Contrasting effects of t10,c12- and c9,t11-conjugated linoleic acid isomers on the fatty acid profiles of mouse liver lipids.

The purpose of this study was to examine the effects of two purified isomers of CLA (c9,t11-CLA and t10,c12-CLA) on the weights and FA compositions of hepatic TG, phospholipids, cholesterol esters, and FFA. Eight-week-old female mice (n = 6/group) were fed either a control diet or diets supplemented with 0.5% c9,t11-CLA or t10,c12-CLA isomers for 8 wk. Weights of liver total lipids and those of individual lipid fractions did not differ between the control and the c9,t11-CLA groups. Livers from animals fed the t10, c12-CLA diet contained four times more lipids than those of the control group; this was mainly due to an increase in the TG fractions (fivefold), but cholesterol (threefold), cholesterol esters (threefold), and FFA (twofold) were also significantly increased. Although c9,t11-CLA did not significantly alter the weights of liver lipids when compared with the control group, its intake was associated with significant reductions in the weight percentage (wt% of total FAME) of 18:1n-9 and 18:1n-7 in the TG fraction and with significant increases in the weight percentage of 18:2n-6 in the TG, cholesterol ester, and phospholipid fractions. On the other hand, t10,c12-CLA intake was linked with a significant increase in the weight percentage of 18:1n-9 and a decrease in that of 18:2n-6 in all lipid fractions. These changes may be the result of alterations in the activity of delta9-desaturase (stearoyl CoA desaturase) and the enzymes involved in the metabolism of 18:2n-6. Thus, the two isomers differed not only in their effects on the weights of total liver lipids and lipid fractions but also on the FA profile of the lipid fractions.

The effect of dietary docosahexaenoic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans.

The effect of dietary docosahexaenoic acid (DHA) in the absence of eicosapentaenoic acid (EPA) has been studied infrequently in humans under controlled conditions. This 120-d study followed healthy, adult male volunteers who lived in the metabolic research unit (MRU) of the Western Human Nutrition Research Center for the entire study. The basal (low-DHA) diet consisted of natural foods (30 en% fat, 15 en% protein, and 55 en% carbohydrate), containing < 50 mg/d of DHA, and met the recommended daily intake for all essential nutrients. The high-DHA (intervention) diet was similar except that 6 g/d of DHA in the form of a triglyceride containing 40% DHA replaced an equal amount of safflower oil in the basal diet. The subjects (ages 20 to 39) were within -10 to +20% of ideal body weight, nonsmoking, and not allowed alcohol in the MRU. Their exercise level was constant, and their body weights were maintained within 2% of entry level. They were initially fed the low-DHA diet for 30 d. On day 31, six subjects (intervention, group A) were placed on the high-DHA diet; the other four subjects (controls, group B) remained on the low-DHA diet. Platelet aggregation in platelet-rich plasma was determined using ADP, collagen, and arachidonic acid. No statistical differences could be detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the high-DHA diet. The prothrombin time, activated partial thromboplastin time, and the antithrombin-III levels in the subjects were determined, and, again, there were no statistically significant differences in these three parameters when their values were compared before and after the subjects consumed the high-DHA diet. In addition, the in vivo bleeding times did not show any significant difference before and after the subjects consumed the high-DHA diet (9.4 +/- 3.1 min before and 8.0 +/- 3.4 min after). Platelets from the volunteers exhibited more than a threefold increase in their DHA content from 1.54 +/- 0.16 to 5.48 +/- 1.21 (wt%) during the DHA feeding period. The EPA content of the subjects' platelets increased from 0.34 +/- 0.12 to 2.67 +/- 0.91 (wt%) during the high-DHA diet despite the absence of EPA in the subjects' diets. The results from this study on blood clotting parameters and in vitro platelet aggregation suggest that adding 6 g/d of dietary DHA for 90 d to a typical Western diet containing less than 50 mg/d of DHA produces no observable physiological changes in blood coagulation, platelet function, or thrombotic tendencies in healthy, adult males.

The effect of dietary docosahexaenoic acid on plasma lipoproteins and tissue fatty acid composition in humans.

