19 May 2008

Treating obesity with electricity

The implantable device developed by Enteromedics, which blocks the activity of the branches of the vagus nerve going to the stomach with the help of electrical impulses, has demonstrated the first successes in clinical trials of a new method of treating obesity.

The experimental device appeared in the wake of the fight against the obesity epidemic as an alternative to surgical methods for reducing stomach capacity (usually such operations are offered to people with a body mass index above 35). These methods are effective, but only a small part of patients agree to them. Many are afraid of the possible consequences of surgery, as well as the need to adhere to certain dietary restrictions and take dietary supplements throughout their lives (nevertheless, in the United States, the number of such operations increased from about 100,000 in 2003 to 200,000 in 2007.

The alternative treatment method proposed by the authors – VBLOC therapy - uses an electrical stimulator to block the signals of the vagus nerve connecting the brain to the digestive organs and regulating the activity of hormones and other factors involved in the formation of feelings of satiety and hunger. The vagus nerve causes the stomach to stretch when we start eating. If the stomach does not stretch, saturation occurs very quickly.

The proposed procedure consists in laparoscopic implantation of small electrodes in the immediate vicinity of the vagus nerve fibers located in the apex of the stomach. The regulator implanted under the skin (picture on the left) sends high-frequency electrical impulses to the electrodes that block the signals of the vagus nerve (diagram in the middle of the figure). The absence of nerve impulses that cause relaxation of the stomach muscles in response to food intake and stimulate the release of digestive enzymes and hydrochloric acid accelerates the onset of satiety and slows down the digestive process. The majority of participants in the initial clinical trials of the method noted a decrease in hunger and rapid satiety. Perhaps the only disadvantage of this method, which the developers do not hide, but also do not advertise too much, is a device for adjusting the operation of the implant (photo on the right).

In the first nine test participants, excess body fat decreased by almost 30% over 9 months of follow-up. According to preliminary results of larger-scale trials, patients who have undergone the procedure consume about 500 calories less per day. The effectiveness of gastric banding and the creation of a bypass gastric anastomosis is somewhat higher, but doctors consider the results very promising.

Enteromedics is currently recruiting participants to conduct larger-scale (300 patients) placebo-controlled clinical trials in the USA and Australia. Two–thirds of the participants will have the device activated immediately after implantation, and the remaining third - a few months later. The researchers will compare patients' weight loss and other factors of interest to them, as well as observe all participants for four years to assess the long-term effects of the procedure.

The idea of blocking the vagus nerve for the treatment of obesity arose by chance. In the 50s, surgeons often resorted to removing part of the vagus nerve, which regulates the secretion of gastric juice, in the treatment of ulcers. Many of those who underwent this operation noted a decrease in hunger and lost weight. However, the effect lasted only 2-3 months, during which the body adapted to the new conditions. The authors believe that periodic blocking of vagus nerve activity will exclude the launch of such compensatory mechanisms.

Experts warn that the new device, which is only one of dozens of medical approaches to the treatment of obesity being developed worldwide, must undergo multi-stage testing and its effectiveness remains questionable.

Earlier attempts to use electrical stimulation for the treatment of obesity led to contradictory results due to the lack of information about the mechanisms of their action. One of the problems is the selection of the type of electrical signals. The authors claim that the high-frequency signals used in VBLOC therapy, which completely block the activity of the vagus nerve, are the optimal solution to the problem. To date, the long-term effects of such a blockade have not yet been studied, but more than 100 patients have already undergone the procedure without serious side effects. Information about mild side effects has not yet been published by the company.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of TechnologyReview


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