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

To investigate the role of insulin on Ca2+ regulation of vascular smooth muscle cells (VSMC) in hypertension, the effect of insulin on Ca2+ transport and intracellular free calcium concentration ([Ca2+]i) was measured in cultured VSMC from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Insulin produced a substantial increase in 45Ca uptake as well as [Ca2+]i in quiescent cultured VSMC. The stimulatory effects of insulin were completely inhibited by diltiazem, and partially by H-7, TMB-8, and 5-N,N(hexamethylene)amiloride (HMA), but not by W-7 or trifluoroperazine. Insulin-sensitive 45Ca uptake of SHR VSMC was significantly smaller than that of WKY VSMC. Insulin-sensitive increase in [Ca2+]i of SHR VSMC was also smaller than that of WKY VSMC. It is concluded that insulin increases 45Ca uptake, leading to an increase in [Ca2+]i, presumably through the voltage-dependent Ca2+ channel, intracellular Ca2+ release, or protein kinase C mediated mechanisms in cultured VSMC. A blunted response of insulin-sensitive Ca2+ uptake and [Ca2+]i in SHR VSMC suggests the differential regulation of Ca2+ transport in response to insulin in primary hypertension.
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PMID:Decreased insulin-sensitive Ca2+ transport in cultured vascular smooth muscle cells from spontaneously hypertensive rats. 128 39

Points of agreement: (1) In IDDM, hypertension occurs in patients who have already developed nephropathy, probably in the microalbuminuric phase. (2) Hypertension is an important accelerator of the development of diabetic nephropathy. (3) Hypertension, obesity and NIDDM are often associated, and insulin resistance is commonly observed in all three states. (4) Antihypertensive therapy retards the development of diabetic nephropathy in IDDM and reduces proteinuria in NIDDM. (5) The choice of antihypertensive agent in the diabetic patient must be based upon the efficacy of the drug as well as avoidance of side effects including deleterious influence on glucose, insulin and lipid levels and renoprotection. (6) Carefully conducted long-term comparative trials between different classes of antihypertensive drugs in microalbuminuric IDDM and NIDDM patients are essential. Points of major controversy: (1) Detection of IDDM patients prone to the development of diabetic nephropathy can be performed by measuring specific parameters such as erythrocyte Na(+)-Li+ countertransport activity. (2) Insulin resistance is a pathogenic mechanism rather than purely an association with hypertension and obesity. (3) A certain class of antihypertensive agents--ACE inhibitors--confers a specific renoprotective effect in diabetic nephropathy, in addition to its effects upon systemic blood pressure. (4) Reduction of blood pressure should be considered in the normotensive microalbuminuric diabetic patient. (5) Microalbuminuria is a sufficient 'surrogate endpoint' for the progression of renal failure.
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PMID:Meeting report of the International Society of Hypertension Conference on Hypertension and Diabetes. 131 6

The spontaneous hypertensive rat is an animal model characterized by a syndrome of hypertension, insulin resistance and hyperinsulinaemia. To elucidate whether in analogy to other insulin resistant animal models an inactivity of the insulin receptor kinase or an alteration of the glucose transporter (GLUT 4) level in the skeletal muscle might contribute to the pathogenesis of insulin resistance we determined insulin receptor kinase activity and GLUT 4 level in the hindlimbs of spontaneous hypertensive rats and normotensive control rats. Normotensive normoinsulinaemic Lewis and Wistar rats were used as insulin sensitive controls, obese Zucker rats were used as an insulin resistant control with known reduced skeletal muscle insulin receptor kinase activity. Binding of 125I-insulin, crosslinking of 125I-B26-insulin, autophosphorylation in vitro with 32P-ATP and phosphorylation of the synthetic substrate Poly (Glu 4: Tyr 1) were performed after partial purification of solubilized receptors on wheat germ agglutinin columns. GLUT 4 levels were determined by Western blotting of subcellular muscle membranes. Insulin receptors from spontaneous hypertensive rats compared to those from Lewis and Wistar rats showed no difference of the binding characteristics or the in vitro auto- and substrate phosphorylation activity of the receptor, while in the Zucker rats the earlier described insulin receptor kinase defect was clearly evident. Western blots of subcellular muscle membrane fractions with antibodies against GLUT 4 revealed no difference in transporter levels. These data suggest that insulin resistance in spontaneous hypertensive rats is caused neither by an insulin receptor inactivity nor by a decreased number of glucose transporters in the skeletal muscle.
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PMID:Normal insulin receptor tyrosine kinase activity and glucose transporter (GLUT 4) levels in the skeletal muscle of hyperinsulinaemic hypertensive rats. 132 60

