Associations of whole blood gene expression with menopausal status and hormone therapy use in the NOWAC postgenome cohort

Abstract We aimed to evaluate associations of whole blood gene expression and immune cell composition with menopausal status and hormone therapy (HT) use among women who had never been diagnosed with cancer in the Norwegian Women and Health (NOWAC) postgenome cohort. This cross-sectional study comprised microarray-based gene expression profiles obtained from the whole blood samples of 1,428 women, estimated white blood cell (WBC) proportions, as well as relevant information from questionnaires. We used gene-wise linear regression models to identify differentially expressed genes (DEGs), and functional enrichment analyses to determine their corresponding biological functions. The study’s novel evaluation of blood gene expression profiles in relation to menopausal status revealed over 1,400 DEGs in the post-vs-premenopausal comparison; the DEGs’ biological functions were primarily linked to immune responses, cell-cell adhesion, cognition, muscle system processes, and reproduction. Adjusting for estimated WBC proportions substantially reduced the number of DEGs to 26, and terms related to immune responses in biological functions were no longer enriched. Additionally, separate analyses of postmenopausal women identified over 200 DEGs associated with HT use, and these DEGs were linked to oestrogen-dependent gene expression and RHO GTPases signalling. The distribution of several WBCs varied across menopausal status and HT use groups. This is the first study to investigate associations between whole blood gene expression and menopausal status, and the largest to investigate associations to postmenopausal HT use. Menopause-related transcriptional differences were largely driven by changes in circulating WBC composition, whereas HT use was associated with a less distinct, oestrogen-responsive gene expression signature resembling a more premenopausal profile. These findings highlight the systemic impact of menopause and the central role of immune cell composition in whole blood gene expression during menopause and suggest that oestrogen status, whether endogenous or via HT, has measurable systemic molecular effects.