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In Japan, school lunches are provided to elementary and secondary student, not only for ensuring the intake of well-balanced and nutritious meal, but also hoping to improve their dietary habits. In this article, the authors review the effects of a school lunch program on the bone mass and dietary habits. The school lunch program was divided into 3 groups:a group provided with a complete school lunch, a group provided with only milk supplements, and a group provided with no supplement. The calcaneal bone mass was significantly higher in both primary and the junior high-school students given complete lunches compared with that in the other groups. Moreover, the intake of milk and milk products besides school lunches was more frequent in the groups that received complete lunches. The results suggest that the school lunch program, particularly that providing complete lunches, contributed to increasing the bone mass and improving the dietary habits.

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Increasing calcium (Ca) intake is important for female athletes with a risk of weak bone caused by inadequate food intake. The aim of the present study was to examine the preventive effect of Ca supplementation on low bone strength in young female athletes with inadequate food intake, using the rats as an experimental model. Seven-week-old female Sprague-Dawley rats were divided into four groups: the sedentary and ad libitum feeding group (SED), voluntary running exercise and ad libitum feeding group (EX), voluntary running exercise and 30% food restriction group (EX-FR), and a voluntary running exercise, 30% food-restricted and high-Ca diet group (EX-FR+Ca). To Ca supplementation, we used 1.2% Ca diet as "high-Ca diet" that contains two-fold Ca of normal Ca diet. The experiment lasted for 12 weeks. As a result, the energy availability, internal organ weight, bone strength, bone mineral density, and Ca absorption in the EX-FR group were significantly lower than those in the EX group. The bone strength and Ca absorption in the EX-FR+Ca group were significantly higher than those in the EX-FR group. However, the bone strength in the EX-FR+Ca group did not reach that in the EX group. These results suggested that Ca supplementation had a positive effect on bone strength, but the effect was not sufficient to prevent lower bone strength caused by food restriction in young female athletes.

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Reduced estrogen secretion and low calcium (Ca) intake are risk factors for bone loss and arterial calcification in female rodents. To evaluate the effects of Ca intake at different amounts on bone mass changes and arterial calcification, 8-wk-old female Wistar rats were randomly placed in ovariectomized (OVX) control and OVX with vitamin D3 plus nicotine (VDN) treatment groups. The OVX with VDN rats were then divided into six groups to receive different amounts of Ca in their diets: 0.01%, 0.1%, 0.3%, 0.6%, 1.2%, or 2.4% Ca. After 8 wk of administration, low Ca intake groups with 0.01% and 0.1% Ca diets had significantly reduced bone mineral density (BMD) and bone mechanical properties as compared with those of the other groups, whereas high Ca intake groups with 1.2% and 2.4% Ca diets showed no differences as compared with the 0.6% Ca intake group. For both the 0.01% and 2.4% Ca intake groups, Ca levels in their thoracic arteries were significantly higher as compared with those of the 0.6% Ca diet group, and that was highly correlated with serum PTH levels. An increase in relative BMP-2 mRNA expression in the arterial tissues of the 0.01% and 2.4% Ca diet groups was also observed. These results suggested that extremely low Ca intake during periods of estrogen deficiency may be a possible risk for the complications of reduced BMD and arterial calcification and that extremely high Ca intake may promote arterial calcification with no changes in BMD.

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There is a concern that the combination of exercise with food intake reduction has a risk of reducing bone strength and bone mass in young female athletes. We examined the influence of the interaction of voluntary running exercise and food restriction on bone in young female rats. Seven-week-old female Sprague-Dawley rats were divided into four groups: the sedentary and ad libitum feeding group (SED), voluntary running exercise and ad libitum feeding group (EX), sedentary and 30 % food restriction group (SED-FR), and voluntary running exercise and 30 % food restriction group (EX-FR). The experiment lasted 12 weeks. Statistical analysis was carried out by two-way analysis of variance with exercise and restriction as the between-subjects factors. As a result, there were significant interactions of running and restriction on energy availability, breaking force, breaking energy, and bone mineral density (BMD). Breaking force and energy in the EX group were significantly higher than in the SED group; breaking force and energy were significantly lower in the EX-FR group than in the EX group, and breaking force in the EX-FR group was significantly lower than that in the SED-FR group. BMD in the EX-FR group was significantly lower than in the EX and SED-FR groups. These results suggest that food restriction induced low bone strength in young female rats engaging in voluntary running exercise. Also, through the interaction of exercise and food restriction, voluntary running exercise combined food restriction, unlike ad libitum feeding conditions, induced low bone strength, and low BMD in young female rats.

