The role of folic acid in the prevention of cardiovascular disease

The Polypill: A New Alternative in the Prevention and Treatment of Cardiovascular Disease

Cardiovascular disease (CVD) is the primary cause of death and disability worldwide. Although age-standardized CVD mortality rates decreased globally by 14.5% between 2006 and 2016, the burden of CVD remains disproportionately higher in low- and middle-income countries compared to high-income countries. Even though proven, effective approaches based on multiple-drug intake aimed at the prevention and treatment of CVD are currently available, poor adherence, early discontinuation of treatment, and suboptimal daily execution of the prescribed therapeutic regimes give rise to shortfalls in drug exposure, leading to high variability in the responses to the prescribed medications. Wald and Law, in their landmark paper published in BMJ 2003, hypothesized that the use of a fixed-dose combination of statins, β-blockers, angiotensin receptor blockers, angiotensin-converting enzyme inhibitors, and aspirin (classic Polypill composition) may increase adherence and decrease CVD by up to 80% when prescribed as primary prevention or in substitution of traditional protocols. Since then, many clinical trials have tested this hypothesis, with comparable results. This review aims to describe the available clinical trials performed to assess the impact of fixed-dose combinations on adherence, cost-effectiveness, and the risk factors critical to the onset of CVD.

The Role of Amino Acids in Endothelial Biology and Function

The vascular endothelium acts as an important component of the vascular system. It is a barrier between the blood and vessel wall. It plays an important role in regulating blood vessel tone, permeability, angiogenesis, and platelet functions. Several studies have shown that amino acids (AA) are key regulators in maintaining vascular homeostasis by modulating endothelial cell (EC) proliferation, migration, survival, and function. This review summarizes the metabolic and signaling pathways of AAs in ECs and discusses the importance of AA homeostasis in the functioning of ECs and vascular homeostasis. It also discusses the challenges in understanding the role of AA in the development of cardiovascular pathophysiology and possible directions for future research.

Relationship between dietary inflammatory index, hs-CRP level in the second trimester and neonatal birth weight: a cohort study

The aim of this study was to investigate whether diet plays a role in the effect of inflammation on birth weight. The normal pre-pregnancy body mass index and healthy single pregnant women without classical inflammatory were recruited at 16-20 weeks of pregnancy and provided blood sample to measure plasma high sensitive C-reactive protein (hs-CRP) level. The Dietary Inflammatory Index (DII) score was calculated by a three-day 24 h recall method, and a cohort of 307 eligible pregnant women was established. According to birth weight, the subjects were divided into three groups: normal birth weight (NBW) group, low birth weight (LBW) group, and high birth weight (HBW) group. The hs-CRP level and DII score were significantly different between NBW and LBW groups. The risk of higher hs-CRP in the pro-inflammatory dietary group was 1.89 times than the control group (95% CI: 1.05, 3.42). The risk of LBW with higher hs-CRP was 3.81 times than normal hs-CRP (95% CI: 1.26, 11.56). The risk of LBW in the pro-inflammatory dietary group was 10.44 times than in the anti-inflammatory dietary group (95%CI: 1.29, 84.61). The pro-inflammatory dietary in the second trimester affects the hs-CRP level, showing a positive correlation. And both of two factors increase the risk of LBW.

Empirically derived dietary patterns and serum inflammatory markers in Iranian female teachers: A cross-sectional study

AIM

To examine the relationship between dietary patterns and inflammatory markers including serum high sensitivity C-reactive protein (hs-CRP) and interleukin 17A (IL-17A) in females.

METHODS

In the present cross-sectional study in female teachers living in Yazd, central Iran, data on anthropometric measurements and general information were gathered. A food frequency questionnaire was completed by participants and then, subjects were invited to give blood samples. Major dietary patterns were derived using principal component analysis and serum inflammatory markers were compared according to quintiles of dietary patterns scores.

