Effects of methionine supplementation on the incidence of dietary fat induced myocardial lesions in the rat

A Dietary Supply of Docosahexaenoic Acid Early in Life Is Essential for Immune Development and the Establishment of Oral Tolerance in Female Rat Offspring

BACKGROUND

The early postnatal period is critical for immunity, and feeding docosahexaenoic acid (DHA) has been demonstrated to affect immune development.

OBJECTIVE

The objective of this study was to determine the importance of feeding DHA during suckling and/or weaning on immune function and oral tolerance (OT).

METHODS

Sprague-Dawley rats were randomly assigned to 1 of 2 nutritionally adequate diets throughout lactation (21 d): a control (n = 12, 0% DHA) diet or a DHA (n = 8, 0.9% DHA) diet. At 11 d, suckled pups from each dam were randomly assigned to a mucosal OT challenge: placebo or ovalbumin. At week 5, all pups systemically received ovalbumin + adjuvant to induce systemic immunization. At 21 d, pups from each dam were randomly assigned to 1 of the 2 diets for 21 d in a factorial design after which immune function and OT were assessed.

RESULTS

Feeding dams DHA during lactation resulted in a 40-60% higher splenocyte production of interleukin (IL)-10 when stimulated with concanavalin A, lipopolysaccharide (LPS), or ovalbumin and a 100% higher production of interferon (IFN)-γ with LPS (P < 0.05) than feeding the control diet to the pups. In comparison with pups fed the control diet, feeding DHA at weaning resulted in a 25% lower type 1 T helper (IL-1β) and type 2 T helper (IL-6) response by splenocytes after LPS stimulation and a 33% lower plasma concentration of ovalbumin-specific immunoglobulin (Ig) G (P < 0.05). Pups that did not receive additional DHA during the study had a 70% higher plasma concentration of ovalbumin-specific IgE than did the pups that received DHA at suckling and/or weaning (P < 0.05).

CONCLUSIONS

Feeding additional DHA during suckling had a beneficial programming effect on the ability of immune cells to produce IFN-γ and IL-10, and feeding DHA during weaning resulted in a lower inflammatory response. Providing no dietary DHA in either of the critical periods of immune development prevented the establishment of OT in female rat offspring.

Protection of intestinal occludin tight junction protein by dietary gangliosides in lipopolysaccharide-induced acute inflammation

OBJECTIVES

Intestinal permeability and barrier function are regulated by expression of tight junction proteins. Lipopolysaccharide (LPS), tumor necrosis factor-alpha, and interleukin-1beta induce expression of nitric oxide (NO) and reduce the expression of gut tight junction proteins. The purpose of this study was to determine whether dietary gangliosides (GGs) increase the concentration of the anti-inflammatory cytokine interleukin-10 (IL-10) in response to LPS, thereby inhibiting NO production and protecting gut occludin tight junction protein from degradation.

MATERIALS AND METHODS

Rats were fed semipurified diets with (n = 16) or without (n = 16) GGs (0.1% w/w of total lipid). After 2 weeks of feeding, animals were injected with saline (n = 8/diet group) or LPS (n = 8/diet group) (IP, 3 mg mL(-1) kg(-1)). Intestinal tissue, mucosa, and blood sample were collected 6 hours post-LPS exposure. The effect of dietary GGs on production/expression of IL-10, NO, inducible NO synthase, and occludin protein was determined.

RESULTS

Dietary GGs increased IL-10 content in intestinal mucosa significantly by 32-fold (P < 0.0001) and in plasma by 2.4-fold (P < 0.001). Feeding animals a ganglioside-enriched diet decreased total NO content in intestinal mucosa and plasma by 44% and 30%, respectively, and inhibited inducible NO synthase expression following LPS exposure compared with control animals. Dietary GGs reduced the degradation of occludin tight junction protein in response to LPS.

CONCLUSIONS

Dietary GGs inhibit degradation of gut occludin tight junction protein during LPS-induced acute inflammation. Thus, dietary GGs have a role in protecting the integrity of the intestinal barrier during acute gut inflammation.

Dietary ganglioside inhibits acute inflammatory signals in intestinal mucosa and blood induced by systemic inflammation of Escherichia coli lipopolysaccharide

