Carotid atherosclerosis in virologically suppressed HIV patients: comparison with a healthy sample and prediction by cardiovascular risk equations.

OBJECTIVES: To compare the prevalence of carotid atherosclerosis in virologically suppressed HIV patients with that of a community sample, and to evaluate the capacity of various cardiovascular risk (CVR) equations for predicting carotid atherosclerosis. METHODS: This was a cross-sectional study with two randomly selected groups: HIV patients from an HIV unit and a control group drawn from the community. Participants were matched by age (30-80 years) and sex without history of cardiovascular disease. Carotid plaque, common carotid intima-media thickness (cc-IMT) and subclinical atherosclerosis (carotid plaque and/or cc-IMT > 75th percentile) were assessed by carotid ultrasound. The Systematic Coronary Risk Evaluation (SCORE), Framingham, REGICOR, reduced Data Collection on Adverse Effects of Anti-HIV Drugs (D:A:D), and COMVIH equations were applied, and their abilities to predict carotid plaque were compared using the area under the curve (AUC). RESULTS: Each group included 379 subjects (77.8% men, age 49.7 years). Duration of antiretroviral therapy was 15.5 years. There were no differences between the groups for carotid plaque (HIV, 33.2%; control, 31.3%), mean cc-IMT (HIV, 0.63 mm; control, 0.61 mm) or subclinical atherosclerosis (HIV, 42.9%; control, 47.9%). Thymidine analogues were independently associated with subclinical atherosclerosis in HIV-infected patients. CVR equations revealed AUCs between 0.715 and 0.807 for prediction of carotid plaque; prediction was better in the control group and did not improve when HIV-adapted scales were used. CONCLUSIONS: The features of carotid atherosclerosis did not differ between the HIV-infected and the control group, although CVR equations were more predictive for carotid plaque in controls than in HIV-infected patients. HIV-specific equations did not improve prediction.

Electronegative LDL induces priming and inflammasome activation leading to IL-1ß release in human monocytes and macrophages.

BACKGROUND: Electronegative LDL (LDL(−)), a modified LDL fraction found in blood, induces the release of inflammatory mediators in endothelial cells and leukocytes. However, the inflammatory pathways activated by LDL(−) have not been fully defined. We aim to study whether LDL(−) induced release of the first-wave proinflammatory IL-1ß in monocytes and monocyte-derived macrophages (MDM) and the mechanisms involved. METHODS: LDL(−) was isolated from total LDL by anion exchange chromatography. Monocytes and MDM were isolated from healthy donors and stimulated with LDL(+) and LDL(−) (100 mg apoB/L). RESULTS: In monocytes, LDL(−) promoted IL-1ß release in a time-dependent manner, obtaining at 20 h-incubation the double of IL-1ß release induced by LDL(−) than by native LDL. LDL(−)-induced IL-1ß release involved activation of the CD14-TLR4 receptor complex. LDL(−) induced priming, the first step of IL-1ß release, since it increased the transcription of pro-IL-1ß (8-fold) and NLRP3 (3-fold) compared to native LDL. Several findings show that LDL(−) induced inflammasome activation, the second step necessary for IL-1ß release. Preincubation of monocytes with K+ channel inhibitors decreased LDL(−)-induced IL-1ß release. LDL(−) induced formation of the NLRP3-ASC complex. LDL(−) triggered 2-fold caspase-1 activation compared to native LDL and IL-1ß release was strongly diminished in the presence of the caspase-1 inhibitor Z-YVAD. In MDM, LDL(−) promoted IL-1ß release, which was also associated with caspase-1 activation. CONCLUSIONS: LDL(−) promotes release of biologically active IL-1ß in monocytes and MDM by induction of the two steps involved: priming and NLRP3 inflammasome activation. SIGNIFICANCE: By IL-1ß release, LDL(−) could regulate inflammation in atherosclerosis.

Prevalence of metabolic syndrome among human immunodeficiency virus-infected subjects is widely influenced by the diagnostic criteria.

