The anti-inflammatory effect of neuropeptide Y (NPY) in rats is dependent on dipeptidyl peptidase 4 (DP4) activity and age

The role of nutrient sensing dysregulation in anorexia of ageing: The little we know and the much we don't

The age-related decline in appetite and food intake - termed "anorexia of ageing" - is implicated in undernutrition in later life and hence provides a public health challenge for our ageing population. Eating behaviour is controlled, in part, by homeostatic mechanisms which sense nutrient status and provide feedback to appetite control regions of the brain. Such feedback signals, propagated by episodic gut hormones, are dysregulated in some older adults. The secretory responses of appetite-related gut hormones to feeding are amplified, inducing a more anorexigenic signal which is associated with reduced appetite and food intake. Such an augmented response would indicate an increase in gut sensitivity to nutrients. Consequently, this review explores the role of gastrointestinal tract nutrient sensing in age-related appetite dysregulation. We review and synthesise evidence for age-related alterations in nutrient sensing which may explain the observed hormonal dysregulation. Drawing on what is known regarding elements of nutrient sensing pathways in animal models, in other tissues of the body, and in certain models of disease, we identify potential causal mechanisms including alterations in enteroendocrine cell number and distribution, dysregulation of cell signalling pathways, and changes in the gut milieu. From identified gaps in evidence, we highlight interesting and important avenues for future research.

Calorie restriction partially attenuates sickness behavior induced by viral mimetic poly I:C

Calorie restriction (CR) has been shown to extend the mean and maximum lifespan in both preclinical and clinical settings. We have previously demonstrated that CR attenuates lipopolysaccharide (LPS)-induced fever and sickness behavior. CR also leads to reductions in pro-inflammatory and increases in anti-inflammatory profiles. LPS is a bacterial mimetic; however, few studies have explored this phenomenon utilizing a viral mimetic, such as polyinosinic:polycytidylic acid (poly I:C). Dose-dependently, poly I:C induced an increase in core body temperature (Tb), with the largest dose (5000 µg/kg) resulting in a 1.62 °C ( ± 0.23 °C) Tb increase at 7 h post-injection in ad libitum mice and was associated with reduced home-cage locomotor activity. We then investigated the effect of 50% CR for 28 days to attenuate fever and sickness behavior induced by a poly I:C (5000 µg/kg) viral immune challenge. CR resulted in the partial attenuation of fever and sickness behavior measures post-poly I:C. The freely fed, control mice demonstrated a 2.02 °C ( ± 0.22 °C) increase in Tb at 7 h post-injection compared to the CR poly I:C group which demonstrated an increase in Tb of 0.94 °C ( ± 0.27 °C). Locomotor patterns post-injection were different, CR mice displayed a reduction in activity during the light phase, and the control group displayed a reduction during the dark phase. CR moderately attenuated the neuroinflammatory response with a reduction in microglial density in the ventromedial nucleus of the hypothalamus. The fever and sickness behavior attenuation seen after CR may be driven by similar anti-inflammatory processes as after LPS; however, further investigation is required.

Neuropeptide Y Promotes Human M2 Macrophage Polarization and Enhances p62/SQSTM1-Dependent Autophagy and NRF2 Activation

Neuropeptide Y (NPY) is an abundantly expressed peptide capable of modulating innate and adaptive immune responses and regulating chemotaxis and cytokine secretion by macrophages. Abnormal regulation of NPY is involved in the development of atherosclerosis. The inflammatory infiltrate within atherosclerotic plaque is characterized by accumulation of macrophages, which are subject to reprogram their phenotypes in response to environmental signals. Macrophage number and phenotype influence plaque fate. Here, we investigated the effect of NPY on the changes in phenotype and functions of human macrophages, from the pro-inflammatory phenotype M1 to the reparative M2, indicative of atherosclerosis regression or stabilization. Human monocytes were differentiated in vitro into macrophages with M-CSF (M0) and polarized towards an M1 phenotype with IFN-γ plus LPS M(IFN-γ/LPS) or M2 with IL-10 (M IL-10) and further challenged with NPY (10-7-10-9 M) for 8-36 h. Cell phenotype and functions were analyzed by immunofluorescence and immunochemical analyses. NPY affected macrophage surface markers and secretome profile expression, thus shifting macrophages toward an M2-like phenotype. NPY also prevented the impairment of endocytosis triggered by the oxysterol 7-keto-cholesterol (7KC) and prevented 7KC-induced foam cell formation by reducing the lipid droplet accumulation in M0 macrophages. NPY-treated M0 macrophages enhanced the autophagosome formation by upregulating the cell content of the autophagy markers LC3-II and p62-SQSTM1, increased activation of the anti-oxidative transcription factor NRF2 (NF-E2-related factor 2), and subsequently induced its target gene HMOX1 that encodes heme oxygenase-1. Our findings indicate that NPY has a cytoprotective effect with respect to the progression of the inflammatory pathway, both enhancing p62/SQSTM1-dependent autophagy and the NRF2-antioxidant signaling pathway in macrophages. NPY signaling may have a crucial role in tissue homeostasis in host inflammatory responses through the regulation of macrophage balance and functions within atherosclerosis.

Regenerating Skeletal Muscle Compensates for the Impaired Macrophage Functions Leading to Normal Muscle Repair in Retinol Saturase Null Mice

Skeletal muscle repair is initiated by local inflammation and involves the engulfment of dead cells (efferocytosis) by infiltrating macrophages at the injury site. Macrophages orchestrate the whole repair program, and efferocytosis is a key event not only for cell clearance but also for triggering the timed polarization of the inflammatory phenotype of macrophages into the healing one. While pro-inflammatory cytokines produced by the inflammatory macrophages induce satellite cell proliferation and differentiation into myoblasts, healing macrophages initiate the resolution of inflammation, angiogenesis, and extracellular matrix formation and drive myoblast fusion and myotube growth. Therefore, improper efferocytosis results in impaired muscle repair. Retinol saturase (RetSat) initiates the formation of various dihydroretinoids, a group of vitamin A derivatives that regulate transcription by activating retinoid receptors. Previous studies from our laboratory have shown that RetSat-null macrophages produce less milk fat globule-epidermal growth factor-factor-8 (MFG-E8), lack neuropeptide Y expression, and are characterized by impaired efferocytosis. Here, we investigated skeletal muscle repair in the tibialis anterior muscle of RetSat-null mice following cardiotoxin injury. Our data presented here demonstrate that, unexpectedly, several cell types participating in skeletal muscle regeneration compensate for the impaired macrophage functions, resulting in normal muscle repair in the RetSat-null mice.

