Gene therapy attenuates the elevated blood pressure and glucose intolerance in an insulin-resistant model of hypertension

A rise in Proteobacteria is an indicator of gut-liver axis-mediated nonalcoholic fatty liver disease in high-fructose-fed adult mice

Current evidence suggests that high fructose intake results in gut dysbiosis, leading to endotoxemia and NAFLD onset. Thus, the hypothesis of the study was that an enhanced Proteobacteria proportion in the cecal microbiota could be the most prominent trigger of NAFLD through enhanced endotoxin (LPS) in adult high-fructose-fed C57BL/6 mice. Male C57BL/6 mice received a control diet (n = 10, C: 76% of energy as carbohydrates, 0% as fructose) or high-fructose diet (n = 10, HFRU: 76% of energy as carbohydrate, 50% as fructose) for 12 weeks. Outcomes included biochemical analyses, 16S rDNA PCR amplification, hepatic stereology, and RT-qPCR. The groups showed similar body masses during the whole experiment. However, the HFRU group showed greater water intake and blood pressure than the C group. The HFRU group showed a significantly lower amount of Bacteroidetes and a predominant rise in Proteobacteria, implying increased LPS. The HFRU group also showed enhanced de novo lipogenesis (Chrebp expression), while beta-oxidation was decreased (Ppar-alpha expression). These results agree with the deposition of fat droplets within hepatocytes and the enhanced hepatic triacylglycerol concentrations, as observed in the photomicrographs, where the HFRU group had a higher volume density of steatosis than the C group. Thus, we confirmed that a rise in the Proteobacteria phylum proportion was the most prominent alteration in gut-liver axis-induced hepatic steatosis in HFRU-fed C57BL/6 mice. Gut dysbiosis and fatty liver were observed even in the absence of overweight in this dietary adult mouse model.

Study on the correlation and predictive value of serum pregnancy-associated plasma protein A, triglyceride and serum 25-hydroxyvitamin D levels with gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a concern due to its rapid increase in incidence in recent years.

AIM

To investigate the correlation and predictive value of serum pregnancy-associated plasma protein A (PAPP-A), triglyceride (TG), and 25-hydroxyvitamin D [25-(OH)D] with GDM in early pregnancy.

METHODS

A total of 99 patients in early pregnancy admitted to Peking University International Hospital from November 2015 to September 2017 were included, and underwent a fasting glucose test and oral glucose tolerance test screening at 24-28 wk of pregnancy. Of these cases with GDM, 51 were assigned to group A and the remaining 48 cases without GDM were enrolled in group B. Serum PAPP-A, TG and 25-(OH)D in the two groups were compared and their correlation with blood sugar was analyzed. In addition, their diagnostic value in GDM was determined using receiver operating characteristic (ROC) curve analysis.

RESULTS

Group A had markedly lower serum PAPP-A and 25-(OH)D levels and a significantly higher serum TG level than group B, with statistical significance (P < 0.05). Furthermore, Pearson analysis identified that PAPP-A and 25-(OH)D levels were negatively correlated with fasting blood glucose (FBG) levels (r = -0.605, P < 0.001), (r = -0.597, P < 0.001), while TG and FBG levels were positively correlated (r = 0.628, P < 0.001). The sensitivity, specificity, area under the curve (AUC) and optimal cut-off value of serum PAPP-A level in the diagnosis of GDM were 72.55%, 82.35%, 0.861 and 16.340, respectively, while the sensitivity of TG in diagnosing GDM was 86.27%, the specificity was 66.67%, the AUC was 0.813, with an optimal cut-off value of 1.796. The corresponding sensitivity, specificity, AUC and optimal cut-off value of serum 25-(OH)D were 64.71%, 70.59%, 0.721 and 23.140, respectively. Moreover, multivariate logistic regression analysis revealed that FBG, vascular endothelial growth factor, Flt-1, serum PAPP-A, TG, and 25-(OH)D were related risk factors leading to GDM in patients.

CONCLUSION

Serum PAPP-A, TG, and 25-(OH)D levels are all correlated with blood glucose changes in GDM, and are independent factors affecting the occurrence of GDM and have certain value in the diagnosis of GDM.

