1
|
Sharma AK, Khandelwal R, Wolfrum C. Futile lipid cycling: from biochemistry to physiology. Nat Metab 2024; 6:808-824. [PMID: 38459186 DOI: 10.1038/s42255-024-01003-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 02/02/2024] [Indexed: 03/10/2024]
Abstract
In the healthy state, the fat stored in our body isn't just inert. Rather, it is dynamically mobilized to maintain an adequate concentration of fatty acids (FAs) in our bloodstream. Our body tends to produce excess FAs to ensure that the FA availability is not limiting. The surplus FAs are actively re-esterified into glycerides, initiating a cycle of breakdown and resynthesis of glycerides. This cycle consumes energy without generating a new product and is commonly referred to as the 'futile lipid cycle' or the glyceride/FA cycle. Contrary to the notion that it's a wasteful process, it turns out this cycle is crucial for systemic metabolic homeostasis. It acts as a control point in intra-adipocyte and inter-organ cross-talk, a metabolic rheostat, an energy sensor and a lipid diversifying mechanism. In this Review, we discuss the metabolic regulation and physiological implications of the glyceride/FA cycle and its mechanistic underpinnings.
Collapse
Affiliation(s)
- Anand Kumar Sharma
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| | - Radhika Khandelwal
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland
| | - Christian Wolfrum
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| |
Collapse
|
2
|
Allard C, Miralpeix C, López-Gambero AJ, Cota D. mTORC1 in energy expenditure: consequences for obesity. Nat Rev Endocrinol 2024; 20:239-251. [PMID: 38225400 DOI: 10.1038/s41574-023-00934-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/29/2023] [Indexed: 01/17/2024]
Abstract
In eukaryotic cells, the mammalian target of rapamycin complex 1 (sometimes referred to as the mechanistic target of rapamycin complex 1; mTORC1) orchestrates cellular metabolism in response to environmental energy availability. As a result, at the organismal level, mTORC1 signalling regulates the intake, storage and use of energy by acting as a hub for the actions of nutrients and hormones, such as leptin and insulin, in different cell types. It is therefore unsurprising that deregulated mTORC1 signalling is associated with obesity. Strategies that increase energy expenditure offer therapeutic promise for the treatment of obesity. Here we review current evidence illustrating the critical role of mTORC1 signalling in the regulation of energy expenditure and adaptive thermogenesis through its various effects in neuronal circuits, adipose tissue and skeletal muscle. Understanding how mTORC1 signalling in one organ and cell type affects responses in other organs and cell types could be key to developing better, safer treatments targeting this pathway in obesity.
Collapse
Affiliation(s)
- Camille Allard
- University of Bordeaux, INSERM, Neurocentre Magendie, Bordeaux, France
| | | | | | - Daniela Cota
- University of Bordeaux, INSERM, Neurocentre Magendie, Bordeaux, France.
| |
Collapse
|
3
|
Sharma AK, Khandelwal R, Wolfrum C. Futile cycles: Emerging utility from apparent futility. Cell Metab 2024:S1550-4131(24)00087-1. [PMID: 38565147 DOI: 10.1016/j.cmet.2024.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/15/2024] [Accepted: 03/11/2024] [Indexed: 04/04/2024]
Abstract
Futile cycles are biological phenomena where two opposing biochemical reactions run simultaneously, resulting in a net energy loss without appreciable productivity. Such a state was presumed to be a biological aberration and thus deemed an energy-wasting "futile" cycle. However, multiple pieces of evidence suggest that biological utilities emerge from futile cycles. A few established functions of futile cycles are to control metabolic sensitivity, modulate energy homeostasis, and drive adaptive thermogenesis. Yet, the physiological regulation, implication, and pathological relevance of most futile cycles remain poorly studied. In this review, we highlight the abundance and versatility of futile cycles and propose a classification scheme. We further discuss the energetic implications of various futile cycles and their impact on basal metabolic rate, their bona fide and tentative pathophysiological implications, and putative drug interactions.
Collapse
Affiliation(s)
- Anand Kumar Sharma
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| | - Radhika Khandelwal
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland
| | - Christian Wolfrum
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| |
Collapse
|
4
|
Reckziegel P, Petrovic N, Cannon B, Nedergaard J. Perfluorooctanoate (PFOA) cell-autonomously promotes thermogenic and adipogenic differentiation of brown and white adipocytes. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 271:115955. [PMID: 38237396 DOI: 10.1016/j.ecoenv.2024.115955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/29/2023] [Accepted: 01/06/2024] [Indexed: 02/05/2024]
Abstract
Perfluorooctanoic acid (PFOA) is a synthetic organofluoride surfactant associated with several toxic effects in humans and animals. Particularly, it has been observed that PFOA treatment of mice results in weight loss associated with recruited brown adipose tissue (BAT), including an increased amount of uncoupling protein 1 (UCP1). The molecular mechanism behind this BAT recruitment is presently unknown. To investigate the existence of possible cell-autonomous effects of PFOA, we treated primary cultures of brown and white (inguinal) adipocytes with PFOA, or with the non-fluorinated equivalent octanoate, or with vehicle, for 48 h (from day 5 to day 7 of differentiation). PFOA in itself increased the gene expression (mRNA levels) of UCP1 and carnitine palmitoyltransferase 1A (CPT1α) (thermogenesis-related genes) in both brown and white adipocytes. In addition, PFOA increased the expression of fatty acid binding protein 4 (FABP4) and peroxisome proliferator-activated receptor α (PPARα) (adipogenesis-related genes). Also the protein levels of UCP1 were increased in brown adipocytes exposed to PFOA. This increase was more due to an increase in the fraction of cells that expressed UCP1 than to an increase in UCP1 levels per cell. The PFOA-induced changes were even more pronounced under simultaneous adrenergic stimulation. Octanoate induced less pronounced effects on adipocytes than did PFOA. Thus, PFOA in itself increased the levels of thermogenic markers in brown and white adipocytes. This could enhance the energy metabolism of animals (and humans) exposed to the compound, resulting in a negative energy balance, leading to diminished fitness.
