The ACTN3 R577X polymorphism affects the lipid profile and the prognosis of nutritional intervention in HIV-positive patients

The hypothesis of the present study is that the polymorphisms in the APOC3, CEPT, ACE, and ACTN3 genes can affect the outcome of nutritional intervention and the plasma lipid profile of HIV+ patients. To test the hypothesis, genetic material was collected from buccal cells, and serum was collected for biochemical analysis. Sixty-five patients were analyzed. The incorporation of protease inhibitor (PI) was more frequent in women (77% vs 33% in men). Nutritional intervention improved anthropometric parameters independent of the genotype. Patients with the RR genotype for the ACTN3 R577X polymorphism had lower glycemia (RR = 95.4 ± 6.5 mg/dL, RX = 102.6 ± 10.6 mg/dL, XX = 110.1 ± 16.3 mg/dL; P = .03) and a greater reduction in low-density lipoproteins (LDL) after intervention (LDL: RR = -23.7 ± 15.8 mg/dL, RX = 1.32 ± 5.13 mg/dL, XX = 30.21 ± 24.4 mg/dL; P = .01). Patients using PI had a negative response to dietary intervention regarding the levels of high-density lipoprotein (-2.4 ± 1.70 with PI, 2.56 ± 1.60 mg/dL without PI; P = .02), very low density lipoprotein (0.84 ± 2.73 with IP, -5.46 ± 3.37 mg/dL without PI; P = .03), and triglycerides (1.79 ± 13.22 with PI, -34.00 ± 17.67 mg/dL without PI; P = .052). This response was also independent of the genotype (P > 0.05) and suggested the need for oral lipid-lowering drugs in all HIV+ patients using PI. Our results indicate that the ACTN3 R577X polymorphism is a good predictor of both the lipid profile and the prognosis of nutritional intervention in reducing LDL in HIV+ patients.

Mechanism of action of a peroxisome proliferator-activated receptor (PPAR)-delta agonist on lipoprotein metabolism in dyslipidemic subjects with central obesity

CONTEXT

Dyslipidemia increases the risk of cardiovascular disease in obesity. Peroxisome proliferator-activated receptor (PPAR)-δ agonists decrease plasma triglycerides and increase high-density lipoprotein (HDL)-cholesterol in humans.

OBJECTIVE

The aim of the study was to examine the effect of GW501516, a PPAR-δ agonist, on lipoprotein metabolism. Design, Setting, and Intervention: We conducted a randomized, double-blind, crossover trial of 6-wk intervention periods with placebo or GW501516 (2.5 mg/d), with 2-wk placebo washout between treatment periods.

PARTICIPANTS

We recruited 13 dyslipidemic men with central obesity from the general community.

MAIN OUTCOME MEASURES

We measured the kinetics of very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein-, and low-density lipoprotein (LDL)-apolipoprotein (apo) B-100, plasma apoC-III, and high-density lipoprotein (HDL) particles (LpA-I and LpA-I:A-II).

RESULTS

GW501516 decreased plasma triglycerides, fatty acid, apoB-100, and apoB-48 concentrations. GW501516 decreased the concentrations of VLDL-apoB by increasing its fractional catabolism and of apoC-III by decreasing its production rate (P < 0.05). GW501516 reduced VLDL-to-LDL conversion and LDL-apoB production. GW501516 increased HDL-cholesterol, apoA-II, and LpA-I:A-II concentrations by increasing apoA-II and LpA-I:A-II production (P < 0.05). GW501516 decreased cholesteryl ester transfer protein activity, and this was paralleled by falls in the triglyceride content of VLDL, LDL, and HDL and the cholesterol content of VLDL and LDL.

CONCLUSIONS

GW501516 increased the hepatic removal of VLDL particles, which might have resulted from decreased apoC-III concentration. GW501516 increased apoA-II production, resulting in an increased concentration of LpA-I:A-II particles. This study elucidates the mechanism of action of this PPAR-δ agonist on lipoprotein metabolism and supports its potential use in treating dyslipidemia in obesity.

Parallel increase of plasma apoproteins C-II and C-III in Type 2 diabetic patients

AIMS

To determine plasma levels of apoprotein (apo) C-II and apoprotein C-III in Type 2 diabetic patients and to examine the clinical and biological factors that are associated with elevated apoC concentrations.

METHODS

We measured apoC-II and apoC-III in total plasma and in non-high-density lipoprotein fractions by an immunoturbidimetric assay in 88 Caucasian Type 2 diabetic patients and in 138 healthy control subjects.

RESULTS

Plasma levels of both apoC-II and apoC-III were increased in Type 2 diabetic patients. The clinical conditions associated with an increase of plasma apoC-II and apoC-III were abdominal obesity, body mass index, poor glycaemic control and lack of insulin treatment. However, when multivariate analysis was used, plasma apoCs levels correlated with triglyceride levels only. The apoC-III/apoC-II ratio was similar in the Type 2 diabetic and control subjects.

CONCLUSIONS

Our study shows the parallel increase of apoC-II and C-III in Type 2 diabetic patients. This parallel increase is related to hypertriglyceridaemia only.

