Danielle Cristina Fonseca

Tissue-specific methylation profile in obese patients with type 2 diabetes before and after Roux-en-Y gastric bypass

Eating habits, lifestyles, and exposure to specific environmental factors can greatly impact the risk of developing type 2 diabetes (T2D), influence the genome epigenetically, and affect the expression of genes, including genes related to glycemic control, at any stage of life. The epigenetic mechanism underlying obesity and T2D pathogenesis remains poorly understood. Conventional strategies for the treatment of obesity and its comorbidities often have poor long-term adherence, and pharmacological interventions are limited. Bariatric surgery is the most effective current option to treat severe obesity, and Roux-en-Y gastric bypass (RYGB) is the most applied technique worldwide. Epigenetic changes differ depending on the approach used to treat obesity and its associated comorbidities (clinical or surgical). Compared to primary clinical care, bariatric surgery leads to much greater loss of body weight and higher remission rates of T2D and metabolic syndrome, with methylation profiles in promoter regions of genes in obese individuals becoming similar to those of normal-weight individuals. Bariatric surgery can influence DNA methylation in parallel with changes in gene expression pattern. Changes in clinical biomarkers that reflect improvements in glucose and lipid metabolism after RYGB often occur before major weight loss and are coordinated by surgery-induced changes in intestinal hormones. Therefore, the intestine methylation profile would assist in understanding the mechanisms involved in improved glycemic control after bariatric surgery. The main objectives in this area for the future are to identify epigenetic marks that could be used as early indicators of metabolic risk, and to develop treatments able to delay or even reverse these epigenetic changes. Studies that provide the “human epigenetic profile” will be of considerable value to identify tissue-specific epigenetic signatures and their role in the development of chronic diseases. Further studies should apply methods based on global analysis of the genome to identify methylated sites associated with disease and epigenetic marks associated with the remodeling response to bariatric surgery. This review describes the main epigenetic alterations associated with obesity and T2D and the potential role of RYGB in remodeling these changes.

Gastrointestinal Transcriptomic Response of Metabolic Vitamin B12 Pathways in Roux-en-Y Gastric Bypass

OBJECTIVES: Vitamin B12 (B12) deficiency after Roux‐en‐Y gastric bypass (RYGB) is highly prevalent and may contribute to postoperative complications. Decreased production of intrinsic factor owing to gastric fundus removal is thought to have a major role, but other components of B12 metabolism may also be affected. We evaluated changes in the expression levels of multiple B12 pathway‐encoding genes in gastrointestinal (GI) tissues to evaluate the potential roles in contributing to post‐RYGB B12 deficiency. METHODS: During double‐balloon enteroscopy, serial GI biopsies were collected from 20 obese women (age, 46.9±6.2 years; body mass index, 46.5±5.3u2009kg/m2) with adult‐onset type 2 diabetes (fasting plasma glucose ≥126u2009mg/dl; hemoglobin A1c≥6.5%) before and, at the same site, 3 months after RYGB. Gene expression levels were assessed by the Affymetrix Human GeneChip 1.0 ST microarray. Findings were validated by real‐time quantitative PCR (RT–qPCR). RESULTS: Gene expression levels with significant changes (P≤0.05) included: transcobalamin I (TCN1) in remnant (−1.914‐fold) and excluded (−1.985‐fold) gastric regions; gastric intrinsic factor (GIF) in duodenum (−0.725‐fold); and cubilin (CUBN) in duodenum (+0.982‐fold), jejunum (+1.311‐fold), and ileum (+0.685‐fold). Validation by RT–qPCR confirmed (P≤0.05) observed changes for TCN1 in the remnant gastric region (−0.132‐fold) and CUBN in jejunum (+2.833‐fold). CONCLUSIONS: RYGB affects multiple pathway‐encoding genes that may be associated with postoperative B12 deficiency. Decreased TCN1 levels seem to be the main contributing factor. Increased CUBN levels suggest an adaptive genetic reprogramming of intestinal tissue aiming to compensate for impaired intestinal B12 delivery.

