Circulating leptin is associated with oxidized LDL in postmenopausal women

Factors that predict weight loss success differ by diet intervention type

Background

Many types of diet intervention can achieve negative energy balance and successful weight loss in persons with obesity. However, within any dietary strategy, there is large inter-individual variation in the weight loss response. The aim of this study is to determine factors that predict weight loss success for diet interventions that vary by macronutrient and caloric composition.

Methods

Participants with BMI 30.0 to 49.9 kg/m2 self-selected one of three diet intervention trials for weight loss: low carbohydrate (LOW CHO), low fat (LOW FAT), or low calorie (LOW KCAL). Multivariable regression models were developed to determine the significance of predictor demographic, body composition, metabolic, clinical, and dietary variables for each diet type.

Results

Weight loss over 12-16 weeks averaging -5.1 ± 4.0 kg from baseline weight, p < 0.001, was not significantly different among diet types. Several different factors were identified that account for the inter-individual variance in weight loss success. Regardless of diet type, the most robust predictor of weight loss success was completion of the intervention, accounting for 20-30% of the variance. Factors predicting diet intervention completion were age, physical activity level, blood leptin level, blood pressure, and the amount of weight loss occurring. Differences by diet type in cardiometabolic risk factor reduction were identified with LOW CHO decreasing glycemia/insulinemia factors, LOW FAT decreasing lipidemia factors, and LOW KCAL decreasing inflammatory factors.

Conclusion

These data provide evidence to inform more precise and personalized approaches to diet intervention for weight loss and cardiometabolic health.

Regulation of cardiovascular health and disease by visceral adipose tissue-derived metabolic hormones

Visceral adipose tissue (VAT) is a metabolic organ known to regulate fat mass, and glucose and nutrient homeostasis. VAT is an active endocrine gland that synthesizes and secretes numerous bioactive mediators called 'adipocytokines/adipokines' into systemic circulation. These adipocytokines act on organs of metabolic importance like the liver and skeletal muscle. Multiple preclinical and in vitro studies showed strong evidence of the roles of adipocytokines in the regulation of metabolic disorders like diabetes, obesity and insulin resistance. Adipocytokines, such as adiponectin and omentin, are anti-inflammatory and have been shown to prevent atherogenesis by increasing nitric oxide (NO) production by the endothelium, suppressing endothelium-derived inflammation and decreasing foam cell formation. By inhibiting differentiation of vascular smooth muscle cells (VSMC) into osteoblasts, adiponectin and omentin prevent vascular calcification. On the other hand, adipocytokines like leptin and resistin induce inflammation and endothelial dysfunction that leads to vasoconstriction. By promoting VSMC migration and proliferation, extracellular matrix degradation and inflammatory polarization of macrophages, leptin and resistin increase the risk of atherosclerotic plaque vulnerability and rupture. Additionally, the plasma concentrations of these adipocytokines alter in ageing, rendering older humans vulnerable to cardiovascular disease. The disturbances in the normal physiological concentrations of these adipocytokines secreted by VAT under pathological conditions impede the normal functions of various organs and affect cardiovascular health. These adipokines could be used for both diagnostic and therapeutic purposes in cardiovascular disease.

Oxidized LDL Modify the Human Adipocyte Phenotype to an Insulin Resistant, Proinflamatory and Proapoptotic Profile

Little information exists in humans on the regulation that oxidized low-density lipoprotein (oxLDL) exerts on adipocyte metabolism, which is associated with obesity and type 2 diabetes. The aim was to analyze the oxLDL effects on adipocytokine secretion and scavenger receptors (SRs) and cell death markers in human visceral adipocytes. Human differentiated adipocytes from visceral adipose tissue from non-obese and morbidly obese subjects were incubated with increasing oxLDL concentrations. mRNA expression of SRs, markers of apoptosis and autophagy, secretion of adipocytokines, and glucose uptake were analyzed. In non-obese and in morbidly obese subjects, oxLDL produced a decrease in insulin-induced glucose uptake, a significant dose-dependent increase in tumor necrosis factor-α (TNF-α), IL-6, and adiponectin secretion, and a decrease in leptin secretion. OxLDL produced a significant increase of Lox-1 and a decrease in Cxcl16 and Cl-p1 expression. The expression of Bnip3 (marker of apoptosis, necrosis and autophagy) was significantly increased and Bcl2 (antiapoptotic marker) was decreased. OxLDL could sensitize adipocytes to a lower insulin-induced glucose uptake, a more proinflammatory phenotype, and could modify the gene expression involved in apoptosis, autophagy, necrosis, and mitophagy. OxLDL can upregulate Lox-1, and this could lead to a possible amplification of proinflammatory and proapoptotic effects of oxLDL.

Oxidized low-density lipoprotein in postmenopausal women

BACKGROUND

Oxidized low-density lipoprotein (oxLDL) leads to atherosclerosis and cardiovascular disease, the most frequent causes of death worldwide. After menopause, lipid and lipoprotein metabolism changes and women are at greater risk of cardiovascular disease compared to fertile women. The aim of this study was to determine the prevalence of serum oxLDL in postmenopausal women and to identify possible associations of clinical and laboratory features with oxLDL in these patients.

