Hyperviscosity syndrome in a hypercholesterolemic patient with primary biliary cirrhosis

Use of therapeutic plasma exchange to remove lipoprotein X in a patient with vanishing bile duct syndrome presenting with cholestasis, pseudohyponatremia, and hypercholesterolemia: A case report and review of literature

INTRODUCTION

Lipoprotein X (Lp-X) is an abnormal lipoprotein found in multiple disease conditions, including liver dysfunction and cholestasis. High Lp-X concentrations can interfere with some laboratory testing that may result in spurious results. The detection of Lp-X can be challenging, and there is currently a lack of consensus regarding the management of Lp-X other than treating the underlying disease.

CASE PRESENTATION

A 42-year-old female with Hodgkin's lymphoma treated with dexamethasone, high dose cytarabine and cisplatin and vanishing bile duct syndrome confirmed by liver biopsy presented with cholestasis, pseudohyponatremia (sodium, 113 mmol/L; reference range 136-146 mmL/L; serum osmolality, 303 mOsm/kg), and hypercholesterolemia (> 2800 mg/dL, reference range < 200 mg/dL). Lp-X was confirmed by lipoprotein electrophoresis (EP). Although she did not manifest any specific signs or symptoms, therapeutic plasma exchange (TPE) was initiated based on laboratory findings of extreme hypercholesterolemia, spuriously abnormal serum sodium, and HDL values, and the potential for short- and long-term sequelae such as hyperviscosity syndrome, xanthoma, and neuropathy. During the hospitalization, she was treated with four 1.0 plasma volume TPE over 6 days using 5% albumin for replacement fluid. After the first TPE, total cholesterol (TC) decreased to 383 mg/dL and sodium was measured at 131 mmol/L. The patient was transitioned into outpatient maintenance TPE to eliminate the potential of Lp-X reappearance while the underlying disease was treated. Serial follow-up laboratory testing with lipoprotein EP showed the disappearance of Lp-X after nine TPEs over a 10-week period.

LITERATURE REVIEW

There are seven and four case reports of Lp-X treated with TPE and lipoprotein apheresis (LA), respectively. While all previous case reports showed a reduction in TC levels, none had monitored the disappearance of Lp-X after completing a course of therapeutic apheresis.

CONCLUSION

Clinicians should have a heightened suspicion for the presence of abnormal Lp-X in patients with cholestasis, hypercholesterolemia, and pseudohyponatremia. Once Lp-X is confirmed by lipoprotein EP, TPE should be initiated to reduce TC level and remove abnormal Lp-X. Most LA techniques are not expected to be beneficial since Lp-X lacks apolipoprotein B. Therefore, we suggest that inpatient course of TPE be performed every other day until serum sodium, TC and HDL levels become normalized. Outpatient maintenance TPE may also be considered to keep Lp-X levels low while the underlying disease is treated. Serum sodium, TC, and HDL levels should be monitored while on maintenance TPE.

Pseudohyponatremia: Mechanism, Diagnosis, Clinical Associations and Management

Pseudohyponatremia remains a problem for clinical laboratories. In this study, we analyzed the mechanisms, diagnosis, clinical consequences, and conditions associated with pseudohyponatremia, and future developments for its elimination. The two methods involved assess the serum sodium concentration ([Na]_S) using sodium ion-specific electrodes: (a) a direct ion-specific electrode (ISE), and (b) an indirect ISE. A direct ISE does not require dilution of a sample prior to its measurement, whereas an indirect ISE needs pre-measurement sample dilution. [Na]_S measurements using an indirect ISE are influenced by abnormal concentrations of serum proteins or lipids. Pseudohyponatremia occurs when the [Na]_S is measured with an indirect ISE and the serum solid content concentrations are elevated, resulting in reciprocal depressions in serum water and [Na]_S values. Pseudonormonatremia or pseudohypernatremia are encountered in hypoproteinemic patients who have a decreased plasma solids content. Three mechanisms are responsible for pseudohyponatremia: (a) a reduction in the [Na]_S due to lower serum water and sodium concentrations, the electrolyte exclusion effect; (b) an increase in the measured sample's water concentration post-dilution to a greater extent when compared to normal serum, lowering the [Na] in this sample; (c) when serum hyperviscosity reduces serum delivery to the device that apportions serum and diluent. Patients with pseudohyponatremia and a normal [Na]_S do not develop water movement across cell membranes and clinical manifestations of hypotonic hyponatremia. Pseudohyponatremia does not require treatment to address the [Na]_S, making any inadvertent correction treatment potentially detrimental.

