Retinol-binding protein 4 levels are associated with measures of liver and renal function and oxidant/antioxidant status in obese children

Interplay of retinol binding protein 4 with obesity and associated chronic alterations (Review)

Obesity is a multifactorial disease, defined as excessive fat deposition in adipose tissue. Adipose tissue is responsible for the production and secretion of numerous adipokines that induce metabolic disorders. Retinol-binding protein 4 (RBP4) is an adipokine that transports vitamin A or retinol in the blood. High levels of RBP4 are associated with development of metabolic disease, including obesity, insulin resistance (IR), metabolic syndrome, and type 2 diabetes (T2D). The present review summarizes the role of RBP4 in obesity and associated chronic alterations. Excessive synthesis of RBP4 contributes to inflammatory characteristic of obesity by activation of immune cells and release of proinflammatory cytokines, such as TNFα and ILs, via the Toll-like receptor/JNK pathway. The retinol-RBP4 complex inhibits insulin signaling directly in adipocytes by activating Janus kinase 2 (JAK2)/STAT5/suppressor of cytokine signaling 3 signaling. This mechanism is retinol-dependent and requires vitamin A receptor stimulation by retinoic acid 6 (STRA6). In muscle, RBP4 is associated with increased serine 307 phosphorylation of insulin receptor substrate-1, which decreases its affinity to PI3K and promotes IR. In the liver, RBP4 increases hepatic expression of phosphoenolpyruvate carboxykinase, which increases production of glucose. Elevated serum RBP4 levels are associated with β-cell dysfunction in T2D via the STRA6/JAK2/STAT1/insulin gene enhancer protein 1 pathway. By contrast, RBP4 induces endothelial inflammation via the NF-κB/nicotinamide adenine dinucleotide phosphate oxidase pathway independently of retinol and STRA6, which stimulates expression of proinflammatory molecules, such as vascular cell adhesion molecule 1, E-selectin, intercellular adhesion molecule 1, monocyte chemoattractant protein 1 and TNFα. RBP4 promotes oxidative stress by decreasing endothelial mitochondrial function; overall, it may serve as a useful biomarker in the diagnosis of obesity and prognosis of associated disease, as well as a potential therapeutic target for treatment of these diseases.

Early changes in laboratory tests predict liver function damage in patients with moderate coronavirus disease 2019: a retrospective multicenter study

Background

Most patients with coronavirus disease 2019 demonstrate liver function damage. In this study, the laboratory test data of patients with moderate coronavirus disease 2019 were used to establish and evaluate an early prediction model to assess the risk of liver function damage.

Methods

Clinical data and the first laboratory examination results of 101 patients with moderate coronavirus disease 2019 were collected from four hospitals’ electronic medical record systems in Jilin Province, China. Data were randomly divided into training and validation sets. A logistic regression analysis was used to determine the independent factors related to liver function damage in patients in the training set to establish a prediction model. Model discrimination, calibration, and clinical usefulness were evaluated in the training and validation sets.

Results

The logistic regression analysis showed that plateletcrit, retinol-binding protein, and carbon dioxide combining power could predict liver function damage (P < 0.05 for all). The receiver operating characteristic curve showed high model discrimination (training set area under the curve: 0.899, validation set area under the curve: 0.800; P < 0.05). The calibration curve showed a good fit (training set: P = 0.59, validation set: P = 0.19; P > 0.05). A decision curve analysis confirmed the clinical usefulness of this model.

Conclusions

In this study, the combined model assesses liver function damage in patients with moderate coronavirus disease 2019 performed well. Thus, it may be helpful as a reference for clinical differentiation of liver function damage.

Trial registration retrospectively registered.

Circulating retinol binding protein 4 levels in coronary artery disease: a systematic review and meta-analysis

BACKGROUND

Retinol binding protein 4 (RBP4) has been proposed to play a role in the pathophysiology of coronary artery disease (CAD), but previous findings on the association of RBP4 levels with CAD are inconsistent.

