Ex vivo gene therapy of familial hypercholesterolemia.

Familial hypercholesterolemia (FH) is an autosomal dominant disorder caused by a deficiency in the receptor that clears low density lipoprotein (LDL) from the serum (reviewed in Ref. 1 and 2). Patients with one abnormal LDL receptor allele have moderate elevations in plasma LDL and suffer premature coronary artery disease (CAD). Approximately 5% of all patients under 45 who have had a myocardial infarction carry this trait. Patients with two abnormal LDL receptor genes (homozygous deficient patients) have severe hypercholesterolemia and life-threatening coronary artery disease in childhood. Strategies for treating patients with FH are directed at lowering the plasma level of LDL. In heterozygotes, this is accomplished through the administration of drugs that stimulate the expression of LDL receptor from the normal allele (2). This therapeutic approach is not effective in the treatment of homozygous deficient patients, especially those that retain less than 2% of residual LDL receptor activity. Partial amelioration of hyperlipidemia has been achieved in some homozygous deficient patients by diverting the portal circulation through a portacaval anastomosis (3) and by chronic plasmapheresis therapy (4). A more direct approach has been to correct the deficiency of hepatic LDL receptor by transplanting a liver that expresses normal levels of LDL receptor. Three patients that survived this procedure normalized their serum LDL-cholesterol (5-9). We have used an authentic animal model for FH, the Watanabe Heritable Hyperlipidemic rabbit (WHHL), to develop gene therapies for the homozygous form of FH (10-13). The WHHL rabbit has a mutation in its LDL receptor gene which renders the receptor completely dysfunctional (12) leading to severe hypercholesterolemia, diffuse atherosclerosis, and premature death. The potential efficacy of gene therapy for FH is supported by a series of studies we have performed in the WHHL rabbit in which we have achieved metabolic improvement (14-18). Liver tissue was removed from WHHL rabbits and used to isolate hepatocytes and establish primary cultures. A functional rabbit LDL receptor gene was transduced into a high proportion of hepatocytes using recombinant retroviruses, and the genetically corrected cells were transplanted into the animal from which they were derived. Transplantation of the genetically corrected, autologous hepatocytes was associated with a 30-40% decrease in serum cholesterol that persisted for the duration of the experiment (4 months, Ref. 18). Recombinant derived LDL receptor RNA was detected in liver for at least 6 months. There was no apparent immunological response to the recombinant derived LDL receptor.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dietary fish oil stimulates hepatic low density lipoprotein transport in the rat.

These studies were undertaken to examine the effect of fish oil, safflower oil, and hydrogenated coconut oil on the major processes that determine the concentration of low density lipoprotein (LDL) in plasma, i.e., the rate of LDL production and the rates of receptor-dependent and receptor-independent LDL uptake in the various organs of the body. When fed at the 20% level, fish oil reduced plasma LDL-cholesterol levels by 38% primarily by increasing LDL receptor activity in the liver. Dietary safflower oil also increased hepatic LDL receptor activity; however, since the rate of LDL production also increased, plasma LDL-cholesterol levels remained essentially unchanged. Hydrogenated coconut oil had no effect on LDL receptor activity but increased the rate of LDL-cholesterol production causing plasma LDL-cholesterol levels to increase 46%. Dietary fish oil had no effect on the receptor-dependent transport of asialofetuin by the liver, suggesting that the effect of fish oil on hepatic LDL receptor activity was specific and not due to a generalized alteration in the physical properties of hepatic membranes. Finally, dietary fish oil increased hepatic cholesteryl ester levels and suppressed hepatic cholesterol synthesis rates, suggesting that the up-regulation of hepatic LDL receptor activity in these animals was not simply a response to diminished cholesterol availability in the liver.     

Dietary fatty acids regulate hepatic low density lipoprotein (LDL) transport by altering LDL receptor protein and mRNA levels.

