Reduction In Apo Research Articles

Apolipoprotein E4 Domain Interaction Induces Endoplasmic Reticulum Stress and Impairs Astrocyte Function

Domain interaction, a structural property of apolipoprotein E4 (apoE4), is predicted to contribute to the association of apoE4 with Alzheimer disease. Arg-61 apoE mice, a gene-targeted mouse model specific for domain interaction, have lower brain apoE levels and synaptic, functional, and cognitive deficits. We hypothesized that domain interaction elicits an endoplasmic reticulum (ER) stress in astrocytes and an unfolded protein response that targets Arg-61 apoE for degradation. Primary Arg-61 apoE astrocytes had less intracellular apoE than wild-type astrocytes, and unfolded protein response markers OASIS (old astrocyte specifically induced substance), ATF4, and XBP-1 and downstream effectors were up-regulated. ER stress appears to cause global astrocyte dysfunction as glucose uptake was decreased in Arg-61 apoE astrocytes, and astrocyte-conditioned medium promoted neurite outgrowth less efficiently than wild-type medium in Neuro-2a cell cultures. We showed age-dependent up-regulation of brain OASIS levels and processing in Arg-61 apoE mice. ER stress and astrocyte dysfunction represent a new paradigm underlying the association of apoE4 with neurodegeneration.

Altered Calcium Handling Between Healthy And Atherosclerotic Vascular Smooth Muscle

In order for smooth muscle (SM) contraction and relaxation to proceed efficiently, Ca2+ handling is under tight regulation. The cyclic strain associated with hypertension is thought to play an initiating role in atherosclerosis, suggesting dysregulation of SM Ca2+ handling may be a contributing factor. Peroxynitrite (ONOO−), the reaction product of superoxide and nitric oxide, forms in diseased vessels and has been demonstrated to induce SM cell relaxation. In this study, we assessed function and expression levels of sarcoplasmic reticulum Ca2+ handling proteins; the inositol 1,4,5-trisphosphate receptor (IP3R) and the Ca2+ATPase (SERCA) in both healthy and atherosclerotic aorta. ONOO− dose-dependently relaxed U46619 pre-contracted aorta from both control and atherosclerotic ApoE−/− mice (2 months high fat diet) [51.2 ± 4.7% and 78.5 ± 4.3% maximal relaxation, respectively (3 × 10−5 ONOO−)]. This relaxation was antagonised in both C57 and ApoE−/− by the addition of either 3μM thapsigargin (TG), a SERCA inhibitor, or 60μM 2-aminoethoxydiphenyl borate (2-APB), an IP3R blocker. In control aorta, relaxation was 4.3 ± 5% (TG), p<0.001; n=7 and 14.6 ± 6.2% (2-APB) p=0.001; n=9. In ApoE−/− aorta, % relaxation was 22.09 ± 3.1 (TG) p<0.001; n=8 and 7 ± 5.9% (2-APB) p<0.001; n=7. There was no significant difference between endothelial denuded or intact vessels. These data indicate an alteration in the effect of Ca2+ handling protein inhibitors between control and ApoE−/− mice. This has been further correlated to expression of both SERCA and IP3R proteins. Studies with the potassium channel blocker tetraethylammonium (TEA) indicate plasma membrane hyperpolarisation is an effector of ONOO− induced relaxation [31.2% relaxation reduction with TEA in C57 aorta, p=0.002 vs 35.5% reduction in ApoE−/−, p=0.022]. We provide additional evidence, through myography and biochemical analysis, of a time-dependent correlation between atherosclerotic development and SM Ca2+ handling machinery modulation.

Enhancement of a modified Mediterranean-style, low glycemic load diet with specific phytochemicals improves cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia in a randomized trial

