Multigene testing of moderate-risk genes: be mindful of the missense.

BACKGROUND: Moderate-risk genes have not been extensively studied, and missense substitutions in them are generally returned to patients as variants of uncertain significance lacking clearly defined risk estimates. The fraction of early-onset breast cancer cases carrying moderate-risk genotypes and quantitative methods for flagging variants for further analysis have not been established. METHODS: We evaluated rare missense substitutions identified from a mutation screen of ATM, CHEK2, MRE11A, RAD50, NBN, RAD51, RINT1, XRCC2 and BARD1 in 1297 cases of early-onset breast cancer and 1121 controls via scores from Align-Grantham Variation Grantham Deviation (GVGD), combined annotation dependent depletion (CADD), multivariate analysis of protein polymorphism (MAPP) and PolyPhen-2. We also evaluated subjects by polygenotype from 18 breast cancer risk SNPs. From these analyses, we estimated the fraction of cases and controls that reach a breast cancer OR≥2.5 threshold. RESULTS: Analysis of mutation screening data from the nine genes revealed that 7.5% of cases and 2.4% of controls were carriers of at least one rare variant with an average OR≥2.5. 2.1% of cases and 1.2% of controls had a polygenotype with an average OR≥2.5. CONCLUSIONS: Among early-onset breast cancer cases, 9.6% had a genotype associated with an increased risk sufficient to affect clinical management recommendations. Over two-thirds of variants conferring this level of risk were rare missense substitutions in moderate-risk genes. Placement in the estimated OR≥2.5 group by at least two of these missense analysis programs should be used to prioritise variants for further study. Panel testing often creates more heat than light; quantitative approaches to variant prioritisation and classification may facilitate more efficient clinical classification of variants.

DHA-enriched phospholipid diets modulate age-related alterations in rat hippocampus.

Our previous work on rat hippocampus showed that a loss of docosahexaenoic acid (DHA) occurs in the fatty acid composition of phosphatidylethanolamine (PE), plasmenylethanolamine (PmE) and phosphatidylserine (PS) with increasing age. The present study investigated whether a DHA-enriched phospholipid dietary supplement could restore DHA levels and cholinergic activity. Male rats were fed a balanced diet containing both linoleic and alpha-linolenic acids until the age of 2, 18 and 21 months. From 18 to 21 months, one subgroup received a diet supplemented with DHA-enriched phospholipids from egg yolk (E-PL), and another a diet with DHA-enriched phospholipids from pig brain (B-PL). Compared to the control diet, the E-PL diet restored the proportion of polyunsaturated fatty acids (PUFAs: 22:6n-3 and 20:4n-6) in PE and PmE, while enhancing spontaneous and evoked-acetylcholine (Ach) release. The B-PL diet had no effect on PUFAs, but increased basal extracellular levels of Ach in 21-month-old rats as compared to the age-matched control. Our results show that supplementation with DHA-enriched egg PL can enhance Ach release and correct PUFA composition.

Polyunsaturated fatty acids and cerebral function: focus on monoaminergic neurotransmission.

More and more reports in recent years have shown that the intake of polyunsaturated fatty acids (PUFA) constitutes an environmental factor able to act on the central nervous system (CNS) function. We recently demonstrated that the effects of PUFA on behavior can be mediated through effects on the monoaminergic neurotransmission processes. Supporting this proposal, we showed that chronic dietary deficiency in alpha-linolenic acid in rats induces abnormalities in several parameters of the mesocortical and mesolimbic dopaminergic systems. In both systems, the pool of dopamine stored in presynaptic vesicles is strongly decreased. This may be due to a decrease in the number of vesicles. In addition, several other factors of dopaminergic neurotransmission are modified according to the system affected. The mesocortical system seems to be hypofunctional overall [e.g., decreased basal release of dopamine (DA) and reduced levels of dopamine D2 (DAD2) receptors]. In contrast, the mesolimbic system seems to be hyperfunctional overall (e.g., increased basal release of DA and increased levels of DAD2 receptors). These neurochemical changes are in agreement with modifications of behavior already described with this deficiency. The precise mechanisms explaining the effects of PUFA on neurotransmission remain to be clarified. For example, modifications of physical properties of the neuronal membrane, effects on proteins (receptors, transporters) enclosed in the membrane, and effects on gene expression and/or transcription might occur. Whatever the mechanism, it is therefore assumed that interactions exist among PUFA, neurotransmission, and behavior. This might be related to clinical findings. Indeed, deficits in the peripheral amounts of PUFA have been described in subjects suffering from neurological and psychiatric disorders. Involvement of the monoaminergic neurotransmission function has been demonstrated or hypothesized in several of these diseases. It can therefore be proposed that functional links exist among PUFA status, neurotransmission processes, and behavioral disorders in humans. Animal models are tools of choice for the understanding of such links. Improved prevention and complementary treatment of neurological and psychiatric diseases can be expected from these studies.

