galanin-like-peptide and alarin

Alarin is a member of the galanin family of neuropeptides that is widely expressed in the central nervous system and peripheral tissues in humans and rodents. It was initially isolated fifteen years ago in ganglionic cells of human neuroblastoma. Subsequently, it was demonstrated to be broadly distributed in the blood vessels, skin, eyes, peripheral and central nervous systems, thymus, gastrointestinal tract, and endocrine organs of different species. Alarin is a 25 amino acid neuropeptide derived from the alternative splicing of the GALP gene, missing exon 3. It is found to be involved in several physiological functions that include feeding behavior, energy homeostasis, glucose homeostasis, body temperature, and reproduction. It has also vasoactive, anti-inflammatory, anti-edema, and antimicrobial activities. However, the physiological effects of alarin have not been fully elucidated and the receptors that mediate these effects are not currently known. Unearthing the novel biological effects of alarin and its unidentified receptors will therefore be a task in future biomedical research. In addition, alarin is involved in various disease conditions, such as metabolic syndrome, obesity, insulin resistance, type 2 diabetes, diabetic retinopathy, hypertension, cardiac fibrosis, polycystic ovarian syndrome, and depression. Thus, alarin may serve as a promising tool for future pharmacological treatment and diagnosis. But further research is awaited to confirm whether alarin has a protective or pathological role in these diseases. This article provides a comprehensive review on the evolving implications of alarin in a variety of physiological and disease conditions, and its future perspectives.

Topics: Amino Acids; Anti-Infective Agents; Anti-Inflammatory Agents; Diabetes Mellitus, Type 2; Galanin; Galanin-Like Peptide; Glucose; Humans; Neuropeptides

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.

Topics: Animals; Diabetes Mellitus, Type 2; Female; Galanin; Galanin-Like Peptide; Glucose; Glucose Intolerance; Humans; Insulin Resistance; Male; Mice; Peptide Hormones; Receptors, Galanin; Sex Factors

It is essential for the species survival that an efficient coordination between energy storage and reproduction through endocrine regulation. The neuropeptide galanin, one of the endocrine hormones, can potently coordinate energy metabolism and the activities of hypothalamic-pituitary-gonadal reproductive axis to adjust synthesis and release of metabolic and reproductive hormones in animals and humans. However, few papers have summarized the regulative effect of the galanin family members on the link of energy storage and reproduction as yet. To address this issue, this review attempts to summarize the current information available about the regulative effect of galanin, galanin-like peptide and alarin on the metabolic and reproductive events, with special emphasis on the interactions between galanin and hypothalamic gonadotropin-releasing hormone, pituitary luteinizing hormone and ovarian hormones. This research line will further deepen our understanding of the physiological roles of the galanin family in regulating the link of energy metabolism and reproduction.

Topics: Animals; Energy Metabolism; Galanin; Galanin-Like Peptide; Humans; Reproduction

Alarin has been reported to be relative to food intake and an increase in body weight. However, to date, no report has demonstrated the relationship between circulating alarin and diabetes in humans.. The objective of this study is to gain insight into the possible role of alarin in humans.. 164 patients with newly diagnosed type 2 diabetes mellitus (nT2DM), 112 IGT and 134 healthy subjects were recruited for this study. In an interventional study, 29 nT2DM patients were treated by a weekly GLP-1RA for 6 months. Plasma alarin concentrations were measured by ELISA.. Circulating alarin concentrations were significantly higher in both IGT and nT2DM subjects than in healthy individuals (0.40 ± 0.14 and 0.54 ± 0.24 vs 0.37 ± 0.10 μg/L, P < .05 or P < .01), whereas in T2DM patients, circulating alarin levels were higher than in IGT subjects. Circulating alarin positively correlated with FBG, HbA1c, HOMA-IR, AUCglucose and TNFα (P < .05 or P < .01). Multivariate logistic regression revealed that circulating alarin levels were correlated with IGT and T2DM. GLP-1RA treatment for 6 months increased circulating alarin levels in T2DM patients (from 0.34 ± 0.10 for baseline, to 0.39 ± 0.14 for 12 weeks, and finally to 0.38 ± 0.15 μg/L for 24 weeks; vs. pre-treatment P < .05).. These data suggest that alarin might be involved in the pathogenesis of T2DM in humans.. ChiCTR-OCS-13003185 (18/03/2013 ).

Topics: Adult; Aged; Aged, 80 and over; Biomarkers; Cross-Sectional Studies; Cytokines; Diabetes Mellitus, Type 2; Double-Blind Method; Female; Galanin-Like Peptide; Glucagon-Like Peptide-1 Receptor; Glucose Tolerance Test; Humans; Hypoglycemic Agents; Male; Middle Aged; Treatment Outcome

