Perilipin, C/EBPα, and C/EBPβ mRNA abundance in longissimus muscle and different adipose tissues of Holstein and Charolais cattle

Effects of High-Fat Feeding on Skeletal Muscle Gene Expression in Diabetic Goto-Kakizaki Rats

In the present report, we examined the responses of diabetic Goto-Kakizaki (GK) rats and control Wistar-Kyoto (WKY) rats fed either a standard chow or high-fat diet (HFD) from weaning to 20 weeks of age. This comparison included gene expression profiling of skeletal muscle using Affymetrix gene array chips. The expression profiling is interpreted within the context of a wide array of physiological measurements. Genes whose expressions are different between the 2 strains regardless of diet, as well as genes that differ between strains only with HFD, were identified. In addition, genes that were regulated by diet in 1 or both strains were identified. The results suggest that both strains respond to HFD by an increased capacity to oxidize lipid fuels in the musculature but that this adaptation occurs more rapidly in WKY rats. The results also demonstrated an impaired cytokine signalling and heightened inflammatory status in the GK rats.

Molecular heterogeneities of adipose depots - potential effects on adipose-muscle cross-talk in humans, mice and farm animals

Adipose tissue is considered as a major endocrine organ that secretes numerous proteins called adipokines. The heterogeneous nature of adipose tissue in different parts of the body suggests respective heterogeneity of proteomes and secretomes. This review consolidates knowledge from recent studies targeting the diversity of different adipose depots affecting the pattern of secreted adipokines and discusses potential consequences for the cross-talk between adipose and skeletal muscle in humans, rodent models and farm animals. Special attention is paid to muscle-associated fat depots like inter- and intramuscular fat that become focus of attention in the context of the rather new notion of skeletal muscle as a major endocrine organ. Understanding the complexity of communication between adipocytes and skeletal muscle cells will allow developing strategies for improvement of human health and for sustainable production of high quality meat.

Fatty acid profiles and adipogenic gene expression of various fat depots in Japanese Black and Holstein steers

Objective of the study was to assess the breed effect on fatty acid (FA) composition of different adipose tissues and on mRNA expression of genes involved in adipogenesis and fat metabolism. Japanese Black (JB) and Holstein (HS) steers were kept under equivalent conditions with high energy intake resulting in large differences in intramuscular fat (IMF) accumulation in longissimus muscle (LM). The relative FA composition of muscle, intermuscular fat, visceral fat, and perirenal fat was comparable between JB and HS steers. Circulating fatty acids were also similar in both breeds. Most relevant breed effects were identified in IMF, underlining the uniqueness of this adipose tissue site. JB steers had more monounsaturated FA and less saturated FA. Perilipin 1 and adipose differentiation-related protein (ADFP) mRNA levels were higher in IMF of JB. The results suggest advanced maturity of IMF cells in JB and altered local conditions in muscle influencing IMF accumulation and composition.

MicroRNA-130b and microRNA-374b mediate the effect of maternal dietary protein on offspring lipid metabolism in Meishan pigs

To investigate whether the effect of maternal dietary protein on offspring lipid metabolism is mediated by microRNA (miRNA), fourteen Meishan sows were fed either low-protein (LP, half of standard protein (SP) level, n 7) or SP (n 7) diets throughout gestation and lactation periods. PPAR-γ and CCAAT/enhancer-binding protein-β (C/EBP-β) protein expression was evaluated. The expression of miRNA predicted to directly target PPAR-γ and C/EBP-β in the subcutaneous fat of offspring at weaning age was determined, and the functions of these potential miRNA were verified. The results showed that piglet body weight and back fat thickness were significantly decreased in the LP group compared with the SP group (P< 0·05). The protein level of PPAR-γ was significantly decreased and C/EBP-β protein expression was also decreased, though not significantly (P= 0·056), in the subcutaneous fat of the LP group. Furthermore, miRNA expression analysis showed that miR-130b, targeting the PPAR-γ 3′-untranslated region (UTR), and miR-374b, targeting the C/EBP-β 3′-UTR, were significantly increased in the LP group compared with the SP group; other candidate regulatory miRNA were expressed similarly in both groups. Dual luciferase activity assay results indicated that miR-130b directly recognised and bound to the 3′-UTR of PPAR-γ and thereby suppressed PPAR-γ gene expression. Similar results were found for miR-374b and the 3′-UTR of C/EBP-β. The present study showed that miR-130b and miR-374b are involved in the effect of maternal dietary protein on offspring lipid metabolism in pigs. These results shed new light on our understanding of the maternal effect on offspring lipid deposition.

