Review

Authors: Joshua D Rabinowitz, Sven Enerbäck

Lactate, perhaps the best-known metabolic waste product, was first isolated from sour milk, in which it is produced by lactobacilli. Whereas microbes also generate other fermentation products, such as ethanol or acetone, lactate dominates in mammals. Lactate production increases when the demand for ATP and oxygen exceeds supply, as occurs during intense exercise and ischaemia. The build-up of lactate in stressed muscle and ischaemic tissues has established lactate's reputation as a deleterious waste product. In this Perspective, we summarize emerging evidence that, in mammals, lactate also serves as a major circulating carbohydrate fuel. By providing mammalian cells with both a convenient source and sink for three-carbon compounds, circulating lactate enables the uncoupling of carbohydrate-driven mitochondrial energy generation from glycolysis. Lactate and pyruvate together serve as a circulating redox buffer that equilibrates the NADH/NAD ratio across cells and tissues. This reconceptualization of lactate as a fuel-analogous to how Hans Christian Andersen's ugly duckling is actually a beautiful swan-has the potential to reshape the field of energy metabolism.

Topics: Animals; Citric Acid Cycle; Energy Metabolism; Glucose; Glycolysis; Humans; Lactic Acid

PubMed: 32694798
DOI: 10.1038/s42255-020-0243-4

Review

Authors: Natalya N Pavlova, Jiajun Zhu, Craig B Thompson...

Metabolism of cancer cells is geared toward biomass production and proliferation. Since the metabolic resources within the local tissue are finite, this can lead to nutrient depletion and accumulation of metabolic waste. To maintain growth in these conditions, cancer cells employ a variety of metabolic adaptations, the nature of which is collectively determined by the physiology of their cell of origin, the identity of transforming lesions, and the tissue in which cancer cells reside. Furthermore, select metabolites not only serve as substrates for energy and biomass generation, but can also regulate gene and protein expression and influence the behavior of non-transformed cells in the tumor vicinity. As they grow and metastasize, tumors can also affect and be affected by the nutrient distribution within the body. In this hallmark update, recent advances are incorporated into a conceptual framework that may help guide further research efforts in exploring cancer cell metabolism.

Topics: Energy Metabolism; Humans; Neoplasms; Nutrients

PubMed: 35123658
DOI: 10.1016/j.cmet.2022.01.007

Review

Authors: M Rigoulet, C L Bouchez, P Paumard...

In living cells, growth is the result of coupling between substrate catabolism and multiple metabolic processes that take place during net biomass formation and maintenance processes. During growth, both ATP/ADP and NADH/NAD molecules play a key role. Cell energy metabolism hence refers to metabolic pathways involved in ATP synthesis linked to NADH turnover. Two main pathways are thus involved in cell energy metabolism: glycolysis/fermentation and oxidative phosphorylation. Glycolysis and mitochondrial oxidative phosphorylation are intertwined through thermodynamic and kinetic constraints that are reviewed herein. Further, our current knowledge of short-term and long term regulation of cell energy metabolism will be reviewed using examples such as the Crabtree and the Warburg effect.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Cell Physiological Phenomena; Energy Metabolism; Glycolysis; Kinetics; NAD; Oxidative Phosphorylation

PubMed: 32717222
DOI: 10.1016/j.bbabio.2020.148276

Review

Authors: Matthew R Zanotelli, Jian Zhang, Cynthia A Reinhart-King...

Altered tissue mechanics and metabolism are defining characteristics of cancer that impact not only proliferation but also migration. While migrating through a mechanically and spatially heterogeneous microenvironment, changes in metabolism allow cells to dynamically tune energy generation and bioenergetics in response to fluctuating energy needs. Physical cues from the extracellular matrix influence mechanosignaling pathways, cell mechanics, and cytoskeletal architecture to alter presentation and function of metabolic enzymes. In cancer, altered mechanosensing and metabolic reprogramming supports metabolic plasticity and high energy production while cells migrate and metastasize. Here, we discuss the role of mechanoresponsive metabolism in regulating cell migration and supporting metastasis as well as the potential of therapeutically targeting cancer metabolism to block motility and potentially metastasis.

