BDNF Val66Met polymorphism is associated with HPA axis reactivity to psychological stress characterized by genotype and gender interactions.
BACKGROUND
A key protein in maintaining neuronal integrity throughout the life span is brain-derived neurotrophic factor (BDNF). The BDNF gene is characterized by a functional polymorphism, which has been associated with stress-related disorders such as anxiety-related syndromes and depression, prompting us to examine individual responses by Genotype and Sex to a standardized social stress paradigm. Gender differences in BDNFxstress responses were posited because estrogen induces synthesis of BDNF in several brain regions.


METHODS
97 university students (51 females and 46 males) participated in a social stress procedure (Trier Social Stress Test, TSST). Indices of stress were derived from repeated measurement of cortisol, blood pressure, and heart rate during the TSST. All subjects were genotyped for the Val66Met polymorphism.


RESULTS
Tests of within-subject effects showed a significant three-way interaction (SPSS GLM repeated measures: Time (eight levels)xBDNF (val/val, val/met)xSex: p=0.0002), which reflects gender differences in the pattern of cortisol rise and decline during the social challenge. In male subjects, val/val homozygotes showed a greater rise in salivary cortisol than val/met heterozygotes. In female subjects, there was a trend for the opposite response, which is significant when area under the curve increase (AUCi) was calculated for the val/val homozygotes to show the lowest rise. Overall, the same pattern of results was observed for blood pressure and heart rate.


CONCLUSIONS
These results indicate that a common, functionally significant polymorphism in the BDNF gene modulates HPA axis reactivity and regulation during the TSST differently in men and women. Findings may be related to gender differences in reactivity and vulnerability to social stress.
Shalev
Idan
I
Neurobiology, Hebrew University, Jerusalem, Israel.
Lerer
Elad
E
Israel
Salomon
S
Uzefovsky
Florina
F
Gritsenko
Inga
I
Mankuta
David
D
Ebstein
Richard P
RP
Kaitz
Marsha
M
D000328:Adult; D001794:Blood Pressure; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics*; D005260:Female; D005838:Genotype; D006339:Heart Rate; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D008297:Male; D010913:Pituitary-Adrenal System / Q000502:physiology*; D011110:Polymorphism, Genetic; D012463:Saliva / Q000378:metabolism; D012727:Sex Characteristics; D013315:Stress, Psychological / Q000235:genetics* / Q000378:metabolism*
D019208:Brain-Derived Neurotrophic Factor; D006854:Hydrocortisone