Written by Amani Gardner
Edited by Amani Gardner, Craig Beall and Katherine Pye
Estimated read time: 4 minutes
Hypoglycaemia is a condition in which the amount of glucose in the blood (which the body uses for energy) drops below normal levels, potentially threatening brain function. When this happens, a molecule called AMPK (AMP-activated protein kinase) steps in to restore the amount of energy available. AMPK acts in several ways and different parts of the body to achieve this:
1. Moving glucose into cells
When AMPK is activated, it can make it easier for glucose to enter the cell from the blood. How does it do this?
Cells have small transporters on their surface, which glucose can use to enter from the blood. When AMPK is activated, it can cause the insertion of spare transporters onto the surface of the cell, creating more avenues that the glucose can use to enter.
2. Burning fat.
While glucose is the primary source of ATP, energy can also come from stored fat. When AMPK is activated, it shifts the focus away from storing fat and instead stimulates the breakdown and burning of existing fat to generate ATP. This ensures energy production continues even when glucose is scarce.
3. Increasing metabolism.
A region of the brain called the hypothalamus is particularly important for sensing our overall energy needs. When excess energy is available the hypothalamus can increase the body’s energy expenditure. On the other hand, when energy levels are low, AMPK in the hypothalamus can increase appetite, amp up the amount of glucose the body produces, and decrease exergy expenditure e.g. heat production.
4. Inhibiting protein production.
One major function of cells is to make proteins. Proteins are complex molecules that do most of the work in a cell and are needed for the structure, function, and regulation of tissues and organs. Production of proteins is an energy-intensive process task. When energy levels are low, AMPK inhibits protein production, conserving energy for critical tasks.
5. Recycling components of the cell.
Autophagy is the process of recycling parts of the cell, whereby damaged or misfolded proteins and cellular components can be recycled and recovered. This process, driven by AMPK, can actually contribute to energy production by providing fuel for mitochondria (a part of the cell that is vital for energy production).
Aside from its role in energy regulation AMPK also contributes to many other processes in the body including:
1. Oxygen delivery
When the body is lacking oxygen (either at high altitudes or during sleep) AMPK activation may help to protect the body against breathing instability. Indeed, high-altitude populations in the Andes have changes in the gene that encodes part of AMPK, helping them survive in the low oxygen environment.
2. Fertility
AMPK is found in the ovary and testes and can affect the production of sex hormones in many animal species. Energy availability is essential for reproduction and an absence of AMPK can reduce fertility in both sexes.
3. Blood flow
AMPK can stimulate the release of a messenger molecule called nitric oxide, which causes blood vessels to widen, thereby increasing the flow of blood.
4. Aging
AMPK activation gradually declines with age. Some research has shown that calorie restriction (which activates AMPK) can extend lifespan. It is thought that AMPK increases longevity through autophagy (cell recycling) and inhibiting protein production.
5. Inflammation
Many conditions are worsened by chronic inflammation. AMPK helps counteract inflammation by suppressing NF-κB, a key molecule involved in inflammatory pathways.