Serum lipocalin-2 as an insulin resistance marker in patients with polycystic ovary syndrome

Impact of Smoking and Obesity on the Selected Peptide Hormones and Metabolic Parameters in the Blood of Women with Polycystic Ovary Syndrome-Preliminary Study

We investigated the effects of tobacco smoke exposure and abnormal body weight on selected peptide hormones and their association with metabolic and hormonal disorders in women with polycystic ovary syndrome (PCOS). The study group included 88 women with PCOS and 28 women without the disease. In women with PCOS, chemerin, lipocalin, and apelin concentrations were influenced by overweight and obesity status, with the highest concentrations observed in those with a body mass index (BMI) ≥ 30.0. Exposure to tobacco smoke significantly increased only lipocalin-2 concentration. The disease itself did not affect the concentrations of chemerin, lipocalin, and apelin. Additionally, we found a positive correlation between chemerin concentration and fasting glucose, fasting insulin, and triglycerides levels, while a negative correlation was observed with high-density lipoprotein (HDL-C) concentration. In the smoking subgroup, chemerin concentration was positively correlated with free testosterone concentration and the free androgen index and negatively associated with sex hormone-binding globulin concentration. Our findings indicate that abnormal body weight has a stronger impact than tobacco smoke exposure on metabolic and hormonal disorders in women with PCOS, highlighting the important role of weight control in such individuals. However, smoking appears to be an additional factor that intensifies hormonal disorders associated with adipose tissue.

Overview of the expression patterns and roles of Lipocalin 2 in the reproductive system

The 25 kDa-sized protein Lipocalin 2 (LCN2) was originally isolated from human neutrophil granulocytes more than 30 years ago. LCN2 is an emerging player in innate immune defense, as it reduces bacterial growth due to its ability to sequester iron-containing bacterial siderophores. On the other hand, LCN2 also serves as a transporter for various hydrophobic substances due to its β-barrel shaped structure. Over the years, LCN2 has been detected in many other cell types including epithelial cells, astrocytes, and hepatocytes. Studies have clearly shown that aberrant expression of LCN2 is associated with a variety of disorders and malignancies, including several diseases of the reproductive system. Furthermore, LCN2 was proposed as a non-invasive prognostic and/or diagnostic biomarker in this context. Although several studies have shed light on the role of LCN2 in various disorders of the female and male reproductive systems, including tumorigenesis, a comprehensive understanding of the physiological function of LCN2 in the reproductive tract is still lacking. However, there is evidence that LCN2 is directly related to fertility, as global depletion of Lcn2 in mice has a negative effect on their pregnancy rate. Since LCN2 expression can be regulated by steroid hormones, it is not surprising that its expression fluctuates greatly during remodeling processes in the female reproductive tract, especially in the uterus. Well-founded details about the expression and regulation of LCN2 in a healthy reproductive state and also about possible changes during reproductive aging could contribute to a better understanding of LCN2 as a target in various diseases. Therefore, the present review summarizes current knowledge about LCN2 in the reproductive system, including studies in rodents and humans, and discusses changes in LCN2 expression during pathological events. The limited data suggest that LCN2 is expressed and regulated differently in healthy male and female reproductive organs.

Modified Cangfu Daotan decoction ameliorates polycystic ovary syndrome with insulin resistance via NF-κB/LCN-2 signaling pathway in inflammatory microenvironment

This study explored the possible connection between the insulin resistance-targeting protein adipokine lipocalin-2 (LCN-2) and NF-κB signaling pathway in the inflammatory microenvironment in PCOS-IR model rats to determine the pharmacological mechanism of modified Cangfu Daotan decoction (MCDD) intervention for PCOS-IR. We used a high-fat diet (42 days) combined with letrozole (1 mg/kg/day, 42 days) to establish a PCOS-IR rat model. From the third week after modeling, the rats were given continuous administration of MCDD (high dose with 31.68 g/kg, medium dose with 15.84 g/kg, and low dose with 7.92 g/kg) for 28 days. Serum, ovarian tissue, liver, and adipose tissue were collected after the last gavage. Enzyme-linked immunosorbent assay, hematoxylin-eosin (HE) staining, Masson staining, qRT-PCR, and Western blot experiments were performed to detect various indicators. Our results showed that MCDD could reduce body weight and abdominal fat weight; restore normal estrous cycle and ovarian function; alleviate fatty liver; regulate HOMA-IR and OGTT index; reduce serum inflammatory factor levels, LCN-2 level, and gene expression; and regulate the insulin signal transduction and NF-κB pathways in PCOS-IR rats. Thus, MCDD may play a role in improving ovarian function in PCOS-IR rats by downregulating NF-κB/LCN-2 proteins and upregulating the gene expression of Insr/Irs-1/Glut4 in the insulin signaling pathway in the inflammatory environment.

