Severe acquired (secondary) high-density lipoprotein deficiency

Clinical characteristics of cardiovascular patients with extremely low levels of high-density lipoprotein cholesterol

Background

Extremely low levels of high-density lipoprotein cholesterol (HDL-C) are related to high cardiovascular mortality. The underlying mechanism is not well known. This research aims to study the clinical characteristics of cardiovascular patients with extremely low levels of HDL-C.

Methods

All cardiovascular patients in a single Chinese cardiology center that were admitted from January to December 2019 were reviewed. The clinical characteristics of those with HDL-C<20 mg/dL were investigated.

Results

A total of 20,655 individuals were enrolled. Of these, 52.17 % were males, and the average age was 58.20 ± 12.98 years old. The prevalence of HDL-C<20 mg/dL was 0.47 % for all patients (N=98) and 1.05 % for inpatients. Of those with HDL-C<20 mg/dL, 88.8 % were inpatients, and 77.6 % were males. Their average age was 60.7 ± 15.1 years. Compared with matched patients with normal HDL-C, systemic inflammation (OR= 5.556, 95% CI 2.798–11.030), hypoalbuminemia (OR=5.714, 95% CI 2.702–12.085), hyperuricemia (OR=5.156, 95% CI 2.560–10.386), low T3 syndrome (OR=4.278, 95% CI 1.627–11.245), anemia (OR=3.577, 95% CI 1.680–7.617), diabetes (OR=3.534, 95% CI 1.693–7.376) and hypertriglyceridemia (OR=2.493, 95% CI 1.264–4.918) were identified as adverse concomitant factors of extremely low HDL-C. HDL-C levels were inversely correlated with the total risk scores in patients with HDL-C<20 mg/dL (r=-0.381, P<0.001) and more significantly correlated in patients with HDL-C<15 mg/dL (r=-0.511, P=0.004).

Conclusions

Extremely low levels of HDL-C tend to occur more frequently in males, older individuals and inpatients. For cardiovascular patients, extremely low levels of HDL-C are usually due to the presence of multiple adverse factors with relatively severe conditions. This could explain the high cardiovascular mortality of individuals with extremely low levels of HDL-C.

Progressively decreasing plasma high-density lipoprotein cholesterol levels preceding diagnosis of smoldering myeloma

We report a case of disappearing high-density lipoprotein (HDL) syndrome caused by oxidative modification of HDL and by autoantibodies against modified HDL, with subsequent diagnosis of myeloma. An elderly Caucasian man had normal lipid levels with HDL cholesterol (HDL-C) levels in the upper 70 mg/dL range from 1999 to 2003. In 2003, his HDL-C levels began to progressively fall, and by 2011, they were undetectable (<5 mg/dL) when measured with a Beckman Synchron LX auto analyzer. Analyses of the plasma sample from 2011 using ultracentrifugation (Vertical Auto Profile), nuclear magnetic resonance, and Ace EXCEL auto analyzer have shown that HDL-C levels were easily detectable (47-54 mg/dL), although reduced compared with his pre-2003 values. Analyses of his plasma sample from 2011 also showed the presence of lipid-adducted apolipoprotein A1 (apoA1) and high titer of antibodies against the adducted apoA1. Interestingly, a negative correlation between HDL-C levels and the titer of antibodies against apoA1 adducts was found in the control cohort. Finally, we show that in the mouse system, an antibody against apoA1 increases the clearance of HDL from plasma. This case of smoldering myeloma preceded by acquired, severe HDL-C deficiency, likely because of oxidative modifications of the HDL protein leading to the formation of autoantibodies, interference with clinical measurement of HDL-C, and increased plasma clearance of HDL, adds to the list of diagnostic considerations for unexplained HDL-C decreases over time.

Interleukin 10 promotes macrophage uptake of HDL and LDL by stimulating fluid-phase endocytosis

OBJECTIVE

Highly elevated plasma levels of interleukin-10 (IL-10) are causally associated with "Disappearing HDL Syndrome" and low plasma LDL-cholesterol, but the underlying mechanism is poorly understood. Fluid-phase endocytosis, a process highly dependent on actin dynamics, enables cells to internalize relatively high amounts of extracellular fluids and solutes. We sought to investigate whether IL-10 induces lipoprotein uptake by fluid-phase endocytosis in macrophages.

