Characteristics of the obesogenic environment around schools are associated with body fat and low-grade inflammation in Brazilian children.

OBJECTIVE: To assess the association of obesogenic environmental characteristics around schools with body adiposity and adipokine concentrations in Brazilian children. DESIGN: Cross-sectional study. Body adiposity was assessed using the dual-energy X-ray absorptiometry. Concentrations of leptin, adiponectin, retinol-binding protein 4 (RBP4) and chemerin were measured. Predominantly ultra-processed food (UPF) stores, public physical activity (PA) facilities, green spaces, walkability, traffic accidents and crime were evaluated. The neighbourhood unit was the 400 m (0·25 miles) road network buffer around schools. The association of environmental characteristics with body adiposity and adipokine concentrations was assessed by linear regression models using generalised estimating equations. SETTING: Urban schools (n 24), Viçosa, Minas Gerais, Brazil. PARTICIPANTS: Children aged 8 and 9 years (n 378). RESULTS: A higher density of predominantly UPF stores and a lower percentage of green space were associated with higher total (ß: 0·12; 95 % CI 0·06, 0·18 and ß: -0·10; 95 % CI -0·16, -0·04, respectively) and android body fat (ß: 0·28; 95 % CI 0·13, 0·43 and ß: -0·18; 95 % CI -0·32, -0·04, respectively). In addition, the densities of PA facilities and crime were inversely associated with leptin concentrations. Traffic accidents density and percentage of green spaces around schools had, respectively, a positive and an inverse association with concentrations of adiponectin and RBP4. CONCLUSIONS: Obesogenic environmental characteristics around schools were associated with total and android body fat, as well as with pro-inflammatory adipokine concentrations in Brazilian children from a medium-sized city.

Higher serum uric acid is associated with body fat, retinol-binding protein 4, and antioxidative status in Brazilian children.

OBJECTIVE: The aim of this study was to evaluate the association of serum uric acid (SUA) with adiposity, adipokines, and anti- and oxidative markers in Brazilian children. METHODS: This was a cross-sectional investigation with 378 children ages 8 to 9 y in Viçosa, Minas Gerais, Brazil. Information on sociodemographic and lifestyle characteristics was obtained via questionnaires, and body fat was determined by dual energy x-ray absorptiometry. We compared the distributions of adiposity (total and central), adipokines (adiponectin, chemerin, leptin, and retinol-binding protein 4 [RBP4]), anti- and oxidative markers (plasma ferric reducing antioxidant power [FRAP], superoxide dismutase [SOD], and malondialdehyde [MDA]) by SUA categories using linear regression. RESULTS: SUA was positively associated with total and central fat. Every standard deviation (SD) of SUA was related, respectively, to a 3.4 (95% confidence interval [CI], 2.4-4.4), 4 (95% CI, 2.8-5.1), 4.2 (95% CI, 2.9-5.5), and 3.5 (95% CI, 2.4-4.6) units higher of total, truncal, android, and gynoid fat. We found a positive association of SUA with RBP4 and FRAP, and a negative association with MDA. Every SD of SUA was related, respectively, to 0.1 (95% CI, 0.01-0.1) and 7.8 (95% CI, 5.5-10.1) units higher of RBP4 and FRAP; and to -0.3 (95% CI, -0.5 to -0.1) units lower of MDA. CONCLUSIONS: SUA was positively associated with adiposity, RBP4, and antioxidative status in Brazilian children.

Interplay of retinol binding protein 4 with obesity and associated chronic alterations (Review).