Association between FGF19, FGF21 and lipocalin-2, and diabetes progression in PCOS

Women with polycystic ovary syndrome (PCOS) have an increased risk of developing type 2 diabetes. FGF19, FGF21 and lipocalin-2 have emerged as important markers of metabolic risk. This study aims to compare the levels of FGF19, FGF21 and lipocalin-2 between subjects with or without PCOS, and to investigate the relationship between proteins and diabetes progression. In this nested case-control cohort study, 128 Chinese PCOS women and 128 controls were recruited and followed-up. All subjects underwent the oral glucose tolerance test for the evaluation of glycaemic status. Baseline serum protein levels were measured using ELISA. Compared with controls, PCOS subjects had higher levels of FGF19 (P < 0.001) and FGF21 (P = 0.022), but had lower lipocalin-2 (P < 0.001). In total, 20.8% of PCOS and 9.2% of controls developed diabetes over a mean duration of 10.4 ± 1.2 and 11.3 ± 0.5 years, respectively. Logistic regression analyses suggested FGF19 was positively associated with diabetes progression in controls, after adjusting for age, follow-up duration, waist and fasting glucose (P = 0.026, odds ratio (OR) (95% CI): 7.4 (1.3-43.6)), and the positive relationship between FGF21 and diabetes progression in controls was attenuated by adjusting for age and follow-up duration (P = 0.183). Lipocalin-2 was positively correlated with diabetes progression in PCOS group (P = 0.026, OR (95% CI)): 2.5 (1.1-5.6)); however, this became attenuated after adjusting for waist and fasting glucose (P = 0.081). In conclusion, there is differential expression of FGF19, FGF21, and lipocalin-2 in PCOS. The serum level of FGF19, and FGF21 is associated with diabetes progression in women without PCOS, while lipocalin-2 was related to diabetes progression in PCOS women.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Lipocalin 2 regulates iron homeostasis, neuroinflammation, and insulin resistance in the brains of patients with dementia: Evidence from the current literature

Dementia accompanied by memory loss is considered one of the most common neurodegenerative diseases worldwide, and its prevalence is gradually increasing. Known risk factors for dementia include genetic background, certain lifestyle and dietary patterns, smoking, iron overload, insulin resistance, and impaired glucose metabolism in the brain. Here, we review recent evidence on the regulatory role of lipocalin 2 (LCN2) in dementia from various perspectives. LCN2 is a neutrophil gelatinase-associated protein that influences diverse cellular processes, including the immune system, iron homeostasis, lipid metabolism, and inflammatory responses. Although its functions within the peripheral system are most widely recognized, recent findings have revealed links between LCN2 and central nervous system diseases, as well as novel roles for LCN2 in neurons and glia. Furthermore, LCN2 may modulate diverse pathological mechanisms involved in dementia. Taken together, LCN2 is a promising therapeutic target with which to address the neuropathology of dementia.

Lipocalin-2 in Diabetic Complications of the Nervous System: Physiology, Pathology, and Beyond

Lipocalin-2 (LCN2) is a 25 kDa secreted protein that belongs to the family of lipocalins, a group of transporters of small hydrophobic molecules such as iron, fatty acids, steroids, and lipopolysaccharide in circulation. LCN2 was previously found to be involved in iron delivery, pointing toward a potential role for LCN2 in immunity. This idea was further validated when LCN2 was found to limit bacterial growth during infections in mice by sequestering iron-laden siderophores. Recently, LCN2 was also identified as a critical regulator of energy metabolism, glucose and lipid homeostasis, and insulin function. Furthermore, studies using Lcn2 knockout mice suggest an important role for LCN2 in several biobehavioral responses, including cognition, emotion, anxiety, and feeding behavior. Owing to its expression and influence on multiple metabolic and neurological functions, there has emerged a great deal of interest in the study of relationships between LCN2 and neurometabolic complications. Thorough investigation has demonstrated that LCN2 is involved in several neurodegenerative diseases, while more recent studies have shown that LCN2 is also instrumental for the progression of diabetic complications like encephalopathy and peripheral neuropathy. Preliminary findings have shown that LCN2 is also a promising drug target and diagnostic marker for the treatment of neuropathic complications from diabetes. In particular, future translational research related to LCN2, such as the development of small-molecule inhibitors or neutralizing antibodies against LCN2, appears essential for exploring its potential as a therapeutic target.

