Use of glucagon-like peptide-1 receptor agonists among individuals on basal insulin requiring treatment intensification

As Type 2 diabetes progresses, treatment is intensified with additional therapies in an effort to manage hyperglycaemia effectively and therefore avoid complications. When greater efficacy is required, options for injectable treatments include glucagon-like peptide-1 receptor agonists and insulin, which may be added on to oral glucose-lowering treatments. Among individuals receiving long-acting basal insulin as their first injectable treatment, ~40-60% are unable to achieve or maintain their target HbA_1c goals. For these people, treatment intensification options are relatively limited and include the addition of short-acting prandial insulin or a glucagon-like peptide-1 receptor agonist. Glucagon-like peptide-1 receptor agonists vary in their effects, with short- and long-acting agents having a greater impact on postprandial and fasting hyperglycaemia, respectively. Studies comparing treatment intensification options have found both glucagon-like peptide-1 receptor agonists and prandial insulin to be effective in reducing HbA_1c concentrations; however, recipients of glucagon-like peptide-1 receptor agonists lost weight and had a greater frequency of gastrointestinal adverse events, whereas those receiving prandial insulin gained weight and had a greater incidence of hypoglycaemia. In addition to the separate administration of a glucagon-like peptide-1 receptor agonist and basal insulin, fixed-ratio combinations of a glucagon-like peptide-1 receptor agonist and basal insulin offer a single administration for both treatments but have less flexibility in dose titration than treatment with their individual components. For individuals who require treatment intensification beyond basal insulin, use of these various options allows physicians to target the individual needs of their patients for the achievement of optimal long-term glycaemic control.

Rezeptorszintigraphie mit 111In-Pentetreotid beiendokrinen gastroenteropankreatischenTumoren

Die Rezeptorszintigraphie mit 111In-Pentetreotid ist ein komplementäres bildgebendesVerfahren mit einer Sensitivität von 88%, um bei Patienten mitklinischen und biochemischen Symptomen eines endokrinen Tumors desGastrointestinaltraktes oder des Pankreas den Primärtumor und dessen Metastasen zu lokalisieren. Als Ganzkörperszintigraphie erfaßt sie jede Körperregionund stellt auch kleine Tumoren dar, die mit den übrigen bildgebendenVerfahren nicht oder nur schwer zu entdecken sind. Bei 104 Patienten mit GEP-Tumoren oder nach operativer Entfernung eines solchen Tumors erwiessich die Rezeptorszintigraphie als dem Ultraschall und der Computertomographie bei 34% in der Aussagekraftüberlegen, bei 52% als gleich und bei 14%als unterlegen.

Clinical relevance of anti-exenatide antibodies: safety, efficacy and cross-reactivity with long-term treatment

AIMS

Antibody formation to therapeutic peptides is common. This analysis characterizes the time-course and cross-reactivity of anti-exenatide antibodies and potential effects on efficacy and safety.

METHODS

Data from intent-to-treat patients in 12 controlled (n = 2225,12-52 weeks) and 5 uncontrolled (n = 1538, up to 3 years) exenatide twice-daily (BID) trials and 4 controlled (n = 653,24-30 weeks) exenatide once weekly (QW) trials with 1 uncontrolled period (n = 128,52 weeks) were analysed.

RESULTS

Mean titres peaked early (6-22 weeks) and subsequently declined. At 30 weeks, 36.7% of exenatide BID patients were antibody-positive; 31.7% exhibited low titres (≤125) and 5.0% had higher titres (≥625). Antibody incidence declined to 16.9% (1.4% higher titre) at 3 years. Similarly, 56.8% of exenatide QW patients were antibody-positive (45.0% low/11.8% higher titre) at 24-30 weeks, declining to 45.4% positive (9.2% higher titre) at 52 weeks. Treatment-emergent anti-exenatide antibodies from a subset of patients tested did not cross-react with human GLP-1 or glucagon. Other than injection-site reactions, adverse event rates in antibody-positive and antibody-negative patients were similar. Efficacy was robust in both antibody-negative and antibody-positive patients (mean HbA1c change: -1.0 and -0.9%, respectively, exenatide BID; -1.6% and -1.3% exenatide QW). No correlation between change in HbA1c and titre was observed for exenatide BID, although mean reductions were attenuated in the small subset of patients (5%) with higher titres. A significant correlation was observed for exenatide QW with no difference between antibody-negative and low-titre patients, but an attenuated mean reduction in the subset of patients (12%) with higher titres.

CONCLUSIONS

Low-titre anti-exenatide antibodies were common with exenatide treatment (32% exenatide BID, 45% exenatide QW patients), but had no apparent effect on efficacy. Higher-titre antibodies were less common (5% exenatide BID, 12% exenatide QW) and within that titre group, increasing antibody titre was associated with reduced average efficacy that was statistically significant for exenatide QW. Other than injection-site reactions, anti-exenatide antibodies did not impact the safety of exenatide.

