The role of renin–angiotensin system inhibition in the treatment of hypertension in metabolic syndrome: are all the angiotensin receptor blockers equal?

Hypertension in Metabolic Syndrome: Novel Insights

BACKGROUND

Metabolic syndrome (MetS) is characterized by the simultaneous presence of obesity, hypertension, dyslipidemia and hyperglycemia in an individual, leading to increased cardiovascular disease (CVD) risk. It affects almost 35% of the US adult population, while its prevalence increases with age. Elevated blood pressure is the most frequent component of the syndrome; however, until now, the optimal antihypertensive regiment has not been defined.

OBJECTIVE

The purpose of this review is to present the proposed definitions for the metabolic syndrome, as well as the prevalence of hypertension in this condition. Moreover, evidence regarding the metabolic properties of the different antihypertensive drug classes and their effect on MetS will be displayed.

METHODS

A comprehensive review of the literature was performed to identify data from clinical studies for the prevalence, pathophysiology and treatment of hypertension in the metabolic syndrome.

RESULTS

Hypertension is present in almost 80% of patients with metabolic syndrome. The use of thiazide diuretics and b-blockers has been discouraged in this population; however, new evidence suggests their use under specific conditions. Calcium channel blockers seem to exert a neutral effect on MetS, while renin-angiotensin system inhibitors are believed to be of the most benefit, although differences exist between the different agents of this category.

CONCLUSION

Controversy still exists regarding the optimal antihypertensive treatment for hypertension in MetS. Due to the high prevalence of hypertension in this population, more data from clinical trials are needed in the future.

Milk-Derived Tripeptides IPP (Ile-Pro-Pro) and VPP (Val-Pro-Pro) Enhance Insulin Sensitivity and Prevent Insulin Resistance in 3T3-F442A Preadipocytes

There is great interest in developing naturally derived compounds, especially bioactive peptides with potential insulin sensitizing effects and/or preventing insulin resistance. Previously, we showed adipogenic and insulin mimetic actions of IPP (Ile-Pro-Pro) and VPP (Val-Pro-Pro), the milk-derived tripeptides on cultured preadipocytes, in addition to their previously characterized antihypertensive and anti-inflammatory functions. However, the effect of these peptides on insulin signaling is not known. Therefore, we examined IPP and VPP effects on insulin signaling in preadipocytes, a well-established model for studying insulin signaling. Our results suggested both peptides enhanced insulin signaling and contributed toward the prevention of insulin resistance in the presence of tumor necrosis factor (TNF). Inhibition of inflammatory mediator NF-kB under TNF stimulation was a likely contributor to the prevention of insulin resistance. VPP further enhanced the expression of glucose transporter 4 (GLUT4) in adipocytes and restored glucose uptake in TNF-treated adipocytes. Our data suggested the potential of these peptides in the management of conditions associated with impairments in insulin signaling.

Association of cardiac NT pro-β-type natriuretic peptide with metabolic and endothelial risk factors in young obese hypertensive patients: a perspective on the hypothalamic pituitary adrenal axis activation

BACKGROUND

In practice, there is increasing recognition of the importance of hypothalamic pituitary adrenal axis in the cardiovascular disease progression. The association of brain natriuretic peptide with obesity and characteristics of the metabolic syndrome in adults and aged patients is well established, but that in pediatrics needs thorough elucidation.

AIM

The aim of this study was to assess the association of hypothalamic pituitary adrenal axis mediators (cortisol and aldosterone) with plasma NT-pro β-type natriuretic peptide (NT-proBNP) levels on metabolic, immune-inflammatory and endothelial markers in young obese pediatric patients.

METHODS

This is achieved by recruitment of 60 young (13-17 years) obese pediatric cohorts who are further subclassified according to their stage of hypertension; normotensive, prehypertensive and hypertensive patients.

RESULTS

The study showed significant differences in the metabolic parameters (glucose, insulin and HOMA-index) among the three obese young patient groups. Levels of cortisol and aldosterone, as well as NT-proBNP levels are positively associated with characteristics of the metabolic syndrome; blood pressure, BMI, HOMA index in all three obese groups. However, their association to the lipid profile was insignificant. These increases aligned harmonically with the assessed immune-inflammatory markers; CRP, TNF-α, and IL-23, as well as levels of sICAM, sVCAM and p-selectin, reflecting the involvement of mast cells and inflammatory effects on the vascular endothelium. ROC analysis revealed their beneficial addition as promising biomarkers for a better prognostic profile of hypertension-induced cardiovascular risk.

