Organotropic chemopreventive effects of n-3 unsaturated fatty acids in a rat multi-organ carcinogenesis model.

Organotropic chemopreventive effects of n-3 unsaturated fatty acids were studied using a multi-organ carcinogenesis model in male rats. Rats were treated with diethylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU), N-butyl-N-4-hydroxybutylnitrosamine (BBN), 1,2-dimethylhydrazine (DMH) and dihydroxy-di-n-propylnitrosamine (DHPN) during the first 7 weeks, and then given unsaturated fatty acid (UFAs), docosahexaenoic acid (n-3, C(22:6)) (DHA), eicosapentaenoic acid (n-3, C(20:5)) (EPA), linoleic acid (n-6, C(18:2)) (LA) or oleic acid (n-9, C(18:1)) (OA) at a dose of 1.0 ml/rat, 3 times a week by gavage for the consecutive 30 weeks. All rats were fed a low LA basal diet throughout the experiment and a calorie-restricted basal diet during the period of UFAs feeding administration. DHA significantly reduced tumor size and numbers in the large intestine as compared to OA treatment. Furthermore, DHA showed a tendency to inhibit carcinogenesis in the small intestine and lung. EPA also showed a tendency to inhibit intestinal carcinogenesis. On the other hand, LA showed a tendency to inhibit lung carcinogenesis, but to promote large intestinal carcinogenesis. However these UFAs did not influence preneoplastic and neoplastic lesion development in the liver, kidney, and urinary bladder. Levels of the administered fatty acids were clearly increased in the serum and organs. In contrast, arachidonic acid (AA) levels in the large and small intestines and liver were markedly decreased by treatment with DHA and EPA. Decreased levels of AA in the large intestine correlated well with tumor incidence, although the number of glutathione S-transferase-positive (GST-P(+)) foci showed an inverse correlation with AA levels. The data thus provide evidence that an organotropism exists with regard to the influence of UFAs on carcinogenesis, which correlates with reduction of tissue AA levels in the target organs.

Dietary effects of eicosapentaenoic and docosahexaenoic acid esters on lipid metabolism and immune parameters in Sprague-Dawley rats.

Sprague-Dawley rats were fed eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) ethyl esters at the 2% level for 3 weeks to clarify their effects on immune functions. In the rats fed EPA or DHA, serum cholesterol, triglyceride, and phospholipid (PL) levels were significantly lower than those in the rats fed safflower oil. In PL fractions of serum, liver, lung, splenocytes, and peritoneal exudate cells (PEC), increases in linoleic and dihomo-gamma-linolenic acid contents and a decrease in arachidonic acid (AA) content were observed in the rats fed EPA or DHA. In addition, the EPA content increased in the rats fed EPA and DHA. In the rats fed EPA or DHA, a decrease of LTB4 productivity and an increase of LTBs productivity were observed in the PEC, in response to the treatment with 5 microM calcium ionophore A23187 for 20 min. The changes in leukotriene production were more marked in EPA-fed rats than in DHA-fed rats. These results suggest that dietary EPA affects lipid metabolism and leukotriene synthesis more strongly than DHA.

Dietary effect of EPA-rich and DHA-rich fish oils on the immune function of Sprague-Dawley rats.

The dietary effect of fish oils (FOs) rich in eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on the immune function of Sprague-Dawley rats was compared with that of safflower oil. After 3 weeks of feeding at the 10% level of a dietary fat, the IgG and IgM production by splenocytes and IgG production by mesenteric lymph node (MLN) lymphocytes were significantly higher in the FO-fed rats, while no significant difference was found in IgA or IgE productivity by both the spleen and MLN lymphocytes. In the FO-fed rats, peritoneal exudate cells released a lower amount of LTB4, reflecting their lower arachidonic acid level, and a higher amount of LTB5, reflecting their higher EPA level in phospholipids. On these EPA-rich FO exerted a stronger effect than DHA-rich FO immune functions.

The effect of docosahexaenoic acid on plasma catecholamine concentrations and glucose tolerance during long-lasting psychological stress: a double-blind placebo-controlled study.

We previously found that docosahexaenoic acid (DHA) intake prevented aggression from increasing at times of mental stress. In the present study, we investigated whether DHA intake modified the plasma catecholamines and cortisol of medical students during a 9-wk period of final exams. We also investigated the effects of DHA intake on a 75 g oral glucose tolerance test (oGTT). Fourteen medical students participated in the present study. They were randomly allocated to either control or DHA group in a double-blind manner. Subjects in the control group (4 males and 3 females) took 10 control capsules/d, each capsule containing 280 mg of mixed plant oil, and those in the DHA group (4 males and 3 females) took 10 DHA capsules/d containing 1.5 g DHA for 9 wk, during which subjects underwent more than 20 stressful final exams. At the start and end of the study, plasma catecholamines (epinephrine, norepinephrine (NE) and dopamine) and cortisol were measured; a 75 g oGTT was also performed. There were no intra- or intergroup differences in plasma glucose concentrations. However, NE concentrations were significantly reduced after DHA administration (-31%, p < 0.03). The other catecholamines and cortisol did not change significantly. The plasma ratio of epinephrine to NE increased in every DHA subject (+78%, p < 0.02), and intergroup differences were significant (p < 0.03). We conclude that these effects of DHA may be applied to people under long-lasting psychological stress to prevent stress-related diseases.