BACKGROUND: The aim of this study was to compare the prevalence of metabolic syndrome in human immunodeficiency virus (HIV)-infected patients treated with highly active antiretroviral therapy (HAART), using the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III), European Group for the Study of Insulin Resistance (EGIR), and International Diabetes Federation (IDF) definitions. METHODS: A cross-sectional study was carried out with 159 consecutive adult HIV-infected subjects (120 males and 39 females) under HAART. Anthropometric and laboratory parameters were measured by standard methods. Hyperinsulinemia was defined by a fasting concentration >75th percentile of values obtained in healthy individuals (107.5 pmol/L). RESULTS: The prevalence of ATP III-defined metabolic syndrome was 10.1%; it was 28.3% according to EGIR criteria and 15.1% using the IDF definition. The concordance between the definitions was low (kappa coefficient ranging between 0.134 and 0.296). All subjects with EGIR-defined metabolic syndrome had hyperinsulinemia, but only 50% of those with ATP III-defined metabolic syndrome and 62.5% in the IDF metabolic syndrome population had hyperinsulinemia. CONCLUSIONS: The inclusion of hyperinsulinemia as a criterion in the EGIR metabolic syndrome definition made it more discriminative than the ATP III definition, both in men and women, and than the IDF definition in men to identify metabolic syndrome in HIV-infected subjects under HAART.

Modificaciones aterogénicas de las partículas LDL en los pacientes con diabetes / Atherogenic modifications of LDL particles in diabetic patients

Las manifestaciones clínicas de la enfermedad arteriosclerótica constituyenla principal complicación en la población con diabetes mellitus,y son responsables del 50-70% de las muertes en estos pacientes.No se conocen con precisión los mecanismos responsables del desarrolloacelerado de arteriosclerosis en la diabetes, aunque los procesosderivados de la situación de hiperglucemia y de dislipemiadiabética desempeñan un papel importante. Ambos mecanismos estánestrechamente relacionados y pueden considerarse como doscaras de la misma moneda. Existen modifi caciones cualitativas de laslipoproteínas de baja densidad (LDL) bien conocidas, como el incrementode la proporción de partículas LDL pequeñas y densas o departículas con mayor carga electronegativa. Estas modifi caciones,que alteran las características fi sicoquímicas y biológicas de las partículasLDL, están implicadas en los mecanismos comunes mediantelos que la hiperlipemia y la hiperglucemia producen un aumento delos procesos arterioscleróticos en los pacientes con diabetes(AU)

Clinical manifestations derived from atherosclerosis are the leadingcomplications in patients with diabetes mellitus, being responsible of50-70% of deaths in these individuals. The precise link between accelerateddevelopment of atherosclerosis and diabetes is not completelyunderstood, although mechanisms related with hyperglycemiaand diabetic dyslipidemia play an important role. Both mechanismsare closely related and frequently are two faces of the same coin.There are well-recognized qualitative modifications of low-densitylipoproteins, such as an increased percentage of small, dense LDLparticles with higher electronegative charge. These modifications disturbingphysicochemical and biological characteristics of LDL particlesand are involved in the common mechanisms by which dyslipidemiaand hyperglycemia promote increased atherosclerosis indiabetic patients(AU)

The inflammatory properties of electronegative low-density lipoprotein from type 1 diabetic patients are related to increased platelet-activating factor acetylhydrolase activity.

AIMS/HYPOTHESIS: Chemical and biological characteristics of LDL(-) from type 1 diabetic subjects were analysed. The diabetic patients were studied during poor and optimised glycaemic control. MATERIALS AND METHODS: Total LDL was subfractionated into electropositive LDL(+) and electronegative LDL(-) by anion exchange chromatography and the lipid and protein composition of the two determined. RESULTS: LDL(-) differed from LDL(+) in that it had higher triglyceride, non-esterified fatty acids, apoE, apoC-III and platelet-activating factor acetylhydrolase (PAF-AH), as well as lower apoB relative content. No evidence of increased oxidation was observed in LDL(-). LDL(-) increased two-fold the release of interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) in endothelial cells, suggesting an inflammatory role. Optimisation of glycaemic control after insulin therapy decreased the proportion of LDL(-), but did not modify the composition of LDL subfractions, except for a decrease in PAF-AH activity in LDL(-). The possibility that LDL(-) could be generated by non-enzymatic glycosylation was studied. Fructosamine and glycated LDL content in LDL subfractions from type 1 diabetic patients was greater than in LDL subfractions isolated from normoglycaemic subjects, and decreased after glycaemic optimisation in both subfractions. However, no difference was observed between LDL(+) and LDL(-) before and after insulin therapy. CONCLUSIONS/INTERPRETATION: These results provide evidence that LDL(-) is not produced by glycosylation. Nevertheless, LDL(-) from diabetic patients displays inflammatory potential reflected by the induction of chemokine release in endothelial cells. This proatherogenic effect could be related to the high PAF-AH activity in LDL(-).