Intensive insulin therapy with insulin lispro in patients with type 1 diabetes reduces the frequency of hypoglycemic episodes

In a randomized, open-label, controlled cross-over trial, 107 patients with type 1 diabetes were treated with either regular human insulin or insulin lispro, a rapid-acting insulin analogue. After a lead-in period of 2 to 4 weeks, the patients were randomized to receive intensified insulin treatment with one of the insulins. NPH-human insulin was used for basal substitution in both groups. The crossover took place after 3 months of treatment. Efficacy and safety of the drugs were established by the assessment of hemoglobin A1c, pretest blood glucose, 1 and 2-hour postprandial glucose excursions, number of hypoglycemic episodes, daily insulin doses, body weight, insulin antibodies, and the number and severity of adverse events. A questionnaire comprised of four primary domains was used to measure some quality of life aspects of the patients. Both treatment regimens were well tolerated. While no differences were seen in the hemoglobin A1c values, there was a trend for a decrease in the pretest blood glucose levels and significant decreases of the 1 and 2-hour postprandial glucose excursions in the patients treated with insulin lispro. The number of hypoglycemic episodes was also significantly lower in the insulin lispro treatment period. The evaluation of the quality of life questionnaire revealed an improvement in the patients treatment satisfaction for the insulin lispro group. During treatment with insulin lispro, the basal insulin doses increased slightly. However, the total daily insulin doses decreased to a greater extent with insulin lispro as compared to regular human insulin. Human insulin-specific antibody binding values at endpoint were not different for the two treatments. In conclusion, intensive insulin treatment with insulin lispro therapy results in improved postprandial glycemic control and HbA1c levels at least equal to the treatment with regular human insulin but with less hypoglycemia and more treatment satisfaction for the patient.

Interim analysis of the effects of exenatide treatment on A1C, weight and cardiovascular risk factors over 82 weeks in 314 overweight patients with type 2 diabetes

AIM

Exenatide, an incretin mimetic for the adjunct treatment of type 2 diabetes (DM2), reduced A1C and weight in 30-week placebo-controlled trials. This analysis examined the effects of exenatide on glycaemic control and weight over an 82-week period in patients with DM2 unable to achieve adequate glycaemic control with sulphonylurea (SU) and/or metformin (MET).

METHODS

This interim analysis is of 314 patients who received exenatide in the 30-week placebo-controlled trials and subsequently in 52 weeks of open-label uncontrolled extension studies for 82 weeks of exenatide in total. Patients continued their SU and/or MET regimens throughout.

RESULTS

Patients completed 82 weeks of exenatide treatment [n = 314, 63% M, age 56 +/- 10 years, weight 99 +/- 21 kg, body mass index 34 +/- 6 kg/m2, A1C 8.3 +/- 1.0% (mean +/- SD)]. Reduction in A1C from baseline to week 30 [-0.9 +/- 0.1% (mean +/- SE)] was sustained to week 82 (-1.1 +/- 0.1%), with 48% of patients achieving A1C < or = 7% at week 82. At week 30, exenatide reduced body weight (a secondary endpoint) from baseline (-2.1 +/- 0.2 kg), with progressive reduction at week 82 (-4.4 +/- 0.3 kg). Similar results were observed for the intent-to-treat population (n = 551), with reductions in A1C and weight at week 82 of -0.8 +/- 0.1% and -3.5 +/- 0.2 kg respectively. The 82-week completer cohort showed statistically significant improvement in some cardiovascular risk factors. The most frequent adverse events were generally mild-to-moderate nausea and hypoglycaemia.

CONCLUSION

In summary, 82 weeks of adjunctive exenatide treatment in patients with DM2 treated with SU and/or MET resulted in sustained reduction in A1C and progressive reduction in weight, as well as improvement in some cardiovascular risk factors.

Exenatide: effect of injection time on postprandial glucose in patients with Type 2 diabetes

AIMS

Exenatide is an incretin mimetic whose effect on glycaemic control in patients with Type 2 diabetes is currently under investigation. This study assessed the effect of injection time relative to a standardized meal on postprandial pharmacodynamics of exenatide in patients with Type 2 diabetes.

METHODS

Eighteen patients participated in this single-centre, open-label, placebo-controlled, randomized, six-way crossover study. Patients received subcutaneous injections of either placebo (-15 min) or 10 microg of exenatide at -60, -15, 0, +30 or +60 min relative to a standardized breakfast meal on six consecutive days. Serial blood samples were assayed for plasma glucose and insulin concentrations.

RESULTS

For all exenatide treatments, incremental postprandial glucose area under the postprandial plasma glucose curve from zero to 6 h (AUC0-6 h) was significantly reduced compared with placebo. When exenatide was administered before (-60, -15 min) or with the meal (0 min), peak postprandial glucose concentrations were significantly decreased (P < 0.0001 for all treatments) compared with placebo. Post-meal exenatide administration (+30, P < 0.05; +60 min, P = 0.21) resulted in smaller peak glucose reductions and in some patients transient low plasma glucose concentrations were reported. Peak plasma insulin concentrations in the pre-meal treatments were significantly lower than placebo (P < 0.05 for all treatments), while post-meal dosing groups exhibited a trend towards higher insulin peaks compared with placebo. The most common adverse events related to exenatide were headache, nausea, dyspepsia and vomiting, and were generally of mild-to-moderate intensity.

CONCLUSIONS

In this study, all exenatide treatments demonstrated reductions in postprandial plasma glucose excursions compared with placebo. Pre-meal and with meal administration of exenatide produced greater reduction of postprandial glucose excursions compared with post-meal administration. These data support flexible dosing of exenatide at any time within 60 min before a meal.

Insulin lispro in the treatment of patients with type 2 diabetes mellitus after oral agent failure

