apoA-I Concentrations Research Articles

Peripheral apolipoprotein E proteins and their binding to LRP1 antagonize Alzheimer’s disease pathogenesis in the brain during peripheral chronic inflammation

C-reactive protein (CRP) impacts apolipoprotein E4 (ApoE4) allele to increase Alzheimer’s disease (AD) risk. However, it is unclear how the ApoE protein and its binding to LRP1 are involved. We found that ApoE2 carriers had the highest but ApoE4 carriers had the lowest concentrations of blood ApoE in both humans and mice; blood ApoE concentration was negatively associated with AD risk. Elevation of peripheral monomeric CRP (mCRP) reduced the expression of ApoE in ApoE2 mice, while it decreased ApoE-LRP1 binding in the brains of ApoE4 mice that was characterized by Proximity Ligation Assay. Both serum ApoE and brain ApoE-LRP1 binding were positively associated with the expression of pericytes that disappeared after mCRP treatment, and negatively associated with brain tauopathy and neuroinflammation in the presence of mCRP. In ApoE-/- mice, mCRP reduced the brain expression levels of synaptophysin and PSD95 and the positive relationship between ApoE-LRP1 binding and synaptophysin or PSD95 expression disappeared. Our study suggests that blood ApoE protects against AD pathogenesis by binding to LRP1 during peripheral chronic inflammation.

Dietary Monounsaturated and Polyunsaturated Fatty Acids are Comparable in their Effects on Hepatic Apolipoprotein mRNA Abundance and Liver Lipid Concentrations when Substituted for Saturated Fatty Acids in Cynomolgus Monkeys

Although studies have shown that saturated and polyunsaturated fats can mediate plasma lipid and apolipoprotein (apo) concentrations at the mRNA level, there is little data on the role of monounsaturated fats. We determined hepatic lipid and apo mRNA levels in 10 cynomolgus monkeys fed three diets that provided 30% of energy as fat with 0.1% cholesterol by weight and differed solely by the substitution of saturated, mono- and polyunsaturated fats as 60% of total fat energy. Total, LDL, and HDL cholesterol, as well as LDL apo B, HDL apo A-I and HDL total apo C concentrations, were reduced with the mono- and polyunsaturated fat diets relative to the saturated fat diet. Although fat saturation did not significantly affect hepatic apo A-I, B, C-II, or E mRNA abundance, hepatic apo C-III mRNA concentrations were uniformly lower (-23%, P < 0.01) with the mono- and polyunsaturated fat diets than with the saturated fat diet. Interestingly, liver triglycerides were significantly elevated with the monounsaturated fat diet relative to the saturated fat diet, but no other differences in hepatic lipids were noted among diets. Hepatic triglyceride composition was shown to reflect dietary fatty acid composition, with liver triglycerides enriched in myristic and palmitic fatty acids during the saturated fat diet, oleic acid during the monounsaturated fat diet and linoleic acid during the polyunsaturated fat diet. We conclude that dietary monounsaturated fats are comparable to polyunsaturated fats in their effects on hepatic lipid and apo mRNA levels in this species, with both unsaturated fats significantly reducing only hepatic apo C-III mRNA abundance relative to saturated fat.

Apolipoprotein A1 and serum amyloid A in dogs with sepsis and septic shock.

Apolipoprotein-A1 (Apo-A1) acts as a negative acute phase protein (APP) during inflammatory states, and has a potential prognostic value in people and dogs with sepsis. The aim of this retrospective study was to investigate the association of serum Apo-A1 concentration with disease severity, multiorgan dysfunction syndrome (MODS) and outcome in a population of dogs with sepsis, and to assess its correlation with major canine APPs. Ninety-nine dogs with uncomplicated sepsis (n = 78) or septic shock (n = 21) were included. The serum concentration of Apo-A1, C-reactive protein (CRP) and serum amyloid A (SAA) were recorded, alongside the canine acute patient physiologic and laboratory evaluation fast (APPLEfast) score and the presence of MODS. Dogs with septic shock had significantly lower serum Apo-A1 concentrations (106.3 ± 22.7 mg/dl; reference interval: 123.0-142.3 mg/dl), higher APPLEfast score (30, 13-38) and greater frequency of MODS (67%) compared to those with uncomplicated sepsis (117.9 ± 19.3 mg/dl; 25, 6-33 and 8%, respectively) (P = 0.0201; P = 0.0005; P < 0.0001, respectively). Similarly, dogs with MODS had significantly lower serum Apo-A1 concentrations (104.1 ± 4.6 mg/dl) and higher APPLEfast score values (31, 13-38) compared to those without MODS (118.32 ± 2.1 mg/dl and 26, 6-33, respectively) (P = 0.0050 and P = 0.0038, respectively). Conversely, neither CRP nor SAA were different between these groups. No difference in serum APPs concentrations was detected between survivors and non-survivors. Significant negative correlations were detected between serum Apo-A1 and SAA (P = 0.0056, r = -0.277), and between serum Apo-A1 and the APPLEfast score (P = 0.0027, r = -0.3). In this population, higher values of the APPLEfast score and the presence of MODS were independently associated with a higher risk of death. Our study shows that Apo-A1 is a useful biomarker of sepsis severity in dogs, since it is decreased in those with septic shock and MODS. Further prospective investigations are deemed to evaluate the applicability of Apo-A1 to predict sepsis course and response to treatment in septic dogs.

