Choline metabolites and incident cardiovascular disease in a prospective cohort of adults: Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

The potential role for choline metabolite trimethylamine N-oxide (TMAO) in cardiovascular disease (CVD) has garnered much attention, but there have been limited data from diverse population-based cohorts. Furthermore, few studies have included circulating choline and betaine, which can serve as precursors to TMAO and may independently influence CVD.

OBJECTIVE

We quantified prospective associations between 3 choline metabolites and 19-y incident CVD in a population-based cohort and tested effect modification of metabolite-CVD associations by kidney function.

METHODS

Data were from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a prospective cohort with recruitment from 4 US urban centers (year 0: 1985-1986, n = 5115, ages 18-30). The analytic sample included 3444 White and Black males and females, aged 33 to 45, who attended the year 15 follow-up exam and did not have prevalent CVD. TMAO, choline, and betaine were quantitated from stored plasma (-70°C) using liquid-chromatography mass-spectrometry. Nineteen-year incident CVD events (n = 221), including coronary heart disease and stroke, were identified through adjudicated hospitalization records and linkage with the National Death Register.

RESULTS

Plasma choline was positively associated with CVD in Cox proportional hazards regression analysis adjusted for demographics, health behaviors, CVD risk factors, and metabolites (hazard ratio: 1.24; 95% CI: 1.09, 1.40 per standard deviation-unit choline). TMAO and betaine were not associated with CVD in an identically adjusted analysis. There was statistical evidence for effect modification by kidney function with CVD positively associated with TMAO and negatively associated with betaine at lower values of estimated glomerular filtration rate (interaction P values: 0.0046 and 0.020, respectively).

CONCLUSIONS

Our findings are consistent with a positive association between plasma choline and incident CVD. Among participants with lower kidney function, TMAO was positively, and betaine negatively, associated with CVD. These results further our understanding of the potential role for choline metabolism on CVD risk.

Maternal dietary deficiencies in folic acid or choline worsen stroke outcomes in adult male and female mouse offspring

Maternal one-carbon metabolism plays an important role in early life programming. There is a well-established connection between the fetal environment and the health status of the offspring. However, there is a knowledge gap on how maternal nutrition impacts stroke outcomes in offspring. The aim of our study was to investigate the role of maternal dietary deficiencies in folic acid or choline on stroke outcomes in 3-month-old offspring. Adult female mice were fed a folic acid-deficient diet, choline-deficient diet, or control diet 4 weeks before pregnancy. They were continued on diets during pregnancy and lactation. Male and female offspring were weaned onto a control diet and at 2 months of age were subjected to ischemic stroke within the sensorimotor cortex via photothrombotic damage. Mothers maintained on either a folic acid-deficient diet or choline-deficient diet had reduced levels of S-adenosylmethionine in the liver and S-adenosylhomocysteine in the plasma. After ischemic stroke, motor function was impaired in 3-month-old offspring from mothers receiving either a folic acid-deficient diet or choline-deficient diet compared to the animals receiving a control diet. In brain tissue, there was no difference in ischemic damage volume. When protein levels were assessed in ischemic brain tissue, there were lower levels of active caspase-3 and hypoxia-inducible factor 1α in males compared to females and betaine levels were reduced in offspring from the mothers receiving a choline-deficient diet. Our results demonstrate that a deficient maternal diet at critical time points in neurodevelopment results in worse stroke outcomes. This study emphasizes the importance of maternal diet and the impact it can have on offspring health.

Construction of a novel choline metabolism-related signature to predict prognosis, immune landscape, and chemotherapy response in colon adenocarcinoma

BACKGROUND

Colon adenocarcinoma (COAD) is a common digestive system malignancy with high mortality and poor prognosis. Accumulating evidence indicates that choline metabolism is closely related to tumorigenesis and development. However, the efficacy of choline metabolism-related signature in predicting patient prognosis, immune microenvironment and chemotherapy response has not been fully clarified.

