[Show abstract][Hide abstract] ABSTRACT: Pig production has increased in hot climate countries over recent years but the effect of exposure to high temperatures on the health status of farm animals has not been investigated thoroughly. It is not clear how the ambient temperature (Ta) might influence responses to inflammatory challenge in pigs and the aim of the present study was to evaluate the effects of high Ta on performance and physiological parameters of growing pigs subjected to repeated administration of Escherichia coli lipopolysaccharide (LPS).
Thirty-seven pigs, each fitted with a jugular catheter, were assigned to one of two Ta conditions: thermo-neutral (TN, 24 °C), or high (HT, 30 °C). After a 14-day adaptation period, and a 7-day measurement period, pigs were administered five repeated injections of LPS at 48 h intervals. Irrespective of Ta, the LPS challenge reduced feed consumption and increased plasma pro-inflammatory cytokines, haptoglobin and cortisol. However, the extent of these responses was greater in pigs at TN than HT. In both groups, plasma thyroxine and triiodothyronine concentrations decreased, following the first LPS injection and thereafter returned to baseline, which occurred faster at HT than at TN. Moreover, the LPS challenge decreased growth and feed efficiency in pigs kept at TN, which was not observed in pigs kept at HT. The results suggest a greater capacity of pigs to limit the physiological and metabolic disturbances caused by inflammatory challenge, when kept at HT, compared to TN.
The Veterinary Journal 01/2014; · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Meat quality depends on skeletal muscle structure and metabolic properties. While most studies carried on pigs focus on the Longissimus muscle (LM) for fresh meat consumption, Semimembranosus (SM) is also of interest because of its importance for cooked ham production. Even if both muscles are classified as glycolytic muscles, they exhibit dissimilar myofiber composition and metabolic characteristics. The comparison of LM and SM transcriptome profiles undertaken in this study may thus clarify the biological events underlying their phenotypic differences which might influence several meat quality traits.
Muscular transcriptome analyses were performed using a custom pig muscle microarray: the 15 K Genmascqchip. A total of 3823 genes were differentially expressed between the two muscles (Benjamini-Hochberg adjusted P value ≤0.05), out of which 1690 and 2133 were overrepresented in LM and SM respectively. The microarray data were validated using the expression level of seven differentially expressed genes quantified by real-time RT-PCR. A set of 1047 differentially expressed genes with a muscle fold change ratio above 1.5 was used for functional characterization. Functional annotation emphasized five main clusters associated to transcriptome muscle differences. These five clusters were related to energy metabolism, cell cycle, gene expression, anatomical structure development and signal transduction/immune response.
This study revealed strong transcriptome differences between LM and SM. These results suggest that skeletal muscle discrepancies might arise essentially from different post-natal myogenic activities.
PLoS ONE 01/2014; 9(5):e96491. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Meat quality (MQ) results from complex phenomenon and despite improved knowledge on MQ development, its variability remains high. The identification of biomarkers and the further development of rapid tests would thus be helpful to evaluate MQ in pork industries. Using transcriptomics, the present study aimed at identifying biomarkers of eight pork quality traits: ultimate pH, drip loss, lightness, redness, hue angle, intramuscular fat, shear force and tenderness, based on an experimental design inducing a high variability in MQ. Associations between microarray gene expression and pork traits (n=50 pigs) highlighted numerous potential biomarkers of MQ. Using quantitative RT-PCR, 113 transcript-trait correlations including 40 of these genes were confirmed (P<0.05, |r|≤0.73), out of which 60 were validated (P<0.05, |r|≤0.68) on complementary experimental data (n=50). Multiple regression models including 3 to 5 genes explained up to 59% of MQ trait variability. Moreover, functional analysis of correlated-trait genes provided information on the biological phenomena underlying MQ.