This study assessed the safety profile and efficacy of a new combination therapy (insulin lispro plus sulfonylurea) in patients with type 2 diabetes mellitus experiencing secondary oral agent failure. A total of 423 patients were randomly assigned to 3 treatment groups: preprandial insulin lispro plus sulfonylurea (L + S), bedtime neutral protamine Hagedorn (NPH) insulin plus sulfonylurea (N + S), and preprandial insulin lispro plus bedtime NPH insulin (L + N). Mean decreases in glycosylated hemoglobin from baseline were 1.60%+/-1.27% for patients receiving L + S, 1.21%+/-1.21% for those receiving N + S, and 1.40%+/-1.46% for those receiving L + N (within treatment, P<0.001; for L + S vs. N + S, P = 0.003). Fasting blood glucose level was higher in patients receiving L + S (171+/-46.5 mg/dL) or L + N (166+/-52.5 mg/dL) than in those receiving N + S (144+/-48.2 mg/dL) (P<0.001, for both comparisons). Conversely, postprandial blood glucose level was lower in patients receiving L + S (165+/-41.6 mg/dL) or L + N (165+/-46.3 mg/dL) than in those receiving N + S (213+/-58.3 mg/dL) (P<0.001, for both comparisons). The overall rate of hypoglycemia (episodes per 30 days) was not statistically significant when the L + S, N + S, and L + N therapies were compared (0.99+/-1.74 vs. 0.87+/-2.31 vs. 1.16+/-2.38, respectively). The rate of nocturnal hypoglycemia was lowest in the L + S group (0.00+/-0.00 vs. 0.10+/-0.37 for the N + S group vs. 0.15+/-0.54 for the L + N group; P = 0.004). L + S, which has a safety profile equal to those of N + S and L + N, is an effective treatment for patients with type 2 diabetes who experience oral sulfonylurea agent failure. L + S offers an alternative to these established combination therapies in patients whose type 2 diabetes cannot be controlled with a sulfonylurea alone.

Mealtime treatment with insulin analog improves postprandial hyperglycemia and hypoglycemia in patients with non-insulin-dependent diabetes mellitus. Multicenter Insulin Lispro Study Group

BACKGROUND

Insulin lispro is an insulin analog that was recently developed particularly for a mealtime therapy. It has a fast absorption rate and short duration of action. The efficacy of insulin lispro in the clinical therapy of patients with non-insulin-dependent diabetes mellitus (NIDDM) has not been tested.

OBJECTIVES

To compare insulin lispro and human regular insulin in the mealtime treatment of patients with NIDDM.

METHODS

A 6-month, randomized, multinational (16 countries), multicenter (80 sites) clinical trial with an open-label, crossover design was performed in 722 patients with NIDDM. Insulin lispro was injected immediately before and human regular insulin 30 to 45 minutes before the meal.

RESULTS

Throughout the study, the postprandial rise in serum glucose levels was significantly lower during insulin lispro than human regular insulin treatment. At end point the rise (mean +/- SEM) in serum glucose levels was 30% lower at 1 hour (2.6 +/- 0.1 mmol/L [46.8 +/- 1.8 mg/ dL] for lispro vs 3.7 +/- 0.1 mmol/L [66.6 +/- 1.8 mg/dL] for human regular insulin) and 53% lower 2 hours after the test meal (1.4 +/- 0.1 mmol/L [25.2 +/- 1.8 mg/dL] for lispro vs 3.0 +/- 0.1 mmol/L [54.0 +/- 1.8 mg/dL] for human regular insulin) with insulin lispro compared with human regular insulin therapy (P < .001 for both intervals). During insulin lispro therapy the rate of hypoglycemia overall (P = .01) and overnight (P < .001) was lower and the number of asymptomatic hypoglycemic episodes was smaller (P = .03) than during human regular insulin therapy. Associated with a similar 13% increase (P < .001) in the total daily insulin dose, the glycosylated hemoglobin level decreased (P < .001) equally in both treatment groups. Serum lipid and lipoprotein levels remained unchanged. There were no differences in the adverse events between the 2 treatment groups.

CONCLUSIONS

Compared with human regular insulin therapy, mealtime therapy with insulin lispro reduced postprandial hyperglycemia and may decrease the rate of mild hypoglycemic episodes in patients with NIDDM.

Reduction of postprandial hyperglycemia and frequency of hypoglycemia in IDDM patients on insulin-analog treatment. Multicenter Insulin Lispro Study Group

Insulin lispro, an insulin analog recently developed particularly for mealtime therapy, has a fast absorption rate and a short duration of action. We compared insulin lispro and regular human insulin in the mealtime treatment of 1,008 patients with IDDM. The study was a 6-month randomized multinational (17 countries) and multicenter (102 investigators) clinical trial performed with an open-label crossover design. Insulin lispro was injected immediately before the meal, and regular human insulin was injected 30-45 min before the meal. Throughout the study, the postprandial rise in serum glucose was significantly lower during insulin lispro therapy. At the endpoint, the postprandial rise in serum glucose was reduced at 1 h by 1.3 mmol/l and at 2 h by 2.0 mmol/l in patients treated with insulin lispro (P < 0.001). The rate of hypoglycemia was 12% less with insulin lispro (6.4 +/- 0.2 vs. 7.2 +/- 0.3 episodes/30 days, P < 0.001), independent of basal insulin regimen or HbA1c level. The reduction was observed equally in episodes with and without symptoms. When the total number of episodes for each patient was analyzed according to the time of occurrence, the number of hypoglycemic episodes was less with insulin lispro than with regular human insulin therapy during three of four quarters of the day (P < 0.001). The largest relative improvement was observed at night. In conclusion, insulin lispro improves postprandial control, reduces hypoglycemic episodes, and improves patient convenience, compared with regular human insulin, in IDDM patients.

Improved mealtime treatment of diabetes mellitus using an insulin analogue. Multicenter Insulin Lispro Study Group

The absorption of regular human insulin from subcutaneous injection sites is delayed due to the self-association of insulin to multimeric forms. The insulin analogue insulin lispro has a weak self-association and a fast absorption rate. We examined the safety and efficacy of insulin lispro in the premeal treatment of patients with diabetes mellitus. A 12-month study was performed in 336 patients with insulin-dependent diabetes mellitus (IDDM) and 295 patients with non-insulin-dependent diabetes mellitus (NIDDM). The patients were randomized to inject either regular human insulin 30 to 45 minutes before eating, or insulin lispro immediately before each meal, in addition to basal insulin. The postprandial rise in serum glucose was lower in patients receiving insulin lispro than in those receiving regular human insulin therapy. At end point the increment was significantly lower at 1 hour (35%) and at 2 hours (64%) after the meal in IDDM patients; in NIDDM patients, the increment was nonsignificantly lower at 1 hour (19%) and significantly lower at 2 hours (48%). IDDM patients receiving insulin lispro achieved significantly lower glycated hemoglobin (HbA1c) levels in patients receiving regular human insulin (8.1% vs 8.3%). In NIDDM patients, HbA1c levels decreased equally in both treatment groups. Due to its fast absorption rate, insulin lispro improves postprandial control in diabetes. Insulin lispro can be considered one step toward optimal insulin therapy and improved patient convenience.

