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

A fructose-enriched diet induces an increase in blood pressure associated with metabolic alterations in rats. Our hypothesis was that an increase in protein kinase C (PKC) activation, reported in the acute period of fructose overload, and an impaired vessel's response to vasoactive substances contribute to maintain elevated blood pressure levels in the chronic period. The aims of this study were to investigate in this animal model of hypertension: (1) if the increase in PKC activation was also found in the chronic stage; (2) the involvement of nitric oxide and insulin in the vessel's response; and plasma atrial natriuretic factor and nitrites/nitrates (nitric oxide metabolites) behavior. We evaluated the effects of: PKC-stimulator 12,13-phorbol dibutyrate, phenylephrine, insulin, nitric oxide synthase-inhibitor NG-nitro-L-arginine methyl esther (L-NAME) and PKC-inhibitor Calphostin C on aortic rings responses of Sprague-Dawley rats: fructose-fed and control. The fructose-fed group showed higher contractility to 12,13-phorbol dibutyrate than the control group in aortic rings pre-incubated with insulin, and this difference disappeared with L-NAME. The response to phenylephrine in rings pre-incubated with Calphostin C was decreased in the fructose-fed group and increased with Calphostin C plus L-NAME. Fructose-fed rats showed higher levels of plasma atrial natriuretic factor and nitrites/nitrates than controls. In conclusion, chronic fructose feeding seems to develop an impaired response to insulin, dependent on nitric oxide, suggesting a PKC alteration. Vasorelaxant agents, such as atrial natriuretic factor and nitric oxide, would behave as compensatory mechanisms in response to high blood pressure.
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PMID:Impaired response to insulin associated with protein kinase C in chronic fructose-induced hypertension. 1252 77

This study investigates gene therapy with human tissue kallikrein as a treatment for fructose-induced hypertension in rats. Hypertension was induced by addition of 10% fructose to drinking water. Fructose-fed rats also had increased serum insulin and triglycerides, decreased urine osmolarity, increased urine volume and endothelin-1, and increased aortic endothelin-1, endothelin-A receptor, and angiotensin II receptor type 1 mRNA levels. Fructose-induced hypertensive and control rats were injected intravenously with a construct containing the human tissue kallikrein cDNA. Two weeks after injection of hypertensive rats, systolic blood pressure and serum insulin levels normalized, urine osmolarity increased, urine endothelin-1 levels decreased, and aortic endothelin-1, endothelin-A receptor, and angiotensin II receptor type 1 mRNA levels decreased. In contrast, injection of the human tissue kallikrein cDNA had minimal effect on blood pressure or insulin levels in control rats. These results suggest that gene therapy with human tissue kallikrein may have potential as a treatment for hypertension and associated insulin resistance. Moreover, our data suggest that the beneficial effects of human tissue kallikrein on these parameters are associated with changes in endothelin-1, endothelin-A receptor, and angiotensin II receptor type 1 expression.
Hypertension 2003 Nov
PMID:Gene therapy with human tissue kallikrein reduces hypertension and hyperinsulinemia in fructose-induced hypertensive rats. 1456 97

Reduced extravasation of macromolecules in skeletal muscle has recently been documented in the fructose-fed rat model, corroborating a hypothesis that a functional obliteration of muscle regional microcirculation might lead to hypertension and restrict access of nutrients and hormones to their target cells. The goal of this study was to assess the impact of a treatment with rosiglitazone on the reduced muscle vasopermeability observed previously in the fructose-fed rat model. Fructose-fed Sprague-Dawley rats were gavaged with rosiglitazone (10 micromol kg(-1) per day; n = 21) or the vehicle only (n = 19) for 3 consecutive weeks before assessing the extravasation of Evans Blue (EB) dye in vivo in distinct muscle groups. Relative to control group, rosiglitazone reduced mean arterial blood pressure (Delta = -16.7%, P < 0.001), plasma insulin (Delta= -39.1%, P < 0.05) and plasma triglyceride (Delta= -32.8 %, P < 0.01) concentrations in a significant manner. Plasma VEGF concentrations were significantly lower in the rosiglitazone-treated animals compared to the control animals (32.7 +/- 0.8 pg ml(-1) versus 46.1 +/- 1.2 pg ml(-1), P < 0.001). While no changes were observed in the lungs or the kidneys, fructose-fed rats treated with rosiglitazone had a 30-50% increase (P < 0.005) in the extravasation of EB regardless of the skeletal muscle group studied (rectus femoris, soleus, gastrocnemius lateralis, vastus lateralis and tibialis cranalis). In homogenates of skeletal muscles (vastus lateralis) of fructose-fed rats, rosiglitazone resulted in a significant increase in NO synthase (NOS) activity (Delta = +41.9 %, P < 0.003) as well as endothelial NOS immunoreactive mass (Delta = +37.8 %, P < 0.01) compared to the control animals. There was no change in the immunoreactive level of the nNOS isoform, the most abundant muscle isoform, or in the immunoreactive levels of VEGF. In conclusion, rosiglitazone appears to restore a vascular dysfunction previously documented in the skeletal muscle microcirculation, as evidenced by improved skeletal muscle vasopermeability and upregulation of the muscle endothelium-NO system in the fructose-fed rat model. These effects on muscle per se might also result in a partial improvement of the insulin resistance phenomenon by improving the distribution of nutrients and insulin to skeletal muscle. This effect appears to be independent of circulating levels of VEGF since changes in plasma concentrations of this permeability factor were lower in the rosiglitazone-treated group.
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PMID:Rosiglitazone increases extravasation of macromolecules and endothelial nitric oxide synthase in skeletal muscles of the fructose-fed rat model. 1513 Jul 75