METHOD

After clinical examination and completing a clinical questionnaire, an ultrasound examination of both carotid arteries was conducted and blood was drawn from 533 postmenopausal women. oxLDL concentration was determined using proton NMR spectroscopy.

RESULTS

Oxidized LDL was detected in 12.4% (95% confidence interval 9.7-15.5) of postmenopausal women with a median of 0.18 mg/dl (interquartile range 0.10-0.43). Although intima-media thickness did not differ, postmenopausal women with serous oxLDL had more often atherosclerotic plaques compared to women without oxLDL (6/66 vs. 0/467; P < 0.01). Higher concentrations of high-density lipoprotein, impaired glucose intolerance, and DBP were independently associated with the occurrence of oxLDL. If oxLDL was present, higher high-density lipoprotein and glucose intolerance were associated with higher concentrations of oxLDL. In contrast, higher blood urea concentrations were associated with lower concentrations of oxLDL.

CONCLUSION

This study presents the prevalence and concentration of oxLDL in postmenopausal women and demonstrates that oxLDL concentration can be quantified by proton NMR spectroscopy in large patient samples. The data suggest that oxLDL may be a biomarker for incipient atherosclerotic changes in postmenopausal women. In contrary to the association of dyslipoproteinemia and diabetes, higher blood urea concentrations were associated with lower concentrations of oxLDL.

Gene polymorphisms and increased DNA damage in morbidly obese women

Obesity is characterized by increased adipose tissue mass resulting from a chronic imbalance between energy intake and expenditure. Furthermore, there is a clearly defined relationship among fat mass expansion, chronic low-grade systemic inflammation and reactive oxygen species (ROS) generation; leading to ROS-related pathological events. In the past years, genome-wide association studies have generated convincing evidence associating genetic variation at multiple regions of the genome with traits that reflect obesity. Therefore, the present study aimed to evaluate the relationships among the gene polymorphisms ghrelin (GHRL-rs26802), ghrelin receptor (GHSR-rs572169), leptin (LEP-rs7799039), leptin receptor (LEPR-rs1137101) and fat mass and obesity-associated (FTO-rs9939609) and obesity. The relationships among these gene variants and the amount of DNA damage were also investigated. Three hundred Caucasian morbidly obese and 300 eutrophic (controls) women were recruited. In summary, the results demonstrated that the frequencies of the GHRL, GHSR, LEP and LEPR polymorphisms were not different between Brazilian white morbidly obese and eutrophic women. Exceptions were the AA-FTO genotype and allele A, which were significantly more frequent in obese women than in the controls (0.23% vs. 0.10%; 0.46 vs. 0.36, respectively), and the TT-FTO genotype and the T allele, which were less frequent in morbidly obese women (p<0.01). Furthermore, significant differences in the amount of genetic lesions associated with FTO variants were observed only in obese women. In conclusion, this study demonstrated that the analyzed SNPs were not closely associated with morbid obesity, suggesting they are not the major contributors to obesity. Therefore, our data indicated that these gene variants are not good biomarkers for predicting risk susceptibility for obesity, whereas ROS generated by the inflammatory status might be one of the causes of DNA damage in obese women, favoring genetically related diseases as obesity comorbidities.

Regulation of thrombomodulin expression and release in human aortic endothelial cells by cyclic strain

Background and Objectives

Thrombomodulin (TM), an integral membrane glycoprotein expressed on the lumenal surface of vascular endothelial cells, promotes anti-coagulant and anti-inflammatory properties. Release of functional TM from the endothelium surface into plasma has also been reported. Much is still unknown however about how endothelial TM is regulated by physiologic hemodynamic forces (and particularly cyclic strain) intrinsic to endothelial-mediated vascular homeostasis.

Methods

This study employed human aortic endothelial cells (HAECs) to investigate the effects of equibiaxial cyclic strain (7.5%, 60 cycles/min, 24 hrs), and to a lesser extent, laminar shear stress (10 dynes/cm², 24 hrs), on TM expression and release. Time-, dose- and frequency-dependency studies were performed.

Results

Our initial studies demonstrated that cyclic strain strongly downregulated TM expression in a p38- and receptor tyrosine kinase-dependent manner. This was in contrast to the upregulatory effect of shear stress. Moreover, both forces significantly upregulated TM release over a 48 hr period. With continuing focus on the cyclic strain-induced TM release, we noted both dose (0–7.5%) and frequency (0.5–2.0 Hz) dependency, with no attenuation of strain-induced TM release observed following inhibition of MAP kinases (p38, ERK-1/2), receptor tyrosine kinase, or eNOS. The concerted impact of cyclic strain and inflammatory mediators on TM release from HAECs was also investigated. In this respect, both TNFα (100 ng/ml) and ox-LDL (10–50 µg/ml) appeared to potentiate strain-induced TM release. Finally, inhibition of neither MMPs (GM6001) nor rhomboids (3,4-dichloroisocoumarin) had any effect on strain-induced TM release. However, significantly elevated levels (2.1 fold) of TM were observed in isolated microparticle fractions following 7.5% strain for 24 hrs.

Conclusions

A preliminary in vitro investigation into the effects of cyclic strain on TM in HAECs is presented. Physiologic cyclic strain was observed to downregulate TM expression, whilst upregulating in a time-, dose- and frequency-dependent manner the release of TM.

