Upregulated TNF Expression 1 Year After Bariatric Surgery Reflects a Cachexia-Like State in Subcutaneous Adipose Tissue

Metabolic Recovery with the Persistence of Proinflammatory Leucocyte Dysfunction After Bariatric Intervention for Obesity

PURPOSE

A suitable option for severe obesity treatment is a surgical approach. After surgery, metabolic markers and weight frequently return to adequate values; however, concerning systemic inflammatory mediators, the results are inconsistent. Furthermore, it has been suggested that leucocyte function may be affected even after weight normalization. This study aimed to determine if the surgical treatment of obesity influences the production of cytokines by LPS-stimulated as a function of leucocytes.

MATERIALS AND METHODS

We performed a cross-sectional study that investigated the production of cytokines in response to lipopolysaccharide (LPS) along a kinetic of simulation by leucocytes recovered from individuals with normal weight (NW, n = 8), persons living with obesity (Ob, n = 7), persons living with obesity and diabetes mellitus (Ob-DM, n = 17), and persons that used to live with obesity who underwent bypass surgery (fOb + bypass, n = 8) and recover normal weigh.

RESULTS

IL-6 levels were significantly higher in the Ob and fOb + bypass groups than in NW (p = 0.043). IL-10 secretion without LPS was significantly higher in the NW group than in the other groups explored (p < 0.05). When exposed to LPS, the IL-10 levels increased in all groups except the NW group. As also observed for IL-18 and IL-33, the secretion curve of the fOb + bypass group was more similar to the Ob group, even when they had reached normal weight, as opposed to the NW group.

CONCLUSION

Our results show that in patients with fOb + bypass, inflammatory and anti-inflammatory cytokine production dynamics remain disrupted even with improved metabolic control and normal weight recovery.

Differential Gene Expression of Subcutaneous Adipose Tissue among Lean, Obese, and after RYGB (Different Timepoints): Systematic Review and Analysis

The main roles of adipose tissue include triglycerides storage and adipokine secretion, which regulate energy balance and inflammation status. In obesity, adipocyte dysfunction leads to proinflammatory cytokine production and insulin resistance. Bariatric surgery is the most effective treatment for obesity, the gold-standard technique being Roux-en-Y gastric bypass (RYGB). Since metabolic improvements after RYGB are clear, a better understanding of adipose tissue molecular modifications could be derived from this study. Thus, the aim of this systematic review was to find differentially expressed genes in subcutaneous adipose tissue of lean, obese and post-RYGB (distinct timepoints). To address this objective, publications from 2015-2022 reporting gene expression (candidate genes or transcriptomic approach) of subcutaneous adipose tissue from lean and obese individuals before and after RGYB were searched in PubMed, Elsevier, and Springer Link. Excluded publications were reviews, studies analyzing serum, other types of tissues, or bariatric procedures. A risk-of-bias summary was created for each paper using Robvis, to finally include 17 studies. Differentially expressed genes in post-RYGB vs. obese and lean vs. obese were obtained and the intersection among these groups was used for analysis and gene classification by metabolic pathway. Results showed that the lean state as well as the post-RYGB is similar in terms of increased expression of insulin-sensitizing molecules, inducing lipogenesis over lipolysis and downregulating leukocyte activation, cytokine production and other factors that promote inflammation. Thus, massive weight loss and metabolic improvements after RYGB are accompanied by gene expression modifications reverting the "adipocyte dysfunction" phenomenon observed in obesity conditions.

Impact of Bariatric Surgery on Adipose Tissue Biology

Bariatric surgery (BS) procedures are actually the most effective intervention to help subjects with severe obesity achieve significant and sustained weight loss. White adipose tissue (WAT) is increasingly recognized as the largest endocrine organ. Unhealthy WAT expansion through adipocyte hypertrophy has pleiotropic effects on adipocyte function and promotes obesity-associated metabolic complications. WAT dysfunction in obesity encompasses an altered adipokine secretome, unresolved inflammation, dysregulated autophagy, inappropriate extracellular matrix remodeling and insufficient angiogenic potential. In the last 10 years, accumulating evidence suggests that BS can improve the WAT function beyond reducing the fat depot sizes. The causal relationships between improved WAT function and the health benefits of BS merits further investigation. This review summarizes the current knowledge on the short-, medium- and long-term outcomes of BS on the WAT composition and function.

