The effect of aerobic exercise on intrahepatocellular and intramyocellular lipids in healthy subjects - PubMed (original) (raw)
Clinical Trial
The effect of aerobic exercise on intrahepatocellular and intramyocellular lipids in healthy subjects
Andrea Egger et al. PLoS One. 2013.
Abstract
Background: Intrahepatocellular (IHCL) and intramyocellular (IMCL) lipids are ectopic lipid stores. Aerobic exercise results in IMCL utilization in subjects over a broad range of exercise capacity. IMCL and IHCL have been related to impaired insulin action at the skeletal muscle and hepatic level, respectively. The acute effect of aerobic exercise on IHCL is unknown. Possible regulatory factors include exercise capacity, insulin sensitivity and fat availability subcutaneous and visceral fat mass).
Aim: To concomitantly investigate the effect of aerobic exercise on IHCL and IMCL in healthy subjects, using Magnetic Resonance spectroscopy.
Methods: Normal weight, healthy subjects were included. Visit 1 consisted of a determination of VO2max on a treadmill. Visit 2 comprised the assessment of hepatic and peripheral insulin sensitivity by a two-step hyperinsulinaemic euglycaemic clamp. At Visit 3, subcutaneous and visceral fat mass were assessed by whole body MRI, IHCL and IMCL before and after a 2-hours aerobic exercise (50% of VO(2max)) using ¹H-MR-spectroscopy.
Results: Eighteen volunteers (12M, 6F) were enrolled in the study (age, 37.6±3.2 years, mean±SEM; VO(2max), 53.4±2.9 mL/kg/min). Two hours aerobic exercise resulted in a significant decrease in IMCL (-22.6±3.3, % from baseline) and increase in IHCL (+34.9±7.6, % from baseline). There was no significant correlation between the exercise-induced changes in IMCL and IHCL and exercise capacity, subcutaneous and visceral fat mass and hepatic or peripheral insulin sensitivity.
Conclusions: IMCL and IHCL are flexible ectopic lipid stores that are acutely influenced by physical exercise, albeit in different directions.
Trial registration: ClinicalTrial.gov NCT00491582.
Conflict of interest statement
Competing Interests: The authors have declared that no competing interests exist.
Figures
Figure 1. Flow sheet of patients, intervention and analysis.
Flow sheet of enrolled patients, intervention and analysis of data. IMCL = intramyocellular lipids.
Figure 2. Study protocol.
The clinical protocol included three visits and two periods. Period 1: weight maintaining diet, period 2: no physical activity, high fat diet (as additional fat snacks, 0.75 g fat/kgBW for 1.5 days prior to visit 3). Visit 1 Spiroergometry (calculation of 50% VO2max, trial on the treadmill). Visit 2 Two-step hyperinsulinaemic euglycaemic clamp using stable isotope technique. Visit 3 Assessment of intramyocellular (IMCL) and intrahepatocellular lipids (IHCL) before and after two hours aerobic exercise at 50% VO2max. Measurements of subcutaneous and visceral fat mass using MRI imaging.
Figure 3. Effect of aerobic exercise on intramyocellular (IMCL) and intrahepatocellular lipids (IHCL).
**Figure 3a Individual IMCL and IHCL measurements before (pre) and after (post) a 2h-aerobic exercise at 50% VO2max of each subject. A significant decrease in IMCL (p<0.005) and a significant increase in IHCL (p<0.002) was documented. The diagram on the far right is a blow up of the IHCL data depicted in the middle part to show the changes in IHCL for volunteers with low IHCL levels. Figure 3b Changes (mean ± 1 SEM) of IMCL and IHCL (in % from baseline) following a 2h-aerobic exercise at 50% VO2max.
Figure 4. Effect of aerobic exercise on serum free fatty acid concentrations.
Individual (left) and overall (mean ± 1 SEM) levels of circulating FFA during the course of the 2 h-aerobic exercise at 50% VO2max.
References
- Boesch C, Machann J, Vermathen P, Schick F (2006) Role of proton MR for the study of muscle lipid metabolism. NMR Biomed 19: 968–988. - PubMed
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