Blood protein levels shift significantly from childhood through early adulthood

Blood protein levels change markedly already during childhood and adolescence, and differences between girls and boys become increasingly pronounced with age. This is shown by a new study in Nature Communications from Karolinska Institutet in collaboration with colleagues from SciLifeLab and KTH Royal Institute of Technology. The results suggest that blood protein levels change over the course of a lifetime, rendering adult reference values inadequate for children and adolescents.

In the study, the researchers analysed blood samples from 100 participants in the population-based BAMSE cohort at ages 4, 8, 16 and 24 years. Using advanced protein technology, over 5,000 proteins were measured, of which just over 3,500 could be tracked over time. More than half of these proteins changed with age even during childhood.

The greatest changes were observed between the ages of 8 and 16, a period that coincides with puberty. Many proteins increased sharply during this time, only to decrease again in early adulthood, whilst others showed more gradual increases or decreases from childhood to adulthood.

Our study shows that reference values from adults cannot be used when interpreting protein levels in children and adolescents. Protein levels are strongly age-dependent even early in life, says one of the lead authors.” 

Sophia Björkander, assistant professor and docent at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet

The researchers also identified clear gender differences. In early childhood, the differences were few, but from adolescence onwards they increased markedly. By the age of 24, around 30 per cent of proteins differed between women and men, including those linked to growth, metabolism, the immune system and reproductive processes.

”Gender differences become very clear from adolescence and early adulthood. This shows that both age and gender are fundamental biological factors that must be taken into account when proteins are used as biomarkers”, says Sophia Björkander.

Blood proteins are used as biomarkers

Today, blood proteins are widely used as biomarkers to detect, for example, inflammation, hormonal imbalance, cardiovascular disease and metabolic disorders. An important finding from the study is that different levels of proteins in children may reflect normal development rather than disease.

”By mapping protein development, we are creating a reference that can be used to identify early deviations. This opens up possibilities for risk assessment of chronic diseases and more personalised medicine”, says senior/last author Erik Melén, project leader at BAMSE and professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet.

The researchers point out that the number of participants is limited and that the results primarily apply to a relatively homogeneous population.

The study is part of the Human Disease Blood Atlas, which is a resource within the Human Protein Atlas and is based on the Swedish BAMSE cohort. The BAMSE project is jointly run by the Department of Clinical Science and Education, Södersjukhuset and the Institute of Environmental Medicine, both at Karolinska Institutet, as well as the Centre for Occupational and Environmental Medicine, Region Stockholm.

The research has been funded by, among others, the Swedish Research Council, Region Stockholm, the Swedish Heart-Lung Foundation and the Knut and Alice Wallenberg Foundation.