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PubMed1994

Conjugated linoleic acid suppresses mammary carcinogenesis and proliferative activity of the mammary gland in the rat.

Conjugated linoleic acid (CLA) is a collective term which refers to a mixture of positional and geometric isomers of linoleic acid. It is naturally occurring in meat and dairy products. We have previously reported (Ip, C., Chin, S. F., Scimeca, J. A., and Pariza, M. W. Cancer Res., 51: 6118-6124, 1991) that 1% CLA in the diet suppressed mammary carcinogenesis in rats given a high dose (10 mg) of 7,12-dimethylbenz(a)anthracene. In the present study, dietary CLA between 0.05 and 0.5% was found to produce a dose-dependent inhibition in mammary tumor yield when fed chronically to rats treated with a lower dose (5 mg) of 7,12-dimethylbenz(a)anthracene. Short-term CLA feeding for 5 weeks, from weaning to the time of carcinogen administration at 50 days of age, also offered significant protection against subsequent tumor occurrence. This period corresponds to maturation of the mammary gland to the adult stage in the rat. The inhibitory response to short-term CLA exposure was observed with the use of 2 different carcinogens: 7,12-dimethylbenz(a)anthracene and methylnitrosourea. The fact that CLA was protective in the methylnitrosourea model suggests that it may have a direct modulating effect on susceptibility of the target organ to neoplastic transformation. The proliferative activity of the mammary epithelium was assessed by the incorporation of bromodeoxyuridine. Immunohistochemical staining results showed that CLA reduced the labeling index of the lobuloalveolar compartment, but not that of the ductal compartment of the mammary tree. Since the lobuloalveolar structures are derived from the terminal end buds which are the sites of carcinogenic transformation, the above finding is consistent with the bioassay data of tumor inhibition. Thus, changes in gland development and morphogenesis may be a locus of action of CLA in modulating mammary carcinogenesis. CLA is a unique anticarcinogen because it is present in foods from animal sources. Furthermore, its efficacy in cancer protection is manifest at dietary concentrations which are close to the levels consumed by humans.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Fatty acid composition of serum cholesteryl esters and erythrocyte membranes as indicators of linoleic acid intake in man.

We compared the suitability of the linoleic-oleic acid ratio (L:O) of serum cholesteryl esters and erythrocyte membranes as indicators of dietary fatty acid composition. Forty-seven volunteers received a mixed natural diet with a polyunsaturated-saturated fatty acids ratio (P:S) of 0.2 for 3 wk and with P:S 2.0 for another 3 wk (HA group, 24 subjects) or vice versa (HY group, 23 subjects). Duplicate portion analysis revealed that dietary fat type was the only variable. The change in L:O in cholesteryl esters relative to the low P:S diet was 91.3 +/- 25.9% (means +/- SD) in the HA group and 85.1 +/- 18.8% in the HY group. The changes in erythrocyte membranes were 33.0 +/- 7.9% in the HA group and 22.8 +/- 4.9% in the HY group. Thus the effect on erythrocyte fatty acids was smaller but also less variable and the precision of the two measures was similar. Therefore the L:O of either blood component can be used as a marker of a subject's adherence to experimental diets differing in type of fat.

Cholesterol Esters↗
PubMed2002

The n-3 and n-6 polyunsaturated fatty acid composition of plasma phospholipids in pregnant women and their infants. relationship with maternal linoleic acid intake.

The availability of long-chain polyunsaturated fatty acids during infancy has been related to neonatal growth and development. Fatty acid concentration at birth is an important predictor of postnatal level. The primary aim of this study was to provide a description of the distribution of n-3 and n-6 polyunsaturated fatty acids in the plasma phospholipid fraction of pregnant women remaining on a Western-style diet and their neonates. The plasma phospholipid polyunsaturated fatty acid composition was determined by gas-liquid chromatography in 889 mother-infant pairs. Blood samples were taken during the first, second and third trimester of pregnancy, at delivery, and from the umbilical vein at birth. Mean (+/- SD) fatty acid concentrations are reported in mg/l and as percentage of total fatty acids (% wt/wt). In addition, the 10th, 25th, 50th, 75th and 90th percentiles are given. The distribution of docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) concentrations in umbilical plasma phospholipids is also reported as a function of gestational age and maternal linoleic acid intake during pregnancy. This data can be be used as a reference for future studies and may aid in identifying term infants with a relatively low long-chain polyene status at birth.