Cholesterol 7α-Hydroxylase Gene-204A/C Polymorphism in Normal and Gestational Diabetic Pregnancies

To investigate the cholesterol 7α-hydroxylase gene ( CYP7A1)-204A/C single nucleotide polymorphism and its relationship with the blood lipid levels of pregnant women with gestational diabetes mellitus (GDM) and normal pregnant women. The genotype and allele frequencies of CYP7A1-204A/C gene polymorphism of 1037 normal pregnant women, the normal controls, and 627 pregnant women with GDM were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and blood glucose (Glu) were measured by enzymatic assay. Chemiluminescence determination of plasma insulin (Ins) was conducted. Apolipoproteins A1 (apoA1) and B (apoB) were measured by the turbidimetric immunoassay. Allele frequencies of A and C at the CYP7A1-204A/C polymorphic locus were 0.586 and 0.414, respectively, in the GDM group and 0.557 and 0.443, respectively in the control group. The distribution of genotype frequencies in both groups showed conformity with the Hardy-Weinberg principle. There was no significant difference in allele and genotype frequencies between the GDM group and the control group. In the control group, carriers of the genotype AA were associated with significantly higher concentrations of apoA1 and lower levels of Ins and homeostatic model assessment of insulin resistance (HOMA-IR) compared with those with genotype CC (all P<0.05). In the non-obese subgroup of the control subjects, carriers of the genotype CC were associated with significantly higher plasma TG or apoA1 levels compared with those with genotype AA ( P<0.05). In the GDM group, carriers with genotype AA of CYP7A1-204A/C polymorphism had elevated levels of gestational weight gain (GWG) compared with those with genotype CC ( P<0.05). These results suggest that 204A/C polymorphism in the CYP7A1 gene is not associated with GDM, but may be closely associated with gestational weight gain in pregnant women with GDM. Variants in this locus are strongly associated with plasma apoA1, Ins, and HOMA-IR levels in the controls and elevated plasma TG levels in non-obese controls.

Hypercholesterolemia Induced by Cholesterol- or Cystine-Enriched Diets is Characterized by Different Plasma Lipoprotein and Apolipoprotein Concentrations in Rats

This study examined the effects of diet-induced hypercholesterolemia on plasma apolipoprotein (apo) concentrations and hepatic apolipoprotein mRNA levels in rats. Hypercholesterolemia was induced by feeding rats diets containing an excess of either cholesterol or cystine. After cholesterol feeding, plasma apo E and apo B concentrations were lower (-65%, P < 0.001) and greater (+39%, P < 0.01), respectively, compared with control diet-fed rats. After cystine feeding, plasma apo B and apo E concentrations were greater (+46%, P < 0.01 and +75%, P < 0.001, respectively) and plasma apo A-IV concentration was lower (-29%, P < 0.001) than in rats fed control diet. After cholesterol or cystine feeding, a tendency (one-way ANOVA, P = 0.08) for greater apo B mRNA level (+42% and +47%, respectively) was observed compared with control diet-fed rats. No difference emerged between groups for apo E and apo A-I mRNA levels. An opposite effect of cholesterol and cystine feeding was shown for apo A-IV mRNA level, i.e., higher after cholesterol feeding (+47%, P < 0.05) and lower after cystine feeding (-65%, P < 0.01). From this work, it seems that hypercholesterolemia induced by dietary cholesterol or by increased cholesterogenesis in cystine-fed rats is characterized by different plasma lipoprotein and apolipoprotein concentrations and is associated with different apolipoprotein gene expression in the liver.

