scholarly journals HepatocyteGHR/STAT5b Signaling Protects Against Liver Injury in NAFLD/NASH Mice Models Independent of Steatosis

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A48-A49
Author(s):  
Mercedes del Río-Moreno ◽  
Mari C Vazquez-Borrego ◽  
Mariyah Mahmood ◽  
Andre Sarmento-Cabral ◽  
Grace Guzman ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Liver Injury ◽  
De Novo ◽  
Corn Oil ◽  
Direct Action ◽  
Liver Weight ◽  
De Novo Lipogenesis ◽  
Wild Type ◽  
Alcoholic Fatty Liver ◽  
Liver Health

Abstract Non-alcoholic fatty liver disease (NAFLD) represents a spectrum of pathologies ranging from simple steatosis to non-alcoholic steatohepatitis (NASH) that can lead to cirrhosis and hepatocellular carcinoma. Clinical and mouse studies indicate GH-signaling is reduced in NAFLD. We reported that chow-fed mice, with adult-onset, hepatocyte-specific GH receptor knockdown (aHepGHRkd) develop steatosis, and with age, a mild NASH-like phenotype. In the present study, we sought to determine if aHepGHRkd accelerates the development of steatosis and fibrosis in the context of diets shown in wild-type male mice, after 6 months of feeding, to produce mild NASH (60% fat [lard] + sucrose in the drinking water [HFS] or a severe NASH-like phenotype (40% fat, with partially hydrogenated corn-oil; 2% cholesterol; 20% fructose [HFCF]). Since aHepGHRkd is associated with a reduction in active STAT5b, aHepGHRkd mice were treated with either a hepatocyte-specific adenoviral-associated vector that expresses constitutively active STAT5b (AAV-TBGp-STAT5bCA = STAT5bCA) or a AAV-Null vector. After only 3 months of feeding either the HFS or HFCF diet, aHepGHRkd, but not GHR-intact controls, mice exhibited clear fibrosis, associated with higher levels of plasma alanine aminotransferase (ALT). STAT5bCA treatment of aHepGHRkd mice reduced fibrosis, as well as plasma ALT. Of note, hepatic TG content did not differ between the treatment groups, within diet. Preliminary studies used GC-MS to reveal aHepGHRkd, in the context of HFS diet, increased hepatic fatty acid ratios indicative of enhanced de novo lipogenesis, while STAT5bCA reversed this effect. These results suggest GHR/STAT5b may protect against liver injury not by controlling absolute fat accumulation, but by modifying the fatty acid composition of hepatic lipids. Finally, in order to determine if STAT5bCA could also reverse established diet-induced NASH, wild-type mice were fed the HFCF diet for 6 months and then treated with AAV-STAT5bCA or AAV-Null vectors, and followed for an additional 3 months. Preliminary findings show STAT5bCA modestly reduced liver weight with no changes in TG content. However, STAT5bCA prevented the rise in plasma ALT observed in Null-treated controls. Of note, some mice developed hepatic tumors, where the number and size of visible tumors was reduced by STAT5bCA. Importantly, in all models examined thus far, changes in the liver phenotype could not be clearly attributed to changes in systemic metabolism, supporting a direct action of GHR/STAT5b signaling on liver health. Taken together, these results suggest that enhancing hepatocyte STAT5b activity could prevent/treat diet-induced NASH. How STAT5b mediates these effects, and if there are other players involved, remains to be elucidated.

EXTH-27. MOLECULAR CHARACTERIZATION AND PRECLINICAL DEVELOPMENT OF NOVEL SMALL MOLECULE INHIBITOR SPECIFIC FOR WILD-TYPE IDH1 FOR FERROPTOSIS INDUCTION IN GLIOBLASTOMA

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi169-vi169
Author(s):  
Kevin Murnan ◽  
Serena Tommasini-Ghelfi ◽  
Lisa Hurley ◽  
Corey Dussold ◽  
Daniel Wahl ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Cell Death ◽  
Plasma Membrane ◽  
Fatty Acid ◽  
Unsaturated Fatty Acids ◽  
De Novo ◽  
De Novo Lipogenesis ◽  
Therapeutic Modality ◽  
Wild Type ◽  
Genetic Ablation

