A rapid and simple method for measurement of total protein in very low density lipoproteins by the Lowry assay

The potential ameliorating effect of vitamin E on bleomycin - induced lung fibrosis in adult albino rats

Lung fibrosis is a critical interstitial lung disease with poor prognosis. There is an urgent need to develop a proper and cost-effective therapeutic modality that can reverse and/or ameliorate lung fibrosis. Vitamin E is one of the widely investigated dietary antioxidants which has been linked to improvement of many health problems. The current study was conducted to evaluate the possible roles of vitamin E in prevention and treatment of bleomycin (BLM) induced lung fibrosis. Physiological, anatomical, histopathological and immunohistochemical studies were done to assess and compare between the structure and function of the lung tissue in lung fibrosis model, early and late treated groups with vitamin E. Furthermore, measurement of transforming growth factor-β(TGF-β), E-cadherin, Smad-3, BAX, BCL2, malondialdehyde (MDA), and superoxide dismutase (SOD) were done. The study revealed that administration of vitamin E helped to improve signs of lung fibrosis, as reflected by amelioration of structure and functions of lungs as well as the decrease in TGF-β levels and inhibition of α-SMA/collagen I profibrotic pathway. These findings highlight the importance of administration of vitamin E as a prophylactic agent prior to BLM therapy and as an adjuvant treatment in cases of lung fibrosis.

Human small-intestinal gluten-degrading bacteria and its potential implication in celiac disease

Celiac disease (CeD) is an immune-mediated chronic disorder triggered by the ingestion of wheat gluten in genetically predisposed individuals. Gluten is a major food ingredient, infamously containing proline and glutamine-rich domains that are highly resistant to digestion by mammalian proteolytic enzymes. Thus, adhering to a gluten-free diet (GFD) is the only known treatment for CeD, albeit with many complications. Therefore, any therapy that eliminates the gluten immunogenic part before it reaches the small intestine is highly desirable. Probiotic therapy containing gluten-degrading bacteria (GDB) and their protease enzymes are possibly new approaches to treating CeD. Our study aimed to identify novel GDB from the duodenal biopsy of the first-degree relative (FDR) subjects (relatives of diseased individuals who are healthy but susceptible to celiac disease) with the potential to reduce gluten immunogenicity. Using the gluten agar plate technique, bacterial strains Brevibacterium casei NAB46 and Staphylococcus arlettae R2AA77 displaying glutenase activity were screened, identified, and characterized. Whole-genome sequencing found gluten-degrading prolyl endopeptidase (PEP) in the B. casei NAB46 genome and glutamyl endopeptidase (GEP) in the S. arlettae R2AA77 genome. Partially purified PEP has a specific activity of 1.15 U/mg, while GEP has a specific activity of 0.84 U/mg, which are, respectively, 6- and 9-fold times higher after concentrating the enzymes. Our results showed that these enzymes could hydrolyse immunotoxic gliadin peptides recognized in western blot using an anti-gliadin antibody. Additionally, a docking model was proposed for representative gliadin peptide PQPQLPYPQPQLP in the active site of the enzymes, where the residues of the N-terminal peptide extensively interact with the catalytic domain of the enzymes. These bacteria and their associated glutenase enzymes efficiently neutralize gliadin immunogenic epitopes, opening possibilities for their application as a dietary supplement in treating CeD patients.

Phytoaccumulation of zinc from contaminated soil using ornamental plants species Helianthus annuus L. and Tagetes erecta L

Intensive research on hyperaccumulator plant species provides an alternative method to cleanup heavy metal contaminated sites using these plants. Helianthus annuus and Tagetes erecta are suitable hyperaccumulator plant species for removing zinc (Zn) from contaminated soil because of their high phytoremediation effectiveness. The present study focused on to evaluate comparative efficacy of Zn accumulation using H. annuus and T. erecta. Plantlets were exposed to different Zn concentrations (10, 50, 100, 300, and 500 mg kg^-1) for 20, 40, and 60 days while changes in morphological, biochemical, and enzyme activity markers were evaluated. The concentration of Zn in various plant parts was determined using an atomic absorption spectrophotometer (AAS). After 60 days H. annuus showed greatest accumulation of Zn in the root and shoot (216.7 and 109.5 mg kg^-1), whereas the Zn accumulation T. erecta (209.5 and 97.84 mg kg^-1) was found comparatively less in the root and shoot. The result showed increased polyphenol and proline concentrations with increasing Zn concentrations which were maximal in H. annuus 6.642 mg g^-1 and 25.474 µmol g^-1, respectively. At 60 days, APX (4.145 mM mg^-1), CAT (2.558 mM mg^-1), and GR (52.23 mM mg^-1) antioxidant enzymatic activities were observed with higher concentrations. Analysis of ultrastructure confirmed Zn transport and localization in root and shoot tissues examined through FESEM-EDX, Fluorescence microscopy, and optical microscopy. The present research findings concluded with the high amount of removal of Zn from contaminated soil using H. annuus and T. erecta for ecofriendly approach to soil cleanup followed by sustainable agriculture.

Protective role of antifusarial eco-friendly agents (Trichoderma and salicylic acid) to improve resistance performance of tomato plants

Fusarium wilt triggered great losing in tomato plants quality and quantity in all worlds. In the recent experiment, physiological resistance performance in tomato seedlings using Trichoderma harzianum and salicylic acid (SA) either (individual or combination) anti Fusarium had been studied. In vitro antifungal prospective of T. harzianum and SA against F. oxysporum were also examined. A noticeable antifungal capacity with highest activity of 10 and 8 mm ZOI after the treatment with the T. harzianum and SA. Also, Trichoderma have great ability to decreasing Fusarium growth by 25% inhibition at dual culture method. The MIC of SA was 1.5 mM to reduce Fusarium growth. For more ultrastructure by TEM of Fusarium treated with SA and Trichoderma showed alteration of cell wall as well as cytoplasmic components of mycelium, macroconidia and microconida. In the current experiment, ameliorative potentials of T. harzianum and SA either (individual or combination) via soil or foliar application were administered to the Fusarium- infected tomato plants and then disease index, growth indicators, photosynthetic pigments, metabolic markers, and antioxidant isozymes were assessed. The achieved result indicates that T. harzianum and SA through two modes (foliar and soil) lowered PDI by 12.50 and 20.83% and produced great protecting ability by 86.36 and 72.2%. The results revealed, infected seedlings exhibited high decrement in all tested growth characters, photosynthetic pigment contents, contents of total carbohydrate and protein, whereas proline, phenols and enzymes’ activity were elevated under Fusarium infectivity. It was concluded that use of combination (T. harzianum and SA) acted as a commercially eco-friendly instrument for intensifying the defense system of tomato plants against Fusarium wilt.

Antioxidant and immunomodulatory effect of AKSS16-LIV01 – a multi herbal formulation against ethanol induced liver dysfunction in mice

Background

Liver complication arises commonly due to high alcohol consumption rate. Majority of the people residing in both developed and under developed countries consuming alcohol face various liver complications such as liver fibrosis, fatty liver, liver cirrhosis and even hepatocellular carcinoma. Invention of safe and symptomatic medication to overcome this situation is a new challenge worldwide. The main objective of the study is to deliver a safe and symptomatic medication to reduce the ethanol induced liver dysfunction.

Methods

In this study we have developed a multi herbal formulation (AKSS-16-LIV01) which minimised liver damage against various toxicants. Swiss albino mice were divided into seven groups where ethanol induced damage was observed for weeks followed by sanative response observation by our herbal formulation. The groups are normal control group, ethanol treated group (50% v/v), AKSS16-LIV01 low dose (75 mg/kg/day) pre-treated group, AKSS16-LIV01 middle dose (150 mg/kg/day) pre-treated group, AKSS16-LIV01 high dose (300 mg/kg/day) pre-treated group, Sylimarin pre-treated group (100 mg/kg/day) and only AKSS16-LIV01 (300 mg/kg/day) treated group.

Results

The results potrayed significant elevation of various biochemical parameters, lipid profile parameters, lipid peroxidation, nitric oxide (NO) concentration, nitric oxide synthase level and pro inflammatory cytokines level i.e. tumor necrosis factor (TNF-α) and transforming growth factor (TGF-β1) in the ethanol induced mice. On the other hand serum total protein, total albumin, albumin globulin ratio and level of tissue antioxidant enzymes activity (SOD, CAT, GSH and GPx) were significantly reduced by ethanol. Dose depended therapeutic application of the formulation (AKSS16-LIV01) significantly suppressed all the relevant above parameters and protected the liver from ethanol induced fibrogenesis. Apart from this gross morphology of the liver, H&E liver histology and massontrichrome&serius red examination of the liver section strongly supported the hepatoprotive effect of the formulation as compared with standard drug Sylimarin. Result of the study implies that developed multi herbal formulation (AKSS16-LIV01) at a dose of 300 mg/kg/day gave the best optimum response to reduce the ethanol intoxication.

