Differential pattern of glycogen accumulation after protein phosphatase 1 glycogen-targeting subunit PPP1R6 overexpression, compared to PPP1R3C and PPP1R3A, in skeletal muscle cells

Background PPP1R6 is a protein phosphatase 1 glycogen-targeting subunit (PP1-GTS) abundant in skeletal muscle with an undefined metabolic control role. Here PPP1R6 effects on myotube glycogen metabolism, particle size and subcellular distribution are examined and compared with PPP1R3C/PTG and PPP1R3A/GM. Results PPP1R6 overexpression activates glycogen synthase (GS), reduces its phosphorylation at Ser-641/0 and increases the extracted and cytochemically-stained glycogen content, less than PTG but more than GM. PPP1R6 does not change glycogen phosphorylase activity. All tested PP1-GTS-cells have more glycogen particles than controls as found by electron microscopy of myotube sections. Glycogen particle size is distributed for all cell-types in a continuous range, but PPP1R6 forms smaller particles (mean diameter 14.4 nm) than PTG (36.9 nm) and GM (28.3 nm) or those in control cells (29.2 nm). Both PPP1R6- and GM-derived glycogen particles are in cytosol associated with cellular structures; PTG-derived glycogen is found in membrane- and organelle-devoid cytosolic glycogen-rich areas; and glycogen particles are dispersed in the cytosol in control cells. A tagged PPP1R6 protein at the C-terminus with EGFP shows a diffuse cytosol pattern in glucose-replete and -depleted cells and a punctuate pattern surrounding the nucleus in glucose-depleted cells, which colocates with RFP tagged with the Golgi targeting domain of β-1,4-galactosyltransferase, according to a computational prediction for PPP1R6 Golgi location. Conclusions PPP1R6 exerts a powerful glycogenic effect in cultured muscle cells, more than GM and less than PTG. PPP1R6 protein translocates from a Golgi to cytosolic location in response to glucose. The molecular size and subcellular location of myotube glycogen particles is determined by the PPP1R6, PTG and GM scaffolding.

PGC-1α induces mitochondrial and myokine transcriptional programs and lipid droplet and glycogen accumulation in cultured human skeletal muscle cells

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) is a chief activator of mitochondrial and metabolic programs and protects against atrophy in skeletal muscle (skm). Here we tested whether PGC-1α overexpression could restructure the transcriptome and metabolism of primary cultured human skm cells, which display a phenotype that resembles the atrophic phenotype. An oligonucleotide microarray analysis was used to reveal the effects of PGC-1α on the whole transcriptome. Fifty-three different genes showed altered expression in response to PGC-1α: 42 upregulated and 11 downregulated. The main gene ontologies (GO) associated with the upregulated genes were mitochondrial components and processes and this was linked with an increase in COX activity, an indicator of mitochondrial content. Furthermore, PGC-1α enhanced mitochondrial oxidation of palmitate and lactate to CO2, but not glucose oxidation. The other most significantly associated GOs for the upregulated genes were chemotaxis and cytokine activity, and several cytokines, including IL-8/CXCL8, CXCL6, CCL5 and CCL8, were within the most highly induced genes. Indeed, PGC-1α highly increased IL-8 cell protein content. The most upregulated gene was PVALB, which is related to calcium signaling. Potential metabolic regulators of fatty acid and glucose storage were among mainly regulated genes. The mRNA and protein level of FITM1/FIT1, which enhances the formation of lipid droplets, was raised by PGC-1α, while in oleate-incubated cells PGC-1α increased the number of smaller lipid droplets and modestly triglyceride levels, compared to controls. CALM1, the calcium-modulated δ subunit of phosphorylase kinase, was downregulated by PGC-1α, while glycogen phosphorylase was inactivated and glycogen storage was increased by PGC-1α. In conclusion, of the metabolic transcriptome deficiencies of cultured skm cells, PGC-1α rescued the expression of genes encoding mitochondrial proteins and FITM1. Several myokine genes, including IL-8 and CCL5, which are known to be constitutively expressed in human skm cells, were induced by PGC-1α.