Our previous study demonstrated that feeding ganglioside increased total ganglioside content while decreasing cholesterol and caveolin-1 content in developing rat intestinal lipid microdomains. Cholesterol or caveolin depletion in membranes inhibits inflammatory signaling by disrupting microdomain structure. We hypothesized that dietary ganglioside-induced reduction in cholesterol content will reduce proinflammatory mediators in the intestinal mucosa after acute exposure to bacterial endotoxin. Weanling rats were fed semipurified diets with 0.1% (wt/wt of total fat) gangliosides (treatment) or without ganglioside (control). After 2 weeks of feeding, half of animals from each diet group were injected with saline or lipopolysaccharide (LPS) endotoxin (Escherichia coli serotype O111:B4, intraperitoneal, 3 mg/kg body weight) to induce acute gut inflammation. Intestinal mucosa and blood were collected after 6 h. The effect of dietary ganglioside on proinflammatory mediators including cholesterol, platelet-activating factor, prostaglandin E2, leukotriene B4 (LTB4), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha) was determined in inflamed mucosa and blood. Feeding animals the control diet increased cholesterol content in intestinal lipid microdomains by 92% after LPS injection compared with saline injection. Animals fed the ganglioside diet significantly decreased cholesterol content in lipid microdomains by 60% compared with animals fed the control diet. Feeding animals the ganglioside diet increased total ganglioside content by 90% while decreasing platelet-activating factor content by 45% in the inflamed mucosa by acute systemic exposure to LPS compared with animals fed the control diet. When animals were fed the ganglioside diet, the levels of prostaglandin E2, LTB4, IL-1beta, and TNF-alpha were lower in inflamed mucosa, and LTB4, IL-1beta, and TNF-alpha were decreased in plasma by 41%, 58%, and 55% compared with control animals, respectively. The present study demonstrates that dietary gangliosides inhibit proinflammatory signals in the intestine and blood induced by acute inflammation of LPS and suggests therapeutic potential in the treatment and management of acute local and systemic inflammatory diseases.

L-methionine reduces oxidant stress in endothelial cells: role of heme oxygenase-1, ferritin, and nitric oxide

The amino acid L-methionine is known to exert antioxidant effects by as yet unidentified mechanisms. In the present study, L-methionine led to a concentration-dependent induction of the antioxidant proteins heme oxygenase-1 (HO-1) and ferritin in cultured endothelial cells (ECV 304). HO-1 protein expression was accompanied by an increased catalytic activity of the enzyme. Long-term pre-incubation of endothelial cells with L-methionine reduced NADPH-mediated radical formation by up to 60%. The antioxidant effect of L-methionine was mimicked by the HO-1 product bilirubin, which suppressed free radical formation almost completely. Reduction of superoxide generation by L-methionine was inhibited in the presence of the nitric oxide (NO) synthase inhibitor L-NMMA, suggesting the involvement of endogenous NO in L-methionine-dependent cytoprotection. These findings demonstrate that L-methionine reduces free radical formation in endothelial cells, possibly through induction of heme oxygenase-1 and ferritin. This novel, indirect antioxidant action might be relevant for the preventive potential of methionine and methionine rich diets under conditions of inflammation and oxidative stress.

Dietary ganglioside decreases cholesterol content, caveolin expression and inflammatory mediators in rat intestinal microdomains

Membrane microdomains rich in cholesterol and sphingolipids, including gangliosides (GGs), are known to be important regions for cell signaling and binding sites for various pathogens. Cholesterol depletion inhibits the cellular entry of pathogens and also reduces inflammatory signals by disrupting microdomain structure. Our previous study showed that dietary gangliosides increased total ganglioside incorporation while decreasing cholesterol in the intestinal mucosa. We hypothesized that diet-induced reduction in cholesterol content in the intestinal mucosa disrupts microdomain structure resulting in reduced pro-inflammatory signals. Male weanling Sprague-Dawley rats were fed semipurified diets for 2 weeks. Experimental diets were formulated to include either ganglioside-enriched lipid (GG diet, 0.02% gangliosides [w/w of diet] ) or polyunsaturated fatty acid (PUFA diet, 1% arachidonic acid and 0.5% docosahexaenoic acid, w/w of total fat), in a control diet containing 20% fat. Levels of cholesterol, GG, caveolin, platelet activating factor (PAF), and diglyceride (DG) were measured in the microdomain isolated from the intestinal brush border. The GG diet increased total gangliosides by 50% with a relative increase in GD3 and a relative decrease in GM3. Cholesterol content was also reduced by 23% in the intestinal microdomain. These changes resulted in a significant decrease in the ratio of cholesterol to ganglioside. The GG diet and the PUFA diet were both associated with reduction in caveolin, PAF, and DG content in microdomains, whereas no change occurred in the ganglioside profile of animals fed the PUFA diet. Dietary gangliosides decrease the cholesterol/ganglioside ratio, caveolin, PAF and DG content in microdomains thus exerting a potential anti-inflammatory effect during gut development.

Diet-induced changes in membrane gangliosides in rat intestinal mucosa, plasma and brain

OBJECTIVES

The objective of this study was to determine if dietary gangliosides induce changes in the ganglioside content of intestinal mucosa, plasma and brain and to identify where GM3 and GD3 are localized in the enterocyte membrane.

METHODS

Male 18-day-old Sprague-Dawley rats were fed a semipurified diet containing 20% (w/w) fat. The control diet contained triglyceride, reflecting the fat formulation of an existing infant formula. Two experimental diets were formulated by adding sphingomyelin (1% w/w of total fat) or a ganglioside-enriched lipid (0.1% w/w of total fat) to the control diet fat. The ganglioside fraction of ganglioside-enriched lipid diet contained more than 80% GD3. After 2 weeks of feeding, the total and individual ganglioside and cholesterol content was measured in small intestinal mucosa, plasma and brain.

