151
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Vikram A, Tripathi DN, Kumar A, Singh S. Oxidative stress and inflammation in diabetic complications. Int J Endocrinol 2014; 2014:679754. [PMID: 24876838 PMCID: PMC4026976 DOI: 10.1155/2014/679754] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 03/16/2014] [Indexed: 11/28/2022] Open
Affiliation(s)
- Ajit Vikram
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, IA 52246, USA
- *Ajit Vikram:
| | - Durga Nand Tripathi
- Centre for Translational Cancer Research, IBT, Texas A&M HSC, Houston, TX 77030, USA
| | - Ashutosh Kumar
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Hyderabad, Andhra Pradesh 500037, India
| | - Sandeep Singh
- Centre for Genetic Diseases and Molecular Medicine, Central University of Punjab, Mansa Road, Bathinda, Punjab 151001, India
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152
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Prevention of hyperglycemic signal pathways in metabolic syndrome carotid artery of rats. Transl Stroke Res 2013; 3:466-72. [PMID: 24323833 DOI: 10.1007/s12975-012-0205-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 07/10/2012] [Accepted: 07/30/2012] [Indexed: 10/28/2022]
Abstract
Obesity is the major risk factor for metabolic syndrome and atherosclerotic cardiocerebrovascular diseases and induces insulin resistance characterized by a dysfunction of insulin to activate insulin receptor /insulin receptor substrate 1(IRS-1)/phosphoinositide 3-kinase (PI3K)/Akt pathway. Zucker fatty rats (8 weeks) were treated with vehicle (0.5 % methyl cellulose in physiological saline, p.o.), amlodipine (3 mg/kg/day, p.o.), atorvastatin (10 mg/kg/day, p.o.), or the combination of amlodipine plus atorvastatin (3 + 10 mg/kg/day, p.o.) for 28 days, and anti-insulin-like growth factor 1 (IGF-1)/IRS-1/PI3K/Akt pathways were evaluated. Our present immunohistochemical study first demonstrated that a combination of amlodipine plus atorvastatin treatment prevented an arteriosclerotic process compared to the single treatment with amlodipine or atorvastatin with strong recoveries of pTyr IRS-1, pPI3K, and pAkt expressions and with remarkable restraints of IGF-1 and pSer IRS-1. As a result, combination therapy with amlodipine plus atorvastatin showed a strong synergistic effect to prevent atherosclerotic processes. The present study newly suggests a synergistic benefit of combination therapy with amlodipine plus atorvastatin for strong prevention of atherosclerotic processes, which could reduce the clinical risk of cerebrovascular events for obesity patients.
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153
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Blumensatt M, Wronkowitz N, Wiza C, Cramer A, Mueller H, Rabelink MJ, Hoeben RC, Eckel J, Sell H, Ouwens DM. Adipocyte-derived factors impair insulin signaling in differentiated human vascular smooth muscle cells via the upregulation of miR-143. Biochim Biophys Acta Mol Basis Dis 2013; 1842:275-83. [PMID: 24333576 DOI: 10.1016/j.bbadis.2013.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 11/15/2013] [Accepted: 12/02/2013] [Indexed: 02/08/2023]
Abstract
Cardiovascular complications are common in patients with type 2 diabetes. Adipokines have been implicated in the induction of proliferative and pro-atherogenic alterations in human vascular smooth muscle cells (hVSMC). Other reports demonstrated the importance of the miRNA cluster miR-143/145 in the regulation of VSMC homeostasis and insulin sensitivity. Here we investigated whether the detrimental effects of adipokines on hVSMC function could be ascribed to alterations in miR-143/145 expression. The exposure of hVSMC to conditioned media (CM) from primary human subcutaneous adipocytes increased the expression of smooth muscle α-actin (SMA), and the miR-143/145 cluster, but markedly impaired the insulin-mediated phosphorylation of Akt and its substrate endothelial nitric oxide synthase (eNOS). Furthermore, CM promoted the phosphorylation of SMAD2 and p38, which have both been linked to miR-143/145 induction. Accordingly, the induction of miR-143/145 as well as the inhibition of insulin-mediated Akt- and eNOS-phosphorylation was prevented when hVSMC were treated with pharmacological inhibitors for Alk-4/5/7 and p38 before the addition of CM. The transfection of hVSMC with precursor miR-143, but not with precursor miR-145, resulted in impaired insulin-mediated phosphorylation of Akt and eNOS. This inhibition of insulin signaling by CM and miR-143 is associated with a reduction in the expression of the oxysterol-binding protein-related protein 8 (ORP8). Finally, the knock-down of ORP8 resulted in impaired insulin-mediated phosphorylation of Akt in hVSMC. Thus, the detrimental effects of adipocyte-derived conditioned media on insulin action in primary hVSMC can be ascribed to the Alk- and p38-dependent induction of miR-143 and subsequent downregulation of ORP8.
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MESH Headings
- Adipocytes/cytology
- Adipocytes/metabolism
- Adult
- Blotting, Western
- Cell Differentiation/drug effects
- Cells, Cultured
- Culture Media, Conditioned/metabolism
- Culture Media, Conditioned/pharmacology
- Female
- HEK293 Cells
- Humans
- Insulin/metabolism
- Insulin/pharmacology
- MicroRNAs/genetics
- Middle Aged
- Muscle, Smooth, Vascular/cytology
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Phosphorylation/drug effects
- RNA Interference
- Receptors, Steroid/genetics
- Receptors, Steroid/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction/drug effects
- Smad2 Protein/genetics
- Smad2 Protein/metabolism
- Up-Regulation/drug effects
- p38 Mitogen-Activated Protein Kinases/genetics
- p38 Mitogen-Activated Protein Kinases/metabolism
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Affiliation(s)
- Marcel Blumensatt
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany
| | - Nina Wronkowitz
- Paul-Langerhans-Group for Integrative Physiology, German Diabetes Center, Duesseldorf, Germany
| | - Claudia Wiza
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany
| | - Andrea Cramer
- Paul-Langerhans-Group for Integrative Physiology, German Diabetes Center, Duesseldorf, Germany
| | - Heidi Mueller
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany
| | - Martijn J Rabelink
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Rob C Hoeben
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Juergen Eckel
- Paul-Langerhans-Group for Integrative Physiology, German Diabetes Center, Duesseldorf, Germany
| | - Henrike Sell
- Paul-Langerhans-Group for Integrative Physiology, German Diabetes Center, Duesseldorf, Germany
| | - D Margriet Ouwens
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany; Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
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154
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Stakos DA, Boudoulas KD, Gaillard TR, Schuster DP, Osei K, Boudoulas H. Regional and overall aortic function in nondiabetic individuals with insulin resistance and normal glucose tolerance. J Clin Endocrinol Metab 2013; 98:4457-63. [PMID: 24064690 PMCID: PMC3816260 DOI: 10.1210/jc.2013-2276] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Accepted: 09/05/2013] [Indexed: 11/19/2022]
Abstract
CONTEXT Insulin resistance is associated with altered vascular function in diabetes. OBJECTIVE The objective of the study was to define the overall and regional aortic function as well as the changes of aortic function over time in nondiabetic individuals with insulin resistance and a normal oral glucose tolerance test (OGTT). DESIGN This was a cross-sectional and longitudinal analysis with 12 months follow-up. SETTING The setting of the study was in primary care. PATIENTS Nondiabetic individuals (n = 181, mean age 42 ± 8 y) with a normal OGTT and insulin resistance as defined by the insulin sensitivity index (ISI) participated in the study. INTERVENTIONS ISI was estimated from serial measurements of plasma insulin and glucose during an iv glucose tolerance test. Ascending and abdominal aortic distensibility (AoD) and stiffness index-β (AoSI) were assessed using echocardiography. Carotid-to-femoral artery pulse wave velocity (PWVc-f; an index of overall aortic function) was measured from carotid and femoral arteries Doppler flow velocities recorded simultaneously with an electrocardiogram. Associations between ISI, AoD, AoSI, and PWVc-f were assessed using linear regression analyses and ANOVA. Differences between baseline and 12 months were compared using a paired t test. MAIN OUTCOME MEASURES AoD and AoSI associations as well as changes over a 12-month period in relation to ISI were measured. RESULTS Ascending AoD (P = .01) and ascending AoSI (P = .025) were significantly associated with ISI; in contrast, abdominal AoD and AoSI and PWVc-f did not. Changes in AoD, AoSI, and PWVc-f over time were more prominent in individuals with low ISI compared with those with high ISI. CONCLUSIONS The significant associations between ISI and aortic function suggest that insulin resistance may affect the cardiovascular system, even when OGTT is normal.
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Affiliation(s)
- Dimitrios A Stakos
- PhD, AssistantDemocritus University of Thrace, Dragana, 68100 Alexandroupolis, Greece.
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155
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Abstract
In healthy individuals, the vascular endothelium regulates an intricate balance of factors that maintain vascular homeostasis and normal arterial function. Functional disruption of the endothelium is known to be an early event that underlies the development of subsequent cardiovascular disease (CVD) including atherosclerosis and coronary heart disease. In addition, the rising global epidemic of type 2 diabetes is a significant problem conferring a significantly higher risk of CVD to individuals in whom endothelial dysfunction is also notable. This review first summarises the role of endothelium in health and explores and evaluates the impact of diabetes on endothelial function. The characteristic features of insulin resistance and other metabolic disturbances that may underlie long-term changes in vascular endothelial function (metabolic memory) are described along with proposed cellular, molecular and epigenetic mechanisms. Through understanding the underlying mechanisms, novel targets for future therapies to restore endothelial homeostasis and 'drive' a reparative cellular phenotype are explored.
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Affiliation(s)
- Anna C Roberts
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Genetics, Health and Therapeutics (LIGHT), University of Leeds, Leeds, UK
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156
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Muniyappa R, Yavuz S. Metabolic actions of angiotensin II and insulin: a microvascular endothelial balancing act. Mol Cell Endocrinol 2013; 378:59-69. [PMID: 22684034 PMCID: PMC3478427 DOI: 10.1016/j.mce.2012.05.017] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 05/29/2012] [Indexed: 01/01/2023]
Abstract
Metabolic actions of insulin to promote glucose disposal are augmented by nitric oxide (NO)-dependent increases in microvascular blood flow to skeletal muscle. The balance between NO-dependent vasodilator actions and endothelin-1-dependent vasoconstrictor actions of insulin is regulated by phosphatidylinositol 3-kinase-dependent (PI3K)--and mitogen-activated protein kinase (MAPK)-dependent signaling in vascular endothelium, respectively. Angiotensin II acting on AT₂ receptor increases capillary blood flow to increase insulin-mediated glucose disposal. In contrast, AT₁ receptor activation leads to reduced NO bioavailability, impaired insulin signaling, vasoconstriction, and insulin resistance. Insulin-resistant states are characterized by dysregulated local renin-angiotensin-aldosterone system (RAAS). Under insulin-resistant conditions, pathway-specific impairment in PI3K-dependent signaling may cause imbalance between production of NO and secretion of endothelin-1, leading to decreased blood flow, which worsens insulin resistance. Similarly, excess AT₁ receptor activity in the microvasculature may selectively impair vasodilation while simultaneously potentiating the vasoconstrictor actions of insulin. Therapeutic interventions that target pathway-selective impairment in insulin signaling and the imbalance in AT₁ and AT₂ receptor signaling in microvascular endothelium may simultaneously ameliorate endothelial dysfunction and insulin resistance. In the present review, we discuss molecular mechanisms in the endothelium underlying microvascular and metabolic actions of insulin and Angiotensin II, the mechanistic basis for microvascular endothelial dysfunction and insulin resistance in RAAS dysregulated clinical states, and the rationale for therapeutic strategies that restore the balance in vasodilator and constrictor actions of insulin and Angiotensin II in the microvasculature.
