Serum Retinol-binding Protein 4 Concentrations Research Articles

Retinol-binding protein 4 as a promising serum biomarker for the diagnosis and prognosis of hepatocellular Carcinoma

BackgroundThe prognosis of hepatocellular carcinoma (HCC) is universally poor. Early diagnosis plays a pivotal role in determining the outcome of HCC. MethodsWe employed a comparative proteomics approach to identify potential biomarkers and validated the application of retinol-binding protein 4 (RBP4) as a biomarker for HCC. RBP4 protein expression was examined in liver tissues from 80 HCC patients through immunohistochemical analysis. Serum RBP4 concentrations were measured by ELISA in a cohort comprising 290 HCC patients, matched 202 chronic hepatitis B patients and 269 healthy controls. Survival data were collected from HCC patients. The diagnostic and prognostic values of RBP4 were evaluated using receiver operating curve (ROC) analysis. ResultsThe validation results demonstrated a significant reduction in RBP4 levels in both liver tissues and serum samples from HCC patients. ROC analysis of the diagnostic value of RBP4 revealed an AUC of 0.879 (95 % CI: 0.854∼0.903) for HCC. When combined with AFP, the AUC increased to 0.919, with a sensitivity of 87.9 % and specificity of 80 %. Survival analysis revealed significantly reduced overall survival time in individuals with low-expression of RBP4 compared to those with high-expression. The joint prognostic model exhibited an AUC of 0.926 (95 % CI: 0.888∼0.964), which was significantly higher than that of AFP alone (AUC=0.809; P <0.0001). ConclusionsRBP4 shows a great potential as a biomarker with appreciable diagnostic value, complementing the AFP in HCC diagnosis. Additionally, it holds promise as a prognostic biomarker that, when integrated into a combined prognostic model, could greatly improve HCC prognosis efficiency.

Does Retinol-Binding Protein 4 (holo- and apo-RBP4) Increase or Remain Constant in Sera from Patients with Hypothyroidism?

Retinol-binding protein 4 (RBP4) is a retinol transporter in the blood plasma. Many diseases alter the plasma or serum levels of RBP4. Since serum RBP4 concentrations have been reported to decrease in hyperthyroidism, this study investigated whether serum RBP4 concentrations increased or remained constant in hypothyroidism. In sera from patients with hypothyroidism (n=71), hyperthyroidism (n=30), and healthy subjects (n=20), serum concentrations of RBP4 (sum of holo- and apo-RBP4), retinol, albumin, creatinine, and related constituents were measured, and RBP4/retinol molar ratio (as an index of apo-RBP4) and estimated glomerular filtration rate (eGFR) were calculated. The results showed that serum RBP4 concentrations tended to increase with decreasing free thyroxine concentrations, but there were no significant differences among patients with hypothyroidism, hyperthyroidism, and healthy subjects. When patients with hypothyroidism were subdivided by serum RBP4 level using 2.1 μmol/L cut-off value, patients with >2.1 μmol/L were revealed to be patients with older age having lower tri-iodothyronine, higher holo-RBP4, higher apo-RBP4, higher retinol, higher RBP4/retinol molar ratio, and lower eGFR than those in patients with <2.1 μmol/L. Multiple regression analysis showed significant associations between serum RBP4 levels and explanatory variables (retinol and eGFR). Although serum levels of RBP4 prior to the onset of renal dysfunction may affect the present concentrations, we conclude that the increase of serum RBP4 (both holo- and apo-RBP4) in patients with hypothyroidism was attributed to the decline in eGFR. In contrast, serum RBP4 concentration remained constant without renal dysfunction.

Are variants of the RBP4 gene associated with serum retinol-binding protein 4 concentrations and carotid intima-media thickness values in women with obesity?

IntroductionSeveral studies showed the correlation of retinol-binding protein 4 (RBP4) with increased cardiovascular risk - including higher values of carotid intima-media thickness (cIMT) - particularly in individuals with obesity. ObjectivesOur study aimed to investigate the impact of rs10882273; rs3758538; rs3758539, and rs7094671 RBP4 gene variants on RBP4 serum concentrations as well as cIMT values (a marker of subclinical atherosclerosis) among female patients with obesity. Patients and methodsWe recruited 74 women with obesity and 24 women without obesity as a study and control group, respectively. The genotypic and allelic frequencies of RBP4 gene variants were evaluated for associations with serum RBP4 and cIMT. ResultsThe median serum RBP4 concentrations were 20.30 µg/mL and 19.80 µg/mL in the patients and control group, respectively (p = 0.740). No significant differences were seen in cIMT values between the two studied groups (0.60 [0.50–1.00] vs. 0.60 ± 0.10 in the patient and control group, respectively); however, the results were close to reaching significance (p = 0.071), similar as in observed association of the minor haplotype AA for rs7084671 and rs375839 with female obesity (p = 0.0559). The correlation analysis showed no significant differences between RBP4 gene variants with serum RBP4 and cIMT. ConclusionsAccording to our knowledge, this is the first study investigating the association between RBP4 gene variants and serum RBP4 and cIMT among Polish female patients with obesity. However, our results show that genetic variants rs10882273, rs3758538, rs3758539, and rs7094671 of the RBP4 gene are not associated with RBP4 serum concentrations or cIMT values among women with obesity.

