Plasma leptin levels are associated with abnormal fibrinolysis in men and postmenopausal women

Adipokines are possible risk markers for aortic stenosis requiring surgery

OBJECTIVES

Aortic stenosis (AS) is the most prevalent valvular heart disease among adults. The adipocyte-derived hormones, leptin and adiponectin, have profound metabolic actions. We examined whether these adipokines are independently associated with future aortic valve replacement (AVR).

DESIGN

In this longitudinal case-control study, we identified 336 cases who had undergone AVR due to AS, and who had previously participated in population-based health surveys. Two referents were matched to each case and leptin and adiponectin concentrations were analysed from stored baseline survey samples. Uni- and multivariable logistic regression analyses were used to estimate the risk of future AVR. An additional cohort was identified for validation including 106 cases with AVR and 212 matched referents.

RESULTS

Median age (interquartile range (IQR)) in years at survey was 59.9 (10.4) and at surgery 68.3 (12.7), and 48% were women. An elevated concentration of leptin was not associated with future AVR (odds ratio [95% confidence interval]) (1.10 [0.92-1.32]), although leptin was associated with a higher risk in patients with coronary artery disease (CAD) having more than 5 years between survey and AVR (1.41 [1.08-1.84]). Adiponectin was not associated with higher risk for future AVR (0.95 [0.82-1.11]), although after stratification for age, higher levels were associated with reduced risk for AVR in persons aged ≥60 years at surgery (0.79 [0.64-0.98]). In the validation study, leptin was associated with future AVR whereas adiponectin was not. None of the associations remained significant after adjustment for body mass index (BMI).

CONCLUSIONS

The adipokine leptin may promote the development of AS.

Plasma Levels of Leptin and Risk of Future Incident Venous Thromboembolism

BACKGROUND

 Circulating levels of leptin, an adipocyte-derived hormone, are frequently elevated in obesity. Leptin has been reported to upregulate prothrombotic hemostatic factors in vitro and could potentially mediate venous thromboembolism (VTE) risk in obesity. However, whether leptin is associated with VTE remains uncertain.

OBJECTIVE

 This article investigates the association between plasma leptin and risk of incident VTE, and the potential of leptin to mediate VTE risk in obesity.

METHODS

 A population-based nested case-control study with 416 VTE cases and 848 age- and sex-matched controls was derived from the Tromsø Study. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for VTE across leptin quartiles. Analyses were performed separately in men and women using sex-specific quartile cut-offs determined in controls.

RESULTS

 In the age-adjusted model, the VTE risk increased across leptin quartiles, particularly in men. Compared with the lowest quartile, the ORs for VTE in the highest quartile were 1.70 (95% CI 1.04-2.79) in men and 1.36 (95% CI 0.85-2.17) in women. However, with additional adjustment for body mass index (BMI), risk estimates were markedly attenuated in men (OR 1.03, 95% CI 0.55-1.93) and women (OR 0.82, 95% CI 0.45-1.48). The ORs for VTE were increased in obese men and women (BMI ≥ 30 kg/m²) and were only marginally affected after adjustment for leptin.

CONCLUSION

 Our results indicate that the apparent association between plasma leptin levels and VTE risk is confounded by BMI and that leptin is not a relevant mediator for VTE risk in obesity.

The Association Between Serum/Plasma Leptin Levels and Obstructive Sleep Apnea Syndrome: A Meta-Analysis and Meta-Regression

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with various adipokines. Leptin, a common adipokine, has attracted considerable attention of many researchers in recent years. So far, there has been little agreement on whether blood leptin levels differ in patients with OSAS. Thus, this meta-analysis examined the relationship between serum/plasma leptin levels and the occurrence of OSAS.

METHOD

WanFang, Embase, CNKI, Medline, SinoMed, Web of Science, and PubMed were searched for articles before March 30, 2021, with no language limitations. STATA version 11.0 and R software version 3.6.1 were used to analyze the obtained data. The weighted mean difference and correlation coefficients were used as the main effect sizes with a random-effects model and a fixed-effects model, respectively. Trial sequential analysis was conducted using dedicated software.

RESULT

Screening of 34 publications identified 45 studies that met the inclusion criteria of this meta-analysis and meta-regression. Our results suggested that plasma/serum leptin levels were remarkably higher in individuals with OSAS than in healthy individuals. Subgroup analyses were performed based on OSAS severity, ethnicity, age, body mass index, assay type, and sample source. The serum and plasma leptin levels were increased in nearly all OSAS subgroups compared to those in the corresponding control groups. Meta-regression analysis indicated that age, BMI, severity, assay approaches, study design, PSG type and ethnicity did not have independent effect on leptin levels. Furthermore, a positive relationship between the serum/plasma leptin level and apnea-hypopnea index (AHI) was found in the meta-analysis. The results of the trial sequential analysis suggested that the enrolled studies surpassed the required information size, confirming that our study findings were reliable.

CONCLUSION

Our study results demonstrate that OSAS patients have higher leptin levels in serum/plasma compared to controls, and the serum/plasma leptin level is positively correlated with AHI, especially in adults.

Leptin affects the inflammatory response after STEMI

Leptin is an adipose tissue-derived hormone primarily involved in the regulation of food intake. Leptine has been shown to have a much broader role than just regulating body weight and appetite in response to food intake: among the others, it has been associated with increased ROS production and inflammation, factors involved in the restoration of an effective myocardial reperfusion after myocardial revascularization. Our study, to our best knowledge, is the first showing a direct relationship between leptin serum levels, inflammatory mediators of the ischemia reperfusion damage and effective myocardial reperfusion in patients with ST elevation myocardial infarction undergoing primary percutaneous coronary intervention. Our findings suggest that leptin serum levels are directly associated with the inflammatory response during an acute myocardial infarction and may have a role in risk stratification in this clinical setting.

