Retinol-binding Protein 4 Gene Research Articles

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

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

Molecular and functional characterization of the retinol-binding protein 4 (RBP4) in hepatocytes of Schizothorax prenanti in response to palmitic acid.

Retinol-binding protein 4 (RBP4) protein is a kind of adipokines synthesized and secreted by the liver, which has been verified to play important roles in liver metabolism and energy homeostasis. However, the effects of RBP4 on hepatic lipid accumulation are still elusive in fish. In the present study, we cloned and characterized the RBP4 gene in Schizothorax prenanti (S. prenanti). RBP4 gene was specifically expressed in the liver and abdominal adipose tissue. Palmitic acid (PA; 400μM) can significantly increase lipid deposition in primary hepatocytes after 12h of treatment. Furthermore, RBP4 knockdown can relieve the excessive lipid deposition and endoplasmic reticulum stress in the hepatocytes caused by PA. The inhibition of RBP4 abolished the ability of PA to induce the expression of genes involved in lipogenesis and endoplasmic reticulum stress. These results demonstrate that RBP4 inhibition attenuated PA-induced lipid deposition and endoplasmic reticulum stress in hepatocytes of S. prenanti. This study could contribute to improve the understanding of RBP4 functions in the PA-induced lipid deposition in hepatocytes of fish.

The Effects of Soyferment-Tempeh on Lipid Profile, Retinol-Binding Protein 4 (RBP4), and Phosphoenolpyruvate Carboxykinase (PEPCK) Gene Expression in Type 2 Diabetic Mice

Diabetes Type 2 can cause oxidative stress leading to the accumulation of reactive oxygen species. Soyferment-Tempeh, a fermented soybean product with aerobic and anaerobic R. oligosporus incubation has a high antioxidant content of isoflavones that can regulate oxidative stress in diabetes. In this study, we evaluate the effects of Soyferment-Tempeh on lipid profile, Retinol-Binding Protein 4 (RBP4), and Phosphoenolpyruvate Carboxykinase (PEPCK) gene expression in type 2 diabetic mice. A total of 30 mice with the age of eight weeks were divided into six groups as follows: A) nondiabetic, B) diabetic mice, C) diabetic mice with metformin, D), E), and F) diabetic mice with Soyferment-Tempeh doses of 10, 20, or 40mg/100g body weight (BW), respectively, were administered treatments orally by gavages. Blood was collected for assessment of blood glucose level, and lipid profile before and after 3 weeks of the administration. After sacrificing the mice, livers were used for RBP4 and PEPCK gene expression assessment. Supplementation with three different doses of Soyferment-Tempeh in streptozotocin-induced diabetic mice for 21 days significantly (p<0.001) reduced blood glucose level, total cholesterol, triglycerides, low-density lipoprotein level, atherogenic index, and increased high-density lipoprotein level. There was a significant decrease in RBP4 gene expression in the Soyferment-Tempeh of dose 10mg/100g BW treatment groups (p<0.05), while the PEPCK gene expression did not significantly differ (p>0.05). These results demonstrate that supplementation with Soyferment-Tempeh decreases blood glucose level, atherogenic index, improves lipid profile, and decreases RBP4.

Plasma RBP4 Level in Association with Body Composition, Metabolic Profile, STRA6 and RBP4 Gene Polymorphisms in Obese Romanian Children.

BackgroundPediatric obesity continues to remain a serious health concern which has significantly increased the morbidity risk in adulthood. Recent studies have analyzed the impact of the two adipokines, RBP4 (retinol binding protein 4) and STRA6 (stimulated by retinoic acid 6) in pediatric obese subjects with contradictory results.MethodsAn observational study was conducted in the Pediatric and Endocrinology Departments, Targu-Mures, Romania, including 213 children between 5–17 years of age, divided into two groups according to body mass index (BMI) standard deviation score (SDS): case (overweight or obese) and control (normal SDS). Age, sex, basic anthropometric and biochemical measurements and genotype of rs3758539, and rs10882280 for RBP4 gene and rs974456 and rs351224 of STRA6 gene were analyzed. Statistical analysis used SPSS v. 25.0, with a level of significance α = 0.05.ResultsThere is no association between the two gene’s polymorphisms and obesity in our pediatric population. In regression analysis, with HOMA IR (homeostatic model assessment of insulin resistance) as the outcome, the plasmatic level of RBP4 and fat mass percentage are significant predictors, with the model explaining 42% of the HOMA variability. Hypercholesterolemia was significantly associated with male sex, carrying variant allele and heterozygote status of rs10882280 RBP4 gene and wild-type allele rs351224 of STRA6 gene.ConclusionThere is no significant association between obesity and SNPs of the RBP4 and STRA6 in our population, but they seem to play a role in insulin resistance and hypercholesterolemia.