METHODS AND RESULTS

Macrophages (RAW264.7, Kupffer and human) were incubated with vehicle (PBS) or IL-10 (20 ng/ml) for 7 days. Uptake of HDL, LDL, and/or fluid-phase endocytosis probes (albumin-Alexa680®, 70 kDa FITC-Dextran and Lucifer Yellow, LY) was evaluated by FACS. Intracellular cofilin and phosphorylated cofilin (p-cofilin) levels were determined by immunoblotting. Macrophage uptake of lipoproteins and probes was non-saturable and increased after IL-10 incubation (p < 0.0001). Furthermore, pre-incubation with fluid-phase endocytosis inhibitors (LY294002, Latrunculin A, and Amiloride) significantly reduced uptake (p < 0.05). IL-10 increased the cofilin/p-cofilin ratio (p = 0.021), signifying increased cofilin activation and hence filamentous actin. Consistently, phalloidin staining revealed increased filamentous actin in macrophages after IL-10 treatment (p = 0.0018). Finally, RNA-seq analysis demonstrated enrichment of gene sets related to actin filament dynamics, membrane ruffle formation and endocytosis in IL-10-treated macrophages (p < 0.05). IL-10 did not alter mRNA levels of Ldlr, Vldlr, Scarb1, Cd36 or Lrp1. In primary human monocyte-derived macrophages and murine Kupffer cells, IL-10 incubation also increased uptake of lipoproteins, albumin and LY (p < 0.01).

CONCLUSIONS

Interleukin-10 induces the uptake of HDL and LDL by fluid-phase endocytosis by increasing actin-filament rearrangement in macrophages, thus providing a plausible mechanism contributing to "Disappearing HDL Syndrome".

Low level of serum HDL-cholesterol with increased sIL-2R predicts a poor clinical outcome for patients with malignant lymphoma and adult T-cell leukemia-lymphoma

Low concentrations of high-density lipoprotein cholesterol (HDL-C) have been reported in patients with hematological malignancies. However, the proof of decreased HDL-C in hematological malignancies and its association with clinical outcomes remain unclear. We analyzed 140 Japanese patients with malignant lymphoma (ML) and adult T-cell leukemia-lymphoma (ATLL). HDL-C, LDL-C and soluble interleukin-2 receptor (sIL-2R) were measured. Treatment decisions were determined with established protocols. HDL-C was 0.98 ± 0.45 mmol/l in patients and 1.51 ± 0.35 mmol/l in controls (P < 0.001). LDL-C was lower in patients than in controls (2.76 ± 0.96, 3.16 ± 0.76 mmol/l, respectively, P < 0.001). HDL-C was the lowest in ATLL (0.81 ± 0.37 mmol/l), modest in non-Hodgkin lymphoma (1.09 ± 0.42 mmol/l) and the highest in Hodgkin's disease (1.14 ± 0.68 mmol/l), (P = 0.0019). Inverse correlation was found between HDL-C and sIL-2R (r = -0.6584, P < 0.001). Categorized patients into 3 subgroups according to HDL-C (<0.52, 0.52-1.02 and ≥1.03 mmol/l), sIL-2R were the highest (median, 36,675; IQR, 17,180-92,600 U/mL) in patients with HDL-C < 0.52 mmol/l, modest (2386, 1324-8340) in HDL-C 0.52-1.02 mmol/l and the lowest (761, 450-1596) in HDL-C ≥ 1.03 mmol/l (P < 0.001). In Cox regression model, the lowest HDL-C levels, <0.52 mmol/l, were associated with poorer clinical outcome and the hazard ratio was 5.73 (95%CI, 3.09-10.50; P < 0.001). In Kaplan-Meier analysis according to HDL-C tertiles (<0.78, 0.78-1.10 and ≥1.11 mmol/l), patients with lowest HDL-C tertile showed inferior overall survival with a median follow-up of 23 months (P < 0.001). We concluded that cytokine-induced low levels of HDL-C in patients with ML and ATLL has independent prognostic significance, and suggesting an early indicator of poorer outcome.

Interaction Between Peroxisome Proliferator Activated Receptor δ and Epithelial Membrane Protein 2 Polymorphisms Influences HDL-C Levels in the Chinese Population

Peroxisome proliferator activated receptors (PPARs) are transcription factors involved in the regulation of key metabolic pathways. Numerous in vivo and in vitro studies have established their important roles in lipid metabolism. A few SNPs in PPAR genes have been reported to be associated with lipid levels. In this study, we aimed to investigate the interactive effects between single nucleotide polymorphisms (SNPs) in three PPAR isoforms α/δ/γ and other genetic variants across the genome on plasma high-density lipoprotein-cholesterol (HDL-C) levels. Study subjects (N = 2003) were genotyped using Illumina HumanOmniZhongHua-8 Beadchip. Fifty-three tag SNPs ± 100 kb of PPAR α, δ, and γ (r(2) < 0.2) were selected. The effect of interactions between PPAR SNPs and those across the genome on HDL-C was tested using linear regression models. One statistically significant interaction influencing HDL-C was detected between PPARδ SNP rs2267668 and epithelial membrane protein 2 (EMP2) downstream SNP rs7191411 (N = 1993, β = 0.74, adjusted P = 0.022). This interaction was successfully replicated in the meta-analysis of two additional Chinese cohorts (N = 3948, P = 0.01). The present study showed a novel SNP × SNP interaction between rs2267668 in PPARδ and rs7191411 in EMP2 that has significant impact on circulating HDL-C levels in the Singaporean Chinese population.