Neuropeptide Y attenuates cardiac remodeling and deterioration of function following myocardial infarction

Plasma levels of neuropeptide Y (NPY) are elevated in patients with acute myocardial infarction (AMI), but its role in AMI remains unclear, which was examined here in NPY wild-type/knockout (WT/KO) mice treated with/without exogenous NPY and its Y1 receptor antagonist (Y1Ra) BIBP 3226. We found that AMI mice lacking NPY developed more severe AMI than WT mice with worse cardiac dysfunction, progressive cardiac inflammation and fibrosis, and excessive apoptosis but impairing angiogenesis. All of these changes were reversed when the NPY KO mice were treated with exogenous NPY in a dose-dependent manner. Interestingly, treatment with NPY also dose dependently attenuated AMI in WT mice, which was blocked by BIBP 3226. Phenotypically, cardiac NPY was de novo expressed by infiltrating macrophages during the repairing or fibrosing process in heart-failure patients and AMI mice. Mechanistically, NPY was induced by transforming growth factor (TGF)-β1 in bone marrow-derived macrophages and signaled through its Y1R to exert its pathophysiological activities by inhibiting p38/nuclear factor κB (NF-κB)-mediated M1 macrophage activation while promoting the reparative M2 phenotype in vivo and in vitro. In conclusion, NPY can attenuate AMI in mice. Inhibition of cardiac inflammation and fibrosis while enhancing angiogenesis but reducing apoptosis may be the underlying mechanisms through which NPY attenuates cardiac remodeling and deterioration of function following AMI.

Intracolonic Neuropeptide Y Y1 Receptor Inhibition Attenuates Intestinal Inflammation in Murine Colitis and Cytokine Release in IBD Biopsies

We have demonstrated that neuropeptide Y (NPY) can regulate pro-inflammatory signaling in the gut via cross-talk with the pro-inflammatory cytokine tumor necrosis factor (TNF). Here, we investigated if selective blocking of NPY receptors, NPY1R or NPY2R, using small molecule non-peptide antagonists (BIBP-3222 for NPY1R and BIIE-0246 for NPY2R) in the colon could attenuate intestinal inflammation by lowering TNF levels (BIBP - N-[(1R)]-4-[(Aminoiminomethyl)amino-1-[[[(4-hydroxyphenyl)methyl]amino]carbonyl]butyl-α-phenylbenzeneacetamide; BIIE - N-[(1S)-4-[(Aminoiminomethyl)amino]-1-[[[2-(3,5-dioxo-1,2-diphenyl-1,2,4-triazolidin-4-yl)ethyl]amino]carbonyl]butyl]-1-[2-[4-(6,11-dihydro-6-oxo-5H-dibenz[b,e]azepin-11-yl)-1-piperazinyl]-2-oxoethyl]-cyclopentaneacetamide). Colitis was induced using dextran sodium sulfate in drinking water for 7 days, or by adoptive T-cell transfer in RAG-/- mice. Colonic biopsies from healthy subjects (n = 10) and IBD patients (n = 34, UC = 20, CD = 14) were cultured ex vivo in presence or absence of NPY antagonists (100 µM, 20 h), and cytokine release into culture supernatants was measured by ELISA. Intracolonic administration of BIBP (but not BIIE) significantly reduced clinical, endoscopic, and histological scores, and serum TNF, interleukin (IL)-6, and IL-12p70 in DSS colitis; it also significantly attenuated histological damage and serum IL-6 in T-cell colitis (P < .05). Intracolonic administration of BIBP significantly reduced TNF and interferon (IFN)-γ release from UC biopsies, whereas BIIE downregulated only IFN-γ (P < .05). BIBP significantly reduced TNF and interferon (IFN)-γ release from UC biopsies, whereas BIIE downregulated only IFN-γ (P < .05). Our data suggest a promising therapeutic value for NPY1R inhibition in alleviating intestinal inflammation in UC, possibly as enemas to IBD patients.

High-Speed Characterization of Vocal Fold Vibrations in Normally Cycling and Postmenopausal Women: Randomized Double-Blind Analyses

Purpose The aim of this study was to examine the influence of menstrual cycle phases (follicular, ovulatory, luteal, and ischemic) and hormone levels (estradiol, testosterone, progesterone, and neuropeptide Y) on vocal fold vibrations in reproductive and postmenopausal women. Method Glottal area waveforms were extracted from high-speed videoendoscopy during sustained phonation, inhalation phonation, and voice onset/offset in the reproductive (n = 15) and postmenopausal (n = 13) groups. Linear mixed-model analysis was conducted to evaluate hormone levels and high-speed videoendoscopy outcome variables between the reproductive and postmenopausal groups. In the reproductive group, simple linear regression and multiple regression were conducted to determine the effects of hormones on the dependent variables. Results Group differences between reproductive and postmenopausal women were identified for stiffness index, oscillatory onset time, and oscillatory offset time. Neuropeptide Y hormone in the ischemic phase significantly predicted changes in the reproductive group for some dependent variables; however, the relationship varied for sustained phonation and inhalation phonation. Conclusion These findings provide preliminary evidence that vocal fold vibrations in the reproductive group are different predominantly in the ischemic phase due to neuropeptide Y changes.

