Metabolite Pools Research Articles

Raised concerns about the safety of barley grains and straw: A Swiss survey reveals a high diversity of mycotoxins and other fungal metabolites

Barley can be contaminated with a wide range of fungal secondary metabolites, including various mycotoxins that reduce the quality and safety of raw materials as well as cause economic losses. A survey was conducted for the crop seasons 2016 and 2017 to analyse fungal metabolites, including mycotoxins, in grain and straw samples of barley, which originated from fields across Switzerland. In total, 253 grain and 237 straw samples were analysed by LC-MS/MS detecting 87 and 86 fungal metabolites, respectively, which are reported to be produced by Fusarium, Alternaria, Claviceps, Aspergillus, Penicillium and other genera. None of the grain samples exceeded the permitted limits of mycotoxins set by the European Commission. With regard to straw, three and six samples exceeded the guidance levels set for raw grains for deoxynivalenol and the sum of T-2 and HT-2, respectively. Nevertheless, some samples contained high concentrations of unregulated fungal metabolites, e.g. enniatins, infectopyron, zinniol and rubellin D. This was more frequently observed in straw and, to a lesser extent, in grains, suggesting that the presence of fungal metabolites in straw material should not be neglected. Our study demonstrated that both grain and straw matrices of barley represent large pools of various fungal secondary metabolites, most of them with undetermined toxicity. Hence, future studies should focus on the toxicology of the predominant fungal metabolites that occurred at elevated concentrations as well as the health impact of co-occurrence of toxins primarily with metabolites that revealed strong correlations.

Dynamic control over feedback regulatory mechanisms improves NADPH flux and xylitol biosynthesis in engineered E. coli

We report improved NADPH flux and xylitol biosynthesis in engineered E. coli. Xylitol is produced from xylose via an NADPH dependent reductase. We utilize 2-stage dynamic metabolic control to compare two approaches to optimize xylitol biosynthesis, a stoichiometric approach, wherein competitive fluxes are decreased, and a regulatory approach wherein the levels of key regulatory metabolites are reduced. The stoichiometric and regulatory approaches lead to a 20-fold and 90-fold improvement in xylitol production, respectively. Strains with reduced levels of enoyl-ACP reductase and glucose-6-phosphate dehydrogenase, led to altered metabolite pools resulting in the activation of the membrane bound transhydrogenase and an NADPH generation pathway, consisting of pyruvate ferredoxin oxidoreductase coupled with NADPH dependent ferredoxin reductase, leading to increased NADPH fluxes, despite a reduction in NADPH pools. These strains produced titers of 200 g/L of xylitol from xylose at 86% of theoretical yield in instrumented bioreactors. We expect dynamic control over the regulation of the membrane bound transhydrogenase as well as NADPH production through pyruvate ferredoxin oxidoreductase to broadly enable improved NADPH dependent bioconversions or production via NADPH dependent metabolic pathways.

Branched Chain Lipid Metabolism As a Determinant of the N-Acyl Variation of Streptomyces Natural Products.

Branched-chain fatty acids (BCFA) are encountered in Gram-positive bacteria, but less so in other organisms. The bacterial BCFA in membranes are typically saturated, with both odd- and even-numbered carbon chain lengths, and with methyl branches at either the ω-1 (iso) or ω-2 (anteiso) positions. The acylation with BCFA also contributes to the structural diversity of microbial natural products and potentially modulates biological activity. For the tunicamycin (TUN) family of natural products, the toxicity toward eukaryotes is highly dependent upon N-acylation with trans-2,3-unsaturated BCFA. The loss of the 2,3-unsaturation gives modified TUN with reduced eukaryotic toxicity but crucially with retention of the synergistic enhancement of the β-lactam group of antibiotics. Here, we infer from genomics, mass spectrometry, and deuterium labeling that the trans-2,3-unsaturated TUN variants and the saturated cellular lipids found in TUN-producing Streptomyces are derived from the same pool of BCFA metabolites. Moreover, non-natural primers of BCFA metabolism are selectively incorporated into the cellular lipids of TUN-producing Streptomyces and concomitantly produce structurally novel neo-branched TUN N-acyl variants.

