Lower Docosahexaenoic Acid Levels Research Articles

Sperm fatty acid composition in subfertile men

Introduction The lipid composition of spermatozoa plays an important role for successful fertilization. Patients and methods In the present study, we analyzed the fatty acid (FA) composition of spermatozoa of normozoospermic, asthenozoospermic, oligozoospermic and oligoasthenozoospermic men. Results Spermatozoa from asthenozoospermic ( P<0.01), oligozoospermic ( P<0.05) and oligoasthenozoospermic men ( P<0.05) had lower levels of docosahexaenoic acid (22:6w3, DHA) than those from normozoospermic men. In oligozoospermic and asthenozoospermic men, spermatozoa 18:0 content was higher than that of normozoospermics ( P<0.01 and P<0.001, respectively). 18:1w9 was higher in oligoasthenozoospermic and oligozoospermic samples when compared with normozoospermic samples ( P<0.05 for both). While from the point of view of total w6 FAs there was no significant difference among the groups, the w6/w3 ratio was significantly higher in asthenozoospermic samples than in normozoospermic samples ( P<0.05). Monounsaturated fatty acids (MFA) were higher in oligozoospermic samples ( P<0.05) than in normozoospermic samples, polyunsaturated fatty acids (PUFA) were lower in asthenozoospermic ( P<0.01), oligoasthenozoospermic ( P<0.05) and oligozoospermic samples ( P<0.05) than in normozoospermic samples. Saturated fatty acids (SFA) were significantly higher in asthenozoospermic ( P<0.01) and oligozoospermic samples ( P<0.05) compared with normozoospermic samples. In correlation analysis, there were significant positive correlations between DHA with sperm motility ( r = 0.53 ), sperm concentration ( r = 0.36 ) and normal sperm morphology ( r = 0.30 ). In addition, there were significant correlations between PUFA with sperm motility ( r = 0.50 ), sperm concentration ( r = 0.35 ), and normal sperm morphology ( r = 0.28 ), and between w6/w3 with sperm motility ( r = - 0.47 ), sperm concentration ( r = - 0.27 ), and normal sperm morphology( r = - 0.24 ). Discussion These suggest that decreased DHA and PUFA, and increased w6/w3 in spermatozoa may be related to infertility in oligo- and/or asthenozoospermic men.

Omega-3 Polyunsaturated Essential Fatty Acid Status as a Predictor of Future Suicide Risk

Low levels of docosahexaenoic acid, a polyunsaturated fatty acid, and elevated ratios of omega-6/omega-3 fatty acids are associated with major depression and, possibly, suicidal behavior. Predicting risk of future suicidal behaviors by essential fatty acid status merits examination. Plasma polyunsaturated fatty acid levels in phospholipids were measured in 33 medication-free depressed subjects monitored for suicide attempt over a 2-year period. Survival analysis examined the association of plasma polyunsaturated fatty acid status and pathological outcome. Seven subjects attempted suicide on follow-up. A lower docosahexaenoic acid percentage of total plasma polyunsaturated fatty acids and a higher omega-6/omega-3 ratio predicted suicide attempt. A low docosahexaenoic acid percentage and low omega-3 proportions of lipid profile predicted risk of suicidal behavior among depressed patients over the 2-year period. If confirmed, this finding would have implications for the neurobiology of suicide and reduction of suicide risk.

Not Just any Fat for Cystic Fibrosis? Docosahexaenoic Acid in Cystic Fibrosis

Once the genetic defect of cystic fibrosis (CF), the most common autosomal recessive disease, was discovered, there was hope for quick positive results with gene-therapy. These did not came true, however. Recent CF mice studies by Freedman et al. demonstrated a disease reversal by high doses of docosahexaenoic acid (DHA). Although it is known for long that the same essential fatty acid imbalance with low levels of DHA is present in CF patients and that DHA has anti- inflammatory actions, caution is urged to prevent false expectations when we extrapolate mice model results. This review explores the present scientific data on DHA supplementation in CF.

