Caplacizumab reduces the frequency of major thromboembolic events, exacerbations and death in patients with acquired thrombotic thrombocytopenic purpura

Essentials Acquired thrombotic thrombocytopenic purpura (aTTP) is linked with significant morbidity/mortality. Caplacizumab's effect on major thromboembolic (TE) events, exacerbations and death was studied. Fewer caplacizumab-treated patients had a major TE event, an exacerbation, or died versus placebo. Caplacizumab has the potential to reduce the acute morbidity and mortality associated with aTTP.

SUMMARY

Background Acquired thrombotic thrombocytopenic purpura (aTTP) is a life-threatening autoimmune thrombotic microangiopathy. In spite of treatment with plasma exchange and immunosuppression, patients remain at risk for thrombotic complications, exacerbations, and death. In the phase II TITAN study, treatment with caplacizumab, an anti-von Willebrand factor Nanobody® was shown to reduce the time to confirmed platelet count normalization and exacerbations during treatment. Objective The clinical benefit of caplacizumab was further investigated in a post hoc analysis of the incidence of major thromboembolic events and exacerbations during the study drug treatment period and thrombotic thrombocytopenic purpura-related death during the study. Methods The Standardized Medical Dictionary for Regulatory Activities (MedDRA) Query (SMQ) for 'embolic and thrombotic events' was run to investigate the occurrence of major thromboembolic events and exacerbations in the safety population of the TITAN study, which consisted of 72 patients, of whom 35 received caplacizumab and 37 received placebo. Results Four events (one pulmonary embolism and three aTTP exacerbations) were reported in four patients in the caplacizumab group, and 20 such events were reported in 14 patients in the placebo group (two acute myocardial infarctions, one ischemic stroke, one hemorrhagic stroke, one pulmonary embolism, one deep vein thrombosis, one venous thrombosis, and 13 aTTP exacerbations). Two of the placebo-treated patients died from aTTP during the study. Conclusion In total, 11.4% of caplacizumab-treated patients and 43.2% of placebo-treated patients experienced one or more major thromboembolic events, experienced an exacerbation, or died. This analysis shows the potential for caplacizumab to reduce the risk of major thromboembolic morbidities and mortality associated with aTTP.

Consensus on the standardization of terminology in thrombotic thrombocytopenic purpura and related thrombotic microangiopathies

Essentials An international collaboration provides a consensus for clinical definitions. This concerns thrombotic microangiopathies and thrombotic thrombocytopenic purpura (TTP). The consensus defines diagnosis, disease monitoring and response to treatment. Requirements for ADAMTS-13 are given.

SUMMARY

Background Thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS) are two important acute conditions to diagnose. Thrombotic microangiopathy (TMA) is a broad pathophysiologic process that leads to microangiopathic hemolytic anemia and thrombocytopenia, and involves capillary and small-vessel platelet aggregates. The most common cause is disseminated intravascular coagulation, which may be differentiated by abnormal coagulation. Clinically, a number of conditions present with microangiopathic hemolytic anemia and thrombocytopenia, including cancer, infection, transplantation, drug use, autoimmune disease, and pre-eclampsia and hemolysis, elevated liver enzymes and low platelet count syndrome in pregnancy. Despite overlapping clinical presentations, TTP and HUS have distinct pathophysiologies and treatment pathways. Objectives To present a consensus document from an International Working Group on TTP and associated thrombotic microangiopathies (TMAs). Methods The International Working Group has proposed definitions and terminology based on published information and consensus-based recommendations. Conclusion The consensus aims to aid clinical decisions, but also future studies and trials, utilizing standardized definitions. It presents a classification of the causes of TMA, and criteria for clinical response, remission and relapse of congenital and immune-mediated TTP.

A single center review of the experience with mitomycin C (MMC) and the risk of thrombotic thrombocytopenic purpura (TTP)/hemolytic uremic syndrome (HUS)

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Background: MMC related TTP/HUS has been reported between 4 and 15%, with a higher incidence in patients receiving cumulative doses of 60 mg or higher. It tends to occur within 4 months of drug administration independently of patients’ cancer status. The ability of MMC to upregulate enzymes relevant for new cytototoxic agents (topoisomerase I for CPT-11 and thymidine phosphorylase for capecitabine) make phamacobiologically based therapeutic combinations including MMC attractive. Methods: All patients (n=100) that participated in four institutional clinical studies from 2000 through 2004 were included. The studies were OSU 9947 (phase I trial of CPT-11 and MMC in solid tumors, n=31) OSU 0151 (phase II trial of CPT-11 and MMC in advanced esophageal and stomach cancer, n=41) OSU 0155 (phase II trial of CPT-11 and MMC in patients with refractory breast cancer, n=26) OSU 0330 (phase I study of capecitabine and MMC in patients with advanced GI tumors n=2). In each study, the maximum cumulative dose of MMC was 36 mg/m2. All patients were followed for clinical signs or symptoms of TTP/HUS including the presence of anemia, thrombocytopenia and renal insufficiency and had a thorough review of the peripheral smear. Results: The median cumulative dose was 12 mg/m2 (range 3–36 mg/m2). No patients met the clinical diagnosis of TTP/HUS except for one patient had anemia, thrombocytopenia and renal insufficiency but did not manifest any other findings consistent with TTP/HUS such as changes in mental status, azotemia or any other clinical symptom. The laboratory abnormalities resolved without intervention within seven days with subsequent continuation on the clinical trial. Conclusions: In this study we have demonstrated that by capping the cumulative dose of MMC to 36 mg/m2, the incidence of TTP/HUS is minimal. Furthermore, our preliminary analysis of an additional 100 patients treated with MMC at OSU shows no reported cases of TTP/HUS (additional data will be presented at the meeting). Since MMC is effective in a wide variety of solid tumors including breast, lung and GI malignancies and is inexpensive and easy to administer, further exploration of MMC in the treatment of solid malignancies is indicated including rational combination studies.

No significant financial relationships to disclose.

