Plasma apoB Research Articles

Anti-Atherogenic Properties of Allium ursinum Liophylisate: Impact on Lipoprotein Homeostasis and Cardiac Biomarkers in Hypercholesterolemic Rabbits.

The present investigation evaluates the capacity of Allium ursinum (wild garlic) leaf lyophilisate (WGLL; alliin content: 0.261%) to mitigate cardiovascular damage in hypercholesterolemic rabbits. New Zealand rabbits were divided into three groups: (i) cholesterol-free rabbit chow (control); (ii) rabbit chow containing 2% cholesterol (hypercholesterolemic, HC); (iii) rabbit chow containing 2% cholesterol + 2% WGLL (hypercholesterolemic treated, HCT); for eight weeks. At the zero- and eight-week time points, echocardiographic measurements were made, along with the determination of basic serum parameters. Following the treatment period, after ischemia-reperfusion injury, hemodynamic parameters were measured using an isolated working heart model. Western blot analyses of heart tissue followed for evaluating protein expression and histochemical study for the atheroma status determination. WGLL treatment mediated increases in fractional shortening; right ventricular function; peak systolic velocity; tricuspidal annular systolic velocity in live animals; along with improved aortic and coronary flow. Western blot analysis revealed WGLL-associated increases in HO-1 protein and decreases in SOD-1 protein production. WGLL-associated decreases were observed in aortic atherosclerotic plaque coverage, plasma ApoB and the activity of LDH and CK (creatine kinase) in plasma. Plasma LDL was also significantly reduced. The results clearly demonstrate that WGLL has complex cardioprotective effects, suggesting future strategies for its use in prevention and therapy for atherosclerotic disorders.

ω-3 Fatty Acid Ethyl Esters Diminish Postprandial Lipemia in Familial Hypercholesterolemia.

Impaired postprandial chylomicron metabolism induces hypertriglyceridemia and may increase the risk of atherosclerotic cardiovascular disease. Omega-3 fatty acid ethyl ester (ω-3 FAEE) supplementation decreases plasma triglycerides. However, its effect on postprandial chylomicron metabolism in familial hypercholesterolemia (FH) has not yet been investigated. We aimed to examine the effect of ω-3 FAEE supplementation on postprandial responses in plasma triglycerides, very-low-density lipoprotein (VLDL) apolipoprotein B (apoB)-100, and apoB-48 in FH patients receiving standard cholesterol-lowering treatment. We carried out an 8-week open-label, randomized, crossover intervention trial to test the effect of oral supplementation with 4 g/d ω-3 FAEE (46% eicosapentaenoic acid and 38% docosahexaenoic acid) on postprandial triglyceride, VLDL-apoB-100, and apoB-48 responses in FH patients after ingestion of an oral fat load. Plasma total and incremental triglyceride, VLDL-apoB-100, and apoB-48 0- to 10-hour area under the curve (AUC). ω-3 FAEE supplementation significantly (P < .05 in all) reduced concentrations of fasting plasma triglyceride (-20%), apoB (-8%), VLDL-apoB-100 (-26%), and apoB-48 (-36%); as well as systolic blood pressure (-6%) and diastolic blood pressure (-6%). Postprandial triglyceride and VLDL-apoB-100 total AUCs (-19% and -26%, respectively; P < .01) and incremental AUCs (-18% and -35%, respectively; P < .05), as well as postprandial apoB-48 total AUC (-30%; P < .02) were significantly reduced by ω-3 FAEE supplementation. Supplementation with ω-3 FAEEs improves postprandial lipemia in FH patients receiving standard care; this may have implications for further reducing atherosclerotic cardiovascular disease in this high-risk patient group.

Risk factors, topographic patterns and mechanism analysis of intracranial atherosclerotic stenosis ischemic stroke

Background: The association between topographic patterns, risk factors and stroke mechanisms of ICAS in first-ever stroke remains unknown. Methods: A large sample sized retrospective study was performed on first-ever ICAS ischemic stroke using DWI and MRA. Results: Hypertension (60.92%), cigarette smoking (26.82%), MCA (76.65%) and multiple vessels (65.37%) stenosis, were the major factors favoring different mechanisms. Subcortical lesions were the most occurring topographic patterns (41.4%). The common mechanism was LBO (66.3%). Statistical analysis showed a significant relationship between lesion patterns and mechanisms (r = 0.384, P = 0.001). Single mechanism had the higher apoB/apoAI ratio (P = 0.005) and levels of plasma apoB (P = 0.007) compared with multiple mechanisms. The anterior circulation stroke were more multiple mechanisms as compared to the posterior circulation stroke (P = 0.001). LBO was more prevalent in posterior circulation stroke than in anterior circulation stroke (P = 0.001). Conclusions: The topographic patterns of ischemic lesions is helpful in early identification of different mechanisms of ICAS. Monitoring apoB and apoB/apoA1 may help to predict the mechanism of stroke with ICAS. The prevalence of mechanisms differ between anterior and posterior circulation stroke with ICAS.

