Serum omentin-1, inflammation and carotid atherosclerosis in patients with non-diabetic chronic kidney disease

Omentin roles in physiology and pathophysiology: an up-to-date comprehensive review

Omentin (intelectin) was first detected in the visceral omental adipose tissue. It has mainly two isoforms, omentin-1 and -2, with isoform-1 being the main form in human blood. It possesses insulin-sensitizing, anti-inflammatory, anti-atherogenic, cardio-protective, and oxidative stress-decreasing effects. Omentin's cardiovascular protective actions are caused by the improved endothelial cell survival and function, increased endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) bioavailability, enhanced vascular smooth muscle cells (VSMCs) relaxation with reduced proliferation, decreased inflammation, and suppressed oxidative stress. Omentin may also have a potential role in different cancer types and rheumatic diseases. Thus, omentin is an excellent therapeutic target in many diseases, including diabetes mellitus (DM), metabolic syndrome (MetS), cardiovascular diseases (CVDs), inflammatory diseases, and cancer. This review demonstrates the physiological functions of omentin in ameliorating insulin resistance (IR), vascular function, and inflammation and its possible share in managing obesity-linked diseases, such as metabolic disorders, DM, and cardiovascular conditions.

Omentin-1 Levels and Outcomes in Incident Peritoneal Dialysis Patients

Rationale & Objective

Omentin-1 is an adipokine with anti-inflammatory and cardioprotective properties. The objective of this study was to determine the prognostic role of plasma omentin-1 levels in incident peritoneal dialysis (PD) patients.

Study Design

Retrospective analysis of prospective cohort.

Setting & Participants

152 incident PD patients.

Predictors

Plasma omentin-1 level, adipose tissue omentin-1 messenger RNA (mRNA) expression.

Outcomes

Patient survival, technique survival, hospital admission, and duration of stay.

Analytical Approach

Time-to-event survival analyses; linear regression for hospitalization.

Results

The mean age was 58.4 ± 11.7 years; 102 were men, and 92 had diabetes. There was no significant correlation between plasma omentin-1 level and its adipose tissue mRNA expression. A higher plasma omentin-1 level quartile was not associated with patient survival (P = 0.92) or technique survival (P = 0.83) but had a modest correlation with a lower number of hospital admissions (P = 0.07) and shorter duration of hospital stay (P = 0.04). In adjusted models using multivariable linear regression, a higher plasma omentin-1 level quartile remained significantly associated with fewer hospital admissions (β, -0.13; 95% CI, -0.26 to -0.002; P = 0.05) and shorter hospitalization duration (β, -0.20; 95% CI, -0.38 to -0.02; P = 0.03).

Limitations

Observational study with baseline measures only.

Conclusions

Plasma omentin-1 level was not associated with patient survival, technique survival, or peritonitis, but higher plasma omentin-1 levels were associated with fewer hospital admissions and shorter duration of hospitalization among incident PD patients.

Circulating Omentin-1, Sustained Inflammation and Hyperphosphatemia at the Interface of Subclinical Atherosclerosis in Chronic Kidney Disease Patients on Chronic Renal Replacement Therapy

Background and Objectives: Subclinical atherosclerosis, reflected by abnormal carotid intima–media thickness (cIMT), is pervasive among chronic kidney disease patients on chronic renal replacement therapy (RRT), being mostly influenced by uremia-related rather than traditional risk factors. Materials and Methods: In this pilot study, we measured circulating levels of Omentin-1, a recently discovered adipokine with strong anti-atherogenic properties, in a heterogeneous cohort of 77 asymptomatic RRT individuals (40 chronic kidney transplant recipients, Ktx; and 37 chronic hemodialysis patients, HD) and in 30 age-matched controls. Results: Omentin-1 was increased in RRT individuals as compared with controls (p = 0.03). When stratifying for renal replacement modality, we found Ktx patients to have significantly lower Omentin-1 than HD patients (p = 0.01). Lower Omentin-1 levels were also found among RRT individuals with pathological cIMT (168.7 [51.1–457.8] vs. 474.9 [197.2–1432.1]; p = 0.004). Our multivariate correlations analysis revealed Omentin-1 as the most robust independent predictor of carotid atherosclerosis (β-0.687; p = 0.03), even more than total cholesterol, diastolic BP and age, and this adipokine was at the crossroad of a complex interplay with sustained inflammation (high CRP and ferritin) and hyperphosphatemia in predicting higher cIMT values. Conclusion: The findings reported extend to renal patients with advanced disease, with the possible involvement of Omentin-1 in the pathogenesis of atherosclerosis. This may set the stage for future interventional studies of Omentin-1 replacement to retard atherosclerosis progression, as it is currently being investigated in other disease settings.

