Effect of diet on the replenishment of intramyocellular lipids after exercise.
BACKGROUND
Muscle triglycerides are important as a source of energy and in relation to metabolic sensitivity. However, the classic biopsy method does not distinguish intra- from extracellular fat, and their regulation by exercise and diet is largely unknown. Magnetic resonance spectroscopy (MRS) is available to assess the intramyocellular lipid (IMCL) pool non-invasively in humans.


OBJECTIVE
The aim of this work was to use sequential MRS measurements of IMCL and glycogen to explore the role of three levels of dietary fat on the replenishment of these energy stores after exercise.


METHODS
Following 2 h of exercise, two subjects (S1, S2) were fed one of three diets (15%, 40% or 70% fat energy), each on a separate occasion. IMCL and glycogen were measured by MRS in the tibialis anterior muscle before, after exercise, and at 10 and at 32 h of recovery.


RESULTS
Initial IMCL concentration (mmol.kg-1: 3.0 in S1 and 1.8 in S2) was reduced to 70% after exercise. The rate of replenishment was minimal with the low-fat (mmol.kg-1.24 h-1: 0.7 and 0.0) and much higher with both higher fat diets (mmol.kg-1.24 h-1: 3.1 and 3.2 in S1, 0.7 and 0.9 in S2). Glycogen and IMCL replenishments were inversely correlated.


CONCLUSIONS
IMCL and glycogen can vary acutely in response to diet after exercise. Studies are needed to determine if such variations occur within the range of ordinary diets and to clarify the functional significance of IMCL in differently active individuals.
Décombaz
J
J
Department of Clinical Research, MR-Spectroscopy and Methodology, MR-Center 1, University and Inselspital, 3010 Bern, Switzerland.
Fleith
M
M
Hoppeler
H
H
Kreis
R
R
Boesch
C
C
D000328:Adult; D002247:Carbon Isotopes; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*
D002247:Carbon Isotopes; D004041:Dietary Fats; D008055:Lipids; D006003:Glycogen