DNA methylation of genes regulating appetite and prediction of weight loss after bariatric surgery in obese individuals

A case control study investigating the methylation levels of GHRL and GHSR genes in alcohol use disorder

BACKGROUND

Alcohol use disorder (AUD) is a relapsing disease described as excessive use of alcohol. Evidence of the role of DNA methylation in addiction is accumulating. Ghrelin is an important peptide known as appetite hormone and its role in addictive behavior has been identified. Here we aimed to determine the methylation levels of two crucial genes (GHRL and GHSR) in ghrelin signaling and further investigate the association between methylation ratios and plasma ghrelin levels.

METHODS

Individuals diagnosed with (n = 71) and without (n = 82) AUD were recruited in this study. DNA methylation levels were measured through methylation-sensitive high-resolution melting (MS-HRM). Acylated ghrelin levels were detected by ELISA. The GHRL rs696217 polymorphism was analyzed by the standard PCR-RFLP method.

RESULTS

GHRL was significantly hypermethylated (P < 0.0022) in AUD between 25 and 50% methylation than in control subjects but no significant changes of GHSR methylation were observed. Moreover, GHRL showed significant positive correlation of methylation ratio between 25 and 50% with age. A significant positive correlation between GHSR methylation and ghrelin levels in the AUD group was determined (P = 0.037). The level of GHRL methylation and the ghrelin levels showed a significant association in the control subjects (P = 0.042).

CONCLUSION

GHSR and GHRL methylation levels did not change significantly between control and AUD groups. However, GHRL and GHSR methylations seemed to have associations with plasma ghrelin levels in two groups. This is the first study investigating the DNA methylation of GHRL and GHSR genes in AUD.

Epigenetic Marks as Predictors of Metabolic Response to Bariatric Surgery: Validation from an Epigenome Wide Association Study

Little is known about the potential role of epigenetic marks as predictors of the resolution of obesity-related comorbidities after bariatric surgery. In this study, 20 patients were classified according to the metabolic improvement observed 6 months after sleeve gastrectomy, based on the diagnosis of metabolic syndrome, into responders if metabolic syndrome reversed after bariatric surgery (n = 10) and non-responders if they had metabolic syndrome bariatric surgery (n = 10). Blood DNA methylation was analyzed at both study points using the Infinium Methylation EPIC Bead Chip array-based platform. Twenty-six CpG sites and their annotated genes, which were previously described to be associated with metabolic status, were evaluated. Cg11445109 and cg19469447 (annotated to Cytochrome P450 2E1 (CYP2E1) gene) were significantly more hypomethylated in the responder group than in the non-responder group at both study points, whilst cg25828445 (annotated to Nucleolar Protein Interacting With The FHA Domain Of MKI67 Pseudogene 3 (NIFKP3) gene) showed to be significantly more hypermethylated in the non-responder group compared to the responder group at both study points. The analysis of the methylation sites annotated to the associated genes showed that CYP2E1 had 40% of the differentially methylated CpG sites, followed by Major Histocompatibility Complex, Class II, DR Beta 1 (HLA-DRB1) (33.33%) and Zinc Finger Protein, FOG Family Member 2 (ZFPM2) (26.83%). Cg11445109, cg19469447 and cg25828445 could have a role in the prediction of metabolic status and potential value as biomarkers of response to bariatric surgery.

Investigation of GHSR methylation levels in thymomas from patients with Myasthenia Gravis

BACKGROUND

Hypermethylation of the growth hormone secretagogue receptor gene (GHSR) is increasingly observed in human cancers, suggesting that it could represent a pan-cancer biomarker of clinical interest. However, little is still known concerning GHSR methylation levels in thymic epithelial tumors, and particularly in thymomas from patients with Myasthenia Gravis (TAMG).

MATERIAL AND METHODS

In the present study we collected DNA samples from circulating lymphocytes and surgically resected tumor tissues of 65 TAMG patients, and from the adjacent healthy thymic tissue available from 43 of them. We then investigated GHSR methylation levels in the collected tissues searching for correlation with the clinical characteristics of the samples.

RESULTS

GHSR hypermethylation was observed in 18 thymoma samples (28%) compared to the healthy thymic tissues (P < 1 × 10^-4), and those samples were particularly enriched in advanced disease stages than stage I (94% were in stage II or higher). GHSR was demethylated in the remaining 47 thymomas, as well as in all the investigated healthy thymic samples and in circulating lymphocytes.

