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Kazuyuki Shimizu - One of the best experts on this subject based on the ideXlab platform.

  • importance of understanding the main Metabolic Regulation in response to the specific pathway mutation for Metabolic engineering of escherichia coli
    Computational and structural biotechnology journal, 2012
    Co-Authors: Yu Matsuoka, Kazuyuki Shimizu
    Abstract:

    Recent Metabolic engineering practice was briefly reviewed in particular for the useful metabolite production such as natural products and biofuel productions. With the emphasis on systems biology approach, the Metabolic Regulation of the main Metabolic pathways in E. coli was discussed from the points of view of enzyme level (allosteric and phosphorylation/ dephosphorylation) Regulation, and gene level (transcriptional) Regulation. Then the effects of the specific pathway gene knockout such as pts, pgi, zwf, gnd, pyk, ppc, pckA, lpdA, pfl gene knockout on the metabolism in E. coli were overviewed from the systems biology point of view with possible application for strain improvement point.

  • Metabolic Regulation of escherichia coli and its phob and phor genes knockout mutants under phosphate and nitrogen limitations as well as at acidic condition
    Microbial Cell Factories, 2011
    Co-Authors: Lolo Wal Marzan, Kazuyuki Shimizu
    Abstract:

    The phosphorus compounds serve as major building blocks of many biomolecules, and have important roles in signal transduction. The phosphate is involved in many biochemical reactions by the transfer of phosphoryl groups. All living cells sophisticatedly regulate the phosphate uptake, and survive even under phosphate-limiting condition, and thus phosphate metabolism is closely related to the diverse metabolism including energy and central carbon metabolism. In particular, phosphorylation may play important roles in the Metabolic Regulation at acidic condition and nitrogen limiting condition, which typically appears at the late growth phase in the batch culture. Moreover, phosphate starvation is a relatively inexpensive means of gene induction in practice, and the phoA promoter has been used for overexpression of heterologous genes. A better understanding of phosphate Regulation would allow for optimization of such processes. The effect of phosphate (P) concentration on the metabolism in Escherichia coli was investigated in terms of fermentation characteristics and gene transcript levels for the aerobic continuous culture at the dilution rate of 0.2 h-1. The result indicates that the specific glucose consumption rate and the specific acetate production rate significantly increased, while the cell concentration decreased at low P concentration (10% of the M9 medium). The increase in the specific glucose uptake rate may be due to ATP demand caused by limited ATP production under P-limitation. The lower cell concentration was also caused by less ATP production. The less ATP production by H+-ATPase may have caused less cytochrome reaction affecting in quinone pool, and caused up-Regulation of ArcA/B, which repressed TCA cycle genes and caused more acetate production. In the case of phoB mutant (and also phoR mutant), the fermentation characteristics were less affected by P-limitation as compared to the wild type where the PhoB regulated genes were down-regulated, while phoR and phoU changed little. The phoR gene knockout caused phoB gene to be down-regulated as well as PhoB regulated genes, while phoU and phoM changed little. The effect of pH together with lower P concentration on the Metabolic Regulation was also investigated. In accordance with up-Regulation of arcA gene expression, the expressions of the TCA cycle genes such as sdhC and mdh were down-regulated at acidic condition. The gene expression of rpoS was up-regulated, and the expression of gadA was up-regulated at pH 6.0. In accordance with this, PhoB regulated genes were up-regulated in the wild type under P-rich and P-limited conditions at pH 6.0 as compared to those at pH 7.0. Moreover, the effect of nitrogen limitation on the Metabolic Regulation was investigated, where the result indicates that phoB gene was up-regulated, and PhoB regulated genes were also up-regulated under N-limitation, as well as nitrogen-regulated genes. The present result shows the complicated nature of the Metabolic Regulation for the fermentation characteristics upon phosphate limitation, acidic condition, and nitrogen limitation based on the transcript levels of selected genes. The result implies that the Regulations under phosphate limitation, acidic condition, and nitrogen limitation, which occur typically at the late growth phase of the batch culture, are interconnected through RpoS and RpoD together with Pho genes.

Katya B. Rubinow - One of the best experts on this subject based on the ideXlab platform.

