Hypertriglyceridaemia secondary to liver disease

Profoundly Disturbed Lipoproteins in Cirrhotic Patients: Role of Lipoprotein-Z, a Hepatotoxic LDL-like Lipoprotein

Detailed information regarding lipoprotein concentrations and subfractions in cirrhotic patients before and after orthotopic liver transplantation (OLT) is lacking. Lipoprotein-Z (LP-Z) is a recently characterised abnormal, hepatotoxic free cholesterol-rich low-density lipoprotein (LDL)-like lipoprotein. We determined the lipoprotein profiles, including LP-Z, in cirrhotic patients and OLT recipients and assessed the prognostic significance of LP-Z on the OLT waiting list. We performed analyses in cirrhotic transplant candidates and non-cirrhotic OLT recipients. A population-based cohort was used as reference. The setting was a University hospital. Lipoprotein particle concentrations and subfractions were measured by nuclear magnetic resonance spectroscopy. In the cirrhotic patients (N = 130), most measures of triglyceride-rich lipoproteins (TRL), LDL, and high-density lipoproteins (HDL) were much lower compared to the OLT recipients (N = 372) and controls (N = 6027) (p < 0.01). In the OLT recipients, many lipoprotein variables were modestly lower, but HDL-cholesterol, triglycerides, and TRL and HDL size were greater vs. the control population. LP-Z was measurable in 40 cirrhotic patients and 3 OLT recipients (30.8% vs. 0.8%, p < 0.001). The cirrhotic patients with measurable LP-Z levels had profoundly lower HDL-cholesterol and particle concentrations (p < 0.001), and worse Child Pugh Turcotte classifications and MELD scores. The presence of LP-Z (adjusted for age, sex, and MELD score) predicted worse survival in cirrhotic patients (HR per 1 LnSD increment: 1.11, 95%CI 1.03−1.19, p = 0.003). In conclusion, cirrhotic patients have considerably lower plasma concentrations of all major lipoprotein classes with changes in lipoprotein subfraction distribution. After OLT, these lipoprotein abnormalities are in part reversed. LP-Z is associated with cirrhosis. Its presence may translate in disturbed HDL metabolism and worse survival.

Changes in Serum Lipid Profiles among Canine Patients Suffering from Chronic Hepatitis

Hyperlipidemia is a risk factor for nonalcoholic fatty liver disease (NAFLD) in humans. However, the association between serum lipids and canine chronic hepatitis remains unknown. In this study, serum lipids, hepatic profiles, and hepatic ultrasound scores of healthy dogs and dogs with chronic hepatitis were evaluated. Serum triglyceride and cholesterol concentrations were significantly higher (p < 0.01) in dogs with chronic hepatitis. There were 62.2% of dogs with chronic hepatitis accompanied by hypertriglyceridemia, hypercholesterolemia, or both. Positive correlations were observed between serum ALT and cholesterol (r = 0.8287, p < 0.01), serum ALP and cholesterol (r = 0.8436, p < 0.01), serum GGT and cholesterol (r = 0.5640, p < 0.01), serum bile acid and cholesterol (r = 0.3310, p < 0.01) and serum ALP and triglycerides (r = 0.2582, p < 0.05). No significant differences were found between ultrasound scores of diseased dogs with and without hypertriglyceridemia and diseased dogs with and without hypercholesterolemia. Canine chronic hepatitis is associated with hyperlipidemia. A significant positive association was identified between hyperlipidemia, especially hypercholesterolemia, liver enzymes, and bile acid concentration in dogs suffering from chronic hepatitis. The underlying mechanisms connecting hyperlipidemia and canine chronic hepatitis remain elusive.

Biochemical and histopathological study in rats intoxicated with carbontetrachloride and treated with camel milk

The unique characters of camel’s milk make it used extensively in the field of medicine as anti-microbial, anti-diabetic and hepatoprotective agent. The lack of studies demonstrating the protective effect of camel’s milk against hepatotoxic compound was the main reason beyond the conduction of the current experiment which aimed to investigate the protective effects of camel’s milk against carbontetrachloride (CCl₄) induced hepatotoxicity. Therefore, 24 rats were fed on standard diet and divided into four groups. Rats of the first group and second groups were injected i/p with paraffin oil and received either tap water (control 1) or camel’s milk (control 2), respectively. Rats of the third and fourth groups were injected i/p with CCl₄ and received either tap water or camel’s milk, respectively. At the end of the experiment (5 weeks), blood and liver samples were collected for biochemical and histopathological analysis. The present findings revealed that, CCl₄ elevated serum enzyme activities of liver and some biochemical parameters, but these effects were prevented by the treatment of rats with camel milk. Histopathologically, a great amount of mononuclear cells infiltration, necrotic cells and few fibroblasts were observed in liver of CCl₄ treated group. The present study concluded that camel milk treatment may play a protective role against CCl₄-induced liver damages in rats. These protective effects were in the form of improving of liver enzyme activities, blood biochemical parameters and histological picture of liver of intoxicated rats. In the future, examination of the liver protective effect of camel milk against CCl₄ in dose dependant manner could be investigated.

A case of type 2 diabetes and metastatic liver cancer exhibiting hypercholesterolemia with abnormal lipoproteins

Although the appearance of abnormal lipoproteins in liver diseases is well known, the precise analyses of abnormal lipoproteins remain elusive. Here, we report a 71-year-old woman with type 2 diabetes whose serum cholesterol levels were elevated to 560 mg/dL over a 4-month period. High-performance liquid chromatography demonstrated the presence of lipoprotein-X and lipoprotein-Y and sigmoid colon cancer and multiple liver metastases were found by colonoscopy and computed tomography. Remission of the primary colon cancer and liver lesions was achieved by chemotherapy with oxaliplatin and fluorouracil and her serum cholesterol went back to basal levels associated with the disappearance of abnormal lipoproteins.

