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Agoncillo M, Yu J, Gunton JE. The Role of Vitamin D in Skeletal Muscle Repair and Regeneration in Animal Models and Humans: A Systematic Review. Nutrients 2023; 15:4377. [PMID: 37892452 PMCID: PMC10609905 DOI: 10.3390/nu15204377] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 10/04/2023] [Accepted: 10/05/2023] [Indexed: 10/29/2023] Open
Abstract
Vitamin D deficiency, prevalent worldwide, is linked to muscle weakness, sarcopenia, and falls. Muscle regeneration is a vital process that allows for skeletal muscle tissue maintenance and repair after injury. PubMed and Web of Science were used to search for studies published prior to May 2023. We assessed eligible studies that discussed the relationship between vitamin D, muscle regeneration in this review. Overall, the literature reports strong associations between vitamin D and skeletal myocyte size, and muscle regeneration. In vitro studies in skeletal muscle cells derived from mice and humans showed vitamin D played a role in regulating myoblast growth, size, and gene expression. Animal studies, primarily in mice, demonstrate vitamin D's positive effects on skeletal muscle function, such as improved grip strength and endurance. These studies encompass vitamin D diet research, genetically modified models, and disease-related mouse models. Relatively few studies looked at muscle function after injury, but these also support a role for vitamin D in muscle recovery. The human studies have also reported that vitamin D deficiency decreases muscle grip strength and gait speed, especially in the elderly population. Finally, human studies reported the benefits of vitamin D supplementation and achieving optimal serum vitamin D levels in muscle recovery after eccentric exercise and surgery. However, there were no benefits in rotator cuff injury studies, suggesting that repair mechanisms for muscle/ligament tears may be less reliant on vitamin D. In summary, vitamin D plays a crucial role in skeletal muscle function, structural integrity, and regeneration, potentially offering therapeutic benefits to patients with musculoskeletal diseases and in post-operative recovery.
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Affiliation(s)
- Miguel Agoncillo
- Centre for Diabetes, Obesity and Endocrinology (CDOE), The Westmead Institute for Medical Research, The University of Sydney, Sydney 2145, Australia
| | - Josephine Yu
- Centre for Diabetes, Obesity and Endocrinology (CDOE), The Westmead Institute for Medical Research, The University of Sydney, Sydney 2145, Australia
| | - Jenny E. Gunton
- Centre for Diabetes, Obesity and Endocrinology (CDOE), The Westmead Institute for Medical Research, The University of Sydney, Sydney 2145, Australia
- Faculty of Medicine and Health, The University of Sydney, Sydney 2145, Australia
- Department of Diabetes and Endocrinology, Westmead Hospital, Sydney 2145, Australia
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2
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Stokie JR, Abbott G, Howlett KF, Hamilton DL, Shaw CS. Intramuscular lipid utilization during exercise: a systematic review, meta-analysis, and meta-regression. J Appl Physiol (1985) 2023; 134:581-592. [PMID: 36656983 DOI: 10.1152/japplphysiol.00637.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Intramuscular lipid (IMCL) utilization during exercise was controversial as numerous studies did not observe a decline in IMCL content post-exercise when assessed in muscle biopsies using biochemical techniques. Contemporary techniques including immunofluorescence microscopy and 1H-magnetic resonance spectroscopy (1H-MRS) offer advantages over biochemical techniques. The primary aim of this systematic review, meta-analysis, and meta-regression was to examine the net degradation of IMCL in response to an acute bout of cycling exercise in humans, as assessed with different analytical approaches. A secondary aim was to explore the factors influencing IMCL degradation including feeding status, exercise variables, and participant characteristics. A total of 44 studies met the inclusion criteria using biochemical, immunofluorescence, and 1H-MRS techniques. A meta-analysis was completed using a random effects model and percentage change in IMCL content calculated from the standardized mean difference. Cycling exercise resulted in a net degradation of IMCL regardless of technique (total effect -23.7%, 95% CI = -28.7 to -18.7%) and there was no difference when comparing fasted versus fed-state exercise (P > 0.05). IMCL degradation using immunofluorescence techniques detected larger effects in type I fibers compared with whole muscle using biochemical techniques (P = 0.003) and in type I fibers compared with type II fibers (P < 0.001). Although IMCL degradation was associated with exercise duration, V̇o2max, and BMI, none of these factors independently related to the change in IMCL content. These findings provide strong evidence that the analytical approach can influence the assessment of IMCL degradation in human skeletal muscle in response to exercise.
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Affiliation(s)
- Jayden R Stokie
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Deakin University, Geelong, Victoria, Australia
| | - Gavin Abbott
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Deakin University, Geelong, Victoria, Australia
| | - Kirsten F Howlett
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Deakin University, Geelong, Victoria, Australia
| | - David L Hamilton
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Deakin University, Geelong, Victoria, Australia
| | - Christopher S Shaw
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences, Deakin University, Geelong, Victoria, Australia
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3
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Barrett JS, Whytock KL, Strauss JA, Wagenmakers AJM, Shepherd SO. High intramuscular triglyceride turnover rates and the link to insulin sensitivity: influence of obesity, type 2 diabetes and physical activity. Appl Physiol Nutr Metab 2022; 47:343-356. [PMID: 35061523 DOI: 10.1139/apnm-2021-0631] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance is caused, at least in part, by the presence of high concentrations of harmful lipid metabolites, such as diacylglycerols and ceramides in muscle. Several mechanistic differences between obese sedentary individuals and their highly trained counterparts have been identified, which determine the differential capacity for IMTG synthesis and breakdown in these populations. In this review, we first describe the most up-to-date mechanisms by which a low IMTG turnover rate (both breakdown and synthesis) leads to the accumulation of lipid metabolites and results in skeletal muscle insulin resistance. We then explore current and potential exercise and nutritional strategies that target IMTG turnover in sedentary obese individuals, to improve insulin sensitivity. Overall, improving IMTG turnover should be an important component of successful interventions that aim to prevent the development of insulin resistance in the ever-expanding sedentary, overweight and obese populations. Novelty: A description of the most up-to-date mechanisms regulating turnover of the IMTG pool. An exploration of current and potential exercise/nutritional strategies to target and enhance IMTG turnover in obese individuals. Overall, highlights the importance of improving IMTG turnover to prevent the development of insulin resistance.
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Affiliation(s)
- J S Barrett
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - K L Whytock
- Translational Research Institute, AdventHealth, Orlando, FL 32804, USA
| | - J A Strauss
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - A J M Wagenmakers
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - S O Shepherd
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
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4
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Reactive Oxygen Species (ROS) and Antioxidants as Immunomodulators in Exercise: Implications for Heme Oxygenase and Bilirubin. Antioxidants (Basel) 2022; 11:antiox11020179. [PMID: 35204062 PMCID: PMC8868548 DOI: 10.3390/antiox11020179] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/12/2022] [Accepted: 01/14/2022] [Indexed: 02/07/2023] Open
Abstract
Exercise is commonly prescribed as a lifestyle treatment for chronic metabolic diseases as it functions as an insulin sensitizer, cardio-protectant, and essential lifestyle tool for effective weight maintenance. Exercise boosts the production of reactive oxygen species (ROS) and subsequent transient oxidative damage, which also upregulates counterbalancing endogenous antioxidants to protect from ROS-induced damage and inflammation. Exercise elevates heme oxygenase-1 (HO-1) and biliverdin reductase A (BVRA) expression as built-in protective mechanisms, which produce the most potent antioxidant, bilirubin. Together, these mitigate inflammation and adiposity. Moderately raising plasma bilirubin protects in two ways: (1) via its antioxidant capacity to reduce ROS and inflammation, and (2) its newly defined function as a hormone that activates the nuclear receptor transcription factor PPARα. It is now understood that increasing plasma bilirubin can also drive metabolic adaptions, which improve deleterious outcomes of weight gain and obesity, such as inflammation, type II diabetes, and cardiovascular diseases. The main objective of this review is to describe the function of bilirubin as an antioxidant and metabolic hormone and how the HO-1-BVRA-bilirubin-PPARα axis influences inflammation, metabolic function and interacts with exercise to improve outcomes of weight management.
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5
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Seibert JT, Najt CP, Heden TD, Mashek DG, Chow LS. Muscle Lipid Droplets: Cellular Signaling to Exercise Physiology and Beyond. Trends Endocrinol Metab 2020; 31:928-938. [PMID: 32917515 PMCID: PMC7704552 DOI: 10.1016/j.tem.2020.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/09/2020] [Accepted: 08/13/2020] [Indexed: 12/21/2022]
Abstract
Conventionally viewed as energy storage depots, lipid droplets (LDs) play a central role in muscle lipid metabolism and intracellular signaling, as recognized by recent advances in our biological understanding. Specific subpopulations of muscle LDs, defined by location and associated proteins, are responsible for distinct biological functions. In this review, the traditional view of muscle LDs is examined, and the emerging role of LDs in intracellular signaling is highlighted. The effects of chronic and acute exercise on muscle LD metabolism and signaling is discussed. In conclusion, future directions for muscle LD research are identified. The primary focus will be on human studies, with inclusion of select animal/cellular/non-muscle studies as appropriate, to provide the underlying mechanisms driving the observed findings.
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Affiliation(s)
- Jacob T Seibert
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Charles P Najt
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Timothy D Heden
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Douglas G Mashek
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, University of Minnesota, Minneapolis, MN 55455, USA
| | - Lisa S Chow
- Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, University of Minnesota, Minneapolis, MN 55455, USA.
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6
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Ramírez-Vélez R, Ezzatvar Y, Izquierdo M, García-Hermoso A. Effect of exercise on myosteatosis in adults: a systematic review and meta-analysis. J Appl Physiol (1985) 2020; 130:245-255. [PMID: 33180646 DOI: 10.1152/japplphysiol.00738.2020] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Muscle tissue typically contains only small amounts of adipose tissue, and the excess deposition of adiposity is considered a pathological phenomenon termed myosteatosis. Several studies have assessed the effects of exercise alone on the severity of myosteatosis, and some studies have reported promising results. We performed a systematic review and meta-analysis to investigate the effects of exercise interventions on myosteatosis (i.e., lipid infiltration and muscle radiation attenuation). Studies were identified through a systematic search of three databases and limited to randomized controlled trials (RCTs) focused on evaluating the effect of exercise interventions on lipid infiltration and/or muscle attenuation in adults. Thirteen studies met the inclusion criteria, and 12 were included in the meta-analysis (n = 465, 84.7% women). The volume of lipid infiltration was decreased in the exercise group compared with the control group [Hedges' g = -0.45, 95% confidence interval (CI), -0.74 to -0.16; P = 0.008, I2 = 0%], and the degree of muscle radiation attenuation was increased (Hedges' g = 0.67, 95% CI, 0.22 to 1.13; P = 0.009, I2 = 59.3%). Based on meta-regression analyses, there were no significant effects of mean age at baseline (lipid infiltration, β = -0.008, 95% CI, -0.035 to 0.019; P = 0.495; muscle radiation attenuation, β = -0.013, 95% CI, -0.036 to 0.011; P = 0.248) and intervention duration (lipid infiltration, β = -0.008, 95% CI, -0.028 to 0.010; P = 0.311; muscle radiation attenuation, β = -0.018, 95% CI, -0.050 to 0.014; P = 0.230) on the effect size estimates. Overall, our findings indicate that exercise can significantly improve muscle quality in populations at risk of developing obesity and sarcopenia-related disability.NEW & NOTEWORTHY Muscle tissue typically contains only small amounts of adipose tissue, and the excess deposition of adiposity is considered a pathological phenomenon termed myosteatosis. The volume of lipid infiltration tissue was decreased in the exercise group compared with the control group, and muscle attenuation coefficient was increased. Based on the meta-regression analyses, the mean age at baseline and intervention duration did not affect the effect size estimates for lipid infiltration tissue and muscle radiation attenuation.
