Performance of capsule endoscopy for the detection of small intestinal neuroendocrine tumors in familial carcinoid: a prospective single-site study.

BACKGROUND AND AIMS: Small-bowel neuroendocrine tumors (NETs) are slow growing, clinically silent tumors whose prognosis depends on disease stage. Members of kindreds with a familial form of small intestinal NETs (SI-NETs) represent a high-risk population for whom early detection improves disease outcome. Our aim was to determine the utility of small-bowel capsule endoscopy (SB-CE) for screening high-risk asymptomatic relatives from kindreds with familial carcinoid. METHODS: One hundred seventy-four asymptomatic subjects with a family history (≥2 family members) of SI-NETs were screened under Protocol NCT00646022, Natural History of Familial Carcinoid Tumor at the National Institutes of Health. All patients were imaged with SB-CE and 18fluoro-dihydroxphenylalanine (18F-DOPA) positron emission tomography (PET)/CT, and results were independently analyzed. Patients with a positive imaging study underwent surgical exploration. RESULTS: Thirty-five of 174 asymptomatic subjects screened for SI-NETs were positive on either SB-CE or 18F-DOPA PET. Thirty-two of 35 patients with a positive study were confirmed at surgery. SB-CE was positive in 28 of 32 patients with confirmed tumors for a per-patient sensitivity of 87.5%. SB-CE had a specificity of 97.3% and a negative predictive value of 96.5%. The average tumor number and size were 7.7 and 5.0 mm, respectively, and 81.2% of patients had multiple tumors. 18F-DOPA PET/CT had a similar sensitivity of 84% versus surgery. CONCLUSIONS: SB-CE is a sensitive and specific method comparable with 18F-DOPA PET/CT for screening high-risk patients with familial SI-NET. (Clinical trial registration number: NCT00646022.).

Tissue- and cell-specific properties of enterochromaffin cells affect the fate of tumorigenesis toward nonendocrine adenocarcinoma of the small intestine.

Small intestinal neuroendocrine tumors (SI-NETs) are serotonin-secreting well-differentiated neuroendocrine tumors of putative enterochromaffin (EC) cell origin. However, EC cell-derived tumorigenesis remains poorly understood. Here, we examined whether the gain of Myc and the loss of RB1 and Trp53 function in EC cells result in SI-NET using tryptophan hydroxylase 1 (TPH1) Cre-ERT2-driven RB1fl Trp53fl MycLSL (RPM) mice. TPH1-Cre-induced gain of Myc and loss of RB1 and Trp53 function resulted in endocrine or neuronal tumors in pancreas, lung, enteric neurons, and brain. Lineage tracing indicated that the cellular origin for these tumors was TPH1-expressing neuroendocrine, neuronal, or their precursor cells in these organs. However, despite that TPH1 is most highly expressed in EC cells of the small intestine, we observed no incidence of EC cell tumors. Instead, the tumor of epithelial cell origin in the intestine was exclusively nonendocrine adenocarcinoma, suggesting dedifferentiation of EC cells into intestinal stem cells (ISCs) as a cellular mechanism. Furthermore, ex vivo organoid studies indicated that loss of functions of Rb1 and Trp53 accelerated dedifferentiation of EC cells that were susceptible to apoptosis with expression of activated MycT58A, suggesting that the rare dedifferentiating cells escaping cell death went on to develop adenocarcinomas. Lineage tracing demonstrated that EC cells in the small intestine were short-lived compared with neuroendocrine or neuronal cells in other organs. In contrast, EC cell-derived ISCs were long-lasting and actively cycling and thus susceptible to transformation. These results suggest that tissue- and cell-specific properties of EC cells such as rapid cell turnover and homeostatic dedifferentiation, affect the fate and rate of tumorigenesis induced by genetic alterations and provide important insights into EC cell-derived tumorigenesis.NEW & NOTEWORTHY Small intestinal neuroendocrine tumors are of putative enterochromaffin (EC) cell origin and are the most common malignancy in the small intestine, followed by adenocarcinoma. However, the tumorigenesis of these tumor types remains poorly understood. The present lineage tracing studies showed that tissue- and cell-specific properties of EC cells such as rapid cell turnover and homeostatic dedifferentiation affect the fate and rate of tumorigenesis induced by genetic alterations toward a rare occurrence of adenocarcinoma.

GPR40 deficiency worsens metabolic syndrome-associated periodontitis in mice.

