Systematic Review and Meta-Analysis of Endurance Exercise Training Protocols for Mice

Endurance exercise associated with a fructooligosaccharide diet modulates gut microbiota and increases colon absorptive area

BACKGROUND AND AIM

Fructooligosaccharide (FOS) supplementation can stimulate beneficial intestinal bacteria growth, but little is known about its influence on training performance. Therefore, this study analyzed FOS and exercise effects on gut microbiota and intestinal morphology of C57Bl/6 mice.

METHODS

Forty male mice were divided into four groups: standard diet-sedentary (SDS), standard diet-exercised (SDE), FOS supplemented (7.5% FOS)-sedentary (FDS), and FOS supplemented-exercised (FDE), n = 10 each group. Exercise training consisted of 60 min/day, 3 days/week, for 12 weeks.

RESULTS

SDE and FDE groups had an increase in aerobic performance compared to the pretraining period and SDS and FDS groups (P < 0.01), respectively. Groups with FOS increased colonic crypts size (P < 0.05). The FDE group presented rich microbiota (α-diversity) compared to other groups. The FDE group also acquired a greater microbial abundance (β-diversity) than other groups. The FDE group had a decrease in the Ruminococcaceae (P < 0.002) and an increase in Roseburia (P < 0.003), Enterorhabdus (P < 0.004) and Anaerotruncus (P < 0.006).

CONCLUSIONS

These findings suggest that aerobic exercise associated with FOS supplementation modulates gut microbiota and can increase colonic crypt size without improving endurance exercise performance.

Aerobic exercise training mitigates tumor growth and cancer-induced splenomegaly through modulation of non-platelet platelet factor 4 expression

Exercise training reduces the incidence of several cancers, but the mechanisms underlying these effects are not fully understood. Exercise training can affect the spleen function, which controls the hematopoiesis and immune response. Analyzing different cancer models, we identified that 4T1, LLC, and CT26 tumor-bearing mice displayed enlarged spleen (splenomegaly), and exercise training reduced spleen mass toward control levels in two of these models (LLC and CT26). Exercise training also slowed tumor growth in melanoma B16F10, colon tumor 26 (CT26), and Lewis lung carcinoma (LLC) tumor-bearing mice, with minor effects in mammary carcinoma 4T1, MDA-MB-231, and MMTV-PyMT mice. In silico analyses using transcriptome profiles derived from these models revealed that platelet factor 4 (Pf4) is one of the main upregulated genes associated with splenomegaly during cancer progression. To understand whether exercise training would modulate the expression of these genes in the tumor and spleen, we investigated particularly the CT26 model, which displayed splenomegaly and had a clear response to the exercise training effects. RT-qPCR analysis confirmed that trained CT26 tumor-bearing mice had decreased Pf4 mRNA levels in both the tumor and spleen when compared to untrained CT26 tumor-bearing mice. Furthermore, exercise training specifically decreased Pf4 mRNA levels in the CT26 tumor cells. Aspirin treatment did not change tumor growth, splenomegaly, and tumor Pf4 mRNA levels, confirming that exercise decreased non-platelet Pf4 mRNA levels. Finally, tumor Pf4 mRNA levels are deregulated in The Cancer Genome Atlas Program (TCGA) samples and predict survival in multiple cancer types. This highlights the potential therapeutic value of exercise as a complementary approach to cancer treatment and underscores the importance of understanding the exercise-induced transcriptional changes in the spleen for the development of novel cancer therapies.

Aged gastrocnemius muscle of mice positively responds to a late onset adapted physical training

Introduction: A regular physical training is known to contribute to preserve muscle mass and strength, maintaining structure and function of neural and vascular compartments and preventing muscle insulin resistance and inflammation. However, physical activity is progressively reduced during aging causing mobility limitations and poor quality of life. Although physical exercise for rehabilitation purposes (e.g., after fractures or cardiovascular events) or simply aiming to counteract the development of sarcopenia is frequently advised by physicians, nevertheless few data are available on the targets and the global effects on the muscle organ of adapted exercise especially if started at old age. Methods: To contribute answering this question for medical translational purposes, the proteomic profile of the gastrocnemius muscle was analyzed in 24-month-old mice undergoing adapted physical training on a treadmill for 12 weeks or kept under a sedentary lifestyle condition. Proteomic data were implemented by morphological and morphometrical ultrastructural evaluations. Results and Discussion: Data demonstrate that muscles can respond to adapted physical training started at old age, positively modulating their morphology and the proteomic profile fostering protective and saving mechanisms either involving the extracellular compartment as well as muscle cell components and pathways (i.e., mitochondrial processes, cytoplasmic translation pathways, chaperone-dependent protein refolding, regulation of skeletal muscle contraction). Therefore, this study provides important insights on the targets of adapted physical training, which can be regarded as suitable benchmarks for future in vivo studies further exploring the effects of this type of physical activity by functional/metabolic approaches.