A rapid test for the diagnosis of thrombotic thrombocytopenic purpura using surface enhanced laser desorption/ionization time-of-flight (SELDI-TOF)-mass spectrometry

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP), a life-threatening thrombotic microangiopathy, requires immediate diagnosis and plasma exchange therapy. Development of TTP is related to functional deficiency of ADAMTS-13 protease that leads to the accumulation of ultra large von Willebrand factor (VWF) and subsequent platelet thrombosis. Currently no clinical test is available for the rapid detection of ADAMTS-13 activity.

OBJECTIVES

The goal is to devise a novel method to rapidly detect functional activity of ADAMTS-13 and improve clinical outcome.

METHODS AND RESULTS

A recombinant VWF substrate containing the ADAMTS-13 cleavage site and a 6X Histidine tag was cleaved by ADAMTS-13 in a dose-dependent manner, generating approximately 7739 Da peptide containing a 6X Histidine tag. This cleaved peptide, bound to an IMAC/Nickel ProteinChip, was quantified using Surface Enhanced Laser Desorption/Ionization Time-of-flight Mass Spectrometry (SELDI-TOF-MS). The assay is capable of quantifying ADAMTS-13 activity as low as 2.5% in plasma within 4 h. When the cleaved peptide was quantified as a ratio of an internal control peptide, the test displayed good reproducibility, with an average inter-assay coefficient of variation (CV) of < 33%. Further validation revealed a mean ADAMTS-13 activity of 92.5% +/- 16.6% in 39 healthy donors. Sixteen patients with idiopathic TTP displayed mean ADAMTS-13 activity of 1.73% +/- 3.62%. Further utility of this novel method includes determining the inhibitory titer of ADAMTS-13 antibody in cases of acquired TTP.

CONCLUSIONS

We have devised a novel SELDI-TOF-MS assay that offers a rapid, cost-effective, and functionally relevant test for timely diagnosis and management of TTP.

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)

Continuous subcutaneous octreotide infusion: dose-response relationships between metabolic effects and octreotide clearance in patients with insulin-dependent (type 1) diabetes

Octreotide (Sandostatin), a potent and long-acting octapeptide analogue of somatostatin, exhibits variable metabolic effects in type 1 diabetes. We have postulated that interindividual variability in octreotide metabolism could be responsible in part for the differences in metabolic responses reported in previous clinical studies. To this end, we determined plasma levels and MCR of octreotide during 24-hour continuous SC infusion (low dose, 200 micrograms; high dose, 400 micrograms) in nine female, C peptide-negative patients with type 1 diabetes. The metabolic effects of the analogue were assessed by measuring serum glucose, free insulin, glucagon, GH, and PP levels before and at 1- to 2-hour intervals during each dose of the analogue or control (0.9% saline solution) infusion in a single-blind randomized manner. Mean daytime (0800-0000 hours) and bedtime (0000-0800 hours) serum glucose levels decreased significantly (p less than 0.05 to 0.02) during analogue therapy compared with control. Mean serum free insulin levels were significantly (p less than 0.02) greater during octreotide infusion compared with control, despite the similar daily insulin requirements. Both doses of the analogue effectively suppressed 24-hour GH by 50%, glucagon by 50%, and PP by 80%. Steady-state octreotide levels varied considerably among patients (low, mean +/- SEM), 1000 +/- 101, range 638 to 1375 pg/ml; high, mean 1940 +/- 147, range 1032 to 2462 pg/ml). Although mean MCR values were similar with both doses, we observed greater interindividual variability (low, mean 2.45 +/- 0.30, range 1.31 to 3.78 ml/kg/min; high, mean 2.36 +/- 0.19, range 1.68 to 3.48 ml/kg/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic effects of long-acting somatostatin analogue (sandostatin) in type I diabetic patients on conventional therapy

We evaluated the effectiveness of a more potent and longer-acting somatostatin analogue (SMS 201-995) as an adjunct to insulin therapy, in a double-blind placebo-controlled randomized study of 26 C-peptide-negative type I (insulin-dependent) diabetic patients (20 women, 6 men, aged 22-40 yr) on their conventional drug regimens for 12 wk. Eight patients received a low dose (10 micrograms) of the analogue, 9 received a high dose (50 micrograms) of the analogue, and 9 received placebo subcutaneously before breakfast and dinner. Twenty-four-hour serum glucose, free insulin, plasma growth hormone (GH), and glucagon profiles were obtained before and during treatment at 4-wk intervals. The mean age, duration of diabetes, daily insulin dose, and body weight were not significantly different among the groups. The mean weekly capillary blood glucose values and exogenous insulin requirements were not changed by the SMS 201-995 therapy. Mean glycosylated hemoglobin A1 levels were unchanged in both the analogue- and placebo-treated groups at wk 12. Basal and postprandial glucose, free insulin, GH, and glucagon profiles were not influenced by the SMS 201-995 therapy throughout the study. Nocturnal glucose turnover rates (D-[3-3H]glucose technique) remained unaltered by the analogue therapy. Dose-dependent gastrointestinal (GI) adverse effects (e.g., diarrhea) were documented in the analogue-treated patients. Visual acuity and fundic photomicrographs of our patients were not changed by the analogue therapy. In conclusion, the prominent adverse GI effects our patients experienced preclude the use of larger doses of the analogue that may be necessary to suppress GH and glucagon and improve glucose control in type I diabetic patients.

Comparison of the effects of continuous subcutaneous infusion and split-mixed injection of insulin on nerve function in type I diabetes mellitus

Comparable groups of type I diabetic patients (n = 19) were matched for age, duration of diabetes, mean HbA1 values, insulin requirements, degree of neuropathy, and the mean of nerve conduction velocities (CV) in median, ulnar, and peroneal motor and median, ulnar, and sural sensory nerves. One group (n = 9) was managed with continuous subcutaneous infusion of (regular) insulin (CSII); the other (n = 10) with split-mixed injections of (intermediate and regular) insulin (SMII). After 12 months, glucose regulation was equally and significantly improved in both groups (P less than 0.005), although it was not sufficiently intense to normalize mean total glycosylated hemoglobin values in either group. Furthermore treatment produced no difference between groups in the values for mean amplitude of glycemic excursions, 12 month average of consecutive M-values or in clinical evaluation. However, in the CSII group, mean CV had increased 6.4% (2.75 + 0.56 m/s; mean +/- SEM) versus 1.3% (0.57 +/- 0.54 m/s) in the SMII group (P less than 0.005). Multivariate analysis on a nerve-by-nerve basis found significantly improved conduction in 2/6 nerves (median motor; ulnar sensory) in the CSII group compared to the SMII group. These results suggest that CSII may provide a more favorable microenvironment for nerve repair.

