Abstract
Bone mineral density (BMD) is of concern in Prader-Willi syndrome (PWS). This study compared responses to a physical activity intervention in bone parameters and remodeling markers in youth with PWS (n = 45) and youth with non-syndromic obesity (NSO; n = 66). Measurements occurred at baseline (PRE) and after 24 weeks (POST) of a home-based active games intervention with strengthening and jumping exercises (intervention group = I) or after a no-intervention period (control group = C). Dual x-ray absorptiometry scans of the hip and lumbar spine (L1-L4) determined BMD and bone mineral content (BMC). Bone markers included fasting bone-specific alkaline phosphatase (BAP) and C-terminal telopeptide of type I collagen (CTx). Both I and C groups increased their hip BMD and BMC (p < 0.001). Youth with PWS-I increased their spine BMC from PRE to POST (p < 0.001) but not youth with PWS-C (p = 1.000). Youth with NSO (I and C) increased their spine BMC between PRE and POST (all p < 0.001). Youth with PWS showed lower BAP (108.28 ± 9.19 vs. 139.07 ± 6.41 U/L; p = 0.006) and similar CTx (2.07 ± 0.11 vs.1.84 ± 0.14 ng/dL; p = 0.193) than those with NSO regardless of time. Likely, the novelty of the intervention exercises for those with PWS contributed to gains in spine BMC beyond growth. Bone remodeling markers were unaltered by the intervention.
Highlights
Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder characterized by hypotonia, developmental delay, poor motor competence, and commonly low levels of spontaneous physical activity (PA) [1]
Hypothalamic hypogonadism, central hypothyroidism, and growth hormone deficiency, common features of the syndrome, may contribute to short stature and poor bone mineralization [1]. This poor bone density was shown in previous studies in which most adults with PWS had not been on growth hormone replacement therapy (GHRT) [2,3]
In a recent study in youth with PWS who had been on GHRT for at least two years, we showed that youth with PWS showed lower Bone mineral density (BMD) at the hips than height-matched controls with obesity [4]
Summary
Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder characterized by hypotonia, developmental delay, poor motor competence, and commonly low levels of spontaneous physical activity (PA) [1]. Hypothalamic hypogonadism, central hypothyroidism, and growth hormone deficiency, common features of the syndrome, may contribute to short stature and poor bone mineralization [1] This poor bone density was shown in previous studies in which most adults with PWS had not been on growth hormone replacement therapy (GHRT) [2,3]. Weight-bearing exercise applies mechanical forces on the bones through the ground reaction forces and the contractile activity of the muscles [6] These physical forces induce strain in the bone and depending on the magnitude of such strain may serve to prevent bone loss or induce bone mass accumulation. The general consensus is that PA is associated with bone accrual and bone strength during childhood but the exact duration and intensity required are yet to be determined [8]
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