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Affiliation(s)
- Robinson Ramírez-Vélez
- Navarrabiomed, Universidad Pública de Navarra-Complejo Hospitalario de Navarra, Instituto de Investigación Sanitaria de Navarra, Pamplona, Spain
| | - Yasmin Ezzatvar
- Exercise Intervention for Health Research Group, Department of Physiotherapy, Universitat de València, Valencia, Spain
| | - Mikel Izquierdo
- Navarrabiomed, Universidad Pública de Navarra-Complejo Hospitalario de Navarra, Instituto de Investigación Sanitaria de Navarra, Pamplona, Spain.,Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable, Instituto de Salud Carlos III, Madrid, Spain
| | - Antonio García-Hermoso
- Navarrabiomed, Universidad Pública de Navarra-Complejo Hospitalario de Navarra, Instituto de Investigación Sanitaria de Navarra, Pamplona, Spain.,Laboratorio de Ciencias de la Actividad Física, el Deporte y la Salud, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Santiago, Chile
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7
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Tobias IS, Galpin AJ. Moving human muscle physiology research forward: an evaluation of fiber type-specific protein research methodologies. Am J Physiol Cell Physiol 2020; 319:C858-C876. [DOI: 10.1152/ajpcell.00107.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Human skeletal muscle is a heterogeneous tissue composed of multiple fiber types that express unique contractile and metabolic properties. While analysis of mixed fiber samples predominates and holds value, increasing attention has been directed toward studying proteins segregated by fiber type, a methodological distinction termed “fiber type-specific.” Fiber type-specific protein studies have the advantage of uncovering key molecular effects that are often missed in mixed fiber homogenate studies but also require greater time and resource-intensive methods, particularly when applied to human muscle. This review summarizes and compares current methods used for fiber type-specific protein analysis, highlighting their advantages and disadvantages for human muscle studies, in addition to recent advances in these techniques. These methods can be grouped into three categories based on the initial processing of the tissue: 1) muscle-specific fiber homogenates, 2) cross sections of fiber bundles, and 3) isolated single fibers, with various subtechniques for performing fiber type identification and protein quantification. The relative implementation for each unique methodological approach is analyzed from 83 fiber type-specific studies of proteins in live human muscle found in the literature to date. These studies have investigated several proteins involved in a wide range of cellular functions that are important to muscle tissue. The second half of this review summarizes key findings from this ensemble of fiber type-specific human protein studies. We highlight examples of where this analytical approach has helped to improve understanding of important physiological topics such as insulin sensitivity, muscle hypertrophy, muscle fatigue, and adaptation to different exercise programs.
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Affiliation(s)
- Irene S. Tobias
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Andrew J. Galpin
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
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8
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Gemmink A, Schrauwen P, Hesselink MKC. Exercising your fat (metabolism) into shape: a muscle-centred view. Diabetologia 2020; 63:1453-1463. [PMID: 32529413 PMCID: PMC7351830 DOI: 10.1007/s00125-020-05170-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/23/2020] [Indexed: 12/11/2022]
Abstract
Fatty acids are an important energy source during exercise. Training status and substrate availability are determinants of the relative and absolute contribution of fatty acids and glucose to total energy expenditure. Endurance-trained athletes have a high oxidative capacity, while, in insulin-resistant individuals, fat oxidation is compromised. Fatty acids that are oxidised during exercise originate from the circulation (white adipose tissue lipolysis), as well as from lipolysis of intramyocellular lipid droplets. Moreover, hepatic fat may contribute to fat oxidation during exercise. Nowadays, it is clear that myocellular lipid droplets are dynamic organelles and that number, size, subcellular distribution, lipid droplet coat proteins and mitochondrial tethering of lipid droplets are determinants of fat oxidation during exercise. This review summarises recent insights into exercise-mediated changes in lipid metabolism and insulin sensitivity in relation to lipid droplet characteristics in human liver and muscle. Graphical abstract.
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Affiliation(s)
- Anne Gemmink
- Department of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200 MD, Maastricht, the Netherlands
| | - Patrick Schrauwen
- Department of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200 MD, Maastricht, the Netherlands
| | - Matthijs K C Hesselink
- Department of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200 MD, Maastricht, the Netherlands.
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9
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Strauss JA, Shepherd DA, Macey M, Jevons EFP, Shepherd SO. Divergence exists in the subcellular distribution of intramuscular triglyceride in human skeletal muscle dependent on the choice of lipid dye. Histochem Cell Biol 2020; 154:369-382. [PMID: 32627050 PMCID: PMC7532971 DOI: 10.1007/s00418-020-01898-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2020] [Indexed: 01/19/2023]
Abstract
Despite over 50 years of research, a comprehensive understanding of how intramuscular triglyceride (IMTG) is stored in skeletal muscle and its contribution as a fuel during exercise is lacking. Immunohistochemical techniques provide information on IMTG content and lipid droplet (LD) morphology on a fibre type and subcellular-specific basis, and the lipid dye Oil Red O (ORO) is commonly used to achieve this. BODIPY 493/503 (BODIPY) is an alternative lipid dye with lower background staining and narrower emission spectra. Here we provide the first quantitative comparison of BODIPY and ORO for investigating exercise-induced changes in IMTG content and LD morphology on a fibre type and subcellular-specific basis. Estimates of IMTG content were greater when using BODIPY, which was predominantly due to BODIPY detecting a larger number of LDs, compared to ORO. The subcellular distribution of intramuscular lipid was also dependent on the lipid dye used; ORO detects a greater proportion of IMTG in the periphery (5 μm below cell membrane) of the fibre, whereas IMTG content was higher in the central region using BODIPY. In response to 60 min moderate-intensity cycling exercise, IMTG content was reduced in both the peripheral (− 24%) and central region (− 29%) of type I fibres (P < 0.05) using BODIPY, whereas using ORO, IMTG content was only reduced in the peripheral region of type I fibres (− 31%; P < 0.05). As well as highlighting some methodological considerations herein, our investigation demonstrates that important differences exist between BODIPY and ORO for detecting and quantifying IMTG on a fibre type and subcellular-specific basis.
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Affiliation(s)
- Juliette A Strauss
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, L3 3AF, UK.
| | - Daisy A Shepherd
- Clinical Epidemiology and Biostatistics Unit, Murdoch Children's Research Institute, Royal Children's Hospital, Victoria, 3052, Australia.,Department of Paediatrics, The University of Melbourne, Victoria, 3010, Australia
| | - Myfanwy Macey
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, L3 3AF, UK
| | - Emily F P Jevons
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, L3 3AF, UK
| | - Sam O Shepherd
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, L3 3AF, UK
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10
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Jevons EFP, Gejl KD, Strauss JA, Ørtenblad N, Shepherd SO. Skeletal muscle lipid droplets are resynthesized before being coated with perilipin proteins following prolonged exercise in elite male triathletes. Am J Physiol Endocrinol Metab 2020; 318:E357-E370. [PMID: 31935113 DOI: 10.1152/ajpendo.00399.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Intramuscular triglycerides (IMTG) are a key substrate during prolonged exercise, but little is known about the rate of IMTG resynthesis in the postexercise period. We investigated the hypothesis that the distribution of the lipid droplet (LD)-associated perilipin (PLIN) proteins is linked to IMTG storage following exercise. Fourteen elite male triathletes (27 ± 1 yr, 66.5 ± 1.3 mL·kg-1·min-1) completed 4 h of moderate-intensity cycling. During the first 4 h of recovery, subjects received either carbohydrate or H2O, after which both groups received carbohydrate. Muscle biopsies collected pre- and postexercise and 4 and 24 h postexercise were analyzed using confocal immunofluorescence microscopy for fiber type-specific IMTG content and PLIN distribution with LDs. Exercise reduced IMTG content in type I fibers (-53%, P = 0.002), with no change in type IIa fibers. During the first 4 h of recovery, IMTG content increased in type I fibers (P = 0.014), but was not increased more after 24 h, where it was similar to baseline levels in both conditions. During recovery the number of LDs labeled with PLIN2 (70%), PLIN3 (63%), and PLIN5 (62%; all P < 0.05) all increased in type I fibers. Importantly, the increase in LDs labeled with PLIN proteins only occurred at 24 h postexercise. In conclusion, IMTG resynthesis occurs rapidly in type I fibers following prolonged exercise in highly trained individuals. Furthermore, increases in IMTG content following exercise preceded an increase in the number of LDs labeled with PLIN proteins. These data, therefore, suggest that the PLIN proteins do not play a key role in postexercise IMTG resynthesis.
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Affiliation(s)
- Emily F P Jevons
- Research Institute of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Kasper D Gejl
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
| | - Juliette A Strauss
- Research Institute of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Niels Ørtenblad
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
| | - Sam O Shepherd
- Research Institute of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
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11
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Whytock KL, Parry SA, Turner MC, Woods RM, James LJ, Ferguson RA, Ståhlman M, Borén J, Strauss JA, Cocks M, Wagenmakers AJM, Hulston CJ, Shepherd SO. A 7‐day high‐fat, high‐calorie diet induces fibre‐specific increases in intramuscular triglyceride and perilipin protein expression in human skeletal muscle. J Physiol 2020; 598:1151-1167. [DOI: 10.1113/jp279129] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/13/2020] [Indexed: 12/24/2022] Open
Affiliation(s)
- K. L. Whytock
- Research Institute of Sport and Exercise Science, Tom Reilly Building LJMU Liverpool L3 3AF UK
| | - S. A. Parry
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - M. C. Turner
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - R. M. Woods
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - L. J. James
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - R. A. Ferguson
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - M. Ståhlman
- Wallenberg Laboratory, Sahlgrenska Academy University of Gothenburg Gothenburg Sweden
| | - J. Borén
- Wallenberg Laboratory, Sahlgrenska Academy University of Gothenburg Gothenburg Sweden
| | - J. A. Strauss
- Research Institute of Sport and Exercise Science, Tom Reilly Building LJMU Liverpool L3 3AF UK
| | - M. Cocks
- Research Institute of Sport and Exercise Science, Tom Reilly Building LJMU Liverpool L3 3AF UK
| | - A. J. M. Wagenmakers
- Research Institute of Sport and Exercise Science, Tom Reilly Building LJMU Liverpool L3 3AF UK
| | - C. J. Hulston
- School of Sport, Exercise and Health Sciences Loughborough University Loughborough LE11 3TU UK
| | - S. O. Shepherd
- Research Institute of Sport and Exercise Science, Tom Reilly Building LJMU Liverpool L3 3AF UK
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12
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Mardani I, Tomas Dalen K, Drevinge C, Miljanovic A, Ståhlman M, Klevstig M, Scharin Täng M, Fogelstrand P, Levin M, Ekstrand M, Nair S, Redfors B, Omerovic E, Andersson L, Kimmel AR, Borén J, Levin MC. Plin2-deficiency reduces lipophagy and results in increased lipid accumulation in the heart. Sci Rep 2019; 9:6909. [PMID: 31061399 PMCID: PMC6502866 DOI: 10.1038/s41598-019-43335-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 04/23/2019] [Indexed: 12/18/2022] Open
Abstract
Myocardial dysfunction is commonly associated with accumulation of cardiac lipid droplets (LDs). Perilipin 2 (Plin2) is a LD protein that is involved in LD formation, stability and trafficking events within the cell. Even though Plin2 is highly expressed in the heart, little is known about its role in myocardial lipid storage. A recent report shows that cardiac overexpression of Plin2 result in massive myocardial steatosis suggesting that Plin2 stabilizes LDs. In this study, we hypothesized that deficiency in Plin2 would result in reduced myocardial lipid storage. In contrast to our hypothesis, we found increased accumulation of triglycerides in hearts, and specifically in cardiomyocytes, from Plin2−/− mice. Although Plin2−/− mice had markedly enhanced lipid levels in the heart, they had normal heart function under baseline conditions and under mild stress. However, after an induced myocardial infarction, stroke volume and cardiac output were reduced in Plin2−/− mice compared with Plin2+/+ mice. We further demonstrated that the increased triglyceride accumulation in Plin2-deficient hearts was caused by altered lipophagy. Together, our data show that Plin2 is important for proper hydrolysis of LDs.
