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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin resistance and hyperinsulinemia have been observed in essential hypertension. The selective impairment of glucose metabolism in skeletal muscle may accompanied hyperinsulinemia and raise blood pressure through sympathetic nervous system and/or renin-angiotensin system activation, renal sodium retention, proliferation of vascular smooth muscle and leptin. Recently, molecular techniques have applied for investigating the mechanisms of insulin resistance. The mutation of insulin receptor gene, changes of muscle fiber composition and muscle blood flow, abnormalities of insulin signal transduction, and TNF-alpha are considered as involvement of insulin resistance in the skeletal muscle. While further study will be necessary to clarify the mechanisms of insulin resistance and hypertension.
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PMID:[Insulin resistance syndrome]. 1139 82

The epidemic of type 2 diabetes and impaired glucose tolerance is one of the main causes of morbidity and mortality worldwide. In both disorders, tissues such as muscle, fat and liver become less responsive or resistant to insulin. This state is also linked to other common health problems, such as obesity, polycystic ovarian disease, hyperlipidaemia, hypertension and atherosclerosis. The pathophysiology of insulin resistance involves a complex network of signalling pathways, activated by the insulin receptor, which regulates intermediary metabolism and its organization in cells. But recent studies have shown that numerous other hormones and signalling events attenuate insulin action, and are important in type 2 diabetes.
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PMID:Insulin signalling and the regulation of glucose and lipid metabolism. 1174 12

There is extensive experimental evidence that sex steroids and insulin interact in their actions on tissues. At physiological levels, testosterone and oestradiol are thought to be involved in maintaining normal insulin sensitivity. However, outside this 'physiological window' these steroids may promote insulin resistance. Considerable research has been carried out on polycystic ovarian syndrome, a common disorder associated with excessive androgen production and insulin resistance. Hyperinsulinaemia in patients with this condition is believed to stimulate ovarian androgen production, and there is also evidence that androgens act directly on peripheral tissues to promote insulin resistance. There is the potential for a vicious circle to develop with increasing androgen production and insulin resistance. The molecular basis of this insulin resistance has been reported to involve reduced insulin receptor autophosphorylation, reduced expression and translocation of insulin-responsive glucose transporters and defects of the insulin signalling pathway distal to the insulin receptor. These defects await full characterization. Insulin-sensitizing agents can reverse many of the effects of insulin resistance and may have a future place in the treatment of polycystic ovarian syndrome and other conditions associated with steroid-induced insulin resistance. Recognition and treatment of sex steroid-associated insulin resistance at an early stage in patients may reduce their risk of developing Type II (non-insulin-dependent) diabetes mellitus, hypertension and dyslipidaemia, and so may improve fertility and reduce cardiovascular risk. Here we review the interplay between sex steroids and insulin resistance, and consider the implications this has for clinical conditions.
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PMID:Sex steroids and insulin resistance. 1183 35

To better understand the intracellular signaling mechanism that causes the association of insulin resistance and hyperlipidemia with cardiovascular diseases, we specifically looked at the ability of lysophosphatidylcholine (lysoPC) to inhibit the Akt activation induced by insulin in cultured rat aortic vascular smooth muscle cells. LysoPC inhibited the insulin-induced phosphorylation of Akt at Ser473, and the inhibition was concentration dependent. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, inhibited the insulin-induced phosphorylation of Akt. LysoPC stimulated PKC phosphorylation at Ser660, which was inhibited by the PKC inhibitor GF109203X. The PKC-alpha/beta-selective inhibitor Go6976 also blocked the PMA- and lysoPC-induced inhibition of Akt phosphorylation by insulin. PKC-alpha, but not PKC-beta, is expressed in vascular smooth muscle cells, and overexpression of PKC-alpha, but not PKC-beta or PKC-delta, inhibited insulin-induced Akt activation. LysoPC rapidly stimulated PKC-alpha translocation to the membrane. In contrast, pretreatment with the p42/44 mitogen-activated protein kinase kinase inhibitor PD98059 or the p38 mitogen-activated protein kinase inhibitor SB203580 did not block the lysoPC-induced inhibition of Akt phosphorylation by insulin. In addition, lysoPC inhibited the insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-1 but not that of the insulin receptor beta subunit or insulin binding. PMA treatment or PKC-alpha overexpression also inhibited the tyrosine phosphorylation of IRS-1. From these data, we conclude that lysoPC negatively regulates the insulin signal at the point of IRS-1 through PKC-alpha in the vasculature, which may explain the association of hyperlipidemia with hyperinsulinemia in cardiovascular diseases.
Hypertension 2002 Feb
PMID:Lysophosphatidylcholine inhibits insulin-induced Akt activation through protein kinase C-alpha in vascular smooth muscle cells. 1188 99

