Factors that influence retinol-binding protein 4-transthyretin interaction are not altered in overweight subjects and overweight subjects with type 2 diabetes mellitus

Plasma Transthyretin Levels and Risk of Type 2 Diabetes Mellitus and Impaired Glucose Regulation in a Chinese Population

Plasma transthyretin may be engaged in glucose regulation. We aimed to investigate the association between plasma transthyretin levels and the risk of newly diagnosed T2DM and impaired glucose regulation (IGR) in a Chinese population. We conducted a case-control study including 1244 newly diagnosed T2DM patients, 837 newly diagnosed IGR patients, and 1244 individuals with normal glucose tolerance (NGT) matched by sex and age. Multivariate logistic regression analysis was utilized to estimate the independent association of plasma transthyretin concentrations with the risk of T2DM and IGR. Plasma transthyretin concentrations were significantly higher in T2DM and IGR patients compared with control subjects (p < 0.005). After multiple adjustment and comparison with the lowest quartile of plasma transthyretin concentrations, the odds ratios (95% confidence intervals) of T2DM and IGR in the highest quartile were 2.22 (1.66, 2.98) and 2.29 (1.72, 3.05), respectively. Plasma transthyretin concentrations also showed a great performance in predicting the risk of T2DM (AUC: 0.76). Moreover, a potential nonlinear trend was observed. Our results demonstrated that higher plasma transthyretin concentrations, especially more than 290 mg/L, were associated with an increased risk of T2DM and IGR. Further studies are warranted to confirm our findings and elucidate the potential mechanisms.

Blood retinol and retinol-binding protein concentrations are associated with diabetes: a systematic review and meta-analysis of observational studies

PURPOSE

The associations between blood retinol, retinol-binding protein (RBP) concentrations and diabetes mellitus were inconsistent in literature. The objective is to investigate these associations by a systematic review and meta-analysis and provide basis for clinical intervention.

METHODS

PubMed, Web of science, and Cochrane databases were searched from the beginning to July 1, 2021. A total of 13 studies on retinol and 31 studies on RBP are included in the current meta-analysis.

RESULTS

The blood retinol concentration was significantly lower in the type I diabetes mellitus (T1DM) [standardized mean difference (SMD) (95% CI): - 0.59 (- 0.81, - 0.37), P < 0.01] and gestational diabetes mellitus (GDM) patients [SMD (95% CI): - 0.54 (- 0.87, - 0.20), P < 0.01] than in the controls. However, the difference was not significant between the type II diabetes mellitus (T2DM) patients and the controls. The RBP concentration was significantly higher in the diabetic patients than in the controls [SMD (95% CI): 0.24 (0.12, 0.35), P < 0.01]. Particularly, the RBP concentration was significantly higher in the T2DM and GDM patients.

CONCLUSION

The blood retinol concentration was negatively associated with T1DM and GDM, while the blood RBP concentration was positively associated with T2DM and GDM. Future work should use a more sensitive retinol measurement method like retinol isotope dilution method to confirm whether blood retinol concentration differs between the diabetes patients and the controls.

Proteomic and Structural Manifestations of Cardiomyopathy in Rat Models of Obesity and Weight Loss

Obesity cardiomyopathy increases the risk of heart failure and death. Obesity is curable, leading to the restoration of the heart phenotype, but it is not clear if there are any after-effects of obesity present after weight loss. We characterize the proteomic landscape of obesity cardiomyopathy with an evaluation of whether the cardiac phenotype is still shaped after weight loss. Cardiomyopathy was validated by cardiac hypertrophy, fibrosis, oversized myocytes, and mTOR upregulation in a rat model of cafeteria diet-induced developmental obesity. By global proteomic techniques (LC-MS/MS) a plethora of molecular changes was observed in the heart and circulation of obese animals, suggesting abnormal utilization of metabolic substrates. This was confirmed by increased levels of cardiac ACSL-1, a key enzyme for fatty acid degradation and decreased GLUT-1, a glucose transporter in obese rats. Calorie restriction and weight loss led to the normalization of the heart's size, but fibrosis was still excessive. The proteomic compositions of cardiac tissue and plasma were different after weight loss as compared to control. In addition to morphological consequences, obesity cardiomyopathy involves many proteomic changes. Weight loss provides for a partial repair of the heart's architecture, but the trace of fibrotic deposition and proteomic alterations may occur.

