Pair-fed Sham Research Articles

Sleeve Gastrectomy Provides Cardioprotection from Oxidative Stress In Vitro Due to Reduction of Circulating Myeloperoxidase.

Bariatric surgery, including sleeve gastrectomy (SG), improves systolic and diastolic function, which is independent of weight loss in rodent models. The cause of weight loss-independent improvements in cardiac function are unknown but may originate from the gastrointestinal tract. In this study, we investigated whether a circulating blood factor is a mechanism for acute cardioprotection after SG by testing the utility of rodent SG plasma to reduce metabolic stress in vitro. For the initial experiment, obese male Zucker rats underwent SG, ad lib sham, or pair-fed sham surgeries (n = six SG, n = eight SH, n = eight PF). For all other studies, a second group of Zucker rats underwent SG or ad lib sham surgeries (n = eight SH, n = six SG). Six weeks following surgery, plasma was collected from each group, both in the fasting and post-prandial (pp) state. This plasma was then pooled per surgical group and nutrient state and tested in multiple in vitro cell culture and extra-cellular assays to determine the effect of SG on myotubular metabolic stress compared to the sham surgeries. Post-prandial SG plasma (ppSG), but not fasting SG, pp, or fasting sham plasma, reduced the metabolic stress of the H9c2 cells as measured by lactate dehydrogenase (LDH) release (p < 0.01). Unlike SG, weight reduction through pair-feeding did not prevent H9c2 metabolic stress. The PpSG plasma had the slowest rate of extracellular hydrogen peroxide consumption and peroxidatic activity compared to the pp sham, fasting SG, and fasting sham groups. Redox testing of plasma with aminiobenzoic acid hydrazide and edaravone suggested a pattern supporting myeloperoxidase (MPO), or other peroxidases, as the primary component responsible for reduced metabolic stress with ppSG plasma. The PpSG plasma contained 35% less circulating MPO protein as compared to the pp sham and fasting SG plasma. The plasma from an MPO global knockout rat also prevented metabolic stress of the H9c2 cells, compared to the significant increase in LDH release from the plasma of the WT controls (p < 0.01). The MPO global knockout plasma also had a rate of extracellular hydrogen peroxide consumption and peroxidatic activity comparable to the ppSG plasma. These studies suggest that one of the weight loss-independent mechanisms by which SG improves myocellular function could be a reduced pro-oxidative environment due to lower circulating levels of MPO. It appears that the gastrointestinal tract is of critical importance to these findings, as the MPO levels were only lowered after enteral, nutrient stimulation in the SG rats. If this surgical effect is confirmed in humans, SG may be a unique surgical treatment for multiple diseases with a pathogenesis of inflammation and oxidative damage, including obesity-associated heart failure with preserved ejection fraction.

A pilot study about the development and characterization of a Roux en Y gastric bypass model in obese Yucatan minipigs

Performing the Roux-en-Y gastric bypass (RYGBP) in obese Yucatan minipigs provides an opportunity to explore the mechanisms behind the effects of this surgery in controlled environmental and nutritional conditions. We hypothesized that RYGBP in these minipigs would induce changes at multiple levels, as in obese humans. We sought to characterize RYGBP in a diet-induced obese minipig model, compared with a pair-fed sham group. After inducing obesity with an ad libitum high-fat/high-sugar diet, we performed RYGBP (n = 7) or sham surgery (n = 6). Oral glucose tolerance tests (OGTT) were performed before and after surgery. Histological analyses were conducted to compare the alimentary limb at sacrifice with tissue sampled during RYGBP surgery. One death occurred in the RYGBP group at postoperative day (POD) 3. Before sacrifice, weight loss was the same across groups. GLP-1 secretion (OGTT) was significantly higher at 15, 30 and 60 min at POD 7, and at 30 and 60 min at POD 30 in the RYGBP group. Incremental insulin area under the curve increased significantly after RYGBP (p = 0.02). RYGBP induced extensive remodeling of the alimentary limb. Results show that RYGBP can be safely performed in obese minipigs, and changes mimic those observed in humans.

