Moderating effects of reduced morning and evening questionnaire scores on the association between urinary phthalate metabolites and inflammatory cytokines among Chinese young adults: A human biomonitoring study

Abstract

Although previous findings have suggested that phthalate exposure was related to inflammation in young adults, little is known about whether chronotype, measured by the reduced Morning and Evening Questionnaire (rMEQ), reflects a moderating or mediating effect of phthalate exposure on inflammation. To address these gaps, this study examined the correlation of phthalate metabolites with inflammatory cytokines in Chinese young adults and explored the moderating effects of rMEQ scores in this association. From April to May 2019, 1179 young adults were recruited from 2 universities in Hefei and Shangrao cities. Among them, 1135 completed valid self-administered questionnaires, 1012 provided sufficient urine samples for phthalate metabolites analysis, and 744 provided fasting blood samples for the determination of inflammatory cytokines levels. The high-performance liquid chromatography-tandem mass spectrometry was adopted to determine the concentration of urinary phthalate metabolites. A liquid-phase protein suspension chip detection instrument was utilized to detect the levels of inflammatory cytokines in the supernatant. The rMEQ was adopted as a measure of chronotype. The generalized linear model was established to determine the association of phthalate metabolites with inflammatory cytokines. Moderating analysis was used to examine whether rMEQ scores moderated the relationships of phthalate metabolites with inflammatory cytokines. The median concentrations of phthalate metabolites ranged from 2.74 to 107.22 ng/mL. The mean levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were 0.78 ± 0.21 pg/mL and 0.34 ± 0.26 pg/mL, respectively. The generalized linear model results revealed that monobutyl phthalate (MBP) was weakly but significantly positively correlated with TNF-α. According to gender and further stratified analysis, the results showed that MBP and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) were weakly but significantly positively correlated with TNF-α and IL-1β only among females. Furthermore, the moderating effects analysis results indicated that rMEQ scores have a negative moderating role among MBP, MEOHP and TNF-α. Phthalate exposure was significantly positively correlated with inflammatory cytokines in young adults, and rMEQ scores played a negative moderating role in this association. This study has the potential to offer useful insights for the prevention and control of chronic inflammation among young adults.