Glycine and glycine receptor signalling in non-neuronal cells

A multifunctional "three-in-one" fluorescent theranostic system for hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is the main cause of postoperative liver dysfunction and liver failure. Traditional separation of HIRI diagnosis and therapy confers several disadvantages, including the inability to visualize the therapeutic and asynchronous action. However, developing a versatile material with integrated diagnosis and treatment for HIRI remains a great challenge. Given that hypochlorous acid (HOCl) plays a crucial oxidative role in HIRI, we developed a single-component multifunctional fluorescent theranostic platform (MB-Gly) with a "three-in-one" molecular design incorporating a near-infrared fluorophore methylene blue, glycine and a HOCl-response unit, which could not only provide real-time visualization of HIRI but also boost targeted drug delivery. Using MB-Gly, we were able to achieve real-time and dynamic monitoring of HOCl during HIRI in hepatocytes and mouse livers and reduce the liver damage in hepatocytes and mice. RNA sequencing illustrated the therapeutic role of MB-Gly associated with changes in gene expression related to apoptosis, oxidative stress, metabolism and inflammation. To the best of our knowledge, this is the first multifunctional fluorescent theranostic system for HIRI reported to date. Our smart "three-in-one" approach shines light on the etiology and pathogenesis of HIRI, providing profound insights into the development of potential therapeutic targets.

GABA-mediated inhibition of human CD4+ T cell functions is enhanced by insulin but impaired by high glucose levels

BACKGROUND

γ-aminobutyric acid (GABA), known as the main inhibitory neurotransmitter in the brain, exerts immunomodulatory functions by interaction with immune cells, including T cells. Metabolic programs of T cells are closely linked to their effector functions including proliferation, differentiation, and cytokine production. The physiological molecules glucose and insulin may provide environmental cues and guidance, but whether they coordinate to regulate GABA-mediated T cell immunomodulation is still being examined.

METHODS

CD4+ T cells that were isolated from blood samples from healthy individuals and from patients with type 1 diabetes (T1D) were activated in vitro. We carried out metabolic assays, multiple proximity extension assay (PEA), ELISA, qPCR, immunoblotting, immunofluorescence staining, flow cytometry analysis, MS-based proteomics, as well as electrophysiology and live-cell Ca2+ imaging.

FINDINGS

We demonstrate that GABA-mediated reduction of metabolic activity and the release of inflammatory proteins, including IFNγ and IL-10, were abolished in human CD4+ T cells from healthy individuals and patients with T1D when the glucose concentration was elevated above levels typically observed in healthy people. Insulin increased GABAA receptor-subunit ρ2 expression, enhanced the GABAA receptors-mediated currents and Ca2+ influx. GABA decreased, whereas insulin sustained, hexokinase activity and glycolysis in a glucose concentration-dependent manner.

INTERPRETATION

These findings support that metabolic factors, such as glucose and insulin, influence the GABA-mediated immunomodulation of human primary T cells effector functions.

FUNDING

The Swedish Children's Diabetes Foundation, The Swedish Diabetes Foundation, The Swedish Research Council 2018-02952, EXODIAB, The Ernfors Foundation, The Thurings Foundation and the Science for Life Laboratory.

Glycine by enteral route does not improve major clinical outcomes in severe COVID-19: a randomized clinical pilot trial

There is a worrying scarcity of drug options for patients with severe COVID-19. Glycine possesses anti-inflammatory, cytoprotective, endothelium-protective, and platelet-antiaggregant properties, so its use in these patients seems promising. In this open label, controlled clinical trial, inpatients with severe COVID-19 requiring mechanical ventilation randomly received usual care (control group) or usual care plus 0.5 g/kg/day glycine by the enteral route (experimental group). Major outcomes included mortality, time to weaning from mechanical ventilation, total time on mechanical ventilation, and time from study recruitment to death. Secondary outcomes included laboratory tests and serum cytokines. Patients from experimental (n = 33) and control groups (n = 23) did not differ in basal characteristics. There were no differences in mortality (glycine group, 63.6% vs control group, 52.2%, p = 0.60) nor in any other major outcome. Glycine intake was associated with lower fibrinogen levels, either evaluated per week of follow-up (p < 0.05 at weeks 1, 2, and 4) or as weighted mean during the whole hospitalization (608.7 ± 17.7 mg/dl vs control 712.2 ± 25.0 mg/dl, p = 0.001), but did not modify any other laboratory test or cytokine concentration. In summary, in severe COVID-19 glycine was unable to modify major clinical outcomes, serum cytokines or most laboratory tests, but was associated with lower serum fibrinogen concentration.Registration: ClinicalTrials.gov NCT04443673, 23/06/2020.

Urinary metabolic characterization of advanced tuberculous meningitis cases in a South African paediatric population

Tuberculous meningitis (TBM) is a severe form of tuberculosis with high neuro-morbidity and mortality, especially among the paediatric population (aged ≤12 years). Little is known of the associated metabolic changes. This study aimed to identify characteristic metabolic markers that differentiate severe cases of paediatric TBM from controls, through non-invasive urine collection. Urine samples selected for this study were from two paediatric groups. Group 1: controls (n = 44): children without meningitis, no neurological symptoms and from the same geographical region as group 2. Group 2: TBM cases (n = 13): collected from paediatric patients that were admitted to Tygerberg Hospital in South Africa on the suspicion of TBM, mostly severely ill; with a later confirmation of TBM. Untargeted 1H NMR-based metabolomics data of urine were generated, followed by statistical analyses via MetaboAnalyst (v5.0), and the identification of important metabolites. Twenty nine urinary metabolites were identified as characteristic of advanced TBM and categorized in terms of six dysregulated metabolic pathways: 1) upregulated tryptophan catabolism linked to an altered vitamin B metabolism; 2) perturbation of amino acid metabolism; 3) increased energy production-metabolic burst; 4) disrupted gut microbiota metabolism; 5) ketoacidosis; 6) increased nitrogen excretion. We also provide original biological insights into this biosignature of urinary metabolites that can be used to characterize paediatric TBM patients in a South African cohort.

The Warburg effect alters amino acid homeostasis in human retinal endothelial cells: implication for proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) remains a leading cause of blindness despite progress in screening and treatment. Recently, the Warburg effect, a metabolic alteration affecting amino acid (AA) metabolism in proliferating cells, has drawn attention regarding its role in PDR. This study aimed to investigate the impact of the Warburg effect on AA metabolism in human retinal endothelial cells (HRECs) subjected to PDR-associated risk factors and validate the findings in patients with PDR. In vitro experiments exposed HRECs to high glucose (HG) and/or hypoxia (Hyp), known inducers of the Warburg effect. The HG + Hyp group of HRECs exhibited significant differences in non-essential AAs with aliphatic non-polar side chains, mainly driven by elevated glycine concentrations. Pathway enrichment analysis revealed several glycine metabolism-related pathways significantly altered due to the Warburg effect induced by HG + Hyp. Crucially, vitreous humor samples from PDR patients displayed higher glycine levels compared to non-diabetic and diabetic patients without PDR. The odds ratio for PDR patients with glycine levels above the cut-off of 0.0836 µM was 28 (p = 0.03) compared to non-PDR controls. In conclusion, this study provides mechanistic insights into how a specific Warburg effect subtype contributes to glycine accumulation in PDR and supports glycine's potential as a biomarker for PDR pathogenesis.

Pretransplant systemic metabolic profiles in allogeneic hematopoietic stem cell transplant recipients - identification of patient subsets with increased transplant-related mortality

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is used in the treatment of high-risk acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS); however, the treatment has high risk of severe transplantation-related mortality (TRM). In this study, we examined pretransplantation serum samples derived from 92 consecutive allotransplant recipients with AML or MDS. Using nontargeted metabolomics, we identified 1274 metabolites including 968 of known identity (named biochemicals). We further investigated metabolites that differed significantly when comparing patients with and without early extensive fluid retention, pretransplantation inflammation (both being associated with increased risk of acute graft-versus-host disease [GVHD]/nonrelapse mortality) and development of systemic steroid-requiring acute GVHD (aGVHD). All three factors are associated with TRM and were also associated with significantly altered amino acid metabolism, although there was only a minor overlap between these three factors with regard to significantly altered individual metabolites. Furthermore, steroid-requiring aGVHD was especially associated with altered taurine/hypotaurine, tryptophan, biotin, and phenylacetate metabolism together with altered malate-aspartate shuttle and urea cycle regulation. In contrast, pretransplantation inflammation was associated with a weaker modulation of many different metabolic pathways, whereas extensive fluid retention was associated with a weaker modulation of taurine/hypotaurine metabolism. An unsupervised hierarchical cluster analysis based on the 13 most significantly identified metabolites associated with aGVHD identified a patient subset with high metabolite levels and increased frequencies of MDS/MDS-AML, steroid-requiring aGVHD and early TRM. On the other hand, a clustering analysis based on metabolites that were significantly altered for aGVHD, inflammation, and fluid retention comparison groups identified a patient subset with a highly significant association with TRM. Our study suggests that the systemic pretransplantation metabolic profiles can be used to identify patient subsets with an increased frequency of TRM.