Comparative bioavailability of dietary alpha-linolenic and docosahexaenoic acids in the growing rat.

Animal and human studies have indicated that developing mammals fed only alpha-linolenic acid (18:3n-3) have lower docosahexaenoic acid (22:6n-3) content in brain and tissue phospholipids when compared with mammals fed 18:3n-3 plus 22:6n-3. The aim of this study was to test the hypothesis that low bioavailability of dietary 18:3n-3 to be converted to 22:6n-3 could partly explain this difference in fatty acid accretion. For that purpose, we determined the partitioning of dietary 18:3n-3 and 22:6n-3 between total n-3 fatty acid body accumulation, excretion, and disappearance (difference between the intake and the sum of total n-3 fatty acids accumulated and excreted). This was assessed using the quantitative method of whole-body fatty acid balance in growing rats fed the same amount of a 5% fat diet supplying either 18:3n-3 or 22:6n-3 at a level of 0.45% of dietary energy (i.e., 200 mg/100 g diet). We found that 58.9% of the total amount of 18:3n-3 ingested disappeared, 0.4% was excreted in feces, 21.2% accumulated as 18:3n-3 (50% in total fats and 46% in the carcass-skin compartment), and 17.2% accumulated as long-chain derivatives (14% as 22:6n-3 and 3.2% as 20:5n-3 + 22:5n-3). Similar results were obtained from the docosahexaenoate balance (as % of the total amount ingested): disappearance, 64.5%; excretion, 0.5%; total accumulation, 35% with 30.1% as 22:6n-3. Thus, rats fed docosahexaenoate accumulated a twofold higher amount of 22:6n-3, which was mainly deposited in the carcass-skin compartment (68%). Similar proportions of disappearance of dietary 18:3n-3 and 22:6n-3 lead us to speculate that these two n-3 polyunsaturated fatty acids were beta-oxidized in the same amount.

Plasma fatty acid levels in autistic children.

Phospholipid fatty acids are major structural components of neuronal cell membranes, which modulate membrane fluidity and hence function. Evidence from clinical and biochemical sources have indicated changes in the metabolism of fatty acids in several psychiatric disorders. We examined the phospholipid fatty acids in the plasma of a population of autistic subjects compared to mentally retarded controls. Our results showed a marked reduction in the levels of 22: 6n-3 (23%) in the autistic subjects, resulting in significantly lower levels of total (n-3) polyunsaturated fatty acids (PUFA) (20%), without significant reduction in the (n-6) PUFA series, and consequently a significant increase in the (n-6)/(n-3) ratio (25%). These variations are discussed in terms of potential differences in PUFA dietary intake, metabolism, or incorporation into cellular membranes between the two groups of subjects. These results open up interesting perspectives for the investigation of new biological indices in autism. Moreover, this might have new therapeutic implications in terms of child nutrition.

Age-related changes in ethanolamine glycerophospholipid fatty acid levels in rat frontal cortex and hippocampus.

Morphological and biochemical alterations are associated with a progressive age-related cognitive deficit. Plasmenylethanolamine, the major brain plasmalogen, may be modified during aging because of a possible antioxidant role and involvement in synaptic transmission. Two- and 18-month-old rats were used to study the effect of aging on the levels and acyl composition of plasmenylethanolamine (PmE), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in the frontal cortex and hippocampus. Aging only reduced significantly the PE levels in the frontal cortex. In 18-month-old rats, the fatty acid composition of the three phospholipid classes studied showed an increase of monounsaturated fatty acid (18:1 n-9 and 20:1 n-9) and a decrease in polyunsaturated fatty acid (PUFAs), essentially docosahexaenoic acid (DHA). DHA was markedly decreased in hippocampus PE. DHA, but also arachidonic acid, were considerably lower in frontal cortex PmE. PS modifications were similar in both regions. Hippocampus and frontal cortex underwent specific age-induced modifications in PmE and PE acyl composition. This could produce different effects on the functional ability of these two structures involved in the processes of specific memorization.

