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Data on postoperative chylous ascites (CA) after pediatric liver transplantation (LT) are scarce. This retrospective study was conducted to identify the incidence, risk factors, management, and outcomes of postoperative CA in a large single-center pediatric LT cohort (2000-2016). The study cohort comprised 317 LTs (153 living donors and 164 deceased donors) in 310 recipients with a median age of 2.7 years. The incidence of CA was 5.4% (n = 17), diagnosed after a median time of 10 days after LT. Compared with chylomicron detection in peritoneal fluid (the gold standard), a triglyceride cutoff value of 187 mg/dL in peritoneal fluid showed insufficient sensitivity (31%) for CA diagnosis. In univariate logistic regression analyses, ascites before LT, younger age, and lower weight, height, and height-for-age z score at LT were associated with CA. Symptomatic management of CA included peritoneal drain (100%) and diuretics (76%). Therapeutic interventions included very low-fat or medium-chain triglyceride-rich diets (94%) and intravenous octreotide (6%), leading to CA resolution in all patients. CA was associated with prolonged hospital length of stay (LOS; 40 days in the CA group versus 24 days in the non-CA group; P = 0.001) but not with reduced patient or graft survival rates after a median follow-up time of 14 years. In conclusion, CA in the pediatric LT recipient is a relatively uncommon complication associated with increased hospital LOS and morbidity. Measurement of chylomicrons is recommended in patients with ascites that is more severe or persistent than expected. Dietary interventions are effective in most patients., (Copyright © 2019 by the American Association for the Study of Liver Diseases.)

Background: The aim of this study was to investigate cholesterol and triglyceride levels in the chylomicron fraction of preterm infants at birth and during the early postnatal period., Methods: The subjects consisted of 133 infants (81 boys and 52 girls): 74 were term infants born at 37-41 weeks of gestation and 59 were preterm infants born at 29-36 weeks of gestation. Cholesterol and triglyceride in the chylomicron fraction were measured using high-performance liquid chromatography., Results: Compared with term infants, preterm infants had higher cholesterol and lower triglyceride in the chylomicron fraction, both in cord blood and at 1 month after birth. Thus, the chylomicron triglyceride/cholesterol ratio was significantly lower in preterm infants than in term infants in cord blood and at 1 month of age. On single regression analysis the chylomicron triglyceride/cholesterol ratio correlated positively with gestational age at birth (r = 0.331, P = 0.0003) and at 1 month (r = 0.221, P = 0.0119)., Conclusions: Preterm infants have a less-lipidated chylomicron composition at birth and at 1 month of age. Some prenatal factors may persist to influence chylomicron lipidation during the early postnatal period., (© 2018 Japan Pediatric Society.)

Background: Prolonged postprandial hypertriglyceridemia is a potential risk factor for cardiovascular diseases. In the context of obesity, this is associated with a chronic imbalance of lipid partitioning oriented toward storage and not toward β-oxidation., Objective: We tested the hypothesis that the physical structure of fat in a meal can modify the absorption, chylomicron transport, and further metabolic handling of dietary fatty acids., Design: Nine normal-weight and 9 obese subjects were fed 40 g milk fat (+[(13)C]triacylglycerols), either emulsified or nonemulsified, in breakfasts of identical composition. We measured the postprandial triacylglycerol content and size of the chylomicron-rich fraction, plasma kinetics of [(13)C]fatty acids, exogenous lipid oxidation with breath-test/indirect calorimetry, and fecal excretion., Results: The emulsified fat resulted in earlier (>1 h) and sharper chylomicron and [(13)C]fatty acid peaks in plasma than in spread fat in both groups (P < 0.0001). After 2 h, the emulsified fat resulted in greater apolipoprotein B-48 concentrations (9.7 ± 0.7 compared with 7.1 ± 0.9 mg/L; P < 0.05) in the normal-weight subjects than did the spread fat. In the obese subjects, emulsified fat resulted in a 3-fold greater chylomicron size (218 ± 24 nm) compared with the spread fat (P < 0.05). The emulsified fat induced higher dietary fatty acid spillover in plasma and a sharper (13)CO(2) appearance, which provoked increased exogenous lipid oxidation in each group: from 45% to 52% in normal-weight subjects (P < 0.05) and from 40% to 57% in obese subjects (P < 0.01)., Conclusion: This study supports a new concept of "slow vs fast fat," whereby intestinal absorption can be modulated by structuring dietary fat to modulate postprandial lipemia and lipid β-oxidation in humans with different BMIs. This trial was registered at clinicaltrials.gov as NCT01249378.

We developed a new method to evaluate the antioxidant effect of food products in a biological system. The antioxidant status of HepG2 cells was quantified after incubation with postprandial human chylomicrons after the intake of vegetable products. Three subjects consumed in a meal a vegetable soup containing 8.4 mg of β-carotene and 9 mg of lycopene. After 5 h, the subjects consumed a second meal without carotenoids. Blood samples were collected at basal time and every hour for 9 h. Chylomicrons were isolated from serum samples and used for both carotenoid quantification and HepG2 stimulation. Carotenoid in chylomicrons followed an inter-individual and bimodal carotenoid response. We demonstrated the antioxidant effect of postprandial chylomicrons in HepG2 at the time of maximum carotenoid concentration of chylomicrons with respect to basal time. This cell-based assay seems to be a useful method to evaluate the antioxidant effect of fruit and vegetable products in a biological system.

We previously established an analysis method for determining the cholesterol levels of five major lipoprotein classes [HDL, LDL, intermediate density lipoprotein (IDL), VLDL, and chylomicrons] in serum by an anion-exchange (AEX)-HPLC method, but lipoprotein(a) [Lp(a)], a well-known risk factor for atherosclerotic diseases, was not determinable. Therefore, we established new AEX-HPLC separation conditions for analyzing the cholesterol levels of six lipoprotein classes, including Lp(a). Serum lipoproteins were separated by HPLC with a diethylaminoethyl-ligand nonporous polymer-based column by elution with a stepwise gradient of the sodium perchlorate concentration. In this improved method, HDL, LDL, IDL, VLDL, chylomicrons, and Lp(a) were each eluted from the column. The cholesterol levels of the eluted lipoproteins were measured enzymatically by a postcolumn reaction. The within-day assay and between-day assay coefficients of variation for the lipoprotein cholesterol levels were in the ranges of 0.29-11.86% and 0.57-11.99%, respectively. The Lp(a) cholesterol levels determined by AEX-HPLC were significantly correlated with the amounts of Lp(a) protein measured by an immunoturbidimetry method available commercially (r = 0.9503, P < 0.0001). Taken together, this AEX-HPLC method may be effectively applied to the analysis of serum lipoproteins with high levels of Lp(a).

