scholarly journals Somatostatin receptor subtypes 1 and 4 redundantly regulate neprilysin, the major amyloid-beta degrading enzyme in brain

2020 ◽  
Author(s):  
Per Nilsson ◽  
Karin Sörgjerd ◽  
Naomasa Kakiya ◽  
Hiroki Sasaguri ◽  
Naoto Watamura ◽  
...  
Keyword(s):  
Mouse Model ◽  
Amyloid Beta ◽  
Molecular Layer ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Receptor Subtypes ◽  
Double Knockout ◽  
Degrading Enzyme ◽  
Somatostatin Receptor Subtypes ◽  
Ad Mouse Model

Alzheimer’s disease (AD) brains are characterized by increased levels of the pathogenic amyloid beta (Aβ) peptide, which accumulates into extracellular plaques. Finding a way to lower Aβ levels is fundamental for the prevention and treatment of AD. Neprilysin is the major Aβ degrading enzyme which is regulated by the neuropeptide somatostatin. Here we used a combination of in vitro and in vivo approaches to identify the subtype specificity of the five somatostatin receptors (SSTs) expressed in the brain, involved in the regulation of neprilysin. Using a battery of Sst double knockout (dKO) mice we show that neprilysin is regulated by SST1 and SST4 in a redundant manner. Sst1 and Sst4 dKO mice exhibit a specific decrease of presynaptic neprilysin in the Lacunosum molecular layer. Moreover, a genetic deficiency of Sst1 and Sst4 in amyloid beta precursor protein (App) knock-in mice, an AD mouse model, aggravates the Aβ pathology in the hippocampus. As a first proof of concept towards an Aβ-lowering strategy involving neprilysin, we demonstrate that treatment with an agonist selective for SST1 and SST4 ameliorates the Aβ pathology and improves cognition in the App knock-in AD mouse model.

Novel insights in somatostatin receptor physiology

2007 ◽  
Vol 156 (suppl_1) ◽  
pp. S3-S11 ◽  
Author(s):  
Giovanni Tulipano ◽  
Stefan Schulz
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogs ◽  
Receptor Subtypes ◽  
Ligand Complex ◽  
Endosomal Sorting ◽  
Intracellular Vesicle ◽  
Molecular Events ◽  
Somatostatin Receptor Subtypes

The experimental data reviewed in the present paper deal with the molecular events underlying the agonist-dependent regulation of the distinct somatostatin receptor subtypes and may suggest important clues about the clinical use of somatostatin analogs with different pattern of receptor specificity for the in vivo targeting of tumoral somatostatin receptors. Somatostatin receptor subtypes are characterized by differential β-arrestin trafficking and endosomal sorting upon agonist binding due, at least in part, to the differences in their C-terminal tails. Moreover, the subcellular expression pattern of somatostatin receptor subtypes and their activity in response to agonist treatment are affected by intracellular complements, such as proteins involved in intracellular vesicle trafficking. Different somatostatin analogs may induce distinct conformations of the receptor/ligand complex, preferentially coupled to either receptor signaling or receptor endocytosis.

scholarly journals Somatostatin receptor expression in parathyroid neoplasms

2019 ◽  
Vol 8 (8) ◽  
pp. 1213-1223 ◽  
Author(s):  
Sara Storvall ◽  
Helena Leijon ◽  
Eeva Ryhänen ◽  
Johanna Louhimo ◽  
Caj Haglund ◽  
...  
Keyword(s):  
Primary Hyperparathyroidism ◽  
Parathyroid Carcinoma ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Receptor Expression ◽  
Benign Tumors ◽  
Receptor Subtypes ◽  
Receptor Imaging ◽  
Somatostatin Receptor Subtypes ◽  
Parathyroid Adenomas

