dinoprost and Hyperhomocysteinemia

An elevated plasma total homocysteine level (tHcy) is considered an independent risk factor for atherosclerosis. The mechanisms by which hyperhomocysteinemia induces atherosclerosis are only partially understood, but promotion of LDL oxidation and endothelial injury have been suggested. The purpose of this study was to test the hypothesis that a high plasma tHcy is associated in men with increased in vivo lipid peroxidation, as measured by plasma F2-isoprostane concentrations. We investigated this association in a subset of the participants in the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study. Of 256 male participants, a subsample of 100 consecutive men was selected for F2-isoprostane assays. The mean tHcy was 11.0 micromol/L, and the mean F2-isoprostanes was 29.6 ng/L. The simple correlation coefficient for association between tHcy and F2-isoprostane was 0.40 (P<0.001). In a linear regression model, the variables with the strongest associations with F2-isoprostane were tHcy (standardized coefficient 0.33, P<0.001), serum triglycerides (0.21, P=0.042), carbohydrate-deficient transferrin (0.15, P=0.132), and plasma lipid-standardized alpha-tocopherol (-0.11, P=0.252) (R2=0.24, P<0. 001 for model). Plasma F2-isoprostane levels increased linearly across quintiles of tHcy (P<0.001). The unadjusted mean (95% confidence interval) F2-isoprostanes was 47.5% greater in the highest tHcy quintile (37.4, 31.1 to 43.6 ng/L) than in the lowest quintile (25.3, 21.3 to 29.3 ng/L). Adjustment for the strongest other determinants of F2-isoprostane reduced this difference to 28. 2% (P=0.010). Our present data suggest that elevated fasting plasma tHcy is associated with enhanced in vivo lipid peroxidation in men.

Topics: Arteriosclerosis; Ascorbic Acid; beta Carotene; Dinoprost; Double-Blind Method; Fasting; Humans; Hyperhomocysteinemia; Linear Models; Lipid Peroxidation; Male; Middle Aged; Risk Factors; Transferrin; Triglycerides; Vitamin E

Topics: Aged; Antioxidants; Biomarkers; Catalase; Dinoprost; Female; Glutathione Peroxidase; Homocysteine; Humans; Hyperhomocysteinemia; Hypertension; Male; Malondialdehyde; Middle Aged; Nitric Oxide; Oxidative Stress; Peroxides; Risk Factors; Superoxide Dismutase

The methylenetetrahydrofolate reductase (MTHFR) 677 C→T polymorphism may be associated with elevated total homocysteine (tHcy) levels, an independent risk factor for cardiovascular disease. It was the study objective to evaluate in vivo lipid peroxidation and platelet activation in carriers of the MTHFR 677 C→T polymorphism and in non-carriers, in relation to tHcy and folate levels. A cross-sectional comparison of urinary 8-iso-prostaglandin (PG)F(2α) and 11-dehydro-thromboxane (TX)B(2) (markers of in vivo lipid peroxidation and platelet activation, respectively) was performed in 100 carriers and 100 non-carriers of the polymorphism. A methionine-loading test and folic acid supplementation were performed to investigate the causal relationship of the observed associations. Urinary 8-iso-PGF(2α) and 11-dehydro-TXB(2) were higher in carriers with hyperhomocysteinaemia than in those without hyperhomocysteinaemia (p<0.0001). Hyperhomocysteinaemic carriers had lower folate levels (p=0.0006), higher urinary 8-iso-PGF(2α) (p<0.0001) and 11-dehydro-TXB(2) (p<0.0001) than hyperhomocysteinaemic non-carriers. On multiple regression analysis, high tHcy (p<0.0001), low folate (p<0.04) and MTHFR 677 C→T polymorphism (p<0.001) independently predicted high rates of 8-iso-PGF(2α) excretion. Methionine loading increased plasma tHcy (p=0.002), and both urinary prostanoid metabolites (p=0.002). Folic acid supplementation was associated with decreased urinary 8-iso-PGF(2α) and 11-dehydro-TXB2 excretion (p<0.0003) in the hyperhomocysteinaemic group, but not in the control group, with substantial inter-individual variability related to baseline tHcy level and the extent of its reduction. In conclusion, hyperhomocysteinaemia due to the MTHFR 677 C→T polymorphism is associated with enhanced in vivo lipid peroxidation and platelet activation that are reversible, at least in part, following folic acid supplementation. An integrated biomarker approach may help identifying appropriate candidates for effective folate supplementation.