Gastric Bypass Increases Circulating Bile Acids and Activates Hepatic Farnesoid X Receptor (FXR) but Requires Intact Peroxisome Proliferator Activator Receptor Alpha (PPARα) Signaling to Significantly Reduce Liver Fat Content

BackgroundWe interrogate effects of gastric bypass (RYGB), compared with a low-calorie diet, on bile acid (BA), liver fat, and FXR, PPARα, and targets in rats with obesity and non-alcoholic fatty liver disease (NAFLD). MethodsMale Wistar rats received a high-fat diet (obese/NAFLD, n=24) or standard chow (lean, n=8) for 12 weeks. Obese/NAFLD rats had RYGB (n=11), sham operation pair-fed to RYGB (pair-fed sham, n=8), or sham operation (sham, n=5). Lean rats had sham operation (lean sham, n=8). Post-operatively, five RYGB rats received PPARα antagonist GW6417. Sacrifice occurred at 7 weeks. We measured weight changes, fasting total plasma BA, and liver % steatosis, triglycerides, and mRNA expression of the nuclear receptors FXR, PPARα, and their targets SHP and CPT-I. ResultsAt sacrifice, obese sham was heavier (p<0.01) than all other groups that had lost similar weight loss. Obese sham had lower BA levels and lower hepatic FXR, SHP, and CPT-I mRNA expression than lean sham (P<0.05, for all comparisons). RYGB had increased BA levels compared with obese and pair-fed sham (P<0.05, for both), while pair-fed sham had BA levels, similar to obese sham. Compared with pair-fed sham, RYGB animals had increased liver FXR and PPARα expression and signaling (P<0.05). Percentage of steatosis was lower in RYGB and lean sham, relative to obese and pair-fed sham (P<0.05, for all comparisons). PPARα inhibition after RYGB resulted in similar weight loss but higher liver triglyceride content (P=0.01) compared with RYGB alone. ConclusionsRYGB led to greater liver fat loss than low-calorie diet, an effect associated to increased fasting BA levels and increased expression of modulators of liver fat oxidation, FXR, and PPARα. However, intact PPARα signaling was necessary for resolution of NAFLD after RYGB.

Sleeve gastrectomy prevents hypertension associated with unique shifts in the gut microbiome.

Bariatric surgery results in resolution of hypertension in over 50% of patients. While weight loss is a critical component to hypertension resolution after bariatric surgery, there may also be weight loss-independent mechanisms. We hypothesized that sleeve gastrectomy (SG) initiates changes in the gut microbiome which reduce postoperative blood pressure. Male, obese Zucker rats underwent SG, pair-fed sham, or ad-lib-fed sham surgery. Blood pressure measurements were performed 1 week pre-operatively, and at 2 and 6weeks post-operatively. The stool microbiome composition was determined by 16S rDNA gene at 6weeks post-operatively. Regression Random Forest modeling was performed to determine an association of the microbial composition with blood pressure. SG and pair-fed rats weighed significantly less than ad-lib-fed sham rats throughout the post-surgical period. At 6weeks after surgery, SG rats had a significantly lower systolic blood pressure (149.2 ± 1.99mmHg) than pair-fed (164.7 ± 7.87, p < 0.001) or ad-lib-fed sham rats (167.1 ± 2.41mmHg, p < 0.001). There was a significant difference in multiple measures of beta diversity between SG rats and pair-fed and ad-lib-fed sham rats. 45.11% of the difference in blood pressure variability between samples was explained with the regression Random Forest model. SG in a rat model prevented hypertension progression independent of weight loss with changes in beta diversity and gut bacterial composition associated with the blood pressure outcome. These findings further support the metabolic efficacy of SG in treating hyperglycemia, cardiac dysfunction, and now hypertension, independent of obesity class.

