Disruption of the plasminogen activator inhibitor 1 gene reduces the adiposity and improves the metabolic profile of genetically obese and diabetic ob/ob mice

Blood PAI-1 and cardiovascular and metabolic risk factors among the middle-aged women from SWAN study

The research on the role of plasminogen activator inhibitor-1 (PAI-1) in cardiovascular and metabolic diseases is insufficient. We aimed to explore whether elevated blood PAI-1 levels are significantly related to increased cardiovascular and metabolic risk factors in a midlife women population. Data were obtained from baseline characteristics in Study of Women's Health Across the Nation (SWAN) study. Multivariable linear regression models were performed to examine for the trends of associations between PAI-1 and cardiovascular and metabolic risk factors (systolic BP, diastolic BP, fasting blood glucose, insulin, HDL-C, LDL-C, TG and TC), respectively. Smooth curve demonstrated gradual upward trends on associations of blood PAI-1 levels with LDL-C, TG, TC, fasting blood glucose, insulin, systolic BP and diastolic BP (all P < 0.05) and a gradual downward trend of PAI-1 levels with HDL-C (P < 0.05). Multivariable linear regression models still indicated that increased blood PAI-1 levels were associated with higher cardiovascular and metabolic risk after confounding factors including age, race/ethnicity, ever smoked regularly, alcohol in last 24 h, menopausal status, total family income and BMI were controlled for. Moreover, we observed that the independent associations between blood levels of PAI-1 and cardiovascular and metabolic risk factors examined by stratified analysis were not influenced by age, smoking status, menopausal status and BMI, respectively. Our analysis showed that increased blood PAI-1 levels were associated with higher level for cardiovascular and metabolic risk factors which mainly causes to higher possibility of cardio-cerebrovascular diseases in a large-sample midlife women subjects.

PAI-1 Interaction with Sortilin Related Receptor-1 is Required for Lung Fibrosis

Plasminogen activator inhibitor-1 (PAI-1) has been previously shown to promote lung fibrosis via a mechanism that requires an intact vitronectin (VTN) binding site. In the present study, employing two distinct murine fibrosis models, we find that VTN is not required for PAI-1 to drive lung scarring. This result suggested the existence of a previously unrecognized profibrotic PAI-1-protein interaction involving the VTN-binding site for PAI-1. Using an unbiased proteomic approach, we identified sortilin related receptor 1 (SorlA) as the most highly enriched PAI-1 interactor in the fibrosing lung. We next investigated the role of SorlA in pulmonary fibrosis and found that SorlA deficiency protected against lung scarring in a murine model. We further show that, while VTN deficiency does not influence fibrogenesis in the presence or absence of PAI-1, SorlA is required for PAI-1 to promote scarring. These results, together with data showing increased SorlA levels in human IPF lung tissue, support a novel mechanism through which the potent profibrotic mediator PAI-1 drives lung fibrosis and implicate SorlA as a new therapeutic target in IPF treatment.

Increased plasminogen activator inhibitor-1 (PAI-1) and its associations with metabolic risk in healthy young adults with early life stress

OBJECTIVES

We aimed to characterize the interplay between early life stress (ELS), metabolic syndrome (MetS), and plasminogen activator inhibitor-1 (PAI-1), a major inhibitor of the fibrinolytic system implicated in cardiometabolic diseases. We also examined the understudied intersection of ELS, physical activity and PAI-1.

METHODS

Healthy young adults ages 18-40 (N=200; 68% female) were recruited from the community. Participants with ELS (N=118) experienced childhood maltreatment, and the majority (n=92) also experienced childhood parental loss. Control participants (N=82) had no history of childhood maltreatment or parental loss. Participants had no current cardiometabolic or thrombotic conditions. Fasting plasma samples were assessed for markers of metabolic risk and total PAI-1 using the Bio-Plex Pro Human Diabetes Panel (Bio-Rad Laboratories). A composite metabolic risk z-score (MetS risk) was computed from the mean standardized z-scores of waist-to-height ratio, systolic and diastolic blood pressure, triglycerides, total cholesterol, LDL and HLD cholesterol, fasting plasma glucose, and hemoglobin A1c.

RESULTS

We found that a history of ELS was linked to both higher PAI-1 levels and a higher MetS risk score. ELS was associated with a higher MetS Z-score in adulthood via increased circulating PAI-1 levels (Average Causal Mediation Effect [ACME]= 0.07, p = 0.036). ELS was also linked to increased PAI-1 levels via greater MetS z-scores (ACME = 0.02, p < 0.001). There was a significant interaction effect of ELS and exercise on PAI-1 levels (p = 0.03), such that engaging in higher levels of daily exercise was linked to lower PAI-1 levels in individuals with ELS.

CONCLUSION

Healthy young adults with ELS have elevated PAI-1 levels and metabolic risk scores. Among individuals with ELS, exercise is linked to lower PAI-1 levels, suggesting a potential direction for early intervention.

Intracellular tPA-PAI-1 interaction determines VLDL assembly in hepatocytes

Apolipoprotein B (apoB)-lipoproteins initiate and promote atherosclerotic cardiovascular disease. Plasma tissue plasminogen activator (tPA) activity is negatively associated with atherogenic apoB-lipoprotein cholesterol levels in humans, but the mechanisms are unknown. We found that tPA, partially through the lysine-binding site on its Kringle 2 domain, binds to the N terminus of apoB, blocking the interaction between apoB and microsomal triglyceride transfer protein (MTP) in hepatocytes, thereby reducing very-low-density lipoprotein (VLDL) assembly and plasma apoB-lipoprotein cholesterol levels. Plasminogen activator inhibitor 1 (PAI-1) sequesters tPA away from apoB and increases VLDL assembly. Humans with PAI-1 deficiency have smaller VLDL particles and lower plasma levels of apoB-lipoprotein cholesterol. These results suggest a mechanism that fine-tunes VLDL assembly by intracellular interactions among tPA, PAI-1, and apoB in hepatocytes.

Streptozotocin-Induced Type 1 and 2 Diabetes Mellitus Mouse Models Show Different Functional, Cellular and Molecular Patterns of Diabetic Cardiomyopathy

The main cause of morbidity and mortality in diabetes mellitus (DM) is cardiovascular complications. Diabetic cardiomyopathy (DCM) remains incompletely understood. Animal models have been crucial in exploring DCM pathophysiology while identifying potential therapeutic targets. Streptozotocin (STZ) has been widely used to produce experimental models of both type 1 and type 2 DM (T1DM and T2DM). Here, we compared these two models for their effects on cardiac structure, function and transcriptome. Different doses of STZ and diet chows were used to generate T1DM and T2DM in C57BL/6J mice. Normal euglycemic and nonobese sex- and age-matched mice served as controls (CTRL). Immunohistochemistry, RT-PCR and RNA-seq were employed to compare hearts from the three animal groups. STZ-induced T1DM and T2DM affected left ventricular function and myocardial performance differently. T1DM displayed exaggerated apoptotic cardiomyocyte (CM) death and reactive hypertrophy and fibrosis, along with increased cardiac oxidative stress, CM DNA damage and senescence, when compared to T2DM in mice. T1DM and T2DM affected the whole cardiac transcriptome differently. In conclusion, the STZ-induced T1DM and T2DM mouse models showed significant differences in cardiac remodeling, function and the whole transcriptome. These differences could be of key relevance when choosing an animal model to study specific features of DCM.

