Impaired local Vitamin D3 metabolism contributes to IL-36g overproduction in epithelial cells in chronic rhinosinusitis with nasal polyps

BACKGROUND

Vitamin D (VD) possesses immunomodulatory properties, but its role in chronic rhinosinusitis with nasal polyps (CRSwNP) remains poorly studied. Herein, we aim to explore the regulation and function of VD3 in CRSwNP.

METHODS

25-hydroxyvitamin D3 (25VD3) levels in serum and tissue lysates were detected by ELISA. The expression of VD receptor (VDR) and cytochrome P450 family 27 subfamily B member 1 (CYP27B1), the enzyme that converts 25VD3 to the active 1,25-hydroxyvitamin D3 (1,25VD3), and their expression regulation in human nasal epithelial cells (HNECs) were studied by RT-PCR, western blotting, immunofluorescence, and flow cytometry. RNA sequencing was performed to identify genes regulated by 1,25VD3 in HNECs. HNECs and polyp tissue explants were treated with 1,25VD3, 25VD3, and dexamethasone.

RESULTS

25VD3 levels in serum and nasal tissue lysates were decreased in patients with eosinophilic and noneosinophilic CRSwNP than control subjects. The expression of VDR and CYP27B1 were reduced in eosinophilic and noneosinophilic CRSwNP, particularly in nasal epithelial cells. VDR and CYP27B1 expression in HNECs were downregulated by interferon y and poly (I:C). Polyp-derived epithelial cells demonstrated an impaired ability to convert 25VD3 to 1,25VD3 than control tissues. 1,25VD3 and 25VD3 suppressed IL-36y production in HNECs and polyp tissues, and the effect of 25VD3 was abolished by siCYP27B1 treatment. Tissue 25VD3 levels negatively correlated with IL-36y expression and neutrophilic inflammation in CRSwNP.

CONCLUSION

Reduced systemic 25VD3 level, local 1,25VD3 generation and VDR expression result in impaired VD3 signaling activation in nasal epithelial cells, thereby exaggerating IL-36y production and neutrophilic inflammation in CRSwNP.

In silico characterization of the novel SDR42E1 as a potential vitamin D modulator

The short-chain dehydrogenase/reductase (SDR) superfamily encompasses enzymes that play essential roles in the metabolism of steroid hormones and lipids. Despite an enigmatic function, recent genetic studies have linked the novel SDR 42 extended-1 (SDR42E1) gene to 25-hydroxyvitamin D levels. This study investigated the potential SDR42E1 functions and interactions with vitamin D using bioinformatics and molecular docking studies. Phylogenetic analysis unveiled that the nucleotide sequences of human SDR42E1 exhibit high evolutionary conservation across nematodes and fruit flies. Molecular docking analysis identified strong binding affinities between SDR42E1 and its orthologs with vitamin D3 and essential precursors, 8-dehydrocholesterol, followed by 7-dehydrocholesterol and 25-hydroxyvitamin D. The hydrophobic interactions observed between the protein residues and vitamin D compounds supported the predicted transmembrane localization of SDR42E1. Our investigation provides valuable insights into the potential role of SDR42E1 in skin vitamin D biosynthesis throughout species. This provides the foundation for future research and development of targeted therapies for vitamin D deficiency and related health conditions.

The effects of vitamin D on different types of cells

Vitamin D is neccessary for regulation of calcium and phosphorus metabolism in bones, affects imunity, the cardiovascular system, muscles, skin, epithelium, extracellular matrix, the central nervous system, and plays arole in prevention of aging-associated diseases. Vitamin D receptor is expressed in almost all types of cells and its activation leads to modulation of different signaling pathways. In this review, we have analysed the current knowledge of 1,25-dihydroxyvitamin D3 or 25-hydroxyvitamin D3 effects on metabolism of cells important for the function of the cardiovascular system (endothelial cells, vascular smooth muscle cells, cardiac cells and pericytes), tissue healing (fibroblasts), epithelium (various types of epithelial cells) and the central nervous system (neurons, astrocytes and microglia). The goal of this review was to compare the effects of vitamin D on the above mentioned cells in in vitro conditions and to summarize what is known in this field of research.

Changes in miRNA expression in the lungs of pigs supplemented with different levels and forms of vitamin D

BACKGROUND

Vitamin D is an immunomodulator, and its effects have been linked to many diseases, including the pathogenesis of cancer. However, the effect of vitamin D supplementation on the regulation of gene expression of the lungs is not fully understood. This study aims to determine the effect of the increased dose of cholecalciferol and a combination of cholecalciferol + calcidiol, as well as the replacement of cholecalciferol with calcidiol, on the miRNA profile of healthy swine lungs.

METHODS AND RESULTS

The swine were long-term (88 days) supplemented with a standard dose (2000IU/kg) of cholecalciferol and calcidiol, the increased dose (3000 IU/kg) of cholecalciferol, and the cholecalciferol + calcidiol combination: grower: 3000 IU/Kg of vitamin D (67% of cholecalciferol and 33% of calcidiol), finisher 2500 IU/Kg of vitamin D (60% of cholecalciferol and 40% of calcidiol). Swine lung tissue was used for Next Generation Sequencing (NGS) of miRNA. Long-term supplementation with the cholecalciferol + calcidiol combination caused significant changes in the miRNA profile. They embraced altered levels of the expression of miR-150, miR-193, miR-145, miR-574, miR-340, miR-381, miR-148 and miR-96 (q-value < 0.05). In contrast, raising the dose of cholecalciferol only changed the expression of miR-215, and the total replacement of cholecalciferol with calcidiol did not significantly affect the miRNAome profile.

CONCLUSIONS

The functional analysis of differentially expressed miRNAs suggests that the use of the increased dose of the cholecalciferol + calcidiol combination may affect tumorigenesis processes through, inter alia, modulation of gene regulation of the TGF- β pathway and pathways related to metabolism and synthesis of glycan.

25(OH)D3 improves granulosa cell proliferation and IVF pregnancy outcomes in patients with endometriosis by increasing G2M+S phase cells

BACKGROUND

The 25-hydroxyvitamin D3 (25 (OH) D3) is crucial for follicular development. This study aimed to investigate the relationship between the level of 25 (OH) D3 in endometriosis patients, pregnancy outcomes of in vitro fertilization (IVF), and the underlying mechanism.

METHODS

The 25 (OH) D3 levels in serum and follicular Fluid (FF) samples were detected using enzyme-linked immunosorbent assay (ELISA). Clinical features and pregnancy outcomes of endometriosis patients were also compared between the deficient group (< 20 ug/ml) and the adequate group (≥ 20 ug/ml). The effects of 25 (OH) D3 on the proliferation and cell cycle of human ovarian granulosa cells were respectively detected by CCK-8 assay and flow cytometry (FCM). The differentially expressed genes (DEGs) in granulosa cells of endometriosis and tubal infertility patients were screened from GEO database. The effects of 25 (OH) D3 on the expressions of CDKN2D, PPARA, TGFB2 and THBD were determined using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

The levels of 25 (OH) D3 in serum and FF samples were decreased in endometriosis patients. The deficient group had fewer embryos that can be transferred, lower quality embryos and lower clinical pregnancy rates. Adequate 25 (OH) D3 levels in FF samples was a protective factor for live birth outcome in endometriosis patients. 25 (OH) D3 enhanced the proliferation capacity of granulosa cells (the concentration of 10 nM was the most significant) and increased the proportion of G2M + S phase cells. The expression of CDKN2D was decreased and TGFB2 and THBD were significantly upregulated.

CONCLUSIONS

25 (OH) D3 deficiency may be associated with poor IVF pregnancy outcomes in endometriosis patients. 25 (OH) D3 promotes ovarian granulosa cell proliferation by promoting the ability of cells to divide, and may accelerate cell cycle progression by up-regulating THBD and down-regulating CDKN2D expression.

Inactivation of vitamin D2 metabolites by human CYP24A1

Vitamin D is found in two forms in humans, D3 produced in the skin and D2 solely from the diet. Both 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D) are oxidised and inactivated by CYP24A1, a tightly regulated mitochondrial enzyme that controls serum levels of these secosteroids. The pathways of oxidation of 25(OH)D2 and 1,25(OH)2D2, particularly 25(OH)D2, by human CYP24A1 are not well characterized. The aim of this study was to further elucidate these pathways, and to compare the kinetics of metabolism of 25(OH)D2 and 1,25(OH)2D2 with their vitamin D3 counterparts. We used expressed and partially purified human CYP24A1 with substrates dissolved in the membrane of phospholipid vesicles, to mimic the inner mitochondrial membrane. We found that the major pathways for side chain oxidation of 25(OH)D2 and 1,25(OH)2D2 were identical and that predominant intermediates of 25(OH)D2 metabolism could be converted to the corresponding intermediates in the pathway of 1,25(OH)2D2 oxidation by 1α-hydroxylation by CYP27B1. The initial steps in the CYP24A1-mediated oxidation involved hydroxylation at the C24R position, and another unknown position where the alcohol was oxidised to an aldehyde. The 24R-hydroxylation was followed by hydroxylation at C26 or C28, or cleavage between C24 and C25 to produce the 24-oxo-25,26,27-trinor derivative. All of these products were further oxidised, with 24-oxo-25,26,27-trinor-1(OH)D2 giving a product tentatively identified as 24-oxo-25,26,27-trinor-1,28(OH)2D2. The catalytic efficiency (kcat/Km) of CYP24A1 for initial 25(OH)D2 hydroxylation was similar to that for 25(OH)D3, indicating that they have similar rates of inactivation at low substrate concentrations, supporting that vitamins D2 and D3 are equally effective in maintaining serum 25(OH)D concentrations. In contrast, the kcat/Km value for 1,25(OH)2D3 was almost double that for 1,25(OH)2D2 indicating a lower rate of inactivation of 1,25(OH)2D2 at a low substrate concentration, suggesting that it has increased metabolic stability in vivo.