METHODS

Choline metabolism-related differentially expressed genes (DEGs) between normal and COAD tissues were screened using datasets from The Cancer Genome Atlas (TCGA), Kyoto Encyclopedia of Genes and Genomes (KEGG), AmiGO2 and Reactome Pathway databases. Two choline metabolism-related genes (CHKB and PEMT) were identified by univariate and multivariate Cox regression analyses. TCGA-COAD was the training cohort, and GSE17536 was the validation cohort. Patients in the high- and low-risk groups were distinguished according to the optimal cutoff value of the risk score. A nomogram was used to assess the prognostic accuracy of the choline metabolism-related signature. Calibration curves, decision curve analysis (DCA), and clinical impact curve (CIC) were used to improve the clinical applicability of the prognostic signature. Gene Ontology (GO) and KEGG pathway enrichment analyses of DEGs in the high- and low-risk groups were performed. KEGG cluster analysis was conducted by the KOBAS-i database. The distribution and expression of CHKB and PEMT in various types of immune cells were analyzed based on single-cell RNA sequencing (scRNA-seq). The CIBERSORT and ESTIMATE algorithms evaluated tumor immune cell infiltration in the high- and low-risk groups. Evaluation of the half maximal inhibitory concentration (IC50) of common chemotherapeutic drugs based on the choline metabolism-related signature was performed. Small molecule compounds were predicted using the Connectivity Map (CMap) database. Molecular docking is used to simulate the binding conformation of small molecule compounds and key targets. By immunohistochemistry (IHC), Western blot, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) experiments, the expression levels of CHKB and PEMT in human, mouse, and cell lines were detected.

RESULTS

We constructed and validated a choline metabolism-related signature containing two genes (CHKB and PEMT). The overall survival (OS) of patients in the high-risk group was significantly worse than that of patients in the low-risk group. The nomogram could effectively and accurately predict the OS of COAD patients at 1, 3, and 5 years. The DCA curve and CIC demonstrate the clinical utility of the nomogram. scRNA-seq showed that CHKB was mainly distributed in endothelial cells, while PEMT was mainly distributed in CD4+ T cells and CD8+ T cells. In addition, multiple types of immune cells expressing CHKB and PEMT differed significantly. There were significant differences in the immune microenvironment, immune checkpoint expression and chemotherapy response between the two risk groups. In addition, we screened five potential small molecule drugs that targeted treatment for COAD. Finally, the results of IHC, Western blot, and qRT-PCR consistently showed that the expression of CHKB in human, mouse, and cell lines was elevated in normal samples, while PMET showed the opposite trend.

CONCLUSION

In conclusion, we constructed a choline metabolism-related signature in COAD and revealed its potential application value in predicting the prognosis, immune microenvironment, and chemotherapy response of patients, which may lay an important theoretical basis for future personalized precision therapy.

Choline Metabolism and Risk of Atrial Fibrillation and Heart Failure in the PREDIMED Study

BACKGROUND

Few studies have examined the associations of trimethylamine-N-oxide (TMAO) and its precursors (choline, betaine, dimethylglycine, and L-carnitine) with the risk of atrial fibrillation (AF) and heart failure (HF). This study sought to investigate these associations.

METHODS

Prospective associations of these metabolites with incident AF and HF were examined among participants at high cardiovascular risk in the PREDIMED study (PREvención con DIeta MEDiterránea) after follow-up for about 10 years. Two nested case-control studies were conducted, including 509 AF incident cases matched to 618 controls and 326 HF incident cases matched to 426 controls. Plasma levels of TMAO and its precursors were semi-quantitatively profiled with liquid chromatography tandem mass spectrometry. Odds ratios were estimated with multivariable conditional logistic regression models.

RESULTS

After adjustment for classical risk factors and accounting for multiple testing, participants in the highest quartile vs. the lowest quartile of baseline choline and betaine levels had a higher risk of AF [OR (95% CI): 1.85 (1.30-2.63) and 1.57 (1.09-2.24), respectively]. The corresponding OR for AF for extreme quartiles of dimethylglycine was 1.39 (0.99-1.96). One SD increase in log-transformed dimethylglycine was positively associated with AF risk (OR, 1.17; 1.03-1.33). The corresponding ORs for HF for extreme quartiles of choline, betaine, and dimethylglycine were 2.51 (1.57-4.03), 1.65 (1.00-2.71) and 1.65 (1.04-2.61), respectively. TMAO and L-carnitine levels were not associated with AF or HF.