The controversy over the use of cholesteryl ester transfer protein inhibitors: is there some light at the end of the tunnel?

According to epidemiological studies, there is no clear relationship between the plasma cholesteryl ester transfer protein (CETP) concentration and the development of atherosclerosis in human populations. Although some studies suggest that increased CETP activity relates to undesirable profiles of plasma lipoproteins, promoting an anti-atherogenic plasma lipoprotein profile by drugs that inhibit CETP has not succeeded in preventing atherosclerosis in humans. This review describes 28 investigations in human populations dealing with plasma CETP, 11 in mice that express human CETP and seven in animals (six in rabbits and one in mice) in which plasma CETP activity was inhibited by drugs. Present review shows that models in mice expressing human CETP are not illuminating because they report increase as well reduction of atherosclerosis. However, investigations in rabbits and mice that develop severe hypercholesterolaemia clearly indicate that impairment of the plasma CETP activity elicits protection against the development of atherosclerosis; in all of these experiments are attained substantial reductions of the atherogenic lipoproteins, namely, plasma apoB containing lipoproteins. These models are strong indicators that the benefit in preventing atherosclerosis should be earned in cases of hyperlipidemia by CETP inhibitors.

Human PCSK9 promotes hepatic lipogenesis and atherosclerosis development via apoE- and LDLR-mediated mechanisms.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of hepatic low-density lipoprotein (LDL) receptors (LDLR), thereby, decreasing hepatocyte LDL-cholesterol (LDL-C) uptake. However, it is unknown whether PCSK9 has effects on atherogenesis that are independent of lipid changes. The present study investigated the effect of human (h) PCSK9 on plasma lipids, hepatic lipogenesis, and atherosclerotic lesion size and composition in transgenic mice expressing hPCSK9 (hPCSK9tg) on wild-type (WT), LDLR⁻/⁻, or apoE⁻/⁻ background. hPCSK9 expression significantly increased plasma cholesterol (+91%), triglycerides (+18%), and apoB (+57%) levels only in WT mice. The increase in plasma lipids was a consequence of both decreased hepatic LDLR and increased hepatic lipid production, mediated transcriptionally and post-transcriptionally by PCSK9 and dependent on both LDLR and apoE. Despite the lack of changes in plasma lipids in mice expressing hPCSK9 and lacking LDLR (the main target for PCSK9) or apoE (a canonical ligand for the LDLR), hPCSK9 expression increased aortic lesion size in the absence of apoE (268 655 ± 97 972 µm² in hPCSK9tg/apoE⁻/⁻ vs. 189 423 ± 65 700 µm(2) in apoE⁻/⁻) but not in the absence of LDLR. Additionally, hPCSK9 accumulated in the atheroma and increased lesion Ly6C(hi) monocytes (by 21%) in apoE⁻/⁻ mice, but not in LDLR⁻/⁻ mice. PCSK9 increases hepatic lipid and lipoprotein production via apoE- and LDLR-dependent mechanisms. However, hPCSK9 also accumulate in the artery wall and directly affects atherosclerosis lesion size and composition independently of such plasma lipid and lipoprotein changes. These effects of hPCSK9 are dependent on LDLR but are independent of apoE.

Evaluation of Lipid Profile and Apolipoproteins in Essential Hypertensive Patients.

Essential hypertension is one of the most common diseases of the Indian population contributing greatly to the morbidity, mortality and economic burden. It has a strong association with cardiovascular disease and abnormal lipid metabolism. Not only the traditional lipid parameters, but also the novel lipid components like Apo A1 and Apo B100 also have been identified to play a role. The present study was done to evaluate serum lipid profile and Apo A1, Apo B 100 in essential hypertensive patients and correlate their values with the degree of hypertension. Fasting samples from 55 age and sex matched controls and 55 essential hypertensives were tested for plasma glucose, serum urea, creatinine, lipid profile, apo A1 and apo B100. The cases were subclassified based on the severity of hypertension according to JNC criteria. The study showed a significantly raised value for serum cholesterol, triacylglycerol, Low Density Lipoprotein (LDL), Very Low-Density Lipoprotein (VLDL) in the hypertensive patients than the control group whereas serum High-Density Lipoprotein (HDL) registered a fall in the cases. Apo A1 revealed a non-significant fall in the hypertensive patients. In contrast, there was a rise in the serum apo B100 in the cases. Apo B100/apo A1 ratio was significantly raised in both stage I and stage II hypertensive patients in comparision to the controls. When correlated, serum apo A1 revealed a negative association where as serum apo B 100 showed a positive association with systolic and diastolic bloood pressure. Both LDL/HDL and apoB100/apo A1 and apo B100 revealed a significant positive association with both SBP and DBP. However, apoB100/apo A1 revealed a more positive association in comparision to LDL/HDL ratio (r=0.749, p<0.001, r=0.756, p<0.001 vs r=0.336, p<0.000, r=0.312, p<0.001). Apo B100/apoA1 has emerged as an important complementary parameter in addition to traditional lipid ratio for evaluation of risk for future cardiovascular disease.