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MESH Headings
- Angiotensin II/metabolism
- Animals
- Blood Flow Velocity
- Capillaries/metabolism
- Capillaries/pathology
- Capillaries/physiopathology
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/pathology
- Endothelium, Vascular/physiopathology
- Humans
- Insulin/metabolism
- Insulin Resistance
- MAP Kinase Signaling System
- Muscle, Skeletal/blood supply
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Nitric Oxide/metabolism
- Phosphatidylinositol 3-Kinases/metabolism
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 2/metabolism
- Renin-Angiotensin System
- Vasoconstriction
- Vasodilation
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Affiliation(s)
- Ranganath Muniyappa
- Clinical Endocrine Section, Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, United States.
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157
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Mima A. Diabetic nephropathy: protective factors and a new therapeutic paradigm. J Diabetes Complications 2013; 27:526-30. [PMID: 23619194 DOI: 10.1016/j.jdiacomp.2013.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/25/2013] [Accepted: 03/19/2013] [Indexed: 10/26/2022]
Abstract
Diabetic nephropathy (DN) is the most common cause of chronic kidney disease (CKD) and its number has been increasing. CKD is a worldwide threat to health but the precise mechanism of this problem is not fully appreciated. It is believed that hyperglycemia is one of the most important metabolic factors in the development of DN. Multiple molecular mechanisms have been proposed to mediate hyperglycemia's adverse effects on kidney. To identify targets for therapeutic intervention, most studies have focused on understanding how abnormal levels of such metabolities cause DN. However, there have been few reports regarding endogenous renal protective factors. Thus, recognition of the importance of this could be providing a new perspective for understanding the development of DN and a new therapeutic paradigm to combat DN.
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Affiliation(s)
- Akira Mima
- Department of Nephrology, Graduate School of Medicine, Institute of Health Biosciences, University of Tokushima, Tokushima, Japan.
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158
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Kujiraoka T, Satoh Y, Ayaori M, Shiraishi Y, Arai-Nakaya Y, Hakuno D, Yada H, Kuwada N, Endo S, Isoda K, Adachi T. Hepatic extracellular signal-regulated kinase 2 suppresses endoplasmic reticulum stress and protects from oxidative stress and endothelial dysfunction. J Am Heart Assoc 2013; 2:e000361. [PMID: 23954796 PMCID: PMC3828781 DOI: 10.1161/jaha.113.000361] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Background Insulin signaling comprises 2 major cascades: the insulin receptor substrate/phosphatidylinositol 3′‐kinase/protein kinase B and Ras/Raf/mitogen‐activated protein kinase/kinase/ERK pathways. While many studies on the tissue‐specific effects of the insulin receptor substrate/phosphatidylinositol 3′ ‐kinase/protein kinase B pathway have been conducted, the role of the other cascade in tissue‐specific insulin resistance has not been investigated. High glucose/fatty acid toxicity, inflammation, and oxidative stress, all of which are associated with insulin resistance, can activate ERK. The liver plays a central role in metabolism, and hepatosteatosis is associated with vascular diseases. The aim of study was to elucidate the role of hepatic ERK2 in hepatosteatosis, metabolic remodeling, and endothelial dysfunction. Methods and Results We created liver‐specific ERK2 knockout mice and fed them with a high‐fat/high‐sucrose diet for 20 weeks. The high‐fat/high‐sucrose diet–fed liver‐specific ERK2 knockout mice exhibited a marked deterioration in hepatosteatosis and metabolic remodeling represented by impairment of glucose tolerance and decreased insulin sensitivity without changes in body weight, blood pressure, and serum cholesterol/triglyceride levels. In the mice, endoplasmic reticulum stress was induced together with decreased mRNA and protein expressions of hepatic sarco/endoplasmic reticulum Ca2+‐ATPase 2. In a hepatoma cell line, inhibition of ERK activation– induced endoplasmic reticulum stress only in the presence of palmitate. Vascular reactive oxygen species were elevated with upregulation of nicotinamide adenine dinucleotide phosphate oxidase1 (Nox1) and Nox4 and decreased phosphorylation of endothelial nitric oxide synthase, which resulted in the remarkable endothelial dysfunction in high‐fat/high‐sucrose diet–fed liver‐specific ERK2 knockout mice. Conclusions Hepatic ERK2 suppresses endoplasmic reticulum stress and hepatosteatosis in vivo, which results in protection from vascular oxidative stress and endothelial dysfunction. These findings demonstrate a novel role of hepatic ERK2 in obese‐induced insulin resistance in the protection from hepatovascular metabolic remodeling and vascular diseases.
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Affiliation(s)
- Takehiko Kujiraoka
- Division of Cardiovascular Medicine, Department of Internal Medicine, National Defense Medical College, Sayama, Japan
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159
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Li Q, Park K, Li C, Rask-Madsen C, Mima A, Qi W, Huang KM, King GL. Induction of vascular insulin resistance and endothelin-1 expression and acceleration of atherosclerosis by the overexpression of protein kinase C-β isoform in the endothelium. Circ Res 2013; 113:418-27. [PMID: 23759514 PMCID: PMC3893704 DOI: 10.1161/circresaha.113.301074] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 06/11/2013] [Indexed: 01/26/2023]
Abstract
RATIONALE Loss of insulin action in the endothelium can cause endothelial dysfunction and atherosclerosis. Hyperglycemia and elevated fatty acids induced by diabetes mellitus can activate protein kinase C-β isoforms and selectively inhibit insulin signaling via phosphatidylinositol 3-kinase/Akt pathway to inhibit the activation of endothelial nitric oxide synthase and metabolic actions. OBJECTIVE To demonstrate that overexpressing protein kinase C-β2 isoform in endothelial cells can cause selective insulin resistance and exacerbate atherosclerosis in the aorta. METHODS AND RESULTS Protein kinase C-β2 isoform was overexpressed in endothelial cells using a promoter of vascular endothelial cell cadherin. These mice were cross-bred with apoE-/- mice [Tg (Prkcb)apoE-/-]. On a Western diet, Tg(Prkcb)apoE-/- and apoE-/- mice did not differ in systemic insulin sensitivity, glucose tolerance, plasma lipid, or blood pressure. Insulin action in endothelial cells and femoral artery from Tg(Prkcb)apoE-/- mice was impaired by ≈40% with respect to Akt/endothelial nitric oxide synthase activation, and leukocyte-endothelial cell binding increased in cultured lung endothelial cells from Tg(Prkcb)apoE-/- mice compared with that from apoE-/- mice. Basal and angiotensin-stimulated big endothelin-1 levels were elevated in Tg(Prkcb)apoE-/- mice compared with apoE-/- mice. The severity of atherosclerosis in the aorta from Tg(Prkcb)apoE-/- mice increased by ≈70% as measured by en face fat staining and plaque content of the number of smooth muscle cells, macrophages, and extracellular matrix. CONCLUSIONS Specific protein kinase C-β2 activation in the endothelial cells caused dysfunction and accelerated atherosclerosis because of loss of insulin-stimulated Akt/endothelial nitric oxide synthase activation and angiotensin-induced increases in endothelin-1 expression.
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Affiliation(s)
- Qian Li
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Kyoungmin Park
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Chenzhong Li
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Christian Rask-Madsen
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Akira Mima
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Weier Qi
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
| | - Koji MizutaniPaul Huang
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
- Cardiovascular Research Center and Cardiology Division,
Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114
USA
| | - George L. King
- Dianne Nunnally Hoppes Laboratory for Diabetes Complications,
Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School,
Boston, MA 02215 USA
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160
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Low Wang CC, Lu L, Leitner JW, Sarraf M, Gianani R, Draznin B, Greyson CR, Reusch JEB, Schwartz GG. Arterial insulin resistance in Yucatan micropigs with diet-induced obesity and metabolic syndrome. J Diabetes Complications 2013; 27:307-15. [PMID: 23558108 PMCID: PMC3696427 DOI: 10.1016/j.jdiacomp.2013.02.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 01/29/2013] [Accepted: 02/21/2013] [Indexed: 12/11/2022]
Abstract
AIM Metabolic syndrome affects a large proportion of the population and increases cardiovascular disease risk. Because metabolic syndrome often co-exists clinically with atherosclerosis, it is difficult to distinguish the respective contributions of the components to vascular abnormalities. Accordingly, we utilized a porcine dietary model of metabolic syndrome without atherosclerosis to investigate early abnormalities of vascular function and signaling. METHODS Thirty-two Yucatan micropigs were fed either a high-fat, high-simple-sugar, high-calorie (HFHS) or standard chow diet (STD) for 6 months. Neither diet contained added cholesterol. Blood pressure and flow-mediated vasodilatation were assessed at baseline and 6 months. Aortas were harvested at 6 months to assess histology, insulin signaling, and endothelial nitric oxide (eNOS) phosphorylation. RESULTS HFHS pigs developed characteristics of metabolic syndrome including obesity, dyslipidemia, and insulin resistance, but without histologic evidence of atherosclerosis. Although arterial intima-media thickness did not differ between groups, vascular dysfunction in HFHS was manifest by increased blood pressure and impaired flow-mediated vasodilation of the femoral artery. Compared with STD, aortas from HFHS exhibited increased p85α expression and Ser307 IRS-1 phosphorylation, and blunted insulin-stimulated IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. In the absence of insulin stimulation, aortic Akt Ser473-phosphorylation was greater in HFHS than in STD. With insulin stimulation, Akt phosphorylation increased in STD, but not HFHS. Insulin-induced Ser1177-phosphorylation of eNOS was decreased in HFHS, compared with STD. CONCLUSIONS Pigs with metabolic syndrome develop early vascular dysfunction and aortic insulin signaling abnormalities, and could be a useful model for early human vascular abnormalities in this condition.
