DIET AND IMMUNE FUNCTION RELATED TO INFECTIOUS AND ALLERGIC DISEASE
Location: Diet, Genomics and Immunology Lab
Title: Supplemental dietary inulin influences expression of iron and inflammation related genes in young pigs
Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 23, 2009
Publication Date: November 1, 2009
Citation: Yasuda, K., Dawson, H.D., Wasmuth, E.V., Roneker, C.A., Chen, C., Urban, J.F., Welch, R.M., Miller, D.D., Lei, X.G. 2009. Supplemental dietary inulin influences expression of iron and inflammation related genes in young pigs. Journal of Nutrition. 139(11):2018-2023.
Interpretive Summary: Inulin is a soluble fiber, naturally found in leeks, artichokes, asparagus, onions, and bananas, that may be used as a supplemental carbohydrate source with purported health benefits when added to the diet. Similar to starches in edible plants, there are different forms of inulin due to varying carbohydrate chain length. We showed previously that iron status improved in pigs fed one type of inulin. The mechanism underlying this observation was not determined, and the effects of other types of inulin were not tested. In the current study, we investigated the effects on iron status of three different formulations of inulin added to a basic diet using a targeted functional genomics approach, and measurement of blood hemoglobin concentration and liver ferritin protein as markers of iron metabolism. Although the three formulations of inulin had similar effects on iron status, the gene expression profiles of proteins involved in iron transport and storage were differentially affected. All three formulations, however, reduced the expression of the pro-inflammatory cytokine TNF-alpha, as well as several other inflammation-related genes. These data suggest that inulin may increase the absorption of minerals like iron by suppressing local inflammation in the intestine. This information will be important to researchers interested in iron metabolism and plant breeders who do research on changing the composition of inulin in edible plants.
We have previously shown improved hemoglobin repletion efficiency by supplementing a 50:50 mixture of short (P95) and long-chain (HP) inulin (Synergy 1, BENEO-Orafti, Tienen, Belgium) into a corn-soybean meal basal diet (BD) for young pigs. In the present study, weanling pigs (5 or 6-wk old) were fed the BD, or the BD + 4% of P95, HP, or Synergy 1 (50:50 mixtures of HP and P95) for 5 or 7 wk. Blood hemoglobin concentrations of pigs were measured weekly, and digesta samples were collected at the end of trial. In a replicate experiment, total RNA was isolated from the liver and mucosa of duodenum, ileum, cecum, and colon of all pigs at the end of the trial. Relative mRNA expression of 27 genes, including iron and inflammatory-related genes, were quantified using real-time quantitative-PCR. While all three types of inulin resulted in similar improvements (P < 0.05) in blood hemoglobin and liver ferritin protein concentrations, neither type of inulin was detectable in the digesta of the cecum or colon. Supplemental inulin enhanced the expression of iron-storing protein genes, but decreased that of inflammation-related genes. Such effects were more pronounced (P < 0.05) in the mucosa of the lower than the upper gut, and were seen on seven genes in liver. In conclusion, all three types of inulin shared similar efficacy and possibly similar mode of action in improving dietary iron utilization by young pigs. Suppressing inflammation-induced genes that can negatively influence iron metabolism may help explain the beneficial effect of inulin.