Characteristics of WBN/Kob diabetic fatty rats supplemented with a fructose-rich diet as a metabolic syndrome model: response to a GLP-1 receptor agonist

The incidence of metabolic syndrome is rapidly increasing worldwide, and adequate animal models are crucial for studies on its pathogenesis and therapy. In the search of an adequate experimental model to simulate human metabolic syndrome, the present study was performed to examine the pharmacological response of WBN/Kob-Lepr^fa (WBKDF) rats supplemented with a fructose-rich diet (FRD) to liraglutide, a GLP-1 receptor agonist. Male WBKDF rats fed FRD at 7 weeks of age were divided into 3 groups, and administered liraglutide (75, 300 µg/kg subcutaneously) or saline (control group), once daily for 4 weeks. All rats in the control group became overweight, and developed hyperglycemia, hypertension and dyslipidemia as they aged. The rats given liraglutide exhibited a dose-dependent reduction in body weight, visceral fat content and food intake compared with control rats. In addition, liraglutide suppressed the development of hyperglycemia, hypertension and dyslipidemia. An intravenous glucose tolerance test revealed that liraglutide improved glucose tolerance, insulin secretion and insulin resistance. On histological examination, decreased hepatic fatty degeneration was observed in the liraglutide groups. The present study demonstrated that liraglutide protected against obesity, hyperglycemia, hypertension, dyslipidemia, and hepatic steatosis in WBKDF rats fed FRD, suggesting that WBKDF rats fed FRD may be a useful model to investigate the etiology of human metabolic syndrome.

Pressor recovery after acute stress is impaired in high fructose-fed Lean Zucker rats

Insulin resistance is a powerful predictor of cardiovascular disease; however, the mechanistic link remains unclear. This study aims to determine if early cardiovascular changes associated with short‐term fructose feeding in the absence of obesity manifest as abnormal blood pressure control. Metabolic dysfunction was induced in Lean Zucker rats by short‐term high‐fructose feeding. Rats were implanted with telemetry devices for the measurement of mean arterial blood pressure (MAP) and subjected to air jet stress at 5 and 8 weeks after feeding. Additional animals were catheterized under anesthesia for the determination of MAP and blood flow responses in the hind limb and mesenteric vascular beds to intravenous injection of isoproterenol (0.001–0.5 μm), a β‐adrenergic agonist. Metabolic dysfunction in high‐fructose rats was not accompanied by changes in 24‐h MAP. Yet, animals fed a high‐fructose diet for 8 weeks exhibited a marked impairment in blood pressure recovery after air‐jet stress. Dose‐dependent decreases in MAP and peripheral blood flow in response to isoproterenol treatment were significantly attenuated in high‐fructose rats. These data suggest that impaired blood pressure recovery to acute mental stress precedes the onset of hypertension in the early stages of insulin resistance. Further, blunted responses to isoproterenol implicate β₂‐adrenergic sensitivity as a possible mechanism responsible for altered blood pressure control after short‐term high‐fructose feeding.

Sympathetic overactivity precedes metabolic dysfunction in a fructose model of glucose intolerance in mice

Consumption of high levels of fructose in humans and animals leads to metabolic and cardiovascular dysfunction. There are questions as to the role of the autonomic changes in the time course of fructose-induced dysfunction. C57/BL male mice were given tap water or fructose water (100 g/l) to drink for up to 2 mo. Groups were control (C), 15-day fructose (F15), and 60-day fructose (F60). Light-dark patterns of arterial pressure (AP) and heart rate (HR), and their respective variabilities were measured. Plasma glucose, lipids, insulin, leptin, resistin, adiponectin, and glucose tolerance were quantified. Fructose increased systolic AP (SAP) at 15 and 60 days during both light (F15: 123 ± 2 and F60: 118 ± 2 mmHg) and dark periods (F15: 136 ± 4 and F60: 136 ± 5 mmHg) compared with controls (light: 111 ± 2 and dark: 117 ± 2 mmHg). SAP variance (VAR) and the low-frequency component (LF) were increased in F15 (>60% and >80%) and F60 (>170% and >140%) compared with C. Cardiac sympatho-vagal balance was enhanced, while baroreflex function was attenuated in fructose groups. Metabolic parameters were unchanged in F15. However, F60 showed significant increases in plasma glucose (26%), cholesterol (44%), triglycerides (22%), insulin (95%), and leptin (63%), as well as glucose intolerance. LF of SAP was positively correlated with SAP. Plasma leptin was correlated with triglycerides, insulin, and glucose tolerance. Results show that increased sympathetic modulation of vessels and heart preceded metabolic dysfunction in fructose-consuming mice. Data suggest that changes in autonomic modulation may be an initiating mechanism underlying the cluster of symptoms associated with cardiometabolic disease.

