Genetics, Diet, and Season Are Associated with Serum 25-Hydroxycholecalciferol Concentration in a Yup'ik Study Population from Southwestern Alaska

Diet quality is positively associated with intake of traditional foods and does not differ by season in remote Yup'ik communities

This study evaluated whether traditional food intake and diet quality differed by season in Yup'ik communities and examined the relationship between intake of traditional food groups and diet quality. Data were collected from 38 participants, ages 14-79 years, from two Yup'ik communities in Southwest Alaska from 2008 to 2010. Self-reported intake (24-h recalls) and dietary biomarker (nitrogen stable isotope ratio) data were collected twice in distinct seasons. Diet quality was assessed using the Healthy Eating Index. A paired sample t-test was used to test for seasonal differences in traditional food intake and diet quality, and linear regression was used to evaluate associations between traditional food intake and diet quality. Total traditional food intake and overall diet quality did not significantly differ by season, but there were differences in traditional food group intake and diet quality component scores. Diet quality was strongly associated with intake of traditional food groups including fish, tundra greens, and berries. Given the strong relationship between traditional food intake and diet quality, policies should aim to ensure continued access to traditional foods in Yup'ik communities amid environmental changes in the circumpolar North.

Impact of a Prenatal Vitamin D Supplementation Program on Vitamin D Deficiency, Rickets and Early Childhood Caries in an Alaska Native Population

Background: Early childhood rickets increased in Alaska Native children after decreases in vitamin D-rich subsistence diet in childbearing-aged women. We evaluated the impact of routine prenatal vitamin D supplementation initiated in Alaska’s Yukon Kuskokwim Delta in Fall 2016. Methods: We queried electronic health records of prenatal women with 25(OH) vitamin D testing during the period 2015−2019. We evaluated 25(OH)D concentrations, vitamin D3 supplement refills, and decayed, missing, and filled teeth (dmft) scores and rickets in offspring. Results: Mean 25(OH)D concentrations increased 36.5% from pre- to post-supplementation; the percentage with deficient 25(OH)D decreased by 66.4%. Women with ≥ 60 vitamin D3 refill days had higher late pregnancy 25(OH)D concentrations than those with no refill days (p < 0.0001). Women with late pregnancy insufficient 25(OH)D concentrations had offspring with higher dmft scores than those with sufficient 25(OH)D (RR 1.3, p < 0.0001). Three children were diagnosed with nutritional rickets during the period 2001−2021, and none after 2017. Conclusions: These findings suggest that prenatal vitamin D supplementation can improve childhood outcomes in high-risk populations with high rates of rickets.

Tribal Deliberations about Precision Medicine Research: Addressing Diversity and Inequity in Democratic Deliberation Design and Evaluation

Deliberative democratic engagement is used around the globe to gather informed public input on contentious collective questions. Yet, rarely has it been used to convene individuals exclusively from Indigenous communities. The relative novelty of using this approach to engage tribal communities and concerns about diversity and inequities raise important methodological questions. We describe the design and quality outcomes for a 2.5-day deliberation that elicited views of American Indian and Alaska Native (AIAN) leaders about the potential value and ethical conduct of precision medicine research (PMR), an emerging approach to research that investigates the health effects of individual genetic variation in tandem with variation in health-relevant practices, social determinants, and environmental exposures. The event met key goals, such as relationship and rapport formation, cross-site learning, equality of opportunity to participate, and respect among participants in the context of disagreement.