Response of oxidative stress biomarkers to a 16-week aerobic physical activity program, and to acute physical activity, in healthy young men and women.

Physical activity (PA) is associated with a reduced risk of coronary heart disease, and may favorably modify the antioxidant-prooxidant balance. This study assessed the effects of aerobic PA training on antioxidant enzyme activity, oxidized LDL concentration, and LDL resistance to oxidation, as well as the effect of acute PA on antioxidant enzyme activity before and after the training period. Seventeen sedentary healthy young men and women were recruited for 16 weeks of training. The activity of superoxide dismutase in erythrocytes (E-SOD), glutathione peroxidase in whole blood (GSH-Px), and glutathione reductase in plasma (P-GR), and the oxidized LDL concentration and LDL composition, diameter, and resistance to oxidation were determined before and after training. Shortly before and after this training period they also performed a bout of aerobic PA for 30 min. The antioxidant enzyme activity was also determined at 0 min, 30 min, 60 min, 120 min, and 24 h after both bouts of PA. Training induces an increase in GSH-Px (27.7%), P-GR (17.6%), and LDL resistance to oxidation, and a decrease in oxidized LDL (-15.9%). After the bout of PA, an increase in E-SOD and GSH-Px was observed at 0 min, with a posterior decrease in enzyme activity until 30-60 min, and a tendency to recover the basal values at 120 min and 24 h. Training did not modify this global response pattern. Regular PA increases endogenous antioxidant activity and LDL resistance to oxidation, and decreases oxidized LDL concentration; 30 min of aerobic PA decreases P-GR and B-GSH-Px activity in the first 30-60 min with a posterior recovery.

Apo(B)-dependent dyslipidemic phenotypes in type 1 diabetic patients.

BACKGROUND: The prevalence of apo(B)-dependent dyslipidemic phenotypes, which are associated with cardiovascular disease, is increased in normocholesterolemic type 2 diabetic patients. Our aim was to determine the impact of including apo(B) in the evaluation of normocholesterolemic type 1 diabetic patients. METHODS: A total of 123 type 1 diabetic patients (47% male, age 36.6+/-12.5 years) were included. The apo(B) cut-off point (1.14 g/l) was obtained from a group of 53 normolipidemic control subjects of similar age and gender distribution; for low density lipoprotein cholesterol (LDLc), triglycerides, and high density lipoprotein cholesterol (HDLc), we used the cut-off points recommended by the National Cholesterol Education Program. LDLc was determined by ultracentrifugation or Friedewald's equation, depending on triglyceride concentrations, and apo(B) by immunoturbidimetry. RESULTS: A total of 113 (92%) type 1 diabetic patients were normocholesterolemic, and 13% of these were dyslipidemic. The frequency of hyperapo(B) was similar in normocholesterolemic patients and controls (6.2 vs. 9.4%, respectively). Diabetic patients with hyperapo(B) had poorer glycemic control, higher total cholesterol, triglycerides, and LDLc, and a lower HDLc and LDLc/apo(B) ratio. CONCLUSIONS: Unlike type 2 diabetes, type 1 diabetes is not associated with an increased prevalence of hyperapo(B)-dependent dyslipidemic phenotypes. Thus, only in patients with poor glycemic control who display other components of diabetic dyslipidemia, typical for type 2 diabetes, does determining apo(B) concentrations provide additional information in type 1 diabetes.

Effect of glycemic optimization on electronegative low-density lipoprotein in diabetes: relation to nonenzymatic glycosylation and oxidative modification.