The concentration of LDL in plasma is strongly influenced by the amount and the type of lipid in the diet. Recent studies in the hamster have shown that dietary fatty acids differentially affect circulating LDL levels primarily by altering receptor-dependent LDL uptake in the liver. To investigate the mechanistic basis of this effect, rates of receptor-dependent LDL transport in the liver were correlated with LDL receptor protein and mRNA levels in hamsters fed safflower oil or coconut oil and varying amounts of cholesterol. Hepatic LDL receptor activity was significantly lower in animals fed coconut oil than in animals fed safflower oil at all levels of cholesterol intake (26, 53, and 61% lower at cholesterol intakes of 0, 0.06, and 0.12%, respectively). These fatty acid-induced changes in hepatic LDL receptor activity were accompanied by parallel changes in hepatic LDL receptor protein and mRNA levels, suggesting that dietary fatty acids regulate the LDL receptor pathway largely at the mRNA level.     

Low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase gene expression in human mononuclear leukocytes is regulated coordinately and parallels gene expression in human liver.

The liver plays a key regulatory role in cholesterol metabolism. Two proteins are central in this role; the LDL receptor and 3-hydroxy-3-methylglutaryl CoA reductase (HMG CoA reductase), the rate-limiting enzyme in cholesterol biosynthesis. In the current investigation, we have used a sensitive nonradioactive method to study the regulation of LDL receptor and HMG CoA reductase mRNA levels in liver biopsy samples and freshly isolated mononuclear leukocytes from 13 patients who underwent cholecystectomy for gallstones. mRNA copy numbers were determined by PCR amplification of reverse-transcribed RNA using synthetic RNA as an internal standard. Incorporation of digoxigenin-11-dUTP during amplification allowed direct detection and quantitation of mRNA levels by chemiluminescence. These experiments showed that the average number of LDL receptor mRNA molecules in liver (21 +/- 3 x 10(4)/micrograms of RNA) and mononuclear leukocytes (24 +/- 3 x 10(4)/micrograms of RNA) are indistinguishable, whereas the number of HMG CoA reductase molecules in liver (107 +/- 15 x 10(4)/micrograms of RNA) is smaller than that in mononuclear leukocytes (158 +/- 21 x 10(4)/micrograms of RNA, P < 0.05). These numbers correspond to an average of 1-6 copies of LDL receptor mRNA and 5-42 copies of HMG CoA reductase mRNA per cell. There was a significant correlation between the numbers of LDL receptor (P = 0.0005) and HMG CoA reductase (P = 0.003) mRNA molecules in liver and mononuclear leukocytes. Furthermore, the numbers of copies of HMG CoA reductase and LDL receptor mRNA were correlated with each other in both liver (P = 0.02) and mononuclear leukocytes (P = 0.01), consistent with coordinate regulation. These data demonstrate that the mechanisms which regulate mRNA levels in liver and mononuclear cells are similar and suggest that freshly isolated mononuclear cells can be used to predict HMG CoA reductase and LDL receptor mRNA levels in liver.     

Unexpected inhibition of cholesterol 7 alpha-hydroxylase by cholesterol in New Zealand white and Watanabe heritable hyperlipidemic rabbits.

We investigated the effect of cholesterol feeding on plasma cholesterol concentrations, hepatic activities and mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and hepatic LDL receptor function and mRNA levels in 23 New Zealand White (NZW) and 17 Watanabe heritable hyperlipidemic (WHHL) rabbits. Plasma cholesterol concentrations were 9.9 times greater in WHHL than NZW rabbits and rose significantly in both groups when cholesterol was fed. Baseline liver cholesterol levels were 50% higher but rose only 26% in WHHL as compared with 3.6-fold increase with the cholesterol diet in NZW rabbits. In both rabbit groups, hepatic total HMG-CoA reductase activity was similar and declined > 60% without changing enzyme mRNA levels after cholesterol was fed. In NZW rabbits, cholesterol feeding inhibited LDL receptor function but not mRNA levels. As expected, receptor-mediated LDL binding was reduced in WHHL rabbits. Hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels were 2.8 and 10.4 times greater in NZW than WHHL rabbits. Unexpectedly, cholesterol 7 alpha-hydroxylase activity was reduced 53% and mRNA levels were reduced 79% in NZW rabbits with 2% cholesterol feeding. These results demonstrate that WHHL as compared with NZW rabbits have markedly elevated plasma and higher liver cholesterol concentrations, less hepatic LDL receptor function, and very low hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels. Feeding cholesterol to NZW rabbits increased plasma and hepatic concentrations greatly, inhibited LDL receptor-mediated binding, and unexpectedly suppressed cholesterol 7 alpha-hydroxylase activity and mRNA to minimum levels similar to WHHL rabbits. Dietary cholesterol accumulates in the plasma of NZW rabbits, and WHHL rabbits are hypercholesterolemic because reduced LDL receptor function is combined with decreased catabolism of cholesterol to bile acids.     

