Effects of dietary n-3 polyunsaturated fatty acids on phospholipid composition and calcium transport in mouse cardiac sarcoplasmic reticulum

Sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity during the transition to endothermy in an altricial bird

Sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) is a transmembrane pump critical to muscle calcium cycling during contraction, and SERCA has also been proposed as the basis for a non-shivering thermogenesis mechanism in birds. Despite its potential importance to both shivering and non-shivering thermogenesis, the activity of this transporter has rarely been studied in altricial birds, and never during the developmental transition from ectothermy to endothermy. Here, we describe SERCA activity in the pectoralis muscle and heart ventricle of red-winged blackbird (Agelaius phoeniceus) nestlings, fledglings and adults. Additionally, using a diet manipulation, we tested the hypothesis that muscle SERCA activity is affected by dietary fatty acid composition, as has been shown in some previous studies. In blackbird hearts, SERCA activity increased throughout development and into adulthood, conspicuously jumping higher just prior to fledging. In pectoralis muscle, SERCA activity increased throughout the nestling period, but then declined after fledging, an effect we attribute to remodeling of the muscle from a primarily heat-generating organ to a primarily force-generating organ. SERCA activity of the pectoralis muscle was correlated with the proportion of linoleic acid in muscle phospholipids when including all ages in the control group. However, in diet-manipulated birds, there was no consistent relationship between SERCA activity and muscle membrane fatty acid composition at any tested age (5-9 days old). It is unclear whether SERCA might be affected by developmental changes in fatty acid composition at younger ages.

Sarcolemmal dependence of cardiac protection and stress-resistance: roles in aged or diseased hearts

Disruption of the sarcolemmal membrane is a defining feature of oncotic death in cardiac ischaemia-reperfusion (I-R), and its molecular makeup not only fundamentally governs this process but also affects multiple determinants of both myocardial I-R injury and responsiveness to cardioprotective stimuli. Beyond the influences of membrane lipids on the cytoprotective (and death) receptors intimately embedded within this bilayer, myocardial ionic homeostasis, substrate metabolism, intercellular communication and electrical conduction are all sensitive to sarcolemmal makeup, and critical to outcomes from I-R. As will be outlined in this review, these crucial sarcolemmal dependencies may underlie not only the negative effects of age and common co-morbidities on myocardial ischaemic tolerance but also the on-going challenge of implementing efficacious cardioprotection in patients suffering accidental or surgically induced I-R. We review evidence for the involvement of sarcolemmal makeup changes in the impairment of stress-resistance and cardioprotection observed with ageing and highly prevalent co-morbid conditions including diabetes and hypercholesterolaemia. A greater understanding of membrane changes with age/disease, and the inter-dependences of ischaemic tolerance and cardioprotection on sarcolemmal makeup, can facilitate the development of strategies to preserve membrane integrity and cell viability, and advance the challenging goal of implementing efficacious 'cardioprotection' in clinically relevant patient cohorts. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Calcium and phosphorus bioavailability in rats consuming oil from either raw sardines or sardines fried in olive oil Biodisponibilidad de calcio y fósforo en ratas alimentadas con grasa de sardina cruda o frita con aceite de oliva

Three diets were prepared containing 8% olive oil (OO), fresh sardine ( Clupea pilchardus) oil (SO), and oil from sardines fried in olive oil (FSO), respectively. After in vitro digestion, soluble (dialyzed and nondialyzed) and insoluble Ca and P fractions were determined. In vitro Ca availability tended to be higher with SO, and even more so with FSO, than with OO, while that of P increased only slightly with FSO. Growing rats consumed the diets for 28 days. Food intake and body weight increased with FSO more than with OO, but decreased markedly with SO, due to an imbalance in the n-3/n-6 fatty acid ratio. Absorption efficiencies of Ca and P were higher with SO than with the other diets during days 5-12. Because urinary Ca excretion was also greater with SO, apparent retention of both Ca and P was lower with this diet. With SO, carcass content of Ca and P was low but their concentrations were high. Apparent retention of these minerals and their carcass content were similar or higher with FSO than with OO. Therefore, although availability of Ca and P from raw and fried sardine oil diets was sufficient in vitro, consumption of raw sardine oil as the only dietary fat produced changes in calcium and phosphorus bioavailability, an effect of sardine oil which disappeared after frying in olive oil.

