Insulin sensitizing property of Indigofera mysorensis extract.

Indigofera mysorens is a shrub used for its antidiabetic activity in rural India. Here, we elucidate the antidiabetic potential of Indigofera mysorensis extract. Ethanolic extract of the whole shrub of Indigofera (EEI) at 300 mg/kg for 10 days, produced a 63% reduction in plasma glucose, 41% reduction in plasma triglyceride and 77% reduction in plasma insulin levels in insulin resistant db/db mice, which is better than insulin sensitizer, troglitazone (400 mg/kg). EEI unlike sulphonylureas failed to show any acute hypoglycemic effect in normoglycemic Swiss albino mice (SAM). Even in a chronic study (10 days) in SAM, EEI (300 mg/kg) like insulin sensitizers showed no effect on plasma glucose, but an 81% reduction in plasma insulin levels. When challenged with 3 gm/kg sucrose, SAM treated with EEI (300 mg/kg, 7 days) failed to show any effect on the absorption of sugar, whereas standard drug, acarbose (10 mg/kg) showed 52% reduction in the area under the plasma glucose curve. EEI failed to show any significant transactivation of PPARgamma, a proposed target of synthetic insulin sensitizers. Taken together, our data indicate that the antidiabetic effect of the ethanolic extract of Indigofera is due to its insulin sensitizing property and is clearly different from that of sulfonylurea or acarbose.

Synthesis of conformationally constrained analogues of linezolid: structure-activity relationship (SAR) studies on selected novel tricyclic oxazolidinones.

In an effort to discover potent antibacterials based on the entropically favored "bioactive conformation" approach, we have designed and synthesized a series of novel tricyclic molecules mimicking the conformationally constrained structure of the oxazolidinone antibacterial, Linezolid 1. The structure 3 obtained by this approach was synthesized and found to be moderately active against a panel of Gram-positive organisms tested. Further introduction of a fluorine atom in the aromatic ring of compound 3 as in Linezolid resulted in some excellent compounds possessing potent antibacterial activity. The thus obtained lead molecule 16 was further fine-tuned by structure-activity relationship studies on the amide functionality leading to a number of novel tricyclic oxazolidinone derivatives. Some particularly interesting compounds include the thioamides 36 and 37, thiocarbamate 41, and thiourea 45. The in vitro activity results of amide homologues of 16 (compounds 25-30) revealed that compounds up to four carbon atoms on the amide nitrogen retain the activity. In general, thioamides and thiocarbamates are more potent when compared to the corresponding amides and carbamates.

Ragaglitazar: a novel PPAR alpha PPAR gamma agonist with potent lipid-lowering and insulin-sensitizing efficacy in animal models.

Ragaglitazar [(-) DRF 2725; NNC 61-0029] is a coligand of PPARalpha and PPARgamma. In ob/ob mice, ragaglitazar showed significant reduction in plasma glucose, triglyceride and insulin (ED50 values <0.03, 6.1 and <0.1 mg kg-1). These effects are three-fold better than rosiglitazone and KRP-297. In Zucker fa/fa rats, ragaglitazar showed dose-dependent reduction in triglyceride and insulin, hepatic triglyceride secretion and triglyceride clearance kinetics (maximum of 74, 53, 32 and 50% at 3 mg kg-1), which are better than rosiglitazone and KRP-297. In a high-fat-fed hyperlipidaemic rat model, the compound showed an ED50 of 3.95, 3.78 mg kg-1 for triglyceride and cholesterol lowering, and 0.29 mg kg-1 for HDL-C increase. It also showed improvement in clearance of plasma triglyceride and hepatic triglyceride secretion rate. All these effects are 3-10-fold better than fenofibrate and KRP-297. Ragaglitazar treatment showed significant reduction in plasma Apo B and Apo CIII levels, and increase in liver CPT1 and CAT activity and ACO mRNA. Significant increase of both liver and fat LPL activity and fat aP2 mRNA was also observed. In a high-fat-fed hamster model, ragaglitazar at 1 mg kg-1 showed 83 and 61% reduction in triglyceride and total cholesterol, and also 17% reduction in fat feed-induced body weight increase. In these hyperlipidaemic animal models, PPARgamma ligands failed to show any significant efficacy. Taken together, ragaglitazar shows better insulin-sensitizing and lipid-lowering potential, as compared to the standard compounds.

