Serotonin transporter gene promoter polymorphism affects the severity of binge eating in general population

Objective

The s-allele of the 5-HTTLPR has been suggested to lead to the development of less efficient and less flexible 5-HT system and has been associated to different forms of psychopathology. It has also been shown that alterations in serotonergic activity contribute to the pathophysiology of binge eating but it is not clear which changes in 5-HT function observed in eating disorder patients represent trait vs state effect. We investigated the association between the 5-HTTLPR and binge eating in a population-representative sample of women, and tested whether the 5-HTTLPR genotype influences the severity of binge eating.

Methods

The sample was based on women participating in the third wave of the Estonian Children Personality, Behaviour and Health Study. EDI-2 subscales – drive for thinness and bulimia – were used to assess eating behaviour and attitudes. Barratt Impulsiveness Scale (BIS-11) and State and Trait Anxiety Inventory (STAI) were used to measure impulsivity and anxiety. Participants were genotyped for the 5-HTTLPR.

Results

There was no 5-HTTLPR genotype effect on binge eating even after the covarying effect of impulsivity and anxiety was controlled for. However, women prone to binge eating and carrying the s-allele showed significantly higher levels of bulimia scores, and among them, women with s/s genotype had also higher levels of state anxiety and tendency for higher impulsivity.

Conclusions

While the 5-HTTLPR genotype does not predict symptoms of eating disorder in general population, the s-allele, and especially the s/s genotype increases the risk for affective instability and symptom severity.     

Low serum BDNF and food intake regulation: A possible new explanation of the pathophysiology of eating disorders

Background

Several lines of evidence suggest that brain-derived neurotrophic factor (BDNF) plays an important role in weight regulation and eating behavior, and poorly balanced diets lead to a decrease in blood BDNF levels. However, studies regarding BDNF blood levels in eating disorders (ED) have yielded inconsistent results. We measured serum concentrations of BDNF and assessed behavior and cognition related to eating in ED patients and control subjects.

Methods

Forty female drug-free patients [19 with anorexia nervosa (AN), 21 with bulimia nervosa (BN)], who did not meet the diagnostic criteria for depressive disorder, and 24 age-matched normal control subjects were enrolled in the current study. We evaluated eating-related psychopathology and depressive symptoms using the Eating Disorder Inventory-2 (EDI-2), Eating Attitude Test-26 (EAT-26) and the Hamilton Depression Rating Scale (HDRS), and measured serum BDNF levels by an enzyme-linked immunosorbent assay.

Results

Compared to normal controls, serum levels of BDNF were significantly reduced in AN, but not in BN. There was a significant positive correlation between serum BDNF levels and BMI in both AN patients (r = .649, p = .003) and BN patients (r = .626, p = .002). However, no correlation between serum BDNF levels and BMI was detected in the controls. Furthermore, there was a significant negative correlation between serum BDNF levels and the oral control subscale scores of EAT in both AN patients (r = − .506, p = .027) and BN patients (r = − .511, p = .018); whereas, no correlation was detected in normal controls.

Conclusion

Our study demonstrated that individuals showing more extreme food intake regulation were those with lower serum BDNF levels. This finding is contrary to that in mice where mice with reduced BDNF levels showed aberrant eating behavior. This result suggests that BDNF is no longer functioning appropriately in ED patients, which could be an important factor in the pathophysiological of ED.