The effect of insulin therapy on low-density lipoprotein (LDL) oxidizability, proportion of electronegative LDL [LDL(-)] and LDL composition was studied in 33 type 2 diabetic patients. Before glycemic control improvement, type 2 diabetic subjects presented higher triglyceride and very low-density lipoprotein cholesterol and lower high-density lipoprotein cholesterol than 25 healthy matched subjects. Furthermore, their LDL was more susceptible to oxidation (lag phase 45.9 +/- 5.4 min vs. 49.7 +/- 7.6 min, P < 0.05), contained a higher proportion of LDL(-) (19.0 +/- 8.7% vs. 14.3 +/- 5.5%, P < 0.05), and was enriched in triglyceride and depleted in cholesterol and phopholipids. Lipoprotein profile improved after glycemic optimization but failed to change either LDL oxidizability (45.3 +/- 6.2 min) or LDL(-) (17.9 +/- 8.2%). These data suggest that oxidation rather than nonenzymatic glycosylation could be related to the high LDL(-) found in these patients and disagree with results obtained in a previous study of type 1 diabetic patients. A second study was conducted in 10 type 1 and 10 type 2 diabetic subjects under insulin therapy, and the proportions of glycated LDL (gLDL) and LDL(-) were determined. Basal gLDL (2.8 +/- 0.6%) and LDL(-) (20.7 +/- 6.1%) decreased in type 1 diabetics after glycemic optimization (1.9 +/- 0.6% and 15.4 +/- 3.4%, respectively; P < 0.05). In type 2 patients, even though gLDL decreased (from 2.2 +/- 0.6% to 1.6 +/- 0.6%, P < 0.05) no effect was observed on LDL(-) (from 17.3 +/- 2.9% to 16.0 +/- 4.3%). We conclude that nonenzymatic glycosylation, which appears as a determinant of the high proportion of LDL(-) in type 1 diabetes, does not play a major role in LDL(-) generation in type 2 diabetes.

Hiperprolactinemia por macroprolactina y disfunción eréctil / Hyperprolactinemia due to macroprolactin and erectile dysfunction

Se describe el caso de un varón de 61 años asistido por disfunción eréctil asociada a hiperprolactinemia. Las imágenes hipofisarias obtenidas por RMN y TAC fueron normales, y los tratamientos llevados a cabo con agonistas dopaminérgicos no mejoraron la función eréctil, aunque normalizaron las concentraciones de prolactina. A pesar de la persistencia de hiperprolactinemia, el paciente recuperó espontáneamente su función eréctil al resolverse de manera favorable sus problemas de relación con su pareja sexual. La causa de la hiperprolactinemia se encontró posteriormente al demostrar, mediante cromatografía de filtración en gel, que la forma mayoritaria de prolactina en el suero del enfermo (62-66 por ciento) correspondía a macroprolactina, especie molecular desprovista de actividad biológica in vivo. Este hallazgo condujo al diagnóstico final de disfunción eréctil psicógena. La macroprolactinemia confundió y retrasó el diagnóstico correcto, promovió la realización de exploraciones costosas e indujo tratamientos innecesarios. Casos como éste apoyan la utilidad del escrutinio de macroprolactinemia entre los pacientes con hiperprolactinemia, sobre todo en aquellos cuyos datos bioquímicos no se corresponden claramente con los clínicos (AU)

Prevalence and phenotypic distribution of dyslipidemia in type 1 diabetes mellitus: effect of glycemic control.

BACKGROUND: Data on the prevalence of dyslipidemia in type 1 diabetes mellitus are scarce and are based on total triglyceride and total cholesterol concentrations alone. OBJECTIVE: To assess the effect of glycemic optimization on the prevalence of dyslipidemia and low-density lipoprotein cholesterol (LDL-C) concentrations requiring intervention in patients with type 1 diabetes. PATIENTS: A total of 334 adults with type 1 diabetes and 803 nondiabetic control subjects. METHODS: Levels of glycosylated hemoglobin, total cholesterol, total triglyceride, high-density lipoprotein cholesterol (HDL-C), and LDL-C were assessed at baseline and after 3 to 6 months of intensive therapy with multiple insulin doses. RESULTS: Levels of LDL-C greater than 4.13 mmol/L (>160 mg/dL) and total triglyceride greater than 2.25 mmol/L (>200 mg/dL) and low HDL-C levels (<0.9 mmol/L [<35 mg/dL] in men or <1.1 mmol/L [<45 mg/dL] in women) were found in 16%, 5%, and 20% of patients and 13%, 6%, and 9% of controls, respectively (P<.001 for HDL-C). Diabetic women showed more hypercholesterolemia than nondiabetic women (15.6% vs 8.5%; P =.04). After glycemic optimization (mean +/- SD glycosylated hemoglobin decrease, 2.2 +/- 1.96 percentage points), the prevalence of LDL-C levels greater than 4.13 mmol/L (>160 mg/dL) became lower in diabetic men than in nondiabetic men (9.7% vs 17.5%; P =.04), but women showed frequencies of dyslipidemia similar to their nondiabetic counterparts. The proportion of patients with LDL-C concentrations requiring lifestyle (>2.6 mmol/L [>100 mg/dL]) or drug (>3.4 mmol/L [>130 mg/dL]) intervention decreased from 78% and 42% to 66% and 26%, respectively. CONCLUSIONS: Low HDL-C is the most frequent dyslipidemic disorder in patients with poorly controlled insulin-treated type 1 diabetes, and a high proportion show LDL-C levels requiring intervention. Less favorable lipid profiles could explain the absence of sex protection in diabetic women. The improvement caused by glycemic optimization puts forward intensive therapy as the initial treatment of choice for dyslipidemia in poorly controlled type 1 diabetes.