CONCLUSIONS

Our findings support the role of the choline metabolic pathway in the pathogenesis of AF and HF.

ChoK-Full of Potential: Choline Kinase in B Cell and T Cell Malignancies

Aberrant choline metabolism, characterized by an increase in total choline-containing compounds, phosphocholine and phosphatidylcholine (PC), is a metabolic hallmark of carcinogenesis and tumor progression. This aberration arises from alterations in metabolic enzymes that control PC biosynthesis and catabolism. Among these enzymes, choline kinase α (CHKα) exhibits the most frequent alterations and is commonly overexpressed in human cancers. CHKα catalyzes the phosphorylation of choline to generate phosphocholine, the first step in de novo PC biosynthesis. CHKα overexpression is associated with the malignant phenotype, metastatic capability and drug resistance in human cancers, and thus has been recognized as a robust biomarker and therapeutic target of cancer. Of clinical importance, increased choline metabolism and CHKα activity can be detected by non-invasive magnetic resonance spectroscopy (MRS) or positron emission tomography/computed tomography (PET/CT) imaging with radiolabeled choline analogs for diagnosis and treatment monitoring of cancer patients. Both choline-based MRS and PET/CT imaging have also been clinically applied for lymphoid malignancies, including non-Hodgkin lymphoma, multiple myeloma and central nervous system lymphoma. However, information on how choline kinase is dysregulated in lymphoid malignancies is very limited and has just begun to be unraveled. In this review, we provide an overview of the current understanding of choline kinase in B cell and T cell malignancies with the goal of promoting future investigation in this area.

Associations between Plasma Choline Metabolites and Genetic Polymorphisms in One-Carbon Metabolism in Postmenopausal Women: The Women's Health Initiative Observational Study

BACKGROUND

Choline plays an integral role in one-carbon metabolism in the body, but it is unclear whether genetic polymorphisms are associated with variations in plasma choline and its metabolites.

OBJECTIVES

This study aimed to evaluate the association of genetic variants in choline and one-carbon metabolism with plasma choline and its metabolites.

METHODS

We analyzed data from 1423 postmenopausal women in a case-control study nested within the Women's Health Initiative Observational Study. Plasma concentrations of choline, betaine, dimethylglycine (DMG), and trimethylamine N-oxide were determined in 12-h fasting blood samples collected at baseline (1993-1998). Candidate and tagging single-nucleotide polymorphisms (SNPs) were genotyped in betaine-homocysteine S-methyltransferase (BHMT), BHMT2, 5,10-methylenetetrahydrofolate reductase (MTHFR), methylenetetrahydrofolate dehydrogenase (NADP+ dependent 1) (MTHFD1), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), and 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR). Linear regression was used to derive percentage difference in plasma concentrations per variant allele, adjusting for confounders, including B-vitamin biomarkers. Potential effect modification by plasma vitamin B-12, vitamin B-6, and folate concentrations and folic-acid fortification periods was examined.

RESULTS

The candidate SNP BHMT R239Q (rs3733890) was associated with lower concentrations of plasma betaine and DMG concentrations (-4.00% and -6.75% per variant allele, respectively; both nominal P < 0.05). Another candidate SNP, BHMT2 rs626105 A>G, was associated with higher plasma DMG concentration (13.0%; P < 0.0001). Several tagSNPs in these 2 genes were associated with plasma concentrations after correction for multiple comparisons. Vitamin B-12 status was a significant effect modifier of the association between the genetic variant BHMT2 rs626105 A>G and plasma DMG concentration.

CONCLUSIONS

Genetic variations in metabolic enzymes were associated with plasma concentrations of choline and its metabolites. Our findings contribute to the knowledge on the variation in blood nutrient concentrations in postmenopausal women.

