Trans-11 Conjugated Linoleic Acid Isomer Research Articles

Probiotics from the bovine raw milk of Lahaul valley showed cis-9, trans-11 conjugated linoleic acid isomer and antioxidant activity with food formulation ability

Dairy foods, especially of bovine origin, are the most common carriers of probiotics and conjugated linoleic acid (CLA)-producing microorganisms. The present study isolated probiotic strains from raw cow milk of the Lahaul valley capable of producing cis-9, trans-11 CLA isomer, besides exhibiting antioxidant properties with food formulation abilities. After preliminary probiotic screening, 34 strains were obtained, with 21 qualifying all the probiotic attributes and passing safety analysis. The seven most statistically promising probiotics were further explored for CLA production (16.87–28.01 μg/mL), and showed cis-9, trans-11 CLA isomer production as confirmed by GC-MS. To establish genomic evidence for safety analysis, whole genome sequencing was conducted for Enterococcus faecalis LJM:05, resulting in the deduction of antibiotic-resistance and virulence genes (lower identity scores). Based on the superior probiotic attributes, antioxidant, and CLA-producing properties, the strain Latilactobacillus curvatus LGM:16 was used to develop the curdled milk, with a legal, viable count (7.55 log10 CFU/mL) under pH ∼4.15 for 28 days of storage periods (4 °C). Scanning electron microscopic examination revealed microstructural changes after fermentation in the curdled milk compared to the control. The findings highlighted the role of indigenous probiotic strains with superior probiotic features, antioxidant activity, and CLA-producing ability in functional food formulation.

Mexican tropical cream cheese yield using low-fat milk induced by trans-10, cis-12 conjugated linoleic acid: effect of palmitic acid

ABSTRACTThe trans-10, cis-12 isomer of conjugated linoleic acid (CLA) reduces milk fat in dairy cows, causing a lower cheese yield. This could be mitigated by adding palmitic acid (PA) to the diet, as it stimulates fat synthesis in mammary gland. The objective of this study was to evaluate the effect of adding PA to the diet of grazing dairy cows complemented with trans-10, cis-12 CLA on the yield and fatty acid (FA) profile of Mexican tropical cream cheese. The lowest cheese yield was the result of the treatment with CLA alone. Supplementing PA to the cows with low fat concentration in their milk, from the effect of the trans-10, cis-12 isomer, mitigates the decrease in cheese yield. The process of cheese making does not modify the profile of FAs, so the supplemented cis-9, trans-11 CLA isomer transfers to the cheese, giving added value to the Mexican tropical cream cheese.

Physicochemical evaluation of sheep milk yogurts containing different levels of inulin

The present study aimed to evaluate the physicochemical parameters of sheep milk yogurt smoothies (SMY) containing inulin at different levels (0, 2, 4, and 6%). Titratable acidity and pH, yogurt bacteria counts, fatty acids profile, and healthy lipid indices were evaluated during 28 d of refrigerated storage. As expected for yogurts, Streptococcus thermophilus counts decreased 1 to 3 log cycles and Lactobacillus delbrueckii ssp. bulgaricus counts decreased 1 to 2 cycles from d 1 to 28. The protective effect of inulin on bacteria survival and viability in the food matrix was not verified in the prebiotic SMY during storage, regardless of inulin level. Although lower post-acidification was observed in prebiotic SMY due to inulin addition, no changes were verified in short-chain fatty acids (SCFA) or polyunsaturated fatty acids (PUFA). In contrast, an increase in medium- and long-chain fatty acids (MCFA and LCFA) and monounsaturated fatty acids (MUFA) was observed during storage in all SMY. The most significant levels of fatty acids in SMY were oleic acid, followed by palmitic and myristic acids. A high positive correlation between conjugated linoleic acid (CLA) and oleic acid (r=0.978) was observed. The cis-9,trans-11 CLA isomer represented approximately 78% of total PUFA and 2% of total fatty acids, whereas α-linoleic acid comprised about 22% PUFA and 1% of total fatty acids in SMY. The fatty acid changes during storage were associated with the metabolic activity of the starter bacteria, especially for oleic acid and cis-9,trans-11 CLA isomer. Thus, the SMY represented a great source of these compounds. We observed that inulin levels did not affect fatty acids. A nonsignificant decrease in atherogenic index was observed during storage in all SMY, and a positive correlation (r=0.973) was found between atherogenic index and thrombogenic index of SMY. High correlations were observed between lauric and myristic acids and saturated fatty acids (r=0.907 and r=0.894, respectively), providing evidence of their atherogenic and thrombogenic potential. A negative correlation was observed between stearic acid and atherogenic index (r=−0.612) and between oleic acid and atherogenic index. Sheep milk yogurt could be characterized as a food with low atherogenic and thrombogenic risk because of its healthy lipid composition. Therefore, addition of inulin to SMY could be a good option to improve functionality of this food matrix for dairy companies wishing to enter the functional food market.

