Objective To observe the short-term and long-term effects of leptin on hepatic glucose oxidation and glucokinase gene expression. Methods Rat hepatic cell line BRL was incubated with leptin of different doses (range from 10?ng/ml-200?ng/ml) for 1?h or 24?h. Glucose oxidation was determined by liquid scintillation counting. Glucokinase gene expression (corrected by β-actin) was determined by reverse transcription semi-quantitative polymerase chain reaction. Results Treatment with leptin 10?ng/ml for 1?h had no significant effects on glucose oxidation in hepatic cells. However, at the doses ranging from 50?ng/ml to 200?ng/ml, leptin significantly inhibited glucose oxidation. These effects disappeared when the hepatic cells were exposed to leptin for 24?h. Glucokinase mRNA expression was reduced significantly after both 1?h and 24?h exposure to leptin (100?ng/ml) as compared to that of the control group. Conclusion A low dose of leptin has no significant effect on glucose oxidation in hepatic cells. A relatively high dose of leptin has an acute inhibitory effect on the glucose oxidation in hepatic cells. This effect may likely involve the inhibition of glucokinase gene expression. The inhibitory effect on glucose oxidation is transient and disappears with prolonged exposure time.
The yeast Pichia pastoris was transformed by the multi\|copy Pichia expression vector that can express secreted human albumin.The high level expression of cell line was selected after screening.The expression of human recombinant albumin in Pichia pastoris induced by different methods were compared.The retio of secreted human albumin is 80% in total secreted proteins and the expression level reaches as high as is 10g/L.