BACKGROUND AND OBJECTIVE: G protein-coupled receptor 40 (GPR40) is a receptor for medium- and long-chain free fatty acids (FFAs). GPR40 activation improves type 2 diabetes mellitus (T2DM), metabolic syndrome (MetS), and the complications of T2DM and MetS. Periodontitis, a common oral inflammatory disease initiated by periodontal pathogens, is another complication of T2DM and MetS. Since FFAs play a key role in the pathogenesis of MetS which exacerbates periodontal inflammation and GPR40 is a FFA receptor with anti-inflammatory properties, it is important to define the role of GPR40 in MetS-associated periodontitis. MATERIALS AND METHODS: We induced MetS and periodontitis by high-fat diet and periodontal injection of lipopolysaccharide (LPS), respectively, in wild-type and GPR40-deficient mice and determined alveolar bone loss and periodontal inflammation using micro-computed tomography, histology, and osteoclast staining. We also performed in vitro study to determine the role of GPR40 in the expression of proinflammatory genes. RESULTS: The primary outcome of the study is that GPR40 deficiency increased alveolar bone loss and enhanced osteoclastogenesis in control mice and the mice with both MetS and periodontitis. GPR40 deficiency also augmented periodontal inflammation in control mice and the mice with both MetS and periodontitis. Furthermore, GPR40 deficiency led to increased plasma lipids and insulin resistance in control mice but had no effect on the metabolic parameters in mice with MetS alone. For mice with both MetS and periodontitis, GPR40 deficiency increased insulin resistance. Finally, in vitro studies with macrophages showed that deficiency or inhibition of GPR40 upregulated proinflammatory genes while activation of GPR40 downregulated proinflammatory gene expression stimulated synergistically by LPS and palmitic acid. CONCLUSION: GPR40 deficiency worsens alveolar bone loss and periodontal inflammation in mice with both periodontitis and MetS, suggesting that GPR40 plays a favorable role in MetS-associated periodontitis. Furthermore, GPR40 deficiency or inhibition in macrophages further upregulated proinflammatory and pro-osteoclastogenic genes induced by LPS and palmitic acid, suggesting that GPR40 has anti-inflammatory and anti-osteoclastogenic properties.

GPR40 deficiency is associated with hepatic FAT/CD36 upregulation, steatosis, inflammation, and cell injury in C57BL/6 mice.

G-protein-coupled receptor 40 (GPR40) is highly expressed in pancreatic islets, and its activation increases glucose-stimulated insulin secretion from pancreas. Therefore, GPR40 is considered as a target for type 2 diabetes mellitus (T2DM). Since nonalcoholic fatty liver disease (NAFLD) is associated with T2DM and GPR40 is also expressed by hepatocytes and macrophages, it is important to understand the role of GPR40 in NAFLD. However, the role of GPR40 in NAFLD in animal models has not been well defined. In this study, we fed wild-type or GPR40 knockout C57BL/6 mice a high-fat diet (HFD) for 20 wk and then assessed the effect of GPR40 deficiency on HFD-induced NAFLD. Assays on metabolic parameters showed that an HFD increased body weight, glucose, insulin, insulin resistance, cholesterol, and alanine aminotransferase (ALT), and GPR40 deficiency did not mitigate the HFD-induced metabolic abnormalities. In contrast, we found that GPR40 deficiency was associated with increased body weight, insulin, insulin resistance, cholesterol, and ALT in control mice fed a low-fat diet (LFD). Surprisingly, histology and Oil Red O staining showed that GPR40 deficiency in LFD-fed mice was associated with steatosis. Immunohistochemical analysis showed that GPR40 deficiency also increased F4/80, a macrophage biomarker, in LFD-fed mice. Furthermore, results showed that GPR40 deficiency led to a robust upregulation of hepatic fatty acid translocase (FAT)/CD36 expression. Finally, our in vitro studies showed that GPR40 knockdown by siRNA or a GPR40 antagonist increased palmitic acid-induced FAT/CD36 mRNA in hepatocytes. Taken together, this study indicates that GPR40 plays an important role in homeostasis of hepatic metabolism and inflammation and inhibits nonalcoholic steatohepatitis by possible modulation of FAT/CD36 expression.

Validity of Secretin Stimulation Testing on Proton Pump Inhibitor Therapy for Diagnosis of Zollinger-Ellison Syndrome.