Absence of hepatic extraction of gastric inhibitory polypeptide in conscious dogs

Fractional hepatic extraction of gastric inhibitory polypeptide was examined in conscious unrestrained dogs with catheters in the portal vein, hepatic vein, and the carotid artery and Doppler flow probes on the portal vein and hepatic artery. Following a control period, endogenous gastric inhibitory polypeptide was stimulated by oral administration of glucose with and without prior infusion of atropine. In other experiments, gastric inhibitory polypeptide (20 ng/kg/min) was infused into the portal system in association with peripheral infusion of glucose. In none of these experiments was it possible to demonstrate any significant fractional hepatic extraction of gastric inhibitory polypeptide.

Exercise adaptation responses for gastric inhibitory polypeptide (GIP) and insulin in obese children. Possible extra-pancreatic effects

Thirteen obese children and matched controls were fed a mixed meal, and responses were evaluated at fixed intervals for glucose, insulin, and gastric inhibitory polypeptide (GIP). The obese children were evaluated before and within 48 h after completion of a 5-mo exercise training program (ETP). The ETP included three aerobic exercise sessions per week and modest diet restrictions. Caloric expenditure was increased by approximately 300 kcal/exercise session. Weight gain was minimal over the 5 mo. An unexpected increase in GIP response and improved insulin tolerance were recorded for the obese children post-ETP. GIP values were higher (P less than 0.05) at 30 and 60 min and led to a highly significant elevation (P less than 0.01) of the integrated GIP response for post-ETP obese versus both pre-ETP and normal-weight controls. Insulin values were lower (P less than 0.05) at 30 and 60 min and led to a lower integrated insulin response (P less than 0.0585) for post-ETP obese children. However, the obese children continued to secrete more insulin (P less than 0.05) than normal-weight controls. Glucose tolerance, similar for pre-ETP obese subjects and controls, did not change in post-ETP children. Exercise-induced improvement in glucose utilization in these obese children was associated with an increase in GIP secretion. This contrasts with reports that calorie restriction will improve glucose utilization with decreased insulin and GIP secretion. The study demonstrates a previously unreported uncoupling of GIP and insulin secretion and suggests shifts in peripheral tissue sensitivity to insulin-induced glucose uptake. These shifts may, in part, be influenced by GIP.

Identification of tissue insulin receptors: use of a unique in vivo radioreceptor assay

An in vivo radioreceptor assay for polypeptide hormones has been developed and applied to the identification of tissue insulin receptors. The theoretical basis for this assay is presented elsewhere in this issue. 125I-insulin and 131I-albumin were infused into male rats with increasing amounts of unlabeled insulin. Plasma samples were taken at 1-min intervals until the animals were killed at 5 min. Tissue samples were excised and weighed and the activity due to each isotope counted. By comparing the differential distribution of the labeled tracers and applying the results to a compartment model, the specific, displaceable binding of insulin to tissue receptors could be demonstrated. Binding was detected in the liver, muscle, fat, adrenal glands, pancreas, small intestines, and spleen.

Theoretical basis for a new in vivo radioreceptor assay for polypeptide hormones

To date the in vivo identification and quantitation of specific hormone receptors has been difficult, time consuming, and lacking in sensitivity. We present the theory underlying a new in vivo radioreceptor assay for polypeptide hormones based on receptor theory derived from in vitro investigations and in vivo kinetic and autoradiographic studies. The assay was developed from a tissue model and a theory of hormone distribution. Measuring the labeled hormone distributed between the plasma and interstitial space in the presence or absence of excess unlabeled hormone permits the accurate determination of hormone specifically bound to receptors. This approach eliminates the problem of nonspecific binding due to free tracer, hormone degradation products, or labeled non-hormone molecules. A receptor compartment and specific binding of hormone are calculated from only four measured parameters: total tissue labeled hormone, tissue albumin, plasma labeled hormone, and plasma albumin. The method is applicable to most tissues and hormones under a variety of conditions and permits simultaneous comparison of multiple tissues in the same animal under identical conditions.

Production of 12-hydroxyeicosatetraenoic acid and vitamin E status in platelets from type I human diabetic subjects

Vitamin E content and biosynthesis of 12-hydroxyeicosatetraenoic acid (12-HETE) have been measured in platelets from type I diabetic subjects and age- and sex-matched, nondiabetic control subjects. Platelets from diabetic subjects synthesized significantly greater quantities of 12-HETE than did platelets from control subjects when 12-HETE synthesis was induced by thrombin or collagen, either in the presence or absence of indomethacin. Platelet conversion of exogenously added arachidonic acid (AA) to 12-HETE was not significantly different between the diabetic and control groups in the absence of indomethacin, although a small but significant increase in the conversion of AA to 12-HETE was present in the diabetic group platelets when indomethacin was added to the reaction. Vitamin E content was significantly reduced in platelets from the diabetic subjects, when compared with platelets from the control subjects, although plasma vitamin E levels were not significantly different between the two groups. Thrombin- and collagen-induced platelet 12-HETE synthesis demonstrated a significant negative linear correlation with platelet vitamin E content when measurements from both diabetic and control groups were combined. The above data suggest a relationship between low vitamin E content and increased 12-HETE synthesis in platelets from type I diabetic subjects.

