Additive beneficial effects of fenofibrate combined with candesartan in the treatment of hypertriglyceridemic hypertensive patients

Effect of Fibrate Treatment on Circulating Adipokine Levels: A Systematic Review and Meta-analysis of Randomized Clinical Trials

BACKGROUND

Fibrates are widely used in the treatment of dyslipidemia and associated metabolic abnormalities; however, their effects on adipokines are unclear.

AIM OF THE STUDY

This meta-analysis of clinical trials aimed to evaluate the effect of fibrates on circulating adipokine levels.

METHODS

Only randomized controlled trials investigating the impact/effect of fibrate treatment on circulating adipokine levels were included from searches in PubMed-Medline, SCOPUS, ClinicalTrials.gov, Web of Science, and Google Scholar databases. A random effects model and the generic inverse variance method were used for the meta-analysis. Sensitivity analysis was conducted using the leave-one-out method.

RESULTS

This meta-analysis of 22 clinical trials showed a significant reduction on/in leptin (WMD: -1.58 ng/mL, 95% CI: -2.96, -0.20, p = 0.02, I2 = 0%), plasminogen activator inhibitor-1 (PAI-1) (WMD: -13.86 ng/mL, 95% CI: -26.70, -1.03, p = 0.03, I2 = 99%), and visfatin (WMD: -1.52 ng/mL, 95% CI: -2.49, -0.56, p = 0.002, I2 = 0%) after fibrate therapy; no significant effect was observed on adiponectin (WMD: -0.69 µg/ml, 95% CI: -1.40, 0.02, p = 0.06, I2 = 83%) and resistin (WMD: -2.27 ng/mL, 95% CI: -7.11, 2.57, p = 0.36, I2 = 0%). The sensitivity analysis was robust only for visfatin, while the effect size was sensitive to one arm for leptin, four for adiponectin, and two for PAI-1.

CONCLUSION

This meta-analysis showed that fibrate treatment significantly improves adipokine levels with a decrease in leptin, PAI-1, and visfatin, suggesting potential additional clinical therapeutic benefits through/of fibrate treatment on adipose tissue.

Effect of Renal Denervation on the Plasma Adiponectin Concentration in Patients with Resistant Hypertension

(1) Introduction: Adiponectin is synthetized by white adipose tissue and has anti-diabetic, anti-atherosclerotic, anti-thrombotic, anti-inflammatory, and cardioprotective properties. In patients with arterial hypertension, plasma concentration of adiponectin is lower than in healthy subjects. Renal denervation, i.e., percutaneous ablation of fibers from the sympathetic nervous system located in the wall of the renal arteries by radio frequency waves, is a method of resistant arterial hypertension treatment. (2) The aim of this single center, interventional, clinical study was to assess the effect of renal denervation on the plasma adiponectin concentration in patients with resistant arterial hypertension. (3) Materials and methods: 28 patients (13 women, 15 men) aged 54.4 ± 9.2 years with resistant hypertension who underwent renal denervation using Simplicity catheters (Medtronic, Inc., Northridge, CA, USA) were enrolled in the study. Plasma adiponectin concentration was determined using the Human Adiponectin ELISA Kit (Otsuka Pharmaceutical Co, Tokyo, Japan) before the renal denervation and 6 and 12 months after this procedure. (4) Results: Blood pressure (BP) values before renal denervation and 6 and 12 months after this procedure were as follows: systolic BP 190.4 ± 24.5, 160.8 ± 14.5, 155.7 ± 17.9 mmHg (p < 0.001) and diastolic BP 111.7 ± 18.9, 88.9 ± 8.3, 91.2 + 10.2 mmHg (p < 0.001), respectively. Body mass index (BMI) before renal denervation, 6 and 12 months after this procedure were 31.5 ± 4.2, 30.5 ± 4.4, 30.2 ± 4.0 kg/m2, (p = 0.057), respectively. Plasma adiponectin concentration before the renal denervation and 6 and 12 months after this procedure were 4.79 (3.95; 9.49), 7.58 (5.04; 9.51), 6.62 (4.57; 11.65) [µg/mL] (p = 0.007), respectively. (5) Conclusions: Plasma adiponectin concentration increases significantly after successful renal denervation in patients with resistant hypertension. Higher plasma adiponectin concentration may participate—beyond blood pressure reduction—in the cardiovascular benefits related to successful renal denervation; however’ clinical consequences of these results need further investigations.

The Role of Peroxisome Proliferator-Activated Receptors in Preeclampsia

Preeclampsia is a common pregnancy-related hypertensive disorder. Often presenting as preexisting or new-onset hypertension complicated by proteinuria and/or end-organ dysfunction, preeclampsia significantly correlates with maternal and perinatal morbidity and mortality. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins that regulate gene expression. In order to investigate the role of PPARs in the pathophysiology of preeclampsia, we conducted a literature review using the MEDLINE and LIVIVO databases. The search terms "peroxisome proliferator-activated receptor", "PPAR", and "preeclampsia" were employed and we were able to identify 35 relevant studies published between 2002 and 2022. Different study groups reached contradictory conclusions in terms of PPAR expression in preeclamptic placentae. Interestingly, PPARγ agonists alone, or in combination with well-established pharmaceutical agents, were determined to represent novel, potent anti-preeclamptic treatment alternatives. In conclusion, PPARs seem to play a significant role in preeclampsia.

Serum triglyceride levels and incidence of hypertension in a general Japanese population: ISSA-CKD study

The aim of this study was to clarify the relationship between fasting and nonfasting serum triglyceride (TG) levels and the incidence of hypertension in a general Japanese population. We conducted a population-based retrospective cohort study using annual health check-up data of residents of Iki City, Nagasaki Prefecture, Japan. A total of 3202 participants without hypertension at baseline were included in the present analysis. TG levels were classified as quartile 1 (<0.82 mmol/L), quartile 2 (0.83-1.13 mmol/L), quartile 3 (1.14-1.70 mmol/L) and quartile 4 (≥1.71 mmol/L) for men, and as quartile 1 (<0.70 mmol/L), quartile 2 (0.71-0.96 mmol/L), quartile 3 (0.97-1.34 mmol/L) and quartile 4 (≥1.35 mmol/L) for women. The outcome was incident hypertension. During an average follow-up of 4.4 years, 983 participants developed hypertension, according to the Cox proportional hazards model. The annual incidence of hypertension increased with an elevation in TG levels for men (5.88% in quartile 1, 8.30% in quartile 2, 7.62% in quartile 3, and 9.82% in quartile 4). This association was significant, even after adjustment for other risk factors: hazard ratio 1.41 [95% CI 1.07-1.85] for quartile 2, 1.30 [0.99-1.71] for quartile 3, and 1.59 [1.22-2.08] for quartile 4 compared with quartile 1 (p = 0.041 for trend). In contrast, there was no clear association between serum TG levels and the incidence of hypertension after adjustment for confounding factors among women (p = 0.240 for trend). High levels of serum TG were associated with the future incidence of hypertension in a general population of Japanese men but were not associated with that in women. Casual serum triglyceride levels and incidence of hypertension in a general Japanese population: ISSA-CKD study.