Impact of scaling and root planing on salivary and serum plasminogen activator inhibitor-1 expression in patients with periodontitis with and without type 2 diabetes mellitus

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is significantly enhanced in insulin resistance and inflammation and ascribed as a proinflammatory marker. This study aimed to compare and correlate salivary and serum PAI-1 and alpha 2-macroglobulin (α2MG) in patients with periodontitis with and without type 2 diabetes mellitus (T2DM) and also appraise the consequence of periodontal treatment on these biomarkers.

METHODS

Sixty subjects enlisted were split into two groups; Group 1 consisted of 30 systemically healthy subjects with Stage II and III, generalized, Grade B, C periodontitis while Group 2 consisted of 30 patients with periodontitis and well-controlled T2DM (PDM). Salivary and serum PAI-1 and α2MG levels were estimated by enzyme-linked immunosorbent assay and allied with clinical parameters before and 3 months post non-surgical periodontal therapy (NSPT). Data were statistically analyzed using student t-test and Spearman correlation.

RESULTS

Analogous improvements in clinical periodontal markers were experienced in both groups after initial periodontal treatment. Estimates of salivary and serum PAI-1 and α2MG were higher among the PDM group compared with periodontitis alone at baseline. Significant diminution in estimates of biomarkers was noted 3 months after NSPT. In the PDM group, there was also an improvement in glycemic control.

CONCLUSIONS

NSPT positively impacted both groups. Noteworthy expression of salivary and serum PAI-1 in patients with periodontitis and diabetes insinuates a possible role of the adipokine in periodontal inflammation and glucose level regulation. Salivary PAI-1 could thus be used as a diagnostic biomarker to detect disease activity and to track periodontal therapy response.

The Association of Acute Phase Proteins in Stress and Inflammation-Induced T2D

Acute phase proteins (APPs), such as plasminogen activator inhibitor-1 (PAI-1), serum amyloid A (SAA), and C-reactive protein (CRP), are elevated in type-2 diabetes (T2D) and are routinely used as biomarkers for this disease. These APPs are regulated by the peripheral mediators of stress (i.e., endogenous glucocorticoids (GCs)) and inflammation (i.e., pro-inflammatory cytokines), with both implicated in the development of insulin resistance, the main risk factor for the development of T2D. In this review we propose that APPs, PAI-1, SAA, and CRP, could be the causative rather than only a correlative link between the physiological elements of risk (stress and inflammation) and the development of insulin resistance.

Adipokines, Hepatokines and Myokines: Focus on Their Role and Molecular Mechanisms in Adipose Tissue Inflammation

Chronic low-grade inflammation in adipose tissue (AT) is a hallmark of obesity and contributes to various metabolic disorders, such as type 2 diabetes and cardiovascular diseases. Inflammation in ATs is characterized by macrophage infiltration and the activation of inflammatory pathways mediated by NF-κB, JNK, and NLRP3 inflammasomes. Adipokines, hepatokines and myokines - proteins secreted from AT, the liver and skeletal muscle play regulatory roles in AT inflammation via endocrine, paracrine, and autocrine pathways. For example, obesity is associated with elevated levels of pro-inflammatory adipokines (e.g., leptin, resistin, chemerin, progranulin, RBP4, WISP1, FABP4, PAI-1, Follistatin-like1, MCP-1, SPARC, SPARCL1, and SAA) and reduced levels of anti-inflammatory adipokines such as adiponectin, omentin, ZAG, SFRP5, CTRP3, vaspin, and IL-10. Moreover, some hepatokines (Fetuin A, DPP4, FGF21, GDF15, and MANF) and myokines (irisin, IL-6, and DEL-1) also play pro- or anti-inflammatory roles in AT inflammation. This review aims to provide an updated understanding of these organokines and their role in AT inflammation and related metabolic abnormalities. It serves to highlight the molecular mechanisms underlying the effects of these organokines and their clinical significance. Insights into the roles and mechanisms of these organokines could provide novel and potential therapeutic targets for obesity-induced inflammation.

A Serpin With a Finger in Many PAIs: PAI-1's Central Function in Thromboinflammation and Cardiovascular Disease

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor (serpin) superfamily. PAI-1 is the principal inhibitor of the plasminogen activators, tissue plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). Turbulence in the levels of PAI-1 tilts the balance of the hemostatic system resulting in bleeding or thrombotic complications. Not surprisingly, there is strong evidence that documents the role of PAI-1 in cardiovascular disease. The more recent uncovering of the coalition between the hemostatic and inflammatory pathways has exposed a distinct role for PAI-1. The storm of proinflammatory cytokines liberated during inflammation, including IL-6 and TNF-α, directly influence PAI-1 synthesis and increase circulating levels of this serpin. Consequently, elevated levels of PAI-1 are commonplace during infection and are frequently associated with a hypofibrinolytic state and thrombotic complications. Elevated PAI-1 levels are also a feature of metabolic syndrome, which is defined by a cluster of abnormalities including obesity, type 2 diabetes, hypertension, and elevated triglyceride. Metabolic syndrome is in itself defined as a proinflammatory state associated with elevated levels of cytokines. In addition, insulin has a direct impact on PAI-1 synthesis bridging these pathways. This review describes the key physiological functions of PAI-1 and how these become perturbed during disease processes. We focus on the direct relationship between PAI-1 and inflammation and the repercussion in terms of an ensuing hypofibrinolytic state and thromboembolic complications. Collectively, these observations strengthen the utility of PAI-1 as a viable drug target for the treatment of various diseases.

A Narrative Review on Plasminogen Activator Inhibitor-1 and Its (Patho)Physiological Role: To Target or Not to Target?

Plasminogen activator inhibitor-1 (PAI-1) is the main physiological inhibitor of plasminogen activators (PAs) and is therefore an important inhibitor of the plasminogen/plasmin system. Being the fast-acting inhibitor of tissue-type PA (tPA), PAI-1 primarily attenuates fibrinolysis. Through inhibition of urokinase-type PA (uPA) and interaction with biological ligands such as vitronectin and cell-surface receptors, the function of PAI-1 extends to pericellular proteolysis, tissue remodeling and other processes including cell migration. This review aims at providing a general overview of the properties of PAI-1 and the role it plays in many biological processes and touches upon the possible use of PAI-1 inhibitors as therapeutics.

Genetic factors associated with obesity risks in a Kazakhstani population

Objectives

There is limited published literature on the genetic risks of chronic inflammatory related disease (eg, obesity and cardiovascular disease) among the Central Asia population. The aim is to determine potential genetic loci as risk factors for obesity for the Kazakhstani population.

Setting

Kazakhstan.

Participants

One hundred and sixty-three Kazakhstani nationals (ethnic groups: both Russians and Kazakhs) were recruited for the cross-sectional study. Linear regression models, adjusted for confounding factors, were used to examine the genetic associations of single nucleotide polymorphisms (SNPs) in 19 genetic loci with obesity (73 obese/overweight individuals and 90 controls).

Results

Overall, logistic regression analyses revealed genotypes C/T in CRP (rs1205), A/C in AGTR1 (rs5186), A/G in CBS (rs234706), G/G in FUT2 (rs602662), A/G in PAI-1 (rs1799889), G/T (rs1801131) and A/G (rs1801133) in MTHFR genes significantly decrease risk of overweight/obesity. After stratification for ethnicity, rs234706 was significantly associated with overweight/obesity in both Russians and Kazakhs, while rs1800871 was significant in Kazakhs only.

Conclusions

This study revealed that variations in SNPs known to be associated with cardiovascular health can also contribute to the risks of developing obesity in the population of Kazakhstan.