There is scant evidence concerning the relationship of alarin concentrations for polycystic ovary syndrome (PCOS) status in the existing literature. Therefore, we aimed to reveal the relationship about predictive value of serum alarin concentrations for PCOS risk in infertile women.. This prospective case-control study included a total of 151 infertile women who met eligibility criteria of the study. Infertile women diagnosed with PCOS formed the study group (n = 80). Women with diagnoses of unexplained infertility constituted the control group (n = 71). The biochemical analyses of serum concentrations of lipid profiles, estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-Mullerian hormone (AMH) and alarin were performed.. There were no differences for the study parameters, including age, body mass index, fasting glucose, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, total triglyceride, E2, and FSH levels in either group. Serum LH, AMH, alarin concentrations, and antral follicle counts had higher values in the PCOS group compared with the controls. Correlation analysis revealed that serum alarin levels were significantly positively correlated with LH and AMH levels, only in the PCOS group. Multivariate binary logistic regression analysis demonstrated that infertile women with high alarin concentrations were significantly more likely to develop PCOS (OR = 1.77, 95% CI = 0.095-0.332, p < 0.001).. Higher serum concentrations of alarin and a positive correlation with serum LH levels were found in infertile women with PCOS. This evidence supported that high alarin concentrations might play a role in the development of PCOS.

Topics: Anti-Mullerian Hormone; Case-Control Studies; Female; Follicle Stimulating Hormone; Galanin-Like Peptide; Humans; Infertility, Female; Polycystic Ovary Syndrome

Many experimental data indicate interactions between peptides involved in the control of food intake, energy homeostasis and adrenocortical hormone release. Glucocorticoids stimulate or inhibit the secretion of orexigenic and anorexigenic peptides, which in turn are involved in the regulation of adrenal growth, structure and function. Galanin-like peptide (Galp) and alarin (Ala) are involved in the regulation of food intake. Galp and Ala mRNAs have already been shown to be present in the arcuate nucleus (ARC) of the hypothalamus in both rats and mice.. To investigate the expression of Ala, Galp and their receptors in the hypothalamus and pituitary and adrenal glands of the rat hypothalamic-pituitary-adrenal (HPA) axis after intraperitoneal administration of peptides in vivo.. Experimental in vivo models were used: acute and long-term exposure to peptides.. The expression of Galp, Ala, their receptors, and steroidogenesis enzymes was analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). Statistically significant expression changes were found in the hypothalamus and pituitary after 1-hour exposure to the peptides, such as a decrease in corticotropin-releasing hormone (CRH) expression after Ala, Galp and adrenocorticotropic hormone (ACTH) administration, and a decrease in the expression of receptors for galanin (Gal) (Galr1 and Galr2). In the pituitary, there was a statistically significant increase in the expression of Ala, Galr1, Galr2, and Galr3 receptors 1 h after Galp administration. In the adrenal glands, only a statistically significant decrease in Galr2 expression was observed after 1 h of Ala 0.5 administration. The mRNA expression of steroidogenesis enzymes also changed: for example, the expression of cholesterol desmolase increased 24 h after Ala peptide administration.. The results indicate that the peptides tested under in vivo conditions can alter the expression of the peptides tested, as well as of Galp, Ala and Gal receptors and steroidogenesis enzymes - Cyp11a1 (cholesterol desmolase), Cyp11b1 (11β-hydroxylase) and Cyp11b2 (aldosterone synthase).

Topics: Adrenal Glands; Animals; Cholesterol Side-Chain Cleavage Enzyme; Galanin-Like Peptide; Gene Expression; Hypothalamo-Hypophyseal System; Mice; Pituitary-Adrenal System; Rats

Diabetic retinopathy is a disease seen with microvascular complications as a result of hyperglycemia and insulin resistance. Alarin and Adipsin are molecules with a role in energy and glucose metabolism. The aim of this study was to determine plasma and aqueous levels of Alarin and Adipsin in patients with and without diabetic retinopathy to evaluate their potential roles in diabetic retinopathy.. The study included one eye from each of 20 cataract patients without diabetes (C), 20 cataract patients with diabetes and without diabetic retinopathy (DM + C), and 20 cataract patients with diabetes and diabetic retinopathy (DR + C). Plasma and aqueous humour samples were taken from all patients during the cataract operation. Alarin and Adipsin levels were examined with the enzyme-linked immunosorbent assay (ELISA) method.. Both plasma and aqueous Alarin levels were significantly higher in the patients with diabetic retinopathy than in the control group (p < 0.001, p = 0.006). Adipsin levels were found to be significantly higher in plasma in the control group than in the DR + C group and significantly higher in aqueous in the DR + C group than in the control group (p < 0.001, p < 0.001).. These findings suggest that Alarin and Adipsin may play important role in diabetic retinopathy.

Topics: Aqueous Humor; Cataract; Complement Factor D; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Enzyme-Linked Immunosorbent Assay; Galanin-Like Peptide; Humans

Alarin could alleviate myocardial infarction-induced heart failure. The present study was to explore whether alarin could alleviate myocardial hypertrophy via inhibiting cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling pathway to attenuate autophagy. Myocardial hypertrophy was induced by angiotensin (Ang) II infusion in vivo in mice and by Ang II treatment of neonatal rat cardiomyocytes (NRCMs) in vitro. The Ang II-induced hypertrophy and fibrosis of the heart were alleviated after alarin administration in mice. The increased atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and beta-myosin heavy chain (β-MHC), and the decreased alpha-myosin heavy chain (α-MHC) induced by Ang II were reversed by alarin treatment in NRCMs. Alarin inhibited the increases of cAMP and PKA in NRCMs. Treatment with cAMP or overexpression of PKA blocked the attenuating effects of alarin on Ang II-induced hypertrophy in NRCMs. Alarin reduced the Ang II-induced increases of LC3, Beclin 1, autophagy-related gene (Atg)3 and Atg5 in NRCMs. The overexpression of cAMP and PKA reversed the alleviating effects of alarin on the increased autophagy induced by Ang II in NRCMs. These results indicated that alarin could moderate cardiac remodeling. Alarin improved myocardial hypertrophy via inhibiting the cAMP/PKA signaling pathway to attenuate autophagy.

