Comparison of test performance of two commonly used multiplex assays to measure micronutrient and inflammatory markers in serum: results from a survey among pregnant women in South Africa

The combined sandwich-ELISA (s-ELISA; VitMin Lab, Germany) and the Quansys Q-Plex™ Human Micronutrient Array (7-Plex) are multiplex serum assays that are used to assess population micronutrient status in low-income countries. We aimed to compare the agreement of five analytes, α-1-acid glycoprotein (AGP), C-reactive protein (CRP), ferritin, retinol-binding protein 4 (RBP4) and soluble transferrin receptor (sTfR) as measured by the 7-Plex and the s-ELISA. Serum samples were collected between March 2016 and December 2017. Pregnant women (n 249) were recruited at primary healthcare clinics in Johannesburg, and serum samples were collected between March 2016 and December 2017. Agreement between continuous measurements was assessed by Bland-Altman plots and concordance measures. Agreement in classifications of deficiency or inflammation was assessed by Cohen's kappa. Strong correlations (r > 0·80) were observed between the 7-Plex and s-ELISA for CRP and ferritin. Except for CRP, the 7-Plex assay gave consistently higher measurements than the s-ELISA. With the exception of CRP (Lin's ρ = 0·92), there was poor agreement between the two assays, with Lin's ρ < 0·90. Discrepancies of test results difference between methods increased as the serum concentrations rose. Cohen's kappa for all the five analytes was < 0·81 and ranged from slight agreement (vitamin A deficiency) to substantial (inflammation and Fe deficiency) agreement. The 7-Plex 1.0 is a research and or surveillance tool with potential for use in low-resource laboratories but cannot be used interchangeably with the s-ELISA. Further optimising and validation is required to establish its interchangeability with other validated methods.

The level of serum retinol-binding protein is associated with diabetic mild cognitive impairment

BACKGROUND

Several studies have shown that retinol-binding protein (RBP) is linked to diabetes and neurodegenerative diseases. However, no studies have elucidated the relationship between RBP and diabetic cognitive disorders.

OBJECTIVE

To determine whether the change characteristics of serum RBP are associated with alterations in cognitive functioning in type 2 diabetes mellitus (T2DM).

METHODS

In this study, 252 patients with T2DM and 34 people as healthy controls were included. According to the Montreal Cognitive Assessment (MoCA), the diabetic subjects were divided into the mild cognitive impairment (MCI) group and the Non-MCI group. Demographic characteristics and clinical indicators as well as serum RBP levels were analyzed.

RESULTS

The serum RBP levels in the MCI group were lower compared with the Non-MCI group (P = 0.02). The level of RBP was higher in the diabetes without MCI group than in the healthy control (P < 0.001). Serum RBP levels were positively correlated with MoCA scores (r = 0.178, P = 0.003). Binary Logistic regression model analysis showed that low RBP [odds ratio (OR) = 0.936], old age (OR = 1.074), high fasting blood glucose (OR = 1.164), and low fasting C-peptide (OR = 0.722) may be independent risk factors for diabetic MCI. The ROC curve of serum RBP for predicting diabetic MCI showed that the area under the curve was 0.630.

CONCLUSIONS

Our study revealed an association between serum RBP and diabetic MCI. Serum RBP levels in diabetic MCI are lower and correlated with cognitive function.

Urinary orosomucoid and retinol binding protein levels as early diagnostic markers for diabetic kidney Disease

BACKGROUND

Diabetic kidney disease (DKD) is the most common microvascular complication of diabetes, which has been a major cause of end-stage renal failure. Diagnosing diabetic kidney disease is important to prevent long-term kidney damage and determine the prognosis of patients with diabetes. In this study, we investigated the clinical significance of combined detection of urine orosomucoid and retinol-binding protein for early diagnosis of diabetic kidney disease.

METHODS

We recruited 72 newly diagnosed patients with type 2 diabetes and 34 healthy persons from August 2016 to July 2018 at the First Affiliated Hospital of Henan Polytechnic University (Jiaozuo Second People's Hospital). Using the Mogensen grading criteria, participants were classified as having diabetes or diabetic kidney disease, and healthy persons constituted the control group. Urine orosomucoid and retinol-binding protein levels were measured and correlated with other variables.

RESULTS

With the aggravation of renal damage, the level of urinary mucoid protein gradually increased. Urinary retinol-binding protein and microalbumin levels were significantly higher in the diabetes group than in control and nephropathy groups. Orosomucoid and retinol-binding protein might be independent risk factors for diabetes and diabetic kidney disease. Urinary orosomucoid significantly correlated with retinol-binding protein and microalbumin levels in the diabetic kidney disease group.

CONCLUSION

Elevated urine orosomucoid and retinol-binding protein levels can be detected in the early stages of type 2 diabetic kidney disease. Both of these markers are important for diabetic kidney disease detection and early treatment.

A comparative study on indicators of vitamin A status and risk factors for sensitivity and specificity of the methods to detect vitamin A deficiency

BACKGROUND

Serum retinol (SR) and retinol-binding protein (RBP) are commonly used indicators, but they are affected by infections and inflammation. This study aimed to assess the sensitivity and specificity of VA indicators to detect vitamin A deficiency (VAD) in 36-59-month-old children living in a rural area in Burkina Faso.

METHODS

In a community-based study, two cross-sectional surveys were carried out from November 2016 to September 2017 in the health district of Dandé in Burkina Faso. The surveys included 115 children 36-59 months old. Indicators of VA and inflammation assessed in all children included SR, RBP and total liver VA reserves (TLR) estimated by retinol isotope dilution, and inflammation markers (C-reactive protein (CRP) and alpha 1-acid glycoprotein (AGP)). We calculated the sensitivity, specificity, positive and negative predictive values. In addition, the effects of inflammation, helminth infection, and season on sensitivity and specificity were assessed.

