Verification studies of tryptophan and kynurenine determination using HPLC and evaluation of the kynurenine pathway and neopterin levels in human colostrum samples.

Colostrum, the first breast fluid produced by mammals after giving birth, is followed by breast milk, which serves as the sole source of nutrients for breastfed newborns and infants. Tryptophan, an essential amino acid, plays a crucial role in the development and maturation of the central nervous system in infants. Tryptophan is primarily degraded through the kynurenine pathway. Owing to its sensitivity to dietary intake, immune-mediated tryptophan degradation is assessed by the kynurenine-to-tryptophan ratio, with a focus on one of the rate-limiting enzymes in the pathway. This study involved the validation of the simultaneous determination of tryptophan and kynurenine using HPLC. The validated method was then used to detect levels of tryptophan and kynurenine, as well as to calculate the kynurenine-to-tryptophan ratio in colostrum samples. Simultaneously, these results were compared with colostrum neopterin levels measured using commercial enzyme-linked immunosorbent assay kits. The mean levels for tryptophan, kynurenine, and neopterin were 17.3 ± 62.4 µM, 0.45 ± 0.03 µM, and 28.9 ± 2.6 nM, respectively. This study is among the few that have evaluated these parameters in colostrum samples. Neopterin levels secreted by the mammary gland were found not to be correlated with tryptophan degradation, a process influenced by the mother's nutritional status.

Opposite Auxin Dynamics Determine the Gametophytic and Embryogenic Fates of the Microspore.

The microspore can follow two different developmental pathways. In vivo microspores follow the gametophytic program to produce pollen grains. In vitro, isolated microspores can be reprogrammed by stress treatments and follow the embryogenic program, producing doubled-haploid embryos. In the present study, we analyzed the dynamics and role of endogenous auxin in microspore development during these two different scenarios, in Brassica napus. We analyzed auxin concentration, cellular accumulation, the expression of the TAA1 auxin biosynthesis gene, and the PIN1-like efflux carrier gene, as well as the effects of inhibiting auxin biosynthesis by kynurenine on microspore embryogenesis. During the gametophytic pathway, auxin levels and TAA1 and PIN1-like expression were high at early stages, in tetrads and tapetum, while they progressively decreased during gametogenesis in both pollen and tapetum cells. In contrast, in microspore embryogenesis, TAA1 and PIN1-like genes were upregulated, and auxin concentration increased from the first embryogenic divisions. Kynurenine treatment decreased both embryogenesis induction and embryo production, indicating that auxin biosynthesis is required for microspore embryogenesis initiation and progression. The findings indicate that auxin exhibits two opposite profiles during these two microspore developmental pathways, which determine the different cell fates of the microspore.

Metabolomic analysis shows dysregulation in amino acid and NAD+ metabolism in palmitate treated hepatocytes and plasma of non-alcoholic fatty liver disease spectrum.

There is an alarming increase in incidence of fatty liver disease worldwide. The fatty liver disease spectrum disease ranges from simple steatosis (NAFL) to steatohepatitis (NASH) which culminates in cirrhosis and cancer. Altered metabolism is a hallmark feature associated with fatty liver disease and palmitic acid is the most abundant saturated fatty acid, therefore, the aim of this study was to compare metabolic profiles altered in hepatocytes treated with palmitic acid and also the differentially expressed plasma metabolites in spectrum of nonalcoholic fatty liver. The metabolites were analyzed by liquid chromatography-mass spectrometry (LC-MS) platform. Hepatocyte cell lines PH5CH8 and HepG2 cells when treated with 400 µM dose of palmitic acid showed typical features of steatosis. Metabolomic analysis of lipid treated hepatocyte cell lines showed differential changes in phenylalanine and tyrosine pathways, fatty acid metabolism and bile acids. The key metabolites tryptophan, kynurenine and carnitine differed significantly between subjects with NAFL, NASH and those with cirrhosis. As the tryptophan-kynurenine axis is also involved in denovo synthesis of NAD+, we found significant alterations in the NAD+ related metabolites in both palmitic acid treated and also fatty liver disease with cirrhosis. The study underscores the importance of amino acid and NAD+supplementation as promising strategies in fatty liver disorder.

