Comparison of the effects of Roux-en-Y gastric bypass and ileal transposition surgeries on food intake, body weight, and circulating peptide YY concentrations in rats

Effects of bariatric surgery and dietary intervention on insulin resistance and appetite hormones over a 3 year period

To examine an impact of three types of bariatric surgery compared with dietary intervention (DIET), on concurrent changes in Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and appetite hormones over 3 years. Fifty-five adults were studied during phase of weight loss (0-12 months) and during weight stability (12-36 months) post intervention. Measurements of HOMA-IR, fasting and postprandial PYY and GLP1, adiponectin, CRP, RBP4, FGF21 hormones and dual-Xray absorptiometry were performed throughout the study. All surgical groups achieved significant reductions in HOMA-IR with greatest difference between Roux-en-Y gastric bypass and DIET (- 3.7; 95% CI - 5.4, - 2.1; p = 0.001) at 12-36 months. Initial (0-12 months) HOMA-IR values were no different to DIET after adjustment for the lost weight. During 12-36 months, after controlling for treatment procedure and weight, for every twofold increase in postprandial PYY and adiponectin, HOMA-IR decreased by 0.91 (95% CI - 1.71, - 0.11; p = 0.030) and by 0.59 (95% CI - 1.10, - 0.10; p = 0.023) respectively. Initial, non-sustained changes in RBP4 and FGF21 were not associated with HOMA-IR values. While initial rapid weight loss reduces insulin resistance, the enhanced secretions of PYY and adiponectin may contribute to weight-independent improvements in HOMA-IR during weight stability.Clinical trial registration: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12613000188730.

Gut-brain mechanisms underlying changes in disordered eating behaviour after bariatric surgery: a review

Bariatric surgery results in long-term weight loss and an improved metabolic phenotype due to changes in the gut-brain axis regulating appetite and glycaemia. Neuroendocrine alterations associated with bariatric surgery may also influence hedonic aspects of eating by inducing changes in taste preferences and central reward reactivity towards palatable food. However, the impact of bariatric surgery on disordered eating behaviours (e.g.: binge eating, loss-of-control eating, emotional eating and 'addictive eating'), which are commonly present in people with obesity are not well understood. Increasing evidence suggests gut-derived signals, such as appetitive hormones, bile acid profiles, microbiota concentrations and associated neuromodulatory metabolites, can influence pathways in the brain implicated in food intake, including brain areas involved in sensorimotor, reward-motivational, emotional-arousal and executive control components of food intake. As disordered eating prevalence is a key mediator of weight-loss success and patient well-being after bariatric surgery, understanding how changes in the gut-brain axis contribute to disordered eating incidence and severity after bariatric surgery is crucial to better improve treatment outcomes in people with obesity.

Early Postoperative Exposure to High-Fat Diet Does Not Increase Long-Term Weight Loss or Fat Avoidance After Roux-en-Y Gastric Bypass in Rats

Background

Bariatric surgery alters food preferences in rats and reportedly decreases desire to consume high-fat high-sugar food in humans. The aim of this study was to investigate whether early post-operative exposure to high-fat food could increase body weight loss after Roux-en-Y gastric bypass (RYGB) by triggering fat avoidance.

Methods

Male Wistar rats underwent either RYGB (n = 15) or sham-operations (n = 16). Preoperatively a standardized 4-choice cafeteria diet [dietary options: low-fat/low-sugar (LFLS), low-fat/high-sugar (LFHS), high-fat/low-sugar (HFLS), high-fat/high-sugar (HFHS)] was offered. First, each option was available for 4 days, thereafter rats were offered the 4 options simultaneously for 3 days preoperatively. Post-surgery, 8 rats in the RYGB- and 8 in the sham-group were exposed to a high-fat content diet (Oatmeal + 30% lard, OM+L) for 10 days, while 7 RYGB rats and 8 sham-rats received OM alone. From the 11th postoperative day, the 4-choice cafeteria diet was reintroduced for 55-days. The intake of all available food items, macronutrients and body weight changes were monitored over 8 weeks. Main outcomes were long-term body-weight and daily change in relative caloric intake during the postoperative cafeteria period compared to the preoperative cafeteria.

Results

During the first 12 days of postoperative cafeteria access, RYGB-rats exposed to OM+L had a higher mean caloric intake per day than RYGB rats exposed to OM alone (Δ10 kCal, P_adj = 0.004), but this difference between the RYGB groups disappeared thereafter. Consequently, in the last 33 days of the postoperative cafeteria diet, the mean body weight of the RYGB+OM+L group was higher compared to RYGB+OM (Δ51 g, P_adj < 0.001). RYGB rats, independently from the nutritional intervention, presented a progressive decrease in daily consumption of calories from fat and increased their daily energy intake mainly from non-sugar carbohydrates. No such differences were detected in sham-operated controls exposed to low- or high fat postoperative interventions.

