Effect of short-term folic acid supplementation on insulin sensitivity and inflammatory markers in overweight subjects

Folic acid delays development of atherosclerosis in low-density lipoprotein receptor-deficient mice

Many studies support the cardioprotective effects of folic acid (FA). We aimed to evaluate the utility of FA supplementation in preventing the development of atherosclerotic in low‐density lipoprotein receptor‐deficient (LDLR−/−) mice and to elucidate the molecular processes underlying this effect. LDLR−/− mice were randomly distributed into four groups: control group, HF group, HF + FA group and the HF + RAPA group. vascular smooth muscle cells (VSMCs) were divided into the following four groups: control group, PDGF group, PDGF + FA group and PDGF + FA + RAPA group. Blood lipid levels, oxidative stress and inflammatory cytokines were measured. Atherosclerosis severity was evaluated with oil red O staining. Haematoxylin and eosin (H&E) staining was used to assess atherosclerosis progression. Immunohistochemical staining was performed with antismooth muscle α‐actin (α‐SMA) antibodies and anti‐osteopontin (OPN) antibodies that demonstrate VSMC dedifferentiation. The protein expression of α‐SMA, OPN and mechanistic target of rapamycin (mTOR)/p70S6K signalling was detected by Western blot analysis. FA and rapamycin reduced serum levels of total cholesterol, triacylglycerol, LDL, inhibiting oxidative stress and the inflammatory response. Oil red O and H&E staining demonstrated that FA and rapamycin inhibited atherosclerosis. FA and rapamycin treatment inhibited VSMC dedifferentiation in vitro and in vivo, and FA and rapamycin attenuated the mTOR/p70S6K signalling pathway. Our findings suggest that FA attenuates atherosclerosis development and inhibits VSMC dedifferentiation in high‐fat‐fed LDLR−/− mice by reduced lipid levels and inhibiting oxidative stress and the inflammatory response through mTOR/p70S6K signalling pathway.

Adipocyte Expression of SLC19A1 Links DNA Hypermethylation to Adipose Tissue Inflammation and Insulin Resistance

CONTEXT

Insulin resistance (IR) is promoted by a chronic low-grade inflammation in white adipose tissue (WAT). The latter might be regulated through epigenetic mechanisms such as DNA methylation. The one carbon cycle (1CC) is a central metabolic process governing DNA methylation.

OBJECTIVE

To identify adipocyte-expressed 1CC genes linked to WAT inflammation, IR, and their causal role.

DESIGN

Cohort study.

SETTING

Outpatient academic clinic.

PARTICIPANTS

Obese and nonobese subjects.

METHODS

Gene expression and DNA methylation arrays were performed in subcutaneous WAT and isolated adipocytes. In in vitro differentiated human adipocytes, gene knockdown was achieved by small interfering RNA, and analyses included microarray, quantitative polymerase chain reaction, DNA methylation by enzyme-linked immunosorbent assay and pyrosequencing, protein secretion by enzyme-linked immunosorbent assay, targeted metabolomics, and luciferase reporter and thermal shift assays.

MAIN OUTCOME MEASURES

Effects on adipocyte inflammation.

RESULTS

In adipocytes from obese individuals, global DNA hypermethylation was associated positively with gene expression of proinflammatory pathways. Among the 1CC genes, IR in vivo and proinflammatory gene expression in WAT were most strongly and inversely associated with SLC19A1, a gene encoding a membrane folate carrier. SLC19A1 knockdown in human adipocytes perturbed intracellular 1CC metabolism, induced global DNA hypermethylation, and increased expression of proinflammatory genes. Several CpG loci linked SLC19A1 to inflammation; validation studies were focused on the chemokine C-C motif chemokine ligand 2 (CCL2) in which methylation in the promoter (cg12698626) regulated CCL2 expression and CCL2 secretion through altered transcriptional activity.

CONCLUSIONS

Reduced SLC19A1 expression in human adipocytes induces DNA hypermethylation, resulting in increased expression of specific proinflammatory genes, including CCL2. This constitutes an epigenetic mechanism that might link dysfunctional adipocytes to WAT inflammation and IR.

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.

A prospective association between dietary folate intake and type 2 diabetes risk among Korean adults aged 40 years or older: the Korean Multi-Rural Communities Cohort (MRCohort) Study

It has not been well established whether dietary folate intake reduces the risk of diabetes development. We aimed to clarify the prospective association between dietary folate intake and type 2 diabetes (T2D) risk among 7333 Korean adults aged 40 years or older who were included in the Multi-Rural Communities Cohort. Dietary folate intake was estimated from all 106 food items listed on a FFQ, not including folate intake from supplements. Two different measurements of dietary folate intake were used: the baseline consumption and the average consumption from baseline until just before the end of follow-up. The association between folate intake and T2D risk was determined through a modified Poisson regression model with a robust error estimator controlling for potential confounders. For 29 745 person years, 319 cases of diabetes were ascertained. In multivariable analyses, dietary folate intake was inversely associated with risk of T2D for women, not for men. For women, the incidence rate ratio of diabetes in the third tertile compared with the first tertile was 0·57 (95 % CI 0·38-0·87, P for trend=0·0085) in the baseline consumption model and 0·64 (95 % CI 0·43-0·95, P for trend=0·0244) in the average consumption model. These inverse associations was found in both normal fasting blood glucose group and impaired fasting glucose group among women. Among non-users of multinutrients and vitamin supplements, the significant inverse association remained. Thus, higher dietary intake of folate is prospectively associated with lower risk of diabetes for women.

Folic acid prevents cardiac dysfunction and reduces myocardial fibrosis in a mouse model of high-fat diet-induced obesity

Background

Folic acid (FA) is an antioxidant that can reduce reactive oxygen species generation and can blunt cardiac dysfunction during ischemia. We hypothesized that FA supplementation prevents cardiac fibrosis and cardiac dysfunction induced by obesity.

Methods

Six-week-old C57BL6/J mice were fed a high-fat diet (HFD), normal diet (ND), or an HFD supplemented with folic acid (FAD) for 14 weeks. Cardiac function was measured using a transthoracic echocardiographic exam. Phenotypic analysis included measurements of body and heart weight, blood glucose and tissue homocysteine (Hcy) content, and heart oxidative stress status.

Results

HFD consumption elevated fasting blood glucose levels and caused obesity and heart enlargement. FA supplementation in HFD-fed mice resulted in reduced fasting blood glucose, heart weight, and heart tissue Hcy content. We also observed a significant cardiac systolic dysfunction when mice were subjected to HFD feeding as indicated by a reduction in the left ventricular ejection fraction and fractional shortening. However, FAD treatment improved cardiac function. FA supplementation protected against cardiac fibrosis induced by HFD. In addition, HFD increased malondialdehyde concentration of the heart tissue and reduced the levels of antioxidant enzyme, glutathione, and catalase. HFD consumption induced myocardial oxidant stress with amelioration by FA treatment.

Conclusion

FA supplementation significantly lowers blood glucose levels and heart tissue Hcy content and reverses cardiac dysfunction induced by HFD in mice. These functional improvements of the heart may be mediated by the alleviation of oxidative stress and myocardial fibrosis.

Dietary Intake after Weight Loss and the Risk of Weight Regain: Macronutrient Composition and Inflammatory Properties of the Diet

Weight regain after successful weight loss is a big problem in obesity management. This study aimed to investigate whether weight regain after a weight loss period is correlated with the macronutrient composition and/or the inflammatory index of the diet during that period. Sixty one overweight and obese adults participated in this experimental study. Subjects lost approximately 10% of their initial weight by means of very low-calorie diet for five weeks, or a low calorie diet for 12 weeks. After that, subjects in both groups followed a strict weight maintenance diet based on individual needs for four weeks, which was followed by a nine-month weight maintenance period without dietary counseling. Anthropometrics and dietary intake data were recorded before weight loss (baseline) and during the weight maintenance period. On average, participants regained approximately half of their lost weight. We found no evidence that macronutrient composition during the weight maintenance period was associated with weight regain. The dietary inflammatory index (r = 0.304, p = 0.032) was positively correlated with weight regain and remained significant after correction for physical activity (r = 0.287, p = 0.045). Our data suggest that the inflammatory properties of diet play a role in weight regain after weight loss in overweight and obese adults.

