DHA, gene expression, protein folding and cancer

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Or why you should take a quality DHA EPA supplement just because.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2533412/




Exploring how dietary factors interact with and modulate signaling pathways to promote or counteract cancer development and progression constitutes a major challenge. The purpose of the present study was to examine whether n-3 PUFAs like DHA exert their cytotoxicity by changing gene expression patterns and signaling pathways regulating cell growth. We found that ER stress is established already after 3 h treatment with DHA, as demonstrated by increased levels of phosphorylated eIF2α, a hallmark of ER stress. Phosphorylation of eIF2α adapts cells to various conditions of stress by attenuation of protein synthesis. We found that the n-3 PUFAs DHA and EPA, but not OA, cause phosphorylation of eIF2α, thereby generally inhibiting translation initiation. This is in agreement with previous results showing that inhibition of translation initiation mediates the antiproliferative action of EPA in NIH 3T3 cells by decreased levels of cyclin D1 (40).

Increased expression of genes downstream of phosphorylated eIF2α is mediated through induction of the transcription factor ATF4 (14). Genes with ATF4 binding sites are involved in restoring ER homeostasis in response to various stresses (41). Several downstream targets of ATF4 are affected at the mRNA and protein level in our study, indicating that ER stress induced by DHA in SW620 cells is mediated through the ER-localized PERK pathway. Induction of the UPR is initiated by dissociation of PERK from the ER-resident chaperone BiP. However, the protein level of BiP remained constant at all time points. Pimpl et al. (42) have reported that transcriptional induction of BiP rarely leads to increased protein levels of BiP/GRP78, this being due to increased turnover.
UPR is activated to restore cellular homeostasis and induces transcription of genes encoding proteins that mediate ER-associated degradation in response to prolonged ER stress. A large number of 20S and 26S proteasomal subunits were up-regulated in SW620 cells. The proteasome plays a central role in proteolysis of ubiquitinated proteins and are responsible for cleaving many regulatory proteins, like cyclins and members of the NFκB family (43).

Prolonged ER stress may cause induction of apoptosis. We show that even though the ER stress-related caspases 4 and 7 are up-regulated in DHA-treated SW620 cells, active caspase 7 is not detectable. On the other hand, active caspase 7 was detected in SW480 cells (data not shown). Chen and Istfan (44) have studied the apoptotic response to DHA in several cell lines, among these SW480 and SW620. A DNA ladder was observed after incubation with DHA (150 μM) for 24 h in SW480, but not in SW620 cells; this is in accordance with our results. Previously, we were not able to detect apoptosis by the TUNEL-assay in either SW480 or SW620 (5). This may indicate that the survival threshold is not exceeded in these cells within the time period assayed and concentration used.
ER is the principal site for protein synthesis and folding, Ca2+ storage and signaling, as well as biosynthesis of fatty acids and cholesterol.

Any perturbation that interferes with these activities promotes ER stress and initiates the UPR. We found that DHA treatment mobilizes Ca2+ from ER into the cytosol, in agreement with previous results investigating the effects of n-3 and n-6 PUFAs (40, 45–47), but the mechanism is not known. Our results indicate that calcium release induced by DHA may be linked to induction of ER stress. A redistribution of cholesterol from intracellular regulatory compartments like ER to DHA-cholesteryl ester-enriched lipid droplets (5), causing functional depletion of cholesterol in the ER could potentially lead to ER stress and Ca2+ mobilization, since total cholesterol is not increased (this work). Harding et al. (21) have shown that compounds that deplete cellular cholesterol stores activate an integrated stress response (ISR) by promoting ER stress.

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1. Another paper from Italy describes how DHA affects protein cleavage

in the brain, and people who have a genetic defect that disallows the production of long chain fatty acids may be at a greater risk for neurodegenerative diseases. The Inuit Indians consume 17 to 19 grams of fatty acids daily... we get about ONE.

http://www.ncbi.nlm.nih.gov/pubmed/19747490

J Mol Biol. 2009 Nov 20;394(1):94-107. Epub 2009 Sep 8.
Molecular insights into the interaction between alpha-synuclein and docosahexaenoic acid.
De Franceschi G, Frare E, Bubacco L, Mammi S, Fontana A, de Laureto PP.
CRIBI Biotechnology Centre, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy.

