Positive association between plasma antioxidant capacity and n-3 PUFA in red blood cells from women.

PUFA are susceptible to oxidation. However, the chain-reaction of lipid peroxidation can be interrupted by antioxidants. Whether an increased concentration of PUFA in the body leads to decreased antioxidant capacity and/or increased consumption of antioxidants is not known. To elucidate the relationship between plasma total antioxidant capacity (TAC), the concentration of antioxidant vitamins, and the proportion of PUFA in red blood cells (RBC), plasma TAC was measured by a Trolox equivalent antioxidant capacity assay in blood samples from 99 Icelandic women. Concentrations of tocopherols and carotenoids in the plasma were determined by HPLC, and the FA composition of RBC total lipids was analyzed by GC. Plasma TAC and the plasma concentration of alpha-tocopherol correlated positively with the proportion of total n-3 PUFA, 20:5n-3, and 22:6n-3 in RBC, whereas the plasma lycopene concentration correlated negatively with the proportion of total n-3 PUFA and 20:5n-3. On the other hand, plasma TAC correlated negatively with the proportion of n-6 PUFA in RBC. Plasma TAC also correlated positively with the plasma concentration of alpha-tocopherol, alcohol consumption, and age. Both the plasma concentration of alpha-tocopherol and age correlated positively with the proportion of n-3 PUFA in RBC; however, n-3 PUFA contributed independently to the correlation with plasma TAC. Because the proportion of n-3 PUFA in RBC reflects the consumption of n-3 PUFA, these results suggest that dietary n-3 PUFA do not have adverse effects on plasma TAC or the plasma concentration of most antioxidant vitamins.

[The effect of dietary fish oil on bacterial growth in vivo.].

OBJECTIVE: Epidemiological studies have indicated that high intake of w-3 fatty acids influence various diseases such as cardiovascular diseases and autoimmune disorders. These fatty acids are essential in the diet since the body can not form them de novo. Fish oil is rich in w-3 fatty acids but the w-3 content of vegetable oil is low. The research group has shown increased survival of mice fed cod liver oil enriched diet versus mice fed corn oil enriched diet when infected with Klebsiella pneumoniae intramuscularly. In the present study we investigated the effect of dietary fish oil on bacterial growth in vivo. MATERIAL AND METHODS: Mice were fed fish oil enriched diet and a control group was fed corn oil enriched diet for six weeks and then the mice were infected with Klebsiella pneumoniae intramuscularly. The mice were sacrificed at various time intervals and bacteria were counted in blood and in the infected muscle. RESULTS: The bacteria count in blood and tissue was not significantly different between the two groups although a trend was noted towards more growth in the control group. CONCLUSIONS: We conclude that fish oil does not significantly affect bacterial growth in vivo. Hopefully, future research will reveal the pathophysiological effect of fish oil.

Beneficial effects of cytokine induced hyperlipidemia.

Infection, inflammation and trauma induce marked changes in the plasma levels of a wide variety of proteins (acute phase response), and these changes are mediated by cytokines. The acute phase response is thought to be beneficial to the host. The host's response to injury also results in dramatic alterations in lipid metabolism and circulating lipoprotein levels which are mediated by cytokines. A large number of cytokines including TNF, the interleukins, and the interferons increase serum triglyceride levels. This rapid increase (1-2 h) is predominantly due to an increase in hepatic VLDL secretion while the late increase may be due to a variety of factors including increased hepatic production of VLDL or delayed clearance secondary to a decrease in lipoprotein lipase activity and/or apolipoprotein E levels on VLDL. In animals other than primates, cytokines also increase serum cholesterol levels, most likely by increasing hepatic cholesterol. Cytokines increase hepatic cholesterol synthesis by stimulating HMG CoA reductase gene expression and decrease hepatic cholesterol catabolism by inhibiting cholesterol 7 alpha-hydroxylase, the key enzyme in bile acid synthesis. Injury and/or cytokines also decrease HDL cholesterol levels and induce alterations in the composition of HDL. The content of SAA and apolipoprotein J increase, apolipoprotein A1 may decrease, and the cholesterol ester content decreases while free cholesterol increases. Additionally, key proteins involved in HDL metabolism are altered by cytokines; LCAT activity, hepatic lipase activity, and CETP levels decrease. These changes in lipid and lipoprotein metabolism may be beneficial in a number of ways including: lipoproteins competing with viruses for cellular receptors, apolipoproteins neutralizing viruses, lipoproteins binding and targeting parasites for destruction, apolipoproteins lysing parasites, redistribution of nutrients to cells involved in the immune response and/or tissue repair, and lipoproteins binding toxic agents and neutralizing their harmful effects. Thus, cytokines induce marked changes in lipid metabolism that lead to hyperlipidemia which represents part of the innate immune response and may be beneficial to the host.

