A large high-density lipoprotein enriched in apolipoprotein C-I: a novel biochemical marker in infants of lower birth weight and younger gestational age

CONTEXT

Low birth weight is associated with increased cardiovascular disease in adulthood, and differences in the molecular weight, composition, and quantity of lipoprotein subclasses are associated with coronary artery disease.

OBJECTIVE

To determine if there are novel patterns of lipoprotein heterogeneity in low-birth-weight infants.

DESIGN, SETTING, AND PARTICIPANTS

Prospective study at a US medical center of a representative sample of infants (n = 163; 70 white and 93 black) born at 28 or more weeks of gestational age between January 3, 2000, and September 27, 2000. This sample constituted 20% of all infants born during the study period at this site.

MAIN OUTCOME MEASURES

Plasma levels and particle sizes of lipoprotein subclasses and plasma concentrations of lipids, lipoproteins (high-density lipoprotein [HDL] and low-density lipoprotein [LDL]), and apolipoproteins.

RESULTS

An elevated lipoprotein peak of a particle with density between 1.062 and 1.072 g/mL was identified using physical-chemical methods. This subclass of large HDL was enriched in apolipoprotein C-I (apo C-I). Based on the amount of the apo C-I-enriched HDL peak, 156 infants were assigned to 1 of 4 groups: 0 (none detected), 17%; 1 (possibly present), 41%; 2 (probably present), 22%; 3 (elevated), 19%. Infants in group 3, compared with those in the other 3 groups, had significantly (P<.001) lower mean birth weight (2683.7 vs 3307.1 g) and younger mean gestational age (36.2 vs 39.3 wk). After correction for age, infants in group 3 had significantly higher levels of total and large HDL cholesterol and of total and large LDL cholesterol and LDL particle number. However, infants in group 3 had lower levels of small HDL, very low-density lipoproteins, and triglycerides than infants in the other 3 groups. This lipoprotein profile differed from that in infants born small for gestational age, who had significantly higher triglyceride (P<.001) and apo B (P = .04) levels, but lower levels of total and large HDL cholesterol (P<.001) and apo A-I (P<.001).

CONCLUSIONS

Because apo C-I-enriched HDL, and purified apo C-I alone, promotes apoptosis in vitro, increased amounts of this particle may have physiological significance and identify a novel group of low-birth-weight infants apparently distinct from traditionally classified small-for-gestational-age infants.

The common insertional polymorphism in the APOC1 promoter is associated with serum apolipoprotein C-I levels in Hispanic children

We examined the effect of APOC1-317insCGTT allele status (HpaI RFLP, deletion [H1] and insertion [H2] alleles) on serum apolipoprotein (apo) C-I level in 362 Hispanic children in the Columbia University BioMarkers Study. The H2 allele was present in 147 subjects (40.6%). Serum apoC-I was 20% lower in the presence of the H2 allele in APOE epsilon3/epsilon3 homozygotes (P=0.003) but did not differ by H2 status in epsilon4 carriers. Insufficient numbers of epsilon2 carriers (N=45) were present for analysis. In multivariate analysis in the epsilon3/epsilon3 context, after adjusting for potential covariate effects and familial aggregation, the mean effect of H2/* versus H1/H1 on apoC-I level, was estimated to be 2.15+/-0.55mg/dl (P<0.0025). Plasma triglyceride level was weakly correlated with serum apoC-I level (Pearson's r=0.17, P<0.001) but was highly correlated with serum apoC-III (Pearson's r=0.74, P<0.0001). Nevertheless, presence of the H2 allele was not significantly associated with serum apoC-III level. Thus, the effect of APOC1 genotype on serum apoC-I level was not due to apoC-I level serving as a surrogate for triglyceride level. The APOC1-317insCGTT allele is a commonly polymorphic genetic marker that is associated with serum apoC-I level in the APOE epsilon3/epsilon3 context. These findings suggest that the mechanism of the previously described association with plasma TG is, at least in part, related to the correlation of the polymorphism with the level of expression of apoC-I.

Increased apoC-III production is a characteristic feature of patients with hypertriglyceridemia

