Fatty acid composition of several muscles and adipose tissues of pigs fed n-3 PUFA rich diets.

During two months, sixty Pietrain×(Landrace×Large White) finishing pigs (50.7 to 115.2kg live weight) received diets containing various levels of C18:3n-3 from linseed and C22:6n-3 from Schizochytrium microalgae to increase the content of these fatty acids (FA) in their lean and fat tissues. Samples of tissues have been extracted from the carcass at the slaughterhouse. Tissues of pigs fed linseed had the highest C18:3n-3 and C20:3n-3 contents, while the C20:4, C20:5 and C22:6n-3 contents increased in tissues with microalgae diets. Diaphragm was fatter, but contained less monounsaturated FA, total n-6 and n-3 polyunsaturated FA (PUFA) than longissimus thoracis et lumborum and semimembranosus muscles due to their different roles. The leaf fat was the most saturated and monounsaturated tissue, regardless of the diet. Adipose tissues located in extremities contained more n-3 and n-6 PUFA than adipose tissues located in the middle of the carcass. This study showed the existence of a PUFA gradient depending on tissue location.

n-3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction.

In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of muscle mass. The hypothesis that n-3 PUFA, which modulate protein homoeostasis via effects on insulin sensitivity, could contribute to maintain muscle mass during energy restriction was tested in rats fed a high-fat diet (4 weeks) rich in 18 : 1 n-9 (oleic acid, OLE-R), 18 : 3 n-3 (α-linolenic acid, ALA-R) or n-3 long-chain (LC-R) fatty acid and then energy restricted (8 weeks). A control group (OLE-ad libitum (AL)) was maintained with AL diet throughout the study. Rats were killed 10 min after an i.v. insulin injection. All energy-restricted rats lost weight and fat mass, but only the OLE-R group showed a significant muscle loss. The Gastrocnemius muscle was enriched with ALA in the ALA-R group and with LC-PUFA in the ALA-R and LC-R groups. The proteolytic ubiquitin-proteasome system was differentially affected by energy restriction, with MAFbx and muscle ring finger-1 mRNA levels being decreased in the LC-R group (-30 and -20 %, respectively). RAC-α serine/threonine-protein kinase and insulin receptor substrate 1 phosphorylation levels increased in the LC-R group (+70 %), together with insulin receptor mRNA (+50 %). The ALA-R group showed the same overall activation pattern as the LC-R group, although to a lesser extent. In conclusion, dietary n-3 PUFA prevent the loss of muscle mass associated with energy restriction, probably by an improvement in the insulin-signalling pathway activation, in relation to enrichment of plasma membranes in n-3 LC-PUFA.

Maternal 18:3n-3 favors piglet intestinal passage of LPS and promotes intestinal anti-inflammatory response to this bacterial ligand.

We recently observed that maternal 18:3n-3 increases piglet jejunal permeability. We hypothesized that this would favor intestinal lipopolysaccharide (LPS) passage and alter gut immune system education toward this bacterial ligand. Sows were fed 18:3n-3 or 18:2n-6 diets throughout gestation and lactation. In each litter, two piglets were given oral Gram-negative spectrum antibiotic from post-natal day (PND) 14 to 28. All piglets were weaned on a regular diet at PND28. 18:3n-3 piglets exhibited greater jejunal permeability to FITC-LPS at PND28. Levels of 18:3n-3 but neither 20:5n-3 nor 20:4n-6 were greater in mesenteric lymph nodes (MLN) of 18:3n-3 piglets. Jejunal explant or MLN cell cytokine responses to LPS were not influenced by the maternal diet. Antibiotic increased jejunal permeability to FITC-LPS and lowered the level of 20:5n-3 in MLN, irrespective of the maternal diet. At PND52, no long-lasting effect of the maternal diet or antibiotic treatment on jejunal permeability was noticed. 18:3n-3 and 20:4n-6 levels were greater and lower, respectively, in MLN of 18:3n-3 compared to 18:2n-6 piglets. IL-10 production by MLN cells in response to LPS was greater in the 18:3n-3 group, irrespective of the neonatal antibiotic treatment. IL-8 secretion by jejunal explants in response to LPS was lower in antibiotic-treated 18:3n-3 compared to 18:2n-6 piglets. Finally, proportion of MHC class II(+) antigen-presenting cells was greater in 18:3n-3 than 18:2n-6 MLN cells. In conclusion, maternal 18:3n-3 directs the intestinal immune response to LPS toward an anti-inflammatory profile beyond the breastfeeding period; microbiota involvement seems dependent of the immune cells considered.

