Fatty Acid-deficient Rats Research Articles

Dietary pentadecanoic acid supplementation at weaning in essential fatty acid-deficient rats shed light on the new family of odd-chain n-8 PUFAs

Pentadecanoic acid (C15:0) is a saturated odd-chain fatty acid (OCFA), mainly found in dairy products. Its physiological and nutritional effects are still unknown, yet some recent evidences suggest it might be beneficial to human health. Moreover, pentadecanoic acid has recently been suspected of having essential roles in humans, although the mechanisms are not described. We therefore questioned the potential essentiality of this fatty acid (FA). We investigated in vivo the effect of a C15:0 supplementation on essential fatty acid (EFA) deficient Wistar rats. Female rats were fed an EFA-deficient diet 2 weeks before mating, during pregnancy and lactation. Weaned pups were fed the EFA-deficient diet or were switched to a diet supplemented with C15:0 or linoleic acid (LA) for 11 weeks. A control group was fed with EFA during the whole study. Since LA deficiency is known to induce growth delay, weights were measured throughout the experiment and FA content in collected tissues were analyzed to evaluate biochemical markers of the deficiency. As expected, EFA-deficient rats showed growth retardation, compared to control rats. Supplementation of C15:0 at weaning increased early growth rate compared to deficient animals, as also did the supplementation of C18:2 n-6. Furthermore, the supplementation of C15:0 in the diet of EFA-deficient animals induced the previously undescribed synthesis of odd-chain PUFAs of the n-8 family (C19:3, C21:3 and C21:4 n-8). These results suggest dietary C15:0 might counteract EFA induced growth retardation, possibly through the synthesis of odd-chain n-8 PUFAs, yet mechanisms are to be deciphered for further validation.

Effects of Fish Oil Supplementation during the Suckling Period on Auditory Neural Conduction in n-3 Fatty Acid-Deficient Rat Pups.

Omega-3 fatty acid, particularly in the form of fish oil, has a structural and biological role in various systems of the body. The auditory and nervous systems are both influenced by omega-3 fatty acids, with omega-3 deficiency having devastating effects on both systems. Numerous studies have attempted to investigate this further. This study aimed to evaluate neural conduction in n-3 fatty acid-deficient rat pups following supplementation with fish oil during the suckling period. In this interventional and experimental study, omega-3 fatty acids from fish oil (FO) were fed to rat pups of n-3 polyunsaturated fatty acid (PUFA)-deficient dams. Changes in auditory neural conduction were compared with those of control and n-3 PUFA-deficient groups using auditory brainstem response (ABR). The parameters of interest were P1, P3, and P4 absolute latency, P1-P3, P1-P4, and P3-P4 interpeak latency (IPL), and P4/P1 amplitude ratio. The rat pups were given oral FO, 5 ml/g weight for 17 days, between the age of 5 and 21 days. No significant group differences were observed in P1 and P3 absolute latency (P>0.05), but there was a significant difference in P4 (P≤0.05). The n-3 PUFA-deficient + vehicle group had the most prolonged (the worst) P1-P4 IPL and P3-P4 IPL compared with control and n-3 PUFA-deficient + FO groups. There was no significant difference in P1-P4 IPL and P3-P4 IPL between the n-3 PUFA-deficient + FO group and the control group (P>0.05). There was a significant effect of diet on P1-P4 IPL and P3-P4 IPL between groups (P≤0.05). The results of present study showed the effect of omega-3 deficiency on auditory neural structure during pregnancy and the lactation period. Additionally, we observed reduced reduction in devastating effects on neural conduction in n-3 fatty acid-deficient rat pups following the supplementation of FO during the suckling period.