LPS and cytokines regulate extra hepatic mRNA levels of apolipoproteins during the acute phase response in Syrian hamsters.

Altered hepatic expression of apolipoproteins occurs during the acute phase response. Here we examined whether the acute phase response alters extra hepatic expression of apolipoproteins. Syrian hamsters were injected with endotoxin (LPS), tumor necrosis factor (TNF), interleukin (IL)-1, or the combination of TNF + IL-1 and mRNAs for serum amyloid A (apoSAA), apolipoprotein (apo) J, apo E. apo A-I, and apo D, were analyzed. LPS increased mRNA levels for apoSAA in all tissues examined. LPS and TNF + IL-1 increased mRNA levels for apo J in kidney, heart, stomach, intestine, and muscle. Individually, TNF and IL-1 were less potent than the combination of the two cytokines. LPS decreased mRNA levels for apo E in all tissues, except for mid and distal intestine. TNF and IL-1 were less effective than LPS. LPS, TNF + IL-1 and TNF decreased mRNA levels for apo A-I in duodenum. mRNA for apo D decreased in heart, were unchanged in brain and increased in muscle, following LPS. The widespread extra hepatic regulation of the apolipoproteins during the acute phase response may be important for the alterations in lipid metabolism that occur during infection and inflammation as well as the immune response.

Dietary fish oil supplementation increases survival in mice following Klebsiella pneumoniae infection.

The effect of dietary fish-oil supplementation on survival of NMRI mice after Klebsiella pneumoniae infection was investigated. 30 mice in each group were fed a fish-oil enriched diet, olive-oil enriched diet or standard chow diet. After 6 weeks, the mice were injected intramuscularly with Klebsiella pneumoniae. After 120 h the survival of the mice fed fish-oil enriched diet was 40%, while the survival for mice fed standard or olive-oil enriched diets was 20% and 25%, respectively. The survival curve over 120 h was significantly improved (p = 0.0034) for mice fed a fish-oil enriched diet, compared to the survival curves for mice fed the other 2 diets. The study was repeated by comparing the survival of mice fed a fish-oil enriched diet to those given a corn-oil enriched diet. After 120 h the survival curve for mice fed the fish-oil enriched diet was significantly better compared to the survival curve for mice given the corn-oil enriched diet (p = 0.01). A fish-oil enriched diet therefore increases survival in mice following Klebsiella pneumoniae infection, whether compared to a standard diet, olive-oil enriched diet or corn-oil enriched diet.

[Dietary fish-oil supplementation increases survival in mice following Klebsiella pneumoniae infection.].

INTRODUCTION: Epidemiological studies have shown that high intake of omega-3 fatty acids correlates with low incidence of various diseases such as cardiovascular diseases, asthma, diabetes mellitus and various auto-immune disorders. It may therefore be suggested that omega-3 fatty acids have substantial impact on the immune system. Studies of the effect of omega-3 fatty acids on survival in bacterial infections have however been contradicting. A Dutch study from 1991 showed increased survival in mice fed fish-oil following infection with Klebsiella pneumoniae. Because of the contradicting results the authors conducted a study with the hypothesis that fish-oil intake increases survival after severe Klebsiella pneumoniae infection. METHODS: Thirty mice were fed fish-oil enriched diet (10%), olive-oil enriched diet (10%) or standard chow diet. After six weeks the mice were injected intramuscularly with l.óxlO2 cfu of Klebsiella pneumoniae. The survival was measured at regular time intervals for 120 hours. RESULTS: After 56 hours, 93% of the mice fed fish-oil were alive and 68% and 40% of the mice fed olive-oil and standard chow respectively. The overall survival after 120 hours was 40% in the fish-oil group, 25% in the olive-oil group and 20% in the standard group. The survival after 120 hours of the mice fed the fish-oil enriched diet was significantly better when compared to the two other groups (p=0.0034). DISCUSSION: We conclude that fish-oil enriched diet increases survival of NMRI mice following infection with Klebsiella pneumoniae when compared to olive-oil supplementation or standard chaw. We therefore conclude that the difference in survival is probably based on the effect of omega-3 fatty acid on the immune system. The immunological pathway is still unknown and our results encourage further studies.