Impact of Altered Trehalose Metabolism on Physiological Response of Penicillium chrysogenum Chemostat Cultures during Industrially Relevant Rapid Feast/Famine Conditions

Due to insufficient mass transfer and mixing issues, cells in the industrial-scale bioreactor are often forced to experience glucose feast/famine cycles, mostly resulting in reduced commercial metrics (titer, yield and productivity). Trehalose cycling has been confirmed as a double-edged sword in the Penicillium chrysogenum strain, which facilitates the maintenance of a metabolically balanced state, but it consumes extra amounts of the ATP responsible for the repeated breakdown and formation of trehalose molecules in response to extracellular glucose perturbations. This loss of ATP would be in competition with the high ATP-demanding penicillin biosynthesis. In this work, the role of trehalose metabolism was further explored under industrially relevant conditions by cultivating a high-yielding Penicillium chrysogenum strain, and the derived trehalose-null strains in the glucose-limited chemostat system where the glucose feast/famine condition was imposed. This dynamic feast/famine regime with a block-wise feed/no feed regime (36 s on, 324 s off) allows one to generate repetitive cycles of moderate changes in glucose availability. The results obtained using quantitative metabolomics and stoichiometric analysis revealed that the intact trehalose metabolism is vitally important for maintaining penicillin production capacity in the Penicillium chrysogenum strain under both steady state and dynamic conditions. Additionally, cells lacking such a key metabolic regulator would become more sensitive to industrially relevant conditions, and are more able to sustain metabolic rearrangements, which manifests in the shrinkage of the central metabolite pool size and the formation of ATP-consuming futile cycles.

Reprogramming of Nucleotide Metabolism Mediates Synergy between Epigenetic Therapy and MAP Kinase Inhibition.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare but often lethal cancer that is diagnosed at a median age of 24 years. Optimal management of patients is not well defined, and current treatment remains challenging, necessitating the discovery of novel therapeutic approaches. The identification of SMARCA4-inactivating mutations invariably characterizing this type of cancer provided insights facilitating diagnostic and therapeutic measures against this disease. We show here that the BET inhibitor OTX015 acts in synergy with the MEK inhibitor cobimetinib to repress the proliferation of SCCOHT in vivo Notably, this synergy is also observed in some SMARCA4-expressing ovarian adenocarcinoma models intrinsically resistant to BETi. Mass spectrometry, coupled with knockdown of newly found targets such as thymidylate synthase, revealed that the repression of a panel of proteins involved in nucleotide synthesis underlies this synergy both in vitro and in vivo, resulting in reduced pools of nucleotide metabolites and subsequent cell-cycle arrest. Overall, our data indicate that dual treatment with BETi and MEKi represents a rational combination therapy against SCCOHT and potentially additional ovarian cancer subtypes.

Glandular trichomes of the flowers and leaves in Millingtonia hortensis (Bignoniaceae).

Three types of the glandular trichomes are developed on the flowers and leaves of Millingtonia hortensis. Morphology, cell ultrastructure and content of the volatile compounds are specific to each trichome type. The aim of this study was to characterize the structural and histochemical features of the glandular trichomes (GTs) of two types localized on the different flower parts and leaves in Millingtonia hortensis, as well as to identify the composition of the internal pool of metabolites. The peltate GTs are most common; they are founded on peduncle, calyx, ovary, and leaves. GTs consist of 12-24-cell disk-shaped head and a single-celled neck. The capitate GTs are located on corolla tube and have four to eight-cell head, single-celled neck and a wide multicellular stalk. A series of histochemical reactions and fluorescent microscopy revealed the various substances in the chemical composition of GTs. Acid polysaccharides are predominately identified in the capitate trichomes of the corolla tube and peltate trichomes of calyx, terpenes present in larger quantity in the trichomes of the corolla tube and ovary, whilst phenolic substances prevail in the trichomes of the calyx and ovary. GTs of each type are characterized by specific ultrastructural traits. Smooth endoplasmic reticulum (SER) and leucoplasts prevail in the peltate trichomes of peduncle, calyx and ovary; Golgi apparatus is the common organelle in the capitate trichomes of the corolla tube and peltate trichomes of calyx; the huge aggregates of the RER cisterns there are in cytoplasm of all leaf trichomes. Synthesized secretion accumulates in the subcuticular cavity of all GTs except the leaf peltate trichomes. In the trichomes of the leaves secretion is stored in the thick upper cell wall with the wide cutinized layer. For the first time content of the internal pool of metabolites from the flowers and leaves was identified by GC-MS. Seventeen compounds, including alcohols, fatty acid derivatives, monoterpenes, sesquiterpenes, and benzenoids were identified. 1-octen 3-ol, 3-carene, methyl salicylate, p-hydroxybenzeneethanol and 1-hydroxy-2,4-di-tertbutyl-benzene were the main compounds of the flower scent. We consider GTs of the reproductive organs in M. hortensis synthesizing acid polysaccharides and volatile compounds as secretory structures attracting of pollinators, whereas the leaf peltate trichomes accumulating predominately non-volatile phenols, protect young vegetative shoots against small herbivorous insects and pathogens.