RESULTS

The ganglioside-enriched lipid diet significantly increased total gangliosides in the intestinal mucosa, plasma and brain compared with the control diet. The ganglioside-enriched lipid diet significantly increased the level of GD3 (7.5% w/w) in the intestine compared with control (3.2% w/w) while decreasing the level of GM3, the major ganglioside in the intestine. The ratio of cholesterol to ganglioside in the intestinal mucosa, plasma and brain decreased significantly in rats fed the ganglioside-enriched lipid diet compared with controls. Confocal microscopy showed that GM3 is exclusively localized in the apical membrane of the enterocyte whereas GD3 is primarily localized in the basolateral membrane.

CONCLUSIONS

: The authors conclude that dietary ganglioside is absorbed in the small intestine and transported to different membrane sites, altering ganglioside levels in the intestinal mucosa, plasma and brain and thus possibly having the potential to change developing enterocyte function (and possibly that of other cell lines).

Starvation and feeding a high-carbohydrate, low-fat diet regulate the expression sterol regulatory element-binding protein-1 in chickens

In mammalian liver, the mature form of sterol regulatory element-binding protein-1c (SREBP-1c) is an important activator of a wide array of genes involved in triacylglycerol biosynthesis. Starvation and feeding a high-carbohydrate, low-fat diet modulate the concentration of mature SREBP-1c primarily by a pretranslational mechanism. It is not known whether alterations in nutritional status regulate the concentration of SREBPs in nonmammalian species. In this study, we found that in previously starved chicks, feeding a high-carbohydrate, low-fat diet stimulated a robust increase (14-fold at 5 h of feeding) in the concentration of mature SREBP-1 in liver. Feeding a high-carbohydrate, low-fat diet also increased the concentration of precursor SREBP-1 and SREBP-1 messenger RNA in chick liver; however, the magnitude of this effect was substantially lower than that observed for mature SREBP-1. DNA binding experiments demonstrated that 3 protein complexes containing SREBP bound the acetyl-CoA carboxylase-alpha (ACCalpha) sterol regulatory element (SRE) in chick liver and that the binding activity of 2 of these complexes was increased by consumption of a high-carbohydrate, low-fat diet. Additional analyses showed that feeding a high-carbohydrate, low-fat diet had no effect on the concentration of mature SREBP-2 and the binding of SREBP-2 to the ACCalpha SRE in chick liver. These results indicate that alterations in the concentration of mature SREBP-1 play a role in mediating the effects of starvation and feeding a high-carbohydrate, low-fat diet on ACCalpha transcription in chick liver and that diet-induced changes in mature SREBP-1 concentration in chick liver are mediated primarily by a posttranslational mechanism.

Dietary n-3 FA modulate long and very long chain FA content, rhodopsin content, and rhodopsin phosphorylation in rat rod outer segment after light exposure

A previous study has shown that the long and very long chain FA (VLCFA) content of the rat retina responds to changes in dietary n-6/n-3 ratio of the fat fed (1). The present study tested whether similar changes in these FA are associated with alterations in rhodopsin content and rhodopsin phosphorylation after light treatment. Weanling rats were fed diets containing 20% (w/w, 40% energy) fat with either high (4.8%, w/w) or low (1.2%, w/w) n-3 FA. After 6 wk of feeding, half of the animals in each group were exposed to light for 48 h at 350 lx or were kept in complete darkness. In the rod outer segment, the high n-3 diet treatment increased the level of 20:5n-3 and 22:6n-3 and reduced the levels of 20:4n-6 and 24:4n-6 in PC, PE, and PS. After the feeding of a high n-3 FA diet, total n-3 pentaenoic VLCFA from C24 to C34 increased in PC, whereas the n-6 tetra- and pentaenoic VLCFA decreased. No changes occurred in n-3 hexaenoic VLCFA regardless of the level of 22:6n-3 in the diet. After light exposure, animals fed a high n-3 FA diet showed reduction in 22:6n-3 as well as in n-6 and n-3 VLCFA in PC. FFA and TG fractions contained increased levels of both 20:4n-6 and 22:6n-3 after light exposure. Dark-adapted rhodopsin content and rhodopsin phosphorylation in the rod outer segment of rats fed the low n-3 FA diet were higher than in animals fed a high n-3 FA diet. After light exposure, animals fed the low n-3 FA diet lost more rhodopsin compared to animals fed the high n-3 FA diet, resulting in less phosphorylation of rhodopsin. Results indicate that the FA composition, rhodopsin content, and phosphorylation in visual cells is influenced by the dietary n-3 FA fed as well as by light exposure. The results also imply that 22:6n-3 may not be the precursor for synthesis of hexaenoic VLCFA.

