Plasma levels of leptin, omentin, collagenous repeat-containing sequence of 26-kDa protein (CORS-26) and adiponectin before and after oral glucose uptake in slim adults

The relationship between adipose tissue RAAS activity and the risk factors of prediabetes: a systematic review and meta-analysis

METHODS

This systematic review was developed in compliance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-2020) standards. This was accomplished by searching clinical MeSH categories in MEDLINE with full texts, EMBASE, Web of Science, PubMed, Cochrane Library, Academic Search Complete, ICTRP and ClinicalTrial.gov. Reviewers examined all the findings and selected the studies that satisfied the inclusion criteria. The Downs and Black Checklist was used to assess for bias, followed by a Review Manager v5. A Forrest plot was used for the meta-analysis and sensitivity analysis. The protocol for this review was registered with PROSPERO CRD42022320252.

RESULTS

The clinical studies (n = 2) comprised 1065 patients with prediabetes and 1103 normal controls. The RAAS measurements were completed in the adipose tissue. The RAAS components, renin and aldosterone were higher in the prediabetic (PD) compared to the control [mean difference (MD) = 0.16, 95% CI 0.16 (-0.13, 0.45), p = 0.25]. Furthermore, the PD group demonstrated higher triglycerides mean difference [MD = 7.84, 95% CI 7.84 (-9.84, 25.51), p = 0.38] and increased BMI [MD = 0.13, 95% CI 0.13 (-0.74, 0.99), p = 0.77] compared to the control. The overall quality of the studies was fair with a median score and range of 17 (16-18).

CONCLUSION

The current study highlights the relationship between increased BMI, RAAS and insulin resistance which is a predictor of prediabetes. The renin is slightly higher in the prediabetes group without any statistical significance, aldosterone is rather negatively associated with prediabetes which may be attributed to the use of anti-hypertensive treatment.

CTRP3 and serum triglycerides in children aged 7-10 years

INTRODUCTION

The prevalence of obesity-related disorders has been steadily increasing over the past couple of decades. Diseases that were once only detected in adults are now prevalent in children, such as hyperlipidemia. The adipose tissue-derived hormonal factor C1q TNF Related Protein 3 (CTRP3) has been linked to triglyceride regulation especially in animal models. However, the relationship between circulating CTRP3 levels and obesity-related disorders in human subjects is controversial. CTRP3 can circulate in different oligomeric complexes: trimeric (<100 kDa), middle molecular weight (100-300 kDa), and high molecular weight (HMW) oligomeric complexes (>300 kDa). Previous work has identified that it is not the total amount of CTRP3 present in the serum, but the specific circulating oligomeric complexes that appear to be indicative of the relationship between CTRP3 and serum lipids levels. However, this work has not been examined in children. Therefore, the purpose of this study was to compare the levels of different oligomeric complexes of CTRP3 and circulating lipid levels among young children (aged 7-10 years).

METHODS

Morphometric data and serum samples were collected and analyzed from a cross-sectional population of 62 children of self-identified Hispanic origin from a community health center, between 2015 and 2016. Serum analysis included adiponectin, insulin, leptin, ghrelin, glucagon, C-reactive peptide, triglyceride, cholesterol, IL-6, TNF, and CTRP3. Correlation analyses were conducted to explore the relationships between CTRP3 and other biomarkers.

RESULTS

Total CTRP3 concentrations were significantly positively correlated with total cholesterol and HDL cholesterol. Whereas, HMW CTRP3 was not significantly associated with any variable measured. Conversely, the middle molecular weight (MMW) CTRP3 was negatively correlated with triglycerides levels, and very low-density lipoprotein (VLDL), insulin, and body mass index (BMI). The negative correlations between MMW CTRP3 and triglycerides and VLDLs were particularly strong (r2 = -0.826 and -0.827, respectively).

CONCLUSION

Overall, these data indicate that the circulating oligomeric state of CTRP3 and not just total CTRP3 level is important for understanding the association between CTRP3 and metabolic diseases. Further, this work indicates that MMW CTRP3 plays an important role in triglyceride and VLDL regulation which requires further study.

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

Serum CTRP3 Levels In Obese Children: A Potential Protective Adipokine Of Obesity, Insulin Sensitivity And Pancreatic β Cell Function

PURPOSE

CTRP3 is a novel peptide that has recently emerged as an important regulatory adipokine of obesity and related metabolic disease. Little is known about its role in children. The current study aimed to investigate the potential role of CTRP3 in obese children and explore its relationships with insulin sensitivity, pancreatic β cell function, and obesity-related markers.