Protective Effects of Ginger (Zingiber officinale) Extract against Diabetes-Induced Heart Abnormality in Rats.

BackgroundDiabetic cardiomyopathy is an important causal factor in morbidity and mortality among diabetic patients, and currently, no effective means are available to reverse its pathological progress. The purpose of the present study was to investigate the effect of ginger extract on apolipoproteins (apo) A and B, hyperhomocysteinemia, cathepsin G and leptin changes, as well as cardiac fibrosis and heart muscle cell proliferation under hyperglycemic conditions in vivo.MethodsTwenty-four male Wistar rats were divided into three groups, namely: control, non-treated diabetic, and ginger extract-treated diabetic groups. The ginger extract-treated diabetic group received a 50 mg daily dose of ginger extract intragastrically for 6 weeks.ResultsThe results revealed concurrent significant increases in plasma C-reactive protein (CRP), homocysteine (Hcy), cathepsin G and apoB levels and decreases in apoA and leptin levels in the non-treated diabetic group compared to the control group. Moreover, heart structural changes, including fibrosis and heart muscle cell proliferation, were observed in non-treated diabetic rats compared to the control rats. Significant amelioration of changes in the heart structure together with restoration of the elevated levels of Hcy and CRP, leptin, cathepsin G, and apoA and B were found in the ginger extract-treated diabetic group compared to the non-treated diabetic group.ConclusionThe findings indicated that ginger extract significantly reduces heart structural abnormalities in diabetic rats and that these effects might be associated with improvements in serum apo, leptin, cathepsin G, and Hcy levels and with the antioxidant properties of ginger extract.

In vivo evidence for chylomicrons as mediators of postprandial inflammation

Background and aimsThe postprandial situation is a pro-inflammatory condition most likely linked to the development of atherosclerosis. We evaluated the relationship between apolipoprotein (apo) B48 and fasting and postprandial leukocyte activation markers. MethodsLeukocyte activation markers and apo B48 were determined in 80 subjects with and without coronary artery disease (CAD). Twelve healthy subjects underwent an oral fat loading test (up to 8 h). ResultsFasting apo B48 was significantly higher in patients with CAD (n = 47, 8.1 ± 5.2 mg/L) than in subjects without CAD (n = 33, 5.9 ± 3.9 mg/L, p = 0.022). Fasting apo B48 and triglycerides correlated positively with fasting monocyte CD11b and neutrophil CD66b expression. Plasma apo B48 and leukocyte activation markers increased after an oral fat load. No correlations were found between fasting or postprandial triglycerides and postprandial leukocyte activation markers. We observed no correlations between postprandial apo B48 and postprandial neutrophil CD11b or CD66b expression. ConclusionThis study suggests that chylomicron remnants may be responsible for postprandial leukocyte activation in the circulation. The postprandial chylomicron response may be a stronger mediator of postprandial inflammation than postprandial triglyceridemia.

Familial Hypercholesterolemia: new therapeutic approaches

Familial Hypercholesterolemia (FH) is caused by a mutation in the gene that encodes the low-density lipoprotein (LDL) receptor, resulting in very high levels of circulating LDL-cholesterol and endothelial damage during time. Apoprotein B, activated by LDL receptor, and PCSK9 (proprotein convertase subtilisin / kexin type 9 serine Protease), that impairs the clearance of LDL receptors, are important additional mechanisms that lead to increase LDL-cholesterol. The prevalence of Homozigous form (HoFH) is estimated to be 1 per 1 million individuals and, if untreated, proximal coronary disease or aortic valve disease frequently occurs during childhood and most affected patients suffer from fatal coronary disease before the age of 30. Heterozygous condition (HeFH) occurs in about 1/380-500 individuals. The levels of LDL-cholesterol in this form may greatly vary but the disease is always asymptomatic until adult age when there is a high risk of early cardiovascular disease. Lifestyle intervention and maximal statin therapy are the mainstays of treatment. In patients that not achieve LDL-C targets, primarly HoFH patients, adjunctive lipoprotein apheresis is recommended where available. Biological agents represents to date a new therapeutic approach for this not so rare condition. The PCSK9 pathway is one of the best examples of how genetics has led to identification of a new target for cholesterol management. Different PCSK9 inhibitors (alirocumab, evolocumab) are now available [1]. Mipomersen is an antisense oligonucleotide (ASO) that targets apoliporotein B-100 mRNA and disrupts its function: it is distributed mainly to the liver where it silences apoB mRNA, thereby reducing hepatic apoB-100 and giving rise to reductions in plasma total cholesterol, LDL-cholesterol, and apoB concentrations [2]. Lomitapide is a microsomal triglyceride transfer protein (MTP) inhibitor. MTP resides in the lumen of the endoplasmic reticulum, thereby preventing the assembly of apo B–containing lipoproteins in enterocytes and hepatocytes. This inhibition leads to a reduction in the synthesis of chylomicrons and very low–density lipoprotein, resulting in a reduction in plasma LDL levels [3].

