Two new types of research appearing on April 18 in the journal Cell Metabolism shows that the circadian clock is the main factor in how the body responds to physical exertion.
The new study mainly focuses on variant components of exercise, thereby complementing each other. On the basis of this work alone, it’s too quick to define what or when is the best time for you to go for a jog. But at least in the laboratory, an exercise in the evening time seems to be more productive, while the human lifestyles are much more complexed and so this area of research is only just beginning.
Gad Asher of the Dept. of Biomolecular Sciences at the Weizmann Institute of Science says “It’s quite well known that almost every aspect of our physiology and metabolism is dictated by the circadian clock.” Gad Asher is the senior author of one of the studies. Further added he said “This is true not only in humans but in every organism that is sensitive to light. We decided to ask whether there is a connection between the time of day and exercise performance.”
Along with this Paolo Sassone-Corsi of the Center for Epigenetics and Metabolism at the University of California adds “Circadian rhythms dominate everything we do.”
Irvine, who is senior author of the other paper also help us understand the exercise time by telling that in last studies proposed that at least 50% of body metabolism is circadian, and 50% of the metabolites in human body oscillate based on the circadian cycle which directly affects the exercise according to time. In her words, “Previous studies from our lab have suggested that at least 50% of our metabolism is circadian, and 50% of the metabolites in our body oscillate based on the circadian cycle. It makes sense that exercise would be one of the things that’s impacted.”
Both research teams study at the connection between the time of day and exercise performance primarily in mice. Because mice are nocturnal, the only thing they had to do was convert mouse timing to human timing, by differentiating between the active phase and resting phase of the mice rather than using numbers on the clock.
Asher’s group begun with by putting the mouse in treadmills at various times of day when they are in their active phase, and in results, They examined the exercise capability of mouse on various exercise strength and intensities and they finally conclude that overall exercise performance is substantially better (about 50% on average and more in some protocols) in toward the end of their active time named as “mouse evening” compared to the morning time. These daily differences were declined in mice that had mutant clocks — supports a potential role of the clock in the observed variance in exercise performance.
To examine and identify a potential determinant or a causal factor of daily variance in exercise performance, they applied high-throughput metabolomics and transcriptomics on muscle tissue. In “mouse evening” exercise it responds as there were seems higher levels of a metabolite called ZMP (5-aminoimidazole-4-carboxamide ribonucleotide) According to the researchers.
ZMP found by research teams, is well known to activate metabolic pathways that are associated with glycolysis and fatty acid oxidation through activation of AMPK, which is a main cellular metabolic regulator. This simplifies, it is supposed to contribute to the increased exercise capacity in the evening. On this Gad Asher says that “Interestingly, ZMP is an endogenous analog of AICAR [aminoimidazole carboxamide riboside], a compound that some athletes use for doping.”
The researchers also examined 12 human bodies and found similar effects. On overall conclusion, the people that get examined in the study had lower oxygen consumption while exercising in the evening time compared with the morning; this interprets to better exercise efficiency.
Sassone-Corsi’s research team also put mice on treadmills, but they applied different methods. Using high-throughput transcriptomics and metabolomics to look at a wide range of possible factors, they specified the changes and characterized in the mice’s muscle tissue that occurs in return to exercise. This gives a permit them to look at processes like glycolysis (which contributes to sugar metabolism and energy production) and lipid oxidation (fat burning).
They also found that a protein called hypoxia-inducible factor 1-alpha (HIF-1?) plays a crucial role and it is activated by exercise in various ways depending on the time of day.
HIF-1? is a transcription factor that is well known to stimulate certain genes that depend on oxygen levels in tissue. According to Sassone-Corsi “It makes sense that HIF-1? would be important here, but until now we didn’t know that its levels fluctuate based on the time of day.” Further added, “This is a new finding.”
On the basis of the work from the UC Irvine research team, exercise looks to have the most productive which benefits the impact on the metabolism at the starting of the active phase (equivalent to late morning in humans) in contrast with the resting phase (evening).
According to the research team, the circadian clocks have been conserved throughout evolution, but still translating the findings to humans is not so straightforward. One reason is that human bodies have more variation in their chronotypes than mice living in a laboratory. “You may be a morning person, or you may be a night person, and those things have to be taken into account,” Sassone-Corsi says.