The Potential Role of Chemerin, Lipocalin 2, and Apelin in the Diagnosis and Pathophysiology of Gestational Diabetes Mellitus

The exact role of adipokines in the pathogenesis of gestational diabetes mellitus (GDM) still remains not fully clear, and multiple studies have analyzed their potential contribution to the pathophysiology of this pregnancy complication. This study is aimed at evaluating serum chemerin, lipocalin 2, and apelin concentrations in GDM and healthy pregnant patients, assessing the correlation between these adipokines, and suggesting the potential role of these cytokines in the diagnosis and pathophysiology of GDM. The study comprised 237 pregnant women: 153 with GDM and 84 with physiological pregnancy. Serum concentrations of chemerin, lipocalin 2, and apelin were obtained at 24-29 weeks of gestation. The mean concentrations of chemerin and lipocalin 2 were significantly higher in the GDM group. The concentration of apelin was slightly higher in the GDM group, but not statistically significant. The strong positive correlation between chemerin and lipocalin 2 concentrations was noticed in both groups. Our data suggest that maternal chemerin and lipocalin 2 may play a significant role in the pathophysiology of GDM. We imply that these adipokines could potentially be established as novel biomarkers for the early identification of GDM. However, more studies are needed to analyze the effect of these adipokines on glucose metabolism during early pregnancy.

Metabolic Cytokines at Fasting and During Macronutrient Challenges: Influence of Obesity, Female Androgen Excess and Sex

Scope: Cytokines have pleiotropic functions within the organism and their levels may be influenced by obesity, visceral adiposity and sex hormones. Diet composition may also affect their systemic concentrations during fasting and in the postprandial period. Hence, we studied the influence of sex steroids and obesity on the circulating levels of a panel of metabolic cytokines in the fasting state and after single macronutrient challenges. Methods: On alternate days we submitted 17 women with polycystic ovary syndrome (PCOS) (9 non-obese, 8 obese), 17 non-hyperandrogenic control women (9 non-obese, 8 obese) and 19 control men (10 non-obese, 9 obese) to isocaloric oral glucose, lipid and protein loads. Serum levels of omentin-1, vaspin, lipocalin-2, adipsin, PAI-1, chemerin, FGF-21 and FGF-23 were determined by Luminex multiplex technology. Results: During fasting, obese patients presented higher levels of PAI-1, chemerin and adipsin but decreased FGF-23 and omentin-1 compared with non-obese subjects. Vaspin showed sexual dimorphism with lower levels in men than women with PCOS and female controls. Following macronutrient ingestion, most metabolic cytokines presented a similar physiological response consisting of a decrease in circulating concentrations, which was inversely associated with the fasting levels of these molecules. Protein intake caused the major postprandial decrease whereas glucose did not significantly reduce PAI-1, FGF-23 and vaspin, and even increased FGF-21. Regardless of the macronutrient administered, vaspin levels showed a larger reduction in non-obese individuals while the decrease in PAI-1 was particularly noticeable in the obese subgroup. The postprandial reductions of omentin-1 and FGF-23 after glucose and protein loads were influenced by obesity. No major differences were found between patients with PCOS and male and female controls. Conclusions: Obesity, but not PCOS or sex, markedly influences metabolic cytokine levels at fasting and after macronutrient ingestion. The observed postprandial decrease in their circulating concentrations might represent a physiological compensatory mechanism against food-induced inflammation and oxidative stress. This mechanism is altered by obesity and is differently modulated by macronutrients, suggesting a larger contribution of glucose to stressful postprandial responses.

Investigation of galectin-3, lipocalin 2, retinol binding protein (RBP), small dense low-density lipoprotein (sdLDL) in patients with hirsutism

Introduction

Hirsutism is defined as excessive terminal hair in androgen-dependent areas in women. Adipose tissue is no longer regarded as a storage site for triglycerides or as a source of free fatty acids but is currently emerging as a key constituent of energy metabolism secreting numerous enzymes, cytokines, growth factors, and hormones.

Aim

To evaluate serum levels of galectin-3 (Gal3), lipocalin-2 (LCN2), retinol binding protein (RBP), and small dense low-density lipoprotein (sdLDL) in patients with hirsutism and patients co-presenting with polycystic ovary syndrome (PCOS) and hirsutism.

Material and methods

The study included 90 patients that were divided into three groups: (I) patients with idiopathic hirsutism (IH) (n = 30), (II) PCOS patients with hirsutism (H-PCOS) (n = 30), and (III) the control group (n = 30). Informed consent was obtained from each participant. Idiopathic hirsutism was scored using the modified Ferriman-Gallwey (mFG) scoring system and the diagnosis of PCOS was established based on the modified Rotterdam criteria. Human Gal3, LCN2, RBP, and sdLDL levels were analysed using a commercially available double-antigen sandwich enzyme-linked immunosorbent assay.

