Glucose and insulin concentration patterns in cerebrospinal fluid following intravenous glucose injection in humans

The glucose and insulin (IRI) concentration pattern in both peripheral venous blood and cerebrospinal (CSF) were studied in 10 normal weight non-diabetic subjects after glucose load of 0.33 g/kg injected intravenously. A significant increase of glucose induced IRI-response with an IRI-peak concentration after 5 min was found in the peripheral venous blood whereas no changes in both glucose and IRI-levels of the CSF occurred. The basal IRI-CSF-concentration (4.08 +/- 0.6 muU/ml) was five times lower in comparison to the level measured in the venous blood and remained unchanged over the 15 min period of observation. There were not any correlations between peripheral venous blood and CSF concerning the glucose and IRI concentration. The physiological significance of the low insulin concentration in CSF and the delay in the passage of this hormone in CSF is still unclear.