Retinol-binding protein 4 (RBP4) is adipocyte-derived secreted adipokines and elevated RBP4 expression level was closely related to insulin resistance and type II diabetes mellitus. However, the exact mechanisms are unknown. To clarify the mechanism, RBP4 lentivirus particles were packaged to infect porcine preadipocytes. Then porcine preadipocytes were activated by insulin or induced model of insulin resistance. RBP4 interference efficiency and the gene expression of each treatment groups in PI3K/Akt pathways were examined by QRT-PCR and Western blotting. The result shows that RBP4 mRNA and protein expressions were suppressed more than 60% (P < 0.01). Furthermore, no matter under insulin stimulation or insulin resistance, RBP4 knockdown significantly increased the mRNA expressions of AKT2, PI3K, GLUT4 and IRS1 compared with the control. The protein phosphorylate levels of AKT2, PI3K, IRS1 arised, meanwhile enhanced the AKT2, PI3K, GLUT4 total protein expressions. Collectively, knockdown of RBP4 increased the insulin sensitivity through upregulated PI3K/Akt pathways related factors' expression and phosphorylation in porcine adipocytes. This research will provide a new idea to treat insulin resistance related diseases.
Adipocytes ; metabolism ; Animals ; Gene Knockdown Techniques ; Insulin Resistance ; physiology ; Phosphatidylinositol 3-Kinases ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Retinol-Binding Proteins, Plasma ; genetics ; pharmacology ; Signal Transduction ; Swine

Recently the prevalence of both asthma and obesity have increased substantially in many countries. The aim of this study was to evaluate the role of retinol-binding protein (RBP) 4 in childhood asthma and its association with atopy markers, pulmonary function, and bronchial hyperresponsiveness in relation to obesity. We studied 160 children between the ages 6 to 10 yr, including 122 asthmatics and 38 controls. The body mass index, pulmonary function tests, and methacholine challenge tests were measured on the same day. Total eosinophil count, serum total IgE, serum eosinophil cationic protein, and serum RBP4 were measured in all subjects. There was no difference in serum RBP4 levels between the asthmatics and the control group. In all subjects or subgroups, serum RBP4 was not associated with total eosinophil count, serum total IgE, serum eosinophil cationic protein, or PC20. There was no relationship between serum RBP4 and pulmonary function in female asthmatics. Forced expiratory volume in 1 second/forced vital capacity (FVC) and forced expiratory flow between 25% and 75% of FVC contributed to serum RBP4 in male asthmatics. Our findings show an association between RBP4 and pulmonary function in prepubertal male asthmatics. This relationship may indirectly affect the high prevalence of childhood asthma in males.
*Asthma/blood/immunology ; Bronchial Hyperreactivity/blood/immunology ; Bronchial Provocation Tests ; Child ; Female ; Humans ; Male ; Obesity/blood/immunology ; Retinol-Binding Proteins, Plasma/*metabolism

OBJECTIVE: To determine the relation between serum concentration of retinol binding protein (RBP) 4 and markers of bone metabolism, bone mineral density (BMD) in patients with type 2 diabetes mellitus (T2DM). METHODS: A total of 82 patients newly diagnosed with T2DM and 46 subjects with normal glucose tolerance (NGT) enrolled in the cross-sectional study. Subset analyses were performed, dividing subjects on the basis of gender into M-T2DM, F-T2DM, M-NGT, and F-NGT. The serum concentrions of RBP4, osteocalcin (OC) and C-terminal telopeptide of collagen type I (CTX) were measured with ELISA. The BMD was measured by dual-energy X-ray absorptiometry (DXA) with a Hologic QDR4500A device. RESULTS: In both the T2DM groups, lnRBP4 showed a positive relationship with lnCTX (M-T2DM, r=0.564, P<0.01; F-T2DM, r=0.386, P=0.018), but no association with lnOC. After adjusting for age, smoking, creatinine clearance rate (CCr), and waist-to-hip ratio (WHR), lnRBP4 still showed a strong association with lnCTX in the M-T2DM group (r'=0.536, P<0.01), but not in F-T2DM (r'=0.317, P=0.072). In the NGT group, there was no relation between lnRBP4 and lnCTX or lnOC. LnRBP4 showed no association with BMD in all groups. CONCLUSION The level of serum RBP4 may be correlated with the bone metabolism in patients with T2DM.
Adult ; Aged ; Bone Density ; Bone and Bones ; metabolism ; Collagen Type I ; blood ; Cross-Sectional Studies ; Diabetes Mellitus, Type 2 ; blood ; metabolism ; Female ; Humans ; Male ; Middle Aged ; Osteocalcin ; blood ; Peptides ; blood ; Retinol-Binding Proteins, Plasma ; metabolism

