Effects of Bariatric Surgery on Energy Homeostasis

Dynamics of adipose tissue macrophage populations after gastric bypass surgery

OBJECTIVE

This case-control study aimed to analyze the dynamics of macrophage infiltration in subcutaneous adipose tissue following bariatric surgery or conservative treatment of obesity and to clarify whether these features predict the weight loss outcome after the surgery.

METHODS

Subcutaneous tissue samples taken before and 12 months after laparoscopic Roux-en-Y gastric bypass surgery (n = 39) or conservative (n = 43) treatment for obesity were analyzed. Fat cell size was determined, and with CD68 immunohistochemistry, crown-like structures (CLS) were counted and single macrophages were quantitated.

RESULTS

A major decline in CLS density from 4.1 (SD 3.5) to 1.1 (SD 0.8) per 1000 fat cells (p < 0.000) was found, regardless of the degree of weight loss after the surgery. Surgery had no effect on the fraction of infiltrating single-cell macrophages in subcutaneous adipose tissue. The abundance of these macrophage populations before the intervention did not predict the degree of postsurgery weight loss or suboptimal response to the surgery.

CONCLUSIONS

The effect of gastric bypass on adipose tissue inflammatory status associates closely with CLS density even in subjects with suboptimal weight loss. The study suggests that factors related to bypass surgery other than weight loss modify the inflammatory response in adipose tissue.

The Phantom Satiation Hypothesis of Bariatric Surgery

The excitation of vagal mechanoreceptors located in the stomach wall directly contributes to satiation. Thus, a loss of gastric innervation would normally be expected to result in abrogated satiation, hyperphagia, and unwanted weight gain. While Roux-en-Y-gastric bypass (RYGB) inevitably results in gastric denervation, paradoxically, bypassed subjects continue to experience satiation. Inspired by the literature in neurology on phantom limbs, I propose a new hypothesis in which damage to the stomach innervation during RYGB, including its vagal supply, leads to large-scale maladaptive changes in viscerosensory nerves and connected brain circuits. As a result, satiation may continue to arise, sometimes at exaggerated levels, even in subjects with a denervated or truncated stomach. The same maladaptive changes may also contribute to dysautonomia, unexplained pain, and new emotional responses to eating. I further revisit the metabolic benefits of bariatric surgery, with an emphasis on RYGB, in the light of this phantom satiation hypothesis.

Disordered eating and weight loss after bariatric surgery

PURPOSES

Aberrant eating patterns are frequently observed in bariatric patients. Since bariatric operations produce alterations in food transit and in appetite/satiety balance, postoperative eating behavior changes are not surprising.

METHODS

88 consecutive obese patients undergoing Roux-en-Y gastric bypass (RYGBP, 50 cases) and Sleeve Gastrectomy (SG, 38 cases) were retrospectively evaluated. Beside anthropometric data measurement, eating behavior was assessed by direct interview prior to the operation and at the first and second postoperative years: patients were considered as eating disordered (ED) when referred habitual occurrence of binge eating and nibbling/grazing. Weight loss was assessed by percent of BMI loss (% Δ BMI). Together with standard follow-up, patients received additional behavioral/dietetic support upon request.

RESULTS

Postoperative ED patients showed lower % Δ BMI than the not ED ones at one (30.7% ± 8,5 vs. 26.8% ± 10, p < 0.02) and two (32% ± 10.3 vs. 27.4% ± 12.9, p < 0.05) years after operation, the follow-up rate being 82% and 76%, respectively, without differences between RYGBP and SG group. After RYGBP, an improvement of eating behavior was observed (ED patients from 75 to 28% at 1 year and to 27% at 2 years), while no changes were observed after SG. In SG patients, the number of additional behavioral/dietetic support sessions throughout the follow-up was positively associated with % Δ BMI.

DISCUSSION

The postoperative normalization of eating pattern has a role in weight loss after bariatric surgery. Behavioral/dietetic support is indicated in all SG patient, while after RYGBP is useful only when weight loss is unsatisfactory.

LEVEL OF EVIDENCE

III: retrospective cohort study.

