Lower glycemic fluctuations early after bariatric surgery partially explained by caloric restriction

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.

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 impact of bariatric and metabolic surgery on cancer development

Obesity (BMI ≥ 30 kg/m²) with related comorbidities such as type 2 diabetes mellitus, cardiovascular disease, sleep apnea syndrome, and fatty liver disease is one of the most common preventable risk factors for cancer development worldwide. They are responsible for at least 40% of all newly diagnosed cancers, including colon, ovarian, uterine, breast, pancreatic, and esophageal cancer. Although various efforts are being made to reduce the incidence of obesity, its prevalence continues to spread in the Western world. Weight loss therapies such as lifestyle change, diets, drug therapies (GLP-1-receptor agonists) as well as bariatric and metabolic surgery are associated with an overall risk reduction of cancer. Therefore, these strategies should always be essential in therapeutical concepts in obese patients. This review discusses pre- and post-interventional aspects of bariatric and metabolic surgery and its potential benefit on cancer development in obese patients.

Peri-Operative Glycemic Dynamics in a Chinese Patient With Type 2 Diabetes Undergoing Laparoscopic Sleeve Gastrectomy

Obesity and type 2 diabetes (T2D) are prevalent issues in China. Bariatric and metabolic surgery, by reducing the size of the stomach through the removal of a portion of the stomach using laparoscopy (laparoscopic sleeve gastrectomy (LSG)), induces the remarkable remission of T2D inpatients. Plasma glucose (PG) was reported to be at a lower than normal level in Caucasian patients a few weeks after surgery, which is not well-documented in Chinese patients who have a lower body mass index (BMI) compared to Caucasians. Thus, we adopted the use of a continuous glucose monitoring system (CGMS) in a Chinese patient to monitor postoperative glucose levels. We found that the level of PG lowered to the normal range four days after LSG surgery while weight loss was not significantly reduced. It is indicated that the main mechanism of LSG inducing remission of T2DM is the limitation of food intake in addition to the imbalance of a few gastrointestinal hormones such as glucagon-like peptide 1 (GLP-1), Ghrelin. The lower the BMI, the lower the adipose tissue, and the faster the decrease in PG after bariatric and metabolic surgery.

Continuous Glucose Monitoring in Bariatric Patients Undergoing Laparoscopic Sleeve Gastrectomy and Laparoscopic Roux-En-Y Gastric Bypass

BACKGROUND

Few investigations have been conducted that compared blood glucose in patients with diabetes mellitus (DM2) and morbid obesity who had undergone laparoscopic sleeve gastrectomy (LSG) or gastric bypass (LRYGB). We aimed to compare the effects of these procedures using continuous glucose monitoring (CGM).

METHODS

We prospectively studied patients that had qualified for LSG or LRYGB. The inclusion criteria were DM2 of ≤ 5 years, for which patients were taking oral anti-diabetic drugs, or no glucose metabolism disorder; and morbid obesity. CGM was performed between admission and the 10th postoperative day.

RESULTS

We studied 16 patients with DM2 and 16 without. Eighteen patients underwent LSG and 14 underwent LRYGB. The median hemoglobin A1c was 5.5% (5.4-5.9%) in DM2 patients, which did not differ from control (p = 0.460). Preoperative mean daily glucose concentration was similar between DM2 and control patients (p = 0.622). For patients with DM2, LRYGB was associated with more frequent low glucose status, and these episodes lasted longer than in DM2 patients that underwent LSG (p = 0.035 and 0.049, respectively). DM2 patients that underwent LRYGB demonstrated lower glucose concentrations from third postoperative day than those that underwent LSG. Patients without DM2 did not demonstrate differences in daily mean glucose concentrations, or in incidence nor duration of hypoglycemia throughout the observation period.

CONCLUSION

A significantly larger reduction in interstitial glucose concentration is present from third day in patients with DM2 who undergo LRYGB vs. LSG, accompanied by a lower incidence and shorter duration of low glucose episodes.

