Immunomodulation of Labeo rohita juveniles due to dietary gelatinized and non-gelatinized starch

A 60 days experiment was conducted to study the effect of dietary gelatinized (G) and non-gelatinized (NG) starch on immunomodulation of Labeo rohita juveniles. Two hundred and thirty four juveniles (av. wt. 2.53+/-0.04) were randomly distributed in six treatment groups with each of three replicates. Six semi-purified diets containing NG and G corn starch, each at six levels of inclusion (0, 20, 40, 60, 80, 100) were prepared viz., T(1) (100% NG, 0% G starch), T(2) (80% NG, 20% G starch), T(3) (60% NG, 40% G starch), T(4) (40% NG, 60% G starch), T(5) (20% NG, 80% G starch) and T(6) (0% NG, 100% G starch). After a feeding period of 60 days, the juveniles were challenged with Aeromonas hydrophila to study their immunomodulation due to feeding of G and NG starch. RBC and haemoglobin content were significantly (P<0.05) reduced due to bacterial challenge, but dietary starch (G/NG starch) had no effect on it. G:NG starch ratio in the feed had significant effect on total leukocyte count during pre- and post-challenge periods. The leukocyte count concomitantly increased with the increased level of G starch in the diet. Highest albumin/globulin (A/G) ratio was recorded in T6 group (100% G starch) and lowest in T1 group (100% NG starch) group followed by T2 group both in pre- and post-challenge periods. NBT, lysozyme activity, total protein and globulin content were highest in T2 group (80% NG, 20% G starch) both in pre- and post-challenge periods. After challenge with A. hydrophila, the highest survival was recorded in T2 group, whereas lowest survival was recorded in T6 group. Conclusively high level of G starch was found to be immunosuppressive in Labeo rohita juveniles and NG:G starch ratio of 80:20 seems to be optimum for promoting growth and protecting immunity in L. rohita juveniles.     

Effect of dietary carbohydrate on haematology, respiratory burst activity and histological changes in L. rohita juveniles

A feeding trial was conducted for 60 days to delineate the effect of dietary carbohydrate on the haematology, respiratory burst activity and histology in Labeo rohita juveniles. One hundred and forty four fish (av. wt. 10+/-0.15 g) were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets with either 35% or 28% of crude protein were prepared with different amylase concentrations (0, 50, 100 and 150 mgkg(-1)) and starch type (gelatinised, G/non-gelatinised, NG) designated as T1 (NG, 35% CP, 0 mgkg(-1) amylase), T2 (G, 35% CP, 0 mgkg(-1) amylase), T3 (NG, 28% CP, 50 mgkg(-1) amylase), T4 (NG, 35% CP, 50 mgkg(-1) amylase), T5 (G, 28% CP, 50 mgkg(-1) amylase), T6 (G, 35% CP, 50 mgkg(-1) amylase), T7 (NG, 28% CP, 100 mgkg(-1) amylase), T8 (NG, 35% CP, 100 mgkg(-1) amylase), T9 (G, 28% CP, 100 mgkg(-1) amylase), T10 (G, 35% CP, 100 mgkg(-1) amylase), T11 (NG, 28% CP, 150 mgkg(-1) amylase) and T12 (NG, 35% CP, 150 mgkg(-1) amylase). The fish were acclimatised to the experimental conditions for 15 days during which time the control diet was fed. The blood haemoglobin percentage and RBC count was not significantly different (P>0.05) among the various treatments. Highest WBC count, total plasma protein, serum globulin and respiratory burst activity was found at 50 mgkg(-1) dietary amylase supplementation, whereas no variation (P>0.05) was found at 0, 100 and 150 mgkg(-1) dietary amylase supplementation. There was no difference (P>0.05) in the serum albumin and AG ratio among the experimental groups. Feeding either gelatinised or non-gelatinised carbohydrate did not affect the histological structure of the liver, kidney and intestine except in the T4 and T7 groups. The T4 group showed hyperplasia of the intestine and moderate vacuolation in hepatic cells, whereas the T7 group showed hyperplasia of the intestine. Non-gelatinised carbohydrates (46%) along with supplementation with 50 mgkg(-1) amylase stimulated the immune system in L. rohita juveniles. But supplementation of amylase to the gelatinised carbohydrate had no immunostimulating effect.     

