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Astrocytes (also, astroglia) consume huge amounts of glucose and produce lactate regardless of sufficient oxygen availability, indicating a high capacity for aerobic glycolysis. Glycolysis in astrocytes is activated in accordance with neuronal excitation and leads to increases in the release of lactate from astrocytes. Although the fate of this lactate remains somewhat controversial, it is believed to fuel neurons as an energy substrate. Besides providing lactate, astrocytic glycolysis plays an important role in neuroprotection. Among the minor pathways of glucose metabolism, glucose flux to the pentose-phosphate pathway (PPP), a major shunt pathway of glycolysis, is attracting research interest. In fact, PPP activity in astrocytes is five to seven times higher than that in neurons. The astrocytic PPP plays a key role in protecting neurons against oxidative stress by providing neurons with a reduced form of glutathione, which is necessary to eliminate reactive oxygen species. Therefore, enhancing astrocytic glycolysis might promote neuronal protection during acute ischemic stroke. Contrariwise, the dysfunction of astrocytic glycolysis and the PPP have been implicated in the pathogenesis of various neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, and amyotrophic lateral sclerosis, since mitochondrial dysfunction and oxidative stress trigger and accelerate disease progression.

Background Intake of ω-3 PUFAs have been demonstrated to have positive effects on pregnancy outcome, whose receptor, GPR120, regulates several cellular functions including differentiation, metabolism and immune reaction. However, whether GPR120 is involved in decidualization and pregnancy remains unknown. Methods Decidua tissue from women with normal pregnancy and spontaneous abortion were collected to determine the expression profile of GPR120. Abortion mouse models and artificially induced deciduoma in mice were established to evaluate the effect of GPR120 on pregnancy outcome and in vivo decidualization. HESCs and primary DSCs were used to explore the roles of GPR120 in decidualization and mechanisms involved. Findings We found that GPR120 functioned to promote decidualization by upregulating glucose uptake and pentose-phosphate pathway (PPP) of human endometrial stromal cells. Firstly, the expression of GPR120 in decidua of spontaneous abortion was downregulated compared to normal decidua. Lack of GPR120 predisposed mice to LPS or RU486 induced abortion. Decidualization was augmented by GPR120 via improving GLUT1-mediated glucose uptake and G6PD- mediated PPP. FOXO1 was upregulated by GPR120 via activation of ERK1/2 and AMPK signaling and increased the expression of GLUT1. Furthermore, the expression of chemokines and cytokines in decidual stromal cells was enhanced by GPR120. Lastly, GPR120 agonist ameliorated LPS-induced abortion in the mice. Interpretation GPR120 plays significant roles in decidualization and the maintenance of pregnancy, which might be a potential target for diagnosis and treatment of spontaneous abortion. Fund Ministry of Science and Technology of China, National Natural Science Foundation of China, the Program of Science and Technology Commission of Shanghai Municipality.

Deficient bioenergetics and diminished redox conservation have been implicated in the development of cerebral ischemia/reperfusion injury. In this study, the mechanisms underlying the neuroprotective effects of cannabidiol (CBD), a nonpsychotropic compound derived from Cannabis sativa with FDA-approved antiepilepsy properties, were studied in vitro using an oxygen–glucose-deprivation/reperfusion (OGD/R) model in a mouse hippocampal neuronal cell line. CBD supplementation during reperfusion rescued OGD/R-induced cell death, attenuated intracellular ROS generation and lipid peroxidation, and simultaneously reversed the abnormal changes in antioxidant biomarkers. Using the Seahorse XFe24 Extracellular Flux Analyzer, we found that CBD significantly improved basal respiration, ATP-linked oxygen consumption rate, and the spare respiratory capacity, and augmented glucose consumption in OGD/R-injured neurons. The activation of glucose 6-phosphate dehydrogenase and the preservation of the NADPH/NADP+ ratio implies that the pentose-phosphate pathway is stimulated by CBD, thus protecting hippocampal neurons from OGD/R injury. This study is the first to document the neuroprotective effects of CBD against OGD/R insult, which depend in part on attenuating oxidative stress, enhancing mitochondrial bioenergetics, and modulating glucose metabolism via the pentose-phosphate pathway, thus preserving both energy and the redox balance., Graphical abstract fx1, Highlights • Cannabidiol protects hippocampal neurons from OGD/R-induced oxidative stress. • Cannabidiol enhances mitochondrial bioenergetics. • Cannabidiol optimizes glucose metabolism via the pentose-phosphate pathway.