To prepare recombinant human retinol binding protein 4 (RBP4) by using the baculovirus expression system and to detect its immunogenicity, the fusion DNA fragment of secretory signal peptide SS64 and human RBP4 gene was subcloned into a baculovirus transfer vector pFastBac-dual(pFBd), and the corresponding recombinant transfer plasmid was transformed into E. coli strain DH10bac, after transposition recombinant shuttle bacmid was screened out. The logarithmic phase Sf9 cells were transfected with the recombinant bacmid and then the recombinant baculovirus containing hRBP4 expression box were generated. After amplification of recombinant baculovirus, the recombinant baculovirus seeds were obtained. To express human RBP4, logarithmic phase Sf9 cells were infected with the virus seeds and SDS-PAGE and Western blotting were used to detect and identify the expression. Finally, to prepare a batch of RBP4 protein, logarithmic phase Sf9 cells in suspension culture were infected with recombinant baculovirus seeds and the supernatant was harvested after 120 hours post-infection for purification. Finally for preparation of polyclonal antibody and evaluation of immunogenicity, the recombinant hRBP4 from insect cells and from E. coli were immunized rabbits. Restriction enzyme digestion and sequencing confirmed that the recombinant baculovirus transfer plasmid was constructed correctly, and subsequently recombinant RBP4-bacmid was generated successfully. SDS-PAGE and Western blotting analysis suggested that human RBP4 protein was highly expressed in Sf9 cells with the molecular weight of approximately 23 kDa. The recombinant RBP4 protein could be secreted into the medium efficiently, and the expression level was calculated amount of 100 mg/L. Finally the rabbit antiserum was harvested after recombinant RBP4 immunization, therein the titer of antiserum against baculovirus recombinant RBP4 is 1:100 000 whereas the titer of antiserum against E. coli recombinant RBP4 is only 1:10 000. Overall, human RBP4 was high efficiently expressed successfully with good antigenicity in baculovirus system, and high affinity antiserum was obtained. A solid foundation was laid for the next step of the preparation of human serum RBP4 detection kit.
Animals ; Baculoviridae ; genetics ; Blotting, Western ; Cloning, Molecular ; Electrophoresis, Polyacrylamide Gel ; Escherichia coli ; Genetic Vectors ; Humans ; Immune Sera ; Insecta ; Rabbits ; Recombinant Proteins ; biosynthesis ; immunology ; Retinol-Binding Proteins, Plasma ; biosynthesis ; immunology ; Sf9 Cells ; metabolism ; Transfection

PURPOSE: The aim of this study was to determine whether retinol-binding protein 4 (RBP4), adiponectin and high molecular weight (HMW) adiponectin are associated with insulin resistance (IR) and metabolic parameters in non-diabetic hypertensive patients. Also, we sought to compare the predictive values of these adipocytokines for IR in non-diabetic hypertensive patients. MATERIALS AND METHODS: Analyses of RBP4, adiponectin, and HMW adiponectin were performed on 308 non-diabetic hypertensives (148 males, age 58 +/- 10 years, 189 non-metabolic syndrome and 119 metabolic syndrome). The homeostasis model assessment (HOMA) index for IR, lipid profiles, and anthropometric measure-ments were assessed. RESULTS: There was no significant difference in RBP4 levels according to the presence of metabolic syndrome, although adiponectin and HMW adiponectin were significantly lower in metabolic syndrome. Correlation analysis of log RBP4 with IR and metabolic indices revealed that there was no significant correlation of RBP4 with waist circumference (r = 0.056, p = 0.324), HDL cholesterol (r = 0.005, p = 0.934), ApoB/ApoAI ratio (r = 0.066, p = 0.270), and the HOMA index (r = 0.017, p = 0.756). However, adiponectin and HMW adiponectin showed significant correlations with the HOMA index (r = - 0.247, p < 0.001; r = - 0.296, p < 0.001) and metabolic parameters. With IR defined as HOMA index > or = 2.5, HMW adiponectin did not demonstrate a superior predictive value for IR compared to adiponectin (AUC = 0.680 vs. 0.648, p = 0.083). The predictive value of RBP4 for IR was minimal (AUC = 0.534). CONCLUSION: RBP4 was not associated with IR or metabolic indices and the predictive value for IR was minimal in hypertensives. HMW adiponectin didn't have a superior predictive value for IR compared to adiponectin. Therefore, we can suggest that RBP4 and HMW adiponectin don't have more additive information than adiponectin in non-diabetic hypertensives.
Adiponectin/*blood ; Aged ; Enzyme-Linked Immunosorbent Assay ; Female ; Humans ; Hypertension/*blood/*physiopathology ; Insulin Resistance/*physiology ; Male ; Middle Aged ; Radioimmunoassay ; Retinol-Binding Proteins, Plasma/*metabolism ; Risk Factors ; Waist Circumference/physiology

