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DNA methylation plays a very important role in the regulation of gene expression. Under general situations, methylation in a gene promoter region is frequently accompanied by transcriptional suppression, and those genes that are highly methylated display the phenomenon of low expression. In contrast, those genes whose methylation level is low display the phenomenon of active expression. In this study, we conducted DNA methylation analysis on the CpG sites within the promoter regions of five adipose tissue-specific transcriptional factors- Adiponectin, Chemerin, Leptin, Smaf-1, and Vaspin-and examined their messenger RNA (mRNA) expression levels in different mouse tissues. We also performed analyses on the correlation between the DNA methylation levels of these genes and their mRNA expression levels in these tissues. The correlation coefficient for Leptin was the highest, and it displayed a high expression in an adipose tissue-specific manner. Thus, we cloned the regulatory region of Leptin gene and incorporated its promoter into the eukaryotic expression vector pEGFP-N1 and constructed a recombinant plasmid named pEGFP-N1-(p-Lep). This recombinant plasmid was first verified by DNA sequencing and then transfected into mouse pre-adipocytes via electroporation. Measurement of the activity of luciferase (reporter) indicated that p-Lep was capable of driving the expression of the reporter gene. This study has paved a solid basis for subsequent studies on generating transgenic animals. [ABSTRACT FROM AUTHOR]

Obesity can cause insulin resistance and type 2 diabetes. Moderate elevations in bilirubin levels have anti-diabetic effects. This study is aimed at determining the mechanisms by which bilirubin treatment reduces obesity and insulin resistance in a diet-induced obesity (DIO) mouse model. DIO mice were treated with bilirubin or vehicle for 14 days. Body weights, plasma glucose, and insulin tolerance tests were performed prior to, immediately, and 7 weeks post-treatment. Serum lipid, leptin, adiponectin, insulin, total and direct bilirubin levels were measured. Expression of factors involved in adipose metabolism including sterol regulatory element-binding protein (SREBP-1), insulin receptor (IR), and PPARγ in liver were measured by RT-PCR and Western blot. Compared to controls, bilirubin-treated mice exhibited reductions in body weight, blood glucose levels, total cholesterol (TC), leptin, total and direct bilirubin, and increases in adiponectin and expression of SREBP-1, IR, and PPARγ mRNA. The improved metabolic control achieved by bilirubin-treated mice was persistent: at two months after treatment termination, bilirubin-treated DIO mice remained insulin sensitive with lower leptin and higher adiponectin levels, together with increased PPARγ expression. These results indicate that bilirubin regulates cholesterol metabolism, adipokines and PPARγ levels, which likely contribute to increased insulin sensitivity and glucose tolerance in DIO mice. [ABSTRACT FROM AUTHOR]