ABSTRACT
Cellular apoptosis induced by hyperglycemia occurs in many vascular cells and is crucial for the initiation of diabetic pathologies. In the retina, pericyte apoptosis and the formation of acellular capillaries, the most specific vascular pathologies attributed to hyperglycemia, is linked to the loss of platelet-derived growth factor (PDGF)-mediated survival actions owing to unknown mechanisms. Here we show that hyperglycemia persistently activates protein kinase C-delta (PKC-delta, encoded by Prkcd) and p38alpha mitogen-activated protein kinase (MAPK) to increase the expression of a previously unknown target of PKC-delta signaling, Src homology-2 domain-containing phosphatase-1 (SHP-1), a protein tyrosine phosphatase. This signaling cascade leads to PDGF receptor-beta dephosphorylation and a reduction in downstream signaling from this receptor, resulting in pericyte apoptosis independently of nuclear factor-kappaB (NF-kappaB) signaling. We observed increased PKC-delta activity and an increase in the number of acellular capillaries in diabetic mouse retinas, which were not reversible with insulin treatment that achieved normoglycemia. Unlike diabetic age-matched wild-type mice, diabetic Prkcd(-/-) mice did not show activation of p38alpha MAPK or SHP-1, inhibition of PDGF signaling in vascular cells or the presence of acellular capillaries. We also observed PKC-delta, p38alpha MAPK and SHP-1 activation in brain pericytes and in the renal cortex of diabetic mice. These findings elucidate a new signaling pathway by which hyperglycemia can induce PDGF resistance and increase vascular cell apoptosis to cause diabetic vascular complications.
Subject(s)
Apoptosis/physiology , Diabetic Nephropathies , Hyperglycemia , Pericytes/physiology , Protein Kinase C-delta/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 6/metabolism , Animals , Apoptosis/drug effects , Brain/metabolism , Brain/pathology , DNA Fragmentation/drug effects , Diabetic Nephropathies/etiology , Diabetic Nephropathies/metabolism , Diabetic Nephropathies/pathology , Disease Models, Animal , Glucose/metabolism , Glucose/pharmacology , Hyperglycemia/complications , Hyperglycemia/metabolism , Hyperglycemia/pathology , Kidney Cortex/metabolism , Kidney Cortex/pathology , Mice , Mice, Knockout , NF-kappa B/metabolism , Pericytes/drug effects , Platelet-Derived Growth Factor/metabolism , Protein Kinase C-delta/deficiency , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 6/genetics , RNA, Messenger/metabolism , Receptor, Platelet-Derived Growth Factor beta/metabolism , Signal Transduction/geneticsABSTRACT
We investigated lipid and lipoprotein abnormalities in SHRSP fatty rats as a new animal model of metabolic syndrome. We examined differentially expressed genes in the liver, one of the major tissues contributing to lipid metabolism. Using gel filtration high performance liquid chromatography, increased cholesterol concentrations of small particle size low-density lipoprotein (LDL) fractions were observed in SHRSP fatty rats, whereas the Zucker Fatty strain did not show a similar elevation of cholesterol content. Existence of apolipoprotein B in these fractions was confirmed by Western blotting. The small particle size of the LDL fractions was significantly decreased by a 4-week fenofibrate treatment. Microarray analysis identified seventeen genes that were significantly upregulated and ten that were significantly decreased in liver tissues of SHRSP fatty rats compared with levels in SHRSP rats. Stearoyl-coenzyme A desaturase 1, fatty acid synthase, ATP citrate lyase, and sterol regulatory element binding factor 1 genes were among the upregulated genes. These findings suggest that SHRSP fatty rats carry small dense LDL like particles which is a common lipid abnormality in the metabolic syndrome. Three of ten genes upregulated in liver tissues of SHRSP fatty rats play a role in this metabolic abnormality and are a therapeutic target of this metabolic syndrome.
