Maintaining a stable and steady circadian rhythm can be a challenge for many people. Millions of people participate in shift work or work hours that aren’t conducive to getting enough sleep at night. In addition, the demands of modern life can make it difficult to eat at regular hours. The result is that 60 million people in the United States alone have trouble sleeping. This sleep disruption has been linked to a variety of chronic diseases, including Type 2 diabetes. A new study on the circadian rhythm of muscle cells suggests they may be an important part of this connection.
The Circadian Rhythm of Muscle Cells
When most people think of circadian timekeepers, they think of the brain. The brain is indeed important in synchronizing our internal clocks as well as perceiving and adapting to external cues. However, every organ system has its own rhythm and its own set of cues for moving clocks forward or backward. Muscle cells are no exception.
Muscle cells store lipids, or fats, as a potential source of energy. Researchers looking at lipid metabolism in muscle cells noticed that the number of lipids stored in these cells varied widely from hour to hour. Moreover, there was a stable and predictable pattern throughout a 24 hour day in subjects who keep a regular eating and sleeping schedule. Nevertheless, it was difficult to find a measurable trend because the amount of lipids in muscle cells varies widely from person to person.
However, when muscle cells were instead raised in a petri dish, the trends became clear: An internal clock was definitely at play. Moreover, muscles began to show disorganized metabolism of lipids when certain clock genes were disabled.
The Importance of Lipids in the Human Body
This research implies that the circadian rhythm may be crucial in relation to how lipids are stored and metabolized, which in turn could potentially affect almost every area of human health. Lipids are not just a readily broken down source of energy; in fact, they play a variety of roles. Lipids are crucial to synthesizing hormones and other crucial biochemicals. They also make up the cell membrane of every cell in the human body, thus playing a huge role in transporting various substances in and out of cells. This particular function may be part of the reason for formerly proven ties between circadian dysregulation and metabolic disease.
One of the hallmark signs of metabolic disease is a condition known as insulin resistance. When we eat food, our bodies release insulin. Insulin acts as a key, unlocking glucose receptors so fuel can enter cells. Because most foods are converted to glucose in the human body, this step is crucial to good health. When cells, particularly muscle cells, stop responding to insulin, glucose instead remains in the bloodstream. The resulting high blood sugar can have immense negative effects, harming blood vessels and even nerves. When insulin resistance becomes severe, Type 2 diabetes results.
Insulin resistance is common in the United States. There are demonstrable ties to disruptions of the circadian rhythm. Could disrupted lipid usage in muscle cells be part of the reason?
Ties Between Muscular Circadian Rhythm and Disease
Researchers are not sure why a disruption of the circadian rhythm of muscle cells appears to contribute to changes in the behavior of lipids, but the link is definitely there. Muscle cells that had certain circadian clock genes turned off indeed showed disrupted uptake of blood glucose and insulin resistance. Could the changes in lipid composition cells be a contributing factor? It is easy to see how lipids can affect blood glucose metabolism and the uptake of insulin, but more research will need to be done to identify the nature of the link.
Regardless, this research underscores the importance of maintaining a steady daily schedule. Eating and sleeping at the same times every day may be an important way to keep healthy muscle as well as healthy glucose control.
Keeping Internal Clocks in Sync
Could this research be the beginning of innovative new diabetes treatments? More study will be needed to turn this knowledge into applicable medicine. However, the link between the clocks of muscle cells and insulin resistance emphasizes how important it is to keep a healthy circadian rhythm. While this is difficult in the modern world, it is not impossible. Eating and sleeping at the same times every day, even on weekends and holidays, is an important step. Similarly, controlling light levels can be helpful. Our internal clocks stay on time when we get plenty of light exposure during the day yet very little at night—including light from screens. Taking melatonin at night also is a healthy step for people who struggle to fall asleep.
Sleep-wake cycles affect almost every aspect of human health. They appear to have an especially large impact on the way muscle cells process and store lipids. If you want strong muscles and a healthy metabolic system, working hard to maintain a well-regulated circadian rhythm could be an important step.