Impact of inverse relationship between TP53 and CARF on the development of hepatic steatosis and insulin resistance - : Project Summary: With the dramatic increase in obesity and diabetes, the prevalence of nonalcoholic fatty liver diseases (NAFLD) is increasing at an alarming rate worldwide. NAFLD is a significant risk factor for insulin resistance (IR), type 2 diabetes (T2DM), and cardiovascular diseases. We need to understand the underlying molecular mechanisms adequately to manage NAFLD and T2DM clinically. CARF is a novel p53 pathway protein that interacts with p53 and regulate its functions. Previous studies reported that an inverse relationship exists between CARF and p53. We posit that p53-CARF interplay plays a vital role in the outcome of p53 actions responding to various stressors. Our recent publication showed that free fatty acid (FFA)-induced stress suppressed hepatic CARF that triggered fat deposition in the liver, while exogenous delivery of CARF prevented it. Further, we found that silencing of CARF perturbed insulin signaling pathway in hepatocytes. Most intriguingly, expression of PCK1, a key hepatic gluconeogenic gene, was increased after silencing of CARF in hepatocytes. This led us to propose that CARF is a transcriptional regulator of PCK1 and, hence hepatic glucose output and IR. Growing evidence suggests that metabolic stress-induced p53 could alter the cell's metabolic homeostasis leading to the development of NAFLD and IR in both humans and rodents. Notably, our preliminary data further showed that CARF expression was decreased in HFD-fed livers with increased p53, thus establishing an inverse relationship. However, the role of this inverse relationship in metabolic stress and its outcome are unknown. We hypothesize that CARF could be a downstream target of p53 in metabolic stress. Its inhibition drives the development of IR and NAFLD. Using in vitro cellular and in vivo mouse models of NAFLD and IR integrated with the ChIP-sequencing, CUT and RUN sequencing, Co-IP, ITT, GTT, and PTT assays, this study will uncover a novel function of CARF -p53 interplay in the development of NAFLD and IR. Understanding this mechanism could reduce a considerable health burden in the USA and worldwide.