[Show abstract][Hide abstract] ABSTRACT: The molecular mechanisms underlying the genetic control of fat development in humans and livestock species still require characterization. To gain insights on gene expression patterns associated with genetic propensity for adiposity, subcutaneous adipose tissue (SCAT) transcriptomics profiles from two contrasted pig breeds for body fatness were compared. Samples were obtained from Large White (LW; lean phenotype) and Basque pigs (B; low growth and high fat content) at 35 kg (n = 5 per breed) or 145 kg body weight (n = 10 per breed). Using a custom adipose tissue microarray, 271 genes were found to be differentially expressed between the two breeds at both stages, out of which 123 were highly expressed in LW pigs and 148 genes were highly expressed in B pigs. Functional enrichment analysis based on gene ontology (GO) terms highlighted gene groups corresponding to the mitochondrial energy metabolism in LW pigs, whereas immune response was found significantly enriched in B pigs. Genes associated with lipid metabolism, such as ELOVL6, a parameter involved in fatty acid elongation, had a lower expression in B compared with LW pigs. Furthermore, despite enlarged adipocyte diameters and higher plasma leptin concentration, B pigs displayed reduced lipogenic enzyme activities compared with LW pigs at 145 kg. Altogether, our results suggest that the development of adiposity was associated with a progressive worsening of the metabolic status leading to a low-grade inflammatory state, and may thus be of significant interest for both livestock production and human health.
[Show abstract][Hide abstract] ABSTRACT: Since decades, production traits such as growth rate, feed efficiency or body composition have been drastically increased in pigs by genetic selection. Whether this selection impacted animal robustness is still unclear. In this study, we compared Large White (LW) pigs, a breed submitted to intense genetic selection for production traits, and Basque (B) pigs, a local rustic breed, reared in two different housing environments (conventional v. enriched). Adaptation to housing conditions among each breed was evaluated at the level of endocrine and immune traits. These are known to be impacted by housing conditions and breed; however, the interaction effects between genotype and environment are less described. Animals (20 per breed and housing environment) entered the experiment at 35 kg of live weight. Levels of cortisol, acute-phase inflammatory proteins, immunoglobulins and hydrogen peroxide, blood formula, lymphocyte proliferation and in-vitro cytokine expression were measured at ∼115 kg of live weight. Animals were checked for skin injuries during the growing period. At slaughter, at the average live weight of 145 kg, carcasses were examined for pathological conditions of the respiratory tract. The major result was that the two breeds exhibited differences in response to the housing environment. Among the 24 sanitary, endocrine or immune traits investigated, the housing conditions affected eight variables in both breeds (salivary cortisol at 0700 and 1900 h, severity of pneumonia at slaughter) or only in B pigs (severe skin lesions) or LW pigs (salivary cortisol at 1500 h, granulocyte numbers and lymphocyte/granulocyte ratio and lymphocyte proliferation). These observations strengthen the hypothesis that selection for high meat production level might be associated with an increased susceptibility of animals to environmental stressors.
[Show abstract][Hide abstract] ABSTRACT: A family structured population of 325 pigs (females and barrows) was produced as an intercross between 2 commercial sire lines and was subjected to a systematic transcriptome analysis of LM samples obtained shortly after slaughter. Additionally, measurements of meat quality traits of fresh and cooked loin were gathered from the same animals. The transcriptome analysis was achieved by microarray hybridization, using a custom repertoire of 15,000 6mer DNA probes targeting transcripts expressed in growing pig skeletal muscle. These data allowed us to estimate the heritability of expression abundance for each of the quantified RNA species. The abundance of 9,765 RNA was estimated as heritable with a false discovery rate of 5%, from which 1,174 were deemed as highly heritable (h(2) > 0.50). We also observed a large number of transcripts whose LM expression abundance is genetically correlated with 4 meat quality traits: the loin pH measured at 45 min postmortem (pH45), 253 transcripts; the loin cooking loss (CL), 134 transcripts; the cooked loin shear force (SFc), 184 transcripts; and the loin color redness (a*) value, 190 transcripts. Heritable and meat quality genetically correlated transcripts showed an over-representation of biological processes involved in the induction of apoptosis (genetically correlated with CL), complement activation (genetically correlated with SFc), glucose metabolism (genetically correlated with a*), and cation channel activity (genetically correlated with pH45). Overall, the biological functions highlighted in the highly heritable transcripts and the lack of transcript that would be genetically correlated with LM glycolytic potential suggest that the genetic variability of the LM postmortem transcriptome is focused on muscle tissue response to postmortem ischemia and reflects more distantly the antemortem muscle physiology. Because of the contrasting distributions of the genetic correlations between LM RNA concentrations and the different meat quality traits studied, indirect selection strategies of meat quality traits based on measurements of selected LM RNA species could be only proposed for a subset of the analyzed meat characteristics (pH45, SFc, a*, CL). A substantial improvement in the efficiency of selection for these meat quality traits could result from measuring muscle RNA concentrations on selection candidates, if the same genetic parameters can be verified using in vivo-sampled muscles.
