The val158met polymorphism of human catechol-O-methyltransferase (COMT) affects anterior cingulate cortex activation in response to painful laser stimulation - PubMed (original) (raw)

The val158met polymorphism of human catechol-O-methyltransferase (COMT) affects anterior cingulate cortex activation in response to painful laser stimulation

Arian Mobascher et al. Mol Pain. 2010.

Abstract

Background: Pain is a complex experience with sensory, emotional and cognitive aspects. Genetic and environmental factors contribute to pain-related phenotypes such as chronic pain states. Genetic variations in the gene coding for catechol-O-methyltransferase (COMT) have been suggested to affect clinical and experimental pain-related phenotypes including regional mu-opioid system responses to painful stimulation as measured by ligand-PET (positron emission tomography). The functional val158met single nucleotide polymorphism has been most widely studied. However, apart from its impact on pain-induced opioid release the effect of this genetic variation on cerebral pain processing has not been studied with activation measures such as functional magnetic resonance imaging (fMRI), PET or electroencephalography. In the present fMRI study we therefore sought to investigate the impact of the COMT val158met polymorphism on the blood oxygen level-dependent (BOLD) response to painful laser stimulation.

Results: 57 subjects were studied. We found that subjects homozygous for the met158 allele exhibit a higher BOLD response in the anterior cingulate cortex (ACC), foremost in the mid-cingulate cortex, than carriers of the val158 allele.

Conclusion: This result is in line with previous studies that reported higher pain sensitivity in homozygous met carriers. It adds to the current literature in suggesting that this behavioral phenotype may be mediated by, or is at least associated with, increased ACC activity. More generally, apart from one report that focused on pain-induced opioid release, this is the first functional neuroimaging study showing an effect of the COMT val158met polymorphism on cerebral pain processing.

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Figures

Figure 1

Figure 1

BOLD response to laser stimulation. a) Group average. N = 57 subjects. GLM whole-brain analysis. Second-level mixed-effects FLAME. Cluster-corrected threshold Z = 3.5, p = 0.05. Upper row: 3 D surface projection. Lower row: axial slices. R = right. L = left. b) Two-group t-test. _COMT_met/met (N = 19) vs. _COMT_val carriers (N = 38). Voxel-by-voxel analysis restricted to the anterior cingulate cortex (according to the Harvard Oxford atlas). Second-level mixed-effects FLAME. Cluster-corrected threshold Z = 2.3, p = 0.05. Upper row: 3 D surface projection. Lower row: sagittal slices.

Figure 2

Figure 2

Boxplot of COMT genotype effect on fMRI BOLD activation in the anterior cingulate cortex (ACC). Median, 25th percentile, 75th percentile, minimum value, maximum value and outliers are shown. 1 The high BOLD activation in response to laser stimulation in this subject was reproduced in a second experiment that was performed two month later (mean Z value in the ACC = 5.3), suggesting that this 'outlier' is reflecting biological variance in the sample and not a measurement error. Furthermore, the genotype effect on ACC activation remained significant, (F = 7.06; p = 0.01; F = 4.92; p = 0.031 age-corrected) even when this subject was excluded from the analysis.

Figure 3

Figure 3

Regions of interests. Red - anterior cingulate cortex, blue - insula, green - parietal opercular cortex, purple = amygdalae.

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