Iron status influences non-alcoholic fatty liver disease in obesity through the gut microbiome.

BACKGROUND: The gut microbiome and iron status are known to play a role in the pathophysiology of non-alcoholic fatty liver disease (NAFLD), although their complex interaction remains unclear. RESULTS: Here, we applied an integrative systems medicine approach (faecal metagenomics, plasma and urine metabolomics, hepatic transcriptomics) in 2 well-characterised human cohorts of subjects with obesity (discovery n = 49 and validation n = 628) and an independent cohort formed by both individuals with and without obesity (n = 130), combined with in vitro and animal models. Serum ferritin levels, as a markers of liver iron stores, were positively associated with liver fat accumulation in parallel with lower gut microbial gene richness, composition and functionality. Specifically, ferritin had strong negative associations with the Pasteurellaceae, Leuconostocaceae and Micrococcaea families. It also had consistent negative associations with several Veillonella, Bifidobacterium and Lactobacillus species, but positive associations with Bacteroides and Prevotella spp. Notably, the ferritin-associated bacterial families had a strong correlation with iron-related liver genes. In addition, several bacterial functions related to iron metabolism (transport, chelation, heme and siderophore biosynthesis) and NAFLD (fatty acid and glutathione biosynthesis) were also associated with the host serum ferritin levels. This iron-related microbiome signature was linked to a transcriptomic and metabolomic signature associated to the degree of liver fat accumulation through hepatic glucose metabolism. In particular, we found a consistent association among serum ferritin, Pasteurellaceae and Micrococcacea families, bacterial functions involved in histidine transport, the host circulating histidine levels and the liver expression of GYS2 and SEC24B. Serum ferritin was also related to bacterial glycine transporters, the host glycine serum levels and the liver expression of glycine transporters. The transcriptomic findings were replicated in human primary hepatocytes, where iron supplementation also led to triglycerides accumulation and induced the expression of lipid and iron metabolism genes in synergy with palmitic acid. We further explored the direct impact of the microbiome on iron metabolism and liver fact accumulation through transplantation of faecal microbiota into recipient's mice. In line with the results in humans, transplantation from 'high ferritin donors' resulted in alterations in several genes related to iron metabolism and fatty acid accumulation in recipient's mice. CONCLUSIONS: Altogether, a significant interplay among the gut microbiome, iron status and liver fat accumulation is revealed, with potential significance for target therapies. Video abstract.

Publisher Correction: Molecular phenomics and metagenomics of hepatic steatosis in non-diabetic obese women.

In the version of this article originally published, the received date was missing. It should have been listed as 2 January 2018. The error has been corrected in the HTML and PDF versions of this article.

Molecular phenomics and metagenomics of hepatic steatosis in non-diabetic obese women.

Hepatic steatosis is a multifactorial condition that is often observed in obese patients and is a prelude to non-alcoholic fatty liver disease. Here, we combine shotgun sequencing of fecal metagenomes with molecular phenomics (hepatic transcriptome and plasma and urine metabolomes) in two well-characterized cohorts of morbidly obese women recruited to the FLORINASH study. We reveal molecular networks linking the gut microbiome and the host phenome to hepatic steatosis. Patients with steatosis have low microbial gene richness and increased genetic potential for the processing of dietary lipids and endotoxin biosynthesis (notably from Proteobacteria), hepatic inflammation and dysregulation of aromatic and branched-chain amino acid metabolism. We demonstrated that fecal microbiota transplants and chronic treatment with phenylacetic acid, a microbial product of aromatic amino acid metabolism, successfully trigger steatosis and branched-chain amino acid metabolism. Molecular phenomic signatures were predictive (area under the curve = 87%) and consistent with the gut microbiome having an effect on the steatosis phenome (>75% shared variation) and, therefore, actionable via microbiome-based therapies.

k-SLAM: accurate and ultra-fast taxonomic classification and gene identification for large metagenomic data sets.

k-SLAM is a highly efficient algorithm for the characterization of metagenomic data. Unlike other ultra-fast metagenomic classifiers, full sequence alignment is performed allowing for gene identification and variant calling in addition to accurate taxonomic classification. A k-mer based method provides greater taxonomic accuracy than other classifiers and a three orders of magnitude speed increase over alignment based approaches. The use of alignments to find variants and genes along with their taxonomic origins enables novel strains to be characterized. k-SLAM's speed allows a full taxonomic classification and gene identification to be tractable on modern large data sets. A pseudo-assembly method is used to increase classification accuracy by up to 40% for species which have high sequence homology within their genus.

