Molecular cloning of human and bovine LECT2 having a neutrophil chemotactic activity and its specific expression in the liver

Hepatokine leukocyte cell-derived chemotaxin 2 as a biomarker of insulin resistance, liver enzymes, and metabolic dysfunction-associated steatotic liver disease in the general population

AIMS/INTRODUCTION

Leukocyte cell-derived chemotaxin 2 (LECT2) is an obesity-associated hepatokine that causes skeletal muscle insulin resistance. Since LECT2 is up-regulated by the inactivation of the energy sensor AMPK in the liver, we hypothesized that LECT2 has potential as a biomarker for metabolic dysfunction-associated steatotic liver disease (MASLD). Therefore, we investigated whether circulating LECT2 levels are associated with insulin sensitivity, liver enzymes, and MASLD.

MATERIALS AND METHODS

This cross-sectional study included 138 Japanese individuals. Plasma LECT2 levels were measured using fasting blood samples. B-mode ultrasonography was used to assess hepatic steatosis.

RESULTS

The mean age and body mass index (BMI) of participants were 63.5 ± 10.2 years and 23.0 ± 3.1 kg/m2, respectively. Higher LECT2 levels positively correlated with homeostatic model assessment for insulin resistance (HOMA-IR) values and negatively correlated with the quantitative insulin sensitivity check index (QUICKI) among all participants (HOMA-IR; non-standardized β (B) = 6.38, P < 0.01: QUICKI; B = -161, P < 0.01). These correlations were stronger in the low BMI group (HOMA-IR; B = 13.85, P < 0.01: QUICKI; B = -180, P < 0.01). LECT2 levels also positively correlated with gamma-glutamyl transferase levels (B = 0.01, P = 0.01) and alanine aminotransferase levels (B = 0.33, P = 0.02). Higher LECT2 levels correlated with the prevalence of MASLD (odds ratio = 1.14, P = 0.02).

CONCLUSIONS

The present results suggest the potential of plasma LECT2 levels as a biomarker for insulin resistance in individuals who are not overweight and the prevalence of MASLD in the general population.

Single-cell transcriptome sequencing analysis of physiological and immune profiling of crucian carp (Carassius auratus) gills

Gills are the main respiratory organs of fish and bear important physiological and immunological functions, but the functional heterogeneity of interlamellar cell mass (ILCM) at the single-cell level has rarely been reported. Here, we identified 19 cell types from the gills of crucian carp (Carassius auratus) by single-cell RNA sequencing (scRNA-seq) in combination with histological analysis. We annotated ILCM and analyzed its functional heterogeneity at the single-cell level for the first time. Functional enrichment analysis and cell cycle analysis identified ILCM as a type of metabolically active cells in a state of constant proliferation, and identified the major pathways responsible for ILCM immunoregulation. Histological analysis revealed the morphology and positional relationships of 6 cell types. Meanwhile, the gene regulatory network of ILCM was established through weighted gene co-expression network analysis (WGCNA), and one transcription factor and five hub genes related to immunoregulation were identified. We found that pyroptosis might be an important pathway responsible for the immune response of ILCM. Our findings provide an insight into the physiological and immune functions of gills and ILCM at the single-cell level and lay a solid foundation for further exploration of the molecular mechanism of ILCM immunity functions.

Hepatokines: unveiling the molecular and cellular mechanisms connecting hepatic tissue to insulin resistance and inflammation

Insulin resistance arising from Non-Alcoholic Fatty Liver Disease (NAFLD) stands as a prevalent global ailment, a manifestation within societies stemming from individuals' suboptimal dietary habits and lifestyles. This form of insulin resistance emerges as a pivotal factor in the development of type 2 diabetes mellitus (T2DM). Emerging evidence underscores the significant role of hepatokines, as hepatic-secreted hormone-like entities, in the genesis of insulin resistance and eventual onset of type 2 diabetes. Hepatokines exert influence over extrahepatic metabolism regulation. Their principal functions encompass impacting adipocytes, pancreatic cells, muscles, and the brain, thereby playing a crucial role in shaping body metabolism through signaling to target tissues. This review explores the most important hepatokines, each with distinct influences. Our review shows that Fetuin-A promotes lipid-induced insulin resistance by acting as an endogenous ligand for Toll-like receptor 4 (TLR-4). FGF21 reduces inflammation in diabetes by blocking the nuclear translocation of nuclear factor-κB (NF-κB) in adipocytes and adipose tissue, while also improving glucose metabolism. ANGPTL6 enhances AMPK and insulin signaling in muscle, and suppresses gluconeogenesis. Follistatin can influence insulin resistance and inflammation by interacting with members of the TGF-β family. Adropin show a positive correlation with phosphoenolpyruvate carboxykinase 1 (PCK1), a key regulator of gluconeogenesis. This article delves into hepatokines' impact on NAFLD, inflammation, and T2DM, with a specific focus on insulin resistance. The aim is to comprehend the influence of these recently identified hormones on disease development and their underlying physiological and pathological mechanisms.

LECT2 Deletion Exacerbates Liver Steatosis and Macrophage Infiltration in a Male Mouse Model of LPS-mediated NASH

Leukocyte cell-derived chemotaxin 2 (LECT2) is a protein initially isolated as a neutrophil chemotactic factor. We previously found that LECT2 is an obesity-associated hepatokine that senses liver fat and induces skeletal muscle insulin resistance. In addition, hepatocyte-derived LECT2 activates macrophage proinflammatory activity by reinforcing the lipopolysaccharide (LPS)-induced c-Jun N-terminal kinase signaling. Based on these findings, we examined the effect of LECT2 deletion on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) caused by bacterial translocation. We created the bacterial translocation-mediated NAFLD/NASH model using LECT2 knockout mice (LECT2 KO) with 28 times a low-dose LPS injection under high-fat diet feeding conditions. LECT2 deletion exacerbated steatosis and significantly reduced p38 phosphorylation in the liver. In addition, LECT2 deletion increased macrophage infiltration with decreased M1/M2 ratios. LECT2 might contribute to protecting against lipid accumulation and macrophage activation in the liver under pathological conditions, which might be accomplished via p38 phosphorylation. This study provides novel aspects of LECT2 in the bacterial translocation-mediated NAFLD/NASH model.

Antimicrobial Protein LECT2-b Helps Maintain Gut Microbiota Homeostasis via Selectively Targeting Certain Pathogenic Bacteria

Antimicrobial peptides/proteins (AMPs) constitute a critical component of gut immunity in animals, protecting the gut from pathogenic bacteria. However, the interactions between AMPs and gut microbiota remain elusive. In this study, we show that leukocyte-derived chemotaxin-2 (LECT2)-b, a recently discovered AMP, helps maintain gut homeostasis in grass carp (Ctenopharyngodon idella), one of the major farmed fish species globally, by directly regulating the gut microbiota. Knockdown of LECT2-b resulted in dysregulation of the gut microbiota. Specifically, LECT2-b deficiency led to the dominance of Proteobacteria, consisting of proinflammatory bacterial species, over Firmicutes, which includes anti-inflammatory bacteria. In addition, the opportunistic pathogenic bacteria genus Aeromonas became the dominant genus replacing the probiotic bacteria Lactobacillus and Bacillus. Further analysis revealed that this effect was due to the direct and selective inhibition of certain pathogenic bacterial species by LECT2-b. Moreover, LECT2-b knockdown promoted biofilm formation by gut microbiota, resulting in tissue damage and inflammation. Importantly, LECT2-b treatment alleviated the negative effects induced by LECT2-b knockdown. These findings highlight the crucial role of LECT2-b in maintaining the gut microbiota homeostasis and mucosal health. Overall, our study provides important data for understanding the roles of AMPs in the regulation of gut homeostasis in animals.

