Dietary fat has minimal effects on fatty acid metabolism transcript concentrations in pigs

Evaluation of Sodium Stearoyl-2-Lactylate and 1, 3-Diacylglycerol Blend Supplementation in Diets with Different Energy Content on the Growth Performance, Meat Quality, Apparent Total Tract Digestibility, and Blood Lipid Profiles of Broiler Chickens

We evaluated the effects of supplementing an emulsifier blend (sodium stearoyl-2-lactylate and 1, 3-diacylglycerol) in diets with different energy content (normal and 100 kcal/kg reduced) on the growth performance, meat quality, apparent total tract digestibility (ATTD), and blood lipid profile of broiler chickens. Male broiler chickens (n = 1024), with an initial body weight (BW) of 43.60±0.2 g, were used in a 35-day trial. Broiler chickens of similar body weight were randomly allocated to one of four treatment groups in a 2 × 2 factorial arrangement with two levels of dietary energy content and with or without emulsifier blend. Broiler chickens fed on emulsifier blend supplemented diet had a higher body weight gain (BWG) during d 7-21, d 21-35, and overall period (P<0.05), higher BW during overall period (P<0.05), and lower feed conversion ratio (FCR) during d 7-21, d 21-35, and overall period (P<0.05) compared with broilers fed on diets without emulsifier supplementation. Broiler chickens fed on the diet with low energy content had a lower BWG during d 1-7, d 21-35, and overall period (P<0.05), lower BW during overall period, and higher FCR during d 1-7, d 21-35, and overall period (P<0.05). The ATTD of energy tended to decrease in response to low-energy content diet (P<0.10). Drip loss at 7 d post slaughter tended to decrease in response to dietary emulsifier blend supplementation (P<0.10). However, no interactive effects of dietary energy content and emulsifier blend supplementation (P>0.10) were observed on the growth performance, ATTD, blood lipid profiles, meat quality and relative organ weight. In conclusion, dietary emulsifier blend supplementation could improve growth performance, while low dietary energy content would decrease growth performance and ATTD of energy.

Hepatic lipid metabolism is affected by a daily 3-meal pattern with varying dietary crude protein with a pig model

The present study was conducted to evaluate the effects of 3 meals administered daily with varying dietary crude protein (CP) contents on hepatic lipid metabolism with a pig model. Pigs were divided into 3 groups according to the following feeding patterns: feeding a basal CP diet 3 times daily (3C); feeding a high CP diet for breakfast, the basal CP diet for lunch, and a low CP diet for dinner (HCL); and feeding the low CP diet for breakfast, the basal CP diet for lunch, and the high protein diet for dinner (LCH). Three groups took equivalent diet per meal ensuring that every pig was fed with similar dietary formulae daily. Results showed that HCL feeding pattern reduced the relative kidney weight (P < 0.05), and LCH feeding pattern increased the relative liver weight of pigs (P < 0.05) when compared with those in the 3C group. Plasma urea nitrogen (P < 0.01) and lipase (P < 0.05) decreased in the HCL group but increased in the LCH group. Both HCL and LCH feeding patterns reduced plasma triglycerides (P < 0.01), non-esterified fatty acids (NEFA) (P < 0.01), and hepatic crude fat (0.05 < P < 0.10) of pigs. Real-time quantitative PCR (RT-qPCR) results showed that dynamic feeding patterns down-regulated (P < 0.05) the mRNA level of lipid metabolism related genes, including adipose triglyceride lipase (ATGL), acetyl-CoA carboxylase (ACCα), liver X receptor (LXRα) in the liver, and negatively regulate elements of circadian clock, including period 1 (Per1), period 2 (Per2), cryptochrome (Cry2), which in turn, upregulated (P < 0.05) the protein expression of positive regulate element brain and muscle Arnt-like 1 (BMAL1) when compared with 3C group. Overall, our findings suggested that dynamic feeding patterns may affect hepatic lipid metabolism via regulation of the circadian clock.