XperimentR: painless annotation of a biological experiment for the laboratory scientist.

BACKGROUND: Today's biological experiments often involve the collaboration of multidisciplinary researchers utilising several high throughput 'omics platforms. There is a requirement for the details of the experiment to be adequately described using standardised ontologies to enable data preservation, the analysis of the data and to facilitate the export of the data to public repositories. However there are a bewildering number of ontologies, controlled vocabularies, and minimum standards available for use to describe experiments. There is a need for user-friendly software tools to aid laboratory scientists in capturing the experimental information. RESULTS: A web application called XperimentR has been developed for use by laboratory scientists, consisting of a browser-based interface and server-side components which provide an intuitive platform for capturing and sharing experimental metadata. Information recorded includes details about the biological samples, procedures, protocols, and experimental technologies, all of which can be easily annotated using the appropriate ontologies. Files and raw data can be imported and associated with the biological samples via the interface, from either users' computers, or commonly used open-source data repositories. Experiments can be shared with other users, and experiments can be exported in the standard ISA-Tab format for deposition in public databases. XperimentR is freely available and can be installed natively or by using a provided pre-configured Virtual Machine. A guest system is also available for trial purposes. CONCLUSION: We present a web based software application to aid the laboratory scientist to capture, describe and share details about their experiments.

ADAM: automated data management for research datasets.

UNLABELLED: Existing repositories for experimental datasets typically capture snapshots of data acquired using a single experimental technique and often require manual population and continual curation. We present a storage system for heterogeneous research data that performs dynamic automated indexing to provide powerful search, discovery and collaboration features without the restrictions of a structured repository. ADAM is able to index many commonly used file formats generated by laboratory assays and therefore offers specific advantages to the experimental biology community. However, it is not domain specific and can promote sharing and re-use of working data across scientific disciplines. AVAILABILITY AND IMPLEMENTATION: ADAM is implemented using Java and supported on Linux. It is open source under the GNU General Public License v3.0. Installation instructions, binary code, a demo system and virtual machine image and are available at http://www.imperial.ac.uk/bioinfsupport/resources/software/adam.

Strategies towards sequencing complex crop genomes.

A report on the Strategies for de novo assemblies of complex crop genomes workshop held at The Genome Analysis Centre, Norwich, UK, 8-10 October 2012.

Genome expansion and gene loss in powdery mildew fungi reveal tradeoffs in extreme parasitism.

Powdery mildews are phytopathogens whose growth and reproduction are entirely dependent on living plant cells. The molecular basis of this life-style, obligate biotrophy, remains unknown. We present the genome analysis of barley powdery mildew, Blumeria graminis f.sp. hordei (Blumeria), as well as a comparison with the analysis of two powdery mildews pathogenic on dicotyledonous plants. These genomes display massive retrotransposon proliferation, genome-size expansion, and gene losses. The missing genes encode enzymes of primary and secondary metabolism, carbohydrate-active enzymes, and transporters, probably reflecting their redundancy in an exclusively biotrophic life-style. Among the 248 candidate effectors of pathogenesis identified in the Blumeria genome, very few (less than 10) define a core set conserved in all three mildews, suggesting that most effectors represent species-specific adaptations.

Identification of genes selectively disallowed in the pancreatic islet.

We have previously identified two genes, encoding lactate dehydrogenase (Ldha) and the monocarboxylate carrier, MCT1 (Slc16a1) whose expression is remarkably low in pancreatic ß-cells and islets. We sought here to determine whether these may be part of a larger family of genes selectively repressed ("disallowed") in the pancreatic islet. Using new and publicly available microarray data, we undertook a bioinformatic analysis of gene expression in islets and a range of other murine tissues. We compared data sets from three sources of mouse pancreatic islets with a total of 30 datasets from nine tissues, to identify genes with at least five-fold down-regulation in islets. 39 genes were revealed as being specifically repressed in islets. These included Ldha and Slc16a1 as expected but also genes involved in several other metabolic pathways which could affect glucose stimulated insulin secretion. Of these, adenylate kinase 3 (AK3) is a mitochondrial enzyme which acts on GTP, and ornithine aminotransferase (OAT) lies on the pathway converting glutamate to ornithine. The removal of an enzyme which could dissipate mitochondrial GTP levels in beta cells provides support for the theory that mitochondrial GTP may be an important for regulating insulin secretion, whilst blocking an alternative metabolic fate for glutamate is consistent with a signalling role for glutamate. The identification of these genes should inform efforts to generate fully functional ß-cells from stem cell sources, and may provide new targets in type 2 diabetes.