BackgroundAs the worldwide dietary pattern becomes more westernized, the metabolic syndrome is reaching epidemic proportions. Lifestyle modifications including diet and exercise are recommended as first-line intervention for treating metabolic syndrome. Previously, we reported that a modified Mediterranean-style, low glycemic load diet with soy protein and phytosterols had a more favorable impact than the American Heart Association Step 1 diet on cardiovascular disease (CVD) risk factors. Subsequently, we screened for phytochemicals with a history of safe use that were capable of increasing insulin sensitivity through modulation of protein kinases, and identified hops rho iso-alpha acid and acacia proanthocyanidins. The objective of this study was to investigate whether enhancement of a modified Mediterranean-style, low glycemic load diet (MED) with specific phytochemicals (soy protein, phytosterols, rho iso-alpha acids and proanthocyanidins; PED) could improve cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia.MethodsForty-nine subjects with metabolic syndrome and hypercholesterolemia, aged 25–80, entered a randomized, 2-arm, 12-week intervention trial; 23 randomized to the MED arm; 26 to the PED arm. Forty-four subjects completed at least 8 weeks [MED (n = 19); PED (n = 25)]. All subjects were instructed to follow the same aerobic exercise program. Three-day diet diaries and 7-day exercise diaries were assessed at each visit. Fasting blood samples were collected at baseline, 8 and 12 weeks for analysis.ResultsBoth arms experienced equal weight loss (MED: -5.7 kg; PED: -5.9 kg). However, at 12 weeks, the PED arm experienced greater reductions (P < 0.05) in cholesterol, non-HDL cholesterol, triglycerides (TG), cholesterol/HDL and TG/HDL compared with the MED arm. Only the PED arm experienced increased HDL (P < 0.05) and decreased TG/HDL (P < 0.01), and continued reduction in apo B/apo A-I from 8 to 12 weeks. Furthermore, 43% of PED subjects vs. only 22% of MED subjects had net resolution of metabolic syndrome. The Framingham 10-year CVD risk score decreased by 5.6% in the PED arm (P < 0.01) and 2.9% in the MED arm (P < 0.05).ConclusionThese results demonstrate that specific phytochemical supplementation increased the effectiveness of the modified Mediterranean-style low glycemic load dietary program on variables associated with metabolic syndrome and CVD.

Cardioprotective Properties of Fibrates

Several large intervention trials have investigated the potential of fibrates to reduce cardiovascular events. The results have varied widely: positive, with gemfibrozil in the primary prevention Helsinki Heart Study (HHS)1 and the secondary prevention Veterans Administration High Density Lipoprotein Intervention Trial (VA-HIT)2; positive, with reservations related to an increase in noncardiovascular mortality in the primary prevention World Health Organization trial (clofibrate)3; and mixed, with bezafibrate in the secondary prevention Bezafibrate Infarction Prevention (BIP) study4 and with fenofibrate in the combined primary and secondary prevention FIELD study,5 in which positive outcomes were observed only in certain subgroups. Reasons for the differences between the outcomes of these studies are not immediately apparent. Article p 1556 It emerged in post hoc subgroup analyses of the HHS,6 VA-HIT,7 and BIP8 data that fibrate-induced reductions in cardiovascular events were especially great (of the order of 30% to 50%) in subjects with evidence of insulin resistance or other features of the metabolic syndrome, such as dyslipidemia and increased body weight. However, this finding was not replicated with fenofibrate in the FIELD study.5 In another post hoc analysis of VA-HIT, it was found that diabetics with preexisting cardiovascular disease derived a major reduction in future events when treated with gemfibrozil,7 but again, this was not confirmed with fenofibrate in FIELD.5 The observation that the cardioprotective effects of gemfibrozil in the HHS and VA-HIT studies were substantially greater than those found with other fibrates in the World Health Organization, BIP, and FIELD studies may reflect no more than the play of chance. It may also reflect differences in the populations studied in the trials. However, it is possible that gemfibrozil has protective properties that are lacking in other fibrates or that other fibrates have adverse …

The Absence of ABCA1 Decreases Soluble ApoE Levels but Does Not Diminish Amyloid Deposition in Two Murine Models of Alzheimer Disease

ABCA1, a cholesterol transporter expressed in the brain, has been shown recently to be required to maintain normal apoE levels and lipidation in the central nervous system. In addition, ABCA1 has been reported to modulate beta-amyloid (Abeta) production in vitro. These observations raise the possibility that ABCA1 may play a role in the pathogenesis of Alzheimer disease. Here we report that the deficiency of ABCA1 does not affect soluble or guanidine-extractable Abeta levels in Tg-SwDI/B or amyloid precursor protein/presenilin 1 (APP/PS1) mice, but rather is associated with a dramatic reduction in soluble apoE levels in brain. Although this reduction in apoE was expected to reduce the amyloid burden in vivo, we observed that the parenchymal and vascular amyloid load was increased in Tg-SwDI/B animals and was not diminished in APP/PS1 mice. Furthermore, we observed an increase in the proportion of apoE retained in the insoluble fraction, particularly in the APP/PS1 model. These data suggested that ABCA1-mediated effects on apoE levels and lipidation influenced amyloidogenesis in vivo.