Topics: Animals; Cell Movement; Energy Metabolism; Extracellular Matrix; Humans; Mechanotransduction, Cellular; Neoplasm Metastasis; Neoplasms; Tumor Microenvironment

PubMed: 33915111
DOI: 10.1016/j.cmet.2021.04.002

Review

Authors: Gilles Bonvento, Juan P Bolaños

The brain has almost no energy reserve, but its activity coordinates organismal function, a burden that requires precise coupling between neurotransmission and energy metabolism. Deciphering how the brain accomplishes this complex task is crucial to understand central facets of human physiology and disease mechanisms. Each type of neural cell displays a peculiar metabolic signature, forcing the intercellular exchange of metabolites that serve as both energy precursors and paracrine signals. The paradigm of this biological feature is the astrocyte-neuron couple, in which the glycolytic metabolism of astrocytes contrasts with the mitochondrial oxidative activity of neurons. Astrocytes generate abundant mitochondrial reactive oxygen species and shuttle to neurons glycolytically derived metabolites, such as L-lactate and L-serine, which sustain energy needs, conserve redox status, and modulate neurotransmitter-receptor activity. Conversely, early disruption of this metabolic cooperation may contribute to the initiation or progression of several neurological diseases, thus requiring innovative therapies to preserve brain energetics.

Topics: Astrocytes; Brain; Energy Metabolism; Glycolysis; Humans; Neurons

PubMed: 34348099
DOI: 10.1016/j.cmet.2021.07.006

Authors: Ting Li, Christopher Copeland, Anne Le...

Metabolism is a fundamental process for all cellular functions. For decades, there has been growing evidence of a relationship between metabolism and malignant cell proliferation. Unlike normal differentiated cells, cancer cells have reprogrammed metabolism in order to fulfill their energy requirements. These cells display crucial modifications in many metabolic pathways, such as glycolysis and glutaminolysis, which include the tricarboxylic acid (TCA) cycle, the electron transport chain (ETC), and the pentose phosphate pathway (PPP) [1]. Since the discovery of the Warburg effect, it has been shown that the metabolism of cancer cells plays a critical role in cancer survival and growth. More recent research suggests that the involvement of glutamine in cancer metabolism is more significant than previously thought. Glutamine, a nonessential amino acid with both amine and amide functional groups, is the most abundant amino acid circulating in the bloodstream [2]. This chapter discusses the characteristic features of glutamine metabolism in cancers and the therapeutic options to target glutamine metabolism for cancer treatment.

Topics: Citric Acid Cycle; Energy Metabolism; Glutamine; Glycolysis; Humans; Metabolic Networks and Pathways; Neoplasms

PubMed: 34014532
DOI: 10.1007/978-3-030-65768-0_2

Authors: Silvia Maggini, Veronika Óvári, Inmaculada Ferreres Giménez...

The human body, particularly the brain, requires energy, stored in the form of adenosine triphosphate. Energy metabolism during cellular respiration is dependent on the presence of multiple micronutrients, which act as essential components, coenzymes, or precursors at every stage. An adequate supply of multiple micronutrients is vital for efficient energy production. However, micronutrient intakes below the recommended dietary allowance are common, even in industrialized countries. Intakes of vitamins A, D, E, folate, iron, zinc, and selenium are suboptimal across all age groups. Suboptimal micronutrient levels have been shown to contribute to low energy levels, physical and mental fatigue, and impaired cognitive performance and wellbeing - symptoms frequently present in the general population. When supplemented in combination in well-conducted trials, multiple micronutrients ± coenzyme Q10 reduced oxidative stress in chronic fatigue syndrome; in healthy people they increased cerebral blood-flow hemodynamic response, energy expenditure, and fat oxidation; reduced mental and physical fatigue; improved the speed and accuracy of cognitive function during demanding tasks; and reduced stress. The results from these clinical trials suggest that even in industrialized countries, where adults might be assumed to have a healthy, balanced diet, there is a rationale to supplement with multiple micronutrients, including coenzyme Q10, to improve nutritional status, support energy metabolism, and improve subjective wellbeing.

Topics: Diagnostic Self Evaluation; Dietary Supplements; Energy Metabolism; Humans; Micronutrients; Nutritional Status; Recommended Dietary Allowances

PubMed: 34323089
DOI: 10.20960/nh.03788

Review

Authors: Brian Glancy, Daniel A Kane, Andreas N Kavazis...