Prandial glycaemia after a carbohydrate-rich meal in type I diabetic patients: using the rapid acting insulin analogue [Lys(B28), Pro(B29)] human insulin

The time-action profile of the insulin analogue insulin lispro ([Lys(B28), Pro(B29)] human insulin) with its rapid onset and short duration of action might be more suitable to limit hyperglycaemic excursions after a meal rich in rapidly absorbable carbohydrates in comparison to regular human insulin. A randomized, double-blind study was performed in 10 Type I diabetic patients with good metabolic control (HbA1c 7.0 +/- 0.5%). After a baseline period of 3 h (blood glucose clamped at 6.7 mmol l-1, i.v. insulin infusion of 0.2 mU kg-1 min-1 throughout the study), the patients ate a pizza, drank a cola and had a carbohydrate-rich dessert (total carbohydrate content 140 g). Immediately before the meal 15.4 +/- 3.5 U of either insulin preparation were injected subcutaneously. Blood glucose concentrations were monitored continuously thereafter. Following the injection of insulin lispro the area under the blood glucose curve after the meal was 78% of that of regular insulin (1.76 +/- 0.34 vs 2.26 +/- 0.68 mol l-1 *240 min-1; p < 0.01). Maximal blood glucose excursions were higher and were reached later after regular insulin as compared to insulin lispro (11.9 +/- 2.8 vs 9.9 +/- 1.4 mmol l-1; p < 0.05; 66 +/- 37 vs 41 +/- 7 min; p < 0.05). Maximal individual differences in the blood glucose excursions (regular human insulin minus insulin lispro) were 4.8 +/- 2.2 mmol l-1 (p < 0.0001 against zero) after 110 +/- 37 min. In Type 1 diabetic patients prandial blood glucose excursions after a carbohydrate rich meal were reduced after preprandial injection of insulin lispro in comparison to human regular insulin.

Somatostatin analogue octreotide and inhibition of tumour growth in metastatic endocrine gastroenteropancreatic tumours

Antiproliferative treatment of patients with metastatic endocrine gastroenteropancreatic tumours (GEP) is based mainly on chemotherapeutic protocols whereby drug toxicity is a major handicap. Octreotide is the first choice in the control of hormone mediated symptoms. From retrospective and a few prospective studies it has been suggested that octreotide exhibits antiproliferative properties. The prospective German Sandostatin multicentre phase II trial investigated the effects of 200 micrograms octreotide thrice daily for one year on tumour growth and endocrine abnormalities in 103 patients. Octreotide treatment was continued in those patients responding to the drug until tumour progression occurred. In 28 of those with tumour progression during 200 micrograms thrice daily octreotide dose was increased to 500 micrograms thrice daily. The study sample consisted of 52 patients with computed tomography confirmed tumour progression and 13 patients with stable disease before octreotide treatment, whereas no preobservation period was available in 38 patients. Nineteen patients (36.5%) with computed tomography confirmed tumour progression experienced stabilisation of tumour growth lasting for at least three months. Median duration of stable disease was 18 months. At month 12, stable disease continued in 12 patients, declined after 24 months to nine patients, and after 36 months to five patients. Tumour regression has not been seen in this or other subgroups. In the subgroup with stable disease before octreotide, stable disease continued in 53.8% of patients over 12 months. Increase of octreotide dose to 500 micrograms thrice daily did not influence progression seen during the lower dose with the exception of one patient in whom tumour progression changed to stable disease. No association of tumour size response and patients' characteristics could be detected. The results suggest that octreotide inhibits tumour growth in patients with metastasised endocrine GEP tumours. The antiproliferative effect is, at least in some patients, longlasting. Currently, octreotide can only be recommended as an antiproliferative drug if patients with clearly progressive disease show stabilisation after treatment for three to six months.

Effect of the insulin analogue [LYS(B28),PRO(B29)] on blood glucose control

The limitations of conventional regular insulin in intensive insulin therapy are the slow onset of action and the long duration of action. To overcome these problems, the short-acting human insulin analogue [LYS(B28),PRO(B29)] (LYSPRO) was developed. In short-term and long-term clinical trials in healthy volunteers and diabetic patients, the difference in the time-action profile compared to regular insulin could be confirmed. Using LYSPRO without any injection-meal interval leads to reduced postprandial glucose excursions, even compared to the use of regular human insulin 30 minutes prior to the meal. Despite administration of LYSPRO immediately prior to meals, long-term blood glucose did not worsen. In additional studies it was shown that during exercise 3 hours after a meal, the fall of blood glucose was less pronounced in patients treated with LYSPRO as compared to regular human insulin. Thresholds for counterregulatory hormone responses to hypoglycemia were not different in volunteers when hypoglycemia was induced by either pork insulin or human insulin or LYSPRO. A short-acting human insulin analogue like LYSPRO may allow to simulate physiological postprandial insulin levels more closely. Treatment with LYSPRO may improve quality of life of diabetics by providing more flexibility.

