Homocysteine and occlusive arterial disease

Paroxysmal nocturnal hemoglobinuria: a red clot syndrome

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, nonmalignant disorder of hematopoietic stem cells characterized by hemolysis, diminished hematopoiesis, and thrombophilia. We describe a 65-year-old woman with known PNH and peripheral arterial disease who presented with critical limb ischemia and a nonhealing left foot ulcer. She underwent surgical bypass of a diffusely diseased left superficial femoral artery with autologous reversed saphenous vein graft. Her postoperative course was complicated by wound sepsis and PNH exacerbation with resultant graft thrombosis requiring an above-knee amputation. This case highlights several key concepts relevant to the management of vascular surgery patients with PNH: (1) their predisposition for arterial and venous thrombosis; (2) hypercoagulability despite standard anticoagulation regimens; (3) the role of eculizumab (a monoclonal antibody that inhibits complement activation used to treat PNH) in reducing thrombotic complications and hemolysis; and (4) complications associated with the immunosuppressive effects of eculizumab. We recommend careful monitoring of hemolysis and immunosuppression, aggressive anticoagulation, frequent graft surveillance, and early consultation with hematology.

Effect of celecoxib, a cyclooxygenase-2-specific inhibitor, on insulin sensitivity, C-reactive protein, homocysteine, and metabolic profile in overweight or obese subjects

BACKGROUND

The aim of this study was to assess the effect of celecoxib, a cyclooxygenase- 2-specific inhibitor, on insulin sensitivity, C-reactive protein, homocysteine, and metabolic profile in overweight or obese subjects.

METHODS

A randomized, double-blind, placebo-controlled clinical trial was carried out on 12 overweight or obese (body mass index, 25-35 kg/m(2)) male volunteers. Six subjects received celecoxib 200 mg orally in the morning for a period of 4 weeks. Six other individuals took a placebo for the same period of time, as the control group. Before and after the 4-week study period, insulin sensitivity, C-reactive protein, homocysteine levels, and metabolic profile were estimated. To assess insulin sensitivity, the euglycemic-hyperinsulinemic clamp technique was performed.

RESULTS

There were no significant differences in the basal measurements between both groups. C-reactive protein, homocysteine, and metabolic profile were not modified by the pharmacologic intervention with placebo or celecoxib. The insulin sensitivity after celecoxib was significantly higher compared with the basal estimation (3.8 +/- 1.2 vs. 2.8 +/- 1.2 mg/kg/min; p = 0.028). The placebo did not modify the insulin sensitivity.

CONCLUSIONS

The specific inhibition of the cyclooxygenase-2 by celecoxib increased the insulin sensitivity in overweight or obese subjects, without modification in C-reactive protein, homocysteine levels, and metabolic profile.

Relationship of impairment induced by intracellular S-adenosylhomocysteine accumulation with DNA methylation in human umbilical vein endothelial cells treated with 3-deazaadenosine

The aim of this study was to estimate the relationship of endothelial dysfunction induced by intracellular S-adenosylhomocysteine (SAH) accumulation and DNA methylation in human umbilical vein endothelial cells (HUVEC). The isolated HUVEC were incubated with 3-deazaadenosine (DZA) to induce experimental intracellular SAH accumulation. The impairment of HUVEC function was assessed by changes in morphology and proliferative ability. The expression of DNA methyltransferase-1 (DNMT1) and the atherosclerosis related genes [oestrogen receptor-alpha (ER-alpha), extracellular superoxide dismutase (EC-SOD) and monocyte chemoattractant protein-1 (MCP-1)] were analysed using quantitative real-time PCR. Global DNA methylated status was measured using the cytosine extension assay. The methylated patterns of ER-alpha, EC-SOD and MCP-1 genes were determined with methylation-specific PCR. We found that DZA administration increased intracellular SAH levels progressively and simultaneously decreased Hcy content in medium. Moreover, the supplementation induced HUVEC apoptosis, inhibited proliferation ability and DNMT1 mRNA expression (P < 0.05) and furthermore reduced global DNA methylation status (P < 0.05). Correlation analysis showed the presence of a negative correlation between intracellular SAH concentration, proliferative ability, and expression of ER-alpha, EC-SOD, and DNMT1 (r = -0.89, -0.86, -0.92 and -0.88 respectively, P < 0.001); and a positive correlation with MCP-1 expression and DNA [(3)H]-dCTP incorporation (r = 0.89 and 0.93 respectively, P < 0.001). Our results showed that endothelial dysfunction induced by intracellular SAH accumulation is mediated by regulating the expression of atherosclerosis related genes in HUVEC, which is not related with gene promoter methylated patterns, but may be associated with altered global DNA hypomethylated status. These findings suggest that SAH can act as the potential molecular biological marker in the promotion of atherogenesis.