METHODS

A meta-analysis based on observational studies was conducted to evaluate the association between circulating RBP4 levels and CAD. Databases including PubMed, Web of Science, Embase, Google Scholar and ClinicalTrials.gov database were searched for eligible studies published up to 12 July 2021. Standard mean differences (SMDs) with 95% confidence intervals (CIs) were calculated using the inverse variance heterogeneity (IVhet) and random-effects model for data with moderate and high heterogeneity (I² > 30%) and data with low heterogeneity were analysed using a fixed-effects model (I² ≤ 30%). Moreover, a bias-adjusted quality-effects model was generated, and the prediction interval was also calculated under the random-effects model.

RESULTS

Two nested case-control studies, one cohort study and twelve case-control studies with a total of 7111 participants were included. Circulating RBP4 levels in patients with CAD were comparable to those in the controls under the IVhet model (SMD: 0.25, 95% CI: - 0.29-0.79, I²: 96.00%). The quality-effects model produced consistent results. However, the association turned to be significant under the random-effect model (SMD: 0.46, 95% CI: 0.17-0.75, I²: 96.00%), whereas the 95% predictive interval (PI) included null values (95% PI: - 0.82-1.74). Subgroup analyses illustrated a positive relationship between CAD and RBP4 levels in patients with complications (SMD: 1.34, 95% CI: 0.38-2.29, I²: 96.00%). The meta-regression analysis revealed that the mean BMI of patients (P = 0.03) and complication status (P = 0.01) influenced the variation in SMD.

CONCLUSIONS

There was low-quality evidence that patients with CAD exhibited similar circulating RBP4 levels compared with controls, and high inter-study heterogeneity was also observed. Thus, RBP4 might not be a potential risk factor for CAD. Comparisons among different subtypes of RBP4 with larger sample size are needed in the future.

The Association between Serum Retinol-Binding Protein 4 Levels and Cardiovascular Events in Patients with Chronic Kidney Disease

OBJECTIVE

The study aimed to assess whether serum retinol-binding protein 4 (RBP4) is associated with a risk of cardiovascular (CV) events in chronic kidney disease (CKD) patients.

METHODS

One hundred sixty-nine patients with CKD were followed for a mean of 36 months (range, 5-39 months). Serum RBP4 and other laboratory indicators were measured at baseline. The relationship between RBP4 and the risk of CV events was evaluated by using Cox regression analysis.

RESULTS

Patients with higher serum RBP4 levels had a higher rate of CV events and a higher mortality in a univariate analysis (P < 0.001). The multivariate Cox proportional hazard analysis revealed that RBP4 (hazard ratio, 2.259; 95% confidence interval, 2.067-5.489; P = 0.002) is an independent prognostic factor for CV events in patients with CKD. Kaplan-Meier analysis demonstrated that patients with RBP4 above the median value (>33.86 mg/L) had a higher rate of CV events than did patients with RBP4 at or below the median value (≤33.86 mg/L; P < 0.001).

CONCLUSION

RBP4 levels are associated with CV events in patients with CKD. Elevated serum RBP4 levels may indicate an increased risk of CV complications in CKD patients.

Plasma RBP4 Level in Association with Body Composition, Metabolic Profile, STRA6 and RBP4 Gene Polymorphisms in Obese Romanian Children

BACKGROUND

Pediatric obesity continues to remain a serious health concern which has significantly increased the morbidity risk in adulthood. Recent studies have analyzed the impact of the two adipokines, RBP4 (retinol binding protein 4) and STRA6 (stimulated by retinoic acid 6) in pediatric obese subjects with contradictory results.

METHODS

An observational study was conducted in the Pediatric and Endocrinology Departments, Targu-Mures, Romania, including 213 children between 5-17 years of age, divided into two groups according to body mass index (BMI) standard deviation score (SDS): case (overweight or obese) and control (normal SDS). Age, sex, basic anthropometric and biochemical measurements and genotype of rs3758539, and rs10882280 for RBP4 gene and rs974456 and rs351224 of STRA6 gene were analyzed. Statistical analysis used SPSS v. 25.0, with a level of significance α = 0.05.

