The association of fatty acids with prostate cancer risk

Hierarchical joint analysis of marginal summary statistics-Part II: High-dimensional instrumental analysis of omics data

Instrumental variable (IV) analysis has been widely applied in epidemiology to infer causal relationships using observational data. Genetic variants can also be viewed as valid IVs in Mendelian randomization and transcriptome-wide association studies. However, most multivariate IV approaches cannot scale to high-throughput experimental data. Here, we leverage the flexibility of our previous work, a hierarchical model that jointly analyzes marginal summary statistics (hJAM), to a scalable framework (SHA-JAM) that can be applied to a large number of intermediates and a large number of correlated genetic variants-situations often encountered in modern experiments leveraging omic technologies. SHA-JAM aims to estimate the conditional effect for high-dimensional risk factors on an outcome by incorporating estimates from association analyses of single-nucleotide polymorphism (SNP)-intermediate or SNP-gene expression as prior information in a hierarchical model. Results from extensive simulation studies demonstrate that SHA-JAM yields a higher area under the receiver operating characteristics curve (AUC), a lower mean-squared error of the estimates, and a much faster computation speed, compared to an existing approach for similar analyses. In two applied examples for prostate cancer, we investigated metabolite and transcriptome associations, respectively, using summary statistics from a GWAS for prostate cancer with more than 140,000 men and high dimensional publicly available summary data for metabolites and transcriptomes.

Urinary fatty acid biomarkers for prostate cancer detection

The lack of accuracy in the current prostate specific antigen (PSA) test for prostate cancer (PCa) screening causes around 60-75% of unnecessary prostate biopsies. Therefore, alternative diagnostic methods that have better accuracy and can prevent over-diagnosis of PCa are needed. Researchers have examined various potential biomarkers for PCa, and of those fatty acids (FAs) markers have received special attention due to their role in cancer metabolomics. It has been noted that PCa metabolism prefers FAs over glucose substrates for continued rapid proliferation. Hence, we proposed using a urinary FAs based model as a non-invasive alternative for PCa detection. Urine samples collected from 334 biopsy-designated PCa positive and 232 biopsy-designated PCa negative subjects were analyzed for FAs and lipid related compounds by stir bar sorptive extraction coupled with gas chromatography/mass spectrometry (SBSE-GC/MS). The dataset was split into the training (70%) and testing (30%) sets to develop and validate logit models and repeated for 100 runs of random data partitioning. Over the 100 runs, we confirmed the stability of the models and obtained optimal tuning parameters for developing the final FA based model. A PSA model using the values of the patients' PSA test results was constructed with the same cohort for the purpose of comparing the performances of the FA model against PSA test. The FA final model selected 20 FAs and rendered an AUC of 0.71 (95% CI = 0.67-0.75, sensitivity = 0.48, and specificity = 0.83). In comparison, the PSA model performed with an AUC of 0.51 (95% CI = 0.46-0.66, sensitivity = 0.44, and specificity = 0.71). The study supports the potential use of urinary FAs as a stable and non-invasive alternative test for PCa diagnosis.

DHA alleviates high glucose-induced mitochondrial dysfunction in Oreochromis niloticus by inhibiting DRP1-mediated mitochondrial fission

Dynamin-related protein 1 (DRP1) is a key regulator in the maintenance of mammalian glucose homeostasis, but the relevant information remains poorly understood on aquatic animals. In the study, DRP1 is formally described for the first time in Oreochromis niloticus. DRP1 encodes a peptide of 673 amino acid residues that contained three conserved domains: a GTPase domain, a dynamin middle domain and a dynamin GTPase effector domain. DRP1 transcripts are widely distributed in all of the detected seven organs/tissues, and the highest mRNA levels in brain. High-carbohydrate (45 %) fed fish showed a significant upregulation of liver DRP1 expression than that of control (30 %) group. Glucose administration upregulated liver DRP1 expression, with peak values observed at 1 h; then its expression returned to the basal value at 12 h. In the in vitro study, DRP1 over-expression significantly decreased mitochondrial abundance in hepatocytes. DHA significantly increased mitochondrial abundance, transcriptions of mitochondrial transcription factor A (TFAM) and mitofusin 1 and 2 (MFN1 and MFN2) and complex II and III activities of high glucose-treated hepatocyte, whereas the opposite was true for DRP1, mitochondrial fission factor (MFF) and fission (FIS) expression. Together, these findings illustrated that O. niloticus DRP1 is highly conserved, and it participated in glucose control of fish. DHA could alleviate high glucose-induced mitochondrial dysfunction of fish by inhibiting DRP1-mediated mitochondrial fission.

Antioxidant Activity of Docosahexaenoic Acid (DHA) and Its Regulatory Roles in Mitochondria

Reactive oxygen species (ROS) are single-electron-bearing oxidation-reduction products that are mainly produced in mitochondria. Excessive ROS accumulation may lead to oxidative damage. Docosahexaenoic acid (DHA) is an essential component of brain phospholipids and is mainly derived from the diet. Its antioxidant activities have been extensively studied. However, its regulatory roles in mitochondria and the underlying mechanism remain to be elucidated. In this study, the DHA's effect on cellular antioxidant capacity and mitochondrial functions was examined in HepG2 cells. The results showed that 100 μM DHA decreased cellular and mitochondrial ROS levels to 75.2 ± 9.4% (P < 0.05) and 55.1 ± 1.4% (P < 0.01), respectively. It also increased the total antioxidant capacity by 55.6 ± 0.1 and 49.2 ± 1.1% (P < 0.05), based on ABTS and FRAP assay results, respectively. Consistently, it increased the activities and gene expression of major antioxidant enzymes by at least 35 and 40% (P < 0.05), respectively. Furthermore, DHA promoted mitochondrial functions and biogenesis. These data suggested that DHA's antioxidant activity can be attributed to its enhancement of mitochondrial functions and biogenesis. This study may shed light on the molecular mechanisms underlying DHA's function in improving resistance to and relieving the symptoms of chronic disease.

Accurate, sensitive determination of omega-6 and omega-3 polyunsaturated fatty acids in human plasma, urine samples

Quantitative determination of omega-6 and omega-3 polyunsaturated fatty acids in human plasma and urine with high accuracy and precision provides significant information to monitor the underlying etiology of several diseases. In this regard, liquid chromatography-mass spectrometry is a good choice owing to its great selectivity and sensitivity. Additionally, the hybrid quadrupole-time of flight-mass spectrometer systems provides easy identification of target compounds with superior mass measurements. In this study, an analytical method has been developed for simple, accurate and simultaneous determination of linoleic acid, arachidonic acid, docosahexaenoic acid and eicosapentaenoic acid in a short chromatographic analysis period. The developed method is suitable for the quantitative detection of these four compounds with detection limits ranging between 1.1-3.0 ng ml^-1 and its applicability was assessed in human urine and plasma samples. As a result, acceptable accuracy (between 83 and 111%) and good precision (<6%) were obtained for target compounds using matrix matching calibration strategy.

Blood fatty acid patterns are associated with prostate cancer risk in a prospective nested case-control study

BACKGROUND

Circulating fatty acids are highly correlated with each other, and analyzing fatty acid patterns could better capture their interactions and their relation to prostate cancer. We aimed to assess the associations between data-derived blood fatty acid patterns and prostate cancer risk.