Short-Term Dietary Calcium Fortification Increases Fecal Saturated Fat Content and Reduces Serum Lipids in Men

The effect of dietary calcium on fecal fatty acid excretion and serum lipids was tested in a randomized, single-blind metabolic study in 13 healthy men with moderate hypercholesterolemia. A low calcium base diet containing 34% of energy from fat, 13% from saturated fatty acids, 240 mg cholesterol/d and 410 mg Ca/d was compared with a fortified version in which calcium citrate malate was added to orange juice, (550 mg) muffins (750 mg), and two tablets (500 mg) for a total calcium intake of 2200 mg/d. Fecal collections (72 h, d 8, 9, 10) and blood from fasting subjects for lipids and lipoproteins (d 9, 10, 11) were obtained. The percentage of dietary saturated fat excreted per day increased from 6 to 13% with calcium fortification. There was no change in fecal bile acid excretion. The high Ca diet significantly reduced total cholesterol 6% (5.99 to 5.66 mmol/L), LDL cholesterol 11% (4.13 to 3.67 mmol/L), and apolipoprotein B concentrations 7% when compared with the low Ca diet (P < 0.05). There was no change in HDL cholesterol or apolipoprotein A1 concentrations. Urinary calcium excretion increased from 146 to 230 mg/d when the high Ca diet was consumed. Calcium fortification was effective in lowering total and LDL cholesterol concentrations and may be an effective adjunct to cholesterol-lowering diet therapy.

Targeted proteomics using stable isotope labeled protein fragments enables precise and robust determination of total apolipoprotein(a) in human plasma.

Lipoprotein(a), also known as Lp(a), is an LDL-like particle composed of apolipoprotein(a) (apo(a)) bound covalently to apolipoprotein B100. Plasma concentrations of Lp(a) are highly heritable and vary widely between individuals. Elevated plasma concentration of Lp(a) is considered as an independent, causal risk factor of cardiovascular disease (CVD). Targeted mass spectrometry (LC-SRM/MS) combined with stable isotope-labeled recombinant proteins provides robust and precise quantification of proteins in the blood, making LC-SRM/MS assays appealing for monitoring plasma proteins for clinical implications. This study presents a novel quantitative approach, based on proteotypic peptides, to determine the absolute concentration of apo(a) from two microliters of plasma and qualified according to guideline requirements for targeted proteomics assays. After optimization, assay parameters such as linearity, lower limits of quantification (LLOQ), intra-assay variability (CV: 4.7%) and inter-assay repeatability (CV: 7.8%) were determined and the LC-SRM/MS results were benchmarked against a commercially available immunoassay. In summary, the measurements of an apo(a) single copy specific peptide and a kringle 4 specific peptide allow for the determination of molar concentration and relative size of apo(a) in individuals.

Docosahexaenoic Acid-Rich Fish Oil Does Not Affect Serum Lipid Concentrations of Normolipidemic Young Adults

Fish oils, purified eicosapentaenoic acid and docosahexaenoic acid (DHA) have been reported to improve blood lipid concentrations, especially those of triglycerides in humans. However, to our knowledge there have been no double-blind studies investigating the effects of DHA-rich fish oil on blood lipid concentrations. Therefore, we conducted a placebo-controlled double-blind study. Twenty-four healthy, normolipidemic young adults took either DHA-rich fish oil capsules containing 1.5–1.8 g of DHA or control oil capsules containing 97% soybean oil and 3% fish oil for 13 wk. Blood samples were taken at the start and end of the study, and serum lipids concentrations were compared. There were no significant changes over time in the DHA group in the following serum lipids: total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, lipoprotein(a), and apolipoproteins A1 and B. In contrast, apolipoprotein A1 concentrations slightly (10%) but significantly increased over time in the control group. Docosahexaenoic acid at a dose of less than 2 g/d did not change serum lipid concentrations of normolipidemic subjects. The effects of DHA in hyperlipidemic patients remain to be investigated in a double-blind study.