Timing of fructose intake: an important regulator of adiposity

1. Overconsumption of fructose produces glucose intolerance, autonomic abnormalities and renal dysfunction and may be related to the worldwide epidemic of obesity and diabetes. 2. Experiments were conducted to determine whether the time period (light or dark) of fructose consumption influenced the pathological consequences. C57BL mice were given standard chow and assigned to one of three groups: (i) control (n = 10), which received water over a 24 h period; (ii) FL (n = 11), which received 10% fructose solution during the 12 h light period; and (iii) FD (n = 11), which received 10% fructose solution during the 12 h dark period. 3. There was a time related increase in body weight for all groups (P < 0.01, 2 vs 6 wks). There was a greater increase in body fat in the FL group compared with the control and FD groups. The changes in adiposity occurred even though the total caloric intake was not significantly different among the groups (approximately 18 kcal/day). Total fluid (water + fructose) consumption was greater in the FD and FL groups compared with control at 6 weeks. Significant increases were noted for plasma insulin and leptin at 8 weeks, with highest levels in the FL compared with FD group (P < 0.05). There were no significant changes in glucose, glucose tolerance, cholesterol, triglycerides or adiponectin. 4. The results of the present study suggest that there is a mismatch in caloric consumption, metabolism and adiposity as related to the light-dark cycle of fructose consumption. These findings have clinical implications in the control of bodyweight, abdominal fat accumulation and Type 2 diabetes.

Diabetes and cardiovascular autonomic dysfunction: application of animal models

When diabetes is associated with cardiovascular autonomic dysfunction, there is a poor prognosis and increased morbidity and mortality. Information on the mechanisms of diabetes-associated autonomic dysfunction has been provided by advanced studies using physiological, pharmacological, anatomical and molecular methods in experimental animal models of insulin deficiency and resistance. This has been augmented by new approaches which combine diabetes induction with genetically modified animal models. The aim of this review is to outline and discuss the animal models used for the study of insulin deficiency and insulin resistance with a focus on autonomic neural interactions. The goal is to better understand the clinical relevance of cardiovascular autonomic dysfunction associated with diabetes.

Chronic insulin infusion normalizes blood pressure and the gene expressions of angiotensin II type 1 receptor in fructose-fed rats

It remains open to debate whether hyperinsulinemia leads to the development of hypertension. We addressed this issue by investigating the effect of chronic insulin infusion on blood pressure and related parameters in hypertensive fructose-fed rats. Rats were given either normal chow or a fructose-rich diet, and insulin or saline was infused through mini-pumps in the same animals for 14 days. The chronic insulin infusion exerted no effect on the blood pressure of the chow-fed rats. Fructose feeding increased the blood pressure and levels of insulin, triglyceride and fatty acid. Insulin infusion augmented the hyperinsulinemia but normalized the blood pressure and plasma lipids. Plasma angiotensin II was elevated in the fructose-fed rats, while insulin infusion left it unchanged. The expression of angiotensin II type 1 receptor (AT1R) mRNA was doubled in both the aorta and epididymal fat of the fructose-fed rats, while that of angiotensin II type 2 receptor (AT2R) was unaltered. Insulin infusion completely rectified the over-expression of the AT1R gene. Our findings indicate that chronic insulin infusion exacerbates hyperinsulinemia while normalizing blood pressure and the gene expressions of AT1R in insulin-resistant fructose-fed rats, suggesting that endogenous hyperinsulinemia caused by insulin resistance is associated with the development of hypertension, whereas exogenous hyperinsulinemia attenuates hypertension probably due to amelioration of insulin resistance.