Is the Retinol-Binding Protein 4 a Possible Risk Factor for Cardiovascular Diseases in Obesity?

Although many preventive and treatment approaches have been proposed, cardiovascular disease (CVD) remains one of the leading causes of deaths worldwide. Current epidemiological data require the specification of new causative factors, as well as the development of improved diagnostic tools to provide better cardiovascular management. Excessive accumulation of adipose tissue among patients suffering from obesity not only constitutes one of the main risk factors of CVD development but also alters adipokines. Increased attention is devoted to bioactive adipokines, which are also produced by the adipose tissue. The retinol-binding protein 4 (RBP4) has been associated with numerous CVDs and is presumably associated with an increased cardiovascular risk. With this in mind, exploring the role of RBP4, particularly among patients with obesity, could be a promising direction and could lead to better CVD prevention and management in this patient group. In our review, we summarized the current knowledge about RBP4 and its association with essential aspects of cardiovascular disease—lipid profile, intima-media thickness, atherosclerotic process, and diet. We also discussed the RBP4 gene polymorphisms essential from a cardiovascular perspective.

Transcriptional regulation of retinol binding protein 4 by Interleukin-6 via peroxisome proliferator-activated receptor α and CCAAT/Enhancer binding proteins

Interleukin-6 (IL-6) is a major mediator of the acute phase response (APR) that regulates the transcription of acute phase proteins (APPs) in the liver. During APR, the plasma levels of negative APPs including retinol binding protein 4 (RBP4) are reduced. Activation of the IL-6 receptor and subsequent signaling pathways leads to the activation of transcription factors, including peroxisome proliferator-activated receptor alpha (PPARα) and CCAAT/enhancer binding protein (C/EBP), which then modulate APP gene expression. The transcriptional regulation of RBP4 by IL-6 is not fully understood. Therefore, this study aimed to elucidate the molecular mechanisms of PPARα and C/EBP isoforms in mediating IL-6 regulation of RBP4 gene expression. IL-6 was shown to reduce the transcriptional activity of RBP4, and functional dissection of the RBP4 promoter further identified the cis-acting regulatory elements that are responsible in mediating the inhibitory effect of IL-6. The binding sites for PPARα and C/EBP present in the RBP4 promoter were predicted at −1079 bp to −1057 bp and −1460 bp to −1439 bp, respectively. The binding of PPARα and C/EBPs to their respective cis-acting elements may lead to antagonistic interactions that modulate the IL-6 regulation of RBP4 promoter activity. Therefore, this study proposed a new mechanism of interaction involving PPARα and different C/EBP isoforms. This interaction is necessary for the regulation of RBP4 gene expression in response to external stimuli, particularly IL-6, during physiological changes.

Association of RBP-4 gene polymorphisms with follicular cysts in large white sows.

Follicular cysts, which is a common infertility disease, can cause financial losses in pig breeding programmes. The pathogenesis and mechanisms of the formation of follicular cysts are not understood clearly. In our previous study, the concentration of retinol-binding protein 4 (RBP-4) in the follicular fluid (FF) of the ovary with follicular cysts was found to be significantly higher than that of normal ovary, thereby suggesting that RBP-4 may be a candidate biomarker for porcine follicular cysts. To study the association of RBP-4 and follicular cysts further, we detected the polymorphisms of the RBP-4 gene and the presence of follicular cysts by PCR-Restriction fragment length polymorphism (RFLP) assay. In this study, we screened the mutations of RBP-4 gene in 79 sows with follicular cysts and 100 normal sows without cysts. Results showed that +249-63G>C polymorphisms were significantly associated with follicular cysts, and sows with CC genotype in RBP-4 gene had a high risk of developing follicular cysts. Hence, our findings further proved that RBP-4 may be a novel biomarker for follicular cysts, which may be valuable for the diagnosis of follicular cysts and molecular breeding of pigs.

