Somatostatin Peptides Prevent Increased Human Colonic Epithelial Permeability Induced by Hypoxia.

Mesenteric ischemia increases gut permeability and bacterial translocation. In human colon, chemical hypoxia induced by 2,4-dinitrophenol (DNP) activates basolateral intermediate conductance K+ (IK) channels (designated KCa3.1 or KCNN4) and increases paracellular shunt conductance/permeability (GS), but whether this leads to increased macromolecule permeability is unclear. Somatostatin (SOM) inhibits IK channels and prevents hypoxia-induced increases in GS. Thus, we examined whether octreotide (OCT), a synthetic SOM analogue, prevents hypoxia-induced increases GS in human colon and hypoxia-induced increases in total epithelial conductance (GT) and permeability to FITC-dextran 4000 (FITC) in rat colon. The effects of serosal SOM and OCT on increases in GS induced by 100 µM DNP were compared in isolated human colon. The effects of OCT on DNP-induced increases in GT and transepithelial FITC movement were evaluated in isolated rat distal colon. GS in DNP-treated human colon was 52% greater than in controls (P = 0.003). GS was similar when 2 µM SOM was added after or before DNP treatment, in both cases being less (P <0.05) than with DNP alone. 0.2 µM OCT was equally effective preventing hypoxia-induced increases in GS, whether added after or before DNP treatment. In rat distal colon, DNP significantly increased GT by 18% (P = 0.016) and mucosa-to-serosa FITC movement by 43% (P = 0.01), and 0.2 µM OCT pre-treatment completely prevented these changes. We conclude that OCT prevents hypoxia-induced increases in paracellular/macromolecule permeability and speculate it may limit ischemia-induced gut hyperpermeability during abdominal surgery, thereby reducing bacterial/bacterial toxin translocation and sepsis.

Recent advances in the treatment of refractory gastrointestinal angiodysplasia.

Gastrointestinal angiodysplasia (GIA) is a common, acquired, vascular abnormality of the digestive tract, and a frequent cause of bleeding. Refractory GIA criteria usually include recurrent bleeding, transfusions and/or repeat endoscopy. Pharmacological and interventional treatments have been the subject of recent high-quality publications. This review provides an overview of the latest updates on non-endoscopic management of refractory GIA. Aortic valve replacement has shown its efficacy in Heyde syndrome and should be considered if indicated. Anti-angiogenic drugs, such as Octreotide and Thalidomide, are efficient treatments of refractory GIA-related bleeding. Somatostatin analogs should, based on efficacy and tolerance profile, be considered first. In the future, a better understanding of the physiopathology of GIA might help develop new-targeted therapies.

Differential serum levels of CACNA1C, circadian rhythm and stress response molecules in subjects with bipolar disorder: Associations with genetic and clinical factors.

BACKGROUND: Many patients with bipolar disorder (BD) do not respond to or have difficulties tolerating lithium and/or other mood stabilizing agents. There is a need for personalized treatments based on biomarkers in guiding treatment options. The calcium voltage-gated channel CACNA1C is a promising candidate for developing personalized treatments. CACNA1C is implicated in BD by genome-wide association studies and several lines of evidence suggest that targeting L-type calcium channels could be an effective treatment strategy. However, before such individualized treatments can be pursued, biomarkers predicting treatment response need to be developed. METHODS: As a first step in testing the hypothesis that CACNA1C genotype is associated with serum levels of CACNA1C, we conducted ELISA measures on serum samples from 100 subjects with BD and 100 control subjects. RESULTS: We observed significantly higher CACNA1C (p < 0.01) protein levels in subjects with BD. The risk single nucleotide polymorpshism (SNP) (rs11062170) showed functional significance as subjects homozygous for the risk allele (CC) had significantly greater CACNA1C protein levels compared to subjects with one (p = 0.013) or no copies (p = 0.009). We observed higher somatostatin (SST) (p < 0.003) protein levels and lower levels of the clock protein aryl hydrocarbon receptor nuclear translocator-like (ARTNL) (p < 0.03) and stress signaling factor corticotrophin releasing hormone (CRH) (p < 0.001) in BD. SST and period 2 (PER2) protein levels were associated with both alcohol dependence and lithium response. CONCLUSIONS: Our findings represent the first evidence for increased serum levels of CACNA1C in BD. Along with altered levels of SST, ARNTL, and CRH our findings suggest CACNA1C is associated with circadian rhythm and stress response disturbances in BD.

