Traffic-related air pollution associations with cytokeratin-18, a marker of hepatocellular apoptosis, in an overweight and obese paediatric population.

INTRODUCTION: Traffic-related air pollution causes fatty liver, inflammation and fibrosis in animal models, but there have been few studies in humans. OBJECTIVES: To test the hypothesis that traffic-related air pollution causes non-alcoholic fatty liver disease (NAFLD) and increased markers for non-alcoholic steatohepatitis (NASH); and that NAFLD increases liver susceptibility to increased NASH risk. METHODS: Data collected prospectively from 74 overweight or obese children were obtained from the Yale Pediatric Obesity Clinic. Traffic-related air pollution was characterized as vehicle traffic volume on major roads within a 1 km residential buffer, and as residential nitrogen dioxide (NO2 ) exposure. Outcomes were hepatic fat fraction (HFF) measured by magnetic resonance imaging, liver enzymes using standard assays and plasma cytokeratin-18 (CK-18) by immunosorbent assays. RESULTS: Significant non-linear relationships with air pollution and CK-18 were found. Plasma CK-18 at follow-up increased from approximately 150 U/L to almost 200 U/L as residential traffic volume increased from 220 000 vehicle-km to 330 000 vehicle-km, after adjustment for baseline CK-18, age and gender. Among patients with NAFLD at baseline, CK-18 increased from 140 U/L to 200 U/L (a 1.5 standard deviation increase in CK-18) as NO2 increased from 8 to 10 ppb. CONCLUSIONS: Traffic-related air pollution was associated with CK-18. Effects were larger in children with pre-existing NAFLD at study entry.

Hepatocyte-specific Bid depletion reduces tumor development by suppressing inflammation-related compensatory proliferation.

Liver cancer is a major health-care concern and its oncogenic mechanisms are still largely unclear. Persistent hepatocyte cell death is a common feature among various chronic liver diseases, the blocking of which presents as logical treatment. Therefore, we aimed at investigating tumor development in mice with hepatocyte-specific Bid depletion--a BH3-only Bcl-2 family member that amplifies apoptotic death signals. Hepatocyte-specific conditional Bid-knockout mice (Bid(Δhep)) were injected with 25 mg/kg diethylnitrosamine (DEN) at 14 days of age, and liver tumorigenesis was investigated 9 months later. Additionally, different models of acute liver injury were used including: acute high-dose DEN challenge, 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet and carbon tetrachloride (CCL4) injection. Bid(Δhep) mice developed significantly fewer tumors, showed smaller maximal and average tumor size and reduced tumor incidence. In the acute DEN model, 48 h post injection we observed a significant reduction in liver injury in Bid(Δhep) animals, assessed via serum transaminases and liver histopathology. Furthermore, TNF-α, IL-1ß, cJUN and IL-6 mRNA expression was reduced. These findings were accompanied by reduced compensatory hepatocyte proliferation in Bid(Δhep) mice when compared with controls by immunohistochemistry for Ki67 and proliferating cell nuclear antigen 48 h after DEN injection. In the acute CCL4 model, Bid(Δhep) mice displayed reductions in liver injury and inflammation when compared with controls. No differences in liver injury and serum bilirubin levels were detected in Bid(Δhep) and Bid(flo/flo) mice fed with DDC, which induces bile duct injury and a ductular reaction. Our study demonstrates that in DEN-induced hepatocellular carcinoma, the inhibition of hepatocyte death pathways through Bid deletion protects animals from tumorigenesis. These results suggest that reducing hepatocyte cell death, liver inflammation and compensatory proliferation has a stronger beneficial effect than the potential side effect of enhancing tumor cell survival.

Recurrence of Disease Following Liver Transplantation: Nonalcoholic Steatohepatitis vs Hepatitis C Virus Infection.