Effect of vitamin D metabolites and gene expression of vitamin D receptor, and 1-alpha-hydroxylase related to the sperm quality

The incidence of male fertility disorders has increased greatly due to various genetic and lifestyle factors. Recently, it has been hypothesized that vitamin D may be involved with idiopathic infertility. The goal of the study was to determine the effect and relationship between blood vitamin D metabolites, intracellular sperm vitamin D levels, and gene expression of 1-α-hydroxylase and VDR, with regard to semen quality. Seventy volunteers aged 25-45 were involved in the study. According to spermogram analysis, participants were stratified into normozoospermic control group, non-normozoospermic target group, and oligoasthenoteratozoospermic group. Vitamin D metabolites (total 25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol) in blood and spermatozoa were determined by ELISA. Free and bioavailable 25-hydroxycholecalciferol were calculated using the Vermeulen equation. mRNA expression of VDR and 1-α hydroxylase was evaluated by qPCR. Free and bioavailable 25-hydroxycholecalciferol were significantly higher in the control group compared to the target group and compared to the oligoasthenoteratozoospermic group . Intracellular sperm 1,25-dihydroxycholecalciferol was higher in the control group compared to the target group. The mRNA levels of 1- α-hydroxylase were significantly higher in the control samples, while VDR expression was significantly higher in the target group. Significant positive correlations were established between free and bioavailable 25-hydroxycholecalciferol with sperm motility and morphology. Vitamin D metabolites in blood and intracellular sperm 1,25-dihydroxycholecalciferol seem to exert beneficial effects on sperm motility and morphology. Regarding sperm quality, these effects are more pronounced in the free and bioavailable 25OHD compared to the total 25OHD in blood. Higher expression of 1-α-hydroxylase likely leads to higher intracellular levels of 1,25-dihydroxycholecalciferol, which could contribute to sperm motility and morphology. Higher VDR expression may be a compensatory mechanism related to lower intracellular sperm 1,25-dihydroxycholecalciferol.

Analysis of the ability of vitamin D3-metabolizing cytochromes P450 to act on vitamin D3 sulfate and 25-hydroxyvitamin D3 3-sulfate

25-Hydroxyvitamin D3 (25(OH)D3) is present in the human circulation esterified to sulfate with some studies showing that 25(OH)D3 3-sulfate levels are almost as high as unconjugated 25(OH)D3. Vitamin D3 is also present in human serum in the sulfated form as are other metabolites. Our aim was to determine whether sulfated forms of vitamin D3 and vitamin D3 metabolites can be acted on by vitamin D-metabolizing cytochromes P450 (CYPs), one of which (CYP11A1) is known to act on cholesterol sulfate. We used purified, bacterially expressed CYPs to test if they could act on the sulfated forms of their natural substrates. Purified CYP27A1 converted vitamin D3 sulfate to 25(OH)D3 3-sulfate with a catalytic efficiency (k_cat/K_m) approximately half that for the conversion of vitamin D3 to 25(OH)D3. Similarly, the rate of metabolism of vitamin D3 sulfate was half that of vitamin D3 for CYP27A1 in rat liver mitochondria. CYP2R1 which is also a vitamin D 25-hydroxylase did not act on vitamin D3 sulfate. CYP11A1 was able to convert vitamin D3 sulfate to 20(OH)D3 3-sulfate but at a considerably lower rate than for conversion of vitamin D3 to 20(OH)D3. 25(OH)D3 3-sulfate was not metabolized by the activating enzyme, CYP27B1, nor by the inactivating enzyme, CYP24A1. Thus, we conclude that 25(OH)D3 3-sulfate in the circulation may act as a pool of metabolically inactive vitamin D3 to be released by hydrolysis at times of need whereas vitamin D3 sulfate can be metabolized in a similar manner to free vitamin D3 by CYP27A1 and to a lesser degree by CYP11A1.

A preliminary analysis of the variation in circulating 25-hydroxycholecalciferol concentrations in peri-partum spring-calving dairy cows

Vitamin D has a well-established role in regulating the intestinal absorption of minerals but its association with immunity has not been extensively explored in livestock. Although an optimal circulating concentration of 30 ng/ml 25-hydroxycholecalciferol (25(OH)D) is proposed for immune function, it is unknown if this vitamin D concentration is sufficient, particularly for cows under a pasture-based, spring-calving dairy production system. The objectives of this retrospective analysis were to assess circulating vitamin D concentrations in a total of 843 bio-banked serum samples from Holstein-Friesian dairy cows enrolled from 12 spring-calving, pasture-based dairy farms in Ireland. Mean 25(OH)D concentrations were 36.3 ng/ml at calving, 30.7 ng/ml at 7 days post-partum (DPP), and 38.3 ng/ml at 21 DPP. However, mean concentrations masked significant inter-farm and inter-individual variation (P < 0.05). In fact, the proportion of cows with vitamin D insufficiency of < 30 ng/ml was found to be 33.8%, 55.5% and 19.5% at each time point, respectively. In addition, 25(OH)D concentrations correlated positively with immune cell populations (monocytes and lymphocytes) and negatively with blood urea and non-esterified fatty acids (NEFA) at 7 DPP. This is the first report of 25(OH)D concentrations in pasture-based peripartum dairy cows and we show a high degree of variation across farms and between individual animals. Sub-optimal concentrations of vitamin D in some post-partum cows may predispose cattle to multiple metabolic or infectious diseases, and therefore further work is now warranted.

Effects of phytase and 25-hydroxyvitamin D3 supplementation on growth performance and bone development in weaned piglets in Ca- and P-deficient dietary

BACKGROUND

The beneficial function of phytase and 25-hydroxyvitamin D3 (HyD) on the feed utilization rate has been widely investigated. However, studies concerning its influence on weaned piglets largely lag behind. The aim of this study was to investigate the effects of phytase and HyD supplementation on the growth performance and bone development in weaned piglets under dietary Ca and P deficiency.

RESULTS

The results showed that dietary Ca and P deficiency decreased (P < 0.05) the content of serum P in 6-10 kg piglets, as well as reducing (P < 0.05) the contents of serum Ca and P, average daily gain (ADG), bone mineral density (BMD), breaking force (BF), bone ash and femur Ca in 10-20 kg piglets. Compared with the control group, the feed-to-gain ratio (F/G) of 6-10 kg piglets in the Phy group was decreased (P < 0.05), whereas the ADG, blood Ca and P, BMD, BF, bone ash, P apparent digestibility, Ca and P retention rate of 10-20 kg piglets were increased (P < 0.05). The contents of serum osteocalcin and HyD in 6-10 kg piglets and ADG were higher than in the control group (P < 0.05), as well as the contents of serum Ca and HyD in 10-20 kg piglets in the HyD treatment group. Supplementation with both Phy and HyD decreased the F/D (P < 0.05) and increased the contents of serum Ca, P and HyD in 6-10 kg piglets as well as enhancing the ADG, BMD, BF, bone ash, femur Ca and P, serum Ca and P, HyD, and the apparent digestibility and retention of Ca and P (P < 0.05) in 10-20 kg piglets. Supplementation with Phy and HyD in Ca- and P-deficient dietary decreased bone resorption, and improved tight arrangement of collagen fibers and oblique fibers in weaned piglets.

CONCLUSION

These data indicated that supplementation with both 1500 U kg^-1 Phy and 50 μg kg^-1 HyD could enhance dietary Ca and P utilization and promote bone development in low Ca and P dietary, and supplementation with both Phy and HyD had a significant synergy effect compared to single supplement. © 2021 Society of Chemical Industry.

Effects of 25-hydroxyvitamin D3 on growth performance, serum parameters, fecal microbiota, and metabolites in weaned piglets fed diets with low calcium and phosphorus

BACKGROUND

With the development of intensive farming, long-term exposure of pigs to poor light conditions is not conducive to the production of vitamin D₃ , and vitamin D₃ deficiency could affect absorption and metabolism of calcium (Ca) and phosphorus (P). 25-Hydroxyvitamin D₃ (25OHD₃ ) has higher bioactivity than regular vitamin D₃ . This study investigated the effects of 25OHD₃ on performance, serum parameters, fecal microbiota, and metabolites in weaned piglets fed with low Ca-P diet.

RESULTS

It was found that a low Ca-P diet supplemented with 50 μg/kg 25OHD₃ (NC + 25-D) improved (P < 0.05) average daily gain (ADG) in phase 2 and in the overall period of the experiment, and increased (P < 0.05) the immunoglobulin G (IgG), immunoglobulin A (IgA), catalase (CAT), bone-specific alkaline phosphatase (BALP), and osteocalcin (OC) serum content on day 28 compared with a low Ca-P diet (NC), but no differences were observed between a normal Ca-P diet (PC) and the NC + 25-D diet. Compared with NC, the abundance of Firmicutes was higher (P < 0.05) in PC and NC + 25-D. NC + 25-D decreased (P < 0.05) the abundance of Streptococcaceae compared with PC and NC, and increased (P < 0.05) the abundance of Lachnospiraceae compared with NC. Serum 25OHD₃ was negatively correlated with the abundance of fecal Streptococcaceae (P < 0.05), and positively correlated with the abundance of fecal Lachnospiraceae (P < 0.05).

CONCLUSION

Supplementation of 25OHD₃ in a low Ca-P diet improved serum immunity, bone biochemical parameters, and fecal microbiota such as decreased Streptococcaceae abundance and increased Lachnospiraceae abundance, which could subsequently promote growth of piglets. The effects were similar to that of a normal Ca-P diet. © 2021 Society of Chemical Industry.

Hypercalcemia Associated with the Ectopic Expression of 25-hydroxyvitamin D3-1α-hydroxylase in Diffuse Large B-cell Lymphoma

An 82-year-old man was transferred to our hospital due to impaired consciousness. His albumin-corrected calcium level was 14.2 mg/dL, intact parathyroid hormone (PTH) and PTH-related protein levels were reduced, and his 1,25-dihydroxyvitamin D [1,25 (OH) ₂VitD] level was elevated at 71.5 pg/mL. Computed tomography revealed masses on the bilateral ribs. The mass on the rib was biopsied and diagnosed as diffuse large B-cell lymphoma (DLBCL). Immunostaining of the biopsy sample with the anti-CYP27B1 antibody revealed the ectopic expression of 1α-hydroxylase in the lesion. We herein report a rare case of hypercalcemia induced by the overproduction of 1,25 (OH) ₂VitD in DLBCL ectopically expressing 1α-hydroxylase.