A Meta-Analysis of GLP-1 After Roux-En-Y Gastric Bypass: Impact of Surgical Technique and Measurement Strategy

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is an effective treatment for diabetes. Glucagon-like peptide-1 (GLP-1) is a gut hormone that is important to glucose homeostasis.

OBJECTIVE

This study aimed to assess GLP-1 level and its predictors after RYGB.

METHODS

The study design was a meta-analysis. The data sources were MEDLINE, EMBASE, Web of Science, and the Cochrane Databases. The study selection composed of studies with pre- and post-RYGB levels. The main outcomes were as follows: Primary outcome was the change in postprandial GLP-1 levels after RYGB. Secondary outcomes included the changes in fasting glucose, fasting insulin, and fasting GLP-1 levels after RYGB. Meta-regression to determine predictors of changes in GLP-1 levels was performed. Outcomes were reported using Hedge's g.

RESULTS

Twenty-four studies with 368 patients were included. Postprandial GLP-1 levels increased after RYGB (Hedge's g = 1.29, p < 0.0001), while fasting GLP-1 did not change (p = 0.23). Peak postprandial GLP-1 levels gave the most consistent results (I ² = 9.11). Fasting glucose and insulin levels decreased after RYGB (p < 0.0001). Roux limb length was a significant predictor for amount of GLP-1 increase (β = - 0.01, p = 0.02). Diabetes status, amount of weight loss, length of biliopancreatic limb, and time of measurement were not significant predictors (p > 0.05).

CONCLUSION

Postprandial GLP-1 levels increase after RYGB, while fasting levels remain unchanged. Shorter Roux limb length is associated with greater increase in postprandial GLP-1, which may lead to better glycemic control in this population.

Increased Bile Acids and FGF19 After Sleeve Gastrectomy and Roux-en-Y Gastric Bypass Correlate with Improvement in Type 2 Diabetes in a Randomized Trial

BACKGROUND

Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are both effective bariatric procedures to treat type 2 diabetes (T2DM) and obesity. The contribution of changes in bile acids (BAs) and fibroblast growth factor19 (FGF19) to such metabolic improvements is unclear.

METHODS

We examined associations between changes in BAs, FGF19 (fasting and prandial), with changes in body weight, glycemia, and other metabolic variables in 61 obese patients with T2DM before and 1 year after randomization to SG or RYGB.

RESULTS

Weight loss and diabetes remission (defined by HbA1c < 39 mmol/mol [< 5.7%] in the absence of glucose-lowering therapy) after RYGB and SG was similar (mean weight loss - 29 vs - 31 kg, p = 0.50; diabetes remission proportion 37.5 vs 34%, p = 1.0). Greater increments in fasting and prandial levels of total, secondary, and unconjugated BAs were seen after RYGB than SG. Fasting and prandial increases in total (r = - 0.3, p = 0.01; r = - 0.2, p = 0.04), secondary (r = - 0.3, p = 0.01; r = - 0.4, p = 0.01) and unconjugated BA (r = - 0.3, p = 0.01; r = 0.4, p < 0.01) correlated with decreases in HbA1c, but not weight. Changes in 12α-OH/non 12α-OH were positively associated with prandial glucose increments (r = 0.2, p = 0.03), HbA1c (r = 0.3, p = 0.01), and negatively associated with changes in insulinogenc index (r = - 0.3, p = 0.01). Only changes in prandial FGF19 were negatively associated with HbA1c (r = - 0.4, p < 0.01) and visceral fat (r = - 0.3, p = 0.04).

CONCLUSIONS/INTERPRETATION

The association between increases in secondary, unconjugated BAs and improvements in HBA1c (but not weight) achieved after both RYGB and SG suggest manipulation of BA as a potential strategy for controlling T2DM through weight-independent means.

