Abstract
World-wide, millions of women enter preterm labor or have small newborns. Effective biomarkers are needed to identify women at risk for these adverse outcomes. A time and cost effective way to examine any potentially new biomarkers in samples collected during prior studies or trials that had been assayed for other metabolites would be highly useful. Thus, the current study aimed to determine if samples that had been previously thawed and re-frozen could be re-assayed for novel biomarkers, those being lipoprotein composition (sizing, proteome, lipids) and combined cholesterol and cytokine concentrations. Fasting blood was collected from 51 young non-pregnant women and plasma was analyzed for lipoprotein composition and cytokine concentrations after multiple freeze/thaw cycles in the cold or at room temperature and after being stored for 18 months. Plasma LDL-C, HDL-C, total cholesterol, and triglyceride concentrations decreased <6-7% (cholesterols) or <20% (triglyceride) after 7 thaws in the cold, 3 thaws at room temperature, and after 18 months of storage. As these decreases were less than day-to-day reported variation of lipids, they do not appear to be physiologically significant. Cytokine (IL-6, TNF α, IL-8, IL-1β) and hsCRP concentrations decreased by 22%, 8%, 8%, 22%, and 35%, respectively; only IL-6, IL-1β and hsCRP concentrations showed significant decreases greater than day-to-day variations of 20%. For measured triglyceride and cytokine, but not cholesterol concentrations, decreases with freeze/thaw cycles were greater when concentrations were elevated. Multiple thaws also led to changes in lipoprotein sizing, specifically to a shift from medium- and large-sized HDL particles to small-sized HDL particles and from large LDL to IDL. No changes occurred for VLDL particle numbers. Though particle sizes changed, the HDL proteome did not change with multiple thaw cycles or after long term storage. Overall, the results demonstrate that it is possible to use previously obtained frozen samples for plasma cholesterol and triglyceride levels and the lipoprotein proteome, and lipoprotein sizing and cytokine concentrations if one knows the history of the sample as changes should be relative to one another.
Highlights
New biomarkers are needed to identify women at risk for adverse pregnancy outcomes, including those having infants with low birth weight (LBW) or that are born preterm
In the past five years, there are over 800 articles in Pub Med evaluating potential biomarkers for preterm birth and over 350 articles evaluating potential biomarkers for low birth weight infants
The greatest effects occurred after 7 thaws in the cold and included percent decreases of 3.5 ± 0.5, 2.2 ± 0.2, 4.5 ± 0.7 and 8.6 ± 1.1% for LDL-C, HDL-C, total cholesterol, and triglyceride concentrations, respectively
Summary
New biomarkers are needed to identify women at risk for adverse pregnancy outcomes, including those having infants with low birth weight (LBW) or that are born preterm (preterm birth; PTB). World-wide there are greater than 22 million LBW and 15 million PTB infants born each year [1,2]. Preemptive identification of women at risk of adverse pregnancy outcomes would allow for women at high risk to be targeted for monitoring or interventions to improve outcomes. This is especially true in resource-poor settings where a majority of the infants with LBW or PTB are born [1,2] and where medical help is not readily available. In the past five years, there are over 800 articles in Pub Med evaluating potential biomarkers for preterm birth and over 350 articles evaluating potential biomarkers for low birth weight infants
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