Serum Retinol Binding Protein 4 as a Potential Biomarker for Sarcopenia in Older Adults.

Sarcopenia is characterized by progressive loss of muscle mass and function due to aging. Retinol-binding protein 4 (RBP4) is an adipokine with pro-inflammatory effects. However, the change of RBP4 concentration and its role in sarcopenia remains unclear. The aim of this study was to evaluate the association of serum RBP4 level with sarcopenia in the older adults. A total of 816 community-dwelling older adults aged ≥60 years were enrolled. Serum RBP4 was measured by enzyme-linked immunosorbent assay. Appendicular skeletal muscle mass index (ASMI), grip strength, and gait speed were measured. We found that serum RBP4 levels were higher in patients with sarcopenia when compared with those without sarcopenias (44.3 [33.9-57.7] vs 38.0 [28.0-48.4] μg/mL). Receiver operating characteristic curve analysis indicated that the optimal cutoff value of serum RBP4 level that predicted sarcopenia was 38.79 μg/mL with a sensitivity of 67.8% and a specificity of 53.3%. Multivariate logistic regression analysis showed that the subjects with a higher level of RBP4 had a higher risk of sarcopenia (adjusted odds ratio [OR] = 2.036, 95% CI = 1.449-2.861). Serum RBP4 concentration was negatively correlated with grip strength (r = -.098), gait speed (r = -.186), and AMSI (r = -.096). Moreover, serum RBP4 levels were higher in patients with severe sarcopenia when compared with those with moderate sarcopenia (49.0 [37.3-61.2] vs 40.4 [31.3-51.2] μg/mL). Taken together, our results demonstrate that serum RBP4 level is correlated with the risk and severity of sarcopenia in the older adults, indicating that RBP4 might serve as a surrogate biomarker for the screening and evaluation of sarcopenia.

Association Between Circulating Retinol-Binding Protein 4 and Adverse Cardiovascular Events in Stable Coronary Artery Disease.

BackgroundThe predictive role of retinol-binding protein 4 (RBP4) in the adverse prognosis of patients with stable coronary artery disease (CAD) has not been well-defined. We thus conducted this cohort study to investigate the association between circulating RBP4 level and major adverse cardiovascular events (MACEs) in Chinese patients with stable CAD.MethodsPatients with stable CAD and serum RBP4 concentration measurement at admission between July 2012 and January 2015 were included. The primary outcome in this study was incident MACEs, which included acute coronary syndrome, heart failure, stroke, peripheral vascular disease, and cardiovascular death. Cox proportional hazards regression was adopted to investigate the association between RBP4 and the incidence of MACEs.ResultsA total of 840 patients with stable CAD were analyzed. The mean age of patients was 61.2 ± 15.9 years, and 56.1% of them were men. After a median follow-up of 2.3 years, 129 MACEs were observed. Compared to participants exposed to the first quartile of serum RBP4 level, those in the second, the third, and the fourth quartiles had associated hazard ratios (HRs) of 2.38 [95% confidence interval (CI): 1.33–4.26], 2.35 (95% CI: 1.31–4.21), and 2.27 (95% CI: 1.28–4.04) after adjusted for confounders, respectively. Every 5 μg/ml increment in serum RBP4 concentration was associated with an adjusted HR of 1.13 (95% CI: 1.05–1.22) for the occurrence of MACEs. Subgroup analyses suggested no significant modifying effects of baseline characteristics for the association between RBP4 and MACEs in patients with stable CAD.ConclusionOur finding suggested that the higher circulating RBP4 level was significantly associated with an increased risk of MACEs in patients with stable CAD.

