Differences in pig muscle proteome according to HAL genotype: implications for meat quality defects

Proteomics analysis as an approach to understand the formation of pale, soft, and exudative (PSE) pork

We investigated ten pale, soft, and exudative (PSE), and ten normal meat samples from pig carcasses. The meat quality at 0, 5, 12, and 24 h post-mortem and the key enzyme activities at 0 and 24 h post-mortem were determined. We selected three PSE and three normal samples for proteomics analysis at 0 h and 24 h post-mortem. No remarkable differences in pyruvate kinase (PK) and lactate dehydrogenase (LDH) activity were observed between samples at 0 h post-mortem; however, creatine kinase (CK) activity was significantly higher in PSE meat. Hexokinase (HK) activity in PSE samples was higher than that in normal samples at 24 h post-mortem. Bioinformatics analysis of the proteome showed that PSE was related to glycolysis, TCA cycle, oxidative phosphorylation, muscle tissue structure, signal transduction, and molecular chaperones. This research found that proteins such as troponin T slow skeletal muscle isoform X, GADPH, L-lactate dehydrogenase A chain, and gamma-enolase isoform X1 might be responsible for PSE.

Effects of protein posttranslational modifications on meat quality: A review

Meat quality plays an important role in the purchase decision of consumers, affecting producers and retailers. The formation mechanisms determining meat quality are intricate, as several endogenous and exogenous factors contribute during antemortem and postmortem periods. Abundant research has been performed on meat quality; however, unexpected variation in meat quality remains an issue in the meat industry. Protein posttranslational modifications (PTMs) regulate structures and functions of proteins in living tissues, and recent reports confirmed their importance in meat quality. The objective of this review was to provide a summary of the research on the effects of PTMs on meat quality. The effects of four common PTMs, namely, protein phosphorylation, acetylation, S-nitrosylation, and ubiquitination, on meat quality were discussed, with emphasis on the effects of protein phosphorylation on meat tenderness, color, and water holding capacity. The mechanisms and factors that may affect the function of protein phosphorylation are also discussed. The current research confirms that meat quality traits are regulated by multiple PTMs. Cross talk between different PTMs and interactions of PTMs with postmortem biochemical processes need to be explored to improve our understanding on factors affecting meat quality.

Traditional halal slaughter without stunning versus slaughter with electrical stunning of sheep (Ovis aries)

Thirty Nellore crossbred male sheep (Ovis aries) were divided into two groups of 15 animals each and subjected to either pre-slaughter electrical stunning followed by slaughter (ST) or traditional halal slaughter without stunning (NST) to investigate the changes in blood biochemical parameters, meat quality and proteomic profile. Higher (P < .05) pH, water holding capacity and Warner-Bratzler shear force were observed in meat from stunned sheep. Quantitative proteomic approach using DIGE was employed to find a panel of protein markers that could differentiate ST and NST muscle proteome. Comparison of muscle proteome of ST and NST samples by 2D-DIGE and MALDI-TOF/TOF MS analysis revealed 46 significant (P < .05) differentially expressed proteins. Our analysis revealed changes in the abundance of proteins involved in catalytic, structural, and stress related process. Current study has demonstrated variation meat quality and identified important proteins that correlate with meat texture and pre-slaughter stress in sheep that are slaughtered without and with electrical stunning.

Meat quality traits and proteome profile of woody broiler breast (pectoralis major) meat

Woody breast meat has recently become prevalent in the broiler industry in both the United States and European Union. Recent publications have described the meat quality characteristics of woody breast meat as having hardened areas and pale ridge-like bulges at both the caudal and cranial regions of the breast. The present study investigated the meat quality (pH, color, cooking loss, and shear force) and protein quality characteristics (protein and salt-soluble protein content) in woody breast meat as compared to normal breast meat. In addition, the differences in the muscle proteome profiles of woody and normal breast meat were characterized. Results indicated that woody breast meat had a greater average pH (P < 0.0001) and cooking loss (P = 0.001) than normal breast meat, but woody breast meat did not differ in shear force (P > 0.05) in comparison to normal breast meat samples. The L*, a*, and b* values of woody breast fillets were greater than normal breast fillets (P < 0.0001 to L*; P = 0.002 to a*; P = 0.016 to b*). The woody breast meat had more fat (P < 0.0001) and moisture (P < 0.021) and less protein (P < 0.0001) and salt-soluble protein (P < 0.0001) when compared with normal breast fillets. Whole muscle proteome analysis indicated 8 proteins that were differentially expressed (P < 0.05) between normal and woody breast meat samples. The differences in muscle proteome between normal and woody breast meat indicated an increased oxidative stress in woody breast meat when compared to normal meat. In addition, the abundance of some glycolytic enzymes, which are critical to the regeneration of adenosine triphosphate (ATP) in postmortem muscles, was lower in woody breast meat than in normal breast meat. Proteomic differences provide additional information on the biochemical pathways and genetic variations that lead to woody breast meat. Further research should be conducted to elucidate the genetic and nutritional contributions to the proliferation of woody breast meat in the United States.