A high plasma insulin concentration in the presence of a normal or high plasma glucose level appears to be a common feature of glucose intolerance, obesity, and hypertension. Hyperinsulinemia has been recognized as a major risk factor for the development of coronary artery disease independent of blood pressure and plasma lipid levels. All these conditions are frequently associated, particularly in aging, a state itself characterized by hyperinsulinemia. This common association has prompted the hypothesis that hyperinsulinemia may be a causative factor rather than the consequence of obesity, diabetes, hypertension, and hyperlipidemia. If that is the case, defining the nature and mechanisms of hyperinsulinemia becomes of primary interest. Insulin resistance is also a striking feature of all of the above mentioned pathologic states. In the presence of a preserved B-cell function, hyperinsulinemia can represent the mechanism designed to overcome the defect in the biological action of the hormone. For instance, there is a clear-cut age-related decline in the body's sensitivity to insulin. In order to compensate for this defect in insulin-mediated glucose metabolism, the B-cell must increase its secretion. On the other hand, a certain degree of insulin resistance can be induced both in animals and man by prolonged euglycemic hyperinsulinemia. Little is known regarding possible primary defects of the B-cell leading to uncontrolled oversecretion of insulin and subsequent insulin resistance. The primary defect, more probably, resides in an alteration of one or more of the steps whereby insulin exerts it own action. In favor of this hypothesis are the observations that insulin resistance segregates in familial clusters and that the first defect found in normoglycemic relatives of insulin-resistant diabetic patients is a reduced transformation of glucose into glycogen. Whatever is the primary defect, it is likely that a correction of insulin resistance might reduce the circulating levels of plasma insulin, possibly playing a beneficial effect on glucose tolerance, body weight, blood pressure and plasma lipid concentration.
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PMID:[Hyperinsulinism. Causes and mechanisms]. 133 21

The pathophysiology of the frequent association of insulin resistance and hypertension has not been elucidated. The skeletal muscle is the major site of insulin resistance; when stimulated with insulin, the hypertensive skeletal muscles extract less glucose than the normotensive. We postulate that hypertension-related changes in the skeletal muscle microcirculation contribute to the impaired glucose uptake in hypertension. Vascular rarefaction in hypertension impairs the delivery of insulin and glucose to muscle cells. Insulin resistance has been described both in human and experimental hypertension and both conditions are associated with vascular rarefaction. Functional studies (response to whole body or forearm exercise) and anatomic investigations (conjunctival photography, mesenteric and muscle biopsies) show vascular rarefaction in human hypertension. In addition, patients with hypertension are known to have a larger proportion of insulin resistant, poorly vascularized fast twitch muscle fibers. A few interventions can increase or decrease insulin resistance and these effects can be explained on hemodynamic grounds. Beta adrenergic blocking agents aggravate insulin resistance, and their main hemodynamic effect is a decrease of cardiac output. Converting enzyme inhibitors, alpha adrenergic blocking agents and possibly calcium antagonists decrease the insulin resistance, and their major hemodynamic effect is vasodilation. Physical training decreases insulin resistance; a higher capillary density in skeletal muscles is the hallmark of physical training. A hypothesis ought to rest on sufficient supporting data and its validity ought to lend itself to experimental verification. We believe our hypothesis meets both criteria. After outlining the supporting evidence we propose a number of tests to prove or disprove the hypothesis. In addition to the testable hypothesis we also speculate on the possible cause of the frequent association between hypertension and insulin resistance. We propose that both insulin resistance and blood pressure elevation represent a facet of the "defense reaction" which might have offered an early survival advantage and may, over evolutionary times, have fostered natural selection of subjects with both conditions.
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PMID:The interconnection between sympathetics, microcirculation, and insulin resistance in hypertension. 134 45

