Collagens XII and XIV: Two collagen types both associated with bovine muscle and intramuscular lipid metabolism

In continental Europe, intramuscular fat (IMF) content in beef is low but plays a key role in determining flavor. IMF expands inside the extracellular matrix (ECM) of intramuscular connective tissue. This ECM contains among others, collagens XII and XIV, two minor collagens probably involved in muscle metabolism. So, our purpose was to determine if there was an association between the contents in collagens XII and XIV and muscle metabolism. Rectus abdominis (RA, oxidative) and Semitendinosus (ST, oxido-glycolytic) muscles were sampled from steers of two genotypes with high (Angus [Ang], n=10) or low (Limousine [Lim], n=10) intramuscular fat level. Collagens XII and XIV relative abundance was evaluated by Western blot analysis. The characteristic parameters of metabolism were previously measured. Ang muscles contained more collagen XIV than Lim muscles (p<0.001). RA muscle contained more collagen XII than ST muscle (p<0.01). Across the two breeds and muscles, collagen XII was positively correlated with A- and H-fatty acid binding protein (FABP) contents (+0.43 and +0.53, respectively, p<0.05) and activities of three oxidative enzymes (cytochrome-c oxidase: +0.41, isocitrate dehydrogenase [ICDH]: +0.40, citrate synthase [CS]: +0.32) (p<0.05) and collagen XIV was positively correlated with triacylglycerol content (+0.35, p<0.35), A- and H-FABP protein contents (+0.35 and +0.38, respectively, p<0.05) and ICDH (+0.34, p<0.05) and negatively with activities of two enzymes of glycolytic metabolism (phosphofructokinase: -0.31 and lactate dehydrogenase: -0.42, p<0.05). After removing the genotype and muscle effects, only collagen XII remained correlated with A- and H-FABP and CS activity (+0.30, +0.34 and +0.46, respectively, p<0.0505). H-FABP is expressed in various tissues but predominantly in cardiac and oxidative skeletal muscles, whereas A-FABP is exclusively expressed within adipocytes. From these results, we can conclude that collagen XII and XIV are both associated with bovine muscle fiber and intramuscular lipid metabolism, but probably by different mechanisms. As a matter of fact, collagens XII is associated with intramuscular fat differentiation (from its correlation with A-FABP content) and oxidative metabolism (from its correlation with H-FABP content and CS activities) regardless of breed and muscle, whereas type XIV collagen is associated with the same parameters plus enzymes of glycolytic metabolism that discriminate breeds

Are there consistent relationships between major connective tissue components, intramuscular fat content and muscle fibre types in cattle muscle?

peer-reviewedIntramuscular connective tissue (IMCT) is mainly composed of several fibrils (known as total collagen (TCol)) linked between each other by different chemical cross-links (CLs), the whole being embedded in a matrix of proteoglycans (PGs). In the field of beef quality, there is limited information on the role of CLs and PGs. Accordingly, several authors suggest that, to investigate the role of IMCT, it is important to investigate them just like TCol and insoluble collagen (ICol). In muscle, there are two other components, the muscle fibres and intramuscular fat (IMF) content. There are limited data on the relationships between these three components of muscle and then on possibility to independently manipulate these characteristics in order to control the final quality of meat. The present study aimed to investigate whether consistent relationships exist between these different components of muscle. Therefore, the present study compared four muscles of two cattle types (dairy and beef) to determine associations between TCol, ICol, CLs and PGs. Data were analysed across and within muscle (M) and animal type (AT) based on residuals. There was a strong M and AT effect for all muscle characteristics and an interaction M × AT for type I muscle fibres and IMF. Correlations between TCol, ICol and their CLs were M- and AT-independent. Total proteoglycans were positively correlated with TCol and ICol in a muscle-dependent manner irrespective of AT, but no correlation was found with CLs. On the contrary, CLs were negatively correlated with the ratio TPGs : TCol in an M-dependent manner, irrespective of AT. TCol, ICol and CLs were positively and negatively correlated with type IIA and IIB+X muscle fibres only in longissimus thoracis (LT) muscle, regardless the AT. Insoluble collagen was the only parameter of IMCT to be correlated with type I muscle fibres but only in LT muscle, irrespective of AT. There was no correlation between PGs and muscle fibre types, but PGs were the only IMCT component to be related with IMF in an M-dependent manner, irrespective of AT. Finally, there was no correlation between muscle fibre types and IMF content within M and AT. This study revealed that there is a strong relationship between IMCT components irrespective of M, an M-dependent relationship between the IMCT components and muscle fibre types and few (only with PGs) or no relationship between IMF and IMCT and muscle fibres

The effect of extended post-mortem ageing on the Warner–Brazler shear force of longissimus thoracis from beef heifers from two sire breeds, slaughtered at 20 or 25 mo of age

peer-reviewedwere examined. Spring-born Angus × Holstein-Friesian heifers (n = 48) and Belgian Blue × Holstein-Friesian heifers (n = 48) were slaughtered, within sire breed, at 20 or 25 mo of age. Approximately 48 h post-mortem, LT steaks (2.5 cm) were removed, and either stored at −20°C for chemical analysis or vacuum-packed, stored at 2°C for 7, 14 or 28 d post-mortem and then at −20°C pending Warner–Bratzler shear force (WBSF) analysis. Muscle from Angus-sired heifers had higher (P < 0.001) intramuscular fat (IMF) concentration, lower (P < 0.001) proportion of type IIX muscle fibres and higher (P < 0.001) proportion of type IIA and type I muscle fibres compared to muscle from Belgian Blue-sired heifers. Collagen characteristics did not differ between sire breeds. Later slaughter increased (P < 0.001) IMF concentration and decreased (P < 0.001) total and insoluble concentrations and collagen solubility. There were no interactions between the main effects for WBSF and no difference between sire breeds. Later slaughter and increasing the duration of ageing decreased (P < 0.05) WBSF. Based on threshold WBSF values in the literature, all samples would be considered tender (<39 N) after 7 d ageing. Untrained consumers are likely to detect the decrease in WBSF from 7 to 14 d ageing but not due to further ageing. Within the production system examined and based on WBSF data, extending LT ageing to 28 d is not necessary to ensure consumer satisfaction