Distribution of Apolipoprotein E Alleles in a Scottish Healthy Newborn Population

The different alleles of the human apolipoprotein E polymorphism, ApoE Ε2, Ε3, Ε4, have important implications for systemic lipid metabolism, immunological function and for the brain in maintenance and in response to injury. Few studies have focussed on their role in early life. The ApoE alleles and genotypes were ascertained in the cord blood of 371 full-term and normal Scottish newborn infants using PCR methodology. The results were compared to previously published data for Scottish adults in late middle age. There was a marginally significant over-representation of Ε4 and under-representation of Ε3 alleles in healthy infants as compared with adults. Inspection of the individual genotypes confirms the over-representation of ApoE 4/4 and 2/4 with a reduction in ApoE 2/3 and 3/3 when compared with Scottish adults. Although these results may have occurred by chance, the ApoE Ε4 allele may confer an increased risk of premature death.

Lipoprotein Compositional Changes With Combination Hormone Therapy (Conjugated Estrogen And Medroxyprogesterone) in African American Women

To determine whether combination hormone therapy (HT) significantly alters lipoprotein composition in healthy African American women. Postmenopausal African American women, 45 to 65 years old, were randomly assigned to receive daily HT (conjugated equine estrogen, 0.625 mg, and medroxyprogesterone, 2.5 mg) or placebo (treated, 44; placebo, 16) for 12 weeks. Lipoproteins were separated by gradient ultracentrifugation into very-low-density, intermediate-density, and low-density lipoproteins (VLDL, IDL, and LDL) and 3 high-density lipoprotein (HDL) subfractions (light, medium, and dense--L, M, and D). Apolipoprotein (apo) A-I, A-II, C-III, C-II, and C-I were measured by high-performance liquid chromatography. Apo B, phospholipids, triglycerides, cholesterol, and free cholesterol were measured by standard assays. Total plasma cholesterol, triglycerides, LDL apo B, and total apo B did not change during HT. A small, transient reduction occurred in LDL cholesterol, and a persistent reduction was noted in VLDL apo B, apo C-II, and apo C-III. Total HDL phospholipids, cholesterol, apo A-I, and apo A-II increased, whereas the LDL/HDL ratio and the apo B/apo A-I ratio decreased. Cholesterol ester increased in both HDL-L and HDL-M, but only a transient increase occurred in HDL-L phospholipids. Apo A-I increased in HDL-L, HDL-M, and HDL-D; however, a similar increase occurred in HDL-D apo A-I in the control subjects. Moreover, an increase occurred in apo A-II in HDL-M. A reduction in the apo A-II:A-I ratio in HDL-L but not in HDL-M indicated an increase in HDL-L LpA-I particles. The increase in HDL particles in HDL-M was entirely due to an increase in LpA-I:A-II particles. Apo C-III increased in both HDL-L and HDL-M. The absence of changes in the HDL lipid ratios indicated an unaltered lipid composition of these particles. No changes were found in IDL compositional measurements. In 12 treated patients and 4 control subjects, Lp(a) was detected by ultracentrifugation; no changes were noted in Lp(a) composition or quantity with HT. Total Lp(a) measured by enzyme immunosorbent assay showed a trend toward an increase in treated patients after 12 weeks of HT. African American women had a beneficial response to HT by increasing the number of LpA-I particles in HDL-L and LpA-I:A-II particles in HDL-M as well as cholesterol esters in both. There was a small reduction in VLDL apo B (and thus particle number) but only a transient reduction in LDL cholesterol. A shift of apo C-III from VLDL to HDL was noted. No detrimental changes occurred in any lipoprotein subfraction (specifically, no increase in triglycerides).

Atherosclerosis in C3H/HeJ mice reconstituted with apolipoprotein E-null bone marrow.

