Identification of novel peptide hormones in the human proteome by hidden Markov model screening

Peripheral Spexin Inhibited Food Intake in Mice

Spexin (SPX, NPQ), a novel endogenous neuropeptide, was firstly identified by bioinformatics. Spexin gene and protein widely distributed in the central nervous system and peripheral tissues, such as the hypothalamus and digestive tract. The role of spexin in appetite regulation in mammalian is still unclear. The present study was designed to investigate the mechanism and effect of peripheral spexin on food intake in mice. During the light period, an intraperitoneal (i.p.) injection of spexin (10 nmol/mouse) significantly inhibited cumulative food intake at 2, 4, and 6 h after treatment in fasted mice. During the dark period, spexin (1 and 10 nmol/mouse, i.p.) significantly suppressed cumulative food intake at 4 and 6 h after treatment in freely feeding mice. The GALR3 antagonist SNAP37889, not GALR2 antagonist, significantly antagonized the inhibitory effect on cumulative food intake (0-6 h) induced by spexin. Spexin significantly reduced the mRNA level of Npy mRNA, not Agrp, Pomc, Cart, Crh, Orexin, or Mch, in the hypothalamus. Spexin (10 nmol/mouse, i.p.) increased the number of c-Fos positive neurons in hypothalamic AHA and SCN, but not in ARC, DMN, LHA, PVN, SON, or VMH. The hypothalamic p-CaMK2 protein expression was upregulated by spexin. This study indicated that acute peripheral injection of spexin inhibited mouse food intake. The anorectic effect may be mediated by GALR3, and inhibiting neuropeptide Y (NPY) via p-CaMK2 and c-Fos in the hypothalamus.

Spexin and a Novel Cichlid-Specific Spexin Paralog Both Inhibit FSH and LH Through a Specific Galanin Receptor (Galr2b) in Tilapia

Spexin (SPX) is a 14 amino acid peptide hormone that has pleiotropic functions across vertebrates, one of which is involvement in the brain-pituitary-gonad axis of fish. SPX(1) has been identified in each class of vertebrates, and a second SPX (named SPX2) has been found in some non-mammalian species. We have cloned two spexin paralogs, designated as Spx1a and Spx1b, from Nile tilapia (Oreochromis niloticus) that have varying tissue distribution patterns. Spx1b is a novel peptide only identified in cichlid fish, and is more closely related to Spx1 than Spx2 homologs as supported by phylogenetic, synteny, and functional analyses. Kisspeptin, Spx, and galanin (Gal) peptides and their corresponding kiss receptors and Gal receptors (Galrs), respectively, are evolutionarily related. Cloning of six tilapia Galrs (Galr1a, Galr1b, Galr2a, Galr2b, Galr type 1, and Galr type 2) and subsequent in vitro second-messenger reporter assays for Gα_s, Gα_q, and Gα_i suggests that Gal and Spx activate Galr1a/Galr2a and Galr2b, respectively. A decrease in plasma follicle stimulating hormone and luteinizing hormone concentrations was observed with injections of Spx1a or Spx1b in vivo. Additionally, application of Spx1a and Spx1b to pituitary slices decreased the firing rate of LH cells, suggesting that the peptides can act directly at the level of the pituitary. These data collectively suggest an inhibitory mechanism of action against the secretion of gonadotropins for a traditional and a novel spexin paralog in cichlid species.

Galanin peptide family regulation of glucose metabolism

Recent preclinical and clinical studies have indicated that the galanin peptide family may regulate glucose metabolism and alleviate insulin resistance, which diminishes the probability of type 2 diabetes mellitus. The galanin was discovered in 1983 as a gut-derived peptide hormone. Subsequently, galanin peptide family was found to exert a series of metabolic effects, including the regulation of gut motility, body weight and glucose metabolism. The galanin peptide family in modulating glucose metabolism received recently increasing recognition because pharmacological activiation of galanin signaling might be of therapeutic value to improve insuin resistance and type 2 diabetes mellitus. To date, however, few papers have summarized the role of the galanin peptide family in modulating glucose metabolism and insulin resistance. In this review we summarize the metabolic effect of galanin peptide family and highlight its glucoregulatory action and discuss the pharmacological value of galanin pathway activiation for the treatment of glucose intolerance and type 2 diabetes mellitus.

Serum Spexin is Correlated with Lipoprotein(a) and Androgens in Female Adolescents

The Spexin gene is considered the most dysregulated in obese human fat. Limited data suggest that the novel peptide spexin may potentially impact food intake, weight regulation and body adiposity. The aim of this case-control study was to compare fasting serum spexin concentrations between normal weight (NW) and overweight/obese (OB/OW) adolescent females and explore the relationship between circulating spexin and anthropometric, bone and fat mass, metabolic and hormonal parameters. Eighty post-menarcheal females (mean age ± SD 16.23 ± 2.26 years); 55 NW (mean BMI ± SD 19.72 ± 2.52 kg/m²) and 25 OB/OW (mean BMI ± SD 29.35 ± 3.89 kg/m²) participated in the study. Circulating spexin levels did not differ significantly (p = 0.378) between NW (median (interquartile range), 0.26 (0.17) ng/mL) and OB/OW (median (interquartile range), 0.28 (0.06) ng/mL) adolescents and did not correlate with BMI (r_s = −0.090, p = 0.438), % body fat (r_s = −0.173, p = 0.409), glucose or insulin resistance indices derived from fasting and oral glucose tolerance states. In the total study sample, spexin concentrations correlated positively with lipoprotein(a) (r_s = 0.402, p = 0.046). In the OB/OW adolescents spexin levels correlated positively with testosterone (r_s = 0.727, p = 0.011) and free androgen index (r_s = 0.755, p = 0.007). In the NW adolescents, spexin concentrations correlated negatively with dehydroepiandrosterone sulphate (r_s = −0.445, p = 0.038). Results may suggest potential involvement of spexin in the regulation of lipoprotein(a) and of the reproductive/adrenal axis in post-menarcheal adolescent females.

Open reading frame mining identifies a TLR4 binding domain in the primary sequence of ECRG4

The embedding of small peptide ligands within large inactive pre-pro-precursor proteins encoded by orphan open reading frames (ORFs) makes them difficult to identify and study. To address this problem, we generated oligonucleotide (< 100-400 base pair) combinatorial libraries from either the epidermal growth factor (EGF) ORF that encodes the > 1200 amino acid EGF precursor protein or the orphan ECRG4 ORF, that encodes a 148 amino acid Esophageal Cancer Related Gene 4 (ECRG4), a putative cytokine precursor protein of up to eight ligands. After phage display and 3-4 rounds of biopanning for phage internalization into prostate cancer epithelial cells, sequencing identified the 53-amino acid EGF ligand encoded by the 5' region of the EGF ORF and three distinct domains within the primary sequence of ECRG4: its membrane targeting hydrophobic signal peptide, an unanticipated amino terminus domain at ECRG437-63 and a C-terminus ECRG4133-148 domain. Using HEK-blue cells transfected with the innate immunity receptor complex, we show that both ECRG437-63 and ECRG4133-148 enter cells by interaction with the TLR4 immune complex but neither stimulate NFkB. Taken together, the results help establish that phage display can be used to identify cryptic domains within ORFs of the human secretome and identify a novel TLR4-targeted internalization domain in the amino terminus of ECRG4 that may contribute to its effects on cell migration, immune cell activation and tumor suppression.

