Somatostatin

Small Molecule-Drug Conjugates Emerge as a New Promising Approach for Cancer Treatment

Antibody drug conjugates (ADCs) have emerged as a new promising class of anti- cancer agents. However, limitations such as higher costs and unavoidable immunogenicity due to their relatively large structures cannot be ignored. Therefore, the development of lightweight drugs such as small molecule-drug conjugates (SMDCs) based on the ADC design idea has become a new option for targeted therapy. SMDCs are derived from the coupling of small-molecule targeting ligands with cytotoxic drugs. They are composed of three parts: small-molecule targeting ligands, cytotoxic molecules, and linkers. Compared with ADCs, SMDCs can be more rapidly and evenly dispersed into tumor tissues, with low cost and no immunogenicity. In this article, we will give a comprehensive review of different types of SMDCs currently under clinical trials to provide ideas and inspirations for the development of clinically applicable SMDCs.

Somatostatin receptors in congenital hyperinsulinism: Biology to bedside

Congenital hyperinsulinism (CHI), although a rare disease, is an important cause of severe hypoglycemia in early infancy and childhood, causing preventable morbidity and mortality. Prompt diagnosis and appropriate treatment is necessary to prevent hypoglycaemia mediated brain damage. At present, the medical treatment of CHI is limited to diazoxide as first line and synthetic somatostatin receptor ligands (SRLs) as second line options; therefore understanding somatostatin biology and treatment perspectives is important. Under healthy conditions, somatostatin secreted from pancreatic islet δ-cells reduces insulin release through somatostatin receptor induced cAMP-mediated downregulation and paracrine inhibition of β- cells. Several SRLs with extended duration of action are now commercially available and are being used off-label in CHI patients. Efficacy remains variable with the present generation of SRLs, with treatment effect often being compromised by loss of initial response and adverse effects such as bowel ischaemia and hepatobiliary dysfunction. In this review we have addressed the biology of the somatostatin system contexualised to CHI. We have discussed the clinical use, limitations, and complications of somatostatin agonists and new and emerging therapies for CHI.

Antitumoral and Anti-inflammatory Roles of Somatostatin and Its Analogs in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and affects about 8% of cirrhotic patients, with a recurrence rate of over 50%. There are numerous therapies available for the treatment of HCC, depending on cancer staging and condition of the patient. The complexity of the treatment is also justified by the unique pathogenesis of HCC that involves intricate processes such as chronic inflammation, fibrosis, and multiple molecular carcinogenesis events. During the last three decades, multiple in vivo and in vitro experiments have used somatostatin and its analogs (SSAs) to reduce the proliferative and metastatic potential of hepatoma cells by inducing their apoptosis and reducing angiogenesis and the inflammatory component of HCC. Most experiments have proven successful, revealing several different pathways and mechanisms corresponding to the aforementioned functions. Moreover, a correlation between specific effects and expression of somatostatin receptors (SSTRs) was observed in the studied cells. Clinical trials have tested either somatostatin or an analog, alone or in combination with other drugs, to explore the potential effects on HCC patients, in various stages of the disease. While the majority of these clinical trials exhibited minor to moderate success, some other studies were inconclusive or even reported negative outcomes. A complete evaluation of the efficacy of somatostatin and SSAs is still the matter of intense debate, and, if deemed useful, these substances may play a beneficial role in the management of HCC patients.

The retrotrapezoid nucleus and the neuromodulation of breathing

Breathing is regulated by a host of arousal and sleep-wake state-dependent neuromodulators to maintain respiratory homeostasis. Modulators such as acetylcholine, norepinephrine, histamine, serotonin (5-HT), adenosine triphosphate (ATP), substance P, somatostatin, bombesin, orexin, and leptin can serve complementary or off-setting functions depending on the target cell type and signaling mechanisms engaged. Abnormalities in any of these modulatory mechanisms can destabilize breathing, suggesting that modulatory mechanisms are not overly redundant but rather work in concert to maintain stable respiratory output. The present review focuses on the modulation of a specific cluster of neurons located in the ventral medullary surface, named retrotrapezoid nucleus, that are activated by changes in tissue CO₂/H⁺ and regulate several aspects of breathing, including inspiration and active expiration.

Theranostic approaches in nuclear medicine: current status and future prospects

Introduction: Theranostics is an emerging field in which diagnosis and specific targeted therapy are combined to achieve a personalized treatment approach to the patient. In nuclear medicine clinical practice, theranostics is often performed utilizing the same molecule labeled with two different radionuclides, one radionuclide for imaging and another for therapy.Areas covered: The authors review the clinical applications of different radiopharmaceuticals in the field of interest, including the well-established use of radioactive iodine in differentiated thyroid cancer, radiolabeled metaiodobenzylguanidine (MIBG) in neuroblastoma and the clinical impact of peptide radionuclide receptorial therapy (PRRT) in the management of neuroendocrine tumors. Furthermore, the more cutting-edge and recently introduced theranostic approaches will be reviewed, such as the radioligand therapy with ¹⁷⁷Lu-prostate specific membrane antigen (PSMA) and targeted alpha therapy in castration-resistant prostate cancer. Finally, the main applications of PET for the imaging of biomarkers suitable for the non-radionuclide targeted therapy will be covered.Expert opinion: Theranostics is envisaging a revolutionary clinical approach which is deeply connected with the concept of personalized medicine and ruled by a 'patient-centered' vision. In this perspective, the theranostic applications will need well-trained specialists, capable to manage not only the technological aspects of the discipline, but also to deal with the more innovative oncological therapies in a multidisciplinary setting.

Portal Hypertension of a Delayed Onset Following Liver Abscesses in a 12-Month-Old Infant: A Case Report and Review of the Literature

We report a 12-month-old female infant who had a history of neonatal sepsis with liver micro-abscesses that resolved with intravenous antibiotics during neonatal period. During her neonatal admission period, no umbilical vein catheter was inserted. Also, she did not undergo any abdominal surgeries or had a postnatal history of necrotizing enterocolitis. However, the child developed upper gastrointestinal bleeding in form of hematemesis and melena secondary to esophageal varices at the age of 12 months with an extra-hepatic portal vein obstruction with cavernous transformation and portal hypertension subsequently. The child underwent a successful endoscopic injection sclerotherapy. She is now 20-month-old and has portal hypertension but otherwise asymptomatic. We are proposing the possibility of a delayed-onset portal hypertension as a complication of liver abscess and neonatal sepsis.

