Different modes of activating phosphofructokinase, a key regulatory enzyme of glycolysis, in working vertebrate muscle

2002 ◽  
Vol 30 (2) ◽  
pp. 264-270 ◽  
Author(s):  
G. Wegener ◽  
U. Krause
Keyword(s):  
Metabolic Regulation ◽  
Rana Temporaria ◽  
Muscle Metabolism ◽  
Fold Increase ◽  
Whole Body ◽  
Glycolytic Flux ◽  
Open Questions ◽  
Vertebrate Muscle ◽  
Repeated Exercise ◽  
Gastrocnemius Muscles

Glycolytic flux in white muscle can be increased several-hundredfold by exercise. Phosphofructokinase (PFK; EC 2.7.1.11) is a key regulatory enzyme of glycolysis, but how its activity in muscle is controlled is not fully understood. In order not to neglect integrative aspects of metabolic regulation, we have studied in frogs (Rana temporaria) a physiological form of muscle work (swimming) that can be triggered like a reflex. We analysed swimming to fatigue in well rested frogs, recovery from exercise, and repeated exercise after 2 h of recovery. At various times, gastrocnemius muscles were tested for glycolytic intermediates and effectors of PFK. All metabolites responded similarly to the two periods of exercise, with the notable exception of fructose 2,6-bisphosphate (F2,6P2), which we proved to be a most potent activator of frog muscle PFK. The first bout of exercise triggered a more than 10-fold increase in F2,6P2; PFK activity and the content of F2,6P2 in muscle were well correlated. F2,6P2 decreased to pre-exercise levels in fatigued frogs and it virtually disappeared during recovery. Varying by a factor of 70, F2,6P2 was the most dynamic of all metabolites in muscle. Even more surprisingly, F2,6P2 did not respond at all to a second bout of exercise. Other activators of PFK, such as Pi, AMP and ADP, are increased as a consequence of increased ATP turnover in contracting muscle cells. This does not apply to F2,6P2, which is likely to respond to extracellular signals and could be involved in mechanisms by which muscle metabolism is integrated into the metabolism of the whole body. Whether this phenomenon exists in vertebrates other than the frog, and maybe even in humans, and how the content of F2,6P2 in muscle is controlled are intriguing open questions.

Exercise and recovery in frog muscle: metabolism of PCr, adenine nucleotides, and related compounds

1996 ◽  
Vol 270 (4) ◽  
pp. R811-R820 ◽  
Author(s):  
U. Krause ◽  
G. Wegener
Keyword(s):  
Rana Temporaria ◽  
Adenine Nucleotides ◽  
Metabolic Stress ◽  
Muscle Metabolism ◽  
Atp Synthesis ◽  
Amp Deaminase ◽  
Severe Fatigue ◽  
Repeated Exercise ◽  
Tissue Contents

The effects of exercise (swimming), fatigue, and recovery on the intracellular pH (pHi), energy-rich phosphates, and related metabolites were studied in the gastrocnemius muscle of common frogs (Rana temporaria) at 20 degrees C. Exercise caused a rapid decrease in the content of phosphocreatine (PCr) and a corresponding increase in that of Pi. The ATP level remained virtually constant for 1 min; its precipitous decrease during the following minute was associated with a rise in the contents of inosine 5'-monophosphate (IMP) and NH4+, indicating a marked activation of AMP deaminase. Five minutes of swimming caused severe fatigue, which was correlated with decreases in muscle PCr (-85%), ATP (-42%), and pHi (-0.8 units). Recovery appeared almost complete within 2 h, and the frogs were then induced to swim again. During the initial 10 s of this second exercise, ATP synthesis was as high as in the first exercise, but the rate decreased more rapidly between 10 and 60 s, thus indicating that repeated exercise caused increased metabolic stress. IMP formation in working muscle was not strictly correlated with the pHi or the tissue contents of Pi, AMP and ADP, although from studies in vitro AMP deaminase is known to be modulated by these parameters.

scholarly journals β-Hydroxybutyrate Oxidation Promotes the Accumulation of Immunometabolites in Activated Microglia Cells

Metabolites ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 346
Author(s):  
Adrian Benito ◽  
Nabil Hajji ◽  
Kevin O’Neill ◽  
Hector C. Keun ◽  
Nelofer Syed
Keyword(s):  
Metabolic Regulation ◽  
Marker Gene ◽  
Tca Cycle ◽  
Metabolic Reprogramming ◽  
Glycolytic Flux ◽  
Dihydroxyacetone Phosphate ◽  
Glycolytic Intermediate ◽  
Critical Set ◽  
The Tca Cycle ◽  
Bv2 Cells