NK-cell dysfunction of acute myeloid leukemia in relation to the renin–angiotensin system and neurotransmitter genes

Acute myeloid leukemia (AML) is the most heterogeneous hematological disorder and blast cells need to fight against immune system. Natural killer (NK) cells can elicit fast anti-tumor responses in response to surface receptors of tumor cells. NK-cell activity is often impaired in the disease, and there is a risk of insufficient tumor suppression and progression. The aim of this study is to assess the dysfunction of NK cells in AML patients via focusing on two important pathways. We obtained single-cell RNA-sequencing data from NK cells obtained from healthy donors and AML patients. The data were used to perform a wide variety of approaches, including DESeq2 (version 3.9), limma (version 3.26.8) power differential expression analyses, hierarchical clustering, gene set enrichment, and pathway analysis. ATP6AP2, LNPEP, PREP, IGF2R, CTSA, and THOP1 genes were found to be related to the renin–angiotensin system (RAS) family, while DPP3, GLRA3, CRCP, CHRNA5, CHRNE, and CHRNB1 genes were associated with the neurotransmitter pathways. The determined genes are expressed within different patterns in the AML and healthy groups. The relevant molecular pathways and clusters of genes were identified, as well. The cross-talks of NK-cell dysfunction in relation to the RAS and neurotransmitters seem to be important in the genesis of AML.

Glycine ameliorates MBP-induced meiotic abnormalities and apoptosis by regulating mitochondrial-endoplasmic reticulum interactions in porcine oocytes

Monobutyl phthalate (MBP) is the main metabolite of dibutyl phthalate (DBP) in vivo. MBP has a stable structure, can continuously accumulate in living organisms, and has the potentially to harm animal and human reproductive function. In the ovarian follicle microenvironment, MBP may lead to defects in follicular development and steroid production, abnormal meiotic maturation, impaired ovarian function and other reproductive deficits. In this study, SMART-seq was used to investigate the effects of MBP exposure on the in vitro maturation (IVM) and development of porcine oocytes. The results showed that differentially expressed genes after MBP exposure were enriched in the biological processes cytoskeleton, cell apoptosis, endoplasmic reticulum (ER) and mitochondria. Glycine (Gly) improved the developmental potential of porcine oocytes by regulating mitochondrial and ER function. The effect of Gly in protecting oocytes against MBP-induced damage was studied. The results showed that the addition of Gly significantly decreased the rate of MBP-induced spindle abnormalities, decreased the frequency of MBP-induced mitochondria-associated ER membrane (MAM) interactions, and downregulated the protein and gene expression of the linkage molecules Mitofusin 1 (MFN1) and Mitofusin 2 (MFN2) in the MAM. Additionally, treatment with Gly restored the distribution of the 1,4,5-triphosphate receptor 1 (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), further decreasing the intracellular free calcium concentration ([Ca²⁺]_i) levels and mitochondrial Ca²⁺ ([Ca²⁺]_m) , increasing the ER Ca²⁺ ([Ca²⁺]_ER) levels, and thus significantly increasing the ER levels and mitochondrial membrane potential (ΔΨ m). Gly also decreased the levels of reactive oxygen species (ROS) and increased the levels of Glutathione (GSH), oocyte apoptosis-related indicators (Caspase-3 activity and Annexin V) and oocyte apoptosis-related genes (BAX, Caspase 3 and AIFM1). Our results suggest that Gly can ameliorate microtubule cytoskeleton abnormalities and improve oocyte maturation by reducing the defective mitochondrial-ER interactions caused by MBP exposure in vitro.

Exploring the Conformational Impact of Glycine Receptor TM1-2 Mutations Through Coarse-Grained Analysis and Atomistic Simulations

Pentameric ligand-gated ion channels (PLGICs) are a family of proteins that convert chemical signals into ion fluxes through cellular membranes. Their structures are highly conserved across all kingdoms from bacteria to eukaryotes. Beyond their classical roles in neurotransmission and neurological disorders, PLGICs have been recently related to cell proliferation and cancer. Here, we focus on the best characterized eukaryotic channel, the glycine receptor (GlyR), to investigate its mutational patterns in genomic-wide tumor screens and compare them with mutations linked to hyperekplexia (HPX), a Mendelian neuromotor disease that disrupts glycinergic currents. Our analysis highlights that cancer mutations significantly accumulate across TM1 and TM2, partially overlapping with HPX changes. Based on 3D-clustering, conservation, and phenotypic data, we select three mutations near the pore, expected to impact GlyR conformation, for further study by molecular dynamics (MD). Using principal components from experimental GlyR ensembles as framework, we explore the motions involved in transitions from the human closed and desensitized structures and how they are perturbed by mutations. Our MD simulations show that WT GlyR spontaneously explores opening and re-sensitization transitions that are significantly impaired by mutations, resulting in receptors with altered permeability and desensitization properties in agreement with HPX functional data.

Effects of glycine on metabolic syndrome components: a review

PURPOSE

Glycine is the simplest and major amino acid in humans. It is mainly generated in the liver and kidney and is used to produce collagen, creatine, glucose and purine. It is also involved in immune function, anti-inflammatory processes and anti-oxidation reactions. Here, we reviewed the current evidence supporting the role of glycine in the development and treatment of metabolic syndrome components.

METHODS

We searched Scopus, PubMed and EMBASE databases for papers concerning glycine and metabolic syndrome.

RESULTS

Available evidence shows that the amount of glycine synthesized in vivo is insufficient to meet metabolic demands in these species. Plasma glycine levels are lower in subjects with metabolic syndrome than in healthy individuals. Interventions such as lifestyle modification, exercise, weight loss, or drugs that improve manifestations of metabolic syndrome remarkably increase circulating glycine concentrations.

CONCLUSION

Glycine supplementation improves various components of metabolic syndrome including diabetes, obesity, hyperlipidemia and hypertension. In the future, the use of glycine may have a significant clinical impact on the treatment of patients with metabolic syndrome.

Gastric Cancer Pre-Stage Detection and Early Diagnosis of Gastritis Using Serum Protein Signatures

Background: A gastric cancer (GC) diagnosis relies on histopathology. Endoscopy rates are increasing. Helicobacter pylori infection is a major GC risk factor. In an effort to elucidate abundant blood biomarkers, and potentially reduce the number of diagnostic surgical interventions, we investigated sera and biopsies from a cohort of 219 H. pylori positive and negative patients diagnosed with GC, gastritis, and ulcers. This allowed the comparative investigation of the different gastroduodenal diseases, and the exclusion of protein changes resulting from bacterial infection or inflammation of the gastric mucosa when searching for GC-dependent proteins. Methods: High-definition mass spectrometry-based expression analysis of tryptically digested proteins was performed, followed by multivariate statistical and network analyses for the different disease groups, with respect to H. pylori infection status. Significantly regulated proteins differing more than two-fold between groups were shortlisted, and their role in gastritis and GC discussed. Results: We present data of comparative protein analyses of biopsies and sera from patients suffering from mild to advanced gastritis, ulcers, and early to advanced GC, in conjunction with a wealth of metadata, clinical information, histopathological evaluation, and H. pylori infection status. We used samples from pre-malignant stages to extract prospective serum markers for early-stage GC, and present a 29-protein marker panel containing, amongst others, integrin β-6 and glutathione peroxidase. Furthermore, ten serum markers specific for advanced GC, independent of H. pylori infection, are provided. They include CRP, protein S100A9, and kallistatin. The majority of these proteins were previously discussed in the context of cancer or GC. In addition, we detected hypoalbuminemia and increased fibrinogen serum levels in gastritis. Conclusion: Two protein panels were suggested for the development of multiplex tests for GC serum diagnostics. For most of the elements contained in these panels, individual commercial tests are available. Thus, we envision the design of multi-protein assays, incorporating several to all of the panel members, in order to gain a level of specificity that cannot be achieved by testing a single protein alone. As their development and validation will take time, gastritis diagnosis based on the fibrinogen to albumin serum ratio may be a quick way forward. Its determination at the primary/secondary care level for early diagnosis could significantly reduce the number of referrals to endoscopy. Preventive measures are in high demand. The protein marker panels presented in this work will contribute to improved GC diagnostics, once they have been transferred from a research result to a practical tool.