Effects of fenugreek (Trigonella foenum-graecumL.) seed extract supplementation in different energy density diets on growth performance, nutrient digestibility, blood characteristics, fecal microbiota, and fecal gas emission in growing pigs

This study evaluated the efficacy of fenugreek seed extract (FSE) in growing pigs. About 140 growing pigs [(Yorkshire × Landrace) × Duroc] with an average body weight (BW) of 23.70 ± 2.80 kg were used in a 6 wk trial. Treatments were (on as-fed basis) two levels of FSE (FSE0, 0 or FSE0.2, 2 g kg−1basal diet), and two levels of energy [low-energy diet (LED); 3160 or high-energy diet (HED); 3260 kcal kg−1metabolizable energy (ME)]. Pigs in HED and FSE0.2 diets had higher final BW, average daily gain, and gain:feed ratio (G:F) compared with in LED, and FSE0 diets, respectively (P < 0.05). Pigs fed the FSE0.2 and HED diets had higher energy (E) digestibility than the FSE0 and LED diets, respectively (P < 0.05). Pigs fed the FSE0.2 diet increased serum immunoglobulin G (IgG), and reduced total cholesterol (TC) concentration than the FSE0 diet (P < 0.05). Hydrogen sulfide (H2S) and ammonia (NH3) gas emission in FSE0.2 diet were lower than that in FSE0 group (P < 0.05). In conclusion, results indicated that dietary supplementation of FSE improved growth performance, digestibility, serum IgG, reduced serum TC, and noxious gas emission in growing pigs.

Effects of dietary fat saturation on fatty acid composition and gene transcription in different tissues of Iberian pigs

The effect of two diets, respectively enriched with SFA (S) and PUFA (P), on FA tissue composition and gene expression was studied in fattened Iberian pigs. The FA composition of adipose, muscular and liver tissues was affected by dietary treatment. S group showed higher MUFA and MUFA/SFA ratio and lower PUFA and n-6/n-3 ratio than P group in all analyzed tissues. In muscle and liver the extracted lipids were separated into neutral lipids and polar lipid fractions which showed significantly different responses to the dietary treatment, especially in liver where no significant effect of diet was observed in NL fraction. The expression of six candidate genes related to lipogenesis and FA oxidation was analyzed by qPCR. In liver, stearoyl CoA desaturase (SCD), acetyl CoA carboxylase alpha (ACACA) and malic enzyme 1 (ME1) genes showed higher expression in S group. SCD, ACACA, ME1, and fatty acid synthase (FASN) gene expression levels showed a wide variation across the tested tissues, with much higher expression levels observed in adipose tissue than other tissues. Tissue FA profile and gene expression results support the deposition of dietary FA, the lipogenic effect of dietary saturated fat in liver and the employment of saturated dietary fat for endogenous synthesis of MUFA in all the analyzed tissues.

Dietary energy source largely affects tissue fatty acid composition but has minor influence on gene transcription in Iberian pigs

A trial was performed to compare the effects of different dietary sources of MUFA on the fatty acid (FA) composition, lipid metabolism, and gene transcription in different tissues of Iberian pigs. Twenty-seven Iberian male pigs of 28 kg live weight (LW) were divided in 2 groups and fed with 1 of 2 isocaloric diets: a standard diet with carbohydrates as energy source (CH) and a diet enriched with high-oleic sunflower oil (HO). Ham adipose tissue was sampled by biopsy at 44 and 70 kg LW. At 110 kg LW pigs were slaughtered and backfat, loin, and liver tissues were sampled. Animals of the HO group showed higher MUFA content and lower SFA in all the analyzed tissues (P < 0.001). These main effects were established early during the treatment and increased only slightly along time. Small diet effects were also detected on PUFA, which showed differences according to sampling time, tissue, and lipid fraction. Effects of diet on gene expression were explored with a combined approach analyzing adipose tissue transcriptome and quantifying the expression of a panel of key genes implicated in lipogenesis and lipid metabolism processes in backfat, muscle, and liver. Backfat transcriptome showed small effects of diet on gene expression, in number and magnitude. According to the posterior probabilities (PP) of the probe-specific expression differences between dietary groups (PP < 0.01), 37 genes were considered differentially expressed (DE). Gene ontology allowed relating them with several biological functions including lipid metabolic processes. Quantitative PCR confirmed several DE genes in adipose tissue (RXRG, LEP, and ME1; P < 0.0001, P < 0.05, and P < 0.0001, respectively), but no DE gene was found in loin or liver tissues. Joint results agree with a metabolic adjustment of adipose tissue FA levels by the subtle effect of the diet on the regulation of several lipid metabolism pathways, mainly FA oxidation and prostanoid synthesis, with LEP, RXRG, and PTGS2 genes playing mayor roles.

