2 expression levels and circulating LEAP2 plasma levels, as did Leap2 expression after direct exposure to BHB in isolated murine hepatocytes.

CONCLUSION

From our data, we suggest that LEAP2 is downregulated during different states of energy deprivation in both humans and rodents. Furthermore, we here provide evidence that the ketone body, BHB, which is highly upregulated during fasting metabolism, directly downregulates LEAP2 levels. This may be relevant in ghrelin receptor-induced hunger signaling during energy deprivation.

Serum levels of ghrelin and LEAP2 in patients with type 2 diabetes mellitus: correlation with circulating glucose and lipids

Objective

Ghrelin regulates body weight, food intake, and blood glucose. It also regulates insulin secretion from pancreatic islet cells. LEAP2 is a newly discovered endogenous ligand of the growth hormone secretagogue's receptor (GHSR). It not only antagonizes the stimulation of GHSR by ghrelin but also inhibits the constitutive activation of GHSR as an inverse agonist. Type 2 diabetes (T2D) patients have endocrine disorders with metabolic imbalance. Plasma levels of ghrelin and LEAP2 may be changed in obese and T2D patients. However, there is no report yet on circulating LEAP2 levels or ghrelin/LEAP2 ratio in T2D patients. In this study, fasting serum ghrelin and LEAP2 levels in healthy adults and T2D patients were assessed to clarify the association of two hormones with different clinical anthropometric and metabolic parameters.

Design

A total of 16 females and 40 males, ages 23-68 years old normal (n = 27), and T2D patients (n = 29) were enrolled as a cross-sectional cohort.

Results

Serum levels of ghrelin were lower but serum levels of LEAP2 were higher in T2D patients. Ghrelin levels were positively correlated with fasting serum insulin levels and HOMA-IR in healthy adults. LEAP2 levels were positively correlated with age and hemoglobin A1c (HbA1c) in all tested samples. Ghrelin/LEAP2 ratio was negatively correlated with age, fasting blood glucose, and HbA1c.

Conclusions

This study demonstrated a decrease in serum ghrelin levels and an increase in serum LEAP2 levels in T2D patients. LEAP2 levels were positively correlated with HbA1c, suggesting that LEAP2 was associated with T2D development. The ghrelin/LEAP2 ratio was closely associated with glycemic control in T2D patients showing a negative correlation with glucose and HbA1c.

Circulating Liver-Enriched Antimicrobial Peptide-2 Decreases during Male Puberty

Objective

Circulating levels of liver-enriched antimicrobial peptide 2 (LEAP2), a ghrelin receptor antagonist, decrease under caloric restriction and increase in obesity. The role of LEAP2 in male puberty, a phase with accelerated energy demand, is unclear.

Methods

We determined circulating LEAP2 levels in 28 boys with constitutional delay of growth and puberty (CDGP) who participated in a randomized controlled trial (NCT01797718), and were treated with letrozole (n=15) or intramuscular low-dose testosterone (T) (n=13) for 6 months. Blood sampling and dual-energy x-ray absorptiometry-measured body composition were performed at 0, 6, and 12 month visits.

Results

Serum LEAP2 levels decreased significantly during pubertal progression (0-6 mo: mean decrease -4.3 [10.3] ng/ml, p=0.036 and 0-12mo: -3.9 [9.3] ng/ml, p=0.033). Between 0 and 6 months, the changes in serum LEAP2 levels correlated positively with changes in percentage of body fat (rs=0.48, p=0.011), and negatively with growth velocity, and estradiol levels (rs=-0.43, p=0.022, rs=-0.55, p=0.003, respectively). In the T group only, the changes in serum LEAP2 correlated negatively with changes in testosterone and estradiol levels. Between 0 and 12 months, the change in LEAP2 levels correlated negatively with the change in HDL levels (rs= -0.44, p=0.022) and positively with the change in insulin (rs=0.50, p=0.009), and HOMA-IR (rs=0.51, p=0.007) levels.

Conclusions

Circulating LEAP2 levels decreased after induction of puberty reciprocally with increased growth rate and energy demand reflecting the metabolic state of the adolescent. Further, the results suggest that estradiol levels may have a permissive role in downregulating circulating LEAP2 levels.

LEAP-2 Counteracts Ghrelin-Induced Food Intake in a Nutrient, Growth Hormone and Age Independent Manner

Data gleaned recently shows that ghrelin, a stomach derived peptide, and liver-expressed-antimicrobial peptide 2 (LEAP-2) play opposite roles on food intake. However, the data available with LEAP-2 in relation to in vivo studies are still very scanty and some key questions regarding the interplay among ghrelin and LEAP-2 remain to be answered. In this work, using rats and mice, we study fasting-induced food intake as well as testing the effect of diet exposure, e.g., standard diet and high fat diet, in terms of ghrelin-induced food intake. The anorexigenic effect of LEAP-2 on fasting induced food intake appears to be dependent on energy stores, being more evident in ob/ob than in wild type mice and also in animals exposed to high fat diet. On the other hand, LEAP-2 administration markedly inhibited ghrelin-induced food intake in lean, obese (ob/ob and DIO) mice, aged rats and GH-deficient dwarf rats. In contrast, the inhibitory effect on glucose levels can only be observed in some specific experimental models indicating that the mechanisms involved are likely to be quite different. Taken together from these data, LEAP-2 emerged as a potential candidate to be therapeutically useful in obesity.

