Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

High fat diet induced oxidative DNA damage estimated by 8-oxo-7,8-dihydro-2-deoxyguanosine excretion in rats

The role of dietary fats and energy in carcinogenesis has been partly related to oxidative damage to DNA. We have investigated the effect of dietary fat content and saturation on the urinary excretion of 8-oxo-7,8dihydro-2'-deoxyguanosine (8-oxodG) in male and female rats. Groups of Fischer F344 rats (n = 6-10) were fed control chow (3.4% fat) or diets containing 21.8% corn oil or 19.8% coconut oil + 2% corn oil for 12-15 weeks. At the end of the diet intervention period 24h urine was collected for determination of 8-oxodG by HPLC. In the male groups fed control, corn oil and coconut oil diet the excretion of 8-oxodG was 403+/-150, 932+/-198 and 954+/-367pmol/kg 24 h, respectively (p < 0.05). In the female groups fed control and corn oil diet the excretion of 8-oxodG was 752+/-80 and 2206+/-282 pmol/kg 24 h, respectively (p < 0.05). Calculated per whole animal the excretion was 137+/-51, 324+/-70 and 328+/-128 pmol/24 h in the control, corn and coconut oil male groups and 156+/-21 and 464+/-56 pmol/24 h in the control and corn oil female groups, respectively ( p < 0.05). Thus, per animal or per consumed energy there was much less difference in 8-oxodG excretion between the corresponding male and female groups and only significant difference between the high fat groups. There was a close correlation (r = 0.7; p < 0.05) between 8-oxodG excretion and the energy intake. The present study suggests that a high fat diet increases oxidative DNA modification substantially irrespective of the saturation level of the fat. Energy intake appears to be the major determinant of the rate of modification.     

Effect of n-6 and n-3 dietary fatty acids on phospholipid composition of plasma, platelets and aorta in the rat

Female Wistar rats were fed with diets containing as dietary lipids 10% of hydrogenated coconut oil, grape-seed oil, olive oil, linseed oil and fish oil, respectively, for a period of 60 days. At the end of dietary treatment plasma, platelets and aorta phospholipids were extracted and fatty acid spectra determined. Plasma and platelet phospholipids showed the largest diet dependent changes. Anyway in aorta samples too, phospholipids showed marked increase in oleic (olive oil group) linoleic (grape-seed oil group) and alpha linoleic (linseed oil group) acids percentage. Conversely decreased amounts of arachidonic acid were detected in rats fed with diets containing linseed and fish oils. In these samples eicosapentenoic acid partly replaced arachidonic one.     

Effect of fish oil and coconut oil diet on the LDL receptor activity of rat liver plasma membranes

The influence of 4 weeks treatment with fish oil and coconut oil enriched diets on the chemical composition of rat liver plasma membranes and LDL and on the binding of LDL to liver membranes was investigated. Rats fed fish oil diet showed a total, LDL and HDL plasma cholesterol concentration lower than the values observed in rats fed coconut oil and to a lesser extent lower than those of rats fed standard laboratory diet. LDL of rats on fish oil diet had a relative percentage of cholesterol and phospholipid lower, while that of triacylglycerol was greater. Furthermore, fish oil feeding was associated with a greater concentration of n - 3 fatty acids and a lower arachidonic and linoleic acid content in LDL. Liver plasma membranes isolated from fish oil rats showed a higher percentage of n - 3 fatty acids, while only a trace amount of these fatty acids was found in control and coconut oil fed animals. In binding experiments performed with LDL and liver membranes from fish oil fed rats and control rats, binding affinity (Kd = 3.47 +/- 0.93 and 4.56 +/- 1.27, respectively) was significantly higher (P less than 0.05) as compared to that found using membranes and lipoprotein from coconut oil fed rats (Kd = 6.82 +/- 2.69). In cross-binding experiments performed with fish oil LDL and coconut oil liver plasma membranes or coconut oil LDL and fish oil liver plasma membranes, the LDL binding affinity was comparable and similar to that found in fish oil fed animals. No difference was found in the Bmax among all the groups of binding experiments. Our data seem to indicate that during fish oil diet the higher binding affinity of LDL to liver plasma membranes might be partly responsible of the hypocholesterolemic action of marine oil rich diet as compared to saturated diet. Furthermore, the modifications of binding affinity induced by changes of LDL and membrane source, suggest that lipoprotein and liver plasma membrane composition may be an important variable in binding studies.     