Characterization of hepatic low density lipoprotein binding and cholesterol metabolism in normal and homozygous familial hypercholesterolemic subjects.

Patients with familial hypercholesterolemia have elevated levels of plasma low density lipoproteins (LDL), increased hepatic synthesis of apolipoprotein B-containing lipoproteins, defective binding of low density lipoproteins to fibroblasts, and premature atherosclerosis. The role of a hepatic low density lipoprotein receptor in normal man and its importance in the pathogenesis of familial hypercholesterolemia have not been previously determined. In the present study, direct comparison was made of the binding of LDL to hepatic membranes from normal and receptor-negative homozygous familial hypercholesterolemic subjects. The effects of calcium, EDTA, and temperature on the binding of lipoproteins to the hepatic membranes were also evaluated. At 4 degrees C, no significant difference in specific binding of LDL to hepatic membranes from normal and familial hypercholesterolemic subjects was observed. At 37 degrees C, both total and specific binding of LDL were significantly reduced in patients with familial hypercholesterolemia. Hepatic membrane binding of LDL from the two patients homozygous for receptor-negative familial hypercholesterolemia was 53 and 59% of normal. The activity of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase was normal; however, the total hepatic cholesterol and cholesteryl ester content was significantly increased from 53 to 129%. These results indicate that patients with familial hypercholesterolemia have a defect in the interaction of hepatic membranes with low density lipoproteins. This defect may lead to accelerated atherosclerosis by decreasing the cellular catabolism of LDL and enhancing the production of LDL, which is characteristic of patients homozygous for familial hypercholesterolemia.     

Familial dysbetalipoproteinemia. Abnormal binding of mutant apoprotein E to low density lipoprotein receptors of human fibroblasts and membranes from liver and adrenal of rats, rabbits, and cows.

Patients with familial dysbetalipoproteinemia (F. Dys.), also called familial type 3 hyperlipoproteinemia, are homozygous for a mutant allele, Ed, that specifies an abnormal form of apoprotein (apo) E, a prominent constituent of remnant lipoproteins derived from very low density lipoproteins (VLDL) and chylomicrons. Apo E is thought to mediate the removal of remnant lipoproteins from the plasma by virtue of its ability to bind to hepatic lipoprotein receptors. In F. Dys. patients, remnant-like lipoproteins accumulate, apparently because of delayed clearance by the liver. In the current studies, we show that the abnormal protein specified by the Ed allele (apo E-D) from some, but not all, patients with F. Dys. has a markedly deficient ability to bind to low density lipoprotein (LDL) receptors. Apo E was isolated from eight control subjects and nine patients with F. Dys. and incorporated into phospholipid complexes. The complexes were tested for their ability to compete with human 125I-LDL or rabbit 125I-beta-VLDL fo binding to LDL receptors in four assay systems: cultured human fibroblasts, solubilized receptors from bovine adrenal cortex, liver membranes from rats treated with 17 alpha-ethinyl estradiol, and liver membranes from normal rabbits. The apo E-D from six of the nine patients with F. Dys. showed binding affinities for LDL receptors that were reduced by greater than 98% in all receptor assays (group 1 patients). All of these group 1 patients were unequivocally of phenotype apo E-D/D by the criterion of isoelectric focussing. The apo E from the three other F. Dys. patients showed a near normal binding ability in all four of the receptor assays (group 2 patients). One of these group 2 patients appeared to have the apo E-D/D phenotype by isoelectric focussing. In the other two patients in group 2, apo E-D was the predominant protein (phenotype, apo E-D/D), but traces of protein in the region corresponding to normal apo E (apo E-N) were also present. The difference between group 1 and group 2 patients was also apparent when the apo E was iodinated and tested directly for binding to liver membranes from rats treated with 17 alpha-ethinyl estradiol. The 125I-labeled apo E from a group 2 patient, but not a group 1 patient, showed enhanced uptake when perfused through the liver of an estradiol-treated rate, indicating that the receptor binding ability of apo E correlated with uptake in the intact liver. The current studies allow the subdivision of patients with F. Dys. into two groups. In group 1, the elevated plasma level of remnants appears to be due to a diminished receptor binding activity of the abnormal protein specified by the Ed allele; in group 2 patients, the cause of the elevated plasma level of remnants remains to be explained.     

