Acute Effects of Sleeve Gastrectomy on Glucose Variability, Glucose Metabolism, and Ghrelin Response

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

Effect of regional body composition changes on bone density remodeling after sleeve gastrectomy

Background

Sleeve gastrectomy (SG) results in bone mineral density (BMD) loss and varying body composition parameters. However, the effects of body compositions on bone health are controversial. In order to accurately demonstrate their relationship and provide new insights into the causes of BMD loss after sleeve gastrectomy, this study is aimed to investigate the role of changes in body composition in BMD loss 12 months after SG.

Methods

41 Chinese individuals with obesity (25 women and 16 men) who underwent SG were prospectively examined for at least 12 months. Measurements of anthropometrics, body composition, BMD and blood samples were collected.

Results

For 12 months, the femoral neck (FN) BMD and total hip (TH) BMD decreased significantly compared with baseline in both sexes but not lumbar spine (LS) BMD. Greater TH BMD loss was observed in men than in women. For the first 6 months post-SG, the FN BMD loss was positively associated with the estimated fat free mass index (eFFMI) reduction in women (adjusted β = 0.77, P = 0.004) and positively associated with reduction of subcutaneous fat area (SFA) in men (r = 0.931, P = 0.007). For 12 months post-SG, the FN BMD loss was negatively associated with visceral fat area (VFA) reduction in women (adjusted β = -0.58, P = 0.027) and men (adjusted β = -0.68, P = 0.032). TH BMD loss was positively associated with waist circumference reduction in women (r = 0.448, P = 0.028).

Conclusion

FN and TH BMD decrease after SG in both women and men. The changes in body compositions are associated with BMD loss at different time points and bone sites. Our data emphasize the limitation of simply taking the total weight loss (% TWL) as an influencing factor of bone mineral density and the necessity of delineating body composition in relevant studies.

The early effects of sleeve gastrectomy on postprandial chylomicron triglycerides during the progression of type 2 diabetes

BACKGROUND

It remains unclear whether early sleeve gastrectomy (SG) improves postprandial very-low-density lipoprotein (VLDL) as well as chylomicron triglycerides (TGs) in a weight-independent manner in patients with or without type 2 diabetes (DM). Herein we investigated the early effects of SG on postprandial VLDL and chylomicron kinetics.

METHODS

A liquid meal test was performed before and after 1 week of SG. The plasma was collected for postprandial triglyceride-rich lipoprotein kinetics analyses, including VLDLs and chylomicrons, isolated by high-speed ultracentrifugation. Lipidomics and metabolomics were used to profile lipid and metabolite compositions of plasma and postprandial chylomicrons. De novo fatty acid synthesis in intestinal epithelial cells treated with chylomicron metabolites was examined using RT-PCR, immunoblotting, and free fatty acid measurement.

RESULTS

We found that patients with DM had markedly higher VLDL TGs than patients without DM, and such an increase was still retained after SG. In contrast, SG significantly decreased postprandial chylomicron TGs, but surprisingly, the degree of the reduction in patients with DM was less prominent than in patients without DM, confirmed by untargeted lipidomics analysis. Moreover, 5 unique metabolites potentially linked to de novo fatty acid synthesis from the pathway analysis were discovered by further metabolomic analysis of postprandial chylomicrons from patients with DM who underwent SG and verified by In vitro intestinal epithelial cell culture experiments.

CONCLUSIONS

SG in 1 week did not impact postprandial VLDL but decreased chylomicron TGs. Patients with DM keep higher postprandial chylomicron TG concentrations than patients without it after SG, potentially through some unique metabolites that increase intestinal fatty acid synthesis. These results implicate the timing for SG to reach lower intestinal fatty acid synthesis and postprandial chylomicron TG production is prior to the diagnosis of DM to potentially reduce cardiovascular risks.

Use of Continuous Glucose Monitoring in Patients Following Bariatric Surgery: A Scoping Review

The objective of this scoping review was to summarize the emerging literature on the use of continuous glucose monitoring (CGM) in post-bariatric surgery patients, with a focus on its features (e.g., device, mode, and accuracy), as well as purposes and outcomes of utilization. Three databases (PubMed, EMBASE, and Web of Science) were searched to obtain relevant studies. Results suggested that most studies used CGM for 3-7 days under blinded mode. Accuracy data were available in only one study, which reported a mean absolute relative difference of 21.7% for Freestyle Libre. The primary applications of CGM were for elucidating glucose patterns and assessing glycemic treatment outcomes. No study has tested the effect of CGM as an intervention strategy to enhance glucose control.

The role of weight control in the management of type 2 diabetes mellitus: Bariatric surgery

Diabetes mellitus is one of the major epidemics in the United States. It is heavily associated with obesity and multiple metabolic derangements that lead to long term morbidity, mortality as well as financial burden. Although medical therapy has been the mainstay in the management of diabetes mellitus, there remains a large portion of this patient population which struggles to obtain adequate glycemic control and long-term weight control with medical management alone. Bariatric surgery is a powerful tool in combating diabetes mellitus and affects glucose homeostasis through a variety of pathways. While it does provide a durable pathway for weight loss, improvement in glucose homeostasis is not only affected by the weight loss seen after bariatric surgery. Changes in gut hormone secretion, insulin regulation, and gut microbial composition also affect how these operations improve glucose homeostasis. Through improvement in the management of diabetes mellitus, comorbidities including cardiovascular disease, in turn demonstrate improvement. In this article, we will discuss the role of bariatric (metabolic) surgery as it relates to long term weight loss and the impact that weight loss has on improvement in diabetes mellitus.