Fully automated immunoassay for cholesterol uptake capacity to assess high-density lipoprotein function and cardiovascular disease risk

High-density lipoprotein (HDL) cholesterol efflux capacity (CEC), which is a conventional metric of HDL function, has been associated with coronary heart disease risk. However, the CEC assay requires cultured cells and takes several days to perform. We previously established a cell-free assay to evaluate cholesterol uptake capacity (CUC) as a novel measure of HDL functionality and demonstrated its utility in coronary risk stratification. To apply this concept clinically, we developed a rapid and sensitive assay system based on a chemiluminescent magnetic particle immunoassay. The system is fully automated, providing high reproducibility. Measurement of CUC in serum is completed within 20 min per sample without HDL isolation, a notably higher throughput than that of the conventional CEC assay. CUC decreased with myeloperoxidase-mediated oxidation of HDL or in the presence of N-ethylmaleimide, an inhibitor of lecithin: cholesterol acyltransferase (LCAT), whereas CUC was enhanced by the addition of recombinant LCAT. Furthermore, CUC correlated with CEC even after being normalized by ApoA1 concentration and was significantly associated with the requirement for revascularization due to the recurrence of coronary lesions. Therefore, our new assay system shows potential for the accurate measurement of CUC in serum and permits assessing cardiovascular health.

A molecular imprint of intracellular amyloid-beta ApoE interaction correlates with its toxicity molecular imprint of intracellular amyloid beta ApoE interaction.

ApoE isoforms are major genetic risk factors related to Alzheimer's disease (AD), which is associated with the aggregation of the amyloid beta (Aβ) peptide. However, a molecular-level understanding of how ApoE is involved in AD pathology is still lacking. Here we employ a fluorescent lifetime-based assay that reports a specific ApoE-dependent modification of Aβ, both in vitro and in neuronal cells. We explore this phenomenon in several types of cells where the change of lifetime of Aβ oligomers correlates with the relative ApoE content, with the highest effect displayed by primary-cultured rat astrocytes. At the single-molecule level, ApoE-induced modification also produces distinct Aβ oligomers with increased affinity to artificial lipid bilayers. A known peptide inhibitor of Aβ-ApoE interaction, LVFFA, diminishes both the lifetime modification and toxicity of Aβ oligomers in a dose-dependent manner. The correlation between the short lifetime component and Aβ toxicity was corroborated by experiments using two nontoxic Aβ variants. Our data, therefore, establish a clear correlation between the lifetime modification of Aβ and its toxicity. Finally, neuronal stem cells derived from cells obtained from Alzheimer's patients also show the short-lifetime component, the changed oligomeric state, and the increased membrane affinity, which is likely to be relevant for AD. In summary, our assay can provide a direct readout of the toxic ApoE-Aβ interaction in vitro and in cells, which can provide a platform for AD drug discovery.

Identifying the Biomarker Profile of Pre-Frail and Frail People: A Cross-Sectional Analysis from UK Biobank.

This study aimed to compare the biomarker profile of pre-frail and frail adults in the UK Biobank cohort by sex. In total, 202,537 participants (67.8% women, aged 37 to 73 years) were included in this cross-sectional analysis. Further, 31 biomarkers were investigated in this study. Frailty was defined using a modified version of the Frailty Phenotype. Multiple linear regression analyses were performed to explore the biomarker profile of pre-frail and frail individuals categorized by sex. Lower concentrations of apoA1, total, LDL, and HDL cholesterol, albumin, eGFRcys, vitamin D, total bilirubin, apoB, and testosterone (differences ranged from -0.30 to -0.02 per 1-SD change), as well as higher concentrations of triglycerides, GGT, cystatin C, CRP, ALP, and phosphate (differences ranged from 0.01 to 0.53 per 1-SD change), were identified both in pre-frail and frail men and women. However, some of the associations differed by sex. For instance, higher rheumatoid factor and urate concentrations were identified in pre-frail and frail women, while lower calcium, total protein, and IGF-1 concentrations were identified in pre-frail women and frail women and men. When the analyses were further adjusted for CRP, similar results were found. Several biomarkers were linked to pre-frailty and frailty. Nonetheless, some of the associations differed by sex. Our findings contribute to a broader understanding of the pathophysiology of frailty as currently defined.

