Delta Opioid Receptor
Researchers made another amazing discovery in the fight against obesity. It seems that blocking an opioid receptor, mice do not gain weight even on a high calorie diet. According to a study published in The FASEB Journal, researchers from the United States and Europe have found that after blocking the delta opioid receptor, mice become resistant to weight gain and even lose weight .
Researchers conducted this study on two groups of mice: the first was composed of mice lacking delta opioid receptor and the second was that of normal mice. Both groups were fed the same amount of fat, high calorie diet but only the group of normal mice gained weight. The group of mice who lacked delta opioid receptor have not gained weight but actually loosed. Researchers believe that blocking or deleting the gene responsible for delta opioid receptor leads to expression of other genes in brown adipose tissue that stimulate thermogenesis. This way mice were able to maintain energy levels expenditure and not gain weight.
However, Gerald Weissmann, MD, Editor-in-Chief of The FASEB Journal, points out that these findings should not prompt people to adopt a high-calorie diet . It is known that junk food causes many health problems (cardiovascular risk increases, etc.). He added that even if this experiment had positive results in mice, this does not mean that the results will be repeated in humans.
Brown adipose tissue is a special type of fat tissue that is different from normal adipose tissue and it is found mainly in mammals. Histologically, brown fat cells have many mitochondria (the main role of mitochondria is the production of energy). Long time it was thought that brown adipose tissue can not be found in adults but recent studies have revealed that this type of tissue is found also in adults ( head, neck and upper thorax). In newborns, brown adipose tissue plays an important role in thermogenesis, in other words it prevents hypothermia. In adults, it was considered rather useless.
Recently, more and more researchers turned their attention to this type of tissue that may be a new target in the fight against obesity. A study published in The New England Journal of Medicine in 2009 pointed out that the relationship between body mass index and amount of brown adipose tissue in the body is inversely proportional. In other words, brown adipose tissue may play a role in preventing obesity.