Incorporation of conjugated linoleic acid and vaccenic acid into lipids from rat tissues and plasma

The objective of this study was to determine the incorporation of conjugated linoleic acid (CLA) into triacylglycerols (TAG) and phospholipids (PL) of tissues and plasma, and to interpret the role of dietary‐derived vaccenic acid (VA) in increasing the tissue content of CLA (c9,t11) and the influence on the fatty acid profile. We fed five groups of rats semi‐purified diets with varying levels of CLA and VA: control butter with low CLA (c9,t11) and VA; control butter added 5% CLA (c9,t11); control butter added 5% Tonalin [equal amount of CLA (c9,t11) and CLA (t10,c12)]; control butter added 5% VA; butter with high CLA (c9,t11) and VA (H‐CLA), for 3 weeks. The highest incorporation of CLA (c9,t11) was found in adipose tissue, and the lowest was observed in liver. Low intake of CLA (c9,t11) combined with high intake of VA resulted in a higher incorporation of CLA (c9,t11) in tissues due to the conversion of VA to CLA (c9,t11), compared to feeding CLA (c9,t11) without VA. However, in enterocytes, the proportion of CLA (c9,t11) was low after feeding VA, indicating no or only a minor conversion of VA to CLA (c9,t11) in the intestine. The incorporation of CLA (t10,c12) into TAG from plasma and tissues was generally much lower than that of the CLA (c9,t11) isomer, except in the enterocyte TAG, which had similar proportions of the two isomers.     

Alterations in CPT‐1 mRNA and fatty acid profile in hepatic cell lines in response to treatment with t10,c12‐ or c9,t11‐conjugated linoleic acid

Trans10,cis12‐conjugated linoleic acid (t10,c12‐CLA) increases liver weights and hepatic lipids in mice. The purpose of this study was to determine the effects of CLA isomers (t10,c12‐CLA or c9,t11‐CLA) and carnitine palmitoyl transferase‐1 (CPT‐1) inhibitors (etomoxir or hemipalmitoylcarnitinium) on CPT‐1 mRNA, fatty acid profile, and cholesterol synthesis in AML‐12 and HepG2 cells. t10,c12‐CLA was incorporated to a greater extent in both cell lines than c9,t11‐CLA. In addition, t10,c12‐CLA increased the free cholesterol content of AML‐12 and HepG2 cells four‐ and fivefold, respectively. Cells incubated with medium containing CPT‐1 inhibitors or t10,c12‐CLA had higher levels of mRNA for CPT‐1 in both cell lines, indicating an increased fatty acid oxidation in hepatic cell lines due to t10,c12‐CLA. Following treatment withdrawal, percentages of c9,t11‐CLA or t10,c12‐CLA remained elevated in cells initially treated with c9,t11‐CLA or t10,c12‐CLA, suggesting a potential for carryover effects of the CLA isomers. The results presented here demonstrate a potential role for t10,c12‐CLA in the modulation of hepatic fatty acid oxidation and cholesterol synthesis.     

Relative absorption of conjugated linoleic acid as triacylglycerol,free fatty acid and ethyl ester in a functional food matrix

Conjugated linoleic acid (CLA) shows potential benefits in a number of medical conditions, making it a possible target for incorporation into a functional food. Until recently, clinical trials were conducted with various mixtures of CLA isomers, encapsulated as the free acid. The purpose of this study was to examine a mixture of two specific CLA isomers (9c,11t and 10t,12c), incorporated into a functional food either as triacylglycerol, free fatty acid or fatty acid ethyl ester. Differences in absorption between the lipid forms and between the isomers were investigated. The palatability of the different functional‐food formulations was also studied. Significantly less CLA was absorbed into chylomicrons over six hours when fed as fatty acid ethyl ester than when either the triacylglycerol or free fatty acid forms were fed. Further work is recommended, to examine fatty acid ethyl ester absorption over longer periods of time. Most subjects reported that the fatty acid formulation had poor taste characteristics. We conclude that CLA as triacylglycerol is the most suitable form for incorporation into a functional food and that the 9c,11t and 10t,12c CLA isomers are absorbed similarly into chylomicrons.     