BACKGROUND: Nonalcoholic steatohepatitis (NASH) is an increasing indication for orthotopic liver transplantation (OLT) in the United States and other countries. However, the incidence of disease recurrence and natural course following OLT remains incompletely understood. OBJECTIVE: To estimate the incidence of recurrent disease, outcome and identify risk factors associated with disease recurrence in patients undergoing OLT for NASH as compared to those undergoing OLT for HCV cirrhosis. METHODS: We identified all patients with end-stage liver disease secondary to NASH (n=53) or HCV (n=95) cirrhosis who underwent OLT at our institution between 1998 and 2005. Protocol liver biopsies were performed (Day 7, Month 4 and yearly) after OLT, and as clinically indicated. Kaplan-Meier survival analysis was performed to assess the fibrosis progression and survival. Cox regression analysis was performed to identify factors associated with disease recurrence. RESULTS: Five-year survival was 90.5% in NASH vs 88.4% in HCV group (p=0.97). The median (25%ile, 75%ile) follow-up to last available biopsy was 12.7 (5.9, 26.3) months, during which 17 (32%) of NASH patients developed persistent fatty infiltration in their graft, 8 (15%) of whom had accompanying histologic features of recurrent NASH. There was no difference in the prevalence of post-OLT steatosis between HCV and NASH patients after adjusting for time of histologic follow-up (p=0.33). Patients with HCV infection were more likely to develop hepatic fibrosis post-OLT than those with NASH (62.1% vs 18.9%, p<0.001). Multivariate analysis identified post-OLT diabetes (HR=2.0, 95% CI: 1.2-3.2, p=0.007) as an independent risk factor for fibrosis development. Additionally, NASH subjects who received steroids had a significantly higher risk of developing hepatic fibrosis post-OLT than NASH patients who did not receive steroids and all HCV subjects (p<0.001). CONCLUSION: Recurrence of steatosis post-OLT is common. Corticosteroid use may contribute to fibrosis progression in this population.

The natural history of non-alcoholic fatty liver disease in children: a follow-up study for up to 20 years.

OBJECTIVES: The long-term prognosis of non-alcoholic fatty liver disease (NAFLD) in children remains uncertain. We aimed at determining the long-term outcomes and survival of children with NAFLD. DESIGN: Retrospective longitudinal hospital-based cohort study. PATIENTS: Sixty-six children with NAFLD (mean age 13.9 (SD 3.9) years) were followed up for up to 20 years with a total of 409.6 person-years of follow-up. RESULTS: The metabolic syndrome was present in 19 (29%) children at the time of NAFLD diagnosis with 55 (83%) presenting with at least one feature of the metabolic syndrome including obesity, hypertension, dyslipidaemia and/or hyperglycaemia. Four children with baseline normal fasting glucose developed type 2 diabetes 4-11 years after NAFLD diagnosis. A total of 13 liver biopsies were obtained from five patients over a mean of 41.4 (SD 28.8) months showing progression of fibrosis stage in four children. During follow-up, two children died and two underwent liver transplantation for decompensated cirrhosis. The observed survival free of liver transplantation was significantly shorter in the NAFLD cohort as compared to the expected survival in the general United States population of the same age and sex (log-rank test, p<0.00001), with a standardised mortality ratio of 13.6 (95% confidence interval, 3.8 to 34.8). NAFLD recurred in the allograft in the two cases transplanted, with one patient progressing to cirrhosis and requiring re-transplantation. CONCLUSIONS: Children with NAFLD may develop end-stage liver disease with the consequent need for liver transplantation. NAFLD in children seen in a tertiary care centre may be associated with a significantly shorter survival as compared to the general population.

New insights into the pathophysiology of renovascular hypertension.

In recent years, the pathophysiology of renovascular hypertension has been reviewed, and the classic concept that activation of the renin-angiotensin system is solely responsible for the development and maintenance of renovascular hypertension has been challenged. In fact, experimental evidence indicates that other systems, such as the lipoxygenase pathway, may have a more critical role in the long-term maintenance of high blood pressure after renal artery stenosis. Herein we discuss the intrarenal mechanisms that control pressure-induced natriuresis under physiologic conditions and the role of the kidney in the pathophysiology of renovascular hypertension.