A comparison of intact and degraded desmin in cooked and uncooked pork longissimus thoracis and their relationship to pork quality

Identification of different myofiber types in pigs muscles and construction of regulatory networks

BACKGROUND

Skeletal muscle is composed of muscle fibers with different physiological characteristics, which plays an important role in regulating skeletal muscle metabolism, movement and body homeostasis. The type of skeletal muscle fiber directly affects meat quality. However, the transcriptome and gene interactions between different types of muscle fibers are not well understood.

RESULTS

In this paper, we selected 180-days-old Large White pigs and found that longissimus dorsi (LD) muscle was dominated by fast-fermenting myofibrils and soleus (SOL) muscle was dominated by slow-oxidizing myofibrils by frozen sections and related mRNA and protein assays. Here, we selected LD muscle and SOL muscle for transcriptomic sequencing, and identified 312 differentially expressed mRNA (DEmRs), 30 differentially expressed miRNA (DEmiRs), 183 differentially expressed lncRNA (DElRs), and 3417 differentially expressed circRNA (DEcRs). The ceRNA network included ssc-miR-378, ssc-miR-378b-3p, ssc-miR-24-3p, XR_308817, XR_308823, SMIM8, MAVS and FOS as multiple core nodes that play important roles in muscle development. Moreover, we found that different members of the miR-10 family expressed differently in oxidized and glycolytic muscle fibers, among which miR-10a-5p was highly expressed in glycolytic muscle fibers (LD) and could target MYBPH gene mRNA. Therefore, we speculate that miR-10a-5p may be involved in the transformation of muscle fiber types by targeting the MYHBP gene. In addition, PPI analysis of differentially expressed mRNA genes showed that ACTC1, ACTG2 and ACTN2 gene had the highest node degree, suggesting that this gene may play a key role in the regulatory network of muscle fiber type determination.

CONCLUSIONS

We can conclude that these genes play a key role in regulating muscle fiber type transformation. Our study provides transcriptomic profiles and ceRNA interaction networks for different muscle fiber types in pigs, providing reference for the transformation of pig muscle fiber types and the improvement of meat quality.

Degradation and evaluation of myofibril proteins induced by endogenous protease in aquatic products during storage: a review

Myofibril proteins degradation constitutes an important factor in quality deterioration, procedural activation or inhibition of endogenous protease potential regulates autolytic proteolysis-induced softening of post mortem fish muscle. Based on the brief introduction of myofibril proteins degradation in fish skeletal muscle, a detailed description of the main myofibril degradation properties and the distinct role played by endogenous proteases were proposed, which reflects the limitations and challenges of the current research on myofibril hydrolysis mechanisms based on the varied surrounding conditions. In addition, the latest researches on the evaluation method of myofibril proteins degradation were comprehensively reviewed. The potential use of label-free proteomics combined with bioinformatics was also emphasized and has become an important means to in-depth understand protein degradation mechanism.

Myosin Heavy Chain Composition, Rate of Dystrophin and Integrin Degradation and Meat Quality of Pig Longissimus thoracis and psoas major Muscles During Postmortem Aging

This study evaluated myosin heavy chain composition and the effect of aging time (45 min, 24 h, 96 h and 168 h) on meat quality parameters and dystrophin and integrin degradation pattern in longissimus thoracis and psoas major muscles of 24 Polish Landrace fatteners slaughtered at 100 kg body weight. It was found that m. longissimus thoracis had a greater percentage of MyHC-IIB (P≤0.05) and a significantly lower percentage of type I and IIA/IIX (P≤0.05) compared with the m. psoas major. Moreover, psoas major muscle had significantly higher (P≤0.05) pH45, pH24 and lower drip loss values for 45 min to 24 h, 45 min to 96 h and 45 min to 168 h than m. longissimus thoracis. Muscle type also had a significant effect on the rate of dystrophin and integrin degradation postmortem, which were significantly (P≤0.05) more rapidly degraded in the m. longissimus thoracis compared to the m. psoas major. It is concluded from the obtained results that the muscles with a greater percentage of MyHC-IIB show lower pH values, which translates into more rapid rate of integrin and dystrophin degradation. Ultimately, this may contribute to higher drip loss values during refrigerated storage.

