Miriam Kidron

Oral insulin: the rationale for this approach and current developments.

Insulin remains the most effective and durable hypoglycemic agent for the treatment of diabetes. The addition of an effective oral insulin dosage form to the antidiabetes armamentarium may have significant benefits in terms of fostering compliance and adherence among patients, as well as physiologic advantages due to the fact that such a dosage form replicates the natural route of insulin secretion and absorption through the portal vein and targets the liver directly. Several companies have developed technological platforms that protect polypeptides and proteins from enzymatic hydrolysis, enable their transport across the epithelial lining, and promote their absorption from the gastrointestinal tract. A review of the potential physiological rationale and advantages, as well as of current pertinent technologies used specifically with insulin, is herewith provided.

Biochemical and morpho-cytochemical evidence for the intestinal absorption of insulin in control and diabetic rats. Comparison between the effectiveness of duodenal and colon mucosa

SummaryA combined biochemical and morpho-cytochemical investigation was carried out in order to assess insulin absorption by the duodenal and colon epithelium. Insulin was introduced in the lumen of the rat duodenum or colon in combination with sodium cholate and aprotinin. Blood analysis made at several time points has demonstrated a rapid increase in circulating levels of insulin followed by significant and consistent decreases in blood glucose. This indicates that biologically active insulin is absorbed by the intestinal mucosa and transferred to the circulation. Because of the initial high blood glucose levels, the lowering of the glycaemic values was more significant in diabetic animals. Also, levels of circulating insulin remained higher for longer time when the administration was performed in the colon. The integrity of the intestinal wall after insulin administration, evaluated morphologically, was retained. Application of protein A-gold immunocytochemistry has established the pathway for insulin absorption. In both duodenal and colon epithelial cells the labelling for insulin was detected in the endosomal compartment, in the Golgi apparatus and in association with the baso-lateral plasma membrane interdigitations. Some labelling was also present in the interstitial space and in capillary endothelial plasmalemmal vesicles. Insulin introduced in the lumen of the rat duodenum and colon appears thus to be rapidly internalized by the epithelial cells and transferred through a transcytotic pathway to the interstitial space from which it reaches the blood circulation. This exogenous insulin then induces significant decreases in plasma glucose levels which lasts for several hours. The results obtained support the possibility for the clinical development of an oral preparation of insulin.

Morpho-cytochemical and biochemical evidence for insulin absorption by the rat ileal epithelium

SummaryIn order to investigate the mechanism through which insulin is absorbed by the intestinal epithelium and transferred to the circulation where it exercises its biological activity of lowering blood glucose levels, a combined biochemical morpho-cytochemical study was undertaken on rat ileal tissue, in vivo. Insulin was introduced into the lumen of the ileum in combination with sodium cholate and aprotinin and allowed to be absorbed for various periods of time. Analysis of blood samples from the inferior vena cava, at different time points has demonstrated an increase in plasma insulin followed by a decrease in blood glucose levels. The ileal tissues were studied at different time points after the introduction of the insulin, by applying the protein A-gold immunocytochemical technique. Insulin antigenic sites were detected with high resolution, at various levels of the enterocytes but were absent from goblet cells. At 2 to 5 min, the labelling was mainly associated with the microvilli and endocytotic vesicles in the apical portion of the epithelial cells. Some gold particles were in contact with the lateral membranes. At 10 min, the labelling was found at the level of the trans-side of the Golgi apparatus and mainly along the baso-lateral membranes of the epithelial cells. Labelling was also detected in the interstitial space. The control experiments have demonstrated the specificity of the labelling and confirmed the nature of the insulin molecules detected. Furthermore, the morphological study has confirmed that exposure of the tissue to the insulin-cholate-aprotinin solution does not affect the integrity of the epithelium while promoting insulin absorption. Thus, insulin introduced in the lumen of the rat ileum in conjunction with sodium cholate and aprotinin, appears to be rapidly absorbed by the epithelial cells and transferred to the circulation through a transcytotic pathway.