Conclusion

A progressive decrease in daily fat intake over time was observed after RYGB, independently from the nutritional intervention. This finding confirms that macronutrient preferences undergo progressive changes over time after RYGB and supports the role of ingestive adaptation and learning. Early postoperative exposure to high-fat food failed to accentuate fat avoidance and did not lead to superior weight loss in the long-term.

Biliopancreatic Limb Length of Small Intestinal Bypass in Non-obese Goto-Kakizaki (GK) Rats Correlates with Gastrointestinal Hormones, Adipokines, and Improvement in Type 2 Diabetes

BACKGROUND

The purpose of this study was to explore the effects on type 2 diabetes, gastrointestinal hormones, and adipokines after the small intestinal bypass of different biliopancreatic limb (BPL) lengths in non-obese type 2 diabetic rats.

METHOD

Small intestinal bypass with the BPL length at 10cm, 20cm, 30cm, and 40cm, respectively, and sham surgery were performed in non-obese GK rats. Fasting serum was collected at 2 days preoperatively and 1, 3, 6, and 9 weeks postoperatively. Body weight and fasting blood glucose (FBG) were measured during the experiment. Glycated hemoglobin (GHb), fasting insulin (FINS), C-peptide, ghrelin, leptin, adiponectin, and somatostatin were measured postoperatively.

RESULT

Rats with a bypassed length of 40cm died within 5-9 weeks. No statistically significant was observed in body weight between the sham group and the bypass groups at the 9th week postoperatively. FBG, GHb, FINS, C-peptide, and HOMA-IR in the bypass groups were lower than those in the sham group postoperatively and were negatively correlated with BPL length. Ghrelin and leptin declined compared with preoperative but were not associated with BPL length. Adiponectin of the bypass groups increased after operation and was positively correlated with BPL length. Somatostatin remained stable among groups during the experiment.

CONCLUSION

Ghrelin and leptin of non-obese GK rats decreased postoperatively without a linear relationship with the BPL length, while adiponectin increased with positively correlation with the BPL length. In addition, somatostatin remained steady after small intestinal bypass. Further studies are expected to confirm the effect of the BPL length of small intestinal bypass on gastrointestinal hormones and adipokines.

Ileal interposition improves metabolic syndrome parameters in a rat model of metabolic syndrome induced by monosodium glutamate

AIMS

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities. Anatomically restructuring of the gastrointestinal system has recently been an important subject of research in the treatment of MetS and closely related diseases. The aim of this study is to ensure the remission of parameters that define MetS by ileal interposition (IT) and to examine the effect of IT on plasma total GLP-1 and pancreatic GLP-1R expression.

MAIN METHODS

To induce MetS, newborn male Wistar albino rats were given MSG (4 g/mg) on days 0, 2, 4, 6, 8, and 10. The control group was injected with saline. In the 5th month, IT or sham surgery was performed on the MetS rats. The lipid levels, abdominal obesity, insulin level, OGTT, Lee index, HOMA-IR, plasma GLP-1 and pancreas GLP-1R expression were evaluated 2 months after surgery.

KEY FINDINGS

The results showed that IT significantly improved hyperinsulinemia (p = 0.013) and lipid profile (TG p = 0.0001; TCHOL p = 0.018; HDL p = 0.001). Furthermore, it normalized the Lee index (p = 0.006) and insulin resistance. The IT did not affect the secretion of the GLP-1, but the expression levels of pancreas GLP-1R were increased (p = 0.006).

SIGNIFICANCE

IT surgery corrected the MetS parameters in this rat model. The healing effects of IT surgery could be caused by mechanisms in the target tissues of insulin. The decrease in pancreatic GLP-1R levels in the MetS groups might be a compensatory response to the harmful effects of hyperinsulinemia in these groups. These results show that IT can be useful in the treatment of MetS.

Ileal transposition: A non-restrictive bariatric surgical procedure that reduces body fat and increases ingestion-related energy expenditure

BACKGROUND

Ileal Transposition (IT) was developed as a model to study body weight reduction without the restrictive or malabsorptive aspects of other bariatric surgeries, but the exact mechanisms of the alterations in body weight after IT are not completely understood.

OBJECTIVE

To provide a detailed description of the surgical procedure of IT, and describe its effect on energy balance parameters.

METHODS

Adult male Lewis rats underwent either IT (IT+) or sham (IT-) surgery. Following surgery body weight and energy intake were monitored. After attaining weight stability (> 30 days), energy expenditure and its components were assessed using indirect calorimetry at a day of fasting, limited intake, and ad libitum intake. At the end of the study body composition analysis was performed.

RESULTS

IT+ resulted in transiently reduced energy intake, increased ingestion-related energy expenditure (IEE) and decreased body and adipose tissue weight when compared to IT-. At weight stability, neither energy budget (i.e., energy intake - energy expenditure), nor energy efficiency was different in IT+ rats compared to IT-.