Mitochondrial structures were probably observed microscopically in the 1840s, but the idea of oxidative phosphorylation (OXPHOS) within mitochondria did not appear until the 1930s. The foundation for research into energetics arose from Meyerhof's experiments on oxidation of lactate in isolated muscles recovering from electrical contractions in an O atmosphere. Today, we know that mitochondria are actually reticula and that the energy released from electron pairs being passed along the electron transport chain from NADH to O generates a membrane potential and pH gradient of protons that can enter the molecular machine of ATP synthase to resynthesize ATP. Lactate stands at the crossroads of glycolytic and oxidative energy metabolism. Based on reported research and our own modelling in silico, we contend that lactate is not directly oxidized in the mitochondrial matrix. Instead, the interim glycolytic products (pyruvate and NADH) are held in cytosolic equilibrium with the products of the lactate dehydrogenase (LDH) reaction and the intermediates of the malate-aspartate and glycerol 3-phosphate shuttles. This equilibrium supplies the glycolytic products to the mitochondrial matrix for OXPHOS. LDH in the mitochondrial matrix is not compatible with the cytoplasmic/matrix redox gradient; its presence would drain matrix reducing power and substantially dissipate the proton motive force. OXPHOS requires O as the final electron acceptor, but O supply is sufficient in most situations, including exercise and often acute illness. Recent studies suggest that atmospheric normoxia may constitute a cellular hyperoxia in mitochondrial disease. As research proceeds appropriate oxygenation levels should be carefully considered.

Topics: Energy Metabolism; Glycolysis; Mitochondria; NAD; Oxidation-Reduction; Oxidative Phosphorylation

PubMed: 32358865
DOI: 10.1113/JP278930

Review

Authors: Katarzyna Patrycja Dzik, Jan Jacek Kaczor

PURPOSE

This review provides a current perspective on the mechanism of vitamin D on skeletal muscle function with the emphasis on oxidative stress, muscle anabolic state and muscle energy metabolism. It focuses on several aspects related to cellular and molecular physiology such as VDR as the trigger point of vitamin D action, oxidative stress as a consequence of vitamin D deficiency.

METHOD

The interaction between vitamin D deficiency and mitochondrial function as well as skeletal muscle atrophy signalling pathways have been studied and clarified in the last years. To the best of our knowledge, we summarize key knowledge and knowledge gaps regarding the mechanism(s) of action of vitamin D in skeletal muscle.

RESULT

Vitamin D deficiency is associated with oxidative stress in skeletal muscle that influences the mitochondrial function and affects the development of skeletal muscle atrophy. Namely, vitamin D deficiency decreases oxygen consumption rate and induces disruption of mitochondrial function. These deleterious consequences on muscle may be associated through the vitamin D receptor (VDR) action. Moreover, vitamin D deficiency may contribute to the development of muscle atrophy. The possible signalling pathway triggering the expression of Atrogin-1 involves Src-ERK1/2-Akt- FOXO causing protein degradation.

CONCLUSION

Based on the current knowledge we propose that vitamin D deficiency results from the loss of VDR function and it could be partly responsible for the development of neurodegenerative diseases in human beings.

Topics: Animals; Energy Metabolism; Humans; Mitochondria; Muscle, Skeletal; Oxidative Stress; Vitamin D; Vitamin D Deficiency

PubMed: 30830277
DOI: 10.1007/s00421-019-04104-x

Review

Authors: Yu'e Liu, Yihong Sun, Yadong Guo...

Mitochondria are intracellular organelles involved in energy production, cell metabolism and cell signaling. They are essential not only in the process of ATP synthesis, lipid metabolism and nucleic acid metabolism, but also in tumor development and metastasis. Mutations in mtDNA are commonly found in cancer cells to promote the rewiring of bioenergetics and biosynthesis, various metabolites especially oncometabolites in mitochondria regulate tumor metabolism and progression. And mutation of enzymes in the TCA cycle leads to the unusual accumulation of certain metabolites and oncometabolites. Mitochondria have been demonstrated as the target for cancer treatment. Cancer cells rely on two main energy resources: oxidative phosphorylation (OXPHOS) and glycolysis. By manipulating OXPHOS genes or adjusting the metabolites production in mitochondria, tumor growth can be restrained. For example, enhanced complex I activity increases NAD/NADH to prevent metastasis and progression of cancers. In this review, we discussed mitochondrial function in cancer cell metabolism and specially explored the unique role of mitochondria in cancer stem cells and the tumor microenvironment. Targeting the OXPHOS pathway and mitochondria-related metabolism emerging as a potential therapeutic strategy for various cancers.

Topics: Humans; Neoplasms; Mitochondria; Energy Metabolism; Citric Acid Cycle; Oxidative Phosphorylation; Tumor Microenvironment

PubMed: 36778129
DOI: 10.7150/ijbs.81609