Apolipoprotein (apo) C-III plays an important role in regulating plasma triglyceride (TG) metabolism. In order to further investigate the plasma metabolism of apoC-III in hypertriglyceridemic subjects, we have studied the plasma kinetics of VLDL apoC-III, HDL apoC-III and total plasma apoC-III with a primed constant intravenous infusion of deuterated leucine in a group of male patients with mixed hyperlipidemia (type IIb hyperlipoproteinemia, HLP, n=6) and in a group with type III HLP (n=6). Compared to normolipidemic control subjects (n=5), patients with type IIb and type III HLP had significantly higher levels of plasma TG (0.89 +/- 0.15 mmol/l vs 2.56 +/- 0.40 mmol/l vs 8.76 +/- 1.39 mmol/l, respectively, P <0.01), plasma apoC-III (9.5 +/- 0.8 mg/dl vs 20.8 +/- 2.5 mg/dl vs 41.7 +/- 5.6 mg/dl, P <0.01) and VLDL apoC-III (3.6 +/- 0.8 mg/dl vs 14.6 +/- 2.2 mg/dl vs 35.4 +/- 5.1 mg/dl, P <0.01). VLDL apoC-III production rates were significantly elevated in type IIb and type III patients (1.35 +/- 0.23 mg kg(-1) day(-1) vs 3.53 +/- 0.43 mg kg(-1) day(-1) vs 5.60 +/- 0.78 mg kg(-1) day(-1), P <0.01), as were total plasma apoC-III production rates (1.80 +/- 0.22 mg kg(-1) day(-1) vs 4.16 +/- 0.44 mg kg(-1) day(-1) vs 7.26 +/- 0.74 mg kg(-1) day(-1), P <0.01). VLDL apoC-III but not total plasma apoC-III fractional catabolic rates were reduced in type IIb and type III patients. Together with our previous results showing an increase of apoC-III production in patients with type IV HLP, and in overweight subjects with reduced insulin sensitivity, our data suggest that increased apoC-III production is a characteristic feature of patients with hypertriglyceridemia.

Evidence for cross-genotype neutralization of hepatitis C virus pseudo-particles and enhancement of infectivity by apolipoprotein C1

The lack of a cell culture system to support hepatitis C virus (HCV) replication has hampered studies of this frequent cause of chronic liver disease. However, pseudotyped retroviral particles (pp) bearing the HCV envelope glycoproteins have provided a different approach to HCV studies. We used genotype 1a pp to detect neutralizing antibodies (NtAb) in eight chimpanzees and four humans infected with 1a strains, and developed pp of genotypes 2a, 3a, 4a, 5a, and 6a to study crossreactivity. NtAb was detected in one of four chimpanzees and none of three humans with acute resolving infection, suggesting that NtAb is not required for HCV clearance. NtAb were detected at high titer in two of four chimpanzees and, in Patient H, all with persistent infection; responses paralleled humoral responses to envelope 1 and 2 proteins and, in some cases, correlate also with antibodies to the hypervariable region 1, previously thought to be the primary site of neutralization. NtAb raised during 1a infections could neutralize HCVpp of genotypes 4a, 5a, and 6a but had only limited reactivity against 2a and 3a. The detection of high-titer NtAb with cross-genotype reactivity has important implications for the development of active and passive immune-prophylaxis strategies against HCV. Finally, we found that HCVpp infectivity was enhanced by human or chimpanzee sera; apolipoprotein C1 alone or as a component of high-density lipoproteins caused this enhancement. Future studies of the in vivo role of apolipoprotein C1 might provide additional insights into the infection process of HCV.

Adiponectin and other Adipocytokines as Predictors of Markers of Triglyceride-Rich Lipoprotein Metabolism

Background: Adipocytokines are bioactive peptides that may play an important role in the regulation of glucose and lipid metabolism. In this study, we investigated the association of plasma adipocytokine concentrations with markers of triglyceride-rich lipoprotein (TRL) metabolism in men.

Methods: Fasting adiponectin, leptin, resistin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), apolipoprotein (apo) B-48, apo C-III, and remnant-like particle (RLP)-cholesterol concentrations were measured by immunoassays and insulin resistance by homeostasis assessment (HOMA) score in 41 nondiabetic men with a body mass index of 22–35 kg/m2. Visceral and subcutaneous adipose tissue masses (ATMs) were determined by magnetic resonance imaging and total ATM by bioelectrical impedance.

Results: In univariate regression, plasma adiponectin and leptin concentrations were inversely and directly associated with plasma apoB-48, apoC-III, RLP-cholesterol, triglycerides, VLDL-apoB, and VLDL-triglycerides (P &lt;0.05). Resistin, IL-6, and TNF-α were not significantly associated with any of these variables, except for a direct correction between apoC-III and IL-6 (P &lt;0.05). In multivariate regression including HOMA, age, nonesterified fatty acids, and adipose tissue compartment, adiponectin was an independent predictor of plasma apoB-48 (β coefficient = −0.354; P = 0.048), apoC-III (β coefficient = −0.406; P = 0.012), RLP-cholesterol (β coefficient = −0.377; P = 0.016), and triglycerides (β coefficient = −0.374; P = 0.013). By contrast, leptin was not an independent predictor of these TRL markers. Plasma apoB-48, apoC-III, RLP-cholesterol, and triglycerides were all significantly and positively associated with plasma insulin, HOMA, and visceral, subcutaneous, and total ATMs (P &lt;0.05).

