Impact of serum retinol-binding protein 4 levels on regulation of remnant-like particles triglyceride in type 2 diabetes mellitus

Associations of serum transthyretin with triglyceride in non-obese elderly Japanese women independently of insulin resistance, HDL cholesterol, and adiponectin

Objective

Studies are limited on the association between serum transthyretin (TTR), a negative acute phase reactant, and triglyceride (TG).

Research design and methods

TG, TTR, and insulin resistance-related cardiometabolic variables were measured in 159 fasting and 185 nonfasting community-dwelling elderly women aged 50-96 years. Pearson correlation analysis and then stepwise multiple regression analyses were performed to further identify the most significant variables contributing to the variation of fasting and nonfasting TG.

Results

Multiple regression analysis for fasting TG as a dependent variable revealed that TTR (standardized β: 0.299) and HDL cholesterol (standardized β: -0.545) emerged as determinants of TG independently of percentage of body fat, homeostasis model assessment insulin resistance, serum leptin and adiponectin, and plasminogen activator inhibitor-1 (PAI-1) (R ² = 0.36). For nonfasting TG, HDL cholesterol (standardized β: - 0.461), TTR (standardized β: 0.231), nonfasting insulin, a marker of insulin resistance, (standardized β: 0.202), and PAI-1 (standardized β: 0.187) emerged as determinants independently of percentage of body fat, nonfasting glucose, serum leptin and adiponectin, and high-sensitivity C-reactive protein (R ² = 0.45).

Conclusions

Fasting and nonfasting TG showed positive association with TTR in community-dwelling elderly non-obese women independently of insulin resistance, HDL cholesterol, and adiponectin. These findings may provide a clue as to a physiological function of circulating TTR in human: an influence factor of TG-rich lipoproteins in the circulation.

Liraglutide Increases the Catabolism of Apolipoprotein B100-Containing Lipoproteins in Patients With Type 2 Diabetes and Reduces Proprotein Convertase Subtilisin/Kexin Type 9 Expression

OBJECTIVE

Dyslipidemia observed in type 2 diabetes (T2D) is atherogenic. Important features of diabetic dyslipidemia are increased levels of triglyceride-rich lipoproteins and small dense LDL particles, which all have apolipoprotein B100 (apoB100) as a major apolipoprotein. This prompted us to study the effect of the GLP-1 agonist liraglutide on the metabolism of apoB100-containing lipoproteins.

RESEARCH DESIGN AND METHODS

We performed an in vivo kinetic study with stable isotopes (L-[1-¹³C]leucine) in 10 patients with T2D before and after 6 months of treatment with liraglutide (1.2 mg/day). We also evaluated in mice the effect of liraglutide on the expression of genes involved in apoB100-containing lipoprotein clearance.

RESULTS

In patients with T2D, liraglutide treatment significantly reduced plasma apoB100 (0.93 ± 0.13 vs. 1.09 ± 0.11 g/L, P = 0.011) and fasting triglycerides (1.76 ± 0.37 vs. 2.48 ± 0.69 mmol/L, P = 0.005). The kinetic study showed a significant increase in indirect catabolism of VLDL₁-apoB100 (4.11 ± 1.91 vs. 2.96 ± 1.61 pools/day, P = 0.005), VLDL₂-apoB100 (5.17 ± 2.53 vs. 2.84 ± 1.65 pools/day, P = 0.008), and IDL-apoB100 (5.27 ± 2.77 vs. 3.74 ± 1.85 pools/day, P = 0.017) and in catabolism of LDL-apoB100 (0.72 ± 0.22 vs. 0.56 ± 0.22 pools/day, P = 0.005). In mice, liraglutide increased lipoprotein lipase (LPL) gene expression and reduced proprotein convertase subtilisin/kexin type 9 (PCSK9), retinol-binding protein 4 (RBP4), and tumor necrosis factor-α (TNF-α) gene expression in adipose tissue and decreased PCSK9 mRNA and increased LDL receptor protein expression in liver. In vitro, liraglutide directly reduced the expression of PCSK9 in the liver.

CONCLUSIONS

Treatment with liraglutide induces a significant acceleration of the catabolism of triglyceride-rich lipoproteins (VLDL₁, VLDL₂, IDL) and LDL. Liraglutide modifies the expression of genes involved in apoB100-containing lipoprotein catabolism. These positive effects on lipoprotein metabolism may reduce cardiovascular risk in T2D.

Serum levels of retinol-binding protein 4 and the risk of non-small cell lung cancer: A case-control study

Retinol binding protein 4 (RBP4), as an adipokine, has been identified to be associated with several types of cancer. However, no studies have assessed its effect on non-small cell lung cancer (NSCLC) risk. The objective of this study was to assess the association between serum RBP4 levels and the risk of NSCLC.A case-control study design was used to recruit 256 confirmed NSCLC cases and 256 age- and gender-matched healthy controls by frequency between August 2017 and January 2019. Serum RBP4 was measured using enzyme-linked immune absorbent assay before treatment. Unconditional logistic regression analysis was applied to estimate the odds ratio and 95% confidence interval (CI).Serum RBP4 level was significantly higher in NSCLC patients than those in the healthy control group (36.05 ± 8.28 vs 29.54 ± 7.71 μg/mL, P < .05). Higher serum RBP4 level was associated with increased risk of NSCLC (P trend = .001). Compare with those in the lowest tertile, the adjusted odds ratios were 1.85 (95% CIs 1.07-3.2) (P = .029) for the second tertile and 2.18 (95% CIs 1.37-3.45) (P = .001) for the highest tertile after adjusting for confounding variables. No interactions were observed after stratified analyses by body mass index and smoking status (P for interaction: .584 and .357).Our study indicated that serum RBP4 level was positively related to the risk of NSCLC. Additional studies with prospective design are required to confirm this finding.

