Effects of dietary restriction on age-related changes in the phospholipid fatty acid composition of various rat tissues

BACKGROUND AND AIMS: Polyunsaturated fatty acids (PUFAs) are essential components of the cell lipid bilayer and are involved in membrane fluidity and normal functioning, but they are vulnerable to free radical attack. Given the role of oxidative stress in the aging process, age-related changes in phospholipid fatty acid (PLFA) composition in rat liver, kidney and heart were assessed in 3-, 12- and 24-month-old rats fed either ad libitum but only every other day, or daily but only 60% of the quantity normally consumed by age-matched controls. METHODS: Lipids were extracted and phospholipids (PLs) were separated using the solid phase extraction technique, then transesterified and assayed by gas-liquid chromatography. RESULTS: Saturated fatty acids (FAs) did not change significantly with age; mono- and bi-unsaturated FAs decreased in the liver and heart, and the ratio of the former to the latter increased in the liver, kidney and heart. PUFAs increased in the liver and heart. As regards individual FAs, 20:1(n-9) decreased in all organs, 14:1 and 18:1(n-7) increased in the kidney and heart, 18:1(n-9) increased in the kidney, 20:2(n-6), 18:2(n-6) and 22:5(n-3) decreased in the liver and heart, 20:3(n-6) decreased in the kidney and increased in the heart. The most abundant PUFAs, 20:4(n-6) and 22:6(n-3), either remained the same or increased with age. The N-9 family increased in the kidney, the N-7 family increased in the kidney and heart, the N-6 family decreased in all three organs, and the N-3 family increased in the liver and kidney. Dietary restriction (DR) significantly counteracted most of these changes, but changes in some FAs [20:2(n-6) in the heart] were magnified by DR and may not be age-related. CONCLUSIONS: Most age-related changes (that occurred in the rat liver, kidney and heart and were counteracted by the two different types of DR) may be involved in the mechanism of aging.     

Rat brain fatty acid composition: effect of dietary fat and age.

The polyunsaturated fatty acid composition of human brain changes, as well as progressively decreases, with age. To determine if whole brain rat lipid shows similar changes with age, rats born to mothers fed semi-synthetic diets were raised on the same diet as their mothers for varying periods prior to sacrifice. Whole brain lipid composition was determined for female offspring, fed diets containing 20% w (by weight) of either lard or safflower oil, from age 6 days to 730 days. The percentage of 20:4omega6 and 22:6omega6 decreased with age; as in man these changes were compensated for largely by increases in 18:1omega9. In contrast, 22:6omega3 rose gradually from 6 to 730 days of age. Varying the degree of unsaturation and/or the amount of dietary fat, with the exception of lard, did not influence the fatty acid composition of whole brain lipid or of the two major phospholipids, phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC). Lard was found to contain trace amounts of 22:5omega3; this acid was avidly retained in the brain accompanied by corresponding decreases in 22:5omega6. The functional significance of the observed age-related brain lipid changes is unknown; it is likely that the lipid changes are in some way related to the deterioration of the central nervous system with time.     

Intermediates of unsaturated fatty acid oxidation are incorporated in triglycerides but not in phospholipids in tissues from patients with mitochondrial beta-oxidation defects

The fatty acid composition was determined of liver, skeletal muscle and heart obtained post mortem from patients with medium-chain acyl-CoA dehydrogenase deficiency (MCADD), multiple acyl-CoA dehydrogenase deficiency (MADD) and very long-chain acyl-CoA dehydrogenase deficiency (VLCADD). Increased amounts of 4-decenoic acid 10:1(n–6), 5-dodecenoic acid 12:1(n–7), 5-tetradecenoic acid 14:1(n–9), 5,8-tetradecadienoic acid 14:2(n–6) and 7,10-hexadecadienoic acid 16:2(n–6)—intermediates of unsaturated fatty acid oxidation—were found. Fractionation into different lipid classes showed that these fatty acids were exclusively present in the triglyceride fraction. They could not be detected in the free fatty acid fraction or in the phospholipid fraction. Our results suggest that intermediates of unsaturated fatty acid oxidation that accumulate as a consequence of MCADD, MADD and VLCADD are transported to the endoplasmic reticulum for esterification into neutral glycerolipids. The pattern of accumulation is characteristic for each disease, which makes fatty acid analysis of total lipid of post-mortem tissues a useful tool in the detection of mitochondrial fatty acid oxidation defects in patients who died unexpected, for example with sudden infant death syndrome.     

