Glucose tolerance in patients with narcolepsy

Abstract

Study objectives: Obesity is a common feature of narcolepsy. In addition, an increased occurrence of non-insulin dependent diabetes has been reported. So far, it is not known whether glucose metabolism in narcolepsy is disturbed due to, or independently of obesity.

Design: Case-control study.

Setting: Sleep medicine clinic at a research institute.

Patients: We studied 17 patients with narcolepsy/cataplexy compared to 17 healthy controls matched for age, sex, and body mass index (BMI).

Interventions: A 75-g oral glucose tolerance test was performed.

Measurements: Glucose tolerance was determined by computing plasma glucose curve following oral glucose challenge for 240 minutes; insulin sensitivity and insulin secretion by homeostasis model assessment and minimal model analysis.

Results: Standard outcome measures and indices of the oral glucose tolerance test did not differ between the patient group and the group of control subjects.

Conclusions: In this study, no clinically relevant pathologic findings in the glucose metabolism of narcoleptic patients compared to weight matched controls were found. Thus, narcolepsy is unlikely to be a risk factor per se for impaired glucose tolerance or diabetes.

Keywords: Narcolepsy; hypersomnia; hypocretin; metabolism; orexin.

Figures

Figure 1

Mean plasma glucose levels in patients with narcolepsy and control participants during the oral glucose tolerance test (OGTT). Error bars represent SD. There were no significant differences between groups in the sample. To convert glucose to mg/dl, multiply by 18.0182.

Figure 2

Mean plasma glucose levels in patients with narcolepsy and matched control participants during the oral glucose tolerance test (OGTT). (A) Orexin deficient patients (4 f, 8 m). (B) Drug free patients (3 f, 6 m). Error bars represent SD. There were no significant differences between groups in the samples. To convert glucose to mg/dl, multiply by 18.0182.