Folic acid improves endothelial function in children and adolescents with type 1 diabetes

The Effects of Folate Supplementation on Diabetes Biomarkers Among Patients with Metabolic Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Although several studies have evaluated the effect of folate supplementation on diabetes biomarkers among patients with metabolic diseases, findings are inconsistent. This review of randomized controlled trials (RCTs) was performed to summarize the evidence on the effects of folate supplementation on diabetes biomarkers among patients with metabolic diseases. Randomized-controlled trials (RCTs) published in PubMed, EMBASE, Web of Science and Cochrane Library databases up to 1 September 2017 were searched. Two review authors independently assessed study eligibility, extracted data, and evaluated risk of bias of included studies. Heterogeneity was measured with a Q-test and with I2 statistics. Data were pooled by using the fix or random-effect model based on the heterogeneity test results and expressed as standardized mean difference (SMD) with 95% confidence interval (CI). A total of sixteen randomized controlled trials involving 763 participants were included in the final analysis. The current meta-analysis showed folate supplementation among patients with metabolic diseases significantly decreased insulin (SMD -1.28; 95% CI, -1.99, -0.56) and homeostasis model assessment of insulin resistance (HOMA-IR) (SMD -1.28; 95% CI, -1.99, -0.56). However, folate supplementation did not affect fasting plasma glucose (FPG) (SMD -0.30; 95% CI, -0.63, 0.02) and hemoglobin A1C (HbA1c) (SMD -0.29; 95% CI, -0.61, 0.03). The results of this meta-analysis study demonstrated that folate supplementation may result in significant decreases in insulin levels and HOMA-IR score, but does not affect FPG and HbA1c levels among patients with metabolic diseases.

Dietary sodium intake relates to vascular health in children with type 1 diabetes

BACKGROUND AND OBJECTIVE

Children with type 1 diabetes (T1D) have vascular dysfunction and frequently struggle to adhere to dietary recommendations. Limited data exist for the vascular consequences of poor diet quality in children. We aimed to evaluate the association between dietary components and vascular function in children with T1D.

METHODS

Cross-sectional study including 90 children (13.6 [3.5] years, 41 boys) with T1D. They had evaluation of dietary micro and macronutrients (Australian Child and Adolescent Eating Survey), vascular endothelial and smooth muscle function (flow-mediated dilatation and glyceryl trinitrate mediated dilatation [GTN], respectively), clinical and biochemical variables.

RESULTS

Children had a sodium intake of 3.013 (0.76) (mean [SD]) g/day. Vascular smooth muscle dysfunction, as measured by GTN, related to higher daily sodium intake (r = -0.31, P = .003), independent of the inverse relationships between GTN and total energy (r = -0.30, P = .005) and fat intake (r = -0.28, P = .007). Multiregression model showed that an increase in 1 g of daily sodium intake was independently associated with a deterioration of 3 percentage units in GTN (95% CI -4.3, -0.9; P = .003). There was an association between sodium intake and systolic blood pressure after adjustment for age and gender (regression coefficient 2.4; 95% CI 0.5, 4.3; P = .01).

CONCLUSIONS

High dietary sodium intake in children with T1D is common and relates to vascular dysfunction, independently of other dietary intake, blood pressure, and glycemic control.

Effect of Metformin on Vascular Function in Children With Type 1 Diabetes: A 12-Month Randomized Controlled Trial

CONTEXT

Children with type 1 diabetes have vascular dysfunction preceding atherosclerosis. Early interventions are needed to reduce cardiovascular disease.

OBJECTIVE

To evaluate the effect of metformin on vascular function in children with type 1 diabetes.

DESIGN

Twelve-month double-blind, randomized, placebo-controlled trial.

SETTING

Tertiary pediatric diabetes clinic.

PARTICIPANTS

Ninety children (8 to 18 years of age), >50th percentile body mass index (BMI), with type 1 diabetes.

INTERVENTION

Metformin (up to 1 g twice a day) or placebo.

MAIN OUTCOME MEASURE

Vascular function measured by brachial artery ultrasound [flow-mediated dilatation/glyceryl trinitrate-mediated dilatation (GTN)].

RESULTS

Ninety participants were enrolled [41 boys, 13.6 (2.5) years of age, 45 per group], 10 discontinued intervention, and 1 was lost to follow-up. On metformin, GTN improved, independent of glycosylated hemoglobin (HbA1c), by 3.3 percentage units [95% confidence interval (CI) 0.3, 6.3, P = 0.03] and insulin dose reduced by 0.2 U/kg/d (95% CI 0.1, 0.3, P = 0.001) during 12 months, with effects from 3 months. Metformin had a beneficial effect on HbA1c at 3 months (P = 0.001) and difference in adjusted HbA1c between groups during 12 months was 1.0%; 95% CI 0.4, 1.5 (10.9 mmol/mol; 95% CI 4.4, 16.4), P = 0.001. There were no effects on carotid/aortic intima media thickness, BMI, lipids, blood pressure, or other cardiovascular risk factors. Median (95% CI) adherence, evaluated by electronic monitoring, was 75.5% (65.7, 81.5), without group differences. More gastrointestinal side effects were reported on metformin (incidence rate ratio 1.65, 95% CI 1.08, 2.52, P = 0.02), with no difference in hypoglycemia or diabetic ketoacidosis.

CONCLUSIONS

Metformin improved vascular smooth muscle function and HbA1c, and lowered insulin dose in type 1 diabetes children. These benefits and good safety profile warrant further consideration of its use.

Targeting vascular (endothelial) dysfunction

Cardiovascular diseases are major contributors to global deaths and disability-adjusted life years, with hypertension a significant risk factor for all causes of death. The endothelium that lines the inner wall of the vasculature regulates essential haemostatic functions, such as vascular tone, circulation of blood cells, inflammation and platelet activity. Endothelial dysfunction is an early predictor of atherosclerosis and future cardiovascular events. We review the prognostic value of obtaining measurements of endothelial function, the clinical techniques for its determination, the mechanisms leading to endothelial dysfunction and the therapeutic treatment of endothelial dysfunction. Since vascular oxidative stress and inflammation are major determinants of endothelial function, we have also addressed current antioxidant and anti-inflammatory therapies. In the light of recent data that dispute the prognostic value of endothelial function in healthy human cohorts, we also discuss alternative diagnostic parameters such as vascular stiffness index and intima/media thickness ratio. We also suggest that assessing vascular function, including that of smooth muscle and even perivascular adipose tissue, may be an appropriate parameter for clinical investigations.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Effects of a dietary strawberry powder on parameters of vascular health in adolescent males

Previous studies have shown that the intake of freeze-dried strawberry powder (FDSP) improves select markers of cardiovascular health in adults with cardiovascular risk factors; however, whether these improvements can be observed in at-risk adolescents is unknown. A randomised, double-blind, cross-over study enrolled twenty-five overweight or obese males, aged 14-18 years, to consume 50 g of a FDSP or a control powder, daily for 1 week. Before and after each test period, measures of microvascular function, plasma nitrate/nitrite, platelet reactivity and blood lipids were collected at baseline and acutely 1 h after FDSP intake. Acute plasma nitrate/nitrite levels increased 1 h after consuming the FDSP during Study Visit 1 before daily FDSP intake (P<0·001) and during Study Visit 2 after 1 week of FDSP intake (P<0·001) compared with control powder intake. As a group, fasting nitrate/nitrite levels did not significantly change after 1 week of control or FDSP intake. However, for those individuals where fasting nitrate levels increased after short-term FDSP intake compared with controls, an increase in reactive hyperaemia index (RHI) was observed (P=0·014), whereas RHI was unchanged in those individuals who did not have a significant increase in nitrate (P=0·396). Taken together, these data support the concept that strawberries can provide vascular health benefits to heavier adolescent males.

