The joint IAEA, EANM, and SNMMI practical guidance on peptide receptor radionuclide therapy (PRRNT) in neuroendocrine tumours

Peptide receptor radionuclide therapy (PRRNT) is a molecularly targeted radiation therapy involving the systemic administration of a radiolabelled peptide designed to target with high affinity and specificity receptors overexpressed on tumours. PRRNT employing the radiotagged somatostatin receptor agonists (90)Y-DOTATOC ([(90)Y-DOTA(0),Tyr(3)]-octreotide) or (177)Lu-DOTATATE ([(177)Lu-DOTA(0),Tyr(3),Thr(8)]-octreotide or [(177)Lu-DOTA(0),Tyr(3)]-octreotate) have been successfully used for the past 15 years to target metastatic or inoperable neuroendocrine tumours expressing the somatostatin receptor subtype 2. Accumulated evidence from clinical experience indicates that these tumours can be subjected to a high absorbed dose which leads to partial or complete objective responses in up to 30 % of treated patients. Survival analyses indicate that patients presenting with high tumour receptor expression at study entry and receiving (177)Lu-DOTATATE or (90)Y-DOTATOC treatment show significantly higher objective responses, leading to longer survival and improved quality of life. Side effects of PRRNT are typically seen in the kidneys and bone marrow. These, however, are usually mild provided adequate protective measures are undertaken. Despite the large body of evidence regarding efficacy and clinical safety, PRRNT is still considered an investigational treatment and its implementation must comply with national legislation, and ethical guidelines concerning human therapeutic investigations. This guidance was formulated based on recent literature and leading experts' opinions. It covers the rationale, indications and contraindications for PRRNT, assessment of treatment response and patient follow-up. This document is aimed at guiding nuclear medicine specialists in selecting likely candidates to receive PRRNT and to deliver the treatment in a safe and effective manner. This document is largely based on the book published through a joint international effort under the auspices of the Nuclear Medicine Section of the International Atomic Energy Agency.

Neuroendocrine tumors in children and young adults: Incidence, survival, and prevalence in the United States

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Background: Neuroendocrine tumors (NET) arising from the diffuse endocrine system are thought to be quite rare in children and young adults. However, a surprising number of young people have been referred to our neuroendocrine tumor clinic and the NCI has targeted NET as a high priority for development of new diagnostic and therapeutic options. This analysis of the SEER database was undertaken to determine the incidence, prevalence, and survival of NET in young people. Their incidence, prevalence, and survival were compared with neuroblastoma, a related pediatric malignancy arising in the neural crest. Methods: The SEER data were obtained from 9 standard SEER registries for the diagnosis years of 1975 to 2004 using SEER*Stat version 6.4.4. ICD-9 codes related to neuroendocrine tumors and to neuroblastoma were characterized as to patient age, gender, racial and ethnic background, stage, grade, histology, incidence, survival, and prevalence. Results: Neuroendocrine tumors occur more often in females among children and young adults with the most common sites being bronchial, ovarian, and breast. The overall incidence of neuroendocrine tumors was lower than for neuroblastoma in the age range 0–30 years. However, the 30 year limited prevalence of neuroendocrine tumors in the 9 SEER registries was 698 compared to 881 for neuroblastoma. This extrapolated to over 7000 children and young adults with neuroendocrine tumors across the United States. Survival rate of young people with neuroendocrine tumors declined from 84% in 1975–1986 to 80% in the 1987–2004 era. Conclusions: These results indicate that neuroendocrine tumors constitute an unrecognized cancer threat to children and young adults. Survival of children and young adults with neuroendocrine tumors has decreased over the past 30 years in the United States. We recommend the establishment of centers of care for children and young adults diagnosed with neuroendocrine tumors with the expectation that earlier diagnosis coupled with targeted therapies will decrease the incidence of metastatic disease and improve survival.

No significant financial relationships to disclose.

Localization of ectopic corticotropin-producing carcinoid tumor with use of indium-111 pentetreotide scintigraphy

OBJECTIVE

To report on the diagnosis of ectopic corticotropin (adrenocorticotropic hormone [ACTH])-producing bronchial carcinoid tumor by indium-111 pentetreotide (octreotide scan) scintigraphy.

METHODS

We present a case of ectopic ACTH syndrome caused by an occult bronchial carcinoid tumor arising in a lymph node and review the pertinent literature.

RESULTS

Biochemical diagnosis of ACTH syndrome can be difficult, and conventional imaging modalities often do not demonstrate these small carcinoid tumors. After biochemical proof of the presence of ectopic ACTH syndrome in our patient, conventional radiographic studies did not demonstrate any lesions. An octreotide scan showed a lesion in the lung, which was confirmed surgically. ACTH values returned to normal after resection of the lesion, and octreotide scans confirmed the completeness of surgical resection. The carcinoid tumor originated in a lymph node outside the bronchus. The differential diagnosis of ACTH syndrome, the localization of ectopic ACTH-producing tumors, the bronchial carcinoids, and the uniqueness of the carcinoid tumor arising in a lymph node are briefly discussed.

CONCLUSION

Octreotide scintigraphy is useful in localizing occult carcinoid tumors and can be used in the follow-up of patients after successful removal of these tumors.

Somatostatin receptor gene expression in human ocular tissues: RT-PCR and immunohistochemical study

PURPOSE

Somatostatin (SST) analogues have been used to treat proliferative diabetic retinopathy, pseudotumor cerebri, thyroid orbitopathy, and cystoid macular edema. There is a paucity of published data in regards to cell-specific distribution of SST receptors (SSTR) in normal human eye tissues. Gene expression for all five known SSTRs in normal human ciliary body/iris, retina, choroid, and cultured retinal pigment epithelial (RPE) cells were studied.

METHODS

mRNA was isolated from human ocular tissues (iris/ciliary body, retina, and choroid) dissected from eight pairs of normal eyes (9-62 years) and from RPE cells grown in culture. RT-PCR was done for all five SSTRs in all analyzed tissues. Immunohistochemistry for SSTR1 and SSTR2 was performed on eight pairs of normal human eyes (28-74 years) imbedded in paraffin.

RESULTS

SSTR1 to 5 genes are expressed in retina, SSTR1 and SSTR2 genes in cultured RPE cells, and SSTR1, 2, and 4 in ciliary body and choroid. SSTR1 and SSTR2 immunoreactivity (-ir) was observed on a variety of cells within all analyzed tissues including cornea, iris, trabecular meshwork, Schlemm's canal, ciliary processes, ciliary muscle, retina, choroid, cultured RPE cells, and optic nerve.

CONCLUSIONS

SSTR genes are widely expressed in normal human eye tissues, with genes for SSTR1 and SSTR2 being the most widely expressed. Genes for all SSTRs are expressed in retina. SSTR1-ir and SSTR2-ir were observed in all analyzed ocular tissues. Detailed knowledge of SSTRs distribution and function in the human eye will result in a better understanding of their role in health and disease.

Growing vascular endothelial cells express somatostatin subtype 2 receptors

We hypothesized that non-proliferating (quiescent) human vascular endothelial cells would not express somatostatin receptor subtype 2 (sst 2) and that this receptor would be expressed when the endothelial cells begin to grow. To test this hypothesis, placental veins were harvested from 6 human placentas and 2 mm vein disks were cultured in 0.3% fibrin gels. Morphometric analysis confirmed that 50-75% of cultured vein disks developed radial capillary growth within 15 days. Sst 2 gene expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of the RNA from veins before culture and from tissue-matched vein disks that exhibited an angiogenic response. The sst 2 gene was expressed in the proliferating angiogenic sprouts of human vascular endothelium. The presence of sst 2 receptors on proliferating angiogenic vessels was confirmed by immunohistochemical staining and in vivo scintigraphy. These results suggest that sst 2 may be a unique target for antiangiogenic therapy with sst 2 preferring somatostatin analogues conjugated to radioisotopes or cytotoxic agents.

Serum pancreastatin levels predict response to hepatic artery chemoembolization and somatostatin analogue therapy in metastatic neuroendocrine tumors

INTRODUCTION

Neuroendocrine tumors often metastasize to the liver and present with disabling hormonal symptoms. Hepatic artery chemoembolization (HACE) combined with somatostatin therapy, pre-embolization, peri-embolization and post-embolization, at doses to control symptoms, is an aggressive approach that can relieve hormonal symptoms with minimal morbidity and mortality.