Periodic supplementation to infants and young children is encouraged in developing countries by the WHO. We investigated vitamin A (VA) in extrahepatic tissues of piglets after supplementation with retinyl acetate to determine long-term storage. 3, 4-Didehydroretinyl acetate (DRA) as a tracer was used to evaluate uptake from chylomicra in 4 h. Sows were fed a VA-depleted diet throughout pregnancy and lactation. Male castrated piglets (n = 28, 11.6 +/- 0.5 d) from these sows were weaned onto a VA-free diet for 1 wk, assigned to 4 groups, and dosed orally with 0, 26.2, 52.4, or 105 micromol VA. After 10 d, 5.3 micromol DRA was administered to determine short-term uptake of 3, 4-didehydroretinol (DR). Four hours later, piglets were killed; adrenal glands, kidney, lung, and spleen were collected and analyzed for retinol and DR. Retinol concentrations of kidney and adrenal gland were higher than control, but treated groups did not differ. Retinol concentration was highest in kidney (1.70-2.52 nmol/g), followed by adrenal gland (0.30-0.48 nmol/g), lung (0.15-0.21 nmol/g), and spleen (0.11-0.15 nmol/g). Total retinol in kidney and spleen was different among the groups (P < 0.05). Unesterified retinol was the major VA form; the percent retinol of total VA was lowest in adrenal glands. DR did not differ among the groups. In 4 h, the minimum estimated chylomicron contribution to tissue DR was 63-280% higher than the maximum DR exposure from retinol-binding protein. Constant dietary intake may be important in maintaining VA concentrations in extrahepatic tissues.

Background: Vitamin A deficiency is a public health problem in Cameroon. Data on the bioavailability of carotenoid in fruits currently consumed in Cameroon are scarce., Objective: To assess the systemic levels of carotenoids from mangoes and papaya consumed as juice, fresh or dried slices., Methods: Two groups of seven healthy volunteers (24 and 25 years of age; body mass index: 21 and 22 kg/m(2) respectively for subjects fed mango and papaya), were submitted to three types of meal treatments (juice, fresh and dried fruit). On the experiment day, meals served to fasting subjects during breakfast, included bread, yogurt and one of the three forms of fruit. All the treatments lasted only one day during which blood samples were collected three times; during fasting (T(0)), 4 h (T(4)) and 8 h (T(8)) after the test meal. The carotenoids and retinol contents were analysed by high-performance liquid chromatography method., Results: From the major carotenoids present in papaya and mangoes, lutein, alpha-carotene and beta-carotene were found in considerable amounts. Lycopene and cryptoxanthin that were the major carotenoids in papaya samples appeared in low amounts in the chylomicrons. Significant correlations were observed between these carotenoids (at T(0), T(4) and T(8)). The three forms of consumption contributed to the rise of serum retinol levels. A comparison between the three forms revealed that papaya and mangoes consumed in form of juice or fresh fruit are the best forms because they had higher bioavailability values., Conclusion: Association of these different forms of consumptions could lead to a better availability of these fruits throughout the year and therefore efficiently contribute to improve vitamin A status of the population.

Aim: We examined the effect of meal fatty acids on lipid and apolipoprotein concentrations of very low density lipoprotein (VLDL) and chylomicron/chylomicron remnants in lipid fractions with a Svedberg flotation rate (Sf) 60-400 and Sf 20-60., Methods and Results: Six healthy middle-aged men received in random order mixed meals enriched with saturated (SFA), polyunsaturated (PUFA) or monounsaturated (MUFA) fatty acids on 3 occasions. VLDL and chylomicron/chylomicron remnants in the lipid fractions were separated by immunoaffinity chromatography against apo B-100. In the Sf 60-400 chylomicron/chylomicron remnants, triacylglycerol and cholesterol concentrations were significantly lower following PUFA compared with SFA and MUFA (P < or = 0.05). Apolipoprotein (apo) E responses were significantly higher after SFA in chylomicron/chylomicron remnants and VLDL compared with PUFA and MUFA (P < 0.007). However, apo B responses (particle number) were higher following MUFA than SFA (P = 0.039 for chylomicron/chylomicron remnants). Composition of the chylomicron/chylomicron remnants (expressed per particle) revealed differences in their triacylglycerol and apo E contents; in the Sf 60-400 fraction, SFA-rich chylomicron/chylomicron remnants contained significantly more triacylglycerol than MUFA (P = 0.028), more apo E than PUFA- and MUFA-rich particles (P < 0.05) and in the Sf 20-60 fraction, more apo E than MUFA (P = 0.009)., Conclusion: There are specific differences in the composition of chylomicron/chylomicron remnants formed after saturated compared with unsaturated fatty acid-rich meals which could determine their metabolic fate in the circulation and subsequent atherogenicity.

The effects of two sunflower seed oil diets differing in oxidation levels (PV in oils 1 and 190 mequiv O2/kg) on lipoprotein TAG and total lipid oxidation were investigated in growing pigs. For 2 wk, two groups of 10 pigs were fed either of the diets, after which blood samples were collected. A method based on RP-HPLC and electrospray ionization-MS was used for the analysis of oxidized TAG molecules in chylomicrons and VLDL. The baseline diene conjugation method was used for the estimation of in vivo levels of lipoprotein lipid oxidation. TAG molecules with a hydroxy, an epoxy, or a keto group attached to a FA, as well as TAG core aldehydes were detected in the samples. Typically, lipoprotein TAG and total lipids were more oxidized in the pigs fed on the oxidized oil compared with those fed on nonoxidized oil. Oxidation of dietary fat was thus reflected in the lipoprotein oxidation, which confirmed our earlier findings.

We investigated the dietary influence of low and high levels of fish oil, supplemented with or without dietary cholesterol, on the plasma lipoprotein profile in Bio F1B hamsters, a model susceptible to diet-induced hyperlipidaemia. The MIX diet, a diet supplemented with a mixture of lard and safflower-seed oil, was used as the control diet to maintain the saturated MUFA and PUFA levels similar to the fish-oil diet. The animals were fed the specific diets for 2 weeks and fasted for 14 h before killing. The plasma from the animals fed high levels of fish oil was milky and rich in chylomicron-like particles. The plasma total cholesterol, VLDL- and LDL-cholesterol and -triacylglycerol concentrations were significantly higher, whereas HDL-cholesterol was lower in hamsters fed fish oil compared with the MIX-diet-fed hamsters. Increasing the amount of fat in the diet increased plasma lipids in both the fish-oil- and the MIX-diet-fed hamsters; however, this hyperlipidaemic effect of dietary fat level was greater in the hamsters fed the fish-oil diet. The hepatic lipid concentrations were not dramatically different between the fish-oil-fed and the MIX-diet-fed hamsters. However, the hepatic LDL-receptor mRNA levels were significantly low in the fish-oil-fed hamsters compared with the MIX-diet-fed hamsters. Increasing the amount of fish oil in the diet further decreased the hepatic LDL-receptor mRNA expression. It is concluded that F1B hamsters are susceptible to fish-oil-induced hyperlipidaemia, especially at high fat levels, and this increase is partially explained by the inhibition of hepatic LDL-receptor mRNA expression.