Protective effect of Panax ginseng against serum biochemical changes and apoptosis in liver of rats treated with carbon tetrachloride (CCl4)

The purpose of this study was to investigate possible beneficial effects of Panax ginseng (PG) on carbon tetrachloride (CCl(4))-induced acute hepatotoxicity in rats. CCl(4) challenge elevated serum enzyme activities of liver and some biochemical parameters, but these effects were prevented by the pretreatment of rats with PG. Histologically, a great amount of mononuclear cells infiltration, necrotic cells and few fibroblasts were observed in liver of CCl(4) group. Also, CD68(+) and caspase-3 staining cells were diffused in both lobular and portal areas. However, PG pretreatment had a little influence on the number of caspase-3 immunopositive staining cells in the liver, but CD68(+) staining areas were significantly decreased in the PG+CCl(4) when compared to CCl(4) group. We conclude that PG treatment may play a protective role by enhancing liver enzyme activities and recovering biochemical parameters, and improving the changes in histological structure against CCl(4)-induced liver damages in rats.

Glucose, lipid, and lipoprotein levels in sheep naturally infected with Fasciola hepatica

This study was designed to investigate serum glucose, lipid, and lipoprotein in sheep naturally infected with Fasciola hepatica. Ten healthy sheep and 15 infected with F. hepatica were used in study. Serum concentrations of total protein (TP), albumin, glucose, cholesterol, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very-low-density lipoproteins (VLDL), and serum activities of AST, ALT, GGT, and LDH were measured using a Roche-Cobas Integra 800 auto-analyzer. At day 0 (prior to treatment) and on the 28th day (after treatment) the serum concentrations of TP, albumin, glucose, cholesterol, triglyceride, HDL, LDL, and VLDL values in sheep with F. hepatica were significantly lower than those of the control group, while serum activities of AST, ALT, GGT, and LDH of lambs with F. hepatica were significantly higher than those of the control group. At day 56 (after treatment), none of the variables was significantly different between control sheep and those that received treatment for fascioliasis (P > 0.05). Nutritional management may be used to reduce the impact of fascioliasis.

Effects of bezafibrate on dyslipidemia with cholestasis in children with familial intrahepatic cholestasis-1 deficiency manifesting progressive familial intrahepatic cholestasis

No appropriate pharmaceutical therapy has been established for dyslipidemia with cholestasis in progressive familial intrahepatic cholestasis (PFIC)-1. We evaluated the efficacy of bezafibrate in PFIC-1. We monitored the clinical presentation and lipoprotein metabolism of 3 patients, aged 3, 4, and 8 years, with FIC1 deficiency, manifesting PFIC-1, over 12 months of bezafibrate therapy. Pruritus was substantially alleviated in the 3 patients after initiation of bezafibrate. Cholestasis was alleviated in 2 of them. Serum high-density lipoprotein cholesterol and low-density lipoprotein cholesterol increased 1.6- to 2.0-fold and 1.1- to 1.2-fold, respectively; but the values remained low and normal, respectively. Serum lipoprotein X, which was at normal levels before treatment, was elevated to levels above the upper limit of the reference range. High serum triglyceride levels decreased by 15% to 30%, to normal levels, after treatment initiation. The activities of lipoprotein lipase and hepatic triglyceride lipase were increased, but those of high-density lipoprotein regulators remained unchanged. Liver expression of multidrug resistance protein-3, which regulates lipoprotein X synthesis, was enhanced by bezafibrate therapy. Bezafibrate treatment favorably affected pruritus, dyslipidemia, and cholestasis in PFIC-1.

A case of obstructive jaundice with severe hypercholesterolemia probably due to lipoprotein-Y

AIM

We analyzed the lipoproteins of a patient with pancreatic cancer causing obstructive jaundice, with marked hypercholesterolemia.

METHODS

The patient was a 49-year-old female. Serum total cholesterol, triglyceride, LDL-cholesterol and HDL-cholesterol levels were 1,170 mg/dL, 282 mg/dL, 1,070 mg/dL and 53 mg/dL, respectively. Cholesterol ester and lecithin:cholesterol acyltransferase decreased, and so-called remnant like particle-cholesterol increased remarkably.

RESULTS

Fractionation of the patient's serum by polyacrylamide gel disc electrophoresis showed an abundant VLDL fraction, whereas agarose gel electrophoresis demonstrated a high level of beta-lipoprotein. Sepharose 6B gel filtration of the serum revealed that the levels of free cholesterol and apolipoprotein B were high in the VLDL- corresponding fraction.

CONCLUSION

The results suggested that the high cholesterol level was due to the presence of abnormally large particles rich in free cholesterol and apoB, and this abnormal fraction may correspond to lipoprotein-Y that was increased in obstructive jaundice.

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.

Alcohol and lipids

Alcoholic fatty liver and hyperlipemia result from the interaction of ethanol and its oxidation products with hepatic lipid metabolism. An early target of ethanol toxicity is mitochondrial fatty acid oxidation. Acetaldehyde and reactive oxygen species have been incriminated in the pathogenesis of the mitochondrial injury. Microsomal changes offset deleterious accumulation of fatty acids, leading to enhanced formation of triacylglycerols, which are partly secreted into the plasma and partly accumulate in the liver. However, this compensatory mechanism fades with progression of the liver injury, whereas the production of toxic metabolites increases, exacerbating the lesions and promoting fibrogenesis. The early presence of these changes confers to the fatty liver a worse prognosis than previously thought. Alcoholic hyperlipemia results primarily from increased hepatic secretion of very-low-density lipoprotein and secondarily from impairment in the removal of triacylglycerol-rich lipoproteins from the plasma. Hyperlipemia tends to disappear because of enhanced lipolytic activity and aggravation of the liver injury. With moderate alcohol consumption, the increase in high-density lipoprotein becomes the predominant feature. Its mechanism is multifactorial (increased hepatic secretion and increased extrahepatic formation as well as decreased removal) and explains part of the enhanced cholesterol transport from tissues to bile. These changes contribute to, but do not fully account for, the effects on atherosclerosis and/or coronary heart disease attributed to moderate drinking.