[Effect of a Mediterranean-pattern diet on the metabolic response secondary to weight loss; role of the single nucleotide polymorphism (rs16147) of neuropeptide Y]

Introduction

Background and aims: intervention studies that evaluate the effect of rs16147 on metabolic response and weight change after dietary intervention are scarce. We propose to evaluate the role of the rs16147 genetic variant in the metabolic effects produced by a hypocaloric Mediterranean-pattern diet with high content of omega-9. Material and methods: a sample of 363 obese subjects was recruited. At the baseline visit the patients were randomly assigned to one of two hypocaloric diets for 12 weeks (diet M, Mediterranean pattern; diet C, standard hypocaloric). All patients, at baseline and at 12 weeks, had biochemical and anthropometric variables measured, and genotyping performed for the rs16147 variant. Results: in all subjects, and with both diets, the parameters of adiposity, blood pressure, and circulating leptin improved. In obese subjects with allele (A) insulin levels (GG vs. GA + AA) (-0.9 ± 1.1 IU/L vs. -4.4 ± 1.0 IU/L; p = 0.01) and HOMA-IR (-0.3 ± 0.1 units vs. -1.2 ± 0.3 units; p = 0.02) decreased significantly with diet M. Subjects carrying the minor allele showed a significant decrease in basal insulin levels (GG vs. GA + AA) (0.7 ± 0.3 IU/L vs. -2.2 ± 0.9 IU/L: p = 0.02) and HOMA-IR (-0.3 ± 0.2 units vs. -0.7 ± 0.1 units: p = 0.01) after diet C. This decrease in circulating insulin and HOMA-IR levels in patients with allele A was significantly higher with diet M than with diet C. Conclusions: the A allele of the rs16147 variant produces a better metabolic response in terms of insulin resistance and basal insulin secondary to weight loss with two different hypocaloric diets in obese subjects, with improvement being higher with the Mediterranean diet.

Blood Plasma Hormone-Level Influence on Vocal Function

Purpose This preliminary study examined the influence of menstrual cycle phase and hormone levels on acoustic measurements of vocal function in reproductive and postmenopausal females. Mean fundamental frequency (f0), speaking fundamental frequency (Sf0), and cepstral peak prominence (CPP) were evaluated. It was hypothesized that Sf0 and CPP would be lower during the luteal and ischemic phases of the menstrual cycle. Group differences with lower values in postmenopausal females and greater variability in the reproductive females were also hypothesized. Method A mixed factorial analysis of variance was used to examine differences between reproductive and postmenopausal females and the four phases of the menstrual cycle. Separate analyses of variances were implemented for each of the dependent measures. Twenty-eight female participants (15 reproductive cycling, 13 postmenopausal) completed the study. Participants were recorded reading the Rainbow Passage and sustaining the vowel /a/. Mean vocal f0, Sf0, and CPP were determined from the acoustic samples. Blood assays were used to determine estrogen, progesterone, testosterone, and neuropeptide Y levels at four data collection time points. Results Group differences in hormone levels and Sf0 values were established with the postmenopausal group having significantly lower hormone levels and significantly lower Sf0 than the reproductive cycling group across the phases. Analysis of the reproductive group by hormone levels and cycle phase revealed no significant differences for CPP or Sf0 across phases. Higher estrogen was identified in the ovulation phase, and higher progesterone was identified in the luteal phase. Conclusions Significant differences in hormone levels and Sf0 were identified between groups. Within the reproductive cycling group, the lack of significant difference in acoustic measures relative to hormone levels indicated that the measures taken may not have been sensitive enough to identify hormonally mediated vocal function changes. The participant selection may have biased the findings in that health conditions and medications that are known to influence voice function were used as exclusion criteria.

Retinol Saturase Knock-Out Mice are Characterized by Impaired Clearance of Apoptotic Cells and Develop Mild Autoimmunity

Apoptosis and the proper clearance of apoptotic cells play a central role in maintaining tissue homeostasis. Previous work in our laboratory has shown that when a high number of cells enters apoptosis in a tissue, the macrophages that engulf them produce retinoids to enhance their own phagocytic capacity by upregulating several phagocytic genes. Our data indicated that these retinoids might be dihydroretinoids, which are products of the retinol saturase (RetSat) pathway. In the present study, the efferocytosis of RetSat-null mice was investigated. We show that among the retinoid-sensitive phagocytic genes, only transglutaminase 2 responded in macrophages and in differentiating monocytes to dihydroretinol. Administration of dihydroretinol did not affect the expression of the tested genes differently between differentiating wild type and RetSat-null monocytes, despite the fact that the expression of RetSat was induced. However, in the absence of RetSat, the expression of numerous differentiation-related genes was altered. Among these, impaired production of MFG-E8, a protein that bridges apoptotic cells to the α_vβ₃/β₅ integrin receptors of macrophages, resulted in impaired efferocytosis, very likely causing the development of mild autoimmunity in aged female mice. Our data indicate that RetSat affects monocyte/macrophage differentiation independently of its capability to produce dihydroretinol at this stage.

Different effects of high-protein/low-carbohydrate versus standard hypocaloric diet on insulin resistance and lipid profile: Role of rs16147 variant of neuropeptide Y

BACKGROUND AND AIMS

Few studies have assessed the effect of the NPY gene rs16147 variant on metabolic response following a dietary intervention. We evaluated the effect of rs16147 on body weight and biochemical changes after a high-protein/low-carbohydrate hypocaloric diet compared with a standard severe hypocaloric diet over 9 months.

MATERIALS AND METHODS

A population of 270 obese individuals was enrolled. At baseline, participants were randomly allocated to one of two hypocaloric diets, high protein (Diet HP) or standard (Diet S), for a period of 9 months.

RESULTS

After both diets, all genotypes showed decreased body mass index, weight, fat mass, waist circumference, and leptin levels. Participants with the minor allele (A) assigned to the HP diet showed decreases in total cholesterol (-6.5 ± 4.8 vs 10.1 ± 4.1 mg/dL; p < 0.05), LDL cholesterol (-5.9 ± 3.8 vs 9.6 ± 2.4 mg/dL; p < 0.05), triglycerides (-1.0 ± 4.8 vs 16.2 ± 4.1 mg/dL; p < 0.05), insulin (-0.5 ± 2.8 vs 1.7 ± 2.1 UI/L; p < 0.05), HOMA-IR (-0.2 ± 2.1 vs 0.5 ± 2.0 units; p < 0.05), and CRP (-0.3 ± 0.4 vs 1.3 ± 0.2 mg/dL; p < 0.05). Participants with the minor allele assigned to diet S also showed decreases in total cholesterol (-6.1 ± 4.1 vs 14.4 ± 3.1 mg/dL; p < 0.05), LDL-cholesterol (-3.1 ± 2.8 vs 15.0 ± 3.1 mg/dL; p < 0.05), triglycerides (-6.9 ± 4.1 vs 13.2 ± 4.0 mg/dL; p < 0.05), insulin (-0.3 ± 2.1 vs. -1.2 ± 0.2 UI/L: p < 0.05), HOMA-IR (-0.3 ± 2.1 vs. -1.6 ± 1.1 units: p < 0.05), and CRP (-0.4 ± 0.1 vs 1.1 ± 0.2 mg/dL; p < 0.05).