CONCLUSION

Our data show that the primary cause of weight reduction following IT+ is a transient reduction in energy intake. If the increased IEE is related to a higher level of satiety, compensatory feeding to bridge body weight difference between IT+ and IT- rats is less likely to occur.

Ileal Transposition in Rats Reduces Energy Intake, Body Weight, and Body Fat Most Efficaciously When Ingesting a High-Protein Diet

Purpose

Ileal transposition (IT) allows exploration of hindgut effects of bariatric procedures in inducing weight loss and reducing adiposity. Here we investigated the role of dietary macronutrient content on IT effects in rats.

Methods

Male Lewis rats consuming one of three isocaloric liquid diets enriched with fat (HF), carbohydrates (HC), or protein (HP) underwent IT or sham surgery. Body weight, energy intake, energy efficiency, body composition, and (meal-induced) changes in plasma GIP, GLP-1, PYY, neurotensin, and insulin levels were measured.

Results

Following IT, HC intake remained highest leading to smallest weight loss among dietary groups. IT in HF rats caused high initial weight loss and profound hypophagia, but the rats caught up later, and finally had the highest body fat content among IT rats. HP diet most efficaciously supported IT-induced reduction in body weight and adiposity, but (as opposed to other diet groups) lean mass was also reduced. Energy efficiency decreased immediately after IT irrespective of diet, but normalized later. Energy intake alone explained variation in post-operative weight change by 80%. GLP-1, neurotensin, and PYY were upregulated by IT, particularly during (0–60 min) and following 17-h post-ingestive intake, with marginal diet effects. Thirty-day post-operative cumulative energy intake was negatively correlated to 17-h post-ingestive PYY levels, explaining 47% of its variation.

Conclusion

Reduction in energy intake underlies IT-induced weight loss, with highest efficacy of the HP diet. PYY, GLP-1, and neurotensin levels are upregulated by IT, of which PYY may be most specifically related to reduced intake and weight loss after IT.

Comparison of Glucose and Satiety Hormone Response to Oral Glucose vs. Two Mixed-Nutrient Meals in Rats

The obesity epidemic is driving interest in identifying strategies that enhance appetite control by altering the secretion of hormones that regulate satiety and food intake. An appropriate nutrient stimulus, such as a meal or oral nutrient solution, is needed to elicit the secretion of satiety hormones in order to evaluate the impact of dietary and other interventions. Our objective was to compare the effects of oral glucose vs. mixed nutrients on plasma concentrations of glucose and appetite-regulating hormones to determine the most appropriate oral nutrient challenge to trigger robust hormone secretion. A 120 min oral glucose tolerance test (OGTT) was compared with two meal tolerance tests (MTT) of differing formulation to evaluate glucose and satiety hormone responses. Following overnight feed deprivation, male Sprague-Dawley rats were given one of three oral gavages with equal carbohydrate content (2 g CHO/kg) in the form of: (1) Dextrose, (2) Ensure®, or (3) Mixed Meal. A fourth group was given saline as a control. Blood was collected via tail snip and analyzed for glucose, insulin, GLP-1, GIP, PYY, amylin, leptin, and ghrelin. Dextrose resulted in the highest blood glucose at T15 (P = 0.014), while the mixed meal was significantly higher than saline from T30-T120 (P < 0.05). Insulin was higher at T15 with dextrose compared to saline (P = 0.031) and Ensure® (P = 0.033). GLP-1 tAUC was significantly higher with dextrose compared to mixed meal (P = 0.04) while GIP tAUC was higher with dextrose and mixed meal compared to saline (P < 0.05). Changes in tAUC for insulin, amylin, leptin, ghrelin, and PYY did not reach significance. Based on these findings, dextrose appears to provide a robust acute glycemic and hormone response and is therefore likely an appropriate oral solution to reproducibly test the impact of various dietary, surgical, or pharmacological interventions on glucose and satiety hormone response.

Adipose depot-specific effects of ileal interposition surgery in UCD-T2D rats: unexpected implications for obesity and diabetes

Ileal interposition (IT) surgery delays the onset of diabetes in a rat model of type-2 diabetes (UCD-T2DM). Here, to gain a deeper understanding of the molecular events underlying the effects of IT surgery, we examined the changes in the proteome of four white adipose depots (retroperitoneal, mesenteric, inguinal, and epididymal) and plasma-free fatty acid profile in pre-diabetic rats 1.5 months following IT or sham surgery. The IT-mediated changes were exerted mainly in mesenteric fat and spanned from delayed adipocyte maturation to a neuroendocrine remodeling. Conversely, inguinal, retroperitoneal, and epididymal depots showed opposite trends consistent with increased adipocyte maturation and adipogenesis development prior to overt signs of diabetes, probably orchestrated by peroxisome proliferator-activated receptor gamma signaling and higher plasma n-6/n-3 free fatty acid ratios. The resulting scenario suggests a targeted use of surgical strategies that seek to delay or improve diabetes in order to manipulate adipose depot-specific responses to maximize the duration and beneficial effects of the surgery.