METHODS

Chemoembolization was performed using 30 mg of adriamycin, 50 mg of mitomycin, 12 ml of hexabrix, 10 ml of ethiodol, and 360-500-microm particles. Pancreastatin, a split product of chromogranin A, was measured pre-HACE and post-HACE in all patients.

RESULTS

Forty-three chemoebolization procedures were performed in 34 symptomatic patients from December 1995 to August 1999. Seventeen patients had intestinal primaries (50%), seven had pancreatic primaries (20%), five had bronchial primaries (15%), and five had unknown primaries (15%). Systemic pancreastatin levels were improved or stable in 31 patients (78%). Symptoms were improved in these 31 patients (78%). Systemic serotonin levels were improved or stable in 24 patients (60%). Radiographic improvement or stability was seen in 18 patients (45%). Procedural related morbidity included pain, fevers, nausea, vomiting, and transient elevations of liver function studies in 75-100% of patients. There was one procedural related mortality (2%). Less than 20% improvement in pancreastatin levels from baseline was associated with death in five of five patients (100%). This was not observed with serotonin levels.

CONCLUSION

Measurement of serum pancreastatin levels is an easy and useful method to predict success in patients who undergo HACE plus somatostatin therapy for metastatic neuroendocrine tumors to the liver. This therapeutic approach is effective in relieving symptoms in 78% of patients, with minimal major morbidity or mortality.

Combination ACE inhibitor and angiotensin II receptor antagonist therapy in diabetic nephropathy

The benefit of angiotensin-converting enzyme (ACE) inhibitor (i) therapy in diabetic glomerulosclerosis is thought to be largely the result of attenuation of angiotensin II (AngII) effects on blood pressure, glomerular hemodynamics and hypertrophy, and tissue fibrosis. The present study was undertaken to determine whether the addition of AngII receptor antagonist therapy to ACEi therapy in diabetic nephropathy results in attenuation of AngII effects beyond that achieved by ACEi therapy alone. Seven patients were studied as inpatients on the General Clinical Research Center each for 3 consecutive weeks as follows: week 1, the patients' usual regimen which included daily oral moderate to high dose ACEi therapy; week 2, the patients' usual regimen plus oral losartan (an antagonist (a) of the angiotensin type 1 receptor, AT1) 50 mg (n = 3) or 100 mg (n = 4) daily; week 3, return to the patients' usual regimen. Diet, physical activity, and blood glucose were held as constant as possible during the three weeks of daily testing. We found that plasma renin levels increased significantly during combination therapy and then returned to baseline values with discontinuation of AT1a therapy: mean baseline renin values (week 1) 3.0 ng/ml/min +/- 1.1 SE, mean renin values during combination therapy (week 2) 7.0 ng/ml/min +/- 3.2 (p = 0.0078 by Wilcoxon rank sum test), mean renin values after discontinuation of AT1a therapy (week 3) 3.9 ng/ml/min +/- 2.0 (NS compared to baseline values). In addition, 2 patients developed transient hypotension when losartan therapy was initiated. During this short-term study, 24-hour proteinuria, serum creatinine, serum potassium, and plasma aldosterone were not changed significantly by combination therapy. We conclude that in patients with diabetic nephropathy addition of AT1a therapy to ACEi therapy attenuates AngII effects better than ACEi therapy alone. We suggest that combination therapy for the management of diabetic glomerulosclerosis merits further investigation.

Somatostatin receptor gene expression in neuroblastoma

Somatostatin receptor expression is a favorable prognostic factor in human neuroblastoma. Somatostatin receptors have been demonstrated in vitro by pharmacologic analysis of tumor tissue and in vivo by diagnostic radioreceptor scintigraphy. However, which receptor subtypes (sst(1), sst(2), sst(3), sst(4), and sst(5)) are expressed in these tumors has not yet been delineated. We used RT-PCR to analyze expression of the five somatostatin receptor genes in 32 neuroblastoma tumor specimens. All 32 tumor specimens expressed mRNA for c-abl and sst(1); sst(2) mRNA was detected in 27/32 samples and somatostatin mRNA was detected in 30/32 tumor specimens. The remaining receptor subtypes, sst(3), sst(4), and sst(5) were variably expressed. Receptor protein for sst(1) and sst(2) was visualized in tumor neuroblasts as well as in endothelial cells of tumor vessels using immunostaining with specific anti-receptor antibodies. The effect of high expression of somatostatin receptors on cell proliferation was examined in SKNSH neuroblastoma cells transfected with sst(1) and sst(2). SS(14) binding to wild-type SKNSH cells was undetectable; but the native peptide bound with high affinity to the SKNSH/sst(1) and SKNSH/sst(2) neuroblastoma cell lines. Pharmacologic analysis of binding with two long-acting analogues, CH275 and octreotide, confirmed selective expression of sst(1) and sst(2) in stably transfected SKNSH cells. Formation of neuroblastoma xenograft tumors in nude mice was significantly delayed for both SKNSH/sst(1) (P<0.001) and SKNSH/sst(2) (P<0.05) cells compared to wild-type SKNSH. We conclude that: (1) Somatostatin receptors, sst(1) and sst(2), are expressed in the majority of neuroblastomas at diagnosis; and (2) upregulation of functional sst(1) or sst(2) in neuroblastoma cell lines suppresses tumorigenicity in a xenograft model. These observations suggest that somatostatin receptors may be a useful therapeutic target in neuroblastoma.

Desaturation function does not decline after menopause in human females

Aging appears to decrease delta6-desaturase activity in males, but in females it is uncertain. delta6- and delta5-desaturase functions were investigated in pre- and post-menopausal women who were normoglycemic or had type 2 diabetes (2 x 2 factorial, n = 37). Subjects were compared for indicators of diabetic control, estrogen levels, fatty acid profiles and indices of delta6- and delta5-desaturase activity. Diet intakes that were compared to determine whether results were a function of dietary factors known to influence desaturase activity revealed no differences (P>0.05). Post-menopausal women with type 2 diabetes had more 18:2 n6 in serum phospholipids (P<0.05) than did the pre- and post-menopausal control subjects. Fatty acid ratios of 18:3 n6/18:2 n6 indicated greater delta6-desaturase activity for women with type 2 diabetes, but differences were not found between pre- and post-menopausal groups. Significant correlation (P < 0.05) indicates an association between diabetic status and desaturase function, but function did not appear to be affected by menopausal status. In contrast to reports using male subjects, we found no evidence that desaturase function decreased in aging females, as reported for males, or increased as hypothesized in this study.

Carcinoid syndrome caused by an atypical carcinoid of the uterine cervix

Neuroendocrine tumors of the cervix are rare and are often under- or misdiagnosed. Because these tumors are very aggressive, early diagnosis and subsequent treatment are warranted. We describe a 46-yr-old woman with carcinoid syndrome caused by an atypical carcinoid of the uterine cervix. At age 44, she had dysplasia on Pap smear and underwent total abdominal hysterectomy with the diagnosis of adenocarcinoma. Fourteen months postoperatively, she developed the carcinoid syndrome and was found to have numerous liver metastases. Histological and immunohistochemical investigations of biopsy specimens from the patient's liver lesions and original cervical lesion ("adenocarcinoma") suggested that this woman had a primary atypical carcinoid of the uterine cervix with metastases to the liver. Treatment with octreotide and alkylating agents decreased the episodes of flushing and diarrhea within 8 weeks. If an adenocarcinoma of the uterine cervix is diagnosed, atypical carcinoid should be in the differential diagnosis. Symptoms of the carcinoid syndrome should be pursued and, if present, a urinary 5-hydroxyindolacetic acid level should be obtained. Timely diagnosis of a neuroendocrine tumor of the cervix may improve survival.

Intraoperative gamma detection of 125I-lanreotide in women with primary breast cancer

BACKGROUND

Somatostatin receptors are present in most human breast cancers. We performed a pilot trial of intraoperative tumor-gamma detection using the radiolabeled somatostatin analog 125I-lanreotide in 13 women with 14 primary breast carcinomas.

METHODS

All patients were given 125I-lanreotide intravenously before surgery. Patients underwent lumpectomy, and postresection margins were evaluated with the gamma probe. Axillary dissection specimens were evaluated ex vivo.

RESULTS

Seven of 13 women had gamma probe-positive or clinically suspicious margins re-excised at the time of lumpectomy. Four of six probe-positive margins were histologically positive, and two of six probe-positive margins were histologically negative; a single clinically suspicious margin was histologically positive. A total of 270 axillary lymph nodes were evaluated ex vivo by gamma probe and histology. McNemar's contingency tests demonstrated a highly statistical correlation between histology and gamma probe counts (P < .0001).

