DHA Supplementation Attenuates Inflammation-Associated Gene Expression in the Mammary Gland of Lactating Mothers Who Deliver Preterm

Abstract

Background: In a randomized trial of DHA supplementation to lactating mothers who delivered preterm, there were significant increases in DHA status in the mother and her infant.

Objectives: Our objective here was to characterize the mammary gland transcriptomes from the above study. We hypothesized that proinflammatory gene expression would be attenuated in the increased DHA group compared with the standard DHA group.

Methods: In the original trial, mothers delivering at <29 wk gestation at the University of Cincinnati Medical Center and intending to express their milk were randomly assigned to supplementation with 200 mg/d DHA (standard group: STD) or 1000 mg/d DHA (experimental group: EXP) within 7 d of delivery. Here, we conducted RNA-seq transcriptome analysis of n = 5 EXP and n = 4 STD extracellular mammary mRNA samples extracted from the fat layer of milk samples obtained 4 wk postenrollment. Transcripts were assessed for differential expression (false discovery rate adjusted P value <0.05) and clustering between EXP compared with STD groups. Ontological analysis of all differentially expressed genes (DEGs) was performed with Toppcluster.

Results: There were 409 DEGs. We observed 5 main groups of biological processes that were upregulated, including those associated with improved immune regulation and management of oxidative stress; and 3 main groups of biological processes that were downregulated, including 1 associated with immune dysregulation. For example, we observed upregulation of inflammation-inhibiting genes including NFKB inhibitor alpha (NFKBIA; fold-change (FC), adjusted P value: FC = 1.70, P = 0.007) and interleukin-18 binding protein (IL18BP: FC = 2.2, adjusted P = 0.02); and downregulation of proinflammatory genes including interleukin 7 receptor (IL7R: FC = -1.9, adjusted P = 0.02) and interleukin 1 receptor like 1 (IL1RL1: FC = -13.0, adjusted P = 0.02).

Conclusions: Increased DHA supplementation during lactation can modulate the expression of inflammation-related genes within the mammary gland. This might translate to milk composition with a more optimal inflammasome profile. Future research with a larger clinical trial and greater interrogation of clinical outcomes is warranted.

Keywords: RNA sequencing; cytokine; docosahexaenoic acid; human milk; inflammation; lactation physiology; omega-3 fatty acids; premature birth; transcriptome.

FIGURE 1

Derivation of final transcriptome set from the randomized allocation of mothers to the experimental group (EXP: 1000 mg/d DHA) and standard group (STD: 200 mg/d DHA) that took place in the original randomized controlled trial (RCT) (15).

FIGURE 2

Ontological themes that are upregulated in the experimental group (EXP: 1000 mg/d DHA, n = 5) or standard group (STD: 200 mg/d DHA). Weight of line denotes strength of significance. Color indicates ontology category as follows: lime green = pathway, teal = biological process, light teal = mouse phenotype, sage green = human phenotype, lavender = molecular function. Group labels represent our description of overall ontology theme. Ontological analysis of differentially expressed genes was performed in Toppcluster, which draws from >30 ontological repositories, and the figure was generated in Cytoscape.