Whey Protein Components - Lactalbumin and Lactoferrin - Improve Energy Balance and Metabolism

Whey protein promotes weight loss and improves diabetic control, however, less is known of its bioactive components that produce such benefits. We compared the effects of normal protein (control) diet with high protein diets containing whey, or its fractions lactalbumin and lactoferrin, on energy balance and metabolism. Diet-induced obese rats were randomized to isocaloric diets: Control, Whey, Lactalbumin, Lactoferrin, or pair-fed to lactoferrin. Whey and lactalbumin produced transient hypophagia, whereas lactoferrin caused prolonged hypophagia; the hypophagia was likely due to decreased preference. Lactalbumin decreased weight and fat gain. Notably, lactoferrin produced sustained weight and fat loss, and attenuated the reduction in energy expenditure associated with calorie restriction. Lactalbumin and lactoferrin decreased plasma leptin and insulin, and lactalbumin increased peptide YY. Whey, lactalbumin and lactoferrin improved glucose clearance partly through differential upregulation of glucoregulatory transcripts in the liver and skeletal muscle. Interestingly, lactalbumin and lactoferrin decreased hepatic lipidosis partly through downregulation of lipogenic and/or upregulation of β-oxidation transcripts, and differentially modulated cecal bacterial populations. Our findings demonstrate that protein quantity and quality are important for improving energy balance. Dietary lactalbumin and lactoferrin improved energy balance and metabolism, and decreased adiposity, with the effects of lactoferrin being partly independent of caloric intake.

Roux-en-Y gastric bypass in rats progressively decreases the proportion of fat calories selected from a palatable cafeteria diet

Roux-en-Y gastric bypass surgery (RYGB) decreases caloric intake in both human patients and rodent models. In long-term intake tests, rats decrease their preference for fat and/or sugar after RYGB, and patients may have similar changes in food selection. Here we evaluated the impact of RYGB on intake during a "cafeteria"-style presentation of foods to assess if rats would lower the percentage of calories taken from fat and/or sugar after RYGB in a more complex dietary context. Male Sprague-Dawley rats that underwent either RYGB or sham surgery (Sham) were presurgically and postsurgically given 8-days free access to four semisolid foods representative of different fat and sugar levels along with standard chow and water. Compared with Sham rats, RYGB rats took proportionally fewer calories from fat and more calories from carbohydrates; the latter was not attributable to an increase in sugar intake. The proportion of calories taken from protein after RYGB also increased slightly. Importantly, these postsurgical macronutrient caloric intake changes in the RYGB rats were progressive, making it unlikely that the surgery had an immediate impact on the hedonic evaluation of the foods and strongly suggesting that learning is influencing the food choices. Indeed, despite these dietary shifts, RYGB, as well as Sham, rats continued to select the majority of their calories from the high-fat/high-sugar option. Apparently after RYGB, rats can progressively regulate their intake and selection of complex foods to achieve a seemingly healthier macronutrient dietary composition.

Reduced sweet and fatty fluid intake after Roux-en-Y gastric bypass in rats is dependent on experience without change in stimulus motivational potency

Here we assessed how intake reductions induced by Roux-en-Y gastric bypass surgery (RYGB) occur within and across access periods by examining drinking microstructure. After training, RYGB (n = 8-10) or sham-operated (SHAM, n = 12) rats were given 60-min access first to 0.3 M sucrose, then to 5% Intralipid, and finally to milk-chocolate Ensure Plus across 5 days each. Initially, total licks taken during the first meal of sucrose and Intralipid by RYGB and SHAM rats did not differ, but, across subsequent test periods, RYGB rats licked less than SHAM rats. First Ensure meal size also did not differ between RYGB and SHAM rats, but SHAM rats increased licking across test periods while the behavior of RYGB rats remained stable. The intake differences between the surgical groups, when they occurred, were most often due to smaller burst sizes in RYGB rats. Importantly, the surgical-group difference in sucrose and Intralipid intakes could not be explained by altered palatability of these solutions because, throughout testing, both groups had similar early meal licking behavior thought to represent the motivational potency of stimulus orosensory features. Although, overall, RYGB rats displayed lower early meal licking of Ensure relative to the SHAM rats, this appeared to be driven primarily by increases in the latter group across test periods; the RYGB group stayed relatively stable. Collectively, these results suggest that some level of postoral experience with these stimuli and/or their components is necessary before intake differences emerge between surgical groups, and, even when differences occur, often immediate taste-motivated ingestive behavior remains unaltered.