Regulation of rat hepatic low density lipoprotein receptors. In vivo stimulation by growth hormone is not mediated by insulin-like growth factor I.

Growth hormone (GH) has an important role in the regulation of hepatic LDL receptor expression and plasma lipoprotein levels. This investigation was undertaken to evaluate if these effects of GH on hepatic LDL receptors are direct or mediated by insulin-like growth factor I (IGF-I). Two models were studied in which substitution with GH is important for the regulation of hepatic LDL receptors: hypophysectomized rats receiving high-dose ethynylestradiol or challenge with dietary cholesterol. The hypophysectomized rats were hormonally substituted by infusion with dexamethasone and L-thyroxine, and either GH or IGF-I. In both models, GH was essential for maintaining normal expression of LDL receptors. In contrast, despite fully normalized plasma levels, IGF-I did not support the expression of hepatic LDL receptors. Analysis of plasma lipoproteins revealed that substitution with GH, but not with IGF-I, reduced LDL and intermediate density lipoproteins. In addition, determination of hepatic mRNA levels for apo B-100 and apo B-48 indicated that GH may be more effective than IGF-I in the promotion of apo B mRNA editing. In conclusion, GH has specific effects on hepatic LDL receptor expression and plasma lipoprotein levels that are not mediated by IGF-I.     

Molecular analysis of the helper T cell response in murine interstitial nephritis. T cells recognizing an immunodominant epitope use multiple T cell receptor V beta genes with similarities across CDR3.

Soluble fiber consistently lowers plasma total and low density lipoprotein (LDL)-cholesterol concentrations in humans and various animal models including the hamster; however, the mechanism of this effect remains incompletely defined. We performed studies to determine the activity of dietary psyllium on hepatic 7 alpha-hydroxylase, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and LDL receptor expression in the hamster. In animals fed a cholesterol-free semisynthetic diet containing 7.5% cellulose (avicel) as a fiber source, substitution of psyllium for avicel increased hepatic 7 alpha-hydroxylase activity and mRNA levels by 3-4-fold. Comparable effects on 7 alpha-hydroxylase expression were observed with 1% cholestyramine. Psyllium also increased hepatic 7 alpha-hydroxylase activity and mRNA in animals fed a diet enriched with cholesterol and triglyceride. Activation of 7 alpha-hydroxylase was associated with an increase in hepatic cholesterol synthesis that was apparently not fully compensatory since the cholesterol content of the liver declined. Although dietary psyllium did not increase hepatic LDL receptor expression in animals fed the cholesterol-free, very-low-fat diet, it did increase (or at least restore) receptor expression that had been downregulated by dietary cholesterol and triglyceride. Thus, 7.5% dietary psyllium produced effects on hepatic 7 alpha-hydroxylase and LDL metabolism that were similar to those of 1% cholestyramine. Induction of hepatic 7 alpha-hydroxylase activity by dietary psyllium may account, in large part, for the hypocholesterolemic effect of this soluble fiber.     

