Mutations in mitochondrial tRNA genes have been shown to be associated with maternally inherited syn-dromic and non-syndromic deafness. Among those, mutations such as tRNALeu(UUR) 3243A>G associated with syndromic deafness are often present in heteroplasmy, and the non-syndromic deafness-associated tRNA mu-tations including tRNASer(UCN) 7445A>G are often in homoplasmy or in high levels of heteroplasmy. These tRNA mutations are the primary factors underlying the development of hearing loss. However, other tRNA mutations such as tRNAThr 15927G>A and tRNASer(UCN) 7444G>A are insufficient to produce a deafness phe-notype, but always act in synergy with the primary mitochondrial DNA mutations, and can modulate their phenotypic manifestation. These tRNA mutations may alter the structure and function of the corresponding mitochondrial tRNAs and cause failures in tRNAs metabolism. Thereby, the impairment of mitochondrial protein synthesis and subsequent defects in respiration caused by these tRNA mutations, results in mitochon-drial dysfunctions and eventually leads to the development of hearing loss. Here, we summarized the deaf-ness-associated mitochondrial tRNA mutations and discussed the pathophysiology of these mitochondrial tRNA mutations, and we hope these data will provide a foundation for the early diagnosis, management, and treatment of maternally inherited deafness.

Objective To study the influence of Jiang Tang Fang Long formula on insulin production and function in an animal model of diabetic hearing loss. Methods Wistar rats (n=60) were randomly divided into 6 groups (10 in each) to receive no treatment (the normal control, Group A), or to receive intra-peritoneal 55 mg/kg streptozotocin with (Groups C, D and E) or without (Group B) subsequent Jiang Tang Fang Long formula treatment at various doses or Yu Long Wan treatment (Group F). After 60 days, fasting blood glucose (FBG), body weight (BW) and fasting insulin (FINS) were recorded and the HOMA-IR and HOMA-βcalcu-lated. Insulin expression in pancreatic tissues was measured by radioimmunoassay. Results Compared with animals that received streptozotocin without rescue treatment (Group B), animals that received higher doses of Jiang Tang Fang Long formula(Groups D and E) showed improved indices of diabetes manifestation (P<0.05) and improved HOMA-β(P<0.05) in a dose-dependent manner, as well as improved insulin expression in pancreatic islets (P<0.05). The difference between low dose Jiang Tang Fang Long formula treatment (Group C) and Group B was not significant (P>0.05). Conclusion Our results suggest that Jiang Tang Fang Long formula may improve pancreatic β-cells function which may explain its efficacy in treating diabetic hearing loss.