Human circadian system causes a morning peak in prothrombotic plasminogen activator inhibitor-1 (PAI-1) independent of the sleep/wake cycle

Circadian Clocks in the Hematologic System

The hematologic system performs a number of essential functions, including oxygen transport, the execution of the immune response against tumor cells and invading pathogens, and hemostasis (blood clotting). These roles are performed by erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets), respectively. Critically, circadian rhythms are evident in the function of all 3 cell types. In this review, we describe these oscillations, explore their mechanistic bases, and highlight their key implications. Since erythrocytes are anucleate, circadian rhythms in these cells testify to the existence of a nontranscriptional circadian clock. From a clinical perspective, leukocyte rhythms could underlie daily variation in the severity of allergic reactions, the symptoms of chronic inflammatory diseases, and the body’s response to infection, while the rhythmic properties of thrombocytes may explain daily fluctuations in the incidence of heart attack and stroke. Consequently, the efficacy of treatments for these conditions is likely to depend on the timing of their administration. Last, we outline preliminary evidence that circadian disruption in the hematologic system could contribute to the deleterious effects of poor diet, shift work, and alcohol abuse on human health.

PAI-1 Inhibition - Another Therapeutic Option for Cardiovascular Protection

Current research suggest that plasminogen activator inhibitor type 1 (PAI-1) is an important contributor to a number of disease processes. The aim of the current paper is to emphasize the deleterious effects of PAI-1 on cardiovascular diseases development and progression. The plasminogen system is known by its role in hemostasis and thrombosis regulation. Lifestyle changes and pharmacological treatment can regulate PAI-1 levels and functions. Some pharmacologic agents currently used in the management of atherosclerosis and its complications can counteract the deleterious effects of PAI-1.

Evaluating PAI-1 as a biomarker for stress in diving: human serum total PAI-1 is unaltered after 2 h dry exposures to 280 kPa hyperbaric air

Plasminogen activator inhibitor (PAI-1) is induced in the vasculature and secreted into the vascular lumen in response to inflammation and oxidative stress. We have previously reported a fivefold increase in plasma PAI-1 from rats exposed to 708 kPa hyperbaric air. In the current study we assess the potential of human serum total PAI-1 as a biomarker for stress in compressed air diving. Eleven recreational divers, nine males and two females, completed four 2 h hyperbaric air exposures to 280 kPa in a pressure chamber over a period of 2 weeks. The air pressure corresponds to a diving depth of 18 m in water. Serum was collected before the study and again 3 h 30 min after completion of each hyperbaric exposure. All samples were taken in the afternoon to minimize the contribution of circadian variation. The analysis revealed no change in serum total PAI-1 after hyperbaric exposures within the group of divers (P = 0.064), but significant interindividual differences persisted throughout the study (P < 0.0005). A case of decompression sickness after the third round of hyperbaric exposure did not affect PAI-1. In conclusion, compressed air exposure to 280 kPa does not affect serum total PAI-1, and significant interindividual variation in PAI-1 levels may limit its usefulness as a biomarker. This does, however, not give a complete answer regarding PAI-1 in physiologically stressful dives. Further studies with different exposures and timing are needed for that.

Circadian timing of metabolism in animal models and humans

Most living beings, including humans, must adapt to rhythmically occurring daily changes in their environment that are generated by the Earth's rotation. In the course of evolution, these organisms have acquired an internal circadian timing system that can anticipate environmental oscillations and thereby govern their rhythmic physiology in a proactive manner. In mammals, the circadian timing system coordinates virtually all physiological processes encompassing vigilance states, metabolism, endocrine functions and cardiovascular activity. Research performed during the past two decades has established that almost every cell in the body possesses its own circadian timekeeper. The resulting clock network is organized in a hierarchical manner. A master pacemaker, located in the suprachiasmatic nucleus (SCN) of the hypothalamus, is synchronized every day to the photoperiod. In turn, the SCN determines the phase of the cellular clocks in peripheral organs through a wide variety of signalling pathways dependent on feeding cycles, body temperature rhythms, oscillating bloodborne signals and, in some organs, inputs of the peripheral nervous system. A major purpose of circadian clocks in peripheral tissues is the temporal orchestration of key metabolic processes, including food processing (metabolism and xenobiotic detoxification). Here, we review some recent findings regarding the molecular and cellular composition of the circadian timing system and discuss its implications for the temporal coordination of metabolism in health and disease. We focus primarily on metabolic disorders such as obesity and type 2 diabetes, although circadian misalignments (shiftwork or 'social jet lag') have also been associated with the aetiology of human malignancies.