Dietary docosahexaenoic acid supplementation reduces SERCA Ca2+ transport efficiency in rat skeletal muscle

Docosahexaenoic acid (DHA) can reduce the efficiency and increase the energy consumption of Na(+)/K(+)-ATPase pump and mitochondrial electron transport chain by promoting Na(+) and H(+) membrane permeability, respectively. In skeletal muscle, the sarco(endo) plasmic reticulum Ca(2+)-ATPase (SERCA) pumps are major contributors to resting metabolic rate. Whether DHA can affect SERCA efficiency remains unknown. Here, we examined the hypothesis that dietary supplementation with DHA would reduce Ca(2+) transport efficiency of the SERCA pumps in skeletal muscle. Total lipids were extracted from enriched sarcoplasmic reticulum (SR) membranes that were isolated from red vastus lateralis skeletal muscles of rats that were either fed a standard chow diet supplemented with soybean oil or supplemented with DHA for 8 weeks. The fatty acid composition of total SR membrane lipids and the major phospholipid species were determined using electrospray ionization mass spectrometry (ESI-MS). After 8 weeks of DHA supplementation, total SR DHA content was significantly elevated (control, 4.1 ± 1.0% vs. DHA, 9.9 ± 1.7%; weight percent of total fatty acids) while total arachidonic acid was reduced (control, 13.5 ± 0.4% vs. DHA-fed, 9.4 ± 0.2). Similar changes in these fatty acids were observed in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, altogether indicating successful incorporation of DHA into the SR membranes post-diet. As hypothesized, DHA supplementation reduced SERCA Ca(2+) transport efficiency (control, 0.018 ± 0.0002 vs. DHA-fed, 0.014 ± 0.0009) possibly through enhanced SR Ca(2+) permeability (ionophore ratio: control, 2.8 ± 0.2 vs. DHA-fed, 2.2 ± 0.3). Collectively, our results suggest that DHA may promote skeletal muscle-based metabolism and thermogenesis through its influence on SERCA.

Dietary lipid quality and mitochondrial membrane composition in trout: responses of membrane enzymes and oxidative capacities

To examine whether membrane fatty acid (FA) composition has a greater impact upon specific components of oxidative phosphorylation or on overall properties of muscle mitochondria, rainbow trout (Oncorhynchus mykiss) were fed two diets differing only in FA composition. Diet 1 was enriched in 18:1n-9 and 18:2n-6 while Diet 2 was enriched in 22:6n-3. The FA composition of mitochondrial phospholipids was strongly affected by diet. 22:6n-3 levels were twice as high (49%) in mitochondrial phospholipids of fish fed Diet 2 than in those fed Diet 1. 18:2n-6 content of the phospholipids also followed the diets, whereas 18:1n-9 changed little. All n-6 FA, most notably 22:5n-6, were significantly higher in fish fed Diet 1. Nonetheless, total saturated FA, total monounsaturated FA and total polyunsaturated FA in mitochondrial phospholipids varied little. Despite a marked impact of diet on specific FA levels in mitochondrial phospholipids, only non-phosphorylating (state 4) rates were higher in fish fed Diet 2. Phosphorylating rates (state 3), oxygen consumption due to flux through the electron transport chain complexes as well as the corresponding spectrophotometric activities did not differ with diet. Body mass affected state 4 rates and cytochrome c oxidase and F 0 F 1 ATPase activities while complex I showed a diet-specific effect of body mass. Only the minor FA that were affected by body mass were correlated with functional properties. The regulated incorporation of dietary FA into phospholipids seems to allow fish to maintain critical membrane functions even when the lipid quality of their diets varies considerably, as is likely in their natural environment.

Dietary (n-6 : n-3) fatty acids alter plasma and tissue fatty acid composition in pregnant Sprague Dawley rats

The objective of this paper is to study the effects of varying dietary levels of n-6 : n-3 fatty acid ratio on plasma and tissue fatty acid composition in rat. The treatment groups included control rats fed chow diet only, rats fed 50% soybean oil (SBO): 50% cod liver oil (CLO) (1 : 1), 84% SBO: 16% CLO (6 : 1), 96% SBO: 4% CLO (30 : 1). Blood samples were taken at day 15 of pregnancy, and the plasma and tissue were analyzed for fatty acid profile. The n-3 PUFA in plasma of Diet 1 : 1 group was significantly higher than the other diet groups, while the total n-6 PUFA in plasma was significantly higher in Diet 30 : 1 group as compared to the control and Diet 1 : 1 groups. The Diet 1 : 1 group showed significantly greater percentages of total n-3 PUFA and docosahexaenoic acid in adipose and liver tissue, and this clearly reflected the contribution of n-3 fatty acids from CLO. The total n-6 PUFA, linoleic acid, and arachidonic acid were significantly difference in Diet 30 : 1 as compared to Diet 1 : 1 and control group. These results demonstrated that the dietary ratio of n-6 : n-3 fatty acid ratio significantly affected plasma and tissue fatty acids profile in pregnant rat.

