Pioglitazone shift circadian rhythm of blood pressure from non-dipper to dipper type in type 2 diabetes mellitus

Effects of Nondipping Blood Pressure Changes: A Nephrologist Prospect

Blood pressure (BP) variations depend on various internal, environmental, and behavioral factors. BP fluctuations occur both in normotensive and hypertensive people. Although it fluctuates over the 24-hr day and night, the morning BP increases after waking up and declines throughout sleep. It is typical for BP to decrease by 10% to 20%, while sleeping, known as dipping BP. However, if there is no decrease in nighttime mean systolic BP or a drop of less than 10 mmHg, it is called nondipping BP. Conversely, reverse dipping BP means an increase in mean systolic BP instead of a drop during the night. Reverse dipping is observed in hypertension (HTN), diabetes mellitus (DM), chronic kidney disease (CKD), and obstructive sleep apnea (OSA) syndrome. The introduction of ambulatory BP monitoring (ABPM) led to the emergence of identifying normal and elevated BP patterns. Non-dipping BP increases the risk of cardiovascular system (CVS) complications such as left ventricular hypertrophy, proteinuria, glomerular filtration rate (GFR) reduction, and CKD progression. A loss or blunting of the normal BP profile is recognized as a deleterious variant, and restoring abnormal BP patterns has been reported to significantly impact end-organ damage, morbidity, and mortality. In this non-systematic clinically-oriented, comprehensive review, we aim to update the BP variables and the pathophysiology of nondipping BP and point out the areas which need more investigation from a nephrology perspective because the nondipping BP increases the risk of proteinuria, GFR reduction, and CKD progression. A literature search of PubMed, Google, EMBASE, and Google Scholar was conducted. Checks of selected papers and relevant reviews complemented the electronic search. With improved BP measurement methods, the physiology of BP profile variations is readily detectable during the day and night. A nondipping BP profile is a distinct BP pattern that may have significant end-organ damage effects and therapeutic importance for nephrologists. The pathophysiology of the nondipping BP variant must be clarified to prevent complications, and further investigations are required. Furthermore, there is debate about the best BP index to utilize: systolic BP, diastolic BP, mean arterial pressure, or a mixture of all. All these areas are important and need new research projects.

PPARγ (Peroxisome Proliferator-Activated Receptor γ) Deacetylation Suppresses Aging-Associated Atherosclerosis and Hypercholesterolemia

BACKGROUND

Atherosclerosis is a medical urgency manifesting at the onset of hypercholesterolemia and is associated with aging. Activation of PPARγ (peroxisome proliferator-activated receptor γ) counteracts metabolic dysfunction influenced by aging, and its deacetylation displays an atheroprotective property. Despite the marked increase of PPARγ acetylation during aging, it is unknown whether PPARγ acetylation is a pathogenic contributor to aging-associated atherosclerosis.

METHODS

Mice with constitutive deacetylation-mimetic PPARγ mutations on lysine residues K268 and K293 (2KR) in an LDL (low-density lipoprotein)-receptor knockout (Ldlr-/-) background (2KR:Ldlr-/-) were aged for 18 months on a standard laboratory diet to examine the cardiometabolic phenotype, which was confirmed in Western-type diet-fed 2KR:Ldlr+/- mice. Whole-liver RNA-sequencing and in vitro studies in bone marrow-derived macrophages were conducted to decipher the mechanism.

RESULTS

In contrast to severe atherosclerosis in WT:Ldlr-/- mice, aged 2KR:Ldlr-/- mice developed little to no plaque, which was underlain by a significantly improved plasma lipid profile, with particular reductions in circulating LDL. The protection from hypercholesterolemia was recapitulated in Western-type diet-fed 2KR:Ldlr+/- mice. Liver RNA-sequencing analysis revealed suppression of liver inflammation rather than changes in cholesterol metabolism. This anti-inflammatory effect of 2KR was attributed to polarized M2 activation of macrophages. Additionally, the upregulation of core circadian component Bmal1 (brain and muscle ARNT-like 1), perceived to be involved in anti-inflammatory immunity, was observed in the liver and bone marrow-derived macrophages.

CONCLUSIONS

PPARγ deacetylation in mice prevents the development of aging-associated atherosclerosis and hypercholesterolemia, in association with the anti-inflammatory phenotype of 2KR macrophages.

PPAR-γ Agonist Pioglitazone Restored Mouse Liver mRNA Expression of Clock Genes and Inflammation-Related Genes Disrupted by Reversed Feeding

Introduction

The master clock, which is located in the suprachiasmatic nucleus (SCN), harmonizes clock genes present in the liver to synchronize life rhythms and bioactivity with the surrounding environment. The reversed feeding disrupts the expression of clock genes in the liver. Recently, a novel role of PPAR-γ as a regulator in correlating circadian rhythm and metabolism was demonstrated. This study examined the influence of PPAR-γ agonist pioglitazone (PG) on the mRNA expression profile of principle clock genes and inflammation-related genes in the mouse liver disrupted by reverse feeding.