Low levels of docosahexaenoic acid identified in acute coronary syndrome patients with depression

As deficiencies in n-3 PUFAs have been linked separately to depression and to cardiovascular disease, they could act as a higher order variable contributing to the established link between depression and cardiovascular disease. We therefore examine the relationship between depression and omega-3 polyunsaturated fatty acids (n-3 PUFA), including total n-3 PUFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), in patients with acute coronary syndrome (ACS). Plasma phospholipid levels of n-3 PUFA were measured in 100 patients hospitalized with ACS. Current major depressive episode was assessed by the Composite International Diagnostic Interview (CIDI). Depression severity was assessed by the 18-item Depression in the Medically Ill (DMI-18) measure. Patients clinically diagnosed with current depression had significantly lower mean total n-3 PUFA and DHA levels. Higher DMI-18 depression severity scores were significantly associated with lower DHA levels, with similar but non-significant trends observed for EPA and total n-3 PUFA levels. The finding that low DHA levels were associated with depression variables in ACS patients may explain links demonstrated between cardiovascular health and depression, and may have prophylactic and treatment implications.

Blood mononuclear cells and platelets have abnormal fatty acid composition in homozygous sickle cell disease

Leukocyte adhesion to vascular endothelium contributes to vaso-occlusion and widespread organ damage in sickle cell disease (SCD). Previously, we found high expression of the adhesion molecules alphaMbeta2 integrin and L-selectin in HbSS individuals with severe disease. Since membrane n-6 and n-3 polyunsaturated fatty acids modulate cell adhesion, inflammation, aggregation and vascular tone, we investigated the fatty acid composition of mononuclear cells (MNC) and platelets of HbSS patients in steady state (n=28) and racially matched, healthy HbAA controls with similar age and sex distribution living in the same environment (n=13). MNC phospholipids of the patients had lower levels of docosahexaenoic acid (DHA, p<0.01) and increased arachidonic acid (AA, p<0.005) relative to HbAA controls. Similarly, platelets from HbSS patients had less eicosapentaenoic acid (EPA, p<0.05) and more AA (p<0.05) in choline phosphoglycerides (CPG), with reduced DHA (p<0.05) in ethanolamine phosphoglycerides. Platelet CPG had lower DHA levels in SCD patients with complications compared to those without (p<0.05). Reduced cell content of EPA and DHA relative to AA favours the production of aggregatory and proinflammatory eicosanoids that activate leukocytes and platelets. This facilitates inflammation, leukocyte adhesion, platelet aggregation and vaso-occlusion in SCD.

Single-Cell Protein Diet of a Novel Recombinant Vitellogenin Yeast Enhances Growth and Survival of First-Feeding Tilapia (Oreochromis mossambicus) Larvae

Yeast single-cell protein (SCP) is a high-nutrient feed substitute. This study evaluates the dual applications of a novel recombinant Pichia pastoris SMD1168H (SMD) yeast, expressing a tilapia vitellogenin protein (rVtg), as an SCP diet for Artemia and the first-feeding fish larvae. Instar II Artemia fed rVtg, rVtg precultured in 5% fish oil (rVtg-FO), Saccharomyces cerevisiae (SC), or native SMD had greater lipid contents (P < 0.05) than the freshly hatched. Lipid deposition in the Artemia fed rVtg or rVtg-FO was greater (P < 0.05) than in those fed SMD or SC. Diet-induced accumulation of low levels of docosahexaenoic acid [22:6(n-3)] was detected only in Artemia fed the rVtg-based diets. Tilapia (Oreochromis mossambicus) larvae were fed solely yeast diets singly or in combination (d 3-22), or a staggered regimen of yeast (d 3-12) followed by unenriched or yeast-enriched Artemia (d 13-22). The larvae fed rVtg for 22 d increased in length and weight (P < 0.05), whereas those fed SC or SMD suffered growth suppression and high mortality. Such adverse consequences were ameliorated when 50% of SC was substituted with rVtg. The larvae prefed rVtg followed by a dietary switch to Artemia preenriched for 48 h with rVtg or rVtg-FO were greatest in length, had the highest weight gain, and lived the longest. Besides delivering rVtg protein, essential fatty acids and amino acids, rVtg may have probiotic effects in enhancing larval survival. This study suggests the feasibility of using the rVtg yeast as an Artemia booster and an SCP first feed for larvae.