Association between ESR1 and RBP4 genes and litter size traits in a hyperprolific line of Landrace × Large White cross sows

This study was aimed at analysing single-nucleotide polymorphisms in the oestrogen receptor 1 (ESR1) and retinol-binding protein 4 (RBP4) genes in a hyperprolific line of Landrace × Large White (Topigs 20) cross sows (n = 101). The following litter size traits were analysed: total number born, number of born alive and number of weaned piglets. ESR1 and RBP4 genotypes determined on the basis of single-nucleotide polymorphisms were analysed using the least square method with the GLM procedure in SAS with eight effects. The REG procedure was used to calculate the effects of the additive and dominance components. The second parity sows with ESR1 BB genotype had a significantly higher (P < 0.05) number of weaned piglets compared to AB, with a tendency towards difference (P < 0.1) between homozygotes for number of born alive and number of weaned piglets. In the case of the RBP4 gene, the first parity sows of the AA genotype had a significantly higher total number born (P < 0.05) compared with the BB genotype, with a tendency towards difference (P < 0.1) between AA and heterozygotes for total number born, and homozygotes for number of born alive. The BB genotype showed a tendency for higher number of weaned piglets (P < 0.1) as compared with the AA genotype in the third parity sows for the RBP4 gene. In all parities, significant effects (P < 0.05) of parity were recorded for total number born, number of born alive and number of weaned piglets, season of farrowing for total number born, and the ESR1 and RBP4 interaction for number of born alive. In the first parity sows, significant effects (P < 0.05) on total number born were determined for gene interaction and gestation length, the latter also being recorded in the second parity sows. The additive (a) effect of single-nucleotide polymorphisms in RBP4 was significant (P < 0.05) for total number born in all parities as well as in the first parity sows, and dominance effect (d) (P < 0.05) of single-nucleotide polymorphisms in ESR1 for number of weaned piglets in the third parity sows. The obtained results regarding the investigated genes could help to provide a better understanding of the effect of single-nucleotide polymorphisms on litter size and thus promote genetic progress in pig reproduction management.

Retinol-Binding Protein-Dependent Cholesterol Uptake Regulates Macrophage Foam Cell Formation and Promotes Atherosclerosis.

Retinol-binding protein 4 (RBP4) is an adipokine that plays decisive roles in glucose metabolism and insulin sensitivity. Elevated circulating RBP4 levels were reported to be associated with increased risk for cardiovascular disease, but the precise role of RBP4 in atherosclerotic diseases and its mechanisms of action remain elusive. Serum RBP4 levels of 1683 participants from South China were evaluated and the occurrence of major adverse cardiovascular events was followed up for 5 years. Apolipoprotein E-deficient mice infected with RBP4-overexpressing/silencing adenovirus, J774A.1 macrophages, and primary peritoneal macrophages from RBP4 transgenic mice were used for investigating the function of RBP4 in foam cell formation. Prospective cohort studies revealed that baseline serum RBP4 level was an independent predictor for incidence of adverse cardiovascular events after adjustment for traditional risk factors. Increased RBP4 expression was observed in atherosclerotic lesions of aortic specimens from both humans and apolipoprotein E-deficient mice, and RBP4 was localized to areas rich in macrophage foam cells. RBP4 inhibition attenuated whereas overexpression accelerated atherosclerosis progression in apolipoprotein E-deficient mice. Both treatment with exogenous recombinant RBP4 and overexpression of RBP4 gene promoted macrophage-derived foam cell formation through the activation of scavenger-receptor CD36-mediated cholesterol uptake, and RBP4 transcriptionally upregulated CD36 expression in a manner dependent on jun N-terminal kinase and signal transducer and activator of transcription 1. The tyrosine kinase c-Src was identified as the upstream regulator of jun N-terminal kinase-signal transducer and activator of transcription 1-mediated CD36-dependent cholesterol uptake, and RBP4 challenge was found to alter the membrane distribution of c-Src and cause c-Src to partition into lipid-raft membrane subdomains, where the kinase was activated. Lastly, Toll-like receptor 4, but not retinol or stimulated by retinoic acid 6, mediated the inductive effects of RBP4 in macrophages. Inclusion of RBP4 levels in traditional models enhances the predictive ability for the incidence of atherosclerotic events. RBP4 promotes atherogenesis by inducing macrophage-derived foam cell formation.

