A case of Streptococcus canis bacteremia, osteomyelitis, sacroiliitis, myositis, and abscess.

BACKGROUND: Streptococcus canis is a group G beta-hemolytic Streptococcus species which normally resides on the skin and mucosal surfaces of dogs. Although it rarely causes infection in humans, our case and review of relevant literature demonstrate that this multi-host pathogen may be responsible for metastatic infection. We present an appropriate management strategy in such cases. CASE PRESENTATION: A previously healthy 26-year-old male presented to the emergency department with a 2-day history of erythema, pain, and swelling of the left ankle and foot, consistent with acute cellulitis. The patient was initially discharged home with a plan to complete a course of IV cefazolin as an outpatient, but later recalled after two sets of blood cultures grew gram positive cocci. Blood cultures speciated as Streptococcus canis. This was performed by identifying beta hemolytic strep on blood agar, then typed as Lancefield group G, followed by MALDI-TOF which distinguished S. canis. History was unremarkable except for a 2-week history of lower back pain precipitated by a wrestling injury. There was no canine bite or scratch wound, although the patient lives with a dog. CT spine was obtained which demonstrated right piriformis myositis and S1 osteomyelitis. MRI additionally demonstrated right erector spinae myositis, right sacroiliitis, and multiple collections in the right posterior paraspinal soft tissues. Transthoracic echocardiogram did not demonstrate valvular vegetations. The S. canis isolate was pan-susceptible and the patient was ultimately discharged home and completed a 8-week course of IV penicillin G. After completion of therapy, his symptoms, repeat imaging, and biochemical markers suggested resolution of infection on follow-up. CONCLUSIONS: We suggest that management of S. canis bacteremia should involve consideration of screening for metastatic infection and infectious diseases consultation. However, despite its potential for systemic involvement, S. canis is often susceptible to narrow spectrum antibiotics, and may be treated with penicillins.

Fertility preservation counselling in Dutch Oncology Practice: Are nurses ready to assist physicians?

Cancer and its treatments may result in impaired fertility, which could cause long-term distress to cancer survivors. For eligible patients, fertility preservation (FP) is available to secure future reproductive potential. Many physicians, however, feel inhibited about discussing FP. Oncology nurses may serve as an initiator for discussing the subject and provide additional support. Our aim was to investigate their knowledge about FP, the way they apply this, and possible barriers to discussing FP with patients of reproductive age. A questionnaire was administered via mail, Internet and the Dutch Oncology Nursing Congress. Four hundred and twenty-one oncology nurses participated, a third of whom (31.1%) had "sufficient" knowledge of FP. Twenty-eight per cent of participants reported that they "never/hardly ever" discussed FP; 32.2% "almost always/always." FP discussions were more frequently performed by graduate nurses, academic nurses, experienced nurses and nurses with sufficient knowledge. Reasons for not discussing FP were a "lack of knowledge" (25.2%), "poor prognosis" (16.4%) and "lack of time" (10.5%). In conclusion, several obstacles may result in FP not being routinely discussed, specifically a lack of knowledge. Yet nurses feel responsible for addressing the issue, indicating that assistance with FP discussions should be encouraged. Educational training about FP is recommended.

Prevalence of the metabolic syndrome and cardiovascular disease risk in chemotherapy-treated testicular germ cell tumour survivors.

BACKGROUND: Testicular cancer patients have an increased risk for cardiovascular disease (CVD), which might be related to the increased prevalence of the metabolic syndrome (MetS) in this group of patients. METHODS: We assessed the prevalence of MetS and calculated the 10-year CVD risk in a cohort of 255 testicular germ cell tumour survivors (median age, 38.7 years; interquartile range, 31-48) at a mean of 7.8 years after anti-cancer treatment, and compared these with data obtained from 360 healthy men. RESULTS: Survivors had an age-adjusted increased risk for MetS of 1.9 compared with that of healthy controls. The risk for MetS was highest in survivors treated with combination chemotherapy (CT) 2.3 (Adult Treatment Panel of the National Cholesterol Education Program classification) and 2.2 (International Diabetes Federation classification). The risk of MetS was especially increased in survivors with testosterone levels in the lowest quartile (OR, 2.5). Ten-year cardiovascular risk as assessed by the Framingham Risk Score (3.0%) and Systemic Coronary Risk Evaluation (1.7%) algorithms was low, independent of treatment, and was comparable to controls. CONCLUSION: Testicular germ cell tumour survivors have an increased prevalence of MetS, with hypogonadism and CT treatment being clear risk factors for the development of the syndrome. The increased prevalence of MetS was not associated with an increased 10-year cardiovascular risk.