Decreased brain docosahexaenoic acid during development alters dopamine-related behaviors in adult rats that are differentially affected by dietary remediation

Docosahexaenoic acid (DHA) is a major component of neuronal membranes. In rats, low brain levels of DHA during development produce alterations in the mesocortical and mesolimbic dopamine systems. In this study, male Long–Evans rats ( n=6–7 per group) were raised from conception on diets with (control) or without α-linolenic acid, the dietary precursor of DHA. The deficient diet reduced brain DHA to 80% of that of control animals at maturity. At weaning (P21), half of the pups from each deficient litter were changed to a remediation diet enriched in DHA by the addition of fish oil. Beginning at P56, rats were subjected to a battery of behavioral tests. Catalepsy induced by haloperidol (3 mg/kg, i.p.) in deficient animals was 49% of that observed in control animals ( P<0.05). Catalepsy in remediated animals was similar to that observed for control animals. In a test of locomotor activity in a novel environment, deficient animals exhibited 187% of the activity of control animals ( P<0.05). Locomotor activity stimulated by d-amphetamine (0.5 mg/kg, s.c.) in deficient animals was 145% of that observed in control animals ( P<0.05). Basal and amphetamine-stimulated activity of remediated animals was similar to that of deficient animals. Response to a thermal stimulus was not different between groups. These findings demonstrate that rats exposed from conception to a diet that produces a relatively modest decrease in brain DHA content exhibit alterations in adult behavior indicative of altered dopaminergic function. Some of these behavioral alterations were reversed by dietary remediation initiated at weaning.

Restoring the DHA Levels in the Brains of Zellweger Patients

Patients with the Zellweger syndrome and its variants have very low levels of docosahexaenoic acid (DHA) in the brain, retina, and other tissues. Such a marked DHA deficiency could be related to the pathogenesis of peroxisomal disorders. Therefore, restoring the DHA levels in these patients can probably improve the clinical course of the disease. With this rationale, 20 patients with generalized peroxisomal disorders have been treated to date with DHA ethyl ester, at daily doses of 100-500 mg, for variable periods of time. Treatment has been always accompanied by a nutritious diet, normal for the age, in order to provide all the necessary nutrients and avoid a polyunsaturated fatty acid (PUFA) imbalance. The most constant improvement has been normalization of the DHA levels and liver function. Vision has improved in about half the patients and muscle tone has generally increased. Magnetic resonance imaging (MRI) examination revealed improvement of myelination in 9 patients. Significantly, the clinical improvement has been most marked in those patients who started the treatment before 6 mo of age. Biochemically, the plasma very long-chain fatty acids (VLCFA) 26:0 and 26:1n-9 decreased markedly despite the complete diet provided. In erythrocytes, the plasmalogen ratio 18: ODMA/18:0 increased in most cases, and sometimes even normalized. All these beneficial effects suggest that DHA deficiency plays a fundamental role in the pathogenesis of peroxisomal disease. Because DHA accretion is maximal during early brain development, it is essential to initiate the treatment as soon as possible. Otherwise, restoration of brain DHA levels and prevention of further damage will not be possible.

Possible relevance of abnormal fatty acid metabolism in undernutrition: the relationship between oleic acid and growth

Energy, protein, essential fatty acids, vitamins and minerals are all necessary for normal growth and development of children. In undernutrition, there is evidence for abnormal fatty acid metabolism. High levels of oleic acid and low levels of docosahexaenoic acid in plasma phosphatidylcholine have been associated with weight-for-age Z-score shifts to the left (increased prevalence of underweight) and vice versa (reduced prevalence of underweight). An alternative hypothesis is proposed, which describes a possible physiological mechanism whereby ω3 fatty acids contribute to growth. High blood oleic acid levels under conditions of undernutrition are proposed to be an adaptation to conserve glucose in the form of glycogen. Replacement with docosahexaenoic acid under conditions of adequate nutrition enhances membrane functioning so that glucose and energy become available for muscle formation.

Effects of natural and commercial diets on the fatty acid content of European grayling

Eicosaenoic acid (20:1ω9) and docosaenoic acid (22:1ω11) levels were about 10 and 100 times higher in food pellets fed to cultured grayling than in the insect larvae on which wild grayling fed. Among the PUFA, docosahexaenoic acid (DHA) was very high in the pellets, resulting in an unnaturally elevated, and probably unbalanced, ω3/ω6 ratio of 7–13 in the cultured fish whereas the same ratio varied only from 4 to 6 in the wild fish. Despite very low DHA levels in the native food, wild grayling muscle tissue contained relatively high amounts of DHA. DHA is probably not essential in the diet of grayling.

