The objective was to investigate associations of serum vitamin D concentration with depressive symptoms and assess the impact that vitamin D concentration has on the occurrence of depressive symptoms in 20-44-year-old pregnant women, postpartum women, non-pp women (non-pregnant/postpartum women), and men, including a separate subgroup analysis of postpartum breastfeeding and non-breastfeeding women. The study populations were selected from the 2007-2018 NHANES public data. Subjective interview data and objective laboratory data including depressive symptoms, serum vitamin D concentration, nutrient intake, and demographic information were utilized. Two diet patterns were created using principal component analysis, and a Bayesian multinomial model was fit to predict the depression outcomes for each subpopulation. The estimates for the log vitamin D slope parameter were negative for all cohorts; as vitamin D increased, the probability of having no depression increased, while the probability of depression decreased. The pregnant cohort had the steepest vitamin D slope, followed by postpartum women, then non-pp women and men. Higher vitamin D concentration had more impact on decreasing depression risk in pregnant and postpartum women compared to non-pp women and men. Among postpartum women, higher vitamin D concentration had a greater influence on decreasing breastfeeding women\'s depression risk than non-breastfeeding women.

Vitamin D hydroxylation in the liver/kidney results in conversion to its physiologically active form of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. 1,25(OH)2D3 controls gene expression through the nuclear vitamin D receptor (VDR) mainly expressed in intestinal epithelial cells. Cytochrome P450 (CYP) 24A1 is a catabolic enzyme expressed in the kidneys. Interestingly, a recently identified mutation in another CYP enzyme, CYP3A4 (gain-of-function), caused type III vitamin D-dependent rickets. CYP3A are also expressed in the intestine, but their hydroxylation activities towards vitamin D substrates are unknown. We evaluated CYP3A or CYP24A1 activities on vitamin D action in cultured cells. In addition, we examined the expression level and regulation of CYP enzymes in intestines from mice. The expression of CYP3A or CYP24A1 significantly reduced 1,25(OH)2D3-VDRE activity. Moreover, in mice, Cyp24a1 mRNA was significantly induced by 1,25(OH)2D3 in the intestine, but a mature form (approximately 55 kDa protein) was also expressed in mitochondria and induced by 1,25(OH)2D3, and this mitochondrial enzyme appears to hydroxylate 25OHD3 to 24,25(OH)2D3. Thus, CYP3A or CYP24A1 could locally attenuate 25OHD3 or 1,25(OH)2D3 action, and we suggest the small intestine is both a vitamin D target tissue, as well as a newly recognized vitamin D-metabolizing tissue.

The objective was to explore the patterns of contribution from vitamin D metabolites (D2 and D3) to total vitamin D concentrations in Indian families. This cross-sectional study was carried out in slum-dwelling families residing in Pune city. Data on demography, socio-economic status, sunlight exposure, anthropometry, and biochemical parameters (serum 25OHD2, 25OHD3) via the liquid chromatography-tandem mass spectrometry method were collected. The results are presented for 437 participants (5 to 80 years). One-third were vitamin-D-deficient. Intake of foods containing vitamin D2 or D3 was rarely reported. Irrespective of gender, age, and vitamin D status, the contribution of D3 to total 25OHD concentrations far exceeded that of D2 (p < 0.05). The contribution of D2 ranged from 8% to 33% while that of D3 to 25OHD concentrations ranged from 67% to 92%. 25OHD3 is a major contributor to overall vitamin D concentrations, and the contribution of 25OHD2 was found to be negligible. This implies that sunlight and not diet is currently the major source of vitamin D. Considering that lifestyle and cultural practices may lead to insufficient sunlight exposure for large sections of the society, especially women, dietary contribution to vitamin D concentrations through fortification may play an important role in improving the vitamin D status of Indians.

This dataset demonstrates the content of vitamin D3 and 25-hydroxyvitamin D3 (25OHD3) in boiled, grilled, and raw pork for both lean and whole cuts including ribs, tenderloin, shoulder, neck, belly, and center chops. Total fat content in raw pork cuts was determined by the gravimetric method. Quantification analysis using reverse phase high performance liquid chromatography with UV-DAD connected. Purification of fatty acids from proteins was performed using a c18 cartridge, resolving vitamin D3 from its metabolites by subjecting purified samples to polar silica cartridge, purification from sugars by a series of two amino columns, and quantification of vitamin D3 and 25-hydroxyvitamin D3 by injecting purified extracts on C18 SPE column. Grilling samples was conducted in an electric combi oven.