Folic acid improves endothelial dysfunction in type 2 diabetes - an effect independent of homocysteine-lowering

Diabetes is associated with endothelial dysfunction, which in part may be related to uncoupling of the endothelial nitric oxide (NO) synthase enzyme, thus reducing the availability of NO. As folates may potentially reverse the uncoupling of NO synthase, we wanted to determine whether folic acid supplementation could modulate endothelial function and markers of inflammation in patients with type 2 diabetes without vascular disease. Nineteen patients with type 2 diabetes were treated with folic acid (10 mg/day for 2 weeks) versus placebo in a randomized, placebo-controlled, cross-over study with an 8-week washout period between treatments. Fasting endothelium-dependent flow-mediated dilatation (FMD) of the brachial artery, endothelium-independent nitroglycerin-mediated dilatation (NMD), plasma homocysteine, serum lipids, folate, and inflammatory markers (high-sensitivity C-reactive protein, soluble intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, interleukin-18, tumor necrosis factor-alpha) were assessed after each 2-week treatment period. Folic acid supplementation significantly increased folate levels and lowered plasma homocysteine levels. Folic acid significantly improved FMD compared to placebo (5.8 4.8% vs 3.2 2.7%, p 0.02). There were no significant effects of folic acid supplementation on lipids, NMD, or the inflammatory markers. There was no relationship between the change in homocysteine and the improvement in FMD. Thus, 2 weeks of folic acid supplementation can improve endothelial dysfunction in type 2 diabetics independent of homocysteine-lowering, but does not modulate markers of inflammation.

Abnormalities of vascular structure and function in pediatric hypertension

Hypertension is associated with adverse cardiovascular (CV) events in adults. Measures of vascular structure and function, including increased carotid intima-media thickness (cIMT) and elevated arterial stiffness predict hard CV events in adulthood. Newer data suggest that abnormalities in target organ damage are occurring in adolescents and young adults with high blood pressure. In this review, we discuss the techniques for measuring vascular dysfunction in young people and the evidence linking blood pressure levels to this type of target organ damage.

Impact of Health Status and Lifestyle Modifications on Vascular Structure and Function in Children and Adolescents

Until recently cardiovascular disease is often thought of as a disease that manifests itself during middle age. Researchers and clinicians have begun to realize that the initial signs of cardiovascular disease begin early on in childhood with changes present in both vascular structure and function. This increased recognition has resulted in considerable effort to develop accurate and reliable methods to measure as well as track changes in vascular structure and function applicable to study this process in children and adolescents. Certain genetic abnormalities and chronic diseases, which present or emerge in childhood often result in meaningful changes to vascular structure and function, which aid in our understanding of the vascular disease process. In this review, we will discuss different methods of assessing vascular structure and function, the diseases in childhood associated with decrements and maladaptive changes in the vascular system, and whether modification of lifestyle (ie, weight loss, dietary and/or exercise changes) can affect vascular structure and function in children.

A NOS3 polymorphism determines endothelial response to folate in children with type 1 diabetes or obesity

OBJECTIVE

To determine the effect of polymorphisms in NOS3 and folate pathway enzymes on vascular function and folate status and endothelial response to folate in children with diabetes or obesity.

STUDY DESIGN

A total of 244 subjects (age 13.8 ± 2.8 years, 125 males) were studied for NOS3 and/or folate pathway polymorphisms using polymerase chain reaction/restriction fragment length polymorphism, including at baseline: 139 with type 1 diabetes; 58 with obesity; and 47 controls. The effect of NOS3 genotype on endothelial response to folate (5 mg) was assessed in 85 subjects with diabetes and 28 obese subjects who received active treatment during intervention trials. Vascular function (flow-mediated dilatation [FMD] and glyceryl trinitrate-mediated dilatation), clinical, and biochemical measurements were assessed at baseline and 8 weeks in folate intervention studies.

RESULTS

Folate pathway enzyme and NOS3 polymorphisms did not significantly affect baseline vascular function. The polymorphism in intron 4 of endothelial nitric oxide synthase altered endothelial response to folate significantly: in subjects with diabetes FMD improved by 6.4 ± 5% (insertion carriers) vs 2.3 ± 6.6% (deletion carriers), P = .01; in obese subjects FMD improved by 1.8 ± 5.4% (insertion carriers) and deteriorated by -3.2 ± 7.2% (deletion carriers), P = .05. More subjects carrying the insertion normalized FMD after folate supplementation (insertion 64% vs deletion 28%, χ(2) = 10.14, P = .001).

CONCLUSIONS

A NOS3 polymorphism predicts endothelial response to folate in children with diabetes or obesity, with implications for vascular risk and folate intervention studies.

Effects of folic acid on renal endothelial function in patients with diabetic nephropathy: results from a randomized trial

Endothelial dysfunction has been shown to promote podocyte injury and albuminuria in diabetes, highlighting the importance of the interaction between renal endothelial cells and podocytes. Folic acid (FA) improves nitric oxide synthase (NOS) function and reduces progression of diabetic nephropathy in animal models. We tested whether high-dose FA treatment improves renal endothelial function and albuminuria in human subjects with incipient diabetic nephropathy. Following a double-blind, randomized, cross-over design, 28 patients with Type 2 diabetes and albuminuria were allocated to 4 weeks' treatment with placebo and high-dose FA (5 mg/day). Renal nitric oxide (NO) production determined as the response of renal plasma flow (RPF) to NOS inhibition with NG-monomethyl-L-arginine (L-NMMA) (4.25 mg/kg intravenously), renal oxidant stress as response of RPF to vitamin C infusion (3 mg/kg) and albuminuria were determined after each treatment phase. Neither the reduction in RPF to L-NMMA nor the increase in RPF to vitamin C infusion differed between treatment phases (ΔRPF to

L-NMMA

-74±71 ml/min per m2 during placebo compared with -63±56 ml/min per m2 during FA, P=0.57; ΔRPF to vitamin C: +93±118 ml/min per m2 compared with +94±108 ml/min per m2; P=0.70). In line with the lack of effect on the renal endothelium, albuminuria was not affected by FA treatment (110±179 mg/day during placebo compared with 87±146 mg/day during FA; P=0.12). High-dose FA treatment does not improve renal endothelial function and fails to reduce albuminuria in human subjects with diabetic nephropathy. Novel treatment options for oxidant stress and endothelial dysfunction in patients with diabetes are urgently needed.