RESULTS

In total, 320 subjects aged 40.38 ± 8.08 years were included. Three dietary patterns were derived: (i) 'traditional' with a high intake of poultry, salt, eggs, other vegetables and red meat; (ii) 'vegetables and fruits' with a higher intake of tomatoes, yoghurt drinks, green leafy vegetables, dried fruits, fruits, other vegetables and organ meats and (iii) 'dairy and saturated fat' with a high loading of high-fat dairy products, butter, low-fat dairy, margarine, eggs, other vegetables and green leafy vegetables. Participants in the highest quintile of the 'vegetables and fruits' dietary pattern had significantly lower serum hs-CRP levels compared to those in the lowest quintile (3.6 ± 0.4 mg/L vs 2.6 ± 0.4 mg/L, respectively; P < 0.05). None of the dietary patterns were associated with circulating IL-17 levels.

CONCLUSIONS

Higher consumption of fruits and vegetables is inversely associated with serum hs-CRP but not IL-17 levels. Studies investigating the dietary patterns in association with IL-17 in other populations are recommended.

Red blood cell folate as a risk factor for breast cancer among patients at a tertiary hospital in Uganda: a case control study

Background

Folate has been shown to play a complex but unclear role in carcinogenesis, with some studies showing that low folate intake protects against early carcinogenesis while high folate intake promotes advanced carcinogenesis. Other studies have shown that high folate is associated with decreased breast cancer risk and overall survival, yet others found no such association.

This study therefore sought to determine the association between red blood folate levels and breast cancer among women seen at a tertiary Ugandan hospital.

Methods

A case control study was conducted where female patients with a histological diagnosis of breast cancer were recruited as cases, and females without cancer attending other surgical clinics as controls. Demographics and social behavior data were collected and 5mls of blood drawn for laboratory testing of red blood cell (RBC) folate, serum vitamin B12 and RBC count. Ethical approval was obtained.

Results

In this study, a total of 145 women were recruited as 72 cases and 73 controls. The odds of having breast cancer among women with normal folate levels compared to those with low folate levels were 1.4 (95% CI 0.7 to 2.9) P = 0.290. Ninety participants (63%) had low RBC folate and 53 participants (37%) had normal RBC folate. Thirty five (45%) of the women from a rural setting had normal folate levels compared to 18(28%) women from an urban setting.

Conclusions

There was no significant association found between RBC folate and breast cancer among this group of women in Uganda.

Effects of lifestyle interventions on inflammatory markers in the metabolic syndrome

Metabolic syndrome (MetS) is a clustering of cardiovascular risk factors which places individuals at increased risk for cardiovascular morbidity and mortality. In addition to obesity and insulin resistance, inflammation is emerging as a potential etiologic factor of the syndrome. One hypothesis suggests that obesity contributes to insulin resistance through increased production of adipose-derived inflammatory cytokines. Currently, lifestyle change is the first line of treatment for MetS. Only recently, however, have studies begun exploring the effect of lifestyle interventions on the mediation of inflammation in individuals with MetS. This review summarizes the strongest evidence (i.e. randomized controlled trial data) for a role of lifestyle interventions (diet and/or exercise) on the improvement of inflammatory biomarkers in people with MetS. Of six studies assessed, lifestyle interventions were consistently successful at improving the inflammatory and metabolic profiles. Interestingly, improvements in the inflammatory profile were found to be largely independent of obesity. Data currently suggest that alterations in dietary composition may be the most effective lifestyle change, although there is a need for more research in this area.

Fruit and vegetable consumption and its relation to markers of inflammation and oxidative stress in adolescents

BACKGROUND

Fruits and vegetables, foods rich in flavonoids and antioxidants, have been associated with lower risk of stroke, coronary heart disease, and markers of inflammation and oxidative stress in adults. Markers of inflammation and oxidative stress are predictors of coronary heart disease risk; however, it is unknown whether these markers are related to dietary flavonoid and antioxidant intake in youth.

OBJECTIVE

To determine whether greater intakes of fruit and vegetables, antioxidants, folate, and total flavonoids were inversely associated with markers of inflammation and oxidative stress in 285 adolescent boys and girls aged 13 to 17 years.

DESIGN

In this cross-sectional study conducted between February 1996 and January 2000, diet was assessed by a 127-item food frequency questionnaire. Height and weight measurements were obtained and a fasting blood sample drawn. Spearman partial correlation analyses evaluated the relation of intakes of fruit and vegetables, antioxidants, folate, and flavonoids with markers of inflammation (C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and 15-keto-dihydro-PGF(2alpha) metabolite and oxidative stress (urinary 8-iso prostaglandin F(2alpha), an F(2)-isoprostane), adjusting for age, sex, race, Tanner stage, energy intake, and body mass index.

