Conjugated Linoleic Acid (CLA) Mitigates High-Fat Diet (HFD)-Induced Mammary Gland Development Impairment of Pubertal Mice via Regulating CD36 Palmitoylation and Downstream JNK-ERK Pathway.

BackgroundCD36, a vital fatty acid translocase, has been reported to participate in multiple physiological functions through palmitoylation mediated by zinc finger Asp–His–His–Cys-type palmitoyltransferases (DHHCs). This study aimed to investigate the possible involvement of DHHC-mediated CD36 palmitoylation in high-fat diet (HFD)-induced impairment of pubertal mammary gland development and explore the underlying mechanisms involved.MethodsPalmitic acid (PA)-treated HC11 cells were used as the in vitro high-fat model, and the cell proliferation was examined by 5-Ethynyl-2′-deoxyuridine (EdU) incorporation assay. The palmitoylation of CD36 was determined by the acyl–biotin exchange (ABE) method. The expression of CD36, proliferative genes, and signaling molecules was detected by immunoblotting. The cellular localization of CD36 was determined by immunofluorescence. The bindings of CD36 with zinc finger DHHC-type palmitoyltransferases 9 (DHHC9) or Fyn/Lyn were detected by co-immunoprecipitation (Co-IP). The palmitoylation inhibitor 2-bromopalmitate (2BP), DHHC9 knockdown, and point mutation of CD36 cysteine residues were applied to construct a CD36 palmitoylation deficiency model in vitro to investigate the effects of CD36 palmitoylation on HC11 proliferation. In vivo, the pubertal mice were treated with HFD and/or 2BP. Mammary gland morphology was determined by whole mount staining, and the underlying mechanisms were verified by the methods used in the in vitro system.ResultsIn vitro, the palmitoylation inhibitor 2BP eliminated PA-inhibited HC11 proliferation and inhibited CD36 palmitoylation and localization on the plasma membrane. Meanwhile, the binding of DHHC9 and CD36 in PA-treated HC11 cells was repressed by 2BP. In addition, both knockdown of DHHC9 and point mutation of CD36 cysteine residues suppressed the membrane palmitoylation and localization of CD36 and stimulated the proliferation of PA-treated HC11 cells. Furthermore, in PA-treated HC11 cells, the inhibition of CD36 palmitoylation, the knockdown of DHHC9, and the mutation of CD36 cysteine residues resulted in decreased formation of the CD36/Fyn/Lyn complex. Correspondingly, the downstream c-jun n-terminal kinase 1 (JNK1) pathway was inhibited, and the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway was activated. Moreover, inhibition of the JNK pathway with SP600125 promoted the proliferation of PA-treated HC11 cells via activation of the ERK1/2 pathway. In vivo, the palmitoylation inhibitor 2BP ameliorated HFD-induced impairment of mammary gland development in pubertal female mice, which was associated with a decrease in DHHC9-mediated CD36 palmitoylation in the plasma membrane, a reduction in the CD36/Fyn/Lyn complex, inhibition of the JNK1 pathway, and activation of the ERK1/2 pathway.ConclusionsThis study revealed that inhibition of DHHC9-mediated CD36 palmitoylation mitigated HFD-induced impairment of pubertal mammary gland development via the JNK1-ERK1/2 pathway.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1186/s11658-025-00799-3.

The anti-obesity effect of conjugated linoleic acid (CLA) has been well elucidated, but whether CLA affects fat deposition by regulating intestinal dietary fat absorption remains largely unknown. Thus, this study aimed to investigate the effects of CLA on intestinal fatty acid uptake and chylomicron formation and explore the possible underlying mechanisms. We found that CLA supplementation reduced the intestinal fat absorption in HFD (high fat diet)-fed mice accompanied by the decreased serum TG level, increased fecal lipids and decreased intestinal expression of ApoB48 and MTTP. Correspondingly, c9, t11-CLA, but not t10, c12-CLA induced the reduction of fatty acid uptake and TG content in PA (palmitic acid)-treated MODE-K cells. In the mechanism of fatty acid uptake, c9, t11-CLA inhibited the binding of CD36 with palmitoyltransferase DHHC7, thus leading to the decreases of CD36 palmitoylation level and localization on the cell membrane of the PA-treated MODE-K cells. In the mechanism of chylomicron formation, c9, t11-CLA inhibited the formation of the CD36/FYN/LYN complex and the activation of the ERK pathway in the PA-treated MODE-K cells. In in vivo verification, CLA supplementation reduced the DHHC7-mediated total and cell membrane CD36 palmitoylation and suppressed the formation of the CD36/FYN/LYN complex and the activation of the ERK pathway in the jejunum of HFD-fed mice. Altogether, these data showed that CLA reduced intestinal fatty acid uptake and chylomicron formation in HFD-fed mice associated with the inhibition of DHHC7-mediated CD36 palmitoylation and the downstream ERK pathway.