Cholesteryl ester transfer activity in liver disease and cholestasis, and its relation with fatty acid composition of lipoprotein lipids

Liver disease is accompanied by major qualitative and quantitative disturbances in plasma lipoprotein metabolism, the extent and intensity of which depend on the degree of parenchymal damage, cholestasis, or both. The main objective of this study was to determine the cholesteryl ester transfer CETP activity and its association with the lipoprotein neutral lipid composition in patients with either liver cirrhosis or cholestasis, as compared to normal controls. Lipoproteins were isolated by ultracentrifugation, lipids and apolipoproteins were measured by conventional methods, and the fatty acid composition was established by gas chromatography; CETP activity in lipoprotein-deficient plasma was measured by determining the transfer of [3H]cholesteryl esters from HDL to VLDL. Lipoprotein lipase and hepatic lipase activities were measured in post-heparin plasma by radiochemical methods. In patients with liver cirrhosis, low levels of VLDL, HDL, apo B, and Lp(a) were observed, as well as a change in the composition of HDL particles, with increases in the relative proportion of triglyceride and free cholesterol. Respectively, the last two changes could be attributed in part to the low hepatic lipase activity observed in this study, and to the low lecithin:cholesterol acyltransferase activity previously observed by others. In patients with cholestasis, a moderate hyperlipidemia due to the elevation of LDL was found. In contrast, HDL and apo A-I levels were very low reflecting a low number of HDL particles, which also had altered compositions with increases in the triglyceride and free cholesterol contents relative to apo A-I and esterified cholesterol, respectively. As regards the fatty acid composition of lipoprotein lipids, the two groups of patients showed, in general, a lower proportion of linoleic acid and a compensating higher proportion of oleic acid as compared to the controls, changes that were observed in both cholesteryl esters and triglycerides. In contrast, the proportions of oleic and palmitoleic acids in phospholipids were increased, whereas that of stearic acid was decreased in patients as compared to controls. In patients with liver cirrhosis, as well as in controls, no changes were observed in the fatty acid compositions of cholesteryl ester, triglycerides, or phospholipids among the different lipoproteins, which probably reflects the equilibration reached by the action of CETP. In patients with cholestasis, no differences were observed in fatty acid composition among the lipoprotein phospholipids but, interestingly, cholesteryl esters from VLDL had a significantly lower linoleic acid content than those from HDL, whereas triglycerides from VLDL had significantly higher oleic acid and lower linoleic acid contents than those from HDL. This distinct fatty acid composition of the neutral lipids between lipoproteins was associated with a significant decrease (25%) in the cholesteryl ester transfer activity in patients with cholestasis. We suggest that fat malabsorption due to the biliary defect may induce a decrease in cholesteryl ester transfer protein synthesis or section, which in turn would slow the equilibration of the neutral lipids among plasma lipoproteins.

Dyslipoproteinaemia of liver disease

Hepatic diseases differ from most other causes of secondary dyslipidaemia in that the circulating lipoproteins are not only present in abnormal amounts but they frequently also have abnormal composition, electrophoretic mobility and appearance. Pre-beta and alpha bands can be absent on electrophoresis in all types of liver disease although material in the VLDL and HDL ranges can be isolated in the ultracentrifuge. Cholestatic liver disease has been the most extensively studied and the hyperlipidaemia can be extreme with marked elevations of free cholesterol and phospholipids. This results largely from the presence of LP-X, an abnormal LDL, with a vesicular structure that appears in rouleaux formation under the electron microscope. It is virtually specific for cholestasis and familial LCAT deficiency. The LDL, however, is heterogeneous and may also contain a large triglyceride-rich particle (LP-Y) as well as more normal-looking particles, which are none the less depleted in cholesteryl esters and rich in triglycerides. Indeed, when patients with cholestasis are hypertriglyceridaemic the excess triglyceride is to be found predominantly in these two LDL fractions rather than in VLDL. HDL in cholestasis may contain disc-like particles, similar to those newly secreted by the liver and intestine, as well as more normal-looking spherical particles. In extrahepatic obstruction concentrations of HDL and its major apolipoproteins, apoAI and apoAII, are frequently reduced, although a subfraction rich in apoE is often found. In all but the latest stages of chronic intrahepatic cholestasis due to primary biliary cirrhosis, however, HDL, especially HDL2, concentrations are increased, probably due to the presence of a circulating inhibitor of HL. Many of these lipoprotein changes found in cholestasis resemble those of familial LCAT deficiency, although the hyperlipidaemia is not usually so severe in the latter condition. Indeed, in patients with cholestasis but well-preserved LCAT activity many of the characteristic lipoprotein changes, such as LP-X, LP-Y and discoidal HDL, may not be seen. In acute hepatocellular disease, such as alcoholic or viral hepatitis, it is not unusual for the patient to go through a cholestatic phase and many of the same lipoprotein changes may be seen. In cirrhosis without cholestasis the patients are not usually significantly hyperlipidaemic and in advanced cases cholesterol and apoB levels may be reduced. Although LCAT activity and the proportion of plasma cholesterol esterified may also be markedly reduced, LP-X is not usually seen, possibly because the flux of free cholesterol and phospholipid (lecithin), the LCAT substrates, is relatively low. Discoidal HDLs are often present.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcoholic foamy degeneration in Spain. Prevalence and clinico-pathological features

Among 389 consecutive chronic alcoholics in whom a liver biopsy was performed for diagnostic purposes, nine patients (2.3%) had histological changes of "alcoholic foamy degeneration" (AFD), characterized by numerous small fat droplets in the swollen hepatocytes of the centrilobular area. In five cases, there were non-specific clinical features, while the other four cases presented acute hepatic decompensation with jaundice and a reduced prothrombin activity. Seven patients had high serum lipid concentrations including hypertriglyceridemia and hypercholesterolemia, which improved after withdrawal of alcohol intake. In conclusion, AFD has a broad clinicopathological spectrum including asymptomatic patients and other cases with severe liver decompensation manifested by jaundice and reduced prothrombin activity. AFD is usually associated with hyperlipemia.

Inhibition of hepatic triglyceride secretion and exogenous triglyceride clearance in the cholestatic rat

Extrahepatic biliary obstruction in humans and rats leads to hypertriglyceridemia. The observed hypertriglyceridemia could result from either a defect of plasma triglyceride (TG) catabolism or hepatic over-production of TG. To examine these questions we have used the rat model to determine hepatic TG secretion by the Triton WR-1339 methodology (inhibition of peripheral lipolysis) and exogenous TG clearance (after i.v. injection of Intralipid). Four groups of rats were studied: group OB--48 h post-operative--bile-duct obstructed; group DV--bile diverted; group SC--sham-operated controls; and group FC--48 h fasted, unoperated controls. The hepatic TG secretion rate for group OB rats was a factor of 7 lower than that of either group SC or FC, and 5 times lower than that for group DV. There were no differences between the hepatic TG secretion rates of groups DV and FC or SC. After i.v. injection of Intralipid, plasma TG decreased with first-order kinetics. The rate constant was taken as the exogenous TG clearance rate (ETGCR). Mean ETGCR for group OB was a factor of 3 lower than that for either control group; while the ETGCR for group DV was equivalent to the control groups. Thus biliary diversion does not affect hepatic TG secretion or the ETGCR. The apparent cause of the hypertriglyceridemia of cholestasis in the bile-obstructed rat is impaired plasma TG catabolism.