Prognostic value of LECT2 and relevance to immune infiltration in hepatocellular carcinoma

Background: Previous studies have shown that Leukocyte cell-derived chemotaxin2 (LECT2) is associated with the development of HCC. However, there are still no studies with a comprehensive analysis of the role of LECT2 in hepatocellular carcinoma (HCC).

Methods: TCGA data sets were used to analyze the expression of LECT2 in HCC. In addition, the prognostic value of LECT2 in HCC was also investigated. DriverDBv3 was used to analyze the Mutation, CNV, and methylation profiles of LECT2. And, validated by immunohistochemistry in 72 HCC samples. The prognostic value of LECT2 and the correlation with clinicopathological features were analyzed. The GO/KEGG enrichment analysis of LECT2 co-expression and gene set enrichment analysis (GSEA) was performed using the R software package. The PPI interaction network was constructed by Search Tool for the Retrieval of Interacting Genes (STRING) database. Immune infiltration was estimated by the XCELL, TIMER, QUANTISEQ, MCPCOUNTER, EPIC, CIBERSORT abs and CIBERSORT algorithms, and Spearman was used to analyzing their correlation with LECT2. Moreover, we analyzed the correlation of LECT2 expression with immune checkpoint molecules and HLA genes. Finally, we analyzed the IC50 values of six chemotherapeutic drugs by the pRRophetic package.

Results: Reduced LECT2 expression levels found in HCC patients. Moreover, decreased levels of LECT2 were associated with poor overall survival, disease-free survival, disease-specific survival, and progression-free survival. Besides, methylation was significantly associated with LECT2 expression. The functional enrichment analysis revealed that LECT2 may affect HCC progression through various pathways such as JAK/STAT signaling pathway, cell cycle, and pathways in cancer. Additionally, the results showed that LECT2 expression was negatively correlated with immune infiltration of B cells, Neutrophil, Monocyte, Cancer-associated fibroblast, and Myeloid dendritic cell, and positively correlated with T cell CD8⁺ naive, Endothelial cell, and Hematopoietic stem cell. LECT2 expression was negatively correlated with multiple immune checkpoint molecules and HLA genes. Chemosensitivity analysis showed that chemosensitivity was lower in the LECT2 high expression group. We validated the prognostic value of LECT2 and analysis of clinicopathological features showed a lower TNM stage in the group with high expression of LECT2.

Conclusion: Low expression of LECT2 in HCC is closely associated with poor prognosis, LECT2 may have potential clinical applications due to its unique immunological effects.

Adipose tissue LECT2 expression is associated with obesity and insulin resistance in Korean women

OBJECTIVE

Leukocyte cell-derived chemotaxin 2 (LECT2) is an obesity-upregulated hepatokine inducing skeletal muscle insulin resistance. The study's aim was to explore whether LECT2 is expressed in human adipose tissue and whether the expression is dysregulated during obesity and associated with obesity-related metabolic disorders.

METHODS

This study measured metabolic parameters, serum LECT2, and expression of LECT2 and CD209, a gene encoding a putative receptor for LECT2, in abdominal subcutaneous and visceral adipose tissues in women with obesity (with or without type 2 diabetes) and women with normal weight. The expression/secretion of LECT2 and its putative effects were assessed in human adipocytes.

RESULTS

Adipose tissue LECT2 mRNA and serum LECT2 were higher in women with obesity and were significantly correlated with parameters related to insulin resistance. LECT2 was mainly expressed by adipocytes. Both LECT2 and CD209 expression was higher in adipocytes from women with obesity. Incubating adipocytes with substances mimicking the microenvironment of obesity adipose tissue increased LECT2 expression/secretion. LECT2 treatment of adipocytes suppressed insulin-stimulated Akt phosphorylation; it reduced adiponectin (ADIPOQ) and increased leptin (LEP) expression in a CD209-dependent manner.

CONCLUSIONS

This study demonstrates that LECT2 expression in adipose tissue is high in patients with obesity and associated with insulin resistance and suggests that adipocyte-derived LECT2 may contribute to adipose tissue dysfunction.

LECT2: A pleiotropic and promising hepatokine, from bench to bedside

LECT2 (leucocyte cell-derived chemotaxin 2) is a 16-kDa protein mainly produced by hepatocytes. It was first isolated in PHA-activated human T-cell leukaemia SKW-3 cells and originally identified as a novel neutrophil chemotactic factor. However, many lines of studies suggested that LECT2 was a pleiotropic protein, it not only functioned as a cytokine to exhibit chemotactic property, but also played multifunctional roles in some physiological conditions and pathological abnormalities, involving liver regeneration, neuronal development, HSC(haematopoietic stem cells) homeostasis, liver injury, liver fibrosis, hepatocellular carcinoma, metabolic disorders, inflammatory arthritides, systemic sepsis and systemic amyloidosis. Among the above studies, it was discovered that LECT2 could be a promising molecular biomarker and therapeutic target. This review summarizes LECT2-related receptors and pathways, basic and clinical researches, primarily in mice and human, for a better comprehension and management of these diseases in the future.

Leukocyte cell-derived chemotaxin 2 is an antiviral regulator acting through the proto-oncogene MET

Retinoic acid-inducible gene (RIG)-I is an essential innate immune sensor that recognises pathogen RNAs and induces interferon (IFN) production. However, little is known about how host proteins regulate RIG-I activation. Here, we show that leukocyte cell-derived chemotaxin 2 (LECT2), a hepatokine and ligand of the MET receptor tyrosine kinase is an antiviral regulator that promotes the RIG-I-mediated innate immune response. Upon binding to MET, LECT2 induces the recruitment of the phosphatase PTP4A1 to MET and facilitates the dissociation and dephosphorylation of phosphorylated SHP2 from MET, thereby protecting RIG-I from SHP2/c-Cbl-mediated degradation. In vivo, LECT2 overexpression enhances RIG-I-dependent IFN production and inhibits lymphocytic choriomeningitis virus (LCMV) replication in the liver, whereas these changes are reversed in LECT2 knockout mice. Forced suppression of MET abolishes IFN production and antiviral activity in vitro and in vivo. Interestingly, hepatocyte growth factor (HGF), an original MET ligand, inhibits LECT2-mediated anti-viral signalling; conversely, LECT2-MET signalling competes with HGF-MET signalling. Our findings reveal previously unrecognized crosstalk between MET-mediated proliferation and innate immunity and suggest that targeting LECT2 may have therapeutic value in infectious diseases and cancer.

The innate antiviral immune response is an important defense against infection. Here, the authors show that leukocyte cell-derived chemotaxin 2 (LECT2) promotes RIG-I-mediated innate immune responses by preventing its degradation, and inhibits lymphocytic choriomeningitis virus replication in the liver.

LECT2 Is a Novel Antibacterial Protein in Vertebrates

In vertebrates, leukocyte-derived chemotaxin-2 (LECT2) is an important immunoregulator with conserved chemotactic and phagocytosis-stimulating activities to leukocytes during bacterial infection. However, whether LECT2 possesses direct antibacterial activity remains unknown. In this article, we show that, unlike tetrapods with a single LECT2 gene, two LECT2 genes exist in teleost fish, named LECT2-a and LECT2-b Using grass carp as a research model, we found that the expression pattern of grass carp LECT2-a (gcLECT2-a) is more similar to that of LECT2 in tetrapods, while gcLECT2-b has evolved to be highly expressed in mucosal immune organs, including the intestine and skin. Interestingly, we found that gcLECT2-b, with conserved chemotactic and phagocytosis-stimulating activities, can also kill Gram-negative and Gram-positive bacteria directly in a membrane-dependent and a non-membrane-dependent manner, respectively. Moreover, gcLECT2-b could prevent the adherence of bacteria to epithelial cells through agglutination by targeting peptidoglycan and lipoteichoic acid. Further study revealed that gcLECT2-b can protect grass carp from Aeromonas hydrophila infection in vivo, because it significantly reduces intestinal necrosis and tissue bacterial load. More importantly, we found that LECT2 from representative tetrapods, except human, also possesses direct antibacterial activities, indicating that the direct antibacterial property of LECT2 is generally conserved in vertebrates. Taken together, to our knowledge, our study discovered a novel function of LECT2 in the antibacterial immunity of vertebrates, especially teleost fish, greatly enhancing our knowledge of this important molecule.