Effects of type of fat in the diet on iron bioavailability assessed in suckling and weanling rats

Differences in iron bioavailability from human milk and milk formulas may in part be due to differences in lipid composition. We investigated the short and long term effects of diets based on different fats [corn, coconut, olive, or soy oil, human milk fat (HMF) and a formula fat blend (FF)] on iron absorption in rats. Suckling rat pups dosed with 59Fe-labeled diets containing different fat sources were killed after 6 h, and blood and individual tissues were counted. Iron availability was estimated by % 59Fe in blood. Pups dosed with a more saturated fat (coconut oil) had a higher % 59Fe in blood than those fed other fat sources. Weanling rats were used to determine iron bioavailability from fat sources using both the hemoglobin repletion method and whole body counting. Hemoglobin regeneration was significantly higher for rats fed the HMF diet (8.4 +/- 0.5 g/dl) than from the FF diet (6.5+/-0.6 g/dl) or the corn oil diet (less saturated) (6.4 +/- 0.3 g/dl). Rats fed diets based on coconut oil (more saturated) had significantly higher % 59Fe retention (61.6 +/- 1.4) than rats fed diets based on FF (49.8 +/- 3.4). There was a significant positive association between oleic acid in the diet and oleic acid in the intestinal mucosa (r = 0.95, p < 0.05) and between linoleic acid in the diet and linoleic acid in the intestinal mucosa (r = 0.97, p < 0.05) suggesting that the dietary treatment altered the fatty acid composition of the brush border membrane. Our results suggest that saturated fats may increase iron absorption and that part of this may be achieved by changes in the fatty acid composition of the intestinal mucosa. Hemoglobin regeneration and % 59Fe retention data suggest that differences in iron absorption from infant diets may in part be due to differences in fat composition. Therefore, lipid composition of infant formulas should also be taken into consideration as a factor influencing iron bioavailability.     

Effects of dietary linoleic acid on blood pressure and renal function in subtotally nephrectomized rats

The effect of a high linoleic acid diet on blood pressure, renal function, and urinary prostaglandin excretion was studied in rats with decreased renal mass. Subtotally nephrectomized (5/6 nephrectomy) male rats received either a 15% linoleic acid (high linoleic acid, HLA) diet containing 20% safflower oil or a 0.28% linoleic acid (low linoleic acid, LLA) diet containing 20% coconut oil. Sham-operated rats were also placed on either HLA or LLA diet. The subtotal nephrectomized rats developed similar degrees of hypertension during the first 3 weeks after subtotal nephrectomy. However, 4 weeks after subtotal nephrectomy, the rats on HLA diet had significantly lower blood pressure than the rats on LLA diet [HLA 152 +/- 3 (mean +/- SE) mm Hg versus LLA 171 +/- 3 mm Hg]. This difference persisted until termination of the experiment at 7 weeks after subtotal nephrectomy (HLA 159 +/- 7 mm Hg versus LLA 192 +/- 6 mm Hg). The GFR measured 7 weeks after subtotal nephrectomy was significantly lower in both of the subtotally nephrectomized groups. However, the HLA subtotal nephrectomized rats had significantly higher GFR than the LLA-treated rats (HLA 0.23 +/- 0.05 ml/min 100 g versus LLA 0.12 +/- 0.02 ml/min/100 g, P less than 0.05). There was no difference in the GFR or blood pressure in the sham-operated rats treated with HLA or LLA diet. PGE2 excretion was lower in the two groups of subnephrectomized rats, but there was no difference between the HLA and LLA treated rats. Urinary 6-ketoPGF1 alpha was not decreased by subtotal nephrectomy and there was no difference between the dietary groups. However, TXB2 excretion was higher in the groups with subtotal nephrectomy, but there was no difference between the two dietary groups. In conclusion, the HLA diet attenuates the rise in blood pressure after subtotal nephrectomy in the rat and preserves renal function. There was no difference in urinary excretion of PGE2, 6-keto-PFG1 alpha, or thromboxane B2 between the two dietary groups.     