RESULTS

The prevalence of VAD assessed by SR (< 0.7 µmol/L), RBP (< 0.7 µmol/L), and TLR (< 0.1 µmol/g liver) were, respectively, 30.9%, 33.3%, and 0%. Compared to TLR, the specificity, positive predictive value, and negative predictive value of SR were 71.1%, 0%, and 100%, and of RBP, were 68.9%, 0%, and 100%, respectively. The sensitivity was indeterminable for SR and RBP. The specificity of SR and RBP was lower during the dry season. Elevated CRP (> 5.0 mg/L) and AGP (> 1.0 g/L) were detected in 1.9% and 28.6% of children, respectively. The adjustment of VA indicators for inflammation improved SR's specificity to 75.9% and decreased RBP's specificity to 67.8%.

CONCLUSION

No cases of VAD were identified by TLR. However, (inflammation-adjusted) SR and RBP had varying accuracy in the estimation of VAD.

TRIAL REGISTRATION

The study was registered, retrospectively, on 22 March 2018 as a clinical trial with the Pan African Clinical Trials Registry under the number Cochrane South Africa; PACTR201803002999356.

Correlation between glycated hemoglobin A1c, urinary microalbumin, urinary creatinine, β2 microglobulin, retinol binding protein and diabetic retinopathy

BACKGROUND

Retinopathy is the most common microvascular disease of type 2 diabetes, and seriously threatens the life, health and quality of life of patients. It is worth noting that the development of diabetic retinopathy (DR) can be hidden, with few symptoms. Therefore, the preliminary screening of diabetic patients should identify DR as soon as possible, delay disease progression, and play a vital role in its diagnosis and treatment.

AIM

To investigate the correlation between glycated hemoglobin A1c (HbA1c), urinary microalbumin (U-mALB), urinary creatinine (U-CR), mALB/U-CR ratio, β2 microglobulin (β2MG), retinol binding protein (RBP) and DR.

METHODS

A total of 180 patients with type 2 diabetes mellitus attending the Second People’s Hospital of Hefei from January 2022 to August 2022 were retrospectively enrolled by ophthalmologists. Based on whether they had combined retinopathy and its degree, 68 patients with diabetes mellitus without retinopathy (NDR) were assigned to the NDR group, 54 patients with non-proliferative DR (NPDR) to the NPDR group, and 58 patients with proliferative DR to the PDR group. General data, and HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR results were collected from the patients and compared among the groups. Pearson's correlation method was used to analyze the correlation between HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR indices, and multiple linear regression was applied to identify the risk factors for DR. Receiver operator characteristic (ROC) curves were also drawn.

RESULTS

The differences in age, gender, systolic and diastolic blood pressure between the groups were not statistically significantly (P > 0.05), but the difference in disease duration was statistically significant (P < 0.05). The differences in fasting blood glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, and triglyceride between the groups were not statistically significant (P > 0.05). HbA1c in the PDR group was higher than that in the NPDR and NDR groups (P < 0.05). The levels of mALB, β2MG, RBP, mALB/U-CR and U-CR in the PDR group were higher than those in the NPDR and NDR groups (P < 0.05). Multiple linear regression analysis showed that disease duration, HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR were risk factors for the development of DR. The ROC curve showed that the area under the curve (AUC) for the combination of indices (HbA1c + mALB + mALB/U-CR + U-CR + β2MG + RBP) was 0.958, with a sensitivity of 94.83% and specificity of 96.72%, which was higher than the AUC for single index prediction (P < 0.05).

CONCLUSION

HbA1c, mALB, mALB/U-CR, U-CR, β2MG and RBP can reflect the development of DR and are risk factors affecting PDR, and the combination of these six indices has predictive value for PDR.

Insights into the health status of the general population living near an electroplating industry zone: metal elevations and renal impairment

A cross-sectional study was conducted in 2016 in Zhejiang Province, China, to evaluate the body burdens of metals and metalloids associated with renal dysfunction in populations living near electroplating industries. We recruited 236 subjects and performed physical examinations, determined the blood and urinary levels of arsenic (As), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), and selenium (Se) by an inductively coupled plasma mass spectrometer (ICP-MS), and measured three renal impairment biomarkers, namely nacetyl-β-_D-glucosaminidase (NAG), retinol-binding protein (RBP), and β₂-microglobulin (BMG). The proportion of abnormal nasal symptoms in the exposure group (10.1%) was much higher than in the control group (0; p < 0.05). The blood and urinary levels of As, Cd, and Se in the exposure group were significantly higher than those in the control group (p < 0.05). The blood levels of Mn and Pb, as well as the urinary levels of Cr and Ni, were significantly higher in the exposure group than in the control group (p < 0.05). The exposure group demonstrated higher levels of NAG, RBP, and BMG than the control group (0.51 vs. 0.14 mg/g creatinine, 12.79 vs. 9.26 IU/g creatinine, and 1.39 vs. 0.78 mg/g creatinine, respectively; p < 0.05). Urinary BMG was positively correlated with urinary Cd levels (r = 0.223, p < 0.05), while urinary RBP was correlated with blood Cd levels (r = 0.151, p < 0.05) and urinary Cd, Cr, Ni, and Se levels (r = 0.220, 0.303, 0.162, and 0.306, respectively; p < 0.05). In conclusion, our study indicated that a population living in the vicinity of electroplating industries had high body burdens of certain metals and metalloids associated with non-negligible renal dysfunction.

Blood retinol and retinol-binding protein concentrations are associated with diabetes: a systematic review and meta-analysis of observational studies

PURPOSE

The associations between blood retinol, retinol-binding protein (RBP) concentrations and diabetes mellitus were inconsistent in literature. The objective is to investigate these associations by a systematic review and meta-analysis and provide basis for clinical intervention.

METHODS

PubMed, Web of science, and Cochrane databases were searched from the beginning to July 1, 2021. A total of 13 studies on retinol and 31 studies on RBP are included in the current meta-analysis.