Leukocyte cell-derived chemotaxin-2 and fibroblast growth factor 21 in alcohol-induced liver cirrhosis

BACKGROUND

The importance of early diagnosis of alcoholic liver disease underscores the need to seek better and especially non-invasive diagnostic procedures. Leukocyte cell-derived chemotaxin-2 (LECT2) has been widely studied to determine its usefulness in monitoring the course of non-alcoholic fatty liver disease but not for alcoholic liver cirrhosis (ALC).

AIM

To determine the concentration of LECT2 in the blood serum of patients in relation to progressive stages of ALC, its relation to fibroblast growth factor 1 (FGF-1) and FGF-21, and to examine the possible wider use of LECT2 in diagnosing ALC.

METHODS

A retrospective case-control study was conducted with 69 ALC cases and 17 controls with no ALC. Subjects were recruited from the region of Lublin (eastern Poland). Liver cirrhosis was diagnosed based on clinical features, history of heavy alcohol consumption, laboratory tests, and abdominal ultrasonography. The degree of ALC was evaluated according to Pugh-Child criteria (the Pugh-Child score). Blood was drawn and, after centrifugation, serum was collected for analysis. LECT2, FGF-1, and FGF-21 were determined using enzyme-linked immunosorbent assay kits.

RESULTS

The LECT2 Levels in the control group were 18.99 ± 5.36 ng/mL. In the study groups, they declined with the progression of cirrhosis to 11.06 ± 6.47 ng/mL in one group and to 8.06 ± 5.74 ng/mL in the other (P < 0.0001). Multiple comparison tests confirmed the statistically significant differences in LECT2 Levels between the control group and both test groups (P = 0.006 and P < 0.0001). FGF-21 Levels were 44.27 ± 64.19 pg/mL in the first test group, 45.4 ± 51.69 pg/mL in the second (P = 0.008), and 13.52 ± 7.51 pg/mL in the control group. The difference between the control group and the second test group was statistically significant (P = 0.007).

CONCLUSION

We suggest that LECT2 may be a non-invasive diagnostic factor for alcohol-induced liver cirrhosis. The usefulness of LECT2 for non-invasive monitoring of alcohol-induced liver cirrhosis was indirectly confirmed by the multiple regression model developed on the basis of our statistical analysis.

LECT-2 amyloidosis: what do we know?

Amyloidosis is a rare group of diseases characterized by abnormal folding of proteins and extracellular deposition of insoluble fibrils. It can be localized to one organ system or can have systemic involvement. The kidney is the most common organ to be involved in systemic amyloidosis often leading to renal failure and the nephrotic syndrome. The two most common types of renal amyloidosis are immunoglobulin light chain-derived amyloidosis (AL) and reactive amyloidosis (AA). A novel form of amyloidosis (ALECT2) derived from leukocyte chemotactic factor 2 (LECT-2) and primarily involving the kidneys was first described by Benson et al in 2008. The liver was subsequently identified as the second most common organ involved in ALECT2 amyloidosis. LECT-2 is a unique protein that can form amyloid deposits even in its unmutated form. Patients with ALECT2 present with minimal proteinuria in contrast to other forms of amyloidosis especially AL and AA. They may present with slightly elevated serum creatinine. Nephrotic syndrome and hematuria are rare. ALECT2 can be found in association with other types of amyloidosis as well as malignancies or autoimmune diseases. ALECT2 may be confused with amyloidosis associated with light and heavy chain monoclonal gammopathy if the immunofluorescence is positive with anti-light chain and anti-AA sera. The other organs involved are the duodenum, adrenal gland, spleen, prostate, gall bladder, pancreas, small bowel, parathyroid gland, heart, and pulmonary alveolar septa, but consistently uninvolved organs included brain and fibroadipose tissue. A renal biopsy along with characteristic features found on immunohistochemistry and mass spectrometry is diagnostic of ALECT2. ALECT2 should be suspected when all markers for AL and AA are negative. Proper diagnosis of ALECT2 can determine need for supportive care versus more aggressive interventions.

The molecular structure and role of LECT2 or CHM-II in arthritis, cancer, and other diseases

Leukocyte cell-derived chemotaxin-2 (LECT2 or LECT-2), also called chondromodulin II (ChM-II or CHM2) plays a versatile role in various tissues. It was first identified as a chemotactic factor to promote the migration of neutrophils. It was also reported as a hepatokine to regulate glucose metabolism, obesity, and nonalcoholic fatty liver disease. As a secreted factor, LECT2 binds to several cell surface receptors CD209a, Tie1, and Met to regulate inflammatory reaction, fibrogenesis, vascular invasion, and tumor metastasis in various cell types. As an intracellular molecule, it is associated with LECT2-mediated amyloidosis, in which LECT2 misfolding results in insoluble fibrils in multiple tissues such as the kidney, liver, and lung. Recently, LECT2 was found to be associated with the development of rheumatoid arthritis and osteoarthritis, involving the dysregulation of osteoclasts, mesenchymal stem cells, osteoblasts, chondrocytes, and endothelial cells in the bone microenvironment. LECT2 is implicated in the development of cancers, such as hepatocellular carcinoma via MET-mediated PTP1B/Raf1/ERK signaling pathways and is proposed as a biomarker. The mechanisms by which LECT2 regulates diverse pathogenic conditions in various tissues remain to be fully elucidated. Further research to understand the role of LECT2 in a tissue tropism-dependent manner would facilitate the development of LECT2 as a biomarker for diagnosis and therapeutic target.

Plasma Leukocyte Cell-Derived Chemotaxin 2 (LECT2) as a Risk Factor of Coronary Artery Disease: A Cross-Sectional Study

Many studies have shown that leukocyte cell-derived chemotaxin 2 (LECT2) is associated with metabolic disorders, which is a risk factor of arteriosclerosis. We assessed the level of LECT-2 in patients with coronary artery disease (CAD) and its severity and prognosis. We selected 666 participants who underwent coronary angiography in our hospital and included patients with non-CAD, patients with stable angina pectoris (SAP), patients with unstable angina (UA), patients with non-ST-segment elevation myocardial infarction (NSTEMI) and patients with ST-segment elevation myocardial infarction (STEMI). The serum level of LECT-2 was higher in patients with CAD than in patients with non-CAD and was an independent predictor for CAD. Subgroup analysis showed that compared with the SAP group, the UA, NSTEMI, and STEMI groups had higher serum levels of LECT-2. In addition, the level of LECT-2 was related to the SYNTAX score and SYNTAX II score. Finally, patients with acute myocardial infarction (AMI) with elevated levels of LECT-2 had a higher risk of major adverse cardiovascular events (MACEs) within 12 months than those with lower levels of LECT-2. Plasma LECT-2 levels may be useful for the diagnosis of CAD and as predictors of MACE in patients with AMI.