CONCLUSION

Early detection of NT-proBNP, cortisol and aldosterone levels in pre-hypertension stage added to the immune-inflammatory mediators may improve the coronary risk assessment in young Egyptian patients.

The mechanisms by which antidepressants may reduce coronary heart disease risk

BACKGROUND

Depression is known to increase the risk for coronary heart disease (CHD) likely through various pathogenetic actions. Understanding the links between depression and CHD and the effects of mediating these links may prove beneficial in CHD prevention.

METHODS

An integrated model of CHD was used to elucidate pathogenetic pathways of importance between depression and CHD. Using biomarker relative risk data the pathogenetic effects are representable as measurable effects based on changes in biomarkers.

RESULTS

A 'connection graph' presents interactions by illustrating the relationship between depression and the biomarkers of CHD. The use of selective serotonin reuptake inhibitors (SSRIs) is postulated to have potential to decrease CHD risk. Comparing the 'connection graph' of SSRI's to that of depression elucidates the possible actions through which risk reduction may occur.

CONCLUSIONS

The CHD effects of depression appear to be driven by increased inflammation and altered metabolism. These effects might be mediated with the use of SSRI's.

Milk-derived tripeptides IPP (Ile-Pro-Pro) and VPP (Val-Pro-Pro) promote adipocyte differentiation and inhibit inflammation in 3T3-F442A cells

Milk derived tripeptides IPP (Ile-Pro-Pro) and VPP (Val-Pro-Pro) have shown promise as anti-hypertensive agents due to their inhibitory effects on angiotensin converting enzyme (ACE). Due to the key inter-related roles of hypertension, chronic inflammation and insulin resistance in the pathogenesis of metabolic syndrome, there is growing interest in investigating established anti-hypertensive agents for their effects on insulin sensitivity and inflammation. In this study, we examined the effects of IPP and VPP on 3T3-F442A murine pre-adipocytes, a widely used model for studying metabolic diseases. We found that both IPP and VPP induced beneficial adipogenic differentiation as manifested by intracellular lipid accumulation, upregulation of peroxisome proliferator-activated receptor gamma (PPARγ) and secretion of the protective lipid hormone adiponectin by these cells. The observed effects were similar to those induced by insulin, suggesting potential benefits in the presence of insulin resistance. IPP and VPP also inhibited cytokine induced pro-inflammatory changes such as reduction in adipokine levels and activation of the nuclear factor kappa B (NF-κB) pathway. Taken together, our findings suggest that IPP and VPP exert insulin-mimetic adipogenic effects and prevent inflammatory changes in adipocytes, which may offer protection against metabolic disease.

Effects of Losartan vs. Enalapril on the Markers of Metabolic Syndrome

OBJECTIVE

To compare the effects of losartan and enalapril on the markers of metabolic syndrome.

METHODS

One hundred and twenty six newly diagnosed hypertensive patients having other markers of metabolic syndrome participated in this study. The study was performed in the department of pharmacology, college of medicine at Ibn-Sina Teaching Hospital in Mosul city, Iraq, during the period between December 2007 and June 2009. The patients were divided into 2 main groups: 1) Losartan group: consisted of 60 patients, and 2) enalapril group: Consisted of 66 patients. Waist circumference, weight, Body mass index, blood pressure, serum glucose concentration, triglyceride and HDL-cholestrol were measured before and after administration of therapy. The effects of therapy were assessed by statistically comparing the results before and after the drug administration.

RESULTS

Comparison of waist circumference, blood pressure, FSG, triglycerides of the patients before drug administration (baseline data), with those of the controls showed a significant elevation, while HDL-cholesterol showed a significant reduction. A significant reduction of waist circumference, BP, FSG and a significant elevation of HDL-cholesterol were also noted after therapy with both losartan and enalapril.

CONCLUSION

Both losartan and enalapril produced a significant reduction of markers of metabolic syndrome and may be regarded as effective drugs for treatment of hypertension in patients with markers of metabolic syndrome.

