Serum retinol-binding protein 4 is reduced after weight loss in morbidly obese subjects.
BACKGROUND
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.


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/m(2). Fourteen healthy subjects aged 29 +/- 5 yr with a BMI less than 25 kg/m(2) 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 microg/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/m(2), RBP-4 was reduced to 2.0 +/- 0.7 microg/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).


CONCLUSIONS
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.
Haider
Dominik G
DG
Medical University of Vienna, Department of Internal Medicine III, Division of Endocrinology and Metabolism, Allgemeines Krankenhaus Wien, Währinger Gürtel 18-20, 1090 Vienna, Austria.
Schindler
Karin
K
Prager
Gerhard
G
Bohdjalian
Arthur
A
Luger
Anton
A
Wolzt
Michael
M
Ludvik
Bernhard
B
D000328:Adult; D050110:Bariatric Surgery; D001786:Blood Glucose / Q000032:analysis; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood* / Q000601:surgery*; D012177:Retinol-Binding Proteins / Q000032:analysis*; D054839:Retinol-Binding Proteins, Plasma; D015431:Weight Loss / Q000502:physiology*
D001786:Blood Glucose; D007328:Insulin; C101326:RBP4 protein, human; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma