Variations of retinol binding protein 4 levels are not associated with changes in insulin resistance during puberty

A meta-analysis of the association between RBP4 rs3758539 genotype and metabolic syndrome factors

AIM

To explore the link between the RBP4 rs3758539 genotype and metabolic syndrome risk factors and whether the impact of this genetic variation displays any potential race discrepancy.

MATERIALS AND METHODS

This meta-analysis followed the PRISMA guidelines and was registered with PROSPERO (registration no. CRD42023407999). PubMed, Web of Science, Embase, Cochrane Library, Google Scholar, Airiti Library and CINAHL databases were used for the study search until October 2023. We evaluated the methodological quality using the Joanna Briggs Institute checklist and determined the correlation using a random-effects meta-analysis.

RESULTS

The results indicated that individuals with the rs3758539 GA/AA genotype had a higher risk profile, including lower high-density lipoprotein levels [correlation: -0.045, 95% confidence interval (CI): -0.080 to -0.009, p = .015, I2 = 46.9%] and higher body mass index (correlation: 0.117, 95% CI: 0.036-0.197, p = .005, I2 = 82.0%), body fat (correlation: 0.098, 95% CI: 0.004-0.191, p = .041, I2 = 64.0%), and low-density lipoprotein levels (correlation: 0.074, 95% CI: 0.010-0.139, p = .024, I2 = 0%), of developing metabolic syndrome than those with the GG genotype. The subgroup analysis maintained a significantly positive correlation between the rs3758539 GA/AA genotype and body mass index (correlation: 0.163, 95% CI: 0.031-0.289, p = .016, I2 = 88.9%) but a negative correlation with high-density lipoprotein levels (correlation: -0.047, 95% CI: -0.087 to -0.006, p = .025, I2 = 65.7%) in the Asian group only.

CONCLUSION

The current meta-analysis supports a significant link between the RBP4 rs3758539 GA/AA genotype and the metabolic syndrome.

Childhood retinol-binding protein 4 (RBP4) levels predicting the 10-year risk of insulin resistance and metabolic syndrome: the BCAMS study

Background

Elevated retinol-binding protein 4 (RBP4) levels may contribute to the development of metabolic abnormalities, but prospective studies evaluating the association between childhood RBP4 levels and metabolic syndrome (MS) in adulthood are lacking. We investigated whether RBP4 levels during childhood predict cardiometabolic risk at 10-year follow-up.

Methods

The relationships between RBP4 levels, the established adipokines (leptin and adiponectin) and the components of MS were examined in 3445 school-aged children recruited in 2004 for the Beijing Child and Adolescent Metabolic Syndrome study. In 2015, 352 of these individuals completed an in-depth follow-up examination.

Results

Participants with higher childhood RBP4 levels had adverse cardiometabolic profiles at follow-up. Those with incident or persistent MS had higher baseline RBP4 levels than those who never exhibited the elements of MS. Moreover, baseline RBP4 predicted hyperglycemia (OR per SD increase = 1.48, P = 0.009), elevated triglyceride (OR = 1.54, P < 0.001), elevated blood pressures (OR = 1.46, P = 0.015), MS (OR = 1.68, P = 0.002) and insulin resistance (OR = 1.44, P = 0.015) in the 10-year follow-up phase, independent of baseline BMI. Significant improvements were seen for the net reclassification improvement and integrated discrimination index after adding childhood RBP4 levels into the risk models using conventional cardiometabolic risk factors in predicting MS at follow-up (P < 0.05). Leptin and adiponectin demonstrated the expected associations with metabolic disorders.

Conclusions

Childhood RBP4 serves as a risk factor for subsequent development of MS and its components, independent of pediatric obesity. Incorporating childhood RBP4 into conventional cardiometabolic risk assessment models significantly improves the prediction of MS.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0707-y) contains supplementary material, which is available to authorized users.

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.