Journal of Animal Science 03/2012; 90(3):699-708. · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Meat quality depends on physiological processes taking place in muscle tissue, which could involve a large pattern of genes associated with both muscle structural and metabolic features. Understanding the biological phenomena underlying muscle phenotype at slaughter is necessary to uncover meat quality development. Therefore, a muscle transcriptome analysis was undertaken to compare gene expression profiles between two highly contrasted pig breeds, Large White (LW) and Basque (B), reared in two different housing systems themselves influencing meat quality. LW is the most predominant breed used in pig industry, which exhibits standard meat quality attributes. B is an indigenous breed with low lean meat and high fat contents, high meat quality characteristics, and is genetically distant from other European pig breeds.
Transcriptome analysis undertaken using a custom 15 K microarray, highlighted 1233 genes differentially expressed between breeds (multiple-test adjusted P-value<0.05), out of which 635 were highly expressed in the B and 598 highly expressed in the LW pigs. No difference in gene expression was found between housing systems. Besides, expression level of 12 differentially expressed genes quantified by real-time RT-PCR validated microarray data. Functional annotation clustering emphasized four main clusters associated to transcriptome breed differences: metabolic processes, skeletal muscle structure and organization, extracellular matrix, lysosome, and proteolysis, thereby highlighting many genes involved in muscle physiology and meat quality development.
Altogether, these results will contribute to a better understanding of muscle physiology and of the biological and molecular processes underlying meat quality. Besides, this study is a first step towards the identification of molecular markers of pork quality and the subsequent development of control tools.
PLoS ONE 01/2012; 7(3):e33763. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Detection of quantitative trait loci (QTLs) affecting meat quality traits in pigs is crucial for the design of efficient marker-assisted selection programs and to initiate efforts toward the identification of underlying polymorphisms. The RYR1 and PRKAG3 causative mutations, originally identified from major effects on meat characteristics, can be used both as controls for an overall QTL detection strategy for diversely affected traits and as a scale for detected QTL effects. We report on a microsatellite-based QTL detection scan including all autosomes for pig meat quality and carcass composition traits in an F2 population of 1,000 females and barrows resulting from an intercross between a Pietrain and a Large White-Hampshire-Duroc synthetic sire line. Our QTL detection design allowed side-by-side comparison of the RYR1 and PRKAG3 mutation effects seen as QTLs when segregating at low frequencies (0.03-0.08), with independent QTL effects detected from most of the same population, excluding any carrier of these mutations.
Large QTL effects were detected in the absence of the RYR1 and PRKGA3 mutations, accounting for 12.7% of phenotypic variation in loin colour redness CIE-a* on SSC6 and 15% of phenotypic variation in glycolytic potential on SSC1. We detected 8 significant QTLs with effects on meat quality traits and 20 significant QTLs for carcass composition and growth traits under these conditions. In control analyses including mutation carriers, RYR1 and PRKAG3 mutations were detected as QTLs, from highly significant to suggestive, and explained 53% to 5% of the phenotypic variance according to the trait.
Our results suggest that part of muscle development and backfat thickness effects commonly attributed to the RYR1 mutation may be a consequence of linkage with independent QTLs affecting those traits. The proportion of variation explained by the most significant QTLs detected in this work is close to the influence of major-effect mutations on the least affected traits, but is one order of magnitude lower than effect on variance of traits primarily affected by these causative mutations. This suggests that uncovering physiological traits directly affected by genetic polymorphisms would be an appropriate approach for further characterization of QTLs.
