[New targets in pharmacotherapy of type 2 diabetes]. / Neue Targets in der Pharmakotherapie des Typ-2-Diabetes.

The number of people with diabetes is expected to increase worldwide to 360 million within the next 15 years of which 90% will have type 2 diabetes (non-insulin-dependent diabetes mellitus). Established therapies mainly focus on the following principles: increase in plasma insulin, improving insulin sensitivity of tissues, reducing the rate of carbohydrate absorption and gluconeogenesis. The demand on compounds with new mechanisms of action is obvious. This articles summarizes new targets and compounds under development for pharmacotherapy of typ 2 diabetes; at present approx. 180 compounds are going to be developed worldwide.

In vitro and in vivo biotransformation of WMS-1410, a potent GluN2B selective NMDA receptor antagonist.

Structural modification of the GluN2B selective NMDA receptor antagonist ifenprodil led to the 3-benzazepine WMS-1410 with similar GluN2B affinity but higher receptor selectivity. Herein the in vitro and in vivo biotransformation of WMS-1410 is reported. Incubation of WMS-1410 with rat liver microsomes and different cofactors resulted in four hydroxylated phase I metabolites, two phase II metabolites and five combined phase I/II metabolites. With exception of catechol 4, these metabolites were also identified in the urine of a rat treated with WMS-1410. However the metabolites 7, 8 and 12 clearly show that the catechol metabolite 4 was also formed in vivo. As shown for ifenprodil the phenol of WMS-1410 represents the metabolically most reactive structural element. The biotransformation of WMS-1410 is considerably slower than the biotransformation of ifenprodil indicating a higher metabolic stability. From the viewpoint of metabolic stability the bioisosteric replacement of the phenol of WMS-1410 by a metabolically more stable moiety should be favourable.

Studies on the antioxidant activities of some new chromone compounds.

Recent reviews evidence that the naturally occurring compounds containing the chromone skeleton exhibit antiradical activities, providing protection against oxidative stress. The antioxidant activities of 13 new synthesized chromonyl-2,4-thiazolidinediones, chromonyl-2,4-imidazolidinediones and chromonyl-2-thioxoimidzolidine-4-ones were evaluated using in vitro antioxidant assays, including superoxide anion radical (O2(-•)), hydroxyl radical (HO(•)), 2,2-diphenyl-1-picryl-hydrazyl free radical (DPPH(•)) scavenging capacity and total antioxidant capacity ferric ion reducing activity. Superoxide anion radical was produced using potassium superoxide/18-crown-6-ether dissolved in dimethylsulfoxide, and the Fenton-like reaction (Fe(II) + H2O2) was a generator of hydroxyl radicals. Chemiluminescence, spectrophotometry, electron paramagnetic resonance (EPR) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin trap were the measurement techniques. The results showed that the majority of the chromone derivatives tested showed a strong scavenging effect towards free radicals, similar to the chemiluminescence reaction with superoxide anion radical with a high activity, inhibition of the DMPO-OOH radical EPR signal (24-58%), the DMPO-OH radical EPR signal (4-75%) and DPPH radical EPR signal (6-100%) at 1 mmol/L. Several of the examined compounds exhibited the high reduction potentials. The results obtained show that the new synthesized chromone derivatives may directly scavenger reactive oxygen species and thus may play a protective role against oxidative damage.

Testing of Perilla frutescens extract and Vicenin 2 for their antispasmodic effect.

Gastrointestinal discomfort is frequently observed. The effects of Perilla frutescens extract and Vicenin 2 (a compound in this extract) were assayed in rat ileum with or without stimulation with acetylcholine or Ba(2+). Both had no direct spasmolytic effect, but both decreased acetylcholine- or Ba(2+)-induced contraction of rat ileum indicating an antispasmodic effect. This is valuable because effects were only observed when spasms were induced and may disturb the patient. The extract and the compound may be used to maintain and improve gut health.

Impact of ADMA (asymmetric dimethylarginine) on physiology with respect to diabetes mellitus and respiratory system BEAS-2B cells (human bronchial epithelial cells).

