Cilostazol ameliorates metabolic abnormalities with suppression of proinflammatory markers in a db/db mouse model of type 2 diabetes via activation of peroxisome proliferator-activated receptor gamma transcription

Cilostazol protects against gastric ulcers by regulating PPAR-γ, HO-1, PECAM-1, pErk-1, NF-κB, Bcl-2, and cleaved caspase-3 protein expression

Millions of individuals worldwide, across all age groups, suffer from the widespread health issue of gastric ulcers. In many experiments, cilostazol (Cls), a phosphodiesterase-3 inhibitor, was recently shown to have anti-ulcer activity. Notably, Cls increases the expression and transcriptional activity of PPAR-γ in vitro and in vivo. This study aimed to evaluate the protective effect of Cls against ethanol-induced gastric ulcers and clarify the possible underlying mechanisms with an emphasis on the role of PPAR-γ. Male albino rats were treated with ethanol to induce gastric ulcers, or they were pretreated with Cls, omeprazole (Omp), GW9662, or Cls + GW9662 for 14 consecutive days before receiving ethanol. Cls protects against ethanol-induced gastric ulcers. Cls treatment significantly reduced ethanol-induced upregulation of the pro-inflammatory markers (IL-1β, IL-6, TNF-α, and NF-κB), MDA (a marker of lipid peroxidation), and caspase-3 and cleaved caspase-3 (apoptotic markers). On the other hand, Cls treatment counteracted ethanol-induced downregulation of PPAR-γ, pErk-1, HO-1 and GSH (antioxidant markers), PECAM-1 and NO (healing markers), and Bcl-2 (antiapoptotic marker). However, when combined with GW9662, a potent antagonist of PPAR-γ, Cls loses its effects. In conclusion, these results suggest that PPAR-γ and pErk-1 are essential for Cls's protective effects against ethanol-induced gastric ulcers.

New advances of adiponectin in regulating obesity and related metabolic syndromes

Obesity and related metabolic syndromes have been recognized as important disease risks, in which the role of adipokines cannot be ignored. Adiponectin (ADP) is one of the key adipokines with various beneficial effects, including improving glucose and lipid metabolism, enhancing insulin sensitivity, reducing oxidative stress and inflammation, promoting ceramides degradation, and stimulating adipose tissue vascularity. Based on those, it can serve as a positive regulator in many metabolic syndromes, such as type 2 diabetes (T2D), cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), sarcopenia, neurodegenerative diseases, and certain cancers. Therefore, a promising therapeutic approach for treating various metabolic diseases may involve elevating ADP levels or activating ADP receptors. The modulation of ADP genes, multimerization, and secretion covers the main processes of ADP generation, providing a comprehensive orientation for the development of more appropriate therapeutic strategies. In order to have a deeper understanding of ADP, this paper will provide an all-encompassing review of ADP.

A Review of Antidiabetic Medicinal Plants as a Novel Source of Phosphodiesterase Inhibitors: Future Perspective of New Challenges Against Diabetes Mellitus

Intracellular glucose concentration plays a crucial role in initiating the molecular secretory process of pancreatic β-cells through multiple messengers and signaling pathways. Cyclic nucleotides are key physiological regulators that modulate pathway interactions in β -cells. An increase of cyclic nucleotides is controled by hydrolysed phosphodiesterases (PDEs), which degrades cyclic nucleotides into inactive metabolites. Despite the undeniable therapeutic potential of PDE inhibitors, they are associated with several side effects. The treatment strategy for diabetes based on PDE inhibitors has been proposed for a long time. Hence, the world of natural antidiabetic medicinal plants represents an ideal source of phosphodiesterase inhibitors as a new strategy for developing novel agents to treat diabetes mellitus. This review highlights medicinal plants traditionally used in the treatment of diabetes mellitus that have been proven to have inhibitory effects on PDE activity. The contents of this review were sourced from electronic databases, including Science Direct, PubMed, Springer Link, Web of Science, Scopus, Wiley Online, Scifinder and Google Scholar. These databases were consulted to collect information without any limitation date. After comprehensive literature screening, this paper identified 27 medicinal plants that have been reported to exhibit anti-phosphodiesterase activities. The selection of these plants was based on their traditional uses in the treatment of diabetes mellitus. The review emphasizes the antiphosphodiesterase properties of 31 bioactive components derived from these plant extracts. Many phenolic compounds have been identified as PDE inhibitors: Brazilin, mesozygin, artonin I, chalcomaracin, norartocarpetin, moracin L, moracin M, moracin C, curcumin, gallic acid, caffeic acid, rutin, quercitrin, quercetin, catechin, kaempferol, chlorogenic acid, and ellagic acid. Moreover, smome lignans have reported as PDE inhibitors: (+)-Medioresinol di-O-β-d-glucopyranoside, (+)- Pinoresinol di-O-β-d-glucopyranoside, (+)-Pinoresinol-4-O-β-d-glucopyranosyl (1→6)-β-dglucopyranoside, Liriodendrin, (+)-Pinoresinol 4'-O-β-d-glucopyranoside, and forsythin. This review provides a promising starting point of medicinal plants, which could be further studied for the development of natural phosphodiesterase inhibitors to treat diabetes mellitus. Therefore, it is important to consider clinical studies for the identification of new targets for the treatment of diabetes.

