Plasma plasminogen activator inhibitor-I is associated with plasma leptin irrespective of body mass index, body fat mass, and plasma insulin and metabolic parameters in premenopausal women

Leptin in inflammation and autoimmunity

After its discovery as a key controller of metabolic function, leptin has been later extensively implicated in additional functions including important modulatory activities on the innate and adaptive immune response. This review analyzes the known implications of leptin in multiple inflammatory conditions, including autoimmune diseases, and how this knowledge could be instrumental in the design of leptin-based manipulation strategies to help restoration of abnormal immune responses.

Moderate rest intervals are superior to short intervals for improving PAI-1 following exhaustive exercise in recreational weightlifters

This study investigated the influence of short and moderate recovery intervals on lipid profiles and plasminogen activator inhibitor-1 (PAI-1) following exhaustive strength exercise in recreational weightlifters. Seven subjects performed two conditions in a randomized order: short, 90% of one maximum repetition (1RM) and 30-sec rest allowed between sets; moderate, 90% of 1RM and 90-sec rest allowed between sets. Total cholesterol (Chol), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), triacylglycerol (TAG), Chol/HDL-c ratio and PAI-1 concentrations were assessed at baseline, immediately postexercise, and 15- and 30-min postexercise (post-15 and post-30). The LDL-c concentrations decreased and HDL-c concentrations increased in both conditions but without significant differences (LDL-c: 30 sec: pre, 82.0±19.5 mg/dL, immediately, 73.9±16.4 mg/dL, 90 sec: pre, 75.9±30.8 mg/dL, immediately, 66.2±35.5 mg/dL, P=0.423; HDL-c: 30 sec: pre, 53.5±9.2 mg/dL, immediately, 61.4±11.4 mg/dL; 90 sec: pre, 55.8±11.1 mg/dL, immediately, 84.9±27.8, mg/dL; P=0.146). On the other hand, PAI-1 had a tendency to decrease only in the 90-sec condition (pre, 7,754.9±2,927.7 pg/mL; immediately, 5,313.1±4,637.4 pg/mL; P=0.085). There was a positive correlation between PAI-1 and Chol (30 sec: r=0.83, 90 sec: r=0.91; P<0.05), PAI-1 and fat-free mass in both conditions (30 sec post-15: r=0.79, post-30: r=081, P<0.05; 90 sec immediately: r=0.77, post-15: r=0.81; P<0.05), and PAI-1 and TAG only in 30 sec (r=0.87, P<0.05). Short and moderate intervals of recovery improve lipid profiles after heavy strength exercise but only 90 sec induced greater improved in PAI-1 concentration in recreational weightlifters.

Leptin links with plasminogen activator inhibitor-1 in human obesity: the SABPA study

The relationship between obesity and the development of cardiovascular disease is well established. However, the underlying mechanisms contributing to vascular disease and increased cardiovascular risk in the obese remain largely unexplored. Since leptin exerts direct vascular effects, we investigated leptin and the relationship thereof with circulating markers of vascular damage, namely plasminogen activator inhibitor-1 antigen (PAI-1(ag)), von Willebrand factor antigen (vWF(ag)) and urinary albumin-to-creatinine ratio (ACR). The study included a bi-ethnic population of 409 African and Caucasian teachers who were stratified into lean (<0.5) and obese (⩾0.5) groups according to waist-to-height ratio. We obtained ambulatory blood pressure measurements and determined serum leptin levels, PAI-1(ag), vWF(ag) and ACR, as markers of vascular damage. The obese group had higher leptin (P<0.001) and PAI-1(ag) (P<0.001) levels and a tendency existed for higher vWF(ag) (P=0.068). ACR did not differ between the two groups (P=0.21). In single regression analyses positive associations existed between leptin and all markers of vascular damage (all P<0.001) only in the obese group. After adjusting for covariates and confounders in multiple regression analyses, only the association between leptin and PAI-1(ag) remained (R(2)=0.440; β=0.293; P=0.0021). After adjusting for gender, ethnicity and age, additional analyses indicated that leptin also associated with fibrinogen and clot lysis time in both lean and obese groups, which in turn is associated with 24- h blood pressure and pulse pressure. This result provides evidence that elevated circulating leptin may directly contribute to vascular damage, possibly through mechanism related to thrombotic vascular disease.

Leptin and plasminogen activator inhibitor-1 levels in children on chronic dialysis

PURPOSE

In this study, it is aimed to compare the serum leptin and PAI-1 levels and evaluate their relationship in children on hemodialysis (HD) and peritoneal dialysis (PD).

METHOD

Thirty-six patients on HD (mean age: 15.0 ± 2.8 years), 19 patients on PD (mean age: 13.0 ± 3.5 years) and 15 healthy subjects (mean age: 14.5 ± 2.7 years) were included in the study. Laboratory investigations included blood count, biochemical parameters, serum iron, iron binding capacity, parathormone, erythrocyte sedimentation rate, C-reactive protein (CRP), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, serum leptin and PAI-1 levels.

RESULTS

Serum leptin levels were significantly higher in HD group than in control group when the effects of BMI and sex were controlled, while PD and control groups had similar leptin levels. PAI-1 levels were also significantly higher in HD group than in control group, while there was no statistically significant difference in PAI-1 levels of PD and control group. PAI-1 levels and leptin levels were significantly correlated, which was independent of the effect of BMI in both HD and PD groups when they are evaluated separately.