RESULTS

There is no association between the two gene's polymorphisms and obesity in our pediatric population. In regression analysis, with HOMA IR (homeostatic model assessment of insulin resistance) as the outcome, the plasmatic level of RBP4 and fat mass percentage are significant predictors, with the model explaining 42% of the HOMA variability. Hypercholesterolemia was significantly associated with male sex, carrying variant allele and heterozygote status of rs10882280 RBP4 gene and wild-type allele rs351224 of STRA6 gene.

CONCLUSION

There is no significant association between obesity and SNPs of the RBP4 and STRA6 in our population, but they seem to play a role in insulin resistance and hypercholesterolemia.

Evaluation of serum retinol-binding protein-4 levels as a biomarker of poor short-term prognosis in ischemic stroke

The aim was to investigate the relationship between retinol-binding protein 4 (RBP4) levels and short-term functional outcome, and to determine its possible role in acute ischemic stroke (AIS). In a prospective observational study, 299 first-ever AIS who were admitted to our hospital were included. Serum levels of RBP4 were assayed and severity of stroke was evaluated with the National Institutes of Health Stroke Scale (NIHSS) score on admission. The prognostic value of RBP4 to predict the poor outcome within 3 months was compared with the NIHSS and with other known outcome predictors. The median age of the included patients was 66 (interquartile range (IQR): 55-77) years and 155 (51.8%) were women. A poor functional outcome was found in 88 patients (29.4%), and significantly higher RBP4 values were found in poor outcomes rather than good outcomes patients (P<0.001). The poor outcomes distribution across the RBP4 quartiles ranged between 9.3% (first quartile) and 60.8% (fourth quartile). In multivariate models comparing the second(Q2), third, and fourth quartiles against the first quartile of the RBP4, RBP4 in Q3 and Q4 were associated with poor functional outcome, and increased risk of poor functional outcome by 144% (OR: 2.44; 95% confidence interval (CI): 1.22-5.03) and 602% (7.02; 3.11-12.24), respectively. Interestingly, RBP4 improved the NIHSS score (area under the curve (AUC) of the combined model, 0.79; 95% CI: 0.74-0.85; P<0.001). The data showed that elevated serum levels of RBP4 at admission were associated with severity and prognosis of AIS, suggesting that vitamin A metabolism or impaired insulin signaling could be involved.

Proteomic and bioinformatic discovery of biomarkers for diabetic nephropathy

Diabetes is associated with numerous metabolic and vascular risk factors that contribute to a high rate of micro-vascular and macro-vascular disorders leading to mortality and morbidity from diabetic complications. In this case, the major cause of death in overall diabetic patients results from diabetic nephropathy (DN) or renal failure. The risk factors and mechanisms that correspond to the development of DN are not fully understood and so far, no specific and sufficient diagnostic biomarkers are currently available other than micro- or macroalbuminuria. Therefore, this review describes current and novel protein biomarkers in the context of DN as well as probable proteins biomarkers associated with pathological processes for the early stage of DN via proteomics data together with bioinformatics. In addition, the mechanisms involved in early development of diabetic vascular disorders and complications resulting from glucose induced oxidative stress will also be explored.

Childhood retinol-binding protein 4 (RBP4) levels predicting the 10-year risk of insulin resistance and metabolic syndrome: the BCAMS study

Background

Elevated retinol-binding protein 4 (RBP4) levels may contribute to the development of metabolic abnormalities, but prospective studies evaluating the association between childhood RBP4 levels and metabolic syndrome (MS) in adulthood are lacking. We investigated whether RBP4 levels during childhood predict cardiometabolic risk at 10-year follow-up.

