The Effect of Portacaval Shunt on Hepatic Lipoprotein Metabolism in Familial Hypercholesterolemia 1

JOUR:-iAL OF SUR,,,',,,,L ;',.c.:,',.H 39, 369-377 (1985)

( \ JEFFREY M. HOEG, M.D.,2 STEPHEN J. DEMOSKY, JR., B.A., ERNST J. SCHAEFER, M.D., I THOMAS E. STARZL, M.D.,* KENDRICK A, PORTER, M.D.,t AND H. BRYAN BREWER, JR., M.D. Molecular Disease Branch, National Hearl, Lung, and Blood inslirule, NUlionalinslitutes o{Health, Bethesda, Maryland; and "The Department o/Surgery, University of Pittsbwgh School of Medicine, Pillsburgh, Pennsylvania: and tSr Mary's Hospizal School of Medicine, London, United Kingdom

Submitted for publication April 16, 1984

The hyperlipidemia observed in familial hypercholesterolemia can be reduced by portacaval anastomosis, i We report the effects of a portacaval shunt on hepatic morphology and biosynthetic pathways crucial to hepatic cholesterol homeostasis in homozygous receptor-negative familial hypercholesterolemia, Portacaval I anastomosis was associated with a dramatic change in hepatocyte morphology, 28% reduction in plasma' low-density lipoprotein concentration, and a decrease in hepatic total and free cholesterol content by 27 \ and 75%, respectively. Furthermore, the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3- methylgIutaryl coenzyme A reductase was decreased by 56%, Finally, the reduced binding oflow-density \ lipoproteins to hepatic membranes preoperatively was increased following the portacaval shunt. These { com bined results indicate that the changes in circulating lipoprotein concentrations observed after por f tacaval shunt are due to alterations in the metabolic consequences of the defective recognition of low \ density lipoproteins by the liver of familIal hypercholesterolemic subjects, \0 1985 Academic Press, Inc,

INTRODUCTION liver. The initial step in the cellular uptake of circulating LDL is the binding of the lipopro l The mammalian liver plays a central role tein to a receptor in the plasma membrane [8, in lipid and lipoprotein metabolism. It is the I 15], Isolated hepatic membranes from a num primary site for endogenous cholesterol and \ ber of animal species have been shown to con lipoprotein biosynthesis as well as the principal tain a receptor which [1, 23, 26, 28, 55] spe organ for cholesterol excretion through bile r cifically binds LDL. Recently, hepatic mem and bile acid formation [11, 18,48]. Studies branes from normal adult humans have also i in rats [9,19,54], swine [33], and rabbits [27, been demonstrated to bind LDL [16, 22]. 34] indicate that a significant portion of an \ Thus, coordinate control of lipoprotein up injected dose of radiolabeled low-density li \ take, catabolism, and synthesis may occur in poproteins3 is removed by the mammalian t normolipidemic man. I A preliminary account of this work was presented at Familial hypercholesterolemia is an auto Ihe American Federation for Clinical Research Meetings somal dominant disorder characterized clini I held in Washington, D, C. Mav 1983, cally by hypercholesterolemia, xanthomas, , 2To whom correspondence ~hould be addressed: Mo and premature atherosclerosis [24]. By analysis lecular Disease Branch, National Heart, Lung, and Blood I of skin fibroblasts from patients homozygous lnstitute, National Institutes of Health, Building 10, Room l 7N117, Bethesda, Md, 20205, for FH, Brown and Goldstein determined that J Abbreviations used: FH, familial hypercholesterolemia; FH was due to one of several mutations in the I LDL, low-density lipoproteins; SE, standard error of the gene coding for the cellular receptor for LDL 1 mean; PBS, phosphate-buffered saline; BSA, bovine serum [7, 51]. The most frequent allelic mutation re ~butnin; TrisO, tris (hydroxymethyl)aminomethane; !2SI_ \ sulting in FH is the loss of the functional high , I DL, 12sI_labeled low-density lipoproteins; VLDL, very- , OW-density lipoproteins; LPDS, lipoprotein-deficient affinity receptor for LDL and is referred to as serum; HMO-eoA reductase, 3-hydroxy-3-methylglutaryl receptor-negative FH [51]. We have recently toenlYffie A reductase; apoB. apolipoprotein B. demonstrated that the loss of the fibroblast