Metabolic Syndrome in Children and Adolescents: a Critical Approach Considering the Interaction between Pubertal Stage and Insulin Resistance

Pediatricians increasingly diagnose the metabolic syndrome (MetS) in recent years to describe cardiovascular risk and to guide management of the obese child. However, there is an ongoing discussion about how to define the MetS in childhood and adolescence. Since insulin resistance-the major driver of MetS-is influenced by pubertal stage, it is questionable to use definitions for MetS in children and adolescents that do not take into account pubertal status. A metabolic healthy status in prepubertal stage does not predict a metabolic healthy status during puberty. Furthermore, cardiovascular risk factors improve at the end of puberty without treatment. However, having a uniform internationally accepted definition of the MetS for children and adolescents would be very helpful for the description of populations in different studies. Therefore, the concept of MetS has to be revisited under the influence of puberty stage.

Serum levels of retinol binding protein 4 in women with different levels of adiposity and glucose tolerance

OBJECTIVE

Retinol-binding protein 4 (RBP4) is an adipokine responsible for vitamin A (retinol) transportation. Studies associated RBP4 increased levels with severity of type 2 diabetes mellitus (T2DM) and insulin resistance (IR). The study aimed to quantify RBP4 serum standards in women with a wide range of body mass index (BMI) and glucose tolerance level.

SUBJECTS AND METHODS

Cross-sectional study was performed with 139 women divided into three groups: Group 1 (lean-control, n = 45) and Group 2 (obese, n = 53) with normal glucose tolerance and group 3 (obese with T2DM, n = 41), called G1, G2 and G3. Were assessed clinical, biochemical, anthropometric and body composition parameters.

RESULTS

According to data analysis, we obtained in G1 higher RBP4 levels (104.8 ± 76.8 ng/mL) when compared to G2 (87.9 ± 38 ng/mL) and G3 (72.2 ± 15.6 ng/mL) levels. Also, were found: in G1 positive correlations of RBP4 with BMI (r = 0.253), glycated hemoglobin (r = 0.378) and fasting insulin (r = 0.336); in G2 with glycated hemoglobin (r = 0.489); in G3 with glycated hemoglobin (r = 0.330), fasting glucose (r = 0.463), HOMA-IR (r = 0.481).

CONCLUSIONS

Although RBP4 have shown lower levels in diabetic and obese, a strong correlation with HOMA-IR index highlights that, in our study, there is growing IR when there is an increasing in RBP4 levels.

Metabolic syndrome in pediatrics

The ever growing prevalence of childhood obesity is being accompanied by an increase in the pediatric population of diseases once believed to be exclusive of the adulthood such as the metabolic syndrome (MS). The MS has been defined as the link between insulin resistance, hypertension, dyslipidemia, impaired glucose tolerance, and other metabolic abnormalities associated with an increased risk of atherosclerotic cardiovascular diseases in adults. In this review, we will discuss the peculiar aspects of the pediatric MS and the role of novel molecules and biomarkers in its pathogenesis.

Retinol-binding protein 4 and insulin resistance are related to body fat in primary and secondary schoolchildren: the Ouro Preto study

PURPOSE

Evidence suggests that plasma retinol-binding protein 4 (RBP4) and insulin resistance are related to body fat (BF). We aimed to assess the relationship between RBP4 and insulin resistance with obesity in a mixed (skin color) cohort of the Brazilian population.

METHODS

A nested case-control study was conducted in 227 schoolchildren aged 7-14 years. Schoolchildren with a high BF percentage (% BF, ≥ 30 for girls and ≥ 25 for boys) were identified as the obese group (n = 137), and those with lower values were identified as the non-obese group (n = 90). Percentage of body fat (% BF) was determined by tetrapolar bioimpedance (Quantum II, RJL System), RBP4 by enzyme-linked immunosorbent assay (Immunology Consultants Laboratory), plasma fasting insulin by chemiluminescent immunoassay (Access(®) Immunoassay System) and insulin resistance by the homeostasis model insulin resistance (IR(HOMA)) index. Serum lipid profile and arterial blood pressure were evaluated.

RESULTS

The significant independent risk factors associated with obesity were as follows: male sex, increased serum LDL-C, RBP4 and IR(HOMA). Among children with higher RBP4, the association with obesity increased significantly (from 3.1 to 8.5) in the presence of insulin resistance, when compared to higher RBP4 and non-insulin resistance.