Electronegative LDL from normolipemic subjects induces IL-8 and monocyte chemotactic protein secretion by human endothelial cells.

The presence in plasma of an electronegative LDL subfraction [LDL(-)] cytotoxic for endothelial cells (ECs) has been reported. We studied the effect of LDL(-) on the release by ECs of molecules implicated in leukocyte recruitment [interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1)] and in the plasminogen activator inhibitor-1 (PAI-1). LDL(-), isolated by anion-exchange chromatography, differed from nonelectronegative LDL [LDL(+)] in its higher triglyceride, nonesterified fatty acid, apoprotein E and apoprotein C-III, and sialic acid contents. No evidence of extensive oxidation was found in LDL(-); its antioxidant and thiobarbituric acid-reactive substances contents were similar to those of LDL(+). However, conjugated dienes were increased in LDL(-), which suggests that mild oxidation might affect these particles. LDL(-) increased, in a concentration-dependent manner, the release of IL-8 and MCP-1 by ECs and was a stronger inductor of both chemokines than oxidized LDL (oxLDL) or LDL(+). PAI-1 release increased slightly in ECs incubated with both LDL(-) and oxLDL but not with LDL(+). However, no cytotoxic effects of LDL(-) were observed on ECs. Actinomycin D inhibited the release of IL-8 and MCP-1 induced by LDL(-) and oxLDL by up to 80%, indicating that their production is mediated by protein synthesis. Incubation of ECs with N:-acetyl cysteine inhibited production of IL-8 and MCP-1 induced by LDL(-) and oxLDL by >50%. The free radical scavenger butylated hydroxytoluene slightly inhibited the effect of oxLDL but did not modify the effect of LDL(-). An antagonist (BN-50730) of the platelet-activating factor receptor inhibited production of both chemokines by LDL(-) and oxLDL in a concentration-dependent manner. Our results indicate that LDL(-) shows proinflammatory activity on ECs and may contribute to early atherosclerotic events.

Molecular requirements in the recognition of low-density lipoproteins (LDL) by specific platelet membrane receptors.

We have demonstrated that platelet low-density lipoprotein (LDL) receptors differ from classic LDL receptors of nucleated cells. Although positively charged Arg and Lys residues of apoprotein B-100 are known to play a key role in LDL recognition by classic LDL receptors, there are no conclusive data on platelet LDL receptors. This study investigated the molecular requirements of LDL particle recognition by platelet LDL receptors. The involvement of lipid and protein fractions was determined by displacement studies of the binding of 125I-LDL to platelets and fibroblasts (used as a classical LDL receptor model). The role of the protein moiety was evaluated by chemically modifying positively charged apoB residues (Lys, Arg, and Tyr) via copper-induced oxidation, cyclohexanedione, and tetranitromethane, respectively. The involvement of the lipid fraction was determined by ligand binding assays using 125I-LDL particles that had previously been delipidated and subjected to apoB solubilization. The degree of particle modification was analyzed by agarose/acrylamide gel electrophoresis and anion exchange chromatography. Modifying the amino acid residues increased particle electronegativity in the following order of potency: CHD-LDL>TNM-LDL>ox-LDL>native LDL. The results obtained by displacement studies in fibroblasts suggested that the gain in the LDL negative charge was the most important factor in the loss of receptor affinity. The chemical models of protein modification used in our study greatly affected LDL binding to the classical fibroblast receptor. In contrast, there was very slight difference in the displacement capacity on platelet 125I-LDL binding, which suggests that the protein fraction does not play a major role in the interaction of LDL with its platelet receptor. On the other hand, whereas modifying the lipid moiety did not alter the ability of solubilized 125I-apoB to interact with the classical fibroblast LDL receptor, platelet LDL receptors were unable to recognize these particles. In conclusion, our results confirm that the protein fraction plays a key role in the fibroblast LDL-receptor recognition process, whereas the lipid fraction appears to have a more relevant role in platelet LDL-receptor recognition.