Effect of an antiandrogenic H2 receptor antagonist on hepatic regeneration in rats

Because biochemical "feminization" of the liver in males is observed with hepatic regeneration and because the hepatic regenerative response in females is greater than that in males, the possibility that antiandrogens might potentiate liver regeneration was investigated. Before 70% hepatectomy, adult male Wistar rats were treated with cimetidine, an antiandrogenic H2 antagonist, at doses up to 10 times greater than those used clinically. Control animals received either the saline vehicle or ranitidine, an H2 antagonist without antiandrogenic properties. Treatment with cimetidine reduced the hepatic cytosolic androgen receptor content compared with ranitidine treatment. Hepatectomy caused a further reduction in androgen receptor activity in all groups. Hepatic cytosolic estrogen receptor activity was comparable in all groups throughout the study. Moreover, the rate of liver growth and the levels of ornithine decarboxylase and thymidine kinase activity induced as part of the regenerative response were similar in all groups. Thus, cimetidine, despite its ability to bind to androgen receptors, and ranitidine, an H2 receptor antagonist without antiandrogen action, do not modulate the hepatic regenerative response to a 70% partial hepatectomy.     

Hepatic sortilin regulates both apolipoprotein B secretion and LDL catabolism

Genome-wide association studies (GWAS) have identified a genetic variant at a locus on chromosome 1p13 that is associated with reduced risk of myocardial infarction, reduced plasma levels of LDL cholesterol (LDL-C), and markedly increased expression of the gene sortilin-1 (SORT1) in liver. Sortilin is a lysosomal sorting protein that binds ligands both in the Golgi apparatus and at the plasma membrane and traffics them to the lysosome. We previously reported that increased hepatic sortilin expression in mice reduced plasma LDL-C levels. Here we show that increased hepatic sortilin not only reduced hepatic apolipoprotein B (APOB) secretion, but also increased LDL catabolism, and that both effects were dependent on intact lysosomal targeting. Loss-of-function studies demonstrated that sortilin serves as a bona fide receptor for LDL in vivo in mice. Our data are consistent with a model in which increased hepatic sortilin binds intracellular APOB-containing particles in the Golgi apparatus as well as extracellular LDL at the plasma membrane and traffics them to the lysosome for degradation. We thus provide functional evidence that genetically increased hepatic sortilin expression both reduces hepatic APOB secretion and increases LDL catabolism, providing dual mechanisms for the very strong association between increased hepatic sortilin expression and reduced plasma LDL-C levels in humans.     

乙肝相关性肝病患者幽门螺杆菌感染的研究

目的研究慢性乙型肝炎(乙肝)、乙肝肝硬化、乙肝后肝癌等肝病患者幽门螺杆菌(Hp)感染情况。方法收集慢性乙肝、乙肝肝硬化、乙肝后肝癌等肝脏疾病患者273例,日期正常体检人群60例,采用免疫层析法检测患者血清中抗Hp抗体(Hp-IgG),定量PCR检测HBV DNA。结果乙肝相关性肝病患者Hp感染率73.3%,正常体检人群为40.0%,2组比较差异有统计学意义(P<0.01);慢性乙肝、乙肝肝硬化、乙肝后肝癌3组患者Hp感染率分别为62.7%、77.0%、79.7%,后二者Hp明显高于慢性乙肝患者(P<0.05);按病毒载量分级,HBV DNA阴性组Hp感染率低于HBV DNA阳性组,而阳性组按低、中、高分组,各组间Hp感染率分别为69.4%、65.0%、66.1%(P>0.05);乙肝肝硬化患者按Child-push分级后,A、B、C各级之间的Hp感染率分别为51.9%、63.4%、65.6%(P>0.05)。结论 Hp感染可能参与乙肝肝病患者肝脏损伤,显示Hp具有肝细胞毒性作用;肝硬化、肝癌感染率高于慢性乙型肝炎,提示Hp感染与慢性肝病疾病进展和肝癌的发生有一定相关性。     

Lipoprotein clearance mechanisms in LDL receptor-deficient "Apo-B48-only" and "Apo-B100-only" mice.

