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Dietary Supplements for Use in Extreme Sports
Published in Datta Sourya, Debasis Bagchi, Extreme and Rare Sports, 2019
Nicolas J.G. Smith, Matthew Butawan, Richard J. Bloomer
Creatine (Cr) is a naturally occurring organic compound that is synthesized endogenously and consumed in a standard diet. When activated (i.e. combined with a phosphate group to form phospho-creatine [PCr]), PCr is capable of rapidly producing energy by creating adenosine triphosphate (ATP; the energy “currency” of cellular reactions) through a process known as substrate level phosphorylation. This substrate-level phosphorylation is a vital component of energy production during short-duration, high-intensity activities (i.e. 8 s sprint). Research has established that creatine supplementation (CrS) increases muscle Cr concentrations,31,32thereby improving performance on high-intensity exercise (i.e. repeated sprinting and resistance training). Indeed, the International Society of Sports Nutrition has touted creatine monohydrate (the most widely used form of creatine supplementation) as “the most effective ergogenic nutritional supplement” for increasing performance in high-intensity exercise.33 Creatine supplementation has also been shown to enhance performance in sport-specific settings.34 In general, Cr appears to be an effective ergogenic aid capable of eliciting a number of performance enhancing effects.
Biology of microbes
Published in Philip A. Geis, Cosmetic Microbiology, 2006
Glycolysis. Glycolysis, also known as the Embden–Meyerhof pathway, is one of three major pathways that break down sugar to pyruvate. The other major pathways are the Entner–Doudoroff and the pentose phosphate. Glycolysis is considered the most common pathway because it is found in all major groups of microorganisms and functions regardless of the presence of oxygen. Glycolysis is usually divided into two main phases, to better explain how it works. The first is referred to as the 6-carbon sugar stage and involves two phosphorylating steps to convert glucose to fructose-1,6-bis-phosphate. Two molecules of ATP are used to prime this step. The second step is the 3-carbon sugar stage that cleaves the fructose-1,6 bisphosphate into two 3-carbon molecules that are converted to form a total of two pyruvate molecules, two NADH molecules (electron carriers), and four ATP molecules. Because two ATP molecules are used to prime the reaction in step 1, we get a net of two ATP molecules from the reaction. The ATP is formed by a process known as substrate-level phosphorylation since ADP phosphorylation is coupled with the exergonic breakdown of a high-energy substrate molecule.
Energy Provision, Fuel Use and Regulation of Skeletal Muscle Metabolism During The Exercise Intensity/Duration Continuum
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
To meet the ATP needs of exercise, skeletal muscle has an array of metabolic pathways that can synthesize ATP from adenosine diphosphate (ADP) and inorganic phosphate (Pi) at very high rates and for long periods of time (Figure 2.1). These ATP-producing pathways can be categorized as substrate-level phosphorylation (or “anaerobic”) and oxidative phosphorylation (or “aerobic”). The so-called anaerobic energy pathways include the breakdown of phosphocreatine (PCr) to produce ATP and the generation of ATP in the glycolytic pathway, with muscle glycogen as the substrate and lactate as a by-product (Table 2.1). These pathways reside in the cytoplasm and have a much higher rate of ATP production but a smaller capacity for ATP production as compared to the aerobic pathways (77). The production of aerobic ATP in the mitochondria requires oxygen, ADP, and Pi and reducing equivalents (NADH, FADH2) from the metabolism of primarily fat and carbohydrate (CHO). The produced ATP is then moved into the cytoplasm to the various sites of ATP utilization. Skeletal muscle is very dependent on the respiratory and cardiovascular systems to deliver adequate oxygen for the maintenance of aerobic ATP provision, and the by-products of ATP breakdown in the cytoplasm (ADP, Pi) must also be transported back into the mitochondria. Most of the required reducing equivalents are produced directly in the mitochondria in the fat and CHO metabolic pathways and the tricarboxylic acid (TCA) cycle (Figure 2.1). A small amount of NADH produced in the glycolytic pathway can also be shuttled into the mitochondria. In terms of the fuel for oxidative metabolism, CHO oxidation can be activated quickly, has a higher power output, and is a more efficient fuel (kcal/L O2 used) when compared to fat, but does have a lower capacity than fat oxidation. Given that CHO can also be used to provide anaerobic energy, it is clearly the dominant fuel for high-intensity exercise, whether it be in the aerobic or anaerobic (sprinting) domains.