Previous studies showed that reconstitution of atherosclerosis-susceptible C57BL/6 (B6) female mice with apolipoprotein E (apoE)-deficient (apoE(-/-)) bone marrow resulted in markedly increased atherosclerosis, despite the fact that plasma lipid levels were unchanged. To determine whether apoE(-/-) bone marrow would increase atherosclerosis in an atherosclerosis-resistant strain, female C3H/HeJ (C3H) mice were lethally irradiated and reconstituted with bone marrow from either C3H.apoE(-/-) mice or wild-type C3H mice. Four weeks after transplantation, the mice were fed an atherogenic diet for 12 weeks. We found that reconstitution of C3H mice with apoE(-/-) bone marrow resulted in a slight reduction in plasma apoE levels and a dramatic reduction in apoE and apolipoprotein B (apoB) in the aortic wall. Plasma apoB and cholesterol levels were unchanged, as were atherosclerotic lesions at the aortic root. These data indicate that reconstitution of C3H mice with apoE(-/-) bone marrow has no effect on atherosclerosis susceptibility and that apoE promotes accumulation of apoB in the vessel wall.

Defective chylomicron synthesis as a cause of delayed particle clearance in diabetes?

Chylomicron metabolism is abnormal in diabetes and the chylomicron particle may play a very important role in atherosclerosis. The aim of this study was to examine the effect of diabetes on the metabolism of chylomicrons in cholesterol-fed alloxan diabetic and nondiabetic rabbits. Five diabetic rabbits and 5 control rabbits were given [14C]linoleic acid and [3H]cholesterol by gavage. Lymph was collected following cannulation of the lymph duct and radiolabelled chylomicrons were isolated by ultracentrifugation. The chylomicrons from each animal were injected into paired control and diabetic recipients. Lymph apolipoprotein (apo) B48, apo B100, and apo E were measured using sodium dodecyl sulfate–polyacrylamide gradient gel electrophoresis. Mean blood sugar of the diabetic donors and diabetic recipients were 19.7 ± 2.3 and 17.2 ± 3.2 mmol/L. Diabetic rabbits had significantly raised plasma triglyceride (10.8 ± 13.9 versus 0.8 ± 0.5 mmol/L, P < 0.02). There was a large increase in apo B48 in lymph chylomicrons in the diabetic donor animals (0.19 ± 0.10 versus 0.04 ± 0.02 mg/h, P < 0.01) and apo B100 (0.22 ± 0.15 versus 0.07 ± 0.07 mg/h, P < 0.05) and a reduction in apo E on the lymph chylomicron particle (0.27 ± 0.01 versus 0.62 ± 0.07 mg/mg apo B, P < 0.001). Diabetic recipients cleared both control and diabetic chylomicron triglyceride significantly more slowly than control recipients (P < 0.05). Clearance of control chylomicron cholesterol was delayed when injected into diabetic recipients compared to when these chylomicrons were injected into control recipients (P < 0.005). Clearance of diabetic chylomicron cholesterol was significantly slower when injected into control animals compared to control chylomicron injected into control animals (P < 0.02). In this animal model of atherosclerosis, we have demonstrated that diabetes leads to the production of an increased number of lipid and apo E–deficient chylomicron particles. Chylomicron particles from the control animals were cleared more slowly by the diabetic recipient (both triglyceride and cholesterol). The chylomicron particles obtained from the diabetic animals were cleared even more slowly when injected into the diabetic recipient. Although there was an initial delay in clearance of chylomicron triglyceride from the diabetic particle when injected into the control animals, the clearance over the first 15 minutes was not significantly different when compared to the control chylomicron injected into the control animal. On the other hand, the cholesterol clearance was significantly delayed. Thus, diabetes resulted in the production of an increased number of lipid- and apo E–deficient chylomicron particles. These alterations account, in part, for the delay in clearance of these particles.

Effect of weight reduction on the distribution of apolipoprotein A-I in high-density lipoprotein subfractions in obese non–insulin-dependent diabetic subjects

