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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).
Bioartificial organs
Published in Ronald L. Fournier, Basic Transport Phenomena in Biomedical Engineering, 2017
The basic functional cellular units of the liver are called the hepatocytes. Each hepatocyte is about 25 μm in diameter, and there are close to 250 billion of them in the human liver, accounting for 75% of the liver volume. The hepatocytes are metabolically very active and provide an incredible variety of functions. Their role in carbohydrate metabolism includes the storage of excess glucose as glycogen and the release of this stored form of glucose (glycogenolysis) when blood glucose levels are low. In addition, the liver converts other sugars such as galactose and fructose to glucose. If blood glucose levels are low and the glycogen stores are also depleted, then the liver performs a process known as gluconeogenesis wherein glucose is synthesized from amino acids.
Regulation of Blood Glucose
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
There are many harmful, long-term, systemic effects from untreated or poorly treated diabetes mellitus. For example, because liver cells do not receive enough glucose, they attempt to make up the difference by the catabolic metabolic process called gluconeogenesis. In gluconeogenesis, fats and proteins are broken down and certain amino acids are converted to glucose. The long-term effect of this process is wasting or emaciation. The liver, however, becomes fatty because of excessive uptake of free fatty acids by liver cells. Because of low intracellular glucose in non-liver cells, there is poor protein metabolism, which leads to conditions such as poor wound healing, cardiovascular disease, kidney disease, retinal degeneration, and osteoporosis.
Potential effect of Turbinaria decurrens acetone extract on the biochemical and histological parameters of alloxan-induced diabetic rats
Published in International Journal of Environmental Health Research, 2021
Omnia Hamdy Abdel-Karim, Atef Mohamed Abo-Shady, Gehan Ahmed Ismail, Saly Farouk Gheda
GPT or GOT levels are a valuable primary aid in the diagnosis of liver disease as a liver toxicity marker (Mori et al. 2003) and as reflectors of hepatocellular necrosis (Setorki et al. 2010). It has been earlier reported that amino-transferase enzyme activity increments, under deficiency of insulin, were responsible for the increased ketogenesis and gluconeogenesis during diabetic disorders (Felig et al. 1970). In the induced diabetic animals, the changes in the serum enzymes were directly related to the metabolic function change of both AST and ALT enzymes (Asayama et al. 1994). The mechanism by which the serum of both aminotransferases is elevated in diabetic animals may involve augmented release of these enzymes from tissues, mainly the liver, owing to oxidative stress or the progressive glycosylation end-product formation as well as because of liver dysfunction (Mori et al. 2003). Moreover, Ohaeri (2001) reported that liver tissue was necrotized in the induced diabetic rats. Therefore, an elevation in the ALT and AST activities in the serum might be chiefly because of the escape of these enzymes from the cytosol of the liver into the stream of the blood, which gives a sign of hepatotoxic effect in the induced diabetic rats. Alloxan injection, as a diabetic inducer, was harmful and hurt the hepatic tissues, accompanied by an increase in the GOT and GPT enzymes (Aissaoui et al. 2017). All these previous reports conformed with that estimates for AST and ALT levels in this study (Table 2). After algal treatment administration, a reduction of the serum GOT and GPT activities could be, consequently, due to the alleviation of the liver damage.
Adaptive controller based an extended model of glucose-insulin-glucagon system for type 1 diabetes
Published in International Journal of Modelling and Simulation, 2023
Mahour Saoussane, Tadjine Mohammed, Chakir Mesaoud
After 48 h from the start of the fasting period, the blood glucose stays within the safe range because of the increase in the concentration of glucagon, which stimulates the production of glucose by glycogenolysis and gluconeogenesis. The glucagon helps to preserve the blood glucose.