Genetically predicted lipid traits mediate the association between folic acid and atherosclerosis

Atherosclerosis (AS) is one of the most common causes of death from cardiovascular disease, and low folic acid (FA) levels have been reported to be strongly associated with an increased risk of AS. We aimed to obtain causal estimates of the association between FA and AS and to quantify the mediating role of known modifiable risk factors. Based on the largest genome-wide association study (GWAS) from the IEU Open GWAS Project for all human studies, we conducted a two-sample Mendelian randomization (MR) study of genetically predicted FA and AS. A two-step MR design was then used to assess the causal mediating effect of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) on the relationship between FA and AS. This MR analysis showed that genetically determined FA levels [IVW: Odds Ratio (OR) = 0.623, 95% CI 0.421-0.924, P = 0.018] were associated with a reduced risk of AS. Inverse variance weighted (IVW) MR analysis also showed that genetically predicted FA was positively correlated with HDL-C levels (OR = 1.358, 95% CI 1.029-1.792, P = 0.031) and negatively correlated with LDL-C (OR = 0.956, 95% CI 0.920-0.994, P = 0.023) and TG levels (OR = 0.929, 95% CI 0.886-0.974, P = 0.003). LDL-C, HDL-C, and TG mediate 3.00%, 6.80%, and 4.40%, respectively, of the total impact of FA on AS. The combined effect of these three factors accounts for 13.04% of the total effect. Sensitivity analysis verifies the stability and reliability of the results. These results support a potential causal protective effect of FA on AS, with considerable mediation through many modifiable risk factors. Thus, interventions on levels of LDL-C, HDL-C, and TG have the potential to substantially reduce the burden of AS caused by low FA.

Folic acid and plasma lipids: Interactions and effect of folate supplementation

Dyslipidaemia and hyperhomocysteinemia are known risk factors for cardiovascular disease. While it is evident that optimization of plasma lipid is associated with low risk of cardiovascular disease in the general population, it is not yet fully clear whether reduction of homocysteinemia is associated with an improvement in risk in all subjects. The aim of our narrative review is to highlight eventual effects of folate supplementation on LDL-C levels, LDL-C oxidation and atherosclerosis-related complications. A comprehensive literature search was done in electronic database, including PubMed, Web of Science, Cochrane, and Scopus from inception up to January 2024. Based on the available evidence, epidemiological data, pathophysiological observations and meta-analyses of randomized clinical trials suggest that folic acid supplementation may modestly but significantly improve plasma lipid levels, lipid atherogenicity, and atherosclerosis-related early vascular damage, and that folic acid supplementation may significantly reduce the risk of cerebrovascular disease. Considering the low-cost and high safety profile of folic acid, its long-term supplementation could be considered for dyslypidaemic patients in secondary prevention for cardiovascular disease.

Folic acid enhances the cardiovascular protective effect of amlodipine in renal hypertensive rats with elevated homocysteine

OBJECTIVES

To investigate the actions of amlodipine-folic acid (amlodipine-FA) preparation on hypertension and cardiovascular in renal hypertensive rats with hyperhomocysteinemia (HHcy), so as to provide experimental basis for clinical research of amlodipine folic acid tablets.

METHODS

Rats model of renal hypertension with HHcy were established. The rats were randomly divided into groups of model, amlodipine, folic acid (FA) and amlodipine-FA of various dosages. Normal rats were used as normal control group. Blood pressure, Hcy as well as plasma NO, ET-1 and hemodynamics were assayed. Histological alterations of heart and abdominal aorta were also examined.

RESULTS

Compared with the normal group, blood pressure, plasma Hcy, and NO of the rats in model group were significantly increased, while the plasma ET-1 was decreased. Compared with the normal group, the animals in the model group had reduced cardiac function, thickened wall of the aorta and narrowed lumen. In FA group and amlodipine group, the rat plasma NO was increased while ET-1 was decreased, the protective effect of amlodipine-FA group on endothelial cells was further enhanced. In amlodipine group, the rat hemodynamics (LVSP, LVEDP and ±dp/dt_max, et al.) and vascular damage were significantly reduced, while in amlodipine-FA group, the heart function were further improved, and myocardial and vascular hypertrophy were significantly reduced.

CONCLUSIONS

As compared to amlodipine alone, amlodipine -FA can lower both blood pressure and plasma Hcy, significantly enhancing vascular endothelial function to protect the heart and blood vessel in renal hypertensive rats with HHcy.