Release of hepatic lipase and very low density lipoprotein by cultured rat hepatocytes

Primary cultures of rat hepatocytes were used to study the release of hepatic lipase and very low density lipoprotein (VLDL). The presence of hepatic lipase activity was proved by salt-resistance, affinity chromatography and inactivation by a hepatic lipase antibody. Cellular rate of hepatic lipase release increased by prolonged time in culture, whereas VLDL secretion decreased. Oleic acid and dextran-70 had no effect on release of hepatic lipase, whereas VLDL secretion was increased and decreased, respectively. Calcium antagonists (cobalt and verapamil), monensin and cycloheximide inhibited both the release of hepatic lipase and VLDL. Colchicine and chloroquine, which decreased VLDL secretion, had no effect on release of hepatic lipase. The present results suggest that release of hepatic lipase and secretion of VLDL are not coordinated and exhibit different sensitivity towards certain compounds altering secretory functions.

Plasma lipoprotein abnormalities associated with acquired hepatic triglyceride lipase deficiency

Two enzymes, lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL), are released into human plasma after intravenous injection of heparin. LPL is the major enzyme responsible for initiating catabolism of chylomicrons and very-low-density lipoproteins (VLDL). The physiological role of HTGL is less certain. HTGL has been postulated to be an alternate enzyme to LPL in hydrolysis of triglyceride in VLDL and to be an important enzyme for removal of phospholipid from both low-density lipoproteins (LDL) and high-density lipoproteins (HDL). In this latter role, this enzyme would convert larger, lighter lipoprotein particles to smaller denser particles. HTGL deficiency has been found in severe liver disease and with a genetic deficiency of this enzyme. A unique patient is described with acquired hepatic triglyceride lipase deficiency and vitamin A intoxication. This patient developed hypercholesterolemia with an increase in both LDL and HDL. An increased proportion of lighter LDL (LDL1) and HDL (HDL2) was noted. In addition, after administration of heparin there was no shift in the distribution of apoE in plasma fractionated using a column containing 4% agarose. These findings are consistent with a postulated role of HTGL in metabolism of light LDL and HDL particles and some classes of apoE containing lipoproteins.

Effect of heparin-induced lipolysis on the distribution of apolipoprotein e among lipoprotein subclasses. Studies with patients deficient in hepatic triglyceride lipase and lipoprotein lipase

In normal subjects, apolipoprotein E (apo E) is present on very low density lipoproteins (VLDL) (fraction I) and on particles of a size intermediate between VLDL and low density lipoproteins (LDL) (fraction II). The major portion of apo E is, however, on particles smaller than LDL but larger than the average high density lipoproteins (HDL) (fraction III). To investigate the possible role of the vascular lipases in determining this distribution of apo E among the plasma lipoproteins, we studied subjects with primary deficiency of either hepatic lipase or of lipoprotein lipase and compared them with normal subjects. Subjects with familial hepatic triglyceride lipase deficiency (n = 2) differ markedly from normal in that fraction II is the dominant apo E-containing group of lipoproteins. When lipolysis of VLDL was enhanced in these subjects upon release of lipoprotein lipase by intravenous heparin, a shift of the apo E from VLDL into fractions II and III was observed. In contrast, apolipoproteins CII and CIII (apo CII and CIII, respectively) did not accumulate in intermediate-sized particles but were shifted markedly from triglyceride rich lipoproteins to HDL after treatment with heparin. In subjects with primary lipoprotein lipase deficiency (n = 4), apo E was confined to fractions I and III. Release of hepatic triglyceride lipase by heparin injection in these subjects produced a shift of apo E from fraction I to III with no significant increase in fraction II. This movement of apo E from large VLDL and chylomicron-sized particles occurred with little hydrolysis of triglyceride and no significant shift of apo CII or CIII into HDL from triglyceride rich lipoproteins. When both lipoprotein lipase and hepatic triglyceride lipase were released by intravenous heparin injection into normal subjects (n = 3), fraction I declined and the apo E content of fraction III increased by an equivalent amount. Either moderate or no change was noted in the intermediate sized particles (fraction II). These data strongly support the hypothesis that fraction II is the product of the action of lipoprotein lipase upon triglyceride rich lipoproteins and is highly dependent on hepatic triglyceride lipase for its further catabolism. In addition, the hydrolysis by hepatic triglyceride lipase of triglyceride rich lipoproteins in general results in a preferential loss of apo E and its transfer to a specific group of large HDL.

Role of lipoprotein-X in the pathogenesis of cholestatic hypercholesterolemia. Uptake of lipoprotein-X and its effect on 3-hydroxy-3-methylglutaryl coenzyme A reductase and chylomicron remnant removal in human fibroblasts, lymphocytes, and in the rat

Cholestasis is accompanied by the appearance of lipoprotein-X (LP-X) in plasma. This lipoprotein has a high content of unesterified cholesterol and phospholipids and appears to be ineffective in suppressing the enhanced hepatic cholesterogenesis of cholestasis. Its role as a possible causative factor for cholestatic hypercholesterolemia was investigated. When 125I-LP-X was injected into rats, it disappeared rapidly from the circulation. Calculated on the basis of gram wet weight, spleen took up more LP-X than liver. Prior ligation of the bile duct reduced the uptake in spleen. Experiments with isolated perfused rat liver showed that nonparenchymal cells (NPC) took up over eightfold more 125I-LP-X than hepatic parenchymal cells (PC). Incubation of PC, NPC, human lymphocyte suspensions, or fibroblast cultures with LP-X showed that NPC bound more LP-X than PC or fibroblasts. Lymphocytes took up 20-fold more LP-X than PC and the activity of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase was depressed by LP-X. Lymphocytes isolated from cholestatic patients showed low activity of this enzyme. The activity was increased by LP-X in isolated perfused livers, but suppressed in isolated microsomes. LP-X competitively inhibited the uptake of chylomicron remnants in isolated perfused livers and hepatocytes. In contrast, degradation of LDL by perfused livers, which were isolated from ethinyl estradiol-treated rats or human fibroblast cultures, remained unchanged in the presence of LP-X. The results indicate that cholesterol transported by LP-X is mainly taken up by the cells of the reticuloendothelial system. It increases the activity of hepatic HMG-CoA reductase and suppresses remnant uptake, thus emphasizing a major role of LP-X in cholestatic hypercholesterolemia.