PATIENTS AND METHODS

We studied the levels of serum CTRP3 in 48 obese and 36 normal weight pre-puberty children. The levels of blood pressure, lipids, glucose, and insulin were measured, and the values of HOMA-IR, HOMA-β and insulinogenic index were calculated. The correlations of these measurements with CTRP3 levels were analyzed.

RESULTS

In this study, we found that CTRP3 serum levels significantly decreased in obese children compared to controls, and insulin resistant obese subjects have lower CTRP3 levels in contrast with the non-insulin resistant obese subjects. Moreover, serum CTRP3 concentrations significantly decreased, while glucose and insulin concentrations significantly increased after a 3 hrs oral glucose tolerance test in obese children. Furthermore, Serum CTRP3 levels correlated negatively and significantly with BMI, triglycerides, systolic blood pressure, fasting insulin, glucose, HOMA-IR, HOMA-β and insulinogenic index in obese children.

CONCLUSION

In summary, serum CTRP3 levels significantly decreased in obese children, and negatively correlated with insulin resistance and pancreatic β cell function indicators. Therefore, CTRP3 may play a protective role in the glucose homeostasis and tightly related to β cell function as well as obesity-related markers in obese children.

C1q/TNF-Related Protein 3 (CTRP3) Function and Regulation

As the largest endocrine organ, adipose tissue secretes many bioactive molecules that circulate in blood, collectively termed adipokines. Efforts to identify such metabolic regulators have led to the discovery of a family of secreted proteins, designated as C1q tumor necrosis factor (TNF)-related proteins (CTRPs). The CTRP proteins, adiponectin, TNF-alpha, as well as other proteins with the distinct C1q domain are collectively grouped together as the C1q/TNF superfamily. Reflecting profound biological potency, the initial characterization of these adipose tissue-derived CTRP factors finds wide-ranging effects upon metabolism, inflammation, and survival-signaling in multiple tissue types. CTRP3 (also known as CORS26, cartducin, or cartonectin) is a unique member of this adipokine family. In this review we provide a comprehensive overview of the research concerning the expression, regulation, and physiological function of CTRP3. © 2017 American Physiological Society. Compr Physiol 7:863-878, 2017.

Central obesity, type 2 diabetes and insulin: exploring a pathway full of thorns

The prevalence of type 2 diabetes (T2D) is rapidly increasing. This is strongly related to the contemporary lifestyle changes that have resulted in increased rates of overweight individuals and obesity. Central (intra-abdominal) obesity is observed in the majority of patients with T2D. It is associated with insulin resistance, mainly at the level of skeletal muscle, adipose tissue and liver. The discovery of macrophage infiltration in the abdominal adipose tissue and the unbalanced production of adipocyte cytokines (adipokines) was an essential step towards novel research perspectives for a better understanding of the molecular mechanisms governing the development of insulin resistance. Furthermore, in an obese state, the increased cellular uptake of non-esterified fatty acids is exacerbated without any subsequent β-oxidation. This in turn contributes to the accumulation of intermediate lipid metabolites that cause defects in the insulin signaling pathway. This paper examines the possible cellular mechanisms that connect central obesity with defects in the insulin pathway. It discusses the discrepancies observed from studies organized in cell cultures, animal models and humans. Finally, it emphasizes the need for therapeutic strategies in order to achieve weight reduction in overweight and obese patients with T2D.

Serum C1q/TNF-related protein-3 (CTRP3) levels are decreased in obesity and hypertension and are negatively correlated with parameters of insulin resistance

BACKGROUND

Insulin resistance (IR) correlates closely with cardiovascular disease. C1q/TNF-related protein-3 (CTRP3) is a novel adipokine that modulates insulin activity in various diseases. This study investigated the relationship between CTRP3 and IR as well as systemic inflammation in newly diagnosed obese and hypertensive patients (NCT02226471).

METHODS

Serum CTRP3 levels, anthropometric, inflammatory and metabolic parameters were measured in 180 obesity and essential hypertensive patients and in 66 normal weight, normotensive subjects.

