Effect of homocysteine on cytokine production by human endothelial cells and monocytes

Associations between dietary intake of B vitamins and cardiovascular risk factors in elderly men: A cross-sectional study

OBJECTIVE

Low intake of B vitamins can lead to hyperhomocysteinaemia, which is reported as a risk factor for cardiovascular disease (CVD). However, little is known about this relationship. Therefore, we decided to examine the association between dietary intake of B vitamins and cardiovascular risk factors in elderly men.

METHODS

The present cross-sectional study consisted of 357 elderly men. Dietary intake was assessed using a validated and reliable food frequency questionnaire. All biochemical factors [fasting blood sugar (FBS), triglyceride (TG), high-sensitivity C-reactive protein (hs-CRP), interleukin 6 (IL-6) and tumour necrosis factor-α (TNF-α)], waist circumference (WC) and blood pressure (BP) were assessed using standard methods.

RESULTS

A significant inverse association was observed between high dietary intake of total B vitamins (OR_{Total B vitamins} : 0.30; 95% CI: 0.10, 0.86; P = .01) and vitamin B9 (OR_{vitamin B9} : 0.20; 95% CI: 0.02, 0.52; P = .002) with high WC. Furthermore, an inverse association was observed between high dietary intake of vitamin B6 (OR_{vitamin B6} : 0.28; 95% CI: 0.08, 1.00; P = .05) and vitamin B9 (OR_{vitamin B9} : 0.20; 95% CI: 0.06, 0.70; P = .01) with hs-CRP level.

CONCLUSIONS

In elderly men, a high dietary intake of total B vitamins and vitamin B9 was associated with lower odds of having a high WC. Similarly, high dietary intake of vitamin B6 and B9 was associated with lower odds of having a high hs-CRP level.

Alteration of intrapancreatic serotonin, homocysteine, TNF-α, and NGF levels as predisposing factors for diabetes following exposure to 900-MHz waves

Exposure to mobile phone radiation causes deleterious health effects on biological systems. The objects of this study were to investigate the effect of 900-MHz radiofrequency waves (RFW) emitted from base transceiver station antenna on intrapancreatic homocysteine (Hcy), tumor necrosis factor-α (TNF-α), and nerve growth factor (NGF) as predisposing factors involved in pancreatic beta cell damage. Thirty male rats (Sprague-Dawley, 200 ± 10 g) were randomly divided into the control (without any exposure) and exposed groups: short time (2 h/day), long time (4 h/day), and exposed to 900-MHz RFW for 30 consecutive days. On the last days of the experiment, animals were killed and pancreas tissue was dissected out for evaluation of serotonin, Hcy, TNF-α, and NGF. There was a significant decrease in the serotonin and NGF levels in the pancreatic tissue of exposed groups compared to the control group (p < 0.05). Also, the levels of serotonin and NGF in the long-time exposure were significantly lower than the short-time exposure (p < 0.05). However, levels of Hcy and TNF-α were significantly increased in the pancreas of exposed groups compared to the control groups (p < 0.05). Exposure to 900-MHz RFW decreased pancreatic NGF and serotonin levels and increased the proinflammatory markers (Hcy and TNF-α), which can be a predisposing factor for type 2 diabetes.

(2-Carboxyethyl) dimethylsulfonium bromide supplementation in non-fish meal diets for on-growing grass carp (Ctenopharyngodon idella): Beneficial effects on immune function of the immune organs via modulation of NF-κB and TOR signalling pathway

The immune function of immune organs is extremely crucial for maintaining organism health status, which ultimately affects fish growth. Our previous study has found that dietary supplementation of (2-carboxyethyl)dimethylsulfonium Bromide (Br-DMPT) in non-fish meal (NFM) diet could promote the growth of grass carp (Ctenopharyngodon idella), whereas the underlying reason or mechanism for this results is largely unclear. Herein, we further explored whether dietary supplementation of Br-DMPT promoted fish growth is connected with the enhanced immune function in the immune organs (the head kidney, spleen and skin). In this study, 540 fish (216.49 ± 0.29 g) were irregularly distributed to six groups with three replicates (30 fish replicate^-1) and fed corresponding diets group containing a fish meal (FM) diet group and five different NFM diets supplemented with gradational Br-DMPT (0-520.0 mg/kg level) group for 60 days. After the 60-days feeding trial, 8 fish from each replicate were selected and then conducted a challenge test with A. hydrophila for 14 days. Our results indicated that in the NFM diets, appropriate Br-DMPT: (1) significantly decreased the morbidity of skin haemorrhage and lesion after A. hydrophila infection (P < 0.05). (2) significantly improved the innate and adaptive immune components (lysozyme, complement 3, immunoglobulin M and antibacterial peptides et al.) (P < 0.05). (3) increased the gene expressions of main anti-inflammatory cytokines partially by referring to TOR signalling pathway, and decreased the gene expressions of main pro-inflammatory cytokines partially by referring to NF-kB signalling pathway (P < 0.05). Strikingly, no statistical difference could be found in the most of above immune parameters between 260.0 mg/kg Br-DMPT diet group and FM diet group (P > 0.05). Taken together, in non-fish meal diet, appropriate supplementation of Br-DMPT could improve the disease resistance capacity, non-specific immunity and ameliorate inflammation, and simultaneously could mitigate these adverse effects induced by the non-fish meal diet in fish immune organs. Moreover, this study may be helpful to decipher the underlying mechanisms of how Br-DMPT promote fish growth by immune organs and also provide scientific theoretical evidence for the future application of Br-DMPT as a new immunopotentiator in aquaculture industry.

Effects of Folic Acid and Vitamin B12, Alone and in Combination on Cognitive Function and Inflammatory Factors in the Elderly with Mild Cognitive Impairment: A Single-blind Experimental Design

BACKGROUND

Folate and vitamin B12 are well-known as essential nutrients that play key roles in the normal functions of the brain. Inflammatory processes play at least some role in the pathology of AD. Effective nutritional intervention approaches for improving cognitive deficits that reduce the peripheral inflammatory cytokine levels have garnered special attention.

OBJECTIVE

The present study aimed to determine whether supplementation with folic acid and vitamin B12, alone and in combination improves cognitive performance via reducing levels of peripheral inflammatory cytokines.

METHODS

240 participants with MCI were randomly assigned in equal proportion to four treatment groups: folic acid alone, vitamin B12 alone, folic acid plus vitamin B12 or control without treatment daily for 6 months. Cognition was measured with WAIS-RC. The levels of inflammatory cytokines were measured using ELISA. Changes in cognitive function or blood biomarkers were analyzed by repeatedmeasure analysis of variance or mixed-effects models. This trial has been registered with trial number ChiCTR-ROC-16008305.