Effects of natural and commercial diets on the fatty acid content of European grayling

Eicosaenoic acid (20:1ω9) and docosaenoic acid (22:1ω11) levels were about 10 and 100 times higher in food pellets fed to cultured grayling than in the insect larvae on which wild grayling fed. Among the PUFA, docosahexaenoic acid (DHA) was very high in the pellets, resulting in an unnaturally elevated, and probably unbalanced, ω3/ω6 ratio of 7–13 in the cultured fish whereas the same ratio varied only from 4 to 6 in the wild fish. Despite very low DHA levels in the native food, wild grayling muscle tissue contained relatively high amounts of DHA. DHA is probably not essential in the diet of grayling.

Placental nutrition in the viviparous lizardNiveoscincus metallicus: the influence of placental type

The ion, energy, lipid, nitrogen and fat-soluble vitamin contents of freshly ovulated eggs and neonates of the viviparous lizard Niveoscincus metallicus were measured to quantify uptake of nutrients across the placenta. This species is particularly interesting because it has a chorio-allantoic placenta that is intermediate in complexity compared to viviparous species that have been the focus of other studies. Newly ovulated eggs have a wet mass of 79.6+/-4.6 mg and a dry mass of 41.8+/-2.8 mg, compared to the neonates that have a wet mass of 224.2+/-8.2 mg and dry mass of 37.9+/-1.2 mg. Thus, there is no significant net uptake of dry matter across the placenta. Neonates have significantly less lipid (6.2+/-0.4 mg) than eggs (12.7+/-0.5 mg), but no significant difference in nitrogen (4.1+/-0.3 mg) compared to eggs (4.5+/-0.2 mg). Energy densities reflect the protein and lipid composition and the relative dry masses of the eggs and neonates. There is significantly more energy (1029.1+/-80.0 J) in the egg than in the neonate (858.2+/-38.6 J). The increase in the ash content of the neonates (2.9+/-0.2 mg) compared to fresh eggs (2.1+/-0.3 mg) was not significant, even though there was an approximately threefold increase in the amount of sodium (0.11+/-0.01 mg in neonates, 0.34+/-0.01 mg in eggs) and potassium (0.12+/-0.017 in neonates, 0.40+/-0.01 mg in eggs) in neonates compared to eggs. There was no significant uptake of calcium and magnesium during development. The egg lipids consisted of triacylglycerol (66.7+/-2.3 %), phospholipid (18.9+/-0.7 %), cholesteryl ester (4.9+/-1.6 %) and free cholesterol (5.6+/-1.5 %). The egg phospholipid contained comparatively high proportions of arachidonic and eicosapentanoic acids but low levels of docosahexaenoic acid (DHA), whereas the phospholipid of the neonate was greatly enriched in DHA. In the egg, the predominant vitamin E was (&agr;)-tocopherol (62.6+/-3.4 mg g(-)(1)), although there was some (&ggr;)-tocotrienol (3.5+/-0.3 mg g(-)(1)), and vitamin A was present (1.5+/-0.2 mg g(-)(1)). The ratio of neonate dry mass to egg dry mass of N. metallicus (0.91) lies between that of species with type I (0.78) and type III (1.70) chorio-allantoic placentae, confirming our conclusion that the placenta of N. metallicus is functionally intermediate, as well as intermediate in complexity, between these other two types.

Fatty Acid Composition of Fulani ‘Butter Oil’ Made from Cow's Milk

Butter oil is the major cooking oil of the nomadic Fulani of the western Sahel of Africa. It is made from cow's milk and is consumed by all members of society, including pregnant women. In an effort to learn the reasons why the milk of Fulani women contains relatively low percentages of several nutritionally important fatty acids, linoleic acid and docosahexaenoic acid (DHA) in particular, we obtained butter oil in a local market in Kurra Falls, Nigeria and analyzed it for its fatty acid composition. Fatty acid analysis by gas–liquid chromatography revealed that while the butter oil purchased in a local market in Kurra Falls in northern Nigeria contained nutritionally adequate proportions of α -linolenic acid (1.09%), it was a poor source of linoleic acid (1.74%), DHA (0.03%) and arachidonic acid (0.14%). Since butter oil is the cooking oil that is most widely used by the Fulani, the low proportions of critical polyunsaturated fatty acids it contains helps explain the low levels of linoleic acid and DHA in the milk fat of lactating Fulani women. In addition, the low content of polyunsaturated fatty acids in butter oil may ultimately have implications for the general nutrition and growth and development of infants who are exclusively breast-fed by Fulani mothers whose major dietary fat source is butter oil.

