Tracking of serum fatty acid composition: a 6-year follow-up study in Finnish youths.

The composition of fatty acids in serum cholesteryl esters was analyzed with gas chromatography in 759 Finnish boys and girls aged 3-18 years in 1980 and again in the same subjects in 1983 and in 1986. The mean percentage of linoleate (18:2 n-6) increased from 50.85% in 1980 to 52.60% in 1986, while there was a decrease in myristate (14:0), palmitate (16:0), and eicosapentaenoate (20:5 n-3). The percentage of oleate (18:1) did not change. The stability (tracking) of cholesteryl ester fatty acid composition was examined by calculating linear correlation coefficients among the percentages of each fatty acid at the three study points. For linoleate, 3- and 6-year tracking correlations were 0.59-0.61 and 0.50, respectively; they were of about the same magnitude for arachidonate (20:4 n-6) and lower for the other fatty acids. Results indicate that the serum cholesteryl ester fatty acid composition has somewhat lower tracking than the total cholesterol concentration. The changes in the mean fatty acid composition of the study population obviously reflect a shift from saturated to unsaturated dietary fats.     

n-6 Docosapentaenoic acid is not a predictor of low docosahexaenoic acid status in Canadian preschool children

BACKGROUND: The n-3 fatty acid docosahexaenoic acid (DHA; 22:6n-3) is important for neural and visual functional development. In animals, 22:6n-3 deficiency is accompanied by increased docosapentaenoic acid (DPA; 22:5n-6), which suggests that the ratio of 22:6n-3 to 22:5n-6 could be a useful biochemical marker of low n-3 fatty acid status. The n-3 fatty acid status of preschool children has not been described, and data are lacking on whether low 22:6n-3 is accompanied by high 22:5n-6 in humans. OBJECTIVE: We determined n-3 fatty acid status and investigated the relation between 22:6n-3 and 22:5n-6 in children. DESIGN: In Canadian children aged 18-60 mo (n = 84), the n-3 and n-6 fatty acid status of erythrocyte phosphatidylethanolamine was measured, and dietary fat intake was estimated by using a food-frequency questionnaire. RESULTS: The mean (+/- SEM) 22:6n-3 concentration in erythrocyte phosphatidylethanolamine among children was 3.06 +/- 0.13 g/100 g fatty acids (5th-95th percentiles: 1.43-5.79 g/100 g fatty acids). Concentrations of 22:5n-6 increased with increasing 22:6n-3 concentrations in erythrocyte phosphatidylethanolamine (P < 0.01). Mean intakes of linoleic acid (18:2n-6), linolenic acid (18:3n-3), and trans fatty acids were 3.6 +/- 0.2%, 0.7 +/- 0.5%, and 2.0 +/- 1.3%, respectively. Phosphatidylethanolamine 22:6n-3 and 22:5n-3 concentrations were inversely related to the intakes of 18:2n-6 and trans fatty acids, but not to those of total fat or n-3 fatty acids. CONCLUSIONS: The concentration of 22:5n-6 is not a useful biochemical marker of low n-3 fatty acid intake or status in the membrane phosphatidylethanolamine of preschool children. High intakes of 18:2n-6 and trans fatty acids could compromise the incorporation of 22:6n-3 into membrane phospholipids.     

Changes in the maternal essential fatty acid profile during early pregnancy and the relation of the profile to diet

BACKGROUND: Although the pattern of the essential fatty acids (EFAs) changes considerably from week 10 of pregnancy to term, no information is available on changes in EFA concentrations in the early stages of pregnancy. OBJECTIVE: The main objectives were to assess the EFA status, particularly that of 22:6n-3, in women during the first 10 wk of pregnancy and to investigate the relation of EFA status to dietary EFA intake during this period. DESIGN: Healthy women (n = 24) planning to become pregnant were recruited. The fatty acid composition of plasma and erythrocyte phospholipids was determined before and at weeks 4, 6, 8, and 10 of pregnancy. Food intake was assessed at entry into the study and at week 10 of pregnancy by using food-frequency questionnaires. RESULTS: A small but nonsignificant increase in dietary intake of 22:6n-3 was found. The plasma phospholipid content of 22:6n-3 (% by wt) increased continuously during the first 10 wk of pregnancy. At week 10 of pregnancy, the plasma percentages of 16:0, 20:3n-6, and 20:4n-6 had increased significantly, whereas the percentages of the 18-24-carbon saturated fatty acids, 18:2n-6, and the ratio of n-6 to n-3 fatty acids had dropped significantly. The composition of erythrocyte phospholipids showed changes similar to those observed in plasma. CONCLUSIONS: Maternal plasma and erythrocyte phospholipid 22:6n-3 concentrations start to increase in very early pregnancy, which cannot be explained by changes in dietary intake alone. This rise probably represents early maternal adaptations to meet the requirements of highly proliferating and differentiating tissues at this stage of fetal development.     

