Leptin and the vasculature in young adults: The African-PREDICT study

Recipient Pericardial Apolipoprotein Levels Might Be an Indicator of Worse Outcomes after Orthotopic Heart Transplantation

BACKGROUND

End-stage heart failure (ESHF) leads to hypoperfusion and edema formation throughout the body and is accompanied by neurohormonal and immunological alterations. Orthotopic heart transplantation (HTX) has been used as a beneficial option for ESHF. Due to the shortage of donor hearts, the ideal matching and timing of donors and recipients has become more important.

PURPOSE

In this study, our aim was to explore the relationship between the clinical outcomes of HTX and the cytokine and apolipoprotein profiles of the recipient pericardial fluid obtained at heart transplantation after opening the pericardial sac.

MATERIALS AND METHODS

The clinical data and the interleukin, adipokine, and lipoprotein levels in the pericardial fluid of twenty HTX recipients were investigated. Outcome variables included primer graft dysfunction (PGD), the need for post-transplantation mechanical cardiac support (MCS), International Society for Heart and Lung Transplantation grade ≥2R rejection, and mortality. Recipient risk scores were also investigated.

RESULTS

Leptin levels were significantly lower in patients with PGD than in those without PGD (median: 6.36 (IQR: 5.55-6.62) versus 7.54 (IQR = 6.71-10.44); p = 0.029). Higher ApoCII levels (median: 14.91 (IQR: 11.55-21.30) versus 10.31 (IQR = 10.02-13.07); p = 0.042) and ApoCIII levels (median: 60.32 (IQR: 43.00-81.66) versus 22.84 (IQR = 15.84-33.39); p = 0.005) were found in patients (n = 5) who died in the first 5 years after HTX. In patients who exhibited rejection (n = 4) in the first month after transplantation, the levels of adiponectin (median: 74.48 (IQR: 35.51-131.70) versus 29.96 (IQR: 19.86-42.28); p = 0.039), ApoCII (median: 20.11 (IQR: 13.06-23.54) versus 10.32 (IQR: 10.02-12.84); p = 0.007), and ApoCIII (median: 70.97 (IQR: 34.72-82.22) versus 26.33 (IQR: 17.18-40.17); p = 0.029) were higher than in the nonrejection group. Moreover, the pericardial thyroxine (T4) levels (median: 3.96 (IQR: 3.49-4.46) versus 4.69 (IQR: 4.23-5.77); p = 0.022) were lower in patients with rejection than in patients who did not develop rejection.

CONCLUSION

Our results indicate that apolipoproteins can facilitate the monitoring of rejection and could be a useful tool in the forecasting of early and late complications.

Recent progress in leptin signaling from a structural perspective and its implications for diseases

As a multi-potency cytokine, leptin not only plays a crucial role in controlling weight and energy homeostasis but also participates in the metabolic balance in the human body. Leptin is a small helical protein with a molecular weight of 16 kDa. It can interact with multiple subtypes of its receptors to initiate intracellular signal transduction and exerts physiological effects. Disturbances in leptin signaling may lead to obesity and a variety of metabolic diseases. Leptin was also found to be a critical factor in many diseases of the elderly. In this review, we focus on recent advances in the structural and molecular mechanisms of leptin signaling through its receptors with the aim of a deeper understanding of leptin-related diseases.

Sex-specific associations between adipokine profiles and carotid-intima media thickness in the Cameron County Hispanic Cohort (CCHC)

BACKGROUND

Adipokines are hormones secreted from adipose tissue and are associated with cardiometabolic diseases (CMD). Functional differences between adipokines (leptin, adiponectin, and resistin) are known, but inconsistently reported associations with CMD and lack of studies in Hispanic populations are research gaps. We investigated the relationship between subclinical atherosclerosis and multiple adipokine measures.