Persisting chylomicron remnants have been linked to premature atherosclerosis. The analysis of chylomicron remnant concentrations by an oral triglyceride tolerance test, however, is time-consuming for the study subjects and requires large resources in the laboratory. Therefore, only small numbers of subjects have been studied in the past. The aim of this study was to elucidate the prevalence of elevated chylomicron remnants, to identify effectors of chylomicron remnant clearance and to compare chylomicron remnants in the prediction of coronary artery disease with other risk factors. We applied a novel oral triglyceride tolerance test to 423 patients (368 males, 55 females) with a confirmed diagnosis of coronary artery disease (CAD) and to 390 control subjects (295 males, 95 females) in a case-control setting. This study revealed that elevated chylomicron remnant concentrations (retinyl esters > 1.5 micromol/l) are present in 20% of all subjects. Male gender, the apolipoprotein E2 isoform, and higher body mass index were associated with increased chylomicron remnant concentrations. However, chylomicron remnants were lower and plasma triglycerides higher in patients with CAD. We conclude that screening for a delayed clearance of chylomicron remnants is of little clinical value in CAD.

Background: The consumption of a synthetic, randomized, stearic acid-rich triacylglycerol results in decreased postprandial lipemia and activated factor VII (FVII:a) compared with cocoa butter (a nonrandomized, symmetrical, stearic acid-rich triacylglycerol). It was hypothesized that this difference is a consequence of the differences in structure between the 2 triacylglycerols., Objective: The objective was to test whether the consumption of randomized cocoa butter decreases postprandial lipemia and FVII:a., Design: A randomized crossover trial with 17 male subjects compared the effects of meals containing 50 g fat provided as a symmetrical (cocoa butter) or an asymmetrical (randomized cocoa butter) triacylglycerol on postprandial changes in lipids, chylomicron composition, and FVII:a., Results: After randomization, the postprandial area under the curve for plasma triacylglycerol decreased by 41% (P < 0.01). At 3 h the plasma concentrations of triacylglycerol, palmitic acid, stearic acid, and oleic acid were 26%, 18%, 34%, and 19% lower, respectively. The proportion of oleic acid in the sn-2 position of the chylomicron triacylglycerol was reduced from 67.4 mol% to 35.9 mol% and resulted in an increase in the proportion of stearic acid in the sn-2 position from 9.2 mol% to 25.4 mol%. FVII:a did not increase 6 h after consumption of the randomized cocoa butter (: 1.2; 95% CI: -2.7, 4.6 U/L) but increased significantly (: 7.7; 95% CI: 2.5,12.9 U/L) 6 h after consumption of the unrandomized cocoa butter., Conclusions: Symmetrical stearic acid-rich triacylglycerol with oleic acid in the sn-2 position appears to be absorbed more rapidly than is asymmetrical triacylglycerols with long-chain saturated fatty acids in the sn-2 position, which leads to activation of FVII.

Postprandial dyslipidemia may be a major cause of atherosclerosis in diabetes. Microsomal triglyceride transfer protein (MTP) is essential for the synthesis of the chylomicron particle in the intestine and very low-density lipoprotein (VLDL) in the liver. The purpose of the present study was to examine the effect of diabetes on MTP mRNA expression in a rabbit model of diabetes, which develops atherosclerosis. Male New Zealand white rabbits were fed a 0.5% cholesterol diet. Diabetes was induced with alloxan monohydrate. The lymphatic duct was cannulated and lymph collected for isolation of chylomicrons by ultracentrifugation. Apolipoprotein B48 (apo B48) and apo B100 were separated by polyacrylamide gradient gel electrophoresis and quantified by densitometry. MTP mRNA was determined in liver and intestine by RNase protection analysis, and MTP activity was measured. Diabetic animals had significantly increased plasma triglyceride and decreased high-density lipoprotein (HDL) cholesterol (P <.05). They also secreted more lymph chylomicron apo B48 and apo B100 (P <.05) and more lymph chylomicron total and esterified cholesterol/h (P <.05). Lymph chylomicron particles in the diabetic animals contained significantly less lipid/apo B (P <.05). Intestinal MTP activity and mRNA were significantly higher in diabetic compared with control rabbits (0.07 +/- 0.01 v 0.04 +/- 0.015 fluorescent units/microg microsomal protein and 66 +/- 21 v 37 +/- 11 amol MTP mRNA/microg total RNA (P <.005). There was no difference in MTP activity or mRNA expression in the liver. This study suggests that MTP may play an important role in the postprandial dyslipidemia of diabetes., (Copyright 2002, Elsevier Science (USA). All rights reserved.)

Postprandial composition of chylomicron triacylglycerols (TAG) and their clearance may be affected by the molecular weight of TAG, their fatty acid (FA) combinations and the positional distribution of FA in TAG. Delayed postprandial TAG clearance is a risk factor for cardiovascular disease. However, due to the complexity of traditional analysis methods, the composition of individual TAG molecules is frequently overlooked. In this study, chylomicron TAG molecular weight distribution and regioisomerism were followed in 10 healthy female volunteers after two fat loads with identical FA composition but different positional distributions (palm oil and transesterified palm oil). An efficient tandem mass spectrometric method of analysis was applied. During the 6-h observation period, the relative concentrations of TAG with 48:2 [48 acyl carbons and 2 double bonds (ACN:DB)], 50:3 and 50:2 decreased, whereas the proportions of 48:0 (tripalmitin), 52:3 and 54:4 remained constant and the proportion of 54:3 (triolein) increased (P < 0.05). The existence of seven regioisomers containing palmitic, oleic and linoleic acids in different sn-positions was studied. The amount of 1,3-dipalmitoyl-2-oleoyl-sn-glycerol was less (P < 0.05) 1.5 h postprandially than at 2-5 h after palm oil, and less (P < 0.05) at 1.5 h than at 2-6 h after transesterified palm oil. This may be an indication of a loss of palmitic acid in the gut. Taken together, TAG molecular weight composition and to a lesser extent, positional distribution, seem to affect the rates of chylomicron TAG clearance in humans.