Autoimmune Lymphoproliferative Syndrome: A Rare Cause of Disappearing HDL Syndrome

The term disappearing HDL syndrome refers to development of severe high density lipoprotein cholesterol (HDL-C) deficiency in noncritically ill patients with previously normal HDL-C and triglyceride levels. Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of the immune system due to an inability to regulate lymphocyte homeostasis resulting in lymphadenopathy and hepatosplenomegaly. We describe a 17-year-old boy who was evaluated in the lipid clinic for history of undetectable or low HDL-C and low density lipoprotein cholesterol (LDL-C) levels. Past medical history was significant for ALPS IA diagnosed at 10 years of age when he presented with bilateral cervical adenopathy. He was known to have a missense mutation in one allele of the FAS protein extracellular domain consistent with ALPS type 1A. HDL-C and LDL-C levels had been undetectable on multiple occasions, though lipids had not been measured prior to the diagnosis of ALPS. He had been receiving sirolimus for immunosuppression. The HDL-C and LDL-C levels correlated with disease activity and improved to normal levels during times when the activity of ALPS was controlled. This case highlights the importance of considering ALPS as a cause of low HDL-C and LDL-C levels in a child with evidence of lymphoproliferation.

A complex phenotype in a child with familial HDL deficiency due to a novel frameshift mutation in APOA1 gene (apoA-IGuastalla)

BACKGROUND

We describe a kindred with high-density lipoprotein (HDL) deficiency due to APOA1 gene mutation in which comorbidities affected the phenotypic expression of the disorder.

METHODS

An overweight boy with hypertriglyceridemia (HTG) and HDL deficiency (HDL cholesterol 0.39 mmol/L, apoA-I 40 mg/dL) was investigated. We sequenced the candidate genes for HTG (LPL, APOC2, APOA5, GPIHBP1, LMF1) and HDL deficiency (LCAT, ABCA1 and APOA1), analyzed HDL subpopulations, measured cholesterol efflux capacity (CEC) of sera and constructed a model of the mutant apoA-I.

RESULTS

No mutations in HTG-related genes, ABCA1 and LCAT were found. APOA1 sequence showed that the proband, his mother and maternal grandfather were heterozygous of a novel frameshift mutation (c.546_547delGC), which generated a truncated protein (p.[L159Afs*20]) containing 177 amino acids with an abnormal C-terminal tail of 19 amino acids. Trace amounts of this protein were detectable in plasma. Mutation carriers had reduced levels of LpA-I, preβ-HDL and large HDL and no detectable HDL-2 in their plasma; their sera had a reduced CEC specifically the ABCA1-mediated CEC. Metabolic syndrome in the proband explains the extremely low HDL cholesterol level (0.31 mmol/L), which was half of that found in the other carriers. The proband's mother and grandfather, both presenting low plasma low-density lipoprotein cholesterol, were carriers of the β-thalassemic trait, a condition known to be associated with a reduced low-density lipoprotein cholesterol and a reduced prevalence of cardiovascular disease. This trait might have delayed the development of atherosclerosis related to HDL deficiency.

CONCLUSIONS

In these heterozygotes for apoA-I truncation, the metabolic syndrome has deleterious effect on HDL system, whereas β-thalassemia trait may delay the onset of cardiovascular disease.

Elevated interleukin-10: a new cause of dyslipidemia leading to severe HDL deficiency

BACKGROUND

Low high-density lipoprotein cholesterol (HDL-C) is a risk factor for coronary artery disease. Investigating mechanisms underlying acquired severe HDL deficiency in noncritically ill patients ("disappearing HDL syndrome") could provide new insights into HDL metabolism.

OBJECTIVE

To determine the cause of low HDL-C in patients with severe acquired HDL deficiency.