Leptin levels are not affected by enalapril treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men

Leptin, an adipocyte-derived hormone, is involved in the regulation of body weight and is associated with obesity-related complications, notably cardiovascular disease (CVD). A putative link between obesity and CVD could be induction of plasminogen activator inhibitor-1 (PAI-1) synthesis by leptin. In this study, we hypothesized that the beneficial effect of the angiotensin-converting enzyme inhibitor (ACE_i) enalapril on PAI-1 levels is mediated by effects on leptin levels. The association between leptin and components of the fibrinolytic system was evaluated in a non-prespecified post hoc analysis of a placebo-controlled randomized, double-blind trial where the effect of the ACE_i enalapril on fibrinolysis was tested. A total of 46 men and 37 women were randomized to treatment with enalapril or placebo after (median 12 months) an uncomplicated myocardial infarction. At baseline, the participants were stable and had no signs of congestive heart failure. Leptin and fibrinolytic variables (mass concentrations of PAI-1, tissue plasminogen activator (tPA) and tPA-PAI complex) were measured at baseline, and after 10 days, 6 months and 12 months. Enalapril treatment did not change leptin levels, which increased significantly during 1 year of follow-up (p = .007). Changes in leptin levels were strongly associated with changes of tPA mass (p = .001), tPA-PAI complex (p = .003) and of PAI-1 (p = .006) in men, but not in women. Leptin levels are not influenced by treatment with an ACE_i. In contrast, leptin associates strongly with changes in fibrinolytic variables notably with a sex difference, which could be of importance for obesity-related CVD.

Serum leptin is associated with first-ever ischemic stroke, lesion size and stroke severity in a Chinese cohort

OBJECTIVE

Leptin may be associated with cardiovascular disease. We tested to determine whether leptin is a marker for first-ever acute ischemic stroke (AIS) in a nested case-referent study.

METHODS

Consecutive patients with first-ever AIS from May 2017 to December 2017 were included. Referents were matched for sex, age and body mass index. Serum leptin levels and routine tests were examined in both groups.

RESULTS

The median serum level of leptin in the stroke patients was 14.3 (interquartile range [IQR], 7.2-21.7) ng/ml, which was significantly higher (P < 0.001) than in the referents (10.7; 5.7-13.6 ng/ml). There was a positive correlation between serum level of leptin and National Institute of Health Stroke Scale score (r[Spearman] = 0.43, P < 0.001). In addition, serum leptin levels paralleled lesion size. Median serum level of leptin in patients with small lesions, medium lesions and large lesions was 7.3 (IQR, 5.3-14.3) ng/ml, 13.9 (IQR, 7.0-21.3) ng/ml, 20.5 (IQR, 12.4-32.7) ng/ml, respectively (analysis of variance: P < 0.001). In the univariate model matching for sex and age, leptin as a continuous variable was associated with AIS, after adjustment for possible confounders (odds ratio [OR] 1.07, 95% confidence interval [CI]: 1.04-1.11; P < 0.001). After adjusting for all other factors, leptin remained an independent stroke predictor with an adjusted OR of 1.03 (95% CI, 1.00-1.10; P = 0.006). Interestingly, the association between AIS and leptin level was more pronounced among men (adjusted OR = 1.05, 95% CI: 1.01-1.12; P < 0.001) when compared with women (adjusted OR = 1.03, 95% CI: 1.10-1.11; P = 0.009).

CONCLUSION

Serum leptin is associated with first-ever AIS, lesion size and stroke severity in a Chinese cohort.

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.

Short-term response of metabolic hormones to coronary artery bypass surgery

PURPOSE

To explore the response pattern of plasma adipokine and ghrelin levels to coronary artery bypass graft (CABG) surgery in patients with (on-pump) and without (off-pump) cardiopulmonary bypass (CPB).

MATERIAL/METHODS

Sixteen consecutive patients (age: 62 ± 10 years, male: 10) with obstructive coronary artery disease (CAD) who underwent elective CABG surgery with CPB and intraoperative GIK infusion were selected for on-pump group and 19 CAD patients (age: 63 ± 10 years, male: 16) were included in the off-pump group. Blood samples were taken before, during and after surgery. Intraoperative samples were withdrawn simultaneously for peripheral vein and sinus coronarius (SC). Plasma adipokine concentrations were measured by ELISA, those of ghrelin by RIA kits.

RESULTS

In response to surgical intervention there was an early, transient fall in plasma levels of adiponectin (p<0.0001) and resistin (p=0.002) followed by an increase to approach their initial values. Plasma ghrelin also increased (p=0.045), this increase, however, was confined to the period of GIK supported CPB. Plasma insulin (p=0.003) and resistin (p=0.009) was significantly higher in the peripheral vein than in SC. The perioperative hormone profile of patients without CPB (off-pump) proved to be comparable to that of on-pump patients in spite of the insulin administration and greater oxidative and inflammatory stress.

CONCLUSIONS

Adipose tissue-derived factors appear to mediate the metabolic and vascular changes that occur in patients with CABG surgery. Epicardial adipose tissue is unlikely to have major contribution to the development of CAD as adipokines are not elevated in SC independent of the mode of intervention.

The association between serum leptin and post stroke depression: results from a cohort study

BACKGROUND

Depression is a frequent mood disorder that affects around a third of stroke patients and has been associated with poorer outcomes. Our aim was to determine whether there was a relationship between inflammatory markers (leptin) and post-stroke depression (PSD).

METHODS

One hundred and ninety-one ischemic stroke patients admitted to the hospital within the first 24 hours after stroke onset were consecutively recruited and followed up for 3 months. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum levels of leptin at admission. Based on the symptoms, diagnoses of depression were made in accordance with DSM-IV criteria for post-stroke depression at 3 month.