Bariatric surgery can acutely modulate ER-stress and inflammation on subcutaneous adipose tissue in non-diabetic patients with obesity

BACKGROUND

Bariatric surgery, especially Roux-en-Y gastric bypass (RYGB), is the most effective and durable treatment option for severe obesity. The mechanisms involving adipose tissue may be important to explain the effects of surgery.

METHODS

We aimed to identify the genetic signatures of adipose tissue in patients undergoing RYGB. We evaluated 13 obese, non-diabetic patients (mean age 37 years, 100% women, Body mass index (BMI) 42.2 kg/m²) one day before surgery, 3 and 6 months (M) after RYGB.

RESULTS

Analysis of gene expression in adipose tissue collected at surgery compared with samples collected at 3 M and 6 M Post-RYGB showed that interleukins [Interleukin 6, Tumor necrosis factor-α (TNF-α), and Monocyte chemoattractant protein-1(MCP1)] and endoplasmic reticulum stress (ERS) genes [Eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3) and Calreticulin (CALR)] decreased during the follow-up (P ≤ 0.01 for all). Otherwise, genes involved in energy homeostasis [Adiponectin and AMP-activated protein kinase (AMPK)], cellular response to oxidative stress [Sirtuin 1, Sirtuin 3, and Nuclear factor erythroid 2-related factor 2 (NRF2)], mitochondrial biogenesis [Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)] and amino acids metabolism [General control nonderepressible 2 (GCN2)] increased from baseline to all other time points evaluated (P ≤ 0.01 for all). Also, expression of Peroxisome proliferator-activated receptor gamma (PPARϒ) (adipogenesis regulation) was significantly decreased after RYGB (P < 0.05). Additionally, we observed that PGC1α, SIRT1 and AMPK strongly correlated to BMI at 3 M (P ≤ 0.01 for all), as well as ADIPOQ and SIRT1 to BMI at 6 M (P ≤ 0.01 for all).

CONCLUSIONS

Our findings demonstrate that weight loss is associated with amelioration of inflammation and ERS and increased protection against oxidative stress in adipose tissue. These observations are strongly correlated with a decrease in BMI and essential genes that control cellular energy homeostasis, suggesting an adaptive process on a gene expression level during the caloric restriction and weight loss period after RYGB. Trial registration CAAE: 73,585,317.0.0000.5440.

Metabolic adaptations after bariatric surgery: adipokines, myokines and hepatokines

This review addresses the impact of bariatric surgery on the endocrine aspects of white adipose tissue, muscle and the liver. We describe literature supporting the notion that adipokines, myokines and hepatokines likely act in concert and drive many of the long-term metabolic improvements following surgery. Circulating adiponectin is increased while secretion of pro-inflammatory interleukins (1, 6 and 8) decreases, alongside leptin secretion. The metabolic improvements observed in the muscle might relate to reduction of myokines contributing to insulin resistance (including myostatin, brain-derived neurotrophic factor and fibroblast growth factor-21). Subject to exception, hepatokine secretion is generally increased (such as insulin-like growth factor-binding protein 2, adropin and sex hormone-binding globulin). In conclusion, bariatric surgery restores metabolic functions by enhancing the time-dependent secretion of anti-inflammatory, insulin-sensitizing and antilipemic factors. Further research is needed to understand the molecular mechanisms by which these factors may trigger the remission of obesity-related comorbidities following bariatric surgery.

Effect of Bariatric Surgery on Serum Inflammatory Factors of Obese Patients: a Systematic Review and Meta-Analysis

Obesity is one of the main causes of inflammation. Previous studies have reported inconclusive results regarding the effect of bariatric surgery on inflammatory markers. This systematic review and meta-analysis is aimed at describing the effect of bariatric surgery on C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α). PubMed/Medline and Scopus were systematically searched for all eligible studies from inception to June 2018. Results are expressed as weighted mean difference (MD) with 95% confidence intervals (CI) using a random effects model. Overall, 116 studies which evaluated serum CRP, IL-6, and TNF-α after bariatric surgery were included. Pooled effect size showed significant reduction in serum CRP (- 5.30 mg/l, 95% CI - 5.46, - 5.15, P < 0.001), IL-6 (- 0.58 pg/ml, 95% CI - 0.64, - 0.53, P < 0.001), and TNF-α (- 0.20 pg/ml, 95% CI - 0.39, - 0.02, P = 0.031) with significant heterogeneity across studies (> 95% for all factors). Bariatric surgery significantly lowered inflammatory factors; however, baseline BMI, follow-up duration and type of surgery could impact the extent of observed effects.

