A systems biology approach to the pathogenesis of obesity-related nonalcoholic fatty liver disease using reverse phase protein microarrays for multiplexed cell signaling analysis

✍ Scribed by Valerie S. Calvert; Rochelle Collantes; Hazem Elariny; Arian Afendy; Ancha Baranova; Michael Mendoza; Zachary Goodman; Lance A. Liotta; Emanuel F. Petricoin; Zobair M. Younossi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 929 KB
• Volume: 46
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.21688

✦ Synopsis

Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease. Omental adipose tissue, a biologically active organ secreting adipokines and cytokines, may play a role in the development of NAFLD. We tested this hypothesis with reverse-phase protein microarrays (RPA) for multiplexed cell signaling analysis of adipose tissue from patients with NAFLD. Omental adipose tissue was obtained from 99 obese patients. Liver biopsies obtained at the time of surgery were all read by the same hepatopathologist. Adipose tissue was exposed to rapid pressure cycles to extract protein lysates. RPA was used to investigate intracellular signaling. Analysis of 54 different kinase substrates and cell signaling endpoints showed that an insulin signaling pathway is deranged in different locations in NAFLD patients. Furthermore, components of insulin receptor-mediated signaling differentiate most of the conditions on the NAFLD spectrum. For example, PKA (protein kinase A) and AKT/mTOR (protein kinase B/mammalian target of rapamycin) pathway derangement accurately discriminates patients with NASH from those with the non-progressive forms of NAFLD. PKC (protein kinase C) delta, AKT, and SHC phosphorylation changes occur in patients with simple steatosis. Amounts of the FKHR (forkhead factor Foxo1)phosphorylated at S256 residue were significantly correlated with AST/ALT ratio in all morbidly obese patients. Furthermore, amounts of cleaved caspase 9 and pp90RSK S380 were positively correlated in patients with NASH. Specific insulin pathway signaling events are altered in the adipose tissue of patients with NASH compared with patients with nonprogressive forms of NAFLD. Conclusion: These findings provide evidence for the role of omental fat in the pathogenesis, and potentially, the progression of NAFLD. (HEPATOLOGY 2007;46:166-172.) N onalcoholic fatty liver disease (NAFLD) is an important cause of chronic liver disease worldwide. 1,2 NAFLD is strongly associated with metabolic syndrome and insulin resistance, 5-7 and its prevalence is on the rise. 1,2 NAFLD represents a spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). Accumulating evidence suggests that NASH is potentially progressive, whereas simple steatosis (SS), indicated by liver biopsies, follows a more benign course with little or no progression. Therefore, it is important to identify the biological pathways that underlie the pathogenesis of NASH and distinguish it from SS.

Proteomics profiling is the most attractive option among the available high-throughput technologies because almost all drugs target proteins. The profile of intracellular signaling events revealed by proteomics technology could help define the pathogenesis of NAFLD. Additionally, proteomics assays provide effective recapitulation of the post-translational and fluctuating phosphorylation-driven signaling events that occur at the proteome level. Phosphorylation events in the kinasedriven signal networks are particularly important for identifying disease pathogenesis and therapeutic targets. In the past, it has been difficult to measure and quantify protein phosphorylation in cells and tissue spec-