Adipogenic differentiation of adipose tissue-derived human mesenchymal stem cells: effect of gastric bypass surgery.

BACKGROUND: Adipose tissue dysfunction is an important feature of obesity characterized by enlarged adipocytes and marked changes in secretion of cytokines. These changes result in insulin resistance, chronic vascular inflammation, oxidative stress, and activation of the renin-angiotensin system (RAS), eventually leading to type 2 diabetes, obesity-related hypertension, and cardiovascular disease (CVD). Several trials have shown that bariatric surgery significantly reduces these comorbidities. However, there is a gap in knowledge regarding the mechanisms whereby bariatric surgery reduces the burden of CVD in obese individuals. METHOD: Mesenchymal stem cells (MSCs) were isolated from adipose tissue collected from three groups: (1) nonobese control subjects, (2) obese subjects undergoing gastric bypass surgery (GBS), and (3) subjects 1 year or more after GBS. In the study, MSCs were induced to adipogenic differentiation, and RAS-related gene expressions were determined by quantitative polymerase chain reaction. The effect of angiotensin II (Ang II) on adipogenic differentiation of MSCs also was investigated. RESULTS: Angiotensinogen mRNA levels in MSCs and differentiated adipocytes were significantly higher in the obese group than in the nonobese control subjects. Renin mRNA levels were significantly higher in the obese group MSCs than in the nonobese and post-GBS groups. Angiotensin-converting enzyme mRNA levels were significantly lower in the MSCs derived from the post-GBS group than in the obese and nonobese control subjects. Serum Ang II levels were significantly lower in the post-GBS group (52.1 ± 4.2 pg/ml) than in the nonobese (85.4 ± 12.4 pg/ml) and obese (84.7 ± 10.0 pg/ml) groups. Ang II treatment inhibited adipogenesis of MSCs in a dose-dependent manner. The inhibitory effect of Ang II was mainly abolished by PD123319, a receptor 2 blocker. CONCLUSIONS: The adipogenesis of MSCs is inhibited by Ang II treatment. Obese individuals are characterized by an upregulation of the RAS-related gene expressions in adipose tissue. This upregulation resolves in post-GBS subjects.

Lactacystin inhibits 3T3-L1 adipocyte differentiation through induction of CHOP-10 expression.

Hormonal induction triggers a cascade leading to the expression of CCAAT/enhancer-binding protein(C/EBP)alpha and peroxisome proliferator-activated receptor (PPAR) gamma, C/EBPalpha, and PPARgamma turns on series of adipocyte genes that give rise to the adipocyte phenotype. Previous findings indicate that C/EBPbeta, a transcriptional activator of the C/EBPalpha and PPARgamma genes, is rapidly expressed after induction, but lacks DNA-binding activity and therefore cannot activate transcription of the C/EBPalpha and PPARgamma genes early in the differentiation program. Acquisition of DNA-binding activity of C/EBPbeta occurs when CHOP-10, a dominant-negative form of C/EBP family members, is down-regulated and becomes hyperphosphorylated as preadipocytes traverse the G1-S checkpoint of mitotic clonal expansion. Evidences are presented in this report that lactacystin, a proteasome inhibitor, up-regulated the CHOP-10 expression, blocked the DNA-binding activity of C/EBPbeta, and subsequently inhibited MCE as well as adipocyte differentiation.

Identification of a peroxisome proliferator responsive element (PPRE)-like cis-element in mouse plasminogen activator inhibitor-1 gene promoter.

PAI-1 is expressed and secreted by adipose tissue which may mediate the pathogenesis of obesity-associated cardiovascular complications. Evidence is presented in this report that PAI-1 is not expressed by preadipocyte, but significantly induced during 3T3-L1 adipocyte differentiation and the PAI-1 expression correlates with the induction of peroxisome proliferator-activated receptor gamma (PPARgamma). A peroxisome proliferator responsive element (PPRE)-like cis-element (-206TCCCCCATGCCCT-194) is identified in the mouse PAI-1 gene promoter by electrophoretic mobility shift assay (EMSA) combined with transient transfection experiments; the PPRE-like cis-element forms a specific DNA-protein complex only with adipocyte nuclear extracts, not with preadipocyte nuclear extracts; the DNA-protein complex can be totally competed away by non-labeled consensus PPRE, and can be supershifted with PPARgamma antibody. Mutation of this PPRE-like cis-element can abolish the transactivation of mouse PAI-1 promoter mediated by PPARgamma. Specific PPARgamma ligand Pioglitazone can significantly induce the PAI-1 expression, and stimulate the secretion of PAI-1 into medium.

[Conserved region analysis of aac(3)-II gene from E. coli aminoglycoside resistance strain].

According to standard K B method, bacteriostatic tests were performed to screen out aminoglycoside resistance bacteria from 47 strains of isolated E.coli. To analyze correlations between the degree of E.coli aminoglycoside resistance and aac(3)-II gene conserved region, PCR amplified aac(3)-II gene conserved regions and were analyzed by DNA sequencing. The results showed that there were two species of aac(3)-II gene type including 65G and 84T or 65A and 84C in the samples. Strains with high activity of modifying enzyme to gentamicin all were 65G and 84T aac(3)-II gene type.