Gastric bypass in rats does not decrease appetitive behavior towards sweet or fatty fluids despite blunting preferential intake of sugar and fat

After Roux-en-Y gastric bypass surgery (RYGB), patients report consuming fewer fatty and dessert-like foods, and rats display blunted sugar and fat preferences. Here we used a progressive ratio task (PR) in our rat model to explicitly test whether RYGB decreases the willingness of rats to work for very small amounts of preferred sugar- and/or fat-containing fluids. In each of two studies, two groups of rats - one maintained on a high-fat diet (HFD) and standard chow (CHOW) and one given CHOW alone - were trained while water-deprived to work for water or either Ensure or 1.0 M sucrose on increasingly difficult operant schedules. When tested before surgery while nondeprived, HFD rats had lower PR breakpoints (number of operant responses in the last reinforced ratio) for sucrose, but not for Ensure, than CHOW rats. After surgery, at no time did rats given RYGB show lower breakpoints than SHAM rats for Ensure, sucrose, or when 5% Intralipid served postoperatively as the reinforcer. Nevertheless, RYGB rats showed blunted preferences for these caloric fluids versus water in 2-bottle preference tests. Importantly, although the Intralipid and sucrose preferences of RYGB rats decreased further over time, subsequent breakpoints for them were not significantly impacted. Collectively, these data suggest that the observed lower preferences for normally palatable fluids after RYGB in rats may reflect a learned adjustment to altered postingestive feedback rather than a dampening of the reinforcing taste characteristics of such stimuli as measured by the PR task in which postingestive stimulation is negligible.

Ileal Interposition in Rats with Experimental Type 2 Like Diabetes Improves Glycemic Control Independently of Glucose Absorption

Bariatric operations in obese patients with type 2 diabetes often improve diabetes before weight loss is observed. In patients mainly Roux-en-Y-gastric bypass with partial stomach resection is performed. Duodenojejunal bypass (DJB) and ileal interposition (IIP) are employed in animal experiments. Due to increased glucose exposition of L-cells located in distal ileum, all bariatric surgery procedures lead to higher secretion of antidiabetic glucagon like peptide-1 (GLP-1) after glucose gavage. After DJB also downregulation of Na(+)-d-glucose cotransporter SGLT1 was observed. This suggested a direct contribution of decreased glucose absorption to the antidiabetic effect of bariatric surgery. To investigate whether glucose absorption is also decreased after IIP, we induced diabetes with decreased glucose tolerance and insulin sensitivity in male rats and investigated effects of IIP on diabetes and SGLT1. After IIP, we observed weight-independent improvement of glucose tolerance, increased insulin sensitivity, and increased plasma GLP-1 after glucose gavage. The interposed ileum was increased in diameter and showed increased length of villi, hyperplasia of the epithelial layer, and increased number of L-cells. The amount of SGLT1-mediated glucose uptake in interposed ileum was increased 2-fold reaching the same level as in jejunum. Thus, improvement of glycemic control by bariatric surgery does not require decreased glucose absorption.

GLP-1 receptor signaling is not required for reduced body weight after RYGB in rodents

Exaggerated GLP-1 and PYY secretion is thought to be a major mechanism in the reduced food intake and body weight after Roux-en-Y gastric bypass surgery. Here, we use complementary pharmacological and genetic loss-of-function approaches to test the role of increased signaling by these gut hormones in high-fat diet-induced obese rodents. Chronic brain infusion of a supramaximal dose of the selective GLP-1 receptor antagonist exendin-9-39 into the lateral cerebral ventricle significantly increased food intake and body weight in both RYGB and sham-operated rats, suggesting that, while contributing to the physiological control of food intake and body weight, central GLP-1 receptor signaling tone is not the critical mechanism uniquely responsible for the body weight-lowering effects of RYGB. Central infusion of the selective Y2R-antagonist BIIE0246 had no effect in either group, suggesting that it is not critical for the effects of RYGB on body weight under the conditions tested. In a recently established mouse model of RYGB that closely mimics surgery and weight loss dynamics in humans, obese GLP-1R-deficient mice lost the same amount of body weight and fat mass and maintained similarly lower body weight compared with wild-type mice. Together, the results surprisingly provide no support for important individual roles of either gut hormone in the specific mechanisms by which RYGB rats settle at a lower body weight. It is likely that the beneficial effects of bariatric surgeries are expressed through complex mechanisms that require combination approaches for their identification.

Ileal transposition surgery produces ileal length-dependent changes in food intake, body weight, gut hormones and glucose metabolism in rats

BACKGROUND

Enhanced stimulation of the lower gut is hypothesized to play a key role in the weight loss and resolution of diabetes following bariatric surgeries. Ileal transposition (IT) permits study of the effects of direct lower gut stimulation on body weight, glucose homeostasis and other metabolic adaptations without the confounds of gastric restriction or foregut exclusion. However, the underlying mechanisms and the length of the ileum sufficient to produce metabolic benefits following IT surgery remain largely unknown.

OBJECTIVE

To determine the effects of transposing varying lengths of the ileum to upper jejunum on food intake, body weight, glucose tolerance and lower gut hormones, and the expression of key markers of glucose and lipid metabolism in skeletal muscle and adipose tissue in rats.

