Microarray Analysis of Rat Pancreas Reveals Altered Expression of Alox15 and Regenerating Islet-Derived Genes in Response to Iron Deficiency and Overload

Abstract

It is well known that iron overload can result in pancreatic iron deposition, beta-cell destruction, and diabetes in humans. Recent studies in animals have extended the link between iron status and pancreatic function by showing that iron depletion confers protection against beta-cell dysfunction and diabetes. The aim of the present study was to identify genes in the pancreas that are differentially expressed in response to iron deficiency or overload. Weanling male Sprague-Dawley rats (n = 6/group) were fed iron-deficient, iron-adequate, or iron-overloaded diets for 3 weeks to alter their iron status. Total RNA was isolated from the pancreases and pooled within each group for microarray analyses in which gene expression levels were compared to those in iron-adequate controls. In iron-deficient pancreas, a total of 66 genes were found to be differentially regulated (10 up, 56 down), whereas in iron-overloaded pancreas, 164 genes were affected (82 up, 82 down). The most up-regulated transcript in iron-deficient pancreas was arachidonate 15-lipoxygenase (Alox15), which has been implicated in the development of diabetes. In iron-overloaded pancreas, the most upregulated transcripts were Reg1a, Reg3a, and Reg3b belonging to the regenerating islet-derived gene (Reg) family. Reg expression has been observed in response to pancreatic stress and is thought to facilitate pancreatic regeneration. Subsequent qRT-PCR validation indicated that Alox15 mRNA levels were 4 times higher in iron-deficient than in iron-adequate pancreas and that Reg1a, Reg3a, and Reg3b mRNA levels were 17–36 times higher in iron-overloaded pancreas. The elevated Alox15 mRNA levels in iron-deficient pancreas were associated with 8-fold higher levels of Alox15 protein as indicated by Western blotting. Overall, these data raise the possibility that Reg expression may serve as a biomarker for iron-related pancreatic stress, and that iron deficiency may adversely affect the risk of developing diabetes through up-regulation of Alox15.

High-Iron Consumption Impairs Growth and Causes Copper-Deficiency Anemia in Weanling Sprague-Dawley Rats

“…Other investigators have measured growth and Hb levels in rodents fed high-iron diets [ 36 – 38 ], including some studies that have used weanling SD rats [ 39 , 40 ]. In general, most studies documented decrements in body weight after high-iron feeding.…”

“…A mechanistic explanation for altered growth rates was, however, not provided. A few studies also measured Hb levels after high-iron feeding and showed no changes [ 36 , 40 ] or an increase [ 39 ]. Differences between these previous studies and the current investigation could relate to the diets used, the length of feeding, the specific strain of mouse or rat used, and/or to rodent housing conditions.…”

Proteomic Analysis of Disease Stratified Human Pancreas Tissue Indicates Unique Signature of Type 1 Diabetes

“…These data are consistent with the work of Choi et al, [ 40 ], who used subtractive hybridization and DNA sequencing of whole pancreas to demonstrate that Reg3α changes the expression level of islet marker genes, including NEUROD, NKX2.2, PAX4, and PAX6. Furthermore, Reg expression may serve as a biomarker for iron-related pancreatic stress, as iron changes may contribute to diabetes development through up-regulation of Alox15 [ 41 ]. Overall, RegIIIα may represent a novel therapeutic target to modulate beta cell function, survival and regeneration.…”

Nutritional systems biology of type 2 diabetes

“…Another micronutrient of relevance to T2D is iron, because both iron overload and deficiency have been linked to impaired pancreatic function and glucose homeostasis. In a microarray analysis of rat pancreas with either iron deficiency or iron overload, genes involved in lipid transport and encoding pancreatitis-associated proteins were found to be significantly affected in both conditions, thus supporting their involvement in pancreatic functions and T2D (Coffey et al 2014 ). These micronutrient studies, therefore, also point to a role of lipid metabolism/transport as a shared mechanism through which nutrients influence T2D.…”