Effects of folic acid on oxidative damage of kidney in lead-exposed rats

INTRODUCTION

Lead (Pb) has many applications in daily life, but in recent years, various problems caused by lead exposure have aroused people's concern. Folic acid is widely found in fruits and has received more attention for its antioxidant function. However, the role of folic acid in lead-induced kidney injury in rats is unclear. This study was designed to investigate the effects of folic acid on oxidative stress and endoplasmic reticulum stress in the kidney of rats caused by lead exposure.

METHODS

Forty specific pathogen-free male Rattus norvegicus rats were randomly divided into control, lead, intervention, and folic acid groups. The levels of SOD, GSH-Px, GSH, and MDA were measured by biochemical kits. The protein levels of Nrf2, HO-1, CHOP, and GRP78 were measured by immunofluorescence.

RESULTS

This study showed that lead exposure increased the blood levels of lead in mice. However, the intervention of folic acid decreased the levels of lead, but the difference was not statistically significant. Lead exposure causes oxidative stress by decreasing kidney SOD, GSH-Px, and GSH levels and increasing MDA levels. However, folic acid alleviated the oxidative damage caused by lead exposure by increasing the levels of GSH-Px and GSH and decreasing the levels of MDA. Immunofluorescence results showed that folic acid intervention downregulated the upregulation of kidney Nrf2, HO-1, GRP78, and CHOP expression caused by lead exposure.

DISCUSSION

Overall, folic acid alleviates kidney oxidative stress induced by lead exposure by regulating Nrf2 and HO-1, while regulating CHOP and GRP78 to mitigate apoptosis caused by excessive endoplasmic reticulum stress.

Plasma Homocysteine Level Is Independently Associated With Conventional Atherogenic Lipid Profile and Remnant Cholesterol in Adults

Background

Homocysteine (Hcy) is an independent risk factor for cardiovascular disease, while mechanisms are unclear. Despite inconsistent and limited, epidemiological and experimental studies indicated that hyperhomocysteinemia (HHcy) affected lipid metabolism. This study aims to investigate the association of plasma Hcy with traditional lipid profiles and remnant cholesterol (RC) in Chinese adults.

Methods

In total, 7,898 subjects aged 20–79 years who underwent a physical examination at Beijing Chao-Yang Hospital in Beijing were included in this study. Fasting plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), lipoprotein (a) [Lp(a)], Hcy, and other metabolic risk factors were measured by routine automated laboratory methods. RC was calculated as TC minus HDL-C and LDL-C. The linear regression model and logistic regression model were used to assess the relationship between Hcy and lipids after adjusting potential confounders.

Results

Of the subjects, the median level of plasma Hcy was 13.0 μmol/L and 32.3% had HHcy. Plasma Hcy was negatively associated with HDL-C, ApoA1, and Lp(a) and positively associated with TG levels after adjusting age, sex, body mass index, blood pressure, alanine transaminase, aspartate transaminase, creatinine, uric acid, and glucose. HHcy significantly increased the risk of low HDL-C [odds ratio (OR) 1.26; 95%CI (1.11–1.44); p < 0.001]. The net mediation effects of ApoA1 on the relationship between Hcy and HDL-C before and after adjusting confounders were 46.9 and 30.6%, respectively. More interestingly, the RC level was significantly elevated in subjects with HHcy after adjusting other influencing factors (p = 0.025). Hcy presented a positive correlation with RC levels after adjusting the above confounding factors (β = 0.073, p = 0.004), and the correlation was still significant even after controlling other lipids, including TG, LDL-C, HDL-C, ApoA1, ApoB, and Lp(a).

Conclusion

Our study showed that plasma Hcy was not only significantly associated with conventional atherogenic lipids but also independently correlated with RC levels beyond other lipids after controlling potential confounders. This finding proposes that identifying Hcy-related dyslipidemia risk, both traditional lipids and RC residual risk, is clinically relevant as we usher in a new era of targeting Hcy-lowering therapies to fight against dyslipidemia or even cardiovascular disease.

Protective Potential of Uric Acid, Folic Acid, Glutathione and Ascorbic Acid Against the Formation of Toxic Met-Myoglobin

BACKGROUND

Myoglobin is an oxygen binding protein and its dysfunction has been associated with the pathology of several human disorders. This study was undertaken to investigation the role of hydrogen peroxide (H2O2) in the formation of met-myoglobin and the protective potential of four different reductants such as uric acid, folic acid, glutathione and ascorbic acid were also tested against met-myoglobin formation.

METHODS

Human myoglobin was treated with H2O2 in-vitro in order to prepare met-myoglobin. The generation of met-myoglobin was confirmed by UV-visible spectroscopy and its stability was analysed by the treatment of human myoglobin with H2O2 at varying pH or time. High performance liquid chromatography (HPLC) was used to determine the oxidatively modified heme products in met-myoglobin. Spectroscopic analysis was used to identify the protective potential of uric acid, folic acid, glutathione and ascorbic acid against the formation of met-myoglobin.

