Prevalence of Hearing Loss in Type 2 Diabetes Mellitus and Its Association with Severity of Diabetic Neuropathy

Purpose This study assessed the prevalence of hearing loss (HL) in patients with Type 2 Diabetes (T2DM) and its relationship with the presence and severity of diabetic neuropathy. Methods Patients between the ages of 30 to 60 years (both ages inclusive) with T2DM were recruited and divided into three groups. Group 1 included patients without neuropathy. Group 2 had patients with mild neuropathy. Group 3 had patients with moderate and severe neuropathy. After informed consent hearing threshold was assessed using pure tone audiometry (PTA). Results Of the 200 patients recruited, the prevalence of hearing loss was overall 81%. The prevalence was 66.7% in group 1, 80.9% in group 2 and 87.6% in group 3 (p=0.009). Among patients with moderate to severe neuropathy (group 3) 33.3% had clinically significant hearing loss (p=0.015). Age, gender, presence of neuropathy and severity of neuropathy were associated with increased risk of developing hearing loss. Severity of hearing loss worsened with increase in severity of neuropathy. Conclusions Age, gender and severity of neuropathy were associated with increased risk of developing hearing loss. Screening for hearing loss in patients with moderate to severe diabetic neuropathy using self-report questionnaires can help in timely diagnosis and treatment.

Rolipram and Pentoxifylline Combination Ameliorates Experimental Diabetic Neuropathy Through Inhibition of Oxidative Stress and Inflammatory Pathways in the Dorsal Root Ganglion Neurons

Diabetic neuropathy (DN) is the most challenging microvascular complication of diabetes and there is no suitable treatment for it, so the development of new agents to relieve DN is urgently needed. Since oxidative stress and inflammation play an essential role in the development of DN, clearance of these factors are good strategies for the treatment of this disease. According to key role of cyclic adenosine monophosphate (cAMP) in the regulation of oxidative stress and inflammatory pathways, it seems that phosphodiesterase inhibitors (PDEIs) can be as novel drug targets for improving DN through enhancement of cAMP level. The aim of this study was to evaluate the effects of rolipram, a selective PDE4 inhibitor, and pentoxifylline, a general PDE inhibitor on experimental model of DN and also to determine the possible mechanisms involved in the effectiveness of these agents. We investigated the effects of rolipram (1mg/kg) and pentoxifylline (100 mg/kg) and also combination of rolipram (0.5 mg/kg) and pentoxifylline (50 mg/kg), orally for five weeks in rats that became diabetic by STZ (55 mg/kg, i.p.). After treatments, motor function was evaluated by open-field test, then rats were anesthetized and dorsal root ganglion (DRG) neurons isolated. Next, oxidative stress biomarkers and inflammatory factors were assessed by biochemical and ELISA methods, and RT-PCR analysis in DRG neurons. Rolipram and/or pentoxifylline treatment significantly attenuated DN – induced motor function deficiency by modulating distance moved and velocity. Rolipram and/or pentoxifylline treatment dramatically increased the cAMP level, as well as suppressed DN – induced oxidative stress which was associated with decrease in LPO and ROS and increase in TAC, total thiol, CAT and SOD in DRG neurons. On the other hand, the level of inflammatory factors (TNF-α, NF-kB and COX2) significantly decreased following rolipram and/or pentoxifylline administration.The maximum effectiveness was with rolipram and/or pentoxifylline combination on mentioned factors.These findings provide novel experimental evidence for further clinical investigations on rolipram and pentoxifylline combination for the treatment of DN.