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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 diabetes and healthy participants. Trial registration:: NCT03044860. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]