CONCLUSIONS

The overall accuracy of nodal evaluation with 125I-lanreotide/intraoperative gamma detection was 77%; the negative predictive value of this technique was 97%, however. This technique predicted the presence of tumor in 20% of axillary lymph nodes that were negative by routine histology. This technique appears safe and is able to detect positive tumor resection margins and accurately predict axillary lymph node negativity. Further trials of this technique are required to validate its utility.

Synthesis and characterization of multiply-tyrosinated, multiply-iodinated somatostatin analogs

Radio-labeled somatostatin analogs have recently gained popularity as agents useful in intraoperative tumor localization, external scintigraphy and in situ radiotherapy. We have synthesized and characterized a series of novel N-terminally extended multiply-tyrosinated somatostatin analogs that possess high binding affinity for somatostatin receptors, exhibit biological activity comparable to the native peptide and retain these characteristics after iodination. These analogs can be radio-iodinated to high specific activities. Following radioiodination, these analogs exhibit minimal radiolysis and may be clinically useful for tumor localization, scanning and therapy.

Multiple endocrine neoplasia type 2A: a 25-year review

BACKGROUND/PURPOSE

Before 1970, treatment decisions for the thyroid lesions in patients with multiple endocrine neoplasia (MEN) were based on physical findings. For the next 20 years, biological markers assumed a preeminent role, and at present, DNA testing is being used to define the need for therapeutic intervention. This report presents a 25-year review of 22 children with MEN-2A, with a mean follow-up of 12.5 years.

METHODS

All 22 children underwent a total thyroidectomy, and four (18%) were rendered permanently hypoparathyroid. Since 1976, however, only one patient (6.7%) has lost parathyroid function. Despite the fact that biological screening studies routinely were performed once a year in the majority of our patients and surgery was recommended for any elevation in the serum calcitonin (CT) levels, medullary carcinoma of the thyroid (MTC) developed in 17 children (77%) and only five had C cell hyperplasia (CCH). Thirteen of the 17 had macroscopic tumor described by the pathologist, evidence of recurrent disease (MTC-REC) has developed in four children (24%).

RESULTS

There was considerable overlap in both the basal and stimulated CT levels among the five children with CCH, the 13 with localized MTC (MTC-NED), and the four who later had recurrent MTC. The basal calcitonin levels were between 25 and 110 (mean, 58) in the CCH patients, 30 to 1,130 (mean, 184) in the MTC-NED group, and 108 to 201 (mean, 140) in those with recurrent MTC. The corresponding stimulated calcitonin levels were 45 to 417 (mean, 179) in CCH, 111 to 9,510 (mean, 1,407) in MTC-NED, and 449 to 5,093 (mean, 3,383) in MTC-REC.

CONCLUSIONS

(1) Basal and pentagastrin-stimulated CT levels did not reliably discriminate between CCH and MTC and should not be used to define the timing of thyroid surgery in children with MEN-2A. (2) Surgical therapy should be undertaken early in childhood on the basis of molecular genetic testing. (3) Postoperative complications are infrequent in the modern era.

Identification of MEN1 mutations in sporadic enteropancreatic neuroendocrine tumors by analysis of paraffin-embedded tissue

Gastrinomas and other gastrointestinal neuroendocrine tumors may occur sporadically or as part of the inherited syndrome multiple endocrine neoplasia type 1 (MEN1). Mutations in the recently identified MEN1 gene have been described in sporadic gastrinomas and insulinomas. This study describes techniques used to identify mutations in the MEN1 gene in DNA extracted from paraffin-preserved tissue. Two novel mutations are identified in the MEN1 gene from nine archived paraffin-embedded neuroendocrine tumors, demonstrating that retrospective genetic analysis can be used to identify mutations in the MEN1 gene from preserved tissue. Conditions are provided by which paraffin-embedded tissue can be used as a source of genetic material for sequence information of sufficient quality for mutational studies of the MEN1 gene. It should also be possible to apply this retrospective genetic analysis of paraffin-embedded tissue to other disease models.

Cell trafficking, mediator release, and articular metabolism in acute inflammation of innervated or denervated isolated equine joints

OBJECTIVES

To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1 beta (IL-1 beta) in isolated innervated or denervated equine metacarpophalangeal joints.

ANIMALS

One metacarpophalangeal joint of 24 adult horses.

PROCEDURES

The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1 beta. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1 beta, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation.

RESULTS

IL-1 beta induced significant neutrophilic leukocytosis in synovial and synovial membrane. IL-1 beta concentration and returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints.

CONCLUSION

Cellular response to IL-1 beta was rapid and sustained; joint clearance of IL-1 beta was rapid, and endogenous production of IL-1 beta did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage of IL-1 beta was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response.

Intravitreal injection of octreotide acetate

This study was conducted to determine the feasibility of injecting the somatostatin analogue, octreotide acetate (OA), into the vitreous cavity. Previous work suggests that octreotide effectively inhibits angiogenesis in vitro, thus its use in vivo may slow the progression of proliferative eye disease. Fifty micrograms of aqueous OA in 50 microliters aqueous solution was injected into the mid-vitreous of kitten eyes (n = 6), and OA levels were monitored over 4 days. A long-acting release form of octreotide (OA-LAR) was also injected into the mid-vitreous of rabbit eyes at doses of 0.36 (n = 16), 1.1 (n = 1), 2.1 (n = 1), 4.05 (n = 1), 8.2 (n = 1), and 36 mg (n = 3) in solution; and octreotide concentrations were measured at various time points over 42 days. OA concentrations were determined by a highly specific radioimmunoassay. Aqueous octreotide was eliminated rapidly (t1/2 = 16 hours) from the vitreous of the kitten eye, with only negligible amounts recoverable 4 days post-injection. In the long-acting form, OA in the rabbit eye reached peak levels at 28 days. By 42 days, OA levels had declined to the 14-day level. Doses of OA-LAR of 1.1 mg or less produced no gross evidence of clinical toxicity and elicited no grossly visible ocular side effects. Doses greater than 1.1 mg produced significant toxicity, including cataracts and rubeosis. The 28-day peak release for long-acting OA implies that monthly intravitreal injections could provide continual high levels of OA. Intravitreal injection of long-acting OA provides sustained, high concentrations of drug, and deserves further study as a potential treatment of proliferative eye diseases.

Somatostatin expression in human renal cortex and mesangial cells

Somatostatin modulates important physiologic functions of the kidney, including mesangial cell contraction, glomerular prostaglandin synthesis, and phosphate, water and sodium excretion. In diabetic nephropathy, somatostatin inhibits renal hypertrophy. High affinity somatostatin receptors are expressed in the kidney. Circulating somatostatin concentrations, however, are generally well below the affinity constants of known somatostatin receptors. Thus, we hypothesized that somatostatin is produced in the kidney and released locally to act in an autocrine/paracrine manner. Using reverse transcriptase and polymerase chain reaction (RT-PCR) analysis, we found that fresh human renal cortex and cultured human mesangial cells express somatostatin mRNA. Restriction enzyme and Southern blot analysis confirmed that RT-PCR cDNA products were derived from somatostatin mRNA. Radioimmunoassay of mesangial cell culture supernatants demonstrated SS-immunoreactive peptide (87 +/- 30 pg/ml compared to 19 +/- 9 pg/ml in medium not exposed to cells; P < 0.05). In contrast, renal cells did not transcribe detectable levels of vasoactive intestinal peptide (VIP) or neuropeptide Y (NPY) mRNA, nor did they synthesize measurable peptide. Our results demonstrate that renal cells produce somatostatin and suggest that kidney-derived somatostatin may regulate renal function in an autocrine/paracrine manner. Characterization of this pathway may lead to novel methods to alter the course of diabetic nephropathy and other renal diseases.

Vasoactive intestinal polypeptide-secreting tumours: biology and therapy

VIP-secreting tumours are rare, but they produce a dramatic clinical picture, the most prominent feature being profuse, watery diarrhoea and hypokalaemia. VIPomas are malignant and require sophisticated diagnostic and localization techniques in order to identify their presence. Delays in diagnosis are the rule rather than the exception. Improvements in the diagnosis of VIPomas appear to result in an increase in resectability rates. A definitive diagnosis is aided by the determination of plasma VIP concentrations through the use of sensitive radioimmunoassays. With heightened awareness of this syndrome, increasing numbers of patients can be identified and more effective treatments developed for the refractory and recurrent tumours.

