Plasma proprotein convertase subtilisin kexin type 9 levels are related to markers of cholesterol synthesis in familial combined hyperlipidemia.

BACKGROUND AND AIMS: Two recent independent studies showed that patients with familial combined hyperlipidemia (FCHL) have elevated plasma levels of proprotein convertase subtilisin kexin type 9 (PCSK9) and markers of cholesterol synthesis. Both PCSK9 expression and cholesterol synthesis are downstream effects of hepatic activation of sterol regulatory element binding protein 2 (SREBP2). The present study was conducted to study the relationship between plasma PCSK9 and markers of cholesterol synthesis in FCHL. METHODS AND RESULTS: Markers of cholesterol synthesis (squalene, desmosterol, lathosterol), cholesterol absorption (campesterol, sitosterol, cholestanol) and PCSK9 were measured in plasma of FCHL patients (n = 103) and their normolipidemic relatives (NLR; n = 240). Plasma PCSK9, lathosterol and desmosterol levels were higher in FCHL patients than their NLR (p < 0.001, age and sex adjusted). Heritability calculations demonstrated that 35% of the variance in PCSK9 levels could be explained by additive genetic effects (p < 0.001). Significant age- and sex-adjusted correlations were observed for the relationship between PCSK9 and lathosterol, both unadjusted and adjusted for cholesterol, in the overall FCHL population (both p < 0.001). Multivariate regression analyses, with PCSK9 as the dependent variable, showed that the regression coefficient for FCHL status decreased by 25% (from 0.8 to 0.6) when lathosterol was included. Nevertheless, FCHL status remained an independent contributor to plasma PCSK9 (p < 0.001). CONCLUSIONS: The present study confirms the previously reported high and heritable PCSK9 levels in FCHL patients. Furthermore, we now show that high PCSK9 levels are, in part, explained by plasma lathosterol, suggesting that SREBP2 activation partly accounts for elevated PCSK9 levels in FCHL.

Utility of glycated albumin for the diagnosis of diabetes mellitus in a Japanese population study: results from the Kyushu and Okinawa Population Study (KOPS).

AIMS/HYPOTHESIS: Glycated albumin is a measure of the mean plasma glucose concentration over approximately 2-3 weeks. We determined reference values for glycated albumin, and assessed its utility for the diagnosis of type 2 diabetes mellitus in the general population. METHODS: We studied 1,575 men and women (mean age, 49.9 years; range, 26-78 years) who participated in a periodic health examination in a suburban Japanese town. HbA(1c) and fasting plasma concentrations of glucose (FPG) and glycated albumin were measured. Participants with FPG ≥ 7.0 mmol/l or HbA(1c) ≥ 6.5% (48 mmol/mol) were diagnosed as having diabetes. In our laboratory, the glycated albumin assay had intra-assay and inter-assay CVs of 1.1% and 1.6%, respectively. RESULTS: Glycated albumin levels were significantly correlated with HbA(1c) levels (r = 0.766, p < 0.001) and FPG (r = 0.706, p < 0.001). The presence of diabetes was significantly higher in participants with glycated albumin levels between 15.0% and 15.9% (five of 276, 1.81%) than in those with glycated albumin <14% (three of 672, 0.45%) (p = 0.037), and was markedly increased in those with a glycated albumin level >16% (58 of 207, 28.0%). Receiver operating characteristic curve analysis indicated that a glycated albumin level of ≥15.5% was optimal for predicting diabetes, with a sensitivity of 83.3% and a specificity of 83.3%. CONCLUSIONS/INTERPRETATION: There is merit to further investigating the potential for glycated albumin to be used as an alternative measure of dysglycaemia for future research and clinical practice.

Type III hyperlipoproteinemia associated with apolipoprotein E deficiency.

Subjects with type III hyperlipoproteinemia develop premature atherosclerosis and have hyperlipidemia due to an increase in cholesterol-rich very low density lipoproteins (VLDL) of abnormal electrophoretic mobility. Apolipoprotein E is a major protein constituent of VLDL and appears to be important for the hepatic uptake of triglyceride-rich lipoproteins. A new kindred of patients with type III hyperlipoproteinemia is described in which no plasma apolipoprotein E could be detected, consistent with the concept that type III hyperlipoproteinemia may be due to an absence or striking deficiency of apolipoprotein E.