A virulence factor as a therapeutic: the probiotic Enterococcus faecium SF68 arginine deiminase inhibits innate immune signaling pathways
Published in Gut Microbes, 2022
Fereshteh Ghazisaeedi, Jochen Meens, Bianca Hansche, Sven Maurischat, Peter Schwerk, Ralph Goethe, Lothar H. Wieler, Marcus Fulde, Karsten Tedin
Enterococcus faecium SF68 (NCIMB 10415), is an endogenous, intestinal commensal isolate, and a well-characterized member of the lactic acid bacteria (LAB), which has been authorized for use as a probiotic in pharmaceutical preparations and food supplements in humans and animals.10–13 As with many other LAB, the strain metabolizes carbon sources through fermentation and substrate level phosphorylation reactions rather than oxidative phosphorylation for generation of ATP.8,9,14 Glycolysis and fermentation of sugars generates acetate and lactic acid, providing a growth advantage for LAB which are generally resistant to low pH.8,15 Furthermore, production of ATP through catabolism of arginine by the arginine deiminase pathway (ADI) generates ammonia as an end-product contributing to survival in acidified environments, although E. faecium is generally not thought to use arginine as a source of ATP.8
Metabolic profile of the Warburg effect as a tool for molecular prognosis and diagnosis of cancer
Published in Expert Review of Molecular Diagnostics, 2022
Gerardo M. Nava, Luis Alberto Madrigal Perez
Tumors cells that exert the Warburg effect have a highly ATP demand to maintain their anabolic metabolism. The ATP demand is mainly supplied by lactic fermentation in carcinogenic cells [7]. However, it is necessary to consider that respiration in quantitative terms is more efficient via forming ATP, producing up to 32 (~33) ATP moles for glucose mole [23]. In contrast, substrate-level phosphorylation only produces four, two cytoplasmic and two mitochondrial [18]. Thus, to compensate for the lesser ATP production by substrate-level phosphorylation, the cancer cell needs higher glucose uptake rates to maintain its anabolic ATP demand. For example, under normoxic conditions, the time it takes to produce 36 ATP from one glucose to non-tumorigenic cells, tumorigenic cells produce 56 ATP from 13 glucose; while in anoxic conditions generate 26 ATP from 13 glucose [24]. To maintain ATP/ADP ratio, cancer cells have to uptake more glucose to compensate for lessening ATP production via mitochondrial respiration. For this reason, glucose uptake plays a key role in maintaining ATP levels in tumorigenic cells with the Warburg effect.
Investigation of the population dynamics within a Pseudomonas aeruginosa biofilm using a flow based biofilm model system and flow cytometric evaluation of cellular physiology
Published in Biofouling, 2018
Juzwa Wojciech, Myszka Kamila, Białas Wojciech
Another explanation for the observed differences in the percentages of active sub-populations between P. aeruginosa biofilm and planktonic forms results from the fluorogenic redox indicator (RedoxSensor™ Green reagent from Life Technologies) used in this study to measure the cellular redox potential. RedoxSensor™ Green reagent is a substrate for cellular reductases, which are parts of the bacterial electron transport systems related to oxidative phosphorylation and thus to cellular respiration (Kalyuzhnaya et al. 2008). As the reductases are not crucial for substrate-level phosphorylation involved in fermentation processes the observed high levels of reductase activity may indicate the metabolic switch towards the cellular respiration (Kihira et al. 2012). The observed higher percentages of active (sub-population P6) cells among planktonic forms may be due to the exposure of free-living P. aeruginosa cells to high aeration during culture in FBMS, resulting in the aerobic respiration processes that dominated their metabolism. This is consistent with the studies of Heffernan et al. (2009), who observed the superior performance of planktonic cells of Pseudomonas fluorescens over biofilm cells in degradation of xenobiotics. They reported the higher utilization rate of a tested xenobiotic (fluoroacetate) by planktonic cells than by biofilm forms, and concluded that this may be due to both oxygen limitation in the biofilm and the high free-fluoride concentrations recorded in the tubular biofilm reactor used in the study (Heffernan et al. 2009).