Effects of feeding on protein turnover in healthy children and in children with cystic fibrosis

We hypothesized that there is less suppression of whole-body protein breakdown with feeding in patients with cystic fibrosis (CF) who exhibit decreased insulin secretion after a single meal. Using [1-13C]leucine, we measured rates of nonoxidative leucine disappearance (whole-body protein synthesis) and protein breakdown in nine CF patients (6-11 y of age) and five healthy control subjects (8-10 y of age) during feeding and fasting. In the CF patients, synthesis and breakdown (x +/- SD) were 172 +/- 61 and 157 +/- 67 mumol.kg-1.h-1 during feeding and 140 +/- 24 and 178 +/- 26 mumol.kg-1.h-1 during fasting. The respective control values were 129 +/- 27 and 114 +/- 20 mumol.kg-1.h-1 during feeding and 136 +/- 13 and 173 +/- 18 mumol.kg-1.h-1 during fasting. Leucine balance was nearly identical in the two groups. By analysis of variance, there was a significant effect of feeding on protein breakdown but no difference between the groups. However, when each group was analyzed separately, feeding resulted in a 34% decrease in breakdown in the control subjects (P = 0.001) and a 23% increase in synthesis in the CF group (P = 0.058). Plasma insulin concentrations did not differ in the two groups. Thus, feeding may affect protein turnover differently in children with CF than in control children independently of plasma insulin concentration.

Expression of the somatostatin receptor subtype-2 gene predicts response of human pancreatic cancer to octreotide

BACKGROUND

Somatostatin inhibits proliferation of many solid tumors. The current study examines whether inhibition of the growth of pancreatic cancer by the somatostatin analog, octreotide, requires tumor expression of somatostatin receptors.

METHODS

We studied five human pancreatic cancer cell lines, Capan-1, Capan-2, CAV, MIA PaCa-2, and Panc-1. Solid tumors were established in nude mice (n = 20/cell line) by flank injection of tumor cells. Subcutaneous octreotide (500 micrograms/kg/day) was administered by osmotic pumps to 10 of the animals in each group, and the other 10 received control infusions of saline solution. On day 36, the tumors were excised and weighed. Plasma levels of the putative trophic peptides cholecystokinin, epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), and insulin were assessed by radioimmunoassay. Each of the five cell lines was assayed for the presence of cell surface somatostatin receptors by using whole cell competitive binding assays with 125I-somatostatin. Expression of the somatostatin receptor subtype-2 (SSR2) gene was determined with reverse transcriptase-polymerase chain reactions. Southern blot hybridization was used to assess the presence of the SSR2 gene.

RESULTS

Octreotide inhibited tumor growth in the MIA PaCa-2 group (512 +/- 75 mg control versus 285 +/- 71 mg treated; p < 0.05) but had no significant effect on tumor weight in the other four cell lines. Plasma levels of cholecystokinin, epidermal growth factor, insulin-like growth factor-1, and insulin were not altered by chronic octreotide infusion. Cell surface somatostatin receptors and SSR2 gene expression were detected only in the MIA PaCa-2 tumors. The gene for the SSR2 receptor was found in all five tumor lines.

CONCLUSIONS

Octreotide-mediated inhibition of pancreatic cancer growth is dependent on expression of somatostatin receptors. The expression of somatostatin receptors should be considered in the design and interpretation of clinical trials with somatostatin analogs for treatment of pancreatic cancer.

RET mutation screening in MEN2 patients and discovery of a novel mutation in a sporadic medullary thyroid carcinoma

RET germline mutations were found to predispose to the development of three variants of multiple endocrine neoplasia type 2, MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC). We have screened for RET mutations at exons 10, 11, 13, and 16 in leukocyte DNA extracted from 37 individuals, and have identified RET germline mutations in 12 affected individuals from 9 unrelated families. No RET germline mutation was found in 19 individuals with apparent sporadic diseases. We have also screened for RET mutations at exons 10, 11, and 16 in tumor DNA extracted from 13 freshly frozen medullary thyroid carcinomas (MTC). RET mutation was detected in every tumor, either inherited or sporadic, indicating that RET plays an important role in the development of both inherited and sporadic MTC. We initially screened for RET mutations by direct DNA sequencing of the genomic PCR products amplified from patients' leukocyte or tumor DNA. Recently, we utilized the "Cold SSCP" method, nonradioactive single-stranded conformation polymorphism analysis, to screen for RET mutations and have identified a novel mutation, a 6-bp deletion preceding the cysteine-634, in a sporadic MTC.

Calcium reverses octreotide inhibition of insulin and glucagon levels in patients with insulinoma and glucagonoma

Excessive secretion of peptides causes the clinical syndromes associated with functional gastro-intestinal tumours. The somatostatin analogue octreotide acetate inhibits peptide release from a variety of tumours. This study investigated the interactions of calcium and somatostatin analogues on peptide release in two patients, one with a glucagonoma (patient A) and one with an insulinoma (patient B). Peptide responses were evaluated before (fasting levels) and after provocative tests (a 4-hour calcium infusion, an intravenous tolbutamide infusion, a secretin bolus and a standard test meal) in the absence and presence of octreotide acetate treatment (100 micrograms subcutaneously every 8 h). Patients A and B had elevated fasting plasma levels of glucagon and insulin, respectively, which were reduced by octreotide therapy by 73 and 50%, respectively. The peak provoked levels and calculated values for peptide synthesis were lower after octreotide therapy. In both patients, tolbutamide provoked most peptide release, and calcium infusion was the least susceptible to the effects of octreotide therapy. Calcium appears to inhibit octreotide suppression of glucagon and insulin secretion in patients with glucagonoma and insulinoma, respectively. Calcium may stimulate peptide release from endocrine tumours by suppressing the inhibitory effects of endogenous somatostatin. Normalisation of serum calcium, either surgically or pharmacologically, may improve the effectiveness of somatostatin analogue therapy.

Studies in psychoneuroimmunology: psychological, immunological, and neuroendocrinological parameters in Israeli civilians during and after a period of Scud missile attacks

Twenty-two male volunteers in Jerusalem were subjected to a battery of psychological tests at the height of the Iraqi Scud missile attacks on Israeli cities during the 1991 Persian Gulf War and again after the cessation of hostilities. Venous blood samples were taken at each time point. The separated mononuclear cells and plasma were cryopreserved, and a spectrum of immunological and neuroendocrine assays were performed on the preserved samples. Psychological testing indicated levels of anxiety were higher during the war than they were after the war ended, and both anxiety and anger during the hostilities were significantly elevated in comparison with prewar data. During the war, specific war-related pressures were greater than everyday pressures, and problem-focused coping was more evident than emotion-focused coping. Natural-killer cell activity and cell-mediated lympholysis were significantly elevated during the war, as were plasma levels of adrenocorticotrophic hormone, neurotensin, and substance P. The only biological test parameter found to be reduced during the war period was mononuclear cell thymidine incorporated in nonstimulated cultures.

Indium-111-pentetreotide scanning versus conventional imaging techniques for the localization of gastrinoma

BACKGROUND

The present study evaluates 111In-pentetreotide scanning as a method for detection of gastrinomas. Operative findings serve as the benchmark for comparison of the efficacy of 111In-pentetreotide versus conventional imaging studies.

METHODS

Twelve patients (seven female and five male; age, 37 to 80 years) with histologic confirmation of gastrinoma underwent thin section dynamic computed tomography (CT) scanning and 111In-pentetreotide scanning. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 111In-pentetreotide and CT scanning are compared on the basis of tumor size and location.

RESULTS

Thirty discrete foci of intrahepatic and extrahepatic tumors were detected at operation. CT scanning detected three of nine pancreaticoduodenal lesions, whereas eight of these nine extrahepatic primary tumors were imaged by 111In-pentetreotide scanning. No false-positive 111In-pentetreotide scans were noted. The sensitivity of CT scanning for detection of metastatic disease was 56% versus 94% for the 111In-pentetreotide scan. Successful CT imaging was highly dependent on tumor size. No tumor smaller than 1 cm was imaged by CT, whereas four of seven lesions greater than 1 cm were imaged by 111In-pentetreotide scintigraphy. The smallest gastrinoma imaged by 111In-pentetreotide scanning was a 4 mm duodenal tumor.

CONCLUSIONS

111In-pentetreotide scanning was superior to CT scanning for localizing gastrinomas. Further studies are required to determine whether 111In-pentetreotide scans will complement or replace traditional imaging methods.