RESULTS

Urinary F(2)-isoprostane was inversely correlated with intakes of total fruit and vegetables, vitamin C, beta carotene, and flavonoids. Serum C-reactive protein was significantly inversely associated with intakes of fruit (r=-0.19; P=0.004), vitamin C (r=-0.13, P=0.03), and folate (r=-0.18; P=0.004). Serum interleukin-6 was inversely associated with intakes of legumes, vegetables, beta carotene, and vitamin C. Serum tumor necrosis factor-alpha was inversely associated with beta carotene (r=-0.14, P=0.02) and luteolin (r=-0.15, P=0.02).

CONCLUSION

Study results show that the beneficial effects of fruit and vegetable intake on markers of inflammation and oxidative stress are already present by early adolescence and provide support for the Dietary Guidelines for Americans "to consume five or more servings per day" of fruits and vegetables to promote beneficial cardiovascular health.

Clonidine, moxonidine, folic acid, and mecobalamin improve baroreflex function in stroke-prone, spontaneously hypertensive rats

AIM

To investigate the effect of clonidine, moxonidine, folic acid, and mecobalamin on arterial baroreflex (ABR) function in stroke-prone spontaneously hypertensive rats (SHR-SP) and the possible mechanisms involved.

METHODS

Eighty-one SHR-SP were divided into 7 groups. Four groups were designated for the intragastric (ig) administration of clonidine (1.0 and 10.0 microg/kg), moxonidine (0.1 and 1.0 mg/kg), folic acid (1.0 mg/kg), and mecobalamin (1.0 mg/kg). Three groups were for the intracerebroventricular (icv) injection of clonidine (4 microg/4 microL), moxonidine (5 microg/4 microL), and mecobalamin (20 microg/4 microL). Blood pressure (BP) was recorded in the conscious state for 30 min and baroreflex sensitivity (BRS) was determined respectively before and after drug administration.

RESULTS

Clonidine and moxonidine significantly decreased BP, prolonged the heart period (HP), and increased BRS when administered as either ig or icv injections. Both BP and HP were unchanged by ig folic acid or mecobalamin injection. However, BRS was significantly increased by both.

CONCLUSION

Clonidine, moxonidine, folic acid, and mecobalamin improved impaired ABR function in SHR-SP. The central mechanism was involved in this effect of either clonidine or moxonidine. Mecobalamin improved ABR function through the peripheral mechanism.

Folate, vitamin B12 and total homocysteine levels in neonates from Brazil

OBJECTIVE

To determine folates, vitamin B12 and total homocysteine levels among neonates from mothers of low or high socioeconomic status.

DESIGN

We carried out a cross-sectional transversal study comprising 143 neonates from two maternity hospitals in the city of Salvador, Northeast of Brazil. Cord blood samples were obtained at the time of delivery from newborns from low (group 1, n=77) or high (group 2, n=66) socioeconomic status. The vitamin B12 and folates were analyzed by electrochemiluminescence immunoassay and by a competitive test using a natural folate-binding protein (FBP), respectively. Total homocyteine levels were measured by fluorescence polarization immunoassay. Maternal environmental risk factors for pregnancy complications were obtained from all mothers.

RESULTS

Only 2% of women from group 1 received prenatal care/vitamin supplementation, whereas almost all mothers from group 2 (96%) were properly followed. Anemia and/or infections pre- or during pregnancy was more prevalent among mothers of babies from group 1. Folate levels among newborns from group 1 and 2 were 7.38+/-2.71 and 8.83+/-4.06 ng/ml, respectively. No difference in the vitamin B12 levels was determined between groups. In addition, tHcy serum levels were higher among newborns from group 1 compared to those from group 2 (8.54+/-4.06 vs 6.35+/-1.33 micromol/l, respectively; P=0.005).

CONCLUSION

These results demonstrate that unprivileged young woman has limited accesses to prenatal care, present high-risk factors that hamper both maternal and newborn health. Maternal and newborn health status could be improved by simply reinforcing the use of folate-enriched diet. The work presented illustrates the challenges that developing countries have to face in order to provide preventive adequate health care to the population at large.