Omega-3 fatty acid deficient male rats exhibit abnormal behavioral activation in the forced swim test following chronic fluoxetine treatment: Association with altered 5-HT1A and alpha2A adrenergic receptor expression

Omega-3 fatty acid deficiency during development leads to enduing alterations in central monoamine neurotransmission in rat brain. Here we investigated the effects of omega-3 fatty acid deficiency on behavioral and neurochemical responses to chronic fluoxetine (FLX) treatment. Male rats were fed diets with (CON, n = 34) or without (DEF, n = 30) the omega-3 fatty acid precursor alpha-linolenic acid (ALA) during peri-adolescent development (P21–P90). A subset of CON (n = 14) and DEF (n = 12) rats were administered FLX (10 mg/kg/d) through their drinking water for 30 d beginning on P60. The forced swimming test (FST) was initiated on P90, and regional brain mRNA markers of serotonin and noradrenaline neurotransmission were determined. Dietary ALA depletion led to significant reductions in frontal cortex docosahexaenoic acid (DHA, 22:6n-3) composition in DEF (−26%, p = 0.0001) and DEF + FLX (−32%, p = 0.0001) rats. Plasma FLX and norfluoxetine concentrations did not different between FLX-treated DEF and CON rats. During the 15-min FST pretest, DEF + FLX rats exhibited significantly greater climbing behavior compared with CON + FLX rats. During the 5-min test trial, FLX treatment reduced immobility and increased swimming in CON and DEF rats, and only DEF + FLX rats exhibited significant elevations in climbing behavior. DEF + FLX rats exhibited greater midbrain, and lower frontal cortex, 5-HT1A mRNA expression compared with all groups including CON + FLX rats. DEF + FLX rats also exhibited greater midbrain alpha2A adrenergic receptor mRNA expression which was positively correlated with climbing behavior in the FST. These preclinical data demonstrate that low omega-3 fatty acid status leads to abnormal behavioral and neurochemical responses to chronic FLX treatment in male rats.

Senna still causes laxation in rats maintained on a diet deficient in essential fatty acids.

The laxative effect of senna has been investigated in normal and essential fatty acid deficient (EFAD) rats. Oral administration of senna pod extract (7-5-90 mg kg-1) produced a dose-dependent increase in the number of soft faeces excreted by normal rats. Senna 30 mg kg-1 also reversed net absorption of water and increased the prostaglandin (PG) production in the colonic lumen of normal rats by about four times. Oral administration of senna pod extract to rats, maintained on a fat-free diet for 30-90 days, produced diarrhoea and reversed net absorption of water as in normal rats. However, a fat-free diet reduced the PG production drastically in the colonic lumen both in senna-free rats and in senna-treated rats. In EFAD rats carrageenan oedema, but not dextran oedema, was also drastically reduced. Since PG mediation is not present in EFAD rats we conclude that the PG are not essential for laxation induced by senna and that water secretion and PG production in the rat intestinal lumen are unrelated.

Chronic risperidone normalizes elevated pro-inflammatory cytokine and C-reactive protein production in omega-3 fatty acid deficient rats

Prior clinical and preclinical studies suggest that omega-3 fatty acids negatively regulate pro-inflammatory signaling cascades, and that the atypical antipsychotic risperidone up-regulates omega-3 fatty acid biosynthesis. In the present study, we investigated the effects of chronic (40 days) risperidone treatment (3 mg/kg/day) on basal pro-inflammatory cytokine (interleukin-6, IL-6; tumor necrosis factor-alpha, TNFα) and C-reactive protein (CRP) production in control and n-3 fatty acid deficient rats. Relationships with erythrocyte polyunsaturated fatty acid composition were determined. Compared with untreated controls, untreated n−3-deficient rats exhibited significantly greater basal IL-6, TNFα, and CRP production. Following chronic risperidone treatment there were trends for greater IL-6, TNFα, and CRP production in controls, but these did not reach significance. In n−3-deficient rats, chronic risperidone normalized elevated IL-6, TNFα, and CRP levels. Erythrocyte arachidonic acid (20:4 n−6) composition was positively correlated, and erythrocyte eicosapentenoic (20:5 n−3) and docosahexaenoic acid (22:6 n−3) inversely correlated, with plasma IL-6, TNFα, and CRP levels in untreated control and n−3-deficient rats, and these associations were not observed among risperidone-treated rats. The adrenic acid (22:4 n−6)/arachidonic acid ratio, an index of elongase-mediated arachidonic acid biosynthesis, was reduced by risperidone in controls and elevated in n−3-deficient rats. These preclinical data demonstrate that chronic risperidone treatment normalizes constitutively elevated pro-inflammatory cytokine and CRP production in n−3 fatty acid deficient rats but not in controls, and that the mechanism is dissociable from n−3 fatty acid biosynthesis.

