Intramuscular Lipid Research Articles

Pathways for metabolic fuels and oxygen in high performance fish

This paper gives an overview of oxidative fuel metabolism in swimming fish, and known or potential modifications occurring in high-performance species are explored. Carbohydrate catabolism is the only source of ATP for sprint swimming where locomotory muscles operate as closed systems. In contrast, this substrate only plays a very minor role in prolonged swimming. Glucose fluxes have been measured in vivo in several species, but mainly at rest and with somewhat questionable methodologies. High-performance species may be able to sustain higher maximal glucose fluxes that their sedentary counterparts by: a) upregulating gluconeogenesis, b) increasing glucose transporter density or V max of individual transporters, c) storing larger amounts of glycogen in liver and muscle, and d) increasing muscle hexokinase activity. Even though lipids represent a much more important source of energy for sustained swimming, their fluxes have not been measured in vivo , even at rest, probably because of their diversity and complex chemistry. Except for elasmobranchs who do not possess plasma proteins for lipid transport, high-performance fish should be able to sustain high maximal lipid fluxes by: a) elevating lipolytic capacity, b) increasing rates of circulatory lipid transport through modified plasma proteins, c) augmenting intramuscular lipid reserves, and d) upregulating capacity for lipid oxidation in locomotory muscle mitochondria. The quantitative assessment of amino acid oxidation in swimming fish is a priority for future research because protein is probably a dominant metabolic fuel in most swimming fish. Finally, we predict that high-performance species should use proportionately more proteins/lipids and less carbohydrates than low-aerobic fish. Also, and similarly to endurance-adapted mammals, high-performance fish should increase their relative reliance on intramuscular fuel reserves and decrease their relative use of circulatory fuels.

Comparison of factors affecting the tenderness of pigmeat

Tenderness is probably the most important aspect of eating quality in pigmeat although recent industry trends towards leaner carcasses and faster processing times may have tended to reduce it. Two major biological characteristics affecting tenderness are the concentration of intramuscular lipid (marbling fat) and the activity of proteolytic enzymes. This study has compared different levels of three factors which are known to affect these characteristics i.e. breed, feeding level and meat conditioning time. The aim was to contrast production and processing effects on tenderness and provide more information on how it can be controlled.

Comparison of factors affecting the tenderness of pigmeat

Tenderness is probably the most important aspect of eating quality in pigmeat although recent industry trends towards leaner carcasses and faster processing times may have tended to reduce it. Two major biological characteristics affecting tenderness are the concentration of intramuscular lipid (marbling fat) and the activity of proteolytic enzymes. This study has compared different levels of three factors which are known to affect these characteristics i.e. breed, feeding level and meat conditioning time. The aim was to contrast production and processing effects on tenderness and provide more information on how it can be controlled.

Effect of muscle type and food deprivation for 24 hours on the composition of the lipid fraction in muscles of Large White pigs

The present study was designed to examine the lipid composition of a predominantly glycolytic ( M. longissimus lumborum, LL) and a predominantly oxidative ( M. semispinalis capitis, SC) muscle sampled at slaughter from Large White pigs fed or deprived of food for 24 h. The intramuscular lipid content was almost four-fold higher in the red SC than in the white LL. When expressed on a muscle tissue basis, the results indicated that the LL had significantly lower amount of tri-, di- and monoglycerides, free fatty acids, cholesterol and phospholipids than the SC. In both muscles, phosphatidylcholine represented the major constituent of the phospholipid fraction. The difference in phospholipid content between the LL and the SC was significant only for cardiolipin, phosphatidylethanolamine and phosphatidylinositol. When expressed on total lipid basis, the results showed that the SC contained significantly lower amount of phospholipids and higher amount of triglycerides than the LL, thus suggesting that the influence of muscle type on the content of intramuscular lipid was primarily due to a difference in the amount of triglycerides. Food deprivation for 24 h resulted in a significantly higher content of free fatty acids, as expressed on a muscle tissue basis, in both muscles. Relative to total lipid, food deprivation resulted in increased levels of free fatty acids and monoglycerides only in the LL. These results suggest that food deprivation for 24 h induced lipolysis in muscle, as evidenced by a modification in the relative composition of the neutral lipid fraction, but that this effect was muscle-dependent.