The Role of Circulating RBP4 in the Type 2 Diabetes Patients with Kidney Diseases: A Systematic Review and Meta-Analysis

Background

Diabetic nephropathy is a common and serious complication of diabetes mellitus (DM) and is one of the leading causes of end-stage renal disease worldwide. Although there have been many investigations on biomarkers for DN, there is no consistent conclusion about reliable biomarkers. The purpose of this study was to perform a systematic review and meta-analysis of the role of circulating retinol-binding protein 4 (RBP4) in the type 2 diabetes mellitus (T2DM) patients with kidney diseases.

Materials and Methods

We searched the PubMed, MEDLINE, EMBASE, and Web of Science databases for publications. For the 12 cross-sectional studies that we included in the review, we calculated standard mean differences (SMD) with 95% confidence intervals (CI) for continuous data when the applied scales were different. Risk of bias of included trials was assessed by using the Newcastle-Ottawa Scale.

Results

RBP4 concentrations in the micro-, macro-, or micro+macroalbuminuria groups were significantly higher than those in the normal albuminuria group of T2DM patients [P = 0.001, SMD 1.07, 95% CI (0.41, 1.73)]. The estimated glomerular filtration rate (eGFR) was negatively associated with circulating RBP4 concentrations in patients with T2DM [summary Fisher's Z = −0.48, 95% CI (-0.69, -0.26), P < 0.0001]. The albumin-to-creatinine ratio (ACR) was positively associated with circulating RBP4 concentrations in patients with T2DM [summary Fisher's Z = 0.20, 95% CI (0.08, 0.32), P = 0.001].

Conclusion

The levels of circulating RBP4 were significantly higher both in T2DM subjects with micro/macroalbuminuria and in T2DM subjects with declined eGFR. The levels of circulating RBP4 were positively correlated with ACR but negatively correlated with eGFR. Circulating RBP4 could be a reliable biomarker for kidney diseases in T2DM.

The role of retinol-binding protein 4 and its relationship with sex hormones in coronary artery disease

The role of retinol-binding protein 4 (RBP4) in patients with coronary artery disease (CAD) with different sexes has not been clearly established. Sex hormones, especially testosterone (T) and estradiol (E2), have been considered to play an important role in CAD. This study aimed to investigate the role of RBP4 and the possible association between RBP4 and T and E2 in CAD. The study included 658 individuals who underwent coronary angiography (CAG); they were assigned to CAD group (n = 440) and controls (n = 218). CAD group was subdivided into three subgroups. Serum RBP4 and T were assayed by enzyme-linked immunosorbent assay. Serum E2 was measured using electrochemiluminescence immunoassay. For men, RBP4 levels were lower in CAD group, especially those with acute myocardial infarction, than in controls (P < 0.05, P < 0.01, respectively). For women, no significant difference was found in RBP4 levels between both groups. RBP4 was positively correlated with T in male patients with CAD (r = 0.124, P < 0.05). Logistic regression analysis showed that RBP4 was a protective factor for CAD (odds ratio 0.975, 95% confidence interval 0.958-0.993; P = 0.007). In conclusion, RBP4 levels were significantly decreased and positively related with T in men with CAD. Higher RBP4 levels were associated with lower risk of CAD. RBP4 may play a potential protective role for CAD among men.

