Weight loss intervention reduces the risk of kidney stone formation in a rat model of metabolic syndrome.

ABSTRACT

OBJECTIVES: To investigate the effect of weight loss intervention on the urinary stone risk parameters in a rat model of metabolic syndrome. METHODS: In a prevention study, 4-week-old male Otsuka Long-Evans Tokushima "Fatty" rats were randomly assigned to three groups control, food-restricted and food-restricted + exercise-trained groups. In a treatment study, 24-week-old male Otsuka Long-Evans Tokushima "Fatty" rats that had already developed type 2 diabetes were randomly assigned to the same three groups. Blood and 24-h urine chemistry were measured after 16 weeks. RESULTS: In both studies, food-restricted and food-restricted + exercise-trained rats showed significantly higher urinary pH and higher excretion of urinary citrate than control rats. In the prevention study, ion-activity products of calcium oxalate in the food-restricted and food-restricted + exercise-trained groups were significantly lower than that of control rats. In the treatment study, ion-activity products of calcium oxalate index in food-restricted + exercise-trained rats was significantly lower than that of control rats. CONCLUSIONS: Weight loss intervention seems to reduce the risk of uric acid stone formation by improving low urine pH and calcium oxalate stone formation by increasing urinary citrate excretion. The present study provides the first theoretical evidence to support weight loss intervention programs for nephrolithiasis patients with metabolic syndrome.