Proteomic analysis to investigate color changes of chilled beef longissimus steaks held under carbon monoxide and high oxygen packaging

This study investigated the proteome basis for color stability variations in beef steaks packaged under two modified atmosphere packaging (MAP) methods: HiOx-MAP (80% O₂/20% CO₂) and CO-MAP (0.4% CO/30% CO₂/69.6% N₂) during 15 days of storage. The color stability, pH, and sarcoplasmic proteome analysis of steaks were evaluated on days 0, 5, 10 and 15 of storage. Proteomic results revealed that the differential expression of the sarcoplasmic proteome during storage contributed to the variations in meat color stability between the two MAP methods. Compared with HiOx-MAP steaks, some glycolytic and energy metabolic enzymes important in NADH regeneration and antioxidant processes, antioxidant peroxiredoxins (thioredoxin-dependent peroxide reductase, peroxiredoxin-2, peroxiredoxin-6) and protein DJ-1 were more abundant in CO-MAP steaks. The over-expression of these proteins could induce CO-MAP steaks to maintain high levels of metmyoglobin reducing activity and oxygen consumption rate, resulting in CO-MAP steaks exhibiting better color stability than HiOx-MAP steaks during storage.

Proteomic approach to characterize biochemistry of meat quality defects

Proteomics can be used to characterize quality defects including pale, soft, and exudative (PSE) meat (pork and poultry), woody broiler breast meat, reddish catfish fillets, meat toughness, and beef myoglobin oxidation. PSE broiler meat was characterized by 15 proteins that differed in abundance in comparison to normal broiler breast meat, and eight proteins were differentially expressed in woody breast meat in comparison to normal breast meat. Hemoglobin was the only protein that was differentially expressed between red and normal catfish fillets. However, inducing low oxygen and/or heat stress conditions to catfish fillets did not lead to the production of red fillets. Proteomic data provided information pertaining to the protein differences that exist in meat quality defects. However, these data need to be evaluated in conjunction with information pertaining to genetics, nutrition, environment of the live animal, muscle to meat conversion, meat quality analyses and sensory attributes to understand causality, protein biomarkers, and ultimately how to prevent quality defects.

Comparative Proteomic Profiling of Divergent Phenotypes for Water Holding Capacity across the Post Mortem Ageing Period in Porcine Muscle Exudate

Two dimensional Difference Gel Electrophoresis (2-D DIGE) and mass spectrometry were applied to investigate the changes in metabolic proteins that occur over a seven day (day 1, 3 and 7) post mortem ageing period in porcine centrifugal exudate from divergent meat quality phenotypes. The objectives of the research were to enhance our understanding of the phenotype (water holding capacity) and search for biomarkers of this economically significant pork quality attribute. Major changes in protein abundance across nine phenotype-by-time conditions were observed. Proteomic patterns were dominated by post mortem ageing timepoint. Using a machine learning algorithm (l1-regularized logistic regression), a model was derived with the ability to discriminate between high drip and low drip phenotypes using a subset of 25 proteins with an accuracy of 63%. Models discriminating between divergent phenotypes with accuracy of 72% and 73% were also derived comparing respectively, high drip plus intermediate phenotype (considered as one phenotype) versus low drip and comparing low drip plus intermediate phenotype (considered as one phenotype) versus high drip. In all comparisons, the general classes of discriminatory proteins identified include metabolic enzymes, stress response, transport and structural proteins. In this research we have enhanced our understanding of the protein related processes underpinning this phenotype and provided strong data to work toward development of protein biomarkers for water holding capacity.

Recent advances in omic technologies for meat quality management

The knowledge of the molecular organization of living organisms evolved considerably during the last years. The methodologies associated also progressed with the development of the high-throughput sequencing (SNP array, RNAseq, etc.) and of genomic tools allowing the simultaneous analysis of hundreds or thousands of genes, proteins or metabolites. In farm animals, some proteins, mRNAs or metabolites whose abundance has been associated with meat quality traits have been detected in pig, cattle, chicken. They constitute biomarkers for the assessment and prediction of qualities of interest in each species, with potential biomarkers across species. The ongoing development of rapid methods will allow their use for decision-making and management tools in slaughterhouses, to better allocate carcasses or cuts to the appropriate markets. Besides, their application on living animals will help to improve genetic selection and to adapt a breeding system to fulfill expected quality level. The ultimate goal is to propose effective molecular tools for the management of product quality in meat production chains.