Association of Retinol-Binding Protein 4 with Arteriovenous Fistula Dysfunction in Hemodialysis Patients

Background: Arteriovenous fistula (AVF) is the most common vascular access for patients undergoing hemodialysis (HD). Neointimal hyperplasia (NIH) might be a potential mechanism of AVF dysfunction. Retinol-binding protein 4 (RBP4) may play an important role in the pathogenesis of NIH. The aim of this study was to investigate whether AVF dysfunction is associated with serum concentrations of RBP4 in HD subjects. Methods: A cohort of 65 Chinese patients undergoing maintenance HD was recruited between November 2017 and June 2019. The serum concentrations of RBP4 of each patient were measured with the ELISA method. Multivariate logistic regression was used to analyze data on demographics, biochemical parameters, and serum RBP4 level to predict AVF dysfunction events. The cutoff for serum RBP4 level was derived from the highest score obtained on the Youden index. Survival data were analyzed with the Cox proportional hazards regression analysis and Kaplan-Meier method. Results: Higher serum RBP4 level was observed in patients with AVF dysfunction compared to those without AVF dysfunction events (174.3 vs. 168.4 mg/L, p = 0.001). The prevalence of AVF dysfunction events was greatly higher among the high RBP4 group (37.5 vs. 4.88%, p = 0.001). In univariate analysis, serum RBP4 level was statistically significantly associated with the risk of AVF dysfunction (OR = 1.015, 95% CI 1.002–1.030, p = 0.030). In multivariate analysis, each 1.0 mg/L increase in RBP4 level was associated with a 1.023-fold-increased risk of AVF dysfunction (95% CI for OR: 1.002–1.045; p = 0.032). The Kaplan-Meier survival analysis indicated that the incidence of AVF dysfunction events in the high RBP4 group was significantly higher than that in the low-RBP4 group (p = 0.0007). Multivariate Cox regressions demonstrated that RBP4 was an independent risk factor for AVF dysfunction events in HD patients (HR = 1.015, 95% CI 1.001–1.028, p = 0.033). Conclusions: HD patients with higher serum RBP4 concentrations had a relevant higher incidence of arteriovenous dysfunction events. Serum RBP4 level was an independent risk factor for AVF dysfunction events in HD patients.

Retinol binding protein 4 levels relate to the presence and severity of coronary artery disease.

BackgroundThe previous studies have showed that serum retinol binding protein 4 (RBP4) levels increase in metabolic disorders which are closely associated with cardiovascular diseases (CVD). However, the human studies investigating the role of RBP4 in CVD are conflicted. Therefore, we aimed to evaluate the relationship between RBP4 with the presence and severity of coronary artery disease (CAD) in this study.Methods55 patients with presenting acute coronary syndrome (ACS) and 43 control subjects who had various cardiovascular risk factors with normal coronary artery on coronary angiography were included in this study. The serum RBP4 concentrations were measured using ELISA method, clinically and anatomically score models were used to assess the severity of coronary lesion.ResultsSerum RBP4 levels were significantly higher in patients with ACS compared to the without ACS (68.40 ± 47.94 mg/L vs. 49.46 ± 13.64 mg/L; p = 0.014). RBP4 was correlated with GENSINI and SYNTAX I score (r = 0.286 p = 0.034; r = 0.403 p = 0.002 respectively). However, there was no relationship between RBP4 and GRACE score.ConclusionsThe serum RBP4 levels increase in patients with CAD and its increased levels may be correlated with CAD severity.

Retinol-binding protein 4 mRNA translation in hepatocytes is enhanced by activation of mTORC1.

Increased expression of the peptide hormone retinol-binding protein 4 (RBP4) has been implicated in the development of insulin resistance, type 2 diabetes, and visual dysfunction. Prior investigations of the mechanisms that influence RBP4 synthesis have focused solely on changes in mRNA abundance. Yet, the production of many secreted proteins is controlled at the level of mRNA translation, as it allows for a rapid and reversible change in expression. Herein, we evaluated Rbp4 mRNA translation using sucrose density gradient centrifugation. In the liver of fasted rodents, Rbp4 mRNA translation was low. In response to refeeding, Rbp4 mRNA translation was enhanced and RBP4 levels in serum were increased. In H4IIE cells, refreshing culture medium promoted Rbp4 mRNA translation and expression of the protein. Rbp4 mRNA abundance was not increased by either experimental manipulation. Enhanced Rbp4 mRNA translation was associated with activation of the kinase mechanistic target of rapamycin in complex 1 (mTORC1) and enhanced phosphorylation of the translational repressor eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). In H4IIE cells, expression of a 4E-BP1 variant that is unable to be phosphorylated by mTORC1 or suppression of mTORC1 with rapamycin attenuated activity of a luciferase reporter encoding the Rbp4 mRNA 5'-untranslated region (UTR). Purine substitutions to disrupt a terminal oligopyrimidine (TOP)-like sequence in the Rbp4 5'-UTR prevented the suppressive effect of rapamycin on reporter activity. Rapamycin also prevented upregulation of Rbp4 mRNA translation in the liver and reduced serum levels of RBP4 in response to feeding. Overall, the findings support a model in which nutrient-induced activation of mTORC1 upregulates Rbp4 mRNA translation to promote RBP4 synthesis.NEW & NOTEWORTHY RBP4 plays a critical role in metabolic disease, yet relatively little is known about the mechanisms that regulate its production. Herein, we provide evidence for translational control of RBP4 synthesis. We demonstrate that activation of the nutrient-sensitive kinase mTORC1 promotes hepatic Rbp4 mRNA translation. The findings support the possibility that targeting Rbp4 mRNA translation represents an alternative to current therapeutic interventions that lower serum RBP4 concentration by promoting urinary excretion of the protein.

