Role of the Microbiota in Obesity: Effect After Bariatric Surgery

NCT07277465 | Completed

• 1 other identifier: CEIm: 8/21
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief 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.

Conditions

Obese Patients With Bariatric Surgery

Keywords

obesity; gut microbiota; metabolic syndrome

Outcome Measures

Primary Outcomes (2)

• Analyze the changes in the diversity of the intestinal microbiota 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.

  5 years

• Assess differences in the diversity of the intestinal microbiota after bariatric surgery depending on the surgical procedure (Roux-en-Y gastric bypass vs sleeve gastrectomy vs SADI-S).

  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.

  5 years

Secondary Outcomes (25)

• Evaluate the differences in the diversity of the intestinal microbiota depending on whether patients present metabolically healthy obesity (MHO) or metabolically unhealthy obesity (MUHO) before surgery

  5 years

• Evaluate significant changes in body fat mass percentage after bariatric surgery.

  3 years

• Assess significant changes in high-sensitivity C-reactive protein (hs-CRP) as an inflammatory parameter after bariatric surgery.

  3 years

• Evaluate significant changes in C3 protein as an inflammatory parameter after bariatric surgery.

  3 years

• Evaluate significant changes in interleukin 1-beta (IL-1B) levels as a pro-inflammatory molecule after bariatric surgery.

  3 years

Study Arms (1)

Bariatric surgery in patients with obesity

EXPERIMENTAL

Patients will undergo bariatric surgery if they meet the inclusion criteria and are willing to participate in the study.

Procedure: Bariatric surgery

Interventions

Bariatric surgery PROCEDURE

Bariatric surgery according to surgeon's assessment.

Also known as: Roux en-Y bypass, sleeve gastrectomy, Single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S)

Bariatric surgery in patients with obesity

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Patients with a body mass index (BMI) greater than 40 kg/m² (or \> 35 kg/m² with minimum one obesity comorbidity).
• Aged between 18 and 65 years.
• Patients with a known duration of obesity exceeding five years, despite dietary interventions and farmacological treatment.

You may not qualify if:

• Due to the nature of the study, patients with acute or chronic inflammatory diseases, established hepatic or renal insufficiency (defined as transaminase levels ±2 SD from the mean and estimated glomerular filtration rate \[CKD-EPI formula\] \>60), neoplasic diseases, or secondary causes of obesity (e.g., hypothyroidism, Cushing's syndrome) will be excluded.

Sponsors & Collaborators

• Celia Bañuls: lead

Study Sites (1)

FISABIO

Valencia, 46017, Spain

Location

Related Publications (12)

• Nijhawan S, Richards W, O'Hea MF, Audia JP, Alvarez DF. Bariatric surgery rapidly improves mitochondrial respiration in morbidly obese patients. Surg Endosc. 2013 Dec;27(12):4569-73. doi: 10.1007/s00464-013-3125-y. Epub 2013 Aug 24.

  PMID: 23982645 BACKGROUND

• Akalestou E, Miras AD, Rutter GA, le Roux CW. Mechanisms of Weight Loss After Obesity Surgery. Endocr Rev. 2022 Jan 12;43(1):19-34. doi: 10.1210/endrev/bnab022.

  PMID: 34363458 BACKGROUND

• Ciobarca D, Catoi AF, Copaescu C, Miere D, Crisan G. Bariatric Surgery in Obesity: Effects on Gut Microbiota and Micronutrient Status. Nutrients. 2020 Jan 16;12(1):235. doi: 10.3390/nu12010235.

  PMID: 31963247 BACKGROUND

• Cani PD, Van Hul M, Lefort C, Depommier C, Rastelli M, Everard A. Microbial regulation of organismal energy homeostasis. Nat Metab. 2019 Jan;1(1):34-46. doi: 10.1038/s42255-018-0017-4. Epub 2019 Jan 7.

  PMID: 32694818 BACKGROUND

• Aron-Wisnewsky J, Prifti E, Belda E, Ichou F, Kayser BD, Dao MC, Verger EO, Hedjazi L, Bouillot JL, Chevallier JM, Pons N, Le Chatelier E, Levenez F, Ehrlich SD, Dore J, Zucker JD, Clement K. Major microbiota dysbiosis in severe obesity: fate after bariatric surgery. Gut. 2019 Jan;68(1):70-82. doi: 10.1136/gutjnl-2018-316103. Epub 2018 Jun 13.