Expression of Glycogen Phosphorylase Isoforms in Cultured Muscle from Patients with McArdle´s Disease Carrying the p.R771PfsX33 PYGM Mutation

Mutations in the PYGM gene encoding skeletal muscle glycogen phosphorylase (GP) cause a metabolic disorder known as McArdle's disease. Previous studies in muscle biopsies and cultured muscle cells from McArdle patients have shown that PYGM mutations abolish GP activity in skeletal muscle, but that the enzyme activity reappears when muscle cells are in culture. The identification of the GP isoenzyme that accounts for this activity remains controversial.

AMP-activated protein kinase plays an important evolutionary conserved role in the regulation of glucose metabolism in fish skeletal muscle cells

AMPK, a master metabolic switch, mediates the observed increase of glucose uptake in locomotory muscle of mammals during exercise. AMPK is activated by changes in the intracellular AMP:ATP ratio when ATP consumption is stimulated by contractile activity but also by AICAR and metformin, compounds that increase glucose transport in mammalian muscle cells. However, the possible role of AMPK in the regulation of glucose metabolism in skeletal muscle has not been investigated in other vertebrates, including fish. In this study, we investigated the effects of AMPK activators on glucose uptake, AMPK activity, cell surface levels of trout GLUT4 and expression of GLUT1 and GLUT4 as well as the expression of enzymes regulating glucose disposal and PGC1α in trout myotubes derived from a primary muscle cell culture. We show that AICAR and metformin significantly stimulated glucose uptake (1.6 and 1.3 fold, respectively) and that Compound C completely abrogated the stimulatory effects of the AMPK activators on glucose uptake. The combination of insulin and AMPK activators did not result in additive nor synergistic effects on glucose uptake. Moreover, exposure of trout myotubes to AICAR and metformin resulted in an increase in AMPK activity (3.8 and 3 fold, respectively). We also provide evidence suggesting that stimulation of glucose uptake by AMPK activators in trout myotubes may take place, at least in part, by increasing the cell surface and mRNA levels of trout GLUT4. Finally, AICAR increased the mRNA levels of genes involved in glucose disposal (hexokinase, 6-phosphofructokinase, pyruvate kinase and citrate synthase) and mitochondrial biogenesis (PGC-1α) and did not affect glycogen content or glycogen synthase mRNA levels in trout myotubes. Therefore, we provide evidence, for the first time in non-mammalian vertebrates, suggesting a potentially important role of AMPK in stimulating glucose uptake and utilization in the skeletal muscle of fish.

Expressional regulation of key hepatic enzymes of intermediary metabolism in European seabass (Dicentrarchus labrax) during food deprivation and refeeding

We hypothesized that the analysis of mRNA level and activity of key enzymes in amino acid and carbohydrate metabolism in a feeding/fasting/refeeding setting could improve our understanding of how a carnivorous fish, like the European seabass (Dicentrarchus labrax), responds to changes in dietary intake at the hepatic level. To this end cDNA fragments encoding genes for cytosolic and mitochondrial alanine aminotransferase (cALT; mALT), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) were cloned and sequenced. Measurement of mRNA levels through quantitative real-time PCR performed in livers of fasted seabass revealed a significant increase in cALT (8.5-fold induction)while promoting a drastic 45-fold down-regulation of PK in relation to the levels found in fed seabass. These observations were corroborated by enzyme activity meaning that during food deprivation an increase in the capacity of pyruvate generation happened via alanine to offset the reduction in pyruvate derived via glycolysis. After a 3-day refeeding period cALT returned to control levels while PK was not able to rebound. No alterations were detected in the expression levels of G6PDH while 6PGDH was revealed to be more sensitive specially to fasting, as confirmed by a significant 5.7-fold decrease in mRNA levels with no recovery after refeeding. Our results indicate that in early stages of refeeding, the liver prioritized the restoration of systemic normoglycemia and replenishment of hepatic glycogen. In a later stage, once regular feeding is re-established, dietary fuel may then be channeled to glycolysis and de novo lipogenesis.