Intraoperative detection and resection of occult neuroblastoma: a technique exploiting somatostatin receptor expression

Tumor cell expression of specific high-affinity somatostatin receptors has been associated with a favorable prognosis in children with neuroblastoma. The purpose of this study was (1) to document intraoperatively the in vivo binding of the somatostatin analogue 125I-tyr3-octreotide to high-affinity somatostatin receptors expressed on human neuroblastoma, using a hand-held gamma detector; (2) to determine whether gamma-probe detection of radioligand binding to tumor receptors could identify occult malignancy; and (3) to determine the safety and biodistribution of 125I-tyr3-octreotide in children. Six children with stage III or IV neuroblastoma received an intravenous injection of 125I-tyr3-octreotide and underwent operative exploration using gamma-probe detection of radioligand binding to tumor somatostatin receptors. Tissue that demonstrated in vivo binding of 125I-tyr3-octreotide, or that was suspicious for tumor, was extirpated and analyzed by histopathology, immunohistochemistry, and microautoradiography. The biodistribution of 125I-tyr3-octreotide was recorded intraoperatively over time. Tumor tissue from each child also was assayed in vitro for somatostatin receptor expression by competitive binding studies using 125I-tyr3-octreotide. In vivo binding of 125I-tyr3-octreotide to malignant tissue was documented in the five children with a known tumor burden. Seventeen sites of radioreceptor binding were amenable to resection. Histopathological analysis confirmed neuroblastoma in 15 of these specimens. Four of the 15 proven tumor foci were occult malignancies. Every site of histologically proven neuroblastoma demonstrated in vivo binding of 125I-tyr3-octreotide. Five of seven sites histologically negative for neuroblastoma also were negative for in vivo radioreceptor binding. Microautoradiography confirmed in vivo binding of 125I-tyr3-octreotide to tumor cells. Uptake of 125I-tyr3-octreotide in abdominal organs occurred within 15 minutes of injection, was highest in the liver and gallbladder, and decreased over 24 hours. The conclusions were as follows. (1) 125I-tyr3-octreotide binds, in vivo, to somatostatin receptors on neuroblastoma, with 100% sensitivity and 71% specificity. (2) Occult neuroblastoma is found through gamma-probe detection of radioligand binding to receptors. (2) The biodistribution of 125I-tyr3-octreotide reflects the hepatobiliary clearance of this radionuclide. (4) Radioreceptor-guided surgery may safely provide more complete operative staging and cytoreduction of neuroblastoma.

Somatostatin receptor imaging of neuroendocrine tumors with indium-111 pentetreotide (Octreoscan)

Somatostatin, a naturally occurring 14-amino acid peptide, can be thought of as an anti-growth hormone and functional down-regulator of sensitive tissue. Most neuroendocrine tumors seem to possess somatostatin receptors in sufficient abundance to allow successful scintigraphic imaging with radiolabeled somatostatin congeners. Several of these, including Indium-III-DTPA Pentetreotide (Octreoscan [Mallinckrodt Medical, St. Louis, MO]), which was approved for clinical use by the Food and Drug Administration in June 1994, have been of considerable value in scintigraphically identifying various neuroendocrine tumors. The Octreoscan compares favorably with other imaging modalities. The success of somatostatin receptor imaging in evaluating patients with suspected neuroendocrine tumors, including identifying otherwise radiographically occult lesions, has resulted in ranking somatostatin receptor imaging as the prime imaging procedure in patients with suspected neuroendocrine tumors at The Ohio State University.

Consensus statement: octreotide dose titration in secretory diarrhea. Diarrhea Management Consensus Development Panel

Octreotide is an effective therapeutic option in controlling secretory diarrhea of varied etiology. However, marked patient-to-patient differences in the antidiarrheal effects necessitate titration of octreotide dose in individual patients to achieve optimal symptom control. A consensus development panel established guidelines for octreotide dose titration in patients with secretory diarrhea. Overall, the panel recommended an aggressive approach in selecting the initial octreotide dose and in making subsequent dose escalations in patients with secretory diarrhea due to gastrointestinal tumors (eg, carcinoids, VIPomas), AIDS, dumping syndrome, short bowel syndrome, radiotherapy, or chemotherapy. To avoid hypoglycemia in patients with diabetes mellitus-associated secretory diarrhea, the panel recommended a low initial octreotide dose and a conservative titration regimen with close monitoring a blood glucose levels. The end point of therapy should focus on a reduction in diarrhea (frequency of bowel movements or stool volume) rather than normalization of hormonal profile. Overall, octreotide is well tolerated; principal side effects are transient injection site pain and gastrointestinal discomfort. For many patients with secretory diarrhea, octreotide therapy is expected to improve the overall health and quality of life and in the long run will lessen health care costs.

GI hormonal changes in diabetes influence pancreatic cancer growth

Streptozotocin diabetes prevents induction of pancreatic tumors in several animal models, suggesting a pivotal role for islet cell products in the pathogenesis of pancreatic cancer. To test the hypothesis that altered gastrointestinal peptide levels in streptozotocin diabetes influence tumor growth, human pancreatic cancer cells (MIA PaCa-2) were implanted subcutaneously into streptozotocin diabetic nude mice. After 3 weeks, tumors in the control group weighed 43 mg and tumors in the diabetic group weighed 12 mg (P < 0.001). Plasma insulin and IGF-1 levels were significantly decreased in the streptozotocin-treated animals compared to those of control (insulin: 23 microU/ml vs 31 microU/ml, P < 0.001; IGF-1: 254 ng/ml vs 324 ng/ml, P < 0.001). In contrast, somatostatin and glucagon were significantly elevated in the streptozotocin diabetic group relative to control levels (somatostatin: 179 pg/ml vs 54 pg/ml, P < 0.001; glucagon: 290 pg/ml vs 134 pg/ml, P < 0.001). Competitive binding studies revealed specific cell surface receptors for insulin (Kd = 15.5 nM), IGF-1 (Kd = 30.0 nM), and somatostatin (Kd = 2.5 nM) on the MIA PaCa-2 cells. Receptors for glucagon were absent. In an in vitro cell proliferation assay, cell division was promoted by insulin (P < 0.01, max + 11%) and IGF-1 (P < 0.01, max + 10%). Somatostatin inhibited cell division (P < 0.01, max - 18%). No effect was seen with glucagon. The growth of pancreatic cancer, particularly in diabetes, may be influenced by gut peptides in a receptor-dependent fashion.

Cyclic nucleotides and vasoactive intestinal peptide production in a rabbit model of Escherichia coli septicemia

Nitric oxide and vasoactive intestinal peptide (VIP) are potent vasodilators and postulated as inducers of hypotension. These mediators activate guanylate cyclase and adenylate cyclase, respectively, with subsequent biosynthesis of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) producing vascular smooth muscle relaxation and vasodilatation. Cyclic nucleotides and VIP were evaluated during Escherichia coli septicemia in two groups of rabbits; 1) sepsis alone and 2) sepsis and a competitive inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine. Arterial blood was obtained for determination of bacteremia, lactic acidemia, nucleotides, nitrites, and VIP levels. Significant bacteremia, endotoxemia, tachycardia, lactic acidosis, and hypotension occurred in all animals (P < 0.005). Circulating blood levels of cGMP, nitrites, cAMP, and VIP (P < 0.005) increased with development of shock. The NG-monomethyl-L-arginine treated animals had less cGMP, nitrites, cAMP, and VIP produced (P < 0.01). Plasma cGMP levels remained stable, suggesting that stimulated phagocytes in whole blood were responsible for increased cGMP levels. Infusion of VIP produced profound hypotension and lactic acidemia. Results of these experiments provide definitive evidence that nitric oxide and VIP are mediators during septic shock and their messengers are cGMP and cAMP, respectively. In addition, phagocytic stimulation with increased production of cGMP may initiate shock, with these mediators acting synergistically to prolong hypotension.