Subject(s)
Apolipoproteins B/metabolism , Cholesterol, LDL/metabolism , Dyslipidemias/metabolism , Gene Expression Regulation , Lipid Metabolism , Liver/metabolism , Metabolic Syndrome/metabolism , Animals , Apolipoproteins B/genetics , Cholesterol, LDL/genetics , Dyslipidemias/genetics , Dyslipidemias/pathology , Lipid Metabolism/genetics , Liver/pathology , Metabolic Syndrome/genetics , Metabolic Syndrome/pathology , Rats , Rats, Inbred SHR , Rats, Inbred WKY , Rats, Zucker , Species SpecificityABSTRACT
The purpose of this study was to evaluate whether the spontaneously hypertensive rat SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP fatty) is a useful animal model to clarify molecular mechanisms that underlie metabolic syndrome. We investigated histopathologic changes in the cardiovascular organs and metabolic characteristics of SHRSP fatty rats, which are congenic rats from a cross between SHRSP and Zucker fatty (ZF) rats. The aortic wall and cardiac, carotid, and renal arteries from SHRSP and SHRSP fatty rats were thicker than those of ZF rats. The renal cortex in SHRSP and SHRSP fatty rats showed severe glomerulosclerosis. Pancreatic islands in SHRSP fatty and ZF rats showed marked hyperplasia. Steady-state plasma glucose concentrations were higher in SHRSP fatty than in ZF rats. Non-fasting triglyceride levels in SHRSP fatty rats were higher than in ZF rats. DNA synthesis in cultured vascular smooth muscle cells (VSMCs) from SHRSP fatty and SHRSP rats was significantly higher than that in VSMCs from Wistar-Kyoto (WKY) or ZF rats. Levels of platelet-derived growth factor A-chain and transforming growth factor-beta1 mRNAs were higher in VSMCs from SHRSP fatty and SHRSP than from ZF rats. Microarray analysis identified five genes that were significantly upregulated and four genes that were significantly downregulated in visceral adipose tissue of SHRSP fatty rats compared with levels in control strains (SHRSP and ZF rats). These findings suggest that the combination of hypertension and obesity accelerates vascular remodeling, dyslipidemia, and insulin resistance in metabolic syndrome. The phenotype of SHRSP fatty is similar to that of human metabolic syndrome, and therefore, studies of these rats may help clarify the molecular mechanisms that underlie metabolic syndrome in humans.
Subject(s)
Cardiovascular System/metabolism , Gene Expression Profiling , Hypertension/metabolism , Metabolic Syndrome/metabolism , Adipose Tissue/metabolism , Adipose Tissue/pathology , Animals , Blood Glucose/metabolism , Cardiovascular System/pathology , Cells, Cultured , Disease Models, Animal , Epididymis/metabolism , Epididymis/pathology , Hypertension/pathology , Insulin/blood , Insulin Resistance , Kidney Cortex/metabolism , Kidney Cortex/pathology , Male , Metabolic Syndrome/pathology , Muscle, Smooth, Vascular/metabolism , Muscle, Smooth, Vascular/pathology , Pancreas/metabolism , Pancreas/pathology , Platelet-Derived Growth Factor/metabolism , Rats , Rats, Inbred SHR , Rats, Inbred Strains , Rats, Inbred WKY , Rats, Zucker , Transforming Growth Factor beta1/metabolismABSTRACT
Diabetes induces the activation of several protein kinase C (PKC) isoforms in the renal glomeruli. We used PKC-beta(-/-) mice to examine the action of PKC-beta isoforms in diabetes-induced oxidative stress and renal injury at 8 and 24 weeks of disease. Diabetes increased PKC activity in renal cortex of wild-type mice and was significantly reduced (<50% of wild-type) in diabetic PKC-beta(-/-) mice. In wild-type mice, diabetes increased the translocation of PKC-alpha and -beta1 to the membrane, whereas only PKC-alpha was elevated in PKC-beta(-/-) mice. Increases in urinary isoprostane and 8-hydroxydeoxyguanosine, parameters of oxidative stress, in diabetic PKC-beta(-/-) mice were significantly reduced compared with diabetic wild-type mice. Diabetes increased NADPH oxidase activity and the expressions of p47(phox), Nox2, and Nox4 mRNA levels in the renal cortex and were unchanged in diabetic PKC-beta(-/-) mice. Increased expression of endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), and collagens IV and VI found in diabetic wild-type mice was attenuated in diabetic PKC-beta(-/-) mice. Diabetic PKC-beta(-/-) mice were protected from renal hypertrophy, glomerular enlargement, and hyperfiltration observed in diabetic wild-type mice and had less proteinuria. Lack of PKC-beta can protect against diabetes-induced renal dysfunction, fibrosis, and increased expressions of Nox2 and -4, ET-1, VEGF, TGF-beta, CTGF, and oxidant production.
