Diabetes Remission Following Metabolic Surgery: Is GLP-1 the Culprit?

Bariatric surgery improves postprandial VLDL kinetics and restores insulin-mediated regulation of hepatic VLDL production

Dyslipidemia in obesity results from excessive production and impaired clearance of triglyceride-rich (TG-rich) lipoproteins, which are particularly pronounced in the postprandial state. Here, we investigated the impact of Roux-en-Y gastric bypass (RYGB) surgery on postprandial VLDL1 and VLDL2 apoB and TG kinetics and their relationship with insulin-responsiveness indices. Morbidly obese patients without diabetes who were scheduled for RYGB surgery (n = 24) underwent a lipoprotein kinetics study during a mixed-meal test and a hyperinsulinemic-euglycemic clamp study before the surgery and 1 year later. A physiologically based computational model was developed to investigate the impact of RYGB surgery and plasma insulin on postprandial VLDL kinetics. After the surgery, VLDL1 apoB and TG production rates were significantly decreased, whereas VLDL2 apoB and TG production rates remained unchanged. The TG catabolic rate was increased in both VLDL1 and VLDL2 fractions, but only the VLDL2 apoB catabolic rate tended to increase. Furthermore, postsurgery VLDL1 apoB and TG production rates, but not those of VLDL2, were positively correlated with insulin resistance. Insulin-mediated stimulation of peripheral lipoprotein lipolysis was also improved after the surgery. In summary, RYGB resulted in reduced hepatic VLDL1 production that correlated with reduced insulin resistance, elevated VLDL2 clearance, and improved insulin sensitivity in lipoprotein lipolysis pathways.

Central Modulation of Energy Homeostasis and Cognitive Performance After Bariatric Surgery

In moderately or morbidly obese patients, bariatric surgery has been proven to be an effective therapeutic approach to control body weight and comorbidities. Surgery-mediated modulation of brain function via modified postoperative secretion of gut peptides and vagal nerve stimulation was identified as an underlying mechanism in weight loss and improvement of weight-related diseases. Increased basal and postprandial plasma levels of gastrointestinal hormones like glucagon-like peptide 1 and peptide YY that act on specific areas of the hypothalamus to reduce food intake, either directly or mediated by the vagus nerve, are observed after surgery while suppression of meal-induced ghrelin release is increased. Hormones released from the adipose tissue like leptin and adiponectin are also affected and leptin plasma levels are reduced in treated patients. Besides homeostatic control of body weight, surgery also changes hedonistic behavior in regard to food intake and cognitive performance involving the limbic system and prefrontal areas.

Importance of the gastrointestinal tract in type 2 diabetes. Metabolic surgery is more than just incretin effect

Bariatric and metabolic surgery is creating new concepts about how the intestine assimilates food. Recent studies highlight the role of the gastrointestinal tract in the genesis and evolution of type 2 diabetes. This article has been written to answer frequent questions about metabolic surgery results and the mechanisms of action. For this purpose, a non-systematic search of different databases was carried out, identifying articles published in the last decade referring to the mechanisms of action of metabolic techniques. Understanding these mechanisms will help grasp why some surgeries are more effective than others and why the results can be so disparate among patients undergoing the same surgical approach.

Predictive Value of Gut Peptides in T2D Remission: Randomized Controlled Trial Comparing Metabolic Gastric Bypass, Sleeve Gastrectomy and Greater Curvature Plication

BACKGROUND

Our aim was to determine the predictive value of gut hormone changes for the improvement of type 2 diabetes (T2D) following metabolic Roux-en-Y gastric bypass (mRYGB), sleeve gastrectomy (SG), and greater curvature plication (GCP) in a randomized controlled trial. Contradictory results have been obtained regarding the role of gastrointestinal hormones (in particular GLP-1) in beneficial metabolic bariatric surgery outcomes.

METHODS

Forty-five patients with T2D (mean BMI 39.4 ± 1.9 kg/m²) were randomly assigned to mRYGB, SG, or GCP. Anthropometric and biochemical parameters, fasting concentrations of PYY, ghrelin, glucagon, and area under the curve (AUC) of GLP-1 after a standard meal test were determined prior to and at months 1 and 12 after surgery.

RESULTS

Twelve months after surgery, total weight loss percentage was higher and HbA1c lower in the mRYGB group than in the SG and GCP groups (-35.2 ± 8.1 and 5.1 ± 0.6% vs. -27.8 ± 5.4 and 6.2 ± 0.8% vs. -20.5 ± 6.8 and 6.6 ± 1.3%; p = 0.007 and p < 0.001, respectively). Moreover, GLP-1 AUC at months 1 and 12 was greater and T2D remission was higher in mRYGB (80 vs. 53.3 vs. 20%, p < 0.001). Insulin treatment (odds ratio (OR) 0.025, p = 0.018) and the increase in GLP-1 AUC from baseline to month 1 (OR 1.021, p = 0.013) were associated with T2D remission.

CONCLUSIONS

mRYGB achieves a superior rate of weight loss and T2D remission at month 12. Enhanced GLP-1 secretion 1 month after surgery was a determinant of glucose metabolism improvement. Registration number ( http://www.clinicaltrials.gov ): NCT14104758.

