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The establishment of the Saudi Space Commission in 2018 marked a breakthrough for Saudi Arabia, in which the nation expressed its capacity for space exploration. In this context, space medicine is a subspecialty of focus that aims to maintain human health and performance in the extreme environment of outer space based on scientific knowledge concerning the aerodynamic effects on the human body. The field is not widely common and is only now established in a few countries with advanced research capabilities in the field of space exploration. However, there is great potential in space medicine with a multitude of strong research opportunities. This advancing field may result in knowledge that far exceeds the currently known and well-investigated aspects of human health. Nevertheless, progress has been hindered by some challenges, including a limited number of institutions, human resources, and research funding. This article provides a roadmap for the creation, development, and improvement of space medicine in Saudi Arabia.

Astronauts are prone to a condition known as disuse osteoporosis as the microgravity environment negates the need for skeletal weight bearing. Recently, the development of new strategies to study bone loss in microgravity has been advancing at a rapid pace. As a result, several emerging technologies have paved the way for new research into the cellular and physiological mechanisms involved in disuse osteoporosis. In this review, we discuss the most impactful and current methodologies and technologies for both in vivo and in vitro studies of bone loss in space and with simulators on Earth from the past decade. We cover research performed on the International Space Station, uncrewed satellites, head-down tilt bed rest, rodent hindlimb unloading, and 2D/3D clinorotation for cell culture which are all established methods to mechanically unload the skeleton and/or bone cells. We also summarize the experimental findings documenting the changes that occur following exposure to unloading on a macroscopic scale, such as morphometric changes to the bone structure, and on the microscopic scale, such as effects on bone-forming osteoblasts, bone-resorbing osteoclasts, and mechanical stress-sensing osteocytes.

Space flight is an aggregation of the most extreme conditions that can be faced by humans. At present, space crews live and work aboard orbital stations in low Earth's orbits; however, controlled missions to the Moon and Mars planned for the near future will necessitate an extended autonomous existence of crews in the outer space. Although humanity seeks to explore deep space, space flight factors still pose a serious barrier to long-range missions. It is widely known that spaceflight factors disturb homeostatic systems of organism and impact functioning of the majority of physiological systems. According to the current concept, all changes occurring in the physiological systems during space flight are reversible. However, recovery of some systems after exposure in microgravity can be longer than actual mission duration. Nowadays the leading space agencies initiate research programs focused on molecular mechanisms of the spaceflight effects on human organism. It is believed that proteome remodeling in microgravity will shed light on molecular mechanisms and, specifically, signaling networks involved in the adaptive response of organism to the spaceflight environment. However none of the existing post-genomic technologies is applicable onboard spacecraft because of dimensions and mass of instruments, liquid behavior in microgravity and power constraints. Purpose of the review was to systemize the available proteomic data on the effects of spaceflight factors on the human organism obtained after real space flights and in ground simulation experiments. New molecular data will contribute to new physiotherapeutic methods and drugs development preventing undesirable changes in crew health.

The circadian clock is an endogenous time-generating system accountable for the synchrony between the internal and the geophysical time. In recent years, chronobiology research has demonstrated that the circadian regulation of numerous molecular and cellular processes leads to a temporal control of physiology and behaviour. These findings alert to the negative impact on health caused by a disrupted internal timing.

In this review we address the relation between atypical external factors in long-term space flights (or other extreme environments) and circadian clock misalignment, stressing the need of establishing preventive measures to minimize the effect on human health and performance. For this purpose, daily activities of astronauts (or humans living in extreme environments) could be planned according to the individual’s internal biological time, which can be achieved through the synergy between the molecular characterization of the circadian clock and computational predictive mathematical models.

Neuropeptide tyrosine (neuropeptide Y or NPY) is one of the most abundant neuropeptides in the mammalian central nervous system and also widely distributed in the peripheral nervous system. Among the many mediators involved in important physiological and psychological systems, NPY in particular appears to be a multisignaling key peptide. The biological actions of NPY are vast and mediated via the Y₁, Y₂, Y₄, and Y₅ receptors, which are involved in both essential physiological and pathophysiological processes. Here, we discuss various roles of NPY in seven systems: a) regulation of energy homeostasis, b) thermoregulation, c) circadian system, d) sleep, e) nociception, f) emotional behavior, and g) the autonomic nervous system.

NPY regulates a) energy homeostasis with actions at different sites (central and peripheral), via different receptors in various neuronal tissues. Due to its prominent actions in the brain, including stimulating appetite, NPY function has gained importance. However, NPY is more than just an orexigenic peptide. Food intake and decrease in energy expenditure are exerted together by the Y₁ and Y₅ receptors. While the Y₄ receptor exerts anorexigenic effects, the Y₂ receptor has central anorexigenic and peripheral orexigenic properties. The involvement of NPY in b) thermoregulation remains unclear. Although it has been reported that cold exposure activates NPY. Increased or decreased thermogenesis has been observed as a result of NPY administration to different central sites. Central Y₁ and Y₅ receptors inhibit sympatho-adrenal transmitted thermogenesis in peripheral brown adipose tissue. NPY functions as a chemical messenger autonomous of the light-dark-cycle in the c) circadian rhythm and exerts similar phase-shifting effects to those of light. NPY leads to a shortened d) sleep onset and reduced REM latency, but its role in the circadian rhythm seems to be elusive and has not been established. NPY is implicated in e) pain perception and modulates nociception. It has been shown to cause both nociceptive and anti-nociceptive responses.

Moreover, Y receptors are thought to form heterodimers with those of galanin and glutamate to enhance their nociceptive modulatory effects. Especially the role of the Y₂ receptor within this system and all the other systems reveals opposite properties. The different effects of Y₂ receptors are dependent on their central or peripheral location.These opposing effects can be observed in other receptors as well and are likely explained by tissue-specific differences in receptor expression (number and distribution of receptors). Differences in cell type-specific second messenger coupling also play a role. Therefore, centrally located receptors can have a completely different function than peripherally located receptors. The regulation of f) emotional beh