Serum levels of spexin are increased in the third trimester pregnancy with gestational diabetes mellitus

Spexin is a peptide that is involved in energy homeostasis and its expression is influenced by altered glucose metabolism. Gestational diabetes mellitus (GDM) is associated with increased insulin resistance (IR) and pregnancy is a progressive insulin resistant state. We hypothesized that spexin may have an effect on the pathophysiology of GDM which further could help to identify the disease. The aim of this study was to investigate spexin levels in the third trimester pregnancies with GDM and healthy controls. Thirty-nine women with GDM and 39 healthy singleton pregnancies were enrolled in this case-control study. Serum spexin concentrations were measured and correlated to biochemical and clinical parameters. Serum spexin levels were significantly higher in women with GDM (3686.25 ± 348.37 vs. 3472.33 ± 293.93 pg/ml, p=.004). Spexin levels ​​did not differ significantly according to treatment modality. Moreover, spexin levels were significantly positively correlated with homeostasis model assessment of IR (HOMA-IR). Spexin levels were significantly higher in women with GDM and closely related to HOMA-IR in the third trimester pregnancy. This may help to better clarify the pathophysiological role of spexin in GDM.

Spexin alleviates insulin resistance and inhibits hepatic gluconeogenesis via the FoxO1/PGC-1α pathway in high-fat-diet-induced rats and insulin resistant cells

Objective: Recent studies demonstrate circulating serum spexin levels are reduced in obesity or type 2 diabetes mellitus (T2DM) patients and may play a role in glucose metabolism. The mechanism underlying is not known. In this study, we explore whether spexin has a role in insulin resistance and hepatic glucose metabolism.

Methods: The correlation between serum spexin levels and the homeostasis model assessment of insulin resistance (HOMA-IR) was studied in newly diagnosed T2DM patients. After intraperitoneal injection of exogenous spexin for 8 weeks, the effect of spexin on exogenous glucose infusion rates (GIR), and hepatic glucose production (HGP) were assessed by extended hyperinsulinemic-euglycemic clamp in high-fat-diet (HFD)-induced rats. Glucose concentration with CRISPR/Cas9-mediated disruption of spexin expression in HepG2 cells culture was observed. Expression of transcription factors (Forkhead box O1, FoxO1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha, PGC-1α) and key enzymes (G-6-Pase and PEPCK) of gluconeogenesis pathway were observed in vitro and in vivo.

Results: The serum spexin level was significantly low in newly diagnosed T2DM patients as compared with healthy patients and significantly negatively correlated with the HOMA-IR values. Exogenous spexin treatment resulted in weight loss and decrease of HOMA-IR value in high-fat-diet (HFD)-induced rats. The exogenous glucose infusion rates (GIR) were higher in the HFD + spexin group than that in the HFD group (358 ± 32 vs. 285 ± 24 μmol/kg/min, P < 0.05). Steady-state hepatic glucose production (HGP) was also suppressed by ~50% in the HFD + spexin group as compared with that in the HFD group. Furthermore, spexin inhibited gluconeogenesis in dose-dependent and time-dependent manner in the insulin-resistant cell model. CRISPR/Cas9-mediated knockdown of spexin in HepG2 cells activated gluconeogenesis. Moreover, spexin was shown regulating gluconeogenesis by inhibiting FoxO1/PGC-1α pathway, and key gluconeogenic enzymes, (PEPCK and G-6-Pase) in both HFD-induced rats and insulin-resistant cells.

Conclusions: Spexin plays an important role in insulin resistance in HFD-induced rats and insulin-resistant cells. Regulation of the effects of spexin on insulin resistance may hold therapeutic value for metabolic diseases.

Origin and Evolution of the Neuroendocrine Control of Reproduction in Vertebrates, With Special Focus on Genome and Gene Duplications

In humans, as in the other mammals, the neuroendocrine control of reproduction is ensured by the brain-pituitary gonadotropic axis. Multiple internal and environmental cues are integrated via brain neuronal networks, ultimately leading to the modulation of the activity of gonadotropin-releasing hormone (GnRH) neurons. The decapeptide GnRH is released into the hypothalamic-hypophysial portal blood system and stimulates the production of pituitary glycoprotein hormones, the two gonadotropins luteinizing hormone and follicle-stimulating hormone. A novel actor, the neuropeptide kisspeptin, acting upstream of GnRH, has attracted increasing attention in recent years. Other neuropeptides, such as gonadotropin-inhibiting hormone/RF-amide related peptide, and other members of the RF-amide peptide superfamily, as well as various nonpeptidic neuromediators such as dopamine and serotonin also provide a large panel of stimulatory or inhibitory regulators. This paper addresses the origin and evolution of the vertebrate gonadotropic axis. Brain-pituitary neuroendocrine axes are typical of vertebrates, the pituitary gland, mediator and amplifier of brain control on peripheral organs, being a vertebrate innovation. The paper reviews, from molecular and functional perspectives, the evolution across vertebrate radiation of some key actors of the vertebrate neuroendocrine control of reproduction and traces back their origin along the vertebrate lineage and in other metazoa before the emergence of vertebrates. A focus is given on how gene duplications, resulting from either local events or from whole genome duplication events, and followed by paralogous gene loss or conservation, might have shaped the evolutionary scenarios of current families of key actors of the gonadotropic axis.

CSF Proteomics of Patients with Hydrocephalus and Subarachnoid Haemorrhage

Background

The pathophysiology of brain injury following aneurysmal subarachnoid haemorrhage (SAH) is associated with numerous mediators. The aim of the study is to analyse protein changes after SAH in cerebrospinal fluid (CSF) using mass spectrometry (MS).

Methods

CSF samples were obtained from forty-four control subjects, seven good outcome and ten poor outcome SAH patients. CSF samples were collected at specific time intervals after SAH (days 1, 5 and 10). MALDI-TOF (Matrix Assisted Laser Desorption/Ionization Time-of-Flight) and ClinProTools software were utilised for MS, MS/MS (Mass Spectrometry) spectra collection and analysis. Selected masses were identified. The MALDI-TOF profiling experiments allowed for the targeted selection of potential markers in SAH. The study was performed in three steps by comparison of CSF samples: (1) from the control group and SAH patients (both good and poor outcome groups); (2) collected on days 1, 5 and 10 within the groups of poor SAH and good SAH patients, respectively; (3) from poor outcome SAH and good outcome patients at days 1, 5 and 10.

Results

15 new proteins whose CSF level is alternated by SAH presence, SAH treatment outcome and time passed since aneurysm rupture were identified.

Conclusions

We demonstrated new proteins which might play a role in different stages of subarachnoid haemorrhage and could be a new target for further investigation.

Comparing serum concentration of spexin among patients with metabolic syndrome, healthy overweight/obese, and normal-weight individuals

Background: There are many factors related to etiology of metabolic syndrome (MetS) including obesity. Spexin, a peptide hormone released from adipose tissue, is the most down-regulated gene in obese, compared to non-obese adipose tissue. Hence, it potentially contributes to the progression and development of metabolic diseases. This study was designed to evaluate serum concentration of spexin in patients with MetS compared to weight-matched and normal-weight controls.

Methods: In this case-control study, 153 participants (51 per group) were collected from October 2014 to June 2016. The study groups were all matched for age and sex and included overweight/obese individuals with MetS and 2 control groups without MetS (including weight-matched and normal-weight participants). Body composition and serum concentration of spexin and leptin were measured.