CONCLUSION

IR(HOMA) and RBP4 showed significant associations with obesity and traditional CVD risk factors. They might therefore be used as a marker for CVD risk and have clinical implications in the development of comorbidities associated with obesity.

Metabolic syndrome in youth: current insights and novel serum biomarkers

Paralleling the worldwide epidemic in childhood obesity, in the last decade we have observed a rise in the prevalence of metabolic syndrome (MetS) in pediatrics. The MetS comprises a cluster of cardiovascular risk factors. Multiple definitions have been proposed for the syndrome in the pediatric age group, but they are very difficult to test and validate. Thus, in this paper we will discuss the current knowledge in pediatric MetS and the potential role of novel biomarkers in the pathogenesis and diagnosis of MetS.

The association of retinol-binding protein 4 with metabolic syndrome and obesity in adolescents: the effects of gender and sex hormones

OBJECTIVES

Retinol-binding protein 4 (RBP4) has a role in the development of insulin resistance (IR), type 2 diabetes, obesity, and metabolic syndrome among adults. However, data among adolescents are limited, and the effects of gender and sex hormones on RBP4 are not well defined.

MATERIALS/METHODS

A total of 1082 adolescents were enrolled and categorized based on their body mass index. Blood samples were collected, and biochemical characteristics, sex hormones, RBP4 concentrations, and IR were determined.

RESULTS

Testosterone and estradiol were not directly correlated with RBP4 concentrations in both genders. Multivariate regression analysis revealed that fasting plasma glucose (FPG), triglyceride (TG), and testosterone levels were independently associated with RBP4 concentrations in boys; also, there was a trend of increasing RBP4 levels with the severity of obesity.

CONCLUSION

Plasma RBP4 concentrations correlated with obesity and cardiovascular risk factors, predominantly evident in boys. Testosterone, FPG, and TG levels were independent predictors of RBP4 concentrations.

Acute testosterone deprivation reduces insulin sensitivity in men

OBJECTIVE

In men with prostate cancer, androgen deprivation reduces insulin sensitivity; however, the relative roles played by testosterone and estradiol are unknown. To investigate the respective effects of these hormones on insulin sensitivity in men, we employed a model of experimental hypogonadism with or without hormone replacement.

DESIGN

Placebo-controlled, randomized trial.

PARTICIPANTS

Twenty-two healthy male volunteers, 18-55 years old.

METHODS

Following screening, subjects received the gonadotrophin-releasing hormone antagonist acyline plus one of the following for 28 days: Group 1, placebo transdermal gel and placebo pills; Group 2, transdermal testosterone gel 10 g/day plus placebo pills; Group 3, transdermal testosterone gel 10 g/day plus the aromatase inhibitor anastrozole 1 mg/day to normalize testosterone while selectively reducing serum estradiol. Fasting insulin, glucose, adipokines and hormones were measured bi-weekly.

RESULTS

With acyline administration, serum testosterone was reduced by >90% in all subjects in Group 1. In these men, mean fasting insulin concentrations were significantly increased compared with baseline (P = 0·02) at 28 days, despite stable body weight and no changes in fasting glucose concentrations. Decreased insulin sensitivity was also apparent in the insulin sensitivity indices homeostasis model of insulin resistance (P = 0·03) and quantitative insulin sensitivity check index (P = 0·04). In contrast, in Groups 2 and 3, testosterone concentrations remained in the physiologic range, despite significant reduction in mean estradiol in Group 3. In these groups, no significant changes in insulin sensitivity were observed.

CONCLUSIONS

Acute testosterone withdrawal reduces insulin sensitivity in men independent of changes in body weight, whereas estradiol withdrawal has no effect. Testosterone appears to maintain insulin sensitivity in normal men.

RBP4: a controversial adipokine

Adipose tissue is an endocrine organ secreting biologically active factors called adipokines that act on both local and distant tissues. Adipokines have an important role in the development of obesity-related comorbidities not only in adults but also in children and adolescents. Retinol binding protein 4 (RBP4) is a recently identified adipokine suggested to link obesity with its comorbidities, especially insulin resistance, type 2 diabetes (T2D), and certain components of the metabolic syndrome. However, data, especially resulting from the clinical studies, are conflicting. In this review, we summarize up-to-date knowledge on RBP4's role in obesity, development of insulin resistance, and T2D. Special attention is given to studies on children and adolescents. We also discuss the role of possible confounding factors that should be taken into account when critically evaluating published studies or planning new studies on this exciting adipokine.

