Identification of differentially expressed genes in omental adipose tissues of obese patients by suppression subtractive hybridization.

To identify differentially expressed genes between obese individuals and normal control, we have undertaken suppression subtractive hybridization (SSH). Omental adipose tissues were obtained via abdominal surgery for appendicitis in both 13 obese subjects [BMI (body mass index) >30 kg/m2] and 13 normal subjects (BMI >18 and <25 kg/m2). Following SSH, about one thousand clones were sequenced and found to derive from 426 different genes. These predominately expressed genes included genes involved in lipid metabolism, cytokines, signal transduction, GLUT4 translocation, cell cycle and growth, cytoskeleton, and others. Although more detailed analyses are necessary, it is anticipated that further study of genes identified will provide insights into their specific roles in the etiology of obesity.

A resistin binding peptide selected by phage display inhibits 3T3-L1 preadipocyte differentiation.

BACKGROUND: Resistin, a newly discovered cysteine-rich hormone secreted mainly by adipose tissues, has been proposed to form a biochemical link between obesity and type 2 diabetes. However, the resistin receptor has not yet been identified. This study aimed to identify resistin binding proteins/receptor. METHODS: Three cDNA fragments with the same 11 bp 5' sequence were found by screening a cDNA phage display library of rat multiple tissues. As the reading frames of the same 11 bp 5' sequence were interrupted by a TGA stop codon, plaque lift assay was consequently used to prove the readthrough phenomenon. The stop codon in the same 11 bp 5' sequence was replaced by tryptophan, and the binding activity of the coded peptide [AWIL, which was designated as resistin binding peptide (RBP)] with resistin was identified by the confocal microscopy technique and the affinity chromatography experiment. pDual GC-resistin and pDual GC-resistin binding peptide were co-transfected into 3T3-L1 cells to confirm the function of resistin binding peptide. RESULTS: Three cDNA fragments with the same 11 bp 5' sequence were found. The TGA stop codon in reading frames of the same 11 bp 5' sequence was proved to be readthroughed. The binding activity of RBP with resistin was consequently identified. The expression of the resistin binding peptide in 3T3-L1 preadipocytes expressing pDual GC-resistin significantly inhibited the adipogenic differentiation. CONCLUSION: RBP could effectively rescue the promoted differentiation of resistin overexpressed 3T3-L1 preadipocyte.

A mutation in signal peptide of rat resistin gene inhibits differentiation of 3T3-L1 preadipocytes.

AIM: To detect the resistin expression of white adipose tissue in diet-induced obese (DIO) versus diet-resistant (DR) rats, and to investigate the relationship of mutated resistin and 3T3-L1 preadipocytes differentiation. METHODS: RT-PCR and Western Blot were used to detect gene /protein expression. 3T3-L1 cells were cultured, transfected, and induced to differentiation using 0.5 mmol/L 3-isobutyl-1-methylxanthine (MIX), 1 mg/L insulin, and 1 micromol/L dexamethasone. Oil red O staining was applied to detect the degree of preadipocytes differentiation. RESULTS: Expression of resistin mRNA was upregulated in DIO rats and downregulated in DR rats. However, the expression levels varied greatly within the groups. Sequencing of the resistin genes from DIO and DR rats revealed a Leu9Val (C25G) missense mutation within the signal peptide in one DR rat. The mutant resistin inhibited preadipocyte differentiation. Local experiments and Western blotting with tagged resistin fusion proteins identified both mutant and wild type proteins in the cytoplasm and secreted into the culture medium. Computer predictions using the Proscan and Subloc programs revealed four putative phosphorylation sites and a possible leucine zipper motif within the rat resistin protein. CONCLUSION: Resistin-increased differentiation may be inhibited by the mutation-containing precursor protein, or by the mutant non-secretory resistin isoform.

[Expression of TSG-6 gene during 3T3-L1 preadipocyte differentiation and regulative role of tumor necrosis factor-alpha].

