Xylitol normalizes the accelerated hepatic capacity for conversion of amino nitrogen to urea nitrogen in diabetic rats.

In diabetes, the capacity of urea nitrogen synthesis, ie, a substrate-independent measure of the hepatic conversion of amino nitrogen to urea nitrogen, is increased. Xylitol decreases urea synthesis in normal rats. Capacity of urea nitrogen synthesis and nitrogen balance were measured during intravenous alanine loading in control rats, rats with experimental diabetes (streptozocin 75 mg/kg), and rats with experimental diabetes infused with xylitol to 1 mmol/L. In control rats, capacity of urea nitrogen synthesis was 9.4 +/- 1.1 mumol/min per 100 g of body weight, and nitrogen balance -2.7 +/- 1.2 mumol/min per 100 g of body weight. In the diabetics, these values were markedly increased to 26.6 +/- 1.9 and -16.3 +/- 2.1 mumol/min per 100 g of body weight, respectively (p < 0.01). The infusion of xylitol normalized these values to 11.2 +/- 1.0 and -3.6 +/- 2.1 mumol/min per 100 g of body weight for capacity of urea nitrogen synthesis and nitrogen balance, respectively. Xylitol did not change glucagon or insulin. Xylitol improved the nitrogen economy of uncontrolled diabetic rats by decreasing urea synthesis. The mechanism is not settled, but it does not involve insulin or glucagon.