Plasma homocysteine and cysteine and risk of breast cancer in women

Plasma B-vitamin and one-carbon metabolites and risk of breast cancer before and after folic acid fortification in the United States

Prior epidemiologic findings for plasma folate and B-vitamins and breast cancer risk are inconsistent and have not assessed the influence of folic acid fortification. Therefore, we examined the associations of plasma folate, B₁₂ , pyridoxal 5'-phosphate (PLP), homocysteine, cysteine and cysteinylglycine with breast cancer risk, before and after fortification. We conducted a nested case-control study within the prospective Nurses' Health Study. In 1989-1990 (pre-fortification), 32,826 women donated a blood sample and 18,743 donated an additional blood sample in 2000-2001 (post-fortification). Between the first blood collection and 2006, 1874 incident breast cancer cases with at least one blood sample and 367 with two were 1:1 matched to controls. Conditional logistic regression was used to estimate relative risks (RR) and 95% confidence intervals (CI) adjusting for breast cancer risk factors. Overall, higher plasma folate, B₁₂ , PLP, homocysteine, cysteine and cysteinylglycine levels were not associated with breast cancer risk. Associations did not vary by in situ/invasive, hormone receptor status, or tumor molecular subtype. Additionally, associations were null before and after fortification. For example, the RR (95% CI) for the highest versus lowest tertile of 1990 (pre-fortification) plasma folate with 1990-2000 follow-up was 0.93 (0.75-1.16) and for the 2000 plasma folate (post-fortification) with 2000-2006 follow-up the RR (95% CI) was 1.17 (0.79-1.74). Plasma folate, B₁₂ , PLP, homocysteine, cysteine and cysteinylglycine were not significantly associated with breast cancer overall, before and after fortification, or with specific tumor molecular subtypes. However, long term associations (>8 years) after the implementation of fortification could not be examined.

A selective fluorescent sensor for cysteine detection with potential as a white light emitting fluorophore in living cell imaging

A novel fluorescent sensor CysW-1 was introduced for cysteine detection via the cleavage reaction of two fluorophores. Then a relatively steady and practical white light emitting system was successfully generated. The biocompatibility ensured the living cell imaging and further pre-clinical applications.

Semiparametric Bayesian kernel survival model for evaluating pathway effects

Massive amounts of high-dimensional data have been accumulated over the past two decades, which has cultured increasing interests in identifying gene pathways related to certain biological processes. In particular, since pathway-based analysis has the ability to detect subtle changes of differentially expressed genes that could be missed when using gene-based analysis, detecting the gene pathways that regulate certain diseases can provide new strategies for medical procedures and new targets for drug discovery. Limited work has been carried out, primarily in regression settings, to study the effects of pathways on survival outcomes. Motivated by a breast cancer gene-pathway data set, which exhibits the "small n, large p" characteristics, we propose a semiparametric Bayesian kernel survival model (s-BKSurv) to study the effects of both clinical covariates and gene expression levels within a pathway on survival time. We model the unknown high-dimensional functions of pathways via Gaussian kernel machine to consider the possibility that genes within the same pathway interact with each other. To address the multiple comparisons problem under a full Bayesian setting, we propose a similarity-dependent procedure based on Bayes factor to control the family-wise error rate. We demonstrate the outperformance of our approach under various simulation settings and pathways data.

Investigation of altered urinary metabolomic profiles of invasive ductal carcinoma of breast using targeted and untargeted approaches

INTRODUCTION

Invasive ductal carcinoma (IDC) is a type of breast cancer, usually detected in advanced stages due to its asymptomatic nature which ultimately leads to low survival rate. Identification of urinary metabolic adaptations induced by IDC to understand the disease pathophysiology and monitor therapy response would be a helpful approach in clinical settings. Moreover, its non-invasive and cost effective strategy better suited to minimize apprehension among high risk population.

OBJECTIVE

This study aims toward investigating the urinary metabolic alterations of IDC by targeted (LC-MRM/MS) and untargeted (GC-MS) approaches for the better understanding of the disease pathophysiology and monitoring therapy response.

METHODS

Urinary metabolic alterations of IDC subjects (63) and control subjects (63) were explored by targeted (LC-MRM/MS) and untargeted (GC-MS) approaches. IDC specific urinary metabolomics signature was extracted by applying both univariate and multivariate statistical tools.

RESULTS

Statistical analysis identified 39 urinary metabolites with the highest contribution to metabolomic alterations specific to IDC. Out of which, 19 metabolites were identified from targeted LC-MRM/MS analysis, while 20 were identified from the untargeted GC-MS analysis. Receiver operator characteristic (ROC) curve analysis evidenced 6 most discriminatory metabolites from each type of approach that could differentiate between IDC subjects and controls with higher sensitivity and specificity. Furthermore, metabolic pathway analysis depicted several dysregulated pathways in IDC including sugar, amino acid, nucleotide metabolism, TCA cycle etc. CONCLUSIONS: Overall, this study provides valuable inputs regarding altered urinary metabolites which improved our knowledge on urinary metabolomic alterations induced by IDC. Moreover, this study identified several dysregulated metabolic pathways which offer further insight into the disease pathophysiology.