The mammary gland is one of the few organs that continues to develop postnatally through stages including puberty, pregnancy, lactation, and involution. The gland is composed of epithelial and stromal cells that include fibroblasts, adipocytes, endothelial cells, nerve cells, and macrophages. Terminal end bud (TEB) structures are found exclusively in the pubertal developmental stage. The formation of TEBs and side branching drives mammary gland epithelial cell invasion into the mammary fat pad, continuing until the entire fat pad is filled. Pubertal mammary gland morphogenesis integrates a balance of epithelial cell proliferation, differentiation, and apoptosis. Several studies have shown that the interaction between mammary epithelial and stromal cells is crucial for the proper postnatal development of the mammary ductal tree. Interestingly, studies have shown that processes important in mammary gland development are often deregulated during breast cancer tumorigenesis. Thus, understanding the complex signaling network as well as the interactions between the different cell types during mammary gland development will be vital for elucidating the mechanisms underlying breast cancer progression and metastasis. Glycation is the non-enzymatic glycosylation of sugar moieties to biological macromolecules such as protein and DNA which produces reactive metabolites known as advanced glycation end products (AGE's). AGE content in the Western Diet has consistently increased over the last 50 years due to increased consumption of sugar laden and cheap processed/manufactured foods which are high in reactive AGE metabolites. AGE containing food can lead to the accumulation of AGEs in the body overtime leading to pro-inflammatory and pro-oxidant effects when signaling through receptor for advanced glycation end products (RAGE). Leading too many complications associated with diseases including diabetes, Alzheimer's, heart disease and cancer. Preliminary data in our lab has shown that AGEs also have an effect on phosphorylation and signaling of estrogen receptor α (ERα), a key receptor and signaling pathway in the regulation of mammary gland development during puberty. This observation, together with the links between diet, mammary gland development and immune cell recruitment lead us to examine the biological effects of a diet high in AGEs on pubertal mammary gland development in mice. We observed a significant disruption of normal pubertal mammary gland development in mice fed a high AGE diet when compared to mice fed a control diet. Mice fed the high AGE diet showed increases in TEB number as well as width, length and area. We also observed an increase in ductal branching and a decrease in ductal extension. Future studies will assess the role of macrophage recruitment to the developing gland, specifically around the TEBs based on its reported role in normal TEB function. We also plan to assess ERa signaling in mice fed the high AGE diet based on the reported role of estrogen signaling in ductal elongation. Citation Format: Krisanits BA, Nogueira LM, Findlay VJ, Turner DP. Diet, development and predisposition to breast cancer: The impact of sugar derived metabolites (AGEs) on pubertal mammary gland development [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-05-01.

IntroductionPuberty is a period of increased susceptibility to factors that cause increased breast cancer risk in adulthood. Mammary end buds (EBs) that develop during puberty are believed to be the targets of breast cancer initiation. Whereas the role of estrogen (E) has been extensively studied in pubertal mammary gland development, the role of progesterone (P) during puberty is less defined.MethodsPubertal and prepubertal ovariectomized mice were treated with vehicle control (C), E, P, or E+P. Mammary glands from these mice were analyzed for changes in morphology, proliferation, and expression of the downstream targets amphiregulin (AREG) and receptor activator of NF-κB ligand (RANKL).ResultsP, acting specifically through the progesterone receptor, induced increases in mammary gland proliferation and EB formation that were associated with increased AREG expression in ducts and EBs. E, acting specifically through the estrogen receptor, produced similar responses also mediated by AREG. Blocking AREG action by treatment with an EGFR inhibitor completely abrogated the effect of P on EB formation and proliferation and significantly reduced proliferation within ducts. P also increased expression of RANKL, primarily in ducts. Treatment with RANK-Fc, an inhibitor of RANKL, reduced P-dependent proliferation in ducts and to a lesser extent in EB, but did not cause EB regression.ConclusionsThese results demonstrate a novel P-specific effect through AREG to cause EB formation and proliferation in the developing mammary gland both before and during puberty. Thus, hormones and/or factors in addition to E that upregulate AREG can promote mammary gland development and have the potential to affect breast cancer risk associated with pubertal mammary gland development.

