Endocrine Modulation in Long-Term Karate Practitioners

Purpose. Karate is a martial arts discipline which is widely practiced in the Western world as a form of self-defense, as well as a discipline to achieve physical and mental balance. However, little is known with respect to its specific psychobiological effects, particularly in relation to the influence that it may exert on the endocrine system. Thus, in the present study, we examined the effects of karate on several hormonal parameters of the Hypothalamic-Pituitary-Adrenal and Hypothalamic-Pituitary-Thyroid axes in long-time practitioners. Methods. Twenty-two healthy volunteer subjects (12 experimental and 10 controls) participated in the study. Experimental subjects were karate players with a minimum of 3 years of practice in this discipline. Blood samples for the quantification of hormonal parameters were taken in both groups. The Mann-Whitney U test was performed for each variable in order to analyze the differences between groups. Results. Statistically significant differences were found in cortisol and thyroid hormones, with the karate group showing lower levels of these hormones as compared to control. Conclusions. These findings, therefore, reveal that long-term karate practice is associated with a significant endocrine modulation, which suggests interesting psychobiological and clinical implications. Further research is needed to verify these preliminary results, as well as properly assessing its possible use as a psychosomatic intervention tool.

Circadian hormone control in a human-on-a-chip: In vitro biology’s ignored component?

Organs-on-Chips (OoCs) are poised to reshape dramatically the study of biology by replicating in vivo the function of individual and coupled human organs. Such microphysiological systems (MPS) have already recreated complex physiological responses necessary to simulate human organ function not evident in two-dimensional in vitro biological experiments. OoC researchers hope to streamline pharmaceutical development, accelerate toxicology studies, limit animal testing, and provide new insights beyond the capability of current biological models. However, to develop a physiologically accurate Human-on-a-Chip, i.e., an MPS homunculus that functions as an interconnected, whole-body, model organ system, one must couple individual OoCs with proper fluidic and metabolic scaling. This will enable the study of the effects of organ-organ interactions on the metabolism of drugs and toxins. Critical to these efforts will be the recapitulation of the complex physiological signals that regulate the endocrine, metabolic, and digestive systems. To date, with the exception of research focused on reproductive organs on chips, most OoC research ignores homuncular endocrine regulation, in particular the circadian rhythms that modulate the function of all organ systems. We outline the importance of cyclic endocrine regulation and the role that it may play in the development of MPS homunculi for the pharmacology, toxicology, and systems biology communities. Moreover, we discuss the critical end-organ hormone interactions that are most relevant for a typical coupled-OoC system, and the possible research applications of a missing endocrine system MicroFormulator (MES-µF) that could impose biological rhythms on in vitro models. By linking OoCs together through chemical messenger systems, advanced physiological phenomena relevant to pharmacokinetics and pharmacodynamics studies can be replicated. The concept of a MES-µF could be applied to other standard cell-culture systems such as well plates, thereby extending the concept of circadian hormonal regulation to much of in vitro biology. Impact statement Historically, cyclic endocrine modulation has been largely ignored within in vitro cell culture, in part because cultured cells typically have their media changed every day or two, precluding hourly adjustment of hormone concentrations to simulate circadian rhythms. As the Organ-on-Chip (OoC) community strives for greater physiological realism, the contribution of hormonal oscillations toward regulation of organ systems has been examined only in the context of reproductive organs, and circadian variation of the breadth of other hormones on most organs remains unaddressed. We illustrate the importance of cyclic endocrine modulation and the role that it plays within individual organ systems. The study of cyclic endocrine modulation within OoC systems will help advance OoC research to the point where it can reliably replicate in vitro key regulatory components of human physiology. This will help translate OoC work into pharmaceutical applications and connect the OoC community with the greater pharmacology and physiology communities.