Results

No significant difference was found between the three groups with regard to serum Gal3, LCN2, RBP, and sdLDL levels (p > 0.05). Median values were higher in the H-PCOS group than in the other two groups: body weight (median: 76.5 kg) (p < 0.001), waist circumference (median: 82.5 cm) (p = 0.001).

Conclusions

No significant correlation was found between the adipokines that play a role in the aetiology of numerous diseases and some mediators of the lipid metabolism and hirsutism.

Perspectives in Lipocalin-2: Emerging Biomarker for Medical Diagnosis and Prognosis for Alzheimer's Disease

Lipocalin-2 (LCN2), a secreted glycoprotein belonging to the lipocalin superfamily was reported to participate in various biological processes including cell migration, cell survival, inflammatory responses, and insulin sensitivity. LCN2 is expressed in the multiple tissues such as kidney, liver, uterus, and bone marrow. The receptors for LCN2 were additionally found in microglia, astrocytes, epithelial cells, and neurons, but the role of LCN2 in the central nervous system (CNS) has not been fully understood yet. Recently, in vitro, in vivo, and clinical studies reported the association between LCN2 and the risk of Alzheimer's disease (AD). Here, we reviewed the significant evidences showing that LCN2 contributes to the onset and progression of AD. It may suggest that the manipulation of LCN2 in the CNS would be a crucial target for regulation of the pathogenesis and risk of AD.

Lipocalin-2 inhibits autophagy and induces insulin resistance in H9c2 cells

Lipocalin-2 (Lcn2; also known as neutrophil gelatinase associated lipocalin, NGAL) levels are increased in obesity and diabetes and associate with insulin resistance. Correlations exist between Lcn2 levels and various forms or stages of heart failure. Insulin resistance and autophagy both play well-established roles in cardiomyopathy. However, little is known about the impact of Lcn2 on insulin signaling in cardiomyocytes. In this study, we treated H9c2 cells with recombinant Lcn2 for 1 h followed by dose- and time-dependent insulin treatment and found that Lcn2 attenuated insulin signaling assessed via phosphorylation of Akt and p70S6K. We used multiple assays to demonstrate that Lcn2 reduced autophagic flux. First, Lcn2 reduced pULK1 S555, increased pULK1 S757 and reduced LC3-II levels determined by Western blotting. We validated the use of DQ-BSA to assess autolysosomal protein degradation and this together with MagicRed cathepsin B assay indicated that Lcn2 reduced lysosomal degradative activity. Furthermore, we generated H9c2 cells stably expressing tandem fluorescent RFP/GFP-LC3 and this approach verified that Lcn2 decreased autophagic flux. We also created an autophagy-deficient H9c2 cell model by overexpressing a dominant-negative Atg5 mutant and found that reduced autophagy levels also induced insulin resistance. Adding rapamycin after Lcn2 could stimulate autophagy and recover insulin sensitivity. In conclusion, our study indicated that acute Lcn2 treatment caused insulin resistance and use of gain and loss of function approaches elucidated a causative link between autophagy inhibition and regulation of insulin sensitivity by Lcn2.

Lipocalin 2 produces insulin resistance and can be upregulated by glucocorticoids in human adipose tissue

The adipokine lipocalin 2 is linked to obesity and metabolic disorders. However, its role in human adipose tissue glucose and lipid metabolism is not explored. Here we show that the synthetic glucocorticoid dexamethasone dose-dependently increased lipocalin 2 gene expression in subcutaneous and omental adipose tissue from pre-menopausal females, while it had no effect in post-menopausal females or in males. Subcutaneous adipose tissue from both genders treated with recombinant human lipocalin 2 showed a reduction in protein levels of GLUT1 and GLUT4 and in glucose uptake in isolated adipocytes. In subcutaneous adipose tissue, lipocalin 2 increased IL-6 gene expression whereas expression of PPARγ and adiponectin was reduced. Our findings suggest that lipocalin 2 can contribute to insulin resistance in human adipose tissue. In pre-menopausal females, it may partly mediate adverse metabolic effects exerted by glucocorticoid excess.

Matrix metalloproteinases 2 and 9 and MMP9/NGAL complex activity in women with PCOS