Phospholipid incorporation and metabolic conversion of n-3 polyunsaturated fatty acids in the Y79 retinoblastoma cell line.

The metabolic conversion of n-3 fatty acids was studied in the human Y79 retinoblastoma cell line. Cultured cells were exposed to increasing concentrations of either 18:3n-3, 22:5n-3, or 22:6n-3, and their phospholipid fatty acid composition was analyzed after 72 hr. Cells internalized the supplemental fatty acids and proceeded to their metabolic conversion. Supplemental 22:6n-3 was directly esterified into cell phospholipids, at levels typical for normal neural retinas (41% by weight of phosphatidylethanolamine fatty acids, and 24% of phosphatidylcholine fatty acids). In contrast, 18:3n-3 was mainly converted to 20:5n-3 and 22:5n-3, both of which appeared in cell phospholipids after exposure to low external concentrations of 18:3n-3 (10 microg/ml). Y79 cells can proceed to the metabolic conversion of 18:3n-3 through elongation and Delta6- and Delta5-desaturation. When cells were exposed to high external concentrations of 18:3n-3 (30 microg/ml), the supplemental fatty acid was directly incorporated, and its relative content increased in both phospholipid classes to the detriment of all other n-3 fatty acids. Cells cultured in the presence of 22:5n-3 did not incorporate 22:6n-3 into their phospholipids but did incorporate 20:5n-3 and 22:5n-3. The data suggest that Y79 cells can proceed to the microsomal steps of n-3 metabolism, involving elongation, desaturation, and chain shortening of 22C fatty acids. Although Y79 cells avidly used supplemental 22:6n-3 for phospholipid incorporation at levels typical for normal photoreceptor cells, they failed to match such levels through metabolic conversion of n-3 parent fatty acids. The terminal step of the very long-chain polyunsaturated fatty acid synthesis, consisting in Delta6-desaturation followed by peroxisomal chain shortening of 24C-fatty acids, could be rate-limiting in Y79 cells.

Effect of an alpha-linolenic acid-rich diet on rat mammary tumor growth depends on the dietary oxidative status.

To investigate whether the oxidative status of an 18:3(n-3) polyunsaturated fatty acid (PUFA)-enriched diet could modulate the growth of chemically induced rat mammary tumors, three independent experiments were performed. Experiments I and II examined the variation of tumor growth by addition of antioxidant (vitamin E) or a prooxidant system (sodium ascorbate/2-methyl-1,4-naphthoquinone) to a 15% linseed oil diet rich in 18:3(n-3). Experiment III addressed the role of PUFA in the tumor growth modulation by vitamin E. For this purpose, we compared the effect of vitamin E in 15% fat diets containing a high level of 18:3(n-3) (linseed oil, high-PUFA diet) or devoid of 18:3(n-3) (hydrogenated palm/sunflower oil, low-PUFA diet). In Experiments I-III, tumor growth increased in the presence of vitamin E compared with control (without vitamin E). Furthermore, it decreased when prooxidant was added. In contrast, no difference was observed when the diet was low in PUFA, suggesting that sensitivity of PUFA to peroxidation may interfere with tumor growth. This observation was supported by growth kinetic parameter analysis, which indicated that tumor growth resulted from variations in cell loss but not from changes in cell proliferation. These data show that, in vivo, PUFA effects on tumor growth are highly dependent on diet oxidative status.

Blood lipid concentrations of docosahexaenoic and arachidonic acids at birth determine their relative postnatal changes in term infants fed breast milk or formula.

