Gwendolyn Barceló-Coblijn

Alpha-linolenic acid and its conversion to longer chain n−3 fatty acids: Benefits for human health and a role in maintaining tissue n−3 fatty acid levels

There is little doubt regarding the essential nature of alpha-linolenic acid (ALA), yet the capacity of dietary ALA to maintain adequate tissue levels of long chain n-3 fatty acids remains quite controversial. This simple point remains highly debated despite evidence that removal of dietary ALA promotes n-3 fatty acid inadequacy, including that of docosahexaenoic acid (DHA), and that many experiments demonstrate that dietary inclusion of ALA raises n-3 tissue fatty acid content, including DHA. Herein we propose, based upon our previous work and that of others, that ALA is elongated and desaturated in a tissue-dependent manner. One important concept is to recognize that ALA, like many other fatty acids, rapidly undergoes beta-oxidation and that the carbons are conserved and reused for synthesis of other products including cholesterol and fatty acids. This process and the differences between utilization of dietary DHA or liver-derived DHA as compared to ALA have led to the dogma that ALA is not a useful fatty acid for maintaining tissue long chain n-3 fatty acids, including DHA. Herein, we propose that indeed dietary ALA is a crucial dietary source of n-3 fatty acids and its dietary inclusion is critical for maintaining tissue long chain n-3 levels.

The role of n-3 polyunsaturated fatty acids in brain: Modulation of rat brain gene expression by dietary n-3 fatty acids

Rats were fed either a high linolenic acid (perilla oil) or high eicosapentaenoic + docosahexaenoic acid (fish oil) diet (8%), and the fatty acid and molecular species composition of ethanolamine phosphoglycerides was determined. Gene expression pattern resulting from the feeding of n-3 fatty acids also was studied. Perilla oil feeding, in contrast to fish oil feeding, was not reflected in total fatty acid composition of ethanolamine phosphoglycerides. Levels of the alkenylacyl subclass of ethanolamine phosphoglycerides increased in response to feeding. Similarly, levels of diacyl phosphatidylethanolamine molecular species containing docosahexaenoic acid (18:0/22:6) were higher in perilla-fed or fish oil-fed rat brains whereas those in ethanolamine plasmalogens remained unchanged. Because plasmalogen levels in the brains of rats fed a n-3 fatty acid-enriched diet increased, it is plausible, however, that docosahexaenoic acid taken up from the food or formed from linolenic acid was deposited in this phospholipid subclass. Using cDNA microarrays, 55 genes were found to be overexpressed and 47 were suppressed relative to controls by both dietary regimens. The altered genes included those controlling synaptic plasticity, cytosceleton and membrane association, signal transduction, ion channel formation, energy metabolism, and regulatory proteins. This effect seems to be independent of the chain length of fatty acids, but the n-3 structure appears to be important. Because n-3 polyunsaturated fatty acids have been shown to play an important role in maintaining normal mental functions and docosahexaenoic acid-containing ethanolamine phosphoglyceride (18:0/22:6) molecular species accumulated in response to n-3 fatty acid feeding, a casual relationship between the two events can be surmised.

Oleic acid content is responsible for the reduction in blood pressure induced by olive oil

Numerous studies have shown that high olive oil intake reduces blood pressure (BP). These positive effects of olive oil have frequently been ascribed to its minor components, such as α-tocopherol, polyphenols, and other phenolic compounds that are not present in other oils. However, in this study we demonstrate that the hypotensive effect of olive oil is caused by its high oleic acid (OA) content (≈70–80%). We propose that olive oil intake increases OA levels in membranes, which regulates membrane lipid structure (HII phase propensity) in such a way as to control G protein-mediated signaling, causing a reduction in BP. This effect is in part caused by its regulatory action on G protein-associated cascades that regulate adenylyl cyclase and phospholipase C. In turn, the OA analogues, elaidic and stearic acids, had no hypotensive activity, indicating that the molecular mechanisms that link membrane lipid structure and BP regulation are very specific. Similarly, soybean oil (with low OA content) did not reduce BP. This study demonstrates that olive oil induces its hypotensive effects through the action of OA.