Implications of plasma thiol redox in disease

Thiol groups are crucially involved in signaling/homeostasis through oxidation, reduction, and disulphide exchange. The overall thiol pool is the resultant of several individual pools of small compounds (e.g. cysteine), peptides (e.g. glutathione), and thiol proteins (e.g. thioredoxin (Trx)), which are not in equilibrium and present specific oxidized/reduced ratios. This review addresses mechanisms and implications of circulating plasma thiol/disulphide redox pools, which are involved in several physiologic processes and explored as disease biomarkers. Thiol pools are regulated by mechanisms linked to their intrinsic reactivity against oxidants, concentration of antioxidants, thiol-disulphide exchange rates, and their dynamic release/removal from plasma. Major thiol couples determining plasma redox potential (Eh) are reduced cysteine (CyS)/cystine (the disulphide form of cysteine) (CySS), followed by GSH/disulphide-oxidized glutathione (GSSG). Hydrogen peroxide and hypohalous acids are the main plasma oxidants, while water-soluble and lipid-soluble small molecules are the main antioxidants. The thiol proteome and thiol-oxidoreductases are emerging investigative areas given their specific disease-related responses (e.g. protein disulphide isomerases (PDIs) in thrombosis). Plasma cysteine and glutathione redox couples exhibit pro-oxidant changes directly correlated with ageing/age-related diseases. We further discuss changes in thiol-disulphide redox state in specific groups of diseases: cardiovascular, cancer, and neurodegenerative. These results indicate association with the disease states, although not yet clear-cut to yield specific biomarkers. We also highlight mechanisms whereby thiol pools affect atherosclerosis pathophysiology. Overall, it is unlikely that a single measurement provides global assessment of plasma oxidative stress. Rather, assessment of individual thiol pools and thiol-proteins specific to any given condition has more solid and logical perspective to yield novel relevant information on disease risk and prognosis.

Cysteine allows ovarian cancer cells to adapt to hypoxia and to escape from carboplatin cytotoxicity

Ovarian cancer is the second most common gynaecologic malignancy and the main cause of death from gynaecologic cancer, due to late diagnosis and chemoresistance. Studies have reported the role of cysteine in cancer, by contributing for hydrogen sulphide (H2S) generation and as a precursor of glutathione (GSH). However, the role of cysteine in the adaptation to hypoxia and therapy response remains unclear. We used several ovarian cancer cell lines, ES2, OVCAR3, OVCAR8, A2780 and A2780cisR, to clarify cysteine relevance in ovarian cancer cells survival upon hypoxia and carboplatin. Results show that ES2 and OVCAR8 cells presented a stronger dependence on cysteine availability upon hypoxia and carboplatin exposure than OVCAR3 cells. Interestingly, the A2780 cisR, but not A2780 parental cells, benefits from cysteine upon carboplatin exposure, showing that cysteine is crucial for chemoresistance. Moreover, GSH degradation and subsequent cysteine recycling pathway is associated with ovarian cancer as seen in peripheral blood serum from patients. Higher levels of total free cysteine (Cys) and homocysteine (HCys) were found in ovarian cancer patients in comparison with benign tumours and lower levels of GSH were found in ovarian neoplasms patients in comparison with healthy individuals. Importantly, the total and S-Homocysteinylated levels distinguished blood donors from patients with neoplasms as well as patients with benign from patients with malignant tumours. The levels of S-cysteinylated proteins distinguish blood donors from patients with neoplasms and the free levels of Cys in serum distinguish blood from patients with benign tumours from patients with malignant tumours. Herein we disclosed that cysteine contributes for a worse disease prognosis, allowing faster adaptation to hypoxia and protecting cells from carboplatin. The measurement of serum cysteine levels can be an effective tool for early diagnosis, for outcome prediction and follow up of disease progression.

Effects of α-zearalenol on the metabolome of two breast cancer cell lines by 1H-NMR approach

INTRODUCTION

Zearalenone (ZEN) is one of the most widely distributed toxins that contaminates many crops and foods. Its major metabolites are α-Zearalenol (α-zol) and β-Zearalenol. Previous studies showed that ZEN and α-zol have estrogenic properties and are able to induce growth promoting effect in breast tissues.

OBJECTIVIES

Considering that tumorigenesis is dependent on the reprogramming of cellular metabolism and that the evaluation of the cellular metabolome is useful to understand the metabolic changes that can occur during the cancer development and progression or after treatments, aim of our work is to study, for the first time, the effects of α-zol on the metabolomic profile of an estrogen positive breast cancer cell line, MCF-7, and of an estrogen negative breast cancer cell lines MDA-MB231.

METHODS

Firstly, we tested the effects of α-zol on the cell viability after 24, 48 and 72 h of treatments with 10^-10, 10^-8 and 10^-6 M concentrations on breast cancer MCF-7 and MDA-MB231 cell lines in comparison to human non-cancerous breast MCF10A cell line. Then, we evaluated cell cycle progression, levels of reactive oxygen species (ROS) and the metabolomic profiling by ¹H-NMR approach on MCF-7 and MDA-MB231 before and after 72 h treatments. Principal component analysis was used to compare the obtained spectra.

RESULTS

α-zol is resulted able to induce: (i) an increase of the cell viability on MCF-7 cells mainly after 72 h treatment, (ii) a slight decrease of the cell viability on MDA-MB231 cells, and (iii) an increase of cells in S phase of the cell cycle and of ROS only in MCF-7 cells. Moreover, the evaluation of metabolomics profile evidenced that after treatment with α-zol the levels of some metabolites increased in MCF-7 cells whereas decreased slightly in MDA-MB231 cells.

CONCLUSIONS

Our results showed that α-zol was able to increase the protein biosynthesis as well as the lipid metabolism in MCF-7 cells, and, hence, to induce an estrogen positive breast cancer progression.