Distribution of intramuscular lipid throughout M. longissimus thoracis et lumborum in Japanese Black, Japanese Shorthorn, Holstein and Japanese Black crossbreds

Intramuscular lipid content of M. longissimus thoracis et lumborum was determined at five locations within the ribeye muscle from 267 Japanese Black, Japanese Shorthorn, Holstein and Japanese Black crossbred steers and heifers or cows in order to investigate the distribution of marbling. Breed was a highly significant ( P < 0·001) source of variation for amount of marbling at each of the locations measured. Percentage of lipid was higher at the extremities of the muscle than in the middle part and was not affected by sex at any location except for opposite the 6th rib ( P > 0·05). Regression equations were derived which relate the percentage of lipid at various locations within M. longissimus thoracis et lumborum to that opposite the 6th rib. A substantial portion of the variation in marbling observed at the other locations could be accounted for by marbling at the 6th rib ( R 2 = 0·73−0·90). These data confirm that marbling varies within the ribeye muscle but suggest that it is rather consistent in the distribution pattern exhibited by Japanese Black cattle and their crosses.

Effects of grass versus grain on polyunsaturated fatty acids of intramuscular lipids in the lamb

Effects of grass versus grain on polyunsaturated fatty acids of intramuscular lipids in the lamb

Body traits and chemical composition of muscle in the common carp ( Cyprinus carpio L.) as influenced by age and rearing environment

To investigate body traits and muscle chemical composition in common carp as influenced by age and rearing environment, 2000 fry were stocked in two earthen ponds (300 m 2): warm (W), with warm water (refluent from a thermal power station) at about 10 °C above natural temperature, and natural (N), with water from Lake Trasimeno. Because of the different growth rate, W subjects were sampled 3 times (at 12, 15 and 18 months of age) while N-subjects were sampled only once (at 15 months of age). The W 12-month-old fish weighed on average 102 g while N-fish did not reach this weight even at 15 months. At this age, the W subjects showed, in comparison with N-subjects, higher body weight (143 vs. 85 g), component weights, linear measurements (20.94 vs. 17.8 cm), fins (1.80 vs. 1.63g) and filleting remnants (12.80 vs. 11.25%) and lower incidence of skin and head index; no differences resulted in proximate analysis, but muscles of W-fish were richer in saturated fatty acid and in n − 3 PUFA content and showed a higher n-3 n-6 PUFA ratio. By comparison with the 15-month-old subjects collected in October 1992, the 12-month-old W-subjects, collected in July 1992, showed lower fin (0.59 vs. 1.8%), viscera (7.6 vs. 10.2 %) and head (20.36 vs. 22.92%) percentages but higher gill (4.27 vs. 3.24%), filleting remnant (14.99 vs. 12.80%), skin (3.92 vs. 3.37%) and dressing (92.4 vs. 89.79%) percentages. The 18-month-old W-subjects, collected in January 1993, did not differ significantly from the 15-month-old subjects either in body weight (154 vs. 143 g) or in the other traits studied, excluding the incidence of viscera (12.01 vs. 10.21%) and gills (2.69 vs. 3.34%), respectively, in the older subjects. Intramuscular lipid content decreased from July according to a seasonal trend. Allometric coefficient showed tachyauxesis for viscera, pectoral and pelvic fins, skin and total muscle and bradyauxesis for filleting remnants and head.