Expressional regulation of key hepatic enzymes of intermediary metabolism in European seabass (Dicentrarchus labrax) during food deprivation and refeeding

We hypothesized that the analysis of mRNA level and activity of key enzymes in amino acid and carbohydrate metabolism in a feeding/fasting/refeeding setting could improve our understanding of how a carnivorous fish, like the European seabass (Dicentrarchus labrax), responds to changes in dietary intake at the hepatic level. To this end cDNA fragments encoding genes for cytosolic and mitochondrial alanine aminotransferase (cALT; mALT), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) were cloned and sequenced. Measurement of mRNA levels through quantitative real-time PCR performed in livers of fasted seabass revealed a significant increase in cALT (8.5-fold induction)while promoting a drastic 45-fold down-regulation of PK in relation to the levels found in fed seabass. These observations were corroborated by enzyme activity meaning that during food deprivation an increase in the capacity of pyruvate generation happened via alanine to offset the reduction in pyruvate derived via glycolysis. After a 3-day refeeding period cALT returned to control levels while PK was not able to rebound. No alterations were detected in the expression levels of G6PDH while 6PGDH was revealed to be more sensitive specially to fasting, as confirmed by a significant 5.7-fold decrease in mRNA levels with no recovery after refeeding. Our results indicate that in early stages of refeeding, the liver prioritized the restoration of systemic normoglycemia and replenishment of hepatic glycogen. In a later stage, once regular feeding is re-established, dietary fuel may then be channeled to glycolysis and de novo lipogenesis.

Marxism, social metabolism, and ecologically unequal exchange

Authors working on "industrial metabolism" or "social metabolism" look at the economy in terms of flows of energy and materials. Together with the ecological economists, they see the economy as a subsystem of a larger physical system. Marx and Engels followed with a few years’ delay many of the remarkable scientific and technical novelties of their time.

Societal metabolism of societies: the bifurcation between Spain and Ecuador

This paper presents an application of the Multiple-Scale Integrated Assessment of Societal Metabolism to the recent economic history of Ecuador and Spain. Understanding the relationship between the Gross Domestic Product (GDP) and the throughput of matter and energy over time in modern societies is crucial for understanding the sustainability predicament as it is linked to economic growth. When considering the dynamics of economic development, Spain was able to take a different path than Ecuador thanks to the different characteristics of its energy budget and other key variables. This and other changes are described using economic and biophysical variables (both extensive and intensive referring to different hierarchical levels). The representation of these parallel changes (on different levels and describable only using different variables) can be kept in coherence by adopting the frame provided by MSIASM.

Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MUSIASEM): an outline of rationale and theory

This paper presents an outline of rationale and theory of the MuSIASEM scheme (Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism). First, three points of the rationale behind our MuSIASEM scheme are discussed: (i) endosomatic and exosomatic metabolism in relation to Georgescu-Roegen’s flow-fund scheme; (2) the bioeconomic analogy of hypercycle and dissipative parts in ecosystems; (3) the dramatic reallocation of human time and land use patterns in various sectors of modern economy. Next, a flow-fund representation of the MUSIASEM scheme on three levels (the whole national level, the paid work sectors level, and the agricultural sector level) is illustrated to look at the structure of the human economy in relation to two primary factors: (i) human time - a fund; and (ii) exosomatic energy - a flow. The three levels representation uses extensive and intensive variables simultaneously. Key conceptual tools of the MuSIASEM scheme - mosaic effects and impredicative loop analysis - are explained using the three level flow-fund representation. Finally, we claim that the MuSIASEM scheme can be seen as a multi-purpose grammar useful to deal with sustainability issues.

An application of MSIASM to Chinese exosomatic energy metabolism

The methodology of Multi-Scale Integrated The methodology of Multi-Scale Integrated Analysis of Societal Metabolism (MSIASM) is applied to analyze the Chinese economy. This paper presents four tasks: (i) identifying a set of benchmarks that makes it possible to compare various characteristics of the Chinese economy with those of other country groups and the world (level) average; (ii) explaining the differences over the selected set of benchmarks, by looking at the characteristics of the various sub-sectors of the Chinese economy; (iii) understanding existing trends and future feasible future development paths for China by studying the existence of reciprocal constraints between the whole economy and its sub-sectors; and (iv) examining plausible future scenarios of development.

Different trajectories of exosomatic energy metabolism for Brazil, Chile and Venezuela: using the MSIASM approach

Economic development goes hand in hand with an increase in the consumption of natural resources. Some analysts use material flows to describe such relationship [Eurostat 2001, Weisz et al., 2006], or exergy [Ayres et al., 2003]. Instead this paper will use a characterisation of the exosomatic energy metabolism based on expected benchmark values to describe possible constraints to economic development posed by available human time and energy. The aim of the paper is to identify types of exosomatic energy metabolism of different societies to interpret its consequences for economic development. This is done with the application of the accounting methodology called Multi-Scale Integrated Analysis of Societal Metabolism (MSIASM) to the particular case of energy metabolism for the analysis of the economies of Brazil, Chile and Venezuela.

