LEAP2 is a more conserved ligand than ghrelin for fish GHSRs

Physiological roles of ghrelin in the regulation of gastrointestinal motility in vertebrates

Ghrelin is known to be a multifunctional peptide hormone that stimulates not only growth hormone secretion and feeding but also gastrointestinal (GI) functions, including motility, secretion and mucosa proliferation. The aim of this review is to provide a comprehensive overview on the physiological roles of ghrelin in the regulation of GI motility from a comparative perspective. The effects of ghrelin on GI motility differ depending on the species, and ghrelin is a possible regulator of gastric migrating motor complexes (MMCs) in rodents, dogs and house musk shrew (suncus). However, the role of ghrelin has not been clarified in detail in other mammals, including humans and rabbits. Ghrelin is also effective to cause contraction in the GI tract of some non-mammals, but its physiological role is also not clarified at present. Distribution of the growth hormone secretagogue receptor (GHSR, ghrelin receptor) in the GI tract might be connected with the regulatory role of ghrelin in vertebrates. Comparative studies of ghrelin among animals and identification of knowledge gaps must lead us to the functional transition and importance of ghrelin in the GI tract.

LEAP2 in Physiology-A Narrative Review

Liver Enriched Antimicrobial Peptide 2 (LEAP2) is a fascinating peptide that has gained significant attention since its discovery in 2003. Initially identified as an antimicrobial peptide, LEAP2 has more recently been found to play a key role in the regulation of energy metabolism. One of the most notable functions of LEAP2 is its interaction with the ghrelin hormone, which is known for stimulating hunger. LEAP2 acts as an inhibitor of ghrelin, thereby reducing food intake and influencing energy balance. The physiological roles of LEAP2 extend beyond appetite suppression. Studies have shown that LEAP2 has an impact on insulin secretion, suggesting its potential involvement in glucose metabolism and possibly insulin sensitivity, which is crucial in managing conditions like type 2 diabetes. Moreover, LEAP2 levels appear to fluctuate based on factors such as gender, developmental stage, and even interventions like bariatric surgery, which is known for its role in managing obesity and diabetes. Given these findings, LEAP2 shows potential as a therapeutic target, particularly for addressing obesity and metabolic diseases such as type 2 diabetes. Its ability to influence food intake and energy balance makes it a promising candidate for further research into therapies aimed at weight regulation and glycemic control. In the future, LEAP2 could become an important agent in the development of treatments aimed at curbing obesity and its associated metabolic disorders.

Deficiency of leap2 promotes somatic growth in zebrafish: Involvement of the growth hormone system

Purpose

Liver-expressed antimicrobial peptide-2 (LEAP2) is identified as an endogenous antagonist and inverse agonist of the growth hormone secretagogue receptor type 1a (GHSR1a), its effect on the GHSR1a is contrary to the role of GHRELIN. Growth hormone (GH) is a crucial hormone for early development. Previous studies report that LEAP2 dose-dependently attenuates ghrelin-induced GH secretion, and Leap2-knockout mice exhibit increased plasma GH levels after GHRELIN administration. Clinical data revealed a possible correlation between LEAP2 and height development. However, the role of LEAP2 in early development remains unclear. This study aimed to investigate the role of LEAP2 in early development using leap2 mutant zebrafish larvae as a model.

Method

We analyzed the conservation of LEAP2 peptide across multiple species and generated leap2 mutants in zebrafish by CRISPR-Cas9, dynamically observed and measured the growth and development of zebrafish larvae from fertilization to 5 day post fertilization (dpf). In situ hybridization, transcriptome sequencing, quantitative real-time PCR and Western blot were used to detect the expression levels of GH and its signaling in early stage of embryonic development.

Result

Our data demonstrate that zebrafish with a knockout of the leap2 gene display a significant increase in hatching rate, body length, and the distance between their eyes, all without visible developmental defects in the early stages of development. In addition, both RNA and protein analyses revealed a significant increase in GH expression in leap2 mutant.

Conclusion

In general, this study demonstrates that LEAP2 regulates the expression of GH during early development, particularly influencing body length.

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.