Identification of Wandering Masses and Tumor Heterogeneity on 68Ga-DOTATATE and 18F-FDG PET/CT in Metastatic Grade II Neuroendocrine Tumor with Increased Somatostatin Receptor Expression After Combined Chemotherapy and PRRT.

Neuroendocrine tumors (NETs) may manifest as large masses in the abdominopelvic region that exhibit mobility and shifting, potentially leading to diagnostic uncertainty both before and after treatment. A meticulous analysis of PET/CT scans is advantageous in accurately identifying the precise location of large abdominopelvic masses. Tumor heterogeneity may be present in NETs with large abdominopelvic masses and may be easily identified on dual-tracer (68Ga-DOTATATE and 18F-FDG) PET/CT scans. In this scenario, the combined use of chemotherapy and peptide receptor radionuclide therapy is a more effective treatment option than monotherapy. Here, we present a case of a NET with wandering, large, heterogeneous masses in the abdominopelvic regions that were identified using dual-tracer PET/CT. After the administration of temozolomide chemotherapy in a combined chemotherapy-peptide receptor radionuclide therapy approach, we observed an upregulation in the expression of somatostatin receptor in the abdominopelvic masses.

Comparison of 24 vs 72-hour octreotide infusion in acute esophageal variceal hemorrhage - a multi-center, randomized clinical trial.

BACKGROUND: Current guidelines lack clarity about the optimal duration of octreotide therapy for patients with esophageal variceal hemorrhage (EVH). To address this lack of evidence, we conducted a randomized clinical trial (RCT) of 24-hours versus 72-hours continuous infusion of octreotide for patients with EVH. METHODS: This multi-center, prospective RCT (NCT03624517), randomized patients with EVH to 24-hour versus 72-hour infusion of octreotide. Patients were required to undergo esophageal variceal band ligation prior to enrollment. The primary endpoint was rebleeding rate at 72 hours. The study was terminated early due to an inability to recruit during and after the COVID-19 epidemic. RESULTS: For patients randomized to 72-hours (n = 19) of octreotide vs 24-hours (n = 15), there were no differences in the need for transfusion, average pRBC units transfused per patient (3 units vs 2 units), infection (5% vs 0%), mechanical ventilation (11% vs 7%), or the need for vasopressors (5% vs 3%), respectively (none of these differences were statistically significantly different). There were 2 re-bleeding events in the 72-hour group (11%), and no re-bleeding events in the 24-hour group (p = 0.49). 8/15 of patients receiving 24 hours of octreotide were discharged at or before hospital day 3 while none in the 72-hour group was discharged before day 3 (p < 0.001). There was one death (in the 72-hour group) within 30 days. CONCLUSIONS: A 24-hour infusion is non-inferior to a 72-hour infusion of octreotide for prevention of re-bleeding in patients with EVH. We propose that shortened octreotide duration may help reduce hospital stay and related costs in these patients.

Theranostics in Neuroendocrine Tumors: Updates and Emerging Technologies.

Advancements in somatostatin receptor (SSTR) targeted imaging and treatment of well-differentiated neuroendocrine tumors (NETs) have revolutionized the management of these tumors. This comprehensive review delves into the current practice, discussing the use of the various FDA-approved SSTR-agonist PET tracers and the predictive imaging biomarkers, and elaborating on Lu177-DOTATATE peptide receptor radionuclide therapy (PRRT) including the evolving areas of post-therapy imaging practices, PRRT retreatment, and the potential role of dosimetry in optimizing patient treatments. The future directions sections highlight ongoing research on investigational PET imaging radiotracers, future prospects in alpha particle therapy, and combination therapy strategies.

