Retinol-binding Protein Research Articles

Comparison of retinol binding protein 1 with cone specific G-protein as putative effector molecules in cryptochrome signalling.

Vision and magnetoreception in navigating songbirds are strongly connected as recent findings link a light dependent radical-pair mechanism in cryptochrome proteins to signalling pathways in cone photoreceptor cells. A previous yeast-two-hybrid screening approach identified six putative candidate proteins showing binding to cryptochrome type 4a. So far, only the interaction of the cone specific G-protein transducin α-subunit was investigated in more detail. In the present study, we compare the binding features of the G-protein α-subunit with those of another candidate from the yeast-two-hybrid screen, cellular retinol binding protein. Purified recombinant European robin retinol binding protein bound retinol with high affinity, displaying an EC50 of less than 5nM, thereby demonstrating its functional state. We applied surface plasmon resonance and a Förster resonance transfer analysis to test for interactions between retinol binding protein and cryptochrome 4a. In the absence of retinol, we observed no robust binding events, which contrasts the strong interaction we observed between cryptochrome 4a and the G-protein α-subunit. We conclude that retinol binding protein is unlikely to be involved in the primary magnetosensory signalling cascade.

Association Between Retinol-Binding Protein 4 Levels and Hepatitis C Virus Infection: A Meta-Analysis

Background and Objectives: The relationship between circulating retinol-binding protein 4 (RBP4) levels and hepatitis C virus (HCV) infection remains unclear. This study aims to systematically assess RBP4 expression in patients with HCV and its correlation with disease severity. Materials and Methods: We searched the Embase, PubMed, and Cochrane databases for relevant studies up to 1 January 2024. This study was registered on PROSPERO (CRD42023489051). Results: Our analysis included eight studies with 2612 participants (1152 controls and 1282 patients with HCV). Overall, RBP4 levels did not significantly differ between patients with HCV and controls (SMD: −0.36; 95% CI: −0.94, 0.23; p = 0.23). However, in a subgroup of Asian subjects, patients with HCV showed significantly lower RBP4 levels (SMD: −0.40; 95% CI: −0.49, −0.31; p = 0.10). Additionally, a negative correlation between RBP4 levels and disease severity was observed across all studied populations. Conclusions: RBP4 levels may vary due to HCV genotype, ethnicity, and environmental factors. In the context of HCV infection, RBP4 levels appear to reflect the severity of disease progression. Our findings indicate that RBP4 could serve as a biomarker for HCV disease progression. Further research is needed to elucidate the complex mechanisms of RBP4 in HCV infection.

Comparative Phylogeography of Two Specialist Rodents in Forest Fragments in Kenya

The fragmented forests of the Kenya highlands, known for their exceptional species richness and endemism, are among the world’s most important biodiversity hotspots. However, detailed studies on the fauna of these ecosystems—especially specialist species that depend on moist forests, which are particularly threatened by habitat fragmentation—are still limited. In this study, we used mitochondrial genes (cytochrome b and the displacement loop) and a nuclear marker (retinol-binding protein 3) to investigate genetic and morphological diversity, phylogenetic associations, historical divergence, population dynamics, and phylogeographic patterns in two rodent species—the soft-furred mouse (Praomys jacksoni) and the African wood mouse (Hylomyscus endorobae)—across Kenya’s forest landscapes. We found a complex genetic structure, with P. jacksoni exhibiting greater genetic diversity than H. endorobae. The Mt. Kenya P. jacksoni populations are significantly genetically different from those in southwestern forests (Mau Forest, Kakamega Forest, and Loita Hills). In contrast, H. endorobae presented no observable biogeographic structuring across its range. The genetic diversity and geographic structuring patterns highlighted selectively strong effects of forest fragmentation and differing species’ ecological and evolutionary responses to these landscape changes. Our findings further underscore the need for expanded sampling across Kenya’s highland forests to better understand species’ changing diversity and distribution patterns in response to the impacts of human-mediated habitat changes. These insights are critical for informing conservation strategies to preserve biodiversity better in this globally important region.

Retinol binding protein 4 restricts PCV2 replication via selective autophagy degradation of viral ORF1 protein.