Dyslipidemia Increases the Risk of Incident Hypertension in a Large Taiwanese Population Follow-Up Study

Dyslipidemia is an important risk factor for hypertension and is strongly associated with an elevated risk of cardiovascular diseases including atherosclerosis and stroke. In this study, we investigated correlations between lipid profiles, including triglycerides, total cholesterol (Chol), high-and low-density lipoprotein cholesterol (HDL-C/LDL-C), and Chol/HDL-C, and baseline and incident hypertension. A total of 26,965 subjects with 4 years of follow-up data were enrolled from the Taiwan Biobank. In the cross-sectional cohort, associations between the prevalence of hypertension and lipid profiles were examined in all study participants (n = 26,965). In the longitudinal cohort, these associations were further assessed in the participants without baseline hypertension (n = 21,454). Multivariable analysis revealed that those in the second quartile (Q2) of triglycerides (compared to Q1; odds ratio (OR), 1.402; p < 0.001); Q3 of triglycerides (compared to Q1; OR, 1.365; p < 0.001); Q4 of triglycerides (compared to Q1; OR, 1.617; p < 0.001); Q3 of HDL-C (compared to Q1; OR, 0.886; p = 0.042); Q4 of HDL-C (compared to Q1; OR, 0.819; p = 0.002); Q2 of Chol/HDL-C (compared to Q1; OR, 1.144; p = 0.042); Q3 of Chol/HDL-C (compared to Q1; OR, 1.149; p = 0.034); and Q4 of Chol/HDL-C (compared to Q1; OR, 1.225; p = 0.002) were significantly associated with incident hypertension. In summary, high Chol/HDL-C, low HDL-C, and high triglycerides were associated with a higher risk of incident hypertension in the enrolled Taiwanese participants.

Investigating the effect of Fenofibrate on biomarkers of vascular inflammation in L-NAME induced hypertensive rats

This study aims to evaluate the impact of fenofibrate on the levels of (IL-6, hsCRP, Lp-PLA2, sCD40L, and cystatin C) in hypertensive rats. Twenty-four rats were divided into two groups each of twelve. The first group served as the normotensive group, while the second group was regarded as the hypertensive group. Each group was further divided into two subgroups (control and treated). The control subgroups only received a placebo and the treated subgroups were given fenofibrate 30 mg/kg daily orally by gastric gavage for 4 weeks. The level of hsCRP, IL6, and Lp-PLA2 significantly increased, but sCD40L and cystatin C levels were not changed in hypertensive rats. Fenofibrate has significantly reduced the levels of hsCRP and Lp-LPA2 in hypertensive rats while IL6 and sCD40s have not been changed in both groups. In conclusion, Fenofibrate has revealed a pleiotropic anti-inflammatory effect by reducing the level of hsCRP and Lp-LPA2 in hypertensive rats.

Suppression of Adenosine Deaminase and Xanthine Oxidase Activities by Mineralocorticoid and Glucocorticoid Receptor Blockades Restores Renal Antioxidative Barrier in Oral Contraceptive-Treated Dam

OBJECTIVE

We tested the hypothesis that postpartum combined oral contraceptive (COC) treatment would induce oxidative stress via the adenosine deaminase-xanthine oxidase pathway in the kidney. We also sought to determine whether mineralocorticoid receptor (MR) or glucocorticoid receptor (GR ) blockade would suppress the activities of ADA and xanthine oxidase caused by postpartum COC treatment in the kidney.

METHODS

Twenty-four Wistar dams were randomly assigned to 4 groups (n = 6/group). Dams received vehicle (po), COC (1.0 μg ethinylestradiol and 5.0 μg levonorgestrel; po), COC with GR blockade (mifepristone; 80.0 mg/kg; po), and COC with MR blockade (spironolactone; 0.25 mg/kg; po) daily between 3rd and 11th week postpartum.

RESULTS

Data showed that postpartum COC caused increased plasma creatinine and urea, increased renal triglyceride/high-density lipoprotein ratio, free fatty acid accumulation, alanine aminotransferase, gamma-glutamyltransferase, uric acid, and activities of renal XO and ADA. On the other hand, postpartum COC resulted in decreased plasma albumin, renal glutathione, and Na+-K+-ATPase activity with no effect on lactate production. However, MR or GR blockade ameliorated the alterations induced by postpartum COC treatment. The present results demonstrate that MR or GR blockade ameliorates postpartum COC-induced increased activities of ADA and xanthine oxidase and restores glutathione-dependent antioxidative defense.

CONCLUSION

These findings implicate the involvements of GR and MR in renal dysfunctions caused by COC in dams via disrupted glutathione antioxidative barrier.

Role of the Peroxisome Proliferator Activated Receptors in Hypertension

Nuclear receptors represent a large family of ligand-activated transcription factors which sense the physiological environment and make long-term adaptations by mediating changes in gene expression. In this review, we will first discuss the fundamental mechanisms by which nuclear receptors mediate their transcriptional responses. We will focus on the PPAR (peroxisome proliferator-activated receptor) family of adopted orphan receptors paying special attention to PPARγ, the isoform with the most compelling evidence as an important regulator of arterial blood pressure. We will review genetic data showing that rare mutations in PPARγ cause severe hypertension and clinical trial data which show that PPARγ activators have beneficial effects on blood pressure. We will detail the tissue- and cell-specific molecular mechanisms by which PPARs in the brain, kidney, vasculature, and immune system modulate blood pressure and related phenotypes, such as endothelial function. Finally, we will discuss the role of placental PPARs in preeclampsia, a life threatening form of hypertension during pregnancy. We will close with a viewpoint on future research directions and implications for developing novel therapies.

Relationship between casual serum triglyceride levels and the development of hypertension in Japanese

OBJECTIVE

The purpose of the present study was to investigate the effects of serum triglyceride levels on the risk of new-onset hypertension in Japanese.

METHODS

Five thousand nine hundred and thirty-three Japanese workers without hypertension at baseline, who participated in medical check-ups from 2006 to 2018, were followed retrospectively. The participants were divided into quartiles of casual serum triglyceride levels and were followed from the first to last visit of the study period. The outcome was development of hypertension. Risk estimates were computed using Cox's proportional hazards model.

