Unresponsiveness of insulinoma cells to secretin: significance of the secretin test in patients with insulinoma

It is well known that B cells in the pancreas release insulin when stimulated by secretin, but there have been few reports on the response of insulinoma cells to secretin. In five patients with insulinoma, changes in serum immunoreactive insulin (IRI) concentration were measured after the intravenous injection of secretin into the peripheral vein before and after extirpation of the insulinoma. The extirpated insulinomas were cultured and tested for their response to secretin. The rise in serum IRI in response to secretin in patients with insulinoma was significantly slower and smaller than in normal volunteers. After removal of the insulinoma, the response to secretin became prompt and increased with time. Cultured insulinoma cells did not release insulin when stimulated by secretin. Therefore, it is concluded that the response of insulinoma cells to secretin is quite different from that of normal beta cells, and that the function of beta cells in the insulinoma-bearing pancreas is suppressed by the autonomous hypersecretion of insulin by the insulinoma. The extent of the decrease in function of the beta cells in patients with insulinoma can be estimated by the intravenous secretin test. Thus, the secretin test is sometimes useful in the differentiation of hypoglycemia due to insulinoma from that due to beta cell hyperplasia or alimentary hyperinsulinemia.

Glucose metabolism in a patient with insulinoma complicated by hyperosmolar non-ketotic state

A case of a patient with organic hyperinsulinism complicated by the development of hyperosmolar state is described. The hyperosmolar state was induced by vomiting and dehydration during an acute urinary tract infection. Impairment of glucose metabolism was confirmed by the finding of reduced tissue sensitivity to insulin during a euglycaemic clamp.

Inhibition of streptozotocin-induced islet cell tumors and N-nitrosobis(2-oxopropyl)amine-induced pancreatic exocrine tumors in Syrian hamsters by exogenous insulin

The effects of streptozotocin (SZ) and N-nitrosobis(2-oxopropyl)amine (BOP), separately or in combination, on the pancreas, common duct, and gallbladder, all target tissues of BOP, were studied in Syrian golden hamsters. Groups of hamsters were treated with either a single dose (20 mg/kg body weight) of BOP (BOP group), or a single i.p. dose (50 mg/kg body weight) of SZ and 14 days later with a single s.c. injection of the same dose of BOP (SZ + BOP group). Another group of animals was treated similarly with BOP and SZ except that they received twice daily injections of insulin, beginning 1 day after SZ administration and for the duration of the experiment (52 weeks) (SZ + insulin + BOP group). The control group consisted of hamsters treated with a single dose of BOP and daily doses of insulin (insulin + BOP group). Hamsters treated with SZ recovered spontaneously from their diabetes, although the mortality was high (86%). BOP treatment inhibited the diabetogenic effects of SZ in both SZ + BOP and SZ + insulin + BOP groups and reduced the mortality to 43 and 74%, respectively. SZ pretreatment inhibited the incidence of BOP-induced pancreatic ductal/ductular cell carcinomas in the SZ + BOP group (P less than 0.01); this protective effect of SZ on carcinoma development was potentiated by additional treatment with insulin (SZ + insulin + BOP group, P less than 0.001). Although the frequency of BOP-induced tumors in the gallbladder (all polyps) was not altered by either SZ or insulin, the frequency of the common duct polyps was significantly lower in the SZ + insulin + BOP group than in the BOP group (P less than 0.005). Hamsters in the SZ, SZ + BOP, and SZ + insulin + BOP groups developed islet cell adenomas (insulomas). However, the SZ + insulin + BOP group had significantly fewer insulomas than in the SZ + BOP group (P less than 0.0005). The overall data confirm the inhibitory effect of SZ on BOP-induced pancreatic cancer and suggest that this effect is related to the diabetic condition of hamsters rather than insulin deficiency and that intact islets appear to be prerequisite for exocrine pancreatic cancer induction by BOP. On the other hand, the inhibitory action of insulin on insuloma induction by SZ and on ductal/ductular cancer induction by BOP seems to be related to the suppressive effect of this hormone on beta-cell and ductal/ductular cell replication, respectively.

