Serum glucose excretion after Roux-en-Y gastric bypass: a potential target for diabetes treatment.

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-[18F]-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 14C-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.

Excess endocrine growth hormone in acromegaly promotes the aggressiveness and metastasis of triple-negative breast cancer.

Pituitary adenoma-induced excess endocrine growth hormone (GH) secretion can lead to breast cancer development and metastasis. Herein, we used an acromegaly mouse model to investigate the role of excess endocrine GH on triple-negative breast cancer (TNBC) growth and metastasis. Additionally, we aimed to elucidate the molecular mechanism of transcription factor 20 (TCF20)/nuclear factor erythroid 2-related factor 2 (NRF2) signaling-mediated aggressiveness and metastasis of TNBC. Excess endocrine GH induced TCF20 activates the transcription of NRF2 and NRF2-target genes to facilitate TNBC metastasis. Inhibition of GH receptor (GHR) and TCF20 activity using the GHR antagonist or small-interfering RNA-induced gene knockdown resulted in reduced tumor volume and metastasis, suggesting that excess endocrine GH stimulates TCF20/NRF2 pathways in TNBC and promotes metastasis to the lung. GHR inhibitors present an effective therapeutic strategy to prevent TNBC cell growth and metastasis. Our findings revealed functional and mechanistic roles of the GH-TCF20-NRF2 signaling axis in TBNC progression.

Downregulation of miR-216a-5p and miR-652-3p is associated with growth and invasion by targeting JAK2 and PRRX1 in GH-producing pituitary tumours.

Expression of aberrant microRNA (miRNA) is associated with tumour formation, migration, and invasion. However, there is limited information about the epigenetics of pituitary tumorigenesis. This study investigated the role of miRNA expression during the tumorigenesis of growth hormone (GH)-secreting pituitary tumours. miRNA profiling and real-time PCR were used to analyse the mRNA expression profile in sequential pituitary tissues of a unique animal model with a GH-producing pituitary tumour. Selected miRNAs were further validated in GH-producing cell lines and human pituitary tumour samples. The expression of significantly altered miRNAs and their predicted targets, as detected by microarray, was evaluated by real-time PCR, Western blotting, and immunohistochemistry using samples from mouse models and human pituitary tumours. The effect of miRNAs on tumour proliferation and invasion was examined in GH3 cells using the MTS and Matrigel invasion assays. Among the 14 miRNAs whose expression was significantly changed, miR-216a-5p (fold change = -5.638, P -value = 0.014) and miR-652-3p (fold change = -3.482, P -value = 0.010) were constantly and significantly downregulated. Transfection with mimics of miR-216a-5p and miR-652-3p inhibited GH3 proliferation and invasion, whereas inhibitors promoted them. The direct target genes of miR-216a-5p and miR-652-3p were Jak2 and Prrx1, respectively, which were downregulated in GH3 cells transfected with mimics and in serial pituitary gland tissues, including hyperplasic tissues and tumours of acromegalic animal models and pituitary tumour tissues of acromegalic patients. Downregulated miR-216a-5p and miR-652-3p expression may contribute to tumour progression by targeting JAK2 and PRRX1 on GH-producing pituitary tumours.

Novel somatic variants involved in biochemical activity of pure growth hormone-secreting pituitary adenoma without GNAS variant.

We aimed to identify somatic genetic alterations in pure growth hormone (GH)-secreting pituitary adenomas without GNAS variants. Patients with GH-secreting pituitary adenoma who underwent transsphenoidal adenomectomy at Severance Hospital, Yonsei University College of Medicine were recruited. Somatic genetic alterations were profiled by whole-exome sequencing (WES) and targeted resequencing. WES was performed using DNA from nine GH-secreting pituitary tumors and corresponding blood samples. Absence of GNAS variant was confirmed by Sanger sequencing. For targeted resequencing of 140 fixed tissues, 48 WES-derived candidate genes and 7 GH-secreting pituitary adenoma-associated genes were included. Forty-eight genes with 59 somatic variants were identified by WES. In targeted resequencing, variants in 26 recurrent genes, including MAST4, PRIM2, TNN, STARD9, DNAH11, DOCK4, GPR98, BCHE, DARS, CUBN, NGDN, PLXND1, UNC5B, and COL22A1, were identified, but variants in previously reported genes were not detected. BCHE, DARS, NGDN, and UNC5B variants were associated with increased GH-secreting pituitary tumor biochemical activity, which was confirmed in vitro. Although recurrent point variants were rare, several somatic variants were identified in sporadic pure GH-secreting pituitary adenomas. Several somatic variants may affect pathways involved in the tumorigenesis and biochemical activities of GH-secreting pituitary adenomas.