Results: Serum leptin and spexin levels were significantly higher and lower, respectively, in normal-weight compared to overweight/obese groups with/without MetS (p< 0.02). No significant difference was observed in serum leptin and spexin concentrations between the overweight/obese groups with/without MetS (p≥ 0.05). Also, spexin, with cutoff value of 4.6, had 78% sensitivity and 82% specificity for diagnosing overweight/obese from normal-weight participants. Spexin had 78% sensitivity and specificity, with cutoff value of 4.35, in diagnosing MetS participants from normal-weight group.

Conclusion: This study found no correlation between the circulating level of spexin and MetS development. Higher serum concentration of spexin in normal-weight adults compared to the obese participants illustrated the potential role of this novel peptide in obesity.

Small-protein Enrichment Assay Enables the Rapid, Unbiased Analysis of Over 100 Low Abundance Factors from Human Plasma

Unbiased and sensitive quantification of low abundance small proteins in human plasma (e.g. hormones, immune factors, metabolic regulators) remains an unmet need. These small protein factors are typically analyzed individually and using antibodies that can lack specificity. Mass spectrometry (MS)-based proteomics has the potential to address these problems, however the analysis of plasma by MS is plagued by the extremely large dynamic range of this body fluid, with protein abundances spanning at least 13 orders of magnitude. Here we describe an enrichment assay (SPEA), that greatly simplifies the plasma dynamic range problem by enriching small-proteins of 2-10 kDa, enabling the rapid, specific and sensitive quantification of >100 small-protein factors in a single untargeted LC-MS/MS acquisition. Applying this method to perform deep-proteome profiling of human plasma we identify C5ORF46 as a previously uncharacterized human plasma protein. We further demonstrate the reproducibility of our workflow for low abundance protein analysis using a stable-isotope labeled protein standard of insulin spiked into human plasma. SPEA provides the ability to study numerous important hormones in a single rapid assay, which we applied to study the intermittent fasting response and observed several unexpected changes including decreased plasma abundance of the iron homeostasis regulator hepcidin.

Potential functions of esophageal cancer-related gene-4 in the cardiovascular system

Esophageal cancer-related gene-4 (Ecrg4) is cloned from the normal epithelium of the esophagus. It is constitutively expressed in quiescent epithelial cells and downregulated during tumorigenesis, and Ecrg4 expression levels are inversely correlated with the malignant phenotype of tumor cells, validating that Ecrg4 is a real tumor suppressor gene. Unlike other tumor suppressor genes that usually encode membrane or intracellular proteins, Ecrg4 encodes a 148-amino acid pre-pro-peptide that is tethered on the cell surface in epithelial cells, specialized epithelial cells, and human leukocytes, where it can be processed tissue dependently into several small peptides upon cell activation. Ecrg4 is expressed in a wide variety of other cells/tissues, including cardiomyocytes and conduction system of the heart, the glomus cells of the carotid body, adrenal glands, choroid plexus, and leukocytes among others, where it exerts distinct functions, such as promoting/suppressing inflammation, inducing neuron senescence, stimulating the hypothalamus-pituitary-adrenal axis, maintaining the stemness of stem cells, participating in the rhythm and rate control of the heart, and possibly gauging the responsiveness of the cardiovascular system (CVS) to hypoxia, in addition to tumor suppression. Here, we briefly review the latest discoveries on Ecrg4 and its underlying molecular mechanisms as a tumor suppressor and focus on the emerging roles of Ecrg4 in the CVS.

Overexpression of Spexin 1 in the Dorsal Habenula Reduces Anxiety in Zebrafish

Spexin (SPX) is an evolutionarily conserved neuropeptide that is expressed in the mammalian brain and peripheral tissue. Two orthologs are present in the teleost, SPX1 and SPX2. SPX1 is involved in reproduction and food intake. Recently, SPX1 neurons have been found to be located in the specific nuclei of dorsal habenula (dHb) and to project into the interpeduncular nucleus (IPN), in which galanin receptor 2a/2b (GALR2a/2b) expression was also observed. This indicates that habenula SPX1 neurons may interact with GALR2a/2b in the IPN; however, the function of SPX1 in the dHb-IPN neuronal circuit remains unknown. To determine the role of SPX1 in the dHb-IPN neural circuit, we generated transgenic zebrafish overexpressing SPX1 specifically in the dHb. We found that transgenic zebrafish overexpressing SPX1 in the dHb had anxiolytic behaviors compared with their wildtype siblings. Furthermore, quantitative PCR revealed that mRNA expression of galr2a and galr2b in the IPN and serotonin-related genes in the raphe was upregulated in the brains of transgenic zebrafish. Taken together, our data suggest that SPX1 function in the dHb-IPN neural circuits is implicated in the regulation of anxiety behaviors via modulation of the serotoninergic system in zebrafish.

Favorable Changes in Fasting Glucose in a 6-month Self-Monitored Lifestyle Modification Programme Inversely Affects Spexin Levels in Females with Prediabetes

Spexin (SPX) is a novel peptide thought to have a role in various metabolic regulations. Given its presumed body-weight regulatory functions, we aimed to determine whether lifestyle intervention programs on weight loss and fasting glucose (FG) improvement among people with impaired glucose regulation also alter levels of circulating SPX. A total of 160 Saudi adult males and females with prediabetes were randomly selected from a larger cohort (N = 294) who underwent a 6-month lifestyle modification program to improve their glycemic status. Participants were split into two groups based on differences in glucose levels post-intervention, with the first 50% (improved group) having the most significant reduction in FG. SPX was measured at baseline and after 6 months. Changes in SPX was significant only in the improved group [baseline: median (Q1-Q3) of 164 pg/ml (136-227) vs follow-up: 176 pg/ml (146-285); p < 0.01]. When stratified by sex, the significant increase was observed only in females [159 pg/ml (127-252) vs 182.5 (152,369.1); p < 0.01]. Furthermore, SPX levels showed a significant inverse association with FG (β = -0.22, p = 0.003) even after adjustment with age and BMI, again only in females. Circulating SPX levels increase over time in people with prediabetes, particularly women who responded favorably in a 6-month lifestyle intervention program. Whether an unknown mechanism regulating the sexual disparity seen in SPX levels post-intervention exists should be further investigated using a larger sample size.

Esophageal cancer related gene-4 inhibits the migration and proliferation of oral squamous cell carcinoma through BC200 lncRNA/MMP-9 and -13 signaling pathway

Esophageal cancer related gene-4 (ECRG4) inhibits the malignant phenotype of oral squamous cell carcinoma. However, the molecular mechanisms remain to be explored. Using the tongue carcinoma cell line, TCA8113 as a cell model, we showed that forced expression of ECRG4 down-regulated the expression of the BC200 long non-coding RNA (lncRNA) and matrix metalloproteinases (MMP-9 and MMP-13). Restoration of BC200 lncRNA rescued ECRG4-mediated down-regulation of MMP-9 and -13. Furthermore, over-expression of Ecrg4 inhibited cell proliferation and migration, which was abolished by forced expression of BC200 lncRNA in TCA8113 cells. Our results indicate that ECRG4 inhibits the malignant phenotype of TCA8113 cells most likely through suppression of BC200 lncRNA/MMPs signaling pathway, rationalizing that BC200 lncRNA may be a potential target for oral squamous cell carcinoma (OSCC) therapy.

Emerging Roles of NPQ/Spexin in Physiology and Pathology

Spexin (SPX), also called neuropeptide Q (NPQ), is a novel endogenous neuropeptide. Spexin gene and protein are widely expressed in central nervous system and peripheral tissues in humans, rodents, goldfish, etc. A few of physiological and pathological roles of spexin are gradually emerged recently. This article summarized the roles of spexin in feeding behavior, gastrointestinal motility, obesity, diabetes, energy metabolism, endocrine, mental diseases, and cardiovascular function. Given the broad roles of spexin, this neuropeptide has attracted much interest from investigators and will be as a promising future target for novel therapeutic research and drug design.