Folic acid supplementation on homocysteine levels in children taking antiepileptic drugs: A randomized controlled trial

OBJECTIVES

To assess the level of homocysteine (tHcy) in children taking AEDs and to study whether daily oral supplementation of folic acid for 1 month will reduce the tHcy level.

MATERIALS AND METHODS

This was a double-blinded, randomized control trial conducted in Institute of Maternal and Child Health, Kozhikode, India. Totally 60 children were recruited and of them, 48 were enrolled. Of these children, 32 were assigned to the experimental group and 16 to the control group. Baseline data collection and tHcy estimation were done. One mg folic acid tablets were given to the experimental group and placebo tablets to the control group for 30 days. tHcy levels were re-estimated after 1 month follow-up. Statistical significance was tested by χ(2) test, and paired and unpaired t-tests, as appropriate. Correlation was tested by Pearson correlation test and P value less than 0.05 was taken as the cut-off for statistical significance.

RESULTS

Baseline plasma tHcy concentrations in both groups were comparable [11.90 (6.3) and 13.02 (2.4) μmol/l, respectively]. During the follow-up period, no increase in seizure episodes or no serious adverse reactions were noticed in either group. The reduction of tHcy in the experimental group was 1.92 μmol/l (P = 0.04) and in the control group, there was an increase of 1.05 μmol/l (P = 0.16).

CONCLUSIONS

In children on AED treatment, folic acid supplementation may reduce tHcy level and thus reduce CVD risk.

Does metformin improve vascular health in children with type 1 diabetes? Protocol for a one year, double blind, randomised, placebo controlled trial

BACKGROUND

Cardiovascular disease is the leading cause of mortality in Type 1 diabetes (T1D). Vascular dysfunction is an early and critical event in the development of cardiovascular disease. Children with T1D have vascular dysfunction therefore early interventions to improve vascular health are essential to reduce cardiovascular mortality in T1D. Metformin is an insulin sensitising agent which is known to improve vascular health outcomes in type 2 diabetes (T2D) and other individuals with insulin resistance. It has been used safely in children and adolescents with T2D for over 10 years. This study aims to assess the effect of metformin on vascular health in children with T1D.

METHODS/DESIGN

This study is a 12 month, double blind, randomised, placebo controlled trial to determine the effect of metformin on vascular health in children (age 8-18) with T1D. The sample size is 76 with 38 children in the metformin group and 38 children in the placebo group. Vascular health and biochemical markers will be measured at baseline, 3, 6 and 12 months. Vascular function will be measured using flow mediated dilatation and glyceryl trinitrate mediated dilatation of the brachial artery and vascular structure will be measured with carotid and aortic intima media thickness, using standardised protocols.

DISCUSSION

This study will be the first to investigate the effect of metformin on vascular health in children with T1D. It will provide important information on a potential intervention to improve cardiovascular morbidity and mortality in this population at high risk from cardiovascular disease.

TRIAL REGISTRATION

Australia New Zealand Clinical Trials Registry ACTRN12611000148976.

Folate fortification and supplementation do not provide vascular health benefits in type 1 diabetes

OBJECTIVE

To evaluate the lowest effective dose-response of folic acid on endothelial function in children with type 1 diabetes.

STUDY DESIGN

A randomized, double-blind, crossover, placebo-controlled trial was conducted in 20 children with type 1 diabetes (age range 10-18 years) after mandatory folate fortification in Australia. Each child received orally 4 interventions (1 per month)-3 folic acid doses (0.5, 2, and 5 mg) and 1 placebo dose--in random order. The primary outcome was 2-hour postintervention change in endothelial function measured with flow-mediated dilatation (FMD). Thirty-five children with type 1 diabetes from our folic acid interventional trial before folate fortification were used for comparison.

RESULTS

All children completed the study. There were no differences in baseline FMD or folate status between the visits. Folic acid supplementation increased serum folate (P = .0001) and red cell folate (P < .0001), but none of the doses improved FMD (P = .96). Baseline serum folate and red cell folate levels and FMD and glyceryl trinitrate-mediated dilatation were significantly higher in these children compared with children from our trial before mandatory folate fortification (P = .0001, .0001, .014, and .04, respectively).

CONCLUSIONS

Folate status and vascular function have improved in children with type 1 diabetes since the introduction of mandatory folate fortification, but the beneficial endothelial effects of additional folic acid are no longer present.

Adolescents with congenital adrenal hyperplasia because of 21-hydroxylase deficiency have vascular dysfunction

CONTEXT

Patients with congenital adrenal hyperplasia (CAH) because of 21-hydroxylase deficiency have multiple vascular risk factors. Young adults with CAH have increased intima media thickness, but there have been no studies of vascular function and structure in children with CAH.

OBJECTIVE

To establish whether children with CAH have reduced vascular function and increased carotid intima media thickness (cIMT) when compared to healthy and obese children.

DESIGN AND PATIENTS

Cross-sectional study of 14 patients (14.8 years ± 3.2, seven boys) with CAH secondary to 21-hydroxylase deficiency compared to 28 obese and 53 healthy controls.

MEASUREMENTS

All subjects had assessment of endothelial function flow-mediated dilatation, (FMD), smooth muscle function glyceryl tri-nitrate dilatation (GTN) and cIMT. Anthropometric data, resting blood pressure and biochemical variables were also measured.

RESULTS

Congenital adrenal hyperplasia subjects had significantly reduced FMD (4.5 ± 3.0% vs 7.5 ± 5.2%; P = 0.04) and GTN (17.2 ± 1.6% vs 28.4 ± 8.4%; P < 0.001) when compared to controls and the impairment was comparable to the obese cohort. There was no significant difference in cIMT between groups. CAH subjects had increased homoeostasis model of assessment-insulin resistance [HOMA-IR 2.5 (0.2-2.9) vs 1.8 (0.5-4.2); P = 0.04], waist-to-height ratio (0.47 ± 0.05 vs 0.44 ± 0.04; P = 0.02) and higher systolic blood pressure Z score (0.29 ± 0.9 vs-0.24 ± 0.64, P = 0.01) compared to healthy controls but not when compared to obese controls.

CONCLUSIONS

Subjects with CAH have evidence of vascular dysfunction by adolescence.