Background: The results of epidemiologic studies have consistently shown associations between dietary intake or plasma carotenoid status and incidence of cancers and cardiovascular and eye diseases., Objective: The aim was to assess whether vegetable-borne carotenoids (lycopene, lutein, and beta-carotene) compete for intestinal absorption and whether this affects the plasma status of carotenoids in the medium term (ie, after 3 wk)., Design: During 3-wk periods separated by 3-wk washout periods, 20 women were supplemented with either 96 g tomato purée/d (14.98 mg lycopene + 1.50 mg beta-carotene), 92 g cooked chopped spinach/d (11.93 mg lutein + 7.96 mg beta-carotene), 96 g tomato purée/d + 92 g chopped spinach/d, 96 g tomato purée/d + 2 lutein pills (12 mg lutein), or 92 g chopped spinach/d + 1 lycopene pill (15 mg lycopene). Plasma carotenoids were measured before and after each supplementation period. The subjects also participated in postprandial experiments in which they ingested meals containing double amounts of the supplements described above. Carotenoids were measured in chylomicrons to assess the interaction of carotenoids on absorption., Results: Adding a second carotenoid to a meal that provided a first carotenoid diminished the chylomicron response to the first carotenoid. However, cosupplementation with a second carotenoid of a diet supplemented with a first carotenoid did not diminish the medium-term plasma response to the first carotenoid., Conclusion: Consumption of carotenoids from different vegetable sources does not diminish plasma carotenoid concentrations in the medium term, despite the finding in postprandial testing of competitive inhibitory interactions among different carotenoids.

We have previously demonstrated that diabetes is associated with an increase in intestinal microsomal triglyceride transfer protein (MTP) mRNA in both the rat and rabbit models. The present study was designed to investigate the relationship between MTP expression and chylomicron assembly in an insulin resistant non-diabetic animal model. Ten insulin resistant Zucker obese fa/fa rats and ten lean fa/minus sign rats were examined at 8-10 weeks of age. The lymph duct was cannulated and lymph collected for 4 h. Lymph chylomicrons were isolated by ultracentrifugation and their composition determined. RNA was extracted from intestinal mucosa and from the liver. MTP mRNA was measured using the RNase protection assay. Blood sugar in the fatty rats was significantly higher (6.3 +/-1.2 vs. 5.4 +/-0.4 P<0.05) and plasma insulin was almost six times that of the lean rats (P<0.001). Plasma cholesterol and phospholipid but not triglyceride were significantly increased in the obese animals (P<0.01). Obese animals secreted significantly more lymph chylomicron apo B48 (0.05 +/-0.02 vs. 0.02 +/-0.01 mg/h P<0.005), triglyceride (9.7 +/-5.3 vs. 3.8+/-1.9 mg/h P<0.005) and phospholipid (1.5 +/-0.7 vs. 0.4 +/-0.3 mg/h P<0.001). The only difference in the chylomicron particle composition between the two groups was a significant increase in phospholipid (P<0.01). Intestinal MTP mRNA expression was significantly higher in the fatty compared to the lean rats (22.1 +/-9.5 vs. 7.8+/-5.6 amol MTP mRNA/microg total RNA P<0.001) as was hepatic MTP mRNA expression (6.9 +/-3.5 vs. 3.4 +/-1.5 amol MTP mRNA/microg total RNA, P<0.01). Thus in this animal model of insulin resistance, increased MTP, which was associated with increased chylomicron particle number, may play a crucial role in the development of atherosclerosis.

Persisting chylomicron remnant concentrations have been linked to premature atherosclerosis. The analysis of persisting chylomicron remnant concentrations by an oral triglyceride tolerance test, however, is time-consuming for the study subjects and requires large resources in the laboratory. Therefore, only small numbers of subjects have been studied in the past. We describe major improvements of the testing procedure in regard of composition of the fatty meal, of patient testing, and measurement of postprandial remnants. Shifting the time of the (ready-to-use) fatty drink from the morning hours to bedtime was well accepted by the study subjects and allowed the analysis of blood samples drawn at the morning with minimal impact on the participants' time and with minimal interferences by confounding factors (e.g. smoking, additional food intake, physical activity). Chylomicron remnants were measured by fluorometry of the supernatant after ultracentrifugation. This procedure was sensitive, was specific for chylomicron remnants, and was easy to perform. The biological validity of the improved procedure was evaluated by studying type III hyperlipoproteinemia patients and normolipemic apolipoprotein (Apo) E2 homozygotes. In conclusion, this improved test permits the rapid testing for persisting chylomicron remnants in the clinical routine and in large epidemiological studies.

Background: The affinity of intestinal fatty acid binding protein (FABP) for fatty acids is regulated by the polymorphism at codon 54 of the FABP2 gene (alanine-to-threonine shift). We found earlier that the threonine-encoding allele (Thr54) is associated with an increased postprandial lipemic response., Objective: We studied the postprandial responses of individual fatty acids in subjects homozygous for the Thr54 or alanine-encoding allele (Ala54)., Design: Oral-fat-loading tests were performed in 8 subjects homozygous for Thr54 and in 7 subjects homozygous for Ala54., Results: The postprandial responses of most of the 14-18-carbon fatty acids in chylomicron and VLDL triacylglycerols were significantly elevated in the Thr54 homozygotes whereas the relative increases in these fatty acids were not significantly different in both groups. The amounts of 20- and 22-carbon polyunsaturated fatty acids started to increase later than the amounts of shorter ones after the test meal, and the differences between the groups were mostly insignificant. The responses of chylomicron fatty acids correlated positively with postprandial insulin response in the Thr54 homozygotes and inversely in the Ala54 homozygotes. VLDL fatty acid responses correlated with fasting triacylglycerol concentrations in the Ala54 homozygotes but not in the Thr54 homozygotes., Conclusion: The threonine-encoding allele of the FABP2 gene is associated with an increased postprandial response of 14-18-carbon fatty acids but not with changes in the relative amounts of individual fatty acids introduced to chylomicron triacylglycerols.

In previous work we identified a transfer/diffusion process occurring in the postprandial state that more or less contributes to the accumulation of beta-VLDL in familial dysbetalipoproteinemia (FD). Here we present a new theoretical concept underlying chylomicron processing developed on the basis of extended quantitative analyses of fat loading experiments, with both vitamins A and E, performed in patients with familial combined hyperlipidemia (FCH) in comparison to patients with FD and control subjects. Recovery of triglycerides from the fat load in the plasma triglyceride pool was <4%, indicating a very effective lipolysis process with an active remnant generation. Vitamin A from the fat load was, over 48 h, quantitatively recovered in the plasma lipoprotein pool; vitamin E was recovered to 2241%. Nevertheless, transfer/diffusion of both vitamins showed similar patterns. At equilibrium, their contents correlated strongly with the lipoprotein concentrations, the slopes being similar for control subjects and both groups of patients. Only in those FD patients with the highest lipid values, did the vitamin A/lipoprotein mass ratio in the Sf>100 fraction deviate from the total group mean. In the Sf 15-100 fraction, most specific for 'remnants', vitamin A/cholesterol ratios for all subjects were uniform proving that beta-VLDL formation is a thermodynamic process regulated by concentration gradients and the lipophilicity of lipoprotein constituents, not a typical feature for patients with FD. In patients with FD, vitamin A in the plasma pool was recovered excessively (276%) in line with recognition in various pools as a result of the transfer/diffusion process in plasma.

