Blood-brain barrier glucose transporter mRNA is increased in experimental diabetes mellitus

The blood-brain barrier (BBB) glucose transporter activity in vivo is known to be down-regulated in experimental diabetes mellitus. To determine whether parallel changes in BBB glucose transporter mRNA levels occur in experimental diabetes we isolated brain microvessels, which make up the BBB in vivo, from both control and experimental diabetic rats. Microvessel RNA fractions were isolated by cesium chloride density gradient centrifugation and were applied to 1.1% agarose gels for Northern blotting. The blots were probed with [32P]-labeled cDNAs corresponding to the rat brain glucose transporter and a cDNA to alpha-actin was used to monitor the transcript level of a typical housekeeping gene. The study was repeated three times and, in all cases, the BBB glucose transporter mRNA level was increased in experimental diabetes relative to control rats. These studies suggest that factors associated with experimental diabetes mellitus in rats lead to either an increased transcription or a decreased degradation of brain capillary glucose transporter mRNA.