6-gingerol and its derivatives inhibit Helicobacter pylori-induced gastric mucosal inflammation and improve gastrin and somatostatin secretion.

The resistance of Helicobacter pylori (H. pylori) has increased in recent years, prompting a trend in the research and development of new drugs. In our study, three derivatives (JF-1, JF-2, and JF-3) were synthesized using 6-gingerol as the main component, while JF-4, containing both 6-gingerol and 6-shogaol as the main components, was extracted from dried ginger. The minimum inhibitory concentrations (MICs), determined using the ratio dilution method, were 80 µg/mL for JF-1, 40 µg/mL for JF-2, 30 µg/mL for JF-3, 40 µg/mL for JF-4, 60 µg/mL for 6-gingerol standard (SS), and 0.03 µg/mL for amoxicillin (AMX). After treating H. pylori-infected mice, the inflammation of the gastric mucosa was suppressed. The eradication rate of H. pylori was 16.7% of JF-3 low-dose treatment (LDT), 25.0% of JF-3 high-dose treatment (HDT), 16.7% of JF-4 LDT, 16.7% of JF-4 HDT, 30% of SS LDT, 50% of SS HDT, and 36.4% of the positive control group (PCG). The levels of gastrin, somatostatin (SST), IFN-γ, IL-4, and IL-8 were significantly recovered in the JF-3 and JF-4 administration groups, but the effect was stronger in the high-dose group. These results demonstrate that 6-gingerol and its derivatives have significant anti-Helicobacter pylori effects and are promising potential treatments for H. pylori infection.

Novel Detection of Pleomorphic Adenomas via Analysis of 68Ga-DOTATOC PET/CT Imaging.

INTRODUCTION: Currently, the diagnosis of salivary gland tumors using imaging techniques is unreliable. METHODS: In this monocentric retrospective study, we examined patients who received a 68Ga-DOTATOC PET/CT and subsequently underwent a salivary gland tumor resection between 1 January 2010 and 31 December 2021. PET/CT image assessment was compared with somatostatin receptor (SSTR) expression and histology. RESULTS: Thirteen patients (five pleomorphic adenoma (PA) and eight other parotid lesions (OPL)) received a 68Ga-DOTATOC PET/CT. Imaging displayed strong focal tracer uptake in all PA except for one with strong tumor to background discrimination. PA revealed higher SUVmax, SUVmean, liver and blood pool quotients than those of Warthin tumors (WT) and of OPL. In comparison to the contralateral parotid, SUVmax (p = 0.02), SUVmean (p = 0.02), liver quotient (p = 0.03) and blood pool quotient (p = 0.03) were all significantly higher. In contrast, WT and OPL showed in relation to the contralateral parotid no significant differences of SUVmax (WT p = 0.79; OPL p = 0.11), SUVmean (WT p = 1.0; OPL p = 0.08), liver quotient (WT p = 0.5; OPL p = 0.08) and blood pool quotient (WT p = 0.8; OPL p = 0.19). Two PA and one granuloma were not available for examination. In the immunohistochemal analysis, all PA demonstrated the highest intensity of SSTR2 expression (grade 3). Furthermore, PA had a high percentage of cells expressing SSTR2 (20%, 80% and 55%). CONCLUSIONS: A strong tracer uptake in PA was shown in 68Ga-DOTATOC PET/CT. This may allow physicians to utilize radioligated somatostatin analogue PET CT/MR imaging to accurately diagnose PA. Additionally, it may be possible in the future to treat the PA with a noninvasive peptide receptor radionuclide therapy or with somatostatin analogues.

A dorsal hippocampus-prodynorphinergic dorsolateral septum-to-lateral hypothalamus circuit mediates contextual gating of feeding.