Biliopancreatic diversion with duodenal switch leads to better postprandial glucose level and beta cell function than sleeve gastrectomy in individuals with type 2 diabetes very early after surgery

OBJECTIVE

The aim of this study was to compare the short-term effect of sleeve gastrectomy (SG) and biliopancreatic diversion with duodenal switch (DS) in order to determine if exclusion of the upper gastrointestinal tract confers greater metabolic improvement, independent of weight loss.

METHODS

Standard meals were administered before and on day 3 and 4 after SG to assess insulin sensitivity, β-cell function and gastrointestinal hormone responses in matched normoglycemic (NG) and type 2 diabetes (T2D) participants. A third group of matched T2D participants who underwent DS with the same meal test administered prior to and 3days after surgery was also recruited.

RESULTS

Despite significant metabolic improvement, T2D participants failed to fully normalize insulin resistance and β-cell dysfunction 3 and 4days after SG. Our results demonstrate the superiority of DS over SG in terms of short-term improvement in postprandial glucose excursion and β-cell function 3days after the surgery, with similar improvement in hepatic insulin sensitivity.

CONCLUSION

Our findings support the notion that caloric restriction represents an important mechanism to explain the very early anti-diabetic effects observed after bariatric surgery. However, exclusion of the upper gastrointestinal tract also provides further metabolic improvements, possibly mediated by gastrointestinal hormonal responses and altered postprandial glucose absorption.

Effect of Resected Gastric Volume on Ghrelin and GLP-1 Plasma Levels: a Prospective Study

BACKGROUND

The correlation between resected gastric volume (RGV) and neuro-humoral changes (ghrelin and GLP-1) after laparoscopic sleeve gastrectomy (LSG) and their effects on type 2 diabetes mellitus (T2DM) has been evaluated.

MATERIALS

Ninety-eight patients were divided in two groups: RGV <1200 mL (group A: 53 pts) and RGV >1200 mL (group B: 45 pts). Insulin secretion (insulin area under the curve (AUC)), insulinogenic index (IGI) and insulin-resistance (homeostasis model assessment, HOMA_IR) were assessed before and after surgery (at the 3rd day and 6, 12 and 24 months after LSG) using the oral glucose tolerance test (OGTT). At the same time, ghrelin and GLP-1 levels were determined.

RESULTS

A significant difference in T2DM resolution rate was observed after 6, 12 and 24 months in favour of RGV >1200 mL. Group B performed better than group A at the 3rd day and at the 6th, 12th and 24th months with regard to AUC, IGI and HOMA_IR. In both groups, OGTT resulted in decreased ghrelin values and a significant increase in GLP-1 values for group B at the 3rd day and at the 6th and 12th months with no difference at the 24th month.

CONCLUSION

Ghrelin and GLP-1 changes play a role in the regulation of glucose metabolism during the 1st year after LSG. RGV influences ghrelin and GLP-1 plasma levels after LSG, with a significant improvement in the T2DM control.

"Dual-remission" after Roux-en-Y gastric bypass surgery: Glycemic variability cannot always be improved in Chinese obese patients with type 2 diabetes

BACKGROUND

Glycemic variability after Roux-en-Y Gastric Bypass (RYGB) has not been adequately examined in Chinese obese patients with type 2 diabetes (T2D).

OBJECTIVE

We aimed to evaluate glucose variability after RYGB by continuous glucose monitoring (CGM) and then evaluate the remission rate based on the complete diabetes remission criteria combined with normal ranges of CGM for the Chinese population, which we defined as "dual-remission."

SETTING

The study was done at our academic university-affiliated hospital.

METHODS

Over a 3-day period, CGM was performed on 43 Chinese obese T2D patients combined with a mixed-meal test before and 1 year after RYGB. Mean amplitude of glucose excursions (MAGE), standard deviations (SD), and the time that patients' blood glucose levels were≥7.0 mmol/L,≥7.8 mmol/L,≥11.1 mmol/L, and≤3.9 mmol/L within 24 hours was analyzed. Multiple logistic regression analyses were used to identify predictors of "dual-remission."

