Froukje J. Verdam

Human intestinal microbiota composition is associated with local and systemic inflammation in obesity

Intestinal microbiota have been suggested to contribute to the development of obesity, but the mechanism remains elusive. The relationship between microbiota composition, intestinal permeability, and inflammation in nonobese and obese subjects was investigated.

Non-invasive assessment of barrier integrity and function of the human gut

Over the past decades evidence has been accumulating that intestinal barrier integrity loss plays a key role in the development and perpetuation of a variety of disease states including inflammatory bowel disease and celiac disease, and is a key player in the onset of sepsis and multiple organ failure in situations of intestinal hypoperfusion, including trauma and major surgery. Insight into gut barrier integrity and function loss is important to improve our knowledge on disease etiology and pathophysiology and contributes to early detection and/or secondary prevention of disease. A variety of tests have been developed to assess intestinal epithelial cell damage, intestinal tight junction status and consequences of intestinal barrier integrity loss, i.e. increased intestinal permeability. This review discusses currently available methods for evaluating loss of human intestinal barrier integrity and function.

Novel Evidence for Chronic Exposure to Endotoxin in Human Nonalcoholic Steatohepatitis

Background Endotoxin is hypothesized to play an important role in the activation of inflammatory pathways associated with nonalcoholic steatohepatitis (NASH). However, demonstration of hepatic endotoxin exposure is challenging due to the inaccessibility of the portal circulation. Furthermore, reliable measurement of the relatively low endotoxin levels in plasma of patients with liver disease and subsequent interpretation remain difficult. Goals In this study, we used the EndoCab assay that measures endogenous antibodies to the core region of endotoxin to estimate hepatic endotoxin exposure over time. Study IgG levels against endotoxin were measured in peripheral plasma obtained from 21 severely obese patients with NASH and 9 severely obese patients with healthy livers. Results Plasma IgG levels against endotoxin were significantly elevated in patients with NASH compared with patients with healthy livers (48±63 GMU/mL vs. 10±13 GMU/mL). Moreover, these IgG levels progressively increased with NASH grade (grade 1 29±37; grade 2 58±51; grade 3 84±132 GMU/mL, P<0.05). There was no relation between plasma IgG levels and NASH stage. Conclusions Plasma IgG levels against endotoxin were found to be increased in biopsy-proven human NASH and increased with aggravated inflammation in NASH, suggesting a relationship between chronic endotoxin exposure and the severity of human NASH.

Navigating through metaproteomics data - a logbook of database searching

Metaproteomic research involves various computational challenges during the identification of fragmentation spectra acquired from the proteome of a complex microbiome. These issues are manifold and range from the construction of customized sequence databases, the optimal setting of search parameters to limitations in the identification search algorithms themselves. In order to assess the importance of these individual factors, we studied the effect of strategies to combine different search algorithms, explored the influence of chosen database search settings, and investigated the impact of the size of the protein sequence database used for identification. Furthermore, we applied de novo sequencing as a complementary approach to classic database searching. All evaluations were performed on a human intestinal metaproteome dataset. Pyrococcus furiosus proteome data were used to contrast database searching of metaproteomic data to a classic proteomic experiment. Searching against subsets of metaproteome databases and the use of multiple search engines increased the number of identifications. The integration of P. furiosus sequences in a metaproteomic sequence database showcased the limitation of the target‐decoy‐controlled false discovery rate approach in combination with large sequence databases. The selection of varying search engine parameters and the application of de novo sequencing represented useful methods to increase the reliability of the results. Based on our findings, we provide recommendations for the data analysis that help researchers to establish or improve analysis workflows in metaproteomics.

Co-expressed immune and metabolic genes in visceral and subcutaneous adipose tissue from severely obese individuals are associated with plasma HDL and glucose levels: a microarray study