Obesity is a multifactorial disease, defined as excessive fat deposition in adipose tissue. Adipose tissue is responsible for the production and secretion of numerous adipokines that induce metabolic disorders. Retinol­binding protein 4 (RBP4) is an adipokine that transports vitamin A or retinol in the blood. High levels of RBP4 are associated with development of metabolic disease, including obesity, insulin resistance (IR), metabolic syndrome, and type 2 diabetes (T2D). The present review summarizes the role of RBP4 in obesity and associated chronic alterations. Excessive synthesis of RBP4 contributes to inflammatory characteristic of obesity by activation of immune cells and release of proinflammatory cytokines, such as TNFα and ILs, via the Toll­like receptor/JNK pathway. The retinol­RBP4 complex inhibits insulin signaling directly in adipocytes by activating Janus kinase 2 (JAK2)/STAT5/suppressor of cytokine signaling 3 signaling. This mechanism is retinol­dependent and requires vitamin A receptor stimulation by retinoic acid 6 (STRA6). In muscle, RBP4 is associated with increased serine 307 phosphorylation of insulin receptor substrate­1, which decreases its affinity to PI3K and promotes IR. In the liver, RBP4 increases hepatic expression of phosphoenolpyruvate carboxykinase, which increases production of glucose. Elevated serum RBP4 levels are associated with ß­cell dysfunction in T2D via the STRA6/JAK2/STAT1/insulin gene enhancer protein 1 pathway. By contrast, RBP4 induces endothelial inflammation via the NF­κB/nicotinamide adenine dinucleotide phosphate oxidase pathway independently of retinol and STRA6, which stimulates expression of proinflammatory molecules, such as vascular cell adhesion molecule 1, E­selectin, intercellular adhesion molecule 1, monocyte chemoattractant protein 1 and TNFα. RBP4 promotes oxidative stress by decreasing endothelial mitochondrial function; overall, it may serve as a useful biomarker in the diagnosis of obesity and prognosis of associated disease, as well as a potential therapeutic target for treatment of these diseases.

Retinol-binding protein 4 and plasminogen activator inhibitor-1 as potential prognostic biomarkers of non-allergic asthma caused by obesity in adolescents.

BACKGROUND: Non-allergic asthma caused by obesity is a complication of the low-grade chronic inflammation inherent in obesity. Consequently, the serum concentrations of adipokines such as retinol-binding protein 4 (RBP4) and plasminogen activator inhibitor-1 (PAI-1) increase. No gold standard molecule for the prediction of non-allergic asthma among obese patients has been identified. OBJECTIVE: To evaluate RBP4 and PAI-1 as prognostic biomarkers of non-allergic asthma caused by obesity. METHODS: A cross-sectional study between four groups of adolescents: (1) healthy (n = 35), (2) allergic asthma without obesity (n = 28), (3) obesity without asthma (n = 33), and (4) non-allergic asthma with obesity (n = 18). RESULTS: RBP4 was higher in the non-allergic asthma with obesity group than in the obesity without asthma group (39.2 ng/mL [95% confidence interval (CI): 23.8-76.0] vs. 23.5 ng/mL [95% CI: 3.2-33.5], p < 0.01), and PAI-1 was higher in the non-allergic asthma with obesity group than in the obesity without asthma group (21.9 ng/mL [95% CI: 15.7-26.5] vs. 15.9 ng/mL [95% CI: 9.4-18.2], p < 0.05). Receiver operating characteristic (ROC) curve analysis demonstrated that the serum RBP4 cut-off value was >42.78 ng/mL, with an area under the ROC curve (AUC) of 0.741 (95% CI: 0.599-0.853, p = 0.001), considered acceptable. The PAI-1 cut-off value was >12.0 ng/mL, with an AUC of 0.699 (95% CI: 0.554-0.819, p = 0.008), considered fair. CONCLUSIONS: RBP4 may be useful to predict non-allergic asthma among obese adolescents in clinical practice.

The dietary inflammatory index is associated with anti- and pro-inflammatory adipokines in Brazilian schoolchildren.