Conclusion

Result clearly depict that AKSS16-LIV01 may be a safe and nontoxic medication which protect the liver against ethanol induced oxidative injury and maintained pro inflammatory cytokines level in the future.

Graphical Abstract

Metabolic profiling analysis upon acylcarnitines in tissues of hepatocellular carcinoma revealed the inhibited carnitine shuttle system caused by the downregulated carnitine palmitoyltransferase 2

The carnitine shuttle system (CSS) plays a crucial role in the transportation of fatty acyls during fatty acid β-oxidation for energy supplementation, especially in cases of high energy demand, such as in cancer. In this study, to systematically characterize alterations of the CSS in hepatocellular carcinoma (HCC), acylcarnitine metabolic profiling was carried out on 80 pairs of HCC tissues and adjacent noncancerous tissues (ANTs) by using ultra-performance liquid chromatography coupled to mass spectrometry. Twenty-four acylcarnitines classified into five categories were identified and characterized between HCCs and ANTs. Notably, increased saturated long-chain acylcarnitines (LCACs) and decreased short- and medium-chain acylcarnitines (S/MCACs) were simultaneously observed in HCC samples. Subsequent correlation network and heatmap analysis indicated low correlations between LCACs and S/MCACs. The mRNA and protein expressions of carnitine palmitoyltransferase 2 (CPT2) was significantly downregulated in HCC samples, whereas CPT1A expression was not significantly changed. Correspondingly, the relative levels of S/MCACs were reduced and those of LCACs were increased in BEL-7402/CPT2-knockdown cells compared to negative controls. Both results suggested that decreased shuttling efficiency in HCC might be associated with downregulation of CPT2. In addition, decreases in the mRNA expression of acetyl-CoA acyltransferase 2 were also observed in HCC tissues and BEL-7402/CPT2-knockdown cells, suggesting potential low β-oxidation efficiency, which was consistent with the increased expression of stearoyl-CoA desaturase 1 in both samples. The systematic strategy applied in our study illustrated decreased shuttling efficiency of the carnitine shuttle system in HCC and can provide biologists with an in-depth understanding of β-oxidation in HCC.

Metabolomic analysis of polar metabolites in lipoprotein fractions identifies lipoprotein-specific metabolic profiles and their association with insulin resistance

While the molecular lipid composition of lipoproteins has been investigated in detail, little is known about associations of small polar metabolites with specific lipoproteins. The aim of the present study was to investigate the profiles of polar metabolites in different lipoprotein fractions, i.e., very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and two sub-fractions of the high-density lipoprotein (HDL). The VLDL, IDL, LDL, HDL(2), and HDL(3) fractions were isolated from serum of sixteen individuals having a broad range of insulin sensitivity and characterized using comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC×GC-TOFMS). The lipoprotein fractions had clearly different metabolite profiles, which correlated with the particle size and surface charge. Lipoprotein-specific associations of individual metabolites with insulin resistance were identified, particularly in VLDL and IDL fractions, even in the absence of such associations in serum. The results indicate that the polar molecules are strongly attached to the surface of the lipoproteins. Furthermore, strong lipoprotein-specific associations of metabolites with insulin resistance, as compared to their serum profiles, indicate that lipoproteins may be a rich source of tissue-specific metabolic biomarkers.

Effects of moderate exercise on VLDL₁ and Intralipid kinetics in overweight/obese middle-aged men

Prior moderate exercise reduces plasma triglyceride (TG)-rich lipoprotein concentrations, mainly in the large very low-density lipoprotein (VLDL₁) fraction, but the mechanism responsible is unclear. We investigated the effects of brisk walking on TG-rich lipoprotein kinetics using a novel method. Twelve overweight/obese middle-aged men underwent two kinetic studies, involving infusion of Intralipid to block VLDL₁ catabolism, in random order. On the afternoon prior to infusion, subjects either walked on a treadmill for 2 h at ∼50% maximal oxygen uptake or performed no exercise. Multiple blood samples were taken during and after infusion for separation of Intralipid (S(f) 400) and VLDL₁ (S(f) 60-400). VLDL₁-TG and -apoB production rates were calculated from their linear rises during infusion; fractional catabolic rates (FCR) were calculated by dividing linear rises by fasting concentrations. Intralipid-TG FCR was determined from the postinfusion exponential decay. Exercise reduced fasting VLDL₁-TG concentration by 30% (P = 0.007) and increased TG enrichment of VLDL₁ particles [30% decrease in cholesteryl ester (CE)/TG ratio (P = 0.007); 26% increase in TG/apoB ratio (P = 0.059)]. Exercise also increased VLDL₁-TG, VLDL₁-apoB, and Intralipid-TG FCRs by 82, 146, and 43%, respectively (all P < 0.05), but had no significant effect on VLDL₁-TG or -apoB production rates. The exercise-induced increase in VLDL₁-apoB FCR correlated strongly with the exercise-induced changes in VLDL₁ CE/TG (r = -0.659, r = 0.020) and TG/apoB (r = 0.785, P = 0.002) ratios. Thus, exercise-induced reductions in VLDL₁ concentrations are mediated by increased catabolism, rather than reduced production, which may be facilitated by compositional changes to VLDL₁ particles that increase their affinity for clearance from the circulation.

HDMCP uncouples yeast mitochondrial respiration and alleviates steatosis in L02 and hepG2 cells by decreasing ATP and H2O2 levels: a novel mechanism for NAFLD

BACKGROUND/AIMS

To explore the uncoupling activity of hepatocelluar downregulated mitochondrial carrier protein (HDMCP) in a yeast expression system and its function in non-alcoholic fatty liver disease (NAFLD).

METHODS

Molecular cloning and RT-PCR were used for yeast protein expression and uncoupling activity was assessed. Western blot analysis was used to determine HDMCP level in rat NAFLD and steatotic L02 and hepG2 cell models where their presence was confirmed by pathologic (Nile red and H-E staining) and biochemical changes. RNA interference was used to knock down HDMCP level and mitochondrial ATP and hydroperoxide levels were measured for potential mechanism exploration.

RESULTS

We found a significant GDP insensitive uncoupling activity of HDMCP in yeast mitochondria and its increased expression in animal and cell models. HDMCP was significantly increased with culture time and steatosis was aggravated when HDMCP level was knocked down. Furthermore, we found that HDMCP might function through promoting ATP depletion and decreasing H(2)O(2) production.

CONCLUSION

This study adds supportive data to the hypothesis that HDMCP might be a long postulated liver-specific uncoupling protein and broadens our understanding of the pathogenesis of NAFLD. More importantly, HDMCP might become a novel drug target for its ability in alleviating hepatic steatosis.

Additive beneficial effects of amlodipine and atorvastatin in reversing advanced cardiac hypertrophy in elderly spontaneously hypertensive rats

1. Additive beneficial effects on cardiovascular disease have been reported for amlodipine and atorvastatin. However, it is still unclear whether the combination of amlodipine and atorvastatin has additive beneficial effects on the regression of advanced cardiac hypertrophy in hypertension. In the present study, the effects of the drug combination on advanced cardiac hypertrophy were investigated in elderly spontaneously hypertensive rats (SHR). 2. Elderly SHR (36 weeks old) were randomly allocated into four groups of 12: (i) a vehicle-treated control group; (ii) an amlodipine (10 mg/kg per day)-treated group; (iii) an atorvastatin (10 mg/kg per day)-treated group; and (iv) a group treated with a combination of amlodipine and atorvastatin (both at 10 mg/kg per day). Drugs were administered by oral gavage every morning for a period of 12 weeks before hearts were harvested for analysis. 3. Combined administration of amlodipine and atorvastatin significantly suppressed cardiomyocyte hypertrophy, interstitial fibrosis and upregulation of hypertrophic and profibrotic genes, and also improved left ventricular diastolic dysfunction to a greater extent than did amlodipine monotherapy. Further beneficial effects of combination therapy on advanced cardiac hypertrophy were associated with a greater reduction of NADPH oxidase-mediated increases in cardiac reactive oxygen species (ROS), rather than decreased blood pressure and serum cholesterol levels. 4. To elucidate the underlying molecular mechanisms, we examined cardiovascular NADPH oxidase subunits and found that amlodipine clearly attenuated the expression of p47(phox) and p40(phox) and slightly but significantly reduced p22(phox) and Rac-1 levels in heart tissue. Combination treatment with amlodipine plus atorvastatin led to a further reduction in p22(phox), p47(phox) and Rac-1 protein levels compared with amlodipine alone. 5. In conclusion, combined amlodipine and atorvastatin treatment has a greater beneficial effect on advanced cardiac hypertrophy compared with amlodipine monotherapy. The benefits are likely to be related to the additive effects of the drugs on the suppression of NADPH oxidase-mediated ROS generation.