Haemato-immunological responses to dietary yeast RNA, omega-3 fatty acid and beta-carotene in Catla catla juveniles

A preliminary study with 60 days feeding was conducted to study the immunomodulatory role of different immunostimulants like beta-carotene, omega-3 fatty acid and yeast-RNA in Catla catla fingerlings. Two hundred and sixty four fingerlings were randomly distributed into eight treatment groups with each of three replicates. Eight isonitrogenous (crude protein 34.12-35.40%) and isocaloric (458.41-461.48 kcal/100g) purified diets were prepared with graded level of beta-carotene, omega-3 fatty acid and yeast-RNA viz., Control (basal diet), T1 (Basal + 1% omega-3 fatty acid), T2 (Basal + 3% omega-3 fatty acid), T3 (Basal + beta-carotene), T4 (T1 + beta-carotene), T5 (T2 + beta-carotene), T6 (Basal + 0.4% yeast-RNA) and T7 (Basal + 0.8% yeast-RNA). The immunomodulatory effects of dietary immunostimulants were studied in terms of respiratory burst activity (NBT) of blood phagocytes, total leukocyte count, serum total protein, serum globulin, A/G ratio (A/G) and serum lysozyme activity. The respiratory burst activity of T7 group was significantly higher (p<0.05) than the other groups. Haemoglobin content, total erythrocyte count and serum albumin content did not vary among the treatment groups, whereas total leukocyte count, serum globulin content and serum lysozyme activity were found to be highest in T7 group. Relative survival percent after challenge with Aeromonas hydrophila was also highest in T7 (88.88%) group followed by T6 (75.06%) and T4 (66.66%) and the lowest in T2 group. It was observed that total leucocyte count, NBT and lysozyme activity of T2 group fed with high omega-3 fatty acid (3%) was less than (p<0.05) its lower counterparts T1 (1%) and control group. Based on the results of the present study, it concludes that supplementation of yeast-RNA at 0.8% registered higher immunological responses in C. catla juveniles. It is also observed that higher supplementation of omega-3 fatty acid (3%) in the diet causes immunosuppression in C. catla juveniles.     

Dietary yeast RNA supplementation reduces mortality by Aeromonas hydrophila in rohu (Labeo rohita L.) juveniles

A feeding trial was conducted for 60 days to delineate the effect of dietary ribonucleic acid or chitin on haematological parameters, phagocyte respiratory burst and resistance to Aeromonas hydrophila of Labeo rohita juveniles. One hundred and twenty-six (avg. wt. 13.40 +/- 0.17 g) juveniles were randomly distributed in six treatment groups, each one in three replicates. Six isonitrogenous (crude protein: 34.34-35.37%) and isocaloric (414-425 kcal 100 g(-1)) purified diets were prepared with different concentrations of either ribonucleic acid or chitin except the control group, viz., control, T1 (0.1% ribonucleic acid), T2 (0.2% ribonucleic acid), T3 (0.4% ribonucleic acid), T4 (25 mg chitin kg (-1)) and T5 (50 mg chitin kg (-1)). Weight gain %, specific growth rate, feed efficiency ratio, protein efficiency ratio did not vary significantly (P > 0.05) among the experimental groups. Haemoglobin content and total erythrocyte count were observed within the normal range and were not influenced by the dietary immunostimulants. Highest total leukocyte count was found in the T(3) group. The immunomodulatory effects of dietary immunostimulants were studied by using nitroblue tetrazolium (NBT) assay and serum parameters, namely total protein, albumin, globulin and A/G ratio. The respiratory burst activity (NBT) of blood phagocytes was highest in the T3 group followed by the T2 group, which varied significantly (P < 0.05) from other groups. Significantly (P < 0.05) higher total protein, globulin and lower A/G ratio was observed in the T(3) group. The relative percent survival after challenging with Aeromonas hydrophila was highest in the T3 group, compared to the control group, followed by the T2 group. The results indicate that dietary ribonucleic acid at 0.4% enhances phagocyte respiratory burst and protection of Labeo rohita juveniles to challenge by A. hydrophila.     