Genomic instability and metabolism in cancer.

Genomic instability and metabolic reprogramming are among the key hallmarks discriminating cancer cells from normal cells. The two phenomena contribute to the robust and evasive nature of cancer, particularly when cancer cells are exposed to chemotherapeutic agents. Genomic instability is defined as the increased frequency of mutations within the genome, while metabolic reprogramming is the alteration of metabolic pathways that cancer cells undergo to adapt to increased bioenergetic demand. An underlying source of these mutations is the aggregate product of damage to the DNA, and a defective repair pathway, both resulting in the expansion of genomic lesions prior to uncontrolled proliferation and survival of cancer cells. Exploitation of DNA damage and the subsequent DNA damage response (DDR) have aided in defining therapeutic approaches in cancer. Studies have demonstrated that targeting metabolic reprograming yields increased sensitivity to chemo- and radiotherapies. In the past decade, it has been shown that these two key features are interrelated. Metabolism impacts DNA damage and DDR via regulation of metabolite pools. Conversely, DDR affects the response of metabolic pathways to therapeutic agents. Because of the interplay between genomic instability and metabolic reprogramming, we have compiled findings which more selectively highlight the dialog between metabolism and DDR, with a particular focus on glucose metabolism and double-strand break (DSB) repair pathways. Decoding this dialog will provide significant clues for developing combination cancer therapies.

Comparative metabolomics reveals key pathways associated with the synergistic activity of polymyxin B and rifampicin combination against multidrug-resistant Acinetobacter baumannii

Multidrug-resistant (MDR) Acinetobacter baumannii presents a critical challenge to human health worldwide and polymyxins are increasingly used as a last-line therapy. Due to the rapid emergence of resistance during polymyxin monotherapy, synergistic combinations (e.g. with rifampicin) are recommended to treat A. baumannii infections. However, most combination therapies are empirical, owing to a dearth of understanding on the mechanism of synergistic antibacterial killing. In the present study, we employed metabolomics to investigate the synergy mechanism of polymyxin B-rifampicin against A. baumannii AB5075, an MDR clinical isolate. The metabolomes of A. baumannii AB5075 were compared at 1 and 4 h following treatments with polymyxin B alone (0.75 mg/L, i.e. 3 × MIC), rifampicin alone (1 mg/L, i.e. 0.25 × MIC) and their combination. Polymyxin B monotherapy significantly perturbed glycerophospholipid and fatty acid metabolism at 1 h, reflecting its activity on bacterial outer membrane. Rifampicin monotherapy significantly perturbed glycerophospholipid, nucleotide and amino acid metabolism, which are related to the inhibition of RNA synthesis. The combination treatment significantly perturbed the metabolism of nucleotides, amino acids, fatty acids and glycerophospholipids at 1 and 4 h. Notably, the intermediate metabolite pools from pentose phosphate pathway were exclusively enhanced by the combination, while most metabolites from the nucleotide and amino acid biosynthesis pathways were significantly decreased. Overall, the synergistic activity of the combination was initially driven by polymyxin B which impacted pathways associated with outer membrane biogenesis; and subsequent effects were mainly attributed to rifampicin via the inhibition of RNA synthesis. This study is the first to reveal the synergistic killing mechanism of polymyxin-rifampicin combination against polymyxin-susceptible MDR A. baumannii at the network level. Our findings provide new mechanistic insights for optimizing this synergistic combination in patients.