Topics: Angiotensin II; Animals; Autophagy; Cardiomegaly; Cell Line; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Galanin-Like Peptide; Male; Mice; Mice, Inbred C57BL; Myocytes, Cardiac; Rats; Rats, Sprague-Dawley; Receptors, Galanin; Signal Transduction

The present study was to explore whether alarin could alleviate heart failure (HF) and attenuate cardia fibrosis via inhibiting oxidative stress. The fibrosis of cardiac fibroblasts (CFs) was induced by angiotensin (Ang) II. HF models were induced by ligation of the left anterior descending artery to cause ischemia myocardial infarction (MI) in Sprague-Dawley rats. Alarin (1.0 nM/kg/d) was administrated by intraperitoneal injection for 28 days. The decreases of left ventricular (LV) ejection fraction (EF), fractional shortening (FS), the maximum of the first differentiation of LV pressure (LV ± dp/dt

Topics: Angiotensin II; Animals; Fibrosis; Galanin-Like Peptide; Heart Failure; Male; Malondialdehyde; Myocardial Infarction; Oxidative Stress; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta; Vasoconstrictor Agents

We aimed to reveal the association of serum alarin level with POR status of the infertile women in the present study.. The mean adjusted-ages and BMI values of the NOR and POR groups were statistically comparable (. The circulating alarin level was significantly elevated in infertile women with POR patterns. In addition, the alarin level was significantly correlated with the serum LH concentration in the POR pattern.

Topics: Adult; Cross-Sectional Studies; Female; Galanin-Like Peptide; Humans; Infertility, Female; Ovarian Reserve; Prospective Studies

Neuropeptides are involved in the regulation of the sympathetic activity and blood pressure in the paraventricular nucleus of the hypothalamus (PVN). The present study was designed to determine how alarin modulates the renal sympathetic nerve activity (RSNA), arterial blood pressure and mean arterial pressure (MAP) in the PVN, and whether superoxide anions regulate the effects of alarin in the PVN of spontaneously hypertensive rats (SHRs). Acute experiment was carried out with male Wistar-Kyoto rats (WKY) and SHRs under anesthesia. RSNA, systolic blood pressure (SBP), diastolic blood pressure (DBP), and MAP were measured. Alarin microinjection into the PVN increased RSNA (7.8 ± 1.8 vs. 14.8 ± 2.3%), SBP (5.9 ± 1.4 vs. 12.1 ± 1.6 mmHg), DBP (5.1 ± 0.8 vs. 10.0 ± 1.1 mmHg), and MAP (5.4 ± 1.2 vs. 10.7 ± 1.3 mmHg) in WKY rats and SHRs,. Alarin antagonist ala6-25 Cys decreased RSNA, SBP, DBP, and MAP in SHRs, and inhibited the effects of alarin. The alarin level was increased in the PVN of SHR compared to WKY rats. (29.7 ± 4.9 vs. 14.6 ± 2.4 pg/mg protein). PVN microinjection of superoxide anion scavengers tempol and tiron, or NAD(P)H oxidase inhibitor apocynin, decreased RSNA, SBP, DBP, and MAP in SHRs, and inhibited the effects of alarin, but the superoxide dismutase inhibitor diethyldithiocarbamic acid potentiated the effects of alarin. Superoxide anions and NAD(P)H oxidase activity levels in the PVN were increased by alarin, but decreased by alarin antagonist ala6-25 Cys. The alarin-induced increases in superoxide anions and NAD(P)H oxidase activity levels were abolished by pre-treatment with ala6-25 Cys. The results suggest that alarin in the PVN increases sympathetic outflow and blood pressure. The enhanced activity of endogenous alarin in the PVN contributes to sympathetic activation in hypertension, and the superoxide anion is involved in these alarin-mediated processes in the PVN.

Topics: Acetophenones; Animals; Arterial Pressure; Blood Pressure; Cyclic N-Oxides; Galanin-Like Peptide; Heart Rate; Hypertension; Male; Paraventricular Hypothalamic Nucleus; Rats, Inbred WKY; Spin Labels; Superoxides; Sympathetic Nervous System

