Effect of bariatric surgery on liver glucose metabolism in morbidly obese diabetic and non-diabetic patients

The Impact of Sleeve Gastrectomy Combined With Lifestyle Interventions on Anthropometric and Health Outcomes in Adults: A Systematic Review and Meta-Analysis

Weight loss from obesity is a global health concern associated with increased risk of chronic illness and significant healthcare costs. Sleeve gastrectomy is an increasingly popular bariatric surgery option for substantial weight reduction; however, sustained success depends on lifestyle modification. Integrating food, exercise, behavioral, and technology-based interventions into surgery can potentially enhance outcomes and promote weight maintenance. A systematic review and meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) 2020 guidelines, encompassing randomized controlled trials published between 2014 and 2025. Databases like PubMed, Cochrane Library, Embase, Web of Science, and Scopus were searched. Studies included adults (age ≥18 years) with obesity undergoing sleeve gastrectomy and subjected to post-operative lifestyle interventions. The primary outcomes were weight changes, BMI, and body composition, while the secondary outcomes included comorbidities and quality of life. Risk of bias was assessed using the ROB-2 tool (www.cochrane.org). Thirty-one studies with varying follow-up durations (1-60 months) were included. The combined intervention resulted in greater weight loss (5%-30% decrease), improvement in fat mass, BMI, and cardiometabolic profiles compared to usual care. The meta-analysis revealed a high overall effect size for weight reduction, with a value of 2.56 (2.15-2.88) for the high weight reduction group and 1.88 (1.76-1.91) for the low weight reduction group. Heterogeneity among studies was moderate, with I² values ranging from 18% to 46%, indicating some variation in study populations and intervention effects. Technology-augmented interventions, such as wearable devices and mobile apps, provided additional gains in adherence and long-term efficacy. Long-term weight loss maintenance remained a difficulty. Sleeve gastrectomy combined with structured lifestyle interventions significantly improves anthropometric and health outcomes in adults. Technology-derived interventions and behavioral therapy have the potential for improving long-term weight management, but additional studies are required to optimize intervention approaches.

Roux-en-Y gastric bypass improves liver and glucose homeostasis in Zucker diabetic fatty rats by upregulating hepatic trefoil factor family 3 and activating the phosphatidylinositol 3-kinase/protein kinase B pathway

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is effective in ameliorating type 2 diabetes mellitus (T2DM); but its mechanism remains incompletely understood.

OBJECTIVES

This study aimed to investigate whether RYGB improves glucose metabolism by upregulating hepatic trefoil factor family 3 (TFF3) and thereby activating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway.

SETTING

Affiliated Hospital of North Sichuan Medical college in Nanchong city, China.

METHODS

Zucker diabetic fatty (ZDF) rats underwent RYGB or sham surgery (SHAM), and Zucker lean (ZL) rats served as controls (CON). TFF3 expression and PI3K/Akt pathway activity were compared between groups using western blot, immunofluorescence, and RT-qPCR. Adeno-associated virus (AAV) was used to specifically overexpress and interfere with hepatic TFF3. Liver fibrosis and steatosis were assessed using Masson trichrome and Oil Red O staining. HepG2 cells overexpressing or knocking out TFF3 were constructed using lentiviral transfection and CRISPR/Cas9 technology. After verifying the activity of the PI3K/Akt pathway by western blot, rescue experiments were performed on HepG2 cell overexpressing and knocking out TFF3 using LY294002 and 740Y-P, respectively. The activities of gluconeogenic enzymes and glucose uptake capacity in different HepG2 cells were evaluated using qPCR and flow cytometry.

RESULTS

Compared with the SHAM group, the blood glucose, body weight, insulin resistance, and lipid metabolism of ZDF rats in the RYGB group were significantly improved. The expression of TFF3 and PI3K/Akt phosphorylation in the liver of the RYGB group were higher than those of the rats that had undergone SHAM. In addition, compared with the SHAM group, the liver fibrosis and fatty degeneration of RYGB rats were milder, and the activity of gluconeogenic enzymes was lower. After tail vein injection of AAV that specifically overexpresses liver TTF3 in rats in the SHAM group, rats' insulin resistance, glucose tolerance, gluconeogenic enzymes, and other glucose metabolism indicators improved. After tail vein injection of AAV that interferes with liver TFF3 in rats in the RYGB group, rats' glucose metabolism indicators deteriorated. In in vitro experiments, the PI3K/Akt activity of TFF3-knocked-out HepG2 cells was lower than that of other groups. Lower glucose concentration were observed in TFF3-overexpressing cell lines. After rescue experiments, differences were found. The glucose metabolism level of the TFF3-expressing HepG2 cell line was positively correlated with the activity of the PI3K/Akt pathway.

CONCLUSIONS

RYGB regulates the expression of TFF3 in the liver of ZDF rats, thereby activating the PI3K/Akt pathway and improving T2DM.

In vivo mapping of postprandial hepatic glucose metabolism using dynamic magnetic resonance spectroscopy combined with stable isotope flux analysis in Roux-en-Y gastric bypass adults and non-operated controls: A case-control study

AIMS

Roux-en-Y gastric bypass (RYGB) surgery alters postprandial glucose profiles, causing post-bariatric hypoglycaemia (PBH) in some individuals. Due to the liver's central role in glucose homeostasis, hepatic glucose handling might differ in RYGB-operated patients with PBH compared to non-operated healthy controls (HC).

MATERIALS AND METHODS

We enrolled RYGB-operated adults with PBH and HCs (n = 10 each). Participants ingested 60 g of [6,6'-2H2]-glucose (d-glucose) after an overnight fast. Deuterium metabolic imaging (DMI) with interleaved 13C magnetic resonance spectroscopy was performed before and until 150 min post-d-glucose intake, with frequent blood sampling to quantify glucose enrichment and gluco-regulatory hormones until 180 min. Glucose fluxes were assessed by mathematical modelling. Outcome trajectories were described using generalized additive models.

RESULTS

In RYGB subjects, the hepatic d-glucose signal increased early, followed by a decrease, whereas HCs exhibited a gradual increase and consecutive stabilization. Postprandial hepatic glycogen accumulation and the suppression of endogenous glucose production were lower in RYGB patients than in HCs, despite higher insulin exposure, indicating lower hepatic insulin sensitivity. The systemic rate of ingested d-glucose was faster in RYGB, leading to a higher, earlier plasma glucose peak and increased insulin secretion. Postprandial glucose disposal increased in RYGB patients, without between-group differences in peripheral insulin sensitivity.

CONCLUSIONS

Exploiting DMI with stable isotope flux analysis, we observed distinct postprandial hepatic glucose trajectories and parameters of glucose-insulin homeostasis in RYGB patients with PBH versus HCs. Despite altered postprandial glucose kinetics and higher insulin exposure, there was no evidence of impaired hepatic glucose uptake or output predisposing to PBH in RYGB patients.

Decreased liver volume after bariatric surgery and its positive impact on liver function tests and lipid profile

BACKGROUND

Obesity is associated with a higher incidence of fatty liver disease, intrahepatic triglyceride content, and hepatic fibrosis. These abnormalities could progress to severe liver disease.

OBJECTIVES

To evaluate the effects of bariatric surgery (BaS)-induced weight loss on liver volume, hepatic function tests, and lipid profile.

SETTING

Academic Hospital, United States.

METHODS

We conducted a retrospective review of an institutional review board (IRB)-approved database on patients who underwent BaS from 2006 to 2018. To determine changes in liver volume, we reviewed abdominal computed tomography scans before BaS (Group 1) and up to 18 months after (Group 2). Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipid profiles were collected before and after BaS.

RESULTS

Seventy-three patients met the inclusion criteria. Patients were predominantly females 78.1% (57), with an average age of 51.29+12.54 years. The liver volume was 1870.73 + 638.5 mm3 before and 1555.15 + 464.8 after BaS (P = .004). ALT was 36.9 + 25.3 before versus 23.8 + 19.3 after BaS (P = .024).Triglyceride levels changed from 135.62 + 69.98 before to 97.50 + 47.33 after BaS (P = .009). Low-density lipoprotein decreased from 107.9 + 38.1 to 89.6 + 32.8 (P = .048).

CONCLUSIONS

BaS-induced weight loss determines significant liver shrinkage by reducing liver volume, and coincides with improvements in hepatic function tests and lipid profile. Our results suggest that BaS might contribute to reduction of the progression of fatty liver disease to fibrosis.

