Featured Article: Depletion of HDL3 high density lipoprotein and altered functionality of HDL2 in blood from sickle cell patients

Serum Levels of Cholesterol and Lipoproteins in Patients With Symptomatic Paravalvular Leaks

Paravalvular leak (PVL) is a complication of valve replacement surgery which may lead to serious clinical consequences including hemolytic anemia. This study aimed to retrospectively evaluate the effect of successful intervention on serum lipid parameters in patients with PVL. A total of 106 patients (mean age: 57.2 ± 13.6 years, male: 67) who underwent surgical or transcatheter closure for symptomatic PVL were enrolled in this study. During the follow-up period, hemolysis and lipid parameters were evaluated at each clinical visit. This is the first study describing the effects of PVL on lipid metabolism after surgical or transcatheter closure. In the study, 18 patients (17%) had aortic PVL, 84 patients (79%) had mitral PVL, and 4 patients (3.8%) had both aortic and mitral PVL. A total of 59 patients underwent transcatheter closure and 47 patients were treated surgically. Technical success of the procedures was 83%. After successful PVL closure, hemoglobin and haptoglobin levels increased significantly (9.5 ± 1.3 vs 11.9 ± 2.1 g/dl, p <0.001 and 16.6 ± 7.9 vs 34.1 ± 19.9 mg, p <0.001, respectively). A significant increase in total cholesterol (158.9 ± 42.7 vs 209.3 ± 58.7 mg/dl, p <0.001), low-density lipoprotein cholesterol (99.1 ± 33.8 vs 133.9 ± 45.7 mg/dl, p <0.001), and high-density lipoprotein cholesterol (39.8 ± 12.4 vs 44.8 ± 11.7 mg/dl, p <0.001) levels was observed after successful PVL closure. In conclusion, symptomatic patients with PVL had hypocholesterolemia, reflected by low serum lipoprotein levels. After successful PVL closure, an increase in serum lipoprotein levels was observed. The recovery in levels of lipoproteins could be used as a marker of successful PVL closure, and absence of recovery of lipoprotein levels may indicate incomplete closure.

Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1-/- mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.

Cardiovascular Risk Assessment in Children With Chronic Cholestatic Liver Diseases

OBJECTIVES

Chronic cholestatic liver diseases are often associated with disturbed lipid metabolism, which may potentially increase cardiovascular (CV) risk but the evidence is scarce. The aim of the study was to assess factors associated with increased CV risk in children with Alagille syndrome (AGS) and biliary atresia (BA).

METHODS

We investigated 17 patients with AGS, ages 11.0 years (8.4-13.4) and 19 with BA, ages 13.5 years (10.4-15.1) in whom we performed thorough biochemical assessment including lipid profiles and oxidative stress biomarkers, blood pressure (BP)-systolic, diastolic and mean, carotid intima-media thickness (cIMT), and pulse wave velocity (PWV).

RESULTS

There were abnormal lipid profiles in 82% of children with AGS and 52.6% with BA. In AGS group, we observed significantly higher levels of TC, LDL C, APO B, lower glutathione concentration and glutathione peroxidase activity and lower blood pressure, lower cIMT (P = 0.02), cIMT-SDS (P = 0.04), and PWV (P = 0.04). We, however, observed elevated blood pressure in 2/19 patients with BA and none-with AGS (BA vs AGS: P = 0.12), whereas cIMT-SDS was increased only in 2/17 patients with AGS and in 6/19 with BA (P = 0.24), and abnormal PWV-SDS values were detected in 3/17 of AGS and 8/19 of BA patients (P = 0.15). Neither presence of dyslipidemia nor Lp-X correlated with vascular parameters.

CONCLUSIONS

Children with BA and AGS may present with increased cardiovascular risk factors but vascular parameters are not directly related to lipid abnormalities. cIMT and BP should be considered for clinical practice in these cholestatic disorders so as to determine individuals with potential CV risk.

Altered HDL particle in sickle cell disease: decreased cholesterol content is associated with hemolysis, whereas decreased Apolipoprotein A1 is linked to inflammation

Background

Hypocholesterolemia is the most frequently encountered lipid abnormality in sickle cell disease (SCD). We enrolled pediatric patients to determine the relationships between lipid profile and parameters of hemolysis, oxidative stress and chronic inflammation in SCD.

Methods

The study involved 35 pediatric SCD patients and 19 healthy controls. Patients were crisis-free and had not received transfusions for the last 3 months. Total cholesterol, triglyceride, HDL-C, LDL-C, VLDL-C, apolipoprotein A1, apolipoprotein B, LCAT, LDH, bilirubin, haptoglobin, iron, ferritin, hemin, serum amyloid A (SAA), myeloperoxidase (MPO), uric acid, ALT and GGT levels were evaluated in patients’ blood.

