Role of the Microbiota in Obesity: Effect After Bariatric Surgery

Detailed Summary

Several studies have demonstrated that bariatric surgery is effective for inducing weight loss in obese patients. In addition, the effects of this surgery on multiple associated alterations are well known, including changes in the secretion and activity of hormones involved in appetite regulation, satiety, and energy expenditure, as well as alterations in the gut microbiota composition. However, in cases of severe obesity, recent data have challenged the prevailing view, as bacterial species associated with low microbial richness (prior to surgery) appear to change only marginally after bariatric surgery, despite significant metabolic improvements. Our objective is to examine whether gut microbiota and gastrointestinal peptides are further impaired in severe obesity and, additionally, to explore how the microbiota relates to metabolic profile or sex, as well as whether bariatric surgery may differentially correct obesity-related intestinal microbial features. To this end, we propose a prospective, interventional, translational clinical study involving a cohort of 60 obese patients (BMI \> 35 kg/m²) undergoing laparoscopic gastric bypass surgery. Patients will be grouped according to their degree of obesity to assess potential baseline differences and to evaluate the efficacy of the intervention. Furthermore, we will investigate whether these parameters differ according to metabolic profile or sex. Body composition and nutritional status will be assessed, along with cardiovascular risk factors and comorbidities (hypertension, obstructive sleep apnea syndrome, dyslipidemia, type 2 diabetes mellitus, and insulin resistance). Gastrointestinal hormones (ghrelin, GIP, GLP-1, PYY, CCK, and leptin) will be measured in serum using Luminex XMAP technology. The content and diversity of the gut microbiota will be analyzed (16S rRNA amplicon sequencing and shotgun metagenomic sequencing using Illumina MiSeq technology) in stool samples collected before and 6-12 months after surgery. Additionally, individualized dietary follow-up and assessment of participants' quality of life will be conducted.

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