Disease prevention and delayed aging by dietary sulfur amino acid restriction: translational implications

Sulfur amino acids (SAAs) play numerous critical roles in metabolism and overall health maintenance. Preclinical studies have demonstrated that SAA-restricted diets have many beneficial effects, including extending life span and preventing the development of a variety of diseases. Dietary sulfur amino acid restriction (SAAR) is characterized by chronic restrictions of methionine and cysteine but not calories and is associated with reductions in body weight, adiposity and oxidative stress, and metabolic changes in adipose tissue and liver resulting in enhanced insulin sensitivity and energy expenditure. SAAR-induced changes in blood biomarkers include reductions in insulin, insulin-like growth factor-1, glucose, and leptin and increases in adiponectin and fibroblast growth factor 21. On the basis of these preclinical data, SAAR may also have similar benefits in humans. While little is known of the translational significance of SAAR, its potential feasibility in humans is supported by findings of its effectiveness in rodents, even when initiated in adult animals. To date, there have been no controlled feeding studies of SAAR in humans; however, there have been numerous relevant epidemiologic and disease-based clinical investigations reported. Here, we summarize observations from these clinical investigations to provide insight into the potential effectiveness of SAAR for humans.

Excited-state intramolecular proton-transfer (ESIPT) based fluorescence sensors and imaging agents

We review recent advances in the design and application of excited-state intramolecular proton-transfer (ESIPT) based fluorescent probes. These sensors and imaging agents (probes) are important in biology, physiology, pharmacology, and environmental science.

Fluorescent coumarin-based probe for cysteine and homocysteine with live cell application

Cysteine (Cys) and homocysteine (Hcy) are two of important biological thiols and function as important roles in several biological processes. The development of Cys and Hcy probes will help to explore the functions of biothiols in biological systems. In this work, a new coumarin-based probe AC, containing an acryloyl moiety, was developed for Cys and Hcy detection in cells. Cys and Hcy undergo a nucleophilic addition and subsequent cyclization reaction to remove to the acryloyl group and yield a fluorescent product, 7-hydroxylcomuarin. The probe AC showed good selectivity for cysteine and homocysteine over glutathione and other amino acids and had low detection limits of 65nM for Cys and 79nM for Hcy, respectively. Additionally, confocal imaging experiments demonstrated that the probe AC can be applied to visualize Cys and Hcy in living cells.

Breast cancer epidemic in the early twenty-first century: evaluation of risk factors, cumulative questionnaires and recommendations for preventive measures

Rapidly increasing incidence of breast cancer is a new social challenge resulting from a spectrum of internal and external risk factors which appear to be well accepted as an attribute of the early twenty-first century, being, however, new for female sub-populations compared to the past. These include altered socio-economical conditions such as occupational exposure, rotating shift work, specific environmental factors (increased pollution and environmental toxicity, altered dietary habits, quality and composition of meal) as well as consequently shifted and/or adapted physiologic factors such as lower age at menarche, late age of first full-term pregnancy, if any, shorter periods of breastfeeding and later menopause. Consolidated expert statements suggest that over 50 % of all breast cancer cases may be potentially prevented by risk reduction strategy such as regulation of modifiable risk factors. Currently available risk assessment models may estimate potential breast cancer predisposition, in general; however, they are not able to predict the disease manifestation individually. Further, current deficits in risk assessment and effective breast cancer prevention have been recently investigated and summarised as follows: gaps in risk estimation, preventive therapy, lifestyle prevention, understanding of the biology of breast cancer risk and implementation of known preventive measures. This paper overviews the most relevant risk factors, provides recommendations for improved risk assessment and proposes an extended questionnaire for effective preventive measures.

Prospective study of serum cysteine and cysteinylglycine and cancer of the head and neck, esophagus, and stomach in a cohort of male smokers

BACKGROUND

The nonessential amino acid cysteine is known to be involved in many antioxidant and anticarcinogenic pathways. Cysteinylglycine is a pro-oxidant metabolite of glutathione and a precursor of cysteine.

OBJECTIVE

To examine the relation between serum cysteine and cysteinylglycine and risk of gastric adenocarcinomas, esophageal squamous cell carcinomas, and head and neck squamous cell carcinomas, we conducted a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention study of male Finnish smokers aged 50-69 y at baseline.

DESIGN

In total, 170 gastric adenocarcinomas, 68 esophageal squamous cell carcinomas, and 270 head and neck squamous cell carcinomas (identified from the Finnish Cancer Registry) were matched one-to-one with cancer-free control subjects on age and the date of serum collection. We calculated ORs and 95% CIs with the use of a multivariate-adjusted conditional logistic regression.

RESULTS

Cysteine had a U-shaped association with gastric adenocarcinomas; a model that included a linear and a squared term had a significant global P-test (P = 0.036). Serum cysteinylglycine was inversely associated with adenocarcinomas of the gastric cardia (OR for above the median compared with below the median: 0.07; 95% CI: 0.01, 0.70; n = 38 cases) but not for other sites. Both cysteine and cysteinylglycine were not associated with esophageal squamous cell carcinoma or head and neck squamous cell carcinoma.

CONCLUSIONS

We observed associations between serum cysteine and cysteinylglycine with upper gastrointestinal cancer risk. Future studies are needed to replicate these findings. This trial was registered at clininicaltrials.gov as NCT00342992.