370 JOURNAL OF SURGICAL RESEARCH: VOL. 39, NO.5, NOVEMBER 1985

LDL receptor in FH homozygotes is paralleled tissue was obtained; informed consent had by a defect in the hepatic membrane recog been given. Biochemical and morpholOgic nition of LDL [22]. Therefore, the profound studies performed on this tissue are referred hypercholesterolemia and accelerated athero to as "postshunt" values. sclerosis observed in FH may occur as a result The hepatic tissues from normolipidemic of the loss of the hepatic LDL receptor and control subjects were obtained at the time of \ the resulting changes in hepatic lipid and li laparotomy for kidney donation for renal ( poprotein metabolism. transplantation. All hepatic biopsies were per Patients with FH frequently are refractory formed after informed consent had been given ( to all lipid lowering drug regimens. However, and the protocol used for hepatic biopsy and the use of a portacaval anastomosis to shunt portacaval anastomosis was approved by the blood flow from the liver has been shown to human experimentations committee at the be effective in lowering the plasma lipids in U ni versity of Pittsburgh School of Medicine. these patients [42]. The present studies were Lipoprotein preparation. Preparation of performed on hepatic tissue in a receptor-neg human LDL Cd 1.030-1.050) was from 500 ative FH subject to evaluate the effect of the ml plasma collected in 0.01% EDT A by plas portacaval shunt on both the binding ofLDL mapheresis from fasting, healthy volunteers. to hepatic membranes as well as to assess the Lipoproteins were separated by preparative I impact of the portacaval shunt on hepatic ultracentrifugation at 4 DC for 16-24 ill [17] i cholesterol metabolism. using KBr for density gradient adjustment [36]. These subfractions were then dialyzed METHODS 34 hr at 4 DC against 150 vol of phosphate buffered saline (pH 7.0) (GIBCO, Grand Is Patient history. The patient studied was first land, N. Y.). Each isolated lipoprotein fraction noted to be hypercholesterolemic at the age was sterilized by 0.45-j.Lm Millipore filtration of 13. Despite therapeutic trials of cho (Millipore Corp., Bedford, Mass.) and used 1, ~ lestyramine, niacin, hydroxymethylglutamic within 1 month of preparation. 125I_LDL was !: acid, and neomycin, the plasma cholesterol prepared by the iodine monochloride method ranged from 915 to 1210 mg/dl and she de [31] as modified for lipoproteins [4]. A 25- veloped symptomatic coronary artery disease. 30% efficiency of iodination was obtained and The patient's mother (age 40) had a plasma less than 6% of the radioactivity was soluble cholesterol of 462 mg/dl and an LDL choles in the organic phase following a chlorofonn terol of 359 mg/dl. The patient's father was methanol extraction. After dialysis over 24 hr not available for study. Analysis ofLDL bind at 4 DC against 500-600 vol PBS, specific ac ing in skin fibroblasts ofTH demonstrated no tivities ranged from 2.7 to 4.6 X 109 Bq/ml detectable receptor for LDL [22]. Therefore, LDL protein. The LDL protein concentration the patient's genetic, clinical, and biochemical was determined by the method of Lowry et at profiles were consistent with the diagnosis of [30] using bovine serum albumin standard. receptor-negative FH. After Millipore filtration, 1251_LDL was stored At age 21, after suffering two myocardial at 4°C and used within 2-3 weeks of prepa infarctions and receiving a double coronary ration. artery bypass graft, the patient received a ther Liver membrane preparation. Biopsy spec· apeutic portacaval anastomosis at the U ni imens were immediately placed in a beaker versity of Pittsburgh in an effort to lower the and all processing occurred at 4°C similar to plasma lipid concentrations. A liver biopsy that described by others [1. 2]. A.fter mincing taken at the time of the anastomosis provided the tissue with a razor blade. it was washed the basis for the biomedical and histopatho with an ice-cold buffer containing 0.9% (w/v) logic studies referred to as "preshunt" values. NaC!. 1 rru'-1 EDTA. and 10 mM TrisCl (pH Three months after the initial surgery, hepatic 8.0). Homogenization was performed by six .. HOEC ET !'L.: PORTACAVAL SHUNT 371

