Fatty acid composition of red blood cell membranes and risk of squamous cell carcinoma of the skin

Metabolomics and lipidomics signature in celiac disease: a narrative review

Celiac disease (CD) is a chronic immune-mediated inflammatory disease of the small intestine caused by aberrant immune responses to consumed gluten proteins. CD is diagnosed by a combination of the patients reported symptoms, serologic and endoscopic biopsy evaluation of the small intestine; and adherence to a strict gluten-free diet (GFD) is considered the only available therapeutic approach for this disorder. Novel approaches need to be considered for finding new biomarkers to help this disorder diagnosis and finding a new alternative therapeutic method for this group of patients. Metabolomics and lipidomics are powerful tools to provide highly accurate and sensitive biomarkers. Previous studies indicated a metabolic fingerprint for CD deriving from alterations in gut microflora or intestinal permeability, malabsorption, and energy metabolism. Moreover, since CD is characterized by increased intestinal permeability and due to the importance of membrane lipid components in controlling barrier integrity, conducting lipidomics studies in this disorder is of great importance. In the current study, we tried to provide a critical overview of metabolomic and lipidomic changes in CD.

Changes in Human Erythrocyte Membrane Exposed to Aqueous and Ethanolic Extracts from Uncaria tomentosa

Uncaria tomentosa (Willd.) DC is a woody climber species originating from South and Central America that has been used in the therapy of asthma, rheumatism, hypertension, and blood purification. Our previous study showed that U. tomentosa extracts altered human erythrocyte shape, which could be due to incorporation of the compounds contained in extracts into the erythrocyte membrane. The aim of the present study was to determine how the compounds contained in U. tomentosa extracts incorporate into the human erythrocyte membrane. The study has assessed the effect of aqueous and ethanolic extracts from leaves and bark of U. tomentosa on the osmotic resistance of the human erythrocyte, the viscosity of erythrocyte interior, and the fluidity of erythrocyte plasma membrane. Human erythrocytes were incubated with the studied extracts in the concentrations of 100, 250, and 500 µg/mL for 2, 5, and 24 h. All extracts tested caused a decrease in erythrocyte membrane fluidity and increased erythrocyte osmotic sensitivity. The ethanolic extracts from the bark and leaves increased viscosity of the erythrocytes. The largest changes in the studied parameters were observed in the cells incubated with bark ethanolic extract. We consider that the compounds from U. tomentosa extracts mainly build into the outer, hydrophilic monolayer of the erythrocyte membrane, thus protecting the erythrocytes against the adverse effects of oxidative stress.

Fatty acid desaturase activity in mature red blood cells and implications for blood storage quality

BACKGROUND

Increases in the red blood cell (RBC) degree of fatty acid desaturation are reported in response to exercise, aging, or diseases associated with systemic oxidant stress. However, no studies have focused on the presence and activity of fatty acid desaturases (FADS) in the mature RBC.

STUDY DESIGN AND METHODS

Steady state metabolomics and isotope-labeled tracing experiments, immunofluorescence approaches, and pharmacological interventions were used to determine the degree of fatty acid unsaturation, FADS activity as a function of storage, oxidant stress, and G6PD deficiency in human and mouse RBCs.

RESULTS

In 250 blood units from the REDS III RBC Omics recalled donor population, we report a storage-dependent accumulation of free mono-, poly-(PUFAs), and highly unsaturated fatty acids (HUFAs), which occur at a faster rate than saturated fatty acid accumulation. Through a combination of immunofluorescence, pharmacological inhibition, tracing experiments with stable isotope-labeled fatty acids, and oxidant challenge with hydrogen peroxide, we demonstrate the presence and redox-sensitive activity of FADS2, FADS1, and FADS5 in the mature RBC. Increases in PUFAs and HUFAs in human and mouse RBCs correlate negatively with storage hemolysis and positively with posttransfusion recovery. Inhibition of these enzymes decreases accumulation of free PUFAs and HUFAs in stored RBCs, concomitant to increases in pyruvate/lactate ratios. Alterations of this ratio in G6PD deficient patients or units supplemented with pyruvate-rich rejuvenation solutions corresponded to decreased PUFA and HUFA accumulation.

