Comparison of the reactogenicity and immunogenicity of a combined diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated polio (DTPa-HBV-IPV) vaccine, mixed with the Haemophilus influenzae type b (Hib) conjugate vaccine and administered as a single injection, with the DTPa-IPV/Hib and hepatitis B vaccines administered in two simultaneous injections to infants at 2, 4 and 6 months of age.

An open, randomised, multicentre trial was performed to compare the reactogenicity and safety profile of the administration of a hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated polio (DTPa-HBV-IPV) vaccine administered in one injection mixed with Haemophilus influenzae type b (Hib) conjugate vaccine (Group 1) with that of a pentavalent DTPa-IPV vaccine mixed with a Hib vaccine (DTPa-IPV/Hib), simultaneously administered with HBV (Group 2) in two injections in opposite thighs, as a primary vaccination course, to healthy infants at 2, 4 and 6 months of age. A total of 235 completed the study, 120 from Group 1 and 115 from Group 2. Blood samples (pre-vaccination and 1 month after the third dose) were obtained from a subset of infants (Group 1: 40; Group 2: 31) to assess the immune response to vaccination. Local and general solicited symptoms were recorded by parents on diary cards. Seven hundred and five diary cards (Group 1: 360; Group 2: 345) were collected. The clinically relevant and most commonly reported local reaction was pain (infant cried when the limb was moved) in 2.5% (Group 1) and 1.2% (Group 2) of diary cards. Fever was more frequently reported in Group 1 (21% of diary cards) than in Group 2 (12% of diary cards). However only 3 and 2% of doses in Groups 1 and 2, respectively, were responsible for a rectal temperature between 38.6 and 39.5 degrees C and only one case (Group 2) had > or =39.5 degrees C. Other clinically relevant general symptoms were rarely recorded: irritability (2-2.8%), loss of appetite (0.3-0.6%) and drowsiness (0.3-0.3%). All subjects included in the immunogenicity analysis had seroprotective titres to diphtheria, tetanus, polio virus types 1 and 3, Hib. Almost all subjects were seroprotected for anti-polio type 2 and hepatitis B (with the exception of 1 subject in Group 1 for each antigen). The vaccines response rates to pertussis antigens were over 97 and 90% in Groups 1 and 2, respectively. This study shows that, from a clinical perspective, the DTPa-HBV-IPV/Hib vaccine given in a single injection has a similar reactogenicity and safety profile to that of two licensed vaccines (DTPa-IPV/Hib, HBV) given in two simultaneous injections to infants at 2, 4 and 6 months of age. This is a valuable advantage, since in some countries, such as Spain and the UK, an additional injection (for the administration of meningococcal C conjugate vaccine) has been recently included in the infants' vaccination calendars.

Resistance of succinic acid dimethyl ester insulinotropic action to exendin (9-39) amide.

Exendin (9-39) amide (Ex [9-39]) was recently proposed for use in the treatment of alimentary or reactive hypoglycaemia. It was indeed found to antagonise the insulinotropic action of GLP-1 in rats infused with the dimethyl ester of succinic acid (SAD). We have now investigated whether, under comparable experimental conditions, Ex (9-39) also opposes the insulin-releasing action of SAD itself. Since this was not the case, Ex (9-39) could be safely used to abolish the incretin effect of GLP-1 without interfering with the control of insulin secretion by circulating nutrients.

Potentiation of the insulinotropic action of GLP-1 by succinic acid dimethyl ester in fed anaesthetized rats.

The insulinotropic action of GLP-1 is modulated by the nutritional environment of islet B-cells. This study explores whether an ester of succinic acid could be used to potentiate the insulin secretory response to GLP-1 in vivo. Fed anaesthetized male rats received a primed constant infusion (0.5 micromol followed by 0.25 micromol x min(-1) both per g body wt) of succinic acid dimethyl ester (SAD) in saline for 15 min and, at the 5th min of such an infusion, an intravenous injection of GLP-1 (5 pmol/g body wt). The ester provoked a rapid, sustained and reversible increase in plasma insulin concentration. In the SAD-infused rats, the increment in plasma insulin concentration caused by GLP-1 was more pronounced and more sustained than in saline-infused rats. It is proposed, therefore, that suitable succinic acid esters could be used to potentiate the insulinotropic action of GLP-1 in Type II (non-insulin-dependent) diabetes.

Prolongation of the insulinotropic action of glucagon-like peptide 1 by the dimethyl ester of succinic acid in an animal model of type-2 diabetes.

Adult rats, that had been injected with streptozotocin during the neonatal period, received a primed constant infusion of succinic acid dimethyl ester (SAD; 0.5 micromol followed by 0.25 micromol x min(-1), both per g body wt.) in saline for 15 min and, at the 5th min of such an infusion, an intravenous injection of GLP-1 (5 pmol per g body wt.). Within 2 min, the ester increased the plasma insulin concentration by 0.33+/-0.05 nM. Likewise, within 2 min, GLP-1 provoked a marked increase in plasma insulin concentration; such an increase was comparable in rats infused with either saline or SAD, with an overall mean value of 0.93+/-0.07 nM. In the rats infused with SAD, however, the secretory response to GLP-1 appeared more sustained than in the saline-infused animals. For instance, the paired ratio for the insulinogenic index at 10/2 min after GLP-1 injection averaged 30.5+/-4.0% in SAD-infused rats, as compared (P<0.025) to only 17.0+/-2.5% in saline-infused animals. These findings suggest that succinic acid esters could be used to prolong the insulinotropic action of GLP-1 in the treatment of type-2 diabetes.

