Associations between untargeted plasma metabolomic signatures and gut microbiota composition in the Milieu Intérieur population of healthy adults

Recommendations for sample selection, collection and preparation for NMR-based metabolomics studies of blood

BACKGROUND

Metabolic profiling of blood metabolites, particularly in plasma and serum, is vital for studying human diseases, human conditions, drug interventions and toxicology. The clinical significance of blood arises from its close ties to all human cells and facile accessibility. However, patient-specific variables such as age, sex, diet, lifestyle and health status, along with pre-analytical conditions (sample handling, storage, etc.), can significantly affect metabolomic measurements in whole blood, plasma, or serum studies. These factors, referred to as confounders, must be mitigated to reveal genuine metabolic changes due to illness or intervention onset.

REVIEW OBJECTIVE

This review aims to aid metabolomics researchers in collecting reliable, standardized datasets for NMR-based blood (whole/serum/plasma) metabolomics. The goal is to reduce the impact of confounding factors and enhance inter-laboratory comparability, enabling more meaningful outcomes in metabolomics studies.

KEY CONCEPTS

This review outlines the main factors affecting blood metabolite levels and offers practical suggestions for what to measure and expect, how to mitigate confounding factors, how to properly prepare, handle and store blood, plasma and serum biosamples and how to report data in targeted NMR-based metabolomics studies of blood, plasma and serum.

Links between gut microbiota with specific serum metabolite groups in pregnant women with overweight or obesity

BACKGROUND AND AIM

Gut microbiota may regulate metabolism but is incompletely characterized in pregnancy. Our objective was to investigate the relations using omics techniques.

METHODS AND RESULTS

In a cross-sectional setting, fecal and serum samples of 361 healthy pregnant women with overweight or obesity were analyzed with a combinatorial approach of metagenomics and targeted NMR-based metabolomics, with statistical and machine learning techniques to identify and analyze the extent to which the gut microbiota composition and predicted functions would be reflected in the serum metabolome. We identified five biclusters, each of which consisted of a set of gut microbial species and serum metabolites with correlated abundance profiles. Two of the biclusters included metabolites that have been linked to the cardiovascular health; one was linked with factors known to increase the risk i.e., various sizes of lipoprotein subclasses (VLDL and LDL), subclasses of relative lipoprotein lipid concentrations (VLDL, IDL, and LDL), apolipoprotein B, and an inflammation marker, glycoprotein acetylation. These metabolites were associated with abundances of species such as, Enterocloster bolteae and Ruminococcus gnavus. The second bicluster included metabolites linked with a reduced cardiovascular risk, such as different sizes of HDL (high-density lipoprotein), subclasses for relative lipoprotein lipid concentrations and mean diameter for HDL particles, and fatty acid ratios. These metabolites were associated with abundances of species, such as Bacteroides cellulosilyticus and Alistipes finegoldii. We did not observe any biclusters between predicted pathways and serum metabolites.

CONCLUSION

Overall, we identified five biclusters of co-abundant gut bacteria and serum metabolites , of which two were linked to pro-atherogenic and anti-atherogenic properties.

TRIAL REGISTRATION

www.

CLINICALTRIALS

Gov: NCT01922791.

Oxidative Status of Ultra-Processed Foods in the Western Diet

Ultra-processed foods (UPFs) have gained substantial attention in the scientific community due to their surging consumption and potential health repercussions. In addition to their well-established poor nutritional profile, UPFs have been implicated in containing various dietary oxidized sterols (DOxSs). These DOxSs are associated with a spectrum of chronic diseases, including cardiometabolic conditions, cancer, diabetes, Parkinson's, and Alzheimer's disease. In this study, we present a comprehensive database documenting the presence of DOxSs and other dietary metabolites in >60 UPFs commonly consumed as part of the Western diet. Significant differences were found in DOxS and phytosterol content between ready-to-eat (RTE) and fast foods (FFs). Biomarker analysis revealed that DOxS accumulation, particularly 25-OH and triol, can potentially discriminate between RTEs and FFs. This work underscores the potential utility of dietary biomarkers in early disease detection and prevention. However, an essential next step is conducting exposure assessments to better comprehend the levels of DOxS exposure and their association with chronic diseases.

An online atlas of human plasma metabolite signatures of gut microbiome composition

Human gut microbiota produce a variety of molecules, some of which enter the bloodstream and impact health. Conversely, dietary or pharmacological compounds may affect the microbiota before entering the circulation. Characterization of these interactions is an important step towards understanding the effects of the gut microbiota on health. In this cross-sectional study, we used deep metagenomic sequencing and ultra-high-performance liquid chromatography linked to mass spectrometry for a detailed characterization of the gut microbiota and plasma metabolome, respectively, of 8583 participants invited at age 50 to 64 from the population-based Swedish CArdioPulmonary bioImage Study. Here, we find that the gut microbiota explain up to 58% of the variance of individual plasma metabolites and we present 997 associations between alpha diversity and plasma metabolites and 546,819 associations between specific gut metagenomic species and plasma metabolites in an online atlas (https://gutsyatlas.serve.scilifelab.se/). We exemplify the potential of this resource by presenting novel associations between dietary factors and oral medication with the gut microbiome, and microbial species strongly associated with the uremic toxin p-cresol sulfate. This resource can be used as the basis for targeted studies of perturbation of specific metabolites and for identification of candidate plasma biomarkers of gut microbiota composition.

Here, Dekkers et al. characterize associations of 1528 gut metagenomic species with the plasma metabolome in 8583 participants of the SCAPIS Study, and find that gut microbiota explain up to 58% of the variance of individual plasma metabolites.