Effects of a Phosphodiesterase inhibitor on the Browning of Adipose Tissue in Mice

Cilostazol is a selective inhibitor of phosphodiesterase type 3 (PDE3) that increases intracellular cyclic adenosine monophosphate (cAMP), which plays a critical role in the development of the beige phenotype and the activation of its thermogenic program in white adipose tissue (WAT). We investigated the metabolic effects of PDE3B inhibition with cilostazol treatment in the adipose tissue of high-fat diet (HFD)-fed mice. Seven-week-old male C57BL/6J mice were randomly assigned to either the cilostazol or control group. The control group was divided into two groups: the chow diet and HFD. The expression of uncoupling Protein 1 (UCP1) and other brown adipocyte markers was compared. In the HFD-fed cilostazol group, C57BL/6J mice displayed improvements in systemic metabolism, including improved glucose tolerance and lipid profile, but only modest effects on body weight were observed. In the visceral WAT of HFD-fed cilostazol-treated mice, cAMP/protein kinase A (PKA) signaling pathways were activated, resulting in the “browning” phenotype, smaller fat deposits, and enhanced mRNA expression of UCP1 and other brown adipocyte markers. PDE3B appears to be an important regulator of lipid metabolism, insulin sensitivity, and thermogenic programs in adipose tissues. An increase in intracellular cAMP via PDE3B inhibition with cilostazol treatment promoted the browning of visceral WAT.

Effect of cilostazol on carotid plaque volume measured by three-dimensional ultrasonography in patients with type 2 diabetes: The FANCY study

AIMS

To conduct a prospective randomized study to evaluate cilostazol, a phosphodiesterase 3 inhibitor, and compare it with aspirin for the prevention of the progression of atherosclerosis in patients with type 2 diabetes (T2D).

MATERIALS AND METHODS

Fifty patients with T2D and carotid atherosclerotic plaques were randomly assigned to either a 200 mg/d cilostazol (CTZ) group or a 100 mg/d aspirin (ASA) group for 6 months. The primary endpoint was change in plaque volume measured by carotid three-dimensional ultrasonography. The secondary endpoints were changes in carotid intima-media thickness (IMT) and endothelial function, assessed by laser Doppler.

RESULTS

Twenty-four patients in the CTZ group and 23 in the ASA group were included in the final analysis. The mean ± SD age of male (n = 20) and female (n = 16) patients was 62.2 and 59.1 years, respectively. The total plaque volume was slightly decreased in the CTZ group (from 183.8 ± 52.5 to 181.5 ± 54.0 mm³ ; P = .567), but significantly increased in the ASA group (from 112.9 ± 21.2 to 128.5 ± 23.3 mm³ ; P = .043). A significant regression in the maximum IMT was observed only in the CTZ group (right: from 2.19 ± 0.17 to 1.96 ± 0.12 mm; left: from 2.02 ± 0.20 to 1.72 ± 0.19 mm). The CTZ group exhibited an increase in HDL cholesterol and a decrease in triglycerides and liver enzymes.

CONCLUSIONS

Cilostazol treatment for 6 months significantly attenuated the progression of carotid plaque compared with aspirin in patients with T2D (NCT03248401).

Role of Phosphodiesterase in the Biology and Pathology of Diabetes

Glucose metabolism is the initiator of a large number of molecular secretory processes in β cells. Cyclic nucleotides as a second messenger are the main physiological regulators of these processes and are functionally divided into compartments in pancreatic cells. Their intracellular concentration is limited by hydrolysis led by one or more phosphodiesterase (PDE) isoenzymes. Literature data confirmed multiple expressions of PDEs subtypes, but the specific roles of each in pancreatic β-cell function, particularly in humans, are still unclear. Isoforms present in the pancreas are also found in various tissues of the body. Normoglycemia and its strict control are supported by the appropriate release of insulin from the pancreas and the action of insulin in peripheral tissues, including processes related to homeostasis, the regulation of which is based on the PDE- cyclic AMP (cAMP) signaling pathway. The challenge in developing a therapeutic solution based on GSIS (glucose-stimulated insulin secretion) enhancers targeted at PDEs is the selective inhibition of their activity only within β cells. Undeniably, PDEs inhibitors have therapeutic potential, but some of them are burdened with certain adverse effects. Therefore, the chance to use knowledge in this field for diabetes treatment has been postulated for a long time.

Cyclic nucleotide phosphodiesterases: New targets in the metabolic syndrome?

Metabolic diseases have a tremendous impact on human morbidity and mortality. Numerous targets regulating adenosine monophosphate kinase (AMPK) have been identified for treating the metabolic syndrome (MetS), and many compounds are being used or developed to increase AMPK activity. In parallel, the cyclic nucleotide phosphodiesterase families (PDEs) have emerged as new therapeutic targets in cardiovascular diseases, as well as in non-resolved pathologies. Since some PDE subfamilies inactivate cAMP into 5'-AMP, while the beneficial effects in MetS are related to 5'-AMP-dependent activation of AMPK, an analysis of the various controversial relationships between PDEs and AMPK in MetS appears interesting. The present review will describe the various PDE families, AMPK and molecular mechanisms in the MetS and discuss the PDEs/PDE modulators related to the tissues involved, thus supporting the discovery of original molecules and the design of new therapeutic approaches in MetS.

Cilostazol Improves HFD-Induced Hepatic Steatosis by Upregulating Hepatic STAMP2 Expression through AMPK

Nonalcoholic fatty liver disease (NAFLD) is an increasingly studied condition that can progress to end-stage liver disease. Although NAFLD was first described in 1980, a complete understanding of the mechanism and causes of this disease is still lacking. Six-transmembrane protein of prostate 2 (STAMP2) plays a role in integrating inflammatory and nutritional signals with metabolism. Our previous study suggested that STAMP2 may be a suitable target for treating NAFLD. In the current study, we performed a focused drug-screening and found that cilostazol could be a potential STAMP2 enhancer. Thus, we examined whether cilostazol alleviates NAFLD through STAMP2. The in vivo and in vitro pharmacological efficacies of cilostazol on STAMP2 expression and lipid accumulation were analyzed in NAFLD mice induced by high-fat diet (HFD) and in HepG2 cell lines treated by oleic acid (OA), respectively. Cilostazol increased the expression of STAMP2 through transcriptional regulation in vivo and in vitro. Cilostazol also dampened the STAMP2 downregulation caused by the HFD and by OA in vivo and in vitro, respectively. Cilostazol activated AMP-activated protein kinase (AMPK) in vivo and in vitro, and AMPK functions upstream of STAMP2, and reversed downregulation of STAMP2 expression through AMPK in the NAFLD model. Cilostazol ameliorates hepatic steatosis by enhancing hepatic STAMP2 expression through AMPK. Enhancing STAMP2 expression with cilostazol represents a potential therapeutic avenue for treatment of NAFLD.

