angiotensinogen and Fatty-Liver

Angiotensinogen (AGT) is the sole precursor of all angiotensin peptides. Although AGT is generally considered as a passive substrate of the renin-angiotensin system, there is accumulating evidence that the regulation and functions of AGT are intricate. Understanding the diversity of AGT properties has been enhanced by protein structural analysis and animal studies. In addition to whole-body genetic deletion, AGT can be regulated in vivo by cell-specific procedures, adeno-associated viral approaches and antisense oligonucleotides. Indeed, the availability of these multiple manipulations of AGT in vivo has provided new insights into the multifaceted roles of AGT. In this review, the combination of structural and functional studies is highlighted to focus on the increasing recognition that AGT exerts effects beyond being a sole provider of angiotensin peptides.

Topics: Angiotensinogen; Animals; Atherosclerosis; Blood Pressure; Conserved Sequence; Fatty Liver; Humans; Mice; Mice, Transgenic; Obesity; Renin; Renin-Angiotensin System; Structure-Activity Relationship

Recent progress in adipocyte biology delineates that adipocytes not only store excess energy, but also respond to metabolic signals by secreting proteins that exert local, central, and peripheral effects. Among these adipokines are free fatty acids, plasminogen activator inhibitor-1, angiotensinogen, TNFa, leptin and adiponectin. Dysregulation of production of these adipokines and/or imbalance of their actions lead to a wide array of liver and systemic pathophysiology related to NASH such as 1) development of systemic and hepatic insulin resistance, 2) progression from benign fatty liver to steatohepatitis and 3) activation of hepatic fibrogenesis. This review deals with the emerging concept of the adipokine interrelationship with the liver.

Topics: Adipocytes; Adiponectin; Angiotensinogen; Animals; Fatty Liver; Fibrosis; Humans; Insulin Resistance; Leptin; Liver; Plasminogen Activator Inhibitor 1; Tumor Necrosis Factor-alpha

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

Numerous steatotic livers are discarded as unsuitable for transplantation because of their poor tolerance of ischemia-reperfusion(I/R). The injurious effects of angiotensin (Ang)-II and the benefits of Ang-(1-7) in various pathologies are well documented. We examined the generation of Ang II and Ang-(1-7) in steatotic and nonsteatotic liver grafts from Zucker rats following transplantation. We also studied in both liver grafts the effects of Ang-II receptors antagonists and Ang-(1-7) receptor antagonists on hepatic I/R damage associated with transplantation. Nonsteatotic grafts showed higher Ang II levels than steatotic grafts, whereas steatotic grafts showed higher Ang-(1-7) levels than nonsteatotic grafts. Ang II receptor antagonists protected only nonsteatotic grafts against damage, whereas Ang-(1-7) receptor antagonists were effective only in steatotic grafts. The protection conferred by Ang II receptor antagonists in nonsteatotic grafts was associated with ERK 1/2 overexpression, whereas the beneficial effects of Ang-(1-7) receptor antagonists in steatotic grafts may be mediated by NO inhibition. Our results show that Ang II receptor antagonists are effective only in nonsteatotic liver transplantation and point to a novel therapeutic target in liver transplantation based on Ang-(1-7), which is specific for steatotic liver grafts.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Apoptosis; Fatty Liver; Graft Survival; Health; Liver Transplantation; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Peptide Fragments; Rats; Receptors, Angiotensin

Twelve patients with cirrhosis, refractory ascites, and varying degrees of renal failure (creatinine clearance, 5 to 44 ml/min) were studied before and up to 2 weeks following peritoneovenous shunt. Creatinine clearance increased 60% or more in seven patients (group I) and 22% or less in five patients (group II). There were no significant differences in maximum urine output or sodium excretion between groups (group I, 4,272 ml/14 hr, 372 mEq/24 hr; group II, 3,722 ml/24 hr, 255 mEq/24 hr). Aldosterone and renin concentrations were higher in group I and showed a greater decrease after shunting. Renin substrate levels also were higher in group I and rose following shunt insertion, while group II remained low. Ascitic fluid was found to contain renin substrate in concentrations of approximately 25% to 50% of plasma concentrations. Patients with the greatest increase in creatinine clearance showed the largest rise in substrate concentration and fall in renin and aldosterone secretion, suggesting a dynamic relationship between these factors. That a diuresis could occur without significant change in these parameters in five of 12 patients suggests independent control mechanisms for renal salt and water excretion and glomerular filtration in the ascitic patient.

Topics: Aldosterone; Angiotensinogen; Ascites; Creatinine; Diuresis; Fatty Liver; Glomerular Filtration Rate; Kidney; Liver Cirrhosis, Alcoholic; Natriuresis; Peritoneum; Renin; Syndrome; Veins

Topics: Angiotensinogen; Angiotensins; Blood Pressure Determination; Carbon Tetrachloride; Epinephrine; Fatty Liver; Hypertension; Hypertension, Renal; Kidney; Norepinephrine; Pathology; Pharmacology; Rats; Renin; Research; Toxicology