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The Bioenergetics of Mammalian Sperm Motility
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Rhesus monkey spermatozoa obtain energy for motility from fructolysis supplemented by mitochondrial respiration. The rates of aerobic fructolysis and respiration in the absence of fructose were correlated with motility. The spermatozoa oxidized endogenous substrates and pyruvate, succinate, ketoglutarate, and malate stimulated oxygen uptake.56
Detrimental effects of fructose on mitochondria in mouse motor neurons and on C. elegans healthspan
Published in Nutritional Neuroscience, 2022
Divya Lodha, Sudarshana Rajasekaran, Tamilselvan Jayavelu, Jamuna R. Subramaniam
Fructose is metabolized with the help of fructokinase largely in hepatocytes and converted to fructose-1-phosphate. This is then utilized to produce lactate and converted to uric acid or pyruvate which is used by the citric acid cycle to produce energy26. It is also utilized for gluconeogenesis and stored as glycogen in the liver to be used as glucose when necessary. Unlike glucose metabolism or glycolysis, which is tightly regulated by the rate-limiting enzyme phosphofructokinase and depends on the concentration of glucose for metabolism, Fructolysis is regulated loosely by fructokinase and continues till fructose is fully consumed27. This leads to mitochondrial stress (ROS production) which usually precedes dysfunction eventually leading to cell death28. But how fructose affects neurons and its severity of mitochondrial impairment and healthspan of an organism is not understood.
Fructose and hepatic insulin resistance
Published in Critical Reviews in Clinical Laboratory Sciences, 2020
Samir Softic, Kimber L. Stanhope, Jeremie Boucher, Senad Divanovic, Miguel A. Lanaspa, Richard J. Johnson, C. Ronald Kahn
In addition to stimulating lipogenic transcription factors, tracer studies show that fructose carbons can be immediately utilized as substrate in lipogenesis, whereas carbons labeled in glucose molecule are not observed to enter lipids, at least during a short four-hour observation period [31]. The difference in carbon appearance can be explained by increased flux through the fructolysis pathway. Glyceraldehyde-3 phosphate (GA3P) and dihydroxyacetone phosphate (DHAP) are common intermediates of both glycolysis and fructolysis pathways, downstream of which glucose and fructose metabolism is indistinguishable. However, prior to formation of these intermediates fructose is metabolized by KHK and aldolase, both of which are not regulated by insulin or end products of fructolysis. On the other hand, phosphofructokinase, an upstream enzyme in glycolysis pathway, is inhibited by both ATP and citrate [43], which are the products of this pathway. Thus, while both fructose and glucose carbons converge onto a common pathway, fructolysis is not subjected to feedback inhibition and allows for unrestrained flux through the pathway.