Blood lactate increases during incremental exercise at high-intensity workloads, and limited exercise capacity is a characteristic of obese animals. This study examined whether blood lactate changes in response to incremental exercise is disrupted in obese animals. Muscular and hepatic proteins that are critical in lactate metabolism were also investigated. Rats were randomized to either standard chow (control) or high-fat diet (HFD) groups. All animals underwent an incremental treadmill test after 14 wk of diet intervention. Blood lactate levels were measured before and after the treadmill test. Activities of mitochondrial oxidative phosphorylation and glycolysis were examined in muscle tissues. Proteins in the liver and skeletal muscles that participate in the turnover of blood lactate were determined by Western blot. Running time in the incremental treadmill test decreased in the HFD group, and blood lactate accumulated faster in these animals than in the control group. Animals with HFD had a decreased level of hepatic monocarboxylate transporter 2, the protein responsible for blood lactate uptake in the liver. Skeletal muscles of animals with HFD showed greater glycolytic activity and decreased content of lactate dehydrogenase B, which converts lactate to pyruvate. We conclude that blood lactate accumulated faster during incremental exercise in obese animals and was associated with their decreased exercise performance. Changes in the metabolic pattern of muscles and changes of liver and muscle proteins associated with lactate utilization likely contribute to the abnormal response of blood lactate to incremental exercise in obese animals.
This study explored the effects of exercise with either high cognitive load or low cognitive load on cognitive performance and neuroplasticity in healthy elderly. Twenty-eight sedentary community-dwelling seniors participated in this study. Participants were assigned to one of three groups: the control group (C), low-cognitive load exercise group (LE), or high-cognitive load exercise group (HE). Individuals in both exercise groups engaged in moderate-intensity aerobic exercise for 4 months. Resting-state functional MRI and diffusion MRI were used to investigate the effects of intervention on functional and structural connectivity, respectively. Analysis of covariance with baseline, age and the education year as covariates was used to determine the effects of intervention. We found 4 months of exercise with high-cognitive load, but not exercise with low-cognitive load, improved the overall cognitive function of healthy elderly. Additionally, the HE group showed increased resting-state functional connectivity of superior frontal gyrus and anterior cingulate cortex and decreased functional connectivity of middle occipital gyrus and postcentral gyrus. The age-related alterations in local efficiency and betweenness were protected by exercise. Our findings might suggest that exercise with greater cognitive load likely results in greater training effects on cognition and brain connectivity than exercise requiring lower cognitive loads for healthy elderly.
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