[Show abstract][Hide abstract] ABSTRACT: Pork quality is highly variable and availability of relevant predictors of fresh meat quality at slaughter is critical to optimize carcass use and improve its valuation. High throughput gene expression studies have been widely used to describe biological mechanisms underlying variation of several traits but data are scarce regarding their use as tools for development of biomarkers. The GENMASCQ (GENomics enabled Marker Assisted Selection and Certification of Quality in Pork products ) research program was set up to select, using high-throughput gene expression screening, markers of the biological variation mostly appropriate to describe, and ultimately forecast, the sensory quality of an important meat product, accounting for nearly 40 % of meat protein sources in human food. This report describes the characterization of a porcine skeletal muscle microarray, the GenmascqChip 15K, as a new tool to study pig meat quality. This microarray is annotated at nearly 90 % and permits to explore a list of 9169 unique genes.
[Show abstract][Hide abstract] ABSTRACT: A 1000-pig F2 intercross QTL detection experimental population was generated using two commercial sire lines. Independent carriers of HAL n and RN- mutations (10% and 14%, respectively) were included in this population as control genotypes. The effects of HAL n and RN- heterozygous genotypes on fresh and transformed loins and hams were estimated using a mixed model methodology. The results document the unfavorable effects of both mutations on meat quality. Smaller effects of HAL Nn genotype compared to HAL nn or RN-rn+ genotypes were estimated. Interestingly, effects of HAL Nn genotype on meat pH and loin color could be insignificant at 24-h postmortem, but translate into higher water losses on storage and cooking, and result in tougher cooked loin. Using the same methodology, significant effects of the PRKAG3 (RN) I199 allele on ultimate pH values but not on glycolytic potential were observed.
[Show abstract][Hide abstract] ABSTRACT: Residual feed intake (RFI) is defined as the difference between the observed feed intake and that expected based on requirements for maintenance and production. A divergent selection was conducted during 4 generations in Large White male pigs to produce low and high RFI lines. The present study aims at determining the influence of this selection on biochemical and histological traits of skeletal muscle, and relating these changes to correlated effects on growth, carcass composition, and meat quality traits. At 8 d preslaughter, biopsies from the LM were taken in the fed state on 14 females from each RFI line fed ad libitum. Animals were slaughtered at 107.8 ± 8.0 kg of BW without any previous fasting. Samples of LM, semimembranosus (SM), biceps femoris (BFM), and rhomboideus muscles were taken at both 30 min and 24 h postmortem. Myofiber typing was only assessed in LM. Low RFI pigs ("efficient") had leaner carcasses with greater muscle content (P < 0.001), less backfat thickness (P < 0.001), and less intramuscular fat content in all 4 muscles (P < 0.01 to P = 0.04). Their greater muscle content was associated with hypertrophy of all fast-twitch fibers. Glycogen content in all glycolytic muscles (i.e., LM, SM and BFM), was greater in low than high RFI pigs. The greater accumulation of glycogen in LM of low RFI pigs was specifically located in the fast-twitch glycolytic IIBW fibers, which correspond to fibers containing IIb, IIb + IIx, or IIx myosin heavy chains. The difference in muscle glycogen content between RFI line pigs was more significant in the living animals (P = 0.0003) than at 30 min postmortem (P = 0.08). This was associated with a decreased ultimate pH (P = 0.001), and greater lightness of color (P = 0.002) and drip loss (P = 0.04) in LM of low than high RFI line pigs, suggesting that selection for reduced RFI may impair some meat quality traits, such as water-holding capacity. Pigs from the low RFI line exhibited a greater (P = 0.02) percentage of IIBW fibers in LM and tended (P < 0.10) to have less lipid β-oxidative capacity in LM, SM, and BFM. In contrast, no difference (P > 0.10) between lines was found for citrate synthase and lactate dehydrogenase activities, mitochondrial activity, and expression of genes coding for uncoupling proteins 2 and 3. Differences between RFI pigs in plasma leptin, cortisol, and thyroid hormone concentrations are presented and discussed. In conclusion, selection for low RFI influenced muscle properties in a way favoring muscle mass, but likely impairing meat quality.
Journal of Animal Science 12/2010; 89(4):996-1010. · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Intramuscular fat content is important for many meat quality parameters. This work is aimed at identifying functional categories of genes associated with natural variation among individuals in intramuscular fat content to help the design of genetic schemes for high marbling potential. Taking advantage of the global nature of transcriptomic and proteomic technologies, 40 genes were identified as differently expressed between high fat and low fat pig Longissimus muscles at slaughter weight. They are involved in metabolic processes, cell communication, binding, and response to stimulus. Using real-time PCR in muscle biopsies taken earlier in the fattening period, the group with a high intramuscular fat content was also characterized by the down-expression of genes playing a negative role in adipogenesis, such as architectural transcription factor high-motility hook A1, mitogen activated protein-kinase14, and cyclin D1. These results suggest that interindividual variability in intramuscular fat content might arise essentially from differences in early adipogenesis.