Adipose triglyceride lipase (ATGL) clone, expression pattern, and regulation by different lipid sources and lipid levels in large yellow croaker (Pseudosciaena crocea R.)

Adipose triglyceride lipase (ATGL) was recently identified as a triglyceride (TG)-specific lipase. In this study, we first obtained from large yellow croaker fish a 1,820-bp (GenBank ID: HQ916211) ATGL cDNA fragment with a 141-bp 5'UTR, a 1,485-bp open reading frame, and a 194-bp 3'UTR. The predicted fish ATGL had 494 amino acids (GenBank ID: ADY89608) and a calculated molecular weight of 55.1 kDa. ATGL was highly expressed in liver and, to a lesser degree, in heart, muscle, and abdominal fat. ATGL gene expression was high at 4.5 g and then decreased at 157.9 g and increased again at 474.2 g. The effects of lipid levels and lipid sources on ATGL expression in vivo were also investigated. A high-lipid diet decreased ATGL expression in fish significantly (P < 0.01). Fish in soybean oil group exhibited significantly lower ATGL expression than fish in the fish oil and beef tallow groups (P < 0.01). These data enhance our understanding of ATGL in fish lipid metabolism.

Feeding docosahexaenoic acid to pigs reduces blood triglycerides and induces gene expression for fat oxidation

Meadus, W. J., Duff, P., Rolland, D., Aalhus, J. L., Uttaro, B., and Dugan, M. E. R. 2011. Feeding docosahexaenoic acid to pigs reduces triglycerides in blood and induces gene expression for fat oxidation in liver and adipose but not in muscle. Can. J. Anim. Sci. 91: 601–612. The essential fatty acids required in diets of humans are linoleic acid (18:2n-6:LA) and α-linolenic acid (18:3n-3: ALA), and these can be elongated and desaturated to form long-chain omega-6 or omega-3, respectively. Even though not considered essential, consumption of long-chain omega-3 fatty acid is recommended for health benefits, including protection against cardiovascular disease. The omega-3 fatty acid, docosahexanoic acid (DHA), was supplemented in pig diets as a dried biomass of the microalgae Schizochytrium to see if there are unique physiological changes associated with DHA feeding. Pigs were fed a diet with 330 mg (low), 3600 mg (medium) or 9400 mg (high) DHA per day for the last 25 d before slaughter at market weight (∼110 kg). Blood triglycerides (TG) were assayed colormetrically and tissue samples were analyzed for gene expression patterns of RNA by quantitative real-time polymerase chain reaction. Fatty acids were analyzed by gas chromatography. Animal performance appeared to increase with DHA, as shown by a 14% improved feed:gain ratio of 2.74±0.27 (P<0.05). Blood triglycerides were reduced significantly from 0.40±0.23 mM to 0.20±0.09 mM. Pigs accumulated 14 times more DHA in their subcutaneous fat (SQ) (10.67 mg g−1) on the high diet compared with the control diet (0.75 mg g−1). Gene analysis showed that the expression of the fat oxidation biomarkers acyl CoA oxidase 1 (ACOX1), peroxisome proliferator-activated receptors alpha (PPARα) and gamma (PPARγ) were stimulated in the SQ and liver. The delta-6 desaturase (D6D) and elongase (Elov5), which are genes involved in the endogenous synthesis of DHA, were unchanged. Fatty acid synthase (FASN) was stimulated in the liver and muscle of pigs on the high DHA diet. Analysis of gene transcription activity suggested fat metabolism was stimulated in the liver and SQ fat, but the genes involved in the endogenous production of DHA remained unchanged.