CONCLUSION

Fatty acid desaturases are present and active in mature RBCs. Their activity is sensitive to oxidant stress, storage duration, and alterations of the pyruvate/lactate ratio.

The highly unnatural fatty acid profile of cells in culture

The fatty acid profile of cells in culture are unlike those of natural cells with twice the monounsaturated (MUFA) and half the polyunsaturated fatty acids (PUFA) level (Mol%). This is not due to cell lines primarily being derived from cancers but is due to limited access to lipid and an inability to make PUFA de novo as vertebrate cells. Classic culture methods use media with 10% serum (the only exogenous source of lipid). Fetal bovine serum (FBS), the serum of choice has a low level of lipid and cholesterol compared to other sera and at 10% of media provides 2-3% of the fatty acid and cholesterol, 1% of the PUFA and 0.3% of the essential fatty acid linoleic acid (18:2n-6) available to cells in the body. Since vertebrate cell lines cannot make PUFA they synthesise MUFA, offsetting their PUFA deficit and reducing their fatty acid diversity. Stem and primary cells in culture appear to be similarly affected, with a rapid loss of their natural fatty acid compositions. The unnatural lipid composition of cells in culture has substantial implications for examining natural stems cell in culture, and for investigations of cellular mechanisms using cell lines based on the pervasive influence of fats.

Gene Expression Patterns of Cutaneous Squamous Cell Carcinoma and Actinic Keratosis: Biomarkers Screening for Skin Disease Diagnosis

Background

Actinic keratosis (AK) was an intraepidermal tumor which caused by ultraviolet irradiation-induced skin damage.

Objective

The aim was to screen biomarkers for development of skin disease by comparing the gene expression profiles between cutaneous squamous cell carcinoma (CSCC) and AK.

Methods

GSE45216 with 30 cutaneous squamous cell carcinoma patients and 10 actinic keratosis patients were downloaded and significance analysis of microarrays was processed to screen differently expressed genes (DEGs). Fisher's exact test was processed for DEGs enrichment. Pathway relationship network systematically reflected the signal conduction and synergism between enriched pathways based on Kyoto Encyclopedia of Genes and Genomes database. Gene co-expression network was constructed according to gene expression data. Quantitative real-time-PCR was used to verify screened biomarkers.

Results

Total 410 DEGs were screened and enriched into various functions, such as signal transduction and negative regulation of apoptotic process. They also participated into cytokine-cytokine receptor interaction and focal adhesion. The pathway relationship network was constructed with 27 nodes. Hub nodes with higher degree of this network were mitogen-activated protein kinase signaling pathway and apoptosis. The gene co-expression network was constructed with 39 nodes. Thereinto, hub node was ELOVL fatty acid elongase. The expression levels of ELOVL4 and HPGD were significantly higher in CSCC samples than that in AK samples, while the expression levels of INHBA and LAMC2 in CSCC samples were significantly lower than that in AK samples.

Conclusion

These screened genes, including ELOVL4, HPGD, INHBA and LAMC2, played important roles in transformation from AK to CSCC.

Risk of basal cell carcinoma in a randomized clinical trial of aspirin and folic acid for the prevention of colorectal adenomas

BACKGROUND

Aspirin may reduce the risk of several types of cancer.

OBJECTIVES

To evaluate if folic acid is associated with risk of basal cell carcinoma (BCC).

METHODS

BCC incidence was evaluated in a randomized, double-blind, placebo-controlled clinical trial of aspirin (81 mg daily or 325 mg daily for ~3 years) and/or folic acid (1 mg daily for ~6 years) for the prevention of colorectal adenomas among 1121 participants with a previous adenoma. BCC was confirmed by blinded review of pathology reports.

