Serum retinol binding protein 4 and its ratio to serum retinol in obese type 2 diabetic patients

Background:
     Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action,or both, the chronic hyperglycemia of diabetes is associated with longterm damage, dysfunction and failure of various organs, especially the eyes, kidneys, nerves, heart, and blood vessels that impose a tremendous burden on the individual with diabetes and on the health care system.Objective:
     To study the relationship between retinol binding protein -4 (RBP-4) /retinol ratio with insulin resistance in patients with type 2 diabetes mellitus.Subjects and methods:
     A case- control study was performed at Chemistry and Biochemistry Department, College of Medicine, Al-Nahrain University, Baghdad, Iraq from March 2012 to June 2012. Forty five patients and thirty four healthy controls were enrolled in this study. The patients and controls were taken with cluster random sampling method. The present study includes measurements of hbA1c levels by ion-exchange HPLC method. Fasting blood glucose, lipid profile, blood urea and serum creatinine levels were determined by enzymatic colorimetric methods. Fasting serum insulin,retinol binding protein -4 ( RBP-4), retinol levels were measured by enzyme-linked immune sorbent assay in 45 patients with type 2 diabetes mellitus (mean ± SE,MEAN AGE = 52.14 ± 1.01 years).The results were compared with 34 aged matched apparently healthy control subjects (mean age 48.79 ± 1.17 years) divided according to body mass index (BMI) into two groups:
1. Controls with body mass index (BMI) < 25 kg/m2: normal controlgroup (n = 9, mean age = 49.22 ± 1.88 years).2. Controls with body mass index (BMI) ≥ 30 kg/m2: obese control group (n = 25, mean age = 48.38 ± 1.45 years) .
Results:The results showed significant elevation in blood glucose, glycated hemoglobin HbA1c, serum triglyceride TG, serum very low density lipoprotein VLDL, atherogenic index of plasma AIP, fasting insulin resistance index, fasting glucose insulin ratio, Homeostatic model assessment of β-cells (β-cells function) HOMA-β and serum  retinol binding protein 4 in the diabetic patients as compared with both control subjects.High density lipoprotein HDL, insulin and Homeostatic model assessment of insulin resistance HOMA-IR presented significant increase in  T2DM when compared to normal control group but not significant difference when compared to obese Insulin levels and insulin resistance expressed in HOMA –IR showed significant elevation in T2DM as compared to normal control group but
not significant when compared to obese control group.Serum cholesterol, low density lipoprotein showed no significant difference between patients and both control groups Insulin sensitivity index ISI was significantly decreased in T2DM patients as compared to both control groups.Conclusion: It was concluded that serum retinol / retinol binding protein 4 ratio may be considered as indication of type 2 diabetes mellitus rather than RBP 4 itself.