Turning bad fat into good raises hope for tackling obesity

Researchers at the Johns Hopkins University School of Medicine found that by knocking down the expression of an appetite-stimulating protein not only helps cut calorie intake and weight but also it turns white fat into brown one.

"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 study author Sheng Bi, an associate professor at the Johns Hopkins University School of Medicine.

According to scientists, the body produces two fats or adipose tissue. The white one, called the storehouse for the extra calories we eat, ends up being stored in the body, while the brown fat which generates body heat in animals or newborns is considered as good fat.

For the study, published in the journal Cell Metabolism, Bi and his team wanted to see whether suppressing neuropeptide Y (NPY), the appetite-stimulating protein, in the dorsomedial hypothalamus of the brain would decrease body fat in rats.

Located just above the brain stem, the hypothalamus helps regulate thirst, hunger, body temperature, water balance and blood pressure.

In the high-fat group, the control group rats became obese, while those rats in which NPY expression was silenced gained less weight.

The results "made sense", given that NPY has been shown to stimulate eating, said Bi. The less NPY, the less the rats would eat, his team hypothesised. But, the team was surprised when they checked the fat content of rats after death.

In the groin area of the NPY rats, they found not the expected white fat, but the telltale signs of brown fat in its place.

They confirmed this change by looking at levels of mitochondrial uncoupling protein-1, or UCP-1, through which brown fat burns to produce heat.

They used this protein as a marker to determine that the fat that should have been white was instead brown.

Bi said the transformation from white to brown resulting from NPY suppression may be due to activation of brown fat stem cells contained in white fat tissue.

While brown fat seems to vanish in humans as they emerge from infancy, the brown fat stem cells may never disappear and may just become inactive as people age.

It may be possible to transplant or inject brown fat stem cells under the skin to burn white fat and stimulate weight loss, said Bi. "Only future research will tell us if that is possible."