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Affiliation(s)
- Cecilia C Low Wang
- Endocrine Section, VA Medical Center, Denver, and University of Colorado Anschutz Medical Campus/School of Medicine, Aurora, CO, USA.
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161
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Serine phosphorylation sites on IRS2 activated by angiotensin II and protein kinase C to induce selective insulin resistance in endothelial cells. Mol Cell Biol 2013; 33:3227-41. [PMID: 23775122 DOI: 10.1128/mcb.00506-13] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Protein kinase C (PKC) activation, induced by hyperglycemia and angiotensin II (AngII), inhibited insulin-induced phosphorylation of Akt/endothelial nitric oxide (eNOS) by decreasing tyrosine phosphorylation of IRS2 (p-Tyr-IRS2) in endothelial cells. PKC activation by phorbol ester (phorbol myristate acetate [PMA]) reduced insulin-induced p-Tyr-IRS2 by 46% ± 13% and, similarly, phosphorylation of Akt/eNOS. Site-specific mutational analysis showed that PMA increased serine phosphorylation at three sites on IRS2 (positions 303, 343, and 675), which affected insulin-induced tyrosine phosphorylation of IRS2 at positions 653, 671, and 911 (p-Tyr-IRS2) and p-Akt/eNOS. Specific PKCβ2 activation decreased p-Tyr-IRS2 and increased the phosphorylation of two serines (Ser303 and Ser675) on IRS2 that were confirmed in cells overexpressing single point mutants of IRS2 (S303A or S675A) containing a PKCβ2-dominant negative or selective PKCβ inhibitor. AngII induced phosphorylation only on Ser303 of IRS2 and inhibited insulin-induced p-Tyr911 of IRS2 and p-Akt/eNOS, which were blocked by an antagonist of AngII receptor I, losartan, or overexpression of single mutant S303A of IRS2. Increases in p-Ser303 and p-Ser675 and decreases in p-Tyr911 of IRS2 were observed in vessels of insulin-resistant Zucker fatty rats versus lean rats. Thus, AngII or PKCβ activation can phosphorylate Ser303 and Ser675 in IRS2 to inhibit insulin-induced p-Tyr911 and its anti-atherogenic actions (p-Akt/eNOS) in endothelial cells.
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162
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Kubota T, Kubota N, Kadowaki T. The role of endothelial insulin signaling in the regulation of glucose metabolism. Rev Endocr Metab Disord 2013; 14:207-16. [PMID: 23589150 DOI: 10.1007/s11154-013-9242-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The skeletal muscle is one of the major target organs of insulin and plays an essential role in insulin-induced glucose uptake. Some evidence indicates that insulin delivery to skeletal muscle interstitium through the endothelial cells is the rate-limiting step in insulin-stimulated glucose uptake. Researchers have also found that this process is impaired by insulin resistance in type 2 diabetes and obesity. A recent study of ours demonstrated that insulin signaling in the endothelial cells plays a pivotal role in the regulation of glucose uptake by the skeletal muscle. Specifically, impaired insulin signaling in the endothelial cells, with reduction of insulin-induced eNOS phosphorylation, causes attenuation of the insulin-induced capillary recruitment and insulin delivery, which, in turn reduces glucose uptake by the skeletal muscle in high-fat diet-fed mice. Moreover, restoration of the insulin-induced eNOS phosphorylation in the endothelial cells completely reverses the reduction in the capillary recruitment and insulin delivery, and as a result, significantly restores glucose uptake by the skeletal muscle. In the present review, we describe the recent progress in research on the physiological and pathophysiological roles of endothelial insulin signaling in the regulation of insulin-induced glucose uptake by the skeletal muscle.
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Affiliation(s)
- Tetsuya Kubota
- Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
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163
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Mikus CR, Roseguini BT, Uptergrove GM, Morris EM, Rector RS, Libla JL, Oberlin DJ, Borengasser SJ, Taylor AM, Ibdah JA, Laughlin MH, Thyfault JP. Voluntary wheel running selectively augments insulin-stimulated vasodilation in arterioles from white skeletal muscle of insulin-resistant rats. Microcirculation 2013; 19:729-38. [PMID: 22804760 DOI: 10.1111/j.1549-8719.2012.00210.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 07/11/2012] [Indexed: 01/13/2023]
Abstract
BACKGROUND Exercise (RUN) prevents declines in insulin-mediated vasodilation, an important component of insulin-mediated glucose disposal, in rats prone to obesity and insulin resistance. OBJECTIVE Determine whether RUN (1) improves insulin-stimulated vasodilation after insulin resistance has been established, and (2) differentially affects arterioles from red and white muscle. METHODS Insulin signaling and vasoreactivity to insulin (1-1000 μIU/mL) were assessed in 2A from the Gw and Gr of SED OLETF rats at 12 and 20 weeks of age (SED12, SED20) and those undergoing RUN (RUN20) or caloric restriction (CR20; to match body weight of RUN) from 12 to 20 weeks. RESULTS Glucose and insulin responses to i.p. glucose were reduced in RUN20, elevated in SED20 (p < 0.05 vs. SED12), and maintained in CR20. Insulin-stimulated vasodilation was greater in Gw but not Gr, 2As of RUN20 (p < 0.01 vs. all groups), and was improved by ET-1 receptor inhibition in Gw 2As from SED20 and CR20 (p < 0.05). There were no differences in microvascular insulin signaling among groups or muscle beds. CONCLUSIONS RUN selectively improved insulin-mediated vasodilation in Gw 2As, in part through attenuated ET-1 sensitivity/production, an adaptation that was independent of changes in adiposity and may contribute to enhanced insulin-stimulated glucose disposal.
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Affiliation(s)
- Catherine R Mikus
- Division of Cardiology, Duke University Medical Center, Durham, North Carolina, USA
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164
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Kearney MT. Changing the way we think about endothelial cell insulin sensitivity, nitric oxide, and the pathophysiology of type 2 diabetes: the FoxO is loose. Diabetes 2013; 62:1386-8. [PMID: 23613560 PMCID: PMC3636642 DOI: 10.2337/db13-0183] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Mark T Kearney
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, The Light Laboratories, Leeds, UK.
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165
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Wende AR, Symons JD, Abel ED. Mechanisms of lipotoxicity in the cardiovascular system. Curr Hypertens Rep 2013; 14:517-31. [PMID: 23054891 DOI: 10.1007/s11906-012-0307-2] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cardiovascular diseases account for approximately one third of all deaths globally. Obese and diabetic patients have a high likelihood of dying from complications associated with cardiovascular dysfunction. Obesity and diabetes increase circulating lipids that upon tissue uptake, may be stored as triglyceride, or may be metabolized in other pathways, leading to the generation of toxic intermediates. Excess lipid utilization or activation of signaling pathways by lipid metabolites may disrupt cellular homeostasis and contribute to cell death, defining the concept of lipotoxicity. Lipotoxicity occurs in multiple organs, including cardiac and vascular tissues, and a number of specific mechanisms have been proposed to explain lipotoxic tissue injury. In addition, recent data suggests that increased tissue lipids may also be protective in certain contexts. This review will highlight recent progress toward elucidating the relationship between nutrient oversupply, lipotoxicity, and cardiovascular dysfunction. The review will focus in two sections on the vasculature and cardiomyocytes respectively.
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Affiliation(s)
- Adam R Wende
- Program in Molecular Medicine, Division of Endocrinology, Metabolism, and Diabetes, University of Utah School of Medicine, Salt Lake City, 84112, USA
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166
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Mima A, Qi W, King GL. Implications of treatment that target protective mechanisms against diabetic nephropathy. Semin Nephrol 2013; 32:471-8. [PMID: 23062988 DOI: 10.1016/j.semnephrol.2012.07.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Diabetes results in vascular changes and dysfunction, and vascular complications are the leading cause of morbidity and mortality in diabetic patients. There has been a continual increase in the number of diabetic nephropathy patients and epidemic increases in the number of patients progressing to end-stage renal diseases. To identify targets for therapeutic intervention, most studies have focused on understanding how abnormal levels of glucose metabolites cause diabetic nephropathy, which is of paramount importance in devising strategies to combat the development and progression of diabetic nephropathy. However, less studied than the systemic toxic mechanisms, hyperglycemia and dyslipidemia might inhibit the endogenous vascular protective factors such as insulin, vascular endothelial growth factor, and platelet-derived growth factor. In this review, we highlight the importance of enhancing endogenous protective factors to prevent or delay diabetic nephropathy.
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Affiliation(s)
- Akira Mima
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
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167
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Assessment of endothelial dysfunction in childhood obesity and clinical use. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:174782. [PMID: 23691262 PMCID: PMC3649697 DOI: 10.1155/2013/174782] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/06/2013] [Indexed: 12/11/2022]
Abstract
The association of obesity with noncommunicable diseases, such as cardiovascular complications and diabetes, is considered a major threat to the management of health care worldwide. Epidemiological findings show that childhood obesity is rapidly rising in Western society, as well as in developing countries. This pandemic is not without consequences and can affect the risk of future cardiovascular disease in these children. Childhood obesity is associated with endothelial dysfunction, the first yet still reversible step towards atherosclerosis. Advanced research techniques have added further insight on how childhood obesity and associated comorbidities lead to endothelial dysfunction. Techniques used to measure endothelial function were further brought to perfection, and novel biomarkers, including endothelial progenitor cells, were discovered. The aim of this paper is to provide a critical overview on both in vivo as well as in vitro markers for endothelial integrity. Additionally, an in-depth description of the mechanisms that disrupt the delicate balance between endothelial damage and repair will be given. Finally, the effects of lifestyle interventions and pharmacotherapy on endothelial dysfunction will be reviewed.
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168
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Rizos CV, Elisaf MS. Metformin and cancer. Eur J Pharmacol 2013; 705:96-108. [PMID: 23499688 DOI: 10.1016/j.ejphar.2013.02.038] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/16/2013] [Accepted: 02/24/2013] [Indexed: 12/13/2022]
Abstract
Type 2 diabetes mellitus is a rising cause of cardiovascular morbidity and mortality. A number of studies have also identified diabetic patients as having increased risk for the development of cancer. Metformin is a widely prescribed antidiabetic drug with an established efficacy coupled with a favorable safety profile and low cost. An increasing number of studies have associated metformin treatment with a decrease of cancer risk. Moreover, metformin has also been associated with improved outcomes in cancer patients. These possible pleiotropic effects of metformin may establish metformin as a cancer prevention and treatment option. However, any favorable effects of metformin on cancer are not always corroborated by clinical trials. Larger studies are expected to better investigate the possible antineoplastic effects of metformin.
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Affiliation(s)
- Christos V Rizos
- Department of Internal Medicine, School of Medicine, University of Ioannina, Ioannina, Greece
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169
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Affiliation(s)
- Zhenqi Liu
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia Health System, Charlottesville, VA 22908, USA.