Biological clocks, existing in all human organ systems, cycle every 24 hours in a diurnal pattern and control the daily rhythms of human life (e.g., eating vs. fasting, sleep vs. wakefulness), which is essential for health and wellbeing. Disruption of the biological clocks, either by genetic or environmental alteration, disturbs circadian rhythms, which may lead to chronic diseases. Childhood obesity is a risk factor for breast cancer in adult women. Lifestyle changes in the modern world (e.g., energy-dense diets) serve as environmental factors that contribute to alterations in biological clocks and obesity. The present study examined transcriptional rhythmic changes in mammary glands from pubertal MMTV-PyMT mice fed a high-fat diet (HFD). Three-week-old female mice (FVB background) were randomly assigned into three groups - wild-type (WT) mice fed the AIN93G diet and MMTV-PyMT mice fed the AIN93G diet or an HFD for three weeks. At the end of the study, mammary glands were collected every 4 hours over a period of 24 hours (Zeitgeber time 0-24 hours) for RNA-sequencing analysis. The mammary weight was 0.45±0.02, 0.59±0.02, and 0.67±0.02 g for WT mice fed the AIN93G diet and MMTV-PyMT mice fed the AIN93G and HFD, respectively (means ± SEM, all p<0.05 when three groups were compared each other). The rhythmicity analysis using R showed that greater than 1,000 transcripts were classified as “loss of rhythm” when MMTV-PyMT mice (both AIN93G-fed and HFD-fed groups) were compared to WT mice fed the AIN93G diet. Eighteen transcripts were classified as “loss of rhythm” in MMTV-PyMT mice when the HFD was compared to AIN93G diet. Hierarchical clustering analysis showed differentially expressed genes that were significantly altered and KEGG enrichment analysis showed the most upregulated and downregulated metabolic pathways in treatment groups than in the control group at each time point over the 24-hour period. These findings indicates that genetic alterations may have a greater effect than dietary effects on transcriptional rhythmicity in mammary glands from pubertal mice. Citation Format: Lin Yan, Daniel G. Palmer, Huawei Zeng. Alteration to transcriptional rhythmicity in mammary glands from pubertal MMTV-PyMT mice fed a high-fat diet [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 760.

Amino acids have been shown to affect the development of mammary gland (MG). However, it is unclear whether L-arginine promotes the development of pubertal MG. Therefore, our study aims to explore the effect of L-arginine on the development of MG in pubertal mice. To investigate its internal mechanism of action, we will use mouse mammary epithelial cells (mMECs) line. Whole-mount staining showed that L-arginine can promote the extension of MG duct. In vitro, 0.4 mM L-arginine could activate the G protein-coupled receptor family C, group 6, subtype A (GPRC6A)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway and increase the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4EBP1) to promote the synthesis of cell cycle regulatory protein D1 (Cyclin D1), leading to the dissociation of the retinoblastoma tumour suppressor protein (Rb)-E2F1 transcription factor (E2F1) complex in mMECs and releasing E2F1 to promote cell proliferation. Furthermore, GPRC6A was knocked down or inhibition of the PI3K/AKT/mTOR signalling pathway with corresponding inhibitors completely abolished the arginine-induced promotion of mMECs proliferation. In vivo, it was further confirmed that 0.1% L-arginine can activate the PI3K/AKT/mTOR signalling pathway in the MG of pubertal mice. These results were able to indicate that L-arginine stimulates the development of MG in pubertal mice through the GPRC6A/PI3K/AKT/mTOR signalling pathway.

Stearic acid suppresses mammary gland development by inhibiting PI3K/Akt signaling pathway through GPR120 in pubertal mice