Thromboinflammatory Processes at the Nexus of Metabolic Dysfunction and Prostate Cancer: The Emerging Role of Periprostatic Adipose Tissue

Simple Summary

As overweight and obesity increase among the population worldwide, a parallel increase in the number of individuals diagnosed with prostate cancer was observed. There appears to be a relationship between both diseases where the increase in the mass of fat tissue can lead to inflammation. Such a state of inflammation could produce many factors that increase the aggressiveness of prostate cancer, especially if this inflammation occurred in the fat stores adjacent to the prostate. Another important observation that links obesity, fat tissue inflammation, and prostate cancer is the increased production of blood clotting factors. In this article, we attempt to explain the role of these latter factors in the effect of increased body weight on the progression of prostate cancer and propose new ways of treatment that act by affecting how these clotting factors work.

Abstract

The increased global prevalence of metabolic disorders including obesity, insulin resistance, metabolic syndrome and diabetes is mirrored by an increased incidence of prostate cancer (PCa). Ample evidence suggests that these metabolic disorders, being characterized by adipose tissue (AT) expansion and inflammation, not only present as risk factors for the development of PCa, but also drive its increased aggressiveness, enhanced progression, and metastasis. Despite the emerging molecular mechanisms linking AT dysfunction to the various hallmarks of PCa, thromboinflammatory processes implicated in the crosstalk between these diseases have not been thoroughly investigated. This is of particular importance as both diseases present states of hypercoagulability. Accumulating evidence implicates tissue factor, thrombin, and active factor X as well as other players of the coagulation cascade in the pathophysiological processes driving cancer development and progression. In this regard, it becomes pivotal to elucidate the thromboinflammatory processes occurring in the periprostatic adipose tissue (PPAT), a fundamental microenvironmental niche of the prostate. Here, we highlight key findings linking thromboinflammation and the pleiotropic effects of coagulation factors and their inhibitors in metabolic diseases, PCa, and their crosstalk. We also propose several novel therapeutic targets and therapeutic interventions possibly modulating the interaction between these pathological states.

Association of Circulating Omentin-1 with Osteoporosis in a Chinese Type 2 Diabetic Population

Aims

Omentin-1, a newly identified adipokine, has been demonstrated to be associated with bone metabolism, but the results have been inconsistent. Moreover, the potential relationship of circulating omentin-1 with diabetic osteoporosis has never been reported. This study is intended for studying the association between circulating omentin-1, bone mineral density (BMD), prior fragility fractures, and other bone metabolic-related parameters.

Methods

Circulating omentin-1 levels were measured in 172 patients with type 2 diabetes mellitus (T2DM), and participants were divided into the normal BMD group (n = 52), the osteopenia group (n = 66), and the osteoporosis group (n = 54). The relationship between circulating omentin-1 and diabetic osteoporosis and other parameters was analyzed.

Results

Circulating omentin-1 was significantly higher in the osteoporosis group than in the normal group and in the osteopenia group (both P < 0.05). Circulating omentin-1 levels were correlated significantly and positively with sex; high-density lipoprotein cholesterol; apolipoprotein A; and prevalence of prior fragility fractures, diabetic nephropathy, and retinopathy; they were correlated negatively with diastolic blood pressure, triglyceride, hemoglobin, atherogenic index of plasma, osteoporosis self-assessment tool for Asians, BMD at different skeletal sites, and corresponding T scores, irrespective of age, sex, and body mass index (P < 0.01 or P < 0.05). Moreover, circulating omentin-1 was an independent decisive factor for the presence of osteoporosis only in women after multivariate adjustment (odds ratio: 1.069; 95% confidence interval: 1.003-1.139; P < 0.05). Lastly, the analysis of receiver operating characteristic curves revealed that the best cutoff value for circulating omentin-1 to predict diabetic osteoporosis was 15.37 ng/mL (sensitivity: 71.7%; specificity: 58.5%) in female subjects.