3-Epi-25-hydroxyvitamin D3 is a poor substrate for SULT2A1: Analysis of its 3-sulfate in cord plasma and recombinant human SULT2A1 incubate

A variety of metabolites derived from 25-hydroxyvitamin D₃ [25(OH)D₃], including its 3-epimer [Epi-25(OH)D₃] and 3-O-sulfate [25(OH)D₃-3S], is found in human plasma/serum. We hypothesized that the 3-O-sulfate of Epi-25(OH)D₃ [Epi-25(OH)D₃-3S] might be present in plasma/serum. Clarifying this point could improve our understanding of the metabolism of vitamin D₃. In this study, we first carefully analyzed the cord plasma samples by derivatization-assisted liquid chromatography/electrospray ionization-tandem mass spectrometry and demonstrated the occurrence of Epi-25(OH)D₃-3S in the plasma. However, the concentration ratio of Epi-25(OH)D₃-3S to 25(OH)D₃-3S (sulfated form) was infinitely lower than the ratio of Epi-25(OH)D₃ to 25(OH)D₃ (unconjugated form). To determine what caused this result, we next performed an in vitro experiment of the 3-O-sulfation for 25(OH)D₃ and Epi-25(OH)D₃ using the recombinant human sulfotransferase (SULT) 2A1. This in vitro experiment revealed that Epi-25(OH)D₃ is a poor substrate for the 3-O-sulfation catalyzed by SULT2A1 as compared to 25(OH)D₃. This substrate specificity of SULT2A1 would be the main cause for the result obtained from the analysis of the cord plasma samples.

Prevalence and factors associated with hypovitaminosis D in adolescents from a sunny country: Findings from the ERICA survey

Vitamin D plays a role in bone and metabolic health in life long, however hypovitaminosis D is common in different settings. The aim of this study was to describe vitamin D status among adolescents from a large sunny country and analyze associated factors. This was a multicenter, cross-sectional, school-based study. A total of 1152 adolescents age 12-17 from four Brazilian cities, Rio de Janeiro, Fortaleza, Brasília, and Porto Alegre, were included. Anthropometric variables, diet, type of school, race and season of data collection were evaluated. Serum concentrations of 25-hydroxyvitamin D [25(OH)D] were measured and categorized into three levels: ≤ 20 ng/mL, 21-29 ng/mL and ≥ 30 ng/mL. Ordered logistic regression models were used to explore the factors associated with hypovitaminosis D. The prevalence of vitamin D levels below 20 ng/mL, between 21 and 29 ng/mL and above 30 ng/mL was 21 % (95 %CI: 19 %-24 %), 42 % (95 %CI: 39 %-46 %) and 37 % (95 %CI: 33 %-40 %), respectively. In the final adjusted model, hypovitaminosis D was positively associated with gender, center (latitudes), data collected in winter or spring, non-whites, and private school students. A higher proportional odds ratio (POR) for hypovitaminosis D was found among obese boys (POR = 2.2, 95 %CI: 1.1-4.5), but not girls. Adequate dietary intake of vitamin D was a protective factor (POR = 0.4, 95 %CI: 0.2-0.6) against hypovitaminosis D. In conclusion, there is a high prevalence of Brazilian adolescents at risk of hypovitaminosis D, independent of region. Due to their potential benefits, lifestyle changes should be stimulated, including healthier food choices and spending more time outdoors (with sun protection).

Dietary supplementation of 25-hydroxycholecalciferol improves cardiac function and livability in broiler breeder hens-amelioration of blood pressure and vascular remodeling

A supplement of 69 μg 25-hydroxycholecalciferol (25-OH-D3)/kg feed suppressed the mortality in feed-restricted broiler breeder hens and in hens allowed ad libitum feed intake (Ad-hens) in a feeding trial from age 26 to 60 wk. Outcomes for the mechanisms found that 25-OH-D3 relieved systemic hypoxia, pathological cardiac remodeling and arrhythmias, and hepatopathology to improve hens' livability. In the study, we further evaluated the effect of 25-OH-D3 on blood pressure and vascular remodeling relative to cardiac pathogenesis of sudden death (SD). Ad libitum feed intake increased mechanical loading and contributed to maladaptive cardiac hypertrophy as evidenced by consistently elevated peripheral arterial blood pressure in Ad-hens before SD (P < 0.05). In planned longitudinal measurements, Ad-hens also showed higher right ventricle systolic pressure and right ventricle diastolic pressure (RVDP) (P < 0.05). Supplemental 25-OH-D3 relieved peripheral hypertension and prevented time-dependent increases of RVDP in Ad-hens through the renin-angiotensin system and circulating nitric oxide availability and by regulating vascular remodeling including elastin/collagen ratio and smooth muscle cell proliferation in the pulmonary artery for improved elasticity/stiffness (P < 0.05). The antihypertensive effect via the renin-angiotensin system and nitric oxide regulation in respect to heart rate and arrhythmias by 25-OH-D3 were further confirmed in 51 week-old feed-restricted broiler breeder hens challenged with salt loading for 5 wk. Despite feed restriction, the most feed-efficient hens of feed-restricted groups also exhibited cardiac pathological hypertrophy, in conjunction with higher right ventricle systolic pressure, RVDP, plasma nitric oxide levels, and more dramatic arterial remodeling (P < 0.05). These results suggest that peripheral and pulmonary hypertension are the key drivers of SD and that 25-OH-D3 is an effective antihypertensive supplement to alleviate cardiac pathogenesis and improve livability in broiler breeder hens.

A novel caged Cookson-type reagent toward a practical vitamin D derivatization method for mass spectrometric analyses

RATIONALE

25-Hydroxylated vitamin D is the best marker for vitamin D (VD). Due to its low ionization efficiency, a Cookson-type reagent, 1,2,4-triazoline-3,5-dione (TAD), is used to improve the detection/quantification of VD metabolites by liquid chromatography/tandem mass spectrometry (LC/MS/MS). However, the high reactivity of TAD makes its solution stability low and inconvenient for practical use. We here describe the development of a novel caged Cookson-type reagent, and we assess its performances in the quantitative and differential detection of four VD metabolites in serum using LC/MS/MS.

METHODS

Caged 4-(4'-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD) analogues were prepared from 4-(4'-dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione. Their stability and reactivity were examined. The optimized caged DAPTAD (14-(4-(dimethylamino)phenyl)-9-phenyl-9,10-dihydro-9,10-[1,2]epitriazoloanthracene-13,15-dione, DAP-PA) was used for LC/MS/MS analyses of VD metabolites.

RESULTS

The solution stability of DAP-PA in ethyl acetate dramatically improved compared with that of the non-caged one. We measured the thermal retro-Diels-Alder reaction enabling the release of DAPTAD and found that the derivatization reaction was temperature-dependent. We also determined the detection limit and the lower limit of quantifications for four VD metabolites with DAPTAD derivatization.

CONCLUSIONS

DAP-PA was stable enough for mid- to long-term storage in solution. This advantage shall contribute to the detection and quantification of VD in clinical laboratories, and as such to the broader use of clinical mass spectrometry.

Intraocular calcidiol: Uncovering a role for vitamin D in the eye

Vitamin D has emerged as a potentially important molecule in ophthalmology. To date, all ophthalmic data pertaining to vitamin D has been restricted primarily to tear and serum analysis in human patients. Considering the isolated nature of the eye, we sought to determine the presence of intraocular vitamin D in ocular disease.

METHODS

25-Hydroxyvitamin D₃ (25(OH)D₃) concentrations were measured in the eye and blood of 120 participants undergoing ophthalmic procedures. Ocular localization of the 1,25-dihydroxyvitamin D₃-generating (CYP27B1) and deactivating (CYP24A1) hydroxylases was performed by immunohistochemistry. Gene expression of CYP27B1, CYP24A1 and VEGF-A was measured in eyes from patients with and without disease.

RESULTS

25(OH)D₃ was quantified in 112 ocular samples. In 40 cataract patient samples, the average 25(OH)D₃ concentration was 0.057 ng/mL, compared to 72 retinal disease patient samples, average of 0.502 ng/mL (p < 0.001). Intraocular 25(OH)D₃ did not correlate with serum levels of 25(OH)D₃. There was no difference between the level of 25(OH)D₃ measured in the aqueous and vitreous humour. The vitamin D-specific CYPs 27B1 and 24A1, strongly localized to complementary regions of the ciliary body, retinal pigment epithelium and neural retina. Gene expression analysis confirmed retinal CYP27B1 correlated strongly with VEGF-A in eyes from diabetic patients (r = 0.92, p < 0.001).

CONCLUSIONS

Our data confirms that vitamin D is present in the humours of the human eye and that local synthesis/degradation is possible via the ocular CYP27B1 and CYP24A1. This argues for a functional role for local vitamin D production and signaling in the eye and suggests that vitamin D may be an important intraocular mediator in disease pathogenesis.

Assessment of Risk Factors for Fractures in Patients with Type 2 Diabetes over 60 Years Old: A Cross-Sectional Study from Northeast China

AIMS

Previous evidence has demonstrated an increased fracture risk among the population with type 2 diabetes mellitus (T2DM). This study investigated the prevalence of bone fractures in elderly subjects (with and without type 2 diabetes) and identified any fracture risk factors, especially the risk factors for common known fractures in particular diabetic populations.

METHODS

This cross-sectional study was conducted with community-dwelling people over 60 years old in nine communities from the city of Shenyang, which is the capital of Northeast China's Liaoning Province. A total of 3430 elderly adults (2201 females, mean ± standard deviation age 68.16 ± 6.1 years; 1229 males, 69.16 ± 6.7 years) were included. Our study measured the heel bone mineral density (BMD) and used the timed "up and go" (TUG) test and other indicators. In addition, we performed logistic regression analysis to explore the risk factors for fractures in the general population and the diabetic population and to analyze the differences.

RESULTS

The results revealed that a total of 201 elderly persons (5.8%), with an average age of 70.05 ± 6.54 years, suffered from a history of fragility fractures, which affected more females (74.6%) than males (p = 0.001). The prevalence of fractures in the T2DM population was 7.3%, which was much higher than the 5.2% in non-T2DM population (p = 0.001). The prevalence of fractures in the T2DM population was 7.3%, which was much higher than the 5.2% in non-T2DM population (p = 0.001). The prevalence of fractures in the T2DM population was 7.3%, which was much higher than the 5.2% in non-T2DM population (p = 0.001). The prevalence of fractures in the T2DM population was 7.3%, which was much higher than the 5.2% in non-T2DM population (T-score≤-2.5 (OR 1.750) were independent risk factors for fragility fractures in the non-T2DM population, but they were not risk factors in the T2DM population.

CONCLUSIONS

This study found that low BMD and slow TUG time were independent risk factors for fractures in non-T2DM patients, while no associations were found in the T2DM population. Patients with T2DM have a higher risk for fractures even when they have sufficient BMD and a short TUG time. TUG and BMD underestimated the risk for fractures in the T2DM population.