Interrelations between lipoprotein and the elimination of exogenous triglycerides from the circulation in intensive care patients

The interrelations between the fractional turnover rate (k2) of exogenous triglycerides from the circulation and the serum lipoproteins have been studied in 34 intensive care patients who were classified into two groups depending on the severity of the clinical condition. Group I included 13 patients in relatively good clinical condition after elective surgery and Group II consisted of 21 critically ill patients. The k2 values were increased in Group I while Group II patients had K2 values similar to healthy male controls. Low concentrations of total serum TG, VLDL-TG and total serum cholesterol were found in Group I and LDL-TG was raised more than threefold and HDL cholesterol decreased by over 50 percent in Group II. In both groups the cholesterol/TG ratio in VLDL was higher than that of the controls. The negative correlations between K2, total serum TG and VLDL-TG in controls were also found in Group I. In contrast to the control group a positive correlation between K2 and the cholesterol/TG ratio in VLDL was found in Group I, whereas the only correlations found in Group II were between K2 and the concentration of both total serum cholesterol and LDL cholesterol. There was no correlation with HDL lipids in any of the groups. Qualitative changes in the lipoprotein composition and altered characteristics in the tissues which remove Intralipid particles from the circulation may be responsible for many of the changes observed.

Effects of ethinyl-estradiol/noretisterone combinations on serum lipoproteins

Eleven healthy young women (age range 20-28 years) were given three different oral contraceptives (OCs) in random order, each contraceptive for 3 months. Smoking, eating, drinking and habits of physical activity were similar throughout the study period. The combinations were: ethinyl-estradiol/noretisterone (EE/NET) 35 micrograms/0.5 mg, 35 micrograms/1 mg and 50 micrograms/1 mg. The 35/0.5 and the 50/1 EE/NET combinations led to significant weight increases of 2.4 and 1.7 kg, respectively. All EE/NET combinations produced LDL-TG increases, from a pretreatment value of 0.28 +/- 0.04 (SD) mmol/l to 0.34 +/- 0.07, 0.35 +/- 0.06 and 0.42 +/- 0.13 mmol/l (P less than 0.01 for all). LDL-cholesterol increased from 2.99 +/- 0.63 mmol/l to 3.35 +/- 0.62 (P less than 0.01) after 35/1 treatment and to 3.43 +/- 0.62 mmol/l (P less than 0.001) after 50/1 treatment. These two EE/NET combinations also caused significant reductions of HDL-cholesterol, in both cases from a pretreatment value of 1.75 +/- 0.16 mmol/l to 1.64 +/- 0.24 mmol/l (P less than 0.05). Since all values after EE/NET treatment remained well within normal ranges, these low-dose OCs probably have little effect on the development of atherosclerosis due to serum lipoprotein abnormalities. However, our findings suggest that OCs may interfere with the cholesterol ester/TG exchange between LDL and HDL.

Lipoprotein metabolism during acute inhibition of hepatic triglyceride lipase in the cynomolgus monkey

The role of the enzyme hepatic triglyceride lipase was investigated in a primate model, the cynomolgus monkey. Antisera produced against human postheparin hepatic lipase fully inhibited cynomolgus monkey posttheparin plasma hepatic triglyceride lipase activity. Lipoprotein lipase activity was not inhibited by this antisera. Hepatic triglyceride lipase activity in liver biopsies was decreased by 65-90% after intravenous infusion of this antisera into the cynomolgus monkey. After a 3-h infusion of the antisera, analytic ultracentrifugation revealed an increase in mass of very low density lipoproteins (S(f) 20-400). Very low density lipoprotein triglyceride isolated by isopycnic ultracentrifugation increased by 60-300%. Analytic ultracentrifugation revealed an increase in mass of lipoproteins with flotation greater than S(f) 9 (n = 4). The total mass of intermediate density lipoproteins (S(f) 12-20) approximately doubled during the 3 h of in vivo enzyme inhibition. While more rapidly floating low density lipoproteins (S(f) 9-12) increased, the total mass of low density lipoproteins decreased after infusion of the antibodies. The changes in high density lipoproteins did not differ from those in control experiments. In order to determine whether the increases of plasma concentrations of very low density lipoproteins were due to an increase in the rate of synthesis or a decrease in the rate of clearance of these particles, the metabolism of radiolabeled homologous very low density lipoproteins was studied during intravenous infusion of immunoglobulin G prepared from the antisera against hepatic triglyceride lipase (n = 3) or preimmune goat sera (n = 3). Studies performed in the same animals during saline infusion were used as controls for each immunoglobulin infusion. There was a twofold increase in the apparent half-life of the very low density lipoprotein apolipoprotein-B tracer in animals receiving the antibody, consistent with a decreased catabolism of very low density lipoproteins. Concomitantly, the rise in low density lipoprotein apoprotein-B specific activity was markedly delayed. None of these changes were observed during infusion of preimmune immunoglobulin G.Hepatic triglyceride lipase participates with lipoprotein lipase in the hydrolysis of the lipid in very low density lipoproteins, intermediate density lipoproteins, and the larger low density lipoproteins (S(f) 9-12). Thus, hepatic triglyceride lipase appears to function in a parallel role with lipoprotein lipase in the conversion of very low density and intermediate density lipoproteins to low density lipoproteins (S(f) 0-9).