1952-P: Vertical Sleeve Gastrectomy Induces Distinctive Gene Expression Changes in Glucose-Utilizing Peripheral Organs

Vertical sleeve gastrectomy (VSG) improves hyperglycemia and can achieve high rate of diabetes remission. To elucidate the molecular mechanism of VSG, we performed transcriptomic analysis of liver, fat, and muscle tissues in VSG mice compared to both sham and pair-fed sham controls. C57BL/6 mice fed high fat diet were randomly assigned to sham or VSG surgery. Sham-operated mice were fed ad libitum (Sham group) or pair-fed (Sham-PF group) matching their food intake to VSG-operated mice. Body weight, food intake, glucose and insulin tolerance were measured. Comparative transcriptomic analysis of liver, epididymal fat, and soleus muscle using RNA sequencing was performed. VSG decreased body weight and maintained the reduced body weight during the whole study period (up to 8 weeks after surgery). However, food intake was only reduced during the first 2 weeks after surgery in VSG than sham group. Glucose tolerance was improved by VSG after oral glucose load, but this improvement was attenuated after intraperitoneal glucose load. In addition, VSG increased insulin sensitivity than both Sham and Sham-PF group. Clustering and principal component analysis of the gene expression profiles of liver and adipose tissue revealed that Sham-PF was closer to Sham than VSG. The number of DEG was larger in comparison between VSG vs. Sham-PF than that between Sham-PF vs. Sham. The gene expression profile of muscle was not distinctive among the three groups. In pathway analysis, immune response was the common pathway enriched in all three tissues of VSG compared to Sham-PF. These results suggest that VSG induces organ specific changes of gene expression profile in both weight-loss dependent and independent ways. Interestingly, weight-loss independent changes were more robust than weight-loss dependent changes, which suggests that the improvement of hyperglycemia may be induced not only by weight-loss dependent mechanisms, but also by weight-loss independent mechanisms of VSG. Disclosure C. Ahn: None. S. Moon: None. Y. Cho: None. Funding Korean Ministry of Health and Welfare (HI14C1277)

Acetate Affects the Process of Lipid Metabolism in Rabbit Liver, Skeletal Muscle and Adipose Tissue.

Simple SummaryLots of short-chain fatty acids (SCFAs) are produced in the rabbit cecum after dietary fiber fermentation. In addition to supplying energy, SCFAs could regulate lipid metabolism, but the related mechanism is still unknown. In our experiment, we study the effect of acetate (major SCFAs, 70–80%) on rabbit lipid metabolism. The present study found that acetate alters the process of lipid metabolism in rabbit liver, skeletal muscle and adipose tissue, and inferred some signaling pathways related to the process. A mechanism of acetate-regulating lipid metabolism is useful to identify the function in fat metabolism of microbiological products from rabbit and rabbit processes for nutrition metabolism.Short-chain fatty acids (SCFAs) (a microbial fermentation production in the rabbit gut) have an important role in many physiological processes, which may be related to the reduced body fat of rabbits. In the present experiment, we study the function of acetate (a major SCFA in the rabbit gut) on fat metabolism. Ninety rabbits (40 days of age) were randomly divided into three groups: a sham control group (injection of saline for four days); a group experiencing subcutaneous injection of acetate for four days (2 g/kg BM per day, one injection each day, acetate); and a pair-fed sham treatment group. The results show that acetate-inhibited lipid accumulation by promoting lipolysis and fatty acid oxidation and inhibiting fatty acid synthesis. Activated G protein-coupled receptor 41/43, adenosine monophosphate activated protein kinase (AMPK) and extracellular-signal-regulated kinase (ERK) 1/2 signal pathways were likely to participate in the regulation in lipid accumulation of acetate. Acetate reduced hepatic triglyceride content by inhibiting fatty acid synthesis, enhancing fatty acid oxidation and lipid output. Inhibited peroxisome proliferator-activated receptor α (PPARα) and activated AMPK and ERK1/2 signal pathways were related to the process in liver. Acetate reduced intramuscular triglyceride level via increasing fatty acid uptake and fatty acid oxidation. PPARα was associated with the acetate-reduced intracellular fat content.