High fructose feeding induces moderate increases in blood pressure of normal rats, associated with hyperinsulinemia, insulin resistance and impaired glucose tolerance. Increased vascular resistance, and sodium retention have been proposed to contribute to the blood pressure elevation in this model. Taurine, a sulphur-containing amino acid has been reported to have antihypertensive and antinatriuretic actions. In addition, taurine is shown to increase the excretion of nitrite and kinin availability and hence would be expected to improve the vascular tone. In the present study, the involvement of kinins in the blood pressure lowering effect of taurine was investigated by coadministration of Hoe 140, a kinin B(2) receptor antagonist along with taurine. The effects of taurine on plasma and urinary concentrations of sodium and tissue kallikrein activity were studied in high fructose-fed rats. Fructose-fed rats had elevated blood pressure and decreased levels of sodium in urine. Treatment with 2% taurine in drinking water prevented the blood pressure elevation and coadministration of Hoe 140 abolished this effect of taurine in high fructose-fed rats. The findings confirm the antinatriuretic action of taurine and also suggest a role for the kinins in the mechanism of taurine action in diet-induced hypertension.
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PMID:Hoe 140 abolishes the blood pressure lowering effect of taurine in high fructose-fed rats. 1522 11

Various cardiovascular risk factors and disease states similar to those present in type 2 diabetic patients also seem to be present in non-diabetic individuals. This cluster of risk factors has been called syndrome X, also known as metabolic cardiovascular syndrome or insulin resistance syndrome. Vascular wall components changes, including endothelial dysfunction and vascular smooth muscle cell (VSMC) migration and proliferation, could be involved in the cardiovascular alterations associated with this state. Fructose fed rats (FFR) provide a model of dietary-induced insulin resistance, which has been used to assess the pathophysiological mechanisms of the metabolic and cardiovascular changes associated to the syndrome X. FFR have hyperinsulinemia, insulin resistance (altered glucose tolerance test) and hypertriglyceridemia; they also develop moderate hypertension and cardiac hypertrophy. This has been confirmed in male rats of different strains, such as Wistar and Sprague-Dawley, chronically fed with a 60% fructose-chow or 10% fructose in the drinking water. At different levels of the cardiovascular system, FFR exhibit changes in the nitric oxide generation system and in primary cultured proliferation of VSMC from conduit and resistance arteries. These abnormalities were normalized by long-term treatment with pharmacological agents acting on the renin-angiotensin system (RAS), such as angiotensin converting-enzyme inhibitors or angiotensin-AT(1) receptor antagonists, that also lowered blood pressure to control levels and reversed cardiac hypertrophy. Evidence suggests an important role for the RAS in the pathogenic mechanisms involved in this model of syndrome X. Furthermore, beneficial pharmacological intervention seems to be mediated by AT(2) receptors and kinins.
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PMID:Mechanisms of cardiovascular changes in an experimental model of syndrome X and pharmacological intervention on the renin-angiotensin-system. 1532 Aug 17