Determination of apolipoprotein A-I by kinetic nephelometry

Apolipoprotein A-I concentration in human serum was determined by kinetic nephelometry. Under optimal reaction conditions and within the normal physiological range the relation between apolipoprotein A-I concentration and measured rate units it approximately linear. The detection limit of the assay lies at 2 micrograms/ml. The coefficient of variation within one series is 1.44%. The correlation coefficient with alpha-cholesterol, as determined by agarose electrophoresis followed by polyanion precipitation, is better than 0.94. Addition of detergent to serum dilutions increases the reaction rate, suggesting that delipidation changes the antigenic expression of apolipoprotein A-I. The magnitude of this change is constant in normal controls, but not in special pathological cases. The described technique can be recommended for routine use in clinical chemistry for measurement of apolipoprotein A-I.

Inhibition of hepatic chylomicron remnant uptake in the cholestatic rat

[3H]retinal- or [3h]cholesterol- and [14C]fatty acid-labeled chylomicrons and chylomicron remnants were injected intravenously into normal rats and rats subjected to partial or total obstruction of the bile duct 8 or 48 h earlier. The clearance from plasma of the [3H]retinyl and the [3H]cholesteryl esters in 30-120 min was markedly decreased in rats with total obstruction, and the uptake of 3H by the liver was significantly less than in control rats. The elimination of the [14C]triacylglycerol of the native chyle lipoprotein was not significantly affected, and the delayed plasma clearance was seen also when the [3H]lipid ester radioactivity was injected as chylomicron remnants prepared in vitro. If only one of the two main bile duct branches was ligated, the uptake of radioactivity did not differ markedly in the obstructed and unobstructed part of the liver and only small effects on the plasma disappearance were seen. The defective clearance of the chylomicron remnants was thus not related to the obstructed bile flow per se but rather to the consequences of the total obstruction, such as the high plasma bile acid level or the accumulation of abnormal lipoproteins in plasma.

Lipoprotein-X

Lipoprotein-X is an abnormal lipoprotein that appears in the sera of patients with obstructive jaundice, and thus is a sensitive indicator of cholestasis. In patients with familial plasma lecithin, Cholesterol acyltransferase (LCAT) deficiency, there is an inverse relationship between plasma Lp-X levels and LCAT activity. Ultracentrifugation procedures utilized for isolation of Lp-X have shown that it is associated with the low density lipoprotein fraction. Lp-X can be visualized by electrophoresis on either Agar or Agarose. The purity of Lp-X preparations has been documented by immunochemical procedures. The availability of highly purified antisera to Lp-X has served as a basis of one of the assay procedures for this lipoprotein. It's chemical composition has been established. Phospholipids and unesterified cholesterol constitute the bulk of the Lp-X molecule. Electron microscopic studies have demonstrated that Lp-X is a spherical particle which has strong aggregating properties. Membrane bound enzymes have been shown to aggregate with Lp-X. The fact that bile lipoprotein can be converted to Lp-X by the addition of albumin and that Lp-X can be converted to bile lipoprotein by the addition of bile salts offers a possible explanation for the origins of Lp-X. Phospholipases of plasma might play a role in the catabolism of Lp-X. The value and limitations of Lp-X determinations will also be addressed in this review.

Plasma estrogens and hepatic lipase in postheparin plasma with special reference to liver disease

Hepatic lipase and lipoprotein lipase activity in postheparin plasma, plasma total estrogens (estradiol and estrone) and triglycerides were studied in patients with various liver disorders and in a reference group. The activity of hepatic lipase was not correlated to the estrogen level either in patients or in healthy controls. Peroral administration of estradiol valeriate to healthy females resulted, however, in a selective decline in hepatic lipase activity. A slight and not significant reduction was also observed in three infertile women after administration of follitropin (FSH) for a short period. The plasma concentration of estrogens did not correlate with the levels of plasma triglycerides and the relative content of triglycerides in low density lipoproteins either in patients or the controls. Lipase inhibition mediated by increase in estrogens therefore does not seem to exaplin the hypertriglyceridemia observed in patients with liver disease.

A bile-acid-rich high-density lipoprotein (HDL) in acute hepatitis

Severe liver dysfunction is often associated with alterations of plasma lipids and lipoproteins. In this study the high-density lipoprotein (HDL) class has been further investigated. HDL from patients with acute, cholestatic hepatitis (n = 10) was isolated and compared with that of normals. Lipid and protein analyses were performed during the acute stage of the disease, with consequent follow-up studies. It was found that (1) only apo A-I was decreased by 50% in the isolated HDL fractions, whereas apo A-II remained unchanged; apo A-I in total plasma was normal; (2) immunoelectrophoresis of hepatitis HDL against monospecific anti-A-II revealed one precipitin line but two or more bands against anti-A-I; (3) concomitant with an increase of phospholipids and a decrease of triglycerides and the total cholesterol fraction, hepatitis HDL contained 10--12 times more bile acid than normal HDL. Chenodeoxycholic acid was the predominant bile acid. These alterations were fully reversible when patients recovered. These parameters seem to be sensitive markers for the degree of disturbance and restoration of liver function. The structural-functional implications of the observed compositional changes of HDL during cholestasis are discussed.

Pathophysiology of lipoprotein transport

A system for classification of genetic and acquired forms of hyperlipidemia in humans based on lipoprotein physiology is described. Most hyperlipidemia can be accounted for by defects in one of four sites of physiologic regulation: (1) triglyceride-rich lipoprotein production, (2) lipoprotein lipase-mediated triglyceride catabolism, (3) remnant lipoprotein catabolism, and (4) extrahepatic cholesterol-rich lipoprotein catabolism.

Serum total lipids, lipoprotein cholesterol, and apolipoprotein A in acute viral hepatitis and chronic liver disease

Serum total lipids, lipoprotein cholesterol, apolipoprotein A (Apo A), and liver function tests have been investigated in patients with acute viral hepatitis and chronic liver disease. Hypertriglyceridaemia, absence of alpha and pre beta bands on the lipoprotein electrophoresis pattern, low level of Apo A, and presence of abnormal lipoproteins (beta-VLDL and beta2-LP) were observed in the early phase of acute hepatitis. A positive correlation was found between Apo A and high-density lipoprotein cholesterol, and a negative one between Apo A and triglyceride, bile acids, total bilirubin, and serum alanine aminotransferase. Lipoprotein abnormalities found in the early phase of acute hepatitis are probably due to low lecithin-cholesterol acyltransferase activity. The reappearance of alpha lipoprotein and the increase of Apo A are sensitive indices of improvement of liver function. In chronic liver disease low levels of cholesterol and Apo A indicate the severity of liver cell injury.