Plasma IL-1Ra: linking hyperapoB to risk factors for type 2 diabetes independent of obesity in humans.

Background/Objective:Plasma apoB predicts the incidence of type 2 diabetes (T2D); however, the link between apoB-linpoproteins and risks for T2D remain unclear. Insulin resistance (IR) and compensatory hyperinsulinemia characterize prediabetes, and the involvement of an activated interleukin-1 (IL-1) family, mainly IL-1β and its receptor antagonist (IL-Ra), is well documented. ApoB-lipoproteins were reported to promote IL-1β secretion in immune cells; however, in vivo evidence is lacking. We hypothesized that obese subjects with hyperapoB have an activated IL-1 system that explains hyperinsulinemia and IR in these subjects.Subjects/Methods:We examined 81 well-characterized normoglycemic men and postmenopausal women (⩾27 kg m−2, 45–74 years, non-smokers, sedentary, free of chronic disease). Insulin secretion and sensitivity were measured by the gold-standard Botnia clamp, which is a combination of a 1-h intravenous glucose tolerance test (IVGTT) followed by 3-h hyperinsulinemic euglycemic clamp.Results:Plasma IL-1β was near detection limit (0.071–0.216 pg ml−1), while IL-1Ra accumulated at 1000-folds higher (77–1068 pg ml−1). Plasma apoB (0.34–1.80 g l−1) associated significantly with hypersinsulinemia (totalIVGTT: C-peptide r=0.27, insulin r=0.22), IR (M/I=−0.29) and plasma IL-1Ra (r=0.26) but not with IL-1β. Plasma IL-1Ra associated with plasma IL-1β (r=0.40), and more strongly with hyperinsulinemia and IR than apoB, while the association of plasma IL-1β was limited to second phase and total insulin secretion (r=0.23). Adjusting the association of plasma apoB to hyperinsulinemia and IR for IL-1Ra eliminated these associations. Furthermore, despite equivalent body composition, subjects with hyperapoB (⩾80th percentile, 1.14 g l−1) had higher C-peptide secretion and lower insulin sensitivity than those with low plasma apoB (⩽20th percentile, 0.78 g l−1). Adjustment for plasma IL-1 Ra eliminated all group differences.Conclusion:Plasma apoB is associated with hyperinsulinemia and IR in normoglycemic obese subjects, which is eliminated upon adjustment for plasma IL-1Ra. This may implicate the IL-1 family in elevated risks for T2D in obese subjects with hyperapoB.

Lipoprotein Metabolism in APOB L343V Familial Hypobetalipoproteinemia.

Familial hypobetalipoproteinemia (FHBL) is a codominant disorder of lipoprotein metabolism characterized by decreased plasma concentrations of low-density lipoprotein (LDL)-cholesterol and apolipoprotein B (apoB). The objective was to examine the effect of heterozygous APOB L343V FHBL on postprandial triglyceride-rich lipoprotein (TRL) and fasting lipoprotein metabolism. Plasma incremental area under the curve apoB-48 and apoB-48 kinetics were determined after ingestion of a standardized oral fat load using compartmental modeling. Very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein (IDL)-, and LDL-apoB kinetics were determined in the fasting state using stable isotope methods and compartmental modeling. The postprandial incremental area under the curve (0-10 h) in FHBL subjects (n = 3) was lower for large TRL-triglyceride (-77%; P < .0001), small TRL-cholesterol (-83%; P < .001), small TRL-triglyceride (-88%; P < .001), and for plasma triglyceride (-70%; P < .01) and apoB (-63%; P < .0001) compared with controls. Compartmental analysis showed that apoB-48 production was lower (-91%; P < .05) compared with controls. VLDL-apoB concentrations in FHBL subjects (n = 2) were lower by more than 75% compared with healthy, normolipidemic control subjects (P < .01). The VLDL-apoB fractional catabolic rate (FCR) was more than 5-fold higher in the FHBL subjects (P = .07). ApoB production rates and IDL- and LDL-apoB FCRs were not different between FHBL subjects and controls. We conclude that when compared to controls, APOB L343V FHBL heterozygotes show lower TRL production with normal postprandial TRL particle clearance. In contrast, VLDL-apoB production was normal, whereas the FCR was higher in heterozygotes compared with lean control subjects. These mechanisms account for the marked hypolipidemic state observed in these FHBL subjects.