Moderate Effects of Hypoxic Training at Low and Supramaximal Intensities on Skeletal Muscle Metabolic Gene Expression in Mice

The muscle molecular adaptations to different exercise intensities in combination with hypoxia are not well understood. This study investigated the effect of low- and supramaximal-intensity hypoxic training on muscle metabolic gene expression in mice. C57BL/6 mice were divided into two groups: sedentary and training. Training consisted of 4 weeks at low or supramaximal intensity, either in normoxia or hypoxia (FiO2 = 0.13). The expression levels of genes involved in the hypoxia signaling pathway (Hif1a and Vegfa), the metabolism of glucose (Gys1, Glut4, Hk2, Pfk, and Pkm1), lactate (Ldha, Mct1, Mct4, Pdh, and Pdk4) and lipid (Cd36, Fabp3, Ucp2, Hsl, and Mcad), and mitochondrial energy metabolism and biogenesis (mtNd1, mtNd6, CytC, CytB, Pgc1a, Pgc1β, Nrf1, Tfam, and Cs) were determined in the gastrocnemius muscle. No physical performance improvement was observed between groups. In normoxia, supramaximal intensity training caused upregulation of major genes involved in the transport of glucose and lactate, fatty acid oxidation, and mitochondrial biogenesis, while low intensity training had a minor effect. The exposure to hypoxia changed the expression of some genes in the sedentary mice but had a moderate effect in trained mice compared to respective normoxic mice. In hypoxic groups, low-intensity training increased the mRNA levels of Mcad and Cs, while supramaximal intensity training decreased the mRNA levels of Mct1 and Mct4. The results indicate that hypoxic training, regardless of exercise intensity, has a moderate effect on muscle metabolic gene expression in healthy mice.

Exercise ameliorates skeletal muscle insulin resistance by modulating GRK4-mediated D1R expression

Exercise has been recommended as a nonpharmaceutical therapy to treat insulin resistance (IR). Previous studies showed that dopamine D1-like receptor agonists, such as fenoldopam, could improve peripheral insulin sensitivity, while antipsychotics, which are dopamine receptor antagonists, increased susceptibility to Type 2 diabetes mellitus (T2DM). Meanwhile, exercise has been proved to stimulate dopamine receptors. However, whether the dopamine D1 receptor (D1R) is involved in exercise-mediated amelioration of IR remains unclear. We found that the D1-like receptor antagonist, SCH23390, reduced the effect of exercise on lowering blood glucose and insulin in insulin-resistant mice and inhibited the contraction-induced glucose uptake in C2C12 myotubes. Similarly, the opposite was true for the D1-like receptor agonist, fenoldopam. Furthermore, the expression of D1R was decreased in skeletal muscles from streptozotocin (STZ)- and high-fat intake-induced T2DM mice, accompanied by increased D1R phosphorylation, which was reversed by exercise. A screening study showed that G protein-coupled receptor kinase 4 (GRK4) may be the candidate kinase for the regulation of D1R function, because, in addition to the increased GRK4 expression in skeletal muscles of T2DM mice, GRK4 transgenic T2DM mice exhibited lower insulin sensitivity, accompanied by higher D1R phosphorylation than control mice, whereas the AAV9-shGRK4 mice were much more sensitive to insulin than AAV9-null mice. Mechanistically, the up-regulation of GRK4 expression caused by increased reactive oxygen species (ROS) in IR was ascribed to the enhanced expression of c-Myc, a transcriptional factor of GRK4. Taken together, the present study shows that exercise, via regulation of ROS/c-Myc/GRK4 pathway, ameliorates D1R dysfunction and improves insulin sensitivity.

