Fat _max as an index of aerobic exercise performance in mice during uphill running - Fig 2

<p><b>Vo</b>_<b>2</b><b>at increasing running speed while running at inclinations of 20 (A), 30 (B), 40 (C), and 50</b>° <b>(D) in training and sedentary mice (n = 6).</b> The trained mice were housed in cages with a running saucer for 8 weeks. The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Individual data are shown (n = 6).</p

Physiological parameters of training and sedentary group.

<p>Physiological parameters of training and sedentary group.</p

Fat _max as an index of aerobic exercise performance in mice during uphill running - Fig 5

<p><b>Comparison between running time until the exercise intensity that elicits maximum fat oxidation (Fat</b>_<b>max</b><b>, A) and running time until</b> Vo_{2 peak} <b>(B).</b> The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Values are mean ± SD (n = 6). *P < 0.05, ** P<0.01, and *** P<0.001 between training and sedentary groups. † P < 0.05 compared to the corresponding value at 20°.</p

Fat _max as an index of aerobic exercise performance in mice during uphill running - Fig 4

<p><b>Comparison between running speed at the exercise intensity that elicits maximum fat oxidation (Fat</b>_<b>max,</b><b>A) and running speed</b> at Vo_{2 peak} <b>(B).</b> The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Values are mean ± SD (n = 6). *P < 0.05 compared as 0° of inclination. * P< 0.05, ** P<0.01, and *** P<0.001 between training and sedentary groups. † P < 0.05 compared to the corresponding value at 20°.</p

Fat _max as an index of aerobic exercise performance in mice during uphill running - Fig 1

<p><b>Representative changes in Vo</b>_<b>2</b><b>and fat oxidation while running and at inclinations of 40</b>° <b>of training (A) and sedentary (B) mice (n = 6).</b> Vo_{2 peak} is the maximum Vo₂ observed while running. Fat_max is the exercise intensity that elicits maximum fat oxidation. Vo₂ at Fat_max is the observed Vo₂ at the exercise intensity of Fat_max. The treadmill velocity was as follows: 0–5 min, 5 m/min; 5–10 min, 10 m/min; and then increased by 1 m/min every 30 seconds. Each running experiment at different inclinations was conducted at intervals of one day or more. Values are means ± SD (n = 6).</p

Reproducibility of Vo₂ during submaximal running_, Vo_{2 peak,} and Vo₂ at Fat_max during running at an inclination of 40°.

<p>Each mouse ran two times at intervals of one day. The running protocol is described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Linear correlations were analyzed between two tests. CV, coefficient of variation. Individual data are shown (n = 15).</p

Correlations among Vo₂ at Fat_max, Vo2 _peak, running time until fatigue, and plasma lactic acid concentration during running at an inclination of 40°.

<p>The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Linear correlations were analyzed between Vo_{2 peak} and Vo₂ at Fat_max (A), between Vo₂ at Fat_max and plasma lactic acid concentration (B), between Vo_{2 peak} and running time until Vo_{2 peak} (C), and between Vo₂ at Fat_max and running time until fatigue (D). Plasma lactic acid concentration was measured during running at a speed of 24 m/min at the inclination of 40° as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g006" target="_blank">Fig 6</a>. The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Individual data are shown (n = 12).</p

Blood lactate concentration during submaximal running.

<p>The running protocol was described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193470#pone.0193470.g001" target="_blank">Fig 1</a>. Running speed of 18 m/min corresponded to the Fat_max of sedentary group and running speed of 24 m/min corresponded to the half speed of Fat_max of sedentary and training group. Values are mean ± SD (n = 6). †P < 0.05 compared to the corresponding resting value. *P< 0.05, and ***P<0.001 between training and sedentary groups.</p

Fat _max as an index of aerobic exercise performance in mice during uphill running

<div><p>Endurance exercise performance has been used as a representative index in experimental animal models in the field of health sciences, exercise physiology, comparative physiology, food function or nutritional physiology. The objective of the present study was to evaluate the effectiveness of Fat_max (the exercise intensity that elicits maximal fat oxidation) as an additional index of endurance exercise performance that can be measured during running at submaximal exercise intensity in mice. We measured both Fat_max and Vo_{2 peak} of trained ICR mice that voluntary exercised for 8 weeks and compared them with a sedentary group of mice at multiple inclinations of 20, 30, 40, and 50° on a treadmill. The Vo₂ at Fat_max of the training group was significantly higher than that of the sedentary group at inclinations of 30 and 40° (P < 0.001). The running speed at Fat_max of the training group was significantly higher than that of the sedentary group at inclinations of 20, 30, and 40° (P < 0.05). Blood lactate levels sharply increased in the sedentary group (7.33 ± 2.58 mM) compared to the training group (3.13 ± 1.00 mM, P < 0.01) when running speeds exceeded the Fat_max of sedentary mice. Vo₂ at Fat_max significantly correlated to Vo_{2 peak}, running time to fatigue, and lactic acid level during running (P < 0.05) although the reproducibility of Vo_{2 peak} was higher than that of Vo₂ at Fat_max. In conclusion, Fat_max can be used as a functional assessment of the endurance exercise performance of mice during submaximal exercise intensity.</p></div

Endurance performance and energy metabolism during exercise in mice with a muscle-specific defect in the control of branched-chain amino acid catabolism

<div><p>It is known that the catabolism of branched-chain amino acids (BCAAs) in skeletal muscle is suppressed under normal and sedentary conditions but is promoted by exercise. BCAA catabolism in muscle tissues is regulated by the branched-chain α-keto acid (BCKA) dehydrogenase complex, which is inactivated by phosphorylation by BCKA dehydrogenase kinase (BDK). In the present study, we used muscle-specific BDK deficient mice (BDK-mKO mice) to examine the effect of uncontrolled BCAA catabolism on endurance exercise performance and skeletal muscle energy metabolism. Untrained control and BDK-mKO mice showed the same performance; however, the endurance performance enhanced by 2 weeks of running training was somewhat, but significantly less in BDK-mKO mice than in control mice. Skeletal muscle of BDK-mKO mice had low levels of glycogen. Metabolome analysis showed that BCAA catabolism was greatly enhanced in the muscle of BDK-mKO mice and produced branched-chain acyl-carnitine, which induced perturbation of energy metabolism in the muscle. These results suggest that the tight regulation of BCAA catabolism in muscles is important for homeostasis of muscle energy metabolism and, at least in part, for adaptation to exercise training.</p></div