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

doi:10.1016/j.anl.2004.09.006

Auris Nasus Larynx

Volume 31, Issue 4, December 2004, Pages 425-428

https://doi.org/10.1016/j.anl.2004.09.006 Get rights and content

Abstract

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.

Introduction

Zinc is an essential trace element playing a role in several functions in both humans and animals. In fact, zinc deficiency has been linked to the disturbance of growth, special senses including vision, taste and smell [1], [2]. In particular, several lines of clinical evidence have suggested that taste impairment is one of the symptoms of zinc deficiency [3], [4], as corroborated by double-blind, placebo-controlled studies that have shown the efficacy of zinc supplementation in the taste recovery in several zinc-deficient patients [5], [6].

A recent paper reports a case of Cronkhite-Canada syndrome with taste disturbance and normal range plasmatic zinc levels that recovered after zinc supplementation [7]. In another double-blind placebo-controlled study, Yoshida et al. reported the therapeutic effect of zinc picolinate in patients with idiopathic taste disorder with normal zinc levels in the serum [8]. Therefore, it is suggested that zinc deficiency is a predominant factor underlying hypogeusia even when zinc concentrations are within normal ranges in the serum.

In the present study, an attempt was made to prove the hypothesis that hypogeusia is a symptom of zinc deficiency in patients with normal values of zinc in the serum. Apgar and Everett reported the activity of angiotensin converting enzyme (ACE), a zinc dependent enzyme, increased with addition of zinc in the serum of zinc-deficient guinea pigs in vitro, suggesting the presence in the serum of inactive apo-ACE molecules lacking zinc [9]. Recently, Kobayashi et al. reported that the ratio of apo/holo-ACE activities in the serum is a sensitive index of zinc nutrition in humans [10]. In the present study, we used ACE ratio as an index and evaluated the nutritional status of zinc in patients with taste impairment.

Section snippets

Materials and methods

The present study includes patients who visited the Department of Otolaryngology, Tokushima University Hospital complaining of taste impairment and were diagnosed as zinc-deficiency taste impairment (n = 6), idiopathic taste impairment (n = 13) and 30 healthy volunteers. Informed consent regarding the purpose of this study and measurements of zinc concentration and ACE activity in the blood was obtained from each patient. This study was approved by the Ethics Committee of Tokushima University

Results

In volunteers and patients with idiopathic taste impairment, the concentration of zinc in the serum was above 64 μg/dl, while it was below 63 μg/dl in zinc-deficient patients. Indeed, the mean concentrations of zinc in serum were 77.4 ± 8.4 μg/dl (mean ± S.D.) in volunteers, 77.6 ± 8.4 μg/dl in idiopathic group and significantly decreased at 55.7 ± 5.8 μg/dl in the zinc-deficiency group (Fig. 2).

Holo-ACE activities in the serum were 14.7 ± 7.6, 14.1 ± 3.3 and 14.5 ± 4.0 IU/l in volunteers, patients with idiopathic

Discussion

Among the available laboratory tests, zinc concentration in the serum has been widely used to assess zinc deficiency. However, this parameter is known to be modified by several factors, including acute stress and inflammation [13]. Inquiry into more reliable tests has lead to the observation that the activity of zinc-metallo enzymes, such as ribonuclease is a more reliable test for the assessment of zinc deficiency [14], [15]. In the present study, we used the ratio of the apo-ACE activity to

Conclusion

In the present study, we used ACE ratio to evaluate the status of zinc nutrition in patients with taste impairment. In addition to a significant increase in ACE ratio in taste impairment patients with low concentrations of zinc in serum, the ACE ratio was also significantly elevated in taste impairment patients with normal serum values of zinc. These findings indicated that zinc deficiency is a predominant factor underlying hypogeusia even when zinc concentrations are within normal ranges in

Acknowledgements

We are grateful to Dr. H. Kobayashi for his technical supports. This study was partly supported by a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science.

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

Abstract

Objective:

Methods:

Results:

Conclusion:

Introduction

Section snippets

Materials and methods

Results

Discussion

Conclusion

Acknowledgements

Life Sci

Am J Clin Nutr

Auris Nasus Larynx

J Nutr

Biochem Pharmacol

Zinc and the special senses

Ann Intern Med

Clinical and laboratory assessment of zinc deficiency in Dutch children

Biol Trace Elem Res

A double blind study of the effects of zinc suflate on taste and smell dysfunction

Am J Med Sci