Proceedings of The Physiological Society

University College Dublin (2009) Proc Physiol Soc 15, C8

Oral Communications

The maximal rate of lipids oxidation is strain dependant and corrrelated with performance in running mice

L. Mille-Hamard1, E. Henry1, V. L. Billat1

1. Universite Evry-Val d'Essonne, UBIAE INSERM U902, Evry, France.

In mice model, the most currently exercise performance criteria used in running is the maximal running speed (Vpeak) and is considered as an aerobic index (Hoydal et al, 2007), Furthermore links between performance and the lipid metabolism was not explored in mice, despite the fact that the maximal rate of lipid oxidation (Lipox max) has been reported to be a major performance factor and to be training sensitive in man (Brooks and Mercier, 1994, Jeukendrup and Wallis, 2005). Therefore, the purpose of this study is to test the hypothesis that the lipids metabolism and also the anaerobic metabolism, between vVO2max and Vpeak are, as VO2max, consistent performance factors and could be highly heritable, explaining the high performance difference according the mice strains (Lightfoot et al., 2001). Seven FVB (high performer strain) and 7 C57BL6 (low performer) ran an incremental exhaustive run on treadmill in a metabolic chamber until maximal speed (Vpeak) which was taken as the performance criteria. The respiratory gaz exchange (RER) allowed determination of Lipox max and the associated speed (Vlipox) We found that VO2 increased rapidly and significantly at the beginning of the exercise with incresing speed, but VO2 plateaued early until the end of the exercise (51.7 ± 3.4 vs 48.1 ± 3.2 , in FVB and C57 p=0.07). Vpeak was significantly higher than vVO2max in FVB vs. C57 (167±25 vs. 135±44% of vVO2max, p = 0.011). The Vpeak (rI = 0.72, g2 = 0.56), Lipox max (rI = 0.53, g2 = 0.36) and the cross over speeds (rI = 0.83, g2 = 0.71) were highly heritable in constrast with VO2max ( rI = 0.30 g2 = 0.18) and the Accumula ted Oxygen Deficit (AOD) (rI=0.11 g2 = 0.05). However, the anaerobic metabolism, estimated with the AOD, was a consistent factor of performance. Furthermore Lipox max (r = 0.80, p = 0.0006) was highly related with the performance (vPeak) while VO2max (r = 0.57, p = 0.04) and AOD (r = 0.56, p = 0.04) were moderately. Thus the use of Vpeak for aerobic capacity assessment can not be performed independently of the strain and the anaerobic capacity is then a factor of performance eventhought AOD was not heritable. Indeed, at end exercise, RER was higher for the FVB strain, indicating a greater part of glucose oxidation, and a relative higher metabolism sollicitation for this strain. In constrasts with human model, in both strain, the mice had a high Vlipox set between vVO2max and Vpeak. This means that the mice do not rely to the aerobic glycogen metabolism but rather on the lipids and the anaerobic metabolism (glycolysis and phosphagene) (Craig et al., 1995, Pederson et al., 2005). In conclusion, this study demonstrated, for the first time, that the lipid metabolism was not only a consistent performance factor but were also highly heritable, and must also be determined when evaluating aerobic performance in mice.

Where applicable, experiments conform with Society ethical requirements