It is believed that matrix metalloproteinases (MMPs) play important roles in follicular development and pathogenesis of polycystic ovary syndrome (PCOS). However, conflicting results are available about the alteration of MMP2 and MMP9 concentrations or activities in PCOS. In fact, there is no study entirely investigating both concentration and activity of these MMPs and serum levels of their tissue inhibitors TIMP2 and TIMP1, as well as lipocalin-bound form of MMP9 (MMP9/NGAL). Therefore, the thoroughness of previous studies is questionable. This study was conducted to determine circulatory concentration of MMP2, MMP9, MMP9/NGAL complex, TIMP1 and TIMP2 as well as gelatinase activities of MMP2, MMP9 and MMP9/NGAL complex in women with PCOS and controls. Mean age and BMI as well as serum levels of total cholesterol, triacylglycerol, HDL-C, LDL-C, fasting blood sugar (FBS), insulin, estradiol and sex hormone-binding globulin did not differ between groups, whereas a marked decrease in FSH and significant increases in LH, LH/FSH ratio, testosterone and free androgen index were observed. Women with PCOS and controls showed closed concentrations of MMP2, MMP9, MMP9/NGAL, TIMP1 and TIMP2. Gelatinase activity of MMP9 was found significantly higher in PCOS than in controls (64.53±15.32 vs 44.61±18.95 respectively) while patients and healthy subjects showed similar activities of MMP2 and MMP9/NGAL complex. Additionally, PCOS patients showed a higher MMP9/TIMP1 ratio compared with control women. Direct correlations were also observed between circulatory MMP9 level and the concentration and activity of MMP9/NGAL complex. In conclusion, based on the results of present study, we believe that MMP9 may be involved in the pathogenesis of PCOS.

The changes of neutrophil gelatinase-associated lipocalin in plasma and its expression in adipose tissue in pregnant women with gestational diabetes

AIMS

To investigate plasma levels and the expression of neutrophil gelatinase-associated lipocalin (NGAL) in subcutaneous adipose tissue (SAT) in patients with gestational diabetes mellitus (GDM).

METHODS

The study recruited 260 Chinese women divided into three groups: 96 were healthy pregnant women with pre-pregnancy body mass index (pre-pregnancy BMI) below 25kg/m(2) (GROUP 1), 84 were women with GDM with pre-pregnancy BMI below 25kg/m(2) (GROUP 2) and 80 were women with GDM with pre-pregnancy BMI over 25kg/m(2) (GROUP 3). Laboratory and anthropometric measurements were recorded and NGAL plasma levels were determined by ELISA for subjects in all groups. Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of NGAL and tumor necrosis factor-α (TNF-α) in SAT (30 cases in each group).

RESULTS

Our results demonstrated statistically significant elevation in plasma NGAL concentrations in GROUP 2 and GROUP 3 compared with GROUP 1 (p<0.001 for both group comparisons). Moreover, SAT NGAL mRNA (p<0.001 and p<0.001, respectively) and protein (p<0.001 and p<0.001, respectively) expression levels were higher in GROUP 3 than in both GROUP 1 and GROUP 2. Correlations were noted between the plasma NGAL concentration and various parameters of insulin resistance.

CONCLUSIONS

Plasma NGAL may play a role in the development of insulin resistance in GDM, and the high levels of NGAL expression in SAT in overweight women with GDM suggests that NGAL in SAT is associated with obesity in women with GDM.

Epicardial adipose tissue thickness and NGAL levels in women with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with an increased cardiovascular disease (CVD) risk and early atherosclerosis. Epicardial adipose tissue thickness (EATT) is clinically related to subclinical atherosclerosis. In the present study, considering the major role of neutrophil gelatinase-associated lipocalin (NGAL) which is an acute phase protein rapidly releasing upon inflammation and tissue injury, we aimed to evaluate NGAL levels and EATT in PCOS patients and assess their relationship with cardiometabolic factors.

METHODS

64 patients with PCOS and 50 age- and body mass index-matched healthy controls were included in the study. We evaluated anthropometric, hormonal and metabolic parameters. EATT was measured by echocardiography above the free wall of the right ventricle. Serum NGAL and high-sensitive C- reactive protein (hsCRP) levels were measured by ELISA.

RESULTS

Mean EATT was 0,38 +/-0,16 mm in the PCOS group and 0,34 +/-0,36 mm in the control group (p = 0,144). In the obese PCOS group (n = 44) EAT was thicker compared to the obese control group (n = 41) (p = 0.026). Mean NGAL levels of the patients with PCOS were 101,98 +/-21,53 pg/ml, while mean NGAL levels were 107,40 +/-26,44 pg/ml in the control group (p = 0,228). We found a significant positive correlation between EATT and age, BMI, waist circumference, fasting insulin, HOMA-IR, triglyceride and hsCRP levels in PCOS group.

CONCLUSIONS

Thickness of the epicardial adipose tissue can be used to follow the risk of CVD development in obese PCOS cases. However serum NGAL levels do not differ in patients with PCOS and control group.

Epicardial adipose tissue thickness and NGAL levels in women with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with an increased cardiovascular disease (CVD) risk and early atherosclerosis. Epicardial adipose tissue thickness (EATT) is clinically related to subclinical atherosclerosis. In the present study, considering the major role of neutrophil gelatinase-associated lipocalin (NGAL) which is an acute phase protein rapidly releasing upon inflammation and tissue injury, we aimed to evaluate NGAL levels and EATT in PCOS patients and assess their relationship with cardiometabolic factors.