Conclusions

High levels of circulating omentin-1 may be associated with the development of osteoporosis in female diabetic subjects and may be a potential biomarker for diabetic osteoporosis in women.

Omentin-1 in diabetes mellitus: A systematic review and meta-analysis

OBJECTIVE

Previous studies found inconsistent results on the relationship between diabetes mellitus and concentrations of omentin-1. This study performed a systematic review and meta-analysis to summarize previous findings on this relationship.

METHODS

Studies related to this outcome were obtained using a systematic search in the electronic databases of Cochrane Library, PubMed, Embase, SCOPUS, Google Scholar, gray literature and Web of Science in September 2019. The random effects model was used to measure the strength of the association between diabetes mellitus and concentrations of omentin-1, using standardized mean difference.

RESULTS

Forty-two eligible studies were included in the final meta-analysis. There was no significant difference in omentin-1 concentration between patients with type 1 diabetes mellitus and the controls. On the other hand, lower concentration levels of omentin-1 were observed in patients with gestational diabetes mellitus (standardized mean difference:-0.44, 95% confidence interval:-0.76; -0.12, p = 0.007), or type 2 diabetes mellitus (standardized mean difference: -1.74, 95% confidence interval: -2.31; -1.16, p< 0.001) than in the controls.

CONCLUSION

Decreased omentin-1 concentrations may be an important indicator for gestational diabetes mellitus and type 2 diabetes mellitus. More studies are needed to validate this hypothesis and evaluate the role of omentin-1 concentrations in type 1 diabetes mellitus.

Clinical significance of circulating omentin levels in various malignant tumors: Evidence from a systematic review and meta-analysis

Aberrant circulating level of omentin has been reported in various solid tumors. However, whether decreased or increased levels of omentin contribute in cancer risk is remained controversial in different epidemiological studies. This comprehensive meta-analysis of observational studies was conducted to investigate the association between circulating omentin level and human cancer risk. An electronic search of health-related databases, was performed to identify all eligible studies in English, up to July 2019. Combined standard mean difference (SMD) with 95%CI was computed to assess the correlation of omentin levels with human cancer risk in a random effect model. The risk of publication bias was also evaluated using Funnel plot and Egger regression tests. A total of 16 studies with 1106 cases and 3078 healthy controls were included. Pooled SMD analysis based on the cancer type, revealed a strong correlation of omentin level and cancer risk in patients with colorectal (SMD = 2.08, 95%CI: 1.67-2.50, P < 0.001), prostate (SMD = 1.38, 95%CI: 1.15-1.62, P < 0.001), and breast (SMD = -0.78, 95%CI: -1.1, -0.45, P < 0.001) cancers. Elevated circulating omentin levels was also found in cancer patients with BMI ≥ 25 (SMD = 1.33, 95%CI: 0.52-2.15, P = 0.001) indicating a potential role for omentin in development of some obesity-linked cancers. The findings of this meta-analysis indicated a significant association of omentin level with greater risk of colorectal, pancreas, and breast tumors. Circulating omentin level may represent a potential novel biomarker for early detection of colorectal, prostate, and breast cancers especially in overweight/obese subjects. Further prospective well-designed studies are warranted to confirm our findings.

The potential of adipokines as biomarkers and therapeutic agents for vascular complications in type 2 diabetes mellitus

Over the past decades, there has been a major increase in type 2 diabetes (T2D) prevalence in most regions of the world. Diabetic patients are more prone to cardiovascular complications. Accumulating evidence suggests that adipose tissue is not simply an energy storage tissue but it also functions as a secretory tissue producing a variety of bioactive substances, also referred to as adipokines. The balance between pro-inflammatory adipokines and protective adipokines is disturbed in type 2 diabetes, this can be regarded as adipose tissue dysfunction which partly promote the pathogenesis of diabetes complications. In this review, we not only discuss the favorable adipokines like adiponectin, omentin, C1q tumor necrosis factor-related proteins, but also unfavorable ones like resisitin and visfatin, in the aim of finding potential biomarkers recommended for the clinical use in the diagnosis, prognosis and follow up of patients with T2D at high risk of developing cardiovascular diseases as well as leading to new therapeutic approaches.