Glucose-Reducing Effect of the ORMD-0801 Oral Insulin Preparation in Patients with Uncontrolled Type 1 Diabetes: A Pilot Study

The unpredictable behavior of uncontrolled type 1 diabetes often involves frequent swings in blood glucose levels that impact maintenance of a daily routine. An intensified insulin regimen is often unsuccessful, while other therapeutic options, such as amylin analog injections, use of continuous glucose sensors, and islet or pancreas transplantation are of limited clinical use. In efforts to provide patients with a more compliable treatment method, Oramed Pharmaceuticals tested the capacity of its oral insulin capsule (ORMD-0801, 8 mg insulin) in addressing this resistant clinical state. Eight Type I diabetes patients with uncontrolled diabetes (HbA1c: 7.5–10%) were monitored throughout the 15-day study period by means of a blind continuous glucose monitoring device. Baseline patient blood glucose behavior was monitored and recorded over a five-day pretreatment screening period. During the ensuing ten-day treatment phase, patients were asked to conduct themselves as usual and to self-administer an oral insulin capsule three times daily, just prior to meal intake. CGM data sufficient for pharmacodynamics analyses were obtained from 6 of the 8 subjects. Treatment with ORMD-0801 was associated with a significant 24.4% reduction in the frequencies of glucose readings >200 mg/dL (60.1±7.9% pretreatment vs. 45.4±4.9% during ORMD-0801 treatment; p = 0.023) and a significant mean 16.6% decrease in glucose area under the curve (AUC) (66055±5547 mg/dL/24 hours vs. 55060±3068 mg/dL/24 hours, p = 0.023), with a greater decrease during the early evening hours. In conclusion, ORMD-0801 oral insulin capsules in conjunction with subcutaneous insulin injections, well tolerated and effectively reduced glycemia throughout the day. Trial Registration Clinicaltrials.gov NCT00867594.

Copper content and amino acid composition of catechol oxidase from clairette grapes

Abstract Catechol oxidase was purified 330 × from chloroplasts of Clairette grapes. The MW of the enzyme is 80 000 and its Cu content is half an atom per molecule. The amino acid composition of the enzyme is also described.

Studies on the homogeneity of prymnesin, the toxin isolated from Prymnesium parvum Carter

Prymnesin, the purified toxin of Prymnesium parvum Carter, was subjected to a variety of inactivation procedures: Irradiation by visible or ultraviolet light, incubation at 37° and exposure to alkaline media. Inactivation was measured by three assay methods: Lethality for fish, hemolysis of rabbit erythrocytes, and inhibition of the acetylcholine-induced contractions of the small intestine of the guinea pig. It was observed that the rate of destruction of the antispasmodic activity exceeds by far the rate of decline of the ichthyotoxic or hemolytic potency. The heterogeneity of prymnesin is thus established.

Bile salts facilitate the absorption of heparin from the intestine

Heparin was absorbed through the rectal mucosa of rodents and primates only when administered in solutions containing sodium cholate or sodium deoxycholate (DOC). The absorption of heparin was monitored by following the increase in plasma radioactivity after administration of [35S]heparin, and by measurement of its biological effects: plasma lipase activity and prolongation of partial thromboplastin time (PTT). Following administration of the same concn of heparin in solutions lacking bile salts, there was almost no radioactivity in the blood, no prolongation of PTT and no release of plasma lipase activity. The PTT effect was found to be a less sensitive test of heparin absorption than the plasma lipase activity.