High dietary 18:3n-3 increases the 18:3n-3 but not the 22:6n-3 content in the whole body, brain, skin, epididymal fat pads, and muscles of suckling rat pups

The objective of this study was to test the hypothesis that increasing maternal dietary 18:3n-3 by decreasing the 18:2n-6/18:3n-3 ratio will increase the 18:3n-3 and 22:6n-3 content of the whole body, liver, skin (epidermis, dermis, and subcutaneous tissue), epididymal fat pads, and muscles (arms and legs) of 2-wk-old rat pups. Sprague-Dawley dams at parturition were fed semipurified diets containing either a low (18:2n-6 to 18:3n-3 ratio of 24.7:1) or a high (1 8:2n-6 to 18:3n-3 ratio of 1.0:1) 18:3n-3 fatty acid content. During the first 2 wk of life, rat pups received only their dams' milk. Fatty acid composition of the pups' stomach contents (dams' milk), whole body, brain, liver, skin, epididymal fat pads, and muscles was determined. The stomach fatty acid composition of 18:3n-3 reflected the dams' diet. The content of 18:3n-3 in whole body, brain, liver, skin, epididymal fat pads, and muscles was significantly (P< 0.05) greater in rat pups fed the high compared with the low 18:3n-3 fatty acid diet. The 22:6n-3 content of the whole body, brain, skin, epididymal fat pads, and muscles was not quantitatively different in rat pups fed either the low or high 18:3n-3 fatty acid diet. The 20:5n-3 and 22:5n-3 content of the whole body, skin, and epididymal fat pads was significantly increased in rat pups fed the high compared with the low 18:3n-3 fatty acid diet. High content of 18:3n-3 was found in the skin of rat pups fed either a low or high 18:3n-3 fatty acid diet. These findings demonstrate that high maternal dietary 18:3n-3 significantly increases the 18:3n-3 but not the 22:6n-3 content of the whole body, brain, skin, epididymal fat pads, and muscles with approximately 39 and 41% of the whole body 18:3n-3 content being deposited in the skin of suckling rat pups fed either the low or high 18:3n-3 diet, respectively.

Effects of methionine on endogenous antioxidants in the heart

The deficiency of methionine, an essential amino acid, is associated with cardiovascular lesions. Because different types of cardiac pathologies are caused by a decrease in antioxidants, we examined the effects of methionine on myocardial antioxidant enzymes in hemodynamically assessed rats that were treated with methionine (10 mg/ml) in drinking water for 12, 24, and 48 h. Glutathione peroxidase (GSHPx) activity was significantly increased to 150.5 +/- 12.2 and 191.7 +/- 13.7% of the control value at 12 and 24 h, respectively, followed by a decline to 120 +/- 24.6% at 48 h. The mRNA levels of GSHPx at these time points were 151.2 +/- 12.0, 218.7 +/- 35.3, and 173.5 +/- 25.2%, respectively. Superoxide dismutase (SOD) activity was 144.3 +/- 3.7, 114.3 +/- 10.1, and 143.1 +/- 11. 2% at 12, 24, and 48 h, respectively. Catalase (Cat) activity was 272.4 +/- 5.4, 237.8 +/- 16.6, and 224.1 +/- 17.3% of the control value. The expression of Cat and SOD mRNA was unchanged at 12, 24, and 48 h. The lipid peroxidation was decreased by 24.4 +/- 11.2, 54. 9 +/- 0.1, and 6.4 +/- 2.1% at 12, 24, and 48 h, respectively. Methionine had no effect on the ventricular or aortic pressures, heart rate, and myocardial glutathione levels at any of the time points. The study shows that methionine has a significant effect on the myocardial antioxidant enzyme activities, and only changes in GSHPx enzyme activity correlated with the mRNA changes. These antioxidant changes may have a role in the beneficial effects of methionine in pathological rather than physiological conditions.

Diet fat and oral insulin-like growth factor influence the membrane fatty acid composition of suckling rat small intestine

BACKGROUND

Insulin-like growth factor- plays an important role in small intestine development. The presence of insulin-like growth factor-1 and the complexity of the fatty acid composition in breast milk suggests that intestinal development may be influenced by manipulating the levels of these components.

METHODS

To determine whether a physiological dose of insulin-like growth factor-1 would influence sucrase and lactase activity levels, 10-day-old suckling rat pups were treated with an oral gavage of insulin-like growth factor-1. Four diets differing in fat composition were fed to lactating dams. Brush border membranes were isolated from jejunal and ileal segments of suckling rat small intestine. Fatty acid analysis of choline and ethanolamine phospholipids was performed.

RESULTS

Insulin-like growth factor-1 was found to have no effect on the sucrase and lactase activities of suckling rats. Changes in the diet fat composition of the mother's diet indirectly influenced the fatty acid composition of suckling rat small intestine. Insulin-like growth factor-1 decreased ileal C20:4n-6 levels. A correlation was observed between lactase activity and C20:4n-6 and C22:6n-3 levels. As C20:4n-6 levels increased, lactase activity appeared to decline. Increased lactase activity was observed when C22:6n-3 levels increased.

CONCLUSIONS

The changes observed in C20:4n-6 levels in response to oral insulin-like growth factor-1, combined with the apparent trend of increased lactase activity with declining levels of C20:4n-6, may be of significance in the development of the small intestine in early life.

Does increasing dietary linolenic acid content increase the docosahexaenoic acid content of phospholipids in neuronal cells of neonatal rats?