Association of circulating omentin-1 level with lung cancer in smokers

Background: Omentin has recently been considered as an adipokine secreted from visceral fat and is expressed in the lungs, heart, ovary etc. Various studies have shown that omentin may have an anti-inflammatory role in the inflammatory process and the amount of omentin alters in some cancers, such as colorectal, prostate and renal cells cancers, changes. The serum level of omentin, however, remains unknown in non-patient smokers and the smokers afflicted with lung cancer. Therefore, this study examines the serum levels of omentin in smokers suffering from lung cancer.

Methods: The amount of serum omentin was measured in 45 patients with lung cancer and 61 age - and sex - matched controls (30 smokers and 31 non-smokers) using enzyme-linked immunosorbent assay (ELISA) kit. Data were analyzed using SPSS-16, and oneway analysis of variance and Scheffe post hoc test were used to determine and compare the serum levels of omentin in different types of lung malignancies. Significance level was set at p≤0.05.

Results: The amount of circulating omentin for healthy non-smokers and non-patient smokers was 3.55±0.57 ng/l and 5.43±1.95 ng/l, respectively (p<0.001). The serum level of omentin was 3.63±0.70 ng/l for smokers afflicted with cancer (p<0.001 compared with nonpatient smokers: 5.43±1.95).

Conclusion: The meaningful decrease in omentin levels in smokers with lung cancer can be considered as a risk factor in smokers and can use as a significant factor in the prognosis of lung cancer in these people.

The complex effects of adipokines in the patients with kidney disease

Kidney diseases are categorized as the highest prevalent ones with worldwide noticeable incidence. They cause accelerated cardiovascular diseases and noticeable mortalities. Adipose tissue and its messengers, adipokines, are reported to have the highest relationship with end-stage renal diseases or chronic kidney diseases. Over recent years, with shifting of scientists’ mindset from a simple overview of adipose tissue as a fat store to the complex paradigm of this issue as a multipotential secretory organ, the importance of studies on this tissue has emerged.

Immunologic and endocrine functions of adipose tissue: implications for kidney disease

Excess adiposity can induce adverse sequelae in multiple cell types and organ systems. The transition from the lean to the obese state is characterized by fundamental cellular changes at the level of the adipocyte. These changes affect the local microenvironment within the respective adipose tissue but can also affect nonadipose systems. Adipocytes within fat pads respond to chronic nutrient excess through hyperplasia or hypertrophy, which can differentially affect interorgan crosstalk between various adipose depots and other organs. This crosstalk is dependent on the unique ability of the adipocyte to coordinate metabolic adjustments throughout the body and to integrate responses to maintain metabolic homeostasis. These actions occur through the release of free fatty acids and metabolites during times of energy need - a process that is altered in the obese state. In addition, adipocytes release a wide array of signalling molecules, such as sphingolipids, as well as inflammatory and hormonal factors (adipokines) that are critical for interorgan crosstalk. The interactions of adipose tissue with the kidney - referred to as the adipo-renal axis - are important for normal kidney function as well as the response of the kidney to injury. Here, we discuss the mechanistic basis of this interorgan crosstalk, which clearly has great therapeutic potential given the increasing rates of chronic kidney disease secondary to obesity and type 2 diabetes mellitus.

