The effect of different nutrients on insulin sensitivity in 3T3-L1 adipocytes
Date Issued
2005
Date
2005
Author(s)
Chwang, Chi-Jung
DOI
zh-TW
Abstract
Type II diabetes accounts for 90 to 95% of diabetes patients. Muscle and adipose tissue in such individuals have a decreased insulin sensitivity. Decrease in insulin sensitivity reduces translocation of glucose transporter 4（GLUT4） protein to cell membrane upon insulin stimulation. Therefore, cells can not uptake glucose effectively. Insulin modulates animal physiology through a phosphatidylinositol-3-kinase pathway（PI3-kinase pathway) and a mitogen-activated protein kinase pathway（MAP-kinase pathway）. The major regulation of GLUT4 translocation from intracellular vesicle to cell membrane is generated from PI3-kinase pathway.
The purpose of this study were to establish primary cell culture systems for rat adipocytes and preadipocytes and to study the effect of different nutrients on insulin sensitivity in rodent adipocytes.
In the current study, thiazolidinedione（TZD）, glucose, glucosamine（GlcN）, oleic acid（OA）, and docosahexaenoic acid（DHA）were used to treat 3T3-L1 adipocytes. 3T3-L1 adipocytes were incubated in DMEM containing 5 mM glucose plus 5% fetal bovine serum（FBS）as insulin source with different nutrients for 48 hours. Concentration of glycerol in the cultured medium was measured to evaluate the ability of lipolysis in 3T3-L1 adipocytes. In addition, we measured the mRNA concentrations of insulin receptor（IR）, insulin receptor substrate 1（IRS-1）, PI3-K and GLUT 4, genes that are participated in the PI3-kinase pathway. We also measured mRNA concentrations of adiponectin and leptin, two secretive proteins in adipocytes involving energy balance. Western blot was used to determine the concentration of GLUT4 protein on cell membrane in order to estimate the degree of GLUT4 translocation.
In our study, TZD treatment significantly reduced the concentration of glycerol in cultured medium whereas glucose treatment increased the glycerol concentration, indicating that TZD may increase insulin function to reduce lipolysis and high concentration of glucose may reduce insulin function to increase lipolysis in vitro. GlcN treatment increased the GLUT4 protein level on the cell membrane. Whether GlcN can increase insulin function requires further experiment to demonstrate. TZD, glucose, OA and DHA increased the steady state adiponectin mRNA concentration suggesting that theses nutrients may influence cellular function though manipulating the expression of aiponectin.
Several Chinese herbs extracts, Ligustri Fructus, Rhodiola, Lychee Seed, Costus Root, and India Abutilon were used to treat 3T3-L1 adipocytes. We found no significant effect for these herbs on lipolysis and GLUT4 protein concentration on the cell membrane. Rhodiola reduced IR, IRS1, and GLUT4 mRNA concentrations, suggesting that Rhodiola may downregulate the PI3-kinase pathway signal transduction by reducing the mRNA concentrations of the genes involved in this pathway. However, the mechanism of these herbs extracts on PI3-kianse pathway in adipocytes requires further demonstration.
Subjects
脂肪細胞
胰島素敏感性
adipocytes
insulin sensitivity
SDGs
Type
thesis
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