Journal of Agricultural and Food Chemistry 04/2009; 57(9):3808-17. · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two-dimensional electrophoresis was used to compare Longissimus sarcoplasmic protein abundance between two groups (tough meat and tender meat), defined on the basis of extreme Warner-Bratzler shear force values measured on cooked pork. Fourteen protein spots differed in quantity (P<0.05) between the two groups and were identified. Adypocyte fatty acid binding protein and acyl-CoA binding protein involved in lipid traffic and in the control of gene expression regulating cell proliferation and differentiation, and Enoyl-CoA hydratase, aldose reductase and triosephosphate isomerase indirectly related to lipid metabolism were overrepresented in the tender group. The tender group was further characterized by increased levels of proteins involved in protein folding and polymerization (initiation factor elf-3beta, chaperonin subunit 2, profilin II). The results suggest that the lower post-cooking shear force could at least in part be related to muscle adipogenetic and/or myogenetic status of which the possible underlying mechanisms are discussed.
Journal of Agricultural and Food Chemistry 07/2007; 55(14):5834-41. · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To examine cellular and biochemical features of skeletal muscle in response to dietary-induced obesity in a novel Yucatan minipig model of childhood obesity.
From 4 to 16 months of age, minipigs were fed either a recommended human-type diet (NF; n = 4) or were overfed a western-type diet with saturated fat and high-glycemic index carbohydrates (OF, n = 4). Muscle samples (biceps femoris) were histochemically stained for the identification of intramuscular adipocytes, intramyocellular lipid aggregates (oil red O), and myofiber types (myosin ATPase, succinate dehydrogenase). Gene expressions and/or activities of factors involved in lipogenesis, lipolysis, or energetic metabolism were quantified in muscle.
Cross-sectional areas of myofibers paralleled pig body weight (r = 0.86, p < 0.01). The size of intramuscular adipocytes, the relative proportion of oil red O-stained fibers, and total muscle lipid content tended (p < or = 0.10) to increase in response to OF diet. Hormone-sensitive lipase, carnitine palmityl transferase-I, and uncoupling protein 2 mRNA levels were lower (p < 0.05) in OF pigs than in NF pigs. Activities of beta-hydroxyacyl-coenzyme A dehydrogenase and citrate synthase assessing post-carnitine palmityl transferase I events and the proportion of oxidative myofibers were not altered by OF diet. Activity and gene expression of fatty acid synthase were lower (p < 0.02) in OF pigs than in NF pigs.
Overfeeding in Yucatan minipigs reduced the expression levels of three catabolic steps in skeletal muscle that are involved also in the etiology of human obesity.
[Show abstract][Hide abstract] ABSTRACT: Intramuscular fat content is generally associated with improved sensory quality and better acceptability of fresh pork. However, conclusive evidence is still lacking for the biological mechanisms underlying i.m. fat content variability in pigs. The current study aimed to determine whether variations in i.m. fat content of longissimus muscle are related to i.m. adipocyte cellularity, lipid metabolism, or contractile properties of the whole muscle. To this end, crossbred (Large White x Duroc) pigs exhibiting either a high (2.82 +/- 0.38%, HF) or a low (1.15 +/- 0.14%, LF) lipid content in LM biopsies at 70 kg of BW were further studied at 107 +/- 7 kg of BW. Animals grew at the same rate, but HF pigs at slaughter presented fatter carcasses than LF pigs (P = 0.04). The differences in i.m. fat content between the 2 groups were mostly explained by variation in i.m. adipocyte number (+127% in HF compared with LF groups, P = 0.005). Less difference (+13% in HF compared with LF groups, P = 0.057) was noted in adipocyte diameter, and no significant variation was detected in whole-muscle lipogenic enzyme activities (acetyl-CoA carboxylase, P = 0.9; malic enzyme, P = 0.35; glucose-6-phosphate dehydrogenase, P = 0.75), mRNA levels of