BACKGROUND: Factors other than dietary fatty acids could be involved in the variability observed in blood docosahexaenoate (22:6n-3) and arachidonate (20:4n-6) status in formula-fed infants. OBJECTIVE: We considered the 22:6n-3 and 20:4n-6 status at birth to be one of these factors and studied its influence on postnatal changes in term infants fed 4 different diets. DESIGN: The blood phospholipid composition was determined at birth and on day 42 of feeding in 83 term infants fed breast milk, nonsupplemented formula, or 2 different 22:6n-3-supplemented formulas. Relations between 22:6n-3 and 20:4n-6 status at birth and their relative postnatal changes, calculated by the difference between status at the end of the feeding period (6 wk of age) and at birth, were assessed. RESULTS: Postnatal changes in the plasma and erythrocyte phospholipids 22:6n-3 and 20:4n-6 were negatively related to their respective concentrations at birth (P < 0.01) and the slopes of the regression lines were not significantly affected by the type of milk ingested. Adjusted mean values for phospholipid 22:6n-3 in nonsupplemented-formula-fed infants and for 20:4n-6 in formula-fed infants decreased significantly more than they did in the other infant groups (P < 0.02). The status at birth and the type of milk ingested explained 33-64% and 7-47%, respectively, of the variability in postnatal changes. CONCLUSIONS: The status of 22:6n-3 and 20:4n-6 at birth in term infants is one of the major determinants of postnatal changes in these fatty acids. This finding indicates that research is required to characterize environmental, genetic, or both factors, which, in addition to maternal diet, could influence fatty acid status at birth.

n-3 and n-6 fatty acid enrichment by dietary fish oil and phospholipid sources in brain cortical areas and nonneural tissues of formula-fed piglets.

Sufficient availability of both n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFA) is required for optimal structural and functional development in infancy. The question has been raised as to whether infant formulae would benefit from enrichment with 20 and 22 carbon fatty acids. To address this issue, we determined the effect of fish oil and phospholipid (LCPUFA) sources on the fatty acid composition of brain cortical areas and nonneural tissues of newborn piglets fed artificially for 2 wk. They were fed sow milk, a control formula, or the formula enriched with n-3 fatty acids from a low-20:5n-3 fish oil added at a high or a low concentration, or the formula enriched with n-3 and n-6 fatty acids from either egg yolk- or pig brain-phospholipids. Both the fish oil- and the phospholipid-enriched formula produced significantly higher plasma phospholipid 22:6n-3 concentrations than did the control formula. The 22:6n-3 levels in the brain, hepatic, and intestinal phospholipids were significantly correlated with plasma values, whereas cardiac 22:6n-3 content appeared to follow a saturable dose-response. Feeding sow milk resulted in a much higher 20:4n-6 content in nonneural tissues than did feeding formula. Supplementation with egg phospholipid increased the 20:4n-6 content in the heart, red blood cells, plasma, and intestine in comparison to the control formula, while pig brain phospholipids exerted this effect in the heart only. The addition of 4.5% fish oil in the formula was associated with a decline in 20:4n-6 in the cortex, cerebellum, heart, liver, and plasma phospholipids, whereas using this source at 1.5% limited the decline to the cerebellum, liver, and plasma. Whatever the dietary treatment, the phosphatidylethanolamine 20:4n-6 level was 10-20% higher in the brain temporal lobe than in the parietal, frontal, and occipital lobes in the temporal lobe by administering the formula enriched with egg or brain phospholipids. In conclusion, feeding egg phospholipids to neonatal pigs increased both the 22:6n-3 content in the brain and the 20:4n-6 content in the temporal lobe cortex. This source also increased the 22:6n-3 levels in nonneural tissues with only minor alterations of 20:4n-6. These data support the notion that infant formulae should be supplemented with both 22:6n-3 and 20:4n-6 rather than with 22:6n-3 alone.

Dietary fish oil affects monoaminergic neurotransmission and behavior in rats.

We studied the effects of a fish oil enriched diet on fatty acid composition of cerebral membranes and on several neurochemical and behavioral variables of monoaminergic function in rats. The frontal cortex, striatum, hippocampus and cerebellum were studied in rats fed fish oil (FPO, 50% salmon oil + 50% palm oil), which provided an (n-6)/(n-3) polyunsaturated fatty acid (PUFA) ratio of 0.14 versus 6. 19 in controls fed a diet containing a mixture of African peanut oil and rapeseed oil. In the FPO group compared to the control group, the major modifications in fatty acid composition of cerebral membranes included the following: higher levels in 22:6(n-3), lower levels in 20:4(n-6) and a significantly greater proportion of phosphatidylserine. Dopamine levels were 40% greater in the frontal cortex of rats fed FPO than from those fed the control diet. In this cerebral region there was also a reduction in monoamine oxidase B (MAO-B) activity and greater binding to dopamine D2 receptors. By contrast, a lower binding to dopamine D2 receptors (-7%) was observed in the striatum. Ambulatory activity was also reduced in FPO-fed rats, possibly related to observed changes in striatal dopaminergic receptors. This suggested that the level of (n-6) PUFA, which was considerably lower in the FPO diet than in the control diet, could act on locomotion through an effect on striatal dopaminergic function, whereas the high level of (n-3) PUFA could act on cortical dopaminergic function.

