Lactase persistence/non-persistence genetic variants in irritable bowel syndrome in an endemic area for lactose malabsorption

Background and aim: Lactase non-persistence is common in India. We evaluated: (i) frequency of lactase gene (C/T-13910 and G/A-22018) polymorphisms in irritable bowel syndrome (IBS) and healthy controls (HC), (ii) association between these polymorphisms and IBS-subtypes and symptoms.

Methods: A total of 150 IBS patients (Rome-III criteria) and 252 age and gender-matched HC were evaluated for C/T-13910 and G/A-22018 genotypes using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Results: Totals of 79 (52%), 52 (35%) and 19 (13%) patients had diarrhea-predominant IBS (D-IBS), constipation predominant IBS (C-IBS) and alternating diarrhea and constipation IBS (A-IBS), respectively (Rome-III). Frequency of C/T-13910 [genotypes: CC 102 (68%), CT 43 (29%), TT 5 (3%) vs CC 155 (61%), CT 83 (33%), TT 14 (6%), P > 0.05] and G/A-22018 [GG 97 (65%), GA 41 (27%), AA 12 (8%) vs GG 154 (61%), GA 78 (31%), AA 20 (8%), P > 0.05] were similar among IBS and HC. Patients with D-IBS more often had C/T-13910 and G/A-22018 genotypes than C-IBS (CC 71 [90%], CT 6 [8%], TT 2 [2%]) versus (24 [46%], 25 [48%], 3 [6%]), A-IBS (7 [39%], 12 [63%], 0, [0%]) and HC (155 [61%], 83 [33%], 14 [6%]), P < 0.0001 and (GG 69 [87%], GA 6 [8%], AA 4 [5%]) vs (22 [42%], 24 [46%], 6 [12%]) vs (6 [32%], 11 [58%], 2 [10%]), P < 0.0001. IBS with CC and GG genotypes more often had abdominal pain (P = 0.005), distension (P = 0.031) and higher stool frequency (P = 0.003) and reported symptoms following dairy products than non-CC (P < 0.0001).

Conclusion: Though C/T-13910 and G/A-22018 polymorphisms were comparable among IBS and HC, these were more common among D-IBS and reported some symptoms like abdominal pain, bloating and exacerbation by dairy products.