Lipoprotein-X: A Case of Falsely Elevated LDL Hypercholesterolemia

Lipoprotein-X is an extremely rare cause of severe hyperlipidemia. We present a case of a 26-year-old man with primary sclerosing cholangitis who developed lipoprotein X-induced pseudohyponatremia with severe hyponatremia. In this case report, we also discuss the diagnostic approach and the treatment for lipoprotein X. (Level of Difficulty: Advanced.).

Lipoprotein-X and Lipoprotein-Z Induced Hyperviscosity Syndrome in the Setting of Cholestatic Liver Failure

We describe a case referred for worsening hypercholesterolemia in the setting of atorvastatin and fenofibrate-induced liver injury. The patient reported neurological complaints attributed to hyperviscosity syndrome (induced by lipoprotein-X and lipoprotein-Z). Hepatic recovery was associated with reduction of whole blood viscosity and amelioration of neurological symptoms. (Level of Difficulty: Advanced.).

A Simple Fluorescent Cholesterol Labeling Method to Cryoprotect and Detect Plasma Lipoprotein-X

Simple Summary

Lipoprotein-X is an abnormal toxic particle in blood that is highly enriched in cholesterol. Lipoprotein-X forms in patients lacking an enzyme in blood called lecithin-cholesterol-acyl-transferase. With time, lipoprotein-X causes kidney disease in these patients, resulting in death at 40–50 years of age. Lipoprotein-X also forms, at very high levels, in the blood of patients with several different types of liver disease. Such high levels of lipoprotein-X cause additional painful and debilitating problems in these patients that can also be fatal. Currently, difficult and time-consuming tests only available in research laboratories can identify lipoprotein-X in blood. Unfortunately, lipoprotein-X in patient blood samples is unstable outside the body, and so with time becomes undetectable, even more so if it is frozen for evaluation at a later time. We have developed a simple method to label blood-derived lipoprotein-X so that it can be easily detected, and this method also stabilizes lipoprotein-X particles when frozen, enabling its detection after thawing. This methodology can easily be developed into a simple clinical test to identify both types of diseases where lipoprotein-X particles form in the blood and can be used to monitor how well treatments are able to reduce toxic lipoprotein-X in people with these diseases.

Abstract

Lipoprotein-X (LpX) are abnormal nephrotoxic lipoprotein particles enriched in free cholesterol and phospholipids. LpX with distinctive lipid compositions are formed in patients afflicted with either familial LCAT deficiency (FLD) or biliary cholestasis. LpX is difficult to detect by standard lipid stains due to the absence of a neutral lipid core and because it is unstable upon storage, particularly when frozen. We have recently reported that free cholesterol-specific filipin staining after agarose gel electrophoresis sensitively detects LpX in fresh human plasma. Herein, we describe an even more simplified qualitative method to detect LpX in both fresh and frozen–thawed human FLD or cholestatic plasma. Fluorescent cholesterol complexed to fatty-acid-free BSA was used to label LpX and was added together with trehalose in order to cryopreserve plasma LpX. The fluorescent cholesterol bound to LpX was observed with high sensitivity after separation from other lipoproteins by agarose gel electrophoresis. This methodology can be readily developed into a simple assay for the clinical diagnosis of FLD and biliary liver disease and to monitor the efficacy of treatments intended to reduce plasma LpX in these disease states.

Monocyte phenotyping and management of lipoprotein X syndrome

BACKGROUND

Accumulation of lipoprotein X (LpX) in blood can cause severe hypercholesterolemia and cutaneous xanthomas. Monocytes sensitively sense lipid changes in circulation and contribute to inflammation. However, how monocytes respond to LpX is undefined.