Intake of ergosterol increases the vitamin D concentrations in serum and liver of mice

Factors that can modify the bioavailability of orally administered vitamin D are not yet widely known. Ergosterol is a common fungal sterol found in food which has a chemical structure comparable to that of vitamin D. This study aimed to investigate the effect of ergosterol on vitamin D metabolism. Therefore, 36 male wild type-mice were randomly subdivided into three groups (n = 12) and received a diet containing 25 μg vitamin D₃ and either 0 mg (control), 2 mg or 7 mg ergosterol per kg diet for 6 weeks. To elucidate the impact of ergosterol on hepatic hydroxylation of vitamin D, human hepatoma cells (HepG2) were treated with different concentrations of ergosterol. Concentrations of vitamin D₃ and 25-hydroxyvitamin D₃ (25(OH)D₃) in cells, livers and kidneys of mice and additionally 24,25-dihydroxyvitamin D₃ (24,25(OH)₂D₃) in serum were quantified by LC-MS/MS. The concentration of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) in serum was analyzed by commercially-available enzyme immuno assay. The concentrations of cholesterol and triglycerides were analyzed in livers of mice by photometric assays. Analyses revealed that mice receiving 7 mg/kg ergosterol with their diet had 1.3-, 1.7- and 1.5-times higher concentrations of vitamin D₃ in serum, liver and kidney, respectively, than control mice (P < 0.05), whereas no significant effects were observed in mice fed 2 mg/kg ergosterol. The hydroxylation of vitamin D remained unaffected by dietary ergosterol, since the concentration of 25-hydroxyvitamin D₃ in serum and tissues and the concentrations of 1,25(OH)₂D₃ and 24,25(OH)₂D₃ in serum were not different between the three groups of mice. The lipid concentrations in liver were also not affected by dietary ergosterol. Data from the cell culture studies showed that ergosterol did not influence the conversion of vitamin D₃ to 25(OH)D₃. To conclude, ergosterol appears to be a modulator of vitamin D₃ concentrations in the body of mice, without modulating the hydroxylation of vitamin D₃ in liver.

Hypovitaminosis D: Is It Time to Consider the Use of Calcifediol?

Hypovitaminosis D is becoming a notable health problem worldwide. A consensus exists among several different medical societies as to the need for adequate levels of vitamin D for bone and general health. The correct method by which to restore normal vitamin D levels is still a matter of debate. Although cholecalciferol remains the most commonly distributed form of vitamin D supplementation worldwide, several drugs with vitamin D activity are available for clinical use, and making the correct selection for the individual patient may be challenging. In this narrative review, we aim to contribute to the current knowledge base on the possible and appropriate use of calcifediol-the 25-alpha-hydroxylated metabolite-in relation to its chemical characteristics, its biological properties, and its pathophysiological aspects. Furthermore, we examine the trials that have aimed to evaluate the effect of calcifediol on the restoration of normal vitamin D levels. Calcifediol is more soluble than cholecalciferol in organic solvents, due to its high polarity. Good intestinal absorption and high affinity for the vitamin-D-binding protein positively affect the bioavailability of calcifediol compared with cholecalciferol. In particular, orally administered calcifediol shows a much shorter half-life than oral cholecalciferol. Most findings suggest that oral calcifediol is about three- to five-fold more powerful than oral cholecalciferol, and that it has a higher rate of intestinal absorption. Accordingly, calcifediol can be particularly useful in treating diseases associated with decreased intestinal absorption, as well as obesity (given its lower trapping in the adipose tissue) and potentially neurological diseases treated with drugs that interfere with the hepatic cytochrome P-450 enzyme system, resulting in decreased synthesis of calcifediol. Up to now, there has not been enough clinical evidence for its use in the context of osteoporosis treatment.

Vitamin D in Wild and Farmed Atlantic Salmon (Salmo Salar)-What Do We Know?

Salmon have been widely publicized as a good dietary source of vitamin D, but recent data points to large variation in vitamin D content and differences between wild and farmed salmon. We aimed to: (1) investigate the content of vitamin D in Atlantic salmon (Salmo salar) in wild species caught in two different waters, (2) perform a 12-week feeding trial in farmed Salmo salar with 270–1440 µg vitamin D₃/kg feed (4–20 times maximum level in the EU) and (3) conduct a review for the published data on the content of vitamin D in salmonids. Content of vitamin D₃ in the fillet from wild salmon caught in the Baltic Sea and the North Sea was significantly different (p < 0.05), being 18.5 ± 4.6 µg/100 g and 9.4 ± 1.9 µg/100 g, respectively. In the farmed salmon the content ranged from 2.9 ± 0.7 µg vitamin D₃/100 g to 9.5 ± 0.7 µg vitamin D₃/100 g. Data from 2018 shows that farmed salmon contained 2.3–7.3 µg vitamin D₃/100 g. Information on the content of vitamin D in wild and farmed salmonids is very limited, which calls for further research to ensure a sustainable production of salmon with adequate vitamin D.

Levels of 25-hydroxyvitamin D3, biochemical parameters and symptoms of depression and anxiety in healthy individuals

Growing evidence support the role of vitamin D in brain function and behavior. This study investigated the relationship between 25-hydroxyvitamin D₃ [25(OH)D₃] levels, biochemical profile and symptoms of depression and anxiety in healthy individuals. Symptoms of depression were assessed by the Beck Depression Inventory (BDI) and anxiety was evaluated with the State-Trait Anxiety Inventory (STAI). Our sample included 36 individuals, mostly women 27(75%), 36.39 ± 9.72 years old, non-smokers 31(86.1%), body mass index of 26.57 ± 3.92 kg/m², 27.95 ± 7.50% body fat. Participants were divided into those with 25(OH)D₃ levels lower than 40 ng/mL (mean 28.16 ± 7.07) and equal or higher than 40 ng/mL (mean 53.19 ± 6.32). Those with lower 25(OH)D₃ had higher levels of triacylglycerol, triacylglycerol/high density lipoprotein (HDL) ratio, high glucose and homeostatic model assessment of insulin resistance (HOMA-IR) index. No changes were observed in sociodemographic variables, body composition, inflammatory parameters and cortisol. Additionally, in the groups with low and high 25(OH)D₃ levels, STAI state, STAI trait and BDI scores were not statistically different. Levels of 25(OH)D₃ were inversely and independently associated with glucose and HOMA-IR, but not associated with triacylglycerol, depression and anxiety scores. Lower levels of 25(OH)D₃ were associated with dysfunction in glucose metabolism but not with depression and anxiety in healthy individuals.

Calcioic acid: In vivo detection and quantification of the terminal C24-oxidation product of 25-hydroxyvitamin D3 and related intermediates in serum of mice treated with 24,25-dihydroxyvitamin D3

Calcitroic acid, the excretory form of vitamin D, is the terminal product of a 5-step pathway catalyzed by CYP24A1, commencing with C24-hydroxylation of 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃). Catabolism of 25-hydroxyvitamin D₃ (25-OH-D₃) proceeds via analogous steps culminating in calcioic acid; however this C23-truncated acid has not been reported in the circulation. It has recently been shown that 24,25-dihydroxyvitamin D₃ (24,25-(OH)₂D₃) is an important factor in optimal bone fracture healing acting via an effector molecule FAM57B2 to produce lactosylceramide. Administration of 24,25-(OH)₂D₃ was found to restore normal fracture repair in Cyp24a1^-/- mice devoid of 24,25-(OH)₂D₃. We set out to study the multi-step catabolism of D₃ metabolites in vivo using LC-MS/MS methods in vehicle or 24,25-(OH)₂D₃-treated mice. Vehicle-treated Cyp24a1^+/- mice possessed normal levels of serum 24,25-(OH)₂D₃ (7 ng/mL) and 25-OH-D₃-26,23-lactone (4 ng/mL). We also detected 24-oxo-25-OH-D₃ (3 ng/mL) and 24-oxo-23,25-(OH)₂D₃ (0.4 ng/mL); which were not detectable in vehicle-treated Cyp24a1^-/- mice. In 24,25-(OH)₂D₃-treated Cyp24a1^+/- mice, serum 24,25-(OH)₂D₃ rose to 200 ng/mL while 25-OH-D₃-26,23-lactone remained unchanged in comparison to vehicle-treated Cyp24a1^+/- mice Concentration of serum 24-oxo-25-OH-D₃ and 24-oxo-23,25-(OH)₂D₃ rose by 10-fold, when Cyp24a1^+/- mice were treated with 24,25-(OH)₂D₃ Calcioic acid was increased to 0.030 ng/mL for 24,25-(OH)₂D₃-treated Cyp24a1^+/- mice. In 24,25-(OH)₂D₃-treated Cyp24a1^-/- mice, serum 24,25-(OH)₂D₃ rose further to a striking 830 ng/mL due to lack of catabolism of the 24,25-(OH)₂D₃ dose. Serum 1,25-(OH)₂D₃ levels were suppressed in 24,25-(OH)₂D₃-treated Cyp24a1^+/- and Cyp24a1^-/- mice. Circulating 1,24,25-(OH)₃D₃ rose from 73 pg/mL to 106 pg/mL when Cyp24a1^+/- mice were treated with 24,25-(OH)₂D₃. While undetectable in vehicle-treated Cyp24a1^-/- mice, 1,24,25-(OH)₃D₃ rose unexpectedly to 153 pg/mL in 24,25-(OH)₂D₃-treated nulls suggesting conversion of 24,25-(OH)₂D₃ to 1,24,25-(OH)₃D₃ via 1-hydroxylation. Taken together, amplification of 24,25-(OH)₂D₃ catabolism by exogenous doses of this metabolite have enabled detection of downstream C24-oxidation pathway products in vivo, including calcioic acid; and provides a platform for studying alternative routes of vitamin D metabolism that may occur in pathological states including hypervitaminosis D and idiopathic infantile hypercalcemia caused by mutations of CYP24A1.

Concise synthesis of 23-hydroxylated vitamin D3 metabolites

Three 23-hydroxylated vitamin D₃ derivatives, which are metabolites of 25-hydroxyvitamin D₃ produced by CYP24A1 and a related diastereomer, were efficiently synthesized. Each C23 hydroxy unit was constructed by the Claisen condensation reaction with ethyl acetate or the Grignard reaction with 2-methylallymagnesium chloride. Stereochemistry at the C23 position was determined by a modified Mosher's method. The triene structures were constructed by the Wittig-Horner reaction utilizing the A-ring phosphine oxide moiety.