Bioinformatic analysis of Entamoeba histolytica SINE1 elements.

BACKGROUND: Invasive amoebiasis, caused by infection with the human parasite Entamoeba histolytica remains a major cause of morbidity and mortality in some less-developed countries. Genetically E. histolytica exhibits a number of unusual features including having approximately 20% of its genome comprised of repetitive elements. These include a number of families of SINEs - non-autonomous elements which can, however, move with the help of partner LINEs. In many eukaryotes SINE mobility has had a profound effect on gene expression; in this study we concentrated on one such element - EhSINE1, looking in particular for evidence of recent transposition. RESULTS: EhSINE1s were detected in the newly reassembled E. histolytica genome by searching with a Hidden Markov Model developed to encapsulate the key features of this element; 393 were detected. Examination of their sequences revealed that some had an internal structure showing one to four 26-27 nt repeats. Members of the different classes differ in a number of ways and in particular those with two internal repeats show the properties expected of fairly recently transposed SINEs - they are the most homogeneous in length and sequence, they have the longest (i.e. the least decayed) target site duplications and are the most likely to show evidence (in a cDNA library) of active transcription. Furthermore we were able to identify 15 EhSINE1s (6 pairs and one triplet) which appeared to be identical or very nearly so but inserted into different sites in the genome; these provide good evidence that if mobility has now ceased it has only done so very recently. CONCLUSIONS: Of the many families of repetitive elements present in the genome of E. histolytica we have examined in detail just one - EhSINE1. We have shown that there is evidence for waves of transposition at different points in the past and no evidence that mobility has entirely ceased. There are many aspects of the biology of this parasite which are not understood, in particular why it is pathogenic while the closely related species E. dispar is not, the great genetic diversity found amongst patient isolates and the fact, which may be related, that only a small proportion of those infected develop clinical invasive amoebiasis. Mobile genetic elements, with their ability to alter gene expression may well be important in unravelling these puzzles.

Protein identification and quantification by two-dimensional infrared spectroscopy: implications for an all-optical proteomic platform.

Electron-vibration-vibration two-dimensional coherent spectroscopy, a variant of 2DIR, is shown to be a useful tool to differentiate a set of 10 proteins based on their amino acid content. Two-dimensional vibrational signatures of amino acid side chains are identified and the corresponding signal strengths used to quantify their levels by using a methyl vibrational feature as an internal reference. With the current apparatus, effective differentiation can be achieved in four to five minutes per protein, and our results suggest that this can be reduced to <1 min per protein by using the same technology. Finally, we show that absolute quantification of protein levels is relatively straightforward to achieve and discuss the potential of an all-optical high-throughput proteomic platform based on two-dimensional infrared spectroscopic measurements.

Comparative whole-genome analyses reveal over 100 putative phase-variable genes in the pathogenic Neisseria spp.

Previously, a complete genome analysis of Neisseria meningitidis strain MC58 revealed the largest repertoire of putative phase-variable genes described in any species to date. Initial comparisons with two incomplete Neisseria spp. genome sequences available at that time revealed differences in the repeats associated with these genes in the form of polymorphisms, the absence of the potentially unstable elements in some alleles, and in the repertoire of the genes that were present. Analyses of the complete genomes of N. meningitidis strain Z2491 and Neisseria gonorrhoeae strain FA1090 have been performed and are combined with a comprehensive comparative analysis between the three available complete genome sequences. This has increased the sensitivity of these searches and provided additional contextual information that facilitates the interpretation of the functional consequences of repeat instability. This analysis identified: (i) 68 phase-variable gene candidates in N. meningitidis strain Z2491, rather than the 27 previously reported; (ii) 83 candidates in N. gonorrhoeae strain FA1090; and (iii) 82 candidates in N. meningitidis strain MC58, including an additional 19 identified through cross-comparisons with the other two strains. In addition to the 18 members of the opa gene family, a repertoire of 119 putative phase-variable genes is described, indicating a huge potential for diversification mediated by this mechanism of gene switching in these species that is central to their interactions with the host and environmental transitions. Eighty-two of these are either known (14) or strong (68) candidates for phase variation, which together with the opa genes make a total of 100 identified genes. The repertoires of the genes identified in this analysis diverge from the different species groupings, indicating horizontal exchange that significantly affects the species and strain complements of these genes.