angiotensinogen and Hyperglycemia

Activation of the renin-angiotensin system has a pivotal role in the pathogenesis of diabetic complications. However, recent evidence suggests that it may also contribute to the development of diabetes itself. In the endocrine pancreas, all the components of an active renin-angiotensin system are present, which modulate a range of activities including local blood flow, hormone release and prostaglandin synthesis. In both types 1 and 2 diabetes, there is an up-regulation of its expression and activity in the endocrine pancreas. Whether these changes have a direct pathogenetic role or reflect a response to local stress or tissue injury remains to be established. Angiotensin-mediated increases in oxidative stress, inflammation and free fatty acids levels potentially contribute to beta-cell dysfunction in diabetes. In addition, activation of the renin-angiotensin system appears to potentiate the action of other pathogenic pathways including glucotoxicity, lipotoxicity and advanced glycation. In experimental models of type 2 diabetes, blockade of the renin-angiotensin system with angiotensin converting enzyme inhibitors or angiotensin receptor antagonists results in the improvement of islet structure and function. Moreover, the incidence of de novo diabetes appears to be significantly reduced by blockade of the renin-angiotensin system in clinical studies. At least two large controlled trials are currently underway to study the role of renin-angiotensin system in the development of diabetes. It is hoped that these studies will demonstrate the true potential of the blockade of the renin-angiotensin system for the prevention of diabetes.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Diabetes Mellitus; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Fibrosis; Humans; Hyperglycemia; Hypoglycemia; Islets of Langerhans; Pancreas; Peptidyl-Dipeptidase A; PPAR gamma; Receptors, Angiotensin; Renin; Renin-Angiotensin System

In the present study, we evaluated the effect of short term hyperglycemia on renal lesions in a mouse model (Tg26) of HIV-associated nephropathy (HIVAN). Control and Tg26 mice in groups (n=6) were administered either normal saline (FVBN or Tg) or streptozotocin (FVBN+STZ or Tg26+STZ). After two weeks, biomarkers were collected and kidneys were harvested. FVBN+ STZ and Tg26+STZ displayed elevated serum glucose levels when compared to FVBN and Tg26 respectively. Tg26+STZ displayed elevated (P<0.05) blood urea nitrogen (BUN) levels (P<0.05) and enhanced (P<0.01) proteinuria when compared to Tg26. Tg26+STZ displayed enhanced (P<0.001) number of sclerotic glomeruli and microcysts vs. Tg26. Renal tissues of Tg26 displayed down regulation of vitamin D receptor (VDR) expression and enhanced Ang II production when compared to FVBN mice. Hyperglycemia exacerbated down regulation of VDR and production of Ang II in FVBN and Tg mice. Hyperglycemia increased kidney cell reactive oxygen species (ROS) production and oxidative DNA damage in both FVBN and Tg26 mice. In in vitro studies, HIV down regulated podocyte VDR expression and also enhanced renin angiotensin system activation. In addition, both glucose and HIV stimulated kidney cell ROS generation and DNA damage and compromised DNA repair; however, tempol (superoxide dismutase mimetic), losartan (Ang II blocker) and EB1089 (VDR agonist) provided protection against DNA damaging effects of glucose and HIV. These findings indicated that glucose activated the RAS and inflicted oxidative stress-mediated DNA damage via down regulation of kidney cell VDR expression in HIV milieu both in vivo and in vitro.