RESULTS

The blood retinol concentration was significantly lower in the type I diabetes mellitus (T1DM) [standardized mean difference (SMD) (95% CI): - 0.59 (- 0.81, - 0.37), P < 0.01] and gestational diabetes mellitus (GDM) patients [SMD (95% CI): - 0.54 (- 0.87, - 0.20), P < 0.01] than in the controls. However, the difference was not significant between the type II diabetes mellitus (T2DM) patients and the controls. The RBP concentration was significantly higher in the diabetic patients than in the controls [SMD (95% CI): 0.24 (0.12, 0.35), P < 0.01]. Particularly, the RBP concentration was significantly higher in the T2DM and GDM patients.

CONCLUSION

The blood retinol concentration was negatively associated with T1DM and GDM, while the blood RBP concentration was positively associated with T2DM and GDM. Future work should use a more sensitive retinol measurement method like retinol isotope dilution method to confirm whether blood retinol concentration differs between the diabetes patients and the controls.

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

Background

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

Methods

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

Results

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

Conclusions

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

Trial registration retrospectively registered.

Serum Retinol-Binding Protein Levels Are Associated with Nonalcoholic Fatty Liver Disease in Chinese Patients with Type 2 Diabetes Mellitus: A Real-World Study

BACKGROUND

The association of serum retinol-binding protein (RBP) levels with nonalcoholic fatty liver disease (NAFLD) remains controversial. Furthermore, few studies have investigated their relationship in type 2 diabetes mellitus (T2DM) patients. Therefore, the aim of the present study was to explore the association between serum RBP levels and NAFLD in Chinese inpatients with T2DM.

METHODS

This cross-sectional, real-world study included 2,263 Chinese T2DM inpatients. NAFLD was diagnosed by abdominal ultrasonography. The subjects were divided into four groups based on RBP quartiles, and clinical characteristics were compared among the four groups. The associations of both RBP levels and quartiles with the presence of NAFLD were also analyzed.

RESULTS

After adjustment for sex, age, and diabetes duration, there was a significant increase in the prevalence of NAFLD from the lowest to the highest RBP quartiles (30.4%, 40.0%, 42.4%, and 44.7% for the first, second, third, and fourth quartiles, respectively, P<0.001 for trend). Fully adjusted multiple logistic regression analysis revealed that both increased RBP levels (odds ratio, 1.155; 95% confidence interval, 1.012 to 1.318; P=0.033) and quartiles (P=0.014 for trend) were independently associated with the presence of NAFLD in T2DM patients.

CONCLUSION

Increased serum RBP levels were independently associated with the presence of NAFLD in Chinese T2DM inpatients. Serum RBP levels may be used as one of the indicators to assess the risk of NAFLD in T2DM patients.

Transthyretin and retinol-binding protein as discriminators of diabetic retinopathy in type 1 diabetes mellitus

PURPOSE

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM), which is still a major reason for blindness. Transthyretin (TTR) and retinol-binding protein (RBP) are thought to be related to the pathogenesis both in T2DM and T1DM. We aimed to investigate the association between serum levels of TTR, RBP, RBP/TTR ratio, and DR.

METHODS

This retrospective study involved 188 T1DM inpatients divided into two groups: patients with DR (n = 95) and patients without DR (n = 93). Data of serum levels on lipids and inflammation were collected. Multiple logistic regression analysis was performed to research the association between TTR, RBP, RBP/TTR, and diabetic retinopathy in T1DM.

RESULTS

Compared with patients without DR, those with DR have a higher level of TTR (207 versus 195 mg/L, p = 0.034) and RBP4 (36.85 versus 25.68 mg/L, p < 0.001). Significant differences were also observed between two groups with respect to body mass index (BMI), blood pressure (BP), total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), homocysteine, apolipoprotein B (APOB), leucocyte, monocyte, neutrophil, and uric acid (p < 0.05 for all). TTR, RBP, and RBP/TTR were positively correlated with BP, BMI, TG, LDL, homocysteine, APOB, and uric acid. A multivariate logistic regression model revealed individuals with RBP4 level in the highest quartile had 58.95 times higher risk of developing diabetic retinopathy than those in the lowest quartile.

CONCLUSIONS

In conclusion, TTR, RBP, and RBP/TTR ratio are risk factors of DR in T1DM. They are potential markers and targets for diagnosis and treatment of DR.

Decreased circulating retinol binding protein is an independent risk factor for local complications of acute pancreatitis

BACKGROUND

Acute pancreatitis is a common acute abdomen in China. There is a decrease of serum retinol-binding protein (RBP) in some patients, but its clinical significance is not clear.

AIM

To explore the relationship between serum RBP and the severity and complications of AP.

METHODS

The clinical data of AP patients admitted to Jinling Hospital in 2018 within 7 days of onset were analyzed retrospectively. The enrolled patients were divided into either a normal RBP (NRBP) group or a low RBP (LRBP) group according to the serum RBP level. The baseline characteristics, severity, and prognosis of disease were compared between the two groups. Logistic regression analysis was used to explore the independent risk factors for local complications. Receiver operating characteristic (ROC) curve was drawn to evaluate the performance of serum RBP in predicting complications.

RESULTS

A total of 176 patients were enrolled, including 41 in the NRBP group and 135 in the LRBP group. The severity of AP in the LRBP group was significantly more severe than that of the NRBP group (MAP: 15.6% vs 39.0%, MSAP: 53.3% vs 29.3%, SAP: 31.1% vs 31.7%; P < 0.05). The incidence of acute necrotic collection was 70.4% in the LRBP group, significantly higher than that (52.1%) of the NRBP group (P < 0.05). The serum level of RBP in patients with local complications was significantly lower than that in patients without (24.00 (15.00, 27.50) mg/L vs 12.00 (9.00, 22.00) mg/L, P < 0.05). The AUC of serum RBP for predicting local complications was 0.708 (95%CI: 0.615-0.801) and the cut-off value was 15.5 mg/L with a sensitivity 60.4% and specificity 75.7%. The decrease of serum RBP was an independent risk factor for local complications (OR = 5.306, P = 0.003, 95%CI: 1.771-15.896).

CONCLUSION

The level of serum RBP in the acute phase could predict the occurrence of local complications of AP, but has no significant correlation with systemic inflammatory response and remote organ failure.

