In this prospective cohort study encompassing 9,092 Chinese adults, we identified a persistent positive association between plasma AIP levels and the risk of type 2 diabetes, even after comprehensive adjustment for various confounding factors. The robustness of this association was further corroborated by subgroup analyses, underscoring its reliability across different demographic segments. Furthermore, restricted cubic spline (RCS) analysis revealed a nonlinear relationship between AIP and type 2 diabetes risk, manifested as a reverse L-shaped curve with a critical threshold at 0.45. These findings underscore the potential of AIP as a significant early biomarker for predicting type 2 diabetes.
Type 2 diabetes is a chronic condition characterized by a gradual progression over an individual’s lifetime, with an alarming trend of increased diagnoses among younger populations. Once established, type 2 diabetes becomes a lifelong affliction, profoundly impacting quality of life through a range of complications, including both microvascular and macrovascular issues, and imposing a significant economic burden on individuals and healthcare systems alike20,21. Current research underscores that proactive prevention and treatment strategies can markedly mitigate diabetes-related complications and curtail associated healthcare costs22. Evidence suggests that lifestyle interventions, such as dietary modifications and enhanced physical activity, may surpass pharmacological treatments in delaying disease progression and aiding early prevention23. Presently, diabetes biomarkers predominantly focus on indicators related to glucose metabolism. Despite their efficacy, these biomarkers often fall short in predicting and diagnosing type 2 diabetes beyond conventional metrics like fasting blood glucose24. Thus, identifying novel biomarkers for early prediction of type 2 diabetes remains a crucial objective.
While some studies have identified associations between individual plasma lipid components, such as LDL cholesterol, and type 2 diabetes, these components alone may not provide a comprehensive assessment of diabetes risk25. Consequently, researchers have increasingly focused on composite indicators, such as the glucose-triglyceride index, to better evaluate their relationship with type 2 diabetes26. In contrast, the AIP offers a more integrated approach by utilizing plasma lipid profiles. AIP is associated with lipoprotein particle size and reflects the interplay between anti-atherogenic and pro-atherogenic particles. The National Cholesterol Education Program recognizes AIP as a significant marker of plasma atherosclerosis and a dependable predictor of cardiovascular risk27. A longitudinal study involving 8,760 participants from the China Health and Retirement Longitudinal Study demonstrated that variations in AIP from baseline to follow-up were predictive of type 2 diabetes risk. Specifically, individuals with persistently high AIP or those experiencing shifts from high to low or low to high AIP had about a 1.5-fold increased risk of type 2 diabetes compared to those with consistently low AIP levels28. An earlier meta-analysis also affirmed that AIP serves as a straightforward and reliable marker for assessing type 2 diabetes risk29. Furthermore, an analysis of NHANES data corroborated our findings, revealing a reverse L-shaped association between AIP and type 2 diabetes risk, with a notable breakpoint at 0.4513.
We hypothesize that the association between AIP and type 2 diabetes may be explained through several potential mechanisms. Firstly, AIP is a marker of plasma lipoprotein metabolism and exhibits a positive correlation with small dense LDL (sdLDL). SdLDL is known to be a predictor of atherosclerosis due to its small size, low plasma clearance rate, and heightened sensitivity to oxidative stress, which can precipitate inflammation in the subendothelial space30,31. Furthermore, emerging research highlights inflammation as a crucial pathogenic factor in type 2 diabetes32,33. It is proposed that type 2 diabetes represents the culmination of an acute-phase response characterized by substantial cytokine release from adipose tissue and macrophages, which exacerbates cellular dysfunction. This inflammatory process necessitates considerable energy expenditure and is modulated by genetic factors34. Nevertheless, the precise mechanisms through which AIP influences type 2 diabetes remain unclear and warrant further investigation through both basic and clinical research.
This study possesses several notable strengths. Firstly, it features a large sample size, which is comparatively larger than that of other studies examining the association between AIP and type 2 diabetes within the Chinese population, thereby offering a more comprehensive representation of the general Chinese demographic. Secondly, the prospective nature of the cohort study, coupled with an extended follow-up period and a high response rate, provides a robust framework for minimizing biases inherent in cross-sectional studies and enhances the reliability of the findings. Thirdly, leveraging data from the 4C study, the collection of data and diagnosis of diseases were carried out by trained professionals adhering to standardized protocols, which substantially mitigates potential biases stemming from human factors. Finally, the application of RCS and stratified analyses has bolstered the statistical power and affirmed the robustness of the results.
Nevertheless, this study does have several limitations. Firstly, variables that were not accounted for, such as dietary patterns, ethnic differences, and lifestyle factors, could also influence AIP levels. Secondly, since the study primarily involves participants from China, extrapolating the findings to other populations should be approached with caution. Despite these limitations, the robust cohort established in this study significantly strengthens the reliability and validity of the results.