A review of nutritional effects on fat composition of animal products with special emphasis on n-3 polyunsaturated fatty acids.

The fatty acid composition of animal products (eggs, milk and meat) is the reflect of both the tissue fatty acid biosynthesis and the fatty acid composition of ingested lipids. This relationship is stronger in monogastrics (pigs, poultry and rabbits) than in ruminants, where dietary fatty acids are hydrogenated in the rumen. There is an increasing recognition of the health benefits of polyunsaturated fatty acids (PUFA), because these fatty acids are essential for humans. In addition, the ratio n-6/n-3 fatty acids in the human diet is important. This ratio by far exceeds the recommended value of 5. Therefore, inclusion of fish meals, or n-3 PUFA rich oils, or linseed in animal diets is a valid means of meeting consumer demand for animal products that are nutritionally beneficial. The studies that are undertaken on animals mainly use diets supplemented with linseed, as a source of n-3 fatty acids. The use of linseed diets generally leads to an increased n-3 fatty acid content in animal products (egg, meat, milk) in ruminants and monogastrics. Recent studies have also demonstrated that neither the processing nor the cooking affects the PUFA content of pork meat or meat products. The ability of unsaturated fatty acids, especially those with more than two double bonds, to rapidly oxidise, is important in regulating the shelf life of animal products (rancidity and colour deterioration); however, a good way to avoid such problems is to use antioxidant products (such as vitamin E) in the diet. Some studies also show that it is not necessary to feed animals with linseed-supplemented diets for a long time to have the highest increase in PUFA content of the products. So, short-term diet manipulation can be a practical reality for industry. As the market for n-3 PUFA enriched products is today limited in most countries, other studies must be undertaken to develop this kind of production.

Linseed oil in the maternal diet increases long chain-PUFA status of the foetus and the newborn during the suckling period in pigs.

Linseed oil, being rich in 18 : 3n-3, represents an alternative source of n-3 PUFA in the maternal diet. However, little is known about the effect of this oil on the long chain n-3 PUFA composition of offspring, which are required for normal growth and maturation of numerous organs. The main objective of the experiment was therefore to investigate fatty acid composition of tissues from sows at the end of gestation and from piglets during the first week of postnatal life in response to maternal dietary linseed oil intake. Sows received either a lard (LAR)-based diet or a linseed oil (LSO)-based diet during gestation and lactation. Fatty acid composition was evaluated in sow plasma, placenta and milk, and in different tissues of piglets on days 0, 3, 7, 21 and 32. The LSO diet increased the proportions of n-3 PUFA and especially 22 : 6n-3 in the placenta. The carcass of LSO piglets at birth contained greater proportions of 20 : 5n-3, 22 : 5n-3 and 22 : 6n-3. The LSO sow milk exhibited greater proportions of 18 : 3n-3 compared with the LAR sow milk. The piglets suckling LSO sows had greater proportions of 18 : 3n-3, 20 : 5n-3 and 22 : 5n-3 in plasma and carcass. The proportions of 22 : 5n-3 and 22 : 6n-3 were greater in the brain of LSO piglets than in that of LAR piglets during the suckling period. In conclusion, LSO in the maternal diet during gestation and lactation increases 22 : 6n-3 concentrations in the placenta and in the foetus carcass, and it maintains 22 : 6n-3 concentrations in the brain during the first week of postnatal life.