CONCLUSION

Results of our study showed that HD patients had higher leptin and PAI-1 levels and leptin and PAI-1 levels were correlated significantly in both patient groups. The effect of elevated serum leptin and PAI-1 levels on the cardiovascular complications remains to be established.

Cardiometabolic Risk Factors in Children

Considerable evidence has accrued that cardiovascular disease (CVD) has its beginnings during childhood, with some reports of endothelial damage occurring in early adolescence. Thus, early prevention and intervention on developing cardiometabolic risk factors is important. Presently, diet and exercise are strategic parts of any CVD prevention or treatment program. Although diet is important, the effects of exercise training or regular moderate-to-vigorous intensity physical activity go beyond simply modifying the traditional risk factors. For children, the majority of studies show that regular physical activity can lower elevated blood pressure, positively influence lipid profiles, reduce inflammation, and improve vascular functioning. These changes are most evident in children who exercise and lose weight. Despite these potential benefits of physical activity, not all studies on children have found positive effects of habitual physical activity on CVD risk factors. Reasons for these differences are discussed throughout this review. The literature also suggests that habitual physical activity, although meeting guidelines, may not be sufficient for all individuals to bring about changes; thus, to be an effective modality physical activity needs to increase beyond habitual levels or be of a moderate to vigorous intensity. This review provides recent evidence (since 2008) regarding the influence of physical activity on the cardiometabolic risk factors in children.

Plasminogen activator inhitor-1 associates with cardiovascular risk factors in healthy young adults in the Cardiovascular Risk in Young Finns Study

AIMS

Hypofibrinolysis displayed by elevated serum plasminogen activator inhibitor 1 (PAI-1) level has been associated with cardiovascular disease (CVD) and its risk factors such as obesity and insulin resistance. However, no studies have examined associations between PAI-1 and CVD risk factors in healthy subjects. We examined associations between serum PAI-1, ultrasound markers of atherosclerosis and CVD risk factors and whether PAI-1 improves prediction of atherosclerosis over known risk factors in a cohort of asymptomatic adults.

METHODS

We analyzed PAI-1 and CVD risk factors and assessed carotid intima-media thickness (cIMT), distensibility (CDist) and the presence of a carotid atherosclerotic plaque and flow-mediated dilation (FMD) ultrasonographically for 2202 adults (993 men and 1,209 women, aged 30-45 years) participating in the ongoing longitudinal cohort study, The Cardiovascular Risk in Young Finns Study. High cIMT was defined as >90th percentile and/or carotid plaque and low CDist and low FMD as <20th percentile.

RESULTS

In bivariate analyses, PAI-1 correlated directly with cIMT and the risk factors: blood pressure, BMI, waist and hip circumference, alcohol use, total and LDL-cholesterol, triglycerides, glomerular filtration rate, high-sensitivity CRP and glucose (all P<0.005). PAI-1 was higher in men and increased with age. Inverse correlation was observed with CDist, HDL-cholesterol and adiponectin in both sexes, with testosterone and sex hormone binding globulin in men and with creatinine and oral contraceptive use in women (P<0.005). Independent direct associations were observed between PAI-1 and waist circumference, serum triglycerides, insulin, alcohol use and age and inverse with serum creatinine, HDL-cholesterol and adiponectin. PAI-1 did not improve estimation of high cIMT, low CDist and low FMD over conventional risk factors (P for difference in area under curve ≥ 0.37).

CONCLUSION

PAI-1 was independently associated with several known CVD risk factors, especially obesity markers, in both men and women. However, addition of PAI-1 to known risk factors did not improve cross-sectional prediction of high cIMT, low CDist and low FMD suggesting that PAI-1 is not a clinically important biomarker in early atherosclerosis.

The prothrombotic tendency in metabolic syndrome: focus on the potential mechanisms involved in impaired haemostasis and fibrinolytic balance

The metabolic syndrome is a clinical disorder characterized by impairment of glucose metabolism, increased arterial blood pressure, and abdominal obesity. The presence of these clinical features exposes patients to a high risk of atherothrombotic cardiovascular events. The pathogenesis of atherothrombosis in the metabolic syndrome is multifactorial, requiring a close relationship among the main components of the metabolic syndrome, including insulin resistance, alterations of glycaemic and lipid pattern, haemodynamic impairment, and early appearance of endothelial dysfunction. Furthermore, haemostatic alterations involving coagulation balance, fibrinolysis, and platelet function play a relevant role both in the progression of the arterial wall damage and in acute vascular events. The mechanisms linking abdominal obesity with prothrombotic changes in the metabolic syndrome have been identified and partially elucidated on the basis of alterations of each haemostatic variable and defined through the evidence of peculiar dysfunctions in the endocrine activity of adipose tissue responsible of vascular impairment, prothrombotic tendency, and low-grade chronic inflammation. This paper will focus on the direct role of adipose tissue on prothrombotic tendency in patients affected by metabolic syndrome, with adipocytes being able to produce and/or release cytokines and adipokines which deeply influence haemostatic/fibrinolytic balance, platelet function, and proinflammatory state.

Childhood obesity: evidence of an association between plasminogen activator inhibitor-1 levels and visceral adiposity

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) has been considered as a cardiovascular risk factor, mainly because of its strong association with insulin resistance.