Endotoxin and cytokines decrease serum levels and extra hepatic protein and mRNA levels of cholesteryl ester transfer protein in syrian hamsters.

Endotoxin alters the metabolism of lipoproteins, including that of high density lipoprotein (HDL). Cholesteryl ester transfer protein (CETP) facilitates exchange of HDL cholesterol for very low density lipoprotein (VLDL) triglyceride, leading to catabolism of HDL. We investigated the effects of endotoxin and cytokines on CETP in Syrian hamsters. Endotoxin induced a rapid and progressive decrease in serum CETP levels, by 48 h CETP had decreased to < 20% of control levels. Endotoxin also decreased CETP mRNA and protein levels in adipose tissue, heart, and muscle, the tissues with highest levels of CETP mRNA, providing a plausible mechanism for the endotoxin-induced decrease in circulating CETP. Dexamethasone did not mimic the effects of endotoxin on CETP, but the combination of tumor necrosis factor and interleukin-1 did, indicating that these cytokines may in part mediate the effects of endotoxin on CETP. The endotoxin-induced decrease in CETP may help maintain HDL cholesterol levels during infection and inflammation when increased triglyceride levels could drive the exchange of HDL cholesteryl ester for VLDL triglyceride. Maintaining circulating HDL may be important because HDL protects against the toxic effects of endotoxin and provides cholesterol for peripheral cells involved in the immune response and tissue repair.

Effects of endotoxin on lipid metabolism.

Endotoxin, via cytokines, induces marked changes in lipid metabolism which are now considered part of the acute phase response. The endotoxin induced hyperlipidemia may represent a nonspecific immune response that can decrease the toxicity of a variety of harmful biological and chemical agents and serve to redistribute nutrients to cells important in host defense. The endotoxin induced changes in lipid metabolism may therefore be beneficial.

Endotoxin and cytokines increase hepatic messenger RNA levels and serum concentrations of apolipoprotein J (clusterin) in Syrian hamsters.

Infection and inflammation induce alterations in hepatic synthesis and plasma concentrations of the acute phase proteins. Our results show that apolipoprotein (apo) J is a positive acute phase protein. Endotoxin (LPS), tumor necrosis factor (TNF), and interleukin (IL)-1 increased hepatic mRNA and serum protein levels of apo J in Syrian hamsters. Hepatic apo J mRNA levels increased 10- to 15-fold with doses of LPS from 0.1 to 100 micrograms/100 g body weight within 4 h and were elevated for > or = 24 h. Serum apo J concentrations were significantly increased by 16 h and further elevated to 3.3 times that of control, 24 h after LPS administration. Serum apo J was associated with high density lipoprotein and increased fivefold in this fraction, after LPS administration. Hepatic apo J mRNA levels increased 3.5- and 4.6-fold, with TNF and IL-1, respectively, and 8.2-fold with a combination of TNF and IL-1. Serum apo J concentrations were increased 2.3-fold by TNF, 79% by IL-1, and 2.9-fold with a combination of TNF and IL-1. These results demonstrate that apo J is a positive acute phase protein.

Effects of endotoxin and cytokines on lipid metabolism.

Endotoxin, via cytokines, induces marked changes in lipid metabolism: serum VLDL increases, whereas the effect on LDL levels varies among species. The increase in VLDL is caused by stimulation of hepatic VLDL secretion or inhibition of clearance, or both. These alterations can be deleterious or beneficial effects.

Effects of TNF, IL-1, and the combination of both cytokines on cholesterol metabolism in Syrian hamsters.

Infection and inflammation are associated with alterations in lipid metabolism that may be mediated by cytokines such as TNF and IL-1. This study determined the effects of TNF and IL-1 on certain aspects of cholesterol metabolism. TNF or IL-1 administration to Syrian hamsters increased serum cholesterol levels by 17 and 21%, respectively, and decreased HDL cholesterol levels by 20 and 15%, respectively. TNF + IL-1 increased serum cholesterol levels by 58% and decreased HDL cholesterol levels by 58%. TNF or IL-1 increased hepatic HMG CoA reductase mRNA levels by 3.5- and 3-fold, respectively. TNF + IL-1 increased HMG CoA reductase mRNA levels by 7-fold. IL-1 increased hepatic LDL receptor mRNA levels by 2-fold while TNF and a combination of TNF + IL-1 had minimal effects. TNF or IL-1 did not affect hepatic apo E or apo A-I mRNA levels while a combination of TNF + IL-1 decreased both mRNA levels by 50%. Our results demonstrate that TNF and IL-1 similarly affect the parameters of cholesterol metabolism studied. Furthermore, the combination of TNF + IL-1 was, in most cases, more effective than either cytokine alone, and reproduced many of the effects of LPS.

