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Loss of the TNFα function inhibits Wnt/β-catenin signaling, exacerbates obesity development in adolescent spontaneous obese mice.

ABSTRACT: Tumor necrosis factor alpha (TNFα) is an adipokine involved in the regulation of cell differentiation and lipid metabolism, but its specific role has not been clearly understood. We validated a hypothesis that loss of TNFα function would inhibit Wnt/β-catenin signaling and accelerate adipogenesis in adolescent genetic obese mice. Epididymal white adipose tissues (eWAT) from TNFα deficient (TNFα(-/-)), leptin receptor deficient (db/db) and double gene mutant (db/db/TNFα(-/-), DT) male mice were used for comparative analysis of key molecules in Wnt/β-catenin signaling and adipogenic markers by qRT-PCR and western blot techniques. Compared with TNFα(-/-) and WT mice of 28 days old, an obese trait was observed in both db/db and DT mice, while the latter showed more significant body weight gain and eWAT hypertrophy. The mRNA level of key molecules in Wnt/β-catenin pathway was reduced in both obese groups, while the DT group was the lowest. Expression of adipocyte-specific genes was up-regulated during obese development in the two obese groups, while the DT group revealed more correlation than that of db/db group. At the protein level, a down regulation of Wnt10b and β-catenin in obese eWAT showed similar tendency with that of mRNA level. Compared with the lean groups, the levels of adiponectin and PPARγ2 for the obese groups were down-regulated at 21-day-old age, while they were elevated at older age. Our results suggested that deficiency in TNFα inhibited Wnt/β-catenin signaling of the obese eWAT and up-regulated expression of adipokines, and accelerated adipogenesis in genetic obese mice on a chow diet.

SUBMITTER: Gong M

PROVIDER: S-EPMC4006126 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectivesActivation of the Wnt/?-catenin signaling pathway inhibits adipogenesis by maintaining preadipocytes in an undifferentiated state. We investigated the effect of indirubin-3'-oxime (I3O), which was screened as an activator of the Wnt/?-catenin signaling, on inhibiting the preadipocyte differentiation in vitro and in vivo.Methods3T3L1 preadipocytes were differentiated with 0, 4 or 20??M of I3O. The I3O effect on adipocyte differentiation was observed by Oil-red-O staining. Activation of Wnt/?-catenin signaling in I3O-treated 3T3L1 cells was shown using immunocytochemical and immunoblotting analyses for ?-catenin. The regulation of adipogenic markers was analyzed via real-time reverse transcription-PCR (RT-PCR) and immunoblotting analyses. For the in vivo study, mice were divided into five different dietary groups: chow diet, high-fat diet (HFD), HFD supplemented with I3O at 5, 25 and 100?mg?kg(-1). After 8 weeks, adipose and liver tissues were excised from the mice and subject to morphometry, real-time RT-PCR, immunoblotting and histological or immunohistochemical analyses. In addition, adipokine and insulin concentrations in serum of the mice were accessed by enzyme-linked immunosorbent assay.ResultsUsing a cell-based approach to screen a library of pharmacologically active small molecules, we identified I3O as a Wnt/?-catenin pathway activator. I3O inhibited the differentiation of 3T3-L1 cells into mature adipocytes and decreased the expression of adipocyte markers, CCAAT/enhancer-binding protein ? and peroxisome proliferator-activated receptor ?, at both mRNA and protein levels. In vivo, I3O inhibited the development of obesity in HFD-fed mice by attenuating HFD-induced body weight gain and visceral fat accumulation without showing any significant toxicity. Factors associated with metabolic disorders such as hyperlipidemia and hyperglycemia were also improved by treatment of I3O.ConclusionActivation of the Wnt/?-catenin signaling pathway can be used as a therapeutic strategy for the treatment of obesity and metabolic syndrome and implicates I3O as a candidate anti-obesity agent.

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Loss of the TNFα function inhibits Wnt/β-catenin signaling, exacerbates obesity development in adolescent spontaneous obese mice.

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