Serotonin, ghrelin, and motilin gene/receptor/transporter polymorphisms in childhood functional constipation

Functional constipation is the most common form of constipation, and its exact aetiology is still unclear. However, it is known that deficiencies in hormonal factors cause constipation by changing physiological mechanisms. Motilin, ghrelin, serotonin acetylcholine, nitric oxide, and vasoactive intestinal polypeptide are factors that play a role in colon motility. There are a limited number of studies in the literature where hormone levels and gene polymorphisms of serotonin and motilin are examined. Our study aimed to investigate the role of motilin, ghrelin, and serotonin gene/receptor/transporter polymorphisms in constipation pathogenesis in patients diagnosed with functional constipation according to the Rome 4 criteria.

Sociodemographic data, symptom duration, accompanying findings, the presence of constipation in the family, Rome 4 criteria, and clinical findings according to Bristol scale of 200 cases (100 constipated patients and 100 healthy control) who applied to Istanbul Haseki Training and Research Hospital, Pediatric Gastroenterology Outpatient Clinic, between March and September 2019 (6-month period) were recorded. Polymorphisms of motilin-MLN (rs2281820), serotonin receptor-HTR3A (rs1062613), serotonin transporter-5-HTT (rs1042173), ghrelin-GHRL (rs27647), and ghrelin receptor-GHSR (rs572169) were detected by real-time PCR.

There was no difference between the two groups in terms of sociodemographic characteristics. Notably, 40% of the constipated group had a family history of constipation. The number of patients who started to have constipation under 24 months was 78, and the number of patients who started to have constipation after 24 months was 22. There was no significant difference between constipation and control groups in terms of genotype and allele frequencies in MLN, HTR3A, 5-HTT, GHRL, and GHSR polymorphisms (p<0.05). Considering only the constipated group, the rates of gene polymorphism were similar among those with/without a positive family history of constipation, constipation onset age, those with/without fissures, those with/without skin tag, and those with type 1/type 2 stool types according to the Bristol stool scale.

Our study results showed that gene polymorphisms of these three hormones may not be related to constipation in children.