Topics: AIDS-Associated Nephropathy; Angiotensinogen; Animals; Cells, Cultured; Down-Regulation; gag Gene Products, Human Immunodeficiency Virus; Glucose; HEK293 Cells; HIV-1; Humans; Hyperglycemia; Kidney Glomerulus; Mice; Mice, Transgenic; Podocytes; pol Gene Products, Human Immunodeficiency Virus; Proteinuria; Reactive Oxygen Species; Receptors, Calcitriol; Streptozocin

Decrease in endogenous hydrogen sulfide (H2S) was reported to participate in the pathogenesis of diabetic nephropathy (DN). This study is aimed at exploring the relationship between the abnormalities in H2S metabolism, hyperglycemia-induced oxidative stress and the activation of intrarenal renin-angiotensin system (RAS). Cultured renal mesangial cells (MCs) and streptozotocin (STZ) induced diabetic rats were used for the studies. The expressions of angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin II (Ang II) type I receptor (AT1), transforming growth factor-β1 (TGF-β1) and collagen IV were measured by real time PCR and Western blot. Reactive oxygen species (ROS) production was assessed by fluorescent probe assays. Cell proliferation was analyzed by 5'-bromo-2'-deoxyuridine incorporation assay. Ang II concentration was measured by an enzyme immunoassay. AGT, ACE and AT1 receptor mRNA levels and Ang II concentration were increased in high glucose (HG) -treated MCs, the cell proliferation rate and the production of TGF-β1 and of collagen IV productions were also increased. The NADPH oxidase inhibitor diphenylenechloride iodonium (DPI) was able to reverse the HG-induced RAS activation and the changes in cell proliferation and collagen synthesis. Supplementation of H2S attenuated HG-induced elevations in ROS and RAS activation. Blockade on H2S biosynthesis from cystathione-γ-lyase (CSE) by DL-propargylglycine (PPG) resulted in effects similar to that of HG treatment. In STZ-induced diabetic rats, the changes in RAS were also reversed by H2S supplementation without affecting blood glucose concentration. These data suggested that the decrease in H2S under hyperglycemic condition leads to an imbalance between oxidative and reductive species. The increased oxidative species results in intrarenal RAS activation, which, in turn, contributes to the pathogenesis of renal dysfunction.

Topics: Acetophenones; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Blood Glucose; Cell Proliferation; Cells, Cultured; Collagen Type IV; Cystathionine beta-Synthase; Cystathionine gamma-Lyase; Diabetes Mellitus, Experimental; Glucose; Hydrogen Sulfide; Hyperglycemia; Kidney; Losartan; Mesangial Cells; NADPH Oxidases; Onium Compounds; Peptidyl-Dipeptidase A; Rats; Reactive Oxygen Species; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; RNA, Messenger; Transforming Growth Factor beta1

We examined the effects of hyperglycemic conditions on liver metastasis of colorectal cancer (CRC). Angiotensin (A)-II increased growth, invasion, and anti-apoptotic survival in HT29 and CT26 cells. In contrast, angiotensinogen (ATG) increased these features in HT29 cells but not in CT26 cells. HT29 cells expressed A-II type 1 receptor, chymase, and rennin, whereas CT26 cells did not express renin. Renin expression and ATG-induced cell growth, invasion, and survival induced and increased as glucose concentration increased in HT29 cells and also CT26 cells. An inhibitor of renin or chymase abrogated A-II production in HT29 cells. Reduction of hepatic ATG production by cholesterol-conjugated antisense S-oligodeoxynucleotide suppressed liver metastasis of HT29 cells. An examination of 121 CRC patients showed that diabetes in CRC cases was associated with higher blood HbA1c, higher renin and A-II concentrations in the primary tumors, and higher incidence of liver metastasis than in nondiabetic cases. These results suggest that diabetes-associated angiotensin activation enhances liver metastasis of CRC and may therefore provide a possible target for antimetastatic therapy in CRC.