METHODS

Adult male Sprague-Dawley rats (n=9/group) were subjected to IT surgery with translocation of 5, 10 or 20 cm of the ileal segment to proximal jejunum or sham manipulations. Daily food intake and body weight were recorded, and an intraperitoneal glucose tolerance test was performed. Blood samples were assayed for hormones and tissue samples for mRNA (RT-qPCR) and/or protein abundance (immunoblotting) of regulatory metabolic markers.

RESULTS

We demonstrate that IT surgery exerts ileal length-dependent effects on multiple parameters including: (1) decreased food intake and weight gain, (2) improved glucose tolerance, (3) increased tissue expression and plasma concentrations of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), and decreased leptin concentrations and (4) upregulation of key markers of glucose metabolism (glucose transporter-4 (GLUT-4), insulin receptor substrate 1 (IRS-1), adenosine monophosphate-activated protein kinase (AMPK), hexokinase (HK) and phosphofructokinase (PFK)) together with a downregulation of lipogenic markers (fatty acid synthase (FAS)) in muscle and adipose tissue.

CONCLUSIONS

Together, our data demonstrate that the reduction in food intake and weight gain, increase in lower gut hormones, glycemic improvements and associated changes in tissue metabolic markers following IT surgery are dependent on the length of the transposed ileum.

Effects of Roux-en-Y gastric bypass and ileal transposition surgeries on glucose and lipid metabolism in skeletal muscle and liver

BACKGROUND

Roux-en Y gastric bypass (RYGB) and ileal transposition (IT) surgeries produce weight loss and improve diabetic control; however, the mechanisms of glycemic improvements are largely unknown. Because skeletal muscle and liver play a key role in glucose homeostasis, we compared the effects of RYGB and IT surgeries on key molecules of glucose and lipid metabolism in muscle and liver.

METHODS

Sprague-Dawley rats were subjected to RYGB, IT, or sham surgeries; sham-animals were ad-lib fed or pair-fed to RYGB rats (n = 7-9/group). At 8 weeks postoperatively, blood samples were collected for glucagon-like peptide-1 (GLP-1) and insulin analyses by ELISA. Leg muscle and liver tissues were analyzed for mRNA (RT-qPCR) and/or protein abundance (immuno blotting) of important molecules of glucose and lipid metabolism [glucose transporter-4 (GLUT-4), hexokinase, phosphofructokinase (PFK), adenosine monophosphate activated protein kinase-α (AMPKα), cytochrome C oxidase-IV (COX-IV), citrate synthase, carnitine palmitoyl transferase-1 (CPT-1), medium-chain acyl-CoA dehydrogenase (MCAD), peroxisome proliferator-activated receptor gamma co-activator 1 α (PGC-1 α), PGC-1-related coactivator (PRC), uncoupling protein-3 (UCP-3)].

RESULTS

Plasma GLP-1 concentrations were increased comparably with RYGB and IT. RYGB and IT increased muscle GLUT-4 protein content, muscle hexokinase mRNA, and liver PFK mRNA. IT increased muscle AMPKα and COX-IV protein content and liver citrate synthase activity. IT increased muscle CPT-1, MCAD and PRC mRNA, whereas RYGB increased UCP-3 mRNA in muscle and liver, and PGC-1 α mRNA in liver.

CONCLUSION

The data suggest that RYGB and IT surgeries lead to enhanced GLP-1 secretion and produce similar stimulatory effects on important molecules of glucose metabolism but differential effects on key molecules of lipid oxidation in muscle and liver.

Effects of sleeve gastrectomy and ileal transposition, alone and in combination, on food intake, body weight, gut hormones, and glucose metabolism in rats

Bariatric surgeries are hypothesized to produce weight loss and improve diabetes control by multiple mechanisms including gastric restriction and lower gut stimulation; the relative importance of these mechanisms remains poorly understood. We compared the effects of a typical foregut procedure, sleeve gastrectomy, (SG) with a primarily hindgut surgery, ileal transposition (IT), alone and together (SGIT), or sham manipulations, on food intake, body weight, gut hormones, glucose tolerance, and key markers of glucose homeostasis in peripheral tissues of adult male Sprague-Dawley rats (450-550 g, n = 7-9/group). SG, IT, and SGIT surgeries produced transient reduction in food intake and weight gain; the effects of SG and IT on intake and body weight were nonadditive. SG, IT, and SGIT surgeries resulted in increased tissue expression and plasma concentrations of the lower gut hormones glucagon-like peptide-1 and peptide YY and decreased plasma glucose-dependent insulinotropic peptide, insulin, and leptin concentrations. Despite transient effects on intake and weight gain, the SG, IT, and SGIT surgeries produced a significant improvement in glucose tolerance. In support of glycemic improvements, the protein abundance of key markers of glucose metabolism (e.g., GLUT4, PKA, IRS-1) in muscle and adipose tissue were increased, whereas the expression of key gluconeogenic enzyme in liver (G-6-Pase) were decreased following the surgeries. Therefore, our data suggest that enhanced lower gut stimulation following SG, IT, and SGIT surgeries leads to transient reduction in food intake and weight gain together with enhanced secretion of lower gut hormones and improved glucose clearance by peripheral tissues.