Autophagy is a highly conserved degradative process that has been linked to various functions, including defending host cells against pathogens. Although the involvement of autophagy in porcine circovirus 2 (PCV2) infection has become apparent, it remains unclear whether selective autophagy plays a critical role in PCV2 restriction. Here we show that retinol-binding protein 4 (RBP4), an adipokine for retinol carrier, initiates the autophagic degradation of PCV2 ORF1 protein. PCV2 infection increases RBP4 protein levels through MAPK-eIF4E axis in living cells. Ectopic expression of RBP4 or recombinant RBP4 treatment promotes the degradation of ORF1 protein. Mechanistically, RBP4 activates TRAF6 to induce K63-linked ubiquitination of ORF1, leading to SQSTM1/p62-mediated selective autophagy for degradation. Consequently, RBP4 deficiency increases viral loads and exacerbates the pathogenicity of PCV2 in vivo. Collectively, these results identify RBP4 as a key host restriction factor of PCV2 and reveal a previously undescribed antiviral mechanism against PCV2 in infected cells.

Pressure Ulcers and Nutrients: From Established Evidence to Gaps in Knowledge.

Pressure ulcers (PUs) are caused by continuous pressure or friction on the skin that damages tissue, especially over bony prominences. A critical factor in the development and progression of PUs is poor nutritional status, which often involves deficiencies in essential nutrients such as proteins, vitamins (A, C, D, E, K, and the B complex), and trace elements (including zinc, selenium, copper, iron, and manganese). These micronutrients are vital for effective wound healing, as they play significant roles in cellular repair, immune function, and tissue regeneration. Laboratory tests for serum albumin, prealbumin, transferrin, retinol-binding protein, and anthropometric measures like height, weight, and body mass index (BMI) are used to evaluate a patient's nutritional status. Screening tools such as the Mini Nutritional Assessment (MNA), Malnutrition Universal Screening Tool (MUST), LPZ questionnaire, and Subjective Global Assessment (SGA) are commonly employed. Emerging evidence from various studies, including in vitro, in vivo, and clinical trials, underscores the importance of personalized nutritional interventions in managing PUs. Unlike generic dietary plans, tailored nutrition that addresses the specific needs of individuals shows greater potential in promoting wound healing and improving clinical outcomes. This synthesis of existing research highlights the critical influence of micronutrients on the healing process of PUs. It suggests that a personalized approach to nutrition, which takes into account individual patient requirements and deficiencies, is likely to be more effective than a one-size-fits- all strategy in the management of these complex wounds.

Role of Zinc Alpha2-Glycoprotein and Retinol-Binding Protein-4 in Iraqi Women with Thyroid Dysfunctions

Thyroid dysfunction (TD) and diabetes mellitus (DM) are two of the most frequent chronic endocrine disorders. This study included 60 women with thyroid disorders: 30 with hypothyroidism and 30 with hyperthyroidism, aged between 20 and 40 years. This study used 30 healthy women aged 20-40 years as a control group. Anthropometric measurements of Body Mass Index (BMI), hematological analysis of glycated hemoglobin (HbA1c), biochemical parameters (Thyroid-stimulating hormone TSH, Free triiodothyronine FT3, Free thyroxine FT4, Fasting Blood Sugar FBS), and adipokine concentrations zinc-α2-glycoprotein (AZGP-1) and retinol-binding protein-4 (RBP-4) were performed for all participants. The results revealed that the serum levels of zinc-α2-glycoprotein and retinol-binding protein-4 are significantly higher in hyperthyroidism (P<0.0001) compared to both healthy and hypothyroid women. Besides that, zinc-α2-glycoprotein has a negative correlation with TSH in the hyperthyroidism group. In the hypothyroidism group, it correlates positively with retinol-binding protein-4. In addition to that, retinol-binding protein-4 is positively correlated with FT3 and FT4 and negatively correlated with BMI in the hyperthyroidism group. For this reason, we conclude that these adipokines can aid in the diagnosis and monitoring of thyroid disorders, thereby preventing the onset of disease complications associated with type 2 diabetes mellitus. It is important to highlight that women with hypothyroidism are more likely than those with hyperthyroidism to develop diabetes.