Amino Acids Regulate mTORC1 by an Obligate Two-step Mechanism

The mechanistic target of rapamycin complex 1 (mTORC1) coordinates cell growth with its nutritional, hormonal, energy, and stress status. Amino acids are critical regulators of mTORC1 that permit other inputs to mTORC1 activity. However, the roles of individual amino acids and their interactions in mTORC1 activation are not well understood. Here we demonstrate that activation of mTORC1 by amino acids includes two discrete and separable steps: priming and activation. Sensitizing mTORC1 activation by priming amino acids is a prerequisite for subsequent stimulation of mTORC1 by activating amino acids. Priming is achieved by a group of amino acids that includes l-asparagine, l-glutamine, l-threonine, l-arginine, l-glycine, l-proline, l-serine, l-alanine, and l-glutamic acid. The group of activating amino acids is dominated by l-leucine but also includes l-methionine, l-isoleucine, and l-valine. l-Cysteine predominantly inhibits priming but not the activating step. Priming and activating steps differ in their requirements for amino acid concentration and duration of treatment. Priming and activating amino acids use mechanisms that are distinct both from each other and from growth factor signaling. Neither step requires intact tuberous sclerosis complex of proteins to activate mTORC1. Concerted action of priming and activating amino acids is required to localize mTORC1 to lysosomes and achieve its activation.

One-Carbon Metabolism in Prostate Cancer: The Role of Androgen Signaling

Cancer cell metabolism differs significantly from the metabolism of non-transformed cells. This altered metabolic reprogramming mediates changes in the uptake and use of nutrients that permit high rates of proliferation, growth, and survival. The androgen receptor (AR) plays an essential role in the establishment and progression of prostate cancer (PCa), and in the metabolic adaptation that takes place during this progression. In its role as a transcription factor, the AR directly affects the expression of several effectors and regulators of essential catabolic and biosynthetic pathways. Indirectly, as a modulator of the one-carbon metabolism, the AR can affect epigenetic processes, DNA metabolism, and redox balance, all of which are important factors in tumorigenesis. In this review, we focus on the role of AR-signaling on one-carbon metabolism in tumorigenesis. Clinical implications of one-carbon metabolism and AR-targeted therapies for PCa are discussed in this context.

Amino acid changes during transition to a vegan diet supplemented with fish in healthy humans

Purpose

To explore whether changes in dietary protein sources can lower plasma branched-chain amino acids (BCAAs), aromatic amino acids and sulfur amino acids (SAAs) that are often elevated in the obese, insulin-resistant state and in type 2 diabetes.

Methods

Thirty-six subjects (mean age 31 ± 2 years) underwent a voluntary abstinence from meat, poultry, eggs, and dairy products for 6 weeks, while enriching the diet with fish, in fulfillment of a religious fast. Subjects were assessed 1 week before the fast (V1), 1 week after initiation of the fast (V2) and in the last week of the fast (V3). Thirty-four subjects completed all three visits.

Results

Fasting plasma BCAAs decreased at V2 and remained low at V3 (P < 0.001 for all). Valine showed the greatest decline, by 20 and 19 % at V2 and V3, respectively. Phenylalanine and tryptophan, but not tyrosine, also decreased at V2 and V3. The two proteinogenic SAAs, methionine and cysteine, remained stable, but the cysteine product, taurine, decreased from 92 ± 7 μmol/L to 66 ± 6 (V2; P = 0.003) and 65 ± 6 μmol/L (V3; P = 0.003). A progressive decline in plasma glutamic acid, coupled with an increase in glutamine, was observed. Plasma total and LDL cholesterol decreased at V2 and V3 (P < 0.001 for all).

Conclusion

Changing dietary protein sources to plant- and fish-based sources in an ad libitum setting lowers the plasma BCAAs that have been linked to diabetes risk. These findings point to habitual diet as a potentially modifiable determinant of fasting plasma BCAA concentrations.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-016-1237-6) contains supplementary material, which is available to authorized users.

Plasma Riboflavin and Vitamin B-6, but Not Homocysteine, Folate, or Vitamin B-12, Are Inversely Associated with Breast Cancer Risk in the European Prospective Investigation into Cancer and Nutrition-Varese Cohort

BACKGROUND

One-carbon metabolism-important for DNA stability and integrity-may play a role in breast carcinogenesis. However, epidemiologic studies addressing this issue have yielded inconsistent results.

OBJECTIVE

We prospectively investigated associations between breast cancer and plasma folate, riboflavin, vitamin B-6, vitamin B-12, and homocysteine in women recruited to the Varese (Italy) cohort of the EPIC (European Prospective Investigation into Cancer and Nutrition) study.

METHODS

We performed a nested case-control study on women aged 35-65 y at recruitment with a median body mass index of 25.3 kg/m(2) who gave blood samples in 1987-1992 and again in 1993-1998. Breast cancer cases identified by 31 December 2009 were individually matched to controls. RRs of breast cancer (and subtypes defined by hormone receptor status) with 95% CIs were estimated by unconditional logistic regression, controlling for matching factors and breast cancer risk factors.

RESULTS

After a median of 14.9 y, 276 breast cancer cases were identified and matched to 276 controls. Increasing plasma vitamin B-6 was associated with decreased risk of overall (RR: 0.78; 95% CI: 0.63, 0.96 for 1-SD increase), premenopausal (RR: 0.66; 95% CI: 0.48, 0.92 for 1-SD increase), estrogen receptor-positive (RR: 0.79; 95% CI: 0.63, 1.00 for 1-SD increase), and progesterone receptor-positive (RR: 0.72; 95% CI: 0.55, 0.95 for 1-SD increase) breast cancers. Increased plasma vitamin B-6 was also associated with decreased breast cancer risk in alcohol consumers (≥7 g/d) compared with consumption of <7 g/d or nonconsumption (RR: 0.71; 95% CI: 0.51, 0.99). High plasma riboflavin was associated with significantly lower risk in premenopausal women (RR: 0.45; 95% CI: 0.21, 0.94; highest compared with the lowest quartile, P trend = 0.021). Plasma homocysteine, folate, and vitamin B-12 were not associated with breast cancer risk.