OBJECTIVE

We examined the phenotype of monocytes from a patient, who had LpX, severe hypercholesterolemia, and extensive cutaneous xanthomas, and effects of semiselective plasmapheresis therapy (SPPT).

METHOD

Fluorescence-activated cell sorting and adhesion assays were used to examine monocyte phenotype and ex vivo oxidized low-density lipoprotein uptake and adhesion in the patient before and after treatment with SPPT. Effects of plasma from the patient on the phenotype and adhesion of monocytes from a healthy participant were determined.

RESULTS

SPPT improved hypercholesterolemia and cutaneous xanthomas. Before treatment, the patient had lower frequency of nonclassical monocytes but higher frequency of intermediate monocytes than the control participant. Before treatment, monocytes from the patient with LpX showed more intracellular lipid accumulation, alterations in several cell surface markers and intracellular cytokines, as well as enhanced oxidized low-density lipoprotein uptake and reduced adhesion compared with control. After SPPT, the phenotypes of monocytes from the patient with LpX were similar to control monocytes. Incubation with plasma from the patient before treatment as compared with plasma from the control participant or the patient after treatment increased CD11c expression and adhesion of monocytes from a healthy participant.

CONCLUSION

LpX-induced hypercholesterolemia increased lipid accumulation and altered the phenotype of monocytes, which may contribute to cutaneous xanthoma development. Removal of LpX by SPPT reduced lipid accumulation and improved monocyte phenotype, likely contributing to xanthoma resolution.

Novel lecithin: cholesterol acyltransferase-based therapeutic approaches

PURPOSE OF REVIEW

To review recent lecithin:cholesterol acyltransferas (LCAT)-based therapeutic approaches for atherosclerosis, acute coronary syndrome, and LCAT deficiency disorders.

RECENT FINDINGS

A wide variety of approaches to using LCAT as a novel therapeutic target have been proposed. Enzyme replacement therapy with recombinant human LCAT is the most clinically advanced therapy for atherosclerosis and familial LCAT deficiency (FLD), with Phase I and Phase 2A clinical trials recently completed. Liver-directed LCAT gene therapy and engineered cell therapies are also another promising approach. Peptide and small molecule activators have shown efficacy in early-stage preclinical studies. Finally, lifestyle modifications, such as fat-restricted diets, cessation of cigarette smoking, and a diet rich in antioxidants may potentially suppress lipoprotein abnormalities in FLD patients and help preserve LCAT activity and renal function but have not been adequately tested.

SUMMARY

Preclinical and early-stage clinical trials demonstrate the promise of novel LCAT therapies as HDL-raising agents that may be used to treat not only FLD but potentially also atherosclerosis and other disorders with low or dysfunctional HDL.

LCAT protects against Lipoprotein-X formation in a murine model of drug-induced intrahepatic cholestasis

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease characterized by low HDL-C levels, low plasma cholesterol esterification, and the formation of Lipoprotein-X (Lp-X), an abnormal cholesterol-rich lipoprotein particle. LCAT deficiency causes corneal opacities, normochromic normocytic anemia, and progressive renal disease due to Lp-X deposition in the glomeruli. Recombinant LCAT is being investigated as a potential therapy for this disorder. Several hepatic disorders, namely primary biliary cirrhosis, primary sclerosing cholangitis, cholestatic liver disease, and chronic alcoholism also develop Lp-X, which may contribute to the complications of these disorders. We aimed to test the hypothesis that an increase in plasma LCAT could prevent the formation of Lp-X in other diseases besides FLD. We generated a murine model of intrahepatic cholestasis in LCAT-deficient (KO), wild type (WT), and LCAT-transgenic (Tg) mice by gavaging mice with alpha-naphthylisothiocyanate (ANIT), a drug well known to induce intrahepatic cholestasis. Three days after the treatment, all mice developed hyperbilirubinemia and elevated liver function markers (ALT, AST, Alkaline Phosphatase). The presence of high levels of LCAT in the LCAT-Tg mice, however, prevented the formation of Lp-X and other plasma lipid abnormalities in WT and LCAT-KO mice. In addition, we demonstrated that multiple injections of recombinant human LCAT can prevent significant accumulation of Lp-X after ANIT treatment in WT mice. In summary, LCAT can protect against the formation of Lp-X in a murine model of cholestasis and thus recombinant LCAT could be a potential therapy to prevent the formation of Lp-X in other diseases besides FLD.