Adiponectin signaling and its role in bone metabolism

Adiponectin, the most prevalent adipo-cytokine in plasma plays critical metabolic and anti-inflammatory roles is fast emerging as an important molecular target for the treatment of metabolic disorders. Adiponectin action is critical in multiple organs including cardio-vascular system, muscle, liver, adipose tissue, brain and bone. Adiponectin signaling in bone has been a topic of active investigation lately. Human association studies and multiple mice models of gene deletion/modification failed to define a clear cause and effect of adiponectin signaling in bone. The most plausible reason could be the multimeric forms of adiponectin that display differential binding to receptors (adipoR1 and adipoR2) with cell-specific receptor variants in bone. Discovery of small molecule agonist of adipoR1 suggested a salutary role of this receptor in bone metabolism. The downstream signaling of adipoR1 in osteoblasts involves stimulation of oxidative phosphorylation leading to increased differentiation via the likely suppression of wnt inhibitor, sclerostin. On the other hand, the inflammation modulatory effect of adiponectin signaling suppresses the RANKL (receptor activator of nuclear factor κ-B ligand) - to - OPG (osteprotegerin) ratio in osteoblasts leading to the suppression of osteoclastogenic response. This review will discuss the adiponectin signaling and its role in skeletal homeostasis and critically assess whether adipoR1 could be a therapeutic target for the treatment of metabolic bone diseases.

Haematoma scavenging in intracerebral haemorrhage: from mechanisms to the clinic

The products of erythrocyte lyses, haemoglobin (Hb) and haem, are recognized as neurotoxins and the main contributors to delayed cerebral oedema and tissue damage after intracerebral haemorrhage (ICH). Finding a means to efficiently promote absorption of the haemolytic products (Hb and haem) around the bleeding area in the brain through stimulating the function of the body's own garbage cleaning system is a novel clinical challenge and critical for functional recovery after ICH. In this review, available information of the brain injury mechanisms underlying ICH and endogenous haematoma scavenging system is provided. Meanwhile, potential intervention strategies are discussed. Intracerebral blood itself has ‘toxic’ effects beyond its volume effect after ICH. Haptoglobin–Hb–CD163 as well as haemopexin–haem–LRP1 is believed to be the most important endogenous scavenging pathway which participates in blood components resolution following ICH. PPARγ–Nrf2 activates the aforementioned clearance pathway and then accelerates haematoma clearance. Meanwhile, the scavenger receptors as novel targets for therapeutic interventions to treat ICH are also highlighted.

Bridging Type 2 Diabetes and Alzheimer's Disease: Assembling the Puzzle Pieces in the Quest for the Molecules With Therapeutic and Preventive Potential

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are two age-related amyloid diseases that affect millions of people worldwide. Broadly supported by epidemiological data, the higher incidence of AD among type 2 diabetic patients led to the recognition of T2D as a tangible risk factor for the development of AD. Indeed, there is now growing evidence on brain structural and functional abnormalities arising from brain insulin resistance and deficiency, ultimately highlighting the need for new approaches capable of preventing the development of AD in type 2 diabetic patients. This review provides an update on overlapping pathophysiological mechanisms and pathways in T2D and AD, such as amyloidogenic events, oxidative stress, endothelial dysfunction, aberrant enzymatic activity, and even shared genetic background. These events will be presented as puzzle pieces put together, thus establishing potential therapeutic targets for drug discovery and development against T2D and diabetes-induced cognitive decline-a heavyweight contributor to the increasing incidence of dementia in developed countries. Hoping to pave the way in this direction, we will present some of the most promising and well-studied drug leads with potential against both pathologies, including their respective bioactivity reports, mechanisms of action, and structure-activity relationships.

Cilostazol ameliorates collagenase-induced cerebral hemorrhage by protecting the blood-brain barrier

Intracranial hemorrhage remains a devastating disease. Among antiplatelet drugs, cilostazol, a phosphodiesterase 3 inhibitor, was recently reported to prevent secondary hemorrhagic stroke in patients in a clinical trial. The aim of this study was to evaluate whether pre-treatment with cilostazol could decrease the intracranial hemorrhage volume and examine the protective mechanisms of cilostazol. We evaluated the pre-treatment effects of the antiplatelet drug cilostazol on the collagenase-induced intracranial hemorrhage volume and neurological outcomes in mice. To estimate the mechanism of collagenase injury, we evaluated various vascular components in vitro, including endothelial cells, vascular smooth muscle cells, pericytes, and a blood-brain barrier model. Cilostazol pre-treatment reduced the intracranial hemorrhage volume with sufficient inhibition of platelet aggregation, and motor function was improved by cilostazol treatment. Blood-brain barrier permeability was increased by collagenase-induced intracranial hemorrhage, and cilostazol attenuated blood-brain barrier leakage. Terminal deoxynucleotidyl transferase dUTP nick-end labeling and western blot analysis showed that cilostazol prevented pericyte cell death by inducing cyclic adenosine monophosphate-responsive element-binding protein phosphorylation. Cilostazol also prevented endothelial cell death and protected collagen type 4, laminin, and vascular endothelial- and N-cadherins from collagenase injury. In conclusion, cilostazol reduced collagenase-induced intracranial hemorrhage volume by protecting the blood-brain barrier.