Polarized Caco-2 cells can synthesize two distinct density classes of lipoproteins, i.e. chylomicron/VLDL (d<1.006 g/ml) or IDL/LDL density (1.009

Chyloperitoneum is a potential cause of colic in horses. Although rare in horses, chyloperitoneum can develop secondary to tearing of mesenteric adhesions and rupture of mesenteric lymphatic vessels. The prognosis for horses with chyloperitoneum depends on the underlying cause and the response to treatment.

Chylomicrons, the vehicles for the transport of exogeneous triglycerides and cholesterol in the lymph and the blood, were characterized by their size from dynamic light scattering measurements. To achieve an appropriate resolution, correlation data were collected over several hours. Analysis was performed with an extended version of the regularization method CONTIN, and special attention was given to errors in the experimental baseline and to randomness of the residuals. The solutions selected by means of Fisher's F-test by CONTIN agreed with those obtained with the stability plot of Schnablegger and Glatter, when in the case of data of lower statistical accuracy the solution was taken from the lower part of the confidence interval of the F-test. The intensity-weighted size distributions indicated two classes of particle, their mean diameters being 100-140 nm and 330-350 nm. The ability to resolve two peaks of such a size ratio is demonstrated. The numbers of particles associated with the two peaks were estimated by means of the scattering properties of the particles, which showed that the overwhelming majority were small ones. This estimation also suggested that the mean size of the first peak of the number distribution is significantly smaller than the typical size of chylomicrons. This was consistent with the finding that the sample contained not only apolipoprotein B-48 but also a similar amount of apolipoprotein B-100, which is associated with lipoproteins of smaller size. The larger particles of the second peak are probably dietary triglyceride-rich chylomicrons.

We report the development of chylous ascites in a neonate as an uncommon complication during continuous peritoneal dialysis. Cloudy dialysis fluid containing many white blood cells might confuse the diagnosis of chylous ascites with infective peritonitis and result in inappropriate use of antibiotics. Resolution may be critical, since chyle removal during dialysis may result in profound immunosuppression and malnutrition due to lymphocyte and fat losses. After 4 weeks on a modified diet, the chyle leak resolved. The patient returned to breast milk and continues nighttime continuous-cycle peritoneal dialysis without further chyle leak.

The formation of chylomicrons by the intestine is important for the absorption of dietary fats and fat-soluble vitamins (e.g., retinol, alpha-tocopherol). Apo B plays an essential structural role in the formation of chylomicrons in the intestine as well as the VLDL in the liver. We have developed genetically modified mice that express apo B in the liver but not in the intestine. By electron microscopy, the enterocytes of these mice lacked nascent chylomicrons in the endoplasmic reticulum and Golgi apparatus. Because these mice could not form chylomicrons, the intestinal villus enterocytes were massively engorged with fat, which was contained in cytosolic lipid droplets. These mice absorbed D-xylose normally, but there was virtually no absorption of retinol palmitate or cholesterol. The levels of alpha-tocopherol in the plasma were extremely low. Of note, the absence of chylomicron synthesis in the intestine did not appear to have a significant effect on the plasma levels of the apo B-containing lipoproteins produced by the liver. The mice lacking intestinal apo B expression represent the first genetic model of defective absorption of fats and fat-soluble vitamins and provide a useful animal model for studying nutrition and lipoprotein metabolism.

Purpose: We seek to establish normative values for the volume of postoperative neck drainage from patients undergoing ablative oncologic procedures that include a neck dissection and to analyze neck drainage for lipid content to establish guidelines that may be helpful in identifying chylous fistula when this diagnosis is not clinically straightforward., Patients and Materials: Neck drainage obtained through continuous suction percutaneous drainage catheters was evaluated following 23 neck dissections performed on 19 patients. In every case, either radicle or modified type I neck dissection was performed. The volume of drainage was quantitated on a day-to-day basis. In a separate group of 27 patients undergoing neck dissection, neck drainage was compared with serum levels of triglyceride, cholesterol, and chylomicron content., Results: The mean duration of neck drainage was 5 days. Maximum drainage (160 mL) was noted on the first day and dropped daily to less than 10 mL by the fifth postoperative day. A statistically significant difference between serum and neck drainage triglyceride and cholesterol content was observed in nearly all cases. Neck drainage fat content was lower than that noted in serum in nearly all cases. Chylomicron content of 4% was encountered in neck drainage., Conclusions: This study provides normative data on lipid content of neck drainage. With only a rare exception, the triglyceride and cholesterol levels are higher in the serum than in the neck drainage. A triglyceride level of 100 mg/dL seems to be the upper limit of normal (mean plus 1 standard deviation). A low level of chylomicron (> 4%) is consistent with normal healing and may be due to breakdown of fatty tissue.

The lipolysis of rat chylomicron polyenoic fatty acid esters with bovine milk lipoprotein lipase and human hepatic lipase was examined in vitro. Chylomicrons obtained after feeding fish oil or soy bean oil emulsions were used as substrates. The lipolysis was followed by gas chromatography or by using chylomicrons containing radioactive fatty acids. Lipoprotein lipase hydrolyzed eicosapentaenoic (20:5) and arachidonic acid (20:4) esters at a slower rate than the C14-C18 acid esters. More 20:5 and 20:4 thus accumulated in remaining tri- and diacylglycerols. Eicosatrienoic, docosatrienoic and docosahexanoic acids exhibited an intermediate lipolysis pattern. When added together with lipoprotein lipase, hepatic lipase increased the rate of lipolysis of 20:5 and 20:4 esters of both tri- and diacylglycerols. Addition of NaCl (final concentration 1 M) during the course of lipolysis inhibited lipoprotein lipase as well as the enhancing effect of hepatic lipase on triacylglycerol lipolysis. Hepatic lipase however, hydrolyzed diacylglycerol that had already been formed. Chylomicron 20:4 and 20:5 esters thus exhibit a relative resistance to lipoprotein lipase. It is suggested that the tri- and diacylglycerol species containing these fatty acids may accumulate at the surface of the remnant particles and act as substrate for hepatic lipase during a concerted action of this enzyme and lipoprotein lipase.

