From bacteria to biomedicine: Developing therapies exploiting NAD+ metabolism

Prioritizing gut microbial SNPs linked to immunotherapy outcomes in NSCLC patients by integrative bioinformatics analysis

BACKGROUND

The human gut microbiome has emerged as a potential modulator of treatment efficacy for different cancers, including non-small cell lung cancer (NSCLC) patients undergoing immune checkpoint inhibitor (ICI) therapy. In this study, we investigated the association of gut microbial variations with response against ICIs by analyzing the gut metagenomes of NSCLC patients.

METHODS

Strain identification from the publicly available metagenomes of 87 NSCLC patients, treated with nivolumab and collected at three different timepoints (T0, T1, and T2), was performed using StrainPhlAn3. Variant calling and annotations were performed using Snippy and associations between microbial genes and genomic variations with treatment responses were evaluated using MaAsLin2. Supervised machine learning models were developed to prioritize single nucleotide polymorphisms (SNPs) predictive of treatment response. Structural bioinformatics approaches were employed using MUpro, I-Mutant 2.0, CASTp and PyMOL to access the functional impact of prioritized SNPs on protein stability and active site interactions.

RESULTS

Our findings revealed the presence of strains for several microbial species (e.g., Lachnospira eligens) exclusively in Responders (R) or Non-responders (NR) (e.g., Parabacteroides distasonis). Variant calling and annotations for the identified strains from R and NR patients highlighted variations in genes (e.g., ftsA, lpdA, and nadB) that were significantly associated with the NR status of patients. Among the developed models, Logistic Regression performed best (accuracy > 90% and AUC ROC > 95%) in prioritizing SNPs in genes that could distinguish R and NR at T0. These SNPs included Ala168Val (lpdA) in Phocaeicola dorei and Tyr233His (lpdA), Leu330Ser (lpdA), and His233Arg (obgE) in Parabacteroides distasonis. Lastly, structural analyses of these prioritized variants in objE and lpdA revealed their involvement in the substrate binding site and an overall reduction in protein stability. This suggests that these variations might likely disrupt substrate interactions and compromise protein stability, thereby impairing normal protein functionality.

CONCLUSION

The integration of metagenomics, machine learning, and structural bioinformatics provides a robust framework for understanding the association between gut microbial variations and treatment response, paving the way for personalized therapies for NSCLC in the future. These findings emphasize the potential clinical implications of microbiome-based biomarkers in guiding patient-specific treatment strategies and improving immunotherapy outcomes.

Gastrointestinal jumbo phages possess independent synthesis and utilization systems of NAD. MICROBIOME 2024;12:268. [PMID: 39707494 DOI: 10.1186/s40168-024-01984-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

BACKGROUND

Jumbo phages, phages with genomes > 200 kbp, contain some unique genes for successful reproduction in their bacterial hosts. Due to complex and massive genomes analogous to those of small-celled bacteria, how jumbo phages complete their life cycle remains largely undefined.

RESULTS

In this study, we assembled 668 high-quality jumbo phage genomes from over 15 terabytes (TB) of intestinal metagenomic data from 955 samples of 5 animal species (cow, sheep, pig, horse, and deer). Within them, we obtained a complete genome of 716 kbp in length, which is the largest phage genome so far reported in the gut environments. Interestingly, 174 out of the 668 jumbo phages were found to encode all genes required for the synthesis of NAD+ by the salvage pathway or Preiss-Handler pathway, referred to as NAD-jumbo phage. Besides synthesis genes of NAD+, these NAD-jumbo phages also encode at least 15 types of NAD+-consuming enzyme genes involved in DNA replication, DNA repair, and counterdefense, suggesting that these phages not only have the capacity to synthesize NAD+ but also redirect NAD+ metabolism towards phage propagation need in hosts. Phylogenetic analysis and environmental survey indicated NAD-jumbo phages are widely present in the Earth's ecosystems, including the human gut, lakes, salt ponds, mine tailings, and seawater.

CONCLUSION

In summary, this study expands our understanding of the diversity and survival strategies of phages, and an in-depth study of the NAD-jumbo phages is crucial for understanding their role in ecological regulation. Video Abstract.