Polyunsaturated dietary fats change the properties of calcium sparks in adult rat atrial myocytes

This study investigated the effects of dietary omega-3 polyunsaturated fatty acids on calcium handling mechanisms in cardiac myocytes, with the hypothesis that this effect underlies some of the antiarrhythmic properties of these compounds. Adult male Sprague Dawley rats had their standard chow supplemented with either lard (57% saturated and 40% monounsaturated fat), canola oil (60% monounsaturated, 33% polyunsaturated) or fish oil (78% polyunsaturated). Isolated cardiac atrial myocytes from these animals were loaded with fluo-3AM and examined with laser scanning confocal microscopy. The dietary interventions resulted in considerable changes in the membrane phospholipid composition of cardiac cell membranes, particularly the ratio of n-6 to n-3 (2.17 with lard supplement and 1.28 with fish oil supplement). Calcium sparks in myocytes from rats which received saturated fat were significantly more prolonged than those from rats which received fish oil. (Lard = 105.4 +/- 18.9 ms; Fish oil = 43.5 +/- 4.7 ms: mean +/- s.e.m). The results for canola oil were intermediate (56.4 +/- 9.0 ms). The prolongation of the sparks in rats fed lard was primarily due to a higher proportion of sparks with long plateaus and/or slowed kinetics in this group. The frequency of sparks was not significantly different in cells from any group. We conclude that calcium handling mechanisms in rat atrial myocytes are affected by inclusion of different fats in the diet, correlated with changes in the cell membrane phospholipid composition, and speculate that this may underlie some of the antiarrhythmic properties of these dietary compounds.

Dietary alpha-linolenic acid increases the biosynthesis of the choline glycerophospholipids from [14C]CDPcholine in rat liver and kidney but not in brain

The effect of feeding rats for 30 days with diets containing high levels of linoleic acid (sunflower oil, SO) or alpha-linolenic acid (perilla oil, PO) was studied in the liver, kidney and brain. The PO group showed a higher labeling of choline glycerophospholipids (CGP) in liver and kidney but no difference with the SO group in ethanolamine glycerophospholipids (EGP) labeling. The brain displayed the lowest incorporation of both precursors and no difference between the two diets. Analyses of brain CGP and EGP fatty acid composition showed that in the PO group the ratio n-6/n-3 was lower than in the SO group, mainly as a consequence of lower levels of n-6 fatty acids. The mole % of docosahexaenoate (DHA) in these lipids was the same for both groups and only triacylglycerols (TAG) displayed a higher DHA. Therefore, at least in the brain, the magnitude of fatty acid changes observed in CGP and EGP for the PO group does not affect the uptake/incorporation of the precursors into phospholipids.

Inotropic response of rat heart papillary muscle to alpha 1- and beta-adrenoceptor stimulation in relation to dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) and age

The effect of dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) and age on inotropic responses of heart papillary muscle to alpha 1-or beta-adrenoceptor stimulation was examined in young (4 months), middle-aged (12 months) and senescent (27 months) male Wistar rats. From the age of two months the rats were fed a diet containing 2% or 12% of fat by weight varying in PUFA type: a) standard low-fat n-6 PUFA diet, b) high-fat n-6 PUFA diet or c) high-fat n-3 PUFA diet. The inotropic responses to alpha 1-adrenoceptor stimulation with phenylephrine were triphasic (positive, negative, then positive). Young, high-fat n-3 PUFA-fed rats exhibited significantly lower negative and higher positive responses to phenylephrine stimulation, and higher positive responses to isoprenaline stimulation than young, high-fat n-6 PUFA-fed rats. On the other hand, no such dietary-related difference was found between young rats fed a high-fat n-3 PUFA diet and a standard low-fat n-6 PUFA diet. The young high-fat n-6 PUFA-fed rats exhibited inotropic responses similar to those of the middle-aged and senescent rats within the three dietary groups. The time to peak force and the time of half relaxation did not differ within dietary and age groups. The findings indicate that dietary n-6 PUFA-rich supplementation at a young age induces changes resembling the effects of age, as evidenced by decreasing cardiac responses to adrenoceptor agonists, such as phenylephrine or isoprenaline.