In this review, we discuss the sources, formation, metabolism, function, biological activity, and potency of C3-epimers (epimers of vitamin D). We also determine the role of epimerase in vitamin D-binding protein (DBP) and vitamin D receptors (VDR) according to different subcellular localizations. The importance of C3 epimerization and the metabolic pathway of vitamin D at the hydroxyl group have recently been recognized. Here, the hydroxyl group at the C3 position is orientated differently from the alpha to beta orientation in space. However, the details of this epimerization pathway are not yet clearly understood. Even the gene encoding for the enzyme involved in epimerization has not yet been identified. Many published research articles have illustrated the biological activity of C3 epimeric metabolites using an in vitro model, but the studies on in vivo models are substantially inadequate. The metabolic stability of 3-epi-1α,25(OH)2D3 has been demonstrated to be higher than its primary metabolites. 3-epi-1 alpha, 25 dihydroxyvitamin D3 (3-epi-1α,25(OH)2D3) is thought to have fewer calcemic effects than non-epimeric forms of vitamin D. Some researchers have observed a larger proportion of total vitamin D as C3-epimers in infants than in adults. Insufficient levels of vitamin D were found in mothers and their newborns when the epimers were not included in the measurement of vitamin D. Oral supplementation of vitamin D has also been found to potentially cause increased production of epimers in mice but not humans. Moreover, routine vitamin D blood tests for healthy adults will not be significantly affected by epimeric interference using LC-MS/MS assays. Recent genetic models also show that the genetic determinants and the potential factors of C3-epimers differ from those of non-C3-epimers.Most commercial immunoassays techniques can lead to inaccurate vitamin D results due to epimeric interference, especially in infants and pregnant women. It is also known that the LC-MS/MS technique can chromatographically separate epimeric and isobaric interference and detect vitamin D metabolites sensitively and accurately. Unfortunately, many labs around the world do not take into account the interference caused by epimers. In this review, various methods and techniques for the analysis of C3-epimers are also discussed. The authors believe that C3-epimers may have an important role to play in clinical research, and further research is warranted.

The demand for vitamin D testing is increasing in China. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) immunoassay is specific and accurate but requires expensive equipment, experienced operators, and complicated pretreatment of serum. Automated immunoassays are simple and convenient but only determine total 25-hydroxyvitamin D (25OHD). The objective of this study was to quantify 25OHD2 and 25OHD3 in patients to assist clinical physicians and laboratory directors in choosing the most appropriate method to determine 25OHD.
Vitamin D testing was conducted for 23,695 patients in Peking Union Medical College Hospital from May 2015 to January 2017. Using this large data set, the prevalence and levels of 25OHD2 were analyzed. LC-MS/MS was used to separately determine 25OHD2 and 25OHD3.
25OHD2 (≥2.5 ng/mL) was detected in 16.4% (3877/23,695) of patients. Males had a significantly lower incidence of detectable 25OHD2 (p<0.01); 1077 (13.9%) samples contained detectable 25OHD2 (median: 3.7 ng/mL; 2.5%-97.5%: 2.5-17.2 ng/mL). For females, 2800 (17.5%) samples contained detectable 25OHD2 (median: 4.0 ng/mL; range: 2.5-20.6 ng/mL). Of the 3877 patients with detectable 25OHD2, males had a significantly higher level of 25OHD3 (p<0.01). There was no significant difference in total 25OHD. The proportion of 25OHD2 in total 25OHD was 1.3%-100%; 87.5% (3391/3877) of the samples contained <10 ng/mL 25OHD2. 25OHD2 negatively correlated with 25OHD3 (r=-0.197, p<0.01) and positively correlated with total 25OHD (r=0.217, p<0.01).
Prevalence of 25OHD2 in patients tested for vitamin D is relatively high in China. 25OHD2 is significantly negatively correlated with 25OHD3.