Sodium butyrate induces neuroendocrine cytodifferentiation in the insulinoma cell line RINm5F

The differentiating agent sodium butyrate inhibits proliferation and stimulates cell-specific hormone expression in rat insulinoma cells. In this study, we investigated the effect of sodium butyrate on neuroendocrine cytodifferentiation in the rat insulinoma subclone, RINm5F. The cells were cultured with 0.5, 1, or 1.5 mM sodium butyrate for up to 72 h. Ultrastructurally, cells cultured with 1 mM sodium butyrate revealed a more differentiated appearance with an induction of cellular compartments involved in regulated insulin secretion. Morphometric analysis showed a significant elevation of neuroendocrine granule density. The total area of the specific granules was increased after incubation with 1 mM sodium butyrate for 48 and 72 h. Proliferation of RINm5F cells was inhibited by sodium butyrate in a dose-dependent manner. DNA production ceased completely within 24 h at 1.5 mM sodium butyrate. This concentration of sodium butyrate increased the cellular insulin content 8.9-fold and the insulin production 2-fold after 72 h. The insulin release was reduced from 79 +/- 3.5% in controls to 37 +/- 5.6% of total in a 24-h incubation period after 3 days of culture with 1.5 mM sodium butyrate. Insulin mRNA levels increased to a maximum of 324% compared with controls after 48 h of culture with 1.5 mM sodium butyrate. Chromogranin A mRNA levels increased to a similar extent (368 +/- 26%), whereas sodium butyrate did not stimulate the expression of synaptophysin, a major membrane component of small neuroendocrine vesicles. In conclusion, our data suggest the selective induction of neuroendocrine cytodifferentiation by sodium butyrate in RINm5F cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha-subunit and human chorionic gonadotropin-beta immunoreactivity in patients with malignant endocrine gastroenteropancreatic tumours

In the serum of patients with malignant endocrine gastroenteropancreatic (GEP) tumours, both alpha-subunit (alpha-SU), common to all glycoprotein hormones, as well as free beta-subunit of human chorionic gonadotropin (hCG-beta) have been reported to be elevated in a substantial fraction. Both have been discussed as markers of malignancy in these neoplasms. In the present study we evaluated the diagnostic significance of alpha-SU and hCG-beta as serum markers in patients with malignant endocrine gastroenteropancreatic tumours. The study group consisted of 52 patients with endocrine GEP-malignancies (24 nonfunctioning, 23 carcinoid syndromes, four gastrinoma, one glucagonoma), located in the small intestine (n = 29), pancreas (n = 17), colon or rectum (n = 3), retroperitoneum (n = 2) and stomach (n = 1). alpha-SU and hCG-beta immunoreactivity was also assessed in the serum of patients with benign GEP-tumors (five insulinoma, and three gastrinoma). Concentrations of alpha-SU and hCG-beta were determined using two highly sensitive and specific immunoradiometric assays employing two monoclonal antibodies each. In 19 of 52 patients (37%), either alpha-SU (n = 9), hCG-beta (n = 7) or both subunits (n = 3) were elevated. In the subgroup of 24 patients with nonfunctioning GEP-tumours, increased concentrations of either alpha-SU (n = 6) or hCG-beta(n = 3) or both subunits (n = 1) were found in 10 of 24 patients (42%). In four of 23 patients with carcinoid syndrome (17%), either alpha-SU (n = 2), hCG-beta(n = 1) or both subunits (n = 1) were above the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

[Receptor scintigraphy using 111In-pentetreotide in endocrine gastroenteropancreatic tumors]

Receptor scintigraphy with 111In-pentetreotide is a complementary imaging technique with a sensitivity of 88% for the localization of the primary tumor and its metastases in patients presenting with the clinical and biochemical symptoms of an endocrine tumor of the gastrointestinal tract or the pancreas. As a whole-body scintigraphic technique it covers all body regions and is also able to reveal small tumors which can only be detected with difficulty or not at all by the usual imaging methods. In 104 patients with GEP tumors or after operative removal of such tumors, receptor scintigraphy proved to be superior to ultrasound and computed tomography in 34%, equal in 52% and inferior in 14% of the cases.

Preoperative localization of gastrointestinal endocrine tumors using somatostatin-receptor scintigraphy

OBJECTIVE

The purpose of this study was to determine the value of somatostatin-receptor scintigraphy (SRS) in the preoperative localization of gastrointestinal endocrine tumors. The authors report their preliminary experiences with this new technique as compared to conventional imaging studies like computed tomography (CT) and ultrasonography (US).

SUMMARY BACKGROUND DATA

Most endocrine tumors possess high-affinity somatostatin-receptors. Using the stable, 111Indium labelled somatostatin analogue pentatreotid, which binds to these receptors, it is possible to detect somatostatin-receptor-positive tumors scintigraphically.

METHODS

In nine patients with various gastrointestinal endocrine tumors, SRS, CT, and US were performed before surgical exploration. The preoperative imaging studies and intraoperative ultrasound (IOUS) were then compared to findings on surgical exploration.

RESULTS

Twelve primary tumors were found in 8 patients at surgical exploration. These primary tumors were correctly identified with SRS in five patients, with US in four patients, and with CT in three patients. In one patient with the Zollinger-Ellison syndrome, scintigraphy suggested a tumor in the area of the hepatoduodenal ligament, while CT and US had negative results. The underlying gastrinoma could not be identified despite extensive surgical exploration. Scintigraphy, CT, and US showed comparable results in the detection of metastases in four patients.

CONCLUSIONS

The data from this small series suggest that SRS is helpful in the preoperative localization of gastrointestinal endocrine tumors.