INTRODUCTION: Zollinger-Ellison syndrome (ZES) is characterized by gastrinoma-induced hypergastrinemia causing excessive gastric acid secretion. Secretin stimulation tests (SSTs) are required for diagnosis in the majority of patients. Two case reports suggest that proton pump inhibitors (PPIs) cause false SST results. Consequently, PPIs are discontinued to allow hyperchlorhydria to recur; however, uncontrolled acidity can cause life-threatening complications in those with underlying undiagnosed ZES. The aim of this study was to determine whether PPIs influence the validity of SSTs for the diagnosis of ZES. METHODS: A retrospective chart review was performed. Charts of patients who underwent SSTs were reviewed to determine whether they were performed on or off PPI and the test's accuracy by comparing the results with gold standard tests (diagnostic laboratory testing performed off PPI or surgical pathology consistent with gastrinoma). Sensitivity, specificity, and positive predictive value (PPV) of SST on PPI were calculated and results compared with SST off PPI using noninferiority analyses. RESULTS: Twenty-eight patients corresponding to 29 SSTs were performed on PPI, and 70 patients corresponding to 107 SSTs were performed off PPI. Most of them were female and white and had multiple endocrine neoplasia type 1. We found no false-positive or false-negative SSTs on PPI. Sensitivity, specificity, and PPV of SSTs on PPI were determined to be noninferior to SSTs off PPI (P ≤ 0.05 for all). DISCUSSION: In our cohort, SSTs on PPI compared with SSTs off PPI were noninferior for sensitivity, specificity, and PPV. These results suggest that PPI withdrawal before SSTs may not be necessary.

Role of an active reserve stem cell subset of enteroendocrine cells in intestinal stem cell dynamics and the genesis of small intestinal neuroendocrine tumors.

Small intestinal neuroendocrine tumors (SI-NET) are serotonin-secreting well-differentiated neuroendocrine tumors of putative enterochromaffin (EC) cell origin. Recent studies recognize a subset of EC cells that is label-retaining at the +4 position in the crypt and functions as a reserve intestinal stem cell. Importantly, this +4 reserve EC cell subset not only contributes to regeneration of the intestinal epithelium during injury and inflammation but also to basal crypt homeostasis at a constant rate. The latter function suggests that the +4 EC cell subset serves as an active reserve stem cell via a constant rate of dedifferentiation. Characterization of early tumor formation of SI-NET, observed as crypt-based EC cell clusters in many cases of familial SI-NETs, suggests that the +4 active reserve EC cell subset is the cell of origin. This newly discovered active reserve stem cell property of EC cells can account for unique biological mechanisms and processes associated with the genesis and development of SI-NETs. The recognition of this property of the +4 active reserve EC cell subset may provide novel opportunities to explore NETs in the gastrointestinal tract and other organs.

Asymmetric cell division-dominant neutral drift model for normal intestinal stem cell homeostasis.

The normal intestinal epithelium is continuously regenerated at a rapid rate from actively cycling Lgr5-expressing intestinal stem cells (ISCs) that reside at the crypt base. Recent mathematical modeling based on several lineage-tracing studies in mice shows that the symmetric cell division-dominant neutral drift model fits well with the observed in vivo growth of ISC clones and suggests that symmetric divisions are central to ISC homeostasis. However, other studies suggest a critical role for asymmetric cell division in the maintenance of ISC homeostasis in vivo. Here, we show that the stochastic branching and Moran process models with both a symmetric and asymmetric division mode not only simulate the stochastic growth of the ISC clone in silico but also closely fit the in vivo stem cell dynamics observed in lineage-tracing studies. In addition, the proposed model with highest probability for asymmetric division is more consistent with in vivo observations reported here and by others. Our in vivo studies of mitotic spindle orientations and lineage-traced progeny pairs indicate that asymmetric cell division is a dominant mode used by ISCs under normal homeostasis. Therefore, we propose the asymmetric cell division-dominant neutral drift model for normal ISC homeostasis. NEW & NOTEWORTHY The prevailing mathematical model suggests that intestinal stem cells (ISCs) divide symmetrically. The present study provides evidence that asymmetric cell division is the major contributor to ISC maintenance and thus proposes an asymmetric cell division-dominant neutral drift model. Consistent with this model, in vivo studies of mitotic spindle orientation and lineage-traced progeny pairs indicate that asymmetric cell division is the dominant mode used by ISCs under normal homeostasis.

A Pilot Study of Sirolimus in Subjects with Cowden Syndrome or Other Syndromes Characterized by Germline Mutations in PTEN.