The prostaglandin outflow from perfused mesenteric vasculature of rats fed different fats

The effects of dietary n-6 polyunsaturated fatty acids and replacement with saturated fat or fish oil on the prostaglandin outflow from perfused mesenteric vasculature in rats were studied. Seventy-two weanling male rats were fed ad libitum a semi-synthetic diet supplemented with 10% by weight of oil, composed wholly of n-6 fatty acid-rich evening primrose oil, or replaced partly or completely (25, 50, 75 or 100%) by n-6 fatty acid-deficient fish oil or hydrogenated coconut oil for 8 weeks. The outflows of 6-keto-PGF1 alpha, thromboxane B2, and prostaglandin E from the perfused mesenteric vasculature were measured at 60 min-time point after starting the perfusion. In general, the release of prostanoids from the mesenteric vasculature was significantly reduced in rats fed a diet in which evening primrose oil was partly or completely replaced by either hydrogenated coconut or fish oil. This was probably due to the insufficient conversion of linoleic acid to arachidonic acid. The extent of reduction was greater in fish oil-fed than in hydrogenated coconut oil-fed rats, while the levels of arachidonic acid in aortic phospholipids were similar between these two groups. This result implies that the greater reduction of prostaglandin synthesis in rats fed fish oil was due to the inhibitory effect of eicosapentaenoic and docosahexaenoic acids in fish oil on the conversion of arachidonate to eicosanoids.     

Dietary fatty acids and oxidative stress in the heart mitochondria

Our study compared the effects of different oils on oxidative stress in rat heart mitochondria, as well as on plasma parameters used as risk factors for cardiovascular disease. The rats were fed for 16 weeks with coconut, olive, or fish oil diet (saturated, monounsaturated, or polyunsaturated fatty acids, respectively). The cardiac mitochondria from rats fed with coconut oil showed the lowest concentration of oxidized proteins and peroxidized lipids. The fish oil diet leads to the highest oxidative stress in cardiac mitochondria, an effect that could be partly prevented by the antioxidant probucol. Total and LDL cholesterols decreased in plasma of rats fed fish oil, compared to olive and coconut oils fed rats. A diet enriched in saturated fatty acids offers strong advantages for the protection against oxidative stress in heart mitochondria.     

Etheno-DNA adduct formation in rats gavaged with linoleic acid, oleic acid and coconut oil is organ- and gender specific

Intake of linoleic acid (LA) increased etheno-DNA adducts induced by lipid peroxidation (LPO) in white blood cells (WBC) of female but not of male volunteers [J. Nair, C.E. Vaca, I. Velic, M. Mutanen, L.M. Valsta, H. Bartsch, High dietary omega-6 polyunsaturated fatty acids drastically increase the formation of etheno-DNA adducts in white blood cells of female subjects, Cancer Epidemiol. Biomarkers Prev. 6 (1997) 597-601]. Etheno-adducts were measured in rats gavaged with LA, oleic acid (OA) and saturated fatty acid rich coconut oil for 30 days. DNA from organs and total WBC was analyzed for 1, N(6)-ethenodeoxyadenosine (varepsilondA) and 3, N(4)-ethenodeoxycytidine (varepsilondC) by immunoaffinity/(32)P-postlabeling. Colon was the most affected target with LA-treatment, where etheno-adducts were significantly elevated in both sexes. In WBC both adducts were elevated only in LA-treated females. Unexpectedly, OA treatment enhanced etheno-adduct levels in prostate 3-9 fold. Our results in rodents confirm the gender-specific increase of etheno-adducts in WBC-DNA, likely due to LPO induced by redox-cycling of 4-hydroxyestradiol. Colon was a target for LPO-derived DNA-adducts in both LA-treated male and female rats, supporting their role in omega-6 PUFA induced colon carcinogenesis.     

Influence of diet and carnitine palmitoyltransferase I inhibition on myosin and sarcoplasmic reticulum.