Induction of Angiogenesis by a Type III Phosphodiesterase Inhibitor, Cilostazol, Through Activation of Peroxisome Proliferator-Activated Receptor-γ and cAMP Pathways in Vascular Cells

OBJECTIVE

Peripheral arterial disease is highly prevalent in the elderly and in the subjects with cardiovascular risk factors such as diabetes. Approximately 2% to 4% of those affected with peripheral arterial disease commonly complain of intermittent claudication. Cilostazol, a type III phosphodiesterase inhibitor, is the only Food and Drug Administration-approved drug for the treatment of intermittent claudication. Cilostazol has been shown to be beneficial for the improvement of pain-free walking distance in patients with intermittent claudication in a series of randomized clinical trials. However, the underlying mechanism how cilostazol improved intermittent claudication symptoms is still unclear.

APPROACH AND RESULTS

In this study, the effect of cilostazol on ischemic leg was investigated in mouse ischemic hindlimb model. Administration of cilostazol significantly increased the expression of hepatocyte growth factor (HGF), vascular endothelial growth factor, angiopoietin-1, and peroxisome proliferator-activated receptor-γ in vasculature. The capillary density in ischemic leg was also significantly increased in cilostazol treatment group when compared with control and aspirin treatment group. However, an increase in capillary density and the expression of growth factors was almost completely abolished by coadministration of HGF-neutralizing antibody, suggesting that cilostazol enhanced angiogenesis mainly through HGF. In vitro experiment revealed that cilostazol treatment increased HGF production in vascular smooth muscle cells via 2 major pathways: peroxisome proliferator-activated receptor-γ and cAMP pathways.

CONCLUSIONS

Our data suggest that the favorable effects of cilostazol on ischemic leg might be through the angiogenesis through the induction of HGF via peroxisome proliferator-activated receptor-γ and cAMP pathways.

Effects of cilostazol on the progression and regression of symptomatic intracranial artery stenosis: it reduces the risk of ischemic stroke

OBJECTIVE:

To assess the efficacy and safety of cilostazol on the progression and regression of symptomatic intracranial artery stenosis.

DATA RETRIVAL:

We searched the main databases for eligible trials including Medline (from 1966 to June 2014), Embase (from 1980 to June 2014), Cochrane Library (Issue 6, 2014), Chinese National Knowledge Infrastructure (from 1995 to June 2014), Current Controlled Trials (http://controlled-trials.com), Clinical Trials.gov (http://clinicaltrials.gov), and Chinese Clinical Trial Registry (http://www.chictr.org). All studies regarding prevention and treatment of symptomatic intracranial arterial stenosis by cilostazol were collected. The Mesh or text keywords were the English words: “cilostazol, phosphodiesterase 3 inhibitor, atherosclerosis, and ischemic stroke.” No restrictions were put on publications or publication language.

SELECTION CRITERIA:

Grade A or B randomized controlled trials were selected according to the quality of evaluation criteria from the Cochrane Collaboration, in which cilostazol and aspirin were used to evaluate the effects of cilostazol in the treatment of patients with symptomatic intracranial artery stenosis. The quality of study methodology was evaluated based on criteria described in Cochrane Reviewer's Handbook 5.0.1. RevMan 5.2 software was used for data analysis.

MAIN OUTCOME MEASURES:

Clinical efficacy and safety of cilostazol in stopping progression and promoting regression of symptomatic intracranial artery stenosis were measured by magnetic resonance angiography and transcranial Doppler.

RESULTS:

Two randomized controlled trials with a total of 203 patients were included in this study. The results showed that while cilostazol was associated with a significantly reduced progression of intracranial artery stenosis (OR = 0.21, 95%CI: 0.09–0.47, P < 0.01), it had no beneficial effect on symptom regression (OR = 1.42, 95%CI: 0.80–2.51, P = 0.24). During the follow-up period, although some adverse effects developed, including headache, gastrointestinal disturbance, and dizziness, incidences of bleeding were lower than in aspirin-treated patients.

CONCLUSION:

Cilostazol may prevent the progression of symptomatic intracranial artery stenosis, which could reduce the incidence of ischemic stroke.

PTEN upregulation may explain the development of insulin resistance and type 2 diabetes with high dose statins

PURPOSE

Statins increase the incidence of new onset diabetes. Prolonged statin therapy upregulates PTEN expression. PTEN levels are also elevated in diabetic animals. Activation of protein kinase A by cAMP decreases PTEN expression. We assessed whether prolonged treatment with rosuvastatin (ROS) induces glucose intolerance by upregulating Phosphatase and Tensin Homologue on Chromosome 10 (PTEN) in mice receiving normal (ND) or Western Diet (WD) and whether concomitant treatment with cilostazol (CIL, a phosphodiesterase-3 inhibitor) attenuates the effects.

METHODS

PTEN(loxp/cre) or PTEN(+/-) mice received ND or WD without or with ROS (10 mg/kg/day). Wild-type mice received ND or WD without or with ROS, CIL (10 mg/kg/day), or ROS+CIL for 30 days. Fasting insulin and glucose tolerance test were measured as well as PTEN and P-AKT levels in skeletal muscle.

RESULTS

Serum glucose after intraperitoneal injection of glucose was higher in PTEN(loxp/cre) mice receiving WD or ROS and especially WD+ROS. Levels were lower in PTEN(+/-) mice compared to PTEN(loxp/cre) in each treatment group. CIL decreased glucose levels in mice receiving WD, ROS and their combination. Insulin levels were higher in the WD+ROS group. CIL decreased insulin in mice receiving WD+ROS. WD, ROS and especially their combination increased PTEN and decreased P-AKT levels. CIL attenuated the effect of WD, ROS and their combination.

CONCLUSIONS

Long-term ROS can induce diabetes by upregulating PTEN. CIL attenuates these changes. Partial knockdown of PTEN also ameliorates ROS-induced insulin resistance. Further studies are needed to assess the effects of increasing cAMP levels to prevent the induction of diabetes by statins.