Insulin resistance is a frequently occurring abnormality. Although there can be insensitivity to any of insulin's actions, insulin resistance par excellence is a decreased insulin-mediated whole-body glucose disposal rate. A distinction is made between primary and secondary insulin resistance. Primary insulin resistance is of unknown origin, is only partially experimentally reproducible, and is essentially irreversible (spontaneously or by treatment). In addition, it is both pathway-specific (ie, glucose storage) and organ-specific (mostly skeletal muscle), and is compatible with a postreceptor defect in insulin action. Primary insulin resistance is found in a proportion (approximately 25%) of otherwise healthy people, in non-insulin-dependent diabetes mellitus, essential hypertension, and some forms of dyslipidemia. The idea of an insulin resistance syndrome derives from the striking pattern of overlap among these clinical conditions. Their tendency to cluster in the same individuals is evident from both cross-sectional and longitudinal observations. It is proposed that the insulin resistance syndrome is a large constellation of interrelated changes in metabolic, anthropometric, and hemodynamic variables centered around insulin resistance or hyperinsulinemia. There is a significant genetic component, a predisposing influence for non-insulin-dependent diabetes mellitus, hypertension, dyslipidemia, and possibly, a distinct atherogenic potential.
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PMID:The insulin resistance syndrome. 134 29

The present work was carried out to assess the effect of endothelin on the relative synthesis of protein, RNA, and DNA in confluent rat aortic smooth muscle cells (SMC) derived from Wistar-Kyoto (WKY) rats maintained under serum-free medium in the presence or absence of insulin, transferrin, and selenium. Insulin stimulated protein synthesis by 42%. Endothelin (1 x 10(-7) M) rapidly induced protein synthesis by 22% (-insulin) and 30% (+insulin). Prior treatment of SMC for 4 h with endothelin resulted in 50% (-insulin) and 38% (+insulin) increase in protein synthesis. The stimulatory effect of endothelin on protein synthesis could be partially blocked by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, a protein kinase C inhibitor. Atrial natriuretic factor had no effect on either the basal protein synthesis or protein synthesis stimulated by endothelin. Furthermore, endothelin stimulated RNA synthesis by twofold but had no effect on DNA synthesis in SMC derived from WKY rats. In contrast, SMC derived from spontaneously hypertensive rats showed increased DNA synthesis and cell growth after endothelin stimulation. These studies show that this hormone may play a pivotal role in the development of vascular hypertrophy in hypertension.
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PMID:Endothelin stimulates protein synthesis in smooth muscle cells. 137 62

Eighteen patients with mild hypertension (diastolic blood pressure > or = 90 and < 104 mm Hg) and 15 normotensive control subjects were studied. Insulin tolerance tests (ITT) and fasting plasma insulin (FPI) level measurements were performed to evaluate insulin sensitivity. Insulin sensitivity, as measured with the ITT, showed a strong correlation with body mass index (BMI) in the hypertensive and control groups (r = -0.68, p < 0.01 and r = -0.61, p < 0.01, respectively). The fasting insulin levels also correlated significantly with BMI in both groups (r = 0.55, p < 0.05 in the hypertensive and r = 0.76, p < 0.01 in the control group). Insulin sensitivity in the hypertensive subjects whose BMI was < or = 27.0 kg/m2 (nonobese), as measured with the ITT and FPI, was not different from the nonobese normal controls (K(itt), 5.36 +/- 1.74% min-1 versus 5.61 +/- 1.66% min-1, respectively, p > 0.2; FPI, 5.8 +/- 3.4 microU/ml versus 7.1 +/- 2.5 microU/ml, respectively, p > 0.2). Also, insulin sensitivity, as measured with the ITT, was not statistically significantly different between hypertensive and normotensive obese subjects (K(itt), 2.82 +/- 1.55% versus 3.90 +/- 0.67% min-1, respectively, p > 0.1). When fasting plasma insulin levels were compared, a higher level was observed in the obese normotensive subjects than in the obese hypertensive group (FPI, 19.8 +/- 10.0 microU/ml and 11.5 +/- 4.9 microU/ml, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Relationship between insulin sensitivity and degree of obesity in mild hypertension. 141 17