Effects of Obesity and Exercise on Hepatic and Pancreatic Lipid Content and Glucose Metabolism: PET Studies in Twins Discordant for BMI

Obesity and sedentarism are associated with increased liver and pancreatic fat content (LFC and PFC, respectively) as well as impaired organ metabolism. Exercise training is known to decrease organ ectopic fat but its effects on organ metabolism are unclear. Genetic background affects susceptibility to obesity and the response to training. We studied the effects of regular exercise training on LFC, PFC, and metabolism in monozygotic twin pairs discordant for BMI. We recruited 12 BMI-discordant monozygotic twin pairs (age 40.4, SD 4.5 years; BMI 32.9, SD 7.6, 8 female pairs). Ten pairs completed six months of training intervention. We measured hepatic insulin-stimulated glucose uptake using [18F]FDG-PET and fat content using magnetic resonance spectroscopy before and after the intervention. At baseline LFC, PFC, gamma-glutamyl transferase (GT), and hepatic glucose uptake were significantly higher in the heavier twins compared to the leaner co-twins (p = 0.018, p = 0.02 and p = 0.01, respectively). Response to training in liver glucose uptake and GT differed between the twins (Time*group p = 0.04 and p = 0.004, respectively). Liver glucose uptake tended to decrease, and GT decreased only in the heavier twins (p = 0.032). In BMI-discordant twins, heavier twins showed higher LFC and PFC, which may underlie the observed increase in liver glucose uptake and GT. These alterations were mitigated by exercise. The small number of participants makes the results preliminary, and future research with a larger pool of participants is warranted.

β-Cell Function and Insulin Dynamics in Obese Patients With and Without Diabetes After Sleeve Gastrectomy

Improved β-cell function seems to be essential for better glucose homeostasis after Roux-en-Y gastric bypass but is less studied after sleeve gastrectomy (SG). We evaluated the effects of SG on β-cell function in obese patients with diabetes (DM group) and without (control group) in response to both oral and intravenous glucose stimulation. The DM group demonstrated impaired insulin sensitivity and insulin response to glucose before surgery. The insulin sensitivity index of both groups significantly improved after SG. In addition, the insulin response to glucose (early insulinogenic index in oral glucose tolerance test and acute insulin response to glucose in an intravenous glucose tolerance test) increased in the DM group but decreased in the control group. As a result, β-cell function improved significantly in both groups after SG since the disposition index (DI) increased in both. However, the DI of the DM group was not restored to the level of control group up to 1 year after SG. Our results support that obese patients, with and without diabetes, could benefit from SG in β-cell function. For obese patients at risk for or who have been diagnosed with diabetes, interventions should be recommended early to preserve or restore β-cell function, and SG could be an effective choice. Further studies are needed for long-term effects.

ARTICLE HIGHLIGHTS

Advances and challenges in measuring hepatic glucose uptake with FDG PET: implications for diabetes research

The liver plays a crucial role in the control of glucose homeostasis and is therefore of great interest in the investigation of the development of type 2 diabetes. Hepatic glucose uptake (HGU) can be measured through positron emission tomography (PET) imaging with the tracer [18F]-2-fluoro-2-deoxy-D-glucose (FDG). HGU is dependent on many variables (e.g. plasma glucose, insulin and glucagon concentrations), and the metabolic state for HGU assessment should be chosen with care and coherence with the study question. In addition, as HGU is influenced by many factors, protocols and measurement conditions need to be standardised for reproducible results. This review provides insights into the protocols that are available for the measurement of HGU by FDG PET and discusses the current state of knowledge of HGU and its impairment in type 2 diabetes. Overall, a scanning modality that allows for the measurement of detailed kinetic information and influx rates (dynamic imaging) may be preferable to static imaging. The combination of FDG PET and insulin stimulation is crucial to measure tissue-specific insulin sensitivity. While the hyperinsulinaemic-euglycaemic clamp allows for standardised measurements under controlled blood glucose levels, some research questions might require a more physiological approach, such as oral glucose loading, with both advantages and complexities relating to fluctuations in blood glucose and insulin levels. The available approaches to address HGU hold great potential but await more systematic exploitation to improve our understanding of the mechanisms underlying metabolic diseases. Current findings from the investigation of HGU by FDG PET highlight the complex interplay between insulin resistance, hepatic glucose metabolism, NEFA levels and intrahepatic lipid accumulation in type 2 diabetes and obesity. Further research is needed to fully understand the underlying mechanisms and potential therapeutic targets for improving HGU in these conditions.

Impact of patient characteristic factors on the dynamics of liver glucose metabolism: Evaluation of multiparametric imaging with dynamic whole-body 18 F-fluorodeoxyglucose-positron emission tomography

AIMS

To assess the impact of various patient characteristics on the dynamics of liver glucose metabolism using automated multiparametric imaging with whole-body dynamic 18 F-fluorodeoxyglucose (FDG)-positron emission tomography (PET).

MATERIALS AND METHODS

We retrospectively enrolled 540 patients who underwent whole-body dynamic FDG-PET. Three quantitative indices representing hepatic glucose metabolism [mean standardized uptake value normalized by lean body mass (SULmean), metabolic glucose rate (kinetic index) and distribution volume (DV)] were measured from multiparametric PET images produced automatically based on the Patlak plot model. Patient characteristics including age, sex, body mass index, fasting time, blood glucose level, and the presence of diabetes mellitus (DM) or hepatic steatosis (HS) were collected. We examined the correlations between the characteristic factors and three quantitative indices using multiple regression analysis.

RESULTS

The success rate of kinetic analysis using multiparametric PET imaging was 93.3% (504/540). Hepatic SULmean was significantly correlated with age (p < .001), sex (p < .001) and blood glucose level (p = .002). DV was significantly correlated with age (p = .033), sex (p < .001), body mass index (p = .002), fasting time (p = .043) and the presence of HS (p = .002). The kinetic index was significantly correlated with age (p < .001) and sex (p = .004). In the comparison of the healthy, DM and HS groups, patients with DM had a significantly increased SULmean, whereas patients with HS had a significantly decreased DV.

CONCLUSIONS

Our results showed that liver glucose metabolism was influenced by various patient characteristic factors. Multiparametric FDG-PET imaging can be used to analyse the kinetics of liver glucose metabolism in routine clinical practice.

The Effects of Bariatric Surgery on Pharmacokinetics of Drugs: a Review of Current Evidence

PURPOSE OF REVIEW

Obesity constitutes a major public health concern and has been recognized as an epidemic. To date, bariatric surgery remains the most effective way for substantial long-lasting weight loss in severe obesity. The purpose of this review is to summarize how the pharmacokinetics of drugs are affected by the most common types of bariatric surgery, i.e., Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG).

RECENT FINDINGS

Limited data are available regarding the changes in pharmacokinetics of drugs after bariatric surgery. The lack of existing guidelines may lead patients to experience drug toxicity or therapeutic undertreatment. Pharmacokinetic parameters that need to be taken into consideration postoperatively include gastric motility, gastric volume, pH, surface area, bile secretions, carrier proteins, and first-pass metabolism. For drugs with a narrow therapeutic index, other factors need to be monitored closely, including plasma drug levels, patients' clinical outcomes, and laboratory markers. Patients should be followed up frequently and treated in accordance with their response to the drug therapy. Bariatric surgery may affect the pharmacokinetics of various drugs, due to the resultant anatomical changes and the substantial weight loss. Therefore, there is a need to identify those potential changes and adjust patients' medication doses in order to achieve higher efficacy and avoid toxicity.

Enhanced glucose homeostasis via Clostridium symbiosum-mediated glucagon-like peptide 1 inhibition of hepatic gluconeogenesis in mid-intestinal bypass surgery

BACKGROUND

The small intestine is known to play a crucial role in the development and remission of diabetes mellitus (DM). However, the exact mechanism by which mid-small intestinal bypass improves glucose metabolism in diabetic rats is not fully understood.

AIM

To elucidate the mechanisms by which mid-small intestinal bypass improves glucose metabolism.

