Whole-transcriptome profiling of sheep fed with a high iodine-supplemented diet.

Iodine (I) is a micronutrient that mammals need for proper functionality of thyroid gland since it is the main component of thyroid hormones. Besides studies that have investigated the role of I in livestock nutrition, it is also important to know the transcriptomics changes in small ruminants following I supplementation. Therefore, the aim of this study was to investigate the effects of I on the whole blood transcriptome in sheep. Fifteen lactating cross-bred ewes (3 to 4-year-old, 55 to 65 kg BW) at their late lactation period were enrolled in this study. At the beginning, all the animals had a 2-week acclimation period where they were fed with a basal diet which includes an adequate level of I (2 mg I/animal per day) in the form of calcium iodate (CaI2O6). Then, the ewes were randomly divided into two groups and fed in individual troughs: the control group (n = 5) was maintained on basal diet and the experimental group (I, n = 10) was fed for 40 days with a diet containing a high I supplementation (equivalent to 30 mg I/animal per day), in the form of potassium iodide. Whole blood and milk were collected individually at the beginning (T0) and after the 40 days of supplementation (T40). Iodine quantification was assessed in serum and milk sample. Microarray gene expression analysis was performed on whole blood and, filtering data using a fold change >2 with an adjusted P < 0.05, we identified 250 differentially expressed genes (DEGs) in the I group (T40 v. T0). Looking for biological processes associated with our DEGs, we found significant association with cell growth regulation. Thus, our study unveils the role of I supplementation on gene expression in sheep improving the knowledge about micronutrients in animal nutrition.

Transcriptomic signature of high dietary organic selenium supplementation in sheep: A nutrigenomic insight using a custom microarray platform and gene set enrichment analysis.

The objective of this study was to investigate the effect of a high dietary Se supplementation on the whole transcriptome of sheep. A custom sheep whole-transcriptome microarray, with more than 23,000 unique transcripts, was designed and then used to profile the global gene expression of sheep after feeding a high dietary supplementation of organic Se. Lactating crossbred ewes ( = 10; 3 to 4 yr of age and 55 to 65 kg BW) at late lactation (100 ± 8 d in milk) were acclimated to indoor individual pen feeding of a basal control diet (0.40 mg Se/d, sodium selenite) for 4 wk. Sheep were then kept on a diet with an extra (high) supplementation of organic Se (1.45 mg Se/d as Sel-Plex; Alltech Biotechnology Pty Ltd, Dandenong, Victoria, Australia) for 40 d. Whole blood was collected at 2 time points (last day of the acclimatization period [T0] and after 40 d of the organic Se supplementation [T40]), and then total RNA was isolated and labeled for the subsequent microarray analysis. Significance Analysis of Microarrays, using the -statistic, of the microarray data (T40 versus T0) evidenced the up- and downregulation of 942 and 244 transcripts (false discovery rate < 0.05), respectively. Seven genes showed the same trend of expression (up- or downregulation) when tested by quantitative real-time PCR (qPCR) in a cross-validation step. The microarray showed significant upregulation of the following selenoproteins at T40: selenium binding protein 1 (SELENBP1), selenoprotein W1 (SEPW1), glutathione peroxidase 3 (GPX3), and septin 8 (SEPT8). And the expression trends for SEPW1 and SEPT8 were validated using qPCR. Functional annotation of the differentially expressed genes showed the enrichment of several immune system-related biological processes (lymphocyte activation, cytokine binding, leukocyte activation, T cell differentiation, and B cell activation) and pathways (cytokine and interleukin signaling). Moreover, Gene Set Enrichment Analysis evidenced the enrichment of B and T cell receptors signaling pathways, with an enrichment score of 0.63 and 0.59, respectively. Overall, from a global gene expression (whole-transcriptome) point of view, short-term supplementation of a high dietary organic Se to Se-nondeficient sheep results in a transcriptomic signature that mainly reflects an induced immune system and a modulation of transcription effect. Also, the present study provides a custom whole-transcriptome microarray platform that can be used in further global gene expression studies in the ovine species.