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(Arteriosclerosis, Thrombosis, and Vascular Biology. 1997;17:1032-1038.)
© 1997 American Heart Association, Inc.

Articles

Organ Loci of Catabolism of Short Truncations of ApoB

Xian-Feng Zhu; Davide Noto; Rick Seip; Aviv Shaish; ; Gustav Schonfeld

From the Division of Atherosclerosis, Nutrition, and Lipid Research, Washington University School of Medicine, St Louis, Mo (X.F.Z., A.S., G.S.); Cattedra Di Patologia Speciale Medica, E Matodiolgia Clinica, Istituto di Patologia Medica II, Universita di Palermo, Italy (D.N.); and the Human Performance Lab, University of Nebraska, Kearney (R.S.).

Correspondence to Xien-Feng Zhu, Division of Atherosclerosis, Nutrition, and Lipid Research, Washington University School of Medicine, 660 S. Euclid Ave, St. Louis, MO 63110.

	Abstract

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Abstract Truncations of apolipoprotein (apo) B shorter than 3200 amino acids (3200/4536=apoB-70) do not possess the LDL receptor–recognition domain and are not recognized by altered cells with normally functioning LDL receptors. To ascertain which organs remove such truncated apoB–containing particles, we isolated apoB-31–, apoB-38.9–, and apoB-43.7–containing particles from plasmas of familial hypobetalipoproteinemia heterozygous humans by a combination of sequential ultracentrifugation and preparative electrophoresis. Particles with labeled ¹²⁵I- or ¹³¹I-dilactitol tyramine (I-DLT), were injected into New Zealand White rabbits, along with I-DLT–apoB-100–containing LDLs, and the decay of ¹²⁵I- and ¹³¹I-TCA–precipitated counts was followed over 24 hours. At the end of 24 hours, rabbits were anesthetized and their bodies perfused. Organs were removed and homogenized, and TCA-precipitable counts determined. Fractional catabolic rates of apoB truncation particles were two to five times greater than those of apoB-100 LDLs. ApoB truncations accumulated in adrenals at one fifth the rates of apoB-100 LDL, compatible with the functional absences of LDL receptor–recognition domains in truncated apoBs. The major organ of uptake for apoB-100-LDLs was the liver, whereas truncation particles were readily removed by the kidney (kidney: liver uptake ratios were 0.10 to 0.30 for apoB-100 LDLs and 1.03 to 3.77 for truncations). Spleens accumulated little of either apoB-100 or truncation particles, suggesting particles were not "damaged" or aggregated. Thus, the absence of >56% of the carboxyl end of apoB-100 increases the plasma clearance and redirects the organ uptake of the apoB truncation–containing lipoproteins from liver to kidney.

Key Words: lipoproteins • apoB • apoB truncations • dilactitol tyramine

	Introduction

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The low-cholesterol syndromes¹ consist of abetalipoproteinemia, associated with deficiencies of microsomal triglyceride transfer protein,^{2 3 4 5} chylomicron retention disease of unknown etiology,^{6 7} and FHBL, most often defined as <5th percentile LDL cholesterol, which in most kindreds segregates as an autosomal dominant phenotype. In a subset of kindreds, the FHBL phenotype is linked to the apoB gene on chromosome 2. In some of those kindreds, various mutations of the apoB gene specify the formation of a number of COOH-terminal truncated forms of apoB that cosegregate with the FHBL phenotype.^{8 9 10 11} The plasmas of such apoB-100/apoB-truncation FHBL heterozygotes contain two populations of apoB-containing lipoproteins: apoB-100–containing particles and apoB truncation–containing particles. In general, longer truncations (eg, apoB-89 and apoB-75) are distributed among VLDL, IDL, and LDL density particles, and the short truncations (eg, apoB-31 and apoB-38.9) among small, dense LDL and HDL. ApoB-48–containing chylomicrons and chylomicron remnants may also be present in selected individuals.¹² In another subset of FHBL kindreds in which the linkage of the hypobeta phenotype to the apoB gene is present, no products of truncation-specifying mutations are detectable in plasma and the molecular defect(s) responsible for the FHBL phenotype are unknown.¹³ In still other kindreds, the FHBL phenotype appears not to be linked with the apoB gene at all.^{14 15} In both of the latter cases, only apoB-100–containing lipoproteins are detectable.