METHODS

Cross-sectional data from the Cameron County Hispanic Cohort (N = 624; mean age = 50; Female = 70.8%) were utilized to assess associations between adipokines [continuous measures of adiponectin, leptin, resistin, leptin-to-adiponectin ratio (LAR), and adiponectin-resistin index (ARI)] and early atherosclerosis [carotid-intima media thickness (cIMT)]. We adjusted for sex, age, body mass index (BMI), smoking status, cytokines, fasting blood glucose levels, blood pressure, lipid levels, and medication usage in the fully adjusted linear regression model. We conducted sexes-combined and sex-stratified analyses to account for sex-specificity and additionally tested whether stratification of participants by their metabolic status (metabolically elevated risk for CMD as defined by having two or more of the following conditions: hypertension, dyslipidemia, insulin resistance, and inflammation vs. not) influenced the relationship between adipokines and cIMT.

RESULTS

In the fully adjusted analyses, adiponectin, leptin, and LAR displayed significant interaction by sex (p < 0.1). Male-specific associations were between cIMT and LAR [β(SE) = 0.060 (0.016), p = 2.52 × 10-4], and female-specific associations were between cIMT and adiponectin [β(SE) = 0.010 (0.005), p = 0.043] and ARI [β(SE) = - 0.011 (0.005), p = 0.036]. When stratified by metabolic health status, the male-specific positive association between LAR and cIMT was more evident among the metabolically healthy group [β(SE) = 0.127 (0.015), p = 4.70 × 10-10] (p for interaction by metabolic health < 0.1). However, the female-specific associations between adiponectin and cIMT and ARI and cIMT were observed only among the metabolically elevated risk group [β(SE) = 0.014 (0.005), p = 0.012 for adiponectin; β(SE) = - 0.015 (0.006), p = 0.013 for ARI; p for interaction by metabolic health < 0.1].

CONCLUSION

Associations between adipokines and cIMT were sex-specific, and metabolic health status influenced the relationships between adipokines and cIMT. These heterogeneities by sex and metabolic health affirm the complex relationships between adipokines and atherosclerosis.

Leptin treatment has vasculo-protective effects in lipodystrophic mice

Lipodystrophy syndromes are characterized by loss of adipose tissue, metabolic complications, and accelerated atherosclerosis. Adipose tissue deficiency results in reduced levels of the adipokine leptin. We investigated the effects of leptin on the functional properties of endothelial cells and atherogenesis in lipodystrophy. Leptin reduced endothelial to mesenchymal transition-induced expression of mesenchymal genes and prevented impairment of endothelial barrier function. Leptin administration in a lipodystrophy and atherosclerosis mouse model reduced plaque protrusion and endothelial cells with mesenchymal gene expression in vascular plaques. The effects were mediated by the growth/differentiation factor 15. The data identify an important role for leptin in controlling endothelial cell function in lipodystrophy syndromes.

Lipodystrophy syndromes (LDs) are characterized by loss of adipose tissue, metabolic complications such as dyslipidemia, insulin resistance, and fatty liver disease, as well as accelerated atherosclerosis. As a result of adipose tissue deficiency, the systemic concentration of the adipokine leptin is reduced. A current promising therapeutic option for patients with LD is treatment with recombinant leptin (metreleptin), resulting in reduced risk of mortality. Here, we investigate the effects of leptin on endothelial to mesenchymal transition (EndMT), which impair the functional properties of endothelial cells and promotes atherogenesis in LD. Leptin treatment reduced inflammation and TGF-β2–induced expression of mesenchymal genes and prevented impairment of endothelial barrier function. Treatment of lipodystrophic- and atherosclerosis-prone animals (Ldlr^−/−; aP2-nSrebp1c-Tg) with leptin reduced macrophage accumulation in atherosclerotic lesions, vascular plaque protrusion, and the number of endothelial cells with mesenchymal gene expression, confirming a reduction in EndMT in LD after leptin treatment. Treatment with leptin inhibited LD-mediated induction of the proatherosclerotic cytokine growth/differentiation factor 15 (GDF15). Inhibition of GDF15 reduced EndMT induction triggered by plasma from patients with LD. Our study reveals that in addition to the effects on adipose tissue function, leptin treatment exerts beneficial effects protecting endothelial function and identity in LD by reducing GDF15.

