Retinol-binding Protein 4 Levels Research Articles

The association between retinol binding protein 4 and peripheral neuropathy in type 2 diabetic patient

Background & Objective: The most common microvascular consequence of diabetes is peripheral neuropathy. A very common ailment that has a significant impact on a patient's quality of life is peripheral neuropathy (PN). The purpose of this study was to look into the possible link between retinol binding protein 4 (RBP4) and peripheral neuropathy in individuals with type 2 diabetes mellitus (T2D), as the relationship between RBP4 and PN is still unclear. Methodology: We enrolled 152 participants who were matched for age and sex in a case control study during August and December 2023. There were 50 healthy controls, 50 diabetic patients without PN, and 52 diabetic patients with PN. ELISA was used to measure serum RBP4. Results: Diabetic individuals with PN had significantly greater serum levels of RBP4 than diabetic patients without PN (P ˂ 0.001). Increased age (r = 0.262, P ˂ 0.01), DM duration (r = 0.565, P ˂ 0.01), and BMI (r = 0.183, P ˂ 0.05) were all substantially linked with RBP4 levels. RBP4 levels exhibited a negative correlation with high-density lipoproteins (HDL) and a positive correlation with total cholesterol, triglycerides, low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL). Conclusion: Elevated RBP4 level is strongly and independently linked with PN in type 2 diabetic patients, and may play an important role in PN progression. Abbreviations: DM - Diabetes mellitus; PN - peripheral neuropathy; PBP4 - retinol binding protein 4; T2D - type 2 diabetes mellitus Keywords: diabetes mellitus; peripheral neuropathy; retinol binding protein 4. Citation: Nafakhi IA, Abdalsada NH. The association between retinol binding protein 4 and peripheral neuropathy in type 2 diabetic patient. Anaesth. pain intensive care 2024;28(5):908−913; DOI: 10.35975/apic.v28i5.2563 Received: May 03, 2024; Reviewed: June 04, 2024; Accepted: August 23, 2024

Retinol-binding protein 4 is a potential biomarker of changes in lean mass in postmenopausal women.

Identifying biomarkers can help in the early detection of muscle loss and drive the development of new therapies. Research suggests a potential link between retinol-binding protein 4 (RBP4) and muscle mass, particularly in postmenopausal women. This study aimed to examine the association between baseline RBP4 levels and changes in appendicular lean mass (ALM), an indicator of muscle mass, in postmenopausal women. A 12-month follow-up period (n=153) included baseline and 12-month ALM assessments using DXA. ALM was normalized to squared height (ALMI). Baseline evaluations encompassed insulin resistance via HOMA-IR and immunoassay magnetic bead panel measurements of RPB4, IL-6, TNF-α, and IL-10. Postmenopausal women were categorized into higher (n=77) and lower (n=76) RPB4 groups based on baseline RPB4 values. Their changes in ALMI were compared using Mann-Whitney tests. General linear model was employed to evaluate the predictive power of baseline RBP4 for ALMI changes, adjusting for confounding variables: age, physical activity, smoking status, body fat, HOMA-IR, inflammatory markers (TNF-α and IL-6), and anti-inflammatory factor (IL-10). The higher RBP4 group exhibited a more pronounced reduction in ALMI compared to the lower RBP4 group (Higher RBP4 = -0.39kg/m2, 95% CI: -0.48 to -0.31kg/m2vs. Lower RBP4 = -0.24kg/m2, 95% CI: -0.32 to -0.15kg/m2, P=0.011). After adjusting for confounding factors, the association between baseline RBP4 changes and ALMI remained (b = -0.008, SE=0.002, P<0.001), indicating higher baseline RBP4 values linked to greater ALMI reduction. Our findings support RBP4 as a potential biomarker for changes in muscle mass in postmenopausal women.

Long-Term Prognostic Value of Adipocytokines in Patients with Acute Coronary Syndrome: An 8-Year Clinical Prospective Cohort Study.