Measuring the serum level of retinol-binding protein can enhance the treatment of recalcitrant warts

BACKGROUND

Warts are common benign (60%-65%) self-limited tumors of the epidermis caused by human papillomaviruses (HPVs). However, some warts fail to resolve despite of different treatments and become recalcitrant. Vitamin A has antiproliferative and antikeratinizing properties by which the disruption of HPV replication can be occurred. Concentrations of retinol-binding protein (RBP) and retinol in the circulation highly correlate with each others.

AIM

To assess the serum level of RBP in patients with resistant warts to evaluate the possible role of retinol in the disease pathogenesis.

PATIENTS

This case-control study included 30 patients with resistant cutaneous warts (defined as failure of cure after conventional treatment as 12 weeks of salicylic acid application, 4 or more cycles of cryotherapy or electrocautery and/or other physical treatment modalities) and 30 age- and sex-matched healthy controls. RBP level in the serum was measured by ELISA.

RESULTS

There was a significant difference between cases and controls regarding the level of serum RBP (P = .001). However, serum RBP level did not differ significantly regarding sociodemographic or clinical data (P > .05 each). RBP is a good biomarker for significant early detection and discrimination between cases and controls (P = .001) at a cutoff point < 563.3 mg/l with sensitivity (93%) and specificity (80%).

CONCLUSION

Low serum RBP level in our studied patients may suggest an important role of retinol in the resistant warts pathogenesis. Thus measuring serum RBP will help to identify patients who are going to have resistant warts in the future.

Association of urinary non-albumin protein with the different urinary marker for glomerular and tubular damage in patients with type 2 diabetes

BACKGROUND/AIM

In recent years, the diagnostic utility of urinary protein levels has been demonstrated for the early detection and progression of kidney disease. This study aimed to evaluate the associations of the non-albumin protein (NAP) with different urinary marker for tubular and glomerular damage in patients with type 2 diabetes (T2D).

METHODS

In this observational cross-sectional study, 424 patients with T2D duration > 10 years were classified into two groups according to estimated glomerular filtration rate (eGFR). The ratios of different urinary markers (albumin, NAP, total protein, transferrin, retinol-binding protein (RBP), and neutrophil gelatinase-associated lipocalin (NGAL) to creatinine were analyzed.

RESULTS

The levels of urinary biomarkers increased significantly with decrease in eGFR levels. In the group with moderately decreased eGFR, the albumin to-creatinine ratio (ACR), non-albumin protein-to-creatinine ratio (NAPCR), and total protein-to-creatinine ratio (PCR) were independently associated with all urinary markers after being adjusted for risk factors. The area under the receiver operating characteristics (ROC) curve for ACR and PCR had a better diagnostic value than other urinary biomarkers. Comparing ROC curve of NAPCR with other urinary biomarkers, it was significantly better than NGAL/Cr (p = 0.033).

CONCLUSIONS

The findings of the present study confirm that ACR and PCR are diagnostic biomarkers in T2D patients with decreased eGFR. NAPCR in these patients diagnostically only outperformed NGAL/Cr.

Renal function and the oxidative status among children with thalassemia major and healthy controls: A cross-sectional study

BACKGROUND

Renal dysfunction is an underestimated complication of thalassemia major.

OBJECTIVES

The aim of this study is to compare the glomerular and tubular functions in children with β- Thalassemia major (β- TM) with healthy controls and assess the oxidative stress caused by high ferritin levels.

DESIGN AND SETTING

This prospective cross-sectional study was conducted in tertiary care hospital.

METHODS

Complete blood count (CBC), calcium (Ca), urea, creatinine (Cr), serum cystatin C before transfusion and urinary calcium (uCa), creatinine (uCr), protein (UPr) levels were analyzed in fresh samples. Beta-2-microglobulin (uβ2-MG), N- acetylglucosaminidase (uNAG), retinol binding protein (uRBP), malonedialdehyde (uMDA) secretion and creatinine levels were analyzed. Serum total antioxidant capacity (sTAC) and total oxidant capacity (sTOC) were measured with colorimetric micro-ELISA method. Last four serum ferritin values were recorded and the mean value was used for statistical analyzes.

RESULTS

Data from 47 patients and 32 controls were analyzed. The urinary RBP/Cr, Ca/Cr and Protein/Cr, were significantly higher in β-TM group. A statistically insignificant increase in urinary β2MG/Cr, uNAG/Cr, MDA/Cr was also found in the TM group. Proteinuria was present in 46 % (n: 22) and hypercalciuria in 34 % (n: 16) of the patients with β- TM. Serum total antioxidant capacity and total oxidant status (TOS) levels were significantly elevated in the patient group. Serum ferritin was significantly correlated with proteinuria, cystatin C levels, urinary Protein/Cr and uRBP/Cr.

CONCLUSION

Asymptomatic renal dysfunction is prevalent in β- TM patients that necessitate regular screening. Urinary RBP may be useful for early diagnosis.

Subclinical inflammation affects iron and vitamin A but not zinc status assessment in Senegalese children and Cambodian children and women

OBJECTIVE

To assess the impact of the acute-phase response (APR) during inflammation on Fe, Zn and vitamin A biomarkers to allow accurate evaluation of micronutrient status in populations.

DESIGN

Ferritin (FER), soluble transferrin receptor (TfR), retinol-binding protein (RBP), Zn, α1-acid glycoprotein and C-reactive protein concentrations were measured. Correction factors (CF) for each biomarker were calculated as the ratio for groups at different stages of inflammation v. the reference group without inflammation.Setting/SubjectsSenegalese (n 594) and Cambodian schoolchildren (n 2471); Cambodian women of reproductive age (n 2117).

RESULTS

TfR was higher during the incubation phase (CF=1·17) and lower during early and late convalescence (CF=0·87 and 0·78). FER was higher during all phases (CF=0·83, 0·48 and 0·65, respectively). RBP was higher during incubation (CF=0·88) and lower during early convalescence (CF=1·21). No effect of inflammation on Zn status was found.