The renin-angiotensin system: a target of and contributor to dyslipidemias, altered glucose homeostasis, and hypertension of the metabolic syndrome

The renin-angiotensin system (RAS) is an important therapeutic target in the treatment of hypertension. Obesity has emerged as a primary contributor to essential hypertension in the United States and clusters with other metabolic disorders (hyperglycemia, hypertension, high triglycerides, low HDL cholesterol) defined within the metabolic syndrome. In addition to hypertension, RAS blockade may also serve as an effective treatment strategy to control impaired glucose and insulin tolerance and dyslipidemias in patients with the metabolic syndrome. Hyperglycemia, insulin resistance, and/or specific cholesterol metabolites have been demonstrated to activate components required for the synthesis [angiotensinogen, renin, angiotensin-converting enzyme (ACE)], degradation (ACE2), or responsiveness (angiotensin II type 1 receptors, Mas receptors) to angiotensin peptides in cell types (e.g., pancreatic islet cells, adipocytes, macrophages) that mediate specific disorders of the metabolic syndrome. An activated local RAS in these cell types may contribute to dysregulated function by promoting oxidative stress, apoptosis, and inflammation. This review will discuss data demonstrating the regulation of components of the RAS by cholesterol and its metabolites, glucose, and/or insulin in cell types implicated in disorders of the metabolic syndrome. In addition, we discuss data supporting a role for an activated local RAS in dyslipidemias and glucose intolerance/insulin resistance and the development of hypertension in the metabolic syndrome. Identification of an activated RAS as a common thread contributing to several disorders of the metabolic syndrome makes the use of angiotensin receptor blockers and ACE inhibitors an intriguing and novel option for multisymptom treatment.

Long-term impact of multifactorial treatment on new-onset diabetes and related cardiovascular events in metabolic syndrome: a post hoc ATTEMPT analysis

This post hoc analysis of the Assessing The Treatment Effect in Metabolic Syndrome Without Perceptible diabeTes (ATTEMPT) study assesses the 3½ year incidence of new-onset diabetes (NOD) and related cardiovascular disease (CVD) events in patients with metabolic syndrome (MetS), after multifactorial (lifestyle and drug, including atorvastatin) intervention. Patients were randomized to group A (low-density lipoprotein cholesterol [LDL-C] target < 100 mg/dL) and group B (< 130 mg/dL). The incidence of NOD during the 42-month follow-up was very low, 0.83 to 1.00/100 patient-years in patients with MetS and MetS with impaired fasting glucose, respectively. Older age, increased waist circumference, and persistent MetS were determinants of NOD. One CVD nonfatal event occurred in the 28 patients with NOD. Our findings suggest that treating the characteristics of MetS is achievable and beneficial. New-onset diabetes incidence and CVD events were negligible and not different from what is expected in the general population.

Association between the changes in renal function and serum uric acid levels during multifactorial intervention and clinical outcome in patients with metabolic syndrome. A post hoc analysis of the ATTEMPT study

AIM

To assess the effects of long-term multifactorial intervention on renal function and serum uric acid (SUA) levels and their association with estimated cardiovascular disease (eCVD) risk and actual CVD events.

METHODS

This prospective, randomized, target-driven study included 1123 subjects (45.6% men, age 45-65 years) with metabolic syndrome (MetS) but without diabetes or CVD. Patients were randomized to multifactorial treatment. Atorvastatin was titrated from 10-80 mg/day aiming at a low density lipoprotein cholesterol (LDL-C) target of <100 mg/dl (group A) or an LDL-C target of <130 mg/dl (group B). Changes in estimated glomerular filtration rate (eGFR) and SUA levels were recorded in all patients and in the subgroup with stage 3 chronic kidney disease (CKD; eGFR = 30-59 ml/min/1.73 m(2); n = 349). We used ANOVA to compare changes within the same group, unpaired Student t-test to compare results between groups at specific time points, and log-rank test to compare event free survival.

RESULTS

The eCVD-risk reduction was greater in group A. In the overall study population, eGFR increased by 3.5% (p < 0.001) and SUA levels fell by 5.6% (p < 0.001). In patients from group A with stage 3 CKD (group A1; n = 172), eGFR increased by 11.1% (p < 0.001) from baseline and by 7.5% (p < 0.001) in group B1 (n = 177; p < 0.001 vs. the change in group A1). The corresponding fall in SUA levels was 10.7% in group A1 (p < 0.001 vs. baseline) and 8.3% in group B1 (p < 0.001 vs. baseline and group A1). These changes were mainly attributed to atorvastatin treatment. Among the CKD stage 3 patients there were no CVD events in group A1, while 6 events occurred in group B1 (p = 0.014).