sterol-regulatory element binding protein-1 (P = 0.6), or diacylglycerol acyltransferase 1 (P = 0.6). Adipocyte fatty acid binding protein (FABP)-4 protein content in whole LM was 2-fold greater in HF pigs than in LF pigs (P = 0.05), and positive correlation coefficients were found between the FABP-4 protein level and adipocyte number (R2 = 0.47, P = 0.02) and lipid content (R2 = 0.58, P = 0.004). Conversely, there was no difference between groups relative to FABP-3 mRNA (P = 0.46) or protein (P = 0.56) levels, oxidative enzymatic activities (citrate synthase, P = 0.9; beta-hydroxyacyl-CoA dehydrogenase, P = 0.7), mitochondrial (P = 0.5) and peroxisomal (P = 0.12) oxidation rates of oleate, mRNA levels of genes involved in fatty acid oxidation (carnitine-palmitoyl-transferase 1, P = 0.98; peroxisome proliferator-activated receptor delta, P = 0.73) or energy expenditure (uncoupling protein 2, P = 0.92; uncoupling protein 3, P = 0.84), or myosin heavy-chain mRNA proportions (P > 0.49). The current study suggests that FABP-4 protein content may be a valuable marker of lipid accretion in LM and that i.m. fat content and myofiber type composition can be manipulated independently.
Journal of Animal Science 05/2006; 84(5):1083-92. · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Thyroid hormones (THs) have long been known to be involved in the control of thermoregulation in birds and mammals. In particular, they are reported to play a role in the regulation of heat production. The underlying mechanisms could be the stimulation of the nuclear and mitochondrial transcription of several genes involved in energy metabolism and/or a direct action on the activity of components of the mitochondrial respiratory chain. Attention has recently been focussed on a subfamily of mitochondrial anion carriers called uncoupling proteins (UCPs). These proteins are suspected to be involved in a partial dissipation of the mitochondrial proton electrochemical gradient that would uncouple phosphorylations from oxidations and hence produce heat. However, the involvement of uncoupling mechanisms in thermogenesis and particularly in the thermogenic effect of TH is still unclear. The thermogenic role of UCP1, specifically expressed in brown adipose tissue, and its regulation by TH in rodents is quite well recognised, but the involvement in heat production of its mammalian homologues UCP2, ubiquitously expressed, and UCP3, muscle and adipose tissue-specific, as well as the role of the muscular avian UCP (avUCP), are to be further investigated. The expression of the UCP2 and UCP3 genes was shown to be enhanced by TH in muscle of several rodent species, and to be increased in situations where thermogenesis is stimulated, whereas results are more contrasted in pig. There is now increasing evidence that the physiological role of the mammalian UCP3 and UCP2 is rather related to lipid oxidation and/or prevention of reactive oxygen species accumulation than to heat production by uncoupling. The expression of avUCP was also recently demonstrated to be strongly regulated by thyroid status in chicken, and overexpressed in experimental conditions favouring high triiodothyronine concentrations and thermogenesis. However, its real uncoupling activity and contribution to thermogenesis remain to be established.
[Show abstract][Hide abstract] ABSTRACT: The lipoprotein lipase (LPL) hydrolyses circulating triacylglycerol-rich lipoproteins. Thereby, LPL acts as a metabolic gate-keeper for fatty acids partitioning between adipose tissue for storage and skeletal muscle primarily for energy use. Transgenic mice that markedly over-express LPL exclusively in muscle, show increases not only in LPL activity, but also in oxidative enzyme activities and in number of mitochondria, together with an impaired glucose tolerance. However, the role of LPL in intracellular nutrient pathways remains uncertain. To examine differences in muscle nutrient uptake and fatty acid oxidative pattern, transgenic rabbits harboring a DNA fragment of the human LPL gene (hLPL) and their wild-type littermates were compared for two muscles of different metabolic type, and for perirenal fat.