OBJECTIVES: Asymmetric dimethylarginine (ADMA) is a non-selective nitric oxide (NO) synthase inhibitor associated with cardiovascular and metabolic disorders. This study aimed to investigate ADMA with respect to both diabetes and respiratory disease. METHODS: Glucose was determined by hexokinase method, insulin by a radioimmunoassay. Griess test was used for NO assay and cytokinines were assayed by ELISA. Ciliary beat frequency was determined by high speed video using a microscope. KEY FINDINGS: ADMA induced an increase in blood glucose and plasma insulin levels in rats; the ratio of these effects indicates the induction of a diabetic situation (insulin resistance). L-arginine increased blood glucose and initially slightly decreased plasma insulin. A pretreatment with ADMA abolished these effects. ADMA shows similar effects in vitro (insulin-secreting cell line, INS-1 cells). L-arginine increased production of NO, which was reversed by ADMA (INS-1 cells). ADMA also reduced NO production positively modulated by various substances, namely metformin, ciglitazone, losartan and nateglinide, but nevertheless inhibited insulin release induced by these compounds. ADMA stimulated the production of cytokines such as interleukin (IL-6) and macrophage inflammatory protein-2 (MIP-2) (rat IL-8 analogue) from INS-1 cells. 5-Aminoimidazole-4-carboxamide-1-ß-4-ribofuranoside (AICAR), a direct adenosine monophosphate protein kinase (AMPK) activator and anti-inflammatory agent, induced NO production and reduced cytokine release. In contrast to diabetes parameters, ADMA had no effect of on the respiratory system (cytokine secretion from BEAS-2B cells (IL-8, regulated on activation, normal T cell expressed and secreted, and tumour necrosis factor-α), ciliary beat frequency and smooth muscle contraction of rat trachea). CONCLUSIONS: ADMA has a pathophysiological impact leading to a diabetic situation but has no impact on the respiratory system.

Antidiabetic effects of a standardized Egyptian rice bran extract.

An extract was prepared from Egyptian stabilized rice bran and standardized to contain 2% γ-oryzanol in addition to its content of other bioactives, notably tocotrienol and policosanol. The standardized extract was found to have a concentration-dependent effect on insulin release in vitro, which, however, is not mediated by γ-tocotrienol in rice bran (detected by HPLC) as could have been expected. Policosanol and γ-oryzanol have insulinotropic effects. The in vitro data of rice bran directly translate into in vivo data of rats by using a glucose tolerance test (increase in plasma insulin). Tocotrienols are well known for their apoptotic effect on tumor cells; nevertheless, an attempt was made to study glucose uptake in HEP-G2 cells, which needs to induce an insulin-resistant state by TNF-α. The Egyptian rice bran extract has an antidiabetic effect. γ-Oryzanol, which is a possible precursor of the insulinotropic compound ferulic acid, is a candidate for this effect. Therefore, it is reasonable to assume that the prevalence of diabetes or at least a prediabetic (type 2) situation can be ameliorated by the investigated rice bran extract. The potential usefulness of the extract as a nutraceutical is currently undergoing more thorough investigations.

Synthesis and antidiabetic activity of 2,4-thiazolidindione, imidazolidinedione and 2-thioxo-imidazolidine-4-one derivatives bearing 6-methyl chromonyl pharmacophore.

Numerous compounds have been prepared in order to improve the pharmacological profile of insulinotropic activities. In the present paper, we report the synthesis and the in vitro insulin releasing activity of the 6-methyl-chromonyl-2,4-thiazolidinediones (IIIa-c, IVa-c, Va-c). Compounds IIIb, IIIc, IVa-c, Va and Vc (at lower concentration; 0.001 mg/mL) were able to increase insulin release in the presence of 5.6 mmol/L glucose. In this series, the most potent compound is IVa having methyl group at N3 position of TZD ring.

Impact and benefit of A(2B)-adenosine receptor agonists for the respiratory tract: mucociliary clearance, ciliary beat frequency, trachea muscle tonus and cytokine release.

OBJECTIVES: Adenosine is known to induce a bronchospasm in asthma- and COPD patients. The role of A(2B) receptors was investigated with respect to several parameters of the respiratory tract: tonus of smooth muscle, ciliary beat frequency as measured by high-speed video camera connected to a microscope (both in rats) and mucociliary clearance (MCC; transport of a fluorescent dye using a microdialysis procedure) in mice. KEY FINDINGS: NECA (5'-N-ethylcarboxamidoadenosine) (a non-selective adenosine receptor agonist) was able to acutely induce a contraction, which was reversed to a relaxation after repeated dosing. This relaxation was completely abolished by PSB-1115, an A(2B) receptor antagonist. IL-13 (cytokine) was not involved mediating acute contractility effects. MCC was increased by BAY 60-6583 (A(2B) receptor agonist) and NECA (counteracted by the A(2B) receptor antagonist PSB-1115). Activation of A(2B) adenosine receptors by BAY 60-6583 induced an increase of the ciliary beat frequency, which could be reduced by administration of PSB-1115. Several cytokines were increased by NECA although only some are relevant because they are not blocked by A(2B) receptor antagonism. CONCLUSIONS: The A(2B) receptors are involved in airway relaxation, MCC improvement and ciliary beat frequency. A(2B) receptor agonists may be of therapeutic value and should be developed.

Effect of myrtol standardized and other substances on the respiratory tract: ciliary beat frequency and mucociliary clearance as parameters.