RESULTS

During the follow-up period (average: 6.7 years), 946 individuals developed hypertension. The crude incidence rates of hypertension (per 1000 person-years) increased with rising serum triglyceride levels: 10.1 for quartile 1 (<0.76 mmol/l), 19.6 for quartile 2 (0.76-1.17 mmol/l), 26.0 for quartile 3 (1.18-1.84 mmol/l), and 36.5 for quartile 4 (>1.84 mmol/l) (P < 0.0001 for trend). These associations remained significant even after adjustment for other risk factors: the multivariable-adjusted hazard ratio was 1.29 (1.01-1.66) for the second quartile, 1.27 (0.99-1.63) for the third quartile, and 1.39 (1.09-1.77) for the highest quartile compared with the lowest. There were comparable effects of serum triglyceride levels for incidence of hypertension between subgroups defined by sex, obesity, and diabetes (all P > 0.1 for interaction), whereas stronger associations were observed for participants under 40 years of age than for those aged 40 or above (P = 0.002 for interaction).

CONCLUSION

Serum triglyceride levels were significantly associated with development of hypertension in a Japanese worksite population.

Beneficial effects of rosiglitazone and losartan combination in diabetic rats

Diabetes with vascular complication needs strict interventions to retard possible serious complications. This research estimated the possible interaction of rosiglitazone (RGN) with losartan (Los) in diabetic rats. Male Sprague–Dawley rats were randomly divided into nondiabetic rats, diabetic rats, and diabetic rats that received RGN, Los, or a combination of RGN and Los. Measurement of serum glucose, vascular adhesion molecule-1, interleukin-6, tumor necrosis factor-α, aortic lipid peroxide (malondialdehyde), glutathione, superoxide dismutase, and total nitrate/nitrite levels was done. Also, the effects of RGN on the relaxation created by acetylcholine and sodium nitroprusside, contraction of isolated aortic rings provoked by phenylephrine and angiotensin II were determined. Results revealed that RGN or Los had a vasodilating effect to variable degrees indicated by enhanced effects on both acetylcholine-induced relaxation and the antagonistic effect on angiotensin II and phenylephrine-stimulated contraction of diabetic aortas with significant amelioration in serum glucose, vascular adhesion molecule-1, interleukin-6, and tumor necrosis factor-α levels and aortic oxidant/antioxidant balance. Treatment of diabetic rats with a combination of RGN and Los produced a more pronounced effect on the measured parameters compared to the diabetic, RGN-, and Los-treated groups. These findings point out the beneficial effects of RGN and Los combination in diabetic rats.

The Role of PPARγ in Cardiovascular Diseases

The peroxisome proliferator-activated receptors (PPAR) belong to the nuclear superfamily of ligand-activated transcription factors. PPARγ acts as a nutrient sensor that regulates several homeostatic functions. Its disruption can lead to vascular pathologies, disorders of fatty acid/lipid metabolism and insulin resistance. PPARγ can modulate several signaling pathways connected with blood pressure regulation. Firstly, it affects the insulin signaling pathway and endothelial dysfunction by modulation of expression and/or phosphorylation of signaling molecules through the PI3K/Akt/eNOS or MAPK/ET-1 pathways. Secondly, it can modulate gene expression of the renin- angiotensin system – cascade proteins, which potentially slow down the progression of atherosclerosis and hypertension. Thirdly, it can modulate oxidative stress response either directly through PPAR or indirectly through Nrf2 activation. In this context, activation and functioning of PPARγ is very important in the regulation of several disorders such as diabetes mellitus, hypertension and/or metabolic syndrome.

Vascular and metabolic effects of omega-3 fatty acids combined with fenofibrate in patients with hypertriglyceridemia

BACKGROUND

Effects of omega-3 fatty acids (n-3 FA) combined with fenofibrate are not yet investigated, compared with fenofibrate.

METHODS

This was a randomized, single-blind, placebo-controlled, parallel study. Age, sex, and body mass index were matched among groups. All patients were recommended to maintain a low fat diet. Fifty patients with hypertriglyceridemia in each group were given placebo, n-3 FA 2g+fenofibrate 160mg (combination), or fenofibrate 160mg, respectively daily for 2months.

RESULTS

Placebo, combination, and fenofibrate significantly decreased triglycerides by 7%, 41% and 30%, respectively and triglycerides/HDL cholesterol ratio by 11%, 45% and 32%, respectively relative to baseline measurements (all P<0.05 by paired t-test). When compared with placebo and fenofibrate, these with combination were significant (P<0.001 by ANOVA). When compared with placebo, both combination and fenofibrate significantly decreased apolipoprotein B and non-HDL cholesterol and improved flow-mediated dilation and reduced CRP and fibrinogen (all P<0.05 by ANOVA), however, there were no significant differences between combination and fenofibrate. When compared with placebo, both combination and fenofibrate significantly reduced insulin and glucose (both P<0.05 by ANOVA), and improved insulin sensitivity (P=0.005 by ANOVA). However, there were no significant differences between combination and fenofibrate.

CONCLUSIONS

When compared with fenofibrate, combination significantly decreased triglycerides and triglycerides/HDL cholesterol ratio. Otherwise, combination and fenofibrate significantly reduced apolipoprotein B and non-HDL cholesterol and improved flow-mediated dilation and reduced CRP and fibrinogen to a similar extent. Also, combination and fenofibrate significantly improved insulin sensitivity to a similar extent by reducing insulin and glucose in patients with hypertriglyceridemia.

Effect of Angiotensin Receptor Blockers on Flow-Mediated Vasodilation: A Meta-Analysis of Randomized Controlled Trials

Background: In a meta-analysis, we investigated the effects of angiotensin receptor blockers (ARBs) in comparison to placebo or other classes of antihypertensive drugs on endothelial function, which was measured by brachial flow-mediated vasodilation (FMD). Methods: We searched for randomized controlled trials that compared ARBs with placebo or other classes of antihypertensive drugs in improving FMD. A random-effect model was used to compute pooled estimates. Results: In 13 trials (n = 529), ARBs were more efficacious in improving brachial FMD than placebo [pooled weighted mean change difference (WMD) 1.34%, 95% CI, 0.93-1.75%, p < 0.001]. In 15 trials (n = 918), treatment with ARBs had a significant effect on brachial FMD when compared with other antihypertensive drugs (pooled WMD 0.59%, 95% CI, 0.20-0.98%, p = 0.003 with significant heterogeneity). ARBs were also more efficacious in improving brachial FMD than calcium channel blockers (CCBs; pooled WMD 1.61%, 95% CI, 0.72-2.49%, p < 0.001) but not the other classes of drugs (p ≥ 0.072). Conclusions: This meta-analysis shows that ARBs improve brachial FMD, a marker of endothelial function, and that they are superior to placebo and CCBs. There was no significant difference in the effect on brachial FMD between ARBs and the other antihypertensive drugs.