Nonendoscopic management strategies for acute esophagogastric variceal bleeding

Acute variceal bleeding is a potentially life-threatening complication of portal hypertension. Management consists of emergent hemostasis, therapy directed at hemodynamic resuscitation, protection of the airway, and prevention and treatment of complications including prophylactic use of antibiotics. Endoscopic treatment remains the mainstay in the management of acute variceal bleeding in combination with pharmacotherapy aimed at reducing portal pressure. This article intends to highlight only the current nonendoscopic treatment approaches for control of acute variceal bleeding.

Management of bronchial carcinoid: An anaesthetic challenge

Carcinoid tumours pose a great challenge to anaesthesiologist, especially if carcinoid syndrome is present. We report peri-operative management of a patient with carcinoid syndrome who underwent upper lobectomy. Pre-operative optimisation for 10 days before surgery with injection octreotide and administration on the day of surgery as per guidelines was followed (North American Neuroendocrine Tumour Society guidelines). Our main goals were to prevent mediator release, avoidance of triggering factors and management of peri-operative carcinoid crisis. During tumour handling patient developed carcinoid crisis which was effectively treated with intravenous bolus octreotide and increasing rate of infusion.

Islet cell transplantation for the treatment of type 1 diabetes: recent advances and future challenges

Islet transplantation is a well-established therapeutic treatment for a subset of patients with complicated type I diabetes mellitus. Prior to the Edmonton Protocol, only 9% of the 267 islet transplant recipients since 1999 were insulin independent for >1 year. In 2000, the Edmonton group reported the achievement of insulin independence in seven consecutive patients, which in a collaborative team effort propagated expansion of clinical islet transplantation centers worldwide in an effort to ameliorate the consequences of this disease. To date, clinical islet transplantation has established improved success with insulin independence rates up to 5 years post-transplant with minimal complications. In spite of marked clinical success, donor availability and selection, engraftment, and side effects of immunosuppression remain as existing obstacles to be addressed to further improve this therapy. Clinical trials to improve engraftment, the availability of insulin-producing cell sources, as well as alternative transplant sites are currently under investigation to expand treatment. With ongoing experimental and clinical studies, islet transplantation continues to be an exciting and attractive therapy to treat type I diabetes mellitus with the prospect of shifting from a treatment for some to a cure for all.

Revascularization of transplanted pancreatic islets and role of the transplantation site

Since the initial reporting of the successful reversal of hyperglycemia through the transplantation of pancreatic islets, significant research efforts have been conducted in elucidating the process of revascularization and the influence of engraftment site on graft function and survival. During the isolation process the intrinsic islet vascular networks are destroyed, leading to impaired revascularization after transplant. As a result, in some cases a significant quantity of the beta cell mass transplanted dies acutely following the infusion into the portal vein, the most clinically used site of engraftment. Subsequently, despite the majority of patients achieving insulin independence after transplant, a proportion of them recommence small, supplemental exogenous insulin over time. Herein, this review considers the process of islet revascularization after transplant, its limiting factors, and potential strategies to improve this critical step. Furthermore, we provide a characterization of alternative transplant sites, analyzing the historical evolution and their role towards advancing transplant outcomes in both the experimental and clinical settings.

Somatostatin adjunctive therapy for non-variceal upper gastrointestinal rebleeding after endoscopic therapy

AIM: To evaluate the effect of pantoprazole with a somatostatin adjunct in patients with acute non-variceal upper gastrointestinal bleeding (NVUGIB).

METHODS: We performed a retrospective analysis of a prospective database in a tertiary care university hospital. From October 2006 to October 2008, we enrolled 101 patients with NVUGIB that had a high-risk stigma on endoscopy. Within 24 h of hospital admission, all patients underwent endoscopic therapy. After successful endoscopic hemostasis, all patients received an 80-mg bolus of pantoprazole followed by continuous intravenous infusion (8 mg/h for 72 h). The somatostatin adjunct group (n = 49) also received a 250-μg bolus of somatostatin, followed by continuous infusion (250 μg/h for 72 h). Early rebleeding rates, disappearance of endoscopic stigma and risk factors associated with early rebleeding were examined.

RESULTS: Early rebleeding rates were not significantly different between treatment groups (12.2% vs 14.3%, P = 0.766). Disappearance of endoscopic stigma on the second endoscopy was not significantly different between treatment groups (94.2% vs 95.9%, P = 0.696). Multivariate analysis showed that the complete Rockall score was a significant risk factor for early rebleeding (P = 0.044, OR: 9.080, 95% CI: 1.062-77.595).

CONCLUSION: The adjunctive use of somatostatin was not superior to pantoprazole monotherapy after successful endoscopic hemostasis in patients with NVUGIB.

Overexpression of SIRT1 in mouse forebrain impairs lipid/glucose metabolism and motor function

SIRT1 plays crucial roles in glucose and lipid metabolism, and has various functions in different tissues including brain. The brain-specific SIRT1 knockout mice display defects in somatotropic signaling, memory and synaptic plasticity. And the female mice without SIRT1 in POMC neuron are more sensitive to diet-induced obesity. Here we created transgenic mice overexpressing SIRT1 in striatum and hippocampus under the control of CaMKIIα promoter. These mice, especially females, exhibited increased fat accumulation accompanied by significant upregulation of adipogenic genes in white adipose tissue. Glucose tolerance of the mice was also impaired with decreased Glut4 mRNA levels in muscle. Moreover, the SIRT1 overexpressing mice showed decreased energy expenditure, and concomitantly mitochondria-related genes were decreased in muscle. In addition, these mice showed unusual spontaneous physical activity pattern, decreased activity in open field and rotarod performance. Further studies demonstrated that SIRT1 deacetylated IRS-2, and upregulated phosphorylation level of IRS-2 and ERK1/2 in striatum. Meanwhile, the neurotransmitter signaling in striatum and the expression of endocrine hormones in hypothalamus and serum T3, T4 levels were altered. Taken together, our findings demonstrate that SIRT1 in forebrain regulates lipid/glucose metabolism and motor function.