INTRODUCTION: Myrtol standardized is a phytomedicine obtained by distillation, consisting of many constituents. In vitro and in vivo, the major monterpenes, d-limonene, 1,8-cineole, and alpha-pinene, are used as biological marker substances. Myrtol standardized has secretolytic, secretomotor, and mucolytic effects in addition to anti-inflammatory and antioxidative actions. The aim of the study was to investigate the effects of different concentrations of Myrtol standardized on in vivo mucociliary clearance in mice and the ciliary beat frequency (CBF) in rat tracheal rings. METHODS: Data regarding the effects of 1,8-cineole and N-acetylcysteine (NAC) were compared. Salbutamol was used as a positive control. CBF was measured using rat tracheal explants and a high-speed video camera linked to a microscope with specific software equipment. Mucociliary clearance was determined using the microdialysis technique, which measured the acceleration of a fluorescent sample in the trachea in vivo. RESULTS: Myrtol standardized accelerated both CBF and mucociliary transport in a concentration-dependent manner. Significant effects were seen at a concentration of 0.01% Myrtol regarding CBF (P<0.01) and 17.1 mg/kg body weight regarding mucociliary clearance experiments (P<0.05) according to doses relevant to humans. The 1,8-cineole dosage relative to humans only accelerated the mucociliary clearance in vivo without having an effect on the CBF. Extremely high doses of Myrtol were not able to additionally increase the CBF effect in comparison to salbutamol. Compared to NAC, also used in a dosage relative to humans, Myrtol standardized showed a tendency to be more effective. CONCLUSION: In summary, the present data suggest that Myrtol standardized is a pharmacologically important drug which, when used at a dose relative to humans, shows positive effects on both measured parameters, CBF and mucociliary clearance, in vivo.

Bioassay-guided fractionation of a thymol-deprived hydrophilic thyme extract and its antispasmodic effect.

ETHNOPHARMACOLOGICAL RELEVANCE: Extracts from Thymus vulgaris L. and Thymus zygis L. are traditionally used for bronchitis, catarrhs of the respiratory tract and supportive treatment of pertussis. A potential spasmolytic effect is thought to be due to the presence of the monoterpenoid phenols thymol and carvacrol in the extract. Based on previous data the present investigation aimed to clarify if thymol-deprived thyme extracts (as been in use within German drug market) have antispasmodic activity. Additionally compounds responsible for this effect had to be identified. MATERIALS AND METHODS: Thyme fluid extract was subsequently fractionated by FCPC, LPLC, and HPLC and compounds isolated were identified by spectroscopic methods. Bioassay testing was done by quantification of antispasmodic activity in the preconstricted rat smooth muscle trachea model against papaverin as positive control. RESULTS: Thymol-deprived spissum extract (SE) had good antispasmodic activity (-37%, related to the maximum contraction). Bioassay-guided fractionation indicated that rosmarinic acid and apigenin do not contribute to this effect. Luteolin contributed significantly to the antispasmodic activity (-9%). CONCLUSIONS: Thyme extracts have antispasmodic activity, which is at least due to synergistic effects of phenolic volatile oil compounds and the flavone luteolin. Specifications of thyme-containing preparations should refer to this flavone in addition to focusing on the volatile phenols.

Effect of silymarin and harpagoside on inflammation reaction of BEAS-2B cells, on ciliary beat frequency (CBF) of trachea explants and on mucociliary clearance (MCC).

Silymarin and harpagoside are derived from drugs which are used for their protective effects against hepatotoxicity and inflammatory processes. Both are now investigated with respect to the respiratory tract. They were able to reduce the release of the inflammatory cytokine RANTES (regulated on activation, normal T cells expressed and secreted) from BEAS-2B cells in a concentration-dependent manner when stimulated by a cytokine mix (10 ng/mL of TNF- α and IFN- γ). This effect was not due to a possible toxic effect (control experiments using LDH release as a marker). Silymarin but not harpagoside was able to increase ciliary beat frequency. Effects were comparable to positive controls (isoprenaline and salbutamol). Silymarin also increases mucociliary clearance. In conclusion, silymarin should be further investigated for its clinical use in distinct respiratory diseases.

Antiinflammatory effects of ginger and some of its components in human bronchial epithelial (BEAS-2B) cells.

The proinflammatory chemokine interleukin-8 is increased in asthmatic patients. Traditionally, ginger is used as an antiinflammatory drug. An extract and several compounds of Zingiber officinale (ginger) were tested in human bronchial epithelial cells (BEAS-2B cells) with respect to their effect on lipopolysaccharide (LPS)-induced secretion of the proinflammatory chemokine interleukin 8 (IL-8) and RANTES (regulated upon activation, normal T-cell expressed and secreted). An oily extract of ginger rhizome with > 25% total pungent compounds, ginger volatile oil, ar-curcumene and α-pinene reduced the LPS-induced IL-8 secretion (measured by a specific enzyme-linked immunosorbent assay), whereas a spissum extract, the pungents [6]-gingerol and its metabolite [6]-shogaol, and the terpenoids citral and ß-phellandrene showed no effect. The LPS-induced slight increase of RANTES was reduced by volatile oil, ar-curcumene and α-pinene. There was no effect of LPS on TNF-α. Our results suggest that distinct ginger compounds could be used as antiinflammatory drugs in respiratory infections.