Metabolic Syndrome X defined by Reaven is caused by peripheral insuline receptor resistance, leads to hyperinsulinemia regarded as a cause of secondary dyslipidemia, hypertension, hemostatic disturbances, atherosclerosis and insulin as a growth factor takes part in carcinogenesis. Depending on a contribution of the primary risk factors of type 2 Diabetes Mellitus (2-DM) mainly genetic factors and obesity--an independent cause of insulin receptor resistance--glucose intolerance and 2-DM may overlap the Syndrome X. The aims of these studies were to determine in cross-sectional investigation a plasma insulin concentration in subjects aged over 35 years and to assess the clinical usefulness of insulinemia in early diagnosis of diabetes type 2. Investigations were carried out in Krakow town's district with 200,000 inhabitants, out of those 3060 randomly selected subjects (1720 females and 1340 males aged over 35 years) took part in the Polish Multicenter Study on Diabetes Epidemiology (PMSDE) with protocol and methods previously presented. Glucose concentration was determine by enzymatic method, insuline in plasma by IRMA method using ready kits produced by the Swierk-Poland. Logistic multiple regression model was used to estimate the effect of risk factors on the development of glucose intolerance, Chi square test, Fisher test and Mann-Whitney test were used for statistical analysis by means of statistical package BMPD. Fasting insulinemia in persons with normal glucose tolerance and body weight (BMI < 25 and glycemia < 6.1 mmol/l) in subpopulation aged over 35 years was 5.73 (SD = 3.99) in men and 7.05 (SD = 4.67) microU/ml in women. These values were positively correlated with BMI and at the range 25-30 and > 30 increased by 50 and 100% responsively and in 2-nd h in OGTT by five-times. In the persons with glucose intolerance and new-diagnosed 2-DM insulinemia increased 2-3 fold depending on BMI, and gender. In the subgroup with 2-DM and BMI > 30, insulinemia in 2 h-OGTT treated values 152 (SD = 90) in women and 112 (SD = 83.4) microU/ml in men. Obesity and insulinemia in 2 h-OGTT in multiple analysis have been identified as a strong predictors and risk factors of impaired glucose intolerance (IGT) 2-DM fasting insulinemia may be useful as an indicator of the peripheric insulin receptor resistance. The results lead to the conclusions that determination of the plasma insulin concentration may be useful in early diagnosis of IGT and diabetes type 2, and should be monitored in the course of non-pharmacological and pharmacological treatment 2-DM. One of the main goals in the course of treatment of obesity and early phases of the 2-DM should be normalization or at least reduction of hyperinsulinemia. Insulinemia may be regarded also as an important criterion for selection of the oral antidiabetic drugs.
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PMID:[Insulinemia--a marker of early diagnosis and control of efficacy of treatment of type II diabetes]. 1192 88

