Dietary dry bean effects on hepatic expression of stress and toxicity-related genes in rats

Dry bean (Phaseolus vulgaris L.) consumption is associated with reduced risk for a number of chronic diseases. In westernised societies, dry bean consumption is particularly low (approximately 2-4 kg/capita per year) and little information is available about the safety of increasing dietary intake in humans to achieve levels that prevent and control chronic diseases. In anticipation of a human intervention study to address the safety and efficacy of increasing bean consumption, a dose-response study with dietary beans was conducted to establish whether increased bean consumption in rats exhibits changes indicative of hepatic stress or toxicity. Transcript levels from a panel of stress and toxicity-related genes were analysed in female Sprague-Dawley rats fed a dose range of dietary beans that bracketed amounts relevant to human consumption globally. Cooked red bean was incorporated into a purified diet formulation at 0, 7.5, 15, 30 or 60% w/w for the assessment of adaptive patterns of gene expression using quantitative PCR array. Of the eighty-four genes evaluated, the expressions of Cyp3a11, Cyp7a1, Fmo1, Gstm1, Mif and Ugt1a6 were elevated, whereas the expression of Hspa8 was down-regulated. Liver gene expression was not modulated in a manner indicative of an adverse response. Only the expression of the cholesterol 7 alpha hydoxylase and UDP-glucuronosyltransferase genes increased in a dose-dependent manner at nutritionally relevant dietary bean concentrations. These candidate genes may contribute to the health benefits attributed to increased bean consumption.