Microscopic anatomy of the human islet of Langerhans

Human islets of Langerhans are complex micro-organs responsible for maintaining glucose homeostasis. Islets contain five different endocrine cell types, which react to changes in plasma nutrient levels with the release of a carefully balanced mixture of islet hormones into the portal vein. Each endocrine cell type is characterized by its own typical secretory granule morphology, different peptide hormone content, and specific endocrine, paracrine, and neuronal interactions. During development, a cascade of transcription factors determines the formation of the endocrine pancreas and its constituting islet cell types. Differences in ontogeny between the ventrally derived head section and the dorsally derived head, body, and tail section are responsible for differences in innervation, blood supply, and endocrine composition. Islet cells show a close topographical relationship to the islet vasculature, and are supplied with a five to tenfold higher blood flow than the exocrine compartment. Islet microanatomy is disturbed in patients with type 1 diabetes, with a marked reduction in beta-cell content and the presence of inflammatory infiltrates. Histopathological lesions in type 2 diabetes are less pathognomonic with a more limited reduction in beta-cell content and occasional deposition of amyloid in the islet interstitial space.

The effects of somatostatin in the polycystic ovary syndrome

Eighteen obese women (body mass index 30 +/- 6.1 kg/m2) with hyperinsulinaemia and with the polycystic ovary syndrome took octreotide at the dose of 100 mug s.c. The effect of the drug was assessed on plasma levels of gonadotropins luteinising hormone (LH), follicle stimulating hormone (FSH), of insulin, insulin-like growth factor-1 (IGF-1), androstenedione, testosterone, dehydroepiandrosterone sulphate (DHEAS), sex hormone binding globulin (SHBG) and insulin-like growth factor-binding protein-3 (IGFBP-3). Octreotide significantly reduced LH (31.8%), insulin (52%), IGF-1 (14%), androstenedione (22.6%) and testosterone (20%) and increased IGFBP-3 (25%).

[Orthostatic and postprandial hypotension in elderly patients with chronic diseases and disability: prevalence and related factors]

INTRODUCTION

To assess the prevalence of orthostatic hypotension (OH) and postprandial hypotension (PPH) in patients admitted to an intermediate care unit, as well as to analyze the characteristics of these patients.

PATIENTS AND METHODS

Sixty patients were analyzed according to the following criteria: age >65 years, able to take food orally, stand up and/or sit down, and clinically stable. A comprehensive geriatric assessment was carried out and the main diagnosis and the presence of autonomic neuropathy symptoms (ANS) were registered. Blood pressure (BP) was registered in the morning in supine position during the first 3min of postural change (standing or sitting). OH was defined as a decrease in systolic blood pressure (SBP) of 20mm Hg or a decrease in diastolic blood pressure (DBP) of 10mmHg. BP was registered after 15min of sitting and 60min after breakfast. PPH was defined as a decrease in SBP of 20mmHg.

RESULTS

The mean age was 79.1+/-7.8 years. Nine patients (15%) had OH and 29 (48.3%) had PPH. The mean Lawton index (LI) score in patients with OH was 3.1+/-2.1 and was 5.2+/-2.6 in the remaining patients (P<.02). The mean body mass index (BMI) was 23.3+/-3.1 vs. 26.2+/-5.1 (P<.04). ANS was present in all nine patients (100%) with OH but in only 30 (58.8%) of the remaining 51 patients (chi-square=5.71; P<.03).

CONCLUSIONS

PPH was more frequent than OH. Patients with OH had a significantly lower LI score and BMI. The presence of ANS was significantly more frequent in patients with OH. There was no significant relationship between HO and PPH or among the remaining variables studied.

Acute variceal hemorrhage

Variceal bleeding is a frequent and life-threatening complication of portal hypertension. The first episode of variceal bleeding is associated not only with a high mortality, but also with a high recurrence rate in those who survive. Therefore, management should focus on different therapeutic strategies aiming to prevent the first episode of variceal bleeding (primary prophylaxis), to control hemorrhage during the acute bleeding episode (emergency treatment), and to prevent rebleeding (secondary prophylaxis). These strategies involve pharmacological, endoscopic, surgical, and interventional radiological modalities. This article reviews management of acute variceal bleeding.

Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ

This review focuses on the role of the peripheral nervous system in cutaneous biology and disease. During the last few years, a modern concept of an interactive network between cutaneous nerves, the neuroendocrine axis, and the immune system has been established. We learned that neurocutaneous interactions influence a variety of physiological and pathophysiological functions, including cell growth, immunity, inflammation, pruritus, and wound healing. This interaction is mediated by primary afferent as well as autonomic nerves, which release neuromediators and activate specific receptors on many target cells in the skin. A dense network of sensory nerves releases neuropeptides, thereby modulating inflammation, cell growth, and the immune responses in the skin. Neurotrophic factors, in addition to regulating nerve growth, participate in many properties of skin function. The skin expresses a variety of neurohormone receptors coupled to heterotrimeric G proteins that are tightly involved in skin homeostasis and inflammation. This neurohormone-receptor interaction is modulated by endopeptidases, which are able to terminate neuropeptide-induced inflammatory or immune responses. Neuronal proteinase-activated receptors or transient receptor potential ion channels are recently described receptors that may have been important in regulating neurogenic inflammation, pain, and pruritus. Together, a close multidirectional interaction between neuromediators, high-affinity receptors, and regulatory proteases is critically involved to maintain tissue integrity and regulate inflammatory responses in the skin. A deeper understanding of cutaneous neuroimmunoendocrinology may help to develop new strategies for the treatment of several skin diseases.