RESULTS

The serum CTRP3 levels in the obesity group were lower than those in the NW group; these levels were also lower in hypertensive subjects than in normotensive subjects. After adjusting for gender, systolic blood pressure (SBP) and diastolic blood pressure (DBP), a modestly linear relationship was observed between CTRP3 and waist circumference (WC) (r = -0.168, p = 0.009), waist-to-hip ratio (WHR) (r = -0.183, p = 0.004), homeostasis model assessment of IR (HOMA-IR) (r = -0.264, p = 0.000), triglycerides (TG) (r = -0.136, p = 0.034), fasting blood glucose (FBG) (r = -0.155, p = 0.016), fasting insulin (FINS) (r = -0.248, p = 0.000) and homeostasis model assessment of β-cell insulin secretion (HOMA-β) (r = -0.128, p = 0.047). Multiple stepwise regression analysis revealed that gender, DBP and HOMA-IR were independently associated with serum CTRP3 levels.

CONCLUSION

CTRP3 was an independent factor affecting blood pressure and IR, and may play an important role in the pathogenesis of obesity and hypertension.

Diabetic cardiomyopathy: mechanisms and new treatment strategies targeting antioxidant signaling pathways

Cardiovascular disease is the primary cause of morbidity and mortality among the diabetic population. Both experimental and clinical evidence suggest that diabetic subjects are predisposed to a distinct cardiomyopathy, independent of concomitant macro- and microvascular disorders. 'Diabetic cardiomyopathy' is characterized by early impairments in diastolic function, accompanied by the development of cardiomyocyte hypertrophy, myocardial fibrosis and cardiomyocyte apoptosis. The pathophysiology underlying diabetes-induced cardiac damage is complex and multifactorial, with elevated oxidative stress as a key contributor. We now review the current evidence of molecular disturbances present in the diabetic heart, and their role in the development of diabetes-induced impairments in myocardial function and structure. Our focus incorporates both the contribution of increased reactive oxygen species production and reduced antioxidant defenses to diabetic cardiomyopathy, together with modulation of protein signaling pathways and the emerging role of protein O-GlcNAcylation and miRNA dysregulation in the progression of diabetic heart disease. Lastly, we discuss both conventional and novel therapeutic approaches for the treatment of left ventricular dysfunction in diabetic patients, from inhibition of the renin-angiotensin-aldosterone-system, through recent evidence favoring supplementation of endogenous antioxidants for the treatment of diabetic cardiomyopathy. Novel therapeutic strategies, such as gene therapy targeting the phosphoinositide 3-kinase PI3K(p110α) signaling pathway, and miRNA dysregulation, are also reviewed. Targeting redox stress and protective protein signaling pathways may represent a future strategy for combating the ever-increasing incidence of heart failure in the diabetic population.

Serum Omentin 1 Level Is Associated With Coronary Artery Disease and Its Severity in Postmenopausal Women

We evaluated whether serum omentin levels are associated with coronary artery disease (CAD) and its severity among postmenopausal women. We enrolled 193 consecutive postmenopausal women who had undergone coronary angiography for suspected stable CAD. The study population was divided into 2 groups based on the results of coronary angiography (CAD group, n = 110 and control group, n = 83). Omentin 1 levels were measured and disease severity was assessed using the SYNTAX score (SS) in the CAD group. Those patients with angiographic CAD had significantly decreased omentin 1 levels, compared to those without CAD (247.5 + 127.4 vs 506 + 246 ng/mL, P < .001). After adjusting for cardiovascular risk factors, a decreased omentin 1 level was found to be an independent predictor of both angiographic CAD and a high SS. Our data indicate that a decreased omentin 1 level is associated with CAD and its severity among postmenopausal women.

CTRP family: linking immunity to metabolism

It is well known that infectious and inflammatory diseases such as sepsis and severe inflammatory response syndrome are accompanied by metabolic alterations such as insulin resistance. Conversely, metabolic diseases such as visceral obesity and type 2 diabetes are characterized by high levels of proinflammatory cytokines. Metabolism and immunity are linked by proteins of dual function. Adiponectin, a member of the C1q/TNF-related protein (CTRP) family, has attracted much interest because of its anti-inflammatory and insulin-sensitizing effects. To date, 15 additional CTRP family members have been identified that might also play a role in metabolism and immunity. This review focuses on the biochemistry and pleiotropic physiological functions of CTRPs as new molecular mediators connecting inflammatory and metabolic diseases.

C1q/TNF-related protein-3 (CTRP-3) is secreted by visceral adipose tissue and exerts antiinflammatory and antifibrotic effects in primary human colonic fibroblasts

BACKGROUND

The adipokine CTRP-3 (C1q/TNF-related protein-3) belongs to the C1q/TNF-related protein family which antagonizes the effects of lipopolysaccharide (LPS). The aim was to investigate the antiinflammatory and antifibrotic role of CTRP-3 in Crohn's disease (CD).