Differential effects of hyperhomocysteinemia on the lipid profiles and lipid ratios between patients with and without coronary artery disease: A retrospective observational study

This study aimed to investigate the differential effects of hyperhomocysteinemia (HHcy) on lipid profiles and lipid ratios between patients with coronary artery disease (CAD) and without CAD. The data of 872 CAD patients and 774 non-CAD controls were extracted from the information system of hospitalized patients. Serum homocysteine (Hcy), total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (Apo) AI, and ApoB concentrations were detected. HHcy was defined as a serum level of Hcy ≥ 15 μmol/L. The CAD patients had lower levels of HDL-C and ApoAI and higher levels of Hcy than the controls (P < .05). Serum TGs and HDL-C were negatively correlated with Hcy in controls. Serum HDL-C and ApoAI were negatively correlated with Hcy, and the ratios of TC/HDL-C, TG/HDL-C, LDL/HDL-C, and ApoB/ApoAI were positively correlated with Hcy in the CAD patients (P < .05). Although the trends for HHcy to decrease the lipid profiles were not different between the CAD and controls (Pinteraction > 0.05), CAD with HHcy had lower HDL-C and ApoAI levels than those of subjects with normal Hcy; controls with HHcy had lower TC, LDL-C, and ApoB levels than those of subjects with normal Hcy (P < .05). There were different HHcy trends affecting the ratios of TC/HDL-C and LDL/HDL-C between the CAD patients and controls (Pinteraction for TC/HDL-C = 0.025; Pinteraction for LDL/HDL-C = 0.033). CAD patients with HHcy had a higher ratio of TC/HDL-C (P = .022) and LDL/HDL-C (P = .045) than those of patients with normal Hcy, but in the controls, the subjects with HHcy exhibited a trend toward a decreased ratio of TC/HDL-C (P = .481) and LDL/HDL-C (P = .303). There were differential effects of HHcy on the lipid ratios between CAD and non-CAD patients. HHcy was related to higher ratios of TC/HDL-C and LDL/HDL-C in patients with CAD.

Associations of Lipids and Lipid-Lowering Drugs with Risk of Vascular Dementia: A Mendelian Randomization Study.

Accumulating observational studies suggested that hypercholesterolemia is associated with vascular dementia (VaD); however, the causality between them remains unclear. Hence, the aim of this study is to infer causal associations of circulating lipid-related traits [including high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), apolipoprotein A-I (apoA-I), and apolipoprotein B (apoB)] with VaD jointly using univariable MR (uvMR), multivariable MR (mvMR) and bidirectional two-sample MR methods. Then, the summary-data-based MR (SMR) and two-sample MR analysis were conducted to investigate the association of lipid-lowering drugs target genes expression (including HMGCR, PCSK9, NPC1L1, and APOB) and LDL-C level mediated by these target genes with VaD. The results of forward MR analyses found that genetically predicted HDL-C, LDL-C, TG, apoA-I, and apoB concentrations were not significantly associated with the risk of VaD (all p > 0.05). Notably, there was suggestive evidence for a causal effect of genetically predicted VaD on HDL-C via reverse MR analysis [odds ratio (OR), 0.997; 95% confidence interval (CI), 0.994−0.999; p = 0.022]. On the contrary, the MR results showed no significant relationship between VaD with LDL-C, TG, apoA-I, and apoB. The results for the SMR method found that there was no evidence of association for expression of HMGCR, PCSK9, NPC1L1, and APOB gene with risk of VaD. Furthermore, the result of MR analysis provided evidence for the decreased LDL-C level mediated by gene HMGCR reduced the risk of VaD (OR, 18.381; 95% CI, 2.092−161.474; p = 0.009). Oppositely, none of the IVW methods indicated any causal effects for the other three genes. Using genetic data, this study provides evidence that the VaD risk may cause a reduction of HDL-C level. Additionally, the finding supports the hypothesis that lowering LDL-C levels using statins may be an effective prevention strategy for VaD risk, which requires clinical trials to confirm this result in the future.

A novel sandwich impedimetric immunosensor for detection of apolipoprotein-A1 based on the gold nanoparticle-hybridized mercapto-β-cyclodextrin-Pb(II) metal-organic framework.