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Affiliation(s)
- Ismena Mardani
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Knut Tomas Dalen
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Christina Drevinge
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Azra Miljanovic
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Marcus Ståhlman
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Martina Klevstig
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Margareta Scharin Täng
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Per Fogelstrand
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Max Levin
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Matias Ekstrand
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Syam Nair
- Centre of Perinatal Medicine and Health, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden
| | - Björn Redfors
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Elmir Omerovic
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Linda Andersson
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Alan R Kimmel
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Jan Borén
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Malin C Levin
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, Institute of Medicine, the Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden.
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Local In Vivo Measures of Muscle Lipid and Oxygen Consumption Change in Response to Combined Vitamin D Repletion and Aerobic Training in Older Adults. Nutrients 2019; 11:nu11040930. [PMID: 31027191 PMCID: PMC6521174 DOI: 10.3390/nu11040930] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 04/18/2019] [Accepted: 04/22/2019] [Indexed: 12/31/2022] Open
Abstract
Intramyocellular (IMCL), extramyocellular lipid (EMCL), and vitamin D deficiency are associated with muscle metabolic dysfunction. This study compared the change in [IMCL]:[EMCL] following the combined treatment of vitamin D and aerobic training (DAT) compared with vitamin D (D), aerobic training (AT), and control (CTL). Male and female subjects aged 60–80 years with a BMI ranging from 18.5–34.9 and vitamin D status of ≤32 ng/mL (25(OH)D) were recruited to randomized, prospective clinical trial double-blinded for supplement with a 2 × 2 factorial design. Cholecalciferol (Vitamin D3) (10,000 IU × 5 days/week) or placebo was provided for 13 weeks and treadmill aerobic training during week 13. Gastrocnemius IMCL and EMCL were measured with magnetic resonance spectroscopy (MRS) and MRI. Hybrid near-infrared diffuse correlation spectroscopy measured hemodynamics. Group differences in IMCL were observed when controlling for baseline IMCL (p = 0.049). DAT was the only group to reduce IMCL from baseline, while a mean increase was observed in all other groups combined (p = 0.008). IMCL reduction and the corresponding increase in rVO2 at study end (p = 0.011) were unique to DAT. Vitamin D, when combined with exercise, may potentiate the metabolic benefits of exercise by reducing IMCL and increasing tissue-level VO2 in healthy, older adults.
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14
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Schnell DM, Walton RG, Vekaria HJ, Sullivan PG, Bollinger LM, Peterson CA, Thomas DT. Vitamin D produces a perilipin 2-dependent increase in mitochondrial function in C2C12 myotubes. J Nutr Biochem 2018; 65:83-92. [PMID: 30658160 DOI: 10.1016/j.jnutbio.2018.11.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/11/2018] [Accepted: 11/10/2018] [Indexed: 02/08/2023]
Abstract
Vitamin D has been connected with increased intramyocellular lipid (IMCL) and has also been shown to increase mitochondrial function and insulin sensitivity. Evidence suggests that perilipin 2 (PLIN2), a perilipin protein upregulated with calcitriol treatment, may be integral to managing increased IMCL capacity and lipid oxidation in skeletal muscle. Therefore, we hypothesized that PLIN2 is required for vitamin D induced IMCL accumulation and increased mitochondrial oxidative function. To address this hypothesis, we treated C2C12 myotubes with 100 nM calcitriol (the active form of vitamin D) and/or PLIN2 siRNA in a four group design and analyzed markers of IMCL accumulation and metabolism using qRT-PCR, cytochemistry, and oxygen consumption assay. Expression of PLIN2, but not PLIN3 or PLIN5 mRNA was increased with calcitriol, and PLIN2 induction was prevented with siRNA knockdown without compensation by other perilipins. PLIN2 knockdown did not appear to prevent lipid accumulation. Calcitriol treatment increased mRNA expression of triglyceride synthesizing genes DGAT1 and DGAT2 and also lipolytic genes ATGL and CGI-58. PLIN2 knockdown decreased the expression of CGI-58 and CPT1, and was required for calcitriol-induced upregulation of DGAT2. Calcitriol increased oxygen consumption rate while PLIN2 knockdown decreased oxygen consumption rate. PLIN2 was required for a calcitriol-induced increase in oxygen consumption driven by mitochondrial complex II. We conclude that calcitriol increases mitochondrial function in myotubes and that this increase is at least in part mediated by PLIN2.
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Affiliation(s)
| | - R Grace Walton
- Department of Rehabilitation Sciences; Center for Muscle Biology.
| | | | | | | | | | - D Travis Thomas
- Department of Clinical Sciences, University of Kentucky, Lexington, KY 40536.
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15
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Zacharewicz E, Hesselink MKC, Schrauwen P. Exercise counteracts lipotoxicity by improving lipid turnover and lipid droplet quality. J Intern Med 2018; 284:505-518. [PMID: 29331050 DOI: 10.1111/joim.12729] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The incidence of obesity and metabolic disease, such as type 2 diabetes mellitus (T2D), is rising globally. Dietary lipid over supply leads to lipid accumulation at ectopic sites, such as skeletal muscle. Ectopic lipid storage is highly correlated with insulin resistance and T2D, likely due to a loss of metabolic flexibility - the capacity to switch between fat and glucose oxidation upon insulin stimulation - and cellular dysfunction because of lipotoxicity. However, muscle lipid levels are also elevated in endurance-trained athletes, presenting a paradoxical phenotype of increased intramuscular lipids along with high insulin sensitivity - the 'athletes' paradox'. This review focuses on recent human data to characterize intramuscular lipid species in order to elucidate some of the underlying mechanisms driving skeletal muscle lipotoxicity. There is evidence that lipotoxicity is characterized by an increase in bioactive lipid species, such as ceramide. The athletes' paradox supports the notion that regular physical exercise has health benefits that might originate from the alleviation of lipotoxicity. Indeed, exercise training alleviates intramuscular ceramide content in obese individuals without a necessary decrease in ectopic lipid storage. Furthermore, evidence shows that exercise training elevates markers of lipid droplet dynamics such as the PLIN proteins, and triglyceride lipases ATGL and HSL, as well as mitochondrial efficiency, potentially explaining the improved lipid turnover and a reduction in the accumulation of lipotoxic intermediates observed with the athelets' paradox.
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Affiliation(s)
- E Zacharewicz
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - M K C Hesselink
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - P Schrauwen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
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16
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Shafiee G, Asgari Y, Soltani A, Larijani B, Heshmat R. Identification of candidate genes and proteins in aging skeletal muscle (sarcopenia) using gene expression and structural analysis. PeerJ 2018; 6:e5239. [PMID: 30202641 PMCID: PMC6129146 DOI: 10.7717/peerj.5239] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 06/24/2018] [Indexed: 12/25/2022] Open
Abstract
Sarcopenia is an age-related disease characterized by the loss of muscle mass and muscle function. A proper understanding of its pathogenesis and mechanisms may lead to new strategies for diagnosis and treatment of the disease. This study aims to discover the underlying genes, proteins, and pathways associated with sarcopenia in both genders. Integrated analysis of microarray datasets has been performed to identify differentially expressed genes (DEGs) between old and young skeletal muscles. Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were then performed to uncover the functions of the DEGs. Moreover, a protein-protein interaction (PPI) network was constructed based on the DEGs. We have identified 41,715 DEGs, including 19 downregulated and 41,696 upregulated ones, in men. Among women, 3,015 DEGs have been found, with 2,874 of them being upregulated and 141 downregulated genes. Among the top up-regulated and downregulated genes, the ribosome biogenesis genes and genes involved in lipid storage may be closely related to aging muscles in men and women respectively. Also, the DEGs were enriched in the pathways including those of ribosome and Peroxisome proliferator-activated receptor (PPAR) in men and women, respectively. In the PPI network, Neurotrophic Receptor Tyrosine Kinase 1 (NTRK1), Cullin 3 (CUL3) and P53 have been identified as significant hub proteins in both genders. Using the integrated analysis of multiple gene expression profiles, we propose that the ribosome biogenesis genes and those involved in lipid storage would be promising markers for sarcopenia in men and women, respectively. In the reconstructed PPI network, neurotrophic factors expressed in skeletal muscle are essential for motoneuron survival and muscle fiber innervation during development. Cullin E3 ubiquitin ligase (Cul3) is an important component of the ubiquitin-proteasome system-it regulates the proteolysis. P53 is recognized as a central regulator of the cell cycle and apoptosis. These proteins, which have been identified as the most significant hubs, may be involved in aging muscle and sarcopenia.
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Affiliation(s)
- Gita Shafiee
- Chronic Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Yazdan Asgari
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Akbar Soltani
- Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Bagher Larijani
- Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Ramin Heshmat
- Chronic Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
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17
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Whytock KL, Shepherd SO, Wagenmakers AJM, Strauss JA. Hormone-sensitive lipase preferentially redistributes to lipid droplets associated with perilipin-5 in human skeletal muscle during moderate-intensity exercise. J Physiol 2018. [PMID: 29527681 DOI: 10.1113/jp275502] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
KEY POINTS Hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) are the key enzymes involved in intramuscular triglyceride (IMTG) lipolysis. In isolated rat skeletal muscle, HSL translocates to IMTG-containing lipid droplets (LDs) following electrical stimulation, but whether HSL translocation occurs in human skeletal muscle during moderate-intensity exercise is currently unknown. Perilipin-2 (PLIN2) and perilipin-5 (PLIN5) proteins have been implicated in regulating IMTG lipolysis by interacting with HSL and ATGL in cell culture and rat skeletal muscle studies. This study investigated the hypothesis that HSL (but not ATGL) redistributes to LDs during moderate-intensity exercise in human skeletal muscle, and whether the localisation of these lipases with LDs was affected by the presence of PLIN proteins on the LDs. HSL preferentially redistributed to PLIN5-associated LDs whereas ATGL distribution was not altered with exercise; this is the first study to illustrate the pivotal step of HSL redistribution to PLIN5-associated LDs following moderate-intensity exercise in human skeletal muscle. ABSTRACT Hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) control skeletal muscle lipolysis. ATGL is present on the surface of lipid droplets (LDs) containing intramuscular triglyceride (IMTG) in both the basal state and during exercise. HSL translocates to LD in ex vivo electrically stimulated rat skeletal muscle. Perilipin-2- and perilipin-5-associated lipid droplets (PLIN2+ and PLIN5+ LDs) are preferentially depleted during exercise in humans, indicating that these PLINs may control muscle lipolysis. We aimed to test the hypothesis that in human skeletal muscle in vivo HSL (but not ATGL) is redistributed to PLIN2+ and PLIN5+ LDs during moderate-intensity exercise. Muscle biopsies from 8 lean trained males (age 21 ± 1 years, BMI 22.6 ± 1.2 kg m-2 and V̇O2 peak 48.2 ± 5.0 ml min-1 kg-1 ) were obtained before and immediately following 60 min of cycling exercise at ∼59% V̇O2 peak . Cryosections were stained using antibodies targeting ATGL, HSL, PLIN2 and PLIN5. LDs were stained using BODIPY 493/503. Images were obtained using confocal immunofluorescence microscopy and object-based colocalisation analyses were performed. Following exercise, HSL colocalisation to LDs increased (P < 0.05), and was significantly greater to PLIN5+ LDs (+53%) than to PLIN5- LDs (+34%) (P < 0.05), while the increases in HSL colocalisation to PLIN2+ LDs (+16%) and PLIN2- LDs (+28%) were not significantly different. Following exercise, the fraction of LDs colocalised with ATGL (0.53 ± 0.04) did not significantly change (P < 0.05) and was not affected by PLIN association to the LDs. This study presents the first evidence of exercise-induced HSL redistribution to LDs in human skeletal muscle and identifies PLIN5 as a facilitator of this mechanism.