Methods

The relationships between RBP4 levels, the established adipokines (leptin and adiponectin) and the components of MS were examined in 3445 school-aged children recruited in 2004 for the Beijing Child and Adolescent Metabolic Syndrome study. In 2015, 352 of these individuals completed an in-depth follow-up examination.

Results

Participants with higher childhood RBP4 levels had adverse cardiometabolic profiles at follow-up. Those with incident or persistent MS had higher baseline RBP4 levels than those who never exhibited the elements of MS. Moreover, baseline RBP4 predicted hyperglycemia (OR per SD increase = 1.48, P = 0.009), elevated triglyceride (OR = 1.54, P < 0.001), elevated blood pressures (OR = 1.46, P = 0.015), MS (OR = 1.68, P = 0.002) and insulin resistance (OR = 1.44, P = 0.015) in the 10-year follow-up phase, independent of baseline BMI. Significant improvements were seen for the net reclassification improvement and integrated discrimination index after adding childhood RBP4 levels into the risk models using conventional cardiometabolic risk factors in predicting MS at follow-up (P < 0.05). Leptin and adiponectin demonstrated the expected associations with metabolic disorders.

Conclusions

Childhood RBP4 serves as a risk factor for subsequent development of MS and its components, independent of pediatric obesity. Incorporating childhood RBP4 into conventional cardiometabolic risk assessment models significantly improves the prediction of MS.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0707-y) contains supplementary material, which is available to authorized users.

Association of RBP4 genetic variants with childhood obesity and cardiovascular risk factors

BACKGROUND

Recent data suggest that retinol-binding protein 4 (RBP4) gene variants could be associated with a risk of obesity and its co-morbidities, such as metabolic syndrome, which increases the risk of developing type 2 diabetes mellitus and cardiovascular disease.

OBJECTIVES

The present study examined the potential association of RBP4 single nucleotide polymorphisms (SNPs) with childhood obesity and its metabolic complications.

METHODS

Four RBP4 SNPs, rs3758538 (3944A>C), rs3758539 (4406G>A), rs12265684 (12177G>C) and rs34571439 (14684T>G), were genotyped in a population of 180 Spanish Caucasian children (97 obese and 83 normal-weight children). Association of RBP4 SNPs with obesity, metabolic risk factors (blood pressure, triglycerides, high-density lipoprotein cholesterol, insulin resistance) and markers of vascular inflammation, such as high-sensitive C-reactive protein (hs-CRP), was tested.

RESULTS

We found SNP rs3758538 to be associated with obesity (p = 0.007). Specifically, each copy of the minor allele C was associated with an increased risk of obesity, by more than twofold, in respect of being homozygous for the major allele A (odds ratio = 2.4; 95% confidence interval = 1.2-4.8). The rs3758538 and rs34571439 RBP4 SNPs correlated with plasma RBP4 levels. The SNPs rs12265684 and rs34571439 correlated with plasma triglyceride levels. The rs34571439 was also associated to hs-CRP levels. Marginal association of RBP4 SNPs with plasma high-density lipoprotein levels (rs34571439), blood pressure (rs12265684) and insulin resistance (rs3758539) was also observed.

CONCLUSIONS

These findings suggest that childhood obesity may be associated with variations in RBP4 gene. The presence of selective SNPs in the RBP4 gene may account for metabolic complications.

Retinol binding protein 4 in relation to diet, inflammation, immunity, and cardiovascular diseases

Retinol binding protein 4 (RBP4), previously called retinol binding protein (RBP), is considered a specific carrier of retinol in the blood. It is also an adipokine that has been implicated in the pathophysiology of insulin resistance. RBP4 seems to be correlated with cardiometabolic markers in inflammatory chronic diseases, including obesity, type 2 diabetes, metabolic syndrome, and cardiovascular diseases (CVDs). It has recently been suggested that inflammation produced by RBP4 induces insulin resistance and CVD. The clinical relevance of this hypothesis is discussed in this review. Knowledge concerning the association of RBP4 with inflammation markers, oxidative stress, and CVDs as well as concerning the role of diet and antioxidants in decreasing RBP4 concentrations are discussed. Special attention is given to methodologies used in previously published studies and covariates that should be controlled when planning new studies on this adipokine.