BackgroundExcessive accumulation of body fat, in particular in the visceral fat depot, is a major risk factor to develop a variety of diseases such as type 2 diabetes. The mechanisms underlying the increased risk of obese individuals to develop co-morbid diseases are largely unclear.We aimed to identify genes expressed in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) that are related to blood parameters involved in obesity co-morbidity, such as plasma lipid and glucose levels, and to compare gene expression between the fat depots.MethodsWhole-transcriptome SAT and VAT gene expression levels were determined in 75 individuals with a BMI >35 kg/m2. Modules of co-expressed genes likely to be functionally related were identified and correlated with BMI, plasma levels of glucose, insulin, HbA1c, triglycerides, non-esterified fatty acids, ALAT, ASAT, C-reactive protein, and LDL- and HDL cholesterol.ResultsOf the approximately 70 modules identified in SAT and VAT, three SAT modules were inversely associated with plasma HDL-cholesterol levels, and a fourth module was inversely associated with both plasma glucose and plasma triglyceride levels (p < 5.33 × 10-5). These modules were markedly enriched in immune and metabolic genes. In VAT, one module was associated with both BMI and insulin, and another with plasma glucose (p < 4.64 × 10-5). This module was also enriched in inflammatory genes and showed a marked overlap in gene content with the SAT modules related to HDL. Several genes differentially expressed in SAT and VAT were identified.ConclusionsIn obese subjects, groups of co-expressed genes were identified that correlated with lipid and glucose metabolism parameters; they were enriched with immune genes. A number of genes were identified of which the expression in SAT correlated with plasma HDL cholesterol, while their expression in VAT correlated with plasma glucose. This underlines both the singular importance of these genes for lipid and glucose metabolism and the specific roles of these two fat depots in this respect.

Small intestinal alterations in severely obese hyperglycemic subjects

CONTEXT Type 2 diabetes mellitus (DM2) is associated with small intestinal hyperplasia and hypertrophy in rodents. Moreover, the small intestine is increasingly acknowledged to play a role in the pathophysiology of DM2. OBJECTIVE The objective of the study was to investigate the relation between plasma markers of small intestinal function and chronic hyperglycemia in man. DESIGN, SETTING, AND PARTICIPANTS We conducted a cross-sectional observational study of 40 severely obese subjects with chronic hyperglycemia and 30 severely obese subjects without chronic hyperglycemia who were indicated for bariatric surgery. MAIN OUTCOME MEASURES We assessed plasma levels of citrulline, representing small intestinal enterocyte mass, intestinal fatty acid binding protein (I-FABP), a marker of enterocyte loss, and glucagon-like peptide-2, an intestinotrophic factor, and related them to glycated hemoglobin (HbA(1c)) levels. RESULTS Plasma citrulline and I-FABP levels were both significantly elevated in subjects with chronic hyperglycemia (HbA(1c) > 6.0%) compared with subjects with a normal HbA(1c) (≤ 6.0%) (citrulline, 35 ± 2.1 μm vs. 26 ± 1.4 μm, P = 0.001; I-FABP, 140 ± 22 pg/ml vs. 69 ± 14 pg/ml, P = 0.001). Moreover, plasma citrulline and I-FABP levels correlated with HbA(1c) levels (citrulline, r(s) = 0.30, P = 0.02; I-FABP, r(s) = 0.33, P = 0.005). The I-FABP to citrulline ratio was higher in subjects with an elevated HbA(1c) (4.0 vs. 3.1, P = 0.03). Plasma glucagon-like peptide-2 levels were not related to citrulline or I-FABP levels (r(s) = 0.06, P = 0.67; r(s) 0.08, P = 0.54, respectively). CONCLUSION Chronically elevated glucose levels in obese individuals are associated with increased small intestinal enterocyte mass and increased enterocyte loss. These findings argue for the further exploration of the role of the intestine in the pathophysiology of DM2.

Reduced Paneth cell antimicrobial protein levels correlate with activation of the unfolded protein response in the gut of obese individuals

The intestinal microbiota is increasingly acknowledged to play a crucial role in the development of obesity. A shift in intestinal microbiota composition favouring the presence of Firmicutes over Bacteroidetes has been observed in obese subjects. A similar shift has been reported in mice with deficiency of active Paneth cell α‐defensins. We aimed at investigating changes in Paneth cell antimicrobial levels in the gut of obese subjects. Next, we studied activation of the unfolded protein response (UPR) as a possible mechanism involved in altered Paneth cell function. Paneth cell numbers were counted in jejunal sections of 15 severely obese (BMI > 35) and 15 normal weight subjects. Expression of Paneth cell antimicrobials human α‐defensin 5 (HD5) and lysozyme were investigated using immunohistochemistry, qPCR, and western blot. Activation of the UPR was assessed with western blot. Severely obese subjects showed decreased protein levels of both HD5 and lysozyme, while Paneth cell numbers were unchanged. Lysozyme protein levels correlated inversely with BMI. Increased expression of HD5 (DEFA5) and lysozyme (LYZ) transcripts in the intestine of obese subjects prompted us to investigate a possible translational block caused by UPR activation. Binding protein (BiP) and activating transcription factor 4 (ATF4) levels were increased, confirming activation of the UPR in the gut of obese subjects. Furthermore, levels of both proteins correlated with BMI. Involvement of the UPR in the lowered antimicrobial protein levels in obese subjects was strongly suggested by a negative correlation between BiP levels and lysozyme levels. Additionally, indications of ER stress were apparent in Paneth cells of obese subjects. Our findings provide the first evidence for altered Paneth cell function in obesity, which may have important implications for the obesity‐associated shift in microbiota composition. In addition, we show activation of the UPR in the intestine of obese subjects, which may underlie the observed Paneth cell compromise. Copyright