A maternal high-fat, high-sucrose diet alters insulin sensitivity and expression of insulin signalling and lipid metabolism genes and proteins in male rat offspring: effect of folic acid supplementation

A maternal high-fat, high-sucrose (HFS) diet alters offspring glucose and lipid homoeostasis through unknown mechanisms and may be modulated by folic acid. We investigated the effect of a maternal HFS diet on glucose homoeostasis, expression of genes and proteins associated with insulin signalling and lipid metabolism and the effect of prenatal folic acid supplementation (HFS/F) in male rat offspring. Pregnant Sprague-Dawley rats were randomly fed control (CON), HFS or HFS/F diets. Offspring were weaned on CON; at postnatal day 70, fasting plasma insulin and glucose and liver and skeletal muscle gene and protein expression were measured. Treatment effects were assessed by one-way ANOVA. Maternal HFS diet induced higher fasting glucose in offspring v. HFS/F (P=0·027) and down-regulation (P<0·05) of genes coding for v-Akt murine thymoma viral oncogene homolog 2, resistin and v-Raf-1 murine leukaemia viral oncogene homolog 1 (Raf1) in offspring skeletal muscle and acetyl-CoA carboxylase (Acaca), fatty acid synthase and phosphatidylinositol-4,5-biphosphate 3-kinase, catalytic subunit β in offspring liver. Skeletal muscle neuropeptide Y and hepatic Kruppel-like factor 10 were up-regulated in HFS v. CON offspring (P<0·05). Compared with CON, Acaca and Raf1 protein expression levels were significantly lower in HFS offspring. Maternal HFS induced higher homoeostasis model of assessment index of insulin resistance v. CON (P=0·030) and HFS/F was associated with higher insulin (P=0·016) and lower glucose (P=0·025). Maternal HFS diet alters offspring insulin sensitivity and de novo hepatic lipogenesis via altered gene and protein expression, which appears to be potentiated by folate supplementation.

Association between Serum Folate and Insulin Resistance among U.S. Nondiabetic Adults

Recent studies have suggested that epigenetic alterations, particularly DNA methylation, play a crucial role in the pathogenesis of insulin resistance. Folate is a key source of the one-carbon group for DNA methylation, whereas the association and mechanistic linkage between folate status and insulin resistance remains unclear with very limited experimental support. We performed a cross-sectional study of 1530 nondiabetic adults in the 2011–2012 National Health and Nutrition Examination Survey (NHANES). We examined associations between serum folate and insulin resistance using multiple linear regression models adjusted for potential confounders. We detected a significant inverse relationship for serum folate, where a 25% increase in serum folate was associated with a 3.06% (95% CI, −4.72, −1.37) and 2.77% (95% CI, −4.36, −1.77) decline in HOMA-IR and insulin respectively, and a 2.55% (95% CI, 0.93, 4.21) increase in G/I ratio. Our findings demonstrate that serum folate was inversely associated with insulin resistance in U.S. nondiabetic adults.

Associations of MTHFR C677T polymorphism with insulin resistance, results of NURSE Study (Nursing Unacquainted Related Stress Etiologies)

Background

The insulin resistance syndrome is one of the major contributors of metabolic syndrome, diabetes Type 2 and atherosclerotic cardiovascular disease. A common mutation (677C to T; Ala to Val) in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with decreased specific MTHFR activity and elevation of the homocysteine. The aim of this study is investigation of association between MTHFR 677C > T polymorphism with insulin resistance by using HOMA (Homeostasis Model Assessment) index in nurses who are potentially prone to develop insulin resistance because of unfavorable effects of shift work.

Method

Nursing Unacquainted Related Stress Etiologies Study (Nurse Study) was conducted in five different educational hospitals of Tehran University of Medical Science (TUMS). The nurses aged 22–57 who have been referred by the matron were recruited. A self-administered questionnaire was completed. Anthropometric measurements including weight, height, waist and hip circumference in addition to blood pressure were measured. Insulin resistance and Insulin sensitivity were measured using the homeostatic model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) respectively. The detection of MTHFR C677T polymorphism in exon four of MTHFR gene was performed by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis using HINFI restriction enzyme digestion.

Result

A total of 273 subjects were recruited in the study. CT genotype were detected in 51.6% (129) subjects and CC and TT genotype were seen in 9.2% (25) and 35.2% (96) subjects respectively. Participants with TT genotype (9.65 ± 4.00) have significantly lower insulin level than participants with CT genotype (14.12 ± 15.34) (p-value: 0.01). The same significant difference was observed for HOMA index (p-value: 0.03). Result showed that HOMA is lower in subjects who are taking supplements.

Conclusion

Result of this study showed subjects with TT genotype had significantly lower HOMA compare to CT genotype and the same pattern was seen for insulin level. We also found subjects taking supplement have lower HOMA compared to others regardless of their genotype.

Role of folate in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of chronic liver conditions that are characterized by steatosis, inflammation, fibrosis, and liver injury. The global prevalence of NAFLD is rapidly increasing in proportion to the rising incidence of obesity and type 2 diabetes. Because NAFLD is a multifaceted disorder with many underlying metabolic abnormalities, currently, there is no pharmacological agent that is therapeutically approved for the treatment of this disease. Folate is a water-soluble B vitamin that plays an essential role in one-carbon transfer reactions involved in nucleic acid biosynthesis, methylation reactions, and sulfur-containing amino acid metabolism. The liver is the primary organ responsible for storage and metabolism of folates. Low serum folate levels have been observed in patients with obesity and diabetes. It has been reported that a low level of endogenous folates in rodents perturbs folate-dependent one-carbon metabolism, and may be associated with development of metabolic diseases such as NAFLD. This review highlights the biological role of folate in the progression of NAFLD and its associated metabolic complications including obesity and type 2 diabetes. Understanding the role of folate in metabolic disease may position this vitamin as a potential therapeutic for NAFLD.

A pilot study of D-chiro-inositol plus folic acid in overweight patients with type 1 diabetes

AIMS

To improve insulin sensitivity, insulin-sensitizing drugs such as metformin are commonly used in overweight and obese T1D patients. Similarly to metformin, D-chiro-inositol (DCI), as putative mediator of intracellular insulin action, can act as insulin sensitizer. The aim of this pilot study was to evaluate the hypothesis that DCI plus folic acid may improve glucose control reducing insulin resistance in overweight or obese T1D patients.

METHODS

A 24-week randomized control trial was carried out in 26 overweight or obese T1D patients, undergoing intensive insulin therapy. Patients were randomized to 1 g DCI plus 400 mcg folic acid once daily (treated group) or to 400 mcg folic acid only once daily (control group). The primary end point was to evaluate the efficacy of DCI on metabolic control as assessed by HbA1c. As secondary endpoints, BMI and insulin requirement (IR) were evaluated. Paired t test (two tailed) and analysis of variance were used to evaluate differences in HbA1c, BMI and IR at different time points.

RESULTS

A significant reduction in HbA1c levels in treated group versus control group (7.5% ± 0.9 vs. 7.9% ± 1.7, respectively, p < 0.05) was observed. However, no significant reduction in BMI and IR was observed [(BMI 25.7 ± 2.8 vs. 26.7 ± 1.0, respectively, p NS); (IR 0.52 ± 0.26 vs. 0.52 ± 0.19, respectively, p NS)].

CONCLUSIONS

This trial demonstrated for the first time that DCI plus folic acid oral supplementation can improve metabolic control in overweight T1D patients. CLINICALTRIAL.

GOV ID

NCT02730949.

Effect of folic acid and metformin on insulin resistance and inflammatory factors of obese children and adolescents

Background:

Considering the increasing trend of obesity, especially in developing countries such as Iran, and the role of inflammatory factors and insulin resistance (IR) in the occurrence of obesity-related complications as well as the safety of some agents such as folic acid and metformin, this clinical trial was designed to investigate the effect of metformin and folic acid on inflammatory factors and IR among obese children.

Materials and Methods:

In this randomized, double-blind, controlled clinical trial study, sixty obese children aged 6–12 years were enrolled. Selected obese children were randomly allocated in two interventional (1 mg/daily folic acid or 1000 mg metformin for 8 weeks) groups. Biochemical measurements including homeostasis model assessment of IR (HOMA-IR), homocysteine (Hcy), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) were measured between and within the groups before and after trial.

Results:

In each group, thirty obese children were studied. The groups were age- and sex-matched. After folic acid and metformin administration, mean of Hcy, HOMA-IR, TNF-α, and IL-8 decreased significantly (P < 0.05). IL-6 decreased significantly after folic acid use (P < 0.05).

Conclusion:

The findings of this trial indicated that both metformin and folic acid could decrease IR and level of Hcy in obese children and adolescents. The effectiveness of metformin on IR was more significant than folic acid. Regarding the effectiveness of the two studied agents on inflammatory factors, it is suggested that the role of folic acid was superior to metformin. It is suggested that metformin is a proper agent for obese children with IR and folic acid is an appropriate supplement for obese children with increased inflammatory factors.

The Effects of Folate Supplementation on Carotid Intima-Media Thickness and Metabolic Status in Patients with Metabolic Syndrome

BACKGROUND

This study was carried out to evaluate the effects of folate supplementation on carotid intima-media thickness (CIMT) and metabolic status among patients with metabolic syndrome (MetS).

METHODS

This randomized, double-blind, placebo-controlled trial was conducted among 60 patients with type 2 diabetes mellitus and coronary heart disease. They were all overweight in the age range 40-85 years. Participants were randomly divided into 2 groups: group A (n = 30) received 5 mg folate supplements and group B (n = 30) received placebo for 12 weeks.