To examine the role of metabolic signals for ventricular myosin expression and activity of the sarcoplasmic reticulum Ca2+ pump, Wistar rats were treated for 7-8 wk with 5 or 50 mg/kg etomoxir, which inhibits fatty acid utilization. The proportion of myosin V1 was increased (P less than 0.05) with 50 mg/kg etomoxir (75 +/- 5% vs. 62 +/- 6% of control rats), whereas both doses increased the rate of Ca2+ uptake. A carbohydrate-rich fat-free diet or 8% sucrose drinking solutions, however, had no effect on myosin and sarcoplasmic reticulum. When rats were fed diets with an increased content (10 or 20%) of sunflower oil, the calorie intake and myosin V1 increased (56 +/- 8 or 64 +/- 8% vs. 44 +/- 6% of control rats). Isocaloric 10% fat diets of varying fatty acid composition (coconut fat, olive oil, or mackerel oil) also induced a higher calorie intake and increased V1 (64 +/- 6, 60 +/- 9, or 65 +/- 8% for the respective oils vs. 44 +/- 6% of control rats) but did not significantly increase rate of Ca2+ uptake. We concluded that calorie-rich diets changed the myosin expression not by affecting the ratio of fatty acid to glucose utilization but via the increased calorie intake.     

Endogenous formation and significance of 1,N2-propanodeoxyguanosine adducts

The detection of 1,N2-propanodeoxyguanosine adducts in the DNA of rodent and human tissues as endogenous lesions has raised important questions regarding the source of their formation and their roles in carcinogenesis. Both in vitro and in vivo studies have generated substantial evidence which supports the involvement of short- and long-chain enals derived from oxidized polyunsaturated fatty acids (PUFAs) in their formation. These studies show that: (1) the cyclic propano adducts are common products from reactions of enals with DNA bases; (2) they are formed specifically from linoleic acid (LA; omega-6) and docosahexaenoic acid (omega-3) under in vitro stimulated lipid peroxidation conditions; (3) the levels of propano adducts are dramatically increased in rat liver DNA upon depletion of glutathione; (4) the adduct levels are increased in the liver DNA of the CCl4-treated rats and the mutant strain of Long Evans rats which are genetically predisposed to increased lipid peroxidation; and (5) adduct levels are significantly higher in older rats than in newborn rats. These studies collectively demonstrate that tissue lipid peroxidation is a main endogenous pathway leading to propano adduction in DNA. The possible contribution from environmental sources, however, cannot be completely excluded. The mutagenicity of enals and the mutations observed in site-specific mutagenesis studies using a model 1,N2-propanodeoxyguanosine adduct suggest that these adducts are potential promutagenic lesions. The increased levels of the propano adducts in the tissue of carcinogen-treated animals also provide suggestive evidence for their roles in carcinogenesis. The involvement of these adducts in tumor promotion is speculated on the basis that oxidative condition in tissues is believed to be associated with this process.     

Changes in the fatty acid composition of sarcoplasmic reticulum lipids and calcium uptake activity

Supplementing the diet of rats with saflower oil or hydrogenated coconut oil resulted in marked changes in the fatty acid composition of the skeletal muscle sarcoplasmic reticulum hut did not affect such properties of the sarcoplasmic reticulum as the rate of Ca²⁺ uptake, the total amount of Ca²⁺ taken up, the rate and extent of Ca²⁺ release in the cold, and the basal and extra ATPase activities. Both of the oil supplements resulted in large increases in the proportion of linoleic acid in the sarcoplasmic reticulum hut neither of them significantly affected the proportion of polyenoic to saturated + monoenoic fatty acids. The relisons for the unexpectedly high linoleic acid content in the sarcoplasmic reticulum of the hydrogenated coconut oil supplemented rats are not known.     

Dietary n-3 fatty acids,curcumin and capsaicin lower the release of lysosomal enzymes and eicosanoids in rat peritoneal macrophages

Male Wistar rats (12 rats/group) were fed a diet containing 8 wt % coconut oil or groundnut oil or cod-liver oil for a total period of 8 weeks. The diets were also supplemented with 2 wt % groundnut oil for providing essential fatty acids. During the last 2 weeks, 6 rats form each group were additionally given curcumin (30 mg/kg body wt/day) or capsaicin (5 mg/kg body wt/day) in 1 ml groundnut oil. The peritoneal macrophages from rats fed cod-liver oil diet secreted lower levels of lysosomal enzymes collagenase, elastase and hyaluronidase as compared to those from rats fed coconut oil or groundnut oil diets. Curcumin and capsaicin significantly lowered the secretion of these lysosomal enzymes from macrophages in animals given coconut oil or groundnut oil diet. Macrophages from rats fed cod-liver oil secreted lower amounts of prostaglandin E₂, 6-keto PGF_1a, leukotrienes B₄and C₄and also incorporated lesser amounts of [^3H]-arachidonic acid as compared to those given coconut oil or groundnut oil diets. Curcumin and capsaicin lowered the secretion of these eicosanoids and decreased the incorporation of [³H]-arachidonic acid in macrophage lipids. However curcumin and capsaicin significantly increased the secretion of 6-keto PGF_1ain all the groups of animals. These studies indicated that dietary cod-liver oil (rich in n-3 fatty acids), and spice principles curcumin and capsaicin can lower the secretory functions of macrophages in a beneficial manner.     