[Dynamics of the blood serum protein fractions in patients with insulinoma]

Gel electrophoresis was used to study the blood serum of 13 patients with insulinomas who showed marked dysproteinemia in the preoperative period. Enucleation of the tumour or resection of the pancreas were performed depending on the location of the tumours. In the immediate postoperative period dysproteinemia became more pronounced, then a tendency to normalization of the protein spectrum occurred. Dysproteinemia was most pronounced at the zone of the starting peak where insulin-binding proteins are located.

Plasma pancreastatin-like immunoreactivity in various diseases

Plasma pancreastatin (PST)-like immunoreactivity in normal subjects and patients with various diseases was estimated by a RIA, using antiserum raised against a synthetic C-terminal peptide of human PST deduced from the sequence of human chromogranin-A. The mean level +/- SEM was 13.2 +/- 0.6 pmol/L in normal subjects, but was significantly higher in patients with chronic renal failure (526.7 +/- 48.5). An immunoreactive form corresponding to a human PST-like sequence [human chromogranin-A-(250-301)] and a larger form were detected by gel filtration of plasma from these patients, suggesting accumulation of the larger molecular form in these patients. A significant increase in PST-like immunoreactivity was also found in patients with liver cirrhosis (20.8 +/- 3.0 pmol/L), but not in patients with noninsulin-dependent diabetes mellitus, chronic pancreatitis, or pancreatic cancer. Elevated levels were found in 16 of the 21 patients with small cell lung carcinoma examined. High levels were also found in 3 of 11 patients with islet cell tumor.

Fasting insulin levels in normal Kenyan Africans and a case report on insulinoma

The mean fasting insulin level in 30 apparently normal Kenyan Africans was determined by Radio-Immuno Assay (RIA) technique based on coat A-count. The mean value was found as 16.33 microIu/ml with a standard deviation (s.d) of 10.51 microIu/ml. The mean at 95% confidence interval (CI) for the population studied was 16.33 +/- 1.92. The findings are similar to what have been reported among the caucasians. This paper also reports on a case of insulinoma in a young female patient at Kenyatta National Hospital (KNH).

Glucose-stimulated hormone release in rats bearing streptozotocin/nicotinamide-induced islet adenomas: evidence for slow and fast responders

Rats injected with streptozotocin and nicotinamide developed grossly visible islet cell tumors of the pancreas. During i.v. glucose tolerance tests, two populations of tumor-bearing rats were identified: fast responders exhibited significantly lower plasma glucose and markedly elevated plasma immunoreactive insulin (IRI) levels relative to those of the controls. In slow responders, the plasma glucose level was significantly elevated up to 2 h after glucose injection, and the plasma IRI level was lower than that of the controls. During in vitro perfusions with glucose at 300 mg/dl (16.7 mM), tumor-bearing pancreata of fast responders released elevated levels of IRI and immunoreactive somatostatin (IRS); after tumor removal, glucose-stimulated release of these hormones returned to control levels. However, during similar perfusions of pancreata from slow responders, the IRI and IRS release did not decrease after tumor removal, suggesting that the nontumorous pancreatic islets rather than the gross tumors of the slow-responder group were the source of the glucose-stimulated hormone release. These studies demonstrate that gross tumors in the two responder subgroups differ in their glucose-stimulated hormone release.

Lack of diabetogenic action of calcitonin in subjects affected by insulinoma

Calcitonin has been shown to affect calcium handling within cells thus impairing insulin secretion and glucose tolerance in healthy subjects. In the present study we investigate the effects of calcitonin on basal and nutrients-induced plasma glucose and insulin levels variations in healthy subjects (n = 10) and in patients affected by islet cell tumor (n = 6). In healthy subjects calcitonin markedly decreased basal and nutrients-induced plasma insulin levels while in patients with islet cell tumor this calcitonin-mediated effect was lost. So we conclude that the lack of calcitonin effect upon insulin secretion in patients with insulinoma is probably due to the autonomous insulin secretion characterizing islet cell tumor.