To elucidate the predictive values of adipocytokines in patients with acute coronary syndrome (ACS). Overall, 297 patients with ACS were consecutively enrolled in this prospective cohort study between June 2015 and July 2017 and completed follow-up with a median follow-up time of 6.5 years. For consistency, the last visit date was June 20, 2023. Serum levels of retinol-binding protein-4 (RBP4), interleukin-1β (IL-1β), monocyte chemoattractant protein 1(MCP-1), adrenomedullin (ADM), netrin 1 (NTN 1), and omentin were measured using enzyme-linked immunosorbent assay. Follow-up data were collected during clinical visits or through telephone interviews at 1, 3, 6, 12 months, and annually. The primary endpoint was defined as major adverse cardiovascular events (MACEs), including all-cause mortality, rehospitalization for percutaneous coronary intervention, and severe angina requiring rehospitalization. All biomarkers displayed a good diagnostic ability of MACEs. The Kaplan-Meier curve showed that the cumulative survival rates of high level of RBP4, IL-1β, and MCP-1 and low level of the ADM, NTN1, and omentin had lower cumulative survival rates (Log rank tests: all p<0.05). After adjustment in the Cox hazard proportional model, the results were RBP4 ≥ 6.87 ng/mL, hazard ratio (HR)=2.512, p=0.003; IL-1β≥ 58.95 pg/mL, HR=3.809, p<0.001; MCP-1 ≥ 401.75 pg/mL, HR=4.047, p<0.001; ADM≤120.01 ng/mL, HR=3.930, p=0.008; NTN1 ≤63.7 pg/mL, HR=3.345, p=0.007; omentin ≤ 4.54 ng/mL, HR=2.830, p=0.004. P-values for interaction were > 0.05 in the sex, age, and dyslipidemia subgroups. Pro-inflammation adipocytokines RBP4, IL-1β, and MCP-1 increased and anti-inflammation biomarkers ADM, NTN1, and omentin decreased were independently associated with a higher risk of MACEs in patients with ACS.

Serum retinol binding protein 4 in individuals with essential hypertension and type 2 diabetes: A cross-sectional study.

Cardiometabolic disorders, notably primary hypertension and type 2 diabetes, present substantial global health challenges. The intricate interplay between metabolic and cardiovascular pathways has prompted extensive research into molecular mechanisms linking these conditions. The adipokine Retinol Binding Protein 4 (RBP4), initially recognized for retinol transport, has emerged as a potential biomarker in the network of metabolic and cardiovascular dysfunction. Recent studies implicate RBP4 in insulin resistance and its complications, including hypertension. This study explores RBP4 dynamics in patients with primary hypertension and type 2 diabetes, aiming to contribute valuable insights into diagnostic and therapeutic advancements in managing these interconnected disorders. This cross-sectional study, conducted over 2 years in a tertiary healthcare centre of North India, aimed to investigate the serum concentration of Retinol Binding Protein 4 (RBP4) in 119 participants diagnosed with primary hypertension and type 2 diabetes. Ethical guidelines were strictly followed, and comprehensive clinical assessments, including blood pressure measurements, were performed. RBP4 levels were quantified using an ELISA kit, alongside markers of insulin resistance. Statistical analyses, involving t-tests and correlation assessments, sought to unravel potential associations between RBP4, insulin resistance, and blood pressure parameters using SPSS 20.0. The study comprised 61 healthy control (HC) participants and 58 individuals diagnosed with both essential hypertension and type 2 diabetes (EH+T2D). EH+T2D participants were on average older (45.71 ± 9.29 years vs. 40.34 ± 9.47 years, P = 0.002). Dyslipidemia prevalence was markedly higher in EH+T2D (72.4% vs. 11.4%, P < 0.0001), accompanied by disrupted lipid profiles. Serum RBP4 concentration was significantly elevated in EH+T2D (49.17 ± 19.37 mg/L, P < 0.0001), suggesting its potential role in the shared pathophysiology of primary hypertension and type 2 diabetes. Pearson's correlation analysis revealed associations between RBP4 levels, metabolic, and cardiovascular parameters, underscoring its potential as a link between these conditions. Elevated serum RBP4 levels suggest its potential as a novel biomarker in the shared pathophysiology of primary hypertension and type 2 diabetes. The correlation analysis highlights the intricate interplay between metabolic, lipid, and cardiovascular parameters, emphasizing the need for holistic interventions.

Diagnostic and prognostic value of serum Cys-C, retinol-binding protein, and ischemia-modified albumin in patients with coronary heart disease: A diagnostic accuracy study.

The use of 3 biomarkers - cystatin-C (Cys-C), retinol-binding protein (RBP), and ischemia-modified albumin (IMA) - for the clinical classification and outcome of coronary heart disease (CHD) has not been adequately evaluated. We explored the serum levels of these 3 markers and evaluated their diagnostic and prognostic values in patients with CHD. This retrospective case-control study, conducted between June 2017 and June 2018, included 201 patients with CHD hospitalized at the Henan Provincial People's Hospital and 127 healthy individuals from Henan Provincial People's Hospital as controls. Cys-C, RBP, IMA levels, and other laboratory parameters in the 2 groups were determined, and patient outcomes were analyzed. Cys-C, RBP, and IMA levels were higher in the case group than in the control group (P < .05). Logistic regression analysis confirmed that these 3 biomarkers were independent risk factors for CHD. Each indicator has clinical significance in the diagnosis and prognosis of CHD, with RBP being the most significant. The AUC value for CHD detection using a combination of the 3 indicators was 0.783, and the sensitivity and specificity values were 78% and 74.6%, respectively. Simultaneous detection of Cys-C, RBP, and IMA could be an optimal method for early diagnosis and prognosis of CHD.