Detection of Lipoprotein X (LpX): A challenge in patients with severe hypercholesterolaemia

Background

Lipoprotein X (LpX) is an abnormal lipoprotein fraction, which can be detected in patients with severe hypercholesterolaemia and cholestatic liver disease. LpX is composed largely of phospholipid and free cholesterol, with small amounts of triglyceride, cholesteryl ester and protein. There are no widely available methods for direct measurement of LpX in routine laboratory practice. We present the heterogeneity of clinical and laboratory manifestations of the presence of LpX, a phenomenon which hinders LpX detection.

Methods

The study was conducted on a 26-year-old female after liver transplantation (LTx) with severely elevated total cholesterol (TC) of 38 mmol/L and increased cholestatic liver enzymes. TC, free cholesterol (FC), cholesteryl esters (CE), triglycerides, phospholipids, HDL-C, LDL-C, and apolipoproteins AI and B were measured. TC/apoB and FC:CE ratios were calculated. Lipoprotein electrophoresis was performed using a commercially available kit and laboratory-prepared agarose gel.

Results

Commercially available electrophoresis failed to demonstrate the presence of LpX. Laboratory-prepared gel clearly revealed the presence of lipoproteins with γ mobility, characteristic of LpX. The TC/apoB ratio was elevated and the CE level was reduced, confirming the presence of LpX. Regular lipoprotein apheresis was applied as the method of choice in LpX disease and a bridge to reLTx due to chronic liver insufficiency.

Conclusions

The detection of LpX is crucial as it may influence the method of treatment. As routinely available biochemical laboratory tests do not always indicate the presence of LpX, in severe hypercholesterolaemia with cholestasis, any discrepancy between electrophoresis and biochemical tests should raise suspicions of LpX disease.

Lipoprotein-X fifty years after its original discovery

AIMS

To review the formation, catabolism, and the possible atherogenic properties of Lp-X.

DATA SYNTHESIS

The conversion of cholesterol to bile acids is regulated by several mechanisms including cholesterol 7 alpha hydroxylase, fibroblast growth factor 19, and farnesoid X receptors. During cholestasis these mechanisms are altered and there is an accumulation of bile acids and cholesterol in plasma. The hypercholesterolemia observed in cholestasis is due to the presence of an anomalous lipoprotein called lipoprotein-X (Lp-X). Lp-X is a lipoprotein rich in phospholipid and free cholesterol present in plasma of patients with cholestasis and, with some variations, in patients with lecithin-cholesterol-acyl-transferase deficiency (LCAT), and after lipid infusion. Lp-X is formed from a bile lipoprotein moving to the blood vessels where it incorporates small quantities of triglycerides, apo-C and esterified cholesterol and becomes a "mature" Lp-X. The activity of the phosphatidilcholine canalicular transporter Mdr2 P-glycoprotein (homologous to the human ABCB4) is essential for LpX appearance, since its suppression abolishes Lp-X formation. However, the concentration of Lp-X in plasma is determined also by the degree of the cholestasis, the residual liver function, and the LCAT deficiency. The Lp-X catabolism seems to be mediated by the reticuloendothelial system and possibly the kidney.

CONCLUSIONS

Lp-X might be considered a defense mechanism against the toxic effect of free cholesterol in cholestasis. The frequency of cardiovascular events in patients affected by primary biliary cholangitis, in whom the Lp-X is present in high concentration, are not increased. Further studies could now clarify the remaining open questions on the role of Lp-X in the dyslipidemia of cholestasis.

