Associations between concentrations of serum α-klotho and selected urinary monohydroxy metabolites of polycyclic aromatic hydrocarbons: data for US adults aged 40-79 years.

For the first time, the associations between urinary concentrations of oxidant polycyclic aromatic hydrocarbon (PAH) metabolites and serum concentrations of anti-oxidant α-klotho were estimated for US adults aged 40-79 years. Multivariate regression models with α-klotho as dependent variable and one of the urinary metabolite of PAH as independent variables were fitted. In the absence of albuminuria and normal (eGFR > 90 mL/min/1.73 m) kidney function, 10% increases in concentrations of 2-hydroxynaphthalene, 9-hydroxyfluorene, and ∑PAH were associated with 0.25%, 0.32%, and 0.19% decreases in serum α-klotho concentrations. In the absence of albuminuria and near normal (60 <  = eGFR < 90 mL/min/1.73 m) kidney function, 10% increases in concentrations of 1-hydroxynaphthalene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, and ∑PAH were associated with 0.17%, 0.38%, 0.34%, and 0.18% decreases in serum α-klotho concentrations. To what degree, these mild decreases in α-klotho are a matter of concern, is a subject ripe for discussion and additional investigations. When kidney function was normal or near normal but albuminuria was present, the associations between α-klotho and different metabolites of PAH were, more or less, randomly positive or negative and none reached statistical significance. To conclude, exposure to polycyclic aromatic hydrocarbons may result in reduced concentrations of α-klotho, an antiaging protein.