Does Nitric Oxide Have a Role in Eating Disorders?

A team of researchers at the University of Florence, Italy, has turned a spotlight on the possible actions of nitric oxide in the etiology of eating disorders. Nitric oxide (or NO, not to be confused with the anesthetic, nitrous oxide) is a neuromodulator involved in the regulation of body energy balance and food intake. Most of the actions of this gaseous mediator are due to production of cGMP (cyclic guanosine monophosphate).

Animal studies have shown that NO/cGMP is involved in regulation of eating behavior. Nitric oxide plays an important role as a mediator of several hormones involved in body weight control, such as leptin, ghrelin, and cholecystokinine.

A study of 50 patients

To assess the effects of NO in eating disorders, Dr. Alfredo Vannacci and colleagues at the University of Florence studied 62 consecutive female Caucasian outpatients referred for treatment of eating disorders. To be included in the study, persons had to be seeking treatment for an eating disorder for the first time, and could not be taking any medications known to interfere with eating behavior and attitudes. Of the 50 patients in the final study group, 15 (30%) met DSM-IV criteria for anorexia nervosa, restricting subtype (AN-R), 10 (20%) for AN, binge-purge subtype (AN-BP), and 25 (50%) for bulimia nervosa, binge-purge subtype (BN).

Researchers measured plasma nitrite and cGMP levels among the patients and 24 normal female Caucasian controls. About 12 ml of peripheral venous blood was drawn from each student, and then analyzed.

What the levels showed

Plasma nitrite and cGMP levels were significantly higher in eating disorder patients than in healthy controls. Eating Disorder Examination scores were also significantly higher in eating disorder patients than in controls. No significant correlation between clinical and psychopathologic variables, nitrites, and cGMP levels was observed among control. In contrast, among AN patients as a group, nitrites correlated inversely with body mass index. Among BN patients, nitrites correlated directly with the frequency of binge-eating episodes. When AN patients were divided into subgroups, nitrite and cGMP levels were significantly higher in AN-BP patients than in AN-R and BN subjects. According to the authors, this latter result seems to be related to the inverse correlation between nitrite levels and BMI noted in AN patients and to the direct correlation between nitrite levels and binge eating observed in BN patients.

A significant relationship between NO and cGMP levels and the degree of psychopathological impairment (assessed through the EDE) was also observed in BN patients, while the higher levels of nitrites and cGMP reported in AN patients were more strictly correlated with low BMI and high number of binge episodes.

The authors note that a limitation of the study was the small number of participants, and larger studies will help define whether the higher NO and cGMP levels result from AN and BN or play a role in their development.