CONCLUSIONS

Inflammation led to overestimation of Fe status and underestimation of vitamin A status. The response of the biomarker for vitamin A status to inflammation depended on the vitamin A status of the populations. Surprisingly, the assessment of Zn status was hardly affected by inflammation. Different phases of the APR had opposite effects on the assessment of Fe status using TfR. More research is needed to define the correct methods to adjust for inflammation in nutritional studies.

The physiological determinants of low-level urine cadmium: an assessment in a cross-sectional study among schoolchildren

BACKGROUND

Recent studies in children have reported associations of urinary cadmium (U-Cd), used as biomarker of Cd body burden, with renal dysfunction, retarded growth and impaired cognitive development in children. Little is known, however, about factors influencing U-Cd in children and likely to act as confounders.

METHODS

In a cross-sectional study involving 249 schoolchildren (mean age, 5.72 years; 138 boys), we measured the urine concentrations of cadmium, zinc, lead, albumin, alpha₁-microglobulin (A1M), retinol-binding protein, β₂-microglobulin and club cell protein (CC16). Determinants of U-Cd expressed per creatinine or adjusted to specific gravity were identified by multiple regression analyses.

RESULTS

Girls and boys had similar median concentrations of U-Cd (0.22 and 0.24 μg/L, 0.33 and 0.35 μg/g creatinine, respectively). When models were run without including creatinine or specific gravity among independent variables, urinary zinc, urinary A1M and age emerged as the strongest predictors of U-Cd expressed per g creatinine or adjusted to SG. When adding creatinine among predictors, urinary creatinine emerged as an additional strong predictor correlating negatively with U-Cd per g creatinine. This strong residual influence of diuresis, not seen when adding specific gravity among predictors, linked U-Cd to U-A1M or U-CC16 through secondary associations mimicking those induced by Cd nephrotoxity.

CONCLUSIONS

In young children U-Cd largely varies with diuresis, zinc metabolism and urinary A1M. These physiological determinants, unrelated to Cd body burden, may confound the child renal and developmental outcomes associated with low-level U-Cd.

Retinoids, anxiety and peripartum depressive symptoms among Chinese women: a prospective cohort study

BACKGROUND

The current study aimed to investigate whether serum RBP levels can be a key predictor of peripartum depression (PPD).

METHODS

This was a prospective cohort study, conducted at a general teaching hospital in South China. Research participants were evaluated at three time points: the third trimester of pregnancy (T1), after delivery at week one (T2), and after delivery week six (T3) using a set of self-reported questionnaires and blood sample assays.

RESULTS

A total of 156 subjects were included for data analysis. The prevalence of anxiety symptoms ranged from 32.69% to 36.53%. The prevalence of PPD was also high and ranged from 27.56% to 35.89%. In the third trimester, significant predictors of depressive symptoms include serum retinol-binding protein (RBP) concentrations and estradiol levels (P = 0.008 and 0.033, respectively). At one week after delivery, serum concentrations of RBP at T2 were still significant predictors of depressive symptoms (P = 0.020, and serum estradiol concentrations at T1 were a significant predictor (P = 0.010). The most stable predictor of depressive symptoms at T3 was anxiety symptoms, especially at T3 time point (P < 0.001). Serum RBP concentrations at T1 and T2 were still significant predictors of depressive symptoms at T3.

CONCLUSION

A high prevalence of anxiety and depressive symptoms tended to persist in Chinese women during the peripartum period. This study, which found the potential contribution of RBP to the occurrence of PPD, requires that large sample studies be conducted in future with a longer-term follow-up period, in order to confirm its results.

Small-quantity lipid-based nutrient supplements containing different amounts of zinc along with diarrhea and malaria treatment increase iron and vitamin A status and reduce anemia prevalence, but do not affect zinc status in young Burkinabe children: a cluster-randomized trial

Background

We assessed the effects of providing a package of interventions including small-quantity lipid-based nutrient supplements (SQ-LNS) containing 0, 5 or 10 mg zinc and illness treatment to Burkinabe children from 9 to 18 months of age, on biomarkers of zinc, iron and vitamin A status at 18 months and compared with a non-intervention cohort (NIC).

Methods

Using a two-stage cluster randomized trial design, communities were randomly assigned to the intervention cohort (IC) or NIC, and extended family compounds within the IC were randomly assigned to different treatment groups. IC children (n = 2435) were provided with 20 g SQ-LNS/d containing 0, 5 or 10 mg zinc, 6 mg of iron and 400 μg of vitamin A along with malaria and diarrhea treatment. NIC children (n = 785) did not receive the intervention package. At 9 and 18 months, hemoglobin (Hb), zinc, iron and vitamin A status were assessed in a sub-group (n = 404). Plasma concentrations of zinc (pZC), ferritin (pF), soluble transferrin receptor (sTfR) and retinol-binding protein (RBP) were adjusted for inflammation.

Results

At baseline, 35% of children had low adjusted pZC (<65 μg/dL), 93% were anemic (Hb <110 g/L), 25% had low adjusted pF (<12 μg/L), 90% had high adjusted sTfR (>8.3 mg/L) and 47% had low adjusted RBP (<0.94 μmol/L), with no group-wise differences. Compared with the NIC, at 18 months IC children had significantly lower anemia prevalence (74 vs. 92%, p = 0.001) and lower iron deficiency prevalence (13% vs. 32% low adjusted pF and 41% vs. 71% high adjusted sTfR, p < 0.001), but no difference in pZC. Mean adjusted RBP was greater at 18 months in IC vs. NIC (0.94 μmol/L vs. 0.86 μmol/L, p = 0.015), but the prevalence of low RBP remained high in both cohorts. Within the IC, different amounts of zinc had no effect on the prevalence of low pZC or indicators of vitamin A deficiency, whereas children who received SQ-LNS with 10 mg zinc had a significantly lower mean pF at 18 months compared to children who received SQ-LNS with 5 mg zinc (p = 0.034).

Conclusions

SQ-LNS regardless of zinc amount and source provided along with illness treatment improved indicators of iron and vitamin A status, but not pZC.

Trial registration

NCT00944281 (July 21, 2009).

