Project description:In order to understand the molecular mechanism responsible for the therapeutic potential of vitamin D, we conducted an analysis of the liver transcriptome – a central place of metabolic changes. The experiment was carried out on adult female rats (about one year old), n=18, divided into three experimental subjects, receiving different doses of vitamin D for three months: group I - 0, group II - 1000 U/Kg, group III - 5000 U/Kg. After the experiment, the biochemical and haematological parameters of the blood were evaluated. RNA-seq was used to analyze the changes in the liver transcriptome, and Gene Set Enrichment Analysis (GSEA) was used to identify enrichments in gene expression profiles of experimental groups. qPCR was employed to evaluate the expression of several genes connected to cholesterol biosynthesis, metallothioneins, vitamin D metabolism and others. At the end of the experiment, 25(OH) vitamin D concentrations were as follows: group I: 29 ng/ml, group II 43: ng/ml, group III: 70 ng/mL. Considering blood parameters, we observed a lower platelet count (p<0,008) and significantly higher (p<0.02) number of WBC in rats supplemented with 1000 U/Kg than in rats from group III (5000 U/Kg), but no difference between rats from group I and III were detected in these parameters. Moreover, we noted a trend (p<0.06 ) in total cholesterol concentration, suggesting a linear decrease with increasing doses of vitamin D. RNA-seq analysis did not identify any differentially expressed genes with FDR<0.05 in any of the three comparisons. However, GSEA revealed significant activation of the number of processes and pathways. In the I vs III comparison, the most enriched were the genes from the “metallothionein, and TspO/MBR family” (Enrichment Score=8,170, FDR= 0.00006), the genes associated with “glyceraldehyde-3-phosphate dehydrogenase (NAD+) (phosphorylating) activity” (Enrichment Score=5.13, FDR<00049) and the genes associated with “Negative regulation of tumour necrosis factor production” (Enrichment score=1.26, FDR0.0064. qPCR analysis identified significant upregulation of Mt1, Mt2 and Orm1 genes in animals receiving high doses of vitamin D (p<0.025, p<0.025, p<0009, respectively). Moreover, significant downregulation of Srebp2 and Insig2 was observed in both experimental groups when compared to the control group (p<0.003, p<0.036, respectively). Our results support the potential of vitamin D supplementation in ameliorating oxidative stress, inflammation and high blood cholesterol and underlie the need for further studies aimed at identifying optimal vitamin D doses with therapeutic effects.
Project description:Vitamin D deficiency is common among older adults and has been linked to muscle weakness. Vitamin D supplementation has been proposed as a strategy to improve muscle function in older adults. The aim of this study was to investigate the effect of calcifediol (25-hydroxycholecalciferol) on whole genome gene expression in skeletal muscle of vitamin D deficient frail older adults. A double-blind placebo controlled trial was conducted in vitamin D deficient frail older adults (aged above 65), characterized by blood 25-hydroxycholecalciferol concentrations between 20 and 50 nmol/L. Subjects were randomized across the placebo group (n=12) and the calcifediol group (n=10, 10 µg per day). Muscle biopsies were obtained before and after six months of calcifediol or placebo supplementation and subjected to whole genome gene expression profiling using Affymetrix HuGene 2.1ST arrays. Expression of the vitamin D receptor gene was virtually undetectable in human skeletal muscle biopsies. Calcifediol supplementation led to a significant increase in blood 25-hydroxycholecalciferol levels compared to the placebo group. No difference between treatment groups was observed on strength outcomes. The whole transcriptome effects of calcifediol and placebo were very weak. Correcting for multiple testing using false discovery rate did not yield any differentially expressed genes using any sensible cut-offs. P-values were uniformly distributed across all genes, suggesting that low p-values are likely to be false positives. Partial least squares-discriminant analysis and principle component analysis was unable to separate treatment groups. Calcifediol supplementation did not affect the skeletal muscle transcriptome in frail older adults. Our findings indicate that vitamin D supplementation has no effects on skeletal muscle gene expression, suggesting that skeletal muscle may not be a direct target of vitamin D in older adults.