Genomic and functional characterization of the lect2 gene from Siniperca chuatsi

Mandarin fish (Siniperca chuatsi) is an important economic fish in China. Viral and bacterial diseases seriously affect the artificial culture of S. chuatsi. As a carnivorous fish, artificial feed domestication is also an important means to improve the scale of S. chuatsi culture. Therefore, the study of immunology and digestive physiology is very important to the industrial development of S. chuatsi. In this work, we analyzed the expression and function of the S. chuatsi leukocyte cell-derived chemotaxin 2 (Sc-lect2) gene on a basis of next generation, single-molecule long-read sequencing. Sc-lect2 was mainly expressed in the liver but barely expressed in the gill, skin, muscle, kidney, head kidney, brain, stomach, and intestine. When the fish were infected with infectious spleen and kidney necrosis virus and challenged with lipopolysaccharide and polyinosinic-polycytidylic acid, Sc-lect2 expression significantly increased by about 40, 17, and 7-fold, respectively, compared with unstimulated samples. We also found that Sc-lect2 increases by approximately 8-fold after the fish are fed an artificial diet. These results show that mandarin fish liver can not only digest food but also express specific immune genes. Changes in the diet can cause the differential expression of Sc-lect2 genes. Four Sc-lect2 interaction genes were differentially expressed in the skin or blood. Interestingly, miR-145-3p could inhibit Sc-lect2 gene expression by targeting its coding sequence region. One CpG island in the promoter region showed a high level of methylation, suggesting that high methylation does not affect Sc-lect2 gene expression in the liver.

Differentially expressed genes in cotyledon of ewes fed mycotoxins

BACKGROUND

Ergot alkaloids (E+) are mycotoxins produced by the endophytic fungus, Epichloë coenophiala, in tall fescue that are associated with ergotism in animals. Exposure to ergot alkaloids during gestation reduces fetal weight and placental mass in sheep. These reductions are related to vasoconstrictive effects of ergot alkaloids and potential alterations in nutrient transport to the fetus. Cotyledon samples were obtained from eight ewes that were fed E+ (n = 4; E+/E+) or E- (endophyte-free without ergot alkaloids; n = 4; E-/E-) seed during both mid (d 35 to 85) and late (d 85-133) gestation to assess differentially expressed genes associated with ergot alkaloid induced reductions in placental mass and fetal weight, and discover potential adaptive mechanisms to alter nutrient supply to fetus.

RESULTS

Ewes fed E+/E+ fescue seed during both mid and late gestation had 20% reduction in fetal body weight and 33% reduction in cotyledon mass compared to controls (E-/E-). Over 13,000 genes were identified with 110 upregulated and 33 downregulated. Four genes had a |log2FC| > 5 for ewes consuming E+/E+ treatment compared to controls: LECT2, SLC22A9, APOC3, and MBL2. REViGO revealed clusters of upregulated genes associated glucose, carbohydrates, lipid, protein, macromolecular and cellular metabolism, regulation of wound healing and response to starvation. For downregulated genes, no clusters were present, but all enriched GO terms were associated with anion and monocarboxylic acid transport. The complement and coagulation cascade and the peroxisome proliferator-activated receptor signaling pathway were found to be enriched for ewes consuming E+/E+ treatment.

CONCLUSIONS

Consumption of ergot alkaloids during gestation altered the cotyledonary transcriptome specifically related to macronutrient metabolism, wound healing and starvation. These results show that ergot alkaloid exposure upregulates genes involved in nutrient metabolism to supply the fetus with additional substrates in attempts to rescue fetal growth.

The response of glandular gastric transcriptome to T-2 toxin in chicks

This study was conducted to determine the effect of T-2 toxin on the transcriptome of the glandular stomach in chicks using RNA-sequencing (RNA-Seq). Four groups of 1-day-old Cobb male broilers (n = 4 cages/group, 6 chicks/cage) were fed a corn-soybean-based diet (control) and control supplemented with T-2 toxin at 1.0, 3.0, and 6.0 mg/kg, respectively, for 2 weeks. The histological results showed that dietary supplementation of T-2 toxin at 3.0 and 6.0 mg/kg induced glandular gastric injury including serious inflammation, increased inflammatory cells, mucosal edema, and necrosis and desquamation of the epithelial cells in the glandular stomach of chicks. RNA-Seq analysis revealed that there were 671, 1393, and 1394 genes displayed ≥2 (P < 0.05) differential expression in the dietary supplemental T-2 toxin at 1.0, 3.0, and 6.0 mg/kg, respectively, compared with the control group. Notably, 204 differently expressed genes had shared similar changes among these three doses of T-2 toxin. GO and KEGG pathway analysis results showed that many genes involved in oxidation-reduction process, inflammation, wound healing/bleeding, and apoptosis/carcinogenesis were affected by T-2 toxin exposure. In conclusion, this study systematically elucidated toxic mechanisms of T-2 toxin on the glandular stomach, which might provide novel ideas to prevent adverse effects of T-2 toxin in chicks.

Transcriptional regulation of chicken leukocyte cell-derived chemotaxin 2 in response to toll-like receptor 3 stimulation

Objective

Leukocyte cell-derived chemotaxin 2 (LECT2) is associated with several physiological processes including inflammation, tumorigenesis, and natural killer T cell generation. Chicken LECT2 (chLECT2) gene was originally identified as one of the differentially expressed genes in chicken kidney tissue, where the chickens were fed with different calcium doses. In this study, the molecular characteristics and gene expression of chLECT2 were analyzed under the stimulation of toll-like receptor 3 (TLR3) ligand to understand the involvement of chLECT2 expression in chicken metabolic disorders.

Methods

Amino acid sequence of LECT2 proteins from various species including fowl, fish, and mammal were retrieved from the Ensembl database and subjected to Insilco analyses. In addition, the time- and dose-dependent expression of chLECT2 was examined in DF-1 cells which were stimulated with polyinosinic:polycytidylic acid (poly [I:C]), a TLR3 ligand. Further, to explore the transcription factors required for the transcription of chLECT2, DF-1 cells were treated with poly (I:C) in the presence or absence of the nuclear factor κB (NFκB) and activated protein 1 (AP-1) inhibitors.

Results

The amino acid sequence prediction of chLECT2 protein revealed that along with duck LECT2 (duLECT2), it has unique signal peptide different from other vertebrate orthologs, and only chLECT2 and duLECT2 have an additional 157 and 161 amino acids on their carboxyl terminus, respectively. Phylogenetic analysis suggested that chLECT2 is evolved from a common ancestor along with the actinopterygii hence, more closely related than to the mammals. Our quantitative polymerase chain reaction results showed that, the expression of chLECT2 was up-regulated significantly in DF-1 cells under the stimulation of poly (I:C) (p<0.05). However, in the presence of NFκB or AP-1 inhibitors, the expression of chLECT2 is suppressed suggesting that both NFκB and AP-1 transcription factors are required for the induction of chLECT2 expression.

Conclusion

The present results suggest that chLECT2 gene might be a target gene of TLR3 signaling. For the future, the expression pattern or molecular mechanism of chLECT2 under stimulation of other innate immune receptors shall be studied. The protein function of chLECT2 will be more clearly understood if further investigation about the mechanism of LECT2 in TLR pathways is conducted.

Leukocyte cell-derived chemotaxin 2 inhibits development of atherosclerosis in mice

Leukocyte cell-derived chemotaxin 2 (LECT2), a multifunctional hepatokine, is involved in many pathological conditions. However, its role in atherosclerosis remains undefined. In this study, we administered vehicle or LECT2 to male Apoe^-/- mice fed a Western diet for 15 weeks. Atherosclerotic lesions were visualized and quantified with Oil-red O and hematoxylin staining. The mRNA expression levels of MCP-1, MMP-1, IL-8, IL-1β, and TNF-α were analyzed by quantitative real-time polymerase chain reaction. Serum TNF-α, IL-1β, IL-8, MCP-1, and MMP-1 concentrations were measured by enzyme-linked immunosorbent assay. CD68, CD31, and α-SMA, markers of macrophages, endothelial cells, and smooth muscle cells, respectively, were detected by immunostaining. Results showed that LECT2 reduced total cholesterol and low-density lipoprotein concentrations in serum and inhibited the development of atherosclerotic lesions, accompanied by reductions in inflammatory cytokines and lower MCP-1, MMP-1, TNF-α, IL-8, and IL-1β mRNA abundance. Furthermore, LECT2 decreased CD68, but increased α-SMA in atherosclerotic lesions, suggesting an increase in smooth muscle cells and reduction in macrophages. In summary, LECT2 inhibited the development of atherosclerosis in mice, accompanied by reduced serum total cholesterol concentration and lower inflammatory responses.