Identification of cysteinylated transthyretin, a predictive biomarker of treatment response to partially hydrolyzed guar gum in type 2 diabetes rats, by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

Recent evidence has indicated that total fiber intake is inversely related to type 2 diabetes risk. The present study aimed to investigate the effects of chronic administration of partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, on the occurrence of diabetes and its complications, fatty liver and nephropathy. We also identified predictive serum biomarkers of treatment response to PHGG by mass spectroscopy-based proteomic analysis using Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a good model of human non-insulin-dependent diabetes mellitus. In this study, at 5 weeks of age, OLETF rats and control strain Long-Evans Tokushima Otsuka (LETO) rats were fed a control diet or a high-fiber diet (5% PHGG) for 57 weeks. Body weight, food intake, oral glucose tolerance test, plasma insulin levels, and urine glucose and protein levels were regularly measured. Oral glucose tolerance tests (OGTT) and storage of serum in a deep freezer were conducted at the beginning of the experiment and every 4 weeks after overnight fasting during the experiments. PHGG treatment affected neither meal patterns nor the body weight of OLETF and LETO rats. Repeated measure analysis of variance revealed significant differences in fasting plasma glucose and plasma glucose at 2 h after OGTT between control OLETF (OLETF-C) rats and OLETF rats treated with PHGG (OLETF-F). The glucose response determined by the area under the curve of OGTT was significantly greater in OLETF-C rats than that in OLETF-F rats at 25 weeks of age. HOMA-IR, an index of insulin resistance, increased at 25 weeks of age in OLETF-C rats, while this increase was significantly inhibited in OLETF-F rats. At 62 weeks of age, PHGG treatment significantly improved hepatic steatosis as well as renal mesangial matrix accumulation in OLETF rats. To identify the risk marker for diabetes mellitus by SELDI-TOF MS, we collected sera from 21-week-old individuals. Among the 12 specific peaks that were risk marker candidates for diabetes mellitus, the m/z 13,720 peak was identified as that of cysteinylated transthyretin by sequencing of four tryptic peptides using tandem mass spectrometry and peak distribution around the m/z 13,720 peak in the SELDI-TOF spectra. In conclusion, we found that chronic treatment with PHGG improved insulin resistance, delayed the onset of diabetes, and inhibited the development of diabetic complications, as well as identified cysteinylated transthyretin as a predictive biomarker of treatment response to PHGG in OLETF rats.

Involvement of RBP4 in hyperinsulinism-induced vascular smooth muscle cell proliferation

Retinol-binding protein 4 (RBP4) is a newly discovered adipocytokine related to insulin resistance (IR). Hyperinsulinemia and IR are the major risk factors for cardiovascular diseases (CVD). The role of RBP4 in CVD has not yet been determined. The present study was designed to analyze the correlation of RBP4 and CVD risk factors and to evaluate the role of RBP4 in proliferation of vascular smooth muscle cells during hyperinsulinemia and the underlying mechanisms. Plasma RBP4 concentration, IR-related indexes, and cardiovascular risk factors were measured from blood samples of hyperinsulinemic rats (HIns) and control SD rats (Cons). The vascular morphology and the expression of ERK1/2, p-ERK1/2 in arterial tissues of rats were assessed. Different concentrations of RBP4 (1, 4 μg/ml) were used as intervention factor during insulin-induced aortic smooth muscle cells (RASMCs) proliferation. The expression of cell growth signaling pathways was assessed to identify the active pathway during this proliferation. Specifically, ERK1/2 inhibitor PD98059 and JAK2 inhibitor AG490 were used to detect it. RBP4 expression was higher in HIns compared with Cons (p < 0.01). Plasma RBP4 concentrations were positively correlated with TG (r = 0.490), hsCRP (r = 0.565), media thickness (r = 0.890), and p-ERK1/2 protein (r = 0.746) (p < 0.05 each). In cultured RASMCs, RBP4 enhanced insulin-induced proliferation of cells and expression of p-ERK1/2 and p-JAK2. Blockade of ERK1/2 signaling pathway inhibited RBP4-induced proliferation of RASMCs, while suppressing JAK2 remains unchanged. These results suggest that plasma RBP4 concentrations were associated with CVD. In addition, RBP4 increases the proliferation of VSMCs induced by hyperinsulinism via activation of MAPK signaling pathway.

