Serum retinol-binding protein: a link between obesity, insulin resistance, and type 2 diabetes

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 = -0.39 kg/m2, 95% CI: -0.48 to -0.31 kg/m2vs. Lower RBP4 = -0.24 kg/m2, 95% CI: -0.32 to -0.15 kg/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.

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.

Bariatric Surgery in Obesity: Metabolic Quality Analysis and Comparison of Surgical Options

Obesity is a constantly growing health problem which reduces quality of life and life expectancy. Bariatric surgery (BS) for obesity is considered when all other conservative treatment modalities have failed. Comparison of the multidisciplinary programs with BS regarding to the weight loss showed that substantial and durable weight reduction have been achieved only with bariatric surgical treatments. Although laparoscopic sleeve gastrectomy is the most popular BS, it has high long-term failure rates, and it is claimed that one of every three patients will undergo another bariatric procedure within a 10-year period. Although BS provides weight loss and improvement of metabolic comorbidities, in long-term follow-up, weight gain is observed in half of the patients, while decrease in bone mass and nutritional deficiencies occur in up to 90%. Moreover, despite significant weight loss, several psychological aspects of patients are worsened in comparison to preoperative levels. Nearly one-fifth of postoperative patients with "Loss-of-eating control" meet food addiction criteria. Therefore, the benefits of weight loss following bariatric procedures alone are still debated in terms of the proinflammatory and metabolic profile of obesity.

The impact of vitamin A supplementation on thyroid function and insulin sensitivity: implication of deiodinases and phosphoenolpyruvate carboxykinase in male Wistar rats

PURPOSE

Vitamin A is an essential nutrient with vital biological functions. The present study investigated the effect of different doses of vitamin A palmitate at different time intervals on thyroid hormones and glycemic markers.

METHODS

Male rats were administrated vitamin A palmitate at different doses (0, 0.7, 1.5, 3, 6, and 12 mg/kg, oral) and samples were collected at different time intervals of 2, 4, and 6 weeks. The levels of vitamin A, thyroid hormones (T3, T4, and TSH), deiodinases (Dio1 and Dio3), glycemic markers (blood insulin and fasting glucose levels, HOMA IR and HOMA β), retinol-binding protein 4 (RBP4) and the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) were measured.

RESULTS

The findings demonstrated that long-term supplementation with high doses of vitamin A palmitate resulted in hypothyroidism (lower T3 and T4 levels and elevated TSH levels) as well as upregulation of Dio1 and Dio3 expression levels. This effect was associated with elevated glucose and insulin levels, enhanced HOMA IR, and decreased HOMA B index. In addition, prolonged vitamin A supplementation significantly increased RBP4 levels that upregulated the expression of PEPCK.

CONCLUSION

High doses of vitamin A supplementation increased the risk of hypothyroidism, modulated insulin sensitivity, and over a long period, increased the incidence of type 2 diabetes mellitus associated with oxidative stress and hepatitis.

A Label-Free Gold Nanoparticles-Based Optical Aptasensor for the Detection of Retinol Binding Protein 4

Retinol-binding protein 4 (RBP4) has been implicated in insulin resistance in rodents and humans with obesity and T2DM, making it a potential biomarker for the early diagnosis of T2DM. However, diagnostic tools for low-level detection of RBP4 are still lagging behind. Therefore, there is an urgent need for the development of T2DM diagnostics that are rapid, cost-effective and that can be used at the point-of-care (POC). Recently, nano-enabled biosensors integrating highly selective optical detection techniques and specificity of aptamers have been widely developed for the rapid detection of various targets. This study reports on the development of a rapid gold nanoparticles (AuNPs)-based aptasensor for the detection of RBP4. The retinol-binding protein aptamer (RBP-A) is adsorbed on the surface of the AuNPs through van der Waals and hydrophobic interactions, stabilizing the AuNPs against sodium chloride (NaCl)-induced aggregation. Upon the addition of RBP4, the RBP-A binds to RBP4 and detaches from the surface of the AuNPs, leaving the AuNPs unprotected. Addition of NaCl causes aggregation of AuNPs, leading to a visible colour change of the AuNPs solution from ruby red to purple/blue. The test result was available within 5 min and the assay had a limit of detection of 90.76 ± 2.81 nM. This study demonstrates the successful development of a simple yet effective, specific, and colorimetric rapid assay for RBP4 detection.

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.

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

Background

The predictive role of retinol-binding protein 4 (RBP4) in the adverse prognosis of patients with stable coronary artery disease (CAD) has not been well-defined. We thus conducted this cohort study to investigate the association between circulating RBP4 level and major adverse cardiovascular events (MACEs) in Chinese patients with stable CAD.

Methods

Patients with stable CAD and serum RBP4 concentration measurement at admission between July 2012 and January 2015 were included. The primary outcome in this study was incident MACEs, which included acute coronary syndrome, heart failure, stroke, peripheral vascular disease, and cardiovascular death. Cox proportional hazards regression was adopted to investigate the association between RBP4 and the incidence of MACEs.

Results

A total of 840 patients with stable CAD were analyzed. The mean age of patients was 61.2 ± 15.9 years, and 56.1% of them were men. After a median follow-up of 2.3 years, 129 MACEs were observed. Compared to participants exposed to the first quartile of serum RBP4 level, those in the second, the third, and the fourth quartiles had associated hazard ratios (HRs) of 2.38 [95% confidence interval (CI): 1.33-4.26], 2.35 (95% CI: 1.31-4.21), and 2.27 (95% CI: 1.28-4.04) after adjusted for confounders, respectively. Every 5 μg/ml increment in serum RBP4 concentration was associated with an adjusted HR of 1.13 (95% CI: 1.05-1.22) for the occurrence of MACEs. Subgroup analyses suggested no significant modifying effects of baseline characteristics for the association between RBP4 and MACEs in patients with stable CAD.

Conclusion

Our finding suggested that the higher circulating RBP4 level was significantly associated with an increased risk of MACEs in patients with stable CAD.

Associaton of Retinol Binding Protein 4 (RBP4) Levels With Hyperuricemia: A Cross-Sectional Study in a Chinese Population

BACKGROUND

There are few studies on predictive biomarkers for hyperuricemia, and the predictive value of these biomarkers tends to be poor. Additionally, no reports have described the predictive value of retinol binding protein 4 (RBP4) for hyperuricemia.

PURPOSE

This study was performed to evaluate the value of RBP4 for predicting the risk of hyperuricemia in a general population, determine whether RBP4 could be used alone or in combination with other factors to predict the risk of hyperuricemia in the general population, and establish an optimum predictive model.

METHODS

We conducted a population-based cross-sectional survey in 2018, involving a questionnaire, physical examination, and laboratory testing. We enrolled 2303 individuals by stratified random sampling, and 2075 were included in the data analysis after applying the eligibility criteria.

RESULTS

Serum RBP4 level had a highly significant association with hyperuricemia (P<0.001). After adjusting for potential confounders, logistic regression indicated that the risk of hyperuricemia was highest in the highest RBP4 quartile (odds ratio: 7.9, 95% confidence interval [CI]: 4.18-14.84, compared to the lowest quartile). The area under the receiver operating characteristic (ROC) curve (AUC) for RBP4 was 0.749 (95% CI: 0.725-0.774, P<0.001), which was higher than that for all the other predictors assessed. The optimum model for predicting hyperuricemia in the general population consisted of RBP4, sex (male), body mass index, serum creatinine, high-sensitivity C-reactive protein, fasting blood glucose, insulin, and alcohol consumption. The AUC was 0.804 (95% CI: 0.782-0.826, P<0.001).

CONCLUSIONS

RBP4 is strongly associated with hyperuricemia, and its predictive value was higher than that of traditional predictors.

Retinol-binding protein 4 in combination with lipids to predict the regression phenomenon of autism spectrum disorders

BACKGROUND

About 20-40 % of autistic people experience a phenomenon of regression. Retinol binding protein 4 (RBP4) plays an important role as an inflammatory neurotrophic adipokine and is a promising mediator of the fat-brain axis. Abnormal fatty acid metabolism and lipid mediators have been reported to be related to the etiological mechanism in autism, and amelioration of impaired lipid metabolism can be recognized as a treatment strategy for autism. The purpose of this study is to explore the relationship between RBP4, lipids, and the autistic regression phenomenon, and to discuss their potentials as biomarkers for the autistic regression phenomenon.

