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

Abstract

Anatomical site and divergent functionalities of muscles can be related to differences in IMF content, metabolism and adipogenic gene expression. Then, potential differences in different muscles in beef cattle were studied. As a second objective, the main sources of experimental variability associated to RT-qPCR results were analyzed following a nested design in order to implement appropriate experimental designs minimizing gene expression variability. To perform the study Longissimus thoracis (LT), Semitendinosus (SM), Masseter (MS), Sternomandibularis (ST) and subcutaneous adipose tissue (SAT) samples of Pirenaica young bulls (n = 4) were collected for IMF, collagen and protein quantification, analysis of adipocyte size distribution and gene expression (PPARG, CEBPA, FAPB4 and WNT10B). A greater IMF content was observed in MS and SM muscles, which had a bimodal adipocyte size distribution while it was unimodal in the muscles LT and ST. This suggest that the different IMF accretion in the muscles studied might be related to different rates of hyperplasia and hypertrophy and that IMF might develop later in LT and ST muscles. The former differences were not mirrored by the expression of the genes analyzed, which might be related to the different contribution of mature and non-mature adipocytes to the total gene expression. When comparing IMF and SAT gene expression, late and early developing tissues respectively, expression of PPARG, CEBPA and FABP4 was higher in the SAT, in agreement with bigger cell size and numbers. The variability study indicates that the analytical factors that add higher variability to the gene expression are the sampling and RT and therefore, it would be appropriate to include those replicates in the design of future experiments. Based on the results, the use of MS and SM muscles could allow less expensive experimental designs and bigger sample size that could permit the detection of lower relevant differences in gene expression.

<p>Screening and Identification of Differentially Expressed and Adipose Growth-Related Protein-Coding Genes During the Deposition of Perirenal Adipose Tissue in Rabbits</p>

“…16 Wang et al 17 analyzed RNA sequences from the longissimus dorsi muscle of two indigenous Chinese pig breeds and two introduced pig breeds, identifying 85 genes related to muscle growth and 27 genes related to lipid deposition. Similar studies have been reported in cattle, 18,19 sheep, 20,21 chickens 22 and other domestic animals. However, little information exists on genes that regulate the growth of adipose tissue in rabbits.…”

miR‐32‐5p Regulates Lipid Accumulation in Intramuscular Fat of Erhualian Pigs by Suppressing KLF3

“…Generally, IMF‐derived preadipocytes exhibit different differentiation ability compared with SCF‐derived preadipocytes (Gardan et al, 2006), which implies that adipogenesis is inhibited in muscle tissue. Several studies have compared gene expression profiles among different fat tissues using gene expression microarray analysis to identify the genes involved (Kojima et al, 2018; Martínez Del Pino et al, 2017). Our earlier study found that KLF3 expression level differs between IMF and SCF tissues (Liu et al, 2019), and RNA sequencing data by Lim et al also showed KLF3 is one of the differentially expressed genes in longissimus muscle of pigs with high and low IMF content (Lim et al, 2017).…”

Correction for adipocyte size and number in the analysis of differences in gene expression in fat tissues

“…Values considered for simulation were derived from our own data obtained in laboratory (Martínez del Pino, Arana, Alfonso, Mendizábal, & Soret, ) and some related published results (Kociucka et al., ; Komolka et al., ; Livak et al., ; Tichopad et al., ).…”