Total plasma homocysteine, folate, and vitamin B12 status in healthy Iranian adults: the Tehran homocysteine survey (2003-2004)/a cross-sectional population based study

Background

Elevated plasma total homocysteine is an independent risk factor for cardiovascular disease and a sensitive marker of the inadequate vitamin B12 and folate insufficiency. Folate and vitamin B12 have a protective effect on cardiovascular disease. This population based study was conducted to evaluate the plasma total homocysteine, folate, and vitamin B12 in healthy Iranian individuals.

Methods

This study was a part of the Cardiovascular Risk Factors Survey in the Population Lab Region of Tehran University has been designed and conducted based on the methodology of MONICA/WHO Project. A total of 1214 people aged 25–64 years, were recruited and assessed regarding demographic characteristics, homocysteine, folate, and vitamin B12 levels with interview, questionnaires, examination and blood sampling. Blood samples were gathered and analyzed according to standard methods.

Results

The variables were assessed in 1214 participants including 428 men (35.3%) and 786 women (64.7%). Age-adjusted prevalence of hyperhomocysteinemia (Hcy≥15 μmol/L) was 73.1% in men and 41.07% in women (P < 0.0001). Geometric mean of plasma homocysteine was 19.02 ± 1.46 μmol/l in men and 14.05 ± 1.45 μmol/l in women (P < 0.004) which increased by ageing. Age-adjusted prevalence of low serum folate level was 98.67% in men and 97.92% in women. Age-adjusted prevalence of low serum vitamin B12 level was 26.32% in men and 27.2% in women. Correlation coefficients (Pearson's r) between log tHcy and serum folate, and vitamin B12 indicated an inverse correlation (r = -0.27, r = -0.19, P < 0.0001, respectively).

Conclusion

These results revealed that the prevalence of hyperhomocysteinemia, low folate and vitamin B12 levels are considerably higher than other communities. Implementation of preventive interventions such as food fortification with folic acid is necessary.

Endothelial cell dysfunction: can't live with it, how to live without it

Endothelial cell dysfunction is emerging as an ultimate culprit for diverse cardiovascular diseases and cardiovascular complications of chronic renal diseases, yet the definition of this new syndrome, its pathophysiology, and therapy remain poorly defined. Here, I summarize some molecular mechanisms leading from hyperhomocystinemia, elevated asymmetric dimethylarginine, and advanced glycolation end product-modified protein level to the proatherogenic, prothrombogenic, and proinflammatory endothelial phenotype and offer a model of endothelial dysfunction based on the interconnectedness of diverse functions. Finally, several therapeutic strategies to prevent and correct endothelial dysfunction are discussed in the light of uncertainty of their action modulated by the endothelial dysfunction per se.

Comparative analysis of serum homocysteine, folic acid and Vitamin B12 levels in patients with noise-induced hearing loss

OBJECTIVE

The aim of the present study was to determine the levels of homocysteine, folic acid, and Vitamin B12 in subjects with noise-induced hearing loss. Furthermore, possible links between these parameters and noise-induced hearing loss were aimed to be evaluated.

METHODS

In the present study, blood samples were obtained from all subjects after overnight fasting for biochemical analysis. We examined the levels of homocysteine, Vitamin B12 and folic acid levels in subjects with noise-induced hearing loss. Twenty-eight male patients with noise-induced hearing loss (mean age 37 +/- 5 year) were included in the study group whereas the control group was composed of 32 healthy male volunteers (mean age 36 +/- 4 year).

RESULTS

It was found that homocysteine levels of subjects with noise-induced hearing loss as significantly high compared to healthy controls (P < 0.05). On the other hand, Vitamin B12 and folic acid levels of patients with noise-induced hearing loss were determined to be significantly low compared to the controls (P < 0.05 and < 0.01, respectively).

CONCLUSION

Our findings indicate that there might be a link between increased homocysteine levels and noise-induced hearing loss. Since increased homocysteine levels cause elevated levels of free radicals in addition to its atherogenic and thrombogenic effects. Further experimental studies are needed to decipher how this relationship is linked.

