Scientists identify an animal model to study muscle age

There are many parts to getting older, both mentally and physically. When it comes to the infrastructure of the human body – the muscular system that includes muscles, bones, tendons and cartilage – age-related decline is inevitable, and the rate of that decline is negligible. the older we get. Loss of muscle function – and often muscle mass – is called sarcopenia or dynapenia.

For adults in their 40s, sarcopenia is almost invisible – about 3% of muscle mass is lost every decade. For those age 65 and older, however, muscle contraction can progress much faster, with an average loss of muscle mass of 1% per year. More importantly, sarcopenia is also characterized by a decrease in strength, incontinence, reduced physical activity, or difficulty completing daily activities.

The proportion of older adults aged 65+ is expected to more than double by the year 2060, leading research into the process of musculoskeletal decline. Researchers at the Columbine Center for Health Systems at Colorado State University for Healthy Aging believe they have found an animal model that will help them better understand and find ways to reduce the symptoms.

The study, published in Limitations in Psychology: striated muscles in October, for example the use of comparative medicine to understand human diseases and conditions.

Animal models

Scientists often rely on animal models to identify disease progression and study prevention, diagnosis and treatment of conditions. However, until now, no animal model has been able to capture all aspects of human muscle mass.

The current preclinical models rely on loading the muscle, involve imitating a bed in an animal, or have to wait for the animals to become very, very old, and even then they don’t get the same phenotype that gets older than people do. “

Karyn Hamilton, CSU Professor of Health and Exercise Science, Deputy Director, Center for Healthy Aging

In their work, the Hamiliton team found that the Dunkin Hartley guinea pig was a good candidate for a model of aging because the animal was prone to developing osteoarthritis (OA) at an early age.

The two conditions – OA and sarcopenia – appear to be linked in humans: With age, skeletal muscle dysfunction increases the risk for OA, and OA increases the risk for further muscle contraction.

Hamilton joined Dr. Kelly Santangelo – associate professor in the Department of Microbiology, Ornithology and Pathology at CSU, who has been studying primary OA in Hartley guinea pigs for several years – and Professor Associate Professor Raoul Reiser, also in the Department of Health Science and Exercise, to understand how skeletal muscle changes as OA progresses in guinea pigs.

The team recognized that these muscle changes could be similar to muscle aging.

Classic signs

Muscle fusion also changes with age: fast-twitch fibers, which are larger and able to exert stronger forces, decrease in number, and slow-twitch fibers, which are smaller and less metabolically efficient. , tends to increase. Usually when people “lose muscle mass,” it is the large, fast-twitch fibers that are affected. With a decrease in muscle mass also tends to lead to an increase in the amount of fat, or adipose tissue, in the body.

As people age, maintaining muscle activity may be more important than preventing major weight loss.

“What we’ve learned over the decades is that age-related muscle loss and age-related loss of muscle activity don’t always go hand in hand,” Hamilton said. to improve muscle mass, and you may not get an improvement in muscle activity; you can do things to boost muscle activity and you may not get an increase in muscle mass. “

The researchers compared observed muscle changes in Hartley guinea pigs with those in Strain 13 guinea pigs, which tend to develop OA later in life and, therefore, may not they exhibit the same classic signs of muscle growth.

They found some things that are very similar to human muscle growth, such as a decrease in muscle density, possibly due to an increase in fat mass. Although a sense of muscle reduction has not been observed, researchers found a shift toward smaller, slower muscle fibers, as would be expected in human muscle with advanced age.

“If you look at the whole picture, we think that some of the main things that always happen with human muscle growth – which is moving towards a less powerful muscle phenotype, are more slower – clearly modeled in Hartley guinea pigs, “Hamilton said. “And we think if we started looking at even older guinea pigs, we might see more of what people think of as classic sarcopenia.”

Future guidance

This study provides a baseline that allows the team to take multiple directions in future research. One guide is to use action tests to study how muscle and leg strength or movement changes with age in Hartley guinea pigs, and how these changes are indicative of a decline in muscle activity. in older people.

It will be a priority to identify whether Hartley guinea pigs can be a valuable translational model for identifying interventions that demonstrate promise for preventing or slowing the decline in muscle-function. complete skeleton with aging in humans.

In fact, Hamilton and Santangelo have already begun treating guinea pigs with plant-based phytochemicals that target a protective sequence of genes. The treatment appears to reverse some signs of aging at the molecular level by improving mitochondrial function as well as preventing joint degeneration and retaining sides of a gate that usually decays with advancing age.

Overall, Hamilton says she hopes this work can provide researchers with another animal model for studying human age, one that can “successfully translate preclinical results and findings basic science to encourage interventions to increase the range of human health or promote healthy growth. “