strokes of a motor-driven Teflon pestle in a between tU!J.] and ,ree cholesterol. The nano c buffer containing 0.25 M sucrose, 1 mM moles of cholesterol extracted from the biopsy d EDTA, and 10 mM TlisCl (pH 8.0). The ho- samples were normalized to initial sample , rnogenized preparations (10 mg/ml) were weight. le c:ntrifuged for 10 min at 1000g. The super Hepatic en::yme activities. The activity of )f natant solution was recentrifuged for 25 min HMG-CoA Reductase (EC 1.1.1.34) was al at IO,OOOg, followed by ultracentrifugation at quantitated in the 100,000g pellet, as previ :r- 100,OOOg for 60 min. The pellet from this ul ously described [3]. The cholesteryl ester hy

~n tracentrifugation was resuspended in a buffer drolase activity (EC 3.1.1.13) was determined ld containing 150 mM NaCl, 10 mM TrisCl (pH in the cytosolic fraction at both pH 4.0 and he 8.0), and flushed through a 22-gauge needle pH 7.0 [21]. he , iO times. These membranes were recentri Binding of 125J_LDL to liver membranes. Ie. \ fuged for 15 min at 100,OOOg and the mem- Hepatic membrane binding of 125I_LDL was of brane pellets were then frozen in dry ice and assessed using previously described methods ,00 i. stored in liquid nitrogen until used for binding [1, 22, 28]. Briefly, frozen liver membrane as- . assays and quantitation ofHMG-CoA reduc- preparation was thawed and resuspended in ~rs. ( lase activity. The 10,000g supernatant was 50 rnM NaCl, 30 rnM Tris-HCl (pH 7.5) .lYe used for cholesteryl esterase assays . buffer (10-12 mg/ml) and passed through a 17} \ Lipoprotein quantitation. Blood was ob 22-gauge needle. Membranes were then son .ent I tained in 0.01% EDTA from patient TH after icated by five 4-sec pulses at the 55-W setting zed \ a 12- to 14-hr overnight fast, and the plasma using an ultrasonics microtip (Heat Systems ate ( was separated at 4 DC in a refrigerated centri Ultrasonics, Inc., Plainview, N. Y.). From 100 lIs { fuge. Plasma cholesterol and triglycerides were to 200 p.g membrane protein was then added tion ~ quantitated on a Gilford 3500 using previously to a 50 mM NaCl, 20 mM Tris-Cl (pH 7.5) tion described enzymatic methods [32, 52]. HDL buffer containing 1 mM CaCl2 . 125I_LDL was [ lsed cholesterol was determined following dextran added at the indicated concentrations with or was ( sulfate precipitation of plasma. Plasma was without unlabeled LDL with a total assay thod I ultracentrifuged (1.006 g/ml) for 18 hr at mixture volume of 0.1 ml. Incubations were 25- ( 39,000 rpm (4°C) in Beckman 40.3 rotors carried out at 37°C for 30 min at which time and (Beckman, Fullerton, Calif.) and the VLDL preliminary studies had demonstrated that .uble I was separated from the other plasma lipopro equilibrium had been reached. Bound 1251_ lOn ( teins by tube slicing [17]. The cholesterol con LDL was separated from free ligand by a 3 ~4 hr . centration in the 1.006 gJml infranate was min, 100,000g centrifugation of 50 p.l of the e ac l measured, and the VLDL and LDL cholesterol assay mixture through 125 p.l PBS in a 30De q/mJ were calculated. angle rotor in an air-driven ultracentrifuge ation Hepatic cholesterol and cholesteryl ester de (Beckman, Palo Alto, Calif.). The supernatant et at. . termination. Liver biopsy samples from nor was removed from the pellet by vacuum as dard. i mal and familial hypercholesterolemic sub piration, and the pellet was washed once with tored ( jeets were weighed, extracted three times with 125 ill of PBS. The cellulose nitrate tube tips Irepa- chloroform-methanol (2/1 v/v) at 41 