Membranes: a meeting point for lipids, proteins and therapies

•  Introduction •  Membrane lipid composition •  Membrane lipid structure •  Membrane lipid organization ‐  Why so many different lipids? ‐  Lipid mixing and demixing ‐  Lateral pressure ‐  Surface electrostatics •  Role of lipids in cell functions •  Lipid influence in transmembrane protein function ‐  Prokaryotic potassium channel (KcsA) ‐  Mechanosensitive channels ‐  Voltage‐gated potassium channel (KvAP) ‐  Nicotinic acetylcholine receptor (nAcChR) ‐  G protein‐coupled receptors ‐  Other examples •  Non‐permanent proteins in membranes ‐  Proteins that interact reversibly with the bilayers ‐  Proteins that interact irreversibly with the bilayers ‐  Proteins that interact weakly with the membrane ‐  Proteins that interact strongly with the membrane ‐  G proteins and their interactions with membranes ‐  Small monomeric G proteins: the Ras and Ras‐like family ‐  Protein kinase C •  Membrane microdomains and lipid mediators in the control of heat‐shock protein response ‐  Stress sensing and signalling: the membrane sensor theory ‐  Hsp signalling in cancer and diabetes ‐  The role of membrane microdomains ‐  Lipid mediators of the stress response •  A subpopulation of Hsps can interact with and translocate through membranes ‐  Hsp90 in eukaryotic membranes ‐  Hsp70 in cell membranes ‐  Hsp27‐membrane interactions ‐  Secreted Hsps ‐  Representative cases where Hsps interact with membranes or release from the cells •  Concluding remarks

Mitochondrial Lipid Abnormality and Electron Transport Chain Impairment in Mice Lacking α-Synuclein

ABSTRACT The presynaptic protein α-synuclein, implicated in Parkinson disease (PD), binds phospholipids and has a role in brain fatty acid (FA) metabolism. In mice lacking α-synuclein (Snca−/−), total brain steady-state mass of the mitochondria-specific phospholipid, cardiolipin, is reduced 22% and its acyl side chains show a 51% increase in saturated FAs and a 25% reduction in essential n-6, but not n-3, polyunsaturated FAs. Additionally, 23% reduction in phosphatidylglycerol content, the immediate biosynthetic precursor of cardiolipin, was observed without alterations in the content of other brain phospholipids. Consistent with these changes, more ordered lipid head group and acyl chain packing with enhanced rotational motion of diphenylhexatriene (DPH) about its long axis were demonstrated in time-resolved DPH fluorescence lifetime experiments. These abnormalities in mitochondrial membrane properties were associated with a 15% reduction in linked complex I/III activity of the electron transport chain, without reductions in mitochondrial number, complex II/III activity, or individual complex I, II, III, or IV activity. Reduced complex I activity is thought to be a critical factor in the development of PD. Thus, altered membrane composition and structure and impaired complex I/III function in Snca −/− brain suggest a relationship between α-synucleins role in brain lipid metabolism, mitochondrial function, and PD.

Short-term administration of omega 3 fatty acids from fish oil results in increased transthyretin transcription in old rat hippocampus

Reduced brain levels of long chain polyunsaturated fatty acids [arachidonic acid and docosahexanoic acid (DHA)] are observed in elderly subjects and patients with Alzheimers disease. To determine the effects of n-3 fatty acids on aged rat brain, 2-year-old rats were fed fish oil (27% DHA content) for 1 month, and gene expression analysis and fatty acid and molecular species composition of the major phospholipid species were assessed. No significant alteration could be observed in the fatty acid composition of ethanolamine phosphoglycerides and phosphatidylserines with the exception of DHA, which was slightly higher in brains of rats receiving fish oil. However, a drastic reduction in arachidonic acid in phosphatidylinositoles was observed. The expression of 23 genes was altered in response to fish oil feeding in the hippocampus. The transcription of transthyretin (TTR) was induced by 10-fold as evidenced by microarray analysis and confirmed by real-time quantitative RT-PCR. Expression of IL-1 and NO synthase, which has been implicated in the prevention of neurological diseases, was unaltered. TTR is an amyloid β protein scavenger, so an increase in its expression could prevent amyloid aggregate formation. We believe the beneficial effects of fish oil might be common to other agents, i.e., induce TTR expression, like nicotine and Ginkgo biloba extract.

Gene expression and molecular composition of phospholipids in rat brain in relation to dietary n-6 to n-3 fatty acid ratio

Rats were fed from conception till adulthood either with normal rat chow with a linoleic (LA) to linolenic acid (LNA) ratio of 8.2:1 or a rat chow supplemented with a mixture of perilla and soy bean oil giving a ratio of LA to LNA of 4.7:1. Fat content of the feed was 5%. Fatty acid and molecular species composition of ethanolamine phosphoglyceride was determined. Effect of this diet on gene expression was also studied. There was an accumulation of docosahexaenoic (DHA) and arachidonic acids (AA) in brains of the experimental animals. Changes in the ratio sn-1 saturated, sn-2 docosahexaenoic to sn-1 monounsaturated, sn-2 docosahexaenoic were observed. Twenty genes were found overexpressed in response to the 4.7:1 mixture diet and four were found down-regulated compared to normal rat chow. Among them were the genes related to energy household, lipid metabolism and respiration. The degree of up-regulation exceeded that observed with perilla with a ratio of LA to LNA 8.2:1 [Proc. Natl. Acad. Sci. U. S. A. 99 (2002) 2619]. It was concluded that brain sensitively reacts to the fatty acid composition of the diet. It was suggested that alteration in membrane architecture and function coupled with alterations in gene expression profiles may contribute to the observed beneficial impact of n-3 type polyunsaturated fatty acids on cognitive functions.