Cilostazol attenuates ovariectomy-induced bone loss by inhibiting osteoclastogenesis

Background

Cilostazol has been reported to alleviate the metabolic syndrome induced by increased intracellular adenosine 3’,5’-cyclic monophosphate (cAMP) levels, which is also associated with osteoclast (OC) differentiation. We hypothesized that bone loss might be attenuated via an action on OC by cilostazol.

Methodology and Principal Findings

To test this idea, we investigated the effect of cilostazol on ovariectomy (OVX)-induced bone loss in mice and on OC differentiation in vitro, using μCT and tartrate-resistant acid phosphatase staining, respectively. Cilostazol prevented from OVX-induced bone loss and decreased oxidative stress in vivo. It also decreased the number and activity of OC in vitro. The effect of cilostazol on reactive oxygen species (ROS) occurred via protein kinase A (PKA) and cAMP-regulated guanine nucleotide exchange factor 1, two major effectors of cAMP. Knockdown of NADPH oxidase using siRNA of p47^phox attenuated the inhibitory effect of cilostazol on OC formation, suggesting that decreased OC formation by cilostazol was partly due to impaired ROS generation. Cilostazol enhanced phosphorylation of nuclear factor of activated T cells, cytoplasmic 1 (NFAT2) at PKA phosphorylation sites, preventing its nuclear translocation to result in reduced receptor activator of nuclear factor-κB ligand-induced NFAT2 expression and decreased binding of nuclear factor-κB-DNA, finally leading to reduced levels of two transcription factors required for OC differentiation.

Conclusions/Significance

Our data highlight the therapeutic potential of cilostazol for attenuating bone loss and oxidative stress caused by loss of ovarian function.

Effect of cilostazol on carotid intima-media thickness in type 2 diabetic patients without cardiovascular event

We investigated the efficacy of cilostazol treatment for 2 years on the attenuation of carotid intima-media thickness (IMT) progression in type 2 diabetic patients without cardiovascular disease history, as compared with other antiplatelet agents. We recruited a total of 230 type 2 diabetic patients who had undergone IMT measurement twice within 1.5-2.5 years (mean 2.06 ± 0.32 years) interval. Among these participants, we classified them into three groups according to antiplatelet agent administration at baseline: Group I (n = 66), antiplatelet naïve; Group II (n = 75), other antiplatelet agent administration; and Group III (n = 50), cilostazol administration. We then analyzed the changes in clinical characteristics from baseline to 2 years. The changes in annual mean IMT at 2 years were 0.019 ± 0.045 mm/year, -0.001 ± 0.058 mm/year, and -0.019 ± 0.043 mm/year for Group I, II, and III, respectively (P < 0.001). Mean change in total cholesterol, low-density lipoprotein-cholesterol, and triglyceride compared with baseline decreased the most in Group III even after adjustment for statin use. We also observed that the odds ratio of carotid IMT progression at 2 years was the lowest in patients who were treated with cilostazol even after adjustment for change of metabolic parameters. When we categorized patients according to baseline carotid IMT tertile, the efficacy of cilostazol against carotid IMT progression was significant only when baseline IMT was over 0.662 mm (mean 0.801). Two-year treatment with cilostazol strongly inhibited carotid IMT progression compared to other antiplatelet agents in type 2 diabetic patients. This beneficial effect of cilostazol was significant when baseline IMT was thicker than 0.662 mm (mean 0.801 mm).

Cilostazol renoprotective effect: modulation of PPAR-γ, NGAL, KIM-1 and IL-18 underlies its novel effect in a model of ischemia-reperfusion

Cilostazol, a phosphodiesterase-III inhibitor, reportedly exhibits positive effects against ischemia/reperfusion (I/R)-induced injury in several models. However, its potential role against the renal I/R insult has not been elucidated. To test whether the PPAR-γ (of peroxisome proliferator activated receptor gamma) pathway is involved in the cilostazol effect, rats were randomized into sham, I/R, cilostazol (50 and 100 mg/kg per day, orally), pioglitazone (3 and 10 mg/kg per day, orally) and their combination at the low dose levels. Drugs regimens were administered for 14 days prior to the I/R induction. Pretreatment with cilostazol or pioglitazone provided significant protection against the I/R-induced renal injury as manifested by the attenuated serum levels of creatinine, blood urea nitrogen and cystatin C. Both drugs have also opposed the I/R-induced elevation in tissue contents/activity of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (Κim-1), nuclear factor-κB, interleuκin-18, caspase-1, as well as malondialdehyde, iNOS, myeloperoxidase, ICAM-1 and VCAM-1. Nevertheless, the drugs increased both the PPAR-γ transcriptional activity and the content of glutathione. Furthermore, combining the two low doses of both drugs produced effects comparable to that of the high dose level of either drug, advocating the fortification of pioglitazone renoprotective effect when given concomitantly with cilostazol. In conclusion, cilostazol purveyed conceivable novel renoprotective mechanisms and alleviated incidents associated with acute renal injury either alone or in combination with pioglitazone partially via the elevation of PPAR-γ besides the amendment of the aforementioned biomarkers.

Exercise performance and peripheral vascular insufficiency improve with AMPK activation in high-fat diet-fed mice

Intermittent claudication is a form of exercise intolerance characterized by muscle pain during walking in patients with peripheral artery disease (PAD). Endothelial cell and muscle dysfunction are thought to be important contributors to the etiology of this disease, but a lack of preclinical models that incorporate these elements and measure exercise performance as a primary end point has slowed progress in finding new treatment options for these patients. We sought to develop an animal model of peripheral vascular insufficiency in which microvascular dysfunction and exercise intolerance were defining features. We further set out to determine if pharmacological activation of 5'-AMP-activated protein kinase (AMPK) might counteract any of these functional deficits. Mice aged on a high-fat diet demonstrate many functional and molecular characteristics of PAD, including the sequential development of peripheral vascular insufficiency, increased muscle fatigability, and progressive exercise intolerance. These changes occur gradually and are associated with alterations in nitric oxide bioavailability. Treatment of animals with an AMPK activator, R118, increased voluntary wheel running activity, decreased muscle fatigability, and prevented the progressive decrease in treadmill exercise capacity. These functional performance benefits were accompanied by improved mitochondrial function, the normalization of perfusion in exercising muscle, increased nitric oxide bioavailability, and decreased circulating levels of the endogenous endothelial nitric oxide synthase inhibitor asymmetric dimethylarginine. These data suggest that aged, obese mice represent a novel model for studying exercise intolerance associated with peripheral vascular insufficiency, and pharmacological activation of AMPK may be a suitable treatment for intermittent claudication associated with PAD.