Malignant islet cell tumor of the pancreas associated with high plasma calcitonin and somatostatin levels

In this case report we describe a 41-year-old man, without a recognizable preexisting syndrome, who had ascites of massive proportions and died. A malignant tumor of the endocrine pancreas was identified and associated with an extremely high plasma calcitonin level. The plasma somatostatin level was also significantly elevated. Only one previous case report of a tumor with comparable secretory characteristics has been identified.

Suppression of primary and secondary peptides with somatostatin analog in the therapy of functional endocrine tumors

Sandostatin (SMS 201-995 (SMS)), a potent, long acting analog of native somatostatin was used in five patients with functional endocrine tumors (gastrinoma, two patients; insulinoma, one patient; glucagonoma, one, and adult onset nesidioblastosis, one). Primary and secondary peptide levels were obtained during provocation with a test meal, a calcium infusion, a secretin bolus and either a glucagon or tolbutamide bolus. During provocation test, the levels of the primary peptides insulin and C-peptide (nesidioblastosis and insulinoma), gastrin (gastrinoma), glucagon (glucagonoma) and the secondary peptides calcitonin, gastrointestinal peptide, gastrin releasing peptide, motilin, neurotensin, pancreatic polypeptide, somatostatin, substance-P and vasoactive intestinal peptide were obtained at predetermined intervals and quantitated by radioimmunoassay. SMS therapy was begun and peptide levels were again obtained during provocation. SMS suppressed basal primary peptide levels in all patients by more than 50 per cent. In 23 of 26 provocative tests, SMS effectively decreased circulating peptide levels by more than 50 per cent. Thirteen instances of elevated basal secondary peptides were discovered, and SMS universally suppressed these levels by a mean of 54 per cent. Of the 44 provocative tests performed, elevated secondary peptide levels were present in 41. SMS was effective in 31 of these 41 tests. The mean suppression of these provoked secondary peptide levels was 70 per cent. SMS effectively suppresses both basal and provoked peptides and, thus, provides relief of the clinical symptoms induced by pathologic elevations of primary and secondary peptides.

Glucagonoma syndrome

A 53-year-old Japanese man with a skin eruption characteristic of glucagonoma syndrome had had misdiagnoses for 10 years. The plasma glucagon level was not abnormally high on the first admission, and 4 years later the level was elevated as determined by the 30 gm arginine tolerance test. An alpha cell carcinoma detected in the tail of the pancreas was associated with a lymph node metastasis; the skin eruption cleared up 10 days after the partial pancreatectomy with lymphadenectomy. The clinical features of glucagonoma syndrome should be given attention.

A standardized meal stimulation test of the endocrine pancreas for early detection of pancreatic endocrine tumors in multiple endocrine neoplasia type 1 syndrome: five years experience

Forty-nine members of 6 families with multiple endocrine neoplasia type 1 (MEN 1) were investigated with a standardized meal stimulation test to detect the presence of pancreatic endocrine tumors. Fifteen age-matched subjects and 4 patients with primary hyperparathyroidism also were studied. Serum pancreatic polypeptide (PP), gastrin, and insulin as well as plasma glucagon and somatostatin concentrations were determined before and during the test meal. Patients with demonstrable pancreatic endocrine tumors had significantly increased mean basal and peak serum PP (P less than 0.001) and gastrin (P less than 0.001) responses to the meal compared with healthy family members and normal subjects. Seven of 12 MEN 1 patients with parathyroid and pituitary disease but no demonstrable pancreatic endocrine tumors had exaggerated PP and/or gastrin responses to the meal; 4 of them developed pancreatic endocrine tumors, detected by abdominal computerized tomography, 0.5-4 yr later. None of the healthy members of the MEN 1 families or the patients with primary hyperparathyroidism had responses different from those of the normal subjects. Our experience with the meal stimulation test indicates that an elevated basal or exaggerated serum PP and/or gastrin response is an earlier sign of pancreatic involvement in the MEN 1 trait than is abdominal computerized tomography.