Similarity of cruzin, an inhibitor of Trypanosoma cruzi neuraminidase, to high-density lipoprotein.

A specific inhibitor of the neuraminidase of the protozoan parasite Trypanosoma cruzi was isolated recently and named cruzin. It is now shown that cruzin is similar to high-density lipoprotein by amino acid homology, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, by immunoblot analysis, and by isoelectric focusing. Cruzin purified by ion exchange chromatography and high-density lipoprotein isolated by density gradient ultracentrifugation inhibited Trypanosoma cruzi neuraminidase to the same extent. Cruzin or high-density lipoprotein restores to normal the decreased multiplication rate of Trypanosoma cruzi epimastigotes grown in a medium depleted of lipoproteins, suggesting that it may be important for survival of the parasite in nature.

Type III hyperlipoproteinemia: defective metabolism of an abnormal apolipoprotein E.

The apolipoprotein E isolated from plasma of individuals with type III hyperlipoproteinemia (HLP) shows an abnormal pattern when it is examined by isoelectric focusing. Compared to apolipoprotein E from normal subjects, apolipoprotein E isolated from subjects with type III HLP had a decreased fractional catabolic rate in vivo in both type III HLP patients and normal individuals. The delayed catabolism of apolipoprotein E in type III HLP patients may be responsible for the lipid and lipoprotein abnormalities characteristic of these patients.

Distinct hepatic receptors for low density lipoprotein and apolipoprotein E in humans.

Since the liver is a central organ for lipid and lipoprotein synthesis and catabolism, hepatic receptors for specific apolipoproteins on plasma lipoproteins would be expected to modulate lipid and lipoprotein metabolism. The role of hepatic receptors for low density lipoproteins and apolipoprotein E-containing lipoproteins was evaluated in patients with complementary disorders in lipoprotein metabolism: abetalipoproteinemia and homozygous familial hypercholesterolemia. In addition, hepatic membranes from a patient with familial hypercholesterolemia were studied and compared before and after portacaval shunt surgery. The results establish that the human liver has receptors for apolipoproteins B and E. Furthermore, in the human, hepatic receptors for low density lipoproteins and apolipoprotein E are genetically distinct and can undergo independent control.

Tangier disease. High density lipoprotein deficiency due to defective metabolism of an abnormal apolipoprotein A-i (ApoA-ITangier).

Tangier disease is a rare familial disorder characterized by enlarged orange tonsils, transient peripheral neuropathy, hepatosplenomegaly, and lymphadenopathy, as well as striking reductions in plasma high density lipoproteins (HDL) and their major protein constituents, apolipoproteins (apo)A-I and A-II. In order to test the hypothesis that Tangier patients have abnormal apoA-I or apoA-II, the in vitro lipoprotein binding and in vivo metabolic characteristics of these proteins isolated from normal and Tangier plasma, were studied in normal subjects and patients with Tangier disease. After incubation with normal plasma, significantly greater percentages of radiolabeled Tangier apoA-I were associated with the 1.063-g/ml supernate (6%) and the 1.21 g/ml infranate (19%), and a lower percentage with HDL (75%), than those observed for normal apoA-I (2, 8, and 90%, respectively). In contrast, the lipoprotein binding properties of normal and Tangier apoA-II were very similar. Following the injection of radiolabeled normal and Tangier apoA-I into normal subjects (n = 4), the mean residence times of the specific activity for apoA-I(Tangier) were significantly lower, both in plasma (1.29 d) and in HDL (1.34 d), than those observed for normal apoA-I (3.80 and 4.06 d). In Tangier homozygotes the decay rates of these tracers were very rapid and were similar. No significant differences between the kinetics of normal and Tangier apoA-II were observed in normal subjects (n = 2). Tangier homozygotes (n = 3) had mean plasma HDL cholesterol, apoA-I, and apoA-II concentrations that were 4, 2, and 11% of normal (n = 24), respectively, whereas for heterozygotes (n = 3) these values were 46, 62, and 68% of normal. In homozygotes, in contrast to normals or heterozygotes, a significant fraction of both apoA-I and apoA-II were found in the 1.063-g/ml supernate instead of in HDL. Homozygotes had apoA-I(Tangier) synthesis rates and residence times that were 41 and 5% of values observed for normal apoA-I in normal subjects, and for apoA-II in homozygotes, these parameters were 63 and 18% of normal. Heterozygotes had apoA-I synthesis rates and residence times that were 92 and 66% of normal, and for apoA-II these values were 101 and 64% of normal. These data are consistent with the concept that apoA-I(Tangier) is functionally and metabolically distinct from normal apoA-I, and is the cause of the striking hypercatabolism of apoA-I and apoA-II, and the lipoprotein abnormalities observed in Tangier disease.