Analyses of skeletal muscles and adipose tissue showed the expression of the hLPL DNA fragment in tissues of the hLPL group only. Unexpectedly, the activity level of LPL in both tissues was similar in the two groups. Nevertheless, mitochondrial fatty acid oxidation rate, measured ex vivo using [1-(14C)]oleate as substrate, was lower in hLPL rabbits than in wild-type rabbits for the two muscles under study. Both insulin-sensitive glucose transporter GLUT4 and muscle fatty acid binding protein (H-FABP) contents were higher in hLPL rabbits than in wild-type littermates for the pure oxidative semimembranosus proprius muscle, but differences between groups did not reach significance when considering the fast-twitch glycolytic longissimus muscle. Variations in both glucose uptake potential, intra-cytoplasmic binding of fatty acids, and lipid oxidation rate observed in hLPL rabbits compared with their wild-type littermates, were not followed by any modifications in tissue lipid content, body fat, and plasma levels in energy-yielding metabolites.
Expression of intracellular binding proteins for both fatty acids and glucose, and their following oxidation rates in skeletal muscles of hLPL rabbits were not fully consistent with the physiology rules. The modifications observed in muscle metabolic properties might not be directly associated with any LPL-linked pathways, but resulted likely of transgene random insertion into rabbit organism close to any regulatory genes. Our findings enlighten the risks for undesirable phenotypic modifications in micro-injected animals and difficulties of biotechnology in mammals larger than mice.
Lipids in Health and Disease 01/2005; 3:27. · 2.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The optimal utilization of energy substrates in muscle fibers is of primary importance for muscle contraction and whole body physiology. This study aimed to investigate the age-related changes in some indicators of glucose catabolism and fatty acid oxidation in muscles of growing rabbits. Longissimus lumborum (fast-twitch, LL) and semimembranosus proprius (slow-twitch, SMP) muscles were collected at 10 or 20 weeks of age ( n=6 per age). Glucose transporter GLUT4 content was investigated by immunoblot assay. Activity levels of five enzymes were measured: lactate dehydrogenase (LDH) and phosphofructokinase (PFK) for glycolysis; citrate synthase (CS), isocitrate dehydrogenase (ICDH) and -3-hydroxyacyl-coenzyme A dehydrogenase (HAD) for oxidation. Mitochondrial and peroxisomal oxidation rates were assessed on fresh homogenates using [1-14C]-oleate as substrate. At both ages, mitochondrial and peroxisomal oxidations rates, as well as activities of oxidative enzymes were higher in SMP than in LL. In both muscles, the apparent rate of fatty acid oxidation by the mitochondria did not differ between the two ages. However, a decrease in the activities of the three oxidative enzymes was observed in LL, whereas activities of CS and HAD and peroxisomal oxidation rate of oleate increased between the two ages in SMP muscle. In both muscles, LDH activity increased between 10 and 20 weeks, without variations in glucose uptake (GLUT4 transporter content) and in the first step of glucose utilization (PFK activity). In conclusion, mitochondrial oxidation rate of fatty acids and activities of selected mitochondrial enzymes were largely unrelated. Moreover, regulation of energy metabolism with advancing age differed between muscle types.
Journal of Muscle Research and Cell Motility 02/2004; 25(4-5):405-10. · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of breed and body weight (BW) on thermoregulatory abilities were studied on 2–4-h-old Meishan (MS) and European (Piétrain×(Landrace×Large White)) piglets, with BW ranging between 800 and 1800 g. MS piglets (n=17 from nine sows) exhibited similar thermogenic capacities, i.e. summit metabolic rates (SMR), than European piglets (n=19 from 10 sows) in the cold, but BW had breed-specific effects on thermogenic capacities. First, our results confirm that, with the exception of light European piglets, SMR is proportional to BW−1 in 2-h-old animals. Second, MS piglets with BW ranging between 800 and 1300 g have similar ability to increase thermogenesis and to reduce thermolysis in the cold. On the contrary, BW has major effects on maximal thermoregulatory abilities of European piglets, with a linear relation between BW and reduction of heat loss in the cold, and a progressive impairment of thermogenic capacities below a calculated BW of 1125 g. Therefore, European piglets weighing less than 1125 g are particularly at risk in a cold environment, although they cannot be classified as runt animals. Eight additional piglets (four MS and four LW) of average BW within breeds were used to uncover the effect of breed on uncoupling protein (UCP2, UCP3) tissue expression. Expression of UCP2 does not differ but an overexpression of UCP3 is observed in adipose tissue (AT) and skeletal muscle of MS piglets, in good agreement with their higher minimal metabolic rate (MMR).