LESSONS LEARNED: This is the first human interventional study in patients with Cowden syndrome that is driven by inactivation of germline PTEN gene.Single-agent sirolimus, a mTOR inhibitor, suppressed mTOR signaling in surrogate human tissues without significant toxicity. BACKGROUND: Cowden syndrome is characterized by inactivating germline PTEN mutations, which can lead to activation of the PI3K-Akt-mTOR pathway. METHODS: Adult subjects with germline PTEN mutation who met international diagnostic criteria for Cowden syndrome and who had Eastern Cooperative Oncology Group (ECOG) performance status 0-2 and adequate organ function were enrolled. Subjects were treated with a 56-day course of daily oral sirolimus. In addition to symptom assessment and physical examination, dermatologic, endoscopic, neurologic (cerebellar), and radiographic assessments were conducted. Inhibition of the mTOR pathway in benign skin and gastrointestinal (GI) lesion was assessed by immunohistochemistry. RESULTS: A total of 18 patients and 16 families were enrolled. PTEN mutations were located at exons 1-8. Regression of skin and GI lesions was observed by dermoscopy or endoscopy. Neurological evaluation showed improvement in cerebellar function score at 1 month. Immunohistochemistry (IHC) analysis in skin and GI benign lesions showed a decrease in the ratio of phosphorylated (p)S6 to total S6 in response to sirolimus. Ratios of pS6K to total S6 at days 14 and 56 were significantly lower than at baseline (p = .0026, p = .00391, respectively). A 56-day course of sirolimus was well tolerated. CONCLUSION: A 56-day course of sirolimus was well tolerated in subjects with Cowden syndrome and was associated with some evidence of improvement in symptoms, skin and GI lesions, cerebellar function, and decreased mTOR signaling.

Mature enteroendocrine cells contribute to basal and pathological stem cell dynamics in the small intestine.

Lgr5-expressing intestinal stem cells (ISCs) maintain continuous and rapid generation of the intestinal epithelium. Here, we present evidence that dedifferentiation of committed enteroendocrine cells (EECs) contributes to maintenance of the epithelium under both basal conditions and in response to injury. Lineage-tracing studies identified a subset of EECs that reside at +4 position for more than 2 wk, most of which were BrdU-label-retaining cells. Under basal conditions, cells derived from these EECs grow from the bottom of the crypt to generate intestinal epithelium according to neutral drift kinetics that is consistent with dedifferentiation of mature EECs to ISCs. The lineage tracing of EECs demonstrated reserve stem cell properties in response to radiation-induced injury with the generation of reparative EEC-derived epithelial patches. Finally, the enterochromaffin (EC) cell was the predominant EEC type participating in these stem cell dynamics. These results provide novel insights into the +4 reserve ISC hypothesis, stem cell dynamics of the intestinal epithelium, and in the development of EC-derived small intestinal tumors. NEW & NOTEWORTHY The current manuscript demonstrating that a subset of mature enteroendocrine cells (EECs), predominantly enterochromaffin cells, dedifferentiates to fully functional intestinal stem cells (ISCs) is novel, timely, and important. These cells dedifferentiate to ISCs not only in response to injury but also under basal homeostatic conditions. These novel findings provide a mechanism in which a specified cell can dedifferentiate and contribute to normal tissue plasticity as well as the development of EEC-derived intestinal tumors under pathologic conditions.

Polyclonal Crypt Genesis and Development of Familial Small Intestinal Neuroendocrine Tumors.

BACKGROUND & AIMS: Small intestinal neuroendocrine tumors (SI-NETs) are serotonin-secreting well-differentiated neuroendocrine tumors believed to originate from enterochromaffin (EC) cells. Intestinal stem cell (ISC) are believed to contribute to the formation of SI-NETs, although little is known about tumor formation or development. We investigated the relationship between EC cells, ISCs, and SI-NETs. METHODS: We analyzed jejuno-ileal tissue specimens from 14 patients with familial SI-NETs enrolled in the Natural History of Familial Carcinoid Tumor study at the National Institutes of Health from January 2009 to December 2014. Frozen and paraffin-embedded tumor tissues of different stages and isolated crypts were analyzed by in situ hybridization and immunohistochemistry. Tumor clonality was assessed by analyses of mitochondrial DNA. RESULTS: We identified multifocal aberrant crypt-containing endocrine cell clusters (ACECs) that contain crypt EC cell microtumors in patients with familial SI-NETs. RNA in situ hybridization revealed expression of the EC cell and reserve stem cell genes TPH1, BMI1, HOPX, and LGR5(low), in the ACECs and more advanced extraepithelial tumor nests. This expression pattern resembled that of reserve EC cells that express reserve ISC genes; most reside at the +4 position in normal crypts. The presence of multifocal ACECs from separate tumors and in the macroscopic tumor-free mucosa indicated widespread, independent, multifocal tumorigenesis. Analyses of mitochondrial DNA confirmed the independent origin of the ACECs. CONCLUSIONS: Familial SI-NETs originate from a subset of EC cells (reserve EC cells that express reserve ISC genes) via multifocal and polyclonal processes. Increasing our understanding of the role of these reserve EC cells in the genesis of multifocal SI-NETs could improve diagnostic and therapeutic strategies for this otherwise intractable disease.