The Semmes-Weinstein monofilament as a potential predictor of foot ulceration in patients with noninsulin-dependent diabetes

The objective was to evaluate the Semmes-Weinstein monofilament as a potential predictor of foot ulceration. A case-control study was carried out in a teaching hospital clinic specializing in diabetes and hyperlipidemic disorders. Two groups of patients with noninsulin-dependent diabetes mellitus were studied: 168 with no history of foot lesions (No-Ulcer group, aged 58.1 +/- 9.7 years, duration 11.5 +/- 7.8 years) and 14 who had at least one foot ulceration during the last year (foot ulcer group, aged 60.8 +/- 7.8 years', duration 17.1 +/- 10.5 years). The authors defined and measured a "monofilament index" using a size 5.07 Semmes-Weinstein monofilament on three locations on each foot and then measured peroneal nerve current perception thresholds using the Neurometer at three frequencies: 5 Hz, 250 Hz, and 2,000 Hz. The monofilament index score was lower in patients in the foot ulcer group than in patients in the No-Ulcer group (1.71 +/- 2.36 vs 5.21 +/- 1.81, P < 0.001). A cutoff point at an index of 5 out of 6 yielded a sensitivity rate of 85.71% and a false-positive rate of 16.07%. The peroneal nerve current perception threshold was higher (P < 0.005) in patients in the foot ulcer group than in patients in the No-Ulcer group for all frequencies (605.8 +/- 414.6 vs 181.5 +/- 272.3 for 5 Hz; 743.2 +/- 361.7 vs 251.6 +/- 283.7 for 250 Hz; 859.4 +/- 220.2 vs 423.3 +/- 252.6 for 2,000 Hz). (ABSTRACT TRUNCATED AT 250 WORDS)

Detection of occult gastrinomas with iodine 125-labeled lanreotide and intraoperative gamma detection

BACKGROUND

Surgical exploration for gastrinoma has a high failure rate because of small primary tumors and occult metastasis. Despite extensive preoperative and intraoperative tumor localization, only 30% to 40% of patients with gastrinoma are cured by surgery. Two patients with unlocalized gastrinomas were studied with intraoperative gamma detection of an iodine 125-labeled somatostatin analog, lanreotide, to localize their tumors.

METHODS

Both patients were challenged before operation with 100 micrograms of octreotide acetate, and both had circulating gastrin levels suppressed by greater than 50%. Iodine 125-labeled lanreotide (100 to 150 muCi) was injected during exploration, and an intraoperative gamma detector was used to detect tumor binding of the analog.

RESULTS

In patient 1 a single source of increased counts was discovered in a retroduodenal lymph node, which was excised; no other tissue was removed. Histologic study of this node failed to demonstrate tumor; however, the patient's gastrin level was normal (63 pg/ml) 4 months after operation. In patient 2 five areas of increased counts were discovered and excised. Three of these five areas had visible tumor on microscopic examination. Three months after operation the patient's fasting gastrin level was 103 pg/ml.

CONCLUSIONS

Intraoperative gamma detection of radiolabeled peptides may allow the localization of occult tumors that contain specific peptide receptors.

Relationships of Na+ and K+ concentrations to GRP, CGRP, and calcitonin immunoreactivities and Na+,K(+)-ATPase (NKA) inhibitory activity in human breast cyst fluid

BACKGROUND

Although the etiology of gross cystic disease of the breast is unknown, elevated cyst concentrations of potassium (K+) (> 60 mM/L) may be related to symptoms. The purpose of this study was to clarify the mechanism(s) of K+ accumulation in breast cysts.

METHODS

We assayed cyst fluids for factors known to exert effects on K+ transport, namely, endogenous digitalis-like inhibitors of Na+,K(+)-ATPase (NKA) and the neuropeptides gastrin-releasing peptide (GRP), calcitonin (CT), and calcitonin gene-related peptide (CGRP).

RESULTS

Cyst fluid K+ was directly correlated with cyst volume, cyst NKA inhibitory activity (in ouabain equivalents), and cyst concentrations of calcitonin, GRP, and CGRP. Cyst fluid Na+ was inversely correlated with cyst fluid K+, cyst NKA inhibitory activity, cyst volume, and cyst fluid concentrations of calcitonin, GRP, and CGRP. NKA inhibitory activity correlated directly with GRP and CGRP. Immunocytochemistry localized GRP to breast cyst lining cells and areas of ductal and lobular epithelial hyperplasia in biopsies of 15 of 15 cysts and in 5 of 5 breast carcinomas, but not in (0 of 5) normal breast biopsies. Specificity of GRP staining was demonstrated by total abolition of reactivity after adsorption with synthetic GRP, but not after adsorption with synthetic substance P, neurokinin A, or neurokinin B.

CONCLUSIONS

We conclude that both the concentrations of endogenous digitalis-like factors and the neuropeptides calcitonin, GRP, and CGRP in human breast cyst fluids are related to the concentrations of K+ and Na+ in breast cysts and to cyst volume.

Chief cells possess somatostatin receptors regulated by secretagogues acting through the calcium or cAMP pathway

Inhibition both in vivo and in vitro of pepsinogen secretion by somatostatin (SS) and the histological demonstration that fundic D-cells contain long cytoplasmic processes extending to chief cells suggest a possible direct effect of SS on chief cell function. The aim of the present study was to determine whether SS interacts directly with receptors on isolated gastric chief cells and, if so, how SS alters cell function. Binding of 125I-[Tyr11]SS14 to chief cells was saturable, time and temperature dependent, and was inhibited by both SS14 (Ki 1.6 nM) and SS28 (Ki 5.2 nM). SMS-201-995 was 1,300-fold less potent than SS14. Calcium-mobilizing secretagogues reduced binding of 125I-[Tyr11]SS14 with efficacies of cholecystokinin octapeptide (CCK-8) > carbachol > gastrin. Adenosine 3',5'-cyclic monophosphate (cAMP)-activating secretagogues also inhibited binding with efficacies of secretin > vasoactive intestinal polypeptide (VIP). 12-O-tetradecanoylphorbol 13-acetate (TPA) or A-23187 also decreased binding. Analyses demonstrated that CCK-8 and TPA were decreasing the affinity of SS receptors for 125I-[Tyr11]SS14 without affecting their binding capacity. Both SS14 and SS28 at a maximally effective concentration inhibited cAMP production caused by VIP or secretin (20-30%) but did not alter cytosolic calcium ([Ca2+]i), inositol phosphates, or pepsinogen release. We conclude that chief cells possess SS receptors with a high affinity for both SS14 and SS28 but low affinity for SMS-201-995 and thus resemble the SSB receptors described in the rat cerebral cortex. Although occupation of these receptors by SS has no effect on pepsinogen release induced by secretagogues acting through either the calcium or the cAMP pathway, SS receptor occupation is regulated by agents activating phospholipase C, adenylate cyclase, protein kinase C, and [Ca2]i.

Case report: defective beta and alpha cell regulation in patients with hyperinsulinemia and acanthosis nigricans

Beta cell hypersecretion is associated with the syndrome of hyperandrogenism, insulin resistance, and acanthosis nigricans. It is unknown whether concomitant alpha cell secretory dysfunction occurs in patients with this syndrome. The authors evaluated the gastroenteropancreatic hormones in four family members with varying degrees of the hyperandrogenism, insulin resistance, and acanthosis nigricans syndrome. Gastroenteropancreatic hormones were measured during oral glucose tolerance test with and without subcutaneous octreotide injection. The study revealed that the administration of subcutaneous octreotide resulted in suppression of beta cell function (insulin and c-peptide) but had no effect or a delayed effect on alpha cell secretion (glucagon). Furthermore, the severity of glucagon abnormalities paralleled that of beta cell hypersecretion and the clinical and phenotypic manifestations of acanthosis nigricans in our four patients. We speculate that this alpha cell aberration could potentially be involved in the altered glucose homeostasis and perhaps the skin manifestations of this syndrome. Therefore, glucagon levels should be evaluated in the hormonal studies in patients with hyperandrogenism, insulin resistance, and acanthosis nigricans syndrome.

Stimulation of vasoactive intestinal peptide and neurotensin secretion by pentagastrin in a patient with VIPoma syndrome

BACKGROUND

Pancreatic endocrine tumors (PETs) may secrete a variety of peptide hormones, either alone or in combination, and intravenously administered provocative agents have been used to stimulate hormone release to aid in the diagnosis and localization in suspected cases. These features of PETs led us to perform detailed biochemical investigations and provocative testing in a 26-year-old man with a 5 cm vasoactive intestinal peptide (VIP)-secreting tumor of the head of the pancreas.

METHODS

Plasma hormone radioimmunoassays and immunohistochemical studies were performed for a panel of peptide hormones, including VIP, neurotensin, and pancreatic polypeptide (PP). Acid alcohol extracts of tumor specimens were analyzed for these peptide hormones as well. Before operation, four provocative test regimens were administered intravenously after an overnight fast: pentagastrin (0.5 microgram/kg/5 sec); rapid calcium infusion (2 mg/kg/min); a combination of calcium (2 mg/kg/min) followed by pentagastrin (0.5 microgram/kg/min); and secretin (2 clinical units/kg bolus). Blood samples were collected before each test and 1, 2, 3, 5, and 10 minutes after the infusions.