RESULTS

Folate supplementation resulted in a significant reduction in maximum levels of left CIMT (-0.05 ± 0.13 vs. +0.02 ± 0.11 mm, p = 0.01) compared with the placebo. Changes in fasting plasma glucose (-2.2 ± 37.5 vs. +30.2 ± 65.8 mg/dl, p = 0.02), serum insulin concentration (-2.0 ± 10.7 vs. +3.0 ± 7.6 µIU/ml, p = 0.04) and homeostasis of assessment-estimated insulin resistance (-0.6 ± 2.3 vs. +0.9 ± 2.3, p = 0.01) in supplemented patients were significantly different from those of patients in the placebo group. Changes in serum triglycerides (p = 0.04), high-density lipoprotein-cholesterol (p = 0.001), high sensitivity C-reactive protein (p = 0.01) and plasma nitric oxide concentrations (p < 0.001) were significantly different between the supplemented patients and placebo group.

CONCLUSIONS

Overall, 5 mg/day folate supplementation for 12 weeks among patients with MetS had beneficial effects on CIMT and the metabolic status.

Effects of long-term folate supplementation on metabolic status and regression of cervical intraepithelial neoplasia: A randomized, double-blind, placebo-controlled trial

OBJECTIVE

This study was conducted to determine the effects of long-term folate supplementation on regression and metabolic status of patients with cervical intraepithelial neoplasia grade 1 (CIN1).

METHODS

This randomized, double-blind, placebo-controlled trial was performed among 58 women diagnosed with CIN1, ages 18 to 55 y old. Participants were randomly divided into two groups to receive 5 mg/d folate supplements (n = 29) or placebo (n = 29) for 6 mo. Fasting blood samples were taken at baseline and 6 mo after intervention to quantify related markers.

RESULTS

A greater percentage of women in the folate group had regressed CIN1 (83.3 versus 52.0%, P = 0.019) than those in the placebo group. Long-term folate supplementation resulted in a significant decrease in serum insulin levels (-1.6 ± 6.2 versus +2.6 ± 6.9 μIU/mL, P = 0.018) and homeostatic model assessment-beta cell function (HOMA-B) (-13.0 ± 39.0 versus +11.2 ± 42.3, P = 0.028) compared with the placebo. Additionally, plasma glutathione (GSH) levels were significantly increased (+81.5 ± 264.1 versus -220.9 ± 342.5 μmol/L, P < 0.001) and malondialdehyde (MDA) levels were significantly reduced (-1.0 ± 1.1 versus +0.1 ± 1.6 μmol/L, P = 0.004) in the folate group compared to the placebo.

CONCLUSIONS

Taken together, folate supplementation (5 mg/d) for 6 mo among women with CIN1 resulted in its regression as well as led to decreased serum insulin, HOMA-B, plasma MDA and increased plasma GSH levels; however, it did not affect other metabolic profiles.

Effect of folic acid on homocysteine and insulin resistance of overweight and obese children and adolescents

Background:

Considering the increasing trend of childhood obesity and subsequent burden of the disease in Iran and other countries and importance of early life intervention for achieving sustained effect on health of children and adolescents, this study aimed to investigate the effect of two different dose of folic acid on homocysteine (Hcy) level and insulin resistance of obese children.

Materials and Methods:

In this randomized, double-blind controlled clinical trial study, 60 obese and overweight children aged 5–12 years were enrolled. Selected obese children randomly allocated in two interventional (1 mg/day folic acid and 5 mg/day folic acid, for 8 weeks) and one control groups. Biochemical measurements including folic acid, Hcy, insulin and insulin resistance were measured between and within groups before and after trial.

Results:

In each group, 20 obese children were studied. The three groups were age and sex matched. After folic acid administration, mean of Hcy, insulin resistance and insulin decreased significantly in two groups which folic acid administrated with two different doses (P < 0.05). The reduction in studied biochemical variables was similar in two interventional groups (1 and 5 mg folic acid daily) (P > 0.05). Mean differences for Hcy, insulin resistance and insulin, in two intervention groups were significantly higher than the control group (P < 0.0001). Mean differences of Hcy, insulin resistance and insulin, in two intervention groups were not different significantly (P > 0.05).

Conclusion:

The findings of current trial showed that folic acid in two studied doses could be a safe and effective supplement for obese children to reduce Hcy level and insulin resistance, which consequently could prevent obesity-related complications including cardiovascular and metabolic disorders.

Folic Acid Represses Hypoxia-Induced Inflammation in THP-1 Cells through Inhibition of the PI3K/Akt/HIF-1α Pathway

Though hypoxia has been implicated as a cause of inflammation, the underlying mechanism is not well understood. Folic acid has been shown to provide protection against oxidative stress and inflammation in patients with cardiovascular disease and various models approximating insult to tissue via inflammation. It has been reported that hypoxia-induced inflammation is associated with oxidative stress, upregulation of hypoxia-inducible factor 1-alpha (HIF-1α), and production of pro-inflammatory molecules. Whether folic acid protects human monocytic cells (THP-1 cells) against hypoxia-induced damage, however, remains unknown. We used THP-1 cells to establish a hypoxia-induced cellular injury model. Pretreating THP-1 cells with folic acid attenuated hypoxia-induced inflammatory responses, including a decrease in protein and mRNA levels of interleukin (IL)-1β and tumor necrosis factor-alpha (TNF-α), coupled with increased levels of IL-10. Folic acid also reduced hypoxia-induced Akt phosphorylation and decreased nuclear accumulation of HIF-1α protein. Both LY294002 (a selective inhibitor of phosphatidyl inositol-3 kinase, PI3K) and KC7F2 (a HIF-1α inhibitor) reduced levels of hypoxia-induced inflammatory cytokines. We also found that insulin (an Akt activator) and dimethyloxallyl glycine (DMOG, a HIF-1α activator) induced over-expression of inflammatory cytokines, which could be blocked by folic acid. Taken together, these findings demonstrate how folic acid attenuates the hypoxia-induced inflammatory responses of THP-1 cells through inhibition of the PI3K/Akt/HIF-1α pathway.

Folic acid promotes the myogenic differentiation of C2C12 murine myoblasts through the Akt signaling pathway

Folic acid is a water-soluble vitamin in the B-complex group, and an exogenous intake is required for health, growth and development. As a precursor to co-factors, folic acid is required for one-carbon donors in the synthesis of DNA bases and other essential biomolecules. A lack of dietary folic acid can lead to folic acid deficiency and can therefore result in several health problems, including macrocytic anemia, elevated plasma homocysteine levels, cardiovascular disease, birth defects, carcinogenesis, muscle weakness and difficulty in walking. Previous studies have indicated that folic acid exerts a positive effect on skeletal muscle functions. However, the precise role of folic acid in skeletal muscle cell differentiation remains poorly understood. Thus, in the present study, we examined the effects of folic acid on neo-myotube maturation and differentiation using C2C12 murine myoblasts. We found that folic acid promoted the formation of multinucleated myotubes, and increased the fusion index and creatine kinase (CK) activity in a concentration-dependent manner. In addition, western blot analysis revealed that the expression levels of the muscle-specific marker, myosin heavy chain (MyHC), as well as those of the myogenic regulatory factors (MRFs), MyoD and myogenin, were increased in the folic acid-treated myotubes during myogenic differentiation. Folic acid also promoted the activation of the Akt pathway, and this effect was inhibited by treatment of the C2C12 cells with LY294002 (Akt inhibitor). Blocking of the Akt pathway with a specific inhibitor revealed that it was necessary for mediating the stimulatory effects of folic acid on muscle cell differentiation and fusion. Taken together, our data suggest that folic acid promotes the differentiation of C2C12 cells through the activation of the Akt pathway.

Novel relationships between B12, folate and markers of inflammation, oxidative stress and NAD(H) levels, systemically and in the CNS of a healthy human cohort

OBJECTIVE

To evaluate the relationship between folate, cobalamin (Cbl), and homocysteine (Hcy), and markers of inflammation and oxidative stress within the periphery and central nervous system (CNS) of a healthy human cohort.

METHODS

Thirty-five matched cerebrospinal fluid (CSF) and plasma samples were collected from consenting participants who required a spinal tap for the administration of anaesthetic. Plasma concentrations of Hcy and both plasma and CSF levels of folate, Cbl, nicotinamide adenine dinucleotide (NAD(H)) and markers of inflammation (interleukin-6, IL-6), and oxidative stress (F2-isoprostanes, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and total antioxidant capacity (TAC)) were quantified.