Can somatostatin control acute bleeding from oesophageal varices in Schistosoma mansoni patients?[ISRCTN63456799]

BACKGROUND

Management of patients with bleeding oesophageal varices comprises of mainly diagnostic endoscopy, sclerotherapy and band ligation. One of the major problems to do any of the above is the active bleeding which makes any intervention difficult. The neuropeptide hormone somatostatin administered exogenously has caused a reduction in portal hypertension and variceal bleeding in patients suffering from liver cirrhosis. We believe that the symptomatic use of somatostatin for variceal bleeding in Schistosoma mansoni infected subjects can reduce bleeding, thereby alleviating the pathology caused by schistosomiasis.

METHODS/DESIGN

We herein present a study protocol for establishing this neuropeptide as a potential therapeutic agent in schistosomiasis. Adolescent subjects, age range varying from 12-17 years will be selected, based on several inclusion criteria, most important being infection with Schistosoma mansoni with bleeding from oesophageal varices in the last 24 hours. One group of schistosomiasis patients will be treated with somatostatin and praziquantel, the other with propanolol and praziquantel. Survival graphs will be set up to correlate somatostatin administration with survival time. A two part questionnaire will be set up to control treatment outcomes. The pre-treatment part of the clinical questionnaire will identify inclusion criteria questions, the post-treatment part of the questionnaire will identify treatment outcomes.

DISCUSSION

We expect that the administration of somatostatin as a bolus followed by a 24 hour long infusion, will stop bleeding immediately, delay rebleeding as compared to the control study group and delay mortality in the somatostatin treated subjects.

Gastrointestinal motility disturbances in celiac disease

It is quite frequent to recognize celiac patients who show gastrointestinal motor abnormalities in clinical practice. In fact, in 30 to 60% of patients, physical examination and dyspeptic symptoms (epigastric discomfort, early satiety) suggest a gastrointestinal motility disorder. Consistent data are now available on the presence of a disturbed motility of the esophagus, stomach, small intestine, gallbladder, and colon of untreated celiac patients. Gastrointestinal abnormalities differ in different gastrointestinal districts. In fact, esophageal transit, gastric and gallbladder emptying, and orocecal transit time are delayed, while colonic transit is faster. These findings are related to the complex interactions among reduced absorption of food constituent (in particular, fat), neurologic alteration, and hormonal derangement. Motility disorders of the gut are also a predisposing factor in the development of small intestinal bacterial overgrowth and may contribute both to development of symptoms in some untreated celiacs and to the persistence of symptoms after gluten-free diet in some of them. All these alterations fortunately disappear after gluten-free diet, and patients return to well being status. Whatever the initial event in the pathogenesis of the celiac lesions may be, we know for certain at this time that gastrointestinal disturbances play an important role in the genesis of gastrointestinal symptoms in celiac disease and that surveillance for celiac disease in patients complaining of dysmotility-like dyspeptic symptoms should be increased.

Circulating levels of the neuropeptide hormone somatostatin may determine hepatic fibrosis in Schistosoma mansoni infections

The neuropeptide hormone somatostatin reduces fibrosis and Schistosoma-caused clinical morbidity in the rodent model. In our study we aimed to delineate an association between fibrosis and the inability to generate critical levels of endogenous somatostatin in S. mansoni infected subjects. In June 2001, 85 subjects from the district dispensary at Richard Toll in the Medical Region of Saint-Louis, Senegal, were selected. Fifty-seven subjects were infected with S. mansoni of whom 32 were suffering from severe morbidity (SM). Twenty-eight subjects showed an inactive disease status with no evident infection at the actual time of study. All subjects were classified according to age, sex, occupation, height, weight, and parasite eggs per gram. All 85 participated in a water contact and morbidity questionnaire, underwent a clinical examination and donated 5ml of peripheral blood for detecting plasma levels of somatostatin. Ultrasonography detected fibrosis grade in all the subjects. To address whether inherent somatostatin levels determined clinically evident disease severity (epg, hepatomegaly, splenomegaly, hematemesis, ascites), the mean somatostatin values of the inactive disease status group and severe morbidity group were compared. Low somatostatin levels were depicted in subjects with severe morbidity symptoms associated with schistosomiasis as compared to exposed but inactive disease status subjects residing in the same region. Logistic regression analysis indicated that with decreasing somatostatin values the probability of severe morbidity increased with age being a confounding factor. To address whether inherent somatostatin levels determined fibrosis and if this association was significant, plasma somatostatin levels of non-fibrotics (ultrasonographic grading A), and fibrotics (ultrasonographic grading B-E) were compared. In all age groups as well as in adults alone, mean somatostatin levels were higher in the non-fibrotic group as compared to the fibrotics group, the difference being significant. The group B comprised of borderline fibrotic cases, therefore a separate analysis was done between groups A (non-fibrotics) and groups C, D (confirmed fibrotics). Mean somatostatin values were higher in the non-fibrotic group as compared to the fibrotics group, the difference being borderline significant. In schistosomiasis patients, circulating levels of somatostatin by binding to hepatic stellate cells (HSC) may modulate fibrosis. This phenomenon is regulated by age whereas gender and prior treatment have no effect on this association. Host specific somatostatin levels may create a 'preset environment' status that can determine progression to severe fibrosis.

Somatostatin and intestinal schistosomiasis: therapeutic and neuropathological implications in host-parasite interactions

A better insight into the mechanisms regulating the human body can lead to improved knowledge of the patho-physiological processes of many diseases. New therapeutic possibilities can be devised at the level of these regulatory mechanisms. Somatostatin is one of the major regulatory hormones in the central nervous system (CNS) and digestive system. Its wide variety of activities means it is implicated in a broad range of conditions. One symptom common to both the acute and chronic stages of schistosomiasis is intestinal pathology characterized by abdominal pain, diarrhoea that is bloody in more chronic stages, nausea and fever. Some chronic patients develop severe hepatosplenic fibrosis, leading to fatal oesophageal variceal bleeding. In this review we assess the therapeutic potential of somatostatin in the treatment of intestinal pathology associated with schistosomiasis. The activity of somatostatin is mediated via binding to specific cell surface receptors. While we are making progress in studies of the expression and regulation of the different somatostatin receptors, the true role and distribution of each receptor subtype is far from fully understood. Animal models will help to define the specific role of individual receptors in physiological and pathological conditions. The regulation of receptor expression as well as receptor internalization can give us insight into the effect of exogenous somatostatin on schistosomiasis-mediated intestinal pathology, as well as its modulation by intrinsically produced somatostatin levels.