Effects of cis-9, trans-11 and trans-10, cis-12 CLA isomers on liver and adipose tissue fatty acid profile in hamsters

The aim of the present study was to investigate the effect of cis-9, trans-11 and trans-10, cis-12 CLA on FA composition of TAG in epididymal adipose tissue and liver, and of hepatic phospholipids PL. Twenty-four Syrian Golden hamsters were randomly divided into three groups of eight animals each and fed semipurified atherogenic diets supplemented with either 0.5 g/100g diet of linoleic acid or cis-9, trans-11 or trans-12, cis-9 CLA for 6 wk. Total lipids were extracted, and TAG and PL were separated by TLC. FA profile in lipid species from liver and adipose tissue, as well as in feces, was determined by GC. Trans-10, cis-12 CLA feeding significantly reduced linoleic and linolenic acids in TAG from both tissues, leading to reduced total PUFA content. Moreover, in the epididymal adipose tissue docosenoic and arachidonic acids were significantly increased. In liver PL, although no changes in individual FA were observed, total saturated FA (SFA) were decreased. No changes in TAG and PL FA profiles were induced by the cis-9, trans-11 CLA. TAG and PL incorporated cis-9, trans-11 more readily than trans-11, cis-12 CLA. This difference was not due to differential intestinal absorption, as shown by the analysis of feces. We concluded that only trans-10, cis-12 CLA induces changes in FA composition. Whereas increased PUFA content was observed in either liver or adipose tissue TAG, decreased SFA were found in liver PL. Incorporation of cis-9, trans-11 CLA in TAG is greater than that of trans-10, cis-12 CLA, but this is not due to differences in intestinal absorption.     

Dietary CLA Combined with Palm Oil or Ovine Fat Differentially Influences Fatty Acid Deposition in Tissues of Obese Zucker Rats

The effect of dietary conjugated linoleic acid (CLA) supplementation in combination with fat from vegetable versus animal origin on the fatty acid deposition, including that of individual 18:1 and 18:2 (conjugated and non-conjugated) isomers, in the liver and muscle of obese rats was investigated. For this purpose, 32 male Zucker rats were randomly assigned to one of four diets containing palm oil or ovine fat, supplemented or not with 1% of 1:1 cis(c)9,trans(t)11 and t10,c12 CLA isomers mixture. Total fatty acid content decreased in the liver and muscle of CLA-fed rats. In the liver, CLA increased saturated fatty acids (SFA) in 11.9% and decreased monounsaturated fatty acids (MUFA) in 6.5%. n-3 Polyunsaturated fatty acids (PUFA) relative proportions were increased in 30.6% by CLA when supplemented to the ovine fat diet. In the muscle, CLA did not affect SFA but decreased MUFA and PUFA percentages. The estimation of Δ9-indices 16 and 18 suggested that CLA inhibited the stearoyl-CoA desaturase activity in the liver (a decrease of 13–38%), in particular when supplemented to the ovine fat diet. Concerning CLA supplementation, the t10,c12 isomer percentage was 60–80% higher in the muscle than in the liver. It is of relevance that rats fed ovine fat, containing bio-formed CLA, had more c9,t11 CLA isomer deposited in both tissues than rats fed palm oil plus synthetic CLA. These results highlight the importance to further clarify the biological effects of consuming foods naturally enriched in CLA, alternatively to CLA dietary supplementation.     

In vitro genotoxicity/antigenotoxicity testing of some conjugated linoleic acid isomers using comet assay

Recently CLA isomers have received considerable attention as potential anti‐cancer agents. The aim of the study was to assess the genotoxicity/antigenotoxicity in vitro of linoleic acid (LA, c,c‐C18:2, Δ‐9), CLA isomer mixtures and homogeneous CLA TAGs (TriCLA) using the comet assay, to evaluate the effects on the extent of DNA injury in human hepatoma (HepG2) cells. The study was carried out both on commercial CLA (CLAc) and on CLA synthesized from grapestone oil (CLAg). The CLA isomer mixtures had different isomer profiles, determined by silver‐ion HPLC (Ag⁺‐HPLC), in particular CLAc was characterized by four main isomers (t8,c10; c9,t11; t10,c12; c11,t13), while CLAg showed two main isomers (c9,t11; t10,c12). As regards antigenotoxicity testing, LA, TriCLAg, and above all TriCLAc were effective antigenotoxic compounds against ethylmethanesulfonate (EMS) induced genotoxicity, while LA and CLAg were almost equally effective against 4‐nitroquinoline N‐oxide (4NQO) induced DNA damage. Both TriCLAc and TriCLAg showed an increased antigenotoxic activity toward EMS and a lower antigenotoxic activity toward 4NQO, with respect to both CLAc and CLAg. The higher capability of CLAg with respect to CLAc in counteracting the genotoxicity of 4NQO could be due to the different CLA isomer composition. Practical applications: CLA isomers have shown many beneficial health effects both on animals and humans. They are widely used in nutritional supplements, as CLA improves body composition by reducing fat storage. In this regard it is very important to know, besides the chemical and analytical aspects, also genotoxic and antigenotoxic effects of different CLA mixtures. To our best knowledge, few results have been reported on CLA antigenotoxic properties by the comet assay, and no data could be retrieved in the literature for TriCLA antigenotoxicity testing. The obtained results are interesting in that they can increase the knowledge on particular fatty acids used in commercial supplements.     