Association of Serum Retinol-Binding Protein 4 Concentration With Risk for and Prognosis of Amyotrophic Lateral Sclerosis

Knowledge about the metabolic states of patients with amyotrophic lateral sclerosis (ALS) may provide a therapeutic approach. To investigate the association between the onset and prognosis of ALS and serum retinol-binding protein 4 (RBP4) concentration as a biomarker for insulin resistance and vitamin A metabolism. Case-control design for risk factors of ALS; cohort design for prognostic factors within ALS cases. Between October 1, 2010, and June 30, 2014, a population-based case-control study with randomly selected controls was established based on the ALS Registry Swabia in southern Germany, with a target population of 8.4 million inhabitants. Response rates were 64.8% among the cases and 18.7% among the controls. The dates of analysis were April 2016 to May 2017. Serum samples were measured for RBP4. Information on covariates was assessed by an interview-based standardized questionnaire. Main outcomes and measures were adjusted odds ratios for risk of ALS associated with serum RBP4 concentration, as well as time to death associated with RBP4 concentration at baseline in ALS cases only. Conditional logistic regression was applied to calculate multivariable odds ratios for risk of ALS. Survival models were used in cases only to appraise their prognostic value. Data from 289 patients with ALS (mean [SD] age, 65.7 [10.5] years; 172 [59.5%] male) and 504 controls (mean [SD] age, 66.3 [9.8] years; 299 [59.3%] male) were included in the case-control study. Compared with controls, ALS cases were characterized by lower body mass index, less educational attainment, smoking, light occupational work intensity, and self-reported diabetes. The median serum RBP4 concentration was lower in ALS cases than in controls (54.0 vs 59.5 mg/L). In the multivariable model, increasing RBP4 concentration was associated with reduced odds for ALS (top vs bottom quartile odds ratio, 0.36; 95% CI, 0.22-0.59; P for trend <.001), which persisted after further adjustment for renal function and for leptin and adiponectin. Among 279 ALS cases during a median follow-up of 14.5 months, 104 died (mean [SD] age, 68.9 [10.3] years; 56 [53.9%] male). In this ALS cohort, an inverse association was found between serum RBP4 concentration as a continuous measure and survival. RBP4 was inversely related to risk for and prognosis of ALS, suggesting that vitamin A metabolism or impaired insulin signaling could be involved. Further research, including a prospective design and other biological markers, is necessary to clarify the role of insulin resistance in the pathogenesis of ALS.

Identification of Transthyretin Cardiac Amyloidosis Using Serum Retinol-Binding Protein 4 and a Clinical Prediction Model

Transthyretin cardiac amyloidosis (ATTR) is an underrecognized cause of heart failure (HF) in older individuals, owing in part to difficulty in diagnosis. ATTR can result from substitution of valine for isoleucine at codon 122 of the transthyretin (TTR) gene (V122I), present in 3.43% of African American individuals. To examine whether serum retinol-binding protein 4 (RBP4), an endogenous TTR ligand, could be used as a diagnostic test for ATTR V122I amyloidosis. In this combined prospective and retrospective cohort study performed at a tertiary care referral center, 50 African American patients 60 years or older with nonamyloid HF and cardiac wall thickening prospectively genotyped from September 1, 2014, through December 31, 2015, and a comparator cohort of 25 patients with biopsy-proven ATTR V122I amyloidosis recruited from September 1, 2009, through November 31, 2014, comprised the development cohort. Twenty-seven African American patients and 9 patients with ATTR V122I amyloidosis comprised the validation cohort. Circulating RBP4, TTR, B-type natriuretic peptide (BNP), and troponin I (TnI) concentrations and electrocardiographic, echocardiographic, and clinical characteristics were assessed in all patients. Receiver operating characteristic (ROC) analysis was performed to identify optimal thresholds for ATTR V122I amyloidosis identification. A clinical prediction rule was developed using penalized logistic regression, evaluated using ROC analysis and validated in an independent cohort of cases and controls. Age, sex, and BNP and TnI concentrations were similar between the 25 patients with ATTR V122I amyloidosis (mean [SD] age, 72.2 [7.4] years; 18 male [72%]) and the 50 controls (mean [SD] age, 69.2 [5.7] years; 31 male [62%]). Serum RBP4 concentration was lower in patients with ATTR V122I amyloidosis compared with nonamyloid controls (31.5 vs 49.4 µg/mL, P < .001), and the difference persisted after controlling for potential confounding variables. Left ventricular ejection fraction was lower in patients with ATTR V122I amyloidosis (mean [SD], 40% [14%] vs 57% [14%], P < .001), whereas interventricular septal diameter was higher (mean [SD], 16 [3] vs 14 [2] mm, P < .001). The ROC analysis identified RBP4 as a sensitive identifier of ATTR V122I amyloidosis (area under the curve [AUC] = 0.78; 95% CI, 0.67-0.88). A clinical prediction algorithm composed of RBP4, TTR, left ventricular ejection fraction, interventricular septal diameter, mean limb lead QRS voltage, and grade 3 diastolic dysfunction yielded excellent discriminatory capacity for ATTR V122I amyloidosis (AUC = 0.97; 95% CI, 0.93-1.00), whereas a 4-parameter model, including RBP4 concentration, retained excellent discrimination (AUC = 0.92; 95% CI, 0.86-0.99). The models maintained excellent discrimination in the validation cohort. A prediction model using circulating RBP4 concentration and readily available clinical parameters accurately discriminated ATTR V122I amyloidosis from nonamyloid HF in a case-matched cohort. This clinical algorithm may be useful for identification of ATTR V122I amyloidosis in elderly African American patients with HF.