Click-Nucleic-Acid-Containing Codelivery System Inducing Collapse of Cellular Homeostasis for Tumor Therapy through Bidirectional Regulation of Autophagy and Glycolysis.

As a rapid proliferating tissue, tumor cells have to optimize nutrient utilization to withstand harsh conditions. Several approaches have been explored to inhibit the growth and metastasis of tumor by disrupting the reprogrammed tumor metabolism. However, nutrient limitations within solid tumors may induce the metabolic flexibility of malignant cells to sustain growth and survival using one nutrient to fill metabolite pools normally supplied by the other. To overcome this predicament, a promising click-nucleic-acid-containing platform for codelivery of rapamycin, anti-PFKFB4 siRNA, and targeting ligand aptamer AS1411 was applied. PFKFB4 could act as a promising target for tumor therapy for being a molecular fulcrum that could couple glycolysis to autophagy by promoting aggressive metastatic tumors. The downregulation of PFKFB4 can help inhibit the SRC3/Akt/mTOR pathway, leading autophagy to the direction of promoting apoptosis of tumor cells, which is induced by the collapse of tumor cellular homeostasis, while low dosages of rapamycin could decrease surgery-induced immune dysfunction. Enhanced tumor autophagy, favorable in vivo antitumor efficacy, and effective systematic immune activation are observed after treatment, suggesting that autophagy and glycolysis can serve as an integrated target for tumor treatment.

Phthalate exposures and one-year change in body mass index across the menopausal transition

BackgroundThe menopausal transition is a hormonally sensitive period associated with changes in body weight. Phthalates are ubiquitous endocrine disrupting chemicals that could disrupt weight homeostasis, but it is unknown whether this occurs during the menopausal transition. ObjectivesOur objectives were to (1) determine if phthalate exposure in pre- and perimenopausal women was associated with one-year change in body mass index (BMI), and (2) determine if these associations differed across the menopausal transition. MethodsWe addressed our objectives using data from 524 participants enrolled in the Midlife Women's Health Study. We calculated change in BMI from baseline to first follow-up visit approximately one year later. Phthalate exposures were approximated by measuring urinary metabolites in pools of two-to-four spot urine samples collected across a four-week period at baseline. We molar-converted and summed mono-(2-ethylhexyl) phthalate (mEHP), mono (2-ethyl-5-hydroxyhexyl) phthalate (mEHHP), mono (2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono (2-ethyl-5-carboxypentyl) phthalate (mECPP) to approximate exposure to di-(2-ethylhexyl) phthalate (∑DEHP); ∑DEHP, mono (3-carboxypropyl) phthalate (mCPP), and monobenzyl phthalate (mBzP) to approximate exposure to plasticizer phthalates (∑Plastics); and monoethyl phthalate (mEP), monobutyl phthalate (mBP), and monoisobutyl phthalate (miBP) to approximate exposure to phthalates from personal care products (∑PCP). We used multivariable linear regression models to evaluate associations of specific gravity-adjusted ln-transformed phthalate metabolites or sums with one-year BMI change, and also considered whether associations differed depending on each woman's menopausal status change from baseline to first follow-up. ResultsAt baseline, most women were premenopausal (67.8%), non-Hispanic white (67.9%), and college educated (65.8%). Overall, urinary phthalate metabolites or sums were not associated with one-year BMI change. Stratified analysis identified positive associations between ∑DEHP (and three of its metabolites: MEHP, MEHHP, and MEOHP) and one-year BMI change among women who transitioned from peri-to post-menopause from baseline to first follow-up. For example, in these women, with each doubling of ∑DEHP, BMI increased by 0.65 kg/m2 (95%CI: 0.17, 1.13) from baseline to first follow-up. Personal care product-associated phthalate metabolites (mBP and mEP) were negatively associated with one-year BMI change among women who remained perimenopausal from baseline to first follow-up, while miBP and mEP were positively associated with one-year BMI change among women who transitioned from peri-to post-menopause. ConclusionWe found the strongest associations between some phthalates and one-year BMI change in women who transitioned from peri-to post-menopause from baseline to first follow-up. This supports previous evidence that the menopausal transition is a hormonally sensitive period in women's lives. To establish whether phthalate exposure contributes to body weight changes associated with the menopausal transition, substantially more research is needed to corroborate our findings.