Distribution and neuronal circuit of spexin 1/2 neurons in the zebrafish CNS

Spexin (SPX) is a highly conserved neuropeptide that is widely expressed in mammalian brain and peripheral tissue. In teleost, SPX1 is mainly expressed in the brain and ovary, and is involved in reproduction and food intake. A second form of SPX, SPX2, was recently identified in chick, Xenopus, and zebrafish. The expression pattern and roles of SPX2 are unknown. SPX (spx1) is highly expressed in the vertebrate brain, but its distribution, circuits, and interactions with its putative receptor are unknown. Here, we observed expression of spx1 in the midbrain and hindbrain, and spx2 in the hypothalamic preoptic area using in situ RNA hybridization in zebrafish. Analysis of transgenic reporter zebrafish revealed that hindbrain SPX1 neurons are PAX2⁺ inhibitory interneurons and project to the spinal cord, where they interact with galanin receptor 2b (GALR2b) neurons, suggesting that hindbrain SPX1 neurons are reticulospinal neurons. spx1 mRNA and SPX1 reporter expression were observed in dorsal habenula (dHb). SPX1 neurons in the dHb project to the interpeduncular nucleus (IPN), where GALR2a and GALR2b expression was also observed, suggesting that habenula SPX1 neurons may interact with GALR2a/2b in the IPN.

Spexin in the physiology of pancreatic islets-mutual interactions with insulin

Spexin is an interesting peptide, which may play an important role in the regulation of the metabolic homeostasis of an organism. Current knowledge on spexin expression, secretion, and influence on tissues and endocrine glands is very limited. We investigated spexin localization in the endocrine pancreas and measured its in vitro secretion from isolated pancreatic islets at various glucose concentrations, simultaneously monitoring insulin release. Also, gene expression for spexin and insulin was estimated. We found the presence of spexin inside beta cells and an increase in its release from islets after a short term and decrease after a long term following glucose administration. Finally, negative feedback loops between spexin and insulin were found, indicating the presence of multilateral relationships between glucose, insulin, and spexin inside pancreatic islets.

Spexin/NPQ Induces FBJ Osteosarcoma Oncogene (Fos) and Produces Antinociceptive Effect against Inflammatory Pain in the Mouse Model

Spexin/NPQ is a novel highly conserved neuropeptide. It has a widespread expression in the periphery and central nervous system. However, the effects of central spexin on acute inflammatory pain are still unknown. This study explored the mechanisms and effects of supraspinal spexin on inflammatory pain. The results from the mouse formalin test show that i.c.v. administration of spexin decreased licking/biting time during the late and early phases. The nonamidated spexin had no effect on pain response. The antinociception of spexin was blocked by galanin receptor 3 antagonist SNAP 37889. The Galr3 and Adcy4 mRNA levels in the brain were increased after injection with spexin. The antinociceptive effects of spexin were completely reversed by opioid receptor antagonist naloxone and κ-opioid receptor antagonist nor-binaltorphimine dihydrochloride. Spexin up-regulated the dynorphin and κ-opioid receptor gene and protein expression. PCR array assay and real-time PCR analysis show that spexin up-regulated the mRNA level of the FBJ osteosarcoma oncogene (Fos). T-5224, the inhibitor of c FBJ osteosarcoma oncogene (c-Fos)/activator protein 1 (AP-1), blocked the increased mRNA level of Pdyn and Oprk1 induced by spexin. I.C.V. spexin (2.43 mg/kg) increased the number of c-Fos-positive neurons in most subsections of periaqueductal gray. In addition, in the acetic acid-induced writhing test, i.c.v. spexin produced an antinociceptive effect. Our results indicate that spexin might be a novel neuropeptide with an antinociceptive effect against acute inflammatory pain.

Evolution of Structural and Functional Diversity of Spexin in Mammalian and Non-mammalian Vertebrate Species

Spexin (SPX) is a novel neuropeptide, which was first identified in the human genome using bioinformatics. Since then, orthologs of human SPX have been identified in mammalian and non-mammalian vertebrates. The mature sequence of SPX, NWTPQAMLYLKGAQ, is evolutionally conserved across vertebrate species, with some variations in teleost species where Ala at position 13 is substituted by Thr. In mammals, the gene structure of SPX comprises six exons and five introns, however, variation exists within non-mammalian species, goldfish and zebrafish having five exons while grouper has six exons. Phylogenetic and synteny analysis, reveal that SPX is grouped together with two neuropeptides, kisspeptin (KISS) and galanin (GAL) as a family of peptides with a common evolutionary ancestor. A paralog of SPX, termed SPX2 has been identified in non-mammalians but not in the mammalian genome. Ligand-receptor interaction study also shows that SPX acts as a ligand for GAL receptor 2 (2a and 2b in non-mammalian vertebrates) and 3. SPX acts as a neuromodulator with multiple central and peripheral physiological roles in the regulation of insulin release, fat metabolism, feeding behavior, and reproduction. Collectively, this review provides a comprehensive overview of the evolutionary diversity as well as molecular and physiological roles of SPX in mammalian and non-mammalian vertebrate species.

Molecular cloning, characterization and expression analysis of spexin in spotted scat (Scatophagus argus)

Spexin (Spx), a novel neuropeptide, composed of 14 amino acid residues, is evolutionally conserved from fish to mammals. It has been suggested that Spx has pleiotropic functions in mammals. However, reports about Spx are very limited. To clarify the roles of Spx in the regulation of reproduction and food-intake in the spotted scat, the spx (ssspx) gene was cloned and analyzed. Analysis of the tissue distribution by RT-PCR showed that ssspx expression was widespread. During ovary development, expression of ssspx was found to be highest in phase II, moderate in phase III, and at its lowest level in phase IV. Ssspx expression was significantly down-regulated in the hypothalamus after treatment with E₂ both in vitro and in vivo. A significant increase of ssspx was observed after 2 and 7 days of food deprivation. However, the ssspx transcript levels in the 7 day fasting group decreased significantly after refeeding 3 h after the scheduled feeding time. This suggests that ssSpx may be involved in the regulation of reproduction and food-intake in the spotted scat.

Spexin Levels Are Associated with Metabolic Syndrome Components

Background

Spexin (SPX) is a novel peptide that is implicated in obesity and related energy homeostasis in animals and adult humans. Little is known about its role in adults' overall cardiometabolic health. The aim of the study was to determine whether circulating levels of spexin (SPX) is associated with components of metabolic syndrome (MetS).

Methods

The present cross-sectional study included 124 participants (41 males and 83 females; aged 42.4 ± 10.3 y) (MetS group) and 136 (21 male and 115 females; aged 33.1 ± 8.7 y) (non-MetS group). SPX was measured using commercially available assays. Anthropometrics were measured, and fasting serum glucose levels as well as lipid profile were quantified routinely. MetS was screened according to common definitions.

Results

SPX levels were significantly lower in participants with MetS vs. non-MetS (0.18 ng/ml (0.13-0.24) vs. 0.26 ng/ml (0.17-0.50); p < 0.001). In all MetS definitions used, SPX was significantly lower in the MetS group than the non-MetS group using the WHO definition after adjustment for age and BMI. Stratification according to sex revealed that SPX was associated with MetS only in women, and this significance was lost after adjustment for age and BMI.

Conclusions

Lower circulating levels of SPX in adults are modestly associated with components of MetS and are sex-specific. Further studies are necessary to determine whether SPX is associated with harder outcomes such as atherosclerosis and diabetes in the general population.