To study the level of circulating Alarin in obese children and its association with various metabolic parameters.. A total of 86 obese children with a body mass index (BMI) above the 95th percentile were enrolled as the obesity group, and 82 healthy children, matched for age and sex, with a BMI below the 85th percentile were enrolled as the healthy control group. According to the presence or absence of insulin resistance (IR), the obesity group was further divided into an IR group with 27 children and a non-IR group with 59 children. Related anthropometric parameters, including body height, body weight, systolic blood pressure (SBP), and diastolic blood pressure (DBP), were measured, and BMI was calculated. Total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), uric acid (UA), fasting insulin (FINS), and fasting blood glucose (FBG) were measured. The area under the receiver operating characteristic curve (AUC) for glucose and insulin, Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), and whole-body insulin sensitivity index (WBISI) were calculated. ELISA was used to measure the level of circulating Alarin.. The obesity group had a significantly higher level of circulating Alarin than the healthy control group (P<0.01). The IR group had a significantly higher level of circulating Alarin than the non-IR group (P<0.01). Circulating Alarin was positively correlated with BMI, TG, FBG, AUC-glucose, AUC-FINS, and HOMA-IR (P<0.05) and was negatively correlated with WBISI (P<0.05). The circulating Alarin level had a linear regression relationship with BMI, FBG, and HOMA-IR, among which HOMA-IR had the greatest influence on the circulating Alarin level (P<0.05).. There is a significant increase in the circulating Alarin level in obese children, which may be associated with the development of obesity and IR.

Topics: Blood Glucose; Body Mass Index; Child; Galanin-Like Peptide; Humans; Insulin; Insulin Resistance; Obesity

Alarin (AL), a new member of the galanin family, has been localized in various CNS regions, mainly in rodents. Among other effects, it modulates food intake. Therefore, we analyzed the immunohistochemical distribution pattern of AL in human intestinal epithelia. Cryosections of 12 human bowel samples were immunohistochemically double-stained for AL and α-defensin 5 (αD; first set). Two further sets of sections were quadruple-stained either (second set) for AL, chromogranin (CG), synaptophysin (SY), and somatostatin (SO) or (third set) for AL, CG, Peptide Y (PY), and 5-hydroxytryptamine (5-HT). Slides were digitized and quantitative analysis of co-localization rates was undertaken. Small bowel: most of AL-positive cells (56%) were αD-positive Paneth cells located within the base of the crypts (first set). In the second set, about 27% of AL-labeled cells were co-reactive for SY and CG, likely representing entero-endocrine cells. In the third set, the largest subpopulation of AL-positive cells was not co-reactive for other markers applied (89%); most of them were likely Paneth cells. Large bowel: co-localization of AL with αD was not detected (first set). In the second set, AL was frequently co-localized with the other three markers applied (68%). In the third set, AL was frequently co-localized with 5-HT and CG (31%) as well as with PY and 5-HT (22%). Due to its presence in various enteroendocrine as well as Paneth cells, AL may be involved in different physiological and pathological processes.

Topics: Aged; Animals; Epithelial Cells; Female; Galanin-Like Peptide; Humans; Immunohistochemistry; Intestinal Mucosa; Male

Galanin-like peptide (Galp) and alarin (Ala) are 2 new members of the galanin peptide family. Galanin (Gal), the "parental" peptide of the entire family, is known to regulate numerous physiological processes, including energy and osmotic homeostasis, reproduction, food intake, and secretion of adrenocortical hormones. Galp and Ala are known to regulate food intake. In the rat, Galp mRNA has been found in the brain, exclusively in the hypothalamic arcuate nucleus (ARC) and median eminence, which are involved in the regulation of energy homeostasis. Alarin-like immunoreactivity is present in the locus coeruleus (LC) and the ARC of rats and mice.. The aim of the study was to investigate the expression of Ala, Galp and their receptors in the organs of the hypothalamo-pituitary-adrenal (HPA) axis of the rat.. The expression of the examined genes was measured in different models of adrenal growth of the rat in vivo (postnatal ontogenesis, compensatory adrenal growth, adrenocortical regeneration, adrenocorticotropic hormone (ACTH) administration). The expression was evaluated using the Affymetrix® microarray system or quantitative polymerase chain reaction (qPCR).. The expression of Ala gene was observed in each organ of the HPA axis (the hypothalamus, hypophysis and adrenal gland). The elevated level of expression of this gene was observed in the pituitary of 2-day rats, while very low levels of Ala mRNA were observed in the adrenals. Galp mRNA expression was observed only in the hypothalamus and the hypophysis during postnatal ontogenesis. The expression of Gal receptors was demonstrated in the hypothalamus, the hypophysis and the adrenal gland. In different compartments of the adrenal glands of adult, intact male and female rats, the expression of Ala, Galp and galanin receptor 1 (Galr1) genes was negligible, but the expression of galanin receptor 2 (Galr2), galanin receptor 3 (Galr3) and neurotrophic receptor tyrosine kinase 2 (Ntrk2) genes was noticeable.. The examined genes showed different expression levels within the studied HPA axis; some of them were neither expressed in the hypothalamus or the pituitary gland, nor in the adrenal gland.

