Bone Mineral Density and Current Bone Health Screening Practices in Friedreich's Ataxia

Racial diversities in lifespan bone mass: findings from the China BCL Study and US NHANES

BACKGROUND

Bone mass at different life stages is instrumental for developing effective, long-term osteoporosis prevention strategies.

AIM

We aimed to investigate the developmental patterns of bone mass across the entire lifespan among the Chinese population and to compare these patterns with those of different racial groups, including Whites, Blacks and Mexicans in the US population.

DESIGN

A population-based study.

METHODS

Our study analyzed data from the China Body Composition Life-course (2013-2023) Study and the United States National Health and Nutrition Examination Survey (2005-2018). We measured bone mineral content (BMC) and density (BMD) using dual-energy X-ray absorptiometry at various anatomical sites, including the whole-body (WB), lumbar spine, total hip and femoral neck.

RESULTS

In the Chinese population, WB BMC and BMD increased rapidly during childhood and adolescence, with males and females achieving approximately 90.6% and 95.7% of their respective peak bone mass. Peak bone mass for WB, total hip and femoral neck BMC/BMD occurred generally between the ages of 21 and 30, whereas the lumbar spine BMD peak occurred approximately a decade later. After reaching the peak, a gradual bone loss was observed from ages 30 to 40, with an acceleration post age 40, especially in females. Comparative analyses indicated that Chinese individuals exhibited the lowest bone mass levels and accrual rates over their lifespan, followed successively by Whites, Mexicans and Blacks.

CONCLUSION

By exploring bone mass changes and racial disparities among the Chinese and US populations, this study emphasizes the need for establishing sex- and ethnic-specific public health strategies to prioritize bone health throughout the entire life course.

Insulin Sensitivity and Insulin Secretion in Adults With Friedreich's Ataxia: The Role of Skeletal Muscle

INTRODUCTION

Friedreich's ataxia (FRDA) is a multisystem disorder caused by frataxin deficiency. FRDA-related diabetes mellitus (DM) is common. Frataxin supports skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, a mediator of insulin sensitivity. Our objective was to test the association between skeletal muscle health and insulin sensitivity and secretion in adults with FRDA without DM.

METHODS

Case-control study (NCT02920671). Glucose and insulin metabolism (stable-isotope oral glucose tolerance tests), body composition (dual-energy x-ray absorptiometry), physical activity (self-report), and skeletal muscle OXPHOS capacity (creatine chemical exchange saturation transfer magnetic resonance imaging) were assessed.

RESULTS

Participants included 11 individuals with FRDA (4 female), median age 27 years (interquartile range 23, 39), body mass index 26.9 kg/m2 (24.1, 29.4), and 24 controls (11 female), 29 years (26, 39), 24.4 kg/m2 (21.8, 27.0). Fasting glucose was higher in FRDA [91 vs 83 mg/dL (5.0 vs 4.6 mmol/L), P < .05]. Individuals with FRDA had lower insulin sensitivity (whole-body insulin sensitivity index 2.8 vs 5.3, P < .01), higher postprandial insulin secretion (insulin secretory rate incremental area under the curve 30-180 minutes, 24 652 vs 17,858, P < .05), and more suppressed postprandial endogenous glucose production (-.9% vs 26.9% of fasting endogenous glucose production, P < .05). In regression analyses, lower OXPHOS and inactivity explained some of the difference in insulin sensitivity. More visceral fat contributed to lower insulin sensitivity independent of FRDA. Insulin secretion accounting for sensitivity (disposition index) was not different.

CONCLUSION

Lower mitochondrial OXPHOS capacity, inactivity, and visceral adiposity contribute to lower insulin sensitivity in FRDA. Higher insulin secretion appears compensatory and, when inadequate, could herald DM. Further studies are needed to determine if muscle- or adipose-focused interventions could delay FRDA-related DM.

Friedreich ataxia: clinical features and new developments

Friedreich's ataxia (FRDA), a neurodegenerative disease characterized by ataxia and other neurological features, affects 1 in 50,000-100,000 individuals in the USA. However, FRDA also includes cardiac, orthopedic and endocrine dysfunction, giving rise to many secondary disease characteristics. The multifaceted approach for clinical care has necessitated the development of disease-specific clinical care guidelines. New developments in FRDA include the advancement of clinical drug trials targeting the NRF2 pathway and frataxin restoration. Additionally, a novel understanding of gene silencing in FRDA, reflecting a variegated silencing pattern, will have applications to current and future therapeutic interventions. Finally, new perspectives on the neuroanatomy of FRDA and its developmental features will refine the time course and anatomical targeting of novel approaches.