Serum Retinol-Binding Protein 4 Is Reduced after Weight Loss in Morbidly Obese Subjects

• Published in: The journal of clinical endocrinology and metabolism 2007-03, Vol.92 (3), p.1168-1171
• Main Authors: Haider, Dominik G., Schindler, Karin, Prager, Gerhard, Bohdjalian, Arthur, Luger, Anton, Wolzt, Michael, Ludvik, Bernhard
• Format: Article
• Language: English
• Subjects: Adult; Bariatric Surgery; Biological and medical sciences; Blood Glucose - analysis; Endocrinopathies; Female; Fundamental and applied biological sciences. Psychology; Humans; Insulin - blood; Insulin Resistance; Male; Medical sciences; Middle Aged; Obesity, Morbid - blood; Obesity, Morbid - surgery; Retinol-Binding Proteins - analysis; Retinol-Binding Proteins, Plasma; Vertebrates: endocrinology; Weight Loss - physiology
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2006-1839

Context: Administration of retinol-binding protein 4 (RBP-4) impairs insulin sensitivity in animals, and elevated serum concentrations have been associated with insulin resistance in humans. Objective: We have studied whether weight loss influences RBP-4. Patients and Methods: Fasting serum concentrations of RBP-4 were measured before and 6 months after gastric banding surgery in 33 morbidly obese patients aged 40 ± 11 yr with a body mass index (BMI) of 46 ± 5 kg/m2. Fourteen healthy subjects aged 29 ± 5 yr with a BMI less than 25 kg/m2 served as controls. To characterize the association of weight loss with central and peripheral appetite regulation, the signaling protein agouti-related protein (AGRP), the orexigenic hormone ghrelin, and its recently identified antagonist obestatin were determined. Results: At baseline, RBP-4 levels were markedly higher in obese than in lean subjects (2.7 ± 0.5 vs. 0.9 ± 0.5 μg/ml; P < 0.001). In contrast, AGRP and obestatin were lower in obese subjects compared with lean controls (all P < 0.001). Six months after gastric banding, BMI was reduced to 40 ± 5 kg/m2, RBP-4 was reduced to 2.0 ± 0.7 μg/ml, AGRP increased from 1.8 ± 1.1 to 3.4 ± 1.1 ng/ml, ghrelin increased from 93 ± 58 to 131 ± 70 pg/ml, and obestatin increased from 131 ± 52 to 173 ± 35 pg/ml (all P < 0.05). Individual changes of RBP-4 were associated with changes of BMI (r = 0.72), the homeostasis model assessment insulin resistance-index (r = 0.53), and total cholesterol (r = 0.42, for all P < 0.05). Conclusion: Reductions in circulating RBP-4 may contribute to improved insulin resistance in morbidly obese subjects after weight loss. This is accompanied by favorable changes in appetite-regulating hormones, which might support the sustained weight loss after obesity surgery.