Adult↗
PubMed1993

Effects of dietary proteins on linoleic acid desaturation and membrane fluidity in rat liver microsomes.

The effect of dietary protein, casein (CAS) and soybean protein (SOY), on linoleic acid desaturation in liver microsomes was studied in rats. The activity of delta 6 desaturase in total and rough endoplasmic reticula (ER and RER) was significantly higher in the CAS group than in the SOY group. In ER and smooth endoplasmic reticulum, the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene, when incorporated into the membrane, was decreased in the SOY group and accompanied by a reduction in the cholesterol/phospholipid (CHOL/PL) ratio, consistent with an increase in membrane fluidity. In a separate study, the effect of varying dietary proteins, CAS, milk whey protein, egg albumin, SOY, potato protein and wheat gluten, on the relationship between the delta 6 desaturase activity and microsomal membrane fluidity was also examined. The results indicated that the dietary protein-dependent change in the liver microsomal CHOL/PL ratio affected membrane fluidity, and subsequently the activity of delta 6 desaturase in liver microsomes. However, since dietary protein influenced the delta 6 desaturase activity in RER without influencing membrane fluidity, it is possible that some regulation might have taken place at the level of enzyme synthesis.

Animals↗
PubMed2006

Effect of conjugated linoleic acid type, treatment period, and dosage on differentiation of 3T3 cells.

This study was conducted to determine effect of CLA and linoleic acid (LA) on cell differentiation, cellular glycerol-3-phosphate dehydrogenase (GPDH) activity, and FA accumulation in differentiating 3T3-L1 cells (3 isomers x 3 treatment periods x 4 doses). The cells were cultured in 24-well plates for proliferation until confluence. Then they were treated with media containing 0, 10, 35, or 70 mg/L (0, 35, 125, or 250 mmol/L, respectively) of LA, cis9,trans11- or trans10,cis12-CLA during early (day 0-2), intermediate and late (day 3-8), or overall (day 0-8) differentiation periods. Dexamethasone, methyl-isobutylxanthine, and insulin were supplemented to the media only for the early period to induce the differentiation. On day 8 of postconfluence the cells were harvested for Oil Red O staining, analysis of GPDH activity, and determination of the FA Concentration. Cellular LA or CLA was found to accumulate in a dose-response manner, mainly during the intermediate/late period. Treatment with trans10,cis12-CLA lowered (P < 0.05) GPDH activity and the concentration of FA including palmitic acid (16:0) and palmitoleic acid (16:1), especially during the intermediate/late and overall periods, or whenever a high dose of 70 mg/L was applied. This also resulted in a higher (P < 0.05) ratio of saturated FA to monounsaturated FA. Treatment with LA or cis9,trans11-CLA lowered cellular FA only when they applied during the early period at a dose of 70 mg/L. The results demonstrated that the inhibitory effects of CLA on differentiation, GPDH activity, and FA accumulation of 3T3-L1 cells are dependent on the isomer type, treatment period, and dose.

3T3 Cells↗
PubMed1995

Age-related depletion of linoleic acid desaturation in liver microsomes from young spontaneously hypertensive rats.