The blood glucose level increased in parallel with the heart rate following cilostazol administration in three diabetic patients

Cilostazol, a phosphodiesterase III inhibitor, is known to increase the heart rate; however, its effects on glucose metabolism remain unclear. We observed that the blood glucose level varied in parallel with the heart rate immediately after starting or stopping cilostazol therapy in three patients with type 2 diabetes. This finding indicates that cilostazol induces hyperglycemia and tachycardia in a portion of diabetic patients, presumably via similar pharmacological effects on different organs. Much more attention should be paid to the possible effects of cilostazol on glycemic control, including taking into consideration the risk-benefit ratio of cilostazol use and individual circumstances.

Cilostazol improves the response to ischemia in diabetic mice by a mechanism dependent on PPARγ

Cilostazol is effective for the treatment of peripheral ischemia. This compound has several beneficial effects on platelet aggregation, serum lipids and endothelial cells, and we recently found that it enhances collateral blood flow in the ischemic hind limbs of mice. Peroxisome proliferator-activated receptor (PPAR)γ, a receptor for thiazolidinediones, plays a role in angiogenesis. The aim of this work was to investigate the underlying molecular mechanisms and effects of cilostazol in a model of peripheral ischemia in diabetic mice. We induced diabetes in mice by streptozotocin (STZ) administration and studied ischemia-induced angiogenesis in the ischemic hind limbs of cilostazol-treated and untreated control mice. We found that perfusion recovery was significantly improved in treated compared with control diabetic mice. Interestingly, we found that the expression of PPARγ is reduced in ischemic tissues of diabetic mice. Furthermore, we discovered that local inhibition of the activity of this nuclear receptor decreased the angiogenic response to cilostazol treatment. Finally, we noted that this phenomenon is dependent on VEGF and modulated by PPARγ. Cilostazol administration enhances collateral blood flow in the ischemic hind limbs of STZ-induced diabetic mice through a PPARγ-dependent mechanism.

Phosphodiesterase III inhibition increases cAMP levels and augments the infarct size limiting effect of a DPP-4 inhibitor in mice with type-2 diabetes mellitus

PURPOSE

We assessed whether phosphodiesterase-III inhibition with cilostazol (Cil) augments the infarct size (IS)-limiting effects of MK0626 (MK), a dipeptidyl-peptidase-4 (DPP4) inhibitor, by increasing intracellular cAMP in mice with type-2 diabetes.

METHODS

Db/Db mice received 3-day MK (0, 1, 2 or 3 mg/kg/d) with or without Cil (15 mg/kg/d) by oral gavage and were subjected to 30 min coronary artery occlusion and 24 h reperfusion.

RESULTS

Cil and MK at 2 and 3 mg/kg/d significantly reduced IS. Cil and MK had additive effects at all three MK doses. IS was the smallest in the MK-3+Cil. MK in a dose dependent manner and Cil increased cAMP levels (p < 0.001). cAMP levels were higher in the combination groups at all MK doses. MK-2 and Cil increased PKA activity when given alone; however, PKA activity was significantly higher in the MK-2+Cil group than in the other groups. Both MK-2 and Cil increased myocardial levels of Ser(133) P-CREB, Ser(523) P-5-lipoxygenase, Ser(473)P-Akt and Ser(633) P-eNOS. These levels were significantly higher in the MK-2+Cil group. Myocardial PTEN (Phosphatase and tensin homolog on chromosome ten) levels were significantly higher in the Db/Db mice compared to nondiabetic mice. MK-2 and Cil normalized PTEN levels. PTEN levels tended to be lower in the combination group than in the MK and Cil alone groups.

CONCLUSION

MK and Cil have additive IS-limiting effects in diabetic mice. The additive effects are associated with an increase in myocardial cAMP levels and PKA activity with downstream phosphorylation of Akt, eNOS, 5-lipoxygenase and CREB and downregulation of PTEN expression.

Non-alcoholic fatty liver disease and cardiovascular risk

The term "Non-alcoholic fatty liver disease" (NAFLD) covers a series of liver lesions similar to those induced by alcohol, but not caused by alcohol use. The importance of NAFLD lies in the high prevalence in Western societies and, from the point of view of the liver, in its progression from steatosis to cirrhosis and liver cancer. More recently, NAFLD has been found to be associated with lipid metabolism disorders, the deposition of fat outside of the adipocytes, insulin resistance and Metabolic Syndrome. Also attributed to NAFLD is a heightened systemic pro-inflammatory state, which accelerates arteriosclerosis, thereby increasing cardiovascular risk and associated cardiovascular events. Here we provide an update to the etiopathogenesis of NAFLD, its influence on cardiovascular disease, and the treatment options.