METHODS

We conducted a nested case-control study in the Physicians' Health Study. Fatty acids levels were measured in whole blood samples of 476 cases and their matched controls by age and smoking status. Fatty acid patterns were identified using principal component analysis. Conditional logistic regression was used to estimate odds ratio (OR) and 95 % confidence interval (CI).

RESULTS

Two patterns explaining 40.9 % of total variation in blood fatty acid levels were identified. Pattern 1, which mainly reflects polyunsaturated fatty acid metabolism, was suggestively positively related to prostate cancer risk (ORquintile 5 vs. quintile 1 = 1.37, 95 % CI = 0.91-2.05, P trend = 0.07). Pattern 2, which largely reflects de novo lipogenesis, was significantly associated with higher prostate cancer risk (ORquintile5 vs. quintile1 = 1.63, 95 % CI = 1.04-2.55, P trend = 0.02). This association was similar across tumor stage, grade, clinical aggressiveness categories and follow-up time.

CONCLUSION

The two patterns of fatty acids we identified were consistent with known interactions between fatty acid intake and metabolism. A pattern suggestive of higher activity in the de novo lipogenesis pathway was related to higher risk of prostate cancer.

Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults

Studies reporting blood levels of the omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were systematically identified in order to create a global map identifying countries and regions with different blood levels. Included studies were those of healthy adults, published in 1980 or later. A total of 298 studies met all inclusion criteria. Studies reported fatty acids in various blood fractions including plasma total lipids (33%), plasma phospholipid (32%), erythrocytes (32%) and whole blood (3.0%). Fatty acid data from each blood fraction were converted to relative weight percentages (wt.%) and then assigned to one of four discrete ranges (high, moderate, low, very low) corresponding to wt.% EPA+DHA in erythrocyte equivalents. Regions with high EPA+DHA blood levels (>8%) included the Sea of Japan, Scandinavia, and areas with indigenous populations or populations not fully adapted to Westernized food habits. Very low blood levels (≤4%) were observed in North America, Central and South America, Europe, the Middle East, Southeast Asia, and Africa. The present review reveals considerable variability in blood levels of EPA+DHA and the very low to low range of blood EPA+DHA for most of the world may increase global risk for chronic disease.

Omega-3 Fatty Acid Consumption and Prostate Cancer: A Review of Exposure Measures and Results of Epidemiological Studies

Animal studies have shown that dietary omega-3 polyunsaturated fatty acids (n-3) may play a role in the development of prostate cancer, but the results of epidemiologic studies have been equivocal. Associations in humans may vary depending on study design, measurement methodology of fatty acid intake, intake ranges, and stage of cancer development. To address this, we identified 36 published studies through PubMed (Medline) from 1993 through 2013 on long-chain n-3s and prostate cancer. Exposure measurements included dietary assessment and biomarker levels. Associations for total, early, and late stage prostate cancer were examined by subgroup of study design and exposure measure type and by using forest plots to illustrate the relative strength of associations within each subgroup. We also tested for potential threshold effects by considering studies that included measurement cut-points that met intake levels recommended by the American Heart Association. We found no consistent evidence supporting a role of n-3s in either the causation or prevention of prostate cancer at any stage or grade. Results did not vary appreciably by study design, exposure measurement, intake level, or stage of cancer development.

DHA- and EPA-derived resolvins, protectins, and maresins in airway inflammation

Essential fatty acids can serve as important regulators of inflammation. A new window into mechanisms for the resolution of inflammation was opened with the identification and structural elucidation of mediators derived from these fatty acids with pro-resolving capacity. Inflammation is necessary to ensure the continued health of the organism after an insult or injury; however, unrestrained inflammation can lead to injury "from within" and chronic changes that may prove both morbid and fatal. The resolution phase of inflammation, once thought to be a passive event, is now known to be a highly regulated, active, and complex program that terminates the inflammatory response once the threat has been contained. Specialized pro-resolving mediators (SPMs) are biosynthesized from omega-3 essential fatty acids to resolvins, protectins, and maresins and from omega-6 fatty acids to lipoxins. Through cell-specific actions mediated through select receptors, these SPMs are potent regulators of neutrophil infiltration, cytokine and chemokine production, and clearance of apoptotic neutrophils by macrophages, promoting a return to tissue homeostasis. This process appears to be defective in several common human lung diseases, such as asthma and COPD, which are characterized by chronic unrestrained inflammation and significant associated morbidity. Here, we highlight translational research in animal models of disease and with human subjects that sheds light on this rapidly evolving area of science and review the molecular and cellular components of the resolution of lung inflammation.

Effect of individual omega-3 fatty acids on the risk of prostate cancer: a systematic review and dose-response meta-analysis of prospective cohort studies

Epidemiological studies have suggested inconsistent associations between omega-3 polyunsaturated fatty acids (n-3 PUFAs) and prostate cancer (PCa) risk. We performed a dose-response meta-analysis of prospective observational studies investigating both dietary intake and circulating n-3 PUFAs and PCa risk. PubMed and EMBASE prior to February 2014 were searched, and 16 publications were eligible. Blood concentration of docosahexaenoic acid, but not alpha-linolenic acid or eicosapentaenoic acid, showed marginal positive association with PCa risk (relative risk for 1% increase in blood docosahexaenoic acid concentration: 1.02; 95% confidence interval, 1.00-1.05; I(2) = 26%; P = 0.05 for linear trend), while dietary docosahexaenoic acid intake showed a non-linear positive association with PCa risk (P < 0.01). Dietary alpha-linolenic acid was inversely associated with PCa risk (relative risk for 0.5 g/day increase in alpha-linolenic acid intake: 0.99; 95% confidence interval, 0.98-1.00; I(2) = 0%; P = 0.04 for linear trend), which was dominated by a single study. Subgroup analyses indicated that blood eicosapentaenoic acid concentration and blood docosahexaenoic acid concentration were positively associated with aggressive PCa risk and nonaggressive PCa risk, respectively. Among studies with nested case-control study designs, a 0.2% increase in blood docosapentaenoic acid concentration was associated with a 3% reduced risk of PCa (relative risk 0.97; 95% confidence interval, 0.94-1.00; I(2) = 44%; P = 0.05 for linear trend). In conclusion, different individual n-3 PUFA exposures may exhibit different or even opposite associations with PCa risk, and more prospective studies, especially those examining dietary n-3 PUFAs and PCa risk stratified by severity of cancer, are needed to confirm the results.

Omega-3 fatty acids in cardiovascular disease--an uphill battle

In cardiology, results of recent large intervention trials with eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) supplements were neutral. In contrast, in epidemiologic studies, an inverse relation between clinical events and intake of EPA+DHA was found which was steeper for higher levels of EPA+DHA. A standardized way of determining levels is the Omega-3 Index, which is the percentage of EPA+DHA of a total of 26 fatty acids measured in erythrocytes. According to current criteria, a low Omega-3 Index is a cardiovascular risk factor. What can explain this contradiction? Trial participants were recruited irrespective of their baseline status in EPA+DHA - an important predictor of events. Levels of EPA+DHA have a statistically normal distribution; together with the large inter-individual variability of levels' responding to increased intake, this created a large overlap of EPA+DHA levels between intervention and control groups. Moreover, trial participants were advised to take EPA+DHA supplements with breakfast, frequently a low fat meal, resulting in poor bioavailability. As a result, there is an urgent need for new intervention trials in cardiology, for which participants with a low baseline omega-3 index are recruited, and then treated with individually tailored doses of EPA+DHA to a prespecified target range.