Abstract

alpha-Synuclein (alpha-syn) is a 140-residue protein of unknown function, involved in several neurodegenerative disorders, such as Parkinson's disease. Recently, the possible interaction between alpha-syn and polyunsaturated fatty acids has attracted a strong interest. Indeed, lipids are able to trigger the multimerization of the protein in vitro and in cultured cells.

Docosahexaenoic acid (DHA) is one of the main fatty acids (FAs) in cerebral gray matter and is dynamically released following phospholipid hydrolysis. Moreover, it has been found in high levels in brain areas containing alpha-syn inclusions in patients affected by Parkinson's disease. Debated and unsolved questions regard the nature of the molecular interaction between alpha-syn and DHA and the effect exerted by the protein on the aggregated state of the FA.

Here, we show that alpha-syn is able to strongly interact with DHA and that a mutual effect on the structure of the protein and on the physical state of the lipid derives from this interaction. alpha-Syn acquires an alpha-helical conformation in a simple two-state transition. The binding of the protein to the FA leads to a reduction of the size of the spontaneously formed aggregated species of DHA as well as of the critical aggregate concentration of the lipid.

Specifically, biophysical methods and electron microscopy observations indicated that the FA forms oil droplets in the presence of alpha-syn. Limited proteolysis experiments showed that, when the protein is bound to the FA oil droplets, it is initially cleaved in the 89-102 region, suggesting that this chain segment is sufficiently flexible or unfolded to be protease-sensitive.

Subsequent proteolytic events produce fragments corresponding to the first 70-80 residues that remain structured and show high affinity for the lipid. The fact that a region of the polypeptide chain remains accessible to proteases, when interacting with the lipid, suggests that this region could be involved in other interactions, justifying the ambivalent propensity of alpha-syn towards folding or aggregation in the presence of FAs.
PMID: 19747490

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2. www.clinicaltrials.gov

www.clinicaltrials.gov


http://www.clinicaltrials.gov/ct2/show/NCT00440050?term=dha&rank=3

DHA (Docosahexaenoic Acid), an Omega 3 Fatty Acid, in Slowing the Progression of Alzheimer's Disease
This study has been completed.
First Received: February 22, 2007 Last Updated: August 27, 2010 History of Changes
Sponsor: Alzheimer's Disease Cooperative Study (ADCS)
Collaborators: National Institute on Aging (NIA)
Martek Biosciences Corporation
Information provided by: Alzheimer's Disease Cooperative Study (ADCS)
ClinicalTrials.gov Identifier: NCT00440050



>>Detailed Description:
Preliminary studies have shown a reduced risk of Alzheimer's disease (AD) in people consuming increased amounts of fish in their diets. Many of the health benefits of fish are attributed to the abundance of omega 3 fatty acids. Docosahexaenoic Acid (DHA) is the most abundant omega 3 fatty acid in the brain. Data from several animal models supports the hypothesis that DHA may be an effective treatment for AD by means of anti-amyloid, antioxidant, and neuroprotectant mechanisms.

In this study, 400 individuals with mild to moderate AD will participate at approximately 53 study sites throughout the US for 18 months. Participants will be randomized so that 60% will receive approximately 2 grams of DHA, divided into 4 capsules, 2 capsules taken twice a day, while 40% receive an identical placebo.

Potential participants will go to their study site for a screening visit, where eligibility is determined, and if accepted, for a baseline visit where cognitive status, behavioral status, functional status, and global severity of dementia will be assessed. Vital signs and biomarker labs will also be obtained. Subsequent visits will occur every three months for medication checks and, every 6 months, further assessments, physical exams, and labs.

Some participants will also take part in MRI (magnetic resonance imaging) and/or CSF (cerebrospinal fluid) sub-studies. For the MRI sub-study, scans will be done prior to beginning the study medication, and again after 18 months. Likewise, for the CSF sub-study, a lumbar puncture will be done prior to beginning the study medication, and again after 18 months.

Enrollment is restricted to individuals who consume no more than 200 mg of DHA per day, which is almost 300% of the average daily intake in an American diet. Individuals who take fish oil or omega 3 fatty acid supplements are also not eligible. Each visit will include completion of a very brief food frequency questionnaire to monitor dietary DHA levels.<<