Immunoreactivity and expression of amylin in gastroenteropancreatic endocrine tumors

Amylin was isolated from human insulinomas, but there has been only preliminary data regarding whether this peptide can also be detected in other types of gastroenteropancreatic endocrine tumors. In the present study, immunohistochemical staining of 87 gastroenteropancreatic endocrine tumors demonstrated amylin immunoreactivity in 21.8% of the neoplasmas. Thirteen of 15 insulinomas, three of 21 gastrinomas, two of 29 nonfunctioning tumors, and one of 18 carcinoids were amylin-immunoreactive. Seventeen of the 19 amylin-immunoreactive tumors were primarily located in the pancreas, but two tumors were found in the intestine. Measurements of amylin messenger RNA expression in a few tumors revealed amylin synthesis in these tumors. Amylin immunoreactivity did not correlate with invasion and metastasis. However, the rate of curative resections was significantly higher in amylin-immunoreactive tumors. These results demonstrate for the first time that amylin immunoreactivity is not restricted to insulinomas and can also occur rarely in endocrine tumors of the intestine.

Somatostatin analog sandostatin and inhibition of tumor growth in patients with metastatic endocrine gastroenteropancreatic tumors

A prospective study was performed to determine the efficacy of octreotide (Sandostatin; SMS 201-995) 200 micrograms tid in controlling tumor growth. The study included 21 patients with metastasized endocrine GEP tumors: 6 gastrinomas, 8 carcinoid syndromes, 7 nonfunctioning tumors. Treatment was performed for 3 to 59 months (median 15 months). Evaluation of the response to octreotide was facilitated in 12 patients by a pretreatment observation period of 3 to 47 months (median 17 months) during which the natural growth behavior was determined. Based on the presence or absence of a control period prior to treatment, 5 patients were considered to be responders, 7 as questionable responders (no pretreatment phase available), and 9 as nonresponders. None of the 21 patients had documented shrinkage of the tumor mass. The most favorable response was tumor standstill. In all but one responder an escape to an initially favorable response occurred after 6 to 28 months (median 14 months). Proved inhibition of growth was paralleled by a reduction of serum and urine hormone parameters, whereas unaltered progression of tumor growth was observed also in the presence of hormone suppression. Tumor growth and hormone release was inhibited in the absence and presence of somatostatin receptors on the tumor. It is concluded that octreotide exerts a limited effect on metastatic GEP tumor growth. The evaluation of a response to octreotide is facilitated by an observation period prior to the drug that provides information on growth characteristics of the tumor. The presence of octreotide receptors does not predict the success of therapy.

[Standardized surgical concept for the diagnosis and therapy of Zollinger-Ellison syndrome]

Between 1987 and 1991, 16 patients (13 females, three males; mean age 52.4 [33-73] years) with Zollinger-Ellison syndrome (ZES) were treated according to a standardized surgical concept. The diagnostic work-up consisted of measuring serum gastrin levels, pre-operative localization by ultrasound and abdominal computed tomography, as well as extensive staging by laparotomy. As complete a tumour resection as possible was the aim of treatment in 15 patients, while in one patient it was to reduce the tumour mass. In six patients who had resection of a solitary tumour there was no evidence of recurrence after 6-42 months of follow-up. Exploration of the duodenum made it possible to identify and then remove a small gastrinoma of the duodenal wall in three patients. No gastrinoma was found in one patient despite extensive exploration. In a further four patients the laparotomy was purely exploratory, because diffuse metastasization was found. In four patients the primary tumour and, where present, the regional lymph nodes were removed, but the signs of ZES persisted, i.e. the intervention was merely palliative. In one female patient, reduction of tumour mass was necessary because the symptoms could not be controlled by conservative measures: she died postoperatively from toxic hepatitis. This experience indicates that standardized surgical intervention achieves potentially curative results in nearly 40% of patients. Including the duodenum in the surgical exploration allows the identification of even small gastrinomas of the duodenal wall. It is concluded that all patients with ZES but no evidence of diffuse metastases should undergo surgical treatment.

Nucleolar organizer regions and glycoprotein-hormone alpha-chain reaction as markers of malignancy in endocrine tumours of the pancreas

The value of silver staining of nucleolar organizer regions (AgNORs) and human chorionic gonadotropin alpha-chain reaction (HCG-alpha) as markers of malignancy was investigated in 60 primary pancreatic endocrine tumours, 37 of which had metastasized at the time of surgery, and in one of which metastases developed 4 years after surgery. Assessment of AgNORs by digital image analysis revealed few but large AgNORs (mean number 2.5 +/- 1.1; mean area 0.32 +/- 0.1 microns 2) in the 22 benign tumours and many but small AgNORs (mean number 5.1 +/- 1.9, P < 0.05; mean area 0.18 +/- 0.09 microns 2, P < 0.01) in the malignant tumours. Quantification of the number of AgNORs per tumour cell nucleolus (AgNOR distribution score) showed that 96% (26/27) of tumours exhibiting at least 5% of cells with more than six AgNORs per nucleolus showed metastases either at the time of diagnosis or up to 4 years after surgery. HCG-alpha immunoreactive cells were present in 25/38 (66%) malignant tumours and in 4/22 (18%) benign tumours. Combined evaluation of AgNOR distribution and HCG-alpha scores showed a high positive predictive value of 96% in cases with a raised AgNOR distribution score irrespective of the HCG-alpha status. A good negative predictive value (81%) was, however, only obtained if both parameters, AgNOR distribution and HCG-alpha scores, were negative. Thus, investigation of AgNORs and HCG-alpha is helpful in predicting malignancy in a high percentage of pancreatic endocrine tumours.