METHODS

64 patients with PCOS and 50 age- and body mass index-matched healthy controls were included in the study. We evaluated anthropometric, hormonal and metabolic parameters. EATT was measured by echocardiography above the free wall of the right ventricle. Serum NGAL and high-sensitive C- reactive protein (hsCRP) levels were measured by ELISA.

RESULTS

Mean EATT was 0,38 +/-0,16 mm in the PCOS group and 0,34 +/-0,36 mm in the control group (p = 0,144). In the obese PCOS group (n = 44) EAT was thicker compared to the obese control group (n = 41) (p = 0.026). Mean NGAL levels of the patients with PCOS were 101,98 +/-21,53 pg/ml, while mean NGAL levels were 107,40 +/-26,44 pg/ml in the control group (p = 0,228). We found a significant positive correlation between EATT and age, BMI, waist circumference, fasting insulin, HOMA-IR, triglyceride and hsCRP levels in PCOS group.

CONCLUSIONS

Thickness of the epicardial adipose tissue can be used to follow the risk of CVD development in obese PCOS cases. However serum NGAL levels do not differ in patients with PCOS and control group.

Adiposity and insulin resistance in humans: the role of the different tissue and cellular lipid depots

Human adiposity has long been associated with insulin resistance and increased cardiovascular risk, and abdominal adiposity is considered particularly adverse. Intra-abdominal fat is associated with insulin resistance, possibly mediated by greater lipolytic activity, lower adiponectin levels, resistance to leptin, and increased inflammatory cytokines, although the latter contribution is less clear. Liver lipid is also closely associated with, and likely to be an important contributor to, insulin resistance, but it may also be in part the consequence of the lipogenic pathway of insulin action being up-regulated by hyperinsulinemia and unimpaired signaling. Again, intramyocellular triglyceride is associated with muscle insulin resistance, but anomalies include higher intramyocellular triglyceride in insulin-sensitive athletes and women (vs men). Such issues could be explained if the "culprits" were active lipid moieties such as diacylglycerol and ceramide species, dependent more on lipid metabolism and partitioning than triglyceride amount. Subcutaneous fat, especially gluteofemoral, appears metabolically protective, illustrated by insulin resistance and dyslipidemia in patients with lipodystrophy. However, some studies suggest that deep sc abdominal fat may have adverse properties. Pericardial and perivascular fat relate to atheromatous disease, but not clearly to insulin resistance. There has been recent interest in recognizable brown adipose tissue in adult humans and its possible augmentation by a hormone, irisin, from exercising muscle. Brown adipose tissue is metabolically active, oxidizes fatty acids, and generates heat but, because of its small and variable quantities, its metabolic importance in humans under usual living conditions is still unclear. Further understanding of specific roles of different lipid depots may help new approaches to control obesity and its metabolic sequelae.

Sex dimorphism and depot differences in adipose tissue function

Obesity, characterized by excessive adiposity, is a risk factor for many metabolic pathologies, such as type 2 diabetes mellitus (T2DM). Numerous studies have shown that adipose tissue distribution may be a greater predictor of metabolic health. Upper-body fat (visceral and subcutaneous abdominal) is commonly associated with the unfavorable complications of obesity, while lower-body fat (gluteal-femoral) may be protective. Current research investigations are focused on analyzing the metabolic properties of adipose tissue, in order to better understand the mechanisms that regulate fat distribution in both men and women. This review will highlight the adipose tissue depot- and sex-dependent differences in white adipose tissue function, including adipogenesis, adipose tissue developmental patterning, the storage and release of fatty acids, and secretory function. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

Adipokines in reproductive function: a link between obesity and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy associated with infertility and metabolic disorder in women of reproductive age. Dysfunction of adipose tissue has been implicated in the pathophysiology of PCOS. Increasing evidence shows that the dysregulated expression of adipokines, the secreted products of adipose tissue, plays an important role in the pathology of PCOS. Here, we review the role of several identified adipokines that may act as a link between obesity and PCOS. PCOS also reciprocally influences the profile of adipokines. Insight into the underlying mechanisms will help better understand the pathology of PCOS and identify new therapeutic targets of this syndrome.

Study of carbohydrate metabolism indices and adipocytokine profile and their relationship with androgens in polycystic ovary syndrome after menopause

OBJECTIVE

Hyperandrogenism, insulin resistance, and altered adipocytokine levels characterize polycystic ovary syndrome (PCOS) women of reproductive age. Hyperandrogenism persists in postmenopausal PCOS women. In the latter, this study aimed at investigating carbohydrate metabolism, adipocytokines, androgens, and their relationships.

