Maternal immune cell gene expression associates with maternal gut microbiome, milk composition and infant gut microbiome
Background - Prepregnancy overweight and obesity promote deleterious health impacts on both mothers during pregnancy and the offspring. Significant changes in the maternal peripheral blood mononuclear cells (PBMCs) gene expression due to obesity are well-known. However, during pregnancy the impact of overweight on immune cell gene expression and its association with maternal and infant outcomes is not well explored. Methods – Blood samples were collected from healthy normal weight (NW, BMI 18.5-24.9) or overweight (OW, BMI 25-29.9) 2nd parity pregnant women at 12, 24 and 36 weeks of pregnancy. PBMCs were isolated from the blood and subjected to mRNA sequencing. Maternal and infant microbiota were analyzed by 16S rRNA gene sequencing. Integrative multi-omics data analysis was performed to evaluate the association of gene expression with maternal diet, gut microbiota, milk composition, and infant gut microbiota.  Results - Gene expression analysis revealed that 453 genes were differentially expressed in the OW women compared to NW women at 12 weeks of pregnancy, out of which 354 were upregulated and 99 were downregulated. Several up-regulated genes in the OW group were enriched in inflammatory, chemokine-mediated signaling and regulation of interleukin-8 production-related pathways. At 36 weeks of pregnancy healthy eating index score was positively associated with several genes that include, DTD1, ELOC, GALNT8, ITGA6-AS1, KRT17P2, NPW, POT1-AS1 and RPL26. In addition, at 36 weeks of pregnancy, genes involved in adipocyte functions, such as NG2 and SMTNL1, were negatively correlated to human milk 2'FL and total fucosylated oligosaccharides content collected at 1 month postnatally. Furthermore, infant Akkermansia was positively associated with maternal PBMC anti-inflammatory genes that include CPS1 and RAB7B, at 12 and 36 weeks of pregnancy. Conclusions – These findings suggest that prepregnancy overweight impacts the immune cell gene expression profile, particularly at 12 weeks of pregnancy. Further, deciphering the complex association of PBMC's gene expression levels with maternal gut microbiome and milk composition and infant gut microbiome may aid in developing strategies to mitigate obesity-mediated effects. Overall design: Mother-child dyads who were enrolled in the Growing Life, Optimizing Wellness study (Glowing, ClinicalTrials.gov ID:NCT01131117) at Arkansas Children's Nutrition Center were included in the study. Healthy women of 2nd parity, without any pre-existing conditions and who were with either normal weight (NW, BMI 18.5-24.9, n = 9-10) or with overweight (OW, BMI 25-29.9, n = 9-10) were enrolled in the study. Blood samples from the participants were collected at 12, 24, and 36 weeks of gestation for peripheral blood mononuclear cells. PBMCs were isolated using FICO/Lite-LyphoH density gradient method. Maternal dietary factors, gut microbiota at 36 weeks of gestaion, milk components (cytokines and macronutrients) at postnatal 2 weeks, 4 weeks, 2 months and 3 months, milk HMOs at postnatal 2 months and infant microbiome at 1 month of age published previously for the GLOWING study was used to associate with PBMC mRNA gene expression. Differential gene expression between NW and OW was determined using DESeq2 and pathway analysis was performed using DAVID. Association between gene expression and maternal and infant factors was calculated using integrative multi-omics and cross-omic analyses, emplyoing sparse partial least square regression-based modeling.