SNQ2 was identified as a caffeine-resistance gene by screening a genomic library of Saccharomyces cerevisiae in a multicopy vector YEp24. SNQ2 encodes an ATP-binding cassette transporter and is highly homologous to PDR5. Multicopy of PDR5 also conferred resistance to caffeine, while its resistance was smaller than that of SNQ2. Residual caffeine contents were analyzed after transiently exposing cells to caffeine. The ratios of caffeine contents were 21.3 ± 8.8% (YEp24-SNQ2) and 81.9 ± 8.7% (YEp24-PDR5) relative to control (YEp24, 100%). In addition, multicopies of SNQ2 or PDR5 conferred resistance to rhodamine 6G (R6G), which was widely used as a substrate for transport assay. R6G was exported by both transporters, and their efflux activities were inhibited by caffeine with half-maximal inhibitory concentrations of 5.3 ± 1.9 (YEp24-SNQ2) and 17.2 ± 9.6 mM (YEp24-PDR5). These results demonstrate that Snq2p is a more functional transporter of caffeine than Pdr5p in yeast cells.

A novel series of 2,7-substituted 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and biologically evaluated. (S)-2-(2-Furylacryloyl)-7-[2-(2-methylindane-2-yl)-5-methyloxazol-4-yl] methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid tert-butylamine salt (13jE) was identified as a potent human peroxisome proliferator-activated receptor γ (PPARγ)-selective agonist (EC 50 85 nM) and human protein-tyrosine phosphatase 1B (PTP-1B) inhibitor (IC 50 1.0 µM). Compound 13jE partially activated PPARγ, but not PPARα or PPARδ, and antagonized farglitazar, a full PPARγ agonist. C max after the oral administration of 13jE at 10 mg/kg was 28.6 µg/mL (53 µM) in male Sprague-Dawley (SD) rats. Repeated administration of 13jE and rosiglitazone for 14 d at 10 mg/kg/d decreased plasma glucose and triglyceride levels significantly in male KK-A y mice. Rosiglitazone, but not 13jE, significantly increased the plasma volume and liver weight. In conclusion, 13jE showed stronger hypoglycemic and hypolipidemic effects and weaker hemodilution and hepatotoxic effects than rosiglitazone, suggesting that its safer efficacy may be due to its partial PPARγ agonism and PTP-1B inhibition.

No abstract

No abstract

Thiazolidinedione derivatives (troglitazone, pioglitazone and rosiglitazone) improve insulin resistance via peroxisome proliferator-activated receptor g (PPARg) activation, and have been used as anti-diabetic drugs; however, troglitazone was voluntarily withdrawn from the market because of fetal hepatoxicities, and both pioglitazone and rosiglitazone are carefully used because of the risks of fluid expansion, congestive heart failure, obesity and/or bone fracture.1-3) Other than thiazolidinedione derivatives, a great number of non-thiazolidinedione derivatives have been reported as candidates for safer and more efficacious PPARg agonists than thiazolidinedione derivatives. Carboxylate derivatives with PPARg and PPARa agonist activities were expected to exert excellent anti-diabetic activities through the synergistic effects of PPARg-mediated enhancement of insulin sensitivity and PPARa-mediated reduction of plasma lipids. 4) PPARg activation may increase body weight gain via adipocyte differentiation, whereas PPARa activation may decrease body weight gain via increased energy expenditure; however, PPARa/g dual agonists, ragaglitazar, muraglitazar, tesaglitazar and imiglitazar showed carcinogenicity, cardiovascular or hepatic risks, and their clinical development was discontinued. 3,4)Based on this background, newer PPARg agonists with different chemical and biological properties from those of the reported compounds are needed to be developed. We have reported a novel tetrahydroisoquinoline-based PPARg agonist, KY-021, which was considered to be a more efficacious and safer candidate for an anti-diabetic drug than farglitazar, and proposed that a tetrahydroisoquinoline ring is a useful scaffold for PPAR agonists.5,6) The structure-activity relationships in KY-021 derivatives revealed that 2-benzyl but not cyclohexylmethyl, phenyl, benzoyl, or hexyl was the most suitable moiety for interaction with PPARg protein; however, derivatives with aliphatic acyl chain at the 2-position have not yet been synthesized. 6) In the present study, a 2-benzyl group of KY-021 was changed to a hexanoyl, hexenoyl and hexynoyl chain, and the PPAR agonist activities and proteintyrosine phosphatase 1B (PTP-1B) inhibitory activities were evaluated. Among the 2-acyl derivatives, a lead compound 14 for a new type of anti-diabetic drug with PPARa/g agonists and PTP-1B inhibitory activity was found.Chemistry The general approach to the synthesis of (S)-2-substituted-7-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives is outlined in Chart 1. Compound 1 and 2 were prepared according to the previously reported procedure. 6)Acylation of 1 and 2 afforded 2-acyl tetrahydroisoquinoline derivatives 3-8, which were treated with aqueous LiOH to give tetrahydroisoquinoline-3-carboxylic acid derivatives 9-14. As the free form of compound 14 was unstable, 14 was isolated as a tert-butylamine salt. Results and DiscussionWe have previously reported a novel tetrahydroisoquinoline-based PPARg agonist, KY-02...