A Narrative Review of Remnant Cholesterol as an Independent Atherogenic Lipoprotein in Type 2 Diabetes: Pathophysiology and Clinical Implications.

Background: T2DM is characterized not only by chronic hyperglycemia but by a complex disturbance in triglyceride-rich lipoprotein (TRL) metabolism. Among the resulting lipid fractions, remnant cholesterol (RC) has emerged as a potentially independent atherogenic driver that persists despite optimal low-density lipoprotein cholesterol (LDL-C) control. Growing evidence suggests that RC integrates metabolic dysregulation, insulin resistance (IR), and inflammatory signaling, thereby contributing to the "residual risk" of vascular complications in DM. Objective: To evaluate whether RC functions as an independent atherogenic lipoprotein in T2DM and to assess its clinical implications for risk prediction and therapeutic targeting. Methods: This narrative review examined relevant cohort studies, genetic analyses, mechanistic experiments, and clinical trials published in the last decade with emphasis on RC definitions, measurement approaches, associations with macrovascular and microvascular outcomes, and therapeutic modulation. Results: RC elevation in T2DM reflects impaired TRL clearance driven by IR, hepatic VLDL overproduction, and adipose lipolysis. Across large cohorts, RC consistently predicts incident T2DM, major cardiovascular events, renal deterioration, and peripheral arterial disease independent of LDL-C, triglycerides, HbA1c, and inflammatory markers. RC trajectories and visit-to-visit variability further strengthen risk discrimination, suggesting that dynamic fluctuations reflect underlying metabolic instability. Thresholds associated with vascular injury vary across populations (≈0.56-0.80 mmol/L). Therapeutically, high-intensity statins, EPA-based therapy, and emerging APOC3/ANGPTL3 inhibitors lower RC to varying degrees, yet outcome trials targeting RC specifically remain scarce. Conclusion: RC represents a distinct atherogenic entity in T2DM. Its strong and independent associations with cardiovascular and renal events position it as a critical, yet underrecognized, contributor to diabetic vascular risk. Incorporating RC into routine risk assessment and exploring targeted interventions may bridge the persistent gap between LDL-C lowering and actual event reduction. Future studies should prioritize standardized measurement, mechanistic elucidation, and randomized trials directly testing whether lowering RC can modify clinical outcomes.