The Role of Amino Acids in Endothelial Biology and Function

The vascular endothelium acts as an important component of the vascular system. It is a barrier between the blood and vessel wall. It plays an important role in regulating blood vessel tone, permeability, angiogenesis, and platelet functions. Several studies have shown that amino acids (AA) are key regulators in maintaining vascular homeostasis by modulating endothelial cell (EC) proliferation, migration, survival, and function. This review summarizes the metabolic and signaling pathways of AAs in ECs and discusses the importance of AA homeostasis in the functioning of ECs and vascular homeostasis. It also discusses the challenges in understanding the role of AA in the development of cardiovascular pathophysiology and possible directions for future research.

Potential receptors in Fenneropenaeus merguiensis ovary and role of saxophone, the bone morphogenetic protein receptor, in ovarian development

Receptors, which play an initial role in signaling pathways in several physiological processes, including reproduction, are among the several molecular factors that control ovarian development in organisms. This study aimed to identify and study receptors potentially involved in controlling the reproductive process of female banana shrimp, Fenneropenaeus merguiensis. Ovarian transcriptomes derived from 4 developmental stages were generated by RNA sequencing. A total of 53,763 transcripts were obtained from the de novo assembled transcriptome, and 663 genes were identified as receptors. Among them, 185 receptors were differentially expressed during ovarian development. Fifteen of these differentially expressed receptors showed distinct expression patterns that were validated by RT-qPCR. Bone morphogenetic protein receptors (BMPR) and their signaling genes were investigated for their roles in shrimp vitellogenesis. The expressions of F. merguiensis saxophone (FmSax), a BMP type I receptor, and BMP type II receptor (FmBMPRII) as well as FmMad, FmMed, and FmSMAD3 were significantly altered during ovarian development. RNA interference was used to investigate the role of FmSax in vitellogenesis. The result indicated that the expression of vitellogenin (Vg) was significantly reduced in both ovary and hepatopancreas of FmSax-knockdown shrimp compared to control shrimp. Furthermore, in FmSax-silencing shrimp, FmBMPRII, FmMad, and FmMed expressions were decreased as well as Vg expression. These findings suggest that FmSax positively regulates Vg synthesis via the BMP signaling pathway.

Glycine Receptor Subtypes and Their Roles in Nociception and Chronic Pain

Disruption of the inhibitory control provided by the glycinergic system is one of the major mechanisms underlying chronic pain. In line with this concept, recent studies have provided robust proof that pharmacological intervention of glycine receptors (GlyRs) restores the inhibitory function and exerts anti-nociceptive effects on preclinical models of chronic pain. A targeted regulation of the glycinergic system requires the identification of the GlyR subtypes involved in chronic pain states. Nevertheless, the roles of individual GlyR subunits in nociception and in chronic pain are yet not well defined. This review aims to provide a systematic outline on the contribution of GlyR subtypes in chronic pain mechanisms, with a particular focus on molecular pathways of spinal glycinergic dis-inhibition mediated by post-translational modifications at the receptor level. The current experimental evidence has shown that phosphorylation of synaptic α1β and α3β GlyRs are involved in processes of spinal glycinergic dis-inhibition triggered by chronic inflammatory pain. On the other hand, the participation of α2-containing GlyRs and of β subunits in pain signaling have been less studied and remain undefined. Although many questions in the field are still unresolved, future progress in GlyR research may soon open new exciting avenues into understanding and controlling chronic pain.

Protective effects of glycine against lipopolysaccharide-induced intestinal apoptosis and inflammation

Intestinal dysfunction is commonly observed in humans and animals. Glycine (Gly) is a functional amino acid with anti-inflammatory and anti-apoptotic properties. The objective of this study was to test the protective effects of Gly against lipopolysaccharide (LPS)-induced intestinal injury. 28 C57BL/6 mice with a body weight (BW) of 18 ± 2 g were randomly assigned into four groups: CON (control), GLY (orally administered Gly, 5 g/kg BW/day for 6 days), LPS (5 mg/kg BW on day 7, i. p.), and GLY + LPS (Gly pretreatment and LPS administration). Histological alterations, inflammatory responses, epithelial cell apoptosis, and changes of the intestinal microbiota were analyzed. Results showed that, compared with the CON group, mice in the LPS treatment group showed decreased villus height, increased crypt depth, and decreased ratio of villus height to crypt depth, which were significantly attenuated by Gly. Neither LPS nor Gly treatment altered morphology of the distal colon tissues. LPS increased the apoptosis of jejunum and colon epithelial cells and protein abundance of cleaved caspase3 in the jejunum, which were markedly abrogated by Gly. LPS also elevated the mRNA levels of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MYD88), pro-inflammatory cytokines, and chemokines in the jejunum and colon. These alterations were significantly suppressed by Gly. In addition, Gly supplementation attenuated infiltration of CD4+, CD8+ T-lymphocytes, CD11b+ and F4/80+ macrophages in the colon. Furthermore, Gly increased the relative abundance of Mucispirillum, Lachnospiraceae-NK4A136-group, Anaerotruncus, Faecalibaculum, Ruminococcaceae-UCG-014, and decreased the abundance of Bacteroides at genus level. Supplementation with Gly might be a nutritional strategy to ameliorate LPS-induced intestinal injury in mice.

Glycine Ameliorates Endoplasmic Reticulum Stress Induced by Thapsigargin in Porcine Oocytes

The endoplasmic reticulum (ER) is a multifunctional organelle in the cytoplasm that plays important roles in female mammalian reproduction. The endoplasmic reticulum and mitochondria interact to maintain the normal function of cells by maintaining intracellular calcium homeostasis. As proven by previous research, glycine (Gly) can regulate the intracellular free calcium concentration ([Ca²⁺]_i) and enhance mitochondrial function to improve oocyte maturation in vitro. The effect of Gly on ER function during oocyte in vitro maturation (IVM) is not clear. In this study, we induced an ER stress model with thapsigargin (TG) to explore whether Gly can reverse the ER stress induced by TG treatment and whether it is associated with calcium regulation. The results showed that the addition of Gly could improve the decrease in the average cumulus diameter, the first polar body excretion rate caused by TG-induced ER stress, the cleavage rate and the blastocyst rate. Gly supplementation could reduce the ER stress induced by TG by significantly improving the ER levels and significantly downregulating the expression of genes related to ER stress (Xbp1, ATF4, and ATF6). Moreover, Gly also significantly alleviated the increase in reactive oxygen species (ROS) levels and the decrease in mitochondrial membrane potential (ΔΨ m) to improve mitochondrial function in porcine oocytes exposed to TG. Furthermore, Gly reduced the [Ca²⁺]_i and mitochondrial Ca²⁺ ([Ca²⁺]_m) levels and restored the ER Ca²⁺ ([Ca²⁺]_ER) levels in TG-exposed porcine oocytes. Moreover, we found that the increase in [Ca²⁺]_i may be caused by changes in the distribution and expression of inositol 1,4,5-triphosphate receptor (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), while Gly can restore the distribution and expression of IP₃R1 and VDAC1 to normal levels. Apoptosis-related indexes (Caspase 3 activity and Annexin-V) and gene expression Bax, Cyto C, and Caspase 3) were significantly increased in the TG group, but they could be restored by adding Gly. Our results suggest that Gly can ameliorate ER stress and apoptosis in TG-exposed porcine oocytes and can further enhance the developmental potential of porcine oocytes in vitro.

Interplay Between Gut Microbiota and Amino Acid Metabolism in Heart Failure

Heart failure (HF) is a complex clinical syndrome of which the incidence is on the rise worldwide. Cardiometabolic disorders are associated with the deterioration of cardiac function and progression of HF. Recently, there has been renewed interest in gut microbiota (GM) and its metabolites in the cardiovascular disease. HF-caused hypoperfusion could increase intestinal permeability, and a “leaky” bowel leads to bacterial translocation and make its metabolites more easily enter the circulation. Considerable evidence shows that the composition of microbiota and amino acids (AAs) has been altered in HF patients, and AAs could serve as a diagnostic and prognostic biomarker in HF. The findings indicate that the gut–amino acid–HF axis may play a key role in the progression of HF. In this paper, we focus on the interrelationship between the AA metabolism and GM alterations during the development of heart failure. We also discuss the potential prognostic and therapeutic value of the gut–amino acid–HF axis in the cortex of HF.

