It’s not just that your mouth waters when you see delicious food. Your liver also becomes active before the first bite. Scientists showed this Max Planck Institute for Metabolic Research after research into liver cells in mice.
The scientists discovered a mechanism that takes place in our body when we are hungry and see or smell food. Within minutes of seeing food, the mitochondria (cell’s power plants) in the liver cells adapt to prepare the liver for the food to come. These cells are closely involved in sugar metabolism, the process that maintains the glucose level in the blood (also called blood sugar level). The insight could lead to new treatments for type 2 diabetes.
The researchers made this discovery after conducting experiments with mice that were hungry but could not eat. They offered treats to the hungry mice while monitoring the cells in the liver. This showed that after just a few minutes the mitochondria in the liver cells were already carrying out processes that were previously thought to be stimulated only by food intake. “We already knew that our body prepares for food intake by producing saliva and digestive enzymes,” says researcher Sinika Henschke. “But we have now also discovered how quickly and dramatically the mitochondria in the liver cells adapt, even when no food has yet been ingested.”
New signaling route
This preparation for eating starts with the POMC neurons: nerve cells in the hypothalamus that become active within seconds when they see and smell food. These nerve cells then send signals to the liver, as a signal for the mitochondria in the liver cells to prepare themselves for sugar metabolism. This is done by adapting a protein in a process called ‘phosphorylation’ (see box). This phosphorylation then affects the liver’s sensitivity to insulin, a hormone that regulates blood sugar levels and is essential for a properly functioning body. Insulin ensures that glucose from food can be converted into energy.
What is phosphorylation?
Phosphorylation is a biochemical process in which a phosphate group (PO43-) is added to a molecule. This can happen with different molecules, such as proteins, carbohydrates and lipids. The addition of a phosphate group can significantly affect the structure and function of the molecule. In the case of proteins, phosphorylation is an important way to regulate activity. When a protein is phosphorylated, it can change its shape, making it more or less active. Phosphorylation can also affect the binding of other molecules to the protein.
Type 2 diabetes
The discovery is good news for diabetes patients. In people with type 2 diabetes, the body has too little insulin and is also less sensitive to insulin. This discovered signaling pathway may therefore help in the development of new treatments for this type of diabetes. According to Jens Brüning, lead author of the study, this research “demonstrates the close connection between the sensory perception of food, mitochondrial adaptations and insulin sensitivity.” He calls understanding these mechanisms crucial in the fight against type 2 diabetes, where insulin sensitivity plays an important role.
Currently, approximately 1.1 million Dutch people have type 2 diabetes. But the condition is also common worldwide – and the numbers continue to increase. In 2021, around 537 million people worldwide had type 2 diabetes. This is expected to rise to 783 million by 2045. By harnessing the signaling pathway that affects mitochondria in the liver, scientists may be able to develop therapies that improve insulin sensitivity and regulate blood sugar levels.
Want to know if you have diabetes? AI can recognize it from your voice
Researchers from Klick Labs had 267 people – healthy people and diabetics – record a certain sentence on their smartphone six times a day. From more than 18,000 recordings, we managed to identify fourteen sound characteristics that showed a clear difference between healthy people and people with diabetes. “Our study focuses on significant voice variations between people with and without type 2 diabetes. The way healthcare screens for diabetes could completely change,” says lead researcher Jaycee Kaufman about the discovery.