Olive Oil Polyphenols Decrease LDL Concentrations and LDL Atherogenicity in Men in a Randomized Controlled Trial1–3

Background: Olive oil polyphenols have shown protective effects on cardiovascular risk factors. Their consumption decreased oxidative stress biomarkers and improved some features of the lipid profile. However, their effects on LDL concentrations in plasma and LDL atherogenicity have not yet been elucidated.Objective: Our objective was to assess whether the consumption of olive oil polyphenols could decrease LDL concentrations [measured as apolipoprotein B-100 (apo B-100) concentrations and the total number of LDL particles] and atherogenicity (the number of small LDL particles and LDL oxidizability) in humans.Methods: The study was a randomized, cross-over controlled trial in 25 healthy European men, aged 20–59 y, in the context of the EUROLIVE (Effect of Olive Oil Consumption on Oxidative Damage in European Populations) study. Volunteers ingested 25 mL/d raw low-polyphenol-content olive oil (LPCOO; 366 mg/kg) or high-polyphenol-content olive oil (HPCOO; 2.7 mg/kg) for 3 wk. Interventions were preceded by 2-wk washout periods. Effects of olive oil polyphenols on plasma LDL concentrations and atherogenicity were determined in the sample of 25 men. Effects on lipoprotein lipase (LPL) gene expression were assessed in another sample of 18 men from the EUROLIVE study.Results: Plasma apo B-100 concentrations and the number of total and small LDL particles decreased (mean ± SD: by 5.94% ± 16.6%, 11.9% ± 12.0%, and 15.3% ± 35.1%, respectively) from baseline after the HPCOO intervention. These changes differed significantly from those after the LPCOO intervention, which resulted in significant increases of 6.39% ± 16.6%, 4.73% ± 22.0%, and 13.6% ± 36.4% from baseline (P < 0.03). LDL oxidation lag time increased by 5.0% ± 10.3% from baseline after the HPCOO intervention, which was significantly different only relative to preintervention values (P = 0.038). LPL gene expression tended to increase by 26% from baseline after the HPCOO intervention (P = 0.08) and did not change after the LPCOO intervention.Conclusion: The consumption of olive oil polyphenols decreased plasma LDL concentrations and LDL atherogenicity in healthy young men. This trial was registered at www.controlled-trials.com as ISRCTN09220811.

Cardiometabolic and reproductive benefits of early dietary energy restriction and voluntary exercise in an obese PCOS-prone rodent model.

Polycystic ovary syndrome (PCOS) is one of the most common endocrine-metabolic disorders in women of reproductive age characterized by ovulatory dysfunction, hyperandrogenism and cardiometabolic risk. The overweight-obese PCOS phenotype appears to have exacerbated reproductive dysfunction and cardiometabolic risk. In overweight-obese adult women with PCOS, exercise and energy restricted diets have shown limited and inconsistent effects on both cardiometabolic indices and reproductive outcomes. We hypothesized that an early lifestyle intervention involving exercise and dietary energy restriction to prevent or reduce the propensity for adiposity would modulate reproductive indices and cardiometabolic risk in an obese PCOS-prone rodent model. Weanling obese PCOS-prone and Lean-Control JCR:LA-cp rodents were given a chow diet ad libitum or an energy-restricted diet combined with or without voluntary exercise (4 h/day) for 8 weeks. Dietary energy restriction and exercise lowered total body weight gain and body fat mass by 30% compared to free-fed sedentary or exercising obese PCOS-prone animals (P<0.01). Energy restriction induced an increase in exercise intensity compared to free-feeding plus exercise conditions. Energy restriction and exercise decreased fasting plasma triglycerides and apoB48 concentrations in obese PCOS-prone animals compared to free-fed and exercise or sedentary groups. The energy restriction and exercise combination in obese PCOS-prone animals significantly increased plasma sex-hormone binding globulin, hypothalamic cocaine-and amphetamine-regulated transcript (CART) and Kisspeptin mRNA expression to levels of the Lean-Control group, and this was further associated with improvements in estrous cyclicity. The combination of exercise and dietary energy restriction when initiated in early life exerts beneficial effects on cardiometabolic and reproductive indices in an obese PCOS-prone rodent model, and this may be associated with normalization of the hypothalamic neuropeptides, Kisspeptin and CART.