Spexin as a neuroendocrine signal with emerging functions

Spexin (SPX), a novel peptide coevolved with the galanin/kisspeptin family, was first identified by bioinformatics prior to its protein purification/functional studies. Its mature peptide is highly conserved among different vertebrate classes. Based on the studies in mammals and fish models, SPX was found to be widely distributed at tissue level, secreted into systemic circulation, identified at notable levels in central nervous system and peripheral tissues, and has been confirmed/implicated in multiple functions in different tissues/organs, suggesting that SPX may serve as a neuroe​ndocrine signal with pleotropic functions. In this article, different isoforms of SPX and their binding with their cognate receptors GalR2 and GalR3, the biological functions of SPX reported in mammals including GI tract movement, energy balance and weight loss, fatty acid uptake, glucose homeostasis, nociception and cardiovascular/renal functions, as well as the recent findings in fish models regarding the role of SPX in reproduction and feeding control will be reviewed with interesting questions for future investigations.

Spexin Modulates Functions of Rat Endocrine Pancreatic Cells

OBJECTIVES

Spexin is a peptide whose action is poorly understood but which is expressed in many tissues. This encouraged us to investigate the potential role of spexin in the regulation of pancreatic secretion.

METHODS

Cells/islets were incubated with different concentrations of glucose and spexin to measure insulin secretion. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays and BrdU (5-bromo-2'-deoxyuridine) tests were performed to assess the viability and proliferation of pancreatic islets after spexin treatment. Real-time polymerase chain reaction was used to detect messenger RNA expression for insulin, insulin receptor, and Pdx (pancreatic duodenal homeobox-1).

RESULTS

Insulin secretion from cultured cells and isolated islets was reduced by spexin at 16 mM glucose level. In obese rats, insulin secretion was decreased after injection with spexin. Spexin treatment showed an increase in cultured cells and pancreatic islets cell viability and proliferation as well as an increase in proliferating cell nuclear antigen protein level. In contrast, a decrease in insulin and Pdx gene expression was found.

CONCLUSIONS

The effects of spexin on insulin secretion in vitro and in vivo and also on cells viability and proliferation confirm that this peptide may be strongly involved in the pathogenesis of diabetes or its recovery.

Roux-en-Y gastric bypass surgery in youth with severe obesity: 1-year longitudinal changes in spexin

BACKGROUND

Spexin is a novel peptide predominantly produced in human white adipose tissue and has recently been implicated as a potential signal in the regulation of body weight, energy homeostasis, and satiety. The effect of bariatric surgery on spexin is unknown.

OBJECTIVES

To study the effect of Roux-en-Y gastric bypass (RYGB) surgery on endogenous spexin concentration and various risk factors of type 2 diabetes and cardiovascular disease in youth with severe obesity.

SETTING

University hospital, United States METHODS: Spexin, body mass index (BMI), insulin, glucose, total and high molecular weight adiponectin, leptin, and high sensitivity C- reactive protein were measured longitudinally (baseline, 6 mo, and 12 mo) after RYGB surgery in girls with severe obesity (n = 12; age = 16.7 ± 1.5 years; BMI = 51.6 ± 2.9 kg/m²).

RESULTS

Serum spexin concentration increased (P = .01) at 6 months after surgery and stabilized afterward. Spexin level correlated negatively with homeostatic model assessment insulin resistance, HOMA-IR (Spearman correlation r = -.796, P < .001) and positively with high molecular weight adiponectin (Spearman correlation r = .691, P = .011). The change in spexin concentration, from baseline to 6 months after surgery, was inversely correlated with the corresponding change in BMI (Spearman correlation r = -.573, P = .051). Furthermore, the 6-month changes in spexin and HOMA-IR were inversely correlated (slope [standard error, SE] = -.0084 (.0019), P = .001)], even after adjusting for the change in BMI.

CONCLUSIONS

The enhancement of circulating spexin concentration in response to RYGB and correlations with beneficial postoperative changes in various adipokines in youth are novel findings that require further validation.

ECRG4: a new potential target in precision medicine

Given the rapid development in precision medicine, tremendous efforts have been devoted to discovering new biomarkers for disease diagnosis and treatment. Esophageal cancer-related gene-4 (ECRG4), which is initially known as a new candidate tumor suppressor gene, is emerging as a sentinel molecule for gauging tissue homeostasis. ECRG4 is unique in its cytokine-like functional pattern and epigenetically-regulated gene expression pattern. The gene can be released from the cell membrane upon activation and detected in liquid biopsy, thus offering considerable potential in precision medicine. This review provides an updated summary on the biology of ECRG4, with emphasis on its important roles in cancer diagnosis and therapy. The future perspectives of ECRG4 as a potential molecular marker in precision medicine are also discussed in detail.

Serum exosomes contain ECRG4 mRNA that suppresses tumor growth via inhibition of genes involved in inflammation, cell proliferation, and angiogenesis

Esophageal cancer related gene-4 (Ecrg4) has been shown to be a tumor suppressor in many organs. Exosomes are naturally secreted nanosized particles that carry signal molecules including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and messenger RNAs (mRNAs) among others. Upon internalization, exosomes unload their cargos that in turn modulate the biology of the recipient cells. Mounting evidence has shown that exosomal miRNAs are functional. However, reports that exosomes carry functional mRNAs remain scarce. We found that serum exosomes contain ECRG4 open reading frame. To simulate serum exosomal ECRG4, stable cell line expressing ECRG4 was created, from which exosomes were isolated and characterized, and the internalization and the resulting biological effects of exosomal ECRG4 were evaluated. Results showed that serum exosomes contain higher levels of ECRG4 mRNA in healthy individuals than their cancer counterparts. Exosomal ECRG4 can be internalized and unload the encapsulated ECRG4 into recipient cells, which subsequently suppressed cell proliferation in vitro, and inhibited tumor growth in a xenograft mouse model. Mechanistically, ECRG4-containing exosomes, when internalized, suppressed the expression of genes commonly implicated in inflammation, cell proliferation, and angiogenesis. Given that exosome is an ideal vehicle for therapeutics delivery and that ECRG4 is a tumor suppressor gene, the exosomal ECRG4 can be exploited as a formulation for cancer gene therapy.

Relationship of circulating spexin with markers of cardiovascular disease: a pilot study in adolescents with obesity

PURPOSE

Spexin, a novel peptide, has potential implications in obesity, satiety and energy homeostasis. The current study examined the relationship of spexin with various biomarkers of cardiovascular disease and endothelial function in adolescents with obesity.

METHODS

Nineteen adolescents with obesity (age, 15.8 ± 1.7 years) were studied. Spexin, leptin and various cardiovascular disease biomarkers were measured. Endothelial function was assessed by high-resolution Doppler ultrasonography of the right brachial artery.

RESULTS

Spexin concentration (median [interquartile range] 0.38 ng/mL [0.29-0.59 ng/mL]) was inversely correlated (r = -0.50, P = 0.03) with leptin. When participants were clustered into two groups ('high spexin and low leptin' vs. 'low spexin and high leptin'), the odds of having 'low spexin and high leptin' in participants with higher hs-CRP (≥ 3 mg/L) were 12.25 times (95 per cent CI -1 to139, P = 0.026) higher than those of participants with lower hs-CRP (<3 mg/L). Spexin levels, however, were not associated with measures of endothelial function.