No evidence that retinol is protective for skin cancer.

With over 1.5 million new cases annually, skin cancers are the most commonly diagnosed group of cancers worldwide. Among these, melanoma and keratinocyte cancers (KC), comprising squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), are predominant. Retinol, a vitamin A derivative, is essential in the regulation of growth and differentiation of epidermal cells. Moreover, retinol exhibits antioxidant properties, protecting the skin against ultra-violet (UV) radiation induced oxidative damage. Existing research on the impact of retinol on melanoma, SCC and BCC development shows mixed results. Several dietary intake studies have suggested that higher retinol levels reduce skin cancer risk, however, others have failed to find this association. We used two-sample Mendelian randomization (MR) to explore if there is a causal relationship between retinol and the risk of developing melanoma, SCC or BCC. Genetically predicted circulating retinol levels were obtained from a genome wide association study (GWAS) meta-analysis of the INTERVAL (N=11,132) and METSIM (N=6,136) cohorts. Melanoma (30,134 cases and 375,188 controls), SCC (10,557 cases and 537,850 controls) and BCC (36,479 cases and 540,185 controls) risks were derived from published GWAS meta-analyses. We conducted two MR approaches. In the first MR we used a single SNP (rs10882283) that is associated with the levels of Retinol Binding Protein 4 (RBP4) as an instrument variable (IV) for circulating retinol levels. In the second MR we used all independent genetic variants that were strongly associated (P < 5 × 10-8) with retinol levels as IVs. Odds ratios (OR) for skin cancer were calculated for a one standard deviation (SD) increase in genetically predicted retinol levels. The single IV approach revealed that retinol levels were not significantly associated with risk of melanoma (OR = 1.04 [95% confidence interval 0.83, 1.31], P = 0.72), SCC (OR = 1.15 [0.87, 1.51], P = 0.32) or BCC (OR = 1.06 [0.90, 1.23], P = 0.50). Similar null results were observed with the multiple IV approach for melanoma (OR = 1.03 [0.95, 1.11], P = 0.54), SCC (OR = 1.01 [0.91, 1.13], P = 0.83), and BCC (OR = 1.04 [0.96, 1.12], P = 0.38). In conclusion, we found no evidence that circulating retinol levels were causally associated with the development of melanoma, SCC and BCC.

Changes in urinary renal injury markers in children with Mycoplasma pneumoniae pneumonia and a prediction model for related early renal injury

BackgroundThis study aims to analyse changes in urinary kidney injury markers in children with Mycoplasma pneumoniae pneumonia (MPP), investigate the risk factors for MPP-related acute kidney injury (AKI) and establish a model to predict MPP-related AKI.MethodsNinety-five children were enrolled based on the study’s inclusion and exclusion criteria. They were divided into a severe MPP (SMPP) group and a non-SMPP group and then into an AKI group and a non-AKI group according to the presence of AKI. A univariate logistic regression analysis was performed to explore the early risk factors for AKI. Based on a multivariate logistic regression analysis and a least absolute shrinkage and selection operator regression analysis, appropriate variables were selected to establish a prediction model, and R 4.2.2 software was used to draw nomograms and generate a dynamic nomogram website.ResultsSeven urinary kidney injury markers were abnormally elevated in the SMPP group and the non-SMPP group: urinary N-acetyl-β-D-glucosaminidase (NAG), β2-microglobulin, α1-microglobulin, retinol-binding protein, urinary immunoglobulin G, urinary transferrin and urinary microalbumin. Sixteen children were identified with AKI during hospitalisation. The AKI group had higher levels of urinary NAG, α1-microglobulin, β2-microglobulin, urinary microalbumin, urinary transferrin and retinol-binding protein than the non-AKI group (P < 0.05). The MPP-related AKI prediction model consists of four indicators (serum immunoglobulin M [IgM], C-reactive protein [CRP], urine NAG and sputum plug presence) and a dynamic nomogram.ConclusionUrinary kidney injury markers are often elevated in children with MPP; urinary NAG is the marker most likely to be elevated, and it is especially evident in severe cases. The nomogram of the prediction model, comprising serum IgM, CRP, urinary NAG and sputum plug presence, can predict the probability of AKI in children with MPP.

Simultaneous detection of multiple urinary biomarkers in patients with early-stage diabetic kidney disease using Luminex liquid suspension chip technology.