Endothelial dysfunction, inflammation, and oxidative stress in obese children and adolescents: markers and effect of lifestyle intervention

With an increasing prevalence, pediatric obesity is often a prelude to adulthood obesity, and represents a major public health issue. Comorbidities are very common and severe in obese adults, justifying the search for earlier markers or risk factors for cardiovascular diseases in obese children. Endothelial dysfunction has been found to be present in the early stages of atherosclerosis, and can be non-invasively assessed with widely accepted and well-standardized techniques at the macrocirculation level. Endothelial dysfunction at the microcirculation level is less documented in obese children. Obesity in children has been repeatedly and independently correlated to endothelial dysfunction, inflammation and oxidative stress markers, although the relationship between these factors remains to be investigated. However, this would not only allow substantial improvements in risk stratification, but also provide essential data regarding the evolution of endothelial dysfunction in childhood obesity, especially during puberty when pro-inflammatory and pro-oxidative changes, with relative insulin resistance, occur. Therapeutic strategies such as lifestyle interventions in early childhood obesity appear all the more necessary, optimally including both exercise and diet because of their known effects on inflammatory and oxidative stress markers, potentially reversing endothelial dysfunction.

Cardiovascular disease risk in young people with type 1 diabetes

Cardiovascular disease (CVD) is the most frequent cause of death in people with type 1 diabetes (T1D), despite modern advances in glycemic control and CVD risk factor modification. CVD risk identification is essential in this high-risk population, yet remains poorly understood. This review discusses the risk factors for CVD in young people with T1D, including hyperglycemia, traditional CVD risk factors (dyslipidemia, smoking, physical activity, hypertension), as well as novel risk factors such as insulin resistance, inflammation, and hypoglycemia. We present evidence that adverse changes in cardiovascular function, arterial compliance, and atherosclerosis are present even during adolescence in people with T1D, highlighting the need for earlier intervention. The methods for investigating cardiovascular risk are discussed and reviewed. Finally, we discuss the observational studies and clinical trials which have thus far attempted to elucidate the best targets for early intervention in order to reduce the burden of CVD in people with T1D.

Muscle microvascular recruitment predicts insulin sensitivity in middle-aged patients with type 1 diabetes mellitus

AIMS/HYPOTHESIS

Insulin delivery to muscle is rate-limiting for insulin's metabolic action and is regulated by insulin's own action to increase skeletal muscle blood flow and to recruit microvasculature. Microvascular dysfunction has been observed in insulin resistant states. We investigated the relation between insulin's action to recruit microvasculature and its metabolic action in type 1 diabetes.

METHODS

Near euglycaemia was obtained by an overnight insulin infusion during 17 inpatient admissions of participants with type 1 diabetes. This was followed by a 2 h 1 mU kg⁻¹ min⁻¹ euglycaemic-hyperinsulinaemic clamp. Microvascular blood volume (MBV) was assessed using contrast-enhanced ultrasound 10 min before and 30 min after starting the clamp.

RESULTS

We observed that, after overnight modest hyperinsulinaemia (average ≈ 286 pmol/l), MBV was positively related to the steady-state insulin sensitivity measured during the subsequent clamp (r = 0.62, p = 0.008). The more marked hyperinsulinaemia during the clamp (average steady-state insulin ≈ 900 pmol/l) increased MBV in the more insulin resistant participants within 30 min but not in the insulin sensitive participants. The change in MBV during the clamp was negatively correlated to the insulin sensitivity (r = -0.55, p = 0.022). As a result, MBV after 30 min of marked hyperinsulinaemia was comparable between the insulin sensitive and resistant participants.

CONCLUSIONS/INTERPRETATION

We conclude that moderate overnight hyperinsulinaemia recruited microvasculature in the more sensitive participants, while higher levels of plasma insulin were needed for more insulin resistant participants. This suggests that microvascular responsiveness to insulin is one determinant of metabolic insulin sensitivity in type 1 diabetes.

Oxidative stress and endothelial dysfunction: therapeutic implications

In a previous issue of Annals of Medicine, we presented evidence in support of the concept that an abnormally increased production of reactive oxygen species plays a central role in the genesis and progression of cardiovascular disease. While a number of preclinical lines of evidence support this concept, and despite the results of many studies suggesting a beneficial impact of antioxidant drugs on endothelial function, large clinical trials have failed to demonstrate a benefit of antioxidants on cardiovascular outcomes. Studies exploring the possibility that classical antioxidants such as vitamin C, vitamin E, selenium, or folic acid may improve the prognosis of patients with cardiac disease have substantially reported neutral-and occasionally negative-results. In contrast, medications such as statins, ACE inhibitors, certain β-blockers, or angiotensin I receptor blockers, which possess indirect 'ancillary' antioxidant properties, have been associated with beneficial effects in both preclinical studies and large clinical trials. The reasons for the failure of the 'direct' approach to antioxidant therapy, and for the success of the therapy with these drugs, are discussed in the present review.

Effects of oral folate supplementation on serum total homocysteine and cholesterol levels in hyperhomocysteinemic children

BACKGROUND

Hyperhomocysteinemia may be a risk factor for cardiovascular disease even among children. Increased levels of total serum homocysteine (tHcy) may initiate atherosclerosis by modulating increased cholesterol synthesis in the liver. Folate supplementation has been found to reduce homocysteine levels. However, no data have been reported about the relationship between folate supplementation and cholesterol levels in children.

METHODS

Twenty of 26 hyperhomocysteinemic (>95th percentile for age) children underwent a therapeutic intervention of 5 mg of oral folate supplementation twice per week for 2 months.

RESULTS

After the 2-month intervention with folate supplement, tHcy levels were statistically significantly decreased (P < .001), folate levels were significantly increased (P < .001), while total cholesterol levels were significantly improved from 183.8 (115-296 mg/dL) to 160.8 (109-265 mg/dL) (P < .05).

CONCLUSIONS

Folate supplementation may reduce tHcy, serum folate, and total serum cholesterol levels in hyperhomocysteinemic children.

The role of complementary and alternative therapies in pediatric diabetes

Complementary and alternative medicine (CAM), also referred to as holistic, or integrative, medicine, are terms that describe a heterogeneous collection of nontraditional therapies, from chemical substances, to biofeedback, to prayer. This review focuses on CAM in pediatric patients with type 1 and type 2 diabetes. CAM prevalence in this population and the specific modalities that have been studied in children are described. Randomized, placebo-controlled, prospective studies in young adults are evaluated for their applicability to pediatric patients. CAM's "complementary" role is emphasized, as there is evidence of significant morbidity when CAM replaces standard-of-care therapy.