The role of somatostatin in schistosomiasis: a basis for immunomodulation in host-parasite interactions?

This review explores the possible modulatory role of the neuropeptide somatostatin in the outcome of Schistosoma-caused morbidity in man. Somatostatin could play an important role in Schistosoma mansoni-man interactions via its influence on intersystem signalling; therapeutically, via its direct effect on Schistosoma-caused morbidity (fibrosis, granuloma size, portal hypertension, variceal bleeding); and via immunomodulation of Schistosoma-induced inflammatory responses in the liver and intestines. In schistosomiasis-endemic regions two interesting patterns of infection emerge. First, the intensity of infection is higher in children than in adults; secondly, at any given time, only a fraction of Schistosoma-infected individuals develop Symmer's pipe-stem fibrosis. These morbidity patterns cannot be explained on the basis of acquired immunity alone. Somatostatin has an inhibitory effect on hormone, immune and physiological body functions like growth hormone secretion, Interferon (IFN) gamma production, collagen I and III formation and hepatic stellate cell activation. Levels of somatostatin secreted endogenously by man upon the onset of Schistosoma infection may be one factor regulating the activity of the above, and thereby fibrosis in the host. The neuropeptide hormone somatostatin may determine pre-disposition to Schistosoma-caused morbidity.

Esophageal varices. I. Clinical presentation, medical therapy, and endoscopic therapy

The last half century has witnessed great advances in the understanding of the pathogenesis and natural history of portal hypertension in cirrhotics. Several pharmacologic and endoscopic techniques have been developed for the treatment of portal hypertension. The use of these agents in a given patient must be based on an understanding of the stage in the natural history of the disease and the relative efficacy and safety of the available treatment options.

Gastric emptying and plasma neurotensin levels in untreated celiac patients

BACKGROUND

Upper gastrointestinal motor abnormalities could account for some of the dyspeptic symptoms of celiac patients. However, the data on gastric emptying time are conflicting, and the pathophysiology of motor disturbances is still unclear. Neurotensin modulates upper gastrointestinal motor activity, and its postprandial increase is a reliable index of nutrient delivery to the ileum. We therefore assessed both plasma neurotensin levels and gastric emptying in untreated celiacs.

METHODS

The gastric antral area of nine untreated celiac patients and nine controls was measured with ultrasound at base line and every 30 min after a fatty meal (227 kcal, 45% fat); the base-line and postprandial neurotensin plasma levels were determined by means of radioimmunoassay. The data are mean values +/- standard deviation and were analyzed by using non-parametric tests.

RESULTS

The overall and half gastric emptying time were significantly longer in the patients (203+/-32 versus 133+/-15 min, P = 0.0117, and 137+/-32 versus 78+/-11 min, P = 0.0001). The pattern of the changes in antral area was similar in both groups during the observation period as a whole but differed significantly in the first 120 min (P = 0.0343). Base-line neurotensin levels were significantly higher in the patients (41.6+/-23.9 versus 18.2+/-5.5 pg/ml, P = 0.0214) and their net postprandial increase was lower than in controls (15.0+/-15.9 versus 29.8+/-13.0 pg/ml, P = 0.046). In both groups the base-line neurotensin levels were related to the half gastric emptying time (P = 0.023).

CONCLUSIONS

In untreated celiac patients gastric emptying time is longer than in controls and is concomitant with an increase in base-line plasma neurotensin levels.

The adverse effects of octreotide on the healing of colonic anastomoses in rats

Octreotide, a long-acting somatostatin analogue, is widely used in gastrointestinal hypersecretory states and also for endocrine tumors in an attempt to inhibit the paracrine hormones. Although it is well known that octreotide inhibits trophic and anabolic hormones, no research has been conducted on its adverse effects on wound healing. In the present study, groups of rats were given 20 mcg/kg/day octreotide and 100 mg/kg/day hydrocortisone, the latter being the negative control group, starting 5 days preoperatively. The colonic anastomoses were assessed for healing on postoperative days (PODs) 5 and 8 by determining the bursting pressure of the anastomoses, performing histopathological analysis, and measuring the hydroxyproline content of the anastomotic tissues. Octreotide was found to affect anastomotic healing negatively on both PODs 5 and 8, but the negative effect of hydrocortisone was significant only on POD 8. No significant difference was found between the adverse effects of the two agents on POD 8. These findings indicated that octreotide has an adverse effect on the healing of colonic anastomoses in rats.

A novel recognition site for somatostatin-14 on the GABA(A) receptor complex

Functional interactions between gamma-aminobutyric acid (GABA) and somatostatin are suggested by the presence of synaptic contacts between GABA and somatostatin neurons, colocalisation of GABA and somatostatin and reciprocal modulation of somatostatin and GABA release. Nevertheless, a direct interaction of somatostatin with the GABA(A) receptor complex has not yet been investigated. A quantitative autoradiographic technique was used to determine the ability of somatostatin to interact with the [35S]t-butylbicyclophosphothionate [35S]TBPS binding sites of the GABA(A) receptor complex: somatostatin inhibited [35S]TBPS binding with IC50 values in the micromolar range in all brain regions studied. These results demonstrate for the first time a direct interaction between somatostatin and the GABA(A) receptor complex.

Gastrointestinal hormones in short bowel syndrome. Peptide YY may be the 'colonic brake' to gastric emptying

BACKGROUND

Short bowel patients with a jejunostomy have large volume stomal outputs, which may in part be due to rapid gastric emptying of liquid. Short bowel patients with a preserved colon do not have such a high stool output and gastric emptying of liquid is normal.

AIMS

To determine if differences in the gastric emptying rate between short bowel patients with and without a colon can be related to gastrointestinal hormone changes after a meal.

SUBJECTS

Seven short bowel patients with no remaining colon (jejunal length 30-160 cm) and six with jejunum in continuity with a colon (jejunal length 25-75 cm), and 12 normal subjects.