RESULTS

Compared with control group, the folic acid plus vitamin B12 group had significantly greater improvements in serum folate, homocysteine, vitamin B12 and IL-6, TNF-α, MCP-1. The folic acid plus vitamin B12 supplementation significantly changed the Full Scale IQ (effect size d = 0.169; P = 0.024), verbal IQ (effect size d = 0.146; P = 0.033), Information (d = 0.172; P = 0.019) and Digit Span (d = 0.187; P = 0.009) scores. Post hoc Turkey tests found that folic acid and vitamin B12 supplementation was significantly more effective than folic acid alone for all endpoints.

CONCLUSIONS

The combination of oral folic acid plus vitamin B12 in MCI elderly for six months can significantly improve cognitive performance and reduce the levels of inflammatory cytokines in human peripheral blood. The combination of folic acid and vitamin B12 was significantly superior to either folic acid or vitamin B12 alone.

Homocysteine and psoriasis

Psoriasis is caused by a complex interplay among the immune system, genetic background, autoantigens, and environmental factors. Recent studies have demonstrated that patients with psoriasis have a significantly higher serum homocysteine (Hcy) level and a higher prevalence of hyperhomocysteinaemia (HHcy). Insufficiency of folic acid and vitamin B₁₂ can be a cause of HHcy in psoriasis. Hcy may promote the immuno-inflammatory process in the pathogenesis of psoriasis by activating Th1 and Th17 cells and neutrophils, while suppressing regulatory T cells. Moreover, Hcy can drive the immuno-inflammatory process by enhancing the production of the pro-inflammatory cytokines in related to psoriasis. Hcy can induce nuclear factor kappa B activation, which is critical in the immunopathogenesis of psoriasis. There may be a link between the oxidative stress state in psoriasis and the effect of HHcy. Hydrogen sulfide (H₂S) may play a protective role in the pathogenesis of psoriasis and the deficiency of H₂S in psoriasis may be caused by HHcy. As the role of Hcy in the pathogenesis of psoriasis is most likely established, Hcy can be a potential therapeutic target for the treatment of psoriasis. Systemic folinate calcium, a folic acid derivative, and topical vitamin B12 have found to be effective in treating psoriasis.

Plasma Homocysteine and Cardiovascular Organ Damage in a Population with a High Prevalence of Risk Factors

PURPOSE

It is unclear whether plasma homocysteine (Hcy) has a direct noxious impact on the cardiovascular (CV) system or whether its association with cardiovascular events (CVEs) is mediated by established risk factors. To explore the role of Hcy in CV impairment, the study evaluated cross-sectional relationships between plasma Hcy and indices of CV organ damage together with the associations of these indices with the history of CVEs.

METHODS

In 269 patients with a high prevalence of diabetes, dyslipidemia, and hypertension, the carotid intima-media thickness, ankle-brachial index (ABI), reactive hyperemic index, carotid-femoral pulse wave velocity (cfPWV), left ventricular (LV) mass, and cardiac index were measured.

RESULTS

132 patients had carotid plaque, 31 ABI < 0.90, 126 endothelial dysfunction, 66 increased cfPWV, 125 LV hypertrophy (LVH), 153 decreased cardiac index, and 115 a history of CVEs. Plasma Hcy levels were related to LV mass and ABI, after adjustment for covariates and creatinine. Significantly higher Hcy levels were found in patients with LVH (8.5 [4.4] vs 7.6 [2.8] μmol/L; adjusted P = .001) and ABI < 0.9 (10.4 [3.8] vs 7.9 [3.4] μmol/L; adjusted P = .001) than in those with LV mass and ABI within limits. Hcy levels were comparable between patients with and without carotid plaques, increased arterial stiffness, impaired endothelial, and LV pump function. Within markers of CV organ damage, only LVH was associated with a history of CVEs.

CONCLUSION

This study demonstrated an independent association between Hcy and LV mass as well as between LVH and a history of CVEs and suggests that LVH may represent 1 of the pathophysiologic links between Hcy and CV risk.

Homocysteine concentration and adenosine A2A receptor production by peripheral blood mononuclear cells in coronary artery disease patients

Hyperhomocysteinemia is associated with coronary artery disease (CAD). The mechanistic aspects of this relationship are unclear. In CAD patients, homocysteine (HCy) concentration correlates with plasma level of adenosine that controls the coronary circulation via the activation of adenosine A_2A receptors (A_2AR). We addressed in CAD patients the relationship between HCy and A_2AR production, and in cellulo the effect of HCy on A_2AR function. 46 patients with CAD and 20 control healthy subjects were included. We evaluated A_2AR production by peripheral blood mononuclear cells using Western blotting. We studied in cellulo (CEM human T cells) the effect of HCy on A_2A R production as well as on basal and stimulated cAMP production following A_2A R activation by an agonist‐like monoclonal antibody. HCy concentration was higher in CAD patients vs controls (median, range: 16.6 [7‐45] vs 8 [5‐12] µM, P < 0.001). A_2A R production was lower in patients vs controls (1.1[0.62‐1.6] vs 1.53[0.7‐1.9] arbitrary units, P < 0.001). We observed a negative correlation between HCy concentration and A_2A R production (r = −0.43; P < 0.0001), with decreased A_2A R production above 25 µM HCy. In cellulo, HCy inhibited A_2AR production, as well as basal and stimulated cAMP production. In conclusion, HCy is negatively associated with A_2A R production in CAD patients, as well as with A_2A R and cAMP production in cellulo. The decrease in A_2A R production and function, which is known to hamper coronary blood flow and promote inflammation, may support CAD pathogenesis.

Novel insights into the intestinal immune regulatory effects of (2-Carboxyethyl) dimethylsulfonium Bromide (Br-DMPT) in on-growing grass carp (Ctenopharyngodon idella)

The present study evaluated the effects of (2-Carboxyethyl)dimethylsulfonium Bromide (Br-DMPT) supplementation on the intestinal immune function and potential mechanisms of on-growing grass carp (Ctenopharyngodon idella) by feeding fish (initial weight 216.49 ± 0.29 g) five diets with gradational Br-DMPT (0-520 mg/kg diet) concentrations for 60 days and then infecting them with Aeromonas hydrophila for 14 days. Our results firstly indicated that compared with the control group, appropriate Br-DMPT supplementation increased the number of beneficial bacteria Lactobacillus and Bifidobacterium and enteritis resistance, decreased the number of detrimental bacteria Aeromonas and E. coli, and relieved the intestinal histopathological symptoms of fish. In addition, compared with the control group, appropriate Br-DMPT supplementation (1) increased lysozyme (LZ) and acid phosphatase (ACP) activities, as well as complement 3 (C3), C4 and immunoglobulin M (IgM) content; (2) upregulated the mRNA levels of anti-microbial substance: liver expressed anti-microbial peptide (LEAP) -2A, LEAP-2B, hepcidin, β-defensin-1 and Mucin2; (3) partially downregulated the mRNA levels of pro-inflammatory cytokines [interleukin 1β (IL-1β), IL-6, IL-8, IL-12p40, IL-15, IL-17D, tumour necrosis factor α (TNF-α) and interferon γ2 (IFN-γ2)] by inhibiting [IKKβ/IκBα/(NF-κBp65 and c-Rel)] signalling; and (4) partially upregulated the mRNA levels of anti-inflammatory cytokines [IL-4/13A, IL-10, IL-11, transforming growth factor (TGF)-β1] by activating [TOR/(S6K1 and 4E-BP)] signalling. The aforementioned results indicated that appropriate amount of Br-DMPT exerted a positive effect on the regulation of intestinal immune function in fish. Finally, based on enteritis morbidity, the IgM content and the lysozyme activity in the PI, the appropriate levels of Br-DMPT supplementation for on-growing grass carp were established as 295.43, 301.73 and 320.36 mg/kg diet, respectively.

