Infant birth outcomes are associated with DNA damage biomarkers as measured by the cytokinesis block micronucleus cytome assay: the DADHI study

Accumulation of DNA damage in the first 1000 days may increase risk of accelerated ageing and degenerative diseases in adult life such as cancers. The extent of DNA damage in infants and the correlation of maternal factors during pregnancy with neonate birth outcomes and DNA damage is not known in infants born in Australia. Therefore, we performed a prospective cohort study to collect data on DNA damage in lymphocytes of Australian infants (aged 0, 3 and 6 months), using the cytokinesis block micronucleus cytome (CBMN-Cyt) assay. The study also explored correlation of CBMN-Cyt biomarkers with infant birth outcomes and maternal anthropometric and lifestyle variables. Peripheral blood lymphocytes were isolated from the infants at birth (cord blood) (n = 82), 3 months (n = 64) and 6 months (n = 53) after birth. DNA damage biomarkers measured ex vivo in binucleated lymphocytes (BNC) included: micronuclei (MN), nucleoplasmic bridges (NPB) and nuclear buds (NBUD). Apoptotic and necrotic lymphocytes were also scored and nuclear division index (NDI) was measured using the frequency of mono-, bi- and multinucleated lymphocyte. MN and NBUD were also scored in mononucleated lymphocytes (MNC). The mean (± SD) frequency of MN, NPB and NBUD in BNCs at birth was 2.0 (± 1.2), 5.8 (± 3.7) and 11.1 (± 5.7) per 1000 BNC, respectively, and tended to decrease significantly at 3 months (P < 0.01, P < 0.0001, P < 0.001, respectively) and 6 months (P < 0.05, P < 0.0001, P < 0.0001, respectively) after birth relative to cord blood when compared with the same cohort of infants (n = 48 at birth, 48 at 3 months and 39 at 6 months). None of the CBMN cytome biomarkers measured at birth was associated with maternal smoking status, alcohol and folic acid intake during pregnancy. The mean gestation age correlated positively with MN (r = 0.38, P = 0.006), NPB (r = 0.30, P = 0.03) and negatively with NDI (r = -0.29, P = 0.03). Infant birth weight associated positively with MN, NPB and NBUD in cord blood (r = 0.24, P = 0.08; r = 0.32, P = 0.02; r = 0.28, P = 0.04, respectively), birth length associated positively with NPB (r = 0.32, P = 0.02) and NBUD (r = 0.27, P = 0.04) while head circumference associated negatively with apoptotic cells (r = -0.27, P = 0.06). APGAR score at 1 and 5 min after birth associated positively with NDI at birth (r = 0.3, P = 0.05, r = 0.28, P = 0.06, respectively). Mother's weight and body mass index (BMI) recorded at the time of recruitment associated positively with NPB (r = 0.38, P = 0.006, r = 0.32, P = 0.02, respectively) and negatively with APGAR score at 5 min (r = -0.25, P = 0.07). The significant positive associations of infant birth weight and length and maternal BMI with CBMN-Cyt biomarkers suggest the possibility of a genotoxic effect of metabolic processes that promote excessive growth and high BMI.