Duodenal-Jejunal Bypass Surgery Reverses Diabetic Phenotype and Reduces Obesity in db/db Mice

Type 2 diabetes mellitus (T2DM), a complex metabolic disorder typically accompanying weight gain, is associated with progressive β-cell failure and insulin resistance. Bariatric surgery ameliorates glucose tolerance and provides a near-perfect treatment. Duodenal-jejunal bypass (DJB) is an experimental procedure and has been studied in several rat models, but its influence in db/db mice, a transgenic model of T2DM, remains unclear. To investigate the effectiveness of DJB in db/db mice, we performed the surgery and evaluated metabolism improvement. Results showed that mice in DJB group weighed remarkably less than sham group two weeks after surgery. Compared to the preoperative level, postoperative fasting blood glucose (FBG) was dramatically reduced. Statistical analysis revealed that changes in body weight and FBG were significantly correlated. Besides, DJB surgery altered plasma insulin level with approximate 40% reduction. Thus, for the first time we proved that DJB can achieve rapid therapeutic effect in transgenic db/db mice with severe T2DM as well as obesity. In addition, decreased insulin level reflected better insulin sensitivity induced by DJB. In conclusion, our study demonstrates that DJB surgery may be a potentially effective way to treat obesity-associated T2DM.

The Effects of One-Anastomosis Gastric Bypass on Glucose Metabolism in Goto-Kakizaki Rats

BACKGROUND

The improvement in glucose metabolism after bariatric surgery is well established. The aim of this study was to investigate the hormones and glycemic control in diabetes after a one-anastomosis gastric bypass (OAGB) variant in an animal model of non-obese type 2 diabetes mellitus.

METHODS

Thirty-six Goto-Kakizaki rats were randomly assigned to undergo one of the following procedures: OAGB (18 rats) or sham intervention (18 rats). Each group was subdivided into three additional groups according to the time of surgery (early-12 weeks; intermediate-16 weeks; and late-20 weeks). Weight, fasting glycemia, glucose tolerance test (OGTT), and hormone levels (glucagon, insulin, glucagon-like peptide-1 [GLP-1], and glucose-dependent insulinotropic peptide [GIP]) were measured.

RESULTS

All rats maintained their weight. The OGTT showed a significant improvement in glycemic levels in rats with OAGB in all time groups (p < 0.002, for all groups at 60 min). Insulin levels decreased significantly in all animals with OAGB, but glucagon levels increased (glucagon paradoxical response). GLP-1 and GIP increased in rats with OAGB at all times, but was only statistically significant in the early surgery group of GLP-1 (p < 0.005).

CONCLUSION

OAGB in a non-obese diabetic rat model improves glycemic control, with a significant decrease in glucose and insulin levels. This reduction without weight loss suggests a surgically induced enhancement of pancreatic function. It appears that this improvement occurs, although the GLP-1 levels were significantly increased only in the early stages. The paradoxical response of glucagon should be further evaluated.

Sleeve gastrectomy activates the GLP-1 pathway in pancreatic β cells and promotes GLP-1-expressing cells differentiation in the intestinal tract

Db/db mouse was used to study the underlying mechanisms by which Sleeve gastrectomy (SG) improves β-cell function. We investigated β-cell function, plasma active GLP-1 levels, the GLP-1R pathway in β cells and L cell differentiation. After SG, β-cell function was significantly increased, and the GLP-1R-PKCζ-PDX-1 pathway was active in β cells. Plasma active GLP-1 levels, as well as the number of L cells in the jejunum, were significantly increased after SG. The expression of early transcription factors (TF), including Ngn3, FoxA1 and Nkx2.2, was not compromised by chronic hyperglycemia. In contrast, the expression of the downstream TF PAX6 was affected, and this down-regulation could be reversed by SG. So, SG can maintain L cell differentiation, increase plasma active GLP-1 level, sustain the activation of the GLP-1R pathway and improve β cell function in Db/db mice. Our results show that SG can overall improve the function of the entero-insular axis.

Patterns of Weight Loss Response Following Gastric Bypass and Sleeve Gastrectomy

BACKGROUND

Despite the health benefits of bariatric surgery (BS) extend beyond WL, better understanding of the WL response may help improve the outcomes of BS. In this context, we aimed to assess patterns within the variability of weight loss (WL) after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG).

METHODS

WL data from 658 subjects that underwent RYGB (n = 464) or SG (n = 194) as first BS were analyzed. Based on excess WL (EWL), subjects were categorized as good WL responders (EWL ≥ 50 % at nadir weight and throughout follow-up), primarily poor WL responders (1-PWL:EWL < 50 % at nadir weight and thereafter), and secondarily poor WL responders (2-PWL:EWL ≥ 50 % at nadir weight, but <50 % at last follow-up visit). Predictors associated with different WL outcomes were ascertained using regression analysis.