Effect of physical exercise on lipoprotein(a) and low-density lipoprotein modifications in type 1 and type 2 diabetic patients.

To evaluate the effect of physical exercise on blood pressure, the lipid profile, lipoprotein(a) (Lp(a)), and low-density lipoprotein (LDL) modifications in untrained diabetics, 27 diabetic patients (14 type 1 and 13 type 2) under acceptable and stable glycemic control were studied before and after a supervised 3-month physical exercise program. Anthropometric parameters, insulin requirements, blood pressure, the lipid profile, Lp(a), LDL composition, size, and susceptibility to oxidation, and the proportion of electronegative LDL (LDL(-)) were measured. After 3 months of physical exercise, physical fitness improved (maximal O2 consumption [VO2max], 29.6 +/- 6.8 v 33.0 +/- 8.4 mL/kg/min, P < .01). The body mass index (BMI) did not change, but the waist circumference (83.2 +/- 11.8 to 81.4 +/- 11.2 cm, P < .05) decreased significantly. An increase in the subscapular to triceps skinfold ratio (0.91 +/- 0.37 v 1.12 +/- 0.47 cm, P < .01) and midarm muscle circumference ([MMC], 23.1 +/- 3.4 v 24.4 +/- 3.7 cm, P < .001) were observed after exercise. Insulin requirements (0.40 +/- 0.18 v 0.31 +/- 0.19 U/kg/d, P < .05) and diastolic blood pressure (80.2 +/- 10 v 73.8 +/- 5 mm Hg, P < .01) decreased in type 2 diabetic patients. High-density lipoprotein cholesterol (HDL-C) increased in type 1 patients (1.48 +/- 0.45 v1.66 +/- 0.6 mmol/L, P < .05), while LDL cholesterol (LDL-C) decreased in type 2 patients (3.6 +/- 1.0 v3.4 +/- 0.9 mmol/L, P < .01). Although Lp(a) levels did not vary in the whole group, a significant decrease was noted in patients with baseline Lp(a) above 300 mg/L (mean decrease, -13%). A relationship between baseline Lp(a) and the change in Lp(a) (r = -.718, P < .0001) was also observed. After the exercise program, 3 of 4 patients with LDL phenotype B changed to LDL phenotype A, and the proportion of LDL(-) tended to decrease (16.5% +/- 7.4% v 14.0% +/- 5.1%, P = .06). No changes were observed for LDL composition or susceptibility to oxidation. In addition to its known beneficial effects on the classic cardiovascular risk factors, regular physical exercise may reduce the risk of cardiovascular disease in diabetic patients by reducing Lp(a) levels in those with elevated Lp(a) and producing favorable qualitative LDL modifications.

Effect of simvastatin treatment on the electronegative low-density lipoprotein present in patients with heterozygous familial hypercholesterolemia.

Most described modifications of low-density lipoprotein (LDL) cholesterol share an increase in its negative electric charge; in fact, an electronegative form of LDL can be identified and isolated from plasma. Although the exact nature of the chemical modification of electronegative LDL is still controversial, its toxicity on endothelial cells has been demonstrated. Statins have protective effects against cardiovascular disease that are independent of their lipid-lowering action and which could be due, at least in part, to the prevention of LDL modification. We evaluated the effect of 6 months of simvastatin therapy (40 mg/day) on electronegative LDL proportion and LDL susceptibility to in vitro induced oxidation in 21 patients with heterozygous familial hypercholesterolemia (FH). Eleven normolipemic subjects were analyzed as a control group. Total cholesterol as well as LDL and very low density lipoprotein cholesterol, triglycerides, and apoprotein B decreased 30% after the first month of therapy, with no further decreases thereafter. LDL susceptibility to oxidation was similar in FH patients and controls and did not change throughout the treatment. Electronegative LDL proportion was 35.1 +/- 9.9% in FH patients and 9.1 +/- 2.4% in control subjects (p <0.0001) but, in contrast to total LDL cholesterol and the rest of lipid parameters, it decreased to 28.6 +/- 9.1% in the third month and to 21.2 +/- 7.7% in the sixth month of therapy. The decrease in these cytotoxic particles may be a relevant mechanism by which simvastatin protects against cardiovascular disease.