Development of a peptide-modified siRNA nanocomplex for hepatic stellate cells

Insulin-like growth factor 2 receptor (IGF2R) is overexpressed in activated hepatic stellate cells (HSCs) and therefore can be utilized for HSC-specific drug delivery. We recently discovered an IGF2R-specific peptide using a novel biopanning. Here, we adopted biotin-conjugated IGF2R-specific peptide, cholesterol, and vitamin A as the targeting ligands for the neutravidin-based siRNA nanocomplex to deliver PCBP2 siRNA, a potentially antifibrotic agent, to HSCs. Compared to vitamin A and cholesterol, the IGF2R-specific peptide exhibited the highest targeting effect to human LX-2 HSC, rat HSC-T6 cell line, and activated primary rat HSCs. Accordingly, the IGF2R-specific peptide coupled nanocomplex demonstrated higher silencing activity of PCBP2 and better inhibition on the migration of activated HSCs. Compared to free siRNA and the nanocomplexes coupled with vitamin A and cholesterol, the IGF2R-specific peptide coupled nanocomplex showed the highest uptake in the liver and lowest uptake in the lung and kidney of the rats with CCl4-induced liver fibrosis.

Association of retinol-binding protein 4 with metabolic syndrome in first-degree relatives of type 2 diabetic patients

Background:

Retinol-binding protein 4 (RBP4) is known to regulate lipid and glucose metabolism and insulin resistance. The influences of RBP4 on metabolic syndrome (MS) are still unclear. The purpose of this study is to evaluate the association between serum levels of RBP4 and MS components in first-degree relations of type 2 diabetic patients.

Materials and Methods:

This cross-sectional study was performed within the framework of the diabetes prevention project in Isfahan. This study has been conducted during 2012–2013. Seventy-eight subjects participate, with an average age of 43.20 ± 5.29 years. Weight, height, waist and hip circumferences, blood pressure (BP) of participants, fasting plasma glucose, hemoglobin A1c, total cholesterol, high-density lipoprotein cholesterol, triglyceride (TG), and serum RBP4 were measured from fasting blood sample taken from each participant after an overnight fast (12–14 h).

Results:

Systolic and diastolic BP were significantly higher in people in top median of RBP4 (11.8 ± 1.5 vs. 11.0 ± 1.2, P = 0.01 and 7.8 ± 1.0 vs. 7.3 ± 0.9, P = 0.03). Moreover, TG in people with high levels of RBP4 was higher compared with those with low levels of RBP4 (177.7 ± 97.6 vs. 138.7 ± 56.9, P = 0.02). People with low levels of RBP4 had significant greater hip circumferences (107.9 ± 7.5 vs. 104.3 ± 8.0, P = 0.04). There was no correlation between RBP4 and MS in crude model (odds ratio [OR]: 1.00, 0.95–1.05, P = 0.97). This null correlation remained after adjustment for body mass index, age, and physical activity (OR: 0.93, 0.91–1.07, P = 0.31).

Conclusion:

Although RBP4 levels were positively association with some risk factors of MS including hip circumference, TG, and systolic and diastolic BP, it does not seem to be a valuable marker for identification of the MS in the first relative degree of diabetic patients.

Retinol binding protein-4 predicts incident diabetes in Asian Indian men with prediabetes

The association of retinol binding protein-4 (RBP4) with incident type 2 diabetes (T2DM) in Asian Indian middle-aged men with impaired glucose tolerance (IGT) was studied. This was an ancillary analysis of a subsample from a cohort of participants with IGT in a 2 year prospective diabetes prevention program in India. For this analysis, 71 incident T2DM and 76 non-diabetic cases (non-progressors) based on the final glycemic outcome were selected. Baseline serum RBP4 was measured using competitive enzyme immunoassay. Correlations of RBP4 with relevant anthropometric and biochemical variables and also its association with diabetes were assessed using appropriate statistical analyses. Participants who developed T2DM had higher levels of serum RBP4 (21.3 [IQR: 17.7-24.9] µg/mL) compared with non-progressors (17.3 [IQR: 13.1-21.0] µg/mL; P = 0.001). Levels of RBP4 were lower than in Caucasians. Stepwise linear regression analysis showed that body mass index (BMI), systolic blood pressure, triglycerides, and HbA1c had independent associations with RBP4 levels. Multiple logistic regression analyses showed that RBP4 was independently associated with incident diabetes (odds ratio [OR] [95%confidence interval (CI)]: 1.69 [1.18-2.41]; P = 0.004). Adjustment for study group, age, BMI, waist circumference, 2 H plasma glucose, triglycerides, gamma glutamyl transferase, and insulin resistance weakened the significance of its association (OR [95%CI]: 1.65 [1.03-2.66]; P = 0.038).The results of this preliminary analyses showed that baseline serum RBP4 levels were independently associated with incident diabetes in Asian Indian men with IGT. It may be used as an additional predictor of future diabetes.