Role of the Microbiota in Obesity: Effect After Bariatric Surgery

To assess the alpha-diversity of the intestinal microbiota, defined as the average diversity of species in an ecosystem, the Shannon index will be used. The results are interpreted as follows: values less than 2 are considered low in diversity and values greater than 3 are high in species diversity.

To assess the beta-diversity of the intestinal microbiota, defined as the average diversity of species in an ecosystem, the Bray-Curtis index will be used. The results are interpreted as follows: values less than 2 are considered low in diversity and values greater than 3 are high in species diversity.

To asses the differences in alpha-diversity of the intestinal microbiota in both groups, it will be evaluated whether there are significant differences between the Shannon indices of the two groups. The classification of patients between MHO and MUHO will be carried out using the following criteria: MUHO will be considered when patients with obesity present ≥2 metabolic abnormalities, and MHO with ≤1 metabolic abnormalities; the following cardiovascular risk factors are considered metabolic abnormalities: elevated blood pressure (defined as either SBP ≥130 mm Hg, DBP ≥85 mm Hg, or treatment with antihypertensive medications), elevated triglycerides (as fasting triglyceride concentration ≥1.7 mmol/l), low HDL-C levels (defined as HDL-C <1.04 mmol/l, in men, <1.29 mmol/l/l in women, or treatment with lipid-lowering medications), dysglycemia (fasting plasma glucose 5.6 to 6.9 mmol/l, and/or and insulin resistance as HOMA-IR >3.8).

Percentage of body fat mass will be measured by bioelectrical impedance. It is considered to be high when ≥25% in men and ≥30% in women. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Participants will be considered to have achieved an improvement in high-sensitivity C-reactive protein levels if they normalize its value (normality values defined between 0 and 1.69mg/dl).

Participants will be considered to have achieved an improvement in C3 protein if they normalize its value (normality values defined between 81 and 157mg/dl).

IL-1B levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

IL-6 levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

TNF-alpha levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Superoxide dismutase levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

NMR spectra will be used to obtain spectra from serum samples from the cohort. In order to evaluate if there will be significant differences after the dietetic intervention, a PLS-DA model for discrimination between basal and post intervention levels will be performed. Scores plots will be calculated with a 95% confidence interval.

Total ROS levels will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Total glutathione levels will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Total free radicals will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Mitochondrial ROS production will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Superoxide content will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Mitochondrial membrane potential will be assessed by a flow cytometry assay. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Genetic markers of inflammation and metabolic pathways will be analyzed from the faeces samples, in order to identify different clusters of these pathways and determine the potential functions of gut microbiota. For that purpose, transcriptome will be quantified with nanostring techology. The relative quantity of gene expression (fold change) of each gene will be calculated with the comparative 2-ΔΔCT method, and significant differences will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Adipsin levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Resistin levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Leptin will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

PAI-1 levels will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

Ghrelin will be measured using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

GLP-1 levels will be assessed using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

PYY levels will be assessed using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

GIP levels will be assessed using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.

CCK levels will be assessed using the Luminex® 200 analyzer system. A significant improvement will be considered when notable differences are observed in the mean values between groups measured through p-value (<0.05) with a 95% confidence interval.