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August 17, 2015
Long-Term Omega-3 Fatty Acid Supplementation Prevents Expression Changes in Cochlear Homocysteine Metabolism and Ameliorates Progressive Hearing Loss in C57BL/6J Mice

Raquel Martínez-Vega, Teresa Partearroyo, Néstor Vallecillo, Gregorio Varela-Moreiras, María A. Pajares, Isabel Varela-Nieto
The Journal of Nutritional Biochemistry
doi: 10.1016/j.jnutbio.2015.07.011


Omega-3 polyunsaturated fatty acids (PUFAs) are essential nutrients well-known for their beneficial effects, among others on cognitive development and maintenance, inflammation and oxidative stress. Previous studies have shown an inverse association between high plasma levels of PUFAs and age-related hearing loss, and the relationship between low serum folate and elevated plasma homocysteine levels and hearing loss. Therefore, we used C57BL/6J mice and long-term omega-3 supplementation to evaluate the impact on hearing by analyzing their auditory brainstem response (ABR) and distortion product otoacustic emissions (DPOAE) thresholds. The omega-3 group showed significantly lower ABR hearing thresholds (~25 dB SPL) and higher DPOAE amplitudes in mid-high frequencies, when compared to the control group. These changes did not correlate with alterations between groups in plasma homocysteine or serum folate levels as measured by HPLC and a microbiological method, respectively. Ageing in the control group was associated with imbalanced cytokine expression toward increased pro-inflammatory cytokines as determined by RT-qPCR; these changes were prevented by omega-3 supplementation. Genes involved in homocysteine metabolism showed decreased expression during ageing of control animals, and only alterations in Bhmt and Cbs were significantly prevented by omega-3 feeding. Western blotting showed that omega-3 supplementation precluded the CBS protein increase detected in 10 month-old controls, but also produced an increase in BHMT protein levels. Altogether, the results obtained suggest a long-term protective role of omega-3 supplementation on cochlear metabolism and progression of hearing loss.