The objective of this study was to investigate if increasing maternal dietary linolenic acid (18:3n-3) content, by decreasing the 18:2n-6 to 18:3n-3 ratio, could increase the docosahexaenoic acid (22:6n-3) content in phospholipids of neuronal cells of rat pups at 2 weeks of age. Sprague-Dawley dams at parturition were fed semipurified diets containing decreasing ratios of 18:2n-6 to 18:3n-3 from 21.6:1 to 1:1. During the first 2 weeks of life, the rat pups received only their dam's milk. The fatty acid composition of the pups stomach contents (dam's milk) and the phospholipids from neuronal cells were identified and quantitated by gas-liquid chromatography. The stomach 22:6n-3 content analyzed from the rat pups at 2 weeks of age was altered by the maternal diet. Fatty acid analysis of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in neuronal cells of the rat pups showed no significant increase in 22:6n-3 content with increasing 18:3n-3 in the maternal diet (p > 0.05). In contrast, the content of 22:6n-3 in phosphatidylinositol (PI) was significantly increased by change in dietary 18:3n-3 intake from a dietary 18:2n-6 to 18:3n-3 ratio of 7.8:1 to 4.4:1. It is concluded that increasing maternal dietary 18:3n-3 by decreasing the 18:2n-6 to 18:3n-3 ratio does not significantly increase the 22:6n-3 content in PC, PE, and PS in neuronal cells of rat pups at 2 weeks of age.

Dietary lipid composition modifies intestinal morphology and nutrient transport in young rats

BACKGROUND

Varying lipid content of the diet of pregnant and nursing dams results in alterations in sugar and lipid uptake into the intestine of their suckling offspring. In this study, we wished to determine whether the same alterations in dietary lipid result in adaptation of intestinal transport in postweaning rats.

METHODS

During nursing, the dams were fed the same diet that their offspring were fed for 3 more weeks after weaning. These semipurified diets contained: 1) 15.8% of total fatty acids (w/w) as 18:2n-6 and an n6/n3 ratio of 7.3:1; 2) a diet with 17.6% of total fatty acids as 18:2n-6 and an n6/n3 ratio of 4:1; 3) a diet with 16.2% of total fatty acids as 18:2n-6 and 1.2% arachidonic acid (AA); 4) a diet with 16.8% of total fatty acids at 18:2n-6, 1.2% AA and 0.7% docosahexaenoic acid (DHA); and 5) a diet with 16.0% of total fatty acids as 18:2n-6 and 0.7% as DHA. The in vitro uptake of D-glucose, D-fructose, medium- or long-chain fatty acids and cholesterol was assessed in 6-week-old rats.

RESULTS

Feeding AA increased the Vmax for jejunal and ileal uptake of glucose, compared with the high n6/n3 diet. This effect was prevented by adding DHA to the AA diet. The low n6/n3 fatty acid ratio diet decreased uptake of fructose as compared with the high n6/n3 diet, and the increased uptake of fructose with DHA was prevented by adding AA. The incremental change in free energy associated with uptake of medium chain-length fatty acids was lower in the jejunum of animals fed AA plus DHA as compared with the other diet groups. Jejunal uptake of 18:0 was lower for animals fed DHA or AA plus DHA, as compared with AA alone; ileal rate of uptake of long-chain fatty acids was unaffected by diet.

CONCLUSIONS

The intestine of young rats modifies its intestinal morphology and adapts its nutrient transport in response to variations in dietary lipids. In postweaning rats, the potentially undesirable effect of one fatty acid on nutrient uptake may be countered by adding a select second fatty acid to the diet.

Dietary long-chain (n-3) fatty acids facilitate immune cell activation in sedentary, but not exercise-trained rats

Dietary long-chain (n-3) fatty acids from fish oil and low intensity exercise have been reported, independently, to inhibit tumor growth in rats. The mechanism for these effects is not known but may be related to diet and exercise-induced alterations in immune function. To study the individual and combined effects of these interventions on anticancer immune responses, healthy Fischer 344 rats were fed, for 4 wk, one of two semi-purified diets (polyunsaturated to saturated fatty acid ratio = 0.9), which differed only in the composition of fat (200 g/kg) and provided long-chain (n-3) fatty acids at 0 or 33 g/kg of total fat. Rats were randomly assigned to groups in a 2 x 2 experimental design to swim 3 h/d or to remain sedentary. For sedentary rats, dietary (n-3) fatty acids increased (P < 0.05) splenic natural killer (NK) cell cytotoxicity and the percentage of activated (CD71+) T and B cells and macrophages in spleen after concanavalin A stimulation. For exercise-trained rats, feeding the high (n-3) diet decreased (P < 0.05) the percentage of CD71+ T helper and B cells after stimulation. NK cell cytotoxicity, and the percentages of CD71+ T cells, B cells and macrophages after stimulation in the high (n-3)-fed exercise-trained group were not different than those of the low (n-3)-fed sedentary group. Thus individually, but not in combination, long-chain (n-3) fatty acids and low intensity exercise may be advantageous by augmenting cell-mediated immune function and NK cell cytotoxicity in healthy rats.