The metabolism of both the apoB-100– and apoB truncation–containing lipoproteins has been studied,^{16 17 18 19 20} most recently using stable isotopically labeled amino acids as endogenous labels. Because both the apoB-100– and apoB truncation–containing lipoproteins become labeled, it is possible to use apoB-100 as internal control for the apoB truncations. Truncations are produced at lower rates than their apoB-100 counterparts. Indeed, there is a direct correlation between the size of a truncation and its rate of production relative to its counterpart apoB-100.²¹ The FCRs of apoB-89 and apoB-75 truncations are also increased relative to apoB-100.^{17 20} In addition, the production rates of apoB-100 in heterozygotes on average are 30% of those of apoB-100 in sex-, age-, race-, and body mass index–matched normolipidemic control subjects.¹⁶

Relatively little is known about the lipid-transporting functions and tissue loci of catabolism of truncated apoBs. ApoB-100 contains a recognition domain for the LDL receptor between amino acids 3100 and 3500, and the interaction of the apoB-100 domain with the LDL receptor mediates the removal of some VLDL, most IDL, and virtually all LDL particles from plasma.^{22 23} Particles containing apoB truncations long enough to retain the LDL receptor–recognition domain, eg, apoB-89 LDL and apoB-75 LDL, are readily recognized by LDL receptors (indeed, with even higher affinity than apoB-100 LDL) and are removed primarily by liver at higher rates than their counterpart apoB-100 LDLs.^{17 20 24} By contrast, shorter truncations, eg, apoB-31, apoB-37, apoB-38.9, apoB-40, and apoB-67, do not contain the LDL receptor–recognition domain, and apoB-37 and apoB-67 and presumably the others as well do not interact with LDL receptors.^{25 26} It is not clear which, if any, receptors mediate the removal of these shorter truncation–containing particles and into which organs. We report on the decay rates from plasmas of rabbits of three short truncation–containing lipoproteins, apoB-31, apoB-38.9, and apoB-43.7, and on their organ loci of uptakes. The truncation-containing lipoproteins are cleared more rapidly than their apoB-100 counterparts, and while apoB-100 LDLs accumulate predominantly in liver, the truncation particles are readily taken up by kidneys.

	Methods

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Blood Collection
Fasted blood (58 mL) was obtained from previously identified FHBL heterozygous subjects with the following apoB genotypes: apoB100/31, apoB100/38.9, and apoB100/43.7 (Table 1). The blood was drawn into tubes containing EDTA (1 mg/mL) and plasma separated by centrifugation. The following antioxidants and proteolytic inhibitors were added to minimize oxidation of lipoproteins and the cleavage of apoB: aprotinin (100 kallikrein inhibiting units per milliliter, Sigma Chemical Company), EDTA (1 mmol/L), and BHT (300 µmol/L, Eastman Kodak Company). To assess distributions of apoB-100 and apoB-31 among lipoproteins, gel permeation chromatography of whole plasma was performed followed by SDS-gel electrophoreses and immunoblotting of elution fractions with an anti–apoB-100 Mab C1.4.^{17 22}

View this table: [in this window] [in a new window]   Table 1. Characteristics of the Lipoprotein Donors

Isolation of ApoB-100–, ApoB-31–, ApoB-38.9–, and ApoB-43.7–Containing Fractions by Sequential Ultracentrifugation
Under reduced light, plasma density was raised to d=1.019 g/mL by adding potassium bromide (Sigma), and ultracentrifugation was performed at 45 000 rpm, for 18 hours, at 10°C (Model L8M-70 ultracentrifuge, 55.2TI rotor, Beckman). VLDL and IDL were removed by tube slicing. ApoB-100–containing LDLs were isolated by ultracentrifugation at d=1.063 g/mL. Since the majority of apoB-31–, apoB-38.9–, and apoB-43.7–containing lipoproteins float in the HDL density range,^{27 28} the HDL fractions from the apoB-31–, apoB-38.9–, and apoB-43.7–containing plasmas were separated by ultracentrifugation at 1.21 g/mL, (45 000 rpm, 24 hours, at 10°C). The HDL fractions were then concentrated by ultrafiltration (Amicon Centrion-30 and Centrion-100).