METHODS

Streptozotocin (STZ) was used to induce DM in Sprague-Dawley (SD) rats at a dose of 60 mg/kg. The rats were then randomly divided into two groups: The mid-small intestine bypass (MSIB) group and the sham group (underwent switch laparotomy). Following a 6-wk recovery period post-surgery, the rats underwent various assessments, including metabolic parameter testing, analysis of liver glycogen levels, measurement of key gluconeogenic enzyme activity, characterization of the gut microbiota composition, evaluation of hormone levels, determination of bile acid concentrations, and assessment of the expression of the intestinal receptors Takeda G protein-coupled receptor 5 and farnesoid X receptor.

RESULTS

The MSIB group of rats demonstrated improved glucose metabolism and lipid metabolism, along with increased hepatic glycogen content. Furthermore, there was a decrease in the expression of the key gluconeogenic enzymes phosphoenolpyruvate carboxykinase 1 and glucose-6-phosphatase. Importantly, the MSIB group exhibited a substantial increase in the abundances of intestinal Lactobacillus, Clostridium symbiosum, Ruminococcus gnavus, and Bilophila. Moreover, higher levels of secondary bile acids, such as intestinal lithocholic acid, were observed in this group. Remarkably, the changes in the gut microbiota showed a significant correlation with the expression of key gluconeogenic enzymes and glucagon-like peptide 1 (GLP-1) at 6 wk postoperatively, highlighting their potential role in glucose regulation. These findings highlight the beneficial effects of mid-small intestine bypass on glucose metabolism and the associated modulation of the gut microbiota.

CONCLUSION

The findings of this study demonstrate that the introduction of postoperative intestinal Clostridium symbiosum in the mid-small intestine contributes to the enhancement of glucose metabolism in nonobese diabetic rats. This improvement is attributed to the increased inhibition of hepatic gluconeogenesis mediated by GLP-1, resulting in a favorable modulation of glucose homeostasis.

The Role of Vitamin D in Health and Disease: A Narrative Review on the Mechanisms Linking Vitamin D with Disease and the Effects of Supplementation

Vitamin D insufficiency or deficiency (VDD) is a very prevalent condition in the general population. Vitamin D is necessary for optimal bone mineralization, but apart from the bone effects, preclinical and observational studies have suggested that vitamin D may have pleiotropic actions, whereas VDD has been linked to several diseases and higher all-cause mortality. Thus, supplementing vitamin D has been considered a safe and inexpensive approach to generate better health outcomes-and especially so in frail populations. Whereas it is generally accepted that prescribing of vitamin D in VDD subjects has demonstrable health benefits, most randomized clinical trials, although with design constraints, assessing the effects of vitamin D supplementation on a variety of diseases have failed to demonstrate any positive effects of vitamin D supplementation. In this narrative review, we first describe mechanisms through which vitamin D may exert an important role in the pathophysiology of the discussed disorder, and then provide studies that have addressed the impact of VDD and of vitamin D supplementation on each disorder, focusing especially on randomized clinical trials and meta-analyses. Despite there already being vast literature on the pleiotropic actions of vitamin D, future research approaches that consider and circumvent the inherent difficulties in studying the effects of vitamin D supplementation on health outcomes are needed to assess the potential beneficial effects of vitamin D. The evaluation of the whole vitamin D endocrine system, rather than only of 25-hydroxyvitamin D levels before and after treatment, use of adequate and physiologic vitamin D dosing, grouping based on the achieved vitamin D levels rather than the amount of vitamin D supplementation subjects may receive, and sufficiently long follow-up are some of the aspects that need to be carefully considered in future studies.

Evaluation of renal glucose uptake with [18F]FDG-PET: Methodological advancements and metabolic outcomes

BACKGROUND/PURPOSE

Studying renal glucose metabolism non-invasively in humans is an unmet need. Positron emission tomography (PET) is the current gold standard for measuring regional tissue glucose uptake rates, but the most widely used glucose analog ([¹⁸F]FDG) is not a good substrate for sodium-glucose cotransporters (SGLTs). As a consequence, [¹⁸F]FDG spills over into the urine and [¹⁸F]FDG-PET considerably underestimates published rates of whole renal glucose uptake obtained using the arterial-venous difference technique. Our aim was to assess whether [¹⁸F]FDG-PET can be used in the study of renal glucose metabolism in humans.

METHODS

We measured individual [¹⁸F]FDG radioactivity in the urine and estimated intraluminal [¹⁸F]FDG radioactivity concentration; these values were used to correct renal [¹⁸F]FDG-PET data acquired ∼90 min from tracer injection under fasting conditions and during an insulin clamp in 9 lean and 16 obese subjects.

RESULTS

We found that the corrected glucose uptake is consistently higher in the medulla than cortex and that both cortical and medullary glucose uptake are higher in lean than obese participants under both fasting and insulinized conditions. Moreover, cortical but not medullary glucose uptake is increased from the fasting to the insulinized condition.

CONCLUSION

The data show for the first time that [¹⁸F]FDG-PET can still provide relevant physiological information on regional renal glucose uptake on the condition that [¹⁸F]FDG uptake is corrected for tubular radioactivity.

Magnetic Resonance Imaging to Assess Body Composition Change in Adolescents With Obesity After Sleeve Gastrectomy

OBJECTIVES

Metabolic and bariatric surgery is the most effective weight loss treatment for severe obesity. The number of adolescents undergoing sleeve gastrectomy is increasing. We investigated changes in body composition in adolescents undergoing sleeve gastrectomy 12-26 weeks post-operatively using whole-body magnetic resonance imaging (WB-MRI).

METHODS

This prospective cohort study assessed changes in adipose tissue compartments (ie, visceral, subcutaneous, and intermuscular) and muscle in 18 obese adolescents, ages 14-19, 89% female, with body mass index z -score of 2.6 ± 0.25 (range 2.16-3.2). All underwent WB-MRI 1.5-17 weeks pre-operatively and 12-26 weeks post-operatively.

RESULTS

Pre- and post-operative WB-MRI showed decreases in all adipose tissue compartments, as well as decreased skeletal muscle and liver fat fraction ( P < 0.0001). The post-operative percentage loss of adipose tissue in subcutaneous, visceral, and intermuscular compartments (89.0%, 5.8%, 5.2%, respectively) was similar to the pre-operative percentages of corresponding adipose tissue compartments (90.5%, 5.0%, 4.5%, respectively). Of note, participants with obstructive sleep apnea had significantly higher pre-operative volume of subcutaneous and intermuscular adipose tissue than participants without obstructive sleep apnea ( P = 0.003).

CONCLUSIONS

We found, contrary to what is reported to occur in adults, that pre-operative percentage loss of adipose tissue in subcutaneous, visceral, and intermuscular compartments was similar to the post-operative percentage loss of corresponding adipose tissue compartments in adolescents 12-26 weeks after sleeve gastrectomy.

The Effect of Bariatric Surgery on Circulating Levels of Monocyte Chemoattractant Protein-1: A Systematic Review and Meta-Analysis

Background: MCP-1 (monocyte chemoattractant protein) plays an important role in early phases of atherogenesis as well as in plaque destabilization, which causes cardiovascular events to play an important role in low-grade inflammation. Obesity, particularly extreme obesity, is a pivotal risk factor for atherosclerosis and many other diseases. In the early stages, bariatric surgery might stop or slow atherogenesis by suppressing inflammation, but also in later stages, preventing plaque destabilization. The aim of this meta-analysis was to provide an answer as to whether bariatric surgery has a significant effect on circulating MCP-1 level or not. Methods: A systematic literature search in PubMed, Scopus, Embase, and Web of Science was performed from inception to 1 January 2022. Meta-analysis was performed using Comprehensive Meta-Analysis (CMA) V2 software. In order to heterogeneity compensation of studies in terms of study design and treatment duration, the characteristics of the studied populations random-effects model and the generic inverse variance weighting method were used. To investigate the relationship with the estimated effect size, a random-effect meta-regression model was used. To assess the exitance of publication bias in the meta-analysis, the funnel plot, Begg's rank correlation, and Egger's weighted regression tests were used. Results: Meta-analysis of 25 studies with 927 subjects included demonstrated a significant decrease of MCP-1 concentration after bariatric surgery. The data of meta-regression did not indicate any association between the alterations in body mass index (BMI) and absolute difference in MCP-1 levels, but a linear relationship between the changes in MCP-1 and length of follow-up was proven. Conclusions: Bariatric surgery significantly decreases MCP-1 concentration, but there was no association between the changes in BMI and absolute difference in MCP-1 levels before and after the surgery.