The effect of dietary lipid saturation and monensin-Na on the CLA content of lambs’ meat

A study was conducted to investigate the influence of an ionophore antibiotic and lipid saturation within a standard finishing diet on the conjugated linoleic acid (CLA) content of lambs’ meat. Two identical sheep grower diets containing 145 g CP, 282 g NDF and 45 g EE per kg DM were formulated. One diet contained no ionophore antibiotic and the other monensin-Na included at 165 g/ton. These two basal diets were supplemented, according to a 2 x 3 factorial design, with three lipid sources [i.e. 20 g/kg of either beef tallow, sunflower oil or a CLA oil concentrate] differing in saturation level and fatty acid profile. Sixty South African Mutton Merino lambs (31.15 ± 2.83 kg) were randomly allocated to the six treatments. After dietary adaptation of 10 days, the lambs received their respective treatment diets for the remaining period of 51 days. At the end of the study seven lambs (45.11 ± 2.99 kg) were randomly selected per treatment and slaughtered. Muscle and subcutaneous fat tissue from loin chops of each carcass were used for lipid extraction and fatty acid analysis. The supplementation of CLA oil in the diet resulted in a significantly lower vaccenic acid concentration of lamb muscle tissue. In contrast, supplementing sunflower oil increased the linoleic acid concentration of only the subcutaneous fat tissue significantly. Sunflower- and CLA oil supplementation increased the cis-9, trans-11 CLA isomer of both subcutaneous fat and muscle tissues, whereas only the CLA concentrate increased the trans-10, cis-12 isomer of both mentioned tissues significantly. The dietary inclusion of monensin-Na decreased the vaccenic-, linoleic- and CLA (cis-9, trans-11 isomer) concentrations of both lamb subcutaneous fat and muscle tissues significantly. The manipulation of the CLA content of lamb seems to be effective when adding either sunflower oil or a CLA oil concentrate to the finishing diet of lambs. However, this effect is inhibited by the addition of monensin-Na to the same diet.Keywords: Conjugated linoleic acid, cis-9, trans-11 CLA isomer, tallow, sunflower oil, subcutaneous fat

Effects of conjugated linoleic acids on prostaglandin secretion by bovine endometrial epithelial cells in vitro

To determine the effects of 2 conjugated linoleic acid (CLA) isomers (cis-9, trans-11 and trans-10, cis-12) on synthesis of prostaglandin (PG) E(2) and F(2α) and expression of prostaglandin H synthase-2 (PGHS-2) of adult and fetal bovine endometrial epithelial cells in vitro. Primary cultures of endometrial epithelial cells obtained from 4 adult cows and 4 fetal bovine carcasses. Cells were exposed to 0, 50, 100, or 200μM cis-9, trans-11 or trans-10, cis-12 CLA isomers for 24 hours. Culture media collected before and after 6 hours of stimulation of cells with phorbol 12-myristate 13-acetate were assayed to detect PGE(2) and PGF(2α) via ELISA. After stimulation, cells were collected for western blot analysis to quantify PGHS-2. Concentrations of PGF(2α) and PGE(2) were significantly lower in culture media of adult and fetal endometrial epithelial cells exposed to any concentration of either CLA than they were in media of cells not exposed to CLAs. The trans-10, cis-12 CLA isomer seemed to decrease PG production more markedly than did the cis-9, trans-11 CLA isomer. Most concentrations of both CLAs significantly reduced culture media PGE(2):PGF(2α) concentration ratios of cells. Exposure of cells to CLAs did not affect expression of PGHS-2 protein. Results of this study indicated CLAs significantly decreased PGF(2α) and PGE(2) concentrations and PGE(2):PGF(2α) concentration ratios for cultures of adult and fetal endometrial epithelial cells with no apparent effect on PGHS-2 expression. Similar effects in cows could have effects on maternal recognition of pregnancy and immune function.