Plasma lecithin: cholesterol acyltransferase activity modifies the inverse relationship of C-reactive protein with HDL cholesterol in nondiabetic men.

Lecithin:cholesterol acyltransferase (LCAT) is instrumental in high-density lipoprotein (HDL) maturation, but high LCAT levels do not predict low cardiovascular risk. LCAT may affect antioxidative or anti-inflammatory properties of HDL. We determined the relationship of plasma high-sensitivity C-reactive protein (CRP) with LCAT activity and evaluated whether LCAT activity modifies the decreasing effect of HDL cholesterol (HDL-C) on CRP, as an estimate of its anti-inflammatory properties. Plasma HDL-C, apolipoprotein (apo) A-I and LCAT activity (exogenous substrate method) were measured in 260 nondiabetic men without cardiovascular disease. CRP was correlated inversely with HDL-C and apo A-I, and positively with LCAT activity (P<0.01 to 0.001). Multivariate regression analysis demonstrated that age- and smoking-adjusted plasma CRP levels were associated negatively with HDL-C (beta=-0.224, P<0.001) and positively with LCAT activity (beta=0.119, P=0.034), as well as with the interaction between HDL-C and LCAT activity (beta=0.123, P=0.026). There was also an interaction between apo A-I and LCAT activity on CRP (beta=0.159, P=0.005). These relationships remained similar after adjustment for apo B-containing lipoproteins. In conclusion, the inverse relationship of HDL-C with CRP is attenuated by LCAT activity at higher HDL-C levels. It is hypothesized that LCAT could mitigate HDL's anti-inflammatory or antioxidative properties at higher HDL-C concentrations.

Plasma pre beta-HDL formation is decreased by atorvastatin treatment in type 2 diabetes mellitus: Role of phospholipid transfer protein.

UNLABELLED: Atorvastatin lowers plasma phospholipid transfer protein (PLTP) activity, which stimulates pre-beta-HDL generation in vitro. We determined the effect of atorvastatin on pre-beta-HDL formation and its relation with PLTP activity in type 2 diabetes. METHODS: Plasma pre-beta-HDL formation as well as plasma apo A-I, LpA, LpAI:AII, cholesteryl ester transfer protein (CETP) and PLTP activity were measured before and after 30 weeks treatment in 40 patients randomized to atorvastatin 80 mg daily and 41 placebo receiving patients. Pre-beta HDL formation was measured by crossed immunoelectrophoresis under conditions of lecithin:cholesterol acyltransferase (LCAT) inhibition. RESULTS: Plasma pre-beta-HDL formation, triglycerides, LDL cholesterol, PLTP activity, and CETP decreased after statin treatment (all P<0.001 vs placebo), whereas HDL cholesterol increased (P<0.005). Plasma apo A-I, LpAI and LpAI:AII remained unchanged compared to placebo. In all patients combined, the changes in pre-beta-HDL formation were independently related to the decrease in plasma triglycerides (beta=0.31; P=0.006) and PLTP activity (beta=0.23; P=0.038), without a contribution of CETP. In the atorvastatin treated patients, the decrease in pre-beta-HDL formation tended to be related to the decrease in PLTP activity (beta=0.30, P=0.061) after controlling for decreases in triglycerides (beta=0.22, P=0.22). CONCLUSION: High dose atorvastatin decreases the capacity of plasma to generate pre-beta-HDL particles in type 2 diabetic patients, probably via lowering of plasma PLTP activity and triglycerides. This could contribute to an improvement in the atherogenic lipoprotein profile.