RESULTS

Forty-four patients (23.0%) were diagnosed as having major depression at 3 month. Patients with depression showed higher serum leptin levels at 3 month after stroke (32.2 [IQR, 20.8-57.7] v. 9.9 [IQR, 4.6-13.1]ng/ml, respectively; P = 0.000). Serum levels of leptin ≥20 ng/ml were independently associated with PSD [odds ratio (OR) 20.23, 95% confidence interval (CI) 9.11-51.26, P =  0.000], after adjusting for possible confounders.

CONCLUSIONS

Serum leptin levels elevated at admission were found to be associated with PSD and may provide a new proposal for the treatment of PSD.

Pharmacologic prevention of venous thromboembolism in obese patients

Venous thromboembolism, a collective term for pulmonary embolism and deep venous thrombosis accounts for a large amount of mortality and morbidity in hospitalized patients. Obesity has been considered as an important risk factor for the development of venous thromboembolism. Anticoagulation with fixed doses of low molecular weight heparin, anti-factor Xa inhibitors and unfractionated heparin is widely used in hospitals and has shown to be an effective measure in prevention of venous thromboembolism in multiple major randomized, double-blind controlled trials. Appropriate dosing of anticoagulation in obese patients is still controversial, since obese and morbidly obese population of patients is consistently underrepresented or often excluded from most clinical trials, raising a concern for adequacy of standard dosing in this high risk population.

Dysregulated adipokine metabolism in chronic obstructive pulmonary disease

BACKGROUND

Research concerning the involvement of body composition and systemic inflammatory markers in adipokine metabolism in chronic obstructive pulmonary disease (COPD) is still limited. Therefore, we primarily aimed to investigate the adipokine metabolism in relation to these systemic inflammatory biomarkers and to evaluate possible gender-related differences in the adipokine metabolism in patients with COPD.

MATERIALS AND METHODS

One hundred and eighty-six subjects with COPD [mean (SD) FEV(1) %pred: 50 (±16)] and 113 controls, matched for age, gender and body composition were selected from the ECLIPSE cohort. The following serological data were collected: serum levels of leptin, adiponectin and systemic inflammatory biomarkers such as C-reactive protein (CRP), Interleukin-6 (IL-6) and fibrinogen.

RESULTS

Compared with controls, patients with COPD had higher levels of CRP, IL-6, fibrinogen and adiponectin. After stratification for gender, men with COPD had higher CRP, IL6 and fibrinogen levels compared with male controls, while women with COPD had higher levels of CRP and fibrinogen compared with the female controls. Moreover, in both female controls and patients with COPD, leptin correlated with CRP and fibrinogen, while leptin only correlated with CRP in male controls. Adiponectin correlated negatively with CRP, only in patients with COPD. Body mass index and gender were the strongest determinants for both leptin and adiponectin.

CONCLUSIONS

This study shows a gender-dependent dysregulation of adipokine metabolism in patients with COPD compared with BMI-matched controls. Furthermore, results from this study suggest a more prominent role of adiponectin in the systemic response to COPD.

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.

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 and coronary heart disease: prospective study and systematic review

OBJECTIVES

This study sought to better determine the link between leptin and coronary heart disease (CHD).

BACKGROUND

Circulating leptin is considered a risk factor for CHD but larger studies are needed.

METHODS

Leptin levels were measured in 550 men with fatal CHD or nonfatal myocardial infarction and in 1,184 controls nested within a prospective study of 5,661 British men and set in context with a meta-analysis.

RESULTS

Baseline leptin correlated with body mass index (BMI), blood pressure, total cholesterol, triglyceride, and inflammatory markers; correlations persisted after BMI adjustment. The within-person consistency of leptin values over 4 years (correlation coefficient: 0.79; 95% confidence interval [CI]: 0.73 to 0.83) was higher than those of some established cardiovascular risk factors. In a comparison of individuals in the top third with those in the bottom third of baseline leptin, the age- and town-adjusted odds ratio for CHD was 1.25 (95% CI: 0.96 to 1.62), decreasing to 0.98 (95% CI: 0.72 to 1.34) after adjustment for BMI. A systematic review identified 7 prospective reports with heterogeneous findings (I(2) = 60%, 13% to 82%). The combined adjusted risk ratio across all studies was 1.44 (95% CI: 0.95 to 2.16) in a comparison of extreme thirds of leptin levels. The inconsistency between studies was partially explained by sample size, with combined estimates from studies involving >100 CHD cases (1.28, 95% CI: 0.80 to 2.04) being somewhat weaker than those from smaller studies (1.81, 95% CI: 0.76 to 4.31).

CONCLUSIONS

Previous studies appear to have overestimated associations of leptin and CHD risk. Our results suggest a moderate association that is largely dependent on BMI.

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.

A new frame in thromboembolic cardiovascular disease: Adipocytokine

Recent researches have shown that adipocytokines secreted by adipose tissue play an important role in inflammation which is considered to be a crucial step in the pathogenesis of atherosclerosis. Leptin, one of the earlier adipocytokines, is known to play a major role in cardiovascular disease and recent observations suggest that leptin is an independent risk factor for coronary heart disease. Resistin, another recently discovered adipocytokine, has been related to risk factors of atherosclerosis, and in diabetic individuals serum resistin levels correlate well with inflammatory markers and are predictive for the development of cardiovascular disease. Adiponectin, another adipocytokine of interest in recent years, seems to be the most promising one studied to date. In contrast to leptin and resistin, adiponectin seems to be beneficial for health and it is a protective factor and decreased in obesity. However, many other factors derived from adipose tissue have also been discovered, such as interleukin-6, tumor necrosis factor alpha, monocyte chemoattractant protein 1, apelin, visfatin and probably others awaiting discovery in the near future. In this paper, we discussed the role of adipocytokines in the pathogenesis of atherosclerotic cardiovascular disease.