Characterization of immune cells in psoriatic adipose tissue

Background

Adipose tissue normally contains immune cells that regulate adipocyte function and contribute to metabolic disorders including obesity and diabetes mellitus. Psoriasis is associated with increased risk for metabolic disease, which may in part be due to adipose dysfunction, which has not been investigated in psoriasis. There is currently no standardized method for immunophenotyping human adipose tissue. In prior studies, characteristic phenotypic markers of immune cell populations identified in animal models or in other human tissues have been applied in a similar manner to human adipose tissue. Rarely have these populations been verified with confirmatory methodologies or functional studies. Thus, we performed a comprehensive phenotypic and functional analysis of immune cell populations in psoriatic adipose tissue.

Methods

Conventional and imaging flow cytometry were used to define immune cell populations in biopsy specimens of psoriatic adipose tissue (n = 30) including T cells, B cells, NK cells, NKT cells, neutrophils, and macrophages. Relationships between adipose immune cell types and body mass index were determined using Spearman regression analysis, and multivariate linear regression analysis was performed to adjust for cardiometabolic disease risk factors.

Results

These analyses revealed a wide range of cell surface receptors on adipose tissue macrophages, which may serve a dual purpose in immunity and metabolism. Further, both CD16+CD56^Lo and CD16-CD56^Hi NK cells were found to correlate inversely with body mass index. The relationship between the predominant CD16+CD56^Lo NK cell population and body mass index persisted after adjusting for age, sex, diabetes, and tobacco use.

Conclusions

Together, these studies enhance our understanding of adipose immune cell phenotype and function, and demonstrate that examination of adipose tissue may provide greater insight into cardiometabolic pathophysiology in psoriasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0258-2) contains supplementary material, which is available to authorized users.

Perivascular adipose tissue and coronary vascular disease

Coronary perivascular adipose tissue is a naturally occurring adipose tissue depot that normally surrounds the major coronary arteries on the surface of the heart. Although originally thought to promote vascular health and integrity, there is a growing body of evidence to support that coronary perivascular adipose tissue displays a distinct phenotype relative to other adipose depots and is capable of producing local factors with the potential to augment coronary vascular tone, inflammation, and the initiation and progression of coronary artery disease. The purpose of the present review is to outline previous findings about the cardiovascular effects of coronary perivascular adipose tissue and the potential mechanisms by which adipose-derived factors may influence coronary vascular function and the progression of atherogenesis.

Adipokines and the cardiovascular system: mechanisms mediating health and disease

This review focuses on the role of adipokines in the maintenance of a healthy cardiovascular system, and the mechanisms by which these factors mediate the development of cardiovascular disease in obesity. Adipocytes are the major cell type comprising the adipose tissue. These cells secrete numerous factors, termed adipokines, into the blood, including adiponectin, leptin, resistin, chemerin, omentin, vaspin, and visfatin. Adipose tissue is a highly vascularised endocrine organ, and different adipose depots have distinct adipokine secretion profiles, which are altered with obesity. The ability of many adipokines to stimulate angiogenesis is crucial for adipose tissue expansion; however, excessive blood vessel growth is deleterious. As well, some adipokines induce inflammation, which promotes cardiovascular disease progression. We discuss how these 7 aforementioned adipokines act upon the various cardiovascular cell types (endothelial progenitor cells, endothelial cells, vascular smooth muscle cells, pericytes, cardiomyocytes, and cardiac fibroblasts), the direct effects of these actions, and their overall impact on the cardiovascular system. These were chosen, as these adipokines are secreted predominantly from adipocytes and have known effects on cardiovascular cells.

Epicardial perivascular adipose tissue as a therapeutic target in obesity-related coronary artery disease

Adipose tissue is an active endocrine and paracrine organ that may influence the development of atherosclerosis and vascular disease. In the setting of obesity, adipose tissue produces a variety of inflammatory cytokines (or adipokines) that are known to modulate key mechanisms of atherogenesis. In particular, adipose tissue located on the surface of the heart surrounding large coronary arteries (i.e. epicardial perivascular adipose tissue) has been implicated in the pathogenesis of coronary artery disease. The present review outlines our current understanding of the cellular and molecular links between perivascular adipose tissue and atherosclerosis with a focus on potential mechanisms by which epicardial perivascular adipose tissue contributes to obesity-related coronary disease. The pathophysiology of perivascular adipose tissue in obesity and its influence on oxidative stress, inflammation, endothelial dysfunction and vascular reactivity is addressed. In addition, the contribution of specific epicardial perivascular adipose-derived adipokines (e.g. leptin, adiponectin) to the initiation and expansion of coronary disease is also highlighted. Finally, future investigative goals are discussed with an emphasis on indentifying novel therapeutic targets and disease markers within perivascular adipose tissue.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

High plasma leptin levels confer increased risk of atherosclerosis in women with systemic lupus erythematosus, and are associated with inflammatory oxidised lipids

BACKGROUND

Patients with systemic lupus erythematosus (SLE) are at increased risk of atherosclerosis, even after accounting for traditional risk factors. High levels of leptin and low levels of adiponectin are associated with both atherosclerosis and immunomodulatory functions in the general population.