Sleeve Gastrectomy in Obese Zucker Rats Restores Cardiac Function and Geometry Toward a Lean Phenotype Independent of Weight Loss

Bariatric surgery, including sleeve gastrectomy (SG), significantly improves cardiac geometry and function in patients with heart failure. In this study, we used the obese Zucker rat as an animal model of heart failure with preserved ejection fraction (HFpEF) to test the hypothesis that a SG will improve cardiac function independent of weight loss. Obese, male Zucker rats underwent SG, pair-fed sham, or ad-lib sham surgery. Lean Zucker rats also underwent ad-lib sham surgery. Echocardiograms were performed preoperatively and at 6 weeks postoperatively. Obese SG and obese pair-fed sham rats had similar body weights postoperatively. Obese SG and lean, ad-lib, sham rats had a significant increase in postoperative stroke volume, and left ventricular internal diameter in diastole and systole. SG preserved systolic function and significantly improved isovolumetric relaxation time (13.9 ± 2.4 to 11.1 ± 2.1 ms, P = .02) independent of weight loss. SG has a beneficial impact on both systolic and diastolic cardiac function in obese Zucker rats toward a lean phenotype independent of weight loss and caloric restriction. These findings may represent a weight-loss independent mechanism generated from the gastrointestinal tract that has the potential to improve diastolic dysfunction independent of obesity status and translate to patients with HFpEF.

Sleeve gastrectomy in obese Wistar rats improves diastolic function and promotes cardiac recovery independent of weight loss

BackgroundHeart failure with preserved ejection fraction is the most common cause of heart failure and is characterized by impaired diastolic relaxation. Bariatric surgery significantly improves diastolic relaxation, but a mechanism beyond weight loss remains unknown. ObjectivesWe tested the hypothesis that a sleeve gastrectomy (SG) will improve diastolic dysfunction independent of weight loss due to postoperative alterations in the enterocardiac axis. SettingUniversity research laboratory. MethodsMale Wistar rats were fed a high-fat diet (HFD) or low-fat diet (LFD) for 10 weeks and then divided into SG-HFD, pair-fed sham HFD, ad-lib sham HFD, or ad-lib sham LFD groups (n = 9–14 per group). At least 2 months postoperatively, cardiac function, meal tolerance, glucose tolerance, and cardiac gene expression were compared between groups. ResultsOnly the SG cohort showed significant improvements in postoperative diastolic relaxation (isovolumetric relaxation time pre-SG: 14.7 ± 2.3 msec, post-SG: 11.2 ± 1.8 msec, P < .001). SG significantly increased active glucagon-like peptide-1 (P = .03). Compared to pair-fed sham HFD rats, SG-HFD rats had significantly altered mRNA cardiac gene expression, including sarco/endoplasmic reticulum Ca2+-ATPase 2 a (SERCA2 a) (P < .001). ConclusionsSG improves diastolic function independent of weight loss in a rat model of obesity with beneficial alterations in cardiac gene expression of multiple known targets related to cardiac failure, including SERCA2 a. These data support that a greater curve gastrectomy induces beneficial intracellular cardiac signaling for diastolic function mediated by the enterocardiac axis that is independent of weight loss. These findings could translate to offering metabolic surgery to patients with heart failure with preserved ejection fraction.

Duodenal nutrient exclusion improves metabolic syndrome and stimulates villus hyperplasia

ObjectiveSurgical interventions that prevent nutrient exposure to the duodenum are among the most successful treatments for obesity and diabetes. However, these interventions are highly invasive, irreversible and often carry significant...

Molecular and cellular mechanisms of cigarette smoke-induced myocardial injury: prevention by vitamin C.