Type 2 diabetes control in a nonobese rat model using sleeve gastrectomy with duodenal-jejunal bypass (SGDJB)

BACKGROUND

As a new bariatric procedure, sleeve gastrectomy with duodenal-jejunal bypass (SGDJB) needs further assessment. We compared the diabetic control between SGDJB and sleeve gastrectomy (SG) in Goto-Kakizaki (GK) rats, a nonobese rat model of type 2 diabetes. Our aim is firstly to develop a nonobese diabetic rat model for SGDJB and secondly to investigate the feasibility and safety of SGDJB to induce diabetes remission.

METHODS

Fifty 11-week-old male GK rats were divided into five groups: sham-operated SG (SOSG), sham-operated SGDJB (SOSGDJB), control, SG, and SGDJB. Rats were observed for 16 weeks after surgery. The body weight, food intake, glycemic control outcomes, ghrelin, peptide YY (PYY), insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic peptide were measured.

RESULTS

The operated groups showed lower food intake since 4 weeks postoperation and significant weight loss since 6 weeks postoperation. SGDJB and SG surgeries induced a decreased fasting ghrelin level and increased levels of glucose-stimulated insulin, GLP-1, and PYY secretion at 2 and 16 weeks postoperation. Compared with the SG group, the SGDJB group showed higher glucose-stimulated GLP-1 levels. Both SGDJB and SG groups exhibited significant improvement in oral glucose tolerance and insulin tolerance compared with sham-operated and control groups, but there was no difference between the operated groups.

CONCLUSIONS

This nonobese diabetic rat model may be valuable in studying the effect of SGDJB on diabetic control. SGDJB shows similar improvement of glucose metabolism with SG. Our findings do not provide evidence for the foregut-mediated amelioration in glucose homeostasis.

Ileal interposition surgery-induced improvement of hyperglycemia and insulin resistance in Goto-Kakizaki rats by upregulation of TCF7L2 expression

The aim of this study was to investigate the effects of ileal interposition (IT) on glucose and insulin resistance (IR) in type 2 diabetic mellitus (T2DM), and the role of T-cell factor 7-like 2 (TCF7L2), formerly known as TCF4, in the downregulation of hyperglycemia following IT. Goto-Kakizaki (GK) rats subjected to IT surgery (GK-IT group), GK rats subjected to sham surgery (GK-Sham group) and Wistar (WS) rats subjected to sham surgery (WS-Sham group) were investigated in this study. Fasting plasma glucose, body weight, food intake per 1 kg body weight, insulin and a homeostasis model assessment of insulin resistance (HOMA-IR) were measured pre- and post-surgery. The rats were euthanized 28 days post-surgery and the pancreas of each rat was dissected. The expression levels of TCF7L2 mRNA and protein were analyzed by quantitative RT-PCR and western blotting, respectively. Our results revealed that IT improved both fasting plasma glucose levels and IR in GK rats by upregulating the expression of the TCF7L2 protein. IT provides a valuable therapeutic option for patients with T2DM. Upregulation of TCF7L2 protein expression may be a possible mechanism underlying the improvement of T2DM following IT.

Effects of bariatric surgery on glucose homeostasis and type 2 diabetes

Obesity is an important risk factor for type 2 diabetes mellitus (T2DM). Weight loss improves the major factors involved in the pathogenesis of T2DM, namely insulin action and beta cell function, and is considered a primary therapy for obese patients who have T2DM. Unfortunately, most patients with T2DM fail to achieve successful weight loss and adequate glycemic control from medical therapy. In contrast, bariatric surgery causes marked weight loss and complete remission of T2DM in most patients. Moreover, bariatric surgical procedures that divert nutrients away from the upper gastrointestinal tract are more successful in producing weight loss and remission of T2DM than those that simply restrict stomach capacity. Although upper gastrointestinal tract bypass procedures alter the metabolic response to meal ingestion, by increasing early postprandial plasma concentrations of glucagon-like peptide 1 and insulin, it is not clear whether these effects make an important contribution to long-term control of glycemia and T2DM once substantial surgery-induced weight loss has occurred. Nonetheless, the effects of surgery on body weight and metabolic function indicate that bariatric surgery should be part of the standard therapy for T2DM. More research is needed to advance our understanding of the physiological effects of different bariatric surgical procedures and possible weight loss-independent factors that improve metabolic function and contribute to the resolution of T2DM.