Association of serum retinol binding protein 4 with adiposity and pubertal development in Korean children and adolescents

Retinol binding protein 4 (RBP4) has been postulated to provide a new link between obesity and insulin resistance. We aimed to assess the relationship between serum RBP4 and insulin resistance by investigating serum RBP4 levels in children and adolescents according to degree of obesity and pubertal stage. A total of 103 (30 lean, 39 overweight, 34 obese) were evaluated for serum RBP4, adiponectin, insulin, glucose and lipid profiles. RBP4 levels of obese and overweight groups were higher than those of lean group. RBP4 level was higher in pubertal group than in prepubertal group. RBP4 was positively correlated with age, height, weight, body mass index (BMI), abdominal circumference, systolic blood pressure, fasting insulin, homeostatic model assessment of insulin resistance (HOMA-IR), total cholesterol and triglyceride, and inversely with adiponectin. In the multiple linear regression analysis, RBP4 was found to be independently associated with pubertal stage, BMI and triglyceride but not with HOMA-IR. In conclusion, serum RBP4 level is related with degree of adiposity and pubertal development. The association of RBP4 with insulin resistance is supposed to be secondary to the relation between RBP4 and adipose tissue in children and adolescents.

Retinol binding protein 4 (RBP4) is primarily associated with adipose tissue mass in children

OBJECTIVE

Retinol binding protein 4 (RBP4) is a novel adipocytokine that may link obesity and insulin resistance. We aimed to discriminate between primary and secondary associations of RBP4 with obesity and related disease.

DESIGN

We applied clinical and experimental approaches to investigate the association of RBP4 levels with normal development, obesity, metabolic and cardiovascular parameters in 68 lean and 61 obese children.

RESULTS

RBP4 significantly increased with age and pubertal development in healthy lean children. Obese children had significantly higher RBP4 levels compared with lean controls (30.5±1.4 vs. 26.3±1.1 mg/L, P<0.05) and there was a clear association with BMI independent of age (r=0.33, P<0.0001). RBP4 levels correlated significantly with parameters of lipid and glucose metabolism, as well as cardiovascular parameters in univariate analyses. Multiple regression analyses confirmed the strong association of RBP4 with BMI z-score and age, while the association with most metabolic and cardiovascular parameters was abolished. To assess whether the association of RBP4 with obesity may be attributable to adipogenesis, we evaluated RBP4 expression and secretion during adipocyte differentiation using the human SGBS cell line. In preadipocytes, RBP4 mRNA expression was nearly undetectable but increased during differentiation up to approximately 1600-fold (P<0.05). Likewise, RBP4 secretion was restricted to mature adipocytes, further indicating that RBP4 is strongly related to differentiation of adipocytes.

CONCLUSION

RBP4 is a marker of adipose tissue mass and obesity already evident in children. The association of RBP4 with metabolic and cardiovascular sequelae of obesity appears to be secondary to the underlying relationship wtih body fat.

Inflammation, a link between obesity and cardiovascular disease

Obesity, the most common nutritional disorder in industrialized countries, is associated with an increased mortality and morbidity of cardiovascular disease (CVD). Obesity is primarily considered to be a disorder of energy balance, and it has recently been suggested that some forms of obesity are associated with chronic low-grade inflammation. The present paper focuses on the current status of our knowledge regarding chronic inflammation, a link between obesity and CVDs, including heart diseases, vascular disease and atherosclerosis. The paper discusses the methods of body fat evaluation in humans, the endocrinology and distribution of adipose tissue in the genders, the pathophysiology of obesity, the relationship among obesity, inflammation, and CVD, and the adipose tissue-derived cytokines known to affect inflammation. Due to space limitations, this paper focuses on C-reactive protein, serum amyloid A, leptin, adiponectin, resistin, visfatin, chemerin, omentin, vaspin, apelin, and retinol binding protein 4 as adipokines.