Glycogen Depletion (glycogen + depletion)

Distribution by Scientific Domains


Selected Abstracts


Selective Long-Term Electrical Stimulation of Fast Glycolytic Fibres Increases Capillary Supply but not Oxidative Enzyme Activity in Rat Skeletal Muscles

EXPERIMENTAL PHYSIOLOGY, Issue 5 2000
S. Egginton
Glycolytic fibres in rat extensor digitorum longus (EDL) and tibialis anterior (TA) were selectively activated, as demonstrated by glycogen depletion, by indirect electrical stimulation via electrodes implanted in the vicinity of the peroneal nerve using high frequency (40 Hz) trains (250 ms at 1 Hz) and low voltage (threshold of palpable contractions). This regime was applied 10 times per day, each bout being of 15 min duration with 60 min recovery, for 2 weeks. Cryostat sections of muscles were stained for alkaline phosphatase to depict capillaries, succinate dehydrogenase (SDH) to demonstrate oxidative fibres, and periodic acid-Schiff reagent (PAS) to verify glycogen depletion. Specific activity of hexokinase (HK), 6-phosphofructokinase, pyruvate kinase, glycogen phosphorylase and cytochrome c oxidase (COX) were estimated separately in homogenates of the EDL and the predominantly glycolytic cortex and oxidative core of the TA. Stimulation increased the activity of HK but not that of oxidative enzymes in fast muscles. Comparison of changes in oxidative capacity and capillary supply showed a dissociation in the predominantly glycolytic TA cortex. Here, COX was 3.9 ± 0.68 ,M min-1 (g wet wt)-1 in stimulated muscles compared with 3.7 ± 0.52 ,M min-1 (g wet wt)-1 in contralateral muscles (difference not significant), while the percentage of oxidative fibres (those positively stained for SDH) was also similar in stimulated (14.0 ± 2.8%) and contralateral (12.2 ± 1.9%) muscles. In contrast, the capillary to fibre ratio was significantly increased (2.01 ± 0.12 vs. 1.55 ± 0.04, P < 0.01). We conclude that capillary supply can be increased independently of oxidative capacity, possibly due to haemodynamic factors, and serves metabolite removal to a greater extent than substrate delivery. [source]


Spatial insulin signalling in isolated skeletal muscle preparations

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010
Peter Sogaard
Abstract During in vitro incubation in the absence or presence of insulin, glycogen depletion occurs in the inner core of the muscle specimen, concomitant with increased staining of hypoxia-induced-factor-1-alpha and caspase-3, markers of hypoxia and apoptosis, respectively. The aim of this study was to determine whether insulin is able to diffuse across the entire muscle specimen in sufficient amounts to activate signalling cascades to promote glucose uptake and glycogenesis within isolated mouse skeletal muscle. Phosphoprotein multiplex assay on lysates from muscle preparation was performed to detect phosphorylation of insulin-receptor on Tyr1146, Akt on Ser473 and glycogen-synthases-kinase-3 on Ser21/Ser9. To address the spatial resolution of insulin signalling, immunohistochemistry studies on cryosections were performed. Our results provide evidence to suggest that during the in vitro incubation, insulin sufficiently diffuses into the centre of tubular mouse muscles to promote phosphorylation of these signalling events. Interestingly, increased insulin signalling was observed in the core of the incubated muscle specimens, correlating with the location of oxidative fibres. In conclusion, insulin action was not restricted due to insufficient diffusion of the hormone during in vitro incubation in either extensor digitorum longus or soleus muscles from mouse under the specific experimental settings employed in this study. Hence, we suggest that the glycogen depleted core as earlier observed is not due to insufficient insulin action. J. Cell. Biochem. 109: 943,949, 2010. © 2010 Wiley-Liss, Inc. [source]


Diet quality and anthropometry between different sailboarding styles

NUTRITION & DIETETICS, Issue 1 2010
Ioannis DOUMTSIOS
Abstract Aim:, To identify diet quality and basic anthropometric characteristics of sailboarders. Methods:, The study was conducted in 91 sailboarders, who were divided in two groups according to muscle recruitment during sailing; those performing wave or freestyle surfing formed the WF group (n = 46) and those performing slalom or formula the SF group (n = 45), as the first includes more lower-body muscle recruitment. Diet and anthropometry were evaluated during training days and compared between the two study groups. Results:, The WFs demonstrated lower % body fat (21%), circumferences, skinfolds, body mass index (23.9 kg/m2) and fat mass index (5.1 kg/m2) compared with the SFs (body fat 25.2%, body mass index 26.1 kg/m2 and fat mass index 6.6 kg/m2). Dietary intake was similar and both groups presented a negative energy balance, high cholesterol intake and adequacy in the intake of most micronutrients except for vitamin E of the WF group. The windsurfers achieved a low healthy eating index (54.3 and 58.1 for WF and SF respectively), indicative of a diet in need of improvement and reported the post-training consumption of beer and fast food. Conclusion:, Overall findings suggest the need for dietary counselling in windsurfers, as glycogen depletion is crucial in sailboarding, where one athlete consists of the total boat crew thus, glycogen depletion leading to insufficient energy for technical movements while sailing, has direct effect on the result of the race. [source]


Phosphocreatine degradation in type I and type II muscle fibres during submaximal exercise in man: effect of carbohydrate ingestion

THE JOURNAL OF PHYSIOLOGY, Issue 1 2001
Kostas Tsintzas
1The aim of this study was to examine the effect of carbohydrate (CHO) ingestion on changes in ATP and phosphocreatine (PCr) concentrations in different muscle fibre types during prolonged running and relate those changes to the degree of glycogen depletion. 2Five male subjects performed two runs at 70 % maximum oxygen uptake (V,O2,max), 1 week apart. Each subject ingested 8 ml (kg body mass (BM)),1 of either a placebo (Con trial) or a 5.5 % CHO solution (CHO trial) immediately before each run and 2 ml (kg BM),1 every 20 min thereafter. In the Con trial, the subjects ran to exhaustion (97.0 ± 6.7 min). In the CHO trial, the run was terminated at the time coinciding with exhaustion in the Con trial. Muscle samples were obtained from the vastus lateralis before and after each trial. 3Carbohydrate ingestion did not affect ATP concentrations. However, it attenuated the decline in PCr concentration by 46 % in type I fibres (CHO: 20 ± 8 mmol (kg dry matter (DM)),1; Con: 34 ± 6 mmol (kg DM),1; P < 0.05) and by 36 % in type II fibres (CHO: 30 ± 5 mmol (kg DM),1; Con: 48 ± 6 mmol (kg DM),1; P < 0.05). 4A 56 % reduction in glycogen utilisation in type I fibres was observed in CHO compared with Con (117 ± 39 vs. 240 ± 32 mmol glucosyl units (kg DM),1, respectively; P < 0.01), but no difference was observed in type II fibres. 5It is proposed that CHO ingestion during exhaustive running attenuates the decline in oxidative ATP resynthesis in type I fibres, as indicated by sparing of both PCr and glycogen breakdown. The CHO-induced sparing of PCr, but not glycogen, in type II fibres may reflect differential recruitment and/or role of PCr between fibre types. [source]