Spread of Excitation Measurements for the Detection of Electrode Array Foldovers: A Prospective Study Comparing 3-Dimensional Rotational X-ray and Intraoperative Spread of Excitation Measurements

Objective: The optimal positioning of electrode arrays in the cochlea is extremely important. Our standard approach is to use a 3-dimensional rotational x-ray for the intraoperative determination of the position of the electrode array. We wanted to see if spread of excitation (SOE) is useful for determining the electrode array position within the cochlea. Study Design: Prospective blind study design. Setting: Tertiary University Referral Center (Cochlear Implantation Center Amsterdam-Academic Medical Center, University of Amsterdam). Patients: Seventy-two implanted ears with a Cochlear Freedom device. Intervention: After cochlear implantation, we compared the 3-dimensional rotational x-ray imaging and SOE measurements. The investigators were blinded for the intraoperative surgeon findings and also for the imaging findings. Outcome Measure(s): Electrode array foldovers within the cochlea and the reliability of the SOE measurements. Results: We placed implants in 72 ears in this study, and all procedures seemed to be surgically uneventful. To our surprise, we discovered 4 electrode foldovers in this group. Of the 4 foldovers, 3 were corrected intraoperatively. Conclusion: We found that intraoperative imaging and/or electrophysiologic measurements such as the SOE provide very useful information regarding electrode position within the cochlea. Spread of excitation is effective in detecting electrode array foldovers if the audiologist is experienced. Some software modifications are suggested.

Colonic metaproteomic signatures of active bacteria and the host in obesity.

Obesity is associated with the intestinal microbiota in humans but the underlying mechanisms are yet to be fully understood. Our previous phylogenetic study showed that the faecal microbiota profiles of nonobese versus obese and morbidly obese individuals differed. Here, we have extended this analysis with a characterization of the faecal metaproteome, in order to detect differences at a functional level. Proteins were extracted from crude faecal samples of 29 subjects, separated by 1D gel electrophoresis and characterized using RP LC–MS/MS. The peptide data were analyzed in database searches with two complementary algorithms, OMSSA and X!Tandem, to increase the number of identifications. Evolutionary genealogy of genes: nonsupervised orthologous groups (EggNOG) database searches resulted in the functional annotation of over 90% of the identified microbial and human proteins. Based on both bacterial and human proteins, a clear clustering of obese and nonobese samples was obtained that exceeded the phylogenetic separation in dimension. Moreover, integration of the metaproteomics and phylogenetic datasets revealed notably that the phylum Bacteroidetes was metabolically more active in the obese than nonobese subjects. Finally, significant correlations between clinical measurements and bacterial gene functions were identified. This study emphasizes the importance of integrating data of the host and microbiota to understand their interactions.

Non-alcoholic steatohepatitis: A non-invasive diagnosis by analysis of exhaled breath

BACKGROUND & AIMS Histological evaluation of a liver biopsy is the current gold standard to diagnose non-alcoholic steatohepatitis (NASH), but the procedure to obtain biopsies is associated with morbidity and high costs. Hence, only subjects at high risk are biopsied, leading to underestimation of NASH prevalence, and undertreatment. Since analysis of volatile organic compounds in breath has been shown to accurately identify subjects with other chronic inflammatory diseases, we investigated its potential as a non-invasive tool to diagnose NASH. METHODS Wedge-shaped liver biopsies from 65 subjects (BMI 24.8-64.3 kg/m(2)) were obtained during surgery and histologically evaluated. The profile of volatile organic compounds in pre-operative breath samples was analyzed by gas chromatography-mass spectrometry and related to liver histology scores and plasma parameters of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). RESULTS Three exhaled compounds were sufficient to distinguish subjects with (n=39) and without NASH (n=26), with an area under the ROC curve of 0.77. The negative and positive predictive values were 82% and 81%. In contrast, elevated ALT levels or increased AST/ALT ratios both showed negative predictive values of 43%, and positive predictive values of 88% and 70%, respectively. The breath test reduced the hypothetical percentage of undiagnosed NASH patients from 67-79% to 10%, and of misdiagnosed subjects from 49-51% to 18%. CONCLUSIONS Analysis of volatile organic compounds in exhaled air is a promising method to indicate NASH presence and absence. In comparison to plasma transaminase levels, the breath test significantly reduced the percentage of missed NASH patients and the number of unnecessarily biopsied subjects.