Role of PAI-1 in hepatic steatosis and dyslipidemia

Plasminogen activator inhibitor 1 (PAI-1) is a functional biomarker of the metabolic syndrome. Previous studies have demonstrated that PAI-1 is a mechanistic contributor to several elements of the syndrome, including obesity, hypertension and insulin resistance. Here we show that PAI-1 is also a critical regulator of hepatic lipid metabolism. RNA sequencing revealed that PAI-1 directly regulates the transcriptional expression of numerous genes involved in mammalian lipid homeostasis, including PCSK9 and FGF21. Pharmacologic or genetic reductions in plasma PAI-1 activity ameliorates hyperlipidemia in vivo. These experimental findings are complemented with the observation that genetic deficiency of PAI-1 is associated with reduced plasma PCSK9 levels in humans. Taken together, our findings identify PAI-1 as a novel contributor to mammalian lipid metabolism and provides a fundamental mechanistic insight into the pathogenesis of one of the most pervasive medical problems worldwide.

Phosphoproteomics of Acute Cell Stressors Targeting Exercise Signaling Networks Reveal Drug Interactions Regulating Protein Secretion

Exercise engages signaling networks to control the release of circulating factors beneficial to health. However, the nature of these networks remains undefined. Using high-throughput phosphoproteomics, we quantify 20,249 phosphorylation sites in skeletal muscle-like myotube cells and monitor their responses to a panel of cell stressors targeting aspects of exercise signaling in vivo. Integrating these in-depth phosphoproteomes with the phosphoproteome of acute aerobic exercise in human skeletal muscle suggests that co-administration of β-adrenergic and calcium agonists would activate complementary signaling relevant to this exercise context. The phosphoproteome of cells treated with this combination reveals a surprising divergence in signaling from the individual treatments. Remarkably, only the combination treatment promotes multisite phosphorylation of SERBP1, a regulator of Serpine1 mRNA stability, a pro-fibrotic secreted protein. Secretome analysis reveals that the combined treatments decrease secretion of SERPINE1 and other deleterious factors. This study provides a framework for dissecting phosphorylation-based signaling relevant to acute exercise.

Plasminogen activator inhibitor-1 activity and the 4G/5G polymorphism are prospectively associated with blood pressure and hypertension status

OBJECTIVES

Plasminogen activator inhibitor-1 (PAI-1) has consistently shown positive associations with blood pressure (BP). Whether elevations in PAI-1 levels precede or result from raised BP is still under debate and data on prospective studies are limited. Hence, we investigated the prospective associations of PAI-1 and the 4G/5G polymorphism with brachial and central BP and pulse pressure (PP) over a 10-year period.

METHODS

Black South Africans aged 30 years and older were included. Baseline data collection commenced in 2005 (n = 2010) with follow-up data collection in 2010 (n = 1288) and 2015 (n = 926). Plasma PAI-1 activity (PAI-1act), 4G/5G polymorphism genotyping, waist circumference and BP measurements were performed and analysed using sequential regression and mixed models.

RESULTS

In multivariable adjusted analyses, PAI-1act and the 4G/4G (vs. the 5G/5G) genotype increased the odds of developing hypertension in the total group [1.04 (1.01; 1.08) and 1.82 (1.07; 3.12) respectively]. Furthermore, PAI-1act was prospectively associated with brachial SBP (r = 0.0815) and PP (r = 0.0832) in the total group, and with central PP in women (r = 0.1125; all P < 0.05). Addition of waist circumference to the models either decreased or nullified the contribution of PAI-1act to BP and hypertension development.

CONCLUSION

PAI-1act and the 4G/4G (vs. the 5G/5G) genotype increased the odds of developing hypertension. Furthermore, PAI-1act associated prospectively with both brachial and central BP. These associations were mediated in part by central adiposity. The study supports the hypothesis that PAI-1 also contributes to hypertension development rather than solely being a consequence thereof.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

A Noncanonical Role for Plasminogen Activator Inhibitor Type 1 in Obesity-Induced Diabetes

Obesity is a major risk factor for type 2 diabetes because of chronic hepatic inflammation and resultant insulin resistance. Hepatocyte growth factor (HGF) is responsible for resetting hepatic homeostasis after injury following activation by urokinase-type plasminogen activator (u-PA; encoded by the PLAU gene). Plasminogen activator inhibitor type-1 (PAI-1; encoded by the SERPINE1 gene), a u-PA inhibitor and antifibrinolytic agent, is often elevated in obesity and is linked to cardiovascular events. We hypothesized that, in addition to its role in preventing fibrinolysis, elevated PAI-1 inhibits HGF's activation by u-PA and the resultant anti-inflammatory and hepatoprotective properties. Wild-type and PAI-1 knockout (KO) mice on a high-fat diet both became significantly heavier than lean controls; however, the obese KO mice demonstrated improved glucose metabolism compared with wild-type mice. Obese KO mice also exhibited an increase in conversion of latent single-chain HGF to active two-chain HGF, coinciding with an increase in the phosphorylation of the HGF receptor (HGFR or MET, encoded by the MET gene), as well as dampened inflammation. These results strongly suggest that, in addition to its other functions, PAI-mediated inhibition of HGF activation prohibits the resolution of inflammation in the context of obesity-induced type 2 diabetes.

Dual-reporter high-throughput screen for small-molecule in vivo inhibitors of plasminogen activator inhibitor type-1 yields a clinical lead candidate

Plasminogen activator inhibitor type-1 (PAI-1) is a serine protease inhibitor (serpin) implicated in numerous pathological processes, including coronary heart disease, arterial and venous thrombosis, and chronic fibrotic diseases. These associations have made PAI-1 an attractive pharmaceutical target. However, the complexity of the serpin inhibitory mechanism, the inherent metastability of serpins, and the high-affinity association of PAI-1 with vitronectin in vivo have made it difficult to identify pharmacologically effective small-molecule inhibitors. Moreover, the majority of current small-molecule PAI-1 inhibitors are poor pharmaceutical candidates. To this end and to find leads that can be efficiently applied to in vivo settings, we developed a dual-reporter high-throughput screen (HTS) that reduced the rate of nonspecific and promiscuous hits and identified leads that inhibit human PAI-1 in the high-protein environments present in vivo Using this system, we screened >152,000 pure compounds and 27,000 natural product extracts (NPEs), reducing the apparent hit rate by almost 10-fold compared with previous screening approaches. Furthermore, screening in a high-protein environment permitted the identification of compounds that retained activity in both ex vivo plasma and in vivo Following lead identification, subsequent medicinal chemistry and structure-activity relationship (SAR) studies identified a lead clinical candidate, MDI-2268, having excellent pharmacokinetics, potent activity against vitronectin-bound PAI-1 in vivo, and efficacy in a murine model of venous thrombosis. This rigorous HTS approach eliminates promiscuous candidate leads, significantly accelerates the process of identifying PAI-1 inhibitors that can be rapidly deployed in vivo, and has enabled identification of a potent lead compound.

PAI-1 Exacerbates White Adipose Tissue Dysfunction and Metabolic Dysregulation in High Fat Diet-Induced Obesity

Background: Plasminogen activator inhibitor (PAI)-1 levels and activity are known to increase during metabolic syndrome and obesity. In addition, previous studies have implicated PAI-1 in adipose tissue (AT) expansion while also contributing to insulin resistance. As inflammation is also known to occur in AT during obesity, we hypothesized that in a high-fat diet (HFD)-induced obese mouse model PAI-1 contributes to macrophage-mediated inflammation and metabolic dysfunction.