Triglyceride lipase activity in postheparin plasma and plasma lipoproteins in liver disease

Hepatic lipase activity and lipoprotein lipase activity were studied in postheparin plasma from 14 patients with various liver disorders. Plasma lecithin: cholesterol acyltransferase (LCAT) activity and lipoprotein composition and structure were also estimated. Five patients had lower hepatic lipase activity than the lowest control value, and in three of these no hepatic lipase activity was detected. Lipoprotein lipase was low in 5 patients, but in only one of them was hepatic lipase activity also low. Hepatic lipase was not significantly correlated to the concentration of plasma triglycerides, either in controls or in patients, whereas lipoprotein lipase was negatively correlated with plasma triglycerides both in controls and patients. Lipoprotein lipase and LCAT activity, but not hepatic lipase, was negatively correlated to the triglyceride content of the low density lipoproteins (density 1.019-1.063 g/ml) from the patients. No specific lipid or lipoprotein pattern was found in plasma from the patients with a low or without any hepatic lipase activity. The results suggest an important role of lipoprotein lipase and LCAT, for the increased content of triglycerides in the low density lipoproteins in patients with liver disease. The role of hepatic lipase remains unclear.

Influence of bile acids and free fatty acids on physicochemical properties of LP-X

In this study it is demonstrated, that incubation of both, bile acids and free fatty acids with LP-X, the abnormal plasmalipoprotein found in patients suffering from cholestasis or LCAT-deficiency, results in striking alterations of the physico-chemical and immunological properties of LP-X: 1. The cathodic mobility in agar is changed into an anodic mairation of the material. 2. The unique appearance of LP-X on electronmicrographs is altered by the incubation revealing fingerprint like structures. 3. The albumin portion of LP-X becomes immunologically detectable. 4. Bile salts cause marked changes in the hydrated density of the material as determined by zonal ultracentrifugation. 5. In vitro incubation of LP-X with postheparin plasma causes a complete disappearance of LP-X as judged by its typical migration on agar electrophoresis. All these alterations can be prevented or reversed by the addition of albumin in appropriate concentrations. These findinga are important in the light of studies designed to investigate the catabolic action of plasma lipolytic enzymes on LP-X, as well as for follow up studies of LP-X concentrations during the course of disease.

Plasma lipids and lipoproteins in liver disease

There are many changes in the plasma, lipids, and lipoproteins in patients with liver disease. They have proved difficult to study but our understanding of these changes has increased greatly during recent years. In obstructive jaundice hyperlipidaemia is a fairly constant finding and this appears to be due to the regurgitation of phospholipid from the obstructed biliary tree. The plasma lipids tend to fall with parenchymal liver disease. The composition of the lipoproteins depends on the activity of the plasma enzyme lecithin: cholesterol acyl transferase. When LCAT activity is high the individual lipoprotein fractions are normal. When it is reduced all of the lipoprotein fractions are affected but the pattern found with obstruction is quite different from that found with parenchymal disease. The changes in plasma lipoproteins appear to be associated with change in the lipid composition of cellular membranes and this may have important functional implications.

Hepatic lipase and lipoprotein lipase in postheparin plasma in liver disease. relations to plasma proteins

Hepatic lipase (HL) and lipoprotein lipase (LPL) in postheparin plasma have been studied in patients with different liver disorders and in a reference group. The dose of heparin (100 I.U./kg body weight) used intravenously to get maximal release of both HL and LPL was the same in patients and in healthy individuals. The release of HL was maximal in healthy controls after 2-5 min, but in patients with liver disease the maximum was not reached until 15 min after heparin administration. The time course of the release of LPL showed the same pattern in patients and controls. The activity of HL was below the lowest observation in the reference group in 8 out of 20 patients with liver diseases, and was not measurable in 3 of them (2 with chronic active hepatitis and 1 with alcoholic cirrhosis). The activity of hepatic lipase was positively correlated with the levels of coagulation factors and with the concentration of prealbumin in the total patient material. The results indicate that low activity of hepatic lipase is a sign of liver parenchymatous injury, and out study gives indirect evidence of the hepatic origin of this enzyme in man.

Changes in rat serum lipoproteins following ligation of the bile duct

Lipoproteins in the serum of normal and of cholestatic rats have been studied by crossed immunoelectrophoresis coupled with separations by rate and isopycnic density gradient centrifugation and by gel exclusion chromatography. Normal rat serum contained distinct lipoprotein species closely analogous to human VLDL, LDL, HDL2 and HDL3. Three days after ligation of the common bile duct, there were major changes in the lipoproteins of rat serum. The amounts of VLDL, LDL and of a minor HDL component were elevated and several novel types of lipoprotein were detected. Three of these could be identified as the characteristic lipoprotein of cholestasis, LP-X, as an enlarged and modified HDL and as a lipoprotein of density 1.055 g/ml intermediate in size between LDL and VLDL. Some unusually small VLDL particles were also detected. It is concluded that the changes in rat serum lipoproteins following ligation of the common bile duct are very similar to the changes observed in cholestatic disease in human patients.

[Concentration of plasma glycosphingolipids in acute hepatitis (author's transl)]

There are mainly four neutral glycosphingolipids in human blood plasma: Monohexosyl, dihexosyl, trihexosyl and tetrahexosyl ceramide. In patients with viral hepatitis (n=21) during the acute phase all four fractions of plasma glycosphingolipids were elevated compared to healthy subjects (n=23). With the exception of trihexosyl ceramide all fractions demonstrated statistically striking elevations in the acute phase of viral hepatitis. Simultaneously in the acute phase of hepatitis triglycerides and cholesterol in serum were significantly increased. It is concluded the elevation of glycosphingolipid levels in plasma is a metabolic consequence of hyperlipoproteinemia. Furthermore it is supposed that a part of plasma glycosphingolipids is synthezised de novo by the liver like VLDL.

