Elucidation of Molecular Mechanisms of Physiological Variations between Bovine Subcutaneous and Visceral Fat Depots under Different Nutritional Regimes

Abstract

Adipose tissue plays a critical role in energy homeostasis and metabolism. There is sparse understanding of the molecular regulation at the protein level of bovine adipose tissues, especially within different fat depots under different nutritional regimes. The objective of this study was to analyze the differences in protein expression between bovine subcutaneous and visceral fat depots in steers fed different diets and to identify the potential regulatory molecular mechanisms of protein expression. Subcutaneous and visceral fat tissues were collected from 16 British-continental steers (15.5 month old) fed a high-fat diet (7.1% fat, n=8) or a control diet (2.7% fat, n=8). Protein expression was profiled using label free quantification LC-MS/MS and expression of selected transcripts was evaluated using qRT-PCR. A total of 682 proteins were characterized and quantified with fat depot having more impact on protein expression, altering the level of 51.0% of the detected proteins, whereas diet affected only 5.3%. Functional analysis revealed that energy production and lipid metabolism were among the main functions associated with differentially expressed proteins between fat depots, with visceral fat being more metabolically active than subcutaneous fat as proteins associated with lipid and energy metabolism were upregulated. The expression of several proteins was significantly correlated to subcutaneous fat thickness and adipocyte size, indicating their potential as adiposity markers. A poor correlation (r=0.245) was observed between mRNA and protein levels for 9 genes, indicating that many proteins may be subjected to post-transcriptional regulation. A total of 8 miRNAs were predicted to regulate more than 20% of lipid metabolism proteins differentially expressed between fat depots, suggesting that miRNAs play a role in adipose tissue regulation. Our results show that proteomic changes support the distinct metabolic and physiological characteristics observed between subcutaneous and visceral adipose tissue depots in cattle.

Defining the Adipose Tissue Proteome of Dairy Cows to Reveal Biomarkers Related to Peripartum Insulin Resistance and Metabolic Status

“…In addition, the distinctive functions within each location ( Table 1) were comparable to those found in beef adipose; 13 for instance, within the plasma membrane, we identified 16.07% of proteins as enzymes compared to 18.42% in beef adipose, and we identified 5.36% of proteins as transmembrane receptors compared to 7.89% in beef adipose.…”

“…This is in agreement with other studies reporting that proteins involved in lipid metabolism are mostly increased in adipose tissue in IR states. [11][12][13][14] The specific role of several novel proteins that were differentially expressed in the IR adipose of dairy cows is discussed below.…”

Effect of age on bovine subcutaneous fat proteome: Molecular mechanisms of physiological variations during beef cattle growth1

“…For example, gene expression in adipocytes of rats varied by as much as 8.4% across different fat depots (epididymal vs. perirenal fat), whereas this variation was only 0.02% in rats of different age (3, 17, and 30 mo old; Cartwright et al, 2010). In one of our previous studies using the same steers we observed that 51% of the proteins expressed differently because of different fat depot location (subcutaneous vs. visceral fat) and 5.3% differed because of diet (high-vs. low-fat diet; Romao et al, 2013).…”

Adipose depot-specific effects of ileal interposition surgery in UCD-T2D rats: unexpected implications for obesity and diabetes

“…While the understanding of the molecular regulation of adipogenesis is mainly based on information obtained thus far from transcriptome data [12], our approach (the use of proteomics applied to the study of whole fat depots, as opposed to isolated adipocytes) should circumvent the less-than-robust (and gene-specific [13]) correlations between mRNA levels and protein expression [14] that occurs as a result of translational controls exerted by transcription factors, microRNAs, and epigenetic factors, concurrently taking into account metabolic differences between fat depots in vivo.…”