METHODS

Mesenteric adipose tissue (MAT) of patients with CD or colonic cancer (CC) was resected. Human primary colonic lamina propria fibroblasts (CLPF) were isolated from controls and CD patients. Concentrations of chemokines and cytokines in the supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Expression of connective tissue growth factor (CTGF), collagen I, and collagen III was analyzed by real-time polymerase chain reaction (PCR). Recombinant CTRP-3 expressed in insect cells was used for stimulation experiments.

RESULTS

CTRP-3 is synthesized and secreted by MAT resected from patients with CD, ulcerative colitis (UC), CC, and sigma diverticulitis as well as by murine and human mature adipocytes. CTRP-3 had no effect on the basal secretion of MCSF, MIF, or RANTES in MAT of CD and control patients. LPS-stimulation (10 ng/mL) significantly increased IL-8 release in CLPF of CD patients and, to a lesser extent, in cells of controls and of fibrotic CD tissue. CTRP-3 significantly and dose-dependently reduced LPS-induced IL-8 secretion in CLPF within 8 hours after LPS exposure, whereas LPS-induced IL-6 and TNF release was not affected. CTRP-3 inhibited TGF-β production and the expression of CTGF and collagen I in CLPF, whereas collagen III expression remained unchanged.

CONCLUSIONS

CTRP-3 exerts potent antiinflammatory and antifibrotic effects in CLPF by antagonizing the LPS pathway and by targeting the TGF-β-CTGF-collagen I pathway.

Serum omentin-1 and chemerin levels are interrelated in patients with Type 2 diabetes mellitus with or without ischaemic heart disease

AIMS

Omentin-1 and chemerin have been identified as interesting novel adipokines that may modulate insulin action. Also, they have been suggested to be linked to obesity-induced insulin resistance. The aim of this study was to analyse the relationship between these adipokines and interleukin-6, insulin resistance and anthropometric and metabolic variables in patients with Type 2 diabetes mellitus and in patients with Type 2 diabetes who have ischaemic heart disease.

METHODS

Seventy-five individuals with Type 2 diabetes and 15 healthy control subjects were enrolled in this study. Insulin levels, interleukin-6, omentin-1 and chemerin were measured by ELISA.

RESULTS

Serum omentin-1 levels were found to be significantly decreased in patients with Type 2 diabetes (19.7 ± 1 ng/ml) and in patients with Type 2 diabetes with ischaemic heart disease (18.5 ± 1.6 ng/ml) compared with healthy control subjects (27.4 ± 2.6 ng/ml) at P < 0.01. Moreover, serum chemerin levels were found to be significantly increased in patients with Type 2 diabetes (347 ± 14 ng/ml) and in patients with Type 2 diabetes with ischaemic heart disease (341 ± 16.5 ng/ml) compared with healthy control subjects (281 ± 13 ng/ml) at P < 0.01. Interestingly, omentin-1 and chemerin levels were found to be significantly correlated negatively with each other as well as being individually correlated with some selected anthropometric, biochemical and clinical variables. In conclusion, both omentin-1 and chemerin might play as a pivotal role in obesity and its associated disorders as Type 2 diabetes; however, their role in cardiovascular diseases needs to be fully elucidated.

Circulating omentin as a novel biomarker of endothelial dysfunction

Omentin is a novel soluble lectin expressed mainly in the stromal-vascular cells from visceral adipose tissue with vasodilator effect in isolated blood vessels. To gain insight in the relationship between obesity and cardiovascular risk factors, we aimed to explore the interaction among circulating omentin, metabolic parameters, and endothelial function. Circulating omentin (enzyme-linked immunosorbent assay) was studied in 248 white men (148 with normal glucose tolerance (NGT) and 100 with impaired glucose tolerance (IGT)). Insulin sensitivity was measured using the frequently sampled intravenous glucose tolerance test. Vascular reactivity was measured by high-resolution ultrasound of the brachial artery. Circulating omentin concentration was significantly increased in lean compared with overweight and obese subjects (53.7 ± 16.9 vs. 45.2 ± 16.8 and vs. 40.1 ± 15.5 ng/ml, P < 0.0001). Circulating omentin concentration correlated with age, BMI, waist-to-hip ratio (WHR), percentage of fat mass, systolic and diastolic blood pressure, endothelium-dependent and independent vasodilation (EDV and EIV), C-reactive protein, and interleukin-6 (IL-6). In IGT subjects, circulating omentin concentration also correlated with insulin sensitivity, although this association did not remain significant after controlling for BMI. In a multiple linear regression analysis, circulating omentin concentration (P = 0.01), systolic blood pressure (P = 0.04), and BMI (P = 0.04) contributed independently to EDV after controlling for age and C-reactive protein in IGT subjects. In NGT subjects, only circulating omentin concentration (P = 0.01) was significantly associated with EDV. In conclusion, circulating omentin concentration could be a useful marker of endothelial function.