Hyperhomocysteinemia as a Metabolic Risk Factor for Glucose Intolerance Among High-Risk Groups of Chinese Adults

BACKGROUND Impaired glucose tolerance (IGT) is characterized by insulin resistance and causes atherosclerosis. Hyperhomocysteinemia is associated with insulin resistance and predicts cardiovascular diseases. In this study, we assessed the possible association between homocysteine and IGT. MATERIAL AND METHODS This was a cross-sectional study of 118 consecutive subjects with IGT (IGT group) and 128 consecutive subjects with normal glucose tolerance (NGT group). Homocysteine and clinical characteristics were measured. RESULTS The IGT group had higher homocysteine than the NGT group [18.00 (14.00, 22.25) vs. 12.50 (9.00, 15.00) μmol/L, p<0.001]. Homocysteine was positively associated with body mass index (BMI) (r=0.178, p=0.005), triglycerides (r=0.306, p<0.001), fasting blood glucose (FBG) (r=0.312, p<0.001), 2-hour postchallenge glucose (2hPG) (r=0.363, p<0.001), fasting insulin (FINS) (r=0.655, p<0.001), and homeostasis model assessment for insulin resistance (HOMA-IR) (r=0.643, p<0.001), and was negatively correlated with high-density lipoprotein cholesterol (HDL-C) (r=-0.250, p<0.001). After controlling for confounders, hyperinsulinemia (β=7.430, p<0.001) was independently related to hyperhomocysteinemia. In a logistic regression analysis, high triglycerides (OR=1.177, p<0.001) and homocysteine (OR=1.508, p=0.007), and low HDL-C (OR=0.315, p=0.026) were associated with IGT. CONCLUSIONS Patients with IGT have higher homocysteine levels compared with subjects with normal glucose tolerance, and hyperhomocysteinemia might be correlated with IGT.

Vein graft disease in a knockout mouse model of hyperhomocysteinaemia

A major reason for vein graft failure after coronary artery bypass grafting is neointimal hyperplasia and thrombosis. Elevated serum levels of homocysteine (Hcy) are associated with higher incidence of cardiovascular disease, but homocysteine levels also tend to increase during the first weeks or months after cardiac surgery. To investigate this further, C57BL/6J mice (WT) and cystathionine-beta-synthase heterozygous knockout mice (CBS+/-), a mouse model for hyperhomocysteinaemia, underwent interposition of the vena cava of donor mice into the carotid artery of recipient mice. Two experimental groups were examined: 20 mice of each group underwent bypass surgery (group 1: WT donor and WT recipient; group 2: CBS+/- donor and CBS+/- recipient). After 4 weeks, the veins were harvested, dehydrated, paraffin-embedded, stained and analysed by histomorphology and immunohistochemistry. Additionally, serum Hcy levels in CBS knockout animals and in WT animals before and after bypass surgery were measured. At 4 weeks postoperatively, group 2 mice showed a higher percentage of thrombosis compared to controls, a threefold increase in neointima formation, higher general vascularization, a lower percentage of elastic fibres with shortage and fragmentation in the neointima, a lower percentage of acid mucopolysaccharides in the neointima and a more intense fibrosis in the neointima and media. In conclusion, hyperhomocysteinaemic cystathionine-beta-synthase knockout mice can play an important role in the study of mechanisms of vein graft failure. But further in vitro and in vivo studies are necessary to answer the question whether or not homocysteine itself or a related metabolic factor is the key aetiologic agent for accelerated vein graft disease.

Dietary B Vitamins and Serum C-Reactive Protein in Persons With Human Immunodeficiency Virus Infection: The Positive Living With HIV (POLH) Study

BACKGROUND

B vitamins may have beneficial roles in reducing inflammation; however, research on the role of B vitamins in inflammation among HIV-infected persons is lacking.

OBJECTIVE

This study assessed the association between B vitamins and serum C-reactive protein (CRP) concentrations in HIV-infected persons.

METHODS

A cross-sectional survey was conducted among 314 HIV-infected persons (180 men and 134 women) aged 18 to 60 years residing in the Kathmandu, Nepal. High-sensitive and regular serum CRP concentrations were measured by the latex agglutination nephelometry and latex agglutination turbidimetric method, respectively. Dietary intake was assessed using 2 nonconsecutive 24-hour dietary recalls. The relationships between B vitamins and serum CRP concentrations were assessed using multiple regression analysis.

RESULTS

The multivariate-adjusted geometric mean of serum CRP concentrations was significantly decreased with an increasing B vitamins intake across quartiles of niacin (P for trend = .007), pyridoxine (P for trend = .042), and cobalamin (P for trend = .037) in men. In men, the mean serum CRP concentrations in the highest quartiles of niacin, pyridoxine, and cobalamin were 63%, 38%, and 58%, respectively, lower than that in the lowest quartile. In women, the mean serum CRP concentrations in the highest quartiles of riboflavin (P for trend = .084) and pyridoxine (P for trend = .093) were 37% and 47%, respectively, lower than that in the lowest quartile.

CONCLUSION

High intake of niacin, pyridoxine, or cobalamin was independently associated with decreased serum CRP concentrations among HIV-infected men. Further prospective studies are warranted to confirm the role of B vitamins in inflammation among HIV-infected persons.

There are no differences in IL-6, CRP and homocystein concentrations between women whose mothers had AD and women whose mothers did not have AD

A wide range of recent studies have detected inflammation as one of the most influent factors in the appearance and spreading of neurodegenerative brain diseases. We aimed to understand the influence of Interleukin-6 (IL-6), C-reactive protein (CRP) and homocysteine (Hcy) on patients suffering from Alzheimer׳s disease (AD) and on their descendants. Three groups of subjects were analyzed: 55 patients suffering from AD, 51 middle-aged daughters of the patients of the first group, and 53 subjects without positive family history of AD. The results of the conducted research are in accordance with the present scientific knowledge, namely a statistically significant difference for examined parameters has been determined between women suffering from AD and their daughters and control group examinees. No difference was found in serum concentrations of IL-6, highly sensitive C-reactive protein (hsCRP) and Hcy between the groups of the middle-aged descendants of patients with AD and healthy controls without family history of AD. This finding supports the hypothesis that these markers may not play causal role in the development of AD. This is supported by the obtained positive correlation between IL-6 and hsCRP and IL-6 and Hcy in AD patients while there is no such correlation between female subjects with or without a family history of AD.