Early development of essential fatty acid deficiency in rats: Fat-free vs. hydrogenated coconut oil diet

This study examined the effects of feeding an essential fatty acid deficient (EFAD) diet either without fat or with added hydrogenated coconut oil (HCO) on fatty acid profiles in rats. Both diets induced equivalent biochemical evidence of EFAD reflected by the triene/tetraene ratio in plasma phospholipids within 2 weeks. However, the HCO diet led to larger increases of 16:1n7 and 18:1n9 in muscle but smaller increases in fat tissue and plasma triglycerides than the fat-free diet, suggesting greater increases in hepatic de novo lipogenesis with the latter. In addition, the HCO diet led to larger decreases of some 18:3n3 metabolites, particularly 22:6n3, in muscle, fat and brain tissues than the fat-free diet, presumably related to lesser stimulation of elongation and desaturation. Thus, these secondary effects of an EFAD diet on fatty acid metabolism can be modified by the saturated fat in the diet while the primary impact of both diets on development of EFAD is unaffected.

Bone mineral content is positively correlated to n-3 fatty acids in the femur of growing rats

The present study was conducted to determine whether provision of preformed dietary docosapentaenoic acid (DPAn-6) can replace DHA for normal long bone growth as assessed by dual-energy X-ray absorptiometry for mineral content (BMC). A newly modified artificial rearing method was employed to generate n-3 fatty acid-deficient rats. Except the dam-reared (DR; 3.1 % alpha-linolenic acid) group, newborn pups were separated from their mothers at age 2 d and given artificial rat milk containing linoleic acid (LA), or LA supplemented with 1 % DHA (22 : 6n-3; DHA), 1 % DPAn-6 (DPA), or 1 % DHA plus 0.4 % DPAn-6 (DHA/DPA). The rats were later weaned onto similar pelleted diets. At adulthood, the rats were euthanised and bones (femur, tibia, and lumbar vertebrae) collected for tissue fatty acid analysis and bone mineral density (BMD) determination. The analyses showed that long bones such as femur and tibia in DPAn-6-treated rats contained higher DPAn-6 content and generally had the lowest BMC and BMD values. Hence, DPAn-6 did not replace DHA for normal bone growth and maximal BMC in femur, indicating an indispensible role of DHA in bone health. In conclusion, DHA accumulates in the osteoblast-rich and nerve-abundant periosteum of femur; DHA but not EPA appears to be a vital constituent of marrow and periosteum of healthy modelling bone; and both DHA and total n-3 PUFA strongly correlate to BMC.

Perinatal n-3 fatty acid deficiency selectively reduces myo-inositol levels in the adult rat PFC: an in vivo 1H-MRS study

