Astrocyte Dysfunction in Developmental Neurometabolic Diseases.

Astrocytes play crucial roles in maintaining brain homeostasis and in orchestrating neural development, all through tightly coordinated steps that cooperate to maintain the balance needed for normal development. Here, we review the alterations in astrocyte functions that contribute to a variety of developmental neurometabolic disorders and provide additional data on the predominant role of astrocyte dysfunction in the neurometabolic neurodegenerative disease glutaric acidemia type I. Finally, we describe some of the therapeutical approaches directed to neurometabolic diseases and discuss if astrocytes can be possible therapeutic targets for treating these disorders.

Lactic acidosis in biotin-responsive multiple carboxylase deficiency caused by holocarboxylase synthetase deficiency of early and late onset.

Two patients with biotin-responsive multiple carboxylase deficiency, both presenting with predominant lactic acidosis, are reported. One with disease of early neonatal onset had considerable acute neurologic and persistent dermatologic abnormalities. The other, with late juvenile-onset disease, had chronic neurologic abnormalities without dermatologic findings. Early-onset cases generally have been associated with holocarboxylase synthetase deficiency, whereas those of juvenile onset have been characterized as representing defects in intestinal biotin absorption. However, enzyme analyses of fibroblasts from both patients, grown in biotin-deficient medium, revealed markedly diminished activities of pyruvate, propionyl-CoA, and beta-methylcrotonyl-CoA carboxylases, and all three enzymes showed normal activities after growth in biotin-rich medium. Furthermore, lymphoblast enzyme analysis in the patient with disease of early onset had previously revealed a defect in holocarboxylase synthetase, and fibroblast complementation studies showed that both patients belong to the bio complementation group. These findings indicate that considerable clinical heterogeneity exists among patients with holocarboxylase synthetase deficiency, an observation which does not permit differentiation of the biochemical forms of multiple carboxylase deficiency on the basis of age at onset and clinical presentation.