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Maternal Weight Phenotype as a Predictor of Methylation of Obesity-Related CpG Sites in Saliva Samples from Latino Children

ABSTRACT: Epigenetics presents a dynamic approach to assess complex individual variation in obesity susceptibility. However, few studies have examined epigenetic patterns in preschool-age children, despite the relevance of this developmental stage to trajectories of weight gain, because of difficulties obtaining blood tissue samples. This proof of principle study examined DNA methylation in 92 saliva samples, comparing Latino preschool children of normal weight mothers (Body Mass Index [BMI] <27 kg/m2 and WC <90 cm) to children of obese mothers (BMI >30 kg/m2 and WC >100 cm). We hypothesized that salivary DNA methylation patterns in Latino preschool age children born of normal weight vs obese weight mothers would be: 1) associated with maternal BMI phenotype in continuous linear regression analysis; 2) saliva could demonstrate epigenetic variation across individuals; and 3) preschool child saliva would be differentially methylated when comparing those children with obese versus normal weight mothers. One hundred and nineteen CpG sites were significantly (p-value <1.56 X 10-5, p-value adjusted <.05) associated with maternal BMI in linear regression models controlling for child’s age, gender, and BMI. Of these 119 CpG sites, 41 were found within the transcription start site, 5’ UTR, 3’ UTR, or another regulatory region outside of the gene body. Saliva, a practical human tissue to obtain in naturalistic settings and in pediatric populations, was confirmed to be a viable medium for genome-wide epigenetic testing with maternal weight. Although not identical to results yielded from other human tissue types (i.e., cord blood samples), saliva findings indicate potential epigenetic differences in Latino preschool children at risk for pediatric obesity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE72556 | GEO | 2016/02/25

SECONDARY ACCESSION(S): PRJNA294332

REPOSITORIES: GEO

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Project description:Epigenetics presents a dynamic approach to assess complex individual variation in obesity susceptibility. However, few studies have examined epigenetic patterns in preschool-age children, despite the relevance of this developmental stage to trajectories of weight gain, because of difficulties obtaining blood tissue samples. This proof of principle study examined DNA methylation in 92 saliva samples, comparing Latino preschool children of normal weight mothers (Body Mass Index [BMI] <27 kg/m2 and WC <90 cm) to children of obese mothers (BMI >30 kg/m2 and WC >100 cm). We hypothesized that salivary DNA methylation patterns in Latino preschool age children born of normal weight vs obese weight mothers would be: 1) associated with maternal BMI phenotype in continuous linear regression analysis; 2) saliva could demonstrate epigenetic variation across individuals; and 3) preschool child saliva would be differentially methylated when comparing those children with obese versus normal weight mothers. One hundred and nineteen CpG sites were significantly (p-value <1.56 X 10-5, p-value adjusted <.05) associated with maternal BMI in linear regression models controlling for childâs age, gender, and BMI. Of these 119 CpG sites, 41 were found within the transcription start site, 5â UTR, 3â UTR, or another regulatory region outside of the gene body. Saliva, a practical human tissue to obtain in naturalistic settings and in pediatric populations, was confirmed to be a viable medium for genome-wide epigenetic testing with maternal weight. Although not identical to results yielded from other human tissue types (i.e., cord blood samples), saliva findings indicate potential epigenetic differences in Latino preschool children at risk for pediatric obesity. This proof of principle study examined DNA methylation in 92 saliva samples, comparing Latino preschool children of normal weight mothers (Body Mass Index [BMI] <27 kg/m2 and WC <90 cm) to children of obese mothers (BMI >30 kg/m2 and WC >100 cm). Antropometry was measured objectively according to a standardized protocol.Saliva from preschool Latino children at risk for obesity (BMI>50% < 95% participating in WIC/SNAP programs) was collected using the Oragene DNA saliva kit following a strict data collection protocol. DNA extraction was performed as per DNA Genotek's recommendations using the PrepIT L2P reagent. Extracted DNA was stored in individually barcoded cryovials at â80 degrees Fahrenheit. For children, saliva was obtained using the âbaby brushâ approach, in which small sponges attached to plastic handles are inserted between cheek and gumline to absorb saliva .Arrays were processed using standard protocol [34], with 3 samples randomly selected to serve as duplicates and 1 sample run with HapMap DNA to test functionality of reagents. Duplicates were measured for high technique consistency with Pearson correlation coefficient (>.99). Methylation data were quality controlled using Illumina GenomeStudio (V2011.1), Methylation module (V1.9.0). Samples with lower than 98% call rate (i.e. <485,000 probes) were excluded. Any non-specific cross-reacting probes, probes carrying common SNPs (MAF >1%), or any probes with p-values greater than 0.05 for more than 20% of the sample were sequentially excluded. Validation via pyrosequencing was conducted.

Project description:Background: Maternal pre-pregnancy BMI is a critical factor influencing the composition of breast milk. Breast milk has abundant extracellular vesicles (EVs) containing various biological molecules (cargo), including miRNAs. EVs are not degraded in the gastrointestinal system and circulation; thus, breast milk EVs (bEVs) interact with other organs in breastfed infants and modify the gene expression of recipient cells using miRNAs. In maternal obesity, miRNAs in bEVs are deregulated, which might be associated with adverse health outcomes in infants. In this study, we examined 798 miRNAs to determine which miRNAs are altered in the bEVs of obese mothers and their potential impact on breastfed infants. Methods: We recruited healthy nursing mothers who were either obese (BMI≥30) or lean (BMI<25) based on their pre-pregnancy BMI, and delivered a singleton baby in the prior six months. EVs were isolated from breast milk with ultracentrifugation. bEV characteristics were examined by flow cytometry and fluorescence imaging of EV markers. A total of 798 miRNAs were screened using a NanoString human miRNA panel to find deregulated miRNAs in bEVs of obese mothers compared to lean mothers. Results: We included 65 nursing mothers: 47 lean and 18 obese mothers based on pre-pregnancy BMI. After bEV isolation, we confirmed the expression of general EV markers. Out of 37 EV markers, CD326 was the most highly expressed marker in bEVs. From miRNA analysis using NanoString, we found that the most abundant miRNAs include miR-30b-5p, miR-494-3p, and let-7 families, and the list of top 10 miRNAs was not different between lean and obese mothers. Target genes of the top 10 miRNAs were associated with the EGFR, ErbB, and FoxO signaling pathway. Nineteen miRNAs were deregulated in bEVs of obese mothers (adjusted p < 0.05 cut-off), including miR-575, miR-548g-3p, miR-582-3p, and miR-652-5p. The target genes of these miRNAs are associated with lipid metabolism, inflammatory diseases, and nervous/cardiovascular system development. Conclusion: In this study, we demonstrated altered miRNAs in bEVs of obese mothers and identified the pathways of their potential target genes. Our findings will provide insight for future studies investigating the role of bEVs in breastfed infants.

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Maternal Weight Phenotype as a Predictor of Methylation of Obesity-Related CpG Sites in Saliva Samples from Latino Children

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