Trans-10,cis-12 Conjugated linoleic acid promotes bone formation by inhibiting adipogenesis by peroxisome proliferator activated receptor-γ-dependent mechanisms and by directly enhancing osteoblastogenesis from bone marrow mesenchymal stem cells

The bone undergoes continuous remodeling of osteoblastic bone formation and osteoclastic bone resorption to maintain proper bone mass. It is also reported that bone marrow adiposity has a reciprocal role in osteoblasts due to their same origin from mesenchymal stem cells. In addition, one of the key mediators of adipogenesis, peroxisome-proliferator activated receptor-γ (PPARγ), plays a significant role in osteoblastogenesis in bone marrow mesenchymal stem cells. One dietary component that is known to have significant impact on adiposity and bone mass is conjugated linoleic acid (CLA). However, the link between controlling adiposity to improving bone mass by CLA has not been studied intensively. Thus, the purpose of this study is to determine the role of CLA on bone marrow adiposity and bone formation using murine mesenchymal stem cells. The results confirmed that the trans-10,cis-12 CLA, but not the cis-9,trans-11 CLA isomer, significantly inhibited adipogenesis and promoted osteoblastogenesis from mesenchymal stem cells. The inhibition of adipogenesis by the trans-10,cis-12 CLA was mediated by PPARγ; however, the trans-10,cis-12 CLA had a direct effect on osteoblastogenesis which was independent to PPARγ in this model. The trans-10,cis-12 CLA also had significant effects on osteoclastogenesis inhibitory factor, which suggests potential influence of CLA on osteoclastogenesis. Overall, the results suggest that the trans-10,cis-12, but not the cis-9,trans-11 CLA isomer, has a positive impact on bone health by both PPARγ mediated and independent mechanisms in mesenchymal stem cells.

Cross-sectional study of conjugated linoleic acid in adipose tissue and risk of diabetes

Some experimental studies on conjugated linoleic acid (CLA) and insulin regulation suggested that CLA could be associated with risk of diabetes, but epidemiologic studies are lacking. The aim of the study was to test whether the amount of CLA in adipose tissue is associated with risk of diabetes. A cross-sectional design was used to test the study hypothesis in 232 adults with diabetes and 1512 adults without diabetes who lived in Costa Rica. The cis-9, trans-11 and trans-10, cis-12 CLA isomers in adipose tissue and 48 other fatty acids were assessed by using gas chromatography. Prevalence ratios (PRs) and 95% CIs were estimated by using Poisson regression adjusted for potential confounders. The mean (±SD) percentage of total fatty acids of CLA for the cis-9, trans-11 isomer in adipose tissue was 0.57 ± 0.18% in adults without diabetes and 0.53 ± 0.17% in adults with diabetes (P = 0.0078). The trans-10, cis-12 CLA isomer was not detected in adipose tissue. The cis-9, trans-11 CLA isomer was associated with a lower risk of diabetes. In comparison with the first quintile, the PR (95% CI) for the fifth quintile was 0.48 (0.31, 0.76) (P-trend = 0.0005) in the basic and 0.46 (0.29, 0.72) (P-trend = 0.0002) in the multivariable model. Additional adjustment for other fatty acids in adipose tissue including trans-9 16:1, which is a fatty acid that was previously associated with diabetes, did not modify the results. The observed inverse association between the cis-9, trans-11 CLA in adipose tissue and diabetes risk is consistent with the hypothesis that CLA may be involved in insulin regulation.