Systematic review of prostate cancer risk and association with consumption of fish and fish-oils: analysis of 495,321 participants

INTRODUCTION

Fish-oils have a potential role in inflammation, carcinogenesis inhibition and favourable cancer outcomes. There has been increasing interest in the relationship of diet with cancer incidence and mortality, especially for eicosapantaenoic acid (EPA) and docosahexaenoic acid (DHA). This systematic-analysis of the literature aims to review evidence for the roles of dietary-fish and fish-oil intake in prostate-cancer (PC) risk, aggressiveness and mortality.

METHODS

A systematic-review, following PRISMA guidelines was conducted. PubMed, MEDLINE and Embase were searched to explore PC-risk, aggressiveness and mortality associated with dietary-fish and fish-oil intake. 37 studies were selected.

RESULTS

A total of 495,321 (37-studies) participants were investigated. These revealed various relationships regarding PC-risk (n = 31), aggressiveness (n = 8) and mortality (n = 3). Overall, 10 studies considering PC-risk found significant inverse trends with fish and fish-oil intake. One found a dose-response relationship whereas greater intake of long-chain-polyunsaturated fatty acids increased risk of PC when considering crude odds-ratios [OR: 1.36 (95% CI: 0.99-1.86); p = 0.014]. Three studies addressing aggressiveness identified significant positive relationships with reduced risk of aggressive cancer when considering the greatest intake of total fish [OR 0.56 (95% CI 0.37-0.86)], dark fish and shellfish-meat (p < 0.0001), EPA (p = 0.03) and DHA (p = 0.04). Three studies investigating fish consumption and PC-mortality identified a significantly reduced risk. Multivariate-OR (95% CI) were 0.9 (0.6-1.7), 0.12 (0.05-0.32) and 0.52 (0.30-0.91) at highest fish intakes.

CONCLUSIONS

Fish and fish-oil do not show consistent roles in reducing PC incidence, aggressiveness and mortality. Results suggest that the specific fish type and the fish-oil ratio must be considered. Findings suggest the need for large intervention randomised placebo-controlled trials.

α-Linolenic acid: nutraceutical, pharmacological and toxicological evaluation

α-Linolenic acid (ALA), a carboxylic acid with 18 carbons and three cis double bonds, is an essential fatty acid needed for human health and can be acquired via regular dietary intake of foods that contain ALA or dietary supplementation of foods high in ALA, for example flaxseed. ALA has been reported to have cardiovascular-protective, anti-cancer, neuro-protective, anti-osteoporotic, anti-inflammatory, and antioxidative effects. ALA is the precursor of longer chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), but its beneficial effects on risk factors for cardiovascular diseases are still inconclusive. The recommended intake of ALA for cardiovascular health is reported to be 1.1-2.2g/day. Although there are limited toxicological data for ALA, no serious adverse effects have been reported. The evidence on an increased prostate cancer risk in association with dietary ALA is not conclusive. Based on the limited data currently available, it may be concluded that ALA may be beneficial as a nutraceutical/pharmaceutical candidate and is safe for use as a food ingredient.

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.

Nongenotoxic effects and a reduction of the DXR-induced genotoxic effects of Helianthus annuus Linné (sunflower) seeds revealed by micronucleus assays in mouse bone marrow

Background

This research evaluated the genotoxicity of oil and tincture of H. annuus L. seeds using the micronucleus assay in bone marrow of mice. The interaction between these preparations and the genotoxic effects of doxorubicin (DXR) was also analysed (antigenotoxicity test).

Methods

Experimental groups were evaluated at 24-48 h post treatment with N-Nitroso-N-ethylurea (positive control – NEU), DXR (chemotherapeutic), NaCl (negative control), a sunflower tincture (THALS) and two sources of sunflower oils (POHALS and FOHALS). Antigenotoxic assays were carried out using the sunflower tincture and oils separately and in combination with NUE or DXR.

Results

For THALS, analysis of the MNPCEs showed no significant differences between treatment doses (250–2,000 mg.Kg^-1) and NaCl. A significant reduction in MNPCE was observed when THALS (2,000 mg.Kg^-1) was administered in combination with DXR (5 mg.Kg^-1). For POHALS or FOHALS, analysis of the MNPCEs also showed no significant differences between treatment doses (250–2,000 mg.Kg^-1) and NaCl. However, the combination DXR + POHALS (2,000 mg.Kg^-1) or DXR + FOHALS (2,000 mg.Kg^-1) not contributed to the MNPCEs reduction.

Conclusions

This research suggests absence of genotoxicity of THALS, dose-, time- and sex-independent, and its combination with DXR can reduce the genotoxic effects of DXR. POHALS and FOHALS also showed absence of genotoxicity, but their association with DXR showed no antigenotoxic effects.

Resolution of acute inflammation in the lung

Acute inflammation in the lung is essential to health. So too is its resolution. In response to invading microbes, noxious stimuli, or tissue injury, an acute inflammatory response is mounted to protect the host. To limit inflammation and prevent collateral injury of healthy, uninvolved tissue, the lung orchestrates the formation of specialized proresolving mediators, specifically lipoxins, resolvins, protectins, and maresins. These immunoresolvents are agonists for resolution that interact with specific receptors on leukocytes and structural cells to blunt further inflammation and promote catabasis. This process appears to be defective in several common lung diseases that are characterized by excess or chronic inflammation. Here, we review the molecular and cellular effectors of resolution of acute inflammation in the lung.

Dietary fat, fatty acids, and risk of prostate cancer in the NIH-AARP diet and health study

BACKGROUND

Observational studies report inconsistent associations of fat and fatty acids with prostate cancer.

METHODS

We investigated associations between dietary fats and fatty acids and risk of prostate cancer in the NIH-American Association of Retired Persons (AARP) Diet and Health Study. Diet was assessed at baseline with self-administered food-frequency questionnaires. Cases were determined by linkage with state cancer registries. HR and 95% confidence intervals (CI) were estimated with Cox proportional hazards models.

RESULTS

Among 288,268 men with average follow-up of nine years, 23,281 prostate cancer cases (18,934 nonadvanced and 2,930 advanced including 725 fatal cases) were identified. Total fat and mono- and polyunsaturated fat intakes were not associated with incidence of prostate cancer. Saturated fat intake was related to increased risk of advanced prostate cancer (HRQuintile 5 vs. Qunitile 1 (Q1 vs. Q5), 1.21; 95% CI, 1.00-1.46; Ptrend = 0.03) and fatal prostate cancer (HRQ5 vs. Q1, 1.47; 95% CI, 1.01-2.15; Ptrend = 0.04). α-Linolenic acid (ALA) intake was related to increased risk of advanced prostate cancer (HRQ5 vs. Q1, 1.17; 95% CI, 1.04-1.31; Ptrend = 0.01). Eicosapentanoic acid (EPA) intake was related to decreased risk of fatal prostate cancer (HRQ5 vs. Q1, 0.82; 95% CI, 0.64-1.04; Ptrend = 0.02).

CONCLUSION

Our study suggests that the associations of fat and fatty acids differ by prostate cancer severity. Saturated fat, ALA, and EPA intakes were related to the risk of advanced or fatal prostate cancer but not to nonadvanced prostate cancer.

IMPACT

Identifying factors associated with advanced prostate cancer could reduce morbidity and mortality.