CONCLUSION

In obese Caucasians, the presence of the A allele of the rs16147 genetic variant produces a better metabolic response that is secondary to weight loss with two different hypocaloric diets.

Impact of type 1 diabetes mellitus and sitagliptin treatment on the neuropeptide Y system of rat retina

BACKGROUND

Neuropeptide Y (NPY) is a neuromodulator that is expressed in the retina. Increasing evidence suggests that NPY has pronounced anti-inflammatory effects, which might depend on the inhibition of dipeptidyl-peptidase-IV (DPP-IV). The aim of this study was to investigate the impact of type 1 diabetes mellitus (DM) and sitagliptin, a DPP-IV inhibitor, on the NPY system in the retina using an animal model.

METHODS

Type 1 DM was induced in male Wistar rats by an intraperitoneal injection of streptozotocin. Starting 2 weeks after DM onset, animals were treated orally with sitagliptin (5 mg/kg.day) for 2 weeks. The expression of NPY and NPY receptors (Y1 , Y2 and Y5 receptors) was measured by quantitative polymerase chain reaction, Western blot and/or enzyme-linked immunosorbent assay. The immunoreactivity of NPY and NPY receptors was evaluated by immunohistochemistry, and the [35 S]GTPγS binding assay was used to assess the functional binding of NPY receptors.

RESULTS

DM decreased the mRNA levels of NPY in the retina, as well as the protein levels of NPY and Y5 receptor. No changes were detected in the localization of NPY and NPY receptors in the retina and in the functional binding of NPY to all receptors. Sitagliptin alone reduced retinal NPY mRNA levels. The effects of DM on the NPY system were not affected by sitagliptin.

CONCLUSION

DM modestly affects the NPY system in the retina and these effects are not prevented by sitagliptin treatment. These observations suggest that DPP-IV enzyme is not underlying the NPY changes detected in the retina induced by type 1 DM.

Is There a Role for Bioactive Lipids in the Pathobiology of Diabetes Mellitus?

Inflammation, decreased levels of circulating endothelial nitric oxide (eNO) and brain-derived neurotrophic factor (BDNF), altered activity of hypothalamic neurotransmitters (including serotonin and vagal tone) and gut hormones, increased concentrations of free radicals, and imbalance in the levels of bioactive lipids and their pro- and anti-inflammatory metabolites have been suggested to play a role in diabetes mellitus (DM). Type 1 diabetes mellitus (type 1 DM) is due to autoimmune destruction of pancreatic β cells because of enhanced production of IL-6 and tumor necrosis factor-α (TNF-α) and other pro-inflammatory cytokines released by immunocytes infiltrating the pancreas in response to unknown exogenous and endogenous toxin(s). On the other hand, type 2 DM is due to increased peripheral insulin resistance secondary to enhanced production of IL-6 and TNF-α in response to high-fat and/or calorie-rich diet (rich in saturated and trans fats). Type 2 DM is also associated with significant alterations in the production and action of hypothalamic neurotransmitters, eNO, BDNF, free radicals, gut hormones, and vagus nerve activity. Thus, type 1 DM is because of excess production of pro-inflammatory cytokines close to β cells, whereas type 2 DM is due to excess of pro-inflammatory cytokines in the systemic circulation. Hence, methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 DM. Roux-en-Y gastric bypass and similar surgeries ameliorate type 2 DM, partly by restoring to normal: gut hormones, hypothalamic neurotransmitters, eNO, vagal activity, gut microbiota, bioactive lipids, BDNF production in the gut and hypothalamus, concentrations of cytokines and free radicals that results in resetting glucose-stimulated insulin production by pancreatic β cells. Our recent studies suggested that bioactive lipids, such as arachidonic acid, eicosapentaneoic acid, and docosahexaenoic acid (which are unsaturated fatty acids) and their anti-inflammatory metabolites: lipoxin A4, resolvins, protectins, and maresins, may have antidiabetic actions. These bioactive lipids have anti-inflammatory actions, enhance eNO, BDNF production, restore hypothalamic dysfunction, enhance vagal tone, modulate production and action of ghrelin, leptin and adiponectin, and influence gut microbiota that may explain their antidiabetic action. These pieces of evidence suggest that methods designed to selectively deliver bioactive lipids to pancreatic β cells, gut, liver, and muscle may prevent type 1 and type 2 DM.

Retinal Pigment Epithelial Cells Suppress Phagolysosome Activation in Macrophages

Purpose

The eye is an immune-privileged microenvironment that has adapted several mechanisms of immune regulation to prevent inflammation. One of these potential mechanisms is retinal pigment epithelial cells (RPE) altering phagocytosis in macrophages.

Methods

The conditioned media of RPE eyecups from eyes of healthy mice and mice with experimental autoimmune uveitis (EAU) were used to treat primary macrophage phagocytizing pHrodo bacterial bioparticles. In addition, the neuropeptides were depleted from the conditioned media of healthy RPE eyecups and used to treat phagocytizing macrophages. The conditioned media from healthy and EAU RPE eyecups were assayed for IL-6, and IL-6 was added to the healthy conditioned media, and neutralized in the EAU conditioned media. The macrophages were treated with the conditioned media and assayed for fluorescence. The macrophages were imaged, and the fluorescence intensity, relative to active phagolysosomes, was measured. Also, the macrophages were assayed using fluorescent viability dye staining.

Results

The conditioned media from healthy, but not from EAU RPE eyecups suppressed phagolysosome activation. Depletion of the neuropeptides alpha-melanocyte–stimulating hormone and neuropeptide Y from the healthy RPE eyecup conditioned media resulted in macrophage death. In the EAU RPE eyecup conditioned media was 0.96 ± 0.18 ng/mL of IL-6, and when neutralized the conditioned media suppressed phagolysosome activation.