Human and mouse bones physiologically integrate in a humanized mouse model while maintaining species-specific ultrastructure.

Humanized mouse models are increasingly studied to recapitulate human-like bone physiology. While human and mouse bone architectures differ in multiple scales, the extent to which chimeric human-mouse bone physiologically interacts and structurally integrates remains unknown. Here, we identify that humanized bone is formed by a mosaic of human and mouse collagen, structurally integrated within the same bone organ, as shown by immunohistochemistry. Combining this with materials science techniques, we investigate the extracellular matrix of specific human and mouse collagen regions. We show that human-like osteocyte lacunar-canalicular network is retained within human collagen regions and is distinct to that of mouse tissue. This multiscale analysis shows that human and mouse tissues physiologically integrate into a single, functional bone tissue while maintaining their species-specific ultrastructural differences. These results offer an original method to validate and advance tissue-engineered human-like bone in chimeric animal models, which grow to be eloquent tools in biomedical research.

The ability of plasma to stimulate fibroblast cholesterol efflux is associated with the -629C-->A cholesteryl ester transfer protein promoter polymorphism: role of lecithin: cholesterol acyltransferase activity.

A recent population-based study showed that cholesteryl ester transfer protein (CETP) gene variations, which relate to lower plasma CETP, may predict increased cardiovascular risk, in spite of higher HDL cholesterol. Among other functions, CETP activity contributes to cellular cholesterol efflux, an early step in the anti-atherogenic reverse cholesterol transport (RCT) process. We hypothesized that cellular cholesterol efflux stimulating capacity of plasma could be associated with CETP gene variation. In this study, we tested the extent to which the ability of plasma to promote cholesterol efflux from cultured human fibroblasts is associated with CETP gene variation. In 223 men, the -629C-->A CETP promoter polymorphism, plasma lipids, CETP mass, cholesteryl ester transfer (CET), lecithin:cholesterol acyltransferase (LCAT) activity and the ability of plasma to promote cholesterol efflux from human skin fibroblasts, obtained from a single normolipidemic donor, were determined. In -629CC homozygotes (n=52), cholesterol efflux, plasma CETP mass, CET and LCAT activity were higher, whereas HDL cholesterol was lower compared to -629 AA homozygotes (n=62) and -629CA+AA carriers (n=171) (P<0.05 to P<0.001). Univariate correlation analysis showed that cellular cholesterol efflux was related to CETP genotype (P=0.04), plasma CET (P<0.05), LCAT activity (P<0.001) and apo A-I (P<0.05). Multiple linear regression analysis confirmed the independent association of cellular cholesterol efflux to plasma with CETP genotype. In conclusion, an association of cellular cholesterol efflux with the -629C-->A CETP polymorphism, possibly also involving LCAT activity, could provide a mechanism explaining why CETP gene variation, which relates to lower plasma CETP, does not confer diminished cardiovascular risk.

Serum paraoxonase-I activity is unaffected by short-term administration of simvastatin, bezafibrate, and their combination in type 2 diabetes mellitus.

BACKGROUND: The high-density lipoprotein (HDL)-associated anti-oxidative and anti-inflammatory enzyme, paraoxonase-I, has been found previously to be lower in type 2 diabetes mellitus. We studied whether statin and fibrate treatment, alone and in combination, affect serum paraoxonase-I activity in conjunction with changes in HDL cholesterol in diabetic patients. SUBJECTS AND METHODS: A placebo-controlled crossover study was carried out in 14 type 2 diabetic patients to test the effect of 8 weeks of active treatment with simvastatin (40 mg daily), bezafibrate (400 mg daily), and their combination on serum paraoxonase-I activity, measured as its activity towards arylesterase and paraoxon. Serum paraoxonase-I activity was also compared between these diabetic patients and 49 non-diabetic control subjects. RESULTS: Serum arylesterase activity was lower in type 2 diabetic patients compared to control subjects (P < 0.001), but the difference in paraoxonase activity was not significant (P = 0.22). Neither arylesterase (P = 0.24) nor paraoxonase activity (P = 0.37) was increased in response to treatment, despite higher HDL cholesterol and apolipoprotein A-I during combination therapy (P < 0.05 for both). CONCLUSION: Short-term administration of simvastatin and bezafibrate, even when combined, is ineffective in raising serum paraoxonase-I activity in type 2 diabetes.