Strong Correlation Between CTLA-4 and LEF1 Gene Expression Levels in CLL: Targeting of the Wnt/β-Catenin Pathway May Adversely Affect CTLA-4 Expression and Function

Recently published clinical trials have confirmed the effectiveness of anti-CD38 monoclonal antibody therapy in myeloma. Furthermore, in vitro studies of chronic lymphocytic leukaemia (CLL) cells suggest that CD38 expression can be enhanced by treatment with retinoid derivatives and thus may enhance the cytotoxic effects of anti-CD38 therapy. However, retinoids have been shown to have diverse effects on cellular function and we have previously shown that the retinoid drug acitretin upregulates CD38 expression while also reducing cell homing to the chemokine CXCL12 in primary CLL cells.To investigate possible key mechanisms for these effects, we purified CD20+ B cells from the peripheral blood of 20 CLL patients (9 previously treated, 11 untreated) and, using flow cytometry, measured percentage cell surface expression of CD38 and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4, CD152). We also measured gene expression levels of the key retinoid receptor, stimulated by retinoic acid 6 (STRA6) and it's agonist, retinol-binding protein 4 (RBP4), as well as CTLA-4, cyclin D1 (CCND1) and the transcription factors, lymphoid enhancer factor 1 (LEF1) and signal transducer and activator of transcription 3 (STAT3) using RT-PCR. GAPDH was used as a reference gene.Mean percentage surface expression of CD38 and CTLA-4 was 21.96% and 45.25% respectively. Mean ΔCT gene expression levels of CCND1, CTLA-4, LEF1 and STAT3 were 12.03, 5.57 , 5.99 and 8.98 respectively. RBP4 and STRA6 gene expression levels were undetectable in all 20 patients. Gene expression of LEF1 showed significant correlations with CTLA-4 (rs=0.572, p=0.008), CCND1 (rs=0.61, p=0.004) and STAT3 (rs=0.587, p=0.006). There was also a significant correlation between gene expression of CCND1 and of STAT3 (r =0.499, p=0.025). No significant correlations were found between percentage surface expression of CTLA-4 and gene expression levels of either CTLA-4 or of LEF1. A weak negative correlation between percentage surface expression of CTLA-4 and of CD38 was not statistically significant. Comparing untreated and previously treated patients, there was no significant difference in gene expression levels of CTLA-4 and of LEF1 or in surface expression of CTLA-4.The failure to detect RBP4 and STRA6 gene expression in unstimulated peripheral blood CLL cells is evidence against an autocrine retinoid effect in CLL, although upregulation of STRA6 gene expression following stimulation by retinoids might be anticipated. The Wnt signalling pathway has been shown to be active in CLL, including aggressive disease subtypes, highlighting the potential benefits in targeting this pathway. Intriguingly, CTLA-4 expression, although found to be the most highly induced gene following treatment with recombinant Wnt-3a in melanoma cell lines, is associated with a favourable outcome in CLL, possibly by inhibiting cell proliferation and survival. In contrast, expression of LEF1, which is a direct target of the Wnt signalling pathway, is associated with disease progression in CLL. Our finding that CTLA-4 and LEF1 gene expression levels are strongly correlated suggests that further investigation of the relationship between CTLA-4 and the Wnt/β-Catenin pathway in CLL is required and that targeting of the Wnt/β-catenin pathway may have unwanted consequences on CTLA-4 expression and function. DisclosuresQuinn:Celgene: Honoraria; Janssen Cilag: Honoraria.