Adipose Tissue-Derived Omentin-1 Function and Regulation

Omentin-1, also known as intelectin-1, is a recently identified novel adipocytokine of 313 amino acids, which is expressed in visceral (omental and epicardial) fat as well as mesothelial cells, vascular cells, airway goblet cells, small intestine, colon, ovary, and plasma. The level of omentin-1 expression in (pre)adipocytes is decreased by glucose/insulin and stimulated by fibroblast growth factor-21 and dexamethasone. Several lines of experimental evidence have shown that omentin-1 plays crucial roles in the maintenance of body metabolism and insulin sensitivity, and has anti-inflammatory, anti-atherosclerotic, and cardiovascular protective effects via AMP-activated protein kinase/Akt/nuclear factor-κB/mitogen-activated protein kinase (ERK, JNK, and p38) signaling. Clinical studies have indicated the usage of circulating omentin-1 as a biomarker of obesity, metabolic disorders including insulin resistance, diabetes, and metabolic syndrome, and atherosclerotic cardiovascular diseases. It is also possible to use circulating omentin-1 as a biomarker of bone metabolism, inflammatory diseases, cancers, sleep apnea syndrome, preeclampsia, and polycystic ovary syndrome. Decreased omentin-1 levels are generally associated with these diseases. However, omentin-1 increases to counteract the acute phase after onset of these diseases. These findings indicate that omentin-1 may be a negative risk factor for these diseases, and also act as an acute-phase reactant by its anti-inflammatory and atheroprotective effects. Therapeutic strategies to restore omentin-1 levels may be valuable for the prevention or treatment of these diseases. Weight loss, olive oil-rich diet, aerobic training, and treatment with atorvastatin and antidiabetic drugs (metformin, pioglitazone, and exenatide) are effective means of increasing circulating omentin-1 levels. This review provides insights into the potential use of omentin-1 as a biomarker and therapeutic target for these diseases. © 2017 American Physiological Society. Compr Physiol 7:765-781, 2017.

Association of serum omentin levels with cardiac autonomic neuropathy in patients with type 2 diabetes mellitus: a hospital-based study

Background

Whereas a few studies have reported associations of serum omentin levels with subclinical atherosclerosis in patients with diabetes, little information is available with respect to the associations of serum omentin levels and diabetic microvascular complications. The aim of this study was to investigate the relationships of serum omentin levels and vascular complications including cardiac autonomic neuropathy (CAN) in patients with type 2 diabetes mellitus (T2DM).

Methods

We recruited 97 patients who evaluated complications of diabetes. CAN was assessed by five standard cardiovascular reflex tests according to Ewing’s protocol. Diabetic nephropathy (DN), retinopathy (DR), and peripheral neuropathy (DPN) were evaluated. Serum omentin levels were assessed by ELISA. Atherosclerotic burden was evaluated by measuring the brachial-ankle pulse wave velocity (baPWV) and ankle brachial index (ABI).

Results

The prevalence of CAN increased borderline significantly across the omentin tertiles (p = 0.05) and CAN point increased significantly and progressively across the omentin tertiles (p = 0.013). The prevalence of other microvascular complications (DPN, DN, and DR) did not differ among omentin tertiles. The mean levels of baPWV also increased significantly and progressively across the omentin tertiles (p = 0.002). Serum omentin levels were significantly positively correlated with CAN point (p = 0.004) and borderline significantly correlated with baPWV (p = 0.05) after multivariate adjustment. Regarding linear regression analysis for CAN point, univariate regression analysis demonstrated that CAN point associated with omentin, diastolic blood pressure (DBP) and hsCRP. Multiple regression analysis revealed that omentin levels, together DBP and baPWV correlated with CAN point. This present study suggests that serum omentin levels may be independently associate with CAN in patients with T2DM.

Inflammation, Endothelial Dysfunction and Increased Left Ventricular Mass in Chronic Kidney Disease (CKD) Patients: A Longitudinal Study

Introduction

Within this longitudinal study we investigated the association of inflammation markers C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα) and endothelial dysfunction markers intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) with left ventricular mass indexed for height²·⁷¹ (LVMI) in hypertensive predialysis CKD patients.

Material and Methods

From 2004 to 2005, 182 incident consecutive adult patients from the outpatient CKD clinics of two hospitals in Greece with CKD and hypertension or using antihypertensive medication, were included. Of these, 107 patients underwent CRP (mg/l) and LVMI (g/height²·⁷¹) measurements annually for three years.

Results

In the longitudinal analyses, using linear mixed modeling, a higher IL-6 (ß = 1.9 (95%ci:0.38;3.5), inflammation score based on CRP, IL-6 and TNF-α (ß = 5.0 (95%ci:0.72; 9.4) and VCAM-1 (ß = 0.01 (95%ci:0.005;0.02) were associated with higher LVMI. These models were adjusted for age, gender and primary renal disease, and for confounders that on top changed the beta with ≥10%, i.e. diuretic use (for IL-6 and inflammation score).