Conclusions: These data suggest that the plasma adiponectin concentration may not only link abdominal fat, insulin resistance, and dyslipidemia, but may also exert an independent role in regulating TRL metabolism.

Polyunsaturated fatty acids interact with the PPARA-L162V polymorphism to affect plasma triglyceride and apolipoprotein C-III concentrations in the Framingham Heart Study

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a nuclear transcription factor regulating multiple genes involved in lipid metabolism. It was shown that a common leucine to valine (L162V) substitution at the PPARalpha gene (PPARA) is functional and affects transactivation activity of PPARalpha ligands, such as PUFA, on a concentration-dependent basis. The current study examined this gene-nutrient interaction in relation to plasma lipid variables in a population-based study consisting of 1003 men and 1103 women participating in the Framingham cohort and consuming their habitual diets. We found significant gene-nutrient interactions between the L162V polymorphism and total PUFA intake, which modulated plasma triglycerides (TG; P < 0.05) and apolipoprotein C-III (apoC-III; P < 0.05) concentrations. The 162V allele was associated with greater TG and apoC-III concentrations only in subjects consuming a low-PUFA diet (below the population mean, 6% of energy). However, when PUFA intake was high, carriers of the 162V allele had lower apoC-III concentrations. This interaction was significant even when PUFA intake was considered as a continuous variable (P = 0.031 for TG and P < 0.001 for apoC-III), suggesting a strong dose-response effect. When PUFA intake was <4%, 162V allele carriers had approximately 28% higher plasma TG than did 162L homozygotes (P < 0.01). Conversely, when PUFA intake was >8%, plasma TG in 162V allele carriers was 4% lower than in 162L homozygotes. Similar results were obtained for (n-6) and (n-3) fatty acids. Our data show that the effect of the L162V polymorphism on plasma TG and apoC-III concentrations depends on the dietary PUFA, with a high intake triggering lower TG in carriers of the 162V allele.

Decreases in serum apolipoprotein C-III concentration in cows with ethionine-induced fatty liver

To monitor the serum concentration of apolipoprotein C-III (apoC-III), one of the functional apoproteins in lipid metabolism, in cows with ethionine-induced fatty liver, and to investigate the association of apoC-III with liver triglyceride (TG) content and serum biochemical variables, seven nonpregnant nonlactating Holstein cows (3 to 6 years old) were used. Five cows were treated with ethionine, an analogue of methionine, (days 0, 7 and 14). The remaining two controls received saline as the vehicle. Liver TG contents in the treated cows were increased markedly whenever administered, and significant increases were observed at days 14 (666.4%, 85.3 mg/g) and 21 (675.0%, 86.4 mg/g) compared with day 0. In controls, no significant changes in liver TG content and serum biochemical variables were observed during this experiment. The serum apoC-III concentration in the treated cows was decreased drastically after the first administration and fell to the lowest value at day 10 (76.2 microg/ml, 32% of day 0). The apoC-III was significantly (p<0.05) correlated with non-esterified fatty acids (r= -0.526), gamma-glutamyl transpeptidase (r= -0.407), total bilirubin (r= -0.464), positively with apolipoprotein B-100 (apoB-100, r=0.601) and cholesterol ester (r=0.449). Although apoB-100 concentrations were also reduced by the administrations, the concentrations tended to recover smoothly toward the next administration. The distinct difference in change between apoC-III and apoB-100 suggests that apoC-III may be regulated by other pathways, in addition to inhibiting the synthesis of apoproteins by ethionine.

Apolipoprotein C-III protein concentrations and gene polymorphisms in Type 1 diabetes: associations with microvascular disease complications in the DCCT/EDIC cohort

AIM

We investigated the associations of apolipoprotein C-III (apoCIII) protein and apoCIII gene variation with microvascular disease complications in Type 1 diabetes.

METHODS

The serum apoCIII concentration, and both a T(-455)-->C and a SacI gene polymorphisms were determined in 409 patients in the DCCT/EDIC cohort of patients with Type 1 diabetes. Correlations with albumin excretion rate (AER) and the severity of retinopathy were investigated.

RESULTS

Higher apoCIII concentrations were associated (P<.0001) with increased triglycerides (r=.78), total (r=.61) and LDL (r=.40) cholesterol, apoAI (r=.26), and apoB (r=.50), AER (r=.08), and the severity of retinopathy (ETDRS score, r=.11), and these relationships persisted after controlling for age, gender, body mass index (BMI), and HbA1c level. The apoCIII concentration was significantly higher in the group of patients with macroalbuminuria (AERs 300 mg/24 h) compared to the groups with microalbuminuria (AER 40-299 mg/24 h; P<.0001) or normoalbuminuria (AER <40 mg/24 h) (P<.0001). The apoCIII concentration also was significantly higher in the group of patients with severe retinopathy (ETDRS 10-23) compared to those with moderate (ETDRS 4-9; P<.02) or mild retinopathy (ETDRS 1-3; P<.0001). Neither the T(-455)-->C polymorphism nor a SacI polymorphism in the 3' UTR were associated with circulating apoCIII concentrations, nor the severity of nephropathy or retinopathy.