Serum saturated fatty acids containing triacylglycerols are better markers of insulin resistance than total serum triacylglycerol concentrations

AIMS/HYPOTHESIS

The weak relationship between insulin resistance and total serum triacylglycerols (TGs) could be in part due to heterogeneity of TG molecules and their distribution within different lipoproteins. We determined concentrations of individual TGs and the fatty acid composition of serum and major lipoprotein particles and analysed how changes in different TGs and fatty acid composition are related to features of insulin resistance and abdominal obesity.

METHODS

We performed lipidomic analyses of all major lipoprotein fractions using two analytical platforms in 16 individuals, who exhibited a broad range of insulin sensitivity.

RESULTS

We identified 45 different TGs in serum. Serum TGs containing saturated and monounsaturated fatty acids were positively, while TGs containing essential linoleic acid (18:2 n-6) were negatively correlated with HOMA-IR. Specific serum TGs that correlated positively with HOMA-IR were also significantly positively related to HOMA-IR when measured in very-low-density lipoproteins (VLDLs), intermediate-density lipoproteins (IDLs) and LDL, but not in HDL subfraction 2 (HDL(2)) or 3 (HDL(3)). Analyses of proportions of esterified fatty acids within lipoproteins revealed that palmitic acid (16:0) was positively related to HOMA-IR when measured in VLDL, IDL and LDL, but not in HDL(2) or HDL(3). Monounsaturated palmitoleic (16:1 n-7) and oleic (18:1 n-9) acids were positively related to HOMA-IR when measured in HDL(2) and HDL(3), but not in VLDL, IDL or LDL. Linoleic acid was negatively related to HOMA-IR in all lipoproteins.

CONCLUSIONS/INTERPRETATION

Serum concentrations of specific TGs, such as TG(16:0/16:0/18:1) or TG(16:0/18:1/18:0), may be more precise markers of insulin resistance than total serum TG concentrations.

A new combined multicompartmental model for apolipoprotein B-100 and triglyceride metabolism in VLDL subfractions

The use of stable isotopes in conjunction with compartmental modeling analysis has greatly facilitated studies of the metabolism of the apolipoprotein B (apoB)-containing lipoproteins in humans. The aim of this study was to develop a multicompartment model that allows us to simultaneously determine the kinetics of apoB and triglyceride (TG) in VLDL(1) and VLDL(2) after a bolus injection of [(2)H(3)]leucine and [(2)H(5)]glycerol and to follow the catabolism and transfer of the lipoprotein particles. Here, we describe the model and present the results of its application in a fasting steady-state situation in 17 subjects with lipid values representative of a Western population. Analysis of the correlations showed that plasma TG was determined by the VLDL(1) and VLDL(2) apoB and TG fractional catabolic rate. Furthermore, the model showed a linear correlation between VLDL(1) TG and apoB production. A novel observation was that VLDL TG entered the circulation within 21 min after its synthesis, whereas VLDL apoB entered the circulation after 33 min. These observations are consistent with a sequential assembly model of VLDL and suggest that the TG is added to a primordial apoB-containing particle in the liver.

Uptake of acetaldehyde-modified (ethylated) low-density lipoproteins by mouse peritoneal macrophages

The uptake of acetaldehyde-modified (ethylated) low-density lipoproteins (LDLs) by murine peritoneal macrophages is described and compared with the uptake of acetylated LDLs. The fluorescent marker DiI was used. No competition between ethylated and acetylated LDLs was observed. Ethylated LDL uptake was not inhibited by polyinosinic acid or fucoidin. Our conclusion is that uptake of ethylated and acetylated LDLs can be done by two different receptors.

The level of serum lipids, vitamin E and low density lipoprotein oxidation in Wilson's disease patients

The aim of this study was to estimate the level of lipids and of the main serum antioxidant, alpha-tocopherol (vitamin E), and to evaluate the susceptibility of low density lipoprotein (LDL) to oxidation in Wilson's disease patients. It was assumed that enhanced LDL peroxidation caused by high copper levels could contribute to the injury of liver and other tissues. The group investigated comprised 45 individuals with Wilson's disease treated with penicillamine or zinc salts and a control group of 36 healthy individuals. Lipids were determined by enzymatic methods, alpha-tocopherol by high performance liquid chromatography, the susceptibility of LDL to oxidation in vitro by absorption changes at 234 nm during 5 h and end-products of LDL lipid oxidation as thiobarbituric acid reacting substances. In Wilson's disease patients total cholesterol, LDL cholesterol and alpha-tocopherol levels were significantly lower compared with the control group. No difference in LDL oxidation in vitro between the patients and the controls was stated.

CONCLUSION

enhanced susceptibility of isolated LDL for lipid peroxidation in vitro was not observed in Wilson's disease patients. One cannot exclude, however, that because of low alpha-tocopherol level lipid peroxidation in the tissues can play a role in the pathogenesis of tissue injury in this disease.

Effect of heparin-stimulated plasma lipolytic activity on VLDL APO B subclass metabolism in normal subjects

Heparin given intravenously enhances lipolysis, although fasting lipids are not markedly altered in long-term administration. In the present study we investigated heparin-induced acute perturbation of VLDL subclass metabolism. Eight men were examined during a control study and during an 8.5 h infusion of heparin. 2H3-leucine was used as tracer and kinetic constants derived using a non-steady-state model. Heparin infusion increased both plasma lipoprotein and hepatic lipase activity and raised plasma FFAs two-fold (P < 0.001). The fractional catabolic rate (FCR) of VLDL1 apo B increased on heparin (25.7 +/- 4.2 and 10.8 +/- 1.7 pools/d, heparin vs. control, P < 0.02). The FCR of VLDL2 apo B increased to 12.6 +/- 1.9 pools/d on heparin vs. 8.8 +/- 1.1 pools/d during the control (NS). Total VLDL apo B production was not significantly changed (824 +/- 45 and 692 +/- 91 mg/d, heparin vs. control, NS). We conclude that during heparin infusion, the catabolism of especially large triglyceride-rich VLDL1 apo B is greatly increased. However, although the FFA levels were high during the heparin study, the production of total VLDL apo B did not rise. These findings are consistent with the known action of heparin on lipoprotein lipase but indicate that acute increase in plasma FFA levels does not lead to a rise in VLDL apo B production.

Metabolic basis of hypotriglyceridemic effects of insulin in normal men

The mechanism by which acute insulin administration alters VLDL apolipoprotein (apo) B subclass metabolism and thus plasma triglyceride concentration was evaluated in 7 normolipidemic healthy men on two occasions, during a saline infusion and during an 8.5-hour euglycemic hyperinsulinemic clamp (serum insulin, 490 +/- 30 pmol/L). During the insulin infusion, plasma triglycerides decreased by 22% (P < .05), and serum free fatty acid decreased by 85% (P < .05). The plasma concentration of VLDL1 apo B fell 32% during the insulin infusion, while that of VLDL2 apo B remained constant. A bolus injection of [3-(2)H]leucine was given on both occasions to trace apo B kinetics in the VLDL1 and VLDL2 subclasses (Svedberg flotation rate, 60-400 and 20-60, respectively), and the kinetic basis for the change in VLDL levels caused by insulin was examined using a non-steady-state multicompartmental model. The mean rate of VLDL1 apo B synthesis decreased significantly by 35% (P < .05) after 0.5 hour of the insulin infusion (523 +/- 87 mg/d) compared with the saline infusion (808 +/- 91 mg/d). This parameter was allowed to vary with time to explain the fall in VLDL1 concentration. After 8.5 hours of hyperinsulinemia, the rate of VLDL1 apo B synthesis was 51% lower (321 +/- 105 mg/d) than during the saline infusion (651 +/- 81 mg/d, P < .05). VLDL2 apo B production was similar during the saline (269 +/- 35 mg/d) and insulin (265 +/- 37 mg/d) infusions. No significant changes were observed in the fractional catabolic rates of either VLDL1 or VLDL2 apo B. We conclude that acute hyperinsulinemia lowers plasma triglyceride and VLDL levels principally by suppressing VLDL1 apo B production but has no effect on VLDL2 apo B production. These findings indicate that the rates of VLDL1 and VLDL2 apo B production in the liver are independently regulated.