Computing the binding affinity of a ligand buried deep inside a protein with the hybrid steered molecular dynamics

Computing the ligand-protein binding affinity (or the Gibbs free energy) with chemical accuracy has long been a challenge for which many methods/approaches have been developed and refined with various successful applications. False positives and, even more harmful, false negatives have been and still are a common occurrence in practical applications. Inevitable in all approaches are the errors in the force field parameters we obtain from quantum mechanical computation and/or empirical fittings for the intra- and inter-molecular interactions. These errors propagate to the final results of the computed binding affinities even if we were able to perfectly implement the statistical mechanics of all the processes relevant to a given problem. And they are actually amplified to various degrees even in the mature, sophisticated computational approaches. In particular, the free energy perturbation (alchemical) approaches amplify the errors in the force field parameters because they rely on extracting the small differences between similarly large numbers. In this paper, we develop a hybrid steered molecular dynamics (hSMD) approach to the difficult binding problems of a ligand buried deep inside a protein. Sampling the transition along a physical (not alchemical) dissociation path of opening up the binding cavity---pulling out the ligand---closing back the cavity, we can avoid the problem of error amplifications by not relying on small differences between similar numbers. We tested this new form of hSMD on retinol inside cellular retinol-binding protein 1 and three cases of a ligand (a benzylacetate, a 2-nitrothiophene, and a benzene) inside a T4 lysozyme L99A/M102Q(H) double mutant. In all cases, we obtained binding free energies in close agreement with the experimentally measured values. This indicates that the force field parameters we employed are accurate and that hSMD (a brute force, unsophisticated approach) is free from the problem of error amplification suffered by many sophisticated approaches in the literature.

Human biomonitoring of heavy metals in the vicinity of non-ferrous metal plants in Ath, Belgium

BACKGROUND

A previous study revealed an environmental contamination by heavy metals in the vicinity of two non-ferrous metal plants in Ath, Belgium. The purpose of the current cross-sectional study was to estimate exposure of the population to heavy metals in the vicinity of the plants, in comparison with population living further away.

METHODS

We did a random sampling in the general population of Ath in two areas: a central area, including the plants, and a peripheral area, presumably less exposed. We quantified cadmium, lead, nickel, chromium and cobalt in blood and/or urine of children and adults in three age groups: (i) children aged 2.5 to 6 years (n = 98), (ii) children aged 7 to 11 years (n = 74), and (iii) adults aged 40 to 60 years (n = 106). We also studied subclinical health effects by quantifying retinol-binding protein and microalbuminuria, and by means of a Strengths and Difficulties Questionnaire.

RESULTS

We obtained a participation rate of 24 %. Blood lead levels were significantly higher in young children living in the central area (18.2 μg/l ; 95 % CI: 15.9-20.9) compared to the peripheral area (14.8 μg/l ; 95 % CI: 12.6-17.4). We observed no other significant mean difference in metal concentrations between the two areas. In the whole population, blood lead levels were higher in men (31.7 μg/l ; 95 % CI: 27.9-36.1) than in women (21.4 μg/l ; 95 % CI: 18.1-25.3). Urine cadmium levels were 0.06 μg/g creatinine (95 % CI: 0.05-0.07), 0.21 μg/g creatinine (95 % CI: 0.17-0.27), and 0.25 μg/g creatinine (95 % CI: 0.20-0.30) for children, men, and women, respectively.

CONCLUSIONS

Despite higher blood lead levels in young children living close to the plants, observed metal concentrations remain in the range found in other similar biomonitoring studies in the general population and are below the levels of concern for public health.

A longitudinal study on urinary cadmium and renal tubular protein excretion of nickel-cadmium battery workers after cessation of cadmium exposure

PURPOSE

This study aimed to predict the outcome of urinary cadmium (Cd) excretion and renal tubular function by analyzing their evolution through 10 years after Cd exposure ceased.

METHODS

Forty-one female, non-smoking workers were recruited from the year 2004 to 2009 when being removed from a nickel-cadmium battery factory, and they were asked to provide morning urine samples on three consecutive days at enrollment and in every follow-up year until 2014. Urinary Cd and renal tubular function biomarkers including urinary β2-microglobulin (β2-m) and retinol-binding protein (RBP) concentrations were determined with the graphite furnace atomic absorption spectrometry and the enzyme-linked immunosorbent assays, respectively.

RESULTS

The medians of baseline Cd, β2-m and RBP concentrations at enrollment were 6.19, 105.38 and 71.84 μg/g creatinine, respectively. Urinary β2-m and RBP concentrations were both related to Cd concentrations over the years (β absolute-β2-m = 9.16, P = 0.008 and β absolute-RBP = 6.42, P < 0.001, respectively). Cd, β2-m and RBP concentrations in the follow-up years were all associated with their baseline concentrations (β absolute-Cd = 0.61, P < 0.001; β absolute-β2-m = 0.64, P < 0.001; and β absolute-RBP = 0.60, P < 0.001, respectively), and showed a decreasing tendency with the number of elapsed years relative to their baseline concentrations (β relative-Cd = -0.20, P = 0.010; β relative-β2-m = -17.19, P = 0.002; and β relative-RBP = -10.66, P < 0.001, respectively).

CONCLUSIONS

Urinary Cd might eventually decrease to the general population level, and Cd-related tubular function would improve under the baseline conditions of this cohort.

Effect of Omega-3 Supplementation on Lipocalin 2 and Retinol-Binding Protein 4 in Type 2 Diabetic Patients

BACKGROUND

Serum levels of lipocalin 2 (LCN 2) and retinol-binding protein-4 (RBP 4), increase in type 2 diabetes mellitus (T2DM). We sought to determine whether serum LCN 2 and RBP 4 change after an intervention with omega-3 fatty acids supplementation in diabetic patients.

METHODS

Forty-five type 2 diabetic patients from Iranian Diabetic Association in Tehran, Iran in 2013 were randomly recruited into two groups: one group received 4 g/d omega-3 for 10 wk; and the control group received placebo. Blood samples, food intake records, anthropometric measurements were obtained from all participants at the beginning and end of the study.