Genetic and dietary interactions: role of angiotensin AT1a receptors in response to a high-fructose diet

The renin-angiotensin system (RAS) has been implicated in the cardiovascular complications of diabetes. We showed that a high-fructose diet increases blood pressure and plasma angiotensin and impairs glucose tolerance. We investigated the role of angiotensin AT(1a) receptors in the development of fructose-induced cardiovascular and metabolic dysfunction. Male angiotensin AT(1a) knockout (AT1aKO) and wild-type (AT1aWT) mice with arterial telemetric catheters were fed a standard diet or one containing 60% fructose. Fructose increased mean arterial pressure (MAP) in AT1aWT but only during the dark phase (8% increase). In AT1aKO mice, fructose unexpectedly decreased MAP, during both light and dark periods (24 and 13% decrease, respectively). Analytical methods were used to measure systolic arterial pressure (SAP) and pulse interval (PI) variability in time and frequency domains. In fructose-fed AT1aWT mice, there was an increase in SAP variance and its low-frequency (LF) domain (11 +/- 3 vs. 23 +/- 4 mmHg(2), variance, and 7 +/- 2 vs. 17 +/- 3 mmHg(2), LF, control vs. fructose, P < 0.004). There were no changes in SAP variance in AT1aKO mice. Depressor responses to alpha(1)-adrenergic blockade were augmented in fructose-fed AT1a WT compared with AT1aKO mice. Fructose inhibited glucose tolerance with a greater effect in AT1aWT mice. Fructose increased plasma cholesterol in both groups (P < 0.01) and reduced ANG II in AT1aKO mice. Results document prominent interactions between genetics and diet with data showing that in the absence of angiotensin AT(1a) receptors, a fructose diet decreased blood pressure.

Disfunção autonômica cardiovascular no diabetes mellitus experimental

Muitas informações novas têm sido publicadas nos últimos anos a respeito da fisiopatologia da disfunção autonômica cardiovascular em ratos e camundongos diabéticos. Nosso grupo tem estudado o curso temporal das alterações cardiovasculares associadas ao diabetes experimental há alguns anos, obtendo evidências consistentes de grave disautonomia em modelos animais de diabetes. O objetivo deste trabalho foi revisar a contribuição que estudos envolvendo diferentes modelos de deficiência e resistência à insulina têm fornecido para o entendimento, tratamento e prevenção da disfunção autonômica cardiovascular do diabetes.

Nocturnal hypertension in mice consuming a high fructose diet

OBJECTIVE

To investigate the effect of fructose consumption on the light/dark pattern of blood pressure, heart rate and autonomic neural function in mice.

BACKGROUND

Insulin resistant diabetes is associated with hypertension and autonomic dysfunction. There is evidence that the increasing incidence of diabetes may be related to dietary changes, including consumption of high levels of fructose.

DESIGN/METHODS

C57/BL mice, instrumented with radiotelemetric arterial catheters, were fed a control or high fructose diet (60%). Cardiovascular parameters measured were light/dark pattern of mean arterial pressure (MAP), heart rate (HR) and variability (time and frequency domain). We also measured plasma insulin, glucose, lipids and angiotensin II (Ang II) as well as glucose tolerance. In situ hybridization was used to measure brainstem expression of tyrosine hydroxylase (TH) and Ang AT1a mRNA.

RESULTS

Fructose diet (8 weeks) produced an increase in MAP, variance and low frequency domain (14+/-3 vs. 33+/-4 mm Hg(2), variance and 10+/-2 vs. 26+/-4 mm Hg(2), LF, control vs. fructose, P<0.01). The changes occurred only at night, a period of activity for mice. Glucose tolerance was attenuated in the fructose group. Fructose also increased plasma cholesterol (80+/-1 vs. 126+/-2 mg/dl, control vs. fructose, P<0.05) and plasma Ang II (18+/-5 vs.65+/-12 pg/ml, control vs. fructose, P<0.05). Depressor responses to alpha(1)-adrenergic blockade with prasozin were augmented in fructose-fed mice. Using quantitative in situ hybridization, we found that Ang AT1a receptor and TH mRNA expression were significantly increased in the brainstem locus coeruleus.

CONCLUSION

A high fructose diet in mice produced nocturnal hypertension and autonomic imbalance which may be related to activation of sympathetic and angiotensin systems.