Hematopoietic prostaglandin D synthase defines a proeosinophilic pathogenic effector human T(H)2 cell subpopulation with enhanced function.

BACKGROUND: IL-5(+) pathogenic effector T(H)2 (peT(H)2) cells are a T(H)2 cell subpopulation with enhanced proinflammatory function that has largely been characterized in murine models of allergic inflammation. OBJECTIVE: We sought to identify phenotype markers for human peT(H)2 cells and characterize their function in patients with allergic eosinophilic inflammatory diseases. METHODS: Patients with eosinophilic gastrointestinal disease (EGID), patients with atopic dermatitis (AD), and nonatopic healthy control (NA) subjects were enrolled. peT(H)2 and conventional T(H)2 (cT(H)2) cell phenotype, function, and cytokine production were analyzed by using flow cytometry. Confirmatory gene expression was measured by using quantitative RT-PCR. Prostaglandin D2 levels were measured with ELISA. Gut T(H)2 cells were obtained by means of esophagogastroduodenoscopy. RESULTS: peT(H)2 cells were identified as chemoattractant receptor-homologous molecule expressed on T(H)2 cells-positive (CRTH2(+)), hematopoietic prostaglandin D synthase-positive CD161(hi) CD4 T cells. peT(H)2 cells expressed significantly greater IL-5 and IL-13 than did hematopoietic prostaglandin D synthase-negative and CD161(-) cT(H)2 cells. peT(H)2 cells were highly correlated with blood eosinophilia (r = 0.78-0.98) and were present in 30- to 40-fold greater numbers in subjects with EGID and those with AD versus NA subjects. Relative to cT(H)2 cells, peT(H)2 cells preferentially expressed receptors for thymic stromal lymphopoietin, IL-25, and IL-33 and demonstrated greater responsiveness to these innate pro-TH2 cytokines. peT(H)2 but not cT(H)2 cells produced prostaglandin D2. In patients with EGID and those with AD, peT(H)2 cells expressed gut- and skin-homing receptors, respectively. There were significantly greater numbers of peT(H)2 cells in gut tissue from patients with EGID versus NA subjects. CONCLUSION: peT(H)2 cells are the primary functional proinflammatory human T(H)2 cell subpopulation underlying allergic eosinophilic inflammation. The unambiguous phenotypic identification of human peT(H)2 cells provides a powerful tool to track these cells in future pathogenesis studies and clinical trials.

A Hereditary Form of Small Intestinal Carcinoid Associated With a Germline Mutation in Inositol Polyphosphate Multikinase.

BACKGROUND & AIMS: Small intestinal carcinoids are rare and difficult to diagnose and patients often present with advanced incurable disease. Although the disease occurs sporadically, there have been reports of family clusters. Hereditary small intestinal carcinoid has not been recognized and genetic factors have not been identified. We performed a genetic analysis of families with small intestinal carcinoids to establish a hereditary basis and find genes that might cause this cancer. METHODS: We performed a prospective study of 33 families with at least 2 cases of small intestinal carcinoids. Affected members were characterized clinically and asymptomatic relatives were screened and underwent exploratory laparotomy for suspected tumors. Disease-associated mutations were sought using linkage analysis, whole-exome sequencing, and copy number analyses of germline and tumor DNA collected from members of a single large family. We assessed expression of mutant protein, protein activity, and regulation of apoptosis and senescence in lymphoblasts derived from the cases. RESULTS: Familial and sporadic carcinoids are clinically indistinguishable except for the multiple synchronous primary tumors observed in most familial cases. Nearly 34% of asymptomatic relatives older than age 50 were found to have occult tumors; the tumors were cleared surgically from 87% of these individuals (20 of 23). Linkage analysis and whole-exome sequencing identified a germline 4-bp deletion in the gene inositol polyphosphate multikinase (IPMK), which truncates the protein. This mutation was detected in all 11 individuals with small intestinal carcinoids and in 17 of 35 family members whose carcinoid status was unknown. Mutant IPMK had reduced kinase activity and nuclear localization, compared with the full-length protein. This reduced activation of p53 and increased cell survival. CONCLUSIONS: We found that small intestinal carcinoids can occur as an inherited autosomal-dominant disease. The familial form is characterized by multiple synchronous primary tumors, which might account for 22%-35% of cases previously considered sporadic. Relatives of patients with familial carcinoids should be screened to detect curable early stage disease. IPMK haploinsufficiency promotes carcinoid tumorigenesis.

Deletion of GPR40 fatty acid receptor gene in mice blocks mercaptoacetate-induced feeding.