Effects of prebiotics on intestinal physiology, neuropsychological function, and exercise capacity of mice with sleep deprivation

People suffered from insufficient or disrupted sleep due to night shifts, work pressure, and irregular lifestyles. Sleep deprivation caused by inadequate quantity or quality of sleep has been associated with not only increased risk of metabolic diseases, gut dysbiosis, and emotional disorders but also decreased work and exercise performance. In this study, we used the modified multiple platform method (MMPM) to induce pathological and psychological characteristics of sleep deprivation with C57BL/6J male mice, and investigated whether supplementing a prebiotics mixture of short-chain galactooligosaccharides (scGOS) and long-chain fructooligosaccharides (lcFOS) (9:1 ratio) could improve the impacts of sleep deprivation on intestinal physiology, neuropsychological function, inflammation, circadian rhythm, and exercise capacity. Results showed that sleep deprivation caused intestinal inflammation (increased TNFA and IL1B) and decreased intestinal permeability with a significant decrease in the tight junction genes (OCLN, CLDN1, TJP1, and TJP2) of intestine and brain. The prebiotics significantly increased the content of metabolite short-chain fatty acids (acetate and butyrate) while recovering the expression of indicated tight junction genes. In hypothalamus and hippocampus, clock (BMAL1 and CLOCK) and tight junction (OCLN and TJP2) genes were improved by prebiotics, and corticotropin-releasing hormone receptor genes, CRF1 and CRF2, were also significantly regulated for mitigation of depression and anxiety caused by sleep deprivation. Also, prebiotics brought significant benefits on blood sugar homeostasis and improvement of exercise performance. Functional prebiotics could improve physiological modulation, neuropsychological behaviors, and exercise performance caused by sleep deprivation, possibly through regulation of inflammation and circadian rhythm for health maintenance. However, the microbiota affected by prebiotics and sleep deprivation should warrant further investigation.

Antioxidant Molecular Brain Changes Parallel Adaptive Cardiovascular Response to Forced Running in Mice

Physically active lifestyle has huge implications for the health and well-being of people of all ages. However, excessive training can lead to severe cardiovascular events such as heart fibrosis and arrhythmia. In addition, strenuous exercise may impair brain plasticity. Here we investigate the presence of any deleterious effects induced by chronic high-intensity exercise, although not reaching exhaustion. We analyzed cardiovascular, cognitive, and cerebral molecular changes in young adult male mice submitted to treadmill running for eight weeks at moderate or high-intensity regimens compared to sedentary mice. Exercised mice showed decreased weight gain, which was significant for the high-intensity group. Exercised mice showed cardiac hypertrophy but with no signs of hemodynamic overload. No morphological changes in the descending aorta were observed, either. High-intensity training induced a decrease in heart rate and an increase in motor skills. However, it did not impair recognition or spatial memory, and, accordingly, the expression of hippocampal and cerebral cortical neuroplasticity markers was maintained. Interestingly, proteasome enzymatic activity increased in the cerebral cortex of all trained mice, and catalase expression was significantly increased in the high-intensity group; both first-line mechanisms contribute to maintaining redox homeostasis. Therefore, physical exercise at an intensity that induces adaptive cardiovascular changes parallels increases in antioxidant defenses to prevent brain damage.

Animal Models of Exercise From Rodents to Pythons

Acute and chronic animal models of exercise are commonly used in research. Acute exercise testing is used, often in combination with genetic, pharmacological, or other manipulations, to study the impact of these manipulations on the cardiovascular response to exercise and to detect impairments or improvements in cardiovascular function that may not be evident at rest. Chronic exercise conditioning models are used to study the cardiac phenotypic response to regular exercise training and as a platform for discovery of novel pathways mediating cardiovascular benefits conferred by exercise conditioning that could be exploited therapeutically. The cardiovascular benefits of exercise are well established, and, frequently, molecular manipulations that mimic the pathway changes induced by exercise recapitulate at least some of its benefits. This review discusses approaches for assessing cardiovascular function during an acute exercise challenge in rodents, as well as practical and conceptual considerations in the use of common rodent exercise conditioning models. The case for studying feeding in the Burmese python as a model for exercise-like physiological adaptation is also explored.