CONCLUSIONS

High plasma vitamin B-6 and riboflavin may lower breast cancer risk, especially in premenopausal women. Additional research is necessary to further explore these associations.

Haplotypes of the MTHFR gene are associated with an increased risk of breast cancer in a Han Chinese population in Gansu province

Elevated homocysteine levels are a risk factor for breast cancer, although the mechanism underlying this effect is unknown. Genome-wide association studies were used to systematically identify genetic variants which were significantly associated with the circulating homocysteine concentration. To examine the role of homocysteine-related variants in the occurrence of breast cancer, we investigated the association between these variants and breast cancer in a Han Chinese population. Five variants of genome-wide significant homocysteine-related genes were selected for the analysis in a case-control study, with a total of 487 patients with breast cancer and 605 controls. We found that none of the studied polymorphisms were related to the altered breast cancer risk. In the haplotypic analysis, the 5,10-methylenetetrahydrofolate reductase (MTHFR) haplotypes rs12085006A/rs1999594G/rs1801133C (OR = 3.44, 95% CI = 1.58-7.50, P = 0.0019) and rs12085006A/rs1999594G/rs1801133T (OR = 16.21, 95% CI = 2.19- 120.32, P = 0.0065) were significantly associated with an increased breast cancer risk when compared with the wild-type haplotype. Both of the risky MTHFR haplotypes were correlated with decreased MTHFR gene expression and elevated homocysteine concentrations, indicating a genetic component for hyperhomocysteinemia. The MTHFR haplotypes reconstructed with homocysteine-related variants were associated with the occurrence of breast cancer. This finding further emphasizes the importance of homocysteine metabolism genes in breast carcinogenesis and highlights the interplay of diet, genetics, and human cancers. © 2016 IUBMB Life, 68(7):526-534, 2016.

Homocystinuria: Therapeutic approach

Homocystinuria is a disorder of sulfur metabolism pathway caused by deficiency of cystathionine β-synthase (CBS). It is characterized by increased accumulation of homocysteine (Hcy) in the cells and plasma. Increased homocysteine results in various vascular and neurological complications. Present strategies to lower cellular and plasma homocysteine levels include vitamin B6 intake, dietary methionine restriction, betaine supplementation, folate and vitamin B12 administration. However, these strategies are inefficient for treatment of homocystinuria. In recent years, advances have been made towards developing new strategies to treat homocystinuria. These mainly include functional restoration to mutant CBS, enhanced clearance of Hcy from the body, prevention of N-homocysteinylation-induced toxicity and inhibition of homocysteine-induced oxidative stress. In this review, we have exclusively discussed the recent advances that have been achieved towards the treatment of homocystinuria. The review is an attempt to help clinicians in developing effective therapeutic strategies and designing novel drugs against homocystinuria.

Elevated homocysteine level and folate deficiency associated with increased overall risk of carcinogenesis: meta-analysis of 83 case-control studies involving 35,758 individuals

BACKGROUND

Results of the association of folate metabolism and carcinogenesis are conflicting. We performed a meta-analysis to examine the effect of the interaction of serum concentration of homocysteine (Hcy), folate, and vitamin B12 and 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphism on risk of cancer overall.

METHOD

Two reviewers independently searched for all published studies of Hcy and cancer in PubMed, EMBASE-MEDLINE and Chinese databases. Pooled results were reported as odds ratios (ORs) and mean differences and presented with 95% confidence intervals (95% CIs) and 2-sided probability values.

RESULTS

We identified 83 eligible studies of 15,046 cases and 20,712 controls. High level of Hcy but low level of folate was associated with risk of cancer overall, with little effect by type of cancer or ethnicity. Vitamin B12 level was inversely associated with only urinary-system and gastrointestinal carcinomas and for Asian and Middle Eastern patients. As well, MTHFR C677T, A1298C and G1793A polymorphisms were related to elevated serum level of Hcy, and folate and vitamin B12 deficiency. However, only MTHFR C677T homogeneity/wild-type (TT/CC) polymorphism was positively associated with overall risk of cancer.

CONCLUSION

Elevated serum Hcy level and folate deficiency are associated with increased overall risk of cancer.

Hyperhomocysteinemia as a potential contributor of colorectal cancer development in inflammatory bowel diseases: A review

Homocysteine is an amino acid generated metabolically by the S-adenosylmethionine-dependent transmethylation pathway. In addition to being a well-known independent risk factor for coronary heart disease, is also a risk factor for cancer. Patients suffering from inflammatory bowel diseases (IBD) including ulcerative colitis and Crohn’s disease are at increased risk of developing colorectal cancer in comparison to healthy individuals. Furthermore, the risk of hyperhomocysteinaemia is significantly higher in IBD patients when compared with controls. In the present article, we review the mechanisms in which hyperhomocysteinemia may contribute to increased risk of colorectal cancer in IBD patients.

Highly selective two-photon imaging of cysteine in cancerous cells and tissues

Abnormal concentrations of Cys have been reported to be implicated in various health problems, including cancer, neuropathy, and cardiomyopathy.

A miniaturized electrochemical assay for homocysteine using screen-printed electrodes with cytochrome c anchored gold nanoparticles

Electrochemical point-of-care analysis of homocysteine in a drop of the blood plasma samples.