Occurrence of conjugated linoleic acid isomers in beef

The amounts of Δ9,Δ11-conjugated linoleic acid (CLA) isomers were determined in loin-associated fat samples of bulls (n=6) and steers (n=7) by capillary gas chromatography of fatty acid methyl ester (FAME) derivatives. The main CLA-isomer—18:2 c9,t11—provided approximately 0.76 ± 0.15% and 0.86 ± 0.15% of total FAME in bulls and steers, respectively. No differences (P>0.05) were observed between the CLA isomer distribution of bulls (t9,c11, 0.026 ± 0.014%; c9,c11, 0.015 ± 0.008%; and t9,t11, 0.029 ± 0.003%) and steers (t9,c11, 0.027 ± 0.014%; c9,c11, 0.015 ± 0.005%; and t9,t11, 0.030 ± 0.007%).     

Determination of <Emphasis Type="Italic">c</Emphasis>9,<Emphasis Type="Italic">t</Emphasis>11-CLA in major human plasma lipid classes using a combination of methylating methodologies

Isomeric CLA exhibit several significant biological activities in animals and humans and are easily isomerized to their corresponding t,t-CLA isomers during methylation with various acid-catalyzed reagents. To minimize such isomerization and provide a valid quantification of human plasma CLA content, several methylation methods were tested. Plasma neutral lipid, nonesterified FA (NEFA), and polar lipid classes were separated into the following fractions: (i) cholesteryl ester (CE, 1.2 mg/12 mL, 37.5% lipids), (ii) TAG (0.8 mg/12 mL, 25% lipids), (iii) NFFA (0.2 mg/12 mL, 6.2% lipids), (iv) MAG/DAG/cholesterol (0.3 mg/12 mL, 9.4% lipids), and (v) phospholipid (PL, 0.5 mg/20 mL, 15.6% lipids). Data showed that c9,t11-CLA found in TAG, MAG/DAG/cholesterol, and PL fractions were converted to methyl esters with sodium methoxide within 2 h at 55°C. However, the c9,t11-CLA in the CE fraction could not be completely converted to methyl esters by sodium methoxide/acetylchloride in methanol or methanolic KOH; instead, CE was treated with sodium methoxide and methyl acetate in diethyl ether for 1 h. NEFA were converted to methyl esters with trimethylsilyldiazomethane (TMSDAM). All reaction mixtures were monitored by TLC prior to GLC analysis. The highest enrichment of c9,t11-18∶2 (% FA) was in TAG (0.31%), followed by CE (0.14%) and PL (0.13%). The above methylation methods were then applied to a small subset (n=10) of nonfasting plasma lipid fractions to confirm the applicability of these data. Results from this subset of samples also indicated that the greatest enrichment of c9,t11-CLA was present in the TAG fraction (0.39%), followed by CE (0.27%) and PL (0.22%). These data indicate that different plasma fractions have different c9,t11-CLA contents.     

Conjugated linoleic acid (CLA) production and lipase‐catalyzed interesterification of purified CLA with canola oil

In this study, two important isomers of CLA, i.e. c9,t11 and t10,c12, were produced up to ca. 73% of total fatty acids, employing alkali isomerization of safflower oil, followed by purification with only one‐step urea crystallization to 85.6%, while the recovery of the purification process was 35%. Interesterification (acidolysis) of purified CLA with canola oil was then conducted by Thermomyces lanuginosus lipase. The CLA content incorporated into the triacylglycerols (TG) was 26.6 mol‐% after 48 h of reaction time. Physical and chemical properties of the TG were then changed according to the degree of substitution of oleic acid in canola oil with CLA.     