OBJECTIVE

To examine the association between these adipokines and subclinical atherosclerosis in SLE, and also with other known inflammatory biomarkers of atherosclerosis.

METHODS

Carotid ultrasonography was performed in 250 women with SLE and 122 controls. Plasma leptin and adiponectin levels were measured. Lipoprotein a (Lp(a)), oxidised phospholipids on apoB100 (OxPL/apoB100), paraoxonase, apoA-1 and inflammatory high-density lipoprotein (HDL) function were also assessed.

RESULTS

Leptin levels were significantly higher in patients with SLE than in controls (23.7±28.0 vs 13.3±12.9 ng/ml, p<0.001). Leptin was also higher in the 43 patients with SLE with plaque than without plaque (36.4±32.3 vs 20.9±26.4 ng/ml, p=0.002). After multivariate analysis, the only significant factors associated with plaque in SLE were leptin levels in the highest quartile (≥29.5 ng/ml) (OR=2.8, p=0.03), proinflammatory HDL (piHDL) (OR=12.8, p<0.001), age (OR=1.1, p<0.001), tobacco use (OR=7.7, p=0.03) and hypertension (OR=3.0, p=0.01). Adiponectin levels were not significantly associated with plaque in our cohort. A significant correlation between leptin and piHDL function (p<0.001), Lp(a) (p=0.01) and OxPL/apoB100 (p=0.02) was also present.

CONCLUSIONS

High leptin levels greatly increase the risk of subclinical atherosclerosis in SLE, and are also associated with an increase in inflammatory biomarkers of atherosclerosis such as piHDL, Lp(a) and OxPL/apoB100. High leptin levels may help to identify patients with SLE at risk of atherosclerosis.

Systemic lupus erythematosus and cardiovascular disease: prediction and potential for therapeutic intervention

Patients with systemic lupus erythematosus have a significantly increased risk of cardiovascular events due to atherosclerosis. Traditional cardiac risk factors cannot fully explain this increased risk. Recent evidence strongly suggests that atherosclerotic plaque is largely driven by inflammation and an active immunological response, in contrast to the long-held belief that plaque is a passive accumulation of lipids in the arterial wall. Current approaches to the prevention of atherosclerosis in systemic lupus erythematosus involve targeting modifiable cardiac risk factors. Future preventive strategies may include therapies that counteract the immunologic responses that lead to plaque formation.

Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression through reactive oxygen species generation and ERK1/2 activation in 3T3-L1 adipocytes

Plasminogen activator inhibitor-1 (PAI-1) is secreted from adipose tissue and is considered to be a risk factor for both atherosclerosis and insulin resistance. Here we report for the first time that PAI-1 expression is enhanced by oxidized low-density lipoprotein (OxLDL) and its lipid component lysophosphatidylcholine (LPC) in mouse 3T3-L1 adipocytes. In fully differentiated 3T3-L1 cells, OxLDL treatment increased the mRNA expression and protein secretion of PAI-1 in a dose- and time-dependent manner, whereas native LDL had no effect. The addition of an anti-CD36 antibody suppressed OxLDL-stimulated PAI-1 expression by 50%, suggesting that adipose-derived CD36 contributes to roughly half of the PAI-1 expression stimulated by OxLDL. In addition, pharmacological experiments showed that the OxLDL-stimulated enhancement in PAI-1 expression was mediated through the generation of reactive oxygen species (ROS) and phosphorylation of extracellular signal-regulated kinase 1/2. Furthermore, LPC, a major lipid component of OxLDL, was responsible for the enhanced expression of PAI-1 as phospholipase A(2)-treated acetyl LDL, which generates LPC, strongly stimulated PAI-1 expression, whereas acetyl LDL itself had no such activity. These data demonstrate that the uptake of OxLDL and, in particular, its lipid component LPC into adipocytes triggers aberrant ROS-mediated PAI-1 expression, which may be involved in the pathogenesis of metabolic syndrome.

Adipocyte factors, high-sensitive C-reactive protein levels and lipoxidative stress products in overweight postmenopausal women with normal and impaired OGTT

OBJECTIVE

In obese postmenopausal women we assessed leptin and adiponectin, high-sensitive C-reactive protein (hsCRP), serum lipids and lipoxidative stress products: oxidized LDL (oxLDL) and malondialdehyde (MDA), in relation to impaired glucose tolerance (IGT).

METHODS

Thirty-eight overweight/obese postmenopausal women were included in the study. Eighteen with normal glucose metabolism (NGT) and twenty with IGT, as it is diagnosed by OGTT. Serum leptin, adiponectin, hsCRP and MDA were measured at time 0 and 120 min of OGTT while total-cholesterol, LDL, HDL, triglycerides, oxLDL and anti-oxLDL autoantibodies at time 0. Insulin resistance (HOMA)/sensitivity (QUICKI) indexes were estimated.

RESULTS

In subjects with NGT, hsCRP was positively correlated with fasting leptin and HOMA, while in subjects with IGT negatively with QUICKI. In both groups, hsCRP was positively correlated with fasting insulin, body mass index and waist circumference. Fasting adiponectin was positively associated with HDL in both groups and negatively with triglycerides in subjects with NGT as well as with serum glucose levels at time 120 min of OGTT in subjects with IGT. No association was observed between oxLDL and adipokines. A significant positive association was found between oxLDL and HOMA in subjects with IGT. During OGTT there was a significant increase of leptin and MDA levels in both groups.