Oxidative stress is known to be a key factor in the pathogenesis of Parkinson's disease (PD). Neuronal redox status is maintained by glucose metabolism via the pentose-phosphate pathway and it is known that disruption of glucose metabolism is damaging to neurons. Accumulating evidence supports the idea that glucose metabolism is altered in PD and dysregulation of the pentose-phosphate pathway in this disease has recently been shown. In this review, we present an overview of the literature regarding neuronal glucose metabolism and PD, and discuss the implications of these findings for PD pathogenesis and possible future therapeutic avenues. © 2014 Versita and Springer-Verlag.

Background Fermentative hydrogen (H2) production suffers from low carbon-to-H2 yield, to which problem, co-production of ethanol and H2 has been proposed as a solution. For improved co-production of H2 and ethanol, we developed Escherichia coli BW25113 ΔhycA ΔhyaAB ΔhybBC ΔldhA ΔfrdAB Δpta-ackA ΔpfkA (SH8*) and overexpressed Zwf and Gnd, the key enzymes in the pentose-phosphate (PP) pathway (SH8*_ZG). However, the amount of accumulated pyruvate, which was significant (typically 0.20 mol mol−1 glucose), reduced the co-production yield. Results In this study, as a means of reducing pyruvate accumulation and improving co-production of H2 and ethanol, we developed and studied E. coli SH9*_ZG with functional acetate production pathway for conversion of acetyl-CoA to acetate (pta-ackA+). Our results indicated that the presence of the acetate pathway completely eliminated pyruvate accumulation and substantially improved the co-production of H2 and ethanol, enabling yields of 1.88 and 1.40 mol, respectively, from 1 mol glucose. These yields, significantly, are close to the theoretical maximums of 1.67 mol H2 and 1.67 mol ethanol. To better understand the glycolytic flux distribution, glycolytic flux prediction and RT-PCR analyses were performed. Conclusion The presence of the acetate pathway along with activation of the PP pathway eliminated pyruvate accumulation, thereby significantly improving co-production of H2 and ethanol. Our strategy is applicable to anaerobic production of biofuels and biochemicals, both of which processes demand high NAD(P)H. Electronic supplementary material The online version of this article (doi:10.1186/s13068-016-0510-5) contains supplementary material, which is available to authorized users.

A cDNA coding for a plastidic P2-type G6PDH isoform from A cDNA coding for a plastidic P2-type G6PDH isoform from poplar (Populus tremula x tremuloides) has been used to express and purify to homogeneity the mature recombinant protein with a N-terminus His-tag. The study of the kinetic properties of the recombinant enzyme showed an in vitro redox sensing modulation exerted by reduced DTT. The interaction with thioredoxins (TRXs) was then investigated. Five cysteine to serine variants (C145S - C175S - C183S - C195S - C242S) and a variant with a double substitution for Cys175 and Cys183 (C175S/C183S) have been generated, purified and biochemically characterized in order to investigate the specific role(s) of cysteines in terms of redox regulation and NADPH-dependent inhibition. Three cysteine residues (C145, C194, C242) are suggested to have a role in controlling the NADP+ access to the active site, and in stabilizing the NADPH regulatory binding site. Our results also indicate that the regulatory disulfide involves residues Cys175 and Cys183 in a position similar to those of chloroplastic P1-G6PDHs, but the modulation is exerted primarily by TRX m-type, in contrast to P1-G6PDH, which is regulated by TRX f. This unexpected specificity indicates differences in the mechanism of regulation, and redox sensing of plastidic P2-G6PDH compared to chloroplastic P1-G6PDH in higher plants. (Populus tremula x tremuloides) has been used to express and purify to homogeneity the mature recombinant protein with a N-terminus His-tag. The study of the kinetic properties of the recombinant enzyme showed an in vitro redox sensing modulation exerted by reduced DTT. The interaction with thioredoxins (TRXs) was then investigated. Five cysteine to serine variants (C145S - C175S - C183S - C195S - C242S) and a variant with a double substitution for Cys175 and Cys183 (C175S/C183S) have been generated, purified and biochemically characterized in order to investigate the specific role(s) of cysteines in terms of redox regulation and NADPH-dependent inhibition. Three cysteine residues (C145, C194, C242) are suggested to have a role in controlling the NADP+ access to the active site, and in stabilizing the NADPH regulatory binding site. Our results also indicate that the regulatory disulfide involves residues Cys175 and Cys183 in a position similar to those of chloroplastic P1-G6PDHs, but the modulation is exerted primarily by TRX m-type, in contrast to P1-G6PDH, which is regulated by TRX f. This unexpected specificity indicates differences in the mechanism of regulation, and redox sensing of plastidic P2-G6PDH compared to chloroplastic P1-G6PDH in higher plants.