Medullary Thyroid Carcinoma--Circulating Status of Vaspin and Retinol Binding Protein-4 in Iranian Patients.

Vaspin and Retinol binding protein-4 (RBP4) are new adipokines mainly produced by adipose tissue. Considering that medullary thyroid carcinoma (MTC) is a malignant neuroendocrine tumor, and to date the relationship between serum levels of vaspin and RBP4 with MTC has not been studied, in this matched case-control study we evaluated their possible significance to this tumor type. A total of 45 patients with MTC (21 males and 24 females) and 45 healthy persons as a control group (24 males and 21 females) were selected. The two groups were matched for age, sex and body mass index. Serum Vaspin and RBP4 levels were measured by enzyme-linked immunosorbent assay (ELISA) methods in both groups. Also, weight and height were measured and body mass index was calculated too. In total, patients with MTC had significantly higher serum vaspin levels compared to the controls (0.52 ng/ml vs. 0.45 ng/ml, P=0.0241). However, no significant difference was found in serum RBP4 concentrations between the patients with MTC and the controls (15.2±2.55 μg/ml versus 15.1±3.34 μg/ml, p>0.05). The results of this study demonstrated that serum RBP4 levels in MTC patients are not significantly different from those found in healthy individuals and did not correlate with MTC. On the other hand, higher levels of serum vaspin are associated with an increased risk of MTC. Thus Vaspin may be a novel and promising biomarker for diagnosis or confirmation of MTC in conjunction other specific tumor markers.

The effect of topical treatment and psoriasis severity on serum retinol-binding protein-4 levels

Objective: Psoriasis has been considered as chronic systemic disease. Retinol-binding protein-4 (RBP-4) might play a role in psoriasis and its comorbidities. The aim of this study was to investigate the associations between serum RBP-4 levels and disease severity, indicators of inflammation or metabolic syndrome and changes after topical treatment in psoriatic patients. Methods: Thirty-seven patients with relapse of plaque-type psoriasis and 16 healthy volunteers were examined. Blood samples were collected before and after 14 days of therapy. Serum RBP-4 concentrations were examined by enzyme-linked immunosorbent assay for correlation with psoriasis area and severity index (PASI), body mass index (BMI), inflammatory and biochemical markers and with efficacy of topical treatment. Results: RBP-4 serum levels were increased in psoriatics compared to the controls, but without statistical significance (p = 0.2). No significant correlations between investigated adipokine and several indicators of metabolic disorders, nor BMI or PASI were found. A significant negative correlation with CRP was noted. After topical treatment serum RBP-4 level did not significantly change (p = 0.3), despite clinical improvement. Conclusion: RBP-4 might have a protective role in terms of chronic inflammation and comorbidities of psoriasis. The adipokine is presumably not useful in determining severity and the effectiveness of antipsoriatic treatment.

Elevated retinol binding protein 4 induces apolipoprotein B production and associates with hypertriglyceridemia.