RESULTS

The novel data of this study showed that H2O2 induced extensive damage of myoglobin but the treatment with uric acid, folic acid, glutathione or ascorbic acid provides protection of myoglobin against H2O2 induced oxidative damaged. The study apparently proved the protective potential of all these compounds against the toxicity produced by H2O2.

CONCLUSION

This is the first study that shows uric acid, folic acid, glutathione and ascorbic acid provide protection against the generation of toxic met-myoglobin and might be used therapeutically to modify the blood conditions in order to prevent the progression of human disorders associated with myoglobin dysfunction.

Folic acid attenuates remodeling and dysfunction in the aging heart through the ER stress pathway

AIMS

Age-related structure changes and dysfunction of heart are likely to contribute heart failure in elderly people. Recent studies have shown that folic acid supplementation effectively delays age-related declines; nevertheless, the role and mechanism of folic acid in protection against cardiac aging remain unclear. The aim of the current study was to determine whether folic acid inhibits remodeling and dysfunction during the aging process and to elucidate its underlying mechanisms.

MAIN METHODS

Male C57BL/6 mice aged 4 months (adult) and 14 months (aged) were fed a standard diet or a folic acid diet for 6 months. Echocardiograms and histological evaluations were used to detect left ventricle (LV) function, LV remodeling, cardiac fibrosis, apoptosis and oxidative stress. Senescence-associated β-galactosidase activity staining was used to detect cardiac senescence rate. Western blotting was employed to detect the levels of senescence and ER stress signaling.

KEY FINDING

LV hypertrophy was reduced and LV function was preserved in aged mice that consumed folic acid. LV remodeling, fibrosis, apoptosis and oxidative stress were also reduced in mice that consumed folic acid. Senescence-associated β-galactosidase activity staining revealed that folic acid attenuated cardiac senescence by down-regulating p53/p21/p16 levels. Protein assays of myocardial tissue revealed that the ER stress pathway is the important underlying mechanism during cardiac senescence. The involvement of these pathways was confirmed by doxorubicin-induced H9C2 cardiomyocyte senescence.

SIGNIFICANCE

These findings suggest that folic acid prevents age-related cardiac remodeling and dysfunction and attenuates cellular senescence. ER stress responses may be the mechanisms involved in the protective effect of folic acid against cardiac aging.

Folic acid and its metabolite codetermination for pharmacokinetics with circadian rhythms and evaluation of oral bioavailability

OBJECTIVES

Pharmacokinetics of vitamins is still a challenge. In this study, folic acid (FA) was used as a model drug and aimed at investigating a reliable method for its detailed pharmacokinetic evaluations.

METHODS

An high-performance liquid chromatography-tandem mass spectrometry method was developed and performed to determinate the FA and 5-methyltetrahydrofolic acid (5-methylTHF) simultaneously, which was applied to characterize the circadian rhythms as well as the pharmacokinetics of different preparations.

KEY FINDINGS

The plasma concentration of 5-methylTHF in fasted state was twofold higher than that in fed state. The circadian rhythms were studied before the pharmacokinetics and revealed that free FA was almost undetected in blank plasma, while 5-methylTHF had a slight decrement at 12:00. Hence, the pharmacokinetics of FA was conducted and showed that the administration of FA solution resulted in enhancing bioavailability of 5-methylTHF comparing with FA raw material suspension, whereas the free FA level in plasma was similar. The mechanism could be that FA was rapidly metabolized to 5-methylTHF in intestinal epithelial cell after absorption, which revealed that intestinal metabolism would affect its bioavailability.

CONCLUSION

A suitable method was established considering the baseline level, circadian rhythms and intestinal metabolism to investigate the pharmacokinetics of FA for guiding the further research of vitamins.

Postnatal Administration of Homocysteine Induces Cerebellar Damage in Rats: Protective Effect of Folic Acid