A comparison of the effects of cheese and butter on serum lipids, haemostatic variables and homocysteine

Milk fat contains considerable amounts of saturated fatty acids, known to increase serum cholesterol. Little is known, however, about the relative effect of different milk products on risk factors for CHD. The aim of the present study was to compare the effects of Jarlsberg cheese (a Norwegian variety of Swiss cheese) with butter on serum lipoproteins, haemostatic variables and homocysteine. A controlled dietary study was performed with twenty-two test individuals (nine men and thirteen women) aged 23-54 years. The subjects consumed three isoenergetic test diets, with equal amounts of fat and protein, and containing either cheese (CH diet), butter + calcium caseinate (BC diet) or butter + egg-white protein (BE diet). The study was a randomised cross-over study and the subjects consumed each diet for 3 weeks, with 1 week when they consumed their habitual diet in between. Fasting blood samples were drawn at baseline and at the end of each period. Serum was analysed for lipids and plasma for haemostatic variables and homocysteine. Total cholesterol was significantly lower after the CH diet than after the BC diet (-0.27 mmol/l; P=0.03), while the difference in LDL-cholesterol was found to be below significance level (-0.22 mmol/l; P=0.06). There were no significant differences in HDL-cholesterol, triacylglycerols, apo A-I, apo B or lipoprotein (a), haemostatic variables and homocysteine between the diets. The results indicate that, at equal fat content, cheese may be less cholesterol increasing than butter.

Homocysteine Levels, Haemostatic Risk Factors and Restenosis after Carotid Thrombendarterectomy

OBJECTIVES

To investigate the effect of elevated serum homocysteine and haemostatic as well as clinical risk factors on the tendency to restenosis after carotid artery thrombendarterectomy.

DESIGN

A prospective, observational study.

PATIENTS AND METHODS

In the period from October 1999 to October 2002, 86 patients were subjected to 96 carotid endarterectomies because of internal carotid artery stenoses. The carotid stenoses were symptomatic in 86 cases (90%). Fasting plasma homocysteine, fibrinogen, D-dimer and activated protein C resistance were measured the day before surgery. Follow-up was done 1, 3, 6, 12 and 18 months postoperatively and yearly thereafter with clinical assessment and triplex ultrasonography. The median follow-up time was 17 months (range 9-42 months). Freedom from restenosis was estimated with Kaplan-Meier curves, using log-rank test for comparison between groups. Variables found to be significantly related to restenosis rates were included in a multivariate analysis performed with the Cox proportional hazards model. Comparison of means of continuous data between two groups was done with Student's t-test and more than two groups with one-way analysis of variance.

RESULTS

Restenoses within 12 months of the operation occurred in 11 cases (11%). Univariate analysis revealed that plasma homocysteine values < or =10 micromol/l and freedom from ischaemic heart disease were both significantly associated with an increased risk of restenosis (p=0.0076 and 0.0059). However, multivariate analysis showed that only plasma homocysteine values <10 micromol/l were independently and significantly associated with an increased risk of restenosis (p=0.046). There were no associations between the degree of atherosclerotic affection of the precerebral circulation or symptoms on one hand and the levels of homocysteine, fibrinogen, D-dimer and activated protein C resistance on the other.

CONCLUSION

There seems to be an independent, significant association between homocysteine values within the lower two thirds of the normal range and restenosis after carotid endarterectomy. Studies on the biological properties of human endothelial cells from different types of vasculature and different locations, specifically with respect to homocysteine metabolism and its effect, are warranted.

Prevalence and Risk of Thrombophilia Defects in Vascular Patients

This paper reviews the available data on the prevalence of thrombophilia defects in patients with peripheral vascular disease (PVD) and attempts to delineate the risk of failure of vascular intervention in these patients. The prevalence of thrombophilia in stable claudicants is 25% and increases to 40% in those requiring revascularisation, compared to only 11% in the control group. The overall prevalence of thrombophilia defects in patients with premature atherosclerosis appears to be between 15 and 30%. The prevalence in the typical cohort of patients with PVD appears to be similar. All these studies have recruited patients with symptoms significant enough to warrant intervention. The overall prevalence of thrombophilia calculated from these trials, therefore, may not be truly indicative of the general vascular population who may not even present primary or secondary healthcare. The risk of thrombotic occlusion following arterial revascularisation in patients with an identified thrombophilia defect appears to be almost three times that of patients with no evidence of a thrombophilia defect. The best management of these patients has not been determined and needs to be evaluated by prospective randomized trials.

Total plasma homocysteine and primary open-angle glaucoma

PURPOSE

To evaluate total plasma homocysteine (tHcy) levels in patients diagnosed with primary open-angle glaucoma (POAG) and normal subjects.

DESIGN

Case-control study.

METHODS

This study involved 55 POAG patients, 16 patients with secondary open-angle glaucoma or angle-closure glaucoma (non-POAG group), and 39 control healthy subjects undergoing ocular surgery. All glaucoma patients had characteristic glaucomatous optic disk damage and visual field loss. Fasting tHcy concentrations of all study participants were determined using high-performance liquid chromatography. Analysis of variance was used to compare homocysteine levels among the three diagnostic groups, and multivariate analysis was conducted to assess the associations between tHcy and diagnostic group, age, gender, smoking status, systemic hypertension, hyperlipidemia, and cardiovascular or cerebrovascular disease.

RESULTS

Mean +/- standard deviation of tHcy levels in POAG individuals, non-POAG patients and control subjects was 14.90 +/- 6.45 micromol/l, 14.30 +/- 4.35 micromol/l, and 14.81 +/- 4.56 micromol/l, respectively (P =.93; ANOVA). No statistically significant difference was found in the proportion of patients with abnormal tHcy levels among the three diagnostic groups. In multivariate analysis, only age and positive smoking status were significantly correlated with total plasma homocysteine levels.

CONCLUSION

No significant difference was found in plasma homocysteine levels among POAG patients and normal control individuals.