Adiponectin profiles are affected by chronic and acute changes in carbohydrate intake in healthy cats

Adiponectin is a key adipokine that regulates carbohydrate and lipid metabolism. It circulates in stable low (LMW) and high molecular weight (HMW) forms. The aims of this study were to characterize baseline adiponectin profiles (total, LMW and HMW multimers) in healthy cats and to assess the effects of varying dietary carbohydrate content on adiponectin profiles. Cats were maintained on a diet with moderate carbohydrate content (37% metabolisable energy [ME]) for 4 weeks and then randomly allocated to either a low carbohydrate (19% ME) or high carbohydrate (52% ME) diet for 4 weeks. Fasting and postprandial plasma adiponectin profiles were measured by ELISA and sucrose gradient/Western blot. After consuming the moderate carbohydrate diet for 4 weeks, fasting total, HMW and LMW plasma adiponectin concentrations were 5.0±0.6, 2.5±0.5 and 2.6±0.2 μg/mL, respectively. After changing to the low carbohydrate diet, fasting total adiponectin was unchanged but HMW adiponectin increased and LMW adiponectin decreased. No significant postprandial changes were observed. Cats consuming the high carbohydrate diet had increased fasting total and LMW adiponectin with no change in HMW adiponectin. In the postprandial state total adiponectin was reduced and there was a trend towards a decrease in HMW (p=0.086) but not LMW multimers. These data indicate that feline adiponectin multimer profiles are similar to those reported in other species and demonstrate that changes in plasma adiponectin occur in response to chronic and acute carbohydrate intake and these reflect differential changes in adiponectin multimers.

New adipokines vaspin and omentin. Circulating levels and gene expression in adipose tissue from morbidly obese women

BACKGROUND

Vaspin and omentin are recently described molecules that belong to the adipokine family and seem to be related to metabolic risk factors. The objectives of this study were twofold: to evaluate vaspin and omentin circulating levels and mRNA expression in subcutaneous and visceral adipose tissues in non-diabetic morbidly obese women; and to assess the relationship of vaspin and omentin with anthropometric and metabolic parameters, and other adipo/cytokines.

DESIGN

We analysed vaspin and omentin circulating levels in 71 women of European descent (40 morbidly obese [BMI≥40 kg/m2] and 31 lean [BMI≤25]). We assessed vaspin and omentin gene expression in paired samples of visceral and subcutaneous abdominal adipose tissue from 46 women: 40 morbidly obese and 6 lean. We determined serum vaspin and plasma omentin levels with an Enzyme-Linked Immunosorbent Assay and adipose tissue mRNA expression by real time RT-PCR.

RESULTS

Serum vaspin levels in the morbidly obese were not significantly different from those in controls. They correlated inversely with levels of lipocalin 2 and interleukin 6. Vaspin mRNA expression was significantly higher in the morbidly obese, in both subcutaneous and visceral adipose tissue.Plasma omentin levels were significantly lower in the morbidly obese and they correlated inversely with glucidic metabolism parameters. Omentin circulating levels, then, correlated inversely with the metabolic syndrome (MS). Omentin expression in visceral adipose tissue was significantly lower in morbidly obese women than in controls.

CONCLUSIONS

The present study indicates that vaspin may have a compensatory role in the underlying inflammation of obesity. Decreased omentin circulating levels have a close association with MS in morbidly obese women.