The relevance of serum levels of long chain omega-3 polyunsaturated fatty acids and prostate cancer risk: A meta-analysis

OBJECTIVE

Our objective was to systematically analyze the evidence for an association between serum level long chain omega-3 polyunsaturated fatty acid (n-3 PUFA) and prostate cancer risk from human epidemiological studies. STUDY PROCEDURES: We searched biomedical literature databases up to November 2011 and included epidemiological studies with description of long chain n-3 PUFA and incidence of prostate cancer in humans. Critical appraisal was done by two independent reviewers. Data were pooled using the general variance-based method with random-effects model; effect estimates were expressed as risk ratio with 95% confidence interval (CI). Heterogeneity was assessed by Chi(2) and quantified by I(2), publication bias was also determined.

RESULTS

In total, 12 studies were included. Significant negative association was noted between high serum level of n-3 PUFA doc-osapentaenoic acid (DPA) and total prostate cancer risk (RR:0.756; 95% CI 0.599, 0.955; p = 0.019). Likewise, a positive association between high blood level of fish oil contents, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and high-grade prostate tumour incidence (RR:1.381; 95% CI 1.050, 1.817; p = 0.021) was noted; however, this finding was evident only after adjustment was done on interstudy variability through the removal of a lower quality study from the pool.

CONCLUSIONS

High serum levels of long chain n-3 PUFA DPA is associated with reduced total prostate cancer risk. While high blood level of EPA and DHA is possibly associated with increased high-grade prostate tumour risk.

Case-control and prospective studies of dietary α-linolenic acid intake and prostate cancer risk: a meta-analysis

OBJECTIVE

α-Linolenic acid (ALA) is considered to be a cardioprotective nutrient; however, some epidemiological studies have suggested that dietary ALA intake increases the risk of prostate cancer. The main objective was to conduct a systematic review and meta-analysis of case-control and prospective studies investigating the association between dietary ALA intake and prostate cancer risk.

DESIGN

A systematic review and meta-analysis were conducted by searching MEDLINE and EMBASE for relevant prospective and case-control studies.

INCLUDED STUDIES

We included all prospective cohort, case-control, nested case-cohort and nested case-control studies that investigated the effect of dietary ALA intake on the incidence (or diagnosis) of prostate cancer and provided relative risk (RR), HR or OR estimates.

PRIMARY OUTCOME MEASURE

Data were pooled using the generic inverse variance method with a random effects model from studies that compared the highest ALA quantile with the lowest ALA quantile. Risk estimates were expressed as RR with 95% CIs. Heterogeneity was assessed by χ(2) and quantified by I(2).

RESULTS

Data from five prospective and seven case-control studies were pooled. The overall RR estimate showed ALA intake to be positively but non-significantly associated with prostate cancer risk (1.08 (0.90 to 1.29), p=0.40; I(2)=85%), but the interpretation was complicated by evidence of heterogeneity not explained by study design. A weak, non-significant protective effect of ALA intake on prostate cancer risk in the prospective studies became significant (0.91 (0.83 to 0.99), p=0.02) without evidence of heterogeneity (I(2)=8%, p=0.35) on removal of one study during sensitivity analyses.

CONCLUSIONS

This analysis failed to confirm an association between dietary ALA intake and prostate cancer risk. Larger and longer observational and interventional studies are needed to define the role of ALA and prostate cancer.

Blood level omega-3 Fatty acids as risk determinant molecular biomarker for prostate cancer

Previous researches involving dietary methods have shown conflicting findings. Authors sought to assess the association of prostate cancer risk with blood levels of omega-3 polyunsaturated fatty acids (n-3 PUFA) through a meta-analysis of human epidemiological studies in available online databases (July, 2012). After critical appraisal by two independent reviewers, Newcastle-Ottawa Quality Assessment Scale (NOQAS) was used to grade the studies. Six case control and six nested case control studies were included. Results showed nonsignificant association of overall effect estimates with total or advanced prostate cancer or high-grade tumor. High blood level of alpha-linolenic acid (ALA) had nonsignificant positive association with total prostate cancer risk. High blood level of docosapentaenoic acid (DPA) had significant negative association with total prostate cancer risk. Specific n-3 PUFA in fish oil, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) had positive association with high-grade prostate tumor risk only after adjustment of interstudy variability. There is evidence that high blood level of DPA that is linked with reduced total prostate cancer risk and elevated blood levels of fish oils, EPA, and DHA is associated with high-grade prostate tumor, but careful interpretation is needed due to intricate details involved in prostate carcinogenesis and N-3 PUFA metabolism.

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.

Fatty acid patterns and risk of prostate cancer in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Fatty acids in blood may be related to the risk of prostate cancer, but epidemiologic evidence is inconsistent. Blood fatty acids are correlated through shared food sources and common endogenous desaturation and elongation pathways. Studies of individual fatty acids cannot take this into account, but pattern analysis can. Treelet transform (TT) is a novel method that uses data correlation structures to derive sparse factors that explain variation.

OBJECTIVE

The objective was to gain further insight in the association between plasma fatty acids and risk of prostate cancer by applying TT to take data correlations into account.

DESIGN

We reanalyzed previously published data from a case-control study of prostate cancer nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. TT was used to derive factors explaining the variation in 26 plasma phospholipid fatty acids of 962 incident prostate cancer cases matched to 1061 controls. Multiple imputation was used to deal with missing data in covariates. ORs of prostate cancer according to factor scores were determined by using multivariable conditional logistic regression.

RESULTS

Four simple factors explained 38% of the variation in plasma fatty acids. A high score on a factor reflecting a long-chain n-3 PUFA pattern was associated with greater risk of prostate cancer (OR for highest compared with lowest quintile: 1.36; 95% CI: 0.99, 1.86; P-trend = 0.041).

CONCLUSION

Pattern analyses using TT groupings of correlated fatty acids indicate that intake or metabolism of long-chain n-3 PUFAs may be relevant to prostate cancer etiology.

Resolution of inflammation in asthma

The resolution of inflammation in healthy airways is an active process, with specialized mediators and cellular mechanisms enlisted to restore tissue homeostasis. This article focuses on recent discoveries of natural mediators derived from essential fatty acids, including ω-3 fatty acids, with anti-inflammatory and pro-resolving. These pro-resolving mediators serve as agonists at specific receptors. Asthma is an incurable disease of chronic, nonresolving inflammation of the airways. While the biosynthesis of pro-resolving mediators occurs during asthma, defects in their production are associated with disease severity, suggesting that the pathobiology of asthma may result in part from impaired resolution of airway inflammation.

Dietary fatty acid intake and prostate cancer survival in Örebro County, Sweden

Although dietary fat has been associated with prostate cancer risk, the association between specific fatty acids and prostate cancer survival remains unclear. Dietary intake of 14 fatty acids was analyzed in a population-based cohort of 525 Swedish men with prostate cancer in Örebro County (1989-1994). Multivariable hazard ratios and 95% confidence intervals for time to prostate cancer death by quartile and per standard deviation increase in intake were estimated by Cox proportional hazards regression. Additional models examined the association by stage at diagnosis (localized: T0-T2/M0; advanced: T0-T4/M1, T3-T4/M0). Among all men, those with the highest omega-3 docosahexaenoic acid and total marine fatty acid intakes were 40% less likely to die from prostate cancer (P(trend) = 0.05 and 0.04, respectively). Among men with localized prostate cancer, hazard ratios of 2.07 (95% confidence interval: 0.93, 4.59; P(trend) = 0.03) for elevated total fat, 2.39 (95% confidence interval: 1.06, 5.38) for saturated myristic acid, and 2.88 (95% confidence interval: 1.24, 6.67) for shorter chain (C4-C10) fatty acid intakes demonstrated increased risk for disease-specific mortality for the highest quartile compared with the lowest quartile. This study suggests that high intake of total fat and certain saturated fatty acids may worsen prostate cancer survival, particularly among men with localized disease. In contrast, high marine omega-3 fatty acid intake may improve disease-specific survival for all men.

