Publications
Please find below a list of our recent featured papers. You can click to access our PubMed or Google Scholar pages to find a complete list of journal article publications.
Sex-specific influences of APOEε4 genotype on hippocampal neurogenesis and progenitor cells in middle-aged rats
Female sex and Apolipoprotein (APOE) ε4 genotype are top risk factors for late-onset Alzheimer’s disease. This research investigates how these two risk factors might interact to influence biomarkers of brain health at middle age using a rat model. Compared to healthy controls, male rats with hAPOEε4 genotype showed reduced neural stem cell-like cells and new adult-born brain cells and increased microglia (marker of inflammation in the brain) at middle age. In contrast, female rats with hAPOEε4 genotype showed increased new adult-born neurons, but no changes in the other cell types, suggesting a possible compensatory response to the effects of hAPOEε4 at this time point. These results highlight the importance of examining sex-specific pathways in AD, as they may uncover unique protective mechanisms and inform development of tailored treatment strategies.
Estradiol-based Menopausal Hormone Therapy is associated with improved episodic and prospective memory scores in the Canadian Longitudinal Study of Aging
Introduction Menopause and menopausal hormone therapy (MHT) can influence cognition in postmenopausal women, but previous literature remains equivocal about their effects. MHT varies based on formulation and route of administration, both of which influence dose of estradiol (E2), the estrogen with the greatest affinity to the estrogen receptor. Transdermal E2 avoids hepatic conversion and results in higher plasma levels of E2 than oral E2 formulations. The cognitive domains of executive functions, episodic memory and prospective memory are diminished with age, but may be differentially sensitive to MHT, dependent on the brain regions recruited during the task. There is a lack of research investigating the effects of the age of menopause and estradiol (E2)-based MHT on different cognitive domains. Methods Using baseline data from the Canadian Longitudinal Study of Aging, we examined the associations between age of menopause and E2 based MHT on performance in three cognitive domains: episodic memory, prospective memory, and executive functions. Our cohort included 7,251 postmenopausal women who were cognitively healthy, with models adjusted for age, education, and body mass index. Results Earlier age at menopause was significantly associated with lower scores across all cognitive domains. However, for the executive functions domain, an earlier age of menopause was associated with lower scores only in those with grand parity (4 or more children) and there was a greater effect size among APOE ε4 carriers. We found that transdermal E2 was associated with higher episodic memory scores, whereas oral E2 was associated with higher prospective memory scores compared to no MHT. Neither administration route significantly affected executive function. Conclusion These results highlight the differential effects of E2-based MHT depending on route of administration and cognitive domain, and underscore the importance of considering age of menopause and individual characteristics such as reproductive history and genotype status. This work provides clarity to inconsistencies in the literature and informs the development of precision medicine approaches for cognitive aging in postmenopausal people.
Leveraging research into sex differences and steroid hormones to improve brain health
Sex differences, driven in part by steroid hormones, shape the structure and function of the brain throughout the lifespan and manifest across brain health and disease. The influence of steroid hormones on neuroplasticity, particularly in the adult hippocampus, differs between the sexes, which has important implications for disorders and diseases that compromise hippocampus integrity, such as depression and Alzheimer disease. This Review outlines the intricate relationship between steroid hormones and hippocampal neuroplasticity across the adult lifespan and explores how the unique physiology of male and female individuals can affect health and disease. Despite calls to include sex and gender in research, only 5% of neuroscience studies published in 2019 directly investigated the influence of sex. Drawing on insights from depression, Alzheimer disease and relevant hippocampal plasticity, this Review underscores the importance of considering sex and steroid hormones to achieve a comprehensive understanding of disease susceptibility and mechanisms. Such consideration will enable the discovery of personalized treatments, ultimately leading to improved health outcomes for all. Results: We categorized a total of 8,964 Project and Operating grant abstracts awarded from 2009 to 2020 based on their study of female-specific or a 2S/LGBTQ + populations or their mention of sex or gender. Overall, under 3% of grant abstracts funded by CIHR explicitly mentioned sex and/or gender, as 1.94% of grant abstracts mentioned sex, and 0.66% mentioned gender. As one of the goals of SGBA is to inform on health equity and understudied populations with respect to SGBA, we also found that 5.92% of grant abstracts mentioned female-specific outcomes, and 0.35% of grant abstracts focused on the 2S/LGBTQ + community. Conclusions: Although there was an increased number of funded grants with abstracts that mentioned sex and 2S/LGBTQ + health across time, these increases were less than 2% between 2009 and 2020. The percentage of funded grants with abstracts mentioning female-specific health or gender differences did not change significantly over time. The percentage of funding dollars allocated to grants in which the abstracts mentioned sex or gender also did not change substantially from 2009 to 2020, with grant abstracts mentioning sex or female-specific research increasing by 1.26% and 3.47%, respectively, funding allocated to research mentioning gender decreasing by 0.49% and no change for 2S/LGBTQ +-specific health. Our findings suggest more work needs to be done to ensure the public can evaluate what populations will be examined with the funded research with respect to sex and gender to advance awareness and health equity in research. Keywords: 2S/LGBTQ + health; CIHR; Canada; Female; Gender; Research funding; Sex; Women’s health.