Maternal vitamin D and markers of glycaemia during pregnancy in the Belfast centre of the Hyperglycaemia and Adverse Pregnancy Outcome study

AIMS

To measure total 25-hydroxyvitamin D levels in women in mid-pregnancy who participated in the Belfast centre of the Hyperglycaemia and Adverse Pregnancy Outcome (HAPO) observational study, and to investigate the associations between levels of 25-hydroxyvitamin D and markers of gestational diabetes mellitus and lipid biomarkers.

METHODS

A total of 1585 pregnant women had serum samples available for measurement. Participants were recruited from the Royal Jubilee Maternity Hospital, Belfast, Northern Ireland, at 24-32 weeks' gestation, as part of the HAPO study. 25-hydroxyvitamin D concentrations were measured using liquid chromatography tandem mass spectrometry. Glucose, C-peptide and lipid levels were previously analysed in a central laboratory. Statistical analysis was performed.

RESULTS

The median (interquartile range) 25-hydroxyvitamin D concentration during pregnancy was 38.6 (24.1-60.7) nmol/l, with 65.8% of women being vitamin D-deficient (≤50 nmol/l). In regression analysis, the association between maternal 25-hydroxyvitamin D and fasting plasma glucose levels approached significance [regression coefficient -0.017 (95% CI -0.034 to 0.001); P=0.06], and a significant positive association was observed between maternal 25-hydroxyvitamin D and β-cell function [1.013 (95% CI 1.001 to 1.024); P=0.031]. Maternal 25-hydroxyvitamin D level was positively associated with HDL [0.047 (95% CI 0.021 to 0.073) P≤ 0.001] and total cholesterol [0.085 (95% CI 0.002 to 0.167); P=0.044] in regression analysis.

CONCLUSIONS

These results indicate a high prevalence of vitamin D deficiency during pregnancy, which requires identification and treatment; however, only weak associations were observed between 25-hydroxyvitamin D level and markers of glucose and insulin metabolism. This would suggest that these are of doubtful clinical significance.

The use of synthetic and natural vitamin D sources in pig diets to improve meat quality and vitamin D content

This study investigated the effects of synthetic and natural sources of vitamin D biofortification in pig diets on pork vitamin D activity and pork quality. One hundred and twenty pigs (60 male, 60 female) were assigned to one of four dietary treatments for a 55 d feeding period. The dietary treatments were (1)50 μg vitamin D₃/kg of feed; (2)50 μg of 25-hydroxvitamin D₃/kg of feed (25-OH-D₃); (3)50 μg vitamin D₂/kg of feed; (4)50 μg vitamin D₂-enriched mushrooms/kg of feed (Mushroom D₂). The pigs offered the 25-OH-D₃ diet exhibited the highest (P < 0.001) serum total 25-hydroxyvitamin D concentration and subsequently exhibited the highest (P < 0.05) Longissimus thoracis (LT) total vitamin D activity. Mushroom D₂ and 25-OH-D₃ supplementation increased pork antioxidant status. The vitamin D₂-enriched mushrooms improved (P < 0.05) pig performance, carcass weight and LT colour. In conclusion, 25-OH-D₃ is the most successful source for increasing pork vitamin D activity, while Mushroom D₂ may be a new avenue to improve animal performance and pork quality.

The concept of the personal vitamin D response index

Humans are able to synthesize vitamin D₃ in their skin when exposed to UV-B, but seasonal variations, textile coverage and predominant indoor activities often make supplementation with the compound necessary. There is some dispute on the desired vitamin D status, measured via the serum concentration of the most stable vitamin D₃ metabolite, 25-hydroxyvitamin D₃, and the respective recommended daily supplementation. A possible answer may be provided by the concept of the personal vitamin D response index describing the efficiency of the molecular response to supplementation with vitamin D. The concept is based on the fact that vitamin D₃ activates via its metabolite 1α,25-dihydroxyvitamin D₃ the transcription factor vitamin D receptor and thus has a direct effect on the epigenome and transcriptome of many human tissues and cell types. Individuals can be distinguished into high, mid and low responders to vitamin D via measuring vitamin D sensitive molecular parameters, such as changes in the epigenetic status and the respective transcription of genes of mobile immune cells from blood or the level of proteins or metabolites in serum. Thus, we suggest that the need for vitamin D supplementation depends on the vitamin D status in relation to the personal vitamin D response index of an individual rather than on the vitamin D status alone.

Skeletal muscle vitamin D in patients with end stage osteoarthritis of the knee

Muscle function is often impaired in patients with knee osteoarthritis (OA), with reduced strength and increased pain. The role of vitamin D and the vitamin D-endocrine pathway in muscle health has recently been placed in the spotlight, with various groups reporting positive effects on muscle development, function and health. Recently, it has been shown that uptake into muscle of the specialized vitamin D binding protein (DBP) is dependent on the endocytic receptor, megalin. Here we analyse circulating vitamin D, and muscle DBP, megalin and the cognate vitamin D receptor (VDR) in patients with knee OA and compare them to asymptomatic controls. Muscle and blood samples were collected from 19 patients with end-stage OA of the knee and 10 age-matched controls. Muscle biopsies from the OA group were performed during knee replacement surgery and a needle biopsy was used on control volunteers. Immunoblots performed with specific antibodies were used to detect the presence of DBP, megalin, VDR (using the specific D-6 antibody) and albumin in the muscle biopsies. Results were correlated with FoxO1, a key regulator of the ubiquitin-proteasome degradation pathway in muscle. There were no differences in circulating levels of 25 (OH) vitamin D3 between the groups, and no subjects were vitamin D deficient. We found increased VDR, DBP and albumin protein in the muscle from patients with OA compared to controls, with no change in muscle megalin expression. Furthermore, DBP levels in the muscle correlated with FoxO1, suggesting an association between muscle protein breakdown and the activation of the vitamin D-endocrine pathway in muscle surrounding an OA affected joint. We show, for the first time, that the factors involved in the vitamin D-endocrine-pathway are present at higher levels in muscles from OA patients compared to asymptomatic controls. This is despite no differences in circulating 25 (OH) vitamin D levels between the groups. These findings indicate the activation of vitamin D pathway in these muscles that may provide a beneficial compensatory stimulation of the repair process in muscles that are subject to inflammatory and proteolytic processes.

Effectiveness of Calcifediol in Improving Muscle Function in Post-Menopausal Women: A Prospective Cohort Study

INTRODUCTION

The role of vitamin D supplementation on muscle function and physical performance is still debated. Calcifediol is an available treatment for hypovitaminosis D, particularly for extra-skeletal effects. Aim of this prospective cohort study was to evaluate the effectiveness of calcifediol on serum levels of 25(OH)D₃, appendicular muscle strength, physical performance, and prevention of falls in post-menopausal women.

METHODS

We recruited post-menopausal women aged ≥50 years, referring to an outpatient service for the management of osteoporosis over a 18-month period. We included women with a diagnosis of osteoporosis and/or vitamin D deficiency [serum levels of 25(OH)D₃ <30 ng/ml]. All the participants received calcifediol (20 μg, 4 oral drops/day) for a 6-month period. We evaluated at the baseline and after 6 months the following outcomes: serum levels of 25(OH)D₃, appendicular muscle strength, using the Isometric Hand Grip Strength Test and the Knee Isometric Extension Strength Test, physical performance, using the Short Physical Performance Battery (SPPB) and the 4-m gait speed (4MGS), and the risk of falls (percentage of fallers and recurrent fallers and mean number of falls). A sub-analysis was performed in patients with vitamin D deficiency.

RESULTS

We enrolled 113 post-menopausal women, mean aged 68.01 ± 9.13 years. After 6 months of treatment, there was a significant increase in serum levels of 25(OH)D₃ (p < 0.001), appendicular muscle strength (p < 0.001), and physical performance (p = 0.002 at SPPB and p = 0.010 at 4MGS, respectively). At 6 months, the percentage of fallers was lower, although not significantly (p = 0.078), whereas there was a significant reduction both in percentage of recurrent fallers and in the mean number of falls (p < 0.001 and p = 0.020, respectively).

CONCLUSION

Calcifediol was significantly effective in improving serum levels of 25(OH)D₃ and muscle function and in reducing the percentage of recurrent fallers and the mean number of falls in a cohort of post-menopausal women.

Development of an algorithm to predict serum vitamin D levels using a simple questionnaire based on sunlight exposure

Sun exposure is the main determinant of vitamin D production. The aim of this study was to develop an algorithm to assess individual vitamin D status, independently of serum 25(OHD) measurement, using a simple questionnaire, mostly relying upon sunlight exposure, which might help select subjects requiring serum 25(OHD) measurement. Six hundred and twenty adult subjects living in a mountain village in Southern Italy, located at 954 m above the sea level and at a latitude of 40°50'11″76N, were asked to fill the questionnaire in two different periods of the year: August 2010 and March 2011. Seven predictors were considered: month of investigation, age, sex, BMI, average daily sunlight exposure, beach holidays in the past 12 months, and frequency of going outdoors. The statistical model assumes four classes of serum 25(OHD) concentrations: ≤10, 10-19.9, 20-29.9, and ≥30 ng/ml. The algorithm was developed using a two-step procedure. In Step 1, the linear regression equation was defined in 385 randomly selected subjects. In Step 2, the predictive ability of the regression model was tested in the remaining 235 subjects. Seasonality, daily sunlight exposure and beach holidays in the past 12 months accounted for 27.9, 13.5, and 6.4 % of the explained variance in predicting vitamin D status, respectively. The algorithm performed extremely well: 212 of 235 (90.2 %) subjects were assigned to the correct vitamin D status. In conclusion, our pilot study demonstrates that an algorithm to estimate the vitamin D status can be developed using a simple questionnaire based on sunlight exposure.

Oral intake of 7-dehydrocholesterol increases vitamin D3 concentrations in the liver and kidney

INTRODUCTION

Due to the high prevalence of vitamin D deficiency, strategies are needed to improve vitamin D status. Food components can affect vitamin D metabolism and have to be considered when estimating the efficacy of vitamin D supplements. 7-dehydrocholesterol (7-DHC) occurs naturally in food, but its impact on vitamin D metabolism has not yet been examined.