Post-translational modifications of transthyretin affect the triiodonine-binding potential

Transthyretin (TTR) is a visceral protein, which facilitates the transport of thyroid hormones in blood and cerebrospinal fluid. The homotetrameric structure of TTR enables the simultaneous binding of two thyroid hormones per molecule. Each TTR subunit provides a single cysteine residue (Cys₁₀), which is frequently affected by oxidative post-translational modifications. As Cys₁₀ is part of the thyroid hormone-binding channel within the TTR molecule, PTM of Cys₁₀ may influence the binding of thyroid hormones. Therefore, we analysed the effects of Cys₁₀ modification with sulphonic acid, cysteine, cysteinylglycine and glutathione on binding of triiodothyronine (T3) by molecular modelling. Furthermore, we determined the PTM pattern of TTR in serum of patients with thyroid disease by immunoprecipitation and mass spectrometry to evaluate this association in vivo. The in silico assays demonstrated that oxidative PTM of TTR resulted in substantial reorganization of the intramolecular interactions and also affected the binding of T3 in a chemotype- and site-specific manner with S-glutathionylation as the most potent modulator of T3 binding. These findings were supported by the in vivo results, which indicated thyroid function-specific patterns of TTR with a substantial decrease in S-sulphonated, S-cysteinylglycinated and S-glutathionylated TTR in hypothyroid patients. In conclusion, this study provides evidence that oxidative modifications of Cys₁₀ seem to affect binding of T3 to TTR probably because of the introduction of a sterical hindrance and induction of conformational changes. As oxidative modifications can be dynamically regulated, this may represent a sensitive mechanism to adjust thyroid hormone availability.

Serum levels of retinol-binding protein-4 are associated with the presence and severity of coronary artery disease

Background

The interplay between the novel adipokine retinol-binding protein-4 (RBP4) and coronary artery disease (CAD) is still obscure. We investigated the relationship between RBP4 levels and the presence and severity of angiographically proven CAD and determined its possible role in acute myocardial infarction (AMI).

Methods

305 individuals with angiographically proven CAD (CAD-patients), were classified into 2 subgroups: 1) acute myocardial infarction (AMI, n = 141), and 2) stable angina (SA, n = 164). Ninety-one age- and sex-matched individuals without CAD, but with at least 2 classical cardiovascular risk factors, served as controls (non-CAD group). RBP4 serum levels were measured at hospital admission and were analyzed in relation to the coronary severity stenosis, assessed by the Gensini-score and the number of coronary narrowed vessels. Other clinical parameters, including insulin levels, HOMA-IR, hsCRP, glycaemic and lipid profile, and left-ventricular ejection fraction were also assessed.

Results

Serum RBP4 levels were significantly elevated in patients with CAD compared to non-CAD patients (39.29 ± 11.72 mg/L vs. 24.83 ± 11.27 mg/L, p < 0.001). We did not observe a significant difference in RBP4 levels between AMI and SA subgroups (p = 0.734). Logistic regression analysis revealed an independent association of CAD presence with serum RBP4 (β = 0.163, p = 0.006), and hsCRP (β = 0.122, p = 0.022) levels, in the whole study group. Among variables, hsCRP (β = 0.220), HDL (β = −0.150), and RBP4 (β = 0.297), correlated in both univariate and multivariate analysis with CAD severity (R² = 0.422, p < 0.001). Similarly, RBP4 concentrations increased with the number of coronary narrowed vessels (p < 0.05).

Conclusion

Patients with CAD, both SA and AMI, showed elevated RBP4 serum levels. Notably, increased RBP4 concentration seemed to independently correlate with CAD severity, but no with AMI.