Enhanced innate immune parameters in Labeo rohita (Ham.) following oral administration of Bacillus subtilis

The present study assessed the use of Bacillus subtilis in fish as a probiotic. The bacterium was administered orally at three different doses 0.5 x 10(7) (T(2)), 1 x 10(7) (T(3)), 1.5 x 10(7) (T(4)) cfu/g feed to Labeo rohita for two weeks. The positive control group (T(1)) and negative control group (T(5,)) were fed feed without B. subtilis for the same period. On the 15th day blood and serum were sampled to determine respiratory burst activity (NBT assay), differential leukocyte counts (DLC) and serum bactericidal activity. Fishes were challenged intraperitoneally with Aeromonas hydrophila O:18 after two weeks in the treatment groups (T(2), T(3) and T(4)) and also in the positive control group(T(1)), while the negative control group (T(5)) was challenged with phosphate buffered saline (PBS, pH 7.2) only. The respiratory burst activity and DLC were assessed on the 3rd day post-challenge. B. subtilis treated fish showed significantly higher (P<0.05) respiratory burst activity and bactericidal activity during the pre-challenge compared with the control groups. The highest respiratory burst activity (0.37+/-0.03) and serum bactericidal activity were recorded in the group (T(4)) fed feed containing B. subtilis at 1.5 x 10(7)cfu/g feed. Granulocyte numbers were significantly higher (P<0.05) in treatment groups in comparison to the control in both the pre- and post-challenge periods. The result suggests that B. subtilis can enhance certain innate immune responses in rohu.     

Dietary microbial levan enhances cellular non-specific immunity and survival of common carp (Cyprinus carpio) juveniles

A preliminary study with a 75days feeding trial was conducted to study the immunomodulatory effect of microbial levan on Cyprinus carpio juveniles. Five purified isonitrogenous and isocaloric diets with graded levels of levan, namely (T(1)) 0.1% levan, (T(2)) 0.2% levan, (T(3)) 0.5% levan, (T(4)) 1.0% levan, and a control group without levan were fed to five groups of fishes in triplicate. The total erythrocyte count and haemoglobin content was significantly (p<0.05) enhanced in the T(3) group, though the total leucocyte counts, total protein and A/G ratio did not show any significant difference (p>0.05) when compared with the control group. The respiratory burst activity (NBT) of blood phagocytes and lysozyme activity was also highest in T(3) group. The relative survival percentage after challenge with Aeromonas hydrophila was highest (100%) in the T(3) group followed by 83.33% and 66.67% in the T(2) and T(4) groups, respectively. This suggests that microbial levan at 0.5% can be used as a dietary immunostimulant for C. carpio juveniles. This is the first report on microbial levan having an immunomodulatory effect on C. carpio.     

Effect of Mangifera indica kernel as a feed additive on immunity and resistance to Aeromonas hydrophila in Labeo rohita fingerlings

The study evaluated the efficacy of dietary doses of Mangifera indica (mango) kernel on the immune response and disease resistance of Labeo rohita fingerlings against the bacterial pathogen Aeromonas hydrophila infections in. L. rohita fingerlings fed diet containing 0 (Control), 1g, 5 g, 10 g mango kernel kg(-1) dry diet for 60 days. Biochemical (serum total protein, albumin, globulin, albumin:globulin ratio, blood glucose), haematological (WBC, RBC, haemoglobin content) and immunological (superoxide anion production, lysozyme, serum bactericidal activity) parameters of fish were examined at 20, 40 and 60 days of feeding. Fish were challenged with A. hydrophila 60 days post feeding and mortalities were recorded over 10 days post-infection. The results demonstrate that fish fed with mango kernel showed enhanced superoxide anion production, lysozyme, serum bactericidal, serum protein, albumin (P<0.05) compared with the control group. The mortality (%) was recorded up to 10 th day post-challenge. Less survivability was observed in control group (50%) up to day 10 after infection. The survivability was higher in experimental diets. The group fed 5 g kernel kg(-1) dry diet showed highest percentage survival (98%). These results indicate that mango kernel stimulates the immunity and makes L. rohita more resistant to A. hydrophila infection.     