Peptidomimetic-based approach toward inhibitors of microbial trimethylamine lyases

The development of gut microbiota-targeted small molecules represents a promising platform for the identification of new therapeutics based on the implication of human gut bacteria with different diseases. Bacterial trimethylamine (TMA)-lyase (CutC) is expressed in gut bacteria and catalyzes the conversion of choline to TMA. The association of elevated TMA production with various disorders has directed research efforts toward identification of CutC inhibitors. Herein, we introduce peptidomimetics as a promising toolbox for the discovery of CutC inhibitors. Our approach starts with screening a library of peptidomimetics for intestinal metabolic stability followed by in vitro CutC inhibition. Compound 5 was identified from this screening platform with IC₅₀ value of 5.9 ± 0.6 μM for CutC inhibition. Unlike previously reported CutC inhibitors, compound 5 possessed universal CutC inhibitory activity in different bacterial strains. Molecular dynamics simulations suggested a plausible binding site and inhibition mechanism for compound 5. Therefore, compound 5 is a promising lead for further structural optimization in the search for CutC-targeted small molecules.

Structure-guided function discovery of an NRPS-like glycine betaine reductase for choline biosynthesis in fungi

Nonribosomal peptide synthetases (NRPSs) and NRPS-like enzymes have diverse functions in primary and secondary metabolisms. By using a structure-guided approach, we uncovered the function of a NRPS-like enzyme with unusual domain architecture, catalyzing two sequential two-electron reductions of glycine betaine to choline. Structural analysis based on the homology model suggests cation-π interactions as the major substrate specificity determinant, which was verified using substrate analogs and inhibitors. Bioinformatic analysis indicates this NRPS-like glycine betaine reductase is highly conserved and widespread in kingdom fungi. Genetic knockout experiments confirmed its role in choline biosynthesis and maintaining glycine betaine homeostasis in fungi. Our findings demonstrate that the oxidative choline-glycine betaine degradation pathway can operate in a fully reversible fashion and provide insight in understanding fungal choline metabolism. The use of an NRPS-like enzyme for reductive choline formation is energetically efficient compared with known pathways. Our discovery also underscores the capabilities of the structure-guided approach in assigning functions of uncharacterized multidomain proteins, which can potentially aid functional discovery of new enzymes by genome mining.

One-Carbon Metabolism: Biological Players in Epithelial Ovarian Cancer

Metabolism is deeply involved in cell behavior and homeostasis maintenance, with metabolites acting as molecular intermediates to modulate cellular functions. In particular, one-carbon metabolism is a key biochemical pathway necessary to provide carbon units required for critical processes, including nucleotide biosynthesis, epigenetic methylation, and cell redox-status regulation. It is, therefore, not surprising that alterations in this pathway may acquire fundamental importance in cancer onset and progression. Two of the major actors in one-carbon metabolism, folate and choline, play a key role in the pathobiology of epithelial ovarian cancer (EOC), the deadliest gynecological malignancy. EOC is characterized by a cholinic phenotype sustained via increased activity of choline kinase alpha, and via membrane overexpression of the alpha isoform of the folate receptor (FRα), both of which are known to contribute to generating regulatory signals that support EOC cell aggressiveness and proliferation. Here, we describe in detail the main biological processes associated with one-carbon metabolism, and the current knowledge about its role in EOC. Moreover, since the cholinic phenotype and FRα overexpression are unique properties of tumor cells, but not of normal cells, they can be considered attractive targets for the development of therapeutic approaches.