Isolation of ApoB-31–, ApoB-38.9–, and ApoB-43.7–Containing Particles From HDL Fractions
HDL fractions were prestained with Sudan black dye (Fisher Scientific, prepared as previously described²⁹ ). Preparative scale 2% to 16% nondenaturing electrophoretic gradient gels were prepared³⁰ and prerun for 2 to 3 hours at 220 V at 10°C. Then 40 µL of the prestained HDL fractions was loaded into two small lateral gel wells as position markers during the electrophoresis. Concentrated unstained HDL fractions (5 mL) were loaded into a big preparative well in the middle of the gel. Electrophoresis was continued for 12 to 16 hours at 220 V and 10°C in the dark (SE600 series, Hoefer Scientific Instruments). When the electrophoresis was finished, the HDL area on the gel was identified by the stained bands in the two lateral lanes. The wide gel area above the HDL fraction area (which was known to contain the apoB truncation particles from preliminary experiments) was divided and cut into 4 to 6 gel bands. The gel pieces cut from GGE were placed into an electroeluter (model 422, Bio-Rad) and eluted in the GGE running buffer overnight at 8 to 10 mA at 10°C in the dark. The electroeluted samples were dialyzed for 8 hours against two changes of 2 liters each of equilibration buffer (0.9% NaCl and 0.01% EDTA; pH 7.4). Samples were then concentrated with Amicon Centrion-30. Isolated particles were derivatized with I-DLT as described.³¹

To ascertain whether preparative electrophoresis per se could have affected the plasma kinetics or altered the organ distribution of lipoproteins, apoB-100–containing LDL from a single normal donor was isolated by ultracentrifugation alone and also by ultracentrifugation followed by electrophoresis. In addition, on a separate occasion, the apoB-38.9 donor provided plasma from which both the apoB-100– and apoB-38.9–containing particles were isolated under identical conditions of electrophoresis (after preparative ultracentrifugation at appropriate densities).

Protein concentrations were determined by the modification of Markwell et al³² of the Lowry procedure, using BSA as standard. Purities of the apoB truncation particles were assessed by Western blot analysis. The samples were delipidated in Menzel buffer and electrophoresed in 3% to 20% gradient SDS polyacrylamide gels.¹⁶ Protein bands were electrotransferred to immobilon-P (P-15552) membranes (Millipore).¹⁶ Immobilon-P membranes were incubated with 5% (wt/vol) nonfat dry milk in PBS (0.01 mol/L; pH 7.4) followed by incubation with ¹²⁵I-labeled anti-apoB Mab C1.4 (750 000 cpm/mL) or Mab A7D3 (anti-apoA-I). Mab C1.4 is directed against amino acid residues 97 to 401 near the amino terminal of apoB,²² and Mab A7D3 recognizes apoA-I (unpublished observation). Membranes were washed with 0.1% (wt/vol) Triton X-100 and 0.1% (wt/vol) Tween 80 in PBS, dried, and exposed to Kodak XAR-5 film at -70°C for autoradiography.

Plasma Clearance Kinetics and Organ Distributions of Labeled Particles in Rabbits
Labeled truncated apoB-containing lipoproteins and labeled apoB-100–containing LDLs (in 1 mL of sterilized 0.9% NaCl solution) were injected simultaneously into the marginal ear veins of NZW rabbits (female, 3 lb).²⁴ Blood was drawn into EDTA-containing tubes at 1, 5, 10, 20, 40, 60, 120, 240, 480, 720, and 1440 minutes. More than 95% of whole plasma radioactivities were TCA precipitable. Radioactive counts were corrected for spillover (for ¹²⁵I), radionuclide decay (for ¹³¹I), and for counting efficiency. FCRs were calculated by using radioactivities of TCA-precipitable fractions and the two-compartment SAAM model.³³ To ascertain whether the injected particles remained intact as particles during the 24 hours after injection, plasmas collected at selected time points were subjected to gel filtration chromatography on two Superose 6 columns connected in series on the fast protein liquid chromatography system (Pharmacia), and fractions were counted in a gamma counter.

To obtain the organ distributions of radioactivities, 24 hours after injection the NZW rabbits were anesthetized with sodium pentobarbital and their bodies perfused through the left ventricle with sterilized 0.09% NaCl containing heparin (5 U/mL) until the lungs, heart, liver, and kidneys looked pale. The hematocrit of the perfused solution was usually <1%. Samples obtained from the following organs were weighed: skin, adipose tissue, skeletal muscle, bone marrow, esophagus, trachea, lung, stomach, aorta, heart, liver, spleen, pancreas, small intestine, adrenals, kidneys, bladder, and ovary. Whole organs (heart, stomach, liver, spleen, adrenal, and kidney) were weighed directly. Masses of dispersed organs (adipose, skeletal muscle, digestive tube) were estimated from their percentages of the total body mass.³⁴ Tissue pieces were homogenized (Polytron, Brinkmann Instruments) in distilled water (3x volume), incubated for 1 hour at 4°C with TCA (10%, wt/vol), and centrifuged at 2600 rpm for 1 hour at 10°C. Supernatants were removed and precipitates counted. Accumulation of radioiodinated lipoproteins in tissues was expressed on two bases: as dpm per gram tissue (whole organ) x100, divided by either dpm injected or dpm recovered from the whole animal.

