Activation of the renin-angiotensin system in high fructose-induced metabolic syndrome.

High fructose intake induces hyperglycemia and hypertension. However, the mechanism by which fructose induces metabolic syndrome is largely unknown. We hypothesized that high fructose intake induces activation of the renin-angiotensin system (RAS), resulting in hypertension and metabolic syndrome. We provided 11-week-old Sprague-Dawley rats with drinking water, with or without 20% fructose, for two weeks. We measured serum renin, angiotensin II (Ang II), and aldosterone (Aldo) using ELISA kits. The expression of RAS genes was determined by quantitative reverse transcription polymerase chain reaction. High fructose intake increased body weight and water retention, regardless of food intake or urine volume. After two weeks, fructose intake induced glucose intolerance and hypertension. High fructose intake increased serum renin, Ang II, triglyceride, and cholesterol levels, but not Aldo levels. High fructose intake increased the expression of angiotensinogen in the liver; angiotensin-converting enzyme in the lungs; and renin, angiotensin II type 1a receptor (AT1aR), and angiotensin II type 1b receptor (AT1bR) in the kidneys. However, expression of AT1aR and AT1bR in the adrenal glands did not increase in rats given fructose. Taken together, these results indicate that high fructose intake induces activation of RAS, resulting in hypertension and metabolic syndrome.

Upregulation of C/EBPß and TSC2 by an HDAC inhibitor CG200745 protects heart from DOCA-induced hypertrophy.

Histone deacetylases (HDACs) are a vast family divided into four major classes: class I (1, 2, 3, and 8), class II (4, 5, 6, 7, 9 and 10), class III (sirtuin family) and class IV (HDAC11). HDAC inhibition attenuates cardiac hypertrophy through suppression of the mechanistic target of rapamycin complex1 (mTORC1) signaling. HDAC inhibitors upregulate the expression of tuberous sclerosis complex 2 (TSC2), an mTORC1 inhibitor. However, the molecular mechanism underlying HDAC inhibitor-mediated upregulation of TSC2 is unclear. We hypothesized that an HDAC inhibitor, CG200745 (CG), ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling by upregulating of the CCAAT/enhancer-binding protein-ß (C/EBP-ß)/TSC2 pathway. To establish a cardiac hypertrophy model, deoxycorticosterone acetate (DOCA, 40 mg/kg/wk) was subcutaneously injected for 4 weeks into Sprague-Dawley rats. All rats were unilaterally nephrectomized and had free access to drinking water containing 1% NaCl with or without CG of different concentrations. The expression level of TSC2 and C/EBP-ß was measured by quantitative real-time PCR (qRT-PCR) and western blot analysis. Acetylation of C/EBP-ß was analyzed by immunoprecipitation. The recruitment of C/EBP-ß and polymerase II (Pol II) on TSC2 promoter region was analyzed by chromatin immunoprecipitation (ChIP). CG treatment increased the expression of TSC2. In addition, CG treated rats showed an increased in the expression and acetylation of C/EBP-ß, owing to the increase in the recruitment of C/EBP-ß and Pol II at Tsc2 gene promoter. Thus, CG ameliorates cardiac hypertrophy through the inhibition of mTORC1 signaling via upregulation of the C/EBP-ß/TSC2 pathway in DOCA-induced hypertensive rats.

Histone deacetylase inhibitor MGCD0103 protects the pancreas from streptozotocin-induced oxidative stress and ß-cell death.

Inhibition of histone deacetylase (HDAC) suppresses inflammation of pancreatic islets and apoptosis of ß-cells. However, the underlying molecular mechanism is unclear. In the present study, we demonstrate that MGCD0103 (MGCD), an HDAC inhibitor, protects the pancreas from streptozotocin (STZ)-induced oxidative stress and cell death. Sprague-Dawley rats were intraperitoneally injected with STZ (40 mg/kg) to induce type I diabetes. MGCD (10 µg/day) was infused with osmotic mini-pump for 4 weeks. Pancreatic insulin and macrophage infiltration were analyzed by immunohistochemistry. Cellular level of reactive oxygen species (ROS) was evaluated with fluorescence-activated cell sorting. Tetramethylrhodamine ethyl ester was used to analyze mitochondrial membrane potential. Activation of caspase-3 was analyzed by western blotting. Chromatin immunoprecipitation was performed to investigate the binding affinity of specificity protein 1 (SP1) on the promoters of target genes. mRNA expression was analyzed by quantitative real-time polymerase chain reaction. As a result, we found that MGCD infusion ameliorated STZ-induced hyperglycemia, islet deformation, decreased insulin level, and macrophage infiltration. STZ injection promoted the production of ROS, which induced caspase activity and ß-cell death. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL), a mimetic of superoxide dismutase (SOD), reduced STZ-induced caspase activity and ß-cell death. MGCD treatment increased SOD expression and histone acetylation level on promoters. Infusion of MGCD promoted acetylation of SP1 and its enrichment on SOD promoters. Thus, MGCD protects pancreatic ß-cells from STZ-induced oxidative stress and cell death through the induction of antioxidant enzymes such as SODs.