Phosphodiesterase-3 inhibition augments the myocardial infarct size-limiting effects of exenatide in mice with type 2 diabetes

Glucagon-like peptide (GLP)-1 receptor activation increases intracellular cAMP with downstream activation of PKA. Cilostazol (CIL), a phosphodiesterase-3 inhibitor, prevents cAMP degradation. We assessed whether CIL amplifies the exenatide (EX)-induced increase in myocardial cAMP levels and PKA activity and augments the infarct size (IS)-limiting effects of EX in db/db mice. Mice fed a Western diet received oral CIL (10 mg/kg) or vehicle by oral gavage 24 h before surgery. One hour before surgery, mice received EX (1 μg/kg sc) or vehicle. Additional mice received H-89, a PKA inhibitor, alone or with CIL + EX. Mice underwent 30 min of coronary artery occlusion and 24 h of reperfusion. Both EX and CIL increased myocardial cAMP levels and PKA activity. Levels were significantly higher in the EX + CIL group. Both EX and CIL reduced IS. IS was the smallest in the CIL + EX group. H-89 completely blocked the IS-limiting effects of EX + CIL. EX + CIL decreased phosphatase and tensin homolog on chromosome 10 upregulation and increased Akt and ERK1/2 phosphorylation after ischemia-reperfusion. These effects were blocked by H-89. In conclusion, EX and CIL have additive effects on IS limitation in diabetic mice. The additive effects are related to cAMP-induced PKA activation, as H-89 blocked the protective effect of CIL + EX.

Up- and down-regulation of adiponectin expression and multimerization: mechanisms and therapeutic implication

Adiponectin has been receiving a great deal of attention due to its potential therapeutic use for metabolic and cardiovascular disorders. Adiponectin expression levels and multimerization are down-regulated in obesity and up-regulated by insulin sensitizers such as thiazolidinediones (TZDs), metformin, sulfonylurea and resveratrol (RSV). The precise mechanisms underlying adiponectin up- and down-regulation remain largely unknown, but recent studies indicate that the cellular and plasma levels of adiponectin could be regulated at both transcriptional and post-transcriptional levels. At the post-translational level, TZDs and resveratrol promote adiponectin levels and multimerization via up-regulation of disulfide-bond-A oxidoreductase-like protein (DsbA-L). Adiponectin levels are also stimulated by FOXO1 and AMP-activated protein kinase (AMPK), and are suppressed by PKA or silencing mediator of retinoid and thyroid hormone receptors (SMRT). Since multimerization is important not only for adiponectin function but also for stability, increasing adiponectin multimerization has become a promising drug target for the treatment of metabolic diseases and other related disorders.

PDE inhibitors: a new approach to treat metabolic syndrome?

About one third of people in the world suffer from metabolic syndrome (MetS), with symptoms such as hypertension and elevated blood cholesterol, and with increased risk of developing additional diseases such as diabetes mellitus and heart disease. The progression of this multifactorial pathology, which targets various tissues and organs, might necessitate a renewal in therapeutic approaches. Since cyclic nucleotide phosphodiesterases (PDEs), enzymes which hydrolyze cyclic AMP and cyclic GMP, play a crucial role in regulating endocrine and cardiovascular functions, inflammation, oxidative stress, and cell proliferation, all of which contribute to MetS, we wonder whether PDE inhibitors might represent new therapeutic approaches for preventing and treating MetS.

Effect of cilostazol on the progression of carotid intima-media thickness: a meta-analysis of randomized controlled trials

BACKGROUND

It has been well established that cilostazol has anti-proliferative effect against in-stent restenosis. However, it remains unclear whether cilostazol can prevent the progression of carotid atherosclerosis.

METHODS AND RESULTS

We performed a meta-analysis of all relevant randomized controlled trials (RCTs) to evaluate the effect of cilostazol on the progression of carotid intima-media thickness (IMT). Five RCTs with 698 patients [597 subjects with type 2 diabetes mellitus (T2DM)] were included in this study. Cilostazol was associated with a significant reduction in the progression of carotid IMT (WMD, -0.08mm, 95% CI -0.13, -0.04; P=0.00003). Subgroup analysis shows that cilostazol monotherapy or addition to dual antiplatelet therapy (aspirin and clopidogrel) was superior to placebo (WMD, -0.04mm, 95% CI -0.05, -0.03; P<0.00001), no antiplatelet medication (WMD, -0.12mm, 95% CI -0.21, -0.03; P=0.008), aspirin monotherapy (WMD, -0.06mm, 95% CI -0.12, 0.00; P=0.04) or dual antiplatelet therapy (WMD, -0.16mm, 95% CI -0.30, -0.02; P=0.03) in preventing the progression of carotid IMT. Cilostazol resulted in a significant decrease in total cholesterol (WMD -8.47mg/dl, 95% CI -14.18, -2.75; P=0.004) and LDL-C (WMD -8.25mg/dl, 95% CI -14.15, -2.36; P=0.006) and favorable trends in reducing triglyceride (WMD -15.83mg/dl, 95% CI -32.14, 0.48; P=0.06).

CONCLUSION

It suggests that cilostazol may have beneficial effects in preventing the progression of carotid atherosclerosis and improving pro-atherogenic lipid profile, especially in patients with T2DM. Whether the anti-atherosclerotic effect of cilostazol is independent of improving pro-atherogenic dyslipidemia is worth further investigation.

Alterations in cyclic nucleotide phosphodiesterase activities in omental and subcutaneous adipose tissues in human obesity

Objective: To elucidate the activity and expression of cyclic nucleotide phosphodiesterase (PDE) families in omental (OM) and subcutaneous (SC) adipose tissue and adipocytes, and to study alterations in their activity in human obesity.

Design: Cross-sectional, translational research study.

Patients: In total, 25 obese and 9 non-obese subjects undergoing gastrointestinal surgery participated in the study.

Results: Inverse correlations between PDE activities and body mass index (BMI) were seen in both SC and OM adipose tissue. Inverse correlations between total PDE and PDE3 activity and BMI were seen in OM adipocytes but not in SC adipocytes. In both SC and OM adipose tissue of obese patients, total PDE and PDE3 activities were decreased compared with the controls. In SC adipose tissue of Type 2 diabetes (T2D) patients, the PDE activity not inhibitable by PDE3 or PDE4 inhibitors (PDEn) was increased compared with obese non-diabetic patients. In addition to PDE3 and 4 isoforms, PDE7B, PDE9A and PDE10A proteins were also detected in adipose tissue or adipocytes.

