Prolonged respiratory failure responds to conventional therapy in isolated homocysteine remethylation defects.

Isolated remethylation defects are rare inherited diseases caused by a defective remethylation of homocysteine to methionine, preventing various essential methylation reactions to occur. Patients present with a systemic phenotype, which can especially affect the central and peripheral nervous systems leading to epileptic encephalopathy, developmental delay and peripheral neuropathy. Respiratory failure has been described in some cases, caused by both central and peripheral neurological involvement. In published cases, the genetic diagnosis and initiation of appropriate therapy were rapidly performed following respiratory failure and led to a rapid recovery of respiratory insufficiency within days. Here, we present two infantile-onset cases of isolated remethylation defects, cobalamine (Cbl)G and methylenetetrahydrofolate reductase (MTHFR) deficiencies, which were diagnosed after several months of respiratory failure. Disease modifying therapy based on hydroxocobalamin and betaine was initiated and shows a progressive improvement and enabled weaning off respiratory support after 21 and 17 months in CblG and MTHFR patients respectively. We show that prolonged respiratory failure responds to conventional therapy in isolated remethylation defects, but can require a sustained period of time before observing a full response to therapy.

Methionine synthase deficiency: Variable clinical presentation and benefit of early diagnosis and treatment.

Methionine synthase deficiency (cblG complementation group) is a rare inborn error of metabolism affecting the homocysteine re-methylation pathway. It leads to a biochemical phenotype of hyperhomocysteinemia and hypomethioninemia. The clinical presentation of cblG is variable, ranging from seizures, encephalopathy, macrocytic anemia, hypotonia, and feeding difficulties in the neonatal period to onset of psychiatric symptoms or acute neurologic changes in adolescence or adulthood. Given the variable and nonspecific symptoms seen in cblG, the diagnosis of affected patients is often delayed. Medical management of cblG includes the use of hydroxocobalamin, betaine, folinic acid, and in some cases methionine supplementation. Treatment has been shown to lead to improvement in the biochemical profile of affected patients, with lowering of total homocysteine levels and increasing methionine levels. However, the published literature contains differing conclusions on whether treatment is effective in changing the natural history of the disease. Herein, we present five patients with cblG who have shown substantial clinical benefit from treatment with objective improvement in their neurologic outcomes. We demonstrate more favorable outcomes in our patients who were treated early in life, especially those who were treated before neurologic symptoms manifested. Given improved outcomes from treatment of presymptomatic patients, cblG warrants inclusion in newborn screening.

Cationic ß-lactoglobulin nanoparticles as a bioavailability enhancer: comparison between ethylenediamine and polyethyleneimine as cationizers.

Cationic ß-lactoglobulin (CBLG) was synthesized by two strategies: extensive conjugation of ethylenediamine (EDA) and limited cationization with polyethyleneimine (PEI). Both methods provided CBLG with satisfactory water solubility and resistance to peptic digestion. Compared with EDA-derived CBLG (C-EDA), PEI-derived CBLG (C-PEI) exhibited a higher zeta potential (54.2 compared to 32.4mV for C-EDA), which resulted in significantly elevated mucoadhesion (439% and 118% higher than BLG and C-EDA, respectively) in a quartz crystal microbalance (QCM) study. In addition, PEI caused reduced conformational disruption on BLG compared to EDA as evidenced by FTIR measurement. This character, together with the steric hindrance provided by PEI, caused a phenomenal reduction in tryptic digestibility by at least 75% compared to C-EDA. In the presence of aqueous acetone, C-PEI aggregated spontaneously into nanoparticles with average size of 140 nm and narrow size distribution. These merits made C-PEI a useful material that provides desirable solubility and protection for orally administrated nutraceuticals or drugs.