Adipose tissue derived bacteria are associated with inflammation in obesity and type 2 diabetes
Authors: Matthias Blüher
Alyce Crane
Jörg Fallmann
Peter Kovacs
Martin von Bergen
Sven-Bastiaan Haange
Arne Dietrich
Lucas Massier
Niculina Musat
Rima Chakaroun
Henrike Heyne
Michael Stumvoll
Martin Gericke
Shirin Tabei
Konrad David Didt
Journal: Gut (2020)
Discipline: CLINICAL MEDICINE
Keywords: bacterial translocation; inflammation; intestinal permeability; obesity; obesity surgery.
Affiliations: Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany., IFB AdiposityDiseases, University of Leipzig Medical Center, Leipzig, Germany., Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, Leipzig, Germany., Department of Molecular Systems Biology, Helmholtz Center for Environmental Research GmbH - UFZ, Leipzig, Germany., Institute of Human Genetics, University of Leipzig, Leipzig, Germany., Broad Institute of MIT and Harvard, Boston, Massachusetts, USA., Institute of Anatomy and Cell Biology, Martin-Luther University Halle-Wittenberg, Halle, Germany., Institute of Anatomy, University of Leipzig, Leipzig, Germany., University Hospital Leipzig, Clinic for Visceral, Transplantation and Thorax and Vascular Surgery, University of Leipzig, Leipzig, Germany., Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany., Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany .

Abstract:  Objective: Bacterial translocation to various organs including human adipose tissue (AT) due to increased intestinal permeability remains poorly understood. We hypothesised that: (1) bacterial presence is highly tissue specific and (2) related in composition and quantity to immune inflammatory and metabolic burden. Design: We quantified and sequenced the bacterial 16S rRNA gene in blood and AT samples (omental, mesenteric and subcutaneous) of 75 subjects with obesity with or without type 2 diabetes (T2D) and used catalysed reporter deposition (CARD) - fluorescence in situ hybridisation (FISH) to detect bacteria in AT. Results: Under stringent experimental and bioinformatic control for contaminants, bacterial DNA was detected in blood and omental, subcutaneous and mesenteric AT samples in the range of 0.1 to 5 pg/µg DNA isolate. Moreover, CARD-FISH allowed the detection of living, AT-borne bacteria. Proteobacteria and Firmicutes were the predominant phyla, and bacterial quantity was associated with immune cell infiltration, inflammatory and metabolic parameters in a tissue-specific manner. Bacterial composition differed between subjects with and without T2D and was associated with related clinical measures, including systemic and tissues-specific inflammatory markers. Finally, treatment of adipocytes with bacterial DNA in vitro stimulated the expression of TNFA and IL6. Conclusions: Our study provides contaminant aware evidence for the presence of bacteria and bacterial DNA in several ATs in obesity and T2D and suggests an important role of bacteria in initiating and sustaining local AT subclinical inflammation and therefore impacting metabolic sequelae of obesity. 

Retracted: No

PubPeer comments:
 The authors seem to have done everything to ensure that no contamination appears, with excluding contaminants which were present in their negative control. Yet, the proteobacterial section of their results clearly display organisms, which are non-animal associated organisms, frequently found as contaminants (Delftia, Allorhizobium, Xanthomonas, Thahibacter). Chloroflexi and Planctomycetes are also not known to be animal associated. The rest of the data looks partially like gut content, so a hypothesis could be that there is low-level contamination from the sequenced gut content, although this does not explain the mentioned contaminants. The data does not seem to be available, so it is not possible to re-check these results. ,