Metabolic syndrome is an important long term complication in chronic asymptomatic HIV-infected subjects under highly active antiretroviral therapy (HAART), because it can contribute to morbidity and mortality via cardiovascular disease (CVD). Therefore, a predictive marker for early detection of metabolic syndrome may be necessary to prevent CVD in HIV-infected subjects. Retinol-binding protein-4 (RBP-4) has been shown to be associated with metabolic syndrome in various non-HIV-infected populations. We performed a cross-sectional study to evaluate whether serum RBP-4 levels are correlated with metabolic syndrome in HIV-infected subjects receiving HAART. In total, 98 HIV-infected Koreans who had been receiving HAART for at least 6 months were prospectively enrolled. Metabolic syndrome was diagnosed according to the Adult Treatment Panel III criteria, and serum RBP-4 concentrations were measured using human RBP-4 sandwich enzyme-linked immunosorbent assay. Serum RBP-4 levels were significantly higher in HIV-infected subjects receiving HAART with metabolic syndrome (n=33, 33.9+/-7.7 microg/mL) than in those without it (n=65, 29.9+/-7.2 microg/mL) (p=0.012). In multivariate linear regression analysis, the number of components of metabolic syndrome presented and waist circumference were independently, significantly correlated with RBP-4 (p=0.018 and 0.030, respectively). In conclusion, we revealed a strong correlation between RBP-4 and the number of components of metabolic syndrome in HIV-infected subjects receiving HAART.
Adult ; *Antiretroviral Therapy, Highly Active ; Enzyme-Linked Immunosorbent Assay ; Female ; HIV Infections/*blood/*drug therapy ; Humans ; Male ; Metabolic Syndrome X/*blood/*drug therapy ; Middle Aged ; Retinol-Binding Proteins, Plasma/*metabolism

OBJECTIVETo compare the effects of piglitazone and metformin on retinol-binding protein-4 (RBP-4) and adiponcetin (APN) in patients with type 2 diabetes mellitus (T2DM) complicated with Non alcohol fatty acid liver disease (NAFLD).

METHODSTotally 60 T2DM patients complicated with NAFLD were equally and randomly divided into pioglitazone group and metform group. The levels of biochemical indicators including body mass index (BMI), glucose hemoglobin A1C (GHbA1C), insulin resistance (HOMA-IR), fasting blood glucose (FBG), fasting insulin (FIns), and serum triglycerides (TG) as well as serum RBP-4 and APN level were measured pre-treatment and 12 weeks after treatments.

RESULTSAfter 12 weeks of treaments, BMI, FBG, HOMA-IR, GHbA1C, FIns, and TG decreased (all P<0.05) in both piglitazone group and metform group. APN increased (all P<0.05) in both groups. RBP-4 decreased (P<0.05) in piglitazone group. Compare with the metform group, the levels of RBP-4, FIns ,and HOMA-IR decreased and BMI increased in piglitazone group (P<0.05).

CONCLUSIONPiglitazone is superior to metoform in decreasing RBP-4 level and HOMA-IR in patients with T2DM complicated with NAFLD.

Adiponectin ; blood ; Adult ; Aged ; Diabetes Mellitus, Type 2 ; blood ; complications ; drug therapy ; Fatty Liver ; blood ; complications ; Female ; Humans ; Male ; Metformin ; pharmacology ; Middle Aged ; Retinol-Binding Proteins, Plasma ; metabolism ; Thiazolidinediones ; pharmacology

OBJECTIVE: To evaluate the change of plasma level of retinol binding protein 4 (RBP4) in patients with coronary heart disease, and to explore the effect of hyperinsulinemia. METHODS: This study was carried out at Xiangya Hospital of Central South University, China, from September 2009 to May 2010. Thirty patients with coronary artery disease (the CAD group) were confirmed by coronary angiography, 29 patients with CAD plus hyperinsulinemia (the CAD+HIns group), and 30 healthy subjects were enrolled as controls (the control group). The peripheral blood sample from the anticubital vein was collected aseptically in all the subjects to measure the RBP4 by enzyme linked immunosorbent-assay (ELISA). The height, weight, body mass index (BMI) the waist-to-hip ratio (WHR), the blood pressure, the fasting plasma glucose (FPG), the fasting insulin (Fins), the 2-hour postprandial inslulin (2hPIns), and the homeostasis model assessment-insulin resistance index (HOMA-IR) was measured. The lipids, high sensitivity C reactive protein (hsCRP), uric acid(UA), free fatty acids (FFA) were all examined. RESULTS: The level of plasma RBP4 in the CAD+HIns group was higher than that in the CAD group and the control group (both P<0.01), with no significant difference of plasma RBP4 between the CAD group and the control group (P>0.05). Correlation analysis showed that the plasma RBP4 level was significantly correlated with BMI, FPG, FIns, 2hPIns, HOMA-IR, TG, HDL-C, UA, and hsCRP (r=0.259, 0.331, 0.582, 0.452, 0.600, 0.236, -0.290, 0.243, 0.231, respectively; all P>0.05). Multiple regression analysis showed that BMI, 2hPIns, and HOMA-IR were the independent factors related to RBP4. CONCLUSION The plasma level of RBP4 does not increase in the CAD group, but it is high in the CAD +HIns group. RBP4 level is related to BMI, lipids, UA, and other cardiovascular risk factors. BMI, 2hPIns, and HOMA-IR are the independent factors associated with RBP4.
Adult ; Aged ; Case-Control Studies ; Coronary Disease ; blood ; complications ; Female ; Humans ; Hyperinsulinism ; blood ; complications ; Insulin Resistance ; physiology ; Lipids ; blood ; Male ; Middle Aged ; Retinol-Binding Proteins, Plasma ; analysis ; metabolism ; Uric Acid ; blood