The role and mechanism of tryptophan - kynurenine metabolic pathway in depression.

Major depressive disorder (MDD) is a common mental illness characterized by persistent low mood and anhedonia, normally accompanied with cognitive impairment. Due to its rising incidence and high rate of recurrence and disability, MDD poses a substantial threat to patients' physical and mental health, as well as a significant economic cost to society. However, the etiology and pathogenesis of MDD are still unclear. Chronic inflammation may cause indoleamine-2,3-dioxygenase (IDO) to become overactive throughout the body and brain, resulting in excess quinolinic acid (QUIN) and less kynuric acid (KYNA) in the brain. QUIN's neurotoxicity damages glial cells and neurons, accelerates neuronal apoptosis, hinders neuroplasticity, and causes depression due to inflammation. Therefore, abnormal TRP-KYN metabolic pathway and its metabolites have been closely related to MDD, suggesting changes in the TRP-KYN metabolic pathway might contribute to MDD. In addition, targeting TRP-KYN with traditional Chinese medicine showed promising treatment effects for MDD. This review summarizes the recent studies on the TRP-KYN metabolic pathway and its metabolites in depression, which would provide a theoretical basis for exploring the etiology and pathogenesis of depression.

Modulation of immune cell function, IDO expression and kynurenine production by the quorum sensor 2-heptyl-3-hydroxy-4-quinolone (PQS).

Many invasive micro-organisms produce 'quorum sensor' molecules which regulate colony expansion and may modulate host immune responses. We have examined the ability of Pseudomonas Quorum Sensor (PQS) to influence cytokine expression under conditions of inflammatory stress. The administration of PQS in vivo to mice with collagen-induced arthritis (CIA) increased the severity of disease. Blood and inflamed paws from treated mice had fewer regulatory T cells (Tregs) but normal numbers of Th17 cells. However, PQS (1µM) treatment of antigen-stimulated lymph node cells from collagen-immunised mice in vitro inhibited the differentiation of CD4+IFNγ+ cells, with less effect on CD4+IL-17+ cells and no change in CD4+FoxP3+Tregs. PQS also inhibited T cell activation by anti-CD3/anti-CD28 antibodies. PQS reduced murine macrophage polarisation and inhibited expression of IL1B and IL6 genes in murine macrophages and human THP-1 cells. In human monocyte-derived macrophages, IDO1 gene, protein and enzyme activity were all inhibited by exposure to PQS. TNF gene expression was inhibited in THP-1 cells but not murine macrophages, while LPS-induced TNF protein release was increased by high PQS concentrations. PQS is known to have iron scavenging activity and its suppression of cytokine release was abrogated by iron supplementation. Unexpectedly, PQS decreased the expression of indoleamine-2, 3-dioxygenase genes (IDO1 and IDO2), IDO1 protein expression and enzyme activity in mouse and human macrophages. This is consistent with evidence that IDO1 inhibition or deletion exacerbates arthritis, while kynurenine reduces its severity. It is suggested that the inhibition of IDO1 and cytokine expression may contribute to the quorum sensor and invasive actions of PQS.

Direct Effects of Vitamin D Supplementation on Ultramarathon-Induced Changes in Kynurenine Metabolism.

In humans, most free tryptophan is degraded via kynurenine pathways into kynurenines. Kynurenines modulate the immune system, central nervous system, and skeletal muscle bioenergetics. Consequently, kynurenine pathway metabolites (KPMs) have been studied in the context of exercise. However, the effect of vitamin D supplementation on exercise-induced changes in KPMs has not been investigated. Here, we analyzed the effect of a single high-dose vitamin D supplementation on KPMs and tryptophan levels in runners after an ultramarathon. In the study, 35 amateur runners were assigned into two groups: vitamin D supplementation group, administered 150,000 IU vitamin D in vegetable oil 24 h before the run (n = 16); and control (placebo) group (n = 19). Blood was collected for analysis 24 h before, immediately after, and 24 h after the run. Kynurenic, xanthurenic, quinolinic, and picolinic acids levels were significantly increased after the run in the control group, but the effect was blunted by vitamin D supplementation. Conversely, the decrease in serum tryptophan, tyrosine, and phenylalanine levels immediately after the run was more pronounced in the supplemented group than in the control. The 3-hydroxy-l-kynurenine levels were significantly increased in both groups after the run. We conclude that vitamin D supplementation affects ultramarathon-induced changes in tryptophan metabolism.

Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderly Persons with Type 2 Diabetes Mellitus: An Exploratory Randomized Controlled Trial.

Although branched-chain amino acids (BCAA) are known to stimulate myofibrillar protein synthesis and affect insulin signaling and kynurenine metabolism (the latter being a metabolite of tryptophan associated with depression and dementia), the effects of BCAA supplementation on type 2 diabetes (T2D) are not clear. Therefore, a 24-week, prospective randomized open blinded-endpoint trial was conducted to evaluate the effects of supplementation of 8 g of BCAA or 7.5 g of soy protein on skeletal muscle and glycemic control as well as adverse events in elderly individuals with T2D. Thirty-six participants were randomly assigned to the BCAA group (n = 21) and the soy protein group (n = 15). Skeletal muscle mass and HbA1c, which were primary endpoints, did not change over time or differ between groups. However, knee extension muscle strength was significantly increased in the soy protein group and showed a tendency to increase in the BCAA group. Homeostasis model assessment for insulin resistance did not significantly change during the trial. Depressive symptoms were significantly improved in the BCAA group but the difference between groups was not significant. Results suggested that BCAA supplementation may not affect skeletal muscle mass and glycemic control and may improve depressive symptoms in elderly individuals with T2D.

Photoactivatable Immunostimulatory Nanomedicine for Immunometabolic Cancer Therapy.

A rationally designed immunostimulant (CC@SiO2-PLG) with a photoactivatable immunotherapeutic function for synergetic tumor therapy is reported. This CC@SiO2-PLG nanoplatform comprises catalase and a photosensitizer (Ce6) co-encapsulated in a silica capsule, to which an immunostimulant is conjugated through a reactive oxygen species-cleavable linker. After accumulating in tumor tissue, CC@SiO2-PLG generates O2 to relieve tumor hypoxia and promotes the production of singlet oxygen (1O2) upon laser irradiation, resulting in not only tumor destruction but also the release of tumor-associated antigens (TAAs). Simultaneously, the linker breakage by the photoproduced 1O2 leads to the remote-controlled release of conjugated indoleamine 2,3-dioxygenase (IDO) inhibitor from CC@SiO2-PLG and consequent immunosuppressive tumor microenvironment reversion. The released TAAs in conjunction with the inhibition of the IDO-mediated tryptophan/kynurenine metabolic pathway induced a boosted antitumor immune response to the CC@SiO2-PLG-mediated phototherapy. Therefore, the growth of primary/distant tumors and lung metastases in a mouse xenograft model was greatly inhibited, which was not achievable by phototherapy alone.

Involvement of the gut-brain axis in vascular depression via tryptophan metabolism: A benefit of short chain fatty acids.

Cerebral hemodynamic dysfunction and hypoperfusion have been found to underlie vascular depression, but whether the gut-brain axis is involved remains unknown. In this study, a rat model of bilateral common carotid artery occlusion (BCCAO) was adopted to mimic chronic cerebral hypoperfusion. A reduced sucrose preference ratio, increased immobility time in the tail suspension test and forced swim test, and compromised gut homeostasis were found. A promoted conversion of tryptophan (Trp) into kynurenine (Kyn) instead of 5-hydroxytryptamine (5-HT) was observed in the hippocampus and gut of BCCAO rats. Meanwhile, 16S ribosomal RNA gene sequencing suggested a compromised profile of the gut SCFA-producing microbiome, with a decreased serum level of SCFAs revealed by targeted metabolomics analysis. With SCFA supplementation, BCCAO rats exhibited ameliorated depressive-like behaviors and improved gut dysbiosis, compared with the salt-matched BCCAO group. Enzyme-linked immunosorbent assays and quantitative RT-PCR suggested that SCFA supplementation suppressed the conversion of Trp to Kyn and rescued the reduction in 5-HT levels in the hippocampus and gut. In addition to inhibiting the upregulation of inflammatory cytokines, SCFA supplementation ameliorated the activated oxidative stress and reduced the number of microglia and the expression of its proinflammatory markers in the hippocampus post BCCAO. In conclusion, our data suggested the participation of the gut-brain axis in vascular depression, shedding light on the neuroprotective potential of treatment with gut-derived SCFAs.