Coagulation and inflammation markers during atypical or typical antipsychotic treatment in schizophrenia patients and drug-free first-degree relatives

BACKGROUND

Clinical studies suggest that the second generation antipsychotics (APs) clozapine and olanzapine and to a lesser extent the typical antipsychotics may be associated with a procoagulant and proinflammatory state that promotes venous thromboembolism. We evaluated here several blood factors associated with coagulation and inflammation in AP-treated schizophrenia patients and their first-degree relatives.

METHODS

Procoagulant factors (fibrinogen and plasminogen activator inhibitor [PAI-1]), the anticoagulant factor antithrombin III [AT-III], and inflammation-related factors (C-reactive protein [CRP] and leptin) were assessed in patients chronically treated with clozapine (n=29), olanzapine (n=29), typical APs (n=30) and first degree relatives of clozapine (n=23) and olanzapine subjects (n=11).

RESULTS

The typical AP group had the highest CRP level (p=0.013) in spite of having the lowest body mass index (BMI). Patients as a single group had higher CRP levels than relatives (p=0.003). The typical AP group also had the highest AT-III levels (p=0.021). Fibrinogen levels did not differ between the groups (p=0.13). Olanzapine patients displayed the highest PAI-1 and leptin levels among the drug-treated subjects, but values were similar to those observed in their relatives, and were significantly correlated with the BMI.

CONCLUSIONS

A homogeneous negative profile of high inflammation and procoagulant factors along with low levels of anticoagulants was not detected in any group. While preliminary, our results suggest that the observed abnormalities were not related to a direct drug effect, but to elevated BMI (high PAI-1 and leptin in olanzapine-treated patients). We speculate that the high CRP in the typical AP group might be related to poor lifestyle habits, but this must we confirmed in future studies.

Leptin, leptin soluble receptor and coronary atherosclerosis

BACKGROUND

The adipose tissue-related hormone leptin plays an important role in the regulation of body weight. The associations of leptin and leptin soluble receptor (sOb-R) with coronary artery disease (CAD) are not clear.

DESIGN

We measured leptin and sOb-R in 543 consecutive patients (379 men, 164 women) referred for coronary angiography for the evaluation of CAD. Coronary artery stenoses with lumen narrowing > or = 50% were considered significant.

RESULTS

Serum leptin correlated significantly with body mass index (r(s) = 0.443), with insulin resistance as assessed by the homeostasis model for the assessment of insulin resistance (r(s) = 0.339), with serum triglycerides (r(s) = 0.181), with systolic as well as diastolic blood pressure (r(s) = 0.170 and r(s) = 0.133, respectively) and, inversely, with sOb-R (r(s) = -0.346; P < 0.01 for all correlations). Coronary angiography revealed significant coronary artery stenoses in 331 (61%) of our patients. Serum leptin was significantly lower in patients with significant coronary artery stenoses than in patients without such lesions (8.5 +/- 7.8 vs. 13.2 +/- 12.2 ng mL(-1); P < 0.001). Multivariate logistic regression analysis proved serum leptin inversely and independently associated with the presence of significant coronary artery stenoses (standardized adjusted odds ratio 0.746, 95% confidence interval 0.566-0.983, P = 0.038). In contrast to serum concentrations of leptin, serum concentrations of sOb-R did not significantly differ between patients with significant stenoses and those without such lesions (22.4 +/- 8.3 vs. 23.1 +/- 12.1 ng mL(-1); P = 0.655).

CONCLUSIONS

Serum leptin but not sOb-R is significantly lower in patients with angiographically determined CAD. Despite its association with cardiovascular risk factors, leptin should not be simply regarded as a promoter of atherosclerosis.

Leptin and coronary heart disease risk: prospective case control study of British women

OBJECTIVE

Prospective studies have shown a positive association between leptin concentrations and coronary heart disease (CHD) in men, but its effect in women is unclear. Our objective was to examine the association of serum leptin levels with CHD in a prospective study of women.

RESEARCH METHODS AND PROCEDURES

We conducted a prospective (4 year) case (N=165) control (N=335) study nested within a cohort of 4286 British women.

RESULTS

With mutual adjustment for each other and age, social class, smoking, and physical activity, leptin was positively associated with BMI, fasting insulin, total cholesterol, low-density lipoprotein-cholesterol, triglycerides, and hypertension and was inversely associated with homeostasis model assessment insulin sensitivity. Leptin was not associated with CHD risk (age-adjusted relative risk for a doubling of leptin: 1.08 [95% confidence interval (CI): 0.91, 1.29]). This changed little with adjustment for childhood and adult social class, smoking, alcohol, and physical activity but attenuated to 1.00 (95% CI: 0.80, 1.26) with further adjustment for other metabolic risk factors (waist-to-hip ratio, low-density lipoprotein-cholesterol, triglycerides, C-reactive protein, fasting insulin, hypertension).

DISCUSSION

We found no strong statistical evidence that leptin is associated with CHD risk in this study population of older British women. Further research is needed to compare associations of leptin with CHD in men and women and to determine whether the effect varies by gender.

The role of hypoxia inducible factor-1 in cell metabolism--a possible target in cancer therapy

In many cancer types, intratumoural hypoxia is linked to increased expression and activity of the transcription factor hypoxia-inducible factor (HIF-1alpha), which is associated with poor patient prognosis. This increased the interest in HIF-1alpha as a cancer drug target. Further, HIF-1alpha has also a central role in the adaptive cellular programme responding to hypoxia in normal tissues. Many of the HIF-1alpha-regulated genes encode enzymes of metabolic pathways. Therefore, studying the link and the feedback mechanisms between metabolism and HIF-1alpha is of major importance to find new and specific therapeutic strategies.

Does maternal nutrition in pregnancy and birth weight influence levels of CHD risk factors in adult life?