Sex-specific differences in bone mineral density loss after sleeve gastrectomy

Background

Sleeve gastrectomy is an effective bariatric procedure; however, sleeve gastrectomy-related adverse skeletal outcomes have been increasingly reported. High levels of sex hormone-binding globulin (SHBG) have been documented to be a risk factor of bone mineral density (BMD) loss with different effects observed between sexes. The aim of this study was to identify sex-specific changes in BMD following sleeve gastrectomy and to evaluate the role of SHBG in this process.

Methods

This retrospective study included 19 middle-aged men and 30 non-menopausal women with obesity who underwent sleeve gastrectomy in China. Anthropometrics, bone turnover markers, calciotropic hormones, BMD, SHBG, and gonadal steroids were measured preoperatively and at 6 and 12 months postoperatively. Longitudinal changes in BMD, bone turnover markers and SHBG were compared between sexes by linear mixed models. Multiple stepwise regression analysis was used to identify the predictors of BMD loss at the investigated bone sites.

Results

Over the 12-month study period, total hip and femoral neck BMD decreased, while lumbar spine BMD remained largely unchanged in both sexes. Linear mixed models revealed significant sex × time interaction effects in total hip BMD and SHBG, showing that men had a significantly greater reduction in total hip BMD and less increase in SHBG after sleeve gastrectomy than women. In the multivariate model, SHBG was significantly associated with total hip BMD loss in men (adjusted β = −0.533, P = 0.019) but not women while total estrogen was significantly associated with total hip BMD loss in women (adjusted β = 0.508, P = 0.01) but not men.

Conclusion

Significant sex-specific BMD changes were observed after sleeve gastrectomy in the current study. Sleeve gastrectomy-related increase in SHBG may be a specific risk factor for total hip BMD loss in men. Our results indicate that sex-specific screening may be warranted to facilitate personalized postoperative bone care in this population.

Glucose Profiles Assessed by Intermittently Scanned Continuous Glucose Monitoring System during the Perioperative Period of Metabolic Surgery

BACKGROUND

Continuous glucose monitoring (CGM) has been widely used in the management of diabetes. However, the usefulness and detailed data during perioperative status were not well studied. In this study, we described the immediate changes of glucose profiles after metabolic surgery using intermittently scanned CGM (isCGM) in individuals with type 2 diabetes mellitus (T2DM).

METHODS

This was a prospective, single-center, single-arm study including 20 participants with T2DM. The isCGM (FreeStyle Libre CGM) implantation was performed within 2 weeks before surgery. We compared CGM metrics of 3 days before surgery and 3 days after surgery, and performed the correlation analyses with clinical variables.

RESULTS

The mean glucose significantly decreased after surgery (147.0±40.4 to 95.5±17.1 mg/dL, P<0.001). Time in range (TIR; 70 to 180 mg/dL) did not significantly change after surgery in total. However, it was significantly increased in a subgroup of individuals with glycosylated hemoglobin (HbA1c) ≥8.0%. Time above range (>250 or 180 mg/dL) was significantly decreased in total. In contrast, time below range (<70 or 54 mg/dL) was significantly increased in total and especially in a subgroup of individuals with HbA1c <8.0% after surgery. The coefficient of variation significantly decreased after surgery. Higher baseline HbA1c was correlated with greater improvement in TIR (rho=0.607, P=0.005).

CONCLUSION

The isCGM identified improvement of mean glucose and glycemic variability, and increase of hypoglycemia after metabolic surgery, but TIR was not significantly changed after surgery. We detected an increase of TIR only in individuals with HbA1c ≥8.0%.

The need and safety of vitamin supplementation in adults with obesity within 9 months post sleeve gastrectomy (SG): assessment based on intake

The aim of the study was to assess the need and safety of vitamin supplementation in adults with obesity post bariatric surgery (SG), based on intake assessment. Patients with obesity class III, and with obesity class II with comorbidities were followed up at 3, 6 and 9 months post bariatric surgery. Based on a 4-day food record questionnaire, the intake of vitamins and calories was assessed and an interview regarding the consumption of supplements was conducted. The study showed a deficiency in the dietary intake of vitamin D, folate (B₉) and vitamin B₁ (in 93–100% of respondents), vitamins E and C (in 53–67% of respondents), vitamins A, PP and vitamins B₂ and B₆ (in 10 to 23% of respondents) and vitamin B₁₂ (only 1 woman). The intake of multivitamin supplements was implemented by 72% of respondents, independently, all patients were taking a vitamin D supplement. Vitamin deficiencies were only reported in a small percentage of patients (3–17%), who did not take supplements throughout the observation period. Supplementation with vitamins D, E, C, B₁ and folic acid (B₉), used regularly, supplemented the nutritional deficiencies of patients. The intake of vitamin A, B₂, PP, and B₆ with supplements did not significantly affect the overall intake. Supplementation with vitamin B₁₂ turned out to be unjustified to the nutritional recommendations. The dietary and/or supplemental intake of vitamins did not exceed the tolerable upper intake level (UL). The results of the study confirm the need to implement vitamin supplementation for bariatric patients and its safety.