During neuronal and glial cell development diet n-6 to n-3 fatty acid ratio alters the fatty acid composition of phosphatidylinositol and phosphatidylserine

Brain development was examined in the neonatal rat in response to feeding increased levels of 18:3n - 3, 20:4n - 6 or 22:6n - 3 at levels proposed for infant formula. Diets varying in n - 6 to n - 3 fatty acid ratio, with or without 20:4n - 6 and 22:6n - 3 alone or in combination, were fed to nursing dams at parturition and subsequently to weaned pups until six weeks of age. Neuronal and glial cells were isolated from the frontal, cerebellar and hippocampal brain regions of rat pups at birth, one, two, three and six weeks of age. Fatty acid analysis of inositol- and serine- phosphoglycerides indicated that small changes in dietary n - 6 to n - 3 fatty acid ratio significantly affect neuronal and glial cell membrane composition. Fatty acid composition of phosphatidylinositol and phosphatidylserine was distinct and exhibited change with age. Individual brain regions and cell types varied in amount and rate of 20:4n - 6 and 22:6n - 3 accretion. Alteration of brain fatty acid composition reflected the fatty acid composition of the diet fed. If analogous changes occur during human brain development, feeding infants 20:4n - 6 and 22:6n - 3 or a reduced 18:2n - 6 to 18:3n - 3 ratio may alter fatty acid profiles of brain cells.

Small changes of dietary (n-6) and (n-3)/fatty acid content ration alter phosphatidylethanolamine and phosphatidylcholine fatty acid composition during development of neuronal and glial cells in rats

It has been suggested that the fat composition of infant formula should provide arachidonic acid [20:4(n-6)] and docosahexaenoic acid [22:6(n-3)] or increased alpha-linolenic acid [18:3(n-3)] to optimize the (n-3) and (n-6) fatty acid content of brain during infant development. This experiment examined the effects of feeding increased levels of 18:3(n-3), 20:4(n-6) and 22:6(n-3) on brain development in neonatal rats. Diets varying in (n-6) and (n-3) fatty acid content with or without 20:4(n-6) or 22:6(n-3), at levels proposed for infant formula, were fed to nursing dams from parturition and subsequently to weaned pups until 6 wk of age. Neuronal and glial cells were isolated from the frontal region, cerebellum and hippocampus of the brain. Fatty acid analyses of ethanolamine- and choline-phosphoglycerides indicated that small changes in the dietary (n-6)/(n-3) ratio significantly altered neuronal and glial membrane fatty acid composition. Brain regions and cell types varied in amount and rate of 20:4(n-6) and 22:6(n-3) accretion. Fatty acid composition of individual phosphoglycerides was distinct and exhibited changes with age. Inclusion of both 20:4(n-6) and 22:6(n-3) in the diet resulted in alteration of brain fatty acid composition reflecting the fatty acid composition of the diet. If analogous developmental changes occur in human brain, then these results imply that addition of 20:4(n-6) and 22:6(n-3) or a reduced 18:2(n-6):18:3(n-3) ratio in infant formula may result in fatty acid profiles of neuronal and glial cells in formula-fed infants similar to those observed in breast-fed infants.

Dietary L-glutamine supplementation reduces the growth of the Morris Hepatoma 7777 in exercise-trained and sedentary rats

Dietary glutamine supplementation and exercise have been reported independently to enhance immune function and reduce tumor growth. We study the effect of both of these interventions on the growth of the Morris Hepatoma 7777, implanted in 59 female Sprague-Dawley Buffalo rats. Rats were fed a nutritionally complete, purified diet with or without L-glutamine 20 g/kg diet and randomized to swim 3 h/d or to remain sedentary. After 14 d, the mean tumor weight of glutamine-supplemented rats was lower (P < 0.0001) than that of unsupplemented rats (5.8 +/- 0.4 vs. 8.7 +/- 0.5 g, respectively). Exercise did not alter tumor growth. Glutamine supplementation increased [3H] thymidine incorporation by splenocytes incubated with Concanavalin A and the proportion of natural killer cells in spleen, but not cytotoxic activity against YAC-1 cells. Glutamine supplementation did not alter glutamine concentrations in plasma (691 +/- 12 mumol/L) or soleus muscle (5328 +/- 102 pmol/mg) but resulted in higher (P < 0.004) plasma concentrations of leucine, isoleucine and valine, precursors of glutamine. Splenocytes from exercised rats had a higher (P < 0.001) mitogen response than those from sedentary rats. Isolated tumor cells demonstrated high rates of non-oxidative glucose and glutamine metabolism and consumption of glutamine, tryptophan and methionine. However, neither diet nor exercise significantly affected glucose or glutamine metabolism by tumor cells. The precise mechanism of tumor growth suppression by oral glutamine supplementation is not clear but may be related to changes in substrate availability, improved tumor-directed natural killer cytotoxic activity or a faster response to an immune challenge.