C1q/TNF-related protein-3 represents a novel and endogenous lipopolysaccharide antagonist of the adipose tissue

Proteins secreted by adipocytes (adipokines) play an important role in the pathophysiology of type 2 diabetes mellitus and the associated chronic and low-grade state of inflammation. It was the aim to characterize the antiinflammatory potential of the new adipocytokine, C1q/TNF-related protein-3 (CTRP-3), which shows structural homologies to the pleiotropic adipocytokine adiponectin. mRNA and protein expression of CTRP-3 was analyzed by RT-PCR and Western blot. Recombinant CTRP-3 and small interfering RNA-based strategies were used to investigate the effect of CTRP-3 on toll-like receptor (TLR) ligand, lipopolysaccharide (LPS)-, and lauric acid-induced chemokine release of monocytes and adipocytes. Together with complex ELISA-based techniques, a designed TLR4/myeloid differentiation protein-2 fusion molecule shown to bind LPS was used to prove the ability of CTRP-3 to act as endogenous LPS antagonist. CTRP-3 is synthesized in monocytes and adipocytes. The recombinant protein dose-dependently inhibits the release of chemokines in monocytes and adipocytes that were induced by lauric acid, LPS, and other TLR ligands in vitro and ex vivo. CTRP-3 inhibits monocyte chemoattractant protein-1 release in adipocytes, whereas small interfering RNA-mediated knockdown of CTRP-3 up-regulates monocyte chemoattractant protein-1 release, reduces lipid droplet size, and decreases intracellular triglyceride concentration in adipocytes, causing a dedifferentiation into a more proinflammatory and immature phenotype. By using a designed TLR4/MD-2 fusion molecule, it is shown by different techniques that CTRP-3 specifically and effectively inhibits the binding of LPS to its receptor, TLR4/MD-2. CTRP-3 inhibits three basic and common proinflammatory pathways involved in obesity and type 2 diabetes mellitus (adipo-inflammation) by acting as an endogenous LPS antagonist of the adipose tissue.

Effect of atorvastatin and fenofibric acid on adipokine release from visceral and subcutaneous adipose tissue of patients with mixed dyslipidemia and normolipidemic subjects

Because of methodological limitations and conflicting results of studies conducted thus far, the possible involvement of human adipose tissue in pleiotropic effects of statins and fibrates requires better understanding. Samples of visceral and subcutaneous adipose tissue obtained from 23 mixed dyslipidemic patients and 23 normolipidemic subjects were treated in vitro for 48 h with atorvastatin, fenofibric acid or both these agents. Visceral and subcutaneous fat of mixed dyslipidemic patients released more leptin, resistin, interleukin-6, tumor necrosis factor alpha (TNFalpha and plasminogen activator inhibitor-1 (PAI-1), and less adiponectin than respective adipose tissue of patients without lipid abnormalities. In both groups of patients, visceral and subcutaneous tissue varied in the amount of secreted adipokines. In dyslipidemic patients both drugs administered alone affected adipose tissue adiponectin and resistin secretion. Additionally, atorvastatin decreased PAI-1 while fenofibric acid reduced leptin release. A combined administration of atorvastatin and fenofibric acid changed the release of all studied markers by visceral fat but did not affect interleukin-6 and TNFalpha release by subcutaneous tissue. In normolipidemic subjects the effect on adipokine release was more pronounced in visceral fat, in which it was strongest if the drugs were given together. Adipose tissue hormonal activity differs between mixed dyslipidemic and normolipidemic patients and between visceral and subcutaneous adipose tissue. Atorvastatin and fenofibrate exhibit their pleiotropic effects in part by changing the adipokine release by human adipose tissue, regardless of its origin. These effects are stronger in patients with mixed dyslipidemia and are particularly pronounced if atorvastatin and fenofibric acid are given together.

Abnormal glucose tolerance is associated with diminished postload change in leptin levels in women

BACKGROUND

It is generally accepted that the metabolic effects of leptin are diminished in the obese due to leptin resistance. Hormone resistance may develop if diurnal (including meal-related) changes in hormone levels are disrupted. We sought to describe leptin changes after a 75 g oral glucose tolerance test (OGTT) in women with a prior diagnosis of gestational diabetes mellitus (a high risk group for the metabolic syndrome) compared to that in healthy controls.

METHODS

In 2000 a retrospective cohort study was performed on women who had been diagnosed with gestational diabetes mellitus (WHO criteria 1985, n = 57) between 1996 and 1998 and on a healthy control female group (n = 36) all of whom had had a prior pregnancy without any diagnosis of diabetes. All the women underwent a standard 75 g OGTT. Serum leptin was measured by radioimmunoassay before and 90 min after the OGTT.