Protective role of fibrates in cardiac ischemia/reperfusion

Prevention of myocardial injury has been considered as the most important therapeutic challenge of today. Fibrates, the agonists of the peroxisome proliferator-activated receptor (PPAR)-a receptor, have been regarded as potent therapeutic agents in this context. Hence, the present study has been designed to investigate the effect of fibrates, i.e., Clofibrate and Fenofibrate, the potent agonists PPAR-a, on ischemia-reperfusion (I/R)-induced myocardial injury. The isolated Langendorff-perfused rat hearts were subjected to global ischemia for 30 minutes followed by reperfusion for 120 minutes. Myocardial infarct size and the release of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent have been conducted to assess the degree of cardiac injury. Moreover, the oxidative stress in the heart was assessed by measuring lipid peroxidation, superoxide anion generation, and reduced glutathione. Clofibrate and Fenofibrate showed cardioprotection against I/R-induced myocardial injury in rat hearts as assessed in terms of reductions in myocardial infarct size, LDH, and CK levels in coronary effluent along with reduction in I/R-induced oxidative stress. It may be concluded that the observed cardioprotective potential of Clofibrate and Fenofibrate against I/R-induced myocardial injury was due to the reductions in infarct size and oxidative stress.

Adiponectin and cardiovascular health: an update

The global epidemic of obesity is accompanied by an increased prevalence of cardiovascular disease (CVD), in particular stroke and heart attack. Dysfunctional adipose tissue links obesity to CVD by secreting a multitude of bioactive lipids and pro-inflammatory factors (adipokines) with detrimental effects on the cardiovascular system. Adiponectin is one of the few adipokines that possesses multiple salutary effects on insulin sensitivity and cardiovascular health. Clinical investigations have identified adiponectin deficiency (hypoadiponectinaemia) as an independent risk factor for CVD. In animals, elevation of plasma adiponectin by either pharmacological or genetic approaches alleviates obesity-induced endothelial dysfunction and hypertension, and also prevents atherosclerosis, myocardial infarction and diabetic cardiomyopathy. Furthermore, many therapeutic benefits of the peroxisome-proliferator activated receptor gamma agonists, the thiazolidinediones, are mediated by induction of adiponectin. Adiponectin protects cardiovascular health through its vasodilator, anti-apoptotic, anti-inflammatory and anti-oxidative activities in both cardiac and vascular cells. This review summarizes recent findings in the understanding of the physiological role and clinical relevance of adiponectin in cardiovascular health, and in the identification of the receptor and postreceptor signalling events that mediate the cardiovascular actions of adiponectin. It also discusses adiponectin-targeted drug discovery strategies for treating obesity, diabetes and CVD.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Significant differential effects of omega-3 fatty acids and fenofibrate in patients with hypertriglyceridemia

BACKGROUND

Omega-3 fatty acids and fenofibrate are both used to treat patients with hypertriglyceridemia. However, a head-to-head comparison of the lipoprotein and metabolic effects of these two medicines has not been published.

METHODS

This was a randomized, single-blind, placebo-controlled, parallel study. Age, sex, and body mass index were matched among groups. All patients were recommended to maintain a low fat diet. Fifty patients in each group were given placebo, omega-3 fatty acids 2 g (most commonly used dosage in Korean patients), or fenofibrate 160 mg, respectively daily for 2 months.

RESULTS

Omega-3 fatty acids therapy decreased triglycerides by 21% and triglycerides/HDL cholesterol and improved flow-mediated dilation (P<0.01), however, did not significantly change insulin, plasma adiponectin levels, and insulin sensitivity (determined by QUICKI) relative to baseline measurements. Fenofibrate therapy decreased total cholesterol, triglycerides by 29%, and triglycerides/HDL-cholesterol (all P<0.01) and improved flow-mediated dilation when compared with baseline. When compared with placebo and omega-3 fatty acids, fenofibrate therapy decreased non-HDL cholesterol (P<0.001) and triglycerides/HDL cholesterol (P=0.016) while increasing HDL cholesterol (P<0.001) and apolipoprotein AI (P=0.001). Of note, when compared with omega-3 fatty acids, fenofibrate therapy decreased fasting insulin (P=0.023) and increased plasma adiponectin (P=0.002) and insulin sensitivity (P=0.015).

CONCLUSIONS

Omega-3 fatty acids and fenofibrate therapy promoted similar changes in triglycerides and endothelium-dependent dilation. However, fenofibrate therapy had substantially better effects on lipoprotein and metabolic profiles in patients with hypertriglyceridemia.

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.

Fenofibrate: a review of its use in dyslipidaemia

Fenofibrate is a fibric acid derivative indicated for the treatment of severe hypertriglyceridaemia and mixed dyslipidaemia in patients who have not responded to nonpharmacological therapies. The lipid-modifying effects of fenofibrate are mediated by the activation of peroxisome proliferator-activated receptor-α. Fenofibrate also has nonlipid, pleiotropic effects (e.g. reducing levels of fibrinogen, C-reactive protein and various pro-inflammatory markers, and improving flow-mediated dilatation) that may contribute to its clinical efficacy, particularly in terms of improving microvascular outcomes. Fenofibrate improves the lipid profile (particularly triglyceride [TG] and high-density lipoprotein-cholesterol [HDL-C] levels) in patients with dyslipidaemia. Compared with statin monotherapy, fenofibrate monotherapy tends to improve TG and HDL-C levels to a significantly greater extent, whereas statins improve low-density lipoprotein-cholesterol (LDL-C) and total cholesterol levels to a significantly greater extent. Fenofibrate is also associated with promoting a shift from small, dense, atherogenic LDL particles to larger, less dense LDL particles. Combination therapy with a statin plus fenofibrate generally improves the lipid profile to a greater extent than monotherapy with either agent in patients with dyslipidaemia and/or type 2 diabetes mellitus or the metabolic syndrome. In the pivotal FIELD and ACCORD trials in patients with type 2 diabetes, fenofibrate did not significantly reduce the risk of coronary heart disease events to a greater extent than placebo, and simvastatin plus fenofibrate did not significantly reduce the risk of major cardiovascular (CV) events to a greater extent than simvastatin plus placebo. However, the risk of some nonfatal macrovascular events and the incidence of certain microvascular outcomes were reduced significantly more with fenofibrate than with placebo in the FIELD trial, and in the ACCORD trial, patients receiving simvastatin plus fenofibrate were less likely to experience progression of diabetic retinopathy than those receiving simvastatin plus placebo. Subgroup analyses in the FIELD and ACCORD Lipid trials indicate that fenofibrate is of the greatest benefit in decreasing CV events in patients with atherogenic dyslipidaemia. Fenofibrate is generally well tolerated when administered alone or in combination with a statin. Thus, in patients with dyslipidaemia, particularly atherogenic dyslipidaemia, fenofibrate is a useful treatment option either alone or in combination with a statin.