Lipoprotein-X disease in the setting of severe cholestatic hepatobiliary autoimmune disease

Severe cholestatic disease and hyperlipidemia are both commonly encountered by medical professionals. This article reviews the current pathophysiological model of lipoprotein-X syndrome related to 3 cases from 2 academic medical centers in the United States.

Coronary artery disease in primary biliary cirrhosis: A systematic review and meta-analysis of observational studies

AIM

To investigate the association between primary biliary cirrhosis (PBC) and risk of coronary artery disease (CAD).

METHODS

We conducted a systematic review and meta-analysis of published observational studies that reported relative risks, odd ratios, hazard ratios or standardized incidence ratios with 95% confidence intervals (CI) comparing CAD risk in patients with PBC versus non-PBC controls. Pooled risk ratios and 95% confidence intervals were combined using a random-effect model and generic inverse variance of DerSimonian and Laird methods.

RESULT

Four studies with 3362 patients with PBC were identified and included in our data analysis. The pooled risk ratio of CAD in patients with PBC was 1.57 (95% CI, 1.21-2.06). The statistical heterogeneity was low with an I(2) of 38%.

CONCLUSION

Our study demonstrated a statistically significant increased risk of CAD among patients with PBC.

Management of lipoprotein X and its complications in a patient with primary sclerosing cholangitis

Lipoprotein X (LpX) is an abnormal lipoprotein found in conditions such as lecithin:cholesterol acyltransferase deficiency and cholestatic states (e.g., primary biliary cirrhosis and primary sclerosing cholangitis). Management of severe hypercholesterolemia due to LpX with drugs and physical removal methods is not well established in the literature. A case is discussed of a 51-year-old woman who presented with multiple electrolyte abnormalities, xanthomas and neuropathy found to be secondary to LpX in the setting of primary sclerosing cholangitis. This case highlights that oral medications, including statins, may be insufficient to normalize lipid levels or improve clinical symptoms of LpX and presents therapeutic plasma exchange as a safe and effective therapeutic option to treat the morbid sequela of LpX hyperlipidemia.

Blood viscosity in subcortical vascular mild cognitive impairment with versus without cerebral amyloid burden

BACKGROUND

Subcortical vascular dementia (SVaD) is a common form of dementia, attributed to ischemic small-vessel disease. Blood viscosity (BV) may contribute to the pathophysiology of SVaD. However, SVaD patients with coexisting amyloid deposition may not show differences in BV because their small-vessel disease may result from amyloid angiopathy independently of BV. We, therefore, hypothesized that BV might show different changes compared with control subjects in subcortical vascular mild cognitive impairment (svMCI) that refers to the prodromal stage of SVaD according to cerebral amyloid burden detected by the [(11)C] Pittsburgh compound B (PiB) PET (positron emission tomography), and apolipoprotein 4 (ApoE4) genotype (a known risk factor for vascular and parenchymal amyloid).

METHODS

Our subjects consisted of 33 healthy normal controls (NC), 28 patients with PiB(-) svMCI, and 12 with PiB(+) svMCI. They underwent scanning capillary tube viscometer measuring BV during systolic and diastolic phases.

RESULTS

Compared with the NC group, the PiB(-) svMCI group showed increased diastolic blood viscosity (DBV) but no difference in systolic blood viscosity (SBV). By contrast, there was no significant difference in SBV and DBV between the NC and PiB(+) svMCI groups. Within the PiB(+) svMCI group, ApoE4(-) subgroup showed increased DBV compared with the ApoE4(+) subgroup.

CONCLUSIONS

Increased DBV is an important contributor to the development of "pure" svMCI (ie, without cerebral amyloid deposition). The relationship between BV and PiB(+) svMCI differed according to ApoE genotype, suggesting that the pathogenesis of PiB(+) svMCI might also be heterogeneous.

Severe hypercholesterolemia in patients with graft-vs-host disease affecting the liver after stem cell transplantation

OBJECTIVE

To review the available literature on severe hypercholesterolemia occurring in the context of graft-vs-host disease affecting the liver.

METHODS

A literature search was conducted in PubMed for articles on hypercholesterolemia occurring in the context of graft-vs-host disease after allogeneic hematopoietic stem cell transplantation. The review included the type of lipid abnormalities observed, complications, and available management strategies.