CONCLUSIONS

Elevated apoCIII levels have been associated with increased macrovascular disease risk. In the DCCT/EDIC cohort of patients, there was an independent positive association of apoCIII level with microvascular complications of Type 1 diabetes.

Foxo1 mediates insulin action on apoC-III and triglyceride metabolism

The apolipoprotein apoC-III plays an important role in plasma triglyceride metabolism. It is predominantly produced in liver, and its hepatic expression is inhibited by insulin. To elucidate the inhibitory mechanism of insulin in apoC-III expression, we delivered forkhead box O1 (Foxo1) cDNA to hepatocytes by adenovirus-mediated gene transfer. Foxo1 stimulated hepatic apoC-III expression and correlated with the ability of Foxo1 to bind to its consensus site in the apoC-III promoter. Deletion or mutation of the Foxo1 binding site abolished insulin response and Foxo1-mediated stimulation. Likewise, Foxo1 also mediated insulin action on intestinal apoC-III expression in enterocytes. Furthermore, elevated Foxo1 production in liver augmented hepatic apoC-III expression, resulting in increased plasma triglyceride levels and impaired fat tolerance in mice. Transgenic mice expressing a constitutively active Foxo1 allele exhibited hypertriglyceridemia. Moreover, we show that hepatic Foxo1 expression becomes deregulated as a result of insulin deficiency or insulin resistance, culminating in significantly elevated Foxo1 production, along with its skewed nuclear distribution, in livers of diabetic NOD or db/db mice. While loss of insulin response is associated with unrestrained apoC-III production and impaired triglyceride metabolism, these data suggest that Foxo1 provides a molecular link between insulin deficiency or resistance and aberrant apoC-III production in the pathogenesis of diabetic hypertriglyceridemia.

Beneficial effects of weight loss on plasma apolipoproteins in postmenopausal women

A total of 39 postmenopausal women 40-70 years of age and undergoing hormone replacement therapy participated in a 6-month weight reduction program, which consisted of a low calorie diet (5040 KJ/day) and phentermine hydrochloride therapy. Subjects had an average body mass index of 35.95+/-5.32 kg/m(2) and 42.20+/-11.0 kg of total fat. Body mass index, plasma lipids, total and trunk fat, and plasma apoproteins were measured at baseline and after 3 and 6 months of the weight reduction program. Subjects experienced an overall 10% weight loss during the treatment period (P<0.001). Plasma LDL cholesterol and triglycerides were reduced by 18% and 15% (P<0.01) respectively, whereas HDL cholesterol was increased by 9% (P<0.01) over the 6-month period. Plasma apoproteins were significantly affected by weight loss. Plasma apolipoprotein (apo) B concentrations were reduced 6.5% (P<0.01), and apo C-III and apo E were reduced by 9% over 6 months (P<0.01). The observed decreases in plasma apo B were significantly correlated with the observed changes in plasma cholesterol (r=0.356, P<0.01) over 3 months. In addition, changes in plasma triglycerides were correlated with changes in both apo C-III (r=0.436) and apo E (r=0.354) over 6 months. These results suggest that weight loss may have multifactorial effects on lipoprotein metabolism, resulting in better plasma lipid and apoprotein profiles.

Prediction of PPAR-alpha ligand-mediated physiological changes using gene expression profiles

Peroxisome proliferator-activated receptor (PPAR)-alpha controls the transcription of a variety of genes involved in lipid metabolism and is the target receptor for the hypolipidemic drug class of fibrates. In the present study, the molecular and physiological effects of seven different PPAR-activating drugs have been examined in a rodent model of dyslipidemia. The drugs examined were selected to display varying potencies and efficacies toward PPAR-alpha. To help elucidate the link between the gene regulation elicited by PPAR-alpha ligands and the concomitant physiological changes, we have used cDNA microarray analysis to identify smaller gene sets that are predictive of the function of these ligands. A number of genes showed strong correlations to the relative PPAR-alpha efficacy of the drugs. Furthermore, using multivariate analysis, a strong relationship between the drug-induced triglyceride lowering and the transcriptional profiles of the different drugs could be found.