Differences in tissue‐specific lipid composition between embryos of wild and captive breeding alligators (Alligator mississippiensis)

Fertile eggs obtained from alligators reared in captivity typically exhibit high rates of embryonic mortality. Also, the fatty acid composition of the yolk lipid of the captive eggs is markedly different from that observed in eggs from wild alligators, possibly as a result of differences in maternal diet in the two situations. The fatty acid compositions of tissue lipids during the embryonic development of wild and captive alligators were compared. The lipids of liver, adipose tissue and heart of the two types of embryo displayed fatty acid profiles which generally reflected the acyl compositions of the respective yolks. Thus the lipids from these tissues of the captive embryos contained markedly higher proportionate levels of linoleic and linolenic acids, lower levels of palmitoleic acid, and, in general, lower levels of docosahexaenoic acid and other C20 and C22 polyunsaturates, in comparison to the values for the wild embryos. In contrast, the fatty acid composition of the brain phosphoglycerides was very similar in the two types of embryo. Thus, at least in those embryos which had survived during the developmental period studied, the brain was able to maintain a relatively constant fatty acid composition, in spite of major differences between the wild and captive eggs in the proportions of the various fatty acids supplied from the yolk. It is suggested that a major cause of embryonic mortality in the captive embryos could be a failure to maintain an adequate level of docosahexaenoic acid in the developing brain.

Red blood cell fatty acid composition in low‐birth‐weight infants fed either human milk or formula during the first months of life

The fatty acid composition of red blood cell (RBC) phospholipids in low-birth-weight infants was determined immediately after delivery and during the first 3 months of life. In the first study, infants were fed either human milk or two formulas with different fatty acid compositions but no long chain polyunsaturated fatty acids (LCPUFA). Both groups of formula-fed infants had significantly lower levels of docosahexaenoic acid (DHA) in RBC phospholipids compared with breast-fed infants. RBC phospholipid DHA was similar in the two formula groups at all ages. In the second study, infants received either a non-supplemented or a LCPUFA-supplemented formula. DHA remained stable in RBC phospholipids of infants supplemented with LCPUFA, whereas DHA decreased in RBC phospholipids of unsupplemented infants. These results confirm that adding DHA to formulas is more effective than increasing 18:3 n-3 content, in maintaining RBC phospholipid DHA levels.

Relationship between plasma essential fatty acids and smoking, serum lipids, blood pressure and haemostatic and rheological factors

We aimed to determine whether levels of plasma fatty acids are correlated with other potential risk factors for cardiovascular disease, using a sample of patients from a cross-sectional survey of the general population, in the City of Edinburgh. 306 men and women aged 55–74 years of whom half had clinical evidence of arterial disease were tested. The main outcome measures were plasma fatty acids and potential risk factors for cardiovascular disease (age, sex, smoking, blood pressure, serum cholesterol, HDL cholesterol (HDL-C), triglycerides (TGs), lipid peroxides (LPx), plasma fibrinogen, von-Willebrand factor (vWf), β-thromboglobulin (βTG), cross-linked fibrin degradation products (FIBDP) and plasminogen activator inhibitor PAI). High levels of several known risk factors for cardiovascular diseases were associated with low levels of certain essential fatty acids. Eicosapentaenoic (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) were negatively associated with smoking and TG levels. High levels of certain haemostatic factors, including plasma fibrinogen, blood viscosity and LPx were also associated with low levels of EPA, DHA, AA and HDL-C. In conclusion, plasma fatty acids show strong correlations with many potential risk factors for cardiovascular disease, emphasising their possible importance in pathogenesis.

Effects of Dietary Fish Oil during the Fetal and Postnatal Periods on the Learning Ability of Postnatal Rats

The effects of a diet containing fish oil with a low level of docosahexaenoic acid fed during the fetal to newborn stage on the learning ability of postnatal rats were evaluated.Learning ability estimated by the swimming test was superior with the fish oil group of 6-wk-old rats to that with the non-fish oil group. These findings suggest that the ingestion of fish oil, and especially of docosahexaenoic acid, during the period from the fetal to newborn stage, but not during the weaning period, and the accumulation of a large amount of dietary docosahexaenoic acid in the brain of fetal and newborn rats may be related to an improved cerebral function of postnatal rats.

