Date Published: September 26, 2019
Publisher: Public Library of Science
Author(s): KaLynn Harlow, Christina R. Ferreira, Tiago J. P. Sobreira, Theresa Casey, Kara Stewart, Juan J. Loor.
We hypothesized that postnatal development of the vagina is impacted by early nutritional environment. Our objective was to determine if lipid profiles of vaginal swabs were different between postnatal gilts suckled by sow or fed milk replacer the first 48 h after birth, with or without a lard-based fat supplement. Gilts (>1.3 kg) were selected at birth across 8 litters and assigned to one of four treatments: 1) suckled by sow (S, n = 8); 2) suckled by sow plus administration of a fat supplement (SF, n = 5); 3) bottle-fed solely milk replacer (B, n = 8); or 4) bottle-fed solely milk replacer plus administration of a fat supplement (BF, n = 7). At 48 h postnatal, vaginal swabs of gilts were taken with a cytology brush, and lipids were extracted for analysis using multiple reaction monitoring (MRM)-profiling. Lipids extracted from serum collected at 48 h from gilts, milk collected at 24 h from sows, and milk replacer were also analyzed with MRM-profiling. Receiver operating characteristic curve analysis found 18 lipids recovered from vaginal swabs that highly distinguished between S and B gilts [area-under-the-curve (AUC) > 0.9], including phosphatidylethanolamine with 34 carbons and four unsaturations in the fatty acyl residues [PE (34:4)]. Twelve lipids from vaginal swabs highly correlated (r > 0.6; p < 0.01) with nutrition source. Lipids with greater abundance in milk replacer drove association. For example, mean intensity of PE (34:4) was 149-fold higher in milk replacer than colostrum. Consequently, PE (34:4) was found to have 1.6- and 2.12-fold higher levels in serum and vaginal swab samples (p < 0.001), respectively, of B gilts as compared to S gilts. Findings support that vaginal swabs can be used to noninvasively study effects of perinatal nutrition on tissue composition.
Early nutritional environment affects long term health and fertility. In swine, colostrum ingestion is essential for postnatal piglet survival, growth, and development because it provides immunity, nutrients, energy, and bioactive factors [1, 2]. The window of opportunity for milk-borne bioactive factors to influence neonate development is limited, and primarily occurs prior to closure of tight junctions between cells lining the piglet’s gut. Closure of the gut occurs by 48 h postnatal . During the first 48 h postnatal, piglets ingest up to 30% of their body weight in milk . This time-period is a critical developmental period for the gilt reproductive system, including the formation of uterine glands, otherwise known as adenogenesis [5, 6]. Colostrum ingestion significantly affected the developmental trajectory of uterine tissue [7–10]. Replacement gilts with less colostrum consumption than littermates as indicated by blood immunocrit values had reduced litter sizes relative to other sows [11, 12]. Colostrum-deprivation also resulted in significantly different patterns of uterine gene and protein expression .
Screening phase II Method 1 analysis aimed at identifying lipids that discriminated between gilts which suckled sow colostrum versus gilts fed milk replacer the first 48 h postnatal. ROC curve analysis found 18 lipids with AUC ≥ 0.9. The AUC value is a measure of the usefulness of a test, in terms of sensitivity and specificity . Biomarkers with AUC values from 0.9–1.0 are excellent, 0.8–0.9 are good, 0.7–0.8 are fair, and 0.6–0.7 are poor . These 18 lipids are thus excellent candidate markers to detect differences between suckled gilts compared to those that consumed only milk replacer. The most discriminatory lipids identified in Method 1 exhibited higher intensities in bottle-fed animals when compared to suckled gilts. We found a positive correlation of ion intensities of MRMs between nutrition source and swabs of suckled versus bottle-fed gilts, and nutrition source and serum of suckled versus bottle-fed gilts. Comparative analysis of mean ion intensities of the most highly correlated lipids found much higher intensities of lipid signals in milk replacer than in 24 h colostrum samples, and correspondingly higher intensities in serum and vaginal swabs of bottle-fed animals relative to suckled gilts.
Vaginal swab lipidomes were significantly affected by composition of early postnatal diet. Multiple lipid molecules were differentially abundant between gilts exposed to colostrum versus gilts fed milk replacer and gilts provided a fat supplement versus no fat supplementation during the first 48 h of life. Several lipids collected from vaginal swabs were highly correlated with the nutrition source a piglet ingested. Lipids more abundant in milk replacer appeared to be driving the association in the current study. These findings demonstrated that lipid composition of neonatal diet affects tissue composition and thus may affect development, function and overall health and fertility. Moreover, while data support the efficacy of using MRM-lipid profiling of vaginal swabs to detect differences in early postnatal nutritional exposures, findings also highlight a need to modify our approach to determine if biomarkers of colostrum intake can be specifically identified in vaginal swab samples.