Several urinary biomarkers have good diagnostic value for diabetic kidney disease (DKD); however, the predictive value is limited with the use of single biomarkers. We investigated the clinical value of Luminex liquid suspension chip detection of several urinary biomarkers simultaneously. The study included 737 patients: 585 with diabetes mellitus (DM) and 152 with DKD. Propensity score matching (PSM) of demographic and medical characteristics identified a subset of 78 patients (DM = 39, DKD = 39). Two Luminex liquid suspension chips were used to detect 11 urinary biomarkers according to their molecular weight and concentration. The biomarkers, including cystatin C (CysC), nephrin, epidermal growth factor (EGF), kidney injury molecule-1 (KIM-1), retinol-binding protein4 (RBP4), α1-microglobulin (α1-MG), β2-microglobulin (β2-MG), vitamin D binding protein (VDBP), tissue inhibitor of metalloproteinases-1 (TIMP-1), tumor necrosis factor receptor-1 (TNFR-1), and tumor necrosis factor receptor-2 (TNFR-2) were compared in the DM and DKD groups. The diagnostic values of single biomarkers and various biomarker combinations for early diagnosis of DKD were assessed using receiver operating characteristic (ROC) curve analysis. Urinary levels of VDBP, RBP4, and KIM-1 were markedly higher in the DKD group than in the DM group (p < 0.05), whereas the TIMP-1, TNFR-1, TNFR-2, α1-MG, β2-MG, CysC, nephrin, and EGF levels were not significantly different between the groups. RBP4, KIM-1, TNFR-2, and VDBP reached p < 0.01 in univariate analysis and were entered into the final analysis. VDBP had the highest AUC (0.780, p < 0.01), followed by RBP4 (0.711, p < 0.01), KIM-1 (0.640, p = 0.044), and TNFR-2 (0.615, p = 0.081). However, a combination of these four urinary biomarkers had the highest AUC (0.812), with a sensitivity of 0.742 and a specificity of 0.760. The urinary levels of VDBP, RBP4, KIM-1, and TNFR-2 can be detected simultaneously using Luminex liquid suspension chip technology. The combination of these biomarkers, which reflect different mechanisms of kidney damage, had the highest diagnostic value for DKD. However, this finding should be explored further to understand the synergistic effects of these biomarkers.

RBP4 promotes denervation-induced muscle atrophy through STRA6-dependent pathway.

Fat infiltration of skeletal muscle has been recognized as a common feature of many degenerative muscle disorders. Retinol binding protein 4 (RBP4) is an adipokine that has been demonstrated to be correlated with the presence and severity of sarcopenia in the elderly. However, the exact role and the underlying mechanism of RBP4 in muscle atrophy remains unclear. Denervation-induced muscle atrophy model was constructed in wild-type and RBP4 knockout mice. To modify the expression of RBP4, mice were received intramuscular injection of retinol-free RBP4 (apo-RBP4), retinol-bound RBP4 (holo-RBP4) or oral gavage of RBP4 inhibitor A1120. Holo-RBP4-stimulated C2C12 myotubes were treated with siRNAs or specific inhibitors targeting signalling receptor and transporter of retinol 6 (STRA6)/Janus kinase 2 (JAK2)/Signal transducer and activator of transcription 3 (STAT3) pathway. Fat accumulation, myofibre cross-sectional area, myotube diameter and the expression of muscle atrophy markers and myogenesis markers were analysed. The expression levels of RBP4 in skeletal muscles were significantly up-regulated more than 2-fold from 7days and sustained for 28days after denervation. Immunofluorescence analysis indicated that increased RBP4 was localized in the infiltrated fatty region in denervated skeletal muscles. Knockout of RBP4 alleviated denervation-induced fatty infiltration and muscle atrophy together with decreased expression of atrophy marker Atrogin-1 and MuRF1 as well as increased expression of myogenesis regulators MyoD and MyoG. By contrast, injection of retinol-bound holo-RBP4 aggregated denervation-induced ectopic fat accumulation and muscle atrophy. Consistently, holo-RBP4 stimulation also had a dose-dependent effect on the reduction of C2C12 myotube diameter and myofibre cross-sectional area, as well as on the increase of Atrogin-1and MuRF1 expression and decrease of MyoD and MyoG expression. Mechanistically, holo-RBP4 treatment increased the expression of its membrane receptor STRA6 (>3-fold) and promoted the phosphorylation of downstream JAK2 and STAT3. Inhibition of STRA6/JAK2/STAT3 pathway either by specific siRNAs or inhibitors could decrease the expression of Atrogin-1 and MuRF1 (>50%) and decrease the expression of MyoD and MyoG (>3-fold) in holo-RBP4-treated C2C12 myotube. RBP4 specific pharmacological antagonist A1120 significantly inhibited the activation of STRA6/JAK2/STAT3 pathway, ameliorated ectopic fat infiltration and protected against denervation-induced muscle atrophy (30% increased myofibre cross-sectional area) in mice. In conclusion, our data reveal that RBP4 promotes fat infiltration and muscle atrophy through a STRA6-dependent and JAK2/STAT3 pathway-mediated mechanism in denervated skeletal muscle. Our results suggest that lowering RBP4 levels might serve as a promising therapeutic approach for prevention and treatment of muscle atrophy.