Adaptive regulation of feeding depends on linkage of internal states and food outcomes with contextual cues. Human brain imaging has identified dysregulation of a hippocampal-lateral hypothalamic area (LHA) network in binge eating, but mechanistic instantiation of underlying cell-types and circuitry is lacking. Here, we identify an evolutionary conserved and discrete Prodynorphin (Pdyn)-expressing subpopulation of Somatostatin (Sst)-expressing inhibitory neurons in the dorsolateral septum (DLS) that receives primarily dorsal, but not ventral, hippocampal inputs. DLS(Pdyn) neurons inhibit LHA GABAergic neurons and confer context- and internal state-dependent calibration of feeding. Viral deletion of Pdyn in the DLS mimicked effects seen with optogenetic silencing of DLS Pdyn INs, suggesting a potential role for DYNORPHIN-KAPPA OPIOID RECEPTOR signaling in contextual regulation of food-seeking. Together, our findings illustrate how the dorsal hippocampus has evolved to recruit an ancient LHA feeding circuit module through Pdyn DLS inhibitory neurons to link contextual information with regulation of food consumption.

ARNT2 controls prefrontal somatostatin interneurons mediating affective empathy.

Empathy, crucial for social interaction, is impaired across various neuropsychiatric conditions. However, the genetic and neural underpinnings of empathy variability remain elusive. By combining forward genetic mapping with transcriptome analysis, we discover that aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) is a key driver modulating observational fear, a basic form of affective empathy. Disrupted ARNT2 expression in the anterior cingulate cortex (ACC) reduces affect sharing in mice. Specifically, selective ARNT2 ablation in somatostatin (SST)-expressing interneurons leads to decreased pyramidal cell excitability, increased spontaneous firing, aberrant Ca2+ dynamics, and disrupted theta oscillations in the ACC, resulting in reduced vicarious freezing. We further demonstrate that ARNT2-expressing SST interneurons govern affective state discrimination, uncovering a potential mechanism by which ARNT2 polymorphisms associate with emotion recognition in humans. Our findings advance our understanding of the molecular mechanism controlling empathic capacity and highlight the neural substrates underlying social affective dysfunctions in psychiatric disorders.

Gastroenteropancreatic neuroendocrine tumors: Epigenetic landscape and clinical implications.

Neuroendocrine tumors (NETs) are a rare, heterogenous group of neoplasms arising from cells of the neuroendocrine system. Amongst solid tumor malignancies, NETs are notable for overall genetic stability and recent data supports the notion that epigenetic changes may drive NET pathogenesis. In this review, major epigenetic mechanisms of NET pathogenesis are reviewed, including changes in DNA methylation, histone modification, chromatin remodeling, and microRNA. Prognostic implications of the above are discussed, as well as the expanding diagnostic utility of epigenetic markers in NETs. Lastly, preclinical and clinical evaluations of epigenetically targeted therapies in NETs and are reviewed, with a focus on future directions in therapeutic advancement.

Somatostatin-immunoreactive neurons of the rat gut during the development.

Somatostatin (SST) is a peptide expressed in the peripheral and central nervous systems, as well as in endocrine and immune cells. The aim of the current study is to determine the percentage of SST immunoreactive (IR) neurons and their colocalization with choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS), neuropeptide Y (NPY), and glial fibrillary acidic protein (GFAP) in the myenteric plexus (MP) and submucous plexus (SP) of the small intestine (SI) and large intestine (LI) of rats across different age groups from newborn to senescence using immunohistochemistry. In the MP of the SI and LI, the percentage of SST-IR neurons significantly increased during early postnatal development from 12 ± 2.4 (SI) and 13 ± 3.0 (LI) in newborn rats to 23 ± 1.5 (SI) and 18 ± 1.6 (LI) in 20-day-old animals, remaining stable until 60 days of age. The proportion of SST-IR cells then decreased in aged 2-year-old animals to 14 ± 2.0 (SI) and 10 ± 2.6 (LI). In the SP, the percentage of SST-IR neurons significantly rose from 22 ± 3.2 (SI) and 23 ± 1.7 (LI) in newborn rats to 42 ± 4.0 in 20-day-old animals (SI) and 32 ± 4.9 in 30-day-old animals (LI), before declining in aged 2-year-old animals to 21 ± 2.6 (SI) and 28 ± 7.4 (LI). Between birth and 60 days of age, 97-98% of SST-IR neurons in the MP and SP colocalized with ChAT in both plexuses of the SI and LI. The percentage of SST/ChAT neurons decreased in old rats to 85 ± 5.0 (SI) and 90 ± 3.8 (LI) in the MP and 89 ± 3.2 (SI) and 89 ± 1.6 (LI) in the SP. Conversely, in young rats, only a few SST-IR neurons colocalized with nNOS, but this percentage significantly increased in 2-year-old rats. The percentage of SST/NPY-IR neurons exhibited considerable variation throughout postnatal development, with no significant differences across different age groups in both the MP and SP of both intestines. No colocalization of SST with GFAP was observed in any of the studied animals. In conclusion, the expression of SST in enteric neurons increases in young rats and decreases in senescence, accompanied by changes in SST colocalization with ChAT and nNOS.

