Treatment with a proton pump inhibitor improves glycaemic control in Psammomys obesus, a model of type 2 diabetes.

AIMS/HYPOTHESIS: Gastrin has been implicated in islet growth/neogenesis, and proton pump inhibitors (PPIs) have been shown to increase endogenous gastrin levels in animals and humans. Therefore, we investigated the effect of PPIs in a model of type 2 diabetes, Psammomys obesus. METHODS: P. obesus (morning blood glucose [mBG] 16.9 +/- 0.6 mmol/l) were treated with vehicle or different doses (1-15 mg/kg) of lansoprazole for 17 days. RESULTS: Treatment with lansoprazole resulted in up to ninefold dose-dependent increases in endogenous gastrin levels (p < 0.05 for 10 mg/kg lansoprazole vs vehicle). There was a significant reduction in mBG levels in all animals in the high-dose lansoprazole groups during the 17 day treatment period, whereas there was no significant improvement in mBG in animals in the vehicle groups. The mBG at end of study was 18.2 +/- 2.1, 8.7 +/- 2.2 (p < 0.01), and 6.1 +/- 2.3 (p < 0.001) mmol/l for vehicle and lansoprazole 10 and 15 mg/kg, respectively. The animals treated with 15 mg/kg lansoprazole, compared with vehicle, had a 2.3-fold increase in the intensity of insulin staining in beta cells (p=0.0002) and 50% higher beta cell mass (p=0.04). CONCLUSIONS/INTERPRETATIONS: The PPI lansoprazole had significant glucose-lowering effects in an animal model of type 2 diabetes, an effect that is most likely mediated through an increase in endogenous gastrin levels.

Amidated and non-amidated glucagon-like peptide-1 (GLP-1): non-pancreatic effects (cephalic phase acid secretion) and stability in plasma in humans.

The incretin and enterogastrone hormone, GLP-1, occurs in an amidated (GLP-1 (7-36) amide; 75%) and a glycine-extended (GLP-1 (7-37); 25%) form. Their effects on the endocrine pancreas are similar and their overall (mainly renal) elimination rates appear to equal. Assuming that they might differentially affect non-pancreatic targets we investigated the effect of GLP-1 (7-37) infused at 0.7 pmol/kg/min on sham-feeding induced acid secretion in six healthy volunteers. The infusion increased the plasma concentrations from 16+/-2 pmol/l to 45+/-2 pmol/l. This was associated with a 61+/-14% decrease in acid output compared to saline and was not significantly different from that previously observed with GLP-1 (7-36) amide infused at the same rate. We then compared the degradation of the two forms in human plasma at 37 degrees C in vitro. T1/2 values were 32+/-3 (7-37) and 42+/-2 min (7-36) amide (P=0.007). The difference in metabolism persisted after addition of diprotin A, an inhibitor of dipeptidyl peptidase IV, the enzyme responsible for the initial degradation of GLP-1 in plasma, and broader enzyme inhibitors. Thus, the only effect of the amidation of GLP-1 seems to be to enhance its survival in plasma.

Glucagon-like peptide-1-(9-36) amide is a major metabolite of glucagon-like peptide-1-(7-36) amide after in vivo administration to dogs, and it acts as an antagonist on the pancreatic receptor.

This study assesses the importance of metabolites formed following exogenous administration of glucagon-like peptide-1-(7-36) amide (GLP-1). After subcutaneous (s.c.) administration of GLP-1 to dogs the plasma immunoreactivity of GLP-1 measured by two different radioimmunoassays (RIAs) were higher than that measured by a sandwich enzyme-linked immunosorbent assay (ELISA). This discrepancy was due to the formation of the metabolites GLP-1-(9-36) amide, GLP-1-(7-35) and GLP-1-(7-34). Receptor binding studies using baby hamster kidney cells expressing the human pancreatic GLP-1 receptor showed that the affinity of GLP-1-(9-36) amide, GLP-1-(7-35) and GLP-1-(7-34) was 0.95%, 12% and 2.8%, respectively, of the affinity of GLP-1-(7-36) amide. Furthermore, GLP-1-(9-36) amide was shown to be an antagonist to adenylyl cyclase activity, whereas GLP-1-(7-35) and GLP-1-(7-34) were shown to be agonists. GLP-1-(9-36) amide was shown to be present in vivo in amounts up to 10-fold that of GLP-1-(7-36) amide. Due to its low binding affinity, this antagonistic metabolite does not seem to be able to cause physiological antagonism upon s.c. administration of the peptide.

