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AIM: To determine whether intestinal expression of guanylate cyclase activator 2A (GUCA2A) and guanylate cyclase activator 2B (GUCA2B) genes is regulated in obese humans following Roux-en-Y gastric bypass (RYGB), and to evaluate the corresponding guanylin (GN) and uroguanylin (UGN) peptides for potentially contributing to the beneficial metabolic effects of RYGB.METHODS: Enteroendocrine cells were harvested peri- and post-RYGB, and GUCA2A/GUCA2B mRNA expression was compared. GN, UGN and their prohormones (proGN, proUGN) were administered subcutaneously in normal-weight mice to evaluate effects on food intake and glucose regulation. The effect of pro-UGN or UGN overexpression, using adeno-associated virus (AAV) vectors, was assessed in diet-induced obese (DIO) mice. Intracerebroventricular administration of GN and UGN was performed in rats for assessment of putative centrally mediated effects on food intake. GN and UGN, as well as their prohormones, were evaluated for effects on glucose-stimulated insulin secretion (GSIS) in rat pancreatic islets and perfused rat pancreas.RESULTS: GUCA2A and GUCA2B mRNA expression was significantly upregulated in enteroendocrine cells after RYGB. Peripheral administration of guanylins or prohormones did not influence food intake, oral glucose tolerance, and GSIS. Central administration of GN and UGN did not affect food intake in rats. Chronic AVV-mediated overexpression of UGN and proUGN had no effect on body weight or glucose homeostasis in DIO mice.CONCLUSION: GN and UGN, as well as their prohormones, do not seem to play a significant role in body weight regulation and glycemic control, suggesting that guanylin-family peptides do not show promise as targets for the treatment of obesity or diabetes.

Aims/hypothesis: Enteroendocrine K and L cells are pivotal in regulating appetite and glucose homeostasis. Knowledge of their distribution in humans is sparse and it is unknown whether alterations occur in type 2 diabetes. We aimed to evaluate the distribution of enteroendocrine K and L cells and relevant prohormone-processing enzymes (using immunohistochemical staining), and to evaluate the mRNA expression of the corresponding genes along the entire intestinal tract in individuals with type 2 diabetes and healthy participants. Methods: In this cross-sectional study, 12 individuals with type 2 diabetes and 12 age- and BMI-matched healthy individuals underwent upper and lower double-balloon enteroscopy with mucosal biopsy retrieval from approximately every 30 cm of the small intestine and from seven specific anatomical locations in the large intestine. Results: Significantly different densities for cells positive for chromogranin A (CgA), glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide, peptide YY, prohormone convertase (PC) 1/3 and PC2 were observed along the intestinal tract. The expression of CHGA did not vary along the intestinal tract, but the mRNA expression of GCG, GIP, PYY, PCSK1 and PCSK2 differed along the intestinal tract. Lower counts of CgA-positive and PC1/3-positive cells, respectively, were observed in the small intestine of individuals with type 2 diabetes compared with healthy participants. In individuals with type 2 diabetes compared with healthy participants, the expression of GCG and PYY was greater in the colon, while the expression of GIP and PCSK1 was greater in the small intestine and colon, and the expression of PCSK2 was greater in the small intestine. Conclusions/interpretation: Our findings provide a detailed description of the distribution of enteroendocrine K and L cells and the expression of their products in the human intestinal tract and demonstrate significant differences between individuals with type 2 diab