METHODS

A total of 60 autistic individuals (18 with regression phenomenon, 42 without regression phenomenon) (ASD group) and 36 healthy controls were enrolled in this case-control study. The levels of RBP4, total cholesterol (TC), high-density lipoprotein (HDLC), low-density lipoprotein (LDLC), and triglyceride (TG) were measured. Childhood Autism Rating Scale (CARS) is used to assess the severity of autism. Ethical measures were performed in compliance with the current Declaration of Helsinki and written informed consent was obtained from the parents before enrollment of the children and adolescents.

RESULTS

Compared with control subjects, autistic individuals had lower levels of TC (P = 0.007), RBP4 (P = 0.001), and HDLC (P = 0.027). The levels of RBP4 in ASD group were positively correlated with TG (r = 0.355, P = 0.005), HDLC (r = 0.257, P = 0.047), TG/TC (r = 0.376, P = 0.003) and TG/LDLC (r = 0.363, P = 0.004), and were negatively correlated with CARS (r=-0.296, P = 0.003). Further logistic regression demonstrated that decreased RBP4 concentration was associated with the presentation of the autistic regression phenomenon even after the adjustment of the potential confounding factors.

CONCLUSIONS

Serum RBP4 is associated with the autistic regression phenomenon and the severity of ASD. Further studies are needed to expound whether decreased RBP4 participates in the development of the autistic regression phenomenon.

Exploring the mediating role of serum retinol-binding protein 4 in the relationship between sleep quality and insulin resistance in pregnant women

AIMS

We aimed to explore the mediating role of plasma retinol-binding protein 4 (RBP4) in the relationship between sleep quality and insulin resistance (IR) among pregnant women.

METHODS

We conducted a cross-sectional study including 263 pregnant women in the first trimester. Sleep quality was evaluated by Pittsburgh Sleep Quality Index (PSQI). The ELISA and homeostasis model assessment (HOMA) was used to analyze plasma RBP4 and estimate IR. The mediating model was used to analyze the mediating role of RBP4 in the relationship between PSQI score and IR.

RESULTS

In the multivariable linear regression model, the three terms were positively related with each other, PSQI score was positively associated with IR levels (β = 0.55, p < 0.05). In the mediating model, RBP4 levels mediated completely the relationship between PSQI scores and IR levels (β = 0.29, p < 0.0001). The indirect effect of RBP4 in the relation between sleep quality and IR explained 89.10% of total effect.

CONCLUSIONS

RPB4 may play a complete mediating role in the relation between sleep quality and insulin resistance in early pregnancy. Improvements in sleep quality in the first trimester may provide a pathway to reduce plasma RBP4, which is beneficial for less IR and GDM prevention.

Retinol-binding protein 4 is associated with arterial stiffness in early postmenopausal women

OBJECTIVE

Recent evidence in postmenopausal women suggested lack of association between serum levels of retinol-binding protein 4 (RBP4) and subclinical atherosclerosis; however, associations with arterial stiffness in this population remain unexplored. We evaluated the association among RBP4 and cardiovascular risk factors, including homocysteine, a marker involved in retinoic acid synthesis, and indices of arterial stiffness, in a sample of apparently healthy postmenopausal women.

METHODS

This cross-sectional study included 123 healthy postmenopausal women, not on hormone therapy, antihypertensive, or hypolipidemic treatment and with a menopausal age 10 years or less. We performed biochemical/hormonal assessment and sonographic evaluation, including carotid-femoral pulse wave velocity (PWV) and carotid artery stiffness index (SI).

RESULTS

Univariate analysis showed that RBP4 values correlated with age, low-density lipoprotein-cholesterol and estradiol levels. There was a trend of association of SI and PWV with homocysteine and triglycerides. RBP4 differed according to PWV, using the median PWV value as cut-off (RBP4, PWV ≤8.1 vs >8.1 m/s: 10.09 ± 2.05 vs 10.85 ± 1.91 ng/mL, analysis of covariance P value 0.014 adjusted for age, menopausal age, estradiol, pulse pressure). Linear regression analysis showed that PWV was independently associated with RBP4, age, and pulse pressure, whereas SI was independently associated with RBP4. An increase of one standard deviation in RBP4 levels (2.54 ng/mL) was associated with an increase of 0.577 m/s in PWV.

CONCLUSIONS

RBP4 serum levels are associated with arterial stiffness, in a sample of healthy postmenopausal women. If this association is causative, serum RBP4 levels could serve as a marker of arterial stiffness. Prospective studies are required to investigate the significance of our findings. : Video Summary:http://links.lww.com/MENO/A621.

Systematic Quantification of Neurotrophic Adipokines RBP4, PEDF, and Clusterin in Human Cerebrospinal Fluid and Serum

CONTEXT

Data on the presence/quantification of the neurotrophic adipokines retinol-binding protein-4 (RBP4), clusterin, and pigment epithelium-derived factor (PEDF) in human cerebrospinal fluid (CSF) are scarce and migration of these adipokines across of the blood-brain barrier (BBB) is uncertain.

OBJECTIVE

This work aimed to quantify RBP4, PEDF, and clusterin in paired serum and CSF samples of patients undergoing neurological evaluation.

METHODS

A total of 268 patients (109 male, 159 female) were included. Adipokine serum and CSF concentrations were measured by enzyme-linked immunosorbent assay in duplicate.

RESULTS

RBP4 was abundant in serum (mean, 31.9 ± 24.2 μg/mL). The serum concentrations were approximately 145 times higher than in CSF (CSF to serum RBP4 ratio, 8.2 ± 4.3 × 10-3). PEDF was detectable in serum (mean, 30.2 ± 11.7 μg/mL) and concentrations were approximately 25 times higher than in CSF (CSF to serum PEDF ratio, 42.3 ± 15.6 × 10-3). Clusterin serum concentrations were abundant with mean levels of 346.0 ± 114.6 μg/mL, which were approximately 40 times higher than CSF levels (CSF to serum clusterin ratio, 29.6 ± 23.4 × 10-3). RBP4 and PEDF serum levels correlated positively with CSF levels, which were increased in overweight/obese patients and in type 2 diabetic patients. The CSF concentrations of all 3 adipokines increased with BBB dysfunction. RBP4 in CSF correlated positively with inflammatory parameters. In detail, only RBP4 showed the kinetics and associations that are mandatory for a putative mediator of the fat-brain axis.

CONCLUSION

RBP4, PEDF, and clusterin are permeable to the BBB and increase with the measure of BBB dysfunction. RBP4 represents an inflammatory neurotrophic adipokine and is a promising mediator of the fat-brain axis.

Ileal transposition helps to regulate plasma hepatokine levels in obese Zucker (Crl:ZUC(ORL)-Leprfa) rats

We studied the long-term effect of ileal transposition (IT) metabolic surgery on the hepatokines: retinol-binding protein-4 (RBP4), α-2-HS-glycoprotein (aHSG/fetuin-A), and fibroblast growth factor 21 (FGF21), C-reactive protein (CRP) plasma levels, glucose metabolism, body weight, liver histology, as well as total lipids concentration in muscle, liver, and fat tissue of obese Zucker (Crl:ZUC(ORL)-Lepr^fa) rats. 14 adult males were randomly submitted either to IT or SHAM (control) surgery. Pre-operative hepatokines plasma levels were not significantly different in rats submitted to IT or SHAM protocol. Three months after the procedures the plasma levels of RBP4, aHSG, FGF21, and CRP were significantly lower in IT-operated animals when compared to SHAM-operated group. Three and 12 weeks after the IT and SHAM surgery, the AUC_OGTT were significantly lower than AUC_OGTT before the surgery. HOMA-IR was lower in rats after IT surgery in comparison to the SHAM-operated rats. Muscle and liver total lipids concentration was reduced after the IT procedure when compared to pre-IT conditions. IT had a significant reductive impact on the body weight in comparison to SHAM surgery in the 4th, 6th, 8th, and 10th week after the surgery. We conclude that IT reduces hepatokines' plasma concentrations, muscle and liver total lipids concentration but not the inflammatory processes in the liver of Zucker (Crl:ZUC(ORL)-Lepr^fa) rats.

