Rapid cellular enrichment of eicosapentaenoate after a single intravenous injection of a novel medium-chain triacylglycerol:fish-oil emulsion in humans.

BACKGROUND: Dietary deficiency in n-3 (omega-3) polyunsaturated fatty acids (PUFAs) prevails in Western populations and potentially results in adverse health outcomes. To circumvent the slow n-3 PUFA incorporation in phospholipids of key cells after oral supplementation, a new preparation for intravenous bolus injection was developed with 20 g triacylglycerols/100 mL of a mixture of 80% medium-chain triacylglycerols (MCTs) and 20% fish oil (FO) (wt:wt), and 0.4 g alpha-tocopherol/100 mL of the same mixture. OBJECTIVE: Our objective was to document the enrichment of n-3 PUFAs in leukocyte and platelet phospholipids after a bolus intravenous injection of MCT:FO in men. DESIGN: Twelve healthy male subjects received injections over a 5-min period of 50 mL of either MCT:FO or a control MCT:long-chain triacylglycerol (MCT:LCT) emulsion containing 20 g triacylglycerols/100 mL with equal amounts (wt:wt) of MCT and soybean triacylglycerols (LCT) and containing 0.02 g alpha-tocopherol/100 mL; after an 8-wk interval, the subjects received injections of the other preparation. RESULTS: Clinical and biological variables that assessed tolerance and safety remained unchanged. Plasma elimination was faster for MCT:FO than for MCT:LCT (half-life: 24.5 +/- 3.5 min compared with 32.9 +/- 3.0 min; P < 0.025). This was associated with a greater increase in the plasma nonesterified fatty acid concentration. The content of n-3 PUFAs, specifically eicosapentaenoic acid (20:5n-3), increased in leukocyte and platelet phospholipids within 60 min and > or =24 h after MCT:FO injection. CONCLUSION: Bolus intravenous injection of a novel MCT:FO emulsion allows rapid enrichment of cells with n-3 PUFAs.

The metabolic syndrome of omega3-depleted rats. VI. Intestinal phospholipid saturated and monodesaturated fatty acids.

Exposure of normal rats for 3-7 months to an omega3-deprived diet and subsequent exposure to an omega3-enriched diet were recently proposed as a model to study the metabolic consequences of alteration in the dietary supply of omega3 PUFA and their time course. The same animal model was used in the present study, which aimed at characterizing the pattern of saturated and monodesaturated fatty acids in the phospholipids of the duodenum, jejunum, caecum and colon. With one exception (C18:0), the weight content of these fatty acids was lower in the proximal than distal intestinal segments, a situation possibly accounted for by the generation of short-chain fatty acids by the colonic flora and the resulting synthesis of longer fatty acids n colonocytes. The relative weight content of the 8 fatty acids under consideration (C14:0, C16:0, C16:1omega7, C18:0, C18:1omega9, C20:0, C22:0 and C24:0) was higher in the phospholipids of omega3-deprived rats, as compared to control animals. Exposure of either the control animals or omega3-deprived rats for 2-4 weeks to diets containing twice more lipids than the control or omega3-deprived diet given theretofore further increased, as a rule, the relative content of phospholipids in the saturated or monodesaturated fatty acids, such an increase being much more pronounced in the proximal segments of the intestinal tract than in the distal ones. A significant inverse correlation between the phospholipid content in C22:6omega3 and saturated and monodesaturated fatty acids was only observed in the caecum and colon.

The metabolic syndrome of omega3-depleted rats. IV. Intestinal phospholipid omega3 fatty acids.