High-density lipoprotein (HDL) plays an important role in the process of reverse cholesterol transport, which may become suboptimal with increasing body fatness. HDL cholesterol that is reduced in obese subjects paradoxically decreases during weight reduction. To determine how weight reduction affects HDL subclasses that are involved in reverse cholesterol transport, we studied HDL from obese diabetic subjects before and after energy restriction within background diets high in either carbohydrate or monounsaturated fatty acids (MUFAs). Body weight, blood glucose, total cholesterol, and LDL cholesterol decreased after 8 and 12 weeks of weight reduction. With the very-low-fat diet, HDL cholesterol decreased significantly at 8 weeks, but recovered to initial levels after 12 weeks as body weight began to stabilize. Plasma apolipoprotein A-I (apo A-I) decreased substantially and significantly at 8 and 12 weeks with both diets, and was reflected in the reduction of apo A-I in HDL subclasses α1, α2, pre-β1, and pre-β2 + pre-β3. The calculation of the percentage distribution of apo A-I among HDL species showed that only the proportion of pre-β1-HDL decreased, whereas α2-HDL increased. This led to a significant increase in the α1 + α2/pre-β ratio, ie, the ratio of the large cholesterol ″storage” or ″sink” HDL to the HDL ″shuttle” fraction considered to be the initial acceptor of cell cholesterol. These data suggest that despite the reduction in HDL cholesterol and apo A-I, the redistribution of apo A-I in pre-β1-HDL and α-HDL observed with weight reduction appears to revert to the pattern that we have previously reported in lean as opposed to overweight subjects. Copyright © 2000 by W.B. Saunders Company

Lipid and apolipoprotein levels and distribution in patients with hypertriglyceridemia: Effect of triglyceride reductions with atorvastatin

Atorvastatin is a new hepatic hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor that has been demonstrated to be efficacious in reducing both triglyceride (TG) and cholesterol (CHOL) levels in humans. Twenty-seven (N = 27) patients with primary hypertriglyceridemia (TG > 350 mg/dL) were studied before and after 4 weeks on atorvastatin treatment at a dosage of either 20 (n = 16) or 80 (n = 11) mg/d. The present report examines changes in the plasma levels of several apolipoproteins, including apolipoprotein C-II (apoC-II), apoC-III, and apoE, after atorvastatin. Dose-dependent reductions in both CHOL (20.3% v 43.1%) and TG (26.5% v 45.8%) for the low and high dose, respectively, have been reported in these individuals. In addition to the reductions in apoB commonly associated with the use of HMG-CoA reductase inhibitors, significant reductions in apoE (37% and 49%), apoC-II (28% and 42%), and apoC-III (18% and 30%) were observed with this agent at the 20- and 80-mg/d dosage, respectively. Using fast protein liquid chromatography (FPLC) to fractionate whole plasma according to particle size, the effect of atorvastatin on lipid and apolipoprotein distribution in 20 lipoprotein fractions was also determined. Our results indicate that after 4 weeks on atorvastatin, (1) there was a 2-fold increase in the CHOL content as assessed by the CHOL/apoB ratio for 13 subfractions from very-low-density lipoprotein (VLDL) to small low-density lipoprotein (LDL); (2) there was a statistically significant reduction in the percentage of plasma apoB associated with VLDL-sized particles (30.5% v 26.8%); (3) there was a preferential reduction in plasma apoE from non-apoB-containing lipoproteins with treatment; (4) the losses of apoC-II and apoC-III, on the other hand, were comparable for all lipoprotein fractions; and (5) the fraction of plasma TG associated with HDL was increased after treatment. These changes in lipids and apolipoproteins did not depend on the dose of atorvastatin. There was, on the other hand, a dose-dependent reduction in cholesteryl ester transfer protein (CETP) activity, defined as the percentage of 3H-cholesteryl oleate transferred from high-density lipoprotein (HDL) to LDL. CETP activity was reduced by 10.3% and 26.4% with the low and high dose of atorvastatin. Together, these composition data would be consistent with a net reduction in the number of TG-rich lipoproteins that may be explained by (1) a reduction in VLDL synthesis, (2) a preferential removal of VLDL without conversion to LDL, and (3) a preferential accelerated removal of a subpopulation of LDL.

Apolipoproteins in human fetal colon: Immunolocalization, biogenesis, and hormonal regulation