Attenuation of clinical and immunological outcomes during SARS-CoV-2 infection by ivermectin

The devastating pandemic due to SARS-CoV-2 and the emergence of antigenic variants that jeopardize the efficacy of current vaccines create an urgent need for a comprehensive understanding of the pathophysiology of COVID-19, including the contribution of inflammation to disease. It also warrants for the search of immunomodulatory drugs that could improve disease outcome. Here, we show that standard doses of ivermectin (IVM), an anti-parasitic drug with potential immunomodulatory activities through the cholinergic anti-inflammatory pathway, prevent clinical deterioration, reduce olfactory deficit, and limit the inflammation of the upper and lower respiratory tracts in SARS-CoV-2-infected hamsters. Whereas it has no effect on viral load in the airways of infected animals, transcriptomic analyses of infected lungs reveal that IVM dampens type I interferon responses and modulates several other inflammatory pathways. In particular, IVM dramatically reduces the Il-6/Il-10 ratio in lung tissue and promotes macrophage M2 polarization, which might account for the more favorable clinical presentation of IVM-treated animals. Altogether, this study supports the use of immunomodulatory drugs such as IVM, to improve the clinical condition of SARS-CoV-2-infected patients.

Urinary Metabolomics Study of Patients with Bicuspid Aortic Valve Disease

Bicuspid aortic valve (BAV) is the most common congenital heart defect responsible for valvular and aortic complications in affected patients. Causes and mechanisms of this pathology are still elusive and thus the lack of early detection biomarkers leads to challenges in its diagnosis and prevention of associated cardiovascular anomalies. The aim of this study was to explore the potential use of urine Nuclear Magnetic Resonance (NMR) metabolomics to evaluate a molecular fingerprint of BAV. Both multivariate and univariate statistical analyses were performed to compare the urinary metabolome of 20 patients with BAV with that of 24 matched controls. Orthogonal partial least squared discriminant analysis (OPLS-DA) showed statistically significant discrimination between cases and controls, suggesting seven metabolites (3-hydroxybutyrate, alanine, betaine, creatine, glycine, hippurate, and taurine) as potential biomarkers. Among these, glycine, hippurate and taurine individually displayed medium sensitivity and specificity by receiver operating characteristic (ROC) analysis. Pathway analysis indicated two metabolic pathways likely perturbed in BAV subjects. Possible contributions of gut microbiota activity and energy imbalance are also discussed. These results constitute encouraging preliminary findings in favor of the use of urine-based metabolomics for early diagnosis of BAV.

Purinergic-Glycinergic Interaction in Neurodegenerative and Neuroinflammatory Disorders of the Retina

Neurodegenerative–neuroinflammatory disorders of the retina seriously hamper human vision. In searching for key factors that contribute to the development of these pathologies, we considered potential interactions among purinergic neuromodulation, glycinergic neurotransmission, and microglia activity in the retina. Energy deprivation at cellular levels is mainly due to impaired blood circulation leading to increased release of ATP and adenosine as well as glutamate and glycine. Interactions between these modulators and neurotransmitters are manifold. First, P2Y purinoceptor agonists facilitate reuptake of glycine by glycine transporter 1, while its inhibitors reduce reverse-mode operation; these events may lower extracellular glycine levels. The consequential changes in extracellular glycine concentration can lead to parallel changes in the activity of NR1/NR2B type NMDA receptors of which glycine is a mandatory agonist, and thereby may reduce neurodegenerative events in the retina. Second, P2Y purinoceptor agonists and glycine transporter 1 inhibitors may indirectly inhibit microglia activity by decreasing neuronal or glial glycine release in energy-compromised retina. These inhibitions may have a role in microglia activation, which is present during development and progression of neurodegenerative disorders such as glaucomatous and diabetic retinopathies and age-related macular degeneration or loss of retinal neurons caused by thromboembolic events. We have hypothesized that glycine transporter 1 inhibitors and P2Y purinoceptor agonists may have therapeutic importance in neurodegenerative–neuroinflammatory disorders of the retina by decreasing NR1/NR2B NMDA receptor activity and production and release of a series of proinflammatory cytokines from microglial cells.

Glycine ameliorates mitochondrial dysfunction caused by ABT-199 in porcine oocytes

Mitochondria play an important role in controlling oocyte developmental competence. Our previous studies showed that glycine (Gly) can regulate mitochondrial function and improve oocyte maturation in vitro. However, the mechanisms by which Gly affects mitochondrial function during oocyte maturation in vitro have not been fully investigated. In this study, we induced a mitochondrial damage model in oocytes with the Bcl-2-specific antagonist ABT-199. We investigated whether Gly could reverse the mitochondrial dysfunction caused by ABT-199 exposure and whether it is related to calcium regulation. Our results showed that ABT-199 inhibited cumulus expansion, decreased the oocyte maturation rate and the intracellular glutathione (GSH) level, caused mitochondrial dysfunction, which was confirmed by decreased mitochondrial membrane potential (ΔΨm) and the expression of mitochondrial function-related genes PGC-1α, and increased reactiveoxygenspecies (ROS) levelsand the expression of apoptosis-associated genes Bax, Caspase-3, and Cyto C.More importantly, ABT-199-treated oocytes showed an increase in the intracellular free calcium concentration ([Ca2+]i) and had impaired cortical type 1 inositol 1,4,5-trisphosphate receptors (IP3R1) distribution. Nevertheless, treatment with Gly significantly ameliorated mitochondrial dysfunction, oxidative stress, and apoptosis, and Gly also regulated [Ca2+]i levels and IP3R1 cellular distribution, which further protects oocyte maturation in ABT-199-induced porcine oocytes.Taken together, our results indicate that Gly has a protective action against ABT-199-induced mitochondrial dysfunction in porcine oocytes.

Glycine regulates mucosal immunity and the intestinal microbial composition in weaned piglets

Glycine is an amino acid with a diverse array of health benefits regarding metabolism, immunity, and development. The aim of this study was to test the hypothesis that glycine supplementation alters the intestinal microbial composition and improves the intestinal mucosal immunity of weaned piglets. One hundred and twenty-eight weaned piglets divided into 4 groups were fed with a corn- and soybean meal-based diet supplemented with 0 (control), 0.5, 1, or 2% glycine for 7 days. The intestinal microbiota and tissue samples from the control and the 2% glycine-supplemented piglets were collected for determination of the composition of microbial community and the intestinal mucosal barrier function. Piglets fed with diet containing 2% glycine, instead of 0.5% or 1% glycine, presented elevated average daily gain and feed conversion ratio, as compared with the control. 2% glycine enhanced the abundance of mucins in the jejunum and ileum and mRNA level of porcine β-defensin (pBD) 2 and pBD-3, as well as the protein level of secretory immunoglobulin A (sIgA) in the jejunum. The mRNA expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, and the protein level of phosphorylated p38 mitogen-activated protein kinase (MAPK), signal transducer and activator of transcription 3 (STAT3), nuclear factor (NF)-κB p65, and claudin-2 in the jejunum were lower in the 2% glycine group than that in the control. In addition, an elevated ratio of CD4+/CD8+ T lymphocytes was observed in the jejunum of piglets receiving diet supplemented with 2% glycine. The colon content of piglets fed with 2% glycine exhibited a reduction in abundance of pathogenic bacteria (Escherichia-Shigella, Clostridium, and Burkholderiales) and an increase in short-chain fatty acid-producing bacteria (Blautia, Lachnospiraceae, Anaerostipes, and Prevotella) in comparison with the control. We conclude that dietary supplementation with 2% glycine improves the intestinal immunological barrier function and the microbial composition, therefore, contributing to the growth performance of weaned piglets.

Synergistic Effect of β-alanine and Aprotinin on Mesenteric Ischemia

BACKGROUND

Acute mesenteric ischemia arises through sudden interruption of mesenteric blood flow, mostly due to an occlusion of the superior mesenteric artery and is associated with a high mortality of approximately 50% to 90%. In previous studies, the single application of β-alanine or aprotinin caused an ameliorated intestinal damage but without any systemic effects.

METHODS

To analyze the combined effect of β-alanine and aprotinin on acute ischemia and reperfusion of the small intestine, a model with anesthetized rats was used. Ischemia and reperfusion were initiated by occluding and reopening the superior mesenteric artery. After 120 min of ischemia and 180 min of reperfusion, the intestine was analyzed for tissue damage, the activity of the saccharase, and accumulation of granulocytes. In addition, systemic and metabolic as well as inflammatory parameters were measured in blood at certain points in time.

RESULTS

The combination of β-alanine and aprotinin resulted in a clearly stabilized mean arterial blood pressure and blood glucose level during the reperfusion period. Furthermore, the combined administration resulted in significantly reduced tissue damage parameters, cytokine and cell-free hemoglobin concentrations in blood plasma. In addition, the damage to the small intestine was significantly attenuated, so that the animals ultimately survived the entire test period because of the administration of both substances.

CONCLUSIONS

Overall, the simultaneous application of both substances leads to a synergistic protection without the occurrence of undesirable side effects. The combined usage of β-alanine and aprotinin can be seen as a promising approach to inhibit the onset of acute mesenteric ischemia.