METHODS

To detect independent predictors of circulating PAI-1 levels in obese pediatric patients, we evaluated 86 subjects (mean age 10.7 +/- 2.8 years), 42 of whom were male (49%). Subjects were divided in two groups according to body mass index (BMI): obese subjects (n=61) and healthy non-obese controls (n=25). They were also divided by pubertal status. Besides anthropometric data, levels of PAI-1, leptin and biochemical markers of metabolic syndrome were measured.

RESULTS

The obese group had higher levels of PAI-1, leptin and biochemical markers of metabolic syndrome than nonobese controls (p<0.05). However, multivariate regression analysis showed that only puberty progression (p=0.005) and abdominal circumference/height index (p=0.002) remained independent predictors of PAI-1 levels.

CONCLUSION

In pediatric obesity, fat mass accumulation, mainly of visceral fat, and puberty progression were related to high PAI-1 levels, which might in turn contribute to cardiovascular risk.

Imbalance of plasminogen activator inhibitor type-1 (PAI-1) and tissue plasminogen activator (t-PA) activity in patients with Noonan syndrome

BACKGROUND

Patients with Noonan syndrome have been reported to have an increased incidence of bleeding with trauma and surgery. Although various abnormalities of hemostasis have been described in reported series, there has been no consistent abnormality described and none have investigated fibrinolytic pathways.

METHODS

Fibrinolytic parameters including tissue plasminogen activator (t-PA; activity and antigen), plasminogen activator inhibitor type-1 (PAI-1; activity and antigen), plasminogen (activity and antigen), thrombin-antithrombin complex, prothrombin time (PT), and activated partial thromboplastin time where studied in 12 patients with Noonan syndrome (total of 15 data sets). PT and activated partial thromboplastin time were performed locally whereas the fibrinolytic parameters were performed in a single national reference laboratory. Individual results were compared with published age-appropriate norms and the mean values of the study patients were compared with the midpoint of normal range for each component measured. The ratio of PAI-1/t-PA activity was calculated for each set of results and compared with a "normal" value calculated from the midpoint normal range value for each component.

RESULTS

Patients with Noonan syndrome consistently demonstrated an elevation of t-PA activity in relationship to PAI-1 activity and a decreased PAI-1/t-PA ratio (P<0.01 for each comparison).

CONCLUSIONS

Patients with Noonan syndrome seem to have an imbalance in fibrinolytic components favoring fibrinolysis. This may be an important contributor to the bleeding noted in these patients.

Leptin upregulates the expression of plasminogen activator inhibitor-1 in human vascular endothelial cells

A prothrombotic state in obesity may be partially responsible for the higher incidence of atherosclerotic complications. However the factors responsible for this prothrombotic state, linked with high levels of plasminogen activator inhibitor-1 (PAI-1), are not fully known. Leptin is elevated in obesity and studies have shown a positive correlation between leptin and PAI-1 levels in human subjects, along with a negative correlation with tissue-type plasminogen activator (tPA). We tested the hypothesis that leptin induces PAI-1 and inhibits tPA expression using human coronary artery endothelial cells (HCAEC) in culture as these cells play an important role in atherosclerosis. We demonstrate that leptin induces the transcription and translation of PAI-1 in HCAEC. The leptin dependent upregulation of PAI-1 mRNA and protein was comparable to insulin-induced PAI-1 expression. We show leptin concentration (0-150 ng/ml) dependent increases in PAI-1 mRNA and protein after 6 and 12h of leptin administration, respectively. Increased intracellular PAI-1 expression correlates with increased PAI-1 activity in conditioned media and inhibition of specific ERK1/2 pathway by treatment with PD98059 (20-40 microM) inhibits leptin dependent PAI-1 expression. However no changes in tPA expression were seen with time or increasing concentrations of leptin. Also leptin treatment did not alter total tPA concentration or tPA activity in conditioned media. In conclusion, our study shows that leptin upregulates the expression of PAI-1 in vascular endothelial cells via activation of ERK1/2 but does not regulate tPA expression. These studies demonstrate a novel mechanism for the prothrombotic role of leptin in development of atherosclerosis.

Sex-related differences in the associations between hyperleptinemia, insulin resistance and dysfibrinolysis

The adipocyte-derived hormone leptin is associated with insulin resistance and reduced fibrinolytic status--or dysfibrinolysis--in humans. As leptin associates differentially to the development of cardiovascular disease and diabetes in men and women, we hypothesized that leptin and insulin sensitivity are related to dysfibrinolysis in a sex-dependent manner. Thirty-two men and 40 women were recruited from the Monitoring of trends and determinants in Cardiovascular disease (MONICA) population sample, representing the highest and lowest quartiles of fasting insulin levels. Lipids, fibrinolytic status [plasminogen activator inhibitor 1 (PAI-1) activity, tissue plasminogen activator (tPA) mass and activity, and tPA-PAI complex], leptin, testosterone and sex-hormone-binding globulin were measured. Insulin sensitivity was estimated using the euglycaemic clamp technique. Body composition was determined by bioimpedance. Determinants for circulating levels of fibrinolytic factors were explored in a multivariate linear regression analysis. Levels of fibrinolytic variables and estimated insulin sensitivity did not differ between men and women. Leptin was independently associated with reduced fibrinolytic status (high PAI-1 activity, low tPA activity, high tPA mass, and high tPA-PAI complex) in men (P < 0.001-0.002). In women, fat mass and/or insulin sensitivity were related to these factors (P < 0.001-0.03), and leptin only to reduced tPA activity (P = 0.002). Hyperleptinemia, dysfibrinolysis, insulin sensitivity and androgenicity associate differentially in men and women.