We investigated the role of insulin in salt-sensitive hypertension in Dahl salt-sensitive and salt-resistant rats. The rats were kept in metabolic cages, and sodium intake and urinary sodium excretion were measured. In salt-sensitive rats receiving a 0.3% NaCl diet, sodium retention was significantly greater at weeks 1 and 2 in rats that received an insulin infusion than in those receiving a saline infusion. Mean arterial blood pressure and plasma norepinephrine levels were significantly higher at week 3 in insulin-treated rats than in saline-treated rats (mean arterial pressure, 137 +/- 3 mm Hg versus 119 +/- 3 mm Hg, p < 0.05; plasma norepinephrine, 0.40 +/- 0.02 ng/ml versus 0.27 +/- 0.01 ng/ml, p < 0.05). Insulin did not influence sodium retention, mean arterial pressure, or plasma norepinephrine in salt-resistant rats. Coadministration of an alpha-blocker (bunazosin, 10 mg/kg per day for 3 weeks) in salt-sensitive rats abolished the insulin-induced elevations in mean arterial pressure and sodium retention. When salt-sensitive rats were fed a low salt diet (0.03% NaCl), insulin did not raise mean arterial pressure. Thus, insulin elevated blood pressure only in the salt-sensitive model. The sympathetic nervous system and sodium retention in the early phase of insulin overload may contribute to elevation of mean arterial pressure in this model.
Hypertension 1992 Nov
PMID:Blood pressure response to hyperinsulinemia in salt-sensitive and salt-resistant rats. 142 9

The hypothesis of the atherogenic role of endogenous insulin was based on a series of epidemiological studies. Several large-scale prospective studies have demonstrated that diabetes constitutes an independent risk factor for cardiovascular disease. However, neither the duration of diabetes nor the blood glucose level appear to be predictive of the incidence of a cardiovascular accident. More recent prospective studies (Finland, Australia, Paris) in non-diabetic men have shown that hyperinsulinemia, while fasting or after glucose stimulation, constitutes a risk factor for fatal myocardial infarction, but they failed to show whether diabetes or the blood glucose level constituted a risk factor for the disease. Cross-sectional studies have provided similar results. Insulin resistance affects the majority of non-insulin-dependent diabetics and glucose-intolerant patients. It has also been observed in 25 percent of non-obese subjects with a normal glucose tolerance test. Associated hyperinsulinemia prevents the development of diabetes, but diabetes appears when the beta-cell function is altered and can no longer maintain this hyperinsulinemia. However, hyperinsulinemia is not devoid of cardiovascular consequences. Insulin resistance and hyperinsulinemia are also observed in patients with essential hypertension: a correlation between plasma insulin and blood pressure has been reported. These data, together with other experimental arguments, suggest that excessive endogenous insulin may participate in the rise in blood pressure. Furthermore, hypertensive patients have a high risk of coronary heart disease and this risk is not significantly decreased by anti-hypertensive treatments. This is probably related to the presence of other metabolic risk factors associated with insulin resistance: hyperinsulinemia, glucose intolerance, hypertriglyceridemia, decreased HDL cholesterol. These metabolic disorders have been grouped together under the term "syndrome X". All of these risk factors are probably also involved in the development of coronary heart disease in general population. In conclusion, epidemiological studies now suggest that insulin resistance and hyperinsulinemia increase the risk of hypertension and coronary heart disease. A great many experimental studies support this hypothesis. Lastly, it can be proposed that the increased cardiovascular risk in non-insulin-dependent diabetics is related to the fact that they belong to a larger group of insulin-resistant subjects. The management of diabetes, hypertension, and all of the metabolic abnormalities would appear to be the only way of reducing the incidence of cardiovascular disease.
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PMID:[Pathogenic role of hyperinsulinism in macroangiopathy. Epidemiological data]. 143 99


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