RESULTS

One hundred and four of 958 non-Hispanic white participants were diagnosed with BCC over a median follow-up of 13·5 years. Cumulative incidence of BCC was 12% [95% confidence interval (CI) 7-17] for placebo, 16% (95% CI 11-21) for 81 mg aspirin daily and 15% (95% CI 10-20) for 325 mg aspirin daily [hazard ratio (HR) for any aspirin 1·45 (95% CI 0·93-2·26); HR for 81 mg daily 1·57 (95% CI 0·96-2·56); HR for 325 mg daily 1·33 (95% CI 0·80-2·20)]. BCC risk was higher with aspirin use in those without previous skin cancer but lower with aspirin use in those with previous skin cancer (P_interaction = 0·02 for 81 mg aspirin daily; P_interaction = 0·03 for 325 mg aspirin daily). Folic acid supplementation was unrelated to BCC incidence (HR 0·85; 95% CI 0·57-1·27).

CONCLUSIONS

Neither aspirin nor folic acid treatment had a statistically significant effect on risk of BCC. Subgroup analysis suggested that chemopreventive effects of nonsteroidal anti-inflammatory drugs may be specific to those at high risk for BCC.

Erythrocyte Membrane Unsaturated (Mono and Poly) Fatty Acids Profile in Newly Diagnosed Basal Cell Carcinoma Patients

Studies have reported different changes in the fatty acid composition of red blood cell (RBC) total lipids in patients with various types of cancer. It has been indicated that n-3/n-6 ratio plays a key role in the general consequence of skin photocarcinogenesis. However, to our knowledge there was no study examining the unsaturated fatty acid profile in basal cell carcinoma (BCC) patients. So, we explore the fatty acid composition of RBCs in newly diagnosed BCC patients in a hospital-based case-control study. This study has been conducted on new case BCC patients in Razi Hospital, Tehran, Iran. Fatty acid concentration in erythrocyte membranes defined as relative values after extraction, purification and preparation, by gas chromatography.Analysis revealed that heptadecenoic acid (p = 0.010) and oleic acid (p < 0.001) was significantly higher in BCC patients in comparison with control group. Among polyunsaturated fatty acids (PUFAs), linoleic acid (LA), and arachidonic acid (AA) were significantly higher in BCC patients (p < 0.001). It has been indicated that n-3 was significantly lower (p = 0.040) and n-6 was significantly higher (p = 0.002) in BCC patients. In addition, total PUFA (p < 0.001) and n-6 PUFAs/n-3 PUFAs (p = 0.002) were significantly higher in BCC patients compared to the control group. Here we indicated that new case BCC patient had significantly higher n-6 PUFA and lower n-3 along with other differences in unsaturated fatty acid in comparison with healthy subjects. Our study provides evidence that lipids are important in BCC development.

Phospholipid composition of packed red blood cells and that of extracellular vesicles show a high resemblance and stability during storage

Red blood cells (RBCs) are stored up to 35-42days at 2-6°C in blood banks. During storage, the RBC membrane is challenged by energy depletion, decreasing pH, altered cation homeostasis, and oxidative stress, leading to several biochemical and morphological changes in RBCs and to shedding of extracellular vesicles (EVs) into the storage medium. These changes are collectively known as RBC storage lesions. EVs accumulate in stored RBC concentrates and are, thus, transfused into patients. The potency of EVs as bioactive effectors is largely acknowledged, and EVs in RBC concentrates are suspected to mediate some adverse effects of transfusion. Several studies have shown accumulation of lipid raft-associated proteins in RBC EVs during storage, whereas a comprehensive phospholipidomic study on RBCs and corresponding EVs during the clinical storage period is lacking. Our mass spectrometric and chromatographic study shows that RBCs maintain their major phospholipid (PL) content well during storage despite abundant vesiculation. The phospholipidomes were largely similar between RBCs and EVs. No accumulation of raft lipids in EVs was seen, suggesting that the primary mechanism of RBC vesiculation during storage might not be raft -based. Nonetheless, a slight tendency of EV PLs for shorter acyl chains was observed.

