Upregulation of mRNA of retinoid binding protein and fatty acid binding protein by cholesterol enriched-diet and effect of ginger on lipid metabolism.

Aims: We investigated whether a cholesterol enriched-diet upregulated mRNA expression of the lipid metabolism related-proteins, retinoid binding protein (RBP), heart fatty acid binding protein (H-FABP), and cutaneous fatty acid binding protein (C-FABP), in liver and adipose tissue, and examined the effect of ginger on the expression of these genes.

Main Methods: The male rats were divided into 3 groups. Control rats were fed a standard diet, the cholesterol enriched-diet group (Chs) was fed a cholesterol enriched-diet, and the cholesterol enriched-diet and ginger group (ChGs) was fed a cholesterol enriched-diet and ginger (500 mg/day) diet, respectively for 12 weeks. Each mRNA expression level was measured as the ratio of each gene relative to the beta-actin expression level, using semi-quantitative RT-PCR method.

Key Findings: Cholesterol enriched-diet developed hepatic steatosis with hyperlipidemia and increased RBP mRNA expression in the liver, as well as mRNA expression of RBP, H-FABP, and C-FABP in adipose tissue around the left kidney (P<0.05). This is the first report to show the upregulation of H-FABP mRNA in adipose tissue in hyperlipidemic rats. RBP mRNA was expressed in the liver on ChGs slightly lower than Chs (P=0.078).

Significance: These lipid metabolism genes are important indicators of hyperlipidemia. Ginger tends to reduce RBP mRNA expression levels in the liver and visceral fat in hyperlipidemia, and may improve lipid metabolism.