Heterozygous hepatic lipase deficiency, due to two missense mutations R186H and L334F, in the HL gene

Hepatic lipase (HL) is an endothelial enzyme involved in the metabolism of intermediate density lipoproteins (IDL) and high density lipoproteins (HDL) in plasma. In a Finnish pedigree consisting of 18 members belonging to three generations two missense mutations RI86H and L334F in exons 5 and 7 of the HL gene co-segregated with low post-heparin HL activity. Haplotype analysis of the HL gene in family members revealed a high degree of genetic variation and demonstrated that the two missense mutations reside on the same chromosome. In vitro site-directed mutagenesis and expression of the cDNA constructs in COS-1 cells revealed that the R186H mutation leads to a protein that is not secreted while the L334F mutation results in the production of a HL protein that is secreted but has only about 30% of wild type HL activity. Carriers of the mutated HL gene exhibited clearly reduced HL activity and mass in post-heparin plasma. Probably due to their heterozygous carrier status they had only moderate elevation of total triglycerides, IDL, and LDL-triglycerides. The LDL-particles were enriched in triglycerides and depleted of cholesterol. Also their HDL2- and HDL3-particles were enriched in triglycerides.

Interaction of apo E-containing lipoproteins with the LDL receptor-related protein LRP

The low-density lipoprotein (LDL) receptor-related protein (LRP) is a multifunctional cell surface receptor that interacts with apolipoprotein E (apo E)-rich lipoproteins, and alpha2-macroglobulin (alpha2-M) in the activated state (alpha2-M*). Whether LRP is a physiologically relevant lipoprotein receptor for naturally occurring apo E-rich lipoproteins, however, is still under discussion. To address this question, we isolated beta-migrating very low density lipoprotein (beta-VLDL) from rabbits by using gel filtration chromatography. Biochemical analysis of beta-VLDL subfractions demonstrated that we isolated apo E- and cholesterol-rich triglycerides with differences in composition and size. Binding and uptake characteristics of beta-VLDL subfractions and alpha2-M* on mouse peritoneal macrophages (MPM) and Hep G2 cells were examined by electron microscopy. One of the beta-VLDL subfractions, beta-VLDL(II), bound specifically to LRP on MPM and Hep G2. beta-VLDL(II) competed with the binding of alpha2-M* without addition of exogenous apo E. Furthermore, binding and uptake of beta-VLDL(II) and alpha2-M* were not affected by either lactoferrin or Ca2+-free medium. The results indicate that naturally occurring apo E-rich lipoproteins do exist and that they very likely interact with LRP via the same binding site as alpha2-M*.

A study to determine the response of coronary atherosclerosis to raising low high density lipoprotein cholesterol with a fibric-acid derivative in men after coronary bypass surgery. The rationale, design, and baseline characteristics of the LOCAT Study. Lopid Coronary Angiography Trial

Several clinical trials have shown that reducing serum cholesterol levels retards the progression of coronary atherosclerosis assessed by serial angiography. By contrast, as yet no studies have addressed the impact of increasing high density lipoprotein (HDL) cholesterol levels on progression of coronary artery disease (CAD). As HDL cholesterol is inversely related to the risk of CAD, we hypothesize that an intervention that raises low HDL cholesterol concentrations may have a beneficial effect on the course of CAD. Lopid Coronary Angiography Trial (LOCAT) was designed to test this hypothesis. Three hundred and ninety-five men, aged < or = 70 years, all of whom had previously undergone coronary bypass surgery, were randomly assigned to receive either slow-release gemfibrozil, 1200 mg once daily, or a matching placebo for on average 2 1/2 years. The lipid inclusion criteria were HDL cholesterol concentration < or = 1.1 mmol/L, low density lipoprotein (LDL) cholesterol < or = 4.5 mmol/L, and serum triglyceride < or = 4.0 mmol/L. Subjects were not accepted if they had manifest diabetes, body mass index > 30 kg/m2, uncontrolled hypertension, or if they were regular smokers. All randomized subjects underwent baseline coronary angiography, which will be repeated at the end of the study. The angiograms will be analyzed using the Cardiovascular Measurement System, a validated computer-assisted image-analysis and quantitation package. The primary endpoints are the changes in the per-patient mean of 1) the average diameter of evaluable native coronary segments, and 2) the minimal luminal diameter of evaluable stenoses, and 3) the appearance of new lesions. Extensive lipoprotein and other metabolic studies and analyses of genetic polymorphisms are carried out to study the determinants of CAD progression. At baseline, the study subjects were 59.1 +/- 6.8 (mean +/- standard deviation) years old, had a body mass index 26.4 +/- 2.2 kg/m2, and serum triglyceride, serum cholesterol, HDL cholesterol, and LDL cholesterol concentrations 1.64 +/- 0.64, 5.17 +/- 0.64, 0.82 +/- 0.14, and 3.61 +/- 0.53 mmol/L, respectively.

Cholesterol efflux from Fu5AH hepatoma cells induced by plasma of subjects with or without coronary artery disease and non-insulin-dependent diabetes: importance of LpA-I:A-II particles and phospholipid transfer protein

We measured the capacity of human plasma to induce cholesterol efflux from Fu5AH rat hepatoma cells in four groups of men with or without non-insulin-dependent diabetes mellitus (NIDDM) and coronary artery disease (CAD). Plasma from men with both NIDDM and CAD (n = 47) had the lowest efflux capacity (17.3 +/- 3.6%) whereas healthy control subjects with neither diabetes nor CAD (n = 25) had the highest capacity (19.8 +/- 3.4%). The groups with CAD but no diabetes (n = 44) and with NIDDM but no CAD (n = 35) had intermediate efflux values (18.5 +/- 3.8 and 18.5 +/- 3.9%, respectively). In a 2 x 2 factorial ANOVA, the differences were significant with respect to the presence of CAD (P = 0.038) and NIDDM (P = 0.041), with no interaction between the factors. The concentration of HDL particles containing apolipoprotein (apo) A-I but no apo A-II (LpA-I) was not related to efflux capacity in univariate or multivariate analyses. A multivariate regression analysis showed that when controlled for the presence of NIDDM and CAD, the concentration of particles containing both apo A-I and apo A-II (LpA-I:A-II) and plasma phospholipid transfer protein activity were both positively, independently, and significantly (P < 0.001) related to cholesterol efflux capacity.

Effects of postmenopausal estrogen/progestin replacement therapy on LDL particles; comparison of transdermal and oral treatment regimens

The aim of the study was to compare the effects of continuous oral estrogen/progestin therapy to the effects of transdermal estrogen therapy combined with cyclic oral progestin on the properties of LDL particles. Eighty postmenopausal women were randomly allocated to receive either oral (continuous 17-beta-estradiol 2 mg and norethisterone acetate 1 mg per day, E2/NETA) or transdermal therapy (patches delivering continuous 17-beta-estradiol, E2, 0.05 mg/day with sequential oral medroxyprogesterone acetate, MPA, 10 mg/day for 12 days/cycle). The groups had similar mean values and ranges of age, BMI and postmenopausal status. The blood samples were taken at baseline, and twice at 1 year before and after MPA administration. LDL particle size distribution was determined by gradient gel electrophoresis and LDL was isolated by sequential ultracentrifugation for compositional analyses. Concentrations of total LDL mass, LDL cholesterol and LDL protein decreased in the oral treatment group (p < 0.01, p < 0.001 and p < 0.01, respectively), whereas they remained unchanged during the transdermal therapy. Particle size of the major LDL peak remained unchanged during both transdermal and oral therapies. HDL cholesterol concentration decreased significantly in both treatment groups (p < 0.001 for both). Serum triglyceride and HDL cholesterol concentrations were the strongest determinants of LDL particle size ( r = -0.50 and r = 0.54, respectively, p < 0.001 for both). The cholesteryl esters and free cholesterol content of the LDL particles decreased in the oral treatment group (p < 0.05). Phospholipid content of LDL increased in both groups receiving either oral or transdermal therapy (p < 0.01 for both). In conclusion, oral administration of 17-beta-estradiol and norethisterone acetate caused a decrease in LDL mass by decreasing the number and cholesterol content of LDL particles. The concomitant decrease of HDL cholesterol by progestins may partly negate this beneficial effect of LDL lowering.