Technical note: Determination of cell-specific gene expression in bovine skeletal muscle tissue using laser microdissection and reverse-transcription quantitative polymerase chain reaction

Skeletal muscle is a very heterogeneous tissue consisting of diverse cell types with specific transcription profiles. Therefore, the measured mRNA abundance of a certain cell type marker is influenced by the transcriptional activity as well as by the usually unknown number of contributing cells in the sample. In studies on the transcriptional activity of adipogenic genes, as indicators for the development of intramuscular adipocytes, an altered number of adipocytes or respective progenitor cells can mask changes in transcriptional activity. To overcome this problem, we started to use laser microdissection to isolate RNA of adipocytes and muscle fibers separately for downstream analysis. Even muscle fiber types can be collected and analyzed separately. Laser microdissection in combination with biopsy techniques enables gene expression studies of particular cell types during the life cycle of an animal. First experiences using laser microdissection for adipogenic gene expression studies in bovine skeletal muscle are described, and the influence of sample preparation and future challenges are discussed.

Perilipin 1 and perilipin 2 protein localization and gene expression study in skeletal muscles of European cross-breed pigs with different intramuscular fat contents

This study investigated the lipid droplet coat proteins perilipin 1 (PLIN1) and perilipin 2 (PLIN2) localization in pig skeletal muscle and their relationship with intramuscular fat (IMF) content. PLIN1 and PLIN2 proteins were immunostained in semimembranosus muscle cross-sections from two groups of samples divergent for IMF and the gene expression was quantified. PLIN1 localized in the periphery of intramuscular adipocytes, whereas PLIN2 localized within myofibers with high lipid content. The high IMF group showed higher total cross-sectional area of PLIN1-stained adipocytes compared with the low IMF group (P<0.05), while the cross-sectional area and percentage of PLIN2-positive myofibers did not differ between IMF-divergent groups. This suggested that IMF content is mainly determined by extra-myocellular lipids. At mRNA level, PLIN2 expression was higher in high IMF muscles (P<0.05). The results indicate for the first time that in pig muscle PLIN1 and PLIN2 proteins are localized in correspondence with extra and intra-myocellular lipids, respectively.

Proteome differences associated with fat accumulation in bovine subcutaneous adipose tissues

Background

The fat components of red meat products have been of interest to researchers due to the health aspects of excess fat consumption by humans. We hypothesized that differences in protein expression have an impact on adipose tissue formation during beef cattle development and growth. Therefore, in this study we evaluated the differences in the discernable proteome of subcutaneous adipose tissues of 35 beef crossbred steers [Charolais × Red Angus (CHAR) (n = 13) and Hereford × Angus (HEAN) (n = 22)] with different back fat (BF) thicknesses. The goal was to identify specific protein markers that could be associated with adipose tissue formation in beef cows.

Results

Approximately 541-580 protein spots were detected and compared in each crossbred group, and 33 and 36 protein spots showed expression differences between tissues with high and low BF thicknesses from HEAN and CHAR crossbed, respectively. The annexin 1 protein was highly expressed in both crossbred steers that had a higher BF thickness (p < 0.05) and this was further validated by a western blot analysis. In 13 tissues of CHAR animals and 22 tissues of HEAN animals, the relative expression of annexin 1 was significantly different (p < 0.05) between tissues with high and low BF thicknesses.

Conclusion

The increased expression of annexin 1 protein has been found to be associated with higher BF thickness in both crossbred steers. This result lays the foundation for future studies to develop the protein marker for assessing animals with different BF thickness.