Modified release terbutaline (SKP1052) for hypoglycaemia prevention: a proof-of-concept study in people with type 1 diabetes mellitus.

AIMS: In this randomized, single blind, cross-over study 2.5 mg and 5 mg of the modified-release terbutaline formulation (SKP-1052) were compared with conventional immediate-release terbutaline (IRT, 5 mg) and placebo on overnight blood glucose (BG) and hypoglycaemia in 30 subjects with type 1 diabetes mellitus. METHODS: Subjects received subcutaneous injections of insulin glargine (individualized doses) before dinner. SKP-1052, IRT or placebo was administered around 21:00 hours. BG and terbutaline concentrations were monitored overnight for 10 h post-dosing. Endpoints comprised of the nadir BG (BGn 0-10 h, primary endpoint), mean overnight BG (BGmean), morning BG (BGmorning) and hypoglycaemia rates as well as pharmacokinetic (PK) endpoints. RESULTS: SKP-1052 delayed release of terbutaline by 2 h [PK-tmax (mean ± SD) 5.0 ± 2.1 h (2.5 mg) and 4.7 ± 1.7 h (5 mg) vs. 2.6 ± 1.3 h with IRT, p < 0.01, respectively]. Compared with placebo, no significant differences were observed for BGn 0-10 h across treatments, but both 5 mg formulations showed less hypoglycaemic events [10 (IRT), 16 (SKP-1052) vs. 33], higher BGmean (120, 114 and 95 mg/dl) and BGmorning (126, 126 and 101 mg/dl, all comparisons p < 0.05 vs. placebo). Numerically higher BG-levels between 3 and 8 h post-dosing were observed with 2.5 mg SKP-1052 vs. placebo. CONCLUSIONS: Compared with IRT SKP-1052 delays release of terbutaline. 2.5 mg SKP-1052 led to numerically higher BG 3 to 8 h post-dose without fasting hyperglycaemia while 5 mg SKP-1052 resulted in fasting hyperglycaemia vs. placebo. Future studies will investigate optimized doses of SKP-1052 for nocturnal hypoglycaemia prevention.

Signal transduction pathways involved in particulate matter induced relaxation in rat aorta--spontaneous hypertensive versus Wistar Kyoto rats.

UNLABELLED: Previously we reported that in vivo exposure to ambient particulate matter (PM) induces vasodilatation in rat aorta. The purpose of the current study was to investigate the intracellular messengers involved in PM-elicited vasodilatation in aortas from spontaneous hypertensive (SHR) and normotensive (WKY) rats. METHODS: The contribution of three different intracellular pathways, i.e. (1) the NO-cGMP pathway, (2) prostanoids signaling and (3) endothelial hyperpolarisation factors were evaluated by using specific inhibitors (NS2028, Diclofenac and high K-concentration/17-ODYA, respectively). Using antagonists of capsaicin- or histamine receptors we tested potential interactions of PM with these receptors. Particle suspensions (EHC-93), particle filtrates (particle-free) and Cu(2+)- or Zn(2+)-containing solutions were used to obtain cumulative dose-response curves of relaxation in normal and endothelium-denuded rings. RESULTS: Our present data confirm that PM and its soluble components elicit an endothelium-independent vasodilatation in rat aorta rings. The response is mainly linked to the activation of soluble guanylate cyclase (sGC), since its inhibition by NS2028 almost abolished relaxation. Indeed PM suspensions stimulated cGMP production in purified isolated sGC. Neither the receptor nor their signaling pathways played a significant role in the direct relaxation by PM or metals. Vasodilatation responses were significantly higher in SHR than WKY control rats. CONCLUSION: Our data demonstrate that PM elicits a dose-dependent vasodilatation via activation of sGC in vascular smooth muscles. PM components, including soluble transition metals play a major role in this response. The stronger effect in SHR rats is in accordance with the observation that acute effects of PM are mainly seen in patients with underlying cardiovascular diseases.

Signal transduction pathways involved in kinin B(2) receptor-mediated vasodilation in the rat isolated perfused kidney.