RESULTS

Severe hypercholesterolemia can occur in patients who develop graft-vs-host disease after transplant. We describe 8 patients with severe hypercholesterolemia occurring in the context of graft-vs-host disease affecting the liver after hematopoietic stem cell transplantation (7 from the literature and 1 from our institution). No association was observed with a specific age, sex, type of hematologic malignancy, or use of a specific immunosuppressant. The elevated cholesterol is either due to high concentrations of lipoprotein X or low-density lipoprotein. Unlike low-density lipoprotein, lipoprotein X may not be atherogenic.

CONCLUSIONS

Treatment may not be required when lipoprotein X is the major elevated lipoprotein unless hyperviscosity occurs, but treatment is indicated when there is elevation in low-density lipoprotein. Plasmapheresis may be necessary. Ultimate treatment is control of the graft-vs-host disease affecting the liver that would improve or completely resolve the hyperlipidemia.

Hypertriglyceridemic acute pancreatitis during pregnancy: prevention with diet therapy and omega-3 fatty acids in the following pregnancy

Acute pancreatitis complicating pregnancy is rare and has previously been associated with high mortality rates. We report a case of repeated hypertriglyceridemia during pregnancy. During the patient's first pregnancy, acute pancreatitis was elicited in the third trimester by pregnancy-induced hypertriglyceridemia. The patient was treated successfully with a conservative treatment course. The hypertriglyceridemia recurred during her second pregnancy. She carried the pregnancy to term without incident while maintaining a diet low in fat diet and high in omega-3 fatty acids. Early diagnosis and intensive treatment can help to preserve the lives of the patient and the fetus. Prophylactic diet therapy and omega-3 fatty acids may prevent recurrent hypertriglyceridemia during pregnancy.

Severe hypercholesterolemia mediated by lipoprotein X in a pediatric patient with chronic graft-versus-host disease of the liver

We describe a case of extreme hypercholesterolemia, mediated by lipoprotein X, in a 12-year-old Caucasian female who underwent an unrelated allogenic bone marrow transplant for relapsed acute myelocytic leukemia (AML). Her post-transplant course was complicated by severe chronic graft-versus-host disease (GVHD) of the liver. Previously normal serum cholesterol and triglycerides rose to 1,122 mg/dl (29.0 mmol/L) and 1,100 mg/dl (12.4 mmol/L), respectively. Serum cholesterol appeared to be dominantly carried by lipoprotein X. Intra-hepatic cholestasis leading to reflux of bile lipoproteins into the blood stream and subsequent formation of lipoprotein X appears to be the mechanism underlying this phenomenon.

Primary biliary cirrhosis, hyperlipidemia, and atherosclerotic risk: a systematic review

Primary Biliary Cirrhosis (PBC) is a chronic, progressive liver disease associated with markedly elevated serum lipids, but it is not clear if PBC is associated with accelerated atherosclerosis. The present systematic review examined the relationship of PBC to atherosclerotic risk. The lipid abnormalities in PBC are complex, depend on the stage of hepatic dysfunction and affect most lipoprotein classes. Increased cholesterol levels in PBC are primarily due to LP-X, an abnormal LDL particle. LP-X has anti-atherogenic properties and may reduce the atherosclerotic risk. Few studies have examined coronary artery disease (CAD) events in PBC, and none have sufficient sample size of follow-up to determine CAD risk in PBC patients. Nevertheless, one study suggested that 12% of PBC patients died from circulatory system diseases suggesting that lipid treatment is appropriate in some patients. Additional larger scale, prospective studies are required to determine the necessity of lipid treatment in this patient group. In the interim, decisions on the use of lipid lowering agents depend largely on the prognosis of the PBC and physician and patient preference for treatment.

