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Enzyme Nanocapsules for Glucose Sensing and Insulin Delivery
Published in Grunwald Peter, Biocatalysis and Nanotechnology, 2017
Insulin circulates throughout the blood stream until it binds to an insulin receptor. Binding to insulin causes a conformational change of the insulin receptor that activates its kinase domain and induces the autophosphorylation of tyrosine residues on the C-terminus of the receptor, leading to internal signal cascade that allows the glucose transporter 4 (GLUT4) to transport glucose into cells (Fig. 16.1 c) (Yang, 2010). The key consequence of intracellular signal transduction is the increased expression of GLUT4 in the plasma membrane and the immediate activation of glycogen synthase. By the facilitative transport of glucose into the cells, the glucose transporters effectively remove glucose from the blood stream. The glycogen synthase converts the glucose into glycogen and stores it in cells as the glucose reservoir (Halse et al., 2001). The insulin receptors promote the uptake of glucose into various tissues but mainly muscle cells (myocytes) and fat cells (adipocytes) (Czech et al., 1978). When glucose concentration comes down to normal level, the insulin secretion from beta cells slows and stops. The insulin action will be terminated by endocytosis and degradation of GLUT4, which leads to a decrease and finally to an abolished glucose uptake in myoctes and adipocytes (Yang, 2010).
Catabolite Regulation of the Main Metabolism
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
The glycogen synthesis and degradation is highly conserved in many bacteria (Ballicora et al. 2003, Preiss 2009), where glucose 1-phosphate (G1P) is formed from G6P by phosphogluco mutase (Pgm). G1P is then converted to ADP-glucose (ADPG) by means of ADPG phosphorylase (GlgC). The glycogen is then formed from ADPG by glycogen synthase (GlgA), where glycogen branching enzyme (GlgB) catalyzes the formation of branched oligosaccharide chains having α-1,6-glucoside linkage. During the stationary phase after depletion of substrate, glucose units are removed from the nonreducing ends of the glycogen by glycogen phosphorylase (GlgP) and debranching enzyme (GlgX) (Dauvillee et al. 2005, Alonso- Casajus et al. 2006). GlgP activity increases when GlgP binds to HPr of PTS, and this allows the accumulation of glycogen at the late growth phase or the onset of the stationary phase where substrate is still present (Deutscher et al. 2006). In order to prevent ADPG excess accumulation, where it may divert the carbon flux to other metabolic pathways, adenosine diphosphate sugar pyrophosphatase (AspP) catalyzes the breakdown of ADPG (Moran- Zorzano et al. 2008), where its activity is allostericafly activated by FBP (Moran-Zorzano et al. 2007).
Human Energy
Published in Eduardo Rincón-Mejía, Alejandro de las Heras, Sustainable Energy Technologies, 2017
José Antonio Aguilar Becerril, Diana Gabriela Pinedo Catalán, Paola Yazmín Jiménez Colín, Jaime Manuel Aguilar Becerril
In rest phases, glucose is stored in the body after phosphorylation into glycogen through glycogen synthetase. When performing exercises, it is necessary to obtain glucose; a process called glycogenolysis synthesizes 1 molecule of ATP, which is why the net energy efficiency is 37 ATP.
Periodised Carbohydrate Intake Does Not Affect Substrate Oxidation but May Contribute to Endurance Capacity
Published in European Journal of Sport Science, 2023
Meri M. Salokannel, Oona-Mari Hakulinen, Juha P. Ahtiainen
Interestingly, the current training-diet strategy improved the capacity to perform high-intensity exercise. Only FASTED group improved running time in the anaerobic test and had significantly higher lactate concentrations after the intervention than FED. Furthermore, only the FASTED group improved vVO2peak in the VO2peak test and had higher lactate concentrations after the intervention. Both groups improved their VO2peak after the intervention. However, only FASTED improved the vVO2peak that could be explained, at least in part, by enhanced anaerobic capacity, indicated by improved running time in the anaerobic test. It has been shown that training with low CHO availability elevates resting muscle glycogen content (Hansen et al., 2005; Yeo et al. 2008). Hansen et al. (2005) suggested that training with low muscle glycogen availability stimulates glycogen synthase signals, which regulates a glycogen synthesis leading to a greater muscle glycogen content. Thus, it could be suggested that a low CHO training-diet strategy enhanced glycolysis due to increased muscle glycogen content and/or enhancement in glycolysis. Since these factors were not measured in the present study, future studies are needed to investigate the underlying mechanisms to improve capacity to perform high-intensity exercise. When interpreting these results, we should take into account the possible placebo effect if participants in the FASTED group believed that they could perform better after the treatment. This can, at least in part, explain the improved ability to perform high-intensity exercise.
Down stair walking: A simple method to increase muscle mass and performance in 65+ year healthy people
Published in European Journal of Sport Science, 2022
Signe Regnersgaard, Anna K. Knudsen, Filippa O. Lindskov, Marija Mratinkovic, Eckart Pressel, Arthur Ingersen, Flemming Dela
The increase in glycogen content in the CON group only was not unexpected. The energy expenditure was higher compared with eccentric training groups, and it is well known that aerobic, endurance type exercise increases glycogen synthase enzyme activity. It has previously been shown that glycogen synthesis and content after acute eccentric exercise is diminished compared with concentric exercise (Costill et al., 1990; Widrick et al., 1992), although this is not a universal finding (Komi & Viitasalo, 1977).