Methods

Mice were randomly assigned to daytime-feeding and nighttime-feeding groups. Mice in daytime-feeding groups received food from 7 AM to 7 PM, and mice in nighttime-feeding groups received food from 7 PM to 7 AM. PG was administered in the dose of 20 mg/kg per os as aqueous suspension 40 μl at 7 AM or 7 PM. Each group consisted of 12 animals. On day 8 of the feeding intervention, mice were sacrificed by cervical dislocation at noon (05 hours after light onset (HALO)) and midnight (HALO 17). Liver expressions of Bmal1, Clock, Rev-erb alpha, Cry1, Cry2, Per1, Per2, Cxcl5, Nrf2, and Ppar-γ were determined by quantitative reverse transcription PCR. Liver expression of PPAR-γ, pNF-κB, and IL-6 was determined by Western blotting. Glucose, ceruloplasmin, total cholesterol, triglyceride concentrations, and ALT and AST activities were measured in sera by photometric methods. The null hypothesis tested was that PG and the time of its administration have no influence on the clock gene expression impaired by reverse feeding.

Results

Administration of PG at 7 AM to nighttime-feeding mice did not reveal any influence on the expression of the clock or inflammation-related genes either at midnight or at noon. In the daytime-feeding group, PG intake at 7 PM led to an increase in Per2 and Rev-erb alpha mRNA at noon, an increase in Ppar-γ mRNA at midnight, and a decrease in Nfκb (p65) mRNA at noon. In general, PG administration at 7 PM slightly normalized the impaired expression of clock genes and increased anti-inflammatory potency impaired by reversed feeding. This pattern was supported by biochemical substrate levels—glucose, total cholesterol, ALT, and AST activities. The decrease in NF-κB led to the inhibition of serum ceruloplasmin levels as well as IL-6 in liver tissue. According to our data, PG intake at 7 PM exerts strong normalization of clock gene expression with a further increase in Nrf2 and, especially, Ppar-γ and PPAR-γ expression with inhibition of Nfκb and pNF-κB expression in daytime-feeding mice. These expression changes resulted in decreased hyperglycemia, hypercholesterolemia, ALT, and AST activities. Thus, PG had a potent chronopharmacological effect when administered at 7 PM to daytime-feeding mice.

Conclusions

Our study indicates that reversed feeding induced the disruption of mouse liver circadian expression pattern of clock genes accompanied by increasing Nfκb and pNF-κB and IL-6 expression and decreasing Nrf2 and PPAR-γ. Administration of PG restored the clock gene expression profile and decreased Nfκb, pNF-κB, and IL-6, as well as increased Nrf2, Ppar-γ, and PPAR-γ expression. PG intake at 7 PM was more effective than at 7 AM in reversed feeding mice.

A wrinkle in time: circadian biology in pulmonary vascular health and disease

An often overlooked element of pulmonary vascular disease is time. Cellular responses to time, which are regulated directly by the core circadian clock, have only recently been elucidated. Despite an extensive collection of data regarding the role of rhythmic contribution to disease pathogenesis (such as systemic hypertension, coronary artery, and renal disease), the roles of key circadian transcription factors in pulmonary hypertension remain understudied. This is despite a large degree of overlap in the pulmonary hypertension and circadian rhythm fields, not only including shared signaling pathways, but also cell-specific effects of the core clock that are known to result in both protective and adverse lung vessel changes. Therefore, the goal of this review is to summarize the current dialogue regarding common pathways in circadian biology, with a specific emphasis on its implications in the progression of pulmonary hypertension. In this work, we emphasize specific proteins involved in the regulation of the core molecular clock while noting the circadian cell-specific changes relevant to vascular remodeling. Finally, we apply this knowledge to the optimization of medical therapy, with a focus on sleep hygiene and the role of chronopharmacology in patients with this disease. In dissecting the unique relationship between time and cellular biology, we aim to provide valuable insight into the practical implications of considering time as a therapeutic variable. Armed with this information, physicians will be positioned to more efficiently use the full four dimensions of patient care, resulting in improved morbidity and mortality of pulmonary hypertension patients.

Rethinking pioglitazone as a cardioprotective agent: a new perspective on an overlooked drug

Since 1985, the thiazolidinedione pioglitazone has been widely used as an insulin sensitizer drug for type 2 diabetes mellitus (T2DM). Although fluid retention was early recognized as a safety concern, data from clinical trials have not provided conclusive evidence for a benefit or a harm on cardiac function, leaving the question unanswered. We reviewed the available evidence encompassing both in vitro and in vivo studies in tissues, isolated organs, animals and humans, including the evidence generated by major clinical trials. Despite the increased risk of hospitalization for heart failure due to fluid retention, pioglitazone is consistently associated with reduced risk of myocardial infarction and ischemic stroke both in primary and secondary prevention, without any proven direct harm on the myocardium. Moreover, it reduces atherosclerosis progression, in-stent restenosis after coronary stent implantation, progression rate from persistent to permanent atrial fibrillation, and reablation rate in diabetic patients with paroxysmal atrial fibrillation after catheter ablation. In fact, human and animal studies consistently report direct beneficial effects on cardiomyocytes electrophysiology, energetic metabolism, ischemia–reperfusion injury, cardiac remodeling, neurohormonal activation, pulmonary circulation and biventricular systo-diastolic functions. The mechanisms involved may rely either on anti-remodeling properties (endothelium protective, inflammation-modulating, anti-proliferative and anti-fibrotic properties) and/or on metabolic (adipose tissue metabolism, increased HDL cholesterol) and neurohormonal (renin–angiotensin–aldosterone system, sympathetic nervous system, and adiponectin) modulation of the cardiovascular system. With appropriate prescription and titration, pioglitazone remains a useful tool in the arsenal of the clinical diabetologist.