RESULTS

In the peripheral circulation, positive associations were observed between plasma folate and Cbl, and plasma TAC (P ≤ 0.01; P ≤ 0.01) and plasma NAD(H) (P ≤ 0.05; P ≤ 0.05) levels, respectively. Plasma folate was inversely associated with plasma Hcy concentrations (P ≤ 0.05); however, no statistically significant relationships were observed between plasma Hcy and plasma markers of inflammation, oxidative stress, or [NAD(H)]. Within the CNS plasma Hcy correlated positively with CSF IL-6 (P ≤ 0.01) and negatively with CSF NAD(H) (P ≤ 0.05) concentrations. An inverse association was observed between CSF folate and CSF levels of IL-6 (P ≤ 0.05). Unexpectedly, a positive association between CSF Cbl and CSF 8-OHdG levels was also found (P ≤ 0.01).

DISCUSSION

These results indicate that folate and Cbl concentrations may influence the levels of oxidative damage, inflammation, and NAD(H), both systemically and within the CNS.

Vitamin E supplementation is associated with lower levels of C-reactive protein only in higher dosages and combined with other antioxidants: The Cooperative Health Research in the Region of Augsburg (KORA) F4 study

The aim of the present study was to examine the association between intake of five common antioxidative nutrients from supplements and medications (vitamin E, vitamin C, carotenoids, Se, and Zn) and levels of high-sensitivity C-reactive protein (hs-CRP) in the general population. For this purpose, a total of 2924 participants of the population-based Cooperative Health Research in the Region of Augsburg (KORA) F4 study (2006-8) were investigated cross-sectionally. Intake of dietary supplements and medication during the last 7 d was recorded in a personal interview, when participants were asked to show product packages of ingested preparations. Linear regression models were calculated; first, the exposure to regular nutrient intake was treated with a binary response (yes/no); then regularly ingested amounts were divided into quartiles to examine dose-response relationships. Effect of single v. combined supplementation of antioxidants was assessed through the inclusion of interaction terms into the models. Regular intake of any of the five investigated antioxidants per se was not associated with hs-CRP levels. However, dose-response analyses revealed that participants who regularly ingested more than 78 mg vitamin E/d, which corresponds to the upper quartile, had 22% lower hs-CRP levels (95% CI 0·63, 0·97) compared to those of persons who were not exposed to any vitamin E supplementation. Stratified analyses showed that this association was found only in persons who took vitamin E in combination with other antioxidants. The combined supplementation of vitamin E with other antioxidants could thus be a promising strategy for the prevention of inflammation-related diseases in the general population, if further studies could confirm that the proposed association is causal.

The effects of folate supplementation on inflammatory factors and biomarkers of oxidative stress in overweight and obese women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

This study was conducted to determine the effects of folate supplementation on inflammatory factors and biomarkers of oxidative stress among women with polycystic ovary syndrome (PCOS).

DESIGN, PATIENTS AND MEASUREMENTS

This randomized, double-blind, placebo-controlled clinical trial was conducted among 69 women diagnosed with PCOS and aged 18-40 year old. Participants were randomly assigned to three groups receiving the following: (1) folate-1: 1 mg/d folate supplements (N = 23); (2) folate-5: 5 mg/d folate supplements (N = 23) and (3) placebo (N = 23) for 8 weeks. Fasting blood samples were taken at the beginning of the study and after 8 weeks to measure homocysteine (Hcy), inflammatory factors including high-sensitivity C-reactive protein (hs-CRP), nitric oxide (NO), biomarkers of oxidative stress including total antioxidant capacity (TAC), glutathione (GSH), malondialdehyde (MDA) and homoeostatic model assessment-beta cell function (HOMA-B).

RESULTS

Supplementation with 5 mg/d folate resulted in reduced plasma Hcy (-2·23 vs -1·86 and 1·16 μm, respectively, P < 0·05), HOMA-B (-7·63 vs 1·43 and 13·66, respectively, P < 0·05), serum hs-CRP (-212·2 vs -262·4 and 729·8 μg/l, respectively, P < 0·05) and plasma MDA concentrations (-0·48 vs -0·24 and 0·69 μm, respectively, P < 0·01) compared with folate-1 and placebo groups. Furthermore, a significant rise in plasma TAC (0·64 vs -3·53 and -215·47 mm, respectively, P < 0·01) and GSH levels (162·1 vs 195·8 and -158·2 μm, respectively, P < 0·01) was also observed following the administration of 5 mg/d folate supplements compared with folate-1 and placebo groups.

CONCLUSIONS

In conclusion, folate supplementation (5 mg/d) in women with PCOS had beneficial effects on inflammatory factors and biomarkers of oxidative stress.

Metabolic response to folate supplementation in overweight women with polycystic ovary syndrome: a randomized double-blind placebo-controlled clinical trial

SCOPE

This study was conducted to determine the effects of folate supplementation on metabolic profiles in obese women with polycystic ovary syndrome (PCOS).

METHODS AND RESULTS

This randomized double-blind placebo-controlled clinical trial was conducted among 81 obese women (weight range: 65-110 kg) aged 18-40 year old diagnosed with PCOS. Participants were randomly assigned to three groups receiving: (1) Folate-1: 1 mg/day folate supplements (n = 27); (2) Folate-5: 5 mg/day folate supplements (n = 27), and (3) placebo (n = 27) for 8 weeks. Fasting blood samples were taken at baseline and after 8 weeks' intervention to quantify glucose metabolism and lipid concentrations. Folate supplementation (5 mg), compared with folate-1 and placebo, resulted in reduced plasma homocysteine (p-interaction = 0.009), homeostasis model of assessment-insulin resistance score (p-interaction = 0.01), and total cholesterol/HDL-C ratio (p-interaction = 0.01). Furthermore, we found a significant difference in mean change of serum total cholesterol (p-interaction = 0.01), LDL- (p-interaction = 0.007), and non-HDL-cholesterol levels (p = 0.01) in the folate-5 group compared with folate-1 and placebo.

CONCLUSION

5 mg/day folate supplementation for 8 weeks among women with PCOS had beneficial effects on metabolic profiles.

Enhancing the health-promoting effects of tomato fruit for biofortified food

Consumption of tomato fruits, like those of many other plant species that are part of the human diet, is considered to be associated with several positive effects on health. Indeed, tomato fruits are an important source of bioactive compounds with known beneficial effects including vitamins, antioxidants, and anticancer substances. In particular, antioxidant metabolites are a group of vitamins, carotenoids, phenolic compounds, and phenolic acid that can provide effective protection by neutralizing free radicals, which are unstable molecules linked to the development of a number of degenerative diseases and conditions. In this review, we will summarize the recent progress on tomatoes nutritional importance and mechanisms of action of different phytochemicals against inflammation processes and prevention of chronic noncommunicable diseases (e.g., obesity, diabetes, coronary heart disease, and hypertension). In addition, we will summarize the significant progress recently made to improve the nutritional quality of tomato fruits through metabolic engineering and/or breeding.

Short-term folinic acid supplementation improves vascular reactivity in HIV-infected individuals: a randomized trial

OBJECTIVE

HIV-infected individuals present a cluster of conditions that activate or injure the vascular endothelium. The administration of folates may exert beneficial effects on endothelial function in different populations at risk for cardiovascular disease. The aim of this study was to determine the effects of 4 wk of folinic acid supplementation on forearm vascular responses during reactive hyperemia in HIV-infected patients under highly active antiretroviral therapy.

METHODS

This was a prospective, randomized, double-blind, placebo-controlled trial to compare the effects of 4 wk of daily ingestion of 5 mg of folinic acid (n = 15) or placebo (n = 15). Participants had to have been on antiretroviral therapy (ART) for at least 6 mo before enrollment, with undetectable viral load, and CD4 cell count >200 cells/mm(3). Vascular function was evaluated with venous occlusion plethysmography at baseline and after 4 wk, for the determination of brachial artery reactive hyperemia, and after isosorbide dinitrate administration.

RESULTS

The groups were comparable. The mean age of patients was 45 y; there were eight women in each group. There was no difference regarding ART regimen. The supplementation of folinic acid produced a significant improvement in reactive hyperemia (from 14.9 to 21.2 mL•min•100 mL). The same was not observed in placebo group (from 15.3 to 14.6 mL•min•100 mL; group P, 0.017; time P < 0.001; interaction P < 0.001). Endothelium-independent responses remained unchanged.

CONCLUSIONS

Short-term folinic acid supplementation improved vascular reactivity in HIV-infected individuals enrolled in the studied. As folate supplementation is safe and relatively inexpensive, long-term clinical trials should be conducted.

Effect of weight reduction on concentration of plasma total homocysteine in obese Japanese men

SUMMARY

OBJECTIVE

To test whether weight reduction would lower tHcys concentration, and whether adding exercise training to dietary weight reduction would further reduce tHcys concentration over diet alone.

DESIGN

A randomized, controlled, prospective, 14-week weight-loss intervention.

SETTING AND PARTICIPANTS

Forty-eight obese Japanese men aged 27-66 years were assigned to 2 subgroups depending on the type of treatment: diet alone (DA) and diet plus exercise training (DE). Concentration of tHcy was measured in frozen plasma samples by an HPLC method.