Association of RBP4 Genotype with Phenotypic Reproductive Traits of Sows.

PCR-RFLP was applied to a commercial crossbred pig population in order to investigate the association between polymorphism (SNP) of Retinol-binding protein 4 (RBP4) gene and reproductive performance. 400 sows were genotyped and 2000 records of reproductive traits were used in order to retrieve information about the allele frequencies and the association of the RBP4 gene with main reproductive characteristics of the population. A deviation from the Hardy-Weinberg equilibrium was observed as a result of the AB genotype excess. In addition, the AA genotype saw statistically significant higher values of (i) the total number of born piglets (p < 0.05), (ii) the number of piglets born alive (p < 0.01), and (iii) the number of weaned piglets (p < 0.01). The number of the mummified piglets and the number of the piglets born dead did not differ between the various RBP4 genotypes. Interestingly, the AA genotype had a negative impact (p < 0.05) on the number of piglets born dead, resulting indirectly in a larger litter size. In conclusion, the AA genotype and in extension the A allele of RBP4 gene are in favor of producing larger litter size, suggesting that the RBP4 gene may be used in Marker-Assisted Selection (MAS) programs for a rapid improvement of the reproductive characteristics in pigs.

Association of RBP4 genetic variants with childhood obesity and cardiovascular risk factors.

Recent data suggest that retinol-binding protein 4 (RBP4) gene variants could be associated with a risk of obesity and its co-morbidities, such as metabolic syndrome, which increases the risk of developing type 2 diabetes mellitus and cardiovascular disease. The present study examined the potential association of RBP4 single nucleotide polymorphisms (SNPs) with childhood obesity and its metabolic complications. Four RBP4 SNPs, rs3758538 (3944A>C), rs3758539 (4406G>A), rs12265684 (12177G>C) and rs34571439 (14684T>G), were genotyped in a population of 180 Spanish Caucasian children (97 obese and 83 normal-weight children). Association of RBP4 SNPs with obesity, metabolic risk factors (blood pressure, triglycerides, high-density lipoprotein cholesterol, insulin resistance) and markers of vascular inflammation, such as high-sensitive C-reactive protein (hs-CRP), was tested. We found SNP rs3758538 to be associated with obesity (p = 0.007). Specifically, each copy of the minor allele C was associated with an increased risk of obesity, by more than twofold, in respect of being homozygous for the major allele A (odds ratio = 2.4; 95% confidence interval = 1.2-4.8). The rs3758538 and rs34571439 RBP4 SNPs correlated with plasma RBP4 levels. The SNPs rs12265684 and rs34571439 correlated with plasma triglyceride levels. The rs34571439 was also associated to hs-CRP levels. Marginal association of RBP4 SNPs with plasma high-density lipoprotein levels (rs34571439), blood pressure (rs12265684) and insulin resistance (rs3758539) was also observed. These findings suggest that childhood obesity may be associated with variations in RBP4 gene. The presence of selective SNPs in the RBP4 gene may account for metabolic complications.

Association of RBP4 gene variants with adverse lipid profile and obesity

Obesity is currently a worldwide public health problem. Retinol-binding protein4 (RBP4) is a recently discovered adipokine, which is potentially associated with insulin resistance and obesity. We aimed to investigate whether genetic variation within the RBP4 gene is correlated with the obesity and lipid profile in Iranian population. 321 samples were randomly selected from participants of Isfahan Healthy Heart Program (IHHP). Genomic DNA was isolated from peripheral blood cells (PBCs) and HRM-PCR was performed in order to investigate the presence of SNPs, and further sequencing analysis was done from selected subjects according to the differences of HRM curve pattern. Statistical analyses were performed using SPSS v16.00. The difference of the presence of rs3758539 polymorphism between controls and obese patients was significant, but not about rs10882280. We found noticeable association among genetic polymorphisms and biomedical and physical characteristics within investigated population. Our findings suggested that variations in the RBP4 gene were correlated with BMI and polymorphisms more likely could contribute to the development of obesity in our population. Also appraisal of obesity risk factors within each group might be helpful for preventing obesity initiation and could have a possible role in a predisposition to obesity in the Iranians.