Metabolic regulation of immune cells has arisen as a critical set of processes required for appropriate response to immunological signals. While our knowledge in this area has rapidly expanded in leukocytes, much less is known about the metabolic regulation of brain-resident microglia. In particular, the role of alternative nutrients to glucose remains poorly understood. Here, we use stable-isotope (13C) tracing strategies and metabolomics to characterize the oxidative metabolism of β-hydroxybutyrate (BHB) in human (HMC3) and murine (BV2) microglia cells and the interplay with glucose in resting and LPS-activated BV2 cells. We found that BHB is imported and oxidised in the TCA cycle in both cell lines with a subsequent increase in the cytosolic NADH:NAD+ ratio. In BV2 cells, stimulation with LPS upregulated the glycolytic flux, increased the cytosolic NADH:NAD+ ratio and promoted the accumulation of the glycolytic intermediate dihydroxyacetone phosphate (DHAP). The addition of BHB enhanced LPS-induced accumulation of DHAP and promoted glucose-derived lactate export. BHB also synergistically increased LPS-induced accumulation of succinate and other key immunometabolites, such as α-ketoglutarate and fumarate generated by the TCA cycle. Finally, BHB upregulated the expression of a key pro-inflammatory (M1 polarisation) marker gene, NOS2, in BV2 cells activated with LPS. In conclusion, we identify BHB as a potentially immunomodulatory metabolic substrate for microglia that promotes metabolic reprogramming during pro-inflammatory response.

scholarly journals Responses of hypertrophied myocytes to reactive species: implications for glycolysis and electrophile metabolism

2011 ◽  
Vol 435 (2) ◽  
pp. 519-528 ◽  
Author(s):  
Brian E. Sansbury ◽  
Daniel W. Riggs ◽  
Robert E. Brainard ◽  
Joshua K. Salabei ◽  
Steven P. Jones ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Oxygen Consumption ◽  
Energy Demand ◽  
Lactate Production ◽  
Fold Increase ◽  
Cellular Protein ◽  
Reactive Species ◽  
Neonatal Rat ◽  
Glycolytic Flux ◽  
Rat Cardiomyocytes

During cardiac remodelling, the heart generates higher levels of reactive species; yet an intermediate ‘compensatory’ stage of hypertrophy is associated with a greater ability to withstand oxidative stress. The mechanisms underlying this protected myocardial phenotype are poorly understood. We examined how a cellular model of hypertrophy deals with electrophilic insults, such as would occur upon ischaemia or in the failing heart. For this, we measured energetics in control and PE (phenylephrine)-treated NRCMs (neonatal rat cardiomyocytes) under basal conditions and when stressed with HNE (4-hydroxynonenal). PE treatment caused hypertrophy as indicated by augmented atrial natriuretic peptide and increased cellular protein content. Hypertrophied myocytes demonstrated a 2.5-fold increase in ATP-linked oxygen consumption and a robust augmentation of oligomycin-stimulated glycolytic flux and lactate production. Hypertrophied myocytes displayed a protected phenotype that was resistant to HNE-induced cell death and a unique bioenergetic response characterized by a delayed and abrogated rate of oxygen consumption and a 2-fold increase in glycolysis upon HNE exposure. This augmentation of glycolytic flux was not due to increased glucose uptake, suggesting that electrophile stress results in utilization of intracellular glycogen stores to support the increased energy demand. Hypertrophied myocytes also had an increased propensity to oxidize HNE to 4-hydroxynonenoic acid and sustained less protein damage due to acute HNE insults. Inhibition of aldehyde dehydrogenase resulted in bioenergetic collapse when myocytes were challenged with HNE. The integration of electrophile metabolism with glycolytic and mitochondrial energy production appears to be important for maintaining myocyte homoeostasis under conditions of increased oxidative stress.

