[Drinking with increased deuterium content affects the gut microbiome and the antioxidant status of the organism]

As preparations for a manned mission to Mars are currently underway, it is crucial to understand the impact of a drinking ration with a deuterium level corresponding to those found in Martian glaciers on mammals. The objective of the research was to study the dynamics of deuterium levels in laboratory animals and changes in oxidative processes following daily consumption of a drinking ration with a deuterium concentration of 6704‰.

The experiments were conducted on male Wistar rats, which had an initial body weight 270-300 g. The response of laboratory animals to increased deuterium level was studied using 60 Wistar rats. The animals were divided into two groups (30 rats each): Group 1 consumed a drinking ration with a deuterium concentration corresponding to the natural level (-37‰); Group 2 consumed a drinking ration containing 6704‰ deuterium. Five animals were removed from the experiment on days 5, 8, 11, 16, 21 and 31. Fecal, blood and brain samples were collected during these procedures. The stress-protective activity of the drinking ration with a modified isotopic composition was studied using 3 groups of rats (7 rats each). The «Control, -37‰» group consumed water with a deuterium concentration of -37‰. Animals of the «Stress, -37‰» and "Stress, 6704‰" groups consumed water with a deuterium concentration of -37 ‰ and 6704‰, respectively, for 38 days while simulating immobilization stress (4 hours) for 3 days, starting from the 33rd day. Deuterium level in water and blood serum was determined on a NMR spectrometer (Bruker Avance NEO 700 MHz). A DELTA V Advantage isotope mass spectrometer was used to assess deuterium level in lyophilized cerebral cortex. The activity of free radical processes was assessed by the intensity of chemiluminescence of blood plasma and cerebral cortex supernatant. Catalase activity in the cerebral cortex was measured by spectrophotometry, and gene expression levels were determined using realtime polymerase chain reaction (PCR). The proportion of dominant bacterial phyla in the intestinal microbiome was assessed using polymerase chain reaction with phylum-specific primers to 16s rRNA.

Consuming water w ith a deuterium concentration of 6704‰ for 31 days increased its concentration in rat blood plasma from -25±4 to 4425±103 ‰, while in brain tissue, deuterium content increased from -127±7 to 667±32‰. As deuterium accumulated in the body, catalase activity increased (2.2-5.3 fold from the 8th to the 31st day, p<0.05) and the expression of several genes involved in antioxidant protection (Cat, Gclc, Nrf2) changed. Fluctuations in the composition of the intestinal microbiome were observed, especially on the 5th and 8th days of the experiment. These fluctuations resulted in a decrease in Bacteroides by 13 and 22%, respectively, and an increase in Firmicutes by 12 and 16%, respectively. These effects are the result of adaptive responses to stress caused by increased deuterium concentrations in the body's internal environment. The decrease in the intensity of oxidative stress in rat brain and blood after immobilization stress is due to the prolonged intake of water with a deuterium level of 6704‰ and the development of a cross-adaptation effect.

It has been established that increased deuterium levels in the body fluids and tissues of laboratory animals trigger a stress response, activating mechanisms for adaptation to new conditions. This results in activation of the antioxidant system, which enhances the body's protective properties during immobilization stress.