Deciphering lipoprotein(a) atherogenicity with use of high-throughput proteomics

Abstract Background Accumulating observational and genetic evidence suggests that lipoprotein(a) [Lp(a)], is significantly more atherogenic than other apolipoprotein-B containing particles. Systemic inflammation is thought to mediate the atherogenic effects of Lp(a). Previous studies have predominantly focused on single inflammatory biomarkers, an approach that fails to capture the broader molecular response to elevated Lp(a) levels. Purpose The aim of this study was to derive a proteome-wide signature of plasma Lp(a) concentrations and subsequently identify the pathways through which Lp(a) influences the risk of coronary artery disease (CAD). Methods This study included 41,123 UK Biobank participants with baseline Lp(a) measurements who also underwent a proteomic assessment. Relative concentration of 2,920 proteins was quantified in EDTA plasma samples using a high-throughput proximity extension assay. Lp(a)-associated proteins were identified in linear regression models, adjusting for age, sex, body mass index, race, smoking status, estimated glomerular filtration rate, medication use, and apolipoprotein B. Proteins linked with Lp(a) concentration were then evaluated for their association with incident CAD risk using Cox proportional hazards models. Significant traits were further included in pathway enrichment analysis. Results Out of 2,920 analyzed proteins (Figure 1), 140 showed a positive association with Lp(a) concentration, while 336 exhibited a negative association after adjustment for multiple testing (False discovery rate < 0.05). The strongest positive associations were observed for apolipoprotein F, group 10 secretory phospholipase A, and C4b-binding protein beta chain. The strongest negative associations were observed for asporin, aminoacylase-1, and retinol-binding protein 5. Among 140 proteins positively associated with Lp(a), 49 were associated with an increased risk of CAD. Conversely, among the 336 proteins negatively associated with Lp(a), 10 were associated with a decreased risk of CAD. Pathway enrichment analysis (Figure 2) indicated that proteins linked with both Lp(a) levels and CAD risk predominantly upregulated pathways related to peptide-ligand receptor signalling, platelet degranulation, neutrophil degranulation, and cytosolic calcium response. Conversely, pathways related to HDL remodeling, PI3K/AKT, KIT, and nuclear receptor signalling were downregulated. Conclusions The greater atherogenic potential of Lp(a) may be attributable to the modulation of several molecular pathways, particularly those involving platelet and neutrophil responses, cell signalling, and lipoprotein metabolism.

Hepatic stellate cell-targeted chemo-gene therapy for liver fibrosis using fluorinated peptide-lipid hybrid nanoparticles

Exploring precise and effective treatments for liver fibrosis is urgent. The effective therapy for liver fibrosis depends on the specific delivery of antifibrotic drugs to activated hepatic stellate cells (aHSCs). However, this is a challenging task due to pathological barriers, primarily caused by collagen deposition. This study developed vitamin A-functionalized fluorinated peptide/lipid hybrid nanoparticles to co-deliver sorafenib and siRNA against HSP47 (SF-siHSP47@VFPL NPs). This nanoparticle formulation offers significant advantages due to its fluorine‑fluorine and electrostatic interactions, allowing for high SF and siHSP47 loading efficiency and sustained drug release. Importantly, in vitro cell uptake and in vivo biodistribution revealed that VA functionalization significantly improved aHSC-targeted delivery efficiency by engaging retinol-binding protein receptors on HSCs. Furthermore, it dramatically reduced extracellular matrix deposition, as evidenced by diminished levels of liver fibrosis-associated genes (HSP47, TIMP-1, and collagen I), promoting collagen breakdown and preventing collagen production, thus overcoming drug delivery barriers. Thus, SF-siHSP47@VFPL NPs demonstrated optimal antifibrotic effects by triggering apoptosis and ferroptosis in aHSCs. In liver fibrosis mouse models, SF-siHSP47@VFPL NPs remodeled the pathological environment and restored liver functionality through a marked reduction in serum liver transferases, hydroxyproline content, collagen deposition, and α-SMA and CD31 expression in liver tissue, resulting in alleviated liver fibrosis. Consequently, SF-siHSP47@VFPL NPs showed significant potential for HSC-targeted, chemo-gene therapy in the treatment of liver fibrosis.