Gas chromatography-mass spectrometry analysis of effects of dietary fish oil on total fatty acid composition in mouse skin

Altering the fatty acid (FA) composition in the skin by dietary fish oil could provide therapeutic benefits. Although it has been shown that fish oil supplementation enhances EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) abundance in the skin, comprehensive skin FA profiling is needed. We established a gas chromatography-mass spectrometry method, which allows precise quantification of FA profile using small (<24 mm² for mice and <12 mm² for humans) skin specimens that can be readily obtained from live mice and humans. We determined mouse skin FA composition after 2, 4 and 8 weeks of consuming a control diet or a diet supplemented with fish oil. Fish oil markedly enhanced EPA and DHA in mouse skin within 2 weeks, and this increase plateaued after 4 weeks. The FA composition in mouse skin was different from that of serum, indicating that skin has homeostatic control of FA metabolism. Mice fed the control diet designed to simulate Western human diet displayed similar skin FA composition as that of humans. The present study presents a validated method for FA quantification that is needed to investigate the mechanisms of actions of dietary treatments in both mouse and human skin.

Gas chromatography determination of fatty acids in the human erythrocyte membranes - A review

Blood fatty acid measurements can reflect exogenously consumed fatty acids allowing to resolve some metabolic disorders (e.g. diabetes, anorexia) or mental disorders (e.g. depression, anxiety, schizophrenia). For this purpose, fatty acids can be determined in the whole blood or various blood fractions such as the plasma, serum or erythrocytes. Measurement of fatty acids in the whole blood by dried blood spot technique is becoming increasingly popular and is often used mainly for the screening of newborns due to the use of the small sample volume. The most popular is determination of fatty acids in plasma or serum samples. While the profile of plasma fatty acids fluctuates based on daily dietary intake, the red blood cell membrane composition of fatty acids reflects the 2-3 month dietary intake. Such results can be more reflective in contrast to the plasma/serum and therefore the present review will summarize available information on gas chromatography determination of fatty acids in human red blood cell membranes. Selection of extraction and derivatization reagents as well as presentation of chromatographic conditions will be discussed here.

The role of background diet on the effects of eicosapentaenoic acid and docosahexaenoic acid supplementation in healthy pre-menopausal women: a randomized, cross-over, controlled study

Background

The links between dietary fat intake, polyunsaturated fatty acid intake and breast cancer risk remain equivocal, with some studies pointing to improvements in risk upon omega-3 supplementation. However, the background diet is poorly controlled in most studies, potentially confounding this link. Therefore, this study examined the hypothesis that in order to see the benefits of omega-3 fatty acid supplementation, the background diet must be low in fat.

Methods

Of the 56 healthy, pre-menopausal women randomized to one of two experimental arms, consisting of a two-treatment, randomized, cross-over design, 41 completed the 10 month intervention. The two diet phases (habitual and low-fat) were separated by a washout phase, each lasting 3 menstrual cycles. During each diet phase, women were supplemented with 1.2 g eicosapentaenoic acid + docosahexaenoic acid per day.

Results

Red blood cell fatty acid composition indicated that more eicosapentaenoic acid and docosahexaenoic acid was incorporated in the low-fat diet than the habitual diet, though both diet phases resulted in significant increases in the omega-3 to omega-6 ratio. In the context of omega-3 supplementation in breast cancer risk reduction, we also measured fatty acid incorporation into nipple aspirate fluid. Similar changes to red blood cells were noted in nipple aspirate fluid, with higher incorporation of eicosapentaenoic acid in the low-fat diet phase.

Conclusions

These data suggest that the total level of dietary fat has some direct impact on fatty acid partitioning in addition to the recognized importance of fatty acid ratios, and supports the hypothesis that dietary fat intake must be considered a confounder in supplementation trials. Additionally, we demonstrate that n3 supplementation both reaches and imparts improvements in lipid content and n3:n6 at the target breast tissue.

Trial registration

Trial was been retrospectively registered at clinicaltrials.gov (RegNCT02816125).