Vitamin A and Its Multi-Effects on Pancreas: Recent Advances and Prospects

Vitamin A (VA), which is stored in several forms in most tissues, is required to maintain metabolite homeostasis and other processes, including the visual cycle, energy balance, epithelial cell integrity, and infection resistance. In recent years, VA molecules, also known as retinoids, have been extensively explored and used in the treatment of skin disorders and immune-related tumors. To date, several observational and interventional studies have explored the relationship between VA status and the pathogenesis of diabetes. In particular, VA micronutrients have been shown to regulate pancreatic development, β-cell function, pancreatic innate immune responses, and pancreatic stellate cells phenotypes through multiple mechanisms. However, there are still many problems to be proven or resolved. In this review, we summarize and discuss recent and available evidence on VA biological metabolism in the pancreas. Analysis of the effects of VA on metabolism in the pancreas will contribute to our understanding of the supportive physiological roles of VA in pancreas protection.

Potassium supplementation blunts the effects of high salt intake on serum retinol-binding protein 4 levels in healthy individuals

Aims/Introduction

Excessive dietary salt or low potassium intakes are strongly correlated with insulin resistance (IR) and type 2 diabetes mellitus. In epidemiological and experimental studies, increased serum retinol‐binding protein 4 (RBP4) contributes to the pathogenesis of type 2 diabetes mellitus. Herein, we hypothesized that RBP4 might be an adipocyte‐derived “signal” that plays the crucial role in salt‐related insulin resistance or type 2 diabetes mellitus. This study aimed to assess whether salt consumption and potassium supplementation influence serum RBP4 levels in healthy individuals.

Materials and Methods

A total of 42 participants (aged 25–50 years) in a rural area of Northern China were successively provided normal (3 days at baseline), low‐salt (7 days; 3 g/day NaCl) and high‐salt (7 days; 18 g/day) diets, and a high‐salt diet with potassium additive (7 days; 18 g/day NaCl and 4.5 g/day KCl). Urinary sodium and potassium were measured to ensure compliance to dietary intervention. Then, RBP4 levels were evaluated by enzyme‐linked immunosorbent assay.

Results

High salt intake significantly raised serum RBP4 levels in healthy participants (17.5 ± 0.68 vs 28.6 ± 1.02 µg/mL). This phenomenon was abrogated by potassium supplementation (28.6 ± 1.02 vs 17.6 ± 0.88 µg/mL). In addition, RBP4 levels presented positive (r = 0.528, P < 0.01) and negative (r = −0.506, P < 0.01) associations with 24‐h urinary sodium‐ and potassium excretion levels.

Conclusions

RBP4 synthesis is motivated by high salt intake and revoked by potassium supplementation. Our pioneer work has contributed to the present understanding of salt‐induced insulin resistance or type 2 diabetes mellitus.

Understanding Development of Malnutrition in Hemodialysis Patients: A Narrative Review

Hemodialysis (HD) majorly represents the global treatment option for patients with chronic kidney disease stage 5, and, despite advances in dialysis technology, these patients face a high risk of morbidity and mortality from malnutrition. We aimed to provide a novel view that malnutrition susceptibility in the global HD community is either or both of iatrogenic and of non-iatrogenic origins. This categorization of malnutrition origin clearly describes the role of each factor in contributing to malnutrition. Low dialysis adequacy resulting in uremia and metabolic acidosis and dialysis membranes and techniques, which incur greater amino-acid losses, are identified modifiable iatrogenic factors of malnutrition. Dietary inadequacy as per suboptimal energy and protein intakes due to poor appetite status, low diet quality, high diet monotony index, and/or psychosocial and financial barriers are modifiable non-iatrogenic factors implicated in malnutrition in these patients. These factors should be included in a comprehensive nutritional assessment for malnutrition risk. Leveraging the point of origin of malnutrition in dialysis patients is crucial for healthcare practitioners to enable personalized patient care, as well as determine country-specific malnutrition treatment strategies.

Association between new circulating proinflammatory and anti-inflammatory adipocytokines with coronary artery disease

Supplemental Digital Content is available in the text.

The aim of this study was to evaluate the diagnostic and risk predictive value of emerging proinflammatory and anti-inflammatory adipocytokines on coronary artery disease (CAD).

Retinol, Retinoic Acid, and Retinol-Binding Protein 4 are Differentially Associated with Cardiovascular Disease, Type 2 Diabetes, and Obesity: An Overview of Human Studies

Vitamin A is a fat-soluble essential nutrient obtained from plant- and animal-based sources that has roles in growth, vision, and metabolism. Vitamin A circulates mainly as retinol bound to retinol-binding protein 4 (RBP4), and is delivered to tissues and converted to retinoic acid, which is a ligand for several nuclear receptors. In recent years, aspects of vitamin A metabolism have been under scrutiny with regards to the development of metabolic and lifestyle diseases including cardiovascular disease (CVD), type 2 diabetes mellitus (T2DM), and overweight and obesity in humans. Studies have mainly focused on RBP4 in this context, whereas the major circulating form, retinol, and the major bioactive form, retinoic acid, have been overlooked in this regard until recently. As one of the main roles of RBP4 is to deliver retinol to tissues for biological action, the associations of retinol and retinoic acid with these diseases must also be considered. In this review, we summarize and discuss recent and available evidence from human studies with focus on retinol, retinoic acid, and RBP4 and provide an overview of these crucial components of vitamin A metabolism in CVD, T2DM, and obesity. In summary, retinol was found to be both inversely and positively associated with CVD whereas the associations with T2DM and obesity were less clear. Although only a few studies have been published on retinoic acid, it was inversely associated with CVD. In contrast, serum RBP4 was mostly found to be positively associated with CVD, T2DM, and obesity. At present, it is difficult to ascertain why the reported associations differ depending on the compound under study, but there is a clear imbalance in the literature in disfavor of retinol and retinoic acid, which needs to be considered in future human studies.

Are plasma 25-hydroxyvitamin D and retinol levels and one-carbon metabolism related to metabolic syndrome in patients with a severe mental disorder?

There is a scarcity of studies assessing the influence of biomarkers in metabolic syndrome in psychiatric patients. Our aim was to correlate serum or plasma levels of 25-hydroxyvitamin D (25-OH-VD), retinol, vitamin B12 (VB12), folate and homocysteine (Hcy), with the metabolic status, in a sample of 289 outpatients with Schizophrenia or Bipolar Disorder. Logistic regression and multiple linear regressions were performed to assess the ability of biomarkers to predict the presence of MetS, the number of risk factors for MetS, and insulin resistance indexes (HOMA and QUICKI). Regarding the association between biomarkers and the QUICKI index, the model explained 6.8% of the variance, with folate and 25-OH-VD levels contributing significantly to the model. The model predicting the number of MetS risk factors was significant and explained 21.7% of the variance, being 25-OH-VD and retinol the statistically significant factors. As for the impact of biomarkers on MetS, the model was statistically significant, being 25-OH-VD and retinol levels the significant factors.  We report for the first time an association between MetS and both low 25-OH-VD and high retinol concentrations. Inflammation-related biomarkers may help identify patients with a high risk of MetS who might benefit from healthy lifestyle counselling and early intervention.

Relationship of NEFA concentrations to RBP4 and to RBP4/retinol in prepubertal children with and without obesity

BACKGROUND

The regulation of adipose tissue metabolism in early childhood obesity is not well understood. Insulin levels are higher and insulin resistance seems to be present in prepubertal children with obesity but, differing from their behavior in adults with obesity, non-esterified fatty acid (NEFA) concentrations are not increased. Retinol-binding protein (RBP)-4 concentration is associated with obesity and insulin resistance conditions, but the means of this relationship remain unclear, and few studies have taken retinol values into account to evaluate it.

OBJECTIVE

To analyze the relationship between RBP4 concentration and lipolytic products in plasma in 141 prepubertal children aged 6 to 8 years, with and without obesity.

METHODS

Plasma glucose, insulin, triacylglycerols, NEFA, glycerol, leptin, RBP4, and retinol were analyzed in obese and in their normal-weight counterparts. Homeostatic model assessment, quantitative insulin sensitivity check index, and fasting glucose to insulin ratio were calculated as indicators of insulin resistance.

RESULTS

Fasted plasma NEFA concentrations were lower in children with obesity than in their normal weight counterparts, despite leptin, insulin resistance indices, RBP4, retinol, and RBP4/retinol (an index of free-RBP4) being higher. NEFA and glycerol concentrations were inversely correlated with RBP4/retinol in children with obesity but not in those without obesity. In normal weight children, total RBP4 correlated negatively with NEFA and glycerol concentrations and positively with insulin and homeostasis model assessment for insulin resistance. These results indicate that a low saturation of RBP4 with retinol, which implies a higher concentration of free-RBP4, may preserve the antilipolytic function of insulin in adipose tissue in children with obesity.