Abnormal retinal artery responses to stress in patients with type I diabetes

The brachial artery pressure and retinal artery pressure responses to a one-minute cold pressor test were evaluated simultaneously in 14 patients with type I diabetes mellitus (six with and eight without diabetic retinopathy) and 10 age-matched control subjects. Five patients with type I diabetes had autonomic neuropathy. Mean baseline brachial artery pressure and retinal artery pressure were similar in patients with type I diabetes and control subjects. After cold pressor testing, the brachial artery pressure increased significantly (p less than 0.01) compared with baseline values in both groups. Retinal mean arterial pressures increased significantly (p less than 0.001) after cold pressor testing compared with the baseline values only in patients with type I diabetes. Positive correlation was found between the brachial and retinal mean arterial pressures after cold pressor testing (r = 0.48; p less than 0.05) in the diabetic patients but not in the control subjects (r = 0.10; p = NS). No correlation was found between the retinal artery pressure and age of onset of diabetes, duration of diabetes, the presence or absence of diabetic retinopathy, and glycemic control. Four patients with autonomic neuropathy and low retinal artery pressures, which remained unchanged after cold pressor testing, had no diabetic retinopathy. The fifth patient with autonomic neuropathy and exaggerated systolic brachial artery pressure (175 mm Hg) and retinal artery pressure (more than 80 mm Hg) responses had severe background diabetic retinopathy. In conclusion, abnormal retinal artery responses to stress are present in patients with type I diabetes. This may be modified by the presence or absence of both autonomic neuropathy and hypertension. The biologic significance of these findings is yet to be determined.

Action of platelet-activating factor on type 1 diabetic human platelets

Platelets from patients with type 1 diabetes have exhibited more sensitivity to aggregation when compared with platelets from controls without diabetes after challenge with platelet-activating factor (PAF). The production of thromboxane B2 (TxB2) and 12-hydroxyeicosatetraenoic acid (12-HETE) and the release of 5-hydroxytryptamine (5HT) were increased when the platelets were challenged by PAF (5.0 X 10(-6) mol/L and 1.0 X 10(-6) mol/L). The production of TxB2 and 12-HETE and the release of 5HT were related to the irreversible biphasic aggregation profiles observed in the patients with diabetes. Inhibition of thromboxane A2 (TxA2) production by acetylsalicylic acid abolished the secondary wave of aggregation of platelets from patients with diabetes, changing an irreversible aggregation to a reversible one. Inhibition of both TxA2 and 12-HETE production by eicosatetraynoic acid did not contribute further to the inhibition caused by acetylsalicylic acid alone, indicating that 12-HETE was not involved in the secondary wave of aggregation. These data show that the increased aggregation observed in the platelets from the group with diabetes in response to PAF results in part from their higher production of TxA2 and release of 5HT.

Significance of spontaneous ketonuria and serum C-peptide levels in obese type II diabetic patients

Patients with type II diabetes mellitus (type II DM patients) are characteristically obese, hyperinsulinemic, and non-ketosis prone. Recently, we have encountered several obese type II DM patients with either diabetic ketoacidosis or significant ketonuria after insulin withdrawal. There was no evidence of infection, stress, or starvation to explain their ketonuria. Therefore, we assessed serum connecting peptide (C-peptide) response to oral glucose in 14 obese, insulin-treated type II DM patients: 6 with and 8 without episodes of spontaneous ketonuria. The group presenting with ketonuria had low to absent basal and stimulated serum C-peptide responses. The nonketonuric group had higher basal C-peptide (P less than 0.01) concentrations that increased significantly (P less than 0.001) after oral glucose compared with those of the ketonuric group. Clinical characteristics and biochemical control were similar in both groups. Our findings confirm that obese type II diabetes mellitus is a heterogeneous disease with variable fasting and stimulated C-peptide responses. Spontaneous ketonuria could be a feature in the clinical presentation of the patients especially in the presence of both low fasting and stimulated C-peptide levels. The significance of these findings is unclear but suggests individualization in the management of type II DM patients and cautious withdrawal of insulin therapy in such patients. Furthermore, serum C-peptide levels alone cannot be recommended to classify patients into either type I or type II diabetes mellitus.

Interrelation of platelet vitamin E and thromboxane synthesis in type I diabetes mellitus

Platelet vitamin E content and thromboxane A2 (TxA2) synthesis have been investigated in type I diabetic subjects and age- and sex-matched controls. Platelets, but not plasma, from diabetic subjects contained significantly lower vitamin E levels and synthesized significantly greater amounts of TxA2 when challenged with collagen or thrombin than platelets from control subjects. Conversion of exogenously added arachidonic acid to TxA2 was unaltered between platelets from control and diabetic groups. Platelet vitamin E content from control and diabetic groups combined exhibited a significant negative linear correlation with collagen- and thrombin-induced TxA2 production. These data suggest that low platelet vitamin E levels could be a contributing factor to the increased thromboxane synthesis demonstrated by platelets from the above type I diabetic subjects.

Angiotensin II and norepinephrine antagonize the secretory effect of VIP in rat ileum and colon

Vasoactive intestinal polypeptide (VIP) induces intestinal secretion of water and electrolytes in experimental animals and man. We assessed the ability of angiotensin II (AII) and norepinephrine (NE) to block the secretion evoked by VIP, in vivo. Ileal and colonic segments in rats were perfused in situ for two hours with a physiological buffer containing [14C]-PEG-4000 as a volume marker. Saline (0.9% NaCl) was infused intravenously during the first hour and VIP or a combination of VIP plus AII or NE was infused during the second hour. All (0.7 ng/kg/min) alone enhanced water absorption significantly (p less than 0.01) in the ileum and an appreciable, although not a statistically significant, effect was observed in the colon. AII antagonized the secretory effects of VIP in the ileum as well as in the colon. Norepinephrine (5 micrograms/kg/min) also reversed the effect of VIP on the small intestine and colon. Although the mechanism by which AII antagonizes the secretory effects of VIP has not been identified, it is probable that AII promotes absorption, at least in part secondary to release of mucosal NE.

