Insulin Resistance: Common but Often Undetected in Parkinson Disease

As many as 6 of 10 nondiabetic persons with Parkinson disease (PD) may have insulin resistance (IR) despite having normal blood glucose levels, according to the results of a new study.¹ The findings suggest that IR in PD is a common and largely undiagnosed problem, especially in patients who are overweight.

Reduced glucose tolerance has long been recognized as a potential risk factor for PD, and study of its role in the pathology of neurodegeneration has been increasing. The key link between appears to be IR, but its prevalence in PD is unknown.

“There is growing interest in the study of this relationship and the use of diabetes medications in the treatment of PD. However, there is little information regarding the prevalence of insulin resistance in PD,” lead investigator Michele Tagliati, MD, at Cedars-Sinai Medical Center in Los Angeles, said in a press release.² “This study is the first to address this question in a large population of nondiabetic patients.”

The study enrolled 154 nondiabetic patients with PD, all of whose fasting blood glucose and insulin levels were assessed to correlate IR with other metabolic indicators, motor and nonmotor symptoms of PD, and quality of life. Using the homeostatic model assessment (HOMA) index, they determined how many of participants had a reduced response to their own insulin. Their body mass index and other measurements were recorded, and their movement and cognitive performance were measured.

The results showed that 58.4% of the participants had undiagnosed IR despite having a normal fasting glucose level and, in many cases, a normal glycated hemoglobin level. These findings confirmed those of previous studies that IR is more than double in obese persons. Nevertheless, the investigators found a substantially higher percentage (41%) of nonobese PD patients with IR. They found no correlation between IR and cognitive decline.

These findings not only could lead to increased screening of PD patients to detect and correct IR, but also could allow for personalized medicine in which PD patients with IR may be treated with medications targeted to reverse the condition.²

—Michael Gerchufsky

References:

1. Hogg E, Athreya K, Basile C, Tan EE, Kaminski J, Tagliati M. High prevalence of undiagnosed insulin resistance in non-diabetic subjects with Parkinson’s disease. J Parkinsons Dis. 2018;8(2):259-265. doi:10.3233/JPD-181305.
2. Insulin resistance under-diagnosed in non-diabetics with Parkinson’s disease [news release]. Amsterdam, Netherlands: IOS Press; August 3, 2018. https://www.iospress.nl/ios_news/insulin-resistance-under-diagnosed-in-non-diabetics-with-parkinsons-disease/. Accessed August 16, 2018.