A high level of retinol binding protein 4 (RBP4) is reported to be associated with insulin resistance in humans. However, evidence from large-scale populations about the relationship between serum RBP4 and metabolic phenotypes is scarce. In the present study, we aimed to evaluate serum RBP4 distribution and its association with metabolic phenotypes among middle-aged and elderly Chinese. Serum concentrations of RBP4 in a cross-sectional sample of 2780 Chinese population aged 50-70 years old in Guangzhou were measured by ELISA. The mean of serum RBP4 concentration was 28.04 μg/mL for male and 37.76 μg/mL for female (P < .01), respectively. Circulating RBP4 was positively correlated with serum triglyceride and apolipoprotein B (apoB) concentrations. The odds ratio (OR) was substantially higher for hypertriglyceridemia (OR, 3.26; 95% confidence interval, 2.36-4.51) in the highest RBP4 quartile compared with those in the lowest quartile after multiple adjustment for confounders. Furthermore, serum RBP4 was significantly associated with fasting glucose, insulin levels, and homeostasis model assessment index-insulin resistance (HOMA-IR). Moreover, we showed that RBP4 enhanced microsomal triglyceride transfer protein (MTP) expression and activity via up-regulation of protein disulfide isomerase (PDI), suppressed low-density lipoprotein receptor (LDLR) expression, and impaired insulin-signaling pathway, leading to inductions in apoB secretion both in vitro and in vivo. Elevated circulating RBP4 concentrations were associated with higher risk of hypertriglyceridemia by inducing the secretion of triglyceride-rich apoB-containing lipoproteins.

Abstract 2144: Retinoid and carotenoid depletion in patients at high-risk for liver cancer

Abstract Approximately 3.2 million Americans are chronically infected with hepatitis C (HCV), forming the largest group at high-risk for hepatocellular carcinoma (HCC). Oxidative stress due to chronic inflammation impels the progression of chronic liver disease (CLD) &amp; subsequent HCC. Deficiencies in dietary antioxidants such as retinoids and carotenoids may represent a modifiable risk factor for HCC progression. This study aims to identify key predictors of serum antioxidant levels in patients with CLD, to quantify the association between systemic measures of oxidative stress and antioxidant status, and to examine the relationship between retinoid/carotenoid concentrations in serum and hepatic tissue. Patients with HCV undergoing liver biopsy (n=69) provided fasting blood, fresh tissue, urine, and responses to a diet history questionnaire (DHQ). We also collected serum and questionnaire data from healthy volunteers (n=11), and normal liver tissue from public repositories and patients without liver disease (n=11). Serum and tissue retinoid concentrations were obtained by mass spectroscopy. Serum retinol binding protein 4 (RBP4) was quantified by ELISA. Urine 8OHdG and F2α-isoprostanes were determined by mass spectroscopy. Dietary retinoid intake was estimated by DHQ. Associations between diet, serum and tissue retinoids, and urinary oxidative stress markers were assessed by Spearman correlation coefficients. Dietary β-carotene and lutein were associated with their respective serum concentrations (r = 0.24, p = 0.05; r = 0.33, p &amp;lt; 0.01). There was a significant downward trend for serum retinol, lycopene and RBP4 concentrations with progressive fibrosis; mean serum concentrations were lower in subjects with chronic HCV but no fibrosis compared to controls. Urinary isoprostanes levels were inversely correlated with serum retinol (r= -0.22, p = 0.05), β-carotene (r= -0.22 p = 0.05), and RBP4 (r= -0.25 p = 0.03). Urinary 8OHDG did not correlate with any serum retinoids or carotenoids. Serum β-carotene and lycopene were strongly associated with the respective tissue concentrations (r = 0.56, p&amp;lt;.01; r= 0.76 p&amp;lt; 0.01); however, serum retinol and tissue retinyl palmitate did not correlate in this population (r = -0.08 p = 0.55). There was a suggestive downward trend of tissue retinyl palmitate with increasing levels of fibrosis. Depletion of serum retinol, β-carotene, and RBP4 worsens with liver fibrosis severity. RBP4 might be a better marker for vitamin A status due to its stronger association with disease severity. Retinoid and carotenoid levels decline as disease progresses, and our data suggest that this decline occurs early in the disease process, even before fibrosis is apparent. In HCV patients, decreases in retinoid/carotenoid levels are accompanied by an increase in urinary F2α-isoprostanes, an indicator of lipid peroxidation due to oxidative stress. Dietary or chemopreventive strategies for replenishing antioxidant levels should be studied further. Citation Format: Yachana Kataria, Erika Enk Rueter, Ryan Deaton, Donald Jensen, Scott Cotler, Peter Gann. Retinoid and carotenoid depletion in patients at high-risk for liver cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2144. doi:10.1158/1538-7445.AM2014-2144

Association of Adipocytokines: Resistin and Retinol Binding Protein-4 with Severity of Preeclampsia and Insulin Resistance