Gastroenteropancreatic endocrine tumours: effect of Sandostatin on tumour growth. The German Sandostatin Study Group

One hundred and fifteen gastroenteropancreatic (GEP) patients with malignant endocrine tumours entered a prospective multicentre trial (12 patients with gastrinoma, 53 with carcinoid syndrome, 45 with nonfunctioning tumours and 5 with other endocrine GEP tumours) to determine the efficacy of 200 micrograms Sandostatin t.i.d. in the control of tumour growth. This interim report describes the results in 85 patients. Thirty-four patients died, 14 before and 20 after the first follow-up investigation, indicating a 'negative' selection of patients included in the trial and suggesting that Sandostatin is unable to prevent disease progression when it is far advanced. In the evaluation of 68 patients followed up for at least 3 months, partial regression was observed in 4.4%, stable disease in 50% and tumour progression in 45%. An initially favourable response occurred frequently, however, it was followed by a decrease in response, from 54.4% at 3 months to 38% at 12 months, for the whole group of patients. Proven inhibition of tumour growth was mirrored by suppression of serum and urine hormone parameters. It is concluded that Sandostatin exerts a beneficial effect on tumour growth in patients with metastatic endocrine GEP tumours. This beneficial effect decreases with time and is as yet unpredictable in the individual patient.

Gastroenteropancreatic endocrine tumors: effect of Sandostatin on tumor growth. The German Sandostatin Study Group

One hundred fifteen gastroenteropancreatic (GEP) patients with malignant endocrine tumors entered a prospective multicenter trial (12 patients with gastrinoma, 53 with carcinoid syndrome, 45 with nonfunctioning tumors, and five with other endocrine GEP tumors) to determine the efficacy of 200 micrograms Sandostatin three times a day in the control of tumor growth. This interim report describes the results in 85 patients. Thirty-four patients died, 14 before and 20 after the first follow-up investigation, indicating a "negative" selection of patients included in the trial and suggesting that Sandostatin cannot prevent disease progress when it is far advanced. In the evaluation of 68 patients monitored for at least 3 months, partial regression was observed in 4.4%, stable disease in 50%, and tumor progression in 45%. However, an initially favorable response frequently occurred with a decrease in response later: 54.4% at 3 months to 38% at 12 months for the whole group of patients. Proven inhibition of tumor growth was mirrored by suppression of serum and urine hormone parameters. It is concluded that Sandostatin exerts a beneficial effect on tumor growth in patients with metastatic endocrine GEP tumors. This beneficial effect decreases with time and is as yet unpredictable in the individual patient.

Stimulation of insulin release is uncoupled from insulin biosynthesis in tumoral RINm5F cells

RINm5F cells, an insulin-secreting subclone of a rat insulinoma cell line, were incubated in serum-free medium up to 24 hours in the presence or absence of glucagonlike peptide-1(7-36)amide in various concentrations, 3-isobutyl-1 methylxanthine (1 mM), choleratoxin (10 nM), carbachol (1 mM), and potassium (40 mM). Insulin release and biosynthesis were measured by the immunoreactive insulin content of the cells and the medium. Steady-state levels of insulin-specific mRNA were determined by Northern and slot blot analysis. Short-term insulin release is significantly stimulated by all secretagogues tested. A significant increase of insulin biosynthesis by any of the various secretagogues was not detectable on the peptide and mRNA level. Sodium butyrate (1 mM), a differentiating agent, increased insulin-specific mRNA levels in RINm5F cells after 72 hours. In conclusion, substances known to stimulate short-term insulin release in RINm5F cells do not stimulate insulin biosynthesis, indicating an uncoupling of insulin secretion and biosynthesis in these transformed beta cells.

[Somatostatin in preoperative therapy and postoperative diagnosis of a patient with Verner Morrison syndrome]

We report the case of a patient with Verner-Morrison syndrome due to a malignant MEN I-associated vipoma. Marked tumor-associated hypercalcemia could be treated successfully with somatostatin analogues prior to surgical therapy of the pancreatic tumor. Sixteen months after extirpation of the primary tumor recurrent tumor growth was diagnosed; at this time the patient was clinically asymptomatic and had no abnormal laboratory test results. Liver metastases and local metastases were identified using somatostatin receptor scintigraphy. We report and discuss the use of somatostatin in the treatment of tumor-associated symptoms in endocrine tumors and the possibility of identifying endocrine tumors by means of somatostatin receptor scintigraphy.

Atrial natriuretic factor has a weak insulinotropic action in the isolated perfused rat pancreas

The effect of atrial natriuretic factor (ANF; 1, 10, 100, 1000 pmol/l) on insulin release from the isolated perfused rat pancreas was studied. ANF weakly augmented the glucose (10 mmol/l)-stimulated insulin release during the second (controls: 100%; 1 pmol/l: 99%; 10 pmol/l: 149%, P less than 0.05; 100 pmol/l: 111%; 1000 pmol/l 135%), but not the first phase of the secretory response. In contrast, the first, but not the second phase of arginine (10 mmol/l)-stimulated insulin release was significantly enhanced by ANF (1000 pmol/l; controls: 100%; 1000 pmol/l: 235%, P less than 0.05). The hormone did not influence basal insulin secretion. Our data indicate an insulinotropic effect of ANF on the rat pancreas, which is dependent on the utilized background secretagogues.

Interaction of glucagon-like peptide-1 (7-36)amide and cholecystokinin-8 in the endocrine and exocrine rat pancreas

The synergistic impact of glucagon-like peptide-1 (GLP-1) (7-36)amide and cholecystokinin-8 (CCK-8) was studied in the rat pancreas. The GLP-1 (7-36)amide (1 pM-1 microM) had no effect on the basal or CCK-stimulated (1 nM-1 pM) amylase release from isolated pancreatic acini. The insulinotropic action of 0.5 nM GLP-1 (7-36)amide, which weakly stimulated the glucose-induced (6.7 mM) insulin release from the isolated perfused rat pancreas, was strongly potentiated by the addition of CCK-8 (20, 50, and 100 pM) to the perfusate. In concentrations as they occur physiologically after a meal, CCK-8 alone had no significant effect on basal or glucose-stimulated (6.7 mM) insulin secretion. Our data support the assumption that the nutrient-regulated intestinal release of various peptides represents a regulatory system to ensure an adequate insulin response to food intake, at least in rats.