The apoB-to-PCSK9 ratio: A new index for metabolic risk in humans

Proprotein convertase subtilisin/kexin type 9 (PCSK9) shuttles low-density lipoprotein (LDL) receptors for degradation, thus upregulates LDL plasma clearance. Although PCSK9 loss of function is cardioprotective, its role in metabolic risks remains unknown. Increased apoB-lipoproteins uptake into nonhepatic tissues such as white adipose tissue (WAT) induces their dysfunction, which may be favored by lower plasma PCSK9. We hypothesized that lower plasma PCSK9 relative to apoB, or higher apoB-to-PCSK9 ratio, is a better predictor of metabolic disturbances than PCSK9 alone in humans. Thirty-three men and 48 postmenopausal women (>27 kg/m(2), aged 45-74 years, normoglycemic) underwent in-depth assessment of glucose and fat metabolism using high-fat meals, WAT biopsies, intravenous glucose-tolerance tests, and hyperinsulinemia clamps. Plasma apoB correlated positively with fasting and postprandial triglycerides and chylomicron clearance (R = 0.44-0.66) and glucose-stimulated insulin secretion (R = 0.24) and negatively with insulin sensitivity (R = -0.28) and gynoid WAT in situ lipoprotein lipase activity (ie, ex vivo WAT function, R(2) = 0.34). Neither PCSK9 nor LDL cholesterol associated with these risks. In regression analysis that adjusted for body mass index, lower plasma PCSK9 strengthened the association of apoB to WAT dysfunction and insulin resistance. Moreover, plasma apoB-to-PCSK9 ratio correlated positively with all these metabolic risks and further associated positively with android-to-gynoid fat ratio (R = 0.41) and negatively with gynoid fat mass (R = -0.23, all P ≤ .05). No significant sex differences existed in these associations. Lower plasma PCSK9 relative to apoB associates with metabolic risks and WAT dysfunction in normoglycemic obese subjects. We hypothesize that the plasma apoB-to-PCSK9 ratio provides a better clinical index than PCSK9 alone for monitoring early metabolic disturbances that may be promoted by reduction in plasma PCSK9.

Choline deficiency impairs intestinal lipid metabolism in the lactating rat

Choline is a precursor to phosphatidylcholine (PC), a structural molecule in cellular membranes that is crucial for cell growth and function. PC is also required for the secretion of lipoprotein particles from liver and intestine. Choline requirements are increased during lactation when maternal choline is supplied to the offspring through breast milk. To investigate the effect of dietary choline on intestinal lipid metabolism during lactation, choline-supplemented (CS), phosphatidylcholine-supplemented (PCS) or choline-deficient (CD) diets were fed to dams during the suckling period. CD dams had lower plasma triacylglycerol, cholesterol and apoB in the fasted state and following a fat-challenge (P<.05). There was a higher content of neutral lipids and lower content of PC in the intestine of CD dams, compared with CS and PCS fed animals (P<.05). In addition, there was lower (P<.05) villus height in CD dams, which indicated a reduced absorptive surface area in the intestine. Choline is critical for the absorption of fat in lactating rats and choline deficiency alters intestinal morphology and impairs chylomicron secretion by limiting the supply of PC.

Lack of predictive power of plasma lipids or lipoproteins for gestational diabetes mellitus in Japanese women.

Aims/IntroductionTo determine the diagnostic potential of plasma lipids and apolipoproteins in gestational diabetes mellitus (GDM), we carried out a retrospective cohort study of 1,161 Japanese women at 20–28 weeks of gestation who underwent a glucose challenge test (GCT).Materials and MethodsA total of 1,161 Japanese women at 20–28 weeks of gestation underwent a GCT. Participants with a positive test (GCT[+]) underwent a subsequent oral glucose tolerance test. Clinical and biochemical parameters were determined and quantification of apolipoproteins (Apo), including ApoB, ApoB48, ApoA-I and ApoC-III, was carried out.ResultsThe prevalence of GCT(+; with a 130 mg/dL glucose cut-off) and GDM was 20% and 4%, respectively. There was a trend for increased triglycerides and ApoC-III in GDM(+) participants. However, the difference in plasma triglycerides, ApoC-III or ApoB48 did not reach statistical significance between GDM(+) and GDM(−) women. Values of 1-h glucose (P < 0.001) and fasting glucose (P = 0.002) were significant risk factors for GDM.ConclusionsPrediction of GDM using only the ApoC-III value is not easy, although triglycerides and ApoC-III were higher in the GDM(+) group. The present findings show no significant difference in plasma lipid levels between women diagnosed with GDM and those with normal glucose tolerance.