Association between Polymorphisms in Vitamin D Pathway-Related Genes, Vitamin D Status, Muscle Mass and Function: A Systematic Review

An association between vitamin D level and muscle-related traits has been frequently reported. Vitamin D level is dependent on various factors such as sunlight exposure and nutrition. But also on genetic factors. We, therefore, hypothesize that single nucleotide polymorphisms (SNPs) within the vitamin D pathway-related genes could contribute to muscle mass and function via an impact on vitamin D level. However, the integration of studies investigating these issues is still missing. Therefore, this review aimed to systematically identify and summarize the available evidence on the association between SNPs within vitamin D pathway-related genes and vitamin D status as well as various muscle traits in healthy adults. The review has been registered on PROSPERO and was conducted following PRISMA guidelines. In total, 77 studies investigating 497 SNPs in 13 different genes were included, with significant associations being reported for 59 different SNPs. Variations in GC, CYP2R1, VDR, and CYP24A1 genes were reported most frequently, whereby especially SNPs in the GC (rs2282679, rs4588, rs1155563, rs7041) and CYP2R1 genes (rs10741657, rs10766197, rs2060793) were confirmed to be associated with vitamin D level in more than 50% of the respective studies. Various muscle traits have been investigated only in relation to four different vitamin D receptor (VDR) polymorphisms (rs7975232, rs2228570, rs1544410, and rs731236). Interestingly, all of them showed only very low confirmation rates (6-17% of the studies). In conclusion, this systematic review presents one of the most comprehensive updates of the association of SNPs in vitamin D pathway-related genes with vitamin D status and muscle traits in healthy adults. It might be used for selecting candidate SNPs for further studies, but also for personalized strategies in identifying individuals at risk for vitamin D deficiency and eventually for determining a potential response to vitamin D supplementation.

Characterization of CYP3A pharmacogenetic variation in American Indian and Alaska Native communities, targeting CYP3A4*1G allele function

The frequencies of genetic variants in the CYP3A4 and CYP3A5 genes differ greatly across global populations, leading to profound differences in the metabolic activity of these enzymes and resulting drug metabolism rates, with important consequences for therapeutic safety and efficacy. Yet, the impact of genetic variants on enzyme activity are incompletely described, particularly in American Indian and Alaska Native (AIAN) populations. To characterize genetic variation in CYP3A4 and CYP3A5 and its effect on enzyme activity, we partnered with AIAN people living in two regions of Alaska: Yup'ik Alaska Native people living in the Yukon-Kuskokwim Delta region of rural southwest Alaska and AIAN people receiving care at the Southcentral Foundation in Anchorage, Alaska. We identified low frequencies of novel and known variation in CYP3A4 and CYP3A5, including low frequencies of the CYP3A4*1G and CYP3A5*1 variants, and linkage disequilibrium patterns that differed from those we previously identified in an American Indian population in western Montana. We also identified increased activity of the CYP3A4*1G allele in vitro and in vivo. We demonstrated that the CYP3A4*1G allele confers increased protein content in human lymphoblastoid cells and both increased protein content and increased activity in human liver microsomes. We confirmed enhanced CYP3A4-mediated 4β-vitamin D hydroxylation activity in Yup'ik people with the CYP3A4*1G allele. AIAN people in Alaska and Montana who carry the CYP3A4*1G allele-coupled with low frequency of the functional CYP3A5*1 variant-may metabolize CYP3A substrates more rapidly than people with the reference CYP3A4 allele.

Advancing precision public health using human genomics: examples from the field and future research opportunities

Precision public health is a relatively new field that integrates components of precision medicine, such as human genomics research, with public health concepts to help improve population health. Despite interest in advancing precision public health initiatives using human genomics research, current and future opportunities in this emerging field remain largely undescribed. To that end, we provide examples of promising opportunities and current applications of genomics research within precision public health and outline future directions within five major domains of public health: biostatistics, environmental health, epidemiology, health policy and health services, and social and behavioral science. To further extend applications of genomics within precision public health research, three key cross-cutting challenges will need to be addressed: developing policies that implement precision public health initiatives at multiple levels, improving data integration and developing more rigorous methodologies, and incorporating initiatives that address health equity. Realizing the potential to better integrate human genomics within precision public health will require transdisciplinary efforts that leverage the strengths of both precision medicine and public health.