Effect of ethanol on liver triglycerides and fatty acid composition in the golden Syrian hamster

In choice situations, the golden Syrian hamster shows a strong preference to drink an ethanol solution to water alone. Because of the known effects of ethanol on lipid metabolism, its effects on liver fatty acids were therefore studied in the hamster. After a period of 8 weeks during which hamsters had consumed water containing 10% ethanol (4 weeks) and then 15% ethanol (4 weeks), the liver was significantly increased in weight, an effect which was shown to be due to fat accumulation as triglyceride. The fatty acid composition of the liver triglycerides and phospholipids was altered such that monounsaturated fatty acids were very significantly increased and both n-6 and n-3 essential fatty acids were proportionally decreased.     

Fatty acid composition of liver triglycerides in various stages of fat deposition in the parenchyma

Summary In 30 diabetic inpatients the fatty acid pattern of triglycerides in parenchymal liver cells was studied by gas-liquid chromatography. With increasing size of fat droplets, a significant increase in the proportion of palmitic and oleic acid was observed as well as a significant fall of arachidonic (C 20: 4) and eicosapentaenoic acid (C 20: 5).     

Metabolic changes in the tissues of young and old mice. Oxygen consumption with different substrates

Oxidation of malate, glutamate and arginine by the kidney cortex, brain and heart of 17- and 70-week-old mice were studied manometrically. A higher rate of oxidation of malate in all the three tissues was observed indicating an apparent increase in the activity of malic dehydrogenase in old age. The increased rate of oxidation of glutamate in kidney cortex also shows an increase in the activity of glutamic dehydrogenase in this tissue. There was no noticeable change in the oxidation of glutamate by the brain of young and old mice.     

Energy restriction dilutes the changes related to dietary fat type in membrane phospholipid fatty acid composition in rats

To investigate liver cell membrane phospholipid (PL) fatty acid (FA) composition in response to the consumption of different types of dietary fat and graded levels of energy intake, rats were fed for 10 weeks on a diet containing either fish oil, safflower oil, or beef tallow. Within each dietary fat group, subgroups were either provided free access to food or energy-restricted to 85% or 70% of the ad libitum intake by reducing the dietary carbohydrate content while keeping other macronutrient intakes constant. Higher (P < .05) proportions of docosahexaenoic acid, linoleic acid, and monounsaturated FA were observed in the membrane PL of the fish oil, safflower oil, and beef tallow groups, respectively, resembling the FA composition in the diets. However, such modifications of dietary FA composition in, membrane PL FA were influenced by body energy status. The higher docosahexaenoic acid and total n-3 FA content in phosphatidylcholine (PC), sphingomyelin (SPH), and phosphatidylserine (PS) of the ad libitum fish oil group compared with the other dietary groups no longer existed when energy supply was restricted. Therefore, reducing energy intake tended to dilute the changes of membrane PL FA composition occurring as a function of dietary FA composition. These data suggest that the influence of dietary fat type on cellular structure and perhaps function becomes increasingly important with progressively positive energy balance.     

Comparative effects of feeding different fats on fatty acid composition of major individual phospholipids of rat hearts

Comparative effects of feeding dietary linoleic (corn oil), oleic (olive oil), alpha-linolenic (soybean oil) and polyunsaturated fatty acids (fish oil) on lipid content and fatty acid composition of major individual phospholipids of rat hearts were examined. Feeding different diets did not result in lipid accumulation in the heart. Total triglyceride, nonesterified fatty acid, cholesteryl ester and phospholipid levels of heart tissue were not affected by the type of dietary fatty acid. However, heart free cholesterol levels decreased in both animals fed the olive and the fish oil diets. The percentage of individual phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and cardiolipin (CL) did not modify by changes in the dietary fat composition. Heart tissue from animals fed on olive oil were enriched with 18:1 (n-9 + n-7) fatty acid in all phospholipid fractions. Animals fed corn oil contained higher proportions of 18:2 (n-6) for PC, PE and CL, and the ingestion of the soybean oil diet increased 18:2 (n-6) for PC and CL in the same proportion as the ingestion of the corn oil diet. The levels of 22:6 (n-3) were increased in the fish oil-fed group, accompanied by both a decrease in total (n-6) fatty acids and an increase in total (n-3) fatty acids in the three phospholipid fractions. The 20:5 (n-3) was only detected in these animals. These results show that olive oil is as effective as fish oil in reducing heart cholesterol content and support earlier works suggesting the role of fish oil in preventing cardiovascular disease.     