PURPOSE: To investigate the relationship of Children's Dietary Inflammatory Index (C-DII™) scores with body fat distribution and serum adipokines in Brazilian schoolchildren. METHODS: This population-based cross-sectional study enrolled 378 schoolchildren aged 8 and 9 years from Viçosa, Minas Gerais, Brazil. Food consumption was assessed using three 24-h dietary recalls from which C-DII scores were calculated. Serum adipokines [adiponectin, leptin, retinal-binding protein 4 (RBP4), and chemerin] were analyzed in blood samples. Sociodemographic characteristics and sedentary behavior were assessed using a semi-structured questionnaire. Total, truncal, android and gynoid body fat were evaluated by dual-energy X-ray absorptiometry (DXA). We compared the distributions of adiposity measures and serum adipokines by C-DII categories with linear regression, adjusting for potential confounders. RESULTS: The mean sample C-DII was 0.59 ± 0.94 and ranged from - 2.16 to + 2.75. The C-DII was not associated with central and total body fat. However, the C-DII was modestly inversely associated with adiponectin and RBP4, and modestly directly associated with chemerin. These results remained significant after adjusting for body fat. Every 1 SD of C-DII was related, respectively, to a - 0.8 (- 1.5, - 0.03) and to a - 0.1 (- 0.2, - 0.05) units lower mean of adiponectin and RBP4, and to 7.2 (0.3, 14.1) units higher of chemerin. CONCLUSION: Higher C-DII score was modestly inversely and directly associated with anti- and pro-inflammatory adipokines, respectively, in Brazilian children. The development of public health policies is needed to promote healthy eating habits during childhood to prevent the early onset of systemic inflammation and ill health effects later in life.

Maternal hypothyroidism during pregnancy alters the function of the retinol-binding protein 4-mediated mitochondrial permeability conversion pore in the kidneys of offspring rats.

OBJECTIVES: To determine the role of the RBP4/PiC/SIRT3 signaling pathway in the opening of the mitochondria permeability transition pore (mPTP) in offspring rats with hypothyroidism during pregnancy. METHODS: Sixty Sprague-Dawley (SD) rats were employed in this study. Pregnancy was deemed successful when a sperm was found in the uterus. After one week of pregnancy, offspring rats were divided into the following groups: overall hypothyroidism group (OH group), subclinical hypothyroidism group (SCH group), and normal control group (CON group). The establishment of the hypothyroidism model was confirmed when the serum thyroid stimulating hormone (TSH) levels were higher than normal value and TT4 level was within the normal range. The renal mitochondria of offspring rats were extracted on the 14th postnatal day (P14) and 35th postnatal day (P35). RESULTS: At P14, no significant differences in the degree of mPTP opening and expression of phosphoric acid carrier vector (PiC) were detected between the rats in the OH group and the SCH group. However, the expression level of silent mating-type information regulation 3 homolog (SIRT3) was markedly reduced. Retinol-binding protein 4 (RBP4) expression increased in the rats from the OH group, relative to that in those from the SCH group. At P35, the degree of mPTP opening and the expression levels of PiC and RBP4 in the OH group were higher than those in the SCH group. However, SIRT3 expression in the OH group was lower than that observed in the SCH group. CONCLUSION: RBP4 plays an important role in early renal mitochondrial damage and renal impairment in rats suffering from hypothyroidism during pregnancy. The RBP4/PiC/SIRT3 pathway is thus involved in the opening of the renal mPTP in offspring rats with hyperthyroidism.

Urinary DPP4 correlates with renal dysfunction, and DPP4 inhibition protects against the reduction in megalin and podocin expression in experimental CKD.

This study investigated the molecular mechanisms underlying the antiproteinuric effect of DPP4 inhibition in 5/6 renal ablation rats and tested the hypothesis that the urinary activity of DPP4 correlates with chronic kidney disease (CKD) progression. Experiments were conducted in male Wistar rats who underwent 5/6 nephrectomy (Nx) or sham operation followed by 8 wk of treatment with the DPP4 inhibitor (DPP4i) sitagliptin or vehicle. Proteinuria increased progressively in Nx rats throughout the observation period. This increase was remarkably mitigated by sitagliptin. Higher levels of proteinuria in Nx rats compared to control rats were accompanied by higher urinary excretion of retinol-binding protein 4, a marker of tubular proteinuria, as well as higher urinary levels of podocin, a marker of glomerular proteinuria. Retinol-binding protein 4 and podocin were not detected in the urine of Nx + DPP4i rats. Tubular and glomerular proteinuria was associated with the reduced expression of megalin and podocin in the renal cortex of Nx rats. Sitagliptin treatment partially prevented this decrease. Besides, the angiotensin II renal content was significantly reduced in the Nx rats that received sitagliptin compared to vehicle-treated Nx rats. Interestingly, both urinary DPP4 activity and abundance increased progressively in Nx rats. Additionally, urinary DPP4 activity correlated positively with serum creatinine levels, proteinuria, and blood pressure. Collectively, these results suggest that DPP4 inhibition ameliorated both tubular and glomerular proteinuria and prevented the reduction of megalin and podocin expression in CKD rats. Furthermore, these findings suggest that urinary DPP4 activity may serve as a biomarker of renal disease and progression.