CONCLUSIONS

A relationship exists between obesity, insulin and sub-clinical inflammation. Leptin and lipid peroxidation are linked to hyperglycaemic state while oxLDL might be considered as a predictor of insulin resistance. Adiponectin could exert its antiatherogenic effect through HDL independently of the presence of IGT.

Circulating oxidized LDL: a biomarker and a pathogenic factor

PURPOSE OF REVIEW

Oxidized LDL (oxLDL) contributes to many atherogenic steps in the vascular wall, but the significance of oxLDL in circulating blood remains unclear. Recent progress in procedures for measuring both human and murine oxLDL has provided growing evidence of the importance of circulating oxLDL.

RECENT FINDINGS

Circulating oxLDL is elevated in patients with advanced atherosclerosis, such as coronary heart disease and ischemic stroke, and also reflects early atherosclerotic changes and metabolic disorders including diabetes and obesity. In-vitro exposure to oxLDL increased mononuclear cell nuclear factor-kappaB activity, suggesting a pathogenic role of circulating oxLDL in exacerbation of oxidative stress. In addition, adenoviral administration of secreted scavenger receptor-A1, which functions as a decoy, suppresses foam cell formation in LDL receptor-deficient mice via a blockade of modified LDL incorporation into macrophages. Furthermore, when lectin-like oxLDL receptor-1 was ectopically expressed in the liver, circulating oxLDL was reduced, resulting in complete prevention of atherosclerotic progression in apolipoprotein E-deficient mice. Thus, circulating oxLDL impacts atherogenic formation.

SUMMARY

The roles of circulating oxLDL in atherosclerotic pathogenesis are now attracting considerable attention. OxLDL removal from circulating blood is a promising therapeutic strategy against atherosclerosis.

Oxidized LDL and the metabolic syndrome

The metabolic syndrome is a common and complex disorder combining obesity, dyslipidemia, hypertension and insulin resistance. It is associated with a high cardiovascular risk that can only partially be explained by its components. There is evidence that low-grade inflammation and high oxidative stress add to this risk. Oxidized LDL, a marker of lipoprotein-associated oxidative stress, is an emerging cardiovascular risk factor. In this review, we demonstrate that the metabolic syndrome exacerbates oxidized LDL in a feedback loop. We introduce molecular mechanisms underlying this loop. Finally, we demonstrate that weight loss and statin treatment lower metabolic syndrome factors associated with a reduction of oxidized LDL. The current data warrant further investigation into the role of lifestyle and therapeutic interventions that inhibit tissue-associated oxidation of LDL in the prevention of the metabolic syndrome.

A novel oxidized low-density lipoprotein marker, serum amyloid A-LDL, is associated with obesity and the metabolic syndrome

BACKGROUND

The putative association between the novel oxidized low-density lipoprotein markers, serum amyloid A-LDL (SAA-LDL) and alpha1-antitrypsin-LDL (AT-LDL), and obesity and the metabolic syndrome (MetS) has not been previously studied. In the present report, we investigated the levels of SAA-LDL and AT-LDL in relation to the components of the MetS. We also assessed the effect of weight reduction therapy on serum SAA-LDL and AT-LDL levels among obese subjects.

METHODS

The study population included 421 obese Japanese outpatients (185 men and 236 women, mean age: 51.1 years) enrolled in the multicenter Japan Obesity and Metabolic Syndrome Study (JOMS). The novel oxidized low-density lipoprotein markers, serum SAA-LDL and AT-LDL, were measured in all participants.

RESULTS

Circulating SAA-LDL levels were independently associated with the presence and the number of components of the MetS. SAA-LDL levels were also significantly and independently correlated with high-sensitivity C-reactive protein. Notably, successful weight reduction resulted in a significant decrease in circulating SAA-LDL concentrations. Levels of AT-LDL were not associated with the MetS.

CONCLUSIONS

We documented, for the first time, that serum SAA-LDL levels correlate positively with the number of components of the MetS and weight reduction. Whether SAA-LDL may be involved in the pathophysiology of MetS and atherosclerosis deserves further investigation.

Atherogenecity of LDL and unfavorable adipokine profile in metabolically obese, normal-weight woman

OBJECTIVE

The relationship of visceral adiposity with adipocytokines and low-density lipoprotein (LDL) particle distribution and oxidation in Asian metabolically obese, normal-weight (MONW) individuals has not been evaluated. We aimed to investigate the association between visceral adiposity and adipocytokines and cardiovascular disease (CVD) risk factors in MONW Korean women with normal glucose tolerance.

METHODS AND PROCEDURES

We examined the metabolic characteristics of 135 non-obese (BMI <25 kg/m(2)) women aged 25-64 years. Twenty-five women (BMI <25 kg/m(2) and visceral fat adiposity (VFA) > or =100 cm(2)) were classified as MONW and 25 women (BMI <25 kg/m(2) and VFA <100 cm(2)), pair-matched for age, weight, height, and menopausal status, as control group. Plasma lipid profiles and adipocytokines were evaluated in these two groups.