Leptin resistance: a possible interface of inflammation and metabolism in obesity-related cardiovascular disease

Leptin is an adipocyte-derived hormone and cytokine that regulates energy balance through a wide range of functions, including several that are important to cardiovascular health. Increased circulating leptin, a marker of leptin resistance, is common in obesity and independently associated with insulin resistance and cardiovascular disease (CVD) in humans. The mechanisms of leptin resistance include genetic mutation, leptin self-regulation, limited tissue access, and cellular or circulating molecular regulation. Evidence suggests that central leptin resistance causes obesity and that obesity-induced leptin resistance injures numerous peripheral tissues, including liver, pancreas, platelets, vasculature, and myocardium. This metabolic- and inflammatory-mediated injury may result from either resistance to leptin's action in selective tissues, or excess leptin action from adiposity-associated hyperleptinemia. In this sense, the term "leptin resistance" encompasses a complex pathophysiological phenomenon. The leptin axis has functional interactions with elements of metabolism, such as insulin, and inflammation, including mediators of innate immunity, such as interleukin-6. Leptin is even purported to physically interact with C-reactive protein, resulting in leptin resistance, which is particularly intriguing, given C-reactive protein's well-studied relationship to cardiovascular disease. Given that plasma levels of leptin and inflammatory markers are correlated and also predict cardiovascular risk, it is conceivable that part of this risk may be mediated through leptin resistance-related insulin resistance, chronic inflammation, type II diabetes, hypertension, atherothrombosis, and myocardial injury. Leptin resistance and its interactions with metabolic and inflammatory factors, therefore, represent potential novel diagnostic and therapeutic targets in obesity-related cardiovascular disease.

Leptin in acute coronary syndromes: Has the time come for its use in risk stratification?

Leptin, a recently discovered obesity gene product, is primarily involved in the regulation of food intake and energy expenditure. Recent observations suggest that leptin has a much broader biological role other than regulation of body weight and energy metabolism. It has been shown that leptin increases sympathetic nerve activity, stimulates generation of reactive oxygen species, induces platelet aggregation and promotes arterial thrombosis, and is an independent risk factor for coronary heart disease. In this paper, we discussed the role of leptin in the pathogenesis of acute coronary syndromes and its usefulness as a biomarker for risk stratification in acute coronary syndromes.

The emerging role of adipokines as mediators of cardiovascular function: physiologic and clinical perspectives

Interest in the biology of white adipose tissue has increased dramatically since the discovery of leptin in 1994. The identification of the product of the gene obese (ob) threw light on the role of adipose tissue in the physiopathology of obesity-related diseases and spurred the identification of numerous other adipokines, many of a proinflammatory nature. It has become increasingly evident that white adipose tissue-derived cytokines mediate between obesity-related exogenous factors (nutrition and lifestyle) and the molecular events that lead to metabolic syndrome, inflammation, and cardiovascular diseases. Here we review recent adipokine research, with particular attention to the roles of adiponectin, leptin, resistin, visfatin, apelin, omentin, and chemerin in such conditions.

Factors associated with excessive bleeding in cardiopulmonary bypass patients: a nested case-control study

Introduction

Excessive bleeding (EB) after cardiopulmonary bypass (CPB) may lead to increased mortality, morbidity, transfusion requirements and re-intervention. Less than 50% of patients undergoing re-intervention exhibit surgical sources of bleeding. We studied clinical and genetic factors associated with EB.

Methods

We performed a nested case-control study of 26 patients who did not receive antifibrinolytic prophylaxis. Variables were collected preoperatively, at intensive care unit (ICU) admission, at 4 and 24 hours post-CPB. EB was defined as 24-hour blood loss of >1 l post-CPB. Associations of EB with genetic, demographic, and clinical factors were analyzed, using SPSS-12.2 for statistical purposes.

Results

EB incidence was 50%, associated with body mass index (BMI)< 26.4 (25–28) Kg/m², (P = 0.03), lower preoperative levels of plasminogen activator inhibitor-1 (PAI-1) (P = 0.01), lower body temperature during CPB (P = 0.037) and at ICU admission (P = 0.029), and internal mammary artery graft (P = 0.03) in bypass surgery. We found a significant association between EB and 5G homozygotes for PAI-1, after adjusting for BMI (F = 6.07; P = 0.02) and temperature during CPB (F = 8.84; P = 0.007). EB patients showed higher consumption of complement, coagulation, fibrinolysis and hemoderivatives, with significantly lower leptin levels at all postoperative time points (P = 0.01, P < 0.01 and P < 0.01).

Conclusion

Excessive postoperative bleeding in CPB patients was associated with demographics, particularly less pronounced BMI, and surgical factors together with serine protease activation.