CONCLUSIONS

GHSR hypermethylation is not a pan-cancer marker or an early event in TAMG, but occurs in almost 1/4 of them and mainly from stage II onward. Subsequent studies are required to clarify the molecular pathways leading to GHSR hypermethylation in TAMG tissues and their relevance to disease progression.

Factors Influencing Epigenetic Mechanisms: Is There A Role for Bariatric Surgery?

Epigenetics is the interaction between the genome and environmental stimuli capable of influencing gene expression during development and aging. A large number of studies have shown that metabolic diseases are highly associated with epigenetic alterations, suggesting that epigenetic factors may play a central role in obesity. To investigate these relationships, we focus our attention on the most common epigenetic modifications that occur in obesity, including DNA methylation and post-translational modifications of histones. We also consider bariatric surgery as an epigenetic factor, evaluating how the anatomic and physiologic modifications induced by these surgical techniques can change gene expression. Here we discuss the importance of epigenetic mechanisms in chronic disease and cancer, and the role of epigenetic disturbances in obesity, with a focus on the role of bariatric surgery.

SERPINE-1 Gene Methylation and Protein as Molecular Predictors of Laparoscopic Sleeve Gastrectomy Outcome

BACKGROUND

Body weight is subjected to genetic and epigenetic modifiers that might affect the success of weight loss interventions. Because of its possible complications and disparity in patients' response, identification of predictors to the outcome of bariatric surgery is indispensable.

OBJECTIVES

This prospective study aims to investigate serpin peptidase inhibitor type 1 (SERPINE-1) protein and gene methylation as molecular predictors to the outcome of bariatric surgery.

PATIENTS AND METHODS

One hundred participants were enrolled and divided to control group (n = 50) and obese patients who underwent laparoscopic sleeve gastrectomy (LSG) (n = 50). Anthropometric measurements were assessed and blood samples were collected preoperatively and 6 months postoperatively for assessment of SERPINE-1 protein and gene methylation, C-reactive protein (CRP), and homeostatic model assessment of insulin resistance (HOMA-IR). Moreover, subjects were followed for 2 years for weight loss parameters.

RESULTS

Patients with obesity showed high baseline SERPINE-1 protein and gene hypermethylation where LSG was followed by a drop in SERPINE-1 protein level but not gene hypermethylation. Baseline SERPINE-1 gene methylation was negatively related to postoperative weight loss and was the independent predictor to weight loss after LSG. Likewise, postoperative SERPINE-1 protein was negatively related to weight loss with independent expression from its gene methylation state. Furthermore, postoperative SERPINE-1 gene methylation correlated to CRP and HOMA-IR.

CONCLUSION

Baseline SERPINE-1 gene methylation might be a predictor of weight loss after LSG. Meanwhile, postoperative SERPINE-1 protein could be a predictor to weight loss maintenance after LSG. Lastly, postoperative SERPINE-1 gene methylation might serve as an index to postoperative changes in obesity-related comorbidities.

DNA methylation screening after roux-en Y gastric bypass reveals the epigenetic signature stems from genes related to the surgery per se

Background/objectives

Obesity has been associated with gene methylation regulation. Recent studies have shown that epigenetic signature plays a role in metabolic homeostasis after Roux-en Y gastric bypass (RYGB). To conduct a genome-wide epigenetic analysis in peripheral blood to investigate whether epigenetic changes following RYGB stem from weight loss or the surgical procedure per se.

Subjects/methods

By means of the Infinium Human Methylation 450 BeadChip array, global methylation was analyzed in blood of 24 severely obese women before and 6 months after RYGB and in 24 normal-weight women (controls).

Results

In blood cells, nine DMCpG sites showed low methylation levels before surgery, methylation levels increased after RYGB and neared the levels measured in the controls. Additionally, 44 CpG sites associated with the Wnt and p53 signaling pathways were always differently methylated in the severely obese patients as compared to the controls and were not influenced by RYGB. Finally, 1638 CpG sites related to inflammation, angiogenesis, and apoptosis presented distinct methylation in the post-surgery patients as compared to the controls.

Conclusion

Bariatric surgery per se acts on CpGs related to inflammation, angiogenesis, and endothelin-signaling. However, the gene cluster associated with obesity remains unchanged, suggesting that weight loss 6 months after RYGB surgery cannot promote this effect.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0522-7) contains supplementary material, which is available to authorized users.