Regulation of low-density lipoprotein particle size distribution in NIDDM and coronary disease: importance of serum triglycerides

An increase of low-density lipoprotein triglycerides (LDL-Tg) was found to be an independent coronary artery disease (CAD) risk factor for non-insulin-dependent diabetic (NIDDM) patients in a recent prospective study. We examined the composition and size of LDL particles in 50 NIDDM men with angiographically verified CAD (NIDDM+ CAD+) and in 50 NIDDM men without CAD (NIDDM(+)-CAD-) as compared to 50 non-diabetic men with CAD (NIDDM - CAD +) and 31 non-diabetic men without CAD (NIDDM-CAD-). The groups had similar ranges of age and BMI. LDL particle size was determined by gradient gel electrophoresis, and LDL was isolated by sequential ultracentrifugation for compositional analyses. Serum Tg was increased in NIDDM patients as compared to non-diabetic subjects (p < 0.05), and in patients with CAD as compared to subjects without the disease (p < 0.05). LDL cholesterol was lower in NIDDM patients than in non-diabetic subjects (p < 0.001). Mean diameter of LDL particles was less than 255 A, but closely comparable in all groups. The presence of NIDDM was associated with increases of Tg and protein but lowering of free cholesterol in LDL (p < 0.005 for all). In multivariate regression analyses neither NIDDM nor CAD were associated with LDL particle size, but serum Tg was the major determinant of LDL size in both NIDDM and non-diabetic subjects (p < 0.001). When the patients were divided into quartiles according to fasting serum Tg levels, the LDL particle size and free cholesterol content decreased, but Tg and protein contents of LDL particles increased from the lowest to the highest Tg quartile (analysis of variance p < 0.001 for all). When the subjects were categorized into two groups according to the median of VLDL-Tg (1.10 mmol/l) LDL size was associated with VLDL-Tg in the high but not in the low VLDL-Tg group. We conclude that in NIDDM patients with or without CAD serum Tg is the major determinant of the properties of LDL particles. The clinical implication is that in NIDDM serum Tg should be as low as possible to prevent atherogenic changes in LDL.

Inhibition of low density lipoprotein oxidation by myrigalone B, a naturally occurring flavonoid

The influence of myrigalone B, a flavonoid from the fruit exudate of Myrica gale L. on Cu(2+)-induced oxidation of low density lipoprotein from cholesterol fed rabbits was investigated. Myrigalone B was an effective antioxidant, as shown by its ability to dose-dependently prolong the lag time for the formation of conjugated dienes. A 100% increase in lag time corresponds to a myrigalone B concentration of 1.4 +/- 1.1 microM. For alpha-tocopherol, used as a reference, this effect corresponds to a concentration of 1.9 +/- 1.2 microM. Myrigalone B also dose-dependently reduced the maximum rate of formation of conjugated dienes, 1.4 microM causing a 15 +/- 5% reduction, but it had no influence on the maximal amount of conjugated dienes formed.

Effect of cholesterol feeding on the susceptibility of lipoproteins to oxidative modification

In previous studies we have shown that the liver endothelial and Kupffer cells in hypercholesterolemic rabbits are very active in endocytosis of low-density lipoprotein (LDL) and beta-very-low-density lipoprotein (beta-VLDL) (Nenseter et al. (1992) J. Lipid Res. 33, 867-877; Gudmundsen et al. (1993) J. Lipid Res. 34, 589-600). These data raised the question whether subfractions of LDL and beta-VLDL were modified in vivo to forms recognized by the scavenger/oxidized LDL receptors of the non-parenchymal liver cells. The purpose of the present study was to address this question by assessing the effect of cholesterol feeding on the susceptibility of the lipoproteins to oxidative modification in vitro. In addition, the effect of HDL on the lipid peroxidation of LDL was evaluated. LDL and beta-VLDL were isolated from rabbits given a diet supplemented with cholesterol (2% w/w) for 3 weeks. The extent of Cu(2+)-catalyzed oxidation of the lipoproteins was compared with that of LDL from control-fed rabbits. Extent of oxidation assessed by formation of conjugated dienes, lipid peroxides, thiobarbituric acid-reactive substances, relative electrophoretic mobility and uptake of lipoproteins by J774 macrophages suggested that LDL and beta-VLDL from the hypercholesterolemic rabbits were more susceptible to oxidation than LDL from normolipidemic rabbits. HDL protected LDL and beta-VLDL from lipid peroxidation in vitro. Taken together, the increased susceptibility of LDL and beta-VLDL to oxidative modification in vitro, combined with the low levels of alpha-tocopherol, and the reduced ratio of HDL to LDL cholesterol observed in the hypercholesterolemic rabbits, and the protective effect of HDL on the lipid peroxidation of LDL, support the probability that oxidative modification of LDL and beta-VLDL occur in vivo in the hypercholesterolemic rabbits.

High density lipoprotein subfractions, apolipoprotein A-I containing lipoproteins, lipoprotein (a), and cholesterol ester transfer protein activity in alcoholic women before and after ethanol withdrawal

We studied 11 female alcoholics before and after ethanol withdrawal of 2 weeks and 10 healthy normolipidaemic, nonalcoholic women of similar age. In alcoholic women the HDL2 mass was increased by 63% (P < 0.01) on admission and normalized (P < 0.01) during abstention. The concentrations of HDL3 cholesterol and its mass remained unchanged throughout the study. Consistently with the fall of HDL2 gradient gel electrophoresis analyses also demonstrated decrease of the cholesterol concentration of HDL2b and HDL2a (P < 0.05) during alcohol withdrawal. On admission the apo A-II concentration was increased by 48% (P < 0.01) and it was normalized (P < 0.001) during abstention. Among apo A-I containing lipoproteins the most prominent change occurred in Lp A-I:A-II, which fell by 32% (P < 0.01) during 1 week's alcohol withdrawal. During abstention the lipoprotein (a) concentration increased in 10 out of 11 women. In patients cholesteryl ester transfer (CETP) activity increased by 35% (P < 0.01) during 1 week of ethanol withdrawal. On admission postheparin plasma lipoprotein (LPL) and hepatic lipase activities were increased by 25% (P = NS); during 1 week's abstention they both returned to the control level (P < 0.05- < 0.01). In conclusion, chronic alcoholic women display multiple changes of lipoprotein metabolism which are rapidly reversed during abstinence. In contrast to alcoholic men, studied previously by us using the same study design and methods, there was no significant elevation of HDL3 cholesterol and apo A-I. The data suggest that alcohol interferes with several regulatory steps of HDL metabolism which are partly gender dependent.

Different hydrolytic efficiencies of adipose tissue lipoprotein lipase on very-low-density lipoprotein subfractions separated by heparin-Sepharose chromatography

Human very-low-density lipoproteins (VLDL) were subfractionated by heparin-Sepharose chromatography into an unbound (A) and three bound (B, C and D) populations at increasing ionic strengths. Subfractions were characterized regarding their chemical composition and efficiency of triacylglycerol hydrolysis by rat adipose tissue LPL. The triacylglycerol content decreased, whereas the cholesterol and protein contents increased from subfractions A and B to subfraction D. VLDL-D showed the highest apo E/apo C ratio, though all the subfractions contained appreciable apo E. Appearance of VLDL-A resulted from exceeding the binding capacity of the column, since practically all its particles eluted at positions of bound VLDL under re-chromatography. Subfractions B, C and D stimulated LPL activity on emulsified tri[14C]oleoylglycerol to a similar extent, indicating that their apo C-II content was equally effective activating LPL. Incubation of tri[14C]oleoylglycerol labeled VLDL subfractions with fat pad pieces in the presence or absence of heparin resulted in greater hydrolysis and fatty acid uptake for VLDL-B and -C than for VLDL-D, a pattern observed over a wide range of LPL activities in the media. We conclude: (1) any VLDL particle can interact with heparin, which is consistent with the presence of apo E in all the subfractions, and (2) triacylglycerols in apo E-rich VLDL are less efficiently hydrolyzed by LPL than those in apo E-poor particles. We propose that richness in apo E impairs LPL action upon VLDL and decreases the rate of delivery of fatty acids to peripheral tissues.

Analysis of apolipoprotein size distribution by electroimmunoblotting from non-denaturing composite gels

An exponential gradient gel with 0-35% acrylamide and 0.5% agarose was developed for electrophoresis of intact lipoproteins with subsequent electroimmunoblotting. The system resolved in a single gel lipoprotein-associated proteins of sizes from 'free' apoproteins to VLDL. Reproducibility between gels was good (coefficient of variation < 8%). Examination of the effect of mild glutaraldehyde fixation on immunodetection showed variable results (lack of effect on apos (a), AII, and AIV; inhibition of apoB; enhancement of apos AI and E). The composite gel system described here will simplify analysis of apolipoprotein distributions in both health and disease and therefore will likely be useful in future clinical applications.