Folic acid supplementation normalizes the endothelial progenitor cell transcriptome of patients with type 1 diabetes: a case-control pilot study

BACKGROUND

Endothelial progenitor cells play an important role in vascular wall repair. Patients with type 1 diabetes have reduced levels of endothelial progenitor cells of which their functional capacity is impaired. Reduced nitric oxide bioavailability and increased oxidative stress play a role in endothelial progenitor cell dysfunction in these patients. Folic acid, a B-vitamin with anti-oxidant properties, may be able to improve endothelial progenitor cell function. In this study, we investigated the gene expression profiles of endothelial progenitor cells from patients with type 1 diabetes compared to endothelial progenitor cells from healthy subjects. Furthermore, we studied the effect of folic acid on gene expression profiles of endothelial progenitor cells from patients with type 1 diabetes.

METHODS

We used microarray analysis to investigate the gene expression profiles of endothelial progenitor cells from type 1 diabetes patients before (n = 11) and after a four week period of folic acid supplementation (n = 10) compared to the gene expression profiles of endothelial progenitor cells from healthy subjects (n = 11). The probability of genes being differentially expressed among the classes was computed using a random-variance t-test. A multivariate permutation test was used to identify genes that were differentially expressed among the two classes. Functional classification of differentially expressed genes was performed using the biological process ontology in the Gene Ontology database.

RESULTS

Type 1 diabetes significantly modulated the expression of 1591 genes compared to healthy controls. These genes were found to be involved in processes regulating development, cell communication, cell adhesion and localization. After folic acid treatment, endothelial progenitor cell gene expression profiles from diabetic patients were similar to those from healthy controls. Genes that were normalized by folic acid played a prominent role in development, such as the transcription factors ID1 and MAFF. Few oxidative-stress related genes were affected by folic acid.

CONCLUSION

Folic acid normalizes endothelial progenitor cell gene expression profiles of patients with type 1 diabetes. Signaling pathways modulated by folic acid may be potential therapeutic targets to improve endothelial progenitor cell function.

Hs-CRP is associated with weight, BMI, and female sex but not with endothelial function in children with type 1 diabetes

BACKGROUND

Atherosclerosis is an inflammatory process, and high-sensitivity C-reactive protein (Hs-CRP), a marker of inflammation, predicts cardiovascular events in adults. Vascular endothelial and smooth muscle dysfunction, measurable precursors of atherosclerosis, begin in childhood. Therefore, we sought to determine if Hs-CRP is associated with vascular endothelial and smooth muscle dysfunction in children with type 1 diabetes mellitus (T1DM) and healthy control subjects.

METHODS

Hs-CRP and endothelial function assessed by flow-mediated dilatation (FMD) and smooth muscle function assessed by glyceryl-trinitrate (GTN)-induced dilatation were measured in 121 subjects with T1DM aged 14.1 (2.9) yr, of whom 31 were also studied at 4 and 8 wk, and in 33 healthy controls aged 14.2 (3.6) yr.

RESULTS

Hs-CRP did not differ between subjects with T1DM and healthy, age-matched controls. In both controls and subjects with T1DM, Hs-CRP did not relate to FMD or GTN at baseline or at intervals over 8 wk in T1DM. Hs-CRP did not change over time. In T1DM, but not healthy controls, Hs-CRP related to body mass index (BMI) z-score (r = 0.47, p < 0.001), weight z-score (r = 0.41, p < 0.001), and female sex (p = 0.008).

CONCLUSIONS

Hs-CRP is not associated with early vascular dysfunction in children with T1DM. However, in children and adolescents with T1DM, Hs-CRP was associated with female sex and children with higher BMI, suggesting that these groups may be at greater cardiovascular risk. Maintenance of a healthy BMI may be important in the prevention of vascular disease of T1DM.

The effect of long-term homocysteine-lowering on carotid intima-media thickness and flow-mediated vasodilation in stroke patients: a randomized controlled trial and meta-analysis

BACKGROUND

Experimental and epidemiological evidence suggests that homocysteine (tHcy) may be a causal risk factor for atherosclerosis. B-vitamin supplements reduce tHcy and improve endothelial function in short term trials, but the long-term effects of the treatment on vascular structure and function are unknown.

METHODS

We conducted a sub-study of VITATOPS, a randomised, double-blind, placebo-controlled intervention trial designed to test the efficacy of long term B-vitamin supplementation (folic acid 2 mg, vitamin B6 25 mg and vitamin B12 0.5 mg) in the prevention of vascular events in patients with a history of stroke. We measured carotid intima-medial thickness (CIMT) and flow-mediated dilation (FMD) at least two years after randomisation in 162 VITATOPS participants. We also conducted a systematic review and meta-analysis of studies designed to test the effect of B-vitamin treatment on CIMT and FMD.

RESULTS

After a mean treatment period of 3.9 +/- 0.9 years, the vitamin-treated group had a significantly lower mean plasma homocysteine concentration than the placebo-treated group (7.9 micromol/L, 95% CI 7.5 to 8.4 versus 11.8 micromol/L, 95% CI 10.9 to 12.8, p < 0.001). Post-treatment CIMT (0.84 +/- 0.17 mm vitamins versus 0.83 +/- 0.18 mm placebo, p = 0.74) and FMD (median of 4.0%, IQR 0.9 to 7.2 vitamins versus 3.0%, IQR 0.6 to 6.6 placebo, p = 0.48) did not differ significantly between groups. A meta-analysis of published randomised data, including those from the current study, suggested that B-vitamin supplements should reduce CIMT (-0.10 mm, 95% CI -0.20 to -0.01 mm) and increase FMD (1.4%, 95% CI 0.7 to 2.1%). However, the improvement in endothelial function associated with homocysteine-lowering treatment was significant in short-term studies but not in longer trials.

CONCLUSION

Although short-term treatment with B-vitamins is associated with increased FMD, long-term homocysteine-lowering did not significantly improve FMD or CIMT in people with a history of stroke.

Methylenetetrahydrofolate reductase and methionine synthase reductase gene polymorphisms and protection from microvascular complications in adolescents with type 1 diabetes

Folate status has been associated with endothelial dysfunction in adolescents with type 1 diabetes, and elevated total plasma homoocyst(e)ine (tHcy) is a risk for vascular disease in the non-diabetic population. Polymorphisms in genes involved in folate and homocysteine metabolism are implicated in vascular disease. We aimed to determine whether polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) genes are risk factors for early microvascular disease in a large group of adolescents with type 1 diabetes. Four hundred and eighty adolescents were screened annually for retinopathy and microalbuminuria for a median of 4 yr. Molecular analysis for the polymorphisms 677C-->T, 1298A-->C in MTHFR, and 66A-->G in MTRR was performed. The MTRR 66GG genotype reduced the risk for elevated albumin excretion rate (AER) (OR 0.47, CI 0.25, 0.88, p = 0.018) and showed a trend to reduced risk for microalbuminuria (OR 0.27, CI 0.06-1.21, p = 0.09). Survival without elevated AER was increased with the MTRR 66GG genotype (12.4 vs. 9.7 yr, p = 0.04) and with the MTHFR 1298CC genotype (15.2 vs. 10.2 yr, p = 0.007). Conversely, survival without retinopathy was reduced with the MTHFR 677TT and MTRR 66GG combined genotype (6.2 vs. 10.2 yr, p = 0.015). The MTRR 66GG and MTHFR 1298 CC genotypes may confer protection against early nephropathy, possibly because they are associated with lower tHcy. The MTHFR 677 TT was only related to earlier onset retinopathy in combination with MTRR 66GG.