RESULTS

MONW subjects had higher systolic (P < 0.05) and diastolic blood pressure (P < 0.005) and higher concentrations of triacylglycerol (TG) (P < 0.005), insulin (P < 0.01), and free fatty acid (FFA) (P < 0.05) than control subjects. There was no significant difference between two groups in LDL-cholesterol (LDL-C) concentrations; however, MONW subjects had smaller LDL particles (P < 0.01) and higher concentrations of oxidized LDL (ox-LDL) (P < 0.05) compared with controls. Moreover, MONW subjects had higher concentrations of tumor necrosis factor-alpha (TNF-alpha) (P < 0.05), interleukin-6 (IL-6) (P < 0.05) and leptin (P < 0.05), and lower plasma adiponectin concentrations (P < 0.05). Higher intake of saturated fat with lower ratio of polyunsaturated fatty acids (PUFAs) to saturated fatty acids (SFA) and lower fiber intake than normal subjects were found in MONW women.

DISCUSSION

We found an unfavorable inflammatory profile and a more atherogenic LDL profile in MONW female subjects even in the absence of a known CVD risk factors. Moreover, MONW consumed more saturated fat and less fiber than the control group.

Serum leptin, oxidized low density lipoprotein and plasma asymmetric dimethylarginine levels and their relationship with dyslipidaemia in adolescent girls with polycystic ovary syndrome

OBJECTIVE

The aim of this study was to investigate serum leptin, oxidized low density lipoprotein (ox-LDL) and asymmetric dimethylarginine (ADMA) levels and their interaction with dyslipidaemia in adolescents with polycystic ovary syndrome (PCOS).

PATIENTS AND DESIGN

The study group consisted of 23 obese (obPCOS) and 21 nonobese girls with PCOS (nPCOS), and 31 lean healthy controls. PCOS was defined by the National Institutes of Health (NIH) criteria as the presence of chronic oligoanovulation and hyperandrogenism. Fasting leptin, ox-LDL, ADMA and detailed lipid-lipoprotein profile were determined. Atherogenic index (AI) was calculated as [Total cholesterol - HDL cholesterol/HDL cholesterol]. Logarithmic transformations were made for ox-LDL.

RESULTS

Total cholesterol, triglycerides, LDL cholesterol, very low density lipoprotein (VLDL) cholesterol, apolipoprotein B, lipoprotein A levels and AI were higher and apolipoprotein AI was lower in obPCOS compared to those in controls (P < 0.05). LDL cholesterol, apolipoprotein B and lipoprotein A levels were higher in nPCOS compared to controls (P < 0.05). ADMA and ox-LDL levels did not differ in the three groups. Leptin was significantly higher in obPCOS compared with that in the other two groups (P < 0.001) and it was correlated with triglycerides (r = 0.62), VLDL cholesterol (r = 0.45), lipoprotein A (r = 0.38) and AI (r = 0.43) in the PCOS group (P < 0.05).

CONCLUSION

Our data demonstrate that ADMA and ox-LDL levels in adolescent PCOS subjects were not different than those in controls. Abnormal lipid profile was shown in obese and nonobese girls with PCOS and leptin was related with these lipid abnormalities in the PCOS subjects.

Biomarkers of obesity and subsequent cardiovascular events

Obesity is a major risk factor for cardiovascular diseases, but the mechanisms for increased cardiovascular risk in obesity are still unclear. Inflammation and increased oxidative stress are two potential mechanisms proposed to play a major role in the morbidity associated with obesity. Studies that investigate these mechanisms rely on biomarkers, but validated biomarkers for obesity-related cardiovascular outcomes are lacking. By finding optimal biomarkers, diagnostic criteria for cardiovascular diseases can be refined in the obese beyond "traditional" risk factors to identify early pathologic processes. The objective of this review is to identify potential early biomarkers resulting from obesity and associated with cardiovascular disease. Studies were initially identified through the search engine PubMed by using the keywords "obesity" and "biomarker." Subsequently, combinations of the keywords "obesity," "biomarker," "cardiovascular risk," "adipose tissue," "adipokine," "adipocytokine," and "oxidative stress" were used. The SOURCE database and Online Mendelian Inheritance in Man (OMIM) were used to obtain more information on the biomarkers. Results of the searches yielded a large number of potential biomarkers that occur in obesity and which either correlate with traditional cardiovascular risk factors or predict subsequent cardiovascular events. Several biomarkers are promising regarding their biologic properties, but they require further validation in humans.

Endothelial dysfunction and arterial abnormalities in childhood obesity

Rates of overweight and obesity in both adults and children have risen sharply during the past 20 years. The reasons for this escalation in obesity are not fully determined, however, sedentary lifestyle and dietary changes in combination with genetic predisposition are probably involved. Clinical cardiovascular disease, including myocardial infarction and stroke, are usually only manifest in the fifth decade of life or beyond. However, the earliest physical signs of atherosclerosis, the underlying disease process that leads to these events, may be present from early childhood. There are now a variety of noninvasive tests used to assess both the structural and functional properties of the vasculature and in vivo changes suggestive of 'early atherosclerosis' have now been characterised. These have allowed not only an increased understanding of the atherosclerotic changes to the vasculature that accompany overweight and obesity in children, but have also allowed serial study of the effects of diet and exercise interventions on early atherosclerosis changes, in childhood obesity.