Effects of grass versus grain on polyunsaturated fatty acids of intramuscular lipids in the lamb

Effects of grass versus grain on polyunsaturated fatty acids of intramuscular lipids in the lamb

Morphological characteristics and chemical composition of muscle in the mirror carp ( Cyprinus carpio var. specularis) as influenced by body weight

The evolution of morphological traits and muscle chemical composition during growth was analysed by allometric or normal regression (on body weight or total length or total lipid) utilizing a preliminary series of data obtained from mirror carps ranging from 39 to 2776 g body weight. The fish came from earthen ponds fed with warm water (refluent from a thermal power station) at about 10 °C above natural temperature. As regards allometric coefficients of components on body weight, gills (0.70) and filleting remnants (0.85) were the earliest growing while viscera (1.18) and skin (1.11) were the latest. Isoauxesis resulted for fins, excluding pelvic fins that were later growing (1.08). As regards relative growth of lengths and thicknesses on total body length, head length (0.82) was the earliest and abdomen (1.15) and trunk lengths (1.12) were the latest growing; all body thicknesses showed tachyauxesis, particularly on the hind-portions. As regards the chemical composition of muscle, cholesterol (mg/100 g) and the C20:4 and C22:6 percentages showed a linear decreasing trend with increasing body weight, while the opposite resulted for C18:1, SFA and MUFA content. Lipid, C16, C16:1, C20:5 and n − 3 PUFA content presented a decreasing trend followed by an increase, while C18:2 and n − 6 PUFA content showed the opposite behaviour. Intramuscular lipid content influenced the chemical composition of muscle: as lipid content increased, C18:1 also increased, while C18:2 and n − 3 PUFA decreased; C14, C16:1 and MUFA showed an increasing trend followed by a decreasing phase, while C16, C18, C20:4, C22:6, SFA and n − 6 PUFA showed the opposite.

Comparison of five types of pig crosses. II. fresh meat quality and sensory characteristics of dry cured ham

Carcasses of 109 gilts and 119 barrows from crosses including Duroc (DU), Landrace (LR), Large White (LW) and Belgian Landrace (BL) components were used to analyze their meat quality. The crosses were DU × (LR × LW), LW × (DU × LW), LW × (LR × LW), BL × (DU × LW), and BL × (LR × LW). Muscle pH and electrical conductivity were measured in the Longissimus dorsi (LD) and Semimembranosus muscles. Colour, water holding capacity, intramuscular lipid content, total protein and water content was determined on LD muscle. A sample of 32 right hams from each cross were dry-cured. The cushion (which includes the muscles Biceps femoris, Semimembranosus and Semitendinosus) was used for panel and consumer tests. There were no differences in meat quality traits related to PSE condition between DU and LW sired pigs, but BL sired pigs showed a poorer meat quality. Intramuscular fat content was higher in the DU sired pigs. Texture of hams produced by DU sired pigs and BL × (LR × LW were judged softer and more pastier. There were no significant differences between crosses in flavour characteristics. Consumer acceptability was better in LW and DU sired pigs. The DU dam genes in the BL sired pigs improved overall acceptability of the ham with respect to BL × (LR × LW), classified as the poorest ham.

Effects of nutritional planes and brees on intramuscular-lipid deposition in M. longissimus dorsi of steers

The influences of nutritional planes and breeds on intramuscular-lipid (IML) deposition in M. longissimus dorsi were investigated by comparing the relationships between intramuscular lipid percentages (IMLP) in the muscle and side-carcass weight (SCW), carcass-fat percentage (CFP), and slaughter age (SA). Japanese Black (JB) and Japanese Shorthorn (JS) steers were fattened under two (medium-high and high) nutritional planes, which were different only in JB and when the adjusted IMLPs were compared on the basis of SCW or CFP. Breed effects on IML deposition were investigated by using three pure breeds and four crossbred-steer groups. The means of IMLPs in the muscle adjusted to three criteria were significantly different among breeds, the IMLPs of JB and their backcrosses being higher than those of JS and Charolais crosses. IML deposition in steers was highly dependent on the genetic potential of the breeds or bulls used.