Effect of folate-binding protein on intestinal transport of folic acid and 5-methyltetrahydrofolate across Caco-2 cells

BACKGROUND

Milk products are a potential matrix for fortification with synthetic folic acid or natural 5-methyltetrahydrofolate (5-CH3-H4folate) to enhance the daily folate intake. In milk, folate occurs bound to folate-binding proteins (FBP). Our previous studies with an in vitro gastrointestinal model showed that 70% of the initial FBP content of the milk product was retained in the duodenal lumen. While folic acid remained bound to FBP after gastric passage, 5-CH3-H4folate was mainly present as free folate in the duodenal lumen.

AIM OF THE STUDY

To investigate the effect of FBP on the absorption of folic acid and 5-CH3-H4folate from the intestinal lumen.

METHODS

The transport of [3H]-folic acid and [14C]-5-CH3-H4folate across enterocytes was studied in the presence or absence of bovine FBP using monolayers of Caco-2 cells grown on semi-permeable inserts in a two-compartment model. The apparent permeability coefficients (P(app)) of folic acid and 5-CH3-H4folate were determined and compared with the permeability of reference compounds for low (mannitol) and high (caffeine) permeability.

RESULTS

The transport from the apical to the basolateral side of the Caco-2 cells was higher (P < 0.05) for folic acid (P(app) = 1.7*10(-6) cm/s) than for 5-CH3-H4folate (P(app) = 1.4*10(-6) cm/s) after 2 h incubation to 1 microM folic acid or 5-CH3-H4folate test solutions (pH 7). The permeability of folic acid and 5-CH3-H4folate across Caco-2 monolayers appeared to be higher (P < 0.05) than that of mannitol (P(app) = 0.5*10(-6) cm/s) but lower (P < 0.05) than that of caffeine (P(app) = 34*10(-6) cm/s). The addition of FBP to the medium led to a lower (P < 0.05) intestinal transport and cellular accumulation of folic acid and 5-CH3-H4folate.

CONCLUSIONS

Compared to the reference compounds, folic acid and 5-CH3-H4folate showed a moderate permeability across Caco-2 cells, which indicates that folate absorption from the intestinal lumen is not likely to be complete. The intestinal transport of folic acid and 5-CH3-H4folate was found to be dependent on the extent of binding to FBP at the luminal side of the cells.

Serum folate and homocysteine and the incidence of acute coronary events: the Kuopio Ischaemic Heart Disease Risk Factor Study

BACKGROUND

Several, but not all, prospective studies have shown that low folate intakes, low circulating folate concentrations, or high plasma total homocysteine (tHcy) concentrations are associated with an increased risk of coronary artery disease (CAD).

OBJECTIVE

We examined the relations of both serum folate and serum tHcy concentrations with acute coronary events in middle-aged men from eastern Finland who had no CAD at baseline.

DESIGN

In a population-based prospective cohort study, 1027 men aged 46-64 y were examined in 1991-1993 as part of the Kuopio Ischaemic Heart Disease Risk Factor Study. During an average follow-up of 7.7 y (7900 person-years of follow-up), 114 acute coronary events were observed in 61 men who had no previous history of CAD (n = 810).

RESULTS

In a Cox model, compared with men whose serum folate concentrations were in the lowest tertile, those whose concentrations were in the highest tertile had a risk factor-adjusted relative risk of acute coronary events of 0.35 (95% CI: 0.17, 0.73; P = 0.005). Serum tHcy concentrations were not significantly associated with the risk of acute coronary events (for the highest tertile compared with the lowest, adjusted relative risk = 1.03; 95% CI: 0.57, 1.87; P = 0.932).

CONCLUSIONS

The results of this prospective cohort study do not support the hypothesis that a high circulating tHcy concentration is a risk factor for acute coronary events in a male population free of prior heart disease. However, they do suggest that moderate-to-high serum folate concentrations are associated with a greatly reduced incidence of acute coronary events.

