Researchers Explore Non-diabetic Insulin Resistance in Friedreich’s Ataxia

Although Friedreich’s ataxia is a condition with a known cause (a genetic abnormality on chromosome 9 that depletes cells of frataxin protein), some cases of the disease throw clinicians a curve ball. Such was the case for one 48-year-old man with a known diagnosis of Friedreich’s ataxia. He was admitted for care after experiencing swelling in his lower extremities and an abnormal echocardiogram. In the end, clinicians identified he had insulin resistance despite his non-diabetic status.

“Even non-diabetic patients suffering from other diseases with insulin resistance due reduction in affinity of insulin receptors or membrane abnormality could surprise us as in our case,” wrote the authors of the case study, published in Indian Journal of Nuclear Medicine. The authors, Drs. Sushanti Patil and Vikram Lele, of the Jaslok Hospital and Research Center in Mumbai, needed to piece together why the man was experiencing poor cardiac symptoms.

Working off of the man’s medical history of hypertension, obesity, dyslipidemia, and myocardial infarction, his clinicians ordered a positron emission tomography (PET) scan to obtain a functional image that could provide insight to his state of cardiac metabolism. During the procedure, oral glucose administration resulted in high blood glucose levels even after insulin injection. Only after a total of eight units IV insulin did his blood glucose level return to a normal 123 mg/dl.

Continuing with the procedure, the clinicians administered fluorodeoxyglucose and used tetrofosmin images to visualize the man’s heart. The heart was not taking up fluorodeoxyglucose adequately, and there was a severe perfusion defect in the wall of the heart.

This case, among many other cases of Friedreich’s ataxia, exemplifies how multiple organ systems can be affected by the disease — not just the nervous system, which experiences degeneration over time. Indeed, the heart and pancreas are affected by Friedreich’s ataxia, resulting in heart problems and diabetes. However, even non-diabetic patients such as the subject under study can experience insulin resistance. This is a result of poor insulin receptor affinity for insulin due to abnormalities in the cell membrane. The heart is especially affected by glucose metabolism due to its heavy daily energy requirements. Fortunately, most heart problems and insulin metabolism deficits that occur as a result of Friedreich’s ataxia can be treated.