Essential fatty acids in the nutrition of severely neurologically disabled children

Essential fatty acids (EFA) are important for the normal development and functioning of the brain, retina and immune competent cells. Severely neurologically handicapped children often have feeding difficulties, and the composition of the diet may be critical with respect to an optimal nutrient content. The aim of the present investigation was to evaluate if the dietary intakes and serum phospholipid concentrations of EFA were adequate in a group of severely neurologically impaired children in an institution. To achieve this, a prospective study was done. The investigation showed low dietary intakes of both n-6 fatty acids (FA) and n-3 FA. The serum concentrations of total n-6 FA, linoleic acid and 22:6n-3 (docosahexaenoic acid) as proportions of the total serum phospholipid FA concentration were initially low. The serum concentrations of 20:3n-9 and 22:5n-6 cholesterol, triacylglycerol, total saturated FA, total monounsaturated FA and apolipoproteins A-I and B were high compared with levels in a reference group of healthy children. Following supplementation with fish oil and soyabean oil, the serum lipid profile approached normal. We conclude that the study children had suboptimal intakes of EFA and that elevated serum concentrations of 20:3n-9 and 22:5n6 were useful serological markers of suboptimal EFA status. Recommended dietary allowances for EFA given as a percentage of energy underestimate EFA requirements in children with a low energy intake. Severely disabled children with feeding difficulties should probably be monitored with serum phospholipid FA measurements or calculation of dietary absolute intakes of EFA.     

Effect of cholesterol feeding and sex difference on the tissue n-6 and n-3 fatty acid levels in fat-deficient rats treated with linoleate or linolenate

Weanling rats of both sexes fed on a fat-free diet for 8 weeks were given 5 i.p. Injections every 48 hr of 60 mg/100 g body weight of pure ethyl linoleate (LA) or linolenate (LN) with or without 1% dietary cholesterol supplementation. Phospholipid fatty acid compositions in plasma and liver were examined. LA administration increased n-6 fatty acids while LN treatment increased n-3 fatty acids. Cholesterol feeding significantly reduced 20: 4n-6 in LA treated animals and 20: 5n-3 and 22: 6n-3 in LN treated animals. The reductions in males were significantly greater than in females suggesting that the sex difference modulates the cholesterol-induced reduction of n-6 and n-3 fatty acids.     

Effects of linoleate and arachidonate deficiencies on reproduction and spermatogenesis in the cat

The inability of the cat to convert significant quantities of linoleate [18:2(9,12)] to arachidonate [20:4(5,8,11,14]) in the liver makes the cat a useful model for studying the specific physiological roles of these two fatty acids. In these studies, cats were fed purified diets that were either deficient in essential fatty acids (EFAs) or that provided linoleate with or without arachidonate. Male cats that were fed the EFA-deficient diet for approximately 2 years exhibited extensive degeneration of the testes, and the fatty acid composition of testes changed in a manner consistent with EFA deficiency. Linoleate prevented testis degeneration. Levels of arachidonate, 22:4n6, and 22:5n6 were higher in testis phospholipids of cats supplied with linoleate than in the deficient cats, indicating that the testis of the cat has the capacity to desaturate and elongate linoleate. In contrast, female cats that were fed diets lacking arachidonate were unable to bear live kittens, whether linoleate was provided in the diet or not. Arachidonate, supplied by oral supplements of ethyl arachidonate or by animal fat in the diet, significantly improved reproduction. Thus, linoleate appears to meet the requirements for spermatogenesis in males, but dietary arachidonate is essential for adequate reproduction in female cats.     

