ESTUDIOS CLÍNICOS

Superoxide dismutases and their impact upon human health.
Felicity Johnson, Cecilia Giulivi.

Superoxide dismutases (SOD), a group of metal-containing enzymes, have a vital anti-oxidant role in human health, conferred by their scavenging of one of the reactive oxygen species, superoxide anion. Three types of SODs are known in humans, with the most abundant being cytosolic SOD1, identified by its Cu, Zn-containing prosthetic group. The presence of these metals and the coordination to certain amino acids are essential for function. SODs are among the first line of defense in the detoxification of products resulting from oxidative stress. Here, we describe the importance of SOD function, and the need for coordination with other ROS-scavenging enzymes in this pathway of detoxification. The impact of metal-deficient diets (copper or zinc) or incorrect metal ion incorporation (copper chaperone for SOD) onto nascent SOD, are also examined. Finally, human pathologies associated with either SOD dysfunction or decreased activity are discussed with current progress on the development of novel therapies.

Suplementación con zinc para el tratamiento del acúfeno.
Dra. Paula Farías, Dra. Karina Bullo, Lic. Fonoaudiología Valeria Fabeiro, Dr. Jonathan Schain.

El acúfeno es el resultado de la lesión celular parcialmente irreversible en oído interno generado por distintas causas tales como daño acústico inducido por ruido (DAIR), presbiacusia, hipoacusia súbita e hipoacusia neurosensorial de otro origen (HANS). El Zinc es un cofactor de la enzima Superóxido Dismutasa I (SOD I) que modula el estrés oxidativo aumentado por el desbalance entre radicales libres dependientes del oxígeno y las enzimas neutralizantes de los mismos. Un aumento de radicales libres en el oído interno lleva a la disminución de las funciones celulares y al aumento de apoptosis.
El objetivo del trabajo es evaluar la suplementación con Zinc, asociado a vitamina C y vitamina D3, en el tratamiento del acúfeno de causa neurosensorial.

Effects of oral zinc supplementation on patients with noise-induced hearing loss associated tinnitus: A clinical trial.
Chun-Wei Yeh, Leng-Hsuan Tseng, Chao-Hui Yang, Chung-Feng Hwang .

Zinc plays a vital antioxidant role in human metabolism. Recent studies have demonstrated a correlation between noise-induced hearing loss (NIHL) and oxidative injury; however, no investigation has focused specifically on the subgroup of NIHL associated tinnitus patients. We aimed to evaluate the effectiveness of zinc supplementation in treating NIHL associated tinnitus.

Salicylate increased ascorbic acid levels and neuronal activity in the rat auditory cortex.
Qingchuan Duan, Furong Ma, Jie Zhang.

Importance: Clinical observations have implied a central origin for tinnitus and potential therapeutic effects of ascorbic acid (AA); however, the detailed mechanisms remain undetermined. Objective: To investigate changes in the AA levels and neural activity in the auditory cortex (AC) during salicylate-induced tinnitus. Methods: Rats were randomly divided into 3 groups: (1) saline group, which received an intraperitoneal saline injection; (2) SS group, which received an intraperitoneal sodium salicylate (SS) injection (350 mg/kg); and (3) SS+Lido group, which received an intraperitoneal SS injection (350 mg/kg) and lidocaine delivered to the AC by microdialysis. For each group, we firstly used an in vivo microdialysis technique to investigate the concentrations of AA in the AC; and secondly, we recorded the neural activity in the AC using a single-unit recording technique. Results: The AA concentration in the SS group significantly increased after SS injection, whereas that of the saline group did not change. The AA concentration in the SS+Lido group also showed an increasing trend but was significantly lower than that in the SS group. In the electrophysiological study, the spontaneous firing rate of the SS group was significantly higher than that of the saline group. In addition, the proportion of short interval discharges was also higher in the SS group than in the saline group. Both differences were reversed by lidocaine treatment. Interpretation: Our data suggest that the elevation of AA levels in the AC may be related to increased neuronal activity, which may represent the mechanism underlying salicylate-induced tinnitus.

The role of vitamin D in subjective tinnitus—A case-control study.
Magdalena Nowaczewska, Stanisław Osiński, Maria Marzec, Michał Wiciński, Katarzyna Bilicka, Wojciech Kaźmierczak.

Regarding the high prevalence of vitamin D (25(OH)D) deficiency in the population and its possible association with ear diseases, we aimed to investigate the 25(OH)Dserum level in patients with subjective, nonpulsating tinnitus and its effect on tinnitus severity. The study included 201 tinnitus patients and 99 controls. Patient clinical information, including tinnitus characteristics and severity according to Tinnitus Handicap Inventory (THI), loudness assessed by Visual Analogue Scale (VAS), audiometry, and the blood level of vitamin D, was recorded. The level of 25(OH)D in tinnitus patients was significantly decreased compared with the controls (19.86 ± 7.53 and 27.43 ± 8.85 ng/ml, respectively; P value < 0.0001). More patients in the tinnitus group were deficient in vitamin D, compared with the controls (50.7% vs. 22.2% respectively, p < 0.0001). Tinnitus patients with a lower serum level of 25(OH)D (≤15 ng/dl) were significantly younger, had a higher degree of tinnitus severity measured with THI and VAS scales, had higher triglyceride and TSH levels, and a lower HDL level compared with individuals who had higher 25(OH)D level (>15 ng/dl). There was a strong correlation between the 25(OH)D level and THI. Our findings suggest that a large proportion of tinnitus patients suffers from vitamin D deficiency and that the vitamin D level correlates with tinnitus impact. We recommend a vitamin D assessment for all tinnitus patients.

The Price of Immune Responses and the Role of Vitamin D in the Inner Ear.
Béla Büki, Heinz Jünger, Yan Zhang, Yunxia Wang Lundberg.

In this review the authors discuss evidence from the literature concerning vitamin D and temporal bone diseases (benign paroxysmal positional vertigo [BPPV], Menière’s disease [MD], vestibular neuritis, idiopathic facial paralysis, idiopathic acute hearing loss). Common features shared by Menière’s disease, glaucoma, and the possible influence by vitamin D are briefly discussed.