Reciprocal regulation of the cholinic phenotype and epithelial-mesenchymal transition in glioblastoma cells

Glioblastoma (GBM) is the most malignant brain tumor with very limited therapeutic options. Standard multimodal treatments, including surgical resection and combined radio-chemotherapy do not target the most aggressive subtype of glioma cells, brain tumor stem cells (BTSCs). BTSCs are thought to be responsible for tumor initiation, progression, and relapse. Furthermore, they have been associated with the expression of mesenchymal features as a result of epithelial-mesenchymal transition (EMT) thereby inducing tumor dissemination and chemo resistance. Using high resolution proton nuclear magnetic resonance spectroscopy (¹H NMR) on GBM cell cultures we provide evidence that the expression of well-known EMT activators of the ZEB, TWIST and SNAI families and EMT target genes N-cadherin and VIMENTIN is associated with aberrant choline metabolism. The cholinic phenotype is characterized by high intracellular levels of phosphocholine and total choline derivatives and was associated with malignancy in various cancers. Both genetic and pharmacological inhibition of the cardinal choline metabolism regulator choline kinase alpha (CHKα) significantly reduces the cell viability, invasiveness, clonogenicity, and expression of EMT associated genes in GBM cells. Moreover, in some cell lines synergetic cytotoxic effects were observed when combining the standard of care chemotherapeutic temozolomide with the CHKα inhibitor V-11-0711. Taken together, specific inhibition of the enzymatic activity of CHKα is a powerful strategy to suppress EMT which opens the possibility to target chemo-resistant BTSCs through impairing their mesenchymal transdifferentiation. Moreover, the newly identified EMT-oncometabolic network may be helpful to monitor the invasive properties of glioblastomas and the success of anti-EMT therapy.

The Tumor Microenvironment Modulates Choline and Lipid Metabolism

An increase of cellular phosphocholine (PC) and total choline (tCho)-containing compounds as well as alterations in lipids have been consistently observed in cancer cells and tissue. These metabolic changes are closely related to malignant transformation, invasion, and metastasis. The study of cancer cells in culture plays an important role in understanding mechanisms leading to altered choline (Cho) and lipid metabolism in cancer, as it provides a carefully controlled environment. However, a solid tumor is a complex system with a unique tumor microenvironment frequently containing hypoxic and acidic regions and areas of nutrient deprivation and necrosis. Cancer cell–stromal cell interactions and the extracellular matrix may also alter Cho and lipid metabolism. Human tumor xenograft models in mice are useful to mimic the growth of human cancers and provide insights into the influence of in vivo conditions on metabolism. Here, we have compared metabolites, obtained with high resolution ¹H MRS of extracts from human breast and prostate cancer cells in a 2-dimensional (2D) monolayer culture and from solid tumor xenografts derived from these cells, as well as the protein expression of enzymes that regulate Cho and lipid metabolism. Our data demonstrate significant differences in Cho and lipid metabolism and protein expression patterns between human breast and prostate cancer cells in culture and in tumors derived from these cells. These data highlight the influence of the tumor microenvironment on Cho and lipid metabolism.

Effect of Pantethine on Ovarian Tumor Progression and Choline Metabolism

Epithelial ovarian cancer remains the leading cause of death from gynecologic malignancy among women in developed countries. New therapeutic strategies evaluated with relevant preclinical models are urgently needed to improve survival rates. Here, we have assessed the effect of pantethine on tumor growth and metabolism using magnetic resonance imaging and high-resolution proton magnetic resonance spectroscopy (MRS) in a model of ovarian cancer. To evaluate treatment strategies, it is important to use models that closely mimic tumor growth in humans. Therefore, we used an orthotopic model of ovarian cancer where a piece of tumor tissue, derived from an ovarian tumor xenograft, is engrafted directly onto the ovary of female mice, to maintain the tumor physiological environment. Treatment with pantethine, the precursor of vitamin B5 and active moiety of coenzyme A, was started when tumors were ~100 mm³ and consisted of a daily i.p. injection of 750 mg/kg in saline. Under these conditions, no side effects were observed. High-resolution ¹H MRS was performed on treated and control tumor extracts. A dual-phase extraction method based on methanol/chloroform/water was used to obtain lipid and water-soluble fractions from the tumors. We also investigated effects on metastases and ascites formation. Pantethine treatment resulted in slower tumor progression, decreased levels of phosphocholine and phosphatidylcholine, and reduced metastases and ascites occurrence. In conclusion, pantethine represents a novel potential, well-tolerated, therapeutic tool in patients with ovarian cancer. Further in vivo preclinical studies are needed to confirm the beneficial role of pantethine and to better understand its mechanism of action.