Changes in texture, colour and fatty acid composition of male and female pig shoulder fat due to different dietary fat sources

Two experiments with 72 slaughter pigs in each were conducted. Entire males and females were individually fed restricted. Palm kernel-, soybean- and fish-oil were used in varying combinations, giving different dietary fat levels (29-80g/kg) and iodine values ranging from 50 to 131. Shoulder fat was analysed for fatty acid composition (inner and outer layer), firmness and colour. A clear dose-response relationship was seen between fatty acids in diets and in shoulder fat. Interestingly, the very long chain n-3 fatty acids seemed to be deposited more efficiently when additional fat was included in the diet. Both high and low dietary iodine values changed towards less extreme iodine values in fat. Low-fat diets enhanced de novo synthesis of fatty acids. Males revealed a higher percentage of PUFA and a lower percentage of C18:1 and MUFA. Fat firmness, but not colour, was influenced by sex and dietary fat source.

Board-invited review: the biology and regulation of preadipocytes and adipocytes in meat animals

The quality and value of the carcass in domestic meat animals are reflected in its protein and fat content. Preadipocytes and adipocytes are important in establishing the overall fatness of a carcass, as well as being the main contributors to the marbling component needed for consumer preference of meat products. Although some fat accumulation is essential, any excess fat that is deposited into adipose depots other than the marbling fraction is energetically unfavorable and reduces efficiency of production. Hence, this review is focused on current knowledge about the biology and regulation of the important cells of adipose tissue: preadipocytes and adipocytes.

Effect of docosahexaenoic acid and arachidonic acid on the expression of adipocyte determination and differentiation-dependent factor 1 in differentiating porcine adipocytes1

Adipocyte determination and differentiation-dependent factor 1 (ADD1) drives the expression of several lipogenic genes in mammals. Polyunsaturated fatty acids decrease ADD1 mRNA abundance in differentiating porcine adipocytes. The current study was designed to explore the mechanisms by which PUFA inhibit the expression of ADD1 in porcine adipocytes. Porcine preadipocytes were differentiated for 24 h with 0 or 100 microM of docosahexaenoic acid (DHA) and mixtures of different concentrations of antioxidants to investigate the effect of DHA and antioxidants on the ADD1 mRNA abundance. We found the relative mRNA abundance was decreased by the addition of 100 microM DHA to the medium for porcine differentiating adipocytes, and adding an antioxidant mixture to the medium prevented part of the decrease in ADD1 mRNA abundance. These data suggest that DHA decreased the steady-state transcription factor ADD1 mRNA through a mechanism related to fatty acid peroxidation. Indeed, adding 7.5 microM vitamin E (a natural antioxidant) also restored the concentrations of ADD1 and fatty acid synthase mRNA, which were decreased by DHA treatment; however, the DHA or the antioxidant treatment did not change the expression of antioxidation genes (superoxide dismutase 1 and glutathione peroxidase 1) in porcine stromal vascular cells. When supplemented with the eicosanoid synthesis pathway inhibitors, the inhibition of the expression of ADD1 by arachidonic acid was partially recovered. These results suggest that the mechanism by which PUFA decrease ADD1 mRNA is due to the metabolic product of eicosanoids and peroxidation of these PUFA.

Regulation of development and metabolism of adipose tissue by growth hormone and the insulin-like growth factor system