No effects of n-3 fatty acid supplementation on serum total testosterone levels in older men: the Alpha Omega Trial

The intake of the n-3 fatty acids alpha-linolenic acid (ALA), acid (EPA) and docosahexaenoic acid (DHA) has been related to testosterone levels in epidemiological analyses. The aim of this study was to assess whether the n-3 fatty acids affects testosterone levels in post-myocardial infarction (MI) patients, who are at risk of testosterone deficiency. In a double-blind, placebo-controlled trial of low-dose supplementation of n-3 fatty acids, we included 1850 male post-MI patients aged 60-80 years who participated in the Alpha Omega Trial. Patients were randomly allocated to margarines that provided 400 mg/day of EPA-DHA (n = 453), 2 mg/day of ALA (n = 467), EPA-DHA plus ALA (n = 458), or placebo (n = 472). Serum testosterone levels were assessed at baseline and after 41 months using whole day blood samples obtained at the subjects' home or at the hospital. Subjects were on average age of 68.4 (SD 5.3) years old and had baseline mean serum total testosterone of 14.8 (SD 5.6) nmol/L. The four randomized groups did not differ for baseline characteristics. ALA, EPA-DHA, and EPA-DHA plus ALA supplementation did not affect serum total testosterone compared to placebo. Moreover, n-3 fatty acid supplementation did not affect the risk of incident testosterone deficiency (n = 76 with total testosterone <8.0 nmol/L). We conclude that n-3 fatty acids supplementation did not affect serum total testosterone in men who had had a MI.

Associations of whole-blood fatty acids and dietary intakes with prostate cancer in Jamaica

OBJECTIVE

To investigate the association of whole-blood fatty acids and reported intakes of fats with risk of prostate cancer (PCa).

DESIGN

Case-control study of 209 men 40-80 years old with newly diagnosed, histologically confirmed prostate cancer and 226 cancer-free men attending the same urology clinics. Whole-blood fatty acid composition (mol%) was measured by gas chromatography and diet assessed by food frequency questionnaire.

RESULTS

High whole-blood oleic acid composition (tertile 3 vs. tertile 1: OR, 0.37; CI, 0.14-0.0.98) and moderate palmitic acid proportions (tertile 2: OR, 0.29; CI, 0.12-0.70) (tertile 3: OR, 0.53; CI, 0.19-1.54) were inversely related to risk of PCa, whereas men with high linolenic acid proportions were at increased likelihood of PCa (tertile 3 vs. tertile 1: OR, 2.06; 1.29-3.27). Blood myristic, stearic and palmitoleic acids were not associated with PCa. Higher intakes of dietary MUFA were inversely related to prostate cancer (tertile 3 vs. tertile 1: OR, 0.39; CI 0.16-0.92). The principal source of dietary MUFA was avocado intake. Dietary intakes of other fats were not associated with PCa.

CONCLUSIONS

Whole-blood and dietary MUFA reduced the risk of prostate cancer. The association may be related to avocado intakes. High blood linolenic acid was directly related to prostate cancer. These associations warrant further investigation.

Resolvins: natural agonists for resolution of pulmonary inflammation

Inappropriate or excessive pulmonary inflammation can contribute to chronic lung diseases. In health, the resolution of inflammation is an active process that terminates inflammatory responses. The recent identification of endogenous lipid-derived mediators of resolution has provided a window to explore the pathobiology of inflammatory disease and structural templates for the design of novel pro-resolving therapeutics. Resolvins (resolution-phase interaction products) are a family of pro-resolving mediators that are enzymatically generated from essential omega-3 polyunsaturated fatty acids. Two molecular series of resolvins have been characterised, namely E- and D-series resolvins which possess distinct structural, biochemical and pharmacological properties. Acting as agonists at specific receptors (CMKLR1, BLT1, ALX/FPR2 and GPR32), resolvins can signal for potent counter-regulatory effects on leukocyte functions, including preventing uncontrolled neutrophil swarming, decreasing the generation of cytokines, chemokines and reactive oxygen species and promoting clearance of apoptotic neutrophils from inflamed tissues. Hence, resolvins provide mechanisms for cytoprotection of host tissues to the potentially detrimental effects of unresolved inflammation. This review highlights recent experimental findings in resolvin research, and the impact of these stereospecific molecules on the resolution of pulmonary inflammation and tissue catabasis.

Erythrocyte fatty acids and prostate cancer risk: a comparison of methods

The role of fatty acids (FA) in prostate carcinogenesis is unclear. Interest in the inter-relationship among different types of FA has resulted in new analytic approaches to FA and their role in cancer development. We evaluated the association between erythrocyte FA and prostate cancer in 127 prostate cancer patients and 183 screen negative controls. We present three approaches to the analyses of the FA and prostate cancer association; (1) individual or common groups of FA, (2) biologically meaningful FA ratios and (3) principal components analysis. Monounsaturated FA and the alpha-linolenic:eicosapentaenoic ratio were associated with reduced risk of prostate cancer. However, Factor 1, which was strongly correlated with some long chain saturated FA, was associated with an increased risk of prostate cancer. We provide an example of modeling FA and their inter-relationships on the risk of prostate cancer. Comparing three approaches suggests the importance of considering the impact of the entire fatty acid profile in disease prevention.

Association of caveolin-1 and -2 genetic variants and post-treatment serum caveolin-1 with prostate cancer risk and outcomes

BACKGROUND

Caveolin-1 (cav-1) is overexpressed by metastatic prostate cancer (PC) cells. Pre-operative serum cav-1 levels have been shown to be a prognostic marker for PC recurrence. This study evaluated the relationship between post-treatment serum cav-1 levels and single nucleotide polymorphisms (SNPs) in the cav-1 and -2 genes with risk of PC, aggressive PC, PC recurrence or death.

METHODS

Two case-control studies of PC among men in Washington State were combined for this analysis. Cases (n = 1,458) were diagnosed in 1993-1996 or 2002-2005 and identified via a SEER cancer registry. Age-matched controls (n = 1,351) were identified via random digit dialing. Logistic regression was used to assess the relationship between exposures (19 haplotype-tagging SNPs from all subjects and post-treatment serum cav-1 levels from a sample of 202 cases and 226 controls) and PC risk and aggressive PC. Cox proportional hazards regression was used to assess the relationship between exposures and PC recurrence and death.

RESULTS

Rs9920 in cav-1 was associated with an increased relative risk of overall PC (OR(CT + CC) = 1.37, 95% CI = 1.12, 1.68) and aggressive PC (OR(CT + CC) = 1.57, 95% CI = 1.20, 2.06), but not with PC recurrence or death. High post-treatment serum cav-1 levels were not associated with PC risk, aggressive PC, or PC-specific death, but approached a significant inverse association with PC recurrence (hazard ratio = 0.69, 95% CI = 0.47, 1.00).