Intestinal Absorption of Low Molecular Weight Heparin in Animals and Human Subjects

Introduction: We had previously shown that the use of bile salts, which act as surfactants, facilitates the intestinal absorption of large molecules such as those of heparin and insulin. However, the bioavailability of unfractionated heparin (UFH) administered through the large intestine was low. The aim of the present study was to evaluate the absorption of low molecular weight heparin (LMWH) combined with bile salts through the gut mucosa in animals and human subjects. Materials and Methods: LMWH (Fragmin, Kabi-Pharmacia, Stockholm) or UFH with or without sodium cholate (Sch) was administrated rectally in rats and healthy volunteers via a microenema. Absorption was estimated by the activated partial thromboplastin time (aPTT), the plasma anti-factor Xa activity and the plasma lipoprotein lipase (LPL) activation. Results: In groups of 6 rats, LMWH at doses of 100–1,000 U with sodium cholate (10–20 mg/ml) was readily absorbed through the gut mucosa, as indicated by both, anti-factor Xa levels of up to 1 U/ml and a dose-dependent activation of LPL. The absorption was significantly superior to that of UFH with Sch or LMWH given without Sch (p < 0.001). The plasma anti-factor Xa levels in the 6 healthy volunteers who received a microenema containing 25,000 U of LMWH with 20 mg/ml of Sch were 0.38 U/ml at 15 min and 0.1 U/ml at 240 min. LPL activation and aPTT prolongation were also observed in these subjects. The plasma LMWH levels after rectal application were in the same range as those obtained after subcutaneous administration, however the elimination time (t½) was shorter. There were no adverse reactions. Conclusions: Intestinal absorption of LMWH facilitated by Sch is both feasible and safe. A slow release formulation will be needed to prolong the plasma half-life.

ENTERAL ADMINISTRATION OF INSULIN IN THE RAT

1 The effect of the surfactant, Cetomacrogol 1000, on the absorption of insulin across the rectal mucosa has been studied. 2 Rectal administration of microenemata containing Cetomacrogal 1000 and insulin causes a rise in the plasma concentration of insulin and a consequent fall in the blood glucose concentration in diabetic and non‐diabetic rats. 3 The hypoglycaemic response is dependent on both the concentration of surfactant and the dose of insulin administered. 4 The results suggest that the transport of insulin across the rectal mucosa is facilitated by Cetomacrogal 1000.

Novel Glucagon-like Peptide-1 Analog Delivered Orally Reduces Postprandial Glucose Excursions in Porcine and Canine Models

Background: Glucagon-like peptide-1 (GLP-1) and its analogs are associated with a gamut of physiological processes, including induction of insulin release, support of normoglycemia, β-cell function preservation, improved lipid profiles, and increased insulin sensitivity. Thus, GLP-1 harbors significant therapeutic potential for regulating type 2 diabetes mellitus, where its physiological impact is markedly impaired. To date, GLP-1 analogs are only available as injectable dosage forms, and its oral delivery is expected to provide physiological portal/peripheral concentration ratios while fostering patient compliance and adherence. Methods: Healthy, fasting, enterically cannulated pigs and beagle canines were administered a single dose of the exenatide-based ORMD-0901 formulation 30 min before oral glucose challenges. Blood samples were collected every 15 min for evaluation of ORMD-0901 safety and efficacy in regulating postchallenge glucose excursions. Results: Enterically delivered ORMD-0901 was well tolerated by all animals. ORMD-0901 formulations RG3 and AG2 led to reduced glucose excursions in pigs when delivered prior to a 5 g/kg glucose challenge, where area under the curve (AUC)0-120 values were up to 43% lower than in control sessions. All canines challenged with a glucose load with no prior exposure to exenatide, demonstrated higher AUC0-150 values than in their exenatide-treated sessions. Subcutaneous exenatide delivery amounted to a 51% reduction in mean glucose AUC0-150, while formulations AG4 and AG3 prompted 43% and 29% reductions, respectively. Conclusions: When delivered enterically, GLP-1 (ORMD-0901) is absorbed from the canine and porcine gastrointestinal tracts and retains its biological activity. Further development of this drug class in an oral dosage form is expected to enhance diabetes control and patient compliance.