Effectiveness of Nutritional Supplementation in Liver Transplant Recipients during Early Postoperative Course: A Systematic Review and Meta-Analysis

Abstract Background Nutrition is an integral part of health maintenance. The liver is the largest and most important metabolic organ, playing a pivotal role in integrating several biochemical pathways of carbohydrate, fat, protein, and vitamin metabolism. Malnutrition is a common complication of end- stage liver disease (ESLD). Progressive deterioration of nutritional status has been associated with poor outcome in cirrhotic patients. Liver transplantation (LT) revolutionized the management of liver disease. Nutritional therapy is an integral part of liver transplant care. Objective To identity the efficacy of different dietary nutritional supplements as zinc, vit D and immunonutrients (glutamine, omega 3, arginine and ribonucleic acid) for recipient at early post operative course. Material and Methods In this systematic review and meta-analysis we enrolled a total of 7 studies for assessing the clinical outcomes of ICU patients underwent liver transplantation surgery and supplied with dietary supplements during early postoperative period. The studies also assessed the laboratory assessment of patients postoperatively during ICU admission period. Results Regarding postoperative dietary supplementations with HMB, we found significant difference for appendicular skeletal muscle mass (ASMI) regarding the baseline and the postoperative ASMI in the intervention group with HMB. But we did not report significant difference regarding the baseline and the postoperative Fat-free mass index (FFMI) in both intervention and control group with HMB. Also we did not find significant difference between base line and postoperative in both groups for Mid-arm muscle-circumference (MAMC), Fat mass index (FMI), 6-minute walk test (6MWT), and Handgrip (HG). Data Sources Medline databases (PubMed, Medscape, ScienceDirect. EMF-Portal) and all materials available in the Internet till 2021. Conclusion BCAA as dietary supplementation showing a significant favorable effect regarding the baseline and the postoperative BTR levels, also for BCAA levels, Tyrosine levels, prealbumin levels, retinol binding protein and PTINR levels in both intervention and control groups. For HMB, we found significant difference for appendicular skeletal muscle mass (ASMI) regarding the baseline and the postoperative ASMI in the intervention group with HMB. But we did not report significant difference regarding the baseline and the postoperative Fat-free mass index (FFMI) in both intervention and control group with HMB.

Association of selected adipokines with vitamin D deficiency in children with inflammatory bowel disease

BackgroundAdipose tissue is significantly involved in inflammatory bowel disease (IBD). Vitamin D can affect both adipogenesis and inflammation. The aim of this study was to compare the production of selected adipokines, potentially involved in the pathogenesis of IBD - adiponectin, resistin, retinol binding protein 4 (RBP-4), adipocyte fatty acid binding protein and nesfatin-1 in children with IBD according to the presence of 25-hydroxyvitamin D (25(OH)D) deficiency.MethodsThe study was conducted as a case-control study in pediatric patients with IBD and healthy children of the same sex and age. In addition to adipokines and 25(OH)D, anthropometric parameters, markers of inflammation and disease activity were assessed in all participants.ResultsChildren with IBD had significantly higher resistin levels regardless of 25(OH)D levels. IBD patients with 25(OH)D deficiency only had significantly lower RBP-4 compared to healthy controls and also compared to IBD patients without 25(OH)D deficiency. No other significant differences in adipokines were found in children with IBD with or without 25(OH)D deficiency. 25(OH)D levels in IBD patients corelated with RBP-4 only, and did not correlate with other adipokines.ConclusionsWhether the lower RBP-4 levels in the 25(OH)D-deficient group of IBD patients directly reflect vitamin D deficiency remains uncertain. The production of other adipokines does not appear to be directly related to vitamin D deficiency.

Seasonal changes in vitamin A metabolism-related factors in the oviduct of Chinese brown frog (Rana dybowskii)

The oviduct of the Chinese brown frog (Rana dybowskii) expands during pre-brumation rather than the breeding period, exhibiting a special physiological feature. Vitamin A is essential for the proper growth and development of many organisms, including the reproductive system such as ovary and oviduct. Vitamin A is metabolized into retinoic acid, which is crucial for oviduct formation. This study examined the relationship between oviducal expansion and vitamin A metabolism. We observed a significant increase in the weight and diameter of the oviduct in Rana dybowskii during pre-brumation. Vitamin A and its active metabolite, retinoic acid, notably increased during pre-brumation. The mRNA levels of retinol binding protein 4 (rbp4) and its receptor stra6 gene, involved in vitamin A transport, were elevated during pre-brumation compared to the breeding period. In the vitamin A metabolic pathway, the mRNA expression level of retinoic acid synthase aldh1a2 decreased significantly during pre-brumation, while the mRNA levels of retinoic acid α receptor (rarα) and the retinoic acid catabolic enzyme cyp26a1 increased significantly during pre-brumation, but not during the breeding period. Immunohistochemical results showed that Rbp4, Stra6, Aldh1a2, Rarα, and Cyp26a1 were expressed in ampulla region of the oviduct. Western blot results indicated that Aldh1a2 expression was lower, while Rbp4, Stra6, RARα, and Cyp26a1 were higher during pre-brumation compared to the breeding period. Transcriptome analyses further identified differential genes in the oviduct and found enrichment of differential genes in the vitamin A metabolism pathway, providing evidences for our study. These results suggest that the vitamin A metabolic pathway is more active during pre-brumation compared to the breeding period, and retinoic acid may regulate pre-brumation oviductal expansion through Rarα-mediated autocrine/paracrine modulation.