Trial registration

The ClinicalTrials.gov Identifier is: NCT00636766

Proteomic analysis allows for early detection of potential markers of metabolic impairment in very young obese children

Background

Early diagnosis of initial metabolic derangements in young obese children could influence their management; however, this impairment is frequently not overt, but subtle and undetectable by routinely used clinical assays. Our aim was to evaluate the ability of serum proteomic analysis to detect these incipient metabolic alterations in comparison to standard clinical methods and to identify new candidate biomarkers.

Methods

A cross-sectional study of fasting serum samples from twenty-two prepubertal, Caucasian obese (OB; 9.22 ± 1.93 years; 3.43 ± 1.08 BMI-SDS) and twenty-one lean controls (C; 8.50 ± 1.98 years; -0.48 ± 0.81 BMI-SDS) and a prospective study of fasting serum samples from twenty prepubertal, Caucasian obese children (11 insulin resistant [IR]) before (4.77 ± 1.30 BMI-SDS) and after weight reduction (2.57 ± 1.29 BMI-SDS) by conservative treatment in a reference hospital (Pros-OB) was performed. Proteomic analysis (two-dimension-eletrophoresis + mass spectrometry analysis) of serum and comparative evaluation of the sensitivity of routinely used assays in the clinics to detect the observed differences in protein expression level, as well as their relationship with anthropometric features, insulin resistance indexes, lipid profile and adipokine levels were carried out.

Results

Study of the intensity data from proteomic analysis showed a decrease of several isoforms of apolipoprotein-A1, apo-J/clusterin, vitamin D binding protein, transthyretin in OBvs. C, with some changes in these proteins being enhanced by IR and partially reversed after weight loss. Expression of low molecular weight isoforms of haptoglobin was increased in OB, enhanced in IR and again decreased after weight loss, being positively correlated with serum interleukin-6 and NAMPT/visfatin levels. After statistical correction for multiple comparisons, significance remained for a single isoform of low MW haptoglobin (OB vs. C and IR vs. non-IR) and Apo A1 (IR vs. non-IR). Assays routinely used in the clinical setting (ELISA/kinetic nephelometry), only partially confirmed the changes observed by proteomic analysis (ApoA1 and haptoglobin).

Conclusion

Proteomic analysis can allow for the identification of potential new candidate biomarkers as a complement to routinely used assays to detect initial changes in serum markers of inflammation and lipid metabolism impairment in young obese children.

Bioactivities of Compounds from Elephantopus scaber, an Ethnomedicinal Plant from Southwest China

Elephantopus scaber is an ethnomedicinal plant used by the Zhuang people in Southwest China to treat headaches, colds, diarrhea, hepatitis, and bronchitis. A new δ-truxinate derivative, ethyl, methyl 3,4,3′,4′-tetrahydroxy-δ-truxinate (1), was isolated from the ethyl acetate extract of the entire plant, along with 4 known compounds. The antioxidant activity of these 5 compounds was determined by ABTS radical scavenging assay. Compound 1 was also tested for its cytotoxicity effect against HepG2 by MTT assay (IC₅₀ = 60 μM), and its potential anti-inflammatory, antibiotic, and antitumor bioactivities were predicted using target fishing method software.

Retinol-binding protein 4 levels and susceptibility to ischaemic events in men

BACKGROUND

Many efforts in cardiovascular medicine have been focused in the identification of patients at risk of developing an acute ischaemic event. Biomarker discovery studies have become an essential research area, being proteomic technologies an excellent tool for biomarker identification. By applying proteomic approaches, we have detected changes in retinol-binding protein 4 (RBP4) in acute new-onset myocardial infarction patients (AMI) and in high-risk patients with heterozygous familial hypercholesterolaemia (FH).

MATERIALS AND METHODS

Differential serum proteome was analysed by two-dimensional electrophoresis and MALDI-TOF/TOF. Validation studies were performed by ELISA, and functional effects of RBP4 were tested in cell culture experiments.