Enhanced levels of soluble CD40 ligand and C-reactive protein in a total of 312 patients with metabolic syndrome

The metabolic syndrome (MS) is associated with a systemic inflammatory response that plays an important pathogenetic role in atherothrombotic disease. Increasing evidence indicates that CD40-CD40 ligand interactions constitute an important mediator for vascular inflammation. The purpose of this study was to assess whether high-sensitivity C-reactive protein (hs-CRP) and soluble CD40 ligand (sCD40L) levels were increased in patients with MS. During the study period from January 2004 to August 2004, 312 patients with MS and 98 control subjects were included. Anthropometric measurements, blood pressure assessment, electrocardiography, and blood measurements including fasting blood glucose, postprandial blood glucose, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, glycated hemoglobin, white blood cell (WBC), platelets, hs-CRP, and sCD40L were performed. Patients with MS were divided into 3 groups based upon their glucose tolerance (group 1, normal glucose tolerance; group 2, prediabetic group; and group 3, diabetes mellitus). Patients with MS showed a significant increase of WBC, hs-CRP, and sCD40L levels compared with control subjects. The levels of both hs-CRP and sCD40L were positively correlated with body mass index (BMI). High-sensitivity CRP levels were also positively correlated with waist circumferences, fasting blood glucose, postprandial blood glucose, and glycated hemoglobin, and negatively correlated with high-density lipoprotein cholesterol. In patients with MS, both hs-CRP and sCD40L levels were positively correlated with WBC count. We found a positive correlation between sCD40L and platelets. Among the subgroups of patients with MS, the mean levels of WBC, hs-CRP, and sCD40L did not show any significant differences. In conclusion, elevated levels of WBC, hs-CRP, and sCD40L in MS patients provide further insight into the relationship between MS and inflammation. In our study, positive correlations between BMI and both hs-CRP and sCD40L levels suggest that BMI is an important determinant of a chronic inflammatory state in patients with MS. Moreover, this study reports significantly increased levels of WBC, hs-CRP, and sCD40L not only in diabetic subjects with MS but also in prediabetic subjects and nondiabetic subjects with MS compared with control subjects. Our data suggest that MS patients have proinflammatory state independent of their glucose tolerance status. In our study, the positive correlation between the levels of sCD40L and platelets in patients with MS supports previous reports indicating that sCD40L are derived predominantly from platelets.

Current pharmacotherapeutic concepts for the treatment of cardiovascular disease in diabetics

With the growing worldwide obesity epidemic, obesity, type 2 diabetes mellitus and hypertension leading to premature cardiovascular events, are increasingly prevalent. Diabetes mellitus is a significant public health concern and more aggressive management of the condition and its complications, particularly cardiovascular disease, is warranted. Endothelial cell dysfunction is now known to be present at the earliest stages of metabolic syndrome, and insulin resistance and may precede the clinical diagnosis of type 2 diabetes mellitus by several years. The current focus on endothelial cell function as a potential target of pharmacotherapy in the management of cardiovascular disease in diabetics seems warranted, though not all drugs currently prescribed target endothelial cell function equally. In this review, we consider the six classes of drugs currently prescribed for the treatment of hypertension as they impact endothelial cell function and advocate for the development of novel drugs that can repair the endothelium and enhance nitric oxide availability thus preventing future cardiovascular events.

Vascular insulin resistance in prehypertensive rats: role of PI3-kinase/Akt/eNOS signaling

It is well known that systemic insulin resistance is closely associated with the metabolic syndrome including type 2 diabetes and hypertension. However, it remains unclear whether vascular insulin resistance acts as an early etiologic factor for the development of hypertension. Male spontaneously hypertensive rats (SHRs) aged 5 weeks (young) and 15 weeks (adult) were studied and vascular insulin resistance was assessed as the function of isolated aortic vasodilatory response to insulin in vitro. Compared with Wistar-Kyoto (WKY) rats, adult SHRs exhibited significant hypertension with significantly decreased aortic vasodilatation to insulin, whereas young SHRs had normal blood pressure but exhibited similar vascular insulin resistance. Both young and adult SHRs showed significant downregulated expression of PI3-kinase and decreased insulin-stimulated phosphorylations of Akt and eNOS in vascular tissues. Treatment with rosiglitazone (RSG), an insulin sensitizer, for 2 weeks increased vascular PPARgamma expression and restored PI3-kinase/Akt/eNOS-mediated signaling pathway only in young SHRs. More importantly, this treatment improved aortic vasodilatory response to insulin in young but not in adult SHRs. In summary, vascular insulin resistance, characterized by the impairment of PI3-kinase/Akt/eNOS-mediated signaling in vascular endothelium, may play important roles in endothelial dysfunction and subsequent development of hypertension in normotensive young SHRs.

Serum adiponectin is decreased in patients with familial combined hyperlipidemia and normolipaemic relatives and is influenced by lipid-lowering treatment

BACKGROUND AND AIMS

Hypoadiponectinemia has been reported in patients with familial combined hyperlipidemia (FCHL) presenting increased waist circumference and insulin resistance. However, no studies have evaluated this association in non-obese FCHL patients. Moreover, it is unclear whether correction of lipoprotein abnormalities may influence adiponectin levels in FCHL.

METHODS AND RESULTS

We have compared serum levels of adiponectin in 199 non-obese FCHL patients (BMI 25.96+/-3.7), 116 normolipaemic (NL) non-affected relatives (BMI 24.4+/-4.0) and 192 controls (BMI 28.0+/-7.4). In a subgroup of FCHL patients, changes in adiponectin levels after treatment with atorvastatin (n=22) or fenofibrate (n=26) were also evaluated. FCHL patients as well as their NL relatives showed lower serum adiponectin levels compared to controls (9.7+/-5.4 microg/mL, 10.7+/-5.3 microg/mL and 17.3+/-13.7microg/mL, respectively; p<0.0001 for all comparisons). After controlling for confounders, the strongest association with hypoadiponectinemia was observed with family history of FCHL, followed by HDL-C (negatively) and age (positively). These variables jointly explained 15% of the total variance of serum adiponectin levels. After 24-week of treatment, adiponectin was increased by 12.5% (p<0.05) by atorvastatin and was reduced by 10% by fenofibrate, resulting in a treatment difference of 22.5% in favor of atorvastatin (p<0.017).

CONCLUSIONS

FCHL patients showed lower serum adiponectin levels compared to controls. Also normolipaemic relatives of FCHL patients presented decreased levels of adiponectin, suggesting a possible common background in the determination of this abnormality. Overall, these observations indicate that hypoadiponectinemia may be an inherent characteristic of the FCHL phenotype. In FCHL patients hypoadiponectinemia may be partially corrected by atorvastatin but not by fenofibrate treatment.

