The major role of insulin and the insulin receptor (InsR) in the liver is to mediate glucose uptake into hepatocytes to synthesize glycogen and to maintain blood glucose homeostasis. In this study, we investigated the effects of high insulin concentrations on InsR gene expression in calf hepatocytes cultured in vitro. After the cells were cultured for 72 h, insulin was added to the culture solution at final concentrations of 0, 1, 10, 100 or 1000 nM. InsR mRNA expression was determined by semi-quantitative RT-PCR. The results showed that InsR mRNA expression in hepatocytes, adjusted for β-actin expression, decreased dose dependently with increasing insulin concentration. InsR mRNA expression was similar at 1 and 10 nM insulin, but was significantly lower than that in the control. InsR expression was similar at 100 and 1000 nM insulin, but was significantly lower than that in the control, 1 and 10 nM insulin groups. These data suggest that high concentrations of insulin significantly repress InsR mRNA expression in calf hepatocytes, and this inhibition occurs in a dose-dependent manner. Further studies are needed to investigate the mechanisms underlying these effects of insulin.

The decline of spontaneous movement and spatial learning and memory ability could be induced in animals by chronic mild stress, and that may be related to the low activity of central cholinergic M-receptors. Both NSL and DHEA could effectively alleviate the above-mentioned changes.

The objective of the study was to determine expression of gene of insulin receptor (INSR) in adipose tissue of postpartum dairy cows fed diets containing different amounts of energy at the antepartum period. Healthy pregnant dairy cows (n=45) on 21st d of the antepartum were divided into three groups differing in diet composition, namely: control group fed a normal diet, high energy group fed a high energy diet, and low energy group fed a low energy diet. Twenty-one days after parturition, INSR gene expression in adipose tissue was determined by internally controlled reverse transcriptase PCR. The level of INSR mRNA in adipose tissues of cows fed the high energy diet was substantially lower than that in cows fed normal or low energy diets. A relatively higher level of INSR mRNA in the adipose tissue of cows fed low energy diet may be beneficial for gluconeogenesis and lipogenesis, which can relieve an energy negative balance. Reduced level of INSR mRNA in adipose tissue of cows fed high energy diet indicates that the response to insulin has significantly decreased.

Serum concentrations of sodium, potassium, magnesium, and iron were measured in dairy cows with subclinical ketosis. Compared with healthy cows, the subclinically ketotic cows had significantly higher levels of non-esterified fatty acids and β-hydroxybutirate in serum and significantly lower levels of blood glucose (p < 0.01). No significant differences were observed, suggesting that the mineral elements measured are not involved in the pathogenesis of subclinical ketosis.