A widely held view suggests that homocysteine (Hcy) can contribute to neurodegeneration through promotion of oxidative stress. There is evidence that homocysteine is toxic to cerebellar Purkinje neurons in vitro; however, in vivo action of Hcy on Purkinje cell has not been investigated so far. Thus, this study was designed to evaluate the Hcy effects on neonatal rat cerebellum and cerebellar oxidative stress. We also evaluated the folic acid effects on biochemical alterations elicited by hyperhomocysteinemia (hHcy) in the cerebellum. Group I received normal saline, group II received Hcy subcutaneously twice a day at 8-h intervals (0.3-0.6 μmol/g body weight), group III received Hcy + folic acid (0.011 μmol/g body weight), and group IV received folic acid on postnatal day (PD) 4 until 25. On day 25, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in the cerebellum and motor cortex were assayed. Malondialdehyde (MDA) levels were also evaluated as a marker of lipid peroxidation. Rotarod and locomotor activity tests were performed in PD 25-27. Our results indicated that administration of Hcy increased plasma, cortical, and cerebellar total Hcy levels; reduced GPx activity; and induced lipid peroxidation in the cerebellum. Hcy impaired performance on the rotarod in rats. However, treatment with folic acid significantly attenuated motor coordination impairment, GPx activity reduction, the lipid peroxidation process, and significantly reduced plasma total Hcy levels. Histological analysis indicated that Hcy could decrease Purkinje cell count and folic acid prevented this toxic effect. We conclude that Hcy can induce neurotoxicity and folic acid has neuroprotective effects against cerebellar Hcy toxicity.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Folic acid modulates VPO1 DNA methylation levels and alleviates oxidative stress-induced apoptosis in vivo and in vitro

Endothelial cell injury and apoptosis play a primary role in the pathogenesis of atherosclerosis. Moreover, accumulating evidence indicates that oxidative injury is an important risk factor for endothelial cell damage. In addition, low folate levels are considered a contributing factor to promotion of vascular disease because of the deregulation of DNA methylation. We aimed to investigate the effects of folic acid on injuries induced by oxidative stress that occur via an epigenetic gene silencing mechanism in ApoE knockout mice fed a high-fat diet and in human umbilical vein endothelial cells treated with oxidized low-density lipoprotein (ox-LDL). We assessed how folic acid influenced the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG, an oxidative DNA damage marker) and cellular apoptosis in in vivo and in vitro models. Furthermore, we analyzed DNA methyltransferase (DNMT) activity, vascular peroxidase 1 (VPO1) expression, and promoter methylation in human umbilical vein endothelial cells. Our data showed that folic acid reduced 8-OHdG levels and decreased apoptosis in the aortic tissue of ApoE^−/− mice. Likewise, our in vitro experiments showed that folic acid protects against endothelial dysfunction induced by ox-LDL by reducing reactive oxygen species (ROS)-derived oxidative injuries, 8-OHdG content, and the apoptosis ratio. Importantly, this effect was indirectly caused by increased DNMT activity and altered DNA methylation at VPO1 promoters, as well as changes in the abundance of VPO1 expression. Collectively, we conclude that folic acid supplementation may prevent oxidative stress-induced apoptosis and suppresses ROS levels through downregulating VPO1 as a consequence of changes in DNA methylation, which may contribute to beneficial effects on endothelial function.

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Folic acid reduces oxidative stress-induced injuries in atherosclerosis.

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Folic acid decreases 8-OHdG levels and apoptosis in vivo and in vitro.

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Folic acid supplementation increases DNMT levels and regulates VPO1 expression.

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VPO1 expression is modulated by epigenetic silencing via promoter methylation.

Regeneration of glycocalyx by heparan sulfate and sphingosine 1-phosphate restores inter-endothelial communication

Vasculoprotective endothelium glycocalyx (GCX) shedding plays a critical role in vascular disease. Previous work demonstrated that GCX degradation disrupts endothelial cell (EC) gap junction connexin (Cx) proteins, likely blocking interendothelial molecular transport that maintains EC and vascular tissue homeostasis to resist disease. Here, we focused on GCX regeneration and tested the hypothesis that vasculoprotective EC function can be stimulated via replacement of GCX when it is shed. We used EC with [i] intact heparan sulfate (HS), the most abundant GCX component; [ii] degraded HS; or [iii] HS that was restored after enzyme degradation, by cellular self-recovery or artificially. Artificial HS restoration was achieved via treatment with exogenous HS, with or without the GCX regenerator and protector sphingosine 1- phosphate (S1P). In these cells we immunocytochemically examined expression of Cx isotype 43 (Cx43) at EC borders and characterized Cx-containing gap junction activity by measuring interendothelial spread of gap junction permeable Lucifer Yellow dye. With intact HS, 60% of EC borders expressed Cx43 and dye spread to 2.88 ± 0.09 neighboring cells. HS degradation decreased Cx43 expression to 30% and reduced dye spread to 1.87± 0.06 cells. Cellular self-recovery of HS restored baseline levels of Cx43 and dye transfer. Artificial HS recovery with exogenous HS partially restored Cx43 expression to 46% and yielded dye spread to only 1.03 ± 0.07 cells. Treatment with both HS and S1P, recovered HS and restored Cx43 to 56% with significant dye transfer to 3.96 ± 0.23 cells. This is the first evidence of GCX regeneration in a manner that effectively restores vasculoprotective EC communication.