A high-salt diet, which is known to contribute to the pathogenesis of hypertension, is also reportedly associated with insulin resistance. We investigated the effects of a high-salt diet on insulin sensitivity and insulin signaling in salt-sensitive (Dahl-S) and salt resistant (Dahl-R) strains of the Dahl rat. Evaluation of hyperinsulinemic-euglycemic clamp studies and glucose uptake into the isolated soleus muscle revealed that salt loading (8% NaCl) for 4 weeks induced hypertension and significant insulin resistance in Dahl-S rats, whereas no significant effects were observed in Dahl-R rats. Despite the presence of insulin resistance, insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrates, activation of phosphatidylinositol 3-kinase, and phosphorylation of Akt were all enhanced in Dahl-S rats fed a high-salt diet. The mechanism underlying this form of insulin resistance thus differs from that previously associated with obesity and dexamethasone and is likely due to the impairment of one or more metabolic steps situated downstream of phosphatidylinositol 3-kinase and Akt activation. Interestingly, supplementation of potassium (8% KCl) ameliorated the changes in insulin sensitivity in Dahl-S rats fed a high-salt diet; this was associated with a slight but significant decrease in blood pressure. Evidence presented suggest that there is an interdependent relationship between insulin sensitivity and salt sensitivity of blood pressure in Dahl-S rats, and it is suggested that supplementing the diet with potassium may exert a protective effect against both hypertension and insulin resistance in salt-sensitive individuals.
Hypertension 2002 Jul
PMID:High-salt diet enhances insulin signaling and induces insulin resistance in Dahl salt-sensitive rats. 1210 43

Abnormalities in intracellular pH regulation have been proposed to be important in type 2 diabetes and the associated cardiomyopathy and hypertension. We have therefore investigated the dependence of insulin-stimulated glucose transport on cytosolic pH in cardiomyocytes. Insulin treatment of cardiomyocytes resulted in a marked alkalinization of the cytoplasm as measured using carboxy-semi-napthorhodofluor-1. The alkalinizing effect of insulin was blocked by treatment with either cariporide (which inhibits the Na+/H+ exchanger) or by bafilomycin A1 (which inhibits H+-ATPase activity). After treatments with cariporide or bafilomycin A1, insulin stimulation of insulin receptor and insulin receptor substrate-1 phosphorylation and Akt activity were normal. In contrast, glucose transport activity and the levels of functional GLUT4 at the plasma membrane (detected using an exofacial photolabel) were reduced by approximately 50%. Immunocytochemical analysis revealed that insulin treatment caused a translocation of the GLUT4 from perinuclear structures and increased its co-localization with cell surface syntaxin 4. However, neither cariporide nor bafilomycin A1 treatment reduced the translocation of immunodetectable GLUT4 to the sarcolemma region of the cell. It is therefore hypothesized that insulin-stimulated cytosol alkalinization facilitates the final stages of translocation and incorporation of fully functional GLUT4 at the surface-limiting membrane.
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PMID:Insulin-stimulated cytosol alkalinization facilitates optimal activation of glucose transport in cardiomyocytes. 1238 33

Angiotensin II (AII) is involved in the pathogenesis of both hypertension and insulin resistance, though few studies have examined the relationship between the two. We therefore investigated the effects of chronic AII infusion on blood pressure and insulin sensitivity in rats fed a normal (0.3% NaCl) or high-salt (8% NaCl) diet. AII infusion for 12 days significantly elevated blood pressure and significant insulin resistance, assessed by a hyperinsulinemic-euglycemic clamp study and glucose uptake into isolated muscle and adipocytes. High-salt loading exacerbated the effects of AII infusion significantly. Despite the insulin resistance, insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrates, activation of phosphatidylinositol (PI) 3-kinase, and phosphorylation of Akt were all enhanced by AII infusion. Subsequently, to investigate whether oxidative stress induced by AII contributes to insulin resistance, the membrane-permeable superoxide dismutase mimetic, tempol, was administered to AII-infused rats. Chronic AII infusion induced an accumulated plasma cholesterylester hydroperoxide levels, indicating the increased oxidative stress, whereas the treatment with tempol normalized plasma cholesterylester hydroperoxide levels in AII-infused rats. In addition, the treatment with tempol normalized insulin resistance in AII-infused rats, shown as a decreased glucose infusion rate in the hyperinsulinemic euglycemic clamp study and a decreased insulin-induced glucose uptake into isolated skeletal muscle, as well as enhanced insulin-induced PI 3-kinase activation to those in the control rats. These results strongly suggest that AII-induced insulin resistance cannot be attributed to impairment of early insulin-signaling steps and that increased oxidative stress, possibly through impaired insulin signaling located downstream from PI 3-kinase activation, is involved in AII-induced insulin resistance.
Hypertension 2002 Dec
PMID:Angiotensin II-induced insulin resistance is associated with enhanced insulin signaling. 1246 72

