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Barth syndrome (BTHS) is an ultra-rare, X-linked recessive disorder characterized by cardio-skeletal myopathy, exercise intolerance, and growth delay. Oxygen uptake during peak exercise (VO2peak) has been shown to be severely limited in individuals with BTHS however; the trajectory of VO2peak from childhood to young adulthood is unknown. The objective of this study was to describe VO2peak from childhood through young adulthood in BTHS. Methods and Materials: VO2peak over time was presented through cross-sectional (n = 33 participants) and a longitudinal analyses (n = 12 participants). Retrospective data were obtained through maximal exercise testing on a cycle ergometer from individuals with BTHS who were or are currently enrolled in a research study during July 2006-September 2017. Participants included in the cross-sectional analysis were divided into 3 groups for analysis: 1) children (n = 13), 2) adolescents (n = 8), and 3) young adults (n = 12). Participants in the longitudinal analysis had at least two exercise tests over a span of 2–9 years. Results: VO2peak relative to body weight (ml/kgBW/min), fat-free mass (FFM) and by percent of predicted VO2peak obtained were not significantly different between children, adolescents and young adults. VO2peak did not longitudinally change over a mean time of ~5 years in late adolescent and young adult participants with repeated tests. A model including both cardiac and skeletal muscle variables best predicted VO2peak. Conclusions: In conclusion, VO2peak relative to body weight and fat-free mass demonstrates short- and long-term stability from childhood to young adulthood in BTHS with some variability among individuals. [ABSTRACT FROM AUTHOR]

Aims: To determine leg intermuscular (IMAT) and subcutaneous (SQAT) adipose tissue and their relationships with muscle performance and function in obese adults with and without type 2 diabetes and peripheral neuropathy (T2DMPN). Methods: Seventy-nine age-matched obese adults were studied, 13 T2DM, 54 T2DMPN, and 24 obese controls. Leg fat (%IMAT, %SQAT) volumes were quantified using MRI. Ankle plantar flexion (PF) torque and power were assessed with isokinetic dynamometry. Physical function was assessed with 9-item Physical Performance Test (PPT), 6-minute walk distance, single-limb balance, and time to ascend 10 stairs. One-way ANOVAs determined group differences, and multiple regression predicted PPT score from disease status, % IMAT, and PF power. Results: T2DMPN participants had 37% greater IMAT volumes and 15% lower SQAT volumes than controls (p =.01). T2DMPNand T2DMshowed reduced PF torque and power compared to controls. T2DMPNparticipants had lower PPT score, 6-minute walk, single-limb balance, and stair climbing than controls (all p < .05). %IMAT volume correlated inversely, and %SQAT correlated directly, with PPT. Leg %IMAT and disease status predicted 49% of PPT score. Conclusions: T2DMPN may represent a shift in adipose tissue accumulation from SQAT to IMAT depots, which is inversely associated with muscle performance and physical function. [ABSTRACT FROM AUTHOR]