Angiotensin II-induced NADPH oxidase activation impairs insulin signaling in skeletal muscle cells

The renin-angiotensin system (RAS) and reactive oxygen species (ROS) have been implicated in the development of insulin resistance and its related complications. There is also evidence that angiotensin II (Ang II)-induced generation of ROS contributes to the development of insulin resistance in skeletal muscle, although the precise mechanisms remain unknown. In the present study, we found that Ang II markedly enhanced NADPH oxidase activity and consequent ROS generation in L6 myotubes. These effects were blocked by the angiotensin II type 1 receptor blocker losartan, and by the NADPH oxidase inhibitor apocynin. Ang II also promoted the translocation of NADPH oxidase cytosolic subunits p47phox and p67phox to the plasma membrane within 15 min. Furthermore, Ang II abolished insulin-induced tyrosine phosphorylation of insulin receptor substrate 1 (IRS1), activation of protein kinase B (Akt), and glucose transporter-4 (GLUT4) translocation to the plasma membrane, which was reversed by pretreating myotubes with losartan or apocynin. Finally, small interfering RNA (siRNA)-specific gene silencing targeted specifically against p47phox (p47siRNA), in both L6 and primary myotubes, reduced the cognate protein expression, decreased NADPH oxidase activity, restored Ang II-impaired IRS1 and Akt activation as well as GLUT4 translocation by insulin. These results suggest a pivotal role for NADPH oxidase activation and ROS generation in Ang II-induced inhibition of insulin signaling in skeletal muscle cells.

Chronic angiotensin-(1-7) prevents cardiac fibrosis in DOCA-salt model of hypertension

Cardiac remodeling is a hallmark hypertension-induced pathophysiology. In the current study, the role of the angiotensin-(1-7) fragment in modulating cardiac remodeling was examined. Sprague-Dawley rats underwent uninephrectomy surgery and were implanted with a deoxycorticosterone acetate (DOCA) pellet. DOCA animals had their drinking water replaced with 0.9% saline solution. A subgroup of DOCA-salt animals was implanted with osmotic minipumps, which delivered angiotensin-(1-7) chronically (100 ng.kg(-1).min(-1)). Control animals underwent sham surgery and were maintained on normal drinking water. Blood pressure was measured weekly with the use of the tail-cuff method, and after 4 wk of treatment, blood pressure responses to graded doses of angiotensin II were determined by direct carotid artery cannulation. Ventricle size was measured, and cross sections of the heart ventricles were paraffin embedded and stained using Masson's Trichrome to measure interstitial and perivascular collagen deposition and myocyte diameter. DOCA-salt treatment caused significant increases in blood pressure, cardiac hypertrophy, and myocardial and perivascular fibrosis. Angiotensin-(1-7) infusion prevented the collagen deposition effects without any effect on blood pressure or cardiac hypertrophy. These results indicate that angiotensin-(1-7) selectively prevents cardiac fibrosis independent of blood pressure or cardiac hypertrophy in the DOCA-salt model of hypertension.

Fructose feeding increases insulin resistance but not blood pressure in Sprague-Dawley rats

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.

ACE2: A novel therapeutic target for cardiovascular diseases

Hypertension afflicts over 65 million Americans and poses an increased risk for cardiovascular morbidity such as stroke, myocardial infarction and end-stage renal disease resulting in significant mortality. Overactivity of the renin-angiotensin system (RAS) has been identified as an important determinant that is implicated in the etiology of these diseases and therefore represents a major target for therapy. In spite of the successes of drugs inhibiting various elements of the RAS, the incidence of hypertension and cardiovascular diseases remain steadily on the rise. This has lead many investigators to seek novel and innovative approaches, taking advantage of new pathways and technologies, for the control and possibly the cure of hypertension and related pathologies. The main objective of this review is to forward the concept that gene therapy and the genetic targeting of the RAS is the future avenue for the successful control and treatment of hypertension and cardiovascular diseases. We will present argument that genetic targeting of angiotensin-converting enzyme 2 (ACE2), a newly discovered member of the RAS, is ideally poised for this purpose. This will be accomplished by discussion of the following: (i) summary of our current understanding of the RAS with a focus on the systemic versus tissue counterparts as they relate to hypertension and other cardiovascular pathologies; (ii) the newly discovered ACE2 enzyme with its physiological and pathophysiological implications; (iii) summary of the current antihypertensive pharmacotherapy and its limitations; (iv) the discovery and design of ACE inhibitors; (v) the emerging concepts for ACE2 drug design; (vi) the current status of genetic targeting of the RAS; (vii) the potential of ACE2 as a therapeutic target for hypertension and cardiovascular disease treatment; and (viii) future perspectives for the treatment of cardiovascular diseases.