The present study was designed to investigate the microsomal interconversion of linoleic acid (LA) into arachidonic acid (AA) in young spontaneously hypertensive rats (SHR), in relation to the pathogenesis of hypertension. Our results show lower delta 6 and delta 5 desaturase activities (the limiting steps in the bioconversion of LA into AA) in young SHR, as compared to Wistar Kyoto normotensive rats. This impairment of desaturase activities is raised when the blood pressure increases and is related to the age of animals. The fatty acid composition of liver lipids shows a lower proportion of AA and a higher proportion of LA in SHR than in normotensive rats, confirming the depletion of the enzymatic system studied. Such a loss of desaturase activity may be under the control of hormones involved in the regulation of SHR blood pressure.

Aging↗
PubMed2006

Upregulation of liver VLDL receptor and FAT/CD36 expression in LDLR-/- apoB100/100 mice fed trans-10,cis-12 conjugated linoleic acid.

This study explores the mechanisms responsible for the fatty liver setup in mice fed trans-10,cis-12 conjugated linoleic acid (t10c12 CLA), hypothesizing that an induction of low density lipoprotein receptor (LDLR) expression is associated with lipid accumulation. To this end, the effects of t10c12 CLA treatment on lipid parameters, serum lipoproteins, and expression of liver lipid receptors were measured in LDLR(-/-) apoB(100/100) mice as a model of human familial hypercholesterolemia itself depleted of LDLR. Mice were fed t10c12 CLA over 2 or 4 weeks. We first observed that the treatment induced liver steatosis, even in the absence of LDLR. Mice treated for 2 weeks exhibited hypertriglyceridemia with high levels of VLDL and HDL, whereas a 4 week treatment inversely induced a reduction of serum triglycerides (TGs), essentially through a decrease in VLDL levels. In the absence of LDLR, the mRNA levels of other proteins, such as VLDL receptor, lipoprotein lipase, and fatty acid translocase, usually not expressed in the liver, were upregulated, suggesting their involvement in the steatosis setup and lipoprotein clearance. The data also suggest that the TG-lowering effect induced by t10c12 CLA treatment was attributable to both the reduction of circulating free fatty acids in response to the severe lipoatrophy and the high capacity of liver to clear off plasma lipids.

Animals↗
PubMed1982

Effect of linoleic acid on digitalis cardiotoxicity.

Adult male guinea pigs were anesthetized, catheterized and i.v. infused with either saline and then ouabain or with linoleic acid salt and then ouabain. The linoleic acid pretreatment produced a significant delay until the onset of digitalis induced cardiac arrhythmias.

Animals↗
PubMedDate not supplied

[Effect of diets of various levels of linoleic acid on prostanoid biosynthesis and arterial blood pressure in rats].

The authors studied the influence of diets with 0 cal % (diet 1), 9 cal % (diet 2, control) and 16 cal %, according to linoleic acid, on the arterial blood pressure (ABP) and exogenous biosynthesis of prostacyclin (PGI2), PGF2 and PGE2 from 14C-arachidonic acid in isolated aortal rings and thromboxane (TxA2), PGF2 alpha, PGE2 in the suspension of washed platelets. It was established that diet 1 used during 4.5 months led to a rise in the ABP and decreased biosynthesis of all the prostanoids studied, as compared to the control. Linoleic acid excess (diet 3) induced a more pronounced elevation of the ABP and reduction of PGI2 synthesis in the aorta and TxA2 in the washed platelets, as compared to the control.

Animals↗
PubMed1985

High-performance liquid chromatography of linoleic acid hydroperoxides and their corresponding alcohol derivatives.

The four major hydroperoxides derived from autoxidation or lipoxygenase action on linoleic acid or on methyl linoleate and their corresponding alcohol derivatives are resolved by high-performance liquid chromatography on Zorbax SIL 3 micron particulate columns irrigated with hexane-diethyl ether-acetic acid mixtures. The four major linoleic acid hydroperoxides are interconverted at different rates in benzene or carbon tetrachloride solutions but are stable to storage under nitrogen at -70 degrees C for several months.

Alcohols↗
PubMed1992

Differential effects of dietary linoleic acid on mouse skin-tumor promotion and mammary carcinogenesis.