Effect of endotoxin on cholesterol biosynthesis and distribution in serum lipoproteins in Syrian hamsters.

Infection and inflammation increase serum triglyceride and cholesterol levels in rodents and rabbits. Endotoxin (LPS) has been used as a model of infection and its effects on triglyceride metabolism have been previously characterized. In the present study we demonstrate that both low (100 ng/100 g body weight) and high dose (100 micrograms/100 g body weight) LPS increase serum cholesterol levels in hamsters. The increase in serum cholesterol is first observed 16 h after LPS and persists for at least 24 h. This increase is primarily due to an increase in low density lipoprotein (LDL) cholesterol. High density lipoprotein (HDL) cholesterol levels decrease after LPS treatment. Both low and high dose LPS increase hepatic cholesterol synthesis (low dose 85%, high dose 205%) and total HMG-CoA reductase activity (low dose 2.97-fold, high dose 9.96-fold). However, the proportion of HMG-CoA reductase in the active form is reduced by LPS treatment. Additionally, the mass of HMG-CoA reductase protein in the liver, measured by Western blotting, is increased after LPS. Moreover, LPS increases hepatic HMG-CoA reductase mRNA levels (low dose 3.1-fold, high dose 14.2-fold). The increase in hepatic HMG-CoA reductase mRNA levels is first seen 4 h after LPS and persists for at least 24 h. In contrast, LPS had only minimal effects on hepatic LDL receptor protein and mRNA levels. These results suggest that LPS increases serum cholesterol levels by increasing hepatic cholesterol synthesis. LPS administration decreases apoE mRNA levels in the liver while having no effect on apoA-I mRNA levels. These results suggest that HMG-CoA reductase is a member of a group of hepatic proteins that are positively regulated by inflammatory stimuli (acute phase proteins) while apoE can be considered a negative acute phase protein in hamsters. It is possible that increases in hepatic HMG-CoA reductase provide cholesterol that allows for the increased production of lipoproteins and elevations in serum lipid levels that may be beneficial to the body's host defense.

Dietary arachidonate enhances tissue arachidonate levels and eicosanoid production in Syrian hamsters.

Eicosanoids are oxidative derivatives of arachidonic acid. When produced in excess many of them are proinflammatory agents. This study investigates whether dietary arachidonic acid enhances arachidonic acid phospholipid content of various tissues and whether this enrichment increases eicosanoid production. Male Syrian hamsters were divided into four groups and fed diets supplemented with ethyl esters of oleic acid, linoleic acid, arachidonic acid or eicosapentaenoic acid. Differences in the composition of the phospholipid fatty acids were monitored in liver, lung, heart, spleen, kidney, testes, macrophages and platelets. In all tissues analyzed, the phospholipid content of arachidonic acid was significantly higher in the arachidonic dietary group compared with all other dietary groups (average > 50% higher). In contrast, increasing dietary linoleic acid by 50% had little effect on altering tissue arachidonic acid levels. Following in vitro stimulation, macrophages and platelets from animals maintained on arachidonic acid produced, in general, the highest levels of eicosanoids compared with cells from animals fed the other diets. Significant differences were observed in prostaglandin E2 (macrophages) and thromboxane B2 (platelets) formation when compared with the oleic acid and eicosapentaenoic acid dietary groups. The data demonstrate that including low to moderate levels of arachidonic acid in the diet increases macrophage and platelet arachidonic acid levels and may augment eicosanoid production.

Increasing the dietary (n-3) to (n-6) polyunsaturated fatty acid ratio increases tumor necrosis factor production by murine resident peritoneal macrophages without an effect on elicited peritoneal macrophages.

Tumor necrosis factor (TNF), prostaglandin (PG) E2 and 6-keto-PGF1 alpha production by murine peritoneal macrophages was monitored following in vitro stimulation with lipopolysaccharide. Macrophages were obtained from mice fed diets containing increasing ratios of (n-3) to (n-6) fatty acids by addition of (n-3) polyunsaturated fatty acids (PUFA) to the (n-6) fatty acids in the diet, or by substituting (n-3) PUFA for the (n-6) fatty acids in the diet. Increasing the dietary (n-3) to (n-6) fatty acid ratio from 0 to 1 increased both cell-associated and secreted TNF production by resident peritoneal macrophages but did not affect TNF production by macrophages elicited with Complete Freund's Adjuvant (CFA). With increasing dietary (n-3): (n-6) ratio there was a decrease in the prostaglandin production by resident peritoneal macrophages, which may partly explain the increased TNF production. The CFA-elicited macrophages produced less prostaglandin than the resident macrophages, and the lower prostaglandin production may partly explain the lack of effect of dietary (n-3) PUFA on TNF production by CFA-elicited macrophages. Increasing the TNF production by resident macrophages with dietary (n-3) PUFA may be beneficial in enhancing antitumor actions and antipathogenicity; by not increasing the high TNF production of inflammatory macrophages, (n-3) PUFA may protect against undesirable systemic inflammatory effects of overproduction.