Fever is not a symptom of chronic rhinosinusitis.

INTRODUCTION: In the chronic rhinosinusitis (CRS) definition of the RhinoSinusitis Task Force (RSTF) of the American Academy of Otolaryngology-Head and Neck Surgery, fever is one of the minor symptoms. In the EP3OS definition, fever is not mentioned as a contributing factor. The main aim of this study was to evaluate the role of fever in CRS. PATIENTS AND METHODS: Patients with CRS, scheduled for surgery were compared with a control group consisting of patients without CRS, suffering from esthetic complaints or obstruction of the nose. Temperature prior to surgery was measured and analyzed. RESULTS: In both groups, hundred patients were included. In the CRS group the mean temperature was 36.94 degrees C, with a maximum of 37.8 degrees C. The control group revealed a mean temperature of 36.87 degrees C. Analysis demonstrated no significant difference between the mean temperatures of the CRS patients and the controls (p = 0.306). Additional analysis, correcting for possible confounders, did not reveal significant differences between both groups either. DISCUSSION: There have been several attempts to define CRS in the past, but an all including definition or classification system for this disorder does not currently exist. Fever is a factor under discussion. We found no significant difference between the preoperative body temperature in CRS patients and controls. These results suggest that fever is not a relevant symptom in CRS.

The contribution of the pericanalicular matrix to mineral content in human osteonal bone.

The osteocyte lacunar-canalicular network (LCN) penetrates bone and houses the osteocytes and their processes. Despite its rather low volume fraction, the LCN represents an outstanding large surface that is possibly used by the osteocytes to interact with the surrounding mineralized bone matrix thereby contributing to mineral homeostasis. The aim of this study was to quantitatively describe such contributions by spatially correlating the local density of the LCN with the mineral content at the same location in micrometer-sized volume elements in human osteons. For this purpose, 65 osteons from the femur midshaft from healthy adults (n = 4) and children (n = 2) were structurally characterized with two different techniques. The 3D structure of the LCN in the osteons was imaged with confocal laser scanning microscopy after staining the bone samples with rhodamine. Subsequent image analysis provided the canalicular length density, i.e. the total length of the canaliculi per unit volume (µm/µm3). Quantitative information on the mineral content (wt%Ca) from the identical regions was obtained using quantitative backscattered electron imaging. As the LCN-porosity lowers the mineral content, a negative correlation between Ca content and network density was expected. Calculations predict a reduction of around -0.97 fmol Ca per µm of network. However, the experiment revealed for 62 out of 65 osteons a positive correlation resulting in an average additional Ca loading of +1.15 fmol per µm of canalicular network, i.e. an accumulation of mineral has occurred at dense network regions. We hypothesize that this accumulation happens in the close vicinity of canaliculi forming mineral reservoirs that can be utilized by osteocytes. Significant differences found between individuals indicate that the extent of mineral loading of the reservoir zone reflects an important parameter for mineral homeostasis.

Plasma cholesteryl ester transfer protein mass and phospholipid transfer protein activity are associated with leptin in type 2 diabetes mellitus.