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Affiliation(s)
- Katie L Whytock
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool L3 3AF, UK
| | - Sam O Shepherd
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool L3 3AF, UK
| | - Anton J M Wagenmakers
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool L3 3AF, UK
| | - Juliette A Strauss
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool L3 3AF, UK
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18
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Daemen S, van Polanen N, Hesselink MKC. The effect of diet and exercise on lipid droplet dynamics in human muscle tissue. ACTA ACUST UNITED AC 2018. [PMID: 29514886 DOI: 10.1242/jeb.167015] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The majority of fat in the human body is stored as triacylglycerols in white adipose tissue. In the obese state, adipose tissue mass expands and excess lipids are stored in non-adipose tissues, such as skeletal muscle. Lipids are stored in skeletal muscle in the form of small lipid droplets. Although originally viewed as dull organelles that simply store lipids as a consequence of lipid overflow from adipose tissue, lipid droplets are now recognized as key components in the cell that exert a variety of relevant functions in multiple tissues (including muscle). Here, we review the effect of diet and exercise interventions on myocellular lipid droplets and their putative role in insulin sensitivity from a human perspective. We also provide an overview of lipid droplet biology and identify gaps for future research.
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Affiliation(s)
- Sabine Daemen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Nynke van Polanen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Matthijs K C Hesselink
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
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19
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Bergman BC, Perreault L, Strauss A, Bacon S, Kerege A, Harrison K, Brozinick JT, Hunerdosse DM, Playdon MC, Holmes W, Bui HH, Sanders P, Siddall P, Wei T, Thomas MK, Kuo MS, Eckel RH. Intramuscular triglyceride synthesis: importance in muscle lipid partitioning in humans. Am J Physiol Endocrinol Metab 2018; 314:E152-E164. [PMID: 28978544 PMCID: PMC5866414 DOI: 10.1152/ajpendo.00142.2017] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Intramuscular triglyceride (IMTG) concentration is elevated in insulin-resistant individuals and was once thought to promote insulin resistance. However, endurance-trained athletes have equivalent concentration of IMTG compared with individuals with type 2 diabetes, and have very low risk of diabetes, termed the "athlete's paradox." We now know that IMTG synthesis is positively related to insulin sensitivity, but the exact mechanisms for this are unclear. To understand the relationship between IMTG synthesis and insulin sensitivity, we measured IMTG synthesis in obese control subjects, endurance-trained athletes, and individuals with type 2 diabetes during rest, exercise, and recovery. IMTG synthesis rates were positively related to insulin sensitivity, cytosolic accumulation of DAG, and decreased accumulation of C18:0 ceramide and glucosylceramide. Greater rates of IMTG synthesis in athletes were not explained by alterations in FFA concentration, DGAT1 mRNA expression, or protein content. IMTG synthesis during exercise in Ob and T2D indicate utilization as a fuel despite unchanged content, whereas IMTG concentration decreased during exercise in athletes. mRNA expression for genes involved in lipid desaturation and IMTG synthesis were increased after exercise and recovery. Further, in a subset of individuals, exercise decreased cytosolic and membrane di-saturated DAG content, which may help explain insulin sensitization after acute exercise. These data suggest IMTG synthesis rates may influence insulin sensitivity by altering intracellular lipid localization, and decreasing specific ceramide species that promote insulin resistance.
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Affiliation(s)
- Bryan C Bergman
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Leigh Perreault
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Allison Strauss
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Samantha Bacon
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Anna Kerege
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | | | | | | | - Mary C Playdon
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | | | | | | | | | - Tao Wei
- Eli Lilly, Indianapolis, Indiana
| | | | | | - Robert H Eckel
- University of Colorado Anschutz Medical Campus , Aurora, Colorado
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20
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Larsen S, Vigelsø A, Dandanell S, Prats C, Dela F, Helge JW. Simvastatin-Induced Insulin Resistance May Be Linked to Decreased Lipid Uptake and Lipid Synthesis in Human Skeletal Muscle: the LIFESTAT Study. J Diabetes Res 2018; 2018:9257874. [PMID: 30276217 PMCID: PMC6157137 DOI: 10.1155/2018/9257874] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/26/2018] [Accepted: 05/13/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND A prevalent side-effect of simvastatin is attenuated glucose homeostasis. The underlying mechanism is unknown, but impaired lipid metabolism may provide the link. The aim of this study was to investigate whether simvastatin-treated patients had a lower capacity to oxidize lipids and reduced expression of the major proteins regulating lipid uptake, synthesis, lipolysis, and storage in skeletal muscle than matched controls. MATERIALS AND METHODS Ten men were treated with simvastatin (HbA1c: 5.7 ± 0.1%), and 10 healthy men (HbA1c: 5.2 ± 0.1%) underwent an oral glucose tolerance test and a muscle biopsy was obtained. Fat oxidation rates were measured at rest and during exercise. Western blotting was used to assess protein content. RESULTS Patients treated with simvastatin had impaired glucose tolerance compared with control subjects, but fat oxidation at rest and during exercise was compatible. Skeletal muscle protein content of CD36, lipoprotein lipase (LPL), and diacylglycerol acyltransferase (DGAT) 1 were lower, and DGAT 2 tended to be lower in patients treated with simvastatin. CONCLUSIONS Patients treated with simvastatin had a reduced capacity to synthesize FA and diacylglycerol (DAG) into triacylglycerol in skeletal muscle compared to matched controls. Decreased lipid synthesis capacity may lead to accumulation of lipotoxic intermediates (FA and DAG) and hence impair glucose tolerance.
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Affiliation(s)
- Steen Larsen
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Clinical Research Centre, Medical University of Bialystok, Bialystok, Poland
| | - Andreas Vigelsø
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sune Dandanell
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Physiotherapy and Occupational Therapy, Metropolitan University College, Copenhagen, Denmark
| | - Clara Prats
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Flemming Dela
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Geriatrics, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Jørn Wulff Helge
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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21
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Jefferson GE, Schnell DM, Thomas DT, Bollinger LM. Calcitriol concomitantly enhances insulin sensitivity and alters myocellular lipid partitioning in high fat-treated skeletal muscle cells. J Physiol Biochem 2017; 73:613-621. [PMID: 28980208 DOI: 10.1007/s13105-017-0595-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 09/25/2017] [Indexed: 02/08/2023]
Abstract
Vitamin D reduces myocellular insulin resistance, but the effects of vitamin D on intramyocellular lipid (IMCL) partitioning are unknown. The purpose of this study was to understand how calcitriol, the active vitamin D metabolite, affects insulin sensitivity and lipid partitioning in skeletal muscle cells. C2C12 myotubes were treated with calcitriol (100 nM) or vehicle control for 96 h. Insulin-stimulated Akt phosphorylation (Thr 308) was determined by western blot. Intramyocellular triacylglycerol (IMTG), diacylglycerol (DAG), and ceramide content were measured by LC/MS. IMTG partitioning and lipid droplet accumulation were assessed by oil red O. Expression of genes involved in lipid droplet packaging and lipolysis were measured by RT-PCR. Compared to vehicle-treated myotubes, calcitriol augmented insulin-stimulated pAkt. Calcitriol increased total ceramides and DAG in a subspecies-specific manner. Specifically, calcitriol preferentially increased ceramide 24:1 (1.78 fold) and di-18:0 DAG (46.89 fold). Calcitriol increased total IMTG area as assessed by oil red O, but decreased the proportion of lipid within myotubes. Calcitriol increased mRNA content of genes involved in lipid droplet packaging (perilipin 2; PLIN 2, 2.07 fold) and lipolysis (comparative gene identification-58; CGI-58 and adipose triglyceride lipase; ATGL, ~ 1.80 fold). Calcitriol alters myocellular lipid partitioning and lipid droplet packaging which may favor lipid turnover and partially explain improvements in insulin sensitivity.
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Affiliation(s)
- Grace E Jefferson
- Department of Kinesiology and Health Promotion, University of Kentucky, 201 Seaton Bldg, Lexington, KY, 40506, USA
| | - David M Schnell
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - D Travis Thomas
- College of Health Sciences, University of Kentucky, Lexington, KY, USA.,Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Lance M Bollinger
- Department of Kinesiology and Health Promotion, University of Kentucky, 201 Seaton Bldg, Lexington, KY, 40506, USA. .,Center for Muscle Biology, University of Kentucky, Lexington, KY, USA.
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22
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Coker RH, Robinette L, Kern PA. Minimal alteration in muscle lipid genes following stabilized weight loss. Appl Physiol Nutr Metab 2017; 42:1277-1282. [PMID: 28777921 DOI: 10.1139/apnm-2017-0098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Variations in skeletal muscle peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), carntine palmitoyltransferase-1 (CPT-1), perilipin protein 2 (PLIN2), and adipose tissue triglyceride lipase (ATGL), and comparative gene identification-58 (CGI-58) have been described as playing important roles in the metabolic regulation of lipid oxidation, and may influence intramyocellular lipid (IMCL) and muscle lipid droplet size (LDS). While acute changes in caloric balance and/or aerobic capacity may affect lipid metabolism, the influence of sustained weight loss derived from caloric restriction with weight loss (CWL) compared with exercise training with weight loss (EWL) on the abovementioned parameters has not been fully elucidated. Using a combination of metabolic feeding and/or supervised exercise training, we evaluated the influence of stabilized weight loss elicited by CWL compared with EWL without the confounding influence of acute alterations in caloric balance on molecular markers of mitochondrial metabolism and lipid droplet size in middle-aged overweight individuals with impaired glucose tolerance. There were no significant changes in PGC-1α, CPT-1, PLIN2, ATGL and, CGI-58 messenger RNA (mRNA) in CWL and EWL. While there were no changes in ATGL mRNA in CWL, there was a strong trend (P = 0.05) for the ΔATGL mRNA in EWL with stabilized weight loss. There were no significant changes in IMCL or LDS within skeletal muscle in CWL or EWL, respectively. In conclusion, under the conditions of chronic caloric balance following dietary or exercise-based interventions, mediators of mitochondrial function, IMCL and LDS, were largely unaffected. Future studies should focus on intervention-based changes in protein expression and/or phosphorylation and the relationship to physiological endpoints.
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Affiliation(s)
- Robert H Coker
- a Institute of Arctic Biology, University of Alaska-Fairbanks, Fairbanks, AK 99775, USA.,b Center for Translational Research in Aging and Longevity, Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Leizleigh Robinette
- b Center for Translational Research in Aging and Longevity, Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Philip A Kern
- c Department of Internal Medicine, Division of Endocrinology, University of Kentucky, Lexington, KY, USA
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23
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Lipid droplet remodelling and reduced muscle ceramides following sprint interval and moderate-intensity continuous exercise training in obese males. Int J Obes (Lond) 2017; 41:1745-1754. [PMID: 28736444 DOI: 10.1038/ijo.2017.170] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 06/16/2017] [Accepted: 07/14/2017] [Indexed: 12/14/2022]
Abstract
BACKGROUND/OBJECTIVES In obesity, improved muscle insulin sensitivity following exercise training has been linked to the lowering of diacylglycerol (DAG) and ceramide concentrations. Little is known, however, about how improved insulin action with exercise training in obese individuals relates to lipid droplet (LD) adaptations in skeletal muscle. In this study we investigated the hypothesis that short-term sprint interval training (SIT) and moderate-intensity continuous training (MICT) in obese individuals would increase perilipin (PLIN) expression, increase the proportion of LDs in contact with mitochondria and reduce muscle concentrations of DAGs and ceramides. METHODS Sixteen sedentary obese males performed 4 weeks of either SIT (4-7 × 30 s sprints at 200% Wmax, 3 days week) or MICT (40-60 min cycling at ~65% VO2peak, 5 days per week), and muscle biopsies were obtained pre- and post-training. RESULTS Training increased PLIN2 (SIT 90%, MICT 68%) and PLIN5 (SIT 47%, MICT 34%) expression in type I fibres only, and increased PLIN3 expression in both type I (SIT 63%, MICT 67%) and type II fibres (SIT 70%, MICT 160%) (all P<0.05). Training did not change LD content but increased the proportion of LD in contact with mitochondria (SIT 12%, MICT 21%, P<0.01). Ceramides were reduced following training (SIT -10%, MICT -7%, P<0.05), but DAG was unchanged. No training × group interactions were observed for any variables. CONCLUSIONS These results confirm the hypothesis that SIT and MICT results in remodelling of LDs and lowers ceramide concentrations in skeletal muscle of sedentary obese males.