Topics: Adrenal Glands; Animals; Female; Galanin-Like Peptide; Hypothalamo-Hypophyseal System; Hypothalamus; Male; Mice; Oligonucleotide Array Sequence Analysis; Pituitary Gland; Pituitary-Adrenal System; Rats; Real-Time Polymerase Chain Reaction

Alarin has been reported to be related with increased food intake and body weight. The relationship of circulating Alarin with insulin resistance or metabolic syndrome (MetS), however, is unknown. This study aimed to investigate the physiological role of Alarin and its association with MetS in humans.. Newly diagnosed MetS patients (n=237) and age-matched healthy subjects (n=192) were recruited for this study. Oral glucose tolerance test, treadmill exercise, lipid infusions and euglycemic-hyperinsulinemic clamp (EHCs) were performed. Circulating Alarin and TNFα levels were measured by ELISA.. Circulating Alarin levels were significantly higher in MetS patients compared with healthy subjects (0.46 ± 0.22 vs. 0.41 ± 0.14 µg/L, P < 0.01). In all studied subjects, circulating Alarin levels were positively correlated with WC, blood pressure, FBG, triglyceride, HbA1c, HOMA-IR, AUCglucose, and TNFα (P < 0.05 or P < 0.01). Multivariate logistic regression analyses revealed that circulating Alarin levels were correlated with MetS and insulin resistance. There was no significant change of circulating Alarin levels in the subjects with treadmill exercise for 45 min. In healthy individuals, however, glucose challenge, acute hyperglycemia and lipid infusions resulted in increased circulating Alarin levels, while acute hyperinsulinaemia transiently decreased circulating Alarin levels.. The present study provides the evidence that circulating Alarin levels are associated with MetS and insulin resistance.

Topics: Adult; Aged; Circadian Rhythm; Cross-Sectional Studies; Exercise; Female; Galanin-Like Peptide; Humans; Insulin Resistance; Male; Metabolic Syndrome; Middle Aged; Young Adult

Hypothalamic neuropeptides influence the main components of energy balance: metabolic rate, food intake, body weight as well as body temperature, by exerting either an overall anabolic or catabolic effect. The contribution of alarin, the most recently discovered member of the galanin peptide family to the regulation of energy metabolism has been suggested. Our aim was to analyze the complex thermoregulatory and food intake-related effects of alarin in rats. Adult male Wistar rats received different doses of alarin (0.3; 1; 3 and 15μg corresponding approximately to 0.1, 0.33, 1, and 5 nmol, respectively) intracerebroventricularly. Regarding thermoregulatory analysis, oxygen consumption (indicating metabolic rate), core temperature and heat loss (assessed by tail skin temperature) were recorded in an Oxymax indirect calorimeter system complemented with thermocouples and Benchtop thermometer. In order to investigate potential prostaglandin-mediated mechanisms of the hyperthermic effect of alarin, effects of intraperitoneally applied non-selective (indomethacin, 2mg/kg) or selective cyclooxygenase inhibitor (COX-2 inhibitor meloxicam, 1; 2mg/kg) were tested. Effects of alarin on daytime and nighttime spontaneous food intake, as well as, 24-h fasting-induced re-feeding were recorded in an automated FeedScale system. Alarin increased oxygen consumption with simultaneous suppression of heat loss leading to a slow coordinated rise in core temperature. Both applied COX-inhibitors suppressed this action. Alarin failed to induce daytime food intake, but suppressed spontaneous nighttime and also fasting-induced re-feeding food intake. Alarin appears to elicit a slow anorexigenic and prostaglandin-mediated, fever-like hyperthermic response in rats. Such a combination would characterize a catabolic mediator. The potential involvement of alarin in sickness behavior may be assumed.

Topics: Animals; Body Temperature; Body Temperature Regulation; Body Weight; Eating; Energy Metabolism; Galanin; Galanin-Like Peptide; Homeostasis; Injections, Intraventricular; Male; Neuropeptides; Rats, Wistar

Little is known about the physiological or pharmacological properties of alarin, a new neuropeptide belonging to the galanin family. We previously showed that alarin has an antidepressant-like effect and is associated with a decrease in the hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis that is observed in patients with depression using unpredictable chronic mild stress (UCMS) mouse model of depression. However, the mechanisms underlying these effects have not been uncovered. Inflammatory cytokines are reportedly associated with depression. Animal studies and cytokine immune therapy in humans suggest that pro-inflammatory cytokines induce depressive symptomatology and potently activate the HPA axis, whereas anti-inflammatory cytokines may decrease activation. Thus, we first determined the levels of inflammatory cytokines in the blood and brain to evaluate whether the antidepressant-like effect of alarin in UCMS-treated mice is related to its regulation of these inflammatory cytokines. Pro-inflammatory cytokines disrupt the function and/or expression of glucocorticoid receptors (GRs), which mediate the negative feedback of glucocorticoids on the HPA axis to keep it from being overactivated. We next explored the expression level of GRs in the brains of mice subjected to UCMS and to the administration of alarin. We found that intracerebroventricular administration of alarin significantly ameliorated depression-like behaviors in the UCMS-treated mice. Alarin restored the UCMS-induced an increase in the levels of the pro-inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor α and a decrease in the anti-inflammatory cytokine IL-10 level in the blood, prefrontal cortex, hippocampus and hypothalamus. Alarin also reversed the UCMS-induced down-regulation of GR expression in these brain regions. Thus, the antidepressant-like effects of alarin may be mediated by restoring altered pro-inflammatory and anti-inflammatory cytokine levels and GR expression to decrease HPA axis hyperactivity. Our findings provide additional knowledge to interpret the pathophysiology of depression.

