Oxidation of an oral [13C]glucose load at rest and prolonged exercise in trained and sedentary subjects

The purpose of this study was to compare the oxidation of[¹³C]glucose (100 g)ingested at rest or during exercise in six trained (TS) and sixsedentary (SS) male subjects. The oxidation of plasma glucose was alsocomputed from the volume of¹³CO₂and¹³C/¹²Cin plasma glucose to compute the oxidation rate of glucose released from the liver and from glycogen stores in periphery (mainly muscle glycogen stores during exercise). At rest, oxidative disposal of bothexogenous (8.3 ± 0.3 vs. 6.6 ± 0.8 g/h) and liver glucose (4.4 ± 0.5 vs. 2.6 ± 0.4 g/h) was higher in TS than in SS.This could contribute to the better glucose tolerance observed at rest in TS. During exercise, for the same absolute workload [140 ± 5 W: TS = 47 ± 2.5; SS = 68 ± 3 %maximal oxygen uptake(O_{2 max})], [¹³C]glucose oxidationwas higher in TS than in SS (39.0 ± 2.6 vs. 33.6 ± 1.2 g/h),whereas both liver glucose (16.8 ± 2.4 vs. 24.0 ± 1.8 g/h) and muscle glycogen oxidation (36.0 ± 3.0 vs. 51.0 ± 5.4 g/h) were lower. For the same relative workload (68 ± 3% O_{2 max}:TS = 3.13 ± 0.96; SS = 2.34 ± 0.60 lO₂/min), exogenous glucose(44.4 ± 1.8 vs. 33.6 ± 1.2 g/h) and muscle glycogen oxidation (73.8 ± 7.2 vs. 51.0 ± 5.4 g/h) were higher in TS. However,despite a higher energy expenditure in TS, liver glucose oxidation was similar in both groups (22.2 ± 3.0 vs. 24.0 ± 1.8 g/h). Thus exogenous glucose oxidation was selectively favored in TSduring exercise, reducing both liver glucose and muscle glycogen oxidation.

     

Mapping of a conformational epitope shared between E1 and E2 on the serum-derived human hepatitis C virus envelope

Monoclonal antibody D32.10 produced by immunizing mice with a hepatitis C virus (HCV)-enriched pellet obtained from plasmapheresis of a chronically HCV1b-infected patient binds HCV particles derived from serum of different HCV1a- and HCV1b-infected patients. Moreover, this monoclonal has been shown to recognize both HCV envelope proteins E1 and E2. In an attempt to provide novel insight into the membrane topology of HCV envelope glycoproteins E1 and E2, we localized the epitope recognized by D32.10 on the E1 and/or E2 sequence using Ph.D.-12 phage display peptide library technology. Mimotopes selected from the phage display dodecapeptide library by D32.10 shared partial similarities with 297RHWTTQGCNC306 of the HCV E1 glycoprotein and with both 613YRLWHYPCT621 and 480PDQRPYCWHYPPKPC494 of the HCV E2 glycoprotein. Immunoreactivity of D32.10 with overlapping peptides corresponding to these three HCV regions confirmed these localizations and suggested that the three regions identified are likely closely juxtaposed on the surface of serum-derived particles as predicted by the secondary model structure of HCV E2 derived from the tick-borne encephalitis virus E protein. This assertion was supported by the detection of specific antibodies directed against these three E1E2 regions in sera from HCV-infected patients.     

Rm62, a DEAD‐box RNA helicase,complexes with DSP1 in Drosophila embryos

Two main classes of proteins, Polycomb group (PcG) and Trithorax group (TrxG), play a key role in the regulation of homeotic genes. These proteins act in multimeric complexes to remodel chromatin. A third class of proteins named Enhancers of Trithorax and Polycomb (ETP) modulates the activity of TrxG and PcG, but their role remains largely unknown. We previously identified an HMGB‐like protein, DSP1 (Dorsal Switch Protein 1), which was classified as an ETP. Preliminary studies have revealed that DSP1 is involved in multimeric complexes. Here we identify a DEAD‐box RNA helicase, Rm62, as partner of DSP1 in a 250‐kDa complex. Coimmunoprecipitation assays performed on embryo extracts indicate that DSP1 and Rm62 are associated in 3‐ to 12‐h embryos. Furthermore, DSP1 and Rm62 colocalize on polytene chromosomes. Consistent with these results, a mutation in Rm62 enhances a null mutation of dsp1 and also mutations of trxG or PcG, suggesting that Rm62 has characteristics of an ETP. We show here for the first time that an RNA helicase is involved in the maintenance of homeotic genes. genesis 48:244–253, 2010. © 2010 Wiley‐Liss, Inc.     