Topics: Biomarkers; Cardiovascular Diseases; Comorbidity; Cross-Sectional Studies; Diabetes Mellitus; Dinoprost; Dyslipidemias; Folic Acid; Homocystinuria; Humans; Hyperhomocysteinemia; Lipid Peroxidation; Methionine; Methylenetetrahydrofolate Reductase (NADPH2); Muscle Spasticity; Oxidative Stress; Platelet Activation; Polymorphism, Single Nucleotide; Psychotic Disorders; Smoking; Thromboxane B2

Methionine ingestion (100mg/kg) identifies subjects in whom fasting total homocysteine (tHcy) may be normal but the post-methionine load (PML) tHcy is abnormally high.. In 96 subjects [54 M/42 F, 40.4 ± 12.3 yrs old; 28 with the 68 bp844 ins of the cystathionine-β-synthase gene (CBSins+); 20 homozygotes for the C677T mutation of the methylene-tetrahydrofolate reductase gene (MTHFR++); 13 with the combination of the two, and 35 without any of them], we have evaluated in vivo oxidative stress and platelet activation, as reflected by urinary excretions of 8-iso-PGF(2α) and of 11-dehydro-TXB(2) respectively, before and after a methionine load test (PML). A history of early-onset thrombosis (18 arterial, 32 venous, 2 both) was present in 52/96 of them.. Baseline; tHcy was highest in MTHFR++ carriers (p < 0,05); 8-iso-PGF(2α) and 11-dehydro-TXB(2) levels were independent of sex, MTHFR++ and/or CBSins + (p > 0.05). PML; The ~3-fold increase (p < 0.01 vs baseline) in tHcy reached a plateau within 6-8 hrs. Mean PML tHcy was maximal in MTHFR++ carriers (p = 0.000). 8-iso-PGF(2α) and 11-dehydro-TXB(2) increase reached a maximum within 4 hrs. 11-dehydro-TXB(2) increase was highest (p = 0.023 vs baseline) in subjects with a history of thrombosis. Baseline 11-dehydro-TXB(2) and a history of thrombosis independently predicted PML 11-dehydro-TXB(2) (β = 0.287, p = 0.000 and β = 0.308, p = 0.026, respectively).The PML increase in 8-iso-PGF(2α) or in 11-dehydro-TXB(2) were comparable in the different genotypes (p > 0.05).. Regardless genotypes associated with moderate hyperhomocysteinemia, following a methionine loading test, in vivo oxidative stress and platelet activation occur, being the latter maximal in subjects with a history of early-onset thrombosis.

Topics: Adult; Age of Onset; Analysis of Variance; Biomarkers; Case-Control Studies; Chi-Square Distribution; Cystathionine beta-Synthase; Dinoprost; Female; Homocysteine; Homozygote; Humans; Hyperhomocysteinemia; Italy; Linear Models; Male; Methionine; Methylenetetrahydrofolate Reductase (NADPH2); Middle Aged; Mutation; Oxidative Stress; Phenotype; Platelet Activation; Platelet Function Tests; Thrombosis; Thromboxane B2; Time Factors