Proteome changes underpin improved meat quality and yield of chickens (Gallus gallus) fed the probiotic Enterococcus faecium

Background

Supplementation of broiler chicken diets with probiotics may improve carcass characteristics and meat quality. However, the underlying molecular mechanism remains unclear. In the present study, 2D-DIGE-based proteomics was employed to investigate the proteome changes associated with improved carcass traits and meat quality of Arbor Acres broilers (Gallus gallus) fed the probiotic Enterococcus faecium.

Results

The probiotic significantly increased meat colour, water holding capacity and pH of pectoral muscle but decreased abdominal fat content. These meat quality changes were related to the altered abundance of 22 proteins in the pectoral muscle following E. faecium feeding. Of these, 17 proteins have central roles in regulating meat quality due to their biological interaction network. Altered cytoskeletal and chaperon protein expression also contribute to improved water holding capacity and colour of meat, which suggests that upregulation of chaperon proteins maintains cell integrity and prevents moisture loss by enhancing folding and recovery of the membrane and cytoskeletal proteins. The down-regulation of β-enolase and pyruvate kinase muscle isozymes suggests roles in increasing the pH of meat by decreasing the production of lactic acid. The validity of the proteomics results was further confirmed by qPCR.

Conclusions

This study reveals that improved meat quality of broilers fed probiotics is triggered by proteome alterations (especially the glycolytic proteins), and provides a new insight into the mechanism by which probiotics improve poultry production.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1167) contains supplementary material, which is available to authorized users.

2D DIGE proteomic analysis of early post mortem muscle exudate highlights the importance of the stress response for improved water-holding capacity of fresh pork meat

Variation in water-holding capacity (WHC), which presents a major economic burden to the swine industry, is considered to be underpinned by variation at a molecular and biochemical level. High-resolution 2D DIGE followed by MS analysis and Western blot were used to unravel the proteome of muscle exudate, collected following centrifugation, in the pH 4-7 range. A first 2DE-based protein map of this substrate was produced where 89 spots were successfully characterised. Two phenotypes divergent for WHC plus one intermediate were compared with a view to deciphering the biochemical processes impacting on variation in WHC. Twenty spots were observed to be altered across the phenotypes. Of these, 14 represented sixteen proteins including metabolic enzymes, stress response proteins and structural proteins. Triosephosphate isomerase and transferrin showed a major difference between the two extreme phenotypes, and may have potential as biological markers for WHC prediction. Several members of the HSPs family were highlighted. This proteomic study makes an important contribution towards a more detailed molecular view of the processes behind WHC and will provide a valuable resource for future investigations.

Detecting QTL for feed intake traits and other performance traits in growing pigs in a Piétrain-Large White backcross

Knowing the large difference in daily feed intake (DFI) between Large White (LW) and Piétrain (PI) growing pigs, a backcross (BC) population has been set up to map QTL that could be used in marker assisted selection strategies. LW × PI boars were mated with sows from two LW lines to produce 16 sire families. A total of 717 BC progeny were fed ad libitum from 30 to 108 kg BW using single-place electronic feeders. A genome scan was conducted using genotypes for the halothane gene and 118 microsatellite markers spread on the 18 porcine autosomes. Interval mapping analyses were carried out, assuming different QTL alleles between sire families to account for within breed variability using the QTLMap software. The effects of the halothane genotype and of the dam line on the QTL effect estimates were tested. One QTL for DFI (P < 0.05 at the chromosome-wide (CW) level) and one QTL for feed conversion ratio (P < 0.01 at the CW level) were mapped to chromosomes SSC6 - probably due to the halothane alleles - and SSC7, respectively. Three putative QTL for feed intake traits were detected (P < 0.06 at the CW level) on SSC2, SSC7 and SSC9. QTL on feeding traits had effects in the range of 0.20 phenotypic s.d. The relatively low number of QTL detected for these traits suggests a large QTL allele variability within breeds and/or low effects of individual loci. Significant QTL were detected for traits related to carcass composition on chromosomes SSC6, SSC15 and SSC17, and to meat quality on chromosome SSC6 (P < 0.01 at the genome-wide level). QTL effects for body composition on SSC13 and SSC17 differed according to the LW dam line, which confirmed that QTL alleles were segregating in the LW breed. An epistatic effect involving the halothane locus and a QTL for loin weight on SSC7 was identified, the estimated substitution effects for the QTL differing by 200 g between Nn and NN individuals. The interactions between QTL alleles and genetic background or particular genes suggest further work to validate QTL segregations in the populations where marker assisted selection for the QTL would be applied.