The effects of structurally defined triglycerides of differing fatty acid composition on postprandial haemostasis in young,healthy men

The aim of this study was to investigate whether a number of key haemostatic factors were altered when healthy young individuals were challenged with a fat load of physiological size contained within a meal composed of normal ingredients and whether this response was modified when the fatty acid composition of the meal was altered radically. Eight healthy male volunteers each randomly consumed four meals which were identical in terms of gross nutritional content (41% of energy provided as fat, 17% as protein and 42% as carbohydrate) but which differed in fatty acid composition. To reduce the possible influence of fatty acid position within the triglyceride molecule on lipid absorption and subsequent metabolic effects, the structural integrity of 91% of fat (test triglycerides such as 1,3 distearoyl-2-oleoyl glycerol (S-O-S), trioleine (O-O-O), and 1,3 dilinoleoyl-2-oleoyl glycerol, (L-O-L)) in the meals was controlled so that the principal fatty acid in the sn-2 position was oleic acid (18:1n-9). Meals rich in either a test triglyceride or a control oil provided 44±6 g of fat. No significant alterations from fasted values of elevated plasma factor VII coagulant activity (FVII_c) or F₁₊₂ were observed. FVII_a varied significantly over the postprandial time course; however, when expressed as a percentage of the fasting value, the FVII_a responses to O-O-O and L-O-L differed significantly but this was not evident when the absolute values were analysed. Similarly, no difference in plasma fibrinopeptide A (FPA) concentrations were evident. After all four meals, chylomicron contained proportionately more palmitic acid and generally less oleic acid than the ingested lipids. This study clearly demonstrates that postprandial haemostatic responses of young healthy individuals to a physiological fat load are minimal, (irrespective of triglyceride structure).     

Association of fatty acid composition in serum phospholipids with metabolic syndrome and arterial stiffness

Background and aimWe examined the association of fatty acid (FA) composition in serum phospholipids with the features of metabolic syndrome (MetS) and arterial stiffness.MethodsKorean men (n = 593, 30–79yrs) were categorized based on the number of MetS risk factors (RFs) and measured for the markers of MetS, serum phospholipid FA composition and brachial-ankle pulse wave velocity (baPWV), an index for the severity of arterial stiffness.ResultsInsulin resistance (HOMA-IR), baPWV, LDL size, and adiponectin were significantly altered corresponding to the number of MetS RFs. The proportions of total monounsaturated FA, palmitoleic acid (16:1), oleic acid (18:1ω-9) and dihomo-γ-linolenic acid (DGLA, 20:3ω-6) in serum phospholipids, and DGLA/linoleic acid (LA) (20:3ω-6/18:2ω-6), deta9-desaturase activity (D9D-16: 16:1/16:0 and D9D-18: 18:1ω-9/18:0) significantly increased corresponding to the number of MetS RFs, but D5D (20:4ω-6/20:3ω-6) decreased. baPWV positively correlated with HOMA-IR, palmitic acid (16:0), oleic acid, D6D (18:3ω-6/18:2ω-6), DGLA/LA and D9D-18, and negatively with adiponectin, LDL size, LA, docosahexaenoic acid (DHA, 22:6ω-3) and D5D. Multiple stepwise regression models revealed that baPWV was significantly influenced by systolic blood pressure, age, body weight, triglyceride and LA in serum phospholipids (R² = 0.378). Interestingly, baPWV (1419 ± 1 cm/s) and MetS (22%) were highest in individuals with lower proportion of LA (<12.361%) and higher proportion of DGLA (≥1.412%) in serum phospholipid FAs.ConclusionThe features of MetS significantly related to serum phosopholipid FA composition. Particularly, arterial stiffness was associated with LA additively together with DLGA. It may suggest a potential benefit of sufficient amounts of LA in serum or in diet can reduce cardiovascular risk.     

