Hourly analysis of cerebrospinal fluid glucose shows large diurnal fluctuations.

Cerebrospinal fluid analysis is important in the diagnostics of many neurological disorders. Since the influence of food intake on the cerebrospinal fluid glucose concentration and the cerebrospinal fluid/plasma glucose ratio is largely unknown, we studied fluctuations in these parameters in healthy adult volunteers during a period of 36 h. Our observations show large physiological fluctuations of cerebrospinal fluid glucose and the cerebrospinal fluid/plasma glucose ratio, and their relation to food intake. These findings provide novel insights into the physiology of cerebral processes dependent on glucose levels such as energy formation (e.g. glycolysis), enzymatic reactions (e.g. glycosylation), and non-enzymatic reactions (e.g. advanced endproduct glycation).