Comparing the Phenotypes and Trajectories of Human Aging Associated with Exercise or Inactivity

Simply Put

This project aims to increase our understanding of the biology of human aging. As many aspects of getting older are also associated with physical inactivity, this study will investigate groups of both sedentary and physically active young and older people to separate out the effects of aging from the negative effects of inactivity. With a specific focus on muscle and the immune system, our project will combine a unique series of physiological, cellular and molecular investigations to provide further insight in to how the body ages.

Description

This research project seeks to better understand the physiology of human aging and, in particular, to disentangle aging from inactivity-mediated processes. It will perform detailed investigations on young and old, active and inactive, males and females.  There is a particular focus on skeletal muscle and the immune system. The project will use a range of approaches from whole-body physiology to deep molecular phenotyping of cells to address the research aims.

The aged active cohort is represented by 125 master cyclists (84 male, 41 female) first sampled in 2012/13 when they were 55-79 years old. Re-testing of the master cyclists is planned to begin in April / May 2021 when the participants will be 64-88 years old. This will form a nested and unique longitudinal study within the larger cross-sectional project.

In addition to the active older participants, a new cohort of age-matched sedentary individuals (male and females) will be studied in 2021.  This will provide a cross-sectional comparison with the active cohort. The amount of physical activity will be quantified through, training diaries, questionnaire and actigraphy in the week prior to testing. In addition, two groups of young participants aged 18-35 years will be also investigated in this study: 20 young cyclists (10 males and 10 females) and 20 sedentary individuals (10 males and 10 females). This will enable the differentiation of the effects of aging from inactivity processes.

The following analyses will be carried out:

1. Full physiological phenotyping for all cohorts will include measures of: cardiorespiratory fitness (VO₂max), O2 uptake kinetics, blood pressure, lung function, body composition and bone mineral density (DXA), muscle strength and power, nerve conduction velocity, balance, cognitive function,  as well assessment of nutrition, sleep and quality of life.
2. Blood samples will be taken for indices of metabolic health, hormonal status and inflammation.
3. Immune cells will be isolated and phenotype to assess the degree of immune aging.
4. Muscle biopsy samples will be analysed for changes in muscle fibre size, type mitochondrial complex protein content, capillarisation as well as markers of senescence.
5. In addition to muscle, fat and skin biopsies will be obtained assessed for markers of aging process e.g. DNA methylation.  In a collaboration with Dr Maxmim Artyomov (Washington University School of Medicine in St Louis) samples obtained from this study be profiled using multi-omics approaches; including single-cell RNA-seq including TCR-repertoire and CyTOF chromatin profiling, single-cell nuclear RNA-seq, and Whole Genome Bisulfite Sequencing for epigenetic changes.
6. The molecular data from the tissue samples will be integrated with the in vivo physiological data obtained from the participants.

Results

The aims of the research project were twofold.

With a particular focus on skeletal muscle and the immune system, this project aimed to investigate:

In a longitudinal study: the effects of 9 years of healthy, active ageing on biological function in a cohort of recreational cyclists of 82 people.

Many of the older cyclists were tested 9 years ago when they were aged 55 to 79 years of age and in this study, they have been re-tested aged 64 to 88 years. Of 125 master cyclists first sampled in 2012/13, 82 returned to the laboratory for repeat investigation. A significant number of the participants who returned after nine years did not meet the original health criteria, but importantly all were still cycling. Based on their health condition they were divided into 3 groups:

Green (Optimal Ageing): Those who remained healthy with no new diseases – 23 males and 12 females, total 35 people.

Amber (Successful Ageing): Those who returned with a disease, but which was controlled and not predicted to affect their ability to exercise – 14 males and 10 females, total 24 people.

Red (Compromised Health): Those with new conditions likely to impact exercise capacity and compromise physiological function – 16 males and 7 females, total 23 people.

In a cross-sectional study: the effects of healthy active ageing by comparing the older exercising cohort with three groups of newly recruited participants, total 172 people:

healthy older exercisers aged 64-88 yrs – 44 males and 26 females, total 70 people;

healthy older non-exercisers also aged 64-88 yrs – 27 males and 30 females, total 57;

young cyclists aged 18-35 yrs – 12 males and 10 females, total 22; and

young non-exercisers aged 18-35 yrs – 11 males and 12 females, total 23 people.

To best match the health status of older non-exercisers with the older exercisers from the longitudinal study, the master cyclists from the red group were excluded and replaced with newly recruited older exercisers who matched the green health criteria, providing a total of 70 people in the healthy older exerciser group.

Overall, 195 people across the different young and old, exerciser and non-exerciser groups were tested in 2021-2024.

Sample Collection Overview (2021-2024)

In addition to the planned physiological tests and collection of blood and tissue samples, stool, urine and saliva samples were also collected.

Full physiological phenotyping together with deep profiling of muscle biopsy samples were performed at King’s College London, while downstream multiomic profiling (PBMC single-cell RNA-seq, tissue Multiome-seq, plasma proteomics, metabolomics, cytometry & cytokines, WGBS DNA methylation profiling) of collected samples is ongoing at Washington University School of Medicine in St Louis. The immunological analysis together with assessment of gut microbiome composition is ongoing at University of Birmingham.

Integrated analysis of collected data (scRNA-seq, snATAC-seq, Somalogic, Olink, Clinical Biochemistry, Cytokines, Cytometry, VO_2peak, DEXA, Physiology, etc.) is in process.