Plasma total homocysteine level in association with folate, pyridoxine, and cobalamin status among Iranian primary breast cancer patients

Recently the elevated plasma total homocysteine (tHcy) concentration has been concerned as the secondary feature of tumoral proliferation and enhances the likelihood of thrombogenesis in cancer patients. The objective of this study was to determine the associations between folate, cobalamin, and pyridoxine with fasting plasma tHcy concentration in breast cancer (BC) patients. The intake levels of nutrients were assessed using a validated food frequency questionnaire in 141 newly diagnosed BC patients. The plasma tHcy and pyridoxal-5-phosphate were measured using high performance liquid chromatography with fluorescence detector. Plasma tHcy levels were observed to be significantly higher among BC participants with Stage III where the plasma concentrations of folate was also comparatively less (P < 0.05) than other stages. Dietary pyridoxine was even being consumed less at this stage (P < 0.05). The plasma, dietary, and residual variables of folate were inversely correlated with plasma tHcy concentration (P < 0.05). Dietary cobalamin was also associated negatively with tHcy (P < 0.05). The odds ratio of comparing the highest tertile of plasma cobalamin (>394 pmol/l) and folate (>11.4 ng/ml) vs. the lowest categories were associated with reduced odds of high tHcy occurrence with 0.20 (95% confidence interval: 0.04-0.98) and 0.14 (95% confidence interval: 0.03-0.64), respectively. In conclusion, nutrition-related methyl-group insufficiency could lead to imbalance in tHcy metabolism, as a possible cancer marker.

Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis

Background:

Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods:

We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results:

In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case–control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case–control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case–control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions:

Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

Plasma amino acid profiles are associated with biomarkers of breast cancer risk in premenopausal Japanese women

OBJECTIVE

Recently, profiles of plasma amino acids have been utilized to detect diseases including breast cancer. However, there is a possibility that the amino acid status may be associated with the risk of breast cancer. We investigated the relationship of plasma levels of amino acids with levels of sex hormones and insulin-like growth factor (IGF)-1, which are relevant to the etiology of premenopausal breast cancer, in normal premenopausal women.

METHODS

Participants were 350 Japanese women who had regular menstrual cycles less than 40-day long. Fasting plasma samples were assayed for estradiol, testosterone, dehydroepiandrosterone sulfate, sex-hormone-binding globulin (SHBG), and IGF-1. A total of 20 amino acids in plasma were quantified by liquid chromatography-mass spectrometry. Information on lifestyle and reproductive factors was obtained using a self-administered questionnaire.

RESULTS

The plasma arginine level was significantly inversely correlated with plasma levels of total and free estradiol and IGF-1 after adjusting for age, body mass index, and phase of the menstrual cycle. Plasma leucine and tyrosine levels were significantly positively correlated with the free testosterone level. The ratio of plasma asparagine to the total amino acids was significantly positively correlated with SHBG level.

CONCLUSIONS

Plasma levels of some specific amino acids, such as arginine, leucine, tyrosine, and asparagine, were associated with the levels of sex hormones, SHBG, or IGF-1 in premenopausal women. However, the present cross-sectional study cannot provide a cause-effect relation. The implication of amino acids in the etiology of breast cancer needs to be addressed in future studies.

One-carbon metabolism factors and leukocyte telomere length

BACKGROUND

Dietary and genetic factors involved in the one-carbon metabolism pathway may affect telomere length through DNA methylation and synthesis, but this has not been comprehensively investigated in epidemiologic studies.

OBJECTIVE

We cross-sectionally examined associations between dietary and genetic factors in the one-carbon metabolism pathway and relative peripheral blood leukocyte telomere length.

DESIGN

A total of 1715 participants from the Nurses' Health Study (NHS) had measurements of relative telomere length and plasma concentrations of folate, vitamin B-6, vitamin B-12, cysteine, and homocysteine. Food-frequency questionnaire (FFQ) measurements were also used for the assessment of folate, choline, methionine, riboflavin, vitamin B-6, vitamin B-12, and alcohol intakes. Genotyping was performed on 475 participants with telomere measurements on 29 mostly nonsynonymous single-nucleotide polymorphisms (SNPs) involved in one-carbon metabolism. Unconditional logistic and linear regression models were used.

RESULTS

There were no significant dose-response relations between any plasma- or FFQ-measured dietary factors and relative telomere length in multivariate analyses. For folate, vitamin B-6, and vitamin B-12, results from the use of FFQ data were consistent with plasma-biomarker findings. We showed no significant associations that involved SNPs and relative telomere length after we accounted for the false discovery rate.

CONCLUSION

Our analyses involving plasma and questionnaire measurements of one-carbon metabolism factors show that some key dietary and genetic factors in this metabolic network are not associated with relative peripheral blood leukocyte telomere length.

Flavin-dependent enzymes in cancer prevention

Statistical studies have demonstrated that various agents may reduce the risk of cancer's development. One of them is activity of flavin-dependent enzymes such as flavin-containing monooxygenase (FMO)(GS-OX1), FAD-dependent 5,10-methylenetetrahydrofolate reductase and flavin-dependent monoamine oxidase. In the last decade, many papers concerning their structure, reaction mechanism and role in the cancer prevention were published. In our work, we provide a more in-depth analysis of flavin-dependent enzymes and their contribution to the cancer prevention. We present the actual knowledge about the glucosinolate synthesized by flavin-containing monooxygenase (FMO)(GS-OX1) and its role in cancer prevention, discuss the influence of mutations in FAD-dependent 5,10-methylenetetrahydrofolate reductase on the cancer risk, and describe FAD as an important cofactor for the demethylation of histons. We also present our views on the role of riboflavin supplements in the prevention against cancer.

