Detection and the effects of chylomicrons on SREBP-1 in3T3-L1 adipocytes.

• Main Authors: Chiung Ya Chen, 陳瓊雅
• Other Authors: Shao Chun Lu
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/71022176968574828450

碩士 === 國立臺灣大學 === 農業化學研究所 === 89 === Sterol Regulatory Element Binding Proteins ( SREBPs) are members of baic Helix-Loop-Helix Leucine Zipper ( bHLH-LZ) family of transcription factors. To date, three isoforms have been identified, 1a, 1c and 2, encoded by two separate genes. SREBPs are synthesized as 125 kDa precursor proteins that located to the endoplasmic reticulum. The precursor is cleaved by two proteases to release the mature, transcriptionally active 68 kDa amino terminal domain. SREBP-1 preferentially activate genes involved in fatty acid synthesis; SREBP-2 preferentially activate genes involved in cholesterol metabolism. Both in vitro and in vivo studies show SREBP-1 are regulated by nutritional status and hormones. A variety of reports are focused on hepatocytes and liver. These reports are about the effects of fatty acid and dietary PUFA to SREBP-1 in hepatocytes or liver. The regulation of SREBP in liver and in adipose tissue is probably not the same. So in this study , we are trying to observe the effect of chylomicron which is rich in exogenous TG on the expression of SREBP-1 mRNA and protein in adipocyte and adipose tissue. Moreover, establishment for detecting SREBP-1 protein. In Western blot analysis, three antibodies against SREBP-1 we tried the monoclonal antibody IgG2A4 was found to be the best. At the same time, it’s necessary to notice transfer time, transfer method and concentration of antibody. On day 10, fully differentiated 3T3L1 adipocyte were serum-starvated for 16hrs and then transferred to low glucose serum-free DMEM containing 0.5% BSA with or without CM( 200μg TG/mL ) for 6 hrs. There’s no significant difference in the SREBP-1 mRNA level when cells incubated with or without CM( 200μg TG/mL ) for 6hrs (Fig 3-5). However, in both treatment, there’s a substantial increase in the amount of precursor SREBP-1, while a decrease in the amount of mature SREBP-1 (Fig.3-1). Wistar rats were tube fed PBS、corn starch(12Kcal/rat)、soybean oil (12Kcal/rat). Plasma TG is significantly increasing during the first to the third hours in soybean oil group (p<0.05). After tube fed 3hrs, plasma TG and CM-TG are significantly higher in the soybean oil group than the other two groups (p<0.05). After tube fed 1hrs, SREBP-1 mRNA of epididymal fat pad is slightly increasing in corn starch and soybean oil group, but there is no significant diffenence among the corn starch、PBS and soybean oil groups (p>0.05). These data suggests there is no correlation between the concentration of plasma TG or CM-TG and SREBP-1 mRNA of epididymal fat pad in rats( p>0.05). The mechisms between these changes in both adipocyte and adipose tissue is not clear, deserve more investigation.