METHODS

Three groups of male C57BL/6 mice (n=12 per group) were placed on a diet that contained 0, 2.5 or 5mg 7-DHC per kg diet over a period of 6 weeks. Vitamin D and other sterols in the serum, skin, liver and kidney were quantified by LC-MS/MS. The relative mRNA abundance of hepatic genes encoding vitamin D hydroxylation enzymes and transporters was analyzed by real-time RT-PCR.

RESULTS

We found a substantial dose-dependent increase of non-hydroxylated vitamin D₃ in the liver and kidney of mice fed a diet containing 7-DHC. The vitamin D₃ content in the liver was 2.80±0.61pmol/g, 7.34±4.28pmol/g and 12.9±3.58pmol/g in groups that received 0, 2.5 and 5mg/kg 7-DHC, respectively. In the kidney, the vitamin D₃ content of these groups was 1.78±1.17pmol/g, 3.55±1.06 and 6.36±2.29pmol/g, respectively. The serum and tissue concentrations of 25-hydroxyvitamin D₃ (25(OH)D₃) remained unaffected by 7-DHC. The relative mRNA data provided no plausible mechanism for the observed effects of 7-DHC on vitamin D₃. All groups of mice had similar concentrations of cholesterol, desmosterol and 7-DHC in their serum and tissues.

CONCLUSION

The current findings provide the first evidence that dietary 7-DHC seems to affect vitamin D metabolism. The underlying mechanism remains elusive and needs further investigation.

25-Hydroxyvitamin D assays: Potential interference from other circulating vitamin D metabolites

The vitamin D External Quality Assessment Scheme (DEQAS) for 25-hydroxyvitamin D (25-OHD) has approximately 1100 participants in 53 countries using 26 different methods or variants of methods (October 2014). In April 2015, the scheme was extended to cover 24,25-dihydroxyvitamin D (24,25(OH)₂D). Since 2013, the 25-OHD scheme has been accuracy-based with values assigned by the NIST reference measurement procedure (RMP). DEQAS is uniquely placed to assess the accuracy (bias) and specificity of 25-OHD methods in a routine laboratory setting. Other vitamin D metabolites are known to interfere in 25-OHD assays and DEQAS has distributed samples spiked with 3-epi-25-OHD₃ (52.4nmol/L), 24R,25(OH)₂D₃ (14.4nmol/L) and 24S,25(OH)₂D₃ (57.9nmol/L). The 3-epimer showed a cross reactivity of 56% in a competitive protein binding assay but was not detected in any antibody-based methods. Not all HPLC/UV or LC-MS/MS methods were able to resolve 3-epi-25-OHD₃ from 25-OHD₃ and thus overestimated total 25-OHD. The cross reactivity of 24R,25(OH)₂D₃ (24S,25(OH)₂D₃) ranged from <5% (<5%) to 548% (643%) in ligand binding assays. Both 24-hydroxylated metabolites were resolved by HPLC/UV and LC-MS/MS methods and thus caused no complications in the measurement of 25-OHD. Most antibodies to 25-OHD are known to cross-react with dihydroxylated metabolites but interference in some assays was far greater than expected. This may be related to the anomalous behaviour of exogenously added metabolites in these 25-OHD methods.

Vitamin D metabolism and regulation in pediatric MSCs

Vitamin D is crucial for mineral homeostasis and contributes to bone metabolism by inducing osteoblast differentiation of marrow stromal cells (MSCs). We recently reported that MSCs from adults demonstrate 1α-hydroxylase activity in vitro and express vitamin D-related genes; this raises a possible autocrine/paracrine role for D activation in pre-osteoblasts. In this studies, we tested the hypotheses that pediatric MSCs have 1α-hydroxylase activity and express vitamin D-related genes. With IRB approval, we isolated MSCs from discarded excess iliac marrow graft from 6 male and 6 female subjects (age 8-12 years) undergoing alveolar cleft repair. 1α-hydroxylation of substrate 25(OH)D₃ was measured by ELISA for 1α,25(OH)₂D. RT-PCR was used for gene expression. Pediatric MSCs showed a range of 1α-hydroxylase activity in vitro. There was constitutive expression of vitamin D receptor (VDR), megalin, d-hydroxylases (CYP27B1, CYP27A1, CYP2R1, and CYP24A1), and estrogen receptor (ER). There was 2.6-fold greater expression of CYP27B1 and 3.5-fold greater expression of CYP24A1 in MSCs from boys compared with girls. There was 2.4-fold greater expression of ERα and 3.2-fold greater expression of megalin in MSCs from boys. In preliminary studies, treatment of female pediatric MSCs with 10nM 17β-estradiol resulted in upregulation of CYP27B1 and CYP24A1, as well as VDR, megalin, ERα, and ERβ. Treatment with 25(OH)D₃ upregulated CYP27B1, VDR, and ERα. Expression and regulation of vitamin D related genes in pediatric hMSCs reinforces an autocrine/paracrine role for vitamin D in hMSCs. Finding striking gender differences in MSCs from children was not seen with MSCs from adults and adds insight to the metabolic environment of bone and presents a research approach for investigating and optimizing pediatric bone health.

Vitamin D metabolite profiling using liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Liquid chromatography tandem mass spectrometry (LC-MS/MS) has emerged as the latest technology to be used to assay the metabolites of vitamin D. The method uses molecular mass as a detection technique after straightforward extraction and chromatography steps. LC-MS/MS assay provides a level of accuracy and reproducibility not seen before with other methods and is beginning to rival antibody-based methods in terms of sensitivity and convenience. Methods for detection of underivatized and DMEQ-TAD derivatized vitamin D metabolites are evaluated. Sensitivity is improved by 10-100 fold with derivatization and allows for the simultaneous assay of multiple vitamin D metabolites, a process termed vitamin D metabolite profiling. Clinical and research applications of vitamin D metabolite profiling are discussed.

Regioselective hydroxylation of cholecalciferol, cholesterol and other sterol derivatives by steroid C25 dehydrogenase

Steroid C25 dehydrogenase (S25DH) from Sterolibacterium denitrificans Chol-1S is a molybdenum oxidoreductase belonging to the so-called ethylbenzene dehydrogenase (EBDH)-like subclass of DMSO reductases capable of the regioselective hydroxylation of cholesterol or cholecalciferol to 25-hydroxy products. Both products are important biologically active molecules: 25-hydroxycholesterol is responsible for a complex regulatory function in the immunological system, while 25-hydroxycholecalciferol (calcifediol) is the activated form of vitamin D₃ used in the treatment of rickets and other calcium disorders. Studies revealed that the optimal enzymatic synthesis proceeds in fed-batch reactors under anaerobic conditions, with 6-9 % (w/v) 2-hydroxypropyl-β-cyclodextrin as a solubilizer and 1.25-5 % (v/v) 2-methoxyethanol as an organic co-solvent, both adjusted to the substrate type, and 8-15 mM K₃[Fe(CN)₆] as an electron acceptor. Such thorough optimization of the reaction conditions resulted in high product concentrations: 0.8 g/L for 25-hydroxycholesterol, 1.4 g/L for calcifediol and 2.2 g/L for 25-hydroxy-3-ketosterols. Although the purification protocol yields approximately 2.3 mg of pure S25DH from 30 g of wet cell mass (specific activity of 14 nmol min^-1 mg^-1), the non-purified crude extract or enzyme preparation can be readily used for the regioselective hydroxylation of both cholesterol and cholecalciferol. On the other hand, pure S25DH can be efficiently immobilized either on powder or a monolithic silica support functionalized with an organic linker providing NH₂ groups for enzyme covalent binding. Although such immobilization reduced the enzyme initial activity more than twofold it extended S25DH catalytic lifetime under working conditions at least 3.5 times.

Current assays overestimate 25-hydroxyvitamin D3 and underestimate 25-hydroxyvitamin D2 compared with HPLC: need for assay-specific decision limits and metabolite-specific assays

Background: Clinical demand for quick, cheap, precise and accurate 25-hydroxyvitamin D (25(OH)D) results has led to the development of a variety of assay methods. Lack of standardization of these methods has resulted in intermethod disagreement and challenged whether current assays recognize 25(OH)D2 and 25(OH)D3 equally.

Methods: We studied 172 patient samples from hip fracture cases using DiaSorin (DS) and IDS radioimmunoassays and the Nichols Advantage-automated protein binding assay (NA-CLPBA) in comparison to high-performance liquid chromatography (HPLC). 52 patient samples were analysed before and after three months treatment with 1000 IU of daily ergocalciferol (vitamin D2).

Results: Linear regression analysis in pre-treatment samples demonstrated a positive Y-intercept for each immunoassay compared with HPLC, and a slope that varied from 0.64 (IDS) to 0.97 (DS, NA-CLPBA). Bland Altman analysis demonstrated that all the three assays had a proportional positive bias relative to HPLC at values from 20 to 50 nmol/L. Regression analysis of post-treatment samples demonstrated a slope that was not significantly different from zero for the IDS and NA-CLPBA and 0.2 for the DS method, with a positive intercept for all assays of between 8 and 22, indicating less than 50% of 25(OH)D2 measured by HPLC was detected.

Conclusions: These results demonstrate the need for assay-specific decision limits for 25(OH)D3 in order to define appropriate thresholds for treatment institution. Treatment with vitamin D2 may not be accurately monitored with any of the three commercial assays studied. Clinicians and biochemists who continue to use 25(OH)D assays need to be urgently informed of these issues.

Vitamin D Status in Chronic Kidney Disease - UVB Irradiation Is Superior to Oral Supplementation

BACKGROUND

In chronic kidney disease (CKD) a deficiency of 1,25-dihydroxyvitamin D is common. The aim of this review was to compare vitamin D status after oral supplementation of vitamin D3 to that of serial suberythemal irradiation in end-stage kidney disease (ESKD) patients.

PATIENTS AND METHODS

Ninety-five patients, with a mean age of 62 (range=35-82) years, were treated with a mean dose of 35,000 (20,000-60,000) IU vitamin D3 per week for a period of 18 months. Fourteen patients, with a mean age of 51 (range=41-57) years, were whole-body UVB irradiated for over 6 months. From 3 hemodialysis patients skin biopsies were performed.

RESULTS

With oral supplementation 25(OH)D3 increased by 60%. With UV irradiation 25(OH)D3 increased by 400%. Gene expression analysis demonstrated an improvement in the vitamin D receptor (VDR) by 0.65 fold, in 1-alpha-hydroxylase (CYP27B1) by 1.0 fold, and in 25-hydroxylase (CYP2R) by 1.2 fold.