Time-related changes in intramuscular lipids of French dry-cured ham

The aim of this study was to investigate the changes in intramuscular lipids during the processing of French dry-cured hams. In the fresh biceps femoris muscle, the lipid content was on average, 105 mg/g DM with a large individual variation. Glycerides accounted for about 75% of total lipids. During processing for 273 days, phospholipid content decreased markedly whereas free fatty acid content rose from 1·9 mg/g DM to 9·4 mg/g DM. Little change affected the fatty acid composition of both glycerides and phospholipids during processing. After a decrease in the proportion of polyunsaturated fatty acids during the first 2 months, free fatty acid composition remained stable. The results suggest that lipid alteration during dry-curing of hams is due to lipolysis and that lipid oxidation is limited.

Relationship between Japanese beef marbling standard and intramuscular lipid in the M. longissimus thoracis of Japanese Black and American Wagyu Cattle

Japanese Black and American Wagyu steers (n = 155) were slaughtered and graded under typical Japanese production conditions, and then analyzed for percentage ether-extractable fat at the 6th thoracic vertebra. The percentage of intramuscular lipid was used to develop a prediction equation for the Japanese beef marbling standard (BMS) with R 2 = 0·7619.

Effects of clover in the diet of grazed lambs on production and carcass composition

AbstractThe effect of grazing clover on ewes and lambs was studied using nitrogen-fertilized grass (G) and grass/white clover pastures (GC) containing proportionately 0·18 clover. Carcasses of lambs grazed on GC were significantly heavier than carcasses of lambs grazed on G pastures. An interaction with weaning occurred. Carcasses from lambs grazed on GC for 53 days post weaning were 2·3 kg heavier (F &lt; 0·01) but lambs slaughtered at weaning had similar carcass weights. Diet had no effect on relative joint components of carcasses. The effect of clover in the diet on carcass weight was attributed to higher levels of protein retention.Analysis of the fatty acid composition of intramuscular and subcutaneous and perirenal lipids indicated small but significant effects of diet. Lean tissue lipids of lambs grazing clover showed significant increases in C18:2 and reduced C20: 5 fatty acids. In tissue fats there were small increases in C14:0, C16:0 and C18:2 with reduced C18:1 content.Twin suckled lambs grazing GC for 94 days from turn-out in early April showed increased live-weight gain over lambs on G of 336v.287 g/day (s.e.d. 84;P&lt; 0.001). Post weaning live-weight gain of lambs was 173 and 221 g/day on G and GC respectively. Sward height was maintained at 5.18 and 5.24 (s.e.d. 0.075) cm on G and GC paddocks by adjusting ewe numbers. GC pastures carried proportionately 0.82 of the stock on G pastures but output of lamb was similar at 1289 and 1247 kg/ha for G and GC respectively.Results showed that the production penalty of lower stocking rate associated with grass/cloverv.grass fertilized with 190 kg nitrogen per ha was ameliorated by higher lamb live-weight gain and carcass weight without change in joint composition or nutritionally significant change in fatty acid composition of carcass tissues.

The effects of changes in plasma nonesterified fatty acid levels on oxidative metabolism during moderate exercise in patients with non-insulin-dependent diabetes mellitus