AIMS/HYPOTHESIS: We studied the impact of Roux-en-Y gastric bypass (RYGB) on the density and hormonal gene expression of small-intestinal enteroendocrine cells in obese patients with type 2 diabetes.METHODS: Twelve patients with diabetes and 11 age- and BMI-matched controls underwent RYGB followed by enteroscopy ~10 months later. Mucosal biopsies taken during surgery and enteroscopy were immunohistochemically stained for glucagon-like peptide-1 (GLP-1), peptide YY (PYY), cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide (GIP) and prohormone convertase 2 (PC2) and the expression of GCG (encoding preproglucagon), PYY, CCK, GIP, GHRL (encoding ghrelin), SCT (encoding secretin), NTS (encoding neurotensin) and NR1H4 (encoding farnesoid X receptor) was evaluated.RESULTS: The density of cells immunoreactive for GLP-1, CCK and GIP increased in patients after RYGB and the density of those immunoreactive for GLP-1, PYY, CCK and PC2 increased in controls. In both groups, GHRL, SCT and GIP mRNA was reduced after RYGB while PYY, CCK, NTS and NR1H4 gene expression was unaltered. GCG mRNA was upregulated in both groups.CONCLUSIONS/INTERPRETATION: Numerous alterations in the distribution of enteroendocrine cells and their expression of hormonal genes are seen after RYGB and include increased density of GLP-1-, PYY-, CCK-, GIP- and PC2-positive cells, reduced gene expression of GHRL, SCT and GIP and increased expression of GCG.

OBJECTIVE: The aim of this explorative study was to evaluate double-balloon enteroscopy (DBE) as a new tool for collecting mucosal biopsies from well-defined parts of the entire small and large bowel in patients with type 2 diabetes and in matched healthy subjects.MATERIAL AND METHODS: Twelve subjects with type 2 diabetes and 12 body mass index and age-matched healthy subjects underwent anterograde and retrograde DBE under nurse-administered propofol sedation on two separate days. We attempted to collect two mucosal biopsies from every 30 cm from pylorus to rectum.RESULTS: A mean of 21 biopsy sites were sampled in the diabetic group versus 25 in the healthy group. In 4 out of 24 patients (2 [17%] from each group) sampling from the entire gastrointestinal system was possible. Mean depth of maximal insertion (anterograde) was 478 ± 32 cm in patients with type 2 diabetes versus 465 ± 44 cm in healthy subjects (p = 0.81) and with retrograde access 230 ± 36 cm (type 2 diabetes) versus 207 ± 26 cm (healthy subjects).CONCLUSIONS: DBE is a minimally invasive way of collecting fresh biopsies from the entire gastrointestinal tract and, thus provides research and clinical communities with a new possibility to access hitherto unexplored human anatomy and physiology.

Objective Inhibition of dipeptidyl peptidase 4 (DPP-4), is thought to intensify the physiological effects of the incretin hormones. We investigated the effects of DPP-4 inhibition on plasma levels of glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), the incretin effect, glucose tolerance, gastrointestinal-mediated glucose disposal (GIGD) and gastric emptying in healthy subjects. Design Randomised, controlled, open-label. Methods Ten healthy subjects (6 women) (age: 40±5 years (mean±SEM); BMI: 24±3 kg/m2, fasting plasma glucose: 5.1±0.2 mmol/l; HbA1c: 34±1 mmol/mol [5.3±0.1%]) were randomised to two paired study days comprising a 4h 50 g-OGTT with paracetamol (A) and an isoglycaemic i.v. glucose infusion (IIGI) (B), with (A1+B1) and without (A2+B2) preceding administration of the DPP-4 inhibitor sitagliptin. Results Isoglycaemia was obtained in all subjects on the paired study days. Significant increases in fasting levels and OGTT-induced responses of active GLP-1 and GIP were seen after DPP-4 inhibition. No significant impact of DPP-4 inhibition on fasting plasma glucose (5.1±0.1 vs 4.9±0.1 mmol/l, p=0.3), glucose tolerance (AUC for plasma glucose: 151±35 vs 137±26 mmol/l×min, p=0.7) or peak plasma glucose during OGTT (8.5±0.4 vs 8.1±0.3 mmol/l, p=0.3) was observed. Neither incretin effect (40±9 (without DPP-4 inhibitor) vs 40±7% (with DPP-4 inhibitor), p=1.0), glucagon responses (1,395±165 vs 1,223±195 pmol/l×min, p=0.41), GIGD (52±4 vs 56±5%, p=0.40) nor gastric emptying (Tmax for plasma paracetamol: 86±9 vs 80±12 min, p=0.60) changed following DPP-4 inhibition. Conclusions These results suggest that acute increases in active incretin hormone levels do not affect glucose tolerance, GIGD, incretin effect, glucagon responses or gastric emptying in healthy subjects.