ABSTRACT
Title
Retinol-Binding Protein 4 Levels, Insulin Resistance and Lipid Metabolism in Obese Postmenopausal Women: A Pilot Study
Authors
F. Miceli1, E. Cantalupo1, A.P. Lassandro2, M.C. Moruzzi3, P. Villa3
1Institute of Pharmacology, 2Department of Endocrinology, 3Departmentof Obstetrics and Gynaecology Catholic University School of Medicine, Rome, Italy
1Institute of Pharmacology, 2Department of Endocrinology, 3Departmentof Obstetrics and Gynaecology Catholic University School of Medicine, Rome, Italy
Abstract
Background
Retinol-binding protein 4 (RBP4) is an adipocytokine secreted by adipocytes and liver tissue. It is the specific transport protein for retinol (vitamin A) in the circulation. Elevated RBP4 levels cause insulin resistance in mice, and high plasma RBP4 levels were associated with insulin-resistant states in humans. Overweight or central obesity is generally associated with increases in insulin resistance and metabolic risk of cardiovascular disease. The prevalence of these features is highest among middle-aged and older women. The aim of this study is to assess whether RBP4 levels differ in menopausal women with central obesity or Metabolic Syndrome compared with a group of healthy postmenopausal women and to study the relationship between serum RBP4 levels and indices of insulin sensitivity, lipid profile, sex steroids, gonadotropins, and some adipokines that have been shown to be associated with menopausal status and serum estradiol concentration.
Methods
We enrolled 27 healthy postmenopausal women and 53 postmenopausal women (aged 48-57 years) with central obesity or Metabolic Syndrome, evaluated according to the IDF criteria. Serum RBP4 concentration was measured by an enzyme-linked immunosorbent assay (ELISA R & D Systems). In each subject was performed oral glucose tolerance test (OGTT) for evaluating glycemic and insulinemic responses, insulin resistance was determined by homeostasis model assessment (HOMA-IR), lipid profile, sex steroids, gonadotropins, leptin, adipokines and features of the metabolic syndrome was also evaluated. Blood samples were obtained after an overnight fasting.
Results
Serum RBP4 concentrations inthe central obesity / Metabolic Syndrome women are significantly higher than those in healty postmenopausal women. The two group exhibit also significantly different BMI, waist, WHR, fasting insulin, AUC insulin, HOMA and Leptin. No direct correlation has been found in any group between RBP4 levels and insulin-resistance parameters. In the obesity or Metabolic Syndrome women group RBP4 levels positively correlates only with Age and Waist and in healthy postmenopausal group RBP4 levels negatively correlates with fasting Insulin and HOMA-IR.
Conclusion
The evidence that the highest values of serum RBP4 are present in the central obesity / Metabolic Syndrome group agrees with some previous studies reporting that serum RBP4 levels were shown to be highly associated with insulin resistant states in humans. Although these findings need to be validate with an increased number of patients, however they suggest that RBP4 serum levels could exhibit different correlation in menopause in women with central obesity or metabolic Syndrome in comparison to healthy menopausal subjects.
Retinol-binding protein 4 (RBP4) is an adipocytokine secreted by adipocytes and liver tissue. It is the specific transport protein for retinol (vitamin A) in the circulation. Elevated RBP4 levels cause insulin resistance in mice, and high plasma RBP4 levels were associated with insulin-resistant states in humans. Overweight or central obesity is generally associated with increases in insulin resistance and metabolic risk of cardiovascular disease. The prevalence of these features is highest among middle-aged and older women. The aim of this study is to assess whether RBP4 levels differ in menopausal women with central obesity or Metabolic Syndrome compared with a group of healthy postmenopausal women and to study the relationship between serum RBP4 levels and indices of insulin sensitivity, lipid profile, sex steroids, gonadotropins, and some adipokines that have been shown to be associated with menopausal status and serum estradiol concentration.
Methods
We enrolled 27 healthy postmenopausal women and 53 postmenopausal women (aged 48-57 years) with central obesity or Metabolic Syndrome, evaluated according to the IDF criteria. Serum RBP4 concentration was measured by an enzyme-linked immunosorbent assay (ELISA R & D Systems). In each subject was performed oral glucose tolerance test (OGTT) for evaluating glycemic and insulinemic responses, insulin resistance was determined by homeostasis model assessment (HOMA-IR), lipid profile, sex steroids, gonadotropins, leptin, adipokines and features of the metabolic syndrome was also evaluated. Blood samples were obtained after an overnight fasting.
Results
Serum RBP4 concentrations inthe central obesity / Metabolic Syndrome women are significantly higher than those in healty postmenopausal women. The two group exhibit also significantly different BMI, waist, WHR, fasting insulin, AUC insulin, HOMA and Leptin. No direct correlation has been found in any group between RBP4 levels and insulin-resistance parameters. In the obesity or Metabolic Syndrome women group RBP4 levels positively correlates only with Age and Waist and in healthy postmenopausal group RBP4 levels negatively correlates with fasting Insulin and HOMA-IR.
Conclusion
The evidence that the highest values of serum RBP4 are present in the central obesity / Metabolic Syndrome group agrees with some previous studies reporting that serum RBP4 levels were shown to be highly associated with insulin resistant states in humans. Although these findings need to be validate with an increased number of patients, however they suggest that RBP4 serum levels could exhibit different correlation in menopause in women with central obesity or metabolic Syndrome in comparison to healthy menopausal subjects.