Admission plasma leptin level strongly correlates with the success of thrombolytic therapy in patients with acute myocardial infarction

Obesity-associated alterations in coagulation and fibrinolytic factors in favor of thrombosis are well known. Observations suggest that leptin, a recently discovered obesity gene product, in addition to being a satiety factor, induces platelet aggregation, accelerates formation of firm thrombi, and is associated with abnormal fibrinolysis. The authors studied the influence of plasma leptin concentrations on admission within 6 hours of acute myocardial infarction (MI) on the outcome of thrombolytic therapy (TT). Forty-one patients with acute MI who underwent TT were enrolled into the study. Levels of plasma leptin were determined with radioimmunoassay method in samples obtained just before initiation of TT. Patients were initially classified according to the admission plasma leptin concentrations, and it was observed that failure of reperfusion therapy with streptokinase was significantly higher in patients with admission plasma leptin concentrations > or =14 ng/mL (group 2) as compared to patients with admission plasma leptin concentrations <14 ng/mL (group 1). Final failure of TT, identified both by reinfarction and absence of early reperfusion as assessed noninvasively, was observed in 11 patients (39%) in group 1 and in 10 patients (77%) in group 2 (p=0.025). Left ventricular ejection fraction was slightly but significantly higher in group 1 than in group 2 (p=0.031). High plasma leptin concentrations on admission in patients within 6 hours after the onset of acute MI are associated with less TT efficacy. The authors suggest that admission leptin levels may play a role in the management of patients with acute MI.

Hemostasis and fibrinolysis in non-diabetic overweight and obese men and women. Is there still a role for leptin?

OBJECTIVE

Leptin has been associated with disturbances in hemostasis and fibrinolysis, with inconsistent results on the influence of fat mass. However, the influence of the amount of visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT) has not yet been studied. In this study, we investigated the relationship between leptin and fibrinogen, von Willebrand factor antigen (vWF:Ag), and plasminogen-activator inhibitor-1 (PAI-1) activity and determined the influence of associated metabolic variables and VAT versus SAT.

METHODS

Fibrinogen, vWF:Ag, PAI-1,VAT and SAT (CT-scan), and insulin resistance (homeostasis model assessment; HOMA-IR) were measured in 199 women and 81 men with overweight or obesity visiting the weight management clinic of a university hospital.

RESULTS

Leptin did not relate to fibrinogen (r = 0.11 and 0.13 in women and men respectively; P > 0.05), a relationship with vWF:Ag was only found in men (r = 0.31; P = 0.005), while leptin related to PAI-1 activity in both men (r = 0.36; P < 0.001) and women (r = 0.23; P < 0.001). Further analysis showed leptin to have an effect on the variation of PAI-1 independent of VAT and HOMA-IR in women, but not in men. Multiple regression showed HOMA-IR to be the most important determinant of PAI-1, both in men and women, but leptin also showed an independent effect. As for vWF:Ag, leptin was an independent determinant in men only.

CONCLUSIONS

PAI-1 related to leptin levels independent of fat mass percentage, HOMA-IR, and the amount of VAT and SAT. For vWF:Ag this relationship was found only in men, and not in women, while a relationship with fibrinogen could not be demonstrated.

Leptin and atherosclerosis

Leptin, a 167-amino acid peptide hormone produced by white adipose tissue, is primarily involved in the regulation of food intake and energy expenditure. Leptin receptors are expressed in many tissues including the cardiovascular system. Plasma leptin concentration is proportional to body adiposity and is markedly increased in obese individuals. Recent studies suggest that hyperleptinemia may play an important role in obesity-associated cardiovascular diseases including atherosclerosis. Leptin exerts many potentially atherogenic effects such as induction of endothelial dysfunction, stimulation of inflammatory reaction, oxidative stress, decrease in paraoxonase activity, platelet aggregation, migration, hypertrophy and proliferation of vascular smooth muscle cells. Leptin-deficient and leptin receptor-deficient mice are protected from arterial thrombosis and neointimal hyperplasia in response to arterial wall injury. Several clinical studies have demonstrated that high leptin level predicts acute cardiovascular events, restenosis after coronary angioplasty, and cerebral stroke independently of traditional risk factors. In addition, plasma leptin correlates with markers of subclinical atherosclerosis such as carotid artery intima-media thickness and coronary artery calcifications. Inhibition of leptin signaling may be a promising strategy to slow the progression of atherosclerosis in hyperleptinemic obese subjects.

Free testosterone plasma levels are negatively associated with the intima-media thickness of the common carotid artery in overweight and obese glucose-tolerant young adult men

OBJECTIVE

To evaluate the relation between free testosterone (FT) levels and the intima-media thickness of the common carotid artery (IMT-CCA) in overweight and obese glucose-tolerant (NGT) young adult men.

DESIGN

Cross-sectional study of FT and IMT-CCA in obese men.

SUBJECTS

A total of 127 overweight and obese NGT male individuals, aged 18-45 y.

MEASUREMENTS

FT plasma levels; IMT-CCA, as measured by high-resolution B-mode ultrasound imaging; central fat accumulation, as evaluated by waist circumference; body composition, as measured by bioimpedance analysis; insulin resistance, as calculated by homeostatic model assessment (HOMA(IR)); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

IMT-CCA was positively correlated with age, body mass index (BMI), fat mass (FM), waist circumference, and fasting glucose concentrations, and inversely associated with FT levels. After multivariate analysis, IMT-CCA maintained an independent association with BMI, FM, and FT levels. This study indicates that IMT-CCA is negatively associated with FT levels, independent of age, total body fat, central fat accumulation, and fasting glucose concentrations in overweight and obese NGT patients.

CONCLUSION

Hypotestosteronemia may accelerate the development of atherosclerosis and increase the risk for CHD in obese men.

