Genotype moderates breastfeeding–atopy interaction
MedWire News: The relationship between breastfeeding and the development of food sensitization in early childhood is modified by single nucleotide polymorphisms (SNPs) in three genes involved in immunity, conclude researchers.
It is recommended that all infants, including those with a family history of atopy, be breastfed exclusively to 4-6 months of age. Nevertheless, studies into the role of breastfeeding in preventing allergic diseases have been inconclusive.
To further examine the relationship between breastfeeding and allergic disease and determine the effect of genotype, Xiumei Hong, from Northwestern University in Chicago, Illinois, USA, and colleagues studied 970 children from the Boston Birth Cohort.
A standardized questionnaire was used to obtain information on breastfeeding history, and food sensitization was defined as a specific immunoglobulin E (IgE) level ≥0.35 kUA/l to any of eight common food allergens. Participants were also genotyped for 88 potentially functional SNPs in 18 genes involved in innate immunity or T-cell balance.
In all, 37.2% of the children had food sensitization, while 76.2% were breastfed, of whom 27.1% had been breastfed exclusively for ≥4 months. Breastfed children had a significantly higher rate of food sensitization than non-breastfed children, at 39.6% versus 29.4%.
After adjusting for covariables, the team found that breastfed children had a 1.5-fold higher risk for food sensitization than non-breastfed children. This relationship was stronger in children aged ≥2 years than those aged <2 years, at odds ratios (ORs) of 2.3 and 1.1, respectively. There was little difference between children who were breastfed for <4 months and those breastfed for ≥4 months in the risk for food sensitization.
The rs425648 SNP of the interleukin-12 receptor beta1 gene significantly affected the association between breastfeeding and food sensitization risk, such that breastfeeding increased the risk in children with the GG genotype, at an OR of 2.0, but decreased the risk in children with the GT or TT genotype, at an OR of 0.6.
The team notes in the Journal of Allergy and Clinical Immunology that similar interactions were seen for the rs352140 SNP of the toll-like receptor 9 (TLR9) gene and the rs3806933 of the thymic stromal lymphopoietin (TSLP) gene, and became even stronger for all three genes combined.
They conclude: "Given the undoubted health benefits of breastfeeding, our findings should not lead to a change in the general recommendations for breastfeeding.
"Rather our findings should lead to further studies that would allow for a better understanding of the effect of breastfeeding on allergic diseases in the context of individual genetic variation."
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By Liam Davenport