To investigate the effects of omega-3 fatty acid deficiency on phosphatidylinositol signaling in brain, myo-inositol (mI) concentrations were determined in the prefrontal cortex (PFC) of omega-3 fatty acid deficient rats by in vivo proton magnetic resonance spectroscopy ((1)H-MRS). To generate graded deficits in PFC docosahexaenoic acid (22:6n-3) (DHA) composition, perinatal and postweaning alpha-linolenic acid (18:3n-3) (ALA) deficiency models were used. Adult male rats were scanned in a 7T Bruker Biospec system and a (1)H-MRS spectrum acquired from the bilateral medial PFC. Rats were then challenged with SKF83959, a selective agonist at phosphoinositide (PI)-coupled dopamine D(1) receptors. Postmortem PFC fatty acid composition was determined by gas chromatography. Relative to controls, PFC DHA composition was significantly reduced in adult postweaning (-27%) and perinatal (-65%) ALA-deficiency groups. Basal PFC mI concentrations were significantly reduced in the perinatal deficiency group (-21%, P = 0.001), but not in the postweaning deficiency group (-1%, P = 0.86). Among all rats, DHA composition was positively correlated with mI concentrations and the mI/creatine (Cr) ratio. SKF83959 challenge significantly increased mI concentrations only in the perinatal deficiency group (+16%, P = 0.02). These data demonstrate that perinatal deficits in cortical DHA accrual significantly and selectively reduce mI concentrations and augment receptor-generated mI synthesis.

An n-3 fatty acid deficiency impairs rat spatial learning in the Barnes maze.

In this study, the authors demonstrate that rats with n-3 fatty acid deficiency display spatial learning deficits in the Barnes circular maze. Dams were deprived of n-3 fatty acids during pregnancy and lactation, and their offspring were weaned to the same deficient diet. There was a 58% loss of brain docosahexaenoic acid (DHA) in the n-3 fatty acid-deficient rats in comparison to n-3 fatty acid-adequate rats. At 8 weeks of age, deficient rats demonstrated moderate impairment in Barnes maze performance compared with the n-3 fatty acid-adequate rats during the initial training. In the reversal learning task, the n-3 fatty acid-deficient rats showed a profound deficit in performance: They required more time to find a new position of the escape tunnel, which was accompanied by a higher number of errors and perseverations. The n-3 fatty acid-deficient rats had reduced tissue levels of dopamine in the ventral striatum and enhanced levels of the metabolite 3,4-dihydroxyphenylacetic acid in frontal cortex and hypothalamus. In summary, this study demonstrates that rats with low brain DHA have a deficit in spatial reversal learning that could be related to changes in dopamine transmission in critical brain circuits.

Endocannabinoids and Nutrition

The endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) are bioactive lipids derived from the n-6 family of polyunsaturated fatty acids that are essential fatty acids. Symptoms of essential fatty acid deficiency in rats - growth retardation, scaly skin, and increased transepidermal water loss - can mainly be attributed to lack of linoleic acid as a structural element of the epidermis. Arachidonic acid, however, also serve essential functions, particularly in cellular signalling via its precursor role for numerous oxygenated derivatives such as prostaglandins, leukotrienes, hepoxilins and other eicosanoids. Furthermore, arachidonic acid is also a structural part of endocannabinoids that have signalling functions in relation to modulation of neurotransmitter release, which might involve physiological and pathophysiological phenomena such as regulation of appetite, energy metabolism, pain perception, memory and learning. Furthermore, along with AEA formation other acylethanolamides are always formed - e.g., oleoylethanolamide (OEA), that can inhibit food intake, and palmitoylethanolamide, that is anti-inflammatory - possibly through activation of peroxisome proliferator activated receptor alpha (PPAR alpha) and/or GPR119. As all these unsaturated fatty acids are ingested daily in smaller or larger amounts, one can ask whether different dietary fats can affect the levels of these fatty acids in the tissues and thereby the quantitative formation of these bioactive signalling molecules. Generally, in vivo arachidonic-acid-derived eicosanoid production can be increased and decreased by prolonged feeding with pharmacological levels of arachidonic acid and long-chain (n-3) fatty acids (fish oil), respectively. Changes in levels of these two fatty acids within the traditional human diet hardly affects the eicosanoid production, however. Moreover, preliminary data suggest that dietary intake of arachidonic acid and fish oil also doesn't easily affect endocannabinoid formation; however, dietary fat in terms of saturated, polyunsaturated and monounsaturated seems to affect tissue levels of AEA, 2-AG and OEA.

