Maximum aerobic performance in lines of Mus selected for high wheel-running activity: effects of selection, oxygen availability and the mini-muscle phenotype.

Department of Biology, University of California, Riverside, CA 92521, USA.
Journal of Experimental Biology (Impact Factor: 3). 02/2006; 209(Pt 1):115-27. DOI: 10.1242/jeb.01883
Source: PubMed

ABSTRACT We compared maximum aerobic capacity during forced exercise (VO2max) in hypoxia (PO2=14% O2), normoxia (21%) and hyperoxia (30%) of lines of house mice selectively bred for high voluntary wheel running (S lines) with their four unselected control (C) lines. We also tested for pleiotropic effects of the ;mighty mini-muscle' allele, a Mendelian recessive that causes a 50% reduction in hind limb muscle but a doubling of mass-specific aerobic enzyme activity, among other pleiotropic effects. VO2max of female mice was measured during forced exercise on a motorized treadmill enclosed in a metabolic chamber that allowed altered PO2. Individual variation in VO2max was highly repeatable within each PO2, and values were also significantly correlated across PO2. Analysis of covariance showed that S mice had higher body-mass-adjusted VO2max than C at all PO2, ranging from +10.7% in hypoxia to +20.8% in hyperoxia. VO2max of S lines increased practically linearly with PO2, whereas that of C lines plateaued from normoxia to hyperoxia, and respiratory exchange ratio (=CO2 production/VO2max) was lower for S lines. These results suggest that the physiological underpinnings of VO2max differ between the S and C lines. Apparently, at least in S lines, peripheral tissues may sustain higher rates of oxidative metabolism if central organs provide more O2. Although the existence of central limitations in S lines cannot be excluded based solely on the present data, we have previously reported that both S and C lines can attain considerably higher VO2max during cold exposure in a He-O2 atmosphere, suggesting that limitations on VO2max depend on interactions between the central and peripheral organs involved. In addition, mini-muscle individuals had higher VO2max than did those with normal muscles, suggesting that the former might have higher hypoxia tolerance. This would imply that the mini-muscle phenotype could be a good model to test how exercise performance and hypoxia tolerance could evolve in a correlated fashion, as previous researchers have suggested.

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Available from: Theodore Garland, Aug 13, 2015
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    • ". The speed was increased by 15 cm s −1 every 45 s until the mice were unable to maintain the effort level (Rezende et al. 2006). "
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    • "Selection criterion/ method/species BMR response Correlated traits Trait response Reference Mass-corrected BMR/ indirect calorimetry/ laboratory mice (Mus musculus) Increase Food consumption Increase Ksia ˛ _ zek et al. (2009) Voluntary activity Increase Ge ˛bczyn´ski and Konarzewski (2009) VO 2max (treadmill) No change VO 2max (swim elicited) Decrease Ksia ˛ _ zek et al. (2004) Brze ˛k et al. (2007) Core body temperature No change Ge ˛bczyn´ski (2008) Brze ˛k et al. (2012) Mass of heart, liver, kidney, small intestine Increase Ksia ˛ _ zek et al. (2004) Ge ˛bczyn´ski and Konarzewski (2011) Fat mass Decrease Ksia ˛ _ zek et al. (2004) BAT mass Decrease Erythrocyte size Decrease Maciak et al. (2011) Immune response (SRBC) Decrease Ksia ˛ _ zek et al. (2003) Immune response (KLH) Increase Ksia ˛ _ zek and Konarzewski (2012) Mass of spleen and lymph nodes Increase Thymus mass Decrease Oxidative enzyme capacity Increase Ksia ˛ _ zek et al. (2009) Unsaturation index of cell membranes Decrease Brze ˛k et al. (2007) Mass-corrected food intake/ laboratory mice (Mus musculus) Increase Digestive efficiency Increase Hastings et al. (1997) Fat mass Decrease Bunger et al. (1998) Core body temperature No change Hambly et al. (2005) Liver mass (dry) Increase Small intestine length (fresh) Increase Small intestine mass (dry) No change Selman et al. (2001a, b) Large intestine mass (dry) Decrease Pancreas mass (dry) No change Stomach mass (dry) Increase Kidneys mass (dry) No change Heart mass (dry) Increase Lung mass (dry) No change Brain mass (dry) Increase Thyroid mass (dry) Decrease Spleen mass (dry) No change Heat loss/(body mass) 0.75 /direct calorimetry/laboratory mice (Mus musculus) Not measured Food consumption Increase Nielsen et al. (1997b) Voluntary locomotor activity Increase Nielsen et al. (1997a) Mass of liver, heart, spleen Increase Moody et al. (1999) Core body temperature Increase Mousel et al. (2001) T4 level Decrease Kgwatalala and Nielsen (2004) T3 level No change Corticosterone level Increase Expression of UCP-1 Decrease McDaneld et al. (2002) Table 1 continued Selection criterion/ method/species BMR response Correlated traits Trait response Reference Mass-corrected VO 2max / swimming/laboratory mice (Mus musculus) No change Heart mass Increase Ge ˛bczyn´ski and Konarzewski (2009) Mass of liver, kidney, small intestine No change Mass of gastrocnemius Increase Aerobic endurance capacity/ treadmill running/rats (Rattus norvegicus) Not measured Body mass Decrease Koch and Britton (2001) Fat mass Decrease Kirkton et al. (2009) VO 2max Increase Henderson et al. (2002) Mass of heart, lung, liver, kidney, stomach Increase Swallow et al. (2010) Cardiac output Increase Pulmonary function Increase Howlett et al. (2003) Oxidative enzyme capacity Increase Left ventricular cells systolic and diastolic function Increase Small intestine length Decrease Wislöff et al. (2005) Capillary density Increase Henderson et al. (2002) Mitochondrial biogenesis Increase Gonzales et al. (2006) Oxidative enzyme capacity Increase Wislöff et al. (2005) Voluntary locomotor activity/daily wheel running activity/laboratory mice (Mus musculus) No change VO 2max Increase Swallow et al. (1998) Rezende et al. (2006a, b, c) Kane et al. (2008) "
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