  • An intracrine view of sex steroids, immunity, and Metabolic Regulation
    Molecular metabolism, 2018
    Co-Authors: Katya B. Rubinow
    Abstract:

    Abstract Background Over the past two decades, parallel recognition has grown of the importance of both sex steroids and immune activity in Metabolic Regulation. More recently, these discrete areas have been integrated in studies examining the Metabolic effects of sex steroid immunomodulation. Implicit in these studies has been a traditional, endocrine model of sex steroid delivery from the gonads to target cells, including immune cells. Thus, research to date has focused on the Metabolic effects of sex steroid receptor signaling in immune cells. This endocrine model, however, overlooks the extensive capacity of immune cells to generate and metabolize sex steroids, enabling the production of sex steroids for intracrine signaling – that is, sex steroid production for signaling within the cell of origin. Intracrine function allows highly cell-autonomous Regulation of sex steroid exposure, and sex steroid secretion by immune cells could confer paracrine signaling effects in neighboring cells within Metabolic tissues. In this review, immune cell intracrinology will denote sex steroid production within immune cells for either intracrine or paracrine signaling. This intracrine capacity of immune cells has been well established, and prior work has supported its importance in autoimmune disorders, trauma, and cancer. The potential relevance of immune cell intracrine function to the Regulation of energy balance, body weight, body composition, and insulin sensitivity has yet to be explored. Scope of review The following review will detail findings to date regarding the steroidogenic and steroid metabolizing capacity of immune cells, the Regulation of immune cell intracrine function, and the biological effects of immune-derived sex steroids, including the clinical relevance of immune cell intracrinology in fields other than metabolism. These findings will serve as the basis for a proposed model of immune cell intracrinology constituting a new frontier in metabolism research. Major conclusions The development of highly sensitive mass spectrometric methods for sex steroid measurement and quantitation of Metabolic flux now allows unprecedented ability to interrogate sex steroid production, metabolism and secretion by immune cells. Immune cell intracrinology could reveal key mechanisms underlying immune cell-mediated Metabolic Regulation.

  • An intracrine view of sex steroids, immunity, and Metabolic Regulation
    'Elsevier BV', 2018
    Co-Authors: Katya B. Rubinow
    Abstract:

    Background: Over the past two decades, parallel recognition has grown of the importance of both sex steroids and immune activity in Metabolic Regulation. More recently, these discrete areas have been integrated in studies examining the Metabolic effects of sex steroid immunomodulation. Implicit in these studies has been a traditional, endocrine model of sex steroid delivery from the gonads to target cells, including immune cells. Thus, research to date has focused on the Metabolic effects of sex steroid receptor signaling in immune cells. This endocrine model, however, overlooks the extensive capacity of immune cells to generate and metabolize sex steroids, enabling the production of sex steroids for intracrine signaling – that is, sex steroid production for signaling within the cell of origin. Intracrine function allows highly cell-autonomous Regulation of sex steroid exposure, and sex steroid secretion by immune cells could confer paracrine signaling effects in neighboring cells within Metabolic tissues. In this review, immune cell intracrinology will denote sex steroid production within immune cells for either intracrine or paracrine signaling. This intracrine capacity of immune cells has been well established, and prior work has supported its importance in autoimmune disorders, trauma, and cancer. The potential relevance of immune cell intracrine function to the Regulation of energy balance, body weight, body composition, and insulin sensitivity has yet to be explored. Scope of review: The following review will detail findings to date regarding the steroidogenic and steroid metabolizing capacity of immune cells, the Regulation of immune cell intracrine function, and the biological effects of immune-derived sex steroids, including the clinical relevance of immune cell intracrinology in fields other than metabolism. These findings will serve as the basis for a proposed model of immune cell intracrinology constituting a new frontier in metabolism research. Major conclusions: The development of highly sensitive mass spectrometric methods for sex steroid measurement and quantitation of Metabolic flux now allows unprecedented ability to interrogate sex steroid production, metabolism and secretion by immune cells. Immune cell intracrinology could reveal key mechanisms underlying immune cell-mediated Metabolic Regulation. Keywords: Macrophages, Lymphocytes, Estrogens, Androgens, Intracrine, Metabolis

Vučetić, Milica M. - One of the best experts on this subject based on the ideXlab platform.