The role of the low density lipoprotein receptor (LDLR) in the clearance of apo-B48-containing lipoproteins and the role of the LDLR-related protein (LRP) in the removal of apo-B100-containing lipoproteins have not been clearly defined. To address these issues, we characterized LDLR-deficient mice homozygous for an "apo-B48-only" allele, an "apo-B100-only" allele, or a wild-type apo-B allele (Ldlr-/- Apob48/48, Ldlr-/-Apob100/100, and Ldlr-/-Apob+/+, respectively). The plasma apo-B48 and LDL cholesterol levels were higher in Ldlr-/-Apob48/48 mice than in Apob48/48 mice, indicating that the LDL receptor plays a significant role in the removal of apo-B48-containing lipoproteins. To examine the role of the LRP in the clearance of apo-B100-containing lipoproteins, we blocked hepatic LRP function in Ldlr-/-Apob100/100 mice by adenoviral-mediated expression of the receptor-associated protein (RAP). RAP expression did not change apo-B100 levels in Ldlr-/-Apob100/100 mice. In contrast, RAP expression caused a striking increase in plasma apo-B48 levels in Apob48/48 and Ldlr-/-Apob48/48 mice. These data imply that LRP is important for the clearance of apo-B48-containing lipoproteins but plays no significant role in the clearance of apo-B100-containing lipoproteins.     

Interaction of dietary cholesterol and triglycerides in the regulation of hepatic low density lipoprotein transport in the hamster.

These studies report the effects of dietary cholesterol and triglyceride on rates of receptor-dependent and receptor-independent LDL transport in the liver of the hamster. In animals fed diets enriched with 0.1, 0.25, or 1% cholesterol for 1 mo, receptor-dependent LDL transport in the liver was suppressed by 43, 63, and 77%, respectively, and there were reciprocal changes in plasma LDL-cholesterol concentrations. In addition, dietary triglycerides modified the effect of dietary cholesterol on hepatic LDL transport and plasma LDL concentrations so that at each level of cholesterol intake, polyunsaturated triglycerides diminished and saturated triglycerides accentuated the effect of dietary cholesterol. When animals were raised from weaning on diets containing small amounts of cholesterol, the decline in receptor-dependent LDL transport was nearly abolished by the addition of polyunsaturated or monounsaturated triglycerides, but was markedly augmented by the addition of saturated lipids. When animals raised on diets containing cholesterol and saturated triglycerides were returned to the low cholesterol, low triglyceride control diet, hepatic receptor-dependent LDL transport and plasma LDL-cholesterol concentrations returned essentially to normal within 2 wk. Neither receptor-independent LDL transport nor the receptor-dependent uptake of asialofetuin was significantly altered by dietary cholesterol or triglyceride suggesting that the effect of these lipids on hepatic LDL receptor activity was specific and not due to a generalized alteration in the physiochemical properties of hepatic membranes. These studies demonstrate the important role of saturated triglycerides in augmenting the effect of cholesterol in suppressing hepatic LDL receptor activity and elevating LDL-cholesterol levels.     