Fabrication and Simulation of Silicon Nanowire pH Sensor for Diabetes Mellitus Detection

Diabetes Mellitus (DM) is a disease failed to control the balance of blood sugar level due to lack of insulin thereby it effect human health. In Malaysia, there are around 3.9 millions people aged 18 years old and above have diabetes according to National Health and Morbidity Survey 2019. Silicon Nanowire is a nanostructure which has ultra-high sensitivity and non-radioactive that has potential given good performances when applied on pH sensor and biosensor. Silicon nanowire pH sensor and biosensor is an electronic sensor that investigated to improve the sensitivity and accuracy for detecting DM. This project consists of two parts, which are fabrication of silicon nanowire pH sensor and simulation of silicon nanowire biosensor as preliminary study. In fabrication, silicon nanowire of pH sensor is fabricated by conventional lithography process, reaction ion etching (RIE) and metallization to achieved the width of 100 nm silicon nanowire. The pH6, pH7, pH10 and DI water as analytes to analysis the current-voltage (I-V) characteristics of silicon nanowire pH sensor. In second part, the silicon nanowire biosensor as preliminary study is done simulation by Silvaco ATLAS devices simulator. The silicon nanowire with 30 nm in height and 20 nm in width of biosensor is designed and simulated to analyze the performance in terms of sensitivity. I-V characteristics of silicon nanowire biosensor according to different concentration of negative interface charge is determined. The negative interface charge represent as the Retinol Binding Protein 4 (RBP4) which is used to diagnose DM. The I-V characteristic based on the change in current, resistance and conductance to determine sensitivity. Lastly, the sensitivity of silicon nanowire pH sensor obtained 23.9 pS/pH while the sensitivity of simulated silicon nanowire biosensor obtained 3.91 nS/e.cm2. The results shown the more negative charge of concentration analyte attached on surface silicon nanowire has been accumulated more current flow from drain terminal to source terminal. It leads to the resistance becomes highest and obtained good sensitivity. In summary, the silicon nanowire pH sensor exhibited good performance and high sensitivity in detection pH level. The simulated silicon nanowire biosensor is capable of detecting biomolecular interactions charges to obtained high sensitive and accuracy result.

Identification of immune feature genes and intercellular profiles in diabetic cardiomyopathy

BACKGROUND Diabetic cardiomyopathy (DCM) is a multifaceted cardiovascular disorder in which immune dysregulation plays a pivotal role. The immunological molecular mechanisms underlying DCM are poorly understood. AIM To examine the immunological molecular mechanisms of DCM and construct diagnostic and prognostic models of DCM based on immune feature genes (IFGs). METHODS Weighted gene co-expression network analysis along with machine learning methods were employed to pinpoint IFGs within bulk RNA sequencing (RNA-seq) datasets. Single-sample gene set enrichment analysis (ssGSEA) facilitated the analysis of immune cell infiltration. Diagnostic and prognostic models for these IFGs were developed and assessed in a validation cohort. Gene expression in the DCM cell model was confirmed through real time-quantitative polymerase chain reaction and western blotting techniques. Additionally, single-cell RNA-seq data provided deeper insights into cellular profiles and interactions. RESULTS The overlap between 69 differentially expressed genes in the DCM-associated module and 2483 immune genes yielded 7 differentially expressed immune-related genes. Four IFGs showed good diagnostic and prognostic values in the validation cohort: Proenkephalin (Penk) and retinol binding protein 7 (Rbp7), which were highly expressed, and glucagon receptor and inhibin subunit alpha, which were expressed at low levels in DCM patients (all area under the curves > 0.9). SsGSEA revealed that IFG-related immune cell infiltration primarily involved type 2 T helper cells. High expression of Penk (P < 0.0001) and Rbp7 (P = 0.001) was detected in cardiomyocytes and interstitial cells and further confirmed in a DCM cell model in vitro . Intercellular events and communication analysis revealed abnormal cellular phenotype transformation and signaling communication in DCM, especially between mesenchymal cells and macrophages. CONCLUSION The present study identified Penk and Rbp7 as potential DCM biomarkers, and aberrant mesenchymal-immune cell phenotype communication may be an important aspect of DCM pathogenesis.

