Effects of dietary biotin on enhanced sucrose intake and enhanced gustatory nerve responses to sucrose seen in diabetic OLETF rat.

We used the sucrose preference test and taste nerve recording to investigate the effect of dietary biotin on the abnormal sucrose taste sensitivity and preferences seen during the course of diabetes mellitus. For this, we used Otsuka Long-Evans Tokushima fatty (OLETF) rats. The chorda tympani nerve (CT nerve) response to sucrose (> 1 M) was of greater relative magnitude in OLETF rats than in non-diabetic control (Long-Evans Tokushima Lean, LETO) rats, but the responses to other basic taste stimuli (such as HCl, quinine-HCl and L-glutamic acid) did not differ between the two groups. In behavioral experiments using a two-bottle preference test, solution intake for sucrose (> 50 mM) was higher in OLETF rats than in LETO rats. The neural responses to sucrose (1.5-2 M) in OLETF rats were lower when given a biotin-high diet (BH-OLETF) than when given a biotin-basal diet (BB-OLETF), but this was not true of the other basic tastes. However, there were no significant differences between BH-OLETF and BB-OLETF rats in terms of sucrose solution intake. These findings suggest that the enhanced sugar sensitivity observed in OLETF rats is probably the result of a genetic difference between OLETF and LETO rats, though the discrepancy can be modified by the dietary biotin level.