The effect of moderate alcohol intake on serum apolipoprotein A-I-containing lipoproteins and lipoprotein (a)

Two main types of lipoprotein particles are identified within high-density lipoprotein (HDL): those containing both apolipoprotein (apo) A-I and apo A-II (Lp A-I:A-II) and those containing only apo A-I (Lp A-I). To study the effects of prolonged moderate alcohol intake on apo A-I-containing lipoproteins in serum, 60 g/d of ethanol was administered to 10 healthy male volunteers (age, 27 to 45 years) during 3 weeks. The drinking period was preceded and followed by an abstinence period of 3 weeks. The HDL3 cholesterol level increased by 17% (P less than .01) and decreased by 22% (P less than .001) on and off alcohol, respectively. The HDL2 cholesterol increased by 17% (P = NS) during ethanol intake and decreased by 14% during the following abstention (P less than .01). The serum concentration of apo A-I increased by 17% (P less than .001) during drinking and came back to the starting level after 2 weeks of abstention. Ethanol intake caused an increase in the serum levels of both Lp A-I and Lp A-I:A-II, the former explaining one third of the total increase of apo A-I. The Lp (a) concentration decreased by 33% (P less than .05) during the first week of ethanol intake, but increased back to the starting level until the end of drinking. These data suggest that the increment of the antiatherogenic Lp A-I may be one beneficial effect provided by ethanol with respect to coronary heart disease.

Plasma very low density lipoproteins from male rats fed casein or soybean protein diets: a comparison of fatty acid composition and influence on prostanoid production

In studies with male rats fed for 4 wk semipurified diets containing olive oil and casein or soybean protein, protein-dependent effects were observed in the fatty acid composition of the VLDL lipids, especially with regard to the pattern of polyunsaturated fatty acids. Compared with VLDL from rats fed soybean protein diet (S-VLDL), VLDL from casein-fed rats (C-VLDL) contained a greater level of oleic acid, and a reduced level of linoleic acid and arachidonic acid, in the phosphatidylcholine fraction. The proportion of 5,8,11-eicosatrienoic acid, 20:3 (n-9), varied among the different lipid classes. The highest concentration of this fatty acid (13% by weight of total fatty acids) was observed in the phosphatidylinositol fraction of C-VLDL. The level of linoleic acid was approximately halved in the triacylglycerol and cholesteryl ester fractions of C-VLDL compared with S-VLDL. When mouse peritoneal macrophages were incubated with different concentrations of S-VLDL, a saturable accumulation of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) was observed in the cell medium. In contrast, very low levels of 6-keto-PGF1 alpha and TXB2 were observed in the cell medium of macrophages incubated with C-VLDL at different lipoprotein concentrations, suggesting that the composition of VLDL may play an important role in relation to cellular prostanoid metabolism.

Effect of physical training on lipids, lipoproteins, apolipoproteins, lipases, and endogenous sex hormones in men with premature myocardial infarction

In 17 men, aged 27 to 54 years, with myocardial infarction 2 to 10 months before the current exercise study, we aimed to determine whether 3 months of exercise training, at a level designed to elevate high-density lipoprotein cholesterol (HDLC), would be associated with changes in endogenous sex steroid hormones and postheparin lipoprotein and hepatic lipases, and whether the changes in sex hormones, lipids, lipoproteins, apolipoproteins, and physical activity were interrelated. Supervised bicycle ergometry, 30 minutes, 3 days per week, eliciting 75% of maximum heart rate, produced a significant training effect, with a 26% increase in the duration of the exercise test at a standardized, submaximal workload (P less than or equal to .001), and a reduction in heart rate measured at a standardized submaximal workload, P = .08. After 3 months' training, mean HDLC increased 23% (30 to 37 mg/dL), P less than or equal to .001, mean apo A2 increased 19% (43 to 51 mg/dL), P less than or equal to .001, and the ratio of total cholesterol (TC) to HDLC decreased 26% (P less than or equal to .01), while estradiol (E2) levels decreased 45% (50.1 to 27.8 pg/mL), P less than or equal to .0001. After 1 and 2 months' exercise, TC (12% [P less than or equal to .001], 11% [P less than or equal to .01]), and low-density lipoprotein cholesterol (LDLC) (13% [P less than or equal to .01], 12% [P less than or equal to .01]) were reduced. Hepatic lipase decreased 16% (P less than or equal to .01) and 16% (P less than or equal to .05) after 1 and 3 months' exercise. There were no significant changes in apo A1, lipoprotein lipase, testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), or weight. By stepwise regression analysis, after 3 months' training, 66% (P = .0025) of the variance for the increase in HDLC from baseline to day 90 was accounted for independently by a decrease in triglyceride (F = 13.2, P = .003), by reduced heart rate on a fixed submaximal load (F = 12.7, P = .0035), and by a decrease in hepatic lipase (F = 5.5, P = .036). A modest, achievable exercise program can have significant cardiovascular benefit for men after myocardial infarction by ameliorating their hyperestrogenemia, reducing TC and LDLC, improving the TC to HDLC ratio, and elevating HDLC and apo A2. The increment in HDLC was related independently to improved capacity to sustain submaximal exercise and to exercise-induced reductions in triglyceride and postheparin hepatic lipase.

Lipoproteins and acute phase response during acute infection. Interrelationships between C-reactive protein and serum amyloid-A protein and lipoproteins

To study the interrelations between the changes of acute phase proteins and those of serum lipoproteins in acute infections we measured the concentrations of different lipoproteins, serum amyloid-A protein and C-reactive protein and activities of lipoprotein lipase and hepatic lipase during acute and convalescence phase and after complete recovery in 64 patients with infectious diseases (30 with viral infection and 34 with bacterial infection). The maximal decrements of both low density lipoprotein and high density lipoprotein cholesterol correlated significantly with the acute phase levels of C-reactive protein and serum amyloid-A protein. The acute phase concentration of very low density lipoprotein triglyceride correlated inversely to C-reactive protein level (r = -0.31, P less than 0.05) but not to serum amyloid-A protein level. Regression analysis showed that the concentration of C-reactive protein was a significant predictor of very low density lipoprotein triglyceride level in the acute phase of infection but not during convalescence. These results and the previous findings that C-reactive protein binds to low and very low density lipoproteins and that serum amyloid-A protein is associated with high density lipoprotein give credence to the view that C-reactive protein and serum amyloid-A protein interfere with the metabolism of serum lipoproteins during acute phase of infection.

Increased high-density lipoprotein cholesterol concentration in alcoholics is related to low cholesteryl ester transfer protein activity

Cholesteryl ester transfer protein (CETP) facilitates the transfer of cholesteryl esters from HDL to apoB-containing lipoproteins. Since alcoholics have high HDL cholesterol and low LDL cholesterol levels, a defect in cholesteryl ester transfer could be responsible for the alcohol-induced alteration in cholesterol distribution between lipoproteins. To test this hypothesis, we compared CETP activity in plasma from 30 alcoholics without severe liver damage and 16 control subjects. Plasma CETP activity was 28% lower in the alcoholics compared with the controls (P less than 0.001), while the teetotallers among the latter had slightly higher CETP activity than those who consumed alcohol in moderation. CETP activity increased slowly after ethanol withdrawal, but did not reach the control level within the 7-day observation period. A positive correlation was observed between plasma CETP activity and the LDL cholesterol HDL cholesterol ratio (r = 0.480, P less than 0.002), whereas CETP activity showed a negative correlation with HDL cholesterol level (r = -0.467, P less than 0.001). The results indicate that defective transfer of cholesteryl esters from HDL to LDL contributes to the high HDL cholesterol levels in alcoholics.

Serum lipids and lipoproteins in alcoholic women during pregnancy

The concentrations of triglyceride, cholesterol, phospholipids, and proteins in the major lipoprotein fractions (very-low-density lipoprotein [VLDL], low-density lipoprotein [LDL], and high-density lipoproteins [HDL] HDL2 and HDL3) were monitored in 20 pregnant women who chronically abused alcohol and in 15 abstinent pregnant women. Five of the alcohol users gave birth to infants with fetal alcohol syndrome (FAS). Lipoproteins were fractionated by sequential flotation from samples taken at 16, 20, 24, 28, 32, 36, and 40 weeks of gestation and 6 to 8 weeks after delivery. In abstinent women, concentrations of VLDL and LDL triglyceride, cholesterol, phospholipids, and proteins increased in late gestation. Concentrations of HDL2-cholesterol, phospholipids, proteins, and total HDL2 were increased during the 16th to 28th weeks, but HDL3 remained unchanged. Alcohol abuse clearly reduced the normal increase in total and LDL-cholesterol, as well as in LDL phospholipids, proteins, and total LDL during the 24th to 40th weeks. LDL changes were most pronounced in alcoholic women who later produced FAS infants. Alcohol abuse also increased HDL3. Furthermore, in alcohol users, the normal increase in VLDL was accentuated, especially so in women with FAS infants, and that of HDL2 was reduced. The significance of the changes found remains obscure, but they may be related to impaired function of the fetoplacental unit.

