Researchers hope to eventually inject brown fat, or “good fat,” under the skin to burn white fat, or “bad fat”
Researchers from the Johns Hopkins University School of Medicine have made a discovery that could eventually treat obesity in humans.
A recent trio of studies reported that obesity rates have doubled in less than 30 years worldwide. In 1980, 5 percent of men and 8 percent of women were obese. By the end of 2008, 10 percent of men and 14 percent of women were obese. This means that worldwide, 343 million men and 458 million women were obese just three years ago. In addition, another 1.5 billion adults were overweight.
Today, more than two-thirds of U.S. adults are overweight and more than one-third are obese.
Sheng Bi, M.D., study leader and associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, and a team of researchers have now found that reducing the expression of a certain protein in the brains of rats decreases their calorie intake and weight. Also, their fat was transformed into another type of fat that burns off more energy.
Bi and his colleagues made this discovery by studying the two types of fat that the body makes, which are white and brown adipose tissues. White fat stores the extra calories we eat and is found around the mid-section and other places. It has one large droplet of lipid, which is a building block for fat like triglycerides and cholesterol. Brown fat, on the other hand, is a better fat that has several little droplets of lipid, and each little droplet has its own power source to allow for heat generation. Brown fat is known for its energy burning characteristics.
Sheng wanted to figure out if suppressing the neuropeptide Y (NPY) protein in the dorsomedial hypothalamus, which is located right above the brain stem and regulates thirst, hunger, water balance, blood pressure and body temperature, would reduce body fat in rats. NPY is an appetite-stimulating protein.
In the experiment, Sheng had two groups of rats that were both fed a regular diet. One group was a control group while the other was treated with a virus to inhibit NPY expression. Over a five-week period, both groups were observed, and Sheng found that those with NPY suppression were eating less.
The researchers then divided both groups into two, making four groups of rats. One of the treated groups and one of the control groups were given a regular diet while the other control group and treated group were given a high-fat diet.
The results showed that the control group on the regular diet weighed more after 11 weeks than the treated group on the regular diet. As far as the high-fat diet goes, the suppressed NPY group gained less weight than the control group, which became obese.
Sheng explained that the less NPY expressed, the less the rats would eat, thus the more weight lost. In addition, after the rats died, Sheng checked the fat in the bodies and found that brown fat had begun to replace white fat. This was confirmed through the observation of levels of mitochondrial uncoupling protein-1, or UCP-1, “through which brown fat burns to produce heat.” Researchers originally expected to find white fat, but found signs of brown in the groin area of the rats.
Sheng believes this occurred due to brown fat stem cells being contained in white fat tissue. Brown fat is found in infants, but as we age, it fades and is replaced by white fat. Sheng believes that brown fat may not fade completely, but just becomes inactive, as we grow older.
Researchers hope to one day inject brown fat stem cells under the skin in order to burn white fat, which would lead to weight loss in humans.
“If we could get the human body to turn ‘bad fat’ into ‘good fat’ that burns calories instead of storing them, we could add a serious new tool to tackle the obesity epidemic in the United States,” said Sheng.