Novel synthetic ceramide derivatives increase intracellular calcium levels and promote epidermal keratinocyte differentiation

Ceramide is an important constituent of stratum corneum lipids, which act as both physical barriers and signal modulators. We synthesized several ceramide derivatives and investigated their effects on keratinocyte differentiation. RT-PCR and Western blotting showed that the novel synthetic ceramide derivatives K6PC-4 [N-(2,3-dihydroxypropyl)-2-hexyl-3-oxo-decanamide], K6PC-5, [N-(1,3-dihydroxypropyl-2-hexyl-3-oxo-decanamide] and K6PC-9 (N-ethanol-2-hexyl-3-oxo-decanamide) [corrected] These ceramide derivatives elicited a rapid transient increase in intracellular calcium levels, which were measured using laser scanning confocal microscopy. In addition, K6PC-4, K6PC-5, and K6PC-9 stimulated the phosphorylation of p42/44 extracellular signal-regulated kinase and c-Jun N-terminal kinase. In a reconstituted epidermis model, K6PC-4, K6PC-5, and K6PC-9 significantly increased keratin 1 expression in the suprabasal layer. These results indicate that these novel synthetic ceramide derivatives have the potential to promote keratinocyte differentiation, suggesting that the lipid molecules are applicable for treating skin diseases involving abnormal keratinocyte differentiation.

Dietary Polyunsaturated Fat that Is Low in (n-3) and High in (n-6) Fatty Acids Alters the SNARE Protein Complex and Nitrosylation in Rat Hippocampus ,

Docosahexaenoic acid [DHA, 22:6(n-3)] is enriched in brain membrane phospholipids and is important to brain development and function through its influence on neurite outgrowth and neurotransmitter secretion. Fusion of intracellular vesicles with the plasma membrane involving SNARE [soluble N-ethylmaleimide-sensitive fusion (NSF) protein attachment protein receptor] protein assembly, membrane fusion, and then disassembly are events common in membrane extension and neurotransmitter release. We determined whether feeding an (n-3) fatty acid–deficient diet, known to reduce brain phospholipid DHA, alters SNARE protein and SNARE complex expression or protein nitrosylation in the hippocampus of rats. Female rats were fed diets with 1.3 or 0.02% energy (n-3) α-linolenic acid from 2 wk before gestation then throughout gestation and lactation (n = 8/diet), and the male offspring were weaned to the maternal diet. Hippocampus phospholipid fatty acids and SNARE proteins were determined in male offspring at 90 d of age. Hippocampus phospholipid DHA was lower and (n-6) docosapentaenoic acid [DPA, 22:5(n-6)] was higher in the (n-3) fatty acid–deficient rats compared with the control group (P < 0.05). Multiplex Western blots using antibodies to syntaxin, synaptosome-associated protein of 25kDa (SNAP-25), and complexin II, showed higher ternary SNARE complexes but no differences in syntaxin, SNAP-25, or complex II expression in hippocampus of the (n-3) fatty acid–deficient rats compared with the control group (P < 0.05). S-nitrosylation of syntaxin was also significantly lower in the (n-3) fatty acid–deficient rats than in the control group. These studies suggest that altered SNARE complex binding or disassembly could be important in explaining the diverse cellular events associated with altered tissue DHA.

N-3 Fatty Acid Deficiency Induced by a Modified Artificial Rearing Method Leads to Poorer Performance in Spatial Learning Tasks