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Gemmink A, Goodpaster BH, Schrauwen P, Hesselink MKC. Intramyocellular lipid droplets and insulin sensitivity, the human perspective. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1242-1249. [PMID: 28739280 DOI: 10.1016/j.bbalip.2017.07.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 07/18/2017] [Accepted: 07/19/2017] [Indexed: 11/19/2022]
Abstract
Skeletal muscle can store excess fat as subcellular lipid droplets (LDs). While originally viewed as uninteresting static balls of triacylglycerol, it is now clear that myocellular LDs play an active role in myocellular (patho)physiology. In this review we aim to discuss the role of LDs in muscle cell insulin sensitivity and identify parameters which appear to affect this relationship. Moreover, we discuss the application of novel tools permitting detailed examination of these parameters. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Anne Gemmink
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Bret H Goodpaster
- Translational Research Institute for Metabolism and Diabetes, Orlando, FL, USA
| | - Patrick Schrauwen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Matthijs K C Hesselink
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands.
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25
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Koh HCE, Nielsen J, Saltin B, Holmberg HC, Ørtenblad N. Pronounced limb and fibre type differences in subcellular lipid droplet content and distribution in elite skiers before and after exhaustive exercise. J Physiol 2017. [PMID: 28639688 DOI: 10.1113/jp274462] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS Although lipid droplets in skeletal muscle are an important energy source during endurance exercise, our understanding of lipid metabolism in this context remains incomplete. Using transmission electron microscopy, two distinct subcellular pools of lipid droplets can be observed in skeletal muscle - one beneath the sarcolemma and the other between myofibrils. At rest, well-trained leg muscles of cross-country skiers contain 4- to 6-fold more lipid droplets than equally well-trained arm muscles, with a 3-fold higher content in type 1 than in type 2 fibres. During exhaustive exercise, lipid droplets between the myofibrils but not those beneath the sarcolemma are utilised by both type 1 and 2 fibres. These findings provide insight into compartmentalisation of lipid metabolism within skeletal muscle fibres. ABSTRACT Although the intramyocellular lipid pool is an important energy store during prolonged exercise, our knowledge concerning its metabolism is still incomplete. Here, quantitative electron microscopy was used to examine subcellular distribution of lipid droplets in type 1 and 2 fibres of the arm and leg muscles before and after 1 h of exhaustive exercise. Intermyofibrillar lipid droplets accounted for 85-97% of the total volume fraction, while the subsarcolemmal pool made up 3-15%. Before exercise, the volume fractions of intermyofibrillar and subsarcolemmal lipid droplets were 4- to 6-fold higher in leg than in arm muscles (P < 0.001). Furthermore, the volume fraction of intermyofibrillar lipid droplets was 3-fold higher in type 1 than in type 2 fibres (P < 0.001), with no fibre type difference in the subsarcolemmal pool. Following exercise, intermyofibrillar lipid droplet volume fraction was 53% lower (P = 0.0082) in both fibre types in arm, but not leg muscles. This reduction was positively associated with the corresponding volume fraction prior to exercise (R2 = 0.84, P < 0.0001). No exercise-induced change in the subsarcolemmal pool could be detected. These findings indicate clear differences in the subcellular distribution of lipid droplets in the type 1 and 2 fibres of well-trained arm and leg muscles, as well as preferential utilisation of the intermyofibrillar pool during prolonged exhaustive exercise. Apparently, the metabolism of lipid droplets within a muscle fibre is compartmentalised.
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Affiliation(s)
- Han-Chow E Koh
- Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark
| | - Joachim Nielsen
- Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark.,Department of Pathology, SDU Muscle Research Cluster (SMRC), Odense University Hospital, Odense C, Denmark
| | - Bengt Saltin
- Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark
| | | | - Niels Ørtenblad
- Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark
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Shepherd SO, Strauss JA, Wang Q, Dube JJ, Goodpaster B, Mashek DG, Chow LS. Training alters the distribution of perilipin proteins in muscle following acute free fatty acid exposure. J Physiol 2017; 595:5587-5601. [PMID: 28560826 PMCID: PMC5556155 DOI: 10.1113/jp274374] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 05/17/2017] [Indexed: 01/02/2023] Open
Abstract
KEY POINTS The lipid droplet (LD)-associated perilipin (PLIN) proteins promote intramuscular triglyceride (IMTG) storage, although whether the abundance and association of the PLIN proteins with LDs is related to the diverse lipid storage in muscle between trained and sedentary individuals is unknown. We show that lipid infusion augments IMTG content in type I fibres of both trained and sedentary individuals. Most importantly, despite there being no change in PLIN protein content, lipid infusion did increase the number of LDs connected with PLIN proteins in trained individuals only. We conclude that trained individuals are able to redistribute the pre-existing pool of PLIN proteins to an expanded LD pool during lipid infusion and, via this adaptation, may support the storage of fatty acids in IMTG. ABSTRACT Because the lipid droplet (LD)-associated perilipin (PLIN) proteins promote intramuscular triglyceride (IMTG) storage, we investigated the hypothesis that differential protein content of PLINs and their distribution with LDs may be linked to the diverse lipid storage in muscle between trained and sedentary individuals. Trained (n = 11) and sedentary (n = 10) subjects, matched for age, sex and body mass index, received either a 6 h lipid or glycerol infusion in the setting of a concurrent hyperinsulinaemic-euglycaemic clamp. Sequential muscle biopsies (0, 2 and 6 h) were analysed using confocal immunofluorescence microscopy for fibre type-specific IMTG content and PLIN associations with LDs. In both groups, lipid infusion increased IMTG content in type I fibres (trained: +62%, sedentary: +79%; P < 0.05) but did not affect PLIN protein content. At baseline, PLIN2 (+65%), PLIN3 (+105%) and PLIN5 (+53%; all P < 0.05) protein content was higher in trained compared to sedentary individuals. In trained individuals, lipid infusion increased the number of LDs associated with PLIN2 (+27%), PLIN3 (+73%) and PLIN5 (+40%; all P < 0.05) in type I fibres. By contrast, in sedentary individuals, lipid infusion only increased the number of LDs not associated with PLIN proteins. Acute free fatty acid elevation therefore induces a redistribution of PLIN proteins to an expanded LD pool in trained individuals only and this may be part of the mechanism that enables fatty acids to be stored in IMTG.
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Affiliation(s)
- S O Shepherd
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - J A Strauss
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Q Wang
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - J J Dube
- Department of Biology, Chatham University, Pittsburgh, PA, USA
| | - B Goodpaster
- Translational Research Institute for Metabolism & Diabetes, Florida Hospital, Orlando, FL, USA
| | - D G Mashek
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - L S Chow
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
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Watt MJ, Cheng Y. Triglyceride metabolism in exercising muscle. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1250-1259. [PMID: 28652193 DOI: 10.1016/j.bbalip.2017.06.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 06/15/2017] [Accepted: 06/20/2017] [Indexed: 12/21/2022]
Abstract
Triglycerides are stored within lipid droplets in skeletal muscle and can be hydrolyzed to produce fatty acids for energy production through β-oxidation and oxidative phosphorylation. While there was some controversy regarding the quantitative importance of intramyocellular triglyceride (IMTG) as a metabolic substrate, recent advances in proton magnetic resonance spectroscopy and confocal microscopy support earlier tracer and biopsy studies demonstrating a substantial contribution of IMTG to energy production, particularly during moderate-intensity endurance exercise. This review provides an update on the understanding of IMTG utilization during exercise, with a focus on describing the key regulatory proteins that control IMTG breakdown and how these proteins respond to acute exercise and in the adaptation to exercise training. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Matthew J Watt
- Metabolic Disease and Obesity program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; Department of Physiology, Monash University, Clayton, Victoria 3800, Australia.
| | - Yunsheng Cheng
- Metabolic Disease and Obesity program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
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The Flexibility of Ectopic Lipids. Int J Mol Sci 2016; 17:ijms17091554. [PMID: 27649157 PMCID: PMC5037826 DOI: 10.3390/ijms17091554] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 08/30/2016] [Accepted: 09/01/2016] [Indexed: 02/07/2023] Open
Abstract
In addition to the subcutaneous and the visceral fat tissue, lipids can also be stored in non-adipose tissue such as in hepatocytes (intrahepatocellular lipids; IHCL), skeletal (intramyocellular lipids; IMCL) or cardiac muscle cells (intracardiomyocellular lipids; ICCL). Ectopic lipids are flexible fuel stores that can be depleted by physical exercise and repleted by diet. They are related to obesity and insulin resistance. Quantification of IMCL was initially performed invasively, using muscle biopsies with biochemical and/or histological analysis. 1H-magnetic resonance spectroscopy (1H-MRS) is now a validated method that allows for not only quantifying IMCL non-invasively and repeatedly, but also assessing IHCL and ICCL. This review summarizes the current available knowledge on the flexibility of ectopic lipids. The available evidence suggests a complex interplay between quantitative and qualitative diet, fat availability (fat mass), insulin action, and physical exercise, all important factors that influence the flexibility of ectopic lipids. Furthermore, the time frame of the intervention on these parameters (short-term vs. long-term) appears to be critical. Consequently, standardization of physical activity and diet are critical when assessing ectopic lipids in predefined clinical situations.
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29
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Vigelsø A, Gram M, Wiuff C, Hansen CN, Prats C, Dela F, Helge JW. Effects of immobilization and aerobic training on proteins related to intramuscular substrate storage and metabolism in young and older men. Eur J Appl Physiol 2015; 116:481-94. [DOI: 10.1007/s00421-015-3302-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 11/16/2015] [Indexed: 12/12/2022]
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Vigelso A, Prats C, Ploug T, Dela F, Helge JW. Higher muscle content of perilipin 5 and endothelial lipase protein in trained than untrained middle-aged men. Physiol Res 2015; 65:293-302. [PMID: 26447519 DOI: 10.33549/physiolres.933026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A high VO(2)max in middle-age is related to high metabolic flexibility and lowered risk of metabolic diseases. However, the influence of a high VO(2)max induced by years of regular training in middle-age on protein expression related to muscle metabolism is not well studied. This study measures key proteins involved in mitochondrial oxidation, glucose and lipid metabolism in skeletal muscle of trained and untrained middle-aged men. 16 middle-aged men, matched for lean body mass, were recruited into an endurance trained (TR, n=8) or an untrained (CON, n=8) group based on their VO(2)max. A muscle biopsy was obtained from m. vastus lateralis and protein levels were analyzed by Western blotting. The TR had higher protein levels of mitochondrial complex III-V, endothelial lipase (EL) and perilipin 5 compared to the CON. Glycogen synthase (P=0.05), perilipin 3 (P=0.09) and ATGL (P=0.09) tended to be higher in TR than CON, but there was no difference in AKT I/II, HKII, GLUT4 and LPL protein expression. Lastly, there was a positive correlation between plasma HDL and EL (R(2)=0.53, P<0.01). In conclusion, a high VO(2)max in middle-aged men was as expected is reflected in higher muscle oxidative capacity, but also in higher endothelial lipase and perilipin 5 expression and a borderline higher glycogen synthase protein expression, which may contribute to a higher metabolic flexibility.