The binding of folic acid and 5-methyltetrahydrofolate to folate-binding proteins during gastric passage differs in a dynamic in vitro gastrointestinal model

Despite its low natural folate concentration, milk is responsible for 10-15% of the daily folate intake in countries with a high dairy consumption. Milk products can be considered as a potential matrix for folate fortification, e.g., with synthetic folic acid, to enhance the daily intake of folate. In untreated milk, the natural folate, 5-methyltetrahydrofolate (5-CH3-H4folate), is bound to folate-binding proteins (FBP). In this study, the extent of binding to FBP for folic acid and 5-CH3-H4folate was investigated in a dynamic in vitro model simulating human gastric passage. Protein binding of folic acid and 5-CH3-H4folate was characterized using gel-exclusion chromatography. Before gastric passage, folic acid and 5-CH3-H4folate were bound mainly to FBP (76-79%), whereas 7% was free. Folic acid remained bound to FBP to a similar extent after gastric passage. For 5-CH3-H4folate, the FBP-bound fraction gradually decreased from 79 to 5% and the free fraction increased from 7 to 93%. Although folic acid enters the proximal part of the intestine bound to FBP, 5-CH3-H4folate appears to be present mainly as free folate in the duodenal lumen. The stability of FBP was similar in both folate/FBP mixtures, i.e., 70% of the initial FBP content was retained after gastric passage. This study indicated that FBP are partly stable during gastric passage but have different binding characteristics for folic acid and 5-CH3-H4folate in the duodenal lumen. This could result in different bioavailability from folic acid- and 5-CH3-H4folate-fortified milk products.

Folic acid and 5-methyltetrahydrofolate in fortified milk are bioaccessible as determined in a dynamic in vitro gastrointestinal model

Dairy products are a potential matrix for folate fortification to enhance folate consumption in the Western world. Milk folate-binding proteins (FBP) are especially interesting because they seem to be involved in folate bioavailability. In this study, folate bioaccessibility was investigated using a dynamic computer-controlled gastrointestinal model [TNO gastrointestinal model (TIM)]. We used both ultrahigh temperature (UHT)-processed milk and pasteurized milk, differing in endogenous FBP concentrations and fortified with folic acid or 5-methyltetrahydrofolate (5-CH(3)-H(4)folate). To study FBP stability during gastrointestinal passage and the effect of additional FBP on folate bioaccessibility, FBP-fortified UHT and pasteurized milk products were also tested. Folate bioaccessibility and FBP stability were measured by taking samples along the compartments of the gastrointestinal model and measuring their folate and FBP concentrations. Folate bioaccessibility from folic acid-fortified milk products without additional FBP was 58-61%. This was lower (P < 0.05) than that of the 5-CH(3)-H(4)folate-fortified milk products (71%). Addition of FBP reduced (P < 0.05) folate bioaccessibility from folic acid-fortified milk (44-51%) but not from 5-CH(3)-H(4)folate-fortified milk products (72%). The residual FBP levels in the folic acid- and 5-CH(3)-H(4)folate-fortified milk products after gastrointestinal passage were 13-16% and 0-1%, respectively, of the starting amounts subjected to TIM. In conclusion, milk seems to be a suitable carrier for folate, because both folic acid and 5-CH(3)-H(4)folate are easily released from the matrix and available for absorption. However, our results suggest that folic acid remains partly bound to FBP during passage through the small intestine, which reduces the bioaccessibility of folic acid from milk in this model.

Effects of vitamin supplementation and hyperhomocysteinemia on atherosclerosis in apoE-deficient mice

It has been demonstrated that hyperhomocysteinemia (HHcy) accelerates atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice. In this study, vitamin-defined chow diets were used to induce HHcy in apoE(-/-) mice in an attempt to identify possible pathogenic pathways. Six-week-old female apoE(-/-) mice were divided into seven groups: vitamin-defined purified chow diet alone (control), or same diet supplemented with either D,L-homocysteine (upward arrow Hcy) or L-homocystine (upward arrow Hcy-Hcy), or diet high in L-methionine (upward arrow Met), or diet high in B-vitamins (upward arrow vitamin), or diets deficient in folate (downward arrow folate) or vitamin B(6) ( downward arrow B(6)). Eighteen weeks later, plasma total homocysteine (tHcy), lipids and atherosclerotic plaque burden (aortic root, aortic arch, and brachiocephalic trunk) were measured. tHcy levels were similar in the upward arrow vitamin, downward arrow folate, downward arrow B(6) and control groups (9.2-10.1 micromol/l, NS), but elevated mildly in the upward arrow Hcy-Hcy group (16.1 micromol/l) and moderately in the upward arrow Met and upward arrow Hcy groups (53.6 and 51.5 micromol/l, respectively). Mice in the latter two groups had significantly more atherosclerosis in the aortic root. Although B vitamin-supplementation failed to lower tHcy levels, mice had less atherosclerosis in the aortic arch. In summary, dietary methionine and homocysteine, but not homocystine, enhanced the development of atherosclerosis. Supplementation with B vitamins appeared to confer homocysteine-independent protection against atherosclerosis. These results suggest that (1) there may be a threshold level below which homocysteine is not atherogenic; (2) the atherogenic effect of HHcy may be mediated via an intracellular pathway; and/or (3) the anti-atherogenic effect of B vitamins in normohomocysteinemic mice is independent of tHcy levels.