Inflammatory signalling during the perinatal period: Implications for short- and long-term disease risk
During pregnancy and the postpartum, there are dynamic fluctuations in steroid and peptide hormone levels as well as inflammatory signalling. These changes are required for a healthy pregnancy and can persist well beyond the postpartum. Many of the same hormone and inflammatory signalling changes observed during the perinatal period also play a role in symptoms related to autoimmune disorders, psychiatric disorders, and perhaps neurodegenerative disease later in life. In this review, we outline hormonal and immunological shifts linked to pregnancy and the postpartum and discuss the possible role of these shifts in increasing psychiatric, neurodegenerative disease risk and autoimmune symptoms during and following pregnancy. Furthermore, we discuss how key variables such as the number of births (parity) and sex of the fetus can influence inflammatory signalling, and possibly future disease risk, but are not often studied. We conclude by discussing the importance of studying female experiences such as pregnancy and parenting on physiology and disease.
Estrogens dynamically regulate neurogenesis in the dentate gyrus of adult female rats
Estrone and estradiol differentially modulate neuroplasticity and cognition. How they influence the maturation of new neurons in the adult hippocampus, however, is not known. The present study assessed the effects of estrone and estradiol on the maturation timeline of neurogenesis in the dentate gyrus (DG) of ovariectomized (a model of surgical menopause) young adult Sprague–Dawley rats using daily subcutaneous injections of 17β-estradiol, estrone or vehicle. Rats were injected with a DNA synthesis marker, 5-bromo-2-deoxyuridine (BrdU), and were perfused 1, 2, or 3 weeks after BrdU injection and daily hormone treatment. Brains were sectioned and processed for various markers including: sex-determining region Y-box 2 (Sox2), glial fibrillary acidic protein (GFAP), antigen kiel 67 (Ki67), doublecortin (DCX), and neuronal nuclei (NeuN). Immunofluorescent labeling or co-labelling of BrdU with Sox2 (progenitor cells), Sox2/GFAP (neural progenitor cells), Ki67 (cell proliferation), DCX (immature neurons), NeuN (mature neurons) was used to examine the trajectory and maturation of adult-born neurons over time. Estrogens had early (1 week of exposure) effects on different stages of neurogenesis (neural progenitor cells, cell proliferation and early maturation of new cells into neurons) but these effects were less pronounced after prolonged treatment. Estradiol enhanced, whereas estrone reduced cell proliferation after 1 week but not after longer exposure to either estrogen. Both estrogens increased the density of immature neurons (BrdU/DCX-ir) after 1 week of exposure compared to vehicle treatment but this increased density was not sustained over longer durations of treatments to estrogens, suggesting that the enhancing effects of estrogens on neurogenesis were short-lived. Longer duration post-ovariectomy, without treatments with either of the estrogens, was associated with reduced neural progenitor cells in the DG. These results demonstrate that estrogens modulate several aspects of adult hippocampal neurogenesis differently in the short term, but may lose their ability to influence neurogenesis after long-term exposure. These findings have potential implications for treatments involving estrogens after surgical menopause.