Topics: Angiotensin I; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Chymases; Colonic Neoplasms; Diabetes Complications; Diabetes Mellitus; Glucose; Glycated Hemoglobin; HT29 Cells; Humans; Hyperglycemia; Liver Neoplasms; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Invasiveness; Oligoribonucleotides, Antisense; Receptor, Angiotensin, Type 1; Renin; RNA Interference; RNA, Small Interfering

The role of individual supplements necessary for the long-term self-renewal of embryonic stem (ES) cells is poorly characterized in feeder/serum-free culture systems. This study sought to characterize the relationship between the effects of glucose on ES cell proliferation and fibronectin (FN) synthesis, and to assess the mechanisms responsible for these cellular effects of glucose. Treatment of the two ES cells (ES-E14TG2a and ES-R1) with 25 mM glucose (high glucose) increased the expression levels of FN mRNA and protein. In addition, high glucose and ANG II synergistically increased FN expression level, which coincident with data showing that high glucose increased the mRNA expression of angiotensin II (ANG II) type 1 receptor (AT(1)R), angiotensinogen, and FN, but not ANG II type 2 receptor. High glucose also increased the intracellular calcium (Ca(2+)) concentration and pan-protein kinase C (PKC) phosphorylation. Inhibition of the Ca(2+)/PKC pathway blocked high glucose-induced FN expression. High glucose or ANG II also synergistically increased transforming growth factor-beta1 (TGF-beta(1)) expression, while pretreatment with losartan abolished the high glucose-induced increase in TGF-beta(1) production. Moreover, TGF-beta(1)-specific small interfering RNA inhibited high glucose-induced FN expression and c-Jun N-terminal kinase (JNK) activation. The JNK inhibitor SP600125 blocked high glucose-induced FN expression and inhibited cell cycle regulatory protein expression induced by high glucose or TGF-beta(1). In this study, inhibition of AT(1)R, Ca(2+)/PKC, TGF-beta(1), JNK, FN receptor blocked the high glucose-induced DNA synthesis, increased the cell population in S phase, and the number of cells. It is concluded that high glucose increases FN synthesis through the ANG II or TGF-beta1 pathways, which in part mediates proliferation of mouse ES cells.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Calcium Signaling; Cell Count; Cell Proliferation; DNA Replication; Embryonic Stem Cells; Fibronectins; Glucose; Hyperglycemia; JNK Mitogen-Activated Protein Kinases; Losartan; Mice; Phosphorylation; Protein Kinase C; Receptor, Angiotensin, Type 1; RNA, Messenger; Signal Transduction; Transforming Growth Factor beta1

1. Renal tubular epithelial cells can undergo epithelial to mesenchymal transition (EMT) under hyperglycaemic conditions, which is associated with renal interstitial fibrosis. Activation of the renin-angiotensin system (RAS) is involved in diabetic nephropathy. The present study investigated the positive role of angiotensin AT1 receptors in high glucose-induced EMT in cultured tubular epithelial cells. 2. A rat kidney proximal tubular epithelial cell line (NRK-52E) was used in the present study. Levels of EMT makers, namely E-cadherin and vimentin, were estimated using fluorescence immunocytochemistry, mRNA levels of angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and AT1 receptors were determined by real-time polymerase chain reaction, protein levels of E-cadherin, vimentin, fibronectin, matrix metallopeptidase (MMP)-9 and phosphorylated extracellular signal-regulated kinase (ERK) 1/2 were analysed by western blotting and the concentrations of angiotensin (Ang) II and transforming growth factor (TGF)-beta1 in the culture medium were determined by enzyme immunoassay and ELISA. 3. High glucose (30 mmol/L) induced EMT and increased the synthesis of fibronectin and MMP-9. Furthermore, high glucose increased AGT, ACE and AT(1) receptor mRNA levels, as well as AngII and TGF-beta1 concentrations in the culture medium and ERK1/2 phosphorylation. Pretreatment of cells for 15 min with the AT1 receptor antagonist losartan (10(-5) mol/L) attenuated high glucose-induced increases in TGF-beta1 and ERK1/2 phosphorylation and reduced EMT, as well as the consequent synthesis of fibronectin and MMP-9. 4. The results of the present study suggest that the activated local RAS mediates high glucose-induced EMT. By activating AT1 receptors and stimulating TGF-beta1 synthesis, the elevated local RAS participates in high glucose-induced EMT and increased extracellular matrix secretion.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensinogen; Animals; Cadherins; Cell Line; Epithelial Cells; Epithelial-Mesenchymal Transition; Extracellular Matrix; Fibronectins; Glucose; Hyperglycemia; Kidney; Kidney Tubules, Proximal; Losartan; Peptidyl-Dipeptidase A; Rats; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; RNA, Messenger; Transforming Growth Factor beta1

