Expression and regulation of haptoglobin in tissues and in differentiated bovine adipocytes

Abstract

Haptoglobin (Hp) is a protein secreted mainly from the liver to bind hemoglobin and thus prevents iron loss and oxidative stress. Bovine Hp in blood increases during diseases such as mastitis and fatty liver syndrome. This study was conducted to examine the expression and regulation of Hp in differentiated mature bovine adipocytes. Hp expression was confirmed in various tissues and in mature adipocytes but not in the stromal vascular cell fraction using qualitative RT -PCR and quantitative northern blot analysis, respectively. Intravenous injection of Holstein cows with recombinant bovine tumor necrosis factor-α (rbTNF-α) and interferon gamma (rbIFN-γ) significantly increased the serum concentrations of Hp. When mature differentiated bovine adipocytes were incubated with short chain fatty acids, cytokines and hormones, Hp expression was altered. Acetate, butyrate and propionate at a dose of 1 mM significantly up-regulated Hp mRNA abundance. Lipopolysaccharide (LPS) and TNF-α also significantly up-regulated Hp mRNA abundance, while troglitazone and norepinephrine down-regulated it. Our study confirmed expression of Hp in differentiated mature adipocytes and identified LPS, TNF-α, short chain fatty acids, as regulators of Hp mRNA expression in these cells.