Conclusions

The healthy RPE through soluble molecules, including alpha-melanocyte–stimulating hormone and neuropeptide Y, suppresses the activation of the phagolysosome in macrophages. In EAU, the IL-6 produced by the RPE promotes the activation of phagolysosomes in macrophages. These results demonstrate that under healthy conditions, RPE promotes an altered pathway of phagocytized material in macrophages with implications on antigen processing and clearance.

Neuropeptide Y Y2 and Y5 receptors as promising targets for neuroprotection in primary neurons exposed to oxygen-glucose deprivation and in transient focal cerebral ischemia in rats

It was postulated that neuropeptide Y (NPY)-ergic system could be involved in the ischemic pathophysiology, however, the role of particular subtypes of NPY receptors (YRs) in neuroprotection against ischemia is still not well known. Therefore, we investigated the effect of NPY and YR ligands using in vitro and in vivo experimental ischemic stroke models. Our in vitro findings showed that NPY (0.5-1μM) and specific agonists of Y2R (0.1-1μM) and Y5R (0.5-1μM) but not that of Y1R produced neuroprotective effects against oxygen-glucose deprivation (OGD)-induced neuronal cell death, being also effective when given 30min after the end of OGD. The neuroprotective effects of Y2R and Y5R agonists were reversed by appropriate antagonists. Neuroprotection mediated by NPY, Y2R and Y5R agonists was accompanied by the inhibition of both OGD-induced calpain activation and glutamate release. Data from in vivo studies demonstrated that Y2R agonist (10μg/6μl; i.c.v.) not only diminished the infarct volume in rats subjected to transient middle cerebral artery occlusion (MCAO) but also improved selected gait parameters in CatWalk behavioral test, being also effective after delayed treatment. Moreover, we found that a Y5R agonist (10μg/6μl; i.c.v.) did not reduce MCAO-evoked brain damage but improved stride length, when it was given 30min after starting the occlusion. In conclusion, our studies indicate that Y5 and especially Y2 receptors may be promising targets for neuroprotection against ischemic damage.

Neuropeptide Y Negatively Influences Monocyte Recruitment to the Central Nervous System during Retrovirus Infection

Monocyte infiltration into the CNS is a hallmark of several viral infections of the central nervous system (CNS), including retrovirus infection. Understanding the factors that mediate monocyte migration in the CNS is essential for the development of therapeutics that can alter the disease process. In the current study, we found that neuropeptide Y (NPY) suppressed monocyte recruitment to the CNS in a mouse model of polytropic retrovirus infection. NPY(-/-) mice had increased incidence and kinetics of retrovirus-induced neurological disease, which correlated with a significant increase in monocytes in the CNS compared to wild-type mice. Both Ly6C(hi) inflammatory and Ly6C(lo) alternatively activated monocytes were increased in the CNS of NPY(-/-) mice following virus infection, suggesting that NPY suppresses the infiltration of both cell types. Ex vivo analysis of myeloid cells from brain tissue demonstrated that infiltrating monocytes expressed high levels of the NPY receptor Y2R. Correlating with the expression of Y2R on monocytes, treatment of NPY(-/-) mice with a truncated, Y2R-specific NPY peptide suppressed the incidence of retrovirus-induced neurological disease. These data demonstrate a clear role for NPY as a negative regulator of monocyte recruitment into the CNS and provide a new mechanism for suppression of retrovirus-induced neurological disease.

IMPORTANCE

Monocyte recruitment to the brain is associated with multiple neurological diseases. However, the factors that influence the recruitment of these cells to the brain are still not well understood. In the current study, we found that neuropeptide Y, a protein produced by neurons, affected monocyte recruitment to the brain during retrovirus infection. We show that mice deficient in NPY have increased influx of monocytes into the brain and that this increase in monocytes correlates with neurological-disease development. These studies provide a mechanism by which the nervous system, through the production of NPY, can suppress monocyte trafficking to the brain and reduce retrovirus-induced neurological disease.

The Dipeptidyl Peptidase Family, Prolyl Oligopeptidase, and Prolyl Carboxypeptidase in the Immune System and Inflammatory Disease, Including Atherosclerosis

Research from over the past 20 years has implicated dipeptidyl peptidase (DPP) IV and its family members in many processes and different pathologies of the immune system. Most research has been focused on either DPPIV or just a few of its family members. It is, however, essential to consider the entire DPP family when discussing any one of its members. There is a substantial overlap between family members in their substrate specificity, inhibitors, and functions. In this review, we provide a comprehensive discussion on the role of prolyl-specific peptidases DPPIV, FAP, DPP8, DPP9, dipeptidyl peptidase II, prolyl carboxypeptidase, and prolyl oligopeptidase in the immune system and its diseases. We highlight possible therapeutic targets for the prevention and treatment of atherosclerosis, a condition that lies at the frontier between inflammation and cardiovascular disease.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

Aging oppositely affects TNF-α and IL-10 production by macrophages from different rat strains

Altered functions of macrophages with aging contribute to impairment of both innate and adaptive immunity in the elderly. The present study aimed to examine strain specificity of age-related changes in the phenotypic and functional characteristics of macrophages from DA and AO rats, which differ in average life span. Resident peritoneal macrophages from young (10-12 weeks old) and aged (98-104 weeks old) rats were tested for: (a) the surface expression of TLR4 and CD14; (b) the basal and LPS-induced production of TNF-α and IL-10; and (c) the basal and LPS-induced activity of iNOS and arginase, by measuring the levels of NO and urea, respectively, in the culture supernatants. Aging elevated TLR4 macrophage surface density in rats of both strains. Conversely, the age-related decrease in the surface density of CD14 co-receptor was detected only on macrophages from aged DA rats. Accordingly, with aging in DA rats, contrary to AO rats, upon LPS-stimulation both TNF-α and IL-10 levels decreased in culture supernatants. However, in rats of both strains TNF-α stimulation index (LPS-induced over basal production) remained stable with aging, but it was significantly greater in AO rats. Furthermore, with aging, IL-10 stimulation index decreased and increased in DA and AO rats, respectively. Age-related shift in urea stimulation index complied with the changes of IL-10 stimulation index during aging. In conclusion, the study suggests that the preserved ability of macrophages from aged AO rats to synthesize not only proinflammatory TNF-α, but also immunoregulatory IL-10 cytokine most likely contributes to their longer average life compared with DA rats.