Inverse relationship between glucose metabolism and glucose-induced insulin secretion in rat insulinoma cells

Slowly growing X-ray-induced rat insulinomas and derived cell lines have been used as a model system for glucose-induced insulin release. During perfusions of tumors transplanted under the kidney capsule, the carbohydrates glucose and D-glyceraldehyde increased insulin secretion. These stimuli and the amino acids leucine and alanine also provoked insulin release in freshly isolated tumor cells. Under these conditions, glucose utilization had a Km of 4.6 mM and maximal velocity of 0.9 nmol/min/10(6) cells. A continuous cell line was established from such a preparation. In culture, glucose-induced insulin secretion was no longer detectable while responses to D-glyceraldehyde and amino acids were retained. Glucose metabolism in the cell line showed a decrease in Km to 0.7 mM glucose and an increased maximal velocity of 1.4 nmol/min/10(6) cells. Attempts to revert these alterations were undertaken using glucose-deficient culture medium to diminish glycolytic flux. Basal insulin release was lowered, while the growth pattern of the cells remained unchanged. Another approach involved the use of sodium butyrate which has been demonstrated to promote differentiation in other cell systems. Whereas sodium butyrate markedly increased cellular insulin content, the secretory responses were not improved. These results provide evidence that the loss of glucose-induced insulin secretion is paralleled by alterations in glucose metabolism.

Signal transmission after GLP-1(7-36)amide binding in RINm5F cells

Glucagon-like peptide-1(7-36)amide [GLP-1(7-36)amide], probably representing an important incretin, binds to receptors on RINm5F cells resulting in an adenosine 3',5'-cyclic monophosphate increase. Guanine nucleotides (GTP, GTP-gamma-S, GDP-beta-S) decreased the binding of GLP-1(7-36)amide to receptors on RINm5F cell membranes. Further analysis revealed that GTP (10(-4) M) decreased the receptor affinity with an increase of the Kd from 2.5 +/- 0.99 x 10(-10) M to 9.43 +/- 2.16 x 10(-10) M. In cross-linking experiments the amount of labeled peptide linked to receptors was reduced in the presence of GTP (10(-4) M). Further studies investigated the involvement of membrane depolarization or changes in the cytosolic free calcium level in the intracellular signaling of GLP-1(7-36)amide-induced insulin secretion. In contrast to fuel and nonfuel secretagogues, GLP-1(7-36)amide did not cause a depolarization of the membrane potential. This was unaffected by various glucose concentrations (0-20 mM) or by previous cell depolarization by D-glyceraldehyde. Similarly, the cytosolic calcium concentration remained unchanged after addition of GLP-1(7-36)amide (10(-12)-10(-8) M). The effect of guanine nucleotides on binding of GLP-1(7-36)amide indicates that the action of the peptide is mediated by the adenylate cyclase system. GLP-1(7-36)amide binding neither changed the membrane potential nor altered the intracellular calcium concentration, making an involvement of the inositol 1,4,5-trisphosphate pathway or an activation of protein kinase C in the postreceptor signaling after GLP-1(7-36)amide binding unlikely.

Synergistic stimulatory effect of glucagon-like peptide-1 (7-36) amide and glucose-dependent insulin-releasing polypeptide on the endocrine rat pancreas

The interaction of glucagon-like peptide-1 (7-36)amide (GLP-1) and glucose-dependent insulin-releasing polypeptide (GIP) on insulin release from the perfused rat pancreas was studied. The GLP-1 stimulated (0.5 nmol/l), glucose-induced (6.7 mmol/l) insulin secretory answer was enhanced by GIP (0.1, 1.0 and 10.0 nmol/l) to the arterial perfusate. This effect was maximal at 1 nmol/l GIP and smaller but still significant at 0.1 nmol/l GIP. The high GIP concentration of 10 nmol/l GIP did not further increase insulin secretion compared to the stimulation by 1 nmol/l GIP. Our data demonstrate an additive synergistic effect of GLP-1 and GIP on the glucose-induced insulin release. This supports the concept of an action "in concert' of gastrointestinal incretin hormones postprandially released on the endocrine pancreas to guarantee adequate insulin answers after meals.

Characterization of glucose transport in an insulin-secreting cell line

The rat insulinoma-derived RINm5F cell line retains many differentiated functions of islet beta-cells. However, it fails to recognize glucose as an insulin secretagogue in the physiological concentration range. With this cell line, glucose-transport kinetics were investigated, by using a double-label technique with the non-metabolizable glucose analogue 3-O-methylglucose (OMG). RINm5F cells possess a passive glucose-transport system with high capacity and low affinity. Equilibration across the plasma membrane of extracellular OMG concentrations up to at least 20 mM is achieved within 2 min at 37 degrees C. The half-saturation of OMG uptake occurs at 32 mM. At lower temperatures OMG uptake is markedly retarded, with a temperature coefficient (Q10) of 2.9. As indicated by efflux measurements, transport is symmetrical. Cytochalasin B at micromolar concentrations and phlorrhizin in millimolar concentrations are potent inhibitors of OMG uptake. Neutralization of the secreted insulin with antibodies does not alter OMG uptake kinetics. The glucose metabolism of RINm5F cells is much exaggerated compared with that of islet beta-cells. Nonetheless, when measured in parallel to uptake, transport exceeds by far the rate of metabolism at glucose concentrations above 3 mM. Measurements of intracellular D-glucose reveal a lower intracellular glucose concentration relative to the extracellular in RINm5F cells. This seems to be due to abnormalities in the subsequent steps of glucose metabolism, rather than to abnormalities in hexose uptake. The loss of glucose-induced insulin release in RINm5F cells cannot be explained by alterations in hexose transport.