The present investigation aimed at defining the localization of apolipoproteins (apo) A-I, A-IV, B-48, and B-100 along the crypt-villus axis of the human fetal colon, their biogenesis during gestation, and their hormonal regulation. Using immunofluoresence, the distribution of apo A-I and A-IV appeared as a gradient, increasing from the developing crypt to the tip of the villus. On the other hand, apo B-100 staining was found in the crypt and the lower mid-villus region with varying intensities in the upper villus cells, while the 2D8 antibody which recognizes both apo B-100 and B-48, revealed uniform staining along the crypt-villus axis. Apolipoprotein synthesis, determined by [35S] methionine labeling, immunoprecipitation, and SDS-PAGE showed a predominance of apo A-IV (53%), followed by apo A-I (23.9%), apo B-48 (13.4%), and apo B-100 (9.7%). The synthesis of each apolipoprotein was significantly modulated by hydrocortisone, insulin and epidermal growth factor (EGF). Apart from a decrease in apo B-100 exerted by EGF and a reduction in apo A-I resulting from the addition of insulin, the other apolipoproteins were all enhanced. Our data confirm that the fetal colon has the capacity to synthesize apolipoprotein A-I, A-IV, B-48, and B-100 and establish that their synthesis are modulated by hormonal and growth factors known to be involved in the regulatory mechanism of the functional development of human jejunum. J. Cell. Biochem. 70:354–365, 1998. © 1998 Wiley-Liss, Inc.

Apolipoproteins in human fetal colon: Immunolocalization, biogenesis, and hormonal regulation

The present investigation aimed at defining the localization of apolipoproteins (apo) A-I, A-IV, B-48, and B-100 along the crypt-villus axis of the human fetal colon, their biogenesis during gestation, and their hormonal regulation. Using immunofluorescence, the distribution of apo A-I and A-IV appeared as a gradient, increasing from the developing crypt to the tip of the villus. On the other hand, apo B-100 staining was found in the crypt and the lower mid-villus region with varying intensities in the upper villus cells, while the 2D8 antibody which recognizes both apo B-100 and B-48, revealed uniform staining along the crypt-villus axis. Apolipoprotein synthesis, determined by [35S] methionine labeling, immunoprecipitation, and SDS-PAGE showed a predominance of apo A-IV (53%), followed by apo A-I (23.9%), apo B-48 (13.4%), and apo B-100 (9.7%). The synthesis of each apolipoprotein was significantly modulated by hydrocortisone, insulin and epidermal growth factor (EGF). Apart from a decrease in apo B-100 exerted by EGF and a reduction in apo A-I resulting from the addition of insulin, the other apolipoproteins were all enhanced. Our data confirm that the fetal colon has the capacity to synthesize apolipoprotein A-I, A-IV, B-48, and B-100 and establish that their synthesis are modulated by hormonal and growth factors known to be involved in the regulatory mechanism of the functional development of human jejunum.

Suppression of the Protein Tyrosine Phosphatase LAR Reduces Apolipoprotein B Secretion by McA-RH7777 Rat Hepatoma Cells

Apolipoprotein B (apo B) secretion is reduced by insulin in rat hepatocytes. To evaluate possible mechanisms by which insulin action leads to inhibition of apo B secretion, we evaluated the effect of suppression of the protein-tyrosine phosphatase LAR on apo B secretion by McA-RH7777 (McA) rat hepatoma cells. A reduction in cellular LAR levels was accomplished by stable transfection of McA cells with LAR antisense cDNA. Previous studies indicate that LAR-antisense transfectants demonstrate increased insulin receptor signaling. In current studies, reduced LAR expression results in a 60% to 70% reduction in apo B secretion compared with null vector control. The reduction in apo B secretion correlated with a significant decrease in cellular apo B mRNA levels. Results suggests there is a relationship of protein tyrosine phosphorylation with regulation of apo B mRNA abundance in McA cells.

Plasma lipoprotein composition, apolipoprotein(a) concentration and isoforms in β-thalassemia