Both increased and decreased fatty acid (FA) availability contribute to control of food intake. For example, it is well documented that intestinal FA reduces feeding by triggering enterondocrine secretion of satietogenic peptides, such as cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1). In contrast, mechanisms by which decreased FA availability increase feeding are not well understood. Over the past three decades substantial research related to FA availability and increased feeding has involved use of the orexigenic compound mercaptoacetate (MA). Because MA reportedly inhibits FA oxidation, it has been assumed that reduced FA oxidation accounts for the orexigenic action of MA. Recently, however, we demonstrated that MA antagonizes G protein-coupled receptor 40 (GPR40), a membrane receptor for long and medium chain FA. We also demonstrated that, by antagonizing GPR40, MA inhibits GLP-1 secretion and attenuates vagal afferent activation by FA. Because both vagal afferent activation and GLP-1 inhibit food intake, we postulated that inhibition of GPR40 by MA might underlie the orexigenic action of MA. We tested this hypothesis using male and female GPR40 knockout (KO) and wild-type (WT) mice. Using several testing protocols, we found that MA increased feeding in WT, but not GPR40 KO mice, and that GPR40 KO mice gained more weight than WT on a high-fat diet. Metabolic monitoring after MA or saline injection in the absence of food did not reveal significant differences in respiratory quotient or energy expenditure between treatment groups or genotypes. These results support the hypothesis that MA stimulates food intake by blocking FA effects on GPR40.

Calcium-sensing receptor is a physiologic multimodal chemosensor regulating gastric G-cell growth and gastrin secretion.

The calcium-sensing receptor (CaR) is the major sensor and regulator of extracellular Ca(2+), whose activity is allosterically regulated by amino acids and pH. Recently, CaR has been identified in the stomach and intestinal tract, where it has been proposed to function in a non-Ca(2+) homeostatic capacity. Luminal nutrients, such as Ca(2+) and amino acids, have been recognized for decades as potent stimulants for gastrin and acid secretion, although the molecular basis for their recognition remains unknown. The expression of CaR on gastrin-secreting G cells in the stomach and their shared activation by Ca(2+), amino acids, and elevated pH suggest that CaR may function as the elusive physiologic sensor regulating gastrin and acid secretion. The genetic and pharmacologic studies presented here comparing CaR-null mice and wild-type littermates support this hypothesis. Gavage of Ca(2+), peptone, phenylalanine, Hepes buffer (pH 7.4), and CaR-specific calcimimetic, cinacalcet, stimulated gastrin and acid secretion, whereas the calcilytic, NPS 2143, inhibited secretion only in the wild-type mouse. Consistent with known growth and developmental functions of CaR, G-cell number was progressively reduced between 30 and 90 d of age by more than 65% in CaR-null mice. These studies of nutrient-regulated G-cell gastrin secretion and growth provide definitive evidence that CaR functions as a physiologically relevant multimodal sensor. Medicinals targeting diseases of Ca(2+) homeostasis should be reviewed for effects outside traditional Ca(2+)-regulating tissues in view of the broader distribution and function of CaR.

Improving Small Lesion Segmentation in CT Scans using Intensity Distribution Supervision: Application to Small Bowel Carcinoid Tumor.

Finding small lesions is very challenging due to lack of noticeable features, severe class imbalance, as well as the size itself. One approach to improve small lesion segmentation is to reduce the region of interest and inspect it at a higher sensitivity rather than performing it for the entire region. It is usually implemented as sequential or joint segmentation of organ and lesion, which requires additional supervision on organ segmentation. Instead, we propose to utilize an intensity distribution of a target lesion at no additional labeling cost to effectively separate regions where the lesions are possibly located from the background. It is incorporated into network training as an auxiliary task. We applied the proposed method to segmentation of small bowel carcinoid tumors in CT scans. We observed improvements for all metrics (33.5% → 38.2%, 41.3% → 47.8%, 30.0% → 35.9% for the global, per case, and per tumor Dice scores, respectively.) compared to the baseline method, which proves the validity of our idea. Our method can be one option for explicitly incorporating intensity distribution information of a target in network training.

Fully-automated detection of small bowel carcinoid tumors in CT scans using deep learning.