  • Molecular mechanisms of Metabolic Regulation in hibernation and during cold-acclimation in European ground squirrel (Spermophilus citellus)
    Универзитет у Београду Биолошки факултет, 2014
    Co-Authors: Vučetić, Milica M.
    Abstract:

    Fenomen hibernacije predstavlja fascinantan primer plastičnosti kod sisara. Hibernirajući sisari podliježu složenom nizu biohemijskih, fizioloških i bihevioralnih promjena u odgovoru na senzonske energetski-zahtijevne periode kuplovane sa redukovanom dopstupnošću hrane. Cilj disertacije je da se ispitaju promjene ćelijskog metabolizma u tkivima i organima tekunica, ključnim za održanje ukupne energetske homeostaze - mrko i bijelo masno tkivo (engl. brown adipose tissue, BAT i white adipose tissue, WAT), mišići i jetra, tokom perioda aklimacije na nisku temperaturu, kao i u fazi hibernacije. Efekat aklimacije/hibernacije na metaboličko remodeliranje u tkivima i organima tekunica praćen je određivanjem: mitohondrijalnog kapaciteta (genska i/ili proteinska ekspresije komponenti respiratornog lanca i ATP sintaze); termogenog kapaciteta (ekspresija dekuplujućeg proteina 1); ekspresionih profila enzima ključnih metaboličkih puteva: glikolize, β-oksidacije, Krebsovog ciklusa, metabolizama triacilglicerola i glikogena. Ispitivani su i transkripcioni faktori uključeni u metaboličku regulaciju, kao i enzimi antioksidativne odbrane. Takođe, ispitivane su promjene u BAT i depoima WAT na strukturnom i ultrastrukturnom nivou. Mužjaci evropske tekunice Spermophilus citellus su početkom septembra podijeljeni u dvije grupe: kontrolnu, koja je boravila na sobnoj temeraturi (22 ± 1 ºC) i grupu aklimiranu na nisku temperaturu (4 ± 1 ºC). Aktivne, eutermične tekunice, koje nisu ušle u duboku hibernaciju tokom aklimacije, žrtvovane su nakon 1, 3, 7, 12, odnosno 21 dan. Tekunice koje su ušle u hibernaciju žrtvovane su nakon 2-5 dana trajanja hibernacije (kontinuirana rektalna temperatura 4 ºC). BAT, subkutano, retroperitonealno i epididimalno WAT (sWAT, rWAT i eWAT), skeletni mišić (musculus quadriceps) i jetra su uzorkovani odmah po žrtvovanju. Kako bi se ispitali mehanizmi metaboličke regulacije u BAT, specifični za hibernatore, paralelno je rađena komparativna studija aklimacije pacova na nisku temperaturu...The phenomenon of hibernation is a fascinating example of plasticity in mammals. Hibernating mammals are subjected to a complex series of biochemical, physiological and behavioral changes in response to seasonal energy-demanding periods coupled with reduced food availability. The aim of the thesis was to investigate Metabolic changes in the key tissues and organs of the ground squirrel, responsible for maintaining overall energy homeostasis - brown and white adipose tissue (BAT and WAT), skeletal muscle and liver, during the acclimation to low temperature, as well as in the hibernation. Effects of acclimation/hibernation on Metabolic remodeling in the tissues and organs of the ground squirrel were determined by: mitochondrial capacity (gene and/or protein expression of the components of the respiratory chain and ATP synthase); thermogenic capacity (uncoupling protein 1 content), the expression profile of the key Metabolic enzymes involved in: glycolysis, β-oxidation, Krebs cycle, glycogen and triglycerides metabolism. Furthermore, transcription factors involved in the Metabolic Regulation, as well as antioxidant enzymes, were examined. In parallel, we examined the changes in BAT and WAT depots on the structural and ultrastructural level. Males of the European ground squirrel Spermophilus citellus were divided into two groups in early September: the control group, kept at room temperature (22 ± 1 º C) and a group acclimated to low temperature (4 ± 1 ºC). Active, euthermic ground squirrels, which did not enter into deep hibernation during acclimation, were sacrificed after 1, 3, 7, 12, or 21 days. Ground squirrels that entered hibernation were sacrificed after 2-5 days of hibernation (continuous rectal temperature of 4 ºC). BAT, subcutaneous, retroperitoneal and epididimal WAT (sWAT, rWAT and eWAT), skeletal muscle (musculus quadriceps) and liver were sampled. Parallel, in order to examine the mechanisms of Metabolic Regulation in the BAT specific for hibernation, comparative study with rats acclimated to low temperatures, was made. Results show that, when hibernating animals are exposed to low temperature, the cellular metabolism in all examined tissues/organs is initially subordinated to maintaining euthermia, i.e. thermogenic process. In the early period of the cold-exposure, shivering and nonshivering thermogenesis is induced in the muscle and BAT, respectively..