CONCLUSIONS

We found modest evidence for an association with a variant in the cav-1 gene and risk of overall PC and aggressive PC, which merits further study. We found no evidence that higher post-treatment serum cav-1 is associated with risk of aggressive PC or adverse PC outcomes.

Platelet linoleic acid is a potential biomarker of advanced non-small cell lung cancer

New parameters that could be used as tumor markers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of total lipids from erythrocytes and platelets from patients with advanced non-small cell lung cancer (NSCLC), chronic obstructive pulmonary disease (COPD) and asthma to reveal the fatty acids that could be used as NSCLC biomarkers. In our study, 50, 15 and 15 patients with advanced NSCLC, COPD and asthma and 50 healthy subjects were enrolled. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by ROC (receiver operating characteristics) curves analysis to gain information about biomarkers. Sialic acid (SA) and cytokeratins were measured by the thiobarbituric acid and immunoradiometric methods respectively. Useful fatty acid markers were as follows: erythrocytes, 22:0 and linoleic acid (LA, 18:2n6); platelets, 16:0, 18:0, and LA. At the cutoff value to obtain maximum accuracy, the best biomarker was platelet LA, with higher diagnostic yields than the commonly used markers SA or cytokeratins (100%, 76%, 75% and 86% sensitivity, specificity, positive predictive value and accuracy, respectively). These findings suggest that platelet LA might be used as a biomarker of NSCLC in relation to different aspects of the disease process that now needs to be explored.

Are all n-3 polyunsaturated fatty acids created equal?

N-3 Polyunsaturated fatty acids have been shown to have potential beneficial effects for chronic diseases including cancer, insulin resistance and cardiovascular disease. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in particular have been studied extensively, whereas substantive evidence for a biological role for the precursor, alpha-linolenic acid (ALA), is lacking. It is not enough to assume that ALA exerts effects through conversion to EPA and DHA, as the process is highly inefficient in humans. Thus, clarification of ALA's involvement in health and disease is essential, as it is the principle n-3 polyunsaturated fatty acid consumed in the North American diet and intakes of EPA and DHA are typically very low. There is evidence suggesting that ALA, EPA and DHA have specific and potentially independent effects on chronic disease. Therefore, this review will assess our current understanding of the differential effects of ALA, EPA and DHA on cancer, insulin resistance, and cardiovascular disease. Potential mechanisms of action will also be reviewed. Overall, a better understanding of the individual role for ALA, EPA and DHA is needed in order to make appropriate dietary recommendations regarding n-3 polyunsaturated fatty acid consumption.

The relation of alpha-linolenic acid to the risk of prostate cancer: a systematic review and meta-analysis

BACKGROUND

alpha-Linolenic acid (ALA; 18:3n-3) has been associated inconsistently with an increased risk of prostate cancer. Additional studies have become available since the publication of 2 previous meta-analyses.

OBJECTIVE

The objective was to review the published data on the relation between ALA and prostate cancer.

DESIGN

We conducted a systematic review to identify studies that included data on ALA and risk of prostate cancer. Data were pooled from studies that compared the highest ALA quantile with the lowest ALA quantile, and risk estimates were combined by using a random-effects model.

RESULTS

The relation between ALA and prostate cancer is inconsistent across studies. We pooled data from 8 case-control and 8 prospective studies. The summary estimate revealed that high ALA dietary intakes or tissue concentrations are weakly associated with prostate cancer risk (relative risk [RR]: 1.20; 95% CI: 1.01, 1.43). When examined by study type (ie, retrospective compared with prospective or dietary ALA compared with tissue concentration) or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17).

CONCLUSIONS

Studies examining the relation between ALA and prostate cancer have produced inconsistent findings. High ALA intakes or high blood and adipose tissue concentrations of ALA may be associated with a small increased risk of prostate cancer. However, these conclusions are qualified because of the heterogeneity across studies and the likelihood of publication bias.

Circulating fatty acids and prostate cancer risk in a nested case-control study: the Multiethnic Cohort

OBJECTIVE

Dietary fat, including specific fatty acids, has been proposed to contribute to prostate cancer pathogenesis, but findings from the studies based on biomarkers have been conflicting.

METHODS

We examined the association between erythrocyte membrane fatty acid composition and prostate cancer risk in a nested case-control study within a multiethnic cohort of African Americans, Native Hawaiians, Japanese Americans, Latinos, and Whites. Analyses included 376 cases and 729 matched controls. Conditional logistic regression was used to estimate the odds ratios and 95% confidence intervals with adjustment for multiple covariates.

RESULTS

No significant association was found for saturated, mono- and polyunsaturated fatty acid, or for specific n-3 and n-6 fatty acids, even when the analysis was limited to advanced or high grade prostate cancer. In ethnic specific analyses, there was a positive association with palmitic acid in Japanese Americans that was significantly different from the null results in other groups. There was also an increased risk with n-3 fatty acids and the ratio of n-3/n-6 fatty acids in Whites.

CONCLUSION

Although there was a suggestion of ethnic specific associations with some fatty acids, our overall findings do not support a role for fatty acids in prostate carcinogenesis.

Traditional Japanese diet and prostate cancer

The traditional Japanese diet has been suggested by some researchers to be associated with a decreased risk of prostate cancer (PCa). In this paper, we assumed the following three characteristics of the traditional Japanese diet high in soybean products, high in fish, and low in red meat. Isoflavones, polyunsaturated long chain (n - 3) fatty acids, and saturated fatty acids were thought to be micronutrients in biological etiology relevant to soybean products, fish, and red meat, respectively. Analytical epidemiological studies on the risk of PCa were identified using the MEDLINE database from 1998 to 2007. Some published studies showed a negative association of soybean products and isoflavones to PCa risk, an inverse association for fish or polyunsaturated long chain (n - 3) fatty acids such as eicosapentaenic acid (EPA) and docosahexaenoic acid (DHA) with PCa risk, and a positive association of red meat or saturated fatty acids with PCa risk, respectively. In conclusion, although it is possible that the traditional Japanese diet may reduce the risk of PCa through a combination of characteristics such as being high in soybean products, high in fish, and low in red meat, further well-designed epidemiological studies such as nested case-control studies with nutritional analyses of blood samples are needed to confirm this association.

Rapid appearance of resolvin precursors in inflammatory exudates: novel mechanisms in resolution

Resolution of inflammation is essential. Although supplementation of omega-3 fatty acids is widely used, their availability at sites of inflammation is not known. To this end, a multidisciplinary approach was taken to determine the relationship of circulating omega-3 to inflammatory exudates and the generation of resolution signals. In this study, we monitored resolvin precursors in evolving exudates, which initially paralleled increases in edema and infiltrating neutrophils. We also prepared novel microfluidic chambers to capture neutrophils from a drop of blood within minutes that permitted single-cell monitoring. In these, docosahexaenoic acid-derived resolvin D1 rapidly stopped neutrophil migration, whereas precursor docosahexaenoic acid did not. In second organ injury via ischemia-reperfusion, resolvin metabolically stable analogues were potent organ protectors reducing neutrophils. Together, these results indicate that circulating omega-3 fatty acids rapidly appear in inflammatory sites that require conversion to resolvins that control excessive neutrophil infiltration, protect organs, and foster resolution.

A 22-y prospective study of fish intake in relation to prostate cancer incidence and mortality

BACKGROUND

Fish and seafood n-3 fatty acids may prevent or delay the progression of prostate cancer, but epidemiologic studies do not uniformly support this hypothesis.