Alpha-fetoprotein associated with islet cell tumors

Elevated serum levels of alpha-fetoprotein (AFP) (100-1,000 ng/ml) were found in three patients with islet cell tumors. Serial levels correlated with progression of disease, suggesting that AFP could be a useful tumor marker substance for islet cell tumors. Survey sera from an expanded pool of 23 patients with islet cell tumors and nine with carcinoid tumors did not identify additional cases, however, suggesting that elevated AFP levels in these classes of Apudomas are uncommon. Nonetheless, the distinction from other AFP-producing tumors such as hepatocellular carcinoma is clinically important and warrants an awareness of the rare association of AFP with these tumors.

Peptide histidine-methionine immunoreactivity in plasma and tissue from patients with vasoactive intestinal peptide-secreting tumors and watery diarrhea syndrome

The presence of peptide histidine-methionine (PHM)-like peptides has been determined in plasma and tumor specimens from patients with vasoactive intestinal peptide (VIP)-secreting tumors and the watery diarrhea syndrome. All patients had strikingly elevated plasma concentrations of PHM immunoreactivity (median, 1800; range, 500-6800 pmol/liter; n = 12), which were higher than those of VIP (median, 235; range, 50-580 pmol/liter). In patients with other endocrine and nonendocrine pancreatic tumors, plasma PHM concentrations were not significantly different from normal (median, 20; range, 5-60 pmol/liter; n = 28). Plasma samples from patients with diarrhea due to other illnesses also had PHM concentrations that were not significantly different from normal (median, 40; range, 10-80 pmol/liter; n = 23). The gel chromatographic profiles of plasma and tumor extracts from patients with VIP-secreting tumors revealed the presence of at least two molecular forms that reacted with an antiserum directed to the N-terminus of PHM (SY1). The later peak (Kav, 0.50-0.53) corresponded in position to synthetic PHM and also reacted with the PHM-specific antiserum (SY2). The earlier peak (Kav, 0.30-0.37), not reactive with antiserum SY2, corresponded to a large molecular form of PHM-like immunoreactivity previously identified as the predominant form in normal human stomach and plasma, though not in the rest of the intestinal tract. The neuroendocrine nature of the tumors was confirmed by the demonstration of immunostaining with a battery of antisera to neuroendocrine markers. Immunocytochemistry revealed the presence of both VIP and PHM in tumor cells. The presence of high circulating concentrations of PHM-like immunoreactivity in patients with VIP-secreting tumors, as measured with a PHM N-terminus-directed antiserum, SY1, suggests that use of this type of antiserum may provide valuable information in the diagnosis of such tumors. The contribution of the PHM-like peptides to the features of this syndrome is not known.

Lack of suppression of insulin secretion by hyperinsulinemia in a patient with an insulinoma

The regulation of insulin secretion in patients with insulinoma is known to be abnormal. For example, physiological and pharmacological stimuli often fail to stimulate insulin in such patients. Recently, insulin has been found to inhibit its own secretion in normal subjects. To determine if insulin has this effect in patients with insulinoma, we infused insulin at rates of 1 and 10 mU/kg X min in such a patient and in eight normal subjects. Euglycemia was maintained by the euglycemic glucose clamp technique, and endogenous insulin secretion was estimated by measuring plasma C-peptide levels. In the normal subjects, plasma C-peptide declined from 1.60 +/- 0.22 (+/- SEM) to 1.16 +/- 0.17 and 0.82 +/- 0.11 ng/ml during the low and high dose insulin infusions, respectively, indicating 27% (P less than 0.01) and 48% (P less than 0.001) decreases in endogenous insulin secretion at moderately elevated and extremely elevated insulin levels, respectively. In the insulinoma patient, plasma C-peptide was 2.6 ng/ml basally, did not change during the low dose insulin infusion, and rose to 3.4 ng/ml during the high dose insulin infusion. We conclude that the feedback regulation of insulin secretion by insulin that occurs in normal subjects is absent in insulinoma patients. This finding could have pathophysiological and possibly diagnostic significance.

