Objective To investigate the association of phthalates exposure with mitochondrial DNA oxidative damage and copy number in boys based on a case-control study on constitutional delay of growth and puberty (CDGP) and to explore the potential mechanism of phthalates' effect on CDGP.
Methods A case-control study was conducted in a tertiary class A hospital from 2013 to 2014. The recruited 48 cases were 8-15-year-old boys with diagnosed CDGP, and the 60 controls were boys of same age visiting the surgery department of the hospital. Concentrations of mono-n-butyl phthalate (MnBP), mono-methyl phthalate (MMP), mono-ethyl phthalate (MEP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) in urine samples were determined using high performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS). The relationship between phthalates exposure and mitochondrial DNA copy number and mitochondrial DNA oxidative damage were analyzed by t test and using multiple linear regression models.
Results Higher mitochondrial DNA copy numbers and higher urinary MnBP, MMP, MEHP, SumDEHP concentrations were detected in the CDGP boys than those in the controls (P=0.001, 0.017, 0.008, 0.038, 0.020, respectively). The mitochondrial DNA oxidative damage level was not different between the cases and the controls. The urinary MMP, MEHP, and sumDEHP concentrations were positively associated with the mitochondrial DNA copy numbers (P < 0.05), but no association was found between the mitochondrial DNA damage level and the phthalates exposure level.
Conclusion Elevated phthalate levels and mitochondrial DNA copy numbers are found in the CDGP boys compared to the controls. Phthalates exposure might be a risk factor of mitochondrial disfunction.
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