CONCLUSION

Our findings suggest that, in prepubertal children with obesity and insulin resistance, the amount of RBP4/retinol correlates with the antilipolytic response of the adipose tissue to insulin rather than the total RBP4 concentration.

Plasma concentration of Retinol Binding Protein 4 (RBP4) in relation to nutritional status and kidney function in older population of PolSenior Study

PURPOSE

The aim of the study was to assess plasma RBP4 concentration in elderly subjects in relation to nutritional status and kidney function in the population of the PolSenior Study.

MATERIAL AND METHODS

We assessed RBP4, glucose, insulin, albumin, lipid profile, C-reactive protein, (hsCRP) and creatinine concentrations in 2614 PolSenior Study participants (1235 women and 1379 men). The study group was divided based on BMI and HOMA-IR values, and the occurrence of diabetes.

RESULTS

Plasma RBP4 concentration was similar in normal weight, overweight, and obese subgroups, both in women (40.4 vs 40.8 vs 41.8 ng/ml, respectively), and men (41.2 vs 40.3 vs 42.9 ng/ml, respectively). Similar values were found in subjects with HOMA-IR <2.5; ≥2.5 and diabetes, while those with decreased eGFR (<60 ml/min/1.73 m²) were characterized by increased RBP4 levels [46.0 (32.0-64.8) vs 39.4 (28.2-54.9) ng/ml; p < 0.001]. Plasma RBP4 level variability was explained by: age, waist circumference or BMI, and eGFR, but not HOMA-IR and/or hsCRP. The standardized coefficients β (slopes) for BMI and waist circumference were similar.

CONCLUSIONS

The results revealed that in older subjects, circulating RBP4 levels are mostly affected by kidney function and modestly by age, gender, and nutritional status, but not insulin resistance.

Effects of insulin resistance on the association between the circulating retinol-binding protein 4 level and clustering of pediatric cardiometabolic risk factors

OBJECTIVES

Retinol-binding protein 4 (RBP4) and insulin resistance (IR) are clinical parameters associated with cardiometabolic diseases. The mediating and modifying roles of IR on children's susceptibility to cardiometabolic disorders are undetermined. This study investigated the mediating and modifying effects of the homeostatic model assessment of IR (HOMA-IR) on the relationship between the serum RBP4 level and clustering of pediatric cardiometabolic risk factors.

METHODS

We assessed the diet, physical activity, cardiometabolic risk factors, and clinical parameters of 272 randomly selected adolescents from a large-scale cross-sectional study (n = 2727). Two HOMA-IRs (HOMA1-IR and HOMA2-IR) were used to evaluate the designated effects.

RESULTS

Levels of serum RBP4 positively correlated with the levels of the 2 HOMA-based-IRs, and HOMA-IR correlated to all components of pediatric metabolic syndrome (MetS), the number of abnormal components, and a body-weight-weighted principal component score extracted from 12 cardiometabolic risk factors. Increased RBP4 levels had positive effects on waist circumference (WC), triglyceride, and the number of abnormal MetS components (0.310 cm, 1.384 μg/dL, and 0.021 item elevations, respectively), and the HOMA-IRs explained 17.7% to 21.9%, 11.8% to 27.6%, and 23.8% to 25.0% of these effects. The association of WC and the number of abnormal MetS components with the serum RBP4 level was enhanced by higher HOMA-IR (β for interaction, 0.13 and 0.01 for HOMA1-IR, and 0.32 and 0.02 for HOMA2-IR, respectively).

CONCLUSIONS

HOMA-IR is associated with the circulating RBP4 level and cardiometabolic risk factors in adolescents. Pediatric HOMA-IR may have mediating and modifying effects on the positive correlations between RBP4 and the clustering of MetS components.

Adipose tissue-derived cytokines and their correlations with clinical characteristics in Vietnamese patients with type 2 diabetes mellitus

BACKGROUND

Adipokines are involved in the pathogenesis of metabolic disorders including obesity and type 2 diabetes mellitus (T2DM). This study investigates the levels of leptin, resistin, visfatin, secreted frizzled-related protein 5 (SFRP5), monocyte chemoattractant protein-1 (MCP-1) and retinol-binding protein 4 (RBP4) and their correlations with clinical parameters of overweight and T2DM.

METHODS

We recruited overweight 50 patients with T2DM, 88 non-overweight patients with T2DM, 29 overweight and 100 non-overweight individuals devoid of T2DM for this study. The levels of studied adipokines were measured by enzyme-linked immunosorbent assay and correlated with clinical parameters.

RESULTS

The levels of MCP-1 and SFRP5 were decreased while visfatin and RBP4 levels were increased in patients with T2DM compared to those in the control individuals (P < 0.01). Among patients with T2DM, leptin and resistin levels were higher while RBP4 levels were lower in patients with overweight T2DM compared to those in patients with non-overweight T2DM (P < 0.0001, 0.019 and 0.05, respectively). Leptin and MCP-1 levels were correlated with HOMA-IR, QUICKI and HOMA-β. Leptin/MCP-1 ratio was correlated with insulin levels, HOMA-IR and HOMA-β indexes. Resistin/RBP4, visfatin/MCP-1 and MCP-1/RBP4 ratios were strongly correlated with the levels of fasting glucose, HbA1c and HOMA-β. In addition, ROC curve analyses indicated a diagnostic potential of resistin/RBP4 and MCP-1/RBP4 indexes for T2DM (AUC = 0.81 and 0.83, respectively) and β-cell function (AUC = 0.76 and 0.74, respectively).

CONCLUSIONS

Adipokines (leptin, resistin, visfatin, SFRP5, MCP-1, and RBP4) are associated with overweight and T2DM and may serve as a potential prognostic marker and therapeutic intervention for overweight-related T2DM.

Implications of Lipids in Neonatal Body Weight and Fat Mass in Gestational Diabetic Mothers and Non-Diabetic Controls

PURPOSE OF REVIEW

Maternal lipid metabolism greatly changes during pregnancy and we review in this article how they influence fetal adiposity and growth under non-diabetic and gestational diabetic conditions.

RECENT FINDINGS

In pregnant women without diabetes (control), maternal glycemia correlates with neonatal glycemia, neonatal body weight and fat mass. In pregnant women with gestational diabetes mellitus (GDM), maternal glucose correlates with neither neonatal glycemia, neonatal birth weight nor fat mass, but maternal triacylglycerols (TAG), non-esterified fatty acids (NEFA) and glycerol do correlate with birth weight and neonatal adiposity. The proportions of maternal plasma arachidonic (AA) and docosahexaenoic (DHA) acids decrease from the first to the third trimester of pregnancy, and at term these long-chain polyunsaturated fatty acids are higher in cord blood plasma than in mothers, indicating efficient placental transfer. In control or pregnant women with GDM at term, the maternal concentration of individual fatty acids does not correlate with neonatal body weight or fat mass, but cord blood fatty acid levels correlate with birth weight and neonatal adiposity-positively in controls, but negatively in GDM. The proportion of AA and DHA in umbilical artery plasma in GDM is lower than in controls but not in umbilical vein plasma. Therefore, an increased utilization of those two fatty acids by fetal tissues, rather than impaired placental transfer, is responsible for their smaller proportion in plasma of GDM newborns. In control pregnant women, maternal glycemia controls neonatal body weight and fat mass, whereas in mothers with GDM-even with good glycemic control-maternal lipids and their greater utilization by the fetus play a critical role in neonatal body weight and fat mass. We propose that altered lipid metabolism rather than hyperglycemia constitutes a risk for macrosomia in GDM.