Three Hen Strains Fed Photoisomerized <Emphasis Type="Italic">trans,trans</Emphasis> CLA-Rich Soy Oil Exhibit Different Yolk Accumulation Rates and Source-Specific Isomer Deposition

Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA‐rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10–12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA‐rich soybean oil produced by photoisomerization. Diets of 30‐week Leghorns, broilers, and jungle fowl were supplemented with 15 % CLA‐rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC‐FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55 % of total yolk CLA during CLA feeding. However, t‐10,c‐12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c‐9,t‐11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation.     

Two-Step Production of Oil Enriched in Conjugated Linoleic Acids and Diacylglycerol

A two-step process was used to produce diacylglycerol-enriched structured lipid that contained mainly c9,t11 and t10,c12 isomers of conjugated linoleic acids (CLA). First, a structured triacylglycerol (TAG) was synthesized by lipase-catalyzed acidolysis of corn oil with CLA. This structured triacylglycerol contained 30.4 mol% CLA with 45.5% of the CLA mostly located at sn-1,3 positions of the glycerol backbone. Then, lipase-catalyzed glycerolysis was conducted between structured triacylglycerol and glycerol to produce diacylglycerol-enriched structured lipid. The final product contained 6.8% monoacylglycerol, 31.5% diacylglycerol and 61.1% TAG after 48 h reaction. The selected chemical (fatty acid composition, the content of mono-, di-, and triacylglycerol in the reaction product) and physical properties (melting profile) were determined by hihg-performance liquid chromatography (HPLC), gas chromatography (GC), and differential scanning calorimetry (DSC).     

Fatty acid and conjugated linoleic acid isomer profiles in human milk fat

The fatty acid composition of 39 mature human milk samples from four Spanish women collected between 2 and 18 weeks during lactation was studied by gas chromatography. The conjugated linoleic acid (CLA) isomer profile was also determined by silver‐ion HPLC (Ag⁺‐HPLC) with three columns in series. The major fatty acid fraction in milk lipids throughout lactation was represented by the monounsaturated fatty acids, with oleic acid being the predominant compound (36–49% of total fatty acids). The saturated fatty acid fraction represented more than 35% of the total fatty acids, and polyunsaturated fatty acids ranged on average between 10 and 13%. Mean values of total CLA varied from 0.12 to 0.15% of total fatty acids. The complex mixture of CLA isomers was separated by Ag⁺‐HPLC. Rumenic acid (RA, cis‐9 trans‐11 C18:2) was the major isomer, representing more than 60% of total CLA. Trans‐9 trans‐11 and 7‐9 (cis‐trans + trans‐cis) C18:2 were the main CLA isomers after RA. Very small amounts of 8‐10 and 10‐12 C18:2 (cis‐trans + trans‐cis) isomers were detected, as were different proportions of cis‐11 trans‐13 and trans‐11 cis‐13 C18:2. Although most of the isomers were present in all samples, their concentrations varied considerably.     

Analysis of conjugated linoleic acid isomers and content in french cheeses

Conjugated linoleic acid (CLA) occurs in food as a result of microbial enzymatic reactions, free radical-type oxidation, and heat treatment. CLA is found in animal products, such as meat and dairy products, especially in cheeses. The CLA composition of 12 different French cheeses was determined by a combination of different analytical methods: reversed-phase high-performance liquid chromatography (RP-HPLC), gas chromatography-mass spectrometry (GC-MS), GC-Fourier transform infrared (GC-FTIR), and silver nitrate thin-layer chromatography (AgNO₃-TLC). New isomers (Δ8,10- and Δ11,13-octadecadienoic acids with all possible cis and trans configurations) that co-eluted with previously identified isomers (Δ9c,11t-; Δ9t,11c-; Δ10c,12t-; Δ10t,12c-; Δ11c,13c-; Δ9c,11c-; Δ10c,12c-; Δ9t,11t-; Δ10t12t-octadecadienoic acids) were detected. Δ9c,11t-Octadecadienoic acid was the major CLA isomer in these cheeses. All isomers were present in each product, whatever the production process. However, CLA content in the cheeses varied from 5.3 to 15.80 mg/g of cheese fat, which depended primarily on the origin of the milk (season, geography) and somewhat on the production process.     