The fetal-origins hypothesis suggests that maternal and fetal nutrition can have a profound and sustained impact on the health of the offspring in adult life. Although there is abundant literature reporting on the associations between birth weight and disease risk factors, only a handful of studies have been able to examine the relationship between maternal nutrition in pregnancy with the health of offspring in adult life directly. Between 1942 and 1944, nearly 400 pregnant women were recruited into a dietary study to determine whether the wartime dietary rations were sufficient to prevent nutritional deficiencies. Detailed biochemical and clinical assessments were conducted for each of the women, who were followed-up until after delivery. More than 50 years later, approximately one-quarter of the adult offspring were recruited into a study to explore the possible impact of maternal nutrition in pregnancy on CHD risk factors, including glucose tolerance, blood pressure and components of the lipid profile. Results from the present study provide no evidence to support the hypothesis that birth weight or maternal nutrition in pregnancy are associated with CHD risk factors in adult life.

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.

Increased serum leptin concentrations in patients with chronic stable angina pectoris and ST-elevated myocardial infarction

Leptin is an adipocytokine that is produced mainly by adipose tissue; it is also identified in atherosclerotic lesions in human coronary atherosclerosis. However, the relation of serum leptin concentrations to ischemic heart disease (IHD) is still obscure. The aims of the present study were to investigate serum leptin concentrations in patients with ST-elevated myocardial infarction (STEMI) and with chronic stable angina pectoris (CSAP) and to evaluate the possible correlations of leptin to other atherosclerotic risk factors; including serum high sensitive C-reactive protein (Hs-CRP), serum homocysteine, and fibrinogen concentrations. For this purpose, 35 patients with CSAP, 40 with acute STEMI, and 30 control subjects with normal findings from coronary angiography were taken into the study prospectively. Serum leptin concentrations were significantly higher in patients with CSAP and STEMI compared to the control group (7.74 +/-1.34 vs 6.37 +/-1.85 ng/mL, p=0.021 and 8.22 +/-3.13 vs 6.37 +/-1.85 ng/mL, p=0.023, respectively). In addition, serum homocysteine concentrations were significantly increased in patients with CSAP (15.23 +/-5.96 vs 11.40 +/-2.11 micromol/L, p=0.025) and patients with STEMI (15.90 +/-5.02 vs 11.40 +/-2.11 micromol/L, p=0.012) compared to the control group. Serum fibrinogen concentrations were significantly increased only in the CSAP group as compared to controls (4.15 +/-1.39 vs 3.45 +/-1.19 g/L, p=0.025). No significant correlation was found between leptin levels and selected risk factors. In conclusion, serum leptin concentrations were significantly higher in both the CSAP and STEMI groups. However, owing to the lack of correlation between the leptin levels and selected classical coronary risk factors, it may be considered that leptin can be evaluated as one of the independent risk factors for IHD. Further randomized and controlled studies will be required to determine the pathophysiological meaning of the increased leptin levels and the central role between adipocyte function and atherosclerosis.

Plasma leptin: associations with metabolic, inflammatory and haemostatic risk factors for cardiovascular disease

BACKGROUND AND AIM

Leptin, an adipocyte-derived protein, regulating food intake and metabolism has been implicated in the development of coronary heart disease. We have examined the relationship between leptin and vascular risk factors including insulin resistance, metabolic, inflammatory and haemostatic risk factors.

METHODS AND RESULTS

The study was carried out in 3640 non-diabetic men aged 60-79 years drawn from general practices in 24 British towns and who were not on warfarin. Leptin was strongly positively correlated with waist circumference (r=0.58; p<0.0001). Leptin concentrations decreased significantly with increasing physical activity and were lowered in cigarette smokers and elevated in men with pre-existing coronary heart disease and stroke; alcohol intake showed no association with leptin concentration. After adjustment for waist circumference and these lifestyle factors, increased leptin was independently associated with significant increases in insulin resistance, triglycerides, inflammatory markers (interleukin-6, C-reactive protein, fibrinogen, plasma viscosity), coagulation factor VIII, endothelial markers von Willebrand factor, tissue plasminogen activator, and fibrin D-dimer levels; and a decrease in HDL-cholesterol. No association was seen between leptin and blood pressure, total cholesterol, glucose or white cell count after adjusting for waist circumference. Further adjustment for insulin resistance abolished the relationships between leptin and triglycerides and HDL-cholesterol, weakened the associations with the haemostatic factors although they remained significant, but made minor differences to the associations with inflammatory markers.

CONCLUSION

Plasma leptin is associated with insulin resistance, inflammation and disturbances in haemostasis independent of waist circumference, suggesting possible pathways by which leptin may influence risk of cardiovascular disease.

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.

Impaired fibrinolysis and risk for cardiovascular disease in the metabolic syndrome and type 2 diabetes

Patients with the metabolic syndrome are insulin resistant and manifest a cluster of risk factors for cardiovascular disease. Impaired fibrinolysis and increased concentrations in blood of plasminogen activator inhibitor-1 (PAI-1) are related to insulin resistance and abdominal obesity and may contribute to the increased risk for cardiovascular disease in this group. Weight loss, metformin, and thiazolidinediones ameliorate insulin resistance and decrease concentrations of PAI-1. Thus, they may lower risk in patients with the metabolic syndrome.