Influence of postmortem aging and post-aging freezing on pork loin quality attributes

The objectives were to determine 1) the interaction between aging duration and post-aging freezing on pork loin quality attributes and 2) the relationship between pork loin star probe (SP) and Warner-Bratzler shear force (WBS). Loins from 20 carcasses were collected 1 d postmortem. Chops (n = 9; 2.54-cm thick) were fabricated from each loin and vacuum packaged. Four chops from each loin were aged at 4°C for 1, 8, 14, and 21 d and immediately evaluated (Fresh). Four adjacent chops were aged (1, 8, 14, and 21 d), frozen for 14 d, and thawed for evaluation (Frozen). An additional chop was used for evaluation of sarcomere length, intact desmin, and troponin-T degradation. Purge, objective color, pH, subjective color and marbling score, cook loss, SP, and WBS were evaluated at each aging period. Desmin and troponin-T degradation, and sarcomere length were measured on fresh samples at each day of aging. Post-aging freezing had no significant impact on SP, WBS, pH, and subjective color or marbling score at any aging period. Fresh chop purge increased at each day of aging (P < 0.01). Post-aging freezing resulted in greater purge at 1, 8, and 14 d aging (P < 0.01). Fresh chop cook loss was greater than post-aging freezing chop cook loss at 14 and 21 d aging (P < 0.05). Across all aging periods and treatments, SP was correlated (r = 0.85; P < 0.01) with WBS. Fresh chop SP and WBS decreased from 1 to 8 d aging but was not different after 8 d aging. The abundance of intact desmin decreased (P < 0.01) between 1, 8, and 14 d aging. Troponin-T degradation increased (P < 0.01) with each aging period. Sarcomere length was not different across aging periods (P > 0.05). Aging, without freezing, for 14 or 21 d did not improve SP or WBS observed at 8 d, corresponding with changes in desmin degradation.

Analysis of Proteins Associated with Quality Deterioration of Grouper Fillets Based on TMT Quantitative Proteomics during Refrigerated Storage

A TMT (Tandem Mass Tag)-based strategy was applied to elucidate proteins that change in proteomes of grouper fillets during refrigerated storage. In addition, quality analyses on pH, centrifugal loss, color (L *, a *, b *) and texture (hardness, chewiness, and gumminess) for grouper fillets were performed. A total of 64 differentially significant expressed proteins (DSEPs) were found in the results in the Day 0 vs. Day 6 group comparison and the Day 0 vs. Day 12 group comparison. It is worth mentioning that more proteome changes were found in the Day 0 vs. Day 12 comparisons. Bioinformatics was utilized to analyze the DSEP. UniProt Knowledgebase (UniProtKB), Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein interaction network analysis were adopted. All DSEPs were classified into seven areas by function: binding proteins, calcium handling, enzymes, heat shock protein, protein turnover, structural proteins and miscellaneous. The numbers of proteins that correlated closely with pH, centrifugal loss, color (L *, a *, b *) and texture (hardness, chewiness, and gumminess) were 4, 3, 6 and 8, respectively.

Environmentally relevant concentrations of carbamazepine induce liver histopathological changes and a gender-specific response in hepatic proteome of Chinese rare minnows (Gobiocypris rarus)

To assess hepatotoxicity and to determine the underlying mechanisms of carbamazepine (CBZ) toxicity in fish, histopathology and the liver proteome were examined after Chinese rare minnow (Gobiocypris rarus) were exposed to 1, 10, and 100 μg/L CBZ for 28 days. Histopathological changes included disruption of spatial structure, pyknotic nuclei, cellular vacuolization and deformation of cell nuclei, in addition to marked swelling of hepatocytes in all treatment groups. Protein analysis revealed that there were gender-specific responses in rare minnow following exposure, and there were 47 proteins in females and 22 proteins in males identified as differentially abundant following CBZ treatments. Pathway analysis revealed that cellular processes affected by CBZ included apoptosis, cell differentiation, cell proliferation, and the respiratory chain, indicating impaired energy homeostasis. Noteworthy was that 15 proteins identified as different in abundance were associated with carcinogenicity. Relative mRNA levels for select transcripts were consistent with the changes of proteins N-myc downstream regulated gene (NDRG), Tropomyosin 2-Beta (TPM2) and annexin A4 (ANXA4). Protein pyruvate kinase, liver and RBC (PKLR) were increased at 1 and 100 μg/L CBZ without significant difference in transcript levels. These findings characterize molecular responses and histological changes in the liver that generate new insights into CBZ hepatotoxicity in Chinese rare minnow.