Methods: Four- to five-weeks-old male C57B6/6J mice were fed a HFD (45%) for 14 weeks, while age-matched control mice were fed a standard laboratory chow diet (10% fat). Additional studies were performed in PAI-1 knockout mice and wild type mice treated with an inhibitor (PAI-039) of PAI-1. Macrophage polarization were measured by real time PCR.

Results: HFD mice showed increased expression of PAI-1 in visceral white AT (WAT) that also displayed increased macrophage numbers. PAI-1 deficient mice exhibited increased numbers of anti-inflammatory macrophages in WAT and were resistant to HFD-induced obesity. Similarly, pharmacological inhibition of PAI-1 using PAI-039 significantly decreased macrophage infiltration in WAT and improved metabolic status in HFD-induced wild-type mice. Importantly, the numbers of M1 macrophages appeared to be increased by the HFD and decreased by either genetic PAI-1 depletion or PAI-039 treatment.

Conclusions: Collectively, our findings provide support for PAI-1 contributing to the development of inflammation in adipose tissue and explain the mechanism of inflammation modulated by PAI-1 in the disordered metabolism in HFD-induced obesity.

Obesity-Associated Diseases Biomarkers Are Differently Modulated in Lean and Obese Individuals and Inversely Correlated to Plasma Polyphenolic Metabolites After 6 Weeks of Mango (Mangifera indica L.) Consumption

SCOPE

Mangos are a rich source of gallotannin-derived polyphenols that may exert anti-inflammatory effects relevant to obesity-related chronic diseases. This randomized human clinical study investigated the influence of daily mango supplementation for 6 weeks on inflammation and metabolic functions in lean and obese individuals.

METHODS AND RESULTS

Lean (n = 12, body mass index [BMI] 18-26.2 kg m^-2 ) and obese (n = 9, BMI >28.9 kg m^-2 ) participants, aged 18-65 years received daily 400 g of mango pulp for 6 weeks. Inflammatory cytokines, metabolic hormones, and lipid profiles were examined in plasma before and after 6 weeks. In lean participants, systolic blood pressure was lowered by 4 mmHg after 6 weeks. In obese participants, hemoglobin A1c (HbA1c) and plasminogen activator inhibitor-1 (PAI-1) were reduced by 18% and 20%, respectively. Obese participants showed decreased plasma concentrations (area under the curve [AUC] _0-8h ) of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1). Correlation analysis indicates that the beneficial effects of mango supplementation on pro-inflammatory cytokines, PAI-1 and HbA1c, are associated with systemic exposure to polyphenolic metabolites.

CONCLUSIONS

Mango supplementation improves the plasma levels of pro-inflammatory cytokines and metabolic hormones in obese participants. There is a crucial need to investigate the role of lowered polyphenolic absorption in obese individuals on their efficacy in reducing biomarkers for inflammation and other risk factors for chronic diseases.

From mice to men – mouse models in obesity research: What can we learn?

Obesity has become a world-wide epidemic and is associated with diseases such as diabetes, dyslipidaemia, cardiovascular disease and certain types of cancers. Understanding the adipose tissue developmental process, involving adipogenesis, angiogenesis and extracellular matrix remodelling, is therefore crucial to reveal the pathobiology of obesity. Experimental mouse models are extensively used to gain new insights into these processes and to evaluate the role of new key players, in particular proteolytic system components, in adipose tissue development and obesity. In this paper, we will review available in vitro and in vivo murine models of obesity and discuss their value in understanding the mechanisms contributing to obesity.

Thrombosis in central obesity and metabolic syndrome: Mechanisms and epidemiology

Central obesity is a key feature of the metabolic syndrome (metS), a multiplex risk factor for subsequent development of type 2 diabetes and cardiovascular disease. Many metabolic alterations closely related to this condition exert effects on platelets and vascular cells. A procoagulant and hypofibrinolytic state has been identified, mainly underlain by inflammation, oxidative stress, dyslipidaemia, and ectopic fat that accompany central obesity. In support of these data, central obesity independently predisposes not only to atherothrombosis but also to venous thrombosis.

Association of vitronectin and plasminogen activator inhibitor-1 levels with the risk of metabolic syndrome and type 2 diabetes mellitus

It was the objective of this study to investigate the relation between vitronectin and plasminogen activator inhibitor (PAI)-1 plasma levels with nine-year incidences of the metabolic syndrome (MetS) and of type 2 diabetes mellitus (T2DM). Baseline plasma concentrations of vitronectin and PAI-1 were measured in 627 healthy participants from the prospective D.E.S.I.R. cohort who subsequently developed MetS (n=487) and T2DM (n=182) over a nine-year follow-up (42 presented both) and who were matched with two healthy control subjects each by use of a nested case-control design. Parameters composing the MetS explained about 20% of plasma vitronectin levels. An increase of one standard deviation of vitronectin was associated with increased risks of both the MetS (odds ratio [OR] = 1.21 [1.07 – 1.37], p = 0.003) and T2DM (OR = 1.24 [1.01 – 1.53], p = 0.045). Corresponding ORs for PAI-1 levels were 1.46 [1.27 – 1.68] (p < 10−4) and 1.40 [1.14 – 1.72] (p = 0.0012). However, the effects of vitronectin and PAI-1 levels on outcomes were not independent. The vitronectin–MetS association was restricted to individuals with low to modest PAI-1 levels (OR = 1.33 [1.14 – 1.54], p = 0.0003) while no association was observed in individuals with high PAI-1 levels (OR = 0.87 [0.68 – 1.10], p = 0.24), the test for interaction being highly significant (p = 0.0009). In conclusion, baseline plasma vitronectin is a marker of incident MetS at nine years. Its predictive ability for MetS and T2DM should not be assessed independently of PAI-1 levels.

Heart failure and inflammation-related biomarkers as predictors of new-onset diabetes in the general population

BACKGROUND

There is a strong reciprocal relationship between heart failure (HF) and diabetes mellitus (DM). Shared pathophysiological mechanisms might be a possible explanation. Therefore, we hypothesised that biomarkers linked to HF would also predict new-onset type 2 DM in the general population.

METHODS AND RESULTS

We utilized the Prevention of Vascular and Renal End-stage Disease (PREVEND) cohort (mean age 48.9years, 51% female) to study the relationship between HF and DM in 7953 participants free of baseline HF and DM. Multiple HF-related, inflammation-related and renal function-related biomarkers were evaluated regarding their predictive utility in new-onset DM. Incidence of DM in participants who developed HF was 11.8%, versus 5.4% in those who had not developed HF (p<0.001). Incidence of HF in participants who developed DM was 8.5%, versus 3.8% in those who had not developed DM (p<0.001). Classical HF biomarkers, NT-proBNP and hs-TnT were not associated with an increased risk for new-onset DM. However, inflammatory biomarkers hs-CRP [hazard ratio (HR) 1.16, (95% CI 1.05 to 1.29), p=0.005], procalcitonin [HR 1.34, (95% CI 1.07 to 1.69), p=0.012] and PAI-1 [HR 1.55, (95% CI 1.37 to 1.75), p<0.001] remained significantly associated with new-onset DM, even after multivariable adjustment for established predictors of DM.

CONCLUSIONS

Although HF and DM have a strong correlation with each other, systemic biomarkers that predict HF do not have a predictive value in new-onset DM. This suggests that other, indirect, pathophysiological mechanisms related to inflammation may explain their strong relation.

