Preconception exposures and related epigenetic mechanisms in asthma and allergies

Can early puberty environment protect against asthma and allergies in future offspring? New results from this project suggest smoking, overweight and air pollution in your teens might be determinants of asthma and allergy in your future children, especially if you`re male. Despite decades of intensive research in asthma and allergies we do not know how to efficiently prevent these diseases, as the causes are not well understood. Our project uses a new approach by exploring environmental risks before conception, in previous generations. Epigenetic research shows environmental factors can influence which genes are switched on and off, and animal studies find that epigenetic information may be carried across generations through the germ cells. Our early analyses of humans suggested that young men’s environment, particularly during a vulnerable period in early puberty, might influence asthma and allergies in their future offspring. Inheritance of environmental risks across generations is difficult to study in humans since generations span decades. However, this proposal set out to address this challenge, establishing a multidisciplinary team of excellent researchers, the unique international multigeneration RHINESSA studies and high-quality national registries in Nordic study centers. The emergence of western welfare societies during the last century set an intriguing scene for this multi-generation research. We aimed to identify determinants of asthma and allergy that operate before conception (smoking and nicotine containing products, occupation, obesity, diet, anti-bacterial chemicals, microbial diversity, infections, greenspace, air pollution, indoor environment, mental health and quality of life), and to explore time windows of particular vulnerability and potential epigenetic mechanisms. The project generated a valuable cohort resource, including, among other, DNA methylation measurements in 3rd generation offspring, a clinical study of 4th generation offspring, air pollution and greenness estimations, helminth immunology, urinary measurements of personal product metabolites and registry data on specific infections. We developed complex statistical methods to analyze causal relationships and causal chains, while accounting for unknown sources of error for each generation and a multi-centre multi-generation structure. Our mouse studies addressed questions raised from our human studies. Collaboration with historians and textile researchers enlighten exposures over the last century when the parents and grandparents in the RHINESSA studies were born and raised. Our published work supports that father's smoking starting in prepuberty gives more asthma, lower lung function and altered DNA methylation patterns in his future children. We find this in analyzes of human data, both using simple and complex causal statistical methods; in analyses of DNA methylation showing how the father's smoking leave a "signature" on DNA methylation in his adult offspring; and in mouse studies uncovering mechanisms for how smoking young male mice affects sperm and body weight in pups. Father’s smoking was also related to increased fat mass in his sons. Further, even low levels of air pollution in a childhood/teens, and mother's work with disinfectants and cleaning products before conception (in professions such as cleaner, nurse, hairdresser, chef etc) were associated with more asthma (hayfever) in future children. Regarding adolescent obesity, solid analyses revealed more asthma and lower lung function in children of men who became overweight before puberty. Regarding infections, parental childhood tuberculosis as well as raised antibody titre to the parasite Toxocara were associated with more asthma in offspring. Parents' and grandparents' upbringing on a farm was not associated with children's asthma/ allergy. Human studies often use data reported about family members. Validating such information, we found reporting of parental smoking, parental asthma and offspring asthma is very good, mother’s reporting of her births was also mostly very precise, while reporting of parental place of upbringing was less precise. A tool based on body silhouettes back in time was found to reflect previous overweight very well when validated against measured height and weight. During the project period we have published several groundbreaking scientific articles, summarized results in reviews, presented the results in various settings, and obtained extensive media coverage on several occasions. Seven completed and some ongoing PhD thesis are contributing to the project. Overall, the project supports that asthma and allergies origins partly before conception and, in particular, in male prepuberty. This gives new understanding on health in general as well as on the asthma and allergy epidemic, and could profoundly alter policies in pursue of optimal public health.

The ultimate aim of our research is to generate the knowledge that is needed to transform public health strategies in order to efficiently optimising public health by targeting vulnerable periods of importance for future children and grandchildren. By now, the project has achieved the following outcomes and impact • Our research network, anchored at the University of Bergen, is established as a world-leading, interdisciplinary and international centre in multi-generation research on asthma and lung health, in particular, on the importance of father’s prepuberty exposure on offspring health and disease. • We have established an important high-quality multigeneration cohort resource (including large numbers of well-characterised offspring-parent pairs, valuable measurements of e.g. DNA methylation in 1600 offspring of well-characterised parents, and a rich biobank of diverse samples), and conducted validation analyses on reporting about family members. • We have achieved to integrate expertise and methodology of clinicians, epidemiologists, statisticians, epigeneticists and experimental researchers, to develop reliable results on the preconception origins of respiratory health and disease. • Our network has developed statistical methodology for causal inference in multigeneration research, contributing importantly to advance the area of causal statistical modelling based on observational data. • Our research activity has increased the visibility of this research field and inspired further research with this focus. • Our results are becoming disseminated to widely different stakeholders and user groups, e.g. in a policy document to the UK Parliament, and a Norwegian popular book regarding clothing in teenage boys. Outcomes and impacts of the project results that are anticipated • The established cohort resource, statistical-epidemiological methodology and interdisciplinary approach are useful for further multi-generation research, and contribute to inspire further developments of this research field. Our validation studies increase the utility of less extensive data resources. • The understanding of a preconception origin of health and disease – that our lifestyles and behaviours may influence the health of our future children – represents a new paradigm in research and opens for a new paradigm in public health strategies. For example, an intervention aimed at promoting healthier choices in children approaching puberty may improve lifelong health in the individuals themselves as well as in their future offspring, and possibly further generations. Thereby, more health can be gained from fewer resources – a sustainable approach to public health.

The incidence of asthma and allergies increased exponentially with industrialization and urbanization, giving a staggering burden of disease that affects individuals from early childhood. Despite decades of intensive research, we are yet unable to prevent these conditions as the causes are not well understood. A new approach is urgently needed. Our early analyses suggest that the environment before conception might be key to development of asthma and allergies, not least through future fathers, and that puberty might be an important vulnerability period. If true, this will have ground-breaking impact on understanding the asthma and allergy epidemic, and profoundly alter policies in pursue of optimal public health. The concept of inheritance of environmental risks across generations is novel, and by its nature, difficult to study in humans where generations span decades. However, we have established a high-quality original interdisciplinary team that will utilize and develop unique data resources and methods to address this challenge. This proposal aims to identify determinants of asthma and allergy that operate before conception, time windows of particular susceptibility, and epigenetic mechanisms by which these act. I will use cutting-edge epidemiological, epigenetic and experimental methods to address expertly assessed exposures (oral moist tobacco, smoking, occupation, obesity, diet, anti-bacterial chemicals, microbial diversity and infections, greenspace, air pollution, indoor environment, mental health and quality of life). The Nordic countries are uniquely placed for multi-generation research in humans, with high-quality national registries covering the last century - the period of the emerging welfare society. This proposal provides an opportunity for my team to build excellence and become a leading international research group in multi-generation research, a field in which Norway has a potential to be a world key player.