ABSTRACT
BACKGROUND: Enteroendocrine cells are essential for the regulation of glucose metabolism, but it is unknown whether they are associated with clinical features of metabolic syndrome (MetS) and fasting plasma metabolites. OBJECTIVE: We aimed to identify fasting plasma metabolites that associate with duodenal L cell, K cell and delta cell densities in subjects with MetS with ranging levels of insulin resistance. RESEARCH DESIGN AND METHODS: In this cross-sectional study, we evaluated L, K and delta cell density in duodenal biopsies from treatment-naïve males with MetS using machine-learning methodology. RESULTS: We identified specific clinical biomarkers and plasma metabolites associated with L cell and delta cell density. L cell density was associated with increased plasma metabolite levels including symmetrical dimethylarginine, 3-aminoisobutyric acid, kynurenine and glycine. In turn, these L cell-linked fasting plasma metabolites correlated with clinical features of MetS. CONCLUSIONS: Our results indicate a link between duodenal L cells, plasma metabolites and clinical characteristics of MetS. We conclude that duodenal L cells associate with plasma metabolites that have been implicated in human glucose metabolism homeostasis. Disentangling the causal relation between L cells and these metabolites might help to improve the (small intestinal-driven) pathophysiology behind insulin resistance in human obesity.
ABSTRACT
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.
Subject(s)
Diabetes Mellitus, Type 2/metabolism , Enteroendocrine Cells/metabolism , Adult , Aged , Chromogranin A/metabolism , Cross-Sectional Studies , Female , Gastric Inhibitory Polypeptide/metabolism , Gastrointestinal Tract/metabolism , Glucagon-Like Peptide 1/metabolism , Humans , Immunohistochemistry , Male , Middle Aged , Peptide YY/metabolism , Proprotein Convertase 1/metabolism , Proprotein Convertase 2/metabolism , Proprotein Convertases/metabolismABSTRACT
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.