The signal transduction pathways involved in kinin B(2) receptor-related vasodilation were investigated in rat isolated perfused kidneys. During prostaglandin F(2alpha) or KCl-induced constriction, the vasodilator response to a selective B(2) receptor agonist, Tyr(Me)(8)bradykinin (Tyr(Me)(8)BK), was assessed. Tyr(Me)(8)BK produced a concentration- and endothelium-dependent relaxation that was decreased by about 30 - 40% after inhibition of nitric oxide (NO) synthase by N(G)-nitro-L-arginine (L-NOARG) or of cyclo-oxygenase by indomethacin; a greater decrease (about 40 - 50%) was observed after concomitant inhibition of the two pathways. High extracellular K(+) diminished Tyr(Me)(8)BK-induced relaxation by about 75% suggesting a major contribution of endothelium-derived hyperpolarization. The residual response was almost completely suppressed by NO synthase and cyclo-oxygenase inhibition. The K(+) channel inhibitors, tetrabutylammonium (non-specific) and charybdotoxin (specific for Ca(2+)-activated K(+) channel), suppressed Tyr(Me)(8)BK-induced relaxation resistant to L-NOARG and indomethacin. Inhibition of cytochrome P450 (clotrimazole or 7-ethoxyresorufin) decreased the NO/prostanoids-independent relaxation to Tyr(Me)(8)BK by more than 60%, while inhibition of the cannabinoid CB(1) receptor (SR 141716A) had only a moderate effect. Acetylcholine induced a concentration-dependent relaxation with characteristics nearly similar to the response to Tyr(Me)(8)BK. In contrast, the relaxation elicited by sodium nitroprusside was potentiated in the absence of NO (L-NOARG or removal of endothelium) but remained unchanged otherwise. These results indicate that the activation of kinin B(2) receptors in the rat isolated kidney elicits an endothelium-dependent vasorelaxation, mainly dependent on the activation of charybdotoxin-sensitive Ca(2+)-activated K(+) channels. In addition, cytochrome P450 derivatives appear to be involved.

Effects of icatibant on the ramipril-induced decreased in renal lithium clearance in the rat.

The interaction between an inhibitor of angiotensin I converting enzyme (ramipril) and renal lithium handling was analysed in conscious, normotensive Wistar rats in the absence or the presence of a specific bradykinin B2 receptor antagonist, icatibant. The rats were treated for 5 days with ramipril (1 mg/kg/day p.o.) or its vehicle, alone or together with icatibant (0.1 mg/kg/day, s.c. infusion). Lithium chloride (8.3 mg/kg i.p.) was given as a single dose on day 5. Systolic blood pressure and heart rate were measured by tail plethysmography on day 3 (3, 9 and 15 h after ramipril administration) and renal function on day 4 (0-6 and 6-24 h urine sampling) and day 5 (0-6 h urine sampling). In another group of rats, 24 h sodium excretion was assessed during the first 4 days of ramipril treatment. Ramipril decreased renal lithium clearance (90+/-8 vs. 142+/-10 microl/min/100 g, P<0.001, n=24) and increased the fractional lithium reabsorption (74.3+/-1.9 vs. 66.7+/-1.7%, P<0.05) and plasma lithium concentration (0.108+/-0.006 vs. 0.085+/-0.004 mM, P<0.01). Alteration of renal lithium handling by ramipril was associated with a decrease in systolic blood pressure (-15% 3 h after ramipril administration) and sodium excretion (0-6 h after ramipril). The 24-h sodium excretion, however, tended to increase. Icatibant had no effect per se on renal function but attenuated the ramipril-induced decrease in renal lithium clearance (118+/-16 vs. 90+/-8 microl/min/100 g, n=12 and 24 respectively, P<0.05 one-tailed test) and systolic blood pressure. These results suggest that endogenous bradykinin contributes to the ramipril-associated alteration in renal lithium handling. Bradykinin B2 receptor-mediated vasodilation seems to be involved.

Vascular catabolism of bradykinin in the isolated perfused rat kidney.

Kinins in the circulation are rapidly metabolized by several different peptidases. The purpose of this study was to evaluate the contribution of membrane-bound peptidases to kinin metabolism in the renal circulation. Experiments were performed in vitro, in isolated rat kidneys perfused at a constant flow rate (8 ml/min) with Tyrode's solution. The effects of peptidase inhibitors were evaluated on the functional vasodilator response caused by bradykinin (30 nM) or [Tyr(Me)(8)]bradykinin (10 nM) via activation of bradykinin B2 receptors in kidneys precontracted with prostaglandin F2alpha. Angiotensin converting enzyme inhibitors, enalaprilat (3 microM), ramiprilat (1 microM) or lisinopril (1 microM), increased the bradykinin-induced renal vasodilation by 40% or more. Inhibitors of neutral endopeptidase (thiorphan or phosphoramidon, 10 microM), basic carboxypeptidase (DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid or MGTPA, 10 microM) and aminopeptidase P (apstatin, 20 microM) however did not enhance the renal vasodilator response elicited by kinins, whatever tested alone or in the presence of lisinopril. These findings indicate that angiotensin converting enzyme is the major peptidase whose inhibition potentiates the renal bradykinin B2 receptor mediated vasodilator response of kinins. The relative contribution in this potentiation of inhibition of kinin inactivation and of cross-talk of angiotensin converting enzyme with bradykinin B2 receptor remains however to be clarified.