SUBJECTS AND METHODS

Blood sampling from overweight postmenopausal women (25 PCOS and 24 age- and BMI-matched controls) at baseline and during oral glucose tolerance test for measurement of insulin and glucose levels, baseline leptin, adiponectin, visfatin, retinol-binding protein 4, lipocalin-2, androgen, and high-sensitivity C-reactive protein (hs-CRP) levels and for calculation of insulin sensitivity (glucose-to-insulin ratio (G/I), quantitative insulin sensitivity check index, and insulin sensitivity index (ISI)), resistance (homeostasis mathematical model assessment-insulin resistance (HOMA-IR)), secretion (Δ of the area under the curve of insulin (ΔAUCI), first-phase insulin secretion (1st PHIS), and second-phase insulin secretion (2nd PHIS)), and free androgen indices (FAI).

RESULTS

PCOS women had higher insulin secretion indices, hs-CRP, androgen, and FAI levels than controls without differing in baseline glucose, insulin and adipocytokines levels, insulin sensitivity, and resistance indices. In PCOS women, FAI levels correlated positively with baseline insulin, ΔAUCI, HOMA-IR, and ΔAUCG and negatively with G/I; hs-CRP levels correlated positively with ΔAUCI and negatively with ISI. PCOS status, waist circumference, and 17-hydroxyprogesterone (17-OHP) levels were positive predictors for ΔAUCI. In all women, waist circumference was a negative predictor for ISI; 17-OHP and FAI levels were positive predictors respectively for baseline insulin levels and for 1st PHIS and 2nd PHIS.

CONCLUSIONS

Early postmenopausal PCOS women are characterized by hyperinsulinemia but attenuated insulin resistance. PCOS status and waist circumference are predictors of hyperinsulinemia while insulin sensitivity correlates negatively with FAI. The differences reported in adipocytokine levels between PCOS and non-PCOS women in reproductive years seem to disappear after menopause.

Urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels in patients with nonalcoholic fatty liver disease

Background/Aims

Nonalcoholic fatty liver disease (NAFLD), one of the most common forms of chronic liver disease, is closely associated with obesity and insulin resistance (IR). Adipokines secreted by adipose tissue have recently been implicated in initiating and perpetuating the chronic inflammatory state observed in obesity and NAFLD. Recent studies suggest neutrophil gelatinase-associated lipocalin (NGAL) plays a key role in the pathogenesis of IR. The aims of this study were to determine urinary NGAL levels in patients with ultrasonography proven NAFLD and to correlate these levels with the metabolic profile and fibrosis grade in this population.

Methodology

Our cohort consisted of 65 consecutive patients undergoing abdominal ultrasonography for clinical suspicion of NAFLD. Patients were subsequently divided into two groups: no steatosis (n=20) and steatosis (n=45). The stage of fibrosis was measured using a four-point scale. Urinary NGAL was measured by a specific microparticle enzyme immunoassay. The degree of insulin resistance was determined by the homeostatic model assessment (HOMA). Glucose, insulin, lipid profile, and transaminases were also measured.

Results

Urinary NGAL levels correlated with body mass index, HOMA, fasting glucose, and insulin levels in patients with steatosis. Moreover, uNGAL levels were higher in patients with steatosis compared to those with no steatosis (49.8 ng/mL and 22.7 ng/mL, respectively) with a statistically significant difference (p<0.001). A stepwise increase in uNGAL levels from patients without fibrosis (21.7 ng/mL) to patients with cirrhosis (47.4 ng/mL) was noted (p<0.001).

Conclusions

Our study demonstrates that in adult patients with NAFLD, uNGAL levels correlate with BMI, insulin resistance, and lipid profiles, and identifies a novel association between uNGAL levels and hepatocellular injury in these patients.

Small lipid-binding proteins in regulating endothelial and vascular functions: focusing on adipocyte fatty acid binding protein and lipocalin-2

Dysregulated production of adipokines from adipose tissue plays a critical role in the development of obesity-associated cardiovascular abnormalities. A group of adipokines, including adipocyte fatty acid binding protein (A-FABP) and lipocalin-2, possess specific lipid-binding activity and are up-regulated in obese human subjects and animal models. They act as lipid chaperones to promote lipotoxicity in endothelial cells and cause endothelial dysfunction under obese conditions. However, different small lipid-binding proteins modulate the development of vascular complications in distinctive manners, which are partly attributed to their specialized structural features and functionalities. By focusing on A-FABP and lipocalin-2, this review summarizes recent advances demonstrating the causative roles of these newly identified adipose tissue-derived lipid chaperones in obesity-related endothelial dysfunction and cardiovascular complications. The specific lipid-signalling mechanisms mediated by these two proteins are highlighted to support their specialized functions. In summary, A-FABP and lipocalin-2 represent potential therapeutic targets to design drugs for preventing vascular diseases associated with obesity.