Effects of nicotinic acid on concentrations of serum apolipoproteins B, C-I, C-II, C-III and E in hyperlipidemic patients

Twenty-four patients with Type IIa, IIb, III and IV hyperlipoproteinemia (HLP) were treated with 4 g of nicotinic acid daily with the purpose to study its effect on serum apolipoprotein B, C-I, C-II, C-III and E concentrations. Triglyceride and total cholesterol concentrations of whole serum and of different serum lipoprotein fractions were also determined. Analyses were performed prior to and after a drug treatment period of 6 weeks, during which all the patients were weight stable. Treatment caused a decrease in serum concentrations of apolipoproteins C-I, C-II, C-III and E. These highly significant reductions were all positively correlated to a reduction of very low density lipoprotein triglyceride levels of serum (r-values greater than 0.76, p less than 0.001). There were highly significant decreases in serum levels of apolipoprotein B and low density lipoprotein total cholesterol. These reductions were positively intercorrelated (r = 0.55; p less than 0.01). Similar effects were observed in the different HLP types and in both sexes. Treatment resulted in normolipidemia in 12 patients, who were hypercholesterolemic (7 type IIa, 3 type IIb, 2 type III hyperlipoproteinemia) prior to treatment. The serum apolipoprotein B concentrations of these 12 patients fell after therapy to values which, however, remained abnormally high. We suggest that serum lipid adjusting treatment should aim at a normalization not only of serum lipid concentrations but also of the serum apolipoprotein B concentration in order to achieve a maximal antiatherogenic effect.

Circulating triacylglycerol and apoE levels in response to EPA and docosahexaenoic acid supplementation in adult human subjects

High doses ofn–3 PUFA found in fish oils can reduce the circulating concentration of triacylglycerol (TG), which may contribute to the positive impact of these fatty acids on the risk of CVD. The present study aimed to establish the differential impact of EPA and docosahexaenoic (DHA) on plasma lipids and apo in adults. Forty-two normolipidaemic adult subjects completed a double-blind placebo controlled parallel study, receiving an EPA-rich oil (4·8 g EPA/d), DHA-rich oil (4·9 g DHA/d) or olive oil as control, for a period of 4 weeks. No effects of treatment on total cholesterol, LDL-cholesterol or HDL-cholesterol were evident. There was a significant 22 % reduction in TG level relative to the control value following the DHA treatment (P=0·032), with the 15 % decrease in the EPA group failing to reach significance (P=0·258). There were no significant inter-group differences in response to treatment for plasma apoA1, -C3 or -E levels, although a significant 15 % within-group increase in apoE was evident in the EPA (P=0·006) and DHA (P=0·003) groups. In addition, a within-group decrease in the apoA1:HDL-cholesterol ratio was observed in the DHA group, suggesting a positive impact of DHA on HDL particle size. The DHA intervention resulted in a significant increase in the proportion of EPAP=0·000 and DHAP=0·000 in plasma phospholipids, whilst significant increases in EPAP=0·000 and docosapentaenoic acidP=0·002, but not DHAP=0·193, were evident following EPA supplementation (P>0·05). Our present results indicate that DHA may be more efficacious than EPA in improving the plasma lipid profile.

Abnormal glycosylation with hypersialylated O-glycans in patients with Sialuria

Sialuria is an inborn error of metabolism characterized by coarse face, hepatomegaly and recurrent respiratory tract infections. The genetic defect in this disorder results in a loss of feedback control of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine-kinase by CMP-N-acetylneuraminic acid (CMP-NeuAc) resulting in a substantial overproduction of cytoplasmic free sialic acid. This study addresses fibroblast CMP-NeuAc levels and N- and O-glycan sialylation of serum proteins from Sialuria patients. CMP-NeuAc levels were measured with HPLC in fibroblasts. Isoelectric focusing (IEF) of serum transferrin and of apolipoprotein C-III (apoC-III) was performed on serum of three Sialuria patients. Isoforms of these proteins can be used as specific markers for the biosynthesis of N- and core 1 O-glycans. Furthermore, total N- and O-linked glycans from serum proteins were analyzed by HPLC. HPLC showed a clear overproduction of CMP-NeuAc in fibroblasts of a Sialuria patient. Minor changes were found for serum N-glycans and hypersialylation was found for core 1 O-glycans on serum apoC-III and on total serum O-glycans in Sialuria patients. HPLC showed an increased ratio of disialylated over monosialylated core 1 O-glycans. The hypersialylation of core 1 O-glycans is due to the increase of NeuAcalpha2,6-containing structures (mainly NeuAcalpha2-3Galbeta1-3[NeuAcalpha2-6]GalNAc). This may relate to KM differences between GalNAc-alpha2,6-sialyltransferase and alpha2,3-sialyltransferases. This is the first study demonstrating that the genetic defect in Sialuria results in a CMP-NeuAc overproduction. Subsequently, increased amounts of alpha2,6-linked NeuAc were found on serum core 1 O-glycans from Sialuria patients. N-glycosylation of serum proteins seems largely unaffected. Sialuria is the first metabolic disorder presenting with hypersialylated O-glycans.