Associations between Intake of Folate, Methionine, and Vitamins B-12, B-6 and Prostate Cancer Risk in American Veterans

Prostate cancer (PC) is the second leading cause of cancer death in men. Recent reports suggest that excess of nutrients involved in the one-carbon metabolism pathway increases PC risk; however, empirical data are lacking. Veteran American men (272 controls and 144 PC cases) who attended the Durham Veteran American Medical Center between 2004–2009 were enrolled into a case-control study. Intake of folate, vitamin B12, B6, and methionine were measured using a food frequency questionnaire. Regression models were used to evaluate the association among one-carbon cycle nutrients, MTHFR genetic variants, and prostate cancer. Higher dietary methionine intake was associated with PC risk (OR = 2.1; 95%CI 1.1–3.9) The risk was most pronounced in men with Gleason sum <7 (OR = 2.75; 95%CI 1.32– 5.73). The association of higher methionine intake and PC risk was only apparent in men who carried at least one MTHFR A1298C allele (OR = 6.7; 95%CI = 1.6–27.8), compared to MTHFR A1298A noncarrier men (OR = 0.9; 95%CI = 0.24–3.92) (p-interaction = 0.045). There was no evidence for associations between B vitamins (folate, B12, and B6) and PC risk. Our results suggest that carrying the MTHFR A1298C variants modifies the association between high methionine intake and PC risk. Larger studies are required to validate these findings.

A cysteine probe with high selectivity and sensitivity promoted by response-assisted electrostatic attraction

A new turn-on fluorescent probe for fast detection of cysteine in physiological conditions, based on a new response-assisted electrostatic attraction strategy, is reported. The practical utility of the probe in fluorescent protein labeling and subcellular imaging is also demonstrated.

Cysteine and obesity: consistency of the evidence across epidemiologic, animal and cellular studies

PURPOSE OF REVIEW

The concentrations of several plasma amino acids increase in obesity. Notably, plasma total concentrations of the sulphur amino acid cysteine (tCys) are linearly associated with fat mass in large population studies. Animal and cellular experiments support the concept that cysteine may be obesogenic. Here we review experimental and epidemiologic findings linking cysteine and related compounds with fat regulation and obesity.

RECENT FINDINGS

tCys, and to a lesser extent cystathionine, are the only plasma sulphur amino acids consistently associated with human obesity, whereas glutathione is inversely associated with BMI. Supplementing cyste(i)ne in rodents decreases energy expenditure and promotes adiposity, whereas defects of cysteine-synthesizing enzymes decrease body weight. In adipocytes, cysteine inhibits lipolysis and promotes lipogenesis via H2O2 production. Unlike most plasma amino acids, tCys levels do not decrease with gastric bypass-induced weight loss, further supporting the concept that elevated cysteine may be a cause, not a consequence of obesity. Although cysteine products (glutathione, taurine and H2S) are altered in obesity, they do not appear to explain cysteine's effects on body weight.

SUMMARY

Cellular, animal and epidemiologic data are consistent with the view that cysteine is obesogenic. Targeted research linking in-vitro and in-vivo findings is needed to elucidate mechanisms involved.

Serum methionine metabolites are risk factors for metastatic prostate cancer progression

BACKGROUND

Clinical decision for primary treatment for prostate cancer is dictated by variables with insufficient specificity. Early detection of prostate cancer likely to develop rapid recurrence could support neo-adjuvant therapeutics and adjuvant options prior to frank biochemical recurrence. This study compared markers in serum and urine of patients with rapidly recurrent prostate cancer to recurrence-free patients after radical prostatectomy. Based on previous identification of urinary sarcosine as a metastatic marker, we tested whether methionine metabolites in urine and serum could serve as pre-surgical markers for aggressive disease.

METHODOLOGY/PRINCIPAL FINDINGS

Urine and serum samples (n = 54 and 58, respectively), collected at the time of prostatectomy were divided into subjects who developed biochemical recurrence within 2 years and those who remained recurrence-free after 5 years. Multiple methionine metabolites were measured in urine and serum by GC-MS. The role of serum metabolites and clinical variables (biopsy Gleason grade, clinical stage, serum prostate specific antigen [PSA]) on biochemical recurrence prediction were evaluated. Urinary sarcosine and cysteine levels were significantly higher (p = 0.03 and p = 0.007 respectively) in the recurrent group. However, in serum, concentrations of homocysteine (p = 0.003), cystathionine (p = 0.007) and cysteine (p<0.001) were more abundant in the recurrent population. The inclusion of serum cysteine to a model with PSA and biopsy Gleason grade improved prediction over the clinical variables alone (p<0.001).

CONCLUSIONS

Higher serum homocysteine, cystathionine, and cysteine concentrations independently predicted risk of early biochemical recurrence and aggressiveness of disease in a nested case control study. The methionine metabolites further supplemented known clinical variables to provide superior sensitivity and specificity in multivariable prediction models for rapid biochemical recurrence following prostatectomy.

Development of an animal model for chronic mild hyperhomocysteinemia and its response to oxidative damage

The purpose of this study was to develop a chronic chemically induced model of mild hyperhomocysteinemia in adult rats. We produced levels of Hcy in the blood (30μM), comparable to those considered a risk factor for the development of neurological and cardiovascular diseases, by injecting homocysteine subcutaneously (0.03μmol/g of body weight) twice a day, from the 30th to the 60th postpartum day. Controls received saline in the same volumes. Using this model, we evaluated the effect of chronic administration of homocysteine on redox status in the blood and cerebral cortex of adult rats. Reactive oxygen species and thiobarbituric acid reactive substances were significantly increased in the plasma and cerebral cortex, while nitrite levels were reduced in the cerebral cortex, but not in the plasma, of rats subjected to chronic mild hyperhomocysteinemia. Homocysteine was also seen to disrupt enzymatic and non-enzymatic antioxidant defenses in the blood and cerebral cortex of rats. Since experimental animal models are useful for understanding the pathophysiology of human diseases, the present model of mild hyperhomocysteinemia may be useful for the investigation of additional mechanisms involved in tissue alterations caused by homocysteine.