Differential effects of angiotensin II type-1 receptor antisense oligonucleotides on renal function in spontaneously hypertensive rats

The effect of selectively decreasing renal angiotensin II type 1 (AT1) receptor expression on renal function and blood pressure has not been determined. Therefore, we studied the consequences of selective renal inhibition of AT1 receptor expression in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) in vivo. Vehicle, AT1 receptor antisense oligodeoxynucleotides (AS-ODN), or scrambled oligodeoxynucleotides were infused chronically into the cortex of the remaining kidney of conscious, uninephrectomized WKY and SHR on a 4% NaCl intake. Basal renal cortical membrane AT1 receptor protein was greater in SHR than in WKY. In WKY and SHR, AS-ODN decreased renal but not cardiac AT1 receptors. AT1 receptor AS-ODN treatment increased plasma renin activity to a greater extent in WKY than in SHR. However, plasma angiotensin II and aldosterone were increased by AS-ODN to a similar degree in both rat strains. In SHR, sodium excretion was increased and sodium balance was decreased by AS-ODN but had only a transient ameliorating effect on blood pressure. Urinary protein and glomerular sclerosis were markedly reduced by AS-ODN-treated SHR. In WKY, AS-ODN had no effect on sodium excretion, blood pressure, or renal histology but also modestly decreased proteinuria. The major consequence of decreasing renal AT1 receptor protein in the SHR is a decrease in proteinuria, probably as a result of the amelioration in glomerular pathology but independent of systemic blood pressure and circulating angiotensin II levels.

Angiotensin‐converting enzyme 2 as a novel target for gene therapy for hypertension

Less than one-third of patients with hypertension have their blood pressures (BP) controlled with current traditional therapeutic approaches for the treatment and control of hypertension. Pharmacological approaches may have reached a plateau in their effectiveness and thus newer innovative strategies need to be studied not only to increase the number of patients that can achieve BP control, but also to find a way to cure, not just manage, the disease. Continuous advances in gene delivery systems coupled with the completion of the Human Genome Project, now make it possible to investigate genetic means for the treatment and possible cure for hypertension. The renin-angiotensin system (RAS) has long been known to regulate BP, and salt and water metabolism. This system is unique in having both a peripheral circulating system and a tissue-based system. Each of these components have been ascribed a variety of physiological effects that have been associated with not only an increase in BP, but also in a variety of the pathophysiological manifestations associated with hypertension, such as cardiac hypertrophy and kidney dysfunction. We and others have used an antisense gene therapy approach, targeting the classical components of the RAS, to effectively attenuate the development of hypertension and related cardiovascular pathophysiologies in numerous experimental models of hypertension. Recently other components of the RAS have been elucidated and some of these components may be potential targets in a gene therapy approach. This article will focus on angiotensin-converting enzyme 2 (ACE2) as a new, potential target of gene therapy for hypertensive disorders.

Temporal profiling of the transcriptional basis for the development of corticosteroid-induced insulin resistance in rat muscle

Elevated systemic levels of glucocorticoids are causally related to peripheral insulin resistance. The pharmacological use of synthetic glucocorticoids (corticosteroids) often results in insulin resistance/type II diabetes. Skeletal muscle is responsible for close to 80% of the insulin-induced systemic disposal of glucose and is a major target for glucocorticoid-induced insulin resistance. We used Affymetrix gene chips to profile the dynamic changes in mRNA expression in rat skeletal muscle in response to a single bolus dose of the synthetic glucocorticoid methyl-prednisolone. Temporal expression profiles (analyzed on individual chips) were obtained from tissues of 48 drug-treated animals encompassing 16 time points over 72 h following drug administration along with four vehicle-treated controls. Data mining identified 653 regulated probe sets out of 8799 present on the chip. Of these 653 probe sets we identified 29, which represented 22 gene transcripts, that were associated with the development of insulin resistance. These 29 probe sets were regulated in three fundamental temporal patterns. 16 probe sets coding for 12 different genes had a profile of enhanced expression. 10 probe sets coding for eight different genes showed decreased expression and three probe sets coding for two genes showed biphasic temporal signatures. These transcripts were grouped into four general functional categories: signal transduction, transcription regulation, carbohydrate/fat metabolism, and regulation of blood flow to the muscle. The results demonstrate the polygenic nature of transcriptional changes associated with insulin resistance that can provide a temporal scaffolding for translational and post-translational data as they become available.