The enhancer of trithorax and polycomb corto interacts with cyclin G in Drosophila

Background

Polycomb (PcG) and trithorax (trxG) genes encode proteins involved in the maintenance of gene expression patterns, notably Hox genes, throughout development. PcG proteins are required for long-term gene repression whereas TrxG proteins are positive regulators that counteract PcG action. PcG and TrxG proteins form large complexes that bind chromatin at overlapping sites called Polycomb and Trithorax Response Elements (PRE/TRE). A third class of proteins, so-called “Enhancers of Trithorax and Polycomb” (ETP), interacts with either complexes, behaving sometimes as repressors and sometimes as activators. The role of ETP proteins is largely unknown.

Methodology/Principal Findings

In a two-hybrid screen, we identified Cyclin G (CycG) as a partner of the Drosophila ETP Corto. Inactivation of CycG by RNA interference highlights its essential role during development. We show here that Corto and CycG directly interact and bind to each other in embryos and S2 cells. Moreover, CycG is targeted to polytene chromosomes where it co-localizes at multiple sites with Corto and with the PcG factor Polyhomeotic (PH). We observed that corto is involved in maintaining Abd-B repression outside its normal expression domain in embryos. This could be achieved by association between Corto and CycG since both proteins bind the regulatory element iab-7 PRE and the promoter of the Abd-B gene.

Conclusions/Significance

Our results suggest that CycG could regulate the activity of Corto at chromatin and thus be involved in changing Corto from an Enhancer of TrxG into an Enhancer of PcG.     

Oxidation of a glucose polymer during exercise: comparison with glucose and fructose

The purpose of this study was to compare the oxidation of 13C-labeled glucose, fructose, and glucose polymer ingested (1.33 g.kg-1 in 19 ml.kg-1 water) during cycle exercise (120 min, 53 +/- 2% maximal O2 uptake) in six healthy male subjects. Oxidation of exogenous glucose and glucose polymer (72 +/- 15 and 65 +/- 18%, respectively, of the 98.9 +/- 4.7 g ingested) was similar and significantly greater than exogenous fructose oxidation (54 +/- 13%). A transient rise in plasma glucose concentration was observed with glucose ingestion only. However, plasma insulin levels were similar with glucose and glucose polymer ingestions and significantly higher than with water or fructose ingestion. Plasma free fatty acid and glycerol responses to exercise were blunted with carbohydrate ingestion. However, fat utilization was not significantly different with water (82 +/- 14 g), glucose (60 +/- 3 g), fructose (59 +/- 11 g), or glucose polymer ingestion (60 +/- 8 g). Endogenous carbohydrate utilization was significantly lower with glucose (184 +/- 22 g), glucose polymer (187 +/- 31 g), and fructose (211 +/- 18 g) than with water (239 +/- 30 g) ingestion. Plasma volume slightly increased with water ingestion (7.4 +/- 4.5%), but the decrease was similar with glucose (-7.6 +/- 5.1%) and glucose polymer (-8.2 +/- 4.6%), suggesting that the rate of water delivery to plasma was similar with the two carbohydrates.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fluid-electrolyte shift and renin-aldosterone responses to exercise under hypoxia

In order to describe fluid-electrolyte shift and endocrine response to exercise under moderate acute hypoxia, 8 healthy male subjects (24 +/- 3 years old) were evaluated at 40, 60, 80 and 100% VO2 max in normoxic (N) and hypoxic (H) conditions (14.5% O2). VO2 max decreased from 55.5 +/- 1.3 to 45.8 +/- 1.4 ml/kg X min in H condition. Plasma volume reductions with increasing relative workloads were similar in N (9.4%) and H (9.9%) conditions. The rise in plasma osmolality was in part related to blood lactate accumulation which occurred in both conditions. However, variations in plasma solute content and osmolality suggested that exercise under hypoxia results in a greater electrolyte loss from vascular space and in a greater K+ loss from working skeletal muscles. Increase in catecholamine concentrations were similar in normoxic and hypoxic conditions except for lower maximal norepinephrine concentration under hypoxia. Finally, although plasma renin activity increased with workload in both conditions, plasma aldosterone did not significantly change. This dissociation between renin and aldosterone suggest that aldosterone release during exercise might depend upon other factors. However, changes in plasma potassium concentration do not appear as an important stimulus for aldosterone secretion during exercise.     

The MAP kinase ERK and its scaffold protein MP1 interact with the chromatin regulator Corto during Drosophila wing tissue development

Background  

Mitogen-activated protein kinase (MAPK) cascades (p38, JNK, ERK pathways) are involved in cell fate acquisition during development. These kinase modules are associated with scaffold proteins that control their activity. In Drosophila, dMP1, that encodes an ERK scaffold protein, regulates ERK signaling during wing development and contributes to intervein and vein cell differentiation. Functional relationships during wing development between a chromatin regulator, the Enhancer of Trithorax and Polycomb Corto, ERK and its scaffold protein dMP1, are examined here.