Effects of Human Milk Oligosaccharides (HMOs) on Gut Microbiota, Immune System and Metabolism in Adults Wintering Over in Antarctica

The aim of this study is to investigate the effect of supplementation with prebiotics, a specific mixture of carbohydrates found in breast milk (HMOs), as a measure to improve intestinal flora, inflammatory processes in the gut, general immune status, carbohydrate regulation, fat and bone metabolism and neurological changes in Antarctica. The approximately one-year stay at Concordia Station (Antarctica) at an altitude of about 3200 m includes a long journey and subsequent extreme environmental conditions as well as corresponding adaptation mechanisms and is therefore a very good terrestrial model (analogue model) for investigating changes during space stays. Long-term (i.e. > 6 months) exposure to microgravity leads to numerous physiological responses, including impaired glucose tolerance, reduced immune function and bone loss, which can lead to quite severe health consequences. In this analogue model, similar changes, albeit less severe, are observed with regard to the immune system or glucose tolerance as in space flight.

The composition of the diet significantly influences the composition of the intestinal flora. In particular, dietary carbohydrates provide the substrate for certain bacteria that could have a positive effect on health. Prebiotics are defined as substrates that are selectively used by host microorganisms and that provide health benefits. Prebiotics are digested only by gut microorganisms and stimulate the growth or activity of bacteria in the gut that have shown health benefits or improved well-being. The main nutrients for bacterial growth are non-digestible carbohydrates, which by definition are not digested by the host, in this case the human organism (host). Non-digestible carbohydrates include, for example, resistant starch and dextrins, non-starch polysaccharides (NSPs) (e.g. pectins) and non-digestible oligosaccharides (e.g. Raffinose, inulin, etc.). These carbohydrates are fermented by the intestinal bacteria to short-chain fatty acids (SCFAs), mainly acetic acid, propionic acid and butyric acid. This process takes place mainly in the large intestine, but also in the small intestine. SCFAs are rapidly absorbed by the mucosa of the large intestine and exert whole-body effects, contributing, for example, to the host's energy needs or mediating gut-brain communication, which has a major impact on the physiology and health of the host.

HMOs are also prebiotics and are the third most abundant solid component in breast milk. Most of the research published to date on the effects of HMOs has therefore been conducted on infants. HMOs are not digested in the intestine and are mainly utilised in the large intestine by the bacteria that reside there. In infants, it has been shown that HMOs not only promote a healthy composition of the intestinal flora, but also impair the growth of pathogens and modulate the expression of genes involved in inflammation. Several in vitro and in vivo studies have shown antiviral properties of HMOs against various viruses such as rotavirus, norovirus, HIV and influenza. HMOs play a significant role in the immune system by enhancing the immune response. Initial applications of HMOs in adults have supported these findings.

Therefore, this study aims to investigate how daily administration of 5.5 g of an HMO mixture during hibernation at Concordia Station in Antarctica affects:

• glucose tolerance
• inflammatory processes
• immune function
• fat and bone metabolism and
• Well-being