Utility and Diversity: Challenges for Genomic Medicine

Genomic information is poised to play an increasing role in clinical care, extending beyond highly penetrant genetic conditions to less penetrant genotypes and common disorders. But with this shift, the question of clinical utility becomes a major challenge. A collaborative effort is necessary to determine the information needed to evaluate different uses of genomic information and then acquire that information. Another challenge must also be addressed if that process is to provide equitable benefits: the lack of diversity of genomic data. Current genomic knowledge comes primarily from populations of European descent, which poses the risk that most of the human population will be shortchanged when health benefits of genomics emerge. These two challenges have defined my career as a geneticist and have taught me that solutions must start with dialogue across disciplinary and social divides.

Association Between Vitamin D and Uric Acid in Adults: A Systematic Review and Meta-Analysis

Association between vitamin D and uric acid is complex and might be bidirectional. Our study aimed to determine the bidirectional association between vitamin D and uric acid in adults. Using MEDLINE via PubMed and Scopus, we systematically searched for observational or interventional studies in adults, which assessed the association between serum vitamin D and serum uric acid, extracted the data, and conducted analysis by direct and network meta-analysis. The present review included 32 studies, of which 21 had vitamin D as outcome and 11 had uric acid as outcome. Meta-analysis showed a significant pooled beta coefficient of serum uric acid level on serum 25(OH)D level from 3 studies of 0.512 (95% confidence interval: 0.199, 0.825) and a significant pooled odds ratio between vitamin D deficiency and hyperuricemia of 1.496 (1.141, 1.963). The pooled mean difference of serum 25(OH)D between groups with hyperuricemia and normouricemia was non-significant at 0.138 (-0.430, 0.707) ng/ml, and the pooled mean difference of serum uric acid between categories of 25(OH)D were also non-significant at 0.072 (-0.153, 0.298) mg/dl between deficiency and normal, 0.038 (-0.216, 0.292) mg/dl between insufficiency and normal, and 0.034 (-0.216, 0.283) mg/dl between deficiency and insufficiency. In conclusion, increasing serum uric acid might be associated with increasing 25(OH)D level, while vitamin D deficiency is associated with hyperuricemia. These reverse relationships should be further evaluated in a longitudinal study.

Genetic Variation in Cytochrome P450 2R1 and Vitamin D Binding Protein Genes are associated with Vitamin D Deficiency in Adolescents

Background: Genome Wide Association Studies (GWAS) have evaluated several genes related to vitamin D synthesis, metabolism and transport. They have proposed a genetic basis for low levels of vitamin D in the blood. The current study aims to investigate the relationship between certain vitamin D-associated gene variants and vitamin D deficiency in Iranian adolescents. Methods: In this case-control study, the genomic DNA was extracted by Real Time PCR High Resolution Melt (HRM). All measurements were carried out with triple repetition. The following factors were assessed: single nucleotide polymorphisms (SNPs) in Vitamin D binding protein (DBP, rs2282679), 7-Dehydrocholesterol reductase (DHCR7, rs12785878) and Cytochrome P450 2R1 (CYP2R1, rs10741657). Results: the genomic DNA of blood samples obtained from 481 adolescents. Participants with hypovitaminosis D were compared with a control group. The average vitamin D level of sufficient subjects (controls) was 44.88±14.01 ng/mL, while subjects who were insufficient (cases) had an average vitamin D level of 7.03±1.24 ng/mL. No statistically significant differences were found in the allelic and genotypic distributions between genders. The SNP frequency in CYP2R1 (rs10741657) and DBP (rs2282679) in the vitamin D deficient group was significantly higher than in the control group (p-values < 0.001 and 0.01 respectively). There were no statistically significant differences in the DHCR7 SNP (rs12785878) distributions between the Vitamin D deficient group and control group. Conclusion: The present study demonstrated evidence of the ability of the SNPs under investigation to predict circulating vitamin D concentration. Further study is needed to better understand if and how genetic factors contribute to vitamin D levels, and certain skeletal-associated disorders in adolescents.