Retinol Binding Protein 4 Serves as a Potential Tumor Biomarker and Promotes Malignant Behavior in Gastric Cancer.

Gastric cancer (GC) is a highly phenotypically heterogeneous disease and is caused by a combination of factors. Retinol binding protein 4 (RBP4) is a member of a family of lipid transport proteins that are involved in the transport of substances between cells and play a crucial role in a variety of cancers. However, the expression and role of RBP4 in GC remain unknown. In this study, we explored the expression, prognostic significance, immune microenvironment, drug responsiveness and function of associated signaling pathways of RBP4 in GC using web-based bioinformatics tools. Immunohistochemistry and real-time quantitative PCR were utilized to analyze the tissue and cell expression levels of RBP4. CCK-8, colony formation, EDU incorporation, wound healing and transwell assays were applied to demonstrate the effect of RBP4 on GC cell function. Flow cytometric detection of apoptosis after RBP4 knockdown. Nude mice xenograft model elucidates the role of RBP4 for GC in vivo. Related proteins of the RAS signaling pathway were analyzed by employing Western blot assays. RBP4 is highly expressed in GC. RBP4 is closely associated with patient survival and sensitivity to a wide range of antitumor agents. Knockdown of RBP4 promoted apoptosis and inhibited cell proliferation, invasion and migration. RBP4 promotes GC tumorigenesis in vivo. Finally, RBP4 modulates the RAS/RAF/ERK axis. RBP4 may promote gastric carcinogenesis and development through the RAS/RAF/ERK axis and is expected to be a novel target for GC treatment.

Adipocyte HSL is required for maintaining circulating vitamin A and RBP4 levels during fasting

Vitamin A (retinol) is distributed via the blood bound to its specific carrier protein, retinol-binding protein 4 (RBP4). Retinol-loaded RBP4 is secreted into the circulation exclusively from hepatocytes, thereby mobilizing hepatic retinoid stores that represent the major vitamin A reserves in the body. The relevance of extrahepatic retinoid stores for circulating retinol and RBP4 levels that are usually kept within narrow physiological limits is unknown. Here, we show that fasting affects retinoid mobilization in a tissue-specific manner, and that hormone-sensitive lipase (HSL) in adipose tissue is required to maintain serum concentrations of retinol and RBP4 during fasting in mice. We found that extracellular retinol-free apo-RBP4 induces retinol release by adipocytes in an HSL-dependent manner. Consistently, global or adipocyte-specific HSL deficiency leads to an accumulation of retinoids in adipose tissue and a drop of serum retinol and RBP4 during fasting, which affects retinoid-responsive gene expression in eye and kidney and lowers renal retinoid content. These findings establish a novel crosstalk between liver and adipose tissue retinoid stores for the maintenance of systemic vitamin A homeostasis during fasting.

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.