Topics: Animals; Antidepressive Agents; Brain; Cytokines; Depression; Drug Evaluation, Preclinical; Galanin-Like Peptide; Gene Expression; Male; Mice, Inbred C57BL; Receptors, Glucocorticoid

Alarin is a newly derived neuropeptide from a splice variant of the galanin-like peptide gene. We previously showed that alarin has an antidepressant-like effect by increasing the activity of the extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) pathways, mediated by the tropomyosin-related kinase B receptor in the unpredictable chronic mild stress (UCMS) mouse model. Administration of rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, prevents the rapid antidepressant-like effect induced by ketamine in animal models, indicating a vital role of mTOR in depression pathophysiology. mTOR is a target of the ERK and AKT pathways that regulates the initiation of protein translation via its downstream components: ribosomal protein S6 kinase (p70S6K) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Therefore, we hypothesized that the antidepressant-like effects of alarin were achieved by activating ERK/AKT pathways, increasing the activity of mTOR and its downstream signaling components that contribute to protein synthesis required for synaptic plasticity. Our results suggest that intracerebroventricular administration of alarin significantly ameliorates depression-like behaviors in the UCMS mouse model. Furthermore, alarin restored UCMS-induced reductions of p70S6K and post-synaptic density 95 (PSD-95) mRNA levels, and of phospho-mTOR and phospho-4EBP1 in the prefrontal cortex, hippocampus, hypothalamus, and olfactory bulb. Additionally, alarin reversed the UCMS-induced downregulation of PSD-95 and synapsin I protein expression in these brain regions. Thus, the antidepressant-like effects of alarin may be mediated by restoring decreased activity of the mTOR signaling pathway and expression of synaptic proteins. Our findings help advance the understanding of depression pathophysiology.

Topics: Animals; Antidepressive Agents; Depression; Disks Large Homolog 4 Protein; Galanin-Like Peptide; Male; Mice; Neuronal Plasticity; Receptor, trkB; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Messenger; Signal Transduction; Stress, Psychological; TOR Serine-Threonine Kinases

Alarin is a newly identified member of the galanin family of neuropeptides. Until now, research on alarin is limited compared with other members of the galanin family. Unearthing the new biological effects of alarin and its unidentified receptor(s) interests us. We previously showed that alarin has an effect on depression-like behaviors, although the underlying mechanisms are not fully clarified. The present study verified the antidepressant-like effects of alarin using the unpredictable chronic mild stresses (UCMS) paradigm, and explored the mechanism that underlies antidepressant-like effects of alarin in mice. Previous research has shown that TrkB receptor-mediated ERK and AKT signaling pathways participate in depression pathophysiology. Therefore, we aimed to explore whether alarin improved depression-like behaviors by increasing activity of ERK and AKT pathways mediated by TrkB. Results showed that alarin significantly reduced immobility time in the forced swim test and latency to feed in the novelty suppressed feeding test. In addition, decreased p-ERK/ERK and p-AKT/AKT levels in the prefrontal cortex, hippocampus, olfactory bulb, and hypothalamus induced by UCMS were reversed by intracerebroventricular injection of alarin. Results suggested that alarin increased p-ERK/ERK and p-AKT/AKT levels by acting on the TrkB receptor. To verify this hypothesis, mice were pretreated with the TrkB inhibitor K252a (or 0.1% dimethyl sulfoxide, intraperitoneally, 3 days), followed by intracerebroventricular injection of alarin. This resulted in an absence of antidepressant-like effects, as well as no activation of ERK and AKT signaling pathways. Results demonstrate that alarin may exert antidepressant-like effects by targeting TrkB receptor-mediated ERK and AKT signal systems, which could help to identify the alarin receptor.

Topics: Animals; Antidepressive Agents; Brain; Carbazoles; Cyclic AMP Response Element-Binding Protein; Depressive Disorder; Disease Models, Animal; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Galanin-Like Peptide; Indole Alkaloids; Male; Mice, Inbred C57BL; Phosphorylation; Proto-Oncogene Proteins c-akt; Receptor, trkB; Signal Transduction; Stress, Psychological

Extrinsic and intrinsic sources of the autonomic nervous system contribute to choroidal innervation, thus being responsible for the control of choroidal blood flow, aqueous humor production or intraocular pressure. Neuropeptides are involved in this autonomic control, and amongst those, alarin has been recently introduced. While alarin is present in intrinsic choroidal neurons, it is not clear if these are the only source of neuronal alarin in the choroid. Therefore, we here screened for the presence of alarin in human cranial autonomic ganglia, and also in rat, a species lacking intrinsic choroidal innervation. Cranial autonomic ganglia (i.e., ciliary, CIL; pterygopalatine, PPG; superior cervical, SCG; trigeminal ganglion, TRI) of human and rat were prepared for immunohistochemistry against murine and human alarin, respectively. Additionally, double staining experiments for alarin and choline acetyltransferase (ChAT), tyrosine hydroxilase (TH), substance P (SP) were performed in human and rat ganglia for unequivocal identification of ganglia. For documentation, confocal laser scanning microscopy was used, while quantitative RT-PCR was applied to confirm immunohistochemical data and to detect alarin mRNA expression. In humans, alarin-like immunoreactivity (alarin-LI) was detected in intrinsic neurons and nerve fibers of the choroidal stroma, but was lacking in CIL, PPG, SCG and TRI. In rat, alarin-LI was detected in only a minority of cranial autonomic ganglia (CIL: 3.5%; PPG: 0.4%; SCG: 1.9%; TRI: 1%). qRT-PCR confirmed the low expression level of alarin mRNA in rat ganglia. Since alarin-LI was absent in human cranial autonomic ganglia, and only present in few neurons of rat cranial autonomic ganglia, we consider it of low impact in extrinsic ocular innervation in those species. Nevertheless, it seems important for intrinsic choroidal innervation in humans, where it could serve as intrinsic choroidal marker.