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Affiliation(s)
- A Vigelso
- Center for Healthy Aging, Department of Biomedical Sciences, Panum Institute, Copenhagen N, Denmark.
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31
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Ipavec-Levasseur S, Croci I, Choquette S, Byrne NM, Cowin G, O'Moore-Sullivan TM, Prins JB, Hickman IJ. Effect of 1-h moderate-intensity aerobic exercise on intramyocellular lipids in obese men before and after a lifestyle intervention. Appl Physiol Nutr Metab 2015; 40:1262-8. [PMID: 26575100 DOI: 10.1139/apnm-2015-0258] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intramyocellular lipids (IMCL) are depleted in response to an acute bout of exercise in lean endurance-trained individuals; however, it is unclear whether changes in IMCL content are also seen in response to acute and chronic exercise in obese individuals. We used magnetic resonance spectroscopy in 18 obese men and 5 normal-weight controls to assess IMCL content before and after an hour of cycling at the intensity corresponding with each participant's maximal whole-body rate of fat oxidation (Fatmax). Fatmax was determined via indirect calorimetry during a graded exercise test on a cycle ergometer. The same outcome measures were reassessed in the obese group after a 16-week lifestyle intervention comprising dietary calorie restriction and exercise training. At baseline, IMCL content decreased in response to 1 h of cycling at Fatmax in controls (2.8 ± 0.4 to 2.0 ± 0.3 A.U., -39%, p = 0.02), but not in obese (5.4 ± 2.1 vs. 5.2 ± 2.2 A.U., p = 0.42). The lifestyle intervention lead to weight loss (-10.0 ± 5.4 kg, p < 0.001), improvements in maximal aerobic power (+5.2 ± 3.4 mL/(kg·min)), maximal fat oxidation rate (+0.19 ± 0.22 g/min), and a 29% decrease in homeostasis model assessment score (all p < 0.05). However, when the 1 h of cycling at Fatmax was repeated after the lifestyle intervention, there remained no observable change in IMCL (4.6 ± 1.8 vs. 4.6 ± 1.9 A.U., p = 0.92). In summary, there was no IMCL depletion in response to 1 h of cycling at moderate intensity either before or after the lifestyle intervention in obese men. An effective lifestyle intervention including moderate-intensity exercise training did not impact rate of utilisation of IMCL during acute exercise in obese men.
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Affiliation(s)
| | - Ilaria Croci
- a The University of Queensland Diamantina Institute, Brisbane, Australia.,b School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia.,c Mater Research Institute, University of Queensland, Brisbane, Australia
| | - Stéphane Choquette
- d Faculty of Physical Education and Sports, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Nuala M Byrne
- e Bond Institute of Health and Sport, Bond University, Robina, Australia.,f Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
| | - Gary Cowin
- g Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Trisha M O'Moore-Sullivan
- c Mater Research Institute, University of Queensland, Brisbane, Australia.,h Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Australia
| | - Johannes B Prins
- c Mater Research Institute, University of Queensland, Brisbane, Australia
| | - Ingrid J Hickman
- a The University of Queensland Diamantina Institute, Brisbane, Australia.,c Mater Research Institute, University of Queensland, Brisbane, Australia
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32
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Pourteymour S, Lee S, Langleite TM, Eckardt K, Hjorth M, Bindesbøll C, Dalen KT, Birkeland KI, Drevon CA, Holen T, Norheim F. Perilipin 4 in human skeletal muscle: localization and effect of physical activity. Physiol Rep 2015; 3:3/8/e12481. [PMID: 26265748 PMCID: PMC4562567 DOI: 10.14814/phy2.12481] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Perilipins (PLINs) coat the surface of lipid droplets and are important for the regulation of lipid turnover. Knowledge about the physiological role of the individual PLINs in skeletal muscle is limited although lipid metabolism is very important for muscle contraction. To determine the effect of long-term exercise on PLINs expression, 26 middle-aged, sedentary men underwent 12 weeks combined endurance and strength training intervention. Muscle biopsies from m. vastus lateralis and subcutaneous adipose tissue were taken before and after the intervention and total gene expression was measured with deep mRNA sequencing. PLIN4 mRNA exhibited the highest expression of all five PLINs in both tissues, and the expression was significantly reduced after long-term exercise in skeletal muscle. Moreover, PLIN4 mRNA expression levels in muscle correlated with the expression of genes involved in de novo phospholipid biosynthesis, with muscular content of phosphatidylethanolamine and phosphatidylcholine, and with the content of subsarcolemmal lipid droplets. The PLIN4 protein was mainly located at the periphery of skeletal muscle fibers, with higher levels in slow-twitch as compared to fast-twitch skeletal muscle fibers. In summary, we report reduced expression of PLIN4 after long-term physical activity, and preferential slow-twitch skeletal muscle fibers and plasma membrane-associated PLIN4 location.
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Affiliation(s)
- Shirin Pourteymour
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Sindre Lee
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Torgrim M Langleite
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital and Faculty of Medicine University of Oslo, Oslo, Norway
| | - Kristin Eckardt
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Marit Hjorth
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Christian Bindesbøll
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Knut T Dalen
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Kåre I Birkeland
- Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital and Faculty of Medicine University of Oslo, Oslo, Norway
| | - Christian A Drevon
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Torgeir Holen
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
| | - Frode Norheim
- Department of Nutrition, Institute of Basic Medical Science, Faculty of Medicine University of Oslo, Oslo, Norway
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Giordano C, Lemaire C, Li T, Kimoff RJ, Petrof BJ. Autophagy-associated atrophy and metabolic remodeling of the mouse diaphragm after short-term intermittent hypoxia. PLoS One 2015; 10:e0131068. [PMID: 26107816 PMCID: PMC4480857 DOI: 10.1371/journal.pone.0131068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 05/28/2015] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Short-term intermittent hypoxia (IH) is common in patients with acute respiratory disorders. Although prolonged exposure to hypoxia induces atrophy and increased fatigability of skeletal muscle, the response to short-term IH is less well known. We hypothesized that the diaphragm and limb muscles would adapt differently to short-term IH given that hypoxia stimulates ventilation and triggers a superimposed exercise stimulus in the diaphragm. METHODS We determined the structural, metabolic, and contractile properties of the mouse diaphragm after 4 days of IH (8 hours per day, 30 episodes per hour to a FiO2 nadir=6%), and compared responses in the diaphragm to a commonly studied reference limb muscle, the tibialis anterior. Outcome measures included muscle fiber size, assays of muscle proteolysis (calpain, ubiquitin-proteasome, and autophagy pathways), markers of oxidative stress and mitochondrial function, quantification of intramyocellular lipid and lipid metabolism genes, type I myosin heavy chain (MyHC) expression, and in vitro contractile properties. RESULTS After 4 days of IH, the diaphragm alone demonstrated significant atrophy (30% decrease of myofiber size) together with increased LC3B-II protein (2.4-fold) and mRNA markers of the autophagy pathway (LC3B, Gabarapl1, Bnip3), whereas active calpain and E3 ubiquitin ligases (MuRF1, atrogin-1) were unaffected in both muscles. Succinate dehydrogenase activity was significantly reduced by IH in both muscles. However, only the diaphragm exhibited increased intramyocellular lipid droplets (2.5-fold) after IH, along with upregulation of genes linked to activated lipid metabolism. In addition, although the diaphragm showed evidence for acute fatigue immediately following IH, it underwent an adaptive fiber type switch toward slow type I MyHC-expressing fibers, associated with greater intrinsic endurance of the muscle during repetitive stimulation in vitro. CONCLUSIONS Short-term IH induces preferential atrophy in the mouse diaphragm together with increased autophagy and a rapid compensatory metabolic adaptation associated with enhanced fatigue resistance.
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Affiliation(s)
- Christian Giordano
- Meakins-Christie Laboratories and Respiratory Division, McGill University, Montreal, Quebec, Canada
- Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Christian Lemaire
- Meakins-Christie Laboratories and Respiratory Division, McGill University, Montreal, Quebec, Canada
- Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Tong Li
- Meakins-Christie Laboratories and Respiratory Division, McGill University, Montreal, Quebec, Canada
- Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - R. John Kimoff
- Meakins-Christie Laboratories and Respiratory Division, McGill University, Montreal, Quebec, Canada
- Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Basil J. Petrof
- Meakins-Christie Laboratories and Respiratory Division, McGill University, Montreal, Quebec, Canada
- Program for Translational Research in Respiratory Diseases, McGill University Health Centre Research Institute, Montreal, Quebec, Canada
- * E-mail:
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MacPherson REK, Peters SJ. Piecing together the puzzle of perilipin proteins and skeletal muscle lipolysis. Appl Physiol Nutr Metab 2015; 40:641-51. [PMID: 25971423 DOI: 10.1139/apnm-2014-0485] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The regulation of skeletal muscle lipolysis and fat oxidation is a complex process involving multiple proteins and enzymes. Emerging work indicates that skeletal muscle PLIN proteins likely play a role in the hydrolysis of triglycerides stored in lipid droplets and the passage of fatty acids to the mitochondria for oxidation. In adipocytes, PLIN1 regulates lipolysis by interacting with comparative gene identification-58 (CGI-58), an activator of adipose triglyceride lipase (ATGL). Upon lipolytic stimulation, PLIN1 is phosphorylated, releasing CGI-58 to activate ATGL and initiate triglyceride breakdown. The absence of PLIN1 in skeletal muscle leads us to believe that other PLIN family members undertake this role. The focus of this review is on the PLIN family proteins expressed in skeletal muscle: PLIN2, PLIN3, and PLIN5. To date, most studies involving these PLIN proteins have used nonmuscle tissues and cell cultures to determine their potential roles. Results from work in these models support a role for PLIN proteins in sequestering lipases during basal conditions and in potentially working together for lipase translocation and activity during lipolysis. In skeletal muscle, PLIN2 tends to mirror the lipid content and may play a role in lipid droplet growth and stability through lipase interactions on the lipid droplet surface, whereas the skeletal muscle roles of both PLIN3 and PLIN5 seem to be more complex because they are found not only on the lipid droplet, but also at the mitochondria. Clearly, further work is needed to fully understand the intricate mechanisms by which PLIN proteins contribute to skeletal muscle lipid metabolism.
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Affiliation(s)
- Rebecca E K MacPherson
- a Center for Bone and Muscle Health, Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada.,b Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Sandra J Peters
- a Center for Bone and Muscle Health, Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
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MacPherson REK, Castelli LM, Miotto PM, Frendo-Cumbo S, Milburn A, Roy BD, LeBlanc PJ, Ward WE, Peters SJ. A maternal high fat diet has long-lasting effects on skeletal muscle lipid and PLIN protein content in rat offspring at young adulthood. Lipids 2015; 50:205-17. [PMID: 25552350 DOI: 10.1007/s11745-014-3985-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 12/16/2014] [Indexed: 01/08/2023]
Abstract
A maternal high fat diet (HFD) can have adverse effects on skeletal muscle development. Skeletal muscle PLIN proteins (PLIN2, 3 and 5) are thought to play critical roles in lipid metabolism, however effects of HFD on PLIN and lipases (HSL, ATGL, CGI-58) in mothers as well as their offspring have yet to be investigated. The primary objective of this study was to determine whether maternal HFD would influence skeletal muscle lipase and PLIN protein content in offspring at weaning (19 d) and young adulthood (3 mo). Female rats (28 d old, n = 9/group) were fed control (CON, AIN93G, 7% soybean oil) or HFD (AIN93G, 20% lard) for 10 weeks prior to mating and throughout pregnancy and lactation. All offspring were weaned to CON [n = 18/group, 1 female and 1 male pup per litter were studied at weaning (19 d) and 3 mo of age]. There was no effect of sex for the main outcomes measured in plantaris, therefore male and female data was combined. Maternal HFD resulted in higher triacylglycerol content in pups at 3 mo (p < 0.05), as well as in the dams (p = 0.015). Maternal HFD resulted in higher PLIN5 content in pups at weaning and 3 mo (p = 0.05). PLIN2 and PLIN5 content decreased at 3 mo versus weaning (p < 0.001). HFD dams had a higher PLIN3 content (p = 0.016). Diet had no effect on ATGL, CGI-58, or HSL content. In conclusion, exposure to a maternal HFD resulted in higher skeletal muscle lipid and PLIN5 content in plantaris of offspring through to young adulthood.