Effect of dietary hydrogenated fish oil on the plasma lipoprotein profile and on the fatty acid composition of different tissues on the rat

Dietary fatty acids are actively incorporated into membrane lipids, and fat intake can modify the composition and the biochemical activity of cellular membranes and the pattern of plasma lipoproteins. Industrial hydrogenation of polyunsaturated oils leads to the formation of isomeric trans fatty acids which are incorporated into cellular membranes when they are present in the diet. The trans fatty acid amount present in hydrogenated oils depends on the degree of hydrogenation, being high for partially hydrogenated oils and low for highly hydrogenated oils. Hydrogenated fish oil is widely used in some countries for the production of margarine and industrial fats. This study compares the fatty acid composition of plasma, erythrocytes, subcutaneous adipose tissue, and hepatic microsomal membranes and the plasma lipoprotein profile after feeding rats with a synthetic diet containing either fish oil, partially hydrogenated fish oil, or highly hydrogenated fish oil. It is observed that the tissue content of monounsaturated fatty acids increases and that the content of polyunsaturated fatty acids decreases after an increase of the degree of hydrogenation of the dietary fat. Tissues from animals fed partially hydrogenated fish oil show significant amounts of trans fatty acids only. The plasma triacylglyceride composition and the lipoprotein profile are also altered by the degree of hydrogenation of the dietary fat. Triacylglycerides decrease after highly hydrogenated fat feeding only. Total cholesterol and low-density lipoprotein cholesterol are significantly increased after partially hydrogenated fat feeding. Although no direct evidence is presented, this effect may be attributable to the high content of trans isomers of this dietary fat which nutritionally may behave as saturated fatty acids.     

The influence of fish oil diet and norepinephrine treatment on fatty acid composition of rat heart phospholipids and the positional fatty acid distribution in phosphatidylethanolamine

Summary The effect of chronic norepinephrine (NE) administration with increasing dosage from 1–4 mg/kg over a period of 2 weeks was studied on cardiac phospholipids and their fatty acid distribution in rats. Animals were fed a control diet or a 10% cod liver oil (CLO)-enriched diet. The relative distribution of various polyunsaturated fatty acids esterified to the 1- and 2-position of the phosphatidylethanolamine fraction was estimated. NE stress during control feeding significantly reduced the total phospholipid content in rat heart. No differences in the phospholipid class distribution were found. However, CLO feeding as well as chronic NE administration resulted in a decrease of 3 fatty fatty acids, mainly C 18:2 6 and C 20:4 6, which was compensated with an increase in 3 fatty acids, mainly C 20:5 3 and C 22:6 3. The changes in fatty acid composition qualitatively agree with those reported by Gudbjarnason et al. (23), except that the mortality in our NE-treated control or CLO-fed groups was considerably lower. It can probably be attributed to a different mode of NE administration. On the other hand, at the end of the CLO feeding period in rats treated with NE or not, comparing with control fed rats without NE treatment, the incidence rate of ST segment elevation in electrocardiogram (ECG) recorded under light diethylether-induced anesthesia was higher. Independent of whether the fatty acid composition of myocardial phospholipids was dietary or pharmacologically manipulated, most of the polyunsaturated fatty acids were found at the 2-position of the phosphatidylethanolamine molecules. The polyunsaturated fatty acids account for 45–50% of the fatty acyl residues and preferentially occupy the 2-position, where they can exchange for each other.     

Micro-techniques for analysis of human adipose tissue fatty acid composition in dietary studies

Background and aimsAdipose tissue (AT) fatty acid (FA) composition is considered to be the gold standard long-term biomarker of dietary fatty acid intake. Typically this measurement is made directly from samples collected via large-needle-biopsy or incision. However, with growing interest in the role of AT in relation to health, ideally the fatty acid composition would be analysed along with other measurements, such as gene expression or histology, on a single AT sample. Here we assess alternative ways of obtaining AT for measuring FA composition, in some cases in conjunction with other measurements.Methods and resultsThe FA composition of tissue obtained via different methods was compared to that of tissue collected via large-needle or surgical biopsy. Fatty acid composition was not significantly different in AT collected by small-needle mini-biopsy (n = 10), from an RNA ‘lipid layer’ (obtained during RNA extraction, 2 sites, n = 6 for each), or from cryosectioned tissue prepared for histology (n = 10). We also assessed the usefulness of the composition of plasma NEFA as a surrogate marker of subcutaneous AT (n = 58–80). Most FAs in plasma NEFA correlated strongly with those in AT (P < 0.05).ConclusionIt is feasible to measure the FA composition of AT on very small amounts of tissue. Additionally, it is possible to measure FA composition on the lipid rich ‘by-product’ of AT samples undergoing RNA extraction for gene expression. Samples sectioned for histology are also suitable. This provides further opportunities for multidisciplinary collaborations that may lead to a better application of dietary biomarkers.