Effect of dietary virgin olive oil on urinary excretion of etheno-DNA adducts

A significant protective effect against cancer and coronary heart disease has been attributed to the Mediterranean diet, in which olive oil is the main source of fat. Dietary antioxidants, as phenolic compounds from virgin olive oil, are candidates for reducing cancer risk by minimizing oxidatively derived DNA damage. Etheno-DNA adducts are formed as a result of oxidative stress and lipid peroxidation. To evaluate whether phenol-rich virgin olive oil influences urinary excretion of the etheno-DNA adducts epsilonAde, epsilondA, and epsilondC as markers of oxidative stress, a randomized, double-blinded, crossover trial with three intervention periods was conducted in 28 healthy men. Each intervention was of 3 weeks' duration and separated by 2-week washout periods. Twenty-five milliliters of similar olive oils, but with differences in their phenolic content (from 2.7 to 366 mg/kg), were supplied to each subject per day. The urinary excretion of the DNA adducts was assayed by LC-MS/MS in samples before and after consumption of high phenolic content olive oil (virgin). The 24-h excretion rate did not differ significantly between baseline and after virgin olive oil consumption: epsilonAde, 105.5 +/- 40.8 vs 116.4 +/- 53.4 pmol epsilonAde/24 h (p = 0.21); epsilondA, 37.9 +/- 24.8 vs 37.6 17 +/- 24.2 pmol epsilondA/24 h (p = 0.93); and epsilondC, 218.7 +/- 157.2 vs 193.5 +/- 64.7 pmol epsilondC/24 h (p = 0.37). Multiple regression analysis showed a significant association between etheno-DNA adduct excretion rate and the dietary intake of linoleic acid (C18:2, omega-6) in healthy men. Consumption of 25 ml per day of phenol-rich virgin olive oil for 3 weeks did not modify to a significant degree the urinary excretion of etheno-DNA adducts in 28 healthy volunteers.     

Superiority of dietary safflower oil over olive oil in lowering serum cholesterol and increasing hepatic mRnas for the LDL receptor and cholesterol 7alpha-hydroxylase in exogenously hypercholesterolemic (exHC) rats

The exogenously hypercholesterolemic (ExHC) rat is a strain segregated from SD rats with a high response to dietary cholesterol. To understand the underlying mechanism(s) for this hypercholesterolemia, the interactive effects of dietary fatty acid and the susceptibility of rats to dietary cholesterol on the serum cholesterol concentration and hepatic mRNA abundance of the low-density lipoprotein (LDL) receptor, cholesterol 7alpha-hydroxylase (7alpha-hydroxylase) and 3-hydroxyl-3methylglutaryl (HMG) CoA reductase were examined. Both strains were fed on a diet supplemented with 10% each of olive, safflower or coconut oil with or without the addition of 1% cholesterol for one week. The ExHC rats fed on olive, safflower and coconut oil in combination with cholesterol respectively resulted in a 3.5-, 2.0- and 2.1-fold higher serum cholesterol concentration than that in the animals fed on the corresponding dietary fats without any supplementation of cholesterol (p < 0.01 by dietary cholesterol or type of fat). The dietary cholesterol dependent-elevation of serum cholesterol in the SD rats was less than 1.5-fold (p<0.01) and there was no dietary fat effect. The ExHC rats fed on the safflower oil-containing diet supplemented with cholesterol resulted in a higher mRNA abundance of the LDL receptor and 7alpha-hydroxylase than in the corresponding fat-fed rats without cholesterol (p<0.05). There was no dietary cholesterol-dependent change of mRNA abundance in either strain fed on olive or coconut oil, except for a decreased abundance of HMG CoA reductase mRNA in the olive oil-fed ExHC rats and coconut oil-fed Sprague-Dawley (SD) rats (p<0.05). These results indicate that the hepatic mRNA abundance of the LDL receptor and of 7alpha-hydroxylase depended on the dietary combination of cholesterol and a fatty acid and suggest that a linoleic acid-rich diet may alleviate exogenous hypercholesterolemia by activating the process involved in the hepatic uptake and biliary excretion of serum cholesterol.     