Ascorbic acid inhibits the increase in low-density lipoprotein (LDL) susceptibility to oxidation and the proportion of electronegative LDL induced by intense aerobic exercise.

BACKGROUND: We have previously reported the finding of an acute increment in the susceptibility of low-density lipoprotein (LDL) to oxidation and in the proportion of electronegative LDL [LDL(-)] after intense exercise. We have now studied the effect of oral supplementation with 1 g ascorbic acid, immediately before a 4-h athletic race, on the susceptibility of LDL to oxidation, the proportion of LDL(-), and the alpha-tocopherol and lipid peroxides content in LDL, in order to inhibit such deleterious changes, and to confirm the oxidative nature of modifications of LDL induced by exercise. METHODS: We studied seven highly trained runners who received a supplement of 1 g ascorbic acid and a control group of seven who did not receive the supplement. The susceptibility of LDL to oxidation was assessed by measurement of conjugated dienes after CuSO4-induced oxidation, the proportion of LDL(-) was determined by anion exchange chromatography, alpha-tocopherol was quantified by reverse-phase high performance liquid chromatography, and lipid peroxides were measured by the thiobarbituric acid-reactive substances (TBARS) method. RESULTS: After exercise, in the control group there was an increase in both the susceptibility of LDL to oxidation (change in lag phase from 51.4 +/- 4.7 min to 47.0 +/- 4.6 min, P < 0.05) and the proportion of LDL(-) (from 11.1 +/- 1.4% to 13.0 +/- 2.2%, P < 0.05), but these did not occur in the ascorbic acid group (change in lag phase from 49.7 +/- 2.3 min to 50.4 +/- 4.2 min, and in LDL(-) from 9.7 +/- 1.7% to 10.1 +/- 1.7%). No significant changes in the absolute amount of LDL alpha-tocopherol were observed after exercise (ascorbic acid group: 6.65 +/- 0.94 mol/mol apoB before the race, 7.13 +/- 0.88 mol/mol apoB after the race; control group: 7.34 +/-0.69 mol/mol apoB before the race, 7.06 +/- 0.69 mol/mol apoB after the race), but significant differences were found when increments or decrements of alpha-tocopherol were tested (alpha-tocopherol increased 9.9 +/- 11.5% in the ascorbic acid group, and decreased 0.6 +/- 7.3% in the control group; P < 0.018). TBARS did not change after exercise. CONCLUSIONS: We conclude that 1 g ascorbic acid inhibits the increase in LDL susceptibility to oxidation after exercise, preventing this acute pro-atherogenic effect. In addition, the observation that LDL(-) enhancement is prevented by ascorbic acid supports the hypothesis that at least some of the circulating LDL(-) originates from oxidative processes.

LDL from aerobically-trained subjects shows higher resistance to oxidative modification than LDL from sedentary subjects.

We studied the effect of regular intense aerobic exercise on the LDL susceptibility to oxidation and the electronegative LDL-proportion (LDL(-)). A group of 38 well-trained athletes was compared to a group of 38 age-BMI-matched sedentary individuals. Athletes showed higher concentration of total cholesterol (athletes 5.08 +/- 0.70 versus controls 4.65 +/- 0.75 mmol/l, P = 0.0229) and HDL cholesterol (athletes 1.72 +/- 0.47 versus controls 1.46 +/- 0.39 mmol/l, P = 0.0068); total plasma triglyceride, LDL cholesterol and VLDL cholesterol did not differ between trained and untrained subjects. The susceptibility of LDL to oxidation, determined by conjugated dienes formation and expressed as lag phase, was lower in athletes than in sedentaries (trained subjects 47.0 +/- 5.6 versus sedentary subjects 41.9 +/- 5.0 min, P = 0.0002). LDL(-) was similar in both groups (athletes 10.32 +/- 4.70 versus controls 10.26 +/- 3.71%). The antioxidant content in total plasma and isolated LDL (alpha-tocopherol, retinol, lycopene, alpha-carotene and beta-carotene) was quantitated by HPLC in a subgroup of 32 athletes and 32 control subjects. Athletes showed higher amounts of alpha-tocopherol and retinol in plasma, but not in LDL. However, none of these antioxidants correlated with the lag phase time. Trained subjects showed lower prevalence of smoking. However, no differences were observed between smokers and non-smokers concerning lag phase. No significant difference between athletes and sedentaries concerning LDL density, or composition was observed. We conclude that LDL from trained subjects is more resistant to oxidative modification than LDL from sedentary subjects. This observation could not be attributed to conventional antioxidants as alpha-tocopherol and carotene content of LDL was unchanged in trained subjects. Thus, although none of the variables studied appear as a single predictor of the LDL susceptibility to oxidation, an additive effect of the antioxidant content, the presence of some undetermined co-antioxidant, HDL and/or smoking habits cannot be discarded as responsible for the increased resistance to oxidation of LDL in trained subjects.

