Effect of 20% fructose feeding and dietary salt on RNA expression in the renal cortex of rats

Elevated fructose consumption has been associated with metabolic and renal diseases. It is controversial whether kidney problems are a result of systemic metabolic disease or stem, at least in part, from changes due to local fructose metabolism. To study the short-term effect of fructose on genetic programs in renal proximal tubules, the diet for rats in experimental groups was supplemented for 7 days with 20% fructose in the drinking water. Two sets of 8 rats each on different baseline rodent diets were used in this study. 4 animals of each set received fructose in the drinking water while the other 4 served as controls. Animals were sacrificed after the experimental period of 7 days and slices of superficial kidney cortex were used for total RNA extraction. The RNA was analyzed with Affymetrix RaGene-2_0-st. A total of 16 male Sprague-Dawley rats weighing ~150 grams were divided in four dietary groups. Rats were housed in pairs under normal rat housing conditions with a 12-hour light cycle and access to food and fluids ad libitum. One set of 8 rats were fed the normal salt rodent chow Prolab® Isopro® RMH 3000, another set of 8 received the high salt (4% NaCl) chow Harlan TD.92034. 4 rats in each set received a solution of 20% fructose for 7 days, while the other 4 served as controls. In other words, Control group (CNS) received tap water and the normal salt rodent chow, Fructose (FNS) group received a solution of 20% fructose as fluid and the normal salt rodent chow, High-Salt group (CHS) received tap water and the high salt rodent chow, and High-Salt Fructose (FHS) group received a solutiion of 20% fructose and the high salt rodent chow. For tissue collection, rats were anesthetized with ketamine and xylazine, and given 2 IU heparin (IP). After sacrifice, the kidneys were cooled and a ~1 mm-thick slice of superficial cortex taken on a sagittal cut. Total RNA was extracted using miRNeasy Mini Kit (Qiagen; #217004) and the RNA was analyzed using the Affymetrix microarray RaGene-2_0-st.