Leptin in Atherosclerosis: Focus on Macrophages, Endothelial and Smooth Muscle Cells

Increasing adipose tissue mass in obesity directly correlates with elevated circulating leptin levels. Leptin is an adipokine known to play a role in numerous biological processes including regulation of energy homeostasis, inflammation, vascular function and angiogenesis. While physiological concentrations of leptin may exhibit multiple beneficial effects, chronically elevated pathophysiological levels or hyperleptinemia, characteristic of obesity and diabetes, is a major risk factor for development of atherosclerosis. Hyperleptinemia results in a state of selective leptin resistance such that while beneficial metabolic effects of leptin are dampened, deleterious vascular effects of leptin are conserved attributing to vascular dysfunction. Leptin exerts potent proatherogenic effects on multiple vascular cell types including macrophages, endothelial cells and smooth muscle cells; these effects are mediated via an interaction of leptin with the long form of leptin receptor, abundantly expressed in atherosclerotic plaques. This review provides a summary of recent in vivo and in vitro studies that highlight a role of leptin in the pathogenesis of atherosclerotic complications associated with obesity and diabetes.

Adipokines and Subclinical Cardiovascular Disease in Post-Menopausal Women: Study of Women's Health Across the Nation

Background The menopausal transition is characterized by increased cardiovascular risk, weight gain, and increased adiposity for many women. The adipose-derived secretory proteins adiponectin and leptin are associated with insulin resistance, metabolic syndrome, and cardiovascular disease but their role in subclinical atherosclerotic disease is unclear. This cross-sectional study evaluated the associations of adiponectin and leptin with carotid artery intima-media thickness, adventitial diameter, presence of carotid plaques, and brachial-ankle pulse wave velocity (baPWV) in women aged 54 to 65 years. Methods and Results Participants were 1399 women from SWAN (Study of Women's Health Across the Nation), a community-based study of women transitioning through menopause. Carotid ultrasound and baPWV measures were obtained at SWAN follow-up visits 12 or 13, when 97% of participants were post-menopausal. Adipokines were assayed from serum specimens obtained concurrently at these visits. Linear and logistic regression models were used to evaluate adiponectin or leptin, both log-transformed attributable to skewness, in relationship to carotid artery intima-media thickness, adventitial diameter, baPWV, and presence of carotid plaque. Covariates included age, race, study site, smoking, alcohol use, obesity, cardiovascular disease risk factors, and menopausal status. Lower levels of adiponectin were related to greater carotid artery intima-media thickness, wider adventitial diameter, and faster baPWV; associations were attenuated after adjusting for cardiovascular disease risk factors. Higher levels of leptin were associated with greater carotid artery intima-media thickness and wider adventitial diameter in minimally and fully adjusted models, and contrary to expectation, with slower baPWV, particularly among women with diabetes mellitus or obesity. Conclusions Adiponectin and leptin are 2 important inflammatory pathways that may contribute to adverse subclinical cardiovascular disease risk profiles in women at midlife.

Adiponectin, Leptin and Cardiovascular Disorders

The landmark discoveries of leptin and adiponectin firmly established adipose tissue as a sophisticated and highly active endocrine organ, opening a new era of investigating adipose-mediated tissue crosstalk. Both obesity-associated hyperleptinemia and hypoadiponectinemia are important biomarkers to predict cardiovascular outcomes, suggesting a crucial role for adiponectin and leptin in obesity-associated cardiovascular disorders. Normal physiological levels of adiponectin and leptin are indeed essential to maintain proper cardiovascular function. Insufficient adiponectin and leptin signaling results in cardiovascular dysfunction. However, a paradox of high levels of both leptin and adiponectin is emerging in the pathogenesis of cardiovascular disorders. Here, we (1) summarize the recent progress in the field of adiponectin and leptin and its association with cardiovascular disorders, (2) further discuss the underlying mechanisms for this new paradox of leptin and adiponectin action, and (3) explore the possible application of partial leptin reduction, in addition to increasing the adiponectin/leptin ratio as a means to prevent or reverse cardiovascular disorders.

