Objectives: Altered enteroendocrine cell (EEC) function in obesity and type 2 diabetes is not fully understood. Understanding the transcriptional program that controls EEC differentiation is important because some EEC types harbor significant therapeutic potential for type 2 diabetes. Methods: EEC isolation from jejunum of obese individuals with (ObD) or without (Ob) type 2 diabetes was obtained with a new method of cell sorting. EEC transcriptional profiles were established by RNA-sequencing in a first group of 14 Ob and 13 ObD individuals. EEC lineage and densities were studied in the jejunum of a second independent group of 37 Ob, 21 ObD and 22 non obese (NOb) individuals. Results: The RNA seq analysis revealed a distinctive transcriptomic signature and a decreased differentiation program in isolated EEC from ObD compared to Ob individuals. In the second independent group of ObD, Ob and NOb individuals a decreased GLP-1 cell lineage and GLP-1 maturation from proglucagon, were observed in ObD compared to Ob individuals. Furthermore, jejunal density of GLP-1-positive cells was significantly reduced in ObD compared to Ob individuals. Conclusions: These results highlight that the transcriptomic signature of EEC discriminate obese subjects according to their diabetic status. Furthermore, type 2 diabetes is associated with reduced GLP-1 cell differentiation and proglucagon maturation leading to low GLP-1-cell density in human obesity. These mechanisms could account for the decrease plasma GLP-1 observed in metabolic diseases.

With the continuous rise in the worldwide prevalence of obesity and type 2 diabetes, developing therapies regulating body weight and glycemia has become a matter of great concern. Among the current treatments, evidence now shows that the use of intestinal hormone analogs (e.g., GLP1 analogs and others) helps to control glycemia and reduces body weight. Indeed, intestinal endocrine cells produce a large variety of hormones regulating metabolism, including appetite, digestion, and glucose homeostasis. Herein, we discuss how the enteroendocrine system is affected by local environmental and metabolic signals. These signals include those arising from unbalanced diet, gut microbiota, and the host metabolic organs and their complex cross-talk with the intestinal barrier integrity.

Changes in dietary habits have occurred concomitantly with a rise of type 2 diabetes (T2D) and obesity. Intestine is the first organ facing nutrient ingestion and has to adapt its metabolism with these dietary changes. HNF-4γ, a transcription factor member of the nuclear receptor superfamily and mainly expressed in intestine, has been suggested to be involved in susceptibility to T2D. Our aim was to investigate the role of HNF-4γ in metabolic disorders and related mechanisms. Hnf4g^−/− mice were fed high-fat/high-fructose (HF-HF) diet for 6 weeks to induce obesity and T2D. Glucose homeostasis, energy homeostasis in metabolic cages, body composition and stool energy composition, as well as gene expression analysis in the jejunum were analyzed. Despite an absence of decrease in calorie intake, of increase in locomotor activity or energy expenditure, Hnf4g^−/− mice fed with HF-HF are protected against weight gain after 6 weeks of HF-HF diet. We showed that Hnf4g^−/− mice fed HF-HF display an increase in fecal calorie loss, mainly due to intestinal lipid malabsorption. Gene expression of lipid transporters, Fatp4 and Scarb1 and of triglyceride-rich lipoprotein secretion proteins, Mttp and ApoB are decreased in gut epithelium of Hnf4g^−/− mice fed HF-HF, showing the HNF-4γ role in intestine lipid absorption. Furthermore, plasma GLP-1 and jejunal GLP-1 content are increased in Hnf4g^−/− mice fed HF-HF, which could contribute to the glucose intolerance protection. The loss of HNF-4γ leads to a protection against a diet-induced weight gain and to a deregulated glucose homeostasis, associated with lipid malabsorption.

Carbohydrates and sweeteners are detected by the sweet taste receptor in enteroendocrine cells (EECs). This receptor is coupled to the gustducin G-protein, which α-subunit is encoded by GNAT3 gene. In intestine, the activation of sweet taste receptor triggers a signaling pathway leading to GLP-1 secretion, an incretin hormone. In metabolic diseases, GLP-1 concentration and incretin effect are reduced while partly restored after Roux-en-Y gastric bypass (RYGB). We wondered if the decreased GLP-1 secretion in metabolic diseases is caused by an intestinal defect in sweet taste transduction pathway. In our RNA-sequencing of EECs, GNAT3 expression is decreased in patients with obesity and type 2 diabetes compared with normoglycemic obese patients. This prompted us to explore sweet taste signaling pathway in mice with metabolic deteriorations. During obesity onset in mice, Gnat3 expression was downregulated in EECs. After metabolic improvement with enterogastro anastomosis surgery in mice (a surrogate of the RYGB in humans), the expression of Gnat3 increased in the new alimentary tract and glucose-induced GLP-1 secretion was improved. To evaluate if high-fat diet-induced dysbiotic intestinal microbiota could explain the changes in the expression of sweet taste α-subunit G-protein, we performed a fecal microbiota transfer in mice. However, we could not conclude if dysbiotic microbiota impacted or not intestinal Gnat3 expression. Our data highlight that metabolic disorders were associated with altered gene expression of sweet taste signaling in intestine. This could contribute to impaired GLP-1 secretion that is partly rescued after metabolic improvement. NEW & NOTEWORTHY Our data highlighted 1) the sweet taste transduction pathway in EECs plays pivotal role for glucose homeostasis at least at gene expression level; 2) metabolic disorders lead to altered gene expression of sweet taste signaling pathway in intestine contributing to impaired GLP-1 secretion; and 3) after surgical intestinal modifications, increased expression of GNAT3, encoding α-gustducin contributed to metabolic improvement.

Objectives Obesity and type 2 diabetes (T2D) are associated with altered secretion of enteroendocrine hormones, including the glucagon-like peptide-1 (GLP-1). The mechanisms underlying this dysregulation remain poorly understood, partly due to the rarity of enteroendocrine cells (EECs) and technical difficulties in humans. Our aim was to generate an in vitro human jejunal enteroids (HJEs) derived from individuals with obesity and T2D as a simplified intestinal epithelium in a controlled environment, in order to explore GLP-1 secretion in metabolic diseases. Subjects and methods HJEs were obtained from jejunum fragments sampled during gastric bypass surgery in individuals with severe obesity and normoglycemia (Ob, n = 12), prediabetes (ObPreD, n = 12), or T2D (ObD, n = 10). HJEs were characterized through gene and protein expression analyses and immunofluorescence. To promote the EEC lineage, HJEs were treated with the Notch pathway inhibitor DAPT. Active GLP-1 secretion was assessed by ELISA. Results HJEs were successfully generated whatever the metabolic group Ob, ObPreD, ObD, exhibiting epithelial cell lineages and expressing critical genes involved in GLP-1 cell lineage, biosynthesis, and secretion. HJEs secreted active GLP-1 in response to both low and high glucose concentrations, regardless of subject metabolic status. However, HJEs from individuals with severe obesity and T2D exhibited a reduced capacity to release GLP-1 in response to high glucose concentrations compared to those from individuals with severe obesity or with obesity and prediabetes. Conclusions HJEs represent a robust human-derived model to investigate EEC function and GLP-1 secretion in metabolic diseases. While HJEs retain functional GLP-1-producing cells, their secretory capacity is impaired in the presence of T2D, confirming functional endocrine alterations. These findings support the use of HJEs in preclinical studies targeting enteroendocrine dysfunction.