Glucagon-like peptide 1 undergoes differential tissue-specific metabolism in the anesthetized pig.

Glucagon-like peptide 1 (GLP-1) metabolism was studied in halothane-anesthetized pigs (n = 7) using processing-independent (PI) and COOH-terminal (C) radioimmunoassays (RIA) and an enzyme-linked immunosorbent assay (ELISA) specific for biologically active GLP-1. Renal extraction of endogenous GLP-1 was detected by PI-RIA (33.1 +/- 13.3%) and C-RIA (16.0 +/- 6.3%) and by all assays during GLP-1 infusion (ELISA, 69.4 +/- 6.3%; PI-RIA, 32.6 +/- 7.3%; C-RIA, 43.7 +/- 3.4%), indicating substantial fragmentation. Hepatic and pulmonary degradation were undetectable under basal conditions, but exogenous GLP-1 elimination by the liver (43.6 +/- 8.9%) and lungs (10.1 +/- 3.2%) was measured by ELISA, suggesting primarily NH2-terminal degradation. Endogenous GLP-1 extraction by the hindleg was only detected by C-RIA (16.0 +/- 6.3%). During GLP-1 infusion, greater hindleg extraction was measured by ELISA (38.5 +/- 6.8%) and C-RIA (33.0 +/- 6.4%) than by PI-RIA (11.4 +/- 3.2%), indicating limited degradation at each terminus or more substantial COOH-terminal degradation. A shorter (P < 0.01) plasma half-life was revealed by ELISA (1.5 +/- 0.4 min) than by PI-RIA (4.5 +/- 0.6 min) or C-RIA (4.1 +/- 0.5 min). Metabolic clearance rates measured by PI-RIA (20.0 +/- 3.8 ml.min-1.kg-1) and C-RIA (15.5 +/- 1.6 ml.min-1.kg-1) were shorter (P < 0.01) than that measured by ELISA (106.8 +/- 14.7 ml.min-1.kg-1). Tissue-specific differential metabolism of GLP-1 occurs, and NH2-terminal degradation, rendering GLP-1 inactive, is particularly important in its clearance.

Glucagon-like peptide-1(7-37) has a larger volume of distribution than glucagon-like peptide-1(7-36)amide in dogs and is degraded more quickly in vitro by dog plasma.

The pharmacokinetic properties of glucagon-like peptide-1(7-36)amide (GLP-1(7-37) were compared. Four beagle dogs received on 4 separate occasions s.c. bolus doses of 50 micrograms/kg, and 2 min i.v. infusions of 50 micrograms/kg of each peptide. The plasma immunoreactivity of GLP-1 (P-GLP-1-IR) was measured by a sandwich enzyme-linked immunosorbent assay (ELISA). After i.v. infusion, the plasma half-life in the first-phase was 2.1 +/- 0.1 and 2.4 +/- 0.3 min, in the final-phase 68 +/- 6 and 81 +/- 3 min, the total plasma clearance 25 +/- 3 and 22 +/- 4 ml/kg.min, the volume of distribution at steady state 0.16 +/- 0.02 and 0.84 +/- 0.24 l/kg, and the mean residence time 6.2 +/- 0.3 and 36 +/- 5 min for GLP-1(7-36)amide and GLP-1(7-37), respectively. After s.c. administration, the maximum plasma concentration was reached after 15 +/- 5 and 19 +/- 4 min and the absolute bioavailability was 48 +/- 7 and 49 +/- 13% for GLP-1(7-36)amide and GLP-1(7-37), respectively. P-GLP-1-IR, measured by a radioimmunoassay (RIA), was considerably higher than when measured by ELISA. This discrepancy was due to cross-reactivity with metabolites of the parent peptide. The plasma degradation was studied in vitro in dog plasma at 37 degrees C, and the half-lives were found to be 61 +/- 9 and 132 +/- 16 min for GLP-1(7-36)amide and GLP-1(7-37), respectively (n = 6). Bacitracin inhibited the degradation of both peptides.