Linseed oil in the maternal diet during gestation and lactation modifies fatty acid composition, mucosal architecture, and mast cell regulation of the ileal barrier in piglets.

In this study, we investigated the effect of supplementation of the maternal diet with linseed oil [rich in 18:3(n-3)] on fatty acid composition, mucosal architecture, and mast cell regulation of barrier function in piglet ileum. Sixteen sows were fed a lard (LAR)- or a linseed oil (LSO)-based diet during gestation and lactation. Fatty acid composition of maternal RBC at parturition and of milk at d 14 of lactation were determined. Fatty acid composition, villous-crypt structure, and permeability to horseradish peroxidase in Ussing chambers after mast cell degranulation were determined in the ileum of piglets at d 0, 7, and 28. At d 0, 18:3(n-3) and 20:5(n-3) levels were higher, but 22:6(n-3) and 20:4(n-6) levels were lower in both maternal RBC and piglet ileum of the LSO group. Levels of 18:3(n-3) were also higher in the milk of LSO sows. Levels of 18:3(n-3) were higher in LSO piglet ileum at d 7 and 28. Moreover, at d 28, 20:4(n-6) ileal levels tended (P = 0.09) to be lower in LSO than in LAR piglets, in parallel with a lower mRNA expression of Delta5 desaturase. LSO piglets had shorter villi at d 0 and shorter crypts at d 7 compared with LAR piglets. The effect of mast cell degranulation on ileal permeability decreased with age in both groups but reached a minimum sooner in the LSO group (d 7) than in the LAR group (d 28). In conclusion, linseed oil supplementation of the maternal diet profoundly modifies the fatty acid composition, structure, and physiology of the offspring ileum.

Decreased expression of the IGF-II gene during porcine adipose cell differentiation.

IGF-I and IGF-II are known to regulate cell development and recent data suggest a possible role of IGF-II on adipose tissue development. This study was undertaken to examine the IGF system gene expression in porcine differentiating adipocytes. Both adipocytes and stromal-vascular (s/v) cells were isolated from subcutaneous adipose tissue collected from 7-day-old piglets. s/v cells were cultured in chemically defined medium. Compared with isolated adipocytes, IGF-II and IGFBP-5 mRNA levels were very high in freshly isolated s/v cells, whereas IGF-I mRNA levels were lower in s/v cells than in adipocytes. Between day 0 and day 6 of culture, IGF-II and IGFBP-5 gene expression decreased whereas expression levels of late markers of adipocyte differentiation were up-regulated. Cell differentiation was also associated with an increase in the expression of IGF-I, insulin and IGF receptor genes. The current findings suggest that IGF-I and IGF-II have different effects on porcine adipose cell development.

Follow-up of GK rats during prediabetes highlights increased insulin action and fat deposition despite low insulin secretion.

The adult Goto-Kakizaki (GK) rat is characterized by impaired glucose-induced insulin secretion in vivo and in vitro, decreased beta-cell mass, decreased insulin sensitivity in the liver, and moderate insulin resistance in muscles and adipose tissue. GK rats do not exhibit basal hyperglycemia during the first 3 wk after birth and therefore could be considered prediabetic during this period. Our aim was to identify the initial pathophysiological changes occurring during the prediabetes period in this model of type 2 diabetes (T2DM). To address this, we investigated beta-cell function, insulin sensitivity, and body composition in normoglycemic prediabetic GK rats. Our results revealed that the in vivo secretory response of GK beta-cells to glucose is markedly reduced and the whole body insulin sensitivity is increased in the prediabetic GK rats in vivo. Moreover, the body composition of suckling GK rats is altered compared with age-matched Wistar rats, with an increase of the number of adipocytes before weaning despite a decreased body weight and lean mass in the GK rats. None of these changes appeared to be due to the postnatal nutritional environment of GK pups as demonstrated by cross-fostering GK pups with nondiabetic Wistar dams. In conclusion, in the GK model of T2DM, beta-cell dysfunction associated with increased insulin sensitivity and the alteration of body composition are proximal events that might contribute to the establishment of overt diabetes in adult GK rats.