Numerous investigations have been performed in which volunteers have received infusions of triglyceride-rich lipoproteins without apparent screening of the infusates for bacterial endotoxin. This study was designed to examine the capacity of triglyceride-rich lipoproteins to mask their endotoxin content in vitro as measured by a chromogenic modification of the standard Limulus assay. Lipoproteins and lipoprotein-deficient plasma were isolated from normal human plasma by sequential ultracentrifugation under apyrogenic conditions. Individual lipoproteins and a synthetic lipid emulsion were suspended in 10% lipoprotein-deficient plasma. Samples were then incubated at 37 degrees C for 4 hours with increasing concentrations of E. coli (055:B5) endotoxin and assayed for detectable endotoxin activity. The capacity to inhibit detection of endotoxin in 10% lipoprotein-deficient plasma was significantly increased (10 to 100 times) by the addition of VLDL (1.0 mg triglyceride/ml), chylomicrons (1.0 mg triglyceride/ml), or the synthetic lipid emulsion (2.5 mg triglycerides/ml). These data demonstrate that triglyceride-rich lipoproteins, and the synthetic lipid emulsion, can markedly inhibit the detection of endotoxin by the Limulus assay in vitro. In addition to the potential of harm to experimental subjects, infusion of endotoxin could vitiate kinetic studies by direct alteration of lipoprotein metabolism and by inducing changes in hepatic blood flow. Thus experimental protocols that involve the infusion of humans with triglyceride-rich lipoproteins should include detailed testing for the presence of endotoxin.

Dietary fats are converted into chylomicron triacylglycerols via the 2-monoacylglycerol and phosphatidic acid pathways of acylglycerol formation. In view of the known positional and fatty acid specificity of the acyltransferases, the triacylglycerol structures resulting from the two pathways would be expected to differ, but this has not been demonstrated. We have performed stereospecific analyses on the chylomicron triacylglycerols from rats fed menhaden oil and the corresponding fatty acid alkyl esters, which would be expected to be assimilated via the monoacylglycerol and the phosphatidic acid pathways, respectively. The results show a remarkable similarity between the two triacylglycerol types in the fatty acid composition of the sn-1 and sn-3 positions, along with marked differences in the composition of the sn-2 positions. The triacylglycerols from rats fed oil retained about 85% of the original fatty acids in the sn-2 position, including a high proportion of the long chain polyunsaturates (e.g., 5-7% 20:5 and 4-5% 22:6). The triacylglycerols from rats fed the alkyl ester contained large amounts of endogenous fatty acids in the sn-2 position (e.g., 18% 16:1, 14% 18:1, 14% 18:2, and 2.5% 20:4), which approximated the composition of the sn-2 position of the presumed phosphatidic acid intermediates. The sn-1 position contained a much higher proportion of polyunsatured fatty acids (e.g., 12-13% 20:5, 5-6% 22:6) than the sn-2 position (e.g. 2-3% 20:5, 0-0.6% 22:6) of triacylglycerols from rats fed the ester. We conclude that the chylomicron triacylglycerols arising via the 2-monoacylglycerol and the phosphatidic acid pathways differ mainly in the composition of the fatty acids in the sn-2 position. The similarity in the acids of the sn-1 and sn-3 positions of the chylomicron triacylglycerols from rats fed oil or ester is consistent with a hydrolysis of the acylglycerol products of the phosphatidic acid pathway to 2-monoacylglycerols prior to reconversion to triacylglycerols via the monoacylglycerol pathway and secretion as chylomicrons.

Apolipoprotein (apo) E and the two B apolipoproteins, apoB48 and apoB100, are important proteins in human lipoprotein metabolism. Commonly occurring polymorphisms in the genes for apoE and apoB result in amino acid substitutions that produce readily detectable phenotypic differences in these proteins. We studied changes in apoE and apoB phenotypes before and after liver transplantation to gain new insights into apolipoprotein physiology. In all 29 patients that we studied, the postoperative serum apoE phenotype of the recipient, as assessed by isoelectric focusing, converted virtually completely to that of the donor, providing evidence that greater than 90% of the apoE in the plasma is synthesized by the liver. In contrast, the cerebrospinal fluid apoE phenotype did not change to the donor's phenotype after liver transplantation, indicating that most of the apoE in CSF cannot be derived from the plasma pool and therefore must be synthesized locally. The apoB100 phenotype (assessed with immunoassays using monoclonal antibody MB19, an antibody that detects a two-allele polymorphism in apoB) invariably converted to the phenotype of the donor. In four normolipidemic patients, we determined the MB19 phenotype of both the apoB100 and apoB48 in the "chylomicron fraction" isolated from plasma 3 h after a fat-rich meal. Interestingly, the apoB100 in the chylomicron fraction invariably had the phenotype of the donor, indicating that the vast majority of the large, triglyceride-rich apoB100-containing lipoproteins that appear in the plasma after a fat-rich meal are actually VLDL of hepatic origin. The MB19 phenotype of the apoB48 in the plasma chylomicron fraction did not change after liver transplantation, indicating that almost all of the apoB48 in plasma chylomicrons is derived from the intestine. These results were consistent with our immunocytochemical studies on intestinal biopsy specimens of organ donors; using apoB-specific monoclonal antibodies, we found evidence for apoB48, but not apoB100, in donor intestinal biopsy specimens.

Monosaccharide composition was determined in apolipoprotein B-48 (apoB) of chylomicrons of rat mesenteric lymph. Chylomicrons were separated into three fractions based on density. Triglyceride and apolipoprotein content were determined in each. ApoB was isolated and quantified using precipitation with isopropanol. Chylomicrons were collected in lymph under normal conditions, and with Poloxalene 2930 when chylomicron secretion was inhibited. Most of the triglyceride was carried in the least dense fraction, while the highest apoB content was in the most dense fraction under normal conditions. Mannose and galactosamine contents of apoB were similar in all fractions while contents of both glucosamine and galactose were highest in the least dense fraction. When chylomicron secretion was inhibited by Poloxalene, the amount of triglyceride recovered in the least dense fraction was significantly reduced. Despite the inhibition of lipid transport in the least dense fraction of chylomicrons by Poloxalene, there was little change in apoB recoveries and in the relative content of various monosaccharides in the apoB from each of the three fractions as compared to results obtained during lipid absorption under normal conditions. In conclusion, carbohydrate composition of apoB of chylomicrons is heterogeneous and varies with chylomicron density.

The lipids extracted from chylomicrons, chylomicron remnants generated in vivo and hepatic-lipase-treated chylomicrons were emulsified by sonication. These emulsified particles retained the capacity of the native lipoproteins to be differentiated by the liver in vivo, i.e. only the particles derived from remnant and hepatic-lipase-treated chylomicron lipids were efficiently taken up by the liver. To investigate the role of phospholipids in this differentiation process, the phospholipids of all three lipoprotein preparations were separated from the remaining lipids by silicic acid chromatography. The phospholipid-free lipid fraction of chylomicrons was then emulsified with the phospholipids derived from each of the three lipoprotein preparations. Only the particles emulsified with phospholipids derived from remnants and hepatic-lipase-treated chylomicrons were efficiently taken up by the liver in vivo. These results support the proposition that phospholipids modulate the hepatic differentiation between chylomicrons and remnants in vivo.