Effect of two types of fish oil supplementation on plasma and erythrocyte phospholipids in formula-fed term infants.

We studied the effect of docosahexaenoic acid (DHA) supplementation of infant formulas on fatty acid composition of blood phospholipids in term infants. Two fish oil supplemented formulas containing 0.45 wt% DHA and high (0.35%) or low (0.10%) eicosapentaenoic acid (EPA) were fed for 42 days and compared with a standard formula and breast milk. Infants fed supplemented formulas and breast milk had similar time-dependent changes for DHA from birth to day 42, i.e., slight decreases in plasma phospholipids and erythrocyte phosphatidylcholine and no change in erythrocyte phosphatidylethanolamine. Low-EPA formula prevented EPA accumulation but did not limit the significant decrease in arachidonic acid (AA) noted in infants fed high-EPA formula. These results suggest that term infant formulas should be supplemented with DHA-rich EPA, low fish oil and AA to achieve a fatty acid status in formula-fed infants similar to that of breast-fed infants.

Chronic dietary n-3 polyunsaturated fatty acids deficiency affects the fatty acid composition of plasmenylethanolamine and phosphatidylethanolamine differently in rat frontal cortex, striatum, and cerebellum.

As chronic consumption of a diet devoid of n-3 fatty acid induced modification of neurotransmission pathways in the frontal cortex of rats, plasmalogen alteration could occur in this area. Because of the propensity to facilitate membrane fusion, plasmenylethanolamine (PmE), a major plasmalogen of brain, may be involved in synaptic transmission. Female rats were fed diet containing peanut oil [(n-3)-deficient diet] through two generations. Two weeks before mating, half of the female rats of the second generation received a diet containing peanut oil and rapeseed oil (control group). The distribution and acyl composition of major phospholipids, phosphatidylethanolamine and PmE, were measured in the frontal cortex, striatum, and cerebellum of the male progeny of the two groups at 60 d of age. The n-3 polyunsaturated fatty acid (PUFA) deficiency had no effect on the distribution of phospholipids in all brain regions but affected their acyl composition differently. The level of 22:6n-3 was significantly lower and compensated for by higher levels of n-6 fatty acids in all regions and phospholipids studied. However, docosahexaenoic acid, being more concentrated in the PmE of frontal cortex, is also more decreased in the n-3-deficient rats compared to the striatum. By contrast, striatum PmE has retained more 22:6n-3 than PmE of the other regions. In addition, the increase of n-6 PUFA was significantly lower in frontal cortex PmE compared to the striatum and cerebellum PmE. In association with altered neurotransmission observed in frontal cortex of n-3-deficient rats, our results suggest that frontal cortex PmE might be more affected in chronically alpha-linolenic-deficient rats. However, by retaining 22:6n-3, striatum PmE could be most resilient.

Moderate intake of n-3 fatty acids for 2 months has no detrimental effect on glucose metabolism and could ameliorate the lipid profile in type 2 diabetic men. Results of a controlled study.