	Results

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The characteristics of the lipoprotein donors and the references wherein the specific characteristics of the different FHBL truncation mutations are described are given in Table 1. The purity of the isolated apoB-31–containing lipoproteins is documented in Fig 1. Similar data were obtained for the apoB-38.9– and apoB-43.7–containing lipoproteins (data not shown). Each preparation contained only the appropriate apoB truncations and neither apoB-100 nor apoA-I. Lipoproteins labeled with ¹³¹I- or ¹²⁵I-DLT were injected into the ear veins of rabbits. In most cases, paired injections were administered to the same rabbit, one containing the apoB-100 LDL and the other the apoB truncation–containing lipoproteins. Fig 2 shows the decay curves for the three truncations under study. Each truncation-containing particle disappeared from plasma more rapidly than control apoB-100 LDLs, and calculated FCRs were 2.1 to 4.9 times increased (Table 2). The results were comparable whether the two labels were injected into the same rabbit or two different rabbits. To ascertain whether apoB truncation–containing and apoB-100–containing lipoproteins isolated by two different procedures could safely be used for the purposes of this study, we needed to be certain that preparative electrophoresis after preparative sequential ultracentrifugation did not affect the plasma decay of LDL compared with LDL isolated by ultracentrifugation alone. We also wished to assess any effects of antioxidants added during isolations and any effect of ¹²⁵I versus ¹³¹I labels. To minimize any variations, we used LDL isolated from a single normolipidemic donor. FCRs are relatively close to each other and did not consistently depend on the method of isolation, the label used, or the presence of BHT (data not shown). Finally, and most importantly, to avoid any artifactual differences in FCRs or organ distributions due to methods of isolation, we isolated both the truncation- and apoB-100–containing particles from the plasma of the apoB-38.9 donor by combined ultracentrifugation and electrophoresis. The differences in FCRs persisted (Table 2).

View larger version (87K): [in this window] [in a new window]   Figure 1. Analysis of purified apoB-31–containing lipoproteins by immunoblotting. The area between the LDL apoB-100 and the HDL bands in the preparative nondenaturing GGE was divided into four horizontal strips. The gel strips were excised, proteins were electroeluted, and aliquots were subjected to analytic electrophoresis in a 3% to 20% SDS–polyacrylamide gel. The resultant bands were electrotransferred to an immobilon-P membrane, and one part of the membrane was probed with the anti-apoB Mab C1.4 (A). The other part was probed with the anti–apoA-I Mab A7D3 (B). A, Lanes 1 and 2 contain the plasma and the ultracentrifugally isolated LDL (d=1.019 to 1.063) and lane 3 the HDL (d=1.063 to 1.21) of the donor subject (apoB-100/apoB-31). Lanes 4 and 5 contain the purified apoB-31 in lipoproteins eluted from strips 1 and 2 of the preparative gel. Lanes 6 and 7 contain "contaminating" HDL from strips 3 and 4 of the preparative GGE, which does not react with the anti-apoB antibody. B, Lanes 4 and 5 contain apoB-31, which does not react with the anti–apoA-I antibody, and lanes 6 and 7 contain the "contaminating" HDL that does react. An HDL lane is included as positive control.

View larger version (32K): [in this window] [in a new window]   Figure 2. Plasma decay curves of I-DLT/apoB-100 LDL and I-DLT–apoB truncation particles in NZW rabbits. Mean decays of labeled apoB-31, apoB-38.9, and apoB-43.7 particles are shown in three, five, and three rabbits, respectively. Results are mean±SE for each time point. The y axis is expressed as percentage of plasma radioactivity at 1 minute after injection.

View this table: [in this window] [in a new window]   Table 2. FCR of Human I-DLT–ApoB Truncation–Containing and I-DLT–ApoB-100–Containing Lipoproteins in NZW Rabbits

The intactness of the injected particles was maintained during the metabolic study. Aliquots of rabbit plasma collected at various time points from a rabbit injected with labeled LDL/apoB-31 were analyzed by gel permeation chromatography (Fig 3). The labeled apoB-31 lipoproteins eluted between LDL and HDL and displayed some heterogeneity of size. Heterogeneity of apoB-31 particle size was seen also on gel filtration chromatography of whole plasma (Fig 4) and on GGE of whole plasma (Fig 4, inset), suggesting that the heterogeneity was not an artifact of isolation. Since the starting material for isolation of apoB-31 particles was material that floated with HDL, only density gradient ultracentrifugation fractions 31 and beyond (Fig 4) were used as starting material for electrophoretic isolations. These particles eluting with small LDL- and HDL-sized particles are the same ones seen in Fig 3. Although particles remained intact in plasma, their size distributions changed over time, with a preponderance of smaller particles remaining at 24 hours (Fig 3).