Urinary excretion of arginine-vasopressin and prostaglandin E2 in essential fatty acid-deficient rats after oral supplementation with unsaturated fatty acid esters

Essential fatty acid-deficient rats were supplemented with 300 mg/d of pure fatty acid esters: oleate (O), linoleate (L), arachidonate (A), and columbinate (C) for 10 d. The 24-h urine collections from each animal, collected 3 d before supplementations and again the last 3 d of the 10-d supplementation period, were analyzed for volume, and by radioimmunoassay for arginine-vasopressin (AVP) and prostaglandin E2 (PGE2). Linoleate and arachidonate supplements both decreased the initial high urinary AVP excretion, whereas it was further increased by the oleate supplement. There was no effect of columbinate supplementation on urinary AVP excretion. Urinary PGE2 excretion was increased ca. twofold by both linoleate and oleate supplements, increased ca. fivefold by arachidonate supplementation but was unaffected by columbinate supplementation. There was no effect of any of the supplemented fatty acids on urine output. Fatty acid analysis of total kidney lipids revealed a low percentage of 20:3(n-9) in the rats supplemented with (n-6) fatty acid (L, A and C). The triene-tetraene ratio was 1.8 +/- 0.6 (n = 6) in the kidneys of the oleate-supplemented rats. No relationship was found between urinary PGE2 excretion and the percentage of arachidonate or the ratio of 20:3 (n-9)/20:4(n-6) in total kidney lipids. It is suggested that increased urinary AVP excretion in EFA-deficient rats is mainly caused by a change in the renal excretatory mechanism of AVP rather than reflecting an increased plasma AVP concentration. Furthermore it is suggested that renal PGE2 synthesis in vivo is unaffected by high levels of 20:3(n-9) in kidney lipids.     

Both (n-3) and (n-6) fatty acids stimulate wound healing in the rat intestinal epithelial cell line, IEC-6.

The control of proliferation and epithelial restitution are processes that are poorly understood. The effects of (n-3), (n-6) and trans fatty acids on proliferation of subconfluent IEC-6 cultures and restitution of wounded IEC-6 monolayers were investigated. Incorporation of supplemented fatty acids into cellular phospholipid was also assessed. Sulforhodamine B protein dye binding assay was utilized to assess the proliferative effects of fatty acids on growth of IEC-6 cultures. Incorporation of supplemental fatty acids into cellular phospholipid was examined by thin-layer chromatography combined with gas chromatography. The modulation of epithelial restitution was examined by razor blade wounding confluent IEC-6 monolayers grown in media supplemented with various fatty acids. Inhibition of eicosanoid synthesis by indomethacin during the wounding assay was also assessed. Both (n-3) and (n-6) fatty acids significantly inhibited growth of this intestinal epithelial cell model at concentrations above 125 micromol/L. The trans fatty acid, linoelaidate 18:2(n-6)trans, inhibited growth of IEC-6 cells at concentrations above 250 micromol/L. Another trans fatty acid, elaidate 18:1(n-9)trans, was well-tolerated at concentrations as high as 500 micromol/L. Eicosapentanoic 20:5(n-3), linoleic 18:2(n-6), alpha-linolenic 18:3(n-3), gamma-linolenic 18:3(n-6) and arachidonic 20:4(n-6) acids all significantly enhanced cellular migration in the IEC-6 model of wound healing. Eicosapentanoate, linoleate, alpha-linolenate, gamma-linolenate and arachidonate are all capable of improving reconstitution of epithelial integrity following mucosal injury. Inhibition of eicosanoid synthesis reduced the enhancement of restitution by n-6 fatty acids back to control levels.     

Dietary essential fatty acids change the fatty acid profile of rat neural mitochondria over time.

This experiment examined the time course over which the amount of dietary essential fatty acids (EFA) affects brain mitochondrial fatty acids. Weanling rats were fed 20% (wt/wt) fat diets that contained either 4 or 15% (wt/wt of diet) EFA for 1, 2, 3 or 6 wk or a 10% EFA diet for 3 or 6 wk. The EFA ratio [18:2(n-6)/18:3(n-3)] of all diets was approximately 30. Fatty acid analysis of brain mitochondrial phosphatidylethanolamine, phosphatidylcholine and cardiolipin revealed that the largest dietary effect was on 18:2(n-6), which was 30% higher in rats fed the 15 vs. 4% EFA diets after 1 wk. This difference increased to twofold by 3 wk and was still twofold after 6 wk. These results demonstrate several facts: 1) the response of 18:2(n-6) in cardiolipin to dietary EFA is very fast and large, relative to changes in other quantitatively major fatty acids observed in weanling rats; 2) the 18:2(n-6) level in neural cardiolipin stabilizes after 3 wk of feeding at a level dependent upon the amount of dietary EFA; and 3) at least one neural fatty acid, 18:2(n-6), is very sensitive to amounts of dietary EFA that are well above the animal's EFA requirement.     

