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Placental Transcripts Shift With Maternal Obesity

NEW YORK (GenomeWeb) – Mothers-to-be who are obese prior to becoming pregnant may have distinct gene expression patterns in their placental transcriptome at the end of their pregnancy, new research suggests.

As part of an observational cohort study related to maternal weight and pregnancy, researchers from Spain, Sweden, and Germany did array-based transcriptomic profiling on placental tissue samples collected at term from five obese and five normal weight women in Spain. Their results, published in PLOS One yesterday, revealed differential expression for dozens of placental genes in women who were obese before becoming pregnant.

Indeed, maternal obesity seemed to coincide with altered representation of genes in pathways involved in everything from inflammation and immunity to lipid metabolism and blood vessel formation, the team noted, including some genes previously implicated in pregnancy problems such as pre-eclampsia.

"Our study results demonstrate that maternal pre-pregnancy obesity has adverse effects on the placental transcriptome, where previously characterized molecules and molecular pathways involved in placental development and function were dysregulated," senior author Cristina Campoy, a pediatrics researcher affiliated with the University of Granada and the Biohealth Institute of Granada, and her co-authors wrote. "In addition, several new dysregulated molecules and signaling pathways were identified."

Using Affymetrix arrays, the researchers tracked genome-wide transcriptome patterns in placenta samples collected after at-term deliveries from 10 women between the ages of 25 and 35 years old: five women with normal body mass index (BMI) measurements before pregnancy and five women with pre-pregnancy BMIs classified as obese.

The team did not see significant differences in pregnancy outcomes, women with elevated BMIs tended to have babies with slightly bigger, heavier babies. In the placental tissue, it saw 72 genes with differential expression in samples from the obese and normal weight women. Of those, 11 genes were more active in placentas from obese women, while 61 genes appeared to have dialed down expression in the heavier mothers.

The researchers noted that immune-, immunoglobulin-, or inflammation-related genes such as CCL2, HLA-DRB1, or IL1R2 were overrepresented in the differentially expressed gene set, consistent with alterations in pro-inflammatory pathways that other teams have described in human or mouse pregnancies marked by maternal obesity. They also saw expression differences in genes involved in lipid metabolism, glucocorticoid receptor signaling, angiogenesis, and other cancer-related processes. 

The authors cautioned against reading too much into results from a relatively small number of participants. Even so, they said the findings "provide a fundamental resource for better understanding the complex effects of maternal pre-pregnancy obesity on placental transcriptome."