In a paper entitled "High prevalence of low plasma thiamine concentration in diabetes linked to a marker of vascular disease", published in Diabetologia on 4th August, the team found that thiamine concentration in blood plasma was decreased 76% in type 1 diabetic patients and 75% in type 2 diabetic patients.
http://www2.warwick.ac.uk/newsandevents/pressreleases/researchers_find_vitamin/
When we experience a hyperglycemic event this flow diagram shows the four pathways that lead to diabetic complications.
It is remarkable that these effects were achieved by increasing the dietary availability of thiamine to diabetic rats by as little as 20 times the minimum daily allowance – although this was sufficient to prevent thiamine deficiency.
http://www.uninet.edu/cin2003/conf/thornalley/thornalley.html
This flow diagram shows the pentosephosphate pathway being utilized when thiamine is available.