Do novel risk factors differ between men and women aged 18 to 39 years with a high risk of coronary heart disease?

This study aimed to clarify whether high-risk premenopausal women have less atherogenic levels of markers of endothelial dysfunction, oxidation, thrombosis and inflammation, and adipokines than high-risk men of the same age. Thus, we studied levels of these markers and their determinants in 207 men and women aged 18 to 39 years with dyslipidemia and a family history of premature coronary heart disease. Women had favorable levels of E and P selectins, tumor necrosis factor alpha, tissue plasminogen activator, plasminogen activator inhibitor 1, thrombomodulin, thiobarbituric acid reactive substances, and adiponectin compared with men, but had higher levels of high-sensitivity C-reactive protein and leptin (all P < .05) and no difference in the L-arginine/asymmetric dimethyl arginine (ADMA) ratio. This ratio was higher among nonusers of hormonal contraception than among users (P = .02). In multivariate analyses, levels of intercellular adhesion molecule 1 and E selectin were associated with cigarette smoking and dietary sucrose (both P < .05), whereas the L-arginine/ADMA ratio was paradoxically associated with smoking (P < .05). Of 17 novel risk markers, 11 were associated with body mass index after adjustment for age, sex, smoking, and percentage of dietary energy from sucrose (regression coefficients, 0.14-0.62; all P < .05). In conclusion, the findings underscore the female advantage regarding determinants of novel risk markers in young adults at risk of coronary heart disease, although some endothelial dysfunction markers (cellular adhesion molecules, L-arginine/ADMA ratio) were not more favorable in women compared with men. Lifestyle factors including body mass index, dietary sucrose, smoking, and hormones were associated with levels of the markers independent of sex with body mass index being the most prominent factor.

Plasma Levels of Leptin Are Associated with the Plasma Levels of LDL Conjugated Dienes in Children

BACKGROUND

Plasma leptin has been suggested to be involved in the proatherogenic process by increasing oxidative stress. We investigated the relationship between leptin and plasma conjugated diene formation, a measure of LDL oxidation in vivo in schoolchildren.

METHODS

We measured blood lipid profiles, plasma antioxidant vitamins, leptin and diene conjugation in LDL of 118 Korean children (35 overweight-obese vs. 83 normal weight children).

RESULTS

The overweight-obese children showed significantly higher levels of leptin (p < 0.0001), conjugated dienes (p = 0.02), total cholesterol (p < 0.05), triglyceride (p < 0.005) and LDL cholesterol (p < 0.01) and a significantly lower level of plasma lycopene (p < 0.0001) compared with the normal weight children. When all the subjects were classified into the three groups by tertiles of leptin levels, significant differences in circulating conjugated dienes (p < 0.05), lipid-corrected lycopene (p < 0.05), total cholesterol (p < 0.05), triglyceride (p < 0.05) and LDL cholesterol (p < 0.05) were found among the three groups.

CONCLUSION

Our results showed that leptin was positively associated with the LDL conjugated diene formation, which might be related to the proatherogenic process in schoolchildren.

Plasma Leptin and its Relationship with Lipid Peroxidation and Nitric Oxide in Obese Female Patients with or without Hypertension

BACKGROUND

Recent evidence suggested that leptin-induced oxidative stress in human endothelial cells in vivo and increased oxidative stress in human essential hypertension may further contribute to both the development of atherosclerosis and other cardiovascular diseases. We investigated the association of plasma leptin levels with plasma lipid peroxidation and nitric oxide metabolites (NOx) in obese hypertensive atherosclerosis model.

METHODS

Plasma leptin, lipid peroxidation and NOx levels were determined in age-matched non-obese normotensive female subjects (n = 30), obese normotensive female subjects (n = 45), and obese hypertensive female subjects (n = 50). Plasma leptin levels were determined by immunoradiometric method. Lipid peroxidation was determined as thiobarbituric acid reactive substances (TBARS) using spectrophotometric method. NOx levels were determined using enzymatic method.

RESULTS

We found that plasma leptin and TBARS levels were increased in obesity, and obese hypertensives have significantly higher plasma leptin and TBARS levels than obese normotensives (p <0.001 and p <0.001). Obese hypertensives have significantly lower plasma NOx levels than obese normotensives (p <0.001). In univariate and multivariate regression analysis, plasma leptin levels were significantly correlated with TBARS (p <0.01 and p <0.01) in obese subjects. Plasma TBARS were also inversely correlated with NOx in hypertensive obese subjects (r = -0.412, p <0.01).

CONCLUSIONS

Our results have shown that elevated leptin levels may be associated with increased oxidative stress and free-radical-induced decreased NOx levels. Therefore, hyperleptinemia may be an important contributor to the generation of hypertension in obesity.

Circulating oxidized LDL is associated with parameters of the metabolic syndrome in postmenopausal women

Oxidized low-density lipoproteins (ox-LDL) play a significant role in the development of atherosclerosis.