OBJECTIVE

We examined the relation of fish and seafood n-3 fatty acid intakes with prostate cancer incidence and mortality.

DESIGN

We conducted a prospective cohort study among 20,167 men participating in the Physician's Health Study who were free of cancer in 1983.

RESULTS

During 382 144 person-years of follow-up, 2161 men were diagnosed with prostate cancer and 230 died of prostate cancer. Fish intake was unrelated to prostate cancer incidence. Survival analysis among the men diagnosed with prostate cancer revealed that those consuming fish >or=5 times/wk had a 48% lower risk of prostate cancer death than did men consuming fish less than once weekly [relative risk (RR) = 0.52; 95% CI: 0.30, 0.91; P for trend = 0.05]. A similar association was found between seafood n-3 fatty acid intake and prostate cancer mortality (RR(Q5 versus Q1) = 0.64; 95% CI: 0.42, 0.99; P for trend = 0.02). These associations became stronger when the analyses were restricted to clinically detected cases.

CONCLUSION

These results suggest that fish intake is unrelated to prostate cancer incidence but may improve prostate cancer survival.

Fatty acid composition of plasma phospholipids and risk of prostate cancer in a case-control analysis nested within the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Plausible biological mechanisms underlie possible associations between fatty acids in blood and risk of prostate cancer; epidemiologic evidence for an association, however, is inconsistent.

OBJECTIVE

The objectives were to assess the association between plasma phospholipid fatty acids and risk of total prostate cancer by stage and grade.

DESIGN

This was a nested case-control analysis of 962 men with a diagnosis of prostate cancer after a median follow-up time of 4.2 y and 1061 matched controls who were taking part in the European Prospective Investigation into Cancer and Nutrition. The fatty acid composition of plasma phospholipids was measured by gas chromatography, and the risk of prostate cancer was estimated by using conditional logistic regression with adjustment for lifestyle variables.

RESULTS

We found a positive association between palmitic acid and risk of total, localized, and low-grade prostate cancer. The risk of prostate cancer for men in the highest quintile compared with the lowest quintile of palmitic acid was 1.47 (95% CI: 0.97, 2.23; P for trend = 0.032). We found an inverse association between stearic acid and the risk of total, localized, and low-grade prostate cancer; men in the highest quintile of stearic acid had a relative risk of 0.77 (95% CI: 0.56, 1.06; P for trend = 0.03). There were significant positive associations between myristic, alpha-linolenic, and eicosapentaenoic acids and risk of high-grade prostate cancer.

CONCLUSION

The associations between palmitic, stearic, myristic, alpha-linolenic, and eicosapentaenoic acids and prostate cancer risk may reflect differences in intake or metabolism of these fatty acids between the precancer cases and controls and should be explored further.

Multi-targeted therapy of cancer by omega-3 fatty acids

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) are essential fatty acids necessary for human health. Currently, the Western diet contains a disproportionally high amount of n-6 PUFAs and low amount of n-3 PUFAs, and the resulting high n-6/n-3 ratio is thought to contribute to cardiovascular disease, inflammation, and cancer. Studies in human populations have linked high consumption of fish or fish oil to reduced risk of colon, prostate, and breast cancer, although other studies failed to find a significant association. Nonetheless, the available epidemiological evidence, combined with the demonstrated effects of n-3 PUFAs on cancer in animal and cell culture models, has motivated the development of clinical interventions using n-3 PUFAs in the prevention and treatment of cancer, as well as for nutritional support of cancer patients to reduce weight loss and modulate the immune system. In this review, we discuss the rationale for using long-chain n-3 PUFAs in cancer prevention and treatment and the challenges that such approaches pose in the design of clinical trials.

Omega-3 PUFA: good or bad for prostate cancer?

INTRODUCTION

The objective of this meta-analysis was to estimate quantitatively the associations between intake or status of omega-3 polyunsaturated (omega-3 PUFA) fatty acids and occurrence of prostate cancer in observational studies in humans.

METHODS

We combined risk estimates across studies using random-effects models.

RESULTS

The combined estimate showed an increased risk of prostate cancer in men with a high intake or blood level of alpha-linolenic acid (ALA) (combined relative risk (RR) 1.36; 95% CI 1.08-1.70). The association is stronger in the case-control studies (RR 1.84; 95% CI 1.04-3.25) than in the prospective studies (RR 1.10; 0.91-1.32). Ecosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were not significantly associated with prostate cancer.

DISCUSSION

The association between high intake of ALA and prostate cancer is of concern and needs further study. However, the fact that the prospective studies do not show a clear association makes a true effect of intake of ALA on prostate cancer less likely.

Erythrocyte and platelet phospholipid fatty acids as markers of advanced non-small cell lung cancer: comparison with serum levels of sialic acid, TPS and Cyfra 21-1

The phospholipid fatty acid profiles of erythrocytes and platelets from fifty patients with advanced non-small cell lung cancer were investigated using gas chromatography/mass spectrometry, followed by "ROC" curves analysis to gain novel biomarker information. Sialic acid and cytokeratins were also examined. Potentially useful fatty acid markers: Erythrocytes: phosphatidylcholine, 18:2n6 and 20:4n6; phosphatidylethanolamine, 22:4n6 and 22:6n3 + 24:1n9. Platelets: phosphatidylcholine, 22.0; phosphatidylethanolamine, 22:5n3 + 24:0. At the cut-off value to obtain maximum accuracy, the best biomarkers were found in platelets: phosphatidylserine + phosphatidylinositol (PS + PI), 21:0; sphyngomyelin: 20:1n9 and 22:1n9. All these fatty acids showed similar/higher diagnostic yields than the commonly used markers sialic acid or cytokeratins.

Dietary fat intake and risk of prostate cancer in the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Findings from early observational studies have suggested that the intake of dietary fat might be a contributing factor in the etiology of prostate cancer. However, the results from more recent prospective studies do not support this hypothesis, and the possible association between different food sources of fat and prostate cancer risk also remains unclear.

OBJECTIVE

The objectives were to assess whether intakes of dietary fat, subtypes of fat, and fat from animal products were associated with prostate cancer risk.

DESIGN

This was a multicenter prospective study of 142,520 men in the European Prospective Investigation into Cancer and Nutrition (EPIC). Dietary fat intake was estimated with the use of country-specific validated food questionnaires. The association between dietary fat and risk of prostate cancer was assessed by using Cox regression, stratified by recruitment center and adjusted for height, weight, smoking, education, marital status, and energy intake.

RESULTS

After a median follow-up time of 8.7 y, prostate cancer was diagnosed in 2727 men. There was no significant association between dietary fat (total, saturated, monounsaturated, and polyunsaturated fat and the ratio of polyunsaturated to saturated fat) and risk of prostate cancer. The hazard ratio for prostate cancer for the highest versus the lowest quintile of total fat intake was 0.96 (95% CI: 0.84, 1.09; P for trend = 0.155). There were no significant associations between prostate cancer risk and fat from red meat, dairy products, and fish.

CONCLUSION

The results from this large multicenter study suggest that there is no association between dietary fat and prostate cancer risk.

Correlations of dietary patterns with prostate health

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve alpha-methylacyl-CoA racemase activity (required for beta-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.

Chronic cellular hypoxia as the prime cause of cancer: what is the de-oxygenating role of adulterated and improper ratios of polyunsaturated fatty acids when incorporated into cell membranes?

