Effect of dietary alpha-linolenate/linoleate balance on crescent type-anti-glomerular basement membrane nephritis in rats

Effects of chronic high fat diets on renal function and cortical structure in rats

Four groups (n = 5) of male Wistar rats were fed with different high-fat diets from 21 days to 18-mo-old: soybean oil (SO), canola oil (CA), lard and egg yolk (LE) or CA+LE. Blood lipids, serum creatinine and proteinuria as well as the cortical stereology were analyzed. The cholesterol, HDL-C and triglycerides were highest in CA group. No significant differences were found among the groups to serum creatinine and proteinuria. The BP was highest in LE group and intermediate in CA+LE group. SO and CA groups showed glomeruli most preserved in number and size. Absolute volume of tubuli was greatest in LE group. Renal cortical interstitium was greatest in SO group and smallest in CA group. Cortical vessels showed smallest indices in LE group and greatest ones in CA group; SO and CA+LE groups were intermediate. Chronic administration of different types of dietetic lipid can significantly alter blood biochemistry, BP and renal cortical structure in rats. Considering these features, canola oil was the more beneficial lipid, while lard and egg yolk mixture was the worst lipid. The addition of canola oil in the LE mixture normally was not efficient to alter the renal damage except in the cortical vessels.

Effect of dietary oils enriched with n-3 fatty acids on survival of mice

Female mice were fed a conventional diet, shifted at 119 days of age to a diet supplemented with 10 wt % lard (Lar), high-linoleic (n-6) safflower oil (Saf), rapeseed oil (low-erucic, Rap), high-alpha-linolenic (n-3) perilla oil (Per) or a mixture (1:9) of ethyl docosahexaenoate (n-3) and soybean oil (DHA/Soy). Weight gain was less in the Per group than in the other groups at 497 days of age. In the Rap group, proteinuria was more severe than in the Saf, Per and DHA/Soy group, and hepatic triacylglycerol accumulation was greater than in the other groups. The mean survival time of the DHA/Soy group (753 days) was significantly longer than in the Lar group (672 days) and Saf group (689 days); the differences among other groups (e.g., 701 days in the Per group and 712 days in the Rap group) were not statistically significant. Although DHA is more susceptible to auto-oxidation than other major fatty acids in the air, an oil containing DHA was found to increase the survival of mice. Rapeseed oil that decreases the survival time of SHRSP rats was found to be safe in the mouse strain used in this study when survival was an end point.

Dietary docosahexaenoic acid enhances ferric nitrilotriacetate-induced oxidative damage in mice but not when additional alpha-tocopherol is supplemented

Weaning mice were fed a diet supplemented with beef tallow (BT) or BT plus docosahexaenoic acid (DHA) containing 100 mg alpha-tocopherol/kg (alpha-Toc100) or 500 mg alpha-tocopherol/kg (alpha-Toc500) for 4 wk to modify membrane fatty acid unsaturation, and then were administered ferric nitrilotriacetate (Fe-NTA). The mortality caused by Fe-NTA was higher in the group fed the DHA (alpha-Toc100) diet than in the BT diet groups but the DHA (alpha-Toc500) diet suppressed this increase. Serum and kidney alpha-tocopherol contents were slightly influenced by the dietary fatty acids but not significantly. These results indicate that the increased unsaturation of tissue lipids enhances oxidative damage induced by Fe-NTA in mice fed DHA (alpha-Toc100) but not when additional alpha-tocopherol is supplemented. The apparent discrepancy between the observed enhancement by dietary DHA of oxidative damage and the beneficial effects of dietary DHA on the so-called free radical diseases is discussed in terms of strong bolus oxidative stress and moderate chronic oxidative stress.

Effect of dietary linoleate/alpha-linolenate balance on experimentally induced gastric injury in rats