BACKGROUND: Small bowel carcinoid tumor is a rare neoplasm and increasing in incidence. Patients with small bowel carcinoid tumors often experience long delays in diagnosis due to the vague symptoms, slow growth of tumors, and lack of clinician awareness. Computed tomography (CT) is the most common imaging study for diagnosis of small bowel carcinoid tumor. It is often used with positron emission tomography (PET) to capture anatomical and functional aspects of carcinoid tumors and thus to increase the sensitivity. PURPOSE: We compared three different kinds of methods for the automatic detection of small bowel carcinoid tumors on CT scans, which is the first to the best of our knowledge. METHODS: Thirty-three preoperative CT scans of 33 unique patients with surgically-proven carcinoid tumors within the small bowel were collected. Ground-truth segmentation of tumors was drawn on CT scans by referring to available 18 F-DOPA PET scans and the corresponding radiology report. These scans were split into the trainval set (n = 24) and the test positive set (n= 9). Additionally, 22 CT scans of 22 unique patients who had no evidence of the tumor were collected to comprise the test negative set. We compared three different kinds of detection methods, which are detection network, patch-based classification, and segmentation-based methods. We also investigated the usefulness of small bowel segmentation for reduction of false positives (FPs) for each method. Free-response receiver operating characteristic (FROC) curves and receiver operating characteristic (ROC) curves were used for lesion- and patient-level evaluations, respectively. Statistical analyses comparing the FROC and ROC curves were also performed. RESULTS: The detection network method performed the best among the compared methods. For lesion-level detection, the detection network method, without the small bowel segmentation-based filtering, achieved sensitivity values of (60.8%, 81.1%, 82.4%, 86.5%) at per-scan FP rates of (1, 2, 4 ,8), respectively. The use of the small bowel segmentation did not improve the performance ( p = 0.742 $p=0.742$ ). For patient-level detection, again the detection network method, but with the small bowel segmentation-based filtering, achieved the highest AUC of 0.86 with a sensitivity of 78% and specificity of 82% at the Youden point. CONCLUSIONS: The carcinoid tumors in this patient population were very small and potentially difficult to diagnose. The presented method showed reasonable sensitivity at small numbers of FPs for lesion-level detection. It also achieved a promising AUC for patient-level detection. The method may have clinical application in patients with this rare and difficult to detect disease.

Diagnostic value of whole-mount crypt analysis of ileal biopsy specimens for the patients with familial small intestinal neuroendocrine tumors.

Background and Aims: Early-stage small intestinal neuroendocrine tumors (SI-NETs) are generally asymptomatic and difficult to diagnose. As a result, patients often present with late-stage incurable disease. SI-NETs originate from enterochromaffin (EC) cells, which develop enteroendocrine cell (EEC) clusters consisting of a subset of EC cells at the crypt bottom at an early stage of tumor progression. In a familial form of SI-NET, EEC clusters arise in a multifocal and polyclonal fashion. We sought to determine whether early detection and analysis of cryptal EEC clusters could provide insight into the development of SI-NETs and allow successful pre-symptomatic screening for at risk family members of patients with SI-NETs. Methods: Isolated crypts from endoscopic ileal biopsies or surgically removed specimens from 43 patients with familial SI-NET and 20 controls were formalin-fixed, immunostained for chromogranin A, and examined by confocal three-dimensional analysis for the presence of EEC cluster formations. Results: Examination of multiple areas of macroscopic tumor-free mucosa in surgically resected specimens from patients with familial SI-NET revealed widely distributed, independent, multifocal EEC micro-tumor formations of varying sizes. Consistent with this finding, randomly sampled ileal biopsy specimens identified aberrant crypt containing endocrine cell clusters (ACECs) in patients. ACECs were found exclusively in patients (23/43, 53%) and not in controls (0/20). Furthermore, analysis of positions and numbers of EECs in crypts and ACECs indicated significant increases in EECs at the crypt bottom, predominantly at positions 0 and 1' (p < 0.0001 compared to controls), suggesting the progression of EEC accumulation below +4 position as the early process of ACEC formation. These findings also suggested that ACECs were precursors in the development of micro-tumors and subsequent macro-tumors. Conclusion: This study indicates that SI-NETs develop from deep crypt EC cells to become ACECs, micro-tumors, and ultimately gross tumors. This process occurs widely throughout the distal small intestine in patients with familial SI-NETs consistent with but not exclusively explained by germline disease. Finally, analysis of crypts from ileal biopsies could contribute in part to earlier diagnostic screening processes avoiding late-stage presentation of incurable disease.

Loss of PI3k activity of inositol polyphosphate multikinase impairs PDK1-mediated AKT activation, cell migration, and intestinal homeostasis.

Protein kinase B (AKT) is essential for cell survival, proliferation, and migration and has been associated with several diseases. Here, we demonstrate that inositol polyphosphate multikinase (IPMK's) lipid kinase property drives AKT activation via increasing membrane localization and activation of PDK1 (3-Phosphoinositide-dependent kinase 1), largely independent of class I PI3k (cPI3K). Deletion of IPMK impairs cell migration, which is partially associated with the abolition of PDK1-mediated ROCK1 disinhibition and subsequent myosin light chain (MLC) phosphorylation. IPMK is highly expressed in intestinal epithelial cells (IEC). Deleting IPMK in IEC reduced AKT phosphorylation and diminished the number of Paneth cells. Ablation of IPMK impaired IEC regeneration both basally and after chemotherapy-induced damage, suggesting a broad role for IPMK in activating AKT and intestinal tissue regeneration. In conclusion, the PI3k activity of IPMK is necessary for PDK1-mediated AKT activation and intestinal homeostasis.