Sleeve Gastrectomy Surgery Improves Glucose Metabolism by Downregulating the Intestinal Expression of Sodium-Glucose Cotransporter-3

AIMS

Sleeve gastrectomy (SG) has been proven effective in the treatment of obesity and type 2 diabetes. We hypothesized that SGLT3 may play an important role in the mechanism of glucose control and weight loss after SG.

MATERIALS AND METHODS

Daily body weight and food intake were measured in SG and sham-operated mice. Glucose tolerance test, SGLT3 agonist (αMG), and SGLT1 inhibitor (phlorizin) perfusion experiments were used to detect changes in intestinal SGLT3 and SGLT1 activity following SG. Expression of SGLT3a and SGLT1 was assessed at 2 weeks, 1 month after surgery by quantitative PCR and fluorescence immunoassay. Hematoxylin and eosin staining was used to detect morphological changes in the villi. SGLT3 and SGLT1 expression was measured after stimulation of human intestinal epithelial cells (HIEC).

RESULTS

Both the body weight and daily food intake of the SG-treated mice decreased within 30 days after surgery. Oral glucose absorption was significantly reduced at 30 days. The intestinal stimulation proved that SG can improve glucose metabolism, which can be reversed by αMG and enhanced by phlorizin. Villus height and surface area of the intestine in SG mice decreased after surgery. mRNA expression of SGLT3a and SGLT1 decreased at 2 weeks and 1 month after SG, immunofluorescence also confirmed these changes. HIEC stimulation confirmed that αMG could increase the expression of SGLT3 and SGLT1, but the expression of SGLT1 was down regulated when phlorizin was added to the medium.

CONCLUSION

The results suggest that reducing SGLT3 expression might contribute to lowering blood glucose and controlling body weight after SG.

Adipose Tissue Composition in Obesity and After Bariatric Surgery

The adipose tissue is a complex organ that regulates food intake and energy expenditure as well as induces low-grade inflammation. This review deals with changes in the composition and activity of the adipose organ after bariatric surgery, focusing on epicardial and ectopic fat and on relationships between white and brown adipose tissues. Postoperative improvements of ectopic fat and epicardial fat size and composition account for the metabolic recovery and the decreased cardiovascular risk. Following Roux-en-Y gastric bypass or biliopancreatic diversion, a proportional increase in the size and activity of the metabolically active brown adipose tissue was observed, most likely related to the postoperative rearrangement of the entero-hormonal pattern with an increase of GLP-1 production: this aspect would promote the postoperative weight loss and maintenance of post-surgery benefits.

Functional Foods and Lifestyle Approaches for Diabetes Prevention and Management

Functional foods contain biologically active ingredients associated with physiological health benefits for preventing and managing chronic diseases, such as type 2 diabetes mellitus (T2DM). A regular consumption of functional foods may be associated with enhanced anti-oxidant, anti-inflammatory, insulin sensitivity, and anti-cholesterol functions, which are considered integral to prevent and manage T2DM. Components of the Mediterranean diet (MD)-such as fruits, vegetables, oily fish, olive oil, and tree nuts-serve as a model for functional foods based on their natural contents of nutraceuticals, including polyphenols, terpenoids, flavonoids, alkaloids, sterols, pigments, and unsaturated fatty acids. Polyphenols within MD and polyphenol-rich herbs-such as coffee, green tea, black tea, and yerba maté-have shown clinically-meaningful benefits on metabolic and microvascular activities, cholesterol and fasting glucose lowering, and anti-inflammation and anti-oxidation in high-risk and T2DM patients. However, combining exercise with functional food consumption can trigger and augment several metabolic and cardiovascular protective benefits, but it is under-investigated in people with T2DM and bariatric surgery patients. Detecting functional food benefits can now rely on an "omics" biological profiling of individuals' molecular, genetics, transcriptomics, proteomics, and metabolomics, but is under-investigated in multi-component interventions. A personalized approach for preventing and managing T2DM should consider biological and behavioral models, and embed nutrition education as part of lifestyle diabetes prevention studies. Functional foods may provide additional benefits in such an approach.