Betaine supplementation lowers plasma homocysteine in healthy men and women

Elevated levels of plasma total homocysteine are associated with a higher risk of cardiovascular disease. Betaine and 5-methyltetrahydrofolate can remethylate homocysteine into methionine via independent reactions. We determined the effect of daily betaine supplementation, compared with both folic acid and placebo, on plasma concentrations of total homocysteine after an overnight fast and after methionine loading in men and women with mildly elevated homocysteine. Groups of twelve subjects ingested 6 g betaine, 800 micro g folic acid with 6 g placebo or 6 g placebo each day for 6 wk. A methionine-loading test (i.e., ingestion of 100 mg L-methionine/kg body mass) was performed before and after 6 wk of supplementation. Fasting plasma homocysteine decreased by 1.8 micro mol/L (95% confidence interval [CI]: -3.6, 0.0, P < 0.05) in the betaine group and by 2.7 micro mol/L (95% CI: -4.5, -0.9, P < 0.05) in the folic acid group. These changes are relative to the change in the placebo group, in which fasting plasma homocysteine rose by 0.5 micro mol/L. Furthermore, betaine suppressed the total area under the plasma homocysteine-time curve after methionine loading by 221 micro mol. 24 h/L (95% CI: -425, -16, P < 0.05) compared with placebo, whereas folic acid had no effect. In conclusion, betaine appears to be highly effective in preventing a rise in plasma homocysteine concentration after methionine intake in subjects with mildly elevated homocysteine. It is not known whether this potential of betaine to "stabilize" circulating homocysteine concentrations lowers the risk of cardiovascular disease.

Influence of reporting error on the relation between blood folate concentrations and reported folic acid-containing dietary supplement use among reproductive-aged women in the United States

BACKGROUND

Folic acid intake is the most important predictor of blood folate concentrations among nonpregnant women, but the reporting of folic acid-containing supplement use is subject to error.

OBJECTIVE

We assessed the effect of reporting error of supplement use on blood folate concentrations.

DESIGN

Data from the third National Health and Nutrition Examination Survey were analyzed. Respondents to that survey were asked twice about supplement use: ie, during the household interview, to recall use in the previous month, and during the physical examination, to recall use in the previous 24 h. To examine the effect of error reporting, we classified women (aged 15-44 y) into 5 groups according to supplement use in the previous month (nonusers, those ingesting < 400 micro g/d, and those ingesting >or= 400 micro g/d) and in the 24 h before the physical examination (yes or no). We expected nonappreciable differences in red blood cell (RBC) folate concentration by status of 24-h recall within the same category of previous-month use because RBC folate reflects long-term average consumption. We calculated covariate-adjusted means of serum and RBC folate concentrations.

RESULTS

Among women who reported average daily use of >or= 400 micro g folic acid in the previous month, the adjusted mean RBC folate was 436.5 nmol/L (95% CI: 406.7, 466.3 nmol/L) in those who did not take the supplement in the previous 24 h and 519.7 nmol/L (95% CI: 496.2, 543.2 nmol/L) in those who did do so (P < 0.01). This significant difference indicates apparently erroneous reporting of supplement use in the previous month by some participants.

CONCLUSION

The effect of reporting error on blood folate concentrations is important in interpreting survey results, evaluating health education campaigns, and identifying populations needing special education programs.