Limitations in usefulness of single dose intermediate acting insulin: a rapid response pattern in some type I diabetics

Ten Type I insulin-dependent diabetics who were receiving single daily injections of intermediate acting insulin were studied to assess time-response characteristics of this therapy on 24-hour profiles of both glucose and free insulin. Nine of ten patients had undetectable postprandial levels of C-peptide. All patients had insulin antibodies typical of chronically treated Type I diabetes. Mean peak free insulin levels occurred four hours post injection with free insulin rising from 12.3 +/- 1.6 microU/ml to 26.5 +/- 1.4 microU/ml; p less than 0.01. The glucose nadir for the 24-hour profile also occurred at four hours after injection with glucose declining from 199 +/- 29 mg/dl fasting to 155 +/- 5 mg/dl; p less than 0.05. There was significant negative correlation between mean glucose and free insulin throughout the first six hours after insulin injection (r = -0.74; p less than 0.02); no correlation occurred 8 to 12 hours post injection. Two of the ten patients had hypoglycemic symptoms within four hours after their morning insulin. Although free insulin levels remained above basal for 20 hours, single dose intermediate insulin therapy never really controlled postprandial glucose levels after breakfast or lunch. These data suggest there may be limitations in managing Type I diabetics with single dose intermediate insulin. Furthermore, some patients on intermediate acting insulin may have a more rapid than anticipated maximal hypoglycemic response, often within four hours.

Pancreatic polypeptide responses to protein meal challenges in obese but otherwise normal children and obese children with Prader-Willi syndrome

Children with hyperphagia and obesity of Prader-Willi syndrome (PWS) have previously been shown to have blunted pancreatic polypeptide (PP) response to low protein meal stimulation. To evaluate the effects of various protein challenges on PP release in children with PWS, we administered both a low protein (0.2 g/kg) and a high protein (2.0 g/kg) meal stimulation test to 12 children previously diagnosed as having PWS and to an age- and weight-matched group of 19 obese but otherwise normal children. Serum samples were collected just before and for 3 h after meal ingestion. The mean (+/- SD) age was 11.7 +/- 4.2 yr for the PWS group and 10.3 +/- 3.8 yr for the obese group (P = 0.323). The percent ideal body weight for height for the PWS group (mean +/- SD 186 +/- 48%) was not significantly different from the percent ideal body weight for height for the obese group (174 +/- 35%; P = 0.421). Peak PP responses were significantly less for the PWS group than for the obese group for both the low and high protein meal stimulations. The mean (+/- SE) peak PP response with the low protein meal was 76.1 +/- 13 pg/ml for the PWS group and 302 +/- 93 pg/ml for the obese group (P less than 0.05). The mean peak response with the high protein meal was 181 +/- 51 pg/ml for the PWS group and 581 +/- 127 pg/ml for the obese group (P less than 0.01). Glucose rises were similar for both tests, although the PWS group did have a slightly smaller rise in glucose after the low protein stimulation than was observed in the obese group. The insulin response was also significantly less for the low protein meal in the PWS group compared to the low protein insulin response of the obese group. There were no significant differences in the insulin responses observed in both groups with the high protein meal test. This study confirms our previous observation and suggests that many children with PWS have a functional deficiency of PP. Our current study demonstrates that this condition is not a result of their obese condition or an alteration in their response threshold to protein.

Blood insulin, glucose, fructose and gastric inhibitory polypeptide levels in carbohydrate-sensitive and normal men given a sucrose or invert sugar tolerance test

Twelve carbohydrate-sensitive and 12 normal men were selected for the study. Carbohydrate-sensitivity was based on an abnormal insulin response to a sucrose load. The subjects were fed a diet consisting of 45% of the calories as carbohydrate, 40% fat and 15% protein for 5 days prior to a sucrose or invert sugar tolerance test. In a crossover design, subjects were given 2 g/kg body weight of sucrose or invert sugar, and responses of insulin, glucose, fructose and gastric inhibitory polypeptide (GIP) were determined. Blood samples were taken at 0, 0.5, 1, 2 and 3 hours after being given the test loads. Insulin and glucose levels were significantly higher in carbohydrate-sensitive as compared to normal men. Glucose and GIP did not show any significant differences between the two carbohydrate loads. At 1 hour, the carbohydrate-sensitive men given sucrose had significantly higher insulin levels than carbohydrate-sensitive men given invert sugar (disaccharide effect). At 1, 2 and 3 hours, the disaccharide effect was shown in the fructose levels of the carbohydrate-sensitive men. In normal men, the disaccharide effect with levels of fructose was seen at 0.5 and 3 hours. This study indicates that the disaccharide effect on blood insulin cannot be explained by differences in gastric inhibitory polypeptide in unadapted human subjects.

Gastric inhibitory polypeptide (GIP) release by actively transported, structurally similar carbohydrates

Six awake adult dogs prepared with a duodenocutaneous fistula were infused intraduodenally with one of the following solutions: 3% saline, 10% glucose, 20% glucose, 20% galactose, 20% fructose, 20% mannose, 20% sorbitol, 20% maltose, 20% lactose, or 20% sucrose. Both 10 and 20% glucose stimulated GIP release, and the response appeared to be dose related. Actively transported galactose (C-4 epimer) stimulated GIP release, but less than glucose. Fructose (C-2 keto sugar) which is absorbed by facilitated transport did not stimulate GIP release. Mannose (C-2 epimer) which is passively absorbed by diffusion did not release GIP. Sorbitol (reduced alcohol of glucose) which is not absorbed did not release GIP. Of the disaccharides tested, only maltose stimulated the release of GIP. The results suggest that structural integrity of the glucose molecule from the C-1 to C-4 carbon atoms, a free aldehyde group on the C-1 carbon atom, and a cyclic structure are all necessary for both the active transport of glucose and the release of endogenous GIP. It would appear that structurally similar receptors exist for both the active transport of glucose and for the release of GIP.

Diabetic nephropathy. Clinical course in patients treated with the subcutaneous insulin pump

Twelve type I diabetic patients with established diabetic nephropathy were treated for 12 months with the insulin pump to determine whether glucoregulation would influence the clinical course of proteinuria. All of the subjects were known to have arterial hypertension and were receiving antihypertension medication. Despite good glucose control, as assessed by total glycosylated hemoglobin level, two clinical courses were observed: six patients demonstrated a progression in proteinuria and six appeared to experience a reduction in proteinuria. The group demonstrating a progression had significantly higher mean arterial pressure at six and 12 months of study compared with the group with a reduction in proteinuria. These results suggest that arterial hypertension is an important risk factor in the progression of diabetes nephropathy. Further studies should be designed to recognize early proteinuria and hypertension to determine whether mean normal glucose values and BP over a prolonged period will prevent renal failure.

