While breast milk has unique health advantages for infants, the mechanisms by which it regulates the physiology of newborns are incompletely understood. miRNAs have been described as functioning transcellularly, and have been previously isolated in cell-free and exosomal form from bodily liquids (serum, saliva, urine) and tissues, including mammary tissue. We hypothesized that breast milk in general, and milk fat globules in particular, contain significant numbers of known and limited novel miRNA species detectable with massively parallel sequencing. Extracted RNA from lactating mothers before and following short-term treatment with recombinant human growth hormone (rhGH) was smRNA-enriched. smRNA-Seq was performed to generate 124,110,646 36-nt reads. Of these, 31,102,927 (25%) exactly matched known human miRNAs; with relaxing of stringency, 74,716,151 (60%) matched known miRNAs including 308 of the 1018 (29%) mature miRNAs (miRBase 16.0). These miRNAs are predicted to target 9074 genes; the 10 most abundant of these predicted to target 2691 genes with enrichment for transcriptional regulation of metabolic and immune responses. We identified 21 putative novel miRNAs, of which 12 were confirmed in a large validation set that included cohorts of lactating women consuming enriched diets. Of particular interest, we observed that expression of several novel miRNAs were altered by the perturbed maternal diet, notably following a high-fat intake (p<0.05). Our findings suggest that known and novel miRNAs are enriched in breast milk fat globules, and expression of several novel miRNA species is regulated by maternal diet. Based on robust pathway mapping, our data supports the notion that these maternally secreted miRNAs (stable in the milk fat globules) play a regulatory role in the infant and account in part for the health benefits of breast milk. We further speculate that regulation of these miRNA by a high fat maternal diet enables modulation of fetal metabolism to accommodate significant dietary challenges.

Several studies linking alterations in differential placental methylation with pregnancy disorders have implicated (de)regulation of the placental epigenome with fetal programming and later-in-life disease. We have previously demonstrated that maternal tobacco use is associated with alterations in promoter methylation of placental CYP1A1 and that these changes are correlated with CYP1A1 gene expression and fetal growth restriction. In this study we sought to expand our analysis of promoter methylation by correlating it to gene expression on a genome-wide scale. Employing side-by-side IlluminaHG-12 gene transcription with Infinium27K methylation arrays, we interrogated correlative changes in placental gene expression and DNA methylation associated with maternal tobacco smoke exposure at an epigenome-wide level and in consideration of signature gene pathways. We observed that the expression of 623 genes and the methylation of 1024 CpG dinucleotides are significantly altered among smokers, with only 38 CpGs showing significant differential methylation (differing by a methylation level of ≥10%). We identified a significant Pearson correlation (≥0.7 or ≤-0.7) between placental transcriptional regulation and differential CpG methylation in only 25 genes among non-smokers but in 438 genes among smokers (18-fold increase, p < 0.0001), with a dominant effect among oxidative stress pathways. Differential methylation at as few as 6 sites was attributed to maternal smoking-mediated birth weight reduction in linear regression models with Bonferroni correction (p < 1.8 × 10(-6)). These studies suggest that a common perinatal exposure (such as maternal smoking) deregulates placental methylation in a CpG site-specific manner that correlates with meaningful alterations in gene expression along signature pathways.

The metabolic pathways utilized by higher eukaryotic organisms to deal with potentially carcinogenic xenobiotic compounds from tobacco smoke have been well characterized. Carcinogenic compounds such as polycyclic aromatic hydrocarbons are metabolized sequentially in two-phases: in phase I CYP1A1 catalyzes conversion into harmful hydrophilic DNA adducts, while in phase II GSTT1 enables excretion via conjugation into polar electrophiles. In an effort to understand susceptibility to in utero tobacco exposure, we previously characterized known metabolic functional polymorphisms and demonstrated that while deletion of fetal GSTT1 significantly modified birth weight in smokers, no polymorphism fully accounted for fetal growth restriction. Since smoking upregulates CYP1A1 expression, we hypothesized that non-allelic (epigenetic) dysregulation of placental CYP1A1 expression via alterations in DNA methylation (meCpG) may further modify fetal growth. In the present manuscript, we compared placental expression of multiple CYP family members among gravidae, and observed significantly increased CYP1A1 expression among smokers relative to controls (4.4-fold, p<0.05). To fully characterize CYP1A1 meCpG status, bisulfite modification and sequencing of the entire proximal 1 kb promoter (containing 59 CpG sites) was performed. CpG sites immediately proximal to the 5′-XRE transcription factor binding element were significantly hypomethylated among smokers (55.6% vs 45.9% meCpG, p=0.027), a finding which uniquely correlated with placental gene expression (r=0.737, p=0.007). Thus in utero tobacco exposure significantly increases placental CYP1A1 expression in association with differential methylation at a critical XRE element.

