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New Findings r What is the central question of this study?Clinical studies suggest that obesity 'protects' against osteoporosis. However, these studies used only bone densitometry and assessed only one bone site, which is insufficient to enable conclusions to be drawn about the response of the whole skeleton. Furthermore, the effects of exercise on bone responses in obesity have not been explored previously. r What is the main finding and what is its importance?We show that obesity causes osteopetrosis. Therefore, the classical perspective of 'protective effects of obesity' needs to be reviewed, and exercise is an important tool to avoid these alterations and to maintain the homeostasis of bone.A sedentary lifestyle and obesity induce systemic inflammatory responses. Although the effects of physical inactivity on osseous tissue have been well established, the effects of obesity on bone tissue remain controversial. Furthermore, the effects of physical training on bone tissue responses in the presence of diet-induced obesity are unknown. Our aim was to investigate the effects of obesity and physical training at multiple bone sites in rats. Female Wistar rats were divided into the following four groups: (i) control diet, non-trained (C-NT); (ii) high-refined carbohydrate-containing diet, non-trained (HC-NT); (iii) control diet, trained (C-T); and (iv) high-refined carbohydrate-containing diet, trained (HC-T). At 5 months of age, the rats were submitted to daily exercise for 30 min day −1 . After 13 weeks, blood samples, adipose and skeletal tissues were harvested. Two-way ANOVA was applied to detect differences (significance accepted when P ࣘ 0.05). The HC-NT group exhibited increased body mass, adiposity, serum leptin, serum insulin, insulin resistance index and concentrations of tumour necrosis factor-α and interleukin-6. Obese rats (HC-NT) exhibited thickening of nasal bones, trabecular bones in the lumbar vertebrae and long bones in a site-dependent manner. The HC-T group exhibited similar adiposity and inflammatory results. Morphological analysis of the lumbar vertebrae in rats fed the HC diet revealed characteristics of osteopetrosis that were inhibited by exercise. In conclusion, the HC diet induced obesity and inflammatory/hormonal alterations and increased the trabecular bone in a site-dependent manner. However, obesity caused osteopetrosis in the lumbar vertebrae, which could be inhibited by physical training. Although exercise inhibited the

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Obesity is associated with an energy imbalance that results from excessive energy intake, low diet quality, and a sedentary lifestyle. The increased consumption of a high-refined carbohydrate (HC) diet is strongly related to higher adiposity and low-grade inflammation. Aerobic training is a well-known nonpharmacological intervention to treat obesity and metabolic disturbances. However, the mechanisms through which aerobic training ameliorates the low-grade inflammation induced by an HC diet should be further investigated. Our hypothesis herein was that aerobic training would decrease the recruitment of leukocytes in adipose tissue, thereby reducing the levels of cytokines and improving metabolism in mice fed an HC diet. Male Balb/c mice were assigned to the following groups: control diet/nontrained (C-NT), control diet/trained (C-T), high-refined carbohydrate diet/nontrained (HC-NT), and high-refined carbohydrate diet/trained (HC-T). Mice were submitted to moderate-intensity training sessions that consisted of running 60 min per day for 8 weeks. An intravital microscopy technique was performed in vivo in anesthetized mice to visualize the microvasculature of the adipose tissue. The HC diet induced obesity and increased the influx of immune cells into the adipose tissue. In contrast, HC-T mice presented a lower adiposity and adipocyte area. Furthermore, relative to HC-NT mice, HC-T mice showed increased resting energy expenditure, decreased recruitment of immune cells in the adipose tissue, reduced cytokine levels, and ameliorated hyperglycemia and fatty liver deposition. Collectively, our data enhance understanding about the anti-inflammatory effect of aerobic training and shed light on the adipose tissue-mediated mechanisms by which training promotes a healthier metabolic profile.

Background & Aims The precise determination of non-alcoholic fatty liver disease (NAFLD) onset is challenging. Thus, the initial hepatic responses to fat accumulation, which may be fundamental to our understanding of NAFLD evolution and clinical outcomes, are largely unknown. Herein, we chronologically mapped the immunologic and metabolic changes in the liver during the early stages of fatty liver disease in mice and compared this with human NAFLD samples. Methods Liver biopsies from patients with NAFLD (NAFLD activity score [NAS] 2–3) were collected for gene expression profiling. Mice received a high-fat diet for short periods to mimic initial steatosis and the hepatic immune response was investigated using a combination of confocal intravital imaging, gene expression, cell isolation, flow cytometry and bone marrow transplantation assays. Results We observed major immunologic changes in patients with NAS 2–3 and in mice in the initial stages of NAFLD. In mice, these changes significantly increased mortality rates upon drug-induced liver injury, as well as predisposing mice to bacterial infections. Moreover, deletion of Toll-like receptor 4 in liver cells dampened tolerogenesis, particularly in Kupffer cells, in the initial stages of dietary insult. Conclusion The hepatic immune system acts as a sentinel for early and minor changes in hepatic lipid content, mounting a biphasic response upon dietary insult. Priming of liver immune cells by gut-derived Toll-like receptor 4 ligands plays an important role in liver tolerance in initial phases, but continuous exposure to insults may lead to damage and reduced ability to control infections. Lay summary Fatty liver is a very common form of hepatic disease, leading to millions of cases of cirrhosis every year. Patients are often asymptomatic until becoming very sick. Therefore, it is important that we expand our knowledge of the early stages of disease pathogenesis, to enable early diagnosis. Herein, we show that even in the early stages of fatty liver disease, there are significant alterations in genes involved in the inflammatory response, suggesting that the hepatic immune system is disturbed even following minor and undetectable changes in liver fat content. This could have implications for the diagnosis and clinical management of fatty liver disease.

Traditionally, exercise physiology experiments have borne little resemblance to how animals express physical activity in the wild. In this experiment, 15 adult male rats were divided into three equalsized groups: exercise contingent (CON), non-exercise contingent (NON) and sedentary (SED). The CON group was placed in a cage with a running wheel, where the acquisition of food was contingent upon the distance required to run. Every 3 days the distance required to run to maintain food intake at free feeding levels was increased by 90% in comparison to the previous 3 days. The NON group was housed identically to the CON group, but food acquisition was not dependent upon running in the wheel. Finally, the SED group was kept in small cages with no opportunity to perform exercise. A twoway ANOVA with repeated measures was used to determine significant differences in responses between the experimental phases and treatment groups, and ANCOVA was used to analyse growth and tissue mass variables with body length and body mass used separately as covariates. A post hoc Tukey's test was used to indicate significant differences. A Pearson's correlation was used to test the relationship between the distance travelled by the animal and the distance/food ratio. The level of significance was set at P<0.05 for all tests. The CON group showed the hypothesized correlation between distance required to run to obtain food and the mean distance travelled (P<0.001), during 45 days in the contingency phase. This group showed a decrease in body mass, rather than an increase as shown by NON and SED groups. The CON group had a significantly lower body temperature (P<0.05) and adiposity (P<0.05) when compared with the other two groups for the same body size. The present experimental model based on animals choosing the characteristics of their physical exercise to acquire food (i.e. distance travelled, speed and duration) clearly induced physiological effects (body characteristics and internal temperature), which are useful for investigating relevant topics in exercise physiology such as the link between exercise, food and body mass.

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