Arterial function in youth: window into cardiovascular risk

Noninvasive measures of arterial function, such as intima-media thickness (IMT), endothelial function, and arterial stiffness are associated with and are prognostic of cardiovascular events in adults. Postmortem evidence, however, has established that the atherosclerotic process starts in childhood. Furthermore, cardiovascular morbidities in childhood disrupt arterial health and may lead to adverse outcomes in adulthood. Thus it is important to examine the developmental changes in IMT, endothelial function, and arterial stiffness in healthy youth in contrast to the arterial health profile of youth with cardiovascular morbidities and to examine the effect of lifestyle interventions. In healthy youth, IMT may increase slightly, arterial stiffness increases, but there is no change in endothelial function from 5 to 20 years of age. In youth with cardiovascular risk factors there are larger increases in IMT and arterial stiffness, and reductions in endothelial function compared with healthy youth. The reduced arterial function in youth with cardiovascular risk factors may be related to the atherosclerotic process. Exercise and physical activity appear to exert a protective effect on arterial function, and exercise training can improve arterial function in children with cardiovascular risk factors. Furthermore, although diet alone can improve arterial function in children, the combination of exercise and diet appears to be more effective than either intervention alone. Future studies need to focus on the mechanism by which exercise and diet improve arterial function, the most effective types of diet and exercise, and if intervening in childhood leads to favorable outcomes in adulthood.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

Folic acid does not improve endothelial function in obese children and adolescents

OBJECTIVE

Obese children have severe endothelial dysfunction as measured by flow-mediated dilation (FMD). We have shown that folic acid normalizes endothelial function in children with type 1 diabetes who have a similar degree of endothelial dysfunction but lower total plasma homocyst(e)ine (tHcy) and higher folate status. Our aim was to evaluate, for the first time, the effect of folate supplementation on endothelial dysfunction in obese children.

RESEARCH DESIGN AND METHODS

A total of 53 obese subjects (26 male, mean +/- SD age 13.3 +/- 2.2 years, and BMI Z score 2.29 +/- 0.25) participated in a randomized, double-blind, placebo-controlled, parallel trial of oral folic acid (5 mg/day) or placebo for 8 weeks. Before and after the intervention, we assessed endothelial function (FMD), smooth muscle function (glyceryl trinitrate-induced dilatation [GTN]), high-sensitivity C-reactive protein (hsCRP), tHcy, serum folate, red cell folate (RCF), and lipids.

RESULTS

There were no group differences at baseline. FMD did not change with the intervention (folic acid group pre- and postintervention: 6.42 +/- 5.03 and 6.56 +/- 4.79%, respectively, vs. placebo group: 5.17 +/- 3.54 and 5.79 +/- 4.26%, respectively; P = 0.6). Folate supplementation increased serum folate and RCF by 18.4 nmol/l (P < 0.001) and 240.1 nmol/l (P < 0.001), respectively, and decreased tHcy by 0.95 microl (P = 0.008). The intervention did not change GTN, hsCRP, or lipids.

CONCLUSIONS

Folic acid supplementation does not improve endothelial function in obese children without diabetes despite increasing folate status and reducing tHcy. This is in contrast to the response to folate in children with type 1 diabetes.

Obesity, metabolic syndrome, and cardiovascular disease

Early childhood overweight and obesity have alarmingly increased over the years. Adulthood obesity is a well demonstrated significant independent predictor of cardiovascular risk (CVR) and/or mortality, which predisposes to the major components of metabolic syndrome (MS). Evidence of MS in obese children has been also reported associated with biochemical and inflammatory factors that affect vascular physiologic function. Assessment of vascular function can be measured noninvasively in children allowing early detection of endothelial dysfunction and severe increase of arterial stiffness before clinical manifestations of atherosclerosis. Impairment of endothelial function related to the severity of obesity and to the degree of insulin resistance is considered as a condition that confers a premature atherogenicity status and is linked to adult conventional cardiovascular risk factors. Adipose tissue factors that interfere with insulin action and endothelial cell function have also been identified as major precursors of CVR factors. The metabolic and cardiovascular consequences of childhood obesity are well demonstrated and have a major impact on the development of atherosclerosis and lifetime CVR. The development of programs involving both diet and exercise for children with overt overweight/obesity appears to be essential to improve vascular function and metabolic disorders. Such interventions should be complemented by a primary prevention against childhood obesity.

5-methyltetrahydrofolic acid stimulates endothelin-1 production in low density lipoprotein-treated human endothelial cells

BACKGROUND AND AIMS

Several studies have shown the beneficial effects of folate treatment in improving cardiovascular function. However, the mechanisms involved have not been clearly identified. The aim of this study is to determine the effect of folates and vitamin B12 on endothelial vasoconstriction/vasodilatation parameters in cultured human endothelial cells incubated with human low density lipoproteins (LDL).

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVEC) were extracted from recently delivered umbilical cords, cultured until confluence was achieved, and then incubated for 24h with folic acid (FA), 5-methyltetrahydrofolic acid (5-MTHF) or vitamin B12 (B12) in the presence or absence of LDL that was isolated from healthy volunteers. Total nitrites (as a measure of nitric oxide production), thiobarbituric acid reactive species (TBARS, a parameter of lipid peroxidation), and endothelin-1 (ET-1) were determined in the incubation media. None of the vitamins, either in the presence or absence of LDL, was able to modify nitric oxide production by HUVEC. A significant reduction of ET-1 production was observed in LDL-treated cells. This effect was not modified by FA or B12; however, 5-MTHF caused a concentration-dependent increase on ET-1 production, an effect coincidental with reduced TBARS production.

CONCLUSIONS

This study demonstrates for the first time that 5-MTHF, but not FA or B12, increases ET-1 production in LDL-treated endothelial cells. Although this effect was associated with the antioxidant properties of this folate, our results show that additional specific mechanisms involving 5-MTHF-LDL interactions may be operating to regulate endothelial function.

Oster rediscovered--mega-dose folate for symptomatic atherosclerosis

Thirty years ago, Kurt Oster promulgated the avant-garde theory that bovine xanthine oxidase, absorbed intact from homogenized milk, promoted atherogenesis by oxidatively damaging membrane plasmalogens. Under the mistaken impression that folic acid is a xanthine oxidase inhibitor, he administered high-dose folate (80 mg daily) to hundreds of patients afflicted with symptomatic atherosclerosis, and reported marked improvements in angina, intermittent claudication, and wound healing; he also suspected that this regimen was decreasing heart attack risk. The xanthine oxidase theory has since fallen by the wayside, but there is now evidence that folic acid can lessen endothelial oxidative stress by improving the function of "uncoupled" nitric oxide synthase deficient in tetrahydrobiopterin. In light of these new findings, a properly controlled assessment of Oster's mega-dose folate therapy is warranted.