A Review on Coexisting Giants: The Interplay Between Acromegaly and Diabetes Mellitus.

Acromegaly is a rare disease caused mainly by pituitary adenoma, which results in elevated growth hormone (GH) levels and its primary mediator, insulin-like growth factor (IGF-1). The condition causes various complications, including cardiovascular, respiratory, neuropsychiatric, metabolic, and gastrointestinal complications, which affect the patient's quality of life. Metabolically, there has been an increased incidence of acromegaly-associated diabetes mellitus (DM), IGF-1 being the primary mediator, affecting the patient's overall morbidity/mortality and associated surge in cardiovascular events. In the current state of medicine, both nonpharmacologic and pharmacologic approaches in managing acromegaly-associated DM are validated, having their own individualistic positive or negative impact on glucose metabolism. This review article has compiled studies to demonstrate a link between acromegaly. It summarises the existing data on acromegaly associated with DM, explicitly understanding the effect of various medical treatments on glucose homeostasis.

Expression Analysis of SSTR 1, 2 and 3 in Small-cell Lung Cancer Patients as Targets for Future Peptide Receptor Radionuclide Therapy.

BACKGROUND/AIM: Small-cell lung cancer (SCLC) is noted for its high proliferative rate, and while treatable, relapse is common. SCLC is known to potentially express somatostatin receptors (SSTRs). Somatostatin possesses antineoplastic activity through cell-cycle arrest and apoptosis, and angiogenesis inhibition. SSTRs, thus, serve as potential anticancer targets for somatostatin analogue therapies. The aim of the study was to determine the expression rate of SSTR subtypes 1, 2 and 3 in SCLC using immunohistochemistry, and potential predictors of such rates. MATERIALS AND METHODS: A total of 147 human, SCLC paraffin-embedded tissue microarrays with corresponding patient age, sex, TNM staging, and disease stage were utilized. Immunohistochemical analysis was performed using anti-SSTR 1, 2 and 3 antibodies, each calibrated using healthy human pancreatic islets as positive controls. Array slides were counterstained with hematoxylin and scored based on stain intensity and percentage of stained cells. RESULTS: No SCLC samples expressed SSTR 1, whereas SSTR 2 and 3 were expressed in 29.4% and 4.35% of cases respectively. While females had higher expression levels of SSTR 2/3, and there was a trend of decreased SSTR 2 expression with increased age, results were not statistically significant. No correlation between disease stage and SSTR expression was found. Co-expression of both SSTR2 and 3 occurred in 5.3% of patients. CONCLUSION: Immunohisto-chemistry is an efficient screening tool to reveal optimum SCLC patients for somatostatin analogue therapy. Whilst there currently exist no accepted norm or predictors of SSTR expression levels in SCLC patients, this study contributes insight into the receptors' varied expression.

Real-World Study of Lanreotide Autogel in Routine Practice in Patients with Gastroenteropancreatic Neuroendocrine Tumors (GEP-NETs) in Hong Kong and Taiwan.