View larger version (24K): [in this window] [in a new window]   Figure 3. The distribution in rabbit plasma of I-DLT–apoB-31 particles. Aliquots of plasma collected at 5 minutes and at 2, 8, and 24 hours were subjected to gel permeation chromatography. Dotted lines represent radioactivity due to I-DLT–apoB-31 particles. Dashed lines represent plasma cholesterol profiles, with elution positions of rabbit VLDL, LDL, and HDL indicated.

View larger version (22K): [in this window] [in a new window]   Figure 4. Distribution of apoB-100 and apoB-31 in the plasma of the apoB-100/apoB-31 heterozygote donor. The dashed line represents total cholesterol. Solid circles and triangles represent apoB-100 and apoB-31, respectively. The inset in the upper left quadrant shows a Western blot analysis of whole plasmas subjected to nondenaturing GGE (2% to 16%). Inset, lane 1: normal apoB-100/apoB-100; lane 2: apoB-100/apoB-43.7; lane 3: apoB-89/apoB-40; lane 4: apoB-100/apoB-38.9; lane 5: apoB-100/apoB-31; and lane 6: apoB-100/apoB-100. The membrane was probed with anti-apoB Mab C1.4.

Calculated lipoprotein distributions for liver and kidney are shown in Table 3 and for many more organs in Table 4. ApoB-100 LDL localized primarily to liver, with kidney:liver ratios of 0.1 to 0.3. By contrast, large proportions of apoB truncation–containing lipoproteins localized to kidney, with kidney:liver ratios ranging from 1.2 to 3.8. Here too, the method of isolation of lipoproteins did not matter (Table 3 and Fig 5). Of note, apoB-100 LDLs were much more avidly accumulated by the adrenals than were the apoB truncation–containing lipoproteins (Table 5).

View this table: [in this window] [in a new window]   Table 3. Distributions of Human I-DLT–ApoB-100 and I-DLT–ApoB Truncation–Containing Lipoproteins in Kidneys and Livers of NZW Rabbits

View this table: [in this window] [in a new window]   Table 4. Organ Distributions of Human ApoB-100–Containing LDLs Prepared by Ultracentrifugation or by Ultracentrifugation Plus Preparative Electrophoresis

View larger version (35K): [in this window] [in a new window]   Figure 5. Organ distributions of apoB-38.9– and apoB-100–containing particles. Both types of particles were isolated by combined ultracentrifugation and preparative electrophoresis. Results are expressed as dpm per organ divided by dpm recovered from the whole carcass x100. Solid bars represent a paired study, ie, dual labels 125I and 131I injected into one rabbit; open bars represent each label injected into a separate animal.

View this table: [in this window] [in a new window]   Table 5. Organ Distribution of I-DLT–ApoB-100 LDLs and I-DLT–Truncated ApoB Lipoproteins in NZW Rabbits

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
Our aims were to assess the plasma kinetics of disappearance of shorter apoB truncation–containing particles relative to apoB-100 LDLs isolated from the same heterozygous subjects and, even more important, to find the major organ loci of catabolism of truncation particles. We chose the shorter truncations because they do not possess the LDL receptor–recognition domain and therefore, in contrast with the long truncations apoB-89 and apoB-75, which we have studied previously,^{17 20 24} their clearance from plasma would not be expected to be mediated by LDL receptors.^{26 27} We chose to perform the study in rabbits because human apoB-100 particles are metabolized by rabbit tissues as would be predicted from available knowledge of the metabolism of apoB-containing lipoproteins.³⁵ Indeed, apoB-100 LDL, as expected, was removed primarily by liver, with high uptake by adrenals.³⁵