RESULTS

Fasting RBP 4 plasma levels significantly changed after 10 wk supplementation (P = 0.01). The LCN 2 concentrations decreased in omega-3 group, but the changes were not statistically significant. Omega-3 supplementation had no noticeable effect on anthropometric factors.

CONCLUSION

These findings provide a rationale for omega-3 supplements aimed at lowering serum RBP 4 levels in T2DM.

RAGE-mediated inflammation in patients with septic shock

BACKGROUND

The receptor for advanced glycation end-products (RAGE)-pathway is described to be a crucial component of the innate immune response in sepsis. The aims of the present study were, therefore, to delineate the kinetics of membrane-bound RAGE expression, to quantify its soluble isoforms, and to determine the extent of metabolic (e.g., AGE-CML) as well as immunologic (e.g., S100A8/A9) ligands in different inflammatory settings in humans.

MATERIALS AND METHODS

The presented data result from secondary analyses of an observational clinical pilot study, including patients with septic shock (n = 60), postoperative controls (n = 30), and healthy volunteers (n = 30). Surface-bound expression of RAGE by peripheral blood leukocytes was determined by flow cytometry. In addition, plasma levels of sRAGE, esRAGE, AGE-CML, S100A8/A9, S100A8/A9-CML, RBP, RBP-CML, HSA-CML, HMBG-1, and ß-Amyloid were measured using ELISA.

RESULTS

In patients with septic shock, RAGE expression was significantly increased in comparison to both control groups, which was paralleled by a significant increase in sRAGE plasma levels. Formation of AGE-CML was shown to be dependent on the availability of the unmodified protein. However, the total amount of AGE-CML did not differ significantly between septic patients and healthy volunteers at early stages or was even lower in patients with sepsis at later stages. In contrast, immunologic ligands (e.g., S100A8/A9) were shown to be significantly elevated in septic patients within the entire study period.

CONCLUSIONS

Activation of the RAGE-pathway was shown to be of relevance in patients with septic shock, mainly driven by an increase in immunologic (e.g., S100A8/A9) rather than metabolic ligands (e.g., CML-derived AGE-formation).

Effect of Omega-3 Supplementation on Lipocalin 2 and Retinol-Binding Protein 4 in Type 2 Diabetic Patients

BACKGROUND

Serum levels of lipocalin 2 (LCN 2) and retinol-binding protein-4 (RBP 4), increase in type 2 diabetes mellitus (T2DM). We sought to determine whether serum LCN 2 and RBP 4 change after an intervention with omega-3 fatty acids supplementation in diabetic patients.

METHODS

Forty-five type 2 diabetic patients from Iranian Diabetic Association in Tehran, Iran in 2013 were randomly recruited into two groups: one group received 4 g/d omega-3 for 10 wk; and the control group received placebo. Blood samples, food intake records, anthropometric measurements were obtained from all participants at the beginning and end of the study.

RESULTS

Fasting RBP 4 plasma levels significantly changed after 10 wk supplementation (P = 0.01). The LCN 2 concentrations decreased in omega-3 group, but the changes were not statistically significant. Omega-3 supplementation had no noticeable effect on anthropometric factors.

CONCLUSIONS

These findings provide a rationale for omega-3 supplements aimed at lowering serum RBP 4 levels in T2DM.

Analysis of the effect of a novel therapeutic for type 2 diabetes on the proteome of a muscle cell line

Elevated serum retinol-binding protein (RBP) concentration has been implicated in the development of insulin resistance and type 2 diabetes. Two series of small molecules have been designed to lower serum levels by reducing secretion of the transthyretin-RBP complex from the liver and enhancing RBP clearance through the kidney. These small molecules were seen to improve glucose and insulin tolerance tests and to reduce body weight gain in mice rendered diabetic through a high fat diet. A proteomics study was conducted to better understand the effects of these compounds in muscle cells, muscle being the primary site for energy expenditure. One lead compound, RTC-15, is seen to have a significant effect on proteins involved in fat and glucose metabolism. This could indicate that the compound is having a direct effect on muscle tissue to improve energy homeostasis as well as a whole body effect on circulating RBP levels. This newly characterized group of antidiabetic compounds may prove useful in the treatment and prevention of insulin resistance and obesity.

Signaling by retinol and its serum binding protein

Vitamin A, retinol, circulates in blood bound to retinol-binding protein (RBP) which, in turn, associates with transthyretin (TTR) to form a retinol-RBP-TTR ternary complex. At some tissues, retinol-bound (holo-) RBP is recognized by a membrane protein termed STRA6, which transports retinol from extracellular RBP into cells and, concomitantly, activates a JAK2/STAT3/5 signaling cascade that culminates in induction of STAT target genes. STRA6-mediated retinol transport and cell signaling are critically inter-dependent, and they both require the presence of cellular retinol-binding protein 1 (CRBP1), an intracellular retinol acceptor, as well as a retinol-metabolizing enzyme such as lecithin:retinol acyltransferase (LRAT). STRA6 thus functions as a "cytokine signaling transporter" which couples vitamin A homeostasis and metabolism to cell signaling, thereby regulating gene transcription. Recent studies provided molecular level insights into the mode of action of this unique protein.

HIV and schistosomiasis in rural Zimbabwe: the association of retinol-binding protein with disease progression, inflammation and mortality

BACKGROUND

Vitamin A has widespread effects on immune function and is therefore interesting in HIV-infection. Retinol-binding protein (RBP or RBP4) is a negative acute-phase protein and a marker of vitamin A status. Our aim was to investigate the association of RBP with HIV progression, infection with schistosomiasis, inflammatory cytokines, and mortality.

METHODS

The study included 192 HIV-infected and 177 HIV-uninfected individuals from Mupfure in rural Zimbabwe. Of these, 208 were infected with Schistosoma haematobium, 27 with S. mansoni and 48 with both. Plasma RBP, HIV-RNA, CD4 cell count, haemoglobin, cytokines, clinical staging (CDC category), self-reported level of function (Karnoffsky Performance Score, KPS) and schistosomiasis status were assessed at baseline. Participants were followed up for survival 3-4 years post-enrolment.