Identification of potential erythrocyte phospholipid fatty acid biomarkers of advanced lung adenocarcinoma, squamous cell lung carcinoma, and small cell lung cancer

New biomarkers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of the main phospholipid species in erythrocytes from patients with advanced squamous cell lung carcinoma (SCC), lung adenocarcinoma (ADC), and small cell lung cancer (SCLC) and benign lung diseases (chronic obstructive pulmonary disease (COPD) and asthma) to determine the fatty acids that could be use as lung cancer markers. Twenty-eight, 18, 14, 16, and 15 patients with, respectively, SCC, ADC, SCLC, asthma, and COPD and 50 healthy subjects were enrolled in the study. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by receiver operating characteristic (ROC) curve analysis. The fatty acid profiles changed significantly in the different pathologies analyzed. Based on the diagnostic yields and operating characteristics, the most significant fatty acids that might be used as biomarkers were as follows: ADC--arachidonic acid (20:4n6) in phosphatidylcholine and oleic acid (18:1n9) in phosphatidylethanolamine (PE); SCC--eicosapentaenoic acid (20:5n3) in PE and palmitic acid (16:0) in phosphatidylserine + phosphatidylinositol (PS+PI); SCLC--eicosadienoic acid (20:2n6) in PS+PI and lignoceric acid (24:0) in sphingomyelin. In conclusion, fatty acids from erythrocyte phospholipid species might serve as biomarkers in the diagnosis, and probably in other aspects related to clinical disease management, of ADC, SCC, and SCLC.

Erythrocyte fatty acids as potential biomarkers in the diagnosis of advanced lung adenocarcinoma, lung squamous cell carcinoma, and small cell lung cancer

OBJECTIVES

To analyze the fatty acid profiles of erythrocyte total lipids from patients with advanced squamous cell lung carcinoma (SCC), lung adenocarcinoma (ADC), and small cell lung cancer (SCLC) and benign lung diseases (chronic obstructive pulmonary disease [COPD] and asthma) to reveal the fatty acids that could be used as lung cancer biomarkers.

METHODS

Thirty, 20, 15, 17, and 19 patients with SCC, ADC, SCLC, COPD, and asthma, respectively, and 55 healthy participants were enrolled in our study. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by receiver operating characteristic (ROC) curve analysis. Sialic acid (SA) and cytokeratins were measured by the thiobarbituric acid and immunoradiometric methods, respectively.

RESULTS

At least one of the main fatty acids might be used as a biomarker for every type of lung cancer: arachidonic (20:4n6), linoleic (18:2n6), and stearic (18:0) acids for ADC, SCC, and SCLC, respectively. These fatty acids showed diagnostic yields and operating characteristics similar to or higher than the commonly used SA or cytokeratin markers.

CONCLUSIONS

Fatty acids from erythrocyte total lipids might be used as diagnostic biomarkers of lung ADC, SCC, and SCLC. Their use in different aspects of the disease process needs to be explored.

Consumption of omega-3 fatty acids and the risk of skin cancers: a systematic review and meta-analysis

Skin cancers have a higher incidence than all other cancers combined and are a major cause of morbidity worldwide. Laboratory data suggest certain dietary constituents, notably omega-3 polyunsaturated fatty acids (n-3 PUFAs), could potentially protect against skin malignancy, although no large-scale review has been conducted in humans. The objective of this review and meta-analysis was to determine the relationship between dietary n-3 PUFAs and skin cancer incidence. It considered all published randomized controlled trials and observational studies up to March 2013. Five studies (two case-control and three cohort) were identified pertaining to oral n-3 PUFA consumption and incidence of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), melanoma (or a combination) and were included in a random-effects meta-analysis. A further six studies considering nondietary n-3 PUFA exposure (e.g., by tissue analysis) and/or recognized biological markers of skin cancer risk (e.g., p53 expression) were analyzed qualitatively. Dietary n-3 PUFAs were not associated with BCC (pooled OR 1.05, 95% CIs 0.86-1.28). Consumption of high levels of n-3 PUFAs were inversely associated with melanoma, although with only one estimate available (OR 0.52, 95% CI 0.34-0.78), and SCC, although nonsignificantly (pooled OR 0.86, 95% CIs 0.59-1.23). Available evidence is suggestive, but currently inadequate, to support the hypothesis that n-3 PUFAs protect against skin malignancy.