In situ fortification of cereal by-products with vitamin B12: An eco-sustainable approach for food fortification

Vitamin B12 deficiency poses significant health risks, especially among populations with limited access to animal-based foods. This study explores the utilisation of cereal bran by-products, wheat (WB) and oat bran (OB), as substrates for in situ vitamin B12 fortification through solid-state fermentation (SSF) using Propionibacterium freudenreichii. The impact of various precursors addition, including riboflavin, cobalt, nicotinamide and DMBI on vitamin B12 production, along with changes in microbial growth, chemical profiles, and vitamin B12 yields during fermentation was evaluated. Results showed that WB and OB possess favourable constituents for microbial growth and vitamin B12 synthesis. The substrates supplemented with riboflavin, cobalt, and DMBI demonstrated enhanced B12 production. In addition, pH levels are essential in microbial viability and cobalamin biosynthesis. Monosaccharides and organic acids play a crucial role, with maltose showing a strong positive association with B12 production in OB, while in WB, citric acid exhibits significant correlations with various factors.

Phages reconstitute NAD+ to counter bacterial immunity

Bacteria defend against phage infection through a variety of antiphage defence systems1. Many defence systems were recently shown to deplete cellular nicotinamide adenine dinucleotide (NAD+) in response to infection, by cleaving NAD+ into ADP-ribose (ADPR) and nicotinamide2-7. It was demonstrated that NAD+ depletion during infection deprives the phage of this essential molecule and impedes phage replication. Here we show that a substantial fraction of phages possess enzymatic pathways allowing reconstitution of NAD+ from its degradation products in infected cells. We describe NAD+ reconstitution pathway 1 (NARP1), a two-step pathway in which one enzyme phosphorylates ADPR to generate ADPR pyrophosphate (ADPR-PP), and the second enzyme conjugates ADPR-PP and nicotinamide to generate NAD+. Phages encoding NARP1 can overcome a diverse set of defence systems, including Thoeris, DSR1, DSR2, SIR2-HerA and SEFIR, all of which deplete NAD+ as part of their defensive mechanism. Phylogenetic analyses show that NARP1 is primarily encoded on phage genomes, suggesting a phage-specific function in countering bacterial defences. A second pathway, NARP2, allows phages to overcome bacterial defences by building NAD+ using metabolites different from ADPR-PP. Our findings reveal a unique immune evasion strategy in which viruses rebuild molecules depleted by defence systems, thus overcoming host immunity.

Oxygen influences spatial heterogeneity and microbial succession dynamics during Baijiu stacking process

The spontaneous solid-state stacking process (SSSP) of Baijiu is an environmentally friendly and cost-effective process for enriching and assembling environmental microorganisms to guarantee the subsequent fermentation efficiency. In this study, how SSSP create spatial heterogeneity of stacking piles were found through spatiotemporal sampling. The degree of difficulty in oxygen exchange categorizes the stacking pile into depleted (≤4%), transitional (4 %-17 %), and enriched (≥17 %) oxygen-defined layers. This results in variation in succession rates (Vdepleted > Vtransitional > Venriched), which accelerates spatial heterogeneity during SSSP. As a dominant species (65 %-99 %) in depleted and transitional layers, Acetilactobacillus jinshanensis can rapidly reduce oxygen disturbance by upregulating poxL and catE, that sustains spatial heterogeneity. The findings demonstrated the value of oxygen control in shaping spatial heterogeneity during SSSP processes, which can create specific functional microbiome. Adding spatial heterogeneity management will help achieve more precise control of such solid-state fermentation systems.

Exploring NAD+ metabolism and NNAT: Insights from structure, function, and computational modeling

Nicotinamide Adenine Dinucleotide (NAD+), a coenzyme, is ubiquitously distributed and serves crucial functions in diverse biological processes, encompassing redox reactions, energy metabolism, and cellular signalling. This review article explores the intricate realm of NAD + metabolism, with a particular emphasis on the complex relationship between its structure, function, and the pivotal enzyme, Nicotinate Nucleotide Adenylyltransferase (NNAT), also known as nicotinate mononucleotide adenylyltransferase (NaMNAT), in the process of its biosynthesis. Our findings indicate that NAD + biosynthesis in humans and bacteria occurs via the same de novo synthesis route and the pyridine ring salvage pathway. Maintaining NAD homeostasis in bacteria is imperative, as most bacterial species cannot get NAD+ from their surroundings. However, due to lower sequence identity and structurally distant relationship of bacteria, including E. faecium and K. pneumonia, to its human counterpart, inhibiting NNAT, an indispensable enzyme implicated in NAD + biosynthesis, is a viable alternative in curtailing infections orchestrated by E. faecium and K. pneumonia. By merging empirical and computational discoveries and connecting the intricate NAD + metabolism network with NNAT's crucial role, it becomes clear that the synergistic effect of these insights may lead to a more profound understanding of the coenzyme's function and its potential applications in the fields of therapeutics and biotechnology.