A novel sandwich electrochemical impedimetric immunosensor was proposed to detect apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The molybdenum disulfide/graphene quantum dot (MoS2/GQD) nanocomposites were modified on the surface of a glassy carbon electrode (GCE) and used to immobilize the biotinylated antibody (Ab1) with the help of chitosan and glutaraldehyde (denoted as BSA/Ab1/CHIT/MoS2/GQD/GCE). Pb(II)-thiol-β-cyclodextrin metal-organic framework (denoted as Pb-MOF) was synthesized with lead metal ions and thiol-β-cyclodextrin ligands by a one-pot solvothermal method, and then, gold nanoparticles were modified on the surface of Pb-MOF (Pb-MOF-AuNPs) by Au-S bond, which was used as signal label for the recombinant antibody (Ab2). When the immunosensor of BSA/Ab1/CHIT/MoS2/GQD/GCE reacted with Apo-A1, Pb-MOF-AuNPs-Ab2/BSA was connected to the electrode when immunoreaction occurred, and an immune sandwich structure was formed, which led to significantly increased charge transfer resistance of electrochemical probe for ferrocyanide (II)/(III) within the frequency range 10-1 ~ 105Hz at 5 mV amplitude and the potential of 0.180V (vs. SCE). Based on this principle, the quantitative detection of Apo-A1 was established. The relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration showed a linear relationship with a linear coefficient of 0.9989 in the range 1.00pgmL-1 and 1.00μgmL-1 with the limit of detection of 0.30pgmL-1. The selectivity, repeatability, and other performance of the proposed immunosensor were also investigated. The immunosensor was successfully applied to the detection of real serum and urine samples with recovery in the range 96.4 ~ 109.1% (RSD < 3.8%), indicating that it could be helpful for the clinical diagnosis of bladder cancer.

Construction of magnetically recoverable MnZnFe2O4@Ag3PO4 Z-scheme photocatalyst for rapid visible-light-driven phenol degradation.

Visible-light-driven magnetic heterojunction as a promising photocatalysts has received much attention in environmental remediation. In this work, novel Z-scheme heterojunction MnZnFe2O4@Ag3PO4 (MZFO@APO) magnetic photocatalysts with excellent visible-light-driven photocatalytic activity are successfully constructed and characterized. The photocatalytic activity for phenol degradation is measured, and photodegradation mechanism is investigated with EPR, radical trapping experiments, and LC-MS. It turns out that the heterojunction introduced MZFO exhibits good adsorption effect on visible light and the direct Z-scheme bandgap alignment of MZFO and APO significantly improves charge separation and electron transfer, outperforming that of pure APO. MZFO@APO-40% with 40% APO content shows the rapid photodegradation performance, obtaining a 100% removal efficiency of phenol (25mg L-1) after 12-min visible light irradiation, and its kinetic constants are approximately 25.3 and 4.9 times higher than that of P25 TiO2 and pure APO, respectively. Especially, MZFO@APO-40% also possesses a high magnetic separation property and can be efficiently reused for 5 cycles. Additionally, EPR and radical trapping experiments confirm that h+, O2-, and 1O2 are the main active species in the photocatalytic process. Hydroquinone and small molecular organic acids such as maleic acid and oxalic acid are detected by LC-MS, which further indicates that the pathway of phenol degradation involves hydroxylation, open-ring reactions, and mineralization reactions. The novel addition of MZFO in photocatalyst construction has the potential to promote its application in environmental remediation.

Association of apolipoprotein E in peripheral blood and in vivo Alzheimer’s disease pathologies in nondemented older adults

AbstractBackgroundPrevious studies reported the link between apolipoprotein E (apoE) in peripheral blood and risk of Alzheimer’s disease (AD) dementia. However, underlying mechanism for this link remains unclear. We investigated whether serum apoE concentration is associated with in vivo AD pathologies in nondemented older adults.MethodA total 437 nondemented older adults were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE) cohort. All participants underwent comprehensive evaluation including clinical assessment, blood sampling, as well as 11C‐PiB PET and MRI. A subset of participants (N=130) also underwent 18F‐AV1451 PET for measurement of brain tau pathologies. All participants were divided into low, middle, and high apoE concentration tertile groups (i.e., T1, T2, and T3).ResultThere were no significant differences in demographic and clinical variables except the frequency of female and rate of apoE ε4 allele (APOE4) positivity; the lower serum apoE was associated with fewer female (40.1%, 61.6%, and 67.8% for T1, T2, and T3, respectively) and higher APOE4 positivity rate (34.3%, 25.2%, and 16.8%). In terms of AD biomarker, Aβ positivity rate showed significant negative association with serum apoE (40.1%, 31.8%, and 24.8%), which remained significant after adjustment of covariates including age, sex, and diagnosis. In addition, reduced AD‐signature region volume, a neurodegeneration biomarker of AD, was significantly associated with lower serum apoE after controlling the same covariates. With regard to tau biomarker, positivity rate of global tau deposition showed significant negative association with serum apoE level (56.8%, 50%, and 20%) after adjustment of covariates. When we additively controlled the effect of APOE4 positivity, the associations between low serum apoE and greater neurodegeneration and tau positivity remained significant, whereas the association between apoE and Aβ positivity did not reach statistical significance.ConclusionIn the present study, low serum apoE was associated with greater burden of in vivo AD pathologies and such association appears even independent of APOE4 carrier status in regard of tau deposition and neurodegeneration. The finding suggests a potential role of serum apoE as a surrogate marker for in vivo AD pathologies in nondemented older adults.