Activation of Phosphatidylcholine-Specific Phospholipase C in Breast and Ovarian Cancer: Impact on MRS-Detected Choline Metabolic Profile and Perspectives for Targeted Therapy

Elucidation of molecular mechanisms underlying the aberrant phosphatidylcholine cycle in cancer cells plays in favor of the use of metabolic imaging in oncology and opens the way for designing new targeted therapies. The anomalous choline metabolic profile detected in cancer by magnetic resonance spectroscopy and spectroscopic imaging provides molecular signatures of tumor progression and response to therapy. The increased level of intracellular phosphocholine (PCho) typically detected in cancer cells is mainly attributed to upregulation of choline kinase, responsible for choline phosphorylation in the biosynthetic Kennedy pathway, but can also be partly produced by activation of phosphatidylcholine-specific phospholipase C (PC-PLC). This hydrolytic enzyme, known for implications in bacterial infection and in plant survival to hostile environmental conditions, is reported to be activated in mitogen- and oncogene-induced phosphatidylcholine cycles in mammalian cells, with effects on cell signaling, cell cycle regulation, and cell proliferation. Recent investigations showed that PC-PLC activation could account for 20–50% of the intracellular PCho production in ovarian and breast cancer cells of different subtypes. Enzyme activation was associated with PC-PLC protein overexpression and subcellular redistribution in these cancer cells compared with non-tumoral counterparts. Moreover, PC-PLC coimmunoprecipitated with the human epidermal growth factor receptor-2 (HER2) and EGFR in HER2-overexpressing breast and ovarian cancer cells, while pharmacological PC-PLC inhibition resulted into long-lasting HER2 downregulation, retarded receptor re-expression on plasma membrane and antiproliferative effects. This body of evidence points to PC-PLC as a potential target for newly designed therapies, whose effects can be preclinically and clinically monitored by metabolic imaging methods.

High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice

BACKGROUND

Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions.

OBJECTIVE

Our goal was to investigate the impact of high folic acid intake on liver disease and methyl metabolism.

DESIGN

Folic acid-supplemented diet (FASD, 10-fold higher than recommended) and control diet were fed to male Mthfr(+/+) and Mthfr(+/-) mice for 6 mo to assess gene-nutrient interactions. Liver pathology, folate and choline metabolites, and gene expression in folate and lipid pathways were examined.

RESULTS

Liver and spleen weights were higher and hematologic profiles were altered in FASD-fed mice. Liver histology revealed unusually large, degenerating cells in FASD Mthfr(+/-) mice, consistent with nonalcoholic fatty liver disease. High folic acid inhibited MTHFR activity in vitro, and MTHFR protein was reduced in FASD-fed mice. 5-Methyltetrahydrofolate, SAM, and SAM/S-adenosylhomocysteine ratios were lower in FASD and Mthfr(+/-) livers. Choline metabolites, including phosphatidylcholine, were reduced due to genotype and/or diet in an attempt to restore methylation capacity through choline/betaine-dependent SAM synthesis. Expression changes in genes of one-carbon and lipid metabolism were particularly significant in FASD Mthfr(+/-) mice. The latter changes, which included higher nuclear sterol regulatory element-binding protein 1, higher Srepb2 messenger RNA (mRNA), lower farnesoid X receptor (Nr1h4) mRNA, and lower Cyp7a1 mRNA, would lead to greater lipogenesis and reduced cholesterol catabolism into bile.

CONCLUSIONS

We suggest that high folic acid consumption reduces MTHFR protein and activity levels, creating a pseudo-MTHFR deficiency. This deficiency results in hepatocyte degeneration, suggesting a 2-hit mechanism whereby mutant hepatocytes cannot accommodate the lipid disturbances and altered membrane integrity arising from changes in phospholipid/lipid metabolism. These preliminary findings may have clinical implications for individuals consuming high-dose folic acid supplements, particularly those who are MTHFR deficient.