Insulin resistance is perceived as deleterious, associated with conditions as the metabolic syndrome, type 2 diabetes mellitus and critical illness. However, insulin resistance is evolutionarily well preserved and its persistence suggests that it benefits survival. Insulin resistance is important in various states such as starvation, immune activation, growth and cancer, to spare glucose for different biosynthetic purposes such as the production of NADPH, nucleotides in the pentose phosphate pathway and oxaloacetate for anaplerosis. In these conditions, total glucose oxidation by the tricarboxylic acid cycle is actually low and energy demands are largely met by fatty acid and ketone body oxidation. This beneficial role of insulin resistance has consequences for treatment and research. Insulin resistance should be investigated at the cellular, tissue and whole organism level. The metabolic pathways discussed here, should be integrated in the accepted and valid mechanistic events of insulin resistance before interfering with them to promote insulin sensitivity at any cost. (C) 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved

Fermentation with transketolase (tkt) deficient strain of Bacillus is the only reported industrially viable process for production of D-ribose, a commercially important pentose sugar. In addition to direct effects of tkt deficiency, the mutation in non-oxidative part of pentose phosphate pathway (PPP) is known to display several unexpected physiological characteristics such as decreased ability to utilize D-glucose, altered carbon catabolite repression, lack of motility, etc. Here we demonstrate the morphological plasticity of tkt deficient strain of Bacillus pumilus ATCC 21951 and its possible relation with D-ribose productivity, a measure of carbon flux through PPP. The bacilli divide normally in nutrient rich media such as Luria-Bertani (LB) broth while showing cell elongation of up to 20-fold without a visible septum accompanied by moderate to high extracellular D-ribose accumulation in glucose-rich media. The cells stained with DAPI (4'-6-diamidino-2-phenylindole) and anti FtsZ antibody showed nucleoid separation and Z-ring formation in LB broth but not in glucose-rich media. FtsZ protein is known to localize at the future division site forming a ring, called Z-ring, at an early stage in cytokinesis. The strain experiences inhibition or delay in Z-ring formation resulting in cell elongation, possibly due to its altered cell membrane composition resulting from tkt deficiency. We hypothesize that the lack of PPP intermediates may have two effects on the strain: (i) altered the cell membrane leading to delay in Z-ring formation and cell elongation; and (ii) induction of genes of the oxidative part of PPP resulting in D-ribose accumulation. Nutrient rich media such as LB broth may alleviate these metabolite deficiencies thereby restoring normal cell division and inhibiting excessive D-ribose accumulation. The D-ribose productivity and cell elongation may therefore be co-morbid. The results have implications in designing optimal media and monitoring strategy based on morphological analysis.

Besides its essential role at regulating neural functions through cyclic GMP, nitric oxide is emerging as an endogenous physiological modulator of energy conservation for the brain. Thus, nitric oxide inhibits cytochrome c oxidase activity in neurones and glia, resulting in down-regulation of mitochondrial energy production. The subsequent increase in AMP facilitates the activation of 5′-AMP-dependent protein kinase, which rapidly triggers the activation of 6-phosphofructo-1-kinase – the master regulator of the glycolytic pathway – and Glut1 and Glut3 — the main glucose transporters in the brain. In addition, nitric oxide activates glucose-6-phosphate dehydrogenase, the first and rate-limiting step of the pentose–phosphate pathway. Here, we review recent evidences suggesting that nitric oxide exerts a fine control of neuronal energy metabolism by tuning the balance of glucose-6-phosphate consumption between glycolysis and pentose–phosphate pathway. This may have important implications for our understanding of the mechanisms controlling neuronal survival during oxidative stress and bioenergetic crisis.

The pentose-phosphate pathway (PPP) promotes the oxidative decarboxylation of glucose-6-phosphate (G6P) in two consecutive steps, catalyzed by glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), yielding ribulose-5-phosphate (Ru5P) (Figure 1) (Wamelink et al., 2008)., This study has received financial support from the French State in the frame of the “Investments for the future” Programme IdEx and Labex (TRAIL) Bordeaux, reference ANR-10-IDEX-03-02 and ANR-10-LABX-57. JB is funded by MINECO (SAF2013-41177-R), ISCIII (RD12/0043/0021), EU-ITN (608381), NIH/NIDA (1R21DA037678-01), MECD (Programa Estatal de Promocion del Talento y su Empleabilidad en I+D+i, PRX14/00387), and the European Regional Development Fund.