Postprandial release of gastric inhibitory polypeptide (GIP) and pancreatic polypeptide in dogs with pancreatic acinar atrophy. Correction of blunted GIP response by addition of pancreatic enzymes to a meal

In order to evaluate the enteropancreatic hormone axis in dogs with pancreatic acinar atrophy, we measured the release of gastric inhibitory polypeptide and pancreatic polypeptide in response to a standard meal and a meal containing pancreatic enzymes in affected dogs and controls. Postprandial release of pancreatic polypeptide was normal in dogs with pancreatic atrophy and was not affected by addition of pancreatic enzymes to the food. Gastric inhibitory polypeptide was not released after a standard meal in affected dogs, but this blunted response was corrected by the addition of pancreatic enzymes to the food. Feeding the enzyme alone did not stimulate a gastric inhibitory polypeptide response. These results, in part, support similar observations previously reported in children with exocrine pancreatic insufficiency associated with cystic fibrosis. We conclude that dogs with idiopathic pancreatic acinar atrophy can be used as an animal model for future study of enteropancreatic hormonal abnormalities that occur in human beings with exocrine pancreatic insufficiency.

The role of gastric inhibitory polypeptide in the augmented insulin response to sucrose

To evaluate the role of gastric inhibitory polypeptide (GIP) in the augmented insulin response to sucrose, seven normal volunteers ingested four separate meals of 100 g sucrose (S), 50 g glucose (G), 50 g fructose (F), and 50 g glucose + 50 g fructose (G + F). Serum insulin, glucose, and GIP were measured. In each of the 3 h after sugar ingestion the integrated insulin response to (S) was greater than to (G) with the 3-h total being 104% greater. The integrated glucose response to (S) was slightly greater than to (G) in the first and second hours but the differences were not significant. Integrated GIP response to (S) was greater than to (G) in hours 2 and 3. Although significant insulin and glucose responses to (F) occurred in hour 1, G + F led to insulin and glucose responses similar to G. G + F led to greater GIP levels than G in hour 3. These studies show that GIP may play a role in the augmented insulin response to S in hours 2 and 3. This may result from delayed gastric emptying and glucose absorption. The augmentation of insulin to S in the first hour may result from fructose, extra glucose equivalent of the sucrose test solution, or from endocrine mechanisms other than those subserved by GIP.

Spurious elevations in glycosylated hemoglobin (HbA1) secondary to hypertriglyceridemia

Measurement of glycosylated hemoglobin (HbA1) is frequently helpful to clinicians in treating patients with diabetes, since a number of studies show that this reflects a reliable index of diabetic control over time. There are several methods of measuring HbA. The chromatographic method is the most frequently used and is the standard method for large demand. We recently encountered a patient with diabetes mellitus who had substantial lactescent plasma secondary to hypertriglyceridemia that falsely raised the HbA1 level. We examined the patient in detail and determined that triglyceride concentrations greater than 1,750 mg/dL would falsely raise the HbA1 levels. In vitro studies performed by adding lipemic plasma to a control sample confirmed this. Thus, spurious elevations in HbA1 can occur in patients with lactescent plasma. This would further complicate the already existing interrelationship between glucose intolerance and hypertriglyceridemia.

Gastrin Responses to a test meal in patients with familial medullary thyroid carcinoma

The serum gastrin response to a standard test meal was evaluated in patients with familial medullary thyroid carcinoma (MTC) and in normal subjects. Patients with MTC and elevated plasma calcitonin levels had a lower gastrin response to the test meal than did normal persons or MTC patients who had normal calcitonin levels postthyroidectomy. There was no significant difference between the mean gastrin response of the normal group and that of the MTC patients with normal calcitonin levels. The serum gastrin response was studied before and after thyroidectomy in four patients. In all four, the post-operative response was greater than the preoperative one . We conclude that patients with MTC may have reduced gastrin responses to a test meal. This effect may be related to circulating calcitonin, somatostatin, or other factors related to familial MTC.

Improvement of high-density lipoprotein-cholesterol levels. Ambulatory type I diabetics treated with the subcutaneous insulin pump

Twelve ambulatory patients (six women and six men; mean age, 29 years) with type I diabetes were treated with a continuous subcutaneous open-loop insulin pump in an attempt to effect better glucose control. Hemoglobin A1, mean blood glucose, total cholesterol, total triglycerides, low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), and the cholesterol/HDL-C ratio were assessed monthly before and after glucoregulation from five to 14 months (mean, nine months). Mean HDL-C levels increased significantly (52 +/- 4 to 60 +/- 5 mg/dL); mean cholesterol/HDL-C ratios decreased significantly (4.46 +/- 0.43 to 3.89 +/- 0.39). Mean values for triglycerides, total cholesterol, and LDL-C, all initially normal, did not change. Both mean Hb A1 levels and glucose levels fell from 11.2% +/- 0.5% to 9.8% +/- 0.5% and 177 +/- 15 mg/dL to 128 +/- 12 mg/dL, respectively. Insulin requirements decreased from 0.80 +/- 0.08 to 0.61 +/- 0.05 units/kg/24 hr. These results may favorably alter the prediction for development of accelerated atherosclerosis in type I diabetics.

Effects of amino acids and gastric inhibitory polypeptide on insulin release in dogs

Insulin release following intravenous administration of an amino acid solution with and without a simultaneous infusion of varying amounts of porcine gastric inhibitory polypeptide (GIP) was studied in dogs. Group I received a 10-amino acid mixture (300 mosmol/kg iv) at 16.6 ml/min for 1 h; group II, amino acid mixture plus 0.5 micrograms.kg-1.h-1 porcine GIP; group III, amino acid mixture plus 1.0 micrograms.kg-1.h-1 of GIP; group IV (a and b) received either 0.5 or 1.0 micrograms.kg-1.h-1 of GIP alone. Compared to group I, groups II and III had a greater insulin response during the first 30 min of the infusion. Group] IV (a and b) showed no insulin release. Glucose concentrations showed no significant change in all groups. From these results, it is concluded that insulin release after intravenous infusion of an amino acid mixture plus GIP is greater than after amino acids or GIP alone. It appears that this effect is more pronounced in the early phase of insulin release.