Serum leptin is associated with increased pulse pressure and the development of arterial stiffening in adult men: results of an eight-year follow-up study

High leptin levels are associated with an unfavorable cardiometabolic risk profile. A number of studies found a positive association between leptin and vascular damage, but to date, no observational study has evaluated a potential predictive role of leptin for arterial stiffening. Therefore, the aim of this study was to estimate the role of leptin in the incidence of arterial stiffening (pulse pressure >60 mmHg) and changes in pulse pressure in an 8-year follow-up of a sample of adult men (The Olivetti Heart Study). The analysis included 460 men without baseline arterial stiffening and antihypertensive treatment at baseline and at follow-up (age: 50.0 years, BMI: 26.5 kg/m²). At the end of the follow-up period, the incidence of arterial stiffening was 8%. Baseline leptin was significantly greater in the group that developed arterial stiffening and was significantly correlated with pulse pressure changes over time (p < 0.05). According to the median plasma leptin distribution of the whole population, the sample was stratified into two groups: one with leptin levels above the median and the other with leptin levels below the median. Those who had baseline leptin levels above the median had a greater risk of developing arterial stiffening (odds ratio: 2.5, p < 0.05) and a greater increase in pulse pressure over time (beta: 2.1, p < 0.05), also after adjustment for confounders. The results of this prospective study indicate a predictive role of circulating leptin levels for vascular damage, independent of body weight and blood pressure.

Association of Visceral Adiposity Index, Lipid Profile, and Serum Leptin with Glucose Intolerance Risks in Iraqi Obese Patients: A Cross-sectional Study

Aims:

The aim of this study was to evaluate the possibility of using visceral adiposity index (VAI), serum leptin, and lipid profile as indicators of impaired glucose tolerance in Iraqi obese patients.

Subjects and Methods:

A cross-sectional study was performed in Iraqi obese patients of both sexes. Body mass index (BMI), waist circumference, hip circumference, triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), VAI, waist-to-hip ratio (WHR), serum leptin, and 2-h glucose tolerance test (2-h GT) were determined and compared with those of healthy non-obese control group. A correlation analysis was performed to determine the strength of association between the studied markers. Data were adjusted to determine gender differences in this regard.

Statistical Analysis:

Kolmogorov–Smirnov, Shapiro–Wilk analyses, Mann–Whitney U test, and unpaired t test were used for the two-group comparisons once applicable. Pearson’s and Spearman’s correlation analyses were used to measure the relationship levels between the studied variables.

Results:

A total of 144 obese patients were included; the mean age was 37.11 ± 8.2 years and 92 (63.9%) were females. Compared with non-obese subjects, the participants had significantly higher levels of BMI, WC, WHR, VAI, TG, leptin, and 2-h GTObese male subjects had significantly higher values of body weight, WC, HC, VAI, and TG compared with obese females. Elevated 2-h GT was significantly associated with VAI (r = 0.291, P = 0.0004), TG (r = 0.319, P = 0.0001), and LDL-C/HDL-C ratio (r = 0.435, P < 0.0001) in the obese patients only.

Conclusions:

The results provide evidence that VAI, TG, and LDL-C/HDL-C ratio can be suggested as potential markers for the risk assessment of impaired glucose tolerance in Iraqi obese patients.

