title: Elevated retinol binding protein 4 induces apolipoprotein B production and associates with hypertriglyceridemia.
abstract: OBJECTIVE
  A high level of retinol binding protein 4 (RBP4) is reported to be associated with insulin resistance in humans. However, evidence from large-scale populations about the relationship between serum RBP4 and metabolic phenotypes is scarce. In the present study, we aimed to evaluate serum RBP4 distribution and its association with metabolic phenotypes among middle-aged and elderly Chinese.
  
  
  METHODS
  Serum concentrations of RBP4 in a cross-sectional sample of 2780 Chinese population aged 50-70 years old in Guangzhou were measured by ELISA.
  
  
  RESULTS
  The mean of serum RBP4 concentration was 28.04 μg/mL for male and 37.76 μg/mL for female (P < .01), respectively. Circulating RBP4 was positively correlated with serum triglyceride and apolipoprotein B (apoB) concentrations. The odds ratio (OR) was substantially higher for hypertriglyceridemia (OR, 3.26; 95% confidence interval, 2.36-4.51) in the highest RBP4 quartile compared with those in the lowest quartile after multiple adjustment for confounders. Furthermore, serum RBP4 was significantly associated with fasting glucose, insulin levels, and homeostasis model assessment index-insulin resistance (HOMA-IR). Moreover, we showed that RBP4 enhanced microsomal triglyceride transfer protein (MTP) expression and activity via up-regulation of protein disulfide isomerase (PDI), suppressed low-density lipoprotein receptor (LDLR) expression, and impaired insulin-signaling pathway, leading to inductions in apoB secretion both in vitro and in vivo.
  
  
  CONCLUSIONS
  Elevated circulating RBP4 concentrations were associated with higher risk of hypertriglyceridemia by inducing the secretion of triglyceride-rich apoB-containing lipoproteins.
authors.affiliation: Guangdong Provincial Key Laboratory of Food, Nutrition and Health 510080 (Y.L., M.X.), and Department of Nutrition, School of Public Health (Y.L., H.C., J.W., W.Z., R.S., M.X.), Sun Yat-sen University (Northern Campus), 510080 Guangzhou, Guangdong Province, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Hongen
authors.initials: H
authors.lastname: Chen
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wang
authors.forename: Wenjing
authors.initials: W
authors.lastname: Zhou
authors.forename: Ruifang
authors.initials: R
authors.lastname: Sun
authors.forename: Min
authors.initials: M
authors.lastname: Xia
mesh_terms: D000368:Aged; D001055:Apolipoproteins B / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015228:Hypertriglyceridemia / Q000097:blood*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D054839:Retinol-Binding Proteins, Plasma / Q000378:metabolism*
chemical_list: D001055:Apolipoproteins B; D001786:Blood Glucose; D007328:Insulin; C101326:RBP4 protein, human; D054839:Retinol-Binding Proteins, Plasma