Magnesium (Mg) is one of the most abundant ions present in living cells and its plasma concentration is remarkably constant in healthy subjects. Plasma and intracellular Mg concentrations are tightly regulated by several factors. Among them, insulin seems to be one of the most important. In vitro and in vivo studies have demonstrated that insulin may modulate the shift of Mg from extracellular to intracellular space. Intracellular Mg concentration has also been shown to be effective in modulating insulin action (mainly oxidative glucose metabolism), offset calcium-related excitation-contraction coupling, and decrease smooth cell responsiveness to depolarizing stimuli. A poor intracellular Mg concentration, as found in noninsulin-dependent diabetes mellitus (NIDDM) and in hypertensive patients, may result in a defective tyrosine-kinase activity at the insulin receptor level and exaggerated intracellular calcium concentration. Both events are responsible for the impairment in insulin action and a worsening of insulin resistance in noninsulin-dependent diabetic and hypertensive patients. By contrast, in NIDDM patients daily Mg administration, restoring a more appropriate intracellular Mg concentration, contributes to improve insulin-mediated glucose uptake. The benefits deriving- from daily Mg supplementation in NIDDM patients are further supported by epidemiological studies showing that high daily Mg intake are predictive of a lower incidence of NIDDM. In conclusion, a growing body of studies suggest that intracellular Mg may play a key role in modulating insulin-mediated glucose uptake and vascular tone. We further suggest that a reduced intracellular Mg concentration might be the missing link helping to explain the epidemiological association between NIDDM and hypertension.
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PMID:Role of magnesium in insulin action, diabetes and cardio-metabolic syndrome X. 1253 88

Insulin resistance, defined as the decreased ability of insulin to perform its biological functions, is likely to represent the primary physiologic defect underlying the insulin resistance syndrome (IRS), which includes insulin resistance/hyperinsulinemia, glucose intolerance and/or type 2 diabetes mellitus, visceral obesity, hypertension, and dyslipidemia. This constellation of traits is a leading cause of cardiovascular mortality and morbidity. Insulin sensitivity varies widely among individuals. Although environmental provocations including physical inactivity and caloric excess play an important role in the development of obesity and thus insulin resistance, epidemiologic and family studies show that there are also moderate genetic influences on the development of insulin resistance. Extreme forms of insulin resistance may be caused rarely by mutations in the genes for the insulin receptor and peroxisome proliferator-activated receptor gamma. However, the genetic basis for common more moderate forms of insulin resistance is likely to be polygenic and heterogeneous. Evidence further suggests that gene variants may have phenotypic influences on more than one IRS trait (so-called pleiotrophy), which may explain, in part, the clustering of these traits. This article reviews the evidence that insulin resistance has a genetic basis. Progress to date toward identifying specific gene variants are reviewed. Ultimately, the identification of specific gene variants that influence insulin resistance and other IRS traits will have profound influences on our understanding of the molecular and pathophysiologic basis of these disorders, from which new and more effective preventive and therapeutic interventions will be possible.
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PMID:Genetics of insulin resistance. 1264 27


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