Lack of effect of sucralfate on the absorption and pharmacokinetics of rosiglitazone.

The aim of the present study was to investigate the effect of sucralfate pretreatment on the pharmacokinetics of rosiglitazone following a single oral dose in healthy male volunteers. After an over night fast, and according to a randomized schedule, each volunteer (n = 9) received a single oral dose of rosiglitazone 8 mg (Avandia tablets, 4 mg x 2) with or without pretreatment of sucralfate 2 g (Recolfate tablets, 1 g x 2) in an open-label crossover study with a 2-week washout period. Plasma samples were collected over a period of 24 hours at regular intervals. Safety assessment included monitoring of the vital signs, blood parameters, and ECG. No statistically significant differences (p > 0.05) were observed for any of the calculated rosiglitazone pharmacokinetic parameters in the two treatment groups. The mean parameters, AUC0-infinity and Cmax, following rosiglitazone administration alone were 3825.02 ng x h/ml and 664.47 ng/ml, respectively, and for rosiglitazone administered after pretreatment with sucralfate were 4848.19 ng x h/ml and 624.88 ng/ml, respectively. The t(max) for rosiglitazone alone and for rosiglitazone after sucralfate treatments was 1.11 and 1.67 hours, respectively. The mean elimination half-life for rosiglitazone and rosiglitazone after sucralfate treatment was 4.35 and 4.51 hours, respectively. Fraction of rosiglitazone absorbed was calculated by the Wagner-Nelson method, and no statistically significant difference (p > 0.05) was observed for the two treatments. Since sucralfate pretreatment did not show any significant difference in the pharmacokinetics of rosiglitazone, no dose adjustment is warranted for rosiglitazone when it is administered with sucralfate.

Antidiabetic and hypolipidemic potential of DRF 2519--a dual activator of PPAR-alpha and PPAR-gamma.

We investigated the biological activity of Dr. Reddy's Research Foundation (DRF) 2519, a benzoxazinone analogue of the thiazolidinedione class of compounds. In the in vitro transactivation assay, DRF 2519 showed interesting dual activation of Peroxisome Proliferator Activated Receptor (PPAR) alpha and gamma. In insulin-resistant ob/ob mouse model, DRF 2519 showed significant alleviation of insulin resistance and dyslipidemia, which is better than rosiglitazone. Fatty Zucker rats treated with DRF 2519 showed better reduction of plasma insulin, triglyceride and free fatty acid levels than those treated with rosiglitazone. In addition, these rats were able to clear plasma lipids better when challenged with exogenous lipid (i.v.). DRF 2519 treatment resulted in improved plasma lipid profiles in high-fat-fed Sprague-Dawley rats. Treated rats showed better plasma lipid clearance and hepatic triglyceride secretion. When compared to DRF 2519, fenofibrate was comparatively less efficacious while rosigltiazone showed no activity in these models. In ex vivo studies, DRF 2519 showed induction of liver acyl CoA oxidase mRNA and increase in lipoprotein lipase (LPL) protein expression and activity in adipose tissue. In the in vitro studies, DRF 2519 inhibited the lipid biosynthesis and secretion of apolipoprotein B from human hepatoma (Hep)G2 cells. It also enhanced insulin-induced relaxation of rat aortic smooth muscle. These results indicate that DRF 2519, a dual activator of PPAR-alpha and gamma, could be an interesting development candidate in the management of metabolic disorders and associated complications.

3-O-substituted benzyl pyridazinone derivatives as COX inhibitors.

New 3-O-substituted benzyl pyridazinone compounds have been synthesised and evaluated for their cyclooxygenase inhibitory activity and COX-2 selectivity. Among the compounds synthesised, three compounds (11b-11d) have shown in vitro COX-2 selectivity. These compounds have been evaluated for their in vivo potential using carrageenan-induced rat paw edema assay. One compound (11b) showed 32% anti-inflammatory activity at 30 mgkg(-1) dose.

New styryl sulfones as anticancer agents.