Neuropeptide analysis of oral mucosa in diabetic rats

OBJECTIVE

Increasing evidence indicates that different neuropeptide-containing nerve elements are involved in the immune system and influence the inflammation of the gastrointestinal tract. The aim of this study was to investigate the morphological localization and distribution of the different immunoreactive (IR) nerve fibers and immunocompetent cells in the oral mucosa (e.g. tongue, gingiva) and compare the results with data received from streptozotocin (STZ)-induced diabetic rats.

MATERIALS AND METHODS

The different nerve elements and immunocytes were detected by ABC immunohistochemistry.

RESULTS

The IR nerve fibers were found in the tunica propria of oral mucosa with different densities. These IR nerve fibers were mainly located beneath the epithelial lining, around the blood vessels and glands, and some of them were also located in the taste buds. After 2 weeks of STZ treatment the total number of IR nerve fibers, especially the SP and neuropeptide Y (NPY) IR ones, was significantly increased (p < 0.05), as was also the number of immunocytes (lymphocytes, plasma cells, mast cells). Some of these cells also showed immunoreactivity for substance P (SP) and NPY. In several cases the SP IR nerve fibers were found in close proximity to the immunocytes. Electron microscopic investigation also revealed the close association between the IR nerve fibers and immunocompetent cells where the gap was 1 µm or even less.

CONCLUSIONS

The close anatomical associations suggest communication between nerve fibers and immune cells which can be crucial for maintaining mucosal homeostasis and for ensuring an appropriate response to injury.

Neuropeptide Y modulates fracture healing through Y1 receptor signaling

Neuropeptide Y acting via it's Y1 receptor represents a powerful pathway in the control of bone mass. The global or osteoblast-specific Y1 receptor deletion induces pronounced bone anabolic effects in mice. However, the contribution of Y1 receptor deletion in bone repair/healing remained to be clarified. Therefore, in this study we characterized the role of Y1 receptor deletion in fracture healing. Closed tibial fractures were generated in germline (Y1 (-/-) ) and osteoblastic-specific Y1 receptor knockout mice. The progression of tibial repair monitored from 1- until 6-weeks post-fracture demonstrated that in Y1 (-/-) mice there is a delay in fracture repair, as seen by a decrease in bone callus volume and callus strength. Moreover, the histological features included elevated avascular and cartilage area and consequently delayed cartilage removal, and hence impaired union. Interestingly, this delay in bone repair was not related directly to Y1 receptors expressed by mature osteoblasts. These findings suggest that the global absence of the Y1 receptor delays fracture healing, through impairing the early phases of fracture repair to achieve bony union. The data acquired on the role of Y1 receptor signaling disruption in bone regeneration is critical for the design of future therapeutic strategies.

Neuroimmunomodulation in human autoimmune liver disease

Bidirectional interaction between immune and nervous systems is considered an important biological process in health and disease. However, little is known about the mechanisms involved in their interaction in the human liver. This study examines the distribution of intrahepatic NPY, SP immunoreactive (IR) nerve fibers and their antomical relationship with immunocells containing tumor necrosis factor-α (TNF-α) and nuclear factor κB (NF-κB) in patients with autoimmune hepatitis. Liver specimens were obtained from control liver and autoimmune hepatitis patients. The immunoreactivity was determined by immunohisto- and immunocytochemistry and confocal laser microscopy. In hepatitis, the number of NPY-IR and SP-IR nerve fibers increased significantly. These IR nerve fibers were in very close contact with the lymphocytes. In healthy controls, no NPY-IR, SP-IR or NF-κB IR lymphocytes and only a few TNF-α positive cells, were observed. In hepatitis, some of the lymphocytes showed immunoreactivity for SP and NPY in the portal area. Fluorescent double-labeled immunostaining revealed that in these cells NPY did not colocalize with TNF-α or NF-κB. However, some of the SP fluorescence-positive immune cells exhibited immunostaining for p65 of NF-κB, where their labeling was detected in the nuclei. Under the electronmicroscope, these cells could be identified (lymphocytes, plasmacells and mast cells). The gap between the IR nerve fibers and immunocells was 1 μm or even less. Overexpression of SP in lymphocytes may amplify local inflammation, while NPY may contribute to liver homeostasis in hepatitis. Neural immunomodulation (SP antagonists and NPY) might be a novel therapeutic concept in the management of liver inflammation.

End-point effector stress mediators in neuroimmune interactions: their role in immune system homeostasis and autoimmune pathology

Much evidence has identified a direct anatomical and functional link between the brain and the immune system, with glucocorticoids (GCs), catecholamines (CAs), and neuropeptide Y (NPY) as its end-point mediators. This suggests the important role of these mediators in immune system homeostasis and the pathogenesis of inflammatory autoimmune diseases. However, although it is clear that these mediators can modulate lymphocyte maturation and the activity of distinct immune cell types, their putative role in the pathogenesis of autoimmune disease is not yet completely understood. We have contributed to this field by discovering the influence of CAs and GCs on fine-tuning thymocyte negative selection and, in particular, by pointing to the putative CA-mediated mechanisms underlying this influence. Furthermore, we have shown that CAs are implicated in the regulation of regulatory T-cell development in the thymus. Moreover, our investigations related to macrophage biology emphasize the complex interaction between GCs, CAs and NPY in the modulation of macrophage functions and their putative significance for the pathogenesis of autoimmune inflammatory diseases.