Therapeutic applications of circadian rhythms for the cardiovascular system

The cardiovascular system exhibits dramatic time-of-day dependent rhythms, for example the diurnal variation of heart rate, blood pressure, and timing of onset of adverse cardiovascular events such as heart attack and sudden cardiac death. Over the past decade, the circadian clock mechanism has emerged as a crucial factor regulating these daily fluctuations. Most recently, these studies have led to a growing clinical appreciation that targeting circadian biology offers a novel therapeutic approach toward cardiovascular (and other) diseases. Here we describe leading-edge therapeutic applications of circadian biology including (1) timing of therapy to maximize efficacy in treating heart disease (chronotherapy); (2) novel biomarkers discovered by testing for genomic, proteomic, metabolomic, or other factors at different times of day and night (chronobiomarkers); and (3) novel pharmacologic compounds that target the circadian mechanism with potential clinical applications (new chronobiology drugs). Cardiovascular disease remains a leading cause of death worldwide and new approaches in the management and treatment of heart disease are clearly warranted and can benefit patients clinically.

Recent advances in circadian rhythms in cardiovascular system

Growing evidence shows that intrinsic circadian clocks are tightly related to cardiovascular functions. The diurnal changes in blood pressure and heart rate are well known circadian rhythms. Endothelial function, platelet aggregation and thrombus formation exhibit circadian changes as well. The onset of many cardiovascular diseases (CVDs) or events, such as myocardial infarction, stroke, arrhythmia, and sudden cardiac death, also exhibits temporal trends. Furthermore, there is strong evidence from animal models and epidemiological studies showing that disruption of circadian rhythms is a significant risk factor for many CVDs, and the intervention of CVDs may have a time dependent effect. In this mini review, we summarized recent advances in our understanding of the relationship between circadian rhythm and cardiovascular physiology and diseases including blood pressure regulation and myocardial infarction.

Influence of the Cardiomyocyte Circadian Clock on Cardiac Physiology and Pathophysiology

Cardiac function and dysfunction exhibit striking time-of-day-dependent oscillations. Disturbances in both daily rhythms and sleep are associated with increased risk of heart disease, adverse cardiovascular events, and worsening outcomes. For example, the importance of maintaining normal daily rhythms is highlighted by epidemiologic observations that night shift workers present with increased incidence of cardiovascular disease. Rhythmicity in cardiac processes is mediated by a complex interaction between extracardiac (e.g., behaviors and associated neural and humoral fluctuations) and intracardiac influences. Over the course of the day, the intrinsic properties of the myocardium vary at the levels of gene and protein expression, metabolism, responsiveness to extracellular stimuli/stresses, and ion homeostasis, all of which affect contractility (e.g., heart rate and force generation). Over the past decade, the circadian clock within the cardiomyocyte has emerged as an essential mechanism responsible for modulating the intrinsic properties of the heart. Moreover, the critical role of this mechanism is underscored by reports that disruption, through genetic manipulation, results in development of cardiac disease and premature mortality in mice. These findings, in combination with reports that numerous cardiovascular risk factors (e.g., diet, diabetes, aging) distinctly affect the clock in the heart, have led to the hypothesis that aberrant regulation of this mechanism contributes to the etiology of cardiac dysfunction and disease. Here, we provide a comprehensive review on current knowledge regarding known roles of the heart clock and discuss the potential for using these insights for the future development of innovative strategies for the treatment of cardiovascular disease.

Palmolein and olive oil consumed within a high protein test meal have similar effects on postprandial endothelial function in overweight and obese men: A randomized controlled trial

OBJECTIVE

This study assessed the postprandial effects of high fat, high protein meals containing either palmolein or olive oil on endothelial function in overweight/obese men.

DESIGN

28 men (32-65 yr; 25-35 kg/m(2)) consumed, in random order 1 wk apart, isocaloric high protein, high fat meals (2791 kJ, 40 g protein (∼3 g l-arginine), 44 g fat, 21 g carbohydrate) prepared with either 40 g palmolein or 40 g olive oil after an overnight fast. The SFA:MUFA:PUFA ratio of the oils were: palmolein, 42:47:12; olive oil, 17:76:7. Brachial artery flow-mediated dilatation (FMD), circulating endothelial function markers, nitrotyrosine (oxidative stress marker), triglycerides, glucose and insulin were assessed pre-meal and hourly for 5 h. Mixed model procedures were used to analyze the data.

