Transcriptomic profiling of a multiethnic pediatric NAFLD cohort reveals genes and pathways associated with disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common type of chronic liver disease in children. The mechanisms that drive NAFLD disease progression in this specific patient population remain poorly defined. In this study, we obtained liver biopsy samples from a multiethnic cohort of pediatric patients with NAFLD (n = 52, mean age = 13.6 years) and healthy liver controls (n = 5). We analyzed transcriptomic changes associated with NAFLD stages using high-throughput RNA sequencing. Unsupervised clustering as well as pairwise transcriptome comparison distinguished NAFLD from healthy livers. We identified perturbations in pathways including calcium and insulin/glucose signaling occurring early in NAFLD disease, before the presence of histopathologic evidence of advanced disease. Transcriptomic comparisons identified a 25-gene signature associated with the degree of liver fibrosis. We also identified expression of the insulin-like growth factor binding protein (IGFBP) gene family (1/2/3/7) as correlating with disease stages, and it has the potential to be used as a peripheral biomarker in NAFLD. Comparing our data set with publicly available adult and adolescent transcriptomic data, we identified similarities and differences in pathway enrichment and gene-expression profiles between adult and pediatric patients with NAFLD. Regulation of genes including interleukin-32, IGFBP1, IGFBP2, and IGFBP7 was consistently found in both NAFLD populations, whereas IGFBP3 was specific to pediatric NAFLD. Conclusion: This paper expands our knowledge on the molecular mechanisms underlying pediatric NAFLD. It identifies potential biomarkers and directs us toward new therapies in this population.

Hepatocyte Stress Increases Expression of Yes-Associated Protein and Transcriptional Coactivator With PDZ-Binding Motif in Hepatocytes to Promote Parenchymal Inflammation and Fibrosis.

BACKGROUND AND AIMS: Activated hepatocytes are hypothesized to be a major source of signals that drive cirrhosis, but the biochemical pathways that convert hepatocytes into such a state are unclear. We examined the role of the Hippo pathway transcriptional coactivators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in hepatocytes to facilitate cell-cell interactions that stimulate liver inflammation and fibrosis. APPROACH AND RESULTS: Using a variety of genetic, metabolic, and liver injury models in mice, we manipulated Hippo signaling in hepatocytes and examined its effects in nonparenchymal cells to promote liver inflammation and fibrosis. YAP-expressing hepatocytes rapidly and potently activate the expression of proteins that promote fibrosis (collagen type I alpha 1 chain, tissue inhibitor of metalloproteinase 1, platelet-derived growth factor c, transforming growth factor ß2) and inflammation (tumor necrosis factor, interleukin 1ß). They stimulate expansion of myofibroblasts and immune cells, followed by aggressive liver fibrosis. In contrast, hepatocyte-specific YAP and YAP/TAZ knockouts exhibit limited myofibroblast expansion, less inflammation, and decreased fibrosis after CCl4 injury despite a similar degree of necrosis as controls. We identified cellular communication network factor 1 (CYR61) as a chemokine that is up-regulated by hepatocytes during liver injury but is expressed at significantly lower levels in mice with hepatocyte-specific deletion of YAP or TAZ. Gain-of-function and loss-of-function experiments with CYR61 in vivo point to it being a key chemokine controlling liver fibrosis and inflammation in the context of YAP/TAZ. There is a direct correlation between levels of YAP/TAZ and CYR61 in liver tissues of patients with high-grade nonalcoholic steatohepatitis. CONCLUSIONS: Liver injury in mice and humans increases levels of YAP/TAZ/CYR61 in hepatocytes, thus attracting macrophages to the liver to promote inflammation and fibrosis.

Histone acetyltransferase CBP promotes function of SCF FBXL19 ubiquitin E3 ligase by acetylation and stabilization of its F-box protein subunit.

Ubiquitin E3 ligases mediate ubiquitination and degradation of intracellular proteins. We have shown that a relatively new Skp, Cullin, F-box (SCF) protein E3 ligase, SCF FBXL19, has an anti-inflammatory effect and controls actin cytoskeleton dynamics via targeting cell membrane receptor and small GTPases for their ubiquitination and degradation, but the molecular regulation of its subunit FBXL19 stability remains unclear. Here we show that FBXL19 degradation is controlled by the balance between its ubiquitination and acetylation. FBXL19 is an unstable protein with a half-life of ∼3 h. FBXL19 can be polyubiquitinated, and the proteasome inhibitor MG-132 prolongs FBXL19 half-life, suggesting that FBXL19 degradation is mediated in the ubiquitin-proteasome system. FBXL19 can also be acetylated, and enhancing acetylation of FBXL19 by a deacetylase inhibitor reduces FBXL19 ubiquitination levels. Acetylation-mimic FBXL19 mutant exhibits a longer half-life than wild type. An acetyltransferase CBP catalyzes acetylation of FBXL19. Inhibition or down-regulation of CBP reduces FBXL19 stability, whereas it is increased in CBP-overexpressing cells. Taken together, the data indicate that CBP-mediated acetylation reduces ubiquitination and stabilizes FBXL19. Further, we demonstrate that FBXL19 targets small GTPase Cdc42 for its ubiquitination and degradation, whereas this effect is reversed by inhibition of CBP, suggesting that CBP increases the effect of SCF FBXL19 E3 ligase through acetylation and stabilization of FBXL19. Our study reveals a new molecular model for regulation of SCF E3 ligase function by acetylation and stabilization of its subunit F-box protein.-Wei, J., Dong, S., Yao, K., Martinez, M. F. Y. M., Fleisher, P. R., Zhao, Y., Ma, H., Zhao, J. Histone acetyltransferase CBP promotes function of SCF FBXL19 ubiquitin E3 ligase by acetylation and stabilization of its F-box protein subunit.

The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.