Blood levels of intermediary metabolites were measured and indirect calorimetry was performed in 10 otherwise healthy, non-insulin-dependent diabetic (NIDDM) patients before, during, and after 30 minutes of moderate exercise on three occasions in random order at weekly intervals with (1) heparin treatment to increase preexercise plasma nonesterified fatty acid (NEFA) levels (HEPARIN); (2) acipimox, a nicotinic acid analogue, to reduce preexercise plasma NEFA levels (ACIPIMOX); and (3) no manipulation of preexercise plasma NEFA levels (NIL). With ACIPIMOX, preexercise blood levels were significantly reduced for NEFAs and glycerol ( P < .01) and marginally reduced for acetoacetate and 3-hydroxybutyrate (NS) compared with preexercise levels for the other two treatments; these low levels seen with acipimox treatment increased only slightly during exercise and the postexercise period. Plasma NEFA levels increased by approximately 150% ( P < .001) with HEPARIN at the same times. The levels of ketone bodies during either NIL or HEPARIN increased rapidly postexercise by approximately 90% to 110% for both acetoacetate and 3-hydroxybutyrate (both P < .01). Plasma insulin levels tended to be lowest (despite similar plasma glucose levels during the three treatments) with ACIPIMOX, while growth hormone (hGH) and, perhaps, noradrenaline levels were highest both during and after exercise. The respiratory quotient (RQ) was highest with ACIPIMOX ( P < .05 for exercise and postexercise periods compared with the other two treatments), which, compared with NIL, reduced fat oxidation by 27% and 60% and increased carbohydrate oxidation by 29% and 74% during and after exercise, respectively (all P < .05). These changes in substrate oxidation due to ACIPIMOX were almost opposite to those observed with HEPARIN. The increased fat oxidation with exercise during NIL (800%; P < .001 compared with preexercise value) was likely due to increased NEFA supply from the 700% exercise-induced increase in the leg blood flow. In contrast, the 340% increase in NEFA supply with ACIPIMOX could not have accounted for the 900% increase in fat oxidation during exercise ( P < .001 compared with preexercise). It is thus likely that alternative (eg, intramuscular) lipid pools are mobilized for oxidative metabolism during exercise with reduced plasma NEFA levels due to ACIPIMOX, and may constitute an adaptive response. These results support the glucose/fatty acid cycle, albeit in the converse, ie, reduced NEFA availability improves glucose oxidation, and are of likely benefit to the diabetic patient.

Performance, plasma hormones, histochemical and biochemical muscle traits, and meat quality of pigs administered exogenous somatotropin between 30 or 60 kilograms and 100 kilograms body weight.

Forty-five Large White barrows were injected daily i.m. with either excipient from 30 to 100 kg BW (CTRL), excipient from 30 to 60 and porcine somatotropin (pST; 100 micrograms/kg BW) from 60 to 100 kg BW (pST-60), or pST (100 micrograms/kg BW) from 30 to 100 kg BW (pST-30). Somatotropin accelerated overall growth rate (+4 and +9% for pST-60 and pST-30, respectively), increased longissimus (+10.3 and +14.7%) and semitendinosus (+17 and +13%) muscle weights, and decreased backfat (-49 and -58%) and leaf fat (-49 and -53%) weights. The administration of pST resulted in a similar increase in muscle fiber size for all fiber types in both longissimus (LM) and semispinalis (SS) muscles (+21%). Somatotropin had otherwise little effect on muscle fiber types and biochemical traits of LM, whereas dramatic changes were observed in SS. The relative area occupied by Type IIB fibers was increased (+22 and +29%) and that of Type I fibers was decreased (-10 and -15%). In pST-30 animals, myosin ATPase activity (+15%) and native myosin fast isoform proportion (+10%) were augmented, and energy metabolism was more glycolytic (lactate dehydrogenase: +25%) and less oxidative (citrate synthase: -13%; beta-hydroxyacyl-CoA dehydrogenase: -21%). Compared to CTRL animals, administration of pST increased muscle water concentration (LM: +.8 and +1.1%: SS: +3.3 and +3.3%) and decreased intramuscular fat (LM: -29 and -27%; SS: -39 and -50%). The pH measured 45 min and 24 h postmortem, glycogen content, reflectance, and index of light diffusion were mostly not affected by pST treatment. In conclusion, pST had a very favorable effect on growth performance without any important effect on meat quality traits except for the reduction in intramuscular lipid content. The results indicated that the effects of pST on muscular histochemical and biochemical characteristics were different in LM and SS muscles.