Gender differences in the prevalence of vitamin D deficiency in a southern Latin American country: a pilot study

Aim: This study aimed to study the prevalence of vitamin D deficiency, assessing the influence of sex, age, and season of the year.Methods: A cross-sectional study was conducted with 1329 healthy subjects (668 women and 661 men) aged 18-89 years in Santiago, Chile. Age (years), body mass index, medical history, working status, sex, and date of blood sample were collected.Results: Men were slightly older than women (53.1 ± 18.2 vs. 50.0 ± 15.6 years; p < 0.01) and a higher percentage worked outside the home (73.1% vs. 51.9%, p < 0.001). The mean serum concentration of 25-hydroxyvitamin D (25(OH)-D) was 23.3 ± 9.3 ng/ml in women and 20.9 ± 9.5 ng/ml in men (p < 0.001). The levels of 25(OH)-D by season were 26.7 ± 9.0, 23.6 ± 9.7, 19.4 ± 8.5, and 19.1 ± 9.5 ng/ml (for summer, fall, winter, and spring, respectively; p < 0.05). The prevalence of vitamin D deficiency increases with age, rising from 36.5% under 40 years to 48.0% over 60 years (p < 0.004). Male sex, winter and spring, and age showed negative correlation with levels of 25(OH)-D (p < 0.05). Multivariate linear regression showed a final model that incorporates: age (coefficient: -0.06; 95% confidence interval [CI]: -0.09 to -0.03; p < 0.001), male sex (coefficient: -2.00; 95% CI: -2.96 to -1.05; p < 0.001), summer (coefficient: 7.30; 95% CI: 6.17 to 8.43; p < 0.001), and fall (coefficient: 4.27; 95% CI: 3.04 to 5.50; p < 0.001).Conclusions: Vitamin D deficiency is more prevalent in men than in women, in the elderly, and during the winter and spring seasons.

The Nitrogen Isotope Ratio Is a Biomarker of Yup'ik Traditional Food Intake and Reflects Dietary Seasonality in Segmental Hair Analyses

BACKGROUND

The nitrogen isotope ratio (NIR) is a promising index of traditional food intake for an Alaska Native (Yup'ik) population, which can be measured in blood and hair. However, the NIR has not been calibrated to high-quality measures of Yup'ik traditional food intake.

OBJECTIVES

Our primary objective was to examine associations between intakes of Yup'ik traditional food groups, including fish, marine mammals, birds, land mammals, berries, greens, and total traditional foods, and the NIR. In an exploratory analysis, we also examined whether NIR analyzed sequentially along hair could reflect dietary seasonality.

METHODS

We recruited 68 participants from 2 Yup'ik communities in the Yukon Kuskokwim region of Southwest Alaska (49% female, aged 14-79 y). Participants completed 4 unscheduled 24-h food recalls over the period peak of RBC and hair synthesis preceding a specimen collection visit. The NIR was measured in RBCs ( n = 68), a proximal hair section (n = 58), and sequential segments of hair from individuals in the upper 2 quartiles of traditional food intake having hair >6 cm in length, plus 2 low subsistence participants for reference (n = 18). Diet-biomarker associations were assessed using Pearson's correlation and linear regression.

RESULTS

Intakes of fish, marine mammals, berries, and greens were significantly associated with the NIR. The strongest dietary association was with total traditional food intake (R2 = 0.62), which indicated that each 1‰ increase in the RBC NIR corresponded to 8% of energy from traditional foods. Hair NIR appeared to fluctuate seasonally in some individuals, peaking in the summertime.

CONCLUSIONS

Findings support the use of the RBC and hair NIR to assess total traditional food intake in a Yup'ik population. Analyses of sequential hair NIR provided evidence of seasonality in traditional food intake, although seasonal variations were modest relative to interindividual variation.

Negative Impact of 25-hydroxyvitamin D Deficiency on Breast Cancer Survival

Background:

Low 25-hydroxyvitamin D [25(OH)D] levels in serum are associated with breast cancer risk. This study was conducted to determine the impact of 25(OH)D deficiency on survival of breast cancer patients.