Conjugated linoleic acid(CLA)를 비육돈에 급여하여 비육돈 체조직내에 CLA를 축적시키고, CLA가 축적된 돈육의 품질특성에 대한 연구를 수행하였다. CLA는 alkaline isomerization 방법으로 식용유를 이용하여 전체 CLA 이성체가 50%인 CLA를 화학적으로 합성하였다. 대조구는 80<TEX>${\sim}$</TEX>110 kg 까지는 일반사료회사에서 생산하는 사료를 급여하였으며, 처리구 1은 출하(출하체중:110 kg) 2주전부터 일반사료회사에서 생산하는 사료에 CLA를 1.25% 첨가하여 급여하였으며, 처리구 2는 출하 2주전부터 사료 함량에 CLA를 2.5% 첨가하여 급여하였다. 처리구 3은 사료 함량에 1.25% CLA를 첨가하여 4주간 급여하였으며, 처리구 4는 2.5% CLA를 4주간 급여하였다. 급여기간이 끝난 후 일괄적으로 함양도축장에서 도축하여 돈육의 등심부위를 함기포장하여 냉장온도(4<TEX>$^{\circ}C$</TEX>)에서 14일간 저장하면서 각 실험항목을 조사하였다. 저장기간에 따른 돈육등심의 CLA 함량, 콜레스테롤, 지방산 조성, 지방산화, 조직감 및 연도 등을 조사하여 CLA가 축적된 돈육의 저장기간에 따른 품질특성을 규명하고자 하였다. CLA 급여수준과 급여기간이 전단가에 미치는 영향을 조사한 결과 처리구간의 비교에서 저장 8일 까지는 처리구간에 유의적인 차이가 없었지만 저장 11일과 14일에는 대조구가 CLA 급여 처리구에 비하여 유의적으로 낮은 전단가를 보였다(P〈0.05). 모든 처리구들이 저장기간이 경과함에 따라 유의적으로 낮아지는 결과를 보였다(P〈0.05). 경도는 전 저장기간 동안 처리구간의 비교에서 대조구와 CLA 급여 처리구간에는 유의적인 차이가 없었으며, 저장기간의 경과에 따른 변화는 모든 처리구가 저장기간이 경과함에 따라 감소하는 경향을 보였다. 점착성은 대조구와 CLA 급여 처리구간에 뚜렷하게 차이나는 경향이 없고 저장기간이 경과함에 따라 뚜렷한 변화가 없었다. TBARS 변화는 전 저장기간동안 처리구간의 비교에서 CLA를 급여하지 않은 대조구에 비하여 CLA를 급여한 처리구가 유의적으로 낮은 TBARS를 보였다(P〈0.05). 저장기간에 따른 비교에서는 모든 처리구가 저장기간이 경과함에 따라 유의적으로 증가하였다(P〈0.05). 콜레스테롤 함량은 저장 2일에 대조구와 비교해서 CLA 급여 처리구가 유의적으로 낮은 콜레스테롤 함량을 나타내었으며(P〈0.05), T4 처리구가 가장 낮은 콜레스테롤 함량을 나타내었다(P〈0.05). 지방산 조성은 전 저장기간동안 CLA 급여수준과 급여기간이 증가할수록 myristic, palmitic 및 stearic acid 함량은 유의적으로 증가하며(P〈0.05), 반면에 oleic, linoleic 및 arachidonic acid 함량은 유의적으로 감소하였다(P〈0.05). CLA 함량을 보면 CLA를 급여하지 않은 대조구는 CLA가 검출되지 않았지만 CLA 급여 처리구에서는 CLA 급여수준과 급여기간이 증가할수록 육내 축적율이 직선적으로 증가하였다. 이상의 결과를 종합하여 보면 CLA를 육내에 축적시킬 수 있으며, CLA가 축적된 돈육은 저장 중 지방산화를 억제하는 항산화 능력이 있어 고품질 . 고기능성 돈육생산이 가능하다고 사료된다. To investigate the effects of conjugated linoleic acid added diet feeding on CLA accumulation and quality characteristics of pork meat. The CLA used to add in diet was chemically synthesized by alkaline isomerization method with corn oil. Pigs were divided into 5 treatment groups(4 pigs/group) and subjected to one of five treatment diets(0, 1.25% CLA for 2 weeks, 2.5% CLA for 2 weeks, 1.25% CLA for 4 weeks and 2.5% CLA for 4 weeks, CLA diets; total fed diets) before slaughter. Pork loin were collected from the animals(110 kg body weight) slaughtering at the commercial slaughter house. Pork loin meat were aerobic packaged and then stored during 2, 5, 8, 11 and 14 days at 4<TEX>$^{\circ}C$</TEX>. Samples were analyzed for shear force value, texture, TBARS, fatty acid composition, cholesterol and CLA content. CLA treatment groups showed significantly(p〈0.05) higher shear force value compared to those of control group at 11, 14 days of cold storage. All treatments were decreased significantly as the storage period passed. There was a not significantly difference in texture between control and CLA treatment groups. All CLA treatment groups showed significantly(p〈0.05) lower TBARS value than the control. TBARS value was increased significantly during storage in all treatment. CLA treatment groups showed significantly(p〈0.05) lower cholesterol content compared to those of control group. As dietary CLA was increased in feed, the content of CLA was increased, but the control was almost not detected. The contents of CLA were not significantly changed during chilled storage for 14 days. In the change of fatty acid composition, the contents of oleic, linoleic and arachidonic were decreased by dietary CLA-supplementation, whereas the increase level of CLA-supplementation resulted in the higher palmitic and stearic acid. In all results, CLA could be accumulated in pork meat and its antioxidant capability has been indicated. It was suggested that dietary CLA-supplementation could be produced high quality pork.