Long-term efficacy and safety of a new olive oil-based intravenous fat emulsion in pediatric patients: a double-blind randomized study.

BACKGROUND: A new intravenous lipid emulsion (ILE) prepared from a mixture of soybean and olive oils contains only long-chain triacylglycerols, with a low proportion (20%) of polyunsaturated fatty acids and 60% monounsaturated fatty acids. OBJECTIVE: The goal of this randomized, double-blind clinical trial was to assess in children the efficacy and safety of this new ILE compared with a control group receiving a soybean-oil emulsion. DESIGN: Eighteen children received for 2 mo 24% of nonprotein energy (1.80 g kg (-)(1) d(-)(1)) either as the new ILE or a soybean oil-based emulsion. Assessments were performed on days -30, 0, 30, and 60 and the changes (day 60 - day 0) assessed by analysis of variance. RESULTS: There were no significant differences in triacylglycerol, apolipoproteins A-I and B, or HDL cholesterol between the 2 groups, whereas total and LDL cholesterol were higher in the soybean oil group on day 60. The pattern of 20:4n-6 in erythrocyte membranes did not change significantly, nor did the ratio of 20:3n-9 to 20:4n-6. On day 60, 18:1n-9 was significantly higher in the olive oil group, the ratio of Sigma(n)-6 > C(18) + 18:3n-6 to 18:2n-6 was 2.20 +/- 0.09 in the olive oil group and 1.33 +/- 0.16 in the soybean-oil group, and Sigma(n)-3 > C(18) was 3.83 +/- 0.30 in the olive oil group and 4. 03 +/- 0.33 in the soybean-oil group. The peroxidation index was lower after the olive oil treatment. CONCLUSIONS: The olive oil-based emulsion was well tolerated, maintained a normal EFA status, and may be more suitable for prevention of lipid peroxidation than the soybean-oil-based emulsion.     

Influence of fatty acids on cholesterol synthesis of hepatocytes in monolayer culture

The short-term (6-hour) and long-term (72-hour) influences of a wide spectrum of fatty acids on cholesterogenesis in monolayer cultures of rat hepatocytes were studied. A 6-hour addition of 0.5 mmol/liter of oleate to the culture medium raised 3-hydroxy-3-methylglutaryl-CoA reductase [mevalonate:NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34] activity by 62%. Octanoate, palmitate, stearate, linoleate, arachidonate and linolenate did not change enzyme activity significantly under these circumstances. A 72-hour incubation led to a 162% rise of enzyme activity by oleate and a 33% lowering by arachidonate, the other long-chain fatty acids having no significant effect (linoleate, linolenate, palmitate and stearate). These modulations of enzyme activity were paralleled by comparable changes of cholesterogenesis as measured by incorporation of [1-14C]acetate into cholesterol. The results are compatible with the concept that the response of hepatic cholesterogenesis to dietary triglycerides in vivo (observed by earlier investigators) is due to influences of the triglyceride fatty acids on hepatocyte 3-hydroxy-3-methylglutaryl-CoA reductase activity.     

trans Fatty acids in human milk are inversely associated with concentrations of essential all-cis n-6 and n-3 fatty acids and determine trans, but not n-6 and n-3, fatty acids in plasma lipids of breast-fed infants.