Apolipoprotein C-III protein concentrations and gene polymorphisms in type 1 diabetes: associations with lipoprotein subclasses

Serum apolipoprotein C-III (apoCIII) concentration and apoCIII gene polymorphisms have been shown to be a risk factor for cardiovascular disease; however, the underlying mechanisms remain unclear. In addition, no studies have been performed that address these issues in type 1 diabetes. The current study investigated apoCIII protein and apoCIII gene variation in a normotriglyceridemic (82 +/- 57 mg/dL) population of patients with type 1 diabetes, the Diabetes Control and Complications Trial/Epidemiology of Diabetes Intervention and Complications (DCCT/EDIC) cohort. Blood samples were obtained in 409 patients after an overnight fast. Serum apoCIII concentration was highly correlated with multiple changes in lipids and lipoproteins that resulted in an adverse cardiovascular disease risk profile. Higher apoCIII concentrations were associated (P < .0001) with increased triglycerides (r = 0.78), total (r = 0.61) and low-density lipoprotein (LDL) (r = 0.40) cholesterol, apoA-I (r = 0.26), and apoB (r = 0.50), and these relationships persisted after controlling for age, gender, body mass index (BMI), and hemoglobin A1c (HbA1c). Nuclear magnetic resonance (NMR) lipoprotein subclass analyses demonstrated that apoCIII was correlated with an increase in very-low-density lipoprotein (VLDL) subclasses (P = .0001). There also was a highly significant positive relationship between serum apoCIII concentration and the LDL particle concentration in both men (r = 0.49, P = .001) and women (r = 0.40, P = .001), and a highly significant negative relationship between serum apoCIII levels and average LDL particle size in both men (r = -0.37, P = .001) and women (r = -0.22, P = .001) due primarily to an augmentation in the small L1 subclass (r = 0.42, P = .0001). Neither the T(-455) --> C polymorphism affecting an insulin response element in the apoCIII gene promoter nor a SacI polymorphism in the 3'UTR were associated with any alterations in circulating apoCIII concentrations, serum lipids, apolipoprotein concentrations, lipoprotein composition, or parameters measured by NMR lipoprotein subclass analyses. In summary, elevated apoCIII concentration was associated with risk factors for cardiovascular disease in normolipidemic type 1 diabetic patients through associated changes in lipoprotein subfraction distributions, which were independent of apoCIII genotype.

Association of serum apolipoprotein C III levels and apolipoprotein C III gene Sst I polymorphism with carotid intima-media thickness in Chinese type 2 diabetic patients

Apolipoprotein C III (apo C III) plays a central role in regulating plasma metabolism of triglyceride-rich lipoprotein (TRL). The G3238C allele (Sst I) in the 3'-untranslated region has been found to be associated with raised apo C III levels and hypertriglyceridemia (HTG). Some studies suggest that apo C III and the S(2) allele of apo C III gene are independent risk factors for atherosclerotic diseases. To study the potential association between these factors we analyzed the clinical data and their correlations with serum apo C III levels, apo C III gene Sst I polymorphism, and carotid intima-media thickness (IMT) in 78 unrelated Chinese patients with type 2 diabetes. Apo C III gene Sst I polymorphism was examined using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Carotid IMT was measured by color doppler ultrasound examination. Serum apo C III levels were found to be positively associated with plasma TG ( r = 0.527, P < 0.001), TC (r = 0.424, P < 0.001), LDL-C (r = 0.308, P < 0.01) concentrations, and carotid IMT (r =0.359, P < 0.01 ). Multivariate analysis (backward) showed that diastolic blood pressure, apo C III, and fasting insulin levels were independent risk factors of carotid IMT. However, the results did not show the association between S(2) allele and carotid IMT in our diabetic patients. Thus, our study suggested that apo C III is an independent risk factor for atherosclerotic diseases in Chinese type 2 diabetes.

Substitutions of glutamate 110 and 111 in the middle helix 4 of human apolipoprotein A-I (apoA-I) by alanine affect the structure and in vitro functions of apoA-I and induce severe hypertriglyceridemia in apoA-I-deficient mice

Hypertriglyceridemia is a common pathological condition in humans of mostly unknown etiology. Here we report induction of dyslipidemia characterized by severe hypertriglyceridemia as a result of point mutations in human apolipoprotein A-I (apoA-I). Adenovirus-mediated gene transfer in apoA-I-deficient (apoA-I(-)(/)(-)) mice showed that mice expressing an apoA-I[E110A/E111A] mutant had comparable hepatic mRNA levels with WT controls but greatly increased plasma triglyceride and elevated plasma cholesterol levels. In addition, they had decreased apoE and apoCII levels and increased apoB48 levels in very low-density lipoprotein (VLDL)/intermediate-density lipoprotein (IDL). Fast protein liquid chromatography (FPLC) analysis of plasma showed that most of cholesterol and approximately 15% of the mutant apoA-I were distributed in the VLDL and IDL regions and all the triglycerides in the VLDL region. Hypertriglyceridemia was corrected by coinfection of mice with recombinant adenoviruses expressing the mutant apoA-I and human lipoprotein lipase. Physicochemical studies indicated that the apoA-I mutation decreased the alpha-helical content, the stability, and the unfolding cooperativity of both lipid-free and lipid-bound apoA-I. In vitro functional analyses showed that reconstituted HDL (rHDL) particles containing the mutant apoA-I had 53% of scavenger receptor class B type I (SR-BI)-mediated cholesterol efflux capacity and 37% capacity to activate lecithin:cholesterol acyltransferase (LCAT) as compared to the WT control. The mutant lipid-free apoA-I had normal capacity to promote ATP-binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux. The findings indicate that subtle structural alterations in apoA-I may alter the stability and functions of apoA-I and high-density lipoprotein (HDL) and may cause hypertriglyceridemia.