We aimed to test the hypothesis that an enhanced level of reactive oxygen species (ROS) is primarily responsible for the impairment of nitric oxide (NO)-mediated regulation of arteriolar wall shear stress (WSS) in hyperhomocysteinemia (HHcy). Thus flow/WSS-induced dilations of pressurized gracilis muscle arterioles (basal diameter: approximately 170 microm) isolated from control (serum Hcy: 6 +/- 1 microM), methionine diet-induced HHcy rats (4 wk, serum Hcy: 30 +/- 6 microM), and HHcy rats treated with vitamin C, a known antioxidant (4 wk, 150 mg. kg body wt-1.day-1; serum Hcy: 32 +/- 10 microM), were investigated. In vessels of HHcy rats, increases in intraluminal flow/WSS-induced dilations were converted to constrictions. Constrictions were unaffected by inhibition of NO synthesis by N omega-nitro-L-arginine methyl ester (L-NAME). Vitamin C treatment of HHcy rats reversed the WSS-induced arteriolar constrictions to L-NAME-sensitive dilations but did not affect control responses. Similar changes in responses were obtained for the calcium ionophore A-23187. In addition, diastolic and mean arterial blood pressure and serum 8-isoprostane levels (a marker of in vivo oxidative stress) were significantly elevated in rats with HHcy, changes that were normalized by vitamin C treatment. Taken together, our data show that in chronic HHcy long-term vitamin C treatment, by decreasing oxidative stress in vivo, enhanced NO bioavailability, restored the regulation of shear stress in arterioles, and normalized systemic blood pressure. Thus our study provides evidence that oxidative stress is an important in vivo mechanism that is primarily responsible for the development of endothelial dysregulation of WSS in HHcy.

Topics: Animals; Antioxidants; Arterioles; Ascorbic Acid; Blood Pressure; Calcimycin; Dinoprost; F2-Isoprostanes; Hyperhomocysteinemia; Ionophores; Male; Muscle, Skeletal; Nitric Oxide Donors; Oxidative Stress; Penicillamine; Rats; Rats, Wistar; Signal Transduction; Stress, Mechanical; Vascular Resistance

Homocysteine is a risk factor for the development of atherosclerosis and its thrombotic complications. We have employed an animal model to explore the hypothesis that an increase in reactive oxygen species and a subsequent loss of nitric oxide bioactivity contribute to endothelial dysfunction in mild hyperhomocysteinemia. We examined endothelial function and in vivo oxidant burden in mice heterozygous for a deletion in the cystathionine beta-synthase (CBS) gene, by studying isolated, precontracted aortic rings and mesenteric arterioles in situ. CBS(-/+) mice demonstrated impaired acetylcholine-induced aortic relaxation and a paradoxical vasoconstriction of mesenteric microvessels in response to superfusion of methacholine and bradykinin. Cyclic GMP accumulation following acetylcholine treatment was also impaired in isolated aortic segments from CBS(-/+) mice, but aortic relaxation and mesenteric arteriolar dilation in response to sodium nitroprusside were similar to wild-type. Plasma levels of 8-epi-PGF(2alpha) (8-IP) were somewhat increased in CBS(-/+) mice, but liver levels of 8-IP and phospholipid hydroperoxides, another marker of oxidative stress, were normal. Aortic tissue from CBS(-/+) mice also demonstrated greater superoxide production and greater immunostaining for 3-nitrotyrosine, particularly on the endothelial surface. Importantly, endothelial dysfunction appears early in CBS(-/+) mice in the absence of structural arterial abnormalities. Hence, mild hyperhomocysteinemia due to reduced CBS expression impairs endothelium-dependent vasodilation, likely due to impaired nitric oxide bioactivity, and increased oxidative stress apparently contributes to inactivating nitric oxide in chronic, mild hyperhomocysteinemia.

Topics: Acetylcholine; Animals; Aorta; Arteriosclerosis; Cystathionine beta-Synthase; Dinoprost; Disease Models, Animal; Endothelium, Vascular; F2-Isoprostanes; Heterozygote; Humans; Hyperhomocysteinemia; In Vitro Techniques; Lipid Peroxides; Mice; Mice, Mutant Strains; Nitroprusside; Reactive Oxygen Species; Risk Factors; Thrombosis; Tyrosine; Vasodilation