Inhibition of diabetic nephropathy in rats by an oral antidiabetic material extracted from yeast

Diabetic nephropathy is one of the major complications of diabetes. The glucose tolerance factor (GTF) is a dietary agent extracted from several natural sources; the richest among them is brewer's yeast. Extraction and purification of an active and stable GTF preparation from brewer's yeast previously was successful, and a remarkable decrease in plasma glucose and lipids from administration of GTF to animals with type 1 diabetes was demonstrated. The purpose of the present study was to examine whether GTF affects nephropathy in diabetic rats. The average urinary volume and protein excretion throughout the collection period in diabetic rats was 56.95 ± 2.2 ml/d and 5.42 ± 0.95 mg/d, respectively. These values were significantly (P < 0.001 versus baseline values) higher compared with healthy controls (average urine volume 15.12 ± 0.5 ml/d; average protein excretion 0.15 ± 0.08 mg/d). Treatment with GTF reduced average urine volume and protein excretion to 29.1 ± 1.94 ml/d (P < 0.01) and 1.55 ± 1.17 mg/d (P < 0.05), respectively. Kidney weight, which was elevated in diabetic rats, slightly decreased in diabetic animals that were treated with GTF, in association with reduction of lipid peroxidation levels in the renal cortex and the heart. Endothelial nitric oxide immunoreactivity in the renal cortex of both healthy and diabetic rats that were treated with GTF was remarkably lower than that found in renal cortex of untreated diabetic animals. This study demonstrates that yeast-derived material, GTF, can inhibit the development of nephropathy that is induced by diabetes.