Topics: Aged; Animals; Choroid; Female; Galanin-Like Peptide; Ganglia, Autonomic; Humans; Immunohistochemistry; Male; Microscopy, Confocal; Rats; Real-Time Polymerase Chain Reaction; RNA, Messenger

In order to investigate the central effect of alarin on glucose uptake, we administered alarin and/ or its inhibitor, ala6-25Cys into the cerebral ventricles of the type 2 diabetic rats. Then the relative parameters about glucose uptake in skeletal muscles were measured. We found that central treatment with alarin significantly increased the food intake, body weight and glucose infusion rates in hyperinsulinemic euglycemic clamp tests of the animals. Besides, the treatment also enhanced 2-deoxy-[3H]-D-glucose uptake, vesicle-associated membrane protein 2 contents, glucose transporter 4 protein and mRNA expression, as well as pAktThr308, pAktSer473 and total Akt levels in muscle cells, but reduced plasma glucose and insulin levels of the rats. All of the alarin-inducing events may be antagonised by central injection of ala6-25Cys. These results suggest that central administration of alarin stimulates glucose uptake mediated by activation of Akt signal pathway in type 2 diabetic animals.

Topics: Animals; Body Weight; Cell Line; Diabetes Mellitus, Experimental; Eating; Galanin-Like Peptide; Glucose; Glucose Transporter Type 4; Injections, Intraventricular; Insulin; Mice; Muscle, Skeletal; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats

Alarin is a newly identified member of the galanin family of peptides. Galanin has been shown to exert regulatory effects on depression. Similar to galanin in distribution, alarin is also expressed in the medial amygdala and hypothalamus, i.e., regions interrelated with depression. However, it remains a puzzle whether alarin is involved in depression. Accordingly, we established the depression-like mouse model using behavioral tests to ascertain the possible involvement of alarin, with fluoxetine as a positive control. With the positive antidepressant-like effects of alarin, we further examined its relationship to HPA axis activity and brain-derived neurotrophic factor (BDNF) levels in different brain areas in a chronic unpredictable mild stress (CUMS) paradigm. In the acute studies, alarin produced a dose-related reduction in the immobility duration in tail suspension test (TST) in mice. In the open-field test, intracerebroventricular (i.c.v.) injection of alarin (1.0 nmol) did not impair locomotion or motor coordination in the treated mice. In the CUMS paradigm, alarin administration (1.0 nmol, i.c.v.) significantly improved murine behaviors (FST and locomotor activity), which was associated with a decrease in corticotropin-releasing hormone (CRH) mRNA levels in the hypothalamus, as well as a decline in serum levels of CRH, adrenocorticotropic hormone (ACTH) and corticosterone (CORT), all of which are key hormones of the HPA axis. Furthermore, alarin upregulated BDNF mRNA levels in the prefrontal cortex and hippocampus. These findings suggest that alarin may potentiate the development of new antidepressants, which would be further secured with the identification of its receptor(s).

Topics: Adrenocorticotropic Hormone; Animals; Brain-Derived Neurotrophic Factor; Corticotropin-Releasing Hormone; Galanin-Like Peptide; Hypothalamo-Hypophyseal System; Male; Mice; Mice, Inbred C57BL; Pituitary-Adrenal System

Alarin, a regulatory peptide, belongs to the galanin family and plays the same regulatory roles as galanin in orexigenic activity and energy metabolism. Our previous studies had found that galanin might facilitate insulin sensitivity via activation of its central receptors. To date, little is known about whether central alarin may exert similar effects on insulin sensitivity. In order to investigate this, alarin and its specific antagonist, alarin 6-25Cys, were administered into the cerebral ventricles of type 2 diabetic rats (T2DR) to evaluate the changes in insulin resistance. The results indicated that central treatment with alarin significantly increased the body weight of animals, the 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose uptake, the plasma adiponectin levels, the glucose infusion rates in hyperinsulinemic-euglycemic clamp tests, the vesicle-associated membrane protein 2 as well as glucose transporter 4 (GLUT4 (SLC2A4)) protein and mRNA levels, and the ratios of GLUT4 contents in plasma membranes to total cell membranes in adipocytes, but reduced blood glucose and plasma retinol-binding protein 4 levels. These effects of alarin may be inhibited by pretreatment with alarin 6-25Cys. The above-mentioned results suggest that the central alarin projective system may facilitate insulin sensitivity and glucose uptake via the increase in GLUT4 content and GLUT4 translocation from intracellular pools to plasma membranes in T2DR.