Polymorphisms in LEP and NPY genes modify the response to soluble fibre Plantago ovata husk intake on cardiovascular risk biomarkers

The satiating effect of fibre consumption has been related to gut hormones, such as peptide YY and leptin. These peptides may also influence cardiovascular (CVD) risk biomarkers. Nevertheless, there is wide interindividual variation in metabolic responses to fibre consumption. The objective was to investigate differences in the effects of soluble fibre, in the form of Plantago ovata husk (Po-husk) treatment, on CVD risk biomarkers according to selected polymorphisms in genes related to satiety. The study was a multi-centred, double-blind, placebo-controlled, parallel and randomised trial in mild-moderate hypercholesterolaemic patients (age range: 43-67 years). Eight polymorphisms in three genes related to satiety (LEP, NPY and PYY) were identified in 178 participants; 88 patients in the placebo (microcrystalline cellulose 14 g/day) group and 90 in the Po-husk (14 g/day) group, which had added to a low-saturated-fat diet for 8 weeks. The CVD biomarkers measured included the following: lipid profile, blood pressure (BP), glucose, insulin, hs-CRP, oxidised LDL and IL-6. Relative to the placebo, Po-husk consumption lowered the plasma total cholesterol concentration by 3.3 % according to rs7799039 polymorphism in the LEP gene (p < 0.05). Furthermore, the Po-husk reduced systolic BP (mean [95 % CI]) by -8 mmHg (-14.16; -1.90) and hs-CRP by 24.9 % in subjects with the AA genotype of the rs16147 polymorphism in the NPY gene (32 % of our total population; p < 0.05), which remained significant after Bonferroni correction. In conclusion, polymorphisms in the LEP and NPY genes potentiate the response to Po-husk, particularly the effects on systolic BP and the hs-CRP plasma concentration.

Neuroimmunomodulative properties of dipeptidyl peptidase IV/CD26 in a TNBS-induced model of colitis in mice

Causal connections between dipeptidyl peptidase IV, also known as CD26 molecule (DPP IV/CD26) and inflammatory bowel disease (IBD) have been shown, but mechanisms of these interactions are unclear. Our hypothesis was that DPP IV/CD26 could affect the neuroimmune response during inflammatory events. Therefore, we aimed to evaluate its possible role and the relevance of the gut-brain axis in a model of IBD in mice. Trinitrobenzenesulfonic acid-induced (TNBS) colitis was induced in CD26-deficient (CD26(-/-) ) and wild-type (C57BL/6) mice. Pathohistological and histomorphometrical measurements were done. Concentrations and protein expressions of DPP IV/CD26 substrates neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) were determined. Concentrations of IL-6 and IL-10 were evaluated. Investigations were conducted at systemic and local levels. Acute inflammation induced increased serum NPY concentrations in both mice strains, more enhanced in CD26(-/-) mice. Increased NPY concentrations were found in colon and brain of C57BL/6 mice, while in CD26(-/-) animals only in colon. VIP and IL-6 serum and tissue concentrations were increased in both mice strains in acute inflammation, more pronouncedly in CD26(-/-) mice. IL-10 concentrations, after a decrease in serum of both mice strains, increased promptly in CD26(-/-) mice. Decreased IL-10 concentration was found in brain of C57BL/6 mice, while it was increased in colon of CD26(-/-) mice in acute inflammation. DPP IV/CD26 deficiency affects the neuroimmune response at systemic and local levels during colitis development and resolution in mice. Inflammatory changes in the colon reflected on investigated parameters in the brain, suggesting an important role of the gut-brain axis in IBD pathogenesis.

NPY suppressed development of experimental autoimmune encephalomyelitis in Dark Agouti rats by disrupting costimulatory molecule interactions

Neuropeptide Y (NPY) suppressed clinical experimental autoimmune encephalomyelitis (EAE) and reduced numbers of CD28+, CD11b+ and CD80+ cells among spinal cord infiltrating cells at the peak of disease in Dark Agouti rat strain. Suppression of EAE was accompanied by the reduced expression of costimulatory CD80 and CD86 molecules on ED1+ macrophages and OX62+ dendritic cells in draining lymph nodes during the inductive phase of EAE. An inhibitor of dipeptidyl peptidase 4, an enzyme which terminates the action of NPY on Y1 receptor subtype, did not sustain the suppressive effect of NPY on the EAE development, suggesting involvement of Y2 and Y5 receptors.

Neuropeptide Y modulates functions of inflammatory cells in the rat: distinct role for Y1, Y2 and Y5 receptors

Neuropeptide Y (NPY) has been reported to be a potent anti-inflammatory peptide with ability to directly modulate activity of granulocytes and macrophages. The present study aimed to correlate the effects of NPY in vivo on lipopolysaccharide-induced air-pouch exudates cells and in vitro on peripheral blood leukocytes functions. The role of different Y receptors was examined using NPY-related peptides and antagonists with diverse subtype specificity and selectivity for Y receptors. Y1, Y2 and Y5 receptors were detected on air-pouch exudates cells (flow cytometry) and peripheral blood granulocytes (immunocytochemistry). NPY in vivo reduced inflammatory cells accumulation into the air pouch, and decreased their adherence and phagocytic capacity via Y2/Y5 and Y1/Y2 receptors, respectively. Quite the opposite, NPY in vitro potentiated adhesiveness and phagocytosis of peripheral blood granulocytes and monocytes by activating Y1 receptor. The differences between in vivo and in vitro effects of NPY on rat inflammatory cells functions are mostly due to dipeptidyl peptidase 4 activity. In addition, suppressive effect of NPY in vivo is highly dependent on the local microenvironment, peptide truncation and specific Y receptors interplay.

Signaling proteins that influence energy intake may affect unintentional weight loss in elderly persons

After age 70 to 75 years, average body weight decreases both in ailing and healthy people because of a loss of appetite that results in reduced energy intake and the loss of body fat and lean muscle tissue. This so-called anorexia of aging predisposes elderly people to continued pathologic weight loss and malnutrition-major causes of morbidity and mortality. Health care professionals must understand the many factors involved in the anorexia of aging to help older adults prevent unintentional weight loss. Psychological, social, and cultural factors are important effectors; however, physiological factors are emphasized here because they are not thoroughly understood and they make it inherently difficult for most people to alter their body weight. Monoamines, steroid hormones (glucocorticoids and mineralocorticoids), endocannabinoids, and proteins all influence body weight. This review is an analysis of proteins from the brain, pancreas, adipose tissue, and gastrointestinal tract that are known to affect energy intake and energy balance, with an attempt to identify those factors that may change with aging. The articles included in this review were obtained by a PubMed database search using the keywords mouse OR rat OR human AND aged OR aging OR older OR elderly AND adult AND anorexia OR "unintentional weight loss," and each of the individual proteins discussed, as well as from the reference lists of those articles. The results reveal that some proteins may be important in the development of unintentional weight loss in elderly persons, whereas others may not have a significant role. However, many of the proteins that could conceivably have a role in unintentional weight loss have not yet been studied with that question in mind. Preventing unintentional weight loss in older adults is an important goal and further research on the role of proteins important for the maintenance of energy balance and the development of unintentional weight loss in elderly persons is warranted.

