Treatment of diabetes by transplantation of drug-inducible insulin-producing gut cells.

Most patients with type 1 diabetes rely on multiple daily insulin injections to maintain blood glucose control. However, insulin injections carry the risk of inducing hypoglycemia and do not eliminate diabetic complications. We sought to develop and evaluate a regulatable cell-based system for delivery of insulin to treat diabetes. We generated two intestinal cell lines in which human insulin expression is controlled by mifepristone. Insulin mRNA expression was dependent on the mifepristone dose and incubation time and cells displayed insulin and C-peptide immunoreactivity and glucose-induced insulin release following mifepristone treatment. Cell transplantation followed by mifepristone administration reversed streptozotocin (STZ)-induced diabetes in mice, and this effect was dependent on the mifepristone dose delivered. These data support the notion that engineering regulatable insulin expression within a cell already equipped for regulated secretion may be efficacious for the treatment of insulin-dependent diabetes.

YZGD from Paenibacillus thiaminolyticus, a pyridoxal phosphatase of the HAD (haloacid dehalogenase) superfamily and a versatile member of the Nudix (nucleoside diphosphate x) hydrolase superfamily.

YZGD from Paenibacillus thiaminolyticus is a novel bifunctional enzyme with both PLPase (pyridoxal phosphatase) and Nudix (nucleoside diphosphate x) hydrolase activities. The PLPase activity is catalysed by the HAD (haloacid dehalogenase) superfamily motif of the enzyme, and the Nudix hydrolase activity is catalysed by the conserved Nudix signature sequence within a separate portion of the enzyme, as confirmed by site-directed mutagenesis. YZGD's phosphatase activity is very specific, with pyridoxal phosphate being the only natural substrate, while YZGD's Nudix activity is just the opposite, with YZGD being the most versatile Nudix hydrolase characterized to date. YZGD's Nudix substrates include the CDP-alcohols (CDP-ethanol, CDP-choline and CDP-glycerol), the ADP-coenzymes (NADH, NAD and FAD), ADP-sugars, TDP-glucose and, to a lesser extent, UDP- and GDP-sugars. Regardless of the Nudix substrate, one of the products is always a nucleoside monophosphate, suggesting a role in nucleotide salvage. Both the PLPase and Nudix hydrolase activities require a bivalent metal cation, but while PLPase activity is supported by Co2+, Mg2+, Zn2+ and Mn2+, the Nudix hydrolase activity is Mn2+-specific. YZGD's phosphatase activity is optimal at an acidic pH (pH 5), while YZGD's Nudix activities are optimal at an alkaline pH (pH 8.5). YZGD is the first enzyme reported to be a member of both the HAD and Nudix hydrolase superfamilies, the first PLPase to be recognized as a member of the HAD superfamily and the first Nudix hydrolase capable of hydrolysing ADP-x, CDP-x and TDP-x substrates with comparable substrate specificity.