RESULTS

Retinol-binding protein 4 proteomic characterization depicted two spots (pI = 5·4;Mw = 23·01/22·78 kDa) with decreased intensity in AMI patients. Total serum RBP4 levels were decreased in AMI patients (N = 68) compared with controls (N = 132; P < 0·0001). RBP4 was also decreased in FH patients who had an ischaemic event 2 years (±0·3) after their inclusion compared with FH patients without any cardiovascular episode at follow-up (P < 0·001; N = 187). In both cases, changes were limited to men. RBP4 induced a significant increase in eNOS expression in human endothelial vascular cells and in prostaglandin I2 release in coronary vascular smooth muscle cells.

CONCLUSIONS

We show decreased serum RBP4 levels in men in the acute phase of AMI, being this decrease already detected in men with FH previous to the presentation of an ischaemic event. The decrease in RBP4 levels could confer an increased susceptibility to the precipitation of an ischaemic event that could be mediated by the decrease in its vasculoprotective properties through NO and PGI2 .

Retinol-binding protein 4 and its membrane receptor STRA6 control adipogenesis by regulating cellular retinoid homeostasis and retinoic acid receptor α activity

Retinoids are vitamin A (retinol) derivatives and complex regulators of adipogenesis by activating specific nuclear receptors, including the retinoic acid receptor (RAR) and retinoid X receptor (RXR). Circulating retinol-binding protein 4 (RBP4) and its membrane receptor STRA6 coordinate cellular retinol uptake. It is unknown whether retinol levels and the activity of RAR and RXR in adipocyte precursors are linked via RBP4/STRA6. Here, we show that STRA6 is expressed in precursor cells and, dictated by the apo- and holo-RBP4 isoforms, mediates bidirectional retinol transport that controls RARα activity and subsequent adipocyte differentiation. Mobilization of retinoid stores in mice by inducing RBP4 secretion from the liver activated RARα signaling in the precursor cell containing the stromal-vascular fraction of adipose tissue. Retinol-loaded holo-RBP4 blocked adipocyte differentiation of cultured precursors by activating RARα. Remarkably, retinol-free apo-RBP4 triggered retinol efflux that reduced cellular retinoids, RARα activity, and target gene expression and enhanced adipogenesis synergistically with ectopic STRA6. Thus, STRA6 in adipocyte precursor cells links nuclear RARα activity to the circulating RBP4 isoforms, whose ratio in obese mice was shifted toward limiting the adipogenic potential of their precursors. This novel cross talk identifies a retinol-dependent metabolic function of RBP4 that may have important implications for the treatment of obesity.

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.

Effects of retinol binding protein-4 on vascular endothelial cells

The study was designed to investigate the effect of retinol binding protein (RBP)-4 on the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways, which mediate the effects of insulin in vascular endothelial cells. The effects of RBP4 on nitric oxide (NO) and insulin-stimulated endothelin-1 (ET-1) secretion and on phosphorylation (p) of Akt, endothelial NO synthetase (eNOS), and extracellular signal-regulated kinase (ERK)1/2 were investigated in bovine vascular aortic endothelial cells (BAECs). RBP4 showed an acute vasodilatatory effect on aortic rings of rats within a few minutes. In BAECs, RBP4-treatment for 5min significantly increased NO production, but inhibited insulin-stimulated ET-1 secretion. RBP4-induced NO production was not inhibited by tetraacetoxymethylester (BAPTA-AM), an intracellular calcium chelator, but was completely abolished by wortmannin, a PI3K inhibitor. RBP4 significantly increased p-Akt and p-eNOS production, and significantly inhibited p-ERK1/2 production. Triciribine, an Akt inhibitor, and wortmannin significantly inhibited RBP4-induced p-Akt and p-eNOS production. Inhibition of Akt1 by small interfering RNA decreased p-eNOS production enhanced by RBP4 in human umbilical vein endothelial cells. In conclusion, RBP4 has a robust acute effect of enhancement of NO production via stimulation of part of the PI3K/Akt/eNOS pathway and inhibition of ERK1/2 phosphorylation and insulin-induced ET-1 secretion, probably in the MAPK pathway, which results in vasodilatation.