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170
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Abstract
Vascular endothelium is an important insulin target and plays a pivotal role in the development of metabolic insulin resistance provoked by the Western lifestyle. It acts as a "first-responder" to environmental stimuli such as nutrients, cytokines, chemokines and physical activity and regulates insulin delivery to muscle and adipose tissue and thereby affecting insulin-mediated glucose disposal by these tissues. In addition, it also regulates the delivery of insulin and other appetite regulating signals from peripheral tissues to the central nervous system thus influencing the activity of nuclei that regulate hepatic glucose production, adipose tissue lipolysis and lipogenesis, as well as food consumption. Resistance to insulin's vascular actions therefore broadly impacts tissue function and contribute to metabolic dysregulation. Moreover, vascular insulin resistance negatively impacts vascular health by affecting blood pressure regulation, vessel wall inflammation and atherogenesis thereby contributing to the burden of vascular disease seen with diabetes and metabolic syndrome. In the current review, we examined the evidence that supports the general concept of vascular endothelium as a target of insulin action and discussed the biochemical and physiological consequences of vascular insulin resistance.
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Affiliation(s)
- Eugene J Barrett
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA.
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171
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Symons JD, Abel ED. Lipotoxicity contributes to endothelial dysfunction: a focus on the contribution from ceramide. Rev Endocr Metab Disord 2013; 14:59-68. [PMID: 23292334 PMCID: PMC4180664 DOI: 10.1007/s11154-012-9235-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Cardiovascular complications are the leading causes of morbidity and mortality in individuals with obesity, type 2 diabetes mellitus (T2DM), and insulin resistance. Complications include pathologies specific to large (atherosclerosis, cardiomyopathy) and small (retinopathy, nephropathy, neuropathy) vessels. Common among all of these pathologies is an altered endothelial cell phenotype i.e., endothelial dysfunction. A crucial aspect of endothelial dysfunction is reduced nitric oxide (NO) bioavailability. Hyperglycemia, oxidative stress, activation of the renin-angiotensin system, and increased pro-inflammatory cytokines are systemic disturbances in individuals with obesity, T2DM, and insulin resistance and each of these contribute independently and synergistically to decreasing NO bioavailability. This review will examine the contribution from elevated circulating fatty acids in these subjects that lead to lipotoxicity. Particular focus will be placed on the fatty acid metabolite ceramide.
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Affiliation(s)
- J David Symons
- College of Health, University of Utah, School of Medicine, Salt Lake City, UT, USA.
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172
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Eringa EC, Serne EH, Meijer RI, Schalkwijk CG, Houben AJHM, Stehouwer CDA, Smulders YM, van Hinsbergh VWM. Endothelial dysfunction in (pre)diabetes: characteristics, causative mechanisms and pathogenic role in type 2 diabetes. Rev Endocr Metab Disord 2013; 14:39-48. [PMID: 23417760 DOI: 10.1007/s11154-013-9239-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Endothelial dysfunction associated with diabetes and cardiovascular disease is characterized by changes in vasoregulation, enhanced generation of reactive oxygen intermediates, inflammatory activation, and altered barrier function. These endothelial alterations contribute to excess cardiovascular disease in diabetes, but may also play a role in the pathogenesis of diabetes, especially type 2. The mechanisms underlying endothelial dysfunction in diabetes differ between type 1 (T1D) and type 2 diabetes (T2D): hyperglycemia contributes to endothelial dysfunction in all individuals with diabetes, whereas the causative mechanisms in T2D also include impaired insulin signaling in endothelial cells, dyslipidemia and altered secretion of bioactive substances (adipokines) by adipose tissue. The close association of so-called perivascular adipose tissue with arteries and arterioles facilitates the exposure of vascular endothelium to adipokines, particularly if inflammation activates the adipose tissue. Glucose and adipokines activate specific intracellular signaling pathways in endothelium, which in concert result in endothelial dysfunction in diabetes. Here, we review the characteristics of endothelial dysfunction in diabetes, the causative mechanisms involved and the role of endothelial dysfunction(s) in the pathogenesis of T2D. Finally, we will discuss the therapeutic potential of endothelial dysfunction in T2D.
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Affiliation(s)
- Etto C Eringa
- Departments of Physiology, VU University Medical Center, Amsterdam, the Netherlands.
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173
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Muris DMJ, Houben AJHM, Schram MT, Stehouwer CDA. Microvascular dysfunction: an emerging pathway in the pathogenesis of obesity-related insulin resistance. Rev Endocr Metab Disord 2013; 14:29-38. [PMID: 23299657 DOI: 10.1007/s11154-012-9231-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The prevalence of type 2 diabetes mellitus (T2DM) and its major risk factor, obesity, has reached epidemic proportions in Western society. How obesity leads to insulin resistance and subsequent T2DM is incompletely understood. It has been established that insulin can redirect blood flow in skeletal muscle from non-nutritive to nutritive capillary networks, without increasing total blood flow. This results in a net increase of the overall number of perfused nutritive capillary networks and thereby increases insulin-mediated glucose uptake by skeletal muscle. This process, referred to as functional (nutritive) capillary recruitment, has been shown to be endothelium-dependent and to require activation of the phosphatidylinositol-kinase (PI3K) pathway in the endothelial cell. Several studies have demonstrated that these processes are impaired in states of microvascular dysfunction. In obesity, changes in several adipokines are likely candidates to influence insulin signaling pathways in endothelial cells, thereby causing microvascular dysfunction. Microvascular dysfunction, in turn, impairs the timely access of glucose and insulin to their target tissues, and may therefore be an additional cause of insulin resistance. Thus, microvascular dysfunction may be a key feature in the development of obesity-related insulin resistance. In the present review, we will discuss the evidence for this emerging role for the microcirculation as a possible link between obesity and insulin resistance.
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Affiliation(s)
- Dennis M J Muris
- Department of Internal Medicine, Maastricht University Medical Centre (MUMC+), P.O. Box 5800, 6202 AZ, Maastricht, the Netherlands
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174
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Abstract
Insulin resistance is frequently associated with endothelial dysfunction and has been proposed to play a major role in cardiovascular diseases. Insulin exerts pro- and anti-atherogenic actions on the vasculature. The balance between nitric oxide (NO)-dependent vasodilator actions and endothelin-1- dependent vasoconstrictor actions of insulin is regulated by phosphatidylinositol 3-kinase-dependent (PI3K) - and mitogen-activated protein kinase (MAPK)-dependent signaling in vascular endothelium, respectively. During insulin-resistant conditions, pathway-specific impairment in PI3K-dependent signaling may cause imbalance between production of NO and secretion of endothelin-1 and lead to endothelial dysfunction. Insulin sensitizers that target pathway-selective impairment in insulin signaling are known to improve endothelial dysfunction. In this review, we discuss the cellular mechanisms in the endothelium underlying vascular actions of insulin, the role of insulin resistance in mediating endothelial dysfunction, and the effect of insulin sensitizers in restoring the balance in pro- and anti-atherogenic actions of insulin.
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Affiliation(s)
- Ranganath Muniyappa
- Clinical Endocrine Section, Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - James R. Sowers
- Departments of Internal Medicine and Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, Missouri; and Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri
- Corresponding author for proof and reprints: James R. Sowers, MD, Department of Internal Medicine, University of Missouri School of Medicine, One Hospital Drive, Columbia, Missouri, MO 65212,
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175
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Abstract
Insulin resistance is a complex metabolic defect that has several causes dependent on an individual's genetic substrate and the underlying pathophysiologic state. Atherogenic dyslipidemia, hyperinsulinemia, dysglycemia, inflammation associated with obesity, and ectopic steatosis in liver and skeletal muscle all collude to facilitate endothelial dysfunction and predispose to the initiation and propagation of atherosclerosis. As aggressive management of the various risk factors does not seem to abrogate the so-called residual risk, more research is needed to define ways by which intervention can fundamentally alter the metabolic and vascular milieu and slow the pace of atherosclerosis, thus favorably affecting outcomes.
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Affiliation(s)
- Vasudevan A Raghavan
- Division of Endocrinology, Department of Internal Medicine, Texas A&M Health Sciences Center and College of Medicine, Temple, TX 76508, USA.
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176
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Williams KH, Shackel NA, Gorrell MD, McLennan SV, Twigg SM. Diabetes and nonalcoholic Fatty liver disease: a pathogenic duo. Endocr Rev 2013; 34:84-129. [PMID: 23238855 DOI: 10.1210/er.2012-1009] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent data increasingly support a complex interplay between the metabolic condition diabetes mellitus and the pathologically defined nonalcoholic fatty liver disease (NAFLD). NAFLD predicts the development of type 2 diabetes and vice versa, and each condition may serve as a progression factor for the other. Although the association of diabetes and NAFLD is likely to be partly the result of a "common soil," it is also probable that diabetes interacts with NAFLD through specific pathogenic mechanisms. In particular, through interrelated metabolic pathways currently only partly understood, diabetes appears to accelerate the progression of NAFLD to nonalcoholic steatohepatitis, defined by the presence of necroinflammation, with varying degrees of liver fibrosis. In the research setting, obstacles that have made the identification of clinically significant NAFLD, and particularly nonalcoholic steatohepatitis, difficult are being addressed with the use of new imaging techniques combined with risk algorithms derived from peripheral blood profiling. These techniques are likely to be used in the diabetes population in the near future. This review examines the pathogenic links between NAFLD and diabetes by exploring the epidemiological evidence in humans and also through newer animal models. Emerging technology to help screen noninvasively for differing pathological forms of NAFLD and the potential role of preventive and therapeutic approaches for NAFLD in the setting of diabetes are also examined.
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Affiliation(s)
- K H Williams
- Sydney Medical School and the Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
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177
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Abstract
In patients with diabetes, atherosclerosis is the main reason for impaired life expectancy, and diabetic nephropathy and retinopathy are the largest contributors to end-stage renal disease and blindness, respectively. An improved therapeutic approach to combat diabetic vascular complications might include blocking mechanisms of injury as well as promoting protective or regenerating factors, for example by enhancing the action of insulin-regulated genes in endothelial cells, promoting gene programs leading to induction of antioxidant or anti-inflammatory factors, or improving the sensitivity to vascular cell survival factors. Such strategies could help prevent complications despite suboptimal metabolic control.