Abstract IA08: Metabolic compartmentalization in the regulation of chromatin modification

Abstract Metabolic processes are compartmentalized within cells. Many chromatin modifying enzymes utilize metabolites as substrates, and localized metabolite production may play important roles in the regulation of the epigenome. A number of metabolic enzymes have been detected and shown to be dynamically regulated within the nucleus. For example, nuclear localization and phosphorylation of the enzyme ATP-citrate lyase (ACLY) plays a key role in supplying acetyl-CoA for histone acetylation during DNA double strand break repair. A major barrier to understanding metabolic regulation of chromatin modification is the lack of methodology to reliably measure nuclear metabolite levels. In this talk, I will discuss efforts to quantify subcellular acyl-CoA levels, as well as insights into the regulation of nuclear metabolite pools emerging from this work. Citation Format: Kathryn Wellen. Metabolic compartmentalization in the regulation of chromatin modification [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr IA08.

Prenatal exposure to select endocrine disruptors and child behaviour: a multi-pollutant approach based on a cohort with repeated exposure assessments

Background: Recent studies have suggested the involvement of several endocrine disruptors, including synthetic phenols and phthalates, in the development of infant behavioural disorders. These studies usually assessed exposure from one spot urine sample and did not consider mixture effect. Data regarding substitutes of bisphenol A and phthalates are also needed.Methods: We assessed concentrations of 12 phenols, 13 phthalate and 2 non-phthalate plasticizer metabolites in pools of multiple urine samples (up to 42 per individual) collected during the second and third trimesters of pregnancy in 397 women from the French SEPAGES mother-child cohort. Behaviour of their child was described at two years in terms of Externalizing score (related to attention and aggressiveness) and Internalizing score (related to emotion, anxiety/depression, somatic complaints and social withdrawn) using the Child Behaviour CheckList 1.5-5 (CBCL). Associations between prenatal exposure to the chemical mixture and child behaviour were analysed using adjusted linear Weighted Quantile Sum (WQS) regressions stratified on child sex.Results: The WQS indexes were associated with behaviour scores in girls but not in boys. In girls, the Externalizing and Internalizing scores increased by 3.69 points (95% Confidence Interval (CI) [0.92;6.47]) and 2.84 points (95%CI [0.84;4.85]) respectively, for an increase of one tertile of the WQS index (indicating worse behaviour). Main contributors for these associations were triclosan, mono-n-butyl phthalate (MnBP), bisphenol A and molar sum of non-phthalate plasticizer di(isononyl)cyclohexane-1,2-dicarboxylate (ΣDiNCH) for Externalizing score and monobenzyl phthalate (MBzP), ΣDiNCH, monoethyl phthalate (MEP) and MnBP for Internalizing score.Conclusions: These results suggested adverse associations between in utero exposure to a mixture of phenols, phthalates and non-phthalate plasticizers and child behaviour, especially in girls. They also highlighted the relevance of multi-pollutant approaches to more realistically model exposure.

Maternal exposure to plasticizer compounds is inversely associated with gestational weight gain in women with obesity