De novo genome assembly and transcriptome sequencing in foot and mantle tissues of Megaustenia siamensis reveals components of adhesive substances

The semislug Megaustenia siamensis, commonly found in Thailand, is notable for its exceptional capacity to produce biological adhesives, enabling it to adhere to tree leaves even during heavy rainfall. In this study, we generated the first reference genome for M. siamensis using a combination of three sequencing technologies: Illumina's short-read, Pac-Bio's HIFI long-read, and Hi-C. The assembled genome size was 2593 billion base pairs (bp), containing 34,882 protein-coding genes. Our analysis revealed positive selection in pathways associated with the ubiquitin-proteasome system. Furthermore, RNA sequencing of foot and mantle tissues unveiled the primary constituents of the adhesive, including lectin-like proteins (C-lectin, H-lectin, and C1q) and matrilin-like proteins (VWA and EGF). Additionally, antimicrobial peptides were identified. The comprehensive M. siamensis genome and tissue-specific transcriptomic data provided here offer valuable resources for understanding its biology and exploring potential medical applications.

Identification of antibacterial activity of liver-expressed antimicrobial peptide 2 (LEAP2) from primitive vertebrate lamprey

Liver-expressed antimicrobial peptide 2 (LEAP2) is a member of the antimicrobial peptides family and plays a key role in the innate immune system of organisms. LEAP2 orthologs have been identified from a variety of fish species, however, its function in primitive vertebrates has not been clarified. In this study, we cloned and identified Lc-LEAP2 from the primitive jawless vertebrate lamprey (Lethenteron camtschaticum) which includes a 25 amino acids signal peptide and a mature peptide of 47 amino acids. Although sequence similarity was low compared to other species, the mature Lc-LEAP2 possesses four conserved cysteine residues, forming a core structure with two disulfide bonds between the cysteine residues in the relative 1-3 (Cys 58 and Cys 69) and 2-4 (Cys 64 and Cys 74) positions. Lc-LEAP2 was most abundantly expressed in the muscle, supraneural body and buccal gland of lamprey, and was significantly upregulated during LPS and Poly I:C stimulations. The mature peptide was synthesized and characterized for its antibacterial activity against different bacteria. Lc-LEAP2 possessed inhibition of a wide range of bacteria with a dose-dependence, disrupting the integrity of bacterial cell membranes and binding to bacterial genomic DNA, although its inhibitory function is weak compared to that of higher vertebrates. These data suggest that Lc-LEAP2 plays an important role in the innate immunity of lamprey and is of great value in improving resistance to pathogens. In addition, the antimicrobial mechanism of LEAP2 has been highly conserved since its emergence in primitive vertebrates.

The ghrelin receptor GHSR has two efficient agonists in the lobe-finned fish Latimeria chalumnae

The peptide hormone ghrelin (an agonist) and LEAP2 (an antagonist) play important functions in energy metabolism via their receptor GHSR, an A-class G protein-coupled receptor. Ghrelin, LEAP2, and GHSR are widely present from fishes to mammals. However, our recent study suggested that fish GHSRs have different binding properties to ghrelin: a GHSR from the lobe-finned fish Latimeria chalumnae (coelacanth) is efficiently activated by ghrelin, but GHSRs from the ray-finned fish Danio rerio (zebrafish) and Larimichthys crocea (large yellow croaker) have lost binding to ghrelin. Do fish GHSRs use another peptide as their agonist? In the present study we tested to two fish motilins from D. rerio and L. chalumnae because motilin is distantly related to ghrelin. In ligand binding and activation assays, the fish GHSRs from D. rerio and L. crocea displayed no detectable or very low binding to all tested motilins; however, the fish GHSR from L. chalumnae bound to its motilin with high affinity and was efficiently activated by it. Therefore, it seemed that motilin is not a ligand for GHSR in the ray-finned fish D. rerio and L. crocea, but is an efficient agonist for GHSR in the lobe-finned fish L. chalumnae, one of the closest fish relatives of tetrapods. The results of present study suggested that GHSR might have two efficient agonists, ghrelin and motilin, in ancient fishes; however, this feature might be only preserved in some extant fishes with ancient evolutionary origins.