Deleting Gata4 in hepatocytes promoted the progression of NAFLD via increasing steatosis and apoptosis, and desensitizing insulin signaling

AMP deaminase: A crucial regulator in nitrogen stress and lipid metabolism in Mucor circinelloides

Lipid biosynthesis is a significant metabolic response to nitrogen starvation in oleaginous fungi. The oleaginous fungus Mucor circinelloides copes with nitrogen stress by degrading AMP through AMP deaminase (AMPD). However, the mechanism of AMPD in regulating lipogenesis remains largely unclear. To elucidate the mechanism of AMPD in lipid synthesis in this M. circinelloides, we identified two genes (ampd1 and ampd2) encoding AMPD and constructed an ampd double knockout mutant. The engineered M. circinelloides strain elevated cell growth and lipid accumulation, as well as the content of oleic acid (OA) and gamma-linolenic acid (GLA). In addition to the expected increase in transcription levels of genes associated with lipid and TAG synthesis, we observed suppression of lipid degradation and reduced amino acid biosynthesis. This suggested that the deletion of AMPD genes induces the redirection of carbon towards lipid synthesis pathways. Moreover, the pathways related to nitrogen metabolism, including nitrogen assimilation and purine metabolism (especially energy level), were also affected in order to maintain homeostasis. Further analysis discovered that the transcription factors (TFs) related to lipid accumulation were also regulated. This study provides new insights into lipid biosynthesis in M. circinelloides, indicating that the trigger for lipid accumulation is not entirely AMPD-dependent and suggest that there may be additional mechanisms involved in the initiation of lipogenesis.

Biology of childhood hepatoblastoma and the search for novel treatments

Our research laboratory has a longstanding interest in developmental disorders and embryonic tumors, and recent efforts have focused on the pathogenesis of pediatric liver tumors. This review focuses on hepatoblastoma (HB), the most common pediatric liver malignancy. Despite advances in treatment, patients with metastatic HB have a poor prognosis, and survivors often have permanent side effects attributable to chemotherapy. In an effort to improve survival and lessen long-term complications of HB, we have searched for novel molecular vulnerabilities using a combination of patient derived cell lines, metabolomics, and RNA sequencing of human samples at diagnosis and follow-up. These studies have shed light on pathogenesis and identified putative targets for future therapies in children with advanced HB.

FXR and NASH: an avenue for tissue-specific regulation

NASH is within the spectrum of NAFLD, a liver condition encompassing liver steatosis, inflammation, hepatocyte injury, and fibrosis. The prevalence of NASH-induced cirrhosis is rapidly rising and has become the leading indicator for liver transplantation in the US. There is no Food and Drug Administration (FDA)-approved pharmacological intervention for NASH. The farnesoid X receptor (FXR) is essential in regulating bile acid homeostasis, and dysregulation of bile acids has been implicated in the pathogenesis of NASH. As a result, modulators of FXR that show desirable effects in mitigating key characteristics of NASH have been developed as promising therapeutic approaches. However, global FXR activation causes adverse effects such as cholesterol homeostasis imbalance and pruritus. The development of targeted FXR modulation is necessary for ideal NASH therapeutics, but information regarding tissue-specific and cell-specific FXR functionality is limited. In this review, we highlight FXR activation in the regulation of bile acid homeostasis and NASH development, examine the current literature on tissue-specific regulation of nuclear receptors, and speculate on how FXR regulation will be beneficial in the treatment of NASH.