Docosahexaenoic acid (DHA) is a major structural component of the nervous system, and depletion may lead to losses in neural function. Our objective was to demonstrate a deficit in spatial task performance in rats with low brain DHA due to a low n-3 fatty acid intake using a first-generational artificial rearing technique. Newborn rat pups were separated on d 2 and assigned to two artificial rearing groups or a dam-reared control group. Pups were hand fed artificial milk via custom-designed nursing bottles containing either 0.02% (n-3 Def) or 3.1% (n-3 Adq) of total fatty acids as LNA. At d 21, rats were weaned to either n-3 Def or n-3 Adq pelleted diets and several behavioral tasks were evaluated at 9 wk of age. Brain DHA was lower (58% and 61%, p < 0.001) in n-3 Def in comparison to n-3 Adq and dam-reared rats, respectively. At adulthood, the n-3 fatty acid-deficient rats had a significantly greater moving time than the dam-reared group (p < 0.05), but there were no differences among the three groups in the elevated plus maze test. The n-3 fatty acid deficient rats exhibited a longer escape latency (p < 0.05) and poorer memory retention in the Morris water maze compared with n-3 fatty acid adequate and dam-reared rats. We concluded that artificial rearing can be used to produce n-3 fatty acid deficiency in the first generation. This deficiency was associated with significantly reduced spatial learning. Adequate brain DHA levels are required for optimal spatial learning.

An extraordinary degree of structural specificity is required in neural phospholipids for optimal brain function: n‐6 docosapentaenoic acid substitution for docosahexaenoic acid leads to a loss in spatial task performance

This study was conducted to determine whether provision of preformed dietary docosapentaenoic acid (DPAn-6) can replace docosahexaenoic acid (DHA) for brain function as assessed by spatial task performance. A newly modified artificial rearing method was employed to generate n-3 fatty acid-deficient rats. Newborn pups were separated from their mothers at 2 days of age and given artificial rat milk containing linoleic acid (LA), or LA supplemented with 1% DHA (DHA), 1% DPAn-6 (DPA) or 1% DHA plus 0.4% DPAn-6 (DHA/DPA). The animals were then weaned onto similar pelleted diets. At adulthood, behavioural tasks were administered and then the brains were collected for fatty acid analysis. The LA and DPA groups showed a lower (63-65%) brain DHA than the dam-reared, DHA and DHA/DPA groups and this loss was largely compensated for by an increase in brain DPAn-6. The brain fatty acid composition in the DPA group was the same as that in the LA group at adulthood. In the Morris water maze, the LA and DPA groups exhibited a longer escape latency than the dam-reared and DHA groups and had a defect in spatial retention. In conclusion, DPAn-6 could not replace DHA for brain function, indicating a highly specific structural requirement for DHA.

Decrease of brain phospholipid synthesis in free-moving n-3 fatty acid deficient rats.

The autoradiographic method with [14C]-docosahexaenoic acid ([14C]22:6 n-3) was used to determine whether a diet deficient in n-3 fatty acids, inducing a decrease in 22:6 n-3 circulating level, was associated with changes in local rates of phospholipid synthesis in the rat brain. As compared with rats fed a normal diet (peanut plus rapeseed oil), a n-3 fatty acid deficiency [peanut oil group (P group)] induced a generalized decrease (-35 to -76%) of 22:6 n-3 incorporation rates into phospholipids in all the regions examined. This effect was confirmed by using [3H]22:6 n-3 infusion by biochemical analysis and quantifications corrected for the contribution of docosahexaenoate derived from lipid store recycling to the unesterified pool, taken as the precursor pool for phospholipid synthesis in the whole brain. In normal or n-3 fatty acid-deficient rats, the values of the brain-to-plasma 22:6 n-3 specific activity ratio (psi) were similar (0.03), indicating that a considerable endogenous source of 22:6 n-3 (97%), likely derived from phospholipid degradation, dilutes the specific activity of the tracer coming from plasma. Using the specific activity of 22:6 n-3 in plasma instead of brain would thus lead to a gross underestimation of the rate of phospholipid synthesis. The results also demonstrate that the pattern of 14C or 3H distribution in brain lipids was not modified by the n-3 fatty acid-deficient diet. The major lipids labeled were phospholipids, particularly phosphatidylethanolamine. Nevertheless, the unesterified 22:6 n-3 concentrations in plasma and brain were significantly reduced (eight-and threefold, respectively) in the P group. In addition, the proportion of 22:6 n-3 in the brain total lipid fraction, total phospholipids, and phosphatidylcholine, -ethanolamine, and -serine was significantly decreased in n-3 fatty acid-deficient rats. This was partially compensated for by an increase in the 22:5 n-6 level. These results are discussed in relation to the limitation of 22:6 n-3 use to quantify, by the quantitative autoradiographic method, changes in local rates of phospholipid synthesis in rat brain.

