Parkinson's disease pathology is directly correlated to SIRT3 in human subjects and animal models: Implications for AAV.SIRT3-myc as a disease-modifying therapy.

In Parkinson's disease (PD), post-mortem studies in affected brain regions have demonstrated a decline in mitochondrial number and function. This combined with many studies in cell and animal models suggest that mitochondrial dysfunction is central to PD pathology. We and others have shown that the mitochondrial protein deacetylase, SIRT3, has neurorestorative effects in PD models. In this study, to determine whether there is a link between PD pathology and SIRT3, we analysed SIRT3 levels in human subjects with PD, and compared to age-matched controls. In the SNc of PD subjects, SIRT3 was reduced by 56.8 ± 15.5% compared to control, regardless of age (p < 0.05, R = 0.6539). Given that age is the primary risk factor for PD, this finding suggests that reduced SIRT3 may contribute to PD pathology. Next, we measured whether there was a correlation between α-synuclein and SIRT3. In a parallel study, we assessed the disease-modifying potential of SIRT3 over-expression in a seeding model of α-synuclein. In PFF rats, infusion of rAAV1.SIRT3-myc reduced abundance of α-synuclein inclusions by 30.1 ± 18.5%. This was not observed when deacetylation deficient SIRT3H248Y was transduced, demonstrating the importance of SIRT3 deacetylation in reducing α-synuclein aggregation. These studies confirm that there is a clear difference in SIRT3 levels in subjects with PD compared to age-matched controls, suggesting a link between SIRT3 and the progression of PD. We also demonstrate that over-expression of SIRT3 reduces α-synuclein aggregation, further validating AAV.SIRT3-myc as a potential disease-modifying solution for PD.

Brain transplantation of genetically corrected Sanfilippo type B neural stem cells induces partial cross-correction of the disease.

Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB) is a recessive genetic disorder that severely affects the brain due to a deficiency in the enzyme α-N-acetylglucosaminidase (NAGLU), leading to intra-lysosomal accumulation of partially degraded heparan sulfate. There are no effective treatments for this disorder. In this project, we carried out an ex vivo correction of neural stem cells derived from Naglu -/- mice (iNSCs) induced pluripotent stem cells (iPSC) using a modified enzyme in which human NAGLU is fused to an insulin-like growth factor II receptor binding peptide in order to improve enzyme uptake. After brain transplantation of corrected iNSCs into Naglu -/- mice and long-term evaluation of their impact, we successfully detected NAGLU-IGFII activity in all transplanted animals. We found decreased lysosomal accumulation and reduced astrocytosis and microglial activation throughout transplanted brains. We also identified a novel neuropathological phenotype in untreated Naglu -/- brains with decreased levels of the neuronal marker Map2 and accumulation of synaptophysin-positive aggregates. Upon transplantation, we restored levels of Map2 expression and significantly reduced formation of synaptophysin-positive aggregates. Our findings suggest that genetically engineered iNSCs can be used to effectively deliver the missing enzyme to the brain and treat Sanfilippo type B-associated neuropathology.

Feasibility of bioimpedance spectroscopy and long-term functional assessment in critically ill children.

BACKGROUND & AIMS: Lean body mass loss due to critical illness in childhood could be detrimental to long term outcomes, including functional status and quality of life. We describe the feasibility of body composition assessment by bioimpedance spectroscopy (BIS) in the pediatric intensive care unit (PICU), and functional status and quality of life assessments up to 6 months following admission in a cohort of mechanically ventilated, critically ill children. METHODS: We conducted a prospective, observational pilot study in a multidisciplinary PICU. Children aged 1 month to 18 years who required mechanical ventilation, with expected stay in the PICU of at least 5 days were included. We examined the feasibility of consenting, enrolling, and completing baseline and 6-month assessments of BIS variables, Functional Status Scale (FSS), and Pediatric Quality of Life (Peds QL), in eligible patients. RESULTS: Of 32 patients approached, 23 (72%) completed baseline assessments [median (IQR) age 3.4 (1.0, 7.8) years, 14 (61%) male]; 6-month assessments were completed in 15 (65%) enrolled patients. Mean (SD) phase angle at study enrollment was 2.95 (0.93) and the impedance ratio was 0.90 (0.03). Phase angle (rs = -0.58, p = 0.03) and impedance ratio (rs = 0.61, p = 0.02) by BIS were significantly correlated with total FSS at PICU discharge. Median total FSS and FSS tech (feeding and respiratory domains of FSS) scores improved from enrollment [16 (13, 26) and 8 (7, 10)] to 6 months [6 (6, 9) and 2 (2, 4), respectively, p < 0.001]. Median Peds QL total, physical summary and psychosocial summary scores were not significantly different between PICU discharge and 6 months after PICU admission. Correlations between the total 6-month FSS and a) phase angle (-0.45, p = 0.197) and b) impedance ratio (0.56, p = 0.096) at PICU discharge were not significant. CONCLUSIONS: We have demonstrated the feasibility of obtaining bedside BIS measurements in the PICU, and functional and quality of life assessments remotely following PICU discharge. Body composition and long-term assessment of functional outcomes and quality of life must be incorporated in nutrition trials in critically ill children.

Ultrasound Assessment of Quadriceps Femoris Muscle Thickness in Critically Ill Children.

OBJECTIVES: Evaluate the reliability of ultrasound to measure quadriceps femoris muscle thickness in critically ill children and to describe serial changes in quadriceps femoris muscle thickness in relation to fluid balance and nutritional intake. DESIGN: Prospective observational study. SETTING: Tertiary care children's hospital. PATIENTS: Inpatients age 3 months to 18 years recently admitted to the ICU who were sedated and mechanically ventilated at the time of the first ultrasound scan. METHODS: Prospective observational study to examine the reliability of averaged ultrasound measurements of quadriceps femoris muscle thickness. Change in average quadriceps femoris muscle thickness over time was correlated with fluid balance and nutritional intake. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Averaged quadriceps femoris muscle thickness demonstrated good to excellent reliability when comparing pediatric critical care providers to pediatric radiologists and when comparing between different pediatric critical care providers. We found no significant association between fluid balance over 1 or 3 days and change in quadriceps femoris muscle thickness over the same time frame. However, there was a significant association between percent of goal calories (p < 0.001) or percent of goal protein (p < 0.001) over 6 days and change in quadriceps femoris muscle thickness over the same time frame. CONCLUSIONS: Averaged ultrasound measurements of quadriceps femoris muscle thickness demonstrate good to excellent reliability, are not confounded by fluid balance, and are useful for tracking changes in muscle thickness that are associated with nutritional intake. Ultrasound-based assessment of quadriceps femoris is a clinically useful tool for evaluating muscle mass and may be a proxy for nutritional status.