Biomarker discovery in breast cancer serum using 2-D differential gel electrophoresis/ MALDI-TOF/TOF and data validation by routine clinical assays

In the present study, we used 2-D differential gel electrophoresis (2-D DIGE) and MS to screen biomarker candidates in serum samples obtained from 39 patients with breast cancer and 35 controls. First, we pooled the serum samples matched with age and menopausal status. Then, we depleted the two most abundant proteins albumin and IgG by immunoaffinity chromatography under partly denaturing conditions in order to enrich low-abundance proteins and proteins with low molecular weight. Concentrated and desalted samples were labeled with three different CyDyes including one internal standard, pooled from all the samples, and separated with 2-D DIGE in triplicate experiments. Biological variations of the protein expression level were analyzed with DeCyder software and evaluated for reproducibility and statistical significance. The profile of differentially expressed protein spots between patients and controls revealed proapolipoprotein A-I, transferrin, and hemoglobin as up-regulated and three spots, apolipoprotein A-I, apolipoprotein C-III, and haptoglobin alpha2 as down-regulated in patients. Finally, routine clinical immunochemical reactions were used to validate selected candidate biomarkers by quantitative determination of specific proteins in all individual serum samples. The serum level of transferrin correlated well with the 2-D-DIGE results. However, the serum levels of apolipoprotein A-I and haptoglobin could not be detected with the clinical routine diagnostic tests. This demonstrated an advantage 2-D DIGE still has over other techniques. 2-D DIGE can distinguish between isoforms of proteins, where the overall immunochemical quantification does fail due to a lack of isoform-special antibodies.

Proteomic analysis of serum marker proteins in recipient mice with liver cirrhosis after bone marrow cell transplantation

We previously found that transplantation with bone marrow cells (BMCs) improves liver function and liver fibrosis in cirrhotic mice. In the presence of liver damage induced by carbon tetrachloride (CCl4), transplanted BMC migrated into the peri-portal region and trans-differentiated into hepatocytes that produce albumin. Thus under these conditions, BMC transplantation induces liver regeneration. Detecting serum marker proteins is important to monitor the recovery of liver function of cirrhotic mice after BMC transplantation. We therefore initially resolved proteins extracted from serum samples at 48 h after BMC transplantation by 2-DE and compared spot intensity between control and BMC groups of mice. Six protein spots increased in the BMC group compared with the control group. MS revealed that these spots comprised apolipoprotein A1 (apoA1), apolipoprotein C3 (apoC3), vitamin D-binding protein, alpha-1-antitrypsin and proteasome subunit alpha type 1. We subsequently confirmed the levels of apoA1 in serum and liver samples by immunoblotting. ApoA1 increased at early stage (48 h and 1 wk) after BMC transplantation in this mouse model of liver cirrhosis. The early elevation of apoA1 might be useful to predict liver regeneration in cirrhotic mice after BMC transplantation.

Proteomic Analysis of Rat Plasma by SELDI-TOF-MS under the Condition of Prevention of Progressive Adriamycin Nephropathy Using Oral Adsorbent AST-120

AIMS

To determine changes in relative peak intensities of mass-to-charge ratio (m/z) between 2,000 and 15,000, which are difficult to evaluate by 2-dimensional gel electrophoresis, SELDI-TOF-MS (surface-enhanced laser desorption/ionization time of flight-mass spectrometry) proteomic changes in rat models of adriamycin nephropathy with or without AST-120 were investigated.

METHODS

A normal group (n = 5), an adriamycin nephropathy group (n = 9), and an adriamycin nephropathy + AST-120 group (4 g/head/day) (n = 9) were established in SD rats. Anion exchange chips, Q10, washed by 50 mM Tris-HCl pH 8 as a ProteinChip and sinapinic acid were used. The mass range between 2,000 and 15,000 Da was measured. Twenty to 34 weeks after adriamycin 3 mg/kg injection, the adriamycin nephropathy + AST-120 group (plasma creatinine value: 2.1 +/- 0.8 mg/dl) clearly demonstrated slight renal dysfunction compared with that in the adriamycin nephropathy group (5.4 +/- 2.0 mg/dl).

RESULTS

The relative intensities in the adriamycin nephropathy group were significantly higher in 7 peaks (such as 8,640, and 8,822 Da) and lower in 8 peaks (such as 4,188, and 8,358 Da) than those in the normal group. The relationship between the relative intensity of peaks and the plasma creatinine value demonstrated a positive correlation in 11 peaks (such as 8,640, and 8,822 Da), and a negative correlation in 6 peaks (such as 4,188 and 8,358 Da). Although the relative intensities of peaks in the adriamycin nephropathy + AST-120 group were between that of the adriamycin nephropathy group and that of the normal group, the relative intensities of 4 peaks (such as 3,664 and 5,179 Da) in the adriamycin nephropathy + AST-120 group demonstrated higher values than in the two other groups. The m/z 3,664 peak was purified and identified as a C-terminal fragment of apolipoprotein C-III.

CONCLUSION

Low-molecular proteins and peptides in plasma in this chronic renal failure model showed not only increases but also decreases in some peaks. The relative intensities in some peaks increased in the adriamycin nephropathy + AST-120 group more than in the two other groups. One of these peaks was identified as the apolipoprotein C-III fragment. The relationship between these changes and the prevention of progression of chronic renal failure by AST-120 remains to be established.