EDI3 links choline metabolism to integrin expression, cell adhesion and spreading

Endometrial carcinoma differential 3 (EDI3) was the first member of the glycerophosphodiesterase (GDE) protein family shown to be associated with cancer. Our initial work demonstrated that endometrial and ovarian cancer patients with primary tumors overexpressing EDI3 had a higher risk of developing metastasis and decreased survival. Further analysis indicated that EDI3 cleaves glycerophosphocholine to choline and glycerol-3-phosphate, increases the levels of active PKC, and enhances the migratory activity of tumor cells. Despite these initial findings, EDI3 remained mainly uncharacterized. Therefore, to obtain an overview of processes in which EDI3 may be involved, gene array analysis was performed using MCF-7 breast cancer cells after EDI3 knockdown compared with a non-targeting control siRNA. Several biological motifs were altered, including an enrichment of genes involved in integrin-mediated signaling. More specifically, silencing of EDI3 in MCF-7 and OVCAR-3 cells was associated with reduced expression of the key receptor subunit integrin β1, leading to decreased cell attachment and spreading accompanied by delayed formation of cell protrusions. To confirm these results, we stably overexpressed EDI3 in MCF-7 cells which led to elevated integrin β1 expression associated with enhanced cell attachment and spreading - two processes critical for metastasis. In conclusion, our data provide further insight into the role of EDI3 during cancer progression.

In vivo ³¹P magnetic resonance spectroscopic imaging (MRSI) for metabolic profiling of human breast cancer xenografts

PURPOSE

To study cancer associated with abnormal metabolism of phospholipids, of which several have been proposed as biomarkers for malignancy or to monitor response to anticancer therapy. We explored 3D (31) P magnetic resonance spectroscopic imaging (MRSI) at high magnetic field for in vivo assessment of individual phospholipids in two patient-derived breast cancer xenografts representing good and poor prognosis (luminal- and basal-like tumors).

MATERIALS AND METHODS

Metabolic profiles from luminal-like and basal-like xenograft tumors were obtained in vivo using 3D (31) P MRSI at 11.7T and from tissue extracts in vitro at 14.1T. Gene expression analysis was performed in order to support metabolic differences between the two xenografts.

RESULTS

In vivo (31) P MR spectra were obtained in which the prominent resonances from phospholipid metabolites were detected at a high signal-to-noise ratio (SNR >7.5). Metabolic profiles obtained in vivo were in agreement with those obtained in vitro and could be used to discriminate between the two xenograft models, based on the levels of phosphocholine, phosphoethanolamine, glycerophosphocholine, and glycerophosphoethanolamine. The differences in phospholipid metabolite concentration could partly be explained by gene expression profiles.

CONCLUSION

Noninvasive metabolic profiling by 3D (31) P MRSI can discriminate between subtypes of breast cancer based on different concentrations of choline- and ethanolamine-containing phospholipids.

Quantitative (31)P HR-MAS MR spectroscopy for detection of response to PI3K/mTOR inhibition in breast cancer xenografts

PURPOSE

Phospholipid metabolites are of importance in cancer studies, and have been suggested as candidate metabolic biomarkers for response to targeted anticancer drugs. The purpose of this study was to develop a phosphorus ((31) P) high resolution magic angle spinning magnetic resonance spectroscopy protocol for quantification of phosphorylated metabolites in intact cancer tissue.

METHODS

(31) P spectra were acquired on a 14.1 T spectrometer with a triplet (1) H/(13) C/(31) P MAS probe. Quantification of metabolites was performed using the PULCON principle. Basal-like and luminal-like breast cancer xenografts were treated with the dual PI3K/mTOR inhibitor BEZ235, and the impact of treatment on the concentration of phosphocholine, glycerophosphocholine, phosphoethanolamine and glycerophosphoethanolamine was evaluated.

