No abstract

No abstract

No abstract

Changes were investigated in plasma metabolites and physiological and toxicological variables in rats fed for 2 wk on a basal diet or diets with 1.5, 5, 10, 15, and 30% added leucine. In the same experiment, the changes in gene expression in livers of rats fed the basal diet or diets with 5% and 15% added leucine were investigated using DNA microarrays. Cluster analysis of multivariate correlations of metabolites and physiological and toxicological variables indicated that the variables associated with excess nitrogen clustered together with leucine and alpha-ketoisocaproate. The gene expression data, although preliminary, indicated that there was little change in the expression of enzymes of the catabolic pathways for leucine but that there were changes in enzymes associated with nitrogen metabolism and other pathways downstream of leucine catabolism. The data seem consistent with excess leucine exerting its effects through the overloading of nitrogen metabolism and that urea or alpha-ketoisocaproate could be an early marker for the upper limit of adequate intake.

γH2AX, the phosphorylated form of a histone variant H2AX at Ser 139, is already widely used as a biomarker to research the fundamental biology of DNA damage and repair and to assess the risk of environmental chemicals, pollutants, radiation, and so on. It is also beginning to be used in the early non-clinical stage of pharmaceutical drug development as an in vitro tool for screening and for mechanistic studies on genotoxicity. Here, we review the available information on γH2AX-based test systems that can be used to develop drugs and present our own experience of practically applying these systems during the non-clinical phase of drug development. Furthermore, the potential application of γH2AX as a tool for in vivo non-clinical safety studies is also discussed.