Insulin resistance and compensatory hyperinsulinemia often coexist in hypertensive patients, which may play a role in the development of hypertension. Because medullary blood flow (MBF), which is strongly influenced by the nitric oxide (NO) system, is thought to be an important component of blood pressure and sodium balance, we focused particularly on MBF in fructose-induced hypertensive rats. Moreover, it has been reported that the increased reactive oxygen species (ROS) in the kidney may contribute to the development of hypertension. Our study was thus designed to test the hypotheses that MBF is diminished in fructose-hypertensive rats (FFR) and that administration of tempol, a membrane-permeable mimetic of superoxide dismutase (SOD), decreases mean arterial pressure (MAP) by increasing MBF. Male Sprague-Dawley rats (180 to 200 g) were divided into 6 groups: control untreated (C, n = 5), control tempol-treated (in drinking water) (CT, n = 4), control L-arginine-treated (in drinking water) (CA, n = 6), fructose-fed untreated (F, n = 7), fructose-fed tempol-treated (FT, n = 7), and fructose-fed L-arginine-treated rats (in drinking water) (FA, n = 6). MAP and 24-hour urine samples were measured weekly over a 4-week test period. Changes in MBF, cortical blood flow (CBF), and renal blood flow (RBF) were determined by implanted optical fiber-, laser- and pulse-Doppler flow measurement techniques 4 weeks after starting the diet. Fructose feeding resulted in hyperinsulinemia, significantly elevated MAP, decreased MBF without changes in RBF or CBF, and decreased sodium excretion in the F group compared to the C group. Administration of tempol significantly decreased MAP and plasma insulin in contrast to increased MBF and sodium excretion in the FT group compared to those in the F group. Results indicated that MBF played an important role in the development of hypertension in the F group. Impairment of renal medullary NO systems may induce sustained elevation of blood pressure and retention of sodium in fructose-fed rats. The decrease in MAP with an increase of MBF in the FT group is consistent with the hypothesis that tempol increases the level of NO available to influence mechanisms involved in the control of MBF.
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PMID:Superoxide dismustase mimetic tempol decreases blood pressure by increasing renal medullary blood flow in hyperinsulinemic-hypertensive rats. 1537 86

Chronic feeding of fructose to normal rats causes impaired glucose tolerance, loss of tissue sensitivity to insulin, hyperinsulinemia and hypertension. alpha-Lipoic acid (LA), a co-enzyme known for its potent antioxidant effects, stimulates insulin-mediated glucose uptake in clinical and experimental diabetes. The purpose of this study was to examine whether LA can mitigate fructose-induced insulin resistance and associated abnormalities. Male Wistar rats of body weights 150-170 g were divided into 4 groups containing 12 rats each. Control rats received a control diet containing starch and water ad libitum. Fructose rats received a fructose-enriched diet (>60% of total calories). Fructose + LA rats received a fructose diet and LA (35 mg/kg b.w.) intraperitoneally. Control + LA rats received a normal diet and LA (35 mg/kg b.w.) intraperitoneally. After the treatment period of 20 days, blood pressure (BP) was measured. Oral glucose-tolerance test, insulin-sensitivity index, urea and creatinine clearance tests, and plasma and urinary sodium and potassium levels were analysed. Kallikrein activity and nitrite content were assayed. Additionally, the activities of RBC-membrane Na(+)/K(+) ATPase and Ca(2+) ATPase enzymes were assayed. Fructose rats showed increased BP, decreased glucose tolerance, decreased insulin sensitivity and altered sodium and potassium levels and renal clearance. LA supplementation mitigated these alterations. The increase in BP was attenuated and the levels of biochemical parameters were brought close to normal. The BP-lowering effect of LA in fructose rats may be related to improvement in insulin sensitivity.
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PMID:Lipoic acid attenuates hypertension and improves insulin sensitivity, kallikrein activity and nitrite levels in high fructose-fed rats. 1556 49

Insulin resistance (hyperinsulinaemia) is now recognized as a major contributor to the development of glucose intolerance, dyslipidaemia and hypertension in non-insulin-dependent diabetes mellitus (NIDDM) patients. Sedentary lifestyle, consumption of energy-rich diet, obesity, longer lifespan, etc., are important reasons for this rise (J. R. Turtle, Int J Clin Prac 2000; 113: 23). Aqueous extracts of Pterocarpus marsupium Linn bark (PM), Ocimum sanctum Linn leaves (OS) and Trigonella foenumgraecum Linn seeds (FG) have been shown to exert hypoglycaemic/antihyperglycaemic effect in experimental as well as clinical setting. As no work has been carried out so far to assess the effect of PM, OS and FG on fructose-induced hyperglycaemia, hyperinsulinaemia and hypertriglyceridaemia, we undertook this study to assess whether these extracts attenuate the metabolic alteration induced by fructose-rich diet in rats. Five groups of rats (eight each) were fed chow diet, 66% fructose diet, 66% fructose diet + PM leaves extract (1 g/kg/day), 66% fructose diet + OS leaves extract (200 mg/kg/day) and 66% fructose diet + FG seeds extract (2 g/kg/day) for 30 days. Fructose feeding to normal rats for 30 days significantly increased serum glucose, insulin and triglyceride levels in comparison with control. Treatment with all the three plants extract for 30 days significantly lowered the serum glucose levels in comparison with control group. However, only PM extract substantially prevented hypertriglyceridaemia and hyperinsulinaemia, while OS and FG had no significant effect on these parameters. Results of this study, in addition to previous clinical benefits of PM seen in NIDDM subjects, are suggestive of usefulness of PM bark (Vijayasar) in insulin resistance, the associated disorder of type 2 diabetes; however, OS and FG may not be useful. Though several antidiabetic principles (-epicatechin, pterosupin, marsupin and pterostilbene) have been identified in the PM, yet future studies are required to certify their efficacy and safety before clinical scenario.
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PMID:Pterocarpus marsupium extract (Vijayasar) prevented the alteration in metabolic patterns induced in the normal rat by feeding an adequate diet containing fructose as sole carbohydrate. 1595 28