Fatty acid composition of adipose tissue in patients with coronary heart disease

In order to study the relationship between the fatty acid composition of adipose tissue and coronary heart disease (CHD), 34 consecutive male patients with acute myocardial infarction and 33 hospitalized men free of CHD were compared. Patients with diabetes mellitus, endocrine disorders, liver and kidney diseases, recent changes in body weight and deviations from the "normal", customary diet were exlcuded. A statistically significant difference between the two groups was observed only in stearic acid, its proportion being lower in CHD patients (3.25% vs. 4.13%). Using multivariate discriminant analysis, age discriminated best between the groups, followed by stearic acid. The signs observed were positive for the former and negative for the latter. All other acids, relative body weight, and skinfold measurements did not significantly contribute to the discrimination. Age did not correlate with the proportion of stearic acid. Blood lipids from samples taken within 24 h of admission did not significantly differ between the groups. Three months later they had risen considerably in the infarct patients. The metabolic basis of the relationship between CHD and stearic acid is not clear at present. Additional studies are necessary to substantiate the importance of this acid as an indicator of CHD.

Triglyceride lipases in acute hepatitis

Two triglyceride lipases in postheparin plasma, the lipoprotein lipase (LPL) and the hepatic triglyceride lipase (H-TGL) were separated by heparin-sepharose affinity chromatography and studied in controls and patients during the course of acute hepatitis. All three patients had increased content of triglycerides in the low density lipoproteins, and two of them had hypertriglyceridemia. Low activities of both lipases were found in the acute stage of the disease in all three patients. Concomitantly one of the patients had absolute low lecithin: cholesterol acyltransferase (LCAT) activity, and in the two other patients a relative LCAT deficiency was present. The increased content of triglycerides in LDL that may be found in liver disease, may not only be due to low H-TGL and LPL, but also LCAT deficiency.

Formation of lipoprotein-X. Its relationship to bile compounds

In this study we have demonstrated that in native bile, lipids are organized in the form of a lipoprotein (bile LP) carrying albumin as apoprotein. The lipid composition of bile LP is almost identical to lipoprotein-X (LP-X, the characteristic lipoprotein of cholestasis). However, it differs from LP-X inits protein/lipid ratio and immunological and electrophoretic characteristics. Bile lipoprotein can be converted into "LP-X-like" material in vitro by adding albumin or serum to native bile. The LP-X-like material formed in vitro has physicochemical and chemical characteristics similar or identical to LP-X isolated from serum. As bile lipoprotein can be converted into LP-X-like material by the addition of albumin to bile, LP-X can be converted into bile-LP-like particles by adding bile salts to a LP-X-positive serum. Furthermore, experimental connection of the common bile duct to the vena cava is followed after a few hours by the appearance of LP-X-like material in the plasma. These facts taken together strongly suggest that bile LP is a precursor lipoprotein for LP-X and that it refluxes into the plasma pool under cholestatic conditions.

On the metabolism of lipoprotein-X (LP-X)

The characteristic low-density lipoprotein of cholestasis (LP-X) earlier described for humans is found with identical properties in dogs and rats after experimental cholestasis. After ligation of the common bile duct, LP-X may be detected in the plasma within the first 20 hours. A period of marked increase in concentration is followed by decreasing plasma concentrations and LP-X becomes undetectable 7-10 days after ligation of the bile duct in rats. High plasma bile salt concentration may alter the structural integrity of LP-X and may in part be responsible for its disappearance after long-lasting and severe biliary obstruction. Plasma decay curves for isolated LP-X injected intravenously into healthy animals revealed a rapid early fall in concentration followed by a gradual decline. The calculated fractional catabolic rate of LP-X was found to be 0.450 +/- 0.069 for dogs and 1.553 +/- 0.096 for rats corresponding to a mean biological half life of 37.7 +/- 6.4 h or 10.7 +/- 0.6 h, respectively. In vitro LP-X degradation occurs in post-heparin plasma, however, it seems to be too early to speculate on the enzyme activity and on the mode of action responsible for this disappearance.

Plasma lipoproteins in rats with experimental biliary obstruction. I. A chemical study

Acute biliary obstruction in the rat is associated with striking alterations of the plasma level and the physico-chemical properties of plasma lipoproteins. 1. The level of very low density lipproteins (VLDL) in plasma increases from 2 to 3 fold. The chemical composition of VLDL is characterized by a high content of phospholipids and cholesterol and by a diminution of the relative content of triacylglycerols and protein. On cellulose acetate electrophoresis, VLDL show a beta-mobility. 2. The plasma concentration of low density lipoproteins (1.019--1.063 g/ml, LDL2) increases several fold above the control level. Phospholipids and unesterified cholesterol are the major components of this fraction which contains only a minute amount of cholesteryl ester (4%) and triacylglycerols (10%). LDL2 contain a component which migrates to the cathode in 1% agar gel electrophoresis. Separation of LDL2 by gel filtration on 2% agarose column results in the identification of three subfractions. Subfraction I contains a large proportion of cholesterol and triacylgylcerols, subfraction II is rich in unesterified cholesterol and phospholipids whereas subfraction III has a chemical composition fairly similar to that of the control LDL2. 3. The level of high density lipoproteins (HDL) also increases after bile duct ligation. The chemical composition of HDL2 (1.063-1.125 g/ml) is characterized by a high content of unesterified cholesterol and phospholipids and by a remarkable reduction in the content of cholesteryl esters and protein.

On hepatic and extrahepatic postheparin serum lipase activities and the influence of experimental hypercortisolism and diabetes on these activities

This paper shows that the palmitoyl-CoA hydrolase activity of postheparin serum of the rat is mainly derived from the liver. The identity of this activity with the heparin-releasable hepatic triacylglycerol hydrolase activity is established. The consequences of the different substrate specificities of the hepatic and extrahepatic enzymes for the measurement of the overall postheparin serum lipase activity are discussed. Treatment of the rats with either a corticosteroid or with streptozotocin was found to lower the lipolytic activity from the liver and to enhance the extrahepatic activity. Also in human postheparin serum, palmitoyl-CoA hydrolase activity is shown to behave identical with hepatic triacylglycerol hydrolase activity. The possible function of the liver in the serum triacylglycerol metabolism is discussed in connection with the proposed mechanism for the role of extrahepatic lipoprotein lipase in atherogenesis.