Retinol-binding protein type 1 expression predicts poor prognosis in head and neck squamous cell carcinoma

BackgroundHead and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent malignancy worldwide, with high incidence and poor survival rates. RBP1 is highly expressed in several kinds of cancer and plays a potential prognostic factor. However, the relationship between RBP1 and HNSCC were analyzed based on The Cancer Genome Atlas (TCGA) database.Materials and methodsRBP1 expression and clinical information were obtained from the Cancer Genome Atlas (TCGA) database. Tumor tissue and adjacent normal tissue of 6 HNSCC patients were collected to analyze the RBP1 mRNA expression level by quantitative PCR. Cox regression analysis was used to evaluate the prognostic values of RBP1 and clinical data in HNSCC. A nomogram was also established to predict the impact of RBP1 on prognosis based on Cox multivariate results. The methylation level of RBP1 in HNSC and its prognosis were analyzed in UALACN and MethSurv. Finally, the potential biological functions of RBP1 were investigated using gene set enrichment analysis (GSEA) and single sample GSEA (ssGSEA).ResultsThe mRNA expression levels of RBP1 were highly expressed in HNSCC tissue. The Cox analyses demonstrate that highly-expressed RBP1 is an independent prognosis marker(P < 0.05). ROC curve analysis showed that performances of RBP1 (area under the ROC curve: 0.887, sensitivity: 84.1%, specificity: 79.9%). The methylation was increased in HNSCC patients compared with normal subjects(P < 0.05) and was associated with better prognosis at sites cg06208339, cg12298268, cg12497564, cg15288618, cg20532370, cg23448348. Additionally, RBP1 expression is mildly associated with immune cell infiltration and immunological checkpoints.ConclusionRBP1 is overexpressed and associated with poor patient prognosis in head and neck squamous cell carcinoma.

Adipokine/hepatokines profiling of fatty liver in adolescents and young adults: cross-sectional and prospective analyses of the BCAMS study.

The underlying connections between obesity and non-alcoholic fatty liver disease (NAFLD) are not fully understood. One potential link might be the imbalanced adipokines and hepatokines. We aimed to explore the associations between specific adipokines/hepatokines and NAFLD in Chinese youth and to determine how these biomarkers mediate the obesity-NAFLD relationship. We analyzed data from the 10-year follow-up visit of the Beijing Children and Adolescents Metabolic Syndrome (BCAMS) study (n = 509; mean age = 20.2years) for a comprehensive metabolic risk assessment, including liver ultrasound and plasma measurements of adiponectin, leptin, fibroblast growth factor 21 (FGF21), retinol-binding protein 4 (RBP4), and angiopoietin-like protein 8 (ANGPTL8). Longitudinal analysis was performed on a subgroup (n = 307), with complete baseline (mean age = 12.2years) and follow-up data. Mediation models assessed how obesity at baseline and follow-up influence NAFLD through these biomarkers. Participants with NAFLD exhibited a high prevalence of central obesity (90.9%). Both cross-sectional and prospective analyses identified increased RBP4, FGF21, leptin, and decreased adiponectin levels as significant predictors of NAFLD. More adipokine/hepatokine abnormalities were linked to higher NAFLD risk. Furthermore, ratios reflecting adipokine/hepatokine imbalances, including leptin/adiponectin, FGF21/adiponectin, and RBP4/adiponectin, demonstrated stepwise changes correlating with NAFLD severity (all p < 0.05). Mediation analysis indicated that these four adipokines/hepatokines accounted for approximately 72.4% of the central obesity-NAFLD relationship and 80.1% in the subgroup analysis using baseline childhood data. Dysregulated adipokines/hepatokines may explain the onset or progression of obesity-related NAFLD in youths. Higher RBP4, FGF21 and leptin, alongside lower adiponectin, could serve as early biomarkers for NAFLD.

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

Background &amp; 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.