Conclusions: Multiple PDE families are present in human adipose tissue and their activities are differentially affected by obesity and T2D.

Exposure to the JNK inhibitor SP600125 (anthrapyrazolone) during early zebrafish development results in morphological defects

SP600125 (anthrapyrazolone) is a synthetic polyaromatic chemical that inhibits c-Jun N-terminal kinase (JNK) signaling by interfering with phosphorylation of c-Jun. To determine the pharmacological impact of SP600125 on zebrafish development, we incubated embryos in various concentrations of SP600125 from 18 h postfertilization (hpf) to 48 hpf. Embryos treated with 1.25 µm appeared with occasional pericardium edema. Treatment with 12.5 µm resulted in complete mortality by 120 hpf, preventing an assessment of physiological defects. Embryos treated with 5 µm exhibited slowed overall growth, a delay in hatching and numerous morphological defects such as pericardium edema, yolk sac edema, swim bladder deflation, bent vertebrae and eye and jaw malformations. Whole-mount immunohistochemical studies using an anti-acetylated β-tubulin antibody confirmed developmental defects in the nervous system. Within the retina, fish treated with 1.25 µm showed a mild reduction of immunoreactivity. Immunoreactivity in the retina was further reduced in fish treated with 5 µm of SP600125. In these fish, eyes and olfactory organs were half the size compared with other groups. Multiple lenses were observed in 67% of these fish. A second experiment with a shorter exposure period of SP600125 (6 h) presented significantly fewer morphological defects. The treatment led to a delay in hatching, and increased incidences of swim bladder deflation and pericardium edema with increasing concentrations. In summary, SP600125 caused developmental abnormalities during zebrafish organogenesis starting at 1.25 µm and the defects were exacerbated with increasing concentrations. Our study suggests that SP600125 at 1.25 µm and beyond has devastating consequences for zebrafish development.

Jejunum inflammation in obese and diabetic mice impairs enteric glucose detection and modifies nitric oxide release in the hypothalamus

Intestinal detection of nutrients is a crucial step to inform the whole body of the nutritional status. In this paradigm, peripheral information generated by nutrients is transferred to the brain, which in turn controls physiological functions, including glucose metabolism. Here, we investigated the effect of enteric glucose sensors stimulation on hypothalamic nitric oxide (NO) release in lean or in obese/diabetic (db/db) mice. By using specific NO amperometric probes implanted directly in the hypothalamus of mice, we demonstrated that NO release is stimulated in response to enteric glucose sensors activation in lean but not in db/db mice. Alteration of gut to hypothalamic NO signaling in db/db mice is associated with a drastic increase in inflammatory, oxidative/nitric oxide (iNOS, IL-1β), and endoplasmic reticulum stress (CHOP, ATF4) genes expression in the jejunum. Although we could not exclude the importance of the hypothalamic inflammatory state in obese and diabetic mice, our results provide compelling evidence that enteric glucose sensors could be considered as potential targets for metabolic diseases.

Suppression of encephalitogenic T-cell responses by cilostazol is associated with upregulation of regulatory T cells

Cilostazol is a specific phosphodiesterase III inhibitor. Recent data show that cilostazol has anti-inflammatory effects and administration of cilostazol ameliorates experimental autoimmune encephalomyelitis (EAE). In this study, we used a mouse EAE model to explore the role of cilostazol in Th1 and Th17 cell-mediated immune responses. We found that cilostazol suppressed mitogen or antigen-induced T-cell responses and Th17 cell differentiation in vitro, which correlated with enhanced Treg-cell responses. Beginning of oral administration of cilostazol at the onset of EAE significantly inhibited encephalitogenic T cells, reduced the levels of inflammatory cytokines in the central nervous system, and ameliorated the severity of EAE. Moreover, administration of cilostazol markedly enhanced Treg-cell response in vivo. Cilostazol, therefore, may exert its therapeutic effects through upregulation of Treg-cell activity.

Adenosine Monophosphate-Activated Protein Kinase (AMPK) as a New Target for Antidiabetic Drugs: A Review on Metabolic, Pharmacological and Chemical Considerations

In view of the epidemic nature of type 2 diabetes and the substantial rate of failure of current oral antidiabetic drugs the quest for new therapeutics is intensive. The adenosine monophosphate-activated protein kinase (AMPK) is an important regulatory protein for cellular energy balance and is considered a master switch of glucose and lipid metabolism in various organs, especially in skeletal muscle and liver. In skeletal muscles, AMPK stimulates glucose transport and fatty acid oxidation. In the liver, it augments fatty acid oxidation and decreases glucose output, cholesterol and triglyceride synthesis. These metabolic effects induced by AMPK are associated with lowering blood glucose levels in hyperglycemic individuals. Two classes of oral antihyperglycemic drugs (biguanidines and thiazolidinediones) have been shown to exert some of their therapeutic effects by directly or indirectly activating AMPK. However, side effects and an acquired resistance to these drugs emphasize the need for the development of novel and efficacious AMPK activators. We have recently discovered a new class of hydrophobic D-xylose derivatives that activates AMPK in skeletal muscles in a non insulin-dependent manner. One of these derivatives (2,4;3,5-dibenzylidene-D-xylose-diethyl-dithioacetal) stimulates the rate of hexose transport in skeletal muscle cells by increasing the abundance of glucose transporter-4 (GLUT-4) in the plasma membrane through activation of AMPK. This compound reduces blood glucose levels in diabetic mice and therefore offers a novel strategy of therapeutic intervention strategy in type 2 diabetes. The present review describes various classes of chemically-related compounds that activate AMPK by direct or indirect interactions and discusses their potential for candidate antihyperglycemic drug development.