White adipose tissue plays a key role in the regulation of the energy balance of vertebrates. This tissue is also now recognized to secrete a variety of factors such as leptin, which is thought to be involved in the modulation of adipose mass. Unlike other tissues, adipose tissue mass has considerable capacity to expand. The review deals primarily on the regulation of development and metabolism of adipose tissue by growth hormone (GH) and the insulin-like growth factor (IGF) system, with a special focus on the pig. The anti-insulin effects of GH are well-documented in pigs as in other species. In vitro exposure of adipose precursor cells to GH leads to a decrease in differentiation of those cells in pigs, in contrast to data obtained in murine cell lines. In vivo treatment and prolonged in vitro incubation of adipose tissue or isolated adipocytes with GH result in a decrease in glucose transport and lipogenesis, especially at the level of the fatty acid synthase gene, resulting in a reduction of the lipid content and adipose tissue mass. The mechanism by which GH antagonizes insulin stimulation of lipogenesis is still unresolved, as it is not mediated by protein kinase A, protein kinase C and Janus kinase-2 at the signaling level, or upstream stimulatory factor 1 or sterol regulatory element binding protein-1 at the transcriptional level. GH is apparently the main regulator of IGF-I mRNA expression in adipose tissue, however, the effects of IGF-I on this tissue are rather unclear.

Role of fatty acids in adipocyte growth and development1,2

Fat is typically added to diets as a source of energy. The alternative aspects considered here are the use of specific fats to alter the fatty acid profile of adipose tissue toward creation of value-added products and the potential for individual fatty acids to alter gene expression and control adipose tissue development. Emphasis is placed on the omega-3 fatty acids, such as those found in fish oil, and on CLA. The most common association of fatty acids with adipose tissue is related to their storage as triglycerides in mature adipocytes and the consequences of excess accumulation in obesity. Fatty acids and their derivatives also can have hormone-like effects and have been be shown to regulate gene expression in preadipocytes, which ultimately effects their proliferation and differentiation. Long-chain, saturated, and polyunsaturated fatty acids have been shown to regulate transcription factors, such as CCAAT/enhancer binding protein, peroxisome proliferator activated receptor, and other adipose-specific genes, very early in adipocyte development. These effects have the potential to affect fat cell number at maturity. Specifically, there is evidence that the fatty acids in fish oil, such as docosahexaenoic and eicosopentaenoic acids, and fatty acids in the CLA series, decrease preadipocyte proliferation in cell lines and reduce adiposity in rodents. There is little direct evidence of the ability of fatty acids to manipulate adipocyte development in non-rodent species. The genetic, nutritional, and pharmacological manipulation of adipose tissue in meat animals has long been of interest to animal scientists. An understanding of the ability of fatty acids to regulate factors such as adipocyte size and number, particularly in meat animals, would be of great interest. The evidence for regulatory roles of fatty acids in development from rodent and in vitro studies and their potential application to meat animals are reviewed.

The effect of dietary docosahexaenoic acid on the expression of porcine lipid metabolism-related genes1

To study the effect of dietary docosahexaenoic acid (DHA) on the expression of adipocyte determination and differentiation-dependent factor 1 (ADD1) mRNA in pig tissues, weaned, crossbred pigs (30 d of age) were fed either 2% (as-fed basis) tallow or DHA oil for 18 d. Body weight of the pigs was not affected by different dietary fatty acid (FA) compositions. The plasma and liver FA composition reflected the composition of the diet. The adipose tissue and skeletal muscle FA composition only partially reflected the diet, indicating either a slower FA turnover or that a greater proportion of the FA in these tissues is from endogenous FA synthesis. The ADD1 is an important transcription factor that modulates transcription of FA synthase to regulate the endogenous FA synthesis in the liver and adipose tissue. The ADD1 mRNA was decreased (P < 0.05) in the liver of DHA-treated pigs compared with that of the tallow-treated pigs. The diets did not have an effect on the ADD1 mRNA in pig adipose tissue. The ADD1 transcript was not detected in pig skeletal muscle. These results indicate that significant enrichment of liver DHA content inhibits the expression of ADD1 mRNA. Such an effect is similar to that reported in porcine differentiating adipocytes cultured with DHA. The liver and muscle acyl CoA oxidase mRNA concentration was increased (P < 0.05) by DHA oil treatment, suggesting that DHA treatment may increase peroxisomal fatty acid oxidation in these two tissues. Our present observations demonstrate that dietary DHA enrichment not only affects tissue DHA concentration but also mildly modifies the expression of genes related to fatty acid metabolism in the porcine liver and skeletal muscle.