Introduction Parathyroid carcinoma represents a rare cause of primary hyperparathyroidism. Distinguishing carcinoma from the benign tumors underlying primary hyperparathyroidism remains challenging. The diagnostic criteria for parathyroid carcinoma are local and/or metastatic spreading. Atypical parathyroid adenomas share other histological features with carcinomas but lack invasive growth. Somatostatin receptors are commonly expressed in different neuroendocrine tumors, but whether this also holds for parathyroid tumors remains unknown. Aim Our aim is to examine the immunohistochemical expression of somatostatin receptor 1–5 in parathyroid typical adenomas, atypical adenomas and carcinomas. Methods We used a tissue microarray construct from a nationwide cohort of parathyroid carcinomas (n = 32), age- and gender-matched typical parathyroid adenomas (n = 72) and atypical parathyroid adenomas (n = 27) for immunohistochemistry of somatostatin receptor subtypes 1–5. We separately assessed cytoplasmic, membrane and nuclear expression and also investigated the associations with histological, biochemical and clinical characteristics. Results All parathyroid tumor subgroups expressed somatostatin receptors, although membrane expression appeared negligible. Except for somatostatin receptor 1, expression patterns differed between the three tumor types. Adenomas exhibited the weakest and carcinomas the strongest expression of somatostatin receptor 2, 3, 4 and 5. We observed the largest difference for cytoplasmic somatostatin receptor 5 expression. Conclusions Parathyroid adenomas, atypical adenomas and carcinomas all express somatostatin receptor subtypes 1–5. Somatostatin receptor 5 may serve as a potential tumor marker for malignancy. Studies exploring the role of somatostatin receptor imaging and receptor-specific therapies in patients with parathyroid carcinomas are needed.

scholarly journals Somatostatin receptor subtype expression in the human heart: differential expression by myocytes and fibroblasts

2005 ◽  
Vol 187 (3) ◽  
pp. 379-386 ◽  
Author(s):  
William H T Smith ◽  
R Unnikrishnan Nair ◽  
Dawn Adamson ◽  
Mark T Kearney ◽  
Stephen G Ball ◽  
...  
Keyword(s):  
Cardiac Myocytes ◽  
Human Heart ◽  
Cardiac Fibroblasts ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Cell Types ◽  
Somatostatin Analogues ◽  
Receptor Subtypes ◽  
Somatostatin Receptor Subtypes ◽  
Human Cardiac Fibroblasts

In acromegaly, somatostatin receptor ligands (SRLs) can ameliorate left ventricular hypertrophy (LVH) and their use is associated with demonstrable improvements in various parameters of cardiac function. It remains unclear as to whether these beneficial effects are principally attributable to falling GH and IGF-I levels, or whether SRLs exert independent direct effects on the heart via somatostatin receptors. To help address this issue, we have sought to investigate somatostatin receptor expression in human heart. A human heart cDNA library was probed using PCR techniques to determine expression of somatostatin receptor subtypes. Subsequently, human heart biopsies and human cardiac fibroblasts and myocytes were analysed to determine whether expression differed between cardiac chambers or cell types. mRNAs for four of the five somatostatin receptor subtypes (sst1, sst2, sst4 and sst5) were shown to be co-expressed by the human heart. These receptors were present in both atrial and ventricular tissue. Human cardiac myocytes expressed mRNA for only sst1 and sst2, while human cardiac fibroblasts expressed all four subtypes found in whole heart tissue. The expression of functional somatostatin receptors on human cardiac fibroblasts was confirmed by mobilisation of intracellular calcium in response to somatostatin. The presence of cardiac somatostatin receptors raises the possibility of a direct effect of somatostatin analogues on the heart. Furthermore, the differential expression of somatostatin receptor subtypes by human cardiac myocytes and fibroblasts opens up the possibility of differential modulation of the cell types in the heart by subtype-specific somatostatin analogues.

scholarly journals DG3173 (somatoprim), a unique somatostatin receptor subtypes 2-, 4- and 5-selective analogue, effectively reduces GH secretion in human GH-secreting pituitary adenomas even in Octreotide non-responsive tumours

2012 ◽  
Vol 166 (2) ◽  
pp. 223-234 ◽  
Author(s):  
U Plöckinger ◽  
U Hoffmann ◽  
M Geese ◽  
A Lupp ◽  
M Buchfelder ◽  
...  
Keyword(s):  
Dose Response ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Clinical Effectiveness ◽  
Significant Negative Correlation ◽  
Somatostatin Analogues ◽  
Receptor Subtypes ◽  
Gh Secretion ◽  
Somatostatin Receptor Subtypes ◽  
Tumour Characteristics