Pancreatic polypeptide in acute pancreatitis and small-bowel infarction in dogs

Serum and urine concentrations of pancreatic polypeptide (PP) were measured during experimental acute hemorrhagic pancreatitis and small-bowel infarction in dogs. The mean serum PP concentration in animals with pancreatitis increased markedly after 1 hr and remained elevated, while the mean serum PP concentration in the animals with infarction showed a late trend to increase. The urine PP concentration in pancreatitis increased nonsignificantly, whereas, during bowel infarction, there was no increase. In the infarction group, PP clearance correlated with the serum PP concentration. During pancreatitis, PP was cleared independently of the serum PP concentration. The results suggest that during acute hemorrhagic pancreatitis there is an acute release of PP related to immediate cell injury in the pancreas. The high serum concentration of PP may lead to an override of the normal renal handling of PP. In small-bowel infarction there may be a delayed mode of PP release.

Diabetes responsive to intravenous but not subcutaneous insulin: effectiveness of aprotinin

Patients with diabetes that is insensitive to subcutaneous insulin but sensitive to intravenous insulin have recently been described. We have studied this phenomenon is five female diabetics (14 to 31 years of age) who required excessive amounts of insulin (2.5 to 30.0 units per kilogram of body weight per day) to avoid recurrent ketoacidosis. Known causes of insulin resistance were excluded. All patients had normal responses to conventional doses of intravenous insulin (0.35 to 0.9 unit per kilogram per day). Four patients required continuous intravenous infusion of insulin for one to six months. When a mixture of aprotinin (a protease inhibitor) and regular porcine insulin was given subcutaneously, conventional doses (0.7 to 1.4 units per kilogram per day) produced euglycemia; plasma levels of free insulin rose, and ketonuria disappeared. Four patients had episodes of spontaneous, severe hypoglycemia before and during aprotinin therapy, necessitating continuous infusion of glucose for two to 14 days. Although no insulin was administered, hyperinsulinemia (50 to 2000 muU of free insulin per milliliter [359 to 14,350 pmol per liter]) was present. These findings suggest excessive degradation or sequestration of insulin at the site of injection.

Vagal release of IR-VIP and IR-gastrin from the isolated perfused rat stomach

The effects of electrical stimulation of the vagus at varying pulse widths on the release of immunoreactive VIP (IR-VIP) and IR-gastrin have been investigated, using the isolated perfused rat stomach preparation. Electrical stimulation of vagal trunks at a pulse width of 0.1 msec duration yielded no change in basal IR-VIP levels whereas a pulse width of 5.0 msec produced a prompt sustained increase. Stimulation at either pulse width evoked gastrin release. Atropine blocked the vagal release of IR-gastrin but not IR-VIP whereas hexamethonium blocked both responses. Exogenously administered porcine VIP, at concentrations mimicking endogenously released levels, was used in an attempt to reproduce the effects observed by vagal stimulation. Exogenous VIP had no effect on gastrin or somatostatin-like immunoreactivity (SLI) release. These in vitro studies support a role for VIP as a neurotransmitter released from the stomach by low-threshold non-cholinergic vagal fibres, but involving autonomic ganglia.

Thyrotoxicosis and a thyrotropin-secreting pituitary tumor causing unilateral exophthalmos

Hyperthyroidism due to a TSH-secreting pituitary tumor has been noted by a number of investigators. We describe a unique case in which a 17-yr-old female presented with clinical hyperthyroidism, a goiter, and unilateral exophthalmos. Serum T4, free T4, and T3 (RIA) were consistently elevated along with elevated TSH levels (range, 10-100 microunits/ml). Skull x-rays and computed tomography scan revealed a tumor invading the right orbit. Other pituitary function studies were normal and LATs was undetectable. Surgery performed resulted in 70% removal of the pituitary tumor and confirmed the presence of tumor infiltration into the right orbit. TRH tests done pre- and postoperatively (patient still clinically hyperthyroid with elevated T4 and TSH levels) showed TSH and PRL responsiveness. Electron microscopy of the tumor demonstrated features typical of pituitary thyrotrophs. Monolayer cultures of pituitary cells released TSH over time into the media but did not respond to TRH stimulation. Pituitary adenoma tissue content of immunoreactive TSH was 65 microunits/g wet tissue and demonstrated immunosimilarity with human standard. We conclude that the patient had a TSH-secreting pituitary tumor responsive to TRH stimulation.

Blunted pancreatic polypeptide responses in children with obesity of Prader-Willi syndrome

Serum pancreatic polypeptide (PP), gastric inhibitory polypeptide (GIP), insulin and glucose responses to meal stimulation were studied in 10 normal weight patients, 13 normal obese patients and 7 patients with Prader-Willi syndrome (PWS) associated obesity. Serum and plasma concentrations of PP, glucose, insulin and GIP were obtained at 15 min intervals from 0-180 min. after a 275 K calorie meal. Basal and peak responses of glucose, for patients with PWS were significantly lower when compared to normal or obese controls. Basal and peak insulin responses in PWS were significantly greater than those of the normal controls but still less than those of the obese controls. Basal GIP concentrations in the patients with PWS were significantly less than normals and their peak response was less than the obese control group. No significant differences in basal or peak PP responses were noted between normal and obese controls. All 7 patients with PWS had abnormal PP responses. Five failed to show significant PP release after the stimulation; one had a peak response to 130 pg/ml while the 7th patient (PB) had an exaggerated response to 2000 pg/ml. The 6 patients with low or no response had basal PP values of 62 +/- 12 pg/ml and a mean PP peak response of 78 +/- 15 pg/ml. This observation of blunted PP response in a human model of hyperphagia and obesity parallels the animal models and suggests PP may have a significant role in appetite control.

