Transcriptional regulation of hepatic lipogenesis

Raspberry seed flour attenuates high-sucrose diet-mediated hepatic stress and adipose tissue inflammation

Chronic intake of high sucrose (HS) diet exacerbates high-fat (HF) diet-induced obesity and its associated metabolic complications. Previously, we have demonstrated that ellagic acid (EA), an abundant polyphenol found in some fruits and nuts, exerts distinct lipid-lowering characteristics in hepatocytes and adipocytes. In this study, we hypothesized that EA supplementation inhibits HS diet-mediated hepatic toxicity and its accompanied metabolic dysregulation. To test this hypothesis, C57BL/6 male mice were randomly assigned to three isocaloric HF diets (41% calories from fat) containing either no-sucrose (HF), high-sucrose (HFHS), or high-sucrose plus EA (HFHS-R) from raspberry seed flour (RSF, equivalent to 0.03% of EA), and fed for 12weeks. The inclusion of EA from RSF significantly improved HFHS diet-mediated dyslipidemia and restored glucose homeostasis levels similar to the HF diet-fed mice. Despite marginal difference in hepatic triglyceride content, the addition of EA substantially reversed the activation of endoplasmic reticulum (ER) stress and oxidative damage triggered by HFHS diet in the liver. These effects of EA were further confirmed in human hepatoma cells by reducing ER stress and reactive oxygen species (ROS) production. Moreover, HFHS-R diet significantly decreased visceral adipocyte hypertrophy and adipose tissue inflammation evidenced by reduced proinflammatory gene expression and macrophage infiltration. In summary, EA supplementation from RSF was effective in reducing HFHS diet-mediated metabolic complication by attenuating hepatic ER and oxidative stresses as well as adipocyte inflammation. Our results suggest that the inclusion of EA in diets may normalize metabolic insults triggered by HS consumption.

The Role of Nuclear Receptors in the Pathophysiology, Natural Course, and Drug Treatment of NAFLD in Humans

Nonalcoholic fatty liver disease (NAFLD) describes steatosis, nonalcoholic steatohepatitis with or without fibrosis, and hepatocellular carcinoma, namely the entire alcohol-like spectrum of liver disease though observed in the nonalcoholic, dysmetabolic, individual free of competing causes of liver disease. NAFLD, which is a major public health issue, exhibits intrahepatic triglyceride storage giving rise to lipotoxicity. Nuclear receptors (NRs) are transcriptional factors which, activated by ligands, are master regulators of metabolism and also have intricate connections with circadian control accounting for cyclical patterns in the metabolic fate of nutrients. Several transcription factors, such as peroxisome proliferator-activated receptors, liver X receptors, farnesoid X receptors, and their molecular cascades, finely regulate energetic fluxes and metabolic pathways. Dysregulation of such pathways is heavily implicated in those metabolic derangements characterizing insulin resistance and metabolic syndrome and in the histogenesis of progressive NAFLD forms. We review the role of selected NRs in NAFLD pathogenesis. Secondly, we analyze the role of NRs in the natural history of human NAFLD. Next, we discuss the results observed in humans following administration of drug agonists or antagonists of the NRs pathogenically involved in NAFLD. Finally, general principles of treatment and lines of research in human NAFLD are briefly examined.