0e. The containing the membrane pellet were sliced I samples were then extracted overnight with and the radioactivity in the pellet quantitated spec Chloroform-methanol (2/1 v/v) at 30°e. The in a Biogamma II scintillation counter (Beck ,eaker I. chloroform-methanol extracts were blown to man). Specifically bound 125I_LDL was defined ilar to , dryness and the liquid was resuspended in 2- as the difference in 125I_LDL quantitated in .ncing I Propanol (J. T. Baker Chemical Co., Phillips- samples which were incubated with and with ·ashed burg, N. J.). Free and total cholesterol were out 390 p.g of unlabeled LDL. (w/v) i then measured by the enzymatic, fluorimetric Histopathologic studies. One sample of each :1 (pI1 I method of Heider and Boyette [20J. Esterified liver specimen was fixed in 10% neutral for by six , cholesterol was determined as the difference malin and was then processed for examination 372 JOURNAL OF SURGICAL RESEARCH: VOL. 39, NO.5, NOVEMBER 1985 by light microscopy. A second piece of the bi in the LDL cholesterol represented a 28% opsy tissue was fixed in buffered glutaralde change (P < 0.01). Although the concentra hyde, postfixed in osmium tetroxide, and then tions of VLDL, HDL, and total triglycerides embedded in epoxy resin (Epon 812). Some also declined, these changes were not statisti of the liver postshunt tissue was also postfixed cally significant. in osmium and processed for electron mi These changes in lipoprotein concentration croscopy. Ultrathin sections were stained with were paralleled by striking alterations in he lead citrate and examined in a Phillips 300 patocyte morphology (Fig. 1). Before porta electron microscope. The sizes of the mid caval diversion the hepatocytes were enlarged zonal hepatocytes before and after portal di and their cytoplasm was vacuolated. Lipid de version were determined on hematoxylin and posits were demonstrated by staining frozen eosin-stained sections by a method previously sections with Sudan IV. Ultrastructurally, the described [43]. Mid-zonal hepatocytes iden cytoplasmic droplets possessed a double tified in 1.0-,um-thick epoxy resin sections were membrane. The amounts of rough and also used for measuring the length of rough smooth endoplasmic reticulum were normal. endoplasmic reticulum per area of cytoplasm Free polyribosomes were also present in the. by a morphometric method [29]. cytoplasm. Glycogen was abundant. Statistical methods. Statistical comparisons After portacaval shunt, the size of the he of paired and unpaired lipoprotein determi patocytes was nearly halved and the amount nations and biochemical assays were made of fat in the cytoplasm of the liver cells de using two-tailed t tests assuming the samples creased. Ultrastructurally, the lipid droplets were independent [39]. remained enclosed in a double membrane. Morphologic analysis showed that the area of rough endoplasmic reticulum was reduced to RESULTS 47% of the quantity found in the preoperative biopsy. The amount of smooth endoplasmic The effects of portacaval shunt on the lipid reticulum was reduced to 55% compared to and lipoprotein concentrations in the plasma the first biopsy. Free ribosomes were abun in FH are summarized in Table 1. All of the dant. Glycogen particles were rare. Therefore, lipid and lipoprotein concentrations decreased marked alterations in hepatocyte morphology, following the portacaval shunt. The decline of independent of any autolytic artifact, were 291 mg/dl in total cholesterol and 266 mg/dl observed both before and after surgery.