Effect of endurance training on retinol-binding protein4 gene expression and its protein level in adipose tissue and the liver in diabetic rats induced by a high-fat diet and streptozotocin.

The present study was designed to investigate from which tissues the decrease in retinol-binding protein 4 (RBP4) expression could contribute to the improvement of serum RBP4 and insulin resistance (IR) after endurance training. Male 7-week-old Wistar rats were randomly assigned into four groups including control (C), trained (T), diabetic control (DC) and trained diabetic (TD). At 8weeks-of-age, diabetes was induced by a high-fat diet and intraperitoneal injection of low-dose streptozotocin (STZ; 35mg/kg). Rats in the T and TD groups carried out a 7-week exercise program on a motorized treadmill (15-20m/min for 20min/day for 5weeks), whereas the C and DC remained sedentary in their cages. Tissues gene expression and protein levels of RBP4 were assessed by using real-time polymerase chain reaction and western blot, respectively, while serum RBP4 was measured using an enzyme-linked immunosorbent assay kit. Exercise significantly improved IR and reduced serum concentration of RBP4 in the TD group. This reduction of serum RBP4 was accompanied by decreased RBP4 protein expression in visceral fat tissue. In contrast, exercise had no significant effect on RBP4 expression in liver and subcutaneous fat tissue in the TD group. Exercise also significantly decreased RBP4 gene expression in visceral fat tissue and muscle, whereas the effect of exercise on liver RBP4 messenger ribonucleic acid expression was not significant. The present study showed that the mechanism for RBP4 reducing the effect of endurance training could involve decreased RBP4 messenger ribonucleic acid expression and its protein level in adipose tissue in STZ-induced diabetic rats.

RBP4 Gene Variants Are Associated with Insulin Resistance in Women with Previous Gestational Diabetes

Objective. This study aimed to examine possible genetic effects of some retinol binding protein-4 (RBP4) single nucleotide polymorphisms (SNPs) on the risk of gestational diabetes mellitus (GDM). In addition, the SNPs were examined for their possible association with insulin resistance at 6 weeks after delivery. Methods. This was a prospective study of 100 women with GDM and 100 participants with normal gestation who were evaluated at gestational week 30 and 6 weeks postpartum. Three SNPs of RBP4 (rs3758539, rs116736522, and rs34571439) were genotyped using TaqMan assay. The genotype distributions between GDM patients and normal controls were analyzed using logistic regression models. In addition, differences in clinical characteristics among subjects grouped by genotype were assessed using the analysis of covariance test. Results. The frequencies of the rare alleles were not significantly different between GDM patients and controls. However, we identified two variants rs3758539 and rs34571439 associated with insulin levels and insulin resistance in women with previous GDM. Conclusion. Noncoding SNPs of the RBP4 gene are not associated with GDM, but two SNPs showed associations with insulin resistance and insulin levels in women with prior GDM. Additional studies with increased sample size will be necessary in other GDM cohorts.

Genetic polymorphism of retinol binding protein 4 locus and its association with litter traits in pigs

Retinol binding protein 4 (RBP4) gene was investigated to find its association with litter traits using PCR-RFLP method in RBP4 locus. The Msp1 polymorphism was observed in the third intron region of RBP4 gene. Genotypes, AA, AB and BB were observed with frequency of 0.48, 0.28 and 0.24 respectively. Homozygotes were predominant in LWY and crossbred whereas, heterozygote was predominant in Duroc. The frequencies of RBP4 allele A were 0.61 in the LWY, 0.48 in Duroc and 0.71 in the LWY × Ankamali pigs. RBP4/Msp1 genotype had no significant association with litter traits. Sows carrying RBP4 - AA genotype had higher litter size and weight at birth, but not significant. Five single nucleotide polymorphisms were identified in RBP4 565bp fragment nucleotide sequences, 4 were found in intronic regions and 1 silent substitution in exon region.

