| Background With the accelerated life rhythm and altered mode of life, many people have been suffering from chronic sleep deprivation (CSD). Some epidemiological studies have shown that chronic shorter sleep duration was associated with osteoporosis or osteopenia. However, there is still no unified conclusion. The purpose of this study was to assess the effects of CSD on bone mass and bone metabolism in rats, and explore the related possible factors.Method Twenty four rats were randomly divided into CSD group and control (CON) group according to body weight. The CSD rats were intervened by modified multiple platform method (MMPM) to establish an animal model of chronic sleep deprivation, while the CON rats were kept in similar condition. The biochemical parameters, including Serum N-terminal propeptide of type ? procollagen (PINP), N-terminal cross-linking telopeptide of type-? collagen (NTX), growth hormone(GH), estradiol (E2), serum 25(OH)D and calcium (Ca), were evaluated at 0,1,2,3 month. After three months, all rats were sacrificed by an overdose of pentobarbital sodium. The lumbar vertebraes(L4,L5) and bilateral femurs were harvested for micro-CT scans, bone histomorphological analysis and biomechanical test. All statistical comparisons were performed in SPSS (Version 17.0).Results 1. The animal models of CSD were established by MMPM successfully. The body weight of both groups increased over time, but the increase of body weight in the CSD group was significantly less than that in the CON group. There were no significant difference of ALT, AST, CRE, TC, LDL-cholesterol and HDL-cholesterol between the CSD and CON group (P>0.05), whereas the TG levels of CSD group were slightly lower than those of CON group.2. Results of micro-CT scans:The BMD of CSD rats(1312.33±8.94 mg/cm3) was lower than that of CON group(1358.18±10.15 mg/cm3)(P=0.000). Compared with CON group, the BV/TV, Tb.Th and Tb.N of CSD group(26.43 ±3.51%,0.061±0.003 mm,4.45±0.311/mm) were lower than those of CON group(35.00±4.67%,0.069± 0.005 mm,4.95±0.341/mm) by 24.48%,11.59% and 9.05% respectively (P=0.000, P=0.000, P=0.001). The BS/BV and Tb.Sp of CSD group(33.27±2.491/mm,0.20± 0.02 mm) were higher than those of CON group(30.51±2.511/mm,0.17±0.03 mm) by 9.05% and 17.65% respectively(P=0.013, P=0.008).3. Bone histomorphological analysis:The proliferative zone (PZ) of CSD rats was shorter than that of CON rats, and the columnar cells in PZ of CSD rats were smaller than those of CON rats. It suggests that CSD rats had a decreased osteogenesis. And the CSD rats had a increased hypertrophic zone(HZ) of chondrocytes and a decreased osteoid content of the primary spongiosa(PS) zone, indicating impaired mineralization of the newly formed bones. In the secondary spongiosa zone, CSD rats had an increased disconnections and separation among trabecular bone network and a decreased trabecular bone mass.4. Results of biomechanical test:In the compression test of lumbar(L5), the maximum loading and modulus of elasticity of CSD group(178.55±34.85 N, 614.20±80.97 MPa) were significantly lower than those of CON group(207.47±29.36 N,755.18±110.26 MPa) respectively (P=0.039, P=0.002). In the three point bending test of right femur, despite the maximum load, maximum deflection, maximum stress and maximum strain of CSD rats were slightly smaller than those of CON group, the differences were not statistically significant (P>0.05).5. The serum PINP level of CSD group (17.22±3.92?g/L) was lower than that of CON group(20.22±3.01 ?g/L) after one-month intervention(P=0.048), while the serum NTX level of CSD group (29.98±6.64 ng/ml) was lower than that of CON group(36.63±6.43 ng/ml) after three-month intervention(P=0.021). The serum 25(OH)D level of CSD group(16.14±2.23 ?g/L) was lower than that of CON group(19.48±2.77?g/L) after one month (P=0.004). There were no significant differences of GH, E2 and Ca between the CSD and CON group (P>0.05).Conclusion The animal models of CSD could be established by MMPM successfully. The intervention of CSD could lead to decreased bone mass and deteriorating bone microarchitecture, comprising of reduced numbers of trabecular bone, thinner trabecular bone, decreased volume fraction of trabecular bone, increased disconnections and separation among trabecular bone network. The biomechanical performance of cancellous bone becomes poor. Both formation and resorption markers decreased, suggesting that the bone metabolism was in low transformation condition. And the serum levels of 25(OH)D reduced after one-month chronic sleep deprivation, it may be one of the reasons for the changes of bone. However, GH and E2 have not be proved that they were associated with the changes of bone, and the related mechanism of the effect of CSD on bone mass and bone metabolism needs further research. |
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