Control of glycolysis in vertebrate skeletal muscle during exercise

1996 ◽  
Vol 270 (4) ◽  
pp. R821-R829 ◽  
Author(s):  
U. Krause ◽  
G. Wegener
Keyword(s):  
Gastrocnemius Muscle ◽  
Rana Temporaria ◽  
High Capacity ◽  
Repeated Exercise ◽  
Frog Rana Temporaria ◽  
Time Courses ◽  
Fructose 1,6 Bisphosphate ◽  
Assay Conditions

The gastrocnemius muscle of the frog (Rana temporaria) has a high capacity for anaerobic glycolysis from glycogen. Glycolytic metabolites and effectors of phosphofructokinase, particularly the hexose bisphosphates, were followed in muscle during exercise (swimming between 5 s and 5 min), recovery (rest for up to 2 h after 5 min of swimming), and repeated exercise (swimming for up to 60 s after 2 h of recovery). Glycogen phosphorylase and phosphofructokinase were swiftly activated with exercise. The hexose bisphosphates followed markedly different time courses. Fructose 1,6-bisphosphate was transiently increased in both exercise and repeated exercise. This appears to be an effect rather than a cause of phosphofructokinase activation. Glucose 1,6-biphosphate was accumulated only while phosphofructokinase was active and was unchanged at other times. Fructose 2,6-biphosphate showed a 10-fold transient increase on exercise in rested frogs, almost disappeared from the muscle during recovery, and did not change during repeated exercise. Fructose 2,6-biphosphate is a potent activator of phosphofructokinase in vitro under near physiological assay conditions, and it may serve this function also in vivo during exercise. Glucose 1,6-biphosphate could be an activator of phosphofructokinase in repeated exercise when fructose 2,6-biphosphate is not available.

scholarly journals Mitochondrial Biogenesis and Remodeling during Adipogenesis and in Response to the Insulin Sensitizer Rosiglitazone

2003 ◽  
Vol 23 (3) ◽  
pp. 1085-1094 ◽  
Author(s):  
Leanne Wilson-Fritch ◽  
Alison Burkart ◽  
Gregory Bell ◽  
Karen Mendelson ◽  
John Leszyk ◽  
...  
Keyword(s):  
Mitochondrial Biogenesis ◽  
Gradient Centrifugation ◽  
Light And Electron Microscopy ◽  
Fold Increase ◽  
Mitochondrial Proteins ◽  
Whole Body ◽  
Brown Adipocyte ◽  
Insulin Sensitizer ◽  
Adipose Differentiation ◽  
Whole Body Metabolism

ABSTRACT White adipose tissue is an important endocrine organ involved in the control of whole-body metabolism, insulin sensitivity, and food intake. To better understand these functions, 3T3-L1 cell differentiation was studied by using combined proteomic and genomic strategies. The proteomics approach developed here exploits velocity gradient centrifugation as an alternative to isoelectric focusing for protein separation in the first dimension. A 20- to 30-fold increase in the concentration of numerous mitochondrial proteins was observed during adipogenesis, as determined by mass spectrometry and database correlation analysis. Light and electron microscopy confirmed a large increase in the number of mitochondrion profiles with differentiation. Furthermore, mRNA profiles obtained by using Affymetrix GeneChips revealed statistically significant increases in the expression of many nucleus-encoded mitochondrial genes during adipogenesis. Qualitative changes in mitochondrial composition also occur during adipose differentiation, as exemplified by increases in expression of proteins involved in fatty acid metabolism and of mitochondrial chaperones. Furthermore, the insulin sensitizer rosiglitazone caused striking changes in mitochondrial shape and expression of selective mitochondrial proteins. Thus, although mitochondrial biogenesis has classically been associated with brown adipocyte differentiation and thermogenesis, our results reveal that mitochondrial biogenesis and remodeling are inherent to adipose differentiation per se and are influenced by the actions of insulin sensitizers.

Anoxia and adenosine induce increased cerebral blood flow rate in crucian carp

1994 ◽  
Vol 267 (2) ◽  
pp. R590-R595 ◽  
Author(s):  
G. E. Nilsson ◽  
P. Hylland ◽  
C. O. Lofman
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Crucian Carp ◽  
Blood Flow Rate ◽  
Fold Increase ◽  
Liver Glycogen ◽  
Glycolytic Flux ◽  
Brain Blood Flow ◽  
Atp Production ◽  
The Brain

The crucian carp (Carassius carassius) has the rare ability to survive prolonged anoxia, indicating an extraordinary capacity for glycolytic ATP production, especially in a highly energy-consuming organ like the brain. For the brain to be able to increase its glycolytic flux during anoxia and profit from the large liver glycogen store, an increased glucose delivery from the blood would be expected. Nevertheless, the effect of anoxia on brain blood flow in crucian carp has never been studied previously. We have used epireflection microscopy to directly observe and measure blood flow rate on the brain surface (optic lobes) during normoxia and anoxia in crucian carp. We have also examined the possibility that adenosine participates in the regulation of brain blood flow rate in crucian carp. The results showed a 2.16-fold increase in brain blood flow rate during anoxia. A similar increase was seen after topical application of adenosine during normoxia, while adenosine was without effect during anoxia. Moreover, superfusing the brain with the adenosine receptor blocker aminophylline inhibited the effect of anoxia on brain blood flow rate, clearly suggesting a mediatory role of adenosine in the anoxia-induced increase in brain blood flow rate.

