Abstract 412: Saturated Fat Ingestion Impairs HDL Function in Diabetes

Recent studies have suggested that HDL cholesterol efflux may be an important determinant of atherosclerosis and CVD. We hypothesized that environmental factors such as high saturated fat diets may impair HDL cholesterol efflux, and this may be particularly relevant in conditions associated with HDL dysfunction such as uncontrolled type 2 diabetes (T2DM). We studied the effect of an acute ingestion of saturated fat on the HDL function and composition in diabetes. To test this hypothesis, we recruited 4 non-diabetic controls and 6 subjects with poorly controlled (T2DM). Subjects ingested a cup of whip cream and plasma was obtained fasting and 4 hours after the ingestion. We measured cholesterol efflux on ABCA1 transfected BHK cells from HDL isolated by ultracentrifugation. Plasma prebeta1 HDL was assayed by ELISA. To determine how changes in efflux might relate to HDL composition, we developed an HDL proteomics assay using Multiple Reaction Monitoring (MRM) with 60 HDL protein targets using standard isotope peptides on isolated HDL samples. Plasma HDL-C and ApoA1 did not change significantly after the ingestion of the whip cream. The HDL efflux capacity increased in controls by two fold (P =0.05) while it decreased in T2DM by 0.6 (P=0.035). The change in efflux correlated with the change of prebeta1 HDL in controls (R2=0.88, P=0.04) and in T2DM (R2=0.86, P=0.007). Using MRM, we found that Apolipoprotein E (ApoE) and complement 4 beta chain (C4b) protein content that also correlated with the change in efflux. ApoE decreased in controls (Means ±SE area ratio, Pre /Post) (94 ±11/ 70 ±1, P=0.06), and increased in T2DM (58 ±10/ 87 ±20 P=0.06) while C4b was detected after fat ingestion (0/ 10±4, P=0.05) in controls but was not detectable after the fat ingestion in T2DM (2.7± 1.1/ 0, P=0.07). We conclude HDL from patients with poorly controlled T2DM has an impaired capacity to efflux cholesterol after saturated fat ingestion, possibly through mechanisms that involve ApoE and complement C4.