Peroxisome Proliferator-Activated Receptors as Molecular Links between Caloric Restriction and Circadian Rhythm

The circadian rhythm plays a chief role in the adaptation of all bodily processes to internal and environmental changes on the daily basis. Next to light/dark phases, feeding patterns constitute the most essential element entraining daily oscillations, and therefore, timely and appropriate restrictive diets have a great capacity to restore the circadian rhythm. One of the restrictive nutritional approaches, caloric restriction (CR) achieves stunning results in extending health span and life span via coordinated changes in multiple biological functions from the molecular, cellular, to the whole-body levels. The main molecular pathways affected by CR include mTOR, insulin signaling, AMPK, and sirtuins. Members of the family of nuclear receptors, the three peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ take part in the modulation of these pathways. In this non-systematic review, we describe the molecular interconnection between circadian rhythm, CR-associated pathways, and PPARs. Further, we identify a link between circadian rhythm and the outcomes of CR on the whole-body level including oxidative stress, inflammation, and aging. Since PPARs contribute to many changes triggered by CR, we discuss the potential involvement of PPARs in bridging CR and circadian rhythm.

Hyperinsulinemia rather than insulin resistance itself induces blood pressure elevation in high fat diet-fed rats

OBJECTIVE

To investigate if insulin resistance per se or the accompanying hyperinsulinemia induced hypertension and its underlying mechanisms.

METHODS

Sprague-Dawley rats were randomized into normal diet-fed group (ND group) and high-fat diet-fed group (HFD group). Then, the HFD group was further randomly divided into the control group (HFD_C group), the PIO group (treated with pioglitazone), the STZ_DM group (to induce diabetes with streptozotocin) and the DM+Ins group (streptozotocin injection followed by insulin treatment). Insulin sensitivity, plasma insulin, endothelin-1, norepinephrine, aldosterone, angiotensinⅡ and 24-h urinary sodium excretion (USE) levels of the groups were measured and analyzed. A multiple stepwise regression analysis method was applied to exam our hypothesis.

RESULTS

Compared to HFD_C group, the groups with lower plasma insulin, the PIO group and STZ_DM group, showed higher USE and lower blood pressure. The groups with higher plasma insulin (but same level of insulin resistance), the HFD_C group and DM+Ins group, showed lower USE and higher blood pressure. The 24-h urinary sodium excretion was the most important contributor to the significant changes of blood pressure with an R² of 25.2% in this animal experiment.

CONCLUSIONS

It is the compensatory hyperinsulinemia rather than insulin resistance per se that causes blood pressure elevation. The urinary sodium excretion is the key mediator among the multiple mechanisms. Therapies targeting hyperinsulinemia and restricting salt intake may favor a better control of hypertension associated with insulin resistance.

Interplay between the renin-angiotensin system, the canonical WNT/β-catenin pathway and PPARγ in hypertension

PURPOSE OF REVIEW

Heterogeneous causes can determinate hypertension.

RECENT FINDINGS

The renin-angiotensin system (RAS) has a major role in the pathophysiology of blood pressure. Angiotensin II and aldosterone are overexpressed during hypertension and lead to hypertension development and its cardiovascular complications. In several tissues, the overactivation of the canonical WNT/β-catenin pathway leads to inactivation of peroxisome proliferator-activated receptor gamma (PPARγ), while PPARγ stimulation induces a decrease of the canonical WNT/β-catenin pathway. In hypertension, the WNT/β-catenin pathway is upregulated, whereas PPARγ is decreased. The WNT/β-catenin pathway and RAS regulate positively each other during hypertension, whereas PPARγ agonists can decrease the expression of both the WNT/β-catenin pathway and RAS. We focus this review on the hypothesis of an opposite interplay between PPARγ and both the canonical WNT/β-catenin pathway and RAS in regulating the molecular mechanism underlying hypertension. The interactions between PPARγ and the canonical WNT/β-catenin pathway through the regulation of the renin-angiotensin system in hypertension may be an interesting way to better understand the actions and the effects of PPARγ agonists as antihypertensive drugs.