Thrombin promotes diet-induced obesity through fibrin-driven inflammation

Obesity promotes a chronic inflammatory and hypercoagulable state that drives cardiovascular disease, type 2 diabetes, fatty liver disease, and several cancers. Elevated thrombin activity underlies obesity-linked thromboembolic events, but the mechanistic links between the thrombin/fibrin(ogen) axis and obesity-associated pathologies are incompletely understood. In this work, immunohistochemical studies identified extravascular fibrin deposits within white adipose tissue and liver as distinct features of mice fed a high-fat diet (HFD) as well as obese patients. Fibγ390-396A mice carrying a mutant form of fibrinogen incapable of binding leukocyte αMβ2-integrin were protected from HFD-induced weight gain and elevated adiposity. Fibγ390-396A mice had markedly diminished systemic, adipose, and hepatic inflammation with reduced macrophage counts within white adipose tissue, as well as near-complete protection from development of fatty liver disease and glucose dysmetabolism. Homozygous thrombomodulin-mutant ThbdPro mice, which have elevated thrombin procoagulant function, gained more weight and developed exacerbated fatty liver disease when fed a HFD compared with WT mice. In contrast, treatment with dabigatran, a direct thrombin inhibitor, limited HFD-induced obesity development and suppressed progression of sequelae in mice with established obesity. Collectively, these data provide proof of concept that targeting thrombin or fibrin(ogen) may limit pathologies in obese patients.

Plasminogen activator inhibitor links obesity and thrombotic cerebrovascular diseases: The roles of PAI-1 and obesity on stroke

One of the global socioeconomic phenomena occurred during the last decades is the increased prevalence of obesity, with direct consequence on the risk of developing thrombotic disorders. As the physiological inhibitor of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) is well known for its role in fibrinolysis. More and more evidences have shown that PAI-1 involves in physiopathologic mechanisms of many diseases and metabolic disorder. Increased serum level of PAI-1 has been observed in obesity and it also contributes to the development of adipose tissue and then has effects on obesity. Meantime, obesity affects also the PAI-1 levels. These evidences indicate the complicated interaction between PAI-1 and obesity. Many clinic studies have confirmed that obesity relates to the stroke outcome although there are many contradictory results. Simultaneously, correlation is found between plasma PAI-1 and thrombotic cerebrovascular diseases. This article reviews contemporary knowledge regarding the complex interplay of obesity, PAI-1 and stroke.

Novel Role of Endogenous Catalase in Macrophage Polarization in Adipose Tissue

Macrophages are important components of adipose tissue inflammation, which results in metabolic diseases such as insulin resistance. Notably, obesity induces a proinflammatory phenotypic switch in adipose tissue macrophages, and oxidative stress facilitates this switch. Thus, we examined the role of endogenous catalase, a key regulator of oxidative stress, in the activity of adipose tissue macrophages in obese mice. Catalase knockout (CKO) exacerbated insulin resistance, amplified oxidative stress, and accelerated macrophage infiltration into epididymal white adipose tissue in mice on normal or high-fat diet. Interestingly, catalase deficiency also enhanced classical macrophage activation (M1) and inflammation but suppressed alternative activation (M2) regardless of diet. Similarly, pharmacological inhibition of catalase activity using 3-aminotriazole induced the same phenotypic switch and inflammatory response in RAW264.7 macrophages. Finally, the same phenotypic switch and inflammatory responses were observed in primary bone marrow-derived macrophages from CKO mice. Taken together, the data indicate that endogenous catalase regulates the polarization of adipose tissue macrophages and thereby inhibits inflammation and insulin resistance.

A novel plasminogen activator inhibitor-1 inhibitor, TM5441, protects against high-fat diet-induced obesity and adipocyte injury in mice

BACKGROUND AND PURPOSE

Obesity is one of the most prevalent chronic diseases worldwide, and dysregulated adipocyte function plays an important role in obesity-associated metabolic disorder. The level of plasma plasminogen activator inhibitor-1 (PAI-1) is increased in obese subjects, and PAI-1 null mice show improved insulin sensitivity when subjected to high-fat and high-sucrose diet-induced metabolic stress, suggesting that a best-in-class PAI-1 inhibitor may become a novel therapeutic agent for obesity-associated metabolic syndrome. TM5441 is a novel orally active PAI-1 inhibitor that does not cause bleeding episodes. Hence, in the present study we examined the preventive effect of TM5441 on high-fat diet (HFD)-induced adipocyte dysfunction.

EXPERIMENTAL APPROACH

Ten-week-old C57BL/6J mice were fed a normal diet (18% of total calories from fat) or HFD (60% of total calories from fat) for 10 weeks, and TM5441 (20 mg·kg(-1) oral gavage) was administered daily with the initiation of HFD.

KEY RESULTS

TM5441 prevented HFD-induced body weight gain and systemic insulin resistance. TM5441 normalized HFD-induced dysregulated JNK and Akt phosphorylation, suggesting that it prevents the insulin resistance of adipocytes. TM5441 also attenuated the macrophage infiltration and increased expression of pro-inflammatory cytokines, such as inducible nitric oxide synthase, induced by the HFD. In addition, TM5441 prevented the HFD-induced down-regulation of genes involved in mitochondrial biogenesis and function, suggesting that it may prevent adipocyte inflammation and dysregulation by maintaining mitochondrial fitness.

CONCLUSION AND IMPLICATIONS

Our data suggest that TM5441 may become a novel therapeutic agent for obesity and obesity-related metabolic disorders.

Protective effect of composite earthworm powder against diabetic complications via increased fibrinolytic function and improvement of lipid metabolism in ZDF rats

Thrombosis is the leading cause of mortality globally. It is not only a complication but also a risk factor for progression of diabetes. However, alternative oral therapies and prophylaxis with less adverse effect for thrombosis have not been well studied. In this study, composite powder containing earthworm (CEP) was used and its fibrinolytic activity was measured. CEP was found to have a high urokinase-type plasminogen activator like activity in an in vitro assay. It also had significantly shortened euglobulin clot lysis time (ECLT) at 4 and 24 h after ingestion in Sprague Dawley rats. Zucker Diabetic Fatty rats were used to assess the effect of CEP on diabetes and diabetic nephropathy. After 10 weeks of feeding, CEP significantly shortened ECLT and attenuated HbA1c, hepatic lipid accumulation, and urinary albumin excretion and improved glomerular mesangial matrix score. Therefore, CEP may have beneficial effects on diabetes and diabetic nephropathy.

Plasminogen activator inhibitor-1 and type 2 diabetes: a systematic review and meta-analysis of observational studies

An emerging body of evidence has implicated plasminogen activator inhibitor-1 (PAI-1) in the development of type 2 diabetes (T2D), though findings have not always been consistent. We systematically reviewed epidemiological studies examining the association of PAI-1 with T2D. EMBASE, PubMed, Web of Science, and the Cochrane Library were searched to identify studies for inclusion. Fifty-two studies (44 cross-sectional with 47 unique analytical comparisons and 8 prospective) were included. In pooled random-effects analyses of prospective studies, a comparison of the top third vs. bottom third of baseline PAI-1 values generated a RR of T2D of 1.67 (95% CI 1.28–2.18) with moderate heterogeneity (I² = 38%). Additionally, of 47 cross-sectional comparisons, 34(72%) reported significantly elevated PAI-1 among diabetes cases versus controls, 2(4%) reported significantly elevated PAI-1 among controls, and 11(24%) reported null effects. Results from pooled analyses of prospective studies did not differ substantially by study design, length of follow-up, adjustment for various putative confounding factors, or study quality, and were robust to sensitivity analyses. Findings from this systematic review of the available epidemiological literature support a link between PAI-1 and T2D, independent of established diabetes risk factors. Given the moderate size of the association and heterogeneity across studies, future prospective studies are warranted.