Vitamin C is an essential factor for neuronal function and survival, existing in two redox states, ascorbic acid (AA), and its oxidized form, dehydroascorbic acid (DHA). Here, we show uptake of both AA and DHA by primary cultures of rat brain cortical neurons. Moreover, we show that most intracellular AA was rapidly oxidized to DHA. Intracellular DHA induced a rapid and dramatic decrease in reduced glutathione that was immediately followed by a spontaneous recovery. This transient decrease in glutathione oxidation was preceded by an increase in the rate of glucose oxidation through the pentose phosphate pathway (PPP), and a concomitant decrease in glucose oxidation through glycolysis. DHA stimulated the activity of glucose-6-phosphate dehydrogenase, the rate-limiting enzyme of the PPP. Furthermore, we found that DHA stimulated the rate of lactate uptake by neurons in a time- and dose-dependent manner. Thus, DHA is a novel modulator of neuronal energy metabolism by facilitating the utilization of glucose through the PPP for antioxidant purposes. We proposed that the ascorbic acid (AA) taken up by neurons is rapidly oxidized to dehydroascorbic acid (DHA), which inhibits glycolysis and activates the pentose phosphate pathway (PPP), consequently producing NADPH, a critical antioxidant in the recycling of oxidized glutathione (GSSG). In these metabolic conditions, neurons increase lactate uptake, probably using it as an energy source. This data supported the idea that DHA could play a critical role in the modulation of energy metabolism in neurons. We proposed that the ascorbic acid (AA) taken up by neurons is rapidly oxidized to dehydroascorbic acid (DHA), which inhibits glycolysis and activates the pentose phosphate pathway (PPP), consequently producing NADPH, a critical antioxidant in the recycling of oxidized glutathione (GSSG). In these metabolic conditions, neurons increase lactate uptake, probably using it as an energy source. This data supported the idea that DHA could play a critical role in the modulation of energy metabolism in neurons. © 2014 International Society for Neurochemistry., This work was funded by a FONDECYT grant (1100396) to FN as well as grants from the Ministerio de Economía y Competitividad (SAF2013-41177-R), European Regional Development Fund, Instituto de Salud Carlos III (RETICEF, RD12/0043/0021), and Junta de Castilla y León (SA112A12-2) to JPB. DIUC 211031109-1.0 to KS. Centro de Microscopía Avanzada CMA BIOBIO, ACT12 PIA Grant.

Evolution of CO2 from labelled glucose microinjected into frog oocytes in vivo may be ascribed to the pentose-P pathway, as measured by radioactive CO2 production from [1-14C] and [6-14C]glucose. Coinjection of NADP+ and [14C]glucose significantly stimulated 14CO2 production. The effect depends on the amount of NADP+ injected, half maximal stimulation being obtained at 0.13 mM. The increase in CO2 production was also observed with microinjected glucose-1-P, glucose-6-P or fructose-6-P used as substrates. Phenazine methosulfate, mimicked the effects of NADP+. A high NADPH/NADP+ ratio of 4.3 was found in the cells, the intracellular concentration of NADP+ being 19 μM.

Unlike most other cell types, neurons preferentially metabolize glucose via the pentose phosphate pathway (PPP) to maintain their antioxidant status. Inhibiting the PPP in neuronal cell models causes cell death. In rodents, inhibition of this pathway causes selective dopaminergic cell death leading to motor deficits resembling parkinsonism. Using postmortem human brain tissue, we characterized glucose metabolism via the PPP in sporadic Parkinson's disease (PD), Alzheimer's disease (AD), and controls. AD brains showed increased nicotinamide adenine dinucleotide phosphate (NADPH) production in areas affected by disease. In PD however, increased NADPH production was only seen in the affected areas of late-stage cases. Quantifying PPP NADPH-producing enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase by enzyme-linked immunosorbent assay, showed a reduction in the putamen of early-stage PD and interestingly in the cerebellum of early and late-stage PD. Importantly, there was no decrease in enzyme levels in the cortex, putamen, or cerebellum of AD. Our results suggest that down-regulation of PPP enzymes and a failure to increase antioxidant reserve is an early event in the pathogenesis of sporadic PD.