Vascular kinin B(1) and B(2) receptor-mediated effects in the rat isolated perfused kidney - differential regulations.

1. Bradydykinin (BK) and analogs acting preferentially at kinin B(1) or B(2) receptors were tested on the rat isolated perfused kidney. Kidneys were perfused in an open circuit with Tyrode's solution. Kidneys preconstricted with prostaglandin F(2alpha) were used for the analysis of vasodilator responses. 2. BK induced a concentration-dependent renal relaxation (pD(2)=8.9+/-0.4); this vasodilator response was reproduced by a selective B(2) receptor agonist, Tyr(Me)(8)-BK (pD(2)=9.0+/-0.1) with a higher maximum effect (E(max)=78.9+/-6.6 and 55.8+/-4.3% of ACh-induced relaxation respectively, n=6 and 19, P<0.02). Icatibant (10 nM), a selective B(2) receptor antagonist, abolished BK-elicited relaxation. Tachyphylaxis of kinin B(2) receptors appeared when repeatedly stimulated at 10 min intervals. 3. Des-Arg(9)-BK, a selective B(1) receptor agonist, induced concentration-dependent vasoconstriction at micromolar concentration. Maximum response was enhanced in the presence of lisinopril (1 microM) and inhibited by R 715 (8 microM), a selective B(1) receptor antagonist. Des-Arg(9)-[Leu(8)]-BK behaved as an agonist. 4. A contractile response to des-Arg(9)-BK occurred after 1 of perfusion and increased with time by a factor of about three over a 3 h perfusion. This post-isolation sensitization to des-Arg(9)-BK was abolished by dexamethasone (DEX, 30 mg kg(-1) i.p., 3 h before the start of the experiment and 10 microM in perfusate) and actinomycin D (2 microM). Acute exposure to DEX (10 microM) had no effect on sensitized des-Arg(9)-BK response, in contrast to indomethacin (30 microM) that abolished it. DEX pretreatment however had no effect on BK-induced renal vasodilation. 5. Present results indicate that the main renal vascular response to BK consists of relaxation linked to the activation of kinin B(2) receptors which rapidly desensitize. Renal B(1) receptors are also present and are time-dependently sensitized during the in vitro perfusion of the rat kidneys.

[Renal vascular responses of bradykinin in the isolated rat kidney]. / Réponses vasculaires rénales de la bradykinine sur le rein isolé de rat.

Kinins, by an autocrine or paracrine hormonal action, are potent modulators of regional vasomotricity. Their effects on the renal circulation are not well defined. The aim of this study was to analyse the renal vascular response induced by bradykinin, to precise the type(s) of receptor involved and to evaluate the contribution of various peptidases in the local catabolism of the kinin. Experiments were performed on the isolated rat kidney, perfused in an open circuit, at a constant flow of 8 mL/min, with a Tyrode's solution. Vasodilator responses were evaluated after renal vascular tone had been restored by a continuous perfusion with prostaglandin F2 alpha. Infusion of bradykinin (0.1-30 nM) induced a concentration-dependent renal vasorelaxation. A maximal response of 39.5 +/- 2.8% (n = 32) reversion of the tone induced by prostaglandin F2 alpha (about 50% of the maximal response induced by acetylcholine on the same kidneys) was obtained at 30 nM. Bradykinin-induced vasodilatation was completely inhibited by HOE 140 (10 nM), a selective bradykinin B2 receptor antagonist. At a supramaximal concentration of 300 nM, bradykinin-induced vasorelaxation was modulated by a concomitant vasoconstriction. A concentration-dependent vasoconstriction was also obtained with desArg9 bradykinin (1-8 microM), a selective agonist of the bradykinin B1 receptor. The inhibition of neutral endopeptidase by phosphoramidon (10 microM) or the inhibition of carboxypeptidase M by MGTPA (10 microM) did not modify the bradykinin-induced renal vasorelaxation. On the other hand, the inhibition of angiotensin I converting enzyme by lisinopril (1 microM) potentiated by about 32% the vasorelaxant response induced by 30 nM bradykinin (52.3 +/- 11.8% relaxation, n = 5, p < 0.05). Present results demonstrate that 1) bradykinin primarily evokes B2 receptor-linked renal vasodilatation, 2) bradykinin B1 receptors appear also to be present on the rat renal vasculature and 3) angiotensin 1 converting enzyme contributes to the local vascular catabolism of the kinin.