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178
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Eggleston EM, Jahn LA, Barrett EJ. Early microvascular recruitment modulates subsequent insulin-mediated skeletal muscle glucose metabolism during lipid infusion. Diabetes Care 2013; 36:104-10. [PMID: 22961574 PMCID: PMC3526221 DOI: 10.2337/dc11-2399] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To test whether early, insulin-mediated microvascular recruitment in skeletal muscle predicts steady-state glucose metabolism in the setting of physiological elevation of free fatty acid concentrations. RESEARCH DESIGN AND METHODS We measured insulin's microvascular and metabolic effects in 14 healthy young adults during a 2-h euglycemic insulin clamp. Plasma free fatty acid concentrations were raised (Intralipid and heparin infusion) for 3 h before the clamp and maintained at postprandial concentrations during the clamp. Microvascular blood volume (MBV) was measured by contrast-enhanced ultrasound (CEU) continuously from baseline through the first 30 min of the insulin clamp. Muscle glucose and insulin uptake were measured by the forearm balance method. RESULTS The glucose infusion rate (GIR) necessary to maintain euglycemia during the clamp varied by fivefold across subjects (2.5-12.5 mg/min/kg). The early MBV responses to insulin, as indicated by CEU video intensity, ranged widely, from a 39% decline to a 69% increase. During the clamp, steady state forearm muscle glucose uptake and GIR each correlated significantly with the change in forearm MBV (P < 0.01). To explore the basis for the wide range of vascular and metabolic insulin sensitivity observed, we also measured V(O(2max)) in a subset of eight subjects. Fitness (V(O(2max))) correlated significantly with the GIR, the forearm glucose uptake, and the percentage change in MBV during the insulin clamp (P < 0.05 for each). CONCLUSIONS Early microvascular responses to insulin strongly associate with steady state skeletal muscle insulin-mediated glucose uptake. Physical fitness predicts both metabolic and vascular insulin responsiveness.
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Affiliation(s)
- Emma M Eggleston
- Division of Endocrinology, Department of Medicine, University of Virginia Health System, Charlottesville, VA, USA
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179
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Abstract
Women continue to be underrepresented in clinical trials, particularly in Phases I and II of experimental drug studies in spite of legislative guidelines in the USA, Canada, the European Union, Australia, and Japan requiring the inclusion of women in clinical trials. As such, women remain a vulnerable population subject to the adverse effects of pharmacological therapies. Thus, women experience higher rates of adverse drug reactions than do men and for women of reproductive age or who may be pregnant, therapeutic options may be limited. This chapter provides a brief history of inclusion of sex and gender as variables in clinical trials, summarizes governmental legislation for consideration of sex and gender in clinical trials and provides specific examples of drugs which have been withdrawn from the market because of side effects in women. Additional information related to sex and gender in preclinical testing, trial design, challenges to recruitment of women for clinical trials and statistical methods for analysis of data also is considered.
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180
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Streit U, Reuter H, Bloch W, Wahlers T, Schwinger RHG, Brixius K. Phosphorylation of myocardial eNOS is altered in patients suffering from type 2 diabetes. J Appl Physiol (1985) 2012; 114:1366-74. [PMID: 23264539 DOI: 10.1152/japplphysiol.00011.2011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study investigated whether endothelial nitric oxide synthase (eNOS) activation may be dysregulated in cardiac tissue of patients suffering from type 2 diabetes (T2D). We performed immunohistochemical measurements of translocated eNOS activation as well as eNOS phosphorylation at Ser1177, Thr495, Ser 635, Ser114, and of the protein kinase B (Akt) in isolated right atrial trabeculae of patients undergoing cardiac bypass or valve surgery with (n = 12, 68.1 ± 2.5 yr) and without T2D (n = 12, 64.7 ± 2.7 yr). In addition, we investigated oxidative (8-isoprostane) and nitrosative stress markers (nitrotyrosine) as well as the effect of pharmacological stimulation of angiotensin (AT)-receptors on eNOS-phosphorylation. Translocation-dependent eNOS activation was similar in both groups. The same holds true for eNOS phosphorylation at Ser114. eNOS phosphorylation at Ser635 was significantly increased, whereas eNOS phosphorylation of Ser1177 was significantly decreased in the diabetic group paralleled by a decrease in phosphorylation of Akt and Thr495. These alterations were accompanied by a significant decrease in nitrotyrosine. After application of angiotensin II (10 μM, 2 min) for investigation of the AT-receptor-dependent eNOS stimulation, we did not find differences between the increases in eNOS Ser1177-phosphorylation in the nondiabetic (+39.7 ± 23.5%) and in the diabetic group (32.22 ± 11.45%). A simultaneous increase in Akt phosphorylation could not be observed. The present study indicates that T2D goes along with a decrease in eNOS phosphorylation at Ser1177 under basal conditions in cardiac tissue. Whether this may be attributed to the insulin resistance of cardiac muscle has to be further investigated. Receptor-stimulated eNOS activation still works at least for angiotensin II-dependent eNOS activation.
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Affiliation(s)
- Ulrike Streit
- Department of Molecular and Cellular Sport Medicine, German Sport University Cologne, Cologne, Germany
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181
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Tabit CE, Shenouda SM, Holbrook M, Fetterman JL, Kiani S, Frame AA, Kluge MA, Held A, Dohadwala MM, Gokce N, Farb MG, Rosenzweig J, Ruderman N, Vita JA, Hamburg NM. Protein kinase C-β contributes to impaired endothelial insulin signaling in humans with diabetes mellitus. Circulation 2012. [PMID: 23204109 DOI: 10.1161/circulationaha.112.127514] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Abnormal endothelial function promotes atherosclerotic vascular disease in diabetes. Experimental studies indicate that disruption of endothelial insulin signaling, through the activity of protein kinase C-β (PKCβ) and nuclear factor κB, reduces nitric oxide availability. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes mellitus. METHODS AND RESULTS We measured protein expression and insulin response in freshly isolated endothelial cells from patients with type 2 diabetes mellitus (n=40) and nondiabetic controls (n=36). Unexpectedly, we observed 1.7-fold higher basal endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 in patients with diabetes mellitus (P=0.007) without a difference in total eNOS expression. Insulin stimulation increased eNOS phosphorylation in nondiabetic subjects but not in diabetic patients (P=0.003), consistent with endothelial insulin resistance. Nitrotyrosine levels were higher in diabetic patients, indicating endothelial oxidative stress. PKCβ expression was higher in diabetic patients and was associated with lower flow-mediated dilation (r=-0.541, P=0.02). Inhibition of PKCβ with LY379196 reduced basal eNOS phosphorylation and improved insulin-mediated eNOS activation in patients with diabetes mellitus. Endothelial nuclear factor κB activation was higher in diabetes mellitus and was reduced with PKCβ inhibition. CONCLUSIONS We provide evidence for the presence of altered eNOS activation, reduced insulin action, and inflammatory activation in the endothelium of patients with diabetes mellitus. Our findings implicate PKCβ activity in endothelial insulin resistance.
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Affiliation(s)
- Corey E Tabit
- Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA
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182
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Mima A, Hiraoka-Yamomoto J, Li Q, Kitada M, Li C, Geraldes P, Matsumoto M, Mizutani K, Park K, Cahill C, Nishikawa SI, Rask-Madsen C, King GL. Protective effects of GLP-1 on glomerular endothelium and its inhibition by PKCβ activation in diabetes. Diabetes 2012; 61:2967-79. [PMID: 22826029 PMCID: PMC3478518 DOI: 10.2337/db11-1824] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
To characterize glucagon-like peptide (GLP)-1 signaling and its effect on renal endothelial dysfunction and glomerulopathy. We studied the expression and signaling of GLP-1 receptor (GLP-1R) on glomerular endothelial cells and the novel finding of protein kinase A-dependent phosphorylation of c-Raf at Ser259 and its inhibition of angiotensin II (Ang II) phospho-c-Raf(Ser338) and Erk1/2 phosphorylation. Mice overexpressing protein kinase C (PKC)β2 in endothelial cells (EC-PKCβ2Tg) were established. Ang II and GLP-1 actions in glomerular endothelial cells were analyzed with small interfering RNA of GLP-1R. PKCβ isoform activation induced by diabetes decreased GLP-1R expression and protective action on the renal endothelium by increasing its degradation via ubiquitination and enhancing phospho-c-Raf(Ser338) and Ang II activation of phospho-Erk1/2. EC-PKCβ2Tg mice exhibited decreased GLP-1R expression and increased phospho-c-Raf(Ser338), leading to enhanced effects of Ang II. Diabetic EC-PKCβ2Tg mice exhibited greater loss of endothelial GLP-1R expression and exendin-4-protective actions and exhibited more albuminuria and mesangial expansion than diabetic controls. These results showed that the renal protective effects of GLP-1 were mediated via the inhibition of Ang II actions on cRaf(Ser259) and diminished by diabetes because of PKCβ activation and the increased degradation of GLP-1R in the glomerular endothelial cells.
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MESH Headings
- Angiotensin II/metabolism
- Animals
- Cells, Cultured
- Diabetes Mellitus, Experimental/complications
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetic Nephropathies/prevention & control
- Endothelium/drug effects
- Endothelium/enzymology
- Endothelium/metabolism
- Endothelium/pathology
- Exenatide
- Gene Expression Regulation/drug effects
- Glucagon-Like Peptide 1/antagonists & inhibitors
- Glucagon-Like Peptide 1/genetics
- Glucagon-Like Peptide 1/metabolism
- Glucagon-Like Peptide-1 Receptor
- Hypoglycemic Agents/antagonists & inhibitors
- Hypoglycemic Agents/therapeutic use
- Kidney Glomerulus/drug effects
- Kidney Glomerulus/enzymology
- Kidney Glomerulus/metabolism
- Kidney Glomerulus/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Peptides/antagonists & inhibitors
- Peptides/therapeutic use
- Peptides/toxicity
- Protein Kinase C/chemistry
- Protein Kinase C/genetics
- Protein Kinase C/metabolism
- Protein Kinase C beta
- Proto-Oncogene Proteins c-raf/metabolism
- RNA Interference
- Receptors, Glucagon/antagonists & inhibitors
- Receptors, Glucagon/genetics
- Receptors, Glucagon/metabolism
- Signal Transduction/drug effects
- Tissue Culture Techniques
- Venoms/therapeutic use
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Affiliation(s)
- Akira Mima
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Junko Hiraoka-Yamomoto
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Qian Li
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Munehiro Kitada
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Chenzhong Li
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Pedro Geraldes
- Department of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Motonobu Matsumoto
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Koji Mizutani
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Kyoungmin Park
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Christopher Cahill
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - Shin-Ichi Nishikawa
- Laboratory for Stem Cell Biology, RIKEN Center for Developmental Biology, Kobe, Japan
| | - Christian Rask-Madsen
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
| | - George L. King
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
- Corresponding author: George L. King,
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183
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Rask-Madsen C, Kahn CR. Tissue-specific insulin signaling, metabolic syndrome, and cardiovascular disease. Arterioscler Thromb Vasc Biol 2012; 32:2052-9. [PMID: 22895666 DOI: 10.1161/atvbaha.111.241919] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Impaired insulin signaling is central to development of the metabolic syndrome and can promote cardiovascular disease indirectly through development of abnormal glucose and lipid metabolism, hypertension, and a proinflammatory state. However, insulin's action directly on vascular endothelium, atherosclerotic plaque macrophages, and in the heart, kidney, and retina has now been described, and impaired insulin signaling in these locations can alter progression of cardiovascular disease in the metabolic syndrome and affect development of microvascular complications of diabetes mellitus. Recent advances in our understanding of the complex pathophysiology of insulin's effects on vascular tissues offer new opportunities for preventing these cardiovascular disorders.