The SURMetaGIT study: Design and rationale for a prospective pan-omics examination of the gastrointestinal response to Roux-en-Y gastric bypass surgery

Objective To describe the protocol of the SURgically induced Metabolic effects on the Human GastroIntestinal Tract (SURMetaGIT) study, a clinical pan-omics study exploring the gastrointestinal tract as a central organ driving remission of type 2 diabetes mellitus (T2DM) after Roux-en-Y gastric bypass (RYGB). The main points considered in the study’s design and challenges faced in its application are detailed. Methods This observational, longitudinal, prospective study involved collection of gastrointestinal biopsy specimens, faeces, urine, and blood from 25 obese women with T2DM who were candidates for RYGB (20 patients for omics assessment and 5 for omics validation). These collections were performed preoperatively and 3 and 24 months postoperatively. Gastrointestinal transcriptomics; faecal metagenomics and metabolomics; plasma proteomics, lipidomics, and metabolomics; and biochemical, nutritional, and metabolic data were assessed to identify their short- and long-term correlations with T2DM remission. Results Data were collected from 20 patients before and 3 months after RYGB. These patients have nearly completed the 2-year follow-up assessments. The five additional patients are currently being selected for omics data validation. Conclusion The multi-integrated pan-omics approach of the SURMetaGIT study enables integrated analysis of data that will contribute to the understanding of molecular mechanisms involved in T2DM remission after RYGB.

Upregulation of Ghrelin Gene Expression in the Excluded Stomach of Obese Women with Type 2 Diabetes After Roux-en-Y Gastric Bypass in the SURMetaGIT Study

BackgroundMechanisms of type 2 diabetes remission (T2Dr) after Roux-en-Y gastric bypass (RYGB) in obese patients appear to involve gastrointestinal hormones.ObjectiveThe objective of this study is to explore changes in ghrelin plasma levels and ghrelin gastrointestinal gene expression (GHRL) after RYGB, and their relationships to T2Dr.SettingIn 20 obese women with T2D, before and 3xa0months after RYGB, we assessed GHRL expression by microarray and quantitative RT-PCR in gastrointestinal biopsy samples and plasma levels of ghrelin.ResultsAfter RYGB, GHRL expression increased in the excluded stomach (pu2009<u20090.05) with no change in other gastrointestinal sites. There were no significant changes in ghrelin plasma levels and no correlations with T2Dr.ConclusionsAfter RYGB, over-expression of GHRL gene occurs only in the excluded stomach with no correlation to T2Dr.

Reduced intestinal FADS1 gene expression and plasma omega-3 fatty acids following Roux-en-Y gastric bypass

BACKGROUND & AIMSnRoux-en-Y gastric bypass (RYGB) limits food ingestion and may alter the intestinal expression of genes involved in the endogenous synthesis of polyunsaturated fatty acids (PUFAs). These changes may decrease the systemic availability of bioactive PUFAs after RYGB. To study the impact of RYGB on the dietary ingestion and plasma concentration of PUFAs and on the intestinal expression of genes involved in their endogenous biosynthesis in severely obese women with type 2 diabetes.nnnMETHODSnBefore, and 3 and 12 months after RYGB, obese women (nxa0=xa020) self-reported a seven-day dietary record, answered a food frequency query and provided plasma samples for alpha-linolenic (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA) and arachidonic (ARA) acid assessment by gas chromatography. Intestinal biopsies (duodenum, jejunum and ileum) were collected through double-balloon endoscopy before and 3 months after RYGB for gene expression analysis by microarray (Human GeneChip 1.0 ST array) and RT-qPCR validation.nnnRESULTSnCompared to the preoperative period, patients had decreased intakes of PUFAs, fish and soybean oil (pxa0<xa00.05) and lower plasma concentrations of ALA and EPA (pxa0<xa00.001) 3 and 12 months after RYGB. FADS1 gene expression was lower in duodenum (RT-qPCR fold changexa0=xa0-1.620, pxa0<xa00.05) and jejunum (RT-qPCR fold changexa0=xa0-1.549, pxa0<xa00.05) 3 months following RYGB, compared to before surgery.nnnCONCLUSIONnRYGB decreased PUFA ingestion, plasma ALA and EPA levels, and intestinal expression of FADS1 gene. The latter encodes a key enzyme involved in endogenous biosynthesis of PUFAs. These data suggest that supplementation of omega-3 PUFAs may be required for obese patients undergoing RYGB. Clinical Trial Registry number and website: www.clinicaltrials.gov - NCT01251016; Plataforma Brasil - 19339913.0.0000.0068.