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Nutrition and Metabolic Factors
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
As discussed in Chapter 2, glycogen is stored in both the muscle and the liver bound to two enzymes, glycogen synthetase and phosphorylase (79). These enzymes are assisted by two additional enzymes (isozymes): hexokinase (in muscle, liver, and other cells) and glucokinase (only in the liver). Collectively, these enzymes and isozymes are used to help regulate glucose and glycogen by facilitating their synthesis or breakdown based on energy production needs.
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.
Medicinal Plants in Natural Health Care as Phytopharmaceuticals
Published in Anil K. Sharma, Raj K. Keservani, Surya Prakash Gautam, Herbal Product Development, 2020
Studies have demonstrated the hypoglycaemic action and effects of coriander on carbohydrate metabolism. The effect of coriander seeds on carbohydrate metabolism was studied in rats that were fed with a fat-rich cholesterol diet. The spice exhibited noteworthy hypoglycemic action. There was an increase in the concentration of hepatic glycogen as was evident from the increased activity of glycogen synthase. Activities of glycogen phosphorylase and gluconeogenic enzymes revealed decreased rates of glycogenolysis and gluconeogenesis. The increased activities of glucose-6-phosphate dehydrogenase and glycolytic enzymes suggest the utilization of glucose by the pentose phosphate pathway and glycolysis. These observations clearly indicated that coriander seeds demonstrate good hypoglycemic activity through enhanced glycogenesis, glycolysis and decreased glycogenolysis and gluconeogenesis (Aissaoui et al., 2011).
Determination of histopathological effects and myoglobin, periostin gene-protein expression levels in Danio rerio muscle tissue after acaricide yoksorrun-5EC (hexythiazox) application
Published in Drug and Chemical Toxicology, 2023
Yücel Başımoğlu Koca, Serdar Koca, Zübeyde Öztel, Erdal Balcan
We found that following yoksorrun (hexythiazox) treatments, myoglobin level was increased, depending on the skeletal muscle atrophy. This can point at two things: firstly, the acaricide may have reduced the oxygen content of the water. Secondly, oxygen may be insufficient in the muscle tissue due to muscle damage. Therefore, the unknown myoglobin gene expression mechanisms may be induced in intact and/or slightly damaged muscle cells to obtain the required oxygen. On the other hand, previous reports suggested that this pesticide is highly toxic to larvae of Tetranychus urticae but not harmful for deutonymph and adults (Dekeyser 2005, Leviticus et al.2020). More recently, Demaeght et al. (2014) proposed that hexythiazox binds to central pore region of chitin synthase enzyme and block the chitin translocation (Demaeght et al.2014). In a recent study, the regulatory effect of glycogen synthase and glycogen phosphorylase on chitin biosynthesis was investigated (Zhang et al.2019). Glycogen synthase is a key glycosyltransferase in the glycogen biosynthesis. Muscle glycogen is an essential energy source during mechanical action. To evaluate the glycogen content in hexythiazox-treated zebrafish skeletal muscle, we performed PAS technique. Our results indicated that glycogen is decreased upon the pesticide treatment. These data suggest that hexythiazox is not only responsible for the loss of muscle mass in zebrafish but also responsible for the decreasing of glycogen deposits in the skeletal muscles.
Ameliorative effects of tropisetron on liver injury in streptozotocin-induced diabetic rats
Published in Archives of Physiology and Biochemistry, 2021
Shiva Gholizadeh-Ghaleh Aziz, Roya Naderi, Nima Mahmodian
Insulin enhances intracellular glycogen deposition which triggers glycogen synthase and inhibits glycogen phosphorylase. Therefore, as shown in this study, glycogen contents decrease in some tissues, including the liver (Whitton and Hems 1975) in insulin deficiency such as STZ injection. In the present study, tropisetron ameliorated the reduction of liver glycogen content in STZ-induced T1DM. Heimes et al. (2009) reported that tropisetron can increase insulin secretion in an insulin-producing beta cell line in vitro. Thus, the glycogen accumulation effect of tropisetron in diabetic animals seems logical. Interestingly, no significant difference was observed in the glycogen content of the glibenclamide-administered and tropisetron-administered groups in the liver of diabetic rats.
Eight sessions of endurance training decrease fasting glucose and improve glucose tolerance in middle-aged overweight males
Published in Archives of Physiology and Biochemistry, 2021
Stian Jelstad, Thorhildur Ditta Valsdottir, Egil I. Johansen, J⊘rgen Jensen
The interest in the effect of high-intensity interval training (HIIT) on glucose homeostasis has been high lately. The classical model for HIIT is 30-s all-out exercise with 2- to 5-min rest between repetitions of 4 and 10 sets (MacDougall et al.1998). Studies have shown that HIIT reduces fasting glucose (Sandvei et al.2012), increases glucose tolerance (Babraj et al.2009, Sandvei et al.2012), and improves insulin sensitivity (Richards et al.2010). Glycogen breakdown in skeletal muscle is substantial during 30-s all out cycling (Birk and Wojtaszewski 2006), and glycogen content in skeletal muscles is a key regulator of insulin sensitivity (Jensen et al.1997, 2006, Kolnes et al.2015). In both lean, obese, and T2DM patients, 45 min of endurance exercise reduces glycogen content and activates glycogen synthase (Jensen et al.2012), which contributes to improvement in insulin sensitivity and metabolic regulation (Jensen et al.2011).