An Increased Plasma Level of ApoCIII-Rich Electronegative High-Density Lipoprotein May Contribute to Cognitive Impairment in Alzheimer’s Disease

Figure 1. Electronegativity of high-density lipoprotein (HDL) was increased in Alzheimer’s disease (AD) patients. (A) HDL from AD patients show higher relative mobility than controls. (B) Representative patterns of HDL subfractionation by using fast-protein liquid chromatography. The lower panel shows that the percentage and quantity of H5 HDL were elevated in AD patients. Red line: mean value. (C) By using a colorimetric method, lipids were quantified. The lipid components were increased in HDL from AD patients. (D) Apolipoproteins were quantified by mass spectrometry. Results showed that apoCII and apoCIII were all increased. * p < 0.05, ** p < 0.01, *** p < 0.001, compared with controls and AD patients. Abbreviations. H1–H5: the five HDL subfractions divided according to electronegativity; TC: total cholesterol; FC: free cholesterol; CE: cholesteryl ester; TG: triglyceride; PL: phospholipids; ApoCI: apolipoprotein CI; ApoCII: apolipoprotein CII; ApoCIII: apolipoprotein CIIII.

Figure 2. Analysis of function and proinflammatory properties of HDL. (A) Function of reverse cholesterol efflux was decreased in HDL from AD patients. (B) AD-HDL induced vibrant expression of ganglioside GM1 on the membrane of marine macrophages, RAW 264.7 cells. AD-HDL enhanced the higher expression levels of (C) LOX-1 on the membrane and (D) TNF-α in the conditioned culture media. * p < 0.05, ** p < 0.01. Abbreviations. AD: Alzheimer’s disease; PBS: phosphate-buffered saline; Ctl-HDL: HDL from controls; AD-HDL: HDL from AD patients; ABCA1: ATP-binding cassette, sub-family A member 1; LOX-1: lectin-type oxidized LDL receptor; TNF-α: tumor necrosis factor-α.

Figure 3. Analysis of function and proinflammatory properties of HDL subfractions. (A) RCT function was reduced in comparison with H1 HDL from healthy subjects. (B) AD-H5 induced a higher expression level of GM1 on the membrane and co-localized with APOCIII. (C, D) AD-H5 HDL induced p-P65 and TNF-α overexpression in RAW 264.7 cells. * p < 0.05, ** p < 0.01. Abbreviations. AD: Alzheimer’s disease; Ctl: controls; PBS: phosphate-buffered saline; apoCIII: apolipoprotein CIII; GM1: ganglioside GM1; TNF-α: tumor necrosis factor-α.

Figure 4. The post-translational modification of apoA1 and apoE in HDL. The oxidation was found and increased on the position 136 and 172 methionine (136M, 172M) of apoAI (A) peptide sequences WQEEM*ELYR and (B) LSPLGEEM*RDR. The position 126, 143 and 290 methionine (126M, 143M, 290M) of apoE was also oxidized. (C) peptide sequences LGADM*EDVCGR. (D) GEVQAM*LGQSTEELR. (E) SWFEPLVEDM*QR. * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 5. Lipidomics analysis of HDL form AD patients and controls. (A) LPC (dm18:1(9Z)) was significantly increased in all subfractions of AD-HDL in comparison with Ctl-HDL. (B) Eukotriene was significantly decreased in the H5 of Ctl-HDL. (C) Cer(d18:0/25:0) ceramide was elevated in H4 and H5 of AD-HDL in comparison with H1. (D) Ganglioside GM3 was elevated in the H5 of AD-HDL and Ctl-HDL subfractions. (E) Eicosatetraenonyl-CoA was elevated in H3–H5 from Ctl-HDL and H2 and H5 from AD-HDL. (F) Ganglioside GA2 was enhanced in H3–H5 from Ctl-HDL and H2 and H5 from AD-HDL. * p < 0.05, ** p < 0.01, *** p < 0.001: comparison to H1 of either AD patients or controls; † p < 0.05, †† p < 0.01, ††† p < 0.001: comparison between AD patients and controls.