Constitutive induction of pro-inflammatory and chemotactic cytokines in cystathionine beta-synthase deficient homocystinuria

Cystathionine beta-synthase (CBS) deficient homocystinuria (HCU) is an inherited metabolic defect that if untreated, typically results in cognitive impairment, connective tissue disturbances, atherosclerosis and thromboembolic disease. In recent years, chronic inappropriate expression of the inflammatory response has emerged as a major driving force of both thrombosis and atherosclerotic lesion development. We report here a characterization of the abnormalities in cytokine expression induced in both a mouse model of HCU and human subjects with the disease in the presence and absence of homocysteine lowering therapy. HCU mice exhibited highly significant induction of the pro-inflammatory cytokines Il-1alpha, Il-1beta and TNF-alpha. Similarly, in untreated/poorly compliant human subjects with HCU we observed constitutive induction of multiple pro-inflammatory cytokines (IL-1alpha, IL-6, TNF-alpha, Il-17 and IL-12(p70)) and chemotactic chemokines (fractalkine, MIP-1alpha and MIP-1beta) compared to normal controls. These HCU patients also exhibited significant induction of IL-9, TGF-alpha and G-CSF. The expression levels of anti-inflammatory cytokines were unaffected in both HCU mice and human subjects with the disease. In the human subjects, homocysteine lowering therapy was associated with either normalization or significant reduction of all of the pro-inflammatory cytokines and chemokines investigated. We conclude that HCU is a disease of chronic inflammation and that aberrant cytokine expression has the potential to contribute to multiple aspects of pathogenesis. Our findings indicate that anti-inflammatory strategies could serve as a useful adjuvant therapy for this disease.

Associations of plasma homocysteine level with brachial-ankle pulse wave velocity, LDL atherogenicity, and inflammation profile in healthy men

AIMS

To investigate the association of plasma total homocysteine (tHcy) with arterial stiffness, measured as brachial-ankle pulse wave velocity (baPWV), LDL atherogenicity, and inflammation profile in healthy men.

METHODS AND RESULTS

In this cross-sectional study, 612 healthy men aged 31-79 years were classified into quartiles according to plasma tHcy concentration. In the total study population, tHcy concentration showed positive correlation with age (r=0.083, P=0.040), interleukin (IL)-1β (r=0.249, P<0.001), TNF-α (r=0.150, P<0.001), IL-6 (r=0.154, P<0.001), oxidized LDL (oxLDL) (r=0.161, P=<0.001), and baPWV (r=0.087, P=0.032); and negative correlation with folate (r=-0.353, P<0.001) and vitamin B(12) (r=-0.269, P<0.001). In subgroup analysis based on plasma tHcy level, tHcy was associated with baPWV in men with high levels of tHcy (≥ 13.1μmol/L, n=153; r=0.258, P=0.001), but not in those with low-tHcy (<13.1 μmol/L, n=459; r=-0.033, P=0.478). The association between tHcy and baPWV in the high-tHcy group remained significant after adjustment for age, BMI, smoking, drinking, folate, and vitamin B₁₂. In the high-tHcy group, tHcy level was also positively correlated with IL-1β, TNF-α, oxLDL, and blood pressure; and negatively correlated with LDL particle size. In addition, baPWV showed negative correlation with LDL particle size and positive correlation with oxLDL in the high-tHcy group.

CONCLUSION

This study shows an association between high levels of plasma tHcy and more advanced arterial stiffness, smaller LDL particle size, and higher levels of oxLDL and cytokines in men with hyperhomocysteinemia. Enhanced arterial stiffness in hyperhomocysteinemia might be attributed, in part, to Hcy-related LDL atherogenicity.

Increased inflammatory markers in brain and blood of rats subjected to acute homocysteine administration

Hyperhomocysteinemia plays an etiologic role in the pathogenesis of disorders, including homocystinuria and neurodegenerative and cardiovascular diseases. In the present study, we studied the effect of acute administration of homocysteine, similar to that found in homocystinuria, on parameters of inflammation such as cytokines (TNF-alpha, IL-1beta and IL-6), chemokine CCL2 (MCP-1), nitrite and acute phase-proteins (C-reactive protein and alpha(1)-Acid glycoprotein) levels in brain and blood of rats. In addition, a differential count of blood leukocytes was performed. Wistar rats, aged 29 days, received a single subcutaneous injection of saline (control) or homocysteine (0.6 micromol/g body weight). Fifteen minutes, 1 h, 6 h or 12 h after the injection, the rats were sacrificed and serum, hippocampus and cerebral cortex were used. Results showed that homocysteine significantly increased proinflammatory cytokines (TNF-alpha, IL-1beta and IL-6) and chemokine CCL2 (MCP-1) in serum, hippocampus and cerebral cortex. Nitrite levels also increased in hippocampus and cerebral cortex at 15 min, 1 h and 6 h, but not 12 h after homocysteine administration. Acute phase-protein levels were not altered by homocysteine. The percentage of neutrophils and monocytes significantly increased in blood at 15 min and 1 h, but not at 6 h and 12 h after acute hyperhomocysteinemia, when compared to the control group. Our results showed that acute administration of homocysteine increased inflammatory parameters, suggesting that inflammation might be associated, at least in part, with the neuronal and cardiovascular dysfunctions observed in homocystinuric patients.

Effect of supplementation with B vitamins and antioxidants on levels of asymmetric dimethylarginine (ADMA) and C-reactive protein (CRP): a double-blind, randomised, factorial design, placebo-controlled trial

PURPOSE

Cardiovascular risk factors such as elevated levels of asymmetric dimethylarginine (ADMA)/C-reactive protein (CRP) and homocysteine are potentially related to essential micronutrients such as certain B vitamins and antioxidant vitamins. The aim of the present study was to investigate whether supplementation with moderate doses of B vitamins and/or antioxidants could alter either ADMA and/or CRP concentrations in middle-aged, apparently healthy men with mildly elevated homocysteine levels.

METHODS

A randomised, double-blind, factorial design, intervention study was carried out on 132 men with mildly elevated homocysteine levels, allocated to four groups (a) B vitamins alone--1 mg folic acid, 7.2 mg pyridoxine, 0.02 mg cyanocobalamin daily, (b) antioxidants alone--150 mg ascorbic acid, 67 mg vitamin E, 9 mg β-carotene daily, (c) B vitamins with antioxidant vitamins, or (d) placebo. A total of 101 men completed the study to 8 weeks.

RESULTS

When the percentage of baseline ADMA and CRP was examined at 8 weeks, no statistically significant differences were observed between the four groups (p = 0.21 and p = 0.90, respectively). Similar non-significant results were observed when analysis was stratified based on baseline CRP levels (<1.0 mg/L, p = 0.10; ≥1.0 mg/L, p = 0.64) and smoking status (all p ≥ 0.05).