Maternal hypothyroidism during pregnancy alters the function of the retinol-binding protein 4-mediated mitochondrial permeability conversion pore in the kidneys of offspring rats

OBJECTIVES To determine the role of the RBP4/PiC/SIRT3 signaling pathway in the opening of the mitochondria permeability transition pore (mPTP) in offspring rats with hypothyroidism during pregnancy. METHODS Sixty Sprague-Dawley (SD) rats were employed in this study. Pregnancy was deemed successful when a sperm was found in the uterus. After one week of pregnancy, offspring rats were divided into the following groups: overall hypothyroidism group (OH group), subclinical hypothyroidism group (SCH group), and normal control group (CON group). The establishment of the hypothyroidism model was confirmed when the serum thyroid stimulating hormone (TSH) levels were higher than normal value and TT4 level was within the normal range. The renal mitochondria of offspring rats were extracted on the 14th postnatal day (P14) and 35th postnatal day (P35). RESULTS At P14, no significant differences in the degree of mPTP opening and expression of phosphoric acid carrier vector (PiC) were detected between the rats in the OH group and the SCH group. However, the expression level of silent mating-type information regulation 3 homolog (SIRT3) was markedly reduced. Retinol-binding protein 4 (RBP4) expression increased in the rats from the OH group, relative to that in those from the SCH group. At P35, the degree of mPTP opening and the expression levels of PiC and RBP4 in the OH group were higher than those in the SCH group. However, SIRT3 expression in the OH group was lower than that observed in the SCH group. CONCLUSION RBP4 plays an important role in early renal mitochondrial damage and renal impairment in rats suffering from hypothyroidism during pregnancy. The RBP4/PiC/SIRT3 pathway is thus involved in the opening of the renal mPTP in offspring rats with hyperthyroidism.

Micronutrients, Immunological Parameters, and Dengue Virus Infection in Coastal Ecuador: A Nested Case-Control Study in an Infectious Disease Surveillance Program.

BACKGROUND: Micronutrients are known to modulate host immunity, and there is limited literature on this association in the context of dengue virus infection (DENV). METHODS: Using a nested case-control design in a surveillance program, we measured the following: anthropometry; nutritional biomarkers including serum ferritin, soluble transferrin receptor, retinol-binding protein (RBP), 25-hydroxy vitamin D, folate, and vitamin B12; and a panel of immune response markers. We then compared these measures across 4 illness categories: healthy control, nonfebrile DENV, other febrile illness (OFI), and apparent DENV using multivariate polytomous logistic regression models. RESULTS: Among 142 participants, serum ferritin (ng/mL) was associated with apparent DENV compared to healthy controls (odds ratio [OR], 2.66; confidence interval [CI], 1.53-4.62; P = .001), and RBP concentrations (µmol/L) were associated with apparent DENV (OR, 0.03; CI, 0.00-0.30; P = .003) and OFI (OR, 0.02; CI, 0.00-0.24; P = .003). In a subset of 71 participants, interleukin-15 levels (median fluorescent intensity) were positively associated with apparent DENV (OR, 1.09; CI, 1.03-1.14; P = .001) and negatively associated with nonfebrile DENV (OR, 0.89; CI, 0.80-0.99; P = .03) compared to healthy controls. CONCLUSIONS: After adjusting for the acute-phase response, serum ferritin and RBP concentrations were associated with apparent DENV and may represent biomarkers of clinical importance in the context of dengue illness.