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Affiliation(s)
- Rebecca E K MacPherson
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada,
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36
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PPARG Modulated Lipid Accumulation in Dairy GMEC via Regulation of ADRP Gene. J Cell Biochem 2014; 116:192-201. [DOI: 10.1002/jcb.24958] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 08/22/2014] [Indexed: 11/07/2022]
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37
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Shepherd SO, Cocks M, Tipton KD, Witard OC, Ranasinghe AM, Barker TA, Wagenmakers AJM, Shaw CS. Resistance training increases skeletal muscle oxidative capacity and net intramuscular triglyceride breakdown in type I and II fibres of sedentary males. Exp Physiol 2014; 99:894-908. [DOI: 10.1113/expphysiol.2014.078014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- S. O. Shepherd
- Research Institute for Sport & Exercise Sciences; Liverpool John Moores University; Liverpool UK
| | - M. Cocks
- Research Institute for Sport & Exercise Sciences; Liverpool John Moores University; Liverpool UK
| | - K. D. Tipton
- Health and Exercise Sciences Research Group; University of Stirling; Stirling UK
| | - O. C. Witard
- Health and Exercise Sciences Research Group; University of Stirling; Stirling UK
| | - A. M. Ranasinghe
- School of Clinical and Experimental Medicine; Cardiovascular and Respiratory Sciences; University of Birmingham; Birmingham UK
| | - T. A. Barker
- School of Clinical and Experimental Medicine; Cardiovascular and Respiratory Sciences; University of Birmingham; Birmingham UK
| | - A. J. M. Wagenmakers
- Research Institute for Sport & Exercise Sciences; Liverpool John Moores University; Liverpool UK
| | - C. S. Shaw
- Institute of Sport, Exercise & Active Living; Victoria University; Melbourne Victoria Australia
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38
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Bosma M. Lipid homeostasis in exercise. Drug Discov Today 2014; 19:1019-23. [PMID: 24632001 DOI: 10.1016/j.drudis.2014.03.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 03/06/2014] [Indexed: 01/08/2023]
Abstract
Fatty acids (FA) are essential energy substrates during endurance exercise. In addition to systemic supply, intramyocellular neutral lipids form an important source of FA for the working muscle. Endurance exercise training is associated with an increased reliance on lipids as a fuel source, has systemic lipid-lowering effects and results in a remodeling of skeletal muscle lipid metabolism toward increased oxidation, neutral lipid storage and turnover. Interestingly, recent studies have indicated common exercise-induced regulatory pathways for genes involved in skeletal muscle mitochondrial oxidative metabolism and lipid droplet (LD) dynamics. In this review, I discuss lipid homeostasis during acute exercise and adaptations in lipid metabolism upon exercise training in the light of recent advances in the field.
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Affiliation(s)
- Madeleen Bosma
- Department of Cell and Molecular Biology, Karolinska Institutet, PO Box 285, SE-171 77 Stockholm, Sweden.
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39
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Badin PM, Langin D, Moro C. Dynamics of skeletal muscle lipid pools. Trends Endocrinol Metab 2013; 24:607-15. [PMID: 23988586 DOI: 10.1016/j.tem.2013.08.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 07/22/2013] [Accepted: 08/03/2013] [Indexed: 11/20/2022]
Abstract
Intramyocellular triacylglycerol (IMTG) is emerging as an important energy fuel source during muscle contraction and are adaptively increased in response to exercise, without adverse physiological effects. Paradoxically, elevated IMTG content in obese and type 2 diabetics has been linked to insulin resistance, highlighting the importance of IMTG pools in physiology and pathology. Two separate views suggest that IMTG dynamics are determinant for skeletal muscle fat oxidation, and that disruption of IMTG dynamics facilitates the accumulation of lipotoxic intermediates such as diacylglycerols and ceramides that interfere with insulin signaling. Thus, understanding the factors that control IMTG dynamics is crucial. Here we discuss recent literature describing the regulation of IMTG pools with a particular emphasis on lipases and lipid droplet (LD)-associated proteins.
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Affiliation(s)
- Pierre-Marie Badin
- Obesity Research Laboratory, Institut National de la Santé et de la Recherche Médicale (INSERM) Unité Mixte de Recherche (UMR) 1048, Institute of Metabolic and Cardiovascular Diseases (I2MC), Toulouse, France; University of Toulouse, UMR1048, Paul Sabatier University, Toulouse, France
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Abstract
PURPOSE OF REVIEW With the realization that lipid droplets are not merely inert fat storage organelles, but highly dynamic and actively involved in cellular lipid homeostasis, there has been an increased interest in lipid droplet biology. Recent studies have begun to unravel the roles that lipid dropletss play in cellular physiology and provide insights into the mechanisms by which lipid droplets contribute to cellular homeostasis. This review provides a summary of these recent publications on lipid droplet metabolism. RECENT FINDINGS Perilipins have different preferences for associating with triacylglycerol (TAG) or cholesteryl esters, different tissue distributions, and each contributes to lipid metabolism in its unique way. Cell death-inducing DFF45-like effector proteins are not only involved in lipid droplet expansion, but also in the cellular response to stress and lipid secretion. Lipid droplets undergo an active cycle of lipolysis and re-esterification to form microlipid droplets. TAG synthesis for lipid droplet formation and expansion occurs in the endoplasmic reticulum and on lipid droplets, and TAG transfers between lipid droplets during lipid droplet fusion. Lipid droplets interact with the endoplasmic reticulum and mitochondria to facilitate lipid transfer, lipid droplet expansion, and metabolism. SUMMARY Lipid droplets are dynamically active, responding to changes in cellular physiology, as well as interacting with cytosolic proteins and other organelles to control lipid homeostasis.
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Affiliation(s)
- Victor K Khor
- aVeterans Affairs Palo Alto Healthcare System, Palo Alto bDivision of Endocrinology, Stanford University, Stanford, California, USA
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41
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Prats C, Gomez-Cabello A, Nordby P, Andersen JL, Helge JW, Dela F, Baba O, Ploug T. An optimized histochemical method to assess skeletal muscle glycogen and lipid stores reveals two metabolically distinct populations of type I muscle fibers. PLoS One 2013; 8:e77774. [PMID: 24204959 PMCID: PMC3813758 DOI: 10.1371/journal.pone.0077774] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 09/05/2013] [Indexed: 11/18/2022] Open
Abstract
Skeletal muscle energy metabolism has been a research focus of physiologists for more than a century. Yet, how the use of intramuscular carbohydrate and lipid energy stores are coordinated during different types of exercise remains a subject of debate. Controversy arises from contradicting data from numerous studies, which used different methodological approaches. Here we review the “pros and cons” of previously used histochemical methods and describe an optimized method to ensure the preservation and specificity of detection of both intramyocellular carbohydrate and lipid stores. For optimal preservation of muscle energy stores, air drying cryosections or cycles of freezing-thawing need to be avoided. Furthermore, optimization of the imaging settings in order to specifically image intracellular lipid droplets stained with oil red O or Bodipy-493/503 is shown. When co-staining lipid droplets with associated proteins, Bodipy-493/503 should be the dye of choice, since oil red O creates precipitates on the lipid droplets blocking the light. In order to increase the specificity of glycogen stain, an antibody against glycogen is used. The resulting method reveals the existence of two metabolically distinct myosin heavy chain I expressing fibers: I-1 fibers have a smaller crossectional area, a higher density of lipid droplets, and a tendency to lower glycogen content compared to I-2 fibers. Type I-2 fibers have similar lipid content than IIA. Exhaustive exercise lead to glycogen depletion in type IIA and IIX fibers, a reduction in lipid droplets density in both type I-1 and I-2 fibers, and a decrease in the size of lipid droplets exclusively in type I-1 fibers.
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Affiliation(s)
- Clara Prats
- Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| | - Alba Gomez-Cabello
- Faculty of Health and Sport Science, University of Zaragoza, Zaragoza, Spain
| | - Pernille Nordby
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jesper L. Andersen
- Institute of Sports Medicine, Bispebjerg Hospital and Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
| | - Jørn W. Helge
- Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
| | - Flemming Dela
- Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
| | - Otto Baba
- Biostructural Science, Tokyo Medical and Dental University, Tokyo, Japan
| | - Thorkil Ploug
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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42
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Macpherson REK, Vandenboom R, Roy BD, Peters SJ. Skeletal muscle PLIN3 and PLIN5 are serine phosphorylated at rest and following lipolysis during adrenergic or contractile stimulation. Physiol Rep 2013; 1:e00084. [PMID: 24303154 PMCID: PMC3831900 DOI: 10.1002/phy2.84] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 08/11/2013] [Indexed: 02/06/2023] Open
Abstract
In adipose tissue, access of adipose triglyceride and hormone-sensitive lipases (ATGL and HSL) to the lipid droplet depends on PLIN1 phosphorylation, however, PLIN1 is not expressed in skeletal muscle and the phosphorylation of the expressed PLINs has yet to be investigated. Further, direct interactions between skeletal muscle PLINs and HSL are unknown. We investigated the isolated and combined effects of epinephrine and contraction on PLIN-to-lipase interactions as well as phosphorylation. Isolated rat solei were assigned to one of four 30 min in vitro conditions (25°C): (1) rest; (2) intermittent tetanic stimulation (60 Hz for 150 msec; train rate 20/min); (3) 5 nmol/L epinephrine; (4) intermittent tetanic stimulation and 5 nmol/L epinephrine. Immunoprecipitation of serine phosphorylated proteins followed by Western blotting for PLIN2, PLIN3, PLIN5, revealed that only PLIN2 is not phosphorylated under any of the experimental conditions. This is the first study to show that in whole rat skeletal muscle PLIN3 and PLIN5 are serine phosphorylated. The degree of serine phosphorylation remained unchanged following adrenergic and/or contractile stimulation. Oil red O staining of muscle sections for lipid content shows a significant decrease following each condition, confirming lipolysis occurred (P < 0.05). PLIN2, 3, and 5 all interact with HSL and ATGL, but these interactions were unchanged following treatments. Our results show that in skeletal muscle, PLIN2 is not serine phosphorylated at rest or with lipolytic stimulation and that while PLIN3, PLIN5 are serine phosphorylated at rest, the degree of phosphorylation does not change with lipolytic stimulation.