Adipocyte-derived kynurenine promotes obesity and insulin resistance by activating the AhR/STAT3/IL-6 signaling.

Aberrant amino acid metabolism is a common event in obesity. Particularly, subjects with obesity are characterized by the excessive plasma kynurenine (Kyn). However, the primary source of Kyn and its impact on metabolic syndrome are yet to be fully addressed. Herein, we show that the overexpressed indoleamine 2,3-dioxygenase 1 (IDO1) in adipocytes predominantly contributes to the excessive Kyn, indicating a central role of adipocytes in Kyn metabolism. Depletion of Ido1 in adipocytes abrogates Kyn accumulation, protecting mice against obesity. Mechanistically, Kyn impairs lipid homeostasis in adipocytes via activating the aryl hydrocarbon receptor (AhR)/Signal transducer and activator of transcription 3 /interleukin-6 signaling. Genetic ablation of AhR in adipocytes abolishes the effect of Kyn. Moreover, supplementation of vitamin B6 ameliorated Kyn accumulation, protecting mice from obesity. Collectively, our data support that adipocytes are the primary source of increased circulating Kyn, while elimination of accumulated Kyn could be a viable strategy against obesity.

Changes in plasma concentration of kynurenine following intake of branched-chain amino acids are not caused by alterations in muscle kynurenine metabolism.

Administration of branched-chain amino acids (BCAA) has been suggested to enhance mitochondrial biogenesis, including levels of PGC-1α, which may, in turn, alter kynurenine metabolism. Ten healthy subjects performed 60 min of dynamic one-leg exercise at ∼70% of Wmax on two occasions. They were in random order supplied either a mixture of BCAA or flavored water (placebo) during the experiment. Blood samples were collected during exercise and recovery, and muscle biopsies were taken from both legs before, after, and 90 and 180 min following exercise. Ingestion of BCAA doubled their concentration in both plasma and muscle while causing a 30%-40% reduction (P < 0.05 vs. placebo) in levels of aromatic amino acids in both resting and exercising muscle during 3-h recovery period. The muscle concentration of kynurenine decreased by 25% (P < 0.05) during recovery, similar in both resting and exercising leg and with both supplements, although plasma concentration of kynurenine during recovery was 10% lower (P < 0.05) when BCAA were ingested. Ingestion of BCAA reduced the plasma concentration of kynurenic acid by 60% (P < 0.01) during exercise and recovery, whereas the level remained unchanged with placebo. Exercise induced a three- to fourfold increase (P < 0.05) in muscle content of PGC-1α1 mRNA after 90 min of recovery under both conditions, whereas levels of KAT4 mRNA and protein were unaffected by exercise or supplement. In conclusion, the reduction of plasma levels of kynurenine and kynurenic acid caused by BCAA were not associated with any changes in the level of muscle kynurenine, suggesting that kynurenine metabolism was altered in tissues other than muscle.

Sublingual AKBA Exerts Antidepressant Effects in the Aß-Treated Mouse Model.

The 3-O-acetyl-11-keto-ß-boswellic acid (AKBA) is the most active compound of Boswellia serrata proposed for treating neurodegenerative disorders, including Alzheimer's disease (AD), characterized in its early phase by alteration in mood. Accordingly, we have previously demonstrated that an intracerebroventricular injection of soluble amyloid beta 1-42 (Aß) peptide evokes a depressive-like phenotype in rats. We tested the protective effects of AKBA in the mouse model of an Aß-induced depressive-like phenotype. We evaluated the depressive-like behavior by using the tail suspension test (TST) and the splash test (ST). Behavioral analyses were accompanied by neurochemical quantifications, such as glutamate (GLU), kynurenine (KYN) and monoamines, and by biochemical measurements, such as glial fibrillary acid protein (GFAP), CD11b and nuclear factor kappa B (NF-kB), in mice prefrontal cortex (PFC) and hippocampus (HIPP). AKBA prevented the depressive-like behaviors induced by Aß administration, since we recorded a reduction in latency to initiate self-care and total time spent to perform self-care in the ST and reduced time of immobility in the TST. Likewise, the increase in GLU and KYN levels in PFC and HIPP induced by the peptide injection were reverted by AKBA administration, as well as the displayed increase in levels of GFAP and NF-kB in both PFC and HIPP, but not in CD11b. Therefore, AKBA might represent a food supplement suitable as an adjuvant for therapy of depression in early-stage AD.