[Relationship between hippocampal arachidonic acid content and induction of LTP in aged rats].

There are several lines of evidence indicating that membrane AA correlates with the ability of aged rats to sustain LTP. The age-related decrease in membrane AA seems to be triggered by increased lipid peroxidation, which is involved with the decline of LTP. The chronic treatment of DHA could decrease membrane AA without an increase in lipid peroxidation. We have thus investigated the effect of chronic treatment of DHA on hippocampal LTP to assess whether the decrease in membrane AA could directly affect the induction of LTP. The effects of daily supplementation of DHA for 3 months on membrane AA, LTP, and Ca2+ response were evaluated using hippocampal slices from 26-month-old Wistar rats. Chronic treatment of DHA reduced the hippocampal AA significantly, but did not change the amplitude of LTP. Neither 30 mM K+ nor 500 microM NMDA-induced Ca2+ response was affected by chronic treatment of DHA, while the 500 microM carbachol-induced Ca2+ response was reduced. From these results, the reduction of membrane AA might suppress the carbachol-induced Ca2+ response by inhibiting the muscarinic receptor function, IP3 formation and/or Ca2+ release from Ca2+ stores by IP3. However, the reduction of membrane AA is not likely to be a main causal factor of the decline of LTP.

Docosahexaenoic acid does not affect aggression of normal volunteers under nonstressful conditions. A randomized, placebo-controlled, double-blind study.

We previously found that docosahexaenoic acid (DHA) intake prevents aggression enhancement at times of mental stress. In the present study we investigated changes in aggression under nonstressful conditions. Forty-six students of two universities took either DHA-rich fish oil capsules containing 1.5 g DHA (DHA group: 13 males and 9 females) or control oil capsules containing 97% soybean oil plus 3% of another fish oil (control group: 11 males and 13 females) for 3 mon in a double-blind fashion. At the start and end of the study they took an aggression-estimating test (P-F Study) without a stressor component. DHA (5.9 to 8.5%, P < 0.001) and eicosapentaenoic acid (0.7 to 1.5%, P < 0.001) increased in red blood cell phospholipids in the DHA group, while linoleic acid increased slightly (8.3 to 9.1%, P < 0.002) in the soybean oil control group. In the control group, measured aggression levels decreased from 34.8 to 29.4% (P < 0.005), whereas they remained stable in the DHA group (33.5 to 33.8%). The intergroup differences (-5.4 vs. 0.3%) were marginally significant (P < or = 0.05). Aggression levels were stable in the DHA group whether there was stressor (as previously shown) or not. This effect of DHA appears to be interesting, considering the reported association between a low intake of n-3 fatty acids and depression.

Modulation of eosinophil chemotactic activities to leukotriene B4 by n-3 polyunsaturated fatty acids.

Eosinophil accumulation induced by leukotriene B4 appears to be involved in the pathogenesis of allergic diseases. We evaluated the effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on chemotaxis to leukotriene B4 in guinea pig peritoneal eosinophils. Guinea pigs that were sensitized to polymyxin B were administered an intraperitoneal injection of polymyxin B (1 mg/animal) alone or combined with DHA (15 or 50 mg/kg, i.p.), EPA (50 or 100 mg/kg, i.p.), or with linoleic acid (LA) (100 mg/kg, i.p.). Forty hours later, eosinophils were obtained from the intraperitoneal lavage fluid and purified. The chemotactic and chemokinetic responses of eosinophils to leukotriene B4 were measured using a 96-well microchemotaxis chamber. DHA significantly decreased the chemotactic and chemokinetic responses of eosinophils in a dose-dependent fashion. A higher dose of EPA also significantly inhibited both of those responses, whereas LA had no effect. Our results suggested a possible mechanism for the improvement of allergic diseases by dietary supplementation with n-3 PUFA.

Decreased heart rate by acupuncture stimulation in humans via facilitation of cardiac vagal activity and suppression of cardiac sympathetic nerve.

