 Various transport proteins are involved in the transport of thiamine monophosphate TMP and TPP across membranes. These include thiamine transported isoform-1 THTR1 and thiamine transporter isoform-2 THTR2, reduced folate carrier-1 RFC-1, which transports TMP and TPP across cell plasma membranes and the mitochondrial TPP transporter mTHTR. Thiamine and TMPTPP transporters may have abnormal expression in diabetes. Increased THTR1 levels are found in red blood cells RBCs and mononuclear leucocytes of patients with diabetes compared to those of healthy subjects. RBC precursors and leucocytes appeared to up-regulate THTR1 expression in response to decreased thiamine availability. In the presence of hyperglycemia, renal tubular epithelial cells, by contrast, have decreased expression. In both experimental models of diabetes and in human diabetics increased clearance of thiamine has been demonstrated. This precedes the development of microalbuminuria. Patients with microalbuminuria and early decline in glomerular filtration rate had higher fractional excretion of thiamine compared to patients with stable renal function. 