METHODS

The subjects all consumed a 640 kcal meal; blood samples were taken for 180 minutes for measurement of gastrointestinal hormones.

RESULTS

Patients with a colon had high fasting peptide YY values (median 71 pmol/l with a colon; 11 pmol/l normal subjects, p < 0.005) with a normal postprandial rise, but those without a colon had a low fasting (median 7 pmol/l, p = 0.076) and a reduced postprandial peptide YY response (p < 0.050). Motilin values were high in some patients without a colon. In both patient groups fasting and postprandial gastrin and cholecystokinin values were high while neurotensin values were low. There were no differences between patient groups and normal subjects in enteroglucagon, pancreatic polypeptide, or somatostatin values.

CONCLUSIONS

Low peptide YY values in short bowel patients without a colon may cause rapid gastric emptying of liquid. High values of peptide YY in short bowel patients with a retained colon may slow gastric emptying of liquid and contribute to the "colonic brake'.

Prevalence of Helicobacter pylori in acromegalic patients during treatment with octreotide

BACKGROUND

Octreotide, a synthetic long-acting analogue of somatostatin, now has an established role in the treatment of acromegaly. In acromegalic patients treated with octreotide there is an increased incidence of gallstones and possibly gastritis.

OBJECTIVES

(1) To compare the seroprevalence of Helicobacter pylori (H. pylori) infection, in acromegalic patients treated with octreotide to that in patients given other treatment modalities. (2) To study retrospectively the temporal relation between H. pylori acquisition and octreotide treatment.

PATIENTS

Three groups of acromegalic patients were studied; 35 (20 M) had been treated with octreotide, 17 (10 M) with bromocriptine and 19 (12 M) had received no pharmacological intervention (untreated, surgically treated or treated with radiotherapy).

DESIGN/MEASUREMENTS

The presence of H. pylori infection was assessed serologically (Bio-Rad GAP test for IgG), using stored serum, on the most recent sample from each patient and on serial samples from patients treated with octreotide.

RESULTS

The prevalence of H. pylori seropositivity was similar in each treatment group, 34, 35 and 37%, respectively. Mean age and duration of acromegaly were similar in the first two groups. Patients who had never received medical treatment were slightly younger. GH levels were similar in all three groups. Patients on octreotide who were seropositive for H. pylori did not differ from those with negative serology with respect to age, duration of acromegaly, duration of octreotide treatment or serum GH level. Serial samples in octreotide treated patients showed a change in status in only one patient; 18 patients continued with negative serology during a mean period of 30 (range 4-62) months. In each of the 6 patients with persistently positive serology during octreotide treatment, stored samples predating octreotide therapy were shown to have already been positive.

CONCLUSIONS

The seroprevalence of H. pylori infection in acromegalic patients does not appear to be increased in a manner dependent on the type or duration of medical treatment. In particular, octreotide therapy, while causing the development of histological gastritis in some patients, does not appear to induce the development of H. pylori infection.

Early inhibition of myointimal proliferation by angiopeptin after balloon catheter injury in the rabbit

PURPOSE

Coronary artery restenosis after percutaneous transluminal angioplasty occurs in more than 40% of patients. Angiopeptin, a stable synthetic octapeptide analogue of somatostatin, attenuates accelerated coronary artery myointimal thickening in rabbit cardiac allografts and myointimal thickening after arterial injury. In this study the temporal relationship between the angiopeptin treatment schedule and efficacy was explored. The relationship between inhibition of myointimal thickening by angiopeptin and inhibition of vascular cell proliferation was also examined.

METHODS

The aorta and the common and external iliac arteries of the rabbit underwent balloon injury. Angiopeptin (2 to 200 micrograms/kg/day) was administered for 1 day before injury and for 1, 5, and 21 days after injury. Morphometric studies were performed to determine measurement of intimal thickening. Inhibition of vascular cell proliferation by angiopeptin was evaluated by tritiated thymidine incorporation into the balloon-injured rabbit aorta. Thymidine was either administered intraperitoneally or added ex vivo to aorta segments of rabbits treated with angiopeptin (2, 20, or 200 micrograms/kg/day) from 1 day before injury until sacrifice 72 hours later.

RESULTS

Administration of angiopeptin (2 to 200 micrograms/kg/day) significantly reduced intimal thickening by approximately 50% in all three vessels when evaluated 3 weeks after injury. This inhibitory effect was unrelated to duration of treatment and dose. Treatment initiated at the time of injury was found to be effective, but delaying treatment for 8, 18, or 27 hours abrogated the inhibitory effect of angiopeptin on myointimal thickening. Angiopeptin treatment significantly decreased thymidine-labeled nuclei of smooth muscle cells in vitro. Angiopeptin treatment similarly inhibited thymidine uptake in vitro by balloon-injured aorta segments.

CONCLUSION

Angiopeptin significantly inhibits myointimal thickening by inhibiting vascular cell proliferation. Administration of angiopeptin for 2 days is as efficacious as 3 weeks treatment in inhibiting myointimal thickening. Delaying treatment for as little as 8 hours after injury abrogates the inhibitory effects of angiopeptin. This speaks to the importance of early events immediately after vascular tissue injury, suggesting that angiopeptin inhibits the expression of early genes causally related to the vascular injury response and thereby triggering vascular cell proliferation.

Calcitonin, as SMS 201-995, ameliorates the VIPoma syndrome

A 72-year-old woman was referred to our hospital for diarrhea, abdominal and back pain, weight loss, low serum potassium level. Pathological findings and high circulating Vasoactive Intestinal Peptide (VIP) levels allowed us to diagnose "VIPoma syndrome". The patient underwent a treatment with SMS 201-995 with improvement of symptomatology and reduction of circulating VIP levels. After a wash-out period the patient was treated with salmon calcitonin with a net improvement of diarrhea, normalization of potassium serum level and reduction of VIP level. The symptomatology recurred after calcitonin withdrawal. These data confirm the effectiveness of SMS 201-995 in the VIPoma syndrome and suggest that calcitonin may ameliorate symptomatology and reduce circulating VIP level in patients with VIPoma tumor.