Patients with homozygous β-thalassemia show an abnormal lipoprotein profile. In asymptomatic heterozygotes the lipid pattern is less markedly affected but interestingly related to a diminished cardiovascular risk. The extent and significance of these findings are still a matter of debate and no data are available on lipoprotein(a) plasma levels. Seventy patients with homozygous β-thalassemia (HT-P), 70 β-thalassemia trait carriers (TT-C) and 70 sex and age-matched controls were investigated and their plasma lipoprotein profile and apo(a) phenotypes determined. In a subgroup of these same subjects (12 HT-P, 12 TT-C and 24 controls) and in 12 bone marrow-transplanted homozygous β-thalassemic patients (BMT-P) plasma lipoprotein composition was assessed. HT-P disclosed significantly lower total-cholesterol, LDL-cholesterol, HDL-cholesterol, apo A-I, apo B plasma levels and higher triglyceride concentration than TT-C (−7, −11, −8, −8, −13 and +11%, respectively) or controls (−39, −50, −46, −32, −30 and +35%, respectively). All lipoprotein subclasses were triglyceride-enriched, while LDLs were also protein-enriched and HDLs protein-depleted. TT-C disclosed a small but significant reduction in apo A-I and apo B plasma levels but only minor lipoprotein abnormalities with respect to the controls. BMT-P lipoprotein composition was intermediate between HT-P and normal subjects. Apo(a) plasma levels did not differ among the groups. A higher prevalence of `small' apo(a) isoforms was present in HT-P. Within the same `isoform group', apo(a) plasma levels were significantly lower in HT-P than in TT-C or controls. Since liver cirrhosis is almost always present in HT-P, it is conceivable that an altered hepatic apo(a) synthesis or catabolism due perhaps to diminished apolipoprotein glycation may be involved. In TT-C a partially improved cardiovascular risk profile was apparent (low hematocrit, low LDL-cholesterol and apo B), thus justifying the claim for a low prevalence of ischemic heart disease, but no Lp(a) plasma level modification could be detected.

Effect of a diet high in vegetables, fruit, and nuts on serum lipids

We assessed the effect of a diet high in leafy and green vegetables, fruit, and nuts on serum lipid risk factors for cardiovascular disease. Ten healthy volunteers (seven men and three women aged 33 ± 4 years [mean ± SEM]; body mass index, 23 ± 1 kg/m 2) consumed their habitual diet (control diet, 29% ± 2% fat calories) and a diet consisting largely of leafy and other low-calorie vegetables, fruit, and nuts (vegetable diet, 25% ± 3% fat calories) for two 2-week periods in a randomized crossover design. After 2 weeks on the vegetable diet, lipid risk factors for cardiovascular disease were significantly reduced by comparison with the control diet (low-density lipoprotein [LDL] cholesterol, 33% ± 4%, P < .001; ratio of total to high-density lipoprotein [HDL] cholesterol, 21% ± 4%, P < .001; apolipoprotein [apo] B:A-I, 23% ± 2%, P < .001; and lipoprotein (a) [Lp(a)], 24% ± 9%, P = .031). The reduction in apo B was related to increased intakes of soluble fiber ( r = .84, P = .003) and vegetable protein ( r = −.65, P = .041). On the vegetable compared with the control diet, the reduction in total serum cholesterol was 34% to 49% greater than would be predicted by differences in dietary fat and cholesterol. A diet consisting largely of low-calorie vegetables and fruit and nuts markedly reduced lipid risk factors for cardiovascular disease. Several aspects of such diets, which may have been consumed early in human evolution, have implications for cardiovascular disease prevention.

Reduction of intestinal apo A-IV mRNA levels in the cirrhotic rat.

In the present study, intestinal apo A-IV synthesis was investigated using a carbon tetrachloride (CCl4)-induced cirrhosis rat model. Triglyceride (TG) content in rat cirrhotic liver was increased markedly by 170% (P < 0.001) and apo B was increased by 20% (P < 0.05) compared with control levels. These results reflected the steatotic change in the liver. In contrast, TG levels in the small intestine of cirrhotic rats decreased significantly (P < 0.01). In addition, intestinal apo A-IV (jejunum P < 0.001; ileum P < 0.01) and its mRNA levels (jejunum P < 0.01; ileum P < 0.05) were also reduced. The decreased apo A-IV content in the jejunum was confirmed by immunohistochemical analysis. These results indicate that intestinal apo A-IV synthesis in cirrhosis is suppressed, at least under the condition of an overnight fast. Therefore, decreased intestinal apo A-IV synthesis may relate to the decreased ability to absorb fat in cirrhosis, but a fat-loading study will be necessary to confirm this hypothesis. It is unknown from the present study why serum apo A-IV level is not significantly decreased, despite a reduction in apo A-IV synthesis. The clearance of apo A-IV by the liver may be delayed or apo A-IV synthesis may be rather markedly enhanced during fat absorption in liver cirrhosis.

