A clinical mutation in glucokinase causing maturity-onset diabetes in the young type 2 increases enzyme activity.

Glucokinase (GCK) is the pancreatic ß-cell glucose sensor, and its kinetics are key to that purpose. A slow transition step, displayed as non-hyperbolic kinetics, and a low affinity for glucose characterize GCK. Mutations in GCK associated with maturity-onset diabetes of the young type 2 (MODY2) previously described reduce the functionality of the human pancreatic ß-cell, leading to diabetic clinical phenotypes. We present a kinetic characterization of the G448D mutation identified in a MODY2 patient, which is one of the first mutations to exhibit increased functionality. This mutant displays increased activity, high affinity for both Mg2+ -ATP and glucose, hyperbolic kinetics and increased phosphorylation potential. Hyperbolic kinetics and assays in the presence of glycerol indicate that G448D lacks the slow transition step crucial for the pancreatic ß-cell glucose sensor function.

Congenital diaphragmatic hernia: phosphodiesterase-5 and Arginase inhibitors prevent pulmonary vascular hypoplasia in rat lungs.

BACKGROUND: Severe pulmonary hypoplasia related to congenital diaphragmatic hernia (CDH) continues to be a potentially fatal condition despite advanced postnatal management strategies. OBJECTIVE: To evaluate the effect of the antenatal sildenafil and 2(S)-amino-6-boronohexanoic acid (ABH-Arginase inhibitor) on lung volume, pulmonary vascular development, and nitric oxide (NO) synthesis in a Nitrofen-induced CDH rat model. METHODS: Nitrofen-induced CDH rat model was used. Nitrofen was administrated on embryonic day(E) 9,5. At E14, five intervention groups were treated separately: Nitrofen, Nitrofen+Sildenafil, Nitrofen+ABH, Nitrofen+Sildenafil+ABH and Control. At term, offspring's lungs were weighed, some paraffin-embedded for histology, others snap-frozen to analyze eNOS, Arginase I-II expression, and activity. RESULTS: In CDH-bearing offsprings, ABH or Sildenafil+ABH preserved the total lung/body-weight index (p < 0.001), preventing pulmonary vascular smooth muscle cell hyperproliferation and improving lung morphometry. Sildenafil+ABH increased 1.7-fold the lung nitrite levels (p < 0.01) without changes in eNOS expression. Sildenafil and ABH improved the number of pulmonary vessels. CONCLUSION: These results suggest that in this CDH rat model, the basal activity of Arginase participates in the lung volume and, together with phosphodiesterase-5, regulates NOS activity in the term fetal lung. The combined treatment (Sildenafil+ABH) could revert some of the pulmonary features in CDH by improving the local NO synthesis and preventing smooth muscle cell hyperproliferation. IMPACT: This study presents Arginase inhibition as a new therapeutic target and the importance of the combined antenatal treatment to improve pulmonary vascular development in a congenital diaphragmatic hernia (CDH) rat model. This study shows that the action of an Arginase inhibitor (ABH) enhances the effects already described for sildenafil in this model. These results reinforce the importance of prenatal treatments' synergy in recovering the hypoplastic lung in the Nitrofen-induced CDH rat model.