A dietary deprivation in long-chain polyunsaturated omega3 fatty acids initiated in 7-week old normal rats provokes within 3 to 7 months the appearance of several features of the metabolic syndrome. Likewise, within 2 to 4-5 weeks exposure to a flaxseed oil-enriched diet, these anomalies are rapidly corrected. The present study deals with the omega3 fatty acid content of intestinal phospholipids under the same experimental conditions. For the sake of comparison, the control rats were given access during the last 4-5 weeks to either a soybean or flaxseed oil-enriched diet. In control rats, the relative weight content of omega3 fatty acids as well as their product/precursor ratio differed in distinct segments of the intestinal tract (duodenum, jejunum, caecum, colon). Within 3 months of omega3-deprivation, the intestinal content of C18:3omega3, C20:5omega3 and C22:5omega3 reached values below the limit of detection, whilst the C22:6omega3 content progressively decreased down to 10-20% of control values. Within 2 weeks of exposure to the omega3-rich diet, the C18:3omega3, C20:5omega3 and C22:5omega3 content of intestinal phospholipids were higher than control values, whilst that of C22:6omega3 progressively returned to a normal level during the 2 to 4-5 weeks exposure to the flaxseed oil-enriched diet. The results collected in the intestinal cells, which are the first cells exposed to each given diet, reinforce the view that the present animal model is quite suitable to assess the metabolic consequences of both omega3 fatty acid deprivation and replenishment.

The metabolic syndrome of omega3-depleted rats. V. Intestinal phospholipid omega6 fatty acids.

This study aims mainly at investigating the effects of a dietary deprivation and replenishment of omega3 PUFA upon the phospholipid pattern of omega6 PUFA in the duodenum, jejunum, caecum and colon of rats exposed for 3-7 months to an omega3-depleted diet and then eventually exposed for 2-4 weeks to an omega3-rich diet. In control rats, the relative weight content of all omega6 fatty acids differed in the proximal and distal intestinal segments. In the omega3-depleted rats the C18:2omega6, C20:2omega6 and C20:3omega6 content was decreased whilst that of C20:4omega6 and C22:4omega6 was increased. Significant correlations were found in the caecum or colon between the C18:2omega6 or C20:4omega6 content of intestinal phospholipids and their C22:6omega3 content, an increase in the latter content coinciding with an increase in C18:2omega6 and decrease of C20:4omega6. Such was also the case for C20:4omega6, but not C18:2omega6, in the duodenum and jejunum. At these proximal intestinal levels, exposure of the omega3-depleted rats to a flaxseed oil-enriched diet indeed decreased the C18:2omega6 phospholipid content, an effect possibly attributable to the much lower content of C18:2omega6 in the latter diet, as distinct from the sunflower diet offered to the omega3-depleted rats during the first 7 months. However, at more distal intestinal levels, and like in the liver, a deficiency in omega3 fatty acids apparently favours the stepwise conversion of C18:2omega6 to C20:4omega6 and C22:4omega6.

Alteration of lipid fatty acid profile and cationic fluxes in ventricular cardiomyocytes from omega3-depleted rats.

The bolus intravenous injection of a medium-chain triglyceride:fish oil emulsion was recently found to increase within 60 min the cell phospholipid content in long-chain polyunsaturated omega3 fatty acids and, hence, proposed as a potential tool to prevent cardiac arrhythmia in subjects with a decreased dietary intake of such fatty acids. In the present study, ventricular cardiomyocytes from second generation rats depleted in omega3 fatty acids were found to display the same changes in the phospholipid fatty acid pattern as that previously documented in the cardiac muscle and endothelium of such rats, altered 86Rb and 45Ca fluxes with emphasis on a decrease in both K+ inflow and K+ content and an increase in both Ca2+ inflow and content. The alteration of K+ inflow could not be attributed to a decrease in ouabain-sensitive Na+,K+-ATPase activity as measured in cell homogenates. The cationic alterations were corrected, in part at least, by the prior intravenous injection of the medium-chain triglyceride:fish oil emulsion 60 min before sacrifice of the omega3-depleted rats.

The metabolic syndrome of omega3-depleted rats. III. Brain phospholipids.

Rats exposed from 7 weeks after birth and for the ensuing 3 to 7 months to a diet depleted in long-chain polyunsaturated omega3 fatty acids were recently proposed as a new animal model for the metabolic syndrome. The present study aimed mainly at investigating whether, in this new model, the perturbation of the fatty acid total content and pattern of brain phospholipids simulates that previously documented in second-generation omega3-depleted rats. Such was indeed the case, with the apparent exception of changes in the C18:1omega9, C20:0, C22:0 and C24:0 relative content of brain phospholipids. Moreover, the C22:5omega3 content of such phospholipids was unexpectedly lower in the present model than in the second-generation omega3-depleted rats. The changes in brain phospholipids were also monitored when the rats deprived of omega3 fatty acids for 7 months were given access for 2 to 4-5 weeks to a flaxseed oil-enriched diet. Most phospholipid variables were rapidly normalized under the latter experimental conditions. The results obtained under these conditions suggest that an increase in the brain phospholipid C22:5omega3 content may play a key role in the orexigenic effects of exogenous omega3 fatty acids supplied to omega3-depleted animals.