The omentum of obese girls harbors small adipocytes and browning transcripts

Severe obesity (SO) affects about 6% of youth in the United States, augmenting the risks for cardiovascular disease and type 2 diabetes. Herein, we obtained paired omental adipose tissue (omVAT) and abdominal subcutaneous adipose tissue (SAT) biopsies from girls with SO undergoing sleeve gastrectomy (SG), to test whether differences in cellular and transcriptomic profiles between omVAT and SAT depots affect insulin sensitivity differently. Following weight loss, these analyses were repeated in a subgroup of subjects having a second SAT biopsy. We found that omVAT displayed smaller adipocytes compared with SAT, increased lipolysis through adipose triglyceride lipase phosphorylation, reduced inflammation, and increased expression of browning/beiging markers. Contrary to omVAT, SAT adipocyte diameter correlated with insulin resistance. Following SG, both weight and insulin sensitivity improved markedly in all subjects. SAT adipocytes' size became smaller, showing increased lipolysis through perilipin 1 phosphorylation, decreased inflammation, and increased expression in browning/beiging markers. In summary, in adolescent girls with SO, both omVAT and SAT depots showed distinct cellular and transcriptomic profiles. Following weight loss, the SAT depot changed its cellular morphology and transcriptomic profiles into more favorable ones. These changes in the SAT depot may play a fundamental role in the resolution of insulin resistance.

The immune remodel: Weight loss-mediated inflammatory changes to obesity

Obesity is an escalating world problem that contributes to the complexity and cost of treatment of metabolic disorders. Obesity is the result of increased storage of energy in the form of adipose tissue, reducing the quality of daily life, and interfering with longevity. Obesity is also a chronic, low-grade inflammatory disorder. The inflammatory processes affect many organ systems with expanded numbers of immune cells and increased cytokine production. Long-term weight loss is difficult to achieve and maintain. Lifestyle modifications, pharmacologic treatments, and surgical methods are increasingly utilized to ameliorate excess body weight and the comorbidities of obesity, such as diabetes, cardiovascular disease, dyslipidemia, and cancers. Weight loss is also touted to reduce inflammation. Here we review the current literature on human obesity-related systemic and local changes to the immune system and circulating inflammatory mediators. Further, we consider the impact of weight loss to reduce the burden of inflammation, bearing in mind the different methods of weight loss—behavioral change vs. surgical intervention.

Splenectomy fails to attenuate immuno-hematologic changes after rodent vertical sleeve gastrectomy

Bariatric surgery is on the rise for long-term weight loss and produces various positive metabolic health benefits. The mechanisms that produce surgical weight loss are not yet fully understood. Previous studies showed vertical sleeve gastrectomy prior to gestation resulted in reduced peripheral blood lymphocytes measured during pregnancy due to an undetermined etiology. Further, elevated splenic weight has been associated with vertical sleeve gastrectomy surgery. We hypothesized that perhaps altered splenic filtration was trapping circulating lymphocytes and thus reducing peripheral blood lymphocytes in circulation and contributing to increased spleen weight. We posited whether removal of the spleen concomitant with the stomach surgery may result in an improved immune phenotype. We evaluated female long Evans rats having received Sham surgery or vertical sleeve gastrectomy, with or without splenectomy to determine the contribution of the spleen on metabolic and immune factors after vertical sleeve gastrectomy. Vertical sleeve gastrectomy animals lost significant amounts of body mass and fat mass and ate less in comparison to Sham females during the first five post-operative weeks, but there was no specific effect of the loss of spleen on body mass, fat mass, or food intake. During the post-operative week 6, animals were euthanized and blood recovered for cell sorting of immune cells. There was a reduction in CD3+ total T cells, CD3/CD4+ helper T cells, and CD3/CD8+ cytotoxic T cells, main effect of both bariatric surgery (P  < 0.0001) and splenectomy (P  < 0.01). Furthermore, there was a significant increase in CD45RA+ B cells as a result of splenectomy (P  < 0.001), but a significant reduction in B cells as a result of VSG surgery (P  < 0.05). The changes in total T cells but not B cells were strongly correlated with fat mass. Further studies are needed to understand the cause of the immune changes after surgical weight loss.

Bariatric surgery and gene expression in the gut

PURPOSE OF REVIEW

The current review provides an overview of recent literature on new findings related to bariatric surgery and gut gene expression.