CONCLUSIONS

The inverse association between spexin and leptin and the presence of higher concentrations of hs-CRP in adolescents with obesity in the setting of 'low spexin and high leptin' suggest a potential role for spexin in the regulation of satiety and certain cardiovascular risk factors in children with obesity.

Spexin in the half-smooth tongue sole (Cynoglossus semilaevis): molecular cloning, expression profiles, and physiological effects

Spexin (SPX), a novel neuropeptide discovered by the bioinformatics approach, has been shown to exert pleiotropic functions in mammals. However, little information regarding the physiological role of SPX is available in teleosts. As a first step, we cloned the spexin gene from a flatfish, the half-smooth tongue sole. The open reading frame (ORF) of tongue sole spexin contained 363 nucleotides encoding a 120 amino acid (aa) preprohormone with a calculated molecular mass and isoelectric point of 14.06 kDa and 5.86, respectively. The tongue sole SPX precursor contained a 27 aa signal peptide and a 14 aa mature peptide flanked by two dibasic protein cleavage sites (RR and GRR). Tissue distribution analysis showed that spexin mRNA could be detected in various tissues, notably in the brain. In addition, fasting stimulated the hypothalamic expression of spexin mRNA. Intraperitoneal injection of SPX increased gnih and gnrh3 mRNA levels in the hypothalamus; however, SPX inhibited the pituitary expression of gh, fshβ, and gthα mRNAs. Overall, our results reveal the existence of a functional SPX in the tongue sole, which could represent an important factor in the neuroendocrine control of flatfish reproduction and growth, and the spexin mRNA expression is regulated by feeding status.

Spexin Acts as Novel Regulator for Bile Acid Synthesis

Spexin is a novel hormone involved in obesity and diabetes while its biofunctional significance in lipid metabolism is still to be comprehended. Global metabolomic analysis in the present study revealed multiple metabolic pathways altered by spexin intraperitoneal (i.p.) injection in rat serum, which are highlighted by the changes in several bile acid metabolites. In rats, spexin (300 μg/kg) could dramatically reduce hepatic and circulating total bile acids (TBA) level compared with the controls. Correspondingly, treatment with spexin by i.p. injection for 28 days led to significant decrease in serum TBA and gallbladder weight in C57BL/6J mice. In enterohepatic circulation system, spexin effectively reduced TBA levels in mouse liver and gallbladder but not the intestine. Hepatic cholesterol 7α-hydroxylase 1 (CYP7A1) expression, unsurprisingly, was suppressed by spexin injection. Both GALR2 and GALR3 antagonists reversed the inhibitory effects of spexin on concentrations of serum TBA and 7 α-hydroxy-4-cholesten-3-one (C4), and hepatic CYP7A1 expression. Finally, negative correlations were observed between serum spexin and total cholesterol (TC), total bile acid (TBA), tauro-chenodeoxycholate (TCDCA), as well as glycochenodeoxycholate (GCDCA) in 91 healthy volunteers. These findings illuminate the intrinsic importance of spexin in the regulation of bile acid synthesis and metabolism.

A short synthetic peptide fragment of human C2ORF40 has therapeutic potential in breast cancer

C2ORF40 encodes a secreted protein which is cleaved to generate soluble peptides by proteolytic processing and this process is believed to be necessary for C2ORF40 to exert cell type specific biological activity. Here, we reported a short mimic peptide of human C2ORF40 acts potential therapeutic efficacy in human cancer cells in vitro and in vivo. We synthesized a short peptide of human C2ORF40, named C2ORF40 mimic peptide fragment and assessed its biological function on cancer cell growth, migration and tumorigenesis. Cell growth assay showed that C2ORF40 mimic peptide fragment significantly suppressed cell proliferation of breast and lung cancer cells. Moreover, C2ORF40 mimic peptide fragment significantly inhibited the migration and invasion of breast cancer cells. Furthermore, we showed that this peptide suppressed tumorigenesis in breast tumor xenograft model. Cell cycle assay indicated that the C2ORF40 mimic peptide fragment suppressed the growth of tumor cells through inducing mitotic phase arrest. In conclusion, our results firstly suggested that this short synthetic peptide of human C2ORF40 may be a candidate tumor therapeutic agent.

Circulating Spexin Levels Negatively Correlate With Age, BMI, Fasting Glucose, and Triglycerides in Healthy Adult Women

Context

Spexin is a newly identified neuropeptide that is involved in satiety control, glucose, and lipids metabolism. It has also been related to human diseases, such as obesity and type 2 diabetes. However, whether spexin changes with age or not is still unclear.

Objective

The aim of this study is to investigate the relationship between circulating spexin levels and age and to study their interaction effects on body mass index (BMI), fasting glucose, and -lipids.

Design and Participants

This is a cross-sectional study, including 68 healthy adult women whose ages are in a wide range (minimum: 23; median: 38.5; maximum: 64).

Outcome Measures

The serum spexin levels were measured by an enzyme-linked immunosorbent assay. Fasting glucose, total cholesterol, triglycerides (TG), alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, urea, and creatinine were measured by routine biochemical test. Shapiro-Wilk’s test, Spearman and Pearson correlation analyses, χ² test, and two-way analysis of variance were used to interpret the data.

Results

Serum spexin levels are significantly correlated with age (Spearman r = −0.277, P = 0.022), BMI (Spearman r = −0.445, P < 0.001), fasting glucose (Spearman r = −0.302, P = 0.014), and TG (Spearman r = −0.324, P = 0.008). Spexin levels independently predict the risk of high BMI and high fasting glucose. No interaction effects of spexin and age on BMI and fasting glucose were found.

Conclusions

Circulating spexin levels decrease with age, suggesting a possible role of this peptide in aging-related functions and disorders. Further investigations are needed to expand the clinical significance of this finding.

Ecrg4 peptide is the ligand of multiple scavenger receptors

Esophageal cancer-related gene 4 (Ecrg4) encodes a hormone-like peptide that is believed to be involved in a variety of physiological phenomena, including tumour suppression. Recent progress in the study of Ecrg4 has shown that Ecrg4 is a proinflammatory factor and induces the expression of several cytokines and chemokines in macrophages/microglia. However, the detailed molecular mechanisms of Ecrg4 signalling, especially the Ecrg4 receptors, remain poorly understood. Here, using retrovirus-mediated expression cloning, we identified lectin-like oxidised low-density lipoprotein receptor-1 (LOX-1) as a membrane protein that binds amino acid residues 71–132 of Ecrg4 (Ecrg4(71–132)). Moreover, in addition to LOX-1, several scavenger receptors, such as Scarf1, Cd36 and Stabilin-1, facilitated the efficient internalisation of Ecrg4(71–132) into cells. A broad competitive inhibitor of scavenger receptors, polyinosinic acid, reduced both the binding of Ecrg4(71–132) and the activation of NF-κB in microglia. This activation was dependent on MyD88, an adaptor protein that recruits signalling proteins to Toll-like receptors (TLRs), with the consequent induction of various immune responses. These data suggest that multiple scavenger receptors recognise Ecrg4(71–132) and transduce its signals, together with TLRs, in microglia.