Effects of adipocyte-derived cytokines on endothelial functions: implication of vascular disease

Adipose tissue has recently emerged as an active endocrine organ that secretes a variety of metabolically important substances, collectively called adipocytokines or adipokines. In this review we summarize the effects of the adipokines leptin, adiponectin, and resistin on the vasculature and their potential role for pathogenesis of vascular disease. Leptin is associated with arterial wall thickness, decreased vessel distensibility, and elevated C reactive protein (CRP) levels. Leptin possesses procoagulant and antifibrinolytic properties, and it promotes thrombus and atheroma formation, probably through the leptin receptors by promoting vascular inflammation, proliferation, and calcification, and by increasing oxidative stress. Research for development of pharmacologic antagonism for the leptin receptor is currently under way. Adiponectin inhibits the expression of the adhesion molecules ICAM-1, VCAM-1, and P selectin. Therefore, it interferes with monocyte adherence to endothelial cells and their subsequent migration to the subendothelial space, one of the initial events in the development of atherosclerosis. Adiponectin also inhibits the transformation of macrophages to foam cells in vitro and decreases their phagocytic activity. Resistin, discovered in 2001, represents the newest of the adipokines and was named for its ability to promote insulin resistance. Resistin increases the expression of the adhesion molecules VCAM-1 and ICAM-1, up-regulates the monocyte chemoattractant chemokine-1, and promotes endothelial cell activation via ET-1 release. Although many aspects of its function need further clarification, it appears that resistin will add significantly to our knowledge of the pathophysiology of vascular disease and the metabolic syndrome.

Leptin as a new diagnostic tool in chronic heart failure

Leptin, the product of the ob-gene, regulates cellular homeostasis and glycemic control. While initially described as an adipocyte-derived protein with expression and secretion restricted to adipose tissue, recent reports have shown local expression of leptin in several tissues including the skeletal muscle, heart, vessels and brain. Leptin acts through the different isoforms of its receptor which are ubiquitously expressed and can be detected in endothelium, vascular smooth muscle and myocardium. In addition to its metabolic effects, leptin has distinct effects in the cardiovascular system leading to increased production of proinflammatory cytokines and oxidative stress, vascular remodeling and neointima formation as well as cardiomyocyte hypertrophy. Notably, recent clinical studies have linked serum levels of leptin to the occurrence of cardiovascular events such as myocardial infarction and stroke suggesting that leptin promotes pro-atherogenic vascular mechanisms. In contrast, less is known about the role and effects of leptin in the setting of chronic heart failure. We here review the current knowledge on cardiovascular effects of leptin and discuss its potential as a new therapeutic tool in chronic heart failure.

Interactions between fibrinolysis, lipoproteins and leptin related to a first myocardial infarction

BACKGROUND

The summarized importance of haemostatic and metabolic variables (insulin, lipids including lipoprotein (a) [Lp(a)] and leptin) in predicting first myocardial infarction, as well as possible interactions among these variables, have not been reported.

DESIGN

A prospective case-control study nested within the Northern Sweden Health and Disease Cohort.

METHODS

Sixty-two men diagnosed with a first myocardial infarction were sex- and age-matched with 124 controls. Conditional logistic regression was conducted including established risk factors, plasma levels of plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) mass concentration, von Willebrand factor, insulin, proinsulin, specific insulin, apolipoprotein A-I (apo A-I), Lp(a), and leptin. Interaction analysis was also performed for tPA, apo A-I, Lp(a), leptin and proinsulin.

RESULTS

Smoking, low plasma levels of apo A-I and high plasma levels of cholesterol, Lp(a), tPA, PAI-1, proinsulin and leptin were associated with myocardial infarction in univariate conditional logistic regression analysis. High tPA [odds ratio (OR), 21.3; 95% confidence interval (CI), 2.04-222] and Lp(a) (OR, 7.21; 95% CI, 1.31-39.8) and low apo A-I (OR, 0.15; 95% CI, 0.02-0.93) remained significant risk determinants in multivariate analysis with smoking habits, body mass index, hypertension, cholesterol, and diabetes included as covariates. There were non-significant synergic interactions between high Lp(a) and leptin and tPA, respectively, and between high Lp(a) and low apo A-I.

CONCLUSION

Plasma levels of tPA, Lp(a), and apo A-I are independently associated with subsequent development of a first myocardial infarction in men.

Leptin, but not adiponectin, predicts stroke in males

OBJECTIVE

To test whether leptin and adiponectin are risk markers for a first-ever stroke. RESEARCH DESIGN, METHODS AND SUBJECTS: A nested case-referent study identified 276 cases with first-ever stroke (234 cases with ischaemic and 42 with haemorrhagic stroke). Prior to the stroke, they had participated in population-based health surveys in northern Sweden (median time between survey and stroke was 4.9 years). Referents were matched for sex, age, date and type of health survey, and geographical region. Putative risk markers for first-ever stroke, including blood pressure (BP), diabetes, smoking, body mass index (BMI), cholesterol, leptin, and adiponectin, were analysed by conditional logistic regression analysis.

RESULTS

Increased BMI, high cholesterol and fasting glucose levels, diabetes mellitus and hypertension were found in future stroke patients. Whereas leptin levels were higher in male subjects (P = 0.004), adiponectin did not differ between groups. A high leptin level independently predicted stroke in men (OR = 2.46; 95% CI 1.08-5.62) but not in women. Adiponectin levels did not predict stroke. Males with high leptin levels developed stroke faster than males with low leptin levels (P = 0.0009), independently of traditional risk factors.

CONCLUSIONS

Leptin may be an important link to the development of cerebrovascular disease in men, whereas adiponectin does not associate with future stroke.

Leptin, obesity and cardiovascular disease

PURPOSE OF REVIEW

Obesity is a risk factor for cardiovascular diseases. Leptin levels are increased in obesity and leptin exhibits cardiovascular actions that may contribute to increased cardiovascular risk. We review the sympathetic, renal and vascular actions of leptin and their relevance to cardiovascular disease.

RECENT FINDINGS

Leptin possesses cardio-renal actions potentially contributing to obesity-related hypertension including generalized sympathoactivation. However, given that leptin resistance occurs in obesity, it has been difficult to link hyperleptinemia with hypertension. One possibility is that leptin resistance is confined to the metabolic effects of leptin, with preservation of its sympathoexcitatory actions. Other mechanisms may contribute to the pressor effects of leptin. For instance, angiotensin II induces leptin generation. Leptin also potentiates the pressor effect of insulin. Therefore, interactions between angiotensin II and insulin with leptin could have deleterious cardiovascular effects in obesity. Additionally, leptin appears to stimulate vascular inflammation, oxidative stress and hypertophy. These actions may contribute to the pathogenesis of hypertension, atherosclerosis, and left ventricular hypertrophy.