The metabolic syndrome of omega3-depleted rats. I. Liver data.

Second-generation rats depleted in long-chain polyunsaturated omega3 fatty acids were recently proposed as a novel animal model for the metabolic syndrome. In the present study, a dietary deprivation of omega3 acids for 3-7 months was found sufficient to provoke in 6-week-old normal rats the same alteration of the fatty acid content and profile of liver phospholipids and triglycerides as that otherwise prevailing in the second-generation omega3-depleted rats, with emphasis on a severe decrease in their omega3 fatty acid content, alterations in the relative contribution of and ratio between selected long-chain polyunsaturated omega6 fatty acids, saturated and monodesaturated fatty acids and precursors of nervonic acid, and liver steatosis. When the omega3-depleted rats were exposed, after the first 7 months of the present experiments and for 2-4 weeks to a diet supplemented with 5% (w/w) flaxseed oil, most of these hepatic variables returned towards or beyond control values. In both the omega3-depleted rats and control animals, however, the eventual exposure to the flaxseed oil-enriched diet failed to suppress liver steatosis and, on the contrary, provoked a further increase in liver triglyceride content. It is proposed, therefore, that the present approach represents a simple and realistic animal model to study the consequences of omega3-depletion. Moreover, the results suggest that to oppose such consequences, e.g. liver steatosis, it may be necessary to combine the dietary supply of omega3 acids with a suitable control of food intake, in both qualitative and quantitative terms.

Effect of ALA-enriched food supply on cardiovascular risk factors in males.

The outcome of a total dietary approach using a wide range of n-3 polyunsaturated fatty acids (PUFA) enriched food items on cardiovascular diseases called for further investigation. The study objective was to assess the effect of an ALA-enriched food supply on cardiovascular risk factors in healthy males. A dietary intervention (single-blind field trial with pre- and post-measurements) was performed with 59 healthy males in a Belgian prison. Over a period of 12 weeks they were supplied with an n-3 enriched diet (containing 6.5 g n-3 PUFA/day compared to 4 g n-3 PUFA/day in the standard diet) that was substituted for their regular diet, increasing mainly the alpha-linolenic acid intake (from 2.8 to around 5 g/day). The results indicated no impact on subjects waist circumference, weight and BMI or systolic blood pressure. In contrast, the diastolic blood pressure significantly decreased during the intervention period (from 74.6 +/- 8.2 to 71.7 +/- 10.1 mmHg; P < 0.02). Moreover, the HDL-cholesterol level increased in non-smoking participants (from 0.97 +/- 0.25 to 1.06 +/- 0.23 mmol/l; P < 0.03). In summary, the study demonstrated that enrichment of commonly eaten food items with n-3 fatty acids provides the opportunity to increase the n-3 fatty acid intake and to decrease the n-6/n-3 ratio which results in a decreasing diastolic blood pressure and an increase of HDL-cholesterol (in non-smokers).

Oxidative stress produced by circulating microparticles in on-pump but not in off-pump coronary surgery.

