Utilizing prestin as a predictive marker for the early detection of outer hair cell damage.

PURPOSE: To evaluate prestin as a biomarker for the identification of early ototoxicity. MATERIALS AND METHODS: Rats (n = 47) were randomly assigned to five groups: low-dose (LAG) or high-dose (HAG) amikacin (200 and 600 mg/kg/day, respectively, for 10 days), low-dose (LCIS)or high-dose (HCIS) cisplatin (single doses of 5 and 15 mg/kg, respectively, for 3 days), and control (n = 8). At the end of the experiment, measurement of distortion product-evoked otoacoustic emissions (DPOAE) were performed to evaluate hearing, then blood samples and both ear tissues were collected under anesthesia. Prestin levels were determined by ELISA. Cochlear damage was evaluated histologically using a 4-point scoring system. RESULTS: The mean serum prestin levels were 377.0 ±â€¯135.3, 411.3 ±â€¯73.1, 512.6 ±â€¯106.0, 455.0 ±â€¯74.2 and 555.3 ±â€¯47.9 pg/ml for control, LCIS, HCIS, LAG and HAG groups, respectively. There was significant difference between prestin levels of Control-LCIS-HCIS groups (p = 0.031) and prestin levels of Control-LAG-HAG groups (p = 0.003). There were also significant differences in prestin levels between the low- and high-dose cisplatin and amikacin groups (p = 0.028 and p = 0.011, respectively). Each group had significantly lower DPOAE results at 4, 6 and 8 kHz than control groups (p < 0.001). The LAG, HAG, LCIS and HCIS groups had significantly higher cochlear damage scores than the control group (p < 0.05). CONCLUSIONS: Higher doses of cisplatin and amikacin were associated with the greatest increases in serum prestin level and cochlear damage score. The results of this study suggest that prestin is a promising early indicator of cochlear damage.

Cochlear dysfunction in type 2 diabetes: a complication independent of neuropathy and acute hyperglycemia.

The effects of type 2 diabetes on evoked otoacoustic emissions (e-OAEs) elicited by clicks in subjects with normal hearing and the involvement of the central (CNS) and peripheral nervous system and acute hyperglycemia were investigated. In study 1, 110 type 2 diabetic patients and 106 control subjects matched for age and gender were investigated by e-OAEs. Central and peripheral neuropathy were evaluated respectively by auditory brainstem responses (ABRs) and according to San Antonio Consensus Conference criteria. In study 2, 10 healthy and 10 type 2 diabetic men matched for age, all with normal e-OAEs, underwent a 5-hour hyperglycemic clamp study. e-OAE tests were performed before and during the hyperglycemic clamp. In study 1, e-OAEs were impaired in 51.8% (57 of 110) of the diabetic subjects, in comparison to 4.7% (five of 106) of the control group (P < .0001). Diabetics with impaired e-OAEs (e-OAEs-), in comparison to those with normal e-OAEs (e-OAEs+), were older (51.0+/-5.8 v 45.1+/-6.0 years, P < .001), had diabetes longer (11.5+/-4.4 v 7.0+/-3.9 years, P < .001), achieved poorer metabolic control as judged by hemoglobin A1c ([HbA1c] 6.9%+/-0.4% v 6.5%+/-0.3%, P < .001), and had more peripheral neuropathy (46% v 23%, P < .02). No difference was observed between e-OAEs- and e-OAEs+ subjects for retinopathy or nephropathy. Nevertheless, when the duration of diabetes was corrected by multiple regression analysis, the correlation between sensorineural damage and peripheral neuropathy lost significance (P = .12). Diabetic groups (e-OAEs+ and e-OAEs-) showed greater latency in waves I, III, and V and greater interwave latency for waves I to V than the control group, but there was no significant difference in ABRs between e-OAEs+ and e-OAEs- subjects. In study 2, there were no significant changes in e-OAE intensities compared with basal values during the entire hyperglycemic clamp in either type 2 diabetic or control subjects. No difference was observed between the two groups at each time of the clamp. Thus, type 2 diabetic subjects show a higher rate of compromised e-OAEs than healthy individuals. The e-OAE dysfunction does not associate with either an injury to the auditory nervous pathway or diabetic microvasculopathy. The apparent interference of peripheral neuropathy in e-OAEs loses significance when corrected for the duration of diabetes.

Antibodies to glycosphingolipid antigens in patients with immune-mediated cochleovestibular disorders.

HYPOTHESIS: To determine the presence of antibodies against the glycosphingolipid antigen sulfated glucuronic lactosominyl paragloboside (SGLPG) in the sera of patients suspected of immune-mediated cochleovestibular disorders (IMCVD). BACKGROUND: Glycospingolipids are molecules present on the surface of normal nerve cells and are considered antigenic. Previous studies have isolated these antigens in vestibular neuroepithelia, cochleovestibular nerves and endolymphatic sacs. METHODS: The sera of 22 patients suspected of IMCVD were tested for antibodies against the antigen SGLPG. Thin-layer chromatography-immunostaining method was used. RESULTS: Antibody titers were elevated in 63.6% of patients tested. Statistical significance (p < 0.0001) was achieved since reactivity was seen in only 7% of 43 age-matched healthy controls. CONCLUSIONS: Antibodies to SGLPG antigens are present in some patients with IMCVD. Because SGLPD antigens have been previously isolated in the inner ear and the cochleovestibular nerve, these structures can potentially become targets for anti-SGLPG antibodies.