Suppression of enteroendocrine cell glucagon-like peptide (GLP)-1 release by fat-induced small intestinal ketogenesis: a mechanism targeted by Roux-en-Y gastric bypass surgery but not by preoperative very-low-calorie diet.

OBJECTIVE: Food intake normally stimulates release of satiety and insulin-stimulating intestinal hormones, such as glucagon-like peptide (GLP)-1. This response is blunted in obese insulin resistant subjects, but is rapidly restored following Roux-en-Y gastric bypass (RYGB) surgery. We hypothesised this to be a result of the metabolic changes taking place in the small intestinal mucosa following the anatomical rearrangement after RYGB surgery, and aimed at identifying such mechanisms. DESIGN: Jejunal mucosa biopsies from patients undergoing RYGB surgery were retrieved before and after very-low calorie diet, at time of surgery and 6 months postoperatively. Samples were analysed by global protein expression analysis and Western blotting. Biological functionality of these findings was explored in mice and enteroendocrine cells (EECs) primary mouse jejunal cell cultures. RESULTS: The most prominent change found after RYGB was decreased jejunal expression of the rate-limiting ketogenic enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHMGCS), corroborated by decreased ketone body levels. In mice, prolonged high-fat feeding induced the expression of mHMGCS and functional ketogenesis in jejunum. The effect of ketone bodies on gut peptide secretion in EECs showed a ∼40% inhibition of GLP-1 release compared with baseline. CONCLUSION: Intestinal ketogenesis is induced by high-fat diet and inhibited by RYGB surgery. In cell culture, ketone bodies inhibited GLP-1 release from EECs. Thus, we suggest that this may be a mechanism by which RYGB can remove the inhibitory effect of ketone bodies on EECs, thereby restituting the responsiveness of EECs resulting in increased meal-stimulated levels of GLP-1 after surgery.MRC [MRC_MC_UU_12012/3 MRC_MC_UU_12012/5] Wellcome Trust [106262/Z/14/Z, 106263/Z/14/Z, 100574/Z/12/Z]

Medications Activating Tubular Fatty Acid Oxidation Enhance the Protective Effects of Roux-en-Y Gastric Bypass Surgery in a Rat Model of Early Diabetic Kidney Disease

Background: Roux-en-Y gastric bypass surgery (RYGB) improves biochemical and histological parameters of diabetic kidney disease (DKD). Targeted adjunct medical therapy may enhance renoprotection following RYGB. Methods: The effects of RYGB and RYGB plus fenofibrate, metformin, ramipril, and rosuvastatin (RYGB-FMRR) on metabolic control and histological and ultrastructural indices of glomerular and proximal tubular injury were compared in the Zucker Diabetic Sprague Dawley (ZDSD) rat model of DKD. Renal cortical transcriptomic (RNA-sequencing) and urinary metabolomic (1H-NMR spectroscopy) responses were profiled and integrated. Transcripts were assigned to kidney cell types through in silico deconvolution in kidney single-nucleus RNA-sequencing and microdissected tubular epithelial cell proteomics datasets. Medication-specific transcriptomic responses following RYGB-FMRR were explored using a network pharmacology approach. Omic correlates of improvements in structural and ultrastructural indices of renal injury were defined using a molecular morphometric approach. Results: RYGB-FMRR was superior to RYGB alone with respect to metabolic control, albuminuria, and histological and ultrastructural indices of glomerular injury. RYGB-FMRR reversed DKD-associated changes in mitochondrial morphology in the proximal tubule to a greater extent than RYGB. Attenuation of transcriptomic pathway level activation of pro-fibrotic responses was greater after RYGB-FMRR than RYGB. Fenofibrate was found to be the principal medication effector of gene expression changes following RYGB-FMRR, which led to the transcriptional induction of PPARα-regulated genes that are predominantly expressed in the proximal tubule and which regulate peroxisomal and mitochondrial fatty acid oxidation (FAO). After omics integration, expression of these FAO transcripts positively correlated with urinary levels of PPARα-regulated nicotinamide metabolites and negatively correlated with urinary tricarboxylic acid (TCA) cycle intermediates. Changes in FAO transcripts and nicotinamide and TCA cycle metabolites following RYGB-FMRR correlated strongly with improvements in glomerular and proximal tubular injury. Conclusions: Integrative multi-omic analyses point to PPARα-stimulated FAO in the proximal tubule as a dominant effector of treatment response to combined surgical and medical therapy in experimental DKD. Synergism between RYGB and pharmacological stimulation of FAO represents a promising combinatorial approach to the treatment of DKD in the setting of obesity.Health Research BoardHealth Service ExecutiveScience Foundation IrelandUniversity College DublinWellcome TrustSwedish Medical Research CouncilEuropean Foundation for the Study of Diabetes/Boehringer Ingelheim European Diabetes Research ProgrammeHealth and Social Care, Research and Development Division, Northern Irelan