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Affiliation(s)
- Rebecca E K Macpherson
- Department of Kinesiology, Centre for Bone and Muscle Health, Brock University St Catharines, Ontario, L2S 3A1, Canada
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Conte M, Vasuri F, Trisolino G, Bellavista E, Santoro A, Degiovanni A, Martucci E, D'Errico-Grigioni A, Caporossi D, Capri M, Maier AB, Seynnes O, Barberi L, Musarò A, Narici MV, Franceschi C, Salvioli S. Increased Plin2 expression in human skeletal muscle is associated with sarcopenia and muscle weakness. PLoS One 2013; 8:e73709. [PMID: 23977392 PMCID: PMC3744478 DOI: 10.1371/journal.pone.0073709] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 07/22/2013] [Indexed: 11/28/2022] Open
Abstract
Human aging is associated with a progressive loss of muscle mass and strength and a concomitant fat accumulation in form of inter-muscular adipose tissue, causing skeletal muscle function decline and immobilization. Fat accumulation can also occur as intra-muscular triglycerides (IMTG) deposition in lipid droplets, which are associated with perilipin proteins, such as Perilipin2 (Plin2). It is not known whether Plin2 expression changes with age and if this has consequences on muscle mass and strength. We studied the expression of Plin2 in the vastus lateralis (VL) muscle of both healthy subjects and patients affected by lower limb mobility limitation of different age. We found that Plin2 expression increases with age, this phenomenon being particularly evident in patients. Moreover, Plin2 expression is inversely correlated with quadriceps strength and VL thickness. To investigate the molecular mechanisms underpinning this phenomenon, we focused on IGF-1/p53 network/signalling pathway, involved in muscle physiology. We found that Plin2 expression strongly correlates with increased p53 activation and reduced IGF-1 expression. To confirm these observations made on humans, we studied mice overexpressing muscle-specific IGF-1, which are protected from sarcopenia. These mice resulted almost negative for the expression of Plin2 and p53 at two years of age. We conclude that fat deposition within skeletal muscle in form of Plin2-coated lipid droplets increases with age and is associated with decreased muscle strength and thickness, likely through an IGF-1- and p53-dependent mechanism. The data also suggest that excessive intramuscular fat accumulation could be the initial trigger for p53 activation and consequent loss of muscle mass and strength.
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Affiliation(s)
- Maria Conte
- Department of Experimental, Diagnostic and Specialty Medicine and Interdepartmental Centre L Galvani, CIG, University of Bologna, Bologna, Italy.
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44
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Miceli M, Franci G, Dell'Aversana C, Ricciardiello F, Petraglia F, Carissimo A, Perone L, Maruotti GM, Savarese M, Martinelli P, Cancemi M, Altucci L. MePR: a novel human mesenchymal progenitor model with characteristics of pluripotency. Stem Cells Dev 2013; 22:2368-83. [PMID: 23597129 DOI: 10.1089/scd.2012.0498] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Human embryo stem cells or adult tissues are excellent models for discovery and characterization of differentiation processes. The aims of regenerative medicine are to define the molecular and physiological mechanisms that govern stem cells and differentiation. Human mesenchymal stem cells (hMSCs) are multipotent adult stem cells that are able to differentiate into a variety of cell types under controlled conditions both in vivo and in vitro, and they have the remarkable ability of self-renewal. hMSCs derived from amniotic fluid and characterized by the expression of Oct-4 and Nanog, typical markers of pluripotent cells, represent an excellent model for studies on stemness. Unfortunately, the limited amount of cells available from each donation and, above all, the limited number of replications do not allow for detailed studies. Here, we report on the immortalization and characterization of novel mesenchymal progenitor (MePR) cell lines from amniotic fluid-derived hMSCs, whose biological properties are similar to primary amniocytes. Our data indicate that MePR cells display the multipotency potential and differentiation rates of hMSCs, thus representing a useful model to study both mechanisms of differentiation and pharmacological approaches to induce selective differentiation. In particular, MePR-2B cells, which carry a bona fide normal karyotype, might be used in basic stem cell research, leading to the development of new approaches for stem cell therapy and tissue engineering.
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Affiliation(s)
- Marco Miceli
- Dipartimento di Biochimica, Biofisica e Patologia Generale, Seconda Università di Napoli , Napoli, Italy
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45
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MacPherson REK, Ramos SV, Vandenboom R, Roy BD, Peters SJ. Skeletal muscle PLIN proteins, ATGL and CGI-58, interactions at rest and following stimulated contraction. Am J Physiol Regul Integr Comp Physiol 2013; 304:R644-50. [PMID: 23408028 DOI: 10.1152/ajpregu.00418.2012] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Evidence indicates that skeletal muscle lipid droplet-associated proteins (PLINs) regulate lipolysis through protein-protein interactions on the lipid droplet surface. In adipocytes, PLIN1 is thought to regulate lipolysis by directly interacting with comparative gene identification-58 (CGI-58), an activator of adipose triglyceride lipase (ATGL). Upon lipolytic stimulation, PLIN1 is phosphorylated, releasing CGI-58 to fully activate ATGL and initiate triglyceride breakdown. The absence of PLIN1 in skeletal muscle leads us to believe that other PLIN family members undertake this role. Our purpose was to examine interactions between PLIN2, PLIN3, and PLIN5, with ATGL and its coactivator CGI-58 at rest and following contraction. Isolated rat solei were incubated for 30 min at rest or during 30 min of intermittent tetanic stimulation [150-ms volleys at 60 Hz with a train rate of 20 tetani/min (25°C)] to maximally stimulate intramuscular lipid breakdown. Results show that the interaction between ATGL and CGI-58 increased 128% following contraction (P = 0.041). Further, ATGL interacts with PLIN2, PLIN3, and PLIN5 at rest and following contraction. The PLIN2-ATGL interaction decreased significantly by 21% following stimulation (P = 0.013). Both PLIN3 and PLIN5 coprecipitated with CGI-58 at rest and following contraction, while there was no detectable interaction between PLIN2 and CGI-58 in either condition. Therefore, our findings indicate that in skeletal muscle, during contraction-induced muscle lipolysis, ATGL and CGI-58 strongly associate and that the PLIN proteins work together to regulate lipolysis, in part, by preventing ATGL and CGI-58 interactions at rest.
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Affiliation(s)
- Rebecca E K MacPherson
- Brock University, Department of Kinesiology, Centre for Bone and Muscle Health, St. Catharines, Canada.
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Shepherd SO, Cocks M, Tipton KD, Ranasinghe AM, Barker TA, Burniston JG, Wagenmakers AJM, Shaw CS. Sprint interval and traditional endurance training increase net intramuscular triglyceride breakdown and expression of perilipin 2 and 5. J Physiol 2012; 591:657-75. [PMID: 23129790 DOI: 10.1113/jphysiol.2012.240952] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Intramuscular triglyceride (IMTG) utilization is enhanced by endurance training (ET) and is linked to improved insulin sensitivity. This study first investigated the hypothesis that ET-induced increases in net IMTG breakdown and insulin sensitivity are related to increased expression of perilipin 2 (PLIN2) and perilipin 5 (PLIN5). Second, we hypothesized that sprint interval training (SIT) also promotes increases in IMTG utilization and insulin sensitivity. Sixteen sedentary males performed 6 weeks of either SIT (4-6, 30 s Wingate tests per session, 3 days week(-1)) or ET (40-60 min moderate-intensity cycling, 5 days week(-1)). Training increased resting IMTG content (SIT 1.7-fold, ET 2.4-fold; P < 0.05), concomitant with parallel increases in PLIN2 (SIT 2.3-fold, ET 2.8-fold; P < 0.01) and PLIN5 expression (SIT 2.2-fold, ET 3.1-fold; P < 0.01). Pre-training, 60 min cycling at ∼65% pre-training decreased IMTG content in type I fibres (SIT 17 ± 10%, ET 15 ± 12%; P < 0.05). Following training, a significantly greater breakdown of IMTG in type I fibres occurred during exercise (SIT 27 ± 13%, ET 43 ± 6%; P < 0.05), with preferential breakdown of PLIN2- and particularly PLIN5-associated lipid droplets. Training increased the Matsuda insulin sensitivity index (SIT 56 ± 15%, ET 29 ± 12%; main effect P < 0.05). No training × group interactions were observed for any variables. In conclusion, SIT and ET both increase net IMTG breakdown during exercise and increase in PLIN2 and PLIN5 protein expression. The data are consistent with the hypothesis that increases in PLIN2 and PLIN5 are related to the mechanisms that promote increased IMTG utilization during exercise and improve insulin sensitivity following 6 weeks of SIT and ET.
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Affiliation(s)
- S O Shepherd
- School of Sport & Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK
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47
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Shaw CS, Shepherd SO, Wagenmakers AJM, Hansen D, Dendale P, van Loon LJC. Prolonged exercise training increases intramuscular lipid content and perilipin 2 expression in type I muscle fibers of patients with type 2 diabetes. Am J Physiol Endocrinol Metab 2012; 303:E1158-65. [PMID: 22949030 PMCID: PMC3492857 DOI: 10.1152/ajpendo.00272.2012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The aim of the present study was to investigate changes in intramuscular triglyceride (IMTG) content and perilipin 2 expression in skeletal muscle tissue following 6 mo of endurance-type exercise training in type 2 diabetes patients. Ten obese male type 2 diabetes patients (age 62 ± 1 yr, body mass index BMI 31 ± 1 kg/m²) completed three exercise sessions/week consisting of 40 min of continuous endurance-type exercise at 75% V(O₂ peak) for a period of 6 mo. Muscle biopsies collected at baseline and after 2 and 6 mo of intervention were analyzed for IMTG content and perilipin 2 expression using fiber type-specific immunofluorescence microscopy. Endurance-type exercise training reduced trunk body fat by 6 ± 2% and increased whole body oxygen uptake capacity by 13 ± 7% (P < 0.05). IMTG content increased twofold in response to the 6 mo of exercise training in both type I and type II muscle fibers (P < 0.05). A threefold increase in perilipin 2 expression was observed from baseline to 2 and 6 mo of intervention in the type I muscle fibers only (1.1 ± 0.3, 3.4 ± 0.6, and 3.6 ± 0.6% of fibers stained, respectively, P < 0.05). Exercise training induced a 1.6-fold increase in mitochondrial content after 6 mo of training in both type I and type II muscle fibers (P < 0.05). In conclusion, this is the first study to report that prolonged endurance-type exercise training increases the expression of perilipin 2 alongside increases in IMTG content in a type I muscle fiber-type specific manner in type 2 diabetes patients.
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MESH Headings
- Abdominal Fat/pathology
- Adiposity
- Body Mass Index
- Cohort Studies
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Diabetes Mellitus, Type 2/therapy
- Exercise
- Humans
- Insulin Resistance
- Lipid Metabolism
- Male
- Membrane Proteins/metabolism
- Middle Aged
- Mitochondria, Muscle/metabolism
- Mitochondria, Muscle/pathology
- Muscle Fibers, Fast-Twitch/metabolism
- Muscle Fibers, Fast-Twitch/pathology
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle Fibers, Slow-Twitch/pathology
- Overweight/complications
- Oxygen Consumption
- Perilipin-2
- Quadriceps Muscle/metabolism
- Quadriceps Muscle/pathology
- Time Factors
- Triglycerides/metabolism
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Affiliation(s)
- C. S. Shaw
- 1School of Sport and Exercise Sciences, The University of Birmingham, Birmingham, United Kingdom;
- 2Institute of Sport, Exercise, and Active Living, Victoria University, Melbourne, Australia;
| | - S. O. Shepherd
- 1School of Sport and Exercise Sciences, The University of Birmingham, Birmingham, United Kingdom;
| | - A. J. M. Wagenmakers
- 1School of Sport and Exercise Sciences, The University of Birmingham, Birmingham, United Kingdom;
| | - D. Hansen
- 3Jessa Hospital, Heart Centre Hasselt, Hasselt, Belgium;
- 4Faculty of Medicine, Hasselt University, Diepenbeek, Belgium; and
| | - P. Dendale
- 3Jessa Hospital, Heart Centre Hasselt, Hasselt, Belgium;
- 4Faculty of Medicine, Hasselt University, Diepenbeek, Belgium; and
| | - L. J. C. van Loon
- 5Department of Human Movement Sciences, Nutrition and Toxicology Research Institute, Maastricht University Medical Centre, Maastricht, The Netherlands
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