(taken from the application) The R03 candidate has made outstanding progress in the K08 study entitled """"""""Glucocorticoid (GC)-Induced Osteoporosis in Childhood Nephrosis"""""""" (1 K08 DK02523-03). She has enrolled 124 children with nephrotic syndrome (NS) and 150 healthy controls. In the course of these studies, she has identified important limitations of dual energy x-ray absorptiometry (DXA) in the assessment of bone mineralization in children with chronic disease. Although DXA is a widely accepted tool, DXA integrates bone mass in a projected area, prohibiting discrete assessment of cortical and trabecular structure and density. Studies of GC effects in adults have emphasized trabecular sites. However, growth is characterized by rapid expansion of cortical bone, a major determinant of bone strength. In addition, muscle contraction stimulates cortical modeling and children with decreased muscle strength have decreased cortical thickness. A recent animal study underscores the impact of GC on the growing skeleton: young rats treated with GC exhibited severe impairment of cortical expansion and trabecular mineralization. The recent availability of peripheral quantitative computed tomography (pQCT) substantially improves the assessment of bone mineralization. This method quantitates trabecular and cortical bone material properties and architecture, integrating these data to estimate bone strength. The NS subjects studied to date exhibit decreased height and increased adiposity in the setting of substantial GC exposure. However, standard DXA measures failed to demonstrate osteopenia in these subjects. The application of newer volumetric DXA techniques revealed decreased trabecular density in NS. Despite this advance, cortical structure and density could not be addressed due to the limitations of DXA. Therefore, we now propose expanding the current K08 protocol to included pQCT measures of bone structure and strength, and isometric dynamometric measures of muscle strength in the NS subjects and 200 additional healthy controls enrolled in our on-going K08 study. The primary hypotheses are that pQCT and dynamometry will describe more accurately the unique effects of GC on the growing skeleton, and that children with chronic GC therapy will exhibit cortical thinning and decreased muscle strength. The relative contributions of decreased muscle strength, and trabecular and cortical mineralization defects in children with GC-induced osteopenia will have important therapeutic implications. This proposed expansion of the K08 will provide the applicant with an effective springboard to a career as a fully independent investigator.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Small Research Grants (R03)
Project #
1R03DK058200-01
Application #
6189020
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Program Officer
Mcgowan, Joan A
Project Start
2000-09-30
Project End
2001-08-31
Budget Start
2000-09-30
Budget End
2001-08-31
Support Year
1
Fiscal Year
2000
Total Cost
$78,096
Indirect Cost
Name
University of Pennsylvania
Department
Pediatrics
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Leonard, Mary B; Shults, Justine; Zemel, Babette S (2006) DXA estimates of vertebral volumetric bone mineral density in children: potential advantages of paired posteroanterior and lateral scans. J Clin Densitom 9:265-73
Petit, Moira A; Beck, Thomas J; Shults, Justine et al. (2005) Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents. Bone 36:568-76
Leonard, Mary B; Feldman, Harold I; Shults, Justine et al. (2004) Long-term, high-dose glucocorticoids and bone mineral content in childhood glucocorticoid-sensitive nephrotic syndrome. N Engl J Med 351:868-75
Leonard, Mary B; Shults, Justine; Elliott, Dawn M et al. (2004) Interpretation of whole body dual energy X-ray absorptiometry measures in children: comparison with peripheral quantitative computed tomography. Bone 34:1044-52
Leonard, Mary B; Shults, Justine; Wilson, Brenda A et al. (2004) Obesity during childhood and adolescence augments bone mass and bone dimensions. Am J Clin Nutr 80:514-23
Leonard, Mary B; Zemel, Babette S (2002) Current concepts in pediatric bone disease. Pediatr Clin North Am 49:143-73