Study summary · research use only
Multiple dosing strategies with acetyl L-carnitine (ALCAR) fail to alter age-related hearing loss in the Fischer 344/NHsd rat
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
In this rat study, the authors tested acetyl L-carnitine (ALCAR) on age-related hearing loss in the Fischer 344/NHsd rat, which they describe as undergoing progressive high-frequency hearing loss from age 12 months linked to outer hair cell defects and mitochondrial oxidative stress. Three dosing paradigms were used: 24-month-old rats given ALCAR (100 mg/kg, 25 mg/ml in saline) by IP injection daily for one month; 18-month-old rats given ALCAR (100 mg/kg) by oral gavage for 90 days; and 15-month-old rats given ALCAR (100 mg/kg) by gavage for 90 days. Hearing was evaluated by auditory brainstem responses. The abstract reports that hearing thresholds of ALCAR-treated animals were never significantly different from matched controls at any of five test stimuli (5, 10, 20, 40 kHz tone bursts and a click).
Abstract
The Fischer 344/NHsd rat undergoes age-related, progressive, high-frequency hearing loss beginning at age 12 months. The loss has been linked to defects/death in the outer hair cells related to oxidative stress originating in the mitochondria. Acetyl L-carnitine (ALCAR) is known to enhance mitochondrial bioenergetics and membrane efficiency. Therefore, ALCAR was targeted as a possible pharmacologic intervention to prevent, or even restore, hearing loss from aging. Three different paradigms were used to deliver ALCAR to aging Fischer 344/NHsd rats. Rats in each condition had their hearing evaluated by auditory brainstem responses before, during, and after treatment. First, 24-month-old rats were given ALCAR (100 mg/kg dissolved 25 mg/ml in saline) by IP injection daily for one month. Second, 18-month-old rats were given ALCAR (100 mg/kg) by oral gavage for 90 days. Third, 15-month-old rats were given ALCAR (100 mg/kg) by oral gavage for 90 days. Control rats in each condition received saline by i.p. injection or gavage. Hearing thresholds of the three sets of ALCAR-treated animals were never significantly different from their matched controls before, during, or after the treatments at any of the five test stimuli (5, 10, 20, and 40 kHz tone bursts and a click). The current study does not provide evidence that age-related hearing loss in the Fischer 344/NHsd rat can be altered with systemic administration of ALCAR.
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