RECENT FINDINGS

Bariatric surgery modulates the expression of intestinal genes. Experimental and clinical investigations have demonstrated the association of gut rearrangement with changes in intestinal expression of genes related to glucose metabolism. Recent data suggest that bariatric surgery also affects expression of genes belonging to other pathways, including nutrient transporters and metabolism of vitamin B12, decreasing pathway-encoding genes that may contribute to vitamin B12 deficiency in the postoperative period.

SUMMARY

Bariatric surgery is an effective intervention strategy against severe obesity, resulting in sustained weight loss and reduction of comorbidities. Nutritional genomic changes appear in response to bariatric surgery, possibly due to adaptive gut response. Improved understanding of the molecular pathways modulated by this intervention may facilitate weight and comorbidities management.

Bariatric Surgery and Precision Nutrition

This review provides a literature overview of new findings relating nutritional genomics and bariatric surgery. It also describes the importance of nutritional genomics concepts in personalized bariatric management. It includes a discussion of the potential role bariatric surgery plays in altering the three pillars of nutritional genomics: nutrigenetics, nutrigenomics, and epigenetics. We present studies that show the effect of each patient's genetic and epigenetic variables on the response to surgical weight loss treatment. We include investigations that demonstrate the association of single nucleotide polymorphisms with obesity phenotypes and their influence on weight loss after bariatric surgery. We also present reports on how significant weight loss induced by bariatric surgery impacts telomere length, and we discuss studies on the existence of an epigenetic signature associated with surgery outcomes and specific gene methylation profile, which may help to predict weight loss after a surgical procedure. Finally, we show articles which evidence that bariatric surgery may affect expression of numerous genes involved in different metabolic pathways and consequently induce functional and taxonomic changes in gut microbial communities. The role nutritional genomics plays in responses to weight loss after bariatric surgery is evident. Better understanding of the molecular pathways involved in this process is necessary for successful weight management and maintenance.

Duodenal long noncoding RNAs are associated with glycemic control after bariatric surgery in high-fat diet-induced diabetic mice

BACKGROUND

The duodenum plays a role in the mechanism of type 2 diabetes remission after bariatric surgery. Roux-en-Y gastric bypass (RYGB) may change gene expression in the duodenum and metabolism. Long noncoding RNAs (lncRNAs) constitute a novel class of RNAs that regulate gene expression. Little is known about how duodenal lncRNAs respond to RYGB. Logically, studies on the changes of duodenal lncRNAs potentially can lead to an understanding of the mechanisms of bariatric surgery, as well as discovery of antidiabetic drug targets and biomarkers predicting postoperative outcome.

OBJECTIVES

To investigate the expression signature of duodenal lncRNAs associated with glycemic improvement by duodenal-jejunal bypass (DJB), a component of RYGB, on a genome-wide scale in high-fat diet-induced diabetic mice.

SETTING

University medical center.

METHODS

High fat diet-induced diabetic mice were randomized into 2 groups receiving either the DJB or a sham procedure. Microarray was applied to screen the differentially expressed lncRNAs and messenger RNAs (mRNAs) in the duodenum between the DJB and sham groups, and the result was validated by quantitative real-time polymerase chain reaction in another cohort of animals. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the potential lncRNA functions. Based on Pearson correlation analysis, the lncRNA-mRNA and lncRNA-transcription factor (TF) interaction networks were constructed to identify and rank core regulatory lncRNAs and transcription factors.

RESULTS

A total of 301 lncRNAs, including 232 that were upregulated and 69 downregulated (fold change≥2.0), were differentially expressed in the duodenum between the DJB and sham groups. GO enrichment indicated that these lncRNA-coexpressed mRNAs were correlated with biological processes including cell proliferation, digestion, and catabolic and biosynthetic processes. KEGG pathway analysis revealed that in addition to the digestion and absorption signaling pathways, pancreatic secretion- and inflammatory process-related signaling pathways were mostly enriched in the DJB group. In addition, the lncRNA-mRNA interaction network combined with GO and KEGG pathway analysis suggested that as a top-ranked gene, NONMMUG021726 may play an important role in the mechanism of type 2 diabetes remission after DJB.

CONCLUSION

DJB leads to drastic changes in lncRNA and mRNA expressions in the duodenum. The majority of top-ranked lncRNAs and mRNAs have roles in pancreatic secretion and inflammatory processes, implying that bypass of the duodenum may initiate insulin secretion and attenuate inflammation. In addition, modulators of such lncRNAs, most likely NONMMUG021726, have potential to become therapeutic targets or biomarkers for prediction of the outcomes of bariatric surgery.