High-dose folate may improve platelet function in acute coronary syndrome and other pathologies associated with increased platelet oxidative stress

Although nitric oxide of endothelial origin plays a major role in warding off inappropriate thrombus formation, platelets also express the "constitutive" isoform of nitric oxide synthase (cNOS). Activation of this enzyme by calcium influx during platelet aggregation provides an important feedback signal that dampens platelet recruitment. Platelets also express a membrane-bound NAD(P)H oxidase complex, activated by collagen receptors, that produces superoxide. Superoxide can directly quench NO; moreover, by giving rise to peroxynitrite, it can oxidize the cNOS cofactor tetrahydrobiopterin (BH4), thereby suppressing cNOS activity and converting it to superoxide generator. In a canine model of acute coronary syndrome, infusion of BH4 has been shown to prevent thrombus formation. Platelets from patients with acute coronary syndrome produce markedly less NO than do control platelets. A reasonable explanation for these findings is that episodic contact with collagen boosts platelet superoxide production, oxidizing BH4. Since 5-methyltetrahydrofolate can reduce oxidized BH4, or otherwise compensate for its deficiency, supplementation with its precursor folic acid may improve platelet function in acute coronary syndrome and possibly reduce risk for coronary thrombosis in other at-risk patients. Other research demonstrates that superoxide production is increased, and nitric oxide production diminished, in platelets of diabetics; the ability of glutathione--a peroxynitrite scavenger--to largely ameliorate these abnormalities, is consistent with a prominent role for BH4 deficiency in diabetic platelet malfunction. Reports that platelet NO production is decreased, and/or superoxide production increased, in patients with disorders associated with insulin resistance syndrome, suggest that BH4 deficiency--potentially remediable with high-dose folate--may likewise contribute to the platelet hyperreactivity noted in these disorders. Supplemental vitamin C and arginine also have the potential to boost platelet production of NO Increased intakes of taurine, magnesium, gamma-tocopherol, fish oil, and garlic may help to stabilize platelets by additional mechanisms. As a complement to the proven benefits of low-dose aspirin, a supplemental regimen emphasizing these nutrients in appropriate doses may act directly on platelets to further diminish risk for thrombotic episodes.

Vascular endothelial and smooth muscle function relates to body mass index and glucose in obese and nonobese children

CONTEXT

Endothelial and smooth muscle dysfunction are critical precursors of atherosclerosis. These can be detected in children at risk of cardiovascular disease.

OBJECTIVE

The objective of this study is to evaluate endothelial and smooth muscle function and their determinants using flow-mediated dilatation (FMD) and glyceryl trinitrate-mediated dilatation (GTN) in obese, nonobese, and type 1 diabetes mellitus (T1DM) children.

DESIGN

This is a cross-sectional study.

SUBJECTS

The study subjects were 270 children [140 males, mean age 13.7 (2.8) yr] including 58 obese, 53 nonobese, and 159 T1DM children.

MEASUREMENTS

Vascular function (FMD and GTN), body mass index (BMI) z-score, blood pressure, glucose, glycosylated hemoglobin, lipids, folate, homocysteine, and high sensitive C-reactive protein were measured.

RESULTS

FMD and GTN were significantly lower in obese and T1DM compared with nonobese subjects (P < 0.001, P < 0.001). FMD and GTN were similarly reduced in obese and T1DM subjects (P = 0.22, P = 0.28). In all nondiabetic subjects (n = 111), both FMD and GTN were significantly and independently related to BMI z-score (r = -0.28, P = 0.003, beta = -0.36, P < 0.001) and weight z-score (beta = -0.31, P = 0.002; r = -0.52, P < 0.001). FMD related independently to total cholesterol (beta = -0.22, P = 0.02). GTN related independently to vessel diameter (beta = -0.49, P < 0.001). GTN related to glucose within the normal range (r = -0.34, P = 0.001).

CONCLUSIONS

Children with obesity and T1DM have a similar degree of vascular dysfunction. BMI and weight adjusted for age and sex relate to endothelial and smooth muscle function in nonobese and obese children. Glucose relates to smooth muscle function in nonobese nondiabetic children. This suggests a continuum effect of BMI and glucose within the normal range on vascular function in childhood.

Folate and vitamin B6 rapidly normalize endothelial dysfunction in children with type 1 diabetes mellitus

BACKGROUND

Endothelial dysfunction, a precursor of vascular disease, begins early in type 1 diabetes mellitus and is associated with folate status.

METHODS

A randomized, double-blind, placebo-controlled study of folate (5 mg daily) and vitamin B6 (100 mg daily) in 124 children with type 1 diabetes determined the immediate and 8-week effects of these vitamins, alone and in combination, on endothelial function. Endothelial function, assessed as flow-mediated dilation and glyceryltrinitrate-induced dilation with high-resolution ultrasound of the brachial artery, was measured at baseline, at 2 and 4 hours after the first dose (n = 35), and at 4 and 8 weeks of treatment (n = 122).

RESULTS

Flow-mediated dilation normalized in all treatment groups. From baseline to 8 weeks, flow-mediated dilation improved with folate from 2.6% +/- 4.3% (mean +/- SD) to 9.7% +/- 6.0%, with vitamin B6 from 3.5% +/- 4.0% to 8.3% +/- 4.2%, and with folate/vitamin B6 from 2.8% +/- 3.5% to 10.5% +/- 4.4%. This improvement in flow-mediated dilation occurred within 2 hours and was maintained at 8 weeks for each treatment. Flow-mediated dilation in the placebo group, and glyceryltrinitrate-induced dilation in all groups, did not change. Increases in serum folate, red cell folate, and serum vitamin B6 levels related to increases in flow-mediated dilation. Improvement in flow-mediated dilation was independent of changes in total plasma homocyst(e)ine, glucose, hemoglobin A1c, and high-sensitivity C-reactive protein levels. Baseline red cell folate levels and baseline diastolic blood pressure were related inversely to improvement in flow-mediated dilation. Serum triglyceride and low-density lipoprotein cholesterol inversely related to baseline flow-mediated dilation.

CONCLUSIONS

High-dose folate and vitamin B6 normalized endothelial dysfunction in children with type 1 diabetes. This effect was maintained over 8 weeks, with no additional benefit from combination treatment.

