Gene Expression in Rats Fed a Western Diet

Resistant starches (RS), fed as high amylose maize starch (HAMS) or butyrylated HAMS (HAMSB), oppose dietary protein-induced colonocyte DNA damage in rats. In this study, rats were fed diets high in fat (19%) and protein (20%) with different forms of digestible starch (low amylose maize starch (LAMS) or low amylose whole wheat (LAW)) or RS (HAMS, HAMSB, or a whole high amylose wheat (HAW) generated by RNA interference (RNAi)) for 11 wk. A control diet contained 7% fat, 13% protein and LAMS. The aim of this study was to detect changes in the expression of DNA damage and repair genes in response to the above dietary treatments. Distal colon tissues from Sprague Dawley rats fed a variety of diets (see summary) were removed from RNAlater stabilisation reagent (Sigma, Australia) they had been stored in,, placed in 1 ml of TRIzol® Reagent (Invitrogen, Australia) and homogenised usingbeads (mix of 2.5 mm glass and 0.1 - 1.0 mm diameter silicon-zirconian beads) in a MiniBeadbeater-8 (BioSpec Products Inc., USA). Total RNA was extracted (using TRIzol® Reagent manufacturer's instructions) and further purified using RNAeasy mini spin columns (QIAGEN, Australia) with a DNase on-column digestion as per manufacturer's instructions.RNA integrity was checked using a Bioanalyzer 2100 (Agilent Technologies, USA) andquantified using a NanoDrop® ND-1000 Spectrophotometer (Thermo Fisher Scientific, USA). RNA samples with insufficinet quality and quantity were not assayed. The numbers of rats arrayed from each diet were as follows: CON, 5;LAMS, 7; HAMS, 8; HAMSB, 9; LAW, 6; HAW , 8. This gives a total of 43 arrays.