Topics: 4-Chloro-7-nitrobenzofurazan; Adipocytes; Adiponectin; Animals; Blood Glucose; Blotting, Western; Body Weight; Cell Membrane; Deoxyglucose; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Galanin-Like Peptide; Gene Expression; Glucose Transporter Type 4; Injections, Intraventricular; Insulin Resistance; Male; Peptide Fragments; Protein Transport; Rats, Wistar; Retinol-Binding Proteins, Plasma; Reverse Transcriptase Polymerase Chain Reaction; Vesicle-Associated Membrane Protein 2

Alarin is an alternative-splicing form of GALP (galanin-like peptide). It shares only 5 conserved amino acids at the N-terminal region with GALP which is involved in a diverse range of normal brain functions. This study seeks to investigate whether alarin has additional functions due to its differences from GALP. Here, we have shown using a radial diffusion assay that alarin but not GALP inhibited the growth of Escherichia coli (strain ML-35). The conserved N-terminal region, however, remained essential for the antimicrobial activity of alarin as truncated peptides showed reduced killing effect. Moreover, alarin inhibited the growth of E. coli in a similar potency as human cathelicidin LL-37, a well-studied antimicrobial peptide. Electron microscopy further showed that alarin induced bacterial membrane blebbing but unlike LL-37, it did not cause hemolysis of erythrocytes. In addition, alarin is only active against the gram-negative bacteria, E. coli but not the gram-positive bacteria, Staphylococcus aureus. Thus, these data suggest that alarin has potentials as an antimicrobial and should be considered for the development in human therapeutics.

Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Cathelicidins; Cell Membrane; Erythrocytes; Escherichia coli; Galanin-Like Peptide; Hemolysis; Horses; Humans; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Molecular Sequence Data; Staphylococcus aureus

Alarin, a 25 amino acid splice variant of the galanin-like peptide, was originally discovered in gangliocytes of neuroblastic tumors and shown to be expressed in ganglioneuroblastoma and ganglioneuroma but not in undifferentiated neuroblastoma. Recently, in vivo studies have elucidated the physiological functions of alarin in the central nervous system (CNS). Alarin was shown to stimulate food intake, increase body weight, induce luteinizing hormone secretion and stimulate fos-expression in rats; the anatomical localization for these functions correlates well with the varied distribution of the alarin peptide in the brain. Because alarin was originally detected in neuroblastic tumors and is present in a wide range of nuclei in the CNS, we determined in the present study the expression of alarin in a variety of CNS tumors. Immunohistochemical analysis of 179 tumor samples resulted in different alarin-like immunoreactivity (alarin-LI) intensities, which were score-rated from 0 (no alarin stainin), 1 (low intensity), 2 (medium intensity) to 3 (high intensity). Immunohistochemical analyses revealed score 2 or 3 alarin-LI in all choroid plexus tumors (100 %, 7/7) and in the majority of ependymomas (90 %, 52/58), but only in a minority of astrocytomas (15 %, 5/33), meningiomas (14 %, 7/49) and tumors of the cranial nerves (7 %, 1/15). In oligodendrogliomas (0 %, 0/12) and oligoastrocytoma (0 %, 0/5) alarin-LI was not detectable. The high specificity (83 %) of alarin-LI suggests that it might be used as a diagnostic marker for ependymoma in differentiating them from other gliomas such as astrocytomas and oligodendrogliomas.

Topics: Adult; Astrocytoma; Choroid Plexus Neoplasms; Cranial Nerve Neoplasms; Ependymoma; Female; Galanin-Like Peptide; Humans; Immunohistochemistry; Male; Meningioma; Middle Aged; Oligodendroglioma; Sensitivity and Specificity

Previous data from our labs and from others have demonstrated that intracerebroventricular (ICV) injection of alarin has orexigenic activity and significantly increases plasma luteinizing hormone (LH) secretion in a gonadotropin-releasing hormone (GnRH) dependent manner. The purpose of the current experiments was to determine if the amino acids at the amino-terminal end of the alarin peptide are critical for alarin's effects on reproductive and feeding systems. First, we injected male mice ICV with full-length alarin (Ala1-25) or peptide fragments missing residues at the amino-terminal end (Ala3-25 or Ala6-25 Cys). Neither peptide fragment alone, significantly increased food intake in male mice compared to controls. Second, ICV injection of Ala1-25, but not Ala3-25, significantly (p < 0.01) increased GnRH-mediated LH secretion. Surprisingly, Ala6-25 Cys significantly (p < 0.05) inhibited plasma LH secretion and inhibited Ala1-25 actions. In conclusion, elimination of the first five amino acids of alarin not only abolishes the biological activity of alarin, but becomes an antagonist to alarin-specific effects. Furthermore, Ala6-25 Cys seems to act as a specific antagonist to putative alarin receptors and therefore may be an important tool in identifying alarin-specific receptors.

Topics: Animals; Body Temperature; Body Weight; Brain Chemistry; Eating; Galanin-Like Peptide; Gonadotropin-Releasing Hormone; Injections, Intraventricular; Luteinizing Hormone; Male; Mice; Mice, Inbred C57BL; Peptide Fragments; Telemetry