Trans-10, cis-12 conjugated linoleic acid and the PPAR-γ agonist rosiglitazone attenuate lipopolysaccharide-induced TNF-α production by bovine immune cells

Lipopolysaccharide (LPS) modulates innate immunity through alteration of cytokine production by immune cells. The objective of this study was to examine the effect of exogenous conjugated linoleic acid (CLA) and PPAR-γ agonist, rosiglitazone, on LPS-induced tumor necrosis factor α (TNF-α) production by cultured whole blood from prepubertal Holstein heifers (mean age, 5.5 mo). Compared with unstimulated cells, addition of LPS (10 μg/mL) to the culture medium increased ( P < 0.03) peripheral blood mononuclear cell proliferation ≤2.5-fold. Coincubation with interferon γ (5 ng/mL) further stimulated ( P < 0.01) the lymphoproliferative response to LPS. Lipopolysaccharide increased ( P < 0.01) TNF-α concentration in cultured whole blood in a dose- and time-dependent manner. The greatest TNF-α stimulation occurred after 12 h of exposure to 1 μg/mL LPS. Coincubation with trans-10, cis-12 CLA isomer (100 μM) or rosiglitazone (10 μM), a PPAR-γ agonist, decreased ( P < 0.01) LPS-induced TNF-α production by 13% and 29%, respectively. Linoleic acid and cis-9, trans-11 CLA isomer had no detectable effects on LPS-induced TNF-α production in cultured bovine blood. The PPAR-γ agonist-induced TNF-α attenuation was reversed when blood was treated with both rosiglitazone and GW9662, a selective PPAR-γ antagonist. Addition of rosiglitazone to the culture medium tended to reduce nuclear factor-κ Bp65 concentration in nuclear and cytosolic extracts isolated from cultured peripheral blood mononuclear cells. Results show that LPS is a potent inducer of TNF-α production in bovine blood cells and that trans-10, cis-12 CLA and PPAR-γ agonists may attenuate the pro-inflammatory response induced by LPS in growing dairy heifers. Additional studies are needed to fully characterize the involvement of nuclear factor-κ B in LPS signaling in bovine blood cells.

Protection of cortical neurons from excitotoxicity by conjugated linoleic acid

Conjugated linoleic acid (CLA) is an isomeric mixture of 18-carbon polyunsaturated fatty acids with conjugated double bonds derived from linoleic acid. CLA is sourced nutritionally from dairy products and ruminant animal meat and is associated with beneficial heath effects in several disorders, including cancer, atherosclerosis, diabetes, obesity, and inflammation. We investigated the potential for CLA to protect neurons from death in stroke simulated by exposing cultured mouse embryonic cortical neurons to glutamate. CLA (10 30 μM) significantly protected neuronal survival in response to glutamate (3 μM) excitotoxicity when given concurrently with glutamate. CLA (30 μM) also reduced neuron death when given up to 5 h after glutamate exposure (73.1 ± 13.3% protection, p < 0.01), suggesting potential utility as a post-injury therapeutic tool. The cis-9, trans-11 CLA isomer, which comprises about 40% of the commercial CLA mixture used, was identified as the active neuroprotective species. The other major species, trans-10, cis-12 CLA (40%) was without significant neuroprotective effect. CLA significantly increased neuronal Bcl-2 levels when given with glutamate and attenuated glutamate-induced dissipation of mitochondrial membrane potential, suggesting a stabilizing influence on mitochondrial function. These results show that CLA is capable of strong neuroprotective effects in glutamate excitotoxicity at concentrations likely achieved by consumption of CLA as a dietary supplement.

Modulation of lipid droplet size and lipid droplet proteins by trans-10, cis-12 conjugated linoleic acid parallels improvements in hepatic steatosis in obese, insulin-resistant rats

The isomer-specific effects of conjugated linoleic acid (CLA) on hepatic steatosis were assessed in fa/fa Zucker rats, a model for insulin resistance and the metabolic syndrome. Eight weeks of feeding trans-10, cis-12 CLA significantly improved glucose tolerance without changing body weight or visceral adipose mass. The trans-10, cis-12 isomer was also associated with reduced liver lipid content, improved liver function and reduced inflammation; these effects were not observed in rats fed the cis-9, trans-11 CLA isomer. Reduced liver lipid content did not correlate with activation of AMP-activated protein kinase or suppressed activation of sterol-regulatory element binding protein-1, two key regulators of hepatic lipid metabolism. Interestingly, rats fed cis-9, trans-11 CLA had fewer cytoplasmic lipid droplets in hepatocytes compared to rats fed control diet, but these droplets were larger in size. Conversely, fa/fa rats fed the trans-10, cis-12 CLA isomer had greater numbers of hepatic lipid droplets that were smaller in size, resulting in overall lower total lipid within these droplets. Changes in lipid droplets were associated with lower hepatic levels of PERILIPIN-2 (formerly known as adipophilin) in rats fed trans-10, cis-12 CLA, whereas amounts of other members of the PERILIPIN family of lipid droplet proteins were unaffected by dietary CLA. However, CLA isomers differentially affected the subcellular localization of these proteins. Treatment of H4IIE rat hepatoma cells with CLA isomers neither prevented nor reversed, but rather induced cytoplasmic lipid droplet formation, suggesting that the anti-steatotic effects of trans-10, cis-12 CLA are likely indirect and potentially mediated via increased lipid utilization by peripheral tissues.