MICRONUTRIENT STATUS (VITAMINS A AND D) AND ITS EFFECT ON THE SEVERITY OF THE COURSE OF COVID-19 IN CHILDREN

A strong immune response is important during recovery from COVID-19, and its status is infl uenced by several micronutrients. Vitamin D is important in regulating the immune response and protecting against respiratory infections. Vitamin A also has immunomodulatory eff ects, inhibiting viral replication and enhancing immune responses, thereby reducing morbidity and mortality from COVID-19. The aim of research was to study the levels of vitamins A, D, and retinol- binding protein 4 in children with COVID-19, and their associations with the severity of the disease.Material and Methods. 112 children aged 1 month to 18 years with COVID-19 confi rmed by polymerase chain reaction (PCR)in nasal swabs or by a positive serologic test (IgM and IgG or IgM). In all children, vitamin D levels were determined by thecolorimetric enzyme- linked immunosorbent assay (ELISA) using the Monobind test system. Vitamin A and retinol binding protein 4 (RBP4) levels were determined by the colorimetric enzyme- linked immunosorbent assay (ELISA) using the Elabscience test system. Statistical analysis was performed using Stat Plus (its 95 % confi dence interval (95 % CI) was calculated for the mean values, and the Kruskal- Wallis test (H-test) was used as the reliability criterion for checking the equality of the medians of several samples). The level of statistical signifi cance was set at P&lt;0.05). The study was conducted in accordance with the rules of patient safety and ethical principles of scientifi c medical research involving human subjects (2000). The permission to conduct this study was granted by the Bioethics Commission (Protocol No. 73, dated April 3, 2023). The parents (legal representatives) of the patients gave their written consent to the conduct of this study. This study is a fragment of research work «Optimizing the diagnosis of clinical and pathogenetic characteristics of the COVID-19 coronavirus infection in children with comorbid pathology and treatment features» (state registration No. 0123U100064, 2023-2025).Results. The mean age of the children was (7.04±5.75) years (95 % CI 5.96-8.12). According to the severity of the disease,57 children (50.89 %) had a mild course, 43 children (38.39 %) had a moderate course, and 12 children (10.72 %) had a severe course. The concentration of vitamin D in children with mild course of COVID-19 was 30.91 ng/ml, in children with moderate course – 29.10 ng/ml, in children with severe course – 22.42 ng/ml (Р&lt;0.05). The level of vitamin A also varied in children with diff erent severity of the disease: in mild COVID-19 it was 456.10 ng/ml, in moderate – 347.30 ng/ml, and in severe – 242.90 ng/ ml (Р &lt;0.001). At the same time, the level of retinol binding protein 4 was 30.66 ng/ml in mild disease, 33.07 ng/ml in moderate disease and 23.28 ng/ml in severe disease.Conclusions. Children with moderate and severe COVID-19 have signifi cantly lower levels of vitamins A, D, and RBP4compared to uninfected individuals. Vitamin A and RBP4 levels were age-dependent, and vitamin D levels did not show agerelated patterns. Lower levels of vitamins A and D are associated with higher levels of pro-infl ammatory markers – CRP,leukocytes and ESR.

Adipokines in depressed women with and without adverse childhood experiences

BackgroundAdverse childhood experiences (ACE) elevate the risk of both major depressive disorder (MDD) and metabolic diseases. The underlying pathophysiology might include alterations of adipokine levels as a consequence of ACE. In this study, we used a full-factorial design to investigate the levels of select adipokines in women with ACE-only (n = 23), MDD-only (n = 27), ACE+MDD (n = 25) and healthy controls (HC, n = 29) to identify metabolic makers associated with vulnerability and resilience of developing MDD after ACE exposure. MethodsSerum levels of adiponectin, leptin, adiponectin-to-leptin (A/L) ratio, and retinol binding protein 4 (RBP4) were measured using enzyme-linked immunosorbent assay (ELISA). ResultsAdiponectin levels did not differ between groups. Individuals with vs. without MDD showed higher leptin serum concentrations. As predicted, A/L ratio indicated lower values in individuals with vs. without ACE. RBP4 showed a more nuanced pattern with reduced levels in the ACE-only and MDD-only groups compared to HC. Furthermore, the ACE-only group showed lower RBP4 concentrations compared to ACE+MDD. These results were not accounted by BMI or medication status. ConclusionOur results do not support the utility of adiponectin and leptin as predictors of vulnerability or resilience of developing MDD after ACE. In contrast, RBP4 might play a role in resilience towards the development of MDD following ACE. Further research on this more recently discovered adipokine seems warranted.

Reappraisal of serum retinol-binding protein as a surrogate marker for retinol and discovery of a novel retinol estimation formula

Background & AimsSerum retinol (ROH) is commonly used for population level assessment of vitamin A status. High-performance liquid chromatography (HPLC) is considered most accurate method for measuring ROH. However, with the technical difficulty of using HPLC for routine assays, serum retinol-binding protein (RBP) measured by immunological assays is expected to be a surrogate marker for ROH, with reports of a close correlation between serum RBP and ROH. Nevertheless, RBP is not commonly tested to assess vitamin A status with concerns over RBP alterations under various physiopathological conditions. Thus, we reappraised the extent to which RBP could be used as a surrogate marker in representative disorders that alter serum RBP levels. As a related marker, diagnostic utility of transthyretin (TTR) was also evaluated. MethodsTo evaluate the reliability of ROH and RBP assays, specimen stability was assessed in terms of (1) storage at 25, 4, −20, and −80 ºC for 1−28 days, (2) five-cycle freeze-thawing, and (3) fluorescent light exposure for 1−14 days. Sources of variation (sex, age, body mass index [BMI], and drinking habits) and reference intervals for ROH, RBP, and TTR were determined in 617 well-defined healthy individuals. To investigate the influence of disorders that affect serum RBP, patients with five diagnostic groups were enrolled: 26 with chronic kidney disease (CKD); 13 with various malignancies in advanced stages (AdM), 12 with acute bacterial infections (ABI), 6 with liver cirrhosis (LC), and 26 with simple obesity (BMI ≥ 27 kg/m2). ResultsThe stability of RBP and ROH in serum was confirmed under all conditions. In healthy individuals, serum ROH, RBP, and TTR were appreciably high in males with a slight increase in proportion to age and BMI. The major-axis regression line between RBP (x) and ROH (y) in healthy individuals was y = x, with a correlation coefficient of 0.986. In the LC, AdM, and ABI groups, similar strong correlations were observed; however, the regression lines were shifted slightly rightward from the healthy group line, indicating a positive bias in estimating ROH. Interestingly, the same analyses between TTR and ROH revealed similar strong linear relationships in all groups; however, the regression line of each group showed a leftward (opposite) shift from the healthy group line. Based on these observations, we developed a novel regression model composed of RBP and TTR, which proved to be accurate in estimating ROH, even under these pathological conditions. ConclusionsThe perfect RBP-ROH correlation in healthy individuals indicates the utility of RPB as a surrogate marker for ROH. Nevertheless, under RBP-altered conditions, a slight overestimation of ROH is inevitable. However, when the TTR was tested together, the bias can be corrected almost perfectly using the novel ROH estimation formula comprising RBP and TTR.