CONCLUSIONS

Supplementation with moderate doses of B vitamins and/or antioxidants did not alter either ADMA or CRP concentrations in these middle-aged, apparently healthy men with mildly elevated homocysteine levels.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

Hydrogen sulfide and the vasculature: a novel vasculoprotective entity and regulator of nitric oxide bioavailability?

Hydrogen sulfide (H₂S) is a well known and pungent toxic gas that has recently been shown to be synthesised in man from the amino acids cystathionine, homocysteine and cysteine by at least two distinct enzymes; cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H₂S has emerged as a novel and increasingly important mediator in the cardiovascular system but delineating the precise physiology and pathophysiology of H₂S is proving to be complex and difficult to unravel with disparate findings reported with cell types, tissue types and animal species reported. Therefore, in this review we summarize the mechanisms by which H₂S has been proposed to regulate blood pressure and cardiac function, discuss the mechanistic discrepancies reported in the literature as well as the therapeutic potential of H₂S. We also examine the methods of H₂S detection in biological fluids, processes for H₂S removal and discuss the reported blood levels of H₂S in man and animal models of cardiovascular pathology. We also highlight the complex interaction of H₂S with nitric oxide in regulating cardiovascular function in health and disease.

Homocysteine and inflammation as main determinants of oxidative stress in the elderly

Oxidative stress is commonly observed in the elderly and could be involved in age-related diseases. However, the determinants of superoxide anion overproduction are not clearly understood. Superoxide anion production was evaluated using a lucigenin-based chemiluminescence method in 478 elderly subjects (304 women, 174 men; 79.5+/-7.1 years). Homocysteine (HCy) metabolism (homocysteinemia, vitamin B12, plasma, and erythrocyte folates), inflammation (CRP, fibrinogen, alpha-1 acid glycoprotein), lipid parameters (total cholesterol, triglycerides, HDL and LDL cholesterol), and nutritional parameters (albumin, transthyretin) were determined. The results show that HCy levels (p<0.001) and superoxide anion production (p=0.04) increase with aging, but CRP does not. Highest HCy (>20 microM) (OR 1.83 (1.09-3.07), p=0.02) and CRP over 5 mg/L (adjusted OR 2.01 (1.15-3.51), p=0.01) are the main determinants in superoxide anion production in the elderly. These clinical data are confirmed in an in vitro study using THP-1 monocyte-like cells. Incubation with HCy thiolactone (HTL) (0-200 microM) and LPS (0-20 ng/ml) dramatically enhances NADPH oxidase expression and activation. Moreover, a synergic action was evidenced for low concentrations of HTL (20 microM) and LPS (5 ng). Taken together, the clinical data and in vitro experiments support the hypothesis that moderate homocysteinemia and low-grade inflammation synergically enhance NADPH oxidase activity in the elderly.

The role of hyperhomocysteinemia and B-vitamin deficiency in neurological and psychiatric diseases

Hyperhomocysteinemia (HHcy) is related to central nervous system diseases. Epidemiological studies show a positive, dose-dependent relationship between plasma total homocysteine (tHcy) concentration and neurodegenerative disease risk. tHcy is a marker of B-vitamin (folate, B(12), B(6)) status. Hypomethylation, caused by low B-vitamin status and HHcy, is linked to key pathomechanisms of dementia; B-vitamin supplementation could potentially reduce neurological damage. In retrospective studies, the association between tHcy and cognition is impressive; there is also evidence that tHcy-lowering treatment could be effective in primary and secondary stroke prevention. Increased tHcy and low serum folate occur in patients with Parkinson's disease, especially those receiving L-dopa. There is also an association between HHcy and multiple sclerosis, and between B-vitamin status and depression. Studies also confirm a causal role for tHcy in epilepsy, and certain anti-epileptics enhance HHcy. B-vitamin status should be optimized by ensuring sufficient intake in patients with neuropsychiatric diseases. HHcy occurs commonly in the elderly and can contribute to age-related neurodegeneration. Treatment with folic acid, B(12) and B(6) lowers tHcy. For secondary and primary prevention from several neuropsychiatric disorders, it seems prudent to actively identify deficient subjects and ensure sufficient vitamin intake.

Clinical relevance of plasma homocysteine levels in Taiwanese patients with coronary artery disease

Homocysteine (Hcy) has recently been considered as a risk factor for cardiovascular disease. Coronary artery disease (CAD) is the third most common cause of mortality in Taiwan. The objective of our present study is to delineate the relationship between the plasma Hcy level and CAD in Taiwanese using an improved enzymatic method. Blood samples were collected from 86 CAD patients, which include 38 patients with acute coronary syndrome (ACS) and 48 patients with stable CAD, and 89 controls. Plasma Hcy levels were measured by HPLC and enzymatic methods. Plasma Hcy levels were 8.27 +/- 1.74, 8.50 +/-1.88 and 11.76 +/- 4.58 muM in normal controls, patients with stable CAD and those with ACS, respectively. Plasma Hcy levels were elevated in the cohort of ACS patients, as compared with those of normal controls or patients with stable CAD. Within the CAD group, patients with the highest quartile Hcy level (10.18-23.73 muM) had a significantly higher odd ratio for ACS, as compared with those with the lowest quartile Hcy level after multivariate adjustment. Plasma Hcy concentration can be used as an independent risk factor of ACS, particularly for those with a history of CAD. Moreover, our improved enzymatic assay can be automated for large-scale screening of high-risk cohorts.

Blood inflammatory markers and risk of dementia: The Conselice Study of Brain Aging

Incidence studies of blood inflammatory markers as predictors of dementia in older age are few and did not take into account hyperhomocysteinemia, although this condition is associated with both inflammation and increased risk of dementia. We investigated the relationships of baseline serum C-reactive protein (CRP), serum interleukin 6 (IL6), plasma alpha-1-antichymotrypsin, and hyperhomocysteinemia (defined as plasma total homocysteine>15 micromol/L) with risk of incident Alzheimer's disease (AD) and vascular dementia (VaD) in a dementia-free Italian population-based elderly cohort (n=804, 53.2% women, mean age 74 years) with 4 years of follow-up. No inflammatory marker, alone or in combination, predicted AD risk whereas the combination of high CRP and high IL6 was associated with risk of VaD (HR, 2.56; 95%CI, 1.21-5.50) independently of socio-demographic confounders, traditional risk factors and hyperhomocysteinemia. By contrast, in the same model, hyperhomocysteinemia was independently associated with AD (HR, 1.91; 95%CI, 1.02-3.56) but not VaD risk. Blood inflammatory markers are associated with increased VaD risk but do not predict AD, which seems selectively associated with hyperhomocysteinemia.