RESULTS

RBP levels were lower in HIV-infected individuals(p<0.0001). Among HIV-infected individuals, multivariable analysis showed RBP to be positively correlated with CD4 cell count(p=0.050), KPS(p=0.003), and haemoglobin(p<0.0001) and negatively correlated with HIV-RNA(p<0.0001), CDC category(p<0.0001), tumor necrosis factor-receptor II(p<0.0001) and interleukin(IL)-6(p=0.004), as well as with IL-8(p=0.005) and IL-10(p=0.003) for HIV-infected men. Furthermore, among HIV-infected individuals RBP correlated negatively with schistosomiasis(p=0.038) and intensity of infection: circulating anodic antigen(p=0.014), circulating cathodic antigen(p<0.0001) and faecal egg output(p=0.004).

CONCLUSIONS

In HIV-infected individuals, RBP was negatively associated with levels of inflammatory markers, markers of HIV progression, infection with schistosomiasis and markers of schistosomal intensity.

Vitamin A and retinol-binding protein deficiency among chronic liver disease patients

OBJECTIVE

Vitamin A deficiency (VAD) is associated with the progression of chronic liver disease (CLD). The aim in this study was to assess levels of serum retinol and retinol-binding protein (RBP) as well as liver vitamin A stores in the presence of liver cirrhosis and hepatocellular carcinoma.

METHODS

We ascertained the serum retinol and RBP levels of randomly selected CLD patients divided into two groups, one given 1500 UI (n = 89) and the other receiving 2500 UI (n = 89) doses of retinyl palmitate for the relative dose response test. Blood samples were collected in a fasting state and 5 and 7 h after supplementation.

RESULTS

The prevalence of VAD was 62.4%. There was a progressive drop in serum retinol (P < 0.001) and RBP (P = 0.002) according to the severity of the liver disease, and a greater prevalence of severe VAD was noted in cirrhosis Child & Pugh C (52.8%). Fifty percent of the patients presented a low availability of RBP relative to retinol concentration, and there was no peak in RBP levels regardless of the dose of retinyl palmitate administered.

CONCLUSIONS

Our findings suggest serum retinol and RBP are relevant as indicators of vitamin A nutritional status in the presence of CLD. Liver vitamin A store cannot be evaluated using the RDR test because CLD causes a reduction in RBP synthesis and interferes with the mobilization of endogenous vitamin A. Considering how the patients already showed a drop in RBP relative to retinol concentrations, it is reasonable to assume vitamin A supplementation may trigger harmful effects in CLD patients.

Cadmium, type 2 diabetes, and kidney damage in a cohort of middle-aged women

BACKGROUND

It has been proposed that diabetic patients are more sensitive to the nephrotoxicity of cadmium (Cd) compared to non-diabetics, but few studies have examined this in humans, and results are inconsistent.

AIM

To test the hypothesis that women with type 2 diabetes mellitus (DM) or impaired glucose tolerance (IGT) have higher risk of kidney damage from cadmium compared to women with normal glucose tolerance (NGT).

METHODS

All 64-year-old women in Gothenburg, Sweden, were invited to a screening examination including repeated oral glucose tolerance tests. Random samples of women with DM, IGT, and NGT were recruited for further clinical examinations. Serum creatinine was measured and used to calculate estimated glomerular filtration rate (eGFR). Albumin (Alb) and retinol-binding protein (RBP) were analyzed in a 12h urine sample. Cadmium in blood (B-Cd) and urine (U-Cd) was determined using inductively coupled plasma mass spectrometry. Associations between markers of kidney function (eGFR, Alb, and RBP) and quartiles of B-Cd and U-Cd were evaluated in models, including also blood pressure and smoking habits.

RESULTS

The mean B-Cd (n=590) was 0.53 µg/L (median 0.34 µg/L). In multivariable models, a significant interaction was seen between high B-Cd (upper quartile, >0.56 µg/L) and DM (point estimate +0.40 mg Alb/12h, P=0.04). In stratified analyzes, the effect of high B-Cd on Alb excretion was significant in women with DM (53% higher Alb/12h, P=0.03), but not in women with IGT or NGT. Models with urinary albumin adjusted for creatinine showed similar results. In women with DM, the multivariable odds ratio (OR) for microalbuminuria (>15 mg/12h) was increased in the highest quartile of B-Cd vs. B-Cd quartiles 1-3 in women with DM (OR 4.2, 95% confidence interval 1.1-12). No such effect was found in women with IGT or NGT. There were no associations between B-Cd and eGFR or excretion of RBP, and no differences between women with DM, IGT, or NGT regarding effect of B-Cd on eGFR or RBP.

CONCLUSION

The present study provides support for the hypothesis that women with DM have higher risk of renal glomerular damage from cadmium exposure compared to women without DM.

Sensitive ECL immunosensor for detection of retinol-binding protein based on double-assisted signal amplification strategy of multiwalled carbon nanotubes and Ru(bpy)3(2+) doped mesoporous silica nanospheres

A novel electrochemiluminescence (ECL) strategy based on the sandwich-type immunosensor for sensitive detection of retinol-binding protein (RBP) was developed. The primary antibody anti-RBP was immobilized onto multiwalled carbon nanotubes (MWCNTs), which have large surface area and high electrical conductivity. The RBP antigen and Ru-Nafion@SiO2-labeled secondary antibody were then successively conjugated to form sandwich-type immunocomplexes through the specific interaction between antigen and antibody. The ECL signal amplification was significantly improved due to the synergistic effect of MWCNTs and mesoporous silica nanospheres (mSiO2). The developed ECL immunosensor exhibited high sensitivity and specificity for the detection of RBP and responded linearly to the clinically-relevant concentration of RBP from 78 to 5000 ng mL(-1). Moreover, the MWCNT-based ECL immunosensor displayed excellent stability and reproducibility, as well as successfully achieved the detection of RBP in patient urine samples with desirable results. The present work provided a promising technique for the clinical screening of RBP and point-of-care diagnostics.