Retinol Binding Protein-4 Elevation Is Associated with Serum Thyroid-Stimulating Hormone Level Independently of Obesity in Elderly Subjects with Normal Glucose Tolerance

Objective Retinol-binding protein 4 (RBP4) is an adipokine responsible for vitamin A (retinol) transportation. Studies associated RBP4 increased levels with severity of type 2 diabetes mellitus (T2DM) and insulin resistance (IR). The study aimed to quantify RBP4 serum standards in women with a wide range of body mass index (BMI) and glucose tolerance level. Subjects and methods: Cross-sectional study was performed with 139 women divided into three groups: Group 1 (lean-control, n = 45) and Group 2 (obese, n = 53) with normal glucose tolerance and group 3 (obese with T2DM, n = 41), called G1, G2 and G3. Were assessed clinical, biochemical, anthropometric and body composition parameters. Results According to data analysis, we obtained in G1 higher RBP4 levels (104.8 ± 76.8 ng/mL) when compared to G2 (87.9 ± 38 ng/mL) and G3 (72.2 ± 15.6 ng/mL) levels. Also, were found: in G1 positive correlations of RBP4 with BMI (r = 0.253), glycated hemoglobin (r = 0.378) and fasting insulin (r = 0.336); in G2 with glycated hemoglobin (r = 0.489); in G3 with glycated hemoglobin (r = 0.330), fasting glucose (r = 0.463), HOMA-IR (r = 0.481). Conclusions Although RBP4 have shown lower levels in diabetic and obese, a strong correlation with HOMA-IR index highlights that, in our study, there is growing IR when there is an increasing in RBP4 levels.

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Serum Retinol Binding Protein 4 Is Related to Insulin Resistance and Nonoxidative Glucose Metabolism in Lean and Obese Women with Normal Glucose Tolerance

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2008-0077 ◽

2008 ◽

Vol 93 (7) ◽

pp. 2786-2789 ◽

Cited By ~ 30

Author(s):

Irina Kowalska ◽

Marek Strączkowski ◽

Agnieszka Adamska ◽

Agnieszka Nikolajuk ◽

Monika Karczewska-Kupczewska ◽

...

Keyword(s):

Insulin Sensitivity ◽

Glucose Metabolism ◽

Glucose Tolerance ◽

Binding Protein ◽

Normal Glucose Tolerance ◽

Retinol Binding Protein ◽

Entire Group ◽

Obese Women ◽

Euglycemic Hyperinsulinemic Clamp ◽

Normal Glucose

Abstract Context: Retinol-binding protein (RBP) 4 is secreted by adipose tissue and is postulated to be a determinant of insulin sensitivity. The mechanisms of RBP4 insulin desensitizing action remain unclear. Objective: The aim of the present study was to estimate the relationships between serum RBP4 concentration with insulin sensitivity and oxidative and nonoxidative glucose metabolism in lean and obese women. Design and Participants: The study group consisted of 67 women with normal glucose tolerance, 27 lean and 40 overweight or obese. Insulin sensitivity was estimated with the euglycemic hyperinsulinemic clamp. Glucose and lipid oxidation was measured with indirect calorimetry in the basal state and during the last 30 min of the clamp. Nonoxidative glucose metabolism was calculated in insulin-stimulated conditions by subtracting glucose oxidation from total glucose metabolism. Results: There was no difference in serum RBP4 concentration between lean and obese women. Serum RBP4 was inversely related to insulin sensitivity and nonoxidative glucose metabolism in the entire group (r = −0.36, P =0.003 in both cases) and within the subgroups of lean (r = −0.41, P =0.034 and r = −0.41, P =0.031) and obese women (r = −0.41, P =0.009 and r = −0.40, P =0.01, respectively). These relationships were independent of potential confounding factors. RBP4 levels were not associated with oxidative metabolism of glucose or lipid. Conclusions: Our data indicate that serum RBP4 is related to decreased insulin sensitivity, mostly through its association with nonoxidative glucose metabolism.

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