Postprandial plasma retinyl ester response is greater in older subjects compared with younger subjects. Evidence for delayed plasma clearance of intestinal lipoproteins.

Postprandial vitamin A and intestinal lipoprotein metabolism was studied in 86 healthy men and women, aged 19-76 yr. Three independent experiments were carried out. In the first experiment, a supplement dose of vitamin A (3,000 retinol equivalents [RE]) was given without a meal to 59 subjects, aged 22-76 yr. In the second experiment, 20 RE/kg body wt was given with a fat-rich meal (1 g fat/kg body wt) to seven younger subjects (aged less than 50 yr) and seven older subjects (aged greater than or equal to 50 yr). In both experiments, postprandial plasma retinyl ester response increased significantly with advancing age (P less than 0.05). In the third experiment, retinyl ester-rich plasma was infused intravenously into nine young adult subjects (aged 18-30 yr) and nine elderly subjects (aged greater than or equal to 60 yr), and the rate of retinyl ester disappearance from plasma during the subsequent 3 h was determined. Mean (+/- SE) plasma retinyl ester residence time was 31 +/- 4 min in the young adult subjects vs. 57 +/- 8 min in the elderly subjects (P less than 0.05). These data are consistent with the concept that increased postprandial plasma retinyl ester concentrations in older subjects are due to delayed plasma clearance of retinyl esters in triglyceride-rich lipoproteins of intestinal origin.

Increased prevalence of apolipoprotein E4 in type V hyperlipoproteinemia.

Type V hyperlipoproteinemia (HLP) is characterized clinically by hepatosplenomegaly, occasional eruptive xanthomas, and an increased incidence of pancreatitis. These patients have striking hypertriglyceridemia due to increased plasma chylomicron and very low density lipoprotein concentrations in the fasting state, without a deficiency of lipoprotein lipase or its activator protein, apolipoprotein (apo) C-II. ApoE, a protein constituent of triglyceride-rich lipoproteins, has been implicated in the receptor-mediated hepatic uptake of these particles. ApoE has three major alleles: E2, E3, and E4, and the products of these alleles are apoE2, apoE3, and apoE4, respectively. ApoE phenotypes were determined in 30 type V HLP patients as well as in 37 normal volunteers. Among the type V patients, 33.3% were noted to be homozygous, and 40.0% heterozygous for E4 (normal, 2.7 and 21.6%, respectively). These data suggest that apoE4 may play a role in the etiology of the hyperlipidemia in a significant number of type V HLP patients.

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

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

Abnormal in vivo metabolism of apolipoprotein E4 in humans.

Apolipoprotein E (apoE) is important in modulating the catabolism of remnants of triglyceride-rich lipoprotein particles. It is a polymorphic protein with the three common alleles coding for apoE2, apoE3, and apoE4. ApoE3 is considered the normal isoform, while apoE4 is associated both with hypercholesterolemia and type V hyperlipoproteinemia. We quantitated the kinetics of metabolism of apoE4 in 19 normolipidemic apoE3 homozygotes and 1 normolipidemic apoE4 homozygote, and compared this with the metabolism of apoE3 in 12 normolipidemic apoE3 homozygotes. In the apoE3 homozygous subjects, apoE4 was catabolized twice as fast as apoE3, with a mean plasma residence time of 0.37 +/- 0.01 d (+/- SEM) and 0.73 +/- 0.05 (P less than 0.001), respectively. When plasma was fractionated into the lipoprotein subclasses, the greatest amount of labeled apoE4 was present on very low density lipoproteins, while the largest fraction of labeled apoE3 was associated with high density lipoproteins. The plasma apoE concentration was decreased in an apoE4 homozygote compared with the apoE3 homozygotes (3.11 mg/dl vs. 4.83 +/- 0.35 mg/dl). The reduced apoE4 concentration was entirely due to a decreased apoE4 residence time in the apoE4 homozygote (0.36 d vs. 0.73 +/- 0.05 d for apoE3 in apoE3 homozygotes). These results indicate that apoE4 is kinetically different than apoE3, and suggest that the presence of apoE4 in hypercholesterolemic and type V hyperlipoproteinemic individuals may play an important pathophysiological role in the development of these dyslipoproteinemias.