RESULTS

Using multilevel models of change, fasting leptin levels were shown to be associated with body mass index; 10.1% (95% CI 8.1-12.1%) increase per 1 kg/m(2) increase in body mass index), homeostasis model assessment insulin sensitivity; 0.4% (95% CI 0.2-0.7%) decrease per 1% increase in insulin sensitivity); abnormal glucose tolerance (24% decrease, 95% CI 8-37%); and smoking (31% decrease, 95% CI 16-44%). Postload (90 min) leptin levels decreased significantly in women with normal glucose tolerance by 13% (95% CI 8-18%), while no significant change in postload leptin level was apparent in women with abnormal glucose tolerance (3% increase, 95% CI -4% to 29%).

CONCLUSIONS

Disturbed leptin changes were found following an OGTT in women with abnormal glucose tolerance that might be either a cause or a consequence of leptin resistance.

Expression of three intelectins in sheep and response to a Th2 environment

Sheep intelectin1 and sheep intelectin3 (sITLN1 and sITLN3) were cloned and sequenced. The amino acid sequences of sITLN1 and sITLN3 shared 86% and 91% homology with the previously cloned sheep intelectin2 (sITLN2), respectively. Expression of sITLN1 and sITLN3 transcript was demonstrated in abomasum, lung, colon and gastric lymph node, terminal rectum, skin, jejunum, mesenteric lymph node, ileal peyer’s patches, brain, kidney, liver, spleen, skin, ear pinna, heart and ovary in normal sheep tissues. sITLN2 transcript expression was restricted to the abomasal mucosa in normal sheep tissues. Using a non selective chicken anti-intelectin antibody, tissue intelectin protein was demonstrated in mucus neck cells in the abomasum, mucus cells in the colon, free mucus in ileum, goblet cells in the lung, small intestinal epithelium and brush border, epidermal layer of the skin and skin sebaceous glands. The expression of the three sITLN transcripts was examined in two nematode infections in sheep known to induce a Th2 response; a Teladorsagia circumcincta challenge infection model and a Dictyocaulus filaria natural infection. The three sITLN were absent in unchallenged naïve lambs and present in the abomasal mucosa of both naïve and immune lambs following T. circumcincta challenge infection. Upregulation of sITLN2 and sITLN3 was shown in sheep lung following D. filaria natural infection. Intelectins may play an important role in the mucosal response to nematode infections in ruminants.

Peritoneal fluid adipokines: ready for prime time?

BACKGROUND

Visceral adipose tissues secret a variety of adipokines; however, it is not known whether they are present in the peritoneal fluid. It was the aim of this study to investigate peritoneal fluid concentrations of novel (cartonectin, omentin) and classical adipokines (leptin, adiponectin, resistin, visfatin) in patients with ascites.

MATERIAL AND METHODS

Ninety-six patients (71 men and 25 women) undergoing paracentesis were included. Of these, 76 suffered from liver cirrhosis. Adipokines were measured by enzyme-linked immunosorbent assay or Western blot.

RESULTS

Each adipokine was detected in ascites with a broad range. Serum-ascites ratios (SAR) correlated with clinical and laboratory parameters. The main variables influencing peritoneal fluid adipokine concentrations were body mass index (BMI), local inflammation, systemic inflammation and serum adipokine concentrations. Resistin was significantly higher in patients with peritonitis and showed a positive correlation with peripheral leucocytes (white blood cell count). Leptin was correlated with the underlying disease. Visfatin correlated with peripheral white blood cell and C-reactive protein levels. Omentin expression was correlated with ascitic leucocyte count, ascitic albumin concentration and low albumin SAR. BMI was correlated positively with ascitic leptin levels and cartonectin protein levels.

CONCLUSIONS

Peritoneal fluid adipokine concentrations are characterized by individual SARs, depend on the presence of peritonitis, and correlate with underlying disease, BMI and systemic inflammation. The data open a new field of research on the role of the peritoneum and visceral adipokines in gastrointestinal diseases.

The secretory function of adipocytes in the physiology of white adipose tissue

White adipose tissue, previously regarded as a passive lipid storage site, is now viewed as a dynamic tissue. It has the capacity to actively communicate by sending and receiving different types of signals. An overview of these signals, the external modulators that affect adipose tissue and the secreted signaling molecules, the adipokines, is presented. The secretory function is highlighted in relation to energy metabolism, inflammation and the extracellular matrix and placed in the context of adipose tissue biology. We observe that the endocrine function of adipocytes receives much attention, while its paracrine and autocrine functions are underestimated. Also, we provide examples that species specificity should not be neglected. We conclude that adipose tissue primarily is an energy storage organ, well supported by its secretory function.