Why Catalonia will see its energy metabolism increase in the near future: an application of MuSIASEM

This paper applies the so-called Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) to the economy of the Spanish region of Catalonia. By applying Georgescu-Roegen's fund-flow model, it arrives at the conclusion that within a context of the end of cheap oil, the current development model based on the growth of low productivity sectors such as services and construction must change. The change is needed not only because of the increasing scarcity of affordable energy carriers, or because of the increasing environmental impact that the present development represents, but also because of an ageing population that demands labour productivity gains. This will imply industry requiring more energy consumption per worker in order to increase its productivity, and therefore its competitiveness. Thus, we conclude that energy intensity, and exosomatic energy metabolism of Catalonia will increase dramatically in the near future unless major conservation efforts are implemented in both the household and transport sectors.

A first attempt of geographically-distributed Multi-scale integrated analysis of societal and ecosystem metabolism (MuSIASEM): mapping human time and energy throughput in metropolitan Barcelona

This study presents a first attempt to extend the “Multi-scale integrated analysis of societal and ecosystem metabolism (MuSIASEM)” approach to a spatial dimension using GIS techniques in the Metropolitan area of Barcelona. We use a combination of census and commercial databases along with a detailed land cover map to create a layer of Common Geographic Units that we populate with the local values of human time spent in different activities according to MuSIASEM hierarchical typology. In this way, we mapped the hours of available human time, in regards to the working hours spent in different locations, putting in evidence the gradients in spatial density between the residential location of workers (generating the work supply) and the places where the working hours are actually taking place. We found a strong three-modal pattern of clumps of areas with different combinations of values of time spent on household activities and on paid work. We also measured and mapped spatial segregation between these two activities and put forward the conjecture that this segregation increases with higher energy throughput, as the size of the functional units must be able to cope with the flow of exosomatic energy. Finally, we discuss the effectiveness of the approach by comparing our geographic representation of exosomatic throughput to the one issued from conventional methods.

Going beyond energy intensity to understand the energy metabolism of nations: the case of Argentina

The link between energy consumption and economic growth has been widely studied in the economic literature. Understanding this relationship is important from both an environmental and a socio-economic point of view, as energy consumption is crucial to economic activity and human environmental impact. This relevance is even higher for developing countries, since energy consumption per unit of output varies through the phases of development, increasing from an agricultural stage to an industrial one and then decreasing for certain service based economies. In the Argentinean case, the relevance of energy consumption to economic development seems to be particularly important. While energy intensity seems to exhibit a U-Shaped curve from 1990 to 2003 decreasing slightly after that year, total energy consumption increases along the period of analysis. Why does this happen? How can we relate this result with the sustainability debate? All these questions are very important due to Argentinean hydrocarbons dependence and due to the recent reduction in oil and natural gas reserves, which can lead to a lack of security of supply. In this paper we study Argentinean energy consumption pattern for the period 1990-2007, to discuss current and future energy and economic sustainability. To this purpose, we developed a conventional analysis, studying energy intensity, and a non conventional analysis, using the Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) accounting methodology. Both methodologies show that the development process followed by Argentina has not been good enough to assure sustainability in the long term. Instead of improving energy use, energy intensity has increased. The current composition of its energy mix, and the recent economic crisis in Argentina, as well as its development path, are some of the possible explanations.

Italy's urban waste metabolism

The problem of waste management is causing growing concern due to increasing generation rates, the emissions into soil, water and air, the social conflicts derived from the election of disposal sites and the loss of resources and energy among others. In this work, an innovative methodology is used to enable a better understanding of the waste generation and management system in Italy. Two new waste indicators are built to complement the conventional indicators used by official statistics. Then a multi-scale analysis of the Density of Waste Disposed (DWD) is carried out to highlight the territorial diversity of waste performances and test its contribution to detect plausible risky areas. Starting from Italian regions, the scale down goes on to the provincial level and, only for the region of Campania, the municipal one. First, the analysis shows that the DWD is able to complement the information provided by the conventional waste indicators. Second, the analysis shows the limitations of using a unique institutional solution to waste management problems. In this sense the multi-scale analysis provides with a more realistic picture of Italian waste system than using a single scale.