Each truncation-containing particle was removed faster from plasma and had a higher FCR than its normal apoB-100 counterpart (Fig 2 and Table 3). These data are compatible with the increased FCRs displayed by various apoB truncations studied in apoB truncation/ apoB-100 heterozygous humans in vivo. In each human heterozygote there are two populations of lipoproteins, and the apoB-89–,²⁰ apoB-75–,¹⁷ apoB-54.8–, apoB-52– (unpublished data), and apoB-43.7–containing particles³⁶ have higher FCRs than the FCRs of the apoB-100 lipoproteins in the same subjects. This suggests that the rabbit may be metabolizing truncated apoB–containing lipoproteins similarly to humans. There is an unexplained discrepancy between the low FCR of apoB-31 particles in vivo in humans²¹ and the rapid FCR in rabbits (Fig 2). The particles stayed intact in plasma during the 24-hour time of the experiments (Fig 3), ie, we were tracing lipoproteins. The fact that the apoB-100 particles accumulated in the adrenals at about 4 to 50 times the rate of the truncation particles is compatible with the LDL receptor–mediated removal of the former but not the latter (Table 5). Whereas the liver was the major organ of removal of apoB-100 particles, confirming our previous work,^{24 35} the kidney was the major organ of removal of the apoB-38.9 and apoB-43.7 truncation–containing particles (Tables 3 and 5). ApoB-31–containing particles were removed approximately equally by kidney and liver. Perhaps the length of the truncation may affect its organ distribution. It is unlikely that the change in organ sites of catabolism was due to nonspecific "damage" to or aggregation of the truncation-containing particles, because removal of lipoproteins by spleen was low (Table 5).

The method of isolation of apoB truncation–containing particles appears not to have noticeably altered them with respect to size (compare Figs 3 and 4). With respect to biological activity, apoB-100–containing LDLs isolated by ultracentrifugation plus electrophoresis behaved similarly to LDLs isolated only by ultracentrifugation, as judged by similar FCRs and organ distributions. The presence or absence of antioxidants in the isolation buffers appears not to have had a significant effect. Furthermore, when the experiment was repeated using the lipoproteins of donor apoB-38.9, with both apoB-100– and apoB-38.9–containing lipoproteins isolated by ultracentrifugation plus electrophoresis, the FCRs (Table 2) and organ distributions (Fig 5) were similar to those in the rest of the experiments. The removal of proteins by kidneys is not unprecedented. For example, about 30% of apoA-I is removed by kidney in normal subjects. That proportion increases in subjects with low levels of HDL.³⁷ Thus, the apoB truncations with absent LDL receptor domains appeared to be more rapidly removed and to accumulate in kidney. It remains to be determined which cell type in kidney is responsible or which, if any, receptors mediate the clearance of these short apoB truncation-bearing particles.

	Selected Abbreviations and Acronyms

 

apo = apolipoprotein DLT = dilactitol tyramine dpm = disintegrations per minute FCR = fractional catabolic rate FHBL = familial hypobetalipoproteinemia GGE = gradient gel electrophoresis I-DLT = 125I or 131I-DLT Mab = monoclonal antibody NZW = New Zealand White TCA = trichloroacetic acid

	Acknowledgments

 
This work was supported by NIH grant R0-1-HL-42460. We are grateful to Diana Tessereau, RN, for her good relations with our study subjects and for obtaining the blood samples, to Tom Kitchens and Tish Kettler for expert technical help, and to Mary Lou Rheinheimer for preparing the manuscript.

