Low F.prau linked to COVID 19 severity

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Low levels of F. prau linked to more severe COVID infection

Livaux® prebiotic powder, from New Zealand gold kiwifruit, has been clinically shown to increase Faecalibacterium prausnitzii (F. prau) numbers in individuals with low F. prau levels (1). Research show that low levels of F. prau are associated with increased SARS-CoV-2 (Covid-19) virus symptom severity and duration. This finding is covered in a recent NutraIngredients article (2). 

Covid-19 invades cells by a process starting with binding the ACE2 receptor (3). This receptor is found in highest levels on the surfaces of cells of the lungs, and on the surfaces of the cells lining the intestines (4). In the intestines, ACE2 is linked to inflammation and the gut microbiome (5). Covid-19 is known to cause gastrointestinal disturbances, with high incidence of diarrhoea and microbiome dysbiosis (3-9). Viral material has been detected in faeces, even after the respiratory tract tests negative, illustrating the risk of faecal-oral transmission (3) and an urgent need to address these gastrointestinal issues (10). 

In order for the Covid-19 virus to invade intestinal epithelial cells, it must survive transit through the stomach acid. Indeed, individuals on proton pump inhibitors (which reduce stomach acidity) are at risk of increased Covid-19 symptom severity and duration (11-13). Similarly, susceptibility to the virus is age-related (14), and increased age is associated with decreased stomach acidity (4), as well as decreased overall immune function and microbial dysbiosis (15). 

The microbial dysbiosis associated with Covid-19 is well documented, and the bacteria most commonly inversely correlating with presence or severity of Covid-19 symptoms is F. prau.  

For example, recently patients with Covid-19 were shown to have significantly underrepresented F. prau, Eubacterium rectale and Bifidobacterium adolescentis, with the strongest inverse correlations with severity being numbers of F. prau and Bifidobacterium bifidum (16).  

A previous study showed Covid-19 patients had lower numbers of Eubacterium rectale, Ruminococcus obeum, Lachnospiraceae bacterium 1_1_57FAA and F. prau (17). Again, F. prau most strongly negatively correlated with severity, in addition to Alistipes (17). These patients were also shown to have greater numbers of opportunistic pathogens known to cause bacteraemia such as Clostridium hathewayi, Actinomyces viscosus, Bacteroides nordii, and Coprococcus species known to upregulate ACE2 in the gut (17).  

A similar association of increased viral disease severity with lower F. prau has been seen in flu (H1N1) patients (18).  

Decreases in F. prau numbers have not been shown to be associated with infectivity. In another study, individuals with high Covid-19 infectivity had lower abundances of Parabacteroides merdae, Bacteroides stercoris, Alistipes onderdonkii and Lachnospiraceae bacterium 1_1_57FAA (19). However, given that lower numbers of F. prau, Alistipes and Lachnospiraceae bacterium 1_1_57FAA were common across multiple independent studies, this suggests these bacteria occupy guilds that are relevant to mitigating the severity of Covid-19 symptoms. 

Modulating the gut microbiome may be a solution to decrease risk and severity of Covid-19 infection (20, 21) What can be done to address microbiome dysbiosis and increase F. prau numbers? Decreased hygiene and cleanliness has been associated with an increased microbial diversity and decreased Covid-19 susceptibility (22). Conversely, social distancing and its commensurate decrease in microbial transfer and acquisition has been posited to lead to a dangerous decrease in microbial diversity (23). However, decreasing hygiene and social distancing are dangerous, as they are associated with other larger risks (22, 23). A more viable alternative to increase microbial diversity for decreased Covid-19 symptom severity is through food (20). 

The use of probiotics, live microorganisms that confer health benefits when consumed, has been suggested as a viable strategy (20). Indeed, The Natural Health Committee of China has promoted this course of action (20). Similarly, some of the researchers who first definitely established the link between Covid-19 severity and gut microbiota have attempted to create probiotic supplements for this purpose (24). However, F. prau is highly oxygen sensitive and cannot be viably delivered for consumption in adequate live numbers. 

Prebiotics, food which survives digestion and reaches our large intestine to selectively increase the numbers of gut bacteria that confer health benefits, are a better proposition. Diet has been shown to increase F. prau numbers (25), particularly high carbohydrate/low glycemic impact diets (26). In terms of selectively increasing F. prau, Livaux® from New Zealand gold kiwifruit is the only prebiotic clinically shown to increase F. prau levels in individuals with low baseline levels (1). This effect has also been demonstrated in vitro (27). Livaux contains high methoxy pectin, and high methoxy pectic galacturonic acid is a substrate used by F. prau (28). 

References

  1. Blatchford, P.,Stoklosinski, H., Eady, S., Wallace, A., Butts, C., Gearry, R., . . . Ansell, J. (2017). Consumption of kiwifruit capsules increases Faecalibacterium prausnitzii abundance in functionally constipated individuals: A randomised controlled human trial. Journal of Nutritional Science, 6, E52. doi:10.1017/jns.2017.52 
  2. Scattergood, G,https://www.nutraingredients-asia.com/Article/2021/01/12/Microbiome-and-COVID-19-Lower-levels-of-key-gut-bacteria-linked-to-severity-of-disease-and-immune-response-China-data?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSSaccessed 12th January 2021 
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