Peroxisome proliferator-activated receptors as therapeutic targets for heart failure

Heart failure (HF) is a common clinical syndrome that affects more than 23 million individuals worldwide. Despite the marked advances in its management, the mortality rates in HF patients have remained unacceptably high. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription regulators, involved in the regulation of fatty acid and glucose metabolism. PPAR agonists are currently used for the treatment of type II diabetes mellitus and hyperlipidemia; however, their role as therapeutic agents for HF remains under investigation. Preclinical studies have shown that pharmacological modulation of PPARs can upregulate the expression of fatty acid oxidation genes in cardiomyocytes. Moreover, PPAR agonists were proven able to improve ventricular contractility and reduce cardiac remodelling in animal models through their anti-inflammatory, anti-oxidant, anti-fibrotic, and anti-apoptotic activities. Whether these effects can be replicated in humans is yet to be proven. This article reviews the interactions of PPARs with the pathophysiological mechanisms of HF and how the pharmacological modulation of these receptors can be of benefit for HF patients.

The Positive Regulation of eNOS Signaling by PPAR Agonists in Cardiovascular Diseases

Increasing evidence shows that activation of peroxisome proliferator-activated receptors (PPARs) plays an essential role in the regulation of vascular endothelial function through a range of mechanisms, including non-metabolic. Among these, the PPAR-mediated activation of endothelial nitric oxide synthase (eNOS) appears to be of considerable importance. The regulated and sustained bioavailability of nitric oxide (NO) in the endothelium is essential to avoid the development of cardiovascular diseases such as hypertension or atherosclerosis. Therefore, a deeper understanding of the different effects of specific PPAR ligands on NO bioavailability could be useful in the development of novel or multi-targeted PPAR agonists. In this review, we report the most meaningful and up-to-date in vitro and in vivo studies of the regulation of NO production performed by different PPAR agonists. Insights into the molecular mechanisms of PPAR-mediated eNOS activation are also provided. Although findings from animal studies in which the activation of PPARα, PPARβ/δ, or PPARγ have provided clear vasoprotective effects have been promising, several benefits from PPAR agonists are offset by unwanted outcomes. Therefore, new insights could be useful in the development of tissue-targeted PPAR agonists with more tolerable side effects to improve treatment options for cardiovascular diseases.

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.

Peroxisome Proliferator-Activated Receptors and the Heart: Lessons from the Past and Future Directions

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear family of ligand activated transcriptional factors and comprise three different isoforms, PPAR-α, PPAR-β/δ, and PPAR-γ. The main role of PPARs is to regulate the expression of genes involved in lipid and glucose metabolism. Several studies have demonstrated that PPAR agonists improve dyslipidemia and glucose control in animals, supporting their potential as a promising therapeutic option to treat diabetes and dyslipidemia. However, substantial differences exist in the therapeutic or adverse effects of specific drug candidates, and clinical studies have yielded inconsistent data on their cardioprotective effects. This review summarizes the current knowledge regarding the molecular function of PPARs and the mechanisms of the PPAR regulation by posttranslational modification in the heart. We also describe the results and lessons learned from important clinical trials on PPAR agonists and discuss the potential future directions for this class of drugs.

Association of circadian genes with diurnal blood pressure changes and non-dipper essential hypertension: a genetic association with young-onset hypertension

Recent studies have suggested that circadian genes have important roles in maintaining the circadian rhythm of the cardiovascular system. However, the associations between diurnal BP changes and circadian genes remain undetermined. We conducted a genetic association study of young-onset hypertension, in which 24-h ambulatory blood pressure (BP) monitoring was performed. A total of 23 tag single-nucleotide polymorphisms (SNPs) on 11 genes involved in circadian rhythms were genotyped for correlations with diurnal BP variation phenotypes. A permutation test was used to correct for multiple testing. Five tag SNPs within five loci, including rs3888170 in NPAS2, rs6431590 in PER2, rs1410225 in RORββ, rs3816358 in BMAL1 and rs10519096 in RORα, were significantly associated with the non-dipper phenotype in 372 young hypertensive patients. A genetic risk score was generated by counting the risk alleles and effects for each individual. Genotyping was performed in an additional independent set of 619 young-onset hypertensive subjects. Altogether, non-dippers had a higher weighted genetic risk score than dippers (1.67±0.56 vs. 1.54±0.55, P<0.001), and the additive genetic risk score also indicated a graded association with decreased diurnal BP changes (P=0.006), as well as a non-dipper phenotype (P=0.031). After multivariable logistic analysis, only the circadian genetic risk score (odds ratio (OR), 1550; 95% confidence interval (CI), 1.225-1.961, P<0.001) and the use of β-blockers (OR, 1.519; 95% CI, 1.164-1.982, P=0.003) were independently associated with the presence of non-dippers among subjects with young-onset hypertension. Genetic variants in circadian genes were associated with the diurnal phenotype of hypertension, suggesting a genetic association with diurnal BP changes in essential hypertension.