Measurement of very low density and low density lipoprotein apolipoprotein (Apo) B-100 and high density lipoprotein Apo A-I production in human subjects using deuterated leucine. Effect of fasting and feeding.

Six normolipidemic male subjects, after an 8-h overnight fast, were given a bolus injection and then a 15-h constant intravenous infusion of [D3]L-leucine. Subjects were studied in the fasted state and on a second occasion in the fed state (small, physiological meals were given every hour for 15 h). Apolipoproteins were isolated by preparative gradient gel electrophoresis from plasma lipoproteins separated by sequential ultracentrifugation. Incorporation of [D3]L-leucine into apolipoproteins was monitored by negative ionization, gas chromatography-mass spectrometry. Production rates were determined by multiplying plasma apolipoprotein pool sizes by fractional production rates (calculated as the rate of isotopic enrichment [IE] of each protein as a fraction of IE achieved by VLDL (d less than 1.006 g/ml) apo B-100 at plateau. VLDL apo B-100 production was greater, and LDL (1.019 less than d less than 1.063 g/ml) apo B-100 production was less in the fed compared with the fasted state (9.9 +/- 1.7 vs. 6.4 +/- 1.7 mg/kg per d, P less than 0.01, and 8.9 +/- 1.2 vs. 13.1 +/- 1.2 mg/kg per d, P less than 0.05, respectively). No mean change was observed in high density lipoprotein apo A-I production. We conclude that: (a) this stable isotope, endogenous-labeling technique, for the first time allows for the in vivo measurement of apolipoprotein production in the fasted and fed state; and (b) since LDL apo B-100 production was greater than VLDL apo B-100 production in the fasted state, this study provides in vivo evidence that LDL apo B-100 can be produced independently of VLDL apo B-100 in normolipidemic subjects.

Transport of apolipoproteins A-I and A-II by human thoracic duct lymph.

The daily transport of human plasma apolipoproteins A-I and A-II, triglyceride, and total cholesterol from the thoracic duct lymph into plasma was measured in two subjects before and three subjects after renal transplantation. Lymph triglyceride transport was approximately 83% of the daily ingested fat loads, whereas lymph cholesterol transport was consistently greater than the amount of daily ingested cholesterol. Lymph apolipoprotein transport significantly (P < 0.05) exceeded the predicted apolipoprotein synthesis rate by an average of 659+/-578 mg/d for apolipoprotein A-I and 109+/-59 mg/d for apolipoprotein A-II among the five subjects. It is estimated that 22-77% (apolipoprotein A-I) and 28-82% (apolipoprotein A-II) of daily total body apolipoprotein synthesis takes place in the intestine. Lymph high density lipoprotein particles are mostly high density lipoprotein(2b) and high density lipoprotein(2a) and have a greater overall relative triglyceride content and a smaller relative cholesteryl ester content when compared with homologous plasma high density lipoproteins. The major quantity of both lymph apolipoprotein A-I (81+/-8%) and apolipoprotein A-II (90+/-11%) was found within high density lipoproteins with almost all of the remainder found in chylomicrons and very low density lipoproteins. The combined results are consistent with a major contribution of the intestine to total body synthesis of apolipoprotein A-I and apolipoprotein A-II. An important role of lymph in returning filtered apolipoprotein to plasma in association with high density lipoproteins is proposed. Accompanying the return of filtered apolipoprotein to the plasma is a probable transformation, both in size and composition, of at least some of the lymph high density lipoprotein(2b) and high density lipoprotein(2a) particles into high density lipoprotein(3).

Familial apolipoprotein E deficiency.