RESULTS

Body weight decreased significantly for both groups: DA -7.8 ± 3.2 kg and DE -9.1 ± 3.6 kg. A significant decrease was found in tHcys concentration of the DE group (-2.3 ± 5.0 μmol/L) but not of the DA (-0.3 ± 2.7 μmol/L). For subjects with hyperhomocysteinemia (≥15 μmol/L, n = 17), tHcys concentration decreased from 20.1 ± 7.0 to 13.9 ± 3.0 μmol/L (p < 0.01) for the DE group (n = 8) but did not change for the DA group (16.6 ± 1.9 μmol/L → 15.4 ± 2.3 μmol/L, n = 9). Furthermore, to consider a statistical phenomenon "regression to the mean", we excluded two subjects with the highest two tHcys values of the DE group. The DE group (n = 7) still displayed a significant reduction after the exclusion.

CONCLUSIONS

A weight reduction with diet alone did not improve tHcy levels. Adding aerobic exercise training to a dietary weight-reduction program may be effective for a reduction in tHcy.

Folic acid protects against lipopolysaccharide-induced preterm delivery and intrauterine growth restriction through its anti-inflammatory effect in mice

Increasing evidence demonstrates that maternal folic acid (FA) supplementation during pregnancy reduces the risk of neural tube defects, but whether FA prevents preterm delivery and intrauterine growth restriction (IUGR) remains obscure. Previous studies showed that maternal lipopolysaccharide (LPS) exposure induces preterm delivery, fetal death and IUGR in rodent animals. The aim of this study was to investigate the effects of FA on LPS-induced preterm delivery, fetal death and IUGR in mice. Some pregnant mice were orally administered with FA (0.6, 3 or 15 mg/kg) 1 h before LPS injection. As expected, a high dose of LPS (300 μg/kg, i.p.) on gestational day 15 (GD15) caused 100% of dams to deliver before GD18 and 89.3% of fetuses dead. A low dose of LPS (75 μg/kg, i.p.) daily from GD15 to GD17 resulted in IUGR. Interestingly, pretreatment with FA prevented LPS-induced preterm delivery and fetal death. In addition, FA significantly attenuated LPS-induced IUGR. Further experiments showed that FA inhibited LPS-induced activation of nuclear factor kappa B (NF-κB) in mouse placentas. Moreover, FA suppressed LPS-induced NF-κB activation in human trophoblast cell line JEG-3. Correspondingly, FA significantly attenuated LPS-induced upregulation of cyclooxygenase (COX)-2 in mouse placentas. In addition, FA significantly reduced the levels of interleukin (IL)-6 and keratinocyte-derived cytokine (KC) in amniotic fluid of LPS-treated mice. Collectively, maternal FA supplementation during pregnancy protects against LPS-induced preterm delivery, fetal death and IUGR through its anti-inflammatory effects.

Effects of baked products enriched with n-3 fatty acids, folates, β-glucans, and tocopherol in patients with mild mixed hyperlipidemia

OBJECTIVE

To assess whether a diet containing foods enriched with β-glucans (3.6 g/d), folic acid (1600 μg/d), long-chain (800 mg/d) and short-chain (400 mg/d) n-3 fatty acids, and tocopherols (120 mg/d) is able to modulate positively the cardiovascular risk profile in people at slightly increased cardiovascular risk.

METHODS

Sixteen subjects with mild plasma lipid abnormalities were studied according to a randomized crossover design. After a 2-week run-in period, they followed a diet containing baked products enriched with active nutrients (active diet) or a diet containing the same products but without active nutrients (control diet) for 1 month and then crossed over to the other diet. At the end of each period, a test meal of the same composition as the corresponding diet was administered, and plasma samples were obtained before and for 6 hours after the meal. Hunger and satiety were evaluated by the visual analog scale at fasting and after the meal.

RESULTS

Fasting plasma triglycerides were significantly lower after the active versus the control diet (1.56 ± 0.18 vs 1.74 ± 0.16 mmol/l, p < 0.05), as was the postprandial level of chylomicron triglycerides and the insulin peak (p < 0.05). The active diet also reduced fasting homocysteine (8 ± 0.6 vs 10 ± 0.8 μmol/l, p < 0.05) and the feeling of hunger at the fifth and sixth hour (p < 0.05).

CONCLUSIONS

Baked functional products enriched with n-3 fatty acids, folates, β-glucans, and tocopherols within the context of a balanced diet lower fasting and postprandial plasma triglycerides, fasting homocysteinemia, and the postprandial insulin peak. They induce a greater feeling of satiety with possible beneficial implications on energy intake.

Effect of folic acid supplementation on levels of circulating Monocyte Chemoattractant Protein-1 and the presence of intravascular ultrasound derived virtual histology thin-cap fibroatheromas in patients with stable angina pectoris

BACKGROUND

Virtual Histology Intravascular Ultrasound (VH-IVUS) may be used to detect early signs of unstable coronary artery disease. Monocyte Chemoattractant Protein-1 (MCP-1) is linked with coronary atherosclerosis and plaque instability and could potentially be modified by folic acid treatment.

METHODS

In a randomized, prospective study, 102 patients with stable angina pectoris (SAP) received percutaneous coronary intervention and established medical treatment as well as either homocysteine-lowering folic acid/vitamin B12 (± B6) or placebo (± B6) for 1 year before VH-IVUS was performed. The presence of VH-Thin-Cap Fibroatheroma (VH-TCFA) in non-intervened coronary vessels was registered and serum levels of MCP-1 were measured. The patients were subsequently followed for incident myocardial infarction (MI).

RESULTS

Patients treated with folic acid/vitamin B12 had a geometric mean (SD) MCP-1 level of 79.95 (1.49) versus 86.00 (1.43) pg/mL for patients receiving placebo (p-value 0.34). VH-TCFA lesions were present in 7.8% of patients and did not differ between intervention arms (p-value 0.47). Serum levels of MCP-1 were 1.46 (95% CI 1.12 to 1.92) times higher in patients with VH-TCFA lesions than in those without (p-value 0.005). Afterwards, patients were followed for median 2.1 years and 3.8% experienced a myocardial infarction (MI), which in post-hoc Cox regression analyses was independently predicted by both MCP-1 (P-value 0.006) and VH-TCFA (p-value 0.01).

CONCLUSIONS

In patients with SAP receiving established medical treatment, folic acid supplementation is not associated with either presence of VH-TCFA or levels of MCP-1. MCP-1 is however associated with VH-TCFA, a finding corroborated by increased risk for future MI. ClinicalTrials.gov Identifier: NCT00354081.

Folic acid and melatonin ameliorate carbon tetrachloride-induced hepatic injury, oxidative stress and inflammation in rats

This study investigated the protective effects of melatonin and folic acid against carbon tetrachloride (CCl4)-induced hepatic injury in rats. Oxidative stress, liver function, liver histopathology and serum lipid levels were evaluated. The levels of protein kinase B (Akt1), interferon gamma (IFN-γ), programmed cell death-receptor (Fas) and Tumor necrosis factor-alpha (TNF-α) mRNA expression were analyzed. CCl4 significantly elevated the levels of lipid peroxidation (MDA), cholesterol, LDL, triglycerides, bilirubin and urea. In addition, CCl4 was found to significantly suppress the activity of both catalase and glutathione (GSH) and decrease the levels of serum total protein and HDL-cholesterol. All of these parameters were restored to their normal levels by treatment with melatonin, folic acid or their combination. An improvement of the general hepatic architecture was observed in rats that were treated with the combination of melatonin and folic acid along with CCl4. Furthermore, the CCl4-induced upregulation of TNF-α and Fas mRNA expression was significantly restored by the three treatments. Melatonin, folic acid or their combination also restored the baseline levels of IFN-γ and Akt1 mRNA expression. The combination of melatonin and folic acid exhibited ability to reduce the markers of liver injury induced by CCl4 and restore the oxidative stability, the level of inflammatory cytokines, the lipid profile and the cell survival Akt1 signals.

Folate deficiency is associated with oxidative stress, increased blood pressure, and insulin resistance in spontaneously hypertensive rats

BACKGROUND

The role of folate deficiency and associated hyperhomocysteinemia in the pathogenesis of metabolic syndrome is not fully established. In the current study, we analyzed the role of folate deficiency in pathogenesis of the metabolic syndrome in the spontaneously hypertensive rat (SHR).

METHODS

Metabolic and hemodynamic traits were assessed in SHR/Ola rats fed either folate-deficient or control diet for 4 weeks starting at the age of 3 months.

