The loss of muscle mass, also known as sarcopenia, is a condition that's usually seen in people over the age of 50. Older adults with sarcopenia lose, on average, three percent of their muscle strength every year, impairing their physical mobility. The condition also makes them prone to many health problems, which can ultimately shorten their life expectancy. These consequences make sarcopenia a serious health burden in regions where there are many older adults.
Currently, one in 11 people around the world is 65 years old or older, according to the latest World Population Prospects report. By 2050, these numbers are expected to balloon to one in six people. Regions such as Europe and North America are expected to have at least a quarter of their populations be older adults. Countries such as Germany, Italy, and Japan – where the study was conducted – are also estimated to see a decline in their populations within 10 years.
In the study, researchers noted that while muscle loss is a complication that many older adults with diabetes face, the link between the two conditions is ambiguous. They proffered that insulin may have a role to play in sarcopenia: Given its role in cell growth and development, having insufficient amounts of insulin may lead to suppressed cell growth and contribute to a decline in muscle mass.
To test their hypothesis, the team treated mice with streptozotocin, which caused high blood sugar levels (hyperglycemia) and low blood insulin levels (hypoinsulinemia). The team found that mice treated with streptozotocin had a marked loss of muscle mass 21 days after diabetes induction. This indicated that sarcopenia isn't caused by an increase in catabolism or the breakdown of large molecules into smaller units, but by diabetes. They also discovered that in diabetic mice, KLF15 expression was upregulated. KLF15 is a protein linked to muscle atrophy.
Under normal conditions, KLF15 is rapidly degraded, thanks to another protein called WWP1. When WWP1 attaches a small protein called ubiquitin to KLF15, it promotes the degradation of KLF15. However, elevated blood sugar levels decrease WWP1 expression, leading to a rise in KLF15 levels in skeletal muscles.
“We have shown that hyperglycemia, a central disorder in diabetes, promotes skeletal muscle atrophy via a WWP1/KLF15 pathway,” the researchers wrote in their report. “This pathway may thus serve as a therapeutic target for muscle atrophy triggered by diabetes.”
While the risk of losing muscle mass is prevalent, especially among older adults with diabetes, it shouldn't deter them from building muscle. Studies have shown that diabetics who develop their muscles help their bodies remain more sensitive to insulin despite their condition. This is crucial in keeping blood sugar levels in check and managing Type 2 diabetes. In addition, building muscles also benefits the heart, as strong muscles can collect oxygen and nutrients more efficiently than weak ones. (Related: You gotta start ’em young: Teens with healthy muscle mass are less likely to have metabolic syndrome.)
DiabetesScienceNews.com has more stories on understanding the mechanisms behind diabetes.