Effect of cysteamine on insulin release and exocrine pancreatic secretion in vitro

Cysteamine is known to deplete somatostatin from pancreatic D cells. In the isolated perfused rat pancreas we investigated its effects on somatostatin and insulin release as well as exocrine pancreatic secretion in the presence of 16.7 mM glucose and 180 pM CCK-8. At a concentration of 0.1 mM, cysteamine had no significant effect on pancreatic endocrine and exocrine functions. At 10 mM, however, cysteamine released somatostatin (380 +/- 70 vs 100 +/- 20 fmol/20 min), inhibited insulin output (890 +/- 120 vs 13210 +/- 3260 mu units/20 min) and reduced exocrine pancreatic secretion (volume: 12 +/- 2 vs 20 +/- 2 microliters/20 min; lipase: 31 +/- 3 vs 60 +/- 7 units/20 min). We conclude that the complex changes induced by cysteamine are consistent with a physiological role of endogenous somatostatin in the regulation of insulin release. The reduction of exocrine pancreatic secretion, however, was at least in part, if not completely, mediated via the insuloacinar axis rather than a direct effect of cysteamine-released somatostatin on pancreatic acinar cells.

Prevalence of gastritis in patients with acromegaly: untreated and during treatment with octreotide

OBJECTIVE

It has previously been suggested that acromegalic patients treated with the somatostatin analogue octreotide invariably have chronic gastritis. We have examined the prevalence of gastritis in a large group of acromegalic patients, untreated and during treatment with octreotide.

DESIGN

We studied three groups of acromegalic patients: (A) untreated; (B) octreotide-treated; (C) a subgroup of these studied both before and during octreotide therapy.

PATIENTS

Forty-eight patients, grouped as above, with active acromegaly were examined for the presence of gastritis.

MEASUREMENTS

Gastroscopy and histological examination of gastric biopsies for the presence of gastritis and Helicobacter organisms were undertaken. The principal outcome was quantification of the prevalence of gastritis in the various study groups.

RESULTS

Group A: 10 of the 33 patients (30%) had gastritis before any therapy with octreotide. Group B: 17 of 36 patients (47%) on octreotide treatment for 6-59 months (mean 20.5) had gastritis, and this was present in five out of the sub-group of eight patients (62%) treated for over 3 years. Group C: three of 21 patients (14%) developed gastritis during treatment with octreotide for between 6 and 23 months (mean 12.4). There was a highly significant association between the presence of gastritis and the presence of Helicobacter pylori organisms.

CONCLUSIONS

Octreotide therapy of acromegaly may predispose to the development of gastritis, but this remains statistically unproven. Certainly, gastritis is not an invariable consequence of octreotide therapy, even after prolonged periods of treatment. The presence of gastritis is associated with H. pylori infection.

Therapeutic response to somatostatin analogue, BIM 23014, in metastatic prostatic cancer

Metastatic prostate cancer is well known to respond to hormonal manipulations, but once progression occurs new treatment modalities are required. Specific and systemic antitumour therapy is preferable to local treatments such as radiotherapy in such patients. The finding that somatostatin analogue, BIM 23014, inhibits prostatic tumour growth in animal models is of great interest. We treated 25 poor risk patients with progressive metastatic prostate cancer. Sixteen had also failed to respond to 'total androgen blockade'. Two patients have achieved a partial remission, one of which is maintained at over 30 months, and three had stable disease for over 6 months. Side effects have consisted of mild diarrhoea and abdominal cramp in the first few days of treatment in a minority of the patients. These results are encouraging and further randomized studies are in progress.

Cytotoxic and cytostatic effects of antitumor agents induced at the plasma membrane level

A variety of antitumor agents inhibit cell proliferation by interacting with the plasma membrane. They act as growth factor antagonists, growth factor receptor blockers, interfere with mitogenic signal transduction or exert direct cytotoxic effects. The P-glycoprotein encoded by the MDR1 gene represents a transmembrane protein which catalyzes the efflux of various antitumor agents. This membrane protein is the target of compounds acting as Multi-Drug Resistance (MDR)-modulators. Finally, several established antitumor agents which are considered to represent DNA-targeted drugs, including anthracyclines, platinum complexes and alkylating agents, cause a variety of membrane lesions. Their contribution to the antitumor activity of these drugs is discussed.

Experimental and clinical studies with somatostatin analogue octreotide in small cell lung cancer

We have detected somatostatin receptors (SSR) by autoradiography in 3/4 established small cell lung cancer (SCLC) cell lines but not in two non-SCLC cell lines. The growth of 1/3 SSR positive SCLC cell lines was significantly inhibited by the long-acting somatostatin analogue octreotide (SMS 201-995, Sandostatin) 10(-9) M. We treated 20 SCLC patients with octreotide 250 micrograms three times daily for 1 week prechemotherapy (six patients) or at relapse after chemotherapy (14). Octreotide was well tolerated, and serum insulin-like growth factor-I levels were suppressed to 62 +/- 7% of pre-treatment levels. However there was no evidence of anti-tumour activity measured by tumour bulk or serum levels of neuron-specific enolase. In one patient metastatic skin nodules were shown to be SSR positive before and at the end of 2 weeks octreotide. Despite this the patient had progressive disease, and tumour cells obtained by fine needle aspirate before and after treatment showed no growth inhibition when cultured with octreotide immediately or following establishment as a cell line. In summary we saw little correlation between SSR expression and growth inhibition by octreotide, either in vitro or clinically.

