| The purpose of study performed in MANUSCRIPT I is to elucidate the effect of fasting pathways on Nrf2-Keap1/ARE pathway. Few studies exist regarding how fasting affects transporter or the nuclear receptor-regulated pathways which regulation expression. Fasting effects on the Nrf2-Keap1 signaling pathway, which is responsive to oxidative stress and altered redox status have not been elucidated. The observations presented in this study prove that 1) fasting increases Abcc expression through Nrf2- and Sirt1-dependent mechanisms, 2) cAMP/PKA activators increase ARE activation via Nrf2- and Sirt1-dependent mechanisms in vitro, 3) Nrf2 expression is co-ordinately regulated with Pgc-1&agr; and Sirt1 expression and 4) obesity/steatosis diminishes fasting-mediated Abcc induction.;The purpose of study performed in MANUSCRIPT II hypothesized that CR would reverse the NR and drug transporter expression changes previously observed in obesity-induced hepatic steatosis. Given the well-defined association of Nrf2 with Abcc transporter induction, emphasis was placed on the Nrf2 pathway, but other NRs that have been described to regulate transporter expression were also evaluated. Our data herein illustrate that CR differentially regulates NR, biotransformation enzyme, and transporter expression in livers from C57Bl/6 (WT) and Lepob/ob (OB) mice. Furthermore, AMPK and Sirt1 activators differentially modulated transporter and NR expression in lean and steatotic hepatocytes.;In MANUSCRIPT III we demonstrate differential susceptibility of a mouse model, constitutively overexpressing Nrf2 (Keap1-KD mice) to CR. We attribute these changes to novel changes in the miRNA regulatory circuit. We demonstrate that the enhanced susceptibility to CR in Nrf2 overexpressing mice could be partly associated with differential changes in miRNA expression such as miR34a, miR370, miR122 and miR144, especially those known to be involved in regulation of lipogenic as well as fatty acid oxidation genes.;In summary, the studies presented herein demonstrate Nrf2-ARE pathway is a nutrient sensitive pathway that is: (a) activated upon fasting via Sirt1-Pgc-1&agr; dependent mechanisms, (b) negatively regulated upon CR and AMPK pathway, (c) plays a role in development of obesity, and (d) regulates expression of miRNA regulatory circuit thereby changing susceptibility to weight loss and fatty acid metabolism, (e) is a potential target to alleviate metabolic syndrome. (Abstract shortened by UMI.). |