The relationship between circulating irisin, retinol binding protein-4, adiponectin and inflammatory mediators in patients with metabolic syndrome

ABSTRACT Objective We wanted to investigate whether there is a relationship between circulating irisin, retinol binding protein-4 (RBP-4), adiponectin and proinflammatory mediators implicated in the development of insulin resistance (IR) in metabolic syndrome (MetS). Subjects and methods In 180 individuals, including controls and patients with MetS, we measured fasting plasma insulin, high sensitivity C-reactive protein (hsCRP), pentraxin-3 (PTX-3), interleukin-33 (IL-33), irisin, RBP-4, and adiponectin using ELISA kits. Results While fasting plasma hsCRP, PTX-3, IL-33, irisin, RBP-4 concentrations were higher, adiponectin levels were lower in patients with MetS than in controls. A correlation analysis revealed that plasma irisin levels were positively associated with MetS components such as waist circumference and waist-hip ratio, low density lipoprotein (LDL) and markers of systemic inflammation such as PTX-3, hsCRP, uric acid, and RBP-4. Adiponectin levels were negatively associated with waist circumference, waist-hip ratio, PTX-3 and LDL. Conclusions Although the precise mechanisms are still unclear, irisin, RBP-4, adiponectin and PTX-3 are hallmarks of the MetS, which is related to low-grade inflammation. It is conceivable that irisin and adiponectin might contribute to the development of MetS and may also represent novel MetS components. Future clinical studies are needed to confirm and extend these data.

Circulating omentin-1 might be associated with metabolic health status in different phenotypes of body size

ABSTRACT Objective Adipokines are mediators of body composition and are involved in obesity complications. This study aimed to assess the association of circulating omentin-1, vaspin, and RBP-4 with body composition indices and metabolic health status (MHS) in different phenotypes of body size. Subjects and methods A total of 350 subjects were included in the current cross-sectional study. Body composition was measured using a body composition analyzer, and serum concentrations of omentin-1, vaspin, and RBP-4 were assessed by ELISA kits. Results Circulating omentin-1 was significantly (OR = 1.81, 95% CI: 1.00-1.91, P = 0.01) and marginally (OR = 1.63, 95%CI: 1.00-1.75, P = 0.06) associated with MHS in the overweight and obese subjects, respectively. But no association was seen between omentin-1 and MHS in normal-weight subjects. Serum levels of vaspin and RBP-4 were not correlated with MHS. Furthermore, a significant positive correlation was observed between circulating omentin-1 and body mass index (BMI) as well as fat percentage (P = 0.02) in the MHS group. Serum vaspin concentrations were not related to body composition components in both groups. In addition, in the MHS group, circulating RBP-4 was positively correlated with fat percentage and fat mass (FM) (p < 0.0001) and was negatively correlated with fat-free mass (FFM) and total body water (TBW) (p < 0.0001). In contrast, in the metabolically unhealthy group, RBP-4 was negatively correlated with fat percentage, FM, and BMI (p < 0.0001) and was positively correlated with FFM and TBW (p < 0.0001). Conclusions This study showed that circulating levels of omentin-1 are useful predictors of metabolic health status in overweight and obese people.

The relationship between circulating irisin, retinol binding protein-4, adiponectin and inflammatory mediators in patients with metabolic syndrome.

OBJECTIVE: We wanted to investigate whether there is a relationship between circulating irisin, retinol binding protein-4 (RBP-4), adiponectin and proinflammatory mediators implicated in the development of insulin resistance (IR) in metabolic syndrome (MetS). SUBJECTS AND METHODS: In 180 individuals, including controls and patients with MetS, we measured fasting plasma insulin, high sensitivity C-reactive protein (hsCRP), pentraxin-3 (PTX-3), interleukin-33 (IL-33), irisin, RBP-4, and adiponectin using ELISA kits. RESULTS: While fasting plasma hsCRP, PTX-3, IL-33, irisin, RBP-4 concentrations were higher, adiponectin levels were lower in patients with MetS than in controls. A correlation analysis revealed that plasma irisin levels were positively associated with MetS components such as waist circumference and waist-hip ratio, low density lipoprotein (LDL) and markers of systemic inflammation such as PTX-3, hsCRP, uric acid, and RBP-4. Adiponectin levels were negatively associated with waist circumference, waist-hip ratio, PTX-3 and LDL. CONCLUSIONS: Although the precise mechanisms are still unclear, irisin, RBP-4, adiponectin and PTX-3 are hallmarks of the MetS, which is related to low-grade inflammation. It is conceivable that irisin and adiponectin might contribute to the development of MetS and may also represent novel MetS components. Future clinical studies are needed to confirm and extend these data.

Circulating omentin-1 might be associated with metabolic health status in different phenotypes of body size.

OBJECTIVE: Adipokines are mediators of body composition and are involved in obesity complications. This study aimed to assess the association of circulating omentin-1, vaspin, and RBP-4 with body composition indices and metabolic health status (MHS) in different phenotypes of body size. SUBJECTS AND METHODS: A total of 350 subjects were included in the current cross-sectional study. Body composition was measured using a body composition analyzer, and serum concentrations of omentin-1, vaspin, and RBP-4 were assessed by ELISA kits. RESULTS: Circulating omentin-1 was significantly (OR = 1.81, 95% CI: 1.00-1.91, P = 0.01) and marginally (OR = 1.63, 95%CI: 1.00-1.75, P = 0.06) associated with MHS in the overweight and obese subjects, respectively. But no association was seen between omentin-1 and MHS in normal-weight subjects. Serum levels of vaspin and RBP-4 were not correlated with MHS. Furthermore, a significant positive correlation was observed between circulating omentin-1 and body mass index (BMI) as well as fat percentage (P = 0.02) in the MHS group. Serum vaspin concentrations were not related to body composition components in both groups. In addition, in the MHS group, circulating RBP-4 was positively correlated with fat percentage and fat mass (FM) (p < 0.0001) and was negatively correlated with fat-free mass (FFM) and total body water (TBW) (p < 0.0001). In contrast, in the metabolically unhealthy group, RBP-4 was negatively correlated with fat percentage, FM, and BMI (p < 0.0001) and was positively correlated with FFM and TBW (p < 0.0001). CONCLUSIONS: This study showed that circulating levels of omentin-1 are useful predictors of metabolic health status in overweight and obese people.

Comparison of plasma pigment epithelium-derived factor (PEDF), retinol binding protein 4 (RBP-4), chitinase-3-like protein 1 (YKL-40) and brain-derived neurotrophic factor (BDNF) for the identification of insulin resistance.

AIMS: To evaluate and compare the association of four potential insulin resistance (IR) biomarkers (pigment-epithelium-derived factor [PEDF], retinol-binding-protein-4 [RBP-4], chitinase-3-like protein 1 [YKL-40] and brain-derived neurotrophic factor [BDNF]) with objective measures of IR. METHODS: We studied 81 subjects with different metabolic profiles. All participants underwent a 5-point OGTT with calculation of multiple IR indexes. A subgroup of 21 participants additionally underwent a hyperinsulinemic-euglycemic clamp. IR was defined as belonging to the highest quartile of incremental area under the insulin curve (iAUCins), or to the lowest quartile of the insulin sensitivity index (ISI). RESULTS: PEDF was associated with adiposity variables. PEDF and RBP4 increased linearly across quartiles of iAUCins (for PEDF p-trend=0.029; for RBP-4 p-trend=0.053). YKL-40 and BDNF were not associated with any adiposity or IR variable. PEDF and RBP-4 levels identified individuals with IR by the iAUCins definition: A PEDF cutoff of 11.9ng/mL had 60% sensitivity and 68% specificity, while a RBP-4 cutoff of 71.6ng/mL had 70% sensitivity and 57% specificity. In multiple regression analyses simultaneously including clinical variables and the studied biomarkers, only BMI, PEDF and RBP-4 remained significant predictors of IR. CONCLUSIONS: Plasma PEDF and RBP4 identified IR in subjects with no prior diagnosis of diabetes.

Serum RBP4 and CKD: Association with insulin resistance and lipids.

OBJECTIVE: Serum RBP4 is new adipokine and it has been related to insulin resistance and diabetes risk in animal and clinical studies. However, there is controversy on this relationship among CKD patients. In this study, we evaluated the association of serum RBP4 with insulin resistance and cardiovascular risk factors in CKD. METHODS: Baseline data from the PROGREDIR Study (Sao Paulo, Brazil) comprising 454 participants (mainly stages 3 and 4) was analyzed. RESULTS: In univariable analysis, RBP4 was inversely related to renal function, age and HDL, and positively related to other lipids, insulinemia, HOMA, glycemia, albumin, phosphorus and right hepatic lobe diameter. After adjustment for sex, age and eGFR, HOMA and lipids remained associated to RBP4. In multivariable analysis, eGFR and triglyceride remained significantly associated with RBP4, while HOMA showed no longer a significant positive association. An interaction term between RBP4 and eGFR was significantly related to HOMA. CONCLUSIONS: Renal function is inversely related to serum RBP4. As GFR decreases, the relationship between RBP4 and HOMA is attenuated. On the other hand, triglycerides remained strongly related to RBP4 and this was not affected by eGFR, suggesting that in the CKD population triglycerides may be a better marker of RBP4-associated metabolic effects.

Short-Term Detraining does not Change Insulin Sensitivity and RBP4 in Rodents Previously Submitted to Aerobic Exercise.

Elevated serum retinol binding protein 4 (RBP4) levels were previously described in insulin-resistance states. Exercise training can improve insulin sensitivity and RBP4, but the time-response effect of exercise detraining on RBP4 has not been studied. Thus, we examined the effects of exercise training and short-term detraining on insulin resistance, serum RBP4 levels, and GLUT4 expression in spontaneously hypertensive rats (SHR). Thirty-two male SHR, 4 months old, were submitted to 10-week treadmill training, 5 times/week or kept sedentary, followed by a 2- and 4-day detraining period. Body weight, insulin tolerance test, maximum speed in a maximal exercise test, serum RBP4 (ELISA), and epididymal fat GLUT4 expression (Western blot) were measured. Although all rats gained weight (43%, p=0.004) only the trained group showed a reduction (p<0.001) of epididymal fat weight. Detraining did not change these parameters. Exercise training increased insulin sensitivity (26%, p=0.001) and maximum exercise capacity (80%, p<0.001), benefits not lost after detraining. RBP4 levels were reduced in response to exercise training (45%, p<0.001); detraining did not change these benefits. Trained rats had increased GLUT4 expression (microsomal, ~226%; p<0.001 and plasma membrane, ~55%; p=0.011). A slight reduction in GLUT4 expression in the plasma membrane (~28%, p=0.041), but not in the microsomal fraction, was observed after 4 days of detraining. Exercise training is associated with reduced RBP4 levels, increased insulin sensitivity, and epididymal fat GLUT4 expression. Even short periods of detraining (4 days) were shown to be associated with reversal of higher plasma membrane GLUT4.

Adipokines, asymmetrical dimethylarginine, and pulmonary function in adolescents with asthma and obesity.

OBJECTIVE: This study was to investigate whether the metabolic abnormalities of adipokines and asymmetrical dimethylarginine (ADMA) associate with pulmonary function deficits in adolescents with obesity and asthma. METHODS: This study enrolled 28 obese adolescents with asthma, 46 obese adolescents without asthma, 58 normal-weight adolescents with asthma, and 63 healthy control subjects. Serum levels of leptin, high-molecule-weight (HMW) adiponectin, retinol binding protein 4 (RBP4), asymmetrical dimethylarginine (ADMA), and pulmonary function were qualified. RESULTS: The obese subjects had higher levels of leptin and ADMA but lower levels of HMW adiponectin than the normal-weight subjects with or without asthma. The subjects with asthma had higher levels of RBP4 than those without asthma. The obese adolescents with asthma had lowest forced expiratory lung volume in the first second (FEV1)/forced vital capacity (FVC) ratio among the four study groups. In all the study subjects and in the subjects with asthma alone, the FEV1/FVC ratio associated negatively with leptin, however, such association was rendered non-significant when adjusted for BMI. The pulmonary function deficits associated inversely with BMI percentile in the subjects with asthma. However, the decreased FEV1/FVC ratio was not correlated with HMW adiponectin, RBP4 or ADMA. CONCLUSIONS: Our present study confirmed obstructive pattern of pulmonary function characterized by the reduced FEV1/FVC ratio in the obese adolescents with asthma. These pulmonary deficits were associated inversely with the increased BMI percentile.

