Association of apolipoprotein B and excess apolipoprotein B with cardiovascular risk in type 2 diabetes: a prospective cohort study of the UK Biobank.

backgroundResidual cardiovascular risk persists in type 2 diabetes mellitus (T2DM) despite intensive risk-factor management. Apolipoprotein B (apoB) and excess apoB are potentially promising biomarkers for identifying residual cardiovascular risk. We assessed apoB and excess apoB in T2DM for incremental prediction of atherosclerotic cardiovascular disease (ASCVD) risk.

methodsThis prospective cohort included 11,918 UK Biobank participants (mean age 59.7 ± 6.6 years; 61% male) with T2DM and no ASCVD at baseline. Excess apoB was defined as the observed minus predicted apoB, where the predicted value was derived using a linear regression model of apoB on low-density lipoprotein cholesterol (LDL-C) fitted in a statin-naïve reference subset with triglycerides ≤ 1.0 mmol/L. The primary endpoint was incident ASCVD. Secondary endpoints included major adverse cardiovascular events (MACE) and all-cause mortality. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox models. Nonlinearity was assessed using restricted cubic splines. Incremental improvements were quantified using the C-index, net reclassification improvement (NRI).

resultsDuring a median 185.3-month follow-up, 2,548 ASCVD and 1,205 MACE events occurred. ApoB was linearly related to ASCVD and MACE, while excess apoB showed J-shaped associations with a nadir near - 7.5 mg/dL for ASCVD. Both apoB and excess apoB showed positive associations with ASCVD across ascending percentile categories. Versus < 50th percentile, HRs (95% CIs) for ASCVD in higher apoB categories (50-<75th, 75-<90th, ≥ 90th) were 1.31 (1.16-1.49), 1.51 (1.25-1.81), and 1.47 (1.10-1.95); corresponding HRs (95% CIs) for excess apoB were 1.50 (1.36-1.66), 1.45 (1.29-1.63), and 1.53 (1.33-1.76), respectively. Similar but weaker risk gradients were observed for MACE. Neither apoB nor excess apoB was associated with all-cause mortality. Excess apoB yielded greater prediction improvement than apoB (ΔC-index: 0.009 vs. 0.002; NRI: 0.270 vs. 0.101) and better stratified risk in statin users and those with LDL-C ≤ 100 mg/dL (P for interaction < 0.05).

conclusionsIn T2DM, apoB is independently associated with ASCVD but adds limited discrimination over conventional lipids. Excess apoB yielded improved discrimination and reclassification, and may serve as a complementary ASCVD risk marker, particularly in statin-treated settings. However, its clinical application requires external validation and standardization.