METHODS AND RESULTS

Patients with intravascular large B-cell lymphoma (n = 2), diffuse large B-cell lymphoma (n = 1), and autoimmune lymphoproliferative syndrome (n = 1) presenting with markedly decreased HDL-C, low low-density lipoprotein cholesterol (LDL-C), and elevated triglycerides were identified. The abnormal lipoprotein profile returned to normal after therapy in all 4 patients. All patients were found to have markedly elevated serum interleukin-10 (IL-10) levels that also normalized after therapy. In a cohort of autoimmune lymphoproliferative syndrome patients (n = 93), IL-10 showed a strong inverse correlation with HDL-C (R(2) = 0.3720, P < .0001). A direct causal role for increased serum IL-10 in inducing the observed changes in lipoproteins was established in a randomized, placebo-controlled clinical trial of recombinant human IL-10 in psoriatic arthritis patients (n = 18). Within a week of initiating subcutaneous recombinant human IL-10 injections, HDL-C precipitously decreased to near-undetectable levels. LDL-C also decreased by more than 50% (P < .0001) and triglycerides increased by approximately 2-fold (P < .005). All values returned to baseline after discontinuing IL-10 therapy.

CONCLUSION

Increased IL-10 causes severe HDL-C deficiency, low LDL-C, and elevated triglycerides. IL-10 is thus a potent modulator of lipoprotein levels, a potential new biomarker for B-cell disorders, and a novel cause of disappearing HDL syndrome.

A sudden onset and the spontaneous remission of severe hypo-high-density lipoprotein cholesterolemia without serious underlying disease: a case report

BACKGROUND

Severe hypo-high-density lipoprotein (HDL) cholesterolemia is defined by serum values less than 20mg/dl. Few acquired cases, without serious underlying disease, have been reported.

CASE

An asymptomatic 75-y-old man was admitted for evaluation of low serum HDL-cholesterol (HDL-C) levels (2-8 mg/dl). The record of periodic medical examinations revealed that a sudden decrease had occurred 5 y ago. Mild anemia and proteinuria were noted but the liver and thyroid function tests were normal. β-Quantification revealed a relatively low HDL-C (10.8 mg/dl) and the serum lecithin cholesterol acyltransferase (LCAT) activity was low (29.4 nmol/ml/h). Unexpectedly, serum HDL-C levels recovered 2 y after hospital discharge. In addition, the serum LCAT activity, hemoglobin concentrations, and urine protein tests all returned to within the reference interval. Subsequent examinations could not clarify the cause of the sudden onset and spontaneous recovery of the extremely low HDL-C.

CONCLUSIONS

We describe an unusual case of acquired HDL-C deficiency in a 75-y-old man that did not have serious pre-existing disease. Recently, extremely low HDL-C levels in patients with the nephrotic syndrome, associated with acquired LCAT deficiency, have been reported. The present case might illustrate a milder form of this disorder, because the clinical findings show many similarities.

New-onset extremely low levels of high-density lipoprotein cholesterol

We report the case of a 55-year-old man who presented to the outpatient lipid clinic for his scheduled follow-up with severely low high-density lipoprotein cholesterol levels of new onset. Diagnostic workup showed that he was infected by visceral leishmaniasis. He was treated with liposomal amphotericin B and serum lipid levels returned to usual values.

Clinical presentation, laboratory values, and coronary heart disease risk in marked high-density lipoprotein-deficiency states

Our purpose is to provide a framework for diagnosing the inherited causes of marked high-density lipoprotein (HDL) deficiency (HDL cholesterol levels <10 mg/dL in the absence of severe hypertriglyceridemia or liver disease) and to provide information about coronary heart disease (CHD) risk for such cases. Published articles in the literature on severe HDL deficiencies were used as sources. If apolipoprotein (Apo) A-I is not present in plasma, then three forms of ApoA-I deficiency, all with premature CHD,and normal low-density lipoprotein (LDL) cholesterol levels have been described: ApoA-I/C-III/A-IV deficiency with fat malabsorption, ApoA-I/C-III deficiency with planar xanthomas, and ApoA-I deficiency with planar and tubero-eruptive xanthomas (pictured in this review for the first time). If ApoA-I is present in plasma at a concentration <10 mg/dL, with LDL cholesterol that is about 50% of normal and mild hypertriglyceridemia, a possible diagnosis is Tangier disease due to mutations at the adenosine triphosphate binding cassette protein A1 (ABCA1) gene locus. These patients may develop premature CHD and peripheral neuropathy, and have evidence of cholesteryl ester-laden macrophages in their liver, spleen, tonsils, and Schwann cells, as well as other tissues. The third form of severe HDL deficiency is characterized by plasma ApoA-I levels <40 mg/dL, moderate hypertriglyceridemia, and decreased LDL cholesterol, and the finding that most of the cholesterol in plasma is in the free rather than the esterified form, due to a deficiency in lecithin:cholesterol acyltransferase activity. These patients have marked corneal opacification and splenomegaly, and are at increased risk of developing renal failure, but have no clear evidence of premature CHD. Marked HDL deficiency has different etiologies and is generally associated with early CHD risk.