The Spontaneously Diabetic Torii-Lepr(fa) (SDT-fa/fa) rat, a new model of obese type 2 diabetes, shows obesity, hyperglycemia, and hyperlipidemia from 6 weeks of age. Diabetic complications such as nephropathy and cataract are observed with aging; however, blood pressure change with age has not previously been examined. In this study, blood pressure was periodically measured and the change was investigated. Blood pressure in male SDT-fa/fa rats was elevated at 8, 16, and 24 weeks of age, whereas the heart rate was not changed. In addition to hyperglycemia, hyperlipidemia, and proteinuria, hyperleptinemia and increased urine angiotensinogen were observed in SDT-fa/fa rats. Blood pressure and heart rate in the male original SDT (SDT-+/+) rat did not significantly change. In conclusion, the SDT-fa/fa rat is a promising model, showing significant hypertension with diabetes mellitus.

Topics: Angiotensinogen; Animals; Blood Pressure; Diabetes Mellitus, Type 2; Disease Models, Animal; Heart Rate; Hyperglycemia; Hyperlipidemias; Hypertension; Leptin; Male; Obesity; Proteinuria; Rats; Rats, Sprague-Dawley

The renin-angiotensin system (RAS) is a major mediator of renal injury in diabetic nephropathy. Our previous studies demonstrated that 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] plays a renoprotective role by suppressing the RAS, with renin and angiotensinogen (AGT) as the main targets. The mechanism whereby 1,25(OH)(2)D(3) transcriptionally suppresses renin gene expression has been elucidated; however, how vitamin D regulates AGT remains unknown. Exposure of mesangial cells or podocytes to high glucose (HG; 30 mM) markedly stimulated AGT expression. In mesangial cells, the stimulation was inhibited by 1,25(OH)(2)D(3) (20 nM) or NF-kappaB inhibitor BAY 11-7082, suggesting the involvement of NF- kappaB in HG-induced AGT expression and the interaction between 1,25(OH)(2)D(3) and NF-kappaB in the regulation. Plasmid pNF-kappaB-Luc luciferase reporter assays showed that 1,25(OH)(2)D(3) blocked HG-induced NF-kappaB activity. EMSA and ChIP assays demonstrated increased p65/p50 binding to a NF-kappaB binding site at -1734 in the AGT gene promoter upon high glucose stimulation, and the binding was disrupted by 1,25(OH)(2)D(3) treatment. Overexpression of p65/p50 overcame 1,25(OH)(2)D(3) suppression, and mutation of this NF-kappaB binding site blunted 1,25(OH)(2)D(3) suppression of the promoter activity. In mice lacking the vitamin D receptor, AGT mRNA expression in the kidney was markedly increased compared with wild-type mice, and AGT induction in diabetic mice was suppressed by treatment with a vitamin D analog. These data indicate that 1,25(OH)(2)D(3) suppresses hyperglycemia-induced AGT expression by blocking NF-kappaB-mediated pathway.

Topics: Angiotensinogen; Animals; Calcitriol; Cell Line; Diabetic Nephropathies; Drug Interactions; Gene Expression; Glucose; Hyperglycemia; Mesangial Cells; Mice; NF-kappa B; Renin-Angiotensin System; Signal Transduction; Vitamins

