We have previously shown that vitamin D supplementation increases telomerase activity, suggesting an anti-aging effect. In this study, we aim to test the hypothesis that vitamin D supplementation would slow down epigenetic aging, a new marker of biological aging. A randomized clinical trial was previously conducted among 70 overweight/obese African Americans with serum 25-hydroxyvitamin D [25(OH)D] < 50 nmol/L, who were randomly assigned into four groups of 600 IU/d, 2,000 IU/d, 4,000 IU/d of vitamin D₃ supplements or placebo followed by 16-week interventions. Whole genome-wide DNA methylation analysis was conducted in 51 participants. DNA methylation ages were calculated according to the Horvath and the Hannum methods. Methylation-based age acceleration index (∆Age) is defined as the difference between DNA methylation age and chronological age in years. Mixed-effects models were used to evaluate the treatment effects. Fifty-one participants (aged 26.1 ± 9.3 years, 16% are male) were included in the study. After the adjustment of multi-covariates, vitamin D₃ supplementation of 4,000 IU/d was associated with 1.85 years decrease in Horvath epigenetic aging compared with placebo (p value = .046), and 2,000 IU/d was associated with 1.90 years decrease in Hannum epigenetic aging (p value = .044). Serum 25(OH)D concentrations were significantly associated with decreased Horvath ∆Age only (p values = .002), regardless of treatments. Our results suggest that vitamin D supplementation may slow down Horvath epigenetic aging. But the effect on Hannum epigenetic aging is not conclusive. Large-scale and longer duration clinical trials are needed to replicate the findings.

High-sodium diet may modulate the gut microbiome. Given the circulating short-chain fatty acids (SCFAs) are microbial in origin, we tested the hypothesis that the modest sodium reduction would alter circulating SCFA concentrations among untreated hypertensives, and the changes would be associated with reduced blood pressure and improved cardiovascular phenotypes. A total of 145 participants (42% blacks, 19% Asian, and 34% females) were included from a randomized, double-blind, placebo-controlled cross-over trial of sodium reduction with slow sodium or placebo tablets, each for 6 weeks. Targeted circulating SCFA profiling was performed in paired serum samples, which were collected at the end of each period, so as all outcome measures. Sodium reduction increased all 8 SCFAs, among which the increases in 2-methylbutyrate, butyrate, hexanoate, isobutyrate, and valerate were statistically significant ( P s<0.05). Also, increased SCFAs were associated with decreased blood pressure and improved arterial compliance. There were significant sex differences of SCFAs in response to sodium reduction ( P s<0.05). When stratified by sex, the increases in butyrate, hexanoate, isobutyrate, isovalerate, and valerate were significant in females only ( P s0.05). In females, changes in isobutyrate, isovalerate, and 2-methylbutyrate were inversely associated with reduced blood pressures ( P s<0.05). Increased valerate was associated with decreased carotid-femoral pulse wave velocity ( P =0.040). Our results show that dietary sodium reduction increases circulating SCFAs, supporting that dietary sodium may influence the gut microbiome in humans. There is a sex difference in SCFA response to sodium reduction. Moreover, increased SCFAs are associated with decreased blood pressures and improved arterial compliance. Registration—: URL: https://www.clinicaltrials.gov . Unique identifier: NCT00152074.

We conducted an epigenome-wide association study (EWAS) on obesity in healthy youth and young adults and further examined to what extent identified signals influenced gene expression and were independent of cell type composition and obesity-related cardio-metabolic risk factors. Genome-wide DNA methylation data from leukocytes were obtained from 700 African Americans aged 14–36. We also measured genome-wide DNA methylation data from neutrophils as well as genome-wide gene expression data from leukocytes in a subset of samples (n = 188). The EWAS identified 76 obesity-related CpG sites in leukocytes with p < 1 × 10−7. In silico replication in the ARIC study of 2097 African Americans aged 47–70 validated 54 CpG sites. Out of the 54 CpG sites, 29 associations with obesity were novel and 37 were replicated in neutrophils. Fifty one CpG sites were associated with at least one cardio-metabolic risk factor; however, the number reduced to 9 after adjustment for obesity. Sixteen CpG sites were associated with expression of 17 genes in cis, of which 5 genes displayed differential expression between obese cases and lean controls. We also replicated 71.5% of obesity-related CpG sites previously reported. In this study of youth and young adults, we identified 29 novel CpG sites associated with obesity and replicated the majority of the CpG sites previously identified. We further demonstrated that the majority of the obesity-related CpG sites in leukocytes were not driven by cell composition or obesity-related cardio-metabolic risk factors. We also provided the direct link between DNA methylation-gene expression-obesity for 5 genes.

Vitamin D could be beneficial for healthy aging in humans. We previously found that vitamin D supplementation may slow down epigenetic aging in young African American adults. We tested new epigenetic clocks developed for neonates among a multiethnic population, and tested the hypothesis that vitamin D supplementation would slow down the epigenetic gestational age acceleration (GAA) in newborn babies. Ninety-two pregnant women (aged 29.6±4.8 years; 21% African Americans, 28% Hispanics) were randomized to receive 4000 IU/day vitamin D₃ or placebo, plus prenatal vitamins containing 400 IU vitamin D₃ during pregnancy in a randomized controlled trial (RCT). Cord blood genome-wide methylation analysis was performed on the Illumina Infinium MethylationEPIC Beadchip. DNA methylation gestational age was calculated based on two calculations developed by Knight and Bohlin. DNA methylation gestational ages calculated by Knight’s clock and Bohlin’ clock were highly correlated with the gestational age in the placebo group (correlation coefficients=0.88, ps< 0.001, respectively). GAA was associated with higher birth weight (p=0.039). In the entire cohort, vitamin D₃ supplementation was not associated with GAA (p>0.05). However, vitamin D₃ supplementation decreased GAA by both Knight’s clock (β=-0.89, p=0.047) and Bohlin’s clock (β=-0.71, p=0.005) in the African American participants. Vitamin D₃ supplementation may slow down the epigenetic gestational aging process in African American neonates. Long-term follow-up studies are warranted to determine the role of epigenetic age acceleration in the growth and development of offspring.

Emerging evidence suggests that epigenetics regulates telomere dynamics in adults. However, the relationship between these pathways in children and youth remains unknown. Thus, we examined this association in 542 healthy adolescents aged 14 to 18 years old (44.8% African Americans; 55.2% females). Global DNA methylation level (%5-mC) was quantified using ELISA method. Leukocyte telomere length (LTL) was defined as relative telomere to single copy gene (T/S) ratio. Multiple linear regression models, adjusted for age, gender, ethnicity, Tanner stage, BMI, PA, and batch effect, revealed that %5 mC was associated with LTL (adjusted β = 0.17, p < 0.01). %5 mC accounted for 5.0% of the variation for LTL. A significant gender interaction was identified (p < 0.01). There was an association between %5 mC and LTL in females (all ps < 0.01), but not in males. Further sensitivity analyses by race revealed similar associations in African Americans and whites (all ps < 0.03). The present study, for the first time, shows that lower levels of global DNA methylation are associated with shorter telomere lengths in youth, which may decrease genome stability and augment the susceptibility to diseases. Longitudinal studies are warranted to establish the effects of global DNA methylation on LTL maintenance over time.