Normal, healthy male volunteers (n = 6) were fed diets [high docosahexaenoic acid-DHA] containing 6 g/d of DHA for 90 d. The stabilization (low-DHA) diet contained less than 50 mg/d of DHA. A control group (n = 4) remained on the low-DHA diet for the duration of the study (120 d). Blood samples were drawn on study days 30 (end of the stabilization period), 75 (midpoint of the intervention period), and 120 (end of the intervention period). Adipose tissue (AT) samples were taken on days 30 and 120. The plasma cholesterol (C), low density lipoprotein (LDL)-C and apolipoproteins (apo) [Al, B, and lipoprotein (a)] were unchanged after 90 d, but the triglycerides (TAG) were reduced from a mean value of 76.67 +/- 24.32 to 63.83 +/- 16.99 mg/dL (n = 6, P < 0.007 using a paired t-test) and the high density lipoprotein (HDL)-C increased from 34.83 +/- 4.38 mg/dL to 37.83 +/- 3.32 mg/dL (n = 6, P < 0.017 using a paired t-test). The control group showed no significant reduction in plasma TAG levels. Apo-E, however, showed a marked increase in the volunteers' plasma after 90 d on the high-DHA diet, from 7.06 +/- 4.47 mg/dL on study day 30 to 12.01 +/- 4.96 mg/dL on study day 120 (P < 0.002 using a paired t-test). The control subjects showed no significant change in the apo-E in their plasma (8.46 +/- 2.90 on day 30 vs. 8.59 +/- 2.97 on day 120). The weight percentage of plasma DHA rose from 1.83 +/- 0.22 to 8.12 +/- 0.76 after 90 d on the high-DHA diet. Although these volunteers were eating a diet free of eicosapentaenoic acid (EPA), plasma EPA levels rose from 0.38 +/- 0.05 to 3.39 +/- 0.52 (wt%) after consuming the high-DHA diet. The fatty acid composition of plasma lipid fractions--cholesterol esters, TAG, and phospholipid--showed marked similarity in the enrichment of DHA, about 10%, after the subjects consumed the high-DHA diet. The DHA content of these plasma lipid fractions varied from less than 1% (TAG) to 3.5% (phospholipids) at baseline, study day 30. EPA also increased in all plasma lipid fractions after the subjects consumed the high-DHA diet. There were no changes in the plasma DHA or EPA levels in the control group. Consumption of DHA also caused an increase in AT levels of DHA, from 0.10 +/- 0.02 to 0.31 +/- 0.07 (wt%) (n = 6, P < 0.001 using a paired t-test), but the amount of EPA in their AT did not change. Thus, dietary DHA will lower plasma TAG without EPA, and DHA is retroconverted to EPA in significant amounts. Dietary DHA appears to enhance apo-E synthesis in the liver. It appears that DHA can be a safe and perhaps beneficial supplement to human diets.

N-nitrosation and N-nitration of morpholine by nitrogen dioxide: inhibition by ascorbate, glutathione and alpha-tocopherol.

Ascorbate anion and glutathione were found to inhibit the aqueous reaction between nitrogen dioxide (NO2) and morpholine (MOR) and thereby prevented the formation of N-nitrosomorpholine (NMOR) and N-nitromorpholine (NTMOR) at both pH 7.4 and 12.5. These antioxidants are approximately 3 orders of magnitude more reactive towards NO2 than is MOR and may play an important role in the prevention of carcinogen formation in the lung due to inhaled NO2. Ammonium sulfamate was ineffective at preventing nitrosation or nitration by NO2 at either pH 7.4 or 12.5.

Artifactual nitrosation in the lung perfusion apparatus.

Teflon tubing used in the isolated, ventilated and perfused lung apparatus (IVPL) was found to yield artifactually high values for nitrosamine formation after it had been exposed to nitrite. In contrast to an earlier report, we found that submilligram levels of nitrite do not react to form significant quantities of nitrosamine in the IVPL apparatus over a period of 1 h if contamination from the tubing is prevented.