Reversible reduction of phospholipid bound arachidonic acid after low density lipoprotein apheresis. Evidence for rapid incorporation of plasmalogen phosphatidylethanolamine into the red blood cell membrane

In order to evaluate whether acute changes in fatty acids bound to phospholipids in plasma are transmitted into red blood cell membrane (RBCM) phospholipids, molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were analyzed after reduction of apo B containing lipoproteins through low density lipoprotein (LDL) apheresis in patients with severe hypercholesterolemia. As compared to the control, increases and decreases in molecular species with arachidonic acid (20:4) and with linoleic acid (18:2), respectively, at sn-2 of plasma diacyl-PC were seen in the patients before the apheresis. Directly after the procedure, the sum of species of plasma and RBCM PC plus PE with 20:4 were reduced. Two days after apheresis major species of plasma diacyl-PC reapproached preapheresis values while, in contrast, the composition of plasma alkenylacyl(plasmalogen)-PE was distinctly altered. In plasmalogen-PE of RBCM similar modifications were induced by the apheresis as in the same subgroup in plasma. In vitro experiments using vesicles with plasmalogen-PE labeled at sn-2 with either [14C]20:4 or a fluorescent pyrenedecanoyl residue indicated fast incorporation of the subgroup into the RBCM. In contrast, diacyl-PE was not taken up by the RBCM. In conclusion, apo B containing lipoproteins are partially responsible for the supply of phospholipids with arachidonic acid to RBCM, in particular by means of the fast incorporation of plasmalogen-PE. The transmission of changes induced by apheresis in plasma into those of the RBCM suggest that erythrocytes play an important role in the homeostasis of fatty acids bound to plasma phospholipids in vivo.

Effects of a diet restricted in saturated fatty acids and cholesterol on the composition of apolipoprotein A-I-containing lipoprotein particles in the fasting and fed states

To test the hypothesis that diet may exert differential effects on apolipoprotein (apo) A-I--containing high-density-lipoprotein (HDL) particles with (w) and without (w/o) apo A-II [Lp(A-I w A-II) and Lp(A-I w/o A-II)], the effects of a diet low in saturated fatty acids and cholesterol [National Cholesterol Education Panel (NCEP) Step 2 diet] on these lipoproteins were determined in eight normolipidemic subjects, aged 53-74 y, in both the fasting and nonfasting states. Compared with a diet high in saturated fatty acid and cholesterol, consumption of an NCEP diet (6 mo) lowered fasting plasma, low-density-lipoprotein, and HDL cholesterol, and nonfasting plasma cholesterol, triglyceride, and HDL cholesterol (P < 0.05- < 0.005). Phospholipid in fasting and nonfasting Lp(A-I w A-II) and Lp(A-I w/o A-II) was lower during the NCEP diet (P < 0.05-0.001), but reductions in apo A-I or A-II were observed only in Lp(A-I w A-II). In contrast, differences in particle-size profiles were detected in Lp(A-I w/o A-II) but not in Lp(A-I w A-II). These observations provide further evidence that Lp(A-I w A-II) and Lp(A-I w/o A-II) are distinct metabolic entities.

Endotoxin and GM-CSF-mediated down-regulation of macrophage apo E secretion is inhibited by a TNF-specific monoclonal antibody.

Macrophage activation is associated with increased secretion of monokines, proteases, arachidonic acid metabolites, reactive oxygen, and nitrogen intermediates and yet decreased secretion of apolipoprotein E (apo E). Although the kinetics of apo E down-regulation have been investigated, the mechanism(s) involved remains unknown. In the present study, the question of whether macrophage-activating factors such as lipopolysaccharide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF) directly result in apo E down-regulation or indirectly by inducing the secretion of other inflammatory mediators has been investigated. LPS-stimulated macrophages demonstrated a dose-dependent reduction in apo E secretion with a 70% decrease occurring following a 48-h incubation with 20 ng/ml LPS. Coculture of these cells with a neutralizing concentration of a hamster monoclonal antibody against murine tumor necrosis factor (TNF) inhibited the LPS-mediated reduction in apo E secretion. This inhibitory effect resulting from TNF neutralization was not observed using pooled hamster immunoglobulin G, or hamster monoclonals against murine interleukin-1 alpha (IL-1 alpha), IL-1 beta, or interferon-gamma. Similar results were observed when GM-CSF was used to induce apo E down-regulation. The inhibitory effects of TNF neutralization on endotoxin-induced apo E down-regulation were dependent on LPS concentration and were no longer apparent at concentrations greater than 200 ng/ml. These results suggest that an autocrine, TNF-dependent mechanism may play a role in the down-regulation of apo E secretion during macrophage activation.