Effects of dietary supplementation of potential probiotic Pseudomonas aeruginosa VSG-2 on the innate immunity and disease resistance of tropical freshwater fish, Labeo rohita

The effects of dietary Pseudomonas aeruginosa VSG-2 supplementation on innate immunity and protection against Aeromonas hydrophila infection were evaluated in Labeo rohita. Fish were fed for 60 days with control diet or 3 experimental diets containing P. aeruginosa VSG-2 at 10(5), 10(7), and 10(9) cfu g(-l), respectively. Various innate immune parameters were examined at 30 and 60 days post-feeding. Fish were challenged with A. hydrophila 60 days post-feeding and mortalities were recorded over 10 days post-infection. Dietary supplementation of P. aeruginosa VSG-2 significantly increased serum lysozyme and alternative complement pathway (ACP) activities, phagocytosis, and respiratory burst activity in head kidney macrophages of L. rohita throughout the experimental period. Superoxide dismutase (SOD) activity significantly increased after 60 days in the groups fed diets containing 10(7) and 10(9) cfu g(-1) P aeruginosa. Serum IgM levels were significantly higher in the treatment groups than in the control group after 30 days of feeding; however, the opposite result was observed at 60 days. Moreover, fish fed diets containing 10(7) and 10(9) cfu g(-1)P. aeruginosa had significantly higher post-challenge survival rates against A. hydrophila infection. Further, P. aeruginosa VSG-2 was found to be safe for mammals. These results indicate that dietary P. aeruginosa VSG-2 supplementation at 10(7) cfu g(-1) can effectively improve innate immunity and disease resistance in L. rohita.     

Leptin levels in rat offspring are modified by the ratio of linoleic to alpha-linolenic acid in the maternal diet

The supply of polyunsaturated fatty acids (PUFA) is important for optimal fetal and postnatal development. We have previously shown that leptin levels in suckling rats are reduced by maternal PUFA deficiency. In the present study, we evaluated the effect of maternal dietary intake of (n-3) and (n-6) PUFA on the leptin content in rat milk and serum leptin levels in suckling pups. For the last 10 days of gestation and throughout lactation, the rats were fed an isocaloric diet containing 7% linseed oil (n-3 diet), sunflower oil (n-6 diet), or soybean oil (n-6/n-3 diet). Body weight, body length, inguinal fat pad weight, and adipocyte size of the pups receiving the n-3 diet were significantly lower during the whole suckling period compared with n-6/n-3 fed pups. Body and fat pad weights of the n-6 fed pups were in between the other two groups at week one, but not different from the n-6/n-3 group at week 3. Feeding dams the n-3 diet resulted in decreased serum leptin levels in the suckling pups compared with pups in the n-6/n-3 group. The mean serum leptin levels of the n-6 pups were between the other two groups but not different from either group. There were no differences in the milk leptin content between the groups. These results show that the balance between the n-6 and n-3 PUFA in the maternal diet rather than amount of n-6 or n-3 PUFA per se could be important for adipose tissue growth and for maintaining adequate serum leptin levels in the offspring.     

N-3 PUFA improved post-menopausal depression induced by maternal separation and chronic mild stress through serotonergic pathway in rats—effect associated with lipid mediators

Early life maternal separation (MS) increases the vulnerability to depression in rats with chronic mild stress (CMS). N-3 polyunsaturated fatty acids (PUFA) improved depressive behaviors in rats with acute stress; however, their effects on rats with MS+CMS were not apparent. The purpose of the present study was to investigate the hypothesis that lifetime n-3 PUFA supplementation improves post-menopausal depression through the serotonergic and glutamatergic pathways while modulating n-3 PUFA-derived metabolites. Female rats were fed diets of either 0% n-3 PUFA during lifetime or 1% energy n-3 PUFA during pre-weaning, post-weaning, or lifetime periods. Rats were allocated to non-MS or MS groups and underwent CMS after ovariectomy. N-3 PUFA increased brain n-3 PUFA-derived endocannabinoid/oxylipin levels, and reversed depressive behaviors. N-3 PUFA decreased blood levels of adrenocorticotropic hormone and corticosterone, and brain expressions of corticotropin-releasing factor and miRNA-218, which increased the expression of the glucocorticoid receptor. N-3 PUFA decreased the expression of tumor necrosis factor-α, interleukin (IL)-6, IL-1β, and prostaglandin E₂, while increased the expression of miRNA-155. N-3 PUFA also increased brainstem serotonin levels and hippocampal expression of the serotonin-1A receptor, cAMP response element-binding protein (CREB), phospho-CREB, and brain-derived neurotrophic factor. However, n-3 PUFA did not affect brain expression of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subtype 1, N-methyl-D-aspartate receptor subtype 2B, or miRNA-132. Moreover, n-3 PUFA exposure during lifetime caused greater effects than pre- and post-weaning periods. The present study suggested that n-3 PUFA improved depressive behaviors through serotonergic pathway while modulating the metabolites of n-3 PUFA in post-menopausal depressed rats with chronic stress.     