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.

Lipocalin-2, glucose metabolism and chronic low-grade systemic inflammation in Chinese people

Background

Lipocalin-2 is a novel adipokine with connection to insulin resistance. In this study, we aimed to investigate the association of serum lipocalin-2 with glucose metabolism and other metabolic phenotype in a large-scale Chinese population.

Methods

We evaluated serum lipocalin-2 in a cross-sectional sample of 2519 Chinese aged from 50 to 82 year in a Shanghai downtown district by ELISA. Glucose, insulin, lipid profile, inflammatory markers, and adipokines were also measured.

Results

Serum lipocalin-2 was significantly higher in subjects with isolated impaired fasting glucose, isolated impaired glucose tolerance, combined impaired fasting glucose/impaired glucose tolerance and newly-diagnosed type 2 diabetes than in those with normal glucose regulation. Lipocalin-2 elevation was clearly associated with a higher risk for impaired glucose regulation (OR 1.30 for each 10 ng/ml increase in serum lipocalin-2, 95% CI 1.23-1.62, p = 0.009) after adjustment of age, gender, smoking, alcohol drinking, family history of diabetes, serum CRP, serum adiponectin, serum CXCL5, HOMA-IR, BMI, and waist/hip ratio. The OR for participants with impaired glucose regulation and type 2 diabetes was 1.31 (95% CI 1.21-1.69, p < 0.001).

Conclusions

Our findings suggest that elevated serum lipocalin-2 is closely and independently associated with impaired glucose regulation and type 2 diabetes.

Weight loss significantly reduces serum lipocalin-2 levels in overweight and obese women with polycystic ovary syndrome

Serum lipocalin-2 levels are elevated in obese patients. We assessed serum lipocalin-2 levels in polycystic ovary syndrome (PCOS) and the effects of weight loss or metformin on these levels. Forty-seven overweight/obese patients with PCOS [body mass index (BMI) >27 kg/m(2)] were instructed to follow a low-calorie diet, to exercise and were given orlistat or sibutramine for 6 months. Twenty-five normal weight patients with PCOS (BMI <25 kg/m(2)) were treated with metformin for 6 months. Twenty-five normal weight and 25 overweight/obese healthy female volunteers comprised the control groups. Serum lipocalin-2 levels did not differ between overweight/obese patients with PCOS and overweight/obese controls (p = 0.258), or between normal weight patients with PCOS and normal weight controls (p = 0.878). Lipocalin-2 levels were higher in overweight/obese patients with PCOS than in normal weight patients with PCOS (p < 0.001). In overweight/obese patients with PCOS, weight loss resulted in a fall in lipocalin-2 levels (p < 0.001). In normal weight patients with PCOS, treatment with metformin did not affect lipocalin-2 levels (p = 0.484). In conclusion, PCOS per se is not associated with elevated lipocalin-2 levels. Weight loss induces a significant reduction in lipocalin-2 levels in overweight/obese patients with PCOS.

The effects of obesity and polycystic ovary syndrome on serum lipocalin-2 levels: a cross-sectional study

BACKGROUND

Lipocalin-2 is a novel adipokine that appears to play a role in the development of insulin resistance. Serum lipocalin-2 levels are elevated in obese patients. Obesity and insulin resistance are cardinal characteristics of the polycystic ovary syndrome (PCOS). However, there are limited data on serum lipocalin-2 levels in patients with PCOS. The aim of the present study was to assess serum lipocalin-2 levels in PCOS.

METHODS

We studied 200 patients with PCOS and 50 healthy female volunteers.

RESULTS

Serum lipocalin-2 levels were slightly higher in women with PCOS compared with controls (65.4 +/- 34.3 vs. 60.3 +/- 26.0 ng/ml, respectively) but this difference did not reach statistical significance. In contrast, lipocalin-2 levels were higher in overweight/obese women with PCOS than in normal weight women with the syndrome (76.2 +/- 37.3 vs. 54.5 +/- 27.2 ng/ml, respectively; p < 0.001). Serum lipocalin-2 levels were also higher in overweight/obese controls compared with normal weight controls (70.1 +/- 24.9 vs. 50.5 +/- 23.7 ng/ml, respectively; p = 0.004). In the total study population (patients with PCOS and controls), lipocalin-2 levels were independently correlated with the body mass index (p < 0.001). In women with PCOS, lipocalin-2 levels were independently correlated with the waist (p < 0.001).

CONCLUSIONS

Obesity is associated with elevated serum lipocalin-2 levels. In contrast, PCOS does not appear to affect lipocalin-2 levels.