Skeletal muscle metabolism and work capacity: a 31P-NMR study of Andean natives and lowlanders

1991 ◽  
Vol 70 (5) ◽  
pp. 1963-1976 ◽  
Author(s):  
G. O. Matheson ◽  
P. S. Allen ◽  
D. C. Ellinger ◽  
C. C. Hanstock ◽  
D. Gheorghiu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Muscle Metabolism ◽  
Work Capacity ◽  
Calf Muscle ◽  
Whole Body ◽  
Resonance Spectroscopy ◽  
Muscle Work ◽  
Nmr Study ◽  
Nuclear Magnetic

Two metabolic features of altitude-adapted humans are the maximal O2 consumption (VO2max) paradox (higher work rates following acclimatization without increases in VO2max) and the lactate paradox (progressive reductions in muscle and blood lactate with exercise at increasing altitude). To assess underlying mechanisms, we studied six Andean Quechua Indians in La Raya, Peru (4,200 m) and at low altitude (less than 700 m) immediately upon arrival in Canada. The experimental strategy compared whole-body performance tests and single (calf) muscle work capacities in the Andeans with those in groups of sedentary, power-trained, and endurance-trained lowlanders. We used 31P nuclear magnetic resonance spectroscopy to monitor noninvasively changes in concentrations of phosphocreatine [( PCr]), [Pi], [ATP], [PCr]/[PCr] + creatine ([Cr]), [Pi]/[PCr] + [Cr], and pH in the gastrocnemius muscle of subjects exercising to fatigue. Our results indicate that the Andeans 1) are phenotypically unique with respect to measures of anaerobic and aerobic work capacity, 2) despite significantly lower anaerobic capacities, are capable of calf muscle work rates equal to those of highly trained power- and endurance-trained athletes, and 3) compared with endurance-trained athletes with significantly higher VO2max values and power-trained athletes with similar VO2max values, display, respectively, similar and reduced perturbation of all parameters related to the phosphorylation potential and to measurements of [Pi], [PCr], [ATP], and muscle pH derivable from nuclear magnetic resonance. Because the lactate paradox may be explained on the basis of tighter ATP demand-supplying coupling, we postulate that a similar mechanism may explain 1) the high calf muscle work capacities in the Andeans relative to measures of whole-body work capacity, 2) the VO2max paradox, and 3) anecdotal reports of exceptional work capacities in indigenous altitude natives.

scholarly journals Longitudinal Analyses Reveal That Aging-related Alterations in the Intestinal Environment Lead to Gut Dysbiosis With the Potential to Induce Obesity

2020 ◽  
Author(s):  
Yumiko Nakanishi ◽  
Ryouko Nozu ◽  
Masami Ueno ◽  
Kyoji Hioki ◽  
Chiharu Ishii ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Middle Age ◽  
Fecal Microbiota Transplantation ◽  
Fold Increase ◽  
Fecal Microbiota ◽  
Whole Body ◽  
Cellular Functions ◽  
Intestinal Environment ◽  
Gut Dysbiosis ◽  
Specific Pathogen

Abstract Background: Aging is a progressive decline of cellular functions that ultimately affects whole-body homeostasis. Alterations in the gut microbiota associated with aging have been reported, however the molecular basis of the relationships between host aging and the gut microbiota is poorly understood.Result: By using longitudinal microbiome and metabolome characterization, we show that the aging-related alterations in the intestinal environment lead to gut dysbiosis with a potential to induce obesity in mice. In middle-age mice, we observed more than a 2-fold increase in fecal carbohydrates derived from dietary polysaccharides and a significant reduction of gut microbial diversity resembling the microbiota characteristic of obese mice. Consistently, fecal microbiota transplantation from middle-age specific pathogen-free (SPF) mice into young germ-free (GF) mice resulted in increased weight gain and impaired glucose tolerance.Conclusion: Our findings provide new insights into the relationships between host aging and gut dysbiosis and may contribute to the development of a possible solution to aging-related obesity.