A unique kindred with premature cardiovascular disease, tubo-eruptive xanthomas, and type III hyperlipoproteinemia (HLP) associated with familial apolipoprotein (apo) E deficiency was examined. Homozygotes (n = 4) had marked increases in cholesterol-rich very low density lipoproteins (VLDL) and intermediate density lipoproteins (IDL), which could be effectively lowered with diet and medication (niacin, clofibrate). Homozygotes had only trace amounts of plasma apoE, and accumulations of apoB-48 and apoA-IV in VLDL, IDL, and low density lipoproteins. Radioiodinated VLDL apoB and apoE kinetic studies revealed that the homozygous proband had markedly retarded fractional catabolism of VLDL apoB-100, apoB-48 and plasma apoE, as well as an extremely low apoE synthesis rate as compared to normals. Obligate heterozygotes (n = 10) generally had normal plasma lipids and mean plasma apoE concentrations that were 42% of normal. The data indicate that homozygous familial apoE deficiency is a cause of type III HLP, is associated with markedly decreased apoE production, and that apoE is essential for the normal catabolism of triglyceride-rich lipoprotein constituents.

Immunologic effects of national cholesterol education panel step-2 diets with and without fish-derived N-3 fatty acid enrichment.

Reductions in dietary fat, saturated fat, and cholesterol have been recommended to reduce the risk of heart disease in our society. The effects of these modifications on human cytokine production and immune responses have not been well studied. 22 subjects > 40 yr of age were fed a diet approximating that of the current American (14.1% of calories as saturated fatty acids, [SFA], 14.5% monounsaturated fatty acids [MUFA], 6.1% [n-6] polyunsaturated fatty acids [PUFA], 0.8% [n-3] PUFA, and 147 mg cholesterol/1,000 calories) for 6 wk, after which time they consumed (11 in each group) one of the two low-fat, low-cholesterol, high-PUFA diets based on National Cholesterol Education Panel (NCEP) Step 2 recommendations (4.0-4.5% SFA, 10.8-11.6% MUFA, 10.3-10.5% PUFA, 45-61 mg cholesterol/1,000 calories) for 24 wk. One of the NCEP Step 2 diets was enriched in fish-derived (n-3) PUFA (low-fat, high-fish: 0.54% or 1.23 g/d eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA] [121-188 g fish/d]) and the other low in fish-derived (n-3) PUFA (low-fat, low-fish [0.13% or 0.27 g/d EPA and DHA] [33 g fish/d]). Measurements of in vivo and in vitro indexes of immune responses were taken after each dietary period. Long-term feeding of low-fat, low-fish diet enriched in plant-derived PUFA increased blood mononuclear cell mitogenic response to the T cell mitogen Con A, IL-1 beta, and TNF production and had no effect on delayed-type hypersensitivity skin response, IL-6, GM-CSF, or PGE2 production. In contrast, the low-fat, high-fish diet significantly decreased the percentage of helper T cells whereas the percentage of suppressor T cells increased. Mitogenic responses to Con A and delayed-type hypersensitivity skin response as well as the production of cytokines IL-1 beta, TNF, and IL-6 by mononuclear cells were significantly reduced after the consumption of the low-fat, high-fish diet (24, 40, 45, 35, and 34%, respectively; P < 0.05 by two-tailed Student's t test except for IL-1 beta and TNF, which is by one-tailed t test). Our data are consistent with the concept that the NCEP Step 2 diet that is high in fish significantly decreases various parameters of the immune response in contrast to this diet when it is low in fish. Such alterations may be beneficial for the prevention and treatment of atherosclerotic and inflammatory diseases but may be detrimental with regard to host defense against invading pathogens.

Absence of P-selectin delays fatty streak formation in mice.

P-selectin is expressed on activated endothelium and platelets where it can bind monocytes, neutrophils, stimulated T cells, and platelets. Because recruitment of these cells is critical for atherosclerotic lesion development, we examined whether P-selectin might play a role in atherosclerosis. We intercrossed P-selectin-deficient mice with mice lacking the low density lipoprotein receptor (LDLR) because these mice readily develop atherosclerotic lesions on diets rich in saturated fat and cholesterol. The atherogenic diet stimulated leukocyte rolling in the mesenteric venules of LDLR-deficient mice, and the increase in adhesiveness of the vessels was P-selectin-dependent. Most likely due to the reduced leukocyte interaction with the vessel wall, P-selectin-deficient mice on diet for 8-20 wk formed significantly smaller fatty streaks in the cusp region of the aortae than did P-selectin-positive mice. This difference was more prominent in males. At 37 wk on diet, the lesions in the LDLR-deficient animals progressed to the fibrous plaque stage and were distributed throughout the entire aorta; their size or distribution was no longer dependent on P-selectin. Our results show that P-selectin-mediated adhesion is an important factor in the development of early atherosclerotic lesions, and that adhesion molecules such as P-selectin are involved in the complex process of atherosclerosis.

