Diabetes mellitus is a syndrome characterized by abnormal insulin secretion, derangement in carbohydrate and lipid metabolism, and is diagnosed by the presence of hyperglycemia. Also, this syndrome is common risk factors for chronic renal disease. Once it occurs, chronic renal failure and end stage renal disease often increase mortality in those with type 2 diabetes. A decrease in glomerular filtration rate indicates the development of renal disease, and early identification of this event is important in subjects with type 2 diabetes (1, 2).
A new experimental diabetic syndrome in adult rats administered streptozotocin (STZ) and partially protected with a suitable dose of nicotinamide. This syndrome shares a number of features with human type 2 diabetes, and is characterized by moderate stable hyperglycemia, glucose intolerance, altered but significant glucose-stimulated insulin secretion (3, 4).
Streptozotocin (STZ), a N-nitroso-N-methylurea derivative of 2-deoxy-D-glucose, is a diabetogenic agent acting through the selective destruction of pancreatic islet beta cells. It is known that insulin increases the transport of amino acid into the cell and increases the degradation of proteins. It causes changes in the levels of some amino acids. Thus, STZ has some effects on blood and urine amino acid levels. In addition, STZ displays nephrotoxic and hepatotoxic activity. It has been reported that STZ caused cataracts, necrosis of kidney tubules, mesengial proliferation and hyalines of vessels in rats (5).
Extracts of Stevia rebaudiana Bertoni (SrB) have been used for the treatment of diabetes in, for example, Brazil, although a positive effect on glucose metabolism has not been unequivocally demonstrated. In addition to, oral intake of SrB extracts slightly suppresses plasma glucose during an oral glucose tolerance test in healthy subjects. A 35% reduction in blood glucose is also observed in diabetic subjects after oral intake of SrB extracts (2, 6, 7, 8). One of the main constituents of the dry-matter of SrB is the diterpene glycoside, stevioside, which is 200-300 times sweeter than sucrose, and in addition, steviosides have a caloric value of zero. Initial scientific studies have indicated that steviosides can regulate blood glucose levels, are safe for diabetics (2, 7, 8).
Because of promote additional insulin secretion (6, 7), helping to reverse diabetes (2, 6, 7, 8), safe for phenylketonuria patients (8) and help reduce hypertension (19), stevia extract can be used as a medicinal food.
Nitric oxide synthases (NOS) are family of enzymes that synthesize NO and citrulline from L-arginine. Three major subtypes have been identified; two of them, neuronal NOS and endothelial NOS are constitutively expressed and Ca+2/calmodulin-depended, whereas the cytokine-inducible isoform is calcium-independed (9).
Changes of renal nitric oxide (NO) production have been associated with glomerular hyperfiltration, vascular permeability, albuminuria,...