Rats were fed diets containing different ratios of linoleate (18:2 n-6) to alpha-linolenate (18:3 n-3), and the severity of gastric injury induced by ethanol, ischemia/reperfusion and water-immersion stress was compared. On decreasing the 18:2 n-6/18:3 n-3 ratios in the diets, the proportion of arachidonic acid (20:4 n-6) decreased and that of eicosapentaenoic acid (20:5 n-3) increased in the phospholipids of the gastric mucosa, which was associated with decreased mucosal prostaglandin E2 content. Mucosal injury in all the three experimental models was exacerbated significantly in the diet group fed 18:2 n-6/18:3 n-3 ratio of 0.25 (perilla oil) as compared with the groups fed dietary oils with 18:2 n-6/18:3 n-3 ratios of 2.7 (mixture of perilla and safflower oils) and 127 (safflower oil). This adverse effect induced by perilla oil diet was not observed when rats were pretreated with a mild irritant (20% ethanol) prior to challenge with a strong irritant (absolute ethanol). Furthermore, an 18:2 n-6/18:3 n-3 ratio of as low as 1 was found to be in a safe range in the water-immersion stress ulcer model. Thus, oils with very low n-6/n-3 ratios, for example perilla oil, could be used without the risk of the observed adverse effects on experimental gastric injury in people of industrialized countries ingesting foods with n-6/n-3 ratios of above 4. A decrease in the n-6/n-3 ratios to 2 or below is still recommended for the prevention of chronic diseases in the elderly related to atherosclerosis and inflammation.

Effects of low casein and fish oil on hyperlipidemia and proteinuria in nephritic rats

The effects of amino acid-fortified low casein and fish oil (FO) diets on hyperlipidemia and proteinuria were studied in rats with nephrotoxic serum nephritis. After an antiserum injection, rats were maintained for 14 d on four different experimental diets: a 20% casein diet containing corn oil (CO) or FO, or an 8% casein diet supplemented with cystine plus threonine containing CO or FO. The 8% casein diets reduced urinary protein excretion in nephritic rats without inducing severe growth retardation or fatty liver compared with the basal 20% casein diets. Both the 8% casein diet and the FO diet decreased serum cholesterol, triglyceride and phospholipid levels in nephritic rats, and nonesterified fatty acid levels were decreased by FO feeding. In nephritic animals, hepatic cholesterol synthesis was decreased by the 8% casein diets compared with the 20% casein diets, and tended to be reduced by FO feeding between groups at the same casein levels. No effect of diet was observed on fatty acid synthesis among the nephritic rats. FO administration to the nephritic animals suppressed fecal steroid excretion. While lipoprotein lipase activity was unchanged among the nephritic rats, hepatic triglyceride lipase activity was reduced by either the 8% casein or FO diet. The results suggest that the hypolipidemic action of low casein diets may, at least in part, be due to reduced hepatic cholesterol synthesis and suppressed triglyceride secretion from the liver. They also suggest that the hypolipidemic action of FO may, at least in part, be due to reduced hepatic cholesterol synthesis and decreased fatty acid mobilization from peripheral adipose tissue.

Effect of dietary alpha-linolenate/linoleate balance on endotoxin-induced hepatitis in mice

Mice were fed diets with three different ratios of alpha-linolenate (18:3n-3) to linoleate (18:2n-6), and the severity of hepatitis during endotoxic shock was compared. Dietary enrichment with alpha-linolenate increased the severity of hepatitis and the mortality induced by lipopolysaccharide (LPS) in combination with D-galactosamine (GalN). Differences in the dietary alpha-linolenate/linoleate balance were mainly reflected in the levels of arachidonate and eicosapenatenoate in liver phospholipids. Pretreatment of mice with indomethacin was found to also enhance the severity of GalN/LPS-hepatitis. This indicated that cyclooxygenase products of arachidonate may suppress the development of GalN/LPS-hepatitis. The enhancement by high alpha-linolenate diets was not observed when a lethal dose of LPS in the absence of GalN was given. Our results indicate that there are pathophysiological conditions of endotoxin-induced hepatitis under which cyclooxygenase products of arachidonate play protective roles.

Effect of dietary alpha-linolenate/linoleate balance on lipopolysaccharide-induced tumor necrosis factor production in mouse macrophages

We examined the effect of dietary alpha-linolenate (18:3n-3)/linoleate (18:2n-6) balance on lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) production in mouse macrophages. Resident and casein-induced peritoneal macrophages from mice fed a high alpha-linolenate diet produced a higher amount of TNF than in the high linoleate diet group. However, TNF production was not affected by the dietary alpha-linolenate/linoleate balance when thioglycollate- and complete Freund's adjuvant-induced macrophages were stimulated with LPS. Serum TNF levels of mice intraperitoneally injected with LPS was also higher in the high alpha-linolenate group than in the high linoleate group. These diets affected the n-3/n-6 ratios of 20 and 22 carbon highly unsaturated fatty acids in macrophage lipids. Thus, the dietary enrichment with alpha-linolenate was found to enhance TNF production of macrophages isolated under limited conditions.