Identification of Urine Metabolic Biomarkers for Vogt-Koyanagi-Harada Disease

The diagnosis of Vogt-Koyanagi-Harada (VKH) disease is mainly based on a complex clinical manifestation while it lacks objective laboratory biomarkers. To explore the potential molecular biomarkers for diagnosis and disease activity in VKH, we performed an untargeted urine metabolomics analysis by ultra-high-performance liquid chromatography equipped with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS). Through univariate and multivariate statistical analysis, we found 9 differential metabolites when comparing VKH patients with healthy controls, and 26 differential metabolites were identified when comparing active VKH patients with inactive VKH patients. Pathway enrichment analysis showed that glycine, serine and threonine metabolism, and arginine and proline metabolism were significantly altered in VKH versus healthy controls. Lysine degradation and biotin metabolism pathways were significantly altered in active VKH versus inactive VKH. Furthermore, the receiver operating characteristic (ROC) curve analysis revealed that the combination of acetylglycine and gamma-glutamylalanine could differentiate VKH from healthy controls with an area under the curve (AUC) of 0.808. A combination of ureidopropionic acid and 5′-phosphoribosyl-5-amino-4-imidazolecarboxamide (AICAR) had an excellent AUC of 0.958 for distinguishing active VKH from inactive VKH. In summary, this study identified abnormal metabolites in urine of patients with VKH disease. Further studies are needed to confirm whether these metabolites are specific for this disease.

The Effects of Dietary Glycine on the Acetic Acid-Induced Mouse Model of Colitis

Inflammatory bowel disease, a gut disease that is prevalent worldwide, is characterized by chronic intestinal inflammation, such as colitis, and disorder of the gut microbiome. Glycine (Gly) is the simplest amino acid and functions as an anti-inflammatory immune-nutrient and intestinal microbiota regulator. This study aimed at investigating the effect of Gly on colitis induced in mice by intrarectal administration of 5% acetic acid (AA). Bodyweight and survival rates were monitored, and colonic length and weight, serum amino acid concentrations, intestinal inflammation-related gene expression, and colonic microbiota abundances were analyzed. The results showed that Gly dietary supplementation had no effect on the survival rate or the ratio of colonic length to weight. However, Gly supplementation reversed the AA-induced increase in serum concentrations of amino acids such as glutamate, leucine, isoleucine, and valine. Furthermore, Gly inhibited colonic gene expression of interleukin- (IL-) 1β and promoted IL-10 expression in colitis mice. Gly supplementation also reversed the AA-induced reduction in the abundance of bacteria such as Clostridia, Ruminococcaceae, and Clostridiales. This change in the intestinal microbiota was possibly attributable to the changes in colonic IL-10 expression and serum concentrations of valine and leucine. In sum, Gly supplementation regulated the serum concentrations of amino acids, the levels of colonic immune-associated gene expression, and the intestinal microbiota in a mouse model of colitis. These findings enhance our understanding of the role of Gly in regulating metabolism, intestinal immunity, and the gut microbiota in animals afflicted with colitis.

A novel Approach for Non-Invasive Lung Imaging and Targeting Lung Immune Cells

Despite developments in pulmonary radiotherapy, radiation-induced lung toxicity remains a problem. More sensitive lung imaging able to increase the accuracy of diagnosis and radiotherapy may help reduce this problem. Super-paramagnetic iron oxide nanoparticles are used in imaging, but without further modification can cause unwanted toxicity and inflammation. Complex carbohydrate and polymer-based coatings have been used, but simpler compounds may provide additional benefits. Herein, we designed and generated super-paramagnetic iron oxide nanoparticles coated with the neutral natural dietary amino acid glycine (GSPIONs), to support non-invasive lung imaging and determined particle biodistribution, as well as understanding the impact of the interaction of these nanoparticles with lung immune cells. These GSPIONs were characterized to be crystalline, colloidally stable, with a size of 12 ± 5 nm and a hydrodynamic diameter of 84.19 ± 18 nm. Carbon, Hydrogen, Nitrogen (CHN) elemental analysis estimated approximately 20.2 × 10³ glycine molecules present per nanoparticle. We demonstrated that it is possible to determine the biodistribution of the GSPIONs in the lung using three-dimensional (3D) ultra-short echo time magnetic resonance imaging. The GSPIONs were found to be taken up selectively by alveolar macrophages and neutrophils in the lung. In addition, the GSPIONs did not cause changes to airway resistance or induce inflammatory cytokines. Alveolar macrophages and neutrophils are critical regulators of pulmonary inflammatory diseases, including allergies, infections, asthma and chronic obstructive pulmonary disease (COPD). Therefore, pulmonary Magnetic Resonance (MR) imaging and preferential targeting of these lung resident cells by our nanoparticles offer precise imaging tools, which can be utilized to develop precision targeted radiotherapy as well as diagnostic tools for lung cancer, thereby having the potential to reduce the pulmonary complications of radiation.

Assessing the causal association of glycine with risk of cardio-metabolic diseases

Circulating levels of glycine have previously been associated with lower incidence of coronary heart disease (CHD) and type 2 diabetes (T2D) but it remains uncertain if glycine plays an aetiological role. We present a meta-analysis of genome-wide association studies for glycine in 80,003 participants and investigate the causality and potential mechanisms of the association between glycine and cardio-metabolic diseases using genetic approaches. We identify 27 genetic loci, of which 22 have not previously been reported for glycine. We show that glycine is genetically associated with lower CHD risk and find that this may be partly driven by blood pressure. Evidence for a genetic association of glycine with T2D is weaker, but we find a strong inverse genetic effect of hyperinsulinaemia on glycine. Our findings strengthen evidence for a protective effect of glycine on CHD and show that the glycine-T2D association may be driven by a glycine-lowering effect of insulin resistance.

Beta-Aminoisobutyric Acid as a Novel Regulator of Carbohydrate and Lipid Metabolism

The prevalence and incidence of metabolic syndrome is reaching pandemic proportions worldwide, thus warranting an intensive search for novel preventive and treatment strategies. Recent studies have identified a number of soluble factors secreted by adipocytes and myocytes (adipo-/myokines), which link sedentary life style, abdominal obesity, and impairments in carbohydrate and lipid metabolism. In this review, we discuss the metabolic roles of the recently discovered myokine β-aminoisobutyric acid (BAIBA), which is produced by skeletal muscle during physical activity. In addition to physical activity, the circulating levels of BAIBA are controlled by the mitochondrial enzyme alanine: glyoxylate aminotransferase 2 (AGXT2), which is primarily expressed in the liver and kidneys. Recent studies have shown that BAIBA can protect from diet-induced obesity in animal models. It induces transition of white adipose tissue to a "beige" phenotype, which induces fatty acids oxidation and increases insulin sensitivity. While the exact mechanisms of BAIBA-induced metabolic effects are still not well understood, we discuss some of the proposed pathways. The reviewed data provide new insights into the connection between physical activity and energy metabolism and suggest that BAIBA might be a potential novel drug for treatment of the metabolic syndrome and its cardiovascular complications.

Glycine Protects against Hypoxic-Ischemic Brain Injury by Regulating Mitochondria-Mediated Autophagy via the AMPK Pathway

Hypoxic-ischemic encephalopathy (HIE) is detrimental to newborns and is associated with high mortality and poor prognosis. Thus, the primary aim of the present study was to determine whether glycine could (1) attenuate HIE injury in rats and hypoxic stress in PC12 cells and (2) downregulate mitochondria-mediated autophagy dependent on the adenosine monophosphate- (AMP-) activated protein kinase (AMPK) pathway. Experiments conducted using an in vivo HIE animal model and in vitro hypoxic stress to PC12 cells revealed that intense autophagy associated with mitochondrial function occurred during in vivo HIE injury and in vitro hypoxic stress. However, glycine treatment effectively attenuated mitochondria-mediated autophagy. Additionally, after identifying alterations in proteins within the AMPK pathway in rats and PC12 cells following glycine treatment, cyclosporin A (CsA) and 5-aminoimidazole-4-carboxamide-1-b-4-ribofuranoside (AICAR) were administered in these models and indicated that glycine protected against HIE and CoCl₂ injury by downregulating mitochondria-mediated autophagy that was dependent on the AMPK pathway. Overall, glycine attenuated hypoxic-ischemic injury in neurons via reductions in mitochondria-mediated autophagy through the AMPK pathway both in vitro and in vivo.