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Antioxidant lycopene supplementation has been shown to decrease oxidative stress and have beneficial effects on bone health. However, it remains unclear whether lycopene exerts its beneficial effect on bone metabolism through mitigation of oxidative stress in vivo. The aim of this study was to investigate whether lycopene intake protects against bone loss by reducing oxidative stress in ovariectomized rats. Female Sprague-Dawley 6-week-old rats were ovariectomized and randomly divided into four groups according to the lycopene content of their diet: 0, 50, 100, and 200 ppm. The tibial bone mineral density (BMD) in the 50, 100, and 200 ppm groups was significantly higher than that in the 0 ppm group. Serum and urinary bone resorption marker levels were significantly lower in the 50, 100, and 200 ppm groups than in the 0 ppm group. There was no significant difference in systemic oxidative stress markers among all groups. However, systemic oxidative stress levels were inversely correlated with the tibial BMD. Our findings suggest that lycopene intake significantly inhibits bone loss by suppressing bone resorption in ovariectomized rats. Further studies are necessary to clarify the effect of lycopene on oxidative stress in local tissues such as bone tissue.

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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 (n=14) were divided into an ovariectomized group (OVX) (n=8, 0.6% calcium diet) and a sham-operated group (Sham) (n=6, 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 (n=42) were randomized into five groups that received 0.01%, 0.1%, 0.6%, 1.2%, and 2.4% calcium diets (n=10, 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.

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Intake of the antioxidant lycopene has been reported to decrease oxidative stress and have beneficial effects on bone health. However, few in vivo studies have addressed these beneficial effects in growing female rodents or young women. The aim of this study was to investigate the effect of lycopene intake on bone metabolism through circulating oxidative stress in growing female rats. Six-week-old Sprague-Dawley female rats were randomly divided into 3 groups according to the lycopene content in their diet: 0, 50, and 100 ppm. The bone mineral density (BMD) of the lumbar spine and the tibial proximal metaphysis increased with lycopene content in a dose-dependent manner; the BMD in 100 ppm group was significantly higher than in the 0 ppm group. The urine deoxypyridinoline concentrations were significantly lower in the 50 and 100 ppm groups than in the 0 ppm group, and the serum bone-type alkaline phosphatase activity was significantly higher in 100 ppm group than in the 0 ppm group. No difference in systemic oxidative stress level was observed; however, the oxidative stress level inversely correlated with the tibial BMD. Our findings suggested that lycopene intake facilitates bone formation and inhibits bone resorption, leading to an increase of BMD in growing female rats.

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The 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, dual-energy X-ray absormetry, and micro-computed tomography. Four-week-old male Sprague-Dawley 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.

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Athletes, in particular endurance athletes and dancers, are chronically exposed to a state of low energy availability due to insufficient dietary energy intake and massive exercise energy expenditure. Low energy availability sometimes causes bone fragility, thereby increasing the risk of bone disorders. Although the decrease in energy availability shows no sexual dimorphism, epidemiological studies have reported that bone disorders are less frequent in male athletes than in female athletes. We hypothesized that bone tissue was not affected by low energy availability in males. The purpose of this study was to examine the influence of food restriction combined with voluntary running training on bone morphology and strength in adult male rats. Fourteen-week-old male Sprague-Dawley rats were divided randomly into four groups: control (C) group, food restriction (R) group, exercise (Ex) group, and food restriction plus exercise (REx) group. For the R and REx groups, 30 % food restriction was carried out in comparison with the C group. Bone strength, bone mineral density (BMD), bone architecture, and bone turnover rate were measured after a 13-week experimental period. Bone strength was not significantly lower in the REx group compared with the C group. BMD and trabecular bone volume showed no difference among groups. These findings indicate that bone morphology and strength were little affected by food restriction combined with exercise training in adult male rats.

