Polyunsaturated fatty acids and gliomas: a critical review of experimental, clinical, and epidemiologic data

Lipid Alterations in Glioma: A Systematic Review

Gliomas are highly lethal tumours characterised by heterogeneous molecular features, producing various metabolic phenotypes leading to therapeutic resistance. Lipid metabolism reprogramming is predominant and has contributed to the metabolic plasticity in glioma. This systematic review aims to discover lipids alteration and their biological roles in glioma and the identification of potential lipids biomarker. This systematic review was conducted using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Extensive research articles search for the last 10 years, from 2011 to 2021, were conducted using four electronic databases, including PubMed, Web of Science, CINAHL and ScienceDirect. A total of 158 research articles were included in this study. All studies reported significant lipid alteration between glioma and control groups, impacting glioma cell growth, proliferation, drug resistance, patients' survival and metastasis. Different lipids demonstrated different biological roles, either beneficial or detrimental effects on glioma. Notably, prostaglandin (PGE2), triacylglycerol (TG), phosphatidylcholine (PC), and sphingosine-1-phosphate play significant roles in glioma development. Conversely, the most prominent anti-carcinogenic lipids include docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and vitamin D3 have been reported to have detrimental effects on glioma cells. Furthermore, high lipid signals were detected at 0.9 and 1.3 ppm in high-grade glioma relative to low-grade glioma. This evidence shows that lipid metabolisms were significantly dysregulated in glioma. Concurrent with this knowledge, the discovery of specific lipid classes altered in glioma will accelerate the development of potential lipid biomarkers and enhance future glioma therapeutics.

Adherence to plant-based dietary patterns in relation to glioma: a case-control study

Available evidence suggests a favorable association between adherence to a plant-based diet and disease prevention, but data on the link between such dietary intakes and cancer are scarce. We examined the association between the overall plant-based diet (PDI), healthy plant-based diet (hPDI), and unhealthy plant-based diet (uPDI) and risk of glioma. This case–control study was conducted on 128 newly diagnosed glioma patients, and 256 hospital-based controls. Cases were diagnosed by pathological test and controls were selected from hospitalized people in orthopedic and surgical wards. Dietary intakes were assessed using a validated Block-format 123-items food frequency questionnaire. Scores of plant-based dietary patterns were calculated using the method suggested by Satija et al. After controlling for potential confounders, individuals with higher scores of PDI (OR: 0.54, 95% CI: 0.32–0.91, P-trend < 0.001) and hPDI (OR: 0.32, 95% CI: 0.18–0.57, P-trend < 0.001) had significantly lower odds of glioma compared with those with the lowest scores. This association did not change in the fully adjusted model; such that subjects in the highest tertile of PDI and hPDI were 69% and 71% less likely to have glioma compared with those in the lowest tertile. In contrast, higher scores of uPDI was significantly associated with a greater odds of glioma (OR: 2.85, 95% CI: 1.26–6.47, P-trend = 0.02). Adherence to PDI and hPDI was associated with a lower odds of glioma, while greater adherence to uPDI was directly associated with the likelihood of glioma. Further prospective cohort studies are needed to examine our findings.

Egg Consumption in Relation to Glioma: A Case-Control Study

BACKGROUND AND AIMS

Data on the link between egg consumption and brain tumors are limited. The objective of this study was to investigate the association between egg consumption and odds of glioma in Iranian adults.

METHODS

In this hospital-based case-control study, 128 newly-diagnosed cases of glioma and 256 age- and sex-matched controls were enrolled from hospitals. Patients with pathologically confirmed glioma (without any other cancers) were considered eligible. We collected data on dietary intakes, including egg consumption, using a 126-item validated FFQ. Egg consumption was computed from all foods containing this food as their ingredients. Participants were categorized into tertiles of egg consumption. Conditional logistic regression was used to examine the association between egg consumption and glioma.

RESULTS

After adjustment for age, sex and energy intake, individuals in the middle tertile of egg consumption were 58% (OR 0.42; 95% CI 0.24, 0.73) less likely to have glioma compared with those in the lowest tertile. Further adjustment for other potential confounders strengthened the association; such that participants with the greatest consumption of egg intake were 62% (0.38; 0.18, 0.76) less likely to have glioma compared with those with the lowest consumption. Additional controlling for dietary intakes did not change the association significantly (0.39; 0.18, 0.85).

CONCLUSION

We found an inverse association between egg consumption at the amount of almost 2 eggs/week and odds of glioma. Further studies are required to examine this association.

Dietary Polyunsaturated Fat Intake in Relation to Glioma: A Case-Control Study

This study aimed to assess the association of dietary polyunsaturated fatty acid (PUFA) and risk of glioma among the Iranian population. A case-control study carried out among 128 newly diagnosed glioma adult patients with pathologically confirmed samples along with 256 sex- and age-matched controls. Dietary intake was examined by means of a validated semiquantitative food frequency questionnaire (FFQ). Total PUFA intake was computed by summing up dietary PUFAs from all food items in the questionnaire. Participants were categorized based on quartile cut-points of dietary PUFA intake. After taking into account the effect of age, sex and energy intake, individuals in the top quartile of PUFA intake were 77% less likely to have glioma than those in the bottom quartile (OR: 0.23; 95% CI: 0.11-0.48). Further adjustment for other potential variables strengthened the association. Additional controlling of nutrients did not alter the findings (OR: 0.19; 95% CI: 0.04-0.78). When we took into account the effect of body mass index (BMI), we found those in the highest quartile of PUFA intake has lower odds of glioma than those in the lowest (OR: 0.20; 95% CI: 0.05-0.84). We found dietary PUFA intake was inversely associated with risk of glioma in this case-control study on Iranian adults.

Arachidonic acid activates extrinsic apoptotic pathway to enhance tumoricidal action of bleomycin against IMR-32 cells

Bleomycin is a commonly used anti-cancer drug in the management of a variety of cancers. Previously, we showed that arachidonic acid (AA) augmented the growth inhibitory action of bleomycin on IMR-32 (human neuroblastoma cells) in vitro by enhancing oxidative stress. Despite these results, the exact molecular mechanism of cytotoxic action of bleomycin and its augmentation by AA is not known. Our current study revealed that a combination of bleomycin and AA significantly enhanced the expression of FAS gene, which is involved in programmed cell death (apoptosis) and caspases 3 and 8 compared to either bleomycin or AA alone implying that activation of extrinsic apoptotic pathway plays a major role in their (bleomycin + AA) tumoricidal action. It is interesting to note that AA by itself enhanced the expression of FAS and caspases 3 and 8 compared to control. Since caspases have a role in inflammation, cell proliferation, tumour suppression, cell differentiation, neural development and axon guidance and ageing, this may explain pleiotropic actions of AA and their metabolites.

Nuclear Factor of Activated T Cells-dependent Down-regulation of the Transcription Factor Glioma-associated Protein 1 (GLI1) Underlies the Growth Inhibitory Properties of Arachidonic Acid

Numerous reports have demonstrated a tumor inhibitory effect of polyunsaturated fatty acids (PUFAs). However, the molecular mechanisms modulating this phenomenon are in part poorly understood. Here, we provide evidence of a novel antitumoral mechanism of the PUFA arachidonic acid (AA). In vivo and in vitro experiments showed that AA treatment decreased tumor growth and metastasis and increased apoptosis. Molecular analysis of this effect showed significantly reduced expression of a subset of antiapoptotic proteins, including BCL2, BFL1/A1, and 4-1BB, in AA-treated cells. We demonstrated that down-regulation of the transcription factor glioma-associated protein 1 (GLI1) in AA-treated cells is the underlying mechanism controlling BCL2, BFL1/A1, and 4-1BB expression. Using luciferase reporters, chromatin immunoprecipitation, and expression studies, we found that GLI1 binds to the promoter of these antiapoptotic molecules and regulates their expression and promoter activity. We provide evidence that AA-induced apoptosis and down-regulation of antiapoptotic genes can be inhibited by overexpressing GLI1 in AA-sensitive cells. Conversely, inhibition of GLI1 mimics AA treatments, leading to decreased tumor growth, cell viability, and expression of antiapoptotic molecules. Further characterization showed that AA represses GLI1 expression by stimulating nuclear translocation of NFATc1, which then binds the GLI1 promoter and represses its transcription. AA was shown to increase reactive oxygen species. Treatment with antioxidants impaired the AA-induced apoptosis and down-regulation of GLI1 and NFATc1 activation, indicating that NFATc1 activation and GLI1 repression require the generation of reactive oxygen species. Collectively, these results define a novel mechanism underlying AA antitumoral functions that may serve as a foundation for future PUFA-based therapeutic approaches.