Conjugated Linoleic Acid Inhibits Proliferation and Induces Apoptosis of Normal Rat Mammary Epithelial Cells in Primary Culture

Obesity and related diseases are becoming more prevalent. Conjugated linoleic acid (CLA) might be a useful coadjutant treatment helping to decrease fat mass. However, the precise impact of CLA is unclear because the decreased body fat mass is followed by an increase in insulin resistance. This study aimed to evaluate some of the consequences of a high dose of CLA in rats fed a normal low fat or a high fat diet for 30 days. Male Wistar rats were separated into 4 groups (each n = 10): Control group receiving 7% fat (soybean oil); CLA group receiving 4% soybean oil and 3% CLA mixture; animal fat (AF) group, receiving 45% fat (lard); and animal fat plus CLA (AF+CLA) group, receiving 42% lard and 3% CLA mixture. The CLA mixture contained 39.32 mole% c9,t11-CLA and 40.50 mole% t10,c12-CLA. After 30 days, both CLA groups (CLA and AF+CLA groups) developed insulin resistance, with an increase in glucose in the fasting state and in an insulin tolerance test. The CLA group had increased liver weight and percentage of saturated fatty acids in liver and adipose tissue. Feeding the high fat diet resulted in increased hepatic triacylglycerol accumulation and this was exacerbated by dietary CLA. It is concluded that a high dose of CLA mixture increases insulin resistance and exacerbates hepatic steatosis when combined with a high fat diet.

Conjugated linoleic acid (CLA) is an isomer of linoleic acid that has been shown to have many beneficial effects in prevention of atherosclerosis, hypertension, cardiovascular diseases and improve immune function. Although majority of CLA in the diet are derived from dairy product such as milk, however, the content of CLA in milk is affected by cow’s diet. The aim of this study was to investigate the beneficial effect of CLA supplementation in milk for improving lipid profile in high fat diet of rats. Twenty four male Sprague Dawley rats aged 8 weeks were given high fat diet for 3 weeks to induce hypercholesterolemia. Six rats were maintained in standard diet as control. Rats then were divided into 4 groups i.e. normal control, negative control, high fat diet+CLA 0.5%, high fat diet + CLA 0.5% supplemented skim milk, and high fat diet + CLA 0.5% supplemented whole milk. Blood sample was drawn after high fat diet induced hypercholesterolemia and after 4 weeks of treatment for total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL cholesterol), and high density lipoprotein cholesterol (HDL cholesterol) analysis. Body weight was measured each week. Results showed that body weight was significantly increase in all groups received high fat diet (p 0.05). Total cholesterol, triglyceride, and LDL cholesterol was significantly decrease in whole milk followed by significant increase in HDL cholesterol level. Skim milk supplemented with CLA had only modest effect on triglyceride and HDL cholesterol level. In conclusion, CLA supplementation in whole milk improves lipid profile in high fat diet.

