Gunma University

A research group has found that in fruit flies (Drosophila melanogaster), circulating fructose derived from dietary sugar is needed for enhanced egg production after mating. In this species, circulating fructose is required for an increase in germline stem cells, which divide into reproductive cells. This increase leads to enhanced post-mating egg production. These findings may help to determine whether fructose influences the reproduction of mammals, including humans. To many people, the sugars we eat may seem like a luxury that can do more harm than good. But now, researchers from Japan have discovered that in insects, dietary sugars play a key role in reproduction. In a study published recently in Science Advances, a research group led by the University of Tsukuba has revealed for the first time that fructose, which is metabolized from dietary sugar such as glucose, is needed for enhanced egg production in fruit flies. The production and successful development of eggs in organisms depend on the availability of nutrients, because oocytes (the cells that develop into eggs) need a lot of energy to develop into mature eggs. This is especially true of insect oogenesis (the production of eggs in the ovary), which is highly restricted in conditions with insufficient available nutrients. Insect oogenesis is also influenced by mating stimuli that speed up the production of eggs. "Fruit flies (Drosophila melanogaster) are ideal for investigating the mechanisms that link oogenesis, nutrient availability, and mating stimuli," says Professor Ryusuke Niwa, main author of the study. "In this study, we used fruit flies to examine whether nutrition and mating act interdependently to increase germline stem cells (GSCs)." Previous research had shown that in D. melanogaster, nutrition and mating are involved in an observed increase in GSCs, which differentiate into gametes (reproductive cells). In this study, the researchers found that dietary sugars are necessary for this increase in GSCs after mating. Dietary glucose is needed for mating-induced release of neuropeptide F (NPF, a chemical messenger made up of small chains of amino acids). NPF is released from enteroendocrine cells (EECs, which are specialized cells in the gastrointestinal tract and pancreas that perform hormonal functions). NPF then mediates an enhancement of GSC niche signaling (a mechanism that provides the stem cells with the signals that instruct them to self-renew). An unexpected finding was that dietary glucose does not act directly on NPF-positive EECs (EECs capable of secreting NPF). Instead, it contributes to a rise in fructose in the hemolymph (the equivalent of blood in insects) generated via the polyol pathway (a two-step process that converts glucose to fructose). Raised fructose levels stimulate the fructose-specific taste receptor, Gr43a, in NPF-positive EECs, leading to the secretion of NPF. "Our study shows that circulating fructose, derived from sugars in the fruit flies' diet, is required for the increase in GSCs that leads to enhanced egg production after mating," explains Professor Niwa. The results of this study will be applicable to the question of whether circulating fructose also plays an essential role in mammal reproduction. Interesting applications of these findings include investigations of gestational diabetes in humans and the harmful effects of fructose during pregnancy. This work was supported financially by the Ministry of Education, Culture, Sports, Science and Technology of Japan's Grant-in-Aid for Scientific Research on Innovative Areas, the Japan Society for the Promotion of Science's KAKENHI grants, Japan Agency for Medical Research and Development's AMED-CREST grants, and the joint research program of the Institute for Molecular and Cellular Regulation, Gunma University.

It is still a glimpse into the future: Astronauts could be put into artificial hibernation and in this state be better protected from cosmic radiation. At present, there are already promising approaches to follow up such considerations. An international research team now has found decisive indications of the possible benefits of artificial hibernation for radiation resistance. It is still a glimpse into the future: Astronauts could be put into artificial hibernation and in this state be better protected from cosmic radiation. At present, there are already promising approaches to follow up such considerations. An international research team led by the Biophysics Department of the GSI Helmholtzzentrum in Darmstadt now has found decisive indications of the possible benefits of artificial hibernation for radiation resistance. The research partners from Germany, Japan, Italy, the UK and the USA have recently published their results in Scientific Reports, a journal of the Nature Publishing Group. Scientists call the state, which hibernating animals enter, torpor. In this state, life-supporting functions of an organism are reduced: Body temperature is lowered, metabolism is reduced and body functions such as heart rate and respiration rate or oxygen uptake are significantly slowed down. At the molecular level, gene activity and protein biosynthesis are also reduced to a slower pace. In the study now published on synthetic torpor (i.e. a kind of artificially produced hibernation) and protection from ionizing radiation, the scientists demonstrated biological effects suggesting that synthetic torpor increases resistance to radiation. A proof that can be very useful in the long term for astronauts. Space radiation is acknowledged as one of the main health risks for human space exploration. Harmful effects of space radiation are a major challenge, especially for future long-term missions. The majority of radiation dose absorbed by crews in manned interplanetary missions is produced by galactic cosmic radiation (GCR), high-energy charged particles, including densely ionizing heavy ions, produced in distant galaxies. The energy of these particles is so high that shielding of the spacecraft cannot stop them and lead to exposure rates over 200 times higher than the radiation background on Earth over a very long period. For these reasons, radiation countermeasures for future missions are being investigated. "The connections between torpor and radioresistance represent a highly innovative research approach. Our results indicate that synthetic torpor is a promising tool to enhance radioprotection in living organism during long-term space missions. It could thus be an effective strategy to protect humans as they explore the solar system," summarizes Professor Marco Durante, Head of the GSI Biophysics Division. It is already known that naturally hibernating animals acquire radioresistance in this state. However, the recent study is so significant because it is the first time that a hibernation-like biological state was induced in a non-hibernating animal (rat) and radioresistance to high-energy heavy ions could be proved. In experiments at Japan's Gunma University Heavy-ion Medical Center, accelerated carbon ions were used to simulate radiation in space. The other in vitro cell experiments were performed at the GSI/FAIR campus in Darmstadt and were part of the FAIR Phase 0 experimental period. The main results of the research team after irradiation and induction of a synthetic torpor proved the hypotheses: Synthetic hibernation may have protective effects on a lethal dose of C?ions. In addition, synthetic hibernation reduces the tissues damage from total body irradiation. Furthermore, GSI scientists were able to characterize the underlying mechanism in their studies on rat tissue cells. They showed that lower oxygen concentration in the tissues (hypoxia) and reduced metabolism at low temperature (hypothermia) could be two important factors in the prevention of cell damage. The immunohistological analyses indicated that the synthetic torpor spares the tissue from energetic ion radiation. In addition, changes in metabolism at low temperatures could also affect DNA repair. A lot of research is still needed to investigate and better understand the radioprotective effect of synthetic torpor in organs. Currently it is not possible technically to hibernate a human in a safe and controlled way. However, research is progressing. Only recently, the neuronal pathways that control torpor are been unraveled. Now the current publication adds another important component. The Scientific Managing Director of GSI and FAIR, Professor Paolo Giubellino, emphasizes that the international accelerator center FAIR, currently under construction at GSI, will offer unique opportunities for research in the field of cosmic radiation. "Already today, the GSI facility is able to produce beams of heavy nuclei as they occur in cosmic radiation. At FAIR, experiments with a much wider range of particle energies and intensities will be possible. This will allow researchers to study the effects of cosmic radiation on humans and on technical instrumentation, which are fundamentally necessary to make human Mars missions possible. I am very delighted that the European Space Agency ESA has a cooperation with FAIR since many years to foster this field of research."