Oxidation kinetics for <Emphasis Type="Italic">cis</Emphasis>-9,<Emphasis Type="Italic">trans</Emphasis>-11 and <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12 isomers of CLA

The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand, the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested that the autoxidation mechanisms for the CLA and PUFA were essentially the same.     

Effects of conjugated linolenic acid and conjugated linoleic acid on lipid metabolism in mice

The effects of two isomers of conjugated linolenic acid (CLnA), α‐eleostearic acid (α‐ESA) and punicic acid (PA), on body fat and lipid metabolism were investigated, compared with a conjugated linoleic acid (CLA) mixture (primarily cis9,trans11‐ and trans10,cis12‐18:2) and α‐linolenic acid (ALA), a non‐conjugated octadecatrienoic acid, in the present study. ICR mice were fed either a control diet or one of four experimental diets supplemented with 1% α‐ESA, 1% PA, 1% CLA mixture and 1% ALA in the form of triacylglycerols (TAG) for 6 weeks. The weights of perirenal and epididymal adipose tissues were significantly decreased while the liver weight was significantly increased in mice fed CLA, compared with the control. In contrast to CLA, the tissue weights in α—ESA‐, PA‐ and ALA‐fed mice were not affected. No significant differences were observed in TAG, total cholesterol, high‐density lipoprotein and low‐density lipoprotein cholesterol levels among the five groups. The liver TAG level was significantly decreased in mice fed α‐ESA and PA while it was significantly increased in mice fed the CLA mixture. These results indicate that CLnA and CLA have differential effects on body fat mass and liver TAG levels in mice.     

Synthesis of CLA‐enriched TAG by Candida antarctica lipase under vacuum

Conjugated linoleic acid (CLA)‐enriched triacylglycerol (TAG) of 90 wt% was successfully synthesized in 10 h by direct esterification of glycerol and CLA using an immobilized lipase from Candida antarctica under vacuum. The best operating conditions for the synthesis of TAG were investigated according to the three parameters of temperature, enzyme loading, and vacuum. The synthesis of TAG increased with increasing temperature but it did not significantly change above 60°C (p>0.05). The increase of enzyme loading lead to an enhanced conversion of TAG, but enzyme loading of more than 10% (based on the total weight of the substrates) was not effective. Moreover, when vacuum increased, the conversion of TAG increased, but the conversion rate decreased when the vacuum level was too high. The best combination of temperature, enzyme loading, and vacuum level were 60°C, 10% of the total weight of the substrates, and 0.4 kPa, respectively. During the initial 6 h of reaction, Candida antarctica lipase had more selectivity for 10t,12c‐CLA than 9c,11t‐CLA onto the glycerol backbone, and a preference for the incorporation at the sn‐1,3 positions of glycerol rather than at the sn‐2 position.     

Diet‐dependent occurrence of CLA isomers in rumen and duodenal digesta of slaughtered bulls

This study examined the effects of linolenic acid‐rich vs. linoleic acid‐rich feeding system on the occurrence of individual CLA isomers in the rumen and duodenum digesta of German Holstein and German Simmental bulls using Ag⁺‐HPLC/DAD. The diet affected the biosynthesis of individual CLA isomers in the rumen of the bulls of both breeds. The isomer t‐11,c‐13 CLA was detected as the most abundant isomer in the rumen of linolenic acid‐rich diet‐fed bulls, up to six times higher compared to linoleic acid‐rich diet‐fed bulls. However, the main isomer in muscle lipid, c‐9,t‐11 CLA, was produced to a low extent in the rumen of linolenic acid‐rich diet‐fed bulls compared to higher concentrations of this isomer in the rumen of linoleic acid‐rich diet‐fed bulls. The isomers t‐7,c‐9 CLA and t‐8,c‐10 CLA were not present in the rumen samples of bulls fed both diets; however, abundant t‐7,c‐9 CLA was identified in the duodenum. The CLA isomers t‐12,t‐14 CLA and t‐11,t‐13 CLA were identified as the main t,t CLA isomers in the rumen, and were significantly enhanced in the rumen of linolenic acid‐rich diet‐fed compared to linoleic acid‐rich diet‐fed bulls. In contrast to c‐9,t‐11 CLA, the t,t CLA isomers seem to be biosynthesized predominantly in the rumen, further transported via the duodenum and finally deposited in the tissue lipids mainly in linolenic acid‐rich diet‐fed bulls. This was shown earlier for muscle and subcutaneous fat samples from the same animal experiment.     