The gut microbiota is a major regulator of androgen metabolism in intestinal contents

Androgens exert important effects both in androgen-responsive tissues and in the intestinal tract. To determine the impact of the gut microbiota (GM) on intestinal androgen metabolism, we measured unconjugated (free) and glucuronidated androgen levels in intestinal contents from the small intestine, with a low bacterial density, and from cecum and colon, with a high bacterial density. Using a specific, sensitive gas chromatography-tandem mass spectrometry method, we detected high levels of glucuronidated testosterone (T) and dihydrotestosterone (DHT) in small intestinal content of mice of both sexes, whereas in the distal intestine we observed remarkably high levels of free DHT, exceeding serum levels by >20-fold. Similarly, in young adult men high levels of unconjugated DHT, >70-fold higher than in serum, were detected in feces. In contrast to mice with a normal GM composition, germ-free mice had high levels of glucuronidated T and DHT, but very low free DHT levels, in the distal intestine. These findings demonstrate that the GM is involved in intestinal metabolism and deglucuronidation of DHT and T, resulting in extremely high free levels of the most potent androgen, DHT, in the colonic content of young and healthy mice and men

Is the Roux Limb a Determinant for Meal Size After Gastric Bypass Surgery?

The Roux-Y gastric bypass (RYGBP) is an effective weight-reducing procedure but the involved mechanisms of action are obscure. The Roux limb is the intestinal segment that following surgery is the primary recipient for food intake. The aims of the study were to explore the mechanosensory and biomechanical properties of the Roux limb and to make correlations with preferred meal size. Ten patients participated and were examined preoperatively, 6 weeks and 1 year after RYGBP. Each subject ingested unrestricted amounts of a standardized meal and the weight of the meal was recorded. On another study day, the Roux limb was subjected to gradual distension by the use of an intraluminal balloon. Luminal volume–pressure relationships and thresholds for induction of sensations were monitored. At 6 weeks and 1 year post surgery, the subjects had reduced their meal sizes by 62% and 41% (medians), respectively, compared to preoperative values. The thresholds for eliciting distension-induced sensations were strongly and negatively correlated to the preferred meal size. Intraluminal pressure during Roux limb distension, both at low and high balloon volumes, correlated negatively to the size of the meal that the patients had chosen to eat. The results suggest that the Roux limb is an important determinant for regulating food intake after Roux-Y bypass bariatric surgery

Angiotensin II receptor expression and relation to Helicobacter pylori-infection in the stomach of the Mongolian gerbil

<p>Abstract</p> <p>Background</p> <p>The role of the renin-angiotensin system in gastric physiology and disease has as yet been sparsely explored. The first aim of the study was to investigate the baseline presence and location of angiotensin II receptors (AT1R and AT2R) in the stomach of the Mongolian gerbil. A second aim was to elucidate whether the presence of <it>H. pylori </it>infection is associated with changes in the expression of these receptors.</p> <p>Methods</p> <p><it>H. pylori</it>-negative and <it>H. pylori-</it>infected (strain SS1 or TN2GF4) male Mongolian gerbils were investigated. The stomachs were examined at six or 12 months after inoculation by the use of immunohistochemistry, western blot and microscopic morphometry.</p> <p>Results</p> <p>AT1R and AT2R were located in a variety of cells in the gerbil gastric wall, including a subpopulation of endocrine cells in the antral mucosa and inflammatory cells infiltrating <it>H. pylori</it>-infected stomachs. Gerbils infected with the SS1 strain showed a significantly increased antral AT1R protein expression and an increased number of infiltrating polymorphonuclear leucocytes (PMNs) at 12 months. The AT1R protein expression correlated with the number of PMNs and the antral expression of myeloperoxidase.</p> <p>Conclusions</p> <p>Angiotensin II receptors are present in a variety of cells in the gastric wall of the Mongolian gerbil. The results indicate an influence dependent on the <it>H. pylori </it>strain on the gastric AT1R expression and a relationship between gastric AT1R expression and mucosal PMNs infiltration.</p

Direct stimulation of angiotensin II type 2 receptor reduces nitric oxide production in lipopolysaccharide treated mouse macrophages

