Kisspeptin as potential biomarker of environmental chemical mixture effect on reproductive hormone profile: A pilot study in adolescent males

Background: Kisspeptin has been proposed as an effect biomarker to understand the mechanisms by which some environmental chemicals adversely affect the human reproductive system. Objective: To ascertain whether kisspeptin serum protein and DNA methylation levels are associated with exposure to several environmental chemicals (individually and as a mixture) and serum reproductive hormone levels in adolescent males. Methods: Three phenols (bisphenol A [BPA], methyl-paraben [MPB], and benzophenone-3 [BP3]); two toxic metals (arsenic and cadmium); and four metabolites of non-persistent pesticides, including insecticides (2-isopropyl-6- methyl-4-pyrimidinol [IMPy], malathion diacid [MDA], and dimethylcyclopropane carboxylic acid [DCCA]) and fungicides (ethylene thiourea [ETU]) were measured in first-morning urine samples of 133 adolescent males aged 15–17 years from the INMA-Granada cohort. In blood samples collected on the same day, KISS1 gene DNA methylation was measured at four CpGs from the Exon IV, as well as serumlevels of kiss54 protein, total testosterone (T), estradiol (E2), sex hormone binding-globulin, dehydroepiandrosterone sulfate, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). Multiple linear regression and mixture (quantile g-computation) models were fit. Results: UrinaryMDA and DCCA concentrations were associatedwith higher kiss54 levels [%change (95%CI) for each log-unit increase in concentration = 2.90 (0.32;5.56), and 1.93 (0.45,3.43), respectively]; IMPy with lower DNA methylation percentage at CpG1 and total CpGs [% change (95%CI) = −1.15 (−1.96;-0.33): −0.89 (−1.73;- 0.01), respectively]; and BP3 and DCCA with lower total CpGs methylation [−0.53 (−1.04;-0.01) and − 0.69 (−1.37;-0.01), respectively]. The pesticide mixture and the whole chemical mixture were associated with higher kiss54 [% change (95%CI) = 9.09 (3.29;15.21) and 11.61 (3.96;19.82), respectively] and lower methylation levels at several CpGs. Additionally, serum kiss54 in the third tertile was associated with ...