Homocysteine-lowering therapy does not affect inflammatory markers of atherosclerosis in patients with stable coronary artery disease

OBJECTIVES

A high level of total homocysteine (tHcy) is a risk marker for cardiovascular disease (CVD), and is related to inflammation. We wanted to test the effect of homocysteine-lowering B-vitamin therapy, as used in the Western Norway B-vitamin Intervention Trial (WENBIT), on inflammatory markers associated with atherosclerosis.

DESIGN

Single centre, prospective double-blind clinical interventional study, randomised in a 2 x 2 factorial design.

SUBJECTS AND METHODS

Ninety patients (21 female) with suspected coronary artery disease (CAD), aged 38-80 years, were blindly randomised into one of four groups of daily oral treatment with (A) folic acid (0.8 mg)/vitamin B12 (0.4 mg)/vitamin B6 (40 mg), (B) folic acid/vitamin B12, (C) vitamin B6 alone or (D) placebo. Blood samples were collected before and after 6 months of treatment.

RESULTS

Before intervention, median levels of the analytes were: tHcy 11.0 micromol L(-1), neopterin 8.1 nmol L(-1), soluble CD40 ligand (sCD40L) 3.9 ng mL(-1), interleukin (IL)-6 1.9 pg mL(-1), C-reactive protein (CRP) 1.9 mg L(-1) and low-density lipoprotein (LDL) cholesterol 3.3 mmol L(-1). tHcy was significantly associated with neopterin (r = 0.49, P < 0.001) and with IL-6 (r = 0.29, P = 0.01), but not with CRP or sCD40L. Neither treatment with folic acid/B12 nor with B6 induced significant changes in any of these inflammatory biomarkers (P >or= 0.14). In patients receiving folic acid/B12 (groups A and B), tHcy was reduced with 33% (P < 0.001).

CONCLUSIONS

In patients with stable CAD, homocysteine-lowering therapy with B-vitamins does not affect levels of inflammatory markers associated with atherogenesis. Failure to reverse inflammatory processes, may partly explain the negative results in clinical secondary B-vitamin intervention trials.

Homocysteine induces VCAM-1 gene expression through NF-kappaB and NAD(P)H oxidase activation: protective role of Mediterranean diet polyphenolic antioxidants

Hyperhomocysteinemia is a recognized risk factor for vascular disease, but pathogenetic mechanisms involved in its vascular actions are largely unknown. Because VCAM-1 expression is crucial in monocyte adhesion and early atherogenesis, we evaluated the NF-kappaB-related induction of VCAM-1 by homocysteine (Hcy) and the possible inhibitory effect of dietary polyphenolic antioxidants, such as trans-resveratrol (RSV) and hydroxytyrosol (HT), which are known inhibitors of NF-kappaB-mediated VCAM-1 induction. In human umbilical vein endothelial cells (HUVEC), Hcy, at 100 micromol/l, but not cysteine, induced VCAM-1 expression at the protein and mRNA levels, as shown by enzyme immunoassay and Northern analysis, respectively. Transfection studies with deletional VCAM-1 promoter constructs demonstrated that the two tandem NF-kappaB motifs in the VCAM-1 promoter are necessary for Hcy-induced VCAM-1 gene expression. Hcy-induced NF-kappaB activation was confirmed by EMSA, as shown by the nuclear translocation of its p65 (RelA) subunit and the degradation of the inhibitors IkappaB-alpha and IkappaB-beta by Western analysis. Hcy also increased intracellular reactive oxygen species by NAD(P)H oxidase activation, as shown by the membrane translocation of its p47(phox) subunit. NF-kappaB inhibitors decreased Hcy-induced intracellular reactive oxygen species and VCAM-1 expression. Finally, we found that nutritionally relevant concentrations of RSV and HT, but not folate and vitamin B6, reduce (by >60% at 10(-6) mol/l) Hcy-induced VCAM-1 expression and monocytoid cell adhesion to the endothelium. These data indicate that pathophysiologically relevant Hcy concentrations induce VCAM-1 expression through a prooxidant mechanism involving NF-kappaB. Natural Mediterranean diet antioxidants can inhibit such activation, suggesting their possible therapeutic role in Hcy-induced vascular damage.

Homocysteine at pathophysiological concentrations enhances binding of dendritic cells to endothelial cells mediated by DC-SIGN

Elevated plasma homocysteine (Hcy) is an independent risk factor for atherosclerosis, which is recognized as inflammatory and immune responses. The purpose of this study was to investigate the effect of Hcy on the interaction between dendritic cells (DCs) and endothelial cells (ECs) by upregulating the expression of DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) in cultured DCs. The immunophenotype of Hcy-treated DCs was monitored by flow cytometry. Then, they were coincubated with cultured human umbilical vein endothelial cells, and adhesion of DCs to ECs, and migration of DCs through an endothelial monolayer growing on the insert of a transwell plate, were assessed using a confocal microscope and a multi-detection microplate reader. The expression of DC-SIGN on Hcy-stimulated DCs was assessed by Western blot and immunofluorescence staining. The presence of Hcy did not change the phenotype of immature and mature DCs. Hcy promoted adhesion of DCs to ECs and migration in a concentration-dependent fashion. This effect was inhibited by an anti-DC-SIGN monoclonal antibody. The expression of DC-SIGN on DCs was significantly upregulated by Hcy in a concentration-dependent manner. Taken together, our results show for the first time that Hcy can potentiate the adhesion of DCs to ECs and migration by upregulating the expression of DC-SIGN on DCs, suggesting a novel role of Hcy in the pathogenesis of human vascular disease.

Homocysteine in tear fluid of patients with pseudoexfoliation glaucoma

PURPOSE

To evaluate homocysteine (Hcy) concentrations in tear fluid and plasma and their association with B-vitamin levels in patients with pseudoexfoliation glaucoma (PEXG).

PATIENTS AND METHODS

Reflex tear and blood samples were obtained in 30 patients with PEXG and 30 controls. Hcy levels were determined by high-performance liquid chromatography.

RESULTS

Hcy was detected in all tear fluid samples of patients with PEXG and controls. Statistical analysis with t tests showed that patients with PEXG had significantly higher Hcy levels both in tear fluid (237+/-133 nmol/L vs. 128+/-54 nmol/L; P<0.001) and in plasma (14.51+/-4.43 micromol/L vs. 10.22+/-2.77 micromol/L; P<0.001) than control subjects. Hcy in tear fluid correlated significantly with Hcy in plasma (r=0.438, P=0.015) and with serum B12 levels (r=-0.424, P=0.019) in patients with PEXG, but not in controls.

CONCLUSIONS

The study suggests increased Hcy levels in tear fluid and plasma of patients with PEXG. Further investigations are needed to evaluate the possible clinical role of Hcy in ocular surface and systemic disorders associated with PEXG.

Interleukin-6, C-reactive protein and biochemical parameters during prolonged intermittent fasting

BACKGROUND

It is well known that nutritional habits, sleeping patterns and meal frequency have profound effects on maintaining human health. Ramadan is a religious month for Islam, during which Muslims do not eat and drink during the daylight hours. The duration of restricted food and beverage intake is approximately 12 h/day for 1 month, which makes Ramadan a model of prolonged intermittent fasting.