CONCLUSION

Serial suberythemal UVB irradiation of patients with CKD on dialysis is capable to improve serum 25(OH)D3 and 1,25(OH)2D3 by enhancing the skin's ability to activate vitamin D.

UV Irradiation and Pleiotropic Effects of Vitamin D in Chronic Kidney Disease - Benefits on Cardiovascular Comorbidities and Quality of Life

BACKGROUND

Vitamin D3 can be metabolized in the skin to 25(OH)D and 1,25(OH)2D because the skin expresses vitamin D-25-hydroxylase, 25(OH)D-1-alpha-hydroxylase, and the vitamin D receptor. The aim of this review was to discuss the pleiotropic effects after serial suberythemal UVB irradiation with a sun-simulating UV spectrum in end-stage kidney disease patients.

PATIENTS AND METHODS

Fourteen hemodialysis patients, with a mean age of 51 (range 41-57) years, were whole-body UV irradiated over 6 months.

RESULTS

Patients demonstrated an increase in their hematocrit and required less erythropoietin. An increase in maximal oxygen uptake and workload capacity was associated with decreased lactic acid production. The patients demonstrated a decreased heart rate and systolic and diastolic blood pressure with an increase in the R-R-interval and the beat-to-beat-differences.

CONCLUSION

Cardiovascular disease is the most important comorbidity. Exposure to simulated sunlight that contains both UVB and UVA reduce cardiovascular risk factors and improve quality of life.

Evidence for Vitamin D Receptor Expression and Direct Effects of 1α,25(OH)2D3 in Human Skeletal Muscle Precursor Cells

Presence of the vitamin D receptor and direct effects of vitamin D on the proliferation and differentiation of muscle precursor cells have been demonstrated in animal models. However, the effects and mechanisms of vitamin D actions in human skeletal muscle, and the presence of the vitamin D receptor in human adult skeletal muscle, remain to be established. Here, we investigated the role of vitamin D in human muscle cells at various stages of differentiation. We demonstrate that the components of the vitamin D-endocrine system are readily detected in human muscle precursor cells but are low to nondetectable in adult skeletal muscle and that human muscle cells lack the ability to convert the inactive vitamin D-metabolite 25-hydroxy-vitamin D3 to the active 1α,25-dihydroxy-vitamin D3 (1α,25(OH)2D3). In addition, we show that 1α,25(OH)2D3 inhibits myoblast proliferation and differentiation by altering the expression of cell cycle regulators and myogenic regulatory factors, with associated changes in forkhead box O3 and Notch signaling pathways. The present data add novel information regarding the direct effects of vitamin D in human skeletal muscle and provide functional and mechanistic insight to the regulation of myoblast cell fate decisions by 1α,25(OH)2D3.

A High-Calcium and Phosphate Rescue Diet and VDR-Expressing Transgenes Normalize Serum Vitamin D Metabolite Profiles and Renal Cyp27b1 and Cyp24a1 Expression in VDR Null Mice

Vitamin D receptor (VDR)-mediated 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-dependent gene expression is compromised in the VDR null mouse. The biological consequences include: hypocalcemia, hypophosphatemia, elevated parathyroid hormone (PTH) and 1,25(OH)2D3, and consequential skeletal abnormalities. CYP24A1 is a cytochrome P450 enzyme that is involved in the side chain oxidation and destruction of both 1,25(OH)2D3 and 25-hydroxyvitamin D3 (25-OH-D3). In the current studies, we used liquid chromatography-tandem mass spectrometry technology to compare the metabolic profiles of VDR null mice fed either a normal or a calcium and phosphate-enriched rescue diet and to assess the consequence of transgenic expression of either mouse or human VDR genes in the same background. Serum 1,25(OH)2D3 levels in VDR null mice on normal chow were highly elevated (>3000 pg/mL) coincident with undetectable levels of catabolites such as 24,25-(OH)2D3 and 25-OH-D3-26,23-lactone normally observed in wild-type mice. The rescue diet corrected serum Ca(++), PTH, and 1,25(OH)2D3 values and restored basal expression of Cyp24a1 as evidenced by both renal expression of Cyp24a1 and detection of 24,25-(OH)2D3 and the 25-OH-D3-26,23-lactone. Unexpectedly, this diet also resulted in supranormal levels of 3-epi-24,25-(OH)2D3 and 3-epi-25-OH-D3-26,23-lactone. The reappearance of serum 24,25-(OH)2D3 and renal Cyp24a1 expression after rescue suggests that basal levels of Cyp24a1 may be repressed by high PTH. Introduction of transgenes for either mouse or human VDR also normalized vitamin D metabolism in VDR null mice, whereas this metabolic pattern was unaffected by a transgene encoding a ligand binding-deficient mutant (L233S) human VDR. We conclude that liquid chromatography-tandem mass spectrometry-based metabolic profiling is an ideal analytical method to study mouse models with alterations in calcium/phosphate homeostasis.

The impact of vitamin D levels on glycemic control and bone mineral density in postmenopausal women with type 2 diabetes

OBJECTIVES

Whether glycemic control contributes to a decreased number of fractures or favorably impacts bone density in patients with type 2 diabetes mellitus (T2DM)has not been well established. Vitamin D (25 (OH) D3) deficiency appears to be related to glycemic control in patients with T2DM. The aim of this study was to determine the relationship between 25 (OH) D3 levels, glycemic control, bone mineral density (BMD), and the development of osteoporotic fractures (OPF) in postmenopausal women with T2DM.

METHODS

We reviewed the charts of 110 postmenopausal women diagnosed with T2DM. Glycosylated hemoglobin A1c (HbA1c) values over the previous 5 years were recorded and an average was obtained. Based on these values,the patients were divided into three groups: optimal,suboptimal, and poor control. Bone mineral density and 25(OH) D3 levels were also recorded.

RESULTS

In the group of patients with poorly controlled T2DM, 25 (OH) D3 levels were not significantly lower in comparison with the optimal control group 19.29 ± 7.70 vs 17.26 ± 6.93 (p = 0.53). No statistically significant linear relationship between HbA1c and 25 (OH) D3 levels( r(s) = −0.17, p = 0.06) was established. The frequency of osteoporosis and osteopenia was not significantly different between groups. The group with optimal glycemic control had an increased number of OPF events (p = 0.04).

CONCLUSIONS

We do not appreciate a significant relationship between 25 (OH) D3 levels and glucose control or OPF. Therefore, more studies are needed to identify the specific effect of 25 (OH) D3 in T2DM physiopathology.

Tear and serum vitamin D levels in children with allergic rhinoconjunctivitis

BACKGROUND

Although solid cohort studies confirmed a preventative role for the anti-oxidant vitamin D in allergic asthma, a limited number of studies focused on allergic rhinoconjunctivitis (ARC). Here, we aimed to determine 25-hydroxycholecalciferol levels in tear and serum in young allergic rhinoconjunctivitis patients as compared to their apparently healthy matched controls.

METHODS

In total, 22 children with allergic rhinoconjunctivitis and 31 healthy control subjects underwent serum total IgE and 25-hydroxycholecalciferol measurements. Tear levels of 25-hydroxycholecalciferol were also determined in both groups.

RESULTS

The mean serum total IgE level in the ARC group (143.6±132.8IU/ml) was significantly higher than that in the control group (54.8±44.1IU/ml; p=0.03). Serum 25(OH)D levels were significantly higher in the ARC group (34.1±12.7ng/ml) than in the healthy controls (21.8±11.3ng/ml; p=0.001).

CONCLUSIONS

To our knowledge, this is the first reported study to show an association between serum 25-hydroxycholecalciferol and ARC in a childhood group. Higher levels of serum 25-hydroxycholecalciferol in children with allergic rhinoconjunctivitis may indicate a possible aetiopathogenic mechanism in the development of allergic rhinoconjunctivitis. This is also the first report to examine tear fluid vitamin D levels in paediatric ARC patients.

Cardiorenal Syndrome and the Role of the Bone-Mineral Axis and Anemia

The association between chronic kidney disease (CKD) and cardiovascular disease (CVD) is well established, and there is mounting evidence of interorgan cross talk that may accelerate pathologic processes and the progression of organ dysfunction in both systems. This process, termed cardiorenal syndrome (CRS) by the Acute Dialysis Quality Initiative, is considered a major health problem: patients with CKD and CVD are at much higher risk of mortality than patients with either condition alone. To date, the majority of CRS research has focused on neurohormonal mechanisms and hemodynamic alterations. However, mounting evidence suggests that abnormalities in the normal pathophysiology of the bone-mineral axis, iron, and erythropoietin play a role in accelerating CKD and CVD. The goal of this article is to review the role and interrelated effects of the bone-mineral axis and anemia in the pathogenesis of chronic CRS.

Association between 25(OH)D Level, Ultraviolet Exposure, Geographical Location, and Inflammatory Bowel Disease Activity: A Systematic Review and Meta-Analysis

Background

There is no consensus on the vitamin D levels and inflammatory bowel disease (IBD).

Aim

To conduct a systematic review and meta-analysis to analyze the relationship between IBD and 25(OH)D, sun exposure, and latitude, and to determine whether vitamin D deficiency affects the severity of IBD.

Methods

We searched the PubMed, EBSCO, and ClinicalTrials.gov databases to identify all studies that assessed the association between 25(OH)D, sun exposure, latitude, and IBD through November 1, 2014, without language restrictions. Studies that compared 25(OH)D levels between IBD patients and controls were selected for inclusion in the meta-analysis. We calculated pooled standardized mean differences (SMDs) and odds ratios (ORs).

Results

Thirteen case-control studies investigating CD and 25(OH)D levels were included, and eight studies part of above studies also investigated the relationship between UC and 25(OH)D. Both CD patients (SMD: 0.26 nmol/L, 95% confidence interval [CI]: 0.09–0.42 nmol/L) and UC patients (SMD: 0.5 nmol/L, 95% CI: 0.15–0.85 nmol/L) had lower levels of 25(OH)D than controls. In addition, CD patients and UC patients were 1.95 times (OR, 1.95; 95% CI, 1.48–2.57) and 2.02 times (OR, 2.02; 95% CI, 1.13–3.60) more likely to be 25(OH)D deficient than controls. We also included 10 studies investigating the relationship between CD activity and vitamin D. Results showed that patients with active CD (CD Activity Index≥150) were more likely to have low vitamin D levels. In addition, whether low sun exposure and high latitude were related to a high morbidity of CD need to be provided more evidence.