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Affiliation(s)
- Christian Rask-Madsen
- Joslin Diabetes Center, Harvard Medical School, One Joslin Place, Boston, MA 02215, USA
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184
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Imrie H, Viswambharan H, Sukumar P, Abbas A, Cubbon RM, Yuldasheva N, Gage M, Smith J, Galloway S, Skromna A, Rashid ST, Futers TS, Xuan S, Gatenby VK, Grant PJ, Channon KM, Beech DJ, Wheatcroft SB, Kearney MT. Novel role of the IGF-1 receptor in endothelial function and repair: studies in endothelium-targeted IGF-1 receptor transgenic mice. Diabetes 2012; 61:2359-68. [PMID: 22733797 PMCID: PMC3425420 DOI: 10.2337/db11-1494] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
We recently demonstrated that reducing IGF-1 receptor (IGF-1R) numbers in the endothelium enhances nitric oxide (NO) bioavailability and endothelial cell insulin sensitivity. In the present report, we aimed to examine the effect of increasing IGF-1R on endothelial cell function and repair. To examine the effect of increasing IGF-1R in the endothelium, we generated mice overexpressing human IGF-1R in the endothelium (human IGF-1R endothelium-overexpressing mice [hIGFREO]) under direction of the Tie2 promoter enhancer. hIGFREO aorta had reduced basal NO bioavailability (percent constriction to N(G)-monomethyl-l-arginine [mean (SEM) wild type 106% (30%); hIGFREO 48% (10%)]; P < 0.05). Endothelial cells from hIGFREO had reduced insulin-stimulated endothelial NO synthase activation (mean [SEM] wild type 170% [25%], hIGFREO 58% [3%]; P = 0.04) and insulin-stimulated NO release (mean [SEM] wild type 4,500 AU [1,000], hIGFREO 1,500 AU [700]; P < 0.05). hIGFREO mice had enhanced endothelium regeneration after denuding arterial injury (mean [SEM] percent recovered area, wild type 57% [2%], hIGFREO 47% [5%]; P < 0.05) and enhanced endothelial cell migration in vitro. The IGF-1R, although reducing NO bioavailability, enhances in situ endothelium regeneration. Manipulating IGF-1R in the endothelium may be a useful strategy to treat disorders of vascular growth and repair.
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Affiliation(s)
- Helen Imrie
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Hema Viswambharan
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Piruthivi Sukumar
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Afroze Abbas
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Richard M. Cubbon
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Nadira Yuldasheva
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Matthew Gage
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Jessica Smith
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Stacey Galloway
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Anna Skromna
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Sheik Taqweer Rashid
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - T. Simon Futers
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Shouhong Xuan
- Department of Genetics and Development, Columbia University, New York, New York
| | - V. Kate Gatenby
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Peter J. Grant
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Keith M. Channon
- University of Oxford British Heart Foundation Centre of Research Excellence, Oxford, U.K
| | - David J. Beech
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Stephen B. Wheatcroft
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
| | - Mark T. Kearney
- Division of Cardiovascular and Diabetes Research, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, U.K
- Corresponding author: Mark T. Kearney,
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185
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Zhou QG, Fu XJ, Xu GY, Cao W, Liu HF, Nie J, Liang M, Hou FF. Vascular insulin resistance related to endoplasmic reticulum stress in aortas from a rat model of chronic kidney disease. Am J Physiol Heart Circ Physiol 2012; 303:H1154-65. [PMID: 22942179 DOI: 10.1152/ajpheart.00407.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Metabolic insulin resistance has been demonstrated in patients with nondiabetic chronic kidney disease (CKD), yet their vascular insulin signaling remains poorly understood. Here we tested the hypothesis that vascular insulin signaling was impaired and related with endoplasmic reticulum (ER) stress in aortas from the reduced renal mass (RRM) model of CKD. The activity of insulin signaling and markers of ER were determined in aortas from rats with RRM and cultured human umbilical vein endothelial cells. Tyrosine phosphorylation of insulin receptor-β and insulin receptor substrate (IRS)-1 and phosphorylation of protein kinase B and endothelial nitric oxide synthase were all decreased in aorta from RRM rats, whereas serine phosphorylation of IRS-1, a marker of insulin resistance, was increased. In addition, nitric oxide generation and insulin-mediated vasorelaxation were decreased in aortas from RRM rats. Insulin signaling in cultured vascular endothelial cells was impaired by induction of ER stress and was restored in aortas of RRM rats by inhibition of ER stress. Taken together, rats with RRM had vascular insulin resistance that was linked to ER stress. This identified vascular insulin resistance and ER stress as a potential therapeutic target for cardiovascular complications in patients with CKD.
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Affiliation(s)
- Qiu Gen Zhou
- Division of Nephrology, Nanfang Hospital, Southern Medical University, Key Lab for Organ Failure Research, Ministry of Education, Guangzhou, China
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186
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Abstract
Obesity represents a major risk factor for the development of insulin and leptin resistance, ultimately leading to a pleiotropic spectrum of metabolic alterations. However, resistance to both hormones does not uniformly affect all target cells and intracellular signaling pathways. In contrast, numerous clinical phenotypes arise from selective hormone resistance, leading to inhibition of defined intracellular signaling pathways in some tissues, while in other cell types hormone action is maintained or even overactivated. Here, we review the molecular mechanisms and clinical outcomes resulting from selective insulin and leptin resistance, which should ultimately guide future strategies for the treatment of obesity-associated diseases.
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Affiliation(s)
- A Christine Könner
- Department of Mouse Genetics and Metabolism, Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases, Center of Molecular Medicine Cologne, University of Cologne, D-50674 Cologne, Germany
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187
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Lee YJ, Choi DH, Cho GH, Kim JS, Kang DG, Lee HS. Arctium lappa ameliorates endothelial dysfunction in rats fed with high fat/cholesterol diets. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 12:116. [PMID: 22866890 PMCID: PMC3517347 DOI: 10.1186/1472-6882-12-116] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 07/30/2012] [Indexed: 01/04/2023]
Abstract
Background Arctium lappa L. (Asteraceae), burdock, is a medicinal plant that is popularly used for treating hypertension, gout, hepatitis, and other inflammatory disorders. This study was performed to test the effect of ethanol extract of Arctium lappa L. (EAL) seeds on vascular reactivity and inflammatory factors in rats fed a high fat/cholesterol diet (HFCD). Method EAL-I (100 mg·kg−1/day), EAL-II (200 mg·kg−1/day), and fluvastatin (3 mg·kg−1/day) groups initially received HFCD alone for 8 weeks, with EAL supplementation provided during the final 6 weeks. Results Treatment with low or high doses of EAL markedly attenuated plasma levels of triglycerides and augmented plasma levels of high-density lipoprotein (HDL) in HFCD-fed rats. Chronic treatment with EAL markedly reduced impairments of acetylcholine (ACh)-induced relaxation of aortic rings. Furthermore, chronic treatment with EAL significantly lowered systolic blood pressure (SBP) and maintained smooth and flexible intimal endothelial layers in HFCD-fed rats. Chronic treatment with EAL suppressed upregulation of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin in the aorta. Chronic treatment with EAL also suppressed increases in matrix metalloproteinase (MMP)-2 expression. These results suggested that EAL can inhibit HFCD-induced vascular inflammation in the rat model. Conclusion The present study provides evidence that EAL ameliorates HFCD-induced vascular dysfunction through protection of vascular relaxation and suppression of vascular inflammation.
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188
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Javanmard SH, Nematbakhsh M, Feghhi A, Dana N. Hyperinsulinemia may have a protective role in the early stages of atherosclerosis in rabbit model of hypercholesterolemia. J Diabetes Metab Disord 2012; 11:5. [PMID: 23497719 PMCID: PMC3581106 DOI: 10.1186/2251-6581-11-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 08/02/2012] [Indexed: 11/18/2022]
Abstract
Background Hypercholesterolemia causes inflammation and insulin resistance in the vasculature. Previous data suggest that vascular endothelium is a physiological target of insulin. Dyslipidemia and atherosclerosis are disorders with endothelial dysfunction that are associated with an increased production of superoxide anion, and early deficit of nitric oxide (NO) production. We examined alteration of plasma levels of insulin, C-reactive protein (CRP) and total NO metabolites (NOx), as well as fatty streak formation in the rabbit model of hypercholesterolemia. Methods White male rabbits were fed either a high-cholesterol diet (HC; 1% cholesterol, n = 6) or control diet (c, n = 6) for one month. The serum levels of Cholesterol, LDL, HDL, NOx, insulin and CRP were measured before and after study. By the end of study, rabbits' aorta was explored for fatty streak formation. Results The cholesterol-rich diet induced a significant increase in total cholesterol, LDL, and HDL as well as fatty streak lesions in HC group while there were no significant changes of these parameters in control group (p <0.05). There was significant difference in plasma levels of CRP, insulin and total NO metabolite between two groups of experiment. Negative significant correlation of CRP and insulin also was observed in HC rabbits (r = −0.99, p <0.05). Conclusion Parallel NOx and insulin increment and negative correlation of CRP and insulin in HC rabbits may be suggestive a protective role of hyperinsulinemia in early atherosclerosis.