Does overfeeding enhance genotype effects on energy metabolism and lipid deposition in breast muscle of ducks?

We evaluated the effects of genotype (Muscovy, Pekin and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 weeks of age vs ad libitum feeding) on energy metabolism and lipid deposition in breast muscle of ducks. Samples of breast muscle (Pectoralis major) were collected at 14 weeks of age from 8 birds per group. Overfeeding induced an accumulation of lipids in breast muscle (1.5- to 1.7-fold, depending on genotype) mainly induced by triglyceride deposition. It also induced a considerable increase in the amounts (expressed as g/100 g of tissue) of saturated and mono-unsaturated fatty acids (SFA, MUFA), while the amounts of poly-unsaturated fatty acids (PUFA) remained unchanged in hinny and Muscovy ducks or slightly increased in Pekin and mule ducks. In breast muscle, overfeeding decreased the activity of the main enzymes involved in lipogenesis from glucose (glucose-6-phosphate dehydrogenase, G6PDH, malic enzyme, ME, acetyl CoA carboxylase, ACX). Lipoprotein lipase (LPL) activity in Pectoralis major muscle was also significantly decreased (-21%). The ability of muscle tissues to catabolize long-chain fatty acids, as assessed by beta-hydroxyacyl CoA dehydrogenase (HAD) activity, was increased in Pectoralis major muscle, as was cytochrome-c oxidase (COX) activity. Hybrid and Pekin ducks exhibited higher levels of ACX and LPL activity in Pectoralis major muscle than Muscovy ducks, suggesting a greater ability to synthesise lipids in situ, and to take up circulating lipids. Total lipid content in breast muscle of hybrid and Pekin ducks was higher than in that of Muscovy ducks. In hybrid and Pekin ducks, lipid composition of breast muscle was characterized by higher amounts of triglycerides, SFA and MUFA than in Muscovy ducks. Finally, oxidative metabolism was greater in Pectoralis major muscles of hybrid and Pekin ducks than in Muscovy ducks, suggesting an adaptative strategy of muscle energy metabolism according to lipid level.

Does overfeeding enhance genotype effects on liver ability for lipogenesis and lipid secretion in ducks?

We evaluated the effects of genotype (Muscovy, Pekin and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 weeks of age vs ad libitum feeding) on liver ability for lipogenesis and lipid secretion in ducks. Samples of liver and blood were collected at 14 weeks of age from 8 birds per group. Plasma levels of insulin was considerably increased in overfed ducks (1.9-fold), stimulating the hepatic activity of the main enzymes involved in lipogenesis from glucose (glucokinase, GK, glucose-6-phosphate dehydrogenase, G6PDH, malic enzyme, ME, acetyl CoA carboxylase, ACX), while cytochrome-c oxidase (COX) activity, indicating overall oxidation ability of energy-yielding substrates, remained unchanged. Plasma levels of triglycerides, phospholipids and total cholesterol were therefore increased (1.9, 3.7, 1.6 and 1.6-fold, respectively). Glycaemia also significantly increased (+8%). Pekin ducks exhibited higher levels of GK and G6PDH activity in the liver than Muscovy ducks, suggesting a greater ability to use glucose consistent with their lower glycaemia. Muscovy ducks had greater ACX activity, suggesting greater ability to synthesise lipids. However, plasma lipid levels were much higher in Pekin ducks than in Muscovy ducks, suggesting a greater ability to export lipids from the liver. Values for the different criteria measured in this study were intermediate or similar in hinny and mule ducks to those of parental species. The high values for GK, G6PDH, ME and ACX activity in hybrid ducks enabled them to produce heavy fatty livers with the same chemical and lipid composition as Muscovy ducks and characterised by high amounts of triglycerides (around 96% of total lipids), and saturated and mono-unsaturated fatty acids.

Gender-related response of lipid metabolism to dietary fatty acids in the hamster.