  • Molecular mechanisms of Metabolic Regulation in hibernation and during cold-acclimation in European ground squirrel (Spermophilus citellus)
    Belgrade: University of Belgrade Faculty of Biology, 2014
    Co-Authors: Vučetić, Milica M.
    Abstract:

    Fenomen hibernacije predstavlja fascinantan primer plastičnosti kod sisara. Hibernirajući sisari podliježu složenom nizu biohemijskih, fizioloških i bihevioralnih promjena u odgovoru na senzonske energetski-zahtijevne periode kuplovane sa redukovanom dopstupnošću hrane. Cilj disertacije je da se ispitaju promjene ćelijskog metabolizma u tkivima i organima tekunica, ključnim za održanje ukupne energetske homeostaze - mrko i bijelo masno tkivo (engl. brown adipose tissue, BAT i white adipose tissue, WAT), mišići i jetra, tokom perioda aklimacije na nisku temperaturu, kao i u fazi hibernacije. Efekat aklimacije/hibernacije na metaboličko remodeliranje u tkivima i organima tekunica praćen je određivanjem: mitohondrijalnog kapaciteta (genska i/ili proteinska ekspresije komponenti respiratornog lanca i ATP sintaze); termogenog kapaciteta (ekspresija dekuplujućeg proteina 1); ekspresionih profila enzima ključnih metaboličkih puteva: glikolize, β-oksidacije, Krebsovog ciklusa, metabolizama triacilglicerola i glikogena. Ispitivani su i transkripcioni faktori uključeni u metaboličku regulaciju, kao i enzimi antioksidativne odbrane. Takođe, ispitivane su promjene u BAT i depoima WAT na strukturnom i ultrastrukturnom nivou. Mužjaci evropske tekunice Spermophilus citellus su početkom septembra podijeljeni u dvije grupe: kontrolnu, koja je boravila na sobnoj temeraturi (22 ± 1 ºC) i grupu aklimiranu na nisku temperaturu (4 ± 1 ºC). Aktivne, eutermične tekunice, koje nisu ušle u duboku hibernaciju tokom aklimacije, žrtvovane su nakon 1, 3, 7, 12, odnosno 21 dan. Tekunice koje su ušle u hibernaciju žrtvovane su nakon 2-5 dana trajanja hibernacije (kontinuirana rektalna temperatura 4 ºC). BAT, subkutano, retroperitonealno i epididimalno WAT (sWAT, rWAT i eWAT), skeletni mišić (musculus quadriceps) i jetra su uzorkovani odmah po žrtvovanju. Kako bi se ispitali mehanizmi metaboličke regulacije u BAT, specifični za hibernatore, paralelno je rađena komparativna studija aklimacije pacova na nisku temperaturu...The phenomenon of hibernation is a fascinating example of plasticity in mammals. Hibernating mammals are subjected to a complex series of biochemical, physiological and behavioral changes in response to seasonal energy-demanding periods coupled with reduced food availability. The aim of the thesis was to investigate Metabolic changes in the key tissues and organs of the ground squirrel, responsible for maintaining overall energy homeostasis - brown and white adipose tissue (BAT and WAT), skeletal muscle and liver, during the acclimation to low temperature, as well as in the hibernation. Effects of acclimation/hibernation on Metabolic remodeling in the tissues and organs of the ground squirrel were determined by: mitochondrial capacity (gene and/or protein expression of the components of the respiratory chain and ATP synthase); thermogenic capacity (uncoupling protein 1 content), the expression profile of the key Metabolic enzymes involved in: glycolysis, β-oxidation, Krebs cycle, glycogen and triglycerides metabolism. Furthermore, transcription factors involved in the Metabolic Regulation, as well as antioxidant enzymes, were examined. In parallel, we examined the changes in BAT and WAT depots on the structural and ultrastructural level. Males of the European ground squirrel Spermophilus citellus were divided into two groups in early September: the control