Relationship between plasma atherogenic index of plasma (AIP) and Klotho protein: A cross-sectional study

Abstract

Background: The plasma atherogenic index of plasma (AIP) is an indicator that measures the degree of lipid abnormalities and the risk of atherosclerosis, while Klotho protein is a protein with anti-aging biological functions. However, the relationship between these two factors has not been studied. Objective: The aim of this study was to evaluate the association between plasma atherogenic index of plasma (AIP) and serum anti-aging protein Klotho in the US population. Methods: This study utilized a cross-sectional design using data from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. The AIP index was calculated using TG and HDL-C, and the concentration of Klotho protein was measured using an ELISA kit. After adjusting for potential confounding variables, a multivariable linear regression model was used to estimate the relationship between AIP and Klotho protein. Additionally, smooth curve fitting and segmented regression models were applied to test threshold effects and calculate inflection points. Results: The study included 6,155 eligible adults with a mean age of 57.37 ± 10.75 years, of which approximately 48.22% were male. The results of multivariable linear regression showed that after adjusting for potential confounders, AIP was independently negatively associated with Klotho protein (β = -77.91, 95% CI (-131.61, -24.20)), which was consistent with the results when AIP (quartiles) was treated as a categorical variable (p trend = 0.0048). A non-linear relationship was observed between AIP and Klotho protein, with an inflection point at 0.02. On the left side of the inflection point (AIP ≤ 0.02), for every unit increase in AIP, the level of Klotho protein decreased by 200. On the right side of the inflection point (AIP > 0.02), this relationship was not observed. Subgroup analyses showed a stronger association between AIP and Klotho protein levels in females and non-drinkers, with values of -170.31 (-255.62, -94.99) and -306.24 (-520.18, -92.30) respectively. Conclusion: A non-linear relationship exists between AIP and Klotho protein. When AIP is less than 0.02, there is a negative correlation between AIP and Klotho.