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BACKGROUND: Some studies have shown that dietary hydrolyzed collagen peptides (HC) effectively prevent age-related bone loss. However, it is not known whether the intake of HC also has positive effect on bone mass or strength when combined with exercise during growth phase. METHODS: We examined the effects of 11 weeks of HC intake and running exercise on bone mass and strength in growing rats. Rats were randomized into four groups, the 20% casein group (Casein20), the 40% casein group (Casein40), the 20% HC group (HC20), and the 40% HC group (HC40). Each group was further divided into exercise groups (Casein20 + Ex, Casein40 + Ex, HC20 + Ex, HC40 + Ex) and non-exercise group (Casein20, Casein40, HC20, HC40). In the HC intake groups, 30% of casein protein was replaced with HC. Exercise group rats were trained 6 days per week on a treadmill (25-30 m/min, 60 min) for 60 days. After being sacrificed, their bone mineral content (BMC) and bone strength were evaluated. RESULTS: Exercise and dietary HC effects were observed in the adjusted BMC of lumbar spine and tibia among the 20% protein groups (p < 0.001 for exercise; p < 0.05 for dietary HC, respectively). These effects were also noted in the adjusted wet weight and dry weight of femur among the 20% protein groups (p < 0.001, p < 0.01 for exercise; p < 0.01, p < 0.001 for dietary HC, respectively). On the other hand, in adjusted bone breaking force and energy, dietary HC effect was not significant. Among the 40% protein groups, similar results were obtained in the adjusted BMC, femoral weight, bone breaking force, and energy. There were no differences between the 20% protein groups and the 40% protein groups. CONCLUSIONS: The present study demonstrated that moderate HC intake (where the diet contains 20% protein, of which 30% is HC) increased bone mass during growth period and further promoted the effect of running exercise. On the other hand, a higher HC intake (where the diet contains 40% protein, of which 30% is HC) had no more beneficial effect on bone mass than the moderate HC intake.

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Low calcium (Ca) intake is the one of risk factors for both bone loss and medial elastocalcinosis in an estrogen deficiency state. To examine the effect of different amounts of Ca intake on the relationship between bone mass alteration and medial elastocalcinosis, 6-wk-old female SD rats were randomized into ovariectomized (OVX) control or OVX treated with vitamin D(3) plus nicotine injection (VDN) groups. The OVX treated with VDN group was then divided into 5 groups depending on the different Ca content in their diet, 0.01%, 0.1%, 0.6%, 1.2%, and 2.4% Ca intakes. After 8 wk of experimentation, the low Ca intake groups of 0.01% and 0.1% showed a low bone mineral density (BMD) and bone properties significantly different from those of the other groups, whereas the high Ca intake groups of 1.2% and 2.4% showed no difference compared with the OVX control. Only in the 0.01% Ca intake group, a significantly higher Ca content in the thoracic artery was found compared with that of the OVX control. Arterial tissues of the 0.01% Ca intake group showed an increase of bone-specific alkaline phosphatase (BAP) activity, a marker of bone mineralization, associated with arterial Ca content. However, the high Ca intake did not affect arterial Ca content nor arterial BAP activity. These results suggested that a low Ca intake during periods of rapid bone loss caused by estrogen deficiency might be one possible cause for the complication of both bone loss and medial elastocalcinosis.

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Having higher bone mineral density (BMD) during growth is complexly influenced 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 sacrificed, their BMD and bone strength were evaluated. The BMD of tibia, femoral breaking force and energy were significantly lower in the low protein diet groups than the other diet groups. In particular, the femoral breaking energy was significantly 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 significance for increasing not only bone mass but bone strength during growth.