group, kept at room temperature (22 ± 1 º C) and a group acclimated to low temperature (4 ± 1 ºC). Active, euthermic ground squirrels, which did not enter into deep hibernation during acclimation, were sacrificed after 1, 3, 7, 12, or 21 days. Ground squirrels that entered hibernation were sacrificed after 2-5 days of hibernation (continuous rectal temperature of 4 ºC). BAT, subcutaneous, retroperitoneal and epididimal WAT (sWAT, rWAT and eWAT), skeletal muscle (musculus quadriceps) and liver were sampled. Parallel, in order to examine the mechanisms of Metabolic Regulation in the BAT specific for hibernation, comparative study with rats acclimated to low temperatures, was made. Results show that, when hibernating animals are exposed to low temperature, the cellular metabolism in all examined tissues/organs is initially subordinated to maintaining euthermia, i.e. thermogenic process. In the early period of the cold-exposure, shivering and nonshivering thermogenesis is induced in the muscle and BAT, respectively...Fenomen hibernacije predstavlja fascinantan primer plastičnosti kod sisara. Hibernirajući sisari podliježu složenom nizu biohemijskih, fizioloških i bihevioralnih promjena u odgovoru na senzonske energetski-zahtijevne periode kuplovane sa redukovanom dopstupnošću hrane. Cilj disertacije je da se ispitaju promjene ćelijskog metabolizma u tkivima i organima tekunica, ključnim za održanje ukupne energetske homeostaze - mrko i bijelo masno tkivo (engl. brown adipose tissue, BAT i white adipose tissue, WAT), mišići i jetra, tokom perioda aklimacije na nisku temperaturu, kao i u fazi hibernacije. Efekat aklimacije/hibernacije na metaboličko remodeliranje u tkivima i organima tekunica praćen je određivanjem: mitohondrijalnog kapaciteta (genska i/ili proteinska ekspresije komponenti respiratornog lanca i ATP sintaze); termogenog kapaciteta (ekspresija dekuplujućeg proteina 1); ekspresionih profila enzima ključnih metaboličkih puteva: glikolize, β-oksidacije, Krebsovog ciklusa, metabolizama triacilglicerola i glikogena. Ispitivani su i transkripcioni faktori uključeni u metaboličku regulaciju, kao i enzimi antioksidativne odbrane. Takođe, ispitivane su promjene u BAT i depoima WAT na strukturnom i ultrastrukturnom nivou. Mužjaci evropske tekunice Spermophilus citellus su početkom septembra podijeljeni u dvije grupe: kontrolnu, koja je boravila na sobnoj temeraturi (22 ± 1 ºC) i grupu aklimiranu na nisku temperaturu (4 ± 1 ºC). Aktivne, eutermične tekunice, koje nisu ušle u duboku hibernaciju tokom aklimacije, žrtvovane su nakon 1, 3, 7, 12, odnosno 21 dan. Tekunice koje su ušle u hibernaciju žrtvovane su nakon 2-5 dana trajanja hibernacije (kontinuirana rektalna temperatura 4 ºC). BAT, subkutano, retroperitonealno i epididimalno WAT (sWAT, rWAT i eWAT), skeletni mišić (musculus quadriceps) i jetra su uzorkovani odmah po žrtvovanju. Kako bi se ispitali mehanizmi metaboličke regulacije u BAT, specifični za hibernatore, paralelno je rađena komparativna studija aklimacije pacova na nisku temperaturu. Rezultati pokazuju da je, prilikom izlaganja hibernirajućih životinja niskoj temperaturi, ćelijski metabolizam u svim ispitivanim tkivima/organima inicijalno podređen održanju eutermije, tj. termogenom procesu koji se odvija u skeletnim mišićima i BAT. U ranom periodu izlaganja hladnoći, u skeletnim mišićima i BAT, dolazi do indukcije termogeneze (drhteće i nedrhteće), koja je metabolički podržana razlaganjem šećera. Međutim, produkcija toplote u oba termogena organa asocirana je sa energetskim disbalansom, koji je tokom produžene aklimacije najvjerovatnije odgovoran za supresiju puteva potrošnje energije (primarno termogeneze) i pripremu tekunica za ulazak u stanje hipotermije/hipometabolizma. Najveći dio goriva za termogenezu, u ranoj fazi aklimacije, obezbijeđuje se iz visceralnih depoa WAT (posebno eWAT), u kojima je detektovano smanjenje površine adipocitnog profila, usled intenzivne lipolize. Kasnije tokom izlaganja hladnoći, kada se termogeni kapacitet BAT suprimira, u sva tri ispitivana depoa WAT indukovana je aktivnost AMP-aktivirane protein kinase (AMPK), „blokirana” lipoliza i putevi potrošnje energije, a stimulisan oksidativni metabolizam. Jetra tokom aklimacije ima centralno mjesto koordinacije lipidnog i ugljenohidratnog metabolizma. Rezultati disertacije pokazuju da je u fazi duboke hibernacije termogeni kapacitet BAT i skeletnih mišića značajno suprimiran. Takođe, hipoksija-inducibilni factor-1 (HIF-1) ima centralnu ulogu u metaboličkom remodeliranju termogenih organa u fazi hibernacije. Osim suprimiranja energetski-zahtijevnih termogenih procesa, HIF-1 u uslovima hipometabolizma ima ulogu i u regulaciji, tj. indukciji glikolitičkog puta, važne komponente energetske homeostaze tokom hibernacije. Slično reprogramiranje metabolizma dešava se i u visceralnim depoima WAT. Jetra u hibernaciji ostvaruje veoma sličnu metaboličku strategiju kao pri uslovima gladovanja: indukcija katabolizma lipida i supresija razlaganja glukoze, uz istovremenu indukciju glukoneogeneze. Rezultati disertacije ukazuju da je u hibernaciji kapacitet za oksidaciju lipida povećan u svim ispitivanim tkivima/organima, osim u visceralnim depoima WAT. U BAT, intenziviranje puteva oksidacije masnih kiselina primarno služi održanju neophodnog nivoa termogeneze, dok je u skeletnim mišićima i jetri povezano sa adaptacijom na hipotermične/hipometaboličke uslove hibernacije. Uočljuv manji stepen interorganske komunikacije kada je lipidni metabolizam u pitanju, sugeriše da se tokom hibernacije uspostavlja određeni stepen tkivne autonomnosti. Generalno se može zaključiti da karakteristično tkivno-zavisno remodelovanje energetskog metabolizma predstavlja centralnu osovinu i uslov fiziološke plastičnosti hibernatora koja im omogućava brojne prednosti u odnosu na nehibernirajuće srodnike i preživljavanje u nepovoljnim uslovima sredine, bilo da su aktivni i eutermični ili letargični i hipotemični.The phenomenon of hibernation is a fascinating example of plasticity in mammals. Hibernating mammals are subjected to a complex series of biochemical, physiological and behavioral changes in response to seasonal energy-demanding periods coupled with reduced food availability. The aim of the thesis was to investigate Metabolic changes in the key tissues and organs of the ground squirrel, responsible for maintaining overall energy homeostasis - brown and white adipose tissue (BAT and WAT), skeletal muscle and liver, during the acclimation to low temperature, as well as in the hibernation. Effects of acclimation/hibernation on Metabolic remodeling in the tissues and organs of the ground squirrel were determined by: mitochondrial capacity (gene and/or protein expression of the components of the respiratory chain and ATP synthase); thermogenic capacity (uncoupling protein 1 content), the expression profile of the key Metabolic enzymes involved in: glycolysis, β-oxidation, Krebs cycle, glycogen and triglycerides metabolism. Furthermore, transcription factors involved in the Metabolic Regulation, as well as antioxidant enzymes, were examined. In parallel, we examined the changes in BAT and WAT depots on the structural and ultrastructural level. Males of the European ground squirrel Spermophilus citellus were divided into two groups in early