Dietary cystine level affects metabolic rate and glycaemic control in adult mice

Plasma total cysteine (tCys) is strongly and independently associated with obesity in large human cohorts, but whether the association is causal is unknown. Dietary cyst(e)ine increases weight gain in some rodent models. We investigated the body composition, metabolic rate and metabolic phenotype of mature C3H/HeH mice assigned to low-cystine (LC) or high-cystine (HC) diets for 12 weeks.

Compared to LC mice, HC mice gained more weight (P=.004 for 12-week weight gain %), with increased fat mass and lean mass, and lowered O₂ consumption and CO₂ production by calorimetry. The HC mice had 30% increase in intestinal fat/body weight % (P=.003) and ∼twofold elevated hepatic triglycerides (P=.046), with increased expression of hepatic lipogenic factors, peroxisome proliferator-activated receptor-γ and sterol regulatory element binding protein-1. Gene expression of both basal and catecholamine-stimulated lipolytic enzymes, adipose triglyceride lipase and hormone-sensitive lipase was inhibited in HC mice adipose tissue. The HC mice also had elevated fasting glucose (7.0 vs. 4.5 mmol/L, P<.001) and a greater area under the curve (P<.001) in intraperitoneal glucose tolerance tests, with enhanced expression of the negative regulator of insulin signaling, protein tyrosine phosphatase-1B, in liver and adipose tissue.

Overall, high cystine intake promotes adiposity and an adverse metabolic phenotype in mice, indicating that the positive association of plasma tCys with obesity in humans may be causal.

The elevated homocysteine stimulates changes of haemostatic function of plasma isolated from breast cancer patients

The aim of our study was to explain the effect of elevated homocysteine (measured by HPLC) on haemostatic activity of plasma from breast cancer patients (fibrin polymerization and lysis; the thrombin and prothrombin time), because homocysteine (Hcys) induces changes in haemostasis, as well blood clotting as fibrinolysis. Patients were hospitalized in Department of Oncological Surgery, Medical University of Lodz, Poland. All patients have not had preadjuvant therapy, and samples from patients were taken before surgery. We observed that changes of selected parameters of haemostatic properties of plasma, e.g., the prothrombin time and thrombin time were prolonged in plasma from invasive breast cancer when compared with the control group (healthy subjects) and patients with benign breast diseases. Our results showed also that the correlation between the increased amount of Hcys and changes of selected parameters of haemostasis in invasive breast cancer patients exists. Considering the data presented in this study, we suggest that the elevated Hcys in invasive breast cancer patients may induce the changes of haemostatic properties of plasma isolated from these patients.

Prospective study of serum cysteine levels and oesophageal and gastric cancers in China

BACKGROUND

Cancers of the upper gastrointestinal tract remain a significant cause of morbidity and mortality. Cysteine, known to be involved in a myriad of immuno-modulatory, anti-oxidant, and anti-carcinogenic pathways, has not been investigated in the aetiology of oesophageal or gastric cancers. To examine the relationship between serum cysteine concentration and risk of these cancers we conducted a nested case-cohort study within the General Population Nutrition Intervention Trial in Linxian, China.

METHODS

498 oesophageal squamous cell carcinomas (OSCCs) and 255 gastric cardia adenocarcinomas (GCAs) were matched by age and sex to 947 individuals from the wider cohort. We calculated HRs and 95% CIs using the case-cohort estimator for the Cox proportional hazards models, stratified on age and sex, with adjustment for potential confounders.

RESULTS

Higher concentrations of serum cysteine were significantly associated with a lower risk of both OSCC and GCA. For those in the highest quartile of serum cysteine, compared to those in the lowest, the multivariate HRs were 0.70 for OSCC (95% CI 0.51 to 0.98) and 0.59 for GCA (95% CI 0.38 to 0.91). These associations were dose dependent (p for trend=0.006 and 0.008, respectively). These inverse associations were not significantly modified by other risk factors, with the exception of age, where a stronger association was noted among persons in the older age strata.

CONCLUSION

Higher serum concentrations of cysteine were associated with a significantly reduced risk of OSCC and GCA. Cysteine should be further investigated for its potential as a chemopreventive agent for upper gastrointestinal cancers.

The morama bean (Tylosema esculentum): a potential crop for southern Africa

The morama bean is an underutilized leguminous oilseed native to the Kalahari Desert and neighboring sandy regions of Botswana, Namibia, and South Africa (Limpopo, North-West, Gauteng, and Northern Cape provinces), and forms part of the diet of the indigenous population in these countries. It is also known as gemsbok bean, moramaboontjie, elandboontjie, braaiboonjie, marama, marumana, tsi, tsin, gami, and ombanui. It is reported as an excellent source of good quality protein (29-39%); its oil (24-48%) is rich in mono- and di-unsaturated fatty acids and contains no cholesterol. Morama is a good source of micronutrients such as calcium, iron, zinc, phosphate, magnesium, and B vitamins including folate. It is also reported to be a potential source of phytonutrients including phenolic compounds (e.g., tannins), trypsin inhibitors, phytates, and oligosaccharides, components which have been shown in other foods to contribute to health in particular, prevention of noncommunicable diseases such as cardiovascular diseases, diabetes, and some cancers. From a nutritional and health perspective, the morama bean has potential commercial value as a cash crop and value-added products, particularly in the communities where it is found.