TABLE I

THE EFFECT OF PORTACAVAL SHUNT ON PLASMA LIpID AND LIPOPROTEIN CONCENTRATIONS IN FAMILIAL HYPERCHOLESTEROLEMIA

Cholesterol (mg/dl) Triglycerides (mgjdl)

Total VLDL LDL HDL (mgfdl)

Normal a range 126-190 5-25 60-135 35-71 44-107 Preshunt 1034 ± 156 47 ± 17 957 ± 157 27 ± 9 200 ± 57 Postshunt 743 ± 37* 24 ± 6 691 ± 43* 23 ± 3 156 ± 43 % Change 28* 49 28* 15 22

Note. Plasma lipid and lipoproteins were measured five times preshunt and four times postshunt. The values represent the mean ± SE. a "Ionnal values are those reported for the I0-90 percentile for females ages 14-19 from The Lipid Research Clinics Prevalence Study [49]. • These values represent a SIgnificant difference from preshunt values (P < 0.05). • HOEG ET AL.: PORTc\CA" AL SHUNT 373

-......

..~ , .f

PRESHUNT POSTSHUNT D FIG. I. Electron microscopy of hepatic biopsy specimens taken before portacaval shunt (left panel) and \- .\ after portacaval shunt (right panel). The increased cytoplasmic hepatocyte lipid accumulation preshunt decreased after portacaval shunt. Magnification in both specimens is X II ,400. -, {, :e ( The POrtacaval shunt was al", associated cholesterol content in the liver ofTH, but also \ with major changes in hepatic cholesterol on the cholesterol distribution between free \ content (Table 2). Before the portacaval shunt, and esterified forms. , the total cholesterol content in the FH liver was 1.7 times that of normal liver. Although ' TABLE 2 Ithe portacaval shunt reduced total hepatic cholesterol by 27%, the postshunt cholesterol EFFECT OF PORTACAVAL SHUNT ON HEPATIC content was still 21 % higher than normal. The CHOLESTEROL CONTENT IN FAMILIAL HYPERCHOLESTEROLEMIA most striking change included the 75% decline in free cholesterol that was observed after the Hepatic cholesterol (nmole/mg wet tissue) 7 operation. As the free cholesterol declined, the 57 amount of cholesterol in the esterified form Total Free Esterified 43 mcreased by 79%. The normal livers had 24% Normal 5.80 ± 0.46 4.99 ± 0.24 0.81 ± 0.52 of the cholesterol esterified while the FH liver Familial hypercho- ues preshunt had 32% of the cholesterol esterified. lesterolemia By performing the portacaval anastomosis, the Preshunt 9.61 ± 0.21 6.58 ± 0.24 3.03 ± 0.32 tfch fraction of hepatic esterified cholesterol in FH Postshunt 7.04 ± 0.19 1.62 ± 0.34 5.42 ± 0.29

mcreased to 77%. Thus, the portacaval shunt Note. Three replicate samples of hepatic biopsies were measured \ bad a profound effect not only on the absolute and the values represent the mean ± SE.