Conclusion

The results suggest that in predialysis CKD patients, inflammation as well as endothelial dysfunction may play an important role towards the increase in LVMI.

Serum and Vitreous Concentrations of Omentin-1 in Diabetic Retinopathy

Objective. Omentin, a new discovered adipokine, is implicated to inhibit inflammation. Inflammation is one important mechanism of diabetic retinopathy (DR). The purpose of this work was to evaluate serum and vitreous concentrations of omentin-1 in patients with diabetic retinopathy (DR). Methods. This study enrolled 204 diabetic patients (60 without DR, 49 with NPDR, and 95 with PDR) and 65 control subjects. Results. Serum and vitreous omentin-1 levels in PDR patients were markedly decreased compared with those in the other three groups. NPDR patients showed reduced vitreous omentin-1 compared with patients without DR. In addition, control subjects had significantly higher levels of serum and vitreous omentin-1 compared with diabetic patients without DR, NPDR patients, and PDR patients. In addition, serum/vitreous omentin-1 ratio was positively correlated with the development and severity of DR. Conclusion. Serum and vitreous omentin-1 levels, as well as serum/vitreous omentin-1 ratio, are correlated with the presence and severity of DR.

The protective functions of omentin in cardiovascular diseases

Adipose tissue is considered as a large gland that can produce paracrine and endocrine hormones. Growing evidence suggests that adipocytes may link obesity to cardiovascular diseases (CVD). Adipose tissue produces a large number of mediators, which affect metabolism, inflammation and coagulation. Omentin, a novel adipocytokine, has come into the center of interest due to its favorable effects on inflammation, glucose homeostasis and CVD. The present review provides a concise and general overview on the roles of omentin in CVD. The knowledge of these concepts may provide a new strategy to reduce disease risks on CVD in the future.

The relationship of novel adipokines, RBP4 and omentin-1, with carotid atherosclerosis severity and vulnerability

OBJECTIVE

We investigated the relationship of circulating novel adipokines, retinol-binding protein 4 (RBP4) and omentin-1, with advanced carotid atherosclerosis and ultrasound indexes of severity (total plaque area-TPA) and plaque echogenicity and vulnerability (Gray-Scale median - GSM score).

METHODS

We enrolled 225 patients with high-grade carotid stenosis (HGCS) who underwent carotid revascularization (73 Symptomatic patients, 152 asymptomatic patients) and 75 age- and sex-matched, asymptomatic individuals with low-grade (<50%) carotid stenosis (LGCS). Seventy-three individuals without current manifestations of atherosclerotic disease served as control group (COG). All participants underwent carotid ultrasound with TPA and GSM score assessment. Moreover, clinical parameters, metabolic profile, and circulating levels of hsCRP and adipokines were assessed.

RESULTS

RBP4 was significantly elevated in HGCS (51.44 ± 16.23 mg/L) compared to LGCS (38.39 ± 8.85 mg/L), independent of symptoms existence, whereas RBP4 levels in COG were even lower (25.74 ± 10.72 mg/L, p < 0.001 compared to either HGCS or LGCS). Inversely, serum omentin-1 levels were significantly lower across HGCS (490.41 ± 172 ng/ml) and LGCS (603.20 ± 202.43 ng/ml) than COG (815.3 ± 185.32, p < 0.001). Moreover, the considerable difference between HGCS and LGCS (p < 0.001) was exclusively attributed to the excessive suppression of omentin-1 concentrations in symptomatic versus asymptomatic (p = 0.004) patients. HGCS and LGCS did not differ in the rest of clinical and biochemical parameters. In multiple regression analysis, RBP4 (beta = 0.232, p = 0.025) and hsCRP (beta = 0.300, p = 0.004) emerged as independent determinants of TPA in patients with carotid atherosclerosis. Low serum levels of omentin-1 correlated with GSM score and symptoms but that association was lost in multivariate analysis..

CONCLUSION

RBP4 serum levels were significantly elevated in patients with established carotid atherosclerosis and were positively associated with atherosclerosis severity. The association of low serum omentin-1 with carotid plaque echolucency requires further investigation.. ClinicalTrials.gov Identifier: NCT00636766.