BackgroundCardiovascular disease (CVD) remains one of the major killers in modern society. One strong risk factor of CVD is cigarette smoking that causes myocardial injury and leads to the genesis of pathological cardiovascular events. However, the exact toxic component(s) of cigarette smoke (CS) and its molecular and cellular mechanisms for causing myocardial injury leading to heart damage and its prevention are largely unknown.Methodology/Principal FindingsUsing a guinea pig model, here we show that chronic exposure to CS produces myocardial injury that is prevented by vitamin C. Male guinea pigs were fed either vitamin C-deficient (0.5 mg/day) or vitamin C-sufficient (15 mg/day) diet and subjected to CS exposure from 5 Kentucky Research cigarettes (3R4F)/day (6 days/week) in a smoke chamber up to 8 weeks. Pair-fed sham controls were subjected to air exposure instead of CS exposure under similar conditions. Myocardial injury was produced in CS-exposed marginal vitamin C-deficient guinea pigs as evidenced by release of cardiac Troponin-T and I in the serum, oxidative stress, inflammation, apoptosis, thrombosis and collagen deposition in the myocardium. Treatment of rat cardiomyocyte cells (H9c2) in vitro and guinea pigs in vivo with p-benzoquinone (p-BQ) in amounts derived from CS revealed that p-BQ was a major factor responsible for CS-induced myocardial damage. A moderately large dose of vitamin C (15 mg/day) prevented CS/p-BQ-induced myocardial injury. Population based studies indicated that plasma vitamin C levels of smokers without disease were significantly lower (p = 0,0000) than that of non-smokers. Vitamin C levels of CS-related cardiovascular patients were further lower (p = 0.0000) than that of smokers without disease.Conclusions/SignificanceThe results indicate that dietary supplementation of vitamin C may be a novel and simple therapy for the prevention of pathological cardiovascular events in habitual smokers.

Fundectomy-Evoked Osteopenia in Pigs Is Mediated by the Gastric-Hypothalamic-Pituitary Axis

The aim of the study was to determine the effects of gastric impairment in pigs on the axial and peripheral skeletal system properties and to test the hypothesis that fundectomy-evoked osteopenia is related to disturbed gastric-hypothalamic-pituitary axis function. Forty-day-old male piglets were subjected to experimental fundectomy (FX group, n = 6) to induce osteopenia, while sham operation was performed in the controls (SHO group, n = 6). At the age of 8 months, serum samples were collected, and the animals were sacrificed to obtain lumbar vertebrae (L1-L6) and right humerus for analysis. Using quantitative computed tomography (QCT) and dual-energy x-ray absorptiometry (DEXA) methods, bone mineral density and bone mineral content of the vertebrae and humerus were measured. The compression and three-point bending tests were applied to determine mechanical properties of lumbar vertebrae and humerus, respectively. Furthermore, geometric properties of humerus were assessed. Serum concentrations of ghrelin, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and selected macro- and microelements were also determined. Performed fundectomy decreased body weight in pigs by 66% compared with pair-fed sham operated pigs (P < 0.0001). Bone weight, bone mineral density, and bone mineral content of the lumbar vertebrae and humerus were significantly decreased in the fundectomized pigs (P < 0.01). Mechanical parameters of the lumbar spine and humerus were decreased after the fundectomy, as well. Serum concentrations of ghrelin, GH, and IGF-1 were lowered by 74.4%, 90.6%, and 54.6% in the fundectomized pigs, respectively (all P < 0.001). Moreover, the serum concentrations of calcium, magnesium, iron and copper in the fundectomized animals were significantly decreased by 15.5%, 45.3%, 26.7%, and 26.2%, respectively (P <or= 0.05). In conclusion, the results obtained showed that both the disturbed gastric-hypothalamic-pituitary axis function and impaired mineral metabolism are associated with development of postfundectomy osteopenia of axial and peripheral skeleton in pigs.

Impairment of cardiac function and energetics in experimental renal failure.

Cardiac function and energetics in experimental renal failure in the rat (5/6 nephrectomy) have been investigated by means of an isolated perfused working heart preparation and an isometric Langendorff preparation using 31P nuclear magnetic resonance (31P NMR). 4 wk after nephrectomy cardiac output of isolated hearts perfused with Krebs-Henseleit buffer was significantly lower (P < 0.0001) at all levels of preload and afterload in the renal failure groups than in the pair-fed sham operated control group. In control hearts, cardiac output increased with increases in perfusate calcium from 0.73 to 5.61 mmol/liter whereas uremic hearts failed in high calcium perfusate. Collection of 31P NMR spectra from hearts of renal failure and control animals during 30 min normoxic Langendorff perfusion showed that basal phosphocreatine was reduced by 32% to 4.7 mumol/g wet wt (P < 0.01) and the phosphocreatine to ATP ratio was reduced by 32% (P < 0.01) in uremic hearts. During low flow ischemia, there was a substantial decrease in phosphocreatine in the uremic hearts and an accompanying marked increase in release of inosine into the coronary effluent (14.9 vs 6.1 microM, P < 0.01). We conclude that cardiac function is impaired in experimental renal failure, in association with abnormal cardiac energetics and increased susceptibility to ischemic damage. Disordered myocardial calcium utilization may contribute to these derangements.

