Researchers Reveal the Key Element Related to the Activation of Brown Adipocytes
A new study reveals the key element related to the activation of brown adipocytes. The cellular activation results in the burning of the fat molecules, instead of storage. This new discovery allows pharmaceutical companies to start research on new drugs against obesity. Brown adipocytes are responsible for burning calories in order to generate heat. This is a distinct feature, compared to other mammals. Researchers have only recently discovered that brown adipocytes are present in adult humans, contrary to the belief that brown fat is only present in infants. According to recent studies, adult humans possess significant amounts of brown fat along with white fat.
Results of precedent studies have shown that brown adipocytes are mainly activated by low temperatures. However, there’s data suggesting that ingesting high amounts of food also activates the brown fat cells. Activated brown adipocytes are responsible for converting fat molecules to heat.
The research team from the UCSF (University of California, San Francisco) published their results in the journal Cell, on the 12th of October. The main authors of the study are associate professor Yuriy Kirichok, research specialist Polina Lishko and Andriy Federenko, who is now an assistant professor at UCB (University of California, Berkeley).
Their new discovery, regarding the action mechanism of a protein that triggers the biochemical reaction that is involved in the fat burning process, suggest that the possibility to create a drug that would keep this mechanism active is possible. This would increase the fat burning process and thus help patients to lose more weight. However, researchers aren’t yet convinced that this is a valid strategy for weight control.
The relationship between the protein, called UCP1 (uncoupling protein 1) and the heat-generating process has been long known. According to professor Kirichok, even if the protein has high specificity for this process, artificial drugs could prove to be ineffective due to a different cellular response.
“Low levels of brown fat correlate with obesity. We have shown how fatty acids attach directly to UCP1 and help it to break down an electrical potential across the mitochondrial membranes, causing the cell to burn more fat and to generate heat in order to regenerate this potential”, noted professor Kirichok.
Every cell contains mitochondria, which are small organelles that generate energy. This energy is created through oxidative phosphorylation, a metabolic process that converts energy taken from food, into ATP (Adenosine triphosphate). Through this process, the mitochondrial membrane gains a voltage gradient which further helps make ATP.
Compared to other cellular types, the brown adipocytes are packed with mitochondria. This plenitude of mitochondria is responsible for the brown color of the adipocyte. However, unlike in other cells, where mitochondria produces ATP, in the brown adipocytes, it produces heat, with the help of UCP1.
The research team used a technique called “patch clamping” in order to track down the electrical currents and reveal the connection between UCP1 and fatty acids. Through this technique, the researchers were able to track down the electrical activity of each mitochondria in particular.
Professor Kirichok notes that the role of UCP1 has been known for almost 20 years. The connection between fatty-acids and the activation of UCP1 has also been known. However, there were certain doubts regarding the actual mechanism which links the fatty acids to UCP1.
The research team was able to track every change that appears in the electrical currents that move across the mitochondrial membranes. This technique allowed researchers to make suppositions about the biochemical reaction that takes place. Their conclusion was that UCP1 captures the fatty acids and further directs them to transport protons into the mitochondria. With the proton numbers inside the mitochondria rising, the inner electrical membrane potential dissipates. In order to restore and maintain this electrical potential, supplementary cycles of oxidative phosphorylation are needed and thus heat is generated.