The effect of acupuncture stimulation applied to a Ximen point (P4) of a forearm on heart rate was studied in healthy volunteer human subjects. Acupuncture stimulation decreased heart rate, or gave no significant response. The decreased response of heart rate following acupuncture was attenuated by administration of atropine and propranolol. Therefore, the acupuncture-induced response of decrease in heart rate was concluded to be a result of a reciprocal coordination of an increase in cardiac vagal activity and a decrease in cardiac sympathetic activity.

Adverse effects of intraportal chemotherapy on natural killer cell activity in colorectal cancer patients.

BACKGROUND: Adjuvant intraportal chemotherapy has been used with a view to prevent the development of metachronous hepatic metastases following curative resection for colorectal cancer. To evaluate the effects of this therapy on systemic antitumor immunological activity, 35 colorectal cancer patients who underwent curative resection were investigated. METHOD: Among them. 19 had adjuvant intraportal chemotherapy with mitomycin C and 5-fluorouracil (treated group) and 16 had no chemotherapy (untreated group). Natural killer (NK) cell activity, lymphocyte subpopulations, and immunosuppressive acidic protein (IAP) in the peripheral blood were measured serially before and after operation, and the values were compared between the two groups. RESULTS: The NK cell activity and the percentages of CD16 positive and CD56 positive cells were markedly reduced in the treated group postoperatively. Significant difference was also observed between the two groups on the 4th postoperative day in regard to NK cell activity and CD56 positive cells. CONCLUSIONS: Intraportal chemotherapy in our study reduced the NK cell activity and its population in the peripheral blood.

The effect of docosahexaenoic acid on aggression in young adults. A placebo-controlled double-blind study.

41 students took either docosahexaenoic acid (DHA)-rich oil capsules containing 1.5-1.8 grams DHA/day (17 females and 5 males) or control oil capsules containing 97% soybean oil plus 3% fish oil (12 females and 7 males) for 3 mo in a double-blind fashion. They took a psychological test (P-F Study) and Stroop and dementia-detecting tests at the start and end of the study. The present study started at the end of summer vacation and ended in the middle of mental stress such as final exams. In the control group extraggression (aggression against others) in P-F Study was significantly increased at the end of the study as compared with that measured at the start (delta = +8.9%, P = 0.0022), whereas it was not significantly changed in the DHA group (delta = -1.0%). The 95% CI of differences between the DHA and control groups were -16.8 to -3.0%. DHA supplementation did not affect the Stroop and dementia-detecting tests. Thus, DHA intake prevented extraggression from increasing at times of mental stress. This finding might help understand how fish oils prevent disease like coronary heart disease.

The effect of oral administration of eicosapentaenoic and docosahexaenoic acids on acute inflammation and fatty acid composition in rats.

To investigate effects of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) on acute inflammation, we fed rats either of the following four diets: an EPA-rich diet for 5 or 15 days, a DHA-rich diet for 5 or 15 days, a control diet for 5 or 15 days, and standard chow for 15 days. At the end of diets, the carrageenan-induced swelling of footpads was measured. Peritoneal cells were analyzed for their fatty acids in the phospholipid fraction. The swelling was similarly reduced in the EPA and DHA groups (p < 0.05, if fed for 15 days) compared with rats fed the control diet for 15 days. The mean proportion of arachidonic acid (AA) to the sum of highly unsaturated fatty acids was correlated (r = 0.87) to the mean degree of swelling among all dietary groups (n = 7). Effects of EPA and DHA might be explained by the reduced availability of AA for eicosanoid formation represented by the proportion of AA.

Colon cancer prevention with a small amount of dietary perilla oil high in alpha-linolenic acid in an animal model.

BACKGROUND: Epidemiologic and experimental studies suggest that dietary fish oil and vegetable oil high in omega-3 polyunsaturated fatty acids (PUFAs) suppress the risk of colon cancer. The optimal amount to prevent colon carcinogenesis with perilla oil high in omega-3 PUFA alpha-linolenic acid in a 12% medium-fat diet was investigated in female F344 rats. For comparison, safflower oil high in omega-6 PUFA linoleic acid was used. METHODS: Thirty or 25 rats at 7 weeks of age in each group received an intrarectal dose of 2 mg N-methyl-N-nitrosourea 3 times weekly in weeks 1 and 2 and were fed the diets with various levels of perilla oil and safflower oil throughout the experiment. RESULTS: The incidence of colon cancer at the termination of the experiment at week 35 was 40%, 48% and 32% in the rats fed the diets with 3% perilla oil plus 9% safflower oil, 6% perilla oil plus 6% safflower oil, and 12% perilla oil plus 0% safflower oil, respectively, whereas it was 67% in the rats fed the control diet with 0% perilla oil plus 12% safflower oil. The amount of diet consumed and the body weight gain were identical in all of the dietary groups. The ratios of omega-3 PUFA to omega-6 PUFA in the serum and the colonic mucosa at week 35 were increased in parallel to the increased intake of perilla oil. CONCLUSIONS: The results suggest that a relatively small fraction of perilla oil, 25% of total dietary fat, may provide an appreciable beneficial effect in lowering the risk of colon cancer.