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It is not known whether local androgen metabolism is involved in the mechanisms underlying the dehydroepiandrosterone (DHEA) administration-induced improvement of bone mineral density (BMD) in an estrogen-deficiency state. The aim of the present study was to clarify whether DHEA administration would improve local androgen metabolism and BMD in cancellous site of tibia of ovariectomized (OVX) rats. Twenty-two female rats, 6 weeks old, were randomized into three groups: sham-operated rats, OVX control rats, and OVX rats that received DHEA treatment. DHEA was administered intraperitoneally at 20 mg/kg body weight for 8 weeks. The concentrations of free testosterone and dihydrotestosterone (DHT) in cancellous site of tibia did not change as a result of ovariectomy, while the DHT concentration increased following DHEA administration. We revealed that DHEA administration improved the reduction of 17ß- and 3ß-hydroxysteroid dehydrogenases and clearly reversed the reduction of 5α-reductase types 1 and 2 and androgen receptor in the cancellous site of tibia of OVX rats. DHEA administration suppressed estrogen deficiency relative to the decrease in the cancellous BMD, which was positively associated with local DHT concentration. These findings indicate that DHEA administration enhances local bioactive androgen metabolism in the cancellous tibia of young OVX rats, suggesting that local DHT may play a part in the DHEA administration-induced improvement of cancellous BMD.

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Amount of daily calcium (Ca) intake have direct impact on bone metabolism, because of an important mineral component of bone. Two months rearing with less than 0.3% Ca diet clarified effectiveness for a rat model of osteoporosis, resulted in a significant decrease in BMD and bone strength. Besides low Ca diet associated with ovariectomy also induced significant decrease in BMC and BMD in such a short-term. Otherwise precaution for assessment as to an experimental objective ought to be deliberated depend on which part of bone should be evaluated and how long rats should be reared.

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Epidemiological studies have reported an association between arterial calcification and bone loss after menopause. However, the underlying mechanism of the association remains unclear. Therefore, to explore the possible mechanisms of the association, we tried to develop a new combined model rat of ovariectomy (OVX, an animal model of osteoporosis) and vitamin D(3) plus nicotine (VDN rat, an animal model of arterial calcification). We tested them by using sham-operated control rats (SC), OVX control rats (OC), and OVX plus VDN-treated rats (OVN). Dissections were performed twice at 4 (4SC, 4OC, and 4OVN) and 8 (8SC, 8OC, and 8OVN) weeks after treatment. 8OVN showed bone loss and arterial calcification, although 8OC showed only bone loss. Moreover, arterial calcium content was associated with indexes of bone loss at 8 weeks. Thus, the OVN rat is considered a good model to examine the relationship of the two disorders after menopause. Additionally, the arterial endothelin-1 (ET-1, a potent regulator of arterial calcification) levels increased in both 4OVN and 8OVN, and the level was associated with arterial calcium content at 8 weeks. Furthermore, the arterial endothelial nitric oxide synthase (eNOS) protein, which is an enzyme that produces nitric oxide (an antiatherosclerotic substance), was significantly reduced in only 8OVN. Estrogens affect the alterations of the eNOS and ET-1 proteins. Therefore, we suggest that impairment of the ET-1- and NO-producing system in arterial tissue during periods of rapid bone loss by estrogen deficiency might be a mechanism of the relationship between the two disorders seen in postmenopausal women.

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Many epidemiological studies have reported that the severity of arterial diseases such as arterial calcification and stiffness is inversely related to bone loss, i.e., osteoporosis. However, the nature of this relationship is unclear. The purpose of the present study was to examine the influences of estrogen deficiency and/or low-calcium diet (0.1% Ca) on bone metabolism and calcium balance, as well as aortic wall composition and stiffness in young female rats. Twenty-eight 6-week-old female rats were randomized into four groups: OVX-Low calcium (OL) and OVX-Normal calcium groups (ON) were ovariectomized, and Sham-Low calcium (SL) and Sham-Normal calcium groups (SN) were sham-operated. After 12 weeks, the bone mineral density of the lumbar spine and tibial proximal metaphysis were significantly lower in ON than in SN, and also significantly lower in OL than in ON. Additionally, OL rats had significant higher (vs. SN and SL) urinary deoxypyridinoline, but not urinary calcium, excretion at 4 weeks after ovariectomy. However, at 12 weeks after ovariectomy, urinary calcium excretion was significantly higher in OL than in SL, with corresponding increases in two bone turnover markers, bone-type alkaline phosphatase and tartrate-resistant acid phosphatase. Neither estrogen deficiency nor low-calcium diet affected aortic stiffness or elastin degeneration and calcium deposition over the course of the present study, although changes of bone metabolism occurred rapidly. Taken together, these results show that bone loss and arterial stiffness did not progress simultaneously in the present experimental protocol.