Received December 28, 1995; accepted August 8, 1996.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Schonfeld G. The hypobetalipoproteinemias. Annu Rev Nutr. 1995;15:23-34.[Medline] [Order article via Infotrieve]
2. Ricci B, Sharp D, O'Rourke E, Kienzle B, Blinderman L, Gordon D, Smith-Monroy C, Robinson G, Gregg RE, Rader DJ, Wetterau JR. A 30–amino acid truncation of the microsomal triglyceride transfer protein large subunit disrupts its interaction with protein disulfide-isomerase and causes abetalipoproteinemia. J Biol Chem. 1995;270:14281-14285.[Abstract/Free Full Text]
3. Sharp D, Blinderman L, Combs KA, Kienzle B, Ricci B, Wagersmith K, Gil CM, Turck CW, Bouma ME, Rader DJ, Aggerbeck LP, Gregg RE, Gordon DA, Wetterau JR. Cloning and gene defects in microsomal triglyceride transfer protein associated with abetalipoproteinemia. Nature. 1993;365:65-69.[Medline] [Order article via Infotrieve]
4. Shoulders CC, Brett DJ, Bayliss JD, Narcisi TME, Jarmuz A, Grantham TT, Leoni PRD, Bhattacharya S, Pease RJ, Cullen PM, Levi S, Byfield PGH, Purkiss P, Scott J. Abetalipoproteinemia is caused by defects of the gene encoding the 97 kDa subunit of a microsomal triglyceride transfer protein. Hum Mol Genet. 1993;2: 2109-2116.
5. Wetterau JR, Aggerbeck LP, Bouma ME, Eisenberg C, Munck A, Hermier M, Schmitz J, Gay G, Rader DJ, Gregg RE. Absence of microsomal triglyceride transfer protein in individuals with abetalipoproteinemia. Science. 1992;256:999-1001.
6. Roy CC, Levy E, Green PHR, Sniderman A, Letarte J, Buts JP, Orquin J, Brochu P, Weber AM, Morin CL, Marcel Y, Deckelbaum RJ. Malabsorption, hypocholesterolemia, and fat-filled enterocytes with increased intestinal apoprotein B; chylomicron retention disease. Gastroenterology. 1987;92:390-399.[Medline] [Order article via Infotrieve]
7. Patel S, Pessah M, Beucler I, Navarro J, Infante R. Chylomicron retention disease: exclusion of apolipoprotein-B gene defects and detection of mRNA editing in an affected family. Atherosclerosis. 1994;108:201-207.[Medline] [Order article via Infotrieve]
8. Linton MF, Farese RV Jr, Young SG. Familial hypobetalipoproteinemia. J Lipid Res. 1993;34:521-541.[Medline] [Order article via Infotrieve]
9. Young SG, Pullinger CR, Zysow BR, Hofmannradvani H, Linton MF, Farese RV, Terdiman JF, Snyder SM, Grundy SM, Vega GL, Malloy MJ, Kane JP. Four new mutations in the apolipoprotein-B gene causing hypobetalipoproteinemia, including 2 different frameshift mutations that yield truncated apolipoprotein-B proteins of identical length. J Lipid Res. 1993;34:501-507.[Abstract]
10. Schonfeld G. Inherited disorders of lipid transport. Endocrinol Metab Clin North Am. 1990;19:229-257.[Medline] [Order article via Infotrieve]
11. Welty FK, Ordovas J, Schaefer EJ, Wilson PWF, Young SG. Identification and molecular analysis of two apoB gene mutations causing low plasma cholesterol levels. Circulation. 1995;92:2036-2040.[Abstract/Free Full Text]
12. Averna M, Seip RL, Mankowitz K, Schonfeld G. Postprandial lipemia in subjects with hypobetalipoproteinemia and a single intestinal allele for apoB-48. J Lipid Res. 1993;34:1957-1967.[Abstract]
13. Leppert M, Breslow JL, Wu L, Hasstedt S, O'Connell P, Lathrop M, Williams RR, White R, Lalouel JM. Interference of a molecular defect of apolipoprotein B in hypobetalipoproteinemia by linkage analysis in a large kindred. J Clin Invest. 1988;82:847-851.
14. Hobbs HH, Leitersdorf E, Leffert CC, Cryer DR, Brown MS, Goldstein JL. Evidence for a dominant gene that suppresses hypercholesterolemia in a family with defective low density lipoprotein receptors. J Clin Invest. 1989;84:656-664.
15. Fazio S, Sidoli A, Vivenzio A, Maietta A, Giampaoli S, Menotti A, Antonini R, Urbinati G, Baralle FE, Ricci G. A form of familial hypobetalipoproteinemia not due to a mutation in the apolipoprotein-B gene. J lntern Med. 1991;229:41-47.
16. Aguilar-Salinas CA, Barrett PHR, Parhofer KG, Young SG, Tessereau D, Bateman J, Quinn C, Scholfeld G. Apoprotein B-100 production is decreased in subjects heterozygous for truncations of apoprotein B. Arterioscler Thromb Vasc Biol. 1995;15:71-80.[Abstract/Free Full Text]
17. Krul ES, Parhofer KG, Barrett PHR, Wagner RD, Schonfeld G. ApoB-75, a truncation of apolipoprotein-B associated with familial hypobetalipoproteinemia. J Lipid Res. 1992;33:1037-1050.[Abstract]
18. Parhofer KG, Barrett PHR, Bier DM, Schonfeld G. Determination of kinetic parameters of apolipoprotein-B metabolism using amino-acids labeled with stable isotopes. J Lipid Res. 1991;32:1311-1323.[Abstract]