BACKGROUND: Human milk fatty acids vary with maternal dietary fat composition. Hydrogenated dietary oils with trans fatty acids may displace cis n-6 and n-3 unsaturated fatty acids or have adverse effects on their metabolism. The effects of milk trans, n-6, and n-3 fatty acids in breast-fed infants are unclear, although n-6 and n-3 fatty acids are important in infant growth and development. OBJECTIVE: We sought to determine the relations between trans and cis unsaturated fatty acids in milk and plasma phospholipids and triacylglycerols of breast-fed infants, and to identify the major maternal dietary sources of trans fatty acids. DESIGN: We collected milk from 103 mothers with exclusively breast-fed 2-mo-old infants, blood from 62 infants, and 3-d dietary records from 21 mothers. RESULTS: Mean (+/-SEM) percentages of trans fatty acids were as follows: milk, 7.1 +/- 0.32%; infants' triacylglycerols, 6.5 +/- 0. 33%; and infants' phospholipids, 3.7 +/- 0.16%. Milk trans fatty acids, alpha-linolenic acid (18:3n-3), arachidonic acid (20:4n-6), docosahexaenoic acid (22:6n-3) (P < 0.001), and linoleic acid (18:2n-6) (P = 0.007) were each related to the same fatty acid in infant plasma phospholipids. Milk trans fatty acids were inversely related to milk 18:2n-6 and 18:3n-3, but not to milk or infant plasma 20:4n-6 or 22:6n-3. trans Fatty acids represented 7.7% of maternal total fat intake (2.5% of total energy); the major dietary sources were bakery products and breads (32%), snacks (14%), fast foods (11%), and margarines and shortenings (11%). CONCLUSIONS: There were comparable concentrations of trans fatty acids in the maternal diet, breast milk, and plasma triacylglycerols of breast-fed infants. Prepared foods were the major dietary source of trans fatty acids.     

Role of linoleate as an essential fatty acid for the cat independent of arachidonate synthesis

To determine the essential fatty acid (EFA) requirements of the cat, specific pathogen-free kittens were fed either a linoleate-deficient diet or one of two diets containing 5% safflower seed oil (SSO) with or without 0.2% tuna oil. The diets were fed for 82-101 weeks beginning at 3 months of age. The results showed that linoleate is an essential fatty acid for the cat. Linoleate deficiency resulted in reduced feed efficiency (in males), high rates of transepidermal water loss, poor skin and coat condition, and fatty liver. These manifestations of EFA deficiency were prevented by SSO. Tuna oil had no additional effect. Analyses of the fatty acid composition of plasma, erythrocytes and liver lipids revealed that linoleate deficiency caused changes that were qualitatively, but not quantitatively similar to EFA deficiency in the rat. When SSO was provided, linoleate was elongated and desaturated at the delta 5 position to form 20:2n6 and 20:3(5,11,14). However, there was negligible conversion of linoleate to arachidonate. These results indicate that linoleate has specific functions as an EFA, independent of arachidonate synthesis and prostaglandin formation.     

Plasma and erythrocyte essential fatty acids during total parenteral nutrition in infants: effects of a cutaneous supply

In order to prevent essential fatty acid (EFA) deficiency induced by fat-free total parenteral nutrition (TPN), 10 infants on TPN were rubbed three times daily for 20 days using oenethera oil (80% EFA). Total EFA amount provided cutaneously was 1900 mg/kg/d. Plasma and red blood cells phospholipids were determined on days 1 and 20 in these 10 treated and six untreated infants on TPN and compared with those of normal control infants. On day 1, plasma nonessential FA including 20:3 n-9(p less than 0.01) were increased in both TPN groups while 18:2 n-6 and 18:3 n-3 (p less than 0.001 and p less than 0.01) were decreased. On the 20th day, EFA deficiency had worsened with a decrease in plasma level of 20:4 n-6 (p less than 0.02) and a higher than normal triene/tetraene ratio : 3.4 +/- 1.1 and 2.3 +/- 0.6 vs 0.1 +/- 0.1 (p less than 0.02). As for red blood cells phospholipids, 16:0 was increased and 18:2 n-6 and 20:3 n-6 were decreased (p less than 0.05) on day 1. On day 20, these FA were more abnormal while 20:3 n-9 became significantly increased (p less than 0.05). No difference was observed between the TPN groups at any time. These results show that cutaneous application of large amounts of EFA-rich oil is unable to prevent or cure TPN induced EFA deficiency.     