The effect of exogenous hyperinsulinemia on proinsulin secretion in normal man, obese subjects, and patients with insulinoma

To examine possible feedback inhibition of insulin on proinsulin secretion, we measured serum proinsulin levels before and after 120 min of euglycemic hyperinsulinemia (90-100 mU/liter) in 11 normal and 7 obese hyperinsulinemic subjects and 6 patients with beta-cell adenoma (n = 4), carcinoma, or hyperplasia. Baseline proinsulin levels accounted for 19%, 14%, and 56% of the total immunoreactive insulin in the 3 groups, respectively. Compared to normal subjects, baseline proinsulin levels were elevated (P less than 0.02) by 4- and 6-fold in obese subjects and patients with autonomous insulin secretion, respectively, but there was an overlap between the groups. In both normal and obese subjects, hyperinsulinemia suppressed proinsulin secretion by 45-50% (P less than 0.02), whereas no response occurred in the patients. Thus, the 120 min values were clearly different in the patients and the normal or obese subjects. After removal of the adenoma in 4 patients, baseline proinsulin levels and the response to hyperinsulinemia were normalized, but they remained elevated after a partial pancreatectomy or tumor removal in the patients with beta-cell hyperplasia or carcinoma. Thus, proinsulin secretion is under negative feedback control of insulin in both normal man and hyperinsulinemic obese subjects. In patients with insulinoma or beta-cell hyperplasia, this control is lost.

Immunohistochemical study of neuron-specific enolase and CA 19-9 in pancreatic disorders. The value of neuron-specific enolase as a marker for islet cell and nerve tissue

Immunohistochemical studies of neuron-specific enolase were performed on pancreatic tissues from patients with insulinoma, nonfunctioning islet cell tumor, chronic pancreatitis, and pancreatic adenocarcinoma, and from 5 normal patients. The concentration of neuron-specific enolase was also measured in the sera of patients and in the pancreatic tissue, and the tissues were stained for carbohydrate antigen 19-9 by immunohistochemical techniques. Neuron-specific enolase was localized in nerve fibers, normal islet cells, and islet cell tumors; its concentration was elevated only in the tissue of islet cell tumors and in serum from patients with insulinoma. In the pancreatic tissue of pancreatitis or pancreatic adenocarcinoma, various changes in acini and islets were present. The altered islets stained clearly for neuron-specific enolase and could easily be distinguished from altered, unstained acini in cases of pancreatitis or pancreatic adenocarcinoma. Islets in the pancreatic tissue remained intact with various morphologic changes, although acini had degenerated severely. Carbohydrate antigen 19-9 was localized in all the carcinoma cells in the pancreatic tissue and in some of the normal pancreatic ducts. No cells were simultaneously immunostained by anti-neuron-specific enolase and anti-carbohydrate antigen 19-9 antibodies. Thus, neuron-specific enolase is a good marker for islet cell tumor, and is valuable for examining islets in pancreas with various disorders both alone and in combination with other tumor markers.

Hormonal modification of the growth and metabolic effects of a transplantable rat insulinoma