Lipidomic analysis reveals a radiosensitizing role of gamma-linolenic acid in glioma cells

Previous studies have demonstrated that gamma-linolenic acid (GLA) is effective against glioma cells under both in vitro and in vivo conditions. In the present study we determined how GLA alone or in combination with irradiation alters the fatty acid (FA) and lipid profiles, the lipid droplet (LD) content, the lipid biosynthetic gene expression and the apoptosis of glioma cells. In GLA-treated cells direct correlations were found between the levels of various FAs and the expression of the corresponding FA biosynthetic genes. The total levels of saturated and monosaturated FAs decreased in concert with the down-regulation of FASN and SCD1 gene expression. Similarly, decreased FADS1 gene expression was paralleled by lowered arachidonic acid (20:4 n-6) and eicosapentaenoic acid (20:5 n-3) contents, while the down-regulation of FADS2 expression was accompanied by a diminished docosahexaenoic acid (22:6 n-3) content. Detailed mass spectrometric analyses revealed that individual treatments gave rise to distinct lipidomic fingerprints. Following uptake, GLA was subjected to elongation, resulting in dihomo-gamma-linolenic acid (20:3 n-6, DGLA), which was used for the synthesis of the LD constituent triacylglycerols and cholesteryl esters. Accordingly, an increased number of LDs were observed in response to GLA administration after irradiation. GLA increased the radioresponsiveness of U87 MG cells, as demonstrated by an increase in the number of apoptotic cells determined by FACS analysis. In conclusion, treatment with GLA increased the apoptosis of irradiated glioma cells, and GLA might therefore increase the therapeutic efficacy of irradiation in the treatment of gliomas.

The influence of maternal dietary fat on the fatty acid composition and lipid metabolism in the subcutaneous fat of progeny pigs

To investigate the influence of maternal dietary fat intake on the fatty acid composition and lipid metabolism of progeny subcutaneous fat (SQ), fourteen sows were randomly assigned to a control or high fat (HF) group which received a diet containing 8% corn oil starting seven days before farrowing until weaning. The results showed the fatty acid composition in progeny SQ at weaning age generally demonstrated a similar pattern with the sow milk. However, this pattern was not observed at the finishing stage. The stearoyl-CoA desaturase 1 mRNA and protein levels in the progeny SQ of the HF group decreased at both sampling stages when compared with controls. The study demonstrated that maternal dietary fat during lactation significantly affected the fatty acid composition of progeny SQ at the weaning stage, yet no obvious lasting effect was observed in progeny SQ at the finishing stage.

Combination of unsaturated fatty acids and ionizing radiation on human glioma cells: cellular, biochemical and gene expression analysis

Background

Based on previous observations a potential resort in the therapy of the particularly radioresistant glioma would be its treatment with unsaturated fatty acids (UFAs) combined with irradiation.

Methods

We evaluated the effect of different UFAs (arachidonic acid (AA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and oleic acid (OA)) on human U87 MG glioma cell line by classical biochemical end-point assays, impedance-based, real-time cellular and holographic microscopic analysis. We further analyzed AA, DHA, and GLA at morphological, gene and miRNA expression level.

Results

Corresponding to LDH-, MTS assays and real-time cytoxicity profiles AA, DHA, and GLA enhanced the radio sensitivity of glioma cells. The collective application of polyunsaturated fatty acids (PUFAs) and irradiation significantly changed the expression of EGR1, TNF-α, NOTCH1, c-MYC, TP53, HMOX1, AKR1C1, NQO1, while up-regulation of GADD45A, EGR1, GRP78, DDIT3, c-MYC, FOSL1 were recorded both in response to PUFA treatment or irradiation alone. Among the analyzed miRNAs miR-146 and miR-181a were induced by DHA treatment. Overexpression of miR-146 was also detected by combined treatment of GLA and irradiation.

Conclusions

Because PUFAs increased the radio responsiveness of glioma cells as assessed by biochemical and cellular assays, they might increase the therapeutic efficacy of radiation in treatment of gliomas. We demonstrated that treatment with DHA, AA and GLA as adjunct to irradiation up-regulated the expression of oxidative-stress and endoplasmic reticulum stress related genes, and affected NOTCH1 expression, which could explain their additive effects.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-142) contains supplementary material, which is available to authorized users.