Ton H. J. Naber

Murine TNFΔARE Crohn's disease model displays diminished expression of intestinal Ca2+ transporters

Background: Patients suffering from Crohns disease (CD) show increased incidence of low bone mineral density. Investigating this complication is difficult because the exact etiology of CD remains elusive. Mice carrying a deletion in the tumor necrosis factor (TNF) AU‐rich elements (ARE) are reported as a model for human CD and are characterized by elevated TNF‐&agr; levels and inflammations in the terminal ileum. To evaluate whether these mice have a Ca2+ handling problem, this study analyzed the Ca2+ homeostasis in heterozygous TNF&Dgr;ARE mice (TNF&Dgr;ARE/+) in comparison to wildtype littermates. Methods: Beside serum Ca2+ and vitamin D levels, the expression of Ca2+ transporters was analyzed in intestine, kidney and bone using quantitative real‐time PCR, Western blot and immunohistochemistry. Bone scans were performed to measure bone parameters. Results: Ca2+ transporters in duodenum (TRPV6, calbindin‐D9K, PMCA1b) and kidney (TRPV5, calbindin‐D28K, NCX1) showed significantly reduced mRNA expression levels in TNP&Dgr;ARE/+ mice, except for renal TRPV5. In bone, only calbindin‐D9K mRNA displayed a significant down‐regulation. These findings were supported by declined duodenal calbindin‐D9K and renal calbindin‐D28K protein values. Likely, this down‐regulation of Ca2+ transporters in TNP&Dgr;ARE/+ mice is mediated by the 58 ± 9% reduction in serum 1,25(OH)2D3 levels. Diminished expression of Ca2+ transporters combined with unchanged serum Ca2+ levels assumes Ca2+ loss from bone to compensate for the bodys overall Ca2+ shortage. Indeed, microcomputed tomography scanning demonstrated reduced trabecular and corticol bone thickness and volume in TNF&Dgr;ARE/+ mice. This finding is further supported by increased total deoxypyridinoline in serum. Conclusions: Our results imply that TNF&Dgr;ARE/+ mice have a disturbed Ca2+ homeostasis characterized by reduced duodenal and renal Ca2+ transporters, diminished 1,25(OH)2D3 levels, and increased bone resorption associated with profound bone abnormalities.

Food Matrix Effects on Bioaccessibility of β‑Carotene Can be Measured in an in Vitro Gastrointestinal Model

Since the food matrix determines β-carotene availability for intestinal absorption, food matrix effects on the bioaccessibility of β-carotene from two diets were investigated in vitro and compared with in vivo data. The “mixed diet” consisted of β-carotene-rich vegetables, and the “oil diet” contained β-carotene-low vegetables with supplemental β-carotene. The application of extrinsically labeled β-carotene was also investigated. The bioaccessibility of β-carotene was 28 μg/100 μg β-carotene from the mixed diet and 53 μg/100 μg β-carotene from the oil diet. This ratio of 1.9:1 was consistent with in vivo data, where the apparent absorption was 1.9-fold higher in the oil diet than in the mixed diet. The labeled β-carotene was not equally distributed over time. In conclusion, the food matrix effects on bioaccessibility of β-carotene could be measured using an in vitro model and were consistent with in vivo data. The application of extrinsically labeled β-carotene was not confirmed.

Prediction of fruit and vegetable intake from biomarkers using individual participant data of diet-controlled intervention studies.

Fruit and vegetable consumption produces changes in several biomarkers in blood. The present study aimed to examine the dose-response curve between fruit and vegetable consumption and carotenoid (α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin), folate and vitamin C concentrations. Furthermore, a prediction model of fruit and vegetable intake based on these biomarkers and subject characteristics (i.e. age, sex, BMI and smoking status) was established. Data from twelve diet-controlled intervention studies were obtained to develop a prediction model for fruit and vegetable intake (including and excluding fruit and vegetable juices). The study population in the present individual participant data meta-analysis consisted of 526 men and women. Carotenoid, folate and vitamin C concentrations showed a positive relationship with fruit and vegetable intake. Measures of performance for the prediction model were calculated using cross-validation. For the prediction model of fruit, vegetable and juice intake, the root mean squared error (RMSE) was 258.0 g, the correlation between observed and predicted intake was 0.78 and the mean difference between observed and predicted intake was - 1.7 g (limits of agreement: - 466.3, 462.8 g). For the prediction of fruit and vegetable intake (excluding juices), the RMSE was 201.1 g, the correlation was 0.65 and the mean bias was 2.4 g (limits of agreement: -368.2, 373.0 g). The prediction models which include the biomarkers and subject characteristics may be used to estimate average intake at the group level and to investigate the ranking of individuals with regard to their intake of fruit and vegetables when validating questionnaires that measure intake.