Vitamin D receptor regulates intestinal proteins involved in cell proliferation, migration and stress response

BACKGROUND: Genome-wide association studies found low plasma levels of 25-hydroxyvitamin D and vitamin D receptor (VDR) polymorphisms associated with a higher prevalence of pathological changes in the intestine such as chronic inflammatory bowel diseases. METHODS: In this study, a proteomic approach was applied to understand the overall physiological importance of vitamin D in the small intestine, beyond its function in calcium and phosphate absorption. RESULTS: In total, 569 protein spots could be detected by two-dimensional-difference in-gel electrophoresis (2D-DIGE), and 82 proteins were considered as differentially regulated in the intestinal mucosa of VDR-deficient mice compared to that of wildtype (WT) mice. Fourteen clearly detectable proteins were identified by MS/MS and further analyzed by western blot and/or real-time RT-PCR. The differentially expressed proteins are functionally involved in cell proliferation, cell adhesion and cell migration, stress response and lipid transport. Mice lacking VDR revealed higher levels of intestinal proteins associated with proliferation and migration such as the 37/67 kDa laminin receptor, collagen type VI (alpha 1 chain), keratin-19, tropomyosin-3, adseverin and higher levels of proteins involved in protein trafficking and stress response than WT mice. In contrast, proteins that are involved in transport of bile and fatty acids were down-regulated in small intestine of mice lacking VDR compared to WT mice. However, plasma and liver concentrations of cholesterol and triglycerides were not different between the two groups of mice. CONCLUSION: Collectively, these data imply VDR as an important factor for controlling cell proliferation, migration and stress response in the small intestine

Additive effects of lupin protein and phytic acid on aortic calcification in ApoE deficient mice

Lupin proteins have repeatedly been shown to exhibit lipid lowering properties and reduce aortic calcification in atherosclerosis models. Despite many efforts on its identification, the component which is responsible for the observed effects is still under debate. Phytic acid which is generally associated with lupin protein isolates has currently been described as bioactive plant compound. The objective of the study was to determine the role of associated phytic acid for the described lupin protein effects. A two-factorial study with ApoE knockout mice was conducted in which mice received lupin protein isolate or casein with or without phytase. Phytic acid was added to the casein diets to a final concentration identical to the lupin protein diets. Here we show that the serum concentrations of cholesterol, lathosterol and desmosterol were lower and the faecal bile acid excretion was higher in the groups fed lupin proteins than in the groups fed casein (p < 0.05). Mice that received the lupin protein diet containing phytic acid were characterized by a lower aortic calcification than mice of the other three groups (p < 0.05). In conclusion, our results show that the cholesterol lowering properties of lupin protein isolate were not caused by phytic acid. However, the hypocalcific action of lupin proteins appears to depend on the combination of lupin proteins and phytic acid

Tissue-Specific Expression of Monocarboxylate Transporters during Fasting in Mice

<div><p>Monocarboxylates such as pyruvate, lactate and ketone bodies are crucial for energy supply of all tissues, especially during energy restriction. The transport of monocarboxylates across the plasma membrane of cells is mediated by monocarboxylate transporters (MCTs). Out of 14 known mammalian MCTs, six isoforms have been functionally characterized to transport monocarboxylates and short chain fatty acids (MCT1-4), thyroid hormones (MCT8, -10) and aromatic amino acids (MCT10). Knowledge on the regulation of the different MCT isoforms is rare. In an attempt to get more insights in regulation of MCT expression upon energy deprivation, we carried out a comprehensive analysis of tissue specific expression of five MCT isoforms upon 48 h of fasting in mice. Due to the crucial role of peroxisome proliferator-activated receptor (PPAR)-α as a central regulator of energy metabolism and as known regulator of MCT1 expression, we included both wildtype (WT) and PPARα knockout (KO) mice in our study. Liver, kidney, heart, small intestine, hypothalamus, pituitary gland and thyroid gland of the mice were analyzed. Here we show that the expression of all examined MCT isoforms was markedly altered by fasting compared to feeding. Expression of MCT1, MCT2 and MCT10 was either increased or decreased by fasting dependent on the analyzed tissue. MCT4 and MCT8 were down-regulated by fasting in all examined tissues. However, PPARα appeared to have a minor impact on MCT isoform regulation. Due to the fundamental role of MCTs in transport of energy providing metabolites and hormones involved in the regulation of energy homeostasis, we assumed that the observed fasting-induced adaptations of MCT expression seem to ensure an adequate energy supply of tissues during the fasting state. Since, MCT isoforms 1–4 are also necessary for the cellular uptake of drugs, the fasting-induced modifications of MCT expression have to be considered in future clinical care algorithms.</p></div

Relative mRNA concentrations of (A) monocarboxylate transporter (MCT)-1, (B) MCT2 and (C) MCT4 in mouse tissues in response to fasting and PPARα.

