Relative Contributions of Lean and Fat Mass to Bone Mineral Density: Insight From Prader-Willi Syndrome

Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome

Introduction

The incidence of osteopenia and osteoporosis is of concern in adults with Prader-Willi syndrome (PWS). Walking generates reaction forces that could stimulate bone mineralization and is popular in people with PWS. This study compared bone parameters and ground reaction forces (GRF) during gait between young adults with PWS and without PWS and explored associations between bone and GRFs during gait.

Methods

10 adults with PWS, 10 controls with obesity (OB) and 10 with normal weight (NW) matched on sex participated. Segmental and full body dual-energy x-ray absorptiometry scans provided femoral neck, spine, total body minus the head bone mineral density (BMD), bone mineral content (BMC). Vertical GRF, vertical impulse, posterior force and negative impulse were measured during 5 walking trials at a self-selected speed along a 10 m runway.

Results

Multivariate analyses of variance showed that adults with PWS (n = 7-8) had hip and body BMD and BMC comparable (p > .050) to NW and lower (p < .050) than OB. Adults with PWS showed slower speed than NW (p < .050) but similar to OB (p > .050). Adults with PWS presented lower absolute vertical GRF, vertical impulse and negative impulse than OB (p < .050). Pearson r correlations (p < .050) in those with PWS (n = 7-8) indicated that femoral neck BMC was associated with vertical GRF (r = 0.716), vertical impulse (r = 0.780), posterior force (r = -0.805), and negative impulse (r = -0.748). Spine BMC was associated with speed (r = 0.829) and body BMD was associated with speed (r = 0.893), and posterior force (r = -0.780).

Conclusions

Increased BMC in the femoral neck and body were associated with larger breaking forces during walking, a phenomenon normally observed at greater gait speeds. Faster walking speed was associated with greater BMC in the spine and body. Our preliminary results suggest that young adults with PWS could potentially benefit from faster walking for bone health; however, larger prospective studies are needed to confirm this.

Bone Health in Adults With Prader-Willi Syndrome: Clinical Recommendations Based on a Multicenter Cohort Study

CONTEXT

Prader-Willi syndrome (PWS) is a rare complex genetic syndrome, characterized by delayed psychomotor development, hypotonia, and hyperphagia. Hormone deficiencies such as hypogonadism, hypothyroidism, and growth hormone deficiency are common. The combination of hypotonia, low physical activity, and hypogonadism might lead to a decrease in bone mass and increase in fracture risk. Moreover, one would expect an increased risk of scoliosis due to hypotonia and low physical activity.

OBJECTIVE

To study the prevalence and risk factors for skeletal problems (reduced bone mineral density, fractures, and scoliosis) in adults with PWS.

METHODS

We retrospectively collected patient characteristics, medical history, medication, biochemical measurements, dual-energy X-ray absorptiometry scans, and spinal X-rays and reviewed the current literature.

RESULTS

We included 354 adults with PWS (median age 31 years; 43% males), of whom 51 (14%) had osteoporosis (T-score below -2.5) and 143 (54%) had osteopenia (T-score -1 to -2.5). The most prevalent modifiable risk factors for osteoporosis were hypogonadism, insufficient dairy intake, sedentary lifestyle, and corticosteroid use. Male sex was associated with osteoporosis (P = .005). Growth hormone treatment was not associated with osteoporosis. A history of vertebral fractures was present in 10 (3%) and nonvertebral fractures in 59 (17%). Scoliosis was present in 263 (80%), but no modifiable risk factors were identified.

CONCLUSION

Besides scoliosis, osteoporosis is common in adults with PWS. Based on the literature and the risk factors for osteoporosis found in our cohort, we provide practical clinical recommendations to avoid skeletal complications in these vulnerable patients.

The Sun's Vitamin in Adult Patients Affected by Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a genetic disorder characterized by hyperphagia with progressive, severe obesity, and an increased risk of obesity-related comorbidities in adult life. Although low dietary vitamin D intake and low 25-hydroxy vitamin D (25OHD) levels are commonly reported in PWS in the context of bone metabolism, the association of low 25OHD levels with fat mass has not been extensively evaluated in PWS adults. The aims of this study were to investigate the following in PWS adults: (1) 25OHD levels and the dietary vitamin D intake; (2) associations among 25OHD levels with anthropometric measurements and fat mass; (3) specific cut-off values for body mass index (BMI) and fat mass predictive of the 25OHD levels. In this cross-sectional, single-center study we enrolled 30 participants, 15 PWS adults (age 19-41 years and 40% males) and 15 control subjects matched by age, sex, and BMI from the same geographical area (latitude 40° 49' N; elevation 17 m). Fat mass was assessed using a bioelectrical impedance analysis (BIA) phase-sensitive system. The 25OHD levels were determined by a direct competitive chemiluminescence immunoassay. Dietary vitamin D intake data was collected by three-day food records. The 25OHD levels in the PWS adults were constantly lower across all categories of BMI and fat mass compared with their obese counterpart. The 25OHD levels were negatively associated with BMI (p = 0.04), waist circumference (p = 0.03), fat mass (p = 0.04), and dietary vitamin D intake (p < 0.001). During multiple regression analysis, dietary vitamin D intake was entered at the first step (p < 0.001), thus explaining 84% of 25OHD level variability. The threshold values of BMI and fat mass predicting the lowest decrease in the 25OHD levels were found at BMI ≥ 42 kg/m2 (p = 0.01) and fat mass ≥ 42 Kg (p = 0.003). In conclusion, our data indicate that: (i) 25OHD levels and dietary vitamin D intake were lower in PWS adults than in the control, independent of body fat differences; (ii) 25OHD levels were inversely associated with BMI, waist circumference, and fat mass, but low dietary vitamin D intake was the major determinant of low vitamin D status in these patients; (iii) sample-specific cut-off values of BMI and fat mass might help to predict risks of the lowest 25OHD level decreases in PWS adults. The presence of trained nutritionists in the integrated care teams of PWS adults is strongly suggested in order to provide an accurate nutritional assessment and tailored vitamin D supplementations.

Nutritional condition analysis of the older adult patients with femoral neck fracture

BACKGROUND & AIMS

Many factors can contribute to the fracture of femoral neck, nutritional condition appears play a key role. The objective of this study was to investigate the relationship between nutritional condition and femoral neck fracture in an elderly population.

METHODS

A cross-sectional study was carried out among patients aged 55 years old or older, with or without femoral neck fracture. The study sample included 82 newly femoral neck fractured hospitalized patients as experimental group and 106 non-fracture out-patients as control group. Prealbumin, albumin and hemoglobin were evaluated in both femoral neck fracture group and control group. Bioelectrical Impedance Analyzer (BIA) were used to analyze the body composition. Appendicular Lean Mass (aLM) and Fat Mass (FM) were analyzed in different age grade, Percentage of Body Fat (PBF) was analyzed according to Body Mass Index (BMI) level.

RESULTS

Eight-two (male 29, female 53) patients older than 55 years old with femoral neck fracture and 106 (male 43, female 63) orthopaedic out-patients were included in this study. Albumin, prealbumin and hemoglobin in the femoral neck fracture group are significantly lower than the control group. According to the criteria for the Asia Working Group for Sarcopenia (AWGS), the prevalence of sarcopenia in femoral neck fracture group is much higher than in the control group. As for the FM analysis, although the fat mass index in the control group is higher than that in femoral neck fracture group, we did not find any differences in terms of PBF analysis.

CONCLUSIONS

Malnutrition contributes to the development of femoral neck fracture, according to the BIA analysis, aLM, rather than FM is a protection factor for the older people to get rid of femoral neck fracture.