Gender and dietary fatty acids are involved in the regulation of lipid metabolism, disturbances of which can lead to pathologies such as metabolic syndrome or CVD. Possible interactions between these factors were investigated in male and female hamsters fed diets rich in either saturated fatty acids ( "butter" diet) or in alpha-linolenic acid ( "linseed oil" diet). Gender effect predominated over the diet effect on cholesterol (CH) metabolism; compared to males, females exhibited lower concentrations of plasma total CH (-20 %, P<0.001), LDL-CH (-40 %, P<0.001) and HDL-CH (-16 %, P<0.001), together with higher LDL receptor (+40 %) and lower HDL receptor (-60 %) hepatic content. Triacylglycerol (TG) metabolism was affected by diet above all: compared to animals fed the "butter" diet, those fed the "linseed oil" diet exhibited lower plasma (-23 %, P=0.046) and liver TG (-20 %, P=0.026) concentration which may result from both an increased beta-oxidation (P<0.001), without any change in PPARalpha mRNA, and a decreased hepatic lipogenesis (P=0.023), without increased sterol response element binding protein 1c (SREBP1c) mRNA. The response to diet was much more pronounced in males than in females, without gender effect on the transcription level of PPARalpha and SREBP1c. Finally, the "linseed oil" diet decreased the insulin resistance index (-80 %, P<0.001) with a more marked effect in males, in relation to their higher hepatic PPARgamma expression (+90 %, P=0.012). In conclusion, in our model, the response of either TG or CH to dietary fatty acids is modulated differently by gender. The possible relevance of these interactions to dietary practice should be taken into account in man.

Deposition of dietary fatty acids and of de novo synthesised fatty acids in growing pigs: effects of high ambient temperature and feeding restriction.

Predicting aspects of pork quality becomes increasingly important from both a nutritional and a technological point of view. Little information is, however, available concerning the quantitative relation between nutrient intake and fatty acid (FA) deposition at the whole-animal level. In this study, eight blocks of five littermate barrows were used in a comparative slaughter trial. At 24 kg body weight (BW), one pig from each litter was slaughtered to determine the initial FA composition. The other littermates were assigned to one of four feeding levels (ranging from 70 % to 100 % of intake ad libitum) and were given a diet containing 0.36 g/kg lipid and 0.22 g/kg FA. The temperature for each block was maintained at either 23 or 30 degrees C. At 65 kg, the pigs were slaughtered and the body lipid and FA composition was determined. Seventy per cent of the digested n-6 FA and 50 % of the n-3 FA were deposited. The average composition of de novo synthesised FA corresponded to 1.7, 30.3, 2.4, 19.7 and 45.9 % for 14 : 0, 16 : 0, 16 : 1, 18 : 0 and 18 : 1 FA, respectively. At 23 degrees C and for feeding ad libitum, 33 % of 16 : 0 FA was deposited, 1.7 % shortened to 14 : 0, 63 % elongated to 18 : 0 and 2.8 % unsaturated to 16 : 1. Twenty-eight per cent of 18 : 0 FA was deposited and 72 % unsaturated to 18 : 1. At 30 degrees C, 18 : 0 FA desaturation was reduced by 3.5 %. Feed intake and temperature independently affected the elongation of 16 : 0 FA. A reduction in feed intake increased the elongation rate, whereas the increase in temperature reduced the elongation rate.

Dose effect of alpha-linolenic acid on lipid metabolism in the hamster.