Background Redox homeostasis is essential to sustain metabolism and growth. We recently reported that yeast cells meet a gradual increase in imposed NADPH demand by progressively increasing flux through the pentose phosphate (PP) and acetate pathways and by exchanging NADH for NADPH in the cytosol, via a transhydrogenase-like cycle. Here, we studied the mechanisms underlying this metabolic response, through a combination of gene expression profiling and analyses of extracellular and intracellular metabolites and 13 C-flux analysis. Results NADPH oxidation was increased by reducing acetoin to 2,3-butanediol in a strain overexpressing an engineered NADPH-dependent butanediol dehydrogenase cultured in the presence of acetoin. An increase in NADPH demand to 22 times the anabolic requirement for NADPH was accompanied by the intracellular accumulation of PP pathway metabolites consistent with an increase in flux through this pathway. Increases in NADPH demand were accompanied by the successive induction of several genes of the PP pathway. NADPH-consuming pathways, such as amino-acid biosynthesis, were upregulated as an indirect effect of the decrease in NADPH availability. Metabolomic analysis showed that the most extreme modification of NADPH demand resulted in an energetic problem. Our results also highlight the influence of redox status on aroma production. Conclusions Combined 13 C-flux, intracellular metabolite levels and microarrays analyses revealed that NADPH homeostasis, in response to a progressive increase in NADPH demand, was achieved by the regulation, at several levels, of the PP pathway. This pathway is principally under metabolic control, but regulation of the transcription of PP pathway genes can exert a stronger effect, by redirecting larger amounts of carbon to this pathway to satisfy the demand for NADPH. No coordinated response of genes involved in NADPH metabolism was observed, suggesting that yeast has no system for sensing NADPH/NADP+ ratio. Instead, the induction of NADPH-consuming amino-acid pathways in conditions of NADPH limitation may indirectly trigger the transcription of a set of PP pathway genes.

International audience; A single copy gene, encoding a protein highly similar to transketolase from other systems, was identified in the Trypanosoma brucei genome. The gene was expressed in E. coil and the purified protein demonstrated transketolase activity with Km values of 0.2 mM and 0.8 mM respectively for xylulose 5-phosphate and ribose 5-phosphate. A peroxisomal targeting signal (PTS-1) present at the C-terminus of the protein suggested a glycosomal localisation. However, subcellular localisation experiments revealed that while the protein was present in glycosomes it was found mainly within the cytosol and thus has a dual localisation. Transketolase activity was absent from the long slender bloodstream form of the parasite and the protein was not detectable in this life cycle stage, with the RNA present only at low abundance, indicating a strong differential regulation, being present predominantly in the procyclic form. The gene was knocked out from procyclic T. brucei and transketolase activity was lost but no growth phenotype was evident in the null mutants. Metabolite profiling to compare wild type and TKT null mutants revealed substantial increases in transketolase substrate metabolites coupled to loss of sedoheptulose 7-phosphate, a principal product of the transketolase reaction. (C) 2011 Elsevier B.V. All rights reserved.

Summary The effect of ammonium metabolism on the alternative pathways to glycolysis in young barley roots was investigated through measurements of enzyme activities and changes in amino acid levels. The activities of most glycolytic enzymes did not change either before or after the supply of ammonium to young barley plants. By contrast, increases in phosphoenolpyruvate carboxylase [EC 4.1.1.31] and glucose-6P dehydrogenase [EC 1.1.1.49] levels were measured, suggesting the activation of the pentose phosphate and anaplerotic pathways during ammonium assimilation. Electrophoretic analysis indicated at least two different isoforms of glucose-6P dehydrogenase in barley roots, one of which was increased by ammonium supply. Ammonium supply caused a significant increase in the activities of aspartate aminotransferase [EC 2.6.1.1], alanine aminotransferase [EC 2.6.1.2] and asparaginase [EC 3.5.1.1], and an increase in glut-amine and asparagine levels within 48 h. The results obtained seem to indicate the enhancement, by nitrogen assimilation, of both the dark CO2 fixation and the oxidative pentose phosphate pathway, which synthesise metabolic precursors for amino acid synthesis via transaminases. An involvement of anaplerotic CO2 fixation and of the isoforms of glucose-6P in the roots during ammonia assimilation is discussed.

Background Biologically, hydrogen (H2) can be produced through dark fermentation and photofermentation. Dark fermentation is fast in rate and simple in reactor design, but H2 production yield is unsatisfactorily low as