Efficacy of Serum Leptin Level as an Indicator to Predict the Clinical Response of Rosiglitazone in Patients with Type 2 Diabetes Mellitus

Lee, Jae Hyuk; Kim, Soo Kyung; Hur, Kyu Yeon; Choi, Han Seok; Jung, Ji Young; Shim, Wan Sub; Lee, Hyun Joo; Ahn, Chul Woo; Lim, Sung Kil; Kim, Kyung Rae; Lee, Hyun Chul; Cha, Bong Soo

Abstract

BACKGROUND: Leptin is a protein secreted by adipocytes that regulates food intake by acting on the hypothalamus and is correlated with body fat mass. Insulin resistance is also correlated with body fat mass and obesity. Rosiglitazone (RSG) is known as a highly selective and potent agonist for the peroxisome proliferator-activated receptor-gamma (PPARgamma). It improves glycemic control by improving insulin sensitivity in peripheral tissue. This study was performed to evaluate the antidiabetic and insulin sensitizing effects of RSG combination therapy and the efficacy of serum leptin level as an indicator to predict the clinical response of RSG in type 2 diabetic patients with oral agents such as metformin and/or sulfonylurea.
METHODS
The study subjects were 140 type 2 diabetic patients (90 male, 50 female) who received a 12-week course of daily 4 mg RSG, in addition to the previous medications. The glucose level, indices of insulin resistance and metabolic parameters were measured. Serum leptin level was measured by radioimmunoassay before and after RSG treatment. Visceral fat and subcutaneous fat were measured by sonography.
RESULTS
After 12 weeks of RSG treatment, FPG (12.6+/-28.1 mg/dL), HOMAIR (0.3+/-0.9), serum fasting insulin (1.9+/-4.7 microU/mL), SBP and DBP had all decreased significantly, whereas body weight, BMI, waist circumference, WHR, body fat mass, and subcutaneous fat had all increased. Serum leptin level also tended to increase after RSG treatment, but without significance. deltaFPG (delta=value after treatment- value before treatent) was inversely correlated with basal serum leptin level (r=-0.202), basal HOMAIR (r=-0.226) and basal FPG (r=-0.565). There was no correlation between deltaFPG and basal BMI or serum insulin level. RSG treatment showed significant inverse correlation between serum leptin level and deltaHOMAIR (r=-0.416), delta insulin (r=-0.365) and deltaHbA1c (r=-0.189). Serum leptin level was positively correlated with the subcutaneous fat amount (r=0.548), basal BMI (r=0.521), and basal HOMAIR (r=0.343).
CONCLUSION
These results showed that RSG treatment can improve not only hyperglycemia but also insulin resistance in type 2 diabetic patients. The serum leptin level at baseline can be used as an indicator to predict the clinical response of RSG treatment in type 2 diabetes patients.