Potentiation of the insulinotropic and hypoglycemic action of gliquidone by succinic acid esters.

The monoethyl, monopropyl and monoisopropyl esters of succinic acid, administered intravenously at the dose of 2 micromol/g body weight, were found to increase the insulinotropic action of gliquidone (0.2 nmol/g body weight) in anaesthetized rats. The monoisopropyl ester of succinic acid also doubled the hypoglycemic action of gliquidone. These findings indicate that it is possible to design esters of succinic acid that are devoid of the risk of generating methanol by intracellular hydrolysis, and yet susceptible to increase both the insulinotropic and hypoglycemic responses to antidiabetic agents.

In vivo stimulation of insulin release by the monoethyl, monopropyl, monoisopropyl, monoallyl and diallyl esters of succinic acid.

The methyl esters of succinic acid are potent insulin secretagogues, currently under investigation as possible tools in the treatment of non-insulin-dependent diabetes. The in vivo administration of these esters may result, however, in the undesirable generation of methanol. The present study reveals that other esters of succinic acid, such as the monoethyl, monopropyl, monoisopropyl, monoallyl and diallyl esters, stimulate insulin release when administered intravenously in a dose of 2 mumol/g body weight to anaesthetized fed rats. This indicates that several succinic acid esters, that are not susceptible to lead, through their intracellular hydrolysis, to the production of methanol remain efficient in vivo as insulin secretagogues.

Stimulation of insulin release and potentiation of the insulinotropic action of antidiabetic agents by 1,2,3-tri(methylsuccinyl)glycerol ester in anaesthetized rats.

A novel ester of succinic acid (1,2,3-tri(methylsuccinyl)glycerol ester; 3SMG) was found to stimulate insulin release and to potentiate the insulinotropic action of gliquidone and repaglinide when administered intravenously to normal anaesthetized rats in a dose as low as 0.07 mumol g-1 body wt. The ester failed, however, to augment plasma insulin concentration when given enterally. The design of succinic acid esters of high insulinotropic potential might thus allow efficient stimulation of insulin secretion in non-insulin-dependent diabetes, without requiring unpractical high dosage and without running the risk of an undesirable increase in gluconeogenesis.

In vitro and in vivo insulinotropic action of methyl pyruvate.

Methyl pyruvate, when tested at a 10mM concentration, caused a rapid and sustained increase of insulin release evoked by either 7.0 or 16.7 mM D-glucose in the isolated perfused rat pancreas. Under these conditions, methyl pyruvate caused a modest and biphasic stimulation of glucagon release. In anaesthetized fed rats, methyl pyruvate (1.0 to 2.5 mumol/g body wt) given intravenously provoked a short-lived and dose-related increase in plasma insulin concentration, but failed to affect plasma glucagon concentration. D-glucose and methyl pyruvate, when injected together, acted additively upon insulin release. The in vivo secretory response to methyl pyruvate was comparable in fed, overnight fasted and 2-d starved rats, and only slightly decreased in fed animals that were injected with streptozotocin during the neonatal period. These results suggest that methyl pyruvate could be used as an insulinotropic agent to bypass site-specific defects of D-glucose metabolism in the B-cell, such as those found in starvation or non-insulin-dependent diabetes mellitus.

Stimulation of insulin release caused by intraduodenal administration of succinic acid methyl esters.

The methyl esters of succinic and glutamic acid are currently under investigation as possible tools for stimulation of insulin biosynthesis and release in non-insulin-dependent diabetes mellitus. The present study deals with the secretory response of the pancreatic B-cell to these esters after intraduodenal administration to anaesthetized rats. The dimethyl ester of succinic acid and, to a lesser extent, its monomethyl ester both increased the plasma insulin concentration, whilst the dimethyl ester of glutamic acid virtuality failed to do so. The stimulation of insulin release, caused by the dimethyl ester of succinic acid, was faster and more pronounced than that evoked by an equimolar amount of glucose. The present study thus reveals that the latter ester, when administered via the gastrointestinal tract, evokes a more brisk and more ample secretory response of the pancreatic B-cell than that evoked by glucose.

Stimulation of insulin secretion and potentiation of glibenclamide-induced insulin release by the dimethyl ester of glutamic acid in anaesthetized rats.

The dimethyl ester of L-glutamic acid (GME) stimulates insulin release in isolated pancreatic islets and may represent a novel experimental tool in the study of non-insulin-dependent diabetes. In the present study, GME was found both to stimulate insulin secretion and to augment glibenclamide-stimulated insulin release in normal anaesthetized rats. A comparable hierarchy in the magnitude of the secretory response to GME and/or glibenclamide was found in control rats and animals injected with streptozotocin during the neonatal period. In the latter animals, however, the B-cell secretory response was invariably lower than in control animals. It is proposed that GME represents a novel tool to bypass anomalies of glucose transport and metabolism in the beta cell and, hence, to stimulate insulin release and enhance the insulinotropic action of hypoglycaemic sulphonylurea in animal models of non-insulin-dependent diabetes.