Brain Arousal Regulation in Carriers of Bipolar Disorder Risk Alleles.
OBJECTIVE
Recent genome-wide association studies identified a number of chromosomal risk loci for bipolar disorder (BD, 'manic-depressive illness'). According to the vigilance regulation model, the regulation of brain arousal (referred to as 'vigilance') when assessed via EEG is an emerging biomarker linked to the pathogenesis of manic and depressive episodes. On this basis, the present study aimed to assess whether carriers of BD risk alleles differ in brain arousal regulation.


METHODS
Healthy participants of the population-based Leipzig Health Care Study (LIFE) underwent a 20-min eyes-closed resting EEG paradigm. Brain arousal was assessed applying the computer-based Vigilance Algorithm Leipzig (VIGALL). The primary sample (n = 540) was genotyped for ten of the most reliable BD risk variants, of which two qualified for replication (n = 509).


RESULTS
Primary sample analyses revealed Bonferroni-adjusted significance for rs1006737 in CACNA1C (encoding a calcium channel subunit), with risk allele carriers exhibiting relatively steep brain arousal declines. Further, carriers of two risk alleles of rs472913 at 1p32.1 showed generally lower brain arousal levels for the duration of the resting paradigm. However, both associations failed replication.


CONCLUSIONS
Although our initial findings are in line with the vigilance regulation model and convincing in view of the previously reported notable role of ion channelopathies in BD, our results do not provide consistent evidence for a link between BD risk variants and brain arousal regulation. Several between-sample differences may account for this inconsistency. The molecular genetics of brain arousal regulation remain to be clarified.
LIFE - Leipzig Research Centre for Civilization Diseases, Leipzig, Germany.
Philippe
P
Jawinski
Christian
C
Sander
Nicole
N
Mauche
Janek
J
Spada
Jue
J
Huang
Anna
A
Schmidt
Madlen
M
Häntzsch
Ralph
R
Burkhardt
Markus
M
Scholz
Ulrich
U
Hegerl
Tilman
T
Hensch
D000328:Adult; D000368:Aged; D000465:Algorithms; D001143:Arousal / Q000502:physiology*; D001714:Bipolar Disorder / Q000235:genetics*; D001921:Brain / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000235:genetics*; D004569:Electroencephalography; D005260:Female; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D012146:Rest; D012815:Signal Processing, Computer-Assisted
C079146:CACNA1C protein, human; D020746:Calcium Channels, L-Type