Central nervous system mechanisms linking the consumption of palatable high-fat diets to the defense of greater adiposity

The central nervous system (CNS) plays key role in the homeostatic regulation of body weight. Satiation and adiposity signals, providing acute and chronic information about available fuel, are produced in the periphery and act in the brain to influence energy intake and expenditure, resulting in the maintenance of stable adiposity. Diet-induced obesity (DIO) does not result from a failure of these central homeostatic circuits. Rather, the threshold for defended adiposity is increased in environments providing ubiquitous access to palatable, high-fat foods, making it difficult to achieve and maintain weight loss. Consequently, mechanisms by which nutritional environments interact with central homeostatic circuits to influence the threshold for defended adiposity represent critical targets for therapeutic intervention.

Effects of ileal interposition on glucose metabolism in obese rats with diabetes

BACKGROUND

Ileal interposition (IT), in which the distal ileum is transposed isoperistaltically into the proximal jejunum, is considered as a procedure for metabolic or antidiabetes surgery. Our aim was to study the effects of IT on glycemic control, fat metabolism, and hormonal changes in obese rats with spontaneous diabetes.

METHODS

Animals were divided into either an IT or a sham (SH) group. They underwent an oral glucose tolerance test (OGTT) before and 4 and 8 weeks after the operation. All animals were killed 10 weeks after operation for analyses of tissue weight (liver, pancreas, epididymal fat, brown fat), immunoblotting of uncoupling protein-1 (UCP1) protein in brown adipose tissue (BAT), and fasting plasma levels of glucose, insulin, glucagon-like peptide (GLP)-1, peptide YY (PYY), glucose-dependent insulinotropic polypeptide (GIP), and leptin.

RESULTS

Body weight increased postoperatively in both groups compared with preoperative weight, but it did not differ between the 2 groups. Eight weeks postoperatively, integrated blood glucose levels during the OGTT were decreased in IT compared with SH (P < .05). Fasting plasma levels of insulin, GLP-1, and GIP did not differ between the 2 groups, but PYY levels were higher in the IT animals (P < .01). The weight of epididymal and BATs, homeostasis model assessment insulin resistance, and fasting plasma leptin levels were decreased in the IT group (P < .05). Expression of UCP1 was higher in IT than SH animals (P < .05).

CONCLUSION

These results suggest that IT improves glucose and lipid metabolism by decreasing insulin resistance and epididymal fat, and increased expression of UCP1 in BAT might be among the mechanisms responsible.

Challenges and pitfalls of experimental bariatric procedures in rats

INTRODUCTION

The impact of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on obesity and obesity-related diseases is unquestionable. Up to now, the technical descriptions of these techniques in animals/rats have not been very comprehensive.

METHODS

For SG and RYGB, operating time, learning curve, and intraoperative mortality in relation to weight of the rat and type of anesthesia were recorded. Furthermore, a review of the literature on experimental approaches towards SG and RYGB in rats was carried out, merging in a detailed technical description for both procedures.

RESULTS

The data presented here revealed that the mean operating time for SG (69.4 ± 22.2 min (SD)) was shorter than for RYGB (123.0 ± 20.7 min). There is a learning curve for both procedures, resulting in a reduced operating time of up to 60% in SG and 35% in RYGB (p < 0.05; t-test). However, with increased weight, operating time increases to about 80 min for SG and about 120 min for RYGB. Obese rats have an increased intraoperative mortality rate of up to 50%. After gaseous anesthesia the mortality can be even higher. The literature search revealed 40 papers dealing with SG and RYGB in rats. 18 articles (45%) contained neither photographs nor illustrations; 14 articles (35%) did not mention the applied type of anesthesia. The mortality rate was described in 15 papers (37.5%).

CONCLUSION

Experimental obesity surgery in rats is challenging. Because of the high mortality in obese rats operated under gaseous anesthesia, exercises to establish the techniques should be performed in small rats using intraperitoneal anesthesia.

Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy: understanding weight loss and improvements in type 2 diabetes after bariatric surgery

Obesity increases the likelihood of diseases like type 2 diabetes (T2D), heart disease, and cancer, and is one of the most serious public health problems of this century. In contrast to ineffectual prevention strategies, lifestyle modifications, and pharmacological therapies, bariatric surgery is a very effective treatment for morbid obesity and also markedly improves associated comorbidities like T2D. However, weight loss and resolution of T2D after bariatric surgery is heterogeneous and specific to type of bariatric procedure performed. Conventional mechanisms like intestinal malabsorption and gastric restriction do not fully explain this, and potent changes in appetite and the enteroinsular axis, as a result of anatomical reorganization and altered hormonal, neuronal, and nutrient signaling, are the portended cause. Uniquely these signaling changes appear to override vigorous homeostatic defenses of stable body weight and compelling self-gratifying motivations to eat and to reverse defects in beta-cell function and insulin sensitivity. Here we review mechanisms of weight loss and T2D resolution after Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy bariatric surgery, two markedly different procedures with robust clinical outcomes.