Antiatherosclerotic and anti-insulin resistance effects of adiponectin: basic and clinical studies

Adiponectin is a protein secreted by adipose cells that may couple regulation of insulin sensitivity with energy metabolism and serve to link obesity with insulin resistance. Obesity-related disorders characterized by insulin resistance including the metabolic syndrome, diabetes, atherosclerosis, hypertension, and coronary artery disease are associated with both decreased adiponectin levels and endothelial dysfunction. Recent studies demonstrate that adiponectin has insulin-sensitizing effects as well as antiatherogenic properties. Lifestyle modifications and some drug therapies to treat atherosclerosis, hypertension, diabetes, and coronary heart disease have important effects in increasing adiponectin levels, decreasing insulin resistance, and improving endothelial dysfunction. In this review, we discuss insights into the relationships between adiponectin levels, insulin resistance, and endothelial dysfunction that are derived from various therapeutic interventions. The effects of lifestyle modifications and cardiovascular drugs on adiponectin levels and insulin resistance suggest plausible mechanisms that may be important for understanding and treating atherosclerosis and coronary heart disease.

Combination therapy for treatment or prevention of atherosclerosis: focus on the lipid-RAAS interaction

Large clinical trials demonstrate that control of blood pressure or hyperlipidemia reduces risk for cardiovascular events by approximately 30%. Factors that may further reduce remaining risk are not definitively established. One potential target is atherosclerosis, a crucial feature in the pathogenesis of cardiovascular diseases whose development is determined by multiple mechanism including complex interactions between endothelial dysfunction and insulin resistance. Reciprocal relationships between endothelial dysfunction and insulin resistance as well as cross-talk between hyperlipidemia and the rennin-angiotensin-aldosterone system may contribute to development of atherosclerosis. Therefore, one appealing strategy for prevention or treatment of atherosclerosis may be to simultaneously address several risk factors with combination therapies that target multiple pathogenic mechanisms. Combination therapy with statins, peroxisome proliferators-activated receptor agonists, and rennin-angiotensin-aldosterone system blockers demonstrate additive beneficial effects on endothelial dysfunction and insulin resistance when compared with monotherapies in patients with cardiovascular risk factors. Additive beneficial effects of combined therapy are mediated by both distinct and interrelated mechanisms, consistent with both pre-clinical and clinical investigations. Thus, combination therapy may be an important concept in developing more effective strategies to treat and prevent atherosclerosis, coronary heart disease, and co-morbid metabolic disorders characterized by endothelial dysfunction and insulin resistance.

Top-down lipidomics reveals ether lipid deficiency in blood plasma of hypertensive patients

Background

Dyslipoproteinemia, obesity and insulin resistance are integrative constituents of the metabolic syndrome and are major risk factors for hypertension. The objective of this study was to determine whether hypertension specifically affects the plasma lipidome independently and differently from the effects induced by obesity and insulin resistance.

Methodology/Principal Findings

We screened the plasma lipidome of 19 men with hypertension and 51 normotensive male controls by top-down shotgun profiling on a LTQ Orbitrap hybrid mass spectrometer. The analysis encompassed 95 lipid species of 10 major lipid classes. Obesity resulted in generally higher lipid load in blood plasma, while the content of tri- and diacylglycerols increased dramatically. Insulin resistance, defined by HOMA-IR >3.5 and controlled for BMI, had little effect on the plasma lipidome. Importantly, we observed that in blood plasma of hypertensive individuals the overall content of ether lipids decreased. Ether phosphatidylcholines and ether phosphatidylethanolamines, that comprise arachidonic (20∶4) and docosapentaenoic (22∶5) fatty acid moieties, were specifically diminished. The content of free cholesterol also decreased, although conventional clinical lipid homeostasis indices remained unaffected.

Conclusions/Significance

Top-down shotgun lipidomics demonstrated that hypertension is accompanied by specific reduction of the content of ether lipids and free cholesterol that occurred independently of lipidomic alterations induced by obesity and insulin resistance. These results may form the basis for novel preventive and dietary strategies alleviating the severity of hypertension.

Taurine supplementation prevents ethanol-induced decrease in serum adiponectin and reduces hepatic steatosis in rats

Chronic ethanol feeding decreases expression of adiponectin by adipocytes and circulating adiponectin. Adiponectin treatment during chronic ethanol feeding prevents liver injury in mice. Chronic ethanol feeding also increases oxidative and endoplasmic reticulum (ER) stress in adipose tissue. Here we tested the hypothesis that supplemental taurine, an amino acid that functions as a chemical chaperone/osmolyte and enhances cellular antioxidant activity, would prevent ethanol-induced decreases in adiponectin expression and attenuate liver injury. Serum adiponectin concentrations decreased as early as 4 to 7 days after feeding rats a 36% ethanol diet. This rapid decrease was associated with increased oxidative, but not ER, stress in subcutaneous adipose tissue. Taurine prevented ethanol-induced oxidative stress and increased inflammatory cytokine expression in adipose tissue. Ethanol feeding also rapidly decreased expression of transcription factors regulating adiponectin expression (CCAAT/enhancer binding protein alpha; peroxisome proliferator-activated receptor alpha/gamma) in subcutaneous adipose tissue. Taurine prevented the ethanol-induced decrease in CCAAT/enhancer binding protein alpha and peroxisome proliferator-activated receptor alpha, normalizing adiponectin messenger (m)RNA and serum adiponectin concentrations. In the liver, taurine prevented ethanol-induced oxidative stress and attenuated tumor necrosis factor alpha expression and steatosis, at least in part, by increasing expression of genes involved in fatty acid oxidation.

CONCLUSION

In subcutaneous adipose tissue, taurine decreased ethanol-induced oxidative stress and cytokine expression, as well as normalized expression of adiponectin mRNA. Taurine prevented ethanol-induced decreases in serum adiponectin; normalized adiponectin was associated with a reduction in hepatic oxidative stress, tumor necrosis factor alpha expression, and steatosis. Taken together, these data demonstrate that taurine has important protective effects against ethanol-induced tissue injury in both adipose and liver tissue.

Does reversal of oxidative stress and inflammation provide vascular protection?