Pharmacophore-Based Virtual Screening of Novel Competitive Inhibitors of the Neurodegenerative Disease Target Kynurenine-3-Monooxygenase.

The pathogenesis of several neurodegenerative diseases such as Alzheimer's or Huntington's disease has been associated with metabolic dysfunctions caused by imbalances in the brain and cerebral spinal fluid levels of neuroactive metabolites. Kynurenine monooxygenase (KMO) is considered an ideal therapeutic target for the regulation of neuroactive tryptophan metabolites. Despite significant efforts, the known KMO inhibitors lack blood-brain barrier (BBB) permeability and upon the mimicking of the substrate binding mode, are subject to produce reactive oxygen species as a side reaction. The computational drug design is further complicated by the absence of complete crystal structure information for human KMO (hKMO). In the current work, we performed virtual screening of readily available compounds using several protein-ligand complex pharmacophores. Each of the pharmacophores accounts for one of three distinct reported KMO protein-inhibitor binding conformations. As a result, six novel KMO inhibitors were discovered based on an in vitro fluorescence assay. Compounds VS1 and VS6 were predicted to be BBB permeable and avoid the hydrogen peroxide production dilemma, making them valuable, novel hit compounds for further drug property optimization and advancement in the drug design pipeline.

Iron activates microglia and directly stimulates indoleamine-2,3-dioxygenase activity in the N171-82Q mouse model of Huntington's disease.

Huntington's disease (HD) is a neurodegenerative disorder caused by a dominant CAG-repeat expansion in the huntingtin gene. Microglial activation is a key feature of HD pathology, and is present before clinical disease onset. The kynurenine pathway (KP) of tryptophan degradation is activated in HD, and is thought to contribute to disease progression. Indoleamine-2,3-dioxygenase (IDO) catalyzes the first step in this pathway; this and other pathway enzymes reside with microglia. While HD brain microglia accumulate iron, the role of iron in promoting microglial activation and KP activity is unclear. Here we utilized the neonatal iron supplementation model to investigate the relationship between iron, microglial activation and neurodegeneration in adult HD mice. We show in the N171-82Q mouse model of HD microglial morphologic changes consistent with immune activation. Neonatal iron supplementation in these mice promoted neurodegeneration and resulted in additional microglial activation in adults as determined by increased soma volume and decreased process length. We further demonstrate that iron activates IDO, both in brain lysates and purified recombinant protein (EC50 = 1.24 nM). Brain IDO activity is increased by HD. Neonatal iron supplementation further promoted IDO activity in cerebral cortex, altered KP metabolite profiles, and promoted HD neurodegeneration as measured by brain weights and striatal volumes. Our results demonstrate that dietary iron is an important activator of microglia and the KP pathway in this HD model, and that this occurs in part through a direct effect on IDO. The findings are relevant to understanding how iron promotes neurodegeneration in HD.

Targeting Dietary and Microbial Tryptophan-Indole Metabolism as Therapeutic Approaches to Colon Cancer.

Tryptophan metabolism, via the kynurenine (Kyn) pathway, and microbial transformation of tryptophan to indolic compounds are fundamental for host health; both of which are altered in colon carcinogenesis. Alterations in tryptophan metabolism begin early in colon carcinogenesis as an adaptive mechanism for the tumor to escape immune surveillance and metastasize. The microbial community is a key part of the tumor microenvironment and influences cancer initiation, promotion and treatment response. A growing awareness of the impact of the microbiome on tryptophan (Trp) metabolism in the context of carcinogenesis has prompted this review. We first compare the different metabolic pathways of Trp under normal cellular physiology to colon carcinogenesis, in both the host cells and the microbiome. Second, we review how the microbiome, specifically indoles, influence host tryptophan pathways under normal and oncogenic metabolism. We conclude by proposing several dietary, microbial and drug therapeutic modalities that can be utilized in combination to abrogate tumorigenesis.