Effect of cyclosporine on HMG-CoA reductase, cholesterol 7alpha-hydroxylase, LDL receptor, HDL receptor, VLDL receptor, and lipoprotein lipase expressions

Long-term administration of cyclosporine (CsA) has been shown to cause hypercholesteremia, hypertriglyceridemia, and elevations of plasma low-density and very low-density lipoprotein (LDL and VLDL) levels in humans. This study was undertaken to explore the effects of CsA on expressions of the key lipid regulatory enzymes and receptors. Thus, hepatic expressions of cholesterol 7alpha-hydroxylase (the rate-limiting step in cholesterol conversion to bile acids), LDL receptor, and high-density lipoprotein (HDL) receptor proteins, as well as 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were determined in rats treated with CsA (18 mg/kg/day) or placebo for 3 weeks. In addition, skeletal muscle and adipose tissue expressions of lipoprotein lipase and VLDL receptor were measured. Western blot analysis was used for all protein measurements using appropriate antibodies against the respective proteins. CsA-treated animals showed mild but significant elevations of plasma cholesterol and triglyceride concentrations. This was associated with a marked down-regulation of cholesterol 7alpha-hydroxylase in the liver and a severe reduction of lipoprotein lipase abundance in skeletal muscle and adipose tissue. However, hepatic LDL receptor and HDL receptor expressions and HMG-CoA reductase activity were not altered by CsA therapy. Likewise, skeletal muscle and adipose tissue VLDL receptor protein expressions were unaffected by CsA administration under the given condition. In conclusion, CsA administration for 3 weeks resulted in a significant reduction of hepatic cholesterol 7alpha-hydroxylase and marked down-regulation of skeletal muscle and adipose tissue lipoprotein lipase abundance in rats. The former abnormality can contribute to hypercholesterolemia by limiting cholesterol catabolism, whereas the latter may contribute to hypertriglyceridemia and VLDL accumulation by limiting triglyceride-rich lipoprotein clearance in CsA-treated animals.     

Regulation of Hepatic Lipoprotein Receptors in the Dog. RAPID REGULATION OF APOLIPOPROTEIN B,E RECEPTORS, BUT NOT OF APOLIPOPROTEIN E RECEPTORS, BY INTESTINAL LIPOPROTEINS AND BILE ACIDS

Two distinct lipoprotein receptors can be expressed in the dog liver. One is the apolipoprotein (apo-) B,E receptor. This receptor binds apo-B-containing low density lipoproteins (LDL), as well as apo-E-containing lipoproteins, such as the cholesterol-induced high density lipoproteins (HDL_c). The second hepatic lipoprotein receptor is the apo-E receptor. It binds apo-E HDL_c and chylomicron remnants, but not LDL. The present studies were undertaken to determine whether short-term (acute) regulation of the two receptors can occur in response to perturbations in hepatic cholesterol metabolism. The design used three groups of experimental animals: (a) immature dogs (with both hepatic apo-B,E and apo-E receptors expressed), (b) adult dogs (with predominantly the apo-E receptor expressed and little detectable apo-B,E receptor binding activity), and (c) dogs treated with the bile acid sequestrant cholestyramine or those that have undergone biliary diversion (with apo-E receptors and induced apo-B,E receptors).     

Color doppler sonography avoids misinterpretation of the "parallel channel sign" in the sonographic diagnosis of cholestasis.

PURPOSE: The intrahepatic "parallel channel sign" on gray-scale sonograms is generally interpreted as representing dilated bile ducts, but it may also be caused by enlargement of intrahepatic arteries. This study was performed to evaluate the incidence of misinterpretation of the parallel channel sign without color Doppler sonography and the characteristics of patients in whom misinterpretation of the parallel channel sign is likely to occur. METHODS: A total of 1,100 patients were examined by sonography. All patients with a parallel channel sign on gray-scale sonograms underwent color Doppler sonography. In addition, laboratory values related to cholestasis were measured. RESULTS: The parallel channel sign was observed in 57 patients (5.2%). In 35 (61%) of these patients, color Doppler sonography revealed blood flow in both lumina, indicating that the parallel channel sign was not caused by enlarged bile ducts. Eighty-six percent of this group had nonbiliary liver disease; the enlarged hepatic artery branches were associated with liver cirrhosis in 63% of this group. Color Doppler sonography confirmed that the other 22 patients (39%) had an enlarged intrahepatic bile duct. CONCLUSIONS: Use of color Doppler sonography can help avoid misinterpretation of the parallel channel sign, especially in patients with nonbiliary liver disease.