Serum transforming growth factor-beta 1 levels in normoalbuminuric and normotensive patients with type 2 diabetes. Effect of metformin and rosiglitazone

OBJECTIVE: a)To determine serum Transforming Growth Factor-beta 1 (TGF-beta 1) levels in patients with type 2 diabetes who do not have diabetes related complications and in healthy controls, b) to evaluate the effects of metformin and rosiglitazone on TGF-beta 1 levels. DESIGN: In the washout period, 61 patients with Fasting Plasma Glucose levels (FPG) higher than 140 mg/dl, Postprandial Glucose (PPG) levels higher than 180 mg/dl and A1c levels exceeding 6.5% were treated with glimperide. After 4 weeks, 39 of these patients were randomised to receive either metformin or rosiglitazone for 12 weeks. Thirty healthy controls were also studied. RESULTS: There were no significant differences with regard to age, gender, body weight and BMI between patients and healthy controls. Type 2 diabetics had higher waist circumference, FPG, total cholesterol, LDL-cholesterol and triglyceride levels. Baseline TGF-beta 1 levels in diabetics were higher than in controls (29.84 +/- 7.04 ng/ml vs 11.37 +/- 4.06 ng/ml, p < 0.001). Metformin or rosiglitazone did not significantly modify the TGF-beta 1 levels. In a multiple regression analysis FPG was the only variable that was significantly associated with plasma TGF-beta 1 levels. CONCLUSION: The elevated levels of TGF-beta 1 in subjects with type 2 diabetes possibly indicate a tendency for renal and endothelial damage in such patients. The association of TGF-beta 1 with FPG possibly links poor diabetic control to vascular damage, leading to diabetic complications. Lack of changes in the levels of TGF-beta 1 after therapy may reflect inadequate therapy duration.