August 15, 2023 | Researchers at the University of Virginia School of Medicine have identified early biomarkers linked to preeclampsia that could help OB/GYNs better understand which of their patients are at risk of developing the potentially deadly pregnancy complication and perhaps help get at why the condition occurs in the first place. It is currently a bit of a guessing game, according to Charles E. Chalfant, Ph.D., professor of medicine in the division of hematology and oncology and the department of cell biology.
When pregnant women have at-risk markers of preeclampsia—e.g., high body mass index, hypertension, and a prior preeclamptic pregnancy—they have a 50-50 chance of staving off eventual development of the disease by taking low-dose aspirin, he explains. Disease occurrence among the other 50% in the group flagged as being at high risk, as well as women affected by preeclampsia despite the absence of warning signs, remain clinical conundrums.
As recently reported in the Journal of Lipid Research (DOI: 10.1016/j.jlr.2023.100377), Chalfant and his colleagues have come up with a simple blood test predictive of disease development based on quantitative changes in bioactive lipids, and it works even for women on aspirin therapy. The signature of the disease is based on eicosanoids and sphingolipids, two classes of lipids that have been implicated in a range of adverse pregnancy outcomes, quantified in plasma samples collected prior to 24 weeks of gestation.
Intriguingly, the lipid profiles of women varied to a statistically significant degree depending on their self-designated race, Chalfant reports, which could mean that in the future treatments will need to be better tailored to specific patients. Self-identified subjects of Western European descent who developed preeclampsia showed significant decreases in the anti-inflammatory omega-3 polyunsaturated fatty acid, eicosapentaenoic acid, and docosahexaenoic acid, while subjects of self-designated Hispanic origin showed significant and specific increases in the hypotensive agent prostaglandin A2.
For women who self-designated as black, the lipid profile of preeclamptic patients was like the nonracially stratified data. But this was the predominant patient population for the study, Chalfant quickly adds.
The study was also small (57 pregnant women) and “slightly underpowered.” It is now being expanded at the University of Virginia to see if these race-specific, lipid-based biomarkers for preeclampsia can be reproduced.
The collaborative biomarker study came to be thanks to Jerome Strauss III, M.D., Ph.D., former dean of Virginia Commonwealth University (VCU) School of Medicine (now at the University of Pennsylvania) and a longtime researcher and OB/GYN. Chalfant was previously affiliated with VCU, and his colleague and co-author Scott Walsh is a professor of obstetrics and gynecology there.
One of the biggest breakthroughs on the preeclampsia front was the discovery in the 1980s that it could be prevented in half of high-risk pregnant women simply by taking low-dose aspirin. Preeclampsia is a serious and dangerous condition that can result in premature delivery, seizures, and even death, says Chalfant, noting that it is the world’s second-leading cause of maternal death with more than 70,000 lives lost each year. Symptoms—including high blood pressure, kidney problems, and abnormalities in blood clotting—typically appear after 20 weeks.
Approximately 5% to 7% of pregnancies in the United States will be preeclamptic, he adds. But the incidence of preeclampsia has been on the rise and may be related to the higher prevalence of predisposing disorders that include hypertension as well as diabetes, obesity, delay in childbearing, and the use of artificial reproductive technologies (Nutrition Reviews, DOI: 10.1111/nure.12055).
The targets of aspirin therapy are a pair of biomarkers, thromboxane and prostacyclin, continues Chalfant. But since low-dose aspirin doesn’t necessarily stop the disease from developing, the women taking it remain at high risk and need to be closely monitored while researchers continue their quest for other disease-signaling lipids in the blood.
Pregnant women who haven’t been flagged as high-risk but nonetheless develop preeclampsia might fly totally under the radar, he says. Their OB/GY would have no idea whether to put them on low-dose aspirin and wouldn’t do so without cause due to potential side effects. The hope now is that the newly discovered set of lipid biomarkers will make their way to the clinic as a blood test to help doctors decide which patients to refer to a high-risk OB/GYN clinic and put on aspirin therapy.