RESULTS

Compared to SHRs fed a folate-replete diet, SHRs fed a folate-deficient diet showed significantly reduced serum folate (104 ± 5 vs. 11 ± 1 nmol/L, P < 0.0005) and urinary folate excretion (4.3 ± 0.6 vs. 1.2 ± 0.1 nmol/16 h, P < 0.0005) together with a near 3-fold increase in plasma total homocysteine concentration (4.5 ± 0.1 vs 13.1 ± 0.7 μmol/L, P < 0.0005), ectopic fat accumulation in liver, and impaired glucose tolerance. Folate deficiency also increased systolic blood pressure by approximately 15 mm Hg (P < 0.01). In addition, the low-folate diet was accompanied by significantly reduced activity of antioxidant enzymes and increased concentrations of lipoperoxidation products in liver, renal cortex, and heart.

CONCLUSIONS

These findings demonstrate that the SHR model is susceptible to the adverse metabolic and hemodynamic effects of low dietary intake of folate. The results are consistent with the hypothesis that folate deficiency can promote oxidative stress and multiple features of the metabolic syndrome that are associated with increased risk for diabetes and cardiovascular disease.

Nutrient intakes and the common mental disorders in women

BACKGROUND

There is an increasing recognition of the role of nutrition in depression and anxiety. Magnesium, folate and zinc have all been implicated in depressive illness, however there are few data on these nutrients in anxiety disorders and the data from population-studies are limited.

AIMS

In a large, randomly-selected, population-based sample of women, this study aimed to examine the relationship between the dietary intakes of these three micronutrients and clinically determined depressive and anxiety disorders and symptoms.

METHODS

Nutrient intakes were determined using a validated food frequency questionnaire. The General Health Questionnaire-12 measured psychological symptoms, and a clinical interview (Structured Clinical Interview for DSM-IV-TR, non-patient edition) assessed current depressive and anxiety disorders.

RESULTS

After adjustments for energy intake, each standard deviation increase in the intake of zinc, magnesium and folate was associated with reduced odds ratio (OR) for major depression/dysthymia (zinc: OR=0.52, 95% confidence interval (CI) 0.31 to 0.88; magnesium: OR=0.60, 95% CI 0.37 to 0.96; folate: OR=0.66, 95% CI 0.45 to 0.97). There was also an inverse association between the intake of magnesium and zinc and GHQ-12 scores (zinc: zβ=-0.16, 95% CI -0.29 to -0.04; magnesium: -0.14, 95% CI -0.26 to -0.03). These relationships were not confounded by age, socioeconomic status, education or other health behaviours. There was no relationship observed between any nutrient and anxiety disorders.

CONCLUSION

These results demonstrate an association between the dietary intakes of magnesium, folate and zinc and depressive illnesses, although reverse causality and/or confounding cannot be ruled out as explanations.

Immunomodulation in young laying hens by dietary folic acid and acute immune responses after challenge with Escherichia coli lipopolysaccharide

We investigated the effects of dietary folic acid (FA) supplementation on immunological parameters in young laying hens under acute conditions of lipopolysaccharide (LPS) challenge. Twenty-four Shaver White laying hens at 24 wk were fed 2 diets in a completely randomized design. The diets were wheat-soybean based, with either 0 or 4 mg of supplemental FA per kilogram of diet. At 32 wk of age, 6 hens from each dietary treatment were injected intravenously with 8 mg/kg of BW of either LPS or saline. Four hours after injection, blood was collected and the hens were euthanized to obtain spleen and cecal tonsils. Heterophil:lymphocyte ratio, CD3+, CD4+, CD8+ T cells, and CD4+:CD8+ cells in the blood and spleen were not affected by dietary FA. Relative to saline-injected hens, LPS-injected hens had fewer (P < 0.05) CD3+, CD4+, CD8+, and CD4+:CD8+ cells in the blood, and no difference was found in the spleen. Total protein, albumin, and globulin were found to be higher (P < 0.05) in FA-supplemented hens compared with the control. However, total protein, albumin, and globulins decreased (P < 0.05) in the LPS-injected hens compared with the saline control. Expression of interleukin (IL)-1β in cecal tonsils decreased (P < 0.05) in FA-supplemented hens, but no dietary influence was found on the expression of other genes in both the spleen and cecal tonsils. Lipopolysaccharide upregulated (P < 0.05) expression of IL-10 and interferon (IFN)-γ in the spleen, and IL-1β, IL-10, and IFN-γ in the cecal tonsils, whereas the expression of Toll-like receptor (TLR)-4 and IL-8 was not influenced by LPS in the spleen and cecal tonsils. There was a diet × challenge interaction for total IgG, and cytokines IL-1β and IL-18 in the spleen as well as IL-18 in the cecal tonsils. In conclusion, there were few interactions of dietary FA and LPS; however, FA increased biochemical constituents, enhanced generation of total IgG, as well as exhibiting pleoitropic effects in inflammatory responses.

Effect of folic acid supplementation on biochemical indices in overweight and obese men with type 2 diabetes

AIMS

This study performed to determine the effects of folate supplementation on indices of glycemic control, insulin resistance and lipid profile in overweight and obese men with type 2 diabetes under metformin (at least 1500 mg daily) treatment.

METHODS

The study was a double-blind randomized controlled clinical trial. Forty-eight overweight and obese men (aged 58.2±8.9 years; BMI=28.6±2.9 kg/m(2)) with type 2 diabetes participated in the study. Patients were divided randomly into two groups of folic acid (5 mg/d) and placebo. All patients received the tablets for eight weeks.

RESULTS

Supplementation with folic acid led to 8% decrease in HbA1C (p=0.048), 7.5% in fasting blood glucose (p=0.051), 16.2% in serum insulin (p=0.021), 20.5% in insulin resistance (p=0.041) and 21.2% in plasma homocysteine (p=0.000). A significant increase in serum folate and B12 levels (19% and 17.3%, p=0.000, respectively) were observed in the folic acid group, whereas no significant changes occurred in the placebo group. Also, in the folic acid and placebo groups, there were no significant changes in body weight.

CONCLUSIONS

Folic acid supplementation lowered plasma level of homocysteine, improved glycemic control and insulin resistance in patients with type 2 diabetes.

The effect of vitamin-mineral supplementation on CRP and IL-6: a systemic review and meta-analysis of randomised controlled trials

BACKGROUND AND AIMS

Inflammation is regarded as a risk predictor for metabolic syndrome and atherogenesis. The objective of this study was to conduct a systematic review and a meta-analysis to confirm the effect of vitamin-mineral supplementation on cytokine levels.

METHODS AND RESULTS

We searched the PubMed, EMBASE and Cochrane databases up to May 2009 for randomised controlled trials regarding the effect of vitamin-mineral supplementation on C-reactive protein (CRP) and interleukin-6 (IL-6). Eighteen trials with 1747 participants for CRP and nine trials with 1037 participants for IL-6 were included, respectively. Pooled estimates and 95% confidence intervals (CIs) were calculated by fixed- or random-effects model. No significant differences were observed for CRP and IL-6 reduction between the subjects with vitamin-mineral supplementation and placebo control. A dose-dependent manner for different body mass index (BMI) subgroups in CRP analysis was observed (weighted mean difference (WMD), -0.057; 95%CI: -0.753 to 0.639 for BMI<25; WMD, -0.426; 95%CI: -0.930 to 0.079 for 25 ≤ BMI < 30; WMD, -0.491; 95%CI: -1.407 to 0.424 for BMI ≥ 30). However, no significance was detected in meta-regression (-0.046, 95%CI: -0.135 to 0.044). Moreover, the best effect for reduction in CRP levels in a supplementation duration of 4 weeks-6 months (WMD, -0.449; 95%CI: -1.004 to 0.106) was observed compared with supplementation duration less than 4 weeks (WMD, -0.137; 95%CI, -0.816 to 0.541) and more than 6 months (WMD, -0.389; 95%CI, -1.034 to 0.257) without statistical significance (P = 0.059).

CONCLUSION

No statistically significant evidences for the potential dose-dependent manner of BMI and best supplement duration were detected in this study. Large and well-designed studies are recommended to confirm this conclusion.

Relationship between dietary folate intake and plasma monocyte chemoattractant protein-1 and interleukin-8 in heart failure patients

This study aimed to examine the association of dietary vitamin intakes with plasma pro-inflammatory cytokine levels in Korean heart failure patients. Stable outpatients with heart failure were recruited and finally 91 patients were included. Dietary intakes were estimated by a developed semi-quantitative food frequency questionnaire. The simultaneous measurement of 17 cytokines was performed along with analysis of plasma C-reactive protein. Plasma C-reactive protein levels significantly correlated with dietary intakes of vitamin C (r = −0.30, p<0.005), β-carotene (r = −0.23, p<0.05), and folate (r = −0.31, p<0.005). However, these associations were no longer significant after adjusting for traditional risk factors for heart failure. On the other hand, plasma levels of monocyte chemoattractant protein-1 significantly correlated with dietary folate intake (r = −0.31, p<0.001), and plasma interleukin-8 levels significantly correlated with dietary intakes of vitamin C (r = −0.38, p<0.001), β-carotene (r = –0.42, p<0.001), and folate (r = −0.38, p<0.001) after the adjustment. Dietary folate intake was found as a primary influencing factor on plasma levels of monocyte chemoattractant protein-1 (p<0.005, R² = 0.20) and interleukin-8 (p<0.001, R² = 0.32) through a stepwise multiple linear regression analysis. Dietary folate intake was significantly associated with plasma levels of monocyte chemoattractant protein-1 and interleukin-8 which indicates dietary folate may have a potentially beneficial role in the prevention and treatment of heart failure.

