Breaking-Properties and Ash Contents of the Femur of Growing Rat Fed a Low Calcium Diet

et al. 2012

Summary Having higher bone mineral density (BMD) during growth is complexly infl uenced by many factors. For example, nutrition and physical exercise are key factors. However, few studies have investigated the combined effects of these factors. In this study, we investigated the effect of physical exercise and different levels of protein intake on BMD and bone strength of growing male rats. Forty-seven male Wistar rats (5 wk old) were randomized into 10% (Low), 20% (Moderate) and 40% (High) protein diet groups, and each group was further divided into exercise groups (LEx, MEx, HEx) or non-exercise groups (L, M, H). Exercise group rats were trained 6 d per week on a treadmill (25-30 m/min, 60 min) for 60 d. After being sacrifi ced, their BMD and bone strength were evaluated. The BMD of tibia, femoral breaking force and energy were signifi cantly lower in the low protein diet groups than the other diet groups. In particular, the femoral breaking energy was signifi cantly lower in the HEx group than in the H group, while there were no differences between LEx and L or MEx and M. Taken together, our data suggests that a low protein intake could suppress acquisition of bone mass and increasing bone strength during growth. Moreover, a high protein intake could also suppress bone strength during growth in which physical activity was vigorously performed. Therefore, sustaining an adequate protein intake level, around 20% protein intake, may be of signifi cance for increasing not only bone mass but bone strength during growth.

Section: Methodsmentioning

confidence: 99%

Effect of Different Intake Levels of Dietary Protein and Physical Exercise on Bone Mineral Density and Bone Strength in Growing Male Rats

Takeda

Kobayashi

et al. 2012

“…Femur samples were tested by measuring the mechanical properties. The strength of the femoral mid-shaft was assessed by a three-point bending test (DYN-1255, Iio Denki, Tokyo, Japan) using previously described methods (distance between the fulcrum 1 cm, plunger speed 100 mm/min, full scale 50 kg, chart speed 120 cm/min) (22). Breaking force refers to the loading weight (gravitational acceleration) required for bone breaking.…”

Section: Methodsmentioning

confidence: 99%

Food Restriction Causes Low Bone Strength and Microarchitectural Deterioration in Exercised Growing Male Rats

Hattori

Agata

et al. 2014

SummaryThe pathogenesis of bone disorders in young male athletes has not been well understood. We hypothesized that bone fragility is caused by low energy availability, due to insufficient food intake and excessive exercise energy expenditure in young male athletes. To examine this hypothesis, we investigated the influence of food restriction on bone strength and bone morphology in exercised growing male rats, using three-point bending test, dualenergy X-ray absormetry, and micro-computed tomography. Four-week-old male SpragueDawley rats were divided randomly into the following groups: the control (Con) group, exercise (Ex) group, food restriction (R) group, and food restriction plus exercise (REx) group after a 1-wk acclimatization period. Thirty-percent food restriction in the R and REx groups was carried out in comparison with that in the Con group. Voluntary running exercise was performed in the Ex and REx groups. The experimental period lasted 13 wk. At the endpoint of this experiment, the bone strength of the femurs and tibial BMD in the REx group were significantly lower than those in the Con group. Moreover, trabecular bone volume and cortical bone volume in the REx group were also significantly lower than those in the Con group. These findings indicate that food restriction causes low bone strength and microarchitectural deterioration in exercised growing male rats.

“…The bone mineral content (BMC) and BMD of the tibia or lumbar spine were analyzed by dualenergy X-ray absorptiometry (DXA: Aloka DCS-600R, Hitachi Aloka Medical, Ltd., Tokyo, Japan) as previously reported (15). Briefly, the BMC of the lumbar spine was analyzed at the site of L3-L6.…”

Section: Animals and Feeding Protocolmentioning

confidence: 99%

The Relationship between Salivary Calcium Concentration and Differences in Bone Mineral Density Level in Female Rats

Hattori

Agata

et al. 2014

Summary It has not yet been examined whether salivary calcium levels reflect changes in bone mass. The purpose of this study was to investigate the relationship between salivary calcium concentration and differences in bone mineral density due to estrogen deficiency and/or different calcium intake levels in female rats. In Experiment 1, the animals (n514) were divided into an ovariectomized group (OVX) (n58, 0.6% calcium diet) and a shamoperated group (Sham) (n56, 0.6% calcium diet). The bone mineral density (BMD) levels of the tibia and lumbar spine were significantly lower in the OVX group than in the Sham group (p,0.001 and p,0.01, respectively), whereas there was no significant difference in the salivary calcium concentration between the two groups. In Experiment 2, after an ovariectomy operation, the animals (n542) were randomized into five groups that received 0.01%, 0.1%, 0.6%, 1.2%, and 2.4% calcium diets (n510, 10, 6, 8, and 8, respectively). The BMD levels of the tibia and lumbar spine were significantly lower in the 0.01% or 0.1% calcium diet intake groups than in the 0.6%, 1.2%, 2.4% calcium diet intake groups (all p,0.001), whereas there were no differences in the salivary calcium concentration among the groups. In conclusion, the salivary calcium level did not change during periods of decreasing BMD and bone strength induced by estrogen deficiency and/or calcium intake restrictions in female rats.