Subject(s)
Cytokines/genetics , Diabetes Mellitus, Experimental/physiopathology , Oxidative Stress/physiology , Protein Kinase C/genetics , Animals , Blood Glucose/metabolism , Blood Pressure , Body Weight , Diabetes Mellitus, Experimental/genetics , Diabetic Nephropathies/prevention & control , Enzyme Activation , Fibrosis/prevention & control , Gene Expression Regulation , Glomerular Filtration Rate , Kidney Cortex/enzymology , Kidney Cortex/physiology , Kidney Cortex/physiopathology , Mice , Mice, Knockout , Polymerase Chain Reaction , Protein Kinase C/deficiency , Protein Kinase C/metabolism , Protein Kinase C beta , Reference ValuesABSTRACT
1. We established a new animal model of metabolic syndrome, SHRSP fatty (fa/fa) rats, by crossing stroke-prone spontaneously hypertensive rats of the Izumo strain (SHRSP/Izm) to Zucker fatty (ZF) (fa/fa) rats. 2. The SHRSP fatty (fa/fa) rats have a missense mutation of the leptin receptor gene and plasma leptin concentrations are augmented. The SHRSP fatty (fa/fa) rats develop obesity and hypertension simultaneously. 3. Plasma metabolic parameters, including glucose, insulin and total cholesterol and triglyceride levels, were markedly elevated in SHRSP fatty (fa/fa) rats compared with SHRSP/Izm rats. Plasma triglyceride concentrations in SHRSP fatty (fa/fa) rats were significantly elevated compared with those in ZF (fa/fa) rats. The weight of adipose tissues in SHRSP fatty (fa/fa) rats was greater than that of SHRSP/Izm rats. The phenotype of SHRSP fatty (fa/fa) rats is similar to that of human metabolic syndrome.
Subject(s)
Metabolic Syndrome/physiopathology , Adipose Tissue/anatomy & histology , Animals , Blood Glucose/metabolism , Body Composition/physiology , Body Weight/physiology , Cardiovascular Diseases/etiology , Cardiovascular Diseases/genetics , Disease Models, Animal , Hemodynamics/genetics , Hemodynamics/physiology , Insulin/blood , Lipids/blood , Metabolic Syndrome/genetics , Mutation/physiology , Obesity/genetics , Phenotype , Rats , Rats, Inbred SHR , Rats, Zucker , Receptors, Cell Surface/genetics , Receptors, LeptinABSTRACT
1. Recent studies have identified potential beneficial effects of eating nuts, most of which have substantial amounts of monounsaturated fatty acids (MUFA). Macadamia nuts consist of 75% fat by weight, 80% of which is MUFA (palmitoleic acid). 2. To examine variations in serum lipid levels in response to a high-MUFA diet based on macadamia nuts, 3 week interventions of macadamia nuts, coconuts and butter were determined in young, healthy Japanese female students. 3. After 3 weeks intervention, serum concentrations of total cholesterol and low-density lipoprotein-cholesterol were significantly decreased in the macadamia nut and coconut diets and bodyweight and body mass index were decreased in the group fed macadamia nuts, although there were no statistically significant changes in the group fed butter.
Subject(s)
Dietary Fats, Unsaturated/administration & dosage , Fatty Acids, Monounsaturated/administration & dosage , Lipids/blood , Macadamia , Adult , Asian People , Body Mass Index , Body Weight/drug effects , Bread , Butter , Cocos , Diet , Female , HumansABSTRACT
1. A dietary intervention study targeting female students by using cake containing soybean protein and isoflavone was conducted. Female students (n = 120) were divided into three Groups (A, 6.26 g of soybean protein and isoflavone at 50 mg/day; B, 1.36 g soybean protein and isoflavone 50 mg; and C, a wheat puff as placebo). Intervention period was 4 weeks. The ratio of hypercholesterol in each group indicated a high value; A: 25%, B: 17.9% and C: 24.4%. 2. Total cholesterol as well as the rate of hypercholesterolemia decreased in Group A. The average total cholesterol significantly reduced (P < 0.001) from 242 +/- 17 to 220 +/- 25 mg/dL in Group A. 3. Dietary intake of soy protein for 4 weeks could be effective in reducing CHD risk among Japanese female students with a high plasma cholesterol level.