Tryptophan Intake and Metabolism in Older Adults with Mood Disorders.

The role of serotonin in the pathogenesis of depression is well-documented, while the involvement of other tryptophan (TRP) metabolites generated in the kynurenine pathway is less known. The aim of this study was to assess the intake and metabolism of TRP in elderly patients with mood disorders. Ninety subjects in three groups, 30 subjects each, were enrolled in this study: controls (healthy young adults, group I) and elderly individuals without (group II) or with (group III) symptoms of mild and moderate depression, as assessed by the Hamilton Depression Rating Scale (HAM-D) and further referred to as mood disorders. The average TRP intake was evaluated with the nutrition calculator. Urinary levels of TRP, 5-hydroxyindoleacetic acid (5-HIAA), L-kynurenine (KYN), kynurenic acid (KynA), xanthurenic acid (XA), and quinolinic acid (QA) were determined by liquid chromatography with tandem mass spectrometry and related to creatinine level. The average daily intake of TRP was significantly lower in group III than the remaining two groups, but group III was also characterized by higher urinary levels of KYN, KynA, XA, and QA as compared with younger adult individuals and elderly patients without mood disorders. Therefore, mild and moderate depression in the elderly may be associated with a lower intake of TRP and changes in its kynurenine metabolic pathway, which suggests a potential dietary TRP-based intervention in this group of patients.

Hepatic steatosis induced in C57BL/6 mice by a non-ß oxidizable fatty acid analogue is associated with reduced plasma kynurenine metabolites and a modified hepatic NAD+/NADH ratio.

BACKGROUND: Non-alcoholic fatty liver disease is often associated with obesity, insulin resistance, dyslipidemia, and the metabolic syndrome in addition to mitochondrial dysfunction and nicotinamide adenine dinucleotide (NAD+) deficiency. The aim of this study was to investigate how inhibition of mitochondrial fatty acid oxidation using the compound tetradecylthiopropionic acid (TTP) would affect hepatic triacylglycerol level and plasma levels of kynurenine (Kyn) metabolites and nicotinamide. METHODS: 12 C57BL/6 mice were fed a control diet, or an intervention diet supplemented with 0.9% (w/w) tetradecylthiopropionic acid for 14 days. Blood and liver samples were collected, enzyme activities and gene expression were analyzed in liver, in addition to fatty acid composition. Metabolites in the tryptophan/kynurenine pathway and total antioxidant status were measured in plasma. RESULTS: Dietary treatment with tetradecylthiopropionic acid for 2 weeks induced fatty liver accompanied by decreased mitochondrial fatty acid oxidation. The liver content of the oxidized form of NAD+ was increased, as well as the ratio of NAD+/NADH, and these changes were associated by increased hepatic mRNA levels of NAD synthetase and nicotinamide mononucleotide adenyltransferase-3. The downstream metabolites of kynurenine were reduced in plasma whereas the plasma nicotinamide content was increased. Some effects on inflammation and oxidative stress was observed in the liver, while the plasma antioxidant capacity was increased. This was accompanied by a reduced plasma ratio of kynurenine/tryptophan. In addition, a significant decrease in the inflammation-related arachidonic fatty acid in liver was observed. CONCLUSION: Fatty liver induced by short-time treatment with tetradecylthiopropionic acid decreased the levels of kynurenine metabolites but increased the plasma levels of NAD+ and nicotinamide. These changes are most likely not associated with increased inflammation and oxidative stress. Most probably the increase of NAD+ and nicotinamide are generated through the Preiss Handler pathway and/or salvage pathway and not through the de novo pathway. The take home message is that non-alcoholic fatty liver disease is associated with the metabolic syndrome in addition to mitochondrial dysfunction and nicotinamide adenine dinucleotide (NAD+) deficiency. Inducing fatty liver in mice by inhibition of fatty acid oxidation resulted in a concomitant change in kynurenine metabolites increasing the plasma levels of nicotinamides and the hepatic NAD+/NADH ratio, probably without affecting the de novo pathway of kynurenines.