The effect of bariatric surgery in comparison with the control group on the prevention of comorbidities in people with severe obesity: a prospective cohort study

Background

Obesity is a global health priority, particularly in developing countries. The preventive effect of bariatric surgery against obesity-related diseases in the developing countries of the Middle East and North Africa region, where type 2 diabetes mellitus (T2DM), hypertension (HTN), and dyslipidemia prevail, has not been examined.

Method

Severely obese participants who underwent bariatric surgery were compared with their counterparts who underwent no intervention. These patients had been followed up in two prospective cohort studies for three years. We here determined the incidence of new-onset T2DM, HTN, and dyslipidemia and reported absolute and relative risks for the incidence of these comorbidities in the two groups.

Results

In this study, 612 participants in the bariatric surgery group were compared with 593 participants in the control group. During the follow-up period, T2DM developed in eight (2.9%) people in the surgery group and 66 (15.0%) people in the control group (P < 0.001). New-onset HTN and dyslipidemia showed significantly lower frequencies in the surgery group compared to the control group (4 (1.8%) vs. 70 (20.4%) and 33 (14.3%) vs. 93 (31.5%), respectively). Regarding a less favorable metabolic profile in the surgery group at the baseline, the relative risk reductions associated with bariatric surgery were 94, 93, and 55% for the development of T2DM, HTN, and dyslipidemia, respectively.

Conclusion

The risk reduction of obesity-related comorbidities after bariatric surgery should be considered in the decision-making process for public health in the region, which bariatric surgery could result in the prevention of comorbidities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01740-7.

Hepatic Positron Emission Tomography: Applications in Metabolism, Haemodynamics and Cancer

Evaluating in vivo the metabolic rates of the human liver has been a challenge due to its unique perfusion system. Positron emission tomography (PET) represents the current gold standard for assessing non-invasively tissue metabolic rates in vivo. Here, we review the existing literature on the assessment of hepatic metabolism, haemodynamics and cancer with PET. The tracer mainly used in metabolic studies has been [¹⁸F]2-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Its application not only enables the evaluation of hepatic glucose uptake in a variety of metabolic conditions and interventions, but based on the kinetics of ¹⁸F-FDG, endogenous glucose production can also be assessed. 14(R,S)-[¹⁸F]fluoro-6-thia-Heptadecanoic acid (¹⁸F-FTHA), ¹¹C-Palmitate and ¹¹C-Acetate have also been applied for the assessment of hepatic fatty acid uptake rates (¹⁸F-FTHA and ¹¹C-Palmitate) and blood flow and oxidation (¹¹C-Acetate). Oxygen-15 labelled water (¹⁵O-H₂O) has been used for the quantification of hepatic perfusion. ¹⁸F-FDG is also the most common tracer used for hepatic cancer diagnostics, whereas ¹¹C-Acetate has also shown some promising applications in imaging liver malignancies. The modelling approaches used to analyse PET data and also the challenges in utilizing PET in the assessment of hepatic metabolism are presented.

Improvement of Type 2 Diabetes Mellitus and Attenuation of NAFLD Are Associated with the Success of Obesity Therapy

Obesity and type 2 diabetes mellitus (T2D) represent important comorbidities of the metabolic syndrome, which are associated with non-alcoholic fatty liver disease (NAFLD)-related hepatic fibrosis. In total, 160 morbidly obese patients-81 following a low-calorie formula diet (LCD) program and 79 undergoing bariatric surgery (Roux-en-Y gastric bypass, RYGB)-were examined for anthropometric and metabolic parameters at base-line and during 12 months of weight loss, focusing on a putative co-regulation of T2D parameters and liver fibrosis risk. High NAFLD fibrosis scores (NFS) before intervention were associated with elevated HbA1c levels and T2D. Loss of weight and body fat percentage (BFL) were associated with improved glucose and lipid metabolism and reduced risk of NAFLD-related fibrosis, with particularly beneficial effects by RYGB. Both T2D improvement and NFS decrease were positively associated with high BFL. A highly significant correlation of NFS reduction with BFL was restricted to male patients while being absent in females, accompanied by generally higher BFL in men. Overall, the data display the relation of BFL, T2D improvement, and reduced NAFLD-related fibrosis risk during weight loss in morbidly obese individuals induced by diet or RYGB. Furthermore, our data suggest a considerable sexual dimorphism concerning the correlation of fat loss and improved risk of liver fibrosis.

Altered Glucose Metabolism and Glucose Transporters in Systemic Organs After Bariatric Surgery

The Roux-en-Y gastric bypass (RYGB) is highly effective in the remission of obesity and associated diabetes. The mechanisms underlying obesity and type 2 diabetes mellitus remission after RYGB remain unclear. This study aimed to evaluate the changes in continuous dynamic FDG uptake patterns after RYGB and examine the correlation between glucose metabolism and its transporters in variable endocrine organs using ¹⁸F-fluoro-2-deoxyglucose positron emission tomography images. Increased glucose metabolism in specific organs, such as the small intestine and various fat tissues, is closely associated with improved glycemic control after RYGB. In Otsuka Long-Evans Tokushima Fatty rats fed with high-fat diets, RYGB operation increases intestine glucose transporter expression and various fat tissues' glucose transporters, which are not affected by insulin. The fasting glucose decrement was significantly associated with RYGB, sustained weight loss, post-RYGB oral glucose tolerance test (OGTT) area under the curve (AUC), glucose transporter, or glycolytic enzymes in the small bowel and various fat tissues. High intestinal glucose metabolism and white adipose tissue-dependent glucose metabolism correlated with metabolic benefit after RYGB. These findings suggest that the newly developed glucose biodistribution accompanied by increased glucose transporters is a mechanism associated with the systemic effect of RYGB.

Comparable Effects of Sleeve Gastrectomy and Roux-en-Y Gastric Bypass on Basal Fuel Metabolism and Insulin Sensitivity in Individuals with Obesity and Type 2 Diabetes

AIM

Bariatric surgery improves insulin sensitivity and glucose tolerance in obese individuals with type 2 diabetes (T2D), but there is a lack of data comparing the underlying metabolic mechanisms after the 2 most common surgical procedures Roux-en-Y gastric bypass surgery (RYGB) and sleeve gastrectomy (SG). This study was designed to assess and compare the effects of RYGB and SG on fuel metabolism in the basal state and insulin sensitivity during a two-step euglycemic glucose clamp.

MATERIALS AND METHODS

16 obese individuals with T2D undergoing either RYGB (n = 9) or SG (n = 7) were investigated before and 2 months after surgery, and 8 healthy individuals without obesity and T2D served as controls. All underwent a 2 h basal study followed by a 5 h 2-step hyperinsulinemic euglycemic glucose clamp at insulin infusion rates of 0.5 and 1.0 mU/kg LBM/min.

RESULTS

RYGB and SG induced comparable 15% weight losses, normalized HbA1c, fasting glucose, fasting insulin, and decreased energy expenditure. In parallel, we recorded similar increments (about 100%) in overall insulin sensitivity (M-value) and glucose disposal and similar decrements (about 50%) in endogenous glucose production and FFA levels during the clamp; likewise, basal glucose and insulin concentrations decreased proportionally.

CONCLUSION

Our data suggest that RYGB and SG improve basal fuel metabolism and two-step insulin sensitivity in the liver, muscle, and fat and seem equally favourable when investigated 2 months after surgery. This trial is registered with NCT02713555.

The utilization of positron emission tomography in the evaluation of renal health and disease

Purpose

Positron emission tomography (PET) is a nuclear imaging technique that uses radiotracers to visualize metabolic processes of interest across different organs, to diagnose and manage diseases, and monitor therapeutic response. This systematic review aimed to characterize the value of PET for the assessment of renal metabolism and function in subjects with non-oncological metabolic disorders.

Methods

This review was conducted and reported in accordance with the PRISMA statement. Research articles reporting “kidney” or “renal” metabolism evaluated with PET imaging between 1980 and 2021 were systematically searched in Medline/PubMed, Science Direct, and the Cochrane Library. Search results were exported and stored in RefWorks, the duplicates were removed, and eligible studies were identified, evaluated, and summarized.