CONCLUSIONS

Multifactorial intervention in patients with MetS without established CVD improved renal function and reduced SUA levels. These changes were more prominent in stage 3 CKD patients and might have contributed to the reduction in eCVD risk and clinical events. Original study registration number [ClinicalTrials.gov ID: NCT00416741].

Clinical review: The pathogenetic role of cortisol in the metabolic syndrome: a hypothesis

CONTEXT

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities that increase the risk for type 2 diabetes mellitus and vascular disease. The common characteristics of MetS and hypercortisolemic conditions such as Cushing's syndrome (CS) suggest that the pathogenesis of MetS and central obesity might involve prolonged and excessive exposure to glucocorticoids. The present review summarizes the evidence on the potential role of cortisol in the pathogenesis of MetS and discusses new therapeutic approaches for these patients.

EVIDENCE ACQUISITION

Using PubMed, we searched for publications during the last 20 yr regarding the possible pathogenetic role of cortisol in the development of MetS.

EVIDENCE SYNTHESIS

Emerging data suggest that patients with MetS show hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a state of "functional hypercortisolism." The cause for this activation of the HPA axis remains uncertain but may be partly associated with chronic stress and/or low birth weight, which are both associated with increased circulating cortisol levels and greater responsiveness of the HPA axis. Increased exposure to cortisol contributes to increased fat accumulation in visceral depots. However, cortisol metabolism is not only centrally regulated. The action of 11beta-hydroxysteroid dehydrogenase-1 at the tissue level also modulates cortisol metabolism. Increased 11beta-hydroxysteroid dehydrogenase-1 activity in adipose tissue and liver might contribute to the development of several features of the MetS.

CONCLUSIONS

MetS shares many characteristics of CS, and cortisol might play a role in the development of MetS at both a central and a peripheral level.

Chronic treatment with angiotensin AT1 receptor antagonists reduced serum but not bone TGF-beta1 levels in ovariectomized rats

Approximately 50% of hypertensive patients are postmenopausal women; therefore, any antihypertensive therapy must not adversely affect bone loss in this population. Recently, however, concern has been raised that use of angiotensin AT1 receptor antagonists may increase the tendency to develop postmenopausal osteoporosis by decreasing transforming growth factor-beta1 (TGF-beta1), which has been implicated in bone mass maintenance. In the present study, we selected telmisartan and valsartan as representatives of angiotensin AT1 receptor antagonists and used ovariectomized (OVX) rats as a model of human postmenopausal osteoporosis. After 3 months treatment with telmisartan (5 mg/kg daily) or valsartan (10 mg/kg daily), OVX rats showed no signs of adverse effects on bone mineral density of the lumbar vertebrae (L1-L5) or the total femur, nor did treatment affect serum levels of osteocalcin and osteoclast-derived tartrate-resistant acid phosphatase (TRACP-5b). Bone TGF-beta1 content remained unchanged, although treatment with telmisartan and valsartan significantly reduced serum TGF-beta1 levels (p < 0.05). In conclusion, chronic treatment with angiotensin AT1 receptor antagonists reduced serum but not bone TGF-beta1 levels and did not accelerate ovariectomy-induced bone loss in rats.

Standardized arrangement for a guideline-driven treatment of the metabolic syndrome: the SAGE-METS study

AIM

To substantially increase awareness, treatment and effective control of the metabolic syndrome (MetS) and its components.

SUBJECTS AND METHODS

This is a pilot best practice implementation enhancement programme to reduce the estimated cardiovascular disease (CVD) risk in 628 MetS patients with or without diabetes or CVD by improving quality of care. A baseline visit was followed by action to improve adherence to lifestyle advice and drug treatment for CVD risk factors by physicians specifically trained to implement guidelines. Finally, after 6 months, a single-page form was completed, showing if patients were at CVD risk factor target. If not, there was an analysis of the reason why.

RESULTS

The programme was effective in improving utilization of evidence-based treatment in 628 MetS patients. There was a substantially greater patient perception of MetS, an enhancement in compliance with lifestyle advice and increased prescription of evidence-based medication, leading to a 48% (p < 0.0001) improvement in estimated CVD risk. There was a substantial increase in the number of subjects on target for specific CVD risk factors.

CONCLUSIONS

This is the first study to increase adherence to multiple interventions for all MetS components on an outpatient basis, in both primary care and teaching hospital settings. Physician and patient education, distribution of printed guidelines and brochures, and completion of a single-page form motivated both physicians and patients to achieve multiple CVD risk factor guideline goals. The absence of a control group is a limitation of this study. Further work is also needed to establish if the improvements observed are sustained on a long-term basis.