Circadian rhythms, Wnt/beta-catenin pathway and PPAR alpha/gamma profiles in diseases with primary or secondary cardiac dysfunction

Circadian clock mechanisms are far-from-equilibrium dissipative structures. Peroxisome proliferator-activated receptors (PPAR alpha, beta/delta, and gamma) play a key role in metabolic regulatory processes, particularly in heart muscle. Links between circadian rhythms (CRs) and PPARs have been established. Mammalian CRs involve at least two critical transcription factors, CLOCK and BMAL1 (Gekakis et al., 1998; Hogenesch et al., 1998). PPAR gamma plays a major role in both glucose and lipid metabolisms and presents circadian properties which coordinate the interplay between metabolism and CRs. PPAR gamma is a major component of the vascular clock. Vascular PPAR gamma is a peripheral regulator of cardiovascular rhythms controlling circadian variations in blood pressure and heart rate through BMAL1. We focused our review on diseases with abnormalities of CRs and with primary or secondary cardiac dysfunction. Moreover, these diseases presented changes in the Wnt/beta-catenin pathway and PPARs, according to two opposed profiles. Profile 1 was defined as follows: inactivation of the Wnt/beta-catenin pathway with increased expression of PPAR gamma. Profile 2 was defined as follows: activation of the Wnt/beta-catenin pathway with decreased expression of PPAR gamma. A typical profile 1 disease is arrhythmogenic right ventricular cardiomyopathy, a genetic cardiac disease which presents mutations of the desmosomal proteins and is mainly characterized by fatty acid accumulation in adult cardiomyocytes mainly in the right ventricle. The link between PPAR gamma dysfunction and desmosomal genetic mutations occurs via inactivation of the Wnt/beta-catenin pathway presenting oscillatory properties. A typical profile 2 disease is type 2 diabetes, with activation of the Wnt/beta-catenin pathway and decreased expression of PPAR gamma. CRs abnormalities are present in numerous pathologies such as cardiovascular diseases, sympathetic/parasympathetic dysfunction, hypertension, diabetes, neurodegenerative diseases, cancer which are often closely inter-related.

Tick-tock: is your cardiometabolic risk on the clock?

Governing a large amount of cellular processes in mammalian cells is a 24-h regulatory mechanism known as the circadian clock. Through the release of neurohormonal factors, the master central clock is able to regulate the otherwise independent peripheral clocks situated in all vital organs. It has recently been shown that forced misalignment of the circadian cycles, often as a consequence of lifestyle factors, is an independent cardiometabolic risk factor and may thus potentially predispose certain groups, such as nightshift workers, to cardiovascular disease. In this review, we will analyse some of the recent advances regarding circadian clock dysfunction and the development of cardiovascular diseases. Finally, we will touch on the developing link between circadian dysfunction and myocardial infarctions.

PPARs Integrate the Mammalian Clock and Energy Metabolism

Peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptors that function as transcription factors regulating the expression of numerous target genes. PPARs play an essential role in various physiological and pathological processes, especially in energy metabolism. It has long been known that metabolism and circadian clocks are tightly intertwined. However, the mechanism of how they influence each other is not fully understood. Recently, all three PPAR isoforms were found to be rhythmically expressed in given mouse tissues. Among them, PPARα and PPARγ are direct regulators of core clock components, Bmal1 and Rev-erbα, and, conversely, PPARα is also a direct Bmal1 target gene. More importantly, recent studies using knockout mice revealed that all PPARs exert given functions in a circadian manner. These findings demonstrated a novel role of PPARs as regulators in correlating circadian rhythm and metabolism. In this review, we summarize advances in our understanding of PPARs in circadian regulation.

Integration of metabolic and cardiovascular diurnal rhythms by circadian clock

Understanding how the 24-hour blood-pressure rhythm is programmed has been one of the most challenging questions in cardiovascular research. The 24-hour blood-pressure rhythm is primarily driven by the circadian clock system, in which the master circadian pacemaker within the suprachiasmatic nuclei of the hypothalamus is first entrained to the light/dark cycle and then transmits synchronizing signals to the peripheral clocks common to most tissues, including the heart and blood vessels. However, the circadian system is more complex than this basic hierarchical structure, as indicated by the discovery that peripheral clocks are either influenced to some degree or fully driven by temporal changes in energy homeostasis, independent of the light entrainment pathway. Through various comparative genomic approaches and through studies exploiting mouse genetics and transgenics, we now appreciate that cardiovascular tissues possess a large number of metabolic genes whose expression cycle and reciprocally affect the transcriptional control of major circadian clock genes. These findings indicate that metabolic cycles can directly or indirectly affect the diurnal rhythm of cardiovascular function. Here, we discuss a framework for understanding how the 24-hour blood-pressure rhythm is driven by the circadian system that integrates cardiovascular and metabolic function.

Effect of pioglitazone and ramipril on biomarkers of low-grade inflammation and vascular function in nondiabetic patients with increased cardiovascular risk and an activated inflammation: results from the PIOace study

AIMS

This study investigated the effects of pioglitazone (PIO), ramipril (RAM), or their combination (PIRA) on low-grade inflammation in nondiabetic hypertensive patients with increased cardiovascular risk.