Results

Thirty reports met the inclusion criteria. The majority of the studies were prospective (73.33%, n = 22) in nature. The most utilized PET radiotracers were 15O-labeled radio water (H215O, n = 14) and 18F-fluorodeoxyglucose (18F-FDG, n = 8). Other radiotracers used in at least one study were 14(R,S)-(18)F-fluoro-6-thia-heptadecanoic acid (18F-FTHA), 18F-Sodium Fluoride (18F-NaF), 11C-acetate, 68-Gallium (68Ga), 13N-ammonia (13N-NH3), Rubidium-82 (82Rb), radiolabeled cationic ferritin (RadioCF), 11C‐para-aminobenzoic acid (11C-PABA), Gallium-68 pentixafor (68Ga-Pentixafor), 2-deoxy-2-F-fluoro-d-sorbitol (F-FDS) and 55Co-ethylene diamine tetra acetic acid (55Co-EDTA).

Conclusion

PET imaging provides an effective modality for evaluating a range of metabolic functions including glucose and fatty acid uptake, oxygen consumption and renal perfusion. Multiple positron emitting radiolabeled racers can be used for renal imaging in clinical settings. PET imaging thus holds the potential to improve the diagnosis of renal disorders, and to monitor disease progression and treatment response.

Sleeve Gastrectomy Suppresses Hepatic Glucose Production and Increases Hepatic Insulin Clearance Independent of Weight Loss

Bariatric operations induce weight loss, which is associated with an improvement in hepatic steatosis and a reduction in hepatic glucose production. It is not clear whether these outcomes are entirely due to weight loss, or whether the new anatomy imposed by the surgery contributes to the improvement in the metabolic function of the liver. We performed vertical sleeve gastrectomy (VSG) on obese mice provided with a high-fat high-sucrose diet and compared them to diet and weight-matched sham-operated mice (WMS). At 40 days after surgery, VSG-operated mice displayed less hepatic steatosis compared with WMS. By measuring the fasting glucose and insulin levels in the blood vessels feeding and draining the liver, we showed directly that hepatic glucose production was suppressed after VSG. Insulin levels were elevated in the portal vein, and hepatic insulin clearance was elevated in VSG-operated mice. The hepatic expression of genes associated with insulin clearance was upregulated. We repeated the experiment in lean mice and observed that portal insulin and glucagon are elevated, but only insulin clearance is increased in VSG-operated mice. In conclusion, direct measurement of glucose and insulin in the blood entering and leaving the liver shows that VSG affects glucose and insulin metabolism through mechanisms independent of weight loss and diet.

Bariatric surgery and the liver-Mechanisms, benefits, and risks

The prevalence of obesity and metabolic diseases such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) has risen dramatically over the past decades. At present, bariatric surgery is the most effective treatment for this global health problem, through effects on food intake, gut hormone secretion, metabolic signaling pathways, and adipose tissue dysfunction. The liver occupies a central role in carbohydrate, protein, and lipid metabolism. Notably, a reduction in hepatic fat content and an improvement in hepatic insulin resistance are among the earliest beneficial effects of bariatric surgery, which has therefore emerged as an attractive treatment option for NAFLD. However, as the scope and popularity of weight loss surgery have expanded, new questions have arisen regarding its safety in patients with liver cirrhosis, the outcome of liver transplantation in patients with a history of bariatric surgery, and over incidental reports of liver failure following surgery. Studies in humans and rodents have also linked bariatric surgery to an increased risk of developing alcohol use disorder, a major risk factor for liver disease. This review integrates data from clinical and translational research to delineate both the beneficial impact of bariatric surgery on the liver and the potential risks involved.

Intravital imaging of islet Ca2+ dynamics reveals enhanced β cell connectivity after bariatric surgery in mice

Bariatric surgery improves both insulin sensitivity and secretion and can induce diabetes remission. However, the mechanisms and time courses of these changes, particularly the impact on β cell function, are difficult to monitor directly. In this study, we investigated the effect of Vertical Sleeve Gastrectomy (VSG) on β cell function in vivo by imaging Ca²⁺ dynamics in islets engrafted into the anterior eye chamber. Mirroring its clinical utility, VSG in mice results in significantly improved glucose tolerance, and enhanced insulin secretion. We reveal that these benefits are underpinned by augmented β cell function and coordinated activity across the islet. These effects involve changes in circulating GLP-1 levels which may act both directly and indirectly on the β cell, in the latter case through changes in body weight. Thus, bariatric surgery leads to time-dependent increases in β cell function and intra-islet connectivity which are likely to contribute to diabetes remission.

Brain-gut-liver interactions across the spectrum of insulin resistance in metabolic fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named "nonalcoholic fatty liver disease" occurs in about one-third of the general population of developed countries worldwide and behaves as a major morbidity and mortality risk factor for major causes of death, such as cardiovascular, digestive, metabolic, neoplastic and neuro-degenerative diseases. However, progression of MAFLD and its associated systemic complications occur almost invariably in patients who experience the additional burden of intrahepatic and/or systemic inflammation, which acts as disease accelerator. Our review is focused on the new knowledge about the brain-gut-liver axis in the context of metabolic dysregulations associated with fatty liver, where insulin resistance has been assumed to play an important role. Special emphasis has been given to digital imaging studies and in particular to positron emission tomography, as it represents a unique opportunity for the noninvasive in vivo study of tissue metabolism. An exhaustive revision of targeted animal models is also provided in order to clarify what the available preclinical evidence suggests for the causal interactions between fatty liver, dysregulated endogenous glucose production and insulin resistance.

Liver Fat Reduction After Gastric Banding and Associations with Changes in Insulin Sensitivity and β-Cell Function

OBJECTIVE

The aim of this study was to examine the relationship between changes in liver fat and changes in insulin sensitivity and β-cell function 2 years after gastric banding surgery.

METHODS

Data included 23 adults with the surgery who had prediabetes or type 2 diabetes for less than 1 year and BMI 30 to 40 kg/m² at baseline. Body adiposity measures including liver fat content (LFC), insulin sensitivity (M/I), and β-cell responses (acute, steady-state, and arginine-stimulated maximum C-peptide) were assessed at baseline and 2 years after surgery. Regression models were used to assess associations adjusted for age and sex.

RESULTS

Two years after surgery, all measures of body adiposity, LFC, fasting and 2-hour glucose, and hemoglobin A1c significantly decreased; M/I significantly increased; and β-cell responses adjusted for M/I did not change significantly. Among adiposity measures, reduction in LFC had the strongest association with M/I increase (r = -0.61, P = 0.003). Among β-cell measures, change in LFC was associated with change in acute C-peptide response to arginine at maximal glycemic potentiation adjusted for M/I (r = 0.66, P = 0.007). Significant reductions in glycemic measures and increase in M/I were observed in individuals with LFC loss >2.5%.

CONCLUSIONS

Reduction in LFC after gastric banding surgery appears to be an important factor associated with long-term improvements in insulin sensitivity and glycemic profiles in adults with obesity and prediabetes or early type 2 diabetes.

Transcriptomic changes in pancreatic islets, adipose and liver after Roux-en-Y gastric bypass in a diet-induced obese rat model

Roux-en-Y gastric bypass (RYGB) is the most efficient intervention in morbid obesity and promotes metabolic improvements in several peripheral tissues. However, the underlying molecular mechanisms are still poorly understood. To further understand the effects of RYGB on peripheral tissues transcriptomes, we determined transcriptome signatures in pancreatic islets, adipose and liver tissue from diet-induced obese (DIO) rats model following RYGB. Whereas RYGB led to discrete gene expression changes in pancreatic islets, substantial transcriptome changes were observed in metabolic and immune signaling pathways in adipose tissue and the liver, indicating major gene adaptive responses in fat-storing tissues. Compared to RYGB DIO rats, peripheral tissue transcriptome signatures were markedly different in caloric restricted weight matching DIO rats, implying that caloric restriction paradigms do not reflect transcriptomic regulations of RYGB induced weight loss. The present gene expression study may serve as a basis for further investigations into molecular regulatory effects in peripheral tissues following RYGB-induced weight loss.

Effect of Surgically Induced Weight Loss on Biomarkers of Endothelial Dysfunction: a Systematic Review and Meta-Analysis

BACKGROUND

This meta-analysis was performed to assess the effects of bariatric surgery (BS) on the selected markers of endothelial dysfunction, including monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin.

METHODS

PubMed, Scopus, and Google scholar were systematically searched to identify related studies published from inception to November 2019 to find eligible studies.