The effect of conjugated linoleic acid on calcium absorption and bone metabolism and composition in adult ovariectomised rats

The effect of conjugated linoleic acid (CLA) on postmenopausal bone metabolism has not been investigated. Therefore, forty-three adult ovariectomised (OVX) rats (8-9 rats per group) were fed either a control diet containing 40 g/kg soyabean oil (SBO diet) or the SBO diet with 0 (control OVX), 2.5, 5 or 10 g/kg of CLA (replacing soybean oil) for 9 weeks. A group of sham-operated (SH) rats were fed the SBO diet. OVX rats had significantly (P<0.05) lower femoral bone mineral density and macromineral concentration, and intestinal Ca absorption compared to SH rats. CLA supplementation had no effect on these parameters. Ex vivo PGE(2) biosynthesis by bone and urinary Pyr and Dpyr (markers of bone resorption) were significantly higher (P<0.001) in control OVX rats compared with SH rats, and were significantly (P<0.001) lowered by CLA supplementation with 5 and 10, but not 2.5 g/kg diet in OVX rats. In conclusion, CLA supplementation appeared to reduce the rate of bone resorption in adult OVX rats.     

Lipid peroxidation-related 1,N2-propanodeoxyguanosine-DNA adducts induced by endogenously formed 4-hydroxy-2-nonenal in organs of female rats fed diets supplemented with sunflower, rapeseed, olive or coconut oil

Animal and epidemiological studies confirm an impact of the fatty-acid composition in the diet on cancer development. We investigated the role of supplementation of the diet of female F344-rats with sunflower, rapeseed, olive or coconut oil on the formation of the promutagenic, exocyclic 1,N2-propanodeoxyguanosine adduct of the main lipid peroxidation product 4-hydroxy-2-nonenal in the mucosa of the glandular stomach, the small intestine, the colon, the whole kidney and the lung. This adduct is considered as the predominant DNA adduct arising from lipid peroxidation. The correlations between adduct levels and the different fatty acids were not uniform for all organs. No clear relationships between fatty acids and adduct levels were found in the colon. Significant positive correlations were observed between linoleic acid, total polyunsaturated fatty acids (PUFAs), vitamin E and DNA adduct levels in the small intestine and in the kidney. The results indicate an increasing effect on cancer risk in these organs as a result of high intake of linoleic acid. Inverse relationships between linoleic acid, PUFA and vitamin E intake and adduct levels were found in the glandular stomach and the lung. We could not confirm a chemopreventive effect of linolenic acid (C-18 omega-3 PUFA) on the formation of adducts in our animal study, as was shown in white blood cells of women in a previous study. A tendency towards a decrease in adduct levels was seen with monounsaturated fatty acids (MUFAs) in all organs except the lung. Saturated fatty acids showed a significant positive correlation with adduct levels in the mucosa of the glandular stomach and a significant inverse correlation in the small intestine. Saturated fatty acids are not considered to directly influence lipid peroxidation to a major extent.     

Dietary conjugated linoleic acid in the cis-9, trans-11 isoform reduces parathyroid hormone in male, but not female, rats