The lipoprotein electrophoregrams and the cholesterol and triglyceride levels of the pleural fluid were evaluated for patients with chylous pleural effusions, as defined by the presence of a distinctive band of chylomicrons on the lipoprotein electrophoregram, and in patients with nonchylous effusions of various causes. One hundred forty-one patients were studied during a 3-year period. The chylous effusions had strikingly higher triglyceride levels (median 249, range 49 to 2,270 mg/dl) than the nonchylous group (median 33, range 13 to 107 mg/dl); there were no significant differences in cholesterol or protein between the two groups. The gross description of the fluid was a poor indicator of its origin, being described as consistent with chyle in less than 50% of cases of chylous effusions. The triglyceride values distinguished chylous effusion from nonchylous effusion; values greater than 110 mg/dl are highly suggestive of a chylous effusion. Equivocal cases--triglyceride values between 50 and 110 mg/dl--required lipoprotein analysis. Pleural effusions of undetermined cause, regardless of gross appearance of the fluid, require that a screening triglyceride value be obtained to rule out a chylous effusion.

Lipoprotein lipase and hepatic lipase activities are very low in tissues of mice born with genetic combined lipase deficiency (cld/cld). Consequently, if allowed to suckle, the mice develop severe hyperlipemia and die within 3 days. The ultrastructure of capillaries and parenchymal cells in tissues that normally contain lipoprotein lipase and hepatic lipase was studied in tissues from cld/cld and unaffected mice 6 to 24 hours of age. Capillaries in tissues from suckled cld/cld mice were packed with numerous abnormally shaped chylomicrons. There was close contact between surfaces of chylomicrons and the luminal plasma membrane of endothelium. Chylomicrons were sometimes found between endothelial cells and in the subendothelial space in heart, lung, and liver, and in the lumen of lung alveoli. In contrast, capillaries of suckled unaffected mice contained very few chylomicrons, and the subendothelial spaces and lung alveoli were free of chylomicrons. Myocytes of diaphragm and heart from suckled cld/cld mice did not contain lipid droplets, whereas brown adipocytes contained a few small droplets. Parenchymal cells in diaphragm, heart, brown adipose tissue, and lung from suckled unaffected mice contained numerous large lipid droplets. Hepatocytes of suckled cld/cld mice contained small irregularly shaped lipoprotein particles (100 A) in endoplasmic reticulum and Golgi, numerous large lysosomes containing small lipoprotein particles, lipid spheres and lamellar structures, and no intracellular lipid droplets, whereas hepatocytes of suckled unaffected mice contained larger lipoprotein particles (400 A), large lipid droplets, and very few lysosomes. Triacylglycerol of chylomicrons from cld/cld mice was readily hydrolyzed by bovine lipoprotein lipase in vitro, and this effect was not augmented by heat-inactivated serum, indicating that the chylomicrons contained adequate amounts of apoprotein C-II. Thus, the large amount of chylomicrons in capillaries and small amount of lipid droplets in cells of suckled cld/cld mice reflect the very low level of lipoprotein lipase activity in these animals. The findings in hepatocytes indicate that lipoprotein metabolism in liver is markedly disturbed in cld/cld mice.

Electrophoresis of rat apolipoprotein B (apoB) on 5% polyacrylamide gels in the presence of NaDodSO4 separates three major components: PI, which comigrates with human low density lipoprotein (LDL) apoB; PII, a slightly faster-moving satellite band; and PIII, which migrates somewhat more slowly than myosin heavy chain. The proportion of PIII decreases with increasing density of the parent rat lipoprotein, from 90% an 70%, respectively, in chylomicrons and very low density lipoproteins (VLDL), to 7% in the major LDL2 (density 1.038-1.063 g/ml) fraction. A major component that comigrates with rat PIII is a marker for human chylomicron apoB, being absent from human VLDL, intermediate density lipoprotein (IDL), and LDL. Preliminary immunological and peptide mapping data show that rat apoB PI and PIII are closely related structurally, with the latter possibly being a large fragment of the former. Both peptides are synthesized in rat liver and found in Golgi secretory vesicles. Kinetic tracer experiments show that rat PI and PIII are present on separate VLDL particles, both of which are extensively removed from the circulation at the remnant stage, and that the declining PIII-to-PI/II ratios in IDL and LDL may be attributed to the more rapid turnover of PIII-containing lipoproteins at all levels, particularly within the LDL density range.

In this report, we present a rapid method for producing high-quality micrographs suitable for determining the size distributions of particles in concentrated samples of postprandial chylomicrons and chylomicron remnants. The procedure consists of mixing particles with osmium tetroxide in water to stabilize the lipids of the particles. These fixed and positively stained particles are then negatively stained with phosphotungstate in the presence of dilute sucrose. This dual staining procedure prevents the fusion and clustering of chylomicrons during processing for electron microscopy and is effective with particles of different lipid compositions. In addition, this procedure is simple and rapid, adding only one mixing step and 5 min to the preparation time required for conventional negative stains.

1. Human mesenteric lymph chylomicrons were isolated from chylous ascites fluid by ultra-centrifugation and agarose/gel chromatography and their apoprotein composition was analysed by dodecylsulfate/polyacrylamide gel electrophoresis, analytical isoelectric focusing and immuno-chemically. Major components of mesenteric lymph chylomicrons were apoprotein A-I, proteins of Mr less than 15 000 including the C-group apoproteins and a protein of Mr 46 000. Minor components were apoprotein E and a protein of Mr approximately equal to 200 000 (B-like protein). This apoprotein composition was qualitatively identical with that of chylomicrons from intestinal lymph of the rat, but was distinctly different from plasma chylomicrons of humans with fasting chylomicronaemia. 2. The protein of Mr approximately equal to 46 000 has been isolated by preparative dodecylsulfate/polyacrylamide gel electrophoresis from human and rat lymph chylomicrons and was compared to a protein of identical Mr present in rat high-density lipoproteins (apoplipoprotein A-IV) and in the rho less than 1.006 g/ml serum lipoprotein fraction of individual humans with alimentary hypertriglyceridaemia. In both species the 46 000-Mr proteins isolated from lymph and serum were identical according to amino acid composition and isoelectric point in 6 M urea. The human proteins from both sources were also immunologically identical. The similarities in the molecular properties of the human apolipoprotein and rat apolipoprotein A-IV indicate that these proteins are homologous. 3. Plasma levels of human apolipoprotein A-IV determined by electroimmunodiffusion were 14.15 +/- 3.66 mg/100 ml (n = 59), but greater than 90% of the protein was unassociated with the major lipoprotein fractions. It is concluded, that apolipoprotein A-IV is a main protein component of human lymph chylomicrons, that is removed from the particles in the plasma compartment.

To understand the complexity of lipoprotein metabolism and its influence on atherosclerosis, one must be aware of the physiologic characteristics and functions of the different lipoprotein classes, apolipoproteins and enzymes. Understanding of the dynamics of cholesterol and lipoprotein metabolism, especially reverse cholesterol transport, will aid in finding a means of preventing and reversing the atherosclerotic process.