An association between coronary artery calcification score, lipid profile, and selected markers of chronic inflammation in ESRD patients treated with peritoneal dialysis

BACKGROUND

Chronic uremia is considered a proinflammatory state associated with high cardiovascular morbidity and mortality. The aim of the present study is to evaluate the potential relationship between the prevalence of coronary artery calcification (CAC) and selected factors that may be involved in the process of atherogenesis (lipid profile, acute-phase reactants, growth factors, and cytokines).

METHODS

The study group consisted of 43 patients (19 women, 24 men) with a mean age of 50.6 +/- 13.4 years treated with peritoneal dialysis (PD) for a median period of 15 months (range, 2 to 96 months). Only patients with sinus rhythm were included. CAC score (CaSc) was measured using multirow spiral computed tomography (MSCT). As parameters of lipid profile, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides were assayed. C-reactive protein (CRP) and fibrinogen represented the level of acute-phase activation. Proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor-alpha [TNF-alpha]), leptin, and basic fibroblast growth factor (bFGF) also were measured.

RESULTS

Median CaSc equaled 17.9 Agatston units (range, 0 to 5,502 Agatston units). No calcification was detected in 20 subjects (46.5%; CaSc < 10 Agatston units). CaSc correlated with age (R = 0.57; P < 0.0001), body mass index (R = 0.42; P < 0.005), and serum leptin (R = 0.3; P < 0.05) and CRP levels (R = 0.38; P < 0.05). The correlation with PD therapy duration was borderline statistically significant (P = 0.063). Patients with the greatest values for CaSc (> 400 Agatston units) were characterized by significantly greater levels of IL-6, bFGF, and CRP compared with subjects with a CaSc less than 10 Agatston units (P < 0.05 for all). Patients with history of coronary artery disease (CAD) had significantly greater CaSc values (median, 778.6 versus 3.3 Agatston units; P < 0.001) compared with those without CAD. Serum triglyceride levels were significantly greater and HDL cholesterol levels were significantly lower in patients with CAD. The first group also was characterized by significantly greater serum TNF-alpha (P < 0.01) and CRP levels (P < 0.005). In multiple regression analysis, only age was independently associated with CaSc (beta = 0.45; P = 0.002).

CONCLUSION

Our results may suggest an association between CAC and chronic inflammation activity in the mentioned group of patients. To our knowledge, this is the first study reporting the prevalence of CAC in PD patients using the MSCT method. The association between CaSc results and classic, as well as inflammatory, risk factors for CAD found in this study should be interpreted with caution because of its method limitations (cross-sectional design, heterogeneity of study population, and small number of studied patients).

Relationship between high plasma leptin concentrations and metabolic syndrome in obese pre-pubertal children

OBJECTIVE

To evaluate the relationship between serum leptin levels and metabolic syndrome, fasting insulin level and anthropometric index in obese pre-pubertal children.

DESIGN

A cross-sectional study was carried out on obese children.

SUBJECTS

A study was made of 41 obese children (aged 6-9 y) and the same number of non-obese children (control group), matched by age and sex.

METHODS

Body mass index (BMI), waist/hip ratio (WHR) and blood pressure were determined in each child. Serum leptin, glucose, insulin, lipid profile, sex hormone binding globulin (SHBG), plasminogen activator inhibitor-1 (PAI-1), tissue-plasminogen activator (t-PA) and fibrinogen were all measured.

RESULTS

The serum leptin level was significantly higher in obese children (15.47 vs 4.73 ng/ml). In the obese group, leptin showed a positive correlation with BMI (P<0.001), insulin (P<0.001), triglycerides (P<0.05), PAI-1 (P<0.05) and t-PA (P<0.05), and correlated negatively with SHBG (P<0.01), apolipoprotein A-I (P<0.05) and high-density lipoproteins cholesterol (HDL-C) (P<0.05). Corrected for BMI and WHR, leptin (P partial=0.002) is only an independent predictive factor for basal insulin. Using multivariant regression analysis, only insulin (P partial=0.003) and BMI (P partial=0.018) were independent predictive factors for leptin.

CONCLUSION

For this age group, high leptin resistance may be another component of metabolic syndrome, and may be involved in its etiopathogenesis. The involvement of leptin in this syndrome may be indirect, modulating the insulin's action.

Coagulation and fibrinolysis abnormalities in obesity

Abnormalities in coagulation and haemostasis represent a well-known link between obesity and thrombosis (both arterial and venous). Several studies have shown that obese patients have higher plasma concentrations of all pro-thrombotic factors (fibrinogen, vonWillebrand factor (vWF), and factor VII), as compared to non-obese controls, with a positive association with central fat. Similarly, plasma concentrations of plasminogen activator inhibitor-1 (PAI-1) have been shown to be higher in obese patients as compared to non-obese controls and to be directly correlated with visceral fat. Furthermore, obesity is characterized by higher plasma concentrations of anti-thrombotic factors, such as tissue-type plasminogen activator (t-PA) and protein C, as compared to non-obese controls, the increase in these factors being likely to represent a protective response partly counteracting the increase in pro-thrombotic factors. The issue of whether adipose tissue contributes directly to plasma PAI-1, its products stimulating other cells to produce PAI-1, or whether it primarily contributes indirectly has not yet been resolved. It has been proposed that the secretion of interleukin-6 (IL-6) by adipose tissue, combined with the actions of adipose tissue-expressed TNF-alpha in obesity, could underlie the association of insulin resistance with endothelial dysfunction, coagulopathy, and coronary heart disease. The role of leptin in impairing haemostasis and promoting thrombosis has been recently reported. Finally, some hormonal abnormalities (androgen, F, catecholamines) associated with the accumulation of body fat may contribute to the impairment of coagulative pathway in obesity. As to intervention strategies, dietary (i.e., low-fat high-fiber diet) and lifestyle (i.e., physical activity) measures have been demonstrated to be effective in improving the obesity-associated pro-thrombotic risk profile.