Adipose tissue contributes to plasma levels of lipid transfer proteins and is also the major source of plasma adipokines. We hypothesized that plasma cholesteryl ester transfer protein (CETP) mass, phospholipid transfer protein (PLTP) activity and cholesteryl ester transfer (CET, a measure of CETP action) are determined by adipokine levels. In this study, relationships of plasma CETP mass, PLTP activity and CET with leptin, resistin and adiponectin were analyzed in type 2 diabetic patients and control subjects. Plasma PLTP activity (P<0.001), CET (P<0.001), leptin (P=0.003), resistin (P<0.001), high sensitive C-reactive protein (P=0.005), and insulin resistance (HOMA(ir)) (P<0.001) were higher, whereas HDL cholesterol (P<0.001) and plasma adiponectin (P<0.001) were lower in 83 type 2 diabetic patients (32 females) than in 83 sex-matched control subjects. Multiple linear regression analysis demonstrated that in diabetic patients plasma leptin levels were related to plasma CETP mass (P=0.018) and PLTP activity (P<0.001), but not to the other adipokines measured. Plasma CET was inversely correlated with adiponectin in univariate analysis, but this association disappeared in multivariate models that included plasma lipids and CETP. In conclusion, both plasma CETP mass and PLTP activity are associated with plasma leptin in type 2 diabetes. The elevated CET in these patients is not independently related to any of the measured plasma adipokines.

Uptake and degradation of rat and human very low density (remnant) apolipoprotein by parenchymal and non-parenchymal rat liver cells.

1. The relative contribution of parenchymal and non-parenchymal cells to the in vivo hepatic uptake of serum apolipoproteins was measured 30 min after intravenous injection of radioiodinated rat very low density lipoprotein (VLDL) remnants, rat and human VLDL, low density lipoprotein (LDL) and high density lipoprotein (HDL). Using rat VLDL, VLDL-remnants, LDL and HDL, respectively, the non-parenchymal cells contain 4.7, 4.9, 6.1 and 5.3 times the amount of trichloroacetic acid-precipitable radioactivity per mg cell protein as compared to parenchymal cells. For human VLDL, LDL and HDL these values are 5.1, 12.0 and 5.9 respectively. 2. The abilities of homogenates of human liver, rat liver parenchymal cells and rat liver non-parenchymal cells to hydrolyze human and rat iodinated VLDL apoprotein were determined by measuring the amount of trichloroacetic acid-soluble (non-iodide) radioactivity liberated upon incubation at the optimal pH of 4.2. Non-parenchymal cells possess a 8--21-fold higher maximal capacity to degrade VLDL apoprotein per mg of cell protein than parenchymal cells. This factor is 5--6 for VLDL-remnant apoprotein degradation measured at low (suboptimal) apolipoprotein concentrations. 3. It is concluded that, in addition to parenchymal cells, the non-parenchymal cells play an important role in the hepatic uptake and possibly degradation of VLDL-(remnant) apoprotein.

Effect of 4-aminopyrazolo[3,4-d]pyrimidine on the catabolism of high-density lipoprotein apolipoprotein A-I in the rat.

The in vivo turnover and sites of catabolism of O-(4-diazo-3-[125I]iodobenzoyl)sucrose-labelled rat high-density lipoprotein (HDL) apolipoprotein A-I were studied in rats treated for 3 days with 4-aminopyrazolo-[3,4-d]pyrimidine (4APP). It was found that 4APP treatment decreases the serum cholesterol concentration to 6 mg/dl and stimulates the serum decay of labelled HDL. The latter effect could be attributed to an increased catabolism of radioactive HDL apolipoprotein A-I by the liver. When the serum cholesterol concentration was raised to physiological levels by a bolus injection of unlabelled rat HDL, at the time of administration of the labelled HDL, the serum decays and the tissue uptakes of apolipoprotein A-I labelled HDL were identical in 4APP-treated rats and control animals. When a bolus injection of unlabelled human low-density lipoprotein (LDL) was administered to 4APP-treated rats, the serum decay and tissue uptake of apolipoprotein A-I labelled HDL remained rapid. The recovery of radioactivity in the adrenal glands was increased almost 10 fold by 4APP treatment, a phenomenon which was reversed by a bolus injection of unlabelled HDL, but not by injection of unlabelled LDL. It is concluded that treatment of rats with 4APP does not affect the rate of catabolism of rat HDL apolipoprotein A-I, when the serum HDL concentration in the treated animals is restored to physiological levels.

The sites of degradation of purified rat low density lipoprotein and high density lipoprotein in the rat.