INTRODUCTION: There is a lack of data on the efficacy, effectiveness, and safety of lanreotide autogel in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) of Chinese ethnicity. This non-interventional, retrospective study evaluated the effectiveness and safety of lanreotide autogel in patients of Chinese ethnicity with GEP-NETs in clinical practice. METHODS: Patient charts were abstracted from five hospitals in Hong Kong and Taiwan (July-September 2021), where lanreotide autogel is approved for treating GEP-NETs. Included patients were adults with unresectable, metastatic, or locally advanced GEP-NETs who received a first injection (index) of lanreotide autogel 120 mg between 01 January 2017 and 30 June 2020 (planned sample size: N = 30). Follow-up ran from index to a maximum of 48 (± 4) weeks or until disease progression, start of new antitumor treatment, or death. The primary endpoint was progression-free survival (PFS) rate at week 48 (±4), and secondary endpoints included PFS rate at week 24 (±4), estimated using Kaplan-Meier analyses. All analyses were descriptive. RESULTS: Of 27 patients enrolled, 22 (81.5%) had 48 weeks of follow-up. Tumors of pancreatic origin were the most common (73.9%). PFS rate was 0.96 (95% confidence interval: 0.72 - 0.99) at 24 weeks and 0.82 (0.53-0.94) at 48 weeks. Overall, 74.1% patients experienced ≥ 1 treatment-emergent adverse event; none were serious. No deaths were reported. CONCLUSIONS: Lanreotide autogel was well tolerated and showed good tumor control rate in a real-world setting. These findings align with results from previous studies in Caucasian, Japanese, and Korean patients, thus supporting lanreotide autogel for treating patients with GEP-NETs of Chinese ethnicity.

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare cancers that develop in the stomach, intestines, or pancreas. Lanreotide autogel is used to treat GEP-NETs in patients whose tumors cannot be removed by surgery or have spread to other body parts. At the time of the study, lanreotide autogel was not approved in mainland China for treating patients with GEP-NETs. Most clinical trials of lanreotide autogel were conducted in Caucasian patients, so more information is needed on whether lanreotide autogel is effective and well tolerated for treating GEP-NETs in patients of Chinese ethnicity. We performed this study to gain this information. In this study, we retrieved data from the medical records of patients of Chinese ethnicity with GEP-NETs who were treated with lanreotide autogel in Hong Kong and Taiwan. We examined the medical records to understand how these patients responded to lanreotide autogel. The results from this study showed that after 24 weeks of lanreotide autogel treatment, 22 of 23 patients had GEP-NETs that did not worsen. After 48 weeks of treatment, two of these patients had GEP-NETs that grew or spread, resulting in 20 patients with GEP-NETs that did not worsen at the end of the study. No patients had serious side effects related to lanreotide autogel. In conclusion, this study showed that lanreotide autogel is well tolerated and effective for treating patients of Chinese ethnicity with GEP NETs in the real world, which is consistent with results from earlier studies in Caucasian patients. These results support the use of lanreotide autogel in these patients.

Cells and circuits for amygdala neuroplasticity in the transition to chronic pain.

Maladaptive plasticity is linked to the chronification of diseases such as pain, but the transition from acute to chronic pain is not well understood mechanistically. Neuroplasticity in the central nucleus of the amygdala (CeA) has emerged as a mechanism for sensory and emotional-affective aspects of injury-induced pain, although evidence comes from studies conducted almost exclusively in acute pain conditions and agnostic to cell type specificity. Here, we report time-dependent changes in genetically distinct and projection-specific CeA neurons in neuropathic pain. Hyperexcitability of CRF projection neurons and synaptic plasticity of parabrachial (PB) input at the acute stage shifted to hyperexcitability without synaptic plasticity in non-CRF neurons at the chronic phase. Accordingly, chemogenetic inhibition of the PB→CeA pathway mitigated pain-related behaviors in acute, but not chronic, neuropathic pain. Cell-type-specific temporal changes in neuroplasticity provide neurobiological evidence for the clinical observation that chronic pain is not simply the prolonged persistence of acute pain.