Ontogenic expression pattern and genetic polymorphisms of the retinol-binding protein 4 (RBP4) gene in Erlang mountainous chickens

Retinol-binding protein 4 (RBP4) is the only circulatory transport protein for vitamin A. Based on the essential role of vitamin A in chicken reproduction, we measured RBP4 mRNA abundance in Erlang mountainous chickens. We also identified and analyzed the gene polymorphism and its effect on reproduction traits among 349 chickens. The expression of RBP4 mRNA showed specific developmental changes and striking differences among tissues. The mRNA abundance was greatest (P<0.05) in the liver, intermediate in the ovary, kidney, small intestine, oviduct and heart, and lowest in the hypothalamus and pituitary, as compared to all other tissues (P<0.05). We detected one single nucleotide polymorphism (g.19942455C>G) in intron 2 of the RBP4 gene. Three genotypes (CC, CG and GG) were identified, with a significant effect of genotype on the age at first egg (AFE), first egg weight (FEW), total eggs at 300days (TE300), highest continuous laying days (HCLD) and average laying interval (ALI). The GG genotype, where chickens display earlier AFE, more TE300, longer HCLD and shorter ALI, would be genetically advantageous and its selection may improve reproduction traits. These results suggested that the RBP4 gene might play an important role in reproduction traits in chickens.

Retinol binding protein‐4 circulating levels were higher in nonalcoholic fatty liver disease vs. histologically normal liver from morbidly obese women

We aimed to analyze the retinol binding protein-4 (RBP4) messenger RNA (mRNA) expression profiles in adipose tissues and liver of morbidly obese (MO) women with or without nonalcoholic fatty liver disease (NAFLD), and to study the relationships with other pro- and anti-inflammatory adipokines in vivo and in vitro. We performed a cross-sectional analysis of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and liver samples from four lean and 45 MO women with or without NAFLD by enzyme-linked immunosorbent assay and real-time reverse transcription-PCR. We also studied RBP4 expression in HepG2 hepatocytes under various inflammatory stimuli. Circulating RBP4 levels were higher in MO women, and specifically, in MO subjects with NAFLD compared with normal liver controls (lean and MO). RBP4 liver expression was higher in nonalcoholic steatohepatitis (NASH)-moderate/severe than in NASHmild. Overall RBP4 gene expression was higher in liver than in adipose tissues. Among them, the higher expression corresponded to SAT. VAT expression was lower in the MO cohort. In HepG2, RBP4 mRNA expression was reduced by tumor necrosis factor (TNF)-α and increased by adiponectin treatment. The results obtained in MO women with NAFLD, brings up the use of RBP4 and other adipokines as a panel of noninvasive molecular biomarkers when NAFLD is suspected. Further studies are needed with other obesity groups.

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.

Exome Analysis Identified a Novel Mutation in the RBP4 Gene in a Consanguineous Pedigree with Retinal Dystrophy and Developmental Abnormalities

Retinitis Pigmentosa (RP) is a common form of retinal degeneration characterized by photoreceptor degeneration and retinal pigment epithelium (RPE) atrophy causing loss of visual field and acuities. Exome sequencing identified a novel homozygous splice site variant (c.111+1G>A) in the gene encoding retinol binding protein 4 (RBP4). This change segregated with early onset, progressive, and severe autosomal recessive retinitis pigmentosa (arRP) in an eight member consanguineous pedigree of European ancestry. Additionally, one patient exhibited developmental abnormalities including patent ductus arteriosus and chorioretinal and iris colobomas. The second patient developed acne from young age and extending into the 5th decade. Both patients had undetectable levels of RBP4 in the serum suggesting that this mutation led to either mRNA or protein instability resulting in a null phenotype. In addition, the patients exhibited severe vitamin A deficiency, and diminished serum retinol levels. Circulating transthyretin levels were normal. This study identifies the RBP4 splice site change as the cause of RP in this pedigree. The presence of developmental abnormalities and severe acne in patients with retinal degeneration may indicate the involvement of genes that regulate vitamin A absorption, transport and metabolism.