On the basis of reports of rat mammary- and pancreas-tumor models, we hypothesized that an increase in consumption of linoleic acid (LA) would also cause an enhancement in mouse skin-tumor promotion. SEN-CAR mice were placed on diets containing 0.8%, 2.2%, 3.5%, 4.5%, 5.6%, 7.0%, or 8.4% LA, 1 week after initiation with 7,12-dimethylbenz(a)anthracene and 3 weeks before starting promotion with 12-O-tetradecanoylphorbol-13-acetate. An inverse correlation (r = -0.92) was observed between papilloma number and level of LA; however, there was little difference in tumor incidence. A relationship between diet and carcinoma incidence was also found. The fatty acid composition of epidermal phospholipids reflected the dietary LA levels. 12-O-Tetradecanoylphorbol-13-acetate-induced epidermal prostaglandin E2 levels generally decreased with increasing dietary LA. To determine whether this inverse correlation between dietary LA and tumor yield was due to species differences or organ-model differences, a mammary carcinogenesis experiment was performed. SENCAR mice were fed the 0.8%, 4.5%, and 8.4% LA diets. All mice received 6 mg 7,12-dimethylbenz(a)anthracene, administered intragastrically at 1 mg/week. Tumor appearance was delayed in the 0.8% LA diet group, and a positive dose-response relationship between dietary LA and mammary-tumor incidence was observed. These studies suggest that the effect of dietary LA on tumor development is target tissue specific rather than species specific.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Linoleic acid enrichment of serum phosphatidylcholine in humans by low doses of sodium linoleate.

Fifteen volunteers were treated daily during a week with 250 mg of sodium linoleate supply as suppository. A day before and a day after treatment venous blood samples were drawn, high density lipoproteins (HDL) fractionated and 3-sn phosphatidylcholine isolated by thin-layer chromatography from total serum and HDL and their fatty acid composition analyzed by gas-liquid chromatography. The positional esterification of linoleic acid in the phosphatidylcholine molecule was determined by enzymatic hydrolysis. Increases of linoleic acid of 1.8--136.3% in the serum phosphatidylcholine were observed in 14 out of 15 volunteers and an increment of 6.3--32.2% was also detected in the lipid fraction from HDL. In both fractions about 98% of the linoleic acid is located in the C2 position of the phosphatidylcholine molecule. The results reported in the present paper show that it is possible to promote the enrichment of linoleic acid in the phosphatidylcholine fractions of both serum and HDL from humans subjected to low doses of sodium linoleate supply as suppository.

Adolescent↗
PubMed2005

Distribution of conjugated linoleic acid in total and subcellular fractions from normal and cancerous parts of human testes.

The objective of the present study was to examine differences in the fatty acid composition of subcellular fractions from normal and cancerous parts of human testes. The conjugated linoleic acid (CLA) content was significantly higher in total testicular carcinoma (TC), but significantly lower in the mitochondrial fraction of TC in comparison to normal testicular tissue. The subcellular distribution pattern of CLA was similar to that of monounsaturated fatty acids, but different to that of 18:2n-6 (linoleic acid), underlining the different physiological properties of CLA and 18 : 2n-6. Because polyunsaturated fatty acids (PUFAs) have been suggested to have an effect on cancer risk and previous research has found that CLA inhibits the metabolism of 18 : 2n-6 into 20 : 4n-6, the contents of n-6 and n-3 PUFAs were determined. Significant differences were observed for 18 : 2n-6, 18 : 3n-3, 20 : 5n-3, and 22 : 6n-3, with 18 : 2n-6, 18 : 3n-3, and 20 : 5n-3 contents being higher and 22 : 6n-3 content being lower in TC than in normal testicular tissue. These results indicate a changed availability of substrates for the cyclooxygenase (COX) or lipooxygenase (LOX) pathways generating eicosanoids. Although not statistically significant, the reduced content of 20 : 4n-6 shown in this study might be due to an increased metabolism of this fatty acid into eicosanoids.

