Search

This study was conducted to investigate the regulatory mechanism of reactive oxygen species (ROS) on the glycolysis pathway of bovine muscle and its impact on meat tenderness at the early stage of postmortem cold storage. Fresh beef was treated with hydrogen peroxide (H2O2) as a major ROS, N-acetyl-L-cysteine (NAC) as an ROS scavenger, or physiological saline as a control before being stored at 4 ℃. After 0.5, 6, 12, 24, and 48 hours, the glycolysis level and tenderness indices were assessed. In addition, tandem mass tag (TMT)-labeled quantitative proteomics was used for protein identification and quantitative analysis of the samples after 24 hours and for screening of differential proteins in the glycolysis pathway. The findings showed that the glycolysis level increased significantly in the H2O2-treated group, and glycogenolysis and lactic acid accumulation were significantly higher than those in the other two groups (P < 0.05). In contrast, the glycolysis process was significantly suppressed by NAC treatment. The H2O2-treated group reached the ultimate pH after 12 hours, 12 and 36 hours earlier than the control and NAC groups, respectively. The shear force of the H2O2-treated group reached its maximum after 12 hours, and the myofibrillar fragmentation index (MFI) was significantly greater than that of the other two groups after 6–48 hours (P < 0.05), indicating that a higher ROS level can accelerate the tenderization of bovine muscle by enhancing the glycolysis capacity during postmortem refrigeration. Totally eight up-regulated proteins and two down-regulated proteins in the glycolysis pathway were identified in the H2O2-treated versus control groups after 24 hours of refrigeration. Among these proteins, the up-regulated core proteins of phosphoglycerate mutase (PGAM), enolase (ENO), and pyruvate dehydrogenase E1 subunit beta (PDHB) coordinated with the down-regulated pyruvate dehydrogenase E1 subunit alpha (PDHA) to accelerate the glycolysis process. In conclusion, ROS can speed up glycolysis and consequently improve meat tenderness by regulating the expression of key proteins in the glycolysis pathway.

This study aimed to investigate the effect of reactive oxygen species (ROS) on early postmortem energy metabolism in bovine muscle via regulating the expression of hypoxia-inducible factor-1α (HIF-1α). The muscle samples were treated with hydrogen peroxide (H2O2), N-acetyl-L-cysteine (NAC), and normal saline (control), separately. The ROS content, proline hydroxylase (PHD) activity, phosphoinositide-3 kinase/protein kinase B (PI3K/AKT) and HIF-1α expression levels, energy metabolism, and pH were determined at 0.5, 6, 12, 24 and 48 h postmortem. The results revealed that the H2O2-treated group showed a significantly higher ROS content than the other two groups at 0.5 h postmortem (P < 0.05) and remained at a high level within 48 h, while NAC inhibited the accumulation of ROS for a short period of time (during 0.5–12 h) postmortem. The PHD activity in the H2O2-treated group was significantly lower than that in the other two groups during 0.5–48 h (P < 0.05). Meanwhile, the expression levels of PI3K from 0.5 to 12 h and phosphorylated AKT (p-AKT) from 0.5 to 6 h were significantly higher than those in the other groups (P < 0.05). Consequently, the expression level of HIF-1α in the H2O2-treated group was significantly higher than that of the other two groups during 6–48 h (P < 0.05), the rate of glycogenolysis and the rate of increase in R value were significantly faster in the H2O2-treated group during 6–24 h (P < 0.05), and the pH of the H2O2-treated group reached the limit value earlier (at 12 h). In conclusion, ROS can activate the stable expression of HIF-1α by reducing the activity of PHD and up-regulating the PI3K/AKT signaling pathway and consequently accelerate energy metabolism dominated by glycolysis and the decrease in pH in bovine muscle at the initial stage of postmortem aging, which may have a crucial impact on meat quality.

Summary: In this work, deferoxamine (DFO) was injected into Tibetan sheep meat (distilled water as control) to reveal the effects of lysosomal Fe2+ on mitochondrial apoptosis and muscle tenderness. The reactive oxygen species (ROS) content, lysosomal membrane stability, cathepsins activity, mitochondrial membrane permeability transition pore (MPTP), mitochondrial membrane potential (MMP), cytochrome c (Cyt‐c) reduction level, caspase activity, myofibril fragmentation index (MFI) and shear force of Oula Tibetan sheep meat were measured at different ageing times. The results indicated that the ROS content, cathepsins activity, MPTP opening degree, lysosomal membrane stability, caspase‐3/9 activity and MFI of Tibetan sheep meat were significantly decreased after DFO treatment, whilst MMP, shear force and Cyt‐c reduction levels were noticeably increased. Furthermore, correlation analysis and principal component analysis showed that mitochondrial damage was positively correlated with meat tenderness. In sum, the study suggests that lysosomal Fe2+ may promote mitochondrial apoptosis and improve the tenderness of Tibetan sheep meat. [ABSTRACT FROM AUTHOR]

In this study, fuzzy mathematics and response surface modeling were applied to optimize the preparation process of beef liver paste and characterize the proximate composition, sensory and physicochemical qualities, and in vitro simulated digestive properties while refrigerated at 0–4 °C (0, 3, 7, 15, 30, 45, and 60 days). The results showed that the optimal preparation process was 4.8% potato starch, 99.4% water, 10.2% olive oil, and a 3:2 ratio of chicken breast and beef liver. The beef liver paste prepared contained essential amino acids for infants and children, with a protein content of 10.29 g/100 g. During storage, the pH of the beef liver paste decreased significantly (p < 0.05) on day 7, texture and rheological properties decreased significantly after 30 days, a* values increased, L* and b* values gradually decreased, and TVB-N and TBARS values increased significantly (p < 0.05) on day 7 but were below the limit values during the storage period (TVB-N value ≤ 15 mg/100 g, TBARS value ≤ 1 mg/Kg). In vitro simulated digestion tests showed better digestibility and digestive characteristics in the first 15 days. The results of this study provide a reference for the development of beef liver products for infant and child supplementation. [ABSTRACT FROM AUTHOR]

To understand genetic variation and population dispersal in the Yangtze vole Microtus fortis calamorum distributed in the Dongting Lake region, 144 individuals were collected from six habitat patches. The mitochondrial DNA control region was sequenced and 17 haplotypes were observed. Of the six investigated populations, haplotype and nucleotide diversities of those from larger patches were higher than those from smaller patches. Nonparametric correlation analysis showed that patch size had a positive correlation with haplotype diversity (r = 0.943, P < 0.01). A neighbour-joining tree of the 17 haplotypes showed no geographic genetic structure among the six populations. Analysis of isolation by distance showed that genetic differentiation among the six populations was not positively related to geographic distance. Analysis of mismatch distribution indicated that the voles had passed through a population expansion. The pattern of haplotype distribution in the Changsha population suggests that the population was established by a founder effect [Current Zoology 58 (2): 211–220, 2012].