Abstract
Background
Non-alcoholic fatty liver disease (NAFLD) includes simple steatosis (SS) and nonalcoholic steatohepatitis (NASH). It affects 74–98% of individuals with morbid obesity undergoing bariatric surgery (BSX). Among several factors contributing to NAFLD pathogenesis, adipokines secreted by visceral adipose tissue (VAT) can play a role by regulating glucose/lipid metabolism and inflammation.
Aims
This study aims to determine if visceral adipose tissue adipokine and cytokine gene expression are associated with NAFLD (SS and NASH) at the time of BSX.
Methods
Patients were recruited from the Toronto Western Hospital Bariatric Clinic. Demographic data was recorded. The VAT and liver biopsies were collected at the time of bariatric surgery. VAT adipokines and other mediators were assessed by RT-PCR and included markers of thermogenic capacity, inflammation, fibrosis, adipokines, and others. Liver histology was assessed by a pathologist using the Brunt system and individuals were diagnosed as either SS, NASH, or having a healthy liver (HL). Blood samples were collected pre-BSX to measure liver and metabolic syndrome related parameters, including HOMA-IR, HbA1c, liver enzymes, and lipid profile. Anthropometry was also assessed. Groups were compared using Kruskal-Wallis test followed by Wilcoxon ranked sum, or chi-square and Fisher’s exact test as necessary. Data was considered to be statistically significant with a p-value less than 0.05.
Results
We are presenting data on 126 patients, 80.2% females with a median age of 49 and a body mass index (BMI) of 46.9. Fifty-seven patients had SS, 34 had NASH and 35 had a healthy liver (HL). BMI, age, and sex did not differ between the three groups. First, we found that those with NASH had significantly higher VAT expression of fibrosis (Loxl2), inflammation (CCL4 and TGFb1) and proliferation markers (E2F1) and significantly lower expression of adipokines (TNFa and resistin) compared to HL. Also, we found that SS had significantly higher fibrosis (Col3a1, Col6a1, Loxl2, CD9 and Acta2), inflammation (Nox2, TGFb1, IFNg and Clec10a), browning (PPARa, PPARg and Glut1) and proliferation (E2F1) marker expression compared to HL.
Conclusions
Results show that there is a significant difference in the expression pattern of VAT fibrotic and inflammatory markers between HL, SS and NASH patients. The observed increase of inflammatory markers in NAFLD is in line with prior research outlining the ability of inflammatory mediators from VAT to contribute to liver pathology via portal circulation. The relationship between VAT characteristics and NAFLD are important in understanding the widespread metabolic effects of obesity.
Funding Agencies
CIHRCanadian Liver foundation
Antigen- and Cytokine-Driven Accumulation of Regulatory T Cells in Visceral Adipose Tissue of Lean Mice