Storage of human plasma samples leads to alterations in the lipoprotein distribution of apoC-III and apoE

The effect of frozen storage on lipoprotein distribution of apolipoprotein C-III (apoC-III) and apoE was investigated by measuring apoC-III and apoE by ELISA in HDL and apoB-containing lipoproteins of human plasma samples (n = 16) before and after 2 weeks of frozen storage (-20 degrees C). HDLs were separated by heparin-manganese precipitation (HMP) or by fast-protein liquid chromatography (FPLC). Total plasma apoC-III and apoE levels were not affected by frozen storage. HDL-HMP apoC-III and apoE levels were significantly higher in frozen versus fresh samples: 7.7 +/- 0.7 versus 6.7 +/- 0.7 mg/dl (P < 0.05) and 2.0 +/- 0.1 versus 1.2 +/- 0.1 mg/dl (P < 0.001), respectively. HDL-FPLC apoC-III and apoE, but not triglyceride (TG) or cholesterol, levels were also higher in frozen samples: 12.0 +/- 1.2 versus 7.5 +/- 0.6 mg/dl (P < 0.001) and 2.7 +/- 0.2 versus 1.6 +/- 0.2 mg/dl (P < 0.001), respectively. Frozen storage led to a decrease in apoC-III (-17 +/- 9%) and apoE (-19 +/- 9%) in triglyceride-rich lipoprotein. Redistribution of apoC-III and apoE was most evident in samples with high TG levels. HDL apoC-III and apoE levels were also significantly higher when measured in plasma stored at -80 degrees C. Our results demonstrate that lipoprotein distribution of apoC-III and apoE is affected by storage of human plasma, suggesting that analysis of frozen plasma should be avoided in studies relating lipoprotein levels of apoC-III and/or apoE to the incidence of coronary artery disease.

ApoC-I and ApoC-III as potential plasmatic markers to distinguish between ischemic and hemorrhagic stroke

Early diagnosis and immediate therapeutic interventions are crucial factors to reduce the damage extent and the risk of death. Currently, the diagnosis of stroke relies on neurological assessment of the patient and neuro-imaging techniques including computed tomography and/or magnetic resonance imaging scan. An early diagnostic marker of stroke, ideally capable to discriminate ischemic from hemorrhagic stroke would considerably improve patient acute management. Using surface-enhanced laser desorption/ionization (SELDI) technology, we aimed at finding new early diagnostic plasmatic markers of stroke. Strong anionic exchange (SAX) SELDI profiles of plasma samples from 21 stroke patients were compared to 21 samples from healthy controls. Seven peaks appeared to be differentially expressed with significant p values (p < 0.05). Proteins were stripped from the SAX chips, separated on a one-dimensional electrophoresis (1-DE) gel and stained using mass spectrometry (MS)-compatible silver staining. Following in-gel tryptic digestion, the peptides were analyzed by MS. Four candidate proteins were identified as apolipoprotein CI (ApoC-I), apolipoprotein CIII (ApoC-III), serum amyloid A (SAA), and antithrombin-III fragment (AT-III fragment). Assessment of ApoC-I and ApoC-III levels in plasma samples using a sandwich enzyme-linked immunosorbent assay (ELISA) allowed to distinguish between hemorrhagic (n = 15) and ischemic (n = 16) stroke (p < 0.001). To the best of our knowledge, ApoC-I and ApoC-III are the first reported plasmatic biomarkers capable to accurately distinguish between ischemic and hemorrhagic stroke in a small number of patients. It requires further investigation in a large cohort of patients.

Fenofibrate improves the atherogenic lipid profile and enhances LDL resistance to oxidation in HIV-positive adults

BACKGROUND

Low HDL-cholesterol, hypertriglyceridemia (HTG) and occurrence of small dense LDL could be involved in increased cardiovascular risk in HIV-infected patients. This study evaluates the effects of fenofibrate and/or Vitamin E on lipoprotein profile.

DESIGN

Thirty-six HIV-positive adults with fasting triglycerides (TGs) > or =2 mmol/l and stable antiretroviral therapy (ART) were randomly assigned to receive either micronised fenofibrate (200 mg/day) or Vitamin E (500 mg/day) for a first period of 3 months and the association of both for an additional 3-month period.