Fatty acid incorporation is decreased in astrocytes cultured from α-synuclein gene-ablated mice

Because α‐synuclein may function as a fatty acid binding protein, we measured fatty acid incorporation into astrocytes isolated from wild‐type and α‐synuclein gene‐ablated mice. α‐Synuclein deficiency decreased palmitic acid (16:0) incorporation 31% and arachidonic acid [20:4 (n‐6)] incorporation 39%, whereas 22:6 (n‐3) incorporation was unaffected. In neutral lipids, fatty acid targeting of 20:4 (n‐6) and 22:6 (n‐3) (docosahexaenoic acid) to the neutral lipid fraction was increased 1.7‐fold and 1.6‐fold, respectively, with an increase in each of the major neutral lipids. This was consistent with a 3.4‐ to 3.8‐fold increase in cholesteryl ester and triacylglycerol mass. In the phospholipid fraction, α‐synuclein deficiency decreased 16:0 esterification 39% and 20:4 (n‐6) esterification 43% and decreased the distribution of these fatty acids, including 22:6 (n‐3), into this lipid pool. α‐Synuclein gene‐ablation significantly decreased the trafficking of these fatty acids to phosphatidylinositol. This observation is consistent with changes in phospholipid fatty acid composition in the α‐synuclein‐deficient astrocytes, including decreased 22:6 (n‐3) content in the four major phospholipid classes. In summary, these studies demonstrate that α‐synuclein deficiency significantly disrupted astrocyte fatty acid uptake and trafficking, with a marked increase in fatty acid trafficking to cholesteryl esters and triacylglycerols and decreased trafficking to phospholipids, including phosphatidylinositol.

Sphingomyelin and sphingomyelin synthase (SMS) in the malignant transformation of glioma cells and in 2-hydroxyoleic acid therapy

The mechanism of action of 2-hydroxyoleic acid (2OHOA), a potent antitumor compound, has not yet been fully elucidated. Here, we show that human cancer cells have markedly lower levels of sphingomyelin (SM) than nontumor (MRC-5) cells. In this context, 2OHOA treatment strongly augments SM mass (4.6-fold), restoring the levels found in MRC-5 cells, while a loss of phosphatidylethanolamine and phosphatidylcholine is observed (57 and 30%, respectively). The increased SM mass was due to a rapid and highly specific activation of SM synthases (SMS). This effect appeared to be specific against cancer cells as it did not affect nontumor MRC-5 cells. Therefore, low SM levels are associated with the tumorigenic transformation that produces cancer cells. SM accumulation occurred at the plasma membrane and caused an increase in membrane global order and lipid raft packing in model membranes. These modifications would account for the observed alteration by 2OHOA in the localization of proteins involved in cell apoptosis (Fas receptor) or differentiation (Ras). Importantly, SMS inhibition by D609 diminished 2OHOA effect on cell cycle. Therefore, we propose that the regulation of SMS activity in tumor cells is a critical upstream event in 2OHOA antitumor mechanism, which also explains its specificity for cancer cells, its potency, and the lack of undesired side effects. Finally, the specific activation of SMS explains the ability of this compound to trigger cell cycle arrest, cell differentiation, and autophagy or apoptosis in cancer cells.

Brain neutral lipids mass is increased in α‐synuclein gene‐ablated mice

Because α‐synuclein (Snca) has a role in brain lipid metabolism, we determined the impact that Snca deletion had on whole brain lipid composition. We analysed masses of individual phospholipid (PL) classes and neutral lipid mass as well as PL acyl chain composition in brains from wild‐type and Snca‐/‐ mice. Although total brain PL mass was not altered, cardiolipin and phosphatidylglycerol mass decreased 16% and 27%, respectively, in Snca‐/‐ mice. In addition, no changes were observed in plasmalogen or polyphosphoinositide mass. In ethanolamine glycerophospholipids and phosphatidylserine, docosahexaenoic acid (22 : 6n‐3) was decreased 7%, while 16 : 0 was increased 1.1‐fold and 1.4‐fold, respectively. Surprisingly, brain cholesterol, cholesteryl ester, and triacylglycerol mass were increased 1.1‐fold, 1.6‐fold, and 1.4‐fold, respectively in Snca‐/‐ mice. In isolated myelin, cholesterol mass was also increased 1.3‐fold, but because there was also a net increase in myelin PL mass, the cholesterol to PL ratio was unaltered. No changes in the expression of cholesterogenic enzymes were observed, suggesting these did not account for the observed changes in cholesterol. These data extend our previous results in astrocytes and kinetic studies in vivo demonstrating a role for Snca in brain lipid metabolism and demonstrate a clear impact on brain neutral lipid metabolism.