The antioxidant tempol reduces obesity in mice. Here we show that tempol alters the gut microbiome by preferentially reducing the genus Lactobacillus and its bile salt hydrolase (BSH) activity leading to the accumulation of intestinal tauro-b-muricholic acid (T-b-MCA). T-b-MCA is an farnesoid X receptor (FXR) nuclear receptor antagonist, which is involved in the regulation of bile acid, lipid and glucose metabolism. Its increased levels during tempol treatment inhibit FXR signalling in the intestine. High-fat diet-fed intestine-specific Fxr-null (Fxr DIE ) mice show lower diet-induced obesity, similar to tempol-treated wild-type mice. Further, tempol treatment does not decrease weight gain in Fxr DIE mice, suggesting that the intestinal FXR mediates the anti-obesity effects of tempol. These studies demonstrate a biochemical link between the microbiome, nuclear receptor signalling and metabolic disorders, and suggest that inhibition of FXR in the intestine could be a target for anti-obesity drugs.

Purpose: Inhibition of checkpoint kinase 1 has been shown to enhance the cytotoxicity of DNAdamaging targeted chemotherapy through cell cycle checkpoint abrogation and impaired DNA damage repair. A novel checkpoint kinase 1/2 inhibitor, AZD7762, was evaluated for potential enhancement of radiosensitivity for human tumor cells in vitro and in vivo xenografts.Experimental Design: Survival of both p53 wild-type and mutant human cell lines was evaluated by clonogenic assay. Dose modification factors (DMF) were determined from survival curves (ratio of radiation doses for control versus drug treated at 10% survival). Flow cytometry, Western blot, and radiationinduced tumor regrowth delay assays were conducted.Results: AZD7762 treatment enhanced the radiosensitivity of p53-mutated tumor cell lines (DMFs ranging from 1.6-1.7) to a greater extent than for p53 wild-type tumor lines (DMFs ranging from 1.1-1.2). AZD7762 treatment alone exhibited little cytotoxicity to any of the cell lines and did not enhance the radiosensitivity of normal human fibroblasts (1522). AZD7762 treatment abrogated radiationinduced G 2 delay, inhibited radiation damage repair (assessed by γ-H2AX), and suppressed radiationinduced cyclin B expression. HT29 xenografts exposed to five daily radiation fractions and to two daily AZD7762 doses exhibited significant radiation enhancement compared with radiation alone.Conclusions: AZD7762 effectively enhanced the radiosensitivity of mutated p53 tumor cell lines and HT29 xenografts and was without untoward toxicity when administered alone or in combination with radiation. The results of this study support combining AZD7762 with radiation in clinical trials. Clin Cancer Res; 16(7); 2076-84. ©2010 AACR.