Nonlinear association between atherogenic index of plasma and type 2 diabetes mellitus in overweight and obesity patients: evidence from Chinese medical examination data

Abstract

Background: The atherogenic index of plasma (AIP) is closely associated with the onset of diabetes, with obesity being a significant risk factor for type 2 diabetes mellitus (T2DM). However, the association between the AIP and T2DM in overweight and obese populations has been infrequently studied. Therefore, this study aimed to explore this association in overweight and obese individuals with T2DM.

Methods: This cross-sectional analysis utilized data from 40,633 participants with a body mass index (BMI) ≥ 24 kg/m² who were screened from January 2018 to December 2023 at Henan Provincial People's Hospital. Participants were categorized into groups of overweight and obese individuals with and without diabetes according to the T2DM criteria. The AIP, our dependent variable, was calculated using the formula log10 [(TG mol/L)/HDL-C (mol/L)]. We investigated the association between the AIP and T2DM in overweight and obese individuals using multivariate logistic regression, subgroup analysis, generalized additive models, smoothed curve fitting, and threshold effect analysis. Additionally, mediation analysis evaluated the role of inflammatory cells in AIP-related T2DM.

Results: Overweight and obese patients with T2DM exhibited higher AIP levels than those without diabetes. After adjusting for confounders, our results indicated a significant association between the AIP and the risk of T2DM in overweight and obese individuals (odds ratio (OR) = 5.17, 95% confidence interval (CI) 4.69-5.69). Notably, participants with a high baseline AIP (Q4 group) had a significantly greater risk of T2DM than those in the Q1 group, with an OR of 3.18 (95% CI 2.94-3.45). Subgroup analysis revealed that the association between the AIP and T2DM decreased with increasing age (interaction P < 0.001). In overweight and obese populations, the association between AIP and T2DM risk displayed a J-shaped nonlinear pattern, with AIP > - 0.07 indicating a significant increase in T2DM risk. Various inflammatory cells, including neutrophils, leukocytes, and monocytes, mediated 4.66%, 4.16%, and 1.93% of the associations, respectively.

Conclusion: In overweight and obese individuals, the AIP was independently associated with T2DM, exhibiting a nonlinear association. Additionally, the association between the AIP and T2DM decreased with advancing age. Multiple types of inflammatory cells mediate this association.

Keywords: Atherogenic index of plasma; Chinese; Obesity; Type 2 diabetes mellitus.

Fig. 1

Flowchart of participants selection

Fig. 2

Age-adjusted AIP box plots for overweight and obese non-T2DM and T2DM groups. The box indicates the interquartile range (IQR) and the center line indicates the median. Whiskers above and below the box indicate the data range and dots indicate outliers. T2DM type 2 diabetes mellitus, AIP atherogenic index of plasma. P < 0.001, as compared with non-T2DM group

Fig. 3

Generalized additive model with fitting smoothness for the dose–response association between AIP and overweight and obese T2DM risk. The red solid line represents the probability of T2DM occurrence, and the blue dotted line represents the 95% CI curve. T2DM Type 2 Diabetes Mellitus, AIP Atherogenic Index of Plasma. All covariates, including age, sex, occupation, BMI, hypertension, total protein, total bilirubin, ALT, AST, GGT, ALP, Cre, and UA, were adjusted in this model

Fig. 4

The association between AIP of overweight and obese T2DM according to different subgroups. Adjusted for all covariates except for this subgroup of variables. BMI body mass index, ALT alanine aminotransferase, AST aspartate transaminase, GGT glutamyl transpeptidase, ALP Alkaline phosphatase, Cre Creatinine, UA Uric acid, OR odds ratio, CI confidence interval

Fig. 5

The association between AIP of overweight and obese T2DM according to different age groups. T2DM type 2 diabetes mellitus. AIP, atherogenic index of plasma. All covariates including sex, occupation, BMI, hypertension, total protein, total bilirubin, ALT, AST, GGT, ALP, Cre, and UA were adjusted in this model