N-3 polyunsaturated fatty acids prevent the defect of insulin receptor signaling in muscle

A high-fat diet containing polyunsaturated fatty acids (PUFA: n-3 or n-6) given for 4 wk to 5-wk-old male Wistar rats induced a clear hyperglycemia (10.4 +/- 0.001 mmol/l for n-6 rats and 10.1 +/- 0.001 for n-3 rats) and hyperinsulinemia (6.6 +/- 0.8 ng/ml for n-6 rats and 6.4 +/- 1.3 for n-3 rats), signs of insulin resistance. In liver, both diets (n-3 and n-6) significantly reduced insulin receptor (IR) number, IR and IR substrate (IRS)-1 tyrosine phosphorylation, and phosphatidylinositol (PI) 3'-kinase activity. In contrast, in leg muscle, IR density, as determined by Western blotting, was not affected, whereas IR and IRS-1 tyrosine phosphorylation in response to insulin treatment was restored in animals fed with n-3 PUFA to normal; in n-6 PUFA, the phosphorylation was depressed, as evidenced by Western blot analysis using specific antibodies. In addition, PI 3'-kinase activity and GLUT-4 content in muscle were maintained at normal levels in rats fed with n-3 PUFA compared with rats fed a normal diet. In rats fed with n-6 PUFA, both PI 3'-kinase activity and GLUT-4 content were reduced. Furthermore, in adipose tissue and using RT-PCR, we show that both n-3 and n-6 PUFA led to slight or strong reductions in p85 expression, respectively, whereas GLUT-4 and leptin expression was depressed in n-6 rats. The expression was not affected in n-3 rats compared with control rats. In conclusion, a high-fat diet enriched in n-3 fatty acids maintained IR, IRS-1 tyrosine phosphorylation, and PI 3'-kinase activity and total GLUT-44 content in muscle but not in liver. A high-fat diet (n-3) partially altered the expression of p85 but not that of GLUT-4 and leptin mRNAs in adipose tissue.     

Dietary polyunsatured fatty acids (PUFA) differentially modulate melamine-induced preneoplastic urothelial proliferation and apoptosis in mice

A number of experimental and epidemiological studies indicate that dietary polyunsaturated fatty acids (PUFA) play a modulatory role in the development of several cancers. However, literature on the importance of dietary PUFA in urinary-tract tumourigenesis is scarce, and even contradictory. Therefore, our purpose was to evaluate comparatively, several urothelial cellular parameters linked to neoplasia when 180 BALB/c mice were initiated with the tumourigenic agent melamine and fed with two amounts of different PUFA. In experiment 1, mice were fed with 6% of fish oil (enriched in n-3 PUFA, FO), corn oil (enriched in n-6, CO) and olein (enriched in n-9, an EFA deficiency inducer) formulae plus two chow-fed control lots with (CM) and without (C) melamine treatment. In experiment 2, each of the three varieties of PUFA were offered at 10%. Following 18-22 weeks of melamine treatment, animals were autopsied. The liver fatty acid profile showed a close correlation with the dietary sources, exhibiting in the O group macroscopic and biochemical EFA-deficient (EFAD) characteristics. The frequency of simple urothelial hyperplasias (H) and dysplasia/carcinoma in situ (D/CIS) was significantly lower in the FO group, whereas both types of lesions increased in the CO and O groups, compared to the C and CM mice. Increased proliferation and abnormal luminal localized mitosis were more frequently recorded in EFAD mice, whereas abnormal apoptotic/mitosis ratio increased in both olein- and corn-oil-fed animals. This study shows that dietary PUFA modulate differentially normal and pre-neoplastic proliferation when induced by the tumorigenic agent melamine. Fish oil, rich in n-3 fatty acids, exhibits a clear antipromoting activity, whereas the role of n-6 and n-9 PUFA derivatives needs further research.     

