A systems biology approach to understand gut microbiota and host metabolism in morbid obesity: design of the BARIA Longitudinal Cohort Study

INTRODUCTION

Prevalence of obesity and associated diseases, including type 2 diabetes mellitus, dyslipidaemia and non-alcoholic fatty liver disease (NAFLD), are increasing. Underlying mechanisms, especially in humans, are unclear. Bariatric surgery provides the unique opportunity to obtain biopsies and portal vein blood-samples.

METHODS

The BARIA Study aims to assess how microbiota and their metabolites affect transcription in key tissues and clinical outcome in obese subjects and how baseline anthropometric and metabolic characteristics determine weight loss and glucose homeostasis after bariatric surgery. We phenotype patients undergoing bariatric surgery (predominantly laparoscopic Roux-en-Y gastric bypass), before weight loss, with biometrics, dietary and psychological questionnaires, mixed meal test (MMT) and collect fecal-samples and intra-operative biopsies from liver, adipose tissues and jejunum. We aim to include 1500 patients. A subset (approximately 25%) will undergo intra-operative portal vein blood-sampling. Fecal-samples are analyzed with shotgun metagenomics and targeted metabolomics, fasted and postprandial plasma-samples are subjected to metabolomics, and RNA is extracted from the tissues for RNAseq-analyses. Data will be integrated using state-of-the-art neuronal networks and metabolic modeling. Patient follow-up will be ten years.

RESULTS

Preoperative MMT of 170 patients were analysed and clear differences were observed in glucose homeostasis between individuals. Repeated MMT in 10 patients showed satisfactory intra-individual reproducibility, with differences in plasma glucose, insulin and triglycerides within 20% of the mean difference.

CONCLUSION

The BARIA study can add more understanding in how gut-microbiota affect metabolism, especially with regard to obesity, glucose metabolism and NAFLD. Identification of key factors may provide diagnostic and therapeutic leads to control the obesity-associated disease epidemic.

Distinct differences in gut microbial composition and functional potential from lean to morbidly obese subjects

INTRODUCTION

The gut microbiome may contribute to the development of obesity. So far, the extent of microbiome variation in people with obesity has not been determined in large cohorts and for a wide range of body mass index (BMI). Here, we aimed to investigate whether the faecal microbial metagenome can explain the variance in several clinical phenotypes associated with morbid obesity.

METHODS

Caucasian subjects were recruited at our hospital. Blood pressure and anthropometric measurements were taken. Dietary intake was determined using questionnaires. Shotgun metagenomic sequencing was performed on faecal samples from 177 subjects.

RESULTS

Subjects without obesity (n = 82, BMI 24.7 ± 2.9 kg m^-2 ) and subjects with obesity (n = 95, BMI 38.6 ± 5.1 kg m^-2 ) could be clearly distinguished based on microbial composition and microbial metabolic pathways. A total number of 52 bacterial species differed significantly in people with and without obesity. Independent of dietary intake, we found that microbial pathways involved in biosynthesis of amino acids were enriched in subjects with obesity, whereas pathways involved in the degradation of amino acids were depleted. Machine learning models showed that more than half of the variance in body fat composition followed by BMI could be explained by the gut microbiome, composition and microbial metabolic pathways, compared with 6% of variation explained in triglycerides and 9% in HDL.

CONCLUSION

Based on the faecal microbiota composition, we were able to separate subjects with and without obesity. In addition, we found strong associations between gut microbial amino acid metabolism and specific microbial species in relation to clinical features of obesity.

P6208VEgetaRian Diet in patients with Ischemic heart disease (VERDI): an open-label, randomized, prospective, cross-over study

Background

A vegetarian diet (VD) in patients diagnosed with ischemic heart disease (IHD) may reduce future cardiovascular risk.

Purpose

The study hypothesis was that patients diagnosed with IHD can benefit from a VD assessed by multiple risk markers for this type of disease.

Methods

In a crossover study patients diagnosed with IHD, treated by percutaneous coronary intervention and on optimal medical therapy were randomly allocated to a 4-week intervention with ready-made (lunch and dinner) isocaloric VD or meat diet (MD). The primary outcome was change in oxidized low-density lipoprotein cholesterol (LDL-C) levels. Secondary outcomes were difference in changes of blood lipids, weight, body mass index (BMI), blood pressure, heart rate, glycated haemoglobin (HbA1c), number of participants reaching guideline target values, quality of life, gut microbiota, and trimethylamine N-oxide between the two interventions.

Results

31 participants were recruited (median age: 67 years, male sex: 93.5%). Significant between-intervention differences (VD vs MD) were found in oxidized LDL-C (−2.73 U/L; p=0.015), total cholesterol (TC) (−0.13 mmol/L, p=0.01), LDL-C (−0.10 mmol/L; p=0.02), weight (−0.67 kg, p=0.008) and BMI (−0.21 kg/m2, p=0.009). After VD, numerically more subjects reached guideline LDL-C target values (87% vs 77%) but this did not reach statistical significance (p=0.07). During VD intervention the diet led to a significant reduction in oxidized LDL-C, TC, LDL-C, HDL-C, ApoB, and ApoB/ApoA1 ratio.

Conclusions

Our results suggest that in patients with IHD a VD compared to a MD, lowers oxidative stress, improves lipid profile and lowers BMI.

Acknowledgement/Funding

This study is partially funded by ALF and the Swedish Heart and Lung Foundation.

A histidine-kinase cheA gene of Pseudomonas pseudoalcaligens KF707 not only has a key role in chemotaxis but also affects biofilm formation and cell metabolism

A histidine-kinase cheA gene in Pseudomonas pseudoalcaligenes KF707 plays a central role in the regulation of metabolic responses as well as in chemotaxis. Non-chemotactic mutants harboring insertions into the cheA gene were screened for their ability to form biofilms in the Calgary biofilm device. Notably, ≥95% decrease in the number of cells attached to the polystyrene surface was observed in cheA mutants compared to the KF707 wild-type biofilm phenotype. The ability to form mature biofilms was restored to wild-type levels, providing functional copies of the KF707 cheA gene to the mutants. In addition, phenotype micro-arrays and proteomic analyses revealed that several basic metabolic activities and a few periplasmic binding proteins of cheA mutant cells differed compared to those of wild-type cells. These results are interpreted as evidence of a strong integration between chemotactic and metabolic pathways in the process of biofilm development by P. pseudoalcaligenes KF707.