Fructose feeding has been widely reported to cause hypertension in rats, as assessed indirectly by tail cuff plethysmography. Because there are potentially significant drawbacks associated with plethysmography, we determined whether blood pressure changes could be detected by long-term monitoring with telemetry in age-matched male Sprague-Dawley rats fed either a normal or high-fructose diet for 8 weeks. Fasting plasma glucose (171+/-10 versus 120+/-10 mg/dL), plasma insulin (1.8+/-0.5 versus 0.7+/-0.1 microg/L), and plasma triglycerides (39+/-2 versus 30+/-2 mg/dL) were modestly but significantly elevated in fructose-fed animals. Using the hyperinsulinemic euglycemic clamp technique, the rate of glucose infusion necessary to maintain equivalent plasma glucose was significantly reduced in fructose-fed compared with control animals (22.9+/-3.6 versus 41.5+/-2.9 mg/kg per minute; P<0.05). However, mean arterial pressure (24-hour) did not change in the fructose-fed animals over the 8-week period (111+/-1 versus 114+/-2 mm Hg; week 0 versus 8), nor was it different from that in control animals (109+/-2 mm Hg). Conversely, systolic blood pressure measured by tail cuff plethysmography at the end of the 8-week period was significantly greater in fructose-fed versus control animals (162+/-5 versus 139+/-1 mm Hg; P<0.001). Together, these data demonstrate that long-term fructose feeding induces mild insulin resistance but does not elevate blood pressure. We propose that previous reports of fructose-induced hypertension reflect a heightened stress response by fructose-fed rats associated with restraint and tail cuff inflation.
Hypertension 2005 Oct
PMID:Fructose feeding increases insulin resistance but not blood pressure in Sprague-Dawley rats. 1615 89

1.-- In the rat, a fructose-enriched diet induces hyperglycaemia, hypertriglyceridaemia, insulin resistance and hypertension; a model which resembles the human metabolic syndrome. 2.-- Prostanoids, metabolites of arachidonic acid, include vasoactive substances synthesized and released from the vascular wall that have been implicated in the increase of peripheral resistance, one of the mechanisms involved in the fructose-induced hypertension. 3.-- The aim of the present study was to: (i) analyse the effects of the in vitro incubation with fructose on the production and release of prostanoids in rat thoracic aorta and in rat mesenteric bed and (ii) compare the effects of incubation with those of the in vivo acute and chronic treatment of rats with fructose and with the combination of both in vivo and in vitro procedures. 4.-- Blood pressure, glycaemia and triglyceridaemia were significantly elevated in both 4- and 22-week fructose-treated groups. Meanwhile, body and heart weight as well as insulinaemia were similar between experimental animals and controls. 5.-- In aortae, 4 weeks of Fructose treatment did not modify the prostanoid pattern release, but in vitro incubation decreased prostacyclin (PGI(2)) production. However, after 22 weeks, fructose treatment and incubation exerted the same effect. 6.-- In mesenteric bed, after 4 weeks, the incubation and the combination of both procedures reduced the release of the vasodilators PGI(2) and PGE(2), while fructose treatment only diminished the PGE(2) release. On the contrary, the production of the vasoconstrictor thromboxane A(2) (TXA(2)) was enhanced by incubation and both the procedures. After 22 weeks, fructose treatment increased PGI(2) release, while it was reduced by incubation. The combination of both did not modify this peripheral resistance when compared with controls. Finally, incubation of tissues from treated rats increased the release of the vasoconstrictors, PGF(2alpha) and TXA(2). 7.-- In conclusion, the mesenteric bed, a resistance vascular bed, seems to be more sensitive than the aorta, a conductance vessel, to the effects of fructose on prostanoid production. This difference could be related to a more relevant role of resistance vessels in the regulation of peripheral resistance and consequently of blood pressure. The observed effects should contribute to a shift in the balance of the release of prostanoid in favour of vasoconstrictor metabolites. This phenomenon could be related to an increase in the peripheral resistance and the mild hypertension observed in the fructose-treated rats.
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PMID:Oral treatment and in vitro incubation with fructose modify vascular prostanoid production in the rat. 1637 Oct 62


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