Effects Of L-arabinose On The Insulin-mediated PI3K Pathway In Skeletal Muscle

L-arabinose is a kind of pentose with a aldehyde group. Recently, a large number of researches have shown that L-arabinose has a lot of biological activities including lowing blood glucose levels, depressing blood fat levels, reducing blood press levels, decreasing fat accumulation in visceral organs and retarding weight growth. It is widely used in a variety of domains such as food industry, medicine and chemical industry. This paper studied effects of L-arabinose on insulin-mediated PI3K pathway in skeletal muscle of diabetic rats and related mechanism through observation of the state and quadriceps femoris pathological sections of rats, determinations of related physiological and biochemical indexes, and measurements of the gene expression quantity at the molecular level.Firstly, type 2 diabetic rat models were established by feeding the rats with high sugar-fat and intravenous injection of small dosage (30mg/(kg·bw)) of streptozotocin (STZ). The hypoglycemic effects of L-arabinose were studied by gavaged with different dosages of L-arabinose (87.5mg/(kg·bw),175mg/(kg·bw),525mg/(kg·bw)) to the diabetic rats. The results showed that the medium dosage group (175mg/(kg·bw)) and high dosage group (525mg/(kg·bw)) of L-arabinose could significantly decrease blood glucose levels and increase glucose tolerance of diabetic rats. The control group and the medium dosage group (175mg/(kg·bw)) of L-arabinose could significantly decrease glycated serum protein (GSP) levels in normal and diabetic rats, respectively. All the dosage groups of L-arabinose could significantly decreased the serum insulin levels of diabetic rats in a dose-dependent manner, so as to improve insulin resistance, the medium dosage group (175mg/(kg·bw)) and high dosage group (525mg/(kg·bw)) of L-arabinose could significantly decrease the serum C-peptide levels of diabetic rats and improve the biological effects of insulin.Secondly, the improvement of L-arabinose on the skeletal muscle of diabetic rats was studied through the preparation of quadriceps femoris frozen sections and determinations of T-SOD activities, MDA levels and the main signal transduction proteins levels in the insulin-mediated PI3K pathway. The results showed that L-arabinose could markedly raise the proportion of oxidizing muscle fiber in quadriceps femoris of diabetic rats, so as to improve the uptake and utilization of glucose in the skeletal muscle. In the tested dosage range, L-arabinose had no significant effects on diabetic oxidative stress combined with the determinations of T-SOD activities and MDA levels in the serum and skeletal muscle. All the dosage groups of L-arabinose could increase the protein kinase B (PKB) and glucose transporter 4 (GLUT4) levels in a dose-dependent manner, but only the high dosage group (525mg/(kg·bw)) appeared a significant difference.Finally, the RQ-PCR experiments on PI3K, PKB (also called Akt) and GLUT4 mRNA were carried out to investigate the possible related mechanism. The results showed as follows:high dosage group (525mg/(kg-bw)) of L-arabinose could significantly increase the gene expression of main proteins in insulin-mediated PI3K pathway of skeletal muscle compared with the model control group, making the signal transmission in insulin-mediated PI3K pathway enhanced and the sensitivity of the skeletal muscle to insulin improved.