Published on February 8th, 2013 | by George Conte0
Burn more calories with Orexin (hypocretine)
The hormone called “orexin” (or hypocretin) could possibly be the solution to have a stable body weight. A new study of “Research Institute Sanford – Burnham” in Orlando, Florida, which is published in the journal “Cell Metabolism” showed that mice with orexin deficiency, gained more weight when followed the same diet with other mice that did not show lack of the hormone orexin.
Orexin is normally produced in the brain but may be a future solution in the form of supplements for weight loss, although, the researchers note that the new findings are preliminary.
The Orexin – hypocretine hormone
The orexin (also called hypocretin) is a protein that functions as a hormone in the brain. It is secreted by a type of brain cells called orexin neurons and are located in the pituitary. When neurons are active and produce orexin, we’re energetic, full of vitality. When the function of these neurons is suppressed then we feel lethargic and sleepy. Although orexin increases appetite, it also helps in weight loss. How is that possible?
Well, it seems that orexin is involved in the production of brown adipose tissue. This tissue is also called “brown fat”. This is the form of fat that burns calories instead of storing them as with subcutaneous fat.
“Without orexin mice are permanently programmed to be obese. With orexin the brown fat is activated and animals burn more calories,” said assistant professor Ntevantzan Siknter who participated in the study.
To reach their conclusions, the researchers compared normal mice with others that were genetically engineered to exhibit lack of orexin. When animals followed for six weeks a diet high in calories, those that were lacking orexin increased their weight by 45%. At the same time the normal animals that secreted orexin, increased their weight only 15%.
It is characteristic that this large difference in weight gain between the two experimental groups appeared to be true even when the orexin-deficient mice consumed less food than the rest.
More Orexin equals more energy consumption
Based on these findings, the scientists hypothesized that orexin-deficient mice somehow consumed less energy. Indeed, by experimenting, they discovered that after eating food “rich” in fat, normal mice showed an increase in metabolic rate by 13.5% while mice with deficient hormone showed no increase in their metabolism.
The result of the study may not be unconnected with the causes of human obesity. It is known that people with narcolepsy (a sleep disorder characterized mainly by the irresistible desire to sleep) lack orexin, while previous studies have also linked low levels of the hormone with obesity in humans. The measurement of the activity of brown fat in people with orexin deficiency can show whether the mechanism discovered in mice apply to humans, said the researchers. But also they warn that the hormone also causes intense alertness and taking supplements can cause insomnia.
What is the brown adipose tissue?
A mammal, doesn’t only store fat under the skin, but also another type of fat tissue called “brown fat” because of its color. The purpose of the brown adipose tissue is not the storage of fat but the heat. In newborn humans, brown adipose tissue is found in the shoulders and chest accounting for 3-5% of their weight and it is there to protect from the cold. The brown fat cells have many and large mitochondria, burning mostly fat and are very well networked with the nervous system which gives the order to produce heat. The brown fat cells do not use ATP to produce heat but a protein first discovered in animals that hibernate. The brown fat is activated when it is cold and when food enters the body because the nervous system is stimulated in the same way.
For some people brown adipose tissue is easily activated and this makes them keep their weight stable even when they consume more calories than others that don’t activate this tissue. The orexin and possibly other molecules that have not yet been discovered might play a crucial role in the activation of brown fat not only in animals but also in humans.