Both subcutaneously and intravenously administered glucagon-like peptide I are rapidly degraded from the NH2-terminus in type II diabetic patients and in healthy subjects.

To fate of exogenous glucagon-like peptide I (GLP-I)(7-36) amide was studied in nondiabetic and type II diabetic subjects using a combination of high-pressure liquid chromatography (HPLC), specific radioimmunoassays (RIAs), and a sensitive enzyme-linked immunosorbent assay (ELISA), whereby intact biologically active GLP-I and its metabolites could be determined. After GLP-I administration, the intact peptide could be measured using an NH2-terminally directed RIA or ELISA, while the difference in concentration between these assays and a COOH-terminal-specific RIA allowed determination of NH2-terminally truncated metabolites. Subcutaneous GLP-I was rapidly degraded in a time-dependent manner, forming a metabolite, which co-eluted on HPLC with GLP-I(9-36) amide and had the same immunoreactive profile. Thirty minutes after subcutaneous GLP-I administration to diabetic patients (n = 8), the metabolite accounted for 88.5 +/- 1.9% of the increase in plasma immunoreactivity determined by the COOH-terminal RIA, which was higher than the levels measured in healthy subjects (78.4 +/- 3.2%; n = 8; P < 0.05). Intravenously infused GLP-I was also extensively degraded, but no significant differences were seen between the two groups. Intact GLP-I accounted for only 19.9 +/- 3.4% of the increase in immunoreactivity measured with the COOH-terminal RIA in normal subjects (n = 8), and 25.0 +/- 4.8% of the increase in diabetic subjects (n = 8), the remainder being the NH2-terminally truncated metabolite.

Comparison of sandwich enzyme-linked immunoadsorbent assay and radioimmunoassay for determination of exogenous glucagon-like peptide-1(7-36)amide in plasma.

A sensitive sandwich enzyme-linked immunoadsorbent assay (ELISA) for determination of exogenous glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) in plasma samples from pharmacokinetic studies is described. The assay employs an N-terminally directed antibody and a C-terminally directed antibody. The ELISA has a working range from 10 to 500 pmol l-1, and can be applied to plasma samples from humans, dogs, pigs, minipigs, cats, rabbits, and rats. The assay was compared to a validated radioimmunoassay (RIA), employing an antibody directed against the mid-region of GLP-1. After s.c. administration of GLP-1(7-36)amide, the plasma immunoreactivity of GLP-1 (P-GLP-1-IR) measured by ELISA was markedly lower than P-GLP-1-IR measured by RIA. After HPLC fractionation of plasma samples with subsequent RIA and ELISA analyses of the fractions, this difference was shown to be due to cross reaction with biologically inactive fragments of GLP-1(7-36)amide in the RIA but not in the ELISA.

[The importance of CT examination in the diagnosis and therapy of rhino-otogenic intracranial complications]. / Význam CT vysetrení pro diagnostiku a lécbu rinootogennich intrakraniálních komplikací.

Computed tomography in the diagnosis of rhino-otogenic intracranial inflammatory complications made it possible to reduce significantly the morbidity and mortality. It provides more reliable information, than hitherto used pretentious and invasive methods, on the development of inflammatory foci, the dynamics of their development, localization and extent. In correlation with the clinical course and laboratory findings it makes it possible to select an optimal time for operation and to select an optimal surgical approach, or in exceptional instances a conservative procedure. However, false negative findings may also be encountered. In those instances, with regard to the course and symptomatology of these complications, CT must be repeated or another diagnostic method must be selected.