Apolipoprotein C-III isoforms: kinetics and relative implication in lipid metabolism

Apolipoprotein C-III (apoC-III) production rate (PR) is strongly correlated with plasma triglyceride (TG) levels. ApoC-III exists in three different isoforms, according to the sialylation degree of the protein. We investigated the kinetics and respective role of each apoC-III isoform in modulating intravascular lipid/lipoprotein metabolism. ApoC-III kinetics were measured in a sample of 18 healthy men [mean age (+/-SD) 42.1 +/- 9.5 years, body mass index 29.8 +/- 4.6 kg/m2] using a primed-constant infusion of l-(5,5,5-D3) leucine for 12 h. Mono-sialylated and di-sialylated apoC-III (apo-CIII1 and apoC-III2) exhibited similar PRs (means +/- SD, 1.22 +/- 0.49 mg/kg/day vs. 1.15 +/- 0.59 mg/kg/day, respectively) and similar fractional catabolic rates (FCRs) (0.51 +/- 0.13 pool/day vs. 0.61 +/- 0.24 pool/day, respectively). Nonsialylated apoC-III (apoC-III0) had an 80% lower PR (0.25 +/- 0.12 mg/kg/day) and a 60% lower FCR (0.21 +/- 0.07 pool/day) (P < 0.0001 for comparison with CIII1 and CIII2 isoforms). The PRs of apoC-III1 and apoC-III2 were more strongly correlated with plasma TG levels (r > 0.8, P < 0.0001) than was apoC-III0 PR (r = 0.54, P < 0.05). Finally, the PR of apoC-III2 was strongly correlated with the proportion of LDL <255 A (r = 0.72, P = 0.002). These results suggest that all apoC-III isoforms, especially the predominant CIII1 and CIII2 isoforms, contribute to hypertriglyceridemia and that apoC-III2 may play a significant role in the expression of the small, dense LDL phenotype.

Use of Intralipid for kinetic analysis of HDL apoC-III: evidence for a homogeneous kinetic pool of apoC-III in plasma

Apolipoprotein C-III (apoC-III) is an important regulator of lipoprotein metabolism. Radioisotope and stable isotope kinetic studies show differing results in relation to the kinetics of apoC-III in HDL. Kinetic analysis of HDL apoC-III may be difficult because of its low concentration, as well as the presence of other apoproteins at higher concentration, in the HDL fraction. We used Intralipid(R) (IL), known to preferentially extract apoC proteins from plasma, as a means of extracting apoC-III from HDL before apoprotein separation by isoelectric focusing gel electrophoresis for the measurement of tracer enrichment. Protein purity was assessed by an isoleucine-to-leucine (Ile/Leu) ratio, as apoC-III contains no isoleucine. We compared apoC-III kinetics in 14 men using a bolus infusion of deuterated leucine. The Ile/Leu ratio for IL-extracted HDL (IL-HDL) apoC-III (3.0 +/- 0.7%) was not different from that of VLDL apoC-III (2.6 +/- 0.6%) but was significantly lower than that of untreated HDL apoC-III (9.0 +/- 2.9%) (P < 0.001). The isotopic enrichment curves and fractional catabolic rates (FCRs) for IL-HDL apoC-III were not different from those of VLDL apoC-III. In contrast, HDL apoC-III had significantly lower isotopic enrichments and FCRs than IL-HDL apoC-III (P < 0.001). In conclusion, this simple IL method can be used to isolate apoC-III from HDL with minimal interference from other HDL apoproteins, and it demonstrates that the kinetics of apoC-III in VLDL and HDL are similar, supporting the concept of a single kinetically homogeneous pool of apoC-III in plasma.

Metabolic syndrome in aboriginal Canadians: prevalence and genetic associations

OBJECTIVES

The prevalence rates of type 2 diabetes (T2DM) and coronary heart disease (CHD) in Ontario Oji-Cree are among the world's highest. Since metabolic syndrome (MetS) increases risk of T2DM and CHD, we characterized prevalence and putative genetic determinants of MetS in Oji-Cree.

METHODS AND RESULTS

In 515 adult (> or = 18 years old) and 115 adolescent (< 18 years old) Oji-Cree subjects, using the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria, we determined that 29.9% of Oji-Cree adults, and 43.4% of adults > or = 35 years of age, had MetS. Furthermore, 33.9 and 8.7% of female Oji-Cree adults and adolescents, respectively, had MetS. Increased waist girth and depressed HDL cholesterol were the most prevalent individual MetS components, while increased blood pressure was least prevalent. AGT T174M, GNB3 825C>T, and APOC3 -455T>C genotypes were significantly associated with MetS (P = 0.018, 0.0056, and 0.029, respectively) for female adults, whereas FABP2 A54T genotype was associated with MetS (P = 0.040) for female adolescents.

CONCLUSIONS

The high MetS prevalence in Oji-Cree adults, especially women, is consistent with their high risk of T2DM and CHD. Functional polymorphisms in three candidate genes for plasma lipoproteins and blood pressure were associated with MetS in adult Oji-Cree. Furthermore, several female adolescents met the adult MetS criteria, suggesting that the genesis of MetS begins in youth, especially among aboriginal females.

In-vivo metabolism of VLDL-apolipoprotein-B, -CIII and -E in normolipidemic subjects

BACKGROUND AND AIM

ApoE and apoC-III are important components of lipoprotein metabolism. While the function of both apoproteins is relatively well understood, little is known about the in vivo metabolism of these proteins, partly because of the lack of a standardized method to isolate these apoproteins in large sample numbers.