Interaction of beta-very-low-density lipoproteins with rat liver cells

Cholesteryl-ester-rich very-low-density lipoproteins (beta-VLDL) are considered to be atherogenic because in vitro they can provoke cholesterol accumulation in macrophages. The greatest population of macrophages resides inside the liver and in the present study the rat beta-VLDL uptake by the various rat liver cell types is determined in vivo and compared to the uptake of rat VLDL. beta-VLDL isolated from cholesterol-fed rats was iodinated and injected into the rat. After 10 min of circulation, 45% of the injected beta-VLDL was found in the liver. A low-temperature cell-isolation procedure shows that rat liver parenchymal cells form the major site for beta-VLDL uptake (96%) and, consequently, rat liver macrophages (nonparenchymal liver cells) do not perform a quantitatively significant role in the uptake of these lipoproteins. In vitro competition studies indicate that apolipoprotein (apo) E is the site recognised by liver parenchymal cells and even a 600-fold excess of apo-E-free human LDL was an ineffective competitor. Furthermore it can be demonstrated that induction of apo-B,E receptors on liver parenchymal cells by estrogen treatment does not result in a significant increased uptake of beta-VLDL. These data show that recognition of beta-VLDL is presumably exerted by the remnant receptor. Intracellular processing of both the apolipoproteins and phospholipids of beta-VLDL was followed by subcellular distribution studies. It appears that, within 45 min, 75% of the apolipoproteins are degraded and subsequently released from the liver. In contrast the phospholipids remain associated with the liver for a prolonged time and a specific transfer to the mitochondrial fraction is found. It can be concluded that liver parenchymal cells form in vivo the major site for beta-VLDL uptake and it appears that recognition of beta-VLDL is coupled to internalization and processing of both the apolipoproteins and phospholipids by a route which involves the lysosomes.

Effect of copper deficiency on the composition of three high-density lipoprotein subclasses as separated by heparin-affinity chromatography

Copper deficiency in rats produces a hypercholesterolemia with a marked increase in HDL fraction. This study investigated changes in the plasma distribution and composition of HDL subclasses as affected by copper deficiency. Plasma HDL were separated into the following three subclasses by heparin-affinity chromatography: HDL containing no apo E but high in apo A-I (HDL-E0); HDL with an intermediate level of apo E (HDL-E1); and HDL highly enriched in apo E but low in apo A-I (HDL-E2). The compositional analysis showed that the hypercholesterolemia observed in copper-deficient rats was due specifically to an increase in plasma cholesterol carried by HDL-E0. Copper deficiency did not alter the percent distribution of apo A-I in HDL-E0, but lowered the apo A-I content in HDL-E1 and HDL-E2, with an increase in apo E in these subclasses. The total plasma concentration of apo A-I was, however, significantly elevated in Cu-deficient rats, which was attributable to an increase in the total number of circulating HDL particles. No difference was noted between Cu-deficient and control groups in the distribution of free cholesterol or the ratio of free cholesterol to esterified cholesterol in any of the HDL subclasses. The present results and earlier observations suggest that copper deficiency may produce a defect in the plasma clearance or tissue uptake of the HDL subclass high in apo A-I but devoid of apo E (HDL-E0), which may be mediated by the specific apo A-I receptor or non-endocytotic transfer of HDL-E0 cholesterol to the liver. Such metabolic defects may partly explain the simultaneous increases in both plasma HDL cholesterol and apo A-I and altered cholesterol homeostasis observed in copper deficiency.

Comparison of the effects of two different doses of alcohol on serum lipoproteins, HDL-subfractions and apolipoproteins A-I and A-II: a controlled study

Our earlier studies have shown that heavy alcohol intake increases the serum concentration of HDL2. The present study aimed to test which HDL subfraction is affected by moderate alcohol intake, and to examine the time- and dose-dependency of alcohol-induced changes in serum lipoproteins. Therefore, 30 or 60 g day-1 of alcohol were given to 10 healthy male volunteers during two 3-week periods separated by an abstinence period of 3 weeks. Lipoproteins were fractioned by sequential flotation. On both doses the total HDL3 concentrations rose progressively, the maximum increases being 10 and 25% at the end of respective drinking periods. In contrast, the HDL2 increased slightly only on the dose of 60 g day-1. The serum concentrations of apoprotein A-I and A-II increased on both doses but significantly only on the dose of 60 g day-1; the increments being 22 and 35%, respectively. On the basis of these and our earlier findings we conclude that (i) the effects of heavy and moderate alcohol intake on serum HDL-subfractions are different: the former preferentially increases the HDL2 whereas the latter augments the HDL3; (ii) alcohol-induced changes in serum lipoproteins are both time- and dose-dependent.

Apolipoprotein-E-binding proteins of rat liver endothelial cells

In an attempt to characterise the apolipoprotein-E-binding proteins of rat liver endothelial cells, we prepared membranes from monolayer cultures of liver endothelial cells as an enriched source of membrane receptors. The membranes could specifically bind iodinated very-low-density lipoproteins (VLDL) and the binding could be inhibited effectively by unlabelled VLDL and high-density lipoproteins, but only moderately by low-density lipoproteins. To identify the binding proteins, we performed immunoprecipitation studies of solubilised iodinated liver endothelial cells and cell membranes, respectively, using purified apolipoprotein E and monospecific polyclonal IgG directed towards this apolipoprotein. The antibodies together with the bound apolipoprotein E and iodinated liver endothelial cell proteins were harvested with staphylococcal protein A-Sepharose. The immunoprecipitates were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and after autoradiography of the dried gel, the Mr of the liver endothelial cell proteins bound to apolipoprotein E could be determined. Two protein bands with molecular masses of 55-60 and 110, and a weak band of 170 kDa could be detected from intact cells. These proteins were specifically precipitated only in the presence of divalent cations, and might represent cell-surface receptors for apolipoprotein-E-containing lipoproteins. Additional bands were seen when cell membranes were used, the most prominent ones having molecular masses of 32 and 35 kDa. These proteins could be of intracellular origin, or they may be degradation products of the other apolipoprotein-E-binding proteins.

Changes in serum lipoprotein pattern induced by acute infections

To study the effects of acute infections on serum lipids and lipoproteins we measured the concentration and composition of different lipoproteins, apoproteins A-I, A-II, and B, and the activities of plasma postheparin lipolytic enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL) during acute and convalescence phase and after complete recovery in 72 infectious patients (33 with viral infection and 39 with bacterial infection). The mass concentrations of both low density lipoprotein (LDL) (P less than .001) and high density lipoprotein (HDL)2 (P less than .002) were reduced during acute infections due to the lowering of their cholesterol, phospholipid, and protein contents. The reduction of LDL cholesterol was maximal at the acute stage of infection (change -15%, P less than .001) while the reduction of HDL2 cholesterol was maximal during the convalescence (change -35%, P less than .001). During acute infections LDL became triglyceride-enriched (11.8 v 8.6%, P less than .0001) but cholesterol-poor (36.6 v 39.3%, P less than .0001). The ratio of HDL cholesterol/LDL cholesterol was significantly reduced during the convalescence (0.42 +/- 0.15 v 0.53 +/- 0.19, P less than .0001). The concentrations of apo A-I and apo A-II were decreased during acute infections (changes -22%, P less than .001, and -16%, P less than .001, respectively). The very low density lipoprotein (VLDL) was 18% higher during the convalescence period than after the recovery due to the elevations of VLDL triglycerides, cholesterol, and phospholipids. The activity of LPL was reduced both in the acute and convalescence phase, whereas that of HL was reduced only in the acute phase of infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Separation of three compositionally distinct subclasses of rat high density lipoproteins by heparin-affinity chromatography

The composition of 3 subclasses of plasma high density lipoproteins (HDL) separated by heparin-affinity chromatography was characterized. Plasma was obtained from Fischer-344 adult male rats fed a semi-purified diet containing 1% cholesterol. HDL particles were isolated by ultracentrifugation and agarose column chromatography. The purified HDL fraction was applied to a column (1.0 X 28 cm) packed with heparin-Sepharose CL-6B and eluted at 4 degrees C with 5 mM Tris buffer (pH 7.4) with varying concentrations of NaCl. The first peak (P1) eluted with 50 mM NaCl and 25 mM MnCl2 was albumin; the second peak (P2) eluted at 70 mM NaCl accounted for 78% of total plasma HDL-cholesterol (HDL-C) and 82% of total HDL protein. The particles of this HDL subclass measured 113 A in diameter and were devoid of apolipoprotein (apo) E, but high in apo A-I. The third peak (P3) eluted with 290 mM NaCl represented 4.3% of total HDL-C and 6.0% of total HDL protein, and contained apo E (25% of its protein). The average size of the particles was 126 A. The last peak (P4) eluted at 0.6 M NaCl accounted for 18% of total HDL-C and 12% of HDL protein. The particles of P4 were considerably larger in size (156 A) relative to those of P2 and P3, and rich in apo E (73% of its protein) with relatively low concentrations of apo A-I and C. Based on the compositional characteristics and sizes of the particles, the HDL subclasses of P2, P3 and P4 were designated as HDL2 with no apo E, HDL2 with moderate apo E, and HDL1 (or HDLc), respectively. The above results provide evidence for the existence of 3 compositionally distinct subclasses of plasma HDL in the rat, which may differ with regard to their roles in the transport and metabolism of cholesterol.

