Glucose-regulated insulin expression in diabetic rats

Retroviral vectors encoding glucose-responsive promoters driving furin expr ession may provide an amplified, glucose-regulated secretion of insulin. We constructed LhI*TFSN virus to encode a glucose-regulatable transforming gr owth factor alpha promoter controlling furin expression with a viral LTR pr omoter driving constitutive expression of furin-cleavable human proinsulin, Autologous BE rat vascular smooth muscle cells transduced with LhI*TFSN vi rus and cultured in 1.7 and 16.7 mM glucose secreted 50.7 +/- 3.2 and 136.0 +/- 11.0 muU (mean +/- SD) of insulin per 10(6) cells per day, respectivel y. After the onset of diabetes spontaneously diabetic congenic DR lyp/lyp B B rats received stomach implants containing 2 x 10(6) LhI*TFSN-transduced p rimary rat vascular smooth muscle cells. In eight treated rats there was a major reduction in insulin requirement to as low as 25% of pretreatment lev el for up to 3 months and one rat became insulin free without hypoglycemia, Intraperitoneal glucose tolerance tests (IPGTTs) in diabetic rats receivin g control implants did not show the characteristic decline in blood glucose of normal rats after glucose administration. In contrast, diabetic rats re ceiving LhI*TFSN-transduced cells showed significant clearances of blood gl ucose. These data suggest clinically significant levels of glucose-regulate d insulin delivery from implanted vascular smooth muscle cells transduced w ith LhI*TFSN vector.