OBJECTIVE: Tumor necrosis factor alpha-stimulated gene-6 (TSG-6 gene) differentially expressed in adipose tissue of obese and normal human subjects or rats. To explore the relationship between the differential expression of TSG-6 and adipocyte differentiation, adipogenesis and obesity, the present study aimed to investigate the changes of TSG-6 gene expression during 3T3-L1 preadipocyte differentiation and to analyze the regulative role of TNF-alpha on TSG-6 gene expression in matured 3T3-L1 adipocytes. METHODS: 3T3-L1 preadipocytes were cultured in vitro and differentiated into the matured adipocytes. TNF-alpha in different concentrations (0.1 ng/ml, 1.0 ng/ml, 10.0 ng/ml) was added into the culture medium of fully differentiated adipocytes (day 10) for various times (0.5 h, 2 h, 6 h, 12 h, 24 h). Total RNA from these adipocytes was extracted and the levels of TSG-6 gene mRNA expression were evaluated by RT-PCR. RESULTS: (1) In preadipocytes, the level of TSG-6 gene mRNA expression remained low. In the presence of dexamethasone (Dex), MIX and insulin, with the 3T3-L1 preadipocytes being differentiated into the matured adipocytes, the level of TSG-6 gene mRNA expression was upregulated and reached the higher level in fully differentiated adipocytes. There is a significant difference between any two detected phases in the levels of TSG-6 gene mRNA expression (P < 0.05), except that the levels of TSG-6 gene mRNA expression did not increase obviously on day 0 to day 2, day 3 to day 5, day 4 to day 6 and day 7 to day 10 (P > 0.05). (2) Treatment of day 10 3T3-L1 adipocytes with TNF-alpha of different concentrations (0.1 ng/ml, 1.0 ng/ml, 10.0 ng/ml) resulted in a significant decrease in the level of TSG-6 gene mRNA expression. The inhibition effect of TNF-alpha on TSG-6 gene mRNA expression generally tended to be reinforced with the increasing concentrations of TNF-alpha and the elongation of time course, except for the period of 6 - 24 h after the stimulation of 10.0 ng/ml TNF-alpha. When 0.1 ng/ml TNF-alpha was applied, the level of TSG-6 gene expression decreased by 33.73% at 6 h, 97.39% at 12 h. While 1.0 ng/ml TNF-alpha was used, the level of TSG-6 gene expression decreased by 78.68% at 6 h, which remained until 24 h. At a concentration of TNF-alpha up to 10.0 ng/ml, the level of TSG-6 gene expression decreased by 96.27% at 2 h. TSG-6 gene expression was almost fully inhibited. CONCLUSION: (1) TSG-6 gene may be involved in adipocyte differentiation and adipogenesis. (2) TNF-alpha can downregulate the mRNA expression of TSG-6 gene in matured adipocytes. The inhibitory effect of TNF-alpha on TSG-6 gene expression is generally dose-correlated.

Lipolysis and apoptosis of adipocytes induced by neuropeptide Y-Y5 receptor antisense oligodeoxynucleotides in obese rats.

AIM: To investigate the influence of central administration of neuropeptide Y-Y5 receptor antisense oligodeoxynucleotides (ODN) on the body weight and fat pads of high-energy diet-induced obese rats, and the effects on white adipocyte lipolysis and apoptosis. METHODS: Y5 receptor antisense, sense, mismatched oligodeoxynucleotides (ODN) or vehicle were intracerebroventricularly injected, and average adipocyte area was calculated. DNA ladders were measured to evaluate adipocyte apoptosis, and RT-PCR was used to analyze the expression of bcl-2 and bax gene. RESULTS: (1) Central administration of Y5 receptor antisense ODN significantly decreased body weight, fat pads, and average adipocyte area. (2) DNA fragmentation was presented after electrophoresis at both epididymal and retroperitoneal adipose tissue. (3) The expression of bcl-2 gene was downregulated, while the expression of bax was upregulated. CONCLUSION: Lipolysis and adipocyte apoptosis may be important reasons for Y5 receptor antisense therapy.