Homocysteine and atherothrombosis

Atherosclerosis with or without thrombosis superimposed is the most frequent cause of ischemic heart disease (IHD), peripheral arterial disease, and a main cause of stroke. Conflicting results have been reported in genetic, observational, and experimental studies on the relationship between homocysteine and these atherothrombotic diseases. Although cardiovascular complications are common in homocystinuric patients (severe hyperhomocysteinemia), IHD, the most frequent manifestation of atherothrombosis in the general population, appears to be rare. On the basis of findings in individuals with hyperhomocysteinemia of genetic origin, there is in fact no clear evidence for a causal role of homocysteine in the pathogenesis of atherothrombotic disease, and the positive association between plasma homocysteine and IHD observed in many, but not all epidemiologic studies does not prove causality. To infer causality from observational studies, there should be a temporal, consistent, strong, independent, graded (dose-response effect), and duration-dependent relationship between exposure and outcomes, and a biologically plausible mechanism should exist. The relationship between plasma homocysteine levels and IHD does not fulfill these criteria beyond reasonable doubt. In the general population, plasma homocysteine levels are to a great extent determined by dietary habits, and plasma homocysteine could be a marker, or a consequence, of atherothrombosis and/or risk-associated behavior (e.g., a diet low in fruits and vegetables) rather than a cause of atherothrombosis. Experimentally, hyperhomocysteinemia is not in itself atherogenic in normal animals with relatively low plasma cholesterol levels. The homocysteine theory of atherosclerosis should be tested more thoroughly in hypercholesterolemic animals that develop atherosclerosis spontaneously to determine whether elevated plasma homocysteine levels are harmful under atherogenic conditions. A causal role of homocysteine in atherothrombotic disease remains to be established.

Modification of brain aging and neurodegenerative disorders by genes, diet, and behavior

Multiple molecular, cellular, structural, and functional changes occur in the brain during aging. Neural cells may respond to these changes adaptively, or they may succumb to neurodegenerative cascades that result in disorders such as Alzheimer's and Parkinson's diseases. Multiple mechanisms are employed to maintain the integrity of nerve cell circuits and to facilitate responses to environmental demands and promote recovery of function after injury. The mechanisms include production of neurotrophic factors and cytokines, expression of various cell survival-promoting proteins (e.g., protein chaperones, antioxidant enzymes, Bcl-2 and inhibitor of apoptosis proteins), preservation of genomic integrity by telomerase and DNA repair proteins, and mobilization of neural stem cells to replace damaged neurons and glia. The aging process challenges such neuroprotective and neurorestorative mechanisms. Genetic and environmental factors superimposed upon the aging process can determine whether brain aging is successful or unsuccessful. Mutations in genes that cause inherited forms of Alzheimer's disease (amyloid precursor protein and presenilins), Parkinson's disease (alpha-synuclein and Parkin), and trinucleotide repeat disorders (huntingtin, androgen receptor, ataxin, and others) overwhelm endogenous neuroprotective mechanisms; other genes, such as those encoding apolipoprotein E(4), have more subtle effects on brain aging. On the other hand, neuroprotective mechanisms can be bolstered by dietary (caloric restriction and folate and antioxidant supplementation) and behavioral (intellectual and physical activities) modifications. At the cellular and molecular levels, successful brain aging can be facilitated by activating a hormesis response in which neurons increase production of neurotrophic factors and stress proteins. Neural stem cells that reside in the adult brain are also responsive to environmental demands and appear capable of replacing lost or dysfunctional neurons and glial cells, perhaps even in the aging brain. The recent application of modern methods of molecular and cellular biology to the problem of brain aging is revealing a remarkable capacity within brain cells for adaptation to aging and resistance to disease.

The role of risk factors in the development of atherosclerosis

Our understanding of risk factors for atherogenesis has changed significantly over the last decade. In addition to better grasp of the mechanism of action of the "classic" (causal) risk factors, a number of potentially important new factors has emerged. In this review we briefly summarize the evidence of the relation between atherosclerosis and the currently recognized causal risk factors, namely, age, smoking, LDL cholesterol, HDL cholesterol, hypertension, and diabetes. More emphasis has been put on description of the emerging entities such as atherogenic profile of plasma lipoproteins with discussion of LDL and HDL subclasses, Lp(a), homocysteine, and, last but not least, on the role of infection and inflammation in atherogenesis. Whenever possible, we tried to summarize the relevant lines of evidence such as epidemiological, pathological, genetic, and clinical trial data linking the specific factor with atherosclerosis.