Previous research suggested that conjugated linoleic acid (CLA) feeding during the period of pubescent mammary gland development in the rat resulted in diminished mammary epithelial branching which might account for the reduction in mammary cancer risk. Terminal end buds (TEB) are the primary sites for the chemical induction of mammary carcinomas in rodents. One of the objectives of the present study was to investigate the modulation of TEB density by increasing levels of dietary CLA and to determine how this might affect the risk of methylnitrosourea-induced mammary carcinogenesis. The data show a graded and parallel reduction in TEB density and mammary tumor yield produced by 0.5 and 1% CLA. No further decrease in either parameter was observed when CLA in the diet was raised to 1.5 or 2%. Thus, optimal CLA nutrition during pubescence could conceivably control the population of cancer-sensitive target sites in the mammary gland. Since both CLA and linoleic acid are likely to share the same enzyme system for chain desaturation and elongation, it is possible that increased CLA intake may interfere with the further metabolism of linoleic acid. Fatty acid analysis of total lipid showed that CLA and CLA metabolites continued to accumulate in mammary tissue in a dose-dependent manner over the range 0.5-2% CLA. There was no perturbation in tissue linoleic acid, however, linoleic acid metabolites (including 18:3, 20:3 and 20:4) were consistently depressed by up to 1% CLA. Of particular interest was the significant drop in 20:4 (arachidonic acid), which is the substrate for the cyclooxygenase and lipoxygenase pathways of eicosanoid biosynthesis. Thus the CLA dose-response effect on arachidonic acid suppression corresponded closely with the CLA dose-response effect on cancer protection in the mammary gland. This information is critical in providing new insights regarding the biochemical action of CLA.

Forty mice were randomly divided into four groups on the basis of the diet to be fed as follows: 5% (low) fat diet (T1: LF); 20% (high) fat diet (T2: HF); 20% fat containing 1% conjugated linoleic acid (CLA) (T3: HFC); and 20% fat containing 1% CLA with 0.5% biopolymers (T4: HFCB). The high-fat with CLA diet groups (HFC and HFCB) and the low-fat diet group (LF) tended to have lower body weights and total adipose tissue weights than those of the high-fat diet group (HF). Serum leptin and triglyceride were significantly lower in the high fat with CLA-fed groups (HFC and HFCB) and the low-fat diet group (LF) than those in the high-fat diet group (HF). It is noteworthy that the high-fat with CLA and biopolymers group (HFCB) showed the lowest serum triglyceride and cholesterol concentrations. In the high-fat-fed group (HF), voluntary travel distance as a measure of physical activity decreased after three weeks of feeding. However, the CLA-fed groups showed increased physical activity. The groups fed high-fat diets supplemented with CLA alone and with CLA and biopolymers had higher viscosity of small intestinal contents than that in the low- and high-fat dietary groups.

Recent reports have demonstrated that conjugated linoleic acid (CLA) has effects on body fat accumulation. In our previous work, CLA reduced body fat accumulation in mice fed either a high-fat or low-fat diet. Although CLA feeding reduced energy intake, the results suggested that some of the metabolic effects were not a consequence of the reduced food intake. We therefore undertook a study to determine a dose of CLA that would have effects on body composition without affecting energy intake. Five doses of CLA (0.0, 0.25, 0.50, 0.75, and 1.0% by weight) were studied in AKR/J male mice (n = 12/group; age, 39 days) maintained on a high-fat diet (%fat 45 kcal). Energy intake was not suppressed by any CLA dose. Body fat was significantly lower in the 0.50, 0.75, and 1.0% CLA groups compared with controls. The retroperitoneal depot was most sensitive to the effects of CLA, whereas the epididymal depot was relatively resistant. Higher doses of CLA also significantly increased carcass protein content. A time-course study of the effects of 1% CLA on body composition showed reductions in fat pad weights within 2 wk and continued throughout 12 wk of CLA feeding. In conclusion, CLA feeding produces a rapid, marked decrease in fat accumulation, and an increase in protein accumulation, at relatively low doses without any major effects on food intake.

There is no consensus about the effects of conjugated linoleic acid (CLA) on lipid metabolism, especially in animals fed a high-fat diet. Therefore, the objective of the present study was to evaluate the incorporation of CLA isomers into serum, liver and adipose tissue, as well as the oxidative stress generated in rats refed with high-fat diets after a 48 hour fast. Rats were refed with diets containing soybean oil, rich in linoleic acid [7% (Control Group - C) or 20% (LA Group)], CLA [CLA Group - 20% CLA mixture (39.32 mole% c9,t11-CLA and 40.59 mole% t10,c12- CLA)], soybean oil + CLA (LA+CLA Group - 15.4% soybean oil and 4.6% CLA) or animal fat (AF, 20% lard). The CLA group showed lower weight gain and liver weight after refeeding, as well as increased serum cholesterol. The high dietary fat intake induced fat accumulation and an increase in -tocopherol in the liver, which were not observed in the CLA group. Circulating -tocopherol was increased in the CLA and CLA+LA groups. The high- fat diets reduced liver catalase activity. CLA isomers were incorporated into serum and tissues. In this shortterm refeeding experimental model, CLA prevented hepatic fat accumulation, although it produced an increase in serum cholesterol.