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Molecular sport nutrition
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Mark Hearris, Nathan Hodson, Javier Gonzalez, James P. Morton
Glycogen synthesis is mainly regulated by the enzymes glycogen synthase and branching enzyme, which catalyse the incorporation of UDP-glucose into glycogen via α‐1,4‐glycosidic linkages, and the formation of α‐1,6‐branchpoints, respectively (17). Glycogen synthase is stimulated by insulin and by exercise. It is also speculated that glycogen synthase activity is inhibited by glycogen, such that a low muscle glycogen concentration is a stimulus for increased glycogen synthase activity, which may be regulated by protein phosphatase 1. This provides the mechanistic underpinning for glycogen supercompensation.
Biochemical Contributors to Exercise Fatigue
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Arthur J. Cheng, Maja Schlittler, Håkan Westerblad
Glycogen breakdown is controlled by glycogen phosphorylase, which is regulated by covalent phosphorylation, allosteric regulation, and substrate availability (44). Phosphorylase exists in two forms: a phosphorylated form (referred to as phosphorylase a) that is considered to be constitutively active and a non-phosphorylated form (referred to as phosphorylase b) that is fully dependent on AMP for activation and is considered to be essentially inactive in resting muscle (13). Phosphorylation (activation) and dephosphorylation (inactivation) of phosphorylase are catalyzed by specific kinases and phosphatases, respectively (39). Glycogen synthesis is catalyzed by glycogen synthase, and the activity of this enzyme is controlled by phosphorylation in a complex manner (72).
Fuel Metabolism in the Fetus
Published in Emilio Herrera, Robert H. Knopp, Perinatal Biochemistry, 2020
The pathway of glycogen synthesis in the adult is summarized in Figure 6. It involves the activation of a glycogen synthase and the inhibition of a glycogen phosphorylase by mechanisms under the dependence of insulin and glucagon through cAMP-dependent pathways. Glycogen synthase and glycogen phosphorylase exist in active and inactive forms of which interconversion is catalyzed by phosphorylation/dephosphorylation processes under the control of specific kinases and phosphatases. Dephosphorylation of these two enzymes leads to glycogen synthase activation, glycogen phosphorylase inactivation, and glycogen synthesis. Moreover, glycogen phosphorylase in its active form is an inhibitor of the glycogen synthase phosphatase, thus precluding a concomitant synthesis and degradation of glycogen. glucose itself is able to stimulate glycogen synthesis because of the activation of glycogen phosphorylase phosphatase and inhibition of glycogen phosphorylase a, which blocks glycogen breakdown and facilitates glycogen synthesis.
Role of aluminum exposure on Alzheimer’s disease and related glycogen synthase kinase pathway
Published in Drug and Chemical Toxicology, 2023
Sonia Sanajou, Pınar Erkekoğlu, Gönül Şahin, Terken Baydar
Glycogen synthase kinase-3 enzyme regulates glycogen synthesis, glucose transport, metabolism, pro-apoptotic factors, and insulin signaling pathway. This kinase consists of two isomers, GSK3α and GSK3β. GSK3β isoform is the dominant one in the brain controlling various signaling pathways (Hoffmeister et al.2020). It is shown that GSK3 participates in cellular activities, such as the formation of cell structure, regulation of cell cycle, gene expression and transcription, cell apoptosis, protein transcription and protein synthesis, mRNA stability, and lipid deposition and lipid accumulation (Gu et al.2019). In addition, GSK3 plays a role in tumor suppression and neuronal function (Beurel et al.2015). The dysfunction of GSK3 has been reported in pathological conditions like both sporadic and familial types AD, diabetes, bipolar disorder, schizophrenia, inflammation (Jope et al., 2017), and cancers (Walz et al., 2017). As shown in Figure 4, three main signaling pathways inactivate GSK3:
Biochanin A, a soy isoflavone, diminishes insulin resistance by modulating insulin-signalling pathway in high-fat diet-induced diabetic mice
Published in Archives of Physiology and Biochemistry, 2023
Sundaresan Arjunan, Radhiga Thangaiyan, Deivasigamani Balaraman
Elevated levels of glucose synthesis in the liver, diminished glycogen production in liver and glycolysis, are key changes in type-2 diabetes that result in hyperglycaemia as a result declined storage of glycogen in hepatic tissues (Stern et al. 2016). GK and G-6-Pase are key liver enzymes that are involved in glycolysis and gluconeogenesis. GK phosphorylates glucose to glucose-6-phosphate, while G-6-Pase catalyses glucose-6-phosphate to free glucose via dephosphorylation (Zhang et al. 2009). In the existing study, data acquired in diabetic mice verified a statistically significant decrease in liver glycogen storage, diminished activity of GK and augmented activity of glucose-6-phosphatase (Table 4). Meanwhile, BCA treatment in HDF fed recovers these levels, which could be due to diminution of insulin resistance. During Diabetes, Glycogen synthesis in the liver is impaired due to insulin resistance (Musabayane et al. 2005). In this study, the administration of BCA significantly increased hepatic glycogen level in liver and skeletal muscles of HFD mice and this may be connection to an increase in glycolysis and reduction in glycogenolysis.
The effects of microRNA-126 reduced inflammation and apoptosis of diabetic nephropathy through PI3K/AKT signalling pathway by VEGF
Published in Archives of Physiology and Biochemistry, 2022
Zhe Lou, Qiaobei Li, Chunyan Wang, Yinyan Li
PI3K-Akt pro-survival signal pathway is important at the time of physiological and pharmacological preconditioning and postconditioning (Zhang et al. 2016). It can not only be activated by the mechanical stimuli such as ischaemic preconditioning and postconditioning, but also by multiple drugs (Zhang et al. 2016). The activation of such pathway contributes to alleviating cell apoptosis and regulating glucose transport and glycogen synthesis. Thus, it can protect myocardium from ischemia/reperfusion injury (Ha et al.2015). Akt activation can exert cell protective effect and prevent the mitochondrial pathway cell death through activating its downstream effector molecules (Kim et al. 2016). They include endothelial nitric oxide synthase (eNOS) and anti-apoptosis B-cell lymphoma-2 (Bcl-2) (Zhang et al. 2016). Moreover, the inhibition of VEGF increased the up-regulation of miRNA-126 on apoptosis and inflammation in diabetic nephropathy vitro. Yuan et al. suggest that Paeonol promotes microRNA-126 expression to inhibit monocyte adhesion to block the activation of the PI3K/Akt/NF-κB pathway in rabbit atherosclerosis (Yuan et al. 2016).