Dietary vitamin B12, sulfur amino acids, and odd-chain fatty acids affect the responses of rats to nickel deprivation

An experiment was performed to ascertain whether changing the dietary intake of two substances, cystine and margaric acid (heptadecanoic acid), that affect the flux through pathways involving the two vitamin B12-dependent enzymes, methionine synthase and methylmalonyl-CoA mutase, would affect the interaction between nickel and vitamin B12. Rats were assigned to treatment groups of six in a fully crossed, four-factorial arrangement. The independent variables, or factors, were: per kg of fresh diet, nickel analyzed at 25 and 850 micrograms; vitamin B12 supplements of 0 and 50 micrograms; margaric acid supplements of 0 and 5 g; and L-cystine supplements of 0 and 12 g. The diet without cystine was marginally deficient in sulfur amino acids. Nickel affected growth, liver wt/body wt ratio (LB/BW), and a number of variables associated with iron, calcium, zinc, copper, and magnesium metabolism. Most of the effects of nickel were modified by the vitamin B12 status of the rat. In numerous cases, the interaction between nickel and vitamin B12 was dependent on, or altered by, the cystine or margaric acid content of the diet. Thus, the findings showed that the extent and the direction of changes in numerous variables in response to nickel deprivation varied greatly with changes in diet composition. These variables include those previously reported to be affected by nickel deprivation, including growth and the distribution or functioning of iron, calcium, zinc, copper, and magnesium. The findings also support the hypothesis that nickel has a biological function in a metabolic pathway in which vitamin B12 is important.

Does a threshold for the effect of dietary omega-3 fatty acids on the fatty acid composition of nuclear envelope phospholipids exist?

Existence of a dietary maximal level or threshold for incorporation of omega 3 fatty acids into membrane phospholipids is of interest as it may further define understanding of the dietary requirement for omega 3 fatty acids. To test whether feeding increasing levels of dietary omega 3 fatty acids continues to increase membrane omega 3 fatty acid content, weanling rats were fed a nutritionally adequate semipurified diet which provided increasing amounts of C20 and C22 omega 3 fatty acids, such as 20:5 omega 3 and 22:6 omega 3. Dietary 20:5 omega 3 and 22:6 omega 3 were provided by substituting a purified shark oil concentrate of high 22:6 omega 3 content for safflower oil high in 18:2 omega 6. After four weeks of feeding, nuclear envelopes from four animals in each diet group were prepared, lipid was extracted and phospholipids separated. Arachidonic acid content in membrane phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine was significantly reduced by feeding increased dietary levels of omega 3 fatty acids. Decline of 20:4 omega 6 level in phospholipid tended to stabilize when the dietary content of total omega 3 fatty acids reached 4-5% of total fatty acids. Above this level, dietary omega 3 fatty acids did not result in a further decrease in membrane content of 20:4 omega 6. Increase in membrane phospholipid content of 20:5 omega 3 occurred as the dietary intake of omega 3 fatty acids increased from 1.1% to 5% of total fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Histologic abnormalities of large and small coronary arteries, neural structures, and the conduction system of the heart found in postmortem studies of individuals dying from the toxic oil syndrome

Hundreds died and thousands were poisoned by rapeseed oil adulterated with aniline and sold illegally in Spain in 1981. The clinical manifestations, now known as the toxic oil syndrome, include pulmonary hypertension and right ventricular hypertrophy plus widespread vascular and neural lesions in other organs. Many of the late deaths ended with a scleroderma-like illness. Because scleroderma involves the heart, in this study we examined the small and large coronary arteries, neural structures, and conduction system from eight victims dying with the toxic oil syndrome. Dense fibrosis of the sinus node in two hearts resembled changes found in scleroderma. Atrionodal junctional hemorrhages and cystic degeneration of the sinus node present in the other six hearts resembled changes found in lupus erythematosus. Small and large coronary arteries exhibited focal fibromuscular dysplasia and a proliferative cystic myointimal degeneration. This latter abnormality was associated with sloughing of the inner wall and embolization of the detached fragment downstream in the same coronary artery. Every heart had many degenerative lesions within nerves, ganglia, and the coronary chemoreceptor. Both the arterial and neural abnormalities prominently involved the conduction system. Based upon observations by others with experimental feeding of rapeseed oil containing either high or low erucic acid, we suggest that this oil must remain a major suspected cause of the toxic oil syndrome, particularly in conjunction with some as yet unexplained facilitative influence by oleoanilids. If this is so, it is important to reconsider the widely recommended use of any rapeseed oil product as a suitable food for man or other animals.

Methionine-induced positive inotropic effect in rat heart: possible role of phospholipid N-methylation

Perfusion of isolated rat heart with L-methionine produced a positive inotropic effect that was temporally preceded, as well as accompanied, by an increase of methyl group incorporation into N-methylated phospholipids of the myocardium. Maximal increase in contractile force development was associated with maximal methyl group incorporation. Both parameters showed a dose-related dependence on methionine and correlated positively (r = 0.965) upon regression analysis of the data. The presence of adenosine, L-homocysteine thiolactone and erythro-9-(2-hydroxy-3-nonyl) adenine in the perfusion medium inhibited the positive inotropic effect as well as the incorporation of methyl groups into phospholipids. Cycloleucine, an inhibitor of S-adenosylmethionine synthetase, also reduced the increase in contractility by methionine. Methionine-induced positive inotropic effect could be modulated by varying Ca2+ concentration in the perfusate and was inhibited by ryanodine, a blocker of sarcoplasmic reticular Ca2+ release. These observations indicate that L-methionine may serve as a powerful positive inotropic agent and suggest that phospholipid N-methylation plays an important role in functional activity of rat heart.

