Glutaryl-CoA Dehydrogenase Misfolding in Glutaric Acidemia Type 1.

Glutaric acidemia type 1 (GA1) is a neurotoxic metabolic disorder due to glutaryl-CoA dehydrogenase (GCDH) deficiency. The high number of missense variants associated with the disease and their impact on GCDH activity suggest that disturbed protein conformation can affect the biochemical phenotype. We aimed to elucidate the molecular basis of protein loss of function in GA1 by performing a parallel analysis in a large panel of GCDH missense variants using different biochemical and biophysical methodologies. Thirteen GCDH variants were investigated in regard to protein stability, hydrophobicity, oligomerization, aggregation, and activity. An altered oligomerization, loss of protein stability and solubility, as well as an augmented susceptibility to aggregation were observed. GA1 variants led to a loss of enzymatic activity, particularly when present at the N-terminal domain. The reduced cellular activity was associated with loss of tetramerization. Our results also suggest a correlation between variant sequence location and cellular protein stability (p < 0.05), with a more pronounced loss of protein observed with variant proximity to the N-terminus. The broad panel of variant-mediated conformational changes of the GCDH protein supports the classification of GA1 as a protein-misfolding disorder. This work supports research toward new therapeutic strategies that target this molecular disease phenotype.

Early microvascular changes with loss of the glycocalyx in children with type 1 diabetes.

OBJECTIVE: To evaluate the microcirculation of children with type 1 diabetes mellitus who demonstrate no clinical signs of diabetic microangiopathy for the presence of microvascular alterations and glycocalyx perturbation. STUDY DESIGN: Images of sublingual vessels were obtained in 14 children with diabetes (ages 12.8 ± 2.8 years, diabetes duration 6.7 ± 4.3 years) and 14 control patients (ages 11.8 ± 2.8 years) by the use of sidestream dark field imaging and analyzed for total vessel density, vessel surface coverage, vessel diameter distribution, mean flow index, and glycocalyx thickness. Wilcoxon rank sum test and Pearson correlation were used for statistical analysis. RESULTS: We observed profound microcirculatory changes in children with diabetes compared with control patients, with a significant reduction of glycocalyx thickness (0.38 µm vs 0.60 µm; P = .013), which was inversely correlated with blood glucose levels (r = -0.55; P = .003). Furthermore, the percentage of large vessels (>20 µm diameter) was significantly increased (11% vs 6%; P = .023) at the expense of capillaries (<10 µm diameter) with consequent increase in total vessel surface coverage (30% vs 26.0%; P = .041). No differences were seen in total vessel density and mean flow index. CONCLUSIONS: Microvascular alterations, including changes in microvessel distribution and loss of the glycocalyx, can be detected in children with type 1 diabetes mellitus before clinically apparent vascular complications. Our results disclose the glycocalyx as a possible monitoring measurement for earlier detection of diabetic microangiopathy and may provide a basis for new therapeutic strategies aiming at protection or restoration of the glycocalyx.

Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score.

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born ≤ 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS ≤ 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, "soft factors" that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice.