Montserrat Broch, Maria Teresa Auguet, Rafael Ramírez, Montserrat Olona, Carmen Aguilar, Ana Megia, Maria José Alcaide, Rosa Pastor, Salomé Martínez, Enric Caubet, Antonio Garcia-España and Cristóbal Richart
Context and objective
Adipokines are involved in the etiopathology of obesity-related disorders. Since the role of adipokine retinol-binding protein-4 (RBP4) in obesity remains uncertain and its relationship with other adipokines and inflammatory markers has not been examined in detail, we investigated the relationships of RBP4 mRNA expression and circulating protein levels with obesity, anthropometric and metabolic variables, as well as with obesity-related inflammatory markers adiponectin and C-reactive protein.
Subjects and methods
One-hundred and twenty-five subjects participated, 36 lean (body mass index (BMI): <25 kg/m2) and 89 obese (overweight/obese; BMI: ≥25<40) whose anthropometric and metabolic variables were assessed. mRNA expression was quantified by real-time PCR in subcutaneous adipose tissue (s.c.-AT) of 46 subjects.
There was a tendency for circulating RBP4 levels to positively correlate with waist circumference (β=0.29, P=0.08; R
2=0.08), but there was no significant association with the obesity-related parameters analysed. RBP4 and adiponectin mRNA expression levels were similarly downregulated in the s.c.-AT of obese subjects (0.5-fold); however, RBP4 downregulation did not affect its circulating protein levels. The expression of RBP4 and adiponectin was positively correlated even after controlling for confounding factors (β=0.59, P<0.0001; R
In our population, RBP4 circulating levels were not significantly correlated with obesity-related parameters, although a tendency to correlate with waist circumference suggests a relationship with insulin resistance and other metabolic disorders. In addition, our results suggest that the production of RBP4 by other tissues such as liver, rather than s.c.-AT, may be involved in regulating RBP4 circulating levels.
Ximena Terra, Yunuen Quintero, Teresa Auguet, Jose Antonio Porras, Mercé Hernández, Fátima Sabench, Carmen Aguilar, Anna María Luna, Daniel del Castillo and Cristobal Richart
The adipocyte/macrophage fatty acid-binding protein 4 (FABP4) has been described as a biomarker for adiposity and metabolic syndrome (MS). The aims of this study were to assess the relationship between FABP4 and inflammatory cytokines related to obesity, and to evaluate FABP4 mRNA expression in visceral and subcutaneous adipose tissue in non-diabetic morbidly obese women versus healthy lean women.
We analyzed circulating levels of FABP4 in 81 Spanish women: 38 lean (body mass index (BMI)<25 kg/m2) and 43 morbidly obese (BMI>40 kg/m2). We took 30 follow-up blood samples at 6 and 12 months after bariatric surgery. We assessed FABP4 gene expression in samples of subcutaneous abdominal and visceral adipose tissue. Adipose tissue mRNA expression was determined by real-time RT-PCR.
In morbidly obese women, plasma FABP4 levels were significantly higher than in non-obese patients. These levels positively correlated with BMI, homeostasis model assessment of insulin resistance (HOMA2-IR), and plasma glucose and insulin levels. Post-operative FABP4 levels decreased by a maximum of 30% after 12 months. We also found an inverse association between FABP4 and adiponectin levels, and positive correlations between FABP4 and circulating leptin, tumor necrosis factor (TNF) receptors, C-reactive protein (CRP) and interleukin 6 levels. Linear regression analysis revealed that FABP4 was more closely related to HOMA2-IR than adiponectin, CRP, TNF-RI, or leptin. Furthermore, high circulating FABP4 levels were associated with the presence of MS. FABP4 mRNA expression in visceral adipose tissue was related to its circulating levels in morbidly obese women.
Our results indicate that serum FABP4 is associated with inflammatory factors related to obesity and MS in non-diabetic morbidly obese women.