RESULTS

A total of 29 different studies were included. BS reduced the concentrations of MCP-1 (weighted mean difference (WMD) = - 58.91; 95%CI (confidence interval), - 77.10 to - 40.72; P = ˂ 0.001), ICAM-1 (WMD = - 36.58; 95%CI, - 49.65 to - 23.52; P = ˂ 0.001), and E-selectin (WMD = - 11.22; 95%CI, - 14.43 to - 8.01; P < 0.001), but had no significant effect on VCAM-1.

CONCLUSION

Bariatric surgery reduces circulating concentration of MCP-1, ICAM-1, and E-selectin, but not VCAM-1.

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.

Human Bone Marrow Adipose Tissue is a Metabolically Active and Insulin-Sensitive Distinct Fat Depot

CONTEXT

Bone marrow (BM) in adult long bones is rich in adipose tissue, but the functions of BM adipocytes are largely unknown. We set out to elucidate the metabolic and molecular characteristics of BM adipose tissue (BMAT) in humans.

OBJECTIVE

Our aim was to determine if BMAT is an insulin-sensitive tissue, and whether the insulin sensitivity is altered in obesity or type 2 diabetes (T2DM).

DESIGN

This was a cross-sectional and longitudinal study.

SETTING

The study was conducted in a clinical research center.

PATIENTS OR OTHER PARTICIPANTS

Bone marrow adipose tissue glucose uptake (GU) was assessed in 23 morbidly obese subjects (9 with T2DM) and 9 healthy controls with normal body weight. In addition, GU was assessed in another 11 controls during cold exposure. Bone marrow adipose tissue samples for molecular analyses were collected from non-DM patients undergoing knee arthroplasty.

INTERVENTION(S)

Obese subjects were assessed before and 6 months after bariatric surgery and controls at 1 time point.

MAIN OUTCOME MEASURE

We used positron emission tomography imaging with 2-[18F]fluoro-2-deoxy-D-glucose tracer to characterize GU in femoral and vertebral BMAT. Bone marrow adipose tissue molecular profile was assessed using quantitative RT-PCR.

RESULTS

Insulin enhances GU in human BMAT. Femoral BMAT insulin sensitivity was impaired in obese patients with T2DM compared to controls, but it improved after bariatric surgery. Furthermore, gene expression analysis revealed that BMAT was distinct from brown and white adipose tissue.

CONCLUSIONS

Bone marrow adipose tissue is a metabolically active, insulin-sensitive and molecularly distinct fat depot that may play a role in whole body energy metabolism.

Predicting Skeletal Muscle and Whole-Body Insulin Sensitivity Using NMR-Metabolomic Profiling

PURPOSE

Abnormal lipoprotein and amino acid profiles are associated with insulin resistance and may help to identify this condition. The aim of this study was to create models estimating skeletal muscle and whole-body insulin sensitivity using fasting metabolite profiles and common clinical and laboratory measures.

MATERIAL AND METHODS

The cross-sectional study population included 259 subjects with normal or impaired fasting glucose or type 2 diabetes in whom skeletal muscle and whole-body insulin sensitivity (M-value) were measured during euglycemic hyperinsulinemic clamp. Muscle glucose uptake (GU) was measured directly using [18F]FDG-PET. Serum metabolites were measured using nuclear magnetic resonance (NMR) spectroscopy. We used linear regression to build the models for the muscle GU (Muscle-insulin sensitivity index [ISI]) and M-value (whole-body [WB]-ISI). The models were created and tested using randomly selected training (n = 173) and test groups (n = 86). The models were compared to common fasting indices of insulin sensitivity, homeostatic model assessment-insulin resistance (HOMA-IR) and the revised quantitative insulin sensitivity check index (QUICKI).

RESULTS

WB-ISI had higher correlation with actual M-value than HOMA-IR or revised QUICKI (ρ = 0.83 vs -0.67 and 0.66; P < 0.05 for both comparisons), whereas the correlation of Muscle-ISI with the actual skeletal muscle GU was not significantly stronger than HOMA-IR's or revised QUICKI's (ρ = 0.67 vs -0.58 and 0.59; both nonsignificant) in the test dataset.

CONCLUSION

Muscle-ISI and WB-ISI based on NMR-metabolomics and common laboratory measurements from fasting serum samples and basic anthropometrics are promising rapid and inexpensive tools for determining insulin sensitivity in at-risk individuals.

Physiologic Mechanisms of Type II Diabetes Mellitus Remission Following Bariatric Surgery: a Meta-analysis and Clinical Implications

INTRODUCTION

As obesity prevalence grows in the USA, metabolic syndrome is becoming increasingly more common. Current theories propose that insulin resistance is responsible for the hypertension, dyslipidemia, type II diabetes mellitus (T2DM), and low HDL that comprise metabolic syndrome. Bariatric surgery is one potential treatment, and its effects include permanently altering the patient's physiology and glucose regulation. Consequently, patients with T2DM who undergo bariatric surgery often experience tighter glucose control or remission of their T2DM altogether. This meta-analysis aims to explore the physiologic mechanisms underlying T2DM remission following bariatric surgery, which demonstrates effects that could lead to expansion of the NIH criteria for bariatric surgery candidates.

METHODS

A comprehensive search was conducted in PubMed and Scopus. Two independent reviewers conducted title, abstract, and full text review of papers that met inclusion criteria. Papers that measured hormone levels before and after bariatric surgery were included in the meta-analysis. Weighted means and standard deviations were calculated for preoperative and postoperative GLP-1, GIP, ghrelin, and glucagon.

RESULTS

Total postprandial GLP-1 increased following bariatric surgery, which correlated with improvements in measures of glycemic control. Fasting GLP-1, fasting GIP, total postprandial GIP, total fasting ghrelin, and fasting glucagon all decreased, but all changes in hormones evaluated failed to reach statistical significance. Studies also demonstrated changes in hepatic and peripancreatic fat, inflammatory markers, miRNA, and gut microbiota following bariatric surgery.

CONCLUSION

While this meta-analysis sheds light on possible mechanisms, further studies are necessary to determine the dominant mechanism underlying remission of T2DM following bariatric surgery.

Ongoing Inconsistencies in Weight Loss Reporting Following Bariatric Surgery: a Systematic Review

Weight loss is the primary outcome following bariatric surgery; however, its documentation within current literature is heterogeneous and poorly defined, limiting meaningful comparison between studies. Randomized controlled trials from 2012 to 2016 were identified using the Medline database through "Gastric bypass OR sleeve gastrectomy AND weight" search terms. A total of 73 studies with 5948 patients were included. Reporting of preoperative weight was done primarily using mean body mass index (BMI) (87.7%) and mean weight (65.8%). Postoperative weight reporting was more variable, with the most frequently reported measure being mean postoperative BMI (71.2%). Overall, nearly one third of all bariatric literature contained discrepancies that precluded meaningful meta-analysis. Reporting of weight loss following bariatric surgery is becoming increasingly diverse for both pre- and post-operative outcomes. Ongoing heterogeneity will continue to act as a barrier to meaningful comparison of bariatric outcomes until standardized reporting practices become adopted.

Portal Venous Metabolite Profiling After RYGB in Male Rats Highlights Changes in Gut-Liver Axis

After Roux-en-Y gastric bypass (RYGB) surgery, the intestine undergoes structural and metabolic reprogramming and appears to enhance use of energetic fuels including glucose and amino acids (AAs), changes that may be related to the surgery’s remarkable metabolic effects. Consistently, RYGB alters serum levels of AAs and other metabolites, perhaps reflecting mechanisms for metabolic improvement. To home in on the intestinal contribution, we performed metabolomic profiling in portal venous (PV) blood from lean, Long Evans rats after RYGB vs sham surgery. We found that one-carbon metabolism (OCM), nitrogen metabolism, and arginine and proline metabolism were significantly enriched in PV blood. Nitrogen, OCM, and sphingolipid metabolism as well as ubiquinone biosynthesis were also overrepresented among metabolites uniquely affected in PV vs peripheral blood in RYGB-operated but not sham-operated animals. Peripheral blood demonstrated changes in AA metabolism, OCM, sphingolipid metabolism, and glycerophospholipid metabolism. Despite enrichment for many of the same pathways, the overall metabolite fingerprint of the 2 compartments did not correlate, highlighting a unique role for PV metabolomic profiling as a window into gut metabolism. AA metabolism and OCM were enriched in peripheral blood both from humans and lean rats after RYGB, demonstrating that these conserved pathways might represent mechanisms for clinical improvement elicited by the surgery in patients. Together, our data provide novel insight into RYGB’s effects on the gut-liver axis and highlight a role for OCM as a key metabolic pathway affected by RYGB.