Mechanisms that regulate morphogenesis of a highly branched neuron in C. elegans

The shape of an individual neuron is linked to its function with axons sending signals to other cells and dendrites receiving them. Although much is known of the mechanisms for axonal outgrowth, the striking complexity of dendritic architecture has hindered efforts to uncover pathways that direct dendritic branching. Here we review the results of an experimental strategy that exploits the power of genetic analysis and live cell imaging of the PVD sensory neuron in C. elegans to reveal key molecular drivers of dendrite morphogenesis.

Circulating Concentrations of Insulin Resistance-Associated Hepatokines, Selenoprotein P and Leukocyte Cell-Derived Chemotaxin 2, during an Oral Glucose Tolerance Test in Humans

A hepatokine is a collective term for liver-derived secretory factors whose previously-unrecognized functions have been recently elucidated. We have rediscovered selenoprotein P (SeP) and leukocyte cell-derived chemotaxin 2 (LECT2) as hepatokines that are involved in the development of insulin resistance and hyperglycemia. The aim of this study was to determine whether and, if so, how oral glucose loading alters the two hepatokines in humans. We measured concentrations of serum SeP and plasma LECT2 during 75 g oral glucose tolerance test (OGTT) (n = 20) in people with various degrees of glucose tolerance. In OGTT, concentrations of both serum SeP and plasma LECT2 decreased at 120 min compared with the baseline values, irrespective of the severity of glucose intolerance. Decrement of serum SeP during OGTT showed no correlations to the clinical parameters associated with insulin resistance or insulin secretion. In multiple stepwise regression analyses, plasma cortisol was selected as the variable to explain the changes in plasma concentrations of LECT2. The current data reveal the acute inhibitory actions of oral intake of glucose on circulating SeP and LECT2 in humans, irrespective of the severity of glucose intolerance. This study suggests that circulating SeP is regulated by the unknown clinical factors other than insulin and glucose during OGTT.

Pathophysiological significance of hepatokine overproduction in type 2 diabetes

Currently, many studies draw attention to novel secretory factors, such as adipokines or myokines, derived from the tissues that were not originally recognized as endocrine organs. The liver may contribute to the onset of various kinds of pathologies of type 2 diabetes by way of the production of secretory proteins "hepatokines." Using the comprehensive gene expression analyses in human livers, we have rediscovered selenoprotein P and LECT2 as hepatokines involved in the onset of dysregulated glucose metabolism. Overproduction of selenoprotein P, previously reported as a transport protein of selenium, induces insulin resistance and hyperglycemia in type 2 diabetic condition. Selenoprotein P also contributes to vascular complications of type 2 diabetes directly by inducing VEGF resistance in vascular endothelial cells. Notably, selenoprotein P impairs health-promoting effects of exercise by inhibiting ROS/AMPK/PGC-1α pathway in the skeletal muscle through its receptor LRP1. Overproduction of LECT2, previously reported as a neutrophil chemotactic protein, links obesity to insulin resistance in the skeletal muscle. Further studies would develop novel diagnostic or therapeutic procedures targeting hepatokines to combat over-nutrition-related diseases such as type 2 diabetes.

LECT2 promotes inflammation and insulin resistance in adipocytes via P38 pathways

Leukocyte cell-derived chemotaxin 2 (LECT2) is a recently identified novel hepatokine that causes insulin resistance in skeletal muscle by activating c-Jun N-terminal kinase (JNK), thereby driving atherosclerotic inflammation. However, the role of LECT2 in inflammation and insulin resistance in adipocytes has not been investigated. In this study, we report that LECT2 treatment of differentiated 3T3-L1 cells stimulates P38 phosphorylation in a dose-dependent manner. LECT2 also enhanced inflammation markers such as IκB phosphorylation, nuclear factor kappa beta (NF-κB) phosphorylation and IL-6 expression. Moreover, LECT2 treatment impaired insulin signaling in differentiated 3T3-L1 cells, as evidenced by the decreased levels of insulin receptor substrate (IRS-1) and Akt phosphorylation and reduced insulin-stimulated glucose uptake. Furthermore, LECT2 augmented lipid accumulation during 3T3-L1 cell differentiation by activating SREBP1c-mediated signaling. All these effects were significantly abrogated by siRNA-mediated silencing of P38, CD209 expression or a JNK inhibitor. Our findings suggest that LECT2 stimulates inflammation and insulin resistance in adipocytes via activation of a CD209/P38-dependent pathway. Thus, these results suggest effective therapeutic targets for treating inflammation-mediated insulin resistance.

Does bariatric surgery influence plasma levels of fetuin-A and leukocyte cell-derived chemotaxin-2 in patients with type 2 diabetes mellitus?

Background

Fetuin-A and leukocyte cell-derived chemotaxin-2 (LECT-2) are liver-derived proteins. Fetuin-A is an independent risk factor for type 2 diabetes (T2D) and obese patients with T2D have higher plasma fetuin-A levels than those without T2D. LECT-2 has positive correlation with the severity of both obesity and insulin resistance. The changes in plasma fetuin-A are not consistent after bariatric surgery and no studies have investigated the changes in LECT-2 on the obese patients with T2D after bariatric surgery.

Methods

Overall, 18 patients undergoing gastric bypass (GB) and 16 patients undergoing sleeve gastrectomy (SG) were enrolled. The fasting plasma fetuin-A and LECT-2 levels were measured at baseline, one week, three months, and one year after surgery.

Results

Both the GB and SG groups significantly decreased the body mass index (BMI), waist-to-hip ratio, a body shape index; the triglyceride, fasting blood sugar (FBS), hemoglobin A1c, C-peptide levels; and homeostatic model assessment (HOMA-IR) one year after surgery. The SG group showed a decreasing trend in plasma fetuin-A levels one year after SG surgery. There are no significant changes in LECT-2 one year after either GB or SG. Fetuin-A had a near significant negative relationship with insulin (P = 0.056) and HOMA-IR (P = 0.050) in the SG group. Changes in fetuin-A had a significant positive relationship with changes in BMI (P = 0.031) and waist-to-hip ratio (P = 0.031) in the GB group and had a near significant positive correlation with FBS (P = 0.051) in the SG group.

Discussion

Neither GB nor SG modifies plasma levels of plasma fetuin-A or LECT-2 in T2D patients after surgery. The changes in plasma fetuin-A have a positive correlation with those of the BMI and waist-to-hip ratio 12 months after GB.

Low incubation temperature during early development negatively affects survival and related innate immune processes in zebrafish larvae exposed to lipopolysaccharide

In many fish species, the immune system is significantly constrained by water temperature. In spite of its critical importance in protecting the host against pathogens, little is known about the influence of embryonic incubation temperature on the innate immunity of fish larvae. Zebrafish (Danio rerio) embryos were incubated at 24, 28 or 32 °C until first feeding. Larvae originating from each of these three temperature regimes were further distributed into three challenge temperatures and exposed to lipopolysaccharide (LPS) in a full factorial design (3 incubation × 3 challenge temperatures). At 24 h post LPS challenge, mortality of larvae incubated at 24 °C was 1.2 to 2.6-fold higher than those kept at 28 or 32 °C, regardless of the challenge temperature. LPS challenge at 24 °C stimulated similar immune-related processes but at different levels in larvae incubated at 24 or 32 °C, concomitantly with the down-regulation of some chemokine and lysozyme transcripts in the former group. Larvae incubated at 24 °C and LPS-challenged at 32 °C exhibited a limited immune response with up-regulation of hypoxia and oxidative stress processes. Annexin A2a, S100 calcium binding protein A10b and lymphocyte antigen-6, epidermis were identified as promising candidates for LPS recognition and signal transduction.