RESULTS

Complete diabetes remission was achieved in 27 patients (62.8%) 1 year after RYGB. However, MAGE didn't change in the group, and only 18.6% patients met "dual-remission." Compared with patients in the complete remission group, patients in the dual-remission group had a shorter duration of diabetes, younger age, lower glycated hemoglobin (HbA1c) level, and no insulin usage at baseline. Correlation analysis showed MAGE after RYGB was positively correlated with diabetes duration (r = .43, P<.01). Multiple logistic regressions indicated a shorter duration was associated with a higher possibility to achieve dual-remission after adjusting for age, gender, HbA1c, and insulin therapy.

CONCLUSION

Glucose variability can't be effectively improved in most Chinese obese diabetic patients after RYGB. Shorter diabetes duration was associated with higher possibility to achieve "dual-remission."

GLP-1: a mediator of the beneficial metabolic effects of bariatric surgery?

There has been increasing interest in the role that gut hormones may play in contributing to the physiological changes produced by certain bariatric procedures, such as Roux-en-Y gastric bypass and sleeve gastrectomy. Here, we review the evidence implicating one such gut hormone, glucagon-like peptide-1, as a mediator of the metabolic benefits of these two procedures.

Surgery in the treatment of type 2 diabetes mellitus

Background and Aims:

The prevalence of diabetes is increasing worldwide, and most of the cases are type 2 diabetes mellitus. The relationship between type 2 diabetes mellitus and obesity is well established, and surgical treatment is widely used for obese patients with type 2 diabetes mellitus. The aim was to present current knowledge about the possible mechanisms responsible for glucose control after surgical procedures and to review the surgical treatment results.

Material and Methods:

Medical literature was searched for the articles presenting the impact of surgical treatment on glycemic control, long-term results, and possible mechanisms of action among obese individuals with type 2 diabetes mellitus.

Results:

Remission of type 2 diabetes mellitus after bariatric surgery depends on the definition of the remission used. Complete remission rate after surgery with the new criteria is lower than was considered before. Randomized controlled studies demonstrate that surgery is superior to best medical treatment for the patients with type 2 diabetes mellitus. The recurrence of type 2 diabetes mellitus after bariatric surgery is observed in up to 40% of cases with ≥5 years of follow-up. Despite the recurrence of type 2 diabetes mellitus in this group, better glycemic control and lower risk of macrovascular complications are present. Incretin effects on glycemic control after bariatric surgery are well described, but the role of other possible mechanisms (bile acids, microbiota, intestinal gluconeogenesis) in humans is unclear.

Conclusion:

Surgery is an effective treatment of type 2 diabetes mellitus in obese patients. The most optimal surgical procedure for the treatment of obese patients with type 2 diabetes mellitus is still to be established. More research is needed to explore the mechanisms of glycemic control after bariatric surgery.

Effect of bariatric surgery combined with medical therapy versus intensive medical therapy or calorie restriction and weight loss on glycemic control in Zucker diabetic fatty rats