September: the control group, kept at room temperature (22 ± 1 º C) and a group acclimated to low temperature (4 ± 1 ºC). Active, euthermic ground squirrels, which did not enter into deep hibernation during acclimation, were sacrificed after 1, 3, 7, 12, or 21 days. Ground squirrels that entered hibernation were sacrificed after 2-5 days of hibernation (continuous rectal temperature of 4 ºC). BAT, subcutaneous, retroperitoneal and epididimal WAT (sWAT, rWAT and eWAT), skeletal muscle (musculus quadriceps) and liver were sampled. Parallel, in order to examine the mechanisms of Metabolic Regulation in the BAT specific for hibernation, comparative study with rats acclimated to low temperatures, was made. Results show that, when hibernating animals are exposed to low temperature, the cellular metabolism in all examined tissues/organs is initially subordinated to maintaining euthermia, i.e. thermogenic process. In the early period of the cold-exposure, shivering and nonshivering thermogenesis is induced in the muscle and BAT, respectively. Although these processes are Metabolically supported by the breakdown of glucose, the production of heat in both thermogenic organs is associated with energy imbalance. This is likely responsible for suppression of energy consumption pathways (primarly thermogenesis) during the extended acclimation period, and for preparation of ground squirrel to a state of hypothermia/hypometabolism. In the early period of acclimation, the fuel for thermogenesis is preferentially provided from visceral WAT depots (particularly eWAT), wherein decreased adipocyte surface profile, a result of intensive lipolysis, is observed. Later, during exposure to cold, when the thermogenic capacity in BAT is suppressed, activity of AMP-activated protein kinase is induced in all three WAT depots, lipolysis and energy-consuming pathways are "blocked" and oxidative metabolism is stimulated. Liver is central coordinator of the lipid and carbohydrate metabolism during cold acclimation. In the deep hibernation, thermogenic capacity of BAT and skeletal muscle is significantly suppressed. It seems that hypoxia-inducible factor-1 (HIF-1) plays a central role in the Metabolic remodeling of the thermogenic organs in hibernation, by both suppressing the energy-demanding, thermogenic processes, and also, by inducing glycolytic pathway, an important component of energy homeostasis in hypoMetabolic conditions. Similar Metabolic reprogramming occurs in the visceral WAT depots. In hibernation, liver shows analogous Metabolic strategy as in fasting conditions: induction of lipid catabolism and suppression of glucose degradation, with the simultaneous induction of gluconeogenesis. Results indicate that capacity for lipid oxidation is increased in all tested tissues/organs, except in visceral WAT depots, during hibernation. In BAT, the intensification of fatty acid oxidation pathways primarily serves to maintain the necessary level of thermogenesis, whereas in skeletal muscle and liver this is associated with adaptation to hypothermic/hypoMetabolic conditions of hibernation. Noticeable lower level of interorgan communication, when it comes to lipid metabolism, suggests that tissues establish a certain degree of autonomy during hibernation. In general, it can be concluded that characteristic tissue-dependent remodeling of the energy metabolism is the central axis and the precause of physiological plasticity of hibernators that provides them many advantages over the nonhibernating counterparts, and the survival under adverse environmental conditions, whether they are active and euthermic or lethargic and hypothermic