Background/Aims: Phthalates are endocrine disruptors with ubiquitous exposure in pregnant women, but their impact on maternal gestational weight gain (GWG) is unclear. We investigated associations of prenatal exposure with GWG and considered whether associations differed by maternal pre-pregnancy BMI (ppBMI). Methods: In 444 pregnant women from Champaign-Urbana, Illinois, we calculated GWG (kg) from self-reported pre-pregnancy weight and weight at median (range) 34 (29-38) weeks gestation. We quantified 19 phthalate/alternative metabolites in pools of five first-morning cross-pregnancy urines. These reflect exposures to 10 phthalates/alternatives as individual metabolites or molar sums of metabolites from the same phthalate/alternative [e.g. di(2-ethylhexyl) phthalate (SumDEHP), diisononyl phthalate (SumDiNP), di(2-ethylhexyl) terephthalate (SumDEHTP)]. We categorized ppBMI (kg/m2) as under-/normal weight (<25.0), overweight (25.0-29.9), and obese (≥30.0). We used linear regression to assess overall and ppBMI-stratified associations of ln-transformed specific gravity-adjusted biomarker concentrations with GWG, controlling for maternal age, race, ppBMI, parity, smoking status, diet quality, fetal sex, and gestational age at mid-to-late pregnancy weight. Results: These predominately Caucasian/White, college-educated women gained on average 12.1kg through mid-to-late pregnancy and >50% had a normal ppBMI. All women were exposed to measured chemicals, with similar concentrations to U.S. women. Overall, only SumDEHP and SumDEHTP were associated with GWG. Specifically, two-fold increases in SumDEHP and SumDEHTP were associated with 0.8kg lower GWG (95%CI: -1.5, -0.7 and -1.4, -0.2), respectively. However, when stratified by ppBMI, associations were strongest in obese women. Only in obese women, two-fold increases in SumDEHP and SumDiNP were associated with 1.9 and 1.3kg lower GWG, respectively. Similarly, in overweight and obese women, a two-fold increase in SumDEHTP was associated with 1.2 and 1.6kg lower GWG. Conclusions: In obese women, prenatal exposure to phthalates is associated with reduced GWG. Given the importance of appropriate GWG for fetal growth, especially in obese women, these findings should be corroborated in other populations.

Diet quality during pregnancy predicts maternal concentrations of phthalates and phthalate alternatives

Background/Objectives: Phthalates are endocrine disrupting chemicals that may be particularly disruptive during pregnancy. Pregnancy diet is a vehicle for some phthalate exposures. Therefore, we evaluated whether diet quality predicts urinary phthalate/phthalate alternative biomarkers concentrations in pregnant women.Methods: This study includes 427 pregnant women from Champaign-Urbana, Illinois. Alternative Healthy Eating Index (AHEI) scores were estimated from 3-month food frequency questionnaires administered at 34-37 weeks gestation, with higher AHEI scores representing lower chronic diseases risk. We quantified 19 phthalate/phthalate alternative metabolites in cross-pregnancy pools of five first-morning urines in three approximately equal batches based on year of enrollment (2013-2019). In analyses, we used individual metabolites, molar-sums of metabolites of the same parent phthalates (e.g., di(2-ethylhexyl) phthalate (SumDEHP), dibutyl phthalate (SumDBP), di-isononyl phthalate (SumDiNP)) or phthalate replacements (1,2-cyclohexane,dicarboxylic acid diisononyl ester (SumDiNCH), di(2-ethylhexyl) terephthalate (SumDEHTP)). Linear regression models evaluated associations between AHEI and ln-transformed specific-gravity adjusted biomarker concentrations while controlling for demographic/lifestyle characteristics, and stratified by chemical analysis batch.Results: Median AHEI score in these predominantly White, college-educated women was 55.9 (possible 110, range: 24.9-82.4) and varied little across time. Biomarker concentrations were similar to U.S. women and many varied over time: monobenzyl phthalate (MBzP), mono(carboxyisononyl) phthalate (MCNP), mono(3-carboxypropyl) phthalate (MCPP), SumDEHP, and SumDiNP decreased from 2013 to 2019, whereas SumDiNCH and SumDEHTP increased. Women with higher AHEI scores had lower SumDEHP, SumDEHTP, and SumDiNP regardless of time, and MBzP, MCNP, MCPP, and SumDBP only in the earliest batch. The strongest association was between AHEI and SumDEHTP, which decreased by 2.5% for each unit increase in AHEI (95%CI: -3.8, -1.3). Conclusions: In this cohort, pregnant women with high diet quality were the least exposed to plasticizer phthalates/alternatives. While these patterns should be confirmed in other populations, we also noted that associations between diet quality and some phthalates/phthalate alternatives have changed over time.

Dynamic Inventory of Intermediate Metabolites of Cyanobacteria in a Diurnal Cycle.