Impaired hepatocyte binding, uptake and degradation of glucosylated low-density lipoproteins.

The catabolism of low-density lipoproteins (LDL), the major cholesterol-carrying lipoproteins in plasma, is mediated in part via a high-affinity uptake pathway in the liver. Non-enzymatic glucosylation of lysine residues of apolipoprotein B, the major protein of LDL, blocks receptor-mediated uptake of LDL by fibroblasts and endothelial cells. We investigated the effect of the degree of glucosylation on the binding, uptake and degradation of radioiodinated LDL by the human hepatoma cell line Hep G2. Human LDL was glucosylated with 250 mM glucose and 30 mM cyanoborohydride at 37 degrees C. Incubations ranging from 3 to 48 h in duration resulted in the formation of 6-27% of glucitol-lysine adducts as demonstrated by coincubation with [14C]glucose. The degree of glucose incorporation corresponded to the extent of inhibition of binding, uptake and degradation of LDL (10-90%). The data are consistent with the view that glucosylation of LDL markedly impairs their catabolism. This phenomenon may be related to the pathophysiology of the premature atherosclerosis observed in diabetes mellitus.

Molecular cloning and sequence of the cynomolgus monkey apolipoprotein A-II gene.

A clone containing the coding region for cynomolgus monkey (Macaca fascicularis) apolipoprotein A-II has been isolated from a cynomolgus genomic DNA library. The gene spans 1.4 kilobases (kb). The complete nucleic acid sequence of the apolipoprotein A-II gene has been determined, establishing that the gene is interrupted by three intervening sequences of 170, 273 and 394 bp, respectively. The open reading frame encodes a protein of 100 amino acids, and shows 94% sequence similarity with its human equivalent. Both apolipoproteins have identical signal peptide. A noticeable feature is the substitution of mature human Cys-6 for Ser. This change explains the existence of cynomolgus apolipoprotein A-II as a monomer and may have important consequences in the kinetics of this apolipoprotein.

Nucleotide sequences of the Macaca fascicularis apolipoprotein C-III and A-IV genes.

The cynomolgus monkey (Macaca fascicularis) apolipoprotein C-III and apolipoprotein A-IV genes have been isolated from a cynomolgus genomic DNA library and completely sequenced. These genes span 3.1 and 2.8 kilobases (kb), respectively. Apolipoprotein C-III gene is interrupted by three intervening sequences of 613, 135 and 1699 bp, respectively. The open reading frame encodes a protein of 99 amino acids which is 87% similar to the human. The cynomolgus mature protein is 79 residues long. Thr-74 is also present what might allow the formation of O-glycosidic linkage observed in the human protein. Apolipoprotein A-IV gene consist of two intervening sequences of 352 and 774 bp, respectively. The open reading frame encodes a protein of 429 amino acids which is 87% similar to the human. The cynomolgus mature protein is 409 residues long, 33 amino acids longer than the human, due to an insertion of 33 residues in its COOH-terminal region. This insertion is mainly composed of glutamine and glutamic acid, which confers cynomolgus apolipoprotein a higher hydrophilicity.

Effect of fat feeding on human intestinal apolipoprotein B mRNA levels and editing.

Our purpose was to assess the effect of a fat-rich meal on intestinal apolipoprotein B (apoB) mRNA levels and editing. We obtained jejunal biopsies from eight healthy adults in the fasting state and 3 h after a meal containing 1 g/kg of fat. In the fasting state, 93% of the apoB mRNA contained the editing sequence resulting in apoB-48 production. Feeding induced no significant changes in apoB mRNA levels or editing. Our data are consistent with the concept that the significant increase in apoB-48 within triglyceride-rich lipoproteins in postprandial plasma is not due to alterations in apoB gene expression or editing.