Whole-exome sequencing identifies novel protein-altering variants associated with serum apolipoprotein and lipid concentrations

BackgroundDyslipidemia is a major risk factor for cardiovascular disease, and diabetes impacts the lipid metabolism through multiple pathways. In addition to the standard lipid measurements, apolipoprotein concentrations provide added awareness of the burden of circulating lipoproteins. While common genetic variants modestly affect the serum lipid concentrations, rare genetic mutations can cause monogenic forms of hypercholesterolemia and other genetic disorders of lipid metabolism. We aimed to identify low-frequency protein-altering variants (PAVs) affecting lipoprotein and lipid traits.MethodsWe analyzed whole-exome (WES) and whole-genome sequencing (WGS) data of 481 and 474 individuals with type 1 diabetes, respectively. The phenotypic data consisted of 79 serum lipid and apolipoprotein phenotypes obtained with clinical laboratory measurements and nuclear magnetic resonance spectroscopy.ResultsThe single-variant analysis identified an association between the LIPC p.Thr405Met (rs113298164) and serum apolipoprotein A1 concentrations (p=7.8×10−8). The burden of PAVs was significantly associated with lipid phenotypes in LIPC, RBM47, TRMT5, GTF3C5, MARCHF10, and RYR3 (p<2.9×10−6). The RBM47 gene is required for apolipoprotein B post-translational modifications, and in our data, the association between RBM47 and apolipoprotein C-III concentrations was due to a rare 21 base pair p.Ala496-Ala502 deletion; in replication, the burden of rare deleterious variants in RBM47 was associated with lower triglyceride concentrations in WES of >170,000 individuals from multiple ancestries (p=0.0013). Two PAVs in GTF3C5 were highly enriched in the Finnish population and associated with cardiovascular phenotypes in the general population. In the previously known APOB gene, we identified novel associations at two protein-truncating variants resulting in lower serum non-HDL cholesterol (p=4.8×10−4), apolipoprotein B (p=5.6×10−4), and LDL cholesterol (p=9.5×10−4) concentrations.ConclusionsWe identified lipid and apolipoprotein-associated variants in the previously known LIPC and APOB genes, as well as PAVs in GTF3C5 associated with LDLC, and in RBM47 associated with apolipoprotein C-III concentrations, implicated as an independent CVD risk factor. Identification of rare loss-of-function variants has previously revealed genes that can be targeted to prevent CVD, such as the LDL cholesterol-lowering loss-of-function variants in the PCSK9 gene. Thus, this study suggests novel putative therapeutic targets for the prevention of CVD.

Dalcetrapib and anacetrapib increase apolipoprotein E-containing HDL in rabbits and humans

The large HDL particles generated by administration of cholesteryl ester transfer protein inhibitors (CETPi) remain poorly characterized, despite their potential importance in the routing of cholesterol to the liver for excretion, which is the last step of the reverse cholesterol transport. Thus, the effects of the CETPi dalcetrapib and anacetrapib on HDL particle composition were studied in rabbits and humans. The association of rabbit HDL to the LDL receptor (LDLr) in vitro was also evaluated. New Zealand White rabbits receiving atorvastatin were treated with dalcetrapib or anacetrapib. A subset of patients from the dal-PLAQUE-2 study treated with dalcetrapib or placebo were also studied. In rabbits, dalcetrapib and anacetrapib increased HDL-C by more than 58% (P < 0.01) and in turn raised large apo E-containing HDL by 66% (P < 0.001) and 59% (P < 0.01), respectively. Additionally, HDL from CETPi-treated rabbits competed with human LDL for binding to the LDLr on HepG2 cells more than control HDL (P < 0.01). In humans, dalcetrapib increased concentrations of large HDL particles (+69%, P < 0.001) and apo B-depleted plasma apo E (+24%, P < 0.001), leading to the formation of apo E-containing HDL (+47%, P < 0.001) devoid of apo A-I. Overall, in rabbits and humans, CETPi increased large apo E-containing HDL particle concentration, which can interact with hepatic LDLr. The catabolism of these particles may depend on an adequate level of LDLr to contribute to reverse cholesterol transport.