METHODS

In order to evaluate the effects of long-lasting modifications of food intake on inflammatory markers and biochemical parameters 40 healthy volunteers of normal weight [20 females aged between 20 and 38 years, 20 males aged between 23 and 39 years, body mass index (BMI) <25 kg/m(2)] who fasted during Ramadan and another 28 healthy age- and BMI-matched volunteers (14 males, 14 females) who did not fast participated in the study. Venous blood samples were taken 1 week before Ramadan, during the last week of Ramadan and 3 weeks after Ramadan. Serum interleukin-6 (IL-6), C-reactive protein (CRP), homocysteine, vitamin B(12), folate, total cholesterol (TC), triglycerides, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels were measured.

RESULTS

No significant changes were observed in serum total cholesterol, triglycerides and LDL levels. TC/HDL ratio (HDL risk factor) was decreased during and after Ramadan in both genders in the fasting group while there were no changes in the nonfasting group. IL-6 (p < 0.001), CRP (p < 0.001) and homocysteine (p < 0.01) levels were significantly low during Ramadan in the fasting subjects of both genders when compared to basal values (1 week before Ramadan).

CONCLUSION

Our results demonstrate that prolonged intermittent fasting in a model like Ramadan has some positive effects on the inflammatory status of the body and on the risk factors for cardiovascular diseases such as homocysteine, CRP and TC/HDL ratio.

Nontraditional atherosclerotic risk factors and extent of coronary atherosclerosis in patients with combined impaired fasting glucose and impaired glucose tolerance

Partially inconsistent data exist on mutual relations between nontraditional atherosclerotic risk factors, including the magnitude of insulin resistance (IR), as well as on their relevance for atherogenesis in the metabolic syndrome. Subjects exhibiting combined impaired fasting glucose and impaired glucose tolerance (IFG/IGT) are exposed to an exceptionally high risk for atherogenesis and development of type 2 diabetes mellitus. Because of islet Beta-cell dysfunction, the usefulness of commonly used indices of IR is limited in IFG/IGT. Our aim was to assess the relationship between extent of angiographic coronary artery disease (CAD) and nontraditional atherosclerotic risk factors (including IR by a clamp-based golden standard method) in IFG/IGT. Fifty-three subjects (32 men, 21 women; mean age, 55 +/- 11 years) with stable angina, preserved left ventricular systolic function, and IFG/IGT were divided into 3 groups: group A (no coronary stenoses >50%, n = 22), group B (1-vessel CAD, n = 15), and group C (2/3-vessel CAD, n = 16). Insulin sensitivity was quantified by a hyperinsulinemic euglycemic clamp technique and expressed as M. M value, plasma homocysteine (Hcy) level, and asymmetric dimethyl-L-arginine (ADMA)/L-arginine ratio were independent determinants of CAD extent as shown by forward stepwise discriminant function analysis. Compared with group A (M = 32.7 +/- 9.3 micromol/kg fat-free mass [FFM] per minute; Hcy, 8.1 +/- 1.4 micromol/L), lower M and higher Hcy levels were found in group B (M = 16.9 +/- 8.2 micromol/kg FFM per minute, P < .001; Hcy, 11.2 +/- 2.9 micromol/L, P = .003) and C (M = 16.4 +/- 7.8 micromol/kg FFM per minute, P < .001; Hcy, 12.8 +/- 3.9 micromol/L, P < .001). The ADMA/L-arginine ratio was increased in group C (0.0078 +/- 0.0011) compared with group A (0.0063 +/- 0.0013, P = .03) and B (0.0058 +/- 0.0012, P = .01). Multivariate correlates (P < .05) of plasma Hcy concentrations were M (beta = -.34 +/- .12, P = .008), creatinine clearance (beta = -.23 +/- .10, P = .03) and fasting insulin (beta = .25 +/- .12, P = .04). This indicates an additive contribution of IR, plasma Hcy, and elevated ADMA/L-arginine ratio to the extent of angiographic CAD in combined IFG/IGT.

Increased gene expression of scavenger receptors and proinflammatory markers in peripheral blood mononuclear cells of hyperlipidemic males

Interactions between peripheral blood mononuclear cells (PBMCs) and those within plaques are suggested to be pathophysiologically relevant to lipid-induced arteriosclerosis. In this study, gene expressions of scavenger receptors (CD36, CD68), LPS receptor (CD14), proinflammatory (tumor necrosis factor alpha [TNFalpha], CD40, interleukin-1 beta [IL-1beta]) and oxidative stress-related (manganese superoxide dismutase [MnSOD]) markers were analyzed in PBMCs of clinically asymptomatic males with classical proatherogenic risk factors such as smoking and/or hyperlipidemia. PBMCs were isolated from venous blood of normolipidemic non-smokers (n = 10) and smokers (n = 8), and hyperlipidemic non-smokers (n = 9) and smokers (n = 8). RNA from PBMCs was used for PCR analyses. Plasma concentrations of oxidized low-density lipoproteins (oxLDL) were measured by ELISA. The gene expressions of CD36, CD68, CD40, TNFalpha, and MnSOD were significantly higher in PBMCs of hyperlipidemics than in normolipidemics, irrespective of whether they were smoking or not. The individual expression of these genes showed significant positive correlations with each other but also with serum cholesterol or plasma oxLDL concentrations. The higher expressions of scavenger receptors, proinflammatory and oxidative stress-related genes of PBMCs are suggested to result mainly from hyperlipidemia and the accompanied increase of oxLDL concentrations.

High glucose and homocysteine synergistically affect the metalloproteinases-tissue inhibitors of metalloproteinases pattern, but not TGFB expression, in human fibroblasts

AIMS/HYPOTHESIS

Atherosclerosis is particularly aggressive in patients with diabetes. Hyperhomocysteinaemia causes oxidative stress and cytokine secretion: its atherogenic effect is mediated by an enhanced inflammatory response. Matrix metalloproteinases (MMPs) regulate extracellular matrix degradation and remodelling, and contribute to the vulnerability of the atherosclerotic lesion. Fibroblasts contribute to collagen biosynthesis and participate in plaque remodelling via expression and release of MMP2 and MMP9. To explore the role of hyperhomocysteinaemia in cellular pathways involved in plaque growth and stability in diabetic patients, we studied the effect of hyperhomocysteinaemia in human fibroblasts grown in the presence of normal or high glucose concentrations.

MATERIALS AND METHODS

In fibroblasts of five normal subjects, grown at 5.5 or 22 mmol/l glucose and treated with homocysteine, we determined: (1) MMP2, MMP9 and tissue inhibitor of metalloproteinases (TIMP)-1 (an MMP inhibitor) production by western blot analysis; (2) their activity by zymography; (3) TGFB1 expression by real-time PCR; and (4) TGFB, fibronectin and IL6 release by ELISA.

