Acute Vigorous Exercise Decreases Subsequent Non-Exercise Physical Activity and Body Temperature Linked to Weight Gain.

PURPOSE: Exercise benefits the body and mind, but its weight loss effect is less than generally expected. Although this phenomenon is likely due to an exercise intensity-dependent decrease in non-exercise physical activity (NEPA), resulting in a decrease in non-exercise activity thermogenesis, the underlying mechanisms and effects of exercise intensity remain unknown. Here we show that acute vigorous exercise decreases subsequent NEPA and body temperature (BT) in association with body weight gain. METHODS: Adult male C57BL/6 J mice were categorized into three groups: sedentary, moderate exercise, and vigorous exercise, with exercise groups undergoing a 30 min treadmill session. Using an intraperitoneally implanted activity monitor, NEPA and BT were monitored for two days before and three days after exercise. The daily synchrony between NEPA and BT was evaluated using a cross-correlation function. Plasma corticosterone was also detected 6 and 24 h after exercise. RESULTS: Notably, Only the vigorous exercise group exhibited a decline in both NEPA and BT, resulting in body weight gain the following day, despite no observed changes in food intake. Furthermore, vigorous exercise induces a distinct delay in the daily dynamics of NEPA compared to BT. A positive correlation was observed between plasma corticosterone levels and changes in NEPA levels before and after exercise across all exercise groups. CONCLUSIONS: Our findings provide evidence for vigorous exercise-specific reduction in subsequent NEPA, BT, and their synchrony linked to weight gain, likely due to the disturbed circadian rhythm of corticosterone. This is an initial investigation redefining the significance of exercise intensity in beneficial effects beyond the energy expenditure of the exercise itself.

Enlarged housing space and increased spatial complexity enhance hippocampal neurogenesis but do not increase physical activity in mice.

Introduction: Environmental enrichment (EE) improves various health outcomes, such as hippocampal neurogenesis, in rodents, which is thought to be caused, in part, by increased physical activity. However, the specific effect of each enrichment component, such as enlarged housing spaces and increased spatial complexity with a variety of objects, on physical activity remains unclear because of methodological limitations in measuring physical activity. We aimed to examine whether enlarged housing spaces and increased spatial complexity increase physical activity in mice using a body-implantable actimeter. Methods: Adult male C57BL/6J mice were assigned to either standard housing or EE groups. The housing environment in the EE mice was gradually enriched by enlarging the housing space and the placement of a variety of objects. Physical activity was measured using a body-implanted actimeter. Hippocampal neurogenesis was immunohistochemically examined. Results: Enlarged housing spaces and the placement of a variety of objects did not increase physical activity in mice. In contrast, hippocampal neurogenesis was enhanced in the EE mice, suggesting that environmental interventions successfully provided enriched housing conditions for these mice. Conclusions: These results indicate that enlarged housing spaces and increased spatial complexity do not increase physical activity in mice. Furthermore, we found that EE enhanced hippocampal neurogenesis without increasing activity volume. Besides the current understanding that increasing the amount of physical activity is key to improving hippocampal function, our result suggests that the environment in which physical activity takes place is also a crucial contextual factor in determining the impact of physical activity on hippocampal function.

Exercise type influences the effect of an acute bout of exercise on hippocampal neuronal activation in mice.

The effects of exercise on the hippocampus depend on exercise conditions. Exercise intensity is thought to be a dominant factor that influences the effects of exercise on the hippocampus; however, it is uncertain whether the type of exercise influences its effectiveness. This study investigated whether the effect of an acute bout of exercise on hippocampal neuronal activation differs between two different types of exercise: treadmill and rotarod exercise. The intensities of both exercises were matched at just below the lactate threshold (LT), based on blood lactate concentration. Immunohistochemical examination of c-Fos, a marker of neuronal activation, revealed that treadmill exercise at 15 m/min (T15) significantly increased c-Fos expression in all subfields of the hippocampus (dentate gyrus DG, CA1, CA3), but rotarod exercise at 30 rpm (R30) did not, as compared with the respective control groups. These results demonstrate that moderate treadmill exercise more efficiently evokes hippocampal neuronal activation than does intensity-matched rotarod exercise. This suggests that exercise type is another important factor affecting the effects of exercise on the hippocampus.

Social isolation is a direct determinant of decreased home-cage activity in mice: A within-subjects study using a body-implantable actimeter.

NEW FINDINGS: What is the central question of this study? It is generally recognized that social isolation is associated with physical inactivity, but is social isolation a direct determinant of decreased physical activity? What is the main finding and its importance? We conducted a within-subjects experiment with the aid of a body-implantable actimeter. Our results clearly demonstrated that social isolation decreased home-cage activity in mice. This might have resulted from increased immobility and decreased vigorous activity, suggesting that avoidance of social isolation is important to prevention of physical inactivity. ABSTRACT: An inactive lifestyle can have a negative impact on physiological and mental health. Social isolation is associated with physical inactivity; however, it remains uncertain whether social isolation is a direct determinant of decreased physical activity. Hence, we assessed whether social isolation decreases home-cage activity using a within-subjects design and examined the effects of social isolation on hippocampal neurogenesis in mice. This study used a body-implantable actimeter called nanotag, which enabled us to measure home-cage activity despite housing the mice in groups. Initially, we examined the influence of the intraperitoneal implantation of nanotag on home-cage activity. Although nanotag implantation decreased home-cage activity temporarily, at 7 days postimplantation the activity recovered to the same level as that of control (non-implanted) mice, suggesting that implantation of nanotag does not have a negative influence on home-cage activity if mice undergo a 1 week recovery period after implantation. In the main experiment, after the 1 week baseline measurement performed with mice in group housing, the mice were placed in a group or in isolation. Home-cage activity was measured for an additional 4 weeks. Home-cage activity in isolated mice during the dark period decreased by 26% from pre-intervention to the last week of intervention. Furthermore, the reduction in the number of 5 min epochs during which the activity count exceeded 301 (an index of vigorous activity) was significantly larger for isolated mice. Contrary to expectations, social isolation did not impair hippocampal neurogenesis. Our results demonstrate that social isolation is a direct determinant of decreased physical activity, possibly because of reduced vigorous physical activity.