Ray has written on the benefit of niacinamide in treating some cases of Type I diabetes, and I think I posted some studies in France where high dose niacinamide reversed early onset Type I diabetes in children. It looks like combining it with B6 may have additive effects.
http://www.ncbi.nlm.nih.gov/pubmed/23001013
"...Pyridoxine treatment restored diabetes induced alterations in dopamine D(1), D(2) receptors, Insulin receptor, IGF-1, GLUT-3 gene expressions in striatum compared to diabetic rats...Our results suggest the potential role of pyridoxine supplementation in ameliorating diabetes mediated dysfunctions in striatal dopaminergic receptor expressions and insulin signaling. Thus pyridoxine has therapeutic significance in diabetes management."
http://www.ncbi.nlm.nih.gov/pubmed/23001013
"...Pyridoxine treatment restored diabetes induced alterations in dopamine D(1), D(2) receptors, Insulin receptor, IGF-1, GLUT-3 gene expressions in striatum compared to diabetic rats...Our results suggest the potential role of pyridoxine supplementation in ameliorating diabetes mediated dysfunctions in striatal dopaminergic receptor expressions and insulin signaling. Thus pyridoxine has therapeutic significance in diabetes management."