Conclusion

Our study shows that IBD patients have lower vitamin D levels. For active CD patients, vitamin D levels were low. These findings suggest that vitamin D may play an important role in the development of IBD, although a direct association could not be determined in our study.

Tissue content of vitamin D3 and 25-hydroxy vitamin D3 in minipigs after cutaneous synthesis, supplementation and deprivation of vitamin D3

Information regarding the endogenous storages of vitamin D3 after cutaneous vitamin D synthesis compared to oral vitamin D3 supplementation is sparse. Furthermore it is not known whether vitamin D3 can be stored for later use during periods of shortages of vitamin D3. To investigate the endogenous storages of vitamin D3 two studies were carried out in Göttingen minipigs. In study 1 one group of minipigs (n=2) was daily exposed to UV light corresponding to 10-20 min of midday sun and another group (n=2) of pigs were fed up to 60 μg vitamin D3/day corresponding to 3.7-4.4 μg/kg body weight. Study 1 demonstrated that daily UV-exposure of minipigs stimulated the cutaneous synthesis of vitamin D3 and resulted in increasing serum vitamin D3 and 25-hydroxy vitamin D3, but also carcasses containing vitamin D3 and 25-hydroxy vitamin D3. The vitamin D3 content in adipose tissue from the UV-exposed minipigs was 150-260 ng/g and the content was 90-150 ng/g in the orally supplemented minipigs. In study 2, minipigs were UV-exposed daily for 49 days. Subsequently, one group (n=2) was fed a vitamin D-free diet and another group (n=2) was dosed daily with 13C-labeled vitamin D3. The concentrations of vitamin D3 and 25-hydroxy vitamin D3 in serum and skin- and subcutaneous adipose tissue biopsies were repeatedly monitored. Vitamin D3 and 25-hydroxy vitamin D3 were eliminated from the skin and the adipose tissue after UV-exposure was ceased. Supplementation of 13C-vitamin D3 did not seem to affect the decline in the endogenous vitamin D3 in the adipose tissue formed during UV-exposure.

Metabolism of 20-hydroxyvitamin D3 and 20,23-dihydroxyvitamin D3 by rat and human CYP24A1

CYP11A1 hydroxylates vitamin D3 producing 20S-hydroxyvitamin D3 [20(OH)D3] and 20S,23-dihydroxyvitamin D3 [20,23(OH)2D3] as the major and most characterized metabolites. Both display immuno-regulatory and anti-cancer properties while being non-calcemic. A previous study indicated 20(OH)D3 can be metabolized by rat CYP24A1 to products including 20S,24-dihydroxyvitamin D3 [20,24(OH)2D3] and 20S,25-dihydroxyvitamin D3, with both producing greater inhibition of melanoma colony formation than 20(OH)D3. The aim of this study was to characterize the ability of rat and human CYP24A1 to metabolize 20(OH)D3 and 20,23(OH)2D3. Both isoforms metabolized 20(OH)D3 to the same dihydroxyvitamin D species with no secondary metabolites being observed. Hydroxylation at C24 produced both enantiomers of 20,24(OH)2D3. For rat CYP24A1 the preferred initial site of hydroxylation was at C24 whereas the human enzyme preferred C25. 20,23(OH)2D3 was initially metabolized to 20S,23,24-trihydroxyvitamin D3 and 20S,23,25-trihydroxyvitamin D3 by rat and human CYP24A1 as determined by NMR, with both isoforms showing a preference for initial hydroxylation at C25. CYP24A1 was able to further oxidize these metabolites in a series of reactions which included the cleavage of C23-C24 bond, as indicated by high resolution mass spectrometry of the products, analogous to the catabolism of 1,25(OH)2D3 via the C24-oxidation pathway. Similar catalytic efficiencies were observed for the metabolism of 20(OH)D3 and 20,23(OH)2D3 by human CYP24A1 and were lower than for the metabolism of 1,25(OH)2D3. We conclude that rat and human CYP24A1 metabolizes 20(OH)D3 producing only dihydroxyvitamin D3 species as products which retain biological activity, whereas 20,23(OH)2D3 undergoes multiple oxidations which include cleavage of the side chain.

Vitamin D metabolism in nephrotic rats

It is well known that patients with nephrotic syndrome and normal renal function have hypocalcemia in spite of high PTH concentration, caused by the low serum concentration of the active vitamin D metabolite, 1,25(OH)2D, presumably due to its loss in urine. However, it has been uncertain whether the conversion of 25(OH)D into 1,25(OH)2D in the kidney is impaired. In this study, we examined the responsibility of 1,25(OH)2D in PAN-induced nephrotic rats. Sprague-Dawley rats weighing 250 g were given subcutaneous injections 1.5 mg/100 g PAN for 12 days prior to use. Some of these rats were given intraperitoneal injection of 100 IU of 25(OH)D3 for 3 days prior to use and of 10 IU of PTH. We measured Ca2+ in plasma, vitamin D metabolites and mid-molecule PTH in serum, renal 25(OH)D-1-hydroxylase activity in vitro, and response of nephrogenous cyclic AMP to exogenous PTH administration. In nephrotic rats, plasma Ca2+, serum 25(OH)D and 1,25(OH)2D were lower than in control rats, and the serum PTH level was higher than in controls. In 25(OH)D3-injected nephrotic rats, Ca2+ and 1,25(OH)2D were higher than in nephrotic rats, indicating that the decreased level of 1,25(OH)2D in nephrotic rats was partially due to the low serum level of 25(OH)D. Despite the elevation of the serum level of PTH, the Vmax of renal 25(OH)D-1-hydroxylase in nephrotic rats was lower than in controls. Response of nephrogenous cyclic AMP to PTH in nephrotic rats was lower than in controls. Although nephrotic rats had higher PTH levels than control rats, Vmax of renal 25(OH)D-1-hydroxylase and response of cyclic AMP to exogenous PTH administration in nephrotic rats were lower than in controls, suggesting that abnormalities of calcium metabolism in patients with nephrotic syndrome might be partially attributed to the impaired renal response to PTH.

Vitamin D3 increases in abdominal subcutaneous fat tissue after supplementation with vitamin D3

OBJECTIVE

The objective was to assess the amount of vitamin D3 stored in adipose tissue after long-term supplementation with high dose vitamin D3.

DESIGN

A cross-sectional study on 29 subjects with impaired glucose tolerance who had participated in a randomized controlled trial with vitamin D3 20 000 IU (500 μg) per week vs placebo for 3-5 years.

METHODS

Abdominal subcutaneous fat tissue was obtained by needle biopsy for the measurements of vitamin D3 and 25-hydroxyvitamin D3 (25(OH)D3). Body fat was measured with dual-energy X-ray absorptiometry, and serum 25(OH)D3 level was quantified.

RESULTS

In the subjects given vitamin D3, the median concentrations of serum 25(OH)D3, fat vitamin D3, and fat 25(OH)D3 were 99 nmol/l, 209 ng/g, and 3.8 ng/g, respectively; and correspondingly in the placebo group 62  nmol/l, 32 ng/g, and 2.5 ng/g. If assuming an equal amount of vitamin D3 stored in all adipose tissue in the body, the median body store was 6.6 mg vitamin D3 and 0.12 mg 25(OH)D3 in those given vitamin D3.

CONCLUSIONS

Subcutaneous adipose tissue may store large amounts of vitamin D3. The clinical importance of this storage needs to be determined.

Effects of 25-(OH)D3 on fecal Ca and P excretion, bone mineralization, Ca and P transporter mRNA expression and performance in growing female pigs

A study was conducted to examine the effects of 25-hydroxyvitamin D3 (25-(OH)D3) on fecal Ca and P excretion, bone mineralization, performance and the mRNA expression of intestinal transporter genes in growing female pigs. Sixty-day old gilts (n = 24) with an average initial BW of 23.13 ± 1.49 kg were randomly allocated to a control diet (diet 1) containing wheat/corn/soybean meal and 150 IU kg(-1) of Vitamin D3, diet 1 + 50 μg of 25-(OH)D3 kg(-1) (diet 2) and diet 1 + 100 μg of 25-(OH)D3 kg(-1) (diet 3). The pigs were housed in an individual pen and had ad libitum access to feed and water for 42 days, and BWG and feed intake were measured weekly. Measures of bone mineralization and expression of Ca and P transporters mRNA were analyzed using Dual Energy X-Ray Absortiometry (DEXA) and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Fecal Ca and P concentration were significantly reduced (P ≤ 0.05) in pigs fed diets 2 and 3 compared with the control diet. Supplementation of 25-(OH)D3 did not significantly improve bone mineralization, animal performance and intestinal transporters mRNA expression except for SLC34A1, a sodium-dependent phosphate transporter 1. In conclusion, supplementation of 25-(OH)D3 in swine nutrition may not improve animal performance but has the potential to reduce environmental pollution by increasing dietary Ca and P retention while reducing their excretion.

Metabolism of 20-hydroxyvitamin D3 by mouse liver microsomes

20-Hydroxyvitamin D3 [20(OH)D3], the major product of CYP11A1 action on vitamin D3, is biologically active and like 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] can inhibit proliferation and promote differentiation of a range of cells, and has anti-inflammatory properties. However, unlike 1,25(OH)2D3, it does not cause toxic hypercalcemia at high doses and is therefore a good candidate for therapeutic use to treat hyperproliferative and autoimmune disorders. In this study we analyzed the ability of mouse liver microsomes to metabolize 20(OH)D3. The two major products were identified from authentic standards as 20,24-dihydroxyvitamin D3 [20,24(OH)2D3] and 20,25-dihydroxyvitamin D3 [20,25(OH)2D3]. The reactions for synthesis of these two products from 20(OH)D3 displayed similar Km values suggesting that they were catalyzed by the same cytochrome P450. Some minor metabolites were produced by reactions with higher Km values for 20(OH)D3. Some metabolites gave mass spectra suggesting that they were the result of hydroxylation followed by dehydrogenation. One product had an increase in the wavelength for maximum absorbance from 263nm seen for 20(OH)D3, to 290nm, suggesting a new double bond was interacting with the vitamin D-triene chromophore. The two major products, 20,24(OH)2D3 and 20,25(OH)2D3 have both previously been shown to have higher potency for inhibition of colony formation by melanoma cells than 20(OH)D3, thus it appears that metabolism of 20(OH)D3 by mouse liver microsomes can generate products with enhanced activity.