Collapse
Affiliation(s)
- Patrícia Reckziegel
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of São Paulo (USP), São Paulo, Brazil
| | - Natasa Petrovic
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
| |
Collapse
|
5
|
Weiner J, Dommel S, Gebhardt C, Hanschkow M, Popkova Y, Krause K, Klöting N, Blüher M, Schiller J, Heiker JT. Differential expression of immunoregulatory cytokines in adipose tissue and liver in response to high fat and high sugar diets in female mice. Front Nutr 2023; 10:1275160. [PMID: 38024380 PMCID: PMC10655005 DOI: 10.3389/fnut.2023.1275160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 10/23/2023] [Indexed: 12/01/2023] Open
Abstract
A comprehensive understanding of how dietary components impact immunoregulatory gene expression in adipose tissue (AT) and liver, and their respective contributions to metabolic health in mice, remains limited. The current study aimed to investigate the metabolic consequences of a high-sucrose diet (HSD) and a high-fat diet (HFD) in female mice with a focus on differential lipid- and sucrose-induced changes in immunoregulatory gene expression in AT and liver. Female C57BL/6 J mice were fed a purified and macronutrient matched high fat, high sugar, or control diets for 12 weeks. Mice were extensively phenotyped, including glucose and insulin tolerance tests, adipose and liver gene and protein expression analysis by qPCR and Western blot, tissue lipid analyses, as well as histological analyses. Compared to the control diet, HSD- and HFD-fed mice had significantly higher body weights, with pronounced obesity along with glucose intolerance and insulin resistance only in HFD-fed mice. HSD-fed mice exhibited an intermediate phenotype, with mild metabolic deterioration at the end of the study. AT lipid composition was significantly altered by both diets, and inflammatory gene expression was only significantly induced in HFD-fed mice. In the liver however, histological analysis revealed that both HSD- and HFD-fed mice had pronounced ectopic lipid deposition indicating hepatic steatosis, but more pronounced in HSD-fed mice. This was in line with significant induction of pro-inflammatory gene expression specifically in livers of HSD-fed mice. Overall, our findings suggest that HFD consumption in female mice induces more profound inflammation in AT with pronounced deterioration of metabolic health, whereas HSD induced more pronounced hepatic steatosis and inflammation without yet affecting glucose metabolism.
Collapse
Affiliation(s)
- Juliane Weiner
- Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Sebastian Dommel
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany
| | - Claudia Gebhardt
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany
| | - Martha Hanschkow
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Yulia Popkova
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Kerstin Krause
- Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
- Deutsches Zentrum für Diabetesforschung e.V., Neuherberg, Germany
| | - Nora Klöting
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany
| | - Matthias Blüher
- Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany
| | - Jürgen Schiller
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - John T. Heiker
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany
- Institute for Biochemistry, Faculty of Life Sciences, University of Leipzig, Leipzig, Germany
| |
Collapse
|
6
|
Nedergaard J, von Essen G, Cannon B. Brown adipose tissue: can it keep us slim? A discussion of the evidence for and against the existence of diet-induced thermogenesis in mice and men. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220220. [PMID: 37661736 PMCID: PMC10475870 DOI: 10.1098/rstb.2022.0220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 07/12/2023] [Indexed: 09/05/2023] Open
Abstract
The issue under discussion here is whether a decrease in the degree of UCP1 activity (and brown adipose tissue activity in general) could be a cause of obesity in humans. This possibility principally requires the existence of the phenomenon of diet-induced thermogenesis. Obesity could be a consequence of a reduced functionality of diet-induced thermogenesis. Experiments in mice indicate that diet-induced thermogenesis exists and is dependent on the presence of UCP1 and thus of brown adipose tissue activity. Accordingly, many (but not all) experiments indicate that in the absence of UCP1, mice become obese. Whether similar mechanisms exist in humans is still unknown. A series of studies have indicated a correlation between obesity and low brown adipose tissue activity, but it may be so that the obesity itself may influence the estimates of brown adipose tissue activity (generally glucose uptake), partly explaining the relationship. Estimates of brown adipose tissue catabolizing activity would seem to indicate that it may possess a capacity sufficient to help maintain body weight, and obesity would thus be aggravated in its absence. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.
Collapse
Affiliation(s)
- Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Gabriella von Essen
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden
| |
Collapse
|