Comparison of the Duroc and Large White as terminal sire breeds and their effect on pigmeat quality

AbstractThe experiment examined the effect of breed, diet and sex on pig performance and carcass quality. Eight sires of the Duroc and Large White breeds each produced four experimental litters. Two boar and two female pigs from each litter were reared under standard conditions to 38 kg and then one of each sex was allocated to each of two finishing diets. These were cereal-based diets with and without 16 g/kg soya oil. Following slaughter at 80 kg, loin chops taken from half of the pigs (two litters per sire) were subjected to detailed investigation of physical, chemical and organoleptic characteristics. Lifetime live-weight gain was similar for both breeds but Duroc-sired pigs had greater voluntary food intakes and poorer food conversion efficiencies in the finishing stage. They also had greater killing-out proportions (775 v. 755 g/kg, P &lt; 0·001) and backfat thickness at slaughter (284 v. 27·2 mm at P1 + P3, P &lt; 0·05). Fat firmness measured by penetrometer at 4°C was lower in Duroc-sired pigs (738 v. 792 units, P &lt; 0·001). The proportion of extractable intramuscular lipid was greater in chops from Duroc-sired pigs (13·8 v. 10·4 g/kg, P &lt; 0·001). There were no significant effects of breed or diet on the eating quality of the grilled chops as assessed by a trained taste panel and a consumer panel.

Relationships among allozyme heterozygosity, morphology and lipid levels in house sparrows during winter

House sparrows (Passer domesticus) were collected during cold (43 individuals) and warm (31 individuals) periods in February 1982 from farms near Lawrence, Kansas. Fat scores (from flank, rump and furcula) and body mass were measured from the carcasses, which were then reduced to skeletons. Heterozygosity was determined by electrophoresis of three polymorphic allozymes. Pectoral lipid content was determined by petroleum ether extraction. Principal component (PC) analysis was conducted on 14 skeletal measurements. Summed fat score, body mass and pectoral lipid content served as dependent variables in three multiple regressions. Sex, period (cold versus warm), number of heterozygous loci (0–3), and scores of PCI, PC2 and PC3 were independent variables. Each of the dependent variables was also included as an independent variable in regressions in which they were not the dependent variable. Pectoral lipid content was significantly related only to the number of heterozygous loci (R2= 0.18, P= 0.008). Summed fat score differed between sexes and periods (P= 0.012 and 0.001, respectively) when body mass was included in the regression (P &lt; 0 001). Body mass was related to summed fat score as above, and also to body size (PCI, P &lt; 0.0001) and period (P= 0.014). Females exhibited a positive regression between body size and summed fat score (P= 0.007). Body size (PCI) was greater for both sexes in the sample from the warm period (P= 0.022), suggesting that selection for increased body size may have occurred. Increased metabolic efficiency of heterozygous enzymes or individuals is suggested as an explanation for the observed relationship between heterozygosity and intramuscular lipid level.

Effects of exogenous porcine somatotropin (pST) administration on pork meat quality

Two experiments were conducted on Large White pigs in order to assess the effect of porcine somatotropin (pST) administration upon meat quality criteria. No clear trend was observed concerning pH1 or pH2 measurements in Longissimus dorsi (LD), Adductor femoris (AF) and Semi spinalis (SS) muscles or drip loss in LD. Cooking loss in LD was not affected by pST treatment. Intramuscular lipid content was decreased by pST in LD and AF. Only non-polar lipids were affected by pST, whereas polar lipid content was similar in control and pST treated pigs. Percentage polyunsaturated fatty acids was significantly increased by pST in backfat and LD lipids, whereas no clear trend was observed concerning fatty acid composition of AF lipids.

Energy metabolism and fuel utilization

1) Total energy expenditure during marathon training and competition is among the highest reported for any endurance activity. 2) Although training intensity for the marathon may vary between 60-125% of maximal physical working capacity, elite runners must run consistently at about 80-90% of VO2max in order to achieve successful competitive performances. 3) Earlier studies demonstrated that carbohydrate was the preferential fuel for endurance exercise, but more recent studies have suggested a greater role for lipids than previously thought. Also, proteins may contribute as much as 5-10% of the total energy to a marathon performance. 4) The preponderance of Type I and IIA skeletal muscle fibers among marathon runners and their significantly improved storage capacity for intramuscular lipids and increased mitochondrial density may account for increased reliance on oxidation of fats.