ObjectiveSomatostatin analogues (SSA) reduce autonomous GH secretion by activating somatostatin receptors (sst) 2 and 5 in 50–60% of acromegalic patients. However, by inhibiting insulin secretion these SSA reduce glucose tolerance. DG3173 is a novel SSA with additional binding to sst4 and low insulin-suppressing activity. We investigated the effect of DG3173, including its relation to specific tumour characteristics, on GH secretion in human somatotroph adenoma cell cultures (hSA) in comparison with Octreotide.MethodsTwenty-seven hSA were characterised immunohistochemically for their hormone- and sst-expression, granularity and pre-surgical therapy with SSA. GH was determined in supernatants of hSA treated with DG3173 or Octreotide in time- (n=6) and dose–response (n=21) experiments. A positive response was defined as GH suppression to below 80% of baseline.ResultsIn the dose–response experiments DG3173 suppressed GH secretion in more adenomas than Octreotide (10/21 vs 5/21), including 38% (6/16) of Octreotide non-responders. In responders the extent of GH suppression and IC50 were comparable for both SSA. The response-rate of both SSA was higher in monohormonal vs bihormonal adenomas, yet GH declined similarly in both groups. Neither pre-surgical SSA (n=6) nor tumour morphology was related to the GH response. However, semi-quantitative analysis indicated a small but significant negative correlation between the GH response to Octreotide and the immunoreactivity scores of sst2 expression.ConclusionsDG3173 equalled Octreotide in suppressing GH secretion in hSA. Since DG3173 suppressed GH in some Octreotide-non-responsive adenomas, its clinical effectiveness will be worth testing. Moreover, its reduced insulin-suppressive potency would make it a valuable alternative to Octreotide.

Somatostatin receptors

1995 ◽  
Vol 269 (6) ◽  
pp. G813-G820 ◽  
Author(s):  
T. Reisine
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogues ◽  
Receptor Subtypes ◽  
Binding Domains ◽  
Somatostatin Receptor Subtypes ◽  
Selective Agonists ◽  
The Individual ◽  
Subtype Selective ◽  
Biological Actions

Somatostatin induces its biological actions by activating a family of receptor subtypes. The recent cloning of five somatostatin receptor subtypes has led to the development of subtype-selective agonists. These compounds are revealing distinct functions of the individual receptor subtypes. Mutagenesis studies have revealed domains of several of the receptors involved in specific recognition of somatostatin analogues. Molecular modeling of both of these ligand-binding domains and the constrained somatostatin analogues that they interact with may lead to the development of nonpeptide somatostatin drugs that could be useful in the treatment of tumors and various metabolic, gastrointestinal, and central nervous system disorders.

scholarly journals Immunohistochemical Expression of Somatostatin Receptor Subtypes in a Panel of Neuroendocrine Neoplasias

2019 ◽  
Vol 67 (10) ◽  
pp. 735-743 ◽  
Author(s):  
Satu M. Remes ◽  
Helena L. Leijon ◽  
Tiina J. Vesterinen ◽  
Johanna T. Arola ◽  
Caj H. Haglund
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogs ◽  
Membrane Receptors ◽  
Receptor Subtypes ◽  
Receptor Imaging ◽  
Primary Tumors ◽  
Somatostatin Receptor Subtypes ◽  
Negative Controls ◽  
G Protein Coupled

Neuroendocrine neoplasias (NENs) are known to express somatostatin receptors (SSTRs) 1–5, which are G-protein-coupled cell membrane receptors. Somatostatin receptor imaging and therapy utilizes the SSTR expression. Synthetic somatostatin analogs with radioligands are used to detect primary tumors, metastases, and recurrent disease. Receptor analogs are also used for treating NENs. Furthermore, commercially available SSTR antibodies can be used for the immunohistochemical (IHC) detection of SSTRs. We investigated different SSTR antibody clones applying diverse IHC protocol settings to identify reliable clones and feasible protocols for NENs. A tissue microarray including NENs from 12 different primary sites were stained. Only UMB clones were able to localize SSTR on the cell membranes of NENs. SSTR2 (UMB1) emerged as the most common subtype followed by SSTR5 (UMB4) and SSTR1 (UMB7). SSTR3 (UMB5) expression was mainly cytoplasmic. Yet, SSTR4 expression was weak and located primarily in the cytoplasm. Thus, appropriate IHC protocols, including proper positive and negative controls, represent requirements for high-quality NEN diagnostics and for planning personalized therapy.

scholarly journals Somatostatin receptor activation is involved in the control of daily torpor in a seasonal mammal

2015 ◽  
Vol 309 (6) ◽  
pp. R668-R674 ◽  
Author(s):  
Frank Scherbarth ◽  
Victoria Diedrich ◽  
Rebecca A. Dumbell ◽  
Herbert A. Schmid ◽  
Stephan Steinlechner ◽  
...  
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Receptor Activation ◽  
The Body ◽  
Receptor Subtypes ◽  
Marginal Effect ◽  
Hormonal Changes ◽  
Daily Torpor ◽  
Siberian Hamsters ◽  
Somatostatin Receptor Subtypes