Chemerin, retinol binding protein-4, cytokeratin-18 and transgelin-2 presence in sera of patients with non-alcoholic liver fatty disease.

 Background. Chemerin and retinol binding protein-4 (RBP-4) are adipokines which may play a role in the progression of NAFLD. It has been also suggested that cytokeratin-18 (CK-18) could be a marker of hepatocyte caspase-directed death while transgelin-2 production could reflect stage of liver fibrosis. The aim of this study was to evaluate the level of the above adipokines in sera of patients with NAFLD and determine the relation between the level of transgelin-2 and fibrosis-4 index (FIB-4). MATERIAL AND METHODS: Ninety-five subjects included initially to the study were divided into four groups: (I) prediabetics, obese with NAFLD and metabolic syndrome (MS), (II) lean with NAFLD and without MS, (III) obese without NAFLD and MS, and (IV) healthy individuals. We determined the levels of chemerin, RBP-4, transgelin-2 and CK-18 fragments in sera of patients with NAFLD. Moreover, we examined if the levels of CK-18 fragments and transgelin-2 correlates with FIB4 value. RESULTS: Chemerin and RBP-4 were highly expressed in sera of all NAFLD, especially in obese individuals. Chemerin level was also linked to MS. High level of serum CK-18 fragments and transgelin-2 did not correlate with obesity and MS, but seemed to correlate with progression of NAFLD to liver fibrosis. CONCLUSIONS: In conclusion, the production of the two adipokines, chemerin and RBP-4, is strongly associated with obesity in patients with NAFLD. Serum concentrations of CK-18 fragments and transgelin-2 correlate with the severity of NAFLD, but no with obesity.

Caveolin 1 Modulates Aldosterone-Mediated Pathways of Glucose and Lipid Homeostasis.

BACKGROUND: Overactivation of the aldosterone and mineralocorticoid receptor (MR) pathway is associated with hyperglycemia and dyslipidemia. Caveolin 1 (cav-1) is involved in glucose/lipid homeostasis and may modulate MR signaling. We investigated the interplay between cav-1 and aldosterone signaling in modulating insulin resistance and dyslipidemia in cav-1-null mice and humans with a prevalent variant in the CAV1 gene. METHODS AND RESULTS: In mouse studies, cav-1 knockout mice exhibited higher levels of homeostatic model assessment of insulin resistance, cholesterol, and resistin and lower ratios of high- to low-density lipoprotein (all P<0.001 versus wild type). Moreover, cav-1 knockout mice displayed hypertriglyceridemia and higher mRNA levels for resistin, retinol binding protein 4, NADPH oxidase 4, and aldose reductase in liver and/or fat tissues. MR blockade with eplerenone significantly decreased glycemia (P<0.01), total cholesterol (P<0.05), resistin (P<0.05), and described enzymes, with no effect on insulin or triglycerides. In the human study, we analyzed the CAV1 gene polymorphism rs926198 in 556 white participants; 58% were minor allele carriers and displayed higher odds of insulin resistance (odds ratio 2.26 [95% CI 1.40-3.64]) and low high-density lipoprotein (odds ratio 1.54 [95% CI 1.01-3.37]). Aldosterone levels correlated with higher homeostatic model assessment of insulin resistance and resistin and lower high-density lipoprotein only in minor allele carriers. CAV1 gene expression quantitative trait loci data revealed lower cav-1 expression in adipose tissues by the rs926198 minor allele. CONCLUSIONS: Our findings in mice and humans suggested that decreased cav-1 expression may activate the effect of aldosterone/MR signaling on several pathways of glycemia, dyslipidemia, and resistin. In contrast, hyperinsulinemia and hypertriglyceridemia are likely mediated by MR-independent mechanisms. Future human studies will elucidate the clinical relevance of MR blockade in patients with genotype-mediated cav-1 deficiency.