Early-life dentine-based elemental biodynamics and cord blood telomere length

Background: Leukocyte telomere length (LTL) from cord blood is a marker of biological aging and long-term systemic health. Exposure to essential and toxic metals has been shown to influence LTL in a sexually dimorphic manner. However, little is known about the interplay between early-life longitudinal biodynamic patterns of these elements and cord blood LTL, as well as potential sex differences. Methods: From an ongoing longitudinal birth cohort study in Mexico City, we used available tooth samples from 231 children (129 males and 102 females) to generate 16 elemental weekly time series of direct fetal intensities from the second trimester through four to five months after birth. We analyzed the dentine growth rings using Inductively Coupled Plasma Mass Spectrometry to generate time-resolved elemental intensities. The elements included were Li, Mg, Ca, Mn, Co, Ni, Cu, Zn, As, Sr, Mo, Cd, Sn, Ba, Pb, and Bi. LTL was measured in cord blood using qPCR. We used cross-recurrence quantification analysis and entropy-complexity-based measures to generate time-resolved features that quantify the synchronization of elemental biodynamics. A stability-selection approach using five-fold cross-validation of regularized ridge regression was used for feature selection, and covariate-adjusted linear models were used to estimate associations with LTL. Findings: The biodynamic interaction of Mg-Co and Mn-Sn was identified as the most stable feature among male and female children, respectively. In males, higher vertical entropy (i.e., a measure of higher variability) of Mg-Co temporal biodynamics was associated with shorter LTL (β[95%CI]: -0.9[-0.14,-0.03]; p-value<0.01), but not in females (β[95%CI]:-0.02[-0.10,0.06]; p-value=0.60); whereas higher recurrence rate (i.e., a measure of higher synchronicity) of Mn-Sn temporal biodynamics was associated with longer LTL (β[95%CI]: 0.09[0.02,0.16]; p-value=0.01), in females but not in males (β[95%CI], 0.03[-0.04, 0.09]; p-value=0.39). Interpretation: We demonstrate that time-varying multi-elemental synchronization of early-life elemental biodynamics, a potential marker of homeostatic balance, may be associated with cord blood-based telomere length in a sexual dimorphic manner.