SUMMARY

The potential actions of leptin in the pathophysiology of cardiovascular complications of obesity are diverse, despite evidence of leptin resistance to its metabolic actions. However, most information about cardiovascular actions of leptin derives from in-vitro and animal studies. Future research in humans is widely awaited.

Serum leptin is elevated in Saudi Arabian patients with metabolic syndrome and coronary artery disease

AIMS

To compare plasma leptin in Saudi subjects with Type 2 diabetes and coronary heart disease (CHD) with non-diabetic control subjects and to examine the relationship of plasma leptin to other CHD risk factors.

RESEARCH DESIGN AND METHOD

Serum leptin concentrations were measured in 144 Saudi men. Subjects studied included 59 with Type 2 diabetes mellitus [BMI 27.5 (3.7) kg/m2 mean (sd)], 34 with coronary heart disease [BMI 29.6 (1.8) kg/m2], and 51 non-diabetic controls [BMI 28.0 (3.5) kg/m2]. There was no significant difference in BMI between the groups. Fasting serum leptin, lipids, insulin, apolipoproteins and glucose were measured. BMI, blood pressure; smoking habit and age were also recorded. Insulin resistance was assessed using the HOMA model.

RESULTS

Leptin concentrations were significantly higher in diabetic and CHD patients than in controls (P = 0.024 and 0.016, respectively). Multiple regression analysis showed that body weight (P < 0.0006), serum triglyceride concentration (P = 0.046) and systolic blood pressure (P = 0.013) were all significantly related to the logarithm of the serum leptin concentration (R2 = 0.549) in CHD patients. A subgroup analysis, comparing those patients who had the metabolic syndrome, as defined by WHO, with controls, showed higher serum leptin in those with metabolic syndrome (P = 0.05).

CONCLUSIONS

Serum leptin is increased in Saudi subjects with diabetes mellitus, metabolic syndrome and CHD. Leptin may be a marker of risk of CHD, at least in men, and contribute to the CHD risk profile in subjects with insulin resistance. Further studies are needed to evaluate this relationship prospectively.

Antipsychotic-induced venous thromboembolism: a review of the evidence

Psychiatric disorders themselves and treatment with conventional antipsychotic medications have in a number of early studies been associated with venous thromboembolism. In general, information on the relationship between antipsychotics and this possible adverse effect is in the form of case reports and open cross-sectional studies. However, recently the association between conventional antipsychotics and venous thrombosis has been strengthened as a result of the publication of a large, nested, case-control study. In this study, low-potency antipsychotic drugs were more strongly associated with venous thrombosis than high-potency drugs. In addition, recent epidemiological data support an association between the atypical antipsychotic agent clozapine and venous thromboembolism. The risk for venous thromboembolism seems to be highest during the initial months of treatment with antipsychotics. The biological mechanisms responsible for this possible adverse drug reaction are unknown, but a number of hypotheses have been suggested. The increased risk may be the result of drug-induced sedation, obesity, hyperleptinaemia, antiphospholipid antibodies and increased activity in the coagulation system. The association could also be related to underlying risk factors present in patients with psychosis such as smoking. Despite the limitations of present knowledge, clinicians should be aware of this possible adverse drug reaction and should consider interrupting or changing the antipsychotic regimen in patients in whom this reaction is suspected. More studies are needed in order to further elucidate this adverse effect, particularly to determine the incidence rate, possible predisposing factors and the biological mechanisms involved.

Testosterone and diurnal rhythmicity of leptin, TNF-alpha and TNF-II receptor in insulin-resistant myotonic dystrophy patients

OBJECTIVE

To investigate the leptin and TNF systems in relation to testosterone in insulin resistant myotonic dystrophy (DM1) subjects.

DESIGN AND SUBJECTS

Fasting morning samples and diurnal sampling during 24 h. Forty-two DM1 subjects (20 women and 22 men; age 41.5 (28.5-58.7) y, body mass index (BMI) 23.3 (18.6-29.2) kg/m(2); median and 10th and 90th percentile, respectively). Fifty healthy volunteers (23 women and 27 men; age 42 (27.0-56.9) y, BMI 24.0 (20.7-29.7) kg/m(2)). Nine men with DM1 and nine healthy men participated in diurnal sampling.

MEASUREMENTS

Body composition was measured by bioelectric impedance analysis. Circulating levels of leptin, TNF-alpha, TNFR-II, insulin, testosterone and lipids were measured. The number of CTG triplet repeats was analysed.

RESULTS

Basal as well as median 24 h levels of leptin and TNFR-II were significantly increased in DM1 patients, independent of body fat mass. This was associated with higher insulin and lower testosterone levels in DM1 patients. The genetic defect was related to leptin and TNFR-II levels in DM1 patients.

CONCLUSION

Hyperleptinemia in DM1 is clearly linked to the concomitant hypogonadism. The genetic defect may directly or indirectly contribute to increased leptin levels. Increased exposure of cytokines may contribute to insulin resistance and other hormonal disturbances in DM1.

The association between leptin and proinsulin is lost with central obesity

OBJECTIVE

Hyperproinsulinaemia and hyperleptinaemia are interrelated features of the insulin resistance syndrome that are linked to the prospective risk of cardiovascular diseases. Whether the association between leptin and proinsulin is different between groups displaying different degrees of risk for cardiovascular diseases is not known. We therefore examined this association in men versus women and in pre- versus postmenopausal women from a population-based sample.

DESIGN AND SUBJECTS

Healthy subjects (n = 158; 85 men and 73 pre- and postmenopausal women) from the Northern Sweden Monitoring of Trends and Determinants in Cardiovascular Disease population were studied with a cross-sectional design.