Folic acid inhibits lipopolysaccharide-induced inflammatory response in RAW264.7 macrophages by suppressing MAPKs and NF-κB activation

OBJECTIVE

The aim of the present study was to investigate the effects of folic acid on the inflammatory responses to lipopolysaccharide (LPS) in RAW264.7 cells and the signal transduction pathways involved.

METHODS

RAW264.7 macrophages were used. The production of nitric oxide (NO) was determined by the Griess test. The protein levels and mRNA expression of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) were determined by ELISA and RT-PCR, respectively. The phosphorylation of mitogen-activated protein kinases (MAPKs) and nuclear nuclear factor-kappa B (NF-κB) p65 protein were analyzed by Western blotting.

RESULTS

Folic acid inhibited LPS-induced production of NO, TNF-α and IL-1β with decreased mRNAs of inducible nitric oxide synthase (iNOS), TNF-α and IL-1β. Further study showed that folic acid inhibited the LPS-induced phosphorylation of MAPKs and the nuclear translocation of NF-κB.

CONCLUSION

Folic acid inhibits the inflammatory response of RAW 264.7 cells to LPS through inhibiting the MAPKs and NF-κB pathways.

Effects of folic acid supplementation to rations differing in the concentrate to roughage ratio on ruminal fermentation, nutrient flow at the duodenum, and on serum and milk variables of dairy cows

The present study was undertaken to determine the effects of dietary folic acid (FOL) supplementation on ruminal fermentation, duodenal nutrient flow, serum and milk variables, and on B-vitamin concentration in serum. The study was divided into two experiments: in Exp. 1 the forage to concentrate (F:C) ratio of the diet (DM basis) was 34:66 (high concentrate, HC), while in Exp. 2 the F:C ratio was 66:34 (high forage, HF). In addition, the cows received 0 or 1 g FOL/d. In Exp. 1, two German Holstein cows equipped with cannulas in the dorsal sac of the rumen and in the proximal duodenum were dry and five were lactating (186 +/- 144 days in milk); in Exp. 2 four cows were dry and four were lactating (165 +/- 57 days in milk). In cows fed the HC diet, FOL supplementation decreased the ruminally-fermented organic matter. Thus, less energy was available for ruminal microorganisms, which resulted in a reduced microbial crude protein flow at the duodenum. Feeding the HF diet, FOL supplementation only increased the apparent ruminal digestibility of acid detergent fibre (ADF). With the HF diet, FOL had no influence on the serum levels of glucose, non-esterified fatty acids, beta-hydroxybutyrate, urea, thiamine, riboflavin, pyridoxal-5'-phosphate, pyridoxic acid, pyridoxal, pyridoxine, pyridoxamine, pantothenic acid, nicotinamide or nicotinic acid, whereas supplementing FOL to the HC diet lowered the serum glucose and riboflavin levels. In both experiments, the supplementation of FOL had no effects on milk composition. Folic acid supplementation to both diets increased the concentrations of serum 5-methyl-tetrahydrofolate. However, no beneficial effects to dairy cows were obvious. Therefore, to achieve certain results, studies with a higher number of non-fistulated cows would be necessary.

Synergism in hyperhomocysteinemia and diabetes: role of PPAR gamma and tempol

BACKGROUND

Hyperhomocysteinemia (HHcy) and hyperglycemia cause diabetic cardiomyopathy by inducing oxidative stress and attenuating peroxisome proliferator- activated receptor (PPAR) gamma. However, their synergistic contribution is not clear.

METHODS

Diabetic Akita (Ins2+/-) and hyperhomocysteinemic cystathionine beta synthase mutant (CBS+/-) were used for M-mode echocardiography at the age of four and twenty four weeks. The cardiac rings from WT, Akita and hybrid (Ins2+/-/CBS+/-) of Akita and CBS+/- were treated with different doses of acetylcholine (an endothelial dependent vasodilator). High performance liquid chromatography (HPLC) was performed for determining plasma homocysteine (Hcy) level in the above groups. Akita was treated with ciglitazone (CZ) - a PPAR gamma agonist and tempol-an anti-oxidant, separately and their effects on cardiac remodeling were assessed.

RESULTS

At twenty four week, Akita mice were hyperglycemic and HHcy. They have increased end diastolic diameter (EDD). In their heart PPAR gamma, tissue inhibitor of metalloproteinase-4 (TIMP-4) and anti-oxidant thioredoxin were attenuated whereas matrix metalloproteinase (MMP)-9, TIMP-3 and NADPH oxidase 4 (NOX4) were induced. Interestingly, they showed synergism between HHcy and hyperglycemia for endothelial-myocyte (E-M) uncoupling. Additionally, treatment with CZ alleviated MMP-9 activity and fibrosis, and improved EDD. On the other hand, treatment with tempol reversed cardiac remodeling in part by restoring the expressions of TIMP-3,-4, thioredoxin and MMP-9.

CONCLUSIONS

Endogenous homocysteine exacerbates diabetic cardiomyopathy by attenuating PPAR gamma and inducing E-M uncoupling leading to diastolic dysfunction. PPAR gamma agonist and tempol mitigates oxidative stress and ameliorates diastolic dysfunction in diabetes.

Blood folate status and expression of proteins involved in immune function, inflammation, and coagulation: biochemical and proteomic changes in the plasma of humans in response to long-term synthetic folic acid supplementation

We used plasma proteomics to identify human proteins responsive to folate status. Plasma was collected from subjects treated with placebo or 1.2 mg of folic acid daily for 12 weeks in a randomized controlled trial. Homocysteine and folate were measured by immunoassay and uracil misincorporation by electrophoresis. The plasma proteome was assessed by 2-D gel electrophoresis, and proteins were identified by LC MS/MS. 5-methylTHF increased 5-fold (P = 0.000003) in response to intervention. Red cell folate doubled (P = 0.013), and lymphocyte folate increased 44% (P = 0.0001). Hcy and uracil dropped 22% (P = 0.0005) and 25% (P = 0.05), respectively. ApoE A-1, alpha-1-antichymotrypsin, antithrombin, and serum amyloid P were downregulated, while albumin, IgM C, and complement C3 were upregulated (P < 0.05). More than 60 proteins were significantly associated with folate pre- and postintervention (P < 0.01). These were categorized into metabolic pathways related to complement fixation (e.g., C1, C3, C4, Factor H, Factor 1, Factor B, clusterin), coagulation (e.g., antithrombin, alpha-1-antitrypsin, kininogen) and mineral transport (e.g., transthyretin, haptoglobin, ceruloplasmin). Low folate status pre- and post-treatment were associated with lower levels of proteins involved in activation and regulation of immune function and coagulation. Supplementation with synthetic folic acid increased expression of these proteins but did not substantially disrupt the balance of these pathways.

Antagonistic effects of aspirin and folic acid on inflammation markers and subsequent risk of recurrent colorectal adenomas

The Aspirin/Folate Polyp Prevention Trial found that aspirin, but not folic acid, reduced recurrence of colorectal adenomas. This study examined whether treatment effects on inflammation markers explained the trial results. The trial had a factorial design with three aspirin (placebo, 81, and 325 mg/d) and two folic acid (placebo and 1 mg/d) groups. There were 884 subjects who had colonoscopic evaluation for adenomas at year 3 and plasma levels of C-reactive protein (CRP), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), soluble TNF receptor type II (sTNF-R2), and IL-1 receptor antagonist (IL-1Ra) measured at baseline and year 3. Among individuals not receiving folic acid, there was a 4% decrease (mean ratio of year 3 to baseline levels = 0.96, 95% confidence interval [CI] = 0.82 to 1.14) in CRP for a period of 3 years in the 325 mg of aspirin group vs a 20% increase (mean ratio = 1.20, 95% CI = 1.03 to 1.41) in the placebo group (P = .027). By contrast, the reverse was observed among individuals who also received folic acid (P(interaction) = .013). Changes in inflammation markers were not associated with adenoma recurrence. Low-dose aspirin (325 mg/d) is beneficial in stabilizing CRP levels, which may be abrogated by folate. Nevertheless, inflammation markers do not mediate the chemopreventive effect of aspirin on colorectal adenomas.

Randomized clinical trial of folate supplementation in patients with peripheral arterial disease

BACKGROUND

The aim was to determine whether folate supplementation improved arterial function in patients with peripheral arterial disease (PAD).