Autocatalytic cycle in the pathogenesis of diabetes mellitus: biochemical and pathophysiological aspects of metabolic therapy with natural amino acids on the example of glycine

In this work systematization (classification) of biochemical and physiological processes that cause disorders in the human body during the development of diabetes mellitus is carried out. The development of the disease is considered as the interaction and mutual reinforcement of two groups of parallel processes. The first group has a molecular nature and it is associated with impairment of ROS-regulation system which includes NADPH oxidases, RAGE receptors, mitochondria, cellular peroxireductase system and the immune system. The second group has a pathophysiological nature and it is associated with impairment of microcirculation and liver metabolism. The analysis of diabetes biochemistry based on different published references yields a creation of a block diagram evaluating the disease development over time. Two types of autocatalytic processes were identified: autocatalysis in the cascade of biochemical reactions and "cross-section" catalysis, in which biochemical and pathophysiological processes reinforce each other. The developed model has shown the possibility of using pharmacologically active natural metabolite glycine as a medicine inhibiting the development of diabetes. Despite the fact that glycine is a substitute amino acid the drop in the glycine blood concentration occurs even in the early stages of diabetes development and can aggravate the disease. It is shown that glycine is a potential blocker of key autocatalytic cycles, including biochemical and pathophysiological processes. The analysis of the glycine action based on the developed model is in complete agreement with the results of clinical trials in which glycine has improved blood biochemistry of diabetic patients and thereby it prevents the development of diabetic complications.

Oral exposure to the free amino acid glycine inhibits the acute allergic response in a model of cow's milk allergy in mice

The conditionally essential amino acid glycine functions as inhibitory neurotransmitter in the mammalian central nervous system. Moreover, it has been shown to act as an anti-inflammatory compound in animal models of ischemic perfusion, post-operative inflammation, periodontal disease, arthritis and obesity. Glycine acts by binding to a glycine-gated chloride channel, which has been demonstrated on neurons and immune cells, including macrophages, polymorphonuclear neutrophils and lymphocytes. The present study aims to evaluate the effect of glycine on allergy development in a cow's milk allergy model. To this end, C3H/HeOuJ female mice were supplemented with glycine by oral gavage (50 or 100 mg/mouse) 4 hours prior to sensitization with cow's milk whey protein, using cholera toxin as adjuvant. Acute allergic skin responses and anaphylaxis were assessed after intradermal allergen challenge in the ears. Mouse mast cell protease-1 (mMCP-1) and whey specific IgE levels were detected in blood collected 30 minutes after an oral allergen challenge. Jejunum was dissected and evaluated for the presence of mMCP-1-positive cells by immunohistochemistry. Intake of glycine significantly inhibited allergy development in a concentration dependent manner as indicated by a reduction in; acute allergic skin response, anaphylaxis, serum mMCP-1 and serum levels of whey specific IgE. In addition, in-vitro experiments using rat basophilic leukemia cells (RBL), showed that free glycine inhibited cytokine release but not cellular degranulation. These findings support the hypothesis that the onset of cow's milk allergy is prevented by the oral intake of the amino acid glycine. An adequate intake of glycine might be important in the improvement of tolerance against whey allergy or protection against (whey-induced) allergy development.

Confirmation of GLRA3 as a susceptibility locus for albuminuria in Finnish patients with type 1 diabetes

Urinary albumin excretion is an early sign of diabetic kidney disease, affecting every third individual with diabetes. Despite substantial estimated heritability, only variants in the GLRA3 gene have been genome-wide significantly associated (p-value < 5 × 10⁻⁸) with diabetic albuminuria, in Finnish individuals with type 1 diabetes; However, replication attempt in non-Finnish Europeans with type 1 diabetes showed nominally significant association in the opposite direction, suggesting a population-specific effect, but simultaneously leaving the finding controversial. In this study, the association between the common rs10011025 variant in the GLRA3 locus, and albuminuria, was confirmed in 1259 independent Finnish individuals with type 1 diabetes (p = 0.0013), and meta-analysis of all Finnish individuals yielded a genome-wide significant association. The association was particularly pronounced in subjects not reaching the treatment target for blood glucose levels (HbA_1c > 7%; N = 2560, p = 1.7 × 10⁻⁹). Even though further studies are needed to pinpoint the causal variants, dissecting the association at the GLRA3 locus may uncover novel molecular mechanisms for diabetic albuminuria irrespective of population background.

Glycine Transporter-1 and glycine receptor mediate the antioxidant effect of glycine in diabetic rat islets and INS-1 cells

Oxidative stress is the main inducer of β-cell damage, which underlies the pathogenesis of diabetes. Evidence suggests that glycine, a recognized antioxidant, may improve β-cell function; however, its mechanism in protecting diabetic β-cells against oxidative stress has not been directly investigated. Using a streptozotocin-induced diabetic rat model and INS-1 pancreatic β-cells, we evaluated whether glycine can attenuate diabetic β-cell damage induced by oxidative stress. In diabetic rats, glycine stimulated insulin secretion; enhanced plasma glutathione (GSH), catalase and superoxide dismutase levels; reduced plasma 8-hydroxy-2 deoxyguanosine and islet p22^phox levels; and improved islet β-cell mitochondrial degeneration and insulin granule degranulation. In INS-1 cells, glycine reduced the intracellular reactive oxygen species (ROS) concentration and inhibited apoptosis induced by high glucose or H₂O₂. Glycine transporter-1 inhibitor blocked the antioxidative effect of glycine by reducing the intracellular GSH content, and glycine receptor inhibitor reversed the glycine antioxidative effect by blocking p22^phox. Collectively, our findings reveal a mechanism by which glycine protects diabetic β-cells against damage caused by oxidative stress by increasing glycine transporter-1-mediated synthesis of GSH and by reducing glycine receptor-mediated ROS production.

Serum Metabolomic Profiling of All-Cause Mortality: A Prospective Analysis in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study Cohort

Tobacco use, hypertension, hyperglycemia, overweight, and inactivity are leading causes of overall and cardiovascular disease (CVD) mortality worldwide, yet the relevant metabolic alterations responsible are largely unknown. We conducted a serum metabolomic analysis of 620 men in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (1985-2013). During 28 years of follow-up, there were 435 deaths (197 CVD and 107 cancer). The analysis included 406 known metabolites measured with ultra-high-performance liquid chromatography/mass spectrometry-gas chromatography/mass spectrometry. We used Cox regression to estimate mortality hazard ratios for a 1-standard-deviation difference in metabolite signals. The strongest associations with overall mortality were N-acetylvaline (hazard ratio (HR) = 1.28; P < 4.1 × 10-5, below Bonferroni statistical threshold) and dimethylglycine, 7-methylguanine, C-glycosyltryptophan, taurocholate, and N-acetyltryptophan (1.23 ≤ HR ≤ 1.32; 5 × 10-5 ≤ P ≤ 1 × 10-4). C-Glycosyltryptophan, 7-methylguanine, and 4-androsten-3β,17β-diol disulfate were statistically significantly associated with CVD mortality (1.49 ≤ HR ≤ 1.62, P < 4.1 × 10-5). No metabolite was associated with cancer mortality, at a false discovery rate of <0.1. Individuals with a 1-standard-deviation higher metabolite risk score had increased all-cause and CVD mortality in the test set (HR = 1.4, P = 0.05; HR = 1.8, P = 0.003, respectively). The several serum metabolites and their composite risk score independently associated with all-cause and CVD mortality may provide potential leads regarding the molecular basis of mortality.

Role of Neurochemicals in the Interaction between the Microbiota and the Immune and the Nervous System of the Host Organism

This work is concerned with the role of evolutionary conserved substances, neurotransmitters, and neurohormones, within the complex framework of the microbial consortium-immune system-nervous system axis in the human or animal organism. Although the operation of each of these systems per se is relatively well understood, their combined effects on the host organism still await further research. Drawing on recent research on host-produced and microbial low-molecular-weight neurochemicals such as biogenic amines, amino acids, and short-chain fatty acids (SCFAs), we suggest that these mediators form a part of a universal neurochemical "language." It mediates the whole gamut of harmonious and disharmonious interactions between (a) the intestinal microbial consortium, (b) local and systemic immune cells, and (c) the central and peripheral nervous system. Importantly, the ongoing microbiota-host interactivity is bidirectional. We present evidence that a large number of microbially produced low-molecular-weight compounds are identical or homologous to mediators that are synthesized by immune or nervous cells and, therefore, can bind to the corresponding host receptors. In addition, microbial cells specifically respond to host-produced neuromediators/neurohormones because they have adapted to them during the course of many millions of years of microbiota-host coevolution. We emphasize that the terms "microbiota" and "microbial consortium" are to be used in the broadest sense, so as to include, apart from bacteria, also eukaryotic microorganisms. These are exemplified by the mycobiota whose role in the microbial consortium-immune system-nervous system axis researchers are only beginning to elucidate. In light of the above, it is imperative to reform the current strategies of using probiotic microorganisms and their metabolites for treating and preventing dysbiosis-related diseases. The review demonstrates, in the example of novel probiotics (psychobiotics), that many target-oriented probiotic preparations produce important side effects on a wide variety of processes in the host organism. In particular, we should take into account probiotics' capacity to produce mediators that can considerably modify the operation of the microecological, immune, and nervous system of the human organism.