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Menatetrenone (MK-4) is a vitamin K2 homologue that has been used as a therapeutic agent for osteoporosis in Japan. However, there is no far any reported evidence that MK-4 ameliorates a pre-existing condition of reduced bone mineral density (BMD) in vivo. In this study, we evaluated the effect of MK-4 in a rat model of established bone loss through immobilization caused by sciatic neurectomy. Unilateral sciatic neurectomy (SNx) was performed in rats, and 10 or 30 mg/kg of MK-4 or vehicle was administered to the rats three weeks after operation. Seven weeks after operation, the rats were sacrificed and BMD and bone histomorphometric parameters were measured to assess the effects of MK-4. While BMD of the distal femoral metaphysis was significantly decreased after SNx, MK-4 administration increased BMD in the neurectomized rats. Bone formation was decreased continuously and bone resorption was initially increased in SNx rats. Four weeks treatment of MK-4 increased bone formation and suppressed bone resorption. In addition, increased carboxylated osteocalcin and decreased undercarboxylated osteocalcin in serum were observed in MK-4-administered rats. These results indicated that MK-4 rescued bone volume by improving osteoblast dysfunction and accelerating gamma carboxylation of osteocalcin. MK-4 may be useful for treating disuse osteopenia.

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Opinions regarding beverage preference ingestion and osteoporosis differ with cultural background as well as by eating habits, food customs and other lifestyle factors in addition to climate, differences in each country and area. Furthermore, it is conceivable that it differs with or depends on life stages of the individual. Currently, beverage preferences are enjoyed as part of the eating habits in, daily life considered an indispensable food to be enjoyed thoroughly. Therefore, it may be important to drink a beverage preferences in moderate but not to indulge in excessive ingestion in order to build a healthy lifestyle contributing to both a sound mind and a sound body at each individual life stage.

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Adequate calcium intake is one of the most important issues in the prevention and treatment of osteoporosis, which is considered a lifestyle-related disease. However, calcium is a nutrient that is rather difficult to take in appropriate amounts in traditional Japanese eating habits. Therefore, one of the effective means of preventing and treating osteoporosis is to supplement calcium intake, when an insufficient quantity is obtained in the three, daily meals. In addition to increasing the tolerable upper intake levels (UL) of calcium to 2,500 mg/day, and an instruction program for learning how to evaluate the nutritional state, and the right method of utilizing supplements is needed. Furthermore, learning how to balance other nutrients, such as mineral balance, should also be included.

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Lactose promotes the intestinal absorption of calcium independent of the vitamin D endocrine system. This study investigated the effects of lactose on intestinal alkaline phosphatase (ALP) activity in rats. A total of 66 Sprague-Dawley strain female rats (10 weeks old) were divided into two groups: the control and the lactose groups. Animals in the lactose group were fed the experimental diet, in which the 10% of the diet was replaced with lactose. At 0, 3, 7, 14, and 21 days after beginning the experimental diets, rat intestinal segments from the duodenum, jejunum, and ileum were obtained immediately after sacrifice. The segments were slit open longitudinally, and the mucosa was scraped and used for the enzyme assay. The level of intestinal ALP activity in the jejunum from the lactose group was significantly higher than that from the control group. Two kinds of mRNA of rat intestinal ALP (RTIN-1 and RTIN-2) were detected by reverse transcription-polymerase chain reaction (RT-PCR). The level of mRNA expression in the jejunum from the lactose group was enhanced, especially of RTIN-2. This result was compatible with the results of enzymatic activity. These findings suggest that lactose affects intestinal Pi metabolism not only directly, but also in an indirect way via regulation of intestinal ALP expression, especially in the jejunum.

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