Effects of Reserpine Treatment on Dietary Adaptation of the Rat Exocrine Pancreas

Chronic reserpine treatment (500 micrograms/kg) of the rat results in generalized exocrinopathy, impaired pancreatic secretion, and decreased pancreatic amylase. These characteristics are similar to those in cystic fibrosis and are the basis for use of this experimental model for cystic fibrosis. Pancreatic enzymes adapt to diet, but it is not known whether chronic reserpine treatment affects this response. Due to the malnutrition induced by this treatment, another dose of reserpine was required that would alter pancreatic function but not induce malnutrition in order to evaluate dietary adaptation. Male rats (100-120 g) were injected subcutaneously daily for 7 days with 1) no injection (control); 2) 1.0 ml/kg vehicle or sham (pair fed-sham); or 3) reserpine: 500, 50, or 5 micrograms/kg. Food consumption was comparable among control and reserpine-treated (50 and 5 micrograms/kg) rats and significantly greater (200%) than pair fed-sham and 500 micrograms/kg reserpine-treated rats. Pancreatic amylase, however, was significantly lower in all reserpine-treated rats (500 micrograms/kg, 74%; 50 micrograms/kg, 56%; 5 micrograms/kg, 52%) than in control rats. To evaluate dietary adaptation, control and reserpine-treated (5 micrograms/kg) rats were fed high carbohydrate, high fat or high protein diets. Both groups adapted to these diets with the greatest amylase, lipase, and trypsin activities in high carbohydrate-, high fat-, and high protein-fed rats, respectively. Reserpine-treated rats fed high carbohydrate, however, had significantly lower (64%) amylase activity than high carbohydrate-fed control rats. Although reserpine-treated rats can adapt pancreatic enzymes to diet, the adaptation of amylase to carbohydrate is impaired.

Effects of Malnutrition and Chronic Reserpine Treatment on Pancreatic Exocrine Function1

The chronically reserpine-treated rat, an experimental model for cystic fibrosis, exhibits generalized exocrinopathy, impaired pancreatic secretion, and decreased pancreatic amylase. Although chronic reserpine treatment induces malnutrition by decreasing food consumption and growth, the effects of this malnutrition per se on the exocrine pancreas have not been considered. In this study, the effects of chronic reserpine treatment and malnutrition on the exocrine pancreas were determined using pair-fed controls. Male, Sprague-Dawley rats were treated daily subcutaneously for 5 to 7 days with: no injection (control), 1.0 ml/kg vehicle or sham (control-sham, pair fed-sham), or 0.5 mg/kg reserpine (chronically reserpine-treated). Both chronic reserpine-treatment and pair-feeding significantly decreased food consumption (40%), body weight (51 and 59%), total pancreatic amylase (49 and 56%) and specific amylase activity (62 and 61%), pancreatic protein (65 and 75%), and pancreatic weights (62 and 65%) compared to controls. These decreases, however, were comparable between the chronically reserpine-treated and pair fed-sham rats. In contrast, the secretory response to the biologically active cholecystokinin analog cholecystokinin octapeptide was significantly attenuated in isolated pancreatic acini prepared from reserpine-treated rats compared to that from either control or pair-fed sham rats. Malnutrition decreased pancreatic amylase activity and protein comparably to reserpine treatment, but only partially attenuated the secretory response to cholecystokinin octapeptide. Based on the results of this study, pair-fed controls should be used to distinguish between the effects of reserpine alone and the induced malnutrition on pancreatic exocrine function in studies of this experimental model of cystic fibrosis.