Involvement of RBP4 in all‑trans retinoic acid induced cleft palate

The current study was designed to elucidate the mechanism of retinol binding protein 4 (RBP4) in cleft palate induced by all‑trans retinoic acid (atRA). To establish a cleft palate model in C57BL/6J mice, pregnant mice were administered atRA (100 mg/kg) by gavage at the tenth embryonic stage (E10.0). Control groups were given the equivalent volume of corn oil. Pregnant mice were dissected at E12.5, E13.5 and E14.5 to obtain the embryonic palates. The expression levels of RBP4 in the embryonic palatal mesenchyme (EPM) were determined by immunohistochemistry, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting. Human embryonic palatal mesenchymal cells were exposed to atRA to detect the variation in RBP4 induced by atRA in vitro. Small interfering RNA was used to suppress the expression of RBP4, and a plasmid overexpressing RBP4 was used to examine upregulated expression. The cell counting kit‑8 assay was used to evaluate the effect of RBP4 on cell proliferation. The expression levels of p27 and cyclin D1 were determined by RT‑qPCR and western blotting, while the expression levels of extracellular signal‑related kinase (ERK) 1/2 and protein kinase B (AKT) were assessed by western blotting. At E14.5, RBP4 was strongly expressed in the EPM, while it was downregulated following atRA treatment, which induced cleft palate in vivo. In vitro experiments indicated that atRA suppressed the expression of RBP4 and altered the expression of p27 and cyclin D1 to cause growth inhibition. Knockdown of RBP4 resulted in decreased expression of cyclin D1 and increased p27, and suppressed proliferation. Overexpression of RBP4 reversed the inhibitory effect of atRA and promoted proliferation via the ERK1/2 and AKT signaling pathways. These results suggested that RBP4 was involved in cleft palate induced by atRA and it can be suppressed by atRA to cause growth inhibition in the embryonic palate.

Does Bariatric Surgery Improve Obesity Associated Comorbid Conditions

Obesity is a constantly growing health problem which reduces quality of life and life expectancy. Bariatric surgery for obesity is taken into account when all other conservative treatment modalities have failed. Comparison of the multidisciplinary programs with bariatric surgery regarding to weight loss showed that substantial and durable weight reduction have been achieved only with bariatric surgical treatments. However, the benefits of weight loss following bariatric procedures are still debated regarding the pro-inflammatory and metabolic profile of obesity.

High-fat diet-induced plasma protein and liver changes in obese rats can be attenuated by melatonin supplementation

Obesity triggers changes in protein expression in various organs that might participate in the pathogenesis of obesity. Melatonin has been reported to prevent or attenuate such pathological protein changes in several chronic diseases. However, such melatonin effects on plasma proteins have not yet been studied in an obesity model. Using a proteomic approach, we investigated the effect of melatonin on plasma protein profiles after rats were fed a high-fat diet (HFD) to induce obesity. We hypothesized that melatonin would attenuate abnormal protein expression in obese rats. After 10weeks of the HFD, animals displayed increased body weight and fat accumulation as well as increased glucose levels, indicating an obesity-induced prediabetes mellitus-like state. Two-dimensional gel electrophoresis and liquid chromatography-mass spectrometry/mass spectrometry revealed 12 proteins whose expression was altered in response to the HFD and the melatonin treatment. The altered proteins are related to the development of liver pathology, such as cirrhosis (α1-antiproteinase), thrombosis (fibrinogen, plasminogen), and inflammation (mannose-binding protein A, complement C4, complement factor B), contributing to liver steatosis or hepatic cell death. Melatonin treatment most probably reduced the severity of the HFD-induced obesity by reducing the amplitude of HFD-induced plasma protein changes. In conclusion, we identified several potential biomarkers associated with the progression of obesity and its complications, such as liver damage. Furthermore, our findings reveal melatonin's beneficial effect of attenuating plasma protein changes and liver pathogenesis in obese rats.

RBP4: A Culprit for Insulin Resistance in End Stage Renal Disease That Can Be Cleared by Hemodiafiltration

INTRODUCTION

Retinol Binding Protein 4 (RBP4) is mainly excreted by the kidney and plays a pivotal role in insulin resistance (IR). In our study, we evaluated the association between RBP4 and IR in hemodialysis subjects (HD). We also assessed how circulating RBP4 could be influenced by kidney transplant or different dialytic techniques.

METHODS

RBP4 serum levels were evaluated in HD (n = 16) and matched healthy controls (C; n = 16). RBP4 and glucose transporter type 4 (GLUT4) mRNA expressions were also determined in adipose tissue. Circulating RBP4 was evaluated after kidney transplant (n = 7) and in hemodialysis patients (n = 10) enrolled in a cross-over study treated with standard bicarbonate dialysis (BD) or hemodiafiltration (HDF).

RESULTS

HOMA index (P < 0.05) and serum RBP4 (P < 0.005) were higher in HD compared to C. RBP4 levels positively correlated with fasting serum glucose (P < 0.05). RBP4 mRNA was lower in HD compared to C (P < 0.05) and positively correlated with kidney function (P < 0.05) and GLUT4 mRNA (P < 0.001). Transplant or HDF reduced circulating RBP4 (P < 0.01 and P < 0.05, resp.). Our results demonstrate that IR is associated with high circulating RBP4 and that suppressed RBP4 adipose tissue expression is accompanied by reduced GLUT4 expression in HD. Renal transplantation or HDF are effective in lowering serum RBP4 levels.

Long-term Diet and Biomarker Changes after a Short-term Intervention among Hispanic Breast Cancer Survivors: The ¡Cocinar Para Su Salud! Randomized Controlled Trial

BACKGROUND

Among Hispanic breast cancer survivors, we examined the long-term effects of a short-term culturally based dietary intervention on increasing fruits/vegetables (F/V), decreasing fat, and changing biomarkers associated with breast cancer recurrence risk.

METHODS

Spanish-speaking women (n = 70) with a history of stage 0-III breast cancer who completed treatment were randomized to ¡Cocinar Para Su Salud! (n = 34), a culturally based 9-session program (24 hours over 12 weeks, including nutrition education, cooking classes, and food-shopping field trips), or a control group (n = 36, written dietary recommendations for breast cancer survivors). Diet recalls, fasting blood, and anthropometric measures were collected at baseline, 6, and 12 months. We report changes between groups at 12 months in dietary intake and biomarkers using 2-sample Wilcoxon t tests and generalized estimating equation (GEE) models.

RESULTS

At 12 months, the intervention group compared with the control group reported higher increases in mean daily F/V servings (total: +2.0 vs. -0.4; P < 0.01), and nonsignificant decreases in the percentage of calories from fat (-2.2% vs. -1.1%; P = 0.69) and weight (-2.6 kg vs. -1.5 kg; P = 0.56). Compared with controls, participants in the intervention group had higher increases in plasma lutein (+20.4% vs. -11.5%; P < 0.01), and borderline significant increases in global DNA methylation (+0.8% vs. -0.5%; P = 0.06).

CONCLUSIONS

The short-term ¡Cocinar Para Su Salud! program was effective at increasing long-term F/V intake in Hispanic breast cancer survivors and changed biomarkers associated with breast cancer recurrence risk.

IMPACT

It is possible for short-term behavioral interventions to have long-term effects on behaviors and biomarkers in minority cancer patient populations. Results can inform future study designs. Cancer Epidemiol Biomarkers Prev; 25(11); 1491-502. ©2016 AACR.

Expression of retinol binding protein 4 and nuclear factor-κB in diabetic rats with atherosclerosis and the intervention effect of pioglitazone

This study aims to investigate the expression of retinol binding protein 4 (RBP4) and the activity of nuclear factor-kappa B (NF-κB) in diabetic rats with atherosclerosis, and to evaluate the intervention effect of pioglitazone. A total of 75 Wistar rats were randomly divided into four groups: Normal control (NC), diabetic rats (DM1), diabetic rats with atherosclerosis (DM2) and diabetic rats treated with pioglitazone (DM + Pio). The activity of NF-κB, the levels of serum and adipose tissue RBP4, fasting plasma glucose (FPG), fasting insulin (FINS), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), triglycerides (TG) and arteria caudilis systolic blood pressure (SBP) were measured. Percentage of fat mass (PFM), atherogenic index of plasma (AIP) and homeostasis model assessment of insulin resistance (HOMA-IR) were calculated. Compared with the NC and DM + Pio groups, all the parameters mentioned above increased significantly in the DM1 and DM2 groups, with the exception that HDL-c decreased. Pearson analysis showed that RBP4 in serum and adipose tissue were positively associated with TG, LDL-c, FINS, PFM, AIP, HOMA-IR, NF-κB, SBP and negatively associated with HDL-c. Multivariable logistic regression analysis showed that serum RBP4 and TG were predictors for the presence of diabetic atherosclerosis. In conclusion, RBP4 may be an effective predictor for diabetic atherosclerosis; pioglitazone is able to decrease RBP4 and NF-κB, which may partly contribute to its protective effect against diabetic atherosclerosis.

