Obesity is a principal causative factor in the development of metabolic syndrome. Here we report that increased oxidative stress in accumulated fat is an important pathogenic mechanism of obesity-associated metabolic syndrome. Fat accumulation correlated with systemic oxidative stress in humans and mice. Production of ROS increased selectively in adipose tissue of obese mice, accompanied by augmented expression of NADPH oxidase and decreased expression of antioxidative enzymes. In cultured adipocytes, elevated levels of fatty acids increased oxidative stress via NADPH oxidase activation, and oxidative stress caused dysregulated production of adipocytokines (fat-derived hormones), including adiponectin, plasminogen activator inhibitor-1, IL-6, and monocyte chemotactic protein-1. Finally, in obese mice, treatment with NADPH oxidase inhibitor reduced ROS production in adipose tissue, attenuated the dysregulation of adipocytokines, and improved diabetes, hyperlipidemia, and hepatic steatosis. Collectively, our results suggest that increased oxidative stress in accumulated fat is an early instigator of metabolic syndrome and that the redox state in adipose tissue is a potentially useful therapeutic target for obesity-associated metabolic syndrome.

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.

This study investigated the impact of the active efflux mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) at the blood-brain barrier (BBB) on the predictability of the unbound brain concentration (C u,brain ) by the concentration in the cerebrospinal fluid (CSF) (C u,CSF ) in rats. C u,brain is obtained as the product of the total brain concentration and unbound fraction in the brain (f u,brain ) determined in vitro in brain slices. Twenty-five compounds, including P-gp and/or Bcrp substrates, were given a constant intravenous infusion, and their plasma, brain, and CSF concentrations were determined. P-gp and/or Bcrp substrates, such as verapamil, loperamide, flavopiridol, genistein, quinidine, dantrolene, daidzein, cimetidine, and pefloxacin, showed a higher CSF-to-brain unbound concentration ratio (K p,uu,CSF/brain ) compared with non-P-gp and non-Bcrp substrates. K p,uu,CSF/brain values of P-gp-specific (quinidine and verapamil) and Bcrp-specific (daidzein and genistein) substrates were significantly decreased in Mdr1a/ 1b(Ϫ/Ϫ) and Bcrp(Ϫ/Ϫ) mice, respectively. Furthermore, consistent with the contribution of P-gp and Bcrp to the net efflux at the BBB, K p,uu,CSF/brain values of the common substrates (flavopiridol and erlotinib) were markedly decreased in Mdr1a/ 1b(Ϫ/Ϫ)/Bcrp(Ϫ/Ϫ) mice, but only moderately or weakly in Mdr1a/1b(Ϫ/Ϫ) mice and negligibly in Bcrp(Ϫ/Ϫ) mice. In conclusion, predictability of C u,brain by C u,CSF decreases along with the net transport activities by P-gp and Bcrp at the BBB. C u,CSF of non-P-gp and non-Bcrp substrates can be a reliable surrogate of C u,brain for lipophilic compounds.

Satisfactory correction is safely performed by closing-opening wedge osteotomy with a direct visualization of the circumferentially decompressed spinal cord. Although the performance is technically laborious, it offers good correction without jeopardizing the integrity of the spinal cord.

BACKGROUND AND PURPOSEAn ATP-binding cassette (ABC) transporter, breast cancer resistance protein (BCRP)/ABCG2, limits oral bioavailability of sulphasalazine. Here we examined the effect of curcumin, the principal curcuminoid of turmeric, on oral bioavailability of microdoses and therapeutic doses of sulphasalazine in humans. EXPERIMENTAL APPROACHEffects of curcumin were measured on the ATP-dependent sulphasalazine uptake by hBCRP-expressing membrane vesicles and on oral bioavailability of sulphasalazine in wild-type and Bcrp(-/-) mice. Eight healthy Japanese subjects received an oral dose of sulphasalazine suspension (100 mg) or tablets (2 g) alone or after curcumin tablets (2 g). Uptake of sulphasalazine was studied in HEK293 cells transfected with the influx transporter (OATP)2B1. KEY RESULTSCurcumin was a potent hBCRP inhibitor in vitro (Ki 0.70 Ϯ 0.41 mM). Curcumin increased the area under the curve (AUC)0-8 of plasma sulphasalazine eightfold in wild-type mice at 300 and 400 mg·kg -1 , but not in Bcrp(-/-) mice. Curcumin increased AUC0-24 of plasma sulphasalazine 2.0-fold at microdoses and 3.2-fold at therapeutic doses in humans. Non-linearity of the dose-exposure relationship was observed between microdoses and therapeutic doses of sulphasalazine. Sulphasalazine was a substrate for OATP2B1 (Km 1.7 Ϯ 0.3 mM). Its linear index (dose/Km) at the therapeutic dose was high and may saturate OATP2B1. CONCLUSIONS AND IMPLICATIONSCurcumin can be used to investigate effects of BCRP on oral bioavailability of drugs in humans. Besides the limited dissolution, OATP2B1 saturation is a possible mechanism underlying non-linearity in the dose-exposure relationship of sulphasalazine. AbbreviationsABC, ATP-binding cassette; AUC, area under the curve; BCRP, breast cancer resistance protein; CLtot, total body clearance; Ki, inhibition constant Km, Michaelis constant; MRP2, multidrug resistance-associated protein 2; OATP, organic anion-transporting polypeptide; SNP, single nucleotide polymorphism BJP British Journal of Pharmacology