Intravenous infusion of tridocosahexaenoyl-glycerol emulsion into rabbits. Effects on leukotriene B4/5 production and fatty acid composition of plasma and leukocytes.

Leukotriene (LT) B4 is a major chemical activator of PMN. Inhibitory effects of oral administration of docosahexaenoic acid (DHA) on LTB4 synthesis by PMN are known. We intravenously infused tridocosahexaenoyl-glycerol (DHA-TG) emulsion into rabbits in three different doses, namely 0.8, 0.4, or 0.2 g DHA/kg, and investigated the changes in LTB4/5 production by ionophore-activated PMN. The averaged LTB4 production by PMN was significantly reduced to 57 and 59% of baseline at 6 h after the infusion of 0.8 and 0.4 g DHA/kg, respectively (P < 0.05), but not after the infusion of 0.2 g DHA/kg or 0.8 g soybean oil/kg. The combined concentrations of both DHA and eicosapentaenoic acid in the PMN phospholipid fraction were significantly increased at 6 h after the infusion of 0.8 or 0.4 g DHA/kg but not after the infusion of 0.2 g DHA/kg or 0.8 g soybean oil/kg. Oral administration of 0.8 g DHA/kg did not increase DHA or eicosapentaenoic acid in the PMN phospholipid fraction and did not decrease LTB4 production by PMN at 6 h after administration. We suggest that the infusion of 0.4-0.8 g DHA/kg might be beneficial to patients who suffer from diseases that are related to the acute elevation of LTB4 production.

Effect of docosahexaenoic acid on the generation of platelet-activating factor by eosinophilic leukemia cells, Eol-1.

Human eosinophilic leukemia (Eol-1) cells were examined for their ability to generate platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) (PAF) and the effect of supplementation of docosa-hexaenoic acid (C22:6n-3) (DHA) on the PAF synthesis was explored in relation to the fatty acid composition of phospholipids and the liberation of arachidonic acid (C20:4n-6 AA). Although undifferentiated cells did not produce PAF, the exposure of IFN-gamma differentiated Eol-1 to generate PAF in response to the Ca-ionophore. In addition, the IFN-gamma-treated cells acquired the ability to release free fatty acids, approximately 55% of which was found to be AA. When DHA was supplemented into the culture of Eol-1 for 24 h, PAF production decreased by 40 to 50% at concentrations of 3 to 10 microM. On the other hand, supplementation of 10 microM eicosapentaenoic acid (C20:5n-3) did not significantly decrease PAF production. With the supplementation of 10 microM DHA, DHA levels in phospholipid subclasses, including alkylacylglycerophosphocholine, were greatly increased with concurrent decreases in other unsaturated fatty acids. In these cells, the liberation of AA in response to an ionophore was decreased by 55%. Even when DHA was enriched in phospholipids, DHA release in response to ionophore stimulation was almost negligible, indicating that the DHA moiety of phospholipids is not susceptible to the action of phospholipase A2. Furthermore, DHA supplementation appeared to attenuate phospholipase A2 reaction by some unknown mechanism because the decrease in AA release was much more than that for the AA level in phospholipids. Acetyl-CoA:1-alkylGPC acetyltransferase activity of stimulated cell lysate was also reduced by DHA supplementation but the reduction was much less when compared with that of PAF synthesis or AA release. These results implicated that enrichment of DHA attenuates enzymic reactions for PAF synthesis, mainly the initial reaction catalyzed by AA-specific phospholipase, and thereby reduces PAF synthesis in Eol-1.

Directed biosynthesis of new saframycin derivatives with resting cells of Streptomyces lavendulae.

Saframycin A is an antitumor antibiotic produced by Streptomyces lavendulae 314 which falls into the category of the N-heterocyclic quinone group. Biosynthetically the quinone ring is derived from two tyrosine molecules which condense to generate the basic ring system of saframycin A. The side chain also has been found to derive from two amino acids, i.e., glycine and alanine. Supplementation by various amino acid analogs of the side chain produced three new saframycin derivatives with a replaced side chain. These three saframycins, designated Yd-1, Yd-2, and Y3, contained 2-amino-n-butyric acid, glycine, and alanine residues, respectively. in place of the normal N-terminal pyruvic acid in the side chain of saframycin A. Feeding experiments with 13C-labeled dipeptide indicated that the amino acids are probably incorporated in the side chain as a dipeptide unit. It was also found that saframycin A is produced from saframycin Y3 by an enzymatic deamination reaction. Based on these results, saframycin biosynthesis in S. lavendulae is discussed.