Distinct Influence of Omega-3 Fatty Acids on the Plasma Metabolome of Healthy Older Adults.

Omega-3 polyunsaturated fatty acids (n3-PUFA) are well recognized for their potent triglyceride-lowering effects, but the potential influence of these bioactive lipids on other biological processes, particularly in the context of healthy aging, remains unknown. With the goal of gaining new insight into some less well-characterized biological effects of n3-PUFAs in healthy older adults, we performed metabolomics of fasting peripheral blood plasma collected from 12 young adults and 12 older adults before and after an open-label intervention of n3-PUFA (3.9 g/day, 2.7 g eicosapentaenoic [EPA], 1.2 g docosahexaenoic [DHA]). Proton nuclear magnetic resonance (1H-NMR) based lipoprotein subclass analysis revealed the expected reduction in total triglyceride (TG), but also demonstrated that n3-PUFA supplementation reduced very low-density lipoprotein (VLDL) particle number, modestly increased high-density lipoprotein (HDL) cholesterol, and shifted the composition of HDL subclasses. Further metabolite profiling by 1H-NMR and mass spectrometry revealed pronounced changes in phospholipids, cholesterol esters, diglycerides, and triglycerides following n3-PUFA supplementation. Furthermore, significant changes in hydroxyproline, kynurenine, and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF) following n3-PUFA supplementation provide further insight into some less well-recognized biological effects of n3-PUFA supplementation, including possible effects on protein metabolism, the kynurenine pathway, and glucose metabolism.

Kynurenine, 3-OH-kynurenine, and anthranilate are nutrient metabolites that alter H3K4 trimethylation and H2AS40 O-GlcNAcylation at hypothalamus-related loci.

Epigenetic mechanisms can establish and maintain mitotically stable patterns of gene expression while retaining the DNA sequence. These mechanisms can be affected by environmental factors such as nutrients. The importance of intracellular dosages of nutrient metabolites such as acetyl coenzyme A and S-adenosylmethionine, which are utilized as donors for post-translational modifications, is well-known in epigenetic regulation; however, the significance of indirect metabolites in epigenetic regulation is not clear. In this study, we screened for metabolites that function as epigenetic modulators. Because the expression of genes related to hypothalamic function is reportedly affected by nutritional conditions, we used a neural cell culture system and evaluated hypothalamic-linked loci. We supplemented the culture medium with 129 metabolites separately during induction of human-iPS-derived neural cells and used high-throughput ChIP-qPCR to determine the epigenetic status at 37 hypothalamus-linked loci. We found three metabolites (kynurenine, 3-OH-kynurenine, and anthranilate) from tryptophan pathways that increased H3K4 trimethylation and H2AS40 O-GlcNAcylation, resulting in upregulated gene expression at most loci, except those encoding pan-neural markers. Dietary supplementation of these three metabolites and the resulting epigenetic modification were important for stability in gene expression. In conclusion, our findings provide a better understanding of how nutrients play a role in epigenetic mechanisms.

Microbiome and Mental Health, Specifically as It Relates to Adolescents.

PURPOSE OF REVIEW: This article reviews the relationship of the microbiome, the gut-brain axis, and depression. It also will review factors which can influence this relationship, such as chronic stress, medications, and the Western diet typically consumed by adolescents. RECENT FINDINGS: Changes in the gut microbiome increase the release of microbial lipopolysaccharides (LPS) which activate a gut inflammatory response. Gut pro-inflammatory cytokines stimulate the afferent vagal nerve which in turn impacts the hypothalamic-pituitary-adrenal (HPA) axis inducing symptoms associated with depression. Recent research suggests that gut inflammation can induce neuroinflammation which, in turn, stimulates microglia activation and the kynurenine pathway and can activate systemic inflammation-inducing depressive symptoms. Promoting a healthy diet and lifestyle changes, limiting exposure to pesticides, limiting medications that affect the microbiome and the use of such things pre/probiotics and other interventions may complement existing efforts to curb the rise in depression. Alternative and complementary therapies may serve as effective treatments in adolescents with depression.