Summary of the 9th Life Science Symposium: integration of nutrition and exercise sciences

The Life Science Symposium held by the Nutrition Research Committee of the International Life Sciences Institute (ILSI) Japan in 2018, "Fusion of Nutrition and Exercise Sciences Leading to Extension of Healthy Life Expectancy," covered current topics in the science of nutrition and exercise to address extending healthy life expectancy. Presentation topics included (1) lifestyle and gut microbiota; (2) how to use lipids in sports nutrition; (3) the effect and molecular mechanism of improvement of arteriosclerosis by exercise and nutrition; (4) physical activity and nutrition that support brain function; (5) skeletal muscles and food ingredients that support healthy longevity; (6) measures against sarcopenia by exercise and nutrient intake; (7) physical activity/exercise for disease prevention; (8) nutritional epidemiology research for the Japanese population; (9) new developments in health science in viewed from nutrition and intestinal flora; (10) why do Asians develop nonobese metabolic disease?; and (11) social implementation of the health promotion program by ILSI Japan. The speakers emphasized the promotion of research on exercise and nutrition interactions and encouraged social implementation of the research results in public and private sectors.

Negative rebound in hippocampal neurogenesis following exercise cessation

Physical exercise can improve brain function, but the effects of exercise cessation are largely unknown. This study examined the time-course profile of hippocampal neurogenesis following exercise cessation. Male C57BL/6 mice were randomly assigned to either a control (Con) or an exercise cessation (ExC) group. Mice in the ExC group were reared in a cage with a running wheel for 8 wk and subsequently placed in a standard cage to cease the exercise. Exercise resulted in a significant increase in the density of doublecortin (DCX)-positive immature neurons in the dentate gyrus (at week 0). Following exercise cessation, the density of DCX-positive neurons gradually decreased and was significantly lower than that in the Con group at 5 and 8 wk after cessation, indicating that exercise cessation leads to a negative rebound in hippocampal neurogenesis. Immunohistochemistry analysis suggests that the negative rebound in neurogenesis is caused by diminished cell survival, not by suppression of cell proliferation and neural maturation. Neither elevated expression of ΔFosB, a transcription factor involved in neurogenesis regulation, nor increased plasma corticosterone, were involved in the negative neurogenesis rebound. Importantly, exercise cessation suppressed ambulatory activity, and a significant correlation between change in activity and DCX-positive neuron density suggested that the decrease in activity is involved in neurogenesis impairment. Forced treadmill running following exercise cessation failed to prevent the negative neurogenesis rebound. This study indicates that cessation of exercise or a decrease in physical activity is associated with an increased risk for impaired hippocampal function, which might increase vulnerability to stress-induced mood disorders.

Exercise and cerebrovascular plasticity

Aging impairs cerebrovascular plasticity and subsequently leads cerebral hypoperfusion, which synergistically accelerates aging-associated cognitive dysfunction and neurodegenerative diseases associated with impaired neuronal plasticity. On the other hand, over two decades of researches have successfully demonstrated that exercise, or higher level of physical activity, is a powerful and nonpharmacological approach to improve brain function. Most of the studies have focused on the neuronal aspects and found that exercise triggers improvements in neuronal plasticity, such as neurogenesis; however, exercise can improve cerebrovascular plasticity as well. In this chapter, to understand these beneficial effects of exercise on the cerebral vasculature, we first discuss the issue of changes in cerebral blood flow and its regulation during acute bouts of exercise. Then, how regular exercise improves cerebrovascular plasticity will be discussed. In addition, to shed light on the importance of understanding interactions between the neuron and cerebral vasculature, we describe neuronal activity-driven uptake of circulating IGF-I into the brain.