<p>Values represent means ± SD of relative mRNA concentrations of wildtype (WT) and PPARα knockout (KO) mice that were fed <i>ad libitum</i> or fasted for 48 h (n = 16). Data were analyzed by two-way ANOVA. Classification factors were genotype, fasting, and the interaction between both factors. <i>P</i>-values revealed by two-way ANOVA are noted above the figures. Individual means of the treatment groups were compared by Tukey's test in case of variance homogeneity. In case of variance heterogeneity, as revealed by Levene's test, individual means were compared by Games Howell test. Horizontal brackets represent differences between groups in post-hoc comparison (**<i>p</i><0.001, *<i>p</i><0.05). n.e., not evaluable due to extremely low expression.</p

UVB exposure of farm animals: study on a food-based strategy to bridge the gap between current vitamin D intakes and dietary targets.

Vitamin D deficiency is a global health problem. This study aimed to investigate the efficacy of ultraviolet (UV) B radiation for improving vitamin D3 content of eggs and meat. In a two-factorial design hens that received diets with 0 (-D3) or 3,000 IU (+D3) vitamin D3/kg were non-exposed (-UVB) or exposed to UVB radiation (+UVB) for 3 h daily over 4 weeks. Data show that UVB radiation was very effective in raising the vitamin D3 content of egg yolk and meat. Egg yolk from +UVB/-D3 hens had a higher vitamin D3 content (17.5±7.2 µg/100 g dry matter (DM)) than those from the -UVB/+D3 group (5.2±2.4 µg/100 g DM, p<0.01). Vitamin D3 content in egg yolk of vitamin D3-supplemented hens could be further increased by UVB radiation (32.4±10.9 µg/100 g DM). The content of 25-hydroxyvitamin D3 (25(OH)D3) in the egg yolk also increased in response to UVB, although less pronounced than vitamin D3. Meat revealed about 4-fold higher vitamin D3 contents in response to UVB than to dietary vitamin D3 (p<0.001). In conclusion, exposure of hens to UVB is an efficient approach to provide consumers with vitamin D3-enriched foods from animal sources

Relative protein expression of (A) monocarboxylate transporter (MCT)-1 and (B) MCT2 in mouse tissues in response to fasting and PPARα.

<p>Values represent means ± SD of relative protein expression of wildtype (WT) and PPARα knockout (KO) mice that were fed <i>ad libitum</i> or fasted for 48 h (n = 16). Data were analyzed by two-way ANOVA. Classification factors were genotype, fasting, and the interaction between both factors. <i>P</i>-values revealed by two-way ANOVA are noted above the figures. Individual means of the treatment groups were compared by Tukey's test in case of variance homogeneity. In case of variance heterogeneity, as revealed by Levene's test, individual means were compared by Games Howell test. Horizontal brackets represent differences between groups in post-hoc comparison (*<i>p</i><0.05).</p

Primer sequences used in real-time RT-PCR.

<p>Primer sequences used in real-time RT-PCR.</p

Relative mRNA concentration of (A) monocarboxylate transporter (MCT)-8 and (B) MCT10 in mouse tissues in response to fasting and PPARα.

<p>Values represent means ± SD of relative mRNA concentrations of wildtype (WT) and PPARα knockout (KO) mice that were fed <i>ad libitum</i> or fasted for 48 h (n = 16 for liver, kidney, heart, small intestine and hypothalamus, n = 8 for pituitary gland, n = 6 for thyroid gland). Data were analyzed by two-way ANOVA. Classification factors were genotype, fasting, and the interaction between both factors. <i>P</i>-values revealed by two-way ANOVA are noted above the figures. Individual means of the treatment groups were compared by Tukey's test in case of variance homogeneity. In case of variance heterogeneity, as revealed by Levene's test, individual means were compared by Games Howell test. Horizontal brackets represent differences between groups in post-hoc comparison (**<i>p</i><0.001, *<i>p</i><0.05). n.e., not evaluable due to extremely low expression.</p

Relative protein expression of monocarboxylate transporter (MCT)-8 in mouse tissues in response to fasting and PPARα.

<p>Values represent means ± SD of relative protein expression of wildtype (WT) and PPARα knockout (KO) mice that were fed <i>ad libitum</i> or fasted for 48 h (n = 16). Data were analyzed by two-way ANOVA. Classification factors were genotype, fasting, and the interaction between both factors. <i>P</i>-values revealed by two-way ANOVA are noted above the figures. Individual means of the treatment groups were compared by Tukey's test in case of variance homogeneity. In case of variance heterogeneity, as revealed by Levene's test, individual means were compared by Games Howell test. No significant differences in post-hoc comparison were revealed.</p

Final plasma concentrations of (A) non-esterified fatty acids (NEFA), (B) 3-hydroxybutyrate and (C) free thyroxine (fT4) in response to fasting and PPARα.

<p>Values represent means ± SD of plasma concentrations of wildtype (WT) and PPARα knockout (KO) mice that were fed <i>ad libitum</i> or fasted for 48 h (n = 16 for 3-hydroxybutyrate, n = 8 for NEFA and fT4). Data were analyzed by two-way ANOVA. Classification factors were genotype, fasting, and the interaction between both factors. <i>P</i>-values revealed by two-way ANOVA are noted above the figures. Individual means of the treatment groups were compared by Tukey's test in case of variance homogeneity. In case of variance heterogeneity, as revealed by Levene's test, individual means were compared by Games Howell test. Horizontal brackets represent differences between groups in post-hoc comparison (**<i>p</i><0.001, *<i>p</i><0.05).</p