OBJECTIVE: To evaluate the effect of a moderate dose of fish oil on glycemic control and in vivo insulin action in type 2 diabetic men with elevated plasma triacylglycerols and to determine the effect of the same treatment on gene expression of GLUT4, lipoprotein lipase (LPL), and hormone-sensitive lipase (HSL) in the abdominal adipose tissue. RESEARCH DESIGN AND METHODS: A total of 12 type 2 diabetic men were randomly allocated to 2 months of 6 g daily of either fish oil or sunflower oil, separated by a 2-month washout interval, in a double-blind crossover design. RESULTS: For glucose metabolism, 2 months of fish oil supplementation compared with sunflower oil led to similar fasting plasma insulin, glucose, and HbA1c. Basal hepatic glucose production did not increase after fish oil. There was no difference in insulin suppression of hepatic glucose production nor in insulin stimulation of whole-body glucose disposal measured by the euglycemic-hyperinsulinemic clamp. Fish oil did not ameliorate the low mRNA level of GLUT4 in adipose tissue of these patients. For lipid profile, fish oil lowered plasma triacylglycerol more than sunflower oil (P < 0.05) and tended to increase the amount of mRNA of both LPL and HSL in adipose tissue. CONCLUSIONS: A moderate dose of fish oil did not lead to deleterious effects on glycemic control or whole-body insulin sensitivity in type 2 diabetic men, with preserved triacylglycerol-lowering capacities.

Chronic n-3 polyunsaturated fatty acid diet-deficiency acts on dopamine metabolism in the rat frontal cortex: a microdialysis study.

The effects of alpha-linolenic acid diet deficiency on rat dopaminergic metabolism were investigated in the frontal cortex of male 2-3 month-old rats using the microdialysis method. Increased basal levels of dopamine metabolites were observed in the frontal cortex of awake deficient rats, without modification of dopamine levels. Moreover, using KCl perfusion which releases newly synthesized dopamine, no difference was observed in anaesthetized deficient rats versus control rats. In addition, a decrease in dopamine release was observed in anaesthetized deficient rats versus control rats after tyramine stimulation, which is known to induce release of dopamine from vesicular stores. A working model is proposed which suggests that a chronic n-3 polyunsaturated fatty acids (PUFA) deficiency may lead to modifications in the internalization of dopamine in the storage pool in the frontal cortex.

Docosahexaenoic acid concentrations in retinal phospholipids of piglets fed an infant formula enriched with long-chain polyunsaturated fatty acids: effects of egg phospholipids and fish oils with different ratios of eicosapentaenoic acid to docosahexaenoic acid.

Docosahexaenoic acid (DHA; 22:6n-3) is the major fatty acid in the phosphatidylethanolamine of photoreceptor cells. The supply of preformed DHA in milk may play an important role in early human visual development. We examined the effect of adding dietary DHA from yolk or fish oil on its accretion in the retina of newborn piglets fed artificially for 2 wk. DHA-enriched eggs from hens fed rapeseed oil and two fish oils with a high or low ratio of eicosapentaenoic acid (EPA; 20:5n-3) to DHA were used. The basic (conventional) formula contained (% by wt of total fatty acids) 17% linoleic acid (18:2n-6) and 1.3% alpha-linolenic acid (18:3n-3). The yolk-enriched formula also contained 0.5% arachidonic acid (AA; 20:4n-6) and 0.4% DHA. The fish-oil-enriched formulas contained either 0.3% EPA and 0.2% DHA (from salmon oil) or < 0.1% EPA and 0.3% DHA (low-EPA fish oil used at a low concentration), or 0.1% AA, 0.3% EPA, and 0.9% DHA (low-EPA fish oil used at a high concentration). The low-EPA fish oil used at a low concentration can supply the DHA required without increasing the EPA status but only the yolk-enriched formula allowed the artificially reared piglets to attain the same AA status in blood lipids as with sow milk feeding. The DHA concentration plateaued in the retina when it reached 7.5% by wt of total fatty acids in plasma phospholipids. Yolk phospholipids and fish oils are equally potent sources for supplying the highest retinal DHA concentration, which was found to be 41.7% by wt of total fatty acids in phosphatidylethanolamine (compared with 35% without supplementation). Inclusion of 0.2-0.3% DHA ensures maximal DHA accretion in the retina but cosupplementation with AA is necessary to achieve the status with maternal feeding in blood lipids and to prevent any possible imbalance between n-6 and n-3 fatty acids.

Dietary (n-3) polyunsaturated fatty acids improve adipocyte insulin action and glucose metabolism in insulin-resistant rats: relation to membrane fatty acids.

