A Gilbert syndrome-associated haplotype protects against fatty liver disease in humanized transgenic mice
SCIENTIFIC REPORTS
Authors: Landerer, Steffen; Kalthoff, Sandra; Paulusch, Stefan; Strassburg, Christian P.
Abstract
UDP-glucuronosyltransferases 1 A (UGT1A) enzymes are capable of detoxifying a broad range of endo-and xenobiotic compounds, which contributes to antioxidative effects, modulation of inflammation and cytoprotection. In the presence of low-function genetic UGT1A variants fibrosis development is increased in various diseases. This study aimed to examine the role of common UGT1A polymorphisms in NASH. Therefore, htgUGT1A-WT mice and htgUGT1A-SNP mice (carrying a common human haplotype present in 10% of the white population) were fed a high-fat Paigen diet for 24 weeks. Serum aminotransferase activities, hepatic triglycerides, fibrosis development and UGT1A expression were assessed. Microscopic examination revealed higher hepatic fat deposition and a significant induction of UGT1A gene expression in htgUGT1A-WT mice. In agreement with these observations, lower serum aminotransferase activities and lower expression levels of fibrosis-related genes were measured in htgUGT1A-SNP mice. This was accompanied by reduced PPARa protein levels in htgUGT1A-WT but not in SNP mice. Our data demonstrate a protective effect of a UGT1A SNP haplotype, leading to milder hepatic steatosis and NASH. Higher PPARa protein levels in animals with impaired UGT1A activity are the likely result of reduced glucuronidation of ligands involved in PPARa-mediated fatty acid oxidation and may lead to the observed protection in htgUGT1A-SNP mice.
Examining the responses of the zebrafish (Danio rerio) gastrointestinal system to the suspected obesogen diethylhexyl phthalate
ENVIRONMENTAL POLLUTION
Authors: Buerger, Amanda N.; Schmidt, Jordan; Chase, Amanda; Paxaio, Carla; Patel, Tejas N.; Brumback, Babette A.; Kane, Andrew S.; Martyniuk, Christopher J.; Bisesi, Joseph H., Jr.
Abstract
Epidemiological evidence suggests that phthalate plasticizers may act as "obesogens", which are chemicals that exacerbate obesity. The gastrointestinal (GI) system is the primary exposure route for phthalates, however, the relationship between phthalate-driven perturbations of GI system functions that can influence obesity has yet to be examined. To address this knowledge gap, we exposed Danio rerio (zebrafish) for 60 days to either (1) Control feeding (5 mg/fish/day), (2) Overfeeding (20 mg/fish/day) or (3) Overfeeding with diethyl-hexyl phthalate (DEHP) (20 mg/fish/day with 3 mg/kg DEHP). After 60 days, Overfed and Overfed + DEHP zebrafish had elevated body mass, and hepatosomatic and gonadosomatic indices. RNAseq analysis of the GI revealed enrichment of gene networks related to lipid metabolism in the Overfed + DEHP group. Many of the enriched networks were under transcriptional control of peroxisome proliferator activated receptor alpha (ppar alpha), a known modulator of lipid metabolism, immune function, and GI function. Real-time PCR confirmed that ppara was overexpressed in the Overfed + DEHP zebrafish, further revealing a pathway by which DEHP may influence lipid metabolism via the GI. These data increase our understanding of phthalate-driven effects on GI function and lipid metabolism, identifying gut-specific gene networks that may drive phthalate-exacerbated obesity. (C) 2018 Published by Elsevier Ltd.