The proportion of the electronegative low density lipoprotein [LDL( ؊ )] subfraction, which is atherogenic, is increased in type 2 diabetes but is not reduced by glycemic control. Therefore, we evaluated the ability of a new technique, capillary isotachophoresis (cITP), to quantify charge-based LDL subfractions and examined the relation between insulin resistance and the cITP fast-migrating (f) LDL levels. Seventy-five 10-year-old boys were included. The two cITP LDL subfractions, fLDL and major LDL subfractions, were proportional to the LDL protein content within the range of 0.1-0.8 mg/ml LDL protein. Levels of cITP fLDL were positively correlated with triglyceride (TG) levels and negatively correlated with LDL size. Insulin resistance as assessed by the homeostasis model assessment (HOMA-IR) was positively correlated ( P Ͻ 0.01) with cITP fLDL levels ( r ؍ 0.41). The relation between HOMA-IR and cITP fLDL levels depended on TG levels but was independent of body mass index and LDL size. cITP lipoprotein analysis is an accurate and sensitive method for quantifying charge-based LDL subfractions in human plasma, and insulin resistance is related to cITP fLDL independent of LDL size. -Zhang, B., T. Kaneshi, T. Ohta, and K. Saku. Relation between insulin resistance and fast-migrating LDL subfraction as characterized by capillary isotachophoresis. Electronegative low density lipoprotein [LDL( Ϫ )] subfraction in plasma has been shown to have various atherogenic properties [reviewed by Sánchez-Quesada, Benitez, and Ordonez-Llanos (1)]. Although in vitro oxidized LDL can only be taken up by scavenger receptors, LDL( Ϫ ) can also be taken up by LDL receptors to induce vascular cell adhesion molecule-1 expression through the activation of nuclear factor B and adaptor protein 1 (2).Both type 1 and type 2 diabetic patients have been shown to have an increased proportion of LDL( Ϫ ) (3, 4). However, LDL( Ϫ ) in type 1 and type 2 diabetes seems to be of different origins. In type 1 diabetes, nonenzymatic glycosylation has been shown to contribute to the increased proportion of LDL( Ϫ ): glycemic optimization decreased both the glycated LDL and the proportion of LDL( Ϫ ) (3, 4). However, in type 2 diabetes, glycemic control decreased glycated LDL but had no significant effects on the proportion of LDL( Ϫ ) (4, 5). It is not clear whether or not insulin resistance contributes to LDL( Ϫ ) generation in type 2 diabetes.Insulin resistance is known to be associated with increased levels of triglycerides (TGs) (6). Because LDL( Ϫ ) separated by anion-exchange chromatography techniques has been shown to contain higher TG content than the major LDL subfraction (7-9), it is possible that there may be a relation between insulin resistance and LDL( Ϫ ). However, this has not yet been examined. In addition, it would be interesting to know whether or not the relation between insulin resistance and LDL( Ϫ ) depends on TG levels.Insulin resistance is also linked to plasma levels of small, dense LDLs (pattern B lipoprotein phenot...