METHODS AND RESULTS

We developed a new reverse phase HPLC method (acetonitril/phosphate gradient; Aquapore RP-300, 7 microm, 220 x 4.6 mm) to isolate a number of different apoproteins, including apoC-III and apoE from VLDL. This method was then used in a study which aimed at determining VLDL-apoE-3 and VLDL-apoC-III metabolism. In addition VLDL-apoB and LDL-apoB metabolism was determined. Endogenous labeling with d(3)-leucine, mass spectrometry and multicompartmental modeling was used in 6 normolipidemic healthy male subjects. Tracer/tracee ratios of free plasma leucine, VLDL-apoE, -apoC-III, -apoB, and LDL-apoB leucine were determined over 60 h following a bolus of d(3)-leucine (5 mg kg(-1)). In all subjects sufficient apoC-III could be isolated by reverse phase HPLC to derive metabolic parameters, while apoE metabolic parameters could only be determined if apoE plasma concentration was 0.75 mg dl(-1) or higher. Compared to VLDL-apoB (FCR 10.4 +/- 3.3 d(-1), production 17.8 +/- 4.5 mg kg(-1) d(-1)), VLDL-apoE-3 (FCR 1.03 +/- 0.11 d(-1), production 0.50 +/- 0.29 mg kg(-1) d(-1)) and VLDL-apoC-III (FCR 1.67 +/- 1.22 d(-1), production 0.44 +/- 0.24 mg kg(-1) d(-1)) parameters were much lower. This indicates that apoE-3 and apoC-III recirculate in plasma and that only a small fraction of apoE and apoC-III on VLDL is newly synthesized.

CONCLUSIONS

We conclude that HPLC methodology can be used to isolate VLDL-apoC-III and apoE for metabolic studies and that the metabolic fate of apoC-III and apoE is different from that of apoB because both apoproteins recycle through the VLDL fraction.

Impact of APOA5/A4/C3 genetic polymorphisms on lipid variables and cardiovascular disease risk in French men

OBJECTIVE

The goal of the present study was to assess the impact of 4 single nucleotide polymorphisms (SNPs) of APOA5/A4/C3 gene cluster on lipid levels and coronary heart disease (CHD) risk in French men.

METHODS

A total of 442 men with CHD were recruited from the university hospital and compared to 475 men free of CHD from the population of the same geographical area. The APOA5 S19W, APOA5 -l2,238T>C, APOA4 T347S and APOC3 -482C>T SNPs were examined.

RESULTS

The APOA5 S19W polymorphism was associated with plasma triglyceride levels. In multivariate logistic regression analyses the odds ratio (OR [95% Cl]) of hypertriglyceridemia (3rd vs. 1st tertile of triglyceride distribution) was 3.60 [1.38-9.42] in control subjects bearing at least one APOA5 19W variant. Haplotype analyses revealed a significant association between the 2111 haplotype and high triglyceride levels (+1.94 +/- 0.63 vs. 0.74 +/- 0.36 mmol/l for the 1111 haplotype p < 0.002). There was, in contrast, no significant difference in SNP distribution between CHD patients and controls. The age-adjusted OR of CHD were 1.46 [0.96-2.23], 0.79 [0.60-1.05], 0.91 [0.69-1.21] and 0.91 [0.69-l.22] in carriers of the APOA5 19W, APOA5 -12,238C, APOA4 347S and APOC3 -482T variants, respectively. There was also no significant difference in APOA5/A4/C3 haplotype distribution in patients and controls.

CONCLUSION

The APOA5 19W variant is associated with increased plasma triglycerides. However, there is no evidence that APOA5 S19W, -12,238T > C, APOA4 T347S and APCC3 -482C > T SNPs are major risk factors of CHD in French men.

Endogenous apoC-I increases hyperlipidemia in apoE-knockout mice by stimulating VLDL production and inhibiting LPL

Previous studies have shown that overexpression of human apolipoprotein C-I (apoC-I) results in moderate hypercholesterolemia and severe hypertriglyceridemia in mice in the presence and absence of apoE. We assessed whether physiological endogenous apoC-I levels are sufficient to modulate plasma lipid levels independently of effects of apoE on lipid metabolism by comparing apolipoprotein E gene-deficient/apolipoprotein C-I gene-deficient (apoe-/-apoc1-/-), apoe-/-apoc1+/-, and apoe-/-apoc1+/+ mice. The presence of the apoC-I gene-dose-dependently increased plasma cholesterol (+45%; P < 0.001) and triglycerides (TGs) (+137%; P < 0.001), both specific for VLDL. Whereas apoC-I did not affect intestinal [3H]TG absorption, it increased the production rate of hepatic VLDL-TG (+35%; P < 0.05) and VLDL-[35S]apoB (+39%; P < 0.01). In addition, apoC-I increased the postprandial TG response to an intragastric olive oil load (+120%; P < 0.05) and decreased the uptake of [3H]TG-derived FFAs from intravenously administered VLDL-like emulsion particles by gonadal and perirenal white adipose tissue (WAT) (-34% and -25%, respectively; P < 0.05). As LPL is the main enzyme involved in the clearance of TG-derived FFAs by WAT, and total postheparin plasma LPL levels were unaffected, these data demonstrate that endogenous apoC-I suffices to attenuate the lipolytic activity of LPL. Thus, we conclude that endogenous plasma apoC-I increases VLDL-total cholesterol and VLDL-TG dose-dependently in apoe-/- mice, resulting from increased VLDL particle production and LPL inhibition.

Antiretroviral therapy in HIV-positive men is associated with increased apolipoprotein CIII in triglyceride-rich lipoproteins

OBJECTIVES

Dyslipidaemia has become a common problem in HIV disease, especially in patients on current antiretroviral therapy. However, the pathogenic mechanisms involved are not well understood or documented using conventional lipid measurements.