Gastric inhibitory polypeptide hypersecretion in diabetes mellitus: effect of sulfonylurea treatment

We studied gastric inhibitory peptide (GIP) in response to a mixed meal in both adult-onset diabetics and normal controls. The adult-onset diabetic group was also studied for immunoreactive GIP (IR-GIP), insulin, and glucose with a test meal before and after tolazamide therapy. Mean basal and meal-stimulated IR-GIP concentrations were greater (P less than 0.05) in the adult-onset diabetic group than in normal controls. With treatment, mean fasting glucose significantly decreased (P less than 0.05) from 206 +/- 14 to 162 +/- 11 mg/dl, and postprandial glucose concentrations were reduced (P less than 0.05) between 5-180 min. In contrast, after 1 month of treatment with tolazamide, IR-GIP concentrations were not significantly altered. Further, basal and postmeal serum insulin levels were significantly higher (P less than 0.05) after tolazamide therapy. We conclude that the enteroinsular axis in terms of IR-GIP is overactive in adult-onset diabetics; tolazamide therapy does not appear to effect its meal-stimulated response.

The effect of increasing doses of ingested glucose on insulin and gastric inhibitory polypeptide (GIP) concentrations in man

Gastric inhibitory polypeptide (GIP) is insulinotropic in vivo and in vitro. It is released following glucose ingestion and is a leading candidate as a mediator of the enteroinsular axis. To investigate the GIP response to increasing amounts of oral glucose, and its relationship to glucose levels and insulin secretion, fourteen normal volunteers ingested 25, 50 and 75 g of glucose at random with 5-7 days between each test. Serum insulin, glucose and GIP concentrations were measured and total integrated incremental responses were determined. Peak mean responses to glucose, insulin and GIP occurred at 30 min following each glucose ingestion. There were no significant differences in glucose concentrations at any interval with the varying glucose doses. Mean peripheral insulin concentrations were significantly increased after 50 or 75 g of glucose as compared with the 25 g dose (P less than 0.02). Mean GIP concentrations were significantly greater (P less than 0.03) between 15 and 180 min with both the 50 and 75 g glucose stimulus. Total integrated areas under the response curves for glucose, insulin and GIP showed a graded increase in circulating insulin and GIP (P less than 0.01) as the amount of ingested glucose was increased from 25 to 75 g. These findings show that increasing doses of glucose stimulated greater levels of GIP and insulin and further support the insulinotropic properties of endogenous GIP in man.

Vasoactive intestinal polypeptide as a biochemical marker for polymorphonuclear leukocytes

VIP is a 28 amino acid peptide found in highest concentration in central and peripheral nervous tissue. This study measured VIP in pure populations of peripheral blood cells to determine the presence or absence of VIP in noninnervated tissues. Cell populations were purified by Ficoll-hypaque gradient centrifugation followed by dextran sedimentation or differential adherence to culture plates. Platelets were purified by differential centrifugation. VIP was isolated by acid-ethanol extraction and quantified by radioimmunoassay. A mean value of 1.1 +/- 0.6 ng of VIP per 10(8) cells was extracted from PMNs. This peptide appears to be a specific marker for PMNs, since it was not measurable in pure populations of lymphocytes, monocytes, erythrocytes, or platelets. Mononuclear cells obtained from five patients with AML and seven patients with CML contained measurable VIP, whereas mononuclear cells from nine of 10 patients with AMML and from five patients with ALL contained very low or unmeasurable levels of VIP. Thus, although the role of VIP in normal PMN function is unknown, measurement of VIP in leukemic cells may aid in the differential diagnosis of acute leukemias.

Effect of isocaloric exchange of dietary starch and sucrose in humans on the gastric inhibitory polypeptide response to a sucrose load

Ten men and nine women aged 35 to 55 consumed two diets for 6 weeks each in a cross-over design. The diets were composed of identical natural foods and 30% of the calories as either sucrose or wheat starch. Carbohydrate, fat and protein supplied 43, 42, and 15% of the calories, respectively. The dietary pattern consisted of two meals divided so as to provide 10% of the calories at breakfast (7:00 to 8:30 AM) and 90% of the calories at dinner (4:30 to 6:30 PM). Initial body weights were essentially maintained. The gastric inhibitory polypeptide response after a sucrose load (2 g/kg body weight) was significantly greater (P < 0.01) after th subjects consumed the sucrose rather than the starch diet. The gastric inhibitory polypeptide response was significantly greater (P < 0.01) after 6 weeks on diet than during pretest. These results suggest that the increases in insulin levels observed after sucrose feeding may be mediated by an effect on the enteric hormone gastric inhibitory polypeptide.

Metabolic responses of Zucker fatty and lean rats fed carbohydrate diets ad libitum or in meals

In order to study the metabolic effects of dietary sucrose on Zucker rats, young male fatty and lean rats were fed ad libitum or in meals (2 hours/day) for 4 weeks. Diets contained 54% carbohydrate as either sucrose, invert sugar or cooked cornstarch. A genotype effect (fatty versus lean) occurred with the activities of liver and adipose tissue lipogenic enzymes, relative total fat pad size and soluble adipose tissue protein levels in both ad libitum- and meal-fed rats, whereas a genotype effect occurred with food intake and relative liver size only in meal-fed rats and with body weight gain only in ad libitum-fed rats. The significance of diet effects varied with genotype and feeding pattern. The sucrose effect (sucrose versus starch) occurred with food efficiency and body weight gain, activities of liver lipogenic and gluconeogenic enzymes, relative liver size, relative total fat pad size and soluble adipose tissue protein levels in both ad libitum- and meal-fed rats, and with adipose lipogenic enzyme activities in meal-fed rats. The disaccharide effect (sucrose versus invert sugar) occurred with the activities of liver lipogenic enzymes, relative total fat pad size and soluble adipose tissue protein levels in ad libitum-fed rats and was greater in lean than in fatty rats. The data demonstrate that the Zucker fatty and lean rat can be used as sensitive models to study differential effects of dietary carbohydrate.