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189
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Wu X, Chen K, Williams KJ. The role of pathway-selective insulin resistance and responsiveness in diabetic dyslipoproteinemia. Curr Opin Lipidol 2012; 23:334-44. [PMID: 22617754 DOI: 10.1097/mol.0b013e3283544424] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
PURPOSE OF REVIEW Type 2 diabetes mellitus (T2DM) and related syndromes exhibit a deadly triad of dyslipoproteinemia, which leads to atherosclerosis, hyperglycemia, which causes microvascular disease, and hypertension. These features share a common, but unexplained, origin--namely, pathway-selective insulin resistance and responsiveness (SEIRR). Here, we review recent work on hepatic SEIRR indicating that deranged insulin signaling may have a remarkably simple molecular basis. RECENT FINDINGS Comprehensive examination of a set of 18 insulin targets revealed that T2DM liver in vivo exhibits a specific defect in the ability of the NAD(P)H oxidase 4 (NOX4) to inactivate protein tyrosine phosphatase gene family members after stimulation with insulin, and that impairment of this single molecule, NOX4, in cultured hepatocytes recapitulates all features of hepatic SEIRR in vivo. These features include insulin-stimulated generation of an unusual monophosphorylated form of AKT at Thr308 (pT308-AKT) with only weak phosphorylation at Ser473, impaired insulin-stimulated pathways for lowering plasma levels of lipids and glucose, but continued lipogenic pathways and robust extracellular signal-regulated kinase activation. This new study, in combination with important prior work, provides clues to several long-standing mysteries, such as how AKT might regulate lipid-lowering and glucose-lowering pathways that become insulin-resistant but also lipogenic pathways that remain insulin-responsive, as well as a potential role for NOX4 in insulin-stimulated generation of oxysterol ligands for LXR, a key lipogenic factor. SUMMARY These findings suggest a unified molecular explanation for fatty liver, atherogenic dyslipoproteinemia, hyperglycemia, and hence accelerated atherosclerosis and microvascular disease in T2DM, obesity, and related syndromes of positive caloric imbalance.
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Affiliation(s)
- Xiangdong Wu
- Section of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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190
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Guiu B, Petit JM, Capitan V, Aho S, Masson D, Lefevre PH, Favelier S, Loffroy R, Vergès B, Hillon P, Krausé D, Cercueil JP. Intravoxel incoherent motion diffusion-weighted imaging in nonalcoholic fatty liver disease: a 3.0-T MR study. Radiology 2012; 265:96-103. [PMID: 22843768 DOI: 10.1148/radiol.12112478] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE To compare pure molecular diffusion, D, perfusion-related diffusion, D*, and perfusion fraction, f, determined from diffusion-weighted (DW) magnetic resonance (MR) imaging on the basis of the intravoxel incoherent motion (IVIM) theory in patients with type 2 diabetes with and without liver steatosis. MATERIALS AND METHODS This prospective study was approved by the appropriate ethics committee, and written informed consent was obtained from all patients. Between December 2009 and September 2011, 108 patients with type 2 diabetes (51 men, 57 women; mean age, 50 years) underwent 3.0-T single-voxel point-resolved proton MR spectroscopy of the liver (segment VII) to calculate the liver fat fraction from water (4.76 ppm) and methylene (1.33 ppm) peaks, corrected for T1 and T2 decay. Steatosis was defined as a liver fat fraction of at least 5.56%. DW imaging was performed by using a single-shot echo-planar sequence with 11 b values (0, 5, 15, 25, 35, 50, 100, 200, 400, 600, 800 sec/mm2). Liver D, D*, and f were measured and compared in patients with and patients without steatosis (Mann-Whitney test). RESULTS The mean liver fat fraction was 7.8% (standard deviation, 9%; range, 0.99%-45%). Forty patients had liver steatosis. D was significantly lower in steatotic compared with nonsteatotic livers (mean, 1.03×10(-3) mm2/sec±0.23 [standard deviation] vs 1.24×10(-3) mm2/sec±0.15, respectively; P<.0001), as was D* (mean, 72.2×10(-3) mm2/sec±61.4 vs 110.6×10(-3) mm2/sec±79; P=.0025). However, f was significantly higher in steatotic compared with nonsteatotic livers (mean, 33.8%±9.4 vs 26.9%±8.8; P=.0003). CONCLUSION D is significantly decreased in steatosis. The reduction in D* reflects decreased liver parenchymal perfusion in steatosis. Therefore, steatosis can affect diffusion parameters obtained with IVIM.
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Affiliation(s)
- Boris Guiu
- University of Burgundy, INSERM U866, Department of Endocrinology, Diabetology, and Metabolic Diseases, CHU University Hospital, Dijon, France.
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191
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Zhou MS, Schulman IH, Zeng Q. Link between the renin-angiotensin system and insulin resistance: implications for cardiovascular disease. Vasc Med 2012; 17:330-41. [PMID: 22814999 DOI: 10.1177/1358863x12450094] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The incidence of metabolic syndrome is rapidly increasing in the United States and worldwide. The metabolic syndrome is a complex metabolic and vascular disorder that is associated with inappropriate activation of the renin-angiotensin-aldosterone system (RAAS) in the cardiovascular (CV) system and increased CV morbidity and mortality. Insulin activation of the phosphatidylinositol-3-kinase (PI3K) pathway promotes nitric oxide (NO) production in the endothelium and glucose uptake in insulin-sensitive tissues. Angiotensin (Ang) II inhibits insulin-mediated PI3K pathway activation, thereby impairing endothelial NO production and Glut-4 translocation in insulin-sensitive tissues, which results in vascular and systemic insulin resistance, respectively. On the other hand, Ang II enhances insulin-mediated activation of the mitogen-activated protein kinase (MAPK) pathway, which leads to vasoconstriction and pathologic vascular cellular growth. Therefore, the interaction of Ang II with insulin signaling is fully operative not only in insulin-sensitive tissues but also in CV tissues, thereby linking insulin resistance and CV disease. This notion is further supported by an increasing number of experimental and clinical studies indicating that pharmacological blockade of RAAS improves insulin sensitivity and endothelial function, as well as reduces the incidence of new-onset diabetes in high-risk patients with CV disease. This article reviews experimental and clinical data elucidating the physiological and pathophysiological role of the interaction between insulin and RAAS in the development of insulin resistance as well as CV disease.
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Affiliation(s)
- Ming-Sheng Zhou
- Nephrology-Hypertension Section, Veterans Affairs Medical Center, University of Miami Miller School of Medicine, Miami, FL 33125, USA.
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192
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Costa MM, Violato NM, Taboga SR, Góes RM, Bosqueiro JR. Reduction of insulin signalling pathway IRS-1/IRS-2/AKT/mTOR and decrease of epithelial cell proliferation in the prostate of glucocorticoid-treated rats. Int J Exp Pathol 2012; 93:188-95. [PMID: 22583132 DOI: 10.1111/j.1365-2613.2012.00817.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Previous studies by our research group using a model of insulin resistance induced by dexamethasone (DEX) showed that in the rat ventral prostate there was epithelial and smooth muscle cell atrophy and there were also alterations in fibroblasts. Proteins of the insulin signalling pathway are known to be very important for cell proliferation and development. Thus, we investigated the insulin signalling pathway and epithelial proliferation in the rat ventral prostate in this model and correlated the findings with expression of glucocorticoid (GR) and androgen (AR) receptors. Insulin resistance was induced in adult male Wistar rats by injection of DEX (1 mg/kg, ip for 5 consecutive days), whereas control (CTL) rats received saline. DEX treatment resulted in a significant decrease in body weight, but not in prostate weight. Reductions in insulin receptor 1 (IRS-1) (CTL 1.11 ± 0.06; DEX 0.85 ± 0.03), IRS-2 (CTL 0.95 ± 0.05; DEX 0.49 ± 0.04), AKT (CTL 0.98 ± 0.03; DEX 0.78 ± 0.02), mammalian target of rapamycin (mTOR; CTL 0.65 ± 0.08; DEX 0.22 ± 0.05), GR (CTL 1.30 ± 0.09; DEX 0.57 ± 0.10) and AR (CTL 1.83 ± 0.16; DEX 0.55 ± 0.08) protein levels were observed in the prostate of DEX-treated rats. The expression of the IRα-subunit, phosphoinositide 3-kinase, p-AKT, p70(S6K) , extracellular signal-regulated kinase (ERK) and p-ERK was not altered. The frequency of AR-positive cells in the epithelium of the prostate decreased in the glucocorticoid-treated group, and the intensity of the reaction for this receptor in the cell nuclei was lower in this group. Furthermore, the treatment with DEX reduced the frequency of proliferating cell nuclear antigen-positive (PCNA) cells 30-fold. This study suggests that the reduction in the insulin signalling pathway proteins IRS-1/IRS-2/AKT/mTOR in the prostate of DEX-treated rats may be associated with the morphological alterations observed previously.
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Affiliation(s)
- Maitê M Costa
- Department of Physical Education, Faculty of Sciences, São Paulo State University-Unesp, Bauru, São Paulo, Brazil
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193
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Fakhrzadeh H, Alatab S, Sharifi F, Mirarefein M, Badamchizadeh Z, Ghaderpanahi M, Hashemi Taheri AP, Larijani B. Carotid intima media thickness, brachial flow mediated dilation and previous history of gestational diabetes mellitus. J Obstet Gynaecol Res 2012; 38:1057-63. [PMID: 22568764 DOI: 10.1111/j.1447-0756.2011.01829.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
AIM Gestational diabetes mellitus (GDM) is a common pregnancy condition with long-term complications. We examined the association between inflammatory mediators and early atherosclerosis process by measuring the flow mediated dilatation (FMD) of brachial artery and carotid intima media thickness (CIMT) in women with previous GDM (pGDM). MATERIAL AND METHODS Women with and without pGDM with an average of 4 years following the indexed pregnancy, participated in this study. Serum levels of IL-6, hs-CRP, adiponectin, homocystein and other biomedical parameters were measured. The existence of early atherogenesis process was evaluated by measuring CIMT and FMD. RESULTS HOMA-IR and insulin were significantly higher in women with pGDM. Women with pGDM had slightly higher CIMT and significantly lower percent of brachial FMD. FMD and CIMT, adjusted for age and blood pressure, showed the same pattern. FMD showed no correlation with biochemical or inflammatory markers. CONCLUSION Follow-up of this group of women, who are at increased risk of cardiovascular disease, with FMD should be considered.
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Affiliation(s)
- Hossein Fakhrzadeh
- Endocrinology and Metabolism Research Center Radiology Department, Tehran University of Medical Sciences, Tehran, Iran.
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194
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Choi DH, Lee YJ, Kim JS, Kang DG, Lee HS. Cynanchum wilfordii ameliorates hypertension and endothelial dysfunction in rats fed with high fat/cholesterol diets. Immunopharmacol Immunotoxicol 2012; 34:4-11. [PMID: 22176675 DOI: 10.3109/08923973.2011.569889] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hypercholesterolemia increases the incidence of atherosclerosis and its pathologic complications. This study was performed to test the effect of an ethanol extract of Cynanchum wilfordii (ECW) on vascular dysfunction in rats fed with high fat/cholesterol diets (HFCD). Male rats were fed a HFCD consisting of 7.5% cocoa butter and 1.25% cholesterol, with or without 100, 200 mg/day/kg ECW. Rats fed with HFCD increased body weight associated with an increase in plasma low-density lipoprotein (LDL) cholesterol level. Chronic ECW treatment in HFCD-fed rats lessened LDL cholesterol and triglyceride levels as well as elevated high-density lipoprotein (HDL) cholesterol. Chronic ECW treatment recovered the HFCD-induced increase in systolic blood pressure, maintained smooth and soft intima endothelial layers by the decrease of intima-media thickness. ECW significantly recovered the diet-induced decrease in vasorelaxation to acetylcholine, high-dose ECW apparently increased vasorelaxation response to sodium nitroprusside in rats fed with HFCD. ECW clearly restored the HFCD-induced reduction in endothelial nitric oxide (NO) synthase expression and Akt expression levels in aortic tissue, leading to improve endothelial function through an increase in endothelium-derived NO production. Furthermore, treatment of ECW significantly recovered the HFCD-induced decrease in aortic cGMP levels in rats. These findings suggest that ECW ameliorates hypertension and endothelial dysfunction via improvement of NO/cGMP signaling pathway in aortic tissue of rats fed with HFCD, suggesting a vascular protective role for this herb in the treatment and prevention of atherosclerotic vascular disease.