Only over the last decade has the technology even existed to look at between 50 and 100 of these bioactive lipids in a single run “quantitatively and with really high sensitivity,” says Chalfant. The research team used targeted ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry.
Many of the lipids sought out in the latest study were for years exceedingly difficult to quantify consistently and accurately, since measurements had to be done one laborious assay at a time, he adds. Even today, the lipidomics capabilities required for the high-throughput analysis of eicosanoids and sphingolipids is limited in the United States.
Eicosanoids are a class of lipids that are targeted by aspirin as well as ibuprofen and COX-2 inhibitors used to treat a variety of conditions. Within that class are many bioactive molecules unaffected by aspirin, meaning the lipid will persist and usually bind to a receptor on the cell surface and signal itself to regulate anything from coagulation to pain response—or, as was important in the latest study, maturation of the placenta, Chalfant says.
Among the multiple types of sphingolipids examined by the research team were ceramides, sometimes referenced in commercials for their ability to build strong, resilient hair, he notes. The study’s overall focus was on signaling lipids, which are base molecules capable of prompting physiological functions within cells by binding themselves to specific proteins.
A reduced level of ceramide-1-phosphate (C1P) may well have wide-ranging effects on the ability of the placenta to grow, based on various studies that have been done on that lipid, says Chalfant. If it proves to play a causative role, new therapies might be developed to increase the level of C1P.
Levels of an eicosanoid known as dihydroxyeicosatrienoic acid (DHET) was found to be lower in pregnant women who later developed preeclampsia, suggesting that adding it back could potentially be therapeutic, he continues. Conceivably, the DHET is shutting down a pathway for an uncomplicated pregnancy by blocking the production of other downstream bioactive lipids.
Conversely, a heightened level of the eicosanoid known as 20-hydroxyeicosatetraenoic acid (20-HETE) previously linked to cardiovascular issues was newly identified as a biomarker of preeclampsia, which is itself a hypertensive disorder, Chalfant notes. But the link was observed only in the women stratified into the at-risk pregnancy group. “This may start to give us some picture about how we may be able to help the 50% of women who don’t respond as well to aspirin therapy.”
The lipidomic approach could be adapted relatively quickly to the clinic, he says. Clinical tests for steroid hormones, a major class of lipids, are measured with a similar technology. An expansion of the small, published study may be enabled by a repository of roughly 430 patient samples held by the OB/GYN department at the University of Virginia, says Chalfant. “They are all from a general clinic, which makes this a great validation set.”
Based on prevalence statistics, anywhere from 25 to 35 of those pregnancies should be preeclamptic, he says. Researchers hope to run these samples over the next six to eight months and use their lipidomics approach to try and pinpoint those patients based on the pre-identified markers.
Discussions are underway with colleagues at the University of Pennsylvania about the possibility of detecting these bioactive lipids in extracellular vesicles that may be emitted from the placenta, providing their own early warning sign of whether a pregnancy will go physiologically awry, says Chalfant.
If the latest study findings are replicated and validated, one can make the case that the American College of Obstetricians and Gynecologists (ACOG) may need to update its standard-of-care recommendations for who does and doesn’t get aspirin therapy. A certified laboratory may then become interested in developing a clinical-grade test that can be widely assessed by healthcare providers.
Lipids are not just fatty compounds, Chalfant points out. They can also be immunogenetic, making it possible to develop a lysis assay based on the same process used by some at-home pregnancy dipstick tests.
Chromatography might also be deployed at the point of care to detect preeclampsia-associated lipids in a pinprick of blood, much as it is used currently to measure cholesterol during routine physicals, he says. Such tests could easily be sent for processing by major clinical laboratories such as Labcorp and Quest Diagnostics.
All the work related to the preeclampsia biomarkers has been heavily subsidized by the National Institutes of Health. “Your tax dollars are doing well,” says Chalfant. “We do this research because we genuinely want to answer these questions that are going to benefit patients... in hopes that we can give them better [pregnancy] outcomes.”