Effect of glucose tolerance status on PAI-1 plasma levels in overweight and obese subjects

OBJECTIVE

The aim of our study was to examine whether plasminogen activator inhibitor-1 (PAI-1) plasma levels varied as a function of differences in glucose tolerance status independently of body fatness, body-fat distribution, and insulin sensitivity.

RESEARCH METHODS AND PROCEDURES

Plasma PAI-1 antigen levels, along with insulin resistance [measured by homeostatic model assessment (HOMA(IR))], central fat accumulation, body composition, blood pressure, and fasting concentrations of glucose, insulin, and lipids, were measured in 229 overweight and obese [body mass index (BMI) > or =25 kg/m(2)) subjects with normal glucose tolerance (NGT) and in 44 age- and BMI-matched subjects with impaired glucose tolerance (IGT).

RESULTS

Plasma PAI-1 antigen levels were significantly higher in IGT than in NGT subjects. Log PAI-1 was positively correlated with BMI, HOMA(IR), and log insulin, and inversely associated with high-density lipoprotein-cholesterol both in IGT and in NGT individuals. On the other hand, log PAI-1 was positively correlated with waist circumference, fat mass (FM), fat-free mass, systolic and diastolic blood pressure, and log triglycerides only in the NGT group. After multivariate analyses, the strongest determinants of PAI-1 levels were BMI, FM, waist circumference, and high-density lipoprotein cholesterol in the NGT group and only HOMA(IR) in the IGT cohort.

DISCUSSION

This study demonstrates that PAI-1 concentrations are higher in IGT than in NGT subjects. Furthermore, we suggest that the influences of total adiposity, central fat, and insulin resistance, main determinants of PAI-1 concentrations, are different according to the degree of glucose tolerance.

Obesity, haemostasis and the fibrinolytic system

Obese patients are at risk for the development of cardiovascular diseases, which can in part be explained by disturbances in the haemostatic and fibrinolytic systems. Indeed, obese subjects tend to have higher values of fibrinogen, factor VII, factor VIII, von Willebrand factor and plasminogen activator inhibitor compared to non-obese subjects. Abdominal obesity, in particular, has been shown to be associated with disturbances in fibrinogen, factor VIII and von Willebrand factor, while less consistent results have been found for factor VII. Recently it has been demonstrated that the adipocyte itself is able to produce plasminogen activator inhibitor-1, possibly explaining the high levels found in obesity. Different studies have investigated the association between haemostatic and fibrinolytic parameters and the insulin resistance syndrome, often present in obese subjects. Fibrinogen has been found to be related to insulin, but it has been suggested that this relationship is not independent of the accompanying inflammatory reaction. Results from studies on the relationship between insulin resistance and factor VII, factor VIII and von Willebrand factor levels are inconsistent. In contrast, plasminogen activator inhibitor-1 has been found to correlate with all components of the insulin resistance syndrome, and can be considered as a true component of this metabolic syndrome. Weight loss seems to have a beneficial effect on factor VII--probably mediated through a reduction in triglycerides. Data on factor VIII and von Willebrand factor are scarce but weight loss does not seem to have an effect. Fibrinogen does not seem to be reduced by modest weight loss and a more substantial weight loss seems necessary to lower fibrinogen levels. In contrast, both modest and substantial weight loss have been found to significantly reduce plasminogen activator inhibitor-1 levels. In conclusion, the increased cardiovascular risk observed in obesity could in part be explained by the association between insulin resistance and components of the fibrinolytic and haemostatic systems. Whether this relationship is truly causal or indirect needs to be elucidated further.

Effects of leptin on the differentiation and metabolism of human adipocytes

BACKGROUND

Leptin is an adipose protein regulating food intake in the hypothalamus. Animal studies have suggested that leptin also acts in an auto-/paracrine fashion on adipose cell function.

OBJECTIVE

The aim of this study was to investigate the effects of leptin on the differentiation and metabolism of cultured human adipocytes.

MATERIAL

Adipose tissue from young healthy, lean women (body mass index (BMI) <27 kg/m(2)) undergoing elective mammary reduction surgery and young obese individuals (BMI>40 kg/m(2)) undergoing laparoscopic gastric banding.

METHODS

Human preadipocytes in primary culture were induced to undergo differentiation by defined adipogenic factors. Mature adipocytes were isolated by collagenase digestion and kept in culture suspension. Glycero-3-phosphate dehydrogenase (GPDH) activity was used as a marker of adipose differentiation; glucose uptake, lipolysis and PAI-1 secretion were measured as parameters of fat cell function.

RESULTS

Human preadipocytes and adipocytes from lean and obese subjects expressed the long leptin receptor isoform and two of the three short forms as assessed by polymerase chain reaction (PCR). Leptin at a supraphysiological concentration induced a transient increase of GPDH activity, but had no effect on glucose uptake and PAI-1 secretion from human adipocytes. In addition, basal and isoproterenol-stimulated lipolysis as well as the antilipolytic action of insulin in human adipocytes was not significantly affected by leptin exposure.