Methods:

In a retrospective cohort study of 303 patients diagnosed with breast cancer during 2011-2012 at the National Cancer Institute Thailand, all cases were followed up for 7 years. The 25(OH)D was measured by high-performance liquid chromatography (HPLC). Clinical and pathological data were collected. The Chi-square test, Kaplan-Meier and Cox regression model were used to assess the association between 25(OH)D levels and risk of death.

Results:

Of the 303 cases aged between 24 and 78 years 51 (16.8%) died during follow-up from any cause. The mean 25(OH)D levels was 25.1±7.54 ng/ml (8.2 – 61.0 ng/ml). Thirty-three patients (10.9%) were stratified as inadequate or deficient group (<16 ng/ml) with mean survival time of 60.65 months compared to 76.24 months in insufficient or sufficient group (≥16 ng/ml). Multivariate analysis adjusted for age, body mass index, stage, lymph node metastases, and immunohistochemical (IHC) findings (ER, PgR, HER-2, Ki-67 and P53) showed that patients with low 25(OH)D levels (<16 ng/ml) at diagnosis had a significantly higher risk of death (hazard ratio = 2.5-2.9) than the group with high 25(OH)D levels (≥16 ng/ml).

Conclusion:

A concentration of 25(OH)D below 16 ng/ml was found to be independently associated with poor survival in breast cancer patients, regardless of age, lymph node status, stage or breast cancer subtype. An investigation of potential benefit of 25(OH)D supplements appears warranted.

Older women do not have seasonal variations of vitamin D levels: a study from a southern country

OBJECTIVE

The aim was to study whether the seasonal variation of vitamin D [25(OH)-D or calcidiol] is similar or different in younger and older women living in a southern country.

METHODS

Measurement of serum 25(OH)-D concentration in 739 Chilean women aged 20 to 87 years, residents of Santiago (latitude: 33.4° South) who, during a routine gynaecological checkup, agreed to be evaluated.

RESULTS

The mean serum concentration of 25(OH)-D for the group was 24.1 ± 10.5 ng/mL. In women 20 to 39 years, the mean was significantly different from the mean of the ≥60 years old group (25.8 ± 10.6 ng/mL vs 23.9 ± 11.1 ng/mL; P < 0.02). Globally, 38.4% of participants had vitamin D deficiency and 36.1% insufficiency. A deficiency was present in 28.4% of the 20 to 39 years old, and in 43.9% in the ≥60 years old group (P < 0.004). In the whole group, a lower proportion (P < 0.0001) of vitamin D deficiency cases in the youngest women occurred during the summer (23.7%) in comparison to the winter (47.7%). It was observed that the proportion of participants in the 20 to 39 years old group with vitamin D deficiency fell from 48.9% in winter to 4.9% in summer (P = 0.0001). In the older groups, this change (less deficiency) is progressively smaller, 51.2% to 27.6% (P = 0.0020) in women 40 to 59 years old, and it does not happen in women ≥60 years (40% with vitamin D deficiency).

CONCLUSIONS

Serum vitamin D deficiency [25(OH)-D or calcidiol] is highly prevalent in Santiago, especially in older women (≥60 y) throughout the year. In contrast, in younger women (<40 y), the vitamin D deficiency tends to disappear during summer. More epidemiological studies and targeted prevention actions on vitamin D deficiency are warranted.