Association of Vitamin D (D3 & D2) and its 25OHD metabolite (25OHD3 & 25OHD2) exposures with various diseases is an active research area. D3 and D2 dose-equivalency and each form\'s ability to raise 25OHD concentrations are not well-defined. The current work describes a population pharmacokinetic (PK) model for D2 and 25OHD2 and the use of a previously developed D3-25OHD3 PK model [1] for comparing D3 and D2-related exposures. Public-source D2 and 25OHD2 PK data in healthy or osteoporotic populations, including 17 studies representing 278 individuals (15 individual-level and 18 arm-level units), were selected using search criteria in PUBMED. Data included oral, single and multiple D2 doses (400-100,000 IU/d). Nonlinear mixed effects models were developed simultaneously for D2 and 25OHD2 PK (NONMEM v7.2) by considering 1- and 2-compartment models with linear or nonlinear clearance. Unit-level random effects and residual errors were weighted by arm sample size. Model simulations compared 25OHD exposures, following repeated D2 and D3 oral administration across typical dosing and baseline ranges. D2 parent and metabolite were each described by 2-compartment models with numerous parameter estimates shared with the D3-25OHD3 model [1]. Notably, parent D2 was eliminated (converted to 25OHD) through a first-order clearance whereas the previously published D3 model [1] included a saturable non-linear clearance. Similar to 25OHD3 PK model results [1], 25OHD2 was eliminated by a first-order clearance, which was almost twice as fast as the former. Simulations at lower baselines, following lower equivalent doses, indicated that D3 was more effective than D2 at raising 25OHD concentrations. Due to saturation of D3 clearance, however, at higher doses or baselines, the probability of D2 surpassing D3\'s ability to raise 25OHD concentrations increased substantially. Since 25OHD concentrations generally surpassed 75 nmol/L at these higher baselines by 3 months, there would be no expected clinical difference in the two forms.

OBJECTIVE: We aimed to investigate the prevalence of vitamin D deficiency in Chinese lupus patients and to assess the association between vitamin D levels and disease severity.
METHODS: Serum levels of 25OHD3 in 121 patients with systemic lupus erythematosus (SLE) and 150 healthy controls were measured by electrochemiluminescence immunoassay. Data regarding demographics and clinical parameters were collected. Disease activity of SLE was evaluated according to the SLE Disease Activity Index (SLEDAI) score and irreversible organ damage by the Systemic Lupus International Collaborating Clinic/American College of Rheumatology, SLICC/ACR Damage Index (SDI). The multivariate logistic regression model was used to investigate the association between the degree of vitamin D deficiency and SLEDAI or SDI scores.
RESULTS: The prevalence of vitamin D insufficiency (25OHD3 <30 ng/ml) and severe deficiency (25OHD3 <10 ng/ml) in SLE patients was 62.81% and 34.71%, respectively. Logistic regression analysis indicated that the cut-off point of 25OHD3 concentration was 10 ng/ml where its level was correlated with increased SLEDAI (OR 6.420, p = 0.006), but not with the SDI. In addition, hydroxychloroquine treatment lowered the SLEDAI increased by the severe 25OHD3 deficiency (OR 0.280, p = 0.008). Moreover, long disease duration (OR 1.014, p = 0.008) predicted moderate to severe organ damage.
CONCLUSIONS: Vitamin D deficiency is highly prevalent in patients with SLE. Severe deficiency increases the risk for moderate to severe disease activity, but not for organ damage.

BACKGROUND: The accuracy of 25-hydroxyvitamin D3 (25OHD3) measurement on specimens collected into serum separator tubes (SSTs) has been questioned because of possible interference by the gel. Possible interference was investigated in SSTs from Becton Dickinson (BD).
METHODS: Blood specimens were collected simultaneously from 50 normal subjects into plain tubes and SSTs. 25OHD3 was assayed on serum using high performance liquid chromatography (Chromsystems), and Architect (Abbott) and Liaison (Diasorin) immunoassays.
RESULTS: There were no significant differences between 25OHD3 results (means ± SE, nmol/l) obtained from specimens collected into plain tubes and SSTs assayed by HPLC (39.0 ± 2.7 vs. 39.3 ± 2.7), Liaison (32.9 ± 2.2 vs. 32.8 ± 2.3), or Architect (43.1 ± 2.8 vs. 43.2 ± 2.8). In specimens collected into plain tubes and SSTs, 25OHD3 measurements by HPLC correlated significantly (P < 0.0001) with those from the Architect (r = 0.895, r = 0.908) and Liaison (r = 0.907, r = 0.913), respectively.
CONCLUSIONS: The gel in SSTs (BD) does not interfere with the measurement of 25OHD3 by HPLC or common immunoassays. This important finding may enable clinical laboratories to make cost savings by using SSTs without concerns about inaccuracy.