Dysregulation of maternal circulating adipocytokines has been implicated in several obstetrical syndromes including preeclampsia (PE). It has been suggested that adipocytokines provide a molecular link between metabolic derangements and inflammatory response in complicated pregnancies. We aimed in this study to evaluate the relationship between serum levels of Retinol binding protein-4 (RBP-4) and Resistin with clinical, anthropometric and metabolic parameters of PE. This study included 3 groups: group 1 included 50 pregnant females with PE, group 2 included 50 healthy pregnant females and group 3 included 50 healthy non-pregnant female as a control group. For all groups anthropometric and clinical measurements were performed. Serum RBP-4, resistin, insulin were measured by ELISA and Insulin resistance was calculated by Hemostasis model assessment index (HOMA-IR). Our results showed that serum RBP-4 and resistin concentrations were elevated in PE [39(33.25-40.87) ug/ml] & [61(23.5-91.87) ng/ml] compared to normal pregnancy [18.5(8-27.87) ug/ml] & [25.5(12.7-49.12) ng/ml). Moreover, RBP4 but not resistin levels were elevated in severe cases relative to mild cases of PE. Serum levels of RBP4 showed positive significant correlation with [SBP (r=0.38, p= 0.001) & DBP (r=0.32, p=0.01)] which are markers of severity. Fasting insulin was positively correlated with RBP-4 (p=0.04). By multiple linear regression analysis, serum RBP-4 levels were significantly and positively correlated with SBP (P=0.01), while markers of adiposity were not independently associated with resistin. Conclusion: RBP-4 and resistin were up-regulated in PE, furthermore RBP-4 not resistin levels were independently associated with markers of severity of PE. However no clear relationship were observed between HOMA-IR with both RBP-4 and resistin and the role of Insulin resistance in PE was not clearly proved.

Decreased retinol-binding protein 4 in the sera of patients with end-stage renal disease after kidney transplantation.

Retinol-binding protein 4 (RBP4) is a novel adipokine that has been associated with insulin resistance and type 2 diabetes. Patients with end-stage renal disease (ESRD) have very high serum RBP4 levels. However, whether successful kidney transplantation alleviates these elevated serum RBP4 levels is unclear. The serum RBP4 levels of 24 ESRD patients were determined before transplantation and at 1 day, 1 week, and 1 month after kidney transplantation. The control group included 22 healthy subjects. Serum RBP4 concentrations were measured using a commercial kit via the immunologic turbidimetric method, and were related to biomarkers for renal and liver function. The serum RBP4 level of ESRD patients before kidney transplantation (160.8 ± 29.1 mg/L) was approximately 7-fold higher than that of normal controls (22.6 ± 11.0 mg/L; P = 0.000). The serum RBP4 level before transplantation was significantly higher than that at 1 day (65.3 ± 28.4 mg/L), 1 week (48.3 ± 22.9 mg/L), and 1 month after transplantation (53.1 ± 25.5 mg/L; P = 0.000). However, these values were still higher than those of controls (P = 0.000). Univariate regression analysis showed that the percent changes in serum RBP4 concentration before and after kidney transplantation were positively correlated with serum creatinine, blood urea nitrogen, phosphate, and pre-albumin concentrations and negatively correlated with the estimated glomerular filtration rate. The serum RBP4 concentration of patients with ESRD decreased significantly after kidney transplantation; therefore, we found that serum RBP4 concentration was related to renal function.

The Relative Dose Response Test Based on Retinol-Binding Protein 4 Is Not Suitable to Assess Vitamin A Status in Very Low Birth Weight Infants

Background: The relative dose response (RDR) test, which quantifies the increase in serum retinol after vitamin A administration, is a qualitative measure of liver vitamin A stores. Particularly in preterm infants, the feasibility of the RDR test involving blood is critically dependent on small sample volumes. Objectives: This study aimed to assess whether the RDR calculated with retinol-binding protein 4 (RBP4) might be a substitute for the classical retinol-based RDR test for assessing vitamin A status in very preterm infants. Methods: This study included preterm infants with a birth weight below 1,500 g (n = 63, median birth weight 985 g, median gestational age 27.4 weeks) who were treated with 5,000 IU retinyl palmitate intramuscularly 3 times a week for 4 weeks. On day 3 (first vitamin A injection) and day 28 of life (last vitamin A injection), the RDR was calculated and compared using serum retinol and RBP4 concentrations. Results: The concentrations of retinol (p < 0.001) and RBP4 (p < 0.01) increased significantly from day 3 to day 28. On day 3, the median (IQR) retinol-RDR was 27% (8.4-42.5) and the median RBP4-RDR was 8.4% (-3.4 to 27.9), compared to 7.5% (-10.6 to 20.8) and -0.61% (-19.7 to 15.3) on day 28. The results for retinol-RDR and RBP4-RDR revealed no significant correlation. The agreement between retinol-RDR and RBP4-RDR was poor (day 3: Cohen's κ = 0.12; day 28: Cohen's κ = 0.18). Conclusion: The RDR test based on circulating RBP4 is unlikely to reflect the hepatic vitamin A status in preterm infants.