Short Sleep Duration Is Related to Emerging Cardiovascular Risk Factors in Obese Children

OBJECTIVE

The aim of the present study was to evaluate the influence of sleep duration on cardiovascular risk factors in obese children.

METHODS

Cross-sectional analysis of 90 obese children ages 7 to 16 years. Anthropometric and clinical evaluation with specification of dietary and lifestyle habits was carried out during an office visit. Sleep duration was evaluated by the BEARS (B = bedtime issues, E = excessive daytime sleepiness, A = night awakening, R = regularity and duration of sleep, S = snoring) questionnaire on children's sleep characteristics. Sleep time adequacy by age was assessed according to the criteria of the National Sleep Foundation. Biochemical blood variables indicative of metabolic risk (glucose, lipid profile, and insulin) were obtained. Emergent new factors of metabolic risk, including high-sensitive C-reactive protein, γ-glutamyltranspeptidase, homocysteine, retinol-binding protein 4 (RBP4), thyroid-stimulating hormone (TSH), inflammatory markers, and the adipokines leptin, adiponectin, and ghrelin were also evaluated. The relations between the duration of sleep and these variables were analyzed by general lineal model analysis. Significant variables were introduced in logistic regression analysis to determine the odds ratio (OR) and 95% confidence interval (CI) of cardiometabolic factors with respect to sleep.

RESULTS

Children who slept for short duration were significantly more at risk of severe central obesity. In the regression model, the mean arterial pressure (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.02-1.17, P = 0.008), homocysteine (OR 1.41, 95% CI 1.08-1.84, P = 0.013), RBP4 (OR 1.78, 95% CI 1.15-2.78, P = 0.010), and TSH (OR 2.01, 95% CI 1.21-3.34, P = 0.007) remain as significant independent predictors related to short sleep duration. We did not find any association between sleep duration and inflammatory markers or adipokines.

CONCLUSIONS

Short sleep duration increases the severity of obesity and is related to cardiovascular risk factors in children.

Left ventricular diastolic function and cardiometabolic factors in obese normotensive children

BACKGROUND AND AIM

Left ventricular (LV) hypertrophy and diastolic function have been found to be associated with obesity and hypertension in adults. However, there are scarce data about the association of obesity itself to cardiac alteration in children. The aim of this study was to detect early changes in LV structure and function in obese children and whether they are associated with the biomarkers of metabolic risk and endothelial activation.

METHODS AND RESULTS

A total of 130 children aged 7-16 years (88 obese and 42 normal-weight children) were studied. All children had normal resting blood pressure. Two-dimensional ultrasound with M-mode imaging was performed to assess the LV mass index (LVMi), calculated as LV mass/height(2.7), and the peak diastolic of pulmonary venous flow velocity (PVFD). Tissue Doppler imaging was used to analyze ventricular performance through the ratio of the transmitral peak early filling velocity to the early average diastolic peak myocardial velocity (E/E'). The indicators of metabolic control, inflammation, and endothelial cell activation were evaluated. Compared to the controls, the obese subjects had significantly higher LVMi and E/E' and lower PVFD values, the two latest being found especially in severely obese subjects. In the multivariate analysis, the parameters of diastolic function (E/E' and PVFD) were independently associated with obesity, apolipoprotein A1, soluble vascular cell endothelial molecule-1 (sVCAM-1), and retinol-binding protein 4 (RBP4).

CONCLUSION

An echocardiographic evaluation of diastolic function is a useful tool to detect early cardiac changes in obese children. Emergent cardiovascular risk markers such as apolipoprotein A1, RBP4, and sVCAM-1 are associated with the parameters of diastolic function.