Chemopreventive effect of Lagenaria siceraria in two stages DMBA plus croton oil induced skin papillomagenesis

Cancer chemoprevention is a dietary or therapeutic strategy to prevent, suppress, or delay carcinogenesis either at initiation or progression level with nontoxic agents. Use of natural dietary compounds has been a major chemopreventive approach to modulate tumorigenic pathways. In the present study, we have evaluated Lagenaria siceraria (bottle gourd), a common vegetable of Indian household for its chemomodulatory potential. The fruit has been used in traditional medicine for a very long time for health benefits and to cure pain, ulcers, fever, cough, asthma, and other bronchial disorders. However, despite its reported beneficial effect the chemo modulatory potential of this plant has not been reported. Therefore chemopreventive effect of bottle gourd juice (BGJ) was studied against 7,12-dimethylbenz(a)anthracene (DMBA) plus croton oil induced skin papillomagenesis in Swiss albino mice. The effect was studied both at antiinitiation and antiinitiation/promotion level followed by histopathological study. A dose of 2.5% and 5% given in drinking water showed significant decrease in papilloma number, papilloma incidence, papilloma multiplicity, papilloma latency, papilloma volume, and papilloma size in different size range. Histopathological study showed chemopreventive effect by minimizing loss of stratification, a decrease in number of epithelial layers, reducing dermal infiltration and protection for various cytoplasmic changes. Higher dose of BGJ was found to be more effective than lower dose and the chemopreventive effect was maximum for antiinitiation/promotion treatment. Altogether, this study reports the chemopreventive effect of Lagenaria siceraria on skin papillomagenesis for the first time and suggests that its consumption may help in suppression of skin cancer.

Plasma omega-3 and omega-6 concentrations and risk of cutaneous basal and squamous cell carcinomas in Australian adults

Laboratory-based evidence suggests that omega-3 and omega-6 polyunsaturated fatty acids may affect skin photocarcinogenesis, but epidemiologic evidence is inconsistent. In 1,191 White Australian adults, we prospectively investigated associations between baseline plasma concentrations of omega-3 and omega-6 fatty acids and cutaneous basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). Relative risks (RR) and 95% confidence intervals (CI) were estimated on the basis of number of histologically confirmed tumors diagnosed during follow-up (1997-2007). Plasma eicosapentaenoic acid (EPA) concentrations and omega-3/-6 ratio showed significant inverse associations with SCC tumors, comparing higher tertiles with the lowest, in age- and sex-adjusted models (Ptrend = 0.02 and 0.03, respectively) which weakened after adjustment for past sun exposure. Associations between EPA and SCC were stronger among participants with a history of skin cancer at baseline (n = 378; highest vs. lowest tertile: RR = 0.50; 95% CI, 0.28-0.92; Ptrend = 0.01). Total omega-6 was inversely associated with BCC tumors in multivariate models (P = 0.04; highest vs. lowest tertile: RR = 0.71; 95% CI, 0.51-0.99), and more strongly in the subgroup with past skin cancer. Linoleic and linolenic acids were also inversely associated with BCC occurrence in this subgroup. When fatty acids were analyzed as continuous variables, however, there was no evidence of any linear or nonlinear associations. This study provides some support for reduced skin cancer risk with high plasma concentrations of omega-3 and omega-6 fatty acids, but results depended on how fatty acid data were modeled. Further investigation of these associations in larger datasets is needed.

Arachidonic acid and cancer risk: a systematic review of observational studies

Background

An n-6 essential fatty acid, arachidonic acid (ARA) is converted into prostaglandin E₂, which is involved in tumour extension. However, it is unclear whether dietary ARA intake leads to cancer in humans. We thus systematically evaluated available observational studies on the relationship between ARA exposure and the risk of colorectal, skin, breast, prostate, lung, and stomach cancers.