Previously, a mixture of conjugated linoleic acid (CLA) isoforms reduced parathyroid hormone (PTH) in male rats over 8 weeks. The objective herein was to determine which isoform caused the reduction in PTH; whether the effect was sex specific; and whether CLA-induced reductions in PTH were sustained. Male and female weanling rats (n=48) were randomized to a control diet or one made with 0.5% of the diet as cis-9, trans-11 (c9,t11) CLA, 0.5% of the diet as trans-10, cis-12 (t10,c12) CLA or these CLA in a mixture. Measurements made after 4, 8 and 16 weeks were body weight, bioactive PTH, ionized Ca, whole-body and regional bone mineral density (BMD) using dual-energy X-ray absorptiometry. With the use of a factorial design, a sexxc9,t11 CLA interaction was observed that reduced PTH (139.5+/-63.9 vs. 95.8+/-42.4 pg/ml, P=.02) in male rats only. No other effects of c9,t11 CLA were observed. Regarding t10,c12 CLA, no interaction effects were observed, but a main effect was observed to reduce lumbar spine BMD (0.265+/-0.044 vs. 0.255+/-0.044 g/cm(2), P<.01) along with reduced retention of Ca and P at Week 4. No other dietary effects were observed. In summary, the c9,t11 CLA isoform is responsible for reduced PTH and this effect is sex specific; this was true whether fed as a pure isomer or mixed with an equal amount of t10,c12 CLA. Whether such reductions in PTH might be observed in females lacking sex hormones such as ovariectomized rats and also in humans is required to expand health implications of dietary CLA.     

Influence of sex and gonadal hormones on rat-liver and carcass lipids during the development of an essential fatty acid deficiency

1. Groups of intact male and female rats and castrated rats injected with oestradiol or testosterone were given a diet containing hydrogenated coconut oil for 9 weeks, and at intervals the amounts and fatty acid compositions of the carcass and liver lipids were determined. 2. Male rats grew faster and larger, and exhibited typical external essential fatty acid deficiency symptoms sooner than did females. Testosterone-treated castrated male rats were similar to males, and oestradiol-injected castrated male rats resembled females. 3. Intact females maintained a higher linoleic acid concentration in their carcass than did males. Total amounts of carcass linoleic acid remained similar for all groups, only 200mg. being removed in 9 weeks regardless of body size. 4. The amounts of total cholesteryl esters were independent of liver size. They were higher in males and testosterone-treated castrated male rats than in females and oestrogen-treated castrated male rats. 5. Phospholipids represented about 80% of the liver lipids. The total amounts of the phospholipid linoleic acid and arachidonic acid were similar for all groups regardless of liver size, and were not affected appreciably by the deficiency. Females and oestrogen-treated castrated male rats maintained a higher proportion of phospholipid arachidonic acid for longer periods than did their male counterparts. Both the total amounts and the proportions of eicosatrienoic acid and palmitic acid were higher in males than in females. 6. Supplementation of the essential fatty acid-deficient diet with linoleic acid caused a rapid loss of eicosatrienoic acid and palmitic acid with a concomitant increase in stearic acid and arachidonic acid. 7. There were no obvious differences in the way that the essential fatty acids were metabolized or mobilized from adipose tissue of male or female rats during essential fatty acid deficiency. 8. The results indicated that the greater growth rate of the male rats caused them to require and synthesize more phospholipids than did the females. In the absence of adequate amounts of arachidonic acid, eicosatrienoic acid was substituted into the additional phospholipid. The earlier symptoms of essential fatty acid deficiency in the male rat could therefore be ascribed to the higher tissue concentrations of this unnatural phospholipid and its inability to perform the normal metabolic functions of phospholipids.     

Dietary alpha-linolenic acid deficiency in adult rats for 7 months does not alter brain docosahexaenoic acid content, in contrast to liver, heart and testes.

In adult rats, 22:6(n - 3) dietary deficiency does not affect brain membranes, but has a significant effect on some other visceral organs. 60-day-old male rats fed a diet containing sufficient amounts of both linoleic and alpha-linolenic acid were divided into three groups. One group continued the same diet; the second was fed a diet containing 2% sunflower oil, the third was fed 10% sunflower oil (sunflower oil contains linoleic acid, but trace amount of alpha-linolenic acid). Animals were killed different times after receiving the new diets (1 to 31 weeks). For animals fed the diets containing only sunflower oil, deficiency in cervonic acid content (DHA, docosahexaenoic acid, 22:6(n - 3)) was not detected in whole brain, myelin or nerve endings within 31 weeks. In contrast, this acid progressively declined in liver, heart and testes up to 3 weeks and remained nearly stable thereafter. In parallel to the reduction of cervonic acid content, 22:5(n - 6) content increased in liver and heart, but not in testes. It also increased in brain, nerve endings and myelin from week 3, 6 and, 9 respectively. These results suggest that brain cervonic acid is highly preserved or is maintained at the expense of other organs.