Biosynthesis of docosahexaenoic acid in human cells: evidence that two different delta 6-desaturase activities may exist

It has been proposed that synthesis of docosahexaenoic acid (22:6(n-3) in rat hepatocytes occurs by a route independent of delta 4-desaturase, which involves delta 6-desaturation and retroconversion (Voss A., Reinhart M., Sankarappa S. and Sprecher H. (1991) J. Biol. Chem. 266, 19995-20000). However, most cells exhibit these enzymatic activities and nevertheless synthesize low to undectectable amounts of 22:6(n-3). Moreover, there are few data on the occurrence of this pathway in human cells. In the present work, we have analysed the biosynthetic pathway of 22:6(n-3) in human Y-79 retinoblastoma and Jurkat T-cells. Y-79 cells were supplemented with 18:3(n-3) and 20:5(n-3) or incubated with [1-14C]18:3(n-3) and [1-14C]20:5(n-3) and lipids analysed by argentation TLC, reverse-phase TLC and GLC-mass spectrometry. Pulse-chase experiments revealed that synthesis of 22:6(n-3) from 20:5(n-3) in Y-79 cells occurred through two successive elongations, followed by a delta 6-desaturation of 24:5(n-3) to 24:6(n-3) and retroconversion to 22:6(n-3). Incubation of Y-79 cells with [1-14C]18:3(n-3) in medium containing 50 microM trans-9,12-18:2, a potent inhibitor of delta 6-desaturase, caused a reduction of 22:6(n-3) synthesis mainly by interfering with the desaturation of 18:3(n-3). However, when [1-14C]20:5(n-3) was used as precursor, synthesis of 22:6(n-3) was depressed to a lesser extent and mainly by reduction of 24:6(n-3) retroconversion. Neuronal differentiation of Y-79 cells caused a great increase in delta 6-desaturase activity on 18:3(n-3), though the amount of 22:6(n-3) synthesized did not change or diminish, suggesting the existence of a particular delta 6-desaturase involved in the synthesis of 22:6(n-3). The existence of a distinctive delta 6-desaturase activity could also explain why Jurkat cells growing in serum-free medium showed a near 3-fold increase in the synthesis of pentaenes from 18:3(n-3) and, at the same time, a large decrease in the synthesis of 22:6(n-3). The verification of the involvement of two delta 6-desaturase activities in 22:6(n-3) synthesis would have important implications for the formulation of the nutritional requirements of this fatty acid during development.

Oleic acid supplementation reduces oxidant-mediated dysfunction of cultured porcine pulmonary artery endothelial cells

We have previously shown that supplementing cultured porcine pulmonary artery endothelial cells (PAEC) with exogenous oleic acid (18:1 omega 9) alters the fatty acid composition of the cells and reduces oxidant-mediated cytotoxicity. Because the mechanisms by which lipid alterations modulate oxidant susceptibility have not been defined, the ability of 18:1 to reduce hydrogen peroxide (H2O2)-mediated PAEC dysfunction was evaluated. PAEC monolayers on polycarbonate filters were incubated for 3 h in maintenance medium supplemented with either 0.1 mM 18.1 in ethanol vehicle (ETOH) or with an equivalent volume of vehicle alone. Twenty-four hours later monolayers were treated for 30 min with 50 or 100 microM H2O2 in Hanks' balanced salt solution (HBSS) or with HBSS alone (nonoxidant control). As a functional index of PAEC monolayer integrity, the permeability of monolayers to albumin was then measured for 3 h. Treatment with 100 microM H2O2 caused cytotoxicity and progressive increases in PAEC monolayer permeability that were attenuated by 18:1 supplementation, whereas 50 microM H2O2 caused only a transient increase in permeability without cytotoxicity. Supplementation with 18:1 also attenuated H2O2-induced reductions in PAEC adenosine triphosphate (ATP) content and disruption of PAEC microfilament architecture. The ATP content of PAEC monolayers was reversibly reduced in the absence of oxidant stress by incubation with glucose-depleted medium containing deoxyglucose and antimycin A. Metabolic inhibitor-induced ATP depletion increased monolayer permeability and altered cytoskeletal architecture, alterations that resolved during recovery of PAEC ATP content. These results demonstrate that ATP depletion plays a critical role in barrier dysfunction and suggests that the ability of 18:1 to reduce oxidant-mediated PAEC dysfunction and injury may relate directly to its ability to preserve PAEC ATP content.