Genome-wide association study identifies loci associated with milk leukocyte phenotypes following experimental challenge with Streptococcus uberis

Mastitis is a detrimental disease in the dairy industry that decreases milk quality and costs upwards of $2 billion annually. Often, mastitis results from bacteria entering the gland through the teat opening. Streptococcus uberis is responsible for a high percentage of subclinical and clinical mastitis. Following an intramammary experimental challenge with S. uberis on Holstein cows (n = 40), milk samples were collected and somatic cell counts (SCC) were determined by the Dairy Herd Improvement Association Laboratory. Traditional genome-wide association studies (GWAS) have utilized test day SCC or SCC lactation averages to identify loci of interest. Our approach utilizes SCC collected following a S. uberis experimental challenge to generate three novel phenotypes: (1) area under the curve (AUC) of SCC for 0-7 days and (2) 0-28 days post-challenge; and (3) when SCC returned to below 200,000 cells/mL post-challenge (< 21 days, 21-28 days, or > 28 days). Polymorphisms were identified using Illumina's BovineSNP50 v2 DNA BeadChip. Associations were tested using Plink software and identified 16 significant (p < 1.0 × 10^-4) single-nucleotide polymorphisms (SNPs) across the phenotypes. Most significant SNPs were in genes linked to cell signaling, migration, and apoptosis. Several have been recognized in relation to infectious processes (ATF7, SGK1, and PACRG), but others less so (TRIO, GLRA1, CELSR2, TIAM2, CPE). Further investigation of these genes and their roles in inflammation (e.g., SCC) can provide potential targets that influence resolution of mammary gland infection. Likewise, further investigation of the identified SNP with mastitis and other disease phenotypes can provide greater insight to the potential of these SNP as genetic markers.

Cucumis sativus Aqueous Fraction Inhibits Angiotensin II-Induced Inflammation and Oxidative Stress In Vitro

Inflammation and oxidative stress play major roles in endothelial dysfunction, and are key factors in the progression of cardiovascular diseases. The aim of this study was to evaluate in vitro the effect of three subfractions (SFs) from the Cucumis sativus aqueous fraction to reduce inflammatory factors and oxidative stress induced by angiotensin II (Ang II) in human microvascular endothelial cells-1 (HMEC-1) cells. The cells were cultured with different concentrations of Ang II and 0.08 or 10 μg/mL of SF1, SF2, or SF3, or 10 μmol of losartan as a control. IL-6 (Interleukin 6) concentration was quantified. To identify the most effective SF combinations, HMEC-1 cells were cultured as described above in the presence of four combinations of SF1 and SF3. Then, the effects of the most effective combination on the expression of adhesion molecules, the production of reactive oxygen species (ROS), and the bioavailability of nitric oxide (NO) were evaluated. Finally, a mass spectrometry analysis was performed. Both SF1 and SF3 subfractions decreased the induction of IL-6 by Ang II, and C4 (SF1 and SF3, 10 μg/mL each) was the most effective combination to inhibit the production of IL-6. Additionally, C4 prevented the expression of adhesion molecules, reduced the production of ROS, and increased the bioavailability of NO. Glycine, arginine, asparagine, lysine, and aspartic acid were the main components of both subfractions. These results demonstrate that C4 has anti-inflammatory and antioxidant effects.

Ion channel signaling influences cellular proliferation and phagocyte activity during axolotl tail regeneration

Little is known about the potential for ion channels to regulate cellular behaviors during tissue regeneration. Here, we utilized an amphibian tail regeneration assay coupled with a chemical genetic screen to identify ion channel antagonists that altered critical cellular processes during regeneration. Inhibition of multiple ion channels either partially (anoctamin1/Tmem16a, anoctamin2/Tmem16b, KV2.1, KV2.2, L-type CaV channels and H/K ATPases) or completely (GlyR, GABAAR, KV1.5 and SERCA pumps) inhibited tail regeneration. Partial inhibition of tail regeneration by blocking the calcium activated chloride channels, anoctamin1&2, was associated with a reduction of cellular proliferation in tail muscle and mesenchymal regions. Inhibition of anoctamin 1/2 also altered the post-amputation transcriptional response of p44/42 MAPK signaling pathway genes, including decreased expression of erk1/erk2. We also found that complete inhibition via voltage gated K+ channel blockade was associated with diminished phagocyte recruitment to the amputation site. The identification of H+ pumps as required for axolotl tail regeneration supports findings in Xenopus and Planaria models, and more generally, the conservation of ion channels as regulators of tissue regeneration. This study provides a preliminary framework for an in-depth investigation of the mechanistic role of ion channels and their potential involvement in regulating cellular proliferation and other processes essential to wound healing, appendage regeneration, and tissue repair.

Impaired "Glycine"-mia in Type 2 Diabetes and Potential Mechanisms Contributing to Glucose Homeostasis

The onset and/or progression of type 2 diabetes (T2D) can be prevented if intervention is early enough. As such, much effort has been placed on the search for indicators predictive of prediabetes and disease onset or progression. An increasing body of evidence suggests that changes in plasma glycine may be one such biomarker. Circulating glycine levels are consistently low in patients with T2D. Levels of this nonessential amino acid correlate negatively with obesity and insulin resistance. Plasma glycine correlates positively with glucose disposal, and rises with interventions such as exercise and bariatric surgery that improve glucose homeostasis. A role for glycine in the regulation of glucose, beyond being a potential biomarker, is less clear, however. Dietary glycine supplementation increases insulin, reduces systemic inflammation, and improves glucose tolerance. Emerging evidence suggests that glycine, a neurotransmitter, also acts directly on target tissues that include the endocrine pancreas and the brain via glycine receptors and as a coligand for N-methyl-d-aspartate glutamate receptors to control insulin secretion and liver glucose output, respectively. Here, we review the current evidence supporting a role for glycine in glucose homeostasis via its central and peripheral actions and changes that occur in T2D.

Amelioration by glycine of brain damage in neonatal rat brain following hypoxia-ischemia

BACKGROUND

Glycine protected adult brains against injury in an experimental model of stroke, but, because the ischemic response of neonatal brains differs from that of adult brains, we examined the neuroprotective efficacy of glycine and associated mechanisms in an experimental model of neonatal hypoxic-ischemic (HI) encephalopathy.

METHODS

Neonatal (postnatal day 7) Wistar rats were randomly divided into an untreated group (non-HI) and two HI groups that were treated with left common carotid artery ligation and saline control or glycine. After recovery, pups that received surgery were injected i.p. with saline or glycine (800 mg/kg; optimal dose determined in pilot experiments) and were placed in a controlled 8% O₂ chamber for 120 min. Brains were harvested at various times after return to normoxia (several hours-days after HI) for analysis of infarct area, glial activation, cell apoptosis, and tumor necrosis factor-α (TNF-α) expression on histology and reverse transcription-polymerase chain reaction.

RESULTS

Glycine injections induced large (approx. 15-fold) but brief (approx. 2 h) increases in cerebrospinal fluid concentrations. In particular, the glycine group had a >70% decrease in infarct areas compared with controls at 7 days after HI. Glycine also significantly reduced astrocyte reactive transformation, microglia activation, and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive (apoptotic) cell numbers in peri-lesional areas at 3 days after HI, and TNF-α mRNA expression in the injured hemisphere at 12 and 24 h after HI.

CONCLUSION

Glycine protected neonatal rat brains against HI, in part by inhibiting TNF-α-induced inflammation and gliosis. Hence, systemic glycine infusions may have clinical utility for the treatment of HI injury in human newborns.

Attenuation of intestinal ischemia-reperfusion-injury by β-alanine: a potentially glycine-receptor mediated effect

BACKGROUND

Acute mesenteric ischemia is often caused by embolization of the mesenteric arterial circulation. Coherent intestinal injury due to ischemia and following reperfusion get visible on macroscopic and histologic level. In previous studies, application of glycine caused an ameliorated intestinal damage after ischemia-reperfusion in rats. Because we speculated that glycine acted here as a signal molecule, we investigated whether the glycine-receptor agonist β-alanine evokes the same beneficial effect in intestinal ischemia-reperfusion.

MATERIALS AND METHODS

β-alanine (10, 30, and 100 mg/kg) was administered intravenously. Ischemia/reperfusion of the small intestine was initiated by occluding and reopening the superior mesenteric artery in rats. After 90 min of ischemia and 120 min of reperfusion, the intestine was analyzed with regard to macroscopic and histologic tissue damage, the activity of the saccharase, and accumulation of macrophages. In addition, systemic parameters and metabolic ones (e.g., acid-base balance, electrolytes, and blood glucose) were measured at certain points in time.

