[Somatostatin receptor expression in the ileal mucosa of patients with inflammatory bowel disease]

False-Positive 68Ga-DOTATATE PET/CT Findings in Hereditary Hypophosphatemia-Osteomalacia Mimicking Culprit Lesions of Tumor-Induced Osteomalacia

⁶⁸Ga-DOTATATE PET/CT is an important imaging modality for detection of culprit lesions of tumor-induced osteomalacia in clinically symptomatic patients with hypophosphatemia-osteomalacia. Somatostatin receptor expression may at times be observed in inflammatory or granulomatous conditions and in fractures or degenerative bone disease, leading to false-positive scan findings. We present a rare case of hereditary hypophosphatemia-osteomalacia that showed increased false-positive uptake (for possible tumor-induced osteomalacia lesions) in an inflammatory condition of the maxillary sinus and a fracture of the tibia on somatostatin receptor-based ⁶⁸Ga-DOTATATE PET/CT.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.

Increased nerve twigs in small intestinal mucosa with programmed cell death-ligand 1 and somatostatin receptor type 2A expression in recurrent Crohn disease: A case report

RATIONALE

Inflammatory bowel disease (IBD) patients manifest symptoms of disturbed gut function, such as neural sensory-motor changes. Programmed cell death-ligand 1 (PD-L1), normally present in neural tissue, exists in close apposition to the mucosal immune system and intestinal epithelium, and a bi-directional communication is known to occur at these interfaces. Somatostatin has been shown to suppress the inflammatory reaction, and has been used in several clinical trials to treat inflammatory disorders, such rheumatoid arthritis. Recently, somatostatin receptor type 2A, that regulates neurotransmission, proliferation, and apoptosis, has been recognized in IBD. Although prominent abnormalities in the morphology of the enteric nervous system have been observed in idiopathic IBD, they are more marked in Crohn disease.

PATIENT CONCERNS

A 55-year-old woman with recurrent Crohn disease, just surgically treated for ileal resection, have a stenotic complication.

INTERVENTIONS

At surgery 5 cm of preterminal ileum with stenosis and anastomotic ileocolic block was removed.

DIAGNOSES

The histopathology showed a recurrent Crohn in fistulo-stenotic phase; the stenosis was mainly sustained by mass-forming, ganglioneuromatous hyperplasia. Normally very rare, fine nerve twigs extend up into mucosa but we found a new-formed fibrillary network, extending into the inflammation area at the subepithelial luminal site of the mucosa, that was positive to PD-L1 and somatostatin receptor type 2A (SSTR2A) immunostaining but not visualized in routinary stained slides.

OUTCOMES

After surgery the patient was semestrally followed with clinical endoscopic evaluation that results uneventfully.

LESSONS

Our case shows that before surgery neuromatous abnormalities can be predicted by immunostained new-formed twigs in the mucosa.

Molecular mechanisms of somatostatin-mediated intestinal epithelial barrier function restoration by upregulating claudin-4 in mice with DSS-induced colitis

Intestinal barrier dysfunction plays a crucial role in the pathogenesis of ulcerative colitis (UC). Previous studies have shown somatostatin (SST) can protect intestinal barrier structure possibly through upregulating tight junction (TJ) protein expression, but the mechanisms of this upregulation remain undefined. This study aimed to investigate the molecular mechanisms of interaction of SST with its downstream regulatory elements in DSS-induced colitis mice. In DSS-induced colitis mice, exogenous SST supplement (octreotide) effectively ameliorated disease progression, restored colonic barrier structure and function, and stimulated claudin-4 expression. Similar effects were also observed for SST on Caco-2 cells intervened by TNF-α. SST receptor 5 (SSTR5) agonist L-817,818 upregulated the claudin-4 expression whereas the SSTR2 agonist seglitide could not reverse TNF-α-induced reduction of claudin-4. SST treatment significantly decreased the phosphorylation levels of ERK1/2 and p38 induced by TNF-α. PD-98059 (ERK1/2 pathway inhibitor) but not SB-202190 (p38 pathway inhibitor) could reverse TNF-α-induced suppression of claudin-4 expression. Both inhibitors could improve the TJ barrier function damaged by TNF-α. Our studies suggest that the protective effect of SST on intestinal barrier achieved by upregulating claudin-4 expression through activation of SSTR5 and suppression of the ERK1/2 pathways. These findings will benefit the development of novel treatment regimens for UC.