Susceptibility of plasma low- and high-density lipoproteins to oxidation in patients with severe hyperhomocysteinemia.

A moderate increase in plasma homocysteine is increasingly considered an important risk factor of atherosclerosis and thrombosis. However, the mechanisms by which hyperhomocysteinemia induces vascular disease are not well defined. In vitro studies suggest that cysteine and homocysteine can induce oxidative modification of low-density lipoproteins (LDL). This suggestion is relevant because lipoprotein oxidation is thought to play a key role in the development of atherosclerosis and in the triggering of thrombotic events. An attractive model to study this topic is provided by patients with classical homocystinuria, an inherited disease characterized by severe hyperhomocysteinemia and a high incidence of thromboembolisms. We investigated the existence of oxidized LDL and the susceptibility to oxidation of the plasma cholesterol-rich lipoproteins in six patients with severe hyperhomocysteinemia, most likely due to classical homocystinuria, and compared the results with matched controls. The proportion of electronegative LDL and the concentration of thiobarbituric acid reactive substances in native LDL and high-density lipoproteins (HDL) did not differ between patients and controls, suggesting that the proportion of modified lipoproteins is not increased in patients with severe hyperhomocysteinemia. The susceptibility to oxidative modification of plasma LDL and HDL was also similar in the two groups, although the patients had homocysteine levels 18.3-fold higher than controls. Thus, increased oxidative modification is not likely to be a relevant mechanism in explaining their high incidence of vascular disease. A possible explanation for the lack of increased susceptibility to oxidation, as would be expected for the metabolic blockade that cause classical homocystinuria, is the 4.1-fold decrease in the concentration of cysteine in the plasma of patients. As a result the total concentration of homocysteine plus cysteine was slightly lower in patients than in controls. This interpretation implies that more studies are needed on lipoprotein susceptibility to oxidation in patients in which both plasma homocysteine and cysteine concentrations are increased. This metabolic situation may be frequent in the population with moderate hyperhomocysteinemia and vascular disease.

Electronegative low density lipoprotein subform is increased in patients with short-duration IDDM and is closely related to glycaemic control.

We evaluated the effect of improving glycaemic control with intensive insulin therapy on LDL susceptibility to oxidation, electronegative LDL proportion, and LDL subfraction phenotype in a group of 25 patients with short-duration insulin-dependent diabetes mellitus (IDDM); 25 matched healthy control subjects were also studied. LDL susceptibility to oxidation was measured by continuous monitoring of conjugated diene formation. Electronegative LDL was isolated by anion exchange chromatography, and quantified as percentage of total LDL. Six LDL subfractions were isolated by density gradient ultracentrifugation and phenotype A or B classified as the quotient (LDL1-LDL3)/(LDL4-LDL6). Compared to the control group, IDDM subjects with poor glycaemic control showed higher electronegative LDL (19.03 +/- 10.09 vs 9.59 +/- 2.98%, p < 0.001), similar LDL subfraction phenotype and lower susceptibility to oxidation (lag phase 45.6 +/- 8.8 vs 41.2 +/- 4.7 min, p < 0.05). After three months of intensive insulin therapy, HbA1c decreased from 10.88 +/- 2.43 to 5.69 +/- 1.54% (p < 0.001), and electronegative LDL to 13.84 +/- 5.15% (p < 0.05). No changes in LDL susceptibility to oxidation or LDL subfraction phenotype were observed. Electronegative LDL appeared significantly correlated to HbA1c and fructosamine (p < 0.01 and p < 0.001) only in poorly controlled IDDM patients. These findings suggest that high electronegative LDL in IDDM subjects is related to the degree of glycaemic control, and could therefore be due to LDL glycation rather than to LDL oxidation or changes in LDL subfraction phenotype.