Background:
Metabolic syndrome is related to increased cardiovascular disease (CVD) risk. Although continuous metabolic syndrome score (cMets) is a marker of cardiometabolic burden in adolescence, the relationship between cardiometabolic burden and DNA methylation has been rarely assessed at this stage of the life course.
Hypothesis:
Cardiometabolic burden is related to methylation levels in genes related to CVD risk in adolescents.
Methods:
A sample of 263 independent adolescents from the population-based Penn State Child Cohort follow-up exam (N=421) was used in this analysis. cMets was calculated as the sum of standardized residuals of five established cardiometabolic risk factors, namely waist circumference, mean arterial pressure, homeostatic model assessment of insulin resistance, triglycerides, and high density lipoprotein cholesterol (HDL) concentration. cMets was log-transformed to improve the distribution. Peripheral leukocyte DNA was extracted and subjected to enhanced, reduced representation bisulfite sequencing. The assay provided single nucleotide resolution of DNA methylation in cytosine-phosphate-guanine (CpG) sites and surrounding regions. Bases with < 10x coverage were excluded, resulting a total of 1,609,424 methylation sites. Linear regression was used to model the association between site-specific methylation level and cMets. All models were adjusted for age, race, and sex. A p < 10x10
-8
was used to determine statistical significance. The significant sites were mapped to the hg19 assembly and subjected to Ingenuity Pathway Analysis (IPA) wherein mapped gene sets were examined for enrichment of downstream function and diseases. Permutations were further performed to confirm the robustness of our findings.
Results:
On average, the sample was 55% male, 79% white, and aged 16.7 (standard deviation = 2.2) years. cMetS was significantly associated with 52 sites within 43 genes. Among the genes, three were related to glucose tolerance, two to endothelial function, and two more to oxidative stress. IPA indicated that genes associated with these functions were significantly enriched for glucose tolerance (p=0.029), endothelial function (p=0.009), and oxidative stress (p=0.028). Indeed, high cMetS was associated with hypermethylation of
PRKCD
, which is related to diabetes risk, and
PRDX5
, which encodes anti-oxidant peroxiredoxin-5. Higher cMetS also was associated with hypomethylation of
ID3
.
Conclusion:
Despite validation is pending, these preliminary findings suggest that cardiometabolic burden in adolescents is related to DNA methylation in genes related to CVD risk factors in adulthood, including glucose tolerance, endothelial function, and oxidative stress.