RESULTS

Measurement of plasma hormone levels and tumor immunohistochemistry and hormonal extraction studies indicated secretion of VIP, neurotensin, and PP by the tumor. Coexpression of VIP and neurotensin was seen immunohistochemically within some individual tumor cells. Provocative testing resulted in maximal stimulation of VIP and neurotensin secretion with pentagastrin administration, which produced increases in plasma levels of VIP and neurotensin over basal levels of 81% and 87%, respectively. After operation, plasma levels of VIP, neurotensin, and PP were undetectable before and after administration of pentagastrin.

CONCLUSIONS

The results emphasize the importance of comprehensive biochemical evaluation in patients with VIPoma syndrome to detect the production of a range of peptide hormones. Administration of intravenous pentagastrin appears to stimulate release of VIP and NT and should be evaluated further as a provocative agent for the diagnosis and follow-up of patients with these tumors.

Characterization of somatostatin receptors on human neuroblastoma tumors

Neuroblastoma is the most common extracranial solid tumor of children. Neuroblastoma tumors derive from the neural crest and synthesize neurotransmitters including the neuropeptide somatostatin. This study was designed to characterize somatostatin receptors both in primary neuroblastoma tumors and in two neuroblastoma cell lines, SKNSH and IMR32. Somatostatin receptors were identified in 6 of 7 Stage I and II compared to 7 of 19 Stage III and IV tumors. Down-regulation of somatostatin receptor binding was observed in five tumors during disease progression. A lack of high affinity binding of somatostatin was identified as a poor prognostic indicator; negative binding correlated with advanced disease and death. Somatostatin receptor binding was observed in the IMR32 cell line, but not in the SKNSH cell line. IMR32 cells demonstrated a single class of high affinity binding sites for both somatostatin and a synthetic analogue, octreotide (Kd 0.16 +/- 0.05 nM and 0.89 +/- 0.23 nM, respectively). Somatostatin and octreotide inhibited both vasoactive intestinal peptide-mediated and forskolin-mediated cyclic AMP accumulation in IMR32 cells. Somatostatin and octreotide inhibition of signal transduction was attenuated by pretreatment of the cells with pertussis toxin. Octreotide inhibited proliferation of IMR32 cells by 70% in a 6-day culture. In contrast, octreotide did not exhibit high affinity binding in SKNSH cells and had no effect on cyclic AMP accumulation or on proliferation in SKNSH cells. Together, these data indicate that octreotide interacts with high affinity somatostatin receptors to modulate signal transduction and regulate proliferation in neuroblastoma cell lines. These data also suggest that somatostatin receptor expression may be an independent prognostic factor in primary neuroblastoma tumors.

Therapeutic uses of gastrointestinal peptides

The GI tract is one of nature's great pharmacies. Most, if not all, biologically active peptides can be found there, and it is quite likely that others remain to be discovered. Our ability to exploit this resource has expanded considerably over the past two decades. Advances in analytical techniques have allowed investigators to rapidly isolate and purify new compounds from tissue extracts. Sequencing and de novo synthesis of newly discovered peptides are now routine, and the structural modifications required to alter activity and tailor a compound to a particular use are easily made. A number of gastrointestinal peptides or their analogues for use in clinical studies are available from commercial sources (see Table 7). Somatostatin is the first gut peptide to successfully complete development and yield a pharmaceutical compound with a broad range of action. Several of the peptides discussed in this article have similar potential. TRH stands out as a candidate because of its effectiveness in the treatment of experimental spinal cord injury and a variety of shock states. Such a broad range of action in critical fields may justify the intensive development required to yield potent, long-acting, and highly specific analogues. Similarly, the antimetastatic and immunostimulant properties of the enkephalins offer promise for new therapies in the treatment of AIDS, ARC, and cancer. Studies with amylin may lead to new and more precise regimens of blood sugar control in insulin-dependent diabetics and could in turn, prevent some of the worst long-term effects of the disease. The development of effective intranasal forms of GHRH could spare children with GH-GHRH deficiency the distress of repeated injections and help to prevent excessive GH blood levels. Secretin, glucagon, or CGRP might be used one day in cardiovascular emergencies, and VIP or its analogues could prove effective in the treatment of asthma. Although preliminary results with many of these peptides are encouraging, further progress will require the development of standardized experimental models and a more rigorous approach to experimental design. Many of the studies reported here suffered from small patient numbers, a narrow or nonexistent range of doses, or the use of only one or two dosing regimens. Lack of objective criteria for determining the level of response, e.g., in studies of mental illness or degenerative diseases, and the ethical problems of withholding treatment from some patients to establish proper controls further hamper research in this area. If the questions of efficacy and safety are to be resolved, thorough, well-planned trials will be required.

Serum insulin and glucose concentrations in people at risk for type II diabetes. A comparative study of African Americans and Nigerians

OBJECTIVE

To examine the phases of acute insulin release and glucose homeostasis in people of African descent with and without a positive family history of type II diabetes who reside in geographically diverse environments. The prevalence of type II diabetes in people of African descent varies considerably depending on the country of habitat. Family history is recognized as an important risk factor for the development of the disease.

RESEARCH DESIGN AND METHODS

We studied serum glucose and insulin concentrations--before and after intravenous glucose challenge--in glucose-tolerant, first-degree relatives of African-American (n = 18) and Nigerian (n = 20) type II diabetic patients and their respective healthy control subjects (African American, n = 9; Nigerian, n = 18) living in their native countries. The acute first- (t = 0-5 min) and second-phase (t = 10-60 min) insulin releases were calculated as the sum of incremental insulin responses to the intravenous glucose stimulation.

RESULTS

Mean serum glucose levels and glucose decay constant (KG) were not different in the African Americans and Nigerians. Fasting serum insulin in the African-American relatives was significantly greater than the Nigerian relatives (16.0 +/- 3.0 vs. 5.8 +/- 1.7 mU/L, P < 0.05). In contrast, FSI levels in the African-American control subjects were similar to Nigerian control subjects (6.3 +/- 1.4 vs. 4.5 +/- 1.8 mU/L). Acute first- and second-phase insulin levels were 2-3 times (P < 0.01) greater in African Americans than Nigerians, irrespective of family history of diabetes. Comparing the African-American relatives with healthy control subjects, we found significantly (P < 0.05) higher FSI in the relatives; whereas the acute first- (272 +/- 44 vs. 222 +/- 55 mU/L) and second-phase (388 +/- 61 vs. 235 +/- 53 mU/L) serum insulin release tended to be greater, but not significantly different in the relatives. In contrast, the acute first (101 +/- 15 vs. 120 +/- 20 mU/L) and second phase (88 +/- 14 vs. 111 +/- 17 mU/l) of insulin release were slightly lower, but not significantly different, in the Nigerian relatives versus the Nigerian healthy control subjects. In a subgroup of nonobese African-American (n = 11) and Nigerian (n = 11) relatives, and African-American (n = 8) and Nigerian (n = 7) healthy control subjects with a body mass index < 30 kg/m2, the mean fasting and post-stimulation serum glucose were not different. However, serum insulin concentrations in the African Americans were significantly different from those of the Nigerians. The pattern of insulin responses in the nonobese subjects was similar to those of the respective African-American and Nigerian groups.

CONCLUSIONS

Our preliminary study demonstrates greater serum insulin responses and, perhaps, insulin resistance in glucose-tolerant African Americans than in their Nigerian counterparts, irrespective of family history of diabetes and obesity. We conclude that the antecedent lesions leading to the development of type II diabetes may be different in the first-degree relatives of African-American and Nigerian diabetic patients.

Intraoperative localization of neuroendocrine tumors with 125I-TYR(3)-octreotide and a hand-held gamma-detecting probe

BACKGROUND

This study evaluates a novel method of intraoperative localization of endocrine gastroenteropancreatic tumors with a hand-held gamma-detecting probe to detect in situ tumor binding of the radioiodinated somatostatin analog 125I-TYR(3)-octreotide.

METHODS

Seven patients with biochemical and radiologic evidence of a specific endocrine tumor, one patient with biochemical evidence of gastrinoma but no tumor localized by conventional imaging techniques, and four patients with equivocal preoperative biochemical or radiologic study results but suspected of harboring a neuroendocrine tumor underwent abdominal exploration with intraoperative injection of 125I-TYR(3)-octreotide. 298 +/- 63 microCi. A hand-held gamma-detecting probe was used during operation to determine whether gross tumor accumulated the radiolabeled analog and occult tumor could be detected. Positive uptake was defined as tumor/background ratios exceeding 2:1.

