HEALTHMARK investigated the complex associations between diet, microbiota, tryptophan metabolites of microbial metabolism, and metabolic health in a set-up of identification, replication, and validation of associations. The project, organized in five work packages (WP) comprised two observational and two intervention studies. In WP1, the University of Bonn (UB) using the DOrtmund Nutritional and Anthropometric Longitudinally Designed Study identified long-term body mass index trajectories and observed their association with cardiometabolic risk markers (CRM) such as interleukin-18. Besides, long-term overweight was associated with decreased levels of indole-3-acetic acid and several amino acids, including indole-3-carboxaldehyde were associated with elevated C-reactive protein (CRP). Finally, carbohydrate intake was associated with the relative abundance of some gut bacteria, Phascolarctobacterium, Dialister, and Desulfovibrio. In WP2, the German Center for Neurodegenerative Diseases, "Deutsches Zentrum für Neurodegenerative Erkrankungen e. V." (DZNE) using the Rhineland Study developed novel methods to automatically segment body fat distribution from MRI recordings. It was also observed that branched-chain amino acids (BCAA) and aromatic amino acids (AAA) metabolites are important biomarkers of some CRM and partial mediators of the association between visceral adipose tissue and CRM. In WP3, the National Research Institute for Agriculture, Food and Environment, “Institut national de recherche pour l’agriculture, l’alimentation et l’environnement” (INRAE) using the Obesity Study measured plasma levels of tryptophan, and its metabolites, other AAA, and BCAA  before and after surgery-induced weight loss. Severe or morbid obesity was associated with increased ratio kynurenine/tryptophan, high plasma levels of 5-hydroxyindole- 3-acetic acid, and low plasma levels of tryptophan, serotonin, indole-3-propionic acid, indole-3-acetic acid, indole-3-lactic acid, and indoxyl sulfate. Moreover, kynurenine and tryptophan indole metabolites were associated with CRP and interleukin-6. In WP4, the University College Cork/Teagasc (UCC/Teagasc) conducted a clinical investigation on the efficacy of probiotic Lactobacillus mucosae DPC6426 as a nutritional agent to modulate tryptophan metabolism and metabolic biomarkers in mildly hypercholesteremic adults. The counts of Lactobacillus increased in stool samples, but the probiotic had no effect on either total blood cholesterol or microbial diversity. In WP5, the Edmund Mach Foundation, “Fondazione Edmund Mach” (FEM) developed and performed targeted metabolomic profiling of biofluids for the putative biomarkers of metabolic health for the WPs, 672 urine samples from WP1, 1000 plasma samples from WP2, and 104 plasma samples from WP3. FEM also built an in-house spectral library for structural elucidation and comparison of metabolites from these samples. Some samples also underwent untargeted metabolomics profiling.

HEALTHMARK investigated the complex associations between diet, microbiota, tryptophan metabolites of microbial metabolism, and metabolic health in a set-up of identification, replication, and validation of associations. HEALTHMARK observed the association of long term body mass index, visceral adipose tissue and severe or morbid obesity with cardiometabolic risk markers. It also established the link of tryptophan and its metabolites, other aromatic amino acid metabolites and branched-chain amino acids with cardiometabolic risk markers. The project also observed the impact of dietary intake, particularly carbohydrate intake on the composition of the gut microbiome. In addition, probiotic Lactobacillus mucosae DPC6426 did not show effect on total blood cholesterol or gut microbial diversity. Finally, a validated state-of-the-art targeted metabolomic profiling method was used to quantify metabolites in the biofluids within the consortium.