Omentin-1, a novel adipokine, is decreased in overweight insulin-resistant women with polycystic ovary syndrome: ex vivo and in vivo regulation of omentin-1 by insulin and glucose

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with insulin resistance and obesity. Recent studies have shown that plasma omentin-1 levels decrease with obesity. Currently, no data exist on the relative expression and regulation of omentin-1 in adipose tissue of women with PCOS. The objective of this study was to assess mRNA and protein levels of omentin-1, including circulating omentin-1, in omental adipose tissue of women with PCOS and matched control subjects. Ex vivo and in vivo regulation of adipose tissue omentin-1 was also studied.

RESEARCH DESIGN AND METHODS

Real-time RT-PCR and Western blotting were used to assess mRNA and protein expression of omentin-1. Plasma omentin-1 was measured by enzyme-linked immunosorbent assay. The effects of d-glucose, insulin, and gonadal and adrenal steroids on adipose tissue omentin-1 were analyzed ex vivo. The in vivo effects of insulin (hyperinsulinemia) on omentin-1 levels were also assessed by a prolonged insulin-glucose infusion.

RESULTS

In addition to decreased plasma omentin-1 levels in women with PCOS (P < 0.05), compared with control subjects, there was significantly lower levels of omentin-1 mRNA (P < 0.01) and protein (P < 0.05) in omental adipose tissue of women with PCOS (P < 0.01). Furthermore, in omental adipose tissue explants, insulin and glucose significantly dose-dependently decreased omentin-1 mRNA expression, protein levels, and secretion into conditioned media (P < 0.05, P < 0.01). Also, hyperinsulinemic induction in healthy subjects significantly reduced plasma omentin-1 levels (P < 0.01).

CONCLUSIONS

Our novel findings reveal that omentin-1 is downregulated by insulin and glucose. These may, in part, explain the decreased omentin-1 levels observed in our overweight women with PCOS.

Identification of omentin mRNA in human epicardial adipose tissue: comparison to omentin in subcutaneous, internal mammary artery periadventitial and visceral abdominal depots

OBJECTIVE

The purpose of this study was to determine the relative distribution of omentin and visfatin mRNA in human epicardial, peri-internal mammary, upper thoracic, upper abdominal and leg vein subcutaneous adipose tissue as well as the distribution of omentin in the nonfat cells and adipocytes of human omental adipose tissue.

BACKGROUND

Omentin is found in human omentum but not subcutaneous fat. Omentin and visfatin are considered markers of visceral abdominal fat.

RESEARCH DESIGN AND METHODS

The mRNA content of omentin and visfatin was measured by qRT-PCR analysis of fat samples removed from humans undergoing cardiac or bariatric surgery.

RESULTS

Omentin mRNA in internal mammary fat was 3.5%, that in the upper thoracic subcutaneous fat was 4.7% while that in the other subcutaneous fat depots was less than 1% of omentin in epicardial fat. The distribution of visfatin mRNA did not vary between the five depots. Omentin mRNA was preferentially expressed in the nonfat cells of omental adipose tissue since the omentin mRNA content of isolated adipocytes was 9% of that in nonfat cells, and similar results were seen for visfatin. The amount of omentin mRNA in differentiated adipocytes was 0.3% and that of visfatin 4% of that in nonfat cells. The amount of omentin mRNA in preadipocytes was virtually undetectable while that of visfatin was 3% of that in freshly isolated nonfat cells from omental adipose tissue.

CONCLUSION

Omentin mRNA is predominantly found in epicardial and omental human fat whereas visfatin mRNA is found to the same extent in epicardial, subcutaneous and omental fat.

Adipose tissue as an immunological organ: Toll-like receptors, C1q/TNFs and CTRPs

Adipose tissue has long been regarded as a mostly resting tissue that is dedicated solely to energy storage and release. However, in recent years, this view has changed dramatically following new insights into the metabolic and immunological functions of preadipocytes and adipocytes. There are several lines of evidence for the involvement of adipose tissue in innate and acquired immune responses. First, adipocytes are potent producers of proinflammatory cytokines, such as interleukin-6 and tumor necrosis factor (TNF), and chemokines. Furthermore, adipocytes secrete high amounts of adipokines, such as leptin, adiponectin and resistin, that regulate monocyte/macrophage function, and also secrete molecules associated with the innate immune system, such as the C1qTNF-related protein superfamily. Finally, preadipocytes and adipocytes express a broad spectrum of functional Toll-like receptors and the former can convert into macrophage-like cells. Collectively, these data clearly establish the role of adipose tissue as a new member of the immune system.