Effect of photoperiod on the feline adipose transcriptome as assessed by RNA sequencing

Background

Photoperiod is known to cause physiological changes in seasonal mammals, including changes in body weight, physical activity, reproductive status, and adipose tissue gene expression in several species. The objective of this study was to determine the effects of day length on the adipose transcriptome of cats as assessed by RNA sequencing. Ten healthy adult neutered male domestic shorthair cats were used in a randomized crossover design study. During two 12-wk periods, cats were exposed to either short days (8 hr light:16 hr dark) or long days (16 hr light:8 hr dark). Cats were fed a commercial diet to maintain baseline body weight to avoid weight-related bias. Subcutaneous adipose biopsies were collected at wk 12 of each period for RNA isolation and sequencing.

Results

A total of 578 million sequences (28.9 million/sample) were generated by Illumina sequencing. A total of 170 mRNA transcripts were differentially expressed between short day- and long day-housed cats. 89 annotated transcripts were up-regulated by short days, while 24 annotated transcripts were down-regulated by short days. Another 57 un-annotated transcripts were also different between groups. Adipose tissue of short day-housed cats had greater expression of genes involved with cell growth and differentiation (e.g., myostatin; frizzled-related protein), cell development and structure (e.g., cytokeratins), and protein processing and ubiquitination (e.g., kelch-like proteins). In contrast, short day-housed cats had decreased expression of genes involved with immune function (e.g., plasminogen activator inhibitor 1; chemokine (C-C motif) ligand 2; C-C motif chemokine 5; T-cell activators), and altered expression of genes associated with carbohydrate and lipid metabolism.

Conclusions

Collectively, these gene expression changes suggest that short day housing may promote adipogenesis, minimize inflammation and oxidative stress, and alter nutrient metabolism in feline adipose tissue, even when fed to maintain body weight. Although this study has highlighted molecular mechanisms contributing to the seasonal metabolic changes observed in cats, future research that specifically targets and studies these biological pathways, and the physiological outcomes that are affected by them, is justified.

Plasminogen activator inhibitor-1 deficiency ameliorates insulin resistance and hyperlipidemia but not bone loss in obese female mice

We previously demonstrated that plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, is involved in type 1 diabetic bone loss in female mice. PAI-1 is well known as an adipogenic factor induced by obesity. We therefore examined the effects of PAI-1 deficiency on bone and glucose and lipid metabolism in high-fat and high-sucrose diet (HF/HSD)-induced obese female mice. Female wild-type (WT) and PAI-1-deficient mice were fed with HF/HSD or normal diet for 20 weeks from 10 weeks of age. HF/HSD increased the levels of plasma PAI-1 in WT mice. PAI-1 deficiency suppressed the levels of blood glucose, plasma insulin, and total cholesterol elevated by obesity. Moreover, PAI-1 deficiency improved glucose intolerance and insulin resistance induced by obesity. Bone mineral density (BMD) at trabecular bone as well as the levels of osterix, alkaline phosphatase, and receptor activator of nuclear factor κB ligand mRNA in tibia were decreased by HF/HSD in WT mice, and those changes by HF/HSD were not affected by PAI-1 deficiency. HF/HSD increased the levels of plasma TNF-α in both WT and PAI-1-deficient mice, and the levels of plasma TNF-α were negatively correlated with trabecular BMD in tibia of female mice. In conclusion, we revealed that PAI-1 deficiency does not affect the trabecular bone loss induced by obesity despite the amelioration of insulin resistance and hyperlipidemia in female mice. Our data suggest that the changes of BMD and bone metabolism by obesity might be independent of PAI-1 as well as glucose and lipid metabolism.

Effects of voluntary running and soy supplementation on diet-induced metabolic disturbance and inflammation in mice

We investigated the effects of diet (AIN93G or high-fat), physical activity (sedentary or voluntary running), and protein source (casein or soy protein isolate (SPI)) and their interactions on metabolic disturbance and inflammation in mice. After 14 weeks of feeding, the high-fat diet increased body weight gain by 34.5% (p < 0.01), whereas running reduced weight gain by 30.5% (p < 0.01) compared to their respective AIN93G and sedentary controls; SPI did not affect weight gain. The high-fat diet significantly increased plasma concentrations of insulin, glucose, triglycerides, leptin, and monocyte chemotactic protein-1 (MCP-1); running and SPI significantly reduced these parameters compared to their respective controls. The high-fat diet significantly increased and running significantly reduced plasma plasminogen activator inhibitor-1. A unique finding was that SPI supplementation to the high-fat diet reduced plasma insulin by 11% (p < 0.05), MCP-1 by 21% (p = 0.03), and tumor necrosis factor-α (TNF-α) by 50% (p = 0.05) compared to casein. As adipose tissues produce many adipocytokines, including MCP-1 and TNF-α, that contribute to a state of chronic low grade systemic inflammation and facilitate metabolic disturbance in obesity, further investigations are warranted into the roles of soy protein in reducing the risk of obesity.

Body adiposity but not insulin resistance is associated with -675 4G/5G polymorphism in the PAI-1 gene in a sample of Mexican children

OBJECTIVE

To assess whether the -675 4G/5G polymorphism in the plasminogen activator inhibitor-1 gene is associated with obesity and insulin resistance in Mexican children.

METHODS

A cross-sectional study was performed in 174 children, 89 with normal-weight and 85 with obesity, aged from 6 to 13 years. All children were from state of Guerrero, and recruited from three primary schools in the city of Chilpancingo, state of Guerrero, Mexico. Insulin levels were determined by immunoenzymatic assay. The homeostasis model assessment was used to determine insulin resistance. The -675 4G/5G polymorphism in PAI-1 gene was analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The prevalence of insulin resistance in the obese group was higher (49.41%) than in the normal-weight group (16.85%). The 4G/5G PAI-1 polymorphism was found in Hardy Weinberg equilibrium. The 4G/5G genotype contributed to a significant increase in waist-hip ratio (β=0.02, p=0.006), waist circumference (β=4.42, p=0.009), and subscapular skinfold thickness (β=1.79, p=0.04); however, it was not related with insulin resistance.

CONCLUSION

The -675 4G/5G genotype of PAI-1 gene was associated with increase of body adiposity in Mexican children.

Fatty acid-induced production of plasminogen activator inhibitor-1 by adipose macrophages is greater in middle-aged versus younger adult participants

BACKGROUND

Human aging is associated with heightened risk of diabetes and cardiovascular disease. Increased fat mass may contribute to age-related diseases by harboring inflammatory macrophages that produce metabolically important proteins such as plasminogen activator inhibitor-1 (PAI-1). Elevated PAI-1 concentrations have been implicated in the pathogenesis of such aging-related conditions as insulin resistance, obesity, and atherosclerosis. We have previously reported that increased plasma free fatty acid (FFA) concentrations augment both circulating PAI-1 concentrations and PAI-1 production by adipose tissue macrophages (ATMs).

METHODS

Because increasing age is associated with increased infiltration and reactivity of adipose macrophages, we performed euglycemic-hyperinsulinemic clamp studies and adipose tissue biopsies with and without elevated FFA concentrations in 31 nondiabetic participants stratified by age, to determine whether middle-aged individuals manifest heightened insulin resistance and PAI-1 production by ATMs in response to elevated nutrient signals relative to their young adult peers.