Results

Patients had hypocholesterolemia depicted by lower levels of total cholesterol, HDL-C, LDL-C, as well as Apolipoprotein A1 and Apolipoprotein B compared to controls. The chronic hemolysis of SCD was evident in patients by higher LDH and bilirubin and almost undetectable haptoglobin levels. Hemin levels (as a measure of oxidized heme) were significantly increased in patients with SCD. Inflammation markers, SAA and MPO, were significantly increased in the patients as well. There were negative correlations between HDL-C and LDH, and Apo A1 and SAA. Hemin was positively correlated to MPO.

Conclusion

Hemolysis was associated with decreased HDL –C, and Inflammation was linked to decreased apolipoprotein A1 levels in our SCD patients. Therefore, we suggest that the HDL particle is altered during the course of the disease. The altered HDL in SCD may become dysfunctional and result with a slowing down of the reverse cholesterol transport.

Acacia Senegal (Gum Arabic) Supplementation Modulate Lipid Profile and Ameliorated Dyslipidemia among Sickle Cell Anemia Patients

Background

Sickle cell disease (SCD) is an inherited haemolytic anemia with a variable course and severity. Knowledge of prognostic biomarkers may help in the establishment of therapeutic intervention, management, and follow-up of patients. There have been scattered reports of low high-density lipoprotein cholesterol (HDL-C) and increased triglyceride (TG) in SCD patients. In addition, TG levels have been suggested to be elevated in patients with increased endothelial activation. An increased TG level has been associated with haemolysis, vascular dysfunction, and increased prevalence of pulmonary hypertension. Gum Arabic (GA) is an edible, dried, gummy exudate from the acacia Senegal tree. Several studies on GA ingestion have shown reduced plasma cholesterol and low-density lipoprotein (LDL) concentrations in both animals and humans. We investigated GA's therapeutic potential to modulate serum lipids in patients with sickle cell anemia.

Methods

This study recruited and documented secondary outcomes in 47 patients (aged 5–42 years) carrying hemoglobin SS. The patients received 30 g/day of GA for 12 weeks. Total cholesterol, TG, LDL, and HDL were measured before and after GA intake. Cobas C311 (Roche, Germany) automated chemistry analyser was used for direct determination of the values of the lipid profile.

Results

GA significantly decreased total cholesterol (TC), TG, and LDL (p = 0.006, 0.04, and 0.02, resp.). GA showed no effect on HDL level. Baseline serum TG and LDL correlated significantly with the hydrogen peroxide (H₂O₂) level, which is known as an oxidative stress marker (p = 0.003 and 0.04, resp.). None of the lipid profile elements correlated with age.

Conclusion

Our results revealed that dyslipidemia in sickle cell patients is associated with oxidative stress but not associated with age. The findings showed that GA significantly decreased TC, LDL, and TG levels, revealing a novel effect of GA, which is considered a natural dietary fibre that can modulate lipid profile in patients with sickle cell anemia.

Trial Registration

This retrospective trial is registered with ClinicalTrials.gov Identifier: NCT02467257 on 3 June, 2015.

Differences in heme and hemopexin content in lipoproteins from patients with sickle cell disease

BACKGROUND

High blood cholesterol is associated with atherogenesis and endothelial dysfunction. The latter is present in hemolytic diseases, such as sickle cell anemia, whose carriers have hypocholesterolemia and low incidence of coronary artery disease.

OBJECTIVE

We aimed to characterize cholesterol fractions in patients with sickle cell disease and explore the relationship among lipoproteins, varying degrees of hemolysis, and its biomarkers.

METHODS

We recruited 37 healthy individuals, 39 with hemoglobin SC disease, and 40 with sickle cell anemia and quantified cholesterol fractions, heme resulting from hemoglobin breakdown, and its main scavenger protein hemopexin.

RESULTS

Hypocholesterolemia was most significant in patients with sickle cell anemia, and cholesterol levels correlated positively with hemopexin. Nevertheless, patients still had higher relative low-density lipoprotein (LDL) oxidation than healthy subjects. Analysis of lipoproteins isolated by density ultracentrifugation showed that the LDL fraction contained higher concentrations of heme than the high-density lipoprotein (HDL) fraction, whereas HDL contained more hemopexin than LDL, albeit greatly reduced in patients.

CONCLUSION

Our findings show that the abnormally low lipoprotein levels in sickle cell anemia correlate with hemolysis markers, particularly with hemopexin concentrations, along with significant reduction of this heme scavenger in HDL fractions. This may suggest an important role for HDL in the defense against heme-induced endothelial dysfunction in hemolytic diseases.