Low density lipoprotein and high density lipoprotein were isolated from rat serum by sequential ultracentrifugation in the density intervals 1.025-1.050 g/ml and 1.125-1.21 g/ml, respectively. The isolated lipoproteins were radioiodinated using ICl. Low density lipoprotein was further purified by concanavalin A affinity chromatography and concentrated by ultracentrifugation. 95% of the purified low density lipoprotein radioactivity was precipitable by tetramethylurea, while only 4% was associated with lipids. The radioiodinated high density lipoprotein was incubated for 1 h at 4 degrees C with unlabelled very low density lipoprotein, followed by reisolation by sequential ultracentrifugation. Only 3% of the radioactivity was associated with lipids and 90% was present on apolipoprotein A-I. The serum decay curves of labelled and subsequently purified rat low and high density lipoprotein, measured over a period of 28 h, clearly exhibited more than one component, in contrast to the monoexponential decay curves of iodinated human low density lipoprotein. The decay curves were not affected by the methods used to purify the LDL and HDL preparations. The catabolic sites of the labelled rat lipoproteins were analyzed in vivo using leupeptin-treated rats. In vivo treatment of rats with leupeptin did not affect the rate of disappearance from serum of intravenously injected labelled rat low density lipoprotein and high density lipoprotein. Leupeptin-dependent accumulation of radioiodine occurred almost exclusively in the liver after intravenous injection of iodinated low density lipoprotein, while both the liver and the kidneys showed leupeptin-dependent accumulation of radioactivity after injection of iodinated high density lipoprotein.

In vivo uptake of human and rat low density and high density lipoprotein by parenchymal and nonparenchymal cells from rat liver.

The relative contribution of the parenchymal and nonparenchymal rat liver cells to the hepatic uptake of human and rat high density lipoprotein (HDL) and low density lipoprotein (LDL) was determined in vivo. Nonparenchymal cells, isolated 6 h after intravenous injection of iodinated human HDL and LDL, contained respectively 4.2 and 6.3 times the amount of trichloroacetic acid-precipitable radioactivity per mg cell protein as compared to parenchymal cells. For rat iodinated HDL and LDL these factors were 3.4 and 4.1, respectively. These results indicate that nonparenchymal liver cells play a substantial role in the hepatic uptake of human and rat HDL and LDL in vivo.

The effects of probucol on lipoprotein metabolism in the rat.

The effects of probucol on liver and intestinal apolipoprotein, LDL-receptor and hepatic lipase gene expression, as well as plasma lipid and apolipoprotein levels and liver lipase activity were evaluated in male rats. Administration of probucol decreased plasma triacylglycerols, without affecting plasma cholesterol. Plasma apo E and apo B concentrations increased after probucol. Since liver and intestinal apo B and apo E mRNA levels remained unchanged, this increase could be attributed to a delayed clearance by the LDL-receptor, whose mRNA levels dropped by 50% in the liver. For the HDL-apolipoproteins, only liver apo A-IV mRNA levels decreased after probucol, which was reflected by a fall of plasma apo A-IV. Neither hepatic lipase activity nor mRNA levels were significantly influenced by probucol.

Leupeptin as a tool for the detection of the sites of catabolism of rat high-density lipoprotein apolipoproteins A-I and E.

Leupeptin, an inhibitor of lysosomal cathepsin activity, was injected intravenously into male rats. Tissues obtained from leupeptin-treated animals showed a depressed cathepsin activity when compared with tissues from saline-treated control animals. Leupeptin treatment did not change the hepatic activities and subcellular distribution of marker enzymes for mitochondria, microsomes and plasma membranes. Hepatic lysosomal cathepsin activity was specifically inhibited, but the subcellular distribution of all lysosomal marker enzymes tested was changed, indicating the occurrence of enlarged lysosomes in the leupeptin-treated animals. No significant differences were observed in the serum concentrations of protein, cholesterol, cholesteryl esters, phospholipids and apolipoproteins A-I, A-IV and E between leupeptin-treated rats and control animals. When radioiodinated asialofetuin was injected intravenously, the radiolabel was retained for an extended period of time in the liver of leupeptin-treated animals, indicating diminished catabolism of this protein in the liver. When rat high-density lipoprotein, labelled specifically in the apolipoprotein A-I or E moiety was injected intravenously, only the kidneys and the liver showed a leupeptin-induced accumulation of radioactivity. These studies provide evidence for an important contribution of the kidneys and the liver to the in vivo catabolism of high-density lipoprotein apolipoproteins, using a method completely different from sugar-containing labelling compounds.