With the exception of melanoma and non-Hodgkin's lymphoma, the incidence of cancer has peaked in the last several years, but rates and mortality are still high. Moreover, despite 50 years of intensive cancer research increasingly focused on genetic causes, no single unifying cause for cancer has been established. Although it is well-known that tumors are hypoxic, and that there is a correlation between the level of hypoxia and prognosis, with the exception of Warburg's studies, little work has been done to investigate the relationship between hypoxia and cancer. Over 70 years ago, Warburg showed that cells could always be made cancerous by subjecting them to periods of hypoxia. Moreover, he demonstrated that once cells had converted to a cancerous state, reversion could not occur. Modern biochemistry acknowledges that there is a switch from oxidative phosphorylation to glycolysis in tumors that might be concurrent with hypoxia, but does not address the cancer causation. It is our hypothesis that long-term hypoxia of cells in the body, measured in years, is the primary trigger for cancer. We believe that the hypoxia, which has to meet Warburg's findings of a critical 35% reduction in intracellular oxygen levels to initiate cancer, is linked to the incorporation of adulterated, non-oxygenating, or inappropriate polyunsaturated fatty acids (PUFAs) into the phospholipids of cell and mitochondrial membranes. Such incorporation causes changes in membrane properties that impair oxygen transmission into the cell. Trans fats, partially oxidized PUFA entities, and inappropriate omega-6:omega-3 ratios are all potential sources of unsaturated fatty acids that can disrupt the normal membrane structure. In this paper, we explore this hypothesis by examining the evidence, and additionally propose an appropriate PUFA dosage for humans by analyzing requirements and taking into account current PUFA consumption patterns.

A Prospective Study of Polyunsaturated Fatty Acid Levels in Blood and Prostate Cancer Risk

BACKGROUND

Animal models suggest that n-3 fatty acids inhibit prostate cancer proliferation, whereas n-6 fatty acids promote it, but epidemiologic studies do not uniformly support these findings.

METHODS

A nested case-control study was conducted among 14,916 apparently healthy men who provided blood samples in 1982. Blood fatty acid levels were determined for 476 men diagnosed with prostate cancer during a 13-year follow-up and their matched controls. Conditional logistic regression was used to estimate the relative risks (RR) and 95% confidence intervals (95% CI) of total, non-aggressive (stage A/B and Gleason < 7) and aggressive (stage C/D, Gleason >or= 7, subsequent distant metastasis or death) prostate cancer associated with blood levels of specific fatty acids expressed as percentages of total fatty acids.

RESULTS

Whole blood levels of all long-chain n-3 fatty acids examined and of linoleic acid were inversely related to overall prostate cancer risk (RR(Q5vs.Q1), 0.59; 95% CI, 0.38-0.93; P(trend) = 0.01 for total long-chain n-3 fatty acids and RR(Q5vs.Q1), 0.62; 95% CI, 0.41-0.95; P(trend) = 0.03 for linoleic). Blood levels of gamma-linolenic and dihomo-gamma-linolenic acids, fatty acids resulting from the metabolism of linoleic acid, were directly associated with prostate cancer (RR, 1.41; 95% CI, 0.94-2.12; P(trend) = 0.05 for gamma-linolenic and RR, 1.54; 95% CI, 1.03-2.30; P(trend) = 0.02 for dihomo-gamma-linolenic acid). Levels of arachidonic and alpha-linolenic acids were unrelated to prostate cancer.

CONCLUSIONS

Higher blood levels of long-chain n-3 fatty acids, mainly found in marine foods, and of linoleic acid, mainly found in non-hydrogenated vegetable oils, are associated with a reduced risk of prostate cancer. The direct associations of linoleic acid metabolites with prostate cancer risk deserve further investigation.

Risk of colorectal cancer is linked to erythrocyte compositions of fatty acids as biomarkers for dietary intakes of fish, fat, and fatty acids

Consumption of fish rich in n-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid, is suggested to reduce colorectal cancer risk through inhibition of the arachidonic acid (AA) cascade related to tumorigenesis and cell proliferation. High intake of saturated fatty acids (SFAs) may increase the risk. To examine associations between colorectal cancer risk and fatty acid compositions in erythrocyte membranes, as biomarkers for dietary intakes of fish, fat, and fatty acids, we conducted a case-control study with 74 incident cases and 221 noncancer controls (matched by age, sex, and season of sample collection). Erythrocyte fatty acids were measured using an accelerated solvent extraction and a gas-liquid chromatography. Colorectal cancer had no association with dietary intakes of meat, fish, fat, and fatty acids. However, the risk was inversely associated with erythrocyte compositions of docosahexaenoic acid, AA, and PUFAs [the highest to the lowest tertile, odds ratios, 0.36, 0.42, and 0.15; 95% confidence intervals, 0.14-0.93, 0.18-0.95, and 0.05-0.46; P(trend) < 0.05, respectively] and positively with those of palmitic acid, SFAs, and the ratio of SFAs/PUFAs (odds ratios, 6.46, 8.20, and 9.45; 95% confidence intervals, 2.41-17.26, 2.86-23.52, and 2.84-31.43; P(trend) < 0.005, respectively). In conclusion, we could clearly show decreased and increased risks for colorectal cancer related to PUFAs and SFAs compositions in erythrocyte membranes, respectively, but further research is needed to investigate the discrepancy between our findings and the generally accepted role of the AA cascade.

Dietary fatty acids correlate with prostate cancer biopsy grade and volume in Jamaican men

PURPOSE

Jamaica has the highest incidence of prostate cancer in the world. Dietary fat is associated with prostate cancer. The Omega6 polyunsaturated fatty acids have been shown to stimulate prostate carcinogenesis and the Jamaican diet is rich in linoleic acid. We hypothesized positive correlations between Omega6 polyunsaturated fatty acid, prostate specific antigen and prostate biopsy pathology.

MATERIALS AND METHODS

A total of 148 men were enrolled in Kingston, Jamaica. Serum prostate specific antigen and erythrocyte membrane polyunsaturated fatty acids were analyzed. Men with prostate specific antigen 2.6 ng/ml or greater underwent biopsy. Histopathological and statistical analyses were performed on available data.

RESULTS

Of the 54 men who underwent biopsy 24 had prostate cancer, 17 had a Gleason score of 7 or greater and 11 had a tumor volume of 50% or greater. There were significant positive correlations between linoleic acid and Gleason score (p = 0.009), and the linoleic acid-to-docosahexaenoic acid (Omega3) ratio and tumor volume (p = 0.03). There was a significant negative correlation between the arachidonic acid (Omega6)-to-docosapentanoic acid (Omega3) ratio and Gleason score (p = 0.04). Statistical correlations between prostate specific antigen and polyunsaturated fatty acids were inconsistent.

CONCLUSIONS

The positive correlations between linoleic acid and Gleason score, and the linoleic acid-to-docosahexaenoic acid ratio and tumor volume support studies showing that Omega6 polyunsaturated fatty acids stimulate and Omega3 polyunsaturated fatty acids inhibit prostate cancer growth. The negative correlation between the arachidonic acid-to-docosapentanoic acid ratio and Gleason score supports studies that demonstrate increased metabolism of arachidonic acid in prostate cancer to form carcinogenic metabolites, namely prostaglandin E2. Our findings support the association between dietary fatty acids and prostate cancer, and they warrant further dietary and tissue studies in high risk populations.