Cerebral glucose metabolism in type 1 diabetic patients

To evaluate whether cerebral glucose metabolism is impaired in diabetes the [18F]-2-deoxy-2-fluoro-D-glucose method and positron emission tomography were used to determine the regional cerebral metabolic rate of glucose in 12 healthy subjects, 8 newly diagnosed Type 1 diabetic patients 6 Type 1 diabetic subjects without peripheral neuropathy, and 7 Type 1 diabetic patients with symptomatic peripheral neuropathy, all of whom were men. In addition, multimodal evoked potentials were assessed. Cerebral glucose consumption was significantly reduced in the group with neuropathy as compared with the newly diagnosed diabetic patients and the healthy subjects (26.9 +/- 1.0 vs 33.9 +/- 1.9 and 32.5 +/- 1.1 mumol 100 g-1 min-1; p < 0.05), while in the patients without neuropathy it was 30.2 +/- 2.5 mumol 100 g-1 min-1 (NS vs the remaining groups). There were no significant differences between the groups regarding brainstem auditory and visual evoked potentials. No relationship was noted between cerebral glucose metabolism and P300 latency of event-related potentials as an index of cognitive function, but there was an inverse correlation with age (r = -0.42; p < 0.05) and duration of diabetes (r = -0.67; p < 0.05). These results suggest that cerebral glucose metabolism is normal at the time of diagnosis of Type 1 diabetes, but may become altered with both increasing duration of diabetes and age in the absence of central conduction deficits or cognitive dysfunction. Diabetic neuropathy may constitute a possible additional correlate of reduced cerebral glucose consumption.