Cytokines stimulate lipolysis and decrease lipoprotein lipase activity in cultured fat cells by a prostaglandin independent mechanism.

We previously showed that indomethacin blocked the effect of tumor necrosis factor (TNF) and other cytokines on lipolysis. We now show that TNF stimulates prostaglandin (PG) production, enhances lipolysis and decreases lipoprotein lipase (LPL) activity in 3T3-F442A adipocytes and indomethacin blocks these activities, suggesting that the actions of TNF are mediated by PG's. However, exogenous PGE2 at the levels induced by TNF is not sufficient to affect lipolysis or LPL activity and low doses of indomethacin and flurbiprofen block PG production without affecting TNF's action. Interleukin-1 and interferon-alpha and gamma induce lipolysis and decrease LPL activity but do not stimulate much PG production. These results demonstrate that cytokines enhance lipolysis and decrease LPL activity in 3T3 adipocytes by a PG independent mechanism.

Tumor necrosis factor production by murine resident peritoneal macrophages is enhanced by dietary n-3 polyunsaturated fatty acids.

Tumor necrosis factor (TNF) is a macrophage derived peptide that has an antitumor action and modulates immune and inflammatory reactions. Dietary fatty acids may modulate TNF production as dietary n-3 polyunsaturated fatty acids suppress human monocyte TNF production, but enhance its secretion by murine peritoneal macrophages. Mice were maintained for 5 weeks on diets containing different amounts of n-3 and n-6 fatty acids. TNF, PGE2 and 6-keto PGF1 alpha production was monitored following in vitro stimulation of resident peritoneal macrophages with lipopolysaccharide. Macrophages from mice fed the high n-3 diet produced 8-fold more TNF and half the PGE2 produced by macrophages from mice on the other diets. Indomethacin caused an increase in the TNF production by macrophages from mice on all diets but macrophages from mice on the high n-3 diet produced more TNF than macrophages from mice on the other diets. Exogenous PGE2 (100 nM) greatly decreased TNF production by macrophages from mice on all diets, but macrophages from mice on the high n-3 diet secreted 70% more TNF than macrophages from mice fed the other diets, indicating that PGE2 is only partly responsible for the effects observed. The results show that feeding n-3 polyunsaturated fatty acids may cause enhanced TNF production by resident peritoneal macrophages and that PGE2 is partly responsible for the effect.

Effect of increasing the dietary (n-3) to (n-6) polyunsaturated fatty acid ratio on murine liver and peritoneal cell fatty acids and eicosanoid formation.

An incremental increase in the dietary (n-3):(n-6) polyunsaturated fatty acid (PUFA) ratio from 0 to 1.93 in diets containing 15% fat (wt/wt) decreased the total (n-6) PUFA content of phospholipids of the liver and peritoneal cells (macrophage) in mice from 43.1 and 33.6 mol/100 mol to 16.0 and 12.3 mol/100 mol with a concomitant increase of 27.6 and 16.1 mol/100 mol in (n-3) PUFA, respectively. Consumption of (n-3) PUFA increased hepatic (n-3) PUFA levels without changing total PUFA (46.35 vs. 46.87 mol/100 mol), whereas macrophage PUFA levels were decreased. The synthesis of sulfidopeptide leukotrienes (SP-LT) (LTC4 and LTE4) was progressively reduced by increasing dietary (n-3) PUFA, i.e., there was a reduction of 76% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 compared with the control diet. The 5-series SP-LT (LTC5 and LTF5) were produced in all animals consuming (n-3) PUFA and accounted for 62% of all SP-LT synthesized in mice fed the diet containing a 1.93 (n-3):(n-6) PUFA ratio. Synthesis of 6-keto-prostaglandin F1 alpha decreased 81% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 whereas prostaglandin E2 synthesis decreased 44% in mice fed diets with (n-3):(n-6) ratios ranging from 0.41 to 1.93.