Circulating small dense LDL, endothelial injuring factors and fibronectin in healthy postmenopausal women.

BACKGROUND: In postmenopausal women (PMW), an adverse lipoprotein pattern and high risk of coronary artery disease has been described. Studies of the mechanisms promoting the higher atherogenic risk observed in healthy PMW are relevant. We evaluated the interactions among several circulating factors involved in the endothelial injury and inflammation in relation to LDL characteristics, beyond LDL cholesterol. METHODS: Lipoprotein profile, including apolipoproteins A-I and B, small dense LDL, hepatic lipase, cholesterol transfer protein (CETP), LDL composition and oxidability were assessed in PMW (n=30) in comparison to premenopausal (PreMW, n=28). The following emerging factors were measured: homocysteine, phospholipase A2, ferritin, hs-CRP and fibronectin from extracellular vascular matrix. Insulin-resistance was evaluated by waist circumference, HOMA and TG/HDL cholesterol ratios. RESULTS: The risk index apo B/apo A-I was significantly increased in PMW (p<0.0001), PMW showed higher proportion of small dense LDL which correlated with the increase in hepatic lipase activity (p<0.005) and with insulin-resistance markers (p<0.05), but not with CETP. Phospholipase A2 (p<0.05), homocysteine (p<0.005), hs-CRP (p<0.005), fibronectin (p<0.05) and ferritin (p<0.0001) were increased in PMW. LDL oxidability positively correlated with waist (p<0.02), homocysteine (p<0.05), fibronectin (p<0.05), hs-CRP (p<0.04), phospholipase A2 (p<0.05), and small dense LDL (p<0.01). After adjusting by menopausal condition, age and waist, LDL oxidability remained associated with waist (beta: 0.35, p=0.047), homocysteine (beta: 0,36 p<0,038), fibronectin (beta: 0,41 p=0.05), and small dense LDL (beta: 0.36, p=0.027). CONCLUSIONS: Evaluation of classic and non-traditional circulating risk factors in hypoestrogenism reflected endothelial and subendothelial inflammation and subclinical atherogenic processes.

HDL oxidability and its protective effect against LDL oxidation in Type 2 diabetic patients.

Low density lipoprotein (LDL) oxidation is a crucial step in the atherosclerotic process. High density lipoprotein (HDL)-associated enzymes such as paraoxonase could exert a protective effect on LDL oxidation in the arterial wall, an effect which could be impaired in Type 2 diabetes mellitus (T2DM). We studied copper-induced oxidation in LDL and HDL isolated from 17 T2DM patients with fair glycaemic control and HDL-cholesterol within normal range and 17 healthy normolipidaemic control subjects. To evaluate the effect of HDL on LDL oxidation in diabetic and control subjects, we assessed copper-induced oxidation in HDL/LDL mixtures, with each lipoprotein isolated from the same subject. Relationships with HDL chemical composition, alpha-tocopherol content and serum paraoxonase activity were investigated. Oxidation was promoted by lipoprotein incubation with copper and then thiobarbituric acid reactive substances (TBARS), conjugated diene production and electrophoretic mobility in agarose gel were measured. In T2DM subjects HDL oxidation was higher than in controls. However, HDL from diabetics was as effective as control HDL to inhibit LDL oxidation. Neither HDL chemical composition nor serum paraoxonase activity showed any difference as compared to control subjects. In contrast, HDL from T2DM subjects showed a higher alpha-tocopherol content which positively correlated with HDL oxidability. Paraoxonase activity positively and strongly correlated with HDL inhibitory effect on LDL oxidation in patients and controls belonging to the heterozygous activity phenotype. Besides, LDL oxidability showed no differences between patients and controls. These results suggest that fairly-controlled T2DM patients with HDL-cholesterol levels within normal range show: 1) normal HDL ability to inhibit LDL oxidation related to normal paraoxonase activity; 2) higher HDL oxidability in spite of its high alpha-tocopherol content, which could favour tocopherol-mediated peroxidation and 3) normal LDL oxidability possibly due to the lack of significant lipoprotein structural alterations.

Low-density lipoprotein composition and oxidability in atherosclerotic cardiovascular disease.

OBJECTIVES: To characterize low-density lipoprotein (LDL) chemical composition and oxidability in normolipidemic and dyslipidemic patients with atherosclerotic cardiovascular disease, as compared with matched control subjects. To evaluate LDL susceptibility to oxidation, we determined the cutoff points of thiobarbituric reactive substances (TBARS) in LDL after oxidative stress, as well as its resistance to oxidation. DESIGN AND METHODS: LDL (density 1.019-1.063 g/mL) of 24 men with atherosclerotic cardiovascular disease (12 normolipidemic and 12 dyslipidemic patients) and 18 age-matched healthy control men. LDL chemical composition was determined and apo B/cholesterol ratio was calculated. TBARS in native LDL and after 60 and 120 min of LDL oxidation with copper were measured. The conjugated diene production kinetics during LDL incubation with copper were also studied, lag time being an oxidation resistance marker. Cutoff points for the positivity criterion of apoB/cholesterol ratio in LDL and TBARS in native and oxidized LDL were evaluated using the receiver operator characteristic (ROC) graphic method. RESULTS: LDL were triglyceride-enriched, the apoB/cholesterol ratio being higher in patients than in controls, without differences between normolipidemic and dyslipidemic subgroups. We have established the following cutoff values to differentiate between patients and controls: 0.43 mg/mg for the apo B/cholesterol ratio in LDL; 3.0 nmol malondialdehyde/mg protein for TBARS in native LDL; 22 and 80 nmol malondialdehyde/mg protein after 60- and 120-min postoxidative stress, respectively. We did not find differences in the conjugated diene production kinetics between patients and controls. CONCLUSIONS: The enrichment in triglycerides and the high apoB/ cholesterol ratio suggest the presence of an abnormal LDL particle in normolipidemic and dyslipidemic patients. This LDL particle was more susceptible to oxidation. In the ROC analysis, the TBARS plot at 120 min exhibited greater accuracy and better performance than the other LDL oxidability markers.

Prostanoid production in hypoxic rat isolated atria: influence of acute diabetes.

The effects of hypoxia on prostanoid production were studied in atria from normal, acute diabetic and insulin-treated diabetic rats. Diabetes was induced by intravenous administration of 65 mg/kg of streptozotocin, the rats were killed 5 days later. Hypoxia was performed by incubation of the atria during 60 min in nitrogen-equilibrated glucose free Krebs' solution followed by 15 min of reoxygenation. The prostanoids 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) and thromboxane B2 (TXB2), stable metabolites of prostacyclin and TXA2, respectively, as well as PGF2, were measured by reversed phase HPLC-UV. In control atria, the production of 6-keto PGF1 alpha was equivalent to that of PGE2, whereas TXB2 was released in a much smaller amount. In diabetic atria, 6-keto PGF1 alpha production was reduced by 65%, whereas TXB2 release was increased by 158% compared to the controls. When the normal atria were exposed to 60 min of hypoxia, the release of 6-keto PGF1 alpha increased by 142% compared to basal values and remained elevated after 15 min of reoxygenation whereas in diabetic and insulin-treated diabetic tissues the 6-keto PGF1 alpha production was not modified by the hypoxia-reoxygenation period. The release of TXB2 was increased after 60 min hypoxia in normal as well as in diabetic and insulin-treated diabetic tissues and remained elevated during the reoxygenation. The PGE2 output increased only after the onset of the reoxygenation in the three groups studied.(ABSTRACT TRUNCATED AT 250 WORDS)