Effect of a LECT2 on the immune response of peritoneal lecukocytes against Vibrio anguillarum in roughskin sculpin

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multi-functional protein that is mainly synthesized by the liver. However, its role in roughskin scalping is less known. Here, we cloned a leukocyte cell-derived chemotaxin 2 (TfLECT2) genes in the liver of roughskin scalping, Trachidermus fasciatus, and studied its possible role involved in the immune response against Vibrio anguillarum (V. anguillarum) of peritoneal lecukocytes under in vivo conditions. The cDNA sequence of TfLECT2 is 566 bp in size. Its deduced amino acid (aa) sequence comprises 151 residues, of which the first 16 residues form a putative signal peptide and 101 residues compose a typical peptidase M23 domain in the C-terminal region. The domain structure is conserved in all LECT2 proteins, which suggests a close phylogenetic relationship between TfLECT2 and LECT2 in other fish species. Real-time quantitative PCR analysis revealed that TfLECT2 gene expression was dramatically increased in liver after V. anguillarum stimulation. Subsequently, TfLECT2 was prokaryotic expressed and purified to prepare anti-TfLECT2 antibody. After V. anguillarum challenge, leukocytes recruitment and LECT2 levels in peritoneal exudates were increased, and positively correlated with each other. Moreover, recombinant TfLECT2 administration significantly improved immune responses after infection, principally in stimulating the recruitment, phagocytosis and respiratory burst of leukocytes at the site of infection; however, anti-TfLECT2 treatment neutralized these abilities. Therefore, TfLECT2 may trigger the early immune events of peritoneal leukocytes and it will be useful to induce innate immune response of fish.

Leukocyte Cell-Derived Chemotaxin 2-Associated Renal Amyloidosis: A Case Report

Amyloidosis is a disorder characterized by the deposition of abnormal protein fibrils in tissues. Leukocyte cell-derived chemotaxin 2-associated amyloidosis is a recently recognized entity and is characterized by a distinctive clinicopathologic type of amyloid deposition manifested in adults by varying degrees of impaired kidney function and proteinuria. There are only a limited number of cases reported in the literature. We present a 64-year-old Hispanic female with a history of hypertension who was referred for chronic kidney disease management. The review of her laboratory tests revealed a serum creatinine of 1.5–1.8 mg/dL and microalbuminuria (in the presence of a bland urine sediment) in the past year. She denied any history of diabetes, rheumatologic disorders or exposure to intravenous contrast, nonsteroidal anti-inflammatory drugs, herbals, and heavy metals. Serological workup was negative. A renal biopsy showed diffuse infiltration of glomerulus with pale eosinophilic material strongly positive for Congo red stain and a similar eosinophilic material in the interstitium, muscular arteries, and arterioles. Electron microscopy showed marked infiltration of the mesangium, capillary loops, and interstitium with haphazardly arranged fibrillary deposits (9.8 nm thick). Liquid chromatography tandem mass spectrometry confirmed leukocyte cell-derived chemotaxin 2 (LECT2) amyloid deposition. LECT2 amyloidosis (ALECT2) should be suspected in renal biopsy specimens exhibiting extensive and strong mesangial as well as interstitial congophilia. Individuals with LECT2 renal amyloidosis have a varying prognosis. Therapeutic options include supportive measures and consideration of a kidney transplant for those with end-stage renal disease.

Therapeutic Approaches to Nonalcoholic Fatty Liver Disease: Exercise Intervention and Related Mechanisms

Exercise training ameliorates nonalcoholic fatty liver disease (NAFLD) as well as obesity and metabolic syndrome. Although it is difficult to eliminate the effects of body weight reduction and increased energy expenditure-some pleiotropic effects of exercise training-a number of studies involving either aerobic exercise training or resistance training programs showed ameliorations in NAFLD that are independent of the improvements in obesity and insulin resistance. In vivo studies have identified effects of exercise training on the liver, which may help to explain the "direct" or "independent" effect of exercise training on NAFLD. Exercise training increases peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) expression, improves mitochondrial function and leads to reduced hepatic steatosis, inflammation, fibrosis, and tumor genesis. Crosstalk between the liver and adipose tissue, skeletal muscle and the microbiome is also a possible mechanism for the effect of exercise training on NAFLD. Although numerous studies have reported benefits of exercise training on NAFLD, the optimal duration and intensity of exercise for the prevention or treatment of NAFLD have not been established. Maintaining adherence of patients with NAFLD to exercise training regimes is another issue to be resolved. The use of comprehensive analytical approaches to identify biomarkers such as hepatokines that specifically reflect the effect of exercise training on liver functions might help to monitor the effect of exercise on NAFLD, and thereby improve adherence of these patients to exercise training. Exercise training is a robust approach for alleviating the pathogenesis of NAFLD, although further clinical and experimental studies are required.

Hepatokines: linking nonalcoholic fatty liver disease and insulin resistance

Hepatic steatosis is an underlying feature of nonalcoholic fatty liver disease (NAFLD), which is the most common form of liver disease and is present in up to ∼70% of individuals who are overweight. NAFLD is also associated with hypertriglyceridaemia and low levels of HDL, glucose intolerance, insulin resistance and type 2 diabetes mellitus. Hepatic steatosis is a strong predictor of the development of insulin resistance and often precedes the onset of other known mediators of insulin resistance. This sequence of events suggests that hepatic steatosis has a causal role in the development of insulin resistance in other tissues, such as skeletal muscle. Hepatokines are proteins that are secreted by hepatocytes, and many hepatokines have been linked to the induction of metabolic dysfunction, including fetuin A, fetuin B, retinol-binding protein 4 (RBP4) and selenoprotein P. In this Review, we describe the factors that influence the development of hepatic steatosis, provide evidence of strong links between hepatic steatosis and insulin resistance in non-hepatic tissues, and discuss recent advances in our understanding of how steatosis alters hepatokine secretion to influence metabolic phenotypes through inter-organ communication.

Amyloidosis: Insights from Proteomics

Amyloidoses are a spectrum of disorders caused by abnormal folding and extracellular deposition of proteins. The deposits lead to tissue damage and organ dysfunction, particularly in the heart, kidneys, and nerves. There are at least 30 different proteins that can cause amyloidosis. The clinical management depends entirely on the type of protein deposited, and thus on the underlying pathogenesis, and often requires high-risk therapeutic intervention. Application of mass spectrometry-based proteomic technologies for analysis of amyloid plaques has transformed the way amyloidosis is diagnosed and classified. Proteomic assays have been extensively used for clinical management of patients with amyloidosis, providing unprecedented diagnostic and biological information. They have shed light on the pathogenesis of different amyloid types and have led to identification of numerous new amyloid types, including ALECT2 amyloidosis, which is now recognized as one of the most common causes of systemic amyloidosis in North America.

Reduced serum level of leukocyte cell-derived chemotaxin 2 is associated with the presence of diabetic retinopathy

BACKGROUND

Vascular endothelial growth factor (VEGF) signaling is an important pathway in the development of diabetic retinopathy (DR). A recent report showed that leukocyte cell-derived chemotaxin 2 (LECT2) suppresses the VEGF signaling in endothelial cells. However, the clinical relevance of LECT2 in DR is unknown. This study aimed to investigate serum LECT2 levels and the presence of DR.