METHODS

Anthropometric measurements (body mass index and waist circumference) and oral glucose tolerance tests were performed. Enzyme-linked immunosorbent assays were used for the analyses of specific insulin and proinsulin, and radioimmunoassay for leptin. Insulin resistance and beta-cell function were calculated according to the homeostasis assessment model. Partial correlation coefficients adjusted for age and measures of adiposity were calculated and multiple linear regression analyses were performed with leptin as dependent variable.

RESULTS

In nonobese men and premenopausal women and in obese postmenopausal women, leptin was significantly associated with proinsulin after stratification for waist circumference. Furthermore, a multivariate analyses taking age and measures of adiposity into account, showed that high fasting proinsulin was a significant predictor of high leptin in these groups. In contrast, this association was lost with increasing central obesity in men and premenopausal women.

CONCLUSIONS

This study shows that both the degree of adiposity and the hormonal milieu influence the association between circulating leptin and proinsulin in a normal population. Therefore, the insulin resistance syndrome seems to be characterized by lost association between leptin and proinsulin, which may be explained by dysfunction in the adipoinsular axis.

Involvement of leptin in the association between percentage of body fat and cardiovascular risk factors

OBJECTIVES

Recent epidemiologic studies have shown that obesity is associated with elevated blood concentrations of prothrombotic-proinflammatory factors and markers of endothelial dysfunction such as fibrinogen, C-reactive protein (CRP), von Willebrand factor (vWF), and homocysteine. We have assessed whether these markers are associated with percentage of body fat (BF), insulin sensitivity as well as with leptin concentrations.

DESIGN AND METHODS

Twenty-five men aged 49.6 +/- 12.7 yr (mean +/- SD) underwent whole-body air displacement plethysmography (Bod-Pod(R)) for estimating BF. Blood analyses for leptin and several other metabolic and cardiovascular markers were carried out.

RESULTS

Obese subjects had higher levels as compared to controls of BF (37.5 +/- 5.1 vs. 26.0 +/- 6.6, p < 0.01), fibrinogen (3.30 +/- 0.43 vs. 2.67 +/- 0.11, p < 0.01), vWF (136.4 +/- 50.4% vs. 81.6 +/- 12.6%, p < 0.05), and leptin (17.6 +/- 8.7 vs. 6.2 +/- 3.3, p < 0.01), lower concentrations of HDL-cholesterol (1.09 +/- 0.20 vs. 1.51 +/- 0.10, p < 0.001) and lower QUICKI (1/[log(Ins(0)) + log(Glu(0))]) (0.31 +/- 0.03 vs. 0.34 +/- 0.02, p < 0.05). No significant changes were observed in CRP (5.7 +/- 3.4 vs. 3.8 +/- 1.6, p = 0.327) and homocysteine (9.4 +/- 4.2 vs. 8.3 +/- 0.9, p = 0.749). A positive correlation was observed between BF and fibrinogen (r = 0.67, p = 0.0003). Plasma leptin concentrations were correlated with fibrinogen (r = 0.71, p = 0.0001) and CRP (r = 0.43, p = 0.044). After adjustment for BF leptin emerged as a significant predictor of fibrinogen (beta = 0.47, p = 0.023; R(2) = 0.59, p < 0.001). QUICKI was positively correlated with HDL-cholesterol (r = 0.59, p = 0.010) and negatively with fibrinogen (r = -0.53, p = 0.025), CRP (r = -0.52, p = 0.028) and vWF (r = -0.56, p = 0.013).

CONCLUSIONS

Increased BF and impaired insulin sensitivity are associated with increased concentrations of cardiovascular risk factors. Leptin seems to be involved in this elevation and emerges as a predictor of circulating fibrinogen concentrations.

Plasma leptin levels and cardiac sympathetic function in patients with obstructive sleep apnoea-hypopnoea syndrome

BACKGROUND

The control of body weight and cardiac sympathetic function in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) are important because both factors have significant effects on the mortality of these patients. It has recently been reported that OSAHS has a significant effect on the secretion of leptin, a hormone involved in the control of body weight and sympathetic nerve activity. In addition to the circadian rhythm of leptin secretion, the effects of one night of treatment with nasal continuous positive airway pressure (nCPAP) and the mechanism of the effects of nCPAP on nocturnal leptin secretion in patients with OSAHS has not yet been elucidated.

METHODS

Blood samples were obtained at 21.00 hours, 00.00 hours, 03.00 hours, and 06.30 hours from 21 subjects with OSAHS (mean apnoea and hypopnoea index 52.4/h), with and without nCPAP treatment. Iodine-123 (I(123))-meta-iodobenzylguanidine (MIBG) imaging was used to evaluate myocardial sympathetic function before nCPAP treatment.

RESULTS

Plasma leptin reached a peak level at 00:00 hours (p<0.01) in patients with OSAHS, both with and without nCPAP treatment. The first night of nCPAP treatment significantly decreased the plasma leptin levels at 03.00 hours (without nCPAP: mean (SE) 21.6 (4.7) ng/ml; with nCPAP: 19.3 (4.1) ng/ml, p<0.02) and at 06.30 hours (without nCPAP: 17.6 (3.8) ng/ml; with nCPAP: 15.2 (3.2) ng/ml, p<0.01). The magnitude of the decrease in leptin levels after nCPAP treatment was significantly correlated with cardiac sympathetic function measured before nCPAP treatment (p<0.03).

CONCLUSIONS

Patients with OSAHS undergo nocturnal increases in leptin levels in spite of interruption of sleep due to apnoea and hypopnoea, a trend seen in normal subjects. Plasma leptin levels in patients with OSAHS decreased significantly after the first night of nCPAP treatment. Enhanced cardiac sympathetic function in these patients may contribute to the leptin levels before nCPAP treatment and vice versa.