METHODS

Using a cross-sectional design, the prevalence of abnormal standard lipid measurements and novel biomarkers for abnormal lipid metabolism was determined in 271 HIV-positive men from two HIV clinics in Atlanta, GA, USA.

RESULTS

A total of 147 men were treated with protease inhibitors (PIs) for >3 months (54%), 84 were treated with nonnucleoside reverse transcriptase inhibitors (NNRTIs) for >3 months (31%) and 40 had not received antiretroviral therapy in the past 3 months (15%). Patients being treated with a PI had higher total cholesterol and triglyceride (TG) levels than patients on no therapy (P<0.05 for each). Patients in the NNRTI group had higher TG, lower high-density lipoprotein (HDL) levels, and higher low-density lipoprotein (LDL) levels than patients on no therapy (P<0.05 for each). Patients treated with either PIs or NNRTIs were more likely to have higher apolipoprotein CIII (apoCIII) levels (P<0.05 for each) than patients on no therapy. Elevated TG was associated with disproportionably elevated apoCIII levels in both treatment groups.

CONCLUSIONS

In this cross-sectional study of HIV-infected men, either PI or NNRTI therapy elevated levels of TG and apoCIII. Higher concentrations of apoCIII in apoB-containing lipoproteins [very low-density lipoproteins (VLDLs), intermediate density lipoprotein (IDL) and LDLs] have been predictive of an increased incidence of coronary events in clinical trials and more rapid progression of coronary lesions measured by angiography. These findings, on a background of an older population with additional risk factors of smoking and diabetes, portend future atherosclerotic events in these patients.

Estimating the fasting triglyceride concentration from the postprandial HDL-cholesterol and apolipoprotein CIII concentrations

Hypertriglyceridemia is an important risk factor for atherosclerosis. In the fasting state, the triglyceride (TG) concentration is correlated significantly with the high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein CIII (apoCIII) concentrations. A postprandial change is evident in TG, but negligible in HDL-C and apoCIII. We investigated whether the fasting TG concentration could be estimated from the postprandial HDL-C and apoCIII concentrations. We measured the TG, HDL-C, and apoCIII concentrations at seven points a day in 58 inpatients. Multiple regression analysis showed that the actual fasting TG concentration was strongly correlated with the TG concentration estimated from the fasting HDL-C and apoCIII concentrations (ln[TG](fasting)=0.0140[apoCIII](fasting)-0.724[HDL-C](fasting)-0.142, r=0.852, p<0.001). This equation was also fit to the fasting data from 163 outpatients (r=0.883, p<0.001). Although the TG concentration increased by up to 28.2%, the HDL-C and apoCIII concentrations changed little during the day. When we substituted the postprandial HDL-C and apoCIII concentrations for the respective fasting values in this equation, there were still strong positive correlations (r=0.794-0.840) between the actual and estimated fasting TG concentrations throughout the day. In conclusion, the fasting TG concentration can be estimated from the postprandial HDL-C and apoCIII concentrations.

Apolipoproteins C-III and A-V as predictors of very-low-density lipoprotein triglyceride and apolipoprotein B-100 kinetics

OBJECTIVE

We investigated the associations between plasma very-low-density lipoprotein (VLDL)-apolipoprotein (apo)C-III and apoA-V concentrations and the kinetics of VLDL-apoB-100 and VLDL triglycerides in 15 men. We also explored the relationship between these parameters of VLDL metabolism and VLDL-apoC-III kinetics.

METHODS AND RESULTS

ApoC-III, apoB, and triglyceride kinetics in VLDL were determined using stable isotopes and multicompartmental modeling to estimate production rate (PR) and fractional catabolic rate (FCR). Plasma VLDL-apoC-III concentration was significantly and inversely associated with the FCRs of VLDL triglycerides (r=-0.610) and VLDL-apoB (r=-0.791), and positively correlated with the PR of VLDL-apoC-III (r=0.842). However, apoA-V concentration was not significantly associated with any of the kinetic variables. There was a significant association (P<0.01) between the PRs of VLDL triglycerides and VLDL-apoB (r=0.641), and between the FCRs of VLDL triglycerides and VLDL-apoB (r=0.737). In multiple regression analysis, plasma VLDL-apoC-III concentration was a significant predictor of VLDL triglyceride FCR (beta-coefficient=-0.575) and VLDL-apoB FCR (beta-coefficient=-0.839).

CONCLUSIONS

Our findings suggest that increased VLDL-apoC-III concentrations resulting from an overproduction of VLDL-apoC-III are strongly associated with the delayed catabolism of triglycerides and apoB in VLDL. We also demonstrated that the kinetics of VLDL triglycerides and apoB are closely coupled. Our data do not support a role for plasma apoA-V in regulating VLDL kinetics.

Association of apolipoproteins C3 and E with metabolic changes in HIV-infected adults treated with a protease-inhibitor-containing antiretroviral therapy

OBJECTIVE

To examine the relationship between plasma levels of apolipoproteins C3 (APOC3) and E (APOE) and the presence of lipid and carbohydrate metabolism abnormalities or clinical signs of lipodystrophy in HIV-1-infected patients started with a protease-inhibitor-containing antiretroviral therapy.