Characterization of human high-density lipoprotein subclasses LP A-I and LP A-I/A-II and binding to HepG2 cells.

Plasma HDL can be classified according to their apolipoprotein content into at least two types of lipoprotein particles: lipoproteins containing both apo A-I and apo A-II (LP A-I/A-II) and lipoproteins with apo A-I but without apo A-II (LP A-I). LP A-I and LP A-I/A-II were isolated by immuno-affinity chromatography. LP A-I has a higher cholesterol content and less protein compared to LP A-I/A-II. The average particle mass of LP A-I is higher (379 kDa) than the average particle weight of LP A-I/A-II (269 kDa). The binding of 125I-LP A-I to HepG2 cells at 4 degrees C, as well as the uptake of [3H]cholesteryl ether-labelled LP A-I by HepG2 cells at 37 degrees C, was significantly higher than the binding and uptake of LP A-I/A-II. It is likely that both binding and uptake are mediated by apo A-I. Our results do not provide evidence in favor of a specific role for apo A-II in the binding and uptake of HDL by HepG2 cells.

Effect of lipid transfer protein on plasma lipids, apolipoproteins and metabolism of high-density lipoprotein cholesteryl ester in the rat.

The role of human plasma lipid transfer protein (LTP) in lipoprotein metabolism was studied in the rat, a species without endogenous cholesteryl ester and triacylglycerol transfer activity. Partially purified human LTP was injected intravenously into rats. The plasma activity was between 1.5- and 4-fold that of human plasma during the experiments. 6 h after the injection of LTP, a significant increase in serum apoB, and no significant changes in serum total cholesterol, free cholesterol, triacylglycerols, apoA-I, apoE, or apoA-IV were noted. Cholesterol was increased in very-low density and low-density lipoproteins (VLDL and LDL) and decreased in large-sized apoE-rich HDL. ApoA-I-containing particles with a size smaller than in normal rats were present in serum of LTP-treated rats. The mean diameter of HDL particles decreased and apoE, normally present on large-sized HDL, was present on smaller sized particles. The metabolic fate of cholesteryl ester, originally associated with HDL, was studied by injection of [3H]cholesteryl linoleyl ether-labelled apoA-I-rich HDL in the absence and in the presence of LTP. The disappearance of [3H]cholesteryl linoleyl ether, injected as part of apoA-I-rich HDL, from serum was increased in the LTP-treated rats; the t1/2 changed from 3.9 to 2.2 h, resulting in an increased accumulation of [3H]cholesteryl linoleyl ether in the liver. This can be explained by the redistribution of HDL [3H]cholesteryl linoleyl ether to VLDL and LDL in the presence of LTP, leading to the combined contribution of VLDL, LDL and HDL to the hepatic uptake. The present findings show profound effects of LTP on the chemical composition of HDL subspecies, the size of HDL and on the plasma turnover and hepatic uptake of cholesteryl esters originally present in apo A-I-rich HDL.

Endothelial EA.hy 926 cells can be loaded with cationized LDL, but not with acetylated LDL.

EA.hy 926 cells, a human endothelial cell line, show characteristics of differentiated endothelial cells. Endothelial cells normally express membrane scavenger receptors. Therefore modified LDL, eg., acetylated LDL, can be taken up, causing accumulation of mass amounts of cholesterol. We have shown that EA.hy 926 cells cannot be loaded with cholesterol using acetylated LDL, but can be efficiently enriched with cholesterol by incubation with cationized LDL. The loaded cells may serve as models for studies on reverse cholesterol transport.