Retinol-binding protein 4 (RBP4) circulating levels and gestational diabetes mellitus: a systematic review and meta-analysis.

Gestational diabetes mellitus (GDM) is a prevalent condition where diabetes is diagnosed during pregnancy, affecting both maternal and fetal outcomes. Retinol-binding protein 4 (RBP4) is a circulating adipokine which belongs to the lipocalin family and acts as a specific carrier protein that delivers retinol (vitamin A) from the liver to the peripheral tissues. Growing data indicate that circulating RBP4 levels may positively correlate with GDM. Thus, this systematic review and meta-analysis aimed to investigate the potential relationship between circulating RBP4 levels and GDM when measured at various stages of pregnancy. MEDLINE, CINAHL, EMCARE, EMBASE, Scopus, and Web of Science databases were searched to identify studies comparing pregnant women with and without GDM, whose circulating RBP4 levels were measured in at least one pregnancy trimester. Findings were reported using standardized mean difference (SMD) and random-effects models were used to account for variability among studies. Furthermore, the risk of bias was assessed using the RoBANS tool. Out of the 34 studies identified, 32 were included in the meta-analysis (seven with circulating RBP4 levels measured in the first trimester, 19 at 24-28 weeks, and 14 at >28 weeks of pregnancy). RBP4 levels were statistically higher in the GDM group than in controls when measured during all these pregnancy stages, with the noted RBP4 SMD being 0.322 in the first trimester (95% CI: 0.126-0.517; p < 0.001; 946 GDM cases vs. 1701 non-GDM controls); 0.628 at 24-28 weeks of gestation (95% CI: 0.290-0.966; p < 0.001; 1776 GDM cases vs. 1942 controls); and 0.875 at >28 weeks of gestation (95% CI: 0.252-1.498; p = 0.006; 870 GDM cases vs. 1942 non-GDM controls). Significant study heterogeneity was noted for all three pregnancy timepoints. The present findings indicate consistently higher circulating RBP4 levels in GDM cases compared to non-GDM controls, suggesting the potential relevance of RBP4 as a biomarker for GDM. However, the documented substantial study heterogeneity, alongside imprecision in effect estimates, underscores the need for further research and standardization of measurement methods to elucidate whether RBP4 can be utilized in clinical practice as a potential GDM biomarker. PROSPERO (CRD42022340097: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022340097).

Vitamin A Positively Correlates with Secretory Immunoglobulin A: A Cross-Sectional Study in Omicron COVID-19 Outpatients.

Background: Respiratory tract infections remain among the leading causes of mortality worldwide. The COVID-19 pandemic has highlighted the importance of mucosal immunity in defending against infectious agents. Vitamin A is known to influence the production of secretory immunoglobulin A (SIgA) predominantly in the gut, where it is a critical component of the first line of defense on mucosal surfaces. Methods: This cross-sectional study, conducted 14 days post-positive COVID-19 diagnosis, aimed to determine the relationship between the nutritional status of vitamin A and SIgA levels in COVID-19 outpatients. Serum and saliva samples were collected. Vitamin A nutritional status was determined based on the assessment of dietary intake and the analysis of retinol-binding protein 4 (RBP4). SIgA levels were analyzed from salivary samples. In addition, serum antibodies were analyzed. Results: Dietary vitamin A intake and RBP4 levels positively correlated with SIgA. Patients with higher vitamin A intake showed higher SIgA/IgG1 and SIgA/IgG3 ratios, while those with higher RBP4 levels showed higher SIgA/IgM, SIgA/IgG1, and SIgA/IgG2 ratios. Conclusions: These findings underscore a significant correlation between vitamin A nutritional status and SIgA levels in COVID-19 outpatients, which may suggest the potential importance of maintaining optimal vitamin A levels for the prevention of viral infections.