Fatty acid composition of membrane bilayers: Importance of diet polyunsaturated fat balance

In one of the most extensive analyses to date we show that the balance of diet n-3 and n-6 polyunsaturated fatty acids (PUFA) is the most important determinant of membrane composition in the rat under 'normal' conditions. Young adult male Sprague-Dawley rats were fed one of twelve moderate-fat diets (25% of total energy) for 8weeks. Diets differed only in fatty acid (FA) profiles, with saturate (SFA) content ranging 8-88% of total FAs, monounsaturate (MUFA) 6-65%, total PUFA 4-81%, n-6 PUFA 3-70% and n-3 PUFA 1-70%. Diet PUFA included only essential FAs 18:2n-6 and 18:3n-3. Balance between n-3 and n-6 PUFA is defined as the PUFA balance (n-3 PUFA as % of total PUFA) and ranged 1-86% in the diets. FA composition was measured for brain, heart, liver, skeletal muscle, erythrocytes and plasma phospholipids, as well as adipose tissue and plasma triglycerides. The conformer-regulator model was used (slope=1 indicates membrane composition completely conforming to diet). Extensive changes in diet SFA, MUFA and PUFA had minimal effect on membranes (average slopes 0.01, 0.07, 0.07 respectively), but considerable influence on adipose tissue and plasma triglycerides (average slopes 0.27, 0.53, 0.47 respectively). Diet balance between n-3 and n-6 PUFA had a biphasic influence on membrane composition. When n-3 PUFA<10% of total PUFA, membrane composition completely conformed to diet (average slope 0.95), while diet PUFA balance>10% had little influence (average slope 0.19). The modern human diet has an average PUFA balance ~10% and this will likely have significant health implications.     

Dietary fish oil and flaxseed for rabbit does: fatty acids distribution and Δ6-desaturase enzyme expression of different tissues

Standard feeds are imbalanced in term of n-6/n-3 polyunsaturated fatty acids (PUFA) ratio, with a low proportion of the latter. The reproductive system appears to be strongly affected by administration of n-3 PUFA, and ingredients rich in α-linolenic acid (ALA; i.e. vegetable sources) or EPA and DHA acids (i.e. fish oil) can be included in animal diets to balance PUFA intake. The aim of this study was to evaluate the effect of dietary supplementation with flaxseed (ALA) or fish oil (EPA and DHA) on PUFA metabolism in rabbit does. A total of 60 New Zealand White female rabbits were assigned to three experimental groups: control group, FLAX group fed 10% extruded flaxseed and FISH group fed 3% fish oil. Blood, milk, liver and ovaries were collected from the does to assess the lipid composition; furthermore, FADS2 gene expression was assessed in liver and ovary tissues. Reproductive performance of does was also recorded. The fertility rate and number of weaned rabbits improved with n-3 dietary supplementation: does at first parity showed the lowest reproductive results, but the administration of n-3 reduced the gap between primiparous and multiparous does. Feed consumption and milk production were not affected by the feeding regime. The fatty acid composition of milk, plasma, liver and ovaries were widely influenced by diet, showing higher concentrations of n-3 long-chain PUFA (LCP) in does fed with n-3 enriched diets. FISH diet resulted in the highest n-3 LCP enrichment, whereas in the FLAX group, this increase was lower. Blood and milk showed low levels of LCP, whereas liver and ovaries were the main sites of n-3 LCP synthesis and accumulation. Accordingly, although the liver is the main metabolic centre for LCP synthesis, ovaries also have a prominent role in LCP generation. FADS2 expression in liver and ovary tissue was downregulated by FISH administration. In conclusion, the enrichment of diets with n-3 PUFA could be an effective strategy for improving the reproductive performance of does.     