METHODS AND RESULTS

Total cholesterol, HDL-C, LDL-C, triglycerides, apoA1, apoB, apoCIII, lipoprotein composition, LDL size and LDL resistance to copper-induced oxidation were determined before initiation of fenofibrate or Vitamin E, and 3 and 6 months thereafter. Three months of fenofibrate treatment results in a significant decrease in triglycerides (-40%), apoCIII (-21%), total cholesterol (-14%), apoB (-17%) levels, non-HDL-C (-17%), TG/apoA1 ratio in HDL (-27%) associated with an increase in HDL-C (+15%) and apoA1 (+11%) levels. Moreover, fenofibrate increases LDL size and enhances LDL resistance to oxidation. Three months of Vitamin E supplementation only improves LDL resistance to oxidation and addition to fenofibrate results in a slightly greater effect.

CONCLUSION

Fenofibrate therapy improves the atherogenic lipid profile in HIV-positive adults with hypertriglyceridemia.

Atorvastatin decreases apolipoprotein C-III in apolipoprotein B-containing lipoprotein and HDL in type 2 diabetes: a potential mechanism to lower plasma triglycerides

OBJECTIVE

Apolipoprotein (apo)C-III is a constituent of HDL (HDL apoC-III) and of apoB-containing lipoproteins (LpB:C-III). It slows the clearance of triglyceride-rich lipoproteins (TRLs) by inhibition of the activity of the enzyme lipoprotein lipase (LPL) and by interference with lipoprotein binding to cell-surface receptors. Elevated plasma LpB:C-III is an independent risk factor for cardiovascular disease. We studied the effect of atorvastatin on plasma LpB:C-III and HDL apoC-III.

RESEARCH DESIGN AND METHODS

We studied the effect of 30 weeks' treatment with 10 and 80 mg atorvastatin on plasma apoC-III levels in a randomized, double-blind, placebo-controlled trial involving 217 patients with type 2 diabetes and fasting plasma triglycerides between 1.5 and 6.0 mmol/l.

RESULTS

Baseline levels of total plasma apoC-III, HDL apoC-III, and LpB:C-III were 41.5 +/- 10.0, 17.7 +/- 5.5, and 23.8 +/- 7.7 mg/l, respectively. Plasma apoC-III was strongly correlated with plasma triglycerides (r = 0.74, P < 0.001). Atorvastatin 10- and 80-mg treatment significantly decreased plasma apoC-III (atorvastatin 10 mg, 21%, and 80 mg, 27%), HDL apoC-III (atorvastatin 10 mg, 22%, and 80 mg, 28%) and LpB:C-III (atorvastatin 10 mg, 23%, and 80 mg, 28%; all P < 0.001). The decrease in plasma apoC-III, mainly in LpB:C-III, strongly correlated with a decrease in triglycerides (atorvastatin 10 mg, r = 0.70, and 80 mg, r = 0.78; P < 0.001). Atorvastatin treatment also leads to a reduction in the HDL apoC-III-to-HDL cholesterol and HDL apoC-III-to-apoA-I ratios, indicating a change in the number of apoC-III per HDL particle (atorvastatin 10 mg, -21%, and 80 mg, -31%; P < 0.001).

CONCLUSIONS

Atorvastatin treatment resulted in a significant dose-dependent reduction in plasma apoC-III, HDL apoC-III, and LpB:C-III levels in patients with type 2 diabetes. These data indicate a potentially important antiatherogenic effect of statin treatment and may explain (part of) the triglyceride-lowering effect of atorvastatin.

Effect of the combination of methyltestosterone and esterified estrogens compared with esterified estrogens alone on apolipoprotein CIII and other apolipoproteins in very low density, low density, and high density lipoproteins in surgically postmenopausal women

Androgens are known to lower plasma triglycerides, an independent risk factor for coronary heart disease (CHD). Triglycerides are carried in plasma on very low density (VLDL) and low density (LDL) lipoprotein particles. Apolipoprotein CIII (apoCIII), a strong predictor of CHD, impairs the metabolism of VLDL and LDL, contributing to increased triglycerides. The objective of this study was to assess the effect of oral methyltestosterone (2.5 mg/d), added to esterified estrogens (1.25 mg/d), on concentrations of apolipoproteins and lipoproteins, specifically those containing apoCIII, compared with esterified estrogens alone in surgically postmenopausal women. The women in the methyltestosterone plus esterified estrogen group had significant decreases in total triglycerides, apoCI, apoCII, apoCIII, apoE, and high density lipoprotein (HDL) cholesterol compared with those in the esterified estrogen group. The decreases in apoCIII concentrations occurred in VLDL (62%; P = 0.02), LDL (35%; P = 0.001), and HDL (17%; P < 0.0001). There were also decreases in cholesterol and triglycerides concentrations of apoCIII containing LDL, and apoCI concentration of apoCIII containing VLDL. There was no effect on VLDL and LDL particles that did not contain apoCIII or on apoB concentrations. In conclusion, methyltestosterone, when administered to surgically postmenopausal women taking esterified estrogen, has a selective effect to reduce the apoCIII concentration in VLDL and LDL, a predictor of CHD. Methyltestosterone may lower plasma triglycerides through a reduction in apoCIII.