Abstract 321: Lymphatic derived HDL Is an Effective Donor for the Trans-Intestinal Cholesterol Efflux Pathway That Is Impaired During Insulin Resistance

Introduction: Emerging evidence shows that the proximal small intestine secretes cholesterol into the intestinal lumen via the trans-intestinal cholesterol excretion (TICE) pathway. It is thought TICE can contribute up to 30-40% of fecal neutral sterol excretion. Plasma apoB containing lipoproteins are known to donate cholesterol to the TICE pathway whilst conflicting evidence exists on the role for plasma HDL. Due to the anatomical proximity of lymphatic vessels to the basolateral membrane of enterocytes, it may serve as a candidate donor to TICE, but to date this has not been tested. Objective: To determine if HDL derived from mesenteric lymph can act as cholesterol donor for TICE in JCR:LA cp rats as a model of insulin resistance (IR). Methods: Mesenteric lymph was collected following intralipid infusion via lymphatic cannulation from control rats. Lymph HDL was isolated using ultra-density centrifugation and labeled with H3 cholesterol. Jejunal explants were obtained from control and IR rats (as a model of reduced TICE) fed chow or a high fat/cholesterol diet. TICE was measured with Ussing Chambers as appearance of H3-cholesterol labeled lymph HDL using micelles as acceptors. Results: Relative to free cholesterol [FC; used as marker of non-specific lipid permeability], lymph derived HDL TICE was 77% higher in control tissue (n=5, p&lt;0.05) under chow fed conditions, suggestive of an effective donor for TICE. Lymph HDL TICE was also reduced (89%, p&lt;0.05) in IR rats compared to control. Furthermore SR-B1 mRNA was reduced (-65%) in enterocytes from IR rats compared to control, and may explain reduced TICE by lymph HDL in IR. Under conditions of high fat/cholesterol fed diet, TICE from FC [and mannitol as a marker of paracellular transport] was increased in both control and IR rats, suggesting an elevated non-specific permeability of lipids by the basolateral membrane. Conclusions: Consistent with evidence that the lymphatics have a role in reverse cholesterol transport, this data supports that lymph HDL is an effective donor for TICE possibly by the SR-B1 pathway. While we have shown that the lymph HDL TICE pathway may be impaired during insulin resistance, a high fat/cholesterol diet may exacerbate lipid permeability via non-specific efflux pathways.

Abstract 527: Decay of Hepatic and Serum Apolipoprotein(a) Levels is Slower than ApolipoproteinB Following Inhibition of Lipid Synthesis

The association of Lipoprotein(a) (Lp(a)) levels and increased cardiovascular risk is substantiated by human epidemiology, genetics and interventional apheresis studies. Lp(a) is a plasma lipoprotein consisting of a Low Density Lipoprotein (LDL) particle with one molecule of apolipoprotein B100 (ApoB100) covalently linked to one molecule of apolipoprotein(a). Published studies show that apo(a) synthesis and secretion from hepatoma cells is coupled to triglyceride synthesis and secretion, illustrating a point of control for Lp(a) production. The objective of this study is to compare Lp(a), apo(a) and apoB production, secretion and half-life in vivo to understand mechanisms controlling circulating levels of Lp(a). Since rodent species do not express endogenous apo(a), human apo(a) transgenic mice were created and bred with human apoB100 transgenic mice to generate Lp(a)-producing mice. The circulating level of Lp(a) in the transgenic mice is ~3.7 mg/dL that is comparable to 5.4 mg/dL measured in a healthy human subject. To inhibit triglyceride and VLDL secretion in liver, mice were treated with a microsomal triglyceride transfer protein inhibitor (MTPi), and plasma was collected in a time-course. This treatment allowed measurement of plasma Lp(a), apo(a) and apoB half-lives since secretion of nascent VLDL and LDL was blocked. MTPi caused an 81% reduction in cholesterol and 68% reduction in triglycerides after 5 days of treatment. ApoB decreased significantly within 6 hours of treatment and remained low for 5 days. The calculated half-life was 4.6 hours. By contrast, apo(a) and Lp(a) decreased significantly after 3 days of treatment with half-lives of 2.4 and 2.5 days, respectively, illustrating delayed catabolism of apo(a)/Lp(a). Hepatic Lp(a), apo(a) and apoB were decreased significantly after 5 days dosing, indicating that the apolipoproteins were likely degraded and not accumulated in the liver. Treatment of stable HepG2 cells expressing apo(a) with MTPi caused similar difference in Lp(a) and apoB half-lives. These models illustrate rapid decay of apoB, but not apo(a), when lipoprotein particle assembly is blocked, and they provide methods for future mechanistic studies of apo(a) assembly into Lp(a) and its catabolism.