Decreased docosahexaenoic acid levels in retina and pigment epithelium of frogs fed crickets

Whole retina, rod outer segments, and retinal pigment epithelium of frogs ( Rana pipiens) fed crickets for more than 1 year had significantly lower levels of docosahexaenoic acid (22:6n-3) than the same tissues of frogs fed crickets for less than 1 month. Decreases in 22:6n-3 levels in these tissues were compensated for by increases in the n-6 polyunsaturated fatty acids (PUFAs), primarily 22:5n-6. There were no changes in the levels of saturated, monoenoic, or dienoic acids. Analysis of diacyl phospholipid molecular species (PLMS) revealed decreases in both the 22:6(n-3)-containing dipolyenoic molecular species in phosphatidylethanolamine and phosphatidylserine, and the monopolyenoic molecular species in phosphatidylcholine. These PLMS were replaced by species containing 22:5n-6 or other n-6 PUFAs. Examination of fatty acid methyl esters of total lipids extracted from crickets revealed that less than 1 mol% fatty acids were of the n-3 family, while more than 30 mol% were of the n-6 family. Thus, frogs raised on an n-3-deficient diet have reduced levels of n-3 PUFA in their retinas, rod outer segments, and retinal pigment epithelium. Although such changes have been reported for mammals, this is the first report of the effects of n-3 deficiency on the lipids of amphibians.

Abnormal lipid and fatty acid compositions of kidneys from mice with polycystic kidney disease

Renal cyst development in polycystic kidney disease (PKD) involves hyperplastic growth and extensive membrane alterations, suggesting abnormal membrane composition and function. Using thin-layer and gas-liquid chromatography, we analyzed the lipid components of the kidneys from 120-day-old DBA/2FG-pcy (pcy) having PKD as compared to normal DBA/2J (DBA) mice. At sacrifice, kidneys from pcy mice were four times larger than DBA controls, indicating that extensive renal cyst growth had occurred. The ratios of cholesterol/phospholipid, choline glycerophospholipid (GPC)/ethanolamine glycerophospholipid (GPE) and alkenylacyl GPE/diacyl GPE were higher (by 25%, 41% and 72%, respectively) in the cystic kidneys, while total phosphatidylinositol (PI), GPE and cardiolipin (DPG) were lower (by 13%, 23% and 27%, respectively). With respect to fatty acid compositions, there were significantly lower levels of docosahexaenoic acid (DHA, 22:6n-3) and higher levels of adrenic acid (AdA, 22:4n-6) in the phospholipids of pcy mouse kidneys. These changes were not present in serum, indicating that they were not generalized differences. Interestingly, the lower level of DHA in GPE was found to be associated with the alkenylacyl, but not the diacyl species. The fatty acids comprising the product/substrate ratio for the delta 4 desaturase activity were lower across all phospholipids, indicating a possible abnormality in polyunsaturated fatty acid metabolism in this model of PKD. These lipid abnormalities may influence membrane-mediated events such as receptor activation, signal transduction, ion transport and enzyme activities. The renal pathophysiologies associated with PKD may be related to the tissue lipid abnormalities described herein.

Plasma lipid abnormalities in the miniature poodle with progressive rod-cone degeneration

The miniature poodle with progressive rod-cone degeneration (prcd) is a model for human retinitis pigmentosa (RP). Since previous studies from several laboratories have shown abnormalities in plasma lipids in human RP, we examined the plasma lipids of prcd-affected animals. Fasting blood was drawn on three separate occasions from affected and control miniature poodles and on one occasion from normal Irish setters and those affected with a different inherited retinal degeneration (rod-cone dysplasia). Plasma phospholipids from prcd-affected animals had significantly lower levels of docosahexaenoic acid (22:6 omega 3) and cholesterol, compared to control miniature poodles. No differences were observed in plasma levels of phospholipids, vitamin E, or vitamin A, and no lipid differences were found between control and affected Irish setters. The ratios of 22:5 omega 3 to 22:6 omega 3 and of 22:4 omega 6 to 22:5 omega 6 were significantly elevated in prcd-affected poodles compared to controls. Since the conversion of 22:5 omega 3 to 22:6 omega 3 and of 22:4 omega 6 to 22:5 omega 6 is catalysed by a delta 4-desaturase, these results are consistent with a defect in desaturase activity in the prcd-affected poodle.