Immunostimulant effects of Cotinus coggyria on rainbow trout (Oncorhynchus mykiss)

In this study, non-specific immune effects of tetra (Cotinus coggyria) on rainbow trout (Oncorhynchus mykiss) by dietary intake were investigated. Fish were fed daily ad libitum with diets containing 0.5% and 1.0% tetra for 3 weeks. After this period, fish were switched back to the basal diet for additional 6 weeks. Extracellular and intracellular respiratory burst activities, phagocytosis in blood leukocytes, lysozyme activities, and total plasma protein levels were evaluated at the end of the tetra feeding period and every 3 weeks during the basal diet period. Extracellular and intracellular respiratory burst activities, phagocytic activity, lysozyme activity and total protein level parameters of the groups containing 0.5% and 1.0% tetra were higher than the control group at the end of the 3rd, 6th and 9th weeks, respectively (P < 0.05). The highest values of the non-specific immune parameters were observed in the group fed with 1.0% tetra. Tetra groups did not show any significant difference (P > 0.05) in terms of specific growth rate and average weight of the fish.     

n-3 Fatty acids modulate brain glucose transport in endothelial cells of the blood-brain barrier

We have previously shown that glucose utilization and glucose transport were impaired in the brain of rats made deficient in n-3 polyunsaturated fatty acids (PUFA). The present study examines whether n-3 PUFA affect the expression of glucose transporter GLUT1 and glucose transport activity in the endothelial cells of the blood-brain barrier. GLUT1 expression in the cerebral cortex microvessels of rats fed different amounts of n-3 PUFA (low vs. adequate vs. high) was studied. In parallel, the glucose uptake was measured in primary cultures of rat brain endothelial cells (RBEC) exposed to supplemental long chain n-3 PUFA, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, or to arachidonic acid (AA). Western immunoblotting analysis showed that endothelial GLUT1 significantly decreased (-23%) in the n-3 PUFA-deficient microvessels compared to control ones, whereas it increased (+35%) in the microvessels of rats fed the high n-3 PUFA diet. In addition, binding of cytochalasin B indicated that the maximum binding to GLUT1 (Bmax) was reduced in deficient rats. Incubation of RBEC with 15 microM DHA induced the membrane DHA to increase at a level approaching that of cerebral microvessels isolated from rats fed the high n-3 diet. Supplementation of RBEC with DHA or EPA increased the [(3)H]-3-O-methylglucose uptake (reflecting the basal glucose transport) by 35% and 50%, respectively, while AA had no effect. In conclusion, we suggest that n-3 PUFA can modulate the brain glucose transport in endothelial cells of the blood-brain barrier, possibly via changes in GLUT1 protein expression and activity.     

Zinc deficiency and the desaturation of linoleic acid in rats force-fed fat-free diets

Recent studies with rats force-fed zinc-deficient diets containing various types of fat failed to demonstrate a role of zinc in desaturation of linoleic acid. The present study was conducted to investigate the effect of zinc deficiency on desaturation of linoleic acid in rats that were initially force-fed fat-free diets to stimulate activity of desaturases. Therefore, rats were fed zinc-adequate and zinc-deficient fat-free diets for 6 d. After that period, the groups were divided and half of the rats continued feeding the fat-free diet for another 3.5 d whereas the other half was switched to a fat diet by supplementing the fat-free diet with 5% safflower oil. In order to assess desaturation of linoleic acid, fatty acid compositions of liver phosphatidylcholine, ethanolamine, and-serine were considered, particularly levels of individual (n-6) polyunsaturated fatty acids (PUFA). Levels of total and individual (n-6) PUFA were similar in zinc-adequate and zinc-deficient rats fed the fat-free diet throughout the experiment. Addition of 5% safflower oil increased levels of total and individual (n-6) PUFA in both zinc-adequate and zinc-deficient rats. However, total (n-6) PUFA in all types of phospholipids were higher in zinc-adequate rats than in zinc-deficient rats. Additionally, in zinc-deficient rats there were changes of (n-6) PUFA levels typical for impaired Δ5 and Δ6 desaturation: linoleic acid and dihomo-γ-linolenic acid were elevated; arachidonic acid, docosatetraenoic acid, and docosapentaenoic were lowered by zinc deficiency. Therefore, the study shows that zinc deficiency impairs desaturation of linoleic acid in rats force-fed fat-free diets and therefore supports results from former convential zinc deficiency experiments suggesting a role of zinc for desaturation of linoleic acid.     