Bariatric surgery rapidly improves Type 2 diabetes mellitus (T2DM). Our objective was to profile and compare the extent and duration of improved glycemic control following Roux-en-Y gastric (RYGB) bypass surgery and vertical sleeve gastrectomy (SG) and compare against calorie restriction/weight loss and medical combination therapy-based approaches using the Zucker diabetic fatty rat (ZDF) rodent model of advanced T2DM. Male ZDF rats underwent RYGB (n = 15) or SG surgery (n = 10) at 18 wk of age and received postsurgical insulin treatment, as required to maintain mid-light-phase glycemia within a predefined range (10-15 mmol/l). In parallel, other groups of animals underwent sham surgery with ad libitum feeding (n = 6), with body weight (n = 8), or glycemic matching (n = 8) to the RYGB group, using food restriction or a combination of insulin, metformin, and liraglutide, respectively. Both bariatric procedures decreased the daily insulin dose required to maintain mid-light-phase blood glucose levels below 15 mmol/l, compared with those required by body weight or glycemia-matched rats (P < 0.001). No difference was noted between RYGB and SG with regard to initial efficacy. SG was, however, associated with higher food intake, weight regain, and higher insulin requirements vs. RYGB at study end (P < 0.05). Severe hypoglycemia occurred in several rats after RYGB. RYGB and SG significantly improved glycemic control in a rodent model of advanced T2DM. While short-term outcomes are similar, long-term efficacy appears marginally better after RYGB, although this is tempered by the increased risk of hypoglycemia.

Metabolic surgery: action via hormonal milieu changes, changes in bile acids or gut microbiota? A summary of the literature

Obesity and type 2 diabetes remain epidemic problems. Different bariatric surgical techniques causes weight loss and diabetes remission to varying degrees. The underlying mechanisms of the beneficial effects of bariatric surgery are complex, and include changes in diet and behaviour, as well as changes in hormones, bile acid flow, and gut bacteria. We summarized the effects of multiple different bariatric procedures, and their resulting effects on several hormones (leptin, ghrelin, adiponectin, glucagon-like peptide 1 (GLP-1), peptide YY, and glucagon), bile acid changes in the gut and the serum, and resulting changes to the gut microbiome. As much as possible, we have tried to incorporate multiple studies to try to explain underlying mechanistic changes. What emerges from the data is a picture of clear differences between restrictive and metabolic procedures. The latter, in particular the roux-en-Y gastric bypass, induces large and distinctive changes in most measured fat and gut hormones, including early and sustained increase in GLP-1, possible through intestinal bile acid signalling. The changes in bile flow and the gut microbiome are causally inseparable so far, but new studies show that each contributes to the effects of weight loss and diabetes resolution.

Lower fetuin-A, retinol binding protein 4 and several metabolites after gastric bypass compared to sleeve gastrectomy in patients with type 2 diabetes

Background

Bypass of foregut secreted factors promoting insulin resistance is hypothesized to be one of the mechanisms by which resolution of type 2 diabetes (T2D) follows roux-en-y gastric bypass (GBP) surgery.

Aim

To identify insulin resistance-associated proteins and metabolites which decrease more after GBP than after sleeve gastrectomy (SG) prior to diabetes remission.

Methods

Fasting plasma from 15 subjects with T2D undergoing GBP or SG was analyzed by proteomic and metabolomic methods 3 days before and 3 days after surgery. Subjects were matched for age, BMI, metformin therapy and glycemic control. Insulin resistance was calculated using homeostasis model assessment (HOMA-IR). For proteomics, samples were depleted of abundant plasma proteins, digested with trypsin and labeled with iTRAQ isobaric tags prior to liquid chromatography-tandem mass spectrometry analysis. Metabolomic analysis was performed using gas chromatography-mass spectrometry. The effect of the respective bariatric surgery on identified proteins and metabolites was evaluated using two-way analysis of variance and appropriate post-hoc tests.

Results

HOMA-IR improved, albeit not significantly, in both groups after surgery. Proteomic analysis yielded seven proteins which decreased significantly after GBP only, including Fetuin-A and Retinol binding protein 4, both previously linked to insulin resistance. Significant decrease in Fetuin-A and Retinol binding protein 4 after GBP was confirmed using ELISA and immunoassay. Metabolomic analysis identified significant decrease of citrate, proline, histidine and decanoic acid specifically after GBP.

Conclusion

Greater early decrease was seen for Fetuin-A, Retinol binding protein 4, and several metabolites after GBP compared to SG, preceding significant weight loss. This may contribute to enhanced T2D remission observed following foregut bypass procedures.