The growth and metabolic effects of a transplantable radiation-induced rat insulinoma were examined in intact male and female New England Deaconess Hospital (NEDH) rats, and in parathyroidectomised or adrenalectomised male NEDH rats. Subscapular transplantation of insulinoma fragments in intact male rats consistently produced a highly vascularised encapsulated tumour associated with hyperphagia, hyperinsulinaemia and hypoglycaemia which progressed to fatal neuroglycopaenic coma by 30 +/- 0.8 days (mean +/- SEM) and 19 +/- 0.5 days for slow-growing and fast-growing tumour sublines respectively (P less than 0.001). In intact female rats transplanted with the slow-growing subline, the onset of hyperphagia was advanced by 4 days and the severity of hyperinsulinaemia and hypoglycaemia increased (21% and 36%; P less than 0.01 and P less than 0.001, respectively), resulting in a 10% decrease of survival time (P less than 0.05) and a 65% reduction of tumour weight (P less than 0.01). Transplantation of the fast-growing subline into parathyroidectomised male rats, which exhibited a 15-24% (P less than 0.05 - less than 0.01) decrease of plasma calcium, did not modify either the growth or metabolic effects of the tumour. In contrast, transplantation of this subline into adrenalectomised male rats decreased survival time by 32% (P less than 0.001) and reduced final tumour weight by 88% (P less than 0.02) without markedly affecting the onset or magnitude of the hyperinsulinaemia. These results indicate that the growth and metabolic effects of the transplantable NEDH rat insulinoma are modified by the presence of ovarian hormones and by adrenal hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretory response and immunochemical heterogeneity of glucagon in plasma and tumor extracts of a patient with glucagonoma

The secretory response and immunoreactive heterogeneity of glucagon was investigated in a patient with glucagonoma syndrome. After glucose administration, abnormal insulin release accompanied by glucose intolerance were observed, whereas the high glucagon circulating levels were only partially blocked after glucose or somatostatin infusion. Chromatographic fractionation of plasma samples, before and after arginine administration showed that most of the immunoreactivity eluted as true glucagon. Furthermore, when aliquots of the tumor extracts were fractionated by column chromatography or by polyacrylamide gel electrophoresis, most of the immunoreactivity eluted in the 3,500 molecular weight peak. In contrast with previous reports, our results indicate that neoplasia A cells can also manufacture and release into the bloodstream great amounts of genuine glucagon rather than larger glucagon immunoreactive forms. In spite of such findings, in this patient neither diabetes nor hyperglycemia were present.

Euthyroid hyperthyroxinemia and thyroxine-binding prealbumin excess in islet cell carcinoma

This manuscript describes euthyroid hyperthyroxinemia secondary to elevated serum T4-binding prealbumin (TBPA) concentrations in a patient with islet cell carcinoma and reports serum TBPA measurements in other patients with islet cell carcinoma. A 73-yr-old man with a 17-yr history of metastatic islet cell carcinoma was found to have hyperthyroxinemia. His total serum T4 concentration was 18.5 micrograms/dl (normal, 5.5-11.5). Eight years previously, his serum T4 concentration was normal. His free T4 concentration, as determined by equilibrium dialysis, was 1.3 ng/dl (normal, 0.9-2.1). Serum T3, TSH, and T4-binding globulin (TBG) concentrations were normal, as was the TSH response to TRH administration. Polyacrylamide gel electrophoresis of the patient's serum in the presence of tracer amounts of [125I]T4 revealed that, compared to normal sera, [125I]T4 binding to TBPA was increased from 30.0 +/- 6.0% (mean +/- SD) to 52.0%. The distribution of [125I]T3 amont albumin, TBG, and TBPA was normal in this electrophoretic procedure. The concentration of TBPA in the patient's serum was 189 mg/dl. In contrast, the mean serum TBPA concentration in normal men was 40 +/- 4 (mean +/- SD) mg/dl, and that in normal women was 18 +/- 4 mg/dl. Sera from the patient's daughter, his brother, 2 sisters, and 2 male paternal cousins contained normal amounts of TBPA, ranging from 34-47 mg/dl in his male relatives and from 26-30 mg/dl in his female relatives. Serum free T4 index determinations in his relatives also were normal. Serum TBPA concentrations were determined in 14 additional patients with islet cell carcinoma. In 1 of these patients, a man with an insulinoma, serum TBPA was elevated (66 mg/dl). This patient's serum T4 level was 7.3 micrograms/dl, and his free T4 index was 7.0. These data and another study suggest that islet cell carcinoma may rarely produce a TBPA-like protein resulting in an elevated serum TBPA concentration. Markedly elevated serum TBPA is associated with euthyroid hyperthyroxinemia.