METHODS

The study included 230 people with type 2 diabetes mellitus (DM), 95 with DR and 135 without DR. Serum LECT2 levels were measured using an enzyme-linked immunosorbent assay. Data were evaluated using Spearman's rank correlation, univariate and multivariate logistic regression.

RESULTS

Serum LECT2 levels were significantly lower in participants with DM having DR than in those not having DR (35.6±14.9ng/ml vs. 44.5±17.6ng/ml, P<0.001). Spearman's rank correlation analysis revealed a significant association between serum LECT2 levels and the presence of DR (P<0.001). Multiple regression analysis revealed that serum LECT2 levels were independently related to DR (P<0.001).

CONCLUSIONS

These findings indicated that serum LECT2 level is negatively associated with the presence of DR and suggest that low circulating LECT2 level is a risk factor for DR.

Inhibition of VEGF165/VEGFR2-dependent signaling by LECT2 suppresses hepatocellular carcinoma angiogenesis

Hepatocellular carcinoma (HCC) relies on angiogenesis for growth and metastasis. Leukocyte cell-derived chemotaxin 2 (LECT2) is a cytokine and preferentially expressed in the liver. Previous studies have found that LECT2 targets to both immune and tumor cells to suppress HCC development and vascular invasion. Although LECT2 did not affect HCC cells growth in vitro, it still suppressed HCC xenografts growth in immune-deficient mice, suggesting other cells such as stroma cells may also be targeted by LECT2. Here, we sought to determine the role of LECT2 in tumor angiogenesis in HCC patients. We found that LECT2 expression inhibited tumor growth via angiogenesis in the HCC xenograft model. Specifically, we demonstrated that recombinant human LECT2 protein selectively suppressed vascular endothelial growth factor (VEGF)₁₆₅-induced endothelial cell proliferation, migration, and tube formation in vitro and in vivo. Mechanistically, LECT2 reduced VEGF receptor 2 tyrosine phosphorylation and its downstream extracellular signal-regulated kinase and AKT phosphorylation. Furthermore, LECT2 gene expression correlated negatively with angiogenesis in HCC patients. Taken together, our findings demonstrate that LECT2 inhibits VEGF₁₆₅-induced HCC angiogenesis through directly binding to VEGFR2 and has broad applications in treating VEGF-mediated solid tumors.

Crystal Structure of Human Leukocyte Cell-derived Chemotaxin 2 (LECT2) Reveals a Mechanistic Basis of Functional Evolution in a Mammalian Protein with an M23 Metalloendopeptidase Fold

Human leukocyte cell-derived chemotaxin 2 (LECT2), which is predominantly expressed in the liver, is a multifunctional protein. LECT2 is becoming a potential therapeutic target for several diseases of worldwide concern such as rheumatoid arthritis, hepatocellular carcinoma, and obesity. Here, we present the crystal structure of LECT2, the first mammalian protein whose structure contains an M23 metalloendopeptidase fold. The LECT2 structure adopts a conserved Zn(II) coordination configuration but lacks a proposed catalytic histidine residue, and its potential substrate-binding groove is blocked in the vicinity of the Zn(II)-binding site by an additional intrachain loop at the N terminus. Consistent with these structural features, LECT2 was found to be catalytically inactive as a metalloendopeptidase against various types of peptide sequences, including pentaglycine. In addition, a surface plasmon resonance analysis demonstrated that LECT2 bound to the c-Met receptor with micromolar affinity. These results indicate that LECT2 likely plays its critical roles by acting as a ligand for the corresponding protein receptors rather than as an enzymatically active peptidase. The intrachain loop together with the pseudo-active site groove in LECT2 structure may be specific for interactions between LECT2 and receptors. Our study reveals a mechanistic basis for the functional evolution of a mammalian protein with an M23 metalloendopeptidase fold and potentially broadens the implications for the biological importance of noncatalytic peptidases in the M23 family.

Implication of hepatokines in metabolic disorders and cardiovascular diseases

The liver is a central regulator of systemic energy homeostasis and has a pivotal role in glucose and lipid metabolism. Impaired gluconeogenesis and dyslipidemia are often observed in patients with nonalcoholic fatty liver disease (NAFLD). The liver is now recognized to be an endocrine organ that secretes hepatokines, which are proteins that regulate systemic metabolism and energy homeostasis. Hepatokines are known to contribute to the pathogenesis of metabolic syndrome, NAFLD, type 2 diabetes (T2DM), and cardiovascular diseases (CVDs). In this review, we focus on the roles of two major hepatokines, fetuin-A and fibroblast growth factor 21 (FGF21), as well as recently-redefined hepatokines, such as selenoprotein P, angiopoietin-like protein 4 (ANGPTL4), and leukocyte cell-derived chemotaxin 2 (LECT2). We also assess the biology and molecular mechanisms of hepatokines in the context of their potential as therapeutic targets for metabolic disorders and cardiovascular diseases.

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The roles of hepatokines such as fetuin-A, FGF21, selenoprotein P, ANGPTL4, and LECT2

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The molecular mechanisms of hepatokines in metabolic disorders and CVD

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Hepatokines as therapeutic strategies for metabolic disorders and CVD

LECT2 induces atherosclerotic inflammatory reaction via CD209 receptor-mediated JNK phosphorylation in human endothelial cells

OBJECTIVE

Leukocyte cell-derived chemotaxin 2 (LECT2) is a recently discovered novel hepatokine, leading to skeletal muscle insulin resistance by activating c-Jun N-terminal kinase (JNK). However, its role in atherosclerotic inflammatory reactions has not been examined. Therefore, we investigated the function of LECT2 on the expression of vascular adhesion molecules and inflammatory cytokines in human endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) and THP-1 cells were treated with various doses of LECT2 and the functions and signaling pathways were analyzed through Western blot and quantitative real-time PCR (qPCR).

RESULTS

The level of phosphorylated c-Jun N-terminal kinases (JNK) was significantly increased by LECT2 treatment in HUVECs and THP-1 cells, an effect that was not seen in cells treated with CD209 siRNA, a known LECT2 receptor. LECT2 treatment efficiently increased the expression of intercellular adhesion molecule-1 (ICAM-1) and pro-inflammatory cytokines tumor necrosis factor α (TNFα), monocyte chemo-attractant protein-1 (MCP-1), and interleukin-1β (IL-1β) in HUVECs and THP-1 cells. However, all these reactions were significantly reduced in response to treatment with JNK inhibitor. Furthermore, LECT2 treatment significantly exacerbated the adhesion of monocytic cells to human endothelial cells, which was also efficiently attenuated by JNK inhibitor.

CONCLUSIONS

LECT2 significantly induced adhesion molecules and pro-inflammatory cytokines in HUVECs via CD209-mediated JNK phosphorylation, suggesting that liver-derived novel hepatokine, LECT2, might directly mediate in the atherosclerotic inflammatory reactions in human endothelial cells.

LECT2 improves the outcomes in ayu with Vibrio anguillarum infection via monocytes/macrophages

Leukocyte cell-derived chemotaxin 2 (LECT2) is reported to be a cytokine involved in the immune response against pathogenic microorganisms in fish. However, its accurate function in whole fish remains unclear. In this study, we provide the first report on the effect of LECT2 on fish defenses against pathogens in vivo. The administration of recombinant LECT2 improved the survival rate of Vibrio anguillarum infected ayu. The bacterial burden of V. anguillarum infected ayu was decreased in LECT2-treated ayu blood, liver, spleen, and kidney compared with saline control. In bacteria-infected ayu, LECT2 treatment altered the mRNA expression of cytokines, including TNFα, IL-1β, and IL-10, which are all important for the inflammatory response in fish. LECT2 treatment also reduced histological damage in bacteria-infected ayu, and increased peritoneal monocytes/macrophages in both healthy and infected ayu at 12 h post infection. When ayu monocytes/macrophages were depleted by clodronate-liposomes treatment, LECT2 treatment did not increase the survival rate of bacteria-infected fish compared with healthy control fish. Thus our results suggest that LECT2 can modulate host defense in ayu and mediate antibacterial protection against V. anguillarum through monocytes/macrophages.