The Role of Conjugated Linoleic Acid in Breast Cancer Growth and Development

Conjugated linoleic acid (CLA) consists of a group of naturally occurring and synthetic positional and geomet- ric (cis-trans) stereoisomers of the polyunsaturated fatty acid linoleic acid. The cis-9,trans-11 (c9,t11) CLA isomer (the most prevalent form found in ruminant-derived foods) and the trans-10,cis-12 (t10,c12) CLA isomer (present in commer- cial preparations) are the two most widely studied CLA isomers in breast cancer. Studies using both animal and cell cul- ture models indicate that these CLA isomers, when added to the diet or included in the cell culture medium, inhibit mam- mary tumour initiation, promotion and progression in rodents, and alter tumour cell viability in vitro. The mechanism of CLA's anticancer effect is not well understood, but may involve interference with the cell cycle, induction of apoptosis, modulation of gene expression via the activation of peroxisome proliferator-activated receptors, lipid peroxidation, modu- lation of the tumour microenvironment, changes to the structure and/or function of the cell membrane, and interference with growth factor receptor signaling. A greater understanding of the mechanism of action of CLA will support the devel- opment of clinical trials to evaluate the potential effectiveness of CLA in the treatment of breast cancer.

Effect of Conjugated Linoleic Acid (CLA) on Tumor Suppression in Canine Osteosarcoma Cells

Cancer is one of the leading causes of death in the US both in men and women, second to the heart disease. Among types of cancer, osteosarcoma is the most common type of malignant bone cancer. Although there is substantial scientific research focusing on understanding mechanisms of osteosarcoma, the causes of osteosarcoma are largely unknown. One potential mechanism of osteosarcoma involves the non‐steroidal anti‐inflammatory drug‐activated gene 1 (NAG‐1), where NAG‐1 serves as the intermediate key regulator for tumor development and apoptosis for osteosarcoma. Conjugated linoleic acid (CLA) is a fatty acid with anticancer properties in vitro and in vivo studies that occurs naturally in many dairy and beef products. Thus the purpose of this study was to investigate the anticancer effects of CLA isomers on a canine osteosarcoma cell line, CLL 183. The trans‐10,cis‐12 CLA isomer effectively suppressed the tumor cell growth after 72 hour treatment, while the cis‐9,trans‐11 CLA isomer had no effect. Further experiments confirmed that the trans‐10,cis‐12 CLA isomer, but not the cis‐9,trans‐11 isomer, affects NAG‐1 expression. These results support our hypothesis that CLA's anticancer effects are in part mediated by controlling NAG‐1 expression.

Long-Term Feeding of the cis-9,trans-11 Isomer of Conjugated Linoleic Acid Reinforces the Specific Immune Response in Rats

Several effects on the immune system have been ascribed to the cis9,trans11 conjugated linoleic acid (CLA) isomer. We studied whether feeding a diet enriched with an 80:20 CLA isomer mix of cis9,trans11 and trans10,cis12 CLA from gestation to adulthood affects the capacity of adult rats to achieve a specific immune response. Pregnant Wistar rats were fed a 1% CLA diet or a control diet beginning on d 7 of gestation. Weaned pups received the same diet as dams until they were 15 wk old. Rats from both groups were immunized with ovalbumin (OVA) when they were 9 wk old. Dietary CLA enhanced splenocyte OVA-specific proliferation by ∼50% (P < 0.05) and decreased the mitogen-induced proliferative responses of these cells by ∼10–20% (P < 0.05). The diminished splenocyte proliferative response was accompanied by a lower interleukin-2 secretion (P < 0.05). Long-term CLA supplementation did not increase serum, spleen, or mesenteric lymph node production of OVA-specific antibodies (Ab) or the number of spleen anti-OVA Ab-secreting cells. Interestingly, dietary CLA increased intestinal anti-OVA IgA production by ∼75% (P < 0.05). In conclusion, a 1% CLA diet administered from gestation to adulthood enhanced specific systemic cell-mediated immunity as well as the mucosal IgA immune response, whereas it downregulated the polyclonal activation of the immune system. These data support the long-term effects of dietary cis9,trans11 CLA isomer on the immune system.