Abstract Increased de novo synthesis, mobilization and uptake of fatty acids are required to provide sufficient lipids for membrane biogenesis in support of rapid tumor cell division and growth. In addition to their structural roles as components of the plasma membrane, fatty acid-derived lipids regulate ferroptotic cell death, a type of programmed cell death, when oxidized by iron-dependent lipoxygenase enzymes. De novo lipogenesis and the defense against oxidative lipid damage require large amounts of cytosolic NADPH. Our group has recently found that HGG up-regulate wild-type Isocitrate dehydrogenase 1 (referred to hereafter as ‘wt-IDH1high HGG’) to generate large quantities of cytosolic NADPH. RNAi-mediated knockdown of wt-IDH1, alone and in combination with radiation therapy (RT), slows the growth of patient-derived HGG xenografts, while overexpression of wt-IDH1 promotes intracranial HGG growth. Isotope tracer and liquid chromatography-based lipidomic studies indicated that wt-IDH1 supports the de novo biosynthesis of mono-unsaturated fatty acids (MUFAs) and promotes the incorporation of monounsaturated phospholipids into the plasma membrane, while displacing polyunsaturated fatty acid (PUFA) phospholipids. In addition, enhanced NADPH production in wt-IDH1high HGG increases glutathione (GSH) level, reduces reactive oxygen species (ROS), activates the phospholipid peroxidase glutathione peroxidase 4 (GPX4)-driven lipid repair pathway, and dampens the accumulation of PUFA-containing lipid peroxides, known executioners of ferroptosis. To pharmacologically target wt-IDH1,we have used and characterized wt-IDH1i-13, a first-in-class competitive α,β-unsaturated enone (AbbVie). wt-IDH1i-13 potently inhibits wt-IDH1 enzymatic activity, by covalently binding to the NADP+ binding pocket. Our data indicate that wt-IDH1i-13 promotes ferroptosis, which can be rescued by pre-treatment of cells with the peroxyl scavenger and ferroptosis inhibitor ferrostatin. wt-IDH1i-13 is brain-penetrant, and similar to genetic ablation, reduces progression and extends the survival of wt-IDH1high HGG bearing mice, alone and in combination with RT. These studies credential to wt-IDH1i-13 as a novel therapeutic modality for the treatment of wt-IDH1 gliomas.

scholarly journals SUN-LB52 The Protective Effects of Hepatocyte GH Receptor (GHR) Signaling Against Steatosis and Liver Injury Is Sexually Dimorphic and Autonomous of IGF1

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Andre Sarmento-Cabral ◽  
Mercedes del Rio-Moreno ◽  
Mari C Vazquez-Borrego ◽  
Mariyah Mahmood ◽  
Elena Gutierrez-Casado ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Liver Injury ◽  
Fatty Liver ◽  
Negative Feedback ◽  
De Novo ◽  
De Novo Lipogenesis ◽  
Whole Body ◽  
Chow Diet ◽  
Alcoholic Fatty Liver ◽  
Systemic Insulin Resistance

