Objective: The mechanisms underlying type 2 diabetes resolution after Roux-en-Y gastric bypass (RYGB) are unclear. We suspected that glucose excretion may occur in the small bowel based on observations in humans. The aim of this study was to evaluate the mechanisms underlying serum glucose excretion in the small intestine and its contribution to glucose homeostasis after bariatric surgery. Design: 2-Deoxy-2-[ ¹⁸ F]-fluoro-D-glucose (FDG) was measured in RYGB-operated or sham-operated obese diabetic rats. Altered glucose metabolism was targeted and RNA sequencing was performed in areas of high or low FDG uptake in the ileum or common limb. Intestinal glucose metabolism and excretion were confirmed using ¹⁴ C-glucose and FDG. Increased glucose metabolism was evaluated in IEC-18 cells and mouse intestinal organoids. Obese or ob/ob mice were treated with amphiregulin (AREG) to correlate intestinal glycolysis changes with changes in serum glucose homeostasis. Results: The AREG/EGFR/mTOR/AKT/GLUT1 signal transduction pathway was activated in areas of increased glycolysis and intestinal glucose excretion in RYGB-operated rats. Intraluminal GLUT1 inhibitor administration offset improved glucose homeostasis in RYGB-operated rats. AREG-induced signal transduction pathway was confirmed using IEC-18 cells and mouse organoids, resulting in a greater capacity for glucose uptake via GLUT1 overexpression and sequestration in apical and basolateral membranes. Systemic and local AREG administration increased GLUT1 expression and small intestinal membrane translocation and prevented hyperglycaemic exacerbation. Conclusion: Bariatric surgery or AREG administration induces apical and basolateral membrane GLUT1 expression in the small intestinal enterocytes, resulting in increased serum glucose excretion in the gut lumen. Our findings suggest a novel, potentially targetable glucose homeostatic mechanism in the small intestine.

Medullary thyroid cancer originates from parafollicular C-cells in the thyroid. Despite successful thyroidectomy, localizing remnant cancer cells in patients with elevated calcitonin and carcinoembryonic antigen levels remains a challenge. Extranasal odorant receptors are expressed in cells from non-olfactory tissues, including C-cells. This study evaluates the odorant receptor signals from parafollicular C-cells, specifically, the presence of olfactory marker protein, and further assesses the ability of the protein in localizing and treating medullary thyroid cancer. We used immunohistochemistry, immunofluorescent staining, Western blot, RNA sequencing, and real time-PCR to analyze the expression of odorant receptors in mice thyroids, thyroid cancer cell lines, and patient specimens. We used in vivo assays to analyze acetate binding, calcitonin secretion, and cAMP pathway. We also used positron emission tomography (PET) to assess C¹¹-acetate uptake in medullary thyroid cancer patients. We investigated olfactory marker protein expression in C-cells in patients and found that it co-localizes with calcitonin in C-cells from both normal and cancer cell lines. Specifically, we found that OR51E2 and OR51E1 were expressed in thyroid cancer cell lines and human medullary thyroid cancer cells. Furthermore, we found that in the C-cells, the binding of acetate to OR51E2 activates its migration into the nucleus, subsequently resulting in calcitonin secretion via the cAMP pathway. Finally, we found that C¹¹-acetate, a positron emission tomography radiotracer analog for acetate, binds competitively to OR51E2. We confirmed C¹¹-acetate uptake in cancer cells and in human patients using PET. We demonstrated that acetate binds to OR51E2 in C-cells. Using C¹¹-acetate PET, we identified recurrence sites in post-operative medullary thyroid cancer patients. Therefore, OR51E2 may be a novel diagnostic and therapeutic target for medullary thyroid cancer.

Objective: Dopamine agonist (DA) treatment is effective for hyperprolactinemia and reduces tumor size in patients with prolactinoma; however, prolonged DA administration without prolactinoma causes fibrosis around tumor tissues. Therefore, we aimed to identify circulating microRNAs (miRNAs) as potential biomarkers to predict prolactinoma in patients with hyperprolactinemia and pituitary tumors. Design: Plasma samples were collected from 3 comparison groups: (1) patients clinically diagnosed with prolactinoma vs nonfunctioning pituitary adenoma (NFPA) based on response to cabergoline treatment, (2) patients with surgically confirmed prolactinoma vs NFPA, and (3) patients before and after cabergoline treatment. Candidate miRNAs from the initial nCounter assay were validated using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in a larger cohort of 247 patients with hyperprolactinemia and 37 controls. Methods: The nCounter assay was used for miRNA expression profiling, and the qRT-PCR validated the candidate miRNAs in the plasma and tumor tissue samples. Total RNA sequencing was conducted on pituitary tumor tissues to identify transcriptomic alterations. Furthermore, candidate miRNA target genes and their biological roles were analyzed using prolactinoma cell lines. Results: Three miRNA candidates (miR-20a-5p, miR-424-5p, and miR-514a-5p) were selected by analyzing 3 sets of expression comparisons between the 2 groups. Furthermore, the relative miR-20a-5p expression significantly increased in prolactinoma compared with that in normal pituitary glands, NFPA, growth hormone-secreting pituitary adenoma, and adrenocorticotropic hormone-secreting pituitary adenoma. In MMQ and GH4 cells, miR-20a-5p inhibition decreased prolactinoma cell proliferation and prolactin secretion. Conclusions: Circulating miR-20a-5p is a potential biomarker for prolactinoma, which could be associated with responsiveness to DAs.