Serum retinol binding protein 4 is negatively related to estrogen in Chinese women with obesity: a cross-sectional study

BACKGROUND

The association between serum Retinol Binding Protein 4 (RBP4) and obesity is still controversial. Serum RBP4 levels varies by gender, and estradiol may play a role in the difference. To investigate the participation of sex hormones in the association of RBP4 and obesity in humans, we measured serum RBP4, BMI, and sex hormones in 87 women from the outpatient.

METHODS

Eighty-seven subjects of Chinese women origin from the outpatient (aged 40.22 ± 15.54 years) were enrolled. Subjects with diseases affecting the metabolic state or not suitable to participate in this study were excluded. Anthropometrics and laboratory tests, including lipid profile, luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), estradiol (E2),progesterone (PROG), testosterone (TESTO), and dehydroepiandrosterone (DHEA) were conducted. Serum RBP4 was detected by an enzyme immunoassay kit and validated by quantitative Western blotting.

RESULTS

Circulating RBP4 levels were positively associated with BMI, waist circumference, waist-to-hip ratio (WHR), systolic and diastolic (SBP), diastolic blood pressure (DBP), triglycerides (TG), low high-density lipoprotein cholesterol(LDL-c), and testosterone (TESTO) in the total group. While only in obese individuals, serum RBP4 levels were negatively associated with E2. The highest value was in the subjects with both obesity and the low estrogen level. Multiple linear regression analysis revealed that RBP4 correlated independently with TG, TC and insulin in all subjects, TC in non- obese individuals. However, E2 were significantly associated with serum RBP4 only in obese individuals.

CONCLUSIONS

RBP4 could be a marker of obesity-related factors; estrogen was negatively related to RBP4 and might be one of the influential factors.

Hepatic Macrosteatosis Is Partially Converted to Microsteatosis by Melatonin Supplementation in ob/ob Mice Non-Alcoholic Fatty Liver Disease

Background

Obesity is a common risk factor for non-alcoholic fatty liver disease (NAFLD). Currently, there are no specific treatments against NAFLD. Thus, examining any molecule with potential benefits against this condition emerged melatonin as a molecule that influences metabolic dysfunctions. The aim of this study was to determine whether melatonin would function against NAFDL, studying morphological, ultrastuctural and metabolic markers that characterize the liver of ob/ob mice.

Methods

Lean and ob/ob mice were supplemented with melatonin in the drinking water for 8 weeks. Histology and stereology were performed to assess hepatic steatosis and glycogen deposition. Ultrastructural features of mitochondria, endoplasmic reticulum (ER) and their juxtapositions were evaluated in livers of all experimental groups. Furthermore, hepatic distribution and expression of markers of ER and mitochondria (calnexin, ATP sintase β, GRP78 and CHOP) and metabolic dysfunction (RPB4, β-catenin) and cellular longevity (SIRT1) were analyzed.

Results

Melatonin significantly reduced glycemia, identified also by a decrease of hepatic RBP4 expression, reversed macrosteatosis in microsteatosis at the hepatic pericentral zone, enlarged ER-mitochondrial distance and ameliorated the morphology and organization of these organelles in ob/ob mouse liver. Furthermore, in ob/ob mice, calnexin and ATP synthase β were partially restored, GRP78 and CHOP decreased in periportal and midzonal hepatocytes and β-catenin expression was, in part, restored in peripheral membranes of hepatocytes. Melatonin supplementation to ob/ob mice improves hepatic morphological, ultrastructural and metabolic damage that occurs as a result of NAFLD.

Conclusions

Melatonin may be a potential adjuvant treatment to limit NAFLD and its progression into irreversible complications.

Role of adiponectin and some other factors linking type 2 diabetes mellitus and obesity

Because of the intimate association of obesity with type 2 diabetes mellitus (T2DM), during the last two decades, extensive research work is being conducted to find out whether the coexistence of the two is a simple association or there is a positive correlating link between the two. In this article, an attempt has been made to collect and analyse the recent developments in this field and to arrive at a conclusion on the subject. The possible role of several important factors (obtained from adipocytes/not of adipocyte origin) in linking the two has been discussed in detail. Some of the agents, specifically adiponectin, are beneficial (i.e., reduce the incidence of both), while others are harmful (i.e., increase their incidence). From the analysis, it appears that obesity and T2DM are intimately linked.

Retinol binding protein 4 correlates with and is an early predictor of carotid atherosclerosis in type 2 diabetes mellitus patients

The association of retinol binding protein 4 (RBP4) with atherosclerosis of the carotid artery in type 2 diabetes mellitus (T2DM) remains undefined. We aimed to investigate the correlation of RBP4 expression with atherosclerosis of the carotid artery in T2DM. A total of 1,076 subjects were investigated for intima-media thickness of the bilateral common carotid arteries, and they were divided into three groups: in group I, patients had normal neck vascular ultrasound, in group II, intimal carotid artery media thickness was equal to or more than 1 mm, and in group III, carotid artery plaque was present. Height, weight, blood pressure (BP), fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-1 (Apo A-1), apolipoprotein B (Apo B) and lipoprotein (a) (Lp(a)) were determined by routine laboratory methods. RBP4 and high sensitivity C reactive protein (HsCRP) were measured by an enzyme-linked immuno-sorbent assay, and insulin concentration was measured by an electrochemiluminescence sandwich immunoassay. Duration of diabetes, waist and BP, FPG, HbA1c, TG, TC, LDL-C, APOB, Lp(a), HsCRP, RBP4 and homeostasis model assessment insulin resistance index (HOMA-IR) were significantly lower in group I than in the other two groups (P<0.01, P<0.01). Plasma levels of HbA1c, RBP4, LDL-C, TC, HOMA-IR, HsCRP and Lp(a), waist and BP were significantly increased in group III than in group II (P<0.01). Multivariate logistic regression analysis showed that there were seven factors associated with the occurrence of carotid artery atherosclerosis and its risks in descending order were: high LDL-C, high waist, high HsCRP, duration of diabetes, high HOMA-IR, HbA1c and high RBP4. Our finding supported that RBP4 was positively correlated with carotid atherosclerosis in patients with T2DM and could be used as an early predictor of cardiovascular disease.

Gestational diabetes: a risk of puerperal hypovitaminosis A?

The influence of gestational diabetes on vitamin A deficiency in lactating women and, consequently, in their newborn has been verified through a cross-sectional case-control study conducted with volunteer puerperal women. The control group consisted of healthy women and the test group was composed of women with gestational diabetes. One hundred and seven women were recruited, corresponding to 71 controls and 36 cases. Personal, gestational and newborn data were collected directly from medical records during hospitalization. The retinol was determined in maternal colostrum and serum by High Performance Liquid Chromatography. Postpartum women with gestational diabetes were older, had more children and a higher prevalence of cesarean delivery. No difference was found in retinol concentration in maternal milk and serum between the groups. However, it was observed that 16.7% had vitamin A deficiency in the group of patients with diabetes and only 4.1% had such deficiency in the control group. Although no difference was found in colostrum and serum retinol concentration between women with and without gestational diabetes, the individual analysis shows that those with diabetes are at higher risk of being vitamin A deficient.

Vitamins and type 2 diabetes mellitus

The present review evaluates the relationship between type 2 diabetes mellitus and individual or combined vitamins. Antioxidant vitamins A, C and E are found decreased in diabetic subjects, possibly due to an increased need to control the excessive oxidative stress produced by abnormalities in glucose metabolism. On the other hand, retinol binding protein exerts a modulating effect, as it has adipokine functions. With respect to the B group vitamins, thiamin, pyridoxine and biotin have been found decreased but the mechanisms are not clear, however supplementation has shown some improvement of the metabolic control in diabetic patients. The absorption of folic acid and vitamin B12 is importantly decreased by the prolongued use of metformin, which is the first choice drug in uncomplicated diabetes, thus these two nutrients have been found deficient in the disease and most probably need to be supplemented regularly. On the other hand, vitamin D is considered a risk factor for the development of diabetes as well as its complications, particularly cardiovascular ones. Although some studies have found an association of vitamin K intake with glucose metabolism further research is needed. Studies on the use of multivitamin supplements have shown unconclusive results. After reviewing the evidence, no real recommendation on the use of vitamin supplements in type 2 diabetes mellitus can be issued, however patients using metformin during prolongued periods may need folic acid and vitamin B12.