Glucose transport and utilization are altered in the brain of rats deficient in n-3 polyunsaturated fatty acids.

Long-chain polyunsaturated (n-3) fatty acids have been reported to influence the efficiency of membrane receptors, transporters and enzymes. Because the brain is particularly rich in docosahexaenoic acid (DHA, 22:6 n-3), the present study addresses the question of whether the 22:6 n-3 fatty acid deficiency induces disorder in regulation of energy metabolism in the CNS. Three brain regions that share a high rate of energy metabolism were studied: fronto-parietal cortex, hippocampus and suprachiasmatic nucleus. The effect of the diet deficient in n-3 fatty acids resulted in a 30-50% decrease in DHA in membrane phospholipids. Moreover, a 30% decrease in glucose uptake and a 20-40% decrease in cytochrome oxidase activity were observed in the three brain regions. The n-3 deficient diet also altered the immunoreactivity of glucose transporters, namely GLUT1 in endothelial cells and GLUT3 in neurones. In n-3 fatty acid deficient rats, GLUT1-immunoreactivity readily detectable in microvessels became sparse, whereas the number of GLUT3 immunoreactive neurones was increased. However, western blot analysis showed no significant difference in GLUT1 and GLUT3 protein levels between rats deficient in n-3 fatty acids and control rats. The present results suggest that changes in energy metabolism induced by n-3 deficiency could result from functional alteration in glucose transporters.

Long-term n-3 fatty acid deficiency induces no substantial change in the rate of protein synthesis in rat brain and liver.

The influence of long-term n-3 fatty acid deficiency on the rate of protein synthesis in rat brain and liver was investigated in relation to learning behavior or a presumed survival time-shortening factor (SSF) in rapeseed oil, using a large-dose [3H]phenylalanine (Phe) injection method. When Wistar rats were made n-3 fatty acid-deficient by feeding a safflower oil (alpha-linolenate-deficient) diet for 2 generations, conditions under which the safflower oil group had been shown to exhibit altered learning behaviors, compared with the perilla oil group, no significant changes in the rate of protein synthesis were observed compared with the perilla oil (alpha-linolenate-sufficient) or rapeseed oil (alpha-linolenate-sufficient but SSF-containing) groups. However, the rapeseed oil group had a reduced specific radioactivity of free Phe in the cerebral cortex, compared with the safflower oil group. In contrast to the reported observation of very long-term n-3 fatty acid deficiency inducing an almost 2-fold increase in the rate of protein synthesis in the brain, our results indicate that altered learning behavior resulting from n-3 fatty acid deficiency in rats is not associated with any substantial changes in the rate of protein synthesis in the brain.

Modulation of adjuvant-induced arthritis by dietary arachidonic acid in essential fatty acid-deficient rats.