Effects of eprosartan on serum metabolic parameters in patients with essential hypertension

The effect of the anti-hypertensive drug eprosartan on metabolic parameters is currently not extensively documented. We evaluated the effect of eprosartan on parameters involved in atherogenesis, oxidative stress and clotting activity. This open-label unblinded intervention study included 40 adult patients with essential hypertension taking eprosartan. Eprosartan significantly reduced by 8% (p<0.001) the systolic and by 13% (p<.001) the diastolic blood pressure, and in-creased by 24% the time needed to produce oxidative by-products (p=0.001), a marker of oxidative stress. In contrast, ep-rosartan did not alter 8-isoprostane (8-epiPGF2a) levels, another marker of oxidative stress. Additionally, eprosartan re-duced by 14% aspartate aminotransferase and by 21% then alanine aminotransferase activity, while it had a neutral effect on the lipid profile and apolipoprotein levels and did not influence glucose homeostasis, creatinine and uric acid levels. Eprosartan did not affect the clotting/fibrinolytic status (estimated by plasminogen activator inhibitor 1, tissue plasmino-gen activator and a2 antiplasmin levels), or the enzymatic activity of the lipoprotein associated phospholipase A2 (Lp-PLA2) and paraoxonase 1 (PON1). In conclusion, eprosartan should be mainly considered as an anti-hypertensive agent with neutral effects on most of the metabolic parameters in hypertensive patients.

Anti-inflammatory and anti-oxidant properties of telmisartan in cultured human umbilical vein endothelial cells

PURPOSE

To study whether telmisartan, an angiotensin II (AII) receptor blocker (ARB), modulates endothelial inflammation and oxidative cell damage induced by AII-independent stimuli in cultured human umbilical vein endothelial cell (HUVEC)s.

METHODS

Endothelial inflammation, as reflected by increased VCAM-1 and ICAM-1 expression (ELISA), was induced by TNF-alpha, an inflammatory cytokine, and cell damage (COMET and MTT assay) by hydrogen peroxide, a reactive oxygen species. Losartan, another ARB, its active metabolites (EXP-3174, EXP-3179), dexamethasone, a synthetic steroid, and pyrrolidine dithiocarbamate (PDTC), an anti-oxidant, were the controls. The contribution of PPAR-gamma agonism was assessed through synthetic PPAR-gamma agonists and antagonists and the antagonism for AII-type 1 receptor-mediated stimuli by evaluating the interference against cell death induced by AII (MTT assay), a pro-apoptotic peptide that induces oxidative stress. The in vitro scavenging properties for oxyradicals were quantified by the TOSC assay.

RESULTS

Telmisartan and PDTC reduced TNF-alpha-stimulated VCAM-1 in a concentration-dependent manner while losartan, EXP-3174, EXP-3179 and dexamethasone were ineffective. All compounds did not modify ICAM-1 expression. PPAR-gamma agonists or antagonists did not interfere with the effect of telmisartan. Both ARBs antagonized AII-induced cell death but only telmisartan reduced hydrogen peroxide-induced cell damage. Telmisartan scavenged selectively hydroxyl radicals without affecting peroxyl radicals and peroxynitrite.

CONCLUSIONS

Telmisartan modulates pleiotropically TNF-alpha induced VCAM-1 expression and oxidative damage in vascular endothelium, possibly by acting as a hydroxyl radical scavenger. Those anti-inflammatory and antioxidant properties may contribute to the therapeutic effect, although the applicability of these data to the clinical situations has to be verified.

Drug discovery in the metabolic syndrome: context and some recent developments

The metabolic syndrome, encompassing the clinically distinct but related areas of dyslipidaemia, insulin resistance, obesity and vascular disease, offers a wide arena for drug discovery. There is substantial and growing unmet medical need, particularly as the worldwide epidemic of obesity continues to develop. There are also many targets and biological mechanisms that can be exploited. However, the context for clinical development is challenging because of the many ways in which the syndrome can be approached. As with most therapeutic areas, preclinical data provide only limited confidence in the potential of a novel target in humans. In this review, the author outlines the context for drug discovery in the metabolic syndrome, the clinical and biological scope and recent developments in preclinical models. Finally, existing examples of drug targets for a range of biological mechanisms are considered, outlining their biology and points relevant to lead identification and optimisation and clinical development.