The Nonlinear Association Between Adipose Tissue Insulin Resistance and Remnant Cholesterol in Chinese Adults: A Cross-Sectional Study

Background: Adipose tissue insulin resistance (Adipo-IR) is a key driver in the pathogenesis of cardiometabolic diseases. Dyslipidemia, particularly elevated remnant cholesterol (RC), is also strongly associated with cardiometabolic risk and has been recognized as a highly atherogenic lipid marker. Although systemic IR is known to be linked to dyslipidemia and elevated RC, the specific relationship between Adipo-IR and RC remains unclear. This study aimed to investigate the association between Adipo-IR and RC as well as its consistency across different subgroups. Methods: A cross-sectional study was conducted involving 6299 Chinese subjects. Logistic regression was used to assess the associations between Adipo-IR quartiles and elevated calculated RC levels. Restricted cubic splines (RCS) and a two-piecewise model were employed to characterize the dose–response relationship. Subgroup analyses were performed by age, sex, and body mass index (BMI). Results: Participants in higher Adipo-IR quartiles exhibited a significantly increased risk of elevated RC, low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) (all p for trend <0.001). After full adjustment, the odds ratios (95% CI) for the highest versus lowest Adipo-IR quartile were 1.90 (1.58–2.29) for RC, 1.76 (1.47–2.12) for LDL-C, and 4.74 (3.85–5.86) for TG. RCS analysis revealed a nonlinear increasing relationship between Adipo-IR and RC (p for nonlinearity <0.001). An estimated inflection point was identified at an Adipo-IR value of 44.85, with a significant positive association below this point (OR = 1.020, p < 0.001) but not above it (OR = 0.997, p = 0.248). This positive association was generally consistent across age, sex, and BMI subgroups, and interaction tests were not statistically significant except for the Q3 comparison by sex. Conclusions: Adipo-IR showed a nonlinear association with elevated calculated RC, with a positive association below the estimated inflection point of 44.85 in this cohort of Chinese adults.