RESULTS

Hyperhomocysteinaemia increased the production and enzymatic activity of MMP2 and MMP9, the effect being more pronounced in high glucose. Conversely, TIMP1 production was reduced by hyperhomocysteinaemia in both conditions, especially in high glucose. Hyperhomocysteinaemia also stimulated IL6 release, at least in part through nuclear factor-kappaB activation. TGFB1 expression was not affected by hyperhomocysteinaemia either in normal or in high glucose.

CONCLUSIONS/INTERPRETATION

Homocysteine upregulates the MMP-TIMP pathway and IL6 release, the effect being stronger in the presence of high glucose. These actions of homocysteine may contribute to the increased atherogenesis observed in diabetic patients with poor metabolic control.

Asymmetrical dimethylarginine regulates endothelial function in methionine-induced but not in chronic homocystinemia in humans: effect of oxidative stress and proinflammatory cytokines

BACKGROUND

Homocystinemia is a metabolic abnormality associated with endothelial dysfunction and increased cardiovascular disease risk. The underlying mechanisms of these effects, however, are obscure.

OBJECTIVE

We examined the effect of asymmetrical dimethylarginine (ADMA) on endothelial dysfunction in methionine-induced and chronic homocystinemia and evaluated the regulatory role of oxidative stress and proinflammatory cytokines on the release of ADMA.

DESIGN

In this double-blind, placebo-controlled parallel group study, 30 subjects of both sexes (15 with homocystinemia and 15 healthy controls) underwent methionine loading, with simultaneous administration of a combination of vitamin C (2 g) plus alpha-tocopherol (800 IU) or placebo. Endothelial function in forearm resistance vessels and concentrations of ADMA, oxidized LDL, and proinflammatory cytokines were determined at baseline and 4 h after methionine loading.

RESULTS

Both chronic and methionine-induced homocystinemia were associated with increased oxidized LDL (P < 0.01), higher expression of the proinflammatory cytokine interleukin 6 (P < 0.05), and endothelial dysfunction (P < 0.01). Although ADMA rapidly increased in acute homocystinemia (P < 0.01) and was correlated with forearm hyperemic response at 4 h after methionine loading (r = -0.722, P = 0.0001), it was not higher in subjects with high versus low fasting homocysteine. High-dose antioxidant treatment prevented methionine-induced elevation of oxidized LDL and interleukin 6 but failed to prevent the increase in ADMA or endothelial dysfunction.

CONCLUSIONS

Both chronic and methionine-induced homocystinemia are characterized by increased oxidative stress and proinflammatory cytokines, which may contribute to the development of endothelial dysfunction. However, the ADMA pathway is activated only in acute homocystinemia by mechanisms not mediated by oxidized LDL or proinflammatory stimuli.

In vitro effect of homocysteine on nucleotide hydrolysis by blood serum from adult rats

During the past few years, elevated blood levels of homocysteine (Hcy) have been linked to increased risk of premature coronary artery disease, stroke and thromboembolism. These processes can be also related to the ratio adenine nucleotide/adenosine, since extracellularly these nucleotides are associated with modulation of processes such as platelet aggregation, vasodilatation and coronary flow. Furthermore, there are some studies that suggest a relationship between Hcy and plasma adenosine concentrations. The sequential hydrolysis of ATP to adenosine by soluble nucleotidases constitutes one of the systems for rapid inactivation of circulating adenine nucleotides. Thus, the main objective of this study was to evaluate if Hcy can participate in the modulation of the extracellular adenine nucleotide hydrolysis by rat blood serum. Our results showed that Hcy, at final concentrations of 5.0 mM, inhibits in vitro ATP, ADP and AMP hydrolysis by 26, 21 and 16%, respectively. Also Hcy, at final concentrations of 8.0mM, inhibited the in vitro hydrolysis of ATP, ADP and AMP by 46, 44 and 44%, respectively. Kinetic analysis showed that the inhibitions of the three adenine nucleotide hydrolyses in the presence of Hcy, by serum of adult rats, is of the uncompetitive type. The IC50 calculated from the results obtained were 6.52+/-1.75 mM (n = 4), 5.18 +/- 0.64 mM (n = 3) and 5.16 +/- 1.22 mM (n = 3) for ATP, ADP and AMP hydrolysis, respectively.

Association of plasma homocysteine with serum interleukin-6 and C-peptide levels in patients with type 2 diabetes

Hyperhomocysteinemia is an independent risk factor for atherosclerotic disease. Because serum markers of inflammation and the metabolic syndrome are also associated with atherosclerotic disease and insulin resistance, we investigated whether plasma homocysteine (Hcy) levels were associated with serum markers of inflammation and factors of metabolic syndrome in 223 elderly patients with type 2 diabetes mellitus. The levels of plasma Hcy and serum interleukin-6 (IL-6), high-sensitivity C-reactive protein, and C-peptide were measured. The C677T mutation of methylenetetrahydrofolate reductase (MTHFR) gene was detected using the polymerase chain reaction-restriction fragment length polymorphism method. The number of abnormal metabolic factors (presence of diabetes, blood pressure > or =130/85 mm Hg, triglycerides > or =150 mg/dL, high-density lipoprotein cholesterol <35 mg/dL (men) or <39 mg/dL (women), or body mass index >25 kg/m 2 ) was assessed. Elevated plasma Hcy levels correlated significantly with serum IL-6 ( r = 0.25, P < .001), C-peptide ( r = 0.22, P < .01), and the number of abnormal metabolic factors ( r = 0.20, P < .01), but not with C-reactive protein. Multiple linear regression analysis revealed that log-transformed IL-6, serum C-peptide, vitamin B12 , and creatinine were significant determinants of plasma Hcy levels. The correlation between Hcy and IL-6 levels was strongest in those with TT genotype of C677T MTHFR among 3 genotypes. The association between plasma Hcy and serum IL-6 levels supports the hypothesis that the activation of innate immunity is involved in the pathogenesis of arteriosclerosis in patients with diabetes mellitus who are homozygous for the TT genotype of C677T MTHFR.

Homocysteine is positively associated with cytokine IL-18 plasma levels in coronary artery bypass surgery patients

Homocysteine, cytokines (IL-18, IL-6, IL-8) are involved in vascular inflammation and coronary artery disease. Homocysteine influences endothelial IL-6 and IL-8 cytokine expression and release, however, an association between homocysteine and IL-18 has not been previously investigated in endothelial/smooth muscle cells and or in coronary artery disease. We report in 9 coronary artery bypass surgery (CABG) patients a positive correlation r = 0.86 between homocysteine and IL-18 plasma levels (p < 0.05). Plasma IL-18 levels are significantly higher in those patients with elevated homocysteine compared to those with normal levels (p < 0.02; 153 +/- 19 pg/ml versus 116 +/- 14 pg/ml respectively). Our in vitro cell culture studies suggest that the source of IL-18 in CABG patients with elevated homocysteine is not from vascular smooth muscle or endothelial cells.