METHODS

Individuals with PAD were randomly assigned to receive 400 microg folic acid (45 patients) or 5-methyltetrahydrofolate (5-MTHF) (48) daily, or placebo (40) for 16 weeks. Primary endpoints were changes in plasma total homocysteine (tHcy), ankle : brachial pressure index (ABPI) and pulse wave velocity (PWV). Secondary outcomes were changes in plasma inflammatory markers.

RESULTS

Plasma tHcy was significantly reduced in folic acid and 5-MTHF groups compared with controls: median difference: - 2.12 (95 per cent confidence interval - 3.70 to - 0.75) micromol/l (P = 0.002) and - 2.07 (-3.48 to - 0.54) micromol/l (P = 0.007) respectively. ABPI improved significantly: median difference 0.07 (0.04 to 0.11) (P < 0.001) and 0.05 (0.01 to 0.10) (P = 0.009) respectively. Brachial-knee PWV (bk-PWV) decreased significantly in individuals receiving 5-MTHF and tended to be reduced in those taking folic acid compared with controls: median difference: - 1.10 (-2.20 to - 0.20) m/s (P = 0.011) and - 0.90 (-2.10 to 0.00) m/s (P = 0.051) respectively. Plasma levels of inflammatory markers were not affected.

CONCLUSION

Folate administration reduced plasma homocysteine, and slightly improved ABPI and bk-PWV.

Folic acid in general medicine and dermatology

Folic acid is a vitamin B essential for the integrity and function of DNA. Relative deficiency of folic acid may occur in conditions such as pregnancy and hyperproliferative or chronic inflammatory disorders. Folic acid supplementation has been proven to be beneficial in the prevention of neural tube defects and in limiting methotrexate side effects, and may reduce the risk of colorectal cancer. Folate is a critical vitamin in determining plasma homocysteine levels, which in turn is a major risk factor for cardiovascular diseases. The results of large clinical trials with dietary supplementation of folic acid, vitamin B12 and vitamin B6 have shown that this homocysteine-lowering therapy is effective in the secondary prevention of non-fatal strokes, but had no effect in the prevention of fatal cardiovascular diseases. Hyperhomocysteinemia has also been reported in age-related neurological conditions with cognitive impairment (e.g. dementia), and psychiatric disorders such as depression. Elevated homocysteine levels are frequent in patients with chronic immune-mediated disorders including rheumatoid arthritis, systemic lupus erythematosus, chronic plaque psoriasis and psoriatic arthritis, which have in common a tendency to an accelerated atherosclerosis leading to increased deaths from cardiovascular events. Folic acid supplementation appears as a reasonable therapeutic option in patients affected by chronic inflammatory skin diseases, such as moderate to severe psoriasis; in particular, those with concomitant hyperhomocysteinemia, low plasma folate and additional cardiovascular risk factors.

Higher serum folate levels are associated with a lower risk of atopy and wheeze

BACKGROUND

Folic acid is known to be associated with inflammatory diseases, but the relationship between folic acid and allergic diseases is unclear.

OBJECTIVES

The purpose of the study was to examine the relationship between serum folate levels and markers of atopy, wheeze, and asthma.

METHODS

Data were obtained from the 2005-2006 National Health and Nutrition Examination Survey in which serum folate and total IgE levels were measured in 8083 subjects 2 years of age and older. A high total IgE level was defined as greater than 100 kU/L. Allergen-specific IgE levels were measured for a panel of 5 common aeroallergens. Atopy was defined as at least 1 positive allergen-specific IgE level. Doctor-diagnosed asthma and wheeze in the previous 12 months were assessed by means of questionnaire.

RESULTS

Serum folate levels were inversely associated with total IgE levels (P < .001). The odds of a high total IgE level, atopy, and wheeze decreased across quintiles of serum folate levels, indicating a dose-response relationship between serum folate levels and these outcomes. Each of these associations remained statistically significant after adjusting for age, sex, race/ethnicity, and poverty index ratio. Adjusted odds ratios associated with the fifth quintile of folate relative to the first quintile were as follows: high IgE level, 0.70 (95% CI, 0.53-0.92); atopy, 0.69 (95% CI, 0.57-0.85); and wheeze, 0.60 (95% CI, 0.44-0.82). Higher folate levels were also associated with a lower risk of doctor-diagnosed asthma, but this finding was not statistically significant (odds ratio for fifth quintile vs first quintile, 0.84 [95% CI, 0.70-1.02]).

CONCLUSIONS

Serum folate levels are inversely associated with high total IgE levels, atopy, and wheeze.

Selected markers of cardiovascular disease in a population exposed to arsenic from drinking water

This study examined prevalence and serum levels of selected markers of cardiovascular disease in 34 subjects from a Croatian rural population exposed to high levels of arsenic (As) from drinking water (611.89±10.06μg/l). The prevalences of overweight and obese subjects in the population were 32% and 35%. Half the subjects had hypertension, 29% had increased fasting serum glucose level and two were diabetic. Median total cholesterol (5.82mmol/l) and triglycerides (2.15mmol/l) were above the desirable margins. The median C-reactive protein level (1.20mg/l) was slightly higher than previously reported for healthy subjects. Serum Hsp70 level was significantly higher in nonsmokers. Total urinary As levels were positively correlated with age-adjusted serum levels of cobalamin. Near significance were also serum total bilirubin, antibodies to Hsp60 and folate. Tentative investigation of risk factors among subjects classified by tumor necrosis factor-α -308G/A and interleukin-6-174G/C gene polymorphisms was also performed. Collectively, the results are in agreement with the hypothesis of As-induced and/or compounded cardiovascular disease.

Dietary choline and betaine intakes in relation to concentrations of inflammatory markers in healthy adults: the ATTICA study

BACKGROUND

Choline and betaine are found in a variety of plant and animal foods and were recently shown to be associated with decreased homocysteine concentrations.

OBJECTIVE

The scope of this work was to investigate the associations between dietary choline and betaine consumption and various markers of low-grade systemic inflammation.

DESIGN

Under the context of a cross-sectional survey that enrolled 1514 men (18-87 y of age) and 1528 women (18-89 y of age) with no history of cardiovascular disease (the ATTICA Study), fasting blood samples were collected and inflammatory markers were measured. Dietary habits were evaluated with a validated food-frequency questionnaire, and the intakes of choline and betaine were calculated from food-composition tables.

RESULTS

Compared with the lowest tertile of choline intake (<250 mg/d), participants who consumed >310 mg/d had, on average, 22% lower concentrations of C-reactive protein (P < 0.05), 26% lower concentrations of interleukin-6 (P < 0.05), and 6% lower concentrations of tumor necrosis factor-alpha (P < 0.01). Similarly, participants who consumed >360 mg/d of betaine had, on average, 10% lower concentrations of homocysteine (P < 0.01), 19% lower concentrations of C-reactive protein (P < 0.1), and 12% lower concentrations of tumor necrosis factor-alpha (P < 0.05) than did those who consumed <260 mg/d. These findings were independent of various sociodemographic, lifestyle, and clinical characteristics of the participants.

CONCLUSIONS

Our results support an association between choline and betaine intakes and the inflammation process in free-eating and apparently healthy adults. However, further studies are needed to confirm or refute our findings.

Palmitic acid induces production of proinflammatory cytokine interleukin-8 from hepatocytes

Obesity and the metabolic syndrome are closely correlated with hepatic steatosis. Simple hepatic steatosis in nonalcoholic fatty liver disease can progress to nonalcoholic steatohepatitis (NASH), which can be a precursor to more serious liver diseases, such as cirrhosis and hepatocellular carcinoma. The pathogenic mechanisms underlying progression of steatosis to NASH remain unclear; however, inflammation, proinflammatory cytokines, and oxidative stress have been postulated to play key roles. We previously reported that patients with NASH have elevated serum levels of proinflammatory cytokines, such as interleukin-8 (IL-8), which are likely to contribute to hepatic injury. This study specifically examines the effect of hepatic steatosis on IL-8 production. We induced lipid accumulation in hepatocytes (HepG2, rat primary hepatocytes, and human primary hepatocytes) by exposing them to pathophysiologically relevant concentrations of palmitic acid to simulate the excessive influx of fatty acids into hepatocytes. Significant fat accumulation was documented morphologically by Oil Red O staining in cells exposed to palmitic acid, and it was accompanied by an increase in intracellular triglyceride levels. Importantly, palmitic acid was found to induce significantly elevated levels of biologically active neutrophil chemoattractant, IL-8, from steatotic hepatocytes. Incubation of the cells with palmitate led to increased IL-8 gene expression and secretion (both mRNA and protein) through mechanisms involving activation of nuclear factor kappaB (NF-kappaB) and c-Jun N-terminal kinase/activator protein-1.

CONCLUSION

These data demonstrate for the first time that lipid accumulation in hepatocytes can stimulate IL-8 production, thereby potentially contributing to hepatic inflammation and consequent liver injury.

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.