The gonadal function in obese adolescents: review

This review deals with the relationship between obesity in male adolescents and gonadal function. The article is structured in two main paragraphs; the first one is about population studies that have assessed puberty timing and its mode of onset in relation with body weight to evaluate if and how the latter can influence the gonadal function in this phase of life. These studies analyze issues such as increased BMI and early onset of male puberty, gender differences, secular trend toward early onset of puberty in males, effects of a different body composition on male puberty and consequences of a different stage of childhood obesity on the onset of male puberty. The second paragraph examines the possible mechanisms through which, obesity may alter the timing of puberty in young males, including the role of SHBG, leptin, insulin resistance, ghrelin, GH-IGF-1 axis, AR polymorphisms, primary testicular dysfunction, retinol binding protein 4 (RBP-4) and liver function abnormalities. However, despite the numerous studies in the literature, the etiology of gonadal disfunction in obese adolescents on puberty remains uncertain.

The effects of wild blueberry consumption on plasma markers and gene expression related to glucose metabolism in the obese Zucker rat

Impaired fasting blood glucose is one of the landmark signs of metabolic syndrome, together with hyperinsulinemia, dyslipidemia, hypertension, and a chronic proinflammatory, pro-oxidative, and prothrombotic environment. This study investigates the effect of wild blueberry (WB) consumption on blood glucose levels and other parameters involved in glucose metabolism in the obese Zucker rat (OZR), an experimental model of metabolic syndrome. Sixteen OZRs and 16 lean littermate controls (lean Zucker rat [LZR]) were fed an 8% enriched WB diet or a control (C) diet for 8 weeks. Plasma concentrations of glucose, insulin, glycated hemoglobin GHbA1c, resistin, and retinol-binding protein 4 (RBP4) were measured. Expression of the resistin, RBP4, and glucose transporter GLUT4 genes was also determined both in the liver and the abdominal adipose tissue (AAT). Plasma glycated hemoglobin HbA1c, RBP4, and resistin concentrations were significantly lower in OZRs following the WB diet (-20%, -22%, and -27%, respectively, compared to C diet, P<.05). Following WB consumption, resistin expression was significantly downregulated in the liver of both OZRs and LZRs (-28% and -61%, respectively, P<.05), while RBP4 expression was significantly downregulated in the AAT of both OZRs and LZRs (-87% and -43%, respectively, P<.05). All other markers were not significantly affected following WB consumption. In conclusion, WB consumption normalizes some markers related to glucose metabolism in the OZR model of metabolic syndrome, but has no effect on fasting blood glucose or insulin concentrations.

Proteomic identification of novel differentiation plasma protein markers in hypobaric hypoxia-induced rat model

Background

Hypobaric hypoxia causes complex changes in the expression of genes, including stress related genes and corresponding proteins that are necessary to maintain homeostasis. Whereas most prior studies focused on single proteins, newer methods allowing the simultaneous study of many proteins could lead to a better understanding of complex and dynamic changes that occur during the hypobaric hypoxia.

Methods

In this study we investigated the temporal plasma protein alterations of rat induced by hypobaric hypoxia at a simulated altitude of 7620 m (25,000 ft, 282 mm Hg) in a hypobaric chamber. Total plasma proteins collected at different time points (0, 6, 12 and 24 h), separated by two-dimensional electrophoresis (2-DE) and identified using matrix assisted laser desorption ionization time of flight (MALDI-TOF/TOF). Biological processes that were enriched in the plasma proteins during hypobaric hypoxia were identified using Gene Ontology (GO) analysis. According to their properties and obvious alterations during hypobaric hypoxia, changes of plasma concentrations of Ttr, Prdx-2, Gpx -3, Apo A-I, Hp, Apo-E, Fetub and Nme were selected to be validated by Western blot analysis.

Results

Bioinformatics analysis of 25 differentially expressed proteins showed that 23 had corresponding candidates in the database. The expression patterns of the eight selected proteins observed by Western blot were in agreement with 2-DE results, thus confirming the reliability of the proteomic analysis. Most of the proteins identified are related to cellular defense mechanisms involving anti-inflammatory and antioxidant activity. Their presence reflects the consequence of serial cascades initiated by hypobaric hypoxia.

Conclusion/Significance

This study provides information about the plasma proteome changes induced in response to hypobaric hypoxia and thus identification of the candidate proteins which can act as novel biomarkers.

The Roles of Vitamin A in the Regulation of Carbohydrate, Lipid, and Protein Metabolism

Currently, two-thirds of American adults are overweight or obese. This high prevalence of overweight/obesity negatively affects the health of the population, as obese individuals tend to develop several chronic diseases, such as type 2 diabetes and cardiovascular diseases. Due to obesity's impact on health, medical costs, and longevity, the rise in the number of obese people has become a public health concern. Both genetic and environmental/dietary factors play a role in the development of metabolic diseases. Intuitively, it seems to be obvious to link over-nutrition to the development of obesity and other metabolic diseases. However, the underlying mechanisms are still unclear. Dietary nutrients not only provide energy derived from macronutrients, but also factors such as micronutrients with regulatory roles. How micronutrients, such as vitamin A (VA; retinol), regulate macronutrient homeostasis is still an ongoing research topic. As an essential micronutrient, VA plays a key role in the general health of an individual. This review summarizes recent research progress regarding VA's role in carbohydrate, lipid, and protein metabolism. Due to the large amount of information regarding VA functions, this review focusses on metabolism in metabolic active organs and tissues. Additionally, some perspectives for future studies will be provided.

Comparative proteomic analysis of plasma proteins in patients with age-related macular degeneration

AIM

To find the significant altered proteins in age-related macular degeneration (AMD) patients as potential biomarkers of AMD.

METHODS

A comparative analysis of the protein pattern of AMD patients versus healthy controls was performed by means of proteomic analysis using two-dimensional gel electrophoresis followed by protein identification with MALDI TOF/TOF mass spectrometry.

RESULTS

We identified 28 proteins that were significantly altered with clinical relevance in AMD patients. These proteins were involved in a wide range of biological functions including immune responses, growth cytokines, cell fate determination, wound healing, metabolism, and anti-oxidance.

CONCLUSION

These results demonstrate the capacity of proteomic analysis of AMD patient plasma. In addition to the utility of this approach for biomarker discovery, identification of alterations in endogenous proteins in the plasma of AMD patient could improve our understanding of the disease pathogenesis.

Proteomic Analysis of RBP4/Vitamin A in Children with Cleft Lip and/or Palate

Cleft of the lip and/or palate (CLP) is one of the most common congenital craniofacial defects. Non-syndromic CLP (NSCLP) is a multifactorial disease influenced by the interaction of genetic and environmental factors. However, there are few studies reporting on the developmental or metabolic status of babies with NSCLP after birth. In our study, we sought to identify and evaluate the differential expression of serum protein profiles in NSCLP children and unaffected babies. Thus, a 'shotgun proteomics' approach was first used to analyze the plasma proteome of 13 children with NSCLP and 10 control children, aged 2 to 3.5 years. In total, more than 300 proteins were identified in the serum sample. With gene ontology (GO) analysis, we detected many differentially expressed proteins that could be related to NSCLP, including those involved in lipoprotein metabolism, insulin-like growth-factor-related processes, and so on, especially the proteins involved in retinol transport. Retinol binding protein 4 (RBP4), one protein of the retinol transport category, was significantly decreased in the NSCLP group. Thus, serum vitamin A levels were further determined by high-performance liquid chromatography (HPLC). A significant difference (p < .01) was also found in vitamin A concentrations, consistent with the trend of RBP4. Our results indicated that reduced levels of RBP4 and vitamin A were related to newborns with NSCLP and should thus receive more attention. These results also suggest that vitamin A supplementation might be necessary at an early stage.

Elevated serum triglyceride and retinol-binding protein 4 levels associated with fructose-sweetened beverages in adolescents

Background

The metabolic effect of fructose in sugar-sweetened beverages (SSB) has been linked to de novo lipogenesis and uric acid (UA) production.

Objectives

This study investigated the biological effects of SSB consumption on serum lipid profiles and retinol-binding protein 4 (RBP4) among Taiwanese adolescents.

Methods

We evaluated the anthropometric parameters and biochemical outcomes of 200 representative adolescents (98 boys and 102 girls) who were randomly selected from a large-scale cross-sectional study. Data were analyzed using multiple regression models adjusted for covariates.

