Insulin resistance due to dietary iron overload disrupts inner hair cell ribbon synapse plasticity in male mice.

Abstract

To evaluate whether cochlear inner hair cells (IHCs) ribbon synapse plasticity would be interrupted by insulin resistance (IR) due to dietary iron overload, we established an IR model in C57Bl/6 male mice with an iron-enriched diet for 16 weeks. Glucose levels were measured at weeks 4, 8, 12, 16. Glucose tolerance test and insulin tolerance test were performed at week 16 after overnight fasting. Then, auditory brainstem responses (ABRs) measurements were performed for hearing threshold shifts. After ABR measurements, cochleae were harvested for assessment of the number of IHC ribbon synapses by immunostaining, the morphology of cochlear hair cells and spiral ganglion neurons (SGNs) by transmission electron microscopy or immunostaining. Here, we show that IR due to dietary iron overload decreased the number of ribbon synapses, and induced moderate ABR threshold elevations. Besides, additional components including outer hair cells (OHCs), IHCs, and SGNs were unaffected. Moreover, IR did not disrupt the expression of vesicular glutamate transporter 3 (VGLUT3), myosin VIIa and prestin in hair cells. These results indicate that IHC ribbon synapses may be more susceptible to IR due to dietary iron overload.

• Authors: Fei Yu, Shuai Hao, Bo Yang, Yue Zhao, Rui Zhang, Wenyue Zhang, Jun Yang, Jie Chen
• Journal: Neuroscience letters (Neurosci Lett) Vol. 597 Pg. 183-8 (Jun 15 2015) ISSN: 1872-7972 [Electronic] Ireland
• PMID: 25956034 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Amino Acid Transport Systems, Acidic
• Iron, Dietary
• Molecular Motor Proteins
• Myo7a protein, mouse
• Myosin VIIa
• Pres protein, mouse
• vesicular glutamate transporter 3, mouse
• Myosins

Topics

• Amino Acid Transport Systems, Acidic (metabolism)
• Animals
• Evoked Potentials, Auditory, Brain Stem
• Hair Cells, Auditory, Inner (physiology)
• Insulin Resistance
• Iron Overload (metabolism, physiopathology)
• Iron, Dietary (administration & dosage)
• Male
• Mice, Inbred C57BL
• Molecular Motor Proteins (metabolism)
• Myosin VIIa
• Myosins (metabolism)
• Neuronal Plasticity
• Synapses (physiology)