Functional genomics of the muscle response to restraint and transport in chickens

In the present study, we used global approaches (proteomics, transcriptomics, and metabolomics) to assess the molecular basis of the muscle response to stress in chickens. A restraint test, combined with transport for 2 h (RT test) was chosen as the potentially stressful situation. Chickens (6 wk old) were either nontreated (control chickens) or submitted to the RT test (treated chickens). The RT test induced a 6-fold increase in corticosterone concentrations, suggesting hypothalamic-pituitary-adrenal axis activation. The RT test decreased the relative abundance of several hexose phosphates [glucose-1-P (G1P), glucose-6-P (G6P), fructose-6-P (F6P), and mannose-6-P (M6P)] in thigh muscle. In addition, 55 transcripts, among which 39 corresponded to unique annotated genes, were significantly up- (12 genes) or downregulated (27 genes) by treatment. Similarly, 45 proteic spots, among which 29 corresponded to unique annotated proteins, were overexpressed (11 proteins), underexpressed (14 proteins), or only expressed in treated chickens. Integrative analysis of differentially expressed genes and proteins showed that most transcripts and proteins belong to 2 networks whose genes were mainly related with cytoskeleton structure or carbohydrate metabolism. Whereas the decrease in energetic metabolites suggested an activation of glycogenolysis and glycolysis in response to the RT test, the reduced expression of genes and proteins involved in these pathways suggested the opposite. We hypothesized that the prolonged RT test resulted in a repression of glycogenolysis and glycolysis in thigh muscle of chickens. The down-expression of genes and proteins involved in the formation of fiber stress after the RT test suggests a reinforcement of myofibrils in response to stress.

Skeletal muscle proteomics in livestock production

Proteomics allows studying large numbers of proteins, including their post-translational modifications. Proteomics has been, and still are, used in numerous studies on skeletal muscle. In this article, we focus on its use in the study of livestock muscle development and meat quality. Changes in protein profiles during myogenesis are described in cattle, pigs and fowl using comparative analyses across different ontogenetic stages. This approach allows a better understanding of the key stages of myogenesis and helps identifying processes that are similar or divergent between species. Genetic variability of muscle properties analysed by the study of hypertrophied cattle and sheep are discussed. Biological markers of meat quality, particularly tenderness in cattle, pigs and fowl are presented, including protein modifications during meat ageing in cattle, protein markers of PSE meat in turkeys and of post-mortem muscle metabolism in pigs. Finally, we discuss the interest of proteomics as a tool to understand better biochemical mechanisms underlying the effects of stress during the pre-slaughter period on meat quality traits. In conclusion, the study of proteomics in skeletal muscles allows generating large amounts of scientific knowledge that helps to improve our understanding of myogenesis and muscle growth and to control better meat quality.

Proteome changes during meat aging in tough and tender beef suggest the importance of apoptosis and protein solubility for beef aging and tenderization

Within a population of Charolais young bulls, two extreme groups of longissimus thoracis muscle samples, classified according to Warner-Bratzler shear force (WBSF) of 55 degrees C grilled meat, were analyzed by 2D-electrophoresis. Muscle analyses were performed on 4 bulls of the "tender" group (WBSF=27.7+/-4.8 N) and 4 bulls of the "tough" group (WBSF=41.2+/-6.1 N), at 3 post-mortem times: D0, samples taken within 10 min post-mortem; D5 and D21, samples kept at 4 degrees C under vacuum during 5 and 21 days. Proteins of muscle samples were separated in two fractions based on protein solubility in Tris buffer: "soluble" and "insoluble". Proteins of both fractions were separated by 2D-electrophoresis. Evolution of spots during the 3 post-mortem times was analyzed by hierarchical classification (HCA). Three clusters of proteins presenting similar evolution profiles provided accurate classification of post-mortem times and showed the translocation of some chaperone proteins and glycolytic enzymes from the soluble fraction to the insoluble fraction between D0 and D5. Cellular structure dismantlement and proteolysis was observed at D21. Effect of group ("tender" vs "tough") on spot intensities was tested by ANOVA. At D0, higher quantity of proteins of the inner and outer membrane of mitochondria was found in the tender group suggesting a more extensive degradation of mitochondria that may be related to the apoptotic process.