Methods

We searched the PubMed database for articles published up to May 17, 2010. 126 potentially relevant articles from the initial search and 49,670 bibliographies were scrutinised to identify eligible publications by using predefined inclusion criteria. A comprehensive literature search yielded 52 eligible articles, and their reporting quality and methodological quality was assessed. Information on the strength of the association between ARA exposure and cancer risk, the dose-response relationship, and methodological limitations was collected and evaluated with respect to consistency and study design.

Results

For colorectal, skin, breast, and prostate cancer, 17, 3, 18, and 16 studies, respectively, were identified. We could not obtain eligible reports for lung and stomach cancer. Studies used cohort (n = 4), nested case-control (n = 12), case-control (n = 26), and cross-sectional (n = 12) designs. The number of subjects (n = 15 - 88,795), ARA exposure assessment method (dietary intake or biomarker), cancer diagnosis and patient recruitment procedure (histological diagnosis, cancer registries, or self-reported information) varied among studies. The relationship between ARA exposure and colorectal cancer was inconsistent based on ARA exposure assessment methodology (dietary intake or biomarker). Conversely, there was no strong positive association or dose-response relationship for breast or prostate cancer. There were limited numbers of studies on skin cancer to draw any conclusions from the results.

Conclusions

The available epidemiologic evidence is weak because of the limited number of studies and their methodological limitations, but nonetheless, the results suggest that ARA exposure is not associated with increased breast and prostate cancer risk. Further evidence from well-designed observational studies is required to confirm or refute the association between ARA exposure and risk of cancer.

Intake of omega-3 and omega-6 fatty acids and risk of basal and squamous cell carcinomas of the skin: a longitudinal community-based study in Australian adults

Intake of omega-3 and omega-6 fatty acids may modify the risk of basal and squamous cell carcinoma of the skin (BCC and SCC), but population-based evidence is limited and inconsistent. We examined prospectively associations between intake of omega-3 and omega-6 fatty acids estimated from food frequency questionnaires and BCC and SCC incidence among 1322 randomly selected adults in Nambour, Australia. Relative risks (RR) and 95% confidence intervals (CI) were estimated based on histologically confirmed tumors diagnosed between 1997 and 2007. Incidence of BCC was lowest in the middle third of both total omega-6 intake (RR(mv.adj) = 0.74, 95% CI = 0.56-0.97) and linoleic acid intake (RR(mv.adj) = 0.75, 95% CI = 0.57-0.99) compared with the lowest third of intake. Evidence for associations with SCC was weak, though persons with arachidonic acid intake in the middle third had a marginally increased risk of SCC (RR(mv.adj) = 1.42, 95% CI = 1.00-2.02). Consumption of omega-3 fatty acids was not associated with subsequent skin cancer risk. Suggestion that intake of arachidonic acid may be associated with increased SCC incidence and total omega-6 with reduced BCC from our study is still highly uncertain and may be due to chance. These data do not support an association between these fatty acids and risk of BCC or SCC.

The potential of omega-3 fatty acids in the prevention of non-melanoma skin cancer

In toto, there is strong circumstantial evidence from both experimental and clinical studies to support a role for omega-3 FA in the prevention of non-melanoma skin cancer (NMSC). In experimental animal studies there is direct evidence that dietary omega-3 FA inhibits ultraviolet radiation (UVR) carcinogenic expression, with regard to both increased tumor latent period and reduced tumor multiplicity. Equivalent levels of omega-6 FA increase UVR carcinogenic expression. Dietary omega-3 FA dramatically reduces the plasma and cutaneous pro-inflammatory and immunosuppressive PGE(2) levels in mice. Dietary omega-6 FA increases prostaglandin E synthase type 2 (PGE(2)) level. Dietary omega-3 FA significantly reduces the inflammatory response and sustains, or enhances, the delayed type hypersensitivity immune response in mice when compared to an equivalent dietary level of omega-6 FA. Supplementary omega-3 FA significantly increases the UVR-mediated erythema threshold in humans. Supplementary omega-3 FA significantly reduces the level of pro-inflammatory and immunosuppressive PGE(2) levels in Ultraviolet B-irradiated human skin.