Controlled feeding of linoleic acid (LA) or arachidonic acid (AA) to essential fatty acid-deficient (EFAD) rats was used to define the relationship between dietary AA and the inflammatory response evoked during adjuvant-induced arthritis. Based on energy percentage, EFAD rats were fed AA at the human daily equivalent (1x; 5.5 mg/day) or 10 times that amount (10x; 55 mg/day) or, alternatively 0.5x of LA (273 mg/day). Feeding of 0.5x LA restored the plasma level of AA to that in chow-fed controls. In contrast, feeding of 1x AA only partially restored the plasma level of AA; 10x AA was required to fully replete AA. In parallel to the degree of repletion of AA in plasma, there were accompanying decreases in the levels of palmitoleic acid, oleic acid, and Mead acid. Compared to rats fed the standard laboratory chow diet (Control), edema in the primary hind footpads was decreased by 87% in EFAD, 71% in EFAD + 1x AA, 45% in EFAD + 10x AA, and 30% in EFAD + 0.5x LA. The decrease in edema in the footpads of EFAD rats was nearly identical to the decrease in edema in the footpads of Control rats dosed with indomethacin. Hind footpad edema correlated with the final AA plasma level and eicosanoid levels extracted from hind footpad tissue, but not with neutrophil infiltration. The data showed that 0.5x LA and 10x AA, but not 1x AA, could quickly replete AA, accompanied by the synthesis of AA-derived eicosanoids and restoration of edema. These results suggest that in humans consumption of the average daily amount of AA without concurrent ingestion of LA would not alleviate an EFAD state.

Effect of polyunsaturated fatty acids deficiency on oxidative phosphorylation in rat liver mitochondria

Liver mitochondria isolated from controls or polyunsaturated fatty acid (PUFA) deficient rats were studied for oxidative phosphorylation. A PUFA-deficient diet led to a dramatic change in the fatty acid composition of mitochondrial lipid content, similar to that reported in the literature. Besides the changes in lipid composition, mitochondrial volume was enlarged (+45% in state 4 and two-fold in state 3). State 4 respiration was increased together with a decrease in protonmotive force. The non-ohmicity of the relationship between non-phosphorylating respiration and protonmotive force was more pronounced in the PUFA-deficient group. State 3 oxygen consumption as well as the rate of ATP synthesis showed no difference between the two groups, whereas the protonmotive force decreased substantially in mitochondria from PUFA-deficient animals. In contrast, ATP/O ratios were decreased in the PUFA-deficient group when determined at subsaturating ADP concentration. Taken together, these results are in agreement with both an increased non-ohmic proton leak and an increased redox slipping. The relative importance of these two effects on the overall efficiency of oxidative phosphorylation depends on both the rate of oxidative phosphorylation and the maintained protonmotive force. Hence, in isolated mitochondria the respective role of each effect may vary between state 4 and state 3.

Metabolism of orally fed [3H]-eicosapentaenoic and [14C]-arachidonic acid in essential fatty acid-deficient rats.

The metabolism of individual polyunsaturated fatty acids (PUFA) may be influenced differently by nutritional status and nutritional intake. In normal rats, radioactive arachidonic acid (20:4(n-6), is preferentially retained in tissue phospholipids compared to linoleic (18:2(n-6), or eicosapentaenoic acid (20:5(n-3). This study compares the fate of 20:4(n-6) and 20:5(n-3) acids in essential fatty acid-deficient (EFAD) rats. [3H]-20:5 and [14C]-20:4 were fed in a fish oil emulsion to EFAD rats. Tissue lipids were analysed for radioactivity at 1, 2 and 4 h. The conversion of [3H]-20:5 to docosapentaenoic acid (22:5) and docosahexaenoic acid (22:6) was examined using high performance liquid chromatography (HPLC). The recovery of 3H in small intestine was lower than that of 14C (26 vs. 36% after 4 h, p < 0.001), but was higher in the liver (26 of 3H vs. 22% of 14C, p < 0.01), kidneys (1.5 vs. 1.2%, p < 0.001) and colon (0.3 vs. 0.2%, p = 0.01). The percentages of 3H and 14C in phospholipids were investigated in intestine and liver, and were higher in EFAD rats than in normal rats, particularly for phosphatidylethanolamine (PE). The proportions of [3H]-20:5 transformed to 22:5 and 22:6 did not exceed 7% in the intestine and 10% in the liver. In conclusion, the metabolism of dietary fatty acids 20:4 and 20:5 differed less than in normal rats, mainly due to the preferential retention of both fatty acids in phospholipids.