Cell Fractionation↗
PubMed1991

Concentrations of linoleic acid in adipose tissue differ with age in women but not men.

Samples of adipose tissue, taken post-mortem from the anterior abdominal wall near the umbilicus, were obtained from road-accident victims in the Aberdeen area; subjects were of either sex with a wide age distribution (7-88 years). Similar samples were obtained from elderly females (mean age 77) who had died in Aberdeen Royal Infirmary from a variety of causes. Fatty acid compositions of samples were determined by capillary gas chromatography of methyl esters, which were obtained by direct esterification of the adipose tissue. The mean linoleic acid content for all samples was low compared with published values for similar samples from Europe and North America. Cumulative frequency distribution curves for linoleic acid did not differ with age in males but significant differences (P less than 0.001) occurred in females, with decreased concentrations in those aged over 60 compared to younger groups. Concentrations of trans-unsaturated fatty acids ranged between 2 and 7 per cent but did not differ significantly between groups. Low adipose concentrations of linoleic acid are regarded as a reflection of its reduced long-term dietary intake and as a risk factor for the development of coronary heart disease.

Abdominal Muscles↗
PubMedDate not supplied

Analysis of milk-based infant formula. Phase IV. Iodide, linoleic acid, and vitamins D and K: U.S. Food and Drug Administration-Infant Formula Council: collaborative study.

In 1982, the U.S. Food and Drug Administration, the Infant Formula Council and its member companies, contract laboratories, and other government laboratories began a study of analytical methods for the nutrients listed in the Infant Formula Act of 1980. Phases I, II, III, and V have been completed. The present report provides data on Phase IV, in which 13 laboratories collaboratively studied an ion-selective electrode method for analyzing iodide, a gas chromatographic method for linoleic acid, and 2 liquid chromatographic (LC) methods each for vitamins D and K. Data were insufficient to evaluate one each of the LC methods studied for vitamins K and D. The relative standard deviations (RSD) are sufficient for the nutrient levels found in infant formula. RSDs (%) for repeatability (RSDr) and reproducibility (RSDR), respectively, were as follows: iodide, 4.0-11.4 and 13.5-18.2; linoleic acid, 1.0-1.6 and 3.5-5.1; vitamin K1, 3.2-16.0 and 6.2-19.4; and vitamin D3, 4.2 and 35.0. The recommendation to adopt the method for vitamin D was supported by the results of a ministudy. All laboratories were capable of using these methods with little training. The methods for determination of iodide, linoleic acid, and vitamins D and K in ready-to-feed milk-based infant formula have been adopted first action by AOAC International.

Chromatography, Gas↗
PubMed1992

Isolation and characterization of the initial radical adduct formed from linoleic acid and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone in the presence of soybean lipoxygenase.

The spin trapping agent alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) was used to trap the initial radical formed from [U-14C]linoleic acid in the reaction with soybean lipoxygenase. By using low levels of enzyme and relatively short incubation times it was possible to avoid the formation of secondary oxidation products and polymers. The adduct was extracted after methyl esterification, and isolated by a combination of open column chromatography on silicic acid and high pressure liquid chromatography on Spherisorb S5 CN with non-aqueous solvents. The 1:1 POBN-linoleate adduct was characterized by UV, IR and ESR spectra of the appropriate HPLC column fraction, by the ratio of the UV absorption to 14C content, and by mass spectrometry of the reduced (hydroxylamine) form. The results indicated that POBN trapped a linoleic acid carbon-centered radical such that POBN was attached to the fatty acid chain at C-13 or C-9 (two isomers), the linoleate double bonds having become conjugated in the process. The exact locations of the bridges in the two isomers were only tentatively determined. There was no evidence for the presence of oxygen-bridged adducts. The trapped linoleoyl radical adduct provides evidence for the production of a free radical as part of the enzymatic mechanism of soybean lipoxygenase.

Drug Stability↗