Fatty Acid Composition of Yak (Bos grunniens) Cheese Including Conjugated Linoleic Acid and trans-18:1 Fatty Acids

The esterified fatty acid composition of cheese (YC) from yak ( Bos grunniens), reared in the highlands of the Nepalese Himalayas, was studied using capillary gas-liquid chromatography and compared with that of dairy cow Cheddar cheese (DC) purchased in a local market. The YC was collected from Dolakha, Nepal. The YC had a lower (P<0.001) myristic acid (C14:0; 6.7 vs 10.3%, YC vs DC, respectively) and palmitic acid content (C16:0; 23.3 vs 29.2%, YC vs DC, respectively) compared to DC. The YC had a lower (P<0.01) total medium-chain saturated fatty acids (C10:0-C16:0) content compared to DC (36.7 vs 47.3%, YC vs DC, respectively). On the other hand, the YC had a 24.8% higher (P<0.01) level of total long-chain saturated fatty acids (C17:0-C26:0) and a 3.2 times higher (P<0.001) content of total n-3 PUFA than DC. The ratio of n-3 PUFA to n-6 PUFA in YC was 0.87 compared to 0.20 in DC. YC had a 2.8 times higher (P<0.001) total trans-18:1 (9.18 vs 3.31%, YC vs DC, respectively) content. The percentage of vaccenic acid ( trans-11-C18:1) in YC was 4.6 times higher (6.23 vs 1.35% of total fatty acids, YC vs DC, respectively) than in DC. Vaccenic acid constituted 67.9% of total trans-C18:1 in YC. The Delta9-desaturase index for YC was lower than that of DC. The total conjugated linoleic acid (CLA) content in YC was 2.3% of total fatty acids compared to 0.57% in DC. The cis-9, trans-11 CLA isomer in YC constituted 88.5% of the total CLA. The results suggest that cheese from yak, grazed on Himalayan alpine pastures, may have a more healthful fatty acid composition compared to cheese manufactured from dairy cattle fed grain-based diets.

Conjugated linoleic acid (CLA) and obesity

The term conjugated linoleic acid (CLA) refers to several positional and geometric conjugated dienoic isomers of linoleic acid (LA), of which the trans-10,cis-12 isomer has been reported to reduce adiposity and increase lean mass in mice and other animals when included at <or=1% of the diet. However, most dietary CLA in humans is obtained from dairy products, accounting for the cis-9,trans-11 CLA isomer, also known as rumenic acid, for more than 90% of the total CLA intake. Commercial CLA preparations industrially produced, containing trans-10,cis-12 and cis-9,trans-11 CLA isomers in diverse proportions, are attracting consumers' interest because of the purported body fat-lowering effects of CLA, coupled to the perception of a 'natural' compound devoid of harmful effects. Nevertheless, despite numerous studies on CLA effects on body composition for nearly a decade, the mechanisms by which CLA isomers elicit their effects remain largely unknown. The purpose of this paper is to provide an updated review of the studies performed on animals and humans, as well as to describe the potential mechanisms involved in CLA effects on body weight and composition and metabolism. Literature review. Experiments in humans have not been able to show a significant effect on body weight, body composition or weight regain related to either of the CLA isomers. In fact, some studies suggest a tendency towards a decrease in body fat mass and an increase in body lean mass, while some others raise concern about the possibility of deleterious effects of trans-10,cis-12 CLA on lipid profile, glucose metabolism and insulin sensitivity. Evidence regarding effectiveness of CLA in humans is not concluding.

Trans-10, cis-12 conjugated linoleic acid inhibits prolactin-induced cytosolic NADP+ -dependent isocitrate dehydrogenase expression in bovine mammary epithelial cells.