The angiotensin II type 2 receptor (AT2) is upregulated after tissue damage and mediates protective functions in the renin-angiotensin-aldosterone system (RAAS). One of these is to inhibit inducible nitric oxide synthase (iNOS) in activated macrophages. In the present study, we assessed the effect of AT2 receptor ligands on nitric oxide production in murine macrophages as a potential assay to determine the functional activity of an AT2 receptor ligand. Mouse macrophage J744.2 and RAW264.7 were cultivated in lipopolysaccharide (LPS) to induce M1 differentiation and increase iNOS expression. Using Griess reagent and spectrophotometric analysis, the nitric oxide levels were determined, while employing Western blot and immunocytochemistry to determine basal protein expression. Using the first reported selective non-peptide AT2 receptor agonist, compound C21, we conclude that activation of AT2 receptor reduces nitric oxide production in M1 macrophages. Furthermore, the AT2 receptor selective ligand compound C38, a regioisomer of C21, reported as a selective AT2 receptor antagonist exhibits a similar effect on nitric oxide production. Thus, we propose C38 acts as a partial agonist in the macrophage system. Monitoring nitric oxide attenuation in M1 J744.1 and RAW264.7 macrophages provides a new method for characterizing functional activity of AT2 receptor ligands, foreseen to be valuable in future drug discovery programs

Roux limb motility in gastric bypass patients with chronic abdominal pain-is there an association to prescribed opioids?

Background/Aim A number of patients continue to suffer from chronic abdominal pain of unknown origin, which may also lead to a prolonged use of opioid analgesics. Symptoms of abdominal pain, nausea and vomiting in this patient group resemble the characteristics of the Roux stasis Syndrome. The aim was to elucidate relationships between chronic abdominal pain, Roux limb motor activity and opioid analgesics. Methods Roux limb high-resolution manometry and ratings of abdominal pain and quality of life were analysed in 15 gastric bypass patients reporting abdominal pain of unknown origin. Effect of acute opiate administration (morphine i.v.) on fasting Roux limb motor activity was assessed in asymptomatic and morphine-naive gastric bypass patients (n = 9) and compared with an untreated control group (n = 11). Results In the symptomatic patient group, we found disturbed Roux limb motor patterns in 10 out of 15 examinations, but no signs of Roux stasis syndrome. A high prevalence of prescribed opioid analgesics as well as a high number of reoperations in this group. The worst quality of life and the highest number of pain-killing medications were observed among the patients with distal pacemaker activity in Roux limb. In the morphine-naive and asymptomatic patients, morphine increased the muscular tone in the Roux limb during phase III-like motor activity. Summary and Conclusions A majority of the RYGBP patients with chronic abdominal pain had a disturbed Roux limb fasting motility, and there was a high prevalence of prescribed opioid analgesics. In opiate-naive RYGBP patients, acute morphine intravenously increased the muscular tone of the Roux limb

Support for involvement of the renin–angiotensin system in dysplastic Barrett’s esophagus

<p><b>Background and aim:</b> Patients with dysplasia in Barrett’s esophagus (BE) have a considerable risk of developing esophageal adenocarcinoma (EAC). The mucosal expression of the pro-inflammatory angiotensin II receptor type 1 (AT1R) is elevated in these patients, suggesting a role in carcinogenesis. The purpose of this study was to determine whether interference with the renin–angiotensin system (RAS) would influence downstream markers of carcinogenesis.</p> <p><b>Methods:</b> Endoscopic mucosal biopsies from BE patients with low-grade dysplasia (LGD) were sampled before and after a three-week period of RAS-interfering treatment. Thirty patients were randomly allocated to enalapril (ACE inhibitor, 5 mg od), candesartan (AT1R antagonist, 8 mg od), or no drug. The expression of 12 proteins known to be associated with RAS and carcinogenesis was assessed using western blot.</p> <p><b>Results:</b> We found altered expression of several proteins after enalapril treatment (decreased: NFκB, <i>p</i> = .043; NLRP3, <i>p</i> = .050; AMACR, <i>p</i> = .017; and caspase 3, <i>p</i> = .025; increased: p53, <i>p</i> = .050). Candesartan treatment was associated with increased iNOS expression (<i>p</i> = .033). No significant changes were seen in the no-drug group.</p> <p><b>Conclusion:</b> Interference with angiotensin II formation was associated with altered expression of inflammation- and carcinogenesis-related proteins. The present results speak in favor of involvement of angiotensin II in BE dysplasia, but the role of AT1R should be investigated further.</p