Somatostatin modulation of initial fusion pores in Ca2+-triggered exocytosis from mouse chromaffin cells.

Somatostatin, a peptide hormone that activates G-protein-coupled receptors, inhibits the secretion of many hormones. This study investigated the mechanisms of this inhibition using amperometry recording of Ca2+-triggered catecholamine secretion from mouse chromaffin cells. Two distinct stimulation protocols, high-KCl depolarization and caffeine, were used to trigger exocytosis, and confocal fluorescence imaging was used to monitor the rise in intracellular free Ca2+. Analysis of single-vesicle fusion events (spikes) resolved the action of somatostatin on fusion pores at different stages. Somatostatin reduced spike frequency, and this reduction was accompanied by prolongation of pre-spike feet and slowing of spike rise times. This indicates that somatostatin stabilizes initial fusion pores and slows their expansion. This action on the initial fusion pore impacted the release mode to favour kiss-and-run over full-fusion. During a spike the permeability of a fusion pore peaks, declines and then settles into a plateau. Somatostatin had no effect on the plateau, suggesting no influence on late-stage fusion pores. These actions of somatostatin were indistinguishable between exocytosis triggered by high-KCl and caffeine, and fluorescence imaging showed that somatostatin had no effect on stimulus-induced rises in cytosolic Ca2+. Our findings thus demonstrate that the signalling cascades activated by somatostatin target the exocytotic machinery that controls the initial and expanding stages of fusion pores, while having no effect on late-stage fusion pores. As a result of its stronger inhibition of full-fusion compared to kiss-and-run, somatostatin will preferentially inhibit the secretion of large peptides over the secretion of small catecholamines. KEY POINTS: Somatostatin inhibits the secretion of various hormones by activating G-protein-coupled receptors. In this study, we used amperometry to investigate the mechanism by which somatostatin inhibits catecholamine release from mouse chromaffin cells. Somatostatin increased pre-spike foot lifetime and slowed fusion pore expansion. Somatostatin inhibited full-fusion more strongly than kiss-and-run. Our results suggest that the initial fusion pore is the target of somatostatin-mediated regulation of hormone release. The stronger inhibition of full-fusion by somatostatin will result in preferential inhibition of peptide release.

Development of [177Lu]Lu-LNC1010 for peptide receptor radionuclide therapy of nasopharyngeal carcinoma.

PURPOSE: Somatostatin Receptor 2 (SSTR2)-targeted radiopharmaceutical [68Ga]Ga-DOTATATE has potential advantages in the diagnosis of nasopharyngeal carcinoma (NPC). This study introduces a novel long-lasting SSTR2 analogue, LNC1010, based on DOTATATE, a truncated Evans blue-binding moiety, and a polyethylene-glycol linker. We hypothesised that peptide receptor radionuclide therapy (PRRT) is more effective with [177Lu]Lu-LNC1010 than with [177Lu]Lu-DOTATATE in treating metastatic NPC. METHODS: We assessed binding characteristics of LNC1010 in vitro using C666-1 NPC cells and in-vivo pharmacokinetics of [68Ga]Ga/[177Lu]Lu-LNC1010 in C666-1 NPC xenografts via PET and SPECT imaging, biodistribution studies, and PRRT, and compared them with [68Ga]Ga/[177Lu] Lu-labelled DOTATATE. Furthermore, a proof-of-concept approach for imaging and therapy was conducted in a patient with metastatic NPC. RESULTS: LNC1010 exhibited strong uptake and specific affinity for SSTR2 in C666-1 NPC cells. PET and SPECT imaging demonstrated higher uptake and longer tumour retention of [68Ga]Ga/[177Lu]Lu-LNC1010 than [68Ga]Ga/[177Lu]Lu-DOTATATE in C666-1 NPC xenografts, indicating its suitability for PRRT applications in NPCs. Biodistribution studies confirmed the higher uptake and prolonged retention of [177Lu]Lu-LNC1010 than [177Lu]Lu-DOTATATE. In preclinical PRRT studies, [177Lu]Lu-LNC1010 showed greater inhibition of tumour growth in C666-1 NPC xenografts than [177Lu]Lu-DOTATATE. In a subsequent pilot clinical study, PRRT with [177Lu]Lu-LNC1010 achieved favourable therapeutic and negligible side effects in a patient with metastatic NPC. CONCLUSION: [177Lu]Lu-LNC1010 demonstrated increased tumour uptake and prolonged retention in SSTR2-positive NPCs, with superior anti-tumour efficacy to that of [177Lu]Lu-DOTATATE in preclinical studies. These findings suggest that PRRT with [177Lu]Lu-LNC1010 is a promising treatment for advanced NPC, extending the clinical scope of PRRT beyond neuroendocrine tumours.