CONCLUSION

In contrast to animal data, the results of our experiments do not demonstrate significant effects of leptin on main metabolic functions of human adipocytes arguing against a local auto-/paracrine action of leptin in human adipose tissue.

The adipocyte: a model for integration of endocrine and metabolic signaling in energy metabolism regulation

The ability to ensure continuous availability of energy despite highly variable supplies in the environment is a major determinant of the survival of all species. In higher organisms, including mammals, the capacity to efficiently store excess energy as triglycerides in adipocytes, from which stored energy could be rapidly released for use at other sites, was developed. To orchestrate the processes of energy storage and release, highly integrated systems operating on several physiological levels have evolved. The adipocyte is no longer considered a passive bystander, because fat cells actively secrete many members of the cytokine family, such as leptin, tumor necrosis factor-alpha, and interleukin-6, among other cytokine signals, which influence peripheral fuel storage, mobilization, and combustion, as well as energy homeostasis. The existence of a network of adipose tissue signaling pathways, arranged in a hierarchical fashion, constitutes a metabolic repertoire that enables the organism to adapt to a wide range of different metabolic challenges, such as starvation, stress, infection, and short periods of gross energy excess.

Plasma leptin is independently associated with the intima-media thickness of the common carotid artery

OBJECTIVE

To investigate whether intima-media thickness (IMT) of the common carotid artery (CCA), an early marker of asymptomatic atherosclerosis, is significantly and independently associated with plasma concentrations of leptin, an adipose tissue hormone that has recently been proposed as a cardiovascular risk factor in obese patients.

DESIGN

Cross-sectional sample of normal-weight and obese men and women.

SUBJECTS

One-hundred and twenty healthy subjects (52 men and 68 women), aged 18-45 y and with a wide range of BMI, were recruited for the study.

MEASUREMENTS

Fasting plasma leptin concentrations and the IMT of the CCA were measured in all subjects. Leptin concentrations were measured by radioimmunoassay and the IMT of the CCA was quantified by high resolution B-mode ultrasound imaging. Central fat (measured by waist circumference), smoking habits, blood pressure, insulin sensitivity (measured by the insulin tolerance test), and fasting plasma glucose, insulin and lipid pattern (cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol) were also measured.

RESULTS

IMT of the CCA was positively correlated with log leptin concentrations (P<0.005 in men and P<0.001 in women), body mass index (P<0.001 in men and women), waist circumference (P<0.001 in men and women), age (P<0.001 in men and P<0.05 in women), and negatively associated with insulin sensitivity in both sexes (P<0.05). IMT was also directly correlated with cholesterol (P<0.05), LDL-cholesterol (P<0.01) and systolic blood pressure in men (P<0.05), and with diastolic blood pressure levels in women (P<0.05). When a multiple linear regression model was used without body mass index (BMI), the correlation between leptin and IMT was maintained in both men (P<0.01) and women (P<0.005), independent of age, insulin sensitivity, smoking habits, systolic blood pressure, fasting glucose, triglycerides, cholesterol, LDL-cholesterol and HDL-cholesterol. By contrast, BMI-adjusted leptin concentrations were not significantly associated with IMT (Pc (partial correlation): 0.41 in men and 0.15 in women). Moreover, when BMI was entered into a multiple linear regression model without leptin, the correlation between BMI and IMT was maintained in both men (P<0.005) and women (P<0.01), independent of the same parameters.

CONCLUSION

Plasma leptin concentrations are independently associated with the IMT of the CCA, suggesting that the increase of adipose tissue mass (or leptin per se) may have an unfavourable influence on the development of atherosclerosis. However, the association between IMT and leptin seems to be dependent and/or confounded by the relationship between IMT and obesity.

Sex differences in HAART-associated dyslipidaemia

OBJECTIVES

Because female sex protects against dyslipidaemia and atherosclerosis in normal subjects, we aimed to reveal potential sex differences in metabolic side-effects of a newly initiated highly active antiretroviral therapy (HAART) regimen, and to relate these changes to endothelial cell activation as measured by levels of circulating E-selectin (cE-selectin).

DESIGN

Prospective longitudinal cohort study.

SETTING

Tertiary care centre at a University Hospital.

METHODS

HIV-seropositive male (n = 27) and female patients (n = 13) with a plasma viral load of > or = 10 000 copies/ml and 35 healthy controls were enrolled in the study. All participants were weight stable, free of acute opportunistic infections, and had not taken any protease inhibitors before. Serum levels of lipids, insulin, leptin, and cE-selectin were measured before initiation of HAART, and at 3 and 6 months thereafter.

RESULTS

HAART increased serum levels of triglycerides, leptin, and low-density lipoprotein (LDL) cholesterol; these effects were more distinct in women. Fasting insulin levels and the LDL : high density lipoprotein (HDL) ratio increased only in female HIV-infected patients (P < 0.02 versus men). In contrast, endothelial activation, as measured by cE-selectin, decreased more in men (P < 0.02) than in women. As a consequence, women had higher triglycerides and leptin levels after therapy than did men, and the LDL : HDL ratio and cE-selectin levels, which were initially higher in men, were no longer different between the sexes.

CONCLUSIONS

Metabolic adverse effects during HAART are more pronounced in women than in men. Hence, female HIV-infected patients seem to loose part of their natural protection from atherosclerosis during antiretroviral therapy.