Involvement of POMC neurons in LEAP2 regulation of food intake and body weight

Liver-expressed antimicrobial peptide 2 (LEAP2) is a newly discovered antagonist of the growth hormone secretagogue receptor (GHSR) and is considered the first endogenous peptide that can antagonize the metabolic actions of ghrelin. The effects of ghrelin administration on feeding behavior, body weight, and energy metabolism involve the activation of orexigenic neurons in the arcuate nucleus (ARC) of the hypothalamus. It is unclear, however, if LEAP2 applied directly to the ARC of the hypothalamus affects these metabolic processes. Here, we show that overexpression of LEAP2 in the ARC through adeno-associated virus (AAV) reduced food intake and body weight in wild-type (WT) mice fed chow and a high-fat diet (HFD) and improved metabolic disorders. LEAP2 overexpression in the ARC overrides both central and peripheral ghrelin action on a chow diet. Interestingly, this AAV-LEAP2 treatment increased proopiomelanocortin (POMC) expression while agouti-related peptide (AGRP)/neuropeptide Y (NPY) and GHSR levels remained unchanged in the hypothalamus. Additionally, intracerebroventricular (i.c.v.) administration of LEAP2 decreased food intake, increased POMC neuronal activity, and repeated LEAP2 administration to mice induced body weight loss. Using chemogenetic manipulations, we found that inhibition of POMC neurons abolished the anorexigenic effect of LEAP2. These results demonstrate that central delivery of LEAP2 leads to appetite-suppressing and body weight reduction, which might require activation of POMC neurons in the ARC.

The "Adipo-Cerebral" Dialogue in Childhood Obesity: Focus on Growth and Puberty. Physiopathological and Nutritional Aspects

Overweight and obesity in children and adolescents are overwhelming problems in western countries. Adipocytes, far from being only fat deposits, are capable of endocrine functions, and the endocrine activity of adipose tissue, resumable in adipokines production, seems to be a key modulator of central nervous system function, suggesting the existence of an “adipo-cerebral axis.” This connection exerts a key role in children growth and puberty development, and it is exemplified by the leptin–kisspeptin interaction. The aim of this review was to describe recent advances in the knowledge of adipose tissue endocrine functions and their relations with nutrition and growth. The peculiarities of major adipokines are briefly summarized in the first paragraph; leptin and its interaction with kisspeptin are focused on in the second paragraph; the third paragraph deals with the regulation of the GH-IGF axis, with a special focus on the model represented by growth hormone deficiency (GHD); finally, old and new nutritional aspects are described in the last paragraph.

LEAP2 deletion in mice enhances ghrelin's actions as an orexigen and growth hormone secretagogue

Objective

The hormone liver-expressed antimicrobial peptide-2 (LEAP2) is a recently identified antagonist and an inverse agonist of the growth hormone secretagogue receptor (GHSR). GHSR's other well-known endogenous ligand, acyl-ghrelin, increases food intake, body weight, and GH secretion and is lowered in obesity but elevated upon fasting. In contrast, LEAP2 reduces acyl-ghrelin-induced food intake and GH secretion and is found elevated in obesity but lowered upon fasting. Thus, the plasma LEAP2/acyl-ghrelin molar ratio could be a key determinant modulating GHSR signaling in response to changes in body mass and feeding status. In particular, LEAP2 may serve to dampen acyl-ghrelin action in the setting of obesity, which is associated with ghrelin resistance. Here, we sought to determine the metabolic effects of genetic LEAP2 deletion.

Methods

We generated the first known LEAP2-KO mouse line. Food intake, GH secretion, and cellular activation (c-fos induction) in different brain regions following s.c. acyl-ghrelin administration in LEAP2-KO mice and wild-type littermates were determined. LEAP2-KO mice and wild-type littermates were submitted to a battery of tests (such as measurements of body weight, food intake, and body composition; indirect calorimetry, determination of locomotor activity, and meal patterning while housed in metabolic cages) over the course of 16 weeks of high-fat diet and/or standard chow feeding. Fat accumulation was assessed in hematoxylin & eosin-stained and oil red O-stained liver sections from these mice.