The Fat-1 Mouse has Brain Docosahexaenoic Acid Levels Achievable Through Fish Oil Feeding

Fat-1 transgenic mice endogenously convert n-6 to n-3 polyunsaturated fatty acids (PUFA). The aims of this study were to test whether a) fish oil feeding can attain similar brain n-3 PUFA levels as the fat-1 mouse, and b) fat-1 mouse brain docosahexaenoic acid (22:6n-3; DHA) levels can be potentiated by fish oil feeding. Fat-1 mice and their wildtype littermates consumed either a 10% safflower oil (SO) or a 2% fish oil and 8% safflower oil chow (FO). Brain total lipid and phospholipid fraction fatty acids were analyzed using GC-FID. Wildtype mice fed FO chow had similar brain levels of DHA as fat-1 mice fed SO chow. Fat-1 mice fed FO chow had similar brain n-3 PUFA levels as fat-1 mice fed SO chow. In conclusion, brain levels of DHA in the fat-1 mouse can be obtained by and were not further augmented with fish oil feeding.     

n-3 Fatty acids modulate brain glucose transport in endothelial cells of the blood–brain barrier

We have previously shown that glucose utilization and glucose transport were impaired in the brain of rats made deficient in n-3 polyunsaturated fatty acids (PUFA). The present study examines whether n-3 PUFA affect the expression of glucose transporter GLUT1 and glucose transport activity in the endothelial cells of the blood–brain barrier. GLUT1 expression in the cerebral cortex microvessels of rats fed different amounts of n-3 PUFA (low vs. adequate vs. high) was studied. In parallel, the glucose uptake was measured in primary cultures of rat brain endothelial cells (RBEC) exposed to supplemental long chain n-3 PUFA, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, or to arachidonic acid (AA). Western immunoblotting analysis showed that endothelial GLUT1 significantly decreased (−23%) in the n-3 PUFA-deficient microvessels compared to control ones, whereas it increased (+35%) in the microvessels of rats fed the high n-3 PUFA diet. In addition, binding of cytochalasin B indicated that the maximum binding to GLUT1 (Bmax) was reduced in deficient rats. Incubation of RBEC with 15 μM DHA induced the membrane DHA to increase at a level approaching that of cerebral microvessels isolated from rats fed the high n-3 diet. Supplementation of RBEC with DHA or EPA increased the [³H]-3-O-methylglucose uptake (reflecting the basal glucose transport) by 35% and 50%, respectively, while AA had no effect. In conclusion, we suggest that n-3 PUFA can modulate the brain glucose transport in endothelial cells of the blood–brain barrier, possibly via changes in GLUT1 protein expression and activity.     

The effect of dietary fish oils on eicosanoid biosynthesis in peritoneal macrophages is influenced by both dietary N-6 polyunsaturated fats and total dietary fat

Recent research has implicated dietary fish oils in the reduction of eicosanoids formed from arachidonic acid and amelioration of chronic diseases such as coronary heart disease, atherosclerosis and inflammation. Feeding studies were conducted to determine if the efficacy of dietary n-3 polyunsaturated fatty acids (PUFA) from fish oils was influenced by the quantity of n-6 polyunsaturated fatty acids and the total level of fat in the diet. Groups of mice were fed diets composed of 5 and 20% total fat with varying proportions of linoleic acid as a source of n-6 PUFA. Menhaden oil as a source of n-3 PUFA was fed at two levels of n-6 at each level of total fat. Eicosanoid biosynthesis was stimulated and assayed in the mouse peritoneum using zymosan as an inflammatory stimulus. Production of LTE4 and PGE2 was enhanced by increasing n-6 PUFA in the diet at both levels of total fat. High dietary fat significantly suppressed leukotriene (LT) synthesis. Dietary menhaden oil reduced LTE4 and PGE2 synthesis at both levels of dietary n-6 in the low fat study. In animals on 20% dietary fat menhaden oil significantly reduced LT synthesis only at a relatively low dietary n-6 PUFA. On a high n-6 PUFA high fat diets, menhaden oil did not significant affect LTE4 synthesis in response to zymosan stimulation. The results suggest that the effectiveness of fish oils in reducing eicosanoids in response to specific stimulation is influenced by the level of n-6 and the total quantity of fat in the diet.