8290 Hypervitaminosis A Induced Severe Hypercalcemia In A Patient With Cirrhosis

Abstract Disclosure: N. Vennelaganti: None. S. Vennelaganti: None. R.L. Fitzgerald: None. K.C. McCowen: None. Introduction The liver stores vitamin A in hepatic stellate cells and regulates its absorption through bile production and distribution via retinol-binding protein 4 and transthyretin synthesis. Cirrhosis compromises these functions, resulting in vitamin A deficiency, which is inversely linked to the severity of nonalcoholic steatohepatitis. Addressing this deficiency in chronic liver diseases, particularly cirrhosis, is challenging due to the risk of vitamin A toxicity. This case describes a cirrhotic patient who developed hypervitaminosis A, leading to severe hypercalcemia. Clinical Case A 54-year-old male with alcoholic cirrhosis was diagnosed with hypovitaminosis A. He was prescribed 10,000 IU of vitamin A due to a low serum retinol level of less than 0.06 mg/L (reference range: 0.3-1.2 mg/L ). Two months later, he presented to the hospital with an erythematous patchy, scaling facial rash. His serum calcium corrected for albumin was high at 15.6 mg/dL. The rash and hypercalcemia, alongside vitamin A supplementation, raised suspicion of vitamin A toxicity. The patient, however, exhibited no hypercalcemia symptoms. He also had an acute kidney injury. His lab results revealed a PTH level of 10 pg/mL (normal range 15-65 pg/ml) and a normal myeloma screen, as well as normal vitamin D and TSH levels. An elevated PTHrP level of 5.2 pmol/l (normal range 0-2.3) was noted, which was attributed to the kidney injury(Cr 2.55 mg/l, eGFR 23 ml/min). Malignancy was excluded after a pan scan. Hypervitaminosis A is a clinical diagnosis, as serum vitamin A levels correlate poorly with toxicity. His serum retinol was normal at 0.83 mg/l, but his retinyl palmitate was high at 0.38 mg/L(reference range 0-0.10 mg/l), which supported our diagnosis. He received continuous IV 0.9% saline and subcutaneous calcitonin at 4 units/kg twice, and had a reduction in corrected calcium to 11 mg/dL over a week. The vitamin A-induced contact dermatitis improved with topical steroids. He was discharged; two months later, he remained asymptomatic with a corrected calcium of 11.1 mg/dL. He was not interested in further management as he was asymptomatic and serum calcium levels were improving. Labs were, however, notable for worsening renal function of unclear etiology. We will be trending his labs for improvement in serum calcium as the Vitamin A clears from his system. Clinical Lesson Vitamin A supplementation in cirrhotic patients is necessary in those with deficiency but carries a risk of toxicity. There are no definitive hepatology guidelines on the replacement of Vitamin A in patients with cirrhosis. This case emphasizes the importance of awareness of hypervitaminosis A-induced hypercalcemia in this population. Clinicians must carefully monitor and manage Vitamin A levels to avoid toxicity. Further research is essential for the management of this condition in cirrhotic patients. Presentation: 6/2/2024

Methodology for Studying Interactions of Vitamin A Membrane Receptors and Opsin Protein with their Ligands in Generating the Retinylidene Protein.

Distribution of dietary vitamin A/all-trans retinol (ROL) throughout the body is critical for maintaining retinoid function in peripheral tissues and generating the retinylidene protein for visual function. RBP4-ROL is the complex of ROL with retinol-binding protein 4 (RBP4), which is present in the blood. Two membrane receptors, Retinol Binding Protein 4 Receptor 2 (RBPR2) in the liver and STimulated by Retinoic Acid 6 Retinol (STRA6) in the eye, bind circulatory RBP4 and this mechanism is critical for internalizing ROL into cells. Establishing methods to investigate receptor-ligand kinetics is essential in understanding the physiological function of vitamin A receptors for retinoid homeostasis. Using Surface Plasmon Resonance (SPR) assays, we can analyze the binding affinities and kinetic parameters of vitamin A membrane receptors with its physiological ligand RBP4. These methodologies can reveal new structural and biochemical information of RBP4-binding motifs in RBPR2 and STRA6, which are critical for understanding pathological states of vitamin A deficiency. In the eye, internalized ROL is metabolized to 11-cis retinal, the visual chromophore that binds to opsin in photoreceptors to form the retinylidene protein, rhodopsin. The absorbance of light causes the cis-to-trans isomerization of 11-cis retinal, inducing conformational changes in rhodopsin and the subsequent activation of the phototransduction cascade. Decreased concentrations of serum and ocular ROL can impact retinylidene protein formation, which in turn can cause rhodopsin mislocalization, apoprotein opsin accumulation, night blindness, and photoreceptor outer segment degeneration, leading to Retinitis Pigmentosa or Leber Congenital Amaurosis. Therefore, spectrophotometric methodologies to quantify the G protein-coupled receptor opsin-11-cis retinal complex in the retina are critical for understanding mechanisms of retinal cell degeneration in the above-mentioned pathological states. With these comprehensive methodologies, investigators will be able to better assess dietary vitamin A supply in maintaining systemic and ocular retinoid homeostasis, which is critical for generating and maintaining retinylidene protein concentrations in photoreceptors, which is critical for sustaining visual function in humans.