New styryl sulfone compounds have been synthesized and evaluated for their anti-proliferative activity. Among the compounds synthesized, one compound (7k) has shown 51% tumor growth inhibition in mice implanted with HT-29 human carcinoma at 400 mg kg(-1) orally.

Oral bioavailability and pharmacokinetics of DRF-4367, a new COX-2 inhibitor in rats.

The pharmacokinetic characterization of DRF-4367 (a new diaryl pyrazole derivative), a potent selective COX-2 inhibitor was performed in Wistar rats. In the first study, a single dose of 2, 5, 10, 30 or 100 mg/kg DRF-4367 was given orally to rats for investigating the dose proportionality and/or linearity in the pharmacokinetics. In the second study, a single intravenous bolus dose of DRF-4367 was given at a dose of 10 mg/kg to calculate the absolute oral bioavailability, clearance and volume of distribution parameters. Blood samples were drawn at predetermined intervals up to 24 h post-dose. The concentrations of DRF-4367 in various plasma samples were determined by a validated HPLC method. Plasma concentration versus time data was generated following oral and i.v dosing and subjected to a noncompartmental pharmacokinetic analysis. Following oral administration, maximum concentrations of DRF-4367 were achieved at about 3 h and were unchanged with incremental doses. Both Cmax and AUC0-infinity appeared to increases less than proportional to the administered oral doses. While the doses increased in the ratio of 1.0 : 2.5 : 5.0 : 15.0 : 50.0, the mean AUC0-infinity and Cmax increased in the ratios of 1.0 : 2.8 : 4.5 : 8.6 : 14.5 and 1 : 2.4 : 4.1 : 6.2 : 8.3, respectively. Following i.v. administration, the concentration of DRF4367 declined in a monoexponential fashion with terminal elimination half-life of 5.7 h. The systemic clearance and volume of distribution of DRF-4367 in rats were 0.36 L/h/Kg and 2.2 L/Kg respectively after i.v administration. Elimination half-life was unchanged with route of administration and with increase in oral doses. Absolute oral bioavailability of DRF-4367 in the efficacy dose range was 70-80%.

Decreased prevalence of lymphatic filariasis among diabetic subjects associated with a diminished pro-inflammatory cytokine response (CURES 83).

Epidemiological studies have shown an inverse correlation between the incidence of lymphatic filariasis (LF) and the incidence of allergies and autoimmunity. However, the interrelationship between LF and type-2 diabetes is not known and hence, a cross sectional study to assess the baseline prevalence and the correlates of sero-positivity of LF among diabetic subjects was carried out (n = 1416) as part of the CURES study. There was a significant decrease in the prevalence of LF among diabetic subjects (both newly diagnosed [5.7%] and those under treatment [4.3%]) compared to pre-diabetic subjects [9.1%] (p = 0.0095) and non-diabetic subjects [10.4%] (p = 0.0463). A significant decrease in filarial antigen load (p = 0.04) was also seen among diabetic subjects. Serum cytokine levels of the pro-inflammatory cytokines-IL-6 and GM-CSF-were significantly lower in diabetic subjects who were LF positive, compared to those who were LF negative. There were, however, no significant differences in the levels of anti-inflammatory cytokines-IL-10, IL-13 and TGF-beta-between the two groups. Although a direct causal link has yet to be shown, there appears to be a striking inverse relationship between the prevalence of LF and diabetes, which is reflected by a diminished pro-inflammatory cytokine response in Asian Indians with diabetes and concomitant LF.

Antihypertensive effect of ragaglitazar: a novel PPARalpha and gamma dual activator.