RESULTS

Median follow-up was 55.7 months. Nadir EWL ranged 12.4-143.6 %; last follow-up visit EWL ranged -22.1-143.6 % and weight regain (WR) ranged 0-64.1 kg. Good WL was found in 75.7 of the cohort. 1-PWL response (4.7 %) was characterized by lesser WL but similar WR as compared to good WL and was associated with larger BMI and diabetes prior to surgery. 2-PWL response (19.6 %) was characterized by larger WR as compared to the other groups and was more common following SG. Lesser percentage of medical appointments kept was associated with 1-PWL and 2-PWL.

CONCLUSION

Our data show the high inter-individual variability of the WL response at mid-term after RYGB and SG and that poor WL after BS could be illustrated by two different patterns, characterized either by sustained limited WL (1-PWL), or pronounced weight regain (2-PWL).

MANAGEMENT OF ENDOCRINE DISEASE: Metabolic effects of bariatric surgery

Obesity is associated with an increased risk of type 2 diabetes, hypertension, dyslipidemia, cardiovascular disease, osteoarthritis, numerous cancers and increased mortality. It is estimated that at least 2.8 million adults die each year due to obesity-related cardiovascular disease. Increasing in parallel with the global obesity problem is metabolic syndrome, which has also reached epidemic levels. Numerous studies have demonstrated that bariatric surgery is associated with significant and durable weight loss with associated improvement of obesity-related comorbidities. This review aims to summarize the effects of bariatric surgery on the components of metabolic syndrome (hyperglycemia, hyperlipidemia and hypertension), weight loss, perioperative morbidity and mortality, and the long-term impact on cardiovascular risk and mortality.

Glucagon secretion after metabolic surgery in diabetic rodents

Excessive or inadequate glucagon secretion promoting hepatic gluconeogenesis and glycogenolysis is believed to contribute to hyperglycemia in patients with type 2 diabetes. Currently, metabolic surgery is an accepted treatment for obese patients with type 2 diabetes and has been shown to improve glycemic control in Goto-Kakizaki (GK) rats, a lean animal model for type 2 diabetes. However, the effects of surgery on glucagon secretion are not yet well established. In this study, we randomly assigned forty 12- to 14-week-old GK rats to four groups: control group (GKC), sham surgery (GKSS), sleeve gastrectomy (GKSG), and gastric bypass (GKGB). Ten age-matched Wistar rats served as a non-diabetic control group (WIC). Glycemic control was assessed before and 4 weeks after surgery. Fasting- and mixed-meal-induced plasma levels of insulin and glucagon were measured. Overall glycemic control improved in GKSG and GKGB rats. Fasting insulin levels in WIC rats were similar to those for GKC or GKSS rats. Fasting glucagon levels were highest in GKGB rats. Whereas WIC, GKC, and GKSS rats showed similar glucagon levels, without any significant meal-induced variation, a significant rise occurred in GKSG and GKGB rats, 30 min after a mixed meal, which was maintained at 60 min. Both GKSG and GKGB rats showed an elevated glucagon:insulin ratio at 60 min in comparison with all other groups. Surprisingly, the augmented post-procedural glucagon secretion was accompanied by an improved overall glucose metabolism in GKSG and GKGB rats. Understanding the role of glucagon in the pathophysiology of type 2 diabetes requires further research.

Lipidomic profiling before and after Roux-en-Y gastric bypass in obese patients with diabetes

Bariatric surgery is a well-established approach to improve metabolic disease in morbidly obese patients with high cardiovascular risk. The post-operative normalization of lipid metabolism has a central role in the prevention of future cardiovascular events. The aim of the present study therefore was to characterize changes of plasma lipidomic patterns, consisting of 229 lipid species of 13 lipid classes, 3 months after Roux-en-Y gastric bypass (RYGB) in morbidly obese patients with and without diabetes. RYGB resulted in a 15-32% decrease of body mass index, which was associated with a significant reduction of total cholesterol (TC, -28.3%; P=0.02), LDL-cholesterol (LDL-C, -26.8%; P=0.03) and triglycerides (TGs, -63.0%; P=0.05) measured by routine clinical chemistry. HDL-cholesterol remained unchanged. The effect of RYGB on the plasma lipidomic profile was characterized by significant decreases of 87 lipid species from triacylglycerides (TAGs), cholesterol esters (CholEs), lysophosphatidylcholines (LPCs), phosphatidylcholines (PCs), phosphatidylethanolamine ethers (PEOs), phosphatidylinositols (PIs) and ceramides (Cers). The total of plasma lipid components exhibited a substantial decline of 32.6% and 66 lipid species showed a decrease by over 50%. A direct correlation with HbA1C values could be demonstrated for 24 individual lipid species (10 TAG, three CholE, two LPC, one lysophosphatidylcholine ethers (LPCO) (LPC ether), one PC, two phosphatidylcholine ethers (PCO) and five Cer). Notably, two lipid species (TAG 58:5 and PEO 40:5) were inversely correlated with HbA1C. LPCO, as single whole lipid class, was directly related to HbA1C. These data indicate that RYGB-induced modulation of lipidomic profiles provides important information about post-operative metabolic adaptations and might substantially contribute to improvements of glycemic control. These striking changes in the human plasma lipidome may explain acute, weight independent and long-term effects of RYGB on the cardiovascular system, mental status and immune regulation.