Somatostatin analogue RC-160 inhibits the growth of transplanted colon cancer in rats

The effect of somatostatin analogue RC-160 on the growth of DHD/K12 rat colon cancer has been investigated in vivo as well as in vitro. Twenty syngeneic BDIX rats with s.c. implanted tumors were divided randomly into 2 groups. The rats from each group received a daily s.c. injection of either RC-160 (100 micrograms/kg/day) or injection vehicle as control for 37 days starting from the day of tumor inoculation. Tumor volumes were measured every 3-4 days. At the end of the treatment, the mean tumor volume was 504.5 +/- 97.0 mm3 in the control group and 177.8 +/- 60.5 mm3 in the RC-160 treated group (p less than 0.01). The tumor volume doubling time was calculated to be 11 days in the control group and 13.5 days in the RC-160 group, respectively. The tumor growth delay time was 18 days. Using bromodeoxyuridine labelling in vivo, the mean labelling index in the tumors was decreased by 35% (p less than 0.01) after RC-160 treatment. Total protein and total DNA contents in the tumors were decreased by 70.1% (p less than 0.05) and 68.7% (p less than 0.05), respectively. The data indicate that somatostatin analogue RC-160 inhibits the growth of DHD/K12 colon cancer in vivo. In 2 studies in vitro, DHD/K12 cells were cultured for 72 hr with RC-160 and natural somatostatin-14 (S-S-14) at concentrations ranging from 62.5 ng/ml to 2,000 ng/ml. Tumor-cell growth was measured spectrophotometrically by the crystal violet staining assay. No direct effect on tumor cell growth in vitro was observed with either RC-160 or S-S-14, possibly because of the loss of somatostatin receptors in previous passages of the DHD/K12 cell line.

Pharmacokinetics of the long-acting somatostatin analogue octreotide (SMS 201-995) in acromegaly

A single-dose study was performed to examine the pharmacokinetics of subcutaneous octreotide in acromegalic patients and to investigate the relationship between growth hormone and the elimination half-life of the drug. Fourteen acromegalic patients (six men and eight women; age range 35-59 years) who had previously received conventional treatment were studied. Two subjects were on long-term octreotide which had been discontinued 72 h before the study. Octreotide 100 micrograms was administered subcutaneously and plasma samples taken every 10 min for 1 h and then hourly for up to 8 h. Growth hormone was measured at 0, 2 and 8 h. Octreotide was rapidly absorbed with a mean (+/- SEM) t1/2abs of 5.4 min (+/- 0.8) peaking at a mean plasma concentration of 3.4 nmol/l (+/- 0.2) in 27.4 min (+/- 3.7). The monoexponential elimination phase had a mean half-life of 110 min (+/- 9.6). The apparent volume of distribution was 29.4 1 (+/- 1.9) and total clearance was 172 ml/min (+/- 10.4). These results were similar to those obtained in normal volunteers. There was no simple relationship between the level of growth hormone and the half-life of octreotide. Growth hormone levels ranged from 2.5 to 34.0 mIU/l but were only greater than 10 mIU/l in three subjects. Further studies of octreotide pharmacokinetics are needed in untreated patients with acromegaly with raised growth hormone levels.

Effect of octreotide on mouth-to-caecum transit time in healthy subjects and in the irritable bowel syndrome

The effect of a single subcutaneous injection of octreotide (50 micrograms) on mouth-to-caecum transit time was determined in patients with the irritable bowel syndrome who complained of bowel frequency, and in healthy volunteers. The assessment of mouth-to-caecum transit time was performed by monitoring breath hydrogen concentration and noting a sustained 10 p.p.m. rise after ingestion of lactulose 40 ml. Measurements were performed fasting, and on a separate day, after a standard breakfast which included 40 ml lactulose. The studies were performed double-blind in a pre-determined random order. Octreotide prolonged mouth-to-caecum transit time in irritable bowel syndrome patients and healthy subjects by factors of 2.4 and 2.6 after lactulose when fasting, respectively, and by factors of 2.8 and 2.6 after the breakfast which contained lactulose. The upper gastrointestinal transit rate was similar in irritable bowel syndrome patients and healthy controls.

Clinical response to the long acting somatostatin analogue SMS 201-995 in a child with congenital microvillus atrophy

A 27 month old girl with congenital microvillus atrophy received two courses of SMS 201-995, a synthetic long acting analogue of native somatostatin, in an attempt to decrease profuse secretory diarrhoea. During the first trial at 13 months of age fluid and electrolytes administered by parenteral infusion were decreased as measured by water and faecal electrolyte losses. During the second trial of SMS 201-995 at 19 months fluid and electrolyte input were held constant for 14 days. Stool volume declined from 275 ml/kg to 161 ml/kg. Reductions in output of stool electrolytes (Na+, K+, Cl-) were accompanied by an increase in urine fluid output and increased excretion of urinary Na+. Subsequent administration of SMS 201-995 for a nine month period was not associated with adverse side effects or an impairment of growth velocity. These findings suggest that SMS 201-995 may be useful therapy in infants with high output diarrhoea as a result of congenital microvillus atrophy.

Somatostatin effect in postprandial hypoglycemia

The effect of the administration of oral glucose with or without a simultaneous intravenous somatostatin infusion on blood glucose, immunoreactive insulin, C-peptide, and glucagon levels in seven patients with idiopathic postprandial hypoglycemia was studied. Oral glucose alone induced an excessive insulin response and hypoglycemia, whereas a slight suppression in glucagon levels without any increase at the hypoglycemic nadir was observed. The simultaneous administration of somatostatin significantly reduced the insulin response and induced a slower rise of blood glucose; no hypoglycemia developed. Only minor variations in glucagon were observed with respect to the basal test. A rebound in insulin, C-peptide, and glucagon levels was observed at the end of the somatostatin infusion. These data show that somatostatin can suppress glucose-induced hypoglycemia in these subjects, thus suggesting that its long-acting analogues might be worth a therapeutic trial in severe idiopathic postprandial hypoglycemia.

The effects of octreotide, soy polysaccharide, codeine and loperamide on nutrient, fluid and electrolyte absorption in the short-bowel syndrome

Four agents, which could delay intestinal transit, were tested in six short-bowel patients (jejunal length 30-120 cm) on long-term nutritional/electrolyte replacement therapy. Intestinal transit time of a liquid test meal and nutrient, water and sodium absorption were measured during a control study and with each test agent on separate days. Soy polysaccharide tended to increase transit time, but decreased the absorption of water, sodium and nutrients. Codeine phosphate and loperamide caused inconsistent and clinically unimportant changes. Octreotide, a long-acting analogue of somatostatin, delayed transit and increased water, sodium and calorie absorption from the meal. Octreotide appears to have the potential to reduce the need for electrolyte and nutritional supplements in patients with the short-bowel syndrome.