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Cell Physiology
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
The lactate consumed by cells cannot be converted to glucose in most cultured cells. A number of reactions in glycolysis are irreversible. The conversion of pyruvate to glucose in the reverse direction of glycolysis, called gluconeogenesis, requires the expression of a few additional enzymes to counter these irreversible reactions. In mammals, gluconeogenesis primarily occurs in the liver. During the period that cells are consuming lactate, many intermediates derived from glycolysis are still needed for maintaining cellular functions. For example, dihydroxyacetone phosphate (DHAP) is needed for supplying glycerol 3-phosphate for lipid synthesis and NADPH, derived in the PPP, is needed for reductive biosynthesis and for maintaining the cell’s redox balance. Furthermore, glucose 6-phosphate is required to synthesize the glucosamine and galactose that are used in glycan synthesis for the production of recombinant proteins. The glycolysis pathway thus remains active during the lactate-consumption stage. The glucose consumption rate is small, but not zero (Panel 3.17).
Metabolic load comparison between the quarters of a game in elite male basketball players using sport metabolomics
Published in European Journal of Sport Science, 2021
Kayvan Khoramipour, Abbas Ali Gaeini, Elham Shirzad, Kambiz Gilany, Saeed Chashniam, Øyvind Sandbakk
In the second quarter, Valine and Lucien were decreased, whereas Alanine, Glycerol, AcetoAcetic Acid, Acetone, Succinic Acid, Citric Acid, Acetate, and Taurine were increased. Since no previous study has assessed these metabolites in sport, we discuss these metabolic changes in response to previous studies examining bouts of exercise training. Increased Alanine in the second quarter indicates an increased transfer of BCAAs induced Ammonia to the liver (Mougios, 2019), a process called Alanine cycle (Mougios, 2019), which can be considered as a justification for increased Alanine. In addition, glucose reduction and Epinephrine, Glucagon, Growth Hormone and Cortical enhancement can stimulate Alanine Amino transferase converting Pyruvate to Alanine which is Gluconeogenesis precursor and therefore can increase Gluconeogenesis (Daskalaki et al., 2015). Also, several previous studies reported increased Alanine after acute bouts of exercise (Berton et al., 2017; Enea et al., 2010; Hoffman, 2017; Kirwan, Coffey, Niere, Hawley, & Adams, 2009; Netzer et al., 2011; Peake et al., 2014; Pechlivanis et al., 2010; Pechlivanis et al., 2015; Ra et al., 2014; Zafeiridis et al., 2016), which indicates an increase BCAAs metabolism and Gluconeogenesis. Furthermore, Pitti et al. (2019) detected significant changes in aromatic amino acid levels in a soccer game using salivary metabolomics, which was in line with that observed using blood analyses. The increased Glycerol during the second quarter represents an increase in both Gluconeogenesis (as a Gluconeogenesis precursor) and Lipolysis (as a byproduct of 3-acyl glycerol breakdown), which are pathways activated because of glycogen depletion (Mougios, 2019). This is supported by increases of the two ketone bodies, AcetoAcetic Acid and Acetone, most likely due to Glycogen depletion in the second quarter (Evans et al., 2017).