Severe Hypercholesterolemia Associated with Decreased Hepatic Triglyceride Lipase Activity and Pseudohyponatremia in Patients after Allogeneic Stem Cell Transplantation

A 55-year-old woman with Ph-negative acute lymphoblastic leukemia in primary induction failure received allogeneic peripheral blood stem cell transplantation from her HLA-compatible sister. Pseudohyponatremia developed due to extreme hypercholesterolemia of 4091 mg/dL accompanied by lipoprotein X and lipoprotein Y. The hypercholesterolemia was caused by cholestasis due to chronic GVHD and ischemic cholangiopathy. In addition, we found that hepatic triglyceride lipase (HTGL) activity was severely decreased, which could be another novel factor causing extreme hypercholesterolemia after allogeneic transplantation. The total cholesterol has been gradually decreasing followed by the improvement of cholestasis with bezafibrate, ursodeoxycholic acid and prednisone treatments, and by a slight increase in HTGL-protein. To our knowledge, this is the first report to describe the association of decreased HTGL with extreme hypercholesterolemia after allogeneic transplantation.

Severe hypercholesterolemia mediated by lipoprotein X in patients with chronic graft-versus-host disease of the liver

We describe a series of cases of extreme hypercholesterolemia mediated by lipoprotein X in patients with chronic graft-versus-host disease of the liver after an allogeneic bone marrow transplant. All of the patients presented with a total cholesterol in excess of 1000 mg/dl (25.9 mmol/l). At the time they were also noted to have pseudohyponatremia. Cholesterol appeared to be predominantly carried by lipoprotein X. Intrahepatic cholestasis leading to reflux of bile lipoproteins into the bloodstream and subsequent formation of protein X appears to be the mechanism underlying this phenomenon. Complications, including retinal cholesterol thromboembolism and cholesteroloma of the lung have been seen in the patient with the highest cholesterol levels. Severe hypercholesterolemia is an important, and likely more common than previously reported, long-term complication of allogeneic hematopoietic stem cell transplantation. It is important for clinicians to familiarize themselves with the diagnostic and therapeutic challenges this condition presents.

Selective hemapheresis, an effective new approach in the therapeutic management of disorders associated with rheological impairment: mode of action and possible clinical indications

The in vitro measurement of whole-blood viscosity, plasma viscosity, and erythrocyte aggregability is easy to perform, but they only allow a partial insight into the complexity of blood flow characteristics; however, they permit definition of the rheological properties of new hemorheological therapeutic modalities such as extracorporeal plasma therapy as described in this paper. Under more theoretical aspects, it becomes obvious that such hemorheological approaches should either improve the vasomotoric properties of blood vessels, reduce the circulating red blood cell concentration, or improve the viscosity by reducing the concentration of hemorheologically relevant plasma proteins. In this review, the rheological effect of a single apheresis treatment with different devices was compared. Due to their differences in selectivity, the extracorporeal methods have different effects on the rheologically relevant plasma proteins, and, therefore, their rheological effectiveness differs remarkably. Today, the classical blood letting and plasma exchange treatment have been replaced by erythrapheresis and selective devices for extracorporeal plasma treatment, respectively. For more than 10 years, the following 5 more-or-less selective apheresis procedures are commercially available: immunoadsorption, differential filtration, polyanion adsorption by dextrane sulfate as well as by polyacrylate, and polyanion precipitation by heparin as polyanion. The last three procedures are semiselective and, therefore, relatively unspecific whereas immunoadsorption only affects the plasma lipoprotein concentration. Several studies have shown the effective use of extracorporeal hemorheotherapy for the treatment of various diseases including macro- and cryoglobulinemia, Raynaud's disease, hyperlipoproteinemia (often characterized by premature atherosclerosis and coronary heart disease and peripheral arterial occlusive disease), cerebral multi-infarct demention and acute ischemic stroke, sudden hearing loss, and acute occlusion of the central retinal artery.