METHODS

The Aproco (Antiproteases Cohort) Study enrolled 1,181 HIV-1-infected adults in 47 French healthcare centres from May 1997 to June 1998. From December 1998 through July 1999, the APROCO-Metabolic Complications (APROCO-MC) cross-sectional study was performed at the month 20 visit for those patients enrolled in 1997 and at the month 12 visit for those enrolled in 1998. The current analysis presents results from a subset of patients who had undergone additional tests to measure APOC3 and APOE in order to study their relationship with metabolic syndrome (n=157) and abnormal results in an oral glucose tolerance test (n=135).

RESULTS

Increases in triglycerides and non-high-density lipoprotein (HDL) cholesterol were associated with significantly higher levels of APOC3, in both Lp B (lipoproteins containing apolipoprotein B) and Lp non-B (lipoproteins free of apolipoprotein B), and a significant higher level of APOE Lp B. APOC3 and APOC3 Lp non-B were increased when glucose metabolism abnormalities were more severe. The presence of a metabolic syndrome was associated with increased plasma APOC3, APOC3 Lp B and APOC3 Lp non-B levels. In a multiple regression analysis, high levels of APOC3 in Lp B and APOC3 Lp non-B were associated with the presence of clinical signs of lipodystrophy, even after adjustment for triglycerides and HDL-cholesterol levels.

CONCLUSIONS

Lipid and/or glucose metabolism abnormalities in treated HIV-1-infected patients are associated with increased levels of APOC3 and, to a lesser extent, APOE plasma concentrations. Increased values are also related to clinical signs of insulin resistance and lipodystrophy.

Variations in plasma apolipoprotein C-III levels are strong correlates of the triglyceride response to a high-monounsaturated fatty acid diet and a high-carbohydrate diet

The objective of this study was to examine how a diet rich in carbohydrates (high-CHO) vs a diet rich in monounsaturated fatty acids (high MUFA) consumed ad libitum modulated plasma apolipoprotein C-III (apo C-III) levels and to examine the extent to which diet-induced changes in plasma apo C-III were associated with concurrent variations in plasma triglyceride (TG) levels. Forty-seven men (mean age, 35.7 +/- 11.4 years; body mass index, 29.0 +/- 5.1 kg/m2) were randomly assigned to either a high-CHO diet (CHO, 58%; fat, 26%; n = 23) or a high-MUFA diet (CHO, 45%; fat, 40%; MUFA, 22.5%; n = 24), which they consumed for 6 to 7 weeks. Fasting and postprandial lipemia after an oral fat load and fasting plasma apo C-III were measured at the beginning and at the end of the dietary intervention. Ad libitum consumption of the high-CHO diet induced a significant reduction in body weight (-2.6%, P < .0001), but had no impact on plasma apo C-III concentrations and on fasting and postprandial plasma TG levels. In contrast, ad libitum consumption of the high-MUFA diet also resulted in a significant reduction in body weight (-2.3%, P < .01) as well as in significant reductions in plasma apo C-III (-11%, P = .05) and fasting plasma TG (-17%, P < .01). Diet-induced variations in plasma apo C-III concentrations were correlated with changes in fasting and postprandial TG levels both in the high-CHO (r > 0.70, P < .001) and the high-MUFA groups (r > 0.42, P < .05). These results indicate that variations in plasma apo C-III levels are strong correlates of the fasting and postprandial plasma TG responses to high-MUFA and high-CHO diets.

A proteomic study of the apolipoproteins in LDL subclasses in patients with the metabolic syndrome and type 2 diabetes

The exchangeable apolipoproteins present in small, dense LDL (sdLDL) and large, buoyant LDL subclasses were evaluated with a quantitative proteomic approach in patients with the metabolic syndrome and with type 2 diabetes, both with subclinical atherosclerosis and the B LDL phenotype. The analyses included surface-enhanced laser adsorption/ionization, time-of-flight mass spectrometry, and subsequent identification by mass spectrometry or immunoblotting and were carried out in LDL subclasses isolated by ultracentrifugation in deuterium oxide gradients with near physiological salt concentrations. The sdLDLs of both types of patients were enriched in apolipoprotein C-III (apoC-III) and were depleted of apoC-I, apoA-I, and apoE compared with matched healthy controls with the A phenotype. The LDL complexes formed in serum from patients with diabetes with the arterial proteoglycan (PG) versican were also enriched in apoC-III. In addition, there was a significant correlation between the apoC-III content in sdLDL in patients and the apparent affinity of their LDLs for arterial versican. The unique distribution of exchangeable apolipoproteins in the sdLDLs of the patients studied, especially high apoC-III, coupled with the augmented affinity with arterial PGs, may contribute to the strong association of the dyslipidemia of insulin resistance with increased risk for cardiovascular disease.

Immune-regulation of the apolipoprotein A-I/C-III/A-IV gene cluster in experimental inflammation

Apolipoprotein A-IV is a member of the apo A-I/C-III/A-IV gene cluster. In order to investigate its hypothetical coordinated regulation, an acute phase was induced in pigs by turpentine oil injection. The hepatic expression of the gene cluster as well as the plasma levels of apolipoproteins were monitored at different time periods. Furthermore, the involvement of the inflammatory mediators' interleukins 1 and 6 and tumor necrosis factor in the regulation of this gene cluster was tested in cultured pig hepatocytes, incubated with those mediators and apo A-I/C-III/A-IV gene cluster expression at the mRNA level was measured. In response to turpentine oil-induced inflammation, a decreased hepatic apo A-IV mRNA expression was observed (independent of apo A-I and apo C-III mRNA) not correlating with the plasma protein levels. The distribution of plasma apo A-IV experienced a shift from HDL to larger particles. In contrast, the changes in apo A-I and apo C-III mRNA were reflected in their corresponding plasma levels. Addition of cytokines to cultured pig hepatocytes also decreased apo A-IV and apo A-I mRNA levels. All these results show that the down-regulation of apolipoprotein A-I and A-IV messages in the liver may be mediated by interleukin 6 and TNF-alpha. The well-known HDL decrease found in many different acute-phase responses also appears in the pig due to the decreased expression of apolipoprotein A-I and the enlargement of the apolipoprotein A-IV-containing HDL.