Ragaglitazar is a novel and potent dual peroxisome proliferators activated receptor (PPAR) alpha and gamma activator. The aim of this study is to investigate the effect of ragaglitazar on blood pressure and endothelial function in insulin resistant animal model and non-insulin resistant hypertensive models. The effects ragaglitazar were tested in Zucker fa/fa, spontaneously hypertensive rats (SHR), 2 kidney 1clip rat (2K1C) and Wistar Kyoto rats (WKY). Pioglitazone was taken as a comparative standard. Ragaglitazar showed significant reduction (P<0.001) of systolic blood pressure (SBP) in insulin resistant fa/fa rats, with concomitant reduction in plasma triglycerides (TG) and insulin levels while pioglitazone (10 mg kg(-1)) showed significant (P<0.05) but comparatively less reduction. Ragaglitazar in contrast to pioglitazone showed significant reduction (P<0.05) of SBP in SHR, 2K1C while the same dose did not have any effect on normotensive WKY. Ragaglitazar also showed significant improvement in acetylcholine-induced relaxation in isolated aorta of Zucker fa/fa, SHR, 2K1C and also potentiated the insulin-induced vasorelaxation in Zucker fa/fa rats. These findings summarize that ragaglitazar shows significant reduction of BP and improvement in endothelial function not only in insulin resistant but also in non-insulin resistant hypertensive models where standard thiazolidinediones are ineffective. These data indicates that dual PPARalpha and gamma activator ragaglitazar can be beneficial for the treatment of hypertension and vascular disease commonly associated with type 2 diabetes.

Quantitative determination of ragaglitazar in rat plasma by HPLC: validation and application in pharmacokinetic study.

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of ragaglitazar [(-) DRF 2725, NNC 61-0029], a novel anti-diabetic agent, in rat plasma. The assay procedure involved simple liquid/liquid extraction of ragaglitazar and internal standard (IS, troglitazone) from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100 - 5C(18) column (4.6 x 250 mm, 5 micro m). Mobile phase consisting of 0.01 M potassium dihydorgen ortho phosphate (pH 3.2) and acetonitrile (30:70, v/v) was used at a flow rate of 1.0 mL/min. The eluate was monitored using an UV detector set at 240 nm. Ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of IS and ragaglitazar were 6.9 and 12.2 min, respectively. The standard curve for ragaglitazar was linear (r(2) > 0.999) in the concentration range 0.2-100 micro g/mL. Absolute recovery was >87% from rat plasma for both analyte and IS. The lower limit of quantification (LLOQ) of ragaglitazar was 0.2 micro g/mL. The inter- and intra-day precision in the measurement of quality control (QC) samples, 0.2, 1.0, 5.0 and 50 micro g/mL, were in the range 1.32-3.70% relative standard deviation (RSD) and 1.19-9.39% RSD, respectively. Accuracy in the measurement of QC samples was in the range 94.28-107.45%. Analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze/thaw cycles. Stability of ragaglitazar was established for 1 month at -20 degrees C. The application of the assay to a pharmacokinetic study in rats is described.

DRF 2655: a unique molecule that reduces body weight and ameliorates metabolic abnormalities.

OBJECTIVE: Preclinical evaluation of DRF 2655, a peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARgamma agonist, as a body-weight lowering, hypolipidemic and euglycemic agent. RESEARCH METHODS AND PROCEDURES: DRF 2655 was studied in different genetic, normal, and hyperlipidemic animal models. HEK 293 cells were used to conduct the reporter-based transactivation of PPARalpha and PPARgamma. To understand the biochemical mechanism of lipid-, body-weight-, and glucose-lowering effects, activities of key beta-oxidation and lipid catabolism enzymes and gluconeogenic enzymes were studied in db/db mice treated with DRF 2655. 3T3L1 cells were used for adipogenesis study, and HepG2 cells were used to study the effect of DRF 2655 on total cholesterol and triglyceride synthesis using [(14)C]acetate and [(3)H]glycerol. RESULTS: DRF 2655 showed concentration-dependent transactivation of PPARalpha and PPARgamma. In the 3T3L1 cell-differentiation study, DRF 2655 and rosiglitazone showed 369% and 471% increases, respectively, in triglyceride accumulation. DRF 2655 showed body-weight lowering and euglycemic and hypolipidemic effects in various animal models. db/db mice treated with DRF 2655 showed 5- and 3.6-fold inhibition in phosphoenolpyruvate carboxykinase and glucose 6-phosphatase activity and 651% and 77% increases in the beta-oxidation enzymes carnitine palmitoyltransferase and carnitine acetyltransferase, respectively. HepG2 cells treated with DRF 2655 showed significant reduction in lipid synthesis. DISCUSSION: DRF 2655 showed excellent euglycemic and hypolipidemic activities in different animal models. An exciting finding is its body-weight lowering effect in these models, which might be mediated by the induction of target enzymes involved in hepatic lipid catabolism through PPARalpha activation.