BACKGROUND/AIMS: Adipose tissue is an active endocrine organ that secretes various metabolically important substances including adipokines, which represent a link between insulin resistance and nonalcoholic steatohepatitis (NASH). The factors responsible for the progression from simple steatosis to steatohepatitis remain elusive, but adipokine imbalance may play a pivotal role. We evaluated the expressions of adipokines such as visfatin, adipocyte-fatty-acid-binding protein (A-FABP), and retinol-binding protein-4 (RBP-4) in serum and tissue. The aim was to discover whether these adipokines are potential predictors of NASH. METHODS: Polymerase chain reaction, quantification of mRNA, and Western blots encoding A-FABP, RBP-4, and visfatin were used to study tissue samples from the liver, and visceral and subcutaneous adipose tissue. The tissue samples were from biopsy specimens obtained from patients with proven NASH who were undergoing laparoscopic cholecystectomy due to gallbladder polyps. RESULTS: Patients were classified into two groups: NASH, n=10 and non-NASH, n=20 according to their nonalcoholic fatty liver disease Activity Score. Although serum A-FABP levels did not differ between the two groups, the expressions of A-FABP mRNA and protein in the visceral adipose tissue were significantly higher in NASH group than in non-NASH group (104.34 vs. 97.05, P<0.05, and 190.01 vs. 95.15, P<0.01, respectively). Furthermore, the A-FABP protein expression ratio between visceral adipose tissue and liver was higher in NASH group than in non-NASH group (4.38 vs. 1.64, P<0.05). CONCLUSIONS: NASH patients had higher levels of A-FABP expression in their visceral fat compared to non-NASH patients. This differential A-FABP expression may predispose patients to the progressive form of NASH.
Adipose Tissue/metabolism/pathology ; Adult ; Aged ; Fatty Acid-Binding Proteins/genetics/*metabolism ; Fatty Liver/metabolism/*pathology ; *Gene Expression Regulation ; Humans ; Intra-Abdominal Fat/*metabolism ; Liver/metabolism/pathology ; Middle Aged ; Nicotinamide Phosphoribosyltransferase/genetics/metabolism ; RNA, Messenger/metabolism ; Retinol-Binding Proteins, Plasma/genetics/metabolism

Preeclapsia (PE) is a severe disorder that occurs during pregnancy, leading to maternal and fetal morbidity and mortality. PE affects about 3-8% of all pregnancies. In this study, we conducted liquid chromatographymass spectrometry/mass spectrometry (LC-MS/MS) to analyze serum samples depleted of the six most abundant proteins from normal and PE-affected pregnancies to profile serum proteins. A total of 237 proteins were confidently identified with < 1% false discovery rate from the two groups of duplicate analysis. The expression levels of those identified proteins were compared semiquantitatively by spectral counting. To further validate the candidate proteins with a quantitative mass spectrometric method, selective reaction monitoring (SRM) and enzyme linked immune assay (ELISA) of serum samples collected from pregnant women with severe PE (n = 8) or normal pregnant women (n = 5) was conducted. alpha2-HS-glycoprotein (AHSG), retinol binding protein 4 (RBP4) and alpha-1-microglobulin/bikunin (AMBP) and Insulin like growth factor binding protein, acid labile subunit (IGFBP-ALS) were confirmed to be differentially expressed in PE using SRM (P < 0.05). Among these proteins, AHSG was verified by ELISA and showed a statistically significant increase in PE samples when compared to controls.
Adult ; Alpha-Globulins/metabolism ; Amino Acid Sequence ; Biological Markers/blood ; Blood Proteins/*analysis ; Case-Control Studies ; Female ; Humans ; Insulin-Like Growth Factor Binding Proteins/blood ; Molecular Sequence Data ; Pre-Eclampsia/*blood/diagnosis ; Pregnancy ; Proteome/*analysis ; Retinol-Binding Proteins, Plasma/metabolism ; alpha-2-HS-Glycoprotein/metabolism