Alterations of lipids and apolipoprotein CIII in very low density lipoprotein subspecies in type 2 diabetes

AIMS/HYPOTHESIS

Very low density lipoprotein (VLDL) particles are heterogeneous, comprising two main subspecies, VLDL 1 (Sf 60-400) and VLDL 2 (Sf 20-60). The aim of the study was to examine the distribution and composition of VLDL subspecies in type 2 diabetes.

SUBJECTS, MATERIALS AND METHODS

We studied the composition and concentration of triglyceride-rich lipoproteins (TRLs) in 217 type 2 diabetic patients and 93 control subjects between 50 and 75 years of age. Lipoprotein subspecies were separated by density-gradient ultracentrifugation. Apolipoprotein (apo) CIII and apo E in plasma and apo CIII in TRL subspecies were measured by nephelometry and apo CII in serum by a commercial kit using a single radial immunodiffusion method.

RESULTS

The concentrations of VLDL 1, VLDL 2 and intermediate density lipoprotein were significantly increased in type 2 diabetes subjects, the change being most marked for VLDL 1. There was a strong linear correlation between VLDL 1 triglycerides and plasma triglycerides in both groups (r = 0.879, p < 0.001 and r = 0.899, p < 0.001). Diabetic subjects had markedly higher plasma ratios of apo CII:apo CIII and apo CIII:apo E. Despite elevated plasma apo CIII, type 2 diabetic subjects had a relative deficiency of apo CIII in all TRL subspecies, suggesting profound disturbances of apo CIII metabolism.

CONCLUSIONS/INTERPRETATION

The elevation of VLDL 1 triglycerides is the major determinant of plasma triglyceride concentration in normal subjects and in type 2 diabetic individuals. Both apo CIII and apo E metabolism are disturbed in type 2 diabetes.

Association between MspI polymorphism of the APO AI gene and Type 2 diabetes mellitus

AIMS

Genes of the Apo AI/CIII/AIV cluster on chromosome 11 have been related to plasma lipid patterns. The close relationship between carbohydrate metabolism and lipid metabolism warrants investigation of the association between this cluster and Type 2 diabetes mellitus. We therefore examined the possible association between polymorphisms of this cluster and Type 2 diabetes mellitus as part of a study of the prevalence of diabetes and the metabolic syndrome in southern Spain.

METHODS

A total of 1224 persons were selected randomly from the town of Pizarra in the province of Malaga, southern Spain. The sample errors for the prevalence of Type 2 diabetes mellitus and the three polymorphisms studied were all < or = 4%. All subjects underwent phenotyping after an oral glucose tolerance test (75 g) (WHO 1998 criteria) and the XmnI and MspI polymorphisms of Apo AI and the SstI polymorphism of Apo CIII were genotyped.

RESULTS

Those subjects with the mutated AA genotype of the MspI polymorphism (-75 G-->A) of Apo AI had a greater risk of impaired glucose tolerance [odds ratio (OR) = 1.95, CI = 1.02-3.8, P = 0.05], Type 2 diabetes mellitus, both known (OR = 7.38, CI = 1.3-39.7, P = 0.02) and unknown (OR = 3.7, CI = 1.4-9.9, P = 0.009). This risk was independent of age, sex, obesity, triglyceride level, HDL cholesterol and pattern of insulin resistance.

CONCLUSIONS

Pending confirmation in prospective studies, the AA genotype of the MspI polymorphism of the Apo AI gene, within the Apo A-I/C-III/A-IV cluster, seems to be a risk factor for Type 2 diabetes mellitus.

Administration of a PPARalpha agonist increases serum apolipoprotein A-V levels and the apolipoprotein A-V/apolipoprotein C-III ratio

Apolipoprotein A-V (apoA-V) first gained attention as a regulator of triglycerides through transgenic mouse studies. Furthermore, peroxisome proliferator-activated receptor alpha (PPARalpha) agonists such as fenofibrate increase apoA-V mRNA expression. Our group recently developed the first assay to quantitate serum apoA-V levels. Therefore, we sought to determine whether administration of a PPARalpha agonist would increase circulating apoA-V. Cynomolgus monkeys were dosed for 14 days with 0.3 mg/kg/day LY570977 L-lysine, a potent and selective PPARalpha agonist. Blood samples were drawn throughout the treatment period and after a 2 week washout. Administration of the PPARalpha agonist caused a 50% decrease in triglycerides that reversed at washout. Serum apoA-V concentrations increased 2-fold, correlated inversely with triglycerides, and were reversible at washout. The apoA-V/apoC-III ratio increased >2-fold, with this increase also reversible at washout. These data demonstrate for the first time that a PPARalpha agonist increases circulating apoA-V protein levels and the apoA-V/apoC-III ratio.

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.