RESULTS

All three dosages of β-alanine did not change systemic parameters but prevent from hyponatremia during the period of reperfusion. Most importantly, application of 100-mg β-alanine clearly diminished intestinal tissue damage, getting visible on macroscopic and histologic level. In addition, I/R-mediated decrease of saccharase activity and accumulation of macrophages in the small intestine were ameliorated.

CONCLUSIONS

The present study demonstrated that β-alanine was a potent agent to ameliorate I/R-induced injury of the small intestine. Due to its diminishing effect on the accumulation of macrophages, β-alanine is strongly expected to mediate its beneficial effect via glycine receptors.

The Intracellular Loop of the Glycine Receptor: It's not all about the Size

The family of Cys-loop receptors (CLRs) shares a high degree of homology and sequence identity. The overall structural elements are highly conserved with a large extracellular domain (ECD) harboring an α-helix and 10 β-sheets. Following the ECD, four transmembrane domains (TMD) are connected by intracellular and extracellular loop structures. Except the TM3–4 loop, their length comprises 7–14 residues. The TM3–4 loop forms the largest part of the intracellular domain (ICD) and exhibits the most variable region between all CLRs. The ICD is defined by the TM3–4 loop together with the TM1–2 loop preceding the ion channel pore. During the last decade, crystallization approaches were successful for some members of the CLR family. To allow crystallization, the intracellular loop was in most structures replaced by a short linker present in prokaryotic CLRs. Therefore, no structural information about the large TM3–4 loop of CLRs including the glycine receptors (GlyRs) is available except for some basic stretches close to TM3 and TM4. The intracellular loop has been intensively studied with regard to functional aspects including desensitization, modulation of channel physiology by pharmacological substances, posttranslational modifications, and motifs important for trafficking. Furthermore, the ICD interacts with scaffold proteins enabling inhibitory synapse formation. This review focuses on attempts to define structural and functional elements within the ICD of GlyRs discussed with the background of protein-protein interactions and functional channel formation in the absence of the TM3–4 loop.

Maturation and electrophysiological properties of human pluripotent stem cell-derived oligodendrocytes

Rodent‐based studies have shown that the membrane properties of oligodendrocytes play prominent roles in their physiology and shift markedly during their maturation from the oligodendrocyte precursor cell (OPC) stage. However, the conservation of these properties and maturation processes in human oligodendrocytes remains unknown, despite their dysfunction being implicated in human neurodegenerative diseases such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Here, we have defined the membrane properties of human oligodendrocytes derived from pluripotent stem cells as they mature from the OPC stage, and have identified strong conservation of maturation‐specific physiological characteristics reported in rodent systems. We find that as human oligodendrocytes develop and express maturation markers, they exhibit a progressive decrease in voltage‐gated sodium and potassium channels and a loss of tetrodotoxin‐sensitive spiking activity. Concomitant with this is an increase in inwardly rectifying potassium channel activity, as well as a characteristic switch in AMPA receptor composition. All these steps mirror the developmental trajectory observed in rodent systems. Oligodendrocytes derived from mutant C9ORF72‐carryng ALS patient induced pluripotent stem cells did not exhibit impairment to maturation and maintain viability with respect to control lines despite the presence of RNA foci, suggesting that maturation defects may not be a primary feature of this mutation. Thus, we have established that the development of human oligodendroglia membrane properties closely resemble those found in rodent cells and have generated a platform to enable the impact of human neurodegenerative disease‐causing mutations on oligodendrocyte maturation to be studied. Stem Cells2016;34:1040–1053

Principles of targeting endothelial cell metabolism to treat angiogenesis and endothelial cell dysfunction in disease

The endothelium is the orchestral conductor of blood vessel function. Pathological blood vessel formation (a process termed pathological angiogenesis) or the inability of endothelial cells (ECs) to perform their physiological function (a condition known as EC dysfunction) are defining features of various diseases. Therapeutic intervention to inhibit aberrant angiogenesis or ameliorate EC dysfunction could be beneficial in diseases such as cancer and cardiovascular disease, respectively, but current strategies have limited efficacy. Based on recent findings that pathological angiogenesis and EC dysfunction are accompanied by EC-specific metabolic alterations, targeting EC metabolism is emerging as a novel therapeutic strategy. Here, we review recent progress in our understanding of how EC metabolism is altered in disease and discuss potential metabolic targets and strategies to reverse EC dysfunction and inhibit pathological angiogenesis.

Vascular endothelial function is improved by oral glycine treatment in aged rats

Glycine has been used to reduce oxidative stress and proinflammatory mediators in some metabolic disorders; however, its effect on the vasculature has been poorly studied. The aim of this work was to explore the effect of glycine on endothelial dysfunction in aged rats. Aortic rings with intact or denuded endothelium were obtained from untreated or glycine-treated male Sprague-Dawley rats at 5 and 15 months of age. Concentration-response curves to phenylephrine (PHE) were obtained from aortic rings incubated with N(G)-nitro-l-arginine methyl ester (l-NAME), superoxide dismutase (SOD), indomethacin, SC-560, and NS-398. Aortic mRNA expression of endothelial nitric oxide synthase (eNOS), NADPH oxidase 4 (NOX-4), cyclooxygenase 1 (COX-1), cyclooxygenase 2 (COX-2), tumour necrosis factor (TNF)-α, and interleukin-1 β was measured by real time RT-PCR. The endothelial modulation of the contraction by PHE was decreased in aortic rings from aged rats. Glycine treatment improved this modulator effect and increased relaxation to acetylcholine. Glycine augmented the sensitivity for PHE in the presence of l-NAME and SOD. It also reduced the contraction by incubation with indomethacin, SC-560, and NS-398. Glycine increased the mRNA expression of eNOS and decreased the expression of COX-2 and TNF-α. Glycine improved the endothelium function in aged rats possibly by enhancing eNOS expression and reducing the role of superoxide anion and contractile prostanoids that increase the nitric oxide bioavailability.

Combining two repurposed drugs as a promising approach for Alzheimer's disease therapy

Alzheimer disease (AD) represents a major medical problem where mono-therapeutic interventions demonstrated only a limited efficacy so far. We explored the possibility of developing a combinational therapy that might prevent the degradation of neuronal and endothelial structures in this disease. We argued that the distorted balance between excitatory (glutamate) and inhibitory (GABA/glycine) systems constitutes a therapeutic target for such intervention. We found that a combination of two approved drugs – acamprosate and baclofen – synergistically protected neurons and endothelial structures in vitro against amyloid-beta (Aβ) oligomers. The neuroprotective effects of these drugs were mediated by modulation of targets in GABA/glycinergic and glutamatergic pathways. In vivo, the combination alleviated cognitive deficits in the acute Aβ_25–35 peptide injection model and in the mouse mutant APP transgenic model. Several patterns altered in AD were also synergistically normalised. Our results open up the possibility for a promising therapeutic approach for AD by combining repurposed drugs.

Glycine selectively reduces intestinal injury during endotoxemia

BACKGROUND

Glycine is well known to protect the intestine against ischemia-reperfusion injury and during mechanical manipulation. Here, we studied whether glycine protects the small intestine during endotoxemia, even without being the site of the infection.

MATERIALS AND METHODS

Lipopolysaccharide (LPS) was infused at a rate of 1 mg/kg × h over a period of 7 h (subacute endotoxemia) in male Wistar rats. Glycine (single dose: 50 mg/kg × 15 min) was applied intravenously at 180 and 270 min after the beginning of the LPS infusion. Systemic parameters were periodically determined. The small intestine was analyzed for macroscopic (hemorrhages) and histopathologic changes (hematoxylin and eosin staining), and markers of inflammation (myeloperoxidase activity).

RESULTS

Glycine neither decreased mortality nor beneficially affected vital parameters (e.g., mean arterial blood pressure and breathing rate), electrolytes, blood gases including pH and base excess, and plasma parameters of tissue injury such as lactate concentration, hemolysis, and aminotransferases activities during experimental endotoxemia. It, however, specifically diminished the LPS-induced small intestinal injury, as indicated by less intestinal accumulation of blood, less intestinal hemorrhages, and reduced intestinal hemoglobin content.

CONCLUSIONS

The present results demonstrate that glycine selectively protects the small intestine during subacute endotoxemia, even after manifestation of a severe systemic impairment. Because glycine is non-toxic at low doses, an administration of a moderate glycine dose (50-100 mg/kg) may be suitable to protect from intestinal damage during sepsis. Its true clinical potential, however, needs to be verified in further experimental studies and clinical trials.