METHODS AND RESULTS

Patients enrolled in this placebo-controlled, double-blind, randomized, parallel trial (72 male, 77 female, aged 60 ± 9 years, body mass index 30.4 ± 4.7 kg/m(2), duration of hypertension 9 ± 8 years) were treated with either 30/45 mg PIO (dose titration), 2.5/5 mg RAM, or their combination for 12 weeks. A reduction in high-sensitivity C-reactive protein was observed with PIO (-0.89 ± 1.98 mg/liter; -25%) and PIRA (-0.49 ± 2.11 mg/liter; -16%), while an increase was seen with RAM (0.58 ± 2.13 mg/liter; +20%, p < .05 vs PIO and PIRA). The 24-hour blood pressure profile showed a small increase with both monotherapies but a decrease with PIRA (p < .05 vs PIO). Improvements in biomarkers of chronic systemic inflammation and insulin resistance (IR) were observed in the PIO and PIRA arms only [PIO/RAM/PIRA: homeostasis model of assessment of IR: -0.78 ± 1.39 (-29%)/0.15 ± 1.03 (+5%)/ -1.44 ± 2.83 (-40%); adiponectin: 8.51 ± 5.91 (+104%)/ 0.09 ± 2.63 (+1%)/ 8.86 ± 6.37 mg/liter (+107%); matrix metallo-proteinase-9: -48 ± 127 (-12%)/-1 ± 224 (0%)/-60 ± 210 ng/ml (-13%), p < .05 for RAM vs PIO or PIRA in all cases].

CONCLUSIONS

Our 3-month study in nondiabetic hypertensive patients showed a decrease in biomarkers of IR and chronic systemic inflammation with the PIO monotherapy and the PIRA combination only, which may help to explain some findings in other cardiovascular outcome trials.

Metabolic cycles are linked to the cardiovascular diurnal rhythm in rats with essential hypertension

Background

The loss of diurnal rhythm in blood pressure (BP) is an important predictor of end-organ damage in hypertensive and diabetic patients. Recent evidence has suggested that two major physiological circadian rhythms, the metabolic and cardiovascular rhythms, are subject to regulation by overlapping molecular pathways, indicating that dysregulation of metabolic cycles could desynchronize the normal diurnal rhythm of BP with the daily light/dark cycle. However, little is known about the impact of changes in metabolic cycles on BP diurnal rhythm.

Methodology/Principal Findings

To test the hypothesis that feeding-fasting cycles could affect the diurnal pattern of BP, we used spontaneously hypertensive rats (SHR) which develop essential hypertension with disrupted diurnal BP rhythms and examined whether abnormal BP rhythms in SHR were caused by alteration in the daily feeding rhythm. We found that SHR exhibit attenuated feeding rhythm which accompanies disrupted rhythms in metabolic gene expression not only in metabolic tissues but also in cardiovascular tissues. More importantly, the correction of abnormal feeding rhythms in SHR restored the daily BP rhythm and was accompanied by changes in the timing of expression of key circadian and metabolic genes in cardiovascular tissues.

Conclusions/Significance

These results indicate that the metabolic cycle is an important determinant of the cardiovascular diurnal rhythm and that disrupted BP rhythms in hypertensive patients can be normalized by manipulating feeding cycles.

PPARγ: a circadian transcription factor in adipogenesis and osteogenesis

Peroxisome proliferator-activated receptor γ (PPARγ) is a critical factor for adipogenesis and glucose metabolism, but accumulating evidence demonstrates the involvement of PPARγ in skeletal metabolism as well. PPARγ agonists, the thiazolidinediones, have been widely used for the treatment of type 2 diabetes mellitus owing to their effectiveness in lowering blood glucose levels. However, the use of thiazolidinediones has been associated with bone loss and fractures. Thiazolidinedione-induced alterations in the bone marrow milieu-that is, increased bone marrow adiposity with suppression of osteogenesis-could partially explain the pathogenesis of drug-induced bone loss. Furthermore, several lines of evidence place PPARγ at the center of a regulatory loop between circadian networks and metabolic output. PPARγ exhibits a circadian expression pattern that is magnified by consumption of a high-fat diet. One gene with circadian regulation in peripheral tissues, nocturnin, has been shown to enhance PPARγ activity. Importantly, mice deficient in nocturnin are protected from diet-induced obesity, exhibit impaired circadian expression of PPARγ and have increased bone mass. This Review focuses on new findings regarding the role of PPARγ in adipose tissue and skeletal metabolism and summarizes the emerging role of PPARγ as an integral part of a complex circadian regulatory system that modulates food storage, energy consumption and skeletal metabolism.