Effect of dietary n-3 fatty acids on weight gain and liver polar lipid fatty acid composition of fingerling channel catfish

A 10-wk experiment was conducted to determine the effect of supplementing a 5% tristearin basal diet with linoleic acid [18:2(n-6)], linolenic acid [18:3(n-3)], an n-3 highly unsaturated fatty acid (n-3 HUFA) mixture, cod liver oil, corn oil or linseed oil on growth and fatty acid composition of the liver polar lipid fraction of fingerling channel catfish (Ictalurus punctatus). The lowest weight gain was observed in fish fed the basal diet. Weight gain was improved by certain levels of supplemental n-3 fatty acids. Fish fed a diet containing 2% 18:3(n-3) grew at the same rate as fish fed a diet containing 2.5% cod liver oil plus 2.5% corn oil. The best growth rate was observed in fish fed diets containing either 5% cod liver oil or 5% linseed oil. Growth rate was depressed by supplementation with 4% 18:3(n-3) or 1.25% n-3 HUFA mix. No improvement in growth rate was observed with dietary 18:2(n-6). Dietary linolenate was converted to docosahexaenoic acid [22:6(n-3)]. The ratio of 20:3(n-9) to 22:6(n-3) of the fish showing good growth was less than 0.4. The data obtained in this experiment indicate that n-3 fatty acids are essential for channel catfish and that the 18:3(n-3) or n-3 HUFA dietary requirement is 1.0-2.0% or 0.5-0.75%, respectively.     

GROWTH AND CEREBRAL LIPID COMPOSITION DURING MATURATION OF RATS FED VARYING LEVELS OF LINOLEATE AND LINOLENATE

Rats were fed diets containing 3.0, 0.75 or 0.07 percent of the calories as essential fatty acids (EFA) for three generations. In general, growth and fatty acid composition were very similar at the two higher intakes of EFA. The pattern of linoleate series fatty acids in cerebral phosphatidylethanolamine was very similar with all three groups. The increase in linolenate series fatty acids depended on the level of dietary linolenate, was much slower and continued to increase with age.     

Polyunsaturated fatty acids and anthropometric indices of children in rural China

OBJECTIVE: To define fatty acid and macronutrient intakes in a rural Chinese preschool population, and relate these intakes to anthropometric indices. DESIGN: Cross-sectional survey of anthropometry and diet (three 24-h recalls). National Centers for Health Statistics/World Health Organization growth reference charts were used to determine the prevalence of malnutrition (z-scores less than -2 standard deviation (s.d.) below the mean): height-for-age (stunted), weight-for-age (underweight), weight-for-height (wasted) and mid-upper-arm-circumference-for-age (low fat/muscle). SUBJECTS AND SETTING: A total of 196 children aged 1-5 years old were volunteered by their families to participate in the survey, located in Heqing County, Yunnan Province, China. RESULTS: The respective prevalence of stunting, underweight, wasting and low fat/muscle was: 38, 21, 2 and 8%. Daily intakes of linoleic acid (LA; 18:2n-6), alpha-linolenic acid (LNA; 18:3n-3), arachidonic acid (AA; 20:4n-6) and docosahexaenoic acid (DHA; 22:6n-3), averaged for all children, were 2 100+/-1200, 300+/-250, 55+/-35 and 30+/-140 mg/day, respectively. As percent of total fat intake, LA contributed 11.9%, LNA 1.8%, AA 0.3% and DHA 0.2%. Height-for-age and weight-for-age z-scores were negatively correlated with g/kg/day intake of LA and AA (P<0.05). Weight-for-height z-score was negatively correlated with AA g/kg/day intake (P<0.05). CONCLUSIONS: This study provided polyunsaturated fatty acids (PUFA) intakes in rural preschool children in a developing country. The associations of PUFA intake with early childhood growth suggest that growth in preschool-aged children could be significantly and specifically related to n-6 fatty acid intakes.     

Regular exercise modulates muscle membrane phospholipid profile in rats.

