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Multiomics Study Traces Molecular Effects of Endurance Exercise Training in Rats

NEW YORK – Members of the "Molecular Transducers of Physical Activity Consortium" (MoTrPAC) have assembled an extensive collection of molecular responses to endurance exercise in rats, uncovering disease-related genes and pathways, tissue-specific effects, and sex-related adaptations over time.

"Exercise affects nearly all organ systems in either improving health or reducing disease risk, with beneficial effects resulting from cellular and molecular adaptations within and across many tissues and organ systems," researchers at Stanford University; the Broad Institute; the University of Iowa; the University of Florida, Gainesville; the University of California, San Diego; and other centers wrote in one of several studies, published in Nature, Nature Communications, and Nature Metabolism on Wednesday.

For the Nature study, the team performed multiomic analyses on whole blood, blood plasma, and solid samples spanning 18 tissues from male and female 6-month-old laboratory rats that were exposed to up to eight weeks of endurance exercise training.

"We all know exercise is beneficial for us," co-senior and co-corresponding author Stephen Montgomery, a professor of pathology, genetics, and biomedical data science at Stanford University, said in a statement. "But we don't know much about the molecular signals that manifest across the body when people exercise, or how they may change when people train."

"Our study is the first to take a holistic, bodywide look at molecular changes, from proteins to genes to metabolites to fats and energy production," Montgomery added. "It's the broadest profiling yet of the effects of exercise, and it creates an essential map to how it changes the body."

For the exercise program, rats were subjected to increasingly challenging treadmill training marked by gradual upticks in incline, speed, and duration over one, two, four, or eight weeks, they explained, with tissue samples collected 48 hours after the last round of exercise.

Based on genomic, transcriptomic, proteomic, metabolomic, epigenomic, lipidomic, immune system, phosoproteome, acetylproteome, and ubiquitylproteome profiles generated with more than two dozen molecular platforms and nearly 9,500 assay types, the team untangled molecular responses turning up within and across different tissue types over time along the rats' training journey.

"[W]e identified thousands of training-induced changes within and across tissues, including temporal and sex-biased responses, in mRNA transcripts, proteins, post-translational modifications, and metabolites," the authors reported. "Each omic dataset provides unique insights into exercise adaptation, where a holistic understanding requires multiomic analysis."

Along with such molecular and tissue-related shifts in the endurance exercise-exposed rats compared with their sedentary counterparts, the investigators documented distinct physical changes in the animals.

While male rats had lower body fat after exercise, for example, body weight increased in female rats, and aerobic capacity increased in rats from both sexes. In addition, exercise did not lead to body fat declines in the female animals, though sedentary control animals did show an uptick in body fat in the female rats.

In particular, the team saw endurance training adaptations that affected pathways involved in everything from stress or immune responses to metabolic processes or mitochondrial organelle function, among many other molecular and network changes.

While gene activity and regulation varied across tissues tested to some extent, a set of 22 genes involved in pathways for heat shock proteins, tissue remodeling, blood pressure, insulin sensitivity, the immune system, and other pathways showed exercise-related shifts in the heart, lung, liver, kidney, a calf muscle called the gastrocnemius, and subcutaneous white adipose tissue.

"[W]e present the first whole-organisms molecular map of the temporal effects of endurance exercise training in male and female rats and provide multiple insights enabled by this MoTrPAC multiomic data resource," the authors reported, noting that "data and analyses presented in this study will serve as valuable resources for understanding and exploring the multi-tissue molecular effects of endurance training and are provided in a public repository."

Although the study was done in rats, the investigators explained, they saw overlap with exercise-related processes previously found in humans, as well as links to conditions such as tissue injury and repair, cardiovascular health, non-alcoholic fatty liver disease, and inflammatory bowel disease.

"This MoTrPAC resource provides future opportunities to enhance and refine the molecular map of the endurance training response," the authors wrote. "We expect that this dataset will remain an ongoing platform to translate tissue- and sex-specific molecular changes in rats to humans."

In a related Nature Communications paper, Stanford University researchers Stephen Montgomery, Nikolai Vetr, and colleagues studied the gene regulatory consequences of the rats' exercise regimes, particularly when it came to regulatory features with ties to 114 complex traits and conditions.

The team was able to tease out more than 5,500 trait-tissue-gene relationships that are expected to be relevant in humans by analyzing results from MoTrPAC alongside tissue-specific expression quantitative trait data from the Genotype-Tissue Expression (GTEx) project, data from 114 genome-wide association studies encompassing a dozen traits or disease types, data from transcriptome-wide association studies, and more.

"In our study, we have identified multiple tissues and tissue-by-gene pairs where exercise may modify disease risk through gene expression," the author reported, noting that "[d]espite human-rat differences, our unbiased approach identified multiple results that echo established exercise-disease relationships."

In another study, published in Nature Metabolism, investigators from UCSD, Duke University Medical Center, the Oklahoma Medical Research Foundation, the University of Iowa, Pacific Northwest National Laboratory, and elsewhere used MoTrPAC data to explore biological sex-specific responses to exercise training in subcutaneous white adipose tissue from rats exposed to such training.

The study "underscores the powerful impact of sex on adipose tissue biology," the authors wrote, "and provides a rich resource to investigate the [subcutaneous white adipose tissue] response to [exercise training]."