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Affiliation(s)
- Deok Ho Choi
- College of Oriental Medicine and Professional Graduate School of Oriental Medicine, Wonkwang University, Shinyong-dong, Iksan, Jeonbuk, Republic of Korea
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195
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De Boer MP, Meijer RI, Wijnstok NJ, Jonk AM, Houben AJ, Stehouwer CD, Smulders YM, Eringa EC, Serné EH. Microvascular dysfunction: a potential mechanism in the pathogenesis of obesity-associated insulin resistance and hypertension. Microcirculation 2012; 19:5-18. [PMID: 21883642 DOI: 10.1111/j.1549-8719.2011.00130.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The intertwined epidemics of obesity and related disorders such as hypertension, insulin resistance, type 2 diabetes, and subsequent cardiovascular disease pose a major public health challenge. To meet this challenge, we must understand the interplay between adipose tissue and the vasculature. Microvascular dysfunction is important not only in the development of obesity-related target-organ damage but also in the development of cardiovascular risk factors such as hypertension and insulin resistance. The present review examines the role of microvascular dysfunction as an explanation for the associations among obesity, hypertension, and impaired insulin-mediated glucose disposal. We also discuss communicative pathways from adipose tissue to the microcirculation.
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Affiliation(s)
- Michiel P De Boer
- Department of Internal Medicine, VU University Medical Center, Amsterdam, The Netherlands
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196
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Skov V, Knudsen S, Olesen M, Hansen ML, Rasmussen LM. Global gene expression profiling displays a network of dysregulated genes in non-atherosclerotic arterial tissue from patients with type 2 diabetes. Cardiovasc Diabetol 2012; 11:15. [PMID: 22340758 PMCID: PMC3348024 DOI: 10.1186/1475-2840-11-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 02/17/2012] [Indexed: 12/17/2022] Open
Abstract
Background Generalized arterial alterations, such as endothelial dysfunction, medial matrix accumulations, and calcifications are associated with type 2 diabetes (T2D). These changes may render the vessel wall more susceptible to injury; however, the molecular characteristics of such diffuse pre-atherosclerotic changes in diabetes are only superficially known. Methods To identify the molecular alterations of the generalized arterial disease in T2D, DNA microarrays were applied to examine gene expression changes in normal-appearing, non-atherosclerotic arterial tissue from 10 diabetic and 11 age-matched non-diabetic men scheduled for a coronary by-pass operation. Gene expression changes were integrated with GO-Elite, GSEA, and Cytoscape to identify significant biological pathways and networks. Results Global pathway analysis revealed differential expression of gene-sets representing matrix metabolism, triglyceride synthesis, inflammation, insulin signaling, and apoptosis. The network analysis showed a significant cluster of dysregulated genes coding for both intra- and extra-cellular proteins associated with vascular cell functions together with genes related to insulin signaling and matrix remodeling. Conclusions Our results identify pathways and networks involved in the diffuse vasculopathy present in non-atherosclerotic arterial tissue in patients with T2D and confirmed previously observed mRNA-alterations. These abnormalities may play a role for the arterial response to injury and putatively for the accelerated atherogenesis among patients with diabetes.
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Affiliation(s)
- Vibe Skov
- Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark.
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197
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Wu X, Williams KJ. NOX4 pathway as a source of selective insulin resistance and responsiveness. Arterioscler Thromb Vasc Biol 2012; 32:1236-45. [PMID: 22328777 DOI: 10.1161/atvbaha.111.244525] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Type 2 diabetes mellitus and related syndromes exhibit a deadly triad of dyslipoproteinemia, which leads to atherosclerosis; hyperglycemia, which causes microvascular disease; and hypertension. These features share a common, but unexplained, origin-namely, pathway-selective insulin resistance and responsiveness. Here, we undertook a comprehensive characterization of pathway-selective insulin resistance and responsiveness in liver and hepatocytes by examining 18 downstream targets of the insulin receptor, surveying the AKT, ERK, and NAD(P)H oxidase 4 pathways. METHODS AND RESULTS Injection of insulin into hyperphagic, obese type 2 diabetic db/db mice failed to inactivate hepatic protein tyrosine phosphatase gene family members, a crucial action of NAD(P)H oxidase 4 previously thought to be required for all signaling through AKT and ERK. Insulin-stimulated type 2 diabetic livers unexpectedly produced an unusual form of AKT that was phosphorylated at Thr308 (pT308), with only weak insulin-stimulated phosphorylation at Ser473. Remarkably, knockdown or inhibition of NAD(P)H oxidase 4 in cultured hepatocytes recapitulated the entire complicated pattern of pathway-selective insulin resistance and responsiveness seen in vivo-namely, monophosphorylated pT308-AKT, impaired insulin-stimulated pathways for lowering plasma lipids and glucose, but continued lipogenic pathways and robust ERK activation. CONCLUSIONS Functional disturbance of a single molecule, NAD(P)H oxidase 4, is sufficient to induce the key harmful features of deranged insulin signaling in type 2 diabetes mellitus, obesity, and other conditions associated with hyperinsulinemia and pathway-selective insulin resistance and responsiveness.
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Affiliation(s)
- Xiangdong Wu
- Section of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
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198
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Mercurio V, Carlomagno G, Fazio V, Fazio S. Insulin resistance: Is it time for primary prevention? World J Cardiol 2012; 4:1-7. [PMID: 22279598 PMCID: PMC3262393 DOI: 10.4330/wjc.v4.i1.1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/07/2011] [Accepted: 12/14/2011] [Indexed: 02/06/2023] Open
Abstract
Insulin resistance is a clinical condition characterized by a decrease in sensitivity and responsiveness to the metabolic actions of insulin, so that a given concentration of insulin produces a less-than-expected biological effect. As a result, higher levels of insulin are needed to maintain normal glucose tolerance. Hyperinsulinemia, indeed, is one of the principal characteristics of insulin resistance states. This feature is common in several pathologic conditions, such as type 2 diabetes, obesity, and dyslipidemia, and it is also a prominent component of hypertension, coronary heart disease, and atherosclerosis. The presence of endothelial dysfunction, related to insulin resistance, plays a key role in the development and progression of atherosclerosis in all of these disorders. Insulin resistance represents the earliest detectable abnormality in type 2 diabetes, and is one of the major underlying mechanisms of hypertension and cardiovascular diseases. Its early detection could be of great importance, in order to set a therapeutic attack and to counteract the higher risk of diabetes and cardiovascular diseases.
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Affiliation(s)
- Valentina Mercurio
- Valentina Mercurio, Guido Carlomagno, Valeria Fazio, Serafino Fazio, Department of Internal Medicine, Cardiovascular and Immunologic Sciences, Federico II University of Naples, 80131 Napoli, Italy
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199
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Pansuria M, Xi H, Li L, Yang XF, Wang H. Insulin resistance, metabolic stress, and atherosclerosis. Front Biosci (Schol Ed) 2012; 4:916-31. [PMID: 22202099 PMCID: PMC3319745 DOI: 10.2741/s308] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Atherosclerosis, a pathological process that underlies the development of cardiovascular disease, is the primary cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). T2DM is characterized by hyperglycemia and insulin resistance (IR), in which target tissues fail to respond to insulin. Systemic IR is associated with impaired insulin signaling in the metabolic tissues and vasculature. Insulin receptor is highly expressed in the liver, muscle, pancreas, and adipose tissue. It is also expressed in vascular cells. It has been suggested that insulin signaling in vascular cells regulates cell proliferation and vascular function. In this review, we discuss the association between IR, metabolic stress, and atherosclerosis with focus on 1) tissue and cell distribution of insulin receptor and its differential signaling transduction and 2) potential mechanism of insulin signaling impairment and its role in the development of atherosclerosis and vascular function in metabolic disorders including hyperglycemia, hypertension, dyslipidemia, and hyperhomocysteinemia. We propose that insulin signaling impairment is the foremost biochemical mechanism underlying increased cardiovascular morbidity and mortality in atherosclerosis, T2DM, and metabolic syndrome.
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Affiliation(s)
- Meghana Pansuria
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA, 19140
| | - Hang Xi
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA, 19140
| | - Le Li
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140
- School of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310014, PR, China
| | - Xiao-Feng Yang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA, 19140
| | - Hong Wang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, 19140
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA, 19140
- Thrombosis Research Center of Temple University School of Medicine, Philadelphia, PA, 19140
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200
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Maeno Y, Li Q, Park K, Rask-Madsen C, Gao B, Matsumoto M, Liu Y, Wu IH, White MF, Feener EP, King GL. Inhibition of insulin signaling in endothelial cells by protein kinase C-induced phosphorylation of p85 subunit of phosphatidylinositol 3-kinase (PI3K). J Biol Chem 2011; 287:4518-30. [PMID: 22158866 DOI: 10.1074/jbc.m111.286591] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The regulation of endothelial function by insulin is consistently abnormal in insulin-resistant states and diabetes. Protein kinase C (PKC) activation has been reported to inhibit insulin signaling selectively in endothelial cells via the insulin receptor substrate/PI3K/Akt pathway to reduce the activation of endothelial nitric-oxide synthase (eNOS). In this study, it was observed that PKC activation differentially inhibited insulin receptor substrate 1/2 (IRS1/2) signaling of insulin's activation of PI3K/eNOS by decreasing only tyrosine phosphorylation of IRS2. In addition, PKC activation, by general activator and specifically by angiotensin II, increased the phosphorylation of p85/PI3K, which decreases its association with IRS1 and activation. Thr-86 of p85/PI3K was identified to be phosphorylated by PKC activation and confirmed to affect IRS1-mediated activation of Akt/eNOS by insulin and VEGF using a deletion mutant of the Thr-86 region of p85/PI3K. Thus, PKC and angiotensin-induced phosphorylation of Thr-86 of p85/PI3K may partially inhibit the activation of PI3K/eNOS by multiple cytokines and contribute to endothelial dysfunction in metabolic disorders.
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Affiliation(s)
- Yasuhiro Maeno
- Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02115, USA
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