Association of Maternal Vitamin D Deficiency with Early Childhood Caries

Alaska Native (AN) children experience one of the highest reported rates of severe early childhood caries (S-ECC). Serum vitamin D concentrations in AN childbearing women in the Yukon Kuskokwim Delta (YKD) region have decreased since the 1960s to currently low levels, related to a decrease in traditional marine diet. Recent studies suggest an association between prenatal vitamin D (25(OH)D) concentrations in mothers and S-ECC in their infants. We used independent t tests to analyze the influence of prenatal 25(OH)D levels in YKD AN mothers on S-ECC in their children using data collected in the Maternal Organics Monitoring Study (MOMS). Maternal 25(OH)D levels were assessed at prenatal visits and in cord blood. We queried electronic dental records to assess early childhood caries (ECC) status using highest decayed, missing, filled, primary teeth (dmft) scores at 12 to 59 mo of age. We examined prenatal and cord blood for 76 and 57 mother/infant pairs, respectively. Children 12 to 35 mo of age with "deficient" cord blood (25(OH)D <30 nmol/L) had a mean dmft score twice as high as children who were "nondeficient" at birth (9.3 vs. 4.7; P = 0.002). There was no significant difference in mean dmft scores for children aged 36 to 59 mo with deficient versus nondeficient cord blood 25(OH)D (10.9 vs. 8.7 P = 0.14). There was no significant difference in mean dmft scores for children aged 12 to 35 mo whose mothers had "sufficient" versus "insufficient" 25(OH)D during prenatal visits (9.0 vs. 7.4; P = 0.48). In this small sample, children with deficient vitamin D levels in cord blood had a dmft score at 12 to 35 mo 2-fold higher than children with nondeficient cord blood. Maternal 25(OH)D may influence the primary dentition, and improving vitamin D status in pregnant women might affect ECC rates in their infants.

A time for everything and everything in its time - exploring the mechanisms underlying seasonality of COPD exacerbations

Across Europe, COPD affects 23 million people leading to annual health care costs of ~€25.1 billion. This burden is particularly severe during winter months in association with the peak incidence of exacerbation events. Seasonal variation in the health status of patients with COPD places additional and often critical pressure on already strained health care resources. COPD exacerbations are characterized by worsening day-to-day symptoms of an individual and often triggered by respiratory infections, but the process by which this occurs in a seasonal fashion is likely to be multifactorial. In this review, we discuss recent population studies that highlight the impact of seasonality in COPD and review the proposed biological mechanisms underlying this. An appraisal of the role of the host susceptibility and response, environmental triggers and the biology of respiratory pathogens is detailed. The impact of each aspect is considered, and an integrated model of the context for the whole individual and society in general is explored.

Effects of CYP2R1 gene variants on vitamin D levels and status: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

CYP2R1 is a key gene in the vitamin D metabolic pathway. It has been suggested that CYP2R1 gene variants in European populations are associated with concentrations of 25(OH)D, a biomarker of vitamin D levels and status in peripheral blood. However, a comprehensive meta-analysis of this effect including different ethnicities has never been conducted. The objective of this meta-analysis was to evaluate the association between CYP2R1 gene variants and 25(OH)D levels and vitamin D status.

METHODS

PubMed, EMBASE, Web of Science, CNKI and Wanfang databases were systematically searched up to May 2018. Reporting followed PRISMA guidelines. The quality of the evidence was assessed using the STREGA system. Random or fixed effects model combined estimates and sub-group tested for ethnic differences. The I² statistic quantified between-study variation due to heterogeneity.

RESULTS

Sixteen articles with a total of 52,417 participants met the inclusion criteria and were included in the meta-analysis. For rs10741657, GG genotype was associated with a clear descending trend of 25(OH)D levels when compared with the AA genotype [SMD = -2.32, 95% CI (-4.42, -0.20); SMD = -3.46, 95% CI (-6.60, -0.33) and SMD = -0.24, 95% CI (-0.51, -0.03) for total, Caucasian and Asian groups, respectively] with the following heterogeneities I² = 37.9%, 69.2% and 24.5%, respectively. However, under the AG/AA genetic model, significant changes in 25(OH)D levels [SMD and 95% CI: -1.27(-2.32, -0.23)] were only evident in the Caucasian population. The meta-analysis on vitamin D deficiency showed that the risk-allele G was associated with an increased risk of vitamin D deficiency (OR = 1.09; 95% CI = 1.03-1.15, P = 0.002). The association between rs10741657 and increased risk of vitamin D deficiency was significant (OR = 1.42; 95% CI = 1.11-1.83, P = 0.006) under the dominant model (GG + AG/AA), but not under the recessive model (GG/AG + AA), (OR = 1.28; 95% CI = 0.89-1.84, P = 0.181). There was no evidence of publication bias.

