Host genetic regulation of human gut microbial structural variation.

Although the impact of host genetics on gut microbial diversity and the abundance of specific taxa is well established1-6, little is known about how host genetics regulates the genetic diversity of gut microorganisms. Here we conducted a meta-analysis of associations between human genetic variation and gut microbial structural variation in 9,015 individuals from four Dutch cohorts. Strikingly, the presence rate of a structural variation segment in Faecalibacterium prausnitzii that harbours an N-acetylgalactosamine (GalNAc) utilization gene cluster is higher in individuals who secrete the type A oligosaccharide antigen terminating in GalNAc, a feature that is jointly determined by human ABO and FUT2 genotypes, and we could replicate this association in a Tanzanian cohort. In vitro experiments demonstrated that GalNAc can be used as the sole carbohydrate source for F. prausnitzii strains that carry the GalNAc-metabolizing pathway. Further in silico and in vitro studies demonstrated that other ABO-associated species can also utilize GalNAc, particularly Collinsella aerofaciens. The GalNAc utilization genes are also associated with the host's cardiometabolic health, particularly in individuals with mucosal A-antigen. Together, the findings of our study demonstrate that genetic associations across the human genome and bacterial metagenome can provide functional insights into the reciprocal host-microbiome relationship.

Bidirectional relationships between the gut microbiome and sexual traits.

The human gut microbiota is known to be shaped by a variety of environmental factors (diet, drugs, geography and sanitation) and host intrinsic factors (age and sexual development). The differences in gut microbiota between sexes are minimal before adulthood and late adulthood, and marked during adulthood. For instance, consistent higher abundances of Akkermansia and Ruminococcus have been observed in adult women compared to men and most studies have found higher abundances of Prevotella and Fusobacterium (linked to a diet rich in animal proteins) in adult men compared to women. The gut microbiota taxonomy and functionality present in women is more similar to men once reached the menopause. In fact, specific taxa have been associated with the levels of different sexual hormones and their precursors in blood. The gut microbiota composition and circulating testosterone levels are also tightly linked to the extent that microbial signatures can predict its levels in blood. Not only sexual hormones seem to influence the gut microbiome, but also the latter participates in the metabolism of these hormones, with some bacteria being able to metabolize gonadal steroid hormones (one example is 3ß-hydroxysteroid dehydrogenase, a testosterone degrading enzyme). In summary, the relationships between the gut microbiome and sexual traits are bidirectional. In addition, other phenotypes and cultural gender-related factors could drive sex-related differences. It is important to note that other members of the microbiome (Archeae, viruses and fungi) have been largely unexplored in relation to this sexual dimorphism. More research is needed on this topic.

DPP9 as a Potential Novel Mediator in Gastrointestinal Virus Infection.

Dipeptidyl peptidase 9 (DPP9) is a member of the dipeptidyl peptidase IV family. Inhibition of DPP9 has recently been shown to activate the nucleotide-binding domain leucine-rich repeat 1 (NLRP1) inflammasome. NLRP1 is known to bind nucleic acids with high affinity and directly interact with double stranded RNA, which plays a key role in viral replication. DPP9 has also recently emerged as a key gene related to lung-inflammation in critical SARS-CoV-2 infection. Importantly, DPP9 activity is strongly dependent on the oxidative status. Here, we explored the potential role of DPP9 in the gastrointestinal tract. We performed transcriptomics analyses of colon (microarray, n = 37) and jejunal (RNA sequencing, n = 31) biopsies from two independent cohorts as well as plasma metabolomics analyses in two independent cohorts (n = 37 and n = 795). The expression of DPP9 in the jejunum, colon, and blood was significantly associated with circulating biomarkers of oxidative stress (uric acid, bilirubin). It was also associated positively with the expression of transcription factors (NRF-2) and genes (SOD, CAT, GPX) encoding for antioxidant enzymes, but negatively with that of genes (XDH, NOX) and transcription factors (NF-KB) involved in ROS-generating enzymes. Gene co-expression patterns associated with DPP9 identified several genes participating in antiviral pathways in both tissues. Notably, DPP9 expression in the colon and plasma was strongly positively associated with several circulating nucleotide catabolites (hypoxanthine, uric acid, 3-ureidopropionic acid) with important roles in the generation of ROS and viral infection, as well as other metabolites related to oxidative stress (Resolvin D1, glutamate-containing dipeptides). Gene-drug enrichment analyses identified artenimol, puromycin, anisomycin, 3-phenyllactic acid, and linezolid as the most promising drugs targeting these DPP9-associated genes. We have identified a novel potential pathogenic mechanism of viral infection in the digestive tract and promising existing drugs that can be repositioned against viral infection.