HNF4α in Hepatocyte Health and Disease

Role of HNF4α-cMyc Interaction in CDE Diet-Induced Liver Injury and Regeneration

Hepatocyte nuclear factor 4 alpha (HNF4α) is a nuclear factor essential for liver function that regulates the expression of cMyc and plays an important role during liver regeneration. This study investigated the role of the HNF4α-cMyc interaction in regulating liver injury and regeneration using the choline-deficient and ethionine-supplemented (CDE) diet model. Wild-type (WT), hepatocyte-specific HNF4α-knockout (KO), cMyc-KO, and HNF4α-cMyc double KO (DKO) mice were fed a CDE diet for 1 week to induce subacute liver injury. To study regeneration, normal chow diet was fed for 1 week after CDE diet. WT mice exhibited significant liver injury and decreased HNF4α mRNA and protein expression after CDE diet. HNF4α deletion resulted in significantly higher injury with increased inflammation, fibrosis, proliferation, and hepatic progenitor cell activation compared with WT mice after CDE diet but indicated similar recovery. Deletion of cMyc lowered liver injury with activation of inflammatory genes compared with WT and HNF4α-KO mice after CDE diet. DKO mice had a phenotype comparable to that of the HNF4α-KO mice after CDE diet and a complete recovery. DKO mice exhibited a significant increase in hepatic progenitor cell markers both after injury and recovery phase. Taken together, these data show that HNF4α protects against inflammatory and fibrotic changes after CDE diet-induced injury, which is driven by cMyc.

Nuclear hormone receptor NHR-49 is an essential regulator of stress resilience and healthy aging in Caenorhabditis elegans

The genome of Caenorhabditis elegans encodes 284 nuclear hormone receptor, which perform diverse functions in development and physiology. One of the best characterized of these is NHR-49, related in sequence and function to mammalian hepatocyte nuclear factor 4α and peroxisome proliferator-activated receptor α. Initially identified as regulator of lipid metabolism, including fatty acid catabolism and desaturation, additional important roles for NHR-49 have since emerged. It is an essential contributor to longevity in several genetic and environmental contexts, and also plays vital roles in the resistance to several stresses and innate immune response to infection with various bacterial pathogens. Here, we review how NHR-49 is integrated into pertinent signaling circuits and how it achieves its diverse functions. We also highlight areas for future investigation including identification of regulatory inputs that drive NHR-49 activity and identification of tissue-specific gene regulatory outputs. We anticipate that future work on this protein will provide information that could be useful for developing strategies to age-associated declines in health and age-related human diseases.