Previous studies have defined forms of high density lipoproteins (HDL) in rat mesenteric lymph, suggesting that they have a secretory origin. This study describes the isolation and characterization of intestinal intracellular HDL. Two preparations were made as follows: (a) Rat enterocytes were isolated and a Golgi organelle fraction was prepared. (b) Cell homogenates were subjected to nitrogen cavitation and a cytoplasmic fraction was prepared. Lipoproteins were isolated from both preparations by sequential ultracentrifugation. When the HDL fraction (1.07-1.21 g/ml) was subjected to isopyknic density gradient ultracentrifugation, a peak of apoproteins A-I and B (apoA-I and apoB, respectively) was found at a density of 1.11-1.14 g/ml. Electron microscopy of the fraction showed spherical particles ranging in size from 6 to 13 nm. Immunoelectrophoresis revealed a precipitin arc in the alpha region against apoA-I which extended into the pre-beta region where a precipitin arc against apoB was also seen. ApoB antisera depleted the pre-beta particles whereas the alpha migrating particles remained. Lipid analysis of the whole HDL fraction revealed phospholipid, cholesteryl ester, and triglyceride as the major lipids. [3H]leucine was then administered into the duodenum and a radiolabeled intracellular HDL fraction was isolated. The newly synthesized apoproteins of the HDL fraction, as determined by gel electrophoresis, were apoB, apoA-I, and apolipoprotein A-IV (ApoA-IV). Immunoprecipitation of the apoB particles revealed apoA-I and apoA-IV in the supernatant. These data demonstrate that there are at least two intracellular intestinal forms of HDL particles, one of which contains apoB. The other particle contains apoA-I and apoA-IV, has alpha mobility, is spherical, and resembles a particle found in the lymph.

Low density lipoproteins and the triglyceride-rich lipoproteins of human serum each contain proteins of high molecular weight termed apolipoprotein B, which have previously been thought to be identical. We have isolated four species of apolipoprotein B with unique molecular weights and amino acid compositions. We have assigned numerical designations to these species in a centile system based upon their relative apparent Mr in NaDodSO4. One which we term B-100, with an apparent Mr of 549,000 +/- 7650 (SD) determined by NaDodSO4 gel electrophoresis, predominates in low density and very low density lipoproteins and is also present in chylomicrons from thoracic duct lymph or from plasma. Substantial amounts of two large proteins designated B-74 (apparent Mr 407,000 +/- 5790) and B-26 (apparent Mr 144,500 +/- 8970), which appear to be complementary fragments or constituents of the B-100 protein, are found in the low density lipoproteins of many individuals. A distinct protein, B-48, with an apparent Mr of 264,000 +/- 8150 is a major and constant constituent of chylomicrons from thoracic duct lymph or from plasma.

Chylomicron lipid composition in mesenteric lymph fistula rats was followed during duodenal triolein infusion at three rates. Esterified cholesterol decreased progressively in all groups as triglyceride transport continued, and the rate of decrease was reciprocally related to the triolein infusion rate. Suppression of cholesterol ester synthesis may spare unesterified cholesterol for chylomicron membrane formation. Ratios of triglyceride to phospholipid and to unesterified cholesterol increased with the duration of triglyceride secretion, while the chylomicron surface lipid composition remained constant over time. The rate of increase in the core:surface lipid ratios was the same irrespective of the triolein transport rate.

The diagnosis and the clinical course of a 17-year-old white male with chyluria are reported. Cloudy, milky urine appeared spontaneously, in the absence of edema or any signs or symptoms of parasitic infection. Pedal lymphangiography demonstrated the presence of a lymphatic renal fistula, and digital subtraction angiography showed aneurysmal dilatation of the aorta at the level of the renal arteries. This case provided an opportunity to ascertain which of the forms of apolipoprotein B were present in lymph chylomicrons. Apolipoprotein B is needed for chylomicron secretion. It exists in several forms--B-100, B-74, B-48, and B-26. After a meal consisting of fat, chylomicrons in which apolipoprotein B-48 was virtually the only apolipoprotein B present appeared in the urine, while apolipoprotein B-100 was the only apolipoprotein B present in the plasma very low-density lipoproteins. Chyluria disappeared two weeks after institution of a low-fat diet. This case illustrates an interesting, rare cause of chyluria. Because of the presence of chyluria, it was also demonstrated that chylomicrons in which apolipoprotein B-48 is virtually the only apolipoprotein B present are a physiologically normal product of the intestine.

The number of particles and the mass of apoprotein B were measured in samples of rat lymph chylomicrons in order to assign the mass of apoprotein B per particle. Chylomicron numbers were estimated by electron microscopy after negative staining with 2% potassium phosphotungstate at pH 4.8. The distribution of particle numbers was plotted against particle volume. An exponential relationship was found. Integration of the function gave an estimate of the total number of particles for the total chylomicron volume, which was calculated from the chemical composition and the partial specific volumes of the constituents. Apoprotein B was measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two procedures were employed to allow for the influence of artefactual flattening of the chylomicrons on the electron microscope grid. First, it was reasoned that the flattening artefact would be greatest for the largest particles, so measurements of subfractions of smaller chylomicrons would be less affected by flattening. The mass of apoprotein B per particle was 0.48 x 10(6) daltons in the smallest subfraction. Second, a correction was applied such that the apparent volume of the oblate spheroid produced by flattening was converted to the true volume of the native spherical particle. The flattening artefact increased exponentially with particle size and was an inverse power function of the surface tension. At an assumed value of chylomicron surface tension of 2 mN/m, the apoprotein B per particle was 0.47 x 10(6) daltons.

The distribution of apolipoproteins A-I and A-IV among lymph lipoprotein fractions was studied after separation by molecular sieve chromatography, avoiding any ultracentrifugation. Lymph was obtained from rats infused either with a glucose solution or with a triacylglycerol emulsion. Relative to glucose infusion, triacylglycerol infusion caused a 20-fold increase in the output of triacylglycerol, coupled with a 4-fold increase in output of apolipoprotein A-IV. The output of apolipoprotein A-I was only elevated 2-fold. Chromatography on 6% agarose showed that lymph apolipoproteins A-I and A-IV are present on triacylglycerol-rich particles and on particles of the size of HDL. In addition, apolipoprotein A-IV is also present as 'free' apolipoprotein A-IV. The increase in apolipoprotein A-I output is caused by a higher output of A-I associated with large chylomicrons only, while the increase in apolipoprotein A-IV output is reflected by an increased output in all lymph lipoprotein fractions, including lymph HDL and 'free' apolipoprotein A-IV. The increased level of 'free' A-IV, seen in fatty lymph, may contribute to, and at least partly explain, the high concentrations of 'free' apolipoprotein A-IV present in serum obtained from fed animals.