I 374 JOURNAL OF SURGICAL RESEARCH: VOL. 39, NO.5, NOVEMBER 1985

Enzymes central to hepatic cholesterol me pI ....J .. tabolism were quantitated in liver biopsy Cl {' ....J 4' specimens taken before and after surgery (Ta ( fa ble 3). The activities of the enzymes HMG iiI CoA reductase, acid cholesteryl ester hydro pc lase, and neutral cholesteryl ester hydrolase in ( oj the preshunt liver biopsy were comparable to { st the activities observed in normal liver. Al l th though the portacaval shunt had no apparent t m effect on neutral esterase activity, changes in ( m "0'. LDL il'g/ml) both HMG-CoA reductase and acid esterase i sy i activities were observed (Table 3). A 56% de FIG. 2. Specifically bound 12sI_LDL to hepatic memo fo I cline in HMG-CoA reductase activity was branes from normal subjects and a familial hypercholes I re paralleled by a 220% increase in acid esterase terolemia before and after portacaval shunt. Membranes \ ro activity. Thus, portacaval shunt of blood flow were prepared from hepatic biopsy specimens from three i Ll from the liver appreciably altered the enzyme normal subjects (0, N = 3), and familial hypercholester_ '" olemic hepatic tissue preshunt (b.), and postshunt (.). de activities relevant to hepatic cholesterol ho From 100 to 200 ILg of membrane protein was added to I tho meostasis. a 75 mM NaO, 150 mM TrisO, I mM CaCl2 (pH 7.5) SlI The ability of hepatic membranes to spe buffer with the indicated concentrations of 12sI_LDL in i he cifically bind LDL was directly determined in the presence and absence of excess unlabeled LDL. Spe LI membranes isolated from the FH liver before cifically bound I2sI_LDL, defined as the difference in 1251_ LDL bound in the presence and absence of excess unla to and following portacaval anastomosis (Fig. 2). beled LDL, was normalized to the amount of membrane an There was a significant reduction in LDL protein in the sample. Values represent the mean ± SE of I" (, binding to the FH hepatic membranes com triplicate determinations. tal

" pared to binding to hepatic membranes from th( t normolipidemic subjects. After the portacaval the tJ DISCUSSION l~ shunt, however, the specific binding of 1251_ \,/ we ,.'" LDL to the hepatic membranes was signifi The extreme hypercholesterolemia and pa :~ cantly increased compared to preshunt values. rapidly progressive premature cardiovascular str - Thus, portacaval shunt enhanced the hepatic disease observed in familial hypercholesterol rot membrane binding of 125I_LDL. emia have prompted the search for an effec un tive, definitive treatment. After observing a 43 marked decline in serum lipid concentrations an, TABLE 3 with a portacaval shunt for Type I glycogen dn storage disease [47], Starzl and co-workers we THE EFFECT OF PORTACAVAL SHUNT ON HEPATIC successfully employed this procedure to lower tac ENZYMA TIC ACTIVITIES IN FAMILlAL I alt, HYPERCHOLESTEROLEMIA the plasma cholesterol levels in a patient with familial hypercholesterolemia [42]. Subse Chi Enzymatic activity (% control) quent observations oflowered LDL cholesterol tae levels, xanthoma regression, and safety of the qu HMG tet CoA Acid esterase Neutral esterase procedure have been reported by StarzI as well as several other investigators [6, 10, 12, 13, COl Preshunt 129 :!: 26 110 ± 3 92 ± 22 25,40,41,44,54]. Thus, the use of portacaval chI Postshunt 57 ± 4 249:!: 19 102 ± 5 anastomosis appeared to be one of the few to en: Note. The enzymatic actIvity in the FH hepatic tissue was successful hypocholesterolemic maneuvers 10 compared to that from liver taken from three norrnolipidemic patients homozygous for FH. ree subjects. The control speCIfic activnies expressed as pmole/min/ The 28% reduction in total cholesterol and lov mg protein were HMG-CoA reductase 3.24 ± 0.75. acid esterase SYr 71.5:!: 8.34. and neutral esterase 11.4 ± 2.1. Values represent LDL observed in TH after portal diversion was the mean ± SE of three or four replicate samples. typical of the 20-55% decline in these values the HOEG ET AL.: PORTACAVAL SHUNT