To study the effects of dietary fish oil on insulin-stimulated glucose metabolism in adipocytes of insulin-resistant rats (rats fed 50% sucrose and 30% fat), eighteen 5-wk-old Sprague-Dawley rats were fed, for 6 wk, a diet containing 30% fat as either fish oil (FO) or a mixture of vegetable and animal oils [control oils (CO)]. A third reference group was fed a standard diet (62% corn starch and 13% fat). At the end of the 6-wk period, the two experimental groups had comparable plasma glucose concentrations that were higher than that found in the reference group. FO feeding corrected the hyperinsulinemia of the experimental rats (P < 0.05) to reach values in the reference group. Plasma triacylglycerol (P < 0.01) and cholesterol (P < 0.001) concentrations were also lower in rats fed FO than in those fed CO. The body weights of FO-fed rats were similar to that of CO-fed rats, but epididymal adipose tissue weight was lower (P < 0.01). Adipocytes of FO-fed rats, compared with those of CO-fed rats, had high insulin-stimulated glucose transport (P < 0.05), oxidation (P < 0.001) and incorporation into total lipids (P < 0.05). The incorporation of (n-3) polyunsaturated fatty acids in adipocyte membrane phospholipids was higher in FO-fed rats than in those fed CO (P < 0.0001). Insulin action was positively correlated with the fatty acid unsaturation index in membrane phospholipids. Thus dietary fish oil has beneficial effects on insulinemia, plasma lipids and insulin-stimulated glucose metabolism in insulin-resistant slightly diabetic rats.

Does an increase in dietary linoleic acid modify tissue concentrations of cervonic acid and consequently alter alpha-linolenic requirements? Minimal requirement of linoleic acid in adult rats.

Rats were fed a control diet containing both linoleic and alpha-linolenic acid. When 60-days-old they were divided into 8 groups, each receiving the same amount of alpha-linolenic acid, but varying amounts of linoleic acid. When the (n-6)/(n-3) ratio in the diet varied from 2 to 32 (with a constant amount of 150 mg alpha-linolenic acid per 100 g diet), tissue levels of the (n-3) series fatty acids were not significantly modified, except in the liver, heart and testes. In all organs studied, the saturated and monounsaturated fatty acids were practically unchanged. For the (n-6) series fatty acids, arachidonic acid was not significantly affected, in muscle, kidney, brain, myelin, nerve-endings or sciatic nerve, whatever the quantity of linoleic acid in the diet. In liver, arachidonic acid plateaued at 2400 mg linoleic acid/100 g diet and at 400 mg/100 g diet in heart. Results for 22:5(n-6) showed a marked increase in heart, a moderate increase in liver and kidney, and no effect in muscle, testes, brain, myelin, nerve-endings or sciatic nerve. This experiment defined the minimum amount of linoleic acid required in the diet to maintain fatty acids of the linoleic family in the young adult rat. For the first time it was demonstrated that 1200 mg/100 g diet are sufficient for the liver, as evidenced by maintenance of the arachidonic acid concentration. For the other organs, there is either a very marked preservation of this acid, or the dietary level is less than 300 mg/100 g diet. For the essential fatty acid precursors (i.e. linoleic and alpha-linolenic acids), the optimal (n-6)/(n-3) ratio required in the diet is about 8.

alpha-Linolenic acid dietary deficiency alters age-related changes of dopaminergic and serotoninergic neurotransmission in the rat frontal cortex.

The effects of alpha-linolenic acid diet deficiency on rat dopaminergic and serotoninergic neurotransmission systems were investigated in the frontal cortex, striatum, and cerebellum of male rats 2,6,12, and 24 months of age. The diet deficiency induced severe decrease in the 22:6n-3 fatty acid levels in all regions and a compensatory increase in n-6 fatty acid levels. A recovery in the levels of 22:6n-3 was observed in deficient rats between 2 and 12 months of age; however, this recovery was lower in frontal cortex than in striatum and cerebellum. In the striatum and cerebellum, dopaminergic and serotoninergic receptor densities and endogenous dopamine and serotonin levels were affected by aging regardless of the diet. In contrast, a 40-75% lower level of endogenous dopamine in the frontal cortex occurred in deficient rats according to age. The deficiency also induced an 18-46% increase in serotonin 5-HT2 receptor density in the frontal cortex during aging, without variation in endogenous serotonin level, and a 10% reduction in density of dopaminergic D2 receptors. Monoamine oxidase-A and -B activities showed specific age-related variations but regardless of the diet. Our results suggest that a chronically alpha-linolenic-deficient diet specifically affects the monoaminergic systems in the frontal cortex.