Exposure to non-persistent pesticides, BDNF, and behavioral function in adolescent males: Exploring a novel effect biomarker approach.

BACKGROUND: Numerous contemporary non-persistent pesticides may elicit neurodevelopmental impairments. Brain-derived neurotrophic factor (BDNF) has been proposed as a novel effect biomarker of neurological function that could help to understand the biological responses of some environmental exposures. OBJECTIVES: To investigate the relationship between exposure to various non-persistent pesticides, BDNF, and behavioral functioning among adolescents. METHODS: The concentrations of organophosphate (OP) insecticide metabolites 3,5,6-trichloro-2-pyridinol (TCPy), 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMPy), malathion diacid (MDA), and diethyl thiophosphate (DETP); metabolites of pyrethroids 3-phenoxybenzoic acid (3-PBA) and dimethylcyclopropane carboxylic acid (DCCA), the metabolite of insecticide carbaryl 1-naphthol (1-N), and the metabolite of ethylene-bis-dithiocarbamate fungicides ethylene thiourea (ETU) were measured in spot urine samples, as well as serum BDNF protein levels and blood DNA methylation of Exon IV of BDNF gene in 15-17-year-old boys from the INMA-Granada cohort in Spain. Adolescents' behavior was reported by parents using the Child Behavior Check List (CBCL/6-18). This study included 140 adolescents of whom 118 had data on BDNF gene DNA methylation. Multivariable linear regression, weighted quantile sum (WQS) for mixture effects, and mediation models were fit. RESULTS: IMPy, MDA, DCCA, and ETU were detected in more than 70% of urine samples, DETP in 53%, and TCPy, 3-PBA, and 1-N in less than 50% of samples. Higher levels of IMPy, TCPy, and ETU were significantly associated with more behavioral problems as social, thought problems, and rule-breaking symptoms. IMPy, MDA, DETP, and 1-N were significantly associated with decreased serum BDNF levels, while MDA, 3-PBA, and ETU were associated with higher DNA methylation percentages at several CpGs. WQS models suggest a mixture effect on more behavioral problems and BDNF DNA methylation at several CpGs. A mediated effect of serum BDNF within IMPy-thought and IMPy-rule breaking associations was suggested. CONCLUSION: BDNF biomarkers measured at different levels of biological complexity provided novel information regarding the potential disruption of behavioral function due to contemporary pesticides, highlighting exposure to diazinon (IMPy) and the combined effect of IMPy, MDA, DCCA, and ETU. However, further research is warranted.

Bisphenol A induces oxidative stress and decreases levels of insulin receptor substrate 2 and glucose transporter 8 in rat testis.

Bisphenol A (BPA), a monomer present in plastics, is known to impair male reproductive functions. Testis executes high-energy-demanding processes such as spermatogenesis and steroidogenesis, the successful accomplishment of which requires several factors including glucose. In this context, we sought to investigate the effects of low doses of BPA on glucose metabolism in the testis of rats and to delineate whether oxidative stress has any role to play in mediating the effects. Bisphenol A was orally administered to rats at dose levels of 0.005, 0.5, 50, and 500 µg/kg body weight for 45 days. A positive control was maintained by orally administering 17ß-estradiol at a dose of 50 µg/kg body weight. The levels of plasma glucose and insulin were significantly increased, whereas the testicular glucose level significantly decreased following exposure to BPA and estradiol. A dose-dependent increase in the level of hydrogen peroxide (H2O2) and a significant decline in the activities of hexokinase and phosphofructokinase was observed in the testis of rats treated with BPA. Western blot analyses of insulin receptor substrate 2 (IRS-2) and glucose transporter 8 (GLUT-8) in the testis showed a decline in the levels of these proteins following BPA administration. Immunolocalization of GLUT-8 protein in the testis revealed decreased expression of this protein in spermatocytes and developing spermatids of rats exposed to BPA. The results suggest that persistent exposure to low doses of BPA could disturb glucose homeostasis in the testis and thereby impair testicular functions.