ABSTRACT: Iron is an essential nutritional element; its deficiency in the body causes nutritional problems and a decrease in iron storage that can lead to anemia. The liver not only stores iron but is an important metabolic target as well. Dietary iron deficiency is associated with changes in the metabolism of nutrients such as lipids. However, to the best of our knowledge, a global analysis detailing the consequences of iron deficiency in the body has not yet been reported. We performed a comprehensive transcriptome analysis using DNA microarray technology to reveal the effects of iron deficiency on hepatic gene expression. Four-week-old rats were fed an iron-deficient diet or a control diet for 16 days. On day 17, the rats were sacrificed under anesthesia, and their livers were dissected for DNA microarray analysis. We identified 600 up-regulated and 500 down-regulated probe sets to characterize the iron-deficient diet group. The up-regulated probe sets contained genes for enzymes that are involved in cholesterol, amino acid, and glucose metabolisms, as well as in apoptosis. The down-regulated probe sets included genes for enzymes associated with lipid metabolism. Additionally, the 16-day iron-deficient diet induced anemia. Our gene expression analysis revealed that, as a result, cholesterol biosynthesis, gluconeogenesis, and apoptosis due to endoplasmic reticulum stress were accelerated, while fatty acid biosynthesis was suppressed by dietary iron deficiency. Our analysis also showed that cholesterol metabolism, including bile acid biosynthesis, was accelerated in the initial stages of cholesterol accumulation. Experiment Overall Design: Male 3-week-old Sprague Dawley rats were purchased from Charles River Japan (Kanagawa, Japan) and housed in a room conditioned at 24 ± 1°C and 40 ± 5% humidity with a 12-h light-dark cycle (lights on at 08:00). The rats were given a control diet and water for 24 h ad libitum. Diets for rats were obtained from Research Diets, Inc. (New Brunswick, NJ, USA). The composition of the control diet was based on the AIN93G diet , except that cellulose was replaced by Avicel, since cellulose is an ingredient of variable iron content. The iron-deficient diet was prepared by removal of iron (ferric citrate) from the control diet. At day 8, rats were divided into two groups comprising animals of similar body weights. One group (n = 6) was fed the control diet and the other group (n = 7) was fed the iron-deficient diet (iron-deficient diet group). After iron-deficient diet feeding was started, blood hemoglobin levels were measured every two days. Blood samples for hemoglobin measurements were collected from the tail vein, and hemoglobin levels were measured by using the Wako Hemoglobin B test (Wako Pure Chemical Industries, Osaka, Japan). On day 12 of the iron-deficient diet treatment, diets were removed at 17:00, and feeding was conducted between 09:00 and 17:00 for another 4 days. This protocol was intended to synchronize the ratsâ feeding behavior. On day 17 of the iron-deficient diet treatment, rats were fed for 1.5 h prior to sacrifice under anesthesia. Livers were then excised and subsequently immersed in RNAlater (Applied Biosystems Japan, Tokyo, Japan). Blood hemoglobin level of rats fed an iron-deficient diet decreased significantly over the course of the feeding. On day 17, the hemoglobin level in the iron-deficient diet group was 42% of that of the control diet group (P < 0.01).
