Influence of lipolysis and fatty acid availability on fuel selection during exercise

Abstract

The aim of the present study was to investigate the influence of substrate availability on fuel selection during exercise. Eight endurance-trained male cyclists performed 90-min exercise at 70% of their maximal oxygen uptake in a cross-over design, either in rested condition (CON) or the day after 2-h exercise practised at 70% of maximal oxygen uptake (EX). Subjects were given a sucrose load (0.75 g kg(-1) body weight) 45 min after the beginning of the 90-min exercise test. Lipolysis was measured in subcutaneous abdominal adipose tissue (SCAT) by microdialysis and substrate oxidation by indirect calorimetry. Lipid oxidation increased during exercise and tended to decrease during sucrose ingestion in both conditions. Lipid oxidation was higher during the whole experimental period in the EX group (p = 0.004). Interestingly, fuel selection, assessed by the change in respiratory exchange ratio (RER), was increased in the EX session (p = 0.002). This was paralleled by a higher rate of SCAT lipolysis reflected by dialysate glycerol, plasma glycerol, and fatty acids (FA) levels (p < 0.001). Of note, we observed a significant relationship between whole-body fat oxidation and dialysate glycerol in both sessions (r (2) = 0.33, p = 0.02). In conclusion, this study highlights the limiting role of lipolysis and plasma FA availability to whole-body fat oxidation during exercise in endurance-trained subjects. This study shows that adipose tissue lipolysis is a determinant of fuel selection during exercise in healthy subjects.

Lipid droplet-associated proteins in high-fat fed mice with the effects of voluntary running and diet change

“…With high-intensity exercise, the reliance shifts to plasma glucose and especially to muscle glycogen. (Moro et al 2014;Jeukendrup 2002;Romijn et al 1993.) Thus, physical activity is shown to be one of the most potential remodelers of the lipid metabolism in skeletal muscle.…”

“…During moderate-intensity endurance exercise, fat oxidation is shown to be highest (van Loon et al 2001). During exercise, lipolysis in adipose tissue is stimulated and plasma fatty acid concentrations are elevated (Moro et al 2014). Skeletal muscle fatty acid uptake is accordingly increased through sarcolemmal fatty acid transport and binding proteins (Bonen et al 2007).…”

Lipolytic Markers, Insulin and Resting Fat Oxidation are Associated with Maximal Fat Oxidation

“…By contrast, the significant and positive relationship between plasma glycerol concentration during exercise and MFO remained when controlled for resting plasma glycerol concentration and the exercise-induced change in plasma glycerol was significantly and positively correlated with the exercise-induced change in fat oxidation. Others have recently demonstrated that 33 % of the variation in fat oxidation observed during 90 min of exercise at 70 % V O 2max could be explained by the subcutaneous abdominal adipose tissue dialysate glycerol concentration (as a marker of lipolysis) area under the curve during the exercise period [29]. Additionally, previous studies have reported that changes in lipolytic rate (i. e., rate of appearance of whole-body glycerol) coincide temporally with changes in fat oxidation during exercise [7,22].…”

Effects of adipocyte-secreted factors on decidualized endometrial cells: modulation of endometrial receptivity in vitro

“…Although we cannot completely rule out this possibility, this insulin-resistant and hence sparing phenotype has already been observed when bodily energy demands increase and energetic substrate are to be spared for the brain or skeletal muscle [28,30]. We hypothesize that this observed insulin-resistant phenotype at adipocyte level is a physiological response to save energetic substrates (glucose, fatty acids) and hence increase their availability for the endometrium, which can be preparing for a situation of extra energy expenditure.…”