RESULTS

The tumor in all seven patients with gross disease accumulated 125I-TYR(3)-octreotide. Occult tumor beyond that appreciated with preoperative imaging or by routine operative exploration was detected in a patient with carcinoid tumor. In the patient with the occult gastrinoma the probe detected the lesion within the duodenal bulb before duodenotomy and also predicted what proved histologically to be positive peripancreatic adenopathy. There was a single false-positive reading from the stomach in a patient with suspected carcinoid tumor in whom no tumor could be found grossly or histologically. A pancreatic mass that probed negative proved to be an adenocarcinoma of ductal origin.

CONCLUSIONS

Tumor-specific peptide-receptor binding can be detected in situ with 125J-TYR(3)-octreotide and a hand-held gamma-detecting probe. This technique may facilitate neuroendocrine tumor localization and operative cytoreduction.

Exercise training and dietary carbohydrate: effects on selected hormones and the thermic effect of feeding

To determine relationships among dietary carbohydrate, aerobic exercise training, the thermic effect of food (TEF), and hormonal responses to feeding, 8 trained and 7 sedentary men consumed diets providing 15, 45, or 75% of energy as carbohydrate for 5 days. On Day 6, metabolic rate was measured before as well as 30, 60, 90, and 120 min after an 868-kcal liquid test breakfast. Blood was sampled hourly during Day 5 and during each metabolic rate measurement. The trained group had a larger TEF (40 +/- 2.4 vs. 31 +/- 3.0 kcal/2 hrs), greater insulin sensitivity, and greater plasma prolactin and cortisol levels. As carbohydrate in the treatment diet increased, carbohydrate utilization and thyroid stimulating hormone were higher and thyroxine was lower, but TEF was not significantly different. After the test meal, trained individuals had a higher TEF but the carbohydrate content of the treatment diet did not influence TEF.

Glucose and insulin responses to intravenous glucose challenge in relatives of Nigerian patients with non-insulin-dependent diabetes mellitus

We analysed blood insulin and glucose concentrations before and during frequently sampled intravenous glucose tolerance tests (FSIGT) in 2 groups of Nigerian subjects: (A) Control group (n = 18), without a positive family history of diabetes mellitus, and (B) Experimental group (n = 16), comprising age-, sex- and body mass-matched first-degree relatives of patients with non-insulin-dependent diabetes mellitus (NIDDM). In comparison with Group A subjects, those in Group B had: (i) higher fasting plasma glucose level (mean +/- S.E.M. 4.1 +/- 0.1 vs. 3.8 +/- 0.11 mmol/l, P < 0.05); (ii) similar fasting serum insulin levels (6.7 +/- 5.0 vs. 5.8 +/- 5.6 mU/l, P = NS); (iii) lower mean incremental area under the first-phase (t = 0-10 min) post-glucose challenge insulin curve (376.9 +/- 8.8 vs. 435.6 +/- 5.6 mU/min l-1, P < 0.05); (iv) increased incremental area under the second-phase (t = 10-182 min) post-glucose challenge insulin curve (432.9 +/- 11.5 vs. 161.3 +/- 8.7 mU/min l-1, P < 0.05); (v) reduced KG rate constant of glucose elimination (0.97 +/- 0.12 vs. 1.41 +/- 0.12%/min, P < 0.05). These results suggest that the subjects with a positive family history of NIDDM have a reduced beta-cell insulin secretory reserve (from reduced first-phase insulin response), tendency to rebound hyperinsulinemia during the latter phase of the insulin secretory response, a degree of tissue insulin insensitivity (as evident from high fasting plasma glucose despite similar insulin levels) and a diminished glucose disposal rate, in comparison with subjects without a family history of NIDDM. These features predict subsequent development of diabetes and suggest that as in Caucasians, first-degree relatives of Nigerian patients with NIDDM are at greater risk for future development of the disease.

Pancreatic polypeptide infusions reduce food intake in Prader-Willi syndrome

Prader-Willi syndrome is characterized by dramatic hyperphagia and morbid obesity, and is associated with a deficiency in basal and meal-stimulated serum pancreatic polypeptide (PP) levels. Intravenous infusions of pancreatic polypeptide (90 min, 50 pmol/kg/h) restored normal serum PP levels, and a regimen of morning and afternoon PP infusions was found to significantly reduce food intake in Prader-Willi subjects. Food intake was evaluated in a 60-min free-feeding test that shows high reliability and validity. Basal food intake during saline infusions was striking (approximately 60 chicken sandwich quarters), and this intake was reduced overall by approximately 12% during PP infusions. This reduction was apparent only for female subjects, and may have reflected enhanced satiation rather than an overall suppression of food intake. No differences were apparent across subjects, in either basal food intake or the PP-related decrease in food intake, in the presence or absence of the widely recognized chromosomal marker for this syndrome [deletion of 15(q11-q13)]. More specific gene defects as recently reported in these subjects, however, suggest that the Prader-Willi syndrome may represent an important model for the study of food intake regulation.

Mechanisms of action of long-acting analogs of somatostatin

The prolactin secreting rat pituitary tumor cell line, GH3, expresses high affinity receptors for both vasoactive intestinal peptide (VIP) and somatostatin (SS14). VIP induces prolactin secretion by GH3 cells, an action which is antagonized by SS14. This in vitro model was used to examine the mechanism of action of two synthetic somatostatin analogs, D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-OH (octreotide; SMS 201-995) and cyclo(aminoheptanoyl-Phe-D-Trp-Lys-Thr (benzyl)) (cyclic pentapeptide; CPP). Octreotide and CPP bind to the pituitary somatostatin receptor with lower affinity than does SS14 (KD = 1.3 +/- 1.1; 80 +/- 29; 211 +/- 107 nM for SS14, octreotide and CPP, respectively). SS14 and octreotide were equally effective as inhibitors of VIP-mediated accumulation of cAMP (40% and 45% inhibition, respectively, P < 0.01). SS14 and octreotide also inhibited forskolin-mediated accumulation of cAMP (42% and 40% inhibition of cAMP production, respectively; P < 0.01). The inhibitory action of somatostatin and octreotide on both VIP- and forskolin-mediated cAMP accumulation was blocked by pre-treatment of GH3 cells with pertussis toxin (P < 0.001). Neither SS14 nor octreotide affects the apparent affinity of VIP for its specific receptors on GH3 cells; thus, the inhibitory action of SS14 and octreotide appears to be mediated at the locus of the G-protein-adenylate cyclase complex. In contrast, CPP inhibited VIP-mediated cAMP accumulation slightly, but had no effect on forskolin-mediated cAMP production. Pertussis toxin did not attenuate CPP affects on VIP-mediated cAMP accumulation. However, pre-incubation of GH3 cells with CPP decreased the apparent affinity of receptors for VIP, suggesting that effects of CPP are attributable to interference with VIP binding rather than inhibition at the G-protein-adenylate cyclase complex.

Effect of prolonged oral terbutaline therapy on glucose tolerance in pregnancy

OBJECTIVE

Our objective was to elucidate the pathophysiologic effects and potential reversibility of terbutaline-induced changes in carbohydrate metabolism.

STUDY DESIGN

We prospectively evaluated serum glucose, insulin, glucagon, C-peptide, and pancreatic polypeptide levels in response to a 100 gm glucose challenge (oral 3-hour glucose tolerance test) in 17 obstetric patients without complications who were given terbutaline (5 mg orally every 4 hours) for 5 consecutive days between 24 and 32 weeks' gestation. Each patient served as her own control, with day 1 representing pretreatment, day 7 the treatment phase, and day 14 the posttreatment evaluation. Body mass index and posttreatment serum terbutaline levels were also measured.

RESULTS

A significant initial treatment effect (day 1 versus 7) was observed for glucose (elevated), insulin (elevated), insulin/glucose ratio (elevated), and pancreatic polypeptide (elevated). A significant delayed treatment effect (day 1 versus 14) was also observed for insulin (elevated), insulin/glucose ratio (elevated), and pancreatic polypeptide (elevated). Body mass index directly correlated with postchallenge measures of insulin, insulin/glucose ratio, pancreatic polypeptide, and C-peptide. Posttreatment serum terbutaline levels directly correlated with pancreatic polypeptide, but not with other parameters.

CONCLUSIONS

Our data support a dose-independent, terbutaline-induced glucose intolerance mediated by glucagon and caused by diminished insulin sensitivity.