Cruciferous vegetable supplementation in a controlled diet study alters the serum peptidome in a GSTM1-genotype dependent manner

Background

Cruciferous vegetable intake is inversely associated with the risk of several cancers. Isothiocyanates (ITC) are hypothesized to be the major bioactive constituents contributing to these cancer-preventive effects. The polymorphic glutathione-S-transferase (GST) gene family encodes several enzymes which catalyze ITC degradation in vivo.

Methods

We utilized high throughput proteomics methods to examine how human serum peptides (the "peptidome") change in response to cruciferous vegetable feeding in individuals of different GSTM1 genotypes. In two randomized, crossover, controlled feeding studies (EAT and 2EAT) participants consumed a fruit- and vegetable-free basal diet and the basal diet supplemented with cruciferous vegetables. Serum samples collected at the end of the feeding period were fractionated and matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry spectra were obtained. Peak identification/alignment computer algorithms and mixed effects models were used to analyze the data.

Results

After analysis of spectra from EAT participants, 24 distinct peaks showed statistically significant differences associated with cruciferous vegetable intake. Twenty of these peaks were driven by their GSTM1 genotype (i.e., GSTM1+ or GSTM1- null). When data from EAT and 2EAT participants were compared by joint processing of spectra to align a common set, 6 peaks showed consistent changes in both studies in a genotype-dependent manner. The peaks at 6700 m/z and 9565 m/z were identified as an isoform of transthyretin (TTR) and a fragment of zinc α2-glycoprotein (ZAG), respectively.

Conclusions

Cruciferous vegetable intake in GSTM1+ individuals led to changes in circulating levels of several peptides/proteins, including TTR and a fragment of ZAG. TTR is a known marker of nutritional status and ZAG is an adipokine that plays a role in lipid mobilization. The results of this study present evidence that the GSTM1-genotype modulates the physiological response to cruciferous vegetable intake.

Serum retinol binding protein 4 level is related with renal functions in Type 2 diabetes

AIM

We aimed to evaluate the metabolic parameters and diabetes complications which would probably affect the serum retinol-binding protein 4 (RBP4) levels in Type 2 diabetic individuals. In addition to serum RBP4 concentration, the levels of its ligands, serum retinol and transthyretin (TTR) were also considered in this evaluation.

SUBJECTS AND METHODS

Serum RBP4, retinol, and TTR levels were measured in 53 Type 2 diabetic subjects and 30 body mass index (BMI)- matched controls. The molar ratios of RBP4 to retinol and RBP4 to TTR were compared.

RESULTS

While the RBP4 values were similar to those in the control group in Type 2 diabetic patients, the molar ratio of RBP4 to TTR was found to be higher than that of the control group. The serum RBP4 levels in patients who had retinopathy and macrovascular disease were similar to those in patients who did not. However, the RBP4 levels, molar ratios of RBP4 to retinol and RBP4 to TTR in micro- macroalbuminuric patients were found to be significantly higher than in normoalbuminuric subjects and controls. There was no correlation between the RBP4 levels and the patients' age, BMI, duration of diabetes, LDL, triglyceride, serum creatinine, and glycated hemoglobin values. Micro-macroalbuminuria and estimated glomerular filtration rate were independent determinants for increased serum RBP4 levels.

CONCLUSION

According to the data obtained from this study, diabetic retinopathy and cardiovascular complications do not affect the serum RBP4 level in Type 2 diabetes. Renal functions rather than the metabolic factors of diabetes determine the RBP4 level and its relation with its ligands.