LECT2 functions as a hepatokine that links obesity to skeletal muscle insulin resistance

Recent articles have reported an association between fatty liver disease and systemic insulin resistance in humans, but the causal relationship remains unclear. The liver may contribute to muscle insulin resistance by releasing secretory proteins called hepatokines. Here we demonstrate that leukocyte cell-derived chemotaxin 2 (LECT2), an energy-sensing hepatokine, is a link between obesity and skeletal muscle insulin resistance. Circulating LECT2 positively correlated with the severity of both obesity and insulin resistance in humans. LECT2 expression was negatively regulated by starvation-sensing kinase adenosine monophosphate-activated protein kinase in H4IIEC hepatocytes. Genetic deletion of LECT2 in mice increased insulin sensitivity in the skeletal muscle. Treatment with recombinant LECT2 protein impaired insulin signaling via phosphorylation of Jun NH2-terminal kinase in C2C12 myocytes. These results demonstrate the involvement of LECT2 in glucose metabolism and suggest that LECT2 may be a therapeutic target for obesity-associated insulin resistance.

Leukocyte cell-derived chemotaxin 2 (LECT2)–associated amyloidosis is a frequent cause of hepatic amyloidosis in the United States

Leukocyte cell-derived chemotaxin-2–associated amyloidosis (ALect2) is a common cause of systemic amyloidosis involving the liver. Recognition and accurate diagnosis of hepatic ALect2 amyloidosis is essential for accurate management of patients with hepatic amyloidosis.

Characterization of the LECT2 gene and its associations with resistance to the big belly disease in Asian seabass

Leukocyte cell-derived chemotaxin-2 (LECT2) is an important protein of the innate immune system for the defense against bacterial infection. We cloned and characterized the LECT2 gene from Asian seabass (Lates calcarifer). Its complete cDNA consisted of an open reading frame of 459 bp encoding a protein of 152 amino acids. The genomic DNA sequence of this gene consists of four exons and three introns. Quantitative real-time PCR revealed that the LECT2 gene was expressed predominantly in liver while its expression was moderate in spleen and heart, and weak in other tissues. The LECT2 transcript was up-regulated in the kidney, spleen and liver in response to a challenge with a pathogenic bacterium Vibrio harveyi. In addition, we identified three single nucleotide polymorphisms (SNPs) in the LECT2 gene, and found significant associations between these polymorphisms and resistance to the big belly disease. These results suggest that the LECT2 gene play an important role in resistance to bacterial pathogens in fish. The SNP markers in the gene associated with the resistance to bacterial pathogens may facilitate selecting Asian seabass resistant to bacterial diseases.

Leukocyte cell-derived chemotaxin 2 antagonizes MET receptor activation to suppress hepatocellular carcinoma vascular invasion by protein tyrosine phosphatase 1B recruitment

Leukocyte cell-derived chemotoxin 2 (LECT2) has been shown to act as a tumor suppressor in hepatocellular carcinoma (HCC). However, the underlying mechanism has not yet been completely defined. Here, we employ a LECT2-affinity column plus liquid chromatography coupled with tandem mass spectrometry to identify LECT2-binding proteins and found that MET receptor strongly interacted with LECT2 protein. Despite the presence of hepatocyte growth factor, the LECT2 binding causes an antagonistic effect to MET receptor activation through recruitment of protein tyrosine phosphatase 1B. The antagonistic effect of LECT2 on MET activation also mainly contributes to the blockage of vascular invasion and metastasis of HCC. Furthermore, serial deletions and mutations of LECT2 showed that the HxGxD motif is primarily responsible for MET receptor binding and its antagonistic effects.

CONCLUSION

These findings reveal a novel, specific inhibitory function of LECT2 in HCC by the direct binding and inactivation of MET, opening a potential avenue for treating MET-related liver cancer.

Passive protective effect of chicken egg yolk immunoglobulins against experimental Vibrio anguillarum infection in ayu (Plecoglossus altivelis)

Oral administration of chicken egg yolk immunoglobulins (IgY) has attracted much attention as a means for controlling infectious diseases caused by microorganisms. This study evaluated the protective effect of IgY against Vibrio anguillarum infection in ayu, Plecoglossus altivelis. IgY was isolated from egg yolks laid by hens initially immunized with formalin-inactivated V. anguillarum. Lower mortality of ayu was observed in groups treated with anti-V. anguillarum IgY (aVIgY), compared with those treated with saline or with nonspecific IgY (nspIgY). All fish in saline-treated groups died within seven days after bacterial inoculation. The bacterial load in blood, liver, and spleen was significantly lower in fish treated with aVIgY than in fish treated with nspIgY. aVIgY treatment significantly reduced tumor necrosis factor-α (PaTNF-α), interleukin-1β (PaIL-1β), transforming growth factor-β (PaTGF-β), and leukocyte cell-derived chemotaxin-2 (PaLECT2) transcript levels in the head kidney, spleen, and liver of ayu challenged by V. anguillarum, compared with nspIgY treatment. The phagocytic activity of macrophages for V. anguillarum in the presence of specific IgY was significantly higher than that seen for nonspecific IgY. These results suggest that passive immunization by oral intubation with pathogen-specific IgY may provide a valuable treatment for V. anguillarum infection in ayu.

Cloning, characterization and expression of the LECT2 gene in grass carp

An expressed sequence tag of grass carp leukocyte cell-derived chemotaxin 2 (LECT2) gene was screened from an established intestinal cDNA library. Rapid amplification of cDNA ends gave rise to a full-length LECT2 cDNA (gcLECT2) with a complete open-reading frame of 474 bp, encoding 158 amino acids about 17.9 kDa. Homology search and sequence alignment showed that this deduced protein sequence shared a high identity with LECT2 from other vertebrates. Western blotting indicated immunological cross-reactivity occurs between grass carp and human LECT2 protein. This gcLECT2 genomic sequence is 1,868 bp in size, which consists of five exons and four introns. Real-time quantitative PCR analysis revealed that gcLECT2 gene is ubiquitously expressed in different tissues of healthy grass carp including brain, gut, liver, spleen, kidney, muscle and heart, while the expression levels were significantly increased in liver and spleen followed by Aeromonas salmonicida infection. 992 bp 5'-flanking region sequence was cloned and analyzed, where one CAAT box and one GC island were found. Our results showed that the LECT2 is suggested to be most possibly involved in the grass carp's immune response.

Crystallization and preliminary X-ray analysis of human leukocyte cell-derived chemotaxin 2 (LECT2)

Human leukocyte cell-derived chemotaxin 2 (LECT2) is a chemotactic factor for neutrophils that plays multifunctional roles in liver regeneration, regulation of neuritic development and proliferation of chondrocytes and osteoblasts. In addition, the C-terminal region of LECT2 belongs to the zinc metalloendopeptidase M23 (PF01551) family. Purified LECT2 was crystallized using the sitting-drop vapour-diffusion method at 293 K. Crystals of selenomethionine-substituted LECT2 that diffracted X-rays to 1.94 Å resolution were obtained using a reservoir solution consisting of 0.2 M ammonium sulfate, 0.1 M HEPES pH 7.5, 25%(w/v) PEG 8000. The crystal belonged to space group P2₁2₁2₁, with unit-cell parameters a=59.4, b=63.5, c=64.0 Å. The calculated Matthews coefficient (VM=2.10 Å3 Da(-1), solvent content 40%) indicates that the crystal consists of two molecules per asymmetric unit.