HPLC method for the determination of rosiglitazone in human plasma and its application in a clinical pharmacokinetic study.

Rosiglitazone (CAS 155141-29-0, Avandia) is a novel insulin sensitizer used in the treatment of type 2 diabetes. A sensitive high performance liquid chromatography (HPLC) method for its determination in human plasma using fluorescence detection (excitation: 247 nm, emission: 367 nm) with a suitable internal standard (I. S.) is described. Ethyl acetate was used as extraction solvent. A mobile phase consisting of phosphate buffer, acetonitrile and methanol was used at a flow rate of 1.0 ml/min on a C18 column. The absolute recovery was > 90% and the lower limit of quantitation was 5 ng/ml. The intra- and inter-day relative standard deviations ranged from 0.58-6.69% and 0.82-6.63%, respectively. The method described is simple, economical, precise and accurate and has been successfully applied in a pharmacokinetic study conducted in healthy human volunteers.

Pharmacological and pharmacokinetic evaluation of celecoxib prodrugs in rats.

This study demonstrates the utility of an in vitro - in vivo correlative approach in the selection and optimization of a prodrug candidate of celecoxib (CBX), a COX(2) inhibitor. As an initial screening step, a comparative single oral dose pharmacokinetic study was conducted in rats for CBX and its three aliphatic acyl water-soluble prodrugs viz., CBX-acetyl (CBX-AC), CBX-propionyl (CBX-PR) and CBX-butyryl (CBX-BU) at high equimolar dose, 100 mg/kg. Only CBX-BU and CBX-PR converted rapidly to CBX and yielded approximately five-fold greater systemic exposure of CBX than CBX alone or CBX-AC. Rank order of systemic exposure of prodrugs in its intact form was CBX-AC >CBX-PR >CBX-BU. Further in vitro hydrolysis studies of CBX prodrugs in intestinal mucosal suspensions and liver homogenates indicated that CBX-BU is rapidly and completely converted to CBX, whereas CBX-PR and CBX-AC require longer incubation period for complete conversion to CBX. There was a very good correlation of the in vitro and in vivo data supporting CBX-BU as the prodrug of choice. Further in vitro pharmacological studies showed that COX(2) selective inhibition is improved for CBX-BU as compared to CBX-AC and CBX-PR. Dose proportionality in pharmacokinetic studies of CBX-BU and CBX at equimolar oral doses confirmed that relative oral bioavailability of CBX was improved following CBX-BU administration and there was linearity in pharmacokinetics of CBX over a wide dose range (10-100 mg/kg), whereas CBX in its conventional form showed poor bioavailability and lack of dose linearity in pharmacokinetics. The oral bioavailability of CBX from CBX-BU was dose independent and was in the range 78-96%. At a 50% reduced molar dose, CBX-BU showed an equivalent efficacy to that of CBX in the in vivo carrageenan model. Based on the study, water-soluble CBX-BU prodrug can be considered for clinical development in view of its potential advantages.

Synthesis and biological activity of novel pyrimidinone containing thiazolidinedione derivatives.

A series of pyrimidinone derivatives of thiazolidinediones were synthesized. Their biological activity were evaluated in insulin resistant, hyperglycemic and obese db/db mice. In vitro PPARgamma transactivation assay was performed in HEK 293T cells. PMT13 showed the best biological activity in this series. PMT13 (5-[4-[2-[2-ethyl-4-methyl-6-oxo-1,6-dihydro-1-pyrimidinyl]ethoxy]phenylmethyl]thiazolidine-2,4-dione) showed better plasma glucose, triglyceride and insulin-lowering activity in db/db mice than rosiglitazone and pioglitazone. PMT13 showed better PPARgamma transactivation than the standard compounds. Pharmacokinetic study in Wistar rats showed good systemic exposure of PMT13. Twenty-eight day oral toxicity study in Wistar rats did not show any treatment-related adverse effects.