RESULTS

Meal consumption increased serum triglycerides (time effect, P < 0.001); with no meal differences (meal × time interaction, P = 0.93). Serum insulin peaked 1 h post-consumption and returned to pre-meal concentrations by 5 h with both meals (time effect, P < 0.001; meal × time effect, P = 0.68). FMD, serum intercellular adhesion molecule-1 (ICAM-1) and E-selectin did not change (meal × time effect, P > 0.4). Olive oil transiently increased plasma nitrotyrosine after 1 h compared to palmolein (meal × time interaction, P = 0.002) whereas both meals increased serum vascular cell adhesion molecule-1 (VCAM-1) after 1 h (time effect, P < 0.001; meal × time interaction, P = 0.98). Both nitrotyrosine and VCAM-1 returned to pre-meal concentrations after 2 h.

CONCLUSION

In the context of a high protein meal, palmolein similarly to olive oil did not affect postprandial endothelial function in overweight/obese men.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR) (http://www.anzctr.org.au/default.aspx). Trial ID: ACTRN12613000136707.

Altered Daytime Fluctuation Pattern of Plasminogen Activator Inhibitor 1 in Type 2 Diabetes Patients with Coronary Artery Disease: A Strong Association with Persistently Elevated Plasma Insulin, Increased Insulin Resistance, and Abdominal Obesity

This study was aimed at investigating daily fluctuation of PAI-1 levels in relation to insulin resistance (IR) and daily profile of plasma insulin and glucose levels in 26 type 2 diabetic (T2D) patients with coronary artery disease (CAD) (group A), 10 T2D patients without CAD (group B), 12 nondiabetics with CAD (group C), and 12 healthy controls (group D). The percentage of PAI-1 decrease was lower in group A versus group B (4.4 ± 2.7 versus 35.0 ± 5.4%; P < 0.05) and in C versus D (14.0 ± 5.8 versus 44.7 ± 3.1%; P < 0.001). HOMA-IR was higher in group A versus group B (P < 0.05) and in C versus D (P < 0.01). Simultaneously, AUCs of PAI-1 and insulin were higher in group A versus group B (P < 0.05) and in C versus D (P < 0.01), while AUC of glucose did not differ between groups. In multiple regression analysis waist-to-hip ratio and AUC of insulin were independent determinants of decrease in PAI-1. The altered diurnal fluctuation of PAI-1, especially in T2D with CAD, might be strongly influenced by a prolonged exposure to hyperinsulinemia in the settings of increased IR and abdominal obesity, facilitating altogether an accelerated atherosclerosis.

Effects of cryoablation and radiofrequency ablation on endothelial and blood clotting activation

Cryoablation (CA) emerged as an alternative procedure to radiofrequency (RF). The aim of this study was to compare haemostatic system alterations in patients undergoing RF or CA for atrioventricular nodal reentrant tachycardia ablation. von Willebrand factor (vWF), spontaneous whole blood platelet aggregation, prothrombin fragment F1 + 2 (F1 + 2), thrombin-antithrombin complex (TAT), plasminogen activator inhibitor type-1 (PAI-1), and clot lysis time (CLT) were determined in 48 patients (27 CA; 21 RF; 19M/29F, mean age 49.6 ± 17.6 years). Blood samples were obtained before the procedure (T0), immediately after (T1), and 24 h later (T2). At T1 both procedures were associated with a significant increase in levels of the endothelial activation marker vWF. At T2 vWF levels were lower in CA than in RF group. No changes in whole blood platelet aggregation before and after ablation procedures were observed. At T1 both groups determined an increase in blood clotting activation markers, F1 + 2, TAT, and DD. At T2 F1 + 2, TAT and DD levels were similar to baseline values. The comparison between RF and CA showed no significant differences in F1 + 2 and TAT levels, whereas at T1 DD levels were higher in CA group than in RF group. Both procedures induced a significant decrease in CLT, whereas no changes in PAI-1 levels were found. There were no significant differences in CLT and PAI-1 levels. The fibrinolytic efficiency analysis showed that at T1 DD/TAT and DD/F1 + 2 ratios were lower in RF group and remained lower in RF than in CA group at T2. CA procedure may be associated with a lower degree of endothelial damage and with a higher fibrinolytic capacity respect to RF.