Effect of folic acid and betaine supplementation on flow-mediated dilation: a randomized, controlled study in healthy volunteers

OBJECTIVES

We investigated whether lowering of fasting homocysteine concentrations, either with folic acid or with betaine supplementation, differentially affects vascular function, a surrogate marker for risk of cardiovascular disease, in healthy volunteers. As yet, it remains uncertain whether a high concentration of homocysteine itself or whether a low folate status--its main determinant--is involved in the pathogenesis of cardiovascular disease. To shed light on this issue, we performed this study.

DESIGN

This was a randomized, placebo-controlled, double-blind, crossover study.

SETTING

The study was performed at Wageningen University in Wageningen, the Netherlands.

PARTICIPANTS

Participants were 39 apparently healthy men and women, aged 50-70 y.

INTERVENTIONS

Participants ingested 0.8 mg/d of folic acid, 6 g/d of betaine, and placebo for 6 wk each, with 6-wk washout in between.

OUTCOME MEASURES

At the end of each supplementation period, plasma homocysteine concentrations and flow-mediated dilation (FMD) of the brachial artery were measured in duplicate.

RESULTS

Folic acid supplementation lowered fasting homocysteine by 20% (-2.0 micromol/l, 95% confidence interval [CI]: -2.3; -1.6), and betaine supplementation lowered fasting plasma homocysteine by 12% (-1.2 micromol/l; -1.6; -0.8) relative to placebo. Mean (+/- SD) FMD after placebo supplementation was 2.8 (+/- 1.8) FMD%. Supplementation with betaine or folic acid did not affect FMD relative to placebo; differences relative to placebo were -0.4 FMD% (95%CI, -1.2; 0.4) and -0.1 FMD% (-0.9; 0.7), respectively.

CONCLUSIONS

Folic acid and betaine supplementation both did not improve vascular function in healthy volunteers, despite evident homocysteine lowering. This is in agreement with other studies in healthy participants, the majority of which also fail to find improved vascular function upon folic acid treatment. However, homocysteine or folate might of course affect cardiovascular disease risk through other mechanisms.

The vascular endothelium in diabetes: a practical target for drug treatment?

Vascular disease remains a major cause of morbidity and mortality in diabetes mellitus, in spite of recent improvements in outcome, some of which may be modulated by improved endothelial function. Therapeutic strategies aimed directly at preventing, or minimising the extent of, these sequelae are required as an adjunct to treatments directed at normalising the metabolic milieu. The microvasculature, and the endothelium in particular, are early contributors to vascular dysfunction, thus raising the question as to how best to specifically target the endothelium. However, the expansive nature of the microvasculature, the varying demands that tissues have in terms of blood flow, and the heterogeneity that exists amongst cell types in different sites raises potential problems as to the practicality of such an approach. Further-more, temporal and genetic factors in the genesis of diabetic microvascular dysfunction may impact on therapeutic strategies. It is suggested that a systematic approach is required to understand the heterogeneity of the microvasculature, with particular emphasis on relating differences in gene and protein expression with functional properties. Such an approach may then provide the necessary information to allow exploitation of endothelial cell heterogeneity for unique targeted interventions, as well as providing the necessary rationale for pharmacological interventions (both prophylactic and corrective) aimed at the endothelium as a whole.

Early atherosclerosis in childhood: Diagnostic approaches and therapeutic strategies

The long preclinical phase of atherosclerosis involves the interaction of genetic and environmental factors that modulate the progression of disease from early life. Injury to the endothelium is a critical step in atherosclerotic process. Conventional and novel risk factors for coronary artery disease operate from early in life. Noninvasive methods, using mostly ultrasound techniques, have enabled the assessment of early functional and structural arterial disease progression even from the first decade of life. These measures have been shown to be good surrogate markers for atherosclerotic disease progression and future clinical cardiovascular events. Lifestyle and dietary modifications as well as pharmacological interventions have beneficial effects in prevention and restoration of the early arterial changes.

Hyperhomocysteinemia in Children Treated with Antiepileptic Drugs Is Normalized by Folic Acid Supplementation

PURPOSE

To assess the prevalence of hyperhomocysteinemia in pediatric patients treated with antiepileptic drugs (AEDs) and to evaluate the effect of folic acid supplementation on plasma total homocysteine (tHcy) concentrations in hyperhomocysteinemic patients.

METHODS

123 patients from three regional hospitals participated in the study. Patients with hyperhomocysteinemia were included in a 3-month double-blind randomized trial testing oral folic acid supplementation (1 mg/day) versus placebo.

RESULTS

Hyperhomocysteinemia (tHcy >10.4 micromol/L) was present in 19 of 123 patients. Patients with hyperhomocysteinemia were older (13.7 +/- 4 vs. 11.0 +/- 3.9 years) and had significantly lower folate and cobalamin concentrations. Multidrug (two or more) AED treatment and duration of therapy correlated significantly with elevated total homocysteine (tHcy) and low folate. In contrast, polymorphisms in the methylene tetrahydrofolate reductase gene (MTHFR 677 C-->T, 1298 A-->C, 1793 G-->A) had no significant impact on tHcy. Nine of 19 patients with hyperhomocysteinemia were randomized to placebo, whereas the remaining 10 patients received folic acid supplementation. Folic acid supplementation resulted in a significant increase of folate and decrease of tHcy, whereas both parameters remained unchanged in the placebo group.

CONCLUSIONS

Hyperhomocysteinemia is present in 15.5% of children receiving long-term AED treatment. Multidrug treatment and long duration of therapy enhance the risk for hyperhomocysteinemia. Folic acid supplementation significantly reduces tHcy. We recommend assessment of serum folate and plasma tHcy in children receiving AEDs.

Noninvasive assessment of arterial stiffness and risk of atherosclerotic events in children

Noninvasive assessment of vascular dysfunction in the pediatric population has taken advantage of the development of high-resolution ultrasound techniques. The most frequently used methods are the quantification of flow-mediated endothelium-dependent dilation of the brachial artery and measurement of the intima-media thickening of the carotid artery. Both reduced flow-mediated dilation and increased intima-media thickness have been proven to correlate with late cardiovascular events and/or mortality in adults. As these noninvasive methods can easily be applied in children, there have been recent investigations in high-risk pediatric patients harboring classical cardiovascular risk factors. Endothelial dysfunction and increased thickness of the intima media are currently observed in children with familial hypercholesterolemia, obesity, and type 1 diabetes mellitus. The association of early vascular dysfunction with a known risk factor is an important issue as these anomalies precede the formation of atherosclerotic plaques. Therefore, they may help in stratification of the risk for cardiovascular event and to better tailor therapeutic interventions in at risk children. Finally, these methods have been applied in specific pediatric populations, such as children with end-stage renal disease, chronic parenteral nutrition, HIV infection, and coarctation of the aorta. In these conditions, endothelial dysfunction and vascular remodeling are also present early in life and these data raise new possibilities in the understanding of the pathogenesis of atherosclerosis in these populations.