High-intensity training induces EIB in rats through neuron transdifferentiation of adrenal medulla chromaffin cells

2013 ◽  
Vol 304 (9) ◽  
pp. L602-L612 ◽  
Author(s):  
Ruoxi He ◽  
Juntao Feng ◽  
Qiufen Xun ◽  
Qingwu Qin ◽  
Chengping Hu
Keyword(s):  
Adrenal Medulla ◽  
Chromaffin Cells ◽  
Cell Structure ◽  
Fold Increase ◽  
Inflammatory Cells ◽  
Whole Body ◽  
Moderate Intensity ◽  
Sprague Dawley ◽  
Exercise Interventions ◽  
Intensity Training

A high prevalence of exercise-induced bronchoconstriction (EIB) can be found in elite athletes, but the underlying mechanisms remain elusive. Airway responsiveness, NGF and epinephrine (EPI) levels, and chromaffin cell structure in high- (HiTr) and moderate-intensity training (MoTr) rats with or without ovalbumin (OVA) sensitization were measured in a total of 120 male Sprague-Dawley rats. The expression of NGF-associated genes in rat adrenal medulla was tested. Both HiTr and OVA intervention significantly increased airway resistance to aerosolized methacholine measured by whole body plethysmography. HiTr significantly increased inflammatory reaction in the lung with a major increase in peribronchial lymphocyte infiltration, whereas OVA significantly increased the infiltration of various inflammatory cells with an over 10-fold increase in eosinophil level in bronchoalveolar lavage. Both HiTr and OVA intervention upregulated circulating NGF level and peripherin level in adrenal medulla, but downregulated phenylethanolamine N-methyl transferase level in adrenal medulla and circulating EPI level. HiTr + OVA and HiTr + ExhEx (exhaustive exercise) interventions significantly enhanced most of the HiTr effects. The elevated NGF level was significantly associated with neuronal conversion of adrenal medulla chromaffin cells (AMCC). The levels of p-Erk1/2, JMJD3, and Mash1 were significantly increased, but the levels of p-p38 and p-JNK were significantly decreased in adrenal medulla in HiTr and OVA rats. Injection of NGF antiserum and moderate-intensity training reversed these changes observed in HiTr and/or OVA rats. Our study suggests that NGF may play a vital role in the pathogenesis of EIB by inducing neuron transdifferentiation of AMCC via MAPK pathways and subsequently decreasing circulating EPI.

Honeybee flight muscle phosphoglucose isomerase: matching enzyme capacities to flux requirements at a near-equilibrium reaction

1997 ◽  
Vol 200 (8) ◽  
pp. 1247-1254 ◽  
Author(s):  
J Staples ◽  
R Suarez
Keyword(s):  
Ionic Strength ◽  
Flight Muscle ◽  
Equilibrium Constants ◽  
Muscle Metabolism ◽  
Phosphoglucose Isomerase ◽  
Glycolytic Flux ◽  
Cell Water ◽  
Economical Design ◽  
Equilibrium Reactions ◽  
Low Ionic Strength

In honeybee flight muscle, there are close matches between physiological flux rates and the maximal activities (Vmax; determined using crude homogenates) of key enzymes catalyzing non-equilibrium reactions in carbohydrate oxidation. In contrast, phosphoglucose isomerase (PGI), which catalyzes a reaction believed to be close to equilibrium, occurs at Vmax values greatly in excess of glycolytic flux rates. In this study, we measure the Vmax of flight muscle PGI, the kinetic parameters of the purified enzyme, the apparent equilibrium constants for the reaction and the tissue concentrations of substrate and product. Using the Haldane equation, we estimate that the forward flux capacity (Vf) for PGI required to achieve physiological glycolytic flux rates is between 800 and 1070 units ml-1 cell water, approximately 45­60 % of the empirically measured Vmax of 1770 units ml-1 cell water at optimal pH (8.0) and low ionic strength (no added KCl). When measured at physiological pH (7.0) and ionic strength (120 mmol l-1 KCl) with saturating levels of substrate, PGI activity is 1130 units ml-1 cell water, a value close to the calculated Vf. These results reveal a very close match between predicted and measured PGI flux capacities, and support the concept of an economical design of muscle metabolism in systems working at very high metabolic rates.

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