The effect of in utero exposure to a maternal high-fat diet on the peripheral circadian system of the fetus is unknown. Using mRNA copy number analysis, we report that the components of the peripheral circadian machinery are transcribed in the nonhuman primate fetal liver in an intact phase-antiphase fashion and that Npas2, a paralog of the Clock transcription factor, serves as the rate-limiting transcript by virtue of its relative low abundance (10- to 1000-fold lower). We show that exposure to a maternal high-fat diet in utero significantly alters the expression of fetal hepatic Npas2 (up to 7.1-fold, P<0.001) compared with that in control diet-exposed animals and is reversible in fetal offspring from obese dams reversed to a control diet (1.3-fold, P>0.05). Although the Npas2 promoter remains largely unmethylated, differential Npas2 promoter occupancy of acetylation of fetal histone H3 at lysine 14 (H3K14ac) occurs in response to maternal high-fat diet exposure compared with control diet-exposed animals. Furthermore, we find that disruption of Npas2 is consistent with high-fat diet exposure in juvenile animals, regardless of in utero diet exposure. In summary, the data suggest that peripheral Npas2 expression is uniquely vulnerable to diet exposure.

The relationship between dyslipidemia and hearing is unclear. This study was conducted to investigate whether elevated serum lipid levels impact auditory function in humans and in guinea pigs. In the human study, a cross-sectional study of 40 volunteers with dyslipidemia was conducted. Pure tone thresholds, distortion product otoacoustic emissions, and lipid profiles were analyzed. When controlled for patient age and sex, we found that elevated triglycerides were associated with reduced hearing. In the guinea pig study, a prospective study of animals fed a high-fat diet for 14 weeks was conducted. Although the high-fat diet led to a dramatic elevation in the average weight and total cholesterol in all animals (from 61 to 589 mg/dl), there were no meaningful changes in distortion product otoacoustic emission magnitudes. These results suggest that whereas chronic dyslipidemia associated with elevated triglycerides may reduce auditory function, short-term dietary changes may not. KeywordsCochlea; DPOAE; Hypercholesterolemia; Lipid Dyslipidemia is a well-known factor leading to coronary artery disease and atherosclerosis, and is a leading cause of myocardial infarction, stroke, and death in the United States. However, it is unclear whether dyslipidemia is associated with hearing loss. There are two primary lipoprotein fractions constituting total serum cholesterol: low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL). Serum LDL transports cholesterol from the liver, via the circulatory system, to be deposited in other organs, specifically the arteries and heart. In contrast, HDL transports cholesterol from the organs and tissues back to the liver via the circulatory system. The HDL transport system is thought to be beneficial to the cardiovascular system because it reduces the formation of cholesterol plaques in major arteries. Elevated LDL and decreased HDL characterizes coronary artery disease. In addition, an elevated serum triglyceride level is often present, indicating a high level of fat in the bloodstream.Cholesterol is a vital component of eukaryotic cellular membranes because it stabilizes them and modulates lipid and protein translocation across the membrane. Specifically related to Copyright © 2006 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript the cochlea, the lipid composition, fluidity, and stiffness of the outer hair cell lateral wall membrane have been shown to be important to its electromotile function and the cochlear amplifier (1-5). The lateral wall plasma membrane of the outer hair cell also seems to have less cholesterol than other cells (6). These data suggest that outer hair cell function may be particularly sensitive to dyslipidemic states. Histologic changes in the guinea pig cochlea in response to dyslipidemia have been identified in the strial marginal layer and in outer hair cells (7). Hypercholesterolemia may also decrease cochlear vascularity and cause hearing loss.We sought to determine whether dyslipidemia is a...