Researchers have found that skeletal muscles play a large part in regulating the liver’s biological clock. The findings were published in Science Advances.
The circadian rhythm is coordinated by the brain at a general level, but each organ or tissue is also subjected to specific regulation, adjusting to time to optimise their processes. However it was not known how the liver “knows” whether it is day or night.
The liver’s main role is digestion, mainly of fats and sugars: the brain is the main consumer of sugar while skeletal muscle is the main consumer of fat.
Scientists at IRB Barcelona discovered a surprising relationship: that it is skeletal muscle which regulates liver function and determines fat metabolism. Skeletal muscle accomplishes this by secreting a that is transported to the liver through serum is responsible for modulating around 35% of the metabolic functions of the liver. The remaining basal functions of this organ and others related to carbohydrate metabolism are independent of muscle activity and are regulated by the basal circadian rhythm from the brain.
“It’s a very nice discovery because it is the first demonstration of the need for communication between the circadian clocks of tissues and organs outside the brain, and we can see that this communication between muscle and liver is altered by aging,” said study leader Dr Salvador Aznar-Benitah at IRB Barcelona. “When we get older, cells stop obeying the biological clock and begin to perform functions in a non-optimal manner, leading to errors that cause tissues to age.”
The researcher’s results show that the liver does not independently regulate the metabolism of fats and that it is muscle that sends the message that it is time to switch on fatty acid metabolism and how it should go about this. “We didn’t expect to find this connection between the liver and muscle because it wasn’t known previously, but, on second thought, it makes complete sense that fat management is coordinated by one of its main consumers,” said Dr Aznar-Benitah. Carbohydrate metabolism meanwhile is dependent on the basal coordination exercised by the brain.
Source: Institute for Research in Biomedicine (IRB Barcelona)