OBJECTIVE: This study was undertaken to assess whether plasmas isolated during off-pump coronary surgery trigger less oxidative stress than those isolated during on-pump surgery. METHODS AND RESULTS: Plasmas were sampled from patients before (TO), just after (TI) and 24 hours after (T2) cardiac surgery (n=24 on-pump and n=10 off-pump). Rings of rat thoracic aortas were incubated for 20 hours with these different plasmas (100 microl + 4 ml medium) or saline (control). Thereafter, superoxide anion production was assessed by chemiluminescence and the mean signal was expressed as percent of that in the control ring. In rat aorta exposed to plasmas from on-pump CABG patients (n=6), the signal was enhanced by 210 +/- 29% at T1 (P < 0.05) and by 174 +/- 29% at T2 (P < 0.05) versus 53 +/- 12% at T0. Moreover, at T1 and T2, there was an upregulation of p22(phox), the key subunit of NADPH oxidase, the main enzyme involved in oxidative stress of the vascular wall. In contrast, off-pump plasmas did not induce this superoxide production. Incubation with microparticles obtained by ultracentrifugation also markedly enhanced the signal at T1 and T2 (vs. T0) in the on-pump group (but not in the off-pump group). Selective removal of CD34, CD105, CD59, CD146, CD42 microparticles using flow cytometry did not abolish the signal. CRP and SAA plasma levels were enhanced only at T2 in both groups. CONCLUSIONS: Plasmas isolated after on-pump but not off-pump coronary bypass surgery can induce superoxide generation by the vascular wall which seems related to circulating microparticles remaining present at least 24 hours after the procedure that might be of endothelial origin.

Ghrelin interacts with human plasma lipoproteins.

Ghrelin, a peptide hormone produced predominantly by the stomach, stimulates food intake and GH secretion. The Ser(3) residue of ghrelin is mainly modified by a n-octanoic acid. In the human bloodstream, ghrelin circulates in two forms: octanoylated and desacylated. We previously demonstrated that ghrelin is desoctanoylated in human serum by butyrylcholinesterase (EC 3.1.1.8) and other esterase(s), whereas in rat serum, only carboxylesterase (EC 3.1.1.1) is involved. The aims of this study were to determine the role of lipoprotein-associated enzymes in ghrelin desoctanoylation and the role of lipoproteins in the transport of circulating ghrelin. Our results show that ghrelin desoctanoylation mostly occurred in contact with low-density lipoproteins (LDLs) and lipoprotein-poor plasma subfractions. Butyrylcholinesterase and platelet-activating factor acetylhydrolase (EC 3.1.1.47) were responsible for the ghrelin hydrolytic activity of the lipoprotein-poor plasma and LDL subfractions, respectively. Moreover, we observed that ghrelin is associated with triglyceride-rich lipoproteins (TRLs), high-density lipoproteins (HDLs), very high-density lipoproteins (VHDLs), and to some extent LDLs. In conclusion, we report that the presence of the acyl group is necessary for ghrelin interaction with TRLs and LDLs but not HDLs and VHDLs. Ghrelin interacts via its N- and C-terminal parts with HDLs and VHDLs. This suggests that, whereas TRLs mostly transport acylated ghrelin, HDLs and VHDLs transport both ghrelin and des-acyl ghrelin.

Vitamin E: absorption, plasma transport and cell uptake.

PURPOSE OF REVIEW: Large-scale clinical trials have failed to demonstrate a benefit for vitamin E supplementation in cardiovascular prevention. This contrasts with previous epidemiological studies indicating that individuals with high vitamin E status benefit from protection against chronic illnesses, including cardiovascular diseases. These conflicting results suggest that the metabolism of supplemental versus naturally delivered vitamin E and their potential roles, other than a potent antioxidant action, are not fully understood. The purpose of this review is to provide an update on current knowledge on the intestinal absorption of vitamin E, its plasma transport and its supply to cells. The review will also discuss the intravascular metabolism of intravenously delivered vitamin E. RECENT FINDINGS: Although the luminal digestion of vitamin E is fairly well understood, several pathways regulating net vitamin E absorption remain to be elucidated. In several cell types, cholesterol and vitamin E share common mechanisms for cellular uptake (scavenger receptor B type I and LDL receptors) and efflux (ABCA1 transporters). The role of specific binding proteins in alpha-tocopherol intracellular trafficking is increasingly being understood, leading to new insights into the non-antioxidant functions of vitamin E. SUMMARY: Substantial progress has been made in characterizing the plasma transport of vitamin E and its delivery to cells. Mechanisms regulating the balance between the cellular uptake and efflux of vitamin E are under investigation. Vitamin E is not only an antioxidant but may also modulate pathways of cell signalling and gene expression. The translation of this new knowledge into clinical studies will help define future indications for vitamin E supplementation.