Pioglitazone, a peroxisome proliferator activatorreceptor gamma (PPAR-γ) agonist, is an effectiveoral antidiabetic agent. However in recent years,its use is decreasing due to concerns of edema,heart failure, bone fractures and possible risk forbladder cancer. Pioglitazone causes conversionof pre-adipocytes to adipocytes and has beenshown to cause compressive symptoms inconfined spaces like orbit. Carpal tunnel is aclosed space with presence of fatty tissue and itis possible that treatment with pioglitazone candecelerate nerve conduction of the median nerve.To evaluate the impact of pioglitazone on mediannerve electrophysiology in carpal tunnel in type2 diabetes patients, two matched groups of type2 diabetes patients, treated with oral drugs,categorized under pioglitazone or non-pioglitazone group (14 in each group) wereselected. The study was conducted inVivekananda Institute in Medical Sciences andcould only see the light of the day by a generousunrestricted scientific grant by VIMS.Electrophysiological evaluation by nerveconduction velocity of median nerve in the carpaltunneand ulner nerve was done at baseline and3 months.
Results: Majority (54.84%) of our patients withtype 2 diabetes, who underwent NCV testing,although asymptomatic, had electro-physiologically proven carpal tunnel syndrome.This is in conformity to earlier internationalstudies. At 3 months, pioglitazone-category hadinferior amplitude in sensory median nerve butnon-pioglitazone category displayed ameliorationin amplitude in sensory and motor median nerve.There was amelioration of terminal latency insensory ulnar nerve for pioglitazone group. Thustreatment with pioglitazone accentuatesprobability of compressive neuropathy. In spiteof comparable glycemic control over 3 months,patients treated with pioglitazone showedsuperior electrophysiological parameters for theulnar nerve.
Pioglitazone thus appeared to have a beneficialeffect on nerve electrophysiology which wasnullified when the nerve was exposed toentrapment neuropathy.
In conclusion the high prevalence ofasymptomatic CTS in Indian patients, is a novelfinding. The study generates the hypothesis thattype 2 diabetes patients on pioglitazone are atrisk of compressive neuropathy, the pathogenesisof which is established. But the intriguing andunexpected feature of the study was theimprovement in ulnar nerve electrophysiologicalparameters in patients who received pioglitazone,although the glycemic control of these patientswas similar to those not on pioglitazone. Thuspioglitazone has favourable outcome in nerveelectrophysiology which was repealed when thenerve was subjected to compressive neuropathy.Further randomized controlled trials, are neededto establish the role of pioglitazone in diabeticneuropathy.