SummaryCyanobacteria are gaining importance both as hosts for photoautotrophic production of chemicals and as model systems for studies of diurnal lifestyle. The proteome and transcriptome of cyanobacteria have been closely examined under diurnal growth, whereas the downstream effects on the intermediary metabolism have not received sufficient attention. The present study focuses on identifying the cellular metabolites whose inventories undergo dramatic changes in a fast-growing cyanobacterium, Synechococcus elongatus PCC 11801. We identified and quantified 67 polar metabolites, whose inventory changes significantly during diurnal growth, with some metabolites changing by 100-fold. The Calvin-Benson-Bassham cycle intermediates peak at midday to support fast growth. The hitherto unexplored γ-glutamyl peptides act as reservoirs of amino acids. Interestingly, several storage molecules or their precursors accumulate during the dark phase, dispelling the notion that all biosynthetic activity takes place in the light phase. Our results will guide metabolic modeling and strain engineering of cyanobacteria.

Nuclear metabolism and the regulation of the epigenome.

Cellular metabolism has emerged as a major biological node governing cellular behaviour. Metabolic pathways fuel cellular energy needs, providing basic chemical molecules to sustain cellular homeostasis, proliferation and function. Changes in nutrient consumption or availability therefore can result in complete reprogramming of cellular metabolism towards stabilizing core metabolite pools, such as ATP, S-adenosyl methionine, acetyl-CoA, NAD/NADP and α-ketoglutarate. Because these metabolites underlie a variety of essential metabolic reactions, metabolism has evolved to operate in separate subcellular compartments through diversification of metabolic enzyme complexes, oscillating metabolic activity and physical separation of metabolite pools. Given that these same core metabolites are also consumed by chromatin modifiers in the establishment of epigenetic signatures, metabolite consumption on and release from chromatin directly influence cellular metabolism and gene expression. In this Review, we highlight recent studies describing the mechanisms determining nuclear metabolism and governing the redistribution of metabolites between the nuclear and non-nuclear compartments.

Review of Lysine Metabolism with a Focus on Humans

Lysine cannot be synthesized by most higher organisms and, therefore, is an indispensable amino acid (IAA) that must be consumed in adequate amounts to maintain protein synthesis. Although lysine is an abundant amino acid in body proteins, lysine is limited in abundance in many important food sources (e.g. grains). Older observations assigned importance to lysine because animals fed a lysine-deficient diet did not lose weight as fast as animals placed upon other IAA-deficient diets, leading to the theory that there may be a special pool of lysine or metabolites that could be converted to lysine. The first step in the lysine catabolic pathway is the formation of saccharopine and then 2-aminoadipic acid, processes that are mitochondrial. The catabolism of 2-aminoadipic acid proceeds via decarboxylation to a series of CoA esters ending in acetyl-CoA. In mammals, the liver appears to be the primary site of lysine catabolism. In humans, the metabolic and oxidative response of lysine to diets either restricted in protein or in lysine is consistent with what has been measured for other IAAs with isotopically labeled tracers. Intestinal microflora are known to metabolize urea to ammonia and scavenge nitrogen (N) for the synthesis of amino acids. Studies feeding 15N-ammonium chloride or 15N-urea to animals and to humans, demonstrate the appearance of 15N-lysine in gut microbial lysine and in host lysine. However, the amount of 15N-lysine transferred to the host is difficult to assess directly using current methods. It is important to understand the role of the gut microflora in human lysine metabolism, especially in conditions where dietary lysine intake may be limited, but better methods need to be devised.

Bioconversion of ferulic acid into aroma compounds by newly isolated yeast strains of the Latin American biodiversity.