Metabolic benefits of gastric bypass surgery in the mouse: The role of fecal losses

Objective

Roux-en-Y gastric surgery (RYGB) promotes a rapid and sustained weight loss and amelioration of glucose control in obese patients. A high number of molecular hypotheses were previously tested using duodenal-jejunal bypass (DJB) performed in various genetic models of mice with knockouts for various hormones or receptors. The data were globally negative or inconsistent. Therefore, the mechanisms remained elusive. Intestinal gluconeogenesis is a gut function that has been suggested to contribute to the metabolic benefits of RYGB in obese patients.

Methods

We studied the effects of DJB on body weight and glucose control in obese mice fed a high fat-high sucrose diet. Wild type mice and mice with a genetic suppression of intestinal gluconeogenesis were studied in parallel using glucose- and insulin-tolerance tests. Fecal losses, including excretion of lipids, were studied from the feces recovered in metabolic cages.

Results

DJB induced a dramatic decrease in body weight and improvement in glucose control (glucose- and insulin-tolerance) in obese wild type mice fed a high calorie diet, for 25 days after the surgery. The DJB-induced decrease in food intake was transient and resumed to normal in 7–8 days, suggesting that decreased food intake could not account for the benefits. Total fecal losses were about 5 times and lipid losses 7 times higher in DJB-mice than in control (sham-operated and pair-fed) mice, and could account for the weight loss of mice. The results were comparable in mice with suppression of intestinal gluconeogenesis. There was no effect of DJB on food intake, body weight or fecal loss in lean mice fed a normal chow diet.

Conclusions

DJB in obese mice fed a high calorie diet promotes dramatic fecal loss, which could account for the dramatic weight loss and metabolic benefits observed. This could dominate the effects of the mouse genotype/phenotype. Thus, fecal energy loss should be considered as an essential process contributing to the metabolic benefits of DJB in obese mice.

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Duodenal-jejunal bypass (DJB) promotes weight loss in mice fed a high calorie diet.

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DJB induces dramatic fecal energy losses in mice fed a high calorie diet.

•

DJB has no effect in mice fed a control (starch-based) diet.

•

There is no fecal losses in DJB-mice fed a control diet.

•

Fecal energy loss is a cause of body weight loss in DJB-mice fed high calorie diet.

The influence of bariatric surgery on oral drug bioavailability in patients with obesity: A systematic review

Anatomical changes in the gastrointestinal tract and subsequent weight loss may influence drug disposition and thus drug dosing following bariatric surgery. This review systematically examines the effects of bariatric surgery on drug pharmacokinetics, focusing especially on the mechanisms involved in restricting oral bioavailability. Studies with a longitudinal before-after design investigating the pharmacokinetics of at least one drug were reviewed. The need for dose adjustment following bariatric surgery was examined, as well as the potential for extrapolation to other drugs subjected to coinciding pharmacokinetic mechanisms. A total of 22 original articles and 32 different drugs were assessed. The majority of available data is based on Roux-en-Y gastric bypass (RYGBP) (18 of 22 studies), and hence, the overall interpretation is more or less limited to RYGBP. In the case of the majority of studied drugs, an increased absorption rate was observed early after RYGBP. The effect on systemic exposure allows for a low degree of extrapolation, including between drugs subjected to the same major metabolic and transporter pathways. On the basis of current understanding, predicting the pharmacokinetic change for a specific drug following RYGBP is challenging. Close monitoring of each individual drug is therefore recommended in the early postsurgical phase. Future studies should focus on the long-term effects of bariatric surgery on drug disposition, and they should also aim to disentangle the effects of the surgery itself and the subsequent weight loss.

Tissue standardized uptake value is a closer surrogate of blood fluorine-18 fluorodeoxyglucose clearance after division by blood standardized uptake value, illustrated in brain and liver

The numerator and denominator of the left-hand side of the Gjedde-Patlak-Rutland (GPR) equation for measurement of blood fluorine-18 fluorodeoxyglucose (F-FDG) clearance into tissue (Ki) are the standardized uptake values (SUVs) of tissue and blood, respectively. The extent to which normalized time (NT) in the GPR equation exceeds real time depends on half-time of clearance of F-FDG from blood. A literature review shows that NT is fairly constant, about 100 min at 60 min postinjection of F-FDG, in keeping with our own finding of no significant difference in maximum SUV in blood 60 min postinjection of F-FDG between 39 patients with F-FDG-avid malignancy on routine PET/CT (1.74±0.31) and 21 patients with normal PET/CT (1.79±0.32), and similar blood glucose levels (BGLs). Volume of distribution (V0) in the GPR equation is ∼0.4 ml/ml for brain and ∼0.9 ml/ml for lean liver. Using these values of V0 and an NT of 100 min, we used the GPR equation to calculate Ki from our own published values of SUVliver/SUVblood and SUVbrain/SUVblood at 60 min postinjection, obtaining 0.0045 ml/min/ml for liver and 0.036 ml/min/ml for brain at BGL of 5 mmol/l. These values for Ki at this BGL are close to literature values of Ki, which for liver and brain are ∼0.0033 and ∼0.035 ml/min/ml, respectively. We conclude, therefore, that following division with blood pool SUV, tissue SUV becomes a closer surrogate of Ki. This division also eliminates the controversy over which whole body metric to use in the calculation of SUV.

Changes in Bile Acid Metabolism, Transport, and Signaling as Central Drivers for Metabolic Improvements After Bariatric Surgery

PURPOSE OF REVIEW

We review current evidence regarding changes in bile acid (BA) metabolism, transport, and signaling after bariatric surgery and how these might bolster fat mass loss and energy expenditure to promote improvements in type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

The two most common bariatric techniques, Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), increase the size and alter the composition of the circulating BA pool that may then impact energy metabolism through altered activities of BA targets in the many tissues perfused by systemic blood. Recent reports in human patients indicate that gene expression of the major BA target, the farnesoid X receptor (FXR), is increased in the liver but decreased in the small intestine after RYGB. In contrast, intestinal expression of the transmembrane G protein-coupled BA receptor (TGR5) is upregulated after surgery. Despite these apparent conflicting changes in receptor transcription, changes in BAs after both RYGB and VSG are associated with elevated postprandial systemic levels of fibroblast growth factor 19 (from FXR activation) and glucagon-like peptide 1 (from TGR5 activation). These signaling activities are presumed to support fat mass loss and related metabolic benefits of bariatric surgery, and this supposition is in agreement with findings from rodent models of RYGB and VSG. However, inter-species differences in BA physiology limit direct translation and mechanistic understanding of how changes in individual BA species contribute to post-operative improvements of T2D and NAFLD in humans. Thus, details of all these changes and their influences on BAs' biological actions are still under scrutiny. Changes in BA physiology and receptor activities after RYGB and VSG likely support weight loss and promote sustained metabolic improvements.

Physical Activity Associates with Muscle Insulin Sensitivity Postbariatric Surgery

PURPOSE

Bariatric surgery is considered as an effective therapeutic strategy for weight loss in severe obesity. Remission of type 2 diabetes is often achieved after the surgery. We investigated whether increase in self-reported habitual physical activity associates with improved skeletal muscle insulin sensitivity and reduction of fat depots after bariatric surgery.

METHODS

We assessed self-reported habitual physical activity using Baecke questionnaire in 18 diabetic and 28 nondiabetic patients with morbid obesity (median age, 46 yr; body mass index, 42.0 kg·m) before and 6 months after bariatric surgery operation. Insulin-stimulated femoral muscle glucose uptake was measured using fluorodeoxyglucose positron emission tomography method during hyperinsulinemia. In addition, abdominal subcutaneous and visceral fat masses were quantified using magnetic resonance imaging and liver fat content using magnetic resonance spectroscopy. Also, serum proinflammatory cytokines were measured.