Bile duct cells: a novel in vitro model for the study of lipid metabolism and bile acid production

Immortalized bile duct cells (BDC), derived from transgenic mice harboring the SV40 thermosensitive immortalizing mutant gene ts458, were utilized to investigate the role of the biliary epithelium in lipid and sterol metabolism. This cell model closely resembles the in vivo situation because it expresses the specific phenotypic marker cytokeratin 19 (CK-19), exhibits the formation of bile duct-like structures, and displays well-formed microvilli projected from the apical side to central lumen. The BDC were found to incorporate [14C]oleic acid (in nmol/mg protein) into triglycerides (121 +/- 6), phospholipids (PL; 59 +/- 3), and cholesteryl ester (16 +/- 1). The medium lipid content represented 5.90 +/- 0.16% (P < 0. 005) of the total intracellular production, indicating a limited lipid export capacity. Analysis of PL composition demonstrated the synthesis of all classes of polar lipids, with phosphatidylcholine and phosphatidylethanolamine accounting for 60 +/- 1 and 24 +/- 1%, respectively, of the total. Differences in PL distribution were apparent between cells and media. Substantial cholesterol synthesis was observed in BDC, as determined by the incorporation of [14C]acetate suggesting the presence of hydroxymethylglutaryl-CoA (HMG-CoA) reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway. With the use of [14C]acetate and [14C]cholesterol as precursors, both tauro- and glycoconjugates of bile acids were synthesized, indicating the presence of cholesterol 7alpha- and 26R-hydroxylases, the key enzymes involved in bile acid formation. The transport of bile acids was not limited, as shown by their marked accumulation in the medium (>6-fold of cell content). HMG-CoA reductase (53.0 +/- 6.7), cholesterol 7alpha-hydroxylase (15. 5 +/- 0.5), and acyl-CoA:cholesterol acyltransferase (ACAT; 201.7 +/- 10.2) activities (in pmol. min-1. mg protein-1) were present in the microsomal fractions. Our data show that biliary epithelial cells actively synthesize lipids and may directly contribute bile acids to the biliary fluid in vivo. This BDC line thus represents an efficient experimental tool to evaluate biliary epithelium sterol metabolism and to study biliary physiology.

Hyperviscosity syndrome

Hyperviscosity syndrome is clinically manifested by oronasal bleeding, retinal hemorrhages, and variable neurological symptoms. It occurs when resistance to flow of blood increases sharply, resulting in impaired transit through the microcirculatory system. The most common cause of hyperviscosity is increased concentrations of gamma globulins, either monoclonal in malignant disease or polyclonal, usually seen with rheumatic disorders. Increased numbers of red blood cells, as in polycythemia vera, can result in viscous blood. Extreme increases in concentrations of mature and immature white blood cells can also produce hyperviscosity. Treatment with plasma exchange is required when the clinical syndrome is symptomatic. Although plasma exchange is not a completely benign procedure, it represents the most effective method of controlling hyperviscosity.

Dyslipidemias and the secondary prevention of coronary heart disease

Dyslipidemias in patients with coronary heart disease confer a greater risk of ischemic cardiac events than comparable dyslipidemias in people free of disease. A major dyslipidemia can be diagnosed in more than 80% of patients with established premature coronary heart disease. These dyslipidemias constitute not only elevations of low-density lipoprotein cholesterol (hypercholesterolemia) but also indicate abnormalities in the metabolism of triglyceride-rich lipoproteins, high-density lipoproteins, and lipoprotein(a). Clinical trials have demonstrated that therapy to lower low-density lipoprotein levels can delay angiographic progression of coronary stenoses and reduce recurrent cardiac event rates. These clinical benefits from low-density lipoprotein cholesterol lowering may occur as early as 6 to 12 months after initiation of therapy. Intervention strategies for dyslipidemias are directed toward lowering the low-density lipoprotein cholesterol fraction to 90 to 100 mg/dl. This approach begins with dietary modification, weight loss, smoking cessation, and aerobic exercise. Patients with hypercholesterolemia refractory to nonpharmacologic intervention require lipid-lowering agents. The choice of lipid-lowering medications is influenced by concomitant abnormalities of lipoprotein metabolism, such as hypertriglyceridemia or hypoalphalipoproteinemia. Treatment of primary dyslipidemias other than hypercholesterolemia may be warranted in the presence of other cardiac risk factors; however, a broader spectrum of clinical trial data is needed to support or refute this contention.