Postprandial inhibition of gastric ghrelin secretion by long-chain fatty acid through GPR120 in isolated gastric ghrelin cells and mice.

Ghrelin is a gastric peptide hormone that controls appetite and energy homeostasis. Plasma ghrelin levels rise before a meal and fall quickly thereafter. Elucidation of the regulation of ghrelin secretion has been hampered by the difficulty of directly interrogating ghrelin cells diffusely scattered within the complex gastric mucosa. Therefore, we generated transgenic mice with ghrelin cell expression of green fluorescent protein (GFP) to enable characterization of ghrelin secretion in a pure population of isolated gastric ghrelin-expressing GFP (Ghr-GFP) cells. Using quantitative RT-PCR and immunofluorescence staining, we detected a high level of expression of the long-chain fatty acid (LCFA) receptor GPR120, while the other LCFA receptor, GPR40, was undetectable. In short-term-cultured pure Ghr-GFP cells, the LCFAs docosadienoic acid, linolenic acid, and palmitoleic acid significantly suppressed ghrelin secretion. The physiological mechanism of LCFA inhibition on ghrelin secretion was studied in mice. Serum ghrelin levels were transiently suppressed after gastric gavage of LCFA-rich lipid in mice with pylorus ligation, indicating that the ghrelin cell may directly sense increased gastric LCFA derived from ingested intraluminal lipids. Meal-induced increase in gastric mucosal LCFA was assessed by measuring the transcripts of markers for tissue uptake of LCFA, lipoprotein lipase (LPL), fatty acid translocase (CD36), glycosylphosphatidylinositol-anchored HDL-binding protein 1, and nuclear fatty acid receptor peroxisome proliferator-activated receptor-γ. Quantitative RT-PCR studies indicate significantly increased mRNA levels of lipoprotein lipase, glycosylphosphatidylinositol-anchored HDL-binding protein 1, and peroxisome proliferator-activated receptor-γ in postprandial gastric mucosa. These results suggest that meal-related increases in gastric mucosal LCFA interact with GPR120 on ghrelin cells to inhibit ghrelin secretion.

The G-protein-coupled receptor GPR40 directly mediates long-chain fatty acid-induced secretion of cholecystokinin.

BACKGROUND & AIMS: Long-chain fatty acid receptors G-protein-coupled receptor 40 (GPR40) (FFAR1) and GPR120 have been implicated in the chemosensation of dietary fats. I cells in the intestine secrete cholecystokinin (CCK), a peptide hormone that stimulates digestion of fat and protein, but these cells are rare and hard to identify. We sought to determine whether dietary fat-induced secretion of CCK is directly mediated by GPR40 expressed on I cells. METHODS: We used fluorescence-activated cell sorting to isolate a pure population of I cells from duodenal mucosa in transgenic mice that expressed green fluorescent protein under the control of the CCK promoter (CCK-enhanced green fluorescent protein [eGFP] bacterial artificial chromosome mice). CCK-eGFP cells were evaluated for GPR40 expression by quantitative reverse transcription polymerase chain reaction and immunostaining. GPR40(-/-) mice were bred with CCK-eGFP mice to evaluate functional relevance of GPR40 on long-chain fatty acid-stimulated increases in [Ca(2+)]i and CCK secretion in isolated CCK-eGFP cells. Plasma levels of CCK after olive oil gavage were compared between GPR40(+/+) and GPR40(-/-) mice. RESULTS: Cells that expressed eGFP also expressed GPR40; expression of GPR40 was 100-fold greater than that of cells that did not express eGFP. In vitro, linoleic, oleic, and linolenic acids increased [Ca(2+)]i; linolenic acid increased CCK secretion by 53% in isolated GPR40(+/+) cells that expressed eGFP. In contrast, in GPR40(-/-) that expressed eGFP, [Ca(2+)]i response to linoleic acid was reduced by 50% and there was no significant CCK secretion in response to linolenic acid. In mice, olive oil gavage significantly increased plasma levels of CCK compared with pregavage levels: 5.7-fold in GPR40(+/+) mice and 3.1-fold in GPR40(-/-) mice. CONCLUSIONS: Long-chain fatty acid receptor GPR40 induces secretion of CCK by I cells in response to dietary fat.