Apolipoprotein E imbalance in the cerebrospinal fluid of Alzheimer’s disease patients

ObjectiveThe purpose of this study was to examine the levels of cerebrospinal fluid (CSF) apolipoprotein E (apoE) species in Alzheimer’s disease (AD) patients.MethodsWe analyzed two CSF cohorts of AD and control individuals expressing different APOE genotypes. Moreover, CSF samples from the TgF344-AD rat model were included. Samples were run in native- and SDS-PAGE under reducing or non-reducing conditions (with or without β-mercaptoethanol). Immunoprecipitation combined with mass spectrometry or western blotting analyses served to assess the identity of apoE complexes.ResultsIn TgF344-AD rats expressing a unique apoE variant resembling human apoE4, a ~35-kDa apoE monomer was identified, increasing at 16.5 months compared with wild-types. In humans, apoE isoforms form disulfide-linked dimers in CSF, except apoE4, which lacks a cysteine residue. Thus, controls showed a decrease in the apoE dimer/monomer quotient in the APOE ε3/ε4 group compared with ε3/ε3 by native electrophoresis. A major contribution of dimers was found in APOE ε3/ε4 AD cases, and, unexpectedly, dimers were also found in ε4/ε4 AD cases. Under reducing conditions, two apoE monomeric glycoforms at 36 kDa and at 34 kDa were found in all human samples. In AD patients, the amount of the 34-kDa species increased, while the 36-kDa/34-kDa quotient was lower compared with controls. Interestingly, under reducing conditions, a ~100-kDa apoE complex, the identity of which was confirmed by mass spectrometry, also appeared in human AD individuals across all APOE genotypes, suggesting the occurrence of aberrantly resistant apoE aggregates. A second independent cohort of CSF samples validated these results.ConclusionThese results indicate that despite the increase in total apoE content the apoE protein is altered in AD CSF, suggesting that function may be compromised.

Sugar-Sweetened Beverage Consumption and Plasma Lipoprotein Cholesterol, Apolipoprotein, and Lipoprotein Particle Size Concentrations in US Adults

Prospective cohort studies have found a relation between sugar-sweetened beverage (SSB) consumption (sodas and fruit drinks) and dyslipidemia. There is limited evidence linking SSB consumption to emerging features of dyslipidemia, which can be characterized by variation in lipoprotein particle size, remnant-like particle (RLP), and apolipoprotein concentrations. To examine the association between SSB consumption and plasma lipoprotein cholesterol, apolipoprotein, and lipoprotein particle size concentrations among US adults. We examined participants from the Framingham Offspring Study (FOS; 1987-1995, n = 3047) and the Women's Health Study (1992, n = 26,218). Concentrations of plasma LDL cholesterol, apolipoprotein B (apoB), HDL cholesterol, apolipoprotein A1 (apoA1), triglyceride (TG), and non-HDL cholesterol, as well as total cholesterol:HDL cholesterol ratio and apoB:apoA1 ratio, were quantified in both cohorts; concentrations of apolipoprotein E, apolipoprotein C3, RLP-TG, and RLP cholesterol (RLP-C) were measured in the FOS only. Lipoprotein particle sizes were calculated from nuclear magnetic resonance signals for lipoprotein particle subclass concentrations (TG-rich lipoprotein particles [TRL-Ps]: very large, large, medium, small, and very small; LDL particles [LDL-Ps]: large, medium, and small; HDL particles [HDL-Ps]: large, medium, and small). SSB consumption was estimated from food frequency questionnaire data. We examined the associations between SSB consumption and all lipoprotein and apoprotein measures in linear regression models, adjusting for confounding factors such as lifestyle, diet, and traditional lipoprotein risk factors. SSB consumption was positively associated with LDL cholesterol, apoB, TG, RLP-TG, RLP-C, and non-HDL cholesterol concentrations and total cholesterol:HDL cholesterol and apoB:apoA1 ratios; and negatively associated with HDL cholesterol and apoA1 concentrations (P-trend range: <0.0001 to 0.008). After adjustment for traditional lipoprotein risk factors, SSB consumers had smaller LDL-P and HDL-P sizes; lower concentrations of large LDL-Ps and medium HDL-Ps; and higher concentrations of small LDL-Ps, small HDL-Ps, and large TRL-Ps (P-trend range: <0.0001 to 0.001). Higher SSB consumption was associated with multiple emerging features of dyslipidemia that have been linked to higher cardiometabolic risk in US adults.