PPARs, Cardiovascular Metabolism, and Function: Near- or Far-from-Equilibrium Pathways

Peroxisome proliferator-activated receptors (PPAR α, β/δ and γ) play a key role in metabolic regulatory processes and gene regulation of cellular metabolism, particularly in the cardiovascular system. Moreover, PPARs have various extra metabolic roles, in circadian rhythms, inflammation and oxidative stress. In this review, we focus mainly on the effects of PPARs on some thermodynamic processes, which can behave either near equilibrium, or far-from-equilibrium. New functions of PPARs are reported in the arrhythmogenic right ventricular cardiomyopathy, a human genetic heart disease. It is now possible to link the genetic desmosomal abnormalitiy to the presence of fat in the right ventricle, partly due to an overexpression of PPARγ. Moreover, PPARs are directly or indirectly involved in cellular oscillatory processes such as the Wnt-b-catenin pathway, circadian rhythms of arterial blood pressure and cardiac frequency and glycolysis metabolic pathway. Dysfunction of clock genes and PPARγ may lead to hyperphagia, obesity, metabolic syndrome, myocardial infarction and sudden cardiac death, In pathological conditions, regulatory processes of the cardiovascular system may bifurcate towards new states, such as those encountered in hypertension, type 2 diabetes, and heart failure. Numerous of these oscillatory mechanisms, organized in time and space, behave far from equilibrium and are “dissipative structures”.

Circadian rhythms and metabolic syndrome: from experimental genetics to human disease

The incidence of the metabolic syndrome represents a spectrum of disorders that continue to increase across the industrialized world. Both genetic and environmental factors contribute to metabolic syndrome and recent evidence has emerged to suggest that alterations in circadian systems and sleep participate in the pathogenesis of the disease. In this review, we highlight studies at the intersection of clinical medicine and experimental genetics that pinpoint how perturbations of the internal clock system, and sleep, constitute risk factors for disorders including obesity, diabetes mellitus, cardiovascular disease, thrombosis and even inflammation. An exciting aspect of the field has been the integration of behavioral and physiological approaches, and the emerging insight into both neural and peripheral tissues in disease pathogenesis. Consideration of the cell and molecular links between disorders of circadian rhythms and sleep with metabolic syndrome has begun to open new opportunities for mechanism-based therapeutics.

Pressed for time: the circadian clock and hypertension

Hypertension is a major risk factor for cardiovascular disease and death. The "silent" rise of blood pressure that occurs over time is largely asymptomatic. However, its impact is deafening-causing and exacerbating cardiovascular disease, end-organ damage, and death. The present article addresses recent observations from human and animal studies that provide new insights into how the circadian clock regulates blood pressure, contributes to hypertension, and ultimately evolves vascular disease. Further, the molecular components of the circadian clock and their relationship with locomotor activity, metabolic control, fluid balance, and vascular resistance are discussed with an emphasis on how these novel, circadian clock-controlled mechanisms contribute to hypertension.

Effect of Diabetes Medications on Cardiovascular Risk and Surrogate Markers in Patients with Type 2 Diabetes

Objective:

To evaluate the effect of diabetes medications on the risk of cardiovascular disease and surrogate markers.

Data Sources:

Literature was accessed through MEDLINE (1950–July 2008) and PubMed using multiple terms for diabetes, cardiovascular risk, surrogate markers, and diabetes medications. In addition, reference citations from publications were reviewed.

Study Selection and Data Extraction:

English-language articles that met the above criteria, with clinical relevance, were evaluated.

Data Synthesis:

Evidence regarding the effect of diabetes medications on cardiovascular risk is sparse, with information on their effects on surrogate markers more widely available. Recent evidence demonstrates that glycemic control alone may not reduce the risk of macrovascular events. Multiple trials were reviewed to determine the effect of diabetes medications on this risk, as well as the effect on surrogate markers (eg, blood pressure, cholesterol, body weight). Metformin and acarbose demonstrated significant reductions in macrovascular events, including myocardial infarction. Data regarding sulfonylureas, thiazolidinediones, and insulin are conflicting. Pioglitazone may reduce cardiovascular events, except heart failure, whereas rosiglitazone may increase these events. Until direct evidence can be obtained, the full effect of diabetes medications on cardiovascular risk is unknown.

Conclusions:

Current literature provides little support that diabetes medications may lower the risk of cardiovascular events while some agents may increase this risk. Of the drugs available, metformin may be the least detrimental. Current literature regarding other diabetes medications provides conflicting results on their effect on cardiovascular outcomes. In the meantime, practitioners should treat all targets of cardiovascular risk in patients with diabetes.

ACPE Universal Program Numbers:

407-000-09-050-H01-P (Pharmacists); 407-000-09-050-H01-T (Technicians)

Vascular PPARgamma controls circadian variation in blood pressure and heart rate through Bmal1

Thiazolidinediones (TZDs) are PPARgamma activators that exhibit vasculoprotective properties. To determine the vascular function of PPARgamma, we analyzed Tie2Cre/flox and SM22Cre/flox mice. Unexpectedly, both knockout strains exhibited a significant reduction of circadian variations in blood pressure and heart rate in parallel with diminished variations in urinary norepinephrine/epinephrine excretion and impaired rhythmicity of the canonical clock genes, including Bmal1. PPARgamma expression in the aorta exhibited a robust rhythmicity with a more than 20-fold change during the light/dark cycle. Rosiglitazone treatment induced aortic expression of Bmal1 mRNA, and ChIP and promoter assays revealed that Bmal1 is a direct PPARgamma target gene. These studies have uncovered a role for vascular PPARgamma as a peripheral factor participating in regulation of cardiovascular rhythms.

