Mechanisms of simple hepatic steatosis: not so simple after all

Nonalcoholic fatty liver disease is becoming an epidemic. Fat is typically stored in adipose tissue in the form of triglycerides (TGs). The deposition of TGs in the liver is the result of an imbalance between the amount of energy taken in and the amount used. This balance is maintained by a complex interplay between the dietary intake of nutrients, the hormonal response to the nutrients, and their effect on both the liver and adipose tissue. Disruption of this system is what leads to the development of steatosis and is the focus of this article.     

Increased Act1/IL-17R expression in Hirschsprung’s disease

Purpose

Hirschsprung’s disease-associated enterocolitis (HAEC) is the most common cause of morbidity and mortality in Hirschsprung’s disease (HSCR). Altered intestinal epithelial barrier function is implicated in the pathogenesis of HAEC. IL-17 is a proinflammatory cytokine that plays a crucial role in host defense against microbial organisms in the development of inflammatory diseases. Act1 is an essential adaptor molecule required for the IL-17-mediated inflammatory responses via interaction with IL-17 receptor (IL-17R). We designed this study to investigate the hypothesis that Act1/Il-17R expression is upregulated in HSCR.

Methods

We investigated Act1 and IL17R expression in ganglionic andaganglionic bowel of HD patients (n = 10) and controls (n = 10). qPCR, Western blotting and confocal immunofluorescence were performed.

Main results

qPCR and Western blot analysis revealed that Act1 and IL17R are strongly expressed in the aganglionic and ganglionic colon of patients with HSCR. Act1 and IL17R expression was significantly increased in HSCR specimens compared to controls (p < 0.05). Confocal microscopy revealed a markedly increased expression of Act1 and IL17R in the colonic epithelium of patients with HSCR compared to controls.

Conclusion

To our knowledge, we report, for the first time, the expression of Act1 in the human colon. The increased expression of Act1 and Il-17 in the aganglionic and ganglionic bowel in HSCR may result in IL-17-mediated increased inflammatory response leading to the development of HAEC

     

Mesenchymal expression of the <Emphasis Type="Italic">FRAS1/FREM2</Emphasis> gene unit is decreased in the developing fetal diaphragm of nitrofen-induced congenital diaphragmatic hernia

Purpose

Developmental mutations that inhibit normal formation of extracellular matrix (ECM) in fetal diaphragms have been identified in congenital diaphragmatic hernia (CDH). FRAS1 and FRAS1-related extracellular matrix 2 (FREM2), which encode important ECM proteins, are secreted by mesenchymal cells during diaphragmatic development. The FRAS1/FREM2 gene unit has been shown to form a ternary complex with FREM1, which plays a crucial role during formation of human and rodent diaphragms. Furthermore, it has been demonstrated that the diaphragmatic expression of FREM1 is decreased in the nitrofen-induced CDH model. We hypothesized that FRAS1 and FREM2 expression is decreased in the developing diaphragms of fetal rats with nitrofen-induced CDH.

Methods

Pregnant rats were exposed to either nitrofen or vehicle on gestational day 9 (D9), and fetuses were harvested on D13, D15 and D18. Microdissected diaphragms were divided into nitrofen-exposed/CDH and control samples (n = 12 per time-point and experimental group, respectively). Diaphragmatic gene expression levels of FRAS1 and FREM2 were analyzed by qRT-PCR. Immunofluorescence double staining for FRAS1 and FREM2 was combined with the mesenchymal marker GATA4 in order to evaluate protein expression and localization in pleuroperitoneal folds (PPFs) and fetal diaphragmatic tissue.

Results

Relative mRNA expression of FRAS1 and FREM2 were significantly reduced in PPFs of nitrofen-exposed fetuses on D13 (1.76 ± 0.86 vs. 3.09 ± 1.15; p < 0.05 and 0.47 ± 0.26 vs. 0.82 ± 0.36; p < 0.05), developing diaphragms of nitrofen-exposed fetuses on D15 (1.45 ± 0.80 vs. 2.63 ± 0.84; p < 0.05 and 0.41 ± 0.16 vs. 1.02 ± 0.49; p < 0.05) and fully muscularized diaphragms of CDH fetuses on D18 (1.35 ± 0.75 vs. 2.32 ± 0.92; p < 0.05 and 0.37 ± 0.24 vs. 0.70 ± 0.32; p < 0.05) compared to controls. Confocal laser scanning microscopy revealed markedly diminished FRAS1 and FREM2 immunofluorescence in diaphragmatic mesenchyme, which was associated with reduced proliferation of mesenchymal cells in nitrofen-exposed PPFs and fetal CDH diaphragms on D13, D15 and D18 compared to controls.

Conclusion

Decreased mesenchymal expression of FRAS1 and FREM2 in the nitrofen-induced CDH model may cause failure of the FRAS1/FREM2 gene unit to activate FREM1 signaling, disturbing the formation of diaphragmatic ECM and thus contributing to the development of diaphragmatic defects in CDH.