Influence of omega-3 fatty acid treatment on cardiac phospholipid composition and coronary flow of streptozocin-diabetic rats

Cardiac effects of omega-3 fatty acid treatment were studied in streptozocin (STZ)-induced (55 mg/kg intravenously [IV]) diabetic male Wistar rats. Nondiabetic control and STZ-diabetic animals were treated with Promega (0.5 mL/kg/d; Warner-Lambert, Morris Plains, NJ) for a period of 4 weeks beginning 2 weeks after either vehicle or STZ injection. Plasma glucose, triglyceride, and cholesterol concentrations were significantly (P < .05) elevated in diabetic animals; omega-3 fatty acid treatment did not significantly affect these parameters. An isolated working heart preparation was used to determine aortic and coronary flow rates in control, diabetic, treated control, and treated diabetic animals. Aortic and coronary flow rates of untreated STZ-diabetic rats were significantly (P < .05) lower than those of controls over a range of left atrial filling pressures (7.5 to 20 cm water). Both aortic and coronary flow rates of omega-3 fatty acid-treated diabetic animals were significantly (P < .05) increased above those of untreated diabetic rats. Aortic and coronary flow rates of treated diabetic rats paralleled those of control animals; omega-3 fatty acid treatment did not affect aortic or coronary flow rates of control animals. Cardiac phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and sarcoplasmic reticulum (SR) total phospholipid were isolated and the acyl composition was determined. Stearic acid and C22:4, n-6 were significantly reduced in cardiac PE of diabetic animals. Relative to PE acyl species of untreated nondiabetic controls, treated diabetic PE had increased eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA) and reduced C22:4, n-6 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

The calcium uptake of the rat heart sarcoplasmic reticulum is altered by dietary lipid

Small amounts of dietary n-3 fatty acids can have dramatic physiological effects, including the reduction of plasma triglycerides and an elevation of cellular eicosapentanoic (EPA) and docosahexanoic acids (DHA) at the expense of arachidonic acid (AA). We investigated the effects of alterations in the fatty acid compositions of cardiac sarcoplasmic reticulum (CSR) produced by dietary manipulation on the calcium pump protein that is required for energy dependent calcium transport. CSR was isolated from rats fed menhaden oil, which is rich in n-3 fatty acids, and from control animals that were given corn oil. Relative to control membranes, those isolated from rats fed menhaden oil, had a lower content of saturated phospholipids, an increased DHA/AA ratio, and an increased ratio of n-3 to n-6 fatty acids. These changes were associated with a 30% decrease in oxalate-facilitated, ATP-dependent calcium uptake and concomitant decreased Ca-ATPase activity in the membranes from the animals fed menhaden oil. In contrast, there was no alteration in active pump sites as measured by phosphoenzyme formation. Thus, the CSR Ca-ATPase function can be altered by dietary interventions that change the composition, and possibly structure, of the phospholipid membranes thereby affecting enzyme turnover.

Quantitative fatty acid analyses in cultured porcine pulmonary artery endothelial cells: the combined effects of fatty acid supplementation and oxidant exposure

Supplemental fatty acids can modify the oxidant susceptibility of pulmonary artery endothelial cells (PAEC) in monolayer culture. In addition, in vivo dietary modifications have altered tissue and animal susceptibility to a variety of forms of oxidant stress. These modifications of oxidant injury have been attributed to changes in the numbers of fatty acid double bonds in cell lipids. We tested this hypothesis by incubating porcine PAEC in culture medium supplemented with either 0.1 mM oleic acid (18:1 omega 9) or with an equivalent volume of ethanol vehicle alone (ETOH-0.1%) for 3 h. After supplementation, PAEC were exposed to either oxidant stress, 100 microM hydrogen peroxide (H2O2) in Hanks' balanced salt solution (HBSS), or to control condition, HBSS alone, for 30 min. Supplemental PAEC were exposed to HBSS or H2O2 either immediately or 24, 48, or 72 h after supplementation. Supplementation with 18:1 protected PAEC from H2O2-induced injury at all time points. The fatty acid composition of PAEC phospholipid (PL), triglyceride (TG), and free fatty acid (FFA) subclasses was determined using thin layer and gas chromatography. The PL fraction contained the majority of PAEC fatty acids, and H2O2 reduced the polyunsaturates in this fraction regardless of supplementation. Supplementation with 18:1 increased the 18:1 content of PAEC PL, TG, and FFA at all time points, modified other fatty acids to a lesser extent, but failed to alter the overall number of fatty acid double bonds at all time points. These results indicate that modification of double bond number does not fully explain the mechanisms by which changes in lipid composition can modulate oxidant injury.