Significant associations between hemostatic/fibrinolytic systems and accumulation of cardiovascular risk factors in Japanese elementary schoolchildren

The aim of this study was to establish the reference values of hemostatic/fibrinolytic markers and investigate their relationship with physical constitution and cardiovascular risk factors in a normal schoolchildren population. This study comprised 148 healthy Japanese children aged 9-10 years (males 73; females 75). We performed laboratory tests including blood levels of leptin, high-sensitive C-reactive protein (hs-CRP), hemostatic and fibrinolytic markers [plasminogen activator inhibitor 1 (PAI-1), coagulation factor VII (FVII), coagulation factor X (FX), fibrinogen (Fbg), protein C, protein S], as well as common biochemical markers in the morning after an overnight fast. We investigated the mean, 10th, 50th and 90th percentile values of these markers. All parameters were compared between two groups, that is those with body mass index (BMI) 90th percentile or higher and BMI less than 90th percentile, and between subgroups based on the number of cardiovascular risk factors. Multiple-linear regression was used to assess associations between these hematological parameters and the components related to metabolic syndrome (MetS). Alanine aminotransferase (ALT), uric acid, leptin, hs-CRP, and all hemostatic/fibrinolytic markers (PAI-1, FVII, FX, Fbg, protein C, protein S) tested were significantly higher in the group with BMI 90th percentile or higher, and increased with accumulation of cardiovascular risk factors. Multiple-linear regression analysis showed that these values were associated with one or more components related to MetS. Reference values of hemostatic/fibrinolytic markers in Japanese schoolchildren were obtained. Many hemostatic/fibrinolytic markers showed significant association with BMI and accumulation of cardiovascular risk factors in normal Japanese schoolchildren.

Circadian regulation of metabolism

In association with sleep-wake and fasting-feeding cycles, organisms experience dramatic oscillations in energetic demands and nutrient supply. It is therefore not surprising that various metabolic parameters, ranging from the activity status of molecular energy sensors to circulating nutrient levels, oscillate in time-of-day-dependent manners. It has become increasingly clear that rhythms in metabolic processes are not simply in response to daily environmental/behavioral influences, but are driven in part by cell autonomous circadian clocks. By synchronizing the cell with its environment, clocks modulate a host of metabolic processes in a temporally appropriate manner. The purpose of this article is to review current understanding of the interplay between circadian clocks and metabolism, in addition to the pathophysiologic consequences of disruption of this molecular mechanism, in terms of cardiometabolic disease development.

Circadian clock control of endocrine factors

Organisms experience dramatic fluctuations in demands and stresses over the course of the day. In order to maintain biological processes within physiological boundaries, mechanisms have evolved for anticipation of, and adaptation to, these daily fluctuations. Endocrine factors have an integral role in homeostasis. Not only do circulating levels of various endocrine factors oscillate over the 24 h period, but so too does responsiveness of target tissues to these signals or stimuli. Emerging evidence suggests that these daily endocrine oscillations do not occur solely in response to behavioural fluctuations associated with sleep-wake and feeding-fasting cycles, but are orchestrated by an intrinsic timekeeping mechanism known as the circadian clock. Disruption of circadian clocks by genetic and/or environmental factors seems to precipitate numerous common disorders, including the metabolic syndrome and cancer. Collectively, these observations suggest that strategies designed to realign normal circadian rhythmicities hold potential for the treatment of various endocrine-related disorders.

The association between sleep characteristics and prothrombotic markers in a population-based sample: Chicago Area Sleep Study

BACKGROUND AND AIM

Short sleep duration and poor quality sleep are associated with coronary heart disease (CHD) mortality; however, the underlying pathophysiologic process remains unclear. Sleep apnea may confound the association because of its relationship with formation of thrombi, the vascular occlusive process in CHD. We tested whether sleep duration and quality were associated with prothrombotic biomarkers in adults with a low probability of apnea.

METHODS

We included adults aged 35-64 years recruited from the community and who had an apnea hypopnea index <15 after one night of screening (n=506). Sleep duration and maintenance were determined from 7 days of wrist actigraphy; daytime sleepiness was estimated using the Epworth Sleepiness Scale. Factor VIII (FVIII), von Willebrand factor (vWF), thrombin antithrombin (TAT) complexes, and plasminogen activator inhibitor-1 (PAI-1) were measured in fasting blood.

RESULTS

Sleep duration, maintenance, and daytime sleepiness were not associated with FVIII, vWf, or TAT. Sleep maintenance was modestly inversely associated with higher levels of log-transformed PAI-1 (β = -0.07, standard error (SE)=0.03 per 4.8%, p=0.04) following adjustment for demographic characteristics, cardiovascular risk factors, and body mass index (BMI).

CONCLUSIONS

Mild impairment in sleep was modestly associated with activation of coagulation; further study is needed to evaluate the role of fibrinolytic factors in sleep-mediated coronary thrombosis.

PAI at breakfast (whether you like it or not)

In this issue of Blood, Scheer and Shea report that the morning surge of the prothrombotic factor plasminogen activator inhibitor-1 (PAI-1) observed in humans is driven by an endogenous mechanism (as opposed to behavioral/environmental influences).