OBJECTIVE

To investigate the relation between circulating ox-LDL and components of the metabolic syndrome (MS) in a sample of 124 postmenopausal women with varying glucose tolerance status.

METHODS

This cross-sectional study included postmenopausal women not using hormone therapy. Ox-LDL concentrations were measured in plasma by a monoclonal antibody (mAb-4E6) based competition ELISA. LDL peak particle diameter (LDL-PPD) was measured by non-denaturating polyacrylamide gradient gel electrophoresis (PAGGE). Presence of the MS was determined according to the definition of the NCEP-ATPIII.

RESULTS

Circulating ox-LDL concentrations were significantly associated with some factors of the MS such as triglyceride (r=0.48; p<0.0001), high-density lipoprotein cholesterol (r=-0.34; p=0.0001) and fasting plasma glucose concentrations (r=0.21; p=0.02). Ox-LDL concentrations were also associated with LDL cholesterol (r=0.54; p<0.0001), total cholesterol (r=0.48; p<0.0001), LDL apolipoprotein B (r=0.62; p<0.0001) and LDL-PPD (r=-0.18; p<0.05). Moreover, women with the MS had significantly higher ox-LDL concentrations (79.5+/-28.3 U/l) compared to women without the MS (64.2+/-19.9 U/l) (p<0.05).

CONCLUSION

Ox-LDL concentrations are associated with individual components of the MS and are significantly higher in postmenopausal women with MS compared to healthy postmenopausal women.

Role of leptin in blood pressure regulation and arterial hypertension

Leptin is a 16-kDa protein secreted by white adipose tissue that is primarily involved in the regulation of food intake and energy expenditure. Plasma leptin concentration is proportional to the amount of adipose tissue and is markedly increased in obese individuals. Recent studies suggest that leptin is involved in cardiovascular complications of obesity, including arterial hypertension. Acutely administered leptin has no effect on blood pressure, probably because it concomitantly stimulates the sympathetic nervous system and counteracting depressor mechanisms such as natriuresis and nitric oxide (NO)-dependent vasorelaxation. By contrast, chronic hyperleptinemia increases blood pressure because these acute depressor effects are impaired and/or additional sympathetic nervous system-independent pressor effects appear, such as oxidative stress, NO deficiency, enhanced renal Na reabsorption and overproduction of endothelin. Although the cause-effect relationship between leptin and high blood pressure in humans has not been demonstrated directly, many clinical studies have shown elevated plasma leptin in patients with essential hypertension and a significant positive correlation between leptin and blood pressure independent of body adiposity both in normotensive and in hypertensive individuals. In addition, leptin may contribute to end-organ damage in hypertensive individuals such as left ventricular hypertrophy, retinopathy and nephropathy, independent of regulating blood pressure. Here, current knowledge about the role of leptin in the regulation of blood pressure and in the pathogenesis of arterial hypertension is presented.

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.

Adipocyte: a potential target for the treatment of atherosclerosis

Obesity is an independent risk factor for coronary heart disease, whereas the underlying mechanisms have not been fully elucidated. Adipocytes may produce various adipokines with favorable and unfavorable cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to obese associated atherosclerosis. Adipocytes can also function as phagocytes to uptake and degrade oxidized low-density lipoprotein (Ox-LDL), suggesting that adipocytes possibly involve in clearance of Ox-LDL in blood. The dysfunctional adipocytes might be implicated in the atherogenesis. Some cardioprotective drugs mediate their cardiovascular benefits partly through their direct beneficial effects on adipocytes. Therefore, we hypothesized that adipocytes might be potential target for the treatment of atherosclerosis.

Circulating oxidized LDL is associated with increased waist circumference independent of body mass index in men and women

BACKGROUND

Obesity is associated with oxidative stress, and the oxidation of LDL is thought to play a crucial role in the generation of atherosclerotic lesions.

OBJECTIVE

The objective was to describe the association of waist circumference (WC) and body mass index (BMI; in kg/m2) with plasma circulating oxidized LDL (ox-LDL) and C-reactive protein (CRP).

DESIGN

This cross-sectional study included data for circulating ox-LDL and CRP from a subpopulation of 586 men and women enrolled in a population-based survey conducted in 2000 in Girona, Spain. Multivariate analysis was performed to describe the independent association of WC and BMI with ox-LDL and CRP.

RESULTS

Multivariate logistic regression analysis adjusted for lifestyle, educational level, and dietary confounders showed a direct association of WC (quartile distribution) and BMI categories with ox-LDL (P for linear trend = 0.002) and CRP (P for linear trend = 0.004). Subjects in the top quartile of WC and with a BMI > 29.9 were at high risk of elevated circulating concentrations of ox-LDL and CRP. Further adjustment for cardiovascular disease risk factors did not substantially modify these associations. The risk of high ox-LDL concentrations in overweight (BMI = 25.0-29.9) or obese (BMI > or = 30) subjects with a WC < 102 cm (men) or < 88 cm (women) was not significantly different from that in normal-weight subjects with these WCs. In contrast, overweight or obese subjects with higher WCs (WC > or = 102 cm for men and > or = 88 cm for women) were at significantly higher risk of increased ox-LDL.

CONCLUSION

High WC was associated with high concentrations of ox-LDL independently of BMI in the study population.