Effect of obesity and type 2 diabetes, and glucose ingestion on circulating spexin concentration in adolescents

Spexin is a novel peptide that has been reported to be down regulated in obese adults and children and in normoglycemic adults following glucose ingestion. Spexin may therefore have a role in metabolic regulation. The purpose of the current study was to determine the effect of obesity and type 2 diabetes (T2DM), and the effect of glucose ingestion on circulating spexin concentration in adolescents. Boys and girls (mean age 16 years old) classified as healthy normal weight (NW, n = 22), obese (Ob, n = 10), or obese with T2DM (n = 12) completed measurements of body composition, blood pressure, cardiorespiratory fitness, and blood concentrations of glucose, insulin, and lipids. The median fasting serum spexin concentration did not differ between groups (NW: 0.35; Ob: 0.38, T2DM: 0.34 ng/mL, respectively). In 10 NW participants who completed a standard oral glucose tolerance test, spexin concentration was unchanged at 30 and 120 minutes relative to the fasting baseline. Finally, spexin was not significantly correlated with any of the body composition, fitness, or blood biochemical measurements. These data do not support the proposed role of spexin as a metabolic regulator or biomarker of glucose control in adolescents.

Serum Levels of Spexin and Kisspeptin Negatively Correlate With Obesity and Insulin Resistance in Women

Spexin (SPX) and kisspeptin (KISS) are novel peptides relevant in the context of regulation of metabolism, food intake, puberty and reproduction. Here, we studied changes of serum SPX and KISS levels in female non-obese volunteers (BMI<25 kg/m2) and obese patients (BMI>35 kg/m2). Correlations between SPX or KISS with BMI, McAuley index, QUICKI, HOMA IR, serum levels of insulin, glucagon, leptin, adiponectin, orexin-A, obestatin, ghrelin and GLP-1 were assessed. Obese patients had lower SPX and KISS levels as compared to non-obese volunteers (SPX: 4.48±0.19 ng/ml vs. 6.63±0.29 ng/ml; p<0.001, KISS: 1.357±0.15 nmol/l vs. 2.165±0.174 nmol/l; p<0.01). SPX negatively correlated with BMI, HOMA-IR, insulin, glucagon, active ghrelin and leptin. Positive correlations were found between SPX and QUICKI index, McAuley index, serum levels of obestatin, GLP-1 and adiponectin and orexin-A Serum KISS negatively correlated with BMI, HOMA-IR, serum levels of insulin, glucagon, active ghrelin and leptin. KISS positively correlated with QUICKI index, McAuley index and adiponectin. In summary, SPX and KISS show negative correlations with obesity, insulin resistance indices, and hormones known to affect insulin sensitivity in females. Both, SPX and KISS could be therefore relevant in the pathophysiology of obesity and insulin resistance.

Associations of Spexin and cardiometabolic parameters among women with and without gestational diabetes mellitus

Spexin (SPX) is a novel biomarker abundantly expressed in several animal and human tissues implicated in food intake and glucose control, respectively. As new roles for SPX are emerging, the present study explored for the first time, the associations of SPX to several cardiometabolic indices and inflammatory markers in pregnant women, a demographic not yet investigated with respect to SPX. A total of 117 Saudi women subdivided to those with gestational diabetes mellitus (GDM) (N = 63) and those without (N = 54) were included in this cross-sectional study. Anthropometry, glycemic, lipid, vitamin D, adipocytokines and inflammatory markers were measured consecutively at baseline and after the 2nd and 3rd trimesters. Age- and BMI adjusted comparisons revealed that levels of SPX were not significantly different in pregnant women with and without GDM. In all subjects, circulating levels of SPX showed modest associations with glucose (R = 0.18; p = .08) and HOMA β (R = −0.19; p = .09) as well as significant positive associations with total cholesterol (R = 0.25; p = .02), LDL-cholesterol (R = 0.25; p = .02), 25(OH)D (R = 0.22; p = .04), albumin (R = 0.30; p < .01) and IL1β (R = 0.41; p < .01). Stepwise regression analysis also suggested that IL1β, leptin and albumin were the significant predictors of SPX. In summary, SPX levels modestly affect glucose and insulin sensitivity in pregnant women but is not associated with GDM and obesity. The significant association of SPX to ILβ warrants further investigation as to the role of SPX in immune modulation.

Bioinformatics for Prohormone and Neuropeptide Discovery

Neuropeptides and peptide hormones are signaling molecules produced via complex post-translational modifications of precursor proteins known as prohormones. Neuropeptides activate specific receptors and are associated with the regulation of physiological systems and behaviors. The identification of prohormones-and the neuropeptides created by these prohormones-from genomic assemblies has become essential to support the annotation and use of the rapidly growing number of sequenced genomes. Here we describe a methodology for identifying the prohormone complement from genomic assemblies that employs widely available public toolsets and databases. The uncovered prohormone sequences can then be screened for putative neuropeptides to enable accurate proteomic discovery and validation.

Decreased Spexin Levels in Patients with Type 1 and Type 2 Diabetes

BACKGROUND/AIMS

Spexin is a novel peptide which has a potential role as a biomarker of insulin resistance, diabetes, and obesity. Our aim was to measure spexin levels in lean type 1 diabetic patients and its relevance to glycemic parameters without the presence of obesity or insulin resistance.

SUBJECTS AND METHODS

This cross-sectional study included 29 type 1 and 30 type 2 diabetic patients and a control group of 23 healthy subjects with adjusted age, sex, and body mass index (BMI). Height and weight were measured using standard techniques. Glucose levels, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, serum cortisol levels, and spexin levels were measured in each patient.

RESULTS

The median fasting serum spexin levels were significantly lower in patients with type 1 and type 2 diabetes than in control subjects (p = 0.008 and p = 0.041, respectively). Spexin levels were not correlated with glycemic parameters, lipids, BMI, cortisol levels, and thyroid-stimulating hormone (p > 0.05). Only age turned out to be correlated with spexin levels in patients with type 1 diabetes when we analyzed the groups separately. Regression models, including age and diabetes duration, revealed no association between age and spexin levels. Regression models, including cortisol, BMI, and HbA1c, revealed no association with spexin levels within each group.

CONCLUSION

The presence of type 1 diabetes is associated with lower spexin levels, independent of glucose, lipid parameters, and BMI. The expression of spexin in the pancreas apart from the current glycemic control of the patients may be the main determinant of spexin levels in type 1 diabetic patients.

Counter regulation of ECRG4 gene expression by hypermethylation-dependent inhibition and the Sp1 transcription factor-dependent stimulation of the c2orf40 promoter

The human cytokine precursor ECRG4 has been associated with multiple physiological, developmental and pathophysiological processes involving cell proliferation, cell migration, innate immunity, inflammation, cancer progression and metastases. Although down-regulation of ECRG4 gene expression has been largely attributed to hypermethylation of CpG islands in the 5'untranslated region of the ECRG4 promoter, the mechanisms that underlie the dynamics of its regulation have never been systematically described. Here we show that the ECRG4 gene is widely expressed in human tissues and report that its core promoter lies between the -780 to +420 base pairs relative to the ATG start codon of the ECRG4 open reading frame. This sequence, which contains several CpG islands, also includes multiple overlapping Sp1 consensus binding sequences and a putative binding site for NF-kB activation. 5'RACE of mRNA derived from human leukocytes shows that ECRG4 transcription initiates from the guanidine at -11 from the initiation ATG of the ECRG4 open reading frame. While there is no canonical TATA- or CAAT-boxes proximal to this translational initiation site, there is a distal TATA-sequence in the 5'UTR. This region was identified as the sequence targeted by hypermethylation because in vitro methylation of plasmids encoding the ECRG4 promoter abolish promoter activity and the treatment of Jurkat cells (which naturally express ECRG4) with the methylation inhibitor 5-AzaC, increases endogenous ECRG4 expression. Because ChIP assays show that Sp1 binds the ECRG4 promoter, that forced Sp1 expression trans-activates the ECRG4 promoter and Sp1 inhibition with mithramycin inhibits ECRG4 expression, we conclude that the dynamic positive and negative regulatory elements controlling ECRG4 expression include a counter regulation between promoter methylation and Sp1 activation.