We investigated the effect of regular exercise and changes in dietary fatty acid profile on skeletal muscle phospholipid fatty acid profile in rats. Rats were randomly divided into three groups and for 4 wk fed either a carbohydrate-rich diet (CHO, 10 percent of total energy (E%) fat, 20 E% protein, 70 E% CHO) or one of two fat-rich diets (65 E% fat, 20 E% protein, 15 E% CHO) containing predominantly either saturated or monounsaturated fatty acids. Each dietary group was randomly assigned to a trained (6 d/wk, progressive to 60 min, 28 m/min at a 10 degrees incline) or a sedentary group. The effect of training was apparent in the three hindlimb muscles analyzed: red quadriceps, white quadriceps and soleus. The unsaturation index was significantly lower in the trained than in the sedentary groups (206 +/- 2 vs. 215 +/- 2, P < 0. 01), which largely reflected a lower content of arachidonic acid [20:4(n-6): 14.5 +/- 0.5 vs. 16.6 +/- 0.4% of total fatty acids, P < 0.01] and docosahexaenoic acid [22:6(n-3): 11.1 +/- 0.2 vs. 11.7 +/- 0.3% of total fatty acids, P < 0.03] and a concomitant higher content of linoleic acid [18:2(n-6): 20.0 +/- 0.4 vs. 17.8 +/- 0.4% of total fatty acids, P < 0.01]. Training affected skeletal muscle membrane structural composition, and this occurred independently of dietary fatty acid changes. This change likely reflects an increased utilization of highly unsaturated fatty acids for energy, an effect which may have deleterious effects on insulin action.     

Randomised controlled trial of essential fatty acid supplementation in phenylketonuria

OBJECTIVE: The long-chain polyunsaturated fatty acids (LC-PUFA) status of children with PKU is often compromised. LC-PUFA, which are important fatty acids in the development of the CNS, can be synthesised endogenously from the parent essential fatty acids (EFA) provided dietary intakes are adequate. This study was designed to assess the biochemical effect over a 20-week period of a phe-free protein substitute that has been supplemented with a balanced blend of n-3 and n-6 EFAs on LC-PUFA status of children with PKU. DESIGN, SETTING AND SUBJECTS: Fifty three community-living children aged 1-10 years diagnosed with PKU in the newborn period were recruited from seven tertiary centres in the UK and France and randomised to a fat-free control formula or the EFA-supplemented test-treatment formula in an open, prospective study. Forty four children completed the study (20 controls, 24 test-treatments). Fatty acid status was assessed at entry and 20-weeks follow-up. Three day dietary diaries were recorded at 20 weeks' follow-up. The safety, efficacy and palatability of the test-treatment formula were also assessed. RESULTS: The test-treatment group had significantly higher intakes of fat and EFA than the control group. There was a significant between group difference (P=0.04) in increases in median docosahexaenoic acid (DHA) concentrations in erythrocyte phospholipids, which increased by 19% in the test-treatment group and by 0.5% in the control group over the study period. Growth and phe control were satisfactory in all subjects. CONCLUSIONS: Supplementing the diets of children with PKU with a balanced blend of n-6 and n-3 EFA improves DHA status without compromising AA status.     

Comparison of short-term feeding of dietary linoleic and gamma-linolenic acid on plasma and liver cholesterol and fatty acids in hyperchol esterolemic rats

The present study compared the short-term effect of feeding 18:2n-6 and its metabolite, 18:3n-6 on plasma cholesterol and plasma and liver fatty acid composition. Weanling female rats were maintained on a fat-free semi-synthetic diet supplemented with 10% saturated fat, 1% cholesterol and 0.5% bile salt for 5 weeks to induce hypercholesterolemia and fatty liver. The hyper cholesterolemic rats (group H) were then switched to a steroid-free fat-free diet supplemented with either 5% linoleic acid-rich oil (group L, containing 80% 18:2n-6) or 5% gamma-linoilenic acid concentrate (group G, containing 84% 18:3n-6 and 16% 18:2n-6 ethyl esters). After 2 days on the diet, plasma cholesterol and free fatty acid levels in both groups were significantly reduced. The extent of reduction was significantly greater in group G than in group L. The concentrations of triglycerides and phospholipids in plasma were not affected but those in liver were significantly changed by the dietary manipulation (increased liver phospholipids and reduced triglycerides). Both n-6 fatty acid treatments significantly modified the fatty acid compositions in all lipid fractions — reducing the levels of monoun-saturates, and 20:3n-9, but elevating those of n-6 fatty acids. The elevations of C-20 and C-22 n-6 fatty acids were consistently greater in group G than in group L. These results indicate that gamma-linolenate in comparison with linoleate was more effectively and rapidly metabolized into long chain metabolites which might account for the difference in cholesterol-lowering ability between gamma-linolenate and linoleate.