Conjugated linoleic acid (CLA) has been found to exert beneficial effects on lipid profile and repress de novo fatty acid synthesis in mammary gland during lactation. However, the underlying mechanisms responsible for the antilipogenic effects of CLA have not been established. The cytosolic NADP+ -dependent isocitrate dehydrogenase (IDH1) plays a critical role in cholesterol and fatty acid biosynthesis by providing reducing equivalents as NADPH. In previous studies, we documented that the expression of IDH1 in bovine mammary epithelium was modulated by regulators of mammary differentiation and metabolic effectors. In this study, we investigated the short-term effects of prolactin (PRL) and CLA on IDH1 expression in BME-UV bovine mammary epithelial cells. In time-course experiments, we found that the treatment with PRL for 60 and 90 min elicited a significant increase in IDH1 transcript levels. Conversely, the cotreatment of BME-UV cells with PRL plus a CLA mixture for 90 min prevented the accumulation of IDH1 mRNA induced by PRL. In addition, we found that the trans-10, cis-12 CLA, but not the cis-9, trans-11 CLA isomer, inhibited basal- and PRL-induced IDH1 mRNA expression. The inhibitory effects of the trans-10, cis-12 CLA isomer on PRL-induced IDH1 expression accumulation were confirmed by quantitative real time PCR and western-blotting analysis. We propose that the inhibitory effects of CLA on milk fat synthesis in mammary epithelial cells may derive, at least in part, from repression of IDH1 expression.

In sacco studies of conjugated linoleic acid production from various oils in the rumen of sheep

In this experiment sunflower oil, soybean oil and fish oil were incubated in rumen-fistulated adult ewes (n = 5) to study conjugated linoleic acid (CLA) production in the rumen. The individual oils were incubated in nylon bags in the rumen on perlite carrier (40% oil, 60% carrier) over a period of 2, 4, 6, 8, 10 and 12 h for all treatments. During the incubation of each oil primarily the formation of the cis-9, trans-11 isomer of CLA could be observed. Both sunflower and soybean oils showed similar changes in the rumen. After the incubation of these two vegetable oils the proportion of linoleic acid decreased significantly as the duration of incubation increased in the rumen. These changes were accompanied by a significant increase in the amount of cis-9, trans-11 CLA. However, in the case of sunflower oil the rate of formation of the cis-9, trans-11 CLA isomer was significantly higher after the different incubation times as compared to soybean oil. Much lower amounts of CLA were formed when fish oil was incubated in the rumen. The level of cis-9, trans-11 isomer produced during these treatments was 10% less than the amount obtained with the other two oils of vegetable origin. Besides the cis-9, trans-11 isomer, trans-10, cis-12 CLA could also be detected during the incubation of the different oils in the rumen. However, the level of this isomer was low and did not show consistent differences among the treatments. The results of this experiment indicate that the fatty acid composition of the oils and the duration of incubation collectively determine the amount of CLA produced in the first compartment of the forestomach of ruminants.

Effect of dietary supplementation with conjugated linoleic acid on markers of calcium and bone metabolism in healthy adult men

Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism in experimental animals and cells in culture, but there are limited human data available. To investigate the effect of CLA supplementation on biomarkers of calcium and bone metabolism in healthy adult males. The study consisted of a double-blind, placebo-controlled trial in which 60 healthy adult males (aged 39-64 y) were randomly assigned to receive daily either 3.0 g CLA isomer blend (50:50% cis-9,trans-11:trans-10,cis-12 isomers) or a palm/bean oil blend (placebo) for 8 weeks. Urine and blood samples were collected at weeks 0 and 8 and were analysed for biomarkers of calcium and bone metabolism. Supplementation with CLA or placebo for 8 weeks had no significant effects on markers of bone formation (serum osteocalcin and bone-specific alkaline phosphatase) or bone resorption (serum C-telopeptide-related fraction of type 1 collagen degradation products, urinary N-telopeptide-related fraction of type 1 collagen degradation products, urinary pyridinoline and deoxypyridinoline), or on serum or urinary calcium levels. Baseline levels of these biochemical parameters were similar in both groups of subjects. While the placebo had no effect, CLA supplementation resulted in a three-fold increase (P<0.00001) in cis-9,trans-11 CLA isomer in total plasma lipids. Under the conditions tested in this double-blind, placebo-controlled trial in adult men, a CLA supplement of mixed isomers did not affect markers of calcium or bone metabolism. Further investigation of the effects of CLA on calcium and bone metabolism in other gender- and age-groups is warranted.

Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on fatty acid composition of adipose tissues in beef cattle.

Thirty-six Angus x Hereford heifers (365 +/- 60 kg) were used to determine the effects of supplemental dietary lipid sources on fatty acid composition of i.m., perianal (p.a.), and s.c. lipid depots. Lipid was supplied to diets as either corn oil or a rumen-protected conjugated linoleic acid (CLA) salt for two specific treatment periods of either the final 32 or 60 d on feed. Following an initial 56-d feeding period, heifers were fed one of three dietary treatments (DM basis): 1) basal diet containing 88% concentrate and 12% grass hay (CON), 2) basal diet plus 4% corn oil (OIL), or 3) basal diet plus 2% rumen-protected CLA salt (RPCLA) containing 31% CLA. The trans-10, cis-12 CLA concentration was greatest (P < 0.05) for heifers fed RPCLA and OIL diets and least (P < 0.05) for CON, regardless of time on dietary treatment. Heifers fed supplemental RPCLA had greater (P < 0.05) total CLA content than either CON- or OIL-fed heifers. Adipose tissue concentration of trans-11 vaccenic acid (TVA) was less (P < 0.05) for CON than OIL or RPCLA, which did not differ (P > 0.05). Percentages of C18:1 trans-10 were least (P < 0.05) in i.m. lipid compared with p.a. and s.c., which did not differ (P > 0.05). Following 60 d of lipid supplementation, heifers fed OIL and RPCLA had lower (P < 0.05) concentrations of oleic acid and total monounsaturated fatty acids (MUFA) compared with CON. The ratio of cis-9, trans-11 CLA:TVA was higher (P < 0.05) for heifers fed 60 vs. 32 d, but did not differ (P > 0.05) between adipose depots. Feeding OIL increased (P < 0.05) adipose concentration of C18:2 fatty acid, whereas feeding RPCLA increased (P < 0.05) total CLA isomers by 22%. Intramuscular lipid contained the lowest (P < 0.05) percentage of cis-9, trans-11 CLA, total CLA, C18:1 cis-9, C18:1 trans-10, and TVA. Total CLA and cis-9, trans-11 CLA isomers were increased (P < 0.05) in p.a. and s.c. adipose depots, whereas i.m. adipose tissue contained increased (P < 0.05) amounts of total PUFA. Results from this study indicate that short-term lipid supplementation to feedlot cattle can increase adipose tissue CLA concentrations, but only marginally (8.3 to 17.5%). Moreover, observed decreases in oleic acid and total MUFA concentrations of adipose tissues from heifers fed rumen-protected CLA or corn oil suggest that lipid supplementation may decrease delta9 desaturase activity in adipose tissues, which in turn would lower the conversion of TVA to cis-9, trans-11 CLA isomer.

Trans-10, cis-12, but not cis-9, trans-11 CLA isomer, inhibits brown adipocyte thermogenic capacity.

Conjugated linoleic acid (CLA) is reported to have health benefits, including reduction of body fat. Previous studies have shown that brown adipose tissue (BAT) is particularly sensitive to CLA-supplemented diet feeding. Most of them use mixtures containing several CLA isomers, mainly cis-9, trans-11 and trans-10, cis-12 in equal concentration. Our aim was to characterize the separate effects of both CLA isomers on thermogenic capacity in cultured brown adipocytes. The CLA isomers showed opposite effects. Hence, on the one hand, trans-10, cis-12 inhibited uncoupling protein (UCP) 1 induction by norepinephrine (NE) and produced a decrease in leptin mRNA levels. These effects were associated with a blockage of CCAAT-enhancer-binding protein-alpha and peroxisome proliferator-activated receptor-gamma(2) mRNA expression. On the other hand, cis-9, trans-11 enhanced the UCP1 elicited by NE, an effect reported earlier for polyunsaturated fatty acids and also observed here for linoleic acid. These findings could explain, at least in part, the effects observed in vivo when feeding a CLA mixture supplemented diet as a result of the combined action of CLA isomers (reduction of adipogenesis and defective BAT thermogenesis that could be through trans-10, cis-12 and enhanced UCP1 thermogenic capacity through cis-9, trans-11).