-,--.., previously reported [6, 10, 12, 13.25,40-42, decline in parallel with the fall in hepatic con i 44,54]. This decline could occur because ofa tent of total and free cholesterol following fall in the synthesis of cholesterol containing portacaval shunt. JI lipoproteins, an enhanced clearance of the li The distribution and hydrolysis of choles J l poproteins from the plasma, or a combination teryl ester within the FH hepatocyte may re \ of these two possibilities. Metabolic turnover flect aberrant metabolism of cholesteryl ester ~ J ( studies of radiolabeled lipoproteins indicated containing lipoproteins. The LDL receptor ( that the fractional catabolic rate of FH ho mediated uptake mechanism leads to lyso \ mozygotes was significantly less than in nor somal localization and degradation of LDL I ~500 \ mal individuals [5, 37, 38, 50] and that the [8, 15 J. Since TH had no high-affinity LDL r synthesis rate of apoB into LDL was two- to receptor, delivery of LDL to cells could only I, fourfold normal [5, 37, 38]. Bilheimer et al. occur through a pinocytotic or an alternate patic mem- Iypercholes- reported that portacaval shunt in a patient ho pathway for LDL uptake. Such an alternate Membranes mozygous for FH enhanced the clearance of pathway may lead to ineffective delivery of 5 from three j LDL from the circulation by 17% and a 48% cholesteryl ester-rich lipoproteins to appro lCrcholester- i decline was measured in the rate of LDL syn priate subcellular compartments. The exis Istshunt (.). thesis in a patient homozygous for FH [5]. A tence of such an alternate pathway has recently vas added to Ch (pH 7.5) I similar response has been reported in a patient been shown to be the major source of LDL 1251_LDL in ,heterozygous for FH [14]. Thus, the fall in delivery to the liver of the Watanabe heritable rl LDL. Spe- ,LDL observed after portacaval shunt appeared hyperlipidemic (WHHL) rabbit, the only ex :rence in mi_ to result from changes in both LDL synthesis isting animal model for FH [34]. In TH, the . excess unla- Jfmembrane I and removal. portacaval shunt was associated with an in nean ±SEof Since the mammalian liver may be impor crease in the "receptor-independent" binding I tant for both cholesterol and lipoprotein syn ofLDL tei the hepatic membranes (Fig. 2). An thesis as well as degradation, a disruption in enhancement ofLDL transport, though a less I the blood supply rich in hepatotrophic factors efficient alternate pathway, could account for I,• would be anticipated to alter these biochemical the striking modifications observed in hepatic lemia and 1 pathways. As in the present case, the cellular cholesterol metabolism. iiovascular structures involved with lipid and lipoprotein In summary, portacaval shunt in FH has ~holesterol metabolism have consistently been shown to been shown to increase hepatic LDL recog or an effec undergo profound morphologic changes [35, nition, markedly alter the intracellular en Jbserving a 43, 45, 46]. The reduction in hepatocyte size zymes central to cholesterol metabolism, and lcentrations and the development of cytoplasmic lipid modify hepatic cholesterol concentration and \ : I glycogen . droplets in the FH liver after portacaval shunt distribution. These changes parallel the in co-workers ! were similar to the changes induced by por- creased clearance of plasma LDL and reduced ureto lower · tacaval shunt in the dog [45]. These anatomic LDL synthesis observed in FH patients after patient with I alterations are paralleled by biochemical portacaval shunt. By manipulating the meta 42]. Subse I changes observed in the liver of TH after por bolic consequences of the hepatic LDL recep L cholesterol I tacaval shunt. First, quantitative as well as tor loss in FH, more effective therapeutic ap safety of the . qUalitative changes in hepatic cholesterol con- proaches to the hypercholesterolemia and ac Starzl as well tent were observed. Total hepatic cholesterol celerated atherosclerosis present in FH can be 10 12, 13, ICOntent decreased; however, the fraction of developed. ~fP~rtacaval cholesterol in the free form decreased from 68 e of the few l to 23%. Second, the activity of the rate-limiting ACKNOWLEDGMENTS naneuvers in \ enzYme for cholesterol synthesis, HMG-CoA reductase, was reduced by more than half foI We thank Dr. Lee, Dr. Warty, and Dr. Sanghvj at the l . University of Pittsburgh for the use of their laboratory olesterol and OWIng the portacaval shunt. Thus, the bio- facilities for a portion of these studies. We are also grateful diversion was I synthetic. pathway of cholesterol synthesis in to Dr. Dana Fowlkes for his effort in facilitating acquisition 1 these values Ithe FH liver was shown for the first time to of postshunt tissue. I ------,-~-----' ... -. -----

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