Nine yeast strains isolated from Latin American biodiversity were screened for ferulic acid (FA) consumption and conversion into aroma compounds such as vanillin, vanillic acid (VA), and 4-vinylguaiacol (VG). Selected strains (Rhodotorula mucilaginosa UFMG-CM-Y3647, UFMG-CM-Y2190, UFMG-CM-Y665) were evaluated in flask experiments to investigate the influence of the pH media on bioconversion and a two-step process was conducted to maximize the metabolites production. The effect of pH was found to be significantly important for FA bioconversion, as acidic conditions (pH < 6.0) improved VA accumulation, with highest production of 1.14 ± 0.02 and 1.25 ± 0.03 g/L shown by UFMG-CM-Y3647 and UFMG-CM-Y2190, respectively. The two-step process favored 4-VG production for most strains, being UFMG-CM-Y2190 the best producer, its cultures reaching 1.63 ± 0.09 g/L after 55 hr, showing a productivity of 29.59 ± 1.55 mg/(L·hr), as glucose affected the metabolites pool and redirected yeast metabolism. R mucilaginosa UFMG-CM-Y3647 was selected for scaled-up cultivations in a 2-L bioreactor, where pH-controlled pH 5.5 and aeration of 2.5 vvm was found to be the best condition to improve VA productivity, attaining final concentrations of 1.20 ± 0.02 g/L-1 (78% molar yield) and a productivity of 40.82 ± 0.57 mg/(L·hr).

Abstract P238: Bile Acid Metabolites Modulate Hypertension

Hypertension is the single prominent risk factor of epidemic proportions leading to cardiovascular disease and stroke, which comprise the top two reasons for mortality of humans in the modern age. Much of the attention for the unknown causes of hypertension was focused on genetics and dietary salt, but in recent years, host-microbiotal interaction is gaining importance. Host-microbiotal partnership is key for the generation of many bioactive molecules including bile acid (BA) metabolites. Primary bile acids are synthesized and conjugated by the host but deconjugated and further modified to secondary BA by gut commensal bacteria. BA metabolites serve as important ligands for host nuclear receptors and/or G-protein-coupled receptors. These receptors have pivotal roles in blood pressure regulation. However, the effect of the host-microorganism biliary network on blood pressure (BP) remains poorly characterized. Here we report that both dietary salt and genetic factors rewire the composition of bile acids and BP. Specific reductions in conjugated bile acids were noted in human hypertensives as well as in rats with hypertension. Conjugation of bile acids by the host alone, devoid of the deconjugation step by microbiota, was sufficient to decrease BP of germ-free rats compared to germ-free conventionalized rats. Nutritional restoration of the conjugation of bile acids with Taurine increased the availability of circulating conjugated bile acids as ligands and ameliorated host susceptibility to hypertension via BA nuclear receptors and G-protein-coupled receptors. Thus, hosts and their bacterial symbionts can control host BP homeostasis via the resulting pool of bile acid metabolites. Sources of funding: National Institutes of Health (R01HL143082).

Metabolite pools of the reef building coral Montipora capitata are unaffected by Symbiodiniaceae community composition

Some reef corals form stable, dominant or codominant associations with multiple endosymbiotic dinoflagellate species (family Symbiodiniaceae). Given the immense genetic and physiological diversity within this family, Symbiodiniaceae community composition has the potential to impact the nutritional physiology and fitness of the cnidarian host and all associated symbionts. Here we assessed the impact of the symbiont community composition on the metabolome of the coral Montipora capitata in Kāne‘ohe Bay, Hawai‘i, where different colonies can be dominated by stress-tolerant Durusdinium glynnii or stress-sensitive Cladocopium spp. Based on our existing knowledge of these symbiont taxa, we hypothesised that the metabolite profile of D. glynnii-dominated corals would be consistent with poorer nutritional support of the host relative to those corals dominated by Cladocopium spp. However, comparative metabolite profiling revealed that the metabolite pools of the host and symbiont were unaffected by differences in the abundance of the two symbionts within the community. The abundance of the individual metabolites was the same in the host and in the endosymbiont regardless of whether the host was populated with D. glynnii or Cladocopium spp. These results suggest that coral-dinoflagellate symbioses have the potential to undergo physiological adjustments over time to accommodate differences in their resident symbionts. Such mechanisms may involve host heterotrophic compensation (increasing the level of nutrition generated by feeding relative to delivery from the algae), dynamic regulation of metabolic pathways when exchange of metabolites between the organisms differs, and/or modification of both the type and quantity of metabolites that are exchanged. We discuss these adjustments and the implications for the physiology and survival of reef corals under changing environmental regimes.