Results

Increased SSB consumption was associated with increased waist and hip circumferences, body mass index (BMI) values and serum UA, triglyceride (TG) and RBP4 levels. Adolescents who consumed >500 ml/day of beverages half-to-heavily sweetened with high-fructose corn syrup (HFCS) exhibited TG and RBP4 levels 22.7 mg/dl and 13.92 ng/ml higher than non-drinkers, respectively. HFCS drinkers with hyperuricemia had higher TG levels than HFCS drinkers with normal UA levels (98.6 vs. 81.6 mg/dl). The intake of HFCS-rich SSBs and high value of BMI (≥24) interactively reinforced RBP4 levels among overweight/obese adolescents. Circulating RBP4 levels were significantly correlated with weight-related outcomes and TG and UA concentration among HFCS drinkers (r = 0.253 to 0.404), but not among non-drinkers.

Conclusions

High-quantity HFCS-rich beverage consumption is associated with higher TG and RBP4 levels. Hyperuricemia is likely to intensify the influence of HFCS-rich SSB intake on elevated TG levels, and in overweight and obese adolescents, high BMI may modify the action of fructose on higher circulating levels of RBP4.

Associations between tissue visfatin/nicotinamide, phosphoribosyltransferase (Nampt), retinol binding protein-4, and vaspin concentrations and insulin resistance in morbidly obese subjects

Visfatin/Nampt, vaspin, and retinol binding protein-4 (RBP-4) play an important role in insulin resistance. The objectives of this study were to measure visfatin/Nampt, vaspin, and RBP-4 concentrations in blood, liver, muscle, subcutaneous, omental, and mesenteric adipose tissues in morbidly obese subjects and investigate their relationship to insulin resistance. Blood and tissue samples were collected from 38 morbidly obese subjects during Roux-en-Y surgery. Insulin resistance biomarkers were measured using standard kits. Visfatin/Nampt, vaspin, and RBP-4 gene expression levels in tissues were measured using real-time PCR. Their protein concentrations in blood and tissues were measured using ELISA kits. Diabetic subjects had significantly higher homeostasis model of assessment-insulin resistance and age and lower blood HDL-cholesterol concentrations than nondiabetic and prediabetic subjects. Diabetic and prediabetic subjects had significantly higher blood concentrations of visfatin/Nampt and vaspin than nondiabetic subjects. Liver RBP-4 concentrations were positively associated with blood glucose concentrations. Blood insulin resistance biomarker levels were positively associated with visfatin/Nampt concentrations in omental adipose tissue and liver, and vaspin concentrations in mesenteric adipose tissue. In conclusion, the correlations of visfatin/Nampt, vaspin, and RBP-4 with insulin resistance are tissue dependent.

Nutrient deficiencies in patients with obesity considering bariatric surgery: a cross-sectional study

BACKGROUND

Nutritional deficiencies are common after bariatric surgery, but few studies have examined them preoperatively. The objective of this study was to evaluate several vitamins, nutrients, and nutritional markers and their determinants in patients with obesity considering bariatric surgery.

METHODS

Preoperative values of fasting plasma glucose, insulin, lipid profile, 25-hydroxyvitamin D (25(OH)D), parathyroid hormone, thyroid-stimulating hormone, calcium, phosphate, albumin, magnesium, total proteins, liver function tests, iron, ferritin, folate, vitamin A, vitamin B12, selenium, and zinc were evaluated in 267 Caucasian outpatients (74.2% women, aged 40.5±12.6 years) who were considering bariatric surgery. The determinants of nutrient variability were analyzed by linear regression for nutrients with a prevalence of deficiency>10%, i.e., serum 25(OH)D, iron, phosphate, magnesium, and vitamin A.

RESULTS

Prevalence of inadequate concentrations was high for 25(OH)D (67.9% with values ≤ 20 ng/mL), magnesium (35.4%), phosphate (21.6%), iron (18.8%), and vitamin A (16.9%). Multiple deficiencies were common; 28.5%, 12.1%, and 6.3% of patients had 2, 3, and 4 deficiencies, respectively. In multivariate analyses, metabolic characteristics had an important impact on deficiencies, with lower values of 25(OH)D and vitamin A with increasing body mass index, lower values of 25(OH)D and magnesium with increasing fasting plasma glucose, and a positive correlation between vitamin A and triglycerides. Elevated TSH was associated with low iron concentrations.

CONCLUSION

At all ages, micronutrient deficiencies were common, with high prevalence of concentration inadequacies for 25(OH)D, magnesium, phosphate, iron, and vitamin A. High body mass index and high fasting plasma glucose increased the risk of deficiencies, particularly for 25(OH)D. Preoperative screening and correction of deficiencies should be advised.

Stop feeding cancer: pro-inflammatory role of visceral adiposity in liver cancer

Liver cancer is the fifth most common cancer in the world with an estimated over half a million new cases diagnosed every year. Due to the difficulty in early diagnosis and lack of treatment options, the prevalence of liver cancer continues to climb with a 5-year survival rate of between 6% and 11%. Coinciding with the rise of liver cancer, the prevalence of obesity has rapidly increased over the past two decades. Evidence from epidemiological studies demonstrates a higher risk of hepatocellular carcinoma (HCC) in obese individuals. Obesity is recognised as a low-grade inflammatory disease, this is of particular relevance as inflammation has been proposed as the seventh hallmark of cancer development with abdominal visceral adiposity considered as an important source of pro-inflammatory stimuli. Emerging evidence points towards the direct role of visceral adipose tissue rather than generalised body fat in carcinogenesis. Cytokines such as IL-6 and TNF-α secreted from visceral adipose tissue have been demonstrated to induce a chronic inflammatory condition predisposing the liver to a protumourigenic milieu. This review focuses on excess visceral adiposity rather than simple obesity; particularly adipokines and their implications for chronic inflammation, lipid accumulation, insulin resistance, Endoplasmic Reticulum (ER) stress and angiogenesis. Evidence of molecular signalling pathways that may give rise to the onset and progression of HCC in this context are depicted. Delineation of the pro-inflammatory role of visceral adiposity in liver cancer and its targeting will provide better rational and therapeutic approaches for HCC prevention and elimination. The concept of a central role for metabolism in cancer is the culmination of an effort that began with one of the 20th century's leading biochemists and Nobel laureate of 1931, Otto Warburg.

Low Serum retinol-binding protein-4 levels in acute exacerbations of chronic obstructive pulmonary disease at intensive care unit admission is a predictor of mortality in elderly patients

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are thought to be associated with increased mortality in elderly patients. Low retinol-binding protein-4 (RBP4) is associated with a high risk of respiratory infections in the general population. Therefore, we hypothesized that low RBP4 levels are associated with an increased risk of AECOPD and can be used as a biomarker for AECOPD in elderly patients.

METHODS

Enzyme-linked immunosorbent assays were used to assess RBP4 levels in elderly with AECOPD within the first 24 hours after intensive care unit admission. Forty-six elderly patients with stable COPD in outpatient clinics and 50 healthy elderly persons who had physical examinations as outpatients were controls.

RESULTS

In AECOPD patients, RBP4 levels were lower than those in stable COPD patients and healthy controls (59.7 vs 91.2 and 113.6 mg/L, p < 0.001). RBP4 levels were decreased by 30.6% in non-survivors compared with survivors (51.5 vs 74.2 mg/L, p < 0.001). A higher Acute Physiology and Chronic Health Enquiry II (APACHE II) score and Simplified Acute Physiology score (SAPS II) were associated with lower RBP4 levels (r = -0.692, p = 0.024 and r = -0.670, p = 0.015, respectively). RBP4 was positively correlated with creatinine and body mass index, and negatively correlated with C-reactive protein and Global Initiative for Chronic Obstructive Lung Disease stage. Multivariate logistic regression showed that RBP4 was an independent mortality predictor of AECOPD (odds ratio: 0.926, p = 0.007). Analysis of the area under the receiver operating characteristic (AUC) curve showed that RBP4 showed good discrimination (AUC: 0.88; 95% confidence interval: 0.78-0.94; p = 0.008) in predicting mortality. RBP4 improved the prognostic accuracy of mortality for the APACHE II and SAPS II scores.

CONCLUSIONS

Serum RBP4 levels are significantly reduced in elderly AECOPD patients. RBP4 might be a good predictive biomarker for mortality in elderly AECOPD patients in the intensive care unit.