In order to meet dietary requirements, the consumption of alpha-linolenic acid (ALA, 18:3 n-3) must be promoted. However, its effects on triglyceride (TG) and cholesterol metabolism are still controversial, and may be dose-dependent. The effects of increasing dietary ALA intakes (1%, 10%, 20% and 40% of total FA) were investigated in male hamsters. ALA replaced oleic acid while linoleic and saturated FA were kept constant. Triglyceridemia decreased by 45% in response to 10% dietary ALA and was not affected by higher intakes. It was associated with lower hepatic total activities of acetyl-CoA-carboxylase (up to -29%) and malic enzyme (up to -42%), which were negatively correlated to ALA intake (r(2) = 0.33 and r(2) = 0.38, respectively). Adipose tissue lipogenesis was 2-6 fold lower than in the liver and was not affected by dietary treatment. Substitution of 10% ALA for oleic acid increased cholesterolemia by 15% but, as in TG, higher ALA intakes did not amplify the response. The highest ALA intake (40%) dramatically modified the hepatobiliary metabolism of sterols: cholesterol content fell by 45% in the liver and increased by 28% in the faeces. Besides, faecal bile acids decreased by 61%, and contained more hydrophobic and less secondary bile acids. Thus, replacing 10% oleic acid by ALA is sufficient to exert a beneficial hypotriglyceridemic effect, which may be counteracted by the slight increase in cholesterolemia. Higher intakes did not modify these parameters, but a very high dose resulted in adverse effects on sterol metabolism.

Effect of genotype and overfeeding on lipid deposition in myofibres and intramuscular adipocytes of breast and thigh muscles of ducks.

We conducted a study to evaluate the effects of genotype (Muscovy, Pekin and their crossbred, hinny and mule) and overfeeding (14 days from 12 weeks of age) on lipid deposition in myofibres and intramuscular adipocytes of breast and thigh muscles of ducks. Birds of the four genotypes were also reared contemporaneously with a growing diet distributed ad libitum. Muscle samples (Pectoralis major and Sartorius) were collected at 14 weeks of age on 8 ducks per treatment. The muscle fibre typing, the total lipid and triglyceride contents in myofibres and the relative surface occupied by adipocytes on the cross-sectional area of the muscles were determined by histological and image analysis. Overfeeding induced a marked increase of body weight but had no significant effect on the muscle weight, the cross-sectional area (CSA) of myofibres and the muscle typology. In muscles, overfeeding induced a large accumulation of lipids, mainly in adipocytes whose relative surface increased 1.5 fold in P. major and 2.1 fold in Sartorius and an increase in triglyceride content of fast twitch oxydo-glycolytic and glycolytic fibres in P. major only (+ 37 and + 16% respectively). Genotype had no significant effect on the muscle typology. By comparison with the other genotypes, Muscovy ducks exhibited the highest body weight, the highest muscle weight which could partly be explained by the highest fibre CSA and the lowest intramuscular fat content in adipocytes and myofibres (only fast twitch oxydo-glycolytic fibres in P. major). We observed the reverse situation for the Pekin ducks. The crossbred ducks always presented intermediate values except for body weight.

Effect of dietary fats on hepatic lipid metabolism in the growing turkey.

The influence of dietary fatty acids on hepatic capacity of lipid synthesis and secretion was investigated in 7-week-old male turkeys. They were fed 10% of either lard (rich in saturated and monounsaturated fatty acids) or linseed oil (rich in polyunsaturated fatty acids, especially 18:3n-3). Fattening was identical with both diets (0.15-0.20% of abdominal adipose tissue), but the proportion of muscle Pectoralis major was lower with linseed oil (6.6 vs. 7.4%). Specific activities of lipogenic enzymes (ME, G6PDH, ACX, and Delta9-desaturase) were not influenced by the diet, however, FAS activity was lower with linseed oil (14.3 vs. 25.4 nM NADPH fixed/min). Fasting concentrations of lipoproteins synthesized and secreted by the liver, VLDL and HDL, were also lower with linseed oil, as well as plasma concentrations of phospholipids and cholesteryl esters. However, when VLDL catabolism was inhibited by injection of an antiserum against LPL, VLDL concentration was identical in both groups (100-120 mg/l), whereas that of phospholipids and cholesteryl esters, that are transported by HDL mainly, remained lower with linseed oil. Thus, in the growing turkeys, and contrary to mammals and the chicken, feeding n-3 polyunsaturated fatty acids did not decrease hepatic triglyceride synthesis and secretion, nor fattening. By contrast, in this species, n-3 polyunsaturated fatty acids appear to influence mostly HDL metabolism, with a negative impact on muscular growth.