Sarcoplasmic reticulum from rabbit and winter flounder: temperature-dependence of protein conformation and lipid motion

A comparative study of lipids and proteins in sarcoplasmic reticulum (SR) from rabbit and flounder has been undertaken. The protein/phospholipid ratio (w/w) was 3:1 in flounder SR (FSR) and 2.2:1 in rabbit SR (RSR). Both membranes had similar contents of PC (70%) and PI (6%). PE constituted 15% in RSR and 21% in FSR. PS and sphingomyelin were minor components of both SR (less than 4%). There were differences in the unsaturated chains of the total lipid extracts, PC, PE, and PI between FSR and RSR. RSR was high in linoleate and arachidonate while FSR contained substantial amounts of eicosapentaenoate and docosahexaenoate. FTIR spectroscopy revealed that the lipids of both membranes did not undergo a phase transition between 0 and 50 degrees C. The lipids were in the liquid-crystalline state at physiological temperatures and underwent monotonic increases in conformational disorder as the temperature was raised. CD spectra indicated higher content of alpha-helical structure of proteins in RSR than in FSR. Increasing temperature caused diminution of alpha-helix content. Relatively large decreases in ellipticity were observed between 20 degrees C and 40 degrees C for FSR and 30 degrees C and 60 degrees C for RSR. Measurements of intrinsic tryptophan fluorescence as a function of temperature gave similar results for membrane proteins in both FSR and RSR. The rate of change of tryptophan fluorescence and fluorescence lifetimes was constant over the temperature ranges studied, and no abrupt shifts in fluorescence occurred in the temperature regions where ellipticity decreased rapidly.

Fatty acid profiles of brain phospholipid subclasses of rats fed n − 3 polyunsaturated fatty acids of marine or vegetable origin. A two generation study

The effects of dietary n - 3 polyunsaturated fatty acids (PUFA) on fatty acid profiles of rat brain phospholipid subclasses as well as on heart phosphatidylethanolamine through two generations were examined: Three groups of rats were fed 20 weight% fat diets in which approx. 30% of the fatty acids were polyunsaturated, either 17% linoleic acid + 13% C20(-) + C22 polyunsaturates from fish oil or 17% linoleic + 13% alpha-linolenic acid from linseed oil or 30% linoleic acid. The rats of the two generations were killed as adults at 18 weeks of age. The results demonstrated that fish oil was a better source than alpha-linolenic acid for incorporation of n - 3 PUFA into the examined phospholipids. This was seen both in brain and heart tissue and in both generations of rats. In the brain phosphatidylethanolamine (PE) and phosphatidylserine (PS) similar fatty acid profiles were found in 1st and 2nd generation, but fish oil was more efficient than 18:3(n - 3) in increasing the levels of 22:6(n - 3), 20:5(n - 3), 22:5(n - 3) and reducing 20:4(n - 6) and 22:5(n - 6). Fatty acid profiles of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) were affected by dietary fats. In PIP and PIP2 of 2nd generation rats 20:4(n - 6) was reduced from 36 to 29% following fish oil intake, whereas alpha-linolenic acid had no effects. The cholesterol/phospholipid ratio was not affected in the brain, neither was the degree of unsaturation of the phospholipids. In heart PE the highest levels of 20:5(n - 3)(2%) and 22:6(n - 3) (36%) were observed following fish oil intake. However, in rats fed alpha-linolenic acid a considerable increase in the level of 22:6(n - 3) was observed from the 1st (21%) to the 2nd generation (26%).