Localized retinal neuropeptide regulation of macrophage and microglial cell functionality

The functionality of immune cells is manipulated within the ocular microenvironment to protect the sensitive and non-regenerating light-gathering tissue from the collateral damage of inflammation. This is mediated partly by the constitutive presence of immunomodulating neuropeptides. Treating primary resting macrophages with soluble factors produced by the posterior eye induced co-expression of Arginase1 and NOS2. The neuropeptides alpha-melanocyte stimulating hormone and Neuropeptide Y alternatively activated the macrophages to co-express Arginase1 and NOS2 like myeloid suppressor cells. Similar co-expressing cells were found within healthy, but not in wounded retinas. Therefore, the healthy retina regulates macrophage functionality to the benefit of ocular immune privilege.

Metabolic syndrome is a low-grade systemic inflammatory condition

An increase in proinflammatory cytokines, a decrease in endothelial nitric oxide and adiponectin levels and an alteration in hypothalamic peptides and gastrointestinal hormones that regulate satiety, hunger and food intake all occur in metabolic syndrome. Consumption of a diet that is energy dense and rich in saturated and trans-fats by pregnant women and lactating mothers, in childhood and adult life may trigger changes in the hypothalamic and gut peptides and hormones. Such changes modulate immune response and inflammation and lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point' and result in the initiation and development of the metabolic syndrome. Roux-en-gastric bypass induces weight loss, decreases the levels of cytokines and restores hypothalamic neuropeptides and gut hormones and the hypothalamic bodyweight/appetite/satiety set point to normal. Thus, metabolic syndrome is a low-grade systemic inflammatory condition with its origins in the perinatal period and childhood.

An assessment of adverse effects of vildagliptin versus comparators on the liver, the pancreas, the immune system, the skin and in patients with impaired renal function from a large pooled database of Phase II and III clinical trials

AIM

To assess the safety of vildagliptin versus all comparators (ACs) with regard to organs, systems or tissues of particular interest in type 2 diabetes (T2DM) and areas of potential concern with dipeptidyl peptidase-IV (DPP-4) inhibitors.

METHODS

Data were pooled from 38 studies where vildagliptin was given for > or =12 to > 104 weeks in patients with T2DM. Absolute and exposure-adjusted incidence rates and Peto odds ratios (ORs) versus ACs with corresponding 95% confidence intervals (CI) were calculated.

RESULTS

There were > 7000 subject-years of exposure (SYE) to vildagliptin 50 mg bid and > 6500 SYE to ACs. For mild hepatic enzyme elevations with and without elevated bilirubin levels, the ORs for vildagliptin 50 mg bid were 1.24 (95% CI: [0.80, 1.93]) and 1.19 (95% CI: [0.29, 4.90]), respectively. The exposure-adjusted incidences of markedly elevated hepatic enzymes and for enzyme elevations with bilirubin > or = 2x ULN with vildagliptin 50 mg bid were < or = those in the ACs group. For hepatic and pancreatitis-related AEs, the ORs for vildagliptin 50 mg bid were 0.87 (95% CI: [0.64, 1.19]) and 0.70 (95% CI: [0.26, 1.88]), respectively, and for any AE in the infections and infestations SOC, this was 1.04 (95% CI: [0.96, 1.13]). The incidences of skin-related AEs were low and the risk with vildagliptin 50 mg bid was not significantly different from ACs [(OR = 1.10 (95% CI: [0.80, 1.51])].

CONCLUSIONS

The present meta-analyses indicate that vildagliptin was not associated with increased risk of hepatic events or hepatic enzyme elevations indicative of drug-induced liver injury, pancreatitis, infections or skin-related toxicity.

Modulation of granulocyte functions by peptide YY in the rat: age-related differences in Y receptors expression and plasma dipeptidyl peptidase 4 activity

It has been acknowledged that aging exerts detrimental effects on cells of the innate immune system and that neuropeptides, including neuropeptide Y (NPY) and NPY-related peptides fine-tune the activity of these cells through a receptor specific mechanism. The present study investigated the age-dependent potential of peptide YY (PYY) to modulate different granulocyte functions. The PYY reduced the carrageenan-elicited granulocyte accumulation into the air-pouch of aged (24 months) rats, and markedly decreased the phagocytosis of zymosan, as well as the H(2)O(2) production, when applied in vivo (20 microg/air-pouch). The anti-inflammatory effect of PYY was less prominent in adult (8 months) and young (3 months) rats. However, the proportions of granulocytes expressing Y1, Y2 and Y5 receptor subtypes were significantly lower in both aged and young rats when compared to adult rats. Furthermore, the aging was found to be associated with the diminished dipeptidyl peptidase 4 (DP4, an enzyme converting the NPY and PYY to Y2/Y5 receptor selective agonists) activity in plasma. In conclusion, the diverse age-related anti-inflammatory effect of PYY in rats originates from different expression levels of Y1, Y2, and Y5 receptor subtypes in addition to different plasma DP4 activity.

The dipeptidyl peptidase IV family in cancer and cell biology

Of the 600+ known proteases identified to date in mammals, a significant percentage is involved or implicated in pathogenic and cancer processes. The dipeptidyl peptidase IV (DPIV) gene family, comprising four enzyme members [DPIV (EC 3.4.14.5), fibroblast activation protein, DP8 and DP9] and two nonenzyme members [DP6 (DPL1) and DP10 (DPL2)], are interesting in this regard because of their multiple diverse functions, varying patterns of distribution/localization and subtle, but significant, differences in structure/substrate recognition. In addition, their engagement in cell biological processes involves both enzymatic and nonenzymatic capabilities. This article examines, in detail, our current understanding of the biological involvement of this unique enzyme family and their overall potential as therapeutic targets.