Intramyocellular triacylglycerol in prolonged cycling  with high- and low-carbohydrate availability

Johnson, Nathan A.; Stannard, Stephen R.; Mehalski, K.; Trenell, Michael I.; Sachinwalla, Toos; Thompson, Campbell; Thompson, Martin W.

doi:10.1152/japplphysiol.00833.2002

Cited by 59 publications

(68 citation statements)

References 44 publications

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“…Thus our present and previous (64) findings clearly indicate that even untrained individuals can use IMCL as an energy fuel in type IIa fibers during exercise following short-term adaptation to either endurance training or a HFD (64). Our current observations also corroborate earlier findings by other laboratories showing an elevated contribution of IMCL to energy provision in endurance exercise following a period of a HFD in young volunteers (39,71,72). However, in the latter studies, IMCL content was measured in mixed muscle homogenates, and the increased net IMCL degradation was tentatively explained by greater IMCL oxidation in type I fibers.…”

Section: Discussionsupporting

confidence: 93%

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

Proeyen

Szlufcik

Nielens

et al. 2011

Journal of Applied Physiology

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Van Proeyen K, Szlufcik K, Nielens H, Deldicque L, Van Dyck R, Ramaekers M, Hespel P. High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise. J Appl Physiol 111: 108 -116, 2011. First published May 5, 2011 doi:10.1152/japplphysiol.01459.2010In this study, we compared the effects of endurance training in the fasted state (F) vs. the fed state [ample carbohydrate intake (CHO)] on exercise-induced intramyocellular lipid (IMCL) and glycogen utilization during a 6-wk period of a hypercaloric (ϳϩ30% kcal/day) fat-rich diet (HFD; 50% of kcal). Healthy male volunteers (18 -25 yrs) received a HFD in conjunction with endurance training (four times, 60 -90 min/wk) either in F (n ϭ 10) or with CHO before and during exercise sessions (n ϭ 10). The control group (n ϭ 7) received a HFD without training and increased body weight by ϳ3 kg (P Ͻ 0.001). Before and after a HFD, the subjects performed a 2-h constant-load bicycle exercise test in F at ϳ70% maximal oxygen uptake rate. A HFD, both in the absence (F) or presence (CHO) of training, elevated basal IMCL content by ϳ50% in type I and by ϳ75% in type IIa fibers (P Ͻ 0.05). Independent of training in F or CHO, a HFD, as such, stimulated exercise-induced net IMCL breakdown by approximately twofold in type I and by approximately fourfold in type IIa fibers. Furthermore, exercise-induced net muscle glycogen breakdown was not significantly affected by a HFD. It is concluded that a HFD stimulates net IMCL degradation by increasing basal IMCL content during exercise in type I and especially IIa fibers. Furthermore, a hypercaloric HFD provides adequate amounts of carbohydrates to maintain high muscle glycogen content during training and does not impair exercise-induced muscle glycogen breakdown. skeletal muscle; fasted exercise; fat-rich feeding; energy substrate metabolism; muscle lipids IT IS WELL ESTABLISHED THAT dietary factors play an important role in modulating the acute and chronic metabolic responses to endurance exercise (30). In this regard, increased preexercise dietary fat supply stimulates energy provision via fat oxidation during exercise (8,33). By analogy, fatty acid infusion elevates the input of free fatty acids (FFAs) in the energy substrate mix fueling muscle contractions (22, 48a, 49). Furthermore, chronic exposure to a high-fat diet (HFD) also enhances the use of FFAs in endurance exercise (8,9,25,29,(32)(33)(34)58). This is, at least partly, due to upregulation of rate-limiting steps in fat metabolic pathways. Thus FFA oxidation can be stimulated with appropriate chronic exercise and/or nutrition (e.g., HFD), which upregulates pivotal steps in FFA catabolism such as fatty acid translocase (FAT)/CD36 (4, 9), ␤-hydroxyacyl CoA dehydrogenase (␤-HAD) (9, 31), and hormone-sensitive lipase (HSL) (58). However, it is still unclear whether these adaptations are specifically due to the increased FFA supply per se or result from decreased glucose availability. Omission of glucose ingestion during exercise a...

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Section: Discussionsupporting

confidence: 93%

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

Proeyen

Szlufcik

Nielens

et al. 2011

Journal of Applied Physiology

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“…After acute exercise at moderate intensity, most studies report not only a decrease in IMCL in healthy and sedentary subjects (Bucher et al, 2014;Decombaz et al, 2001;Egger et al, 2013;SchrauwenHinderling et al, 2003a;White et al, 2003) but also in endurancetrained athletes (Brechtel et al, 2001b;De Bock et al, 2007;Decombaz et al, 2001;Johnson et al, 2003;Krssak et al, 2000;Rico-Sanz et al, 2000;van Loon et al, 2003a;van Loon et al, 2003b;Vermathen et al, 2012;Zehnder et al, 2005). Importantly, the utilization of IMCL during exercise depends upon the duration and intensity of exercise and the training status of the participant.…”

Section: Effects Of Acute Exercise On Imclmentioning

confidence: 99%

The effect of diet and exercise on lipid droplet dynamics in human muscle tissue

Daemen

Polanen

Hesselink

2018

Journal of Experimental Biology

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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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“…Boesch et al (2) revealed a decrease of IMCL in one subject performing a mountain bike ride over 3 h at about 70% of VO 2max , for the first time using 1 H-MRS to demonstrate that IMCL are metabolized during this form of exercise. In the following years, numerous reports on reduced IMCL levels during exercise were published and reviewed (17,20,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49). It became obvious that both exercise duration and intensity are important factors in determining the reduction of IMCL (39).…”

Section: Various Other Influences Upon Imcl Levelsmentioning

confidence: 99%

Role of proton MR for the study of muscle lipid metabolism

et al. 2006

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1 H-MR spectroscopy (MRS) of intramyocellular lipids (IMCL) became particularly important when it was recognized that IMCL levels are related to insulin sensitivity. While this relation is rather complex and depends on the training status of the subjects, various other influences such as exercise and diet also influence IMCL concentrations. This may open insight into many metabolic interactions; however, it also requires careful planning of studies in order to control all these confounding influences. This review summarizes various historical, methodological, and practical aspects of 1 H-MR spectroscopy (MRS) of muscular lipids. That includes a differentiation of bulk magnetic susceptibility effects and residual dipolar coupling that can both be observed in MRS of skeletal muscle, yet affecting different metabolites in a specific way. Fitting of the intra-(IMCL) and extramyocellular (EMCL) signals with complex line shapes and the transformation into absolute concentrations is discussed. Since the determination of IMCL in muscle groups with oblique fiber orientation or in obese subjects is still difficult, potential improvement with high-resolution spectroscopic imaging or at higher field strength is considered. Fat selective imaging is presented as a possible alternative to MRS and the potential of multinuclear MRS is discussed. 1 H-MRS of muscle lipids allows non-invasive and repeated studies of muscle metabolism that lead to highly relevant findings in clinics and patho-physiology.

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Intramyocellular triacylglycerol in prolonged cycling with high- and low-carbohydrate availability

Cited by 59 publications

References 44 publications

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

The effect of diet and exercise on lipid droplet dynamics in human muscle tissue

Role of proton MR for the study of muscle lipid metabolism

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