RESULTS

Patients lost on average 22.9% of weight during the follow-up period of 6 months (P < 0.001). Self-reported habitual physical activity level increased (P = 0.017). Improvement in skeletal muscle insulin sensitivity was observed only in those patients who reported increase in their physical activity postoperatively (P = 0.018). The increase in self-reported physical activity associated with the loss of visceral fat mass (P = 0.029). Postoperative self-reported physical activity correlated also positively with postoperative hepatic insulin clearance (P = 0.02) and tended to correlate negatively with liver fat content (P = 0.076). Postoperative self-reported physical activity also correlated negatively with serum TNFα, methyl-accepting chemotaxis protein and interleukin 6 levels.

CONCLUSIONS

Self-reported physical activity is associated with reversal of skeletal muscle insulin resistance after bariatric surgery as well as with the loss of visceral fat content and improved postoperative metabolism in bariatric surgery patients.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT00793143 (SLEEVEPASS), NCT01373892 (SLEEVEPET2).

Sleeve Gastrectomy and Roux-en-Y Gastric Bypass Achieve Similar Early Improvements in Beta-cell Function in Obese Patients with Type 2 Diabetes

Bariatric surgery is a treatment option for obese patients with type 2 diabetes mellitus (T2DM). Although sleeve gastrectomy (SG) is growing in favor, some randomized trials show less weight loss and HbA1c improvement compared with Roux-en-Y gastric bypass (RYGB). The study objective was to compare changes in beta-cell function with similar weight loss after SG and RYGB in obese patients with T2DM. Subjects undergoing SG or RYGB were studied with an intravenous glucose tolerance test before surgery and at 5–12% weight loss post-surgery. The primary endpoint was change in the disposition index (DI). Baseline BMI, HbA1c, and diabetes-duration were similar between groups. Mean total weight loss percent was similar (8.4% ± 0.4, p = 0.22) after a period of 21.0 ± 1.7 days. Changes in fasting glucose, acute insulin secretion (AIR), and insulin sensitivity (Si) were similar between groups. Both groups showed increases from baseline to post-surgery in DI (20.2 to 163.3, p = 0.03 for SG; 31.2 to 232.9, p = 0.02 for RYGB) with no significant difference in the change in DI between groups (p = 0.53). Short-term improvements in beta-cell function using an IVGTT were similar between SG and RYGB. It remains unclear if longer-term outcomes are better after RYGB due to greater weight loss and/or other factors.

Brain glucose uptake is associated with endogenous glucose production in obese patients before and after bariatric surgery and predicts metabolic outcome at follow-up

AIMS

To investigate further the finding that insulin enhances brain glucose uptake (BGU) in obese but not in lean people by combining BGU with measures of endogenous glucose production (EGP), and to explore the associations between insulin-stimulated BGU and peripheral markers, such as metabolites and inflammatory markers.

MATERIALS AND METHODS

A total of 20 morbidly obese individuals and 12 lean controls were recruited from the larger randomized controlled SLEEVEPASS study. All participants were studied under fasting and euglycaemic hyperinsulinaemic conditions using fluorodeoxyglucose-positron emission tomography. Obese participants were re-evaluated 6 months after bariatric surgery and were followed-up for ~3 years.

RESULTS

In obese participants, we found a positive association between BGU and EGP during insulin stimulation. Across all participants, insulin-stimulated BGU was associated positively with systemic inflammatory markers and plasma levels of leucine and phenylalanine. Six months after bariatric surgery, the obese participants had achieved significant weight loss. Although insulin-stimulated BGU was decreased postoperatively, the association between BGU and EGP during insulin stimulation persisted. Moreover, high insulin-stimulated BGU at baseline predicted smaller improvement in fasting plasma glucose at 2 and 3 years of follow-up.

CONCLUSIONS

Our findings suggest the presence of a brain-liver axis in morbidly obese individuals, which persists postoperatively. This axis might contribute to further deterioration of glucose homeostasis.

Molecular imaging of diabetes and diabetic complications: Beyond pancreatic β-cell targeting

Diabetes is a chronic non-communicable disease affecting over 400 million people worldwide. Diabetic patients are at a high risk of various complications, such as cardiovascular, renal, and other diseases. The pathogenesis of diabetes (both type 1 and type 2 diabetes) is associated with a functional impairment of pancreatic β-cells. Consequently, most efforts to manage and prevent diabetes have focused on preserving β-cells and their function. Advances in imaging techniques, such as magnetic resonance imaging, magnetic resonance spectroscopy, positron emission tomography, and single-photon-emission computed tomography, have enabled noninvasive and quantitative detection and characterization of the population and function of β-cells in vivo. These advantages aid in defining and monitoring the progress of diabetes and determining the efficacy of anti-diabetic therapies. Beyond β-cell targeting, molecular imaging of biomarkers associated with the development of diabetes, e.g., lymphocyte infiltration, insulitis, and metabolic changes, may also be a promising strategy for early detection of diabetes, monitoring its progression, and occurrence of complications, as well as facilitating exploration of new therapeutic interventions. Moreover, molecular imaging of glucose uptake, production and excretion in specified tissues is critical for understanding the pathogenesis of diabetes. In the current review, we summarize and discuss recent advances in noninvasive imaging technologies for imaging of biomarkers beyond β-cells for early diagnosis of diabetes, investigation of glucose metabolism, and precise diagnosis and monitoring of diabetic complications for better management of diabetic patients.

Short-term interval training alters brain glucose metabolism in subjects with insulin resistance

Brain insulin-stimulated glucose uptake (GU) is increased in obese and insulin resistant subjects but normalizes after weight loss along with improved whole-body insulin sensitivity. Our aim was to study whether short-term exercise training (moderate intensity continuous training (MICT) or sprint interval training (SIT)) alters substrates for brain energy metabolism in insulin resistance. Sedentary subjects ( n = 21, BMI 23.7-34.3 kg/m², age 43-55 y) with insulin resistance were randomized into MICT ( n = 11, intensity≥60% of VO_2peak) or SIT ( n = 10, all-out) groups for a two-week training intervention. Brain GU during insulin stimulation and fasting brain free fatty acid uptake (FAU) was measured using PET. At baseline, brain GU was positively associated with the fasting insulin level and negatively with the whole-body insulin sensitivity. The whole-body insulin sensitivity improved with both training modes (20%, p = 0.007), while only SIT led to an increase in aerobic capacity (5%, p = 0.03). SIT also reduced insulin-stimulated brain GU both in global cortical grey matter uptake (12%, p = 0.03) and in specific regions ( p < 0.05, all areas except the occipital cortex), whereas no changes were observed after MICT. Brain FAU remained unchanged after the training in both groups. These findings show that short-term SIT effectively decreases insulin-stimulated brain GU in sedentary subjects with insulin resistance.

Team Players or Opponents: Coadministration of Selective Glucagon and GLP-1 Receptor Agonists in Obese Diabetic Monkeys

We assessed the therapeutic contribution of the individual components of glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) agonists alone and in combination upon energy homeostasis and glycemic control in diet-induced obese, diabetic nonhuman primates. The pharmacological active dose ranges of selective agonists were established through a dose-finding study, followed by a 6-week chronic study. Repeated subcutaneous administration of a selective GCGR agonist (30 µg/kg once daily) did not affect food intake or body weight, whereas the selective GLP-1R agonist (3 µg/kg once daily) alone decreased energy intake by 18% and body weight by 3.8% ± 0.9%. Combination of both agonists reduced significantly cumulative food intake by 27% and body weight by 6.6% ± 0.9%. Fasting plasma glucose (FPG) was improved by GLP-1R agonist (baseline vs end of study, 176.7 ± 34.0 vs 115.9 ± 16.1 mg/dL). In contrast, groups exposed to GCGR agonist experienced nonsignificant elevations of FPG. More accurate assessment of therapeutic interventions on glucose homeostasis was tested by an IV glucose tolerance test. Glucose excursion was significantly elevated by chronic GCGR agonist administration, whereas it was significantly decreased in GLP-1R agonist-treated monkeys. In the combination group, a nonsignificant increase of glucose excursion was seen, concomitantly with significantly increased insulin secretion. We conclude that chronic glucagon agonism does not affect energy homeostasis in nonhuman primates. In combination with GLP-1R agonism, glucagon agonism synergistically enhances negative energy balance with resulting larger body weight loss. However, adding GCGR to GLP-1R agonism diminishes glycemic control in diabetic monkeys. Therefore, long-term therapeutic implications of using GLP-1R/GCGR coagonists for weight management in diabetes warrants further scrutiny.