  PMID: 29899081 BACKGROUND

• Kootte RS, Levin E, Salojarvi J, Smits LP, Hartstra AV, Udayappan SD, Hermes G, Bouter KE, Koopen AM, Holst JJ, Knop FK, Blaak EE, Zhao J, Smidt H, Harms AC, Hankemeijer T, Bergman JJGHM, Romijn HA, Schaap FG, Olde Damink SWM, Ackermans MT, Dallinga-Thie GM, Zoetendal E, de Vos WM, Serlie MJ, Stroes ESG, Groen AK, Nieuwdorp M. Improvement of Insulin Sensitivity after Lean Donor Feces in Metabolic Syndrome Is Driven by Baseline Intestinal Microbiota Composition. Cell Metab. 2017 Oct 3;26(4):611-619.e6. doi: 10.1016/j.cmet.2017.09.008.

  PMID: 28978426 BACKGROUND

• Sroka-Oleksiak A, Mlodzinska A, Bulanda M, Salamon D, Major P, Stanek M, Gosiewski T. Metagenomic Analysis of Duodenal Microbiota Reveals a Potential Biomarker of Dysbiosis in the Course of Obesity and Type 2 Diabetes: A Pilot Study. J Clin Med. 2020 Jan 29;9(2):369. doi: 10.3390/jcm9020369.

  PMID: 32013181 BACKGROUND

• Amabebe E, Robert FO, Agbalalah T, Orubu ESF. Microbial dysbiosis-induced obesity: role of gut microbiota in homoeostasis of energy metabolism. Br J Nutr. 2020 May 28;123(10):1127-1137. doi: 10.1017/S0007114520000380. Epub 2020 Feb 3.

  PMID: 32008579 BACKGROUND

• Bouter KE, van Raalte DH, Groen AK, Nieuwdorp M. Role of the Gut Microbiome in the Pathogenesis of Obesity and Obesity-Related Metabolic Dysfunction. Gastroenterology. 2017 May;152(7):1671-1678. doi: 10.1053/j.gastro.2016.12.048. Epub 2017 Feb 10.

  PMID: 28192102 BACKGROUND

• Haluzik M, Kratochvilova H, Haluzikova D, Mraz M. Gut as an emerging organ for the treatment of diabetes: focus on mechanism of action of bariatric and endoscopic interventions. J Endocrinol. 2018 Apr;237(1):R1-R17. doi: 10.1530/JOE-17-0438. Epub 2018 Jan 29.

  PMID: 29378901 BACKGROUND

• Murphy R, Clarke MG, Evennett NJ, John Robinson S, Lee Humphreys M, Hammodat H, Jones B, Kim DD, Cutfield R, Johnson MH, Plank LD, Booth MWC. Laparoscopic Sleeve Gastrectomy Versus Banded Roux-en-Y Gastric Bypass for Diabetes and Obesity: a Prospective Randomised Double-Blind Trial. Obes Surg. 2018 Feb;28(2):293-302. doi: 10.1007/s11695-017-2872-6.

  PMID: 28840525 BACKGROUND

• Pareek M, Schauer PR, Kaplan LM, Leiter LA, Rubino F, Bhatt DL. Metabolic Surgery: Weight Loss, Diabetes, and Beyond. J Am Coll Cardiol. 2018 Feb 13;71(6):670-687. doi: 10.1016/j.jacc.2017.12.014.

  PMID: 29420964 BACKGROUND

MeSH Terms

Conditions

Obesity; Metabolic Syndrome

Interventions

Bariatric Surgery; Anastomosis, Roux-en-Y

Condition Hierarchy (Ancestors)

Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Insulin Resistance; Hyperinsulinism; Glucose Metabolism Disorders; Metabolic Diseases

Intervention Hierarchy (Ancestors)

Bariatrics; Obesity Management; Therapeutics; Surgical Procedures, Operative; Anastomosis, Surgical; Digestive System Surgical Procedures

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: November 30, 2025
• First Posted: December 11, 2025
• Study Start: March 3, 2021
• Primary Completion: January 31, 2025
• Study Completion: May 31, 2025
• Last Updated: December 18, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will not share

Locations

ES (1)