Agneta Norén - One of the best experts on this subject based on the ideXlab platform.

  • Metabolic Regulation of nitrogen fixation in Rhodospirillum rubrum.
    Biochemical Society Transactions, 2006
    Co-Authors: Helen Wang, Agneta Norén
    Abstract:

    Nitrogenase activity in Rhodospirillum rubrum is post-translationally regulated by DRAG (dinitrogenase reductase glycohydrolase) and DRAT (dinitrogenase reductase ADP-ribosylation transferase). When a sudden increase in fixed nitrogen concentration or energy depletion is sensed by the cells, DRAG is inactivated and DRAT activated. We propose that the Regulation of DRAG is dependent on its location in the cell and the presence of an ammonium-sensing protein.

  • Metabolic Regulation of nitrogenase in rhodospirillum rubrum studies on drag and drad the regulatory proteins of dinitrogenase reductase
    1998
    Co-Authors: Agneta Norén
    Abstract:

    Nitrogen fixation is catalyzed by nitrogenase, in an ATP-dependent reaction where dinitrogen is reduced to ammonium. Nitrogenase is a protein complex consisting of two proteins; dinitrogenase and dinitrogenase reductase and the reaction is only carried out by prokaryotes. In the photosynthetic bacterium, Rhodospirillum rubrum, nitrogen fixation is regulated at both a genetic and a Metabolic level. The Metabolic Regulation is excerted through post-translational modification of dinitrogenase reductase, causing inactivation of the enzyme when so called switch-off effectors are added. The post-translational modification has been shown to be an ADP-ribosylation on Arg-101 of dinitrogenase reductase. The regulatory proteins are; dinitrogenase reductase ADP-ribosyl transferase (DRAT), catalyzing modification and dinitrogenase reductase activating glycohydrolase (DRAG) catalyzing demodification. Both DRAG and DRAT are subjected to post-translational Regulation in the cell. The internal signals for this Regulation are still not identified and have been the focus of this thesis. By changing the concentration of NAD+ in R.rubrum a reversible decrease in nitrogenase activity could be observed. This decrease in activity was shown to be correlated to a post-translational modification of dinitrogenase reductase by SDS-PAGE and Western blot. The modification is catalyzed by DRAT since studies on a DRAT- mutant show no response at all to additional NAD+. Shortening the switch-off period by addition of NADH generating compounds, confirmed that a change in NAD+ /NADH ratio affects the duration of the switch-off period. Using in vivo fluorometry to study the effect of changes in the NAD+ concentration when nitrogenous switch-off effectors were added, showed that ammonium and glutamine momentarily change the concentration of NAD+. On the basis of these results we suggest that the signal pathway for DRAT activation involves changes in the concentration of NAD+. The membrane associated DRAG is shown to be released by treating the chromatophores with MgGDP, similar treatment with MgGTP, MgATP or MgADP did not result in such a release. Upto 40% of DRAG activity can be found in the supernatant compared to 0.5 M NaCl treated membranes. The chromatophore membranes are shown to have GTPase activity with and without DRAG associated to the membranes indicating the presence of a GTP hydrolyzing protein in the chromatophore membrane. Crosslinking studies demonstrated a high molecular weight complex, that crossreacted with DRAG antibodies. The Regulation of DRAG is suggested by us to be mediated by the chromatophore membrane possibly involving a protein complex with GTPase activity. DRAG is suggested to be active in its soluble form and inactive when bound to the membranes.

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  • Global Metabolic Regulation analysis for Escherichia coli K12 based on protein expression by 2-dimensional electrophoresis and enzyme activity measurement
    Applied Microbiology and Biotechnology, 2003
    Co-Authors: L. Peng, K. Shimizu
    Abstract:

    Regulation of the main Metabolic pathways of Escherichia coli K12 was investigated based on 2-dimensional electrophoresis (2DE) and the measurement of enzyme activities. The cells were grown aerobically in different carbon sources, such as glucose, acetate, gluconate or glycerol. Microaerobic cultivation was also conducted with glucose as a carbon source. Fifty-two proteins could be identified based on 2DE, and 26 enzyme activities from the main Metabolic pathways—including glycolysis, pentose phosphate pathway, TCA cycle, Entner-Doudoroff pathway and fermentative pathway—were assayed. These enzyme activities, together with global and quantitative protein expression, gave us a clear picture of Metabolic Regulation. The results show that, compared with the control experiment with glucose as a carbon source under aerobic conditions, glycolytic enzymes were slightly up-regulated (10-fold) under microaerobic conditions in glucose medium. When acetate was used as a carbon source, pfkA , pykF , ppc and zwf were down-regulated, while fbp , pckA , ppsA and mez were significantly up-regulated. Glyoxylate enzymes such as aceA and aceB were strongly up-regulated (>10-fold) and TCA-cycle-related enzymes were also up-regulated to some extent. With gluconate as a carbon source, edd , eda , fbp and TCA cycle enzymes were up-regulated. With glycerol as a carbon source, fbp and TCA cycle enzymes were up-regulated, while ackA was significantly down-regulated. Protein abundance obtained by 2DE correlated well with enzyme activity, with a few exceptions (e.g., isocitrate dehydrogenase), during aerobic growth on acetate.