Abstract
Adipogenesis is of great importance in beef cattle. Recent findings indicate that glucose, a substrate for fatty acid biosynthesis and retinoic acid enhance a dipogenesis in bovine intramuscular adipocytes. However, other recent findings indicate that Retino l-Binding Protein 4 (RBP4) interferes with glucose uptake and utilization by rodents’ adipocytes. In t his study we examined the regulation of RBP4 expression and its relation to adipogenesis in bovi ne adipocytes. Stromal vascular cells were prepared by collagenase digestion from subcutaneous and intr amuscular adipose tissues of Japanese black steers. RT-PCR revealed that RBP4 mRNA was expressed in bovine adipose tissue. Northern and Western Blot analysis showed that RBP4 was highly expressed and secreted from bovine preadipocytes. However, RBP4 expression and secretion were significantly reduced by induction of the adipogenic differentiation of preadipocytes into ma ture adipocytes. Glucose and retinoic acid have a suppressive effect on RBP4 expression and secretion from intramuscular adipocytes. Retinoic acid significantly decreased RBP4 expression in Japanese black steer subcutaneous adipocytes. Retinoic acid itself had no effect on lipid accumulation in subcu taneous adipocytes however, retinoic acid enhanced lipid accumulation in these adipocytes after additi on of acetate, a substrate for fatty acid biosynthe sis in subcutaneous adipocytes. This study indicated a neg ative correlation between adipogenesis and RBP4 expression in bovine adipocytes and suggests possib le inhibitory effect of RBP4 on adipogenesis.
Highlights
Retinol Binding Protein (RBP), known as Retinol Binding Protein 4 (RBP4), is a single polypeptide chain 21-kDa protein
Stromal vascular cells prepared from Holstein subcutaneous adipose tissue and Japanese black steers subcutaneous and intramuscular adipose tissues were differentiated till day 12
The adipogenic differentiation of these cells was conformed by lipid accumulation in the differentiated cells, which was detected by oil red O stain (Fig. 2A) and expression of adipogenic differentiation marker gene, adipocytes specific fatty acid binding protein
Summary
Retinol Binding Protein (RBP), known as Retinol Binding Protein 4 (RBP4), is a single polypeptide chain 21-kDa protein. Retinol (vitamin A) plays important roles in many physiological functions including cell differentiation through its active form, Retinoic Acid (RA). Glucose has an important role in adipogenesis in bovine intramuscular adipocytes as a substrate for fatty acid biosynthesis (Smith et al, 2009). RBP4 especially that produced from adipose tissue interferes with glucose uptake and utilization in adipocytes of rodents and human (Yang et al, 2005; Ost et al, 2007). Increasing glucose uptake and utilization in intramuscular adipocytes of beef cattle by decreasing RBP4 production and/or increasing blood glucose level, may increase adipogenesis in intramuscular adipose tissue and subsequently improve marbling scores and meat quality. RBP4, retinol and glucose play important roles in adipocytes metabolism, there is no report concerning the regulation of RBP4 expression and its relation to adipogenesis in bovine intramuscular adipocytes. In this study we investigated the correlation between RBP4 expression and adipogenesis in bovine intramuscular adipocytes as well as we examined the regulation of RBP4 expression by RA in bovine adipocytes cultured in the presence of different glucose concentrations
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