A brief history of somatostatin interneuron taxonomy or: how many somatostatin subtypes are there, really?

We provide a brief (and unabashedly biased) overview of the pre-transcriptomic history of somatostatin interneuron taxonomy, followed by a chronological summary of the large-scale, NIH-supported effort over the last ten years to generate a comprehensive, single-cell RNA-seq-based taxonomy of cortical neurons. Focusing on somatostatin interneurons, we present the perspective of experimental neuroscientists trying to incorporate the new classification schemes into their own research while struggling to keep up with the ever-increasing number of proposed cell types, which seems to double every two years. We suggest that for experimental analysis, the most useful taxonomic level is the subdivision of somatostatin interneurons into ten or so "supertypes," which closely agrees with their more traditional classification by morphological, electrophysiological and neurochemical features. We argue that finer subdivisions ("t-types" or "clusters"), based on slight variations in gene expression profiles but lacking clear phenotypic differences, are less useful to researchers and may actually defeat the purpose of classifying neurons to begin with. We end by stressing the need for generating novel tools (mouse lines, viral vectors) for genetically targeting distinct supertypes for expression of fluorescent reporters, calcium sensors and excitatory or inhibitory opsins, allowing neuroscientists to chart the input and output synaptic connections of each proposed subtype, reveal the position they occupy in the cortical network and examine experimentally their roles in sensorimotor behaviors and cognitive brain functions.

Predicting Response to Medical Treatment in Acromegaly via Granulation Pattern, Expression of Somatostatin Receptors Type 2 and 5 and E-Cadherin.

Resistance to first-generation somatostatin receptor ligand (fgSRL) treatment in acromegaly is common, making the identification of biomarkers that predict fgSRL response a desired goal. We conducted a retrospective analysis on 21 patients with acromegaly who underwent surgery and subsequent pharmacological treatment. Through immunohistochemistry (IHC), we assessed the expression of the somatostatin receptor subtypes SSTR2 and SSTR5, E-Cadherin, and cytokeratin granulation pattern (sparsely or densely). Patients were divided into responders and non-responders based on their biochemical response to fgSRL and/or the newer agent, Pasireotide, or the GH-blocker, Pegvisomant. Patients resistant to fgSRL (n = 12) exhibited lower SSTR2 and E-Cadherin expressions. Sparsely granulated tumors were more frequent in the non-responder group. SSTR2 (p = 0.024, r = 0.49) and E-Cadherin (p = 0.009, r = 0.64) positively correlated with the Insulin-like Growth Factor 1 (IGF-1) decrease after fgSRL, while SSTR5 (p = 0.107, r = -0.37) showed a trend towards negative correlation. SSTR5 positivity seemed to be associated with Pasireotide response, albeit the number of treated patients was too low (n = 4). No IHC markers correlated with Pegvisomant response. Our findings suggest that densely granulated tumors, with positive SSTR2 and E-Cadherin seem to be associated with favorable fgSRL responses. The strongest predictive value of the studied markers was found for E-Cadherin, which seems to surpass even SSTR2.