Clinical and animal studies have shown that treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor antagonists slows the progression of nephropathy in diabetes, indicating that Ang II plays an important role in its development. We have reported previously that insulin inhibits the stimulatory effect of high glucose levels on angiotensinogen (ANG) gene expression in rat immortalized renal proximal tubular cells (IRPTCs) via the mitogen-activated protein kinase (p44/42 MAPK) signal transduction pathway. We hypothesize that the suppressive action of insulin on ANG gene expression might be attenuated in renal proximal tubular cells (RPTCs) of rats with established diabetes. Two groups of male adult Wistar rats were studied: controls and streptozotocin (STZ)-induced diabetic rats at 2, 4, 8 and 12 weeks post-STZ administration. Kidney proximal tubules were isolated and cultured in either normal glucose (i.e. 5 mM) or high glucose (i.e. 25 mM) medium to determine the inhibitory effect of insulin on ANG gene expression. Immunoreactive rat ANG (IR-rANG) in culture media and cellular ANG mRNA were measured by a specific radioimmunoassay and reverse transcription-polymerase chain reaction assay respectively. Activation of the p44/42 MAPK signal transduction pathway in rat RPTCs was evaluated by p44/42 MAPK phosphorylation employing a PhosphoPlus p44/42 MAPK antibody kit. Insulin (10(-7) M) inhibited the stimulatory effect of high glucose levels on IR-rANG secretion and ANG gene expression and increased p44/42 MAPK phosphorylation in normal rat RPTCs. In contrast, it failed to affect these parameters in diabetic rat RPTCs. In conclusion, our studies demonstrate that hyperglycaemia induces insulin resistance on ANG gene expression in diabetic rat RPTCs by altering the MAPK signal transduction pathway.

Topics: Angiotensinogen; Animals; Culture Techniques; Diabetes Mellitus, Experimental; Enzyme Activation; Gene Expression Regulation; Hyperglycemia; Insulin; Insulin Resistance; Kidney Tubules, Proximal; Male; Mitogen-Activated Protein Kinase 1; Phosphorylation; Radioimmunoassay; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Elevated plasma angiotensinogen (AGT) levels have been demonstrated in insulin-resistant states such as obesity and type 2 diabetes mellitus (DM2), conditions that are directly correlated to hypertension. We examined whether hyperinsulinemia or hyperglycemia may modulate fat and liver AGT gene expression and whether obesity and insulin resistance are associated with abnormal AGT regulation. In addition, because the hexosamine biosynthetic pathway is considered to function as a biochemical sensor of intracellular nutrient availability, we hypothesized that activation of this pathway would acutely mediate in vivo the induction of AGT gene expression in fat and liver. We studied chronically catheterized lean (approximately 300 g) and obese (approximately 450 g) Sprague-Dawley rats in four clamp studies (n = 3/group), creating physiological hyperinsulinemia (approximately 60 microU/ml, by an insulin clamp), hyperglycemia (approximately 18 mM, by a pancreatic clamp using somatostatin to prevent endogenous insulin secretion), or euglycemia with glucosamine infusion (GlcN; 30 micromol. kg(-1). min(-1)) and equivalent saline infusions (as a control). Although insulin infusion suppressed AGT gene expression in fat and liver of lean rats, the obese rats demonstrated resistance to this effect of insulin. In contrast, hyperglycemia at basal insulin levels activated AGT gene expression in fat and liver by approximately threefold in both lean and obese rats (P < 0.001). Finally, GlcN infusion simulated the effects of hyperglycemia on fat and liver AGT gene expression (2-fold increase, P < 0.001). Our results support the hypothesis that physiological nutrient "pulses" may acutely induce AGT gene expression in both adipose tissue and liver through the activation of the hexosamine biosynthetic pathway. Resistance to the suppressive effect of insulin on AGT expression in obese rats may potentiate the effect of nutrients on AGT gene expression. We propose that increased AGT gene expression and possibly its production may provide another link between obesity/insulin resistance and hypertension.

Topics: Adipose Tissue; Angiotensinogen; Animals; Blood Glucose; Body Composition; Body Weight; Gene Expression Regulation; Glucosamine; Glucose Clamp Technique; Hexosamines; Hyperglycemia; Hyperinsulinism; Infusions, Intravenous; Insulin; Insulin Resistance; Liver; Male; Obesity; Rats; Rats, Sprague-Dawley