RESULTS

We observed that elevating FFA concentrations under euglycemic-hyperinsulinemic clamp conditions induced the same degree of insulin resistance in both middle-aged and younger body mass index-matched adults, whereas systemic PAI-1 concentrations were significantly increased in the middle-aged group. Likewise, elevated FFA and insulin concentrations induced larger increases in PAI-1 gene expression in the whole fat and ATMs of middle-aged compared with younger adult participants.

CONCLUSIONS

These studies reveal a heightened adipose inflammatory response to increased FFA and insulin availability in middle-aged individuals relative to younger adults, suggesting that increased susceptibility to the effects of fatty acid excess may contribute to the pathogenesis of age-related diseases.

Long-term voluntary running improves diet-induced adiposity in young adult mice

The hypothesis of the present study was that physical activity improves diet-induced obesity in young adult mice. Four-week-old male C57BL/6 mice (n=15/group) were fed the AIN93G diet or a 45% high-fat diet (% kJ) with or without access to in-cage activity wheels for 14 weeks. The high-fat diet increased percentage fat body mass compared to the AIN93G diet (P=.042); running reduced percentage fat body mass (P<.0001) and increased percentage lean body mass (P<.0001) in mice fed either diet. Compared with the AIN93G diet, the high-fat diet increased plasma concentrations of insulin (P<.05) and leptin (P<.05) in sedentary mice and inflammatory cytokines monocyte chemotactic protein-1 (MCP-1) (P<.05) and plasminogen activator inhibitor-1 (P<.05) in both sedentary and running mice. The high-fat diet did not affect angiogenic factors vascular endothelial growth factor and platelet-derived growth factor-BB. Running reduced plasma insulin (P<.05) and MCP-1 (P<.05) and increased platelet-derived growth factor-BB (P<.05) in mice fed the high-fat diet. Running reduced leptin (P<.05) and increased plasma vascular endothelial growth factor (P<.0001) regardless of diet fed. In summary, consumption of the high-fat diet increased adiposity in young adult mice; running reduced adiposity, normalized plasma insulin and leptin, and reduced MCP-1 despite continued consumption of the high-fat diet. These results suggest that voluntary running may reduce diet-induced obesity and proinflammation and that young mice may be a useful model of their human age equivalents in studying moderate physical exercise and obesity and obesity-related diseases.

Relationship of metabolic syndrome and its components with -844 G/A and HindIII C/G PAI-1 gene polymorphisms in Mexican children

Background

Several association studies have shown that -844 G/A and HindIII C/G PAI-1 polymorphisms are related with increase of PAI-1 levels, obesity, insulin resistance, glucose intolerance, hypertension and dyslipidemia, which are components of metabolic syndrome. The aim of this study was to analyze the allele and genotype frequencies of these polymorphisms in PAI-1 gene and its association with metabolic syndrome and its components in a sample of Mexican mestizo children.

Methods

This study included 100 children with an age range between 6-11 years divided in two groups: a) 48 children diagnosed with metabolic syndrome and b) 52 children metabolically healthy without any clinical and biochemical alteration. Metabolic syndrome was defined as the presence of three or more of the following criteria: fasting glucose levels ≥ 100 mg/dL, triglycerides ≥ 150 mg/dL, HDL-cholesterol < 40 mg/dL, obesity BMI ≥ 95^th percentile, systolic blood pressure (SBP) and diastolic blood pressure (DBP) ≥ 95^th percentile and insulin resistance HOMA-IR ≥ 2.4. The -844 G/A and HindIII C/G PAI-1 polymorphisms were analyzed by PCR-RFLP.

Results

For the -844 G/A polymorphism, the G/A genotype (OR = 2.79; 95% CI, 1.11-7.08; p = 0.015) and the A allele (OR = 2.2; 95% CI, 1.10-4.43; p = 0.015) were associated with metabolic syndrome. The -844 G/A and A/A genotypes were associated with increase in plasma triglycerides levels (OR = 2.6; 95% CI, 1.16 to 6.04; p = 0.02), decrease in plasma HDL-cholesterol levels (OR = 2.4; 95% CI, 1.06 to 5.42; p = 0.03) and obesity (OR = 2.6; 95% CI, 1.17-5.92; p = 0.01). The C/G and G/G genotypes of the HindIII C/G polymorphism contributed to a significant increase in plasma total cholesterol levels (179 vs. 165 mg/dL; p = 0.02) in comparison with C/C genotype.

Conclusions

The -844 G/A PAI-1 polymorphism is related with the risk of developing metabolic syndrome, obesity and atherogenic dyslipidemia, and the HindIII C/G PAI-1 polymorphism was associated with the increase of total cholesterol levels in Mexican children.

PAI-1, progress in understanding the clinical problem and its aetiology

Plasminogen activator inhibitor-1 (PAI-1, also known as SERPINE1) is a member of the serine protease inhibitor (SERPIN) superfamily and is the primary physiological regulator of urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) activity. Although the principal function of PAI-1 is the inhibition of fibrinolysis, PAI-1 possesses pleiotropic functions besides haemostasis. In the quarter century since its discovery, a number of studies have focused on improving our understanding of PAI-1 functions in vivo and in vitro. The use of Serpine1-deficient mice has particularly enhanced our understanding of the functions of PAI-1 in various physiological and pathophysiological conditions. In this review, the results of recent studies on PAI-1 and its role in clinical conditions are discussed.

Effect of dibutyryl cyclic adenosine monophosphate on the gene expression of plasminogen activator inhibitor-1 and tissue factor in adipocytes

INTRODUCTION

Hypertrophic adipocytes in obese states express the elevated levels of plasminogen activator inhibitor-1 (PAI-1) and tissue factor (TF). An increase in the intracellular concentration of cyclic adenosine monophosphate (cAMP) promotes triglyceride hydrolysis and may improve dysregulation of adipocyte metabolism. Here, we investigate the effect of dibutyryl-cAMP (a phosphodiesterase-resistant analog of cAMP) on the gene expression of PAI-1 and TF in adipocytes.

MATERIALS AND METHODS

Differentiated 3T3-L1 adipocytes were treated with dibutyryl-cAMP and agents that would be expected to elevate intracellular cAMP, including cilostazol (a phosphodiesterase inhibitor with anti-platelet and vasodilatory properties), isoproterenol (a beta adrenergic agonist) and forskolin (an adenylyl cyclase activator). The levels of PAI-1 and TF mRNAs were measured using real-time quantitative reverse transcription-PCR.

RESULTS AND CONCLUSIONS

The treatment of adipocytes with dibutyryl-cAMP resulted in the inhibition of both lipid accumulation and TF gene expression. However, PAI-1 gene expression was slightly but significantly increased by dibutyryl-cAMP. On the other hand, cilostazol inhibited the expression of PAI-1 without affecting lipid accumulation. When the adipocytes were treated with cilostazol in combination with isoproterenol or forskolin, the inhibitory effect of cilostazol on PAI-1 gene expression was counteracted, thus suggesting that inhibition by cilostazol may not be the result of intracellular cAMP accumulation by phosphodiesterase inhibition. These results suggest the implication of cAMP in regulation of the gene expression of TF and PAI-1 in adipocytes. Our findings will serve as a useful basis for further research in therapy for obesity-associated thrombosis.

