Association of distinct alpha(2) adrenoceptor and serotonin transporter polymorphisms with constipation and somatic symptoms in functional gastrointestinal disorders.
BACKGROUND
The role of genetics in the phenotypic manifestations of irritable bowel syndrome (IBS) is unclear. Our aims were: (1) to compare the prevalence of polymorphisms of alpha 2 (alpha(2)) adrenoceptors, norepinephrine transporter, and serotonin transporter protein (soluble carrier protein member 4 (SLC6A4)) promoter in patients with lower functional gastrointestinal disorders (FGID) and in healthy controls; and (2) to test associations of these genetic variations with symptoms of IBS and high somatic symptom scores.


METHODS
Validated bowel and somatic symptom questionnaires characterised the phenotype: 90 with IBS constipation (IBS-C), 128 IBS diarrhoea, 38 IBS alternating bowel function, and 20 chronic abdominal pain. Logistic regression analyses assessed associations of different polymorphisms for alpha(2) adrenoceptor and SLC6A4 with IBS or chronic abdominal pain phenotypes and high somatic score.


RESULTS
Two distinct polymorphisms independently appeared to be associated with the phenotype IBS-C: alpha(2C) Del 322-325 (odds ratio (OR) 2.48 (95% confidence interval (CI) 0.98, 6.28); p = 0.05) and alpha(2A) -1291 (C-->G) (OR 1.66 (95% CI 0.94, 2.92); p = 0.08) relative to wild-type. Overall, the alpha(2C) Del 322-325 polymorphism (alone or combined with other polymorphisms) was also significantly associated with a high somatic symptom score (OR 2.2 (95% CI 1.06, 4.64); p = 0.03). Combinations of polymorphisms were also associated with high somatic scores.


CONCLUSIONS
Functionally distinct alpha(2A) and alpha(2C) adrenoceptor and serotonin transporter polymorphisms are associated with constipation and high somatic symptoms in patients with lower functional gastrointestinal disorders, although the strength of the genetic contribution to the phenotype is unclear.
Kim
H J
HJ
Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Gastroenterology Research Unit, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Camilleri
M
M
Carlson
P J
PJ
Cremonini
F
F
Ferber
I
I
Stephens
D
D
McKinzie
S
S
Zinsmeister
A R
AR
Urrutia
R
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D002352:Carrier Proteins / Q000235:genetics*; D003248:Constipation / Q000235:genetics*; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000235:genetics*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D026901:Membrane Transport Proteins; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics*; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics*; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics*; D050486:Serotonin Plasma Membrane Transport Proteins; D027981:Symporters / Q000235:genetics*
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D018341:Receptors, Adrenergic, alpha-2; C493227:SLC6A2 protein, human; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D027981:Symporters