Effects of dietary salt and fat on taurine excretion in healthy and diseased rats

Taurine modulates renal and cardiovascular function. Although the kidney regulates body taurine status, the impact of renal and cardiovascular risk factors, such as dietary intake of excess NaCl and saturated fat, on renal handling of taurine is less clear. One would predict that the kidney would modulate taurine excretion during dietary NaCl excess to insure adequate osmotic homeostasis. Similarly, fat feeding would be expected to affect taurine homeostasis, as taurine is involved in bile acid conjugation and therefore fat emulsification. To examine these aspects, male rats were divided into four groups: basal fat diet (control), high fat diet (FAT), basal fat and high salt diet (SALT) and a combination of a high fat and salt diet (FATSALT). While the control, FAT and SALT groups excreted similar amounts of taurine; the SALTFAT group excreted significantly more taurine than the other 3 groups. Although all of the dietary regimens increased renal tissue content of taurine, the increases were greatest in the two SALT groups. In a subsequent study, we examined the effect of excess dietary fat on taurine handling by the hypertensive (H) and hypertensive-glucose intolerant (HGI) rat. When fed a basal fat diet, the HGI group excreted more taurine than the H group, an effect likely related to increased endogenous taurine biosynthesis, alterations in renal function or a combination of the two effects. While excess fat intake increased urinary taurine excretion in the H group, it reduced taurine excretion in the HGI group. Nonetheless, kidney taurine content was similar in the 4 groups. Taken together, the data suggest that dietary constituents and preexisting systemic disorders are important modulators of renal handling of taurine.