Plasminogen activator inhibitor 1 is an intracellular inhibitor of furin proprotein convertase

Proprotein convertases (PCs) are a family of serine proteases that are involved in the post-translational processing and activation of a wide range of regulatory proteins. The upstream role of PCs in the control of many physiological and pathological processes generates a growing interest in understanding their regulation. Here, we demonstrate that the serine protease inhibitor plasminogen activator inhibitor 1 (PAI-1) forms an SDS-stable complex with the PC furin, which leads to the inhibition of the intra-Golgi activity of furin. It is known that elevated PAI-1 plasma levels are correlated with the occurrence of the metabolic syndrome and type 2 diabetes, and we show that PAI-1 reduces the furin-dependent maturation and activity of the insulin receptor and ADAM17: two proteins involved in the onset of these metabolic disorders. In addition to demonstrating that PAI-1 is an intracellular inhibitor of furin, this study also provides arguments in favor of an active role for PAI-1 in the development of metabolic disorders.

Angiogenesis and development of adipose tissue

Obesity is a common disorder and related diseases, such as diabetes, atherosclerosis, hypertension, cardiovascular disease and cancer, are a major cause of mortality and morbidity in Western-type societies. Development of obesity is associated with substantial modulation of adipose tissue structure. The plasticity of the adipose tissue is reflected by its remarkable ability to expand or to reduce in size throughout adult lifespan. The expansion of adipose tissue is linked to the development of its vasculature. Indeed, adipogenesis is tightly associated with angiogenesis, as shown by the findings that adipose tissue explants trigger blood vessel formation, whereas in turn adipose tissue endothelial cells promote preadipocyte differentiation. Different components have been identified that play a role in adipose tissue associated angiogenesis. Modulation of angiogenesis may have the potential to impair adipose tissue development and thus may provide a novel therapeutic approach for prevention and treatment of obesity.

Characterization of a novel class of polyphenolic inhibitors of plasminogen activator inhibitor-1

Plasminogen activator inhibitor type 1, (PAI-1) the primary inhibitor of the tissue-type (tPA) and urokinase-type (uPA) plasminogen activators, has been implicated in a wide range of pathological processes, making it an attractive target for pharmacologic inhibition. Currently available small-molecule inhibitors of PAI-1 bind with relatively low affinity and do not inactivate PAI-1 in the presence of its cofactor, vitronectin. To search for novel PAI-1 inhibitors with improved potencies and new mechanisms of action, we screened a library selected to provide a range of biological activities and structural diversity. Five potential PAI-1 inhibitors were identified, and all were polyphenolic compounds including two related, naturally occurring plant polyphenols that were structurally similar to compounds previously shown to provide cardiovascular benefit in vivo. Unique second generation compounds were synthesized and characterized, and several showed IC(50) values for PAI-1 between 10 and 200 nm. This represents an enhanced potency of 10-1000-fold over previously reported PAI-1 inactivators. Inhibition of PAI-1 by these compounds was reversible, and their primary mechanism of action was to block the initial association of PAI-1 with a protease. Consistent with this mechanism and in contrast to previously described PAI-1 inactivators, these compounds inactivate PAI-1 in the presence of vitronectin. Two of the compounds showed efficacy in ex vivo plasma and one blocked PAI-1 activity in vivo in mice. These data describe a novel family of high affinity PAI-1-inactivating compounds with improved characteristics and in vivo efficacy, and suggest that the known cardiovascular benefits of dietary polyphenols may derive in part from their inactivation of PAI-1.

Relationship between pediatric obesity and otitis media with effusion

Although eustachian tube dysfunction and bacterial infection have been shown to cause otitis media with effusion (OME), other etiologies are possible. One of the most common medical conditions in children is obesity, which can have effects throughout the body. Little is known, however, about the relationship between obesity and OME. Obesity may result in altered cytokine expression, gastroesophageal reflux disease, or fat accumulation, all of which may contribute to OME. Conversely, OME may induce taste changes through middle ear cavity inflammation, thus contributing to obesity. A similar pattern of taste change has been shown in patients with gustatory nerve anesthesia. Further research on the relationship between obesity and OME may help to determine the exact etiology of OME and contribute to our knowledge about the causes of obesity.

Novel bis-arylsulfonamides and aryl sulfonimides as inactivators of plasminogen activator inhibitor-1 (PAI-1)

Inactivators of plasminogen activator inhibitor-1 (PAI-1) have been identified as possible treatments for a range of conditions, including atherosclerosis, venous thrombosis, and obesity. We describe the synthesis and inhibitory activity of a novel series of compounds based on bis-arylsulfonamide and aryl sulfonimide motifs that show potent and specific activity towards PAI-1. Inhibitors containing short linking units between the sulfonyl moieties and a 3,4-dihydroxy aryl substitution pattern showed the most potent inhibitory activity, and retained high specificity for PAI-1 over the structurally-related serpin anti-thrombin III (ATIII).

Relationships of PAI-1 levels to central obesity and liver steatosis in a sample of adult male population in southern Italy

To analyse the relationship of PAI-1 plasma levels to echographically determined liver steatosis and cardiometabolic risk factors in a randomly selected sample of 254 adult male participants of the Olivetti Heart Study. Accounting for age and ongoing pharmacological treatment, PAI-1 levels were directly (P < 0.005) associated with body mass index (BMI), waist circumference (WC), serum triglyceride (TG), total cholesterol, insulin, homeostasis model assessment index, gamma-glutamyl transpeptidase and peritoneal fat. At multiple linear regression (MLR) analysis, measures of adiposity and TG exerted significant and quantitatively similar effects on PAI-1 levels. A progressive rise in PAI-1 level was detected with increasing degree of steatosis. A stepwise MLR model was used to evaluate the relative power of cardiometabolic risk factors and liver steatosis on PAI-1 levels. Adjusting for alcohol intake, BMI, WC and peritoneal fat were alternatively included in the model with other variables found to be significantly associated with plasma PAI-1 level. Liver steatosis, serum TG and various indexes of adiposity each had a significant independent impact on PAI-1 plasma level and explained overall 23% of its variability. Abdominal fat, liver steatosis and serum TG levels were significant and independent determinants of PAI-1 plasma level in an unselected sample of adult male population upon adjustment for age and therapy.

Getting the message across: mechanisms of physiological cross talk by adipose tissue

Obesity is associated with resistance of skeletal muscle to insulin-mediated glucose uptake, as well as resistance of different organs and tissues to other metabolic and vascular actions of insulin. In addition, the body is exquisitely sensitive to nutrient imbalance, with energy excess or a high-fat diet rapidly increasing insulin resistance, even before noticeable changes occur in fat mass. There is a growing acceptance of the fact that, as well as acting as a storage site for surplus energy, adipose tissue is an important source of signals relevant to, inter alia, energy homeostasis, fertility, and bone turnover. It has also been widely recognized that obesity is a state of low-grade inflammation, with adipose tissue generating substantial quantities of proinflammatory molecules. At a cellular level, the understanding of the signaling pathways responsible for such alterations has been intensively investigated. What is less clear, however, is how alterations of physiology, and of signaling, within one cell or one tissue are communicated to other parts of the body. The concepts of cell signals being disseminated systemically through a circulating "endocrine" signal have been complemented by the view that local signaling may similarly occur through autocrine or paracrine mechanisms. Yet, while much elegant work has focused on the alterations in signaling that are found in obesity or energy excess, there has been less attention paid to ways in which such signals may propagate to remote organs. This review of the integrative physiology of obesity critically appraises the data and outlines a series of hypotheses as to how interorgan cross talk takes place. The hypotheses presented include the "fatty acid hypothesis,", the "portal hypothesis,", the "endocrine hypothesis,", the "inflammatory hypothesis,", the "overflow hypothesis,", a novel "vasocrine hypothesis," and a "neural hypothesis," and the strengths and weaknesses of each hypothesis are discussed.