CONCLUSION

Published articles provide evidence supporting a major role for the rs10741657 polymorphism of the CYP2R1 gene in determining 25(OH)D levels and the presence of vitamin D deficiency.

Circulating Vitamin D and Overall Survival in Breast Cancer Patients: A Dose-Response Meta-Analysis of Cohort Studies

Studies have shown that vitamin D could have a role in breast cancer survival; however, the evidence of the relationship between patients' vitamin D levels and their survival has been inconsistent. This meta-analysis explores possible dose-response relationships between vitamin D levels and overall survival by allowing for differences in vitamin D levels among populations of the various studies. Studies relating vitamin D (25-OH-D [25-hydroxyvitamin D]) levels in breast cancer patients with their survival were identified by searching PubMed and Embase. A pooled HR (hazard ratio) comparing the highest with the lowest category of circulating 25-OH-D levels were synthesized using the Mantel-Haenszel method under a fixed-effects model. A two-stage fixed-effects dose-response model including both linear (a log-linear dose-response regression) and nonlinear (a restricted cubic spline regression) models were used to further explore possible dose-response relationships. Six studies with a total number of 5984 patients were identified. A pooled HR comparing the highest with the lowest category of circulating 25-OH-D levels under a fixed-effects model was 0.67 (95% confidence interval = 0.56-0.79, P < .001). Utilizing a dose-response meta-analysis, the pooled HR for overall survival in breast cancer patients was 0.994 (per 1 nmol/L), Pfor linear trend < .001. At or above a 23.3 nmol/L threshold, for a 10 nmol/L, 20 nmol/L, or 25 nmol/L increment in circulating 25-OH-D levels, the risk of breast cancer overall mortality decreased by 6%, 12%, and 14%, respectively. There was no significant nonlinearity in the relationship between overall survival and circulating 25-OH-D levels. Our findings suggest that there is a highly significant linear dose-response relationship between circulating 25-OH-D levels and overall survival in patients with breast cancer. However, better designed prospective cohort studies and clinical trials are needed to further confirm these findings.

Dietary Vitamin K and Association with Hepatic Vitamin K Status in a Yup'ik Study Population from Southwestern Alaska

SCOPE

The relationship between dietary vitamin K and plasma PIVKA-II concentration, a biomarker of hepatic vitamin K status, in a Yup'ik study population in southwestern Alaska is investigated.

METHODS AND RESULTS

A total of 659 male and female, self-reported Yup'ik people, ≥14 years of age, were enrolled. Blood is collected for genotyping and plasma PIVKA-II biomarker analysis. A Yup'ik-specific dietary food frequency questionnaire is used to assess vitamin K intake. Among the participants, 22% report not consuming foods rich in vitamin K during the past year and 36% have a PIVKA-II concentration ≥ 2 ng mL-1 , indicating vitamin K insufficiency. The odds of an elevated PIVKA-II concentration are 33% lower in individuals reporting any versus no consumption of vitamin-K-rich foods. The association is significant after adjusting for CYP4F2*3 genotype. Tundra greens are high in vitamin K1 content, but an exploratory analysis suggests that subsistence meat sources have a greater effect on vitamin K status.

CONCLUSIONS

A substantial proportion of the Yup'ik population exhibits vitamin K insufficiency, which is associated with low consumption of vitamin K rich foods and which might affect an individual's response to anticoagulant drugs such as warfarin that target the vitamin K cycle.