Insulin resistance and hypertension

Diminished insulin (Ins) sensitivity is a characteristic feature of various pathological conditions such as the cardiometabolic syndrome, Type 2 diabetes, and hypertension. Persons with essential hypertension are more prone than normotensive persons to develop diabetes, and this propensity may reflect decreased ability of Ins to promote relaxation and glucose transport in vascular and skeletal muscle tissue, respectively. There are increasing data suggesting that ANG II acting through its ANG type 1 receptor inhibits the actions of Ins in vascular and skeletal muscle tissue, in part, by interfering with Ins signally through phosphatidylinositol 3-kinase (PI3K) and its downstream protein kinase B (Akt) signaling pathways. This inhibitory action of ANG II is mediated, in part, through stimulation of RhoA activity and oxidative stress. Activated RhoA and increased reactive oxygen species inhibition of PI3K/Akt signaling results in decreased endothelial cell production of nitric oxide, increased myosin light chain activation with vasoconstriction, and reduced skeletal muscle glucose transport.

Viral vectors as tools for studies of central cardiovascular control

During the last few years physiological genomics has been the most rapidly developing area of physiology. Given the current ease of obtaining information about nucleotide sequences found in genomes and the vast amount of readily available clones, one of the most pertinent tasks is to find out about the roles of the individual genes and their families under normal and pathological conditions. Viral gene delivery into the brain is a powerful tool, which can be used to address a wide range of questions posed by physiological genomics including central nervous mechanisms regulating the cardio-vascular system. In this paper, we will give a short overview of current data obtained in this field using viral vectors and then look critically at the technology of viral gene transfer.

Transgenic amplification of glucocorticoid action in adipose tissue causes high blood pressure in mice

Obesity is closely associated with the metabolic syndrome, a combination of disorders including insulin resistance, diabetes, dyslipidemia, and hypertension. A role for local glucocorticoid reamplification in obesity and the metabolic syndrome has been suggested. The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) regenerates active cortisol from inactive 11-keto forms, and aP2-HSD1 mice with relative transgenic overexpression of this enzyme in fat cells develop visceral obesity with insulin resistance and dyslipidemia. Here we report that aP2-HSD1 mice also have high arterial blood pressure (BP). The mice have increased sensitivity to dietary salt and increased plasma levels of angiotensinogen, angiotensin II, and aldosterone. This hypertension is abolished by selective angiotensin II receptor AT-1 antagonist at a low dose that does not affect BP in non-Tg littermates. These findings suggest that activation of the circulating renin-angiotensin system (RAS) develops in aP2-HSD1 mice. The long-term hypertension is further reflected by an appreciable hypertrophy and hyperplasia of the distal tubule epithelium of the nephron, resembling salt-sensitive or angiotensin II-mediated hypertension. Taken together, our findings suggest that overexpression of 11beta-HSD1 in fat is sufficient to cause salt-sensitive hypertension mediated by an activated RAS. The potential role of adipose 11beta-HSD1 in mediating critical features of the metabolic syndrome extends beyond obesity and metabolic complications to include the most central cardiovascular feature of this disorder.

Genetic targeting of the renin-angiotensin system for long-term control of hypertension

Although traditional approaches are effective for the treatment and control of hypertension, they have not succeeded in curing the disease, and have therefore reached a plateau. As a result of the completion of the Human Genome Project and the continuous advancement in gene delivery systems, it is now possible to investigate genetic means for the treatment and possible cure for hypertension. In this review we discuss the potential of genetic targeting of the renin-angiotensin system for the treatment of hypertension. We provide examples of various approaches that have used antisense technology with a high degree of success. We focus on our own research, which targets the use of antisense of the angiotensin type I receptor in various models of hypertension. Finally, we discuss the future of antisense technology in the treatment of human hypertension.

Gene therapy for cardiovascular disorders: is there a future?

Incidence of cardiovascular disease has reached epidemic proportions in spite of recent advances in improving the efficacy of pharmacotherapeutics. This has led many to conclude that drug therapy has reached a plateau in its effectiveness. As a result, our efforts have been diverted to explore the use of gene transfer approaches for long-term control of these pathophysiological conditions. The purpose of this review is to present various approaches that are being undertaken to provide "proof of principle" for gene therapy for cardiovascular diseases. Finally, we will discuss the future of gene therapy and other new technologies that may further advance this field of therapeutics.