[Electric gustatory threshold in diabetics and its clinical significance]

Impaired taste sensation in type 2 diabetic patients without chronic complications: a case-control study

PURPOSE

Few and contradictory data suggest changes in taste perception in type 2 diabetes (T2DM), potentially altering food choices. We, therefore, analyzed taste recognition thresholds in T2DM patients with good metabolic control and free of conditions potentially impacting on taste, compared with age-, body mass index-, and sex-matched normoglycemic controls.

METHODS

An ascending-concentration method was used, employing sucrose (sweet), sodium chloride (salty), citric acid (sour), and quinine hydrochloride (bitter), diluted in increasing concentration solutions. The recognition threshold was the lowest concentration of correct taste identification.

RESULTS

The recognition thresholds for the four tastes were higher in T2DM patients. In a multiple regression model, T2DM [β = 0.95; 95% CI 0.32-1.58; p = 0.004 (salty); β = 0.61; 0.19-1.03; p = 0.006 (sweet); β = 0.78; 0.15-1.40; p = 0.016 (sour); β = 0.74; 0.22-1.25; p = 0.006 (bitter)] and waist circumference [β = 0.05; 0.01-0.08; p = 0.012 (salty); β = 0.03; 0.01-0.05; p = 0.020 (sweet); β = 0.04; 0.01-0.08; p = 0.020 (sour); β = 0.04; 0.01-0.07; p = 0.007 (bitter)] were associated with the recognition thresholds. Age was associated with salty (β = 0.06; 0.01-0.12; p = 0.027) and BMI with sweet thresholds (β = 0.06; 0.01-0.11; p = 0.019).

CONCLUSIONS

Taste recognition thresholds were higher in uncomplicated T2DM, and central obesity was significantly associated with this impairment. Hypogeusia may be an early sign of diabetic neuropathy and be implicated in the poor compliance of these patients to dietary recommendations.

Expression of alpha-gustducin in the circumvallate papillae of taste buds of diabetic rats

Taste impairment is a complication of Diabetes mellitus and some studies have shown this taste disorder in diabetes. Diabetes can decrease the ability of individuals to detect and recognize sweet, salty and bitter tastes. alpha-Gustducin is a transducin-like G-protein selectively expressed in 20 - 30% of taste receptor cells, which has been shown to be involved in bitter, sweet and umami taste responses. The present study was performed to explore the protein and mRNA expression of alpha-gustducin in the taste buds of diabetic and control rat circumvallate papillae. Our results showed that the positive expression of alpha-gustducin in diabetic rat taste bud cells is higher than that in normal controls as shown by both immunohistochemistry and RT-PCR. There may be some variant of bitter, sweet or umami taste transduction during diabetes and that taste transduction variant may be one cause of diabetic taste impairment.

The application of d.c. electrical stimulation in evoking and recording gustatory brain potentials

Evidence exists which supports the hypothesis that electrical stimulation of appropriate parameters can fulfil the fundamental requirements for an effective evoked potential taste stimulus. Nevertheless, it had previously been considered that electrical taste stimulation is inadequate for evoking gustatory brain potentials. Consequently, the majority of the earlier attempts to record gustatory evoked potentials (GEPs) reported in the literature have employed chemical stimulus techniques. The design of an electrical taste stimulator and its interface to an evoked potential recording unit is described. The first human brain potentials recorded with this system are presented, among which are those attributable to taste pathway activation. Following future work to unequivocally confirm that taste evoked brain potentials are achievable with this system, it has potential to become a clinically valuable tool.