Von Willebrand factor, its cleaving protease (ADAMTS13), and inflammation in young adults: The African-PREDICT study

BACKGROUND

The role of inflammation in the early development of vascular dysfunction remains complex. Interleukin-6 (IL-6) and C-reactive protein (CRP) can cause an acute imbalance in the von Willebrand factor (vWF)-ADAMTS13 interaction, indicating a possible link between markers of haemostasis and low-grade inflammation. To better understand these inter-relationships in the early phases of disease development, we investigated whether vWF and ADAMTS13 associate with the pro-inflammatory markers, IL-6 and CRP in healthy young adults. We considered the role of blood types, sex and race on these relationships.

METHODS

In healthy black and white men and women (n = 1113; 24 ± 5 years; no previous diagnosis or medication use for chronic diseases) we analysed von Willebrand factor antigen (vWF_ag), ADAMTS13, IL-6 and CRP, and grouped blood types as non-O (A, B and AB) and O. Covariates included socioeconomic status, age, estimated glomerular filtration rate, 24-hour systolic blood pressure, waist circumference, glucose, total cholesterol, platelet count, γ-glutamyl transferase and total energy expenditure.

RESULTS

In the total group, vWF_ag was highest in the third tertile of both IL-6 and CRP (p ≤ 0.014), while ADAMTS13 was lowest in the third compared to the first IL-6 tertile (p = 0.006). In multivariate regression, vWF_ag associated positively with IL-6 (Adj R² = 0.169; β = 0.123; p = 0.001) and CRP (Adj R² = 0.163; β=0.094; p = 0.019) in the total group, in the O blood group (all p ≤ 0.051) and white men (all p ≤ 0.035). ADAMTS13 associated negatively with IL-6 (Adj R² = 0.053; β = -0.154; p = 0.015) and CRP (Adj R² = 0.055; β = -0.177; p = 0.009), only in the O blood group.

CONCLUSIONS

Markers of haemostasis associated independently with low-grade inflammation in the O type blood group and white men. An interplay between the haemostatic and inflammatory systems may already exist in young healthy adults and is dependent on blood groups, sex and race. This extends our understanding on the role of inflammation in the early development of vascular dysfunction prior to cardiovascular compromise.

Arterial Stiffness and Endothelial Function in Young Obese Patients - Vascular Resistance Matters

AIM

Motivated by the paradoxical and differing results of the early atherosclerosis related indices - Cardio-Ankle Vascular Index (CAVI) reflecting arterial stiffness and Reactive Hyperemia Index (RHI) evaluating endothelium dependent flow-induced vasodilation - in obesity, we aimed to assess CAVI and RHI in obese adolescents and young adults in the context of differences in systemic vascular resistance (SVR).

METHODS

We examined 29 obese (14f, 15.4 [12.3-18.5] y; BMI: 33.2±4.4 kg.m-2) and 29 non-obese gender and age matched adolescents and young adults (BMI: 21.02±2.3 kg.m-2). CAVI and RHI were measured using VaSera VS-1500 (Fukuda Denshi, Japan) and Endo-PAT 2000 (Itamar Medical, Israel), respectively. Hemodynamic measures were recorded using volume-clamp plethysmography (Finometer Pro, FMS, Netherlands) and impedance cardiography (CardioScreen 2000, Medis GmbH, Germany). SVR and sympathetic activity related indices - Velocity Index (VI) and Heather Index (HI), and LFSAP (spectral power in low frequency band of systolic blood pressure oscillations) were determined.

RESULTS

In obese group, CAVI (4.59±0.88 vs. 5.18±0.63, p=0.002) and its refined version CAVI0 (6.46±1.39 vs.7.33±0.99, p=0.002) were significantly lower. No significant difference in RHI was found. SVR and sympathetic activity indices were all significantly lower in the obese group than in the non-obese group. RHI correlated positively with SVR (r=0.390, p=0.044) in obese subjects.

CONCLUSION

Our results indicate that both indices used for the detection of early atherosclerotic changes are influenced by vascular tone. Vascular resistance could influence CAVI and RHI results impairing their interpretation.