Chronic inflammation is a pathogenic feature of atherosclerosis and cardiovascular disease mediated by substances including angiotensin II, proinflammatory cytokines, and free fatty acids. This promotes generation of reactive oxygen species in vascular endothelial cells and smooth muscle cells, which mediate injury through several mechanisms. Reciprocal relationships between endothelial dysfunction and insulin resistance as well as cross-talk between hyperlipidaemia and the renin-angiotensin-aldosterone system (RAAS) at multiple levels contribute importantly to a variety of risk factors. Therefore, combination therapy that simultaneously addresses multiple mechanisms for the pathogenesis of atherosclerosis is an attractive emerging concept for slowing progression of atherosclerosis. Combined therapy with statins, peroxisome proliferator-activated receptors, and RAAS blockade demonstrates additive beneficial effects on endothelial dysfunction and insulin resistance when compared with monotherapies in patients with cardiovascular risk factors due to both distinct and interrelated mechanisms. These additive beneficial effects of combined therapies are consistent with laboratory and recent clinical studies. Thus, combination therapy may be an important paradigm for treating and slowing progression of atherosclerosis, coronary heart disease, and co-morbid metabolic disorders characterized by endothelial dysfunction and insulin resistance.

Cocoa consumption for 2 wk enhances insulin-mediated vasodilatation without improving blood pressure or insulin resistance in essential hypertension

BACKGROUND

Essential hypertension is characterized by reciprocal relations between endothelial dysfunction and insulin resistance. Cocoa flavanols stimulate production of the vasodilator nitric oxide from vascular endothelium.

OBJECTIVE

The objective was to test the hypothesis that consumption of cocoa may simultaneously lower blood pressure, improve endothelial dysfunction, and ameliorate insulin resistance in subjects with essential hypertension.

DESIGN

We conducted a randomized, placebo-controlled, double-blind, crossover trial of a flavanol-rich cocoa drink (150 mL twice a day, approximately 900 mg flavanols/d) in individuals with essential hypertension (n = 20). Antihypertensive medications were discontinued before study enrollment. After a 7-d cocoa-free run-in period, cocoa or flavanol-poor placebo (approximately 28 mg flavanols/d) treatment for 2 wk was followed by a 1-wk washout and then crossover to the other treatment arm. Blood pressure was measured thrice weekly. At baseline and after each treatment period, we assessed insulin sensitivity (hyperinsulinemic-isoglycemic glucose clamp) and insulin-stimulated changes in brachial artery diameter and forearm skeletal muscle capillary recruitment (Doppler ultrasound with or without microbubble contrast).

RESULTS

Cocoa treatment for 2 wk increased insulin-stimulated changes in brachial artery diameter when compared with placebo [median percentage increase from baseline (25th-75th percentile): 8.3 (4.2-11.3) compared with 5.9 (-0.3 to 9.6); P < 0.04]. Nevertheless, cocoa treatment did not significantly reduce blood pressure or improve insulin resistance and had no significant effects on skeletal muscle capillary recruitment, circulating plasma concentrations of adipocytokines, or endothelial adhesion molecules.

CONCLUSIONS

Daily consumption of flavanol-rich cocoa for 2 wk is not sufficient to reduce blood pressure or improve insulin resistance in human subjects with essential hypertension. This trial was registered at clinicaltrials.gov as NCT00099476.

Vascular and metabolic effects of treatment of combined hyperlipidemia: focus on statins and fibrates

Combined hyperlipidemia results from overproduction of hepatically synthesized apolipoprotein B in very low-density lipoproteins in association with reduced lipoprotein lipase activity. Thus, this condition is typically characterized by concurrent elevations in total cholesterol and triglycerides with decreased high-density lipoprotein cholesterol. High levels of apolipoprotein B-containing lipoproteins, most prominently carried by low-density lipoprotein (LDL) particles, are an important risk factor for coronary heart disease. Statin therapy is highly effective at lowering LDL cholesterol. Despite the benefits of statin treatment for lowering total and LDL cholesterol, many statin-treated patients still have initial or recurrent coronary heart disease events. In this regard, combined therapy with statins and fibrates is more effective in controlling atherogenic dyslipidemia in patients with combined hyperlipidemia than either drug alone. Furthermore, statins and fibrates activate PPARalpha in a synergistic manner providing a molecular rationale for combination treatment in coronary heart disease. Endothelial dysfunction associated with cardiovascular diseases may contribute to insulin resistance so that there may also be additional beneficial metabolic effects of combined statin/fibrates therapy. However, there has been little published evidence that combined therapy is synergistic or even better than monotherapy alone in clinical studies. Therefore, there is a great need to study the effects of combination therapy in patients. When statins are combined with gemfibrozil therapy, this is more likely to be accompanied by myopathy. However, this limitation is not observed when fenofibrate, bezafibrate, or ciprofibrate are used in combination therapy.

Endothelial function, arterial stiffness and lipid lowering drugs

The endothelium is a dynamic organ that plays a pivotal role in cardiovascular homeostasis. Alteration in endothelial function precedes the development of atherosclerosis and contributes to its initiation, perpetuation and clinical manifestations. It has been suggested that the assessment of endothelial function could represent a barometer of vascular health that could be used to gauge cardiovascular risk. This review summarises the various methods used to assess endothelium-dependent vasodilatation and their potential prognostic implications. In addition, the techniques used to evaluate arterial stiffness are discussed. The latter is to some extent controlled by the endothelium and has been the subject of considerable research in recent years. This paper also discusses the effects of lipid lowering treatment on both endothelial function and arterial stiffness.

Cardiovascular actions of insulin

Insulin has important vascular actions to stimulate production of nitric oxide from endothelium. This leads to capillary recruitment, vasodilation, increased blood flow, and subsequent augmentation of glucose disposal in classical insulin target tissues (e.g., skeletal muscle). Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways regulating endothelial production of nitric oxide share striking parallels with metabolic insulin-signaling pathways. Distinct MAPK-dependent insulin-signaling pathways (largely unrelated to metabolic actions of insulin) regulate secretion of the vasoconstrictor endothelin-1 from endothelium. These and other cardiovascular actions of insulin contribute to coupling metabolic and hemodynamic homeostasis under healthy conditions. Cardiovascular diseases are the leading cause of morbidity and mortality in insulin-resistant individuals. Insulin resistance is typically defined as decreased sensitivity and/or responsiveness to metabolic actions of insulin. This cardinal feature of diabetes, obesity, and dyslipidemia is also a prominent component of hypertension, coronary heart disease, and atherosclerosis that are all characterized by endothelial dysfunction. Conversely, endothelial dysfunction is often present in metabolic diseases. Insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling that in vascular endothelium contributes to a reciprocal relationship between insulin resistance and endothelial dysfunction. The clinical relevance of this coupling is highlighted by the findings that specific therapeutic interventions targeting insulin resistance often also ameliorate endothelial dysfunction (and vice versa). In this review, we discuss molecular mechanisms underlying cardiovascular actions of insulin, the reciprocal relationships between insulin resistance and endothelial dysfunction, and implications for developing beneficial therapeutic strategies that simultaneously target metabolic and cardiovascular diseases.