Preparation of conjugated linoleic acid from safflower oil

Synthetically prepared mixtures of conjugated linoleic acid (CLA) are widely used in animal and cell culture studies to investigate the potential effects of the Δ9c, 11t-18:2 isomer found in food products from ruminant animals. Alkali isomerization of linoleic acid is a common method used in the synthesis of a mixture of CLA isomers containing predominantly the Δ9c, 11t-18:2 and Δ10t, 12c-18:2 isomers. Some biological activity might also be mediated by the Δ10t, 12c-18:2 isomer. Currently few published methodologies exist describing procedures for the enrichment of these two isomers. A method is described herein to take advantage of an inexpensive oil, safflower oil, for use in synthesis of CLA and a procedure to enrich the Δ10t, 12c-18:2 isomer.     

High Saturated Fat Diet Alters the Lipid Composition of Triacylglycerol and Polar Lipids in the Femur of Dam and Offspring Rats

Previous work has shown that dietary lipids alter femur lipid composition. Specifically, we have shown that exposure to high saturated fatty acid (SFA) diets in utero, during suckling, or post‐weaning alters femur total lipid composition, resulting in higher percent bone mass in males and females and bone mineral density (BMD) in female offspring with no effect on bone mineral outcomes in dams. Comparatively, high n‐3 polyunsaturated fatty acid (PUFA) diets increase femur polar (PL) lipid n‐3 content, which has been associated with increased bone mineral content and strength. However, the extent that PL or triacylglycerol (TAG) lipids change with high SFA diets is unknown. The current investigation examined the influence of a high SFA diet (20 % lard by weight) on femur PL and TAG lipid composition in 5‐month old female Wistar rats (fed high SFA diet from age 28 days onwards; dams) and their 19‐day old offspring (exposed to high SFA in utero and during suckling; pups). High SFA exposure resulted in increased monounsaturates and decreased n‐3 and n‐6 PUFA in the TAG fraction in both dams and pups, and higher SFA and n‐6:n‐3 ratio in dams only. The PL fraction showed decreased n‐6 PUFA in both dams and pups. The magnitude of the diet‐mediated responses, specifically TAG 18:1 and PL n‐6 PUFA, may have contributed to the previously reported altered BMD, which was supported with correlation analysis. Future research should investigate the relationship of diet‐induced changes in bone lipids on bone structure, as quantified through micro‐computed tomography.     

Conjugated Linoleic Acid Reduces Hepatic Steatosis and Restores Liver Triacylglycerol Secretion and the Fatty Acid Profile During Protein Repletion in Rats

Protein depletion is associated with hepatic steatosis and decreased circulating triacylglycerol (TAG). Since conjugated linoleic acid (CLA) increases lean body mass, protects against muscle catabolism, and modulates lipid metabolism, the aim of this work was to investigate the effects of CLA with two different amounts of dietary fat on the regulation of plasma and hepatic TAG concentration, and its possible connections with changes in fatty acid (FA) profile in plasma, liver and adipose tissue and hepatic oxidative status during protein repletion. Rats were fed a low protein diet (14 days) and then a protein repletion diet (30 days), supplemented or not with CLA, containing 7% (w/w) or 20% (w/w) of fat. Hepatic TAG secretion and removal by muscle and adipose tissue lipoprotein lipase, FA profile and liver oxidative status were evaluated. Protein depletion affected hepatic TAG secretion and peripheral removal, decreasing plasma and increasing liver TAG concentration, whereas protein repletion with CLA improved these abnormalities independently of the amount of dietary fat by increasing hepatic TAG secretion. This prevention in the absence of CLA was not observed. CLA was incorporated in plasma and tissues (adipose > liver > plasma, and c9,t11-CLA > t10,c12-CLA), accompanied by alterations in FA composition, mainly in adipose tissue. The hepatic oxidative stress was overcome by protein repletion. CLA had a beneficial impact on TAG metabolism in protein repleted animals, preventing hepatic steatosis through higher hepatic TAG secretion.