fumarates and Fatty-Liver

Oxidative stress plays a key role in the development of metabolic complications associated with obesity, including insulin resistance and the most common chronic liver disease worldwide, nonalcoholic fatty liver disease. We have recently discovered that the microRNA miR-144 regulates protein levels of the master mediator of the antioxidant response, nuclear factor erythroid 2-related factor 2 (NRF2). On miR-144 silencing, the expression of NRF2 target genes was significantly upregulated, suggesting that miR-144 controls NRF2 at the level of both protein expression and activity. Here we explored a mechanism whereby hepatic miR-144 inhibited NRF2 activity upon obesity via the regulation of the tricarboxylic acid (TCA) metabolite, fumarate, a potent activator of NRF2.. We performed transcriptomic analysis in liver macrophages (LMs) of obese mice and identified the immuno-responsive gene 1 (Irg1) as a target of miR-144. IRG1 catalyzes the production of a TCA derivative, itaconate, an inhibitor of succinate dehydrogenase (SDH). TCA enzyme activities and kinetics were analyzed after miR-144 silencing in obese mice and human liver organoids using single-cell activity assays in situ and molecular dynamic simulations.. Increased levels of miR-144 in obesity were associated with reduced expression of Irg1, which was restored on miR-144 silencing in vitro and in vivo. Furthermore, miR-144 overexpression reduces Irg1 expression and the production of itaconate in vitro. In alignment with the reduction in IRG1 levels and itaconate production, we observed an upregulation of SDH activity during obesity. Surprisingly, however, fumarate hydratase (FH) activity was also upregulated in obese livers, leading to the depletion of its substrate fumarate. miR-144 silencing selectively reduced the activities of both SDH and FH resulting in the accumulation of their related substrates succinate and fumarate. Moreover, molecular dynamics analyses revealed the potential role of itaconate as a competitive inhibitor of not only SDH but also FH. Combined, these results demonstrate that silencing of miR-144 inhibits the activity of NRF2 through decreased fumarate production in obesity.. Herein we unravel a novel mechanism whereby miR-144 inhibits NRF2 activity through the consumption of fumarate by activation of FH. Our study demonstrates that hepatic miR-144 triggers a hyperactive FH in the TCA cycle leading to an impaired antioxidant response in obesity.

Topics: Animals; Carboxy-Lyases; Citric Acid Cycle; Disease Models, Animal; Fatty Liver; Fumarate Hydratase; Fumarates; Humans; Hydro-Lyases; Insulin Resistance; Liver; Macrophages; Male; Mice; Mice, Inbred C57BL; MicroRNAs; NF-E2-Related Factor 2; Obesity; Oxidative Stress; RAW 264.7 Cells; Reactive Oxygen Species; Signal Transduction; Succinates

This study determined whether angiotensinogen (AGT) has angiotensin II-independent effects using multiple genetic and pharmacological manipulations.. All study mice were in low-density lipoprotein receptor -/- background and fed a saturated fat-enriched diet. In mice with floxed alleles and a neomycin cassette in intron 2 of the AGT gene (hypoAGT mice), plasma AGT concentrations were >90% lower compared with their wild-type littermates. HypoAGT mice had lower systolic blood pressure, less atherosclerosis, and diminished body weight gain and liver steatosis. Low plasma AGT concentrations and all phenotypes were recapitulated in mice with hepatocyte-specific deficiency of AGT or pharmacological inhibition of AGT by antisense oligonucleotide administration. In contrast, inhibition of AGT cleavage by a renin inhibitor, aliskiren, failed to alter body weight gain and liver steatosis in low-density lipoprotein receptor -/- mice. In mice with established adiposity, administration of AGT antisense oligonucleotide versus aliskiren led to equivalent reductions of systolic blood pressure and atherosclerosis. AGT antisense oligonucleotide administration ceased body weight gain and further reduced body weight, whereas aliskiren did not affect body weight gain during continuous saturated fat-enriched diet feeding. Structural comparisons of AGT proteins in zebrafish, mouse, rat, and human revealed 4 highly conserved sequences within the des(angiotensin I)AGT domain. des(angiotensin I)AGT, through adeno-associated viral infection in hepatocyte-specific AGT-deficient mice, increased body weight gain and liver steatosis, but did not affect atherosclerosis.. AGT contributes to body weight gain and liver steatosis through functions of the des(angiotensin I)AGT domain, which are independent of angiotensin II production.

Topics: Amides; Amino Acid Sequence; Angiotensin II; Angiotensinogen; Animals; Atherosclerosis; Blood Pressure; Conserved Sequence; Dependovirus; Diet, High-Fat; Disease Models, Animal; Fatty Liver; Fumarates; Genetic Vectors; Genotype; Hepatocytes; Hypertension; Liver; Male; Mice, Inbred C57BL; Mice, Knockout; Models, Molecular; Oligonucleotides, Antisense; Phenotype; Protein Binding; Protein Interaction Domains and Motifs; Receptors, LDL; Renin; Signal Transduction; Time Factors; Transduction, Genetic; Weight Gain

Activation of the renin-angiotensin-system is known to play a role in nonalcoholic steatohepatitis. Renin knockout mice manifest decreased hepatic steatosis. Aliskiren is the first direct renin inhibitor to be approved for clinical use. Our study aims to evaluate the possible therapeutic effects and mechanism of the chronic administration of aliskiren in a dietary steatohepatitis murine model.. Male C57BL/6 mice were fed with a methionine and choline-deficient (MCD) diet to induce steatohepatitis. After 8 weeks of feeding, the injured mice were randomly assigned to receive aliskiren (50 mg·kg(-1) per day) or vehicle administration for 4 weeks. Normal controls were also administered aliskiren (50 mg·kg(-1) per day) or a vehicle for 4 weeks.. In the MCD mice, aliskiren attenuated hepatic steatosis, inflammation and fibrosis. Aliskiren did not change expression of lipogenic genes but increase turnover of hepatic fat by up-regulating peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1a, cytochrome P450-4A14 and phosphorylated AMP-activated protein kinase. Furthermore, aliskiren decreased the hepatic expression of angiotensin II and nuclear factor κB. The levels of oxidative stress, hepatocyte apoptosis, activation of Kupffer cells and hepatic stellate cells, and pro-fibrotic markers were also reduced in the livers of the MCD mice receiving aliskiren.. Aliskiren attenuates steatohepatitis and fibrosis in mice fed with a MCD diet. Thus, the noted therapeutic effects might come from not only the reduction of angiotensin II but also the up-regulation of fatty acid oxidation-related genes.

Topics: Amides; Angiotensin II; Animals; Blotting, Western; Choline; Diet; Fatty Liver; Fumarates; Immunoenzyme Techniques; Inflammation; Insulin; Liver; Male; Methionine; Mice; Mice, Inbred C57BL; Oxidative Stress; Real-Time Polymerase Chain Reaction; Renin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thiobarbituric Acid Reactive Substances; Triglycerides

Topics: Adrenal Glands; Animals; Body Weight; Brain; Cycloheptanes; Digestive System; Fatty Liver; Fumarates; Genitalia; Heart; Kidney; Kidney Tubules; Lung; Lymph Nodes; Parasympatholytics; Propylamines; Rats; Spleen