Insulin therapy induces antiatherogenic changes of serum lipoproteins in noninsulin-dependent diabetes

To study the effects of rigorous insulin therapy on serum lipoproteins in patients with noninsulin-dependent diabetes not controlled with oral agents only, we measured serum lipoproteins, apoproteins, lipolytic enzymes, and glucose disposal using an insulin clamp technique before and after 4 weeks of insulin therapy. Lipoproteins were isolated by ultracentrifugation and high density lipoprotein (HDL) subfractions, by rate-zonal density gradient ultracentrifugation. The group included 11 women and eight men (age 58 +/- 1 years and RBW 125 +/- 4%). Body weight, glycosylated hemoglobin, mean diurnal glucose, plasma free insulin, and glucose uptake (M-value) were 75 vs. 76 kg; 11.9 vs. 8.9%; 234 vs. 124 mg/dl; 12 vs. 27 microU/ml; and 5.0 +/- 0.4 vs. 7.1 +/- 0.6 mg/kg/min before and after insulin therapy, respectively. After insulin therapy there was a decrease of very low density lipoprotein (VLDL) triglyceride (-60%, p less than 0.001) but an increase of HDL2 cholesterol (+21%, p less than 0.001); HDL2 phospholipids (+38%, p less than 0.001); HDL2 proteins (+23%, p less than 0.01); and HDL2 mass (127 +/- 11 vs. 158 +/- 12 mg/dl, p less than 0.001). There was a decrease of HDL3 cholesterol (-13%, p less than 0.05); HDL3 phospholipids (-16%, p less than 0.05); HDL3 proteins (-18%, p less than 0.001); and HDL3 mass (179 +/- 6 vs. 146 +/- 6, p less than 0.01). Zonal profiles showed a redistribution of particles from HDL3 to HDL2. Serum apo A-I increased (p less than 0.05), apo A-II remained constant, but apo B decreased (-29%, p less than 0.001). The most marked change during insulin therapy was a 2.3-fold increase in adipose tissue lipoprotein lipase (LPL) activity (p less than 0.001). The changes of VLDL and HDL subfractions were not explained by respective changes of the blood glucose, free insulin, or M-value. The data indicate that intensive insulin therapy induces antiatherogenic changes in serum lipids and lipoproteins and suggest that the induction of LPL by insulin is the major factor responsible for redistribution of HDL particles from HDL3 to HDL2.

Effects of acipimox on serum lipids, lipoproteins and lipolytic enzymes in hypertriglyceridemia

Two separate studies were carried out with acipimox, a new antilipolytic agent with long-lasting activity. First, in a randomized, double-blind, cross-over study a dose of 750 mg/day of acipimox versus placebo was employed for 60 days in 11 patients with type IV hyperlipoproteinemia. Mean plasma triglyceride levels were reduced after acipimox compared to placebo (434 +/- 60 vs 777 +/- 224 mg/dl, P less than 0.01). Serum total cholesterol fell also significantly after acipimox compared to placebo. No significant alteration was observed in the HDL2/HDL3 ratio or in the concentration or composition of the HDL subfractions. Six patients with severe hypertriglyceridemia (2 type IV and 4 type V) and low lipoprotein lipase (LPL) activity took part in a second, open study, lasting for 9 months. Acipimox was given at a dose of 750 mg/day for the first 6 months and 1200 mg/day for the last period. The response of serum total and VLDL triglycerides was inconsistent. HDL cholesterol was significantly raised (+33.3%) after 9 months of treatment due to changes of HDL2 and HDL3 cholesterol, phospholipid and protein concentrations. LPL activity was markedly reduced in adipose tissue at 9 months. No significant changes occurred in postheparin plasma LPL activity. In contrast, hepatic lipase activity showed a reduction of about 25% from 6 months of treatment onwards.

Semi-automated enzyme-linked immunosorbent assay (ELISA) for the quantification of apolipoprotein B using monoclonal antibodies

A semi-automated competitive, double-antibody, solid-phase enzyme-linked immunosorbent assay for apolipoprotein B (Apo B) has been developed which utilizes microtiter plates with commercially available monoclonal antibodies and alkaline phosphatase-conjugated second antibody. The working range of the assay is 20-200 ng. The concentration of plasma Apo B was 0.88 +/- 0.20 g/l (n = 40) for a random sample of normal adults. The correlation coefficient for this assay, compared to a radial immunodiffusion assay, was 0.95 (slope = 1.13, intercept = -15). The quantification of the samples was not influenced by freezing and thawing, storage at -20 degrees C for up to 9 mth, or the lipoprotein particle on which the Apo B was present. The method is suitable for measurement of apolipoprotein B in either normal or pathological plasma, lipoprotein density classes, and is sensitive enough to quantify Apo B in cell biological and molecular biological investigations.

Effect of marginal zinc deficiency on the apolipoprotein-B content and size of mesenteric lymph chylomicrons in adult rats

To investigate the mechanisms underlining the impaired intestinal absorption of lipids in zinc deficiency, the apo-B content and chemical composition of chylomicrons from marginally zinc-deficient rats fed 2.8 ppm of dietary zinc (ZD) were compared with those from pair-fed (PF) and ad libitum control (CT) groups fed an adequate level (30.8 ppm) of zinc. Chylomicrons, obtained by cannulating the mesenteric lymph, were isolated by ultracentrifugation at 1.3 X 10(6) g/min at 12 C and purified by 2% agarose column chromatography. Apolipoprotein- (apo) B was separated by the method of isopropanol precipitation. The apo-B concentration of chylomicrons was lowered significantly in ZD group. The apo-B contents of chylomicrons in ZD, PF and CT rats, as expressed as % chylomicron protein, were 8.7 +/- 0.1, 11.5 +/- 0.5 and 10.7 +/- 0.7%, respectively. No significant differences were noted between ZD and PF groups in total protein (TP), phospholipid (PL), triglyceride (TG) and cholesterol (CH), although there was a slight decrease in TG and an increase in CH in CT rats compared with ZD and PF groups. The ratio of the core to surface constituents, as determined by TG/(TP + PL), was significantly higher in ZD group relative to the controls, suggesting that chylomicrons from ZD rats were larger. This finding was consistent with the appearance of larger chylomicron particles in the lacteal of the intestinal mucosa following lipid ingestion. These findings suggest that the intestinal synthesis of apo-B may be defective in zinc-deficient rats and may explain in part the impaired absorption of dietary lipids observed in zinc deficiency.

Surface diffusion in human serum lipoproteins

From the viscosity dependence of the 31P NMR signals, the diffusion coefficients DT of phospholipid molecules in the surface monolayer of HDL, LDL and VLDL have been determined. DT for HDL3 and HDL2 are found to be 2.3 X 10(-8) cm2/s and 1.8 X 10(-8) cm2/s, respectively. These values are similar to values reported for diffusion of phospholipid molecules in phospholipid bilayers above the gel to liquid crystalline phase transition temperature. Viscosity dependence of [16,16,16-2H3]phosphatidylcholine incorporated into HDL2 yielded a value similar to that determined by 31P (DT = 1.9 X 10(-8) cm2/s). Slower diffusion coefficients were measured for LDL2 and VLDL. VLDL had a value DT = 9.1 X 10(-9) cm2/s. The diffusion coefficient for LDL2 was 1.4 X 10(-9) cm2/s. Thus, diffusion of phospholipids in LDL2 is a full order of magnitude slower at 25 degrees C than diffusion of phospholipids in the HDLs.