RESULTS

In basal-like xenografts, BEZ235 treatment induced a significant decrease in phosphoethanolamine (-25.6%, P = 0.01) whilst phosphocholine (16.5%, P = 0.02) and glycerophosphocholine (37.3%, P < 0.001) were significantly increased. The metabolic changes could partially be explained by increased levels of phospholipase A2 group 4A (PLA2G4A).

CONCLUSION

(31) P high resolution magic angle spinning magnetic resonance spectroscopy is a useful method for quantitative assessment of metabolic responses to PI3K inhibition. Using the PULCON principle for quantification, the levels of phosphocholine, glycerophosphocholine, phosphoethanolamine, and glycerophosphoethanolamine could be evaluated with high precision and accuracy.

Metabolic consequences of treatment with AKT inhibitor perifosine in breast cancer cells

Activation of the PI3K/Akt pathway is associated with the development of numerous human cancers. As a result, many emerging therapies target this pathway. Previous studies have shown that targeting the PI3K/Akt pathway at the level of PI3K is associated with a drop in phosphocholine (PCho) and a reduction in hyperpolarized lactate production. However, the consequences of targeting downstream of PI3K at the level of Akt have not been investigated. Perifosine is an anticancer alkylphospholipid used in clinical trials. It acts by inhibiting phosphorylation of Akt and has been shown to inhibit CTP-phosphocholine cytidyltransferase (CT). The goal of this study was to identify the MRS-detectable metabolic consequences of treatment with perifosine in MCF-7 breast cancer cells. We found that perifosine treatment led to a 51 ± 5% drop in PCho from 30 ± 5 to 15 ± 1 fmol/cell and a comparable drop in de novo synthesized PCho. This was associated with a drop in choline kinase (ChoK) activity and ChoKα expression. CT inhibition could not be ruled out but likely did not contribute to the change in PCho. We also found that intracellular lactate levels decreased from 2.7 ± 0.5 to 1.5 ± 0.3 fmol/cell and extracellular lactate levels dropped by a similar extent. These findings were consistent with a drop in lactate dehydrogenase expression and associated with a drop in activity of the hypoxia inducible factor (HIF)-1α. The drops in PCho and lactate production following perifosine treatment are therefore mediated downstream of Akt by the drop in HIF-1α, which serves as the transcription factor for both ChoK and lactate dehydrogenase. The metabolic changes were confirmed in a second breast cancer cell line, MDA-MB-231. Taken together, these findings indicate that PCho and lactate can serve as noninvasive metabolic biomarkers for monitoring the effects of inhibitors that target the PI3K/Akt pathway, independent of the step that leads to inhibition of HIF-1α.

Association between composition of the human gastrointestinal microbiome and development of fatty liver with choline deficiency

BACKGROUND & AIMS

Nonalcoholic fatty liver disease affects up to 30% of the US population, but the mechanisms underlying this condition are incompletely understood. We investigated how diet standardization and choline deficiency influence the composition of the microbial community in the human gastrointestinal tract and the development of fatty liver under conditions of choline deficiency.

METHODS

We performed a 2-month inpatient study of 15 female subjects who were placed on well-controlled diets in which choline levels were manipulated. We used 454-FLX pyrosequencing of 16S ribosomal RNA bacterial genes to characterize microbiota in stool samples collected over the course of the study.

RESULTS

The compositions of the gastrointestinal microbial communities changed with choline levels of diets; each individual's microbiome remained distinct for the duration of the experiment, even though all subjects were fed identical diets. Variations between subjects in levels of Gammaproteobacteria and Erysipelotrichi were directly associated with changes in liver fat in each subject during choline depletion. Levels of these bacteria, change in amount of liver fat, and a single nucleotide polymorphism that affects choline were combined into a model that accurately predicted the degree to which subjects developed fatty liver on a choline-deficient diet.

CONCLUSIONS

Host factors and gastrointestinal bacteria each respond to dietary choline deficiency, although the gut microbiota remains distinct in each individual. We identified bacterial biomarkers of fatty liver that result from choline deficiency, adding to the accumulating evidence that gastrointestinal microbes have a role in metabolic disorders.