Synergistic effect of spexin and progesterone on pain sensitivity attenuation in ovariectomized rats

Spexin is a central modulator of nociception. The aim of the present study was to investigate the effect of intra-hippocampal CA3 (IHCA3) injection of spexin and spexin-progesterone co-administration on pain sensitivity in ovariectomized rat. Thirty-five adult female rats were divided into five groups. Sham: the animals received injection of 0.5 μL ACSF by IHCA3. Experiments 1 and 2: the animals received injection of 0.5 μL of spexin bilaterally (10 and 30 nmol/rat respectively). Experiments 3 and 4: the animals received injection of 0.5 μL of spexin bilaterally (10 and 30 nmol/rat respectively) + subcutaneous (s.c.) injection of progesterone (5 mg/kg). Ovariectomy was performed in all groups to eliminate the effects of cyclic changes in the female rats. The formalin test (formalin 2.5%) was performed following the administration of spexin and progesterone. Results showed that bilateral injection of spexin in IHCA3 at both concentrations a significant (P < .05) decrease in the pain sensitivity in the two phases of formalin test. Similarly, the bilateral injection of spexin in IHCA3 at both concentrations following the s.c. injection of progesterone significantly (P < .05) decreases pain sensitivity in two phases of the formalin test. This pain attenuation due to the co-administration of spexin and progesterone was more potent than spexin-induced analgesia. According to the present results, spexin has a modulatory effect on pain sensitivity, which becomes more pronounced by progesterone administration.

Spexin Suppress Food Intake in Zebrafish: Evidence from Gene Knockout Study

Spexin1 (SPX1) is a newly discovered neuropeptide in vertebrates. Its biological function remains to be elucidated. In this study, we have generated the zebrafish spx1 ^-/- mutant lines using transcription activator-like effector nucleases. Phenotypes of the spx1 ^-/- mutant zebrafish were analyzed in order to understand the effects on reproduction and food intake. The reproductive capability is not impaired in spx1 mutant zebrafish. However, we found that the spx1 ^-/- mutant fish had a higher food intake than the wild type (WT) fish. Real-time PCR revealed that the expression level of agouti-relate protein 1 (AgRP1), a significant appetite stimulant, was significantly higher in spx1 ^-/- mutant fish after feeding. Intracranial administration of SPX1 could also reduce the mRNA expression of the AgRP1. These data suggest that SPX1 might decrease the food intake by down regulating the expression level of agrp1. Furthermore, spx1 ^-/- mutant fish exhibited higher glucose, triacylglycerol and cholesterol in the serum than WT fish. However, the hyperphagia did not lead to a higher growth rate or body fat percentage. Taken together, our study suggests that SPX1 may serve as a satiety signal molecular by suppressing the AgRP1 in the brain.

A Potential Role of Esophageal Cancer Related Gene-4 for Atrial Fibrillation

Epidemiological studies have shown a strong correlation between tumor and AF. However, the molecular link between tumor and AF remains unknown. ECRG4, a tumor suppressor gene that is expressed in the A-V node and in sporadic ventricular myocytes, inhibits tumorigenesis and monitors tissue homeostasis by functioning as a ‘sentinel’ molecule gauging inflammatory and cell proliferative responses. To explore the potential physiological function of Ecrg4 in heart, we evaluated its distribution in heart, analyzed its expression in patients with persistent AF and in a canine AF model, and dissected the molecular events downstream of Ecrg4. The results showed that the level of Ecrg4 expression is homogenously high in atria and the conduction systems and in sporadic ventricular myocytes. Importantly, the expression of Ecrg4 was significantly decreased in atrial appendages of AF patients than patients with SR. Moreover, in rapid pacing canine AF models, the expression of ECRG4 in atria was significantly decreased compared to that of the controls. Mechanistically, knockdown ECRG4 in atrial myocytes significantly shortened the APDs, inhibited the expression of Gja1, and activated pro-inflammatory cascades and genes involved in cardiac remodeling. These results suggest that Ecrg4 may play a critical role in the pathogenesis of AF.

Method for rapid optimization of recombinant GPCR protein expression and stability using virus-like particles

Recent innovative approaches to stabilize and crystallize GPCRs have resulted in an unprecedented breakthrough in GPCR crystal structures as well as application of the purified receptor protein in biophysical and biochemical ligand binding assays. However, the protein optimization process to enable these technologies is lengthy and requires iterative overexpression, solubilization, purification and functional analysis of tens to hundreds of protein variants. Here, we report a new and versatile method to screen in parallel hundreds of GPCR variants in HEK293 produced virus-like particles (VLPs) for protein yield, stability, functionality and ligand binding. This approach reduces the time and resources during GPCR construct optimization by eliminating lengthy protein solubilization and purification steps and by its adaptability to many binding assay formats (label or label-free detection). We exemplified the robustness of our VLP method by screening 210 GALR3-VLP variants in a radiometric agonist-based binding assay and a subset of 88 variants in a label-free antagonist-based assay. The resulting GALR3 agonist or antagonist stabilizing variants were then further used for recombinant protein expression in transfected insect cells. The final purified protein variants were successfully immobilized on a biosensor chip and used in a surface plasmon resonance binding assay.

Evolutionary and Comparative Genomics to Drive Rational Drug Design, with Particular Focus on Neuropeptide Seven-Transmembrane Receptors

Seven transmembrane receptors (7TMRs), also known as G protein-coupled receptors, are popular targets of drug development, particularly 7TMR systems that are activated by peptide ligands. Although many pharmaceutical drugs have been discovered via conventional bulk analysis techniques the increasing availability of structural and evolutionary data are facilitating change to rational, targeted drug design. This article discusses the appeal of neuropeptide-7TMR systems as drug targets and provides an overview of concepts in the evolution of vertebrate genomes and gene families. Subsequently, methods that use evolutionary concepts and comparative analysis techniques to aid in gene discovery, gene function identification, and novel drug design are provided along with case study examples.

Ala5-galanin (2-11) is a GAL2R specific galanin analogue

It is over 30years since the regulatory peptide galanin was discovered by Professor Mutt and co-workers. Galanin exerts its effects by binding to three galanin G-protein coupled receptors, namely GAL₁R, GAL₂R and GAL₃R. Each galanin receptor has a different distribution in the central nervous system and the peripheral nervous system as well as distinctive signaling pathways, which implicates that the receptors are involved in different biological- and pathological effects. The delineation of the galaninergic system is however difficult due to a lack of stable, specific galanin receptor ligands. Herein, a new short GAL₂R specific ligand, Ala⁵-galanin (2-11), is presented. The galanin (2-11) modified analogue Ala⁵-galanin (2-11) was tested in ¹²⁵I-galanin competitive binding studies for the three galanin receptors and the G-protein coupled receptor signaling properties was tested by the ability to influence second-messenger molecules like inositol phosphate and cyclic adenosine monophosphate. In addition, two different label-free real-time assays, namely EnSpire® based on an optical biosensor and xCELLigence® based on an electric biosensor, were used for evaluating the signaling properties using cell lines with different levels of receptor expression. Ala⁵-galanin (2-11) was subsequently found to be a full agonist for GAL₂R with more than 375-fold preference for GAL₂R compared to both GAL₁R and GAL₃R. The single amino acid substitution of serine to alanine at position 5 in the short ligand galanin (2-11) resulted in a ligand subsequently unable to bind neither GAL₃R nor GAL₁R, even at concentrations as high as 0.1mM.