Analysis of apolipoprotein A5, c3, and plasma triglyceride concentrations in genetically engineered mice

OBJECTIVE

Both the apolipoprotein A5 and C3 genes have repeatedly been shown to play an important role in determining plasma triglyceride concentrations in humans and mice. In mice, transgenic and knockout experiments indicate that plasma triglyceride levels are strongly altered by changes in the expression of either of these 2 genes. In humans, common polymorphisms in both genes have also been associated with plasma triglyceride concentrations. These similar findings raised the issue of the relationship between these 2 genes and altered triglycerides.

METHODS AND RESULTS

To address this issue, we generated independent lines of mice that either overexpressed ("double transgenic") or completely lacked ("double knockout") both apolipoprotein genes. We report that both "double transgenic" and "double knockout" mice display normal triglyceride concentrations compared with overexpression or deletion of either gene alone. Furthermore, we find that human ApoAV plasma protein levels in the "double transgenic" mice are approximately 500-fold lower than human ApoCIII levels, supporting ApoAV as a potent triglyceride modulator despite its low concentration.

CONCLUSIONS

Together, these data support that APOA5 and APOC3 independently influence plasma triglyceride concentrations but in an opposing manner.

[Levels of apoproteins B, A1 and CIII as markers for cardiovascular risk in lean and obese adolescents]

Cardiovascular disease is a significant health problem affecting the adult population. Because atherosclerosis may begin in childhood, the aim of the present study was to identify biochemical markers for cardiovascular risk at an early stage of life. We studied 79 adolescents (48 girls and 31 boys) whose ages ranged from 13 to 17 years. A medical history (including pubertal stage by Tanner) was obtained from each subject. Anthropometric assessment was established by height, weight, body mass index (BMI), waist and hip circumferences, skinfolds, centrality index and obesity index. After a 12-h fast, basal blood glucose levels, total cholesterol, triglycerides, LDL-C and HDL-C were determined by enzymatic methods, mean basal insulin levels by radio immunoassays and apo A1, B, CIII by turbidimetric immunoassays. According to the BMI and taking 25 Kg/m2 as the cutoff value, 35% of the girls and 16% of the boys were obese. Eighty-five percent of the girls and 58% of the boys were hyperinsulinemic (basal insulin > 12 uU/ml). Circumferences, skinfolds, centrality and obesity index were higher (p < 0.05) in boys than in girls. In both, boys and girls, basal insulin levels were higher than the cutoff insulin value for our lab (>12 microU/ml), with the girls having higher insulin levels than the boys. Apo A1 was negatively associated with the obesity index and positively with HDL-C. Apo B was related to total cholesterol and LDL-C. Apo CIII was associated with basal insulin levels, triglycerides and VLDL-C. Our results suggest that apo CIII might be a good marker for higher insulin levels, insulin resistance and cardiovascular risk in adolescents.

Alteration in lipoprotein lipase activity bound to triglyceride-rich lipoproteins in the postprandial state in type 2 diabetes

Postprandial lipid metabolism is largely dependent upon lipoprotein lipase (LPL), which hydrolyses triglycerides (TGs). The time course of LPL activity in the postprandial state following a single meal has never been studied, because its determination required heparin injection. Recently, we have shown that LPL activity could be accurately measured in nonheparinized VLDL using a new assay aiming to determine the LPL-dependent VLDL-TG hydrolysis. Based on the same principle, we used in this study TG-rich lipoprotein (TRL)-bound LPL-dependent TRL-TG hydrolysis (LTTH) to compare the time course of LPL activity of 10 type 2 diabetics to that of 10 controls, following the ingestion of a lipid-rich meal. The peak TG concentration, reached after 4 h, was 67% higher in diabetics than in controls (P < 0.005). Fasting LTTHs were 91.3 +/- 15.6 in controls versus 70.1 +/- 4.8 nmol NEFA/ml/h in diabetics (P < 0.001). LTTH was increased 2 h postprandially by 190% in controls and by only 89% in diabetics, resulting in a 35% lowering of the LTTH area under the curve in diabetics. Postprandial LTTH was inversely correlated with TG or remnant concentrations in controls but not in diabetics, and with insulin resistance in both groups. These data show that TRL-bound LPL activity increases in the postprandial state and is strongly reduced in type 2 diabetes, contributing to postprandial hypertriglyceridemia.