Concerning the vitamin D reference range: pre-analytical and analytical variability of vitamin D measurement

Unlike other vitamins, the vitamin D concentration in blood varies cyclically over the course of the year in relation to genetic (gender, ethnicity, polymorphisms) and environmental factors (sunlight exposure, diet, food-related or direct vitamin D supplementation, skin pigmentation). Although the major diagnostics manufacturers have recently developed improved automated 25-hydroxy vitamin D immunoassays, the intra- and inter-laboratory variability is still high (especially at low vitamin D concentrations) which might lead to incorrect vitamin D deficiency/insufficiency diagnosis. Moreover, despite recent efforts to standardize the assay and minimize its variability, the current bias for measured vitamin D concentrations is often still above the desirable ± 10% criterion. Because the implications of low vitamin D concentrations in non-skeletal diseases are still partially unknown, international guideline recommendations for establishing meaningful ranges, at any time over the course of the year, irrespective not only of environmental and personal factors but also of instrumental variability, are needed. In this review, we discuss the main factors that influence the variability of vitamin D concentrations and whether a centile curve, individually calculated by a theoretical equation considering such factors, might be better suited than a fixed limit to assess abnormal vitamin D concentrations in otherwise healthy subjects. Vitamin D reference ranges during pregnancy, childhood, or diagnosed illnesses, which merit separate discussion, are beyond the scope of this review.

Declines in traditional marine food intake and vitamin D levels from the 1960s to present in young Alaska Native women

OBJECTIVE

To measure the trends in traditional marine food intake and serum vitamin D levels in Alaska Native women of childbearing age (20-29 years old) from the 1960s to the present.

DESIGN

We measured a biomarker of traditional food intake, the δ15N value, and vitamin D level, as 25-hydroxycholecalciferol (25(OH)D3) concentration, in 100 serum samples from 20-29-year-old women archived in the Alaska Area Specimen Bank, selecting twenty-five per decade from the 1960s to the 1990s. We compared these with measurements of red-blood-cell δ15N values and serum 25(OH)D3 concentrations from 20-29-year-old women from the same region collected during the 2000s and 2010s in a Center for Alaska Native Health Research study.

SETTING

The Yukon Kuskokwim Delta region of south-west Alaska.

SUBJECTS

Alaska Native women (n 319) aged 20-29 years at the time of specimen collection.

RESULTS

Intake of traditional marine foods, as measured by serum δ15N values, decreased significantly each decade from the 1960s through the 1990s, then remained constant from the 1990s through the present (F 5,306=77·4, P<0·0001). Serum vitamin D concentrations also decreased from the 1960s to the present (F 4,162=26·1, P<0·0001).

CONCLUSIONS

Consumption of traditional marine foods by young Alaska Native women dropped significantly between the 1960s and the 1990s and was associated with a significant decline in serum vitamin D concentrations. Studies are needed to evaluate the promotion of traditional marine foods and routine vitamin D supplementation during pregnancy for this population.

DHCR7: A vital enzyme switch between cholesterol and vitamin D production

The conversion of 7-dehydrocholesterol to cholesterol, the final step of cholesterol synthesis in the Kandutsch-Russell pathway, is catalyzed by the enzyme 7-dehydrocholesterol reductase (DHCR7). Homozygous or compound heterozygous mutations in DHCR7 lead to the developmental disease Smith-Lemli-Opitz syndrome, which can also result in fetal mortality, highlighting the importance of this enzyme in human development and survival. Besides serving as a substrate for DHCR7, 7-dehydrocholesterol is also a precursor of vitamin D via the action of ultraviolet light on the skin. Thus, DHCR7 exerts complex biological effects, involved in both cholesterol and vitamin D production. Indeed, we argue that DHCR7 can act as a switch between cholesterol and vitamin D synthesis. This review summarizes current knowledge about the critical enzyme DHCR7, highlighting recent findings regarding its structure, transcriptional and post-transcriptional regulation, and its links to vitamin D synthesis. Greater understanding about DHCR7 function, regulation and its place within cellular metabolism will provide important insights into its biological roles.