| Infants born prematurely are at risk of developing osteopenia and rickets because of limited accretion of bone mass in uterus and a greater need for bone nutrients. Bone mineralization is modulated by genetic, nutritional, hormonal, and mechanical factors. Because the major cause of osteopenia in premature infants is inadequate postnatal calcium and phosphorus intake, most therapeutic efforts to prevent osteopenia of prematurity have focused on nutritional changes. However, nutritional interventions have been only partially successful in improving their bone mineralization. Bone mineralization in premature infants may continue to be inadequate until childhood, further increasing the risk of fracture.The importance of mechanical stimulation for bonedevelopment in premature infants has long been neglected. Several studies have demonstrated that physical activity increases bone density in children, adolescents, and adults, whereas inactivity results in bone resorption and decreased bone mineral density. Currently, the diagnosis of osteopenia is based on the techniques, such as dual-energy x-ray absorptiometry (DEXA) for evaluation of bone mineral content. More recently, quantitative ultrasound (QUS) measurement of bone speed of sound (SOS) was advanced. QUS may be useful in the diagnosis of osteopenia of prematurity. Leptin may play an important physiological role in bone formation.Baby massage consisted of tactile stimulation of the body and passive movements of the limbs, which developed favorable effects. Massage in premature infants resulted in increased weight gain, bone width, and bone mineral density. Recent studies demonstrated that leptin is secreted from human osteoblasts and promotes bone mineralization. By measuring the dynamic changes of serum leptin and insulin like growth factor l(IGF-l) levels and SOS of left tibial in premature infants, we try to explore whether tactile -induced increase in bone mineral density and weight gain is associated with changes in leptin and IGF-1 levels. .Materials and methodsFifty-five newborn infants were recruited from the department of neonatology, Children Hospital, Zhejiang University School of Medicine from April through October 2005. Forty preterm infants with gestational age less than 35 weeks were divided into tactile group and control group at random according to admission time. The tactile group consisted of 20 premature infants (10 males , 10 females),with gestational age of 32.8+1.0 weeks ,birth weight of 1912 + 260 gram . The control group consisted of 20 premature infants (9 males , 11 females),with gestational age of 32.8+ 1.3 weeks, birth weight of 1950 + 300 gram. Fifteen term infants (7 males , 8 females), with gestational age of 39.0+ 1.3weeks, birth weight of 3006 + 356 gram, were recruited as compared with premature infants. Premature infants with intrauterine growth retardation, severe central nervous system disorders, bone or muscular diseases, thyropathy and sepsis were excluded from the study. All consents were obtained from the parents.Venous blood samples for the evaluation of circulating leptin and IGF-1 were collected in the morning (7-8 am) before and at the end of the intervention in both the tactile and the control premature infants. In the meantime, SOS was measured, too.Tactile Protocol: Tactile was performed once per day until 40 weeks gestational age by trainer. The each procedure involves three five-minute sessions.All data were analyzed with SPSS 10.0. Data are presented as mean ± SD. One-Way ANOVA was used to determine difference among three groups. Independent-samples t test was used to determine difference between two groups. Paired-samples t test was used to determine difference in weight, body length, bone SOS, leptin and IGF-1 between two groups. Statistical significance was taken atp<0.05.ResultsOn day 3, no significant differences were found in weight, body length, gestational age, leptin, IGF-land bone SOS between the control and the tactile group. Serum leptin in two preterm groups was significantly lower than that in term infants (p<0.05), and positive correlated with gestational age and birth weight (r=0.858, p<0.05;r=0.859, p<0.05). Concentrations of IGF-1 in two premature groups were significantly lower than that in term infants (p<0.05), and positive correlated with gestational age and birth weight (r=0.629, p<0.05;r=0.500, p<0.05). And bone SOS in two premature groups were significantly lower than that in term infants (p<0.05), and positivelyrelated with gestational age and birth weight (r=0.656, /?<0.05;r=0.562, p<0.05).When two premature groups reached 40 weeks of gestational age, there were significant increase in body weight, body length, serum leptin and IGF-1 in both groups (p<0.05). Serum leptin and body weight in the tactile group were significantly higher than those in the control group (7=5.06, p<0.05;/=3.38, p<0.05, respectively). Bone SOS of the control group decreased significantly than that on day 3, whereas SOS of the tactile group remained stable during the tactile period (significant difference between groups p<0.05). Body length was similar between two groups.Comparison between the term group and the premature tactile group reached 40 weeks gestational age: the levels of serum leptin of the tactile group were significantly higher than those of the term control group (f=4.10,;?<0.05). The levels of serum IGF-1 of the tactile group were lower than those of the term control group, but no significantly difference between them (t=1.34,p>0.05). Body length and weight were similar between two groups 0=0.16, p>0.05;t=\.74, p>0.05), whereas SOS in tactile group was significantly lower than that in the term control group 0=8.4, p<0.05).Conclusion1. Serum leptin, IGF-1 and bone SOS of premature infants are significantly lower than those of term infants. Serum leptin, IGF-1 and bone SOS are positive correlated with gestational age and birth weight respectively.2. Baby massage can attenuate the decrease in bone mineralization after birth in premature infants.3. Baby massage results in increased body weight, serum levels of leptin, but no influence on IGF-1.
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