19. Hardman DA, Pullinger CR, Hamilton RL, Kane JP, Malloy MJ. Molecular and metabolic basis for the metabolic disorder normotriglyceridemic abetalipoproteinemia. J Clin Invest. 1991;88:1722-1729.
20. Parhofer KG, Barrett PH, Bier D, Schonfeld G. Lipoproteins containing the truncated apolipoprotein, apoB-89, are cleared from human plasma more rapidly than apoB-100 containing lipoproteins in vivo. J Clin Invest. 1992;89:1931-1937.
21. Parhofer KG, Barrett PHR, Aguilar-Salinas CA, Schonfeld G. Positive linear correlation between the length of truncated apolipoprotein B and its secretion rate: in vivo studies in apo-B89, apoB-75, apoB-54.8, and apoB-31 heterozygotes. J Lipid Res. 1996;37:844-852.[Abstract]
22. Krul E, Kleinman Y, Kinoshita M, Pfleger B, Oida K, Law A, Scott J, Pease R, Schonfeld G. Regional specificities of monoclonal antihuman apolipoprotein B antibodies. J Lipid Res. 1988;29:937-947.[Abstract]
23. Milne RR, Theolis R Jr, Maurice R, Pease RJ, Weech PK, E Rassart E, Fruchart JC, Scott J, Marcel YL. The use of monoclonal antibodies to localize the low density lipoprotein receptor–binding domain of apolipoprotein B. J Biol Chem. 1989;264:19754-19760.[Abstract/Free Full Text]
24. Parhofer KG, Daugherty A, Kinoshita M, Schonfeld G. Enhanced clearance from plasma of low density lipoproteins containing a truncated apolipoprotein, apoB-89. J Lipid Res. 1990;31:2001-2007.[Abstract]
25. Young SG, Peralta FP, Dubois BW, Curtiss LK, Boyles JK, Witztum JL. Lipoprotein B37, a naturally occurring lipoprotein containing the amino-terminal portion of apolipoprotein B-100, does not bind to apolipoprotein B,E (low density lipoprotein) receptor. J Biol Chem. 1987;262:16604-16611.[Abstract/Free Full Text]
26. Welty FK, Seman L, Yen FT. Purification of the apolipoprotein B-67–containing low density lipoprotein particle and its affinity for the low density lipoprotein receptor. J Lipid Res. 1995;36:2622-2629.[Abstract]
27. Groenewegen WA, Averna MR, Pulai J, Krule ES, Schonfeld G. Apolipoprotein B-38.9 does not associate with apo(a) and forms two distinct HDL density particle populations that are larger than HDL. J Lipid Res. 1994;35:1012-1025.[Abstract]
28. Young SG, Hubl ST, Smith RS, Snyder SM, Terdiman JF. Familial hypobetalipoproteinemia caused by a mutation in the apolipoprotein B gene that results in a truncated species of apolipoprotein B (B-31). J Clin Invest. 1990;85:933-942.
29. McDonald HJ, Ribeiro LP. Ethylene and propylene glycol in the pre-staining of lipoproteins for electrophoresis. Clin Chim Acta. 1959;4:458-459.[Medline] [Order article via Infotrieve]
30. Nichols AV, Krauss RM, Musliner TA. Nondenaturing polyacrylamide gradient gel electrophoresis. Methods Enzymol. 1986;128:417-433.[Medline] [Order article via Infotrieve]
31. Strobel JL, Baynes JW, Thorpe SR. ¹²⁵I-glycoconjugate labels for identifying sites of protein catabolism in vivo: effect of structure and chemistry of coupling to protein on label entrapment in cells after protein degradation. Arch Biochem Biophys. 1985;240:635-645.[Medline] [Order article via Infotrieve]
32. Markwell MA, Haas SM, Bieber LL, Tolbert NE. A modification of the Lowry procedure to simplify protein determination in membrane and lipoprotein samples. Anal Biochem. 1978;87:206-210.[Medline] [Order article via Infotrieve]
33. Berman M. SAAM Manual. Washington, DC: US Department of Health, Education, and Welfare, 1978. US Public Health Service publication NIH 78-180.
34. Latimer HB, Sawin PB. Morphogenetic studies of the rabbit. Anat Rec. 1957;129:457-471.[Medline] [Order article via Infotrieve]
35. Daugherty A, Thorpe SR, Lange LG, Sobel BE, Schonfeld G. Loci of catabolism of ß-very low density lipoprotein in vivo delineated with a residualizing label, 125I-dilactitol tyramine. J Biol Chem. 1985; 260:14564-14570.
36. Srivastava NS, Noto D, Averna M, Pulai J, Srivastava RAK, Cole TG, Latour MA, Patterson BW, Schonfeld G. A new apolipoprotein B truncation (apoB-43.7) in familial hypobetalipoproteinemia: genetic and metabolic studies. Metabolism. 1996;145:1296-1304.
37. Horowitz BS, Goldberg IJ, Merab J, Vanni TM, Ramakrishnan R. Increased plasma and renal clearance of an exchangeable pool of apolipoprotein A-I in subjects with low levels of high density lipoprotein cholesterol. J Clin Invest. 1993;91:1743-1752.

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