Abstract GH dysregulation contributes to the development of non-alcoholic fatty liver disease (NAFLD), however debate remains as to the relative contribution of the direct vs indirect effects of GH, via IGF1. Mouse models with congenital, liver-specific knockout of the GHR, JAK2 or STAT5, as adults exhibit steatosis, glucose intolerance, insulin resistance and white adipose tissue (WAT) lipolysis. It is believed that fatty liver is due to the dramatic reduction in circulating IGF1 altering systemic metabolism, due to loss of the insulin-like effects of IGF1 and the loss of IGF1 negative feedback to the pituitary leading to a rise in GH that promotes systemic insulin resistance and WAT lipolysis shifting the flux of fatty acids to the liver. In addition, low IGF1/high GH alters the development of other metabolically relevant tissues, which could indirectly contribute to the liver phenotype observed with congenital loss of hepatic GH signaling. To directly test the actions of GH on adult hepatocyte function, we developed a mouse model of adult-onset, hepatocyte-specific knockdown of the GHR (aHepGHRkd; 12 week-old, GHRfl/fl mice treated with AAV8-TBGp-Cre). aHepGHRkd enhanced hepatic de novo lipogenesis (DNL), rapidly leading to steatosis in males, but not females. In males, enhanced DNL and steatosis was sustained with age and associated with hepatocyte ballooning, inflammation and mild fibrosis. These changes occurred independent of severe systemic insulin resistance and WAT lipolysis, although the aHepGHRkd mice exhibit low IGF1/high GH similar to that of congenital models. To directly test the role of hepatocyte GHR signaling, independent of changes in IGF1, aHepGHRkd mice were treated with a vector expressing rat IGF1 targeted specifically to hepatocytes (AAV8-TBGp-rIGF1). Mice were fed standard chow diet and tissues collected 8m post-AAV. IGF1 replacement elevated plasma IGF1 in aHepGHRkd mice, resulting in a reduction in plasma GH and pituitary expression of Gh, Ghrhr and Ghsr, indicating negative feedback of IGF1 was restored. In male aHepGHRkd mice, IGF1 replacement reduced insulin and whole body lipid utilization and increased WAT, however it did not reduce steatosis or alter hepatic fatty acid composition indicative of DNL and had minimal effects on liver injury markers. RNAseq analysis of liver extracts showed IGF1 replacement also had no major impact on the differentially expressed genes observed after aHepGHRkd. These results demonstrate that steatosis, DNL and liver injury observed in male aHepGHRkd mice are autonomous of IGF1. Despite the fact that hepatic GHR protein levels were not detectable in both female and male aHepGHRkd mice, females maintained moderate levels of IGF1 and were protected from steatosis. The mechanism by which female mice are protected remains to be elucidated, however is consistent with clinical data indicating pre-menopausal women are resistance to NAFLD.

Abstract 20: Tribbles1 (Trib1) is a Novel Regulator of in vivo Hepatic Fatty Acid Lipogenesis in the Mouse.

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Robert C Bauer ◽  
Jian Cui ◽  
Anthony P Kent ◽  
Daniel J Rader
Keyword(s):  
Fatty Acid ◽  
Transcriptional Control ◽  
De Novo ◽  
Association Studies ◽  
Liver Weight ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Pcr Analysis ◽  
Genome Wide Association Studies

Tribbles1 (TRIB1) was recently identified in genome-wide association studies as being strongly linked to plasma levels of VLDL, HDL, LDL, and TG as well as coronary artery disease in humans. Previous experiments in mice using AAV-mediated hepatic overexpression of Trib1 confirmed this association, as mice overexpressing Trib1 exhibited reductions of 45% and 57% in plasma total cholesterol (TC) and TG, respectively ( Burkhardt et al, 2010 ). Here we report a Trib1 liver-specific knockout mouse (Trib1_LSKO) created through AAV-mediated delivery of Cre recombinase into adult mice with a floxed version of Trib1. Four weeks after infection, Trib1_LSKO mice exhibited 21% and 70% increases in TC and TG, respectively ( p =0.01 and 0.02), as compared to floxed Trib1 littermates infected with null virus (Controls). Trib1_LSKO animals also exhibited a 25% increase in liver weight ( p <0.01), and histological analysis revealed steatotic livers in LSKO mice. Real-time PCR analysis revealed >2-fold increases in the hepatic transcription of genes involved in fatty acid synthesis in Trib1_LSKO mice as compared to Controls. Examination of hepatic lipids revealed a 78% increase in hepatic TG content ( p <0.001) of Trib1_LSKO mouse livers, while no significant change in hepatic cholesterol was observed. When de novo lipogenesis was measured using [3H]-acetate, Trib1_LSKO animals exhibited significantly increased production of TG (3.6-fold, p <0.001), fatty acids (2.2-fold, p =0.02), diacylglycerol (1.8-fold, p <0.01), and phospholipids (2-fold, p =0.05). Microarray analysis of Trib1_LSKO livers compared to Controls revealed greater than 1,600 genes that were significantly altered between the two groups (fold change>1.5, FDR<10%). Pathway analysis suggested that the altered gene set was enriched for genes downstream of C/EBP and C/EBP. Western blot analysis of liver extracts showed increases in both C/EBP and C/EBP levels in Trib1_LSKO mice compared to Controls. In conclusion, Trib1 is a novel regulator of de novo lipogenesis in mice, presumably through the regulation of lipogenic gene transcription. This transcriptional control may be regulated by increased levels of C/EBP and/or C/EBP, or an as yet undetermined target of Trib1.

Sign in / Sign up

Export Citation Format

Share Document