Zinc deficiency in patients with idiopathic taste impairment with regard to angiotensin converting enzyme activity

Objective: The present study aimed at measuring the ratio of apo/holo activities of angiotensin converting enzyme (ACE) ratio in the serum of patients with taste impairment to evaluate their status of zinc nutrition. Methods: Nineteen patients complaining of taste impairment were divided into two groups: zinc-deficiency taste impairment (n = 6) and idiopathic taste impairment (n = 13) and compared to 30 volunteers. Zinc concentrations in the serum were measured by atomic absorption spectrometry (normal values: 64–111 μg/dl). Patients with zincemia values of <63 μg/dl with no history of other disorder or medication known to cause dysgeusia were diagnosed as zinc deficient, while those with the same condition and values >64 μg/dl were considered to belong to the idiopathic group. The activities of ACE in the serum were measured spectrophotometrically as the activity of the holo-ACE, and after addition of 80 μM of zinc to the serum in vitro, the increase of ACE activity over initial value in the serum was determined as that of the apo-ACE. Finally, the apo/holo-ACE activities ratio was used as an index of zinc nutritional status. Results: The mean concentrations of zinc in the serum were 77.4 ± 8.4 μg/dl in volunteers, 77.6 ± 8.4 μg/dl in the idiopathic patients and significantly decreased at 55.7 ± 5.8 μg/dl in zinc-deficiency patients. ACE activities in the serum were 14.7 ± 7.6, 14.5 ± 4.0 and 14.1 ± 3.3 IU/l in volunteers, the idiopathic group and zinc-deficiency taste impairment group, respectively. The mean ACE ratios were 1.10 ± 0.6% in volunteers and significantly increased at 9.8 ± 4.0% in the idiopathic group and at 13.7 ± 6.6% in zinc-deficiency taste impairment group. Conclusion: The results of the present study indicated that zinc deficiency is a predominant factor underlying hypogeusia even when zinc concentrations are within normal ranges in the serum and show that clinically, ACE ratio may be a more sensitive indicator of the zinc nutritional status than measuring zinc concentration in the serum.