Siberian hamsters ( Phodopus sungorus) show spontaneous daily torpor only after ∼2 mo in winter-like short photoperiods (SP). Although some SP-induced hormonal changes have been demonstrated to be necessary for the occurrence of seasonal torpor, the whole set of preconditions is still unknown. Recent findings provide evidence that the hypothalamic pituitary growth axis is involved in endocrine responses to SP exposure in the photoperiodic hamsters. To examine whether suppression of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) secretion affects the incidence of daily torpor, we used two somatostatin receptor agonists, pasireotide (SOM230) and octreotide, with different affinity profiles for receptor subtypes. Pasireotide strikingly increased the torpor frequency in male hamsters compared with sham-treated controls, and torpor duration was often increased, which in some cases exceeded 12 h. In contrast, administration of octreotide reduced the body weight of SP hamsters but had only a marginal effect on torpor frequency in males and no effect in females. Together with measured concentrations of circulating IGF-1, the present results strongly suggest that reduced activity of the GH/IGF-1 axis is not critical for stimulation of torpor expression but activation of specific somatostatin receptors is critical. This putative role for certain somatostatin receptor subtypes in torpor induction provides a promising new approach to unravel the endocrine mechanisms of torpor regulation.

scholarly journals Preclinical and clinical experiences with the role of somatostatin receptors in the treatment of pituitary adenomas

2007 ◽  
Vol 156 (suppl_1) ◽  
pp. S45-S51 ◽  
Author(s):  
Joost van der Hoek ◽  
Steven W J Lamberts ◽  
Leo J Hofland
Keyword(s):  
Pituitary Adenomas ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Physiological Role ◽  
Receptor Subtypes ◽  
Clinical Experiences ◽  
Endocrine Diseases ◽  
Somatostatin Receptor Subtypes ◽  
Preclinical And Clinical Studies

The patho-physiological role of somatostatin receptor subtypes (sst) in neuro endocrine diseases has gained enhanced scientific interest in the past few years. The development of novel somatotropin-release inhibiting factor analogs, both sst-specific and universal ligands, seem promising as a tool to further increase fundamental insights in sst function. Eventually, this research should result in novel medical therapeutic opportunities in patients suffering from neuro-endocrine diseases. In the present review, the functional role of sst in all types of pituitary adenomas, based on recent preclinical and clinical studies, is being discussed.

scholarly journals The clinical–molecular interface of somatostatin, dopamine and their receptors in pituitary pathophysiology

2009 ◽  
Vol 42 (5) ◽  
pp. 361-370 ◽  
Author(s):  
Diego Ferone ◽  
Federico Gatto ◽  
Marica Arvigo ◽  
Eugenia Resmini ◽  
Mara Boschetti ◽  
...  
Keyword(s):  
Medical Treatment ◽  
Dopamine Receptors ◽  
Pituitary Adenomas ◽  
Somatostatin Receptor ◽  
Somatostatin Receptors ◽  
Somatostatin Analogues ◽  
Receptor Activation ◽  
Receptor Subtypes ◽  
Experimental Drugs ◽  
Somatostatin Receptor Subtypes

The role of somatostatin and dopamine receptors as molecular targets for the treatment of patients with pituitary adenomas is well established. Indeed, dopamine and somatostatin receptor agonists are considered milestones for the medical therapy of these tumours. However, in recent years, the knowledge of the expression of subtypes of somatostatin and dopamine receptors in pituitary adenomas, as well as of the coexpression of both types of receptors in tumour cells, has increased considerably. Moreover, recent insights suggest a functional interface of dopamine and somatostatin receptors, when coexpressed in the same cells. This interaction has been suggested to occur via dimerisation of these G-protein-coupled receptors. In addition, there was renewed interest around the concept of cell specificity in response to ligand-induced receptor activation. New experimental drugs, including novel somatostatin analogues, binding to multiple somatostatin receptor subtypes, as well as hybrid somatostatin–dopamine compounds have been generated, and recently a completely novel class of molecules has been developed. These advances have opened new perspectives for the medical treatment of patients with pituitary tumours poorly responsive to the present clinically available drugs, and perhaps also for the treatment of other categories of neuroendocrine tumours. The aim of the present review is to summarise the novel insights in somatostatin and dopamine receptor pathophysiology, and to bring these new insights into perspective for the future strategies in the medical treatment of patients with pituitary adenomas.

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