Abstract 125: Small Dense LDL ApoB Is Catabolized More Slowly Than Large LDL ApoB in Subjects With Combined Hyperlipidemia, and Rosuvastatin Enhances Its Clearance

LDL consists of particles varying in size, density, and composition. Small dense LDL (sdLDL) cholesterol (C) has been shown to be a better predictor of coronary heart disease risk than total LDL-C. Intensive statin therapy significantly lowers sdLDL-C as well as large buoyant LDL (lbLDL)-C. We tested the hypotheses that lbLDL and sdLDL apoB100 have different catabolic rates, and that statin therapy enhances the fractional catabolism of apoB100 in both particles. Six subjects (3 men and 3 women; age 63±5 years [mean±SEM]; BMI 25.5±1.5 kg/m 2 ) with combined hyperlipidemia (triglycerides [TG] 191±50 mg/dl; LDL-C 160±16 mg/dl; HDL-C 43±6 mg/dl) received placebo and rosuvastatin 40 mg/day for 8 weeks each in sequential order. At the end of each phase, the kinetics of apoB100 in triglyceride rich lipoproteins ([TRL] d &lt;1.019 g/ml), lbLDL ( d =1.019-1.044 g/ml), and sdLDL ( d =1.044-1.063 g/ml) were determined using stable isotope methodology, gas chromatography-mass spectrometry, and multicompartmental modeling. Compared to placebo, rosuvastatin markedly decreased the plasma levels of LDL-C (52%; P =0.0002), TG (32%; P =0.06), and total apoB (42%; P &lt;0.0001). ApoB100 pool size in TRL, lbLDL, and sdLDL decreased 32±6%, 39±5%, 41±4%, respectively. These changes were attributable to significant ( P &lt;0.05) increases in apoB100 fractional catabolic rates in TRL (45±16%), lbLDL (131±66%), and sdLDL (97±32%). During both the placebo and rosuvastatin phases, sdLDL apoB100 was catabolized more slowly than lbLDL apoB100 ( P =0.01 and 0.004, respectively). Rosuvastatin did not alter apoB100 production rate or the percent of TRL apoB100 converted to each LDL subfraction. Proteomic analysis of the LDL particles indicated that rosuvastatin increased apoD abundance in lbLDL and decreased apoAIV abundance in sdLDL. No significant effects on other apolipoproteins were noted. These data indicate that sdLDL apoB100 is catabolized significantly more slowly than lbLDL apoB100 in dyslipidemic subjects on placebo or statin therapy. Maximal dose rosuvastatin decreases plasma apoB concentrations by enhancing apoB100 catabolism in TRL, lbLDL, and sdLDL and alters the distribution of minor apolipoproteins in LDL subfractions.

Effects of niacin and omega-3 fatty acids on the apolipoproteins in overweight patients with elevated triglycerides and reduced HDL cholesterol

ObjectivePrescription omega-3 acid ethyl esters (P-OM3) and extended release niacin (ERN) both have beneficial effects on plasma lipids and lipoproteins. The purpose of this study was to describe the effects of mono- and combination (Combo) therapy of these agents in patients with the metabolic syndrome. MethodsVery low density (VLDL), intermediate/low density (IDL/LDL, hereafter LDL), and high density lipoproteins (HDL) were isolated from 56 overweight patients with elevated triglyceride/HDL-C ratios at baseline and after 16 weeks of treatment with placebo, ERN (2g/day), P-OM3 (4g/day), or Combo and then analyzed by quantitative electrophoresis for apolipoproteins (apo) A1, A2, B, C2, C3 and E. Total plasma concentrations and the ratios of each apo with apoB (in VLDL and LDL) and with apoA1 (in HDL) were calculated. An apoC3 glycosylation index (a ratio between di- and mono-sialylated isoforms) was also determined in plasma and in each lipoprotein fraction. ResultsERN reduced plasma apoB (−11%, p < 0.05). Combo increased LDL apoE/apoB ratio (64%, p < 0.01) and LDL apoA1/apoB (91%, p < 0.05). ERN increased the apoC3 glycosylation index only in HDL (37%, p < 0.05), whereas P-OM3 and Combo increased the index in whole plasma (48% and 49%, respectively, p < 0.05 for both) and in every lipoprotein class (VLDL: 26%, p < 0.01 and 26%, p < 0.05; LDL: 55%, p < 0.01 and 61%, p < 0.01; HDL: 43%, p < 0.001 and 44%, p < 0.001, respectively). All findings were significant after adjustment for age, sex, body mass index (BMI), smoking, medications, and baseline apo value. ConclusionsERN produced a beneficial reduction in plasma apoB. The enrichment of LDL with apoE and apoA1 was unique to the Combo group and might be beneficial owing to the atheroprotective properties of apoE and HDL2 (a likely source of apoA1 in LDL fraction). The effect of therapies on the apoC3 glycosylation index is a novel finding, the implications of which will require further study.