Differential expression of miRNA199b-5p as a novel biomarker for sporadic and hereditary parathyroid tumors.

MicroRNAs (miRNAs) are dysregulated in many tumors; however, miRNA regulation in parathyroid tumors remains poorly understood. To identify differentially expressed miRNAs between sporadic and hereditary parathyroid tumors and to analyze their correlation with clinicopathological features, a microarray containing 887 miRNAs was performed; then, the differentially expressed miRNAs were validated by qRT-PCR using 25 sporadic and 12 hereditary parathyroid tumors and 24 normal parathyroid tissue samples. A receiver operating characteristic curve (ROC) analysis was applied to evaluate the utility of the miRNAs for distinguishing parathyroid tumor types. Compared to the miRNAs in the normal parathyroid tissues, 10 miRNAs were differentially expressed between the sporadic and hereditary parathyroid tumors. Seven of these miRNAs (let-7i, miR-365, miR-125a-3p, miR-125a-5p, miR-142-3p, miR-193b, and miR-199b-5p) were validated in the parathyroid tumor samples. Among these miRNAs, only miR-199b-5p was differentially expressed (P < 0.001); miR-199b-5p was significantly downregulated and negatively associated with PTH levels (γ = -0.579, P = 0.002) in the sporadic tumors but was upregulated in the hereditary tumors. This miRNA showed 67% sensitivity and 100% specificity for distinguishing sporadic and hereditary parathyroid tumors. These results reveal altered expression of a miRNA between sporadic and hereditary parathyroid tumors and the potential role of miR-199b-5p as a novel biomarker for distinguishing these two types of parathyroid tumors.

Somatotroph-Specific Aip-Deficient Mice Display Pretumorigenic Alterations in Cell-Cycle Signaling.

Patients with familial isolated pituitary adenoma are predisposed to pituitary adenomas, which in a subset of cases is due to germline inactivating mutations of the aryl hydrocarbon receptor-interacting protein (AIP) gene. Using Cre/lox and Flp/Frt technology, a conditional mouse model was generated to examine the loss of the mouse homolog, Aip, in pituitary somatotrophs. By 40 weeks of age, >80% of somatotroph specific Aip knockout mice develop growth hormone (GH) secreting adenomas. The formation of adenomas results in physiologic effects recapitulating the human syndrome of acromegaly, including increased body size, elevated serum GH and insulin-like growth factor 1 levels, and glucose intolerance. The pretumorigenic Aip-deficient somatotrophs secrete excess GH and exhibit pathologic hyperplasia associated with cytosolic compartmentalization of the cyclin-dependent kinase (CDK) inhibitor p27kip1 and perinuclear accentuation of CDK-4. Following tumor formation, the Aip-deficient somatotrophs display reduced expression of somatostatin receptor subtype 5 with impaired response to octreotide. The delayed tumor emergence, even with loss of both copies of Aip, implies that additional somatic events are required for adenoma formation. These findings suggest that pituitary hyperplasia precedes adenomatous transformation in somatotroph-specific Aip-deficient mice and reveal potential mechanisms involved in the pretumorigenic state that ultimately contribute to transformation.

Vasculoprotective Effects of 3-Hydroxybenzaldehyde against VSMCs Proliferation and ECs Inflammation.

3-hydroxybenzaldehyde (3-HBA) is a precursor compound for phenolic compounds like Protocatechuic aldehyde (PCA). From recent reports, PCA has shown vasculoprotective potency, but the effects of 3-HBA remain unclear. The aim of this study is to investigate the vasculoprotective effects of 3-HBA in endothelial cells, vascular smooth muscle cells and various animal models. We tested effects of 3-HBA in both vitro and vivo. 3-HBA showed that it prevents PDGF-induced vascular smooth muscle cells (VSMCs) migration and proliferation from MTS, BrdU assays and inhibition of AKT phosphorylation. It arrested S and G0/G1 phase of VSMC cell cycle in PI staining and it also showed inhibited expression levels of Rb1 and CD1. In human umbilical vein endothelial cells (HUVECs), 3-HBA inhibited inflammatory markers and signaling molecules (VCAM-1, ICAM-1, p-NF-κB and p-p38). For ex vivo, 3-HBA has shown dramatic effects in suppressing the sprouting from aortic ring of Spargue Dawley (SD) rats. In vivo data supported the vasculoprotective effects of 3-HBA as it inhibited angiogenesis from Matrigel Plug assay in C57BL6 mouse, prevented ADP-induced thrombus generation, increased blood circulation after formation of thrombus, and attenuated neointima formation induced by common carotid artery balloon injury of SD rats. 3-HBA, a novel therapeutic agent, has shown vasculoprotective potency in both in vitro and in vivo.