Molecular Factors Underlying the Deposition of Intramuscular Fat and Collagen in Skeletal Muscle of Nellore and Angus Cattle

Abstract

Studies have shown that intramuscular adipogenesis and fibrogenesis may concomitantly occur in skeletal muscle of beef cattle. Thus, we hypothesized that the discrepancy of intramuscular fat content in beef from Nellore and Angus was associated with differences in intramuscular adipogenesis and fibrogenesis during the finishing phase. To test our hypothesis, longissimus muscle samples of Nellore (n = 6; BW = 372.5 ± 37.3 kg) and Angus (n = 6; BW = 382.8 ± 23.9 kg) cattle were collected for analysis of gene and protein expression, and quantification of intramuscular fat and collagen. Least-squares means were estimated for the effect of Breed and differences were considered at P ≤ 0.05. A greater intramuscular fat content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). No differences were observed for mRNA expression of lipogenic and lipolytic markers ACC, FAS, FABP4, SERBP–1, CPT–2, LPL, and ACOX (P > 0.05) in skeletal muscle of Nellore and Angus cattle. Similarly, no differences were observed in mRNA expression of adipogenic markers Zfp423, PPARγ, and C/EBPα (P>0.05) However, a greater PPARγ protein content was observed in skeletal muscle of Angus compared to Nellore cattle (P≤0.05). A greater abundance of adipo/fibrogenic cells, evaluated by the PDGFRα content, was observed in skeletal muscle of Angus than Nellore cattle (P≤0.05). No differences in fibrogenesis were observed in skeletal muscle of Angus and Nellore cattle, which is in accordance with the lack of differences in intramuscular collagen content in beef from both breeds (P>0.05). These findings demonstrate that difference in intramuscular fat content is associated with a slightly enhanced adipogenesis in skeletal muscle of Angus compared to Nellore cattle, while no difference in fibrogenesis.

Differences in Beef Quality between Angus (Bos taurus taurus) and Nellore (Bos taurus indicus) Cattle through a Proteomic and Phosphoproteomic Approach

“…Furthermore, Nellore had lower content of intramuscular fat (IMF, 2.7 ± 0.08 vs. 3.4 ± 0.08% ether extract). However, the content of total intramuscular collagen did not differ between Angus and Nellore [6]. …”

“…Treatment of fibroblasts with insulin or peroxisome proliferator-activated receptor gamma (PPAR-γ) caused PHB upregulation and induced adipogenesis with increased expression of PPAR-γ [62]. These findings are interesting, because in a parallel study, there was greater abundance of PPAR-γ in Angus muscle [6]. In addition, higher PHB abundance in IMF compared to subcutaneous, perirenal, and intermuscular fat has been observed in pigs [64].…”

“…The animals were confined in covered individual stalls with concrete floor and equipped with drinking and feeding troughs. Detailed information about the diet and its chemical composition were previously published [6]. …”

“…There is an increasing number of studies aiming to understand the molecular mechanisms related to the differences in beef quality between zebu and taurine cattle genotypes [5, 6]. These studies look for biomarkers that might be used in livestock breeding programs.…”

Adiposity and adipogenic gene expression in four different muscles in beef cattle

“…The expression of PPARG and CEBPA have been related to IMF content in cattle in previous works and a positive relationship between the expression of these genes and the amount of fat has been found [50, 57]. Other studies nevertheless did not show such relationship [58, 59]. …”