Effect of maternal dietary fats with variable n-3/n-6 ratios on tissue fatty acid composition in suckling mice

This report examines the distribution of n-3 and n-6 fatty acids in heart, kidney and liver phosphatidylcholine and phosphatidylethanolamine of suckling mice from dams fed a fat-supplemented diet with variable n-3/n-6 ratios. After conception and throughout the pregnancy and lactation period, dams were fed a fat-free liquid diet supplemented with 20% by energy of oil mixtures (fish oil concentrate, rich in 20:5n-3 and 22:6n-3, and safflower oil concentrate, rich in 18:2n-6). The diets contained similar amounts of combined n-3 and n-6 fatty acids but variable ratios of n-3 to n-6 fatty acids (0, 0.25, 0.5, 1, 2 and 4). In 12-day-old suckling mice, as the n-3/n-6 ratio in the maternal diet increased (up to approx. 0.5), the tissue levels of 20:5n-3, 22:5n-3 and 22:6n-3 increased, whereas those of 18:2n-6 and 20:4n-6 decreased. The responses were similar in both phospholipid subclasses, but varied between different tissues. Generally, the n-3/n-6 ratios were significantly greater in pup tissues than in milk fat, indicating preferential incorporation of n-3 over n-6 fatty acids into phospholipids during growth. However, the incorporation of n-3 fatty acids in pups was significantly suppressed whereas that of n-6 fatty acids was increased when 18:2n-6 was replaced by its delta 6-desaturation product, 18:3n-6 (concentrated from evening primrose oil), as the source of n-6 fatty acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of increasing the level of omega-3 fatty acids on rat skeletal muscle sarcoplasmic reticulum

The effect of dietary supplementation with fish oil as compared to corn oil on the lipid dynamics and calcium ATPase activity of rat skeletal sarcoplasmic reticulum was examined. After four-week supplementation with fish oil, the levels of eicosapentaenoic (20:5 omega 3), docosapentaenoic (22:5 omega 3) and docosahexaenoic (22:6 omega 3) acids in the total lipids were 5.3, 5.5 and 28.1% of the total fatty acids, respectively. In contrast, with corn oil only 22:6 was found (8.9%). The level of these fatty acids in phosphatidylethanolamine from the membranes of animals fed fish oil was 4.2 (20:5), 5.4 (22:5) and 49.1% (22:6); and for phosphatidylcholine it was 5.4 (20:5), 4.6 (22:5) and 17.4% (22:6). Again, in corn oil fed animals, only 22:6 was found in appreciable amounts, namely 28.3% in phosphatidylethanolamine and 1.8% in phosphatidylcholine. The steady state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to assess lipid order and was found to be only slightly less for membranes from animals supplemented with fish oil (0.120) as compared to those supplemented with corn oil (0.124). The calcium ATPase was found to be unaffected by supplementation consistent with the observed modest changes in lipid order as well as with suggestions that the enzyme is relatively insensitive to the level of unsaturation. It could be argued that if large increases in fatty acyl polyunsaturation in mammalian cell membranes would lead to marked alterations in bulk membrane lipid motional properties, this may not be in the interest of preserving physiological function.(ABSTRACT TRUNCATED AT 250 WORDS)

Phospholipase A activity of cultured rat ventricular myocyte is affected by the nature of cellular polyunsaturated fatty acids

Fatty acid composition of membrane phospholipids of cultured cardiomyocytes can be modified by the type of polyunsaturated fatty acids (n-3 or n-6 PUFA) constituting the culture medium. In this study, we investigated the effect of fatty acid modification on the activities of the key enzymes involved in the deacylation-reacylation cycle of membrane phospholipids. Results showed that cardiomyocytes grown in the presence of n-6 PUFA exhibited a higher specific alkaline phospholipase A (mainly A2) activity (+34%) and a moderately lower lysophospholipase activity (-17%) than when incubated with n-3 PUFA. AcylCoA:lysophosphatidylcholine acyltransferase, acid lysosomal phospholipase A1 and acylCoA synthetase activities were not significantly altered by changes in cellular PUFA composition. It was demonstrated that the differences between phospholipase A activities of the two types of cultured cells were linked neither to a differential leakage of enzyme nor to oxidative injury to the enzyme through blockage of essential sulfhydryl groups. One likely explanation is that the PUFA-induced changes in membrane composition alter membrane physical properties which, in turn, affect membrane-bound phospholipase A activity. Possible beneficial effects of the n-3 PUFA-induced changes on membrane stability are discussed.