Ghrelin- and GH-induced insulin resistance: no association with retinol-binding protein-4

ObjectiveSupraphysiological levels of ghrelin and GH induce insulin resistance. Serum levels of retinol-binding protein-4 (RBP4) correlate inversely with insulin sensitivity in patients with type 2 diabetes. We aimed to determine whether ghrelin and GH affect RBP4 levels in human subjects.Materials and methodsTo study GH-independent effects of ghrelin, seven hypopituitary men undergoing replacement therapy with GH and hydrocortisone were given ghrelin (5 pmol/kg per min) and saline infusions for 300 min in a randomized, double-blind, placebo-controlled, crossover design. Circulating RBP4 levels were measured at baseline and during a hyperinsulinemic–euglycemic clamp on both study days. To study the direct effects of GH, nine healthy men were treated with GH (2 mg at 2200 h) and placebo for 8 days in a randomized, double-blind, placebo-controlled, crossover study. Serum RBP4 levels were measured before and after treatment, and insulin sensitivity was measured by the hyperinsulinemic–euglycemic clamp technique.ResultsGhrelin acutely decreased peripheral insulin sensitivity. Serum RBP4 concentrations decreased in response to insulin infusion during the saline experiment (mg/l): 43.2±4.3 (baseline) vs 40.4±4.2 (clamp), P<0.001, but this effect was abrogated during ghrelin infusion (mg/l): 42.4±4.5 (baseline) vs 42.9±4.7 (clamp), P=0.73. In healthy subjects, serum RBP4 levels were not affected by GH administration (mg/l): 41.7±4.1 (GH) vs 43.8±4.6 (saline), P=0.09, although GH induced insulin resistance.Conclusionsi) Serum RBP4 concentrations decrease in response to hyperinsulinemia, ii) ghrelin abrogates the inhibitory effect of insulin on circulating RBP4 concentrations, and iii) ghrelin as well as GH acutely induces insulin resistance in skeletal muscle without significant changes in circulating RBP4 levels.

Association of retinol binding protein 4 with risk of gestational diabetes

AimWe investigated association of maternal retinol binding protein 4 (RBP4) with risk of gestational diabetes (GDM). MethodsGDM cases (N=173) and controls (N=187) were selected from among participants of a cohort study of risk factors of pregnancy complications. Early pregnancy (16 weeks on average) serum RBP4 concentration was measured using an ELISA-based immunoassay. Logistic regression was used to estimate unadjusted and adjusted odds ratios (ORs/aORs) and 95% confidence intervals (95%CI). ResultsMean serum RBP4 was significantly higher among GDM cases compared with controls (47.1 vs. 41.1μg/ml, respectively; p-value <0.05). Participants in the highest quartile for serum RBP4 had a 1.89-fold higher risk of GDM compared with participants in the lowest quartile (95%CI: 1.05–3.43). However, this relationship did not reach statistical significance after adjustment for confounders (aOR: 1.54; 95%CI: 0.82–2.90). Women who were ≥35 years old and who had high RBP4 (≥38.3μg/ml, the median) had a 2.31-fold higher risk of GDM compared with women who were <35 years old and had low RBP4 (<38.3μg/ml) (aOR: 2.31; 95%CI: 1.26–4.23; p-value for interaction=0.021). ConclusionOverall, there is modest evidence of a positive association of early pregnancy elevated RBP4 concentration with increased GDM risk, particularly among women with advanced age.

Higher Serum Retinol Binding Protein 4 May be a Predictor of Weak Metabolic Control in Chinese Patients with Type 2 Diabetes Mellitus

To investigate relationships between serum levels of retinol binding protein 4 (RBP4) and clinical and metabolic variables in Chinese patients with type 2 diabetes mellitus. A total of 513 patients (286 males/227 females) provided clinical and lifestyle data and blood and urine samples for analysis. Patients were stratified into four quartile groups according to serum RBP4 concentrations. RBP4 concentration was independently associated with gender, systolic blood pressure, serum triglyceride and creatinine levels, and estimated glomerular filtration rate (eGFR). Hypertension, dyslipidaemia, micro albuminuria and impaired eGFR (<60 ml/min per 1.73 m2) were significantly more prevalent in patients with the highest RBP4 levels than in those with the lowest levels. Increased serum RBP4 was associated with increased risk of hypertension, dyslipidaemia, micro albuminuria and impaired eGFR after adjusting for gender, age, body mass index and duration of diabetes. Serum RBP4 may be a useful marker of overall metabolic control in Chinese patients with type 2 diabetes mellitus.