B-069 Characterization of a panel of antibodies as diagnostics for NASH and NAFL

Abstract Background Nonalcoholic fatty liver disease (NAFLD) is on the rise in Western industrialized countries and associated comorbidities like e.g. cirrhosis are a major cause of liver transplantations in the USA. In NAFLD, excess fat is accumulated in the liver whereas this build-up is not caused by alcohol. NASH (nonalcoholic steatohepatitis) and NAFL (nonalcoholic fatty liver) are two forms of NAFLD. NAFL represents a stage of the disease in which the liver does not exhibit major signs of inflammation or damage, while NASH does. NAFL does not necessarily progress to cause liver damage. NASH on the other hand may cause fibrosis and lead to cirrhosis with a risk of progression into liver cancer. Since NAFLD shows a prevalence of over 24-25% in both the USA and Europe, diagnosis moves more and more into focus. The current gold standard for NASH diagnosis is liver biopsy, and NAFLD as such can also be diagnosed by ultrasound and MRI, among others. A quest for biomarkers is ongoing to develop blood tests that allow NAFLD diagnosis by immunoassays for example. We have developed high affinity and specificity antibodies against four highly discussed marker proteins for NAFLD: RBP4 (Retinol Binding Protein 4), FGF21 (Fibroblast Growth factor 21), CHI3L1 (Chitinase-3-like protein 1) and PAI-1 (Plasminogen activator inhibitor-1). All four markers are discussed to be elevated in NAFLD patient serum. Methods We characterized the developed anti-RBP4 and anti-FGF21 antibodies via an in-house developed Chemiluminescence Immunoassay (CLIA). Results We have determined the limit of quantification (LoQ), limit of detection (LoD) and linear range of measurable concentrations for our antibody pairs. We further conducted spike and recovery experiments showing the precision of the developed antibodies against RBP4 and FGF21. Conclusions Together, we present antibody pairs for RBP4 and FGF21 suitable as a part of a diagnostic panel that has high potential to be applied in the diagnosis of NAFLD.

Silicon Nanowire Biosensors for Diabetes Mellitus Monitoring

The main goal of this research is the development of a label-free biosensor for the detection of diabetes mellitus (DM) using the target molecule retinol-binding protein 4 (RBP4). The enzyme-linked immunosorbent assay (ELISA) approach, currently used to detect DM, is time-consuming and difficult. As a result, label-free biosensors are being considered as an alternative. In this research, silicon nanowires (SiNWs) were selected as the transducer for this biosensor due to their low cost, real-time analysis capability, high sensitivity, and low detection limit. The SiNWs were created using conventional lithography, reactive ion etching (RIE), and physical vapor deposition (PVD), and then dripped with a gold nanoparticle solution to create gold-decorated SiNWs. The surface of the gold-decorated SiNWs was functionalized using 3-aminothiophenol and glutaraldehyde solutions before being immobilized with DM RBP4 antibodies and targets. The electrical characterization of the gold nanoparticle decorated SiNWs biosensor revealed good performance in DM detection. The pH tests confirmed that the SiNWs acted as a transducer, with current proportional to the DM RBP4 concentration. The estimated limit of detection (LOD) and sensitivity for detecting DM RBP4 binding were 0.076 fg/mL and 8.92 nA(g/mL)-1, respectively. This gold nanoparticle decorated SiNWs biosensor performed better than other methods and enabled efficient, accurate, and direct detection of DM. The SiNWs could be used as a distinctive electrical protein biosensor for biological diagnostic purposes. In conclusion, gold nanoparticle deposition offers effective label-free, direct, and high-accuracy DM detection, outperforming previous approaches. Thus, these SiNWs serve as novel electrical protein biosensors for future biological diagnostic applications.

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.

Retinol Binding Protein 4 Is a Marker for Proteinuria in Humans and Zebrafish

Retinol Binding Protein 4 Is a Marker for Proteinuria in Humans and Zebrafish