The effect of dietary methionine on the copper content of tissues and survival of young and old mice

We tested the possibility that methionine might improve the lifespan of male C57BL/6J mice, based upon the ability of methionine to chelate copper. Old mice given 0.05M methionine in their drinking water for 42 days had lower brain copper concentrations (p less than 0.05). The decrease in liver, kidney, and heart copper was not significant when compared to unsupplemented controls. The lifespan of old mice was unchanged by feeding 0.05M methionine. Young mice, however, experienced a 16.9% decrease in their average lifespan and a decreased maximum lifespan when given supplemental methionine. We conclude that dietary supplements of methionine may be useful for removing copper from the brain but they also can increase the rate of senescence in mice.

The methionine and choline status of rat diets and their effects on nutrition and myocardial lesions

This study evaluated for rats the nutritional adequacy of casein-based diets routinely used to test the cardiopathogenicity of vegetable oils. Diets were formulated containing 20% by weight casein, 20% soybean oil and graded levels of choline with and without methionine and were fed to male Sprague-Dawley rats for 16 weeks. Rats fed methionine-supplemented diets had improved growth and food consumption, increased liver lipids mainly in the form of triglycerides and normal amino acid metabolism. On the other hand, choline supplementation reduced liver lipids but had no effect on growth and feed consumption. The results would indicate that diets including 20% casein and 20% oil require methionine supplementation to assure the nutritional adequacy of this high caloric diet. However, in this study there was no evidence to indicate that choline or methionine supplementation affected the heart lesion incidence in male rats. It was therefore concluded that the amount and type of fat in the diet, not the choline and methionine status of the diet, is related to heart lesions in male rats.

Plasma membrane: can its structure and function be modulated by dietary fat?

Compositional analysis of plasma membranes from rats fed nutritionally adequate diets different in fatty acid composition establishes that fundamentally different dietary fat intake results in alteration in structural lipid composition of plasma membranes in brain, liver and the intestinal mucosa. Dietary differences in fatty acid intake altered the fatty acyl tail composition of plasma membrane phospholipids in brain, liver and intestinal mucosa. Diet altered the phospholipid profile observed in brain synaptosomal and liver plasma membrane. Feeding high vs low polyunsaturated to saturated fat diets for 7 days altered the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and monoglucosylceramide isolated from plasma membrane of the intestinal mucosa.

Reduction of myocardial necrosis in male albino rats by manipulation of dietary fatty acid levels

A comprehensive statistical analysis had shown a significant correlation between the incidence of myocardial lesions in male albino rats and the concentration of certain dietary fatty acids. To test this result under controlled conditions, male rats were fed for 16 weeks diets containing 20% by weight soybean oil or a low erucic acid rapeseed (LEAR) oil. Both dietary oils contained substantial amounts of linolenic acid, and both groups developed a high incidence of myocardial necrosis. The addition of dietary saturated fatty acids to the oil in the form of cocoa butter significantly lowered the incidence of heart lesions in both groups. The addition of cocoa butter resulted in increased absorption of saturates and increased growth. Replacement of the cocoa butter by at least an equal amount of synthetic triolein resulted in no significant changes in the cardiopathogenic response compared to the original oils, thus ensuring that the reduction in heart lesions associated with the addition of cocoa butter was not due to dilution of cardiopathogenic compounds in the original vegetable oils. These results support the hypothesis that myocardial lesions in male rats are related to the balance of dietary fatty acids and not to cardiotoxic contaminants in the oils. Changes in the dietary fatty acids did not appear to influence the proportion of the cardiac phospholipids, but their fatty acid composition was markedly influenced. Dietary linolenic acid affected the C22 polyunsaturated fatty acids (PUFA) and dietary saturates increased the level of saturates in cardiac phospholipids. The level of arachidonic acid and total C22 PUFA did not appear to be affected by diet.

Dietary factors affecting the incidence of dietary fat-induced myocardial lesions

Histological study of ventricular muscle was conducted on Sprague-Dawley male rats fed diets containing 20% (w/w) of either soybean oil, low erucic acid rapeseed oil or high erucic acid rapeseed oil. Purified diets providing two levels of intake for choline and inositol or magnesium were fed for 16 weeks to determine whether increased intake of these nutrients reduced myocardial lesion incidence. Diets containing high erucic acid rapeseed oil resulted in a high incidence of degenerative focal myocardial lesions, whereas low erucic acid rapeseed oil feeding resulted in less severe cardiopathological changes. Dietary supplementation providing 0.475% (w/w) choline and 0.635% (w/w) inositol reduced incidence of myocardial lesion for both rapeseed oil treatments indicating that lesion incidence may also be altered by the nutrient composition of the purified diet. Nutritional adaptation by increasing the animals dietary fat intake from 6% (w/w) to 20% (w/w) over an 8-week period had no effect on lesion incidence.