Results

LEAP2-KO mice were more sensitive to s.c. ghrelin. In particular, acyl-ghrelin acutely stimulated food intake at a dose of 0.5 mg/kg BW in standard chow-fed LEAP2-KO mice while a 2× higher dose was required by wild-type littermates. Also, acyl-ghrelin stimulated food intake at a dose of 1 mg/kg BW in high-fat diet-fed LEAP2-KO mice while not even a 10× higher dose was effective in wild-type littermates. Acyl-ghrelin induced a 90.9% higher plasma GH level and 77.2–119.7% higher numbers of c-fos-immunoreactive cells in the arcuate nucleus and olfactory bulb, respectively, in LEAP2-KO mice than in wild-type littermates. LEAP2 deletion raised body weight (by 15.0%), food intake (by 18.4%), lean mass (by 6.1%), hepatic fat (by 42.1%), and body length (by 1.7%) in females on long-term high-fat diet as compared to wild-type littermates. After only 4 weeks on the high-fat diet, female LEAP2-KO mice exhibited lower O₂ consumption (by 13%), heat production (by 9.5%), and locomotor activity (by 49%) than by wild-type littermates during the first part of the dark period. These genotype-dependent differences were not observed in high-fat diet-exposed males or female and male mice exposed for long term to standard chow diet.

Conclusions

LEAP2 deletion sensitizes lean and obese mice to the acute effects of administered acyl-ghrelin on food intake and GH secretion. LEAP2 deletion increases body weight in females chronically fed a high-fat diet as a result of lowered energy expenditure, reduced locomotor activity, and increased food intake. Furthermore, in female mice, LEAP2 deletion increases body length and exaggerates the hepatic fat accumulation normally associated with chronic high-fat diet feeding.

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A novel line of LEAP2-knockout mice was generated.

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LEAP2 deletion sensitizes mice to the GH secretory effects of administered ghrelin.

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LEAP2 deletion reduces ghrelin resistance in diet-induced obese mice.

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HFD-fed female LEAP2-KO mice eat more and gain more body weight and hepatic fat.

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HFD-fed female LEAP2-KO mice exhibit lowered energy expenditure and activity.

LEAP2 has antagonized the ghrelin receptor GHSR1a since its emergence in ancient fish

Recent studies have demonstrated that liver-expressed antimicrobial peptide 2 (LEAP2) antagonizes the ghrelin receptor GHSR1a in mammals. However, its antagonistic function in lower vertebrates has not yet been tested. LEAP2 orthologs have been identified from a variety of fish species; however, previous studies all focused on their antimicrobial activity. To test whether LEAP2 functions as a GHSR1a antagonist in the lowest vertebrates, we studied the antagonism of a fish LEAP2 from Latimeria chalumnae, an extant coelacanth that is one of the closest living fish relatives of tetrapods. Using binding assays, we demonstrated that the coelacanth LEAP2 and ghrelin bound to the coelacanth GHSR1a with IC₅₀ values in the nanomolar range. Using activation assays, we demonstrated that the coelacanth ghrelin activated the coelacanth GHSR1a with an EC₅₀ value in the nanomolar range, and this activation effect was efficiently antagonized by a nanomolar range of the coelacanth LEAP2. In addition, we also showed that the human LEAP2 and ghrelin were as effective as their coelacanth orthologs towards the coelacanth GHSR1a; however, the coelacanth peptides had moderately lower activity towards the human GHSR1a. Thus, LEAP2 serves as an endogenous antagonist of the ghrelin receptor GHSR1a in coelacanth and the ghrelin-LEAP2-GHSR1a system has evolved slowly since its emergence in ancient fish.

LEAP-2: An Emerging Endogenous Ghrelin Receptor Antagonist in the Pathophysiology of Obesity

Liver-expressed antimicrobial peptide 2 (LEAP-2), originally described as an antimicrobial peptide, has recently been recognized as an endogenous blocker of growth hormone secretagogue receptor 1a (GHS-R1a). GHS-R1a, also known as ghrelin receptor, is a G protein-coupled receptor (GPCR) widely distributed on the hypothalamus and pituitary gland where it exerts its major functions of regulating appetite and growth hormone (GH) secretion. The activity of GHS-R1a is controlled by two counter-regulatory endogenous ligands: Ghrelin (activation) and LEAP-2 (inhibition). Ghrelin activates GHS-R1a on the neuropeptide Y/Agouti-related protein (NPY/AgRP) neurons at the arcuate nucleus (ARC) to promote appetite, and on the pituitary somatotrophs to stimulate GH release. On the flip side, LEAP-2, acts both as an endogenous competitive antagonist of ghrelin and an inverse agonist of constitutive GHS-R1a activity. Such a biological property of LEAP-2 vigorously blocks ghrelin's effects on food intake and hormonal secretion. In circulation, LEAP-2 displays an inverse pattern as to ghrelin; it increases with food intake and obesity (positive energy balance), whereas decreases upon fasting and weight loss (negative energy balance). Thus, the LEAP-2/ghrelin molar ratio fluctuates in response to energy status and modulation of this ratio conversely influences energy intake. Inhibiting ghrelin's activity has shown beneficial effects on obesity in preclinical experiments, which sheds light on LEAP-2's anti-obesity potential. In this review, we will analyze LEAP-2's effects from a metabolic point of view with a focus on metabolic hormones (e.g., ghrelin, GH, and insulin), and discuss LEAP-2's potential as a promising therapeutic target for obesity.