Glitazones and the cardiovascular system

PURPOSE OF REVIEW

To chart recent progress on molecular mechanisms of rosiglitazone and pioglitazone in the cardiovascular system.

RECENT FINDINGS

Several classes of oral antidiabetic drugs are available to treat type 2 diabetes, but glitazones offer the unique promise of insulin-sensitizing ability coupled with potential to reverse cardiovascular abnormalities associated with insulin resistance. Currently the two drugs used are rosiglitazone and pioglitazone, marketed as Avandia and Actos. Recent results of different metaanalyses were inconclusive as to whether rosiglitazone caused real adverse effects of myocardial ischemia. Thus, the US Food and Drugs Administration placed a black box warning on Avandia to signal potential of myocardial infarction and heart-related deaths, as a precautionary measure until analyses of all available data provide clarity. Also unresolved is the extent to which the two compounds share modes of action.

SUMMARY

Type II diabetes affects more than 160 million people, approximately 5% of the world's population (http://www.who.org). Recently, questions have been raised about the cardiovascular safety of glitazone antidiabetic drugs. Clearly, there is an urgency to define molecular mechanisms of rosiglitazone and pioglitazone and understand how these drugs may impact patients.

Improvement of glycaemic control by nateglinide decreases systolic blood pressure in drug-naive patients with type 2 diabetes

BACKGROUND

It has been speculated that oral hypoglycaemic agents that block K-ATP channels could potentially increase blood pressure by blocking such channels in vascular myocytes. No information about this issue exists regarding nateglinide.

DESIGN

A multicentre, double-blind, placebo-controlled, randomized trial was conducted in 109 drug-naive 30- to 75-year-old patients with type 2 diabetes and < 5 years of diabetes diagnosis, who are not taking antihypertensive drugs. These patients were assigned to receive placebo or fixed doses of nateglinide (120 mg before each main meal: breakfast, lunch and dinner) and evaluated at weeks 0 and 12 for (i) body mass index and blood pressure; (ii) standard laboratory tests, including haemoglobin A1c (HbA1c) and fasting plasma glucose; and (iii) incremental area under the curve for glucose and C-peptide after a standardized liquid breakfast challenge, homeostasis model assessment (HOMA)-B% (as surrogate of beta-cell activity) and HOMA-S% (as surrogate of insulin sensitivity).

RESULTS

At the end of the follow-up period, patients in the nateglinide group (n = 55), compared to patients in the placebo group (n = 54), showed lower values of HbA1c (6.7 +/- 0.6 vs. 7.2 +/- 0.7%, respectively; P < 0.001), fasting plasma glucose (7.9 +/- 2.1 vs. 8.5 +/- 2.0 mmol L(-1); P = 0.023) and systolic blood pressure (125.3 +/- 15.4 vs. 129.3 +/- 18.7 mmHg; P = 0.015), and higher values of HOMA-B%[75.7 (51.8-99.4) vs. 57.7 (42.2-83.4); P = 0.033]. A positive correlation was found between changes in HbA1c and systolic blood pressure in the nateglinide group (r = 0.355, P = 0.011).

CONCLUSIONS

In drug-naive patients with type 2 diabetes, the improvement in glycaemic control with nateglinide is associated with a decrease in systolic blood pressure.

Pioglitazone opposes neurogenic vascular dysfunction associated with chronic hyperinsulinaemia

BACKGROUND AND PURPOSE

We previously demonstrated that chronic hyperinsulinaemia induced by drinking high levels of fructose augments adrenergic nerve-mediated vasoconstriction and suppresses vasodilatation mediated by calcitonin gene-related peptide (CGRP)-containing (CGRPergic) vasodilator nerves. In this study, the effects of pioglitazone on vascular responses induced by stimulation of adrenergic nerves, CGRPergic nerves and vasoactive agents were investigated in pithed rats given 15% fructose solution to drink (FDR).

EXPERIMENTAL APPROACH

To assess the effect of pioglitazone on the altered vascular responsiveness in the hyperinsulinaemic state in vivo, changes in vascular responses to spinal cord stimulation (SCS) and intravenous bolus injections of noradrenaline, angiotensin II and CGRP were evaluated in pithed control rats and FDR either untreated or treated with pioglitazone.

KEY RESULTS

In the pithed FDR, vasoconstrictor responses to SCS and to injections of noradrenaline and angiotensin II were significantly greater than those of pithed control rats. In pithed FDR with artificially increased blood pressure and blockade of the autonomic ganglia, the vasodilator responses to SCS and CGRP injection were significantly smaller than those of pithed control rats. Oral administration of pioglitazone to FDR for two weeks markedly decreased plasma levels of insulin, triglycerides and blood glucose. In FDR pioglitazone diminished the augmented vasoconstrictor responses to SCS, noradrenaline and angiotensin II, and ameliorated the decrease in vasodilator responses to SCS.

CONCLUSIONS AND IMPLICATIONS

The present results suggest that pioglitazone improves not only insulin resistance, but also the dysfunctions in vascular control regulated by adrenergic and CGRPergic nerves in the hyperinsulinaemic state.