Adiponectin and Cardiovascular Disease

Adiponectin is a protein secreted specifically by adipose cells that may couple regulation of insulin sensitivity with energy metabolism and serve to link obesity with insulin resistance. Obesity-related disorders including the metabolic syndrome, diabetes, atherosclerosis, hypertension, and coronary artery disease are associated with decreased plasma levels of adiponectin, insulin resistance, and endothelial dysfunction. Adiponectin has insulin-sensitizing effects as well as antiatherogenic properties. Lifestyle modifications and some drug therapies to treat atherosclerosis, hypertension, and coronary heart disease have important effects to simultaneously increase adiponectin levels, decrease insulin resistance, and improve endothelial dysfunction. In this review, we discuss insights into the relationships between adiponectin levels, insulin resistance, and endothelial dysfunction that are derived from various therapeutic interventions. The effects of lifestyle modifications and cardiovascular drugs on adiponectin levels and insulin resistance suggest plausible mechanisms that may be important for treating atherosclerosis and coronary heart disease.

Reciprocal relationships between abnormal metabolic parameters and endothelial dysfunction

PURPOSE OF REVIEW

Endothelial dysfunction plays a crucial role in the pathogenesis of atherosclerosis and related cardiovascular diseases. Glucotoxicity, lipotoxicity, and inflammation all independently contribute to development of both endothelial dysfunction and insulin resistance. We review pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance and recent insights from therapeutic interventions to improve both metabolic and vascular function.

RECENT FINDINGS

Shared causal factors such as glucotoxicity, lipotoxicity, and inflammation interact at multiple levels creating reciprocal relationships between insulin resistance and endothelial dysfunction that help to explain frequent clustering of metabolic and cardiovascular disorders. Metabolic abnormalities implicated in the development of insulin resistance, including hyperglycemia, elevated levels of free fatty acids, accumulation of advanced glycation end products, dyslipidemias, and decreased levels of adiponectin, also contribute importantly to endothelial dysfunction. Diet, exercise, cardiovascular drugs, and insulin sensitizers simultaneously improve endothelium-dependent vascular function, reduce inflammation, and improve insulin sensitivity by both distinct and interrelated mechanisms.

SUMMARY

Pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance contribute to clustering of metabolic and cardiovascular diseases represented by the metabolic syndrome. Therapeutic interventions that target endothelial dysfunction or insulin resistance often simultaneously improve both metabolic and vascular function.

Fenofibrate

Fenofibrate is a fibric acid derivative indicated for use in the treatment of primary hypercholesterolaemia, mixed dyslipidaemia and hypertriglyceridaemia in adults who have not responded to nonpharmacological measures. Its lipid-modifying effects are mediated by activation of peroxisome proliferator-activated receptor-alpha. Fenofibrate also has nonlipid (i.e. pleiotropic) effects (e.g. it reduces fibrinogen, C-reactive protein and uric acid levels and improves flow-mediated dilatation). Fenofibrate improves lipid levels (in particular triglyceride [TG] and high-density lipoprotein-cholesterol [HDL-C] levels) in patients with primary dyslipidaemia. Its lipid-lowering profile means that fenofibrate is particularly well suited for use in atherogenic dyslipidaemia (characterised by high TG levels, low HDL-C levels and small, dense low-density lipoprotein [LDL] particles), which is commonly seen in patients with the metabolic syndrome and type 2 diabetes mellitus. Indeed, fenofibrate improves the components of atherogenic dyslipidaemia in patients with these conditions, including a shift from small, dense LDL particles to larger, more buoyant LDL particles. Greater improvements in lipid levels are seen when fenofibrate is administered in combination with an HMG-CoA reductase inhibitor (statin) or in combination with ezetimibe, compared with monotherapy with these agents. In the DAIS study, fenofibrate significantly slowed the angiographic progression of focal coronary atherosclerosis in patients with type 2 diabetes. In terms of clinical outcomes, although no significant reduction in the risk of coronary events was seen with fenofibrate in the FIELD trial in patients with type 2 diabetes, treatment was associated with a significantly reduced risk of total cardiovascular disease (CVD) events, primarily through the prevention of non-fatal myocardial infarction and coronary revascularisation. Subgroup analyses revealed significant reductions in total CVD events and coronary heart disease events in patients with no previous CVD, suggesting a potential role for primary prevention with fenofibrate in patients with early type 2 diabetes. Improvements were also seen in microvascular outcomes with fenofibrate in the FIELD trial. Fenofibrate is generally well tolerated, both as monotherapy and when administered in combination with a statin. Combination therapy with fenofibrate plus a statin appears to be associated with a low risk of rhabdomyolysis; no cases of rhabdomyolysis were reported in patients receiving such therapy in the FIELD trial. Thus, fenofibrate is a valuable lipid-lowering agent, particularly in patients with atherogenic dyslipidaemia.

Treatment of spontaneously hypertensive rats with rosiglitazone and/or enalapril restores balance between vasodilator and vasoconstrictor actions of insulin with simultaneous improvement in hypertension and insulin resistance

Spontaneously hypertensive rats (SHRs) exhibit endothelial dysfunction and insulin resistance. Reciprocal relationships between endothelial dysfunction and insulin resistance may contribute to hypertension by causing imbalanced regulation of endothelial-derived vasodilators (e.g., nitric oxide) and vasoconstrictors (e.g., endothelin-1 [ET-1]). Treatment of SHRs with rosiglitazone (insulin sensitizer) and/or enalapril (ACE inhibitor) may simultaneously improve hypertension, insulin resistance, and endothelial dysfunction by rebalancing insulin-stimulated production of vasoactive mediators. When compared with WKY control rats, 12-week-old vehicle-treated SHRs were hypertensive, overweight, and insulin resistant, with elevated fasting levels of insulin and ET-1 and reduced serum adiponectin levels. In mesenteric vascular beds (MVBs) isolated from vehicle-treated SHRs and preconstricted with norepinephrine (NE) ex vivo, vasodilator responses to insulin were significantly impaired, whereas the ability of insulin to oppose vasoconstrictor actions of NE was absent (versus WKY controls). Three-week treatment of SHRs with